SOC doesn't match Load kwhr in Dashboard

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SOC doesn't match Load kwhr in Dashboard

Postby cgarai on Wed Dec 06, 2017 12:27 pm

Using the OpticsRE Dashboard I quickly added up the total load kwhrs used overnight and compared that with the SOC decline for the same period and they don't match. My understanding is that SOC is supposed to integrate the amperage going in and out of the battery, with the amps into the battery discounted by the Charge Factor. Since I was looking at the period of discharge only, the SOC should have declined by the total load / Battery AH (FNDC setting).

Here is what I observed.
Overnight load: 13.1kwhr (I was charging a Volt plug-in hybrid)
Overnight SOC: 99%-68% = 31% change

Battery AH = 1350. System voltage = 48 V Total capacity = 1350*48= 64.8 kwhr

Overnight capacity used = 13.1/64.8 = 20%

I used 20% but the SOC declined 30%. Why? Have I made an error?

Thanks,
Chris
cgarai
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My RE system: Off Grid System:
Flexware 1000 system with
4 VFX3648s, X-240, 2 Flexmax 80s, FN-DC, HUB10 and a Mate3
controlling 30 Sharp 240w panels and
charging 48V HUP Solar 1 SO-6-85-33 batteries
12kw Isuzu/Mecc Alte diesel generator

Re: SOC doesn't match Load kwhr in Dashboard

Postby David LeBow on Wed Dec 06, 2017 12:29 pm

Hi Chris,

There's a place for your Optics site name in your user forum profile. If you fill that in, it's possible for us to take a look at your data for the time in question.

Thanks,

David
David LeBow
Vice President, Software Engineering


Alpha Technologies Inc. / OutBack Power Technologies
3767 Alpha Way Bellingham WA 98226 USA
http://www.alpha.com
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Re: SOC doesn't match Load kwhr in Dashboard

Postby cgarai on Wed Dec 06, 2017 4:30 pm

I posted the name, assuming it is the name and not the URL.

The time I looked at was 12/5 5pm to 12/6 7am, but it has always seemed that was the case although I never did the arithmetic.

Thanks,
Chris
cgarai
OutBack Expert
 
Posts: 68
Joined: Tue Feb 15, 2005 11:35 pm
Location: Healdsburg, CA
My RE system: Off Grid System:
Flexware 1000 system with
4 VFX3648s, X-240, 2 Flexmax 80s, FN-DC, HUB10 and a Mate3
controlling 30 Sharp 240w panels and
charging 48V HUP Solar 1 SO-6-85-33 batteries
12kw Isuzu/Mecc Alte diesel generator

Re: SOC doesn't match Load kwhr in Dashboard

Postby blackswan555 on Wed Dec 06, 2017 8:37 pm

You could put some of it down to losses, But 10% seems a bit much, It sounds like your FNDC is still in need of more calibration, (especially if the batteries are reasonably new) What are your SGs vs what the FNDC & Optics are telling you ?

Tim

To add, I recommend cross referencing/checking FNDC against SGs frequently on a newer installation, Batteries take about 70 cycles to run in so settings need to be adjusted for that, The FNDC SOC reading will also drift over time, Recheck periodically,
My comments are based on my experience and research, They are not endorsed or checked by Outback.I am an independent British electrician living in Spain, So please take this into account when reading /acting on my post`s.
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Re: SOC doesn't match Load kwhr in Dashboard

Postby cgarai on Thu Dec 07, 2017 3:26 pm

I haven't checked the SGs lately, but that is not the question here. Regardless of the actual battery state the SOC should decrease by the amount of the load energy used. I'm assuming the FNDC and/or the Mate does all this arithmetic and reports it to OpticsRE. Or does OpticsRE take the data and do the math? Somewhere something isn't adding up.

My understanding is that the SOC accuracy depends on system settings. If the Charge Factor isn't right, then the SOC might hit 100% before the batteries are actually at 100%. Or the reverse, where the battery state hits 100% before the SOC does. The SOC is a crude gas gauge, but it ought to be doing the math right.

No one else sees this discrepancy?
cgarai
OutBack Expert
 
Posts: 68
Joined: Tue Feb 15, 2005 11:35 pm
Location: Healdsburg, CA
My RE system: Off Grid System:
Flexware 1000 system with
4 VFX3648s, X-240, 2 Flexmax 80s, FN-DC, HUB10 and a Mate3
controlling 30 Sharp 240w panels and
charging 48V HUP Solar 1 SO-6-85-33 batteries
12kw Isuzu/Mecc Alte diesel generator

Re: SOC doesn't match Load kwhr in Dashboard

Postby Mike Curran on Thu Dec 07, 2017 6:53 pm

I'm guessing here but Optics is probably calculating your overnight load simply by multiplying your FXs' AC output voltage times AC output current, over the overnight time interval. Might there be some reactive power that's not being accounted for in that 13.1kwh? Don't know what the power factor of your Volt charger looks like but that might explain the discrepancy.
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- 2 grid-tied GVFX3524's classic stacked for 120/240VAC
- 12 Surrette/Rolls 2V x 1766Ah
- Hub10.3, Mate3, FNDC, RTS, OpticsRE. Tigo Energy ES maximizers on each PV module.

Westinghouse Solar:
- 30 (2x15) 235W panels with Enphase M215 microinverters, grid-tied.


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