Homemade 100 HP Motor Controller for an Electric Car

This instructable explains how to build your own 100 HP (peak) motor controller for use in an electric car or motorcycle conversion.  It can take any voltage up to 144v, and the peak current is 500 amps.  The cost of the components is a few hundred dollars, which means you can save over $1000 by putting one together yourself.   At 144v, you can expect a top speed of around 75 MPH in a car. 
Check out  http://ecomodder.com/forum/open-revolt-open-source-dc-motor-controller.html
if you want to read about the whole story!

Experience in soldering is important.  If you want to really keep costs down, a mill is helpful, but that work can be outsourced to a local metal shop.

Step 1: Get/Make a power board and control board.

You are going to need a control board and etched power board.  The power board needs to be at least 3 ounce copper.   Ebay is a good place to look for heavy cheap copper clad PCB.  For example:
http://cgi.ebay.com/25-shts-Copper-Clad-Laminate-FR-4-060-9-x-12-3oz-/310244821519?pt=LH_DefaultDomain_0&hash=item483c084a0f

You could print the picture from this link and somehow transfer it onto a piece of heavy blank PCB, and etch it with a dremel if you have a ver y steady hand.  The dimensions are 8"x6".  This link also has the G-code that you can use to etch with a CNC mill or you could give the G-code to a machine shop.
http://ecomodder.com/wiki/index.php/Open_ReVolt/Fab_Files

Picture 2 and 3 below is an example of an early power board I made with a Dremel.

You can get a control board from me or you can make the control board in your favorite PCB layout software using the schematic here::
http://home.cogeco.ca/~tkooistra/Cougar_Controller_Rev2C_Schematic.pdf
And here are some pictures of the PCB layers:
http://home.cogeco.ca/~tkooistra/bottom_layer_rev2C.pdf
http://home.cogeco.ca/~tkooistra/top_layer_rev2C.pdf
http://home.cogeco.ca/~tkooistra/component_layer_rev2C.pdf

A predone control board is Picture 1.

Pictures 7 and 8 are the power board top and bottom.  The 8 solder spots are just where vias were added.

Once you have the 2 boards, you can go to step 2. 

Comments

[anriocarver]

What is the price for one 144Volt 500Amp already built. Ready to use.
My email address is [e-mail]
I leave in Mauritius.

[mihnea1970]

Hi,
I can not download the schematics for the control board. Please help.

[jimmerforpoy]

Does this work for all ev conversions under 144 volts?

[MPaulHolmes]

Yes.

[jongscx]

As a follow-up, Is it possible to "scale down" the design if I'm never getting near the 144V/500A power requirements? Do I just use fewer mosfets and caps?

[Nav]

Okay so I am a novice in all things electric car, but I'm wondering if throwing 4 of these controllers into a car with 4 forklift motors somehow connected to the axle would result in a 400HP car? I'm sure it doesn't work like that but could someone please explain the pros/cons of this to me? Thanks and awesome instructable!

[MPaulHolmes]

Yes you could.

[DieCastoms]

Ok, so.. I have what used to be a small-sized 3-wheeled 24-volt "Mobility Scooter". I am building a large RC vehicle out of it.

I need a motor controller for 24 volts that will run the thing either from a wired throttle or eventually a servo output from an RC receiver OR an actual servo mechanically coupled to a pot that is wired to the controller (This should give perfectly isolated power from the vehicle's 24 volt system and the RC's 6 volt system, yes?)

I WANT to have the option to run it via RC or to be able to plug in a wired controller because the vehicle will be large enough to sit on when complete.

Can someone please suggest a source for such a controller? I DO NOT have the original controller from the Mobility Scooter, or I would gladly just use it. I know I could buy another controller for the chair or a similar model, but I would like to see what else gets suggested, first.

Thank You!

DieCastoms.

[abdellah309]

good job Paul, can you post the schemetic of Mosfet stage.
I'm working on electic car project in Algeria.
Many thanks,

[epuneet]

Is this circuit work for lower power ratings i.e. for 20 Hp motor

[bertzie]

What kind of modifications would need to be done to make it take 170v 2000amp?

[IT BITz]

COOL

[Donotmatthews]

I have a 36v forklift motor, I was wondering if this would suffice for a electric car?

[MPaulHolmes]

Probably! If it weighs at least 60 pounds, and has a 1 hour rating on the name plate of at least 100 amps it should work fine. The voltage rating is almost meaningless.

[steveastrouk]

How many quadrants is this thing ?

Steve

[MPaulHolmes]

I don't know what that means. All I know is that it's for a DC motor. There's a single PWM. Reverse happens by putting the car in reverse, and you go forward by putting the car in 1st, 2nd, ...

[steveastrouk]

Hi,
A quadrant is the measure of motoring and generating, in forward and reverse.

1st quadrant. is motoring forward, 2nd quadrant is motoring backwards, 3rd is generating backwards, and 4th is generating forwards.

You can implement 1st and 2nd quadrant with a relay, you can't do 3 and 4th without a full bridge.

