The EV Discussion List is an email-based forum, used to exchange ideas, information, and experiences relating to electric vehicles. Discussion threads often including advice on design, fabrication, and trouble shooting of EVs, new vehicles under development, changes in state and federal policies that effect EVs, and much more. Members of the list include a wide assortment of folks from around the world, many with extensive backgrounds in electronics, motors, and batteries, but the list also includes beginners and hobbyists as well. Everyone is welcome, and everyone has something to contribute.

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Where are the archives?

All of the email on the EV List is saved in a hypermail archive located at:

http://www.mail-archive.com/ev@listproc.sjsu.edu/

This archive is fully searchable and the search function is limited to the archive. This is an extremely useful tool for finding previously posted information on batteries, controllers, car types, companies, people's contact information, etc. If it's been posted to the list since 10/4/2002, it's in the archive The archive is courtesy of Mike Thompson.

The digests of the messages are also archived in a yahoo group at

http://groups.yahoo.com/group/ev/

The individual messages are also archived in a yahoo group at

http://autos.groups.yahoo.com/group/ev-list-archive/

Due to Yahoo's 64 MB limit, however, this archive usually only goes back about 2 years.

What does the term ICE mean?

ICE is an abbreviation for Internal Combustion Engine; generally meaning either a conventional gasoline or diesel fueled engine. On the EV Discussion List ICE is frequently used as a general reference to conventional automobiles.

What is an electric vehicle (EV)?

An EV (electric vehicle) is a motor vehicle propelled exclusively by electricity. While generally used in reference to electric powered automobiles, a great many non-road going vehicles including forklifts, burden carriers, and golf carts are electric powered. As an extreme example even the Lunar Rover used by the astronauts on the moon would be considered an EV.

What is a hybrid (HEV)?

A hybrid or HEV (hybrid electric vehicle) is a motor vehicle propelled by two sources of power, one of which is electricity. Most HEVs are gas/electric hybrids such as the Toyota Prius. Generally, in order to be considered a hybrid, a vehicle must either be able to move using either power source, or supplement one power source with another. For example a Toyota Prius is a hybrid because it uses two drive systems, one electric powered and one gasoline powered, and can operate on either one. In comparison a diesel/electric locomotive, while it does combine both electric and diesel elements in its drive system, would not be considered a hybrid, because it cannot move without using the diesel engine to supply power. In a diesel/electric locomotive, the electric drive component actually represents a transmission rather than a power source.

What is an neighborhood electric vehicle (NEV)?

An NEV (neighborhood electric vehicle) is a classification for a small electric vehicle designed for low speed operation in restricted areas. By law they are not permitted to exceed 25 miles per hour, or be operated on roads with higher speed limits than 35 MPH. Because of their limited use they are not required to meet all conventional Department of Transportation safety standards. They are not yet legal in many states.

What is a flooded battery?

The term 'Flooded battery' generally refers to a conventional lead-acid battery with a liquid electrolyte inside. These batteries are equipped with removable caps to replenish the water lost during charging. Some EVs, which use these batteries, are equipped with automated watering systems. In addition to lead-acid based batteries, some nickel-cadmium and nickel-iron batteries are made in flooded versions. Flooded batteries tend to be less expensive and more forgiving of overcharging that sealed batteries, but they can require addition cleaning and servicing.

What is a sealed battery?

A sealed battery is one that is not designed to vent to the atmosphere, under routine conditions. A rechargeable flashlight battery is an example of a sealed battery. Sealed batteries do not require the addition of water or other servicing. Sealed batteries tend to be more expensive than flooded batteries, and require more sophisticated charging systems. They are also typically capable of delivering higher currents without damage.

What does AGM mean?

AGM is an abbreviation for Absorbed Glass Mat. This is a method of construction used in some sealed batteries. The mat itself is a sponge-like material that acts as a medium to absorb and retain the liquid electrolyte of the battery. Most AGM batteries can be installed in almost any position.

What does VRLA mean?

VRLA stands for Valve Regulated Lead Acid. VRLA batteries are sealed batteries equipped with pressure safety valves. Under normal conditions these valves stay closed, and prevent any gas escaping or loss of electrolyte. However, if charging currents become too high, or the battery overheats, the gas pressure produced inside the battery may open these valves, causing gases and electrolyte to vent. Once these have escaped there is normally no means to replace them, so the battery will permanently lose some capacity.

What is regen and why is it desirable?

Regen is short for regenerative braking. This basically is a system by which the energy of a decelerating EV is harnessed, either by using the drive motor as a generator, or by driving a separate generator. The electricity created by this process is fed back into the drive battery pack, restoring some of the charge. Regenerative braking seldom has a significant effect on overall range, but it does improve drivability, and reduces brake wear. Most AC drive electric vehicles include this feature, but it is only rarely found on DC drive EVs.

What kind of speed and range does an EV have?

The speed and range of an EV will vary greatly based on the design of the vehicle. Most conversions are easily capable of highway speeds, and average 30 to 60 miles on a charge. Some conversions, built with high performance in mind, have tire spinning power, but shorter range. At the other end of the scale, conversions with a very high percentage of battery weight can have astonishing range, but at the expense of high performance. Basically, what you want from an EV determines how you build it.

For examples of the performance expected from various EV's, browse the EVDL photo album at www.evalbum.com.

Where can I buy a new EV?

Few companies exist to produce new factory-built on-road EV's, but their number is increasing. A few are listed here.

Tesla Motors (www.teslamotors.com)
Commuter cars corp. (www.commutercars.com)

Where can I buy a used EV?

Used EV's are posted for sale on many websites, and occasionally come up for auction on Ebay. One website specializes in them is the "EV Tradin' Post" at http://www.evalbum.com/geobook.html.

Local classifieds are posted on many of the Electric Auto Association local chapter websites. Go to the main EAA website at http://www.eaaev.org for links to the chapter websites.


How much do they cost (new and used)?

"New EV's" usually means those built by OEM's. These vehicles are available, but can be hard to locate. The prices range from 14,900 for a one person sparrow (now out of production) to 100,000 for AC Propulsion's "tZero" sportster or a Tesla roadster.

Used EV's are predominately conversions done by older companies now out of business (like Solar Electric or Jet Industries) or conversions done by individuals. They can be quite reasonable, and range from about 3,000 up. Of course, the price depends on the age and condition of the car, the components installed, and the options on the car, just like it does with ICE vehicles.


Should I buy a used EV or build a conversion?

As with any used car, you probably won't get exactly what you want with a used EV, but it usually costs less than converting a vehicle from scratch, you can have it quickly, and working on a used EV is a great way to get your feet wet in working with EV's, and can be a great "warm-up" to doing a full conversion.

Doing a complete conversion allows you to get exactly the car you want, and can be extremely rewarding. It also usually costs more and takes a lot more time and effort.

Given that people usually seem to hang onto EV's longer than ICE cars, the important thing is to get a car you are comfortable with that suits your needs

What maintenance is required for an EV?

Hardly any compared to an ICE vehicle!

Maintenance unique to EV's is limited to watering and cleaning flooded lead acid batteries (if so equipped), and replacing the brushes on brush type motors. This replacement usually takes place every 50,000 to 100,000 miles.

In addition to these services, EVs will also require brake servicing as in a conventional autombile.

How much does it cost to drive an EV?

Operating costs are where EV's really shine. Costs posted on the EV list by owners who have explored this question have ranged from {answer}.04 per mile to {answer}.10 per mile. Obviously a light aerodynamic vehicle will use less energy per mile (and cost less) than a heavy pickup truck. That is where most of the variation comes in. These are "wire-to-road" numbers. That is, they include everything from the time the power comes out of the plug in the garage to the time it actually moves the vehicle.

The break even point with a gas powered vehicle is usually calculated to be between .50 and .00 per gallon. Most of the country is currently well past this price point.

What can I do to maximize my range?

As far as vehicle design goes, lighter and more aerodynamic is better. The items that contribute the most drag to cars are the wheel wells, the underbelly, the rear view mirrors, and the front and rear shape. Fairings or covers can help. Good detail design and use of lightweight materials can help to reduce weight, although the difference that can be obtained is usually small. It is usually easier to simply choose a light car with high gross vehicle weight ratings.

As far as driving habits, the procedure is to drive as though there were an egg between your foot and the accelerator pedal. Make small corrections only, driving gently. Maximize your coasting where you can, instead of braking and then accelerating again. Finally, travelling more slowly will buy you range due to the batteries typically having more capacity when used at the lower currents that lower speeds require (see the entries on 'Peukert effects' for a detailed explanation). Aerodynamic drag increases with the square of your velocity, so slowing down just a little can have a large effect.

I'm buying a used EV, what do I need to know to use it?

First, ascertain the basic condition of the car, concentrating on the structural condition (you don't want any rust), the steering gear, the brakes, transmission, clutch (if equipped), etc. Then move on to the EV components.

Verify the operation of the main contactor, service disconnect, and charger interlock relay. If any of these items need repair, fix it before driving. These are safety critical items.

The batteries are what usually require the most attention when you buy a used EV. In fact, most used EV's are sold with the caveat that they "need new batteries." For flooded batteries, check to see if any of the cells have exposed plates. If so, add distilled water till it just covers the plates. Charge the batteries and then check the water level again. Water level tends to increase after charging. Add distilled water to 1/8" to 1/4" below the bottoms of the filler necks. If the batteries have sat for more than a week at a time, then an equalizing charge will probably be a good idea after this final topping off of water. (flooded lead-acid batteries ONLY. See tips for care of other battery types elsewhere in this FAQ). If the batteries have been stored, they will be low on capacity. To remedy this, drive the vehicle a short distance (about 1 mile) and recharge. Then repeat the process, but going 2 miles. Gradually extend your distance until you reach your expected range. Batteries perform best when regularly exercised.

Check the tire pressure to ensure that the rolling resistance is minimized. Check the alignment to ensure that it is at zero toe-in angle for further reduction in rolling resistance. Check the batteries for cleanliness, and look for acid leaks and the damage they can cause. Neutralize any spilled acid with baking soda. Remove any corrosion. Check that the battery cables are properly tightened and coated with vaseline or one of the corrosion preventive compounds that are available.

After you have the car operating fairly well, you can check for improperly tightened connections by driving in a high amp draw condition (hills, a higher gear than you would normally use, or heavy footed driving, within the limits of your batteries, of course) for a short distance, then checking for hot connections. If any are quite a bit hotter than the others, then they need to be adjusted.

These steps will ensure your EV is in good driving condition. As to driving one, it is basically the same as driving a regular car, except that you don't have to hold the clutch in at stop lights, and you can start from a stop without using the clutch.

Experiment with your EV instrumentation to determine the best route and driving style to suit your needs. Plan your route in an ICE car before you get your EV. This is a good idea, as you can locate potential "emergency charging points", and try alternate routes, as well as learning where the big hills are. When you drive the route in your EV, find a combination of speed and driving style that minimizes your amp draw, and thus your energy usage.

For tips on driving to maximize your range, see that section elsewhere in this FAQ.
Battery care is a large topic in itself. It also has it's own section in this FAQ.

Can I tow an EV a long distance?

There's no reason you can't tow an EV. Pull the electrical service disconnect as a precaution, and make sure the motor is mechanically disconnected from the drivetrain (i.e. transmission in neutral). Secure all loose items, and in general, take the same precautions you would for any other car under tow.

What are the safety concerns for working with electric vehicles?

1. 1. Electrical Shock
2. 2. Electrical Fire (plasma fire)
3. 3. Chemical Burns
4. 4. Chemical Spills
5. 5. AC Electrical Safety (Charging Issues)

Each of these issues is addressed in its own question and answer in this section

How do I avoid electrical shock?

When working with electrical components:

1. 1. Always assume every component is "hot" or "live"
2. 2. Wear rubber gloves UL listed for 600V isolation
3. 3. Work with one hand behind your back to avoid bridging between circuits
4. 4. Use tools designed or modified to avoid creating shorts when dropped (not "if," but "when" they are dropped - cynicism works in your favor where safety is concerned)
5. 5. Know where all safety devices are and how to use them
6. 6. Check cables and wires to see if they are "hot" before working on or around them. If they are hot, disconnect them. Even after you have disconnected them, remember no. 1 - work on it as though it were live.

What is a plasma fire and how do you put it out (also general fire safety)?

The following was found on the internet from Aaron J. Redd, Post-doc/Fellow, Plasma Physics and Controlled Nuclear Fusion, University of Washington, in response to a question about whether a spark can occur in a vacuum, and whether it is considered "fire" (emphasis added by FAQ editor):

"The short answers: yes, a spark can occur in a vacuum; and, no, the spark isn't really a "fire", but such a spark can start a fire. So it is still a safety hazard.

The spark or electrical arc is not a fire, in the sense that it is actually a superheated gas, also known as plasma. The plasma of the arc does not burn, in the sense that it is sustained by the electrical current traveling through the arc -- just as a wire will heat up when electrical current travels through it, the plasma stays hot because of the current in the arc. In theory, two metal surfaces with a vacuum gap between them can safely hold off an arbitrarily high voltage between them. In the real world, though, there are two important ways for the spark to happen: (1) No vacuum is perfect, so there will be some small amount of gas present. As shown by Paschen in the early 20th century, there is a maximum voltage that can be sustained between two (metal) electrodes, determined by the density of the trace gases in the area and (speaking loosely) the distance between the metal plates. If the voltage is above the so-called Paschen voltage, then there will be an arc between the metal surfaces. Also, the gas doesn't need to be air: helium, neon, hydrogen, carbon dioxide -- any of these will show the same Paschen breakdown. (2) Real surfaces (such as metal surfaces) aren't perfect either, and if the electric field at the surface is too high, then the material will sputter and/or vaporize, creating some gas which can then become an arc plasma.

