UPS overloads when Mac is sleeping

[Dom_apc]

This was originally posted on APC forums on 6/29/2012

---

I have a Back-UPS RS1500 that my Mac tower and peripherals are attached to. When I've lost power it powers everything with no problems. That is unless the computer is asleep. If I get some kind of power fluctuation or lose power when the computer is asleep the UPS goes into overload and I get the high pitched alert sound.
Yes, that sound will wake you up!
So what causes the unit to overload only if the cpu is asleep? Can I do anything about it?

Thanks.

[BillP]

This reply was originally posted by Bill on APC forums on 10/20/2014

---

Hi,

Is the Mac connected to the UPS via USB? If so it may be an issue where the OS is not waking from sleep during the power outage. You can test by powering the OS down and then putting the UPS on battery. If the UPS does not go into overload then it is a conflict with wake on sleep. The solution would be to power the OS down when not in use or disable sleep.

[Dom_apc · Accepted solution]

This was originally posted on APC forums on 6/29/2012

---

I have a Back-UPS RS1500 that my Mac tower and peripherals are attached to. When I've lost power it powers everything with no problems. That is unless the computer is asleep. If I get some kind of power fluctuation or lose power when the computer is asleep the UPS goes into overload and I get the high pitched alert sound.
Yes, that sound will wake you up!
So what causes the unit to overload only if the cpu is asleep? Can I do anything about it?

Thanks.