Fast Calculation of Broadband Battery Impedance Spectra Based on S Transform of Step Disturbance and Response

Abstract

Electrochemical impedance spectroscopy (EIS) is one of the most powerful tools for battery sorting, state estimation, and diagnosis. To obtain EIS, a conventional and time-consuming sweeping sine method is commonly used in a laboratory depending on professional equipment, which is limited for practical applications. For the first time, this article proposed a fast calculation method of broadband battery impedance based on the S transform (ST). It reduces the requirements for the broadband impedance acquisition greatly by processing the step disturbance and response, which can be generated with a common charging/discharging device. For a pouch lithium-ion battery cell, the method can obtain its impedance of 1 kHz–0.01 Hz with the real part errors smaller than 5%. Also, the imaginary part errors of 1.9953–501.19 Hz in the charging case and 1–316.23 Hz in the discharging case are within ±10%. Compared to the sweeping sine method, at least 19% of the acquisition time can be saved. Also, more than 84% of the calculation time is also shortened compared to the previously reported Morlet wavelet transform. For practical guidance, the effects of the algorithm parameters (integration interval, sampling frequency, signal length, and signal amplitude) are also comprehensively studied.