To charge or not to charge --- CR2032 | AVR Freaks
How to Build a 18650 Lithium Battery Charger and Booster Module
This is very easy 3.7 Volt Battery Charger Circuit to indicate the battery is full or empty and… | Battery charger circuit, Lithium battery charger, Battery charger
3.3V Power Failover Supply with USB Li-Ion Charger - Electrical Engineering Stack Exchange