Drastic SOC Change

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JRHill
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Drastic SOC Change

Post by JRHill » Fri Jan 20, 2017 10:46 am

Last night I went though the normal gen set charging cycle for this time of year. All kwh in and out have been consistent every day. However, this morning I noticed that my SOC was still at 99% when, usually, it would be down to 82 to 78%. The battery voltage drop after charging and through the night 'till morning is consistent as well.

New (L16) batteries and the FlexNetDC were placed in service in Aug '15. Yeah, I know it's time to charge the batteries until the SG's show a full charge and reset the FlexNet, but are there any ideas as to why all of a sudden the SOC is suddenly so far from normal? I was kind of hoping to forestall the long charge charge cycle until the snow melted off the panels and the sun got a little higher above the trees before the reset....

Thx all,
Jim
Last edited by JRHill on Sun Jan 22, 2017 3:10 pm, edited 1 time in total.

blackswan555
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Re: Drastic SOC Change

Post by blackswan555 » Sat Jan 21, 2017 5:22 am

Maybe this one ? viewtopic.php?f=28&t=8786

Tim
ps, no I am not going to mention charge till SGs stop rising etc,,,,, But when you do,,,, :mrgreen: You should notice quite an improvement, Batteries take about 70 cycles to run in & reach full capacity, The first EQ may take a while, But you usually smile at the result :grin: (If you are on mainly gen at the mo, Probably worth biting the bullet now if it is going to be more than a few weeks)
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Re: Drastic SOC Change

Post by JRHill » Wed Jan 25, 2017 10:38 am

I've been trying to do an extended Absorb so as to reach a full charge to reset the FNDC. But I keep falling back to Float as I'm checking SGs. Darn, I know it's something simple that I'm not recalling. I even looked in the manuals :-0

What do I change to stay at the Absorb voltage?

TIA,
Jim

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Re: Drastic SOC Change

Post by JRHill » Wed Jan 25, 2017 7:58 pm

I think I found it. Press the Charger hot key > Charger Mode > On. I had Auto selected - though the manual doesn't say, this seems to force the extended Absorb cycle.

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Re: Drastic SOC Change

Post by blackswan555 » Thu Jan 26, 2017 1:45 am

Either put your absorb time to as high as it will go or set your float voltage to the same as absorb,

Tim
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Re: Drastic SOC Change

Post by JRHill » Fri Jan 27, 2017 3:44 pm

blackswan555 wrote:Either put your absorb time to as high as it will go or set your float voltage to the same as absorb,

Tim
Thanks Tim,

FEI (for everyone's Information :-)) This ended up taking multiple days to my surprise. Day one I had to shut down as the SGs were not stabilized and it was too late at night - 9.5 hrs. Day two took 8 hours and I was still checking SGs in the dark. But I got 'em there and then Equalized. I view this as normal maintenance and it feels good in the wallet to be maintaining my batteries as best I can. If anything, some would fault me for not cycling my batteries deeper.

But one thing I was pondering is that there have been several recent posts from people that have inherited or bought into rather substantial systems and are trying to deal with problems that are battery maintenance based, or that is at least probably a key issue. I don't know of the wider scope of technology, other than OutBack, but it's pretty obvious these systems are not for folks that aren't ready or able to do their own maintenance. How much would it have cost to hire in someone who just did what I did over the last few days? Sheesh, battery strings serial and parallel (and multiples of each), cabling, proper charging, battery type, settings, programming and on and on, I cringe at the thought. This is close to me as my wife would have to do these tasks if anything kept me from doing so. Try to write that instruction into manual. (And she's technical - she just doesn't want to do it when she gets home.)

I'm done rambling on....

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Re: Drastic SOC Change

Post by blackswan555 » Fri Jan 27, 2017 4:20 pm

As mentioned, your first EQ is usually a long one :smile: (edited to add, I only just noticed it was August 15,,, no wonder it took a while :grin: ) For the next one the day before you may want to set a high absorb voltage, 29.5 ish & extend absorb time to 6 hrs, Then set a must run to start early that morning so when you get to it batteries are definitely full, That is one way to reduce site/hands on time (I once went to a site that the owner was adamant the batteries were full for me to EQ, 16hrs later I had to give up and go back next day,,,2 of us,, that was not cheap)

