Check the battery first.
I would put a regular light bulb in a lamp. See if it is just as bright on the UPS as when on the grid power.
UPS are pretty reliable. It could be the battery is mostly bad, so the UPS can't or won't charge it enough. G-
Just FYI, some UPS units are "inverting" all the time. Even when on "grid". They run the inverter and just charge the battery at the same time.
I would suggest you test it on the UPS compared to plugged into a wall to be sure.
Just a gotcha I ran into one time a long time ago.
Good luck with it.
TomW
"Education consists mainly of what we have unlearned."--Mark Twain[ Parent ]
Mike "I thought I made a mistake but I was wrong"[ Parent ]
If the output is Really 80V, the lamp will be a lot less bright on UPS power than grid power.
I expect the UPS output is fine. G- [ Parent ]
Peter.[ Parent ]
Assuming 110 ac will have a peak of about 154v then the 50% figure would give an average of 77v.
Most cheap meters read mean but are scaled to show the value as rms of a sine wave.
Allowing for the form factor you should read somewhere just over 80v so that seems reasonable.
As others have said the simplest way is to compare light with a filament lamp against known 110rms.
Flux[ Parent ]
Some contributors have found the UPS has a button to disable the buzzer AFTER they had cut the cable to the beeper!
Regards, dom We only ever use the best fencing wire for our repairs! [ Parent ]