As a concept: Cell configuration change during load

I am new at this and trying to get my head around all the technicalities. An idea I just had please correct me if I am wrong.

If one can change the connection between groups of cells from parallel to series with a flick of a switch.

For pull away to have low down torque, high amp draw at lower voltage have the cell connection I parallel. At higher speed switch to series to up the volt, amp demand to sustain the speed is lower.

What am I missing?

1st problem is you would have to remove power from the controller during the switch from S to P. So the controller would need to reset, the capacitors would either need to drain or charge, and the controller would need to reinitialize the throttle. That could happen fast, but not instant.

the second problem is a matter of practicality. Torque and speed are made by watts. We often say add voltage for more speed, and amps for more power, but that's perspective issue.

If you have a 36 volt 20 amp controller, and you want to go faster, you bump up the voltage. If you want more torque, you increase the amp limit. But that's not the whole story. If you want more torque, you could just increase the voltage, which would give you higher wattage, increasing your torque.

So the best plan is to pick a voltage that gives you your desired maximum speed, then pick an amperage that gives you your desired torque. if you want to govern that for any reason, either install a Cycle analyst and program speed and current limiters into it, or add a 3 speed switch and program it for the power levels you want.

The "volts for speed / amps for torque" theory is a myth, debunked in lab tests by Justin @ ebikes.ca.

If what you want is just to limit WOT (wide open throttle), a 3-speed switch is a good solution.

Ok thanks. Stick to the old principles then

Another issue is that the low voltage cutoff won't be able to function correctly in both cell configurations.

Not happening at a switch flick, on the fly. But you can get controllers with a pretty wide range, and plugging in a few plugs can be done in 10 seconds.

Yeah I know, intolerable to stop for 10 seconds to plug in 72v at the bottom of that hill. Way too much trouble to unplug the battery, and plug back in, in series, with a 24v boost pack in place.

I have one controller that runs 48v-72v with a jumper plugged in. Unplug it and it goes to 120v. That's some pretty good voltage range. That jumper could be put on a simple switch, but I'd still have to stop to change the battery plugs.