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Strange noise from PSU when powered by UPS

2226 Views 8 Replies 6 Participants Last post by  gamefreak94
Whenever the power goes off and the PC starts to draw power from the UPS batteries, I notice that the PSU starts making a strange crackling sound as if a very heavy transformer is at work. The strange thing is that when the PC is powered from the mains (the power is still going through the UPS, but obviously isn't coming from the battery), this noise gets significantly lower and is barely audible.

Also, when running off the batteries, even if I turn the switch at the back of the PSU off, I can still hear that crackling noise, though it's very faint, however, when I power it from the mains, there's absolutely no noise at all.

The PSU I have is an ASUS P55GA 550W and the UPS is an Ablerex 1000L if it helps.

It's interesting to note that I didn't get any such noises from my previous 350W PSU, but then again that cheap Chinese PSU didn't have any safety features like Active PFC in it, so I'm thinking the UPS's output is bad and the PSU is somehow trying to correct it.

Any ideas?
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Got no clue what's up but I don't get this on my Gigabyte Odin 720W + Powercom Black Knight Pro 1000AP combination. My UPS does get quite loud though when powering my system through the battery.

I would suggest completely discharging your UPS though (so let it run till it shuts down from low battery).
The noise is coming from the PSU, not the UPS. The UPS is supposed to get loud on battery mode, cuz its transformer to turn DC power from the batteries to AC power to supply to the PC turns on.

Anyway, I decided to remove the UPS and power the PC directly from the mains instead, I still have it hooked up to a voltage stabilizer so it's not completely vulnerable.

I think there's something wrong with the batteries, they're 3 years old now and barely have any juice in them. They only give like 15 seconds of back-up time while browsing which is just enough to put the PC into hibernate. Otherwise while gaming, they only last like 4 seconds. The only reason I still had it hooked up to the PC was for the sake of surge protection, but I realize it may be doing more harm then good, so until I get a new set of batteries I can't be sure.
with my APC UPS it had some issues with certain 80+ certified psu's. something about the sine wave output when running off batteries. might be something similar.
So can it damage your PSU?
people have fried their entire systems from worn out ups batteries going on the fritz.

probably should replace the battery.
psu with 80+ issue is no surprise when they are trying to draw more watts from the watts it draws and such design means it needs a steady stream of power which batteries can't supply since the stream is less stable once the power from the battery starts to drain, so to maintain the efficiency the psu works harder and puts a strain to its internal components

its a matter of finding a ups with a specs that matches the demands of the psu
I would say part of the issue is the stepped sine waveform that it puts out when running off of the batteries, and is probably exaggerated by the worn out batteries. As posted above, some PSUs have issues with stepped sine AC (UPSs with true sine output tend to cost quite a bit more). I haven't noticed any issues with my setup (APC RS1500/Seasonic M12D 750w), the only noise during battery usage is from the UPS transformer and the fan used to cool it.
Sorry for sorta bumping this but somehow I forgot to read the latest replies. Anyway, my last question: Assuming I pop in a new pair of 12V batteries, is it okay to hook this up to my PC? It will only run off the UPS for like a minute or so before I hibernate it so the PSU won't be stressed for too long.
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