I’ve been toying with the idea of building or converting a vehicle to run on pure electricity. No specifics yet, except for maybe an old '89 astro van I’ve had my eye on, but I think this would prove to be some interesting conversation for all you CD’ers and FIRST’ers in general out there.
First off, what battery technology is the best? The most economical? Longest Lasting? I hear NiMH is good, but whats your say?
What kind of transmission? Leave the auto in and find a motor with a torque curve to match? Manual tranny electrically actuated? CVT?
What type of motor? AC or DC? Brushed or Brushless? Whats a good system voltage?
Drive systems? Who knows where to get real high voltage high current H-Drives? Breakers n such?
Control System? Ditch the hydro and make a servoelectric assist? Electric braking? whats best?
…Anyhow, many questions posed… but whats your opinion? if you were building an electric car, or converting one to electric, what would you do?
I haven’t done any research, but I would say converting an AstroVan would be very difficult and un-economical… its HEAVY! I’d say pick something lighter… (sedan? station-wagon?)
Our team has actually acquired an old VW bug, and plan to make it electric.
As for some places to start, look up a godzilla speed controller, it’s what we plan on using. We have a mentor who builds and races electric cars, and so he’s our primary contact.
There was a company I remember reading about that sold kits to convert Chevy S-10 pick up trucks to electric. (Sorry don’t remember their name or where they were out of .) According to the piece in Popular Mechanics they removed the gas engine and placed the electric in the engine compartment.
They used an adapter to connect it to the manual trans of the truck.
Batteries were placed along the frame under the bed. Not sure what type exactly but think they were regular lead-acid deep cycle batteries.
The truck conversion kits were marketed for use as delivery vans.
Don’t remember their range ect… this was like 15 years ago but they manage normal city driving speeds.
Your Astro van is based on the S-10 frame so the same kit should work on it too. Very interesting idea! Sounds like a fun project.
Keep us posted!
Here’s a link to an company in CA that builds/ sells kits Closed: Electro Automotive their site says 1900 to 3600 lbs curb weight so your van should fit right in.
With batteries, weight is your biggest enemy. Keeping that in mind, I’d go with the Lithium-based battery trend that all consumer electronics have been going with as of late, as they are among the lighest of batteries.
Chances are, you probably won’t need a traditional car transmission if you are using electric motors. Internal combustion engines develop their highest torque at high RPMs, and the highest torque in a car is needed when you first get it moving (e.g. slow RPM). That is why you need transmissions in a car with 3, 4, 5, or 6 gears.
With an electric motor however, you get your highest torque at zero RPM, which is perfectly suited for getting the car rolling. In an electric car, you probably won’t need anything more complicated that a 2-speed transmission, if that. (The Tesla Roadster only has a two speed transmission, however it can run entirely in second-gear if the driver wants.)
Also, you’d get much better results if you use 4 small electric motors (one driving each wheel), than one giant one going through an auto/manual transmissions, differentials, etc. Most modern electric trains no longer have traditional locomotive units, but rather powered wheelsets spread along the length of the train, as this helps with the weight distribution and efficiency of the total system.
You can also use the motors for regenerative dynamic braking, however you’ll still need traditional brakes. (Once you get below a certain speed, dynamic braking will stop generating enough electricity to recharge any batteries/capacitors, so you’ll need traditional brakes to completely stop.)
NiMH batteries are a pain to charge correctly. You can’t deterine their state of charge by measuring their voltage unlike lead acid. That might not be a problem for what you want but it starts becoming annoying for hybrid vehicles.
What type of motor? AC or DC? Brushed or Brushless?
I would say brushless because they require less maintence. Unfortunatly the electronics are more complicated in that you have three phases to control. Most of the home modifications involve modified brushed motors that come from forklifts.
Keeping that in mind, I’d go with the Lithium-based battery trend that all consumer electronics have been going with as of late, as they are among the lighest of batteries.
If you do that I would recomend trying a123’s batteries which shoudn’t catch on fire. I really am leary of using traditional lithium ion batteries in this application because of the risks involved with having a fire that isn’t normally experienced by firefighters. Consumer electronics don’t really experience the type of trauma a car may which would cause the batteries to explode.
Not to shoot down your idea, but have you considered starting out with trying to convert maybe a go kart? This way it is smaller scale and less expensive. This way you can learn the same amount as you go along with spending less money. Then if/when you move to a automobile you know more. And maybe you can use the go kart to ask for sponsors too?
I like your idea, I have been wanting to do it for a long time, but as with any project money is the issue. How much working are you planning on doing? Becuase if you go with a motor pre wheel design there is going to be alot more work compared to just dropping an electric motor and transmission in. You will also nood to make a ton of parts. I have never personally done this but I have looked at alot of stuff online and for one person, a college student none the less, it is going to be a TON of work.
Ive actually read a bit about this in the last couple of popular science/mechanics magazines. The popular choice for batteries is Lithium ion as they becoming smaller and more effcient. Also many of these cars have one motor per wheel and very few have multispeed transmissions.
Li Ion are great, but brutally expensive in the capacities you’ll be needing. Ditto NiMh, but a little bit less expensive. NiCd are OK, but don’t have the instantaneous current output you’ll need. Lead Acid are heavy, but cheap, plentiful and overall have great characteristics. There are many other battery technologies; depending upon your goals and finances you may select even something else (like a liquid sodium system).
