Got a weird problem. I've got a simple home server setup to host some audio/video files for streaming. Since it doesn't do a whole lot, I've got a Rosewill Capstone 450M PSU in the box. The box is hooked up to a Cyberpower CP1500AVRLCD UPS. I've only got a switch plugged into the UPS with the server, so there's very little load on it. About three weeks ago I noticed the server was down, went in and found the UPS' LCD screen just kept flashing and nothing on the Battery/UPS side would get power (stuff on the UPS only side did still get power).

I talked to Cyberpower and they said it was likely the batteries had gone bad. The UPS was 5 years old and I happened to have a spare CP1500AVRLCD lying around (also about 5 years old) so I swapped that in, ordered new batteries for the bad UPS unit and called it a day. Well, this morning I woke up to find the server down again, and once again, the LCD was flashing and it looks like the batteries are shot. My initial thought is there's a power problem, but I had specifically plugged this second UPS into a different outlet on a different circuit back when I swapped it in for the other just to make sure it wasn't that.

Could there be any way the PSU is actually killing the batteries, or is it more likely that being 5 years old, these UPS batteries just happened to be at end of life right around the same time?

Any thoughts?