Uninterruptible Power Supple(UPS)

By princyndieh ·
Dear sir/madam
Am an IT personal who need some tips from you.Am working on a 1500va Interruptible Power Supply (UPS) which can work on AC, but can not back up on battery, the batteries too are good, i will be much grateful if you could help out fix these problem.

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by Dr Dij In reply to Uninterruptible Power Sup ...

if the UPS turns on and you are sure the batteries are good yet it won't provide output voltage, then there is a problem with the UPS electronics. Bad batteries often have a bad battery indicator light. You can also put a voltmeter used to test automobile batteries on the battery.

One other thing to check before you repair the UPS, is the electrical wiring OK? Get a cheap 3 prong outlet analyzer, about $5 at your local electronics store if you have one nearby. This will give a gross indication if miswired.

Bad grounds can cause problems too. And surge protector / UPS does not block bad ground / ground loop problems.

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Another possibility

by Dedlbug In reply to Uninterruptible Power Sup ...

I ran into a bizzare UPS issue too a few months ago. I had a similar UPS from APC (1500XS). It worked fine on a workstation computer. (Dell Optiplex system)
I had this UPS connected to a Dell Poweredge 830 and for some reason, it would not work on battery. The Server would try turn off, reboot, but fail at reboot and it would keep trying, restarting every 30 seconds into the boot process.

I called APC and Dell and after trying a replacement unit, Dell finally stated something about the power supplies in their servers. Not really sure, but the "waves" of the voltage in most Dell servers are different than what most UPS systems can handle. Again, I don't know the technical workings, but in the end, APC shipped me an XS1300. Even though this was a smaller UPS, it worked with the Dell Server.

My point is, it my be the power supply in the computer. Contact the Computer manufacturer and/or UPS manufacturer. I know it sounds goofy, but trust me. Maybe try the UPS on another/different computer.

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by TheChas In reply to Uninterruptible Power Sup ...

CAUTION!!! There are potentially lethal voltages inside a UPS. If you do not have electronics training, I recommend against going any further with repairing your UPS.

About the only thing I would recommend is with the power unplugged, and the battery disconnected, check for internal fuses.
I have repaired a couple of UPS systems that had soldered in internal fuses.

You stated that the batteries are good. Have they been load tested?

Just checking the batteries with a volt-meter is not enough.

If the batteries do hold up under load, and their are no fuses, and no visible burnt components, it's time to start trouble-shooting.

For starters, you need to have the UPS plugged into a grounded outlet and have a load connected to it for most diagnostics. A 60 watt light bulb should work as a test load.

What happens when you operate the test switch on the UPS?

Do you hear a relay click?

Does the load keep running?

If the UPS works when you test it, most of the internal circuitry is working.

Now, plug it into a power strip.

What happens when you turn the power strip off?

In either case, if you don't hear a relay click, the internal voltage detector is not working properly.

If you do hear a relay click, but the load goes off, the DC to AC converter or amplifier is not working.

Any of these circuits can be difficult to troubleshoot without a schematic or years of circuitry experience. And, in the case of the amplifier and relay potentially lethal.

Further, depending on the age of the UPS, it might be cheaper to buy a new unit than to have this one repaired. This is very true if it may need new batteries soon.


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