Battery charge level drops quickly (Smart-UPS 750VA SMT750I) Calibration questions.

[Alex_N]

I've bought a new UPS (APC Smart-UPS, 750VA/500W SMT750I) a month ago and it works fine but there's one thing that bothers me.

During the automatic self-test (that passes OK) the battery charge level drops to 90%. The self test lasts only a couple of seconds and I think a 10% drop is too much. The load on the UPS when the test is performed is about 21%. The runtime indicated by PowerChute Business Edition is 51 Minutes when the battery is fully charged and the load is 21%.

I'm thinking of doing a runtime calibration but I have some questions.

I've read here http://forums.apc.com/thread/15775 that "The calibration is just updating the battery runtime reported and if you don't have a problem with what's reported, no need for a calibration."

The runtime I've got seems OK (51 Minutes when not running on battery), my problem is with the battery charge level. Does the calibration also fixes this?

I've found here http://forums.apc.com/thread/8669?start=0&tstart=0 that "any UPS monitoring/shutdown software should be stopped from running in the background, and the serial cable should be detached from the UPS. This is necessary in order to prevent the software from shutting down the server/UPS due to an on-battery or low-battery condition. "

It's OK if I just disconnect the USB cable from the computer and start the calibration using the LCD display on the unit?

Thank you very much!

[Alex_N]

Experienced a power outage last weekend and I'm happy to say the UPS performed OK. After the initial 10% drop in battery charge it slowed down and after running on battery for about 4 or 5 minutes the charge level was only down to 87%.

I have one more question. I programmed the UPS using Powerchute Business Edition to shut down the computer after 4 minutes of running on battery and it did, but is there a way to put the computer in hibernation instead of shutting it down? I didn't find an option in Powerchute to hibernate instead of shutting down. I use Windows 7 and have hibernation enabled and working.

Thanks!

[Alex_N]

I've bought a new UPS (APC Smart-UPS, 750VA/500W SMT750I) a month ago and it works fine but there's one thing that bothers me.

During the automatic self-test (that passes OK) the battery charge level drops to 90%. The self test lasts only a couple of seconds and I think a 10% drop is too much. The load on the UPS when the test is performed is about 21%. The runtime indicated by PowerChute Business Edition is 51 Minutes when the battery is fully charged and the load is 21%.

I'm thinking of doing a runtime calibration but I have some questions.

I've read here http://forums.apc.com/thread/15775 that "The calibration is just updating the battery runtime reported and if you don't have a problem with what's reported, no need for a calibration."

The runtime I've got seems OK (51 Minutes when not running on battery), my problem is with the battery charge level. Does the calibration also fixes this?

I've found here http://forums.apc.com/thread/8669?start=0&tstart=0 that "any UPS monitoring/shutdown software should be stopped from running in the background, and the serial cable should be detached from the UPS. This is necessary in order to prevent the software from shutting down the server/UPS due to an on-battery or low-battery condition. "

It's OK if I just disconnect the USB cable from the computer and start the calibration using the LCD display on the unit?

Thank you very much!

[Alex_N]

OK, I think I'll postpone the calibration and see how it works during a real power outage. I don't want to stress the battery unnecessarily.

Thanks again for your help.

[BillP]

How many self tests have you done? The more you do, the more dramatic the drop will likely be. It is normal for the percentage to drop 5-8% at least I would say.

The runtime is a complex formula that is calculated from the state of charge (battery charge level) and the load on the UPS. The runtime is one of a couple of factors that affect the state of charge and can be potentially fixed with a run time calibration, but will not necessarily fix the drop of state of charge initial drop.

I've read here http://forums.apc.com/thread/15775 that "The calibration is just updating the battery runtime reported and if you don't have a problem with what's reported, no need for a calibration."

The runtime I've got seems OK (51 Minutes when not running on battery), my problem is with the battery charge level. Does the calibration also fixes this?

This comment is for a "manual calibration."

I honestly don't think a calibration is going to make a huge difference but if you'd prefer to try, then please note the following: If you do the calibration from the front panel command / test menu, you should not need to disconnect the communications cable. Since you are using PowerChute anyway, I recommend that you issue the command via PowerChute.

Please note this will discharge your battery down to between 10-20% and put additional stress on the batteries beyond the self tests you've already done. As I noted, a calibration will not necessarily "fix" the drop of charge you're seeing.

[Alex_N]

Thank you for your answer.

I've only initiated one self-test, the other where performed automatically by the UPS at 14 days since start-up date intervals. The self-test I've initiated was 2 or 3 days after the last self-test performed automatically to let the battery fully charge.

I also have an APC Back-UPS 800VA that I've used before the Smart-UPS 750VA and the battery charge level drop during the self-test was about 1-2%.

[BillP]

Hi again,

Oh, ok.

Well, to begin, comparing Back UPS and Smart UPS is like apples and oranges so I can't really say much beyond that.

I don't think there is much we'll be able to do unfortunately and it is just the way this particular model works but I can understand the concern with a larger drop like 10%. Upon checking though, it appears relatively normal.

[BillP · Accepted solution]

You're very welcome.