Lithium battery discharge circuit.18650 lithium ion battery cell

　　When the battery pack is discharged, the external load is connected to the positive and negative poles BAT+and BAT - at both ends of the battery pack. The discharge current flows through the negative pole BAT - of the battery pack, the charging control switch device, the discharge control switch device, the single lithium battery N~1 in the battery pack, and the positive pole BAT+of the battery pack. The current flow direction is shown in. The discharge undervoltage protection, overcurrent and short-circuit protection control signals of the single lithium battery protection chip in the control circuit of the system are isolated by optocouplers and output in series, providing gate voltage for the conduction of the discharge switch device in the main circuit; Once the battery pack encounters special situations such as undervoltage, overcurrent, and short circuit of a single lithium battery during the discharge process, the corresponding discharge protection control signal of the single lithium battery becomes low and cannot provide gate bias voltage to the discharge control switch device in the main circuit, causing it to turn off and the main circuit to disconnect, thus ending the discharge usage process.

　　Generally, lithium batteries use a constant current constant voltage (TAPER) charging control. When charged at constant voltage, the charging current decreases approximately exponentially. The switching devices of the charging and discharging main circuit in the system can be selected based on the maximum operating current and voltage required by the external circuit.

　　The single lithium battery protection chip of the control circuit can be selected based on the voltage level and protection delay time of the single lithium battery to be protected. The shunt discharge branch resistance can be achieved using power resistors or resistance networks. It is more reasonable to use a resistance network to achieve shunt discharge branch resistance here, which can effectively eliminate the influence of resistance deviation and also reduce thermal power consumption.

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