Can I bypass the controller at full throttle?

[Ryland]

I'm hoping to look at an electric car that needs a speed controller, it also has a Warp 11 motor, so a 500 amp speed controller is really being stressed under peek loads.
So my question is, how would the controller react if it was bypassed while under full load like that? and would it need to be cut out and excluded from powering the car or could it just have a contractor put in parallel?

[MPaulHolmes]

I think it would just go from max amps to zero amps really fast. if it was an open revolt, it would just keep trying to command current that is proportional to the throttle. But zero amps would go through. That would then ramp up the pwm duty to 100%. The newer software would then flag a fault because of the 100% duty/zero current scenario. You would have to lift your foot off the throttle to clear the fault. Older software would just ramp up the duty to 100%. Then, if you suddenly opened the contactor, the controller would act almost like a dead short and if the overcurrent doesn't come on fast enough, things could blow up.

[Ryland]

So in short, it would work it sounds like? an error code would shut the controller down for me and lifting my foot off the accelerator would leave me in the same state as if I had just taken my food off the accelerator... right?
I'm not sure if this will even be needed but I know the question has been asked before in passing so I thought I'd try to get a good clear answer once and for all.
A friend of mine has a 1000 amp controller that is dialed back to 500 amps, he of course has 4/0 wire... huge battery cables! so his whole system could handle 1000 amps, but i drove his EV and at 500 amps it seemed like plenty.
Of course it might not be worth the added cost and trouble to install a bypass contactor like this, instead of just getting a larger controller and of course it's not good for the batteries.

[MPaulHolmes]

As long as you be sure to take your foot off the pedal before opening the contactor (when you are done with the super turbo mode) I think it would be fine.

[bennelson]

Sometime back, I did a "Turbo Button" for the Electro-Metro back when it was running on 72V.

The idea was to increase system voltage for a higher top speed than the PWM controller I could afford would support.

Ryland, it sounds like you want to bypass for increasing current, rather than increasing voltage.

At almost any voltage, 500 amps is a respectable amount of power. You only ever pull peak amperage during really hard acceleration or big hill climbs (or really bad gearing!)

It always seems like the point of good electric car design is to MINIMIZE current, except when you really want some OOOMF! An 11 inch motor by default doesn't draw some tremendously greater amount of current than, say, a 9" would.

I think the easy answer would be just to put a 500 amp controller in the car, and try taking it for a few drives. If you really aren't happy with it, go with a 1000 amp. At some point, the batteries will be the limiting factor!