Effects of floating charge ageing on electrochemical impedance spectroscopy of lead-acid batteries

The lead-acid battery as a direct current emergency power supply to the substation is subjected to long-term floating charge ageing, which is a special working condition. However, there is limited research on estimating the battery life for floating charge ageing. Compared to other parameters, Electrochemical Impedance Spectroscopy (EIS) is closely related to changes in the battery. This paper investigates a simple and effective method based on EIS to estimate the state of health (SOH) of lead-acid batteries used in substation backup power supply. In this paper, a high-temperature floating charge ageing experiment was carried out to simulate the ageing process of backup power supply in a substation and shorten the experimental time. The Pearson correlation coefficient of impedance from 0.01 Hz to 1000 Hz was calculated with the battery's SOH, and the impedances at three frequencies (19.860 Hz, 9.931 Hz, and 3.946 Hz) with high correlation coefficients were selected as indicators of battery SOH. The proposed health indicators and method were validated by batteries retired from the substations, and the results showed that the impedances selected could be used as indicators of lead-acid batteries, with an average estimation error of 2.723 %.