Li-po Charging circuit question (switching between battery and power supply) - Electrical Engineering Stack Exchange
3.7V Lithium Battery Charger Protection Board 5V 1A 2A Li ion Lipo Battery Charging Protect Two in one Module Micro USB Type C|module 5v|module boardmodule charger - AliExpress
Amazon.co.jp: Lipo RLipo Rider Plus LiPo Rider Plus Charger Booster (Charger/Booster) - 5V/2.4A USB Type C : Toys & Games