Industrial computer shuts down with battery backup

[3rdshiftguy]

Folks,
I have an industrial computer that shuts down immediately with battery backup. I installed an APC UPS on the computer to protect it from some recent brownouts, but it didn't work. I contacted my IT department and they gave me a different battery backup. When this one didn't work, we tried another brand all together but the computer still shuts down as soon as it moves to battery power.

This happens without even loading the power management software that comes with the UPS battery backup. So far I have tried an APC, a Tripp-Lite, and a Compu-power brand. Three entirely different units with the same result.

Has anyone ever seen this?

[adam12]

I think you have a sensitive power supply. I have heard that some of the newer computer power supplies do not like the battery backup outputs. If it were a standard power supply in your industrial computer, maybe you could swap it out with an older power supply and see what happens... a little test...

[Cheller]

I did a little investigating with this battery backup problem and I learned a little along the way. I unplugged a typical battery backup on my work bench and put the scope on it. I never realized the output from these battery backups were square waves but that's exactly what they are.



Here's a better look at the just the waveform on the scope:



So I grabbed a 120V isolation transformer that was way overkill for an application like a computer but I wanted to see if there was an improvement.

I had this 120V isolation transformer here:



These transformers definitely improve the quality of the signal but you still don't get that pure sine wave that you would like to see. I think this may help with a power supply being sensitive. I will do more testing, please hold...

[maintech]

I never really paid attention to battery backup outputs before, but it seems like a square wave input would ultimately damage a power supply by generating heat. Maybe the power supply is smarter in your computer than in older models and it recognizes the fact that a square wave is not ideal.

They make pure sine wave battery backups, maybe that is all you need.

[Cheller]

Alright, I've done some homework on this problem with battery backups producing sine waves. Some manufacturers do produce battery backups with pure sine wave outputs. This will fix your problem, they are designed for use with sensitive power supplies. That is, if you are willing to pay; since pure sine wave units are quite costly when you compare them with a battery backup that we associate with a home computer.

Next option that will work is to buy an isolation transformer that is rated to match your computer power requirements. This 150VA isolation transformer from Stancor will work:



Simply plug and play with your existing battery backup...



You can find these at Stancor distributors or on eBay.

[3rdshiftguy]

Thanks, I ended up buying the exact same transformer and it works now. I never realized the output on these battery backups were square.