The non-linear low-frequency impedance of lead/acid batteries during discharge, charge and float operation

The paper presents a systematic experimental study of the impedance of several types of lead/acid batteries (flooded and VRLA) at-different states-of-charge (SOC), superimposed direct currents, and temperatures. A consistent equivalent-circuit model has been extracted from the measured data for the float, open-circuit, discharge, charge, and microcycle operation. The model elements are linked with cell geometry, electrode porosity, reaction kinetics, and diffusion hindrance. The dependence of all impedance parameters on direct current (non-linearity), temperature, SOC, and previous discharge/charge regime is systematically investigated. The lead/acid battery model is discussed with respect to impedance-based battery characterization and monitoring.