Question High-pitched squeal (“coil whine”) from APC Back-UPS Pro Gaming every few minutes - how to eliminate?

[Rollinart]

Hello!

I recently (2-3 month ago) purchased an APC Back-UPS Pro Gaming (BGM-series) and have noticed a very high-pitched squealing or buzzing sound coming from inside the unit every few minutes. It’s not the normal beeps or alerts - it sounds like coil whine (vibration from inductors or capacitors), lasting several seconds each time and then stopping.

Details:
- Model: APC Back-UPS Pro Gaming BGM-2200B
- Firmware/Software: Latest PowerChute, UPS firmware up to date
- Load: ~200 W (desktop PC + monitor), constant
- Mains Voltage: Stable, within 230 V ± 5 %
- Battery Status: 100 % charged
- Input Sensitivity: Set to Low via PowerChute
- Self-Tests: Disabled periodic self-tests in software

Despite these measures, the squeal returns every 1-2 minutes. It does not coincide with on-battery transfer or error beeps; it’s purely a mechanical/electrical noise inside the UPS.

I have a video with this sound.
Does anyone know how to fix it?

Thanks for any help!

 

[Aeacus]

Well, it could be component of the AVR that does that coil whine.

If you pull the plug from UPS to mains, thus forcing UPS to switch to battery power to keep the PC going, does the noise continue (excluding battery power alarm)?

But overall, could be localized issue (e.g only your specific UPS has it), or model fault (all that same series UPSes have the same noise issue).
You could always contact APC and ask them about it. After all, they made it.

 

[Rollinart]

Well, it could be component of the AVR that does that coil whine.

If you pull the plug from UPS to mains, thus forcing UPS to switch to battery power to keep the PC going, does the noise continue (excluding battery power alarm)?

But overall, could be localized issue (e.g only your specific UPS has it), or model fault (all that same series UPSes have the same noise issue).
You could always contact APC and ask them about it. After all, they made it.

When running on battery power only, the noise stops. As soon as I connect it to the mains, the noise starts again.
I could try to contact with APC

 

[Aeacus]

When running on battery power only, the noise stops. As soon as I connect it to the mains, the noise starts again.

Then the noise comes from the direct path from mains, through surge protection, through AVR and to PC.
Since when PC is powered by the battery, surge protection and AVR isn't used. Instead battery DC goes to inverter that turns it into AC, which is then fed to the PC.

Of course, in the direct connection from mains, there's also battery charger in the way as well. But i doubt the battery charger would engage every few mins. Lead-acid battery doesn't discharge that fast on their own, for battery charger to kick in and keep the battery topped up (100% charge) at all times. So, noise most likely either comes from the surge protector or from AVR.