This is UPS based on 18650 to provide you uninterruptable 3.3v and 5v at the same time. You can use this battery shield to power many products like Raspberry Pi, Arduino, esp8266, nodemcu, and esp32 devices. At this version 18650 shield has protection. The output current can reach 2A. This is enough power for 99% of Arduino and esp projects.
Be careful of "+" and "-", You should follow the direction of "+"-" on the PCB. If you put the wrong direction, the charging chip will be destroyed.