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What is the charge protection circuit and discharge protection circuit of lithium ion battery?

Return Listsource:Gratene date: 2021-07-14

1. Lithium-ion battery charging

The maximum charging termination voltage of a single lithium-ion battery is 4.2V. Do not overcharge, otherwise the battery will be scrapped due to the loss of lithium ions in the positive electrode. When charging the lithium-ion battery, the dedicated constant-current and constant-voltage charger should be used. First, charge the battery with constant-current until the voltage at both ends of the lithium-ion battery is 4.2V, and then switch to the constant-voltage charging mode. When the constant voltage charging current drops to 100mA, the charging should be stopped.

Charging current (mA) can be 0.1 ~ 1.5 times of battery capacity, for example: 1350mAh lithium ion battery, the charging current can be controlled between 135mA ~ 2025mA. The conventional charging current can be selected at about 0.5 times the battery capacity, and the charging time is about 2 ~ 3 hours.

2. Discharge of lithium ion batteries

Due to the internal structure of the lithium-ion battery, the lithium ions cannot all move to the positive electrode during the discharge, and part of the lithium ions must be retained in the negative electrode to ensure that the lithium ions can be smoothly embedded into the channel during the next charge. Otherwise, the battery life will be shortened. In order to ensure that some lithium ions remain in the graphite layer after discharge, it is necessary to strictly limit the minimum voltage at discharge termination, that is to say, the lithium ion battery can not overdischarge.

The discharge termination voltage of a single lithium-ion battery is usually 3.0V, and the minimum voltage cannot be lower than 2.5V. Battery discharge time is related to the capacity of the battery and the discharge current. Battery discharge time (hour)= battery capacity/discharge current, and the discharge current of lithium ion battery (mA) should not exceed 3 times of the battery capacity, for example: 1000mAh lithium ion battery, the discharge current should be strictly controlled within 3A, otherwise it will damage the battery.

The design of lithium-ion battery protection circuit is very important. We require the lithium-ion battery power protection chip to achieve the following basic functions: overcharge protection, overdischarge protection, overcurrent protection and short circuit protection. According to the above application requirements of lithium-ion batteries, in order to improve the service life of lithium-ion batteries and ensure the safe use of batteries.

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