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A history of the development of the nickel-hydrogen (Ni-H 2 ) technology at COMSAT Laboratories is presented, starting with the initial exploratory effort in 1970 and extending to the present INTELSAT V Ni-H 2 batteries. The latter are based upon the proven reliability of the NTS-2 Ni-H 2 cell design and the manufacturing procedures developed to fabricate these cells. This paper compares four different Ni-H 2 batteries: the NTS-2 battery, the INTELSAT V flight battery, a 50-A-h battery, and a high-pressure 50-A-h battery. Although all these batteries use the same baseline cell design, the length of the pressure vessel and number of modules in the electrode stack are varied to achieve the desired ampere-hour capacity. Comparisons are made with respect to specific energy, energy per unit volume, structural design, and heat-transfer capability. The maximum specific energy achieved was 60.1 W-h/kg for the high pressure 50-A-h cell.

A recently developed sealed nickel‐hydrogen cell offers considerable promise to develop lightweight, long‐life, rechargeable batteries. The most apparent advantages of this cell are its higher energy and power density as compared with other rechargeable systems including nickel‐cadmium, lead‐acid, and silver‐zinc cells and the regenerative H2‐O2 fuel cell. The energy density for lightweight 50 A‐hr cells shown is 28 W‐hr/lb. The cell enjoys a unique overdischarge protection mechanism which allows for long cycle life at high depth of discharge. Experimental data are presented to define the characteristics of the cell. Over 5000 high rate cycles have been completed on small 1.5 A‐hr cells with good voltage performance. A 50 A‐hr cell has completed to date over 800 cycles discharge to 70% of measured capacity in 1.2 hr.

The nickel-hydrogen battery was first used for satellite energy storage aboard the U.S. Navy's Navigation Technology Satellite-2 (NTS-2). A flight demonstration of this new battery was the prime object of the joint Navy/INTELSAT program. The battery's successful performance proves its usefulness for future satellite applications. The nickel-hydrogen battery supplied spacecraft power for one 30-day eclipse season during which two eclipse periods occurred daily, lasting no longer than one hour. Its unique cell reversal feature was successfully demonstrated several times when the battery was inadvertently discharged completely because the solar array lost track of the sun. The nickel-hydrogen battery also uses a novel concept in which temperature is used for charge control. Strain gauges measure cell pressure, thereby providing information which permits a direct appraisal of the battery's state of charge. The use of cell pressure to control the rate of charge also can be considered a suitable method. This paper describes the results of the environmental test program along with the prelaunch and orbital performance through one eclipse season.

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