Voltage vs. temperature characterization of standard 80 Ah Eagle-Picher NiH2 cells

The electrical and thermal performance of 22 common or standard 80 Ah individual pressure vessel (IPV) nickel-hydrogen (Ni-H₂) cells manufactured with slurry process electrodes and three cycled dry sinter process electrode cells similar to those used on the Hubble Space Telescope (HST) battery have been acceptance tested and characterized over a matrix of operating conditions from 14°F to 86°F. The testing included standard capacity tests and electrical cycling using 96-minute cycling regimens incorporating constant depth of discharge (DOD) cycles with step changes in cell current at two points in the discharge. The testing was performed in both a test cart and an environmental chamber, with some of the cycling repeated under isothermal conditions. The results of the resting included cyclic heat generation during a typical 96-minute cycle, operating capacity data vs. cutoff voltage to generate a temperature-compensated voltage curve, and voltage characteristics suitable to develop a voltage prediction model. Four additional cells were subjected to electrical cycling within an environmental chamber for the purpose of acquiring cyclic heat generation data as a function of state-of-charge, temperature and charge/discharge rate. The testing in the environmental chamber included conditioning cycles and characterization cycles at various load conditions. The voltage characteristics for matrix conditions tested within the chamber matched those obtained for the corresponding testing within the test cart