[SOLVED] Is it Normal when a UPS makes a hissing noice while charging?

[wardeneternal]

Hi,
Today my 10year old Prolink UPS died. So i bought a new Prolink PRO701SFC 650VA Line interactive UPS.

Retailer told me to charge it 6H before using so i pluged it in to let it charge.

While it charges, it makes a constant small hissing like noice. I dont remember if my old one had a noise or not because it required very little attention.

Is this noice normal?

 

[drivinfast247]

Yes. I have 3 different models by APC and when I cycle them they emit a high frequency sound while charging.