[mm89]

I also have an APC Back-UPS. Mine are the Back-UPS 650 model, I have two of them. Both emit an annoying LOUD high-frequency capacitor whirring noise that is audible to my ears even when the loud AC intake fan is blowing in the same room. I'm actually shocked any company would ship a product in this condition, unless all their customers have hearing problems. It's a power strip... it's supposed to be silent. Not like a computer.

If my batteries die, I'll just replace them with non-battery backup strips. Not worth the trouble for me living in a city where power goes out maybe once per year on average for 10 minutes, and I don't have servers that need to stay online anymore.