How to determine cell count?

[BrianG]

Well, they might be getting hot because they are spinning kinda fast if that is their true kv rating. That's what happens with sensorless BL motors too; spin 'em too fast and they heat up. Plus, efficiency starts to fall, so more power is being wasted.

The fact it's sensored simply means there is a Hall-Effect sensor to monitor rotor position. Otherwise, it's like a sensorless motor.

I've never had a sensored setup, so I don't know what their "sweet spot" is.