Once the arc is occurring, more material can be sputtered off from the surface, adding more gas to the plasma arc and pitting the metal surface. This is part of the reason why electrical fires are so hard to fight: the spark that causes the fire won't stop until the electrical current stops, so whoever is fighting the fire first has to shut off the current, and then try to put out the fire.

As for this pitting on the electrode surfaces, it is quite noticeable -- electrodes tend to look very "beat up" after being exposed to arcs.

If your light switches (or any other switches!) generate visible sparks when they are switched on or off, then they need to be replaced immediately. Like I said above, the spark isn't a fire itself, but it can start a fire. "

This is very good information. To stop a plasma arc, you must first stop the current (you DID install a mid-pack service disconnect, didn't you?), and then extinguish anything that is burning. In the case of EV's, the only really flammable thing I can think of is the car interior. The plastic case of the battery may burn, but it is usually polypropylene or ABS, and these burn relatively slowly and in a controlled manner. Take note if using flooded batteries that a plasma event will likely melt holes in some batteries, which will spill acid, so have baking soda around to neutralize it so you can safely mop it up. Users of nickel chemistries should take note that your electrolyte is KOH, a basic electrolyte that may be neutralized with vinegar. A family safety website I found states that baking soda may be used to fight electrical fires (after turning off the current) by throwing handfuls at the base of the flames. This is good information for an emergency, since most of us have baking soda around for working with flooded lead-acid batteries, but it should only be used in an emergency. Really, a class C or ABC fire extinguisher would be quite a bit more effective, and you should have some in your house, anyway, at least in the garage and the kitchen. Fire extinguishers are available at home centers, hardware stores, and discount stores like wal-mart. Class A is for solid items on fire, class B is for liquids, and class C is for electrical. Multiple combinations of classes are available. Just make sure for fighting electrical fires that it is rated for a combination that includes class C.

It should be noted that electrical arcing from an AC power source is much easier to extinguish because it turns itself off 60 times every second. The DC power we deal with in EV's is continuous. The only way to stop it is to break a connection in the circuit somewhere away from the plasma. And if two or more batteries have become "fully involved" in a plasma ball, that may be all she wrote. Even without the voltage added by the other batteries in the string, once the plasma establishes itself between two power sources, it is pretty much self-sustaining until the power is gone. Theoretically, this type of plasma arc can be extinguished by placing an insulator (a darn good one!) between the arc points, if you can locate them. But the arc may be hot enough to simply melt away the insulator. Personally, I wouldn't try this unless someone's life depended on it, because of the risk of serious burns from being that close to the arc.

There's still one more thing to consider: If a plasma event happens, things get very hot. If you are using flooded batteries of any kind, some electrolyte will likely boil into vapor. If you suspect this is happening, then DO NOT APPROACH YOUR VEHICLE! You likely do not have a respirator that will filter sulfuric acid vapor or KOH vapor, and you do NOT want to breathe this stuff!!!

To sum up, plasma events are nasty. Our first response to a plasma event should be to pull every safety disconnect we have. If that does not extinguish the arc, then get everyone away from the vehicle and call 911. You may be tempted to try to move the EV out of any building it is in, so as to keep the building from catching fire. While I would want to do this, too, any safety-minded person would tell you to get out and get help instead. Personally, if it was relatively easy to move it out, and it was not a hazard to approach the car, I would try to push it out of the garage. If you cannot safely approach the car, however, then get everyone else out of the building and call 911.

How do I avoid chemical burns?

The electrolyte in the batteries of an EV is what can cause chemical burns. Wear chemical resistant gloves, long sleeves, and long pants when working with the batteries. Always have an appropriate neutralizing agent available (baking soda for acid, vinegar for KOH). An apron would be a good idea if you work with the electrolyte a lot. Most importantly, WEAR SAFETY GLASSES WITH SIDE SHIELDS!

What do I do in case of a chemical spill?

The main chemical to be concerned with when dealing with an EV is the battery electrolyte. This is sulfuric acid (H2SO4) in lead-acid batteries, and Potassium Hydroxide (KOH), a base, in nickel based batteries such as Nickel-Cadmium, and Nickel-Iron. Use baking soda and water to neutralize acid. Vinegar can be used to neutralize KOH. After neutralization, the leftover constituents are harmless, and may be cleaned up with soap and water. KOH is more dangerous to deal with than the relatively weak H2SO4 solution used in lead acid batteries. Both will burn you if you touch them, however. Wear proper protective clothing, and safety glasses with side shields while working with electrolyte.

What is the maximum DC voltage that is considered safe to work around?

Although there is no cut and dried answer to this question, generally, a 36V max. battery or group thereof is considered safe by the auto industry. This is the basis of the 42V standard being discussed for ICE vehicles.

What are some tips on short-proofing tools?

Wrap exposed metal areas of tools electrical tape with a minimum 600V rating. Cover all exposed metal except what is needed for the tool to function at it's "business end." An alternative is to use a liquid vinyl dip such as those available under many brand names at hardware stores, to coat the handles. It dries to a conformal vinyl rubber coating. It's also good practice to use tools that are too short to bridge between terminals if dropped

What are the guidelines for working around hydrogen?

So your charger didn't shut off all night and you can hear all the batteries gurgling merrily, and you want to know how to NOT blow up the garage.

The required concentration for an ignitable mixture is generally too high to generate from batteries charging in an open space in a garage, but the same might not be true for small spaces like battery boxes. Still, hydrogen is so combustible, that it behooves us to take every precaution.

For battery boxes that are sealed relatively well, draw air out of them with a brushless design fan to the outside of the car while charging. This is only necessary if your boxes are closed and sealed, of course. For the garage, install a CO detector. CO detectors are very sensitive to hydrogen as well as CO. Wire the output to a latching relay instead of to (or in addition to) the piezo speaker that comes with the alarms. Use the relay to trigger a brushless garage vent fan to draw air out of the garage to the outdoors. This would require a manual reset by the user when it triggers on, and the relay could also activate some sort of alarm or indicator inside the house. A bonus is that it also ventilates automatically if CO builds up in the garage.

What are the safety protocols for the AC side of the equation when I charge my EV?

First, grounding. The vehicle chassis should be connected to AC ground.

Second, GFI (ground fault interrupt) circuits should be employed. The NEC requires a Ground Fault Interrupt (GFI) device to be incorporated into the AC wiring used to charge any EV. A GFI (also called a GFCI for Ground Fault Circuit Interrupt) senses the difference in current between the hot and neutral AC lines. When there is a difference, the GFI shuts off the circuit. Some people have argued that a GFI is not required for "every" EV. C'mon folks. Regardless of whether it is or not, GFI breakers and outlets are so common and inexpensive that you really don't have an excuse to not use one. The most inexpensive chargers (K & W and Russco) have them built in, which is handy when opportunity charging.

Third, there is a form of protection called isolation. This is accomplished by running the AC through a transformer with a 1 to 1 ratio (called an isolation transformer) before it goes into the charger. This provides protection because on the secondary side, there is no path to ground, should you accidentally touch a wire. The secondary is floating, just as the traction pack in the EV is floating with respect to the 12V system. However, since it is floating, it can develop what is called a "common mode" voltage. That is, if you were to measure the voltage to ground from either of the secondary lines, it could be very high, though there is still only 120V between the two secondary wires. Theoretically, there is no danger in this, since any connection to ground (by a person accidentally bridging between the wire and ground) only adds a reference point, and the common mode voltage vanishes quickly through the bridge (the person) with little current.

Is it dangerous to have all those batteries in the car?

There are four areas of safety concern when dealing with batteries. Weight, acid, hydrogen, and electrical considerations.

1. Weight should not be a factor in an EV, because the EV is designed with the batteries in mind. Properly designed battery supports (see the appropriate section of this FAQ) withstand high loading and contain the batteries in an accident. Improved suspension components (again, see the appropriate section of this FAQ) restore vehicle handling and ride quality.

2. Battery acid is moderately dilute, but should still be treated with respect. Baking soda should be kept handy to neutralize any that spills while you are maintaining your batteries, and obviously, appropriate safety precautions should be followed (i.e. safety glasses or goggles, gloves, and an apron).

Acid is only a consideration for flooded lead-acid batteries. AGM and VRLA or gel-cell batteries have the acid immobilized and are spill-proof. Even with floodeds, acid is only a danger if a battery ruptures. In everyday use, well cared for flooded batteries do not vent or spill enough acid to be an immediate danger.

In an accident, a properly designed battery enclosure will prevent any acid from entering the passenger compartment.

3. Hydrogen: batteries generate hydrogen gas during charging. That is why battery boxes are ventilated to the outside. Normally there is only a small amount generated, and with a properly designed battery box, it is not a problem. Again, this is only a consideration for flooded batteries. AGM and VRLA types recombine the hydrogen and oxygen inside the battery, and will only vent if charged improperly. The small amount of electrolyte in these batteries further reduces the amount of hydrogen it is possible to vent.

4. Electrical considerations: Proper use of terminal covers and rubber battery terminal boots can help guard against accidental short circuits, as can tools with insulated handles and being very deliberate where you put your tools. Batteries are always "ON".

What about high voltages?

As far as operating an EV goes, the high voltage is transparent to the driver. All of the high voltage traction pack is isolated from the vehicle frame, and multiple safety devices are incorporated to break the circuit in an emergency and on demand. Example include multiple fuses, service disconnects, circuit breakers, and inertia switches. The main contactors also act as a cutoff point.

All of the normal precautions for dealing with high voltage electricity should be followed when working on an EV. These include insulated tools, personal protective equipment, and activating service disconnects before service. Remember: "batteries are always ON".

What is a GFCI circuit?

GFI stands for ground fault interrupt. These circuits measure the difference in current between the hot and neutral legs of an AC circuit. If there is a difference between the two that exceeds a certain current (5 to 15 mA, depending on the manufacturer), the GFI breaks the circuit. these devices may also be referred to as GFCI or ground fault circuit interrupt devices.

Is splashing water into the engine compartment safe?

The motor, cables, and batteries don't mind too much, but some of the electronic components (contactor, heater relay, controller, charger, DC/DC converter) may not be environmentally sealed enough to withstand the automotive environment. Unless the component is listed as being splash-proof, then it should be enclosed or otherwise protected from water.

Is it safe to wash the engine compartment at a car wash?

As discussed in section 6.13, it is usually OK to get the cables and motor wet. The electronic components usually are not sealed enough to withstand this type of treatment, however. A small amount of water is all it takes to seep inside and ruin an expensive DC-DC converter or controller. Generally, EV's stay much cleaner than their ICE counterparts, so power washing the engine compartment will not usually be required. If it does get dirty from road grime, it can usually be easily hand cleaned with a mild soap and water solution.

David Brandt
5/22/01

How do I build a safe EV?

In an EV, the primary safety concerns are electrical safety and battery containment. Having a safe design is of paramount concern when building an EV. It is also fairly easy to do.

The most important thing is to read all you can on the subject. Bob Batson of Electric Vehicles of America produces a free technical paper "Safety First" which you can request by e-mail. The EVA website is at www.inc.com/users/evainc.html?111.

Battery containment techniques are an important part of EV design, as they restore the structural capacity of the car in areas cut out to make room for the batteries, as well as keeping the batteries from becoming projectiles in a crash. Battery box and restraint design is addressed elsewhere in this FAQ list.

Battery care is also addressed elsewhere, but it bears repeating to use appropriate personal protective gear (safety glasses, gloves, etc.) when working with flooded lead acid batteries. Also, keep a box of baking soda nearby to neutralize any spilled acid. These are just the same precautions you would take dealing with a battery in an ICE vehicle.

Leave all the safety devices which were already on the car as an ICE vehicle (like seatbelts and airbags) intact. If you got the donor vehicle from a salvage yard, have these items checked by a qualified mechanic before placing the vehicle into service.

Design your vehicle such that no single failure would be catastrophic. Specific items to pay attention to are as follows:
1) Each series battery string should incorporate a fuse.
2) Incorporate fuses between the front and rear portions of a battery pack.
3) Fuses should be incorporated between parallel packs.
4) Fuse both the positive and negative legs of auxilliary high voltage devices.
5) The main traction circuit should incorporate at least two devices besides fuses capable of interrupting the current from a shorted pack (i.e. a manually activated circuit breaker and a contactor).
6) Take great pains to electrically isolate the traction pack from the car's 12V system, which depends on a body ground. If any accidental contact occurs, it could lead to charging problems, damage 12V devices and/or deliver a nasty shock.
7) If you use an onboard charger, use at least a GFCI protected circuit breaker on the AC input line.

There are some items which are inexpensive to add, but which increase the safety of your EV.
1) An inertia switch is used to sense the accelerations of a crash and cut power to the main contactor. This switch is used in some ICE cars to shut off the electric fuel pump in an accident.
2) A circuit breaker with a remote handle for activation in the cabin is often used as a service disconnect to disconnect main battery power while servicing the car. Disconnecting the power during service should be like pulling the emergency brake - an automatic action that is always performed. It can also double as an emergency shutoff, although separate shutoffs can also be incorporated.
3) If using a DC motor controller, you should know that a failure mode for the power section is to fail shorted. That is, to apply full power to the motor. In this case, leaving the clutch in your conversion adds a safety measure, as anyone familiar with a manual transmission will instinctively depress the clutch and brake in the case of such a failure. This means you won't be careening down the road while fumbling for the disconnect.

Lastly, if you are in doubt about something, ask someone. The EV list is an excellent resource, and EV parts suppliers have extensive experience with EV conversions. They are a great source to ask.

How much does it cost to convert an ICE to EV?

Conversions have been done for less than 5000USD, but that is not the norm. As with many aspects of conversion, what you want from the vehicle affects the cost.

A high performance EV needs a controller that can put a lot of amps into the motor for high torque, and a high voltage battery pack for high speed. The need for high current leads to the selection of advanced AGM batteries, which in turn drives the requirement for sophisticated charging and battery balancing technology. Each of these selections drives up the cost.

