One large data centre that would rather remain anonymous, was able to identify from their battery monitoring that the charger on the UPS had been incorrectly set and was overcharging the batteries.
Battery monitoring strategy
A data centre had UPS systems with 5 strings of batteries per UPS. The batteries needed replacing but they did not have budget for this. Therefore they reduced the number of strings from 5 to 4, identified the good batteries in the strings removed and used these to replace any batteries that were showing signs of failure in the remaining strings. With battery monitoring they were confident of having the back up required and were able to replace any defective batteries with batteries of the same age.