Dual Battery Control for In-Situ Impedance Spectroscopy during Variable Load Demand

The in-situ implementation of battery impedance spectroscopy has gained much attention in recent years, because of its potential to provide comprehensive diagnostic information on the battery’s internal condition, including state of charge and state of health. However, the requirement of steady-state operation to perform impedance measurement clashes with the continuous load variation that is typical of many industrial or commercial applications. To address this challenge, this paper proposes a solution based on two battery packs and a dual control strategy of their respective DC-DC converters, to perform steady-state impedance spectroscopy on one pack, while the other pack responds to the variable power demand from the load. Preliminary experimental validation is performed on a small-scale prototype using LiFePO4 batteries, confirming that the proposed approach allows obtaining comparable impedance results in steady-state and variable load conditions, in a wide frequency range, from 10 mHz to 100 Hz.