SOH diagnostic and prognostic of high energy application by the relationship of health indicators

Battery pack consists of series and parallel combinations depending on the purpose of the application. The battery pack uses many cells, and a degradation of each cell leads to cell-to-cell imbalance and accelerates degradation of the battery pack's performance. It is necessary to reflect the degradation of cell and battery pack. In this paper, a technique for diagnosing battery packs is proposed to reflect both the degradation effects of cells and battery packs. To reflect the effect of degradation, a health indicator is needed to determine the degradation effects of unit cells and the battery pack. In this paper, a cycle life test is performed to analyze the degradation effects using 24S1P battery pack, and health indicators are defined. Pearson`s correlation analysis is performed with the discharged capacity and health indicators. Correlation analysis confirmed the possibility of the proposed health indicators. In addition, a multiple regression model using health indicators is designed and verified for state-of-health (SOH) of unit cells and battery pack.