International Space Station Lithium-ion Batteries for Primary Electric Power System

The International Space Station (ISS) primary Electric Power System (EPS) was designed to utilize Nickel-Hydrogen (Ni-H2) batteries to store electrical energy. The electricity for the space station is generated by its solar arrays, which charge batteries during insolation for subsequent discharge during eclipse. The Ni-H2 batteries are designed to operate at a 35% depth of discharge (DOD) maximum during normal operation in a Low Earth Orbit. Since the oldest of the 48 Ni-H2 battery Orbital Replacement Units (ORUs) has been cycling since September 2006, these batteries are now approaching their end of useful life. In 2010, the ISS Program began the development of Lithium-Ion (Li-Ion) batteries to replace the Ni-H2 batteries. Now deployed, they are the largest Li-Ion batteries ever utilized for a human rated spacecraft.

I. Introduction

Each existing Ni-H2 battery consists of two series connected ORUs. Post-assembly complete, the ISS EPS has a total of 24 batteries (48 ORUs) in orbit. One new Li-ion battery will replace two Ni-H2 ORUs, with double the power capability of the old batteries. One Li-ion battery will directly replace one of the Ni-H2 ORUs; the second Ni-H2 ORU will be replaced using an adapter plate (AP). The AP provides micrometeoroid orbital debris protection and thermal shielding for the exposed battery slot on the integrated equipment assembly (IEA), serves as a power jumper for the ORU series connection and data, and functions as a structure for storage of a non-functional Ni-H2 ORU (See figure 1, Li-Ion battery and adapter plate ORUs). The combined total launch weight of a Li-ion battery and AP will be over 30 percent less than two Ni-H2 ORUs. Fig. 1.

Li-ion battery and adapter plate orus.ease of use