[Andy A.]

The backup battery serves to power the RC during 'brown outs' and as positive voltage on the middle pin of PWM outputs. Effectively this means that it powers servos and saves you from your robot shutting down and resetting under heavy loads and low batteries. In the past we would have loved to have this kind of backup..

The charging circuit published by IFI in the past isn't all that great. Unless your robot is using a great number of servos or sensors powered by a PWM output it probably isn't nessecary to include the backup charging circuit. Simply charging the battery off the robot every few matches is perfectly adequate.

It is however required to include the backup battery on the robot and connected to the RC. The included battery pack is fine, but it is acceptable to replace it with any 7.2v battery pack (these are common in R/C cars, and you can get very high capacity packs if you so desire).

-Andy A.