The study of battery energy storage system deterioration and inconsistency

The large scale battery energy storage system (BESS) has been applied to power grid for fluctuation restraining, however it is not easy to analyze or model the BESS due to complex operational conditions and uncertain parameters. The cell-to-cell variation has impact on both the state of charge (SOC) estimation and BESS capacity, yet the deterioration pattern of battery pack, especially in large scale, is not clear. This paper presents the study of deterioration and inconsistency pattern of BESS, based on the experimental data of life cycle test. The result explains how the inconsistency of battery pack enlarges and the worst cell affects the whole pack. This paper represents a qualitative theory of deterioration in large scale battery pack and is useful for BESS simulation and analysis.