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Mac & Mac Electric Company, Inc.
1410 Iowa Street
Bellingham, WA 98229

360-734-6575 Sales Office & Repair Shop


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www.MacandMacElectric.com
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Some Electric Vehicle (FAQ) & Facts:

* EV's run at the equivalent of $0.48 per gallon: (Geo Metro tested at 70 MPG on electric vs. the original gas engine at 36 MPG)

* Truly zero emissions vehicles? Even if the vehicle is being recharged by a coal fired power plant, the emissions standards for power plants are much more strict than for Autos.

* Electric vehicles are 80 - 90% efficient, compared to diesel at 25 - 40%, and gasoline vehicles at 10 - 15% efficient

* Today’s affordable electric vehicles rang in prices from $10K - $30K

*** Electric Vehicles have a limited range. This is true with today's infrastructure. However I do not see this as a problem with the electric vehicles as much as a problem with today's transportation system. For instance if our highway's carpool lanes were equipped with an electrical tie in (like that of the electric trolley cars of San Francisco) our electric cars could drive indefinitely along the major freeway / highway systems and run on their own battery power only when not on the highways. For instance a commuter could unplug their plug in electric car before leaving home. Drive on battery power to the freeway / highway. Then while driving on the highway, tie into an electrical system where the car is both powered and recharged while driving on the road. The driver would be charged for the power consumed. Then when the commuter reaches their destination they disconnect from the electrical tie in and exit the freeway / highway and drive again on battery power for the rest of the commute... :-)

First, some: EV TERMINOLOGY

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, but can also refer to electric street cars & busses in large cities, and 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 an 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.

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 EV's, 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 driveability, and reduces brake wear. Most AC drive electric vehicles include this feature, but it is only rarely found on DC drive EV's.

Some more typical Customer Questions:

How easy is it to install EV components? Depending on your mechanical experience you may need to solicit some guidance from a local mechanic. Some of our customers have involved their local high school automotive class in the project.

How far will the vehicle be able to travel before needing to be recharged? Most car conversions have a range of 25-45 miles and most truck conversions have a range of 45-55 miles which can be doubled or tripled with Nickel or Lithium batteries (cost approximately $6,000 to $25,000 US). It is important to note that the life expectancy of Lithium batteries is unproven and that Lithium is not approved by the DOT for use in vehicles.

My limited research shows some advantages to an AC motor.  Do you offer this as an option? We do offer AC drive systems for a number of vehicles but the cost is much higher.

Do your DC controllers offer regenerative braking? Yes, it is an option.

Do you have a kit for my car?
We specialize in the VW Type I, Chevy S10/S15 and Geo Metro vehicles but can provide basic component parts for any vehicles.
Mac & Mac Electric (EVWA) can supply all the basic electric drive systems for you to convert almost any vehicle however you would have to build all the vehicle specific parts (example: motor mounts and battery boxes). You would also have to deal with the increased weight of the vehicle by finding and adding heavier springs. We could not help with wiring other than the basic drive system.

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.

Where can I buy a used EV?
Used EV's are posted for sale on many web sites, and occasionally come up for auction on Ebay. One web site 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 web sites. Go to the main EAA web site at http://www.eaaev.org for links to the chapter web sites.

How much do they cost (new and used)?
"New EV's" usually means those built by OEM's. These vehicles are available, MC Electric Vehicles in Seattle Sells a variety of new EV's. . The prices range from 14,900 for a MILES EV 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 5,000 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, EV's will also require brake servicing as in a conventional automobile.

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.

What can I do to maximize my range?
As far as vehicle design goes, lighter and more aerodynamic and light weight 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, traveling more slowly will buy you range due to the batteries typically having more capacity when used at the lower currents that lower speeds require.

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 (40-45psi is best). 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 drive train (i.e. transmission in neutral). Secure all loose items, and in general, take the same precautions you would for any other car under tow.

