There is a small circuit board inside the lithium battery of the mobile phone. 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.

What is the function of the 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 cell, and can also protect and extend the battery life; if an abnormality is detected, the small IC will turn off the MOS to protect the battery cell Role.

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, and it cannot directly charge the mobile phone lithium battery.

Lithium battery charging board function

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: the battery cell voltage rises to 4.2V, it is necessary to switch to constant voltage charging, slowly reducing the charging current.

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.