UPS goes to battery power when mains are on

Hi everyone,

Just a newbie searching for some answers. I have a brand new UPS - came

4 days ago. No name brand, bought to survive 3 second power failures. 650 VA, 390 Watts. The comp has a 400 Watt power supply and there was nothing else on the UPS. Don't expect it to be a full load situation.

After running for a few hours, suddenly the UPS switched to battery power. I shut down the computer as soon as I could. The mains were on, everything in the room was fine. The UPS is behind a surge protector and everything else on the surge protector was working fine - not a glitch.

I checked the UPS on other sockets, and nothing doing - it just kept going to battery power. After a few hours of mucking around, letting the UPS sit, trying it on other outlets, etc - decided that I had blown

40 bucks, and needed to get a better UPS.

Tonight, came back, and checked again. Now the UPS works fine - shows mains are on. Seems to be charging the battery when switched on.

I am confused. Is the UPS working? What happened? Tried restarting the UPS on a different mains socket with no load so can not be an overload. Let it sit for an hour before restarting - can not be overheating. Brand new UPS that worked fine for 12 - 15 hours over 2 days or so.

Any ideas would be greatly appreciated. I would prefer to use the UPS then to throw it out. But I don't want it to quit on me if the power does go out for a few seconds - I would hate to lose some work because of a power failure. Need to be able to save documents and shut down - nothing more than that.

Your help is MUCH MUCH appreciated. Thanks. Have a good weekend.


Reply to
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Keep it. It may have gone through a charging state where it switched over. It should be fine after a day or two of soaking up power.

Reply to
Homer J Simpson

You are suppose to let it charge overnight before connecting to a system. It charges the battery and some will switch to battery power to selftest. You can test it yourself to see how well it works. Just connect a couple desk lamps to it, and then unplug it from mains to see how well it runs the lamps.

Reply to
James Thompson


Powerline voltage can vary without causing noticeable differences in brightness of lighting or functionality of appliances and other electrical devices. What I suspect happened was a drop or increase in line voltage that went far enough to trip the UPS.

Better UPS units have two ways of dealing with this problem. The first method, found even in some cheaper units, is adjustable voltage transfer points. If the unit trips too often, or doesn't react quickly enough, you can reprogram the voltage levels (within a couple of volts) so that it will work properly. The second method involves using a transformer that can boost or cut voltage without going to battery power.

The UPS has surge protection built in. I would recommend plugging it right into the wall and not through an outlet strip or other surge protector.

You should also allow any new UPS (or one that has had its batteries replaced) to charge for 24 hours with no load attached.


Reply to
William R. Walsh

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