The principle of over-protection of 18650 lithium ion battery.

　　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, over-discharge protection and Overcurrent/short circuit protection.

　　Overcharge protection device.

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

　　In addition, attention must also be paid to overcharge detection malfunctions caused by noise to avoid being judged as overcharge protection. Therefore, the delay time needs to be set, and the delay time cannot be less than the noise duration.

　　Over-discharge protection device.

　　When discharged too much, the performance of 18650 lithium ion battery will deteriorate due to the decomposition of the electrolyte, and the number of recharges will decrease. Using lithium battery protection IC can avoid excessive discharge and protect the battery.

　　Principle of over-discharge protection IC: In order to prevent the over-discharge state of the lithium battery, assuming that the lithium battery is connected to a load, when the voltage of the lithium battery is lower than its over-discharge voltage detector (assumed to be), the over-discharge protection will be activated, causing the The power MOSFET changes from open mode to disconnected mode and disconnected discharge to avoid over-discharge and put the battery in 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, over-discharge protection and Overcurrent/short circuit protection.

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