2018 Mac mini shuts down despite UPS

I've been using my 2018 Mac mini (Ventura 13.0.1) with a UPS for almost five years and the behaviour was as expected -- power goes out, UPS takes over, Mac mini keeps running until I can shut it down. 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. I replaced it, and I'm still getting the same behaviour with my mini, but not everything else that is plugged into it. I decided to try another UPS and same thing.


So the issue seems to be the Mac. It feels like something deliberate, like the Mac now is able to tell that it's on battery and not shorepower, and shuts itself down properly, because I never get a message at startup that it had an unexpected shutdown. It just reboots soon as power is restored to the UPS. My UPS isn't connected to my Mac to be feeding it any information.


This wouldn't be a huge issue if I was always work in Mac OS as the computer reboots quickly to put me back where I was at shutdown, but I'm frequently working in Windows (through Parallels) and Windows doesn't have the intelligence of MacOS to be able to recover from a power outage, so it doesn't autosave anything, loses settings on some of my software, and can't restart on its own, so it's a huge hassle to start up again.


Power is very flakey where I am and we have multiple micro-second outages a day during the summer, so I need to figure this out ASAP.


Thank you for any insight anyone can provide!

Mac mini, macOS 13.0

Posted on Jul 23, 2023 3:40 PM

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Jul 23, 2023 10:20 PM in response to Traveling Rae

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).

Sep 17, 2023 3:28 PM in response to Traveling Rae

Update in September, the Mini is still doing this. The problem is definitely the Mini -- Apple must have broken UPS usage in a recent update. Every time I think they are better than everyone else, they do something like this. I've tried multiple UPSes and while everything else stays up and running during an outage, the Mac immediately shuts down. It's not like a loss of power shutdown because when it comes back up, there's no "your Mac was shut down unexpectedly" message. This and the fact that the Mac comes back on the minute the power returns are all the evidence we need that this is deliberate, programmed behaviour. I've never connected a UPS to a Mac and I'm not going to be bullied into having to figure out how to do that when my system worked perfectly for four years. Apple will probably say, but everything on the Mac side comes back up like you left it! Yes, but a) I have huge data losses on the Windows partition, where I'm working and b) I used to be able to keep working for over hours in a power outage! I lost a whole afternoon of work this week because of this new flaw.

Sep 17, 2023 7:54 PM in response to John Galt

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.

Sep 17, 2023 8:16 PM in response to John Galt

This problem started happening when I upgraded to Ventura.


The UPS has been performing flawlessly for two years. The monitors and modem still work when the power goes out. I tried the Mini on three other UPSes and at another location to eliminate wiring issues. I got the same behaviour in both locations on all UPSes.


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. And then the second main power is restored, the Mac reboots, again sensing a difference in its power source. The wiring in both locations is grounded, has the correct voltage. Really, the only thing not working correctly is evidently the Mac.

Sep 17, 2023 8:37 PM in response to Traveling Rae

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.

Sep 18, 2023 4:55 AM in response to Traveling Rae

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.

Sep 18, 2023 5:32 AM in response to Traveling Rae

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.

2018 Mac mini shuts down despite UPS

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