Working principle of battery protection board
The circuit and parameters of lithium battery protection board vary according to the IC and voltage used. The commonly used protection ICs include 8261, dw01 +, CS213, gem5018, etc. among them, the precision of Seiko 8261 series is better, and of course, the price is more expensive. The latter are from Taiwan. Dw01 + and CS213 are basically used in the domestic secondary market. The following is a description of dw01 + with MOS tube 8205a (8pin):
The normal working process of battery protection board
When the cell voltage is between 2.5V and 4.3v, the first and third pins of dw01 output high level (equal to the supply voltage), and the second pin voltage is 0V. At this time, the voltage of the first and third pins of dw01 will be added to the fifth and fourth pins of 8205a respectively. The two electronic switches in 8205a are in the on state because their G pole is connected to the voltage from dw01, that is, the two electronic switches are in the on state. At this time, the negative pole of the cell is directly connected with the p-terminal of the protection plate, and the protection plate has voltage output.
Over discharge protection control principle of battery protection board
When the cell discharges through the external load, the voltage of the cell will slowly decrease. At the same time, dw01 will monitor the cell voltage in real time through R1 resistance. When the cell voltage drops to about 2.3V, dw01 will consider that the cell voltage has been in the over discharge voltage state, and immediately disconnect the output voltage of the first pin to change the voltage of the first pin to 0V. The switch tube in 8205a is closed because the fifth pin has no voltage. At this time, the B - of the cell and the p - of the protection plate are disconnected. That is, the discharge circuit of the cell is cut off, and the cell will stop discharging. The protection plate is in an over discharge state and remains. After the P and P - of the protection board are indirectly charged with the charging voltage, dw01 immediately stops the over discharge state after the charging voltage is detected by B - and outputs the high voltage at the first pin again to turn on the over discharge control tube in 8205a, that is, the B - of the cell is reconnected with the p - of the protection board, and the cell is directly charged by the charger.(battery protection board)