An Empirical Model for State of Charge Estimation Based on Electrochemical Impedance Spectroscopy

Electrochemical Impedance Spectroscopy (EIS) is an accurate method used to study the internal properties of lithium-ion (Li-ion) battery cells. It is important to accurately estimate the State of Charge (SoC) of Li-ion battery cells for safety and longevity considerations. There are several methods to estimate the SoC; however, accurate methods require a lot of computational resources and increase the system complexity. This paper proposes an EIS-based experimental method for SoC estimation based on calculating the area under the EIS magnitude vs. frequency curve and correlating the result with SoC. The results demonstrate a relationship between the EIS magnitude and the SoCs within a certain range and under specific conditions. Furthermore, the suggested method reduces the errors and eliminates the need for fitting the EIS impedance spectrum for SoC estimation.