Speed control capacitors.

[Arct1k]

Yes they help with heat, no it is not about adding it for extra kick on acceleration.

It is about reducing ripple current from batteries under load - use the search on that term...

[VintageMA]

I find this thread interesting. I did a little searching on ripple current to understand it better and basically defined as the AC voltage ripple riding on top of a DC voltage. How extreme it is depends on the ratings of the capacitor and also the frequency of the AC ripple itself.

It's basically the capacitor wasting the current as heat as it charges and discharges current in response to the rising and falling AC voltage riding on te constant DC voltage.

My follow-up question is how is the ripple current generated from the batteries under load? Is it actually the batteries creating the ripple when you accelerate and brake and stop and the voltage of the cells rises and falls? In that case it would seem like the frequency of the current would be very low.

Or is the ripple current something else fired back by the ESC itself?