An EV for everyday use runs the middle of the road. Depending once again on how many features are designed into it, these conversions can cost from 6000 to 10,000 not including the cost of the base vehicle.

If you are just getting into EV's and want to get your feet wet without spending a lot of money, consider buying a used conversion. Usually these are much less expensive (and a lot less work) than doing a conversion right off the bat. Check out the EV tradin' post for used EV's. A used EV can be a great learning experience for those who may not be sure what they want in an EV, and do not know if they want to do a full-up conversion themselves right away.

How do I choose the best car to convert?

This depends largely on what you expect to get out of the vehicle. If you want range above all else, the ability to carry a lot of batteries is an overriding concern, so you would look for a vehicle with a lot of carrying capacity. If performance is your ultimate goal, then a light, aerodynamic vehicle with a high performance suspension would fit the bill best. Some converters combine both of these, and have a motto "less iron and more lead". This is fine, but I speak from experience when I say that a unibody can and does bend over time. This can lead to being permanently out of alignment, with resulting added drag, abnormal tire wear, etc. It is important to make sure that every aspect of the base vehicle can handle the added weight.

The most overriding guideline is to go with a vehicle you really like. Otherwise, you will wind up with an EV you don't care too much for after the uniqueness has worn off. EV owners tend to keep their vehicles a relatively long time, so you want a car you will be happy driving well into the future.

In general, look for a lightweight, relatively aerodynamic vehicle with a high gross vehicle weight rating as compared to the actual weight.

There are many other things to consider besides this, and they are covered in the free technical paper "Choosing a car to convert" available from Bob Batson at Electric Vehicles of America.

How can I build a very fast/quick EV?

If performance is your goal, then your general design guidelines are going to include the following:

1. Start with a small, light, high performance donor vehicle, preferably one that you can get performance suspension parts and brakes for.
2. Choose a controller that can deliver lots of amps to the motor (more amps equals more torque).
3. If using lead-acid batteries, use sealed (AGM style) batteries. This type can deliver high currents more easily than flooded batteries with less capacity loss at higher currents.
4. Choose a battery capacity that is close to what you need with minimal reserves. This will minimize the weight of your battery pack.
5. Use a high voltage (> 120V) battery pack for higher speeds at lower currents. The newest "everyday" controllers will let you use packs of up to 300V nominal. The highest performance EV's use pack voltages of 240 volts and up, with 2000 amp controllers!
5. Don't forget to switch to higher performance brake components, so you can stop just as quickly.

How can I build an electric motorcycle?

The same way you build a car, only smaller.

The basic parts are the same: Batteries, a motor, and motor control. The specifics are different. Magura makes a twist grip throttle that uses a 5 kilo-ohm potentiometer which is a pretty standard value for scooter and some larger motor controllers. Batteries can be whatever you want, from flooded (wet) lead acid to sealed AGM lead-acid, nickel cadmium or nickel metal hydride or lithium. A small, light battery made of more exotic batteries is easier to afford on a motorcycle than a car. A charger is still needed, and the more costly the batteries, the more you want a charger that won't damage the batteries. Just like in a car.

Motors are the one place where motorcycles can be found to be different. While DC conversion cars tend to use series wound brushed DC motors almost exclusively, brushed permanent magnet motors, brushless permanent magnet (synchronous) and series wound motors can all be found on motorcycles. Brushless DC and brush permanent magnet motors are less common on car sized EVs often due to cost (brushless motors usually have expensive and strong magnets) or inadequate power (brush permanent magnet with less powerful and less expensive magnets). But on a lighter motorcycle they might be just fine.

3 phase AC (asynchronous) motors are not common, on motorcycles likely due to inefficiency at such a small (motorcycle) size and the fact that most AC controllers use high voltage which means lots of batteries. That being said, there is no reason that you can't use any of these motors,they just involve tradeoffs. A larger motorcycle perhaps with a sidecar could have 336V of batteries and an AC induction drive, and some minibikes run car starter motors at low voltage (24-48V) and high current.

Motor controllers must match the motor. There may be a few more controllers available to the EV motorcycle crowd because the power requirement is a bit lower and things like forklift or golf car controllers that might be marginal on a car could be just fine on a motorcycle.

Once all the drive parts are collected, then the power transmission needs to be figured out. Chains are relatively inexpensive and parts can be purchased or adapted easily, be it from bicycles or sporty motorcycles. Custom sprocket sizes are fairly common on motorcycles (try sprocketspecialists.com). Belts are also used. Some even use a friction drive on the rear tire, like on the EV Warrior bike. More powerful motorcycles will likely want older motorcycle frames, chains, series wound motors and low voltage (36-48) controllers.

Some people prefer belt drives, which can be quieter and have good efficiency. A Gates Polychain GT belt is a relatively common choice and there is extensive engineering information on the Gates website. There is also a lot of drivetrain componentry available from custom motorcycle shops.

Brakes are important as the conversion will weigh more than the original motorcycle. Most motorcycles have good brakes stock, but bicycle to light motorcycle conversions should consider at least mountain bike disc brakes. And good tires. The "Hookworm" or other "baldy" mountain bike tire will be acceptable on the road. Motorcycle conversions again have less to worry about in this department.

If you want it to be a real motorcycle then it will have to conform with the local and Federal laws. This is easiest to do if you started with a motorcycle and kept the lights, horn, turn signals and such. You may consider low power versions of these components. Often, LED lamps that fit in existing lamp holders are available and they offer better reliability as well as saving the energy to propel you down the road.

Finally, places like the EV discussion list [ http://www.madkatz.com/ev/evlist.html ] or the Yahoo power-assist group [ http://groups.yahoo.com/group/power-assist/ ] have information on EVs and human power assist (EV and ICE) respectively.

How can I build an electric lawn mower?

A lawnmower is an excellent choice for a conversion, since the small engines they use typically pollute far more per gallon of gas used than a car engine. There is also the benefit of being able to mow early or late when it is still cool out without disturbing your neighbors.

There are as many ways to do this as there are different kinds of mowers out there. I discuss push mowers here. In general, the more like a tractor the mower is, the more like a regular EV conversion it will be, both in complexity and expense.

If you are comfortable using a motor with a cord, the expenses are minimal, and the installation is simple. In this configuration, use a standard AC motor of the appropriate HP rating (usually 1-2 HP) in place of the ICE motor. Make sure the motor is rated for outdoor use (enclosed) and is properly cooled. Motors are available from tool warehouses, motor repair shops, motor distributors (look in the yelow pages), and some home stores. Don't forget to check surplus places! Sometimes they have components designed for AC or DC electric mowers at very low cost. Sometimes you will have to have a machine shop machine a special adapter to attach the blade to the motor shaft, but usually these modifications are minimal. Safety items include a switch rated for the appropriate voltage and amperage, and a fuse or circuit breaker. A second switch should be incorporated to automatically open when you take your hands off of the handle, like the ICE cutoff lever on most newer mowers. This can be done by attaching a momentary contact switch of the appropriate rating to the existing ICE dead-man handle. The only difference is that when you grab the handle again after shutting down for a moment, the motor will start up without having to yank on a rope. Of course, you should keep all the guards and safety items that are already on the mower.

If you want to go cordless, then you have to add provisions for battery mounting to the mower, and use either a DC motor or a properly sized inverter. A DC motor should be of the shunt or permanent magnet variety, because a tendency to seek a constant speed is the preferable mode of operation for a mower blade. Usually, DC motors are a little more expensive than AC, and DC switches can be harder to find. A charger must also be provided, though for a push mower, an external charger makes more sense than an onboard.

Can I build an EV with an automatic transmission?

Automatic transmissions have been used in EV conversions, but the modifications required are likely beyond the scope of most enthusiasts. The torque curve of an EV motor/controller combination is not the same as the ICE it replaces, therefore the shift points (what speed/RPM the transmission shifts gears) will have to be changed. In older transmissions this can be accomplished by modifying the valve body within the transmission (the assembly that routes the fluid under pressure, activating the bands), or in the case of more modern transmissions, modifying the computer code that controls the electronic servos inside the transmission. It may also be possible to simply shift into "L2" or "L1" instead of "D". Since the benefits are rather minor, the work required complex, and there is a decrease in overall efficiency compared to a standard transmission, you don't see very many automatic transmission EV's.

An external fluid pump should be used to provide the constant fluid circulation that an automatic requires, and usually derives from the idling ICE.

As in many other aspects of converting a vehicle, it comes down to what you want out of the vehicle. For many, the convenience is worth the slight decrease in efficiency. For others, premium efficiency and control is a requirement, and this requires a manual transmission.

Why do I need a transmission?

Though it can be omitted through careful design, A transmission is usually retained for both performance and practical reasons. To prevent overloading the motor and controller at lower RPM's, it is helpful to use a lower gear to get the motor RPM's up to improve efficiency, torque and motor cooling. At higher speeds it is desirable to use a higher gear to keep the motor from over-revving. An EV motors' torque band is quite a bit wider than an ICE's, so shifting gears doesn't occur as often as with an ICE. Actual gears used will depend on the motor's torque curve, the output of the controller, the transmission's gear ratios and the final drive ratio. In a practical sense, the transmission serves to provide a convenient interface between the motor's output shaft and the vehicle driveline. Since it usually comes with the car and is likely still functioning (usually the ICE dies first), to discard it and custom fabricate this part of the EV driveline would be complex and expensive. EV suppliers can provide adapter plate kits that bolt to the transmission's bell housing and allow many different electric motors to connect to it. By using the vehicle's original transmission in this manner solves a number of engineering issues in conversion EV's.

Should I keep the clutch?

Numerous enthusiasts, and even a few prominent EV parts suppliers, will say that keeping the clutch isn't necessary. It's true, it is possible to operate an EV without the clutch. However, depending on the vehicle, it may be a very desirable thing to keep and really doesn't add much, if at all, to the cost or complexity of the conversion. If the donor vehicle originally had a clutch, all of the necessary hardware is already there, so there's not much reason not to incorporate it.

Inside a manual transmission, synchronizers are used to match the speeds between the gears during a shift. When a clutch is present, those synchronizers only have to speed up or slow down the mass of a couple of gears and a shaft or two during a shift. Without the clutch, and an electric motor permanently coupled to the input, those synchronizers also have to speed up or slow down the entire mass of the rotating motor armature and coupler, which can be as much as 80lbs or more. This increases shift time to a number of seconds, which can get kind of exciting when you need to shift while merging on the freeway or trying to climb a steep grade. Under this severe duty of having to speed up and slow down this 80lb armature mass, it's possible that the synchronizers will be more prone to fail.

Keeping the clutch not only ensures the synchronizers never see a load greater than they were designed for, but offer other advantages. One is a safety feature. If the motor controller ever fails full on and your emergency disconnect doesn't work (or isn't there!), you can push in the clutch and disconnect the runaway motor from the driveline. The motor will be destroyed, but that's better than careening out of control down the street.

During normal EV driving you don't use the clutch quite the same as you would in an ICE, for instance sitting at a stoplight in gear doesn't require you to hold the clutch in, since an electric motor doesn't idle. Starting from a stop doesn't require slipping the clutch, as the motor can accelerate from 0 RPM on up. You also tend to shift much less often, due to the broad torque band most EV motors have. As such, the clutch in an EV will see very light service and should last the life of the EV, in addition to preserving the synchronizers. Add to that the additional motor-disconnect safety feature and this makes keeping the clutch 'desirable,' even if it isn't 'necessary.'

What are the effects of using one separate motor for each drive wheel? Can I remove the differential to save weight or control the motors to emulate a differential?

It depends on the motors.

With series DC motors, the problem is trivial. Wire the two motors in series, and they behave exactly like a normal differential; same torque at both wheels regardless of speed. With one wheel in the air, you have no torque at the other wheel either.

Wire the two motors in parallel, and it behaves like a limited-slip differential. Each motor operates independently, adjusting its speed according to the torque. Same speed, same torque to both wheels. When you turn, the inside wheel slows down a bit, so it delivers a bit more torque.

AC induction motors and PM DC motors are "stiffer" (more change in torque as their speed changes), but basically work the same as the series motors in parallel. When you turn, the inside motor delivers more torque than the outer motor (and more than series motors would have under the same conditions), but not enough to cause problems. It still works as long as you don't try it with extremely tight turning radius (like a skid-steered vehicle).

AC synchronous and brushless DC motors are the only ones where you need a separate controller for each wheel. These motors "fight hard" to run at precisely the speed commanded. With them, you would either use one motor with a differential, or separate controllers for each motor with some control scheme so each runs at the right speed.

Editor's note: Though direct motor drive has been accomplished, It takes careful system design. Usually some sort of reduction is necessary. For example, if one were to direct drive a 23" diameter wheel (tire size 205/50 R15) with a typical EV motor such as an ADC 9" series wound motor, the vehicle would be going about 68 MPh at only 1000 motor RPM. Since these particular motors like to be run at around 5000 RPM for best efficiency, the motor would draw excessive current (requiring a more expensive controller) and generate a lot of excess heat. To perform well would require a lot of torque (and thus current) at low speeds. This drives up the cost as well.

The examples above allow one to eliminate a differential, but a reduction would most likely still be needed. One can be used on each motor, or the two motors can be ganged together on one differential, as on the Solectria EV S-10 trucks.

How much power will I need? (Calculating power used to move a car)

The force required to move a car may be determined mathematically if you know:

• The weight of the vehicle (the total converted weight can be closely estimated by weighing what you take out and what you put in)
  
• The rolling resistance (This can be measured by pulling the car at a constant speed on a flat surface using a spring scale, but it depends on weight, so make sure it is close to the finished weight when you do the measurement)
  
• The drag coefficient and the frontal area of the vehicle (this may be obtained from the dealer, or may be estimated based on similar vehicles)
  

The total force it takes to move a vehicle is the sum of the following:

1. The rolling resistance is pretty much a constant force
   
2. The force due to moving on an incline is Weight multiplied by the sine of the angle of the incline from horizontal
   
3. The aerodynamic force is (drag coefficient) * (frontal area) * (speed)^2 * (air density) / 2
   

NOTES: These calculations are general and intended for estimates only. Appropriate unit conversion factors must be applied. These equations are for steady state and do not take acceleration into account.

