Diffusion-limited self-discharge reaction in the Hubble space telescope battery

The self-discharge rate of aerospace flight-quality nickel-hydrogen batteries is limited by hydrogen diffusion within the nickel electrode active material. A diffusion-limited reaction model is developed which accounts for the observed self-discharge behavior. Effective hydrogen diffusion coefficients were calculated from the open-circuit self-discharge data on Hubble space telescope flight-qualified nickel-hydrogen cells and ranged from 1.12 x 10(-10) cm(2)/sec at 25 degrees C to 7.45 x 10(-12) cm(2)/sec at 0 degrees C.