I walked in our server room on Thursday afternoon to find one of our APS UPS' had a battery fault. They have been in two years, so it was about time to be honest. So I pop on the APS website to find the RBC (replacement battery cartridge) number, and ordered two (so I had a spare). They arrived late yesterday (Monday) and so this morning I am ready to replace them.
I would normally power down the attached equipment, shut off the UPS and swap the cartridge, but then why should I? My UPS claims to have hot swappable batteries. Leave everything attached and running, undo four screws, disconnect the battery cable and pull out the cartridge. Reverse for fitting the new one. Fantastic.
However, with mission critical devices I prefer to do my research. I came across this blog from a consultation and support business Trueblade Systems Inc, who have been through the same issue. They write that on completion of a battery hot swap, the UPS does not clear the battery failure light. To turn this light off, you must power-cycle the device!