IMPEDANCE PARAMETERS OF INDIVIDUAL ELECTRODES AND INTERNAL RESISTANCE OF SEALED BATTERIES BY A NEW NONDESTRUCTIVE TECHNIQUE

A new robust method for the nondestructive determination of impedance parameters of the individual electrodes of sealed batteries has been developed. In this method, a battery is discharged at a constant current of about 2000 h (or less) rate for a few seconds only. The discharge transient of voltage against time is analysed theoretically to give effective double layer capacitances and charge transfer resistances of battery cathode and anode separately, as well as the internal resistance of the battery. Experimental data from discharge transients are processed with a new procedure which is immune to normal measurement errors and which permits a resolution of the parameters of the anodic and cathodic relaxation processes even if their time constants are not far apart. The correctness of the method is verified by simulation studies, and applied to sealed recombinant type lead-acid batteries. Diffusion resistance is shown to be negligible under the test conditions. The effects of switching transients and any series inductance are eliminated by the method. The results are directly relevant to improved battery design and failure analysis.