Nondestructive determination of impedance parameters of the individual electrodes of a nickel/cadmium battery has been developed starting from galvanostatic test and theoretical analysis of the discharge transient of voltage against time. Measurements were carried out on the battery before and after discharges to different states of charge. Experimental data are processed with a new procedure which permits determination of anodic and cathodic relaxation processes. We compare with electrochemical impedance spectroscopy (EIS) to resolve the modelling problems.