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 8000 to 14,000 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.

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 nice, if expensive, 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. 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, brush less permanent magnet (synchronous) and series wound motors can all be found on motorcycles. Brush less DC and brush permanent magnet motors are less common on car sized EV's often due to cost (brush less 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 mini bikes 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. Luckily 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). Others use a friction drive on the rear tire, like 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 web site.

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 EV's 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 yellow pages), and some home stores. 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 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. The 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.

For exciting developments in production EV mower technology, visit www.zeromow.com!

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, I see a transmission as being necessary in an EV 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, and possibly to increase torque as well. 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 drive line. 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 drive line would be complex and expensive. EV suppliers can provide adapter plate kits that bolt to the transmission's bell housing and allow any number of 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?
Discussing keeping the clutch in an EV conversion first requires a clarification of the terms "necessary" and "desirable". Numerous enthusiasts, and even a few prominent suppliers will say that keeping the clutch isn't necessary. It's true, it is possible to operate an EV without the clutch. However, 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 inevitable that the synchronizers will eventually fail. Keeping the clutch not only ensures the synchronizers never see a load greater than they were designed for, but offer other advantages over going clutch less. One is the ability to slip the clutch to allow precise parking and backing maneuvers. Another 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 drive line. 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 not exactly necessary, but very desirable.

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 brush less 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.

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

NOTE: 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 torque 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

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 vehicle. 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 an EV 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 (Traction Motors). It used to be that these were salvaged aircraft starter/generators, or motors cannibalized from other sources, but most on-road EV's now almost universally favor the "advanced DC," "D & D" or "WarP" (a.k.a. Netgain - www.go-ev.com brand motors). These motors are designed for EV conversions, 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 controllers. AC motors are cheapest in price, and while their performance characteristics are different from the traditional series wound DC motors, they have advantages, too. There specialized controllers require a 300VDC input, and are typically the same price as 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. The AC motors are built to NEMA specs so most of the DC EV motor adaptor plates available on line will not work with any of the NEMA motors until someone begins producing the templates needed for them.

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 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 under hood arrangement simpler.

DC systems: The required brush servicing is around 50,000 to 100,000 miles, and can be done in minutes at a competent electric motor shop like ours. It is really not much of a hassle. Either high or low voltage components may be used. 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 their best torque at higher speeds.

What batteries are available?
These batteries are listed in order of their availability and popularity. 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 over voltage or for balancing. this usually leads to a more expensive charging system by a few hundred dollars.
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. These batteries can only be cycled about 600 - 700 times on average.

Next, Adsorbed Glass Mat (AGM) sealed deep cycle lead acid batteries deliver high currents without as much voltage sag as flooded's. 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 a little more up front. These batteries can only be cycled about 1000 - 1500 times on average.

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 charge 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. These batteries can only be cycled about 300 - 1000 times on average.

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
A123 Battery
Altair Nano
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 very high, maximum current draw is limited on some types, and the number currently in use is unknown. Also, the DOT has not yet approved lithium batteries for use in vehicles due to their tendency to catch fire and explode when in contact with water.

What is the best battery for my EV?
Drag racers use Hawkers, Optima's or SVRs (brand names of popular AGM batteries). All of these cost more than flooded batteries but make more watts per pound. They are used by EV 'ers who are looking for light weight and zippy EV's (high performance, short range EV's).

For commuting over longer distances, the flooded golf cart batteries are most popular. These are made by both Trojan and US Battery and come in 6V or 8V versions, all the same physical size. We also offer an AGM the same size and amp hour rating as the most popular flooded golf cart batteries.

See also question on what types of batteries are available. Advanced chemistries are available, but are not widely used yet.

What is the proper way to maintain batteries? (Cleaning and filling batteries)
The following EVDL post discusses how to get the most out of your batteries. I have reproduced it here and in the charging procedures section, as it is very valuable information. Information on filling and cleaning follows.

