For simulating the full discharged and charged states of nickel-cadmium and nickel-hydrogen batteries, thermodynamic characteristics such as the equilibrium E-e and thermoneutral E-T potentials of the cells have been calculated over wide ranges of temperatures (0 degrees-200 degrees C), potassium hydroxide concentrations (0.1-20 mol kg(-1)) and hydrogen pressures (0.1-500 bar). The effects of non-ideality of the hydrogen gas phase and potassium hydroxide aqueous solution were taken into account by using available thermodynamic and experimental data. The effect of temperature, potassium hydroxide concentration, and hydrogen pressures on E-e and E-T have been analyzed.