The resultant force must be changed into torgue at the tire using T = Force * (Tire radius), and then the gear ratios in the transmission and differential must be taken into account. This will tell you the torque that your motor must generate for your vehicle to go that speed. Use of the appropriate motor curves will help to find the ideal gear and how much electrical power must enter the motor. The motor curves and your controller characteristics will tell you how much headroom you have for acceleration at that speed.

For a more detailed estimate, including range, amperage consumption, and voltage sag for different batteries, plug your weight, drag, and rolling resistance numbers into Uve's EV calculator.

How can I calculate the weight and balance of my conversion project?

Before removing any of the ICE components, take the car to a grain elevator, weigh station, or truck stop and weigh the car. All of these locations have scales, and if you explain what you are trying to do, they will likely let you use them for free. Even a certified weight is not very expensive. Weigh the car with just the front wheels on the scales, with just the rear wheels on the scales, and with the entire car on the scales. This will tell you how the weight is distributed between the front and rear axles. To maintain handling and performance, this distribution should be maintained after the conversion.

The vertical weight distribution should also be maintained. The height of the center of gravity of the unconverted car is difficult to measure, but can be estimated as a height just at the top of the engine block. If the converted car maintains a CG height lower than this, the rollover tendency will generally be reduced. The way to do this is to place as many of the added components below this height as much as possible. By far the heaviest portion of most EV's is the batteries, so if they can be placed at or below this height (and they usually are, by being sunk into the floor), the overall CG height is usually maintained or reduced.

A more tedious (but more accurate) way to establish that your converted CG is lower is to use a spreadsheet to calculate the normalized rolling moment of the removed items and added items. It is not necessary to know the "before" CG height when using this spreadsheet, but by carefully recording the CG height of each item removed and added with respect to a fixed reference point on the chassis, the change in CG height can be computed. This is commonly done when aircraft are modified.


What kind of range can I expect from my conversion?

Uve's EV calculator is available to give a lot of information, including range. It is at www.geocities.com/CapeCanaveral/Lab/8679/evcalc.html.

For quick back of the envelope calculations, however, a simple empirical equation which seems to give good results is available. This has been developed by the EV discussion list from a combination of formulas, and has been dubbed the "Neon-Dube" equation by David Dymaxion, its creator, in honor of Paul "Neon" Gooch, and Bill Dube', the primary contributors. It is:

Miles of range = (original weight/converted weight) * (mpg as an ICE car/500) * pounds of batteries.

What motors are available?

The most popular motors for EV's are series wound brushed DC motors. It used to be that these were salvaged aircraft starter/generators, or motors cannabalized from other sources, but most on-road EVs now almost universally favor the "advanced DC," or "WarP" (a.k.a. Netgain - www.go-ev.com brand motors. These motors are designed for EV's, and are available in sizes that are right for most conversions.

That said, there are also conversions using shunt wound and separately excited brushed DC motors, but these require specialized (and thus hard to find) controllers. AC motors are coming down in price, and while their performance characteristics are different from the traditional series wound DC motors, they have advantages, too. They require specialized controllers, and are typically more expensive than their DC counterparts. The reasons to use different types of motors would usually hinge around some of the unique features they can offer, such as regenerative braking.

It is generally agreed that the series wound DC motor most closely matches the torque-speed requirements of everyday driving. they are also a favorite of drag racers due to their high torgue at low RPM's.

Which is better, AC or DC motor?

As with most decisions in building an EV, this depends on what you want to put into and get out of your EV. This issue has been hotly debated on the EV discussion list many times.

AC systems tend to be more expensive, but are slightly more efficient overall, and easily incorporate regenerative braking. Most AC systems require the use of a high voltage (216 or more VDC) battery pack. Finally, most AC systems incorporate all the electronic components in one box, making the underhood arrangement simpler.

DC systems are cheaper at the moment. The required brush servicing is around 50,000 to 100,000 miles, and can be done in minutes at a competent electric motor shop. It is really not much of a hassle. A DC system does not constrain the user to using a high voltage battery pack, though one may be used without difficulty. It is relatively difficult to incorporate regenerative braking when using a series wound DC motor (although it has been done). Other kinds of DC motors better lend themselves to regenerative braking, but require specialized controllers, driving the cost back up.

The most arguable difference is in performance. While DC motors have their best torque at low speeds, AC motors have fixed torque up to a speed where the power becomes constant. AC motors can typically spin a lot faster. This can eliminate the need for a multi-gear transmission, and allow the substitution of a single-speed lightweight gearbox.

What batteries are available?

When selecting a battery type, one must consider many factors, including (in no particular order):

1. Weight
2. Size
3. Cost
4. Capacity (Amp Hours)
5. Voltage
6. If a management system is required to avoid overvoltage or for balancing. this usually leads to a mroe expensive charging system.
7. Maximum Rate of Discharge (Flooded - OK. AGM - Great. Gel - Not so great. Lithium - not so great to good, and Nicad - OK.)
8. Maintenance Required
9. Expected Life Cycles

The flooded lead acid battery is cheap, highly recyclable, and available in a wide variety. These batteries are virtually unbeatable in cost per mile. A deep cycle type must be used. The typical choice is a golf cart battery.

Next, Adsorbed Glass Mat (AGM) sealed deep cycle lead acid batteries can deliver high currents without as much voltage sag as floodeds. They are lower maintenance and do not require watering. Sealed lead acid batteries require careful attention when charging, and may require the use of a battery balancing system or regulators. They also cost more up front.

Gel-Cell sealed lead acid batteries do not have the high current capacity of AGM's, but are maintenance free. They are advertised as not needing chrge regulators or a management system. They are typically used in high voltage EV's such as AC conversions where the high voltage keeps the current under their limits.

Flooded Nickel-cadmium batteries require water, but can be discharged deeply without damage, and can be cycled about 2000-3000 times while retaining 80% of their original capacity. Compare to 1000-1500 for flooded lead, and 300-1000 for sealed lead. They also have the advantage of not losing capacity in cold weather, as all lead acid batteries do. They are not affected nearly as much by the Peukert effect, that is, having a lower effective capacity when being used at higher currents. Nicads do require a special charging regimen, they have strict maximum temperature and current limits, and have a high up front cost. They are second behind flooded lead acid in cost per mile, thanks to their exceptional cycle life.

Several types of lithium-ion and lithium polymer batteries have been made available by companies like

metricmind.com
kokam
valence technologies

and others. These offer great weight advantages, but require the use of a battery management system. Also, availability is dependent on the manufacturers. Up-front cost is high, maximum current draw is limited on some types, and the number currently in use is limited. Few EV conversions currently use lithium, so there would be limited user experience to draw from. One company that has had success using lithium batteries for EV racing is proEV (www.proev.com).

What is the proper way to maintain batteries?

The following EVDL post discusses how to get the most out of your batteries.

Let's anthromorphize a bit, and consider lead-acid batteries as alive; like the family dog.

1. They need exercise; it's good for them. You get the longest life when they are worked to about 50% of their capacity at moderate loads. After they have been loafing for weeks, you will notice a distinct improvement just from giving them moderate exercise.

2. But don't work 'em till they drop! If you drive an EV until it barely moves, the batteries are having a near-death experience! This is outright battricide, and a leading cause of early death.

3. They need to be be fed regularly (charged). Feed as soon as possible after a workout; they don't like to sit around starving after use. Batteries left sitting for days in an undercharged state develop a condition called sulfation.

4. Don't overfeed, or they get fat and have cumulative health problems and so die early. Chronic overcharging is a major cause of early death.

5. Don't underfeed, or they can starve to death. Chronic underfeeding also leads to a weak sickly battery and an early death.

6. Batteries can sit unused for months (hibernate) without needing to be fed. You don't need to put them on a trickle charger; just be sure to feed them occasionally so they stay near full charge.

7. They need fresh, clean water occasionally. Sealed batteries have a built-in watering system, but flooded batteries do not. Be sure to check water levels, and fill with distilled water as needed (dirty water poisons them!)

8. They need to be kept at reasonable temperatures, that you would find comfortable. Not too hot, and not too cold. Lead-acid batteries are "cold-blooded", so the lower the temperature, the slower they get. Likewise, they can't "sweat", so high temperatures cook 'em to death.

9. Batteries can't talk. They won't whine when they're hungry, or cry when you hurt them. You have to check their state of health with instruments, like voltmeters ammeters and hydrometers.

10. There are different "breeds" of batteries, each with its own good and bad points. Slow plodding workhorse floodeds, but long lived. Racehorse AGMs that are fast and powerful, but short lived. Using the wrong breed of battery for the application, or unrealistic expectations leads to disappointing results.

11. And some is just the "luck of the draw". For no obvious reason, identical batteries in the same vehicle will have some die young, and some seem to live forever.

The usual reason you see used EVs that say "needs batteries" is because the previous owner treated the batteries cruelly. Whether by ignorance or laziness, some or all of the above guidelines were violated. But batteries are replaceable, and it usually means you can get the EV "cheap". But such problems can be cured. A little detective work to fix the problems, and then some tender loving care will go a long way toward getting the longest life possible on the next set of batteries.

Flooded batteries tend to form an acidic mist on top of the batteries. This won't hurt the case, but can cause ground faults when charging. Clean batteries with a mild soap and water solution. With flooded batteries, keep the caps on so as not to get any of the solution in the battery. Like the family dog, batteries should be kept clean and dry (although sometimes it is hard to keep them that way).

When filling a flooded battery, first fill only enough to cover any exposed plates (by the way, if any plates are exposed, the battery may be damaged). Then fully charge. Then fill to the manufacturer's recommended height or just beneath the bottom of the filler neck. As batteries charge, the electrolyte heats and expands, so if you filled them before charging, electrolyte could spill out.

How do I design and build a battery box?

A battery box usually consists of the structure (usually a cage-like construction of structural metal), a liner, and insulation. The only part that is absolutely required is the structure. The others are a good idea if you want to keep the batteries clean and warm. The structure can be a cage-like construction of angles and supports, or bent-up sheet metal, which can also serves as a liner.

The structure used to restrain the batteries must be capable of restraining them and keeping them from entering the passenger compartment in an accident. It is either welded or bolted to the structure of the car. Both the structure and the attachment of the structure to the car must withstand crash loads, and restrain the batteries during an accident. NEDRA (National Electric Drag Racing Association) recommends designing the cage to withstand a load of of 8G's (8 times the total weight of the box and all its contents) forwards, backwards, and to each side, as well as 4 G's upwards and downwards. It is acceptable if the structure deforms during a crash, so long as it restrains the batteries.

The liner of a battery box must be resistant to battery electrolyte (sulfuric acid for lead-acid batteries).

Insulation should be resistant to battery acid. Usually plastic foam available in home stores is used. It is always a good idea to test small samples for acid resistance when the material is unknown.

Sometimes a battery heating system is installed for use in cold climates. Various schemes have been used for this, but it usually consists of some sort of tape or pad heating unit, with a remote temperature probe and a thermostat.

Other considerations include keeping acid fumes from building up. If a battery box is sealed, it is vented while charging. this is usually accomplished using a brushless fan - one that does not produce sparks - which is activated while the the charger is plugged in (not just while it is on, as batteries can gas for a while after the charge cycle is through and the charger shuts off). The fan must be brushless because the exhaust vapors contain flammable hydrogen.

What is a battery management system?

A battery management system is a computerized system to monitor battery health, keep them balanced (at the same state of charge), and control charging and discharging to some extent.

This is done because all batteries have very slight differences. Over time, they tend to drift apart in their state of charge. Eventually, after a normal charge, some are completely "full," where any further charging would be bad for them, and others are relatively "empty." The higher current needed to fill up the emptier ones would harm the fuller ones. Since the capacity of a series string is limited to the capacity of the "emptiest" battery (or else it reverses, seriously damaging it), the range of the whole vehicle is limited. To prevent this, some need more charging, and some need less.

Functions of such systems can include gathering such information as temperatures and voltages. (When this is all a system does, it is usually referred to as a battery monitoring system.) A true management system then applies this information to balance and properly charge the batteries.

Some batteries are more tolerant than others of inbalance. Flooded lead acid batteries in particular may be rebalanced by applying a controlled overcharge. This is called equalization. Other battery types, however, are less tolerant of equalizing charges, and require active management systems.

What about battery heaters?

Battery heaters are used to keep the battery temperature at or above room temperature when the ambient temperature drops. These are usually used with lead-acid batteries, since they can lose up to half of their capacity at 32 degrees F.

Heaters can either be powered off of an AC line or by the batteries themselves, and are most effective when used in conjunction with insulated battery boxes. Other battery chemistries (like NiCad) are not affected as much by cold weather.

Are flooded or sealed lead-acid batteries better?

Floodeds come in a wider variety of sizes and are low cost. They have a long life, if they are well cared for. They can tolerate a lot of abuse. They are generally lower in voltage and larger in size than the available sealed batteries.

Sealeds come in fewer sizes and cost more. They usually do not live as long as floodeds, given the same level of care. To care for them properly, regulators or some sort of battery management system is required. They can also tolerate a lot of abuse (just not the same kind).

Floodeds can be slightly undercharged, overcharged, etc., and rebound quite well if the problem is corrected. Sealed batteries have very little tolerance for this sort of abuse. Their lives are shortened quite a bit by even just a couple of these types of episodes.

Sealed batteries, though, can belt out several hundred amps at a time without having very much voltage sag or becoming damaged. Floodeds subjected to the same treatment would sag to a useless voltage level, and potentially boil their electrolyte and even explode.

