A mathematical model of the discharge behavior of the nickel oxide/KOH/LaNi5 battery system is presented. The model shows great sensitivity to the kinetic parameters of the nickel oxide active material. The thickness and porosity of the battery system’s electrodes are optimized in terms of the specific energy and power of the system. Experimental results are presented which show some qualitative agreement with the discharge curves predicted by the model. In this model, diffusion in the nickel oxide active material is neglected based on the findings presented in Appendix A.