Lithium-ion battery charging circuit design

Lithium-ion battery charging circuit design

According to the structural characteristics of lithium-ion batteries, the maximum charge termination voltage should be 4.2V 

and cannot be overcharged. Otherwise, too many lithium ions from the positive electrode will be taken away and the battery 

will be scrapped. Its charging and discharging requirements are relatively high, and a dedicated constant current and constant

voltage charger can be used for charging. Usually, constant current charging reaches 4.2V/section and then it switches to constant 

voltage charging. When the constant voltage charging current drops to less than 100mA, charging should be stopped. Battery capacity

 (for example, for a 1350mAh battery, the charging current can be controlled between 135 and 2025mA). The conventional charging 

current can be selected to be around 0.5 times the battery capacity, and the charging time is about 2 to 3 hours.

Due to the internal structure of the lithium-ion battery, all lithium ions cannot move to the positive electrode during discharge. 

A part of the lithium ions must be retained at the negative electrode to ensure that the lithium ions can be inserted into the channel 

smoothly during the next charge. Otherwise, battery life will be shortened accordingly. In order to ensure that some lithium ions remain

in the graphite layer after discharge, the minimum discharge termination voltage must be strictly limited, which means that the lithium-ion 

battery cannot be over-discharged. The discharge termination voltage is usually 3.0V/section, and the minimum cannot be lower than 

2.5V/section. The length of battery discharge time is related to battery capacity and discharge current.