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 them till they drop! If you drive an EV until it barely moves, the batteries are having a near-death experience! This is outright bad practice, 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 them 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 flooded's, 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 EV's 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, insulation, and possibly a battery heater blanket. The only one 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 is usually a cage-like construction of angles and supports, or it is sheet metal, which 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 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 liner of a battery box must be resistant to battery acid (sulfuric acid). It can be sheet metal. 304 or 304L stainless is ideal, but expensive. Regular sheet steel can be used if it is properly primed and painted. Some EV conversions feature powder coated metal components. Polypropylene can be welded (using plastic welding techniques) into a very nice battery box liner. This is what the battery cases themselves are usually made of. It also provides some insulating value. Plywood may also be used, although acid can attack the glue, causing de lamination. On the other hand, plywood is cheap, and can be replaced as needed.

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 out of the passenger compartment by venting the battery enclosure while charging and discharging. Seal the top of the battery enclosure off from the passenger compartment, and install a brush less fan - one that does not produce sparks (USCG Approved Bilge Fan is good) - 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 brush less 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.

A battery management system keeps the operator informed of the state of health of the batteries to some extent and keeps them balanced to some extent.

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.) It then applies this information to balance and properly charge the batteries.

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

See also Section 13 of this FAQ regarding chargers, charging, and regulators.

What about battery heaters?
Battery heaters are used to keep the battery temperature at or above room temperature when the ambient temperature drops. Since lead acid batteries can lose up to half of their capacity at 32 degrees F., heaters can maintain the range of an EV even in very cold weather. 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.

Usually battery heaters take the form of mat-style heaters that are placed under the batteries.

Which is better, flooded or sealed lead-acid batteries?
Flooded's 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.

Sealed's come in fewer sizes and cost more. They usually do not live as long as flooded's, 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).

Flooded's can be slightly undercharged, overcharged, etc., and rebound quite well if the problem is corrected. Even a recurring problem like having an out of balance pack will not affect their performance too much, although it will shorten their life. The severity of the shortening depends on how bad the problem was and how long it went on. 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. Flooded's 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 flooded's 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.

How do I determine the battery state of charge?
Usually a Voltmeter or E-Meter gauge mounted on the charger/dash will tell you .

Can I mix old and new batteries?
NO!
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 since we have seen it destroy controllers and motors, 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?
No. Not unless they are charged separately. Even then, your total capacity is limited to the capacity of the smallest, weakest battery in order to keep from reversing it. This means that the larger battery is 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.

The only exception to this 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, 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) kind of useless for EV's 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 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 divide 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.

By adjusting the knob of 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.

Another appropriate analogy is that the controller takes the place of the carburetor or fuel injection system in an "ICE" aka: Infernal Combustion Engine:-).

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 controller or a "Chopper" to regulate the DC power from the battery to the motor. They have a myth of lower cost attached to them, thought to be only 1/3 the cost of a similarly sized AC system. This unrealistic cost benefit comes from a lack of knowledge in electric motor shop parts distribution. 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 after the battery pack. 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, programming, or manufacturing. When they do blow up, it is often not cost effective to rebuild them.

And while we're speaking of failed controllers: Properly fusing the system with semiconductor fuses (ultra fast 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.

What controllers are available?
The DC controllers that are available (check the controllers section of the web site for more detail on the most popular) are from Curtis and DCP. The EVCL "Godzilla" controller is also available by special order from the manufacturer. Alltrax is a good Oregon built controller. And Kelly is a leading Chinese controller. 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: We have developed an affordable, "off the shelf" Baldor AC drive system. The only downside is it requires a 300VDC nominal input. Metric mind (www.metricmind.com) also sells surplus inverters and motors manufactured by Siemens. These are very high quality components, with a reasonable price tag, but they also require high voltage input.

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 achieve 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 functions as a voltage divider. This setup uses all the energy that comes from the batteries, but it wastes everything that passes into the resistor as heat, so is very inefficient except at full throttle.

