[thefro526]

Omg we just had the same problem yesterday. After reading the manual I found out that there had to be a short somewhere in the wiring (thats what the light means). So a mentor and I pulled all the PWM cables out to try to find the short (if the light goes out the short is on that cable) but the cables were all find so I checked all of the male connections on the RC and one of the Analog outputs had a small metal shaving across it thus causing the short.

The light has nothing to do with the backup battery, if the backup batery was the issue then the light would light up on the OI. My suggestion to you would be turn your robot on and disable it. Then unplug each wire one by one. If the light goes off the problem is on the line. If they are not your problem then keep the robot on and disabled, get a toothpick or other thin object and run it between each pwm outputs/inputs. This should dislodge any thing that will short the outputs/inputs out.