Low-earth-orbit testing of nickel-hydrogen cells

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Low-earth-orbit testing of nickel-hydrogen cells

McDermott, J.K.

An extensive test program was funded at Martin Marietta Denver Aerospace to establish a LEO data base for nickel-hydrogen cells. Eighty-two (82) nickel-hydrogen cells with a nameplate capacity of 50 ampere-hours were procured from three vendors for the LEO test program. Testing on the first group of cells was initiated in September 1985. The test plan and preliminary test results were reported in 1985. Over 3000 LEO cycles at 60 % depth-of-discharge (DOD) have been completed to date. One cell had failed after only 511 cycles, and data indicates probable failure due to a short within the cell. Minimal voltage degradation has been observed in the remaining cells and test conditions and parameters are stable. A significant loss of capacity was initially observed in several cells. This capacity loss has been associated with the procedure for cell activation and the hydrogen precharge. Preliminary test data indicates that LEO cycling has reconditioned the positive plates, causing a cell capacity increase with cycling. This paper reviews test data up to May 1986, and compares cell designs based upon performance data. The main purpose of this paper is to initiate a nickel-hydrogen LEO data base for the aerospace community, and arouse interest and participation.