We have some 70+ APC Smart-UPS SMT1000RM2U units deployed at small wireless repeater sites. They are monitored via AP9630 management cards. Typically, the battery voltage reported by SNMP is 27.0 volts which seems correct for floating 24 volts of sealed lead acid cells.
However, we now have several sites where the reported battery voltage is much lower most of the time, going up approximately once every week to 27.0 volts for 24-30 hours and then back down for the rest of the interval. I've attached a SNMP record for the last month at one such site.
We recently had a commercial power outage while the battery voltage was reported as 26.0v and indeed, during the power outage, the battery voltage declined much more rapidly than I would have expected had the batteries been correctly floated at 27.0v.