There's lots of good 18650 chargers on thingiverse, but I wanted something a bit more robust and USB-C.
You need:
You can purchase the TP4056 boards and battery terminals from AliExpress, eBay, Amazon, etc.
Instructions
- Buy the parts.
- Download the models - there are two charger board covers to choose from.
- Print the models - the body the right way up, the covers face down.
- Push the 4 battery terminals (springs for negative end, conventionally) through from the top.
- Solder the wire or nickel strip to the battery terminals, and fold them over into the slots in the bottom.
- Push the nickel or wire through the smaller slots. If you're using wire, you may need to drill out the slot a little if the wire is thick.
- Put the boards in place, and cut the wires / nickel strips to length.
- Solder the positive contacts (labelled "+" at the USB end) of the boards together with a short length of wire.
- Do the same for the negative contacts (unlabelled).
- Solder the battery wires/strips to the "B+" and "B-" contacts.
- Install the board cover, making sure the end marked "front" is at the USB-C end.
- Optionally, sharpie the "+" symbols in the battery compartments.
Plug either of the USB sockets into a USB-A -> USB-C supply and charge your batteries. Blue light means it's charging, red light means it has finished.