So essentially, can you do regenerative braking ?

Steve

[MPaulHolmes]

It's intended to just run series wound DC, which I think usually has problems with regenerative braking, since the brushes are usually advanced, so I didn't make it to do regenerative braking.

[steveastrouk]

By "advanced", do you mean the brushes are angled onto the comm. ?

Steve

[MPaulHolmes]

No, there are different sorts of brush timing. neutral mean forward and reverse can be done basically the same, and I think regen is easier then. When you physically move the brushes more one way or the other around the rotor, it helps to reduce arcing and lets you run at a higher voltage, but then you can't run the motor very well in both directions, and you can't do regen.

[steveastrouk]

Thanks for that briefing. Traction motors are not my usual area of expertise - I usually work with precision servo motors, with very low inertias, gold commutators etc !

[bumsugger]

What an absolutely stunning project.............I'm blow away by the ingenuity of it all despite not being into all the "save the planet c*ap" thats floating around at the moment.My one reservation is that,with these electric vehicles all being so bloody silent,just what wattage of horn do you need,'specially if'n youve a motorcycle,lighter and faster than a car,and how do you know that you're not going to "flatten" the battery with all the horn tooting?

[ivanbakas]

There are off the shelf very low power consumption "noise makers" that can make an electric vehicle sound like anything you want. Tesla uses it on their cars.
Lets not let small things like that derail a movement to the right direction

[ac-dc]

How about a standard motorcycle horn?

You won't be tootin' the horn enough to make an appreciable difference in battery pack life, they tend to be under 75W and that for a second or two, but it is possible you could be doing it often enough to be a nuisance. ;)

The main way to be safe on a motorcycle is not by making people hear you, it's by making them see you. People have to look around to drive while their ears may be occupied by a cell phone, stereo, etc.

[bumsugger]

Stil can't H-E-A-R a fast car or bike ENGINE tho' can you??

[Pazzerz]

After following all the links and schematics and BOMs, the thought came to me: Wouldn't it be easier to include all those items in a single .zip file? I have to keep looking to see if I missed something. What do you think?

[MPaulHolmes]

I think that's a really good idea. It's a work in progress, and I still need to transfer some of the G-code from the garage computer which is older than dirt and pre-internet.

[steveastrouk]

I'd've been inclined to put more gate drives on here, those Mosfets take some driving. Have you tried it ?

[MPaulHolmes]

(removed by author or community request)

[steveastrouk]

Do you use low ESR caps ?

[MPaulHolmes]

For electrolytics, they are very low, and 16 in parallel works out to an Equivalent Series Resistance of maybe 18mOhms. They also are rated for 3000 hours at 105 degC, and much much longer than that at lower temperatures. In practice the capacitors outside stays around 60-65 degC in Phoenix in the summer, so they should last quite a while.

[kmpres]

Very nice project! I cut my eye-teeth rebuilding VW Beetles in my teens and wanted to electrify them but electronic controllers back then (mid 70s) were not as advanced or simple to construct as they are today. I'd do it today if I had the space and time. One question: Could you add regenerative breaking to a system like this using just the main motor and differential or would that cause tire traction problems on wet or icy surfaces? Seems to me separate motors in each wheel-well and a system to control them are required and that might be difficult for a DIY VW or Geo Metro conversion, yes?

[wirecutter]

A 500 Amp beetle hot stuff and 75 mph with it, my fist bug only ever reached 65mph with all windows fully closed! A nice instructable
Is there a full circuit of it ?

[MPaulHolmes]

To borrow a phrase from Napoleon Dynamite, HECK YES THERE IS!
http://home.cogeco.ca/~tkooistra/Cougar_Controller_Rev2C_Schematic_All.pdf
 Although that was a older schematic that used 24 470uF ripple caps.  Now I use 16 1000uF ripple caps. 

[madhavdivya]

Great job Ben, can you let us know further details regarding the motor specifications , time and distance between recharging the batteries, etc.

[bmwsid]

I have an electric motor from a Cushman Minit miser, it is 24V D.C. I actually might have 3, but I have one on the bench right now.
If anyone would like to buy it, drop me a note. [e-mail]
I have no idea what shipping would cost, but it is pretty hefty.
716-525-4900

[afbcom]

Hey,

Just a thought, you could eliminate a lot of voltage spike issues by mounting the controller as close to the motor as possible. Any time the length of the wire between the motor controller exceeds the diameter of the wire, the collapse current becomes significant. Since Vpeak = di/dt, and you have a peak current of ~500 amps, if your switching time is <1ms which I'm guessing it is, this will result in a spike of 500 000 volts! These voltage spikes can damage the control circuitry. This is assuming that you are having voltage spike issues to begin with. Regardless it is typically a good idea to mount the power control board as close as possible to the motor.

-alex

[Ziggythewiz]

"Any time the length of the wire between the motor controller exceeds the diameter of the wire"

I'm pretty sure every wire I've ever used was longer than it's diameter.

