So You Want to Build an Electric Car

Last Updated: 10/03/09

Okay, you think you are ready for the big plunge, building an electric car. So, of course, you have a few questions. I collected a list of questions I have been asked. I think this about covers it all, but if I missed one, just ask.

(click on the question to go to the answer)

What is the best car to convert?

There is no "best car" to convert. The vehicle of choice depends on what you want it to do. Porsche 914 conversions tend to be quick and have excellent range, but they aren't much good for hauling a couple of kids to school. Volkswagen Rabbits have room for passengers, but can lack pizzazz. (Not all though, check out Bill Dube's Wabbit) Mini pickups can handle a lot of battery weight, but tend to be rather heavy. Basically, what works for me may not work for you. There are a few general rules. Look for something lightweight with plenty of room inside. Try to avoid anything over 10 years old, because parts availability starts to drop off. Just because a vehicle is free or inexpensive, doesn't make it an ideal conversion. If it was a junky gas car it will be a junky EV too. If you check out the EV Discussion List Photo Album, you will find over 2600 of the most more varied conversions you can imagine.

What kind of motor should I use?

The most commonly used motors in EV conversions are series wound DC motors. Most new parts suppliers carry the Advanced DC or Warp lines of motors. There are also quite a few folks using older General Electric, Baldor, and Prestolite motors. Many older conversions were based on surplus starter/generators. While these are still available, they are difficult to mount, inefficient, and generally incompatible with modern controllers. A conversion based on one of these might be functional, but it would ultimately be disappointing. There are a few decent surplus motors available from time to time. Forklift and elevator motors are usually much to heavy to use, while golf cart motors are too small. Recently, AC drive motors have become available, and it is likely that more conversions will be using them. One current source for AC drive systems is Metric Mind.

What kind of batteries should I use?

At the moment there are really only a few choices for EV batteries.

The first is flooded lead acid batteries, such as golf cart and trolling motor type batteries. While these are reasonably priced, they do require periodic water level checks and cleaning. Dollar for dollar they are the least expensive way to power an EV. For high performance EVs however, they are a poor choice, because of the weight, and inability to handle high current loads (over 600 amps) without losing service life.

A second choice is VRLA, (Valve Regulated Lead Acid) AGM (Absorbed Glass Mat). These are often used in computer backup (UPS) power systems. They are considered sealed, so there is no fluid level to check, and they stay clean, because they don't vent under normal charging. They are able to deliver astonishingly high currents without failing. They do tend to be a bit more expensive, and require more sophisticated charging systems than the flooded batteries. They also usually have a shorter service life.

Another choice is gel cell batteries. These are lead-acid batteries with the electrolyte in a gell format. Due to the methods used in manufacturing them they tend to be very consistent battery to battery within production lot. This reduces the need for the battery management systems used on AGM batteries, though many folks still recommend them on gells as well.

Yet another choice is nickel-cadmium batteries. These have become less available due to regulatory changes in Europe. They tend to be considerably more expensive than conventional lead-acid batteries, but their extraordinarily long service life make them actually less expensive over the life of the vehicle.

Lithium based batteries are finally starting to trickle though to the individual user, but so far not in large numbers. Their long term life span is still a bit of an unknown, though it is quite promissing.

You may have heard about other types of batteries, such as nickel-metal, zinc-air, and many others. When they become available to the general public I will add them here, however, at the moment they are not available outside of test programs.

This link will take you to the MAEAA Links page, where you will find a section called EV Battery Manufacturers.

Where can I buy the parts?

There are a number of EV parts suppliers listed on the MAEAA Links page. Just follow this link to EV Parts Suppliers. Batteries are usually available locally almost anywhere.

Are there any books on how to do a conversion?

