DIY Lithium Battery Charger Circuit - Soldering Mind
Make a 18650 battery charger, Li-ion battery charge controller circuit - YouTube
DIY Dummy 18650 Magnetic Battery Charger Adapter - A solution to charging 26800's and other large cells without having to buy a new charger (details inside) : r/flashlight
How to Build a 18650 Lithium Battery Charger and Booster Module