This was originally posted on APC forums on 2/16/2011
I have, at home, a Mac Pro attached to a Back-UPS ES750. Using native Mac energy saver integration. I'm seeing pretty frequent warning popups on screen saying "Your computer is now running on UPS backup battery power". At the same time, the unit clicks, whirrs and clicks again.
The Mac is a 2008 model, 4 internal drives, with two 24" monitors. I guess it's possible that the unit is overloaded, but its green light remains steady, and I've heard no warning beeping from the unit at all. I don't know how old the battery is, but again, I've had no "low battery" warning noises, nor anything indicating a power fault on the circuit.
I have a small Brother laser printer on the same mains circuit (but not attached to the UPS), and the issue most often occurs when the printer spools up for a job.
Does this sound more like a battery replacement issue, or is the UPS unit insufficient for the task? Or is there something else possibly going on? Any diagnostics I can run on the box to test?