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Step 7: Controller

The controller is an important part of the electric car conversion.

The controller is a solid-state electronic box that controls the power (speed) between the batteries and the motor.

My controller is a Curtis 400 amp peak PWM controller designed for use with series-wound motors. It can run on 48-72 volts.

The higher amperage your controller is, the better your acceleration will be. The higher voltage, the better top speed and efficiency of the car.

Also, keep in mind that amperage is also what defines range in a battery. Capacity is marked in Amp Hours, but draining a battery at double the amps will give you LESS than half the run time! Having a controller running higher voltage will use LESS amps to do the same amount of work.

What's this mean? Buy the highest voltage controller you can afford! 48 volt controllers are cheap, as they are used in so many golf carts. 100V+ controllers get expensive real fast.

My 72V controller seemed to be a good compromise of cost and efficiency. I bought it slightly used on E-Bay for $300.

Follow the schematics available through the controller manufacturer to connect the batteries to the controller and motor with heavy gauge cabling, such as welding cable, with solid, heavy-duty lug terminals on the end.

The controller requires a 0-5Kohm potentiometer as a "throttle". This could be as simple as a $3 Radio Shack part, or as fancy as a purchased, specialty part such as a Curtis PB-6

I split the difference and installed a 0-5K pot inside a free-from-the-junkyard forklift throttle control.

Run the gas pedal cable to the potentiometer, so that when your foot is on the gas, it sends a variable signal to the controller.


