A Novel Method of Open Circuit Voltage Reconstruction for LiFePO4 Battery based on Incremental Capacity Analysis

Abstract

The inconsistencies of capacity and SOC make series-connected cells unable to be completely charged or discharged, which severely restrict the performance of the pack. In this case, the complete open circuit voltage (OCV) curve of cells will not be available, which will affect the accurate estimation of capacity and SOC. Therefore, how to reconstruct the OCV curve of cells without disassembling the pack is of great significance for the BMS to accurately estimate the cell state information and improve the stable operation of the energy storage system. In this paper, a new method to reconstruct OCV of LiFePO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf> battery based on incremental capacity analysis (ICA) is proposed. Feature points closely related to battery aging are extracted based on ICA obtained from OCV curve. By using voltage curve transformation, the optimal transformation coefficients are calculated. Finally, the reconstructed OCV curve segments will be obtained by transforming the OCV curve of other cells in the pack. To verify the method, experiments are conducted with cells connected in series, and the results show that the maximum error of the reconstructed OCV curve does not exceed 2.5%.