The go-kart idea has merit. Just a controller for a typical 100 HP (75 kW!) motor is several thousand dollars, but for a 3 HP go kart they are far less costly.
Do research, more than Popular Science, as they tend to gloss over the practicality and are a bit ‘gee wow, this is the future’. Great for the masses but kinda light for the person trying to implement it.
Don’t let anyone talk you out of though - just approach it with a plan and go in steps. Oh, and post photos!
You could also look here: http://www.electric-cars-plans.com/ These are plans to build an entire car from scratch, but it still might have some answers to some of your questions about what to use to modify an existing car.
What type of project are you interested? Are you more interested in circuits or mechanics?
Do you want it to be road legal?
For giggles, consider setting a super low-budget. I personally think it would be more fun to overhaul a horribly crappy car. Try looking on craigslist something that is super cheap and possibly ugly.
Also, it might be fun to try to build your circuitry from samples.
As for motor selection, big motors are expensive. Go with what you can salvage. If you have a choice, go with brushless. Many many many companies sell driver chips that handle all of the commutation for you.
Well… hey wow lots of replies. The Astro van wasnt set in stone, just had one available for free. I like the idea of trying a smaller vehicle first, also thanks for the links to info websites.
To be honest I am just playing around with the idea for now… looked through some of all your links you gave me and came up with about 8~11 thousand dollars for the conversion. :ahh:
Anyhow… I think you’ll be seeing an electric go kart around this summer in indy…
So did I see you said you want to race electric cars…?
You could start with a relatively low-cost (say a couple grand, depending on how fancy you get) Electrathon race car. We used to build them back in the day before we became team 1346. I’ve put some video up on youtube here: http://www.youtube.com/watch?v=yjO6xp-Tz8Y
There are many, many articles available on the web concerning electric vehicles and mods, etc. While lithium batteries are cool, most conversions still seem to be based upon lead-acid, simply due to the fact that you can get huge amounts of current for relatively low cost.
If you want to work with lithium batteries without breaking the bank, may I suggest using them for radio-controlled electric airplanes? For a few hundred bucks you can build a plane with a thrust to weight ratio greater than the F-22. We are building them in my Engineering 12 class and tried replacing the NiMH batteries with Li-Poly today. We can now launch the airplanes straight up… no taxi… no runway… just straight up like a rocket. Now THAT is cool.
If you want to retrofit a go-kart, you could pull the drive and controls from a used electric golf car. Most electric golf cars run 24-48v, 3-5hp motors, and have max. speed of ~20mph.
I know you can pickup used golf cars very cheap, if they have bad batteries.
If you wanted to spend a little more you could replace the analog controls, most older golf cars use, with digital controls.
Back when I was in Kentucky, we used them Cushman electric trucks for getting around. Well my supervisor and the supervisor from the other shop were in the habit of trying to out do each other in tweaking their shops Cushman to be the fastest, or have the most pulling power.
Ah the memories of cushman drag races in the tunnels on 3rd shift…
and the stinking blue cloud of smoke when you burn up a motor.
Anyhow, you can find old Cushman’s for a grand or two… from there you can build all kinds of things out of them.
And if you want to race… I got a buddy in Lexington KY with the fastest Cushman you’ve ever seen. I could set up a race… hehehe
Well You could easily make a VERY powerful electric go kart from 4 AM 2 CIM 2 speed shifters and 8 small CIM motors. If you saw the video that was posted a while ago ( I don’t remember what team ), but they took an old swerve drive module and was driving people around with 1 CIM motor. The frame should be brutally simple. Get a Kitbot frame, I personally would trust it, as the cross section of the rails has great structure vertically. It is easy to mount to and a nice size. You can then use 6 of the 18 AHr Batteries to power it. That should be fine for a nice short ride. You can do a 4WD config with u joints on the front wheels for the drive or do a 4wd with 4 back wheels or chain up all 4 transmissions to the back 2 wheels (my preference). And run a simple steering mechanism on the front. No need for fancy rack and pinion steering. I have thought about doing this ALOT in recent years, but once again lack of money ahs stopped me.
Another thing you could do is go talk to a mini baja team in your area and see if they would be interested in donating a car to the cause.
Nimh batteries are NOT the way to go. I have recently turned my back on them when they required constant peaking for max output. They are heavy, loose charge very fast, and must be cycled around every 20 days or so. Lipos is what I use now for my r/c cars/boat/planes/helis. As dt mentioned, with lipo you hold the plane in your hand and give it not even 100% full throttle and just release it. A 6 cell 3800mah NIMH pack weighs a pound, a 7.2V 5000mah lipo pack weighs half of that, holds its voltage longer and allows for larger current draws. However, lipos are dangerous if not taken care of. They do blow up and they do set people’s cars/houses on fire if not kept in safe spots. They only do that if cells are unbalanced, or have been damaged but the damage went unnoticed. They are also very expensive :o. Your idea is a great one, as a matter of fact about 2 weeks ago I started thinking of the same thing, but instead converting something like a hatchback. I looked into it and it seems that a DC motor is more optimal than AC. A brushless motor of that size would be more expensive than brushed, and probably hard to find. DC brushed are sold at websites like this one http://www.electroauto.com/
