Changing out some batteries on my server room APC Smart-UPS X 3000 units. One said it had a bad battery, the other was working, but they are the same age, so it can't be too far behind. I installed a new battery in the primary UPS and moved the battery from the primary UPS to the secondary UPS to get a little more life out of it.

Parts Used:
APC RBC117 - https://amzn.to/4baObzc