The backup battery is not always needed to run the robot. its only function is to power the RC and radio when the voltage in the main battery voltage drops. so you should be able to run your robot without it. as for the positive volts from the pwm i can check and let you know tomorrow. there is more info on the backup battery on page 4 of the robot controller reference guide at
http://www.ifirobotics.com/docs/rc-r...01-31-2005.pdf