A comparative study of equivalent circuit models and enhanced equivalent circuit models of lithium-ion batteries with different model structures

Lithium-ion battery model is critical for voltage and state of charge (SOC) determination, and the equivalent circuit model (ECM) is frequently implemented in real -time cases due to low complexity, but the low-SOC-area performance requires improvement. This paper introduces an enhanced equivalent circuit model (EECM) based on electrochemical analysis, in which the surface SOC (SOC_surf) reflects the lithium concentration at the particle surface and is used to determine the terminal voltage. Five empirical based models with different model structures (in which two ECMs and three EECMs included) are selected to compare the model accuracy and complexity. Experiments were carried out on a battery test system with a temperature chamber, and a modified hybrid pulse power characterization (HPPC) profile was employed to measure the battery dynamic response. The genetic algorithm method is implemented in model parameterization, and the voltage estimation accuracy of the five empirical models is compared in SOC range 0~100%. The results show that the EECMs considering SOC_surf provides better accuracy than the traditional ECMs in low-SOC area, and the EECM with one RC component and one DS component provides the optimum performance considering accuracy and complexity.