A Parameter Extraction Method for the Thevenin Equivalent Circuit Model of Li-ion Batteries

This paper presents a novel parameter extraction method for the Thevenin equivalent circuit model of Lithium-ion batteries. The proposed approach represents each of the RC parallel branches of the Thevenin equivalent circuit model of a Lithium-ion battery as a first order linear time-invariant (LTI) system. The resistance and capacitance values for each of the RC branches in the model have been identified as the parameters of a standard LTI system using system identification theory. The proposed approach is easy to implement, as opposed to the existing approaches and yields a good degree of accuracy. The accuracy and effectiveness of the proposed approach have been validated by determining Thevenin equivalent circuit model parameters of a lithium-iron-phosphate battery cell from experimental data obtained by performing controlled pulse discharge tests on the battery cell in the LabView platform. The accuracy of estimated parameters has been validated by developing a Thevenin equivalent circuit model of the battery using extracted parameters, and simulating voltage responses of the battery in Matlab/Simulink platform and comparing the responses with the experimental results.