SOC Modeling Simulation of Equivalent Circuit of Lithium-Sulfur Battery

Battery management system (BMS) includes the main functions of state estimation, safety protection, parameter testing and information management. The most core function of BMS is to estimate state-of-charge (SOC). Prerequisite for BMS to be able to accurately perform SOC estimation is to have a model with high accuracy. In this paper, the impedance spectral characteristics of each SOC point of lithium-sulfur batteries (LiSBs) are tested. First-order resistor-capacitance (RC) equivalent circuit model (ECM) and second-order RC ECM are both established. The experimental data are used to identify the parameters of the model and complete the modeling. MATLAB/Simulink is used to build a simulation platform to complete the simulation verification of LiSBs constant current discharge condition. The simulation results show that the maximum simulation error of the first-order RC ECM is about 3%, and the average value of the errors in the total interval is 19.8 mV. The simulation error of the 2nd-order ECM is 0.9% with an average value of the error in the total interval of 4.3 mV. The 2nd-order ECM fits the actual discharge condition of LiSBs more accurately. The research results of this paper can provide technical support for the development of energy storage systems for green airports.