USB / DC / Solar Lithium Ion/Polymer charger [Rev C] : ID 390 : $17.50 : Adafruit Industries, Unique & fun DIY electronics and kits
Amazon.com: 18650 Battery Charger 4 Bay Smart Universal Charger for Flashlight Headlamp Battery 3.7V Rechargeable Lithium Li ion Batteries Compatible 18650 26650 21700 Battery Charger (Only USB Charger) : Electronics
How to make 3.7 volt battery charger - Electronics Help Care
3.7V 500mA Solar LiPo Battery Charger - RobotShop
Amazon.com: JacobsParts Smallest USB Type C 3.7V Lithium Battery Charger Board 4.2V Charging Module with Protection Circuit and LED Charge Indicators 5V USB-C Input (2 Pack) : Automotive
Auto cut off 3.7 volt Battery charger circuit using Relay, Simple 3.7 volt Battery charger - YouTube
Simple 3.7 volt battery charger with auto cut off - YouTube
81650 3.7v Battery Charger
18650 USB Fast Charging Single Slot Multi Slot BatteryCharger 3.7V/4.2V Battery Charger with Charge Protection Indicator - AliExpress
Auto Cut-Off 3.7 Volt Lithium-Ion Battery Charger Circuit
Make A 3.7v LI-ion Battery Charger Circuit - TechSaw
Auto Cut off 3.7 volt Lithium-ion Battery Charger Circuit - Hackster.io
4PCS 3.7V 3000mAh Li-ion Rechargeable Battery with 2-Slot USB Smart Battery Charger - Walmart.com