Nickel-hydrogen LEO cycling at 20-50 percent DOD

Two NiH2 two-cell packs made up of engineering cells built according to the Hubble Space Telescope design (EPI RNH 90-3) are currently being low-earth-orbit (LEO) cycled at 20-50 percent depth of discharge (DOD). The cells were manufactured by Eagle-Picher Industries, Inc., and activated with electrolyte (KOH) concentrations of 26 percent (pack No.1) and 31 percent (pack No.2), for use during evaluation of the HST cell design. The cells have been grouped according to electrolyte concentration but follow the same test schedule for comparison. This test was set up to study the behavior of NiH2 cells having differing electrolyte concentrations, when operated at relatively high DOD (20-50 percent) in a LEO cycling program. The test was designed specifically to allow the cells to pick their own recharge ratio for varying DOD and varying EOC (end of charge) voltages. The cells are being cycled in a simulated 96-min orbit with 60-min charge and 36-min discharge where an EOC cutoff voltage controls high-rate charging. EOC cutoff voltages vary between 1.48 V and 1.56 V.