[megapix]

Just a little correction on the math for the voltage spike. The voltage is V = L * di/dt where L is the inductance of the wire. For a couple of feet of wire this could be around 1uH (microHenry = 10e-6). So for a 1mSec switching time you would have 0.5V, and for a 1uSec switching time you would have a 500V spike. So it is worth being careful about, but not as severe as your calculation.

[afbcom]

thankyou for the correction. Now that I think about it, 500kvolt is a bit large sounding eh?

[MPaulHolmes]

I've done some voltage spike tests, and at 500amp, the spikes are about 20 or 25v, so it's not too bad. I'm using 200v components, so at 144v, I'm still a fair distance away from danger. The nice thing is, under heavy current, the battery pack voltage sags, so the net result is that the voltage spikes are about 20 or 25v above like 135v in the worst case.

[killersquirel11]

You could also include a TVS diode to protect against the spikes if they are too large

[MPaulHolmes]

Hi Killersquirel11! Great minds think alike! haha. I'm using the P6KE20A-T transient voltage suppressor. Nothing goes over 20v from gate to source, and gate to source is rated for up to 30v, so it's kept safe.

[afbcom]

Cool!

Not that I doubt you, but where are you measuring the spikes. The ones that I am referring to is the reverse against the driving fets from the motor and supply cables to it. If you're getting results around 25 volts then you have done a damm good engineering job and kudos to you sir.

--alex

ps awesome response time

[MPaulHolmes]

Hi afbcom! I measured the voltage spikes from drain to source of the mosfets. Every time the mosfet turns off, the voltage from drain to source goes from nearly zero to full pack voltage, and it wants to keep going past pack voltage. I also use some polypropylene metal film capacitors to help snub the spikes. My friend in Phoenix has a video of the spikes on his oscilloscope. I'll find it. When I tested it in my car, I just used a peak voltage detector (like a crab trap. but instead of crabs, it traps electrons. haha):

[jerkey]

I can't see exactly where you're connecting your measurement probe, but it is necessary to connect both the probe and the ground as closely as possible to the place you're actually measuring, because inductance is playing a huge part in what you're dealing with, and even an inch of wire can have an effect. The voltage spikes are a danger inside the MOSFETs so thats where the probe should be.

Another issue is that the voltage spikes are a result of firing into a reactive load, which is more like a motor prevented from spinning. A freewheeling motor (which I heard) will not cause inductive kickback as much as if you lock the parking brake and do it, you should try that.

A wise teacher of mine who makes giant stepper-motor controllers (and Aerco pre-amps) says that the key to protecting your fets is a combination of small and large diodes (they have different properties) and resistor-capacitor snubbers and most importantly, MOV (Metal Oxide Varistors) which are your first line of defense.

But i definitely know that the spikes are worst when the motor is stalled.

[acelondon]

In the EV community, we use freewheeling diodes to take care of all the inductive kickback from the motor. Ususally rated at LEAST the same as the switching device. My IGBT controller(inspired by Paul's MOSFET controller) will be built for 1200 amps, with 1200 amps of freewheeling diodes, AND be run at 750 amps. Should last a while XD

It's my senior project for college. Great excuse to rip around campus with a less than legal electric car!

[MPaulHolmes]

I didn't make that video. It was actually my beta tester. I've done testing with a locked rotor, and the spikes were around 25v, at least with my peak detector, which was a diode and capacitor. electrons could get in and not back out. That was the crab trap I was referring to above. A locked rotor has almost no resistance, so the current is huge, and the voltage spike is di/dt*L_stray, so a larger change in current definitely gives a larger voltage spike. The nice thing is, there may be optimal ways of doing things, but his controller has run for over a year and a half in sometimes 110 degree weather and it's still going strong, and that was not withstanding my crappy assembly process, since it was the first or 2nd one I put together.

[afbcom]

This just goes to that what you read in a textbook doesn't necessarily apply to the real world! Nice scope. There are commercial products that aren't as well designed as yours... friggin cool!

[acelondon]

Hey Paul, i'm glad you posted this. I've been following your wiki for some time, and that crazy long thread about you controller. It inspired me to make a PIC18 micro/IGBT version for my senior project as an Electrical Engineering student. Your open source concept is what we need in the EV world, not the Iwantaquickbuck outlook most places have. EV's are different than gassies, like keep it that way!

Between you and the Soliton 1, you guys are all the inspiration i need!

[bennelson]

I did another "gravel burnout" test with the 144V controller later. Too bad I shot it with a DSLR that only shoots 24P - it doesn't give the full sense of motion. These tires were REALLY spinning!!! I've gotten a speeding ticket in this car with the Open Source controller....

[bennelson]

Hmm, I can't seem to be able to embed that other video, but here's a link to it: http://www.youtube.com/watch?v=0nIIPsVfUm8

[MPaulHolmes]

Awesome Ben! You stinker, I would never have thought to do a burnout with the ebrake on. hahahaha.

[Mad_Hatter00]

Those are quite possibly the creepiest eyes I have ever seen!