Some nickel-iron, and nickel-metal hydride, cell cycling results

Some cycling experiments were performed on two kinds of cells: nickel-iron and nickel-metal-hydride. A nominal 200 Ampere-hour nickel-iron battery was obtained from Eagle-Picher, Inc. and its initial capacity was determined by cycling at the manufacturer's recommended regime. A single cell was removed from the battery and placed in a cell case designed to provide for quantitative assay of all gases evolved. After determining that no change in ampere-hour capacity of the cell had occurred as a result of the handling of the cell, the cell capacity was reduced to 15 Ampere-hours in a negative-positive-negative configuration by removal of plates and by cutting the remaining plates to approximately one-half the original area. The resultant cell displayed the calculated capacity. At this time the charging regime was changed to include high rate DC, up to 6C, and various forms of non-DC charging, again at high rates. During these experiments, careful assay of the instantaneous quantities of hydrogen and oxygen were performed using gas chromatography. No significant effects of kinds of charging currents upon quantities of gases evolved were found. Some nickel-metal-hydride cells were subjected to cycling experiments. The cells were intended for use in lap-top computers; the capacity was at the 2 Ampere-hour level. A pressure-measuring transducer was affixed to cells under study in such a way that the interior gaseous content of a cell was not allowed to escape, and the void volume of the cell system was not increased by more than about 0.5 ml. Pressure versus state-of-charge results at various temperatures are presented.< >