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I've got a Windows 7 desktop system with an APC UPS to provide backup power during power outages. I've got the UPS connected to the system with a USB cable so that the built-in Windows power utility can monitor the power level, and it's set up to hibernate the system when the battery level gets too low during an extended outage. The system powers down just fine, but when the power is restored to the UPS, the system stays off. How can I get it to turn back on?

Please note that I've already set the Power Management features of the BIOS to "Always On." I imagine the reason it doesn't power back on is because it had a clean shutdown.

For the record, I've tried the APC PowerChute Personal Edition software, which does make it automatically power back on, but it's got a pretty serious bug that keeps it from shutting down the system if someone is logged in remotely.

If at all possible, I'd like to do this without any additional software, but that's probably a long-shot.

[UPDATE] It appears that the way the APC software gets the system to turn back on is by having the UPS turn off the power to the outlets after the system shuts down, and then turning it back on when main power is restored. It does this by sending the UPS a message to turn off the power to the outlets 2 minutes after it starts shutting down the system - long enough to power down most systems. It seems that neither the built-in Windows Power Management or the apcupsd software I tested can perform this function, at least on the test system I've been using.

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  • If it's set to "always on", it should restore power when AC power is restored. If not, the issue is still with the BIOS.
    – David Schwartz
    Commented Aug 29, 2013 at 19:53
  • @DavidSchwartz - Thanks, but from the computer's perspective, it's never actually lost power, because the UPS is providing backup power. Windows shuts itself down, but doesn't set whatever switch the APC software does that allows the UPS to tell the computer that the main power is back up. It's exactly like if you unplug a laptop - it hibernates at a certain battery level, but doesn't automatically power on once you plug it into an outlet again.
    – kevinmicke
    Commented Aug 29, 2013 at 20:04
  • Oh, so you need the UPS to cycle power so the computer will come back on. Or you need wake on USB.
    – David Schwartz
    Commented Aug 29, 2013 at 20:31
  • That could work - any idea how I can make it do that? It's an APC Back-UPS Pro 1000 (BR1000G).
    – kevinmicke
    Commented Aug 29, 2013 at 20:33
  • Many APC SmartUPS models with a network card will do this. It sends a Wake on LAN packet to the device. I do not believe BackUPS Pro models support a NIC. And the NICs are expensive.
    – Dave M
    Commented Nov 28, 2014 at 13:34

3 Answers 3

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Apcupsd does do what you want. Our power here is really bad. In the event of a power failure, my system stays on battery for 2 minutes (my choice) in case it is a short duration. After being on battery for 2 minutes, Apcupsd tells the UPS to cut the power to the PC. The UPS has a built in delay of 2 minutes. Apcupsd then issues the Windows hibernate command, so Windows hibernates. Two minutes after the UPS was sent the command, it cuts power to the PC. When power is restored (or if it was already) then the UPS again provides power. You are correct - since the BIOS sees this as the power was cut then restored, the BIOS will do what you set it to do.

A clean shutdown using a UPS - if the UPS does not cut the power to the PC, regardless of whether the power is restored or not, your PC will remain shutdown because the BIOS didn't see a power cut/restore. The BIOS has no other choice. If, when your system shut down, the BIOS detected that power was still present, what would you want it to do - power up the machine? Then there'd be no way to shut your system down.

BIOS requires that PC loses and then gets back the power.

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  • APCUPSD is a great utility. The website for it is here: apcupsd.org
    – jjz
    Commented Feb 3, 2017 at 16:37
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I found a solution that works for me under Windows 10 with a Back-UPS Pro 1000. I would expect this to work with Windows 7 and other UPS units.

Overview:

The four steps below will cause the PC to enter sleep mode when the UPS switches to battery. When AC power is restored, the PC will resume from Sleep. Also, should the PC's power get cut (while in Sleep mode), when power is again restored, the BIOS setting ensures it will power back on.

  1. Make sure your BIOS is set to always turn the system on, should the power ever get cut. Look for "Restore Power After AC loss", or similarly named setting, and set this to On.

  2. Configure the Windows power option to put the computer to sleep after X minutes. Set Control Panel / Power Options / Put the computer to sleep: 5 minutes.

  3. Change the advanced power options (Control Panel / Power Options) to also put the computer to sleep for Critical and Low battery states.

  4. Under Device Manger, right click on "HID UPS Battery" and then under the "Power Management" tab check "Allow this device to wake the computer". This is what actually causes the system to resume from sleep mode.

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Have you tried going to DEVMGR - open Batteries - RMB on APC UPS - go to the Power Management tab and check mark the box next to "Allow this device to wake up the computer" ?

Cheers !

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