Update! I later switched over to running an Open ReVolt motor controller. It's the same one you can find here on Instructables at http://www.instructables.com/id/Homemade-100-HP-Motor-Controller-for-an-Electric-C/
That controller is good for up to 144V and 500amps.
I'm sorry I just saw how much it cost :) you're amazing!!! :)
Hi :) how much did your conversion cost in total?
<p>This is great! I have a little 1995 Ford Aspire, automatic transmission but manual everything else, with medium mileage (80,000). The plan was to run the little bugger into the ground while saving up for a Leaf...but converting it in advance of that (and selling the engine!) sounds much more appealing. Does this process work with an automatic transmission? And 90s Aspires are basically Geos, right?</p>
<p>Are these the regular lead acid batteries we have in cars to start the engine, lights etc?</p>
<p>Hello</p><p>I want my production Electric Car</p><p>But I do not know where is the best engine and the best battery</p><p>Where To Buy</p><p>Please tell me</p>
why try and build some type of altenator that way while u drive it can charge batteries and drive unlimited
<p>because you would be breaking the first two laws of thermodynamics which make doing that impossible</p>
It is not impossible.
<p>It's possible to build, but it wouldn't work so why bother?</p>
<p>a kers system would be excellent on a setup like this, get back some of that power wasted stopping after all that's supposed to be the general purpose of electric vehicles Is efficiency</p>
<p>Who is your insurance provider? I have spoke with 3 so far and they all wont insure a car with a BOM.</p>
<p>You are my hero ! ;-D<br>I will build my own electric car :-D</p>
<p>This project is so advanced but yet does not look that complicated after all. However, I think you would still require a tyre and rim insurance after being done with the conversion job. This is just to help safeguard yourself against any possible unfortunate events that might follow you in your DIY masterpiece.</p>
<p>but does'nt the motor overheat</p>
<p>but does'nt the motor overheat</p>
<p>but does'nt the motor overheat</p>
Awesome sauce!
I thought that transmissions were only for gasoline cars. Why did you have to put one on an electric car's motor?
<p>Most motorized things require some form of a tranmission, electric, diesel, propane, and gasoline engines all typically do dependin on application. They do so for two reasons, one in earlier rwd cars the crankshaft of the engien couldn't directly be hooked up to the wheels, so a gearbox drive shaft, and rear differencial are needed, to change the direction of the power output. Secondly and more importantly, without a transmission of some form the engine would always be engaged to the wheels, meaning the second you start it up, even while idling it will be moving, constantly moving, and with such a setup the brakes would be fighting the motor all the time making for horrible stopping power and great potential of either a damaged motor or failed brake system, the clutch/torque converter allows them to disengage from eachother, allowing you to stop.</p>
<p>How do you change gears without a clutch?</p>
<p>It's surprisingly easy. Just rev the motor up to the right speed, and push it into gear. It took about a day to get used to for me.</p>
<p>That's how most truck drivers do it...</p>
<p>Automotive transmissions aren't made the same way truck transmissions are. Truckers don't shift like that right off the get go, either. Takes some time of learning the truck and how it shifts by shifting properly. I'll be doing this conversion to a 2009 Base model standard jeep compass, and I'll for sure be keeping the clutch. I guess It'll be easier to maybe take out the clutch? But for longevity, keeping the clutch is the smartest way to do it. <u>In my own opinion!!!</u></p><p>More fun that way as well.</p>
<p>MPaulHolmes, does changing the gears in this way not damage the gears? I'm asking, not to be critical, but because I am hoping to build my own EV. I'm wondering whether I need to try to keep the clutch. It seems like most people don't use a clutch, but to me, that sounds like it would damage the transmission pretty quickly.</p>
<p>Mate that was awesome well done something to be proud of :-)</p><p>One thing is I was wondering to save battery power would there be an advantage installing a light flywheel to install the clutch so you can change gears?</p><p>I know electric motorcycles benefit greatly if they have a manual gearbox.</p><p>It requires a lot less power to take off and maybe a smaller motor could be used.</p><p>It would not be that hard to do.</p><p>Regards Rik</p><p>Home Mechanics</p>
<p>This is a great project, thumbs up..I have 2 points to raise: did u do the math how much $ u will save till batteries ascend to God ? the other thing is what about all those bloody sensors hooked all around the notorious combustion engine ? how to keep them quiet from making the computer stop the car ?...oh.. on a 2nd thought, what can the computer do ? cut the fire from plugs? or shut the carbeurator ? they re kicked out of the car anyhow..still some sensors that bring signals to dash may need to modify.</p>
<p>For someone who claims to have a low level of knowledge about cars I salute your ability to soldier on in any case. I am a mechanic and looking at your project for the hints on how to go about the conversion. LOL</p>
Why did you put a trans. To the motor, i thought that transmissionswere only for gasoline cars, why?
Ever put a solar panel on electric car????
<p>hello</p><p>i wanted to now more about it </p><p>i like elec car wil you help me</p><p>greetings sam</p>
<p>Hi guys,</p><p>you are the pioneers of electric cars so I would like to invite you to join 80edays, the hardest EV endurance test driving around the world! </p><p>I would like to make a link exchange with this great website.</p><p>Kind regards</p><p>Rafael de Mestre</p><p><a href="http://www.80edays.com" rel="nofollow">www.80edays.com</a></p>
<p>Hi Ben! The ecomodder and 300mpg links aren't working.</p>
<p>They worked when I clicked them. Maybe try a different browser or check again later. You can always do a google search if you needed to.</p>
<p>the motor u used is a universal motor(ac/dc) or a PMDC motor??? nice work.</p>
<p>It's a series-wound DC motor, 10.5&quot; diameter, Nissan brand, originally out of a full-size electric forklift.</p>
<p>Thanks for all the great information. Have you found another electric engine as a power source other than from a forklift?</p>
<p>Hey thank you for this intractable! Definitely puts the idea in perspective. The question I have is what do you think would be the weight max of a car you wanted to convert to electric and still be efficient/practical?</p>
<p>Where do you find the batteries that cheap?</p>
<p>With gas being $2.10 a gallon, why would you want to ruin a perfectly good running Geo Metro, which has 3 cylinder engines and averages 50 MPG anyhow? </p>
<p>Gas is only $2/gallon at the moment. In my area, a few years back, it's been as high as $4.50/gallon.</p><p>Electricity is cheap. At my electric company rate a &quot;gallon of electricity&quot; works out to about a dollar, so it's still HALF the cost of even &quot;cheap&quot; gasoline.</p><p>Also, I can make my own electricity, but I can't make my own gasoline. (For example, I can charge a vehicle from this: <a rel="nofollow">http://www.instructables.com/id/Solar-Swing-Set-PV...</a></p><p>Lastly, the Metro actually wasn't in working condition when I bought it. It had a some problems, including the starter and the transmission. The engine did run. When I converted the car, I sold the engine to a Metro owner whose engine had died, so that he could fix his up and keep it running.</p><p>Besides purely the cost of fuel, there's all sorts of other reasons to build an electric car, such as the great learning experience. Also, just test drive an electric car sometime - it FEELS different than a gas car. You can't help but smile!</p>
It's different with an electric motor than with a gas engine. With the motor, there's not all that extra weight of the flywheel and the power of the engine still idling when your foot isn't on the accelerator. Just let off the accelerator, wait a moment, then shift. It's really easy. It's one of those things that's hard to explain, but if you experience it, you just go &quot;Oh, that was easy.&quot;
<p>just a few things that might help, one take the batteries out and buy a cheap generator from harbor fright about 120 and that will give you over 5 hours of use per 1.25 gallons of fuel, and it would atomatically regulate its output based on the demand from the motor, also keep 2 batteries in to bridge the gap between the generator giving more power and the drain for the motor, and 2 buy a thing of 20 gauge nichrome wire and make a coil around a tube put a small fan at one end and attach it to the vent that would normaly be the input from hot air from the engine, and then wire it to a potentiomiter/switch and then 1 battery that way you can turn on off and controll its heat output, and then i want to do this type of project, how hard was it to adapt the motor shaft to the cars transmisssion?</p>
<p>absolutly no. buy a utility trailer and put a generator on it. only need to use the generator when driving over the charging range. then you'd never need to discharge the battery on long trips increasing the balling-ness of your road trip. in fact, get an old VW diesel for the generator. I know it would get good MPG, we took one from Vancouver to Alberta at 15.00 dollars spent on diesel. the Olds that we took that winter was 80 bucks every time we saw a gas station. EV cars plus diesel generator makes long ass road trip.</p>
<p>hola si el auto que tengo que convertir es manual no tengo que montal la volanta para hacer los cambios gracias alfredo</p>
<p>Mr. Nelson, i don`t speak english well but i need your help. I`m a Colombia Mechanical Engeenering, living in the north of Brasil -Amazonia-, working like mechanical automotive teacher, and I am looking for a course in USA about car conversion, including theory and practice. Please send me information. Thank you. </p><p>Gerardo Mu&ntilde;oz Herrera.</p><p>gerardo2502@yahoo.com</p>
Hello, super inspiration and my big dream for many years! BUT, what about technical licence? I don't know US laws, but all european police patrols strictly check the &quot;papers&quot; of a car and &quot;conersion&quot; like this is direct order of very big fine :-(. <br>If it's easy or free in the US, I'm quietly envying, but I'm afraid, nor there is it possible...

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