[Al Skierkiewicz]

As Jim pointed out, current for a motor/Speed controller flows through both wires. Current flowing through a wire (red or black) will develop a voltage across the wire that detracts from the voltage available to the load. If you split the high current wiring as near to the battery as possible(at the Rockwell block), then less voltage is dropped to the circuits downstream. The critical component is the RC which drops out below 8 volts. When that occurs, all PWM outputs are disabled and the RC switches over to the backup battery to stay alive and keep up the modem and communications with the OI. Luckily there is some capacitance in the RC that allows it to weather short duration brownout conditions. If you have 6 drive motors and they all go into stall condition at the same time, it is easy to draw enough current to drop down to 6 or less available volts.