[TubaMorg]

Ok after reading through this thread I've noted a number of objections to the backup charger design from the EE types. However a few people have actually built and used the circuit with no terrible ill effects. The chief complaint seems to be that when the main power is turned off, the backup feeds back into the 12v circuitry. And if I am understanding correctly, this problem doesn't seem to be taken care of with the new design. Other complaints seem to be concerning the charge rate; in other words the voltage supplied to the backup is barely more than what a fully charged backup battery would produce.

Have I summarized correctly?

So, I am thinking that the puny charge rate is fine, as the only real purpose of this circuit is to reduce draw down of the backup battery when using the camera. Other loads are pretty minimal and of negligable concern during competition.

As for the back feed issue:
I believe the problem can be solved by introducing a switch that disconnects the backup from the RC when main power is removed. Best scenario would be to route the pigtail through a relay that disconnects the backup from the RC when main power is turned off. I don't think this is feasible with a Spike, so next best solution is a manual switch. Orrrr, just unplug the backup as part of the robot power down procedure!