PCNS issued shutdown to VMs and ESXi within 5 seconds of being on battery - why?

[stanj]

We needed to switch the UPS from a power strip unit to a building wall outlet to see if it would remove  Site Wiring Fault messages appearing in the APC logs..

When we unplugged the UPS from the power strip and connected to the wall, PCNS started to shut down the VMs and the host.

 I am m not sure why, because it was on battery for about 4 seconds then back to building power via the wall outlet. So I am not sure why PCNS received an alert and PCNS did the shutdown?

The NMC Shutdown Settings are............

Shutdown:

  Low Battery Duration 15 min

  Max Required Delay     6 Min

  Basic Low Battery Duration 600 sec

Duration of Shutdown

    Sleep  0.0 hours

Sync Control Shut:

  Shutdown Delay            600 sec

  Return Delay                     10 sec

NMC status of the batteries shows there is 24 minutes of run time remaining.

PCNS Events are only set to log events.

Below are some of the messages seen in the log

10:15:22 Low Battery Condition occurred

10:15:22 Shutdown Sequence Started on ESXi

10:15:23 Low Battery Condition Solved

10:15:24 UPS Critical: Low Battery resolved on host ESXi

10:15:24 Starting Maintenance Mode task on host ESXi

10:15:24 Shutting Down VMs

10:15:26 UPS no longer running on battery power or output power has been turned on

10:15:40 Battery is discharged

10:15:56 Battery has charged

10:16:17 Battery is discharged

10:16:21 Battery has recharged

[BillP]

Hi,

The log show that the UPS reported a low battery state at 10:15:22 so PCNS started the shut down process. A low battery event is treated as a critical event so by default PowerChute will trigger a shutdown sequence. Even though the event cleared a second later the shutdown cannot be disabled for this events to prevent catastrophic system failure. 

[stanj]

What would cause a Low Battery? 

This is a new system and after restarting, it shows 25min of battery life.

I am also seeing several messages in the NMC log  about distorted input and switching back and for to battery, like

11/14

   6:40:13  UPS: on battery in response to distorted input

   6:40:14  UPS: no longer on battery 

11/19

   7:57:55  UPS: on battery in response to distorted input

   7:57:56  UPS: no longer on battery

   8:03:23  UPS: on battery in response to distorted input

   8:03:25  UPS: no longer on battery

   20:13:53  UPS: on battery in response to distorted input

   20:13:24  UPS: no longer on battery

PCNS has similar entries in its' log

[BillP]

Hi,

The low battery setting on the NMC is at 15 minutes. When the UPS switched to battery and dropped below 15 minutes of runtime the shutdown was triggered. I cannot say why when restarted the UPS reports 25 minutes of runtime. It may have recharged or it may have only momentarily fallen below the threshold but the log shows it reported low battery so PCNS trigger the shutdown. 

[stanj]

The UPS was switched to battery for only 5 seconds when the source was moved from power strip to a wall oulet.  How could the battery have dropped below 15 minutes?

[BillP · Accepted solution]

Hi,

I cannot say for sure but it is possible by disrupting ground the UPS reported the wrong runtime momentarily.