Lithium battery charging needs to be divided into activation charging, constant current charging, constant voltage charging, off charging several processes. Special charge management chips are needed to control the charging process.
Activation charge: when the cell voltage is too low, a small current is used to activate the cell.
Constant current charging: when the cell voltage rises to a certain value, it can be charged quickly with a constant current.
Constant voltage charging: cell voltage rises to 4.2V, it is necessary to change to constant voltage charging, slowly reduce the charging current.
Off charging: after the cell is full, it is necessary to turn off the charging, only with a small current to maintain the full state of the cell.
The main function of the lithium battery charging board is to charge. The input port of the charging board can be connected to a 5.0V mobile phone charger, and the charge management chip on the charging board will provide appropriate charging mode according to the status of the lithium battery.
So if you want to connect the lithium battery of the old mobile phone to the small desk lamp, you still have to connect a 4056 chip of lithium battery charging board, of course, other chip design of lithium battery charging board is also possible.