I had to go in to work today for a UPS Failure. This is a 25kva unit that uses three strings of 12V batteries (36 total). We had planned to replace the batteries later this year. The site had went "dark" and I by-passed the UPS. The batteries came in, but they had to go get a pry bar to remove the old swollen ones.
Batteries were 6 years old, and due to budget constraints could only be budgeted for replacement this year. I opted to go with one string of 12, as we only pull 1.2kva, and have a site generator.