[EricH]

Originally Posted by Greg Marra

Actually, there is a very good reason for the backup battery. If you put a lot of draw on the 12v battery, it's voltage can drop very low. If it drops too low, the RC loses power, shuts off, and then reinitializes when it powers back up. The backup battery keeps this from happening, so even if your motors die a little, you won't have a few seconds of being dead on the field.

Worse, you could lose all robot control for the rest of the match (if your batteries are in atrocious contition). It happened at least once before the backup was introduced in 2004. The team I know of it happening to was jamming the E-stop down, and the robot was still wandering all over the field.