APC Smart-UPS 5000VA RM Noise on battery

[Anonymous user]

Hi!

I wonder if it is normal for the UPS to produce a buzzing noise when it's running on batteries?

The batteries in the unit are in bad condition and I wanted to make sure that the UPS is okay before swapping the batteries. 

I recorded an video of the sound, its easier to diagnostic the sound that way.

[BillP]

Hi Robert,

Thanks for taking the time to do the video. It was hard for me to tell specifically what the buzzing sounded like because of the other general noise though. I did not hear anything very alarming but it does sound slightly different than my UPS of this type. It is normal for it to sound different when the inverter kicks on. The other thing you could do is make sure the noise is not because of a dirty fan and maybe clean it with compressed air for good measure.

[Terry_Kennedy_apc]

I've encountered some variation in the way the inverter transformers in the UPS are "potted" (for others: filled with varnish, epoxy, etc.) which causes the laminations to buzz when the UPS goes to battery. As long as the buzz is constant (volume, pitch, etc.) it is probably fine, as you say.

The main reason I posted this reply is because of the "clean the fan" suggestion. I see a fair amount of equipment that comes in here with problems due to inexperienced people cleaning the fans, so I wanted to provide some advice:

• Do the cleaning with the device powered off (and fan not turning) and prevent the blades from spinning when blowing the dust off. If you have a spare "straw" from another air can, you can use this to hold the blades still while spraying with the duster. Overspeed can damage these fans in a number of different ways, mostly due to bearing failure but sometimes by damaging the speed sensor.
• Wait for the unit to cool down completely - the gas that comes out of dusters is very cold and you can damage / destroy components from "thermal shock" if they are at an elevated temperature and then get a blast of cold gas. Likewise, wait for the part(s) you sprayed to come back to room temperature before powering it back on. You can probably feel the temperature of the air can to decide when it is safe to power the unit back on. Remember, the fan is designed to move air past heat-sensitive components, so when you spray "the fan", the gas will also move past those same heat-sensitive components.
• Unless the fan has "spanish moss" hanging off it, cleaning it will normally only be a cosmetic function. The most common problem with fan speed comes from bearing issues, either grit has gotten into the bearing or the bearing simply wore out. In those cases, the fan needs to be replaced.

[Anonymous user]

that sound can be produced by many things in UPS....but generally its caused by coils and transformers......but it can be a filtering MKP capacitor...

if you dont have a "spot-microphone"  then there is a simple way how to find the noising spot.....get some rubber or plastic but flexible pipe....like 50-60cm is enough....put one side in your ear, and with other side go around from component to component till you hear in your ear the one that produces the loudest noise of that.... (a primitive stetoscope)

if it is a coil...then you should see is there a way to tight it, maybe even some cold solder can be cause....so check that too....anyway, you can get a transparent "electric transformer lacquer" that is used for wires and transformers, and simply paint it, when it dries, it will tight the coil and stop making that noise....

where to find a mentioned lacquer?! ...in any repair shop where they repair electro-motors and producing transformers etc....just ask the owner to give you a spoon of lacquer and it should be enough for your needs 🙂

[Anonymous user · Accepted solution]

I thank you all for the informative responses. 

So the sound isn't normal. I will try to figure out what the cause of the noise is, hopefully I can fix it. I don't believe that something is wrong with the fan/fans, they/it don't seem to make any buzzing sound.

The ups works fine, except for the batteries, Im just worried that it will break or break any of the server that the unit is hooked up to. 

I will try to get it out of the rack and record the sound in a silent environment, but I doubt it will help diagnos the unit and find out what's wrong with it, or if something is just lose.