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. Some VFD's can take DC directly as an input because the internal function of these drives already rectifies the normal AC input to a DC bus voltage which is then inverted back into AC to create the VFD function.

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.

Can I build my own controller?
Probably not, if your asking.

Why does my controller whine?
Whining is a characteristic of the voltage being chopped in DC controllers and of the SCR's firing in ac controllers. What happens in the DC controllers 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.
Baldor AC Controllers can have this programmed out of them.

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.

Can I add regen to my DC EV?
Most DC EV's use series wound motors, which are difficult to add regen to, although their are controllers 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.

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.

What about voltage switching and resistor controllers?
This is old inefficient technology which works just fine, but I don't need to get into stone age lessons here.

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

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.

The chargers discussed below are available from us and the other suppliers listed elsewhere in this FAQ.

Chargers range from small, simple onboard units to large, off board 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 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 transformer less unit, with a current display, but is available with a timed shutoff, and has a slightly better 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 a 132 or 144V pack. The Russco will charge packs from 84 to 144V.

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.

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 K & W BC-250 is next, although its very high price tag (more than the PFC-20 discussed later), makes it much less common. It can charge 72 to 156 volt packs from 120 or 240 VAC. It will interface with the badicheq battery management system, and employs the same basic charging algorithm as most of the other chargers.

The most popular EV charger is the Zivan. It has computer control, and comes with the user's choice of 12 charging algorithms preset into its memory. 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.

Of all those listed above, the Lester is slightly more efficient, due to its slightly better power factor. None of the chargers available to hobbyists have ever employed active power factor correction, until now.

The PFC-20 (and its higher power cousin, the 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 the best features of the units discussed above. They both have 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. It comes preset with a good general purpose charging algorithm, but has a computer control option that lets the user alter the charging profile in any way they want. It also interfaces with the most popular battery regulators (made by the same company).
The PFC line of chargers is offered by Mac & Mac Some special modifications are available on request, for a slight extra charge

What wiring is required to charge in my garage?
EV's 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 2-4 hours.

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.

Can I build my own charger?
Sure.

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.

How can I quick charge my batteries, will it harm my batteries?
Please refer to each battery manufacturers recommendations.

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 EV's use many batteries. In theory, they are all identical, and always charged and discharged equally.

But in practice, there are always small variations even between new batteries, and these differences get larger as the batteries age. There can also be temperature variations, or differences in the load that each battery sees. This means that different batteries are at slightly different states of charge. It becomes difficult to know exactly how much "fuel" you have, or when they are full or empty.

The simple solution is to pretend that all batteries are identical. The "fuel" gauge simply displays the average state of charge of the whole pack. When driving, the vehicle loses power when the weakest or least-charged battery goes dead. Thus, your range is limited by the "weakest-link" battery in the chain. And when charging, the charger deliberately overcharges the entire pack, so even the battery at the lowest state of charge gets fully recharged. This is fine for lower-tech deep-cycle flooded lead-acid and nicad batteries; they tolerate deep discharges and modest overcharging with relatively little loss of life.

But higher-tech batteries are not so tolerant. They are damaged by excessively deep discharges, 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 Regulator (example: BatPro or 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 a bit more sophisticated (example: Powercheq, Badicheq, 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 for flooded lead-acid and nicad batteries, highly desirable for sealed
batteries, and mandatory for high-tech batteries like NiMh and lithium batteries.

What do battery regulators do, and how do they do it?
There are different types of regulators. They will be described separately because they do different things.

First and most common is the dissipative regulator. These are inexpensive devices that wire across the terminals of each battery. They protect the battery from overcharge during charging in order to maximize battery life. This ensures that each battery is fully charged, because you can overcharge a bit to fill up the batteries that need it more without damaging the rest.

