So I bought an APC 550 UPS at the Peterborough Costco. Maybe they hardly go through them, and they're years old. This thing has a lead-acid battery, and those things have to be topped up once in a while. This equipment should have a 'best before' date!
It didn't charge. I couldn't get the voltage past 7 V. I originally followed the instructions, and it lasted 2 days before the dreaded 'double beep'. This is all over the Internet, and I followed the reset instructions and it didn't work. I'm just taking it back to Costco, since the APC support doesn't sound good, and who wants to wait for a battery? One guy on the Internet had successive failures on returns from the same store, so I guess a whole batch can go bad. I'll try a different Costco.
Update: I went back to Costco and got a new one way in the back with the new labelling. The voltage was 12.7 V. I ran apcupsd which is the Linux daemon to monitor it, and everything is perfect. I ran some power tests and it works. You've got to note that only one half of the plugs are battery backed up. (Duh!!)
The unit is one year old, so these things are good for at least a year. I wish I could have tested the old one, probably years old.
Get one way in the back. Kill yourself if you have to. :)
Check the voltage on the battery right away. If below 12V take it back.
Run a utility if you can.
Update2: The official shelf life of these things is 9 months, so a year is pushing it. If it has maintained a voltage above 12V it is probably not damaged.