WASHINGTON     -   Two U.S. astronauts completed a spacewalk out of the International Space Station on Sunday, the first in a series of five spacewalks in October to replace batteries on the far end of the station’s port truss.

Astronauts Christina Koch and Andrew Morgan wrapped up their spacewalk at 2:40 p.m. American Eastern Time, lasting about seven hours and one minute, according to the U.S. space agency NASA.

They installed new lithium-ion batteries that would upgrade the station’s power systems. The existing nickel-hydrogen batteries are being upgraded with more powerful lithium-ion batteries transported to the station aboard the Japanese H-II Transfer Vehicle, which arrived on Sept. 28, according to NASA.

Also, the two astronauts accomplished some get-ahead tasks, including the removal of an additional nickel-hydrogen battery, originally scheduled for the next spacewalk on Oct. 11.

The batteries store power generated by the station’s solar arrays to provide power to the station when the station is not in the sunlight, as it orbits the Earth during orbital night.

Astronauts aboard the International Space Station plan to conduct another nine complex spacewalks in the coming three months, a record cadence since assembly of the space station was completed in 2011, according to NASA.

Space station crew members have conducted 219 spacewalks in support of assembly and maintenance of the orbiting laboratory, spending a total of 57 days, six hours and 27 minutes working outside the station.