How to use a lithium-ion battery protection board
Lithium-ion battery protection boards vary in circuitry and parameters depending on the IC used and the voltage. The following explanation uses the DW01 with an 8205A MOSFET as an example:
1. The normal operating procedure of the lithium-ion battery protection board is as follows: When the cell voltage is between 2.5V and 4.3V, pins 1 and 3 of DW01 output a high level (equal to the supply voltage), and pin 2 outputs 0V. At this time, the voltages of pins 1 and 3 of DW01 are applied to pins 5 and 4 of the 8205A respectively. Since the gate (G) terminal of the 8205A is connected to the voltage from DW01, both electronic switches within the 8205A are in a conducting state, meaning both electronic switches are in the open state. At this time, the negative terminal of the cell is essentially directly connected to the p- terminal of the protection board, and the protection board outputs voltage.
2. Over-discharge protection control principle of the protection board: When the battery cell discharges through an external load, the voltage of the battery cell will gradually decrease. At the same time, the DW01 will monitor the battery cell voltage in real time through resistor R1. When the battery cell voltage drops to about 2.3V, the DW01 will consider that the battery cell voltage is in an over-discharge voltage state and immediately disconnect the output voltage of pin 1, making the voltage of pin 1 0V. The switching transistor in the 8205A will be turned off because there is no voltage at pin 5.
At this time, the B- pin of the battery cell is disconnected from the P- pin of the protection board. This means the battery cell's discharge circuit is cut off, and the battery cell will stop discharging. The protection board remains in an over-discharge state. Once the charging voltage is applied between the P- and P- pins of the protection board, DW01 detects the charging voltage via B- and immediately stops the over-discharge state, re-outputting a high voltage at pin 1. This turns on the over-discharge control transistor in the 8205A, reconnecting the B- pin of the battery cell to the P- pin of the protection board, and the battery cell is then directly charged via the charger.
3. Overcharge Protection Control Principle of Lithium-ion Battery Protection Board: When the battery is charging normally through the charger, the cell voltage will increase with the charging time. When the cell voltage rises to 4.4V, DW01 will consider the cell voltage to be in an overcharge state and immediately disconnect the output voltage at pin 3, making the voltage at pin 3 0V. The switching transistor in 8205A will turn off because there is no voltage at pin 4. At this time, the B- of the cell and the P- of the protection board are disconnected. That is, the charging circuit of the cell is cut off, and the cell will stop charging.
