As far as battery technology goes ... Luckily, [Paul] sent in a great tutorial on building a LiPo charger that works over USB. The board [Paul] came up with is incredibly small – just barely ...

Over at Hackaday.io [AndyHull] popped open some cheap LiPo battery power packs to see if ... and replaced by a connection to outside the pack. The torch output is triggered by two quick presses ...