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What is the Principle of Overprotection of Lithium Batteries?

Nov. 17, 2020

As an 18650 Battery Factory, share with you.

The protection circuit of this lithium-ion battery consists of a protection IC and two power MOSFETs. The protection IC monitors the battery voltage and switches to an external power MOSFET in the event of overcharge and discharge. Its functions include overcharge protection, overdischarge protection and Over current/short circuit protection.

18650 Battery

18650 Battery

The principle of the overcharge protection IC is as follows: When the external charger is charging the lithium battery, in order to prevent the internal pressure from rising due to the temperature rise, the charging needs to be stopped. At this time, the protection IC needs to detect the voltage of the battery, and when it reaches (assuming the overcharge point of the battery is), it is overcharged, which turns the power MOSFET off, and then cuts off charging.

In addition, you must also pay attention to the overcharge detection error caused by noise, so as not to be judged as overcharge protection. Therefore, the delay time needs to be set, and the delay time cannot be less than the noise duration.

When the discharge is too much, the performance of the lithium battery will deteriorate due to the decomposition of the electrolyte, and the number of charging times will decrease. The use of lithium battery protection IC can avoid over-discharge and realize battery protection.

Principle of over-discharge protection IC: In order to prevent the over-discharge state of the lithium battery, suppose the lithium battery is connected to the load. When the voltage of the lithium battery is lower than its over-discharge voltage detector, it will over-discharge protection and make the power MOSFET change from open to Disconnected and disconnected discharge to avoid over-discharge and keep the battery in a standby state, that is, only μA over-discharge current.

The protection circuit of the lithium-ion battery consists of a protection IC and two power MOSFETs. The protection IC monitors the battery voltage and switches to an external power MOSFET in the event of overcharge and discharge. Its functions include overcharge protection, overdischarge protection and Over current/short circuit protection.

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