Thermal behavior and end-of-life characteristics of the nickel-zinc battery

Rechargeable prismatic nickel-zinc batteries are being developed for consumer and mobile applications such as electric bicycles, scooters, vehicles and trolling motor for fishing boats. Nickel-zinc deep-cycle-life performance was improved through the development of a reduced solubility plastic bonded zinc electrode. Individual cells and battery modules achieved 600 cycles at 100% depth of discharge (DOD) while maintaining a high specific energy up to 60 Wh/kg. Routinely cycled to failure of cells and batteries were conducted in order to determine the performance and quality of production cells and examined end-of-life (EOL) characteristics of the nickel-zinc system. A destructive physical analysis is performed at the conclusion of testing to establish the failure mechanism. The typical failure mechanism in the cell is dry-out of the cell pack with a concommitant increase in cell internal resistance and decrease in the utilization of active materials. The thermal behavior of an Evercel model 40 nickel-zinc cell was analyzed. Calorimetric measurements yield a specific heat of 0.38 cal g/sup -1//spl deg/C/sup -1/ for the nickel-zinc system. A thermal model is being developed which will use the data from these studies to predict thermal behavior of the nickel-zinc system for arbitrary size and discharge rate.