[Nut-upsuser] Smart-UPS staying in OB after power return

Kris Jordan nut01.kj at sagebrushnetworks.com
Sun Sep 22 02:34:06 UTC 2013

John Morris wrote, On 9/21/2013 6:19 PM:
> Hi Kris,
> On 09/21/2013 05:11 PM, Kris Jordan wrote:
>> John Morris wrote, On 9/21/2013 11:28 AM:
>>> The most distressing problem is the UPS stays OB after removing and
>>> reapplying utility power.  When power is removed, the UPS goes OB and
>>> upsmon detects the power failure no problem, reporting
>>> 's0-ups0 at localhost is on battery'.  But when power is restored, there is
>>> no clicking of contactors, no switch back to OL, and no detection by
>>> upsmon that power is restored.  The UPS can be manually put back OL with
>>> 'upscmd load.on'.  I would expect the UPS go back OL automatically,
>>> though; am I wrong about this?  (APC forums folk are thus-far silent on
>>> this question.)
>> Pull the batteries and unplug the UPS and press the buttons to fully
>> discharge the UPS. Disconnect the serial/computer interface connection.
>> Re-connect the batteries, plug into utility. Do not re-connect the
>> computer interface. Now that we have rebooted the UPS, see that it works
>> like it should.
> I've done this a few times already after reading a 'braindeading'
> procedure.  With cable installed or not, removing utility power switches
> to battery; restoring power remains on battery.
> Is that how it should work, or not?

Definitely not.

> Since we got the UPS, it has only been under testing without any load 
> (I just plugged a 200W lamp in for fun). These issues have been 
> persistent since the first time the new batteries were installed and 
> the unit was powered up two days ago. My question remains: The on-line 
> LED should not flash incessantly, and removing and restoring mains 
> power should cause the UPS to switch to OB and then back to OL without 
> intervention, correct?


I've not seen this behavior myself even with bad batteries and a wrong 
battery constant. Might want to check the batteries with multimeter to 
be sure. Disconnect and allow them to sit for a day, then check the 
voltage of each one. They should all be fairly balanced, and I would 
expect something just above 13V.

The UPS itself is going to be pretty aged by now if it has been in use 
most of that time.

More information about the Nut-upsuser mailing list