The lithium rechargeable batteries (Li-ion/Li-Po) will be damaged or its cycle life will be shortened if it's over charged or over discharged. Protection Circuit Module is used to protect lithium battery from over-charging, over-discharge, overcurrent, short circuit.

1. The Necessities of Protective Circuit Module and its protection functions
The Lithium battery will expand, leakage or explosion if it's over charged or over discharged. The protective circuit module is designed to avoid this happen when the battery or the charger has problem, or incorrect usage caused the battery failure etc.

    • Overcharge voltage protection
    • Over discharge voltage protection
    • Over-current protection
    • Short circuit protection
    • Battery high temperature protection
    • Battery's internal pressure increase protection

3. Electrical Diagram

   B+: Connect to positive terminal of cell                  B-: Connect to negative terminal of cell
   V+: Positive power supply input for charger           V-: Negative power supply input for charger

4. The Installation of the Protective Circuit Module
The protective circuit module is installed integrated with the battery pack and it should be installed in battery shell. When the charger or related instruments occur problems, the protective circuit can protect the batteries perfectly.

Charging/Discharging

Lithium rechargeable battery must use "Constant Current / Constant Voltage (CC/CV)" charging method. First the battery is charged till it reaches limited voltage 4.2V by using a set constant current and then charged with this constant voltage till the current is below 2mA. It requires high precise charging circuit and protective circuit to control the charge.

Lithium rechargeable battery is not suitable for big current discharge, big current discharge will shorten the discharging time. It will cause high internal temperature of battery and decrease capacity. Over current discharge will damage the battery.