I followed the instructions and it worked perfectly. I used a phone batteries pack (AAA 2.4v 700mAh nimh) with wires. I joined wires with the ones on the board. Soldered them. Puted shrink wrap. Removed the plastic on the pack to fit it. It’s holding the charge better than a brand new Bodygroom.

https://www.batteriesexpert.com/en/small...