A method for sorting cells

Abstract

This invention provides a method for cell capacity classification. For batteries that have completed formation and are ready for capacity classification, deep charging and shallow discharging are performed at high SOC, followed by deep discharging and shallow charging at low SOC. The sum of the capacity after the first deep discharging and the "climbing" capacity is calculated. For activated cells, the capacity difference between each temperature and the capacity at 25°C is calculated. A relationship curve is fitted between this series of capacity differences and the corresponding temperature. All cells can be temperature-corrected using the fitted relationship curve for their respective temperatures. The compensated capacity is the cell's actual capacity. This invention determines the activation level by performing deep charging and shallow discharging at high SOC and deep discharging and shallow charging at low SOC, and by calculating the ratio of the capacity difference during each charge / discharge cycle to the rated capacity. The activated cell capacity is then calculated and grouped. This invention provides accurate activated cell capacity, is quick and cost-effective, and results in smaller actual capacity differences and lower voltage differentials after module assembly.