Paul & Sabrina's cheap DIY 144v motor controller

[madmike8]

Is there a setup information page for the revolt controller? Something that tells what settings can be adjusted, and how? Is there a way to set a motor voltage limit? So, if I ran 120v worth of batteries, can I set the motor to see like a 80v max limit?

Thanks

[harlequin2]

Forgive me for saying so, but that is a strange question! A motor controller works by switching the full battery voltage on and off very rapidly and it controls the motor by varying the on to off ratio, so your motor always "sees" the full battery voltage while the controller is on. Basically, that onff ratio is controlled by the throttle, ie full throttle = always on, no throttle = always off. So you see why that is a strange question.
If you look at the controller pages you will find reference to the controller parameters that may be varied by the user.

[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. Is there a way to set the max? I can't find the settings pages... Then again, I'd you ask my wife, I suck at looking...

[harlequin2]

If you hook up RTD Explorer you will see all of the parameters that can be changed, there's quite a few.

[adamj12b]

Originally Posted by madmike8

Is there a setup information page for the revolt controller? Something that tells what settings can be adjusted, and how? Is there a way to set a motor voltage limit? So, if I ran 120v worth of batteries, can I set the motor to see like a 80v max limit?

Thanks

With the current control board there is no way to control motor output voltage directly. I think there is a way to limit the pwm output but tricking the controller, but I cannot remember how off the top of my head. I will look into it tonight.

The new control board im developing, called The Uprising, will be able to directly control motor voltage and compensate for sag. This way, if you wanted 100V max and had a 120V pack, heavy acceleration could cause a sag under 100v so the controller would then give 100% duty instead of just limiting duty to 83% duty. When the system recovers, and the sag decreases, the controller will start limiting duty to maintain 100V max at the motor.

[MPaulHolmes]

Damien, is there any word on your controller?

madmike8: You could set throttle proportional to PWM duty, and then limit max throttle to whatever level you wanted the max voltage to stop at. It would only be a couple lines of code to add a "max output voltage" variable to the current code.

[bennelson]

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.....

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.

[dave koller]

Ha Ha Ben I thought in Wisconsin we just put a block of wood under the gas pedal

[MPaulHolmes]

hahaha. Ya, basically that's all it's doing. The software equivalent of a piece of firewood.

[bennelson]

Laugh all you want... but,

According to Paul:
" set throttle proportional to PWM duty, and then limit max throttle to whatever level you wanted the max voltage to stop at."

Assuming that the accelerator pedal allows for a range of 0-100% throttle, physically limiting the accelerator (with a block of wood) to the maximum percent voltage you would want would work fine.

I would put that solution more under Yankee Cleverness than Redneck Engineering.

We do sometimes allow ourselves to make things more complicated than they have to be or think that there is only one way to "do things right".

In this case, doing the work in the electronics programming level sounds like the best way to go, but if you want to drive your EV like the kid at the beginning of INDIANA JONES AND THE TEMPLE OF DOOM, I won't stop you!