Research on a fast detection method of self-discharge of lithium battery

The self-discharge of the battery refers to the phenomenon that the capacity of the battery decreases after the battery is charged and placed in the open-circuit state for a period of time, which is the holding ability of the stored electricity of the battery under certain conditions. When the self-discharge of the battery is too large or the self-discharge consistency of the cells in the battery pack is poor, it will affect the cruising range of the new energy electric vehicle and the overall energy storage system. To quickly detect the self-discharge rate of lithium batteries, this paper proposes a rapid detection method to characterize the self-discharge rate by OCV (Open Circuit Voltage) in a short period and at the cell level based on the change of OCV during the battery resting process. This method removes the influence of lithium battery polarization on subsequent analysis by selecting the OCV of the appropriate time. After analyzing the OCV threshold corresponding to each cell from the experimental data obtained by screening, the OCV difference between 12 h and 24 h during the resting process is compared with the corresponding OCV threshold. The ratio of thresholds is normalized. Through the normalized results, the self-discharge rate of each cell is analyzed, and the cell with a larger self-discharge rate is obtained. After that, the self-discharge analysis results within 24 h, and the self-discharge analysis results in the complete resting process for 30d are compared and verified, it is concluded that the results detected by this method are correct, indicating that the self-discharge rapid detection method has high accuracy.