Hey all - I've got several *old* UPSs that I was given.  I've used a few of them these last years after replacing the 12aH batteries.  I replaced the battery in one unit about six months ago only to find that the UPS turned itself off two weeks ago.  So not only did it fail to provide power during an outage but the damn thing didn't even let power flow through it when the power was on.  So utter failure.

These units are so old that the manufacturer's tech support line doesn't even know about them.  They seem like pretty simple designs - do these things go bad?  Or did I just get a bad battery?  I can check the battery voltage after letting it sit for a few hours - maybe that will answer some questions.

Thanks all!

There are things inside that are called MOVs (metal oxide varistors) that can go bad.  I had an older APC brand UPS that the battery had long since died in, but I still kept things plugged into it because it was in a hard to reach place behind a heavy credenza.

Every once in a while, it would trip and kind of 'brown out'.  Finally, a few years back, somebody gave me a newer, bigger, but dead APC UPS and I just replaced battery with a PowerSonic and it's working like a charm.

You can go get new, improved and fresh models for $50, so that's the litmus test.

Chris

Thanks so much, Chris - just what I needed to hear.  Would you recommend going new vs. a refurb with a new battery?

Mine started smoking and sparking one day.

Nuff said - ordering now!

If you can get a ~7Ah, SLA AGM battery for a good price, then a monkey can replace the bad battery, so $20 for the battery, perhaps in lieu of paying $50-$60 for a brand new one at Worst Buy, Office Rape, or even online, might make sense.

If money isn't a concern and you're not pinching pennies, like I was (wasn't going to buy a new one, so fixing the gifted one made sense), then just buy a new one, but it's usually the battery that goes tits up.

I'm into HiFi and have a 25 year old Panamax 1000 surge/power device and it starts tripping for no reason, so I have a little experience with these things.  If the MOVs are going, ditch it, but if you have a spare battery, give that a whirl first, before buying a new one.

Chris

I service almost 100 at work. (college IT ) Yes they can and do go bad. usually it is just batts  but we have had a 10,000 va unit go and take out a 1/3 of the computer room once.

*For the most part*, only the batteries.

In my last job, one of the things I did for almost 20 years was purchase, maintain, and replace about ~100 UPSs.  Over those nearly 20 years, I did have a very small number of UPSs actually fail.  Typically, the charge circuit would start over-charging and ruining batteries, but at least one just failed dead.  But, for the most part (and we talking >90%), all of the UPSs just kept ticking for nearly two decades, just needing battery changes.

Buy good batteries.  We replaced batteries every three years, even if they were still running.  With good batteries, we would see *zero* failures during that time.  With lesser brands, we would see ~5-10% failure during that time.  At one time, my boss made me buy batteries of some unknown brand from one of our partners "to build relations with them".  Of the pallet of batteries that we got, we had ~50% failure within a year, and many of those actually spewed acid and badly corroded the wires/chassis.

Most decent UPSs will occasionally check the status of the battery.  Decent configurations will beep the alarm if the battery is bad.  But I've seen a few that would just shut themselves off when they detected a failed battery, even though mains was still present.    It doesn't *necessarily* mean that the UPS has failed, it could just be that it's very poorly-behaved.

Man, once again I'm so grateful for the wisdom of the hive.  Just bought three decent UPSs, and I will be sure to put decent batteries in them when the time comes.

Would sure be a hell of a thing to come home to a smoldering foundation because a crappy UPS decided today was the day.....

I had an APC unit that was about 10 years gold go bad. I'd already replaced the battery in it once. I put it at the curb and a junk collector grabbed it.

MOVs have been mentioned, also the large capacitors can go bad.

Actually, this is kind of a universal electronics thing. Electrolytic caps (the ones that look like small metal cans) go
bad on just about everything, and the most common point of failure in most electronic devices is the power
supply -- and usually it's the capacitors, and usually the larger ones, that fail.

When the caps go bad, it's not uncommon for there to be a kaboom as well.

If there was one component to stock for SHTF electronics repairs, after fuses it'd probably be an assortment of
electrolytic caps.

What about wiring an external battery when the original fails?  I use one for a pellet stove to smooth power out for the electronics and to allow us to shut down properly should we loose power (if it just goes OFF it can smoke up the house fairly bad).

I was considering a large external AGM battery as it would give more time to shut the stove down.

External batteries work fine (assuming you're matching voltage an using proper wiring/fuses etc.)

I've done the same for one of my UPSs that handles my WISP router, during blackouts I've successfully
determined I now have more backup power than my ISP does. This will throw off any readings on
time remaining if your UPS provides those.

I wouldn't do this if you were running the UPS near its limits, however, as they're probably not
designed to handle an unlimited run time at max thermal load. But very few people run them
anywhere near that. They also sell UPSs that are intended for external battery applications.

Ya the UPS is rated for 600 watts, but the stove only uses between 150-200.

UPS manufacturers usually have a package of their most common repair items for UPSes over a certain size.  They will sell you the package at about 1/3 the cost of retain.  Always big caps in it.

They can go bad.  A lightning strike is one way.  Just random failure of electronics another.  Or random acts of "What were you thinking??"

When my daughter was young she was looking for an outlet for her hair dryer and spotted the handy power strip behind my computer ...

All the magic smoke escaped