Consistency study on 18650 cells used in electric vehicles

The consistency of five different 18650 cells used in electric vehicles both at the initial and aged states was evaluated by electrochemical test and statistical analysis. The effects of current, temperature and voltage on the cell consistency were examined. The results show that, to ensure a reasonable level of the cell consistency, the current rates during the charging and discharging processes should be less than 0.3C and 0.5C, respectively, and the operating temperature should be higher than 0℃. In addition, the cell sorting process is crucial to control the cell consistency. An additional descriptor, the k value, representing the decreasing rate of open circuit voltage during calendar test, should be involved in the cell sorting.