Usually, a newbie EVer is wise to choose floodeds as their first pack, so their education in lead-acid battery care is less expensive and lasts longer. This "training pack" can then be upgraded later, or if the same type are used, the next pack will last much longer.

What about advanced battery chemistries like lithium?

Several types of lithiumbased batteries have been made available by companies like

metricmind.com
kokam
valence technologies

and others. These offer weight advantages, but require the use of a battery management system. Also, availability is dependent on the manufacturers. Up-front cost is high, maximum current draw is limited on some types, and the number currently in use is limited. Few EV conversions currently use lithium, so there would be limited user experience to draw from. One company that has had success using lithium batteries for EV racing is proEV (www.proev.com).

What are the correct charging procedures for a battery?

The following general battery care and charging tips are an excellent overview on battery care. For specific charging recommendations, however, refer to your battery manufacturer's literature.

Let's anthromorphize a bit, and consider lead-acid batteries as alive; like the family dog.

1. They need exercise; it's good for them. You get the longest life when they are worked to about 50% of their capacity at moderate loads. After they have been loafing for weeks, you will notice a distinct improvement just from giving them moderate exercise.

2. But don't work 'em till they drop! If you drive an EV until it barely moves, the batteries are having a near-death experience! This is outright battricide, and a leading cause of early death.

3. They need to be be fed regularly (charged). Feed as soon as possible after a workout; they don't like to sit around starving after use. Batteries left sitting for days in an undercharged state develop a condition called sulfation.

4. Don't overfeed, or they get fat and have cumulative health problems and so die early. Chronic overcharging is a major cause of early death.

5. Don't underfeed, or they can starve to death. Chronic underfeeding also leads to a weak sickly battery and an early death.

6. Batteries can sit unused for months (hibernate) without needing to be fed. You don't need to put them on a trickle charger; just be sure to feed them occasionally so they stay near full charge.

7. They need fresh, clean water occasionally. Sealed batteries have a built-in watering system, but flooded batteries do not. Be sure to check water levels, and fill with distilled water as needed (dirty water poisons them!)

8. They need to be kept at reasonable temperatures, that you would find comfortable. Not too hot, and not too cold. Lead-acid batteries are "cold-blooded", so the lower the temperature, the slower they get. Likewise, they can't "sweat", so high temperatures cook 'em to death.

9. Batteries can't talk. They won't whine when they're hungry, or cry when you hurt them. You have to check their state of health with instruments, like voltmeters ammeters and hydrometers.

10. There are different "breeds" of batteries, each with its own good and bad points. Slow plodding workhorse floodeds, but long lived. Racehorse AGMs that are fast and powerful, but short lived. Using the wrong breed of battery for the application, or unrealistic expectations leads to disappointing results.

11. And some is just the "luck of the draw". For no obvious reason, identical batteries in the same vehicle will have some die young, and some seem to live forever.

The usual reason you see used EVs that say "needs batteries" is because the previous owner treated the batteries cruelly. Whether by ignorance or laziness, some or all of the above guidelines were violated. But batteries are replaceable, and it usually means you can get the EV "cheap". But such problems can be cured. A little detective work to fix the problems, and then some tender loving care will go a long way toward getting the longest life possible on the next set of batteries.


Generally, lead acid batteries are charged by applying a voltage higher than the resting voltage of the battery. The general procedure is to bulk charge (charge at the maximum current the charger can deliver) until the battery reaches acceptance voltage (usually around 2.4 volts per cell, or 14.4 volts per 12V battery, though this can vary depending on the battery type, size, etc.). Then, the battery voltage is held constant while the current is allowed to taper. Charge is discontinued when the current is reduced to a set amount. A more accurate way to determine the cutoff point is to cut off the charge when the voltage change is less than 0.1V per hour, but few chargers implement this algorithm.

Again, for exact voltages and currents for your specific battery, refer to your battery manufacturer's charging data.

How do I determine the battery state of charge (SOC)?

The most accurate way is to dynamically measure current in and out of the batteries, correcting for any effects such as Peukert's effect (see dedicated topin in this FAQ). Amp-Hour meters that can be programmed with the battery capacity and peukert number, such as the Xantrex Link-10 (see the 'meters' section at evparts.com), are the best for this. However, if a battery has been resting (not being used or charged) for at least 24 hours, the state of charge can be indicated by the voltage at rest, and many "state of charge meters" simply use the voltage as an indicator. For the exact relationship between voltage and SOC for your battery, consult the battery manufacturer's literature. Lastly, the SOC of flooded lead acid batteries is directly indicated by the specific gravity of the electrolyte, which can be read using a hydrometer. the specific relationships between the SOC and specific gravity can be different between brands of flooded lead acid battery, so the manufacturer;s literature should again be consulted.

What is the proper way to mount and secure batteries?

The structure used to restrain the batteries must be capable of restraining them and keeping them from entering the passenger compartment in a crash condition. The structure usually consists of structural steel or sheet metal cages or boxes, with some sort of acid proof liner and insulation. Recommended loadings vary, but NEDRA (National Electric Drag Racing Association) recommends designing the cage to withstand a load of of 8G's (8 times the total weight of the cage and all its contents) forwards, backwards, and to each side, as well as 4 G's upwards and downwards. It is acceptable if the structure deforms during a crash, so long as it restrains the batteries.

The batteries should be secured to the cage or box by various means. Some examples are restraining bars that run over the battery tops, straps of metal or nylon, and lids for the battery boxes with spacers to press down on the batteries when fastened.

Can I mix old and new batteries?

It's not recommended. The problem is that the new ones have a different capacity than the old ones. They also charge to a different voltage, and draw different currents when charging. Thus, if you charge a mixed pack with a simple series charger, the old ones will be a bit overcharged, and the new ones will be a bit undercharged. This brings down the life of the whole pack.

The difference usually shows up as an imbalance in the pack, which requires active management of some sort to keep in check. Sealed batteries are much less tolerant of this kind of treatment than flooded batteries.

The older batteries will likely have less capacity than the newer ones, which translates into less range because the range is limited to the capacity of the weakest battery, in order to avoid reversing that battery.

The only time you would want to mix batteries is if some of your pack was damaged or defective, and had to be replaced. In this circumstance, used batteries of a similar age and usage history can be better, if you can find them.

To sum up, avoid it if you can, but if you can't, some sort of bi-directional battery balancing system or careful individual monitoring is necessary to get the most life possible out of you pack.

Can I use two different types or sizes of batteries?

If used in a single series string, the total capacity is limited to the capacity of the smallest, weakest battery in order to keep from reversing it. This means that larger batteries are basically just taking up extra space and weight. Also, different types of batteries have different maximum currents available, so the maximum current you can draw without damaging the battery with the lower current limit is also limited.

If using two different kinds of batteries in parallel strings, then they can be used if they are charged separately, and the smaller batteries are protected from over discharging.

An exception to the rules is if you are designing a "hybrid battery pack". This is a battery pack consisting of strings of two or more types of batteries, each having certain advantages and disadvantages. the mixture is intended to maximize the advantages while minimizing the disadvantages. The separate strings are connected either using electronic voltage converters or by carefully matching the voltage levels during driving. The strings are charged separately.

What is Peukert's Effect, and why should I care?

Lead-Acid batteries have a peculiar property; the amount of amp hours you can get out of one changes depending on how much current you are drawing.

This is called the Peukert effect (named after the gentleman that discovered it). For example a 6V golf cart(GC) battery might have an amp hour rating of 225 AH, but this is at the 20 hour rate (11.25 amps for 20 hours) kinda useless for EVs since they typically draw far more than 11 amps. The rule of thumb is that GC batteries produce about 60% of their 20h rating for 1 hour, or about 125 amps for 1 hr (until it's dead, 80% is about 100 amps).

So a given 6V GC battery can produce 67.5 watts (6V x 11.25A) for 20 hours (or 1.35 KWH) or it can produce 0.75KWH for 1 hour. A 96V string would therefore produce 21.6KWH over 20 hours or 12.96KWH for 1 hour (again these numbers are until the battery is dead). So it all depends on the battery and how fast you drain it.

Peukert has two parts. The Peukert Exponent (usually called Peukert's Number or PN) and the Peukert's Capacity (PC). PC equals how many hours a battery can produce 1 amp, many people just use the 20 hr rating but that's usually going to be wrong(way wrong for GC batteries).

The formula is A^PN*T=PC, where A=Amps and T=time in hours. (The ^ means "raised to the power of.")

I've been using a T-105 battery in my examples, a 6V GC battery made by trojan with a 20hr capacity of 225AH, a PN of 1.24 and a PC of 400Ah. So with this information, first determine how many amps you are going to draw, raise this to the power of 1.24 and then devide 400 by the answer and you will get how many hours it can produce that much current.

Let's say we are going to draw 150 amps. 150^1.24 = 499 400 / 499 = 0.8 hour or about 48 minutes. About 38 minutes if we want to keep our discharge below 80%. If it takes you 150 amps to go 60 mph then you have a range of about 38 miles (at 80%).

Drag racers and high performance EV's typically use AGM batteries with very low Peukert numbers, so the capacity doesn't drop much while they pull large currents. Flooded batteries have higher peukert numbers, but are available in larger sizes and are much less expensive. So it is a trade-off, with the choice made dependent on what the vehicle's "mission" is.

What is a controller?

A controller is a device that controls the the flow of electricity from the batteries to the motor. This is important in an EV in order to have smooth control of vehicle speed.

A controller is much like a household light dimmer switch, only a lot bigger. By adjusting the knob of the dimmer switch, or moving the potentiometer attached the accelerator in an electric car, it signals a larger electronic switch to vary the size of electrical pulses to the load. The load in a house would be the light bulb, in a car it would be the motor.

There is usually a device called a Pot Box which converts the movement of the accelerator pedal or throttle input to a low level electrical signal which the controller can use. The most common Pot box contains a potentiometer with a resistance of 0-5K Ohms with 0 indicating an off position. There are variations to this, such as the inductive throttle sensor, and pot boxes with different resistance ranges, but the 5K pot is the most common for the hobbyist EV market.

Controllers typically come in two basic classes: AC and DC.

AC motors require an AC controller or "Inverter" to run off a DC battery pack. The AC drive systems have advantages including: Higher efficiency, a wider power band and built in regenerative braking (regen).

The DC systems use a PWM or a "Chopper" controller to regulate the DC power from the battery to the motor. They have the advantage of lower cost. This cost benefit comes from a much simpler controller. Because of this, DC systems are by far the most prevalent in the hobbyist conversion market.

Controllers come in many sizes. The common DC size specifications are battery voltage range and maximum motor current.

As an example, a typical electric bicycle controller may be rated for 24 to 36 Volts and 50 Amps. This would indicate that it should run on a battery pack with either a 24 or 36 Volt nominal rating. In actual use a 24 V battery can drop as low as 14 Volts under load and a 36 V battery will rise over 42 volts when being charged, so the controller needs to be able to operate over a wider range than the nominal voltage rating. The motor current rating is usually a peak rating. The controller can supply this much current to the motor for a short period of time ranging from 20 seconds to 5 minutes. If the controller is asked to provide more power than is is rated for, it can overheat. Most modern controllers have built in current limits and temperature cutbacks to protect the electronics in a controller from failing in such a situation.

The peak power rating of a controller, as specified in Watts, is the battery voltage multiplied by the peak current. A 36 Volt 50 Amp bicycle controller would be rated at 1800 Watts. Since 746 Watts = 1 HP, this would be about 2.4 HP. But that's electrical power. Since most electric bicycle motors are no more than 60% efficient the actual shaft HP would be under 1.5 HP. It is important to remember that these rating are also only peaks, and the motor will draw the peak current and voltage at only one particular motor speed.

Some typical controller sizes:
Electric bicycle: 24 to 36 Volts and 50 Amps.
Golf car or go cart: 36 to 48 Volts and 300 Amps.
Slow electric car conversion: 72 to 108 Volts and 400 Amps.
Average electric car conversion: 120 to 144 Volts and 500 Amps.
Fast electric car conversion: 156 to 192 Volts and 600 to 1000 Amps.
Fast electric race car: 200+ Volts and 1000+ amps.
Typical production electric car: 312 Volts and 400 Amps.

The controller is one of the most expensive parts of an EV. Choosing the correct one for your application is a very important task. Many makes and models have a history of blowing up when undersized or due to poor design or manufacturing. When they do blow up, it is often not cost effective to rebuild them.

Properly fusing the system with semiconductor fuses (ultrafast response time) is important to reduce the risk of fire in case of a controller failure. This can also improve the odds that a failed controller might be rebuilt.

Submitted by Otmar, designer of the 'Zilla' controller - www.cafeelectric.com

What controllers are available?

Check the controllers section of the evparts.com website for more detail on the most popular controllers. Most common for street electric car conversions are the Curtis and Cafe Electric "Zilla" controllers. These controllers span the range of system voltage and current from 72V - 336V and from 400A - 1200A. This is enough of a spread to cover virtually every sort of DC powered EV.

AC controllers are currently not widely available, but there is one notable exception. Metric mind (www.metricmind.com) sells surplus inverters and motors manufactured by Siemens. These are very high quality components, with a reasonable price tag (though they are more expensive then a comparable DC system).

How does a DC motor controller work?

The DC motor controllers used in EV's almost always use some form of pulse width modulation (PWM) to vary the power delivered to the motor. This includes SCR, MOSFET, and IGBT based controllers. The controller has a timer which cycles every few milliseconds. The controller functions like a switch that turns on with every cycle of the timer. Based on the throttle setting at the time, the switch is turned off somewhere in the cycle. How much of the time cycle the switch remains on determines how much power is delivered to the motor. The motor sees an "average" voltage, and operates based on that voltage level.

Another type of controller is a contactor controller, which uses a number of contactors to switch the batteries among various combinations of series and parallel to acheive different discrete voltage settings.

