MacPro/UPS shutting down too quickly?

[williemyers]

apologies in advance, as I'd bet this has been covered before - just couldn't find it with Search?
the problem is - in broad, general terms - I have an early 2008 8-core hooked up to an APC UPS XS 900 battery backup. The Mac Pro's a couple of years old, as is the APC.
Lately, when power goes down, the UPS battery kicks in just fine, giving me a few moments to save work, as hoped for. But when the power comes back on - and the UPS switches back from battery to line - the MacPro dies. The problem is that, if it's a really quick "power-off/power-on" (say, about 1 sec. or less), having the MacPro shutting down that quickly leaves no opportunity to save anything!
I would pretty much expect the UPS to be at fault here, but recent reading has lead me to believe that the power supply of the MacPro may also be part of the equation.
So just wondering if anyone else has encountered this type of problem, and suggestions?

 

[DanielCoffey]

It sounds as if the UPS is not switching back from battery to mains cleanly and causing the MP to shut down. If the UPS was working properly, the MP should never know there has been a power incident.

I would advise contacting APC and seeing if your UPS is still covered under warranty. If not, your options would include changing the batteries for a new set or taking advantage of their TradeUPS scheme to get a handsome rebate off a new UPS (something like the SmartUPS SMT1000I for example).

 

[wonderspark]

I'd guess the battery in the UPS is wasted. They don't last forever, even though it might seem like it's fine with the power on. I just replaced my SUA1500 battery, because a quick test showed it only lasted about 12 seconds before giving up when I unplugged it. With a new battery, it went on over 40 minutes unplugged before getting down to the last bar on the display. On a smaller unit like yours after two years, I'd be surprised it even lasts ten seconds when you unplug it.

Also, it might have to do with the total power being put out to everything plugged into the UPS when the power dies. Since it only puts out 540 watts, you may discover that it can't keep up with a Mac Pro during a power event... especially if you have monitors and whatever else plugged into it. I'd look into getting a larger model.