Impedance parameters and the state-of charge. I. Nickel-cadmium battery

The problem of nondestructive determination of the state-of-charge of Ni--Cd batteries has been examined experimentally as well as theoretically the viewpoint of internal impedance. The modulus of the impedance is mainly controlled by diffusion at all states of charge. Even so, a prediction of the state of charge is possible if the equivalent series/parallel capacitance or the a.c. phase shift is measured at a sufficiently low a.c. test frequency (5-30 Hz) which also avoids inductive effects. These results are explained the basis of a uniform transmission-line analog equivalent circuit for the battery electrodes. 17 ref.--BA