I'm thinking of a 2 or 3S 2C pack and 1500 mA, the HV-board takes ~150 mA.
This must be enough for a day flying.
A normal PIC need 5 Volt or 3V3 for low Voltage type.
The four pennlights we use now are just enough to let the show go on, but it's not safe.
Batteries have also a differend unload then lipo's, batteries will be unload slowly and you equipment will be react strange.
Lipo's can hold there Voltage very long high, allmost untill their are empty.