When a battery is fully charged, any more energy put into it goes into heating it up and electrolyzing the water in the electrolyte. This is fine with flooded batteries. They heat up slow, and have plenty of water to keep the plates immersed. But more expensive sealed batteries are typically "starved electrolyte," which means they do not have nearly as much water to give up. What's more, once it's gone, there is no getting it back without disassembling the battery.

Dissipative regulators typically have an adjustable voltage set point, such that above that point, they attach a load across the battery until the voltage drops below the set point, which it does in a second or two. This way, the battery is held at the set point, which is chosen based on the battery type and service (usually 14.7 to 14.9 volts per 12V battery), for the rest of the charge. They are still being charged, just not to the point where they exhibit extreme voltages and vent their precious water vapor. Any gassing that occurs is kept at such a low rate that it is within the battery's capacity to recombine within the case. The most common dissipative regulators are available with a number of options, such as communication with the charger, low battery detection, and the capability to use external loads to handle higher currents.

The other type of regulator is called an additive regulator. As of this writing, these types of regulators do not protect the batteries from overcharging. Instead, they measure the voltage level of each battery, and give it an individual charge either from neighboring batteries or from the pack as a whole. This way, the lower capacity batteries are kept closer to the same level of charge as the higher capacity batteries. Thus, these types of regulators protect the batteries from excessive discharge. Since they usually involve a DC/DC converter and some sort of electronics for control, these types of regulators are usually more expensive than dissipative regulators.

Some brands of additive regulators consume power all the time, and can drain a pack if it is left unused for an extended time. Most kinds only use voltage as a measurement of state of charge, when in reality, batteries at equivalent states of charge may be at slightly different voltages due to the same miniscule differences between the batteries that makes them go out of balance in the first place. So the regulator tries and tries to get the voltage up, all the while it is draining the rest of the pack or the neighboring battery.

Regulators can be an important part of a battery management system. However, a true management system employs more accurate means of measuring SOC than simple voltage measurements, and helps each battery both during charge and discharge.

How do I charge my batteries using a variac?
This information was derived from the EV Discussion List. Special thanks to Lee Hart and Chuck Hurst.

Safety Precautions:

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

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

� 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.

� Turn the variac down to 0 (fully counter-clockwise) before beginning. If something is incorrectly connected, you don't want to hit it with full voltage right off the bat.

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

� Some variac's have been observed to destroy sine-wive 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. I recommend you check every commercial (15 minutes or so). 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 Voltmeter or 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.

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.

What DC to DC converters are available?

GE, Sevcon, etc...

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 like "Powercheq" modules or a Zivan "Smoother", your range will decrease to that of the battery you have tapped. Except for the separate chargers, these devices have low current capacities, so it will take a while for the pack to come back into balance. If you try to charge your batteries 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 small separate 12V battery and/or a DC/DC converter will be much better for your main battery pack.

What tires should I buy? ( load ratings and rolling resistance)
The lowest resistance tires for the appropriate driving conditions.

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 are available that actually track the amp-hours and/or kilowatt-hours used and replaced. E-meters combine the functions of voltmeters and ammeters, add 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 over speeding the electric motor. Ammeters help to keep the currents within limits set by the component manufacturers. Temp meters can give you great information about your expensive motor & controller.

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, Motor & Controller temperature meters, 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, and some temperature devices.

How do you connect and program an E-meter?
You will need to refer to the specific model and manufacturer.

What is a battery monitoring system?
A battery monitoring system is a type of data acquisition 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?
This may be best left to a professional automotive shop.

What springs should I use?
This may be best left to a professional automotive shop.

How can I improve the brakes?
The same way you do on a regular 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?
Yes, you will need to install an electric power steering pump.

How can I heat my EV?
Usually, the place the ICE heater core occupied is more than roomy enough to install one or more propane heaters or ceramic electric heater cores, rated at 1500 Watts, that are available. The electric 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.

How about air conditioning?
Yes, You will need to install an electric ac pump.

