dual redundant voltage regulator

[coloradoz]

I'd like to use 2 11.2 lipo batteries in parallel, and therefore need them both to be regulated down to about 6v. Anyone know of a circuit whereby I can use 2x11.2 v packs together (without explicitly wiring them in parallel first?) It would be ideal that there be a concept of a pack1 and pack2 (kind of like a mini-ups) and a failover if the voltage fell below some threshold.

 

[banjo]

Since you want to regulate the 11.2V down to 6V anyway, the simplest method is to use diodes to isolate the two batteries. Take two diodes and wire the anode of each diode to the "+" terminal of the batteries. Connect the two cathodes in parallel and use this parallel connection to power the 6V regulator. Which ever battery has the highest output voltage will power the circuit. However, the higher voltage battery will not discharge into the lower voltage battery because the series diode will be reverse biased.
The 0.7V drop across the diode is not an issue, because your regulator is dropping the 11.2V to 6V anyway. Therefore, your battery capacity is not reduced.