The Extravehicular Mobility Unit (EMU) used by astronauts during space walks is powered by an 11-cell, silver-zinc battery. The present battery is certified for 6 cycles with a minimum discharge requirement of 7 hours above 16.0 volts at a 3.8 Amp load. Its certified wet-life is 170 days. Operational requirements for the International Space Station (ISS) led to a design capable of 32 cycles over a 425 day wet-life. Other battery parameters including capacity, rate capability, weight, volume, safety and the need for continuing compatibility with the EMU and the Space Shuttle charger dictate that the new battery will also be silver-zinc.