It is also possible to use a (very) large potentiometer set up as a variable resistor as a controller. The resistor funcions as a voltage divider. This setup uses all the energy that comes from the batteries, but it wastes everything that passes into the resistor, so is very inefficient except at full throttle.

3/20/01
David Brandt

How does an AC motor controller work?

For the most common types of AC motors, changing the AC frequency changes the motor speed. An AC motor controller uses the same technology as used in industrial variable speed drives for AC motors (typically called VFD's for variable frequency drive). Most factories have several machines that use these types of drives. Usually, there is a box on the wall with a small display and a couple of buttons. This is the variable frequency drive. These have been around for a long time, and the technology is well developed. Most modern drives of this type use computer-controlled pulse width modulation techniques to generate an AC waveform at the appropriate frequency. All that is needed is to add an inverter to convert the DC from the batteries into the AC waveform that comes into the drives. Some VFD's can take DC directly as an input. The inverter and adjustable frequency drive stages can be combined to some degree, as they both use PWM technology to do their respective jobs.

AC drives for EV's can be very sophisticated, incorporating software into their controllers that helps to increase low-end torque and to enable the motor to function as a generator to help stop the EV (regenerative braking). One company, AC Propulsion, has incorporated software into their AC controller that allows the controller to double as a charger.

3/20/01
David Brandt

Why does my controller whine?

Whining is a characteristic of Curtis controllers, specifically the 1221C and 1231C models. What happens is that at low speeds (and high motor current), the commonly used large motors (ADC 9") did not have the inductance or resistance to let the current fall back into line during the "off" time of the 15 kHz pulse width (see "how does a DC controller work" elsewhere in this FAQ for more definition). To fix this problem, Curtis introduced the "C" models to replace the previous "B" models. The "B" models operated at a constant 15 kHz. The "C" models change to a lower pulse frequency (1.5 kHz) at lower throttle settings. Curtis calls this "frequency shifting." This gives the current time to fall off, so that the next pulse doesn't just increase the current more.

The whine comes from the fact that the 1.5 kHz frequency is right in the middle of the audible range (15 kHz is at the high end). The motor windings "sing" in tune with the PWM'ing of the controller.

Something similar happens when a large AC industrial motor is ramped up to speed using a typical AC drive. As the drive steps up the speed, the motor can be heard to actually play a scale (albeit a little off key) as the frequency changes in small steps.

So controller whining is a part of normal operation for Curtis "C" model controllers. Other brands, like the Auburn and the DCP, operate at a continuous 15-18 kHz, and are designed to properly handle the modern low-inductance, low-resistance EV motors.

David Brandt
7/17/02

Can I add regen to my DC EV?

Most DC EV's use series wound motors, which are difficult to add regen to, although the difficult to obtain Zapi controller is available with regen. A few EV's use shunt or compound wound motors, and the controllers for these usually include regen. The drawback is that they are usually one-off or custom items, and are fairly rare. Design of a controller to add electronic regenerative braking to your DC EV (whether series or shunt wound) is beyond the scope of this FAQ. If you want to learn how to do so, then please pose the question to the EVDL (see questions regarding the EVDL in this FAQ for instructions on how to join). Typically, regen is most easily added to an EV with a series wound motor by adding a separate system. This is usually a purpose built motor or generator actuated via the brake light switch. Again, questions on how to do so are best addressed to the EVDL. David Brandt 7/17/02

Do I really need a controller?

That depends on what you call a controller. A bunch of contactors arranged to step the voltage applied to the motor up and down by switching the batteries around in various combinations of series and parallel is sometimes labeled a contactor controller. The next step up is electronic controllers. First there were SCR controllers, and now they use FET's and IGBT's.

So to truly get by without a controller, you would by definition not have any means of changing the voltage applied to the motor, except a large ON-OFF switch. This approach has been used by some drag racers, who just use a (very, very) large contactor as an on-off switch.

Obviously, this results in (very, very) high currents until the motor gets up to speed. Basically you have no means to control your speed or acceleration. While this can be good on the drag strip, it is obviously downright dangerous in, say, a parking lot.

So simply put, yes, you need a controller for a street EV. But that doesn't mean it has to be complicated. As noted above, a contactor controller is fairly simple and has been used effectively.

David Brandt
7/17/02

What about voltage switching and resistor controllers?

Yes, you can use this. It is known as a 'step starter.' This technology has been used for decades. Since the DC armature has a very low resistance starting by applying full battery pack voltage would draw very large currents. This would harm both the motor and the starter contacts.

What is usually done is to insert starting resistance into the circuit. In traditional industrial setups, this was generally done in three steps and limited the starting voltage and current to about 33%, then 66% then full line voltage. This is just an example so do not use these values verbatim.

The resistors were hard wired in series with the motor and each step was shorted out at an appropriate time to let the motor speed build and let the current drop. The simplest setup was to use a hand driven starting switch with multiple contacts. These are still common on older DC cranes, forklifts and elevators. More complicated methods used timing relays and or motor drive to ensure correct timing.

For a simple real world example, assume a 36 volt motor. Wire 3 batteries in series to get 36 volts. Wire one side of the motor to the negative post. Insert an ammeter between the battery and motor in the lead. Insert a contactor at the positive of the first (12 V) battery. A second relay on the 24 volt positive post and a third on the 36 V positive post. These are connected in parallel on the other motor lead.

Motor start: shut only the 12 V contact for about 3 seconds.
Step one: open the 12V contact shut the 24 V contact and run for 3 seconds.
Step two: open the 24 V contact and shut the 36 volt contact.

You will see the motor accelerate in 3 steps and you will see the current rise in three steps.

The reason this system is not used much any more is that it can be jerky. Also the labor cost of setup and maintenance is fairly high. It is also subject to abuse by operators - Crane operators starting the hoist motor in the 3rd of 5 steps for example to get more power to hoist heavy loads. This is dangerous because of stressing the wire rope, and very hard on the contacts and motor.
What chargers are available?

Chargers range from homemade "bad-boy" chargers to computer controlled, high power onboard units.

EVparts.com offers many chargers and charging components, including regulators. Visit http://www.evparts.com/ for more information. Scroll down to the battery charger section, and click on the link for the appropriate voltage range.

The homemade kind usually consists of a rectifier connected either to the output of a variac or directly to the AC input line. This kind of charger requires constant monitoring and manual control. It is called a bad-boy (or a vari-bad-boy, to quote John Wayland) because it is completely unregulated. If you watch every battery and the AC line like a hawk, and tweak the output appropriately, this can be a fine charger. However, this isn't always possible.

Made-for-EV Chargers range from small, simple onboard units to large, offboard high-power units. The top of the line chargers are both small and high powered. The most popular are discussed here in order of increasing utility. The prices tend to follow the same trend.

At the bottom of the line, there is the K & W BC-20. It is a small, lightweight, SCR based charger that runs off of 120VAC. It has a built in ammeter and GFI and has adjustable current to avoid tripping breakers. It applies maximum current until a preset voltage is reached, at which the current tapers off. The maximum set voltage is then held, with no automatic shutoff. It charges packs from 96 to 144 Volts, although to charge over a 108V pack, it requires an available booster transformer, which adds approximately 15 lb.

Next up is the Russco. It is also a 120VAC input transformerless unit, with a current display, but is power factor corrected, includes a GFI, is available with a timed shutoff, and has a slightly more sophistocated charging algorithm. It also has the ability to charge up to a 120V pack without a booster. Booster transformers are available to allow the Russco to charge higher voltage packs. The Russco will charge packs from 84 to 156V. Different power levels are available.

Two types of large, transformer isolated chargers come next. These are less common, but are available. First is the Lester. It can be ordered as either a 120VAC or 240VAC input, and has high power handling capabilities. Unfortunately, it is not power factor corrected, and is heavy, due to the built in isolation transformer.

The Bycan is similar, but has both 120VAC and 240VAC inputs. It automatically selects between them. It can charge pack voltages of 120, 132, or 144V. It has a switch to automatically run an equalization charge.

The Italian manufactured Zivan is fairly common. It has computer control, and comes with the user's choice of charging algorithms preset into its memory (though the user cannot change these algorithms). Models are available with either 120VAC or 240Vac input (high power model only has 240VAC input), and it has an available temperature probe for temperature compensation. It also has several outputs for relay triggers. It is available in up to a 4.3kW power handling capability. The user can not adjust any of the settings, and no instrumentation is included on the unit. In addition, the Zivan is not power factor corrected.

The PFC-20 (and its higher power cousins, the PFC-30 and PFC-50) is considered the top of the line and state of the art. They are small and light enough to be carried onboard. It combines all of the best features of the units discussed above. They both have very high power handling capability, can charge any pack voltage from 12 to 336 volts, adapt automatically between 120 and 240 VAC, and employ active power factor correction for high efficiency. They have a shutoff timer and the user can select how it is used. They interface with Rudman Regulators. It comes preset with a good general purpose charging algorithm, but has a computer control option available that lets the user alter the charging profile. It does not include a GFI and is not isolated. The use of a GFI on the power outlet is recommended.

What wiring is required to charge in my garage?

EVs can be recharged from any normal AC outlet; special outlets are not required. However, the higher power the outlet, the faster you can recharge. For example, recharging from a US standard 120v 15amp outlet can take 8-16 hours; recharging from a 240v 30amp outlet can recharge in 1/4 the time.

As with any outdoor outlets, the outlet used for recharging your EV should have a ground pin and GFCI (Ground Fault Circuit Interrupter) for safety.

If your charger is NOT in the vehicle, then NEC (National Electric Code) section 625 outlines the requirements for high-powered EV chargers. Since many local building codes reference the NEC, you may have to meet its rather conservative requirements for new construction.

What is power factor correction in a charger and how is it done?

Most low-end high frequency battery chargers today use a simple rectifier circuit consisting of a diode bridge followed by a capacitor bank. Rectified voltage is then brought to the high frequency DC/DC power stage where it is converted into regulated output current or voltage. The rectifier's capacitors significantly affect the current waveform. As the input voltage reaches the stored level in the capacitor, the rectifier diode conducts, allowing the current to flow as long as the line voltage is greater than capacitor's voltage. While the load current is continuously drawn from the capacitor by the DC/DC stage, the capacitor is recharged only during the interval when the input rectifiers conduct. No current flows into the capacitor from any point along the voltage waveform where it is below the capacitor's DC voltage.

High power factor results when the current and voltage have low distortion and are in perfect phase. Low power factor results when either the load current is drawn over only a part of each line cycle (current harmonic distortion) or when the line current is out of phase with the line voltage. The first problem is the result of off-line rectifiers where the input diode does not conduct until the peak of the rectified line voltage waveform exceeds the DC level across the input capacitors.

Power factor represents the ratio of real to apparent power. Low power factor is caused by the apparent power being higher than the real power. Apparent power is the current read on an ammeter times the line voltage. A low power factor is characterized by a higher current than the load actually needs to satisfy its real power requirement. The difference between the current that produces the real power consumed by the load and the current measured on an ammeter is known as the circulating current. It is so called because even though it does no real work, it continuously flows back and forth between the line and the load. This circulating current is at a different frequency and/or phase than the line voltage and does nothing to supply power to the load. The circulating current does heat up the transmission lines supplying the power and it will open fuses and breakers at less than the rated power because the current is real but delivers no real power to the load.

For example, a high frequency charger with 85 percent efficiency and a power factor of 0.60 can produce only 734 watts of real power to a load with 12 amperes from a 120V AC utility mains (12 amperes is the maximum continuous rating of a standard 15 ampere branch circuit). On the other hand, the maximum power that can be used by a load with unity (1.000) power factor is 1440W. Thus, only about half of the power in our example is being used by the load.

Resistive loads have a power factor of one, since current flows through the load proportional to the voltage across it.

Power Factor Correction (PFC) circuits are used in order to improve the poor power factor of standard rectifiers. Various PFC circuits are employed to actively force the input rectifier to conduct over the entire cycle of the input waveform. Most commonly used PFC circuits are in the form of a high frequency boost converter that precedes the input filter capacitor. With a slight reduction in efficiency and by almost doubling the complexity, the PFC boost converter increases the power factor to something between 0.95 and 0.9999. This circuit also operates at an efficiency of 92-95 percent. Equipping our previously discussed 85% efficient charger with a 92% efficient PFC circuit will yield a charger with an overall efficiency of 78% and a power factor of 0.97. At the example conditions of 120V and 12A current, this charger will be able to provide 1,089W to the battery, a 48% increase in the available power!

Another advantage of PFC is that at RMS current of 12A, peak line current will be only 17A. Without PFC, peak current can easily reach 35-40A, causing line voltage distortion and may negatively affecting other equipment connected to the same circuit.

Contributed by Boris Sasic and Joe Smalley
2/28/03

What are battery regulators and balancers for?

Batteries are the "fuel tank" of an electric car. Most vehicles have one big fuel tank, so it is easy to remove and add fuel, and tell how much fuel is in the tank. But most EVs use many batteries. In theory, they are all identical, and always charged and discharged equally. In practice, there are always small variations, and these differences get larger as the batteries age or have temperature variations, or differences in the load that each battery sees.

This means that different batteries are at slightly different states of charge. They reach 'full' earlier or later when charging, which could lead to overcharging (since the charger has not yet reached a voltage which would indicate the pack as a whole is charged). They also reach empty at different times during discharge, which could lead to over-discharging some batteries (because the overall pack staus shows that some capacity is still left), causing them damage.

For flooded lead acid batteries, the solution to keep the batteries at the same state of charge is a small overcharge deliberately applied at regular intervals, called an equalization charge. This uses some extra water, but the benefits outweigh the inconveniences. The sealed lead acid AGM batteries used in EV's are not as tolerant of this type of treatment. They are damaged by excessively deep dishcarges, and excessive charging. Battery regulators and balancers are devices to monitor batteries individually, and add or remove charge from them to keep all batteries "filled up" to the same level.

