Nickel-cadmium (Ni-Cd) batteries were widely deployed by earlier communication satellites and spacecrafts from 1960 to 1995. When advanced designs of nickel-hydrogen (Ni-H2) batteries were available in early 2000, most of the satellites and spacecrafts preferred to use Ni-H2 batteries. ese batteries will be described in detail with an emphasis on reliability and improved electrical performance. For short mission satellites and LEO communication satellites, both the Ni-Cd and Ni-H2 batteries are still being used.