Amazon.com: Onyehn 3.7V Turn 5V 2A Boost Step Up Module Dual USB Charging Circuit Board PCB Board with Led Light for 18650 Lithium Battery Mobile Power Bank DIY 2 Pack : Electronics
USB-Powered Lithium-Ion Battery Charger
3s 3.7v Li-ion battery charger using 3 in 1 25A BMS board -12.6v cell | POWER GEN - YouTube
How to Build a 18650 Lithium Battery Charger and Booster Module