L822 battery.National standard for lithium-ion batteries

　　1. The nominal voltage of lithium-ion batteries is 3.7V (3.6V), and the charging cutoff voltage is 4.2V (4.1V, depending on the brand of the battery cell). (The specification for lithium-ion battery cells states: lithium-ion secondary batteries)

　　2. Requirements for charging lithium-ion batteries (GB/T182872000 specification): Firstly, constant current charging, which means the current is constant, and the battery voltage gradually increases with the charging process. When the terminal voltage of the battery reaches 4.2V (4.1V), constant current charging is changed to constant voltage charging, which means the voltage is constant. The current gradually decreases as the charging process continues based on the saturation degree of the battery cell. When it decreases to 0.01C, it is considered that the charging is terminated. (C is a representation method that compares the nominal capacity of the battery to the current. For example, if the battery has a capacity of 1000mAh, 1C is the charging current of 1000mA. Note that it is mA instead of mAh, and 0.01C is 10mA.) Of course, the standard representation is 0.01C5A, which I have simplified here.

　　3. Why is it believed that 0.01C is the end of charging? This is stipulated in the national standard GB/T18287-2000 and was also discussed. Previously, it was common to end with 20mA, and the industry standard YD/T998-1999 of the Ministry of Posts and Telecommunications also stipulated that regardless of the battery capacity, the stopping current is always 20mA. The 0.01C specified in the national standard helps to charge more fully, which is beneficial for the manufacturer to pass the appraisal. In addition, the national standard stipulates that the charging time should not exceed 8 hours, which means that even if the temperature has not yet reached 0.01C and 8 hours have passed, the charging is considered complete. (Batteries with good quality should reach 0.01C within 8 hours, while batteries with poor quality are meaningless to wait.)

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