State of Health Indication Improvement of the Nickel-Cadmium Battery

In Phase I we measured the internal AC impedance (magnitude and phase) of a single cell, 1.4 ampere-hour Ni-Cd battery and derived values related to the components of an electrical circuit model. We observed variations in internal resistance and capacitance of the battery that showed strong correlation to State of Charge (SOC) and State of Health (SOC). In Phase II we propose to continue the investigation into single cell Ni-Cd batteries to develop a repeatable and accurate algorithm to predict the SOC/SOH over all operating conditions and failure modes. The investigation will be expanded to include multi-cell Ni-Cd batteries (up to 20 cells) and increased capacity up to 20 ampere-hours. With demonstrated results that are repeatable and accurate we will develop the prototype hardware and software necessary to implement the sensing, control and monitor, and the processing of the algorithm. The prototype will be designed for compactness, low cost, and accuracy with the capability to interrogate the battery without interruption of normal operation.