2018 Mac mini shuts down despite UPS

I don't know if this would help you, as you needed an ASAP answer, but it may help somebody else.

I had a similar situation with a Mac Studio hooked up to an APC BX2200MI. Every time the UPS switched to battery, my Mac got brutally turned off. Funny enough, my Windows PC kept going - I guess it's not as sensible as the Mac.

But if I turned on the Mac while on battery, it didn't have any issues. So the problem does not sit with the battery, which is less than nine months old and very rarely used.

After trying everything without any success (short of replacing the UPS and its battery), I finally discovered that, unlike the Windows PC, my Mac was connected to the UPS via an extension cord and not directly to the UPS.

Connecting it directly to the UPS solved my problem and today I got to test it again in a real-life scenario: no more problems.

And then the second main power is restored, the Mac reboots, again sensing a difference in its power source.

What that Mac is "sensing" is restoration of power subsequent to a power failure. You can configure that setting to your liking. Read Change Energy Saver settings on a Mac desktop computer - Apple Support.

Traveling Rae wrote:

No, as I said, I don’t.

That cable controls the shutdown signaling. It is how the Mac can detect when to perform a controlled shutdown prior to battery depletion. (Here ignoring those UPS models with a network connection and a related app.)

As for why the Mac is now shutting down hard when the UPS switches to battery, one possible cause for that can be an issue with the power output provided from the UPS.

And if you’re really on macOS 13.0.1, update to current macOS 13.4.1(c).

The short answer is that you need a better UPS. Whatever you are using is not working the way a UPS is expected to work.

The Mini, like all desktop Macs, cannot possibly know where its power comes from. It's either present, delivering the correct voltage and frequency, or it isn't.

John Galt wrote:

The short answer is that you need a better UPS. Whatever you are using is not working the way a UPS is expected to work.

The Mini, like all desktop Macs, cannot possibly know where its power comes from. It's either present, delivering the correct voltage and frequency, or it isn't.

Yep. I’m supporting a number of Macs (including various minis) connected to UPSes.

All of the UPS models are APC Smart-UPS models.

No issues with any of of the Macs or the UPSes, past the usual and expected battery wear and replacements.

That including a power outage last week (not) effecting multiple Macs, so the UPS failover happened successfully.

If you’ve been an Apple user long enough, you should know that what worked in the past may well not in the future, especially if it’s unsupported and/or imperfect. Apple regularly fixes bugs and tightens up peripheral connectivity when it’s not up to snuff. What one manages to make work today may suddenly not tomorrow. All par for the course.

The communication cable is key to proper working of the UPS. See @kaz &@hoffman’s replies regarding the communication cable and follow their advice.

The Mac is clearly sensing that there is a change to its power source because it doesn't immediately turn off but rather takes the time to shut itself off properly such that I don't get the unexpected shutdown message at reboot.

Fascinating.

I wonder if the Mac prefers solar power over nuclear. Or perhaps hydroelectric, or wind...?

Get a UPS that actually works and your troubles are over.

Traveling Rae wrote:

....A few months ago, it started shutting down as soon as the power cut. Everything else shut down as well, so I figured the problem was the UPS battery. ....

Did you add any new peripherals to the Mac around that time? If so are they bus or line powered?

Also, did you add any new appliances to the same circuit that the Mini is on or anywhere else in your home?

Sometimes you can get strange currents flowing due to grounding (or the lack there of) or kick back currents when power goes out. While any good UPS will be designed to cover most of such circumstances, some oddities can still lead unexpected behavior.

I would suggest to troubleshoot the issue disconnect everything possible from the Mini and from the UPS except the display and mouse and keyboard if they are wired. Then pull the mains plug on the UPS and see what happens.

If it still does it, replace the display with another display or even a TV and repeat this test. If it still does it, Try replacing the power cord on the Mini. There could be an issue where the power cord is "weak" and while still delivering enough power to the Mini under normal circumstances may be catching a switch over glitch that drops the power just enough to shut down the Mini. And yes, cables and power cords can age even if undisturbed for years.

If the first test is successful, then there is one of your peripherals that is creating the odd behavior. If you get to the second test and it is successful, then there is something odd going on with the display during the power switchover.

If all the above fail, there could be an issue with the Mini's power supply itself. In which case, I would get it checked out at an Apple Authorized Service Provider.

Also, you really should make sure that your macOS is current with all updates.

Well unfortunately I am in the same boat, the UPS is connected to the Mac, the Mac recognize it but since several months ago it turns off at any power shortage no mater if it´s 1 second or more. Take in mind I have a very expensive commercial smart UPS with several battery banks providing many hours of blackout. This UPS power the Fiber Modem, the PepLink dual WAN commercial router, the Synology NAS, a couple of external Dual HDD´s on raid1 hooked to the NAS, a Window 11 mini PC, three 27" Samsung monitors, our PABX phone system, several Ubiquity 6 Access Points etc etc and NONE of the devices turn off except this MacMini and is driving me mad because in the past it always worked fine and never turned off !!!!!

I have it plugged into the UPS for the surge protection, and sure enough when the power goes out, there’s no power to my MacBook Pro either.

Your original post indicated a problem with a Mini. Clearly if you are experiencing the same problem with a MBP then something else is going on.

A MacBook Pro always draws power from its internal battery. Disconnecting its power adapter is no different than a utility power failure. A UPS is not involved at all.

My previous reply remains unchanged:

John Galt wrote:

The short answer is that you need a better UPS. Whatever you are using is not working the way a UPS is expected to work.

The Mini, like all desktop Macs, cannot possibly know where its power comes from. ...

The only difference is that a MBP always has power, and it is always provided by its internal battery.

Hi,

Do you connect power condition communication USB cable between Mac mini and UPS?