iMac shutting down when usb cable is connected between iMac and cyberpower ups

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SLH1957 Author

Level 1

5 points

iMac shutting down when usb cable is connected between iMac and cyberpower ups

I have an iMac 21.5" (mid 2018) and a CyberPower Ups CP750LCDM UPS. I have to two connected with a USB cable and using the PowerPanel (1.1.0 ver). I had issues with rebooting the iMac, after some trouble shooting and unplugging all devices and was able to get the iMac to boot fully without issues. When I plug the USB cable for the UPS in, the iMac shuts off.

Does anyone know of issues with Mojave and UPS's. The iMac does not have issue when USB cables are plugged in for other devices.

Thanks

Steve

iMac 21.5" 4K, macOS 10.14

Posted on Feb 28, 2019 5:37 PM

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Answer 1

Top-ranking reply

SLH1957 Author

Level 1

5 points

Mar 2, 2019 9:32 AM in response to SLH1957

Just a quick followup and FYI. It seems that my UPS has gone bad. It is not holding a charge and a short time ago the power went off but click back on within a few seconds and the UPS did not kick in. The battery capacity reading dropped to zero and the mac shut off. Since the battery was not functioning my guess is that the software was seeing a low battery and telling the mac to shut down.

I have ordered a new UPS.

Thanks to everyone for their help.

Steve

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Answer 2

SLH1957 Author

Level 1

5 points

Mar 1, 2019 4:06 AM in response to BDAqua

I deleted the PowerPanel software and the Daemon. Reinstalled both and the problem seems to have stopped. It appears to me anyway that os was some software issue.

Thanks to all

Steve

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Answer 3

leroydouglas

Level 10

200,334 points

Feb 28, 2019 6:03 PM in response to SLH1957

Did you try a different cable?

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Answer 4

SLH1957 Author

Level 1

5 points

Feb 28, 2019 6:22 PM in response to BDAqua

I have the Mac, a second monitor, modem, printer, router plugged into the UPS. Never had trouble before Mojave. I have connected other devices into the usb ports without any problems.

The usb cable between the Mac and UPS is for communications. Something strange is going on. No reason why it should shut the Mac down.

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Answer 5

BDAqua

Level 10

250,259 points

Feb 28, 2019 6:16 PM in response to SLH1957

Sounds like a short somewhere to me, how about of your Mac's power is not plugged into the UPS?

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Answer 6

SLH1957 Author

Level 1

5 points

Feb 28, 2019 6:07 PM in response to leroydouglas

Yes. Just before the iMac shut down, the mouse (bluetooth) stops working. If I leave the usb cable in on reboot, the iMac loads about half way then the screen flashes and the boot continues and then when the login screen appears it shut off.

Without the cable plugged in, everything works as it should.

Steve

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Answer 7

BDAqua

Level 10

250,259 points

Feb 28, 2019 9:40 PM in response to SLH1957

Well yes, of course it shouldn't be shutting the Mac down... yet you yourself says it is, so to figure out the problem we must try to eliminate some things to narrow it down.

It well could be Mojave.

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