CAPE CANAVERAL, Fla. (AP) — Astronauts completed their second spacewalk in under a week Wednesday to replace old batteries outside the International Space Station.

Commander Chris Cassidy and Bob Behnken quickly tackled the big, boxy batteries. For every two outdated batteries coming out, a new and improved one goes in to supply power to the space station on the night side of Earth.

Within a couple hours, the astronauts had installed another new battery, the third one in this latest series of spacewalks that began last Friday. NASA plans to send the pair out twice more in July to finish the battery swap-outs that began in 2017.

The new lithium-ion batteries should last the rest of the space station’s life, according to NASA.