LONG-TERM STORAGE OF NICKEL HYDROGEN CELLS

Representative samples of nickel-hydrogen cells for the INTELSAT VI program were used to evaluate the effects of prolonged storage under passive conditions, such as open-circuit discharged at 0 degree C, room temperature, and minus 20 degree C, and under quasidynamic conditions such as top-off charge and trickle charge. Cell capacity declines when cells are stored open-circuit discharged at room temperature, and a second plateau occurs in the discharge curve. Capacity loss was 47% for a cell with hydrogen precharge and 24. 5% for one with no hydrogen precharge. Capacity recovery was observed following top-off charge storage of cells which had exhibited faded capacity as a result of passive storage at room temperature. Cells stored either at minus 20 degree C or on trickle charge maintained their capacity. At 0 degree C storage, the capacity of all three cells under test was greater than 55 A h (which exceeds the required minimum of 44 A h) after 7 months.