The simplest type is a dissipative regulator (for example, the Rudman Regulator). One goes across each battery. If the voltage during charging indicates that the battery is full, the regulator bypasses any further charging current through a resistor, to prevent that battery from overcharging. The excess charging power is burned up as heat.

A Balancer is more sophisticated (example: Powercheq, Zizan Smoother). These systems also monitor individual battery voltages, but use a small DC/DC converter and switching network to transfer charge from one battery to another. Balancers can thus work to balance batteries even while parked or driving; not just while charging.

Regulators and Balancers thus extend battery life. They are helpful (though not necessary) for flooded lead-acid and nicad batteries, highly desirable for sealed batteries, and mandatory for high-tech batteries like nimh and lithium.

For more information, there is an excellent discussion at http://www.evconvert.com/article/charging-an-electric-car


How do I charge my batteries using a variac?

Safety Precautions:

1. This is a manual procedure. You've got to pay attention, or you'll wind up ruining your batteries.

2. Only use a variac charger with flooded lead-acid batteries! SLA and AGM batteries are much more susceptible to damage. Charging AGM batteries with a variac charger will most likely destroy them.

3. Use fuses all around the charger. Connecting the charger backwards (or otherwise incorrectly) is like short-circuiting the battery pack, and can lead to a lot of overheated, damaged components.

4. Turn the variac down to 0 before beginning. If something is incorrectly connected, you don't want to hit it with full voltage right off the bat.

5. Build a timer for your charger. Overcharging the batteries can permanently damage them.

6. Some variacs have been observed to destroy sine-wave inverters. If you have an inverter, you are advised to remove it from the circuit before charging with your variac.

Required Instrumentation

An ammeter and voltmeter are required to charge with a variac charger. An 'E-meter' combines these functions, and can also measure amp-hours.

Process:

This description attempts to be generic. When numbers are used, they are based on a 144 volt, 100 amp-hour pack.

1. Dead batteries require a starting charge of just a few amps. Turn up the variac until your ammeter shows 2% of C. In one hour, the pack should show its nominal voltage (such as 144v). If not, some battery is damaged; use your voltmeter to check each battery individually; one is probably shorted or reversed, and it will need to be replaced.

2. Turn up the variac. You want to provide as much current as possible for a fast, thorough charge, but you don't want to burn anything up. Check the extension cords, plugs, and charger. If anything is too hot to touch comfortably, the variac is too high. Turn it down immediately. Use your ammeter to determine the maximum current you can safely provide during charging. Remember that using a variac from AC power produces transient DC "ripple" currents; at 12A, the ripple current can be as high as 20A. In fact, 12A has been cited as a reasonable charging current.

3. Watch the ammeter. As your batteries charge, their voltage rises. As the voltage rises, the current falls. To provide constant current, you'll have to turn up the variac. Checking every commercial 15 minutes or so is required. Failing to turn up the variac will not damage the batteries; it will just take longer to charge.

4. Look for full batteries. When any battery reaches 2.5v per cell (15v on a 12v battery), it's full. You don't want to overcharge it, since that will shorten its life and release hydrogen into your battery compartment. You'll have to start turning down the variac to ensure that this battery doesn't get higher than 15v. When your pack isn't balanced, it's almost always the same battery that reaches the limit first; when your pack is balanced, they all reach the limit at the same time. (In that case, you can just use the whole pack's voltage instead of checking each individual battery; for 12 batteries at 15v limits, that's 180v.)

5. Fill the whole pack. You'll have to keep turning down the variac as more batteries fill up. As the batteries reach their full charge, less current will be required. When you reach 2% of C, they're full. You're done; turn the charger off.

6. Equalize the batteries. Let the batteries sit overnight. In the morning, measure each battery's voltage. They should all match (to within 0.05v for 12v batteries, 0.03v for 6v batteries). To charge the weak ones, you can either try charging them separately or running a 2% C charge to the whole pack for a few extra hours. Eventually they'll equalize.

A properly connected E-meter can tell when the batteries are full. This requires setting the minimum charging voltage, the maximum charging current, and the measurement time. When the charging voltage is above the minimum charging voltage at the same time the current is below the maximum charging current, and this condition persists for the measurement time (usually 1 or 5 minutes), the charge indicator on the E-meter will flash green. If the E-meter is equipped with a low-voltage alarm, it will go off at this point; you could use that signal to turn off the charger. Unfortunately, these conditions are difficult to meet with a variac, and almost impossible to meet with even a single damaged battery.

How do chargers, regulators, and balancers work, and how are they different? Also, what components are currently available?

There is an excellent discussion at http://www.evconvert.com/article/charging-an-electric-car

EVparts.com offers many chargers and charging components, including regulators. Visit http://www.evparts.com/ for more information. Scroll down to the battery charger section, and click on the link for the appropriate voltage range.

What is a DC to DC converter and why do I need one?

A DC to DC converter is the EV's electronic equivalent to the alternator on an ICE-powered car. While the motive power, heat, and probably AC for the EV are now powered by the high voltage battery pack, this pack is isolated from the rest of the car for safety reasons, and the rest of the car is still wired for 12 volts. Running things just off of the accessory 12V battery is possible, if you remember to charge it after every trip. However, a DC to DC converter adds a great measure of convenience and confidence, especially for long trips. It uses PWM to step the high voltage from the battery pack down to what an alternator would usually put out (13.5 to 14 Volts), to keep the accessory battery charged. There are even some EV'ers that do away with the accessory battery completely. This is possible if the converter is left on all the time, and provides the 12V to engage the main contactor when you turn the key.

3/20/01
David Brandt

What DC to DC converters are available?

Curtis makes some, as well as Sevcon, though these are typically for lower voltages (Curtis makes models that go as high as 96V, and the Sevcon is rated for 72-128V).

For higher voltages, the DCP 72-336V DC/DC is sometimes available used. Though they are out of production and hard to find, they are of high quality.

Most conversions built today are using a power supply that will run off of DC. These range from computer power supplies to purpose designed battery chargers that happen to run off of DC, such as the IOTA chargers (www.iotaengineering.com).

The IOTA DC/DC's are available in models that supply up to 75A, and they are designed for battery charging. Generally, the 120VAC models are used for up to 156V conversions, and the 220VAC model has been used for up to 288V conversions.

Why can't I just tap the battery pack?

You can. However, the voltage will be a little lower than the 12V components are used to, so lights will be a little dimmer and wipers a little slower, etc. Also, this unbalances the battery pack. Unless you separately charge your batteries, or you have a battery balancing system, you range will decrease to that of the battery you have tapped. If you try to charge your batteries with a series charger while the pack is unbalanced like this, the tapped batteries will be undercharged, while the others will be overcharged. This situation shortens the life of the battery pack. Either a separate 12V battery and/or a DC/DC converter will be much better for your battery pack.

What tires should I buy? ( load ratings and rolling resistance)

This FAQ is being created by volunteers from the EV Discussion List. This question has not yet been answered.

Please consider joining the EV Discussion List and asking this question there. If you do, please mention that your question was not answered in the EV FAQ.

If you would like to contribute to this FAQ, please contact the FAQ editor.


What kind of gauges do I need in my EV?

This really depends on what level of information you feel you need. Anything can be monitored if you really want to monitor it.

The instruments on an EV serve 3 basic purposes:

1) Monitor state of charge

The state of charge is generally indicated by the battery voltage at rest. An expanded scale voltmeter is the simplest instrument available to monitor this, although computerized meters called E-meters (now called the 'link-10' are available that actually track the amp-hours and/or kilowatt-hours used and replaced. E-meters combine the functions of voltmeters and ammeters with other functions, and are reasonably priced.

2) Prevent damage to any components

EV's usually keep the factory tachometer or add an aftermarket one to avoid overspeeding the electric motor. Ammeters help to keep the currents within limits set by the component manufacturers.

3) Provide information that will enable the driver to enhance efficiency or performance

Tachometers help determine shift points to keep the motor in the range for best efficiency or performance. Ammeters help determine where efficiency starts to fall off. The E-meter data can be used to calculate watt-hours per mile (similar to MPG for an ICE car). Monitoring this figure can pinpoint when efficiency starts to fall, even before the driver notices a drop in performance. This can help to warn of dragging brakes, a low tire, etc. before they become a problem.

EV's have been built with instrumentation as simple as just an expanded scale voltmeter to roughly indicate the state of charge of the batteries. Other EV's have been built with separate meters for everything including battery voltage, motor current, battery current, individual battery voltages and currents, battery temperature indicators, and an E-meter. Most EV's are somewhere in between, and have a tachometer, a battery ammeter, and either an expanded scale voltmeter or an E-meter to monitor state of charge.

What is a battery monitoring system?

A battery monitoring system is a type of data aquisition system that keeps track of the status of each battery. Any number of parameters may be monitored, and they typically include temperature, voltage, and sometimes current. These systems usually have some means of interfacing with a portable computer for data logging and analysis purposes.

How do I restore the ride height of my car?

With a bunch of batteries in the car, the ride height is typically lower after conversion. Typically, stiffer springs are used to restore ride comfort and height.

Custom springs may be ordered from a variety of custom car suppliers such as coil springs specialties (http://www.coilsprings.com/). Typically, springs can be made in whatever rate you wish.

If you have leaf springs, such as in a truck conversion, then adding a 'helper' spring leaf with the appropriate rating is an alternative, as is adding another leaf to the spring pack.

Yet another alternative is to insert air bags into existing coil springs or air shocks (such as the 'hijacker' by Gabriel) into existing suspensions.

How can I improve the brakes?

The same way you do on any other car. Install larger diameter rotors/drums, vented/slotted rotors, and high performance pads and shoes. These are usually available at racing or performance shops.

How can I keep the power brakes on my conversion?

In an ICE powered car, the power brakes are assisted by vacuum from the air intake. In an EV, this vacuum is provided by a small 12V vacuum pump, and a switch that turns the pump off when a high enough vacuum level is reached.

Can I have power steering in an EV?

Sure. You need either an extra small motor to turn the pump, or a bracket to run the pump from the traction motor.

The first solution involves some custom fabrication, although early Toyota MR2's had a complete electric power steering system that ran off of the 12V system. This has sucessfully been retrofitted into many conversions. This requires a large DC/DC and acessory battery to support the high current surges.

The second solution works, but not the best. The pump is not moving when you need it the most, at low speeds, and is consuming power when you don't need it, at highway speeds.

The best solution would be to use a separate motor that adjusted the power boost based on speed, with more boost being delivered at lower speeds. Again, this would involve custom fabrication, including designing a controller with a speed sensor interface.

Since most people aren't up for that, they usually look for conversion candidates that have manual steering already, or have a manual option available. The technique of looping the fluid input to the output line of the steering rack and removing the pump on a vehicle with power steering has also been used with success.

How can I heat my EV?

Usually, the place the ICE heater core occupied is more than roomy enough to install one or more ceramic electric heater cores, usually rated at 1500 Watts and for a variety of voltages, that are available at any of the EV parts suppliers. The heater is powered by the main battery pack. The temperature of these cores is self-regulating, and they can be stacked for more heat. The cores are switched by a large relay.

Some systems have a small tank and water heater in the vehicle, and use the existing heater core and a small pump (hydronic heating). Both methods have been used successfully.

Can I keep the air conditioning in an EV?

An EV can have air conditioning in two ways. either use a separate motor to drive the compressor, or drive the compressor from the traction motor tailshaft.

The second method, though easier, has the disadvantage that the AC loses it's 'cool' while you are stopped at a stoplight, etc.

The first method is more difficult to mechanically fabricate, but is simplified electrically by using the existing air conditioning clutch signal to activate a relay to turn on the compressor motor. Thus all wiring inside the dash stays the same. Efficiency can be increased over that of the standard ICE variant by incorporating a small controller to provide a variable speed compressor.

Integrated motor/compressor units are available, but the prices are generally very high since they are still not being mass produced.

What is a pusher trailer?

A pusher trailer is a type of range extender trailer. Pusher trailers are made from a clip of a car that has all of the drive components in one end (example: the rear of a VW bug, or the front of a front wheel drive car). It is hitched to an EV and controlled from inside the EV. The pusher trailer then provides the motive power for long trips, usually for cruising power on the highways.

A pusher trailer is generally (though not universally) considered to be more efficient than the other popular option for range extension. This option is to carry a generator used to turn the EV into a series hybrid. The pusher is usually considered more efficient because there is only one energy conversion step in the pusher(chemical to mechanical), but in a generator trailer or series hybrid, there are several conversions (chemical to mechanical to electrical to chemical (battery storage) to electrical to mechanical). Since each energy conversion step has an inefficiency associated with it, the simpler method of the pusher trailer yields the more efficient range extension method. It is also easier for the hobbyist to build.

Examples of pusher trailers are on Mr. Sharkey's website, and JB's EV and pusher trailer.

David Brandt
7/18/02

Can I put a generator on the un-driven wheels to charge batteries while driving?

At some point, most EV drivers hear this question: "Why can't you put a generator on a wheel to charge the batteries
while you drive? Then you could get more range, couldn't you?"

It seems as if it ought to work -- after all, that's (more or less) how you charge the starting battery on a gas car. But if you think about it, you'll see that in an electric vehicle, it would violate the laws of physics.

Where does the kinetic energy of the vehicle come from? In an electric vehicle, it comes from the batteries. That's the only energy source, unless you have a sail.

The EV's motor converts the batteries' electrical energy into mechanical energy. A generator is the opposite of a motor -- it changes mechanical energy into electrical energy.

Now suppose you drove the back wheels with a motor, and put a generator on a front wheel. When you engaged your front generator, some of the vehicle's kinetic energy would be turned back into electrical energy.

With less kinetic energy, the vehicle would slow down, unless you added more energy drawn from the batteries to replace it.

