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Old 09-22-2012, 12:58 AM   #21
Join Date: Jul 2006
City & State: southern california
Posts: 28
Default Re: Can I test or operate APC Smart UPS 2200 off a single RBC7

Originally Posted by Behemot View Post
Well isn't it obvious the UPS will be buzzing under all circuimstances? You have huge 50/60 Hz transformer inside, you cannot totally avoid resonance. What I have seen so far, when it operates on batteries, the buzzing is much worse.
Attached is a clip of the sound that comes from the 22uF, 150V bipolar yellow capacitor(s) in both the models when charging the batteries.

At 45s into the recording, I turn off the line power - notice how the noise goes away completely when it's running off batteries in the 1000VA (the one which was running when I recorded the noise)

I am sure you will agree this is very different from the gentle hum of a transformer?

If this is a characteristic sound of APC UPS when the batteries are dying, I would like to know if there's a battery I can buy, from say Walmart or Home Depot etc just to see if a new battery makes the noise go away.
Attached Files
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