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General discussion

UPS won't switch on

Dec 2, 2009 6:58AM PST

Hi

I am troubleshooting my UPS. Can you switch-on the UPS without the batteries (just to check)? I think the UPS will only switch to batteries only if cannot detect power from the mains, but my UPS doesn't switch on so I'm not sure if I am right. Can someone verify this?

thanks,
Franko

Discussion is locked

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Make and model??
Dec 2, 2009 10:35AM PST

You said you are troubleshooting but maybe you could tell what the symptoms are. That would be helpful. I'd have to guess that failure to start without a battery in place is normal. No load or excessive load causes some types of power supplies to shut down. There might be a way to rig a dummy load to the charging circuit that would work but I can't tell you how to make such. Look at the battery and see what voltage it provides. If 12v, you could try an automotive head or tail light as these would check through a wide range of current.

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Re: Make and model??
Dec 2, 2009 6:50PM PST

Hi Steven,

The UPS is a Smart Centra 650. It has been working fine for five years (probably more). The first battery replacement was done about two years ago. Just a month ago, the UPS failed to switch to battery on power interruption, but it still can be swithced-on. I assumed the battery needed replacement so I bought a new one.

"I'd have to guess that failure to start without a battery in place is normal." - Do you mean that all UPS cannot "power-on" without a battery in place? That would mean I would have to have a working battery first to check if the UPS itself is the problem.

"Look at the battery and see what voltage it provides." - The battery was bought a week ago, and it measured 12v then. Now, the battery measures 8v only. Do lead-acid batteries self-discharge that much? Btw, I checked the fuse and it's ok. I'm going to check tomorrow to check the transformers.

Thanks,
franko

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I can't speak for all UPS devices
Dec 2, 2009 8:47PM PST

as to whether or not they'll turn on without a battery in place. Here's where a DVM would help. You say the battery measures 12v. What you'd need to do test the battery after a short charging period to see if that voltage increases. If not, you get to test the charging circuit. You can try this with the battery in place but, if it's bad, you may get a false reading. You'd use a dummy load of some kind between the connections that go to the battery. An automotive lamp would probably suffice. You'd measure the voltage across the lamp with the UPS on. If it wouldn't come on then, I'd suspect the UPS is bad. If the lamp lit up but the voltage was low, it's still in the UPS. I'd say the charging voltage should probably be in the area of 13 or so volts but not much more. It needs to be above 12v to charge a 12v battery properly.