When NASA astronauts Mike Hopkins and Victor Glover went on a spacewalk on February 1st, they wrapped up a multi-year effort to replace the aging nickel hydrogen batteries on the ISS with new lithium-ion models. The International Space Station Program approved the development of lithium-ion batteries to replace the station’s aging power storage system back in 2011. Battery production started in 2014, and the first lithium—ion replacements flew to the station aboard JAXA’s Kounotori 6 resupply flight in December 2016. Now, four years after that flight and 14 spacewalks with 13 different astronauts later, the upgrade is finally complete.
Ground controllers used the Canadarm2 robotic arm to position some of the batteries for installation. However, some required additional spacewalks for the locations the arm couldn’t reach. The batteries aren’t quite like the lithium-ion we’re used to, with their space-grade lithium-ion cells and radiant barrier shield. Since lithium-ion technology has greater energy density than nickel-hydrogen, only 24 new batteries were needed to replace the 48 old ones.
The ISS uses batteries to store energy harnessed from the sun with its solar panels, and it taps into those reserves every time it doesn’t have access to sunlight. And that happens often, since the station passes between sunlight and darkness every 45 minutes. That stored power is necessary to keep everything working on the ISS, including the station’s life support systems. Aside from providing the station with much—needed power, the batteries could also give us the insight needed to improve lithium-ion safety.
Now that this particular upgrade is complete, the ISS program will shift its focus to replacing the station’s solar arrays. Six new arrays will be flying aboard SpaceX flights over the next few years to replace the current ones near the end of their 15-year lifespan.