what is "low battery duration"?

[BillP]

I have a brand new UPS and I'm testing this but for the life of me I cannot figure out what this means.  I just had a 1.5 hr conversation with tech support and I'm still confused.  At first she said it was "how long to run on battery before notifying the PCNS clients", then she went into the lab and did 1/2 hr of testing and said it was "how long the UPS has battery power before it runs out".  

Help!

SW

[voidstar_apc]

It is confusing. Imagine it says:

"When on battery and the estimated time before the battery becomes depleted drops below ____, tell everything it must shut down."

Or, using only the 10 hundred most used words:

"When using stored power and the best guess for time before the stored power is used up drops under ____, tell everything it must shut down."

So for example, your fully charged battery provides 45 minutes of electrical power. Suddenly your building experiences a power outage and only emergency lighting and your server remain on. Over time, the UPS' estimate of how long the battery will last decreases, because the server is consumer charge. We don't want the battery to run completely flat for a few reasons: because we want to safely shut down our server, we want to limit use of the battery to prolong its service life, and we want to have charge left over in case power comes back but fails again. So we set the low battery duration to 10 minutes. The power doesn't come back, so eventually the battery can only provide 10 minutes of electrical power. The UPS tells all devices they must shut down if they have not already. At this point, unsurprisingly, the battery can run for 10 more minutes, hence TS' answer. Smart devices attached to the UPS then shut down and tell the UPS to do the same. This take 4 minutes, so the UPS turns off when there's 6 minutes of battery life remaining. Later, power comes back, and when the battery charges to the point where it can provide the "minimum return runtime", the UPS output turns back on.

[BillP]

Ahhh, ok that makes sense.  However, there's one more thing that is confusing:  You can set shutdown parameters on the client AND the UPS card.  In that case, which takes precedence?  For example, in th above scenario, what if I told the PCNS client to shut down 40 min. after a power outage?   The shutdown signal from the card would come at the 35 min. mark after the power went out.  But if I told it to wait 40 min, who wins?

[BillP]

Hi,

Low battery would be reached before the On Battery delay and therefore would take precedence.

[BillP]

Ok, that's good to know.  Just one more thing, what does "maximum required delay" mean and how does it get calculated?  This was another point of confusion when talking to tech support.   It seems to get set to the same value as "low battery duration" when you check off "force negotiation" and click apply. 

[BillP · Accepted solution]

Maximum required delay calculates the delay needed to ensure that each PowerChute client has enough time to shut down safely when the UPS or the PowerChute client initiates a graceful shutdown. Maximum Required Delay is the longest shutdown delay needed by any server listed as a PowerChute Network Shutdown client. This delay is calculated whenever the management interface of the UPS turns on or is reset, or when "Force Negotiation" is selected as Maximum Required Delay. "Force Negotiation" polls each client for information on the time it needs for a graceful shutdown. Two extra minutes to allow for unforeseen circumstances is then added to the calculated time. The negotiation can take up to 10 minutes. If you do not select "Force Negotiation", two minutes is used by default as the shutdown delay for all clients.

Example: you have configured PowerChute Network Shutdown to run a command file and the command file has a delay of 10 minutes when you click on force negotiation the maximum required delay will be changed to 12 minutes if your UPS does not have switched outlet groups. If your UPS has switched outlet groups then the outlet group power off delay that PowerChute is associated with will be increased.

SMT, SMX Smart-UPS have switched outlet groups.

On 8/28/2015 12:12 PM, Shawn said:

It seems to get set to the same value as "low battery duration" when you check off "force negotiation" and click apply. 

That is correct. If you change the low battery duration from the default of 2 minutes to say 8 minutes and click force negotiation the value of maximum required delay is increase to 8 minutes. Also, if your UPS has switched outlet groups the outlet group power off delay will be changed to match the value set for low battery.