Circuit parameters extraction algorithm for a lithium-ion battery charging system incorporated with electrochemical impedance spectroscopy

摘要

In recent years, battery chargers are not only capable of charging a battery, but also can measure the internal impedance spectrum of a battery in real-time. Measured battery impedance represents electrochemical characteristics, which are used to analyze the internal conditions of a battery and can be represented by a circuit model. This paper presents an equivalent circuit parameter extraction algorithm based on the impedance spectrum measurement of a battery. The proposed algorithm is designed using the Nyquist theory and is applicable to lithium ion batteries specifically. The circuit simulation, ac perturbation, and parameter extraction are processed with the measured circuit parameters, which are obtained from electrochemical impedance spectroscopy (EIS) test of a 1000mAh Li-ion battery. It shows 0.0216mΩ difference for Ohmic resistance extraction based on the proposed simulation results and the selected parameters from experiment. The presented algorithm could be applicable to the battery charger, which is capable of obtaining on-line electrochemical impedance spectrum. The algorithm could be useful for a battery management system as well.