This circuit board has charging function and battery discharge protection function, which can charge and discharge simultaneously.
Module characteristics and parameters: 

Input terminal with Micro USB.

You can directly use a mobile phone charger as input to charge the lithium battery. 

Input voltage: 5V Charging cut-off voltage: 4.2V ± 1% 

High charging current: 1000mA 

Battery over discharge protection voltage: 2.5V
Battery overcurrent protection current: 3A 

Board size: 2.6 * 1.7CM 

Usage: Attention: When connecting the battery again, there may be no voltage output between OUT+and OUT -. At this time, charging with 5V voltage can activate the protection circuit. If the battery is short circuited from B+B - and then connected again, it also needs to be charged to activate the protection circuit. When using a mobile phone charger for input, be sure that the charger can output 1A or more, otherwise it may not charge properly The Micro USB socket and its adjacent+- pad are the power input terminals, connected to a 5V voltage. B+is connected to the positive side of the lithium battery, and B - is connected to the negative side of the lithium battery. OUT+and OUT - connect to loads, such as the positive and negative terminals of the mobile boosting board or other loads. Connect the battery to B+B -,
insert the phone charger into the USB socket, the red light indicates charging, and the blue light indicates fully charged.