Yes, I have several favorites. They include:

"Convert It"
by Mike P. Brown
(Future Books 1993) 		amazon book An excellent "dirty hands turning the wrenches" kind of guide to building and maintaining a reliable electric car.
"Build Your Own Electric Vehicle"
by Bob Brant
(TAB Books 1995) 		amazon book Lots of technical information, including details on how all the components actually work.
"The New Electric Vehicles"
by Michael Hackleman
(Home Power Publishing 1996) 		amazon book Wonderful and inspirational pictures, with great details on specific conversions and custom EVs, including solar cars, boats and even airplanes.
"The Complete Book of Electric Vehicles"
by Sheldon R Shacket
(Domus Books 1981) 		A little bit dated, but an excellent history of electric vehicles up to 1980. Includes an interesting look at several older conversions.
"How To Convert To An Electric Car"
by Ted Lucas 		amazon book This is an older book, now out of print, which details a Renault Caravelle conversion, using a surplus generator as a drive motor. Included is information on building an SCR type controller, and a 72 volt battery charger. It is a good look at what EV conversions used to be like.

Clicking on these books will take you to Amazon.com, with a direct link to the book, or you can click here.


amazon book

You can also find these at your local library or book seller.

How far can I go on a charge?

This depends on many many factors including terrain, speed, temperature, driving style, and of course the design of the car. Most conversions average around 50 miles, with some less and some much more. A recent pickup conversion was able to handle over 120 miles of highway driving on one charge. You can see it at: Red Beastie.,

How fast will it go?

Again this depends a lot on the design. Most conversions are fast enough to get a speeding ticket on any highway in the U.S. Acceleration does tend to be slower than the average gas car, with few conversions able to reach 60 in less than 20 seconds, kind of like driving a mini van. On the other hand, some conversions are wickedly quick, and have far more horsepower than they did as gas cars. An electric drag car recently managed 8.100 seconds and 153.6 mph in the quarter mile! That is quick! If your curious about high performance EVs, check out the National Electric Drag Racing Association.

How much will it cost?

The least expensive conversion I know of was done for $1,500. This was a 72 volt, 12 horsepower, Yugo conversion, and many would say, a poor example. While it is certainly a reasonable commuter car, it would never be considered a performance car. Most conversions are done for $8,000 to $12,000. When more "goodies" are added, the more the cost goes up. It also depends on how much repair work the donor car needs.

Is there anyway to make it recharge itself while driving?

In a word, NO. Driving generators off the wheels, adding a windmill on top and similar ideas are often suggested. The problem is the increased drag from such items would be several times greater than the added power they would generate. It is a nice idea, but it won't work. There have been some folks working with pusher trailers to allow the EV to become a hybrid for highway use. You can find some info on one on JB's webpage.

How about solar panels?

Solar panels will work, but are unlikely to supply enough power for a full charge in only one day. The problem is the very small amount of power they generate. If the top of a car were covered with solar panels, and it were parked in direct sunlight for 8 hours, it would only generate enough power to go only a few miles. There have been some folks who have built truck conversions with large solar arrays who have reported being able to cover ten miles or more per day on the power from the solar panels. A scratch built, very light EV with a large solar array might be able to do even better. At the moment the cost of solar panels might make this a fairly expensive project.

How about adding a generator?

This would make it a series hybrid electric. Yes it will work, but there are some issues. One possiblity is a small generator that provides a portion of the power required to drive the EV. For example, if it provided half of the power required, it would double the range of the vehicle. A larger generator, capable of providing 100% of the power needed would make the vehicle only limited by the fuel in the fuel tank. The main problem with both of these concepts is the engines used in small generators. These engines are not subject to the same EPA regulations as automobile engines, so in general they tend to produce several times as much pollution per horsepower-hour as an automobile engine. They also tend to be far less fuel effcient. As a result, most attempts to extend the range of an elecctric vehicle this way creates something that actually causes more air pollution than a conventional car and gets poorer fuel economy. Basically, the advances that have been added to the modern gasoline car, such as electroninc fuel injection, closed loop emission controls, and cayalytic converters all have made the modern gas car a pretty hard act to follow. If one were able to apply that same technology to a small engine driving a generator then one could almost certainly build a range extending generator for an EV that would be cleaner and more fuel efficent than a gas car. The challenge would be in doing that. A number of folks have put together range extending trailers using small car engines to drive large generators. In most cases these seem to work quite well, but the fuel economy is not dramatically better than a conventional gas car. Several universities have built hybrid cars. You can check them out on the MAEAA Links page, just look for High School and University EVs, and then go to the Hybrid section.

If you have any more questions, feel free to email me.
Thanks.


code by jerry