Quote:
Originally Posted by madmike8
True, but isn't the point of PWM to turn it on and off so the motor sees an average voltage... Ie 50% PWM the motor will see an average of 50% of the battery voltage.....
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A friend of mine has a factory converted EV, but it's an older one, and the original controller wasn't very good. (The original may have even been contactor-based!)
A friend of his (who happens to be an electrical engineer who works for the power company) built a custom DC Motor controller. It's not an Open Revolt, just something he made, but he did a really nice job on it.
The neat feature on it is that it can take a higher voltage in and run it to the motor as a lower voltage. I think the idea for it was that he could have a higher voltage battery pack than what the motor was designed for. (I think it was a 72V motor and currently has a 144V battery pack)
The higher voltage pack means lower amp draw, smaller wires, etc. (True, you can get some of the same advantages with "buddy-pairs" or other ways of paralleling batteries, but you quickly get stuck at particular size packs, voltages, # of batteries, etc.)
I remember that the output voltage to the motor was reprogrammable. So, I think that it wasn't a DC/DC setup inside the controller, but rather just used PWM to limit apparent voltage, I think - don't quote me on that.
What I was originally going to suggest is that you could use whatever higher voltage battery pack you want, and then limit PWM duty to whatever the correct percent would be. I don't know exactly how you would do that in the code, but I think Paul stated it pretty straight forward in the post directly above this one.