This was originally posted on APC forums on 3/4/2020
I have a Back-UPS ES 550 and I've had it for a long time (over 10 years probably). A few days ago it started making a very odd noise, which I wouldn't call beeping, more like buzzing as if something inside is broken. I've tried disconnecting the battery, but to no avail. Oddly enough the buttons are not functioning. When I push the On/Off button nothing happens, same goes for the break button. When I plug it into the socket the green LED is solid and it just keeps making this noise. Do you think it makes sense to change the battery? If not is there something, which could save it or should it be directly replaced?