APC says UPS batteries should last three to five years. Your batteries are long past their prime and proabably not reliable. It's unlikely the UPS itself is bad, APC's units are pretty reliable, though far from perfect.

In my experience, gel cell batteries on critical equipment should be scheduled for replacement every three years. In less sensitive locations with few power failures, you might stretch this to four years. Where the batteries are called upon more more often for short outages or smart boost, it may be mecessary to replace batteries every two years. (And I've done all of the above.)

I'm a pretty experience tech with an electronics background. I'm very comfortable replacing APC UPS batteries with correctly sized generic gel cells. The generic cells are far less expensive than APC's packaged battery sets, but to take longer to replace. IMO, it's not difficult if you know much about DC electrical systems.

Otherwise, order replacement battery cartridges and monitor your UPS carefully for a few weeks after its replaced.

Most p

An additional note: Battery life is greatly influenced by two factors: temperature and number of dharge/discharge cycles. A small increase in either will have a noticable negative effect.

So, if you have a warm server room or closet, replace the batteries more often. If the UPS goes into smart boost or discharge more than a few times a year, replace the batteries more often.

Also: Older UPS systems don't always work as well as new ones, the charging circuits can lose their precision. You might want to budget replace the UPS itself after five years or when the servers are upgraded.

--Thanks for the great advice. With a tight budget, that makes my decision easier.
Patrick