[KenWittlief]

if the low battery light comes on then you are stalling your motors, you have a weak battery (an old one or one that is not fully charged), or a bad connection somewhere in your power wires.

Im not certain on this, but I believe the blue backup battery only keeps the RC from resetting when the 12V battery drops low - I believe the outputs to the PWMs are still cuttoff at a certain voltage, so yes, if you pull enough power from the 12V battery to drop the voltage below the threshold, then the victors and spikes will be switched off.

Its possible that you have a poor connection in your power wires somewhere. If you have a terminal or wire that is just barely touching, or poorly crimped - it will have a relatively high resistance, and when your motors draw a lot of current, the voltage will be lost across that bad connection

it could be anywhere from the terminals screwed to the battery posts, to the main breaker, your ground stud, the buss box (black square cube thing) your breaker panels - anywhere between your RC and the battery, that causes the RC to 'see' a lower battery voltage under high current conditions.