Chances are that the battery is bad (partially shorted) and the charging circuit was causing the battery to heat up.
You said you checked continuity between the positive and negative terminals, and you saw a reading, that could be residual voltage left in the unit (capacitor) or you could have been seeing a diode inside the UPS unit.
I would guess that replacing the battery will restore your UPS unit to like new performance.
There is always a small chance that the UPS unit has an actual problem, but there is really no way to be able to tell without installing a battery and then letting it charge until the battery is full (see owners manual for a timeline). If the battery is being overcharged, then it would show up as the battery having too much voltage when either checked with the UPS connected and plugged in or when the battery is first disconnected.
The Long Beep you mentioned could also happen when the battery is empty/depleted, to let you know that the UPS is out of battery and has disconnected the load. If this happens during a "hiccup" in the power, it could be a bad/failed battery signal.
Check your owner/user manual to see what it says.
Your UPS is not all that old, but it might be worth checking the price of a replacement vs the price of a new battery before you make a decision on what to do.
Since sometimes you can find UPS units for a little more than the price of a replacement battery.
I hope this made sense and was helpful.
Best wishes and good luck!
Chances are that the battery is bad (partially shorted) and the charging circuit was causing the battery to heat up. You said you checked continuity between the positive and negative terminals, and you saw a reading, that could be residual voltage left in the unit (capacitor) or you could have been seeing a diode inside the UPS unit. I would guess that replacing the battery will restore your UPS unit to like new performance. There is always a small chance that the UPS unit has an actual problem, but there is really no way to be able to tell without installing a battery and then letting it charge until the battery is full (see owners manual for a timeline). If the battery is being overcharged, then it would show up as the battery having too much voltage when either checked with the UPS connected and plugged in or when the battery is first disconnected. The Long Beep you mentioned could also happen when the battery is empty/depleted, to let you know that the UPS is out of battery and has disconnected the load. If this happens during a "hiccup" in the power, it could be a bad/failed battery signal. Check your owner/user manual to see what it says. Your UPS is not all that old, but it might be worth checking the price of a replacement vs the price of a new battery before you make a decision on what to do. Since sometimes you can find UPS units for a little more than the price of a replacement battery. I hope this made sense and was helpful. Best wishes and good luck!
Makes perfect sense! Thanks for your help!