E-Mail Bag!

by Ben N on October 4, 2010

I often get e-mails from people asking me for advice on building their own electric car.

Unfortunately, all too often, they are in the vein of “how do I build an electric car?” Well, that’s a VERY broad question. It depends on your experience, your budget, and a lot of other factors.

I built my car by doing a LOT of reading, and meeting and talking to anyone I could think of who had experience with electricity and cars.

Today, I got an email from somebody interested in doing an electric car conversion. He did break it down into a few distinct questions, which makes it a whole lot easier to answer.

Q: What kind of controller did you use/build?
At the moment, what’s in the car is a Curtis DC Motor Controller – 72V model 1221. For high speed and long range, you will want as high as a system voltage as possible – 96V minimum, 120 or 144V are both good. The Curtis 1231 controller is a good big/fast controller, but gets pricey too. If you aren’t afraid to try some electronics assembly, you could make your own OPEN REVOLT COUGAR controller (just Google it, you will find it on Ecomodder.com) It’s good fast and cheap, but you build it yourself.

Q: I think I could find an electric forklift motor and I have a donor car vw bug.(maybe a 5 speed car would work out better for distance)

VW Bug is a fine car for conversion, but they are limited in room and weight for batteries. You might need to use more batteries that are physically smaller to fit them all in and still have a high system voltage. Definately use a car with a manual transmission. Lightweight cars are good, but you also have to balance the need for space and weight of batteries. I like hatchbacks. Light trucks like Ford Rangers and Chevy S10s are popular as well. You also want a car that’s easy to find parts for. And remember, convert something YOU like to drive!

Q: the controller is the part that has me question my sanity.
I want to break free of oil addiction.

There are a lot of good reasons to not be on oil, the first step is to admit it, then take action to correct it. I think of it as Oil Anonymous.

Q: My work is 25 miles away the road has a speed limit of 65. can I copy your conversion and make it that far and recharge for return trip?

You will need more batteries in your car than I have in mine. When I was running 12 batteries in my car (144V system voltage) I could get up to just past 70 mph, but that also takes a lot of energy as well. I could go 30 miles on a charge on 144V system. That was with used batteries. You should be able to do a little better on new batteries. My friend with a converted Ranger can do 30-40 miles on a charge.
You would need to be able to charge at work, and make sure it’s a full charge. That might mean buying a pretty decent charger and having access to 240V electricity. Check at your employment to make sure you would be able to charge there (and at what voltage/amperage) before you do your conversion.

Q: do you have a schematic to follow to wire up the motor and controller( the batteries seem strait forward )

The motor controller companies all have schematics for you to follow. When you buy a controller, it will come with instructions on how to hook it up.
It’s not that tough, you just bolt certain cables to certain places. Just do a search on the Curtis or Alltrax controller web sites if you want to see a diagram.

Q: I know the batteries are the most expensive part but it sounds like there are places to pick up new / out of date ones for way less.

Check around. There are battery wholesalers. Also, where do you think there are places that use batteries that have to replace them? Janitorial places? Airports? Cell towers? Talk to all your friends. If you really want used batteries, you can find them. Just make sure you can pick up the batteries. You DON’T want to pay to ship lead-acid!

Q: how far will it travel at 70 mph or do you know?

It takes a lot of energy to travel 70 mph. The best way to to improve economy is to slow down. Even in my gas pickup truck, I drive 55 in the 65 zone.
If you are a motorcycle rider, it IS easier to build an electric motorcycle than it is to build a car. The downside is that you can’t fit as many batteries in. The upside is that you don’t need as many, because the motorcycle is lighter than a car.

Q: I want to be off the grid as it were and would appreciate any and all help.

The great thing about EVs is that you just plug them into the wall to recharge. My house is on a renewable energy program. I get my electricity from solar panels and wind generators, but over the grid. With EVs, you have a choice as to where you power comes from. Charge your EV with solar, wind, or whatever renewable energy you can get. With gas cars, the energy only comes from oil.

As it is right now, my car is NOT designed to go 25 miles each way at 70 mph. Another friend has a Dodge Neon he built that has up to a 50 mile range. The top speed on that car is no more than 65 mph. (has to deal with his gearing) That’s an AC car with 25 batteries in it. A little advanced for a beginner, but that guy happens to be an electronics engineer.

I think that you would need to put a little more money into your project than I did on mine to meet your goals, but they are entirely practical/possible. I’m not sure if the bug will be the best vehicle for what you are trying to do, but if you already have it, it might make a great test platform.

Check out PaulandSabrinasEVstuff.com – Paul there did an inexpensive Bug conversion.

Hope that helps get you started!

{ 2 comments… read them below or add one }

1 Andy July 11, 2019 at 5:32 pm

I want to Solar Charge my Tesla. I am considering the Tesla’s Wall Connector. https://www.tesla.com/support/home-charging-installation/wall-connector.

How many solar panels do I need? What MPPT module is optimal for the intended use? How can safety for the users (wife and kids) and the car be improved to avoid potential accidents?


2 admin July 12, 2019 at 9:01 am

How many solar panels simply depends on how much total energy you want to produce, depending on your climate, latitude, orientation to the sun, and a number of other factors.
Solar is extremely safe. Electric vehicle charging equipment is extremely safe. The worst potential accident with EV Charging equipment is tripping on the cord. Simply hang it up out of the way when not in use, and it’s as safe as it can get.

If you want to know exactly how much solar energy you need to produce to offset how much energy your car uses, that can be calculated.
You may want to simply get an estimate from a solar installer. They would be happy to help you figure out how much energy you would need.

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