Performance Analysis of Lithium Cell Assemblies Considering Parameter Uncertainty

Abstract

This paper presents a procedure to analyze the resulting capacity of batteries assembled from cells with dissimilar parameters. This is relevant for second-life batteries that reuse cells from various previous applications. Considering the disparities in the ElectroMotive Force (EMF) function and in the internal resistance of the cells that make up the battery, we analyze the resulting effective capacity of the battery. The simulations indicate that the imbalances in the EMF functions have greater impact on reducing the effective capacity than the disparities in the internal resistance. The procedure was applied to ensembles using commercial LiFePo 20Ah cells. For this case, it was found that when the EMF functions of the cells differ by at least 30 mV, the capacity was reduced to approximately half the nominal capacity.