If your generator on the EV's front wheel were 100% efficient, and so was your motor, at best you would only break even -- your front generator would be passing to the rear motor and batteries exactly the kinetic energy that the vehicle already has.

That is, the generator would turn the vehicle's mechanical energy into electrical energy at exactly the same rate the motor was turning the electrical energy into mechanical energy.

In other words, you would gain nothing.

But in fact, neither the generator nor the motor is 100% efficient. Each one is typically only 50% to 85% efficient. The result of this scheme is a net ~loss~ in range, not a gain.

So, unless you want the vehicle to slow down, it's just a waste of energy to put a generator on a wheel.

However, there is some use for a generator in an EV. As the above paragraph suggests, you can use it to help stop the vehicle. This allows you to reclaim some kinetic energy, instead of wasting it as heat in the brakes. This is 'regenerative braking' (sometimes also called recuperation). This really ~does~ increase your range, typically by 5 to 20 percent.

However, there's no need for the weight and expense of putting a generator on a front wheel to perform regenerative braking. Instead, with some extra control hardware, you can use the main traction motor. When you take your foot off the accelerator or touch the brake pedal, the vehicle's control system rewires the motor "on the fly" so it works as a generator.

The question is sometimes reworded using a wind generator on the hood to help charge the batteries as you drive. The same arguments apply, since the wind generates force against the blades, causing drag on the vehicle to increase.

What is Article 625?

Article 625 refers to Article 625 of NFPA 70, otherwise known as the National Electrical Code (NEC).

This article references minimum safe installation practices for Electric Vehicle Charging Systems.

Some say that the NEC contradicts itself with this article, since the NEC also states that it does not apply to automotive vehicles.

The NEC is not followed verbatim by every municipality. State, City, and local authorities may have local codes that differ slightly from the NEC. Always check with your local municipality to determine the requirements for your particular installation.

Please consult a qualified electrician or electrical inspector regarding any electrical installation for your home. this includes, but is not limited to, outlets for charging your EV.
What is opportunity charging?

Opportunity charging is simply plugging in whenever you have the opportunity. Examples would be while grocery shopping, at the library, etc. Though you probably won't get a full charge during the half hour you are at Wal-Mart, the charge you do get will give you slightly greater flexibility in where you can go while running your errands. In addition, you will be operating your batteries at a slightly higher average state of charge, which is good for their life span.

David Brandt
1/10/03

Don't EVs just move the pollution somewhere else?

Unless the power plant that generates the power that you use to recharge with gets its power from renewable resources such as wind, photovoltaics, or hydroelectricity, there will still be emissions associated with using an electric car. However, power plant emissions are washed and scrubbed to an extent not possible on a vehicle. A four year study of electric buses and diesel buses running the same route in Oxfordshire county, Ireland yielded the following data (the entire article may be found at evworld.com):

"A joint venture between Oxfordshire County Council and Southern Electric plc (who paid for the vehicles), the project ran for four years using converted Optare 18-seater buses on a deliberately non-economic route, partly suburban and partly through the congested centre of the city. Detailed monitoring demonstrated the environmental friendliness of electric vehicles used as public transport, as well as the reduced maintenance costs and acceptability by passengers.

�				Pollutants (gms/mile)	Diesel	Electric	Savings
				CO2	1331	1058	21%
				CO	7.64	0.18	98%
				NOx+SO2	19.96	11.52	42%
Fuel Consumed (kWh/mile)	Diesel	Electric	Savings	Hydrocarbons	2.74	0.18	93%
	4.9	2.2	55%	Particulates	5.10	0.20	96%

1/11/01
David Brandt

Are there any books on how to build an EV?

There's lots of information available for the prospective EV owner or builder. In addition to this FAQ and the EV maillist, there are popular books, technical books, and government publications devoted to the subject.

A search for "electric vehicle" and Amazon lists over 50 books while Barnes and Noble returns several hundred. Most popular titles are also available (along with good advice) from EV parts dealers and conversion companies. Some of the most often recommended books for the beginner (and probably already in the library of the experienced) are listed here with links to their page on this site:

• Build Your Own Electric Vehicle by Bob Brandt (1995). Technical and converson info... with a slight bias towards small pickup trucks.
  
• Convert It by Michael Brown with Shari Prange (1993) Lots of technical and practical info from those who convert for a living.
  
• From Gasoline to Electric Power by Gary Powers (1997) Very good chronicle of a conversion by a highly motivated amateur.
  
• The New Electric Vehicles by Hackleman (1996) Also covers solar cars, boats and airplanes.
  
• Taking Charge: The Electric Automobile in America by Schiffer (1994) The early history of electric automobiles dating from 1895-1920.
  Battery Book One The care and feeding of lead-acid batteries, from the staff of Curtis Instruments.
  

Are there any websites with more info on EVs?

Here are a few sites. A web search will probably reveal many more.

www.evalbum.com A photo album of EV's of all types www.kartelec.com Electric Go-Karts
www.zeromow.com Electric Mowers
www.nedra.com EV drag racing
www.plasmaboyracing.com More EV drag racing!
www.evconvert.com Two conversion diaries (one ongoing)

David Brandt
11/18/05

Section updated 3-5-03 by David Brandt
Where can I buy the parts to build an EV?

There are many EV parts suppliers on the internet. A few of these are listed below.

EVparts.com (you're there now, so why not go shopping!)

AC Propulsion
Canadian Electric Vehicles, Ltd.
Cloud Electric
Electro Automotive
EV's Northwest
InnEVations
KTA Services, Inc.
Metric Mind
Nu-Kar Electric Vehicles

2/5/01
David Brandt

Are there any tax incentives for EVs?

Yes, at most levels of government. The incentives can include rebates, lower registration fees, special license plates, the use of HOV lanes, special parking spaces and free public charging.

However, a few states actually charge additional fees for EVs to offset the loss in fuel tax revenue. It pays to do your own research before buying or converting an EV, as incentives can sometimes amount to a substantial portion of the vehicle cost.

Enough of the text of some incentives is reproduced below to "get the gist" of them. Be sure to check your state's statutes and tax code for the most up to date information.

In addition to tax credits, there may also be grants and federal tax assistance for business use of EVs. Consult the IRS web site at http://www.irs.gov for details and up-to-date information.

This is the info from the IRS web site concerning privately owned EVs...

Credit for Electric Vehicles

You may be allowed a tax credit if you placed a qualified electric vehicle in service during the year.
Qualified electric vehicle.
This is a motor vehicle that:

1. Has at least four wheels and is manufactured primarily for use on public streets, roads, and highways,
   
2. Is powered primarily by an electric motor that draws its power from rechargeable batteries, fuel cells, or other portable sources of electrical current,
   
3. Is originally used by you, and
   
4. Is acquired for your own use, not for resale.
   

Amount of credit.

The credit is equal to 10% of the cost of the vehicle. However, if the vehicle is a depreciable business asset, you must reduce the cost by any section 179 deduction before figuring the credit. Get Publication 463,Travel, Entertainment, Gift, and Car Expenses,for information on the section 179 deduction.

The credit is limited to 10,000 for each vehicle.
Special rules.
You cannot take the credit if you use the vehicle predominately outside the United States.

The credit will be subject to recapture if, within 3 years after the date you place the vehicle in service, the vehicle is used predominately outside the United States or is modified so that it is no longer eligible for the credit.

How to claim the credit.

To claim the credit, complete Form 8834, and attach it to your Form 1040. Include the credit in your total for line 49, check box d, and write "8834" on the line next to box d.

Form 8834 can be found at http://www.irs.gov

ILLINOIS:

Summary of information taken from the IL EPA web site:
Rebate towards the purchase or conversion of an alternative fuel vehicle. Any business, organization, or individual located in the state is eligible to apply for a rebate under this program. The amount of a rebate is 80 percent of the additional cost of acquiring an alternate fuel vehicle compared to the cost of the same type of conventional vehicle, 80 percent of the additional cost of the domestic renewable fuel compared to the cost of gasoline or diesel fuel, or 80 percent of the cost of the conversion. Only one type of rebate is allowed per vehicle. The rebate amount is limited to 4,000 per vehicle. An applicant may apply for rebates for up to 300 vehicles and for only 150 vehicles at any one location. Any business, organization, or individual located in the state is eligible to apply for a rebate under this program.

Official IL state reference is here.

IL section contributed by John McCain
1/25/2001

COLORADO
Colorado Tax incentives are taken from the State Dept of Revenue. You can find it at http://www.revenue.state.co.us

(look under FYI Documents, then select income tax, then select "Income 09")

A small portion of the text is reproduced below:

Alternative Fuel Income Tax Credits(Revised 10/00)

ALTERNATIVE FUEL VEHICLE CREDIT For tax years beginning on or after July 1, 1998, Colorado income tax credits are available for the purchase of an alternative fuel vehicle, for a motor vehicle that is converted to use alternative fuel, or for the replacement of the power source with a power source that uses alternative fuel. ( C.R.S. ?39-22-516) To qualify, the vehicle must be titled and registered in Colorado and it must be used in connection with a business. If a vehicle is used part of the time for business use and part of the time for personal use, the credit must be prorated in proportion to the percentage of time during the tax year that the motor vehicle was used for business purposes.

For tax years beginning on or after July 1, 2000, alternative fuel vehicles used by individuals for personal use also qualify for this credit.

The credit is a percentage of a. the difference between the cost of the vehicle and the cost of the same or most similar vehicle that uses a traditional fuel, or b. the cost incurred in converting the vehicle to an alternative fuel, or c. the difference between the cost of replacing the power source and the cost of the same or most similar power source that uses a traditional fuel. The percentage of the credit depends on the certification level of the vehicle and the year in which the expenditure is made.

A vehicle can qualify for this credit only one time. The credit for EV's ranges from 50 to 85 percent of the conversion cost.

Qualified entities may apply for this credit with the following forms: "Alternative Fuels Rebate Instructions" (DR 0166)
"Alternative Fuels Rebate Forms" (DR 0167)
"Dealer or Installer Certification Form" (DR 0168)
Colorado information courtesy of Chuck Hendrick
Added 7/17/02
GEORGIA
"A tax credit is allowed against the tax imposed under this article to a taxpayer for the conversion of a conventionally fueled vehicle to a converted vehicle that is registered in the State of Georgia. The amount of the credit shall be equal to 10 percent of the cost of conversion, not to exceed 2,500.00 per converted vehicle."

The Georgia tax information can be found at the state website under "government" at http://www.georgia.gov

You have to contact the Gerogia dept. of natural resources, environmental protection division, mobile and area source program - LEV/ZEV certification. The address is 4244 international parkway, suite 136, Atlanta, GA 31354. The phone number is 404-363-7028. I spoke with James Udi.

If you live nearby they will want to inspect the vehicle to make sure it really has been converted to an alternative fuel. For EV's, they just need to make sure that the electric motor is now the only source of motive power, and that the original fuel system, etc. has been copmpletely removed. They will come to you or they may have you come to them if it is in range. The inspection station is located in Macon, I believe. I live way over in Savannah, so for me they made do with pictures and receipts.

You send in the documentation and fill out a form, then they sign the form and send it back. If you file by mail, you send in the form with the tax return. If you e-file, you keep it unless the tax folks ask to see a copy. The tax credit is up to 00 or the cost of the vehicle, and it can be a new conversion that you did or a used conversion you purchased. Charging stations and other fuel types are also eligible.

Who insures EVs?

Some EV drivers have encountered problems obtaining insurance. This largely stems from the agents simply not knowing about EV's, and/or not being willing to look for the information. To be prepared for this eventuality, it is best if you come to the insurance agent's office with certain information handy. Specifically, have the name and number of another agent for the same company, who is providing a policy of the same sort as what you are interested in to another EV enthusiast elsewhere. This information is available from the EV discussion list. Post your question to the list, and several will be willing to provide contact information for their insurance agents. This information should allow your agent to call and get all the particulars on how to insure that vehicle. If you still encounter difficulty, you may need to try a different company.

The following are companies known to insure EV's. If you encounter problems, contact the EV discussion list (see FAQ section 1 for information on joining and posting). The people there who are currently using these companies will make every effort to help you.

AMICA: Known to have issued liability policies. 1-800-24-AMICA
Farmers: Known to have issued liability, comprehensive, and declared value policies.
Nationwide: Known to have issued liability and other policies (no detail about the level of coverage on the "other" policies).
State Farm: Known to have listed liability policies. Lists the citicar in their rate manual.
USAA: Known to have issued liability policies.
Westfield National: Known to have issued liability and declared value policies.

Sometimes, despite having all of the appropriate information, an agent will still refuse to insure an EV. The best recourse is just to say "OK, thanks anyway," and proceed to another agent. Sometimes a different agent who is willing to dig for the information can give you what you need, even if they work for the same company as the one who refused to insure you.

Note that ANY agent can sell you basic liability insurance, and the propulsion method is irrelevant. Once the agent is willing to call around, they will likely have no problems providing comprehensive or a declared value policy. There is even data that shows a lower accident rate than for ICE cars - probably because EV's are driven less distance, but also because of the care taken by their drivers.

David Brandt 9/22/03

Are there any special fees or requirements to register an EV?

Notice to residents of Oklahoma: While there are no special registration requirements, State law prohibits converting a vehicle to run on electricity unless you are a "certified electric vehicle technician." The law explicitly prohibits installing, modifying, or restoring motors, controllers, power sources, drive trains, and charging systems. The state has study guides for propane and CNG conversion certification exams, but not for the EV exam. The only available training material is a 5-day, 40-hour course at Mid-Del Technology center in Midwest City. The test includes points on Oklahoma law. The law does allow an owner to perform normal maintenance on an EV, so long as it does not involve any manipulation of any high voltage circuitry. On a further note, the exam is relatively simple for anyone who is familiar with EV's and their components.

1/11/01
David Brandt