In the case of a 1A charger, a 5V±10% regulated AC adapter voltage, and battery voltage that varies between 4.2V and 2.5V, the power dissipation can range from 0.3W to 3.0W. Figure 2 shows a typical linear Li+ charger. This circuit uses the MAX1898 and an external p-channel MOSFET to drop the AC adapter voltage to the battery voltage.
There are three methods to charging Li+ batteries: switch-mode, linear and pulse. Each method has its advantages and disadvantages. Switch-mode charging minimizes power dissipation over a wide range of AC adapter voltages, but consume more board space and add complexity compared to linear and pulse charging.
They added: Be sure to use lithium-ion and other such batteries with a battery management system (BMS*). When charging and discharging are repeatedly performed, differences in the charging capacity of the individual cells occur, and if discharging occurs in this condition, overcharging can occur.
This is a charging method where batteries are charged with a constant current from beginning to end. A standard switching power supply is a constant voltage power supply, so it monitors fluctuations in output voltages, inputs the results in the control circuit, and executes constant voltage controlling also known as feedback controlling.
The most appropriate method for charging batteries among them is with a power supply that has constant current voltage drooping type characteristics (Far Left) where a constant current range is used for charging batteries with a constant current. The other two characteristics should not be used to charge batteries.
For a Li+ battery, CCCV (constant current, constant voltage) is the universally accepted charging method. With the exception of the voltage source/resistor method used exclusively for very small capacity (a few mAh) Li+ batteries.