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Nickel-Hydrogen (NiH2) realtime and accelerated low-earth-orbit (LEO) cycle test data at 10°C have been used to generate a model of reliability as a function of depth-of-discharge (DOD). The reliability model is specific to cells incorporating positive electrodes manufactured by the wet slurry process. A cycle life prediction has also been derived from the reliability equation and has been compared to two other predictions: one for NiH2 cells of generic design and one for Nickel-Cadmium (NiCd) hardware. The comparison clearly shows the superiority of NiH2 in LEO. At each DOD for which test data existed in the 5°C to 10°C range, the realtime and accelerated LEO life cycle test data were algebraically fit to a Weibull distribution which passes through the current cycle count of the ongoing tests, none of which have experienced a failure. The analysis was performed for the 15%, 30% and 40% DOD test conditions for “wet slurry” NiH2.

The electrical and thermal performance of a 40 Ah dual stack Nickel-Hydrogen (NiH2) cell has been characterized at 0°C and 10°C. The testing included standard capacity tests and electrical cycling using 100 minute cycling regimens, utilizing one of three modes: 1) Cycling containing 77A pulse loads applied for 6 msec followed by a 24A charge for 6 msec; 2) Constant current, constant depth-of-discharge (DOD) cycles; and 3) Constant DOD cycles with step changes in cell current at three points in the discharge. The testing was performed with the cell in a heat conduction calorimeter. The results of the test included amount of instantaneous heat generation during a typical LEO cycle, pressure vs. cutoff voltage data to establish a temperature-compensated voltage cutoff curve, and voltage characteristics suitable to generate a voltage prediction model. The inductive response to pulse loads is of interest and is discussed in the paper.