Method for Obtaining Battery Pack Health Index Based on Cell Discharge Interval Differences

Lithium-ion battery packs require the construction of a health indicator to indirectly represent their state of degradation. The existing health indicator construction methods based on voltage curves encounter difficulties with parameter selection and the impact of working conditions on the representation ability of the health indicator. To address these issues, this paper proposes a method for constructing a battery pack health indicator based on the differences among the discharge intervals of the cells within the pack. First, the discharge interval of each cell is derived from the online monitored voltage. Next, Euclidean distance is employed to quantify the differences among the discharge intervals. Finally, factor analysis is utilized to fuse the data and obtain the battery pack health indicator. Notably, this approach eliminates the need for parameter selection and does not require consideration of operating conditions. The proposed method has been validated using laboratory test data, with absolute Pearson correlation coefficients of the obtained health indicator exceeding 0.93 across all tested conditions.