Just replaced the battery on my Trust (Oxxtrton) 1000VA UPS, used a Yucel Y9-12 (9AH) battery, diferent make, same spec. as original, cost approx. £28 + P&P from e-bay supplier.
Unit has been in service for just over 2 years, battery completely U/S., maintained minimal load for less than 30 sec's., could well have been U/S for some time earlier as never recently tested.
On re-commissioning, left case open with a 10 amp range Fluke multimeter in the battery circuit to check charging current.
Charging current tapered off nicely to expectation under no load from close to 1 amp to approx. 50 ma. over 8 hour period.
On load test with a 60 W. filiment lamp, close to 6.5 A's was drawn from the battery, obviously the inverter is not very efficient.
Load still going strong after 30 min's so aborted and re-boxed, happy with outcome.
Moral of the story, test UPS operation regularly, battery will eventually fail and certainly with my particular model will not be apparent until called into service, other, higher specification units may be different.