National Aeronautics and Space Administration

lntemational Space Station (ISS) Electric Power System (EPS) utilizes Nickel-Hydrogen (Ni-H__) batteries as part of its power system to store electrical energy. The batteries are charged during insolation and discharged during eclipse. The batteries are designed to operate at a 35 % depth of discharge (DOD) maximum during normal operation. Thirty eight individual pressure vessel (IPV) Ni-H., battery cells are series-connected and packaged in an Orbital Replacement Unit (ORU). Two ORUs are series-connected utilizing a total of 76 cells, to form one battery. The ISS is the first application for low earth orbit (LEO) cycling of this quantity of series-connected cells. The P6 Integrated Equipment Assembly (IEA) containing the initial ISS high-power components was successfully launched on November 30, 2000. The lEA contains 12 Battery Subassembly ORUs (6 batteries) that provide station power during eclipse periods. This paper will describe the battery hardware configuration, operation, and role in providing power to the main power system of the ISS. We will also discuss initial battery start-up and performance data. 1.