A method for measurement and interpretation of impedance spectra for industrial batteries

Impedance spectroscopy is a promising tool for the modeling and diagnosis o f industrial batteries. This paper discusses methodological questions conne cted with the measurement and interpretation of the impedance of such batte ries, especially nonlinearity, voltage drift, stability, reproducibility, h alf-cell measurements, model structure and parameter extraction with respec t to quantities like state of charge (SOC). On the basis of this discussion , a specialized impedance spectroscope for industrial batteries has been de veloped, as well as modifications of the standard electrochemical impedance spectroscopy (EIS) algorithm. A mini-cycle technique is suggested that gai ns additional information compared to classical measurements with continuou s de current offset. Impedance spectra from lead/acid batteries for differe nt de currents, SOCs, and temperatures are presented and analyzed. Referenc e-electrode measurements allow for separation of the half-cell impedances. Emphasis is placed an the limits of experimental reproducibility due to "hi story" of the battery. (C) 2000 Elsevier Science S.A. All rights reserved.