Can I add a small generator? (APUs and generator trailers)
Yes, if you still have room for one.

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 (Like when you see to locomotive engines at the front of a large length of train). 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 web site, and JB's EV and pusher trailer.

What is meant by series or parallel hybrid?
This can mean several ideas. Generally series means in a daisy chain, while parallel looks like a ladder when drawn out. A series hybrid could be if you were to include an optional engine powered generator which would boost the system voltage to a higher voltage to help you attain greater speeds and distance. This would require quite a bit of engineering since your controller and other system components probably are not set up for the changes in system voltage. Where a parallel hybrid could be an engine powered generator which maintains the same system voltage and basically charges the battery pack and provides extra driving energy for longer trips.

Can I charge my EV with solar power?

To date it is not practical to simultaneously drive an EV while charging from the sun. It will work, but it will not extend your range all that much. Plus driving around with solar modules on your vehicle is not wise since PV Modules break when rocks hit them (look at your windshield) You would be pretty disappointed if you invested in a solar charging system that got destroyed from a rock kicking up off the road.

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

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?

Most EV hobbyists are asked this question very often. 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, on a gas car this energy is really consuming
gasoline to perform this function. But if you think about it, you'll see
that in an electric vehicle, it would only be draining down your main pack
while trying to charge it.

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 hybrid generator pack, or 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
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 65% to 96% efficient (depending on the motor you choose). 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 front 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
25 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.

How about a windmill? (A discussion of basic physics. )
Same basic answer as above.

How can I connect to the EVI/Avcon public chargers?
This question has not yet been answered?

Can I plug my home built EV into a GM paddle charger?
Sure, if you can still find one, and if you build a receptacle on your vehicle which will accept the paddle.

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, but it does not since the article is for permanently mounted charging devices in a building or structure within the NEC jurisdiction.

State, City, and local authorities may have local codes which can supercede (make more strict) the NEC. Always check with your local municipality to determine the requirements for your particular installation in your location.

Please consult a licensed electrician or electrical inspector regarding any electrical installation for your home. this includes, but is not limited to, outlets and chargers 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 Trader Joe's, 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.

Don't EV's just move the pollution somewhere else?
You should keep in mind that most automobiles throughout the world are not emissions tested, ever. While power plants are under constant monitoring and regulation. That said, Yes EV power is transferred from the road to the power plant. However since internal combustion engines on average are about 15% efficient and EV's are on average 80% efficient, you are not only getting more foreword driving motion for your buck, you are also polluting a lot less no matter where the energy is offset to. Also, here in WA state over 40% of our energy comes from hydro, and also a little from renewable resources such as wind and photovoltaic's. Also, 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 center 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."

What about disposing of used batteries?
If you turn in your cores instead of dumping them in a dumpster somewhere, the batteries will be recycled.

I read that EV's use more fuel than ICE cars, is this true?
Not even, Even if the vehicle is being recharged by a coal fired power plant, the emissions standards for power plants are much more strict than for Autos. And since Electric vehicles are 65 - 96% efficient, compared to diesel at 25 - 40%, and gasoline vehicles at 10 - 15% efficient . Efficiency matters and is directly proportional to the fuel used to drive you down the road. This is how you can attain $0.10 - $0.30 per gallon equilivant

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 mail list, 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 conversion 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 web sites with more info on EV's?
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)

Are there any tax incentives for EV's?
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 EV's to offset the loss in fuel tax revenue. It pays to do your own research as incentives sometimes change and 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, but this information could be dated. Be sure to check your state's statutes and tax code for the most up to date information.

US Federal Incentives

In addition to tax credits, there may also be grants and federal tax assistance for business use of EV's. 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 EV's...
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

State Incentives
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 .
1/25/2001

Colorado Incentives
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 Incentives
"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 ,500.00 per converted vehicle.

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

(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)

Who insures EV's?
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.

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.