What is the role of mobile phone lithium battery protection board

What is the role of mobile phone lithium battery protection board

Friends who have removed the lithium battery of a mobile phone know that there is a small circuit board in the lithium battery of the mobile phone. Don't underestimate this small board, it can protect the battery from over-discharge, over-charge, over-current, and output short-circuit protection, but it does not have the function of charging the battery.

Analysis of the function of mobile phone lithium battery protection board

There is a small IC on the protection board, as well as a MOS tube and several capacitors and resistors. This small IC can detect the over-voltage, under-voltage, over-current, short-circuit, and over-temperature status of the battery, and can also protect and extend the battery life; if an abnormality is detected, the small IC will shut down the MOS to protect the battery effect.

Because the nominal voltage of the mobile phone lithium battery is 3.7V, the full voltage is 4.2V. It is also possible to charge the lithium battery directly by connecting 4.2V. When the voltage of the lithium battery rises to 4.2V, the charging will stop due to the same voltage. Although it is not as good as a charging board, it can be used as it is, but the output voltage of our mobile phone charger is 5.0V, which cannot directly charge the mobile phone lithium battery.

　　The role of lithium battery charging board

　　 Lithium battery charging needs to be divided into activation charging, constant current charging, constant voltage charging, and shutdown charging. A special charging management chip is needed to control the charging process.

　　 Activation charging: When the cell voltage is too low, the cell will be activated with a smaller current.

　　 Constant current charging: When the cell voltage rises to a certain value, it can be quickly charged with a constant current.

　　 Constant voltage charging: When the battery cell voltage rises to 4.2V, it must be switched to constant voltage charging, and the charging current is slowly reduced.

　　Turn off charging: After the battery is fully charged, it is necessary to turn off the charging, and only use a small current to maintain the full state of the battery.

　　The main function of the lithium battery charging board is charging. The input port of the charging board can be connected to a 5.0V mobile phone charger, and the charging management chip on the charging board will provide a suitable charging method according to the state of the lithium battery.