Intro: Lakerol USB Charger From Old Nokia Batteries
This is my version of the Portable USB Charger by "slipknot rules". Original found at https://www.instructables.com/id/Portable-USB-Charger/
Check his page for schematics, partslist and some good discussion in the comments.
Check my pictures and the comments in them for what i learnt while doing my version...
Btw, if you have all the parts except the 7805 regulator you can find one in an Nintendo 8-bit. Thats how my project started... :-)
And of course I am not liable for any damage that may occur to your devices from using this project.
Li-ion batteries can be potentially dangerous. Handle them with care and NEVER short-circuit.