Case/dock to refresh Xbox 360 controller batteries

I have a couple of play&charge kits for my 360 controllers, but all the batteries don't hold any charge.

Using a more efficient charger like these designed for lipo/nicd/nimh you can refresh the battery and they hold at least 90% of the charge again (1-2 weeks of use). You will need an old 360 controller (maybe this part can be printed too but I had a broken one)

Video (in spanish): https://www.youtube.com/watch?v=OwgZ_S2whiA