Why it isn't my XS 1300 Battery Charging?

[Anonymous user]

Yesterday I noticed that the battery icon on the UPS was showing just an outline and is flashing. I turned the audible alarm back on and it is chirping twice in quick succession every 3 seconds. Total load on the unit is ~ 290 - 300 W, so it's nowhere near being overloaded. I don't have a USB - RJ-45 cable, so I can't use PowerChute. I did pull the batteries - 2 x 12V cells in series. My DVOM read 26.25 VDC for the batteries and 27 VDC across the battery cables. To me, the batteries seem to be fine and I don't understand why they're not charging, or why the UPS is not recognizing them as being charged. Naturally the UPS is out of warranty. Any thoughts as to what the problem might be? I don't want to buy new batteries just to confirm that the backup system on this UPS is toast.