My cell can last me for 2 days without charging.
These charges are not very complicated, a couple of batteries and 2 transformers (to get the desired electric current).
You will need this part:
https://www.sparkfun.com/products/10...rN8hoCfVPw_wcB
Some electric tape, and the amount of rechargeable batteries that make sense for your purposes.
if you want to go fancy, use a soldering iron, (although just electric tape is enough)
Do not forget to put a sticker on it