Sorry, I replied before reading your original question -
The answer is that you should probably get one of the large Curtis 
controllers or one of Cafe Electric's Zilla controllers (with the wait 
time over 6 months probably)
The Curtis controllers are designed for forklifts. They have many medium 
power MOSFETs in parallel. The Zilla controllers use large and powerful 
IGBT modules. The Curtis is the least expensive way to get going unless 
you want to use what they call a contactor controller in which your 
batteries are combined between series and parallel sets with which to 
vary the voltage that reaches the motor. Sometimes a high power resistor 
is also used so that you can have a smooth transition between changes. 
It's not the "cool" solution but if you're just running your beetle on 
60 volts or some such, it should be ok. You aren't going to run your 
beetle on 36v are you? You won't be very happy.
Check out evdl.org too. They would be able to provide much more 
specialized help than the piclist.
The general consensus with everyone who asks about building their own 
500A motor controller because it might be cheaper is that it won't be, 
not even close.
If you want to build one and you have lots of time and money and you 
enjoy difficult challenges, it would be fun.
--
Martin K

peteHVAC wrote:
> I'm adapting a forklift motor to power my trusty 72 beetle.
> So far the mechanical part has been easy. The motor is a 36V 90lb
> monster and I'm guessing it can draw upwards of 500A. Controlling
> this much power has me stumped. I have the SCR control board from
> the forklift but no schematics. I have found a lot of sites selling
> controllers but not too much info on doing it yourself and looking up
> the components for the original controls hasn't turned up anything. If
> anyone can steer me in the right direction I'd be very grateful.
>
> Thanks, Pete 
>   
-- 
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