Aliexpress. A simple TP4056 usb-c charging board costs as little as 50p. For a few pence more you can get a power bank board with a charge controller and a 5v boost converter.
Interesting, I have some TP4056 already, but wouldn't I need some form of "balance" circuitry if I want to connect multiple of these together, to ensure they're all charged and discharged evenly?
On this note, anyone got a tut or links to where I can get an appropriate charge controller/BMS (UK) to do this?
Like the post's author, I've been collecting vape batteries for a while and would love to build a power bank or use them in some IoT projects.