State of charge estimation for Lithium-Ion battery cell considering the influence of aging parameters and operating temperature

Abstract

This article presents a state of charge (SoC) estimation for Lithium-Ion batteries (LiB) based on first-order equivalent circuit model (ECM) that takes into account the aging parameters and operating temperature of the cell. First, the first-order ECM of the cell is proposed considering parameters of the aging process including state of health (SoH) solid electrolyte interphase (SEI) layer resistance, and charge transfer resistance. The parameters of this equivalent circuit model are established for a new cell at different operating temperatures. The model's physical parameters are identified based on experimental data from specific discharge/charge scenarios. Based on the ECM proposed, the SoC estimation algorithm for battery cells using the principle of Sigma Point Kalman Filter (SPKF) filter is applied. The use of the SPKF filter allows for consideration of the non-linearity of the relationship between open circuit voltage and SoC in the model. The parameters describing the cell aging process used in ECM permit representation more accurate of the dynamics of the cell change during operation. The estimated SoC for aged cells corresponding to different SoH values shows that the amount of SoC increase during constant-current charging, full-charging time, and average SoC increase rate during charging depend strongly the aging of the cell. SoC estimation results considering SoH will achieve higher accuracy, especially for cells used in practical applications.