The performance of six 88 Ah Nickel - Hydrogen ( Ni - H2 ) batteries that are used onboard in the Hubble Space Telescope ( Flight Spare Module ( FSM ) and Flight Module 2 ( FM2 ) ) is discussed . These batteries have 22 series cells per battery and a common bus that would enable them to operate at a common voltage . It is launched on April 24 , 1990 . This paper reviews : the cell design , battery specification , system constraints , operating parameters , onboard battery management , and battery performance .