Low Pass Filter Based Lithium-ion Battery Equivalent Circuit Model With High Accuracy

Abstract

The equivalent circuit model (ECM) of lithium batteries provides a simplified way to describe their output behaviors. In this paper, a low pass filter-based ECM of lithium battery is proposed with high accuracy. A voltage source is employed to represent the capability of the lithium battery to store energy chemically, a RC branch paralleled with the voltage source represents the charge transfer process. This RC branch acts as a low pass filter, and the capacitance buffers the charges during charging or discharging process, and this explains the dynamic voltage recovery process. However, with the traditional RC branches-based ECM, the dynamic voltage is realized by the resistance in parallel with the capacitor, which discharges the capacitor and the RC branch is series-connected with the voltage source. The proposed ECM is compared with the 1-RC Thevenin model, which has the same number of model parameters with the proposed model. The parameters are obtained by the hybrid pulse power characterization (HPPC) test. The output voltage accuracy of the 1-RC Thevenin model and the proposed model with LFP battery and NCM battery is verified with different test conditions. The experimental results show that the proposed ECM has higher accuracy, this validates the correctness of the proposed model.