Back-UPS ES 550: Computer repeatedly forced into hibernation

[Anonymous user]

Hi --

I have several Windows XP Pro SP3 PCs at the same office, each connected to a Back-UPS ES 550. I'm having this problem with three (so far) out of the five PCs there:

Any time that there's any power drop, even the most imperceptible power blip that no one in the office even notices, the PCs are immediately ordered to hibernate.

In each PC's Power settings, I have set them up so that they go into hibernation whenever the UPS battery reaches a critical level. "Critical level" is defined as 17% of the battery charge.

Diagnostics in each case show that the batteries are OK. In fact, on each of these three PCs I disabled the hibernation setting, disconnected the UPS from the wall outlet while the PC was running, and ran the PC on battery power for upwards of 10 minutes before plugging the UPS back in. None of the batteries reported a drop to anywhere near the programmed critical level.

One of the UPSes has been service for about two years and had its battery replaced in December. The second UPS is a little over a year old. And the third UPS has only been in service since March. They're each supporting identical HP minitower PCs with identical flat-panel displays. One of the UPSes also supports a small WiFi access point. Otherwise, nothing else is plugged into these devices' battery outlets.

What's causing this, and how do I fix it?

Thanks
CL