Apparent Discrepancy Between Actual & Advertised Battery Runtime

[dale.magnant_apc]

This was originally posted on APC forums on 7/11/2015

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Hello,

We recently purchased a SURTA3000RMXL3U along with one SURT192RMXLBP3U external battery pack for use on a network rack.  Previously we had had two smaller APC units supporting this rack.  The AP9630 cards in the two replaced units and in the new unit indicated a total load of 7 amps or roughly 840 watts.  According to the runtime vs wattage chart on the APC web site for this combination (one SURTA3000RMXL3U UPS unit plus one SURT192RMXLBP3U battery pack) an 840 watt load should equate to roughly 150 minutes of runtime.  When first attached to the rack, the installed AP9630 in the new unit was seeing just a shade under 7 amps and showing a projected run time of about 47 minutes.  The AP9630 indicates that it is in fact detecting one auxiliary battery pack.  I then ran a calibration cycle which took considerable time and ran the battery down to less than 50%.  As I type this, the battery is slowly recharging and is currently at 64% capacity.  Projected runtime is increasing in parallel with battery charge but is currently showing only 30 minutes.

Perhaps I should wait till the battery is fully charged before posting this, but at the rate things are going, the final runtime will be little if any different than before I ran the calibration cycle.  Is there some final recalcualtion of runtime that is done when the battery returns to a full 100% charge?  If not, and the projected runtime continues to advertise about 45 minutes, what explains the discrepancy between this and the runtime charts on the APC website?

Thank You,

[BillP]

This reply was originally posted by Bill on APC forums on 7/13/2015

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Dale,

You wrote

On 7/11/2015 5:02 PM, Dale said:

The AP9630 indicates that it is in fact detecting one auxiliary battery pack. 

When you view the UPS status page does it list 1 external battery pack? You can adjust the number of external battery packs under Configuration - UPS General

[dale.magnant_apc]

This was originally posted on APC forums on 7/13/2015

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Bill,

Thank you for the reply.  Regarding your suggestion - yes, under Configuration/UPS-General, the External Batteries is detecting 1 external battery.

The good new is:  This morning I reran the calibration.  Starting at 100% battery charge, the calibration ran the battery down to somewhere below 30% before completing.  The calibration started at 09:33 and at 11:40 the battery was down to 30% remaining capacity.  Doing a bit of extrapolation, this would equate to a projected full battery draw down of roughly 180 minutes.  This is actually slightly better than what the APC graphs suggest and is certainly more than acceptable.

The bad news is:  As the battery slowly recharges (currently back to 70%) the projected runtime on the Status/UPS screen is showing only 31 minutes.  This suggests that when the battery has returned to full charge the projected runtime will be on the order of 45 minutes.

Conclusion:  It seems that the calibration process does not affect the "Runtime Remaining" figure on the Status/UPS screen - unless it does some final update after the battery returns to 100% charge.  If not, this is rather annoying - little better than a broken fuel gauge.  It does however appear that in the event of an actual loss of power event we will have at least as much runtime as the APC charts suggest.

If the Runtime Remaining value does autoupdate to an accurate figure I will post back with the results.

Thank you,

[BillP]

This reply was originally posted by Angela on APC forums on 7/14/2015

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I would keep in mind too that the runtime that the UPS reports while online should be a really good estimate. Once the UPS operates on battery either because of a power outage or like a runtime calibration that you did, the UPS should continually update that figure based on the load. 

My questions usually are is putting aside what it reports, how much runtime does the UPS actually provide. If I read what you wrote, the UPS lasted to approximately what you'd expect per the chart but just the estimated value you see keeps going back to something that is not accurate. Did I understand correctly?

[dale.magnant_apc]

This was originally posted on APC forums on 7/14/2015

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Angela,

Yes, given the length of time required during the calibration to draw the battery down to 30%, (just over two hours) the "real" runtime should be roughly 180 minutes.  This morning when I looked at the AP9630 it of course now shows the battery back at a full 100% charge.  Once again however, on the Status/UPS page it shows the Runtime Remaining as 45 minutes - not even close to the 180 minute figure.  So, for whatever reason, these two figures are wildly different. 

Thank You,

Dale

[BillP]

This reply was originally posted by Angela on APC forums on 7/14/2015

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Hi Dale,

Thanks for confirming. I checked my notes. This UPS counts its internal battery pack as the 1. I think you should bump the count to 2 for external batteries and see what you get. See below for my notes:

SURTA3000XL:
Defines the number of connected battery packs for proper run time prediction.
1 = internal battery module,
2 = one SURT192XLBP or SURT192XLBPJ,
3 = two SURT192XLBP or SURT192XLBPJ, etc.

I went and searched all of the SURT user's guides way back when as to how external batteries work for each model. Here are all my notes in case anyone else comes across this for other models:

SURTA1500XL/SURTA2000XL:
Defines the number of connected battery packs for proper run time prediction.
1 = internal battery module,
2 = one SURTA48XLBP or SURTA48XLBPJ,
3 = two SURTA48XLBP or SURTA48XLBPJ,
etc.

SURTA3000XL:
Defines the number of connected battery packs for proper run time prediction.
1 = internal battery module,
2 = one SURT192XLBP or SURT192XLBPJ, 
3 = two SURT192XLBP or SURT192XLBPJ, etc.

SURTD3000XLT and SURTD5000XLT:
Defines the number of connected battery packs for proper run time prediction.
1 = one SURT192XLBP or SURT192XLBPJ, 
2 = two SURT192XLBP or SURT192XLBPJ, etc.

SURT3000XLT and SURT5000XLT (non Ds), SURT6000XLT, SURT8000XLT, SURT10000XLT:
Defines the number of connected battery packs for proper run time prediction.
1 = internal battery module,
2 = one SURT192XLBP or SURT192XLBPJ, 
3 = two SURT192XLBP or SURT192XLBPJ, etc.

[dale.magnant_apc]

This was originally posted on APC forums on 7/14/2015

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Angela,

Thank you for the detailed response.  I went ahead and changed the "External Batteries:" setting under Configuration/UPS General from 1 to 2.  Then, flipping back to Status/UPS, and doing a screen refresh, the Runtime Remaining has jumped from the original 45 minutes to 3 hours and 48 minutes.  This is certainly better, though based on the projected runtime during the calibration test, I would say the figure is optimistic by roughly 50 minutes.  (Though I would happily be wrong) Perhaps another calibration test will fine tune this number. 

Clearly, for this particular model, it appears to be necessary to set the external battery count to 2 rather than 1. 

I'll try running another calibration overnight and see if the 3hr 48min figure changes at all.

Thank you for providing the info from the manuals - I would not have readily arrived at that solution.

Dale

[BillP]

This reply was originally posted by Angela on APC forums on 7/15/2015

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Hi Dale,

You're welcome. I am not sure why all the SURT use that external battery pack count differently either...

[lflince_apc · Accepted solution]

This was originally posted on APC forums on 7/28/2019

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Hello, I have the same situation, the difference is that we already configure the ups to two banks, the internal + 1 external = 2, the model of the ups is: Smart-UPS RT 3000 RM XL, when we perform the runtime calibration, the The battery lasts 3 hours and a few minutes, but then when the batteries are 100% charged the Runtime Remaining is only 50-60 minutes. We have already turned it off, disconnected all the charges and turned it on again and the Runtime Remaining continues in 50-60 minutes.