UPS Bad battery or circuitry?

I've got a Power Sentry model 100870 that did not survive a power outage the other day. I don't know how long the power was out but when I got home the UPSs internal fan was running full blast (couldn't tell you if that was normal) and when I reset the unit it quickly started beeping and flashing a battery fault error.

I tried leaving the unit plugged in with no load overnight but still got the fault.
I tried unplugging the unit and leaving it 'empty' for 24 hours but still got the fault.

This unit has a pack of 4 12V batteries in series for 48V. When I tried to remove the pack I found that the batteries were hot and swollen. After cooling down I was able to get them out and found at least one of them was cracked but the pack is still putting out 48V when I test it.

If I have the correct voltage what fault is the unit sensing? Could I have a problem in the unit itself and if so how do I find that out without spending a bunch of cash on new batteries first?

if the batteries are swollen and/cracked or split...

Replace them. How old was the UPS before the outage? Was it an outage due to a spike, was there a surge or lightning strike that overloaded a circuit/transformer?

My suggestion would be to replace the entire unit. top to bottom.

You could try using a car battery to test but as an FYI, Car batteries will offgas and it can potentially be a bad thing in enclosed spaces (fire, explosive, etc)..

Adragontattoo said:

if the batteries are swollen and/cracked or split...

Replace them. How old was the UPS before the outage? Was it an outage due to a spike, was there a surge or lightning strike that overloaded a circuit/transformer?

My suggestion would be to replace the entire unit. top to bottom.

You could try using a car battery to test but as an FYI, Car batteries will offgas and it can potentially be a bad thing in enclosed spaces (fire, explosive, etc)..

Click to expand...

I bought the unit as a referb 2-3 years ago and if I could get another at that price I wouldnt heasitate, but there isnt much chance of that.

As for trying a car battery wouldnt I need 4 of those as well to make up my 48V?
I believe that my area just lost power and we didnt get any kind of spike.

Adragontattoo said:

My suggestion would be to replace the entire unit. top to bottom.

Click to expand...

+1: Power Sentry is third-tier at best; not worth putting any money into it. Likely the batteries are shot, as 2-3 years is typical on these.

Go with a quality APC or CyberPower unit.