Analysis of the relationship between battery internal resistance and SOC

The estimation of battery SOC is the core problem to be solved in the design of BMS. The accuracy of SOC estimation will directly affect the control decision of battery management system, and then affect the service life and efficiency of battery pack. In this paper, the relationship between internal resistance and SOC is analyzed by electrochemical impedance spectroscopy algorithm. It is found that the ohmic resistance RΩ, cathodic polarization resistance R2 and the total internal resistance of the battery in the equivalent circuit decrease with the increase of SOC, while there is no clear corresponding relationship between other element parameters and SOC in the equivalent circuit.