Hey guys, welcome back to the ProjectDIY channel. In this one I’m replacing the battery in our Coredy L900 robot vacuum because it started losing charge crazy fast. It would come off the dock, make it maybe 30–50 feet, and just die completely dead. I’m pretty sure what happened is it got left off the charger while we were gone, got hung up somewhere during its automatic run, and the battery sat discharged for a while—so it was done. I walk through how to take this model apart to get to the battery, because not all robot vacuums have a simple battery door. On the L900 you’ve got to remove the brushes and the screws, pop the cover, and then you can access the battery pack. I also show what I always recommend while you’re in there: clean it out. These things get filthy inside, and dirt/dust is a big detriment to how they operate—especially around the wheels and the front caster. After swapping in the new Amazon replacement pack, I plug it in, route the wire, button everything back up, charge it, and test it. It ran 5–10 minutes right away—already way better than before—so the battery swap did the trick.