18650 lithium ion battery cell

　　What do 18650 lithium ion battery cell SOC and SOH represent?

　　SOC refers to the state of charge, also known as the remaining power consumption, which indicates the ratio of the remaining capacity of the rechargeable battery to the fully charged capacity after it has been used for a period of time or for a long time, usually expressed as a percentage. Its value range is 0~1. When SOC=0, it means complete charge and discharge of the rechargeable battery. When SOC=1, it will fill the rechargeable battery. The SOC of the battery cannot be measured accurately directly. Its size can only be determined based on parameters such as battery DC voltage, battery charging current and internal resistance. Due to the impact of various variable factors such as battery aging, temperature changes, and vehicle operating conditions, the accuracy of SOC may become an urgent problem in the development of battery vehicles.

　　"SOH" refers to the battery's capacity, health level, and performance. To put it simply, it is the ratio of the battery's technical parameters to its rated current after being used for a period of time. A new original battery is 100%, and any damage is 0%. . It is the ratio of the volume released by the battery from full charge to a certain multiple of the cut-off voltage and the relative short-circuit capacity. It is simply the limit volume of the battery. There is a certain correlation between the intracellular resistance and the SOH value. As SOH decreases, the internal resistance of the rechargeable battery also increases. By testing the working voltage, current, temperature and other main parameters, the internal resistance value of the rechargeable battery can be indirectly calculated, and then based on the difference between SOH and battery internal resistance The correlation is used to calculate SOH. However, when the SOH change amplitude is not large, the internal resistance of the rechargeable battery does not change significantly. When the rechargeable battery is severely embrittled, the resistance changes greatly. Therefore, this method has a large data error when the SOH change amplitude is larger than an hour.

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