Nickel-hydrogen load sharing test for RNH-90-9 and RNH-76-3 cells

The relative performance characteristics and load sharing of two designs of Ni-H₂ secondary cells in a system with three power channels was studied. Compatibility of the cell designs and achievement of acceptable depths-of-discharge were verified. A bench test was configured with three strings of seven cells in parallel. One string was composed of RNH-90-9 cells, while the other two strings were RNH-763 cells. Two separate sets of electrical cycles were applied, both at 5°C (41°F), with progressive current step-down as charge control. In the first half of the testing, the electrical cycling consisted of 96-minute cycles repeating after 15-cycles per day were applied. The load applied across the three strings was a constant 350 W, with programmed variations between the cycles using various discharge times and a 700 W discharge pulse which was applied once per day. In the second half of the testing, the same constant 400 W load was applied each cycle. The conclusion of the test is that all cells achieved stable operation in reference to amount of coulombic input/output. Higher recharge ratios were achieved in the second phase of the test. However, probably due to the lower impedance of the RNH-90-9 cells, these cells provided a greater percentage of the total power required. An observation noted was that the RNH-90-9 cells did not reach the temperature-compensated voltage cutoff curve which was developed for the other cell design