[BrianG]

I think what people are saying is this: Yes, a higher geared (larger pinion) does require more work for the motor to propel the vehicle (less rpms per mph), but when braking, the vehicle is now spinning the motor less rpms as well. Likewise, a smaller pinion makes the motor spin faster per mph, and when braking the motor spins faster creating more back-EMF. I can understand the thought process, but the few tests I've run show that low gearing creates the highest back-EMF voltage, but these bursts are short and current is lower; while high gearing creates lower back-EMF voltage, the highest back EMF current, and the pulses lasts longer.

There are several ESC-killing issues; all this talk of one thing is ignoring the rest. All are affected by battery and setup choices:

1) Overcurrent. This is just the result of a setup that is geared too high and/or too heavy using a motor with too high a kv on whatever voltage. Nothing to do with ripple, braking, etc. I think most decently-designed ESCs can handle these bursts currents, but the resulting excessive heat from losses at high currents does shorten component life. Besides, a setup like this is more "on the edge" and if anything goes wrong, too much current can easily be drawn.

2) Braking. This seems like the biggest controversy here. We all know that braking dumps energy back into the battery. Obviously, a better battery has lower resistance, which helps reduce the voltage spike, but brake current can still be very high. The MMM TVS is supposed to clamp the voltage to a safe level (~28v IIRC) so the battery/FETs are not seeing huge voltage surges. But, if that TVS device goes bad (and it's not physically noticeable to the user), those voltages are no longer clamped and excessive voltages can then be present. Personally, no matter how you are geared, braking while running 6s on a larger vehicle is gonna stress everything - that's a lot of energy to shed! Solutions: reduce braking force and/or increase the time span in which braking is applied, use lower voltage (but don't gear up to compensate for lost speed), use mechanical brakes, or use more TVS devices and caps to help deal with those transients.

3) Ripple current. Simply the "AC" current generated by the ESC's PWM pulses. The caps filter these out, but if battery resistance is too high, the increased amplitude of the ripple current overworks the caps, heats them up, and things blow. No matter what the throttle position is, the instantaneous current of the PWM pulses is going to be very high. Lower throttle just means there are fewer ripples, which means overall lower average ripple.