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UPS Suddenly Died

J

jimnms

Gawd
Joined
Mar 15, 2003
Messages
882
I have a CyberPower CP1200AVR UPS that I bought in 2005. I can count on one had the number of times the power has gone out since I've had it. I usually wait about 5 minutes and shut down if the power hasn't come back on, otherwise I shut it down immediately if I know the power won't be back on for a while.

It has been months since there has been a power outage, so the thing hasn't switched over to battery in a while. Friday when I went to turn the computer on, it didn't come on. The UPS was shut down, even though the power button was pushed in. I recycled the power switch, and it seemed fine. Then on Sunday, I was using the computer and the UPS shut off. There was no power spike or brownout. There another UPS on another computer, and it didn't switch to battery or beep or anything.

I reset the power switch, turned the computer back on, but before it even fished the POST, the UPS shut off again. I turn the UPS back on, left everything off, and after 30 seconds or so, it just shuts off.

I had to find a power strip to plug my stuff into since the UPS is dead. I didn't have the UPS software installed, so I downloaded and installed it. I connected it to the computer, ran the software and it shows the UPS in a charging state with 0% battery remaining, yet the UPS isn't humming like it does when it's charging. If I unplug the UPS, it just shuts off, so the batteries have just died.

What could cause the batteries to suddenly die like that? Before this UPS, I had an old APC Back-UPS 450 that I've had since 1998 or so, which still sort of worked when I got this one. I barely had time to shut down before it would run its battery down, but at least it was dieing slowly, not a sudden death like the CyberPower UPS.

I can get replacement batteries for $20 each, it takes 2, so that's $40, which is still cheaper than a new UPS, but I'm worried that something might be wrong with the charging circuit that allowed the batteries to drain down. I'd hate to spend $40 on batteries and find out something else is wrong. Is there any way to make sure that it's just the batteries first?
 
Multimeter time! Measure the charging voltage across each battery (should be at least 13V for a 12V battery) and the charging current (disconnect red battery cable, connect red meter lead to red cable, black meter lead to battery's red, or positive, terminal, set meter to measure amps and move red meter lead from the volts/ohms terminal to the amps or milliamps terminal -- and remember to move it back to the volts/ohms terminal after you're done so you don't short something when measuring its voltage). I think the charging should be around 50-500 mA, but be sure it's in the right direction -- it should be a positive reading if current is flowing into the battery, negative if the battery is being discharged. I think you have to make all the meter connections before the AC is plugged in or else the UPS circuitry may think something is wrong with the battery and won't turn on the current.

If your batteries are low, try charging them with another UPS or backup supply. Do NOT use a car battery charger, not even a trickle charger, because it will put out too much current. A 19V laptop power pack may work safely as a charger, if you connect a 1 watt or larger, 70-100 ohm resistor in series with it and make the connections properly.

If you open up the UPS to work on it, first unplug the AC power AND disconnect the batteries first because an UPS can shock you to death even when it's unplugged. I'd search for cracked solder joints, which are often at connectors and around heavy components and where there's lots of heat (big transistors, big resistors; solder may look dull or bluish). Also do the usual inspections for burnt stuff, swollen electrolytic capacitors, but if there's nothing obvious, proceed to testing the diodes, fuses, and transistors with an ohm meter.
 
I was waiting for a reply from CyberPower before cracking it open, but they were no help.

I already did a few quick tests today, before I saw your reply. I removed the batteries, and they're both down to 8.6-8.7 volts. I connected them back up to the UPS, and measured the volts. Before turning it on, It was at 17.2 volts, then when I turned the UPS on the voltage dropped to around 16, and steadily dropped. Around 15 volts the UPS shut off.

Right after that something distracted me and I forgot to turn my multimeter off. Then I didn't feel like messing with the UPS anymore, and by the time I got back to the UPS business, the multimeter battery was dead.

I have a portable air pump that uses a 12v battery, which is dead, but I haven't thrown it out yet. It uses a 15v. 500mAh charger. I was thinking of opening the air pump and connecting the UPS battery in place of its battery and see if it charges up. I also have a portable jump starter, which has a 12v, 700mAh charger that I could use.

Right now I'm thinking the UPS is the problem, not the batteries. If I can get them charged up and the UPS runs them down, I'll know.

What sucks is this same model UPS sells for $120-150 now, and I only paid $90 for it back in 2005. Why have they gone up in price since then?
 
It took me a while, but I finally confirmed that the UPS is the problem, like I suspected. Using the charger from my 12v air pump, I charged each UPS battery for 24 hours. Then let them sit for a couple of days to make sure they held their charge. After 2 days of sitting, they were both holding right at 13 volts.

I connected them back up to the UPS and it turns on, but as soon as I unplug the UPS it shuts off, it will not run from the batteries. I checked the current with the UPS on and it's drawing a constant 1.7mAh from the batteries. Now I'm stuck with a dead UPS and two good batteries.
 
Oh, I've already completely disassembled it to see if if I could spot any obvious signs of why it failed. I didn't see any sign of leaking capacitors or burned components. It powers on just fine as long as the batteries are connected and have a charge. There's no telling when it failed, since the power hasn't gone out in a while, and it's drawing such a low current from the batteries, it just eventually drained them down so far that it shut off.

I think I'll post it in the FS/FT forum and see if anyone wants the whole thing. Maybe someone with more electrical know how can either fix it, or someone may want it just for the batteries.
 
You could always buy a new UPS which uses compatible batteries and bank on the fact that I'll be a few years before you need to spend money on new batteries. While I too have very few power outages per year, its nice to see the UPS monitoring voltage levels and compensating accordingly.
 
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