Did you notice how much your FNDC was off by ? What were your SGs like before & after ? By you description of time taken they sound to have been pretty low / bad ?
I would watch your SGs for the next few weeks & try to figure when they do stop rising so you can dial in your charge times a little better,

Tim
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Re: Drastic SOC Change

Post by JRHill » Fri Jan 27, 2017 6:35 pm

blackswan555 wrote:Did you notice how much your FNDC was off by ? What were your SGs like before & after ? By you description of time taken they sound to have been pretty low / bad ?
I would watch your SGs for the next few weeks & try to figure when they do stop rising so you can dial in your charge times a little better, Tim
48v system... August 15,, 2015

Tim, I can't quantitatively say how much the FNDC was off as it creeps up without notice as we know. The trigger was the subject of this thread; whatever caused that is still a mystery. The only real, albeit rough, observation was the time taken to get the SGs back in line. Roughly, it took about 2.5x the normal, daily run time of the gen set to get the SGs stabilized and ED'd. It didn't hurt too bad as much of the finish time was at literally at .3 Kw to hold the voltage at absorb (62.4vdc corrected via temp comp to 63,x something). And the EQ was similar after the first few minutes. TG I made the move to the inverter gen set this year. The fuel draw was inconsequential - it idled along keeping the voltage up.. Really cool.

Thx, I hope this helps some folks,
Jim

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Re: Drastic SOC Change

Post by timmartin » Sat Jan 28, 2017 9:53 am

With regards to the original post about the charge being 99% in the morning...

I have had circumstances, usually at night (no sun!) when the generator charging has allowed the FNDC to report a positive Ah value for the batteries. In most circumstances this value is negative and usually during daylight charging when it gets to zero it flat-lines. It will stay at zero while you absorb, eq, etc. If you plot the data you will actually see it slightly go above zero and reset repeatedly, which makes sense as the point of this value is to report how much power has been removed from the batteries (the net value) as an indication of how much needs to be put back on (the corrected value).

So I have seen this go 100's of Ah into the positive range and when charging stops it stays there. Over hours of use it is slowly creeping back down towards zero, but the SOC will report 100% until it hits the horizon and dips into negative values. This has lead me to the EXACT same situation as you where SOC was abnormally high when I woke up after a full night of discharging.

So in summary, it's a bug. A bug we've reported here on the forum and through email support, yet persists.

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Re: Drastic SOC Change

Post by timmartin » Sat Jan 28, 2017 9:59 am

JRHill wrote:... as it creeps up without notice as we know.
FYI SOC can (and often does) jump to 100% before your batteries are actually charged because of a different bug in the logic around net Ah/corrected Ah removed from battery and a tricky bit of logic code the tries to account for drifting values in the wrong direction.

That bug has also been reported but is refuted by Outback, despite my ability to replicate the bug and having shared all the reporting and data possible. They drop the ball and never get back to me... they have horrible follow-through, with customer service discussions not getting responses for months and months. I gave up, seems like they have no intention of fixing bugs in their hardware (FNDC never gets firmware updates).

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Re: Drastic SOC Change

Post by JRHill » Mon Jan 30, 2017 9:43 am

timmartin wrote:With regards to the original post about the charge being 99% in the morning...
Tim, after getting the batteries fully charged per SGs, resetting the FNDC and EQing, the next 24 hours was fine. That first morning after the reset showed the batteries at 89% rather than around 80% before. Great! But that night I accidentally drew the batteries down to 45% and had a shut down before getting up the next morning. I recharged the batteries and absorbed for 6 hours. So, the FNDC is reset to full batteries in their current state/age but after the draw down and recharge, SOC seems "stuck" at 100%. The unit is totally confused. At this point I'm not sure what next steps should be taken. I suppose I'll watch to see what happens for the next few days but I'm thinking it'll take another extended absorb while checking SGs, FNDC reset, and start again. Or maybe I should ask Cortana or Alexa?

Add to that, OpticsRE has been throwing a PARTIAL CONNECTION tantrum for the last 36 hours. It would really help if I had the graphs and various Kwh totals vs gathering the data the long way.

Sheesh....

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Re: Drastic SOC Change

Post by blackswan555 » Mon Jan 30, 2017 10:10 am

I recharged the batteries and absorbed for 6 hours. So, the FNDC is reset to full batteries in their current state/age but after the draw down and recharge, SOC seems "stuck" at 100%. The unit is totally confused. At this point I'm not sure what next steps should be taken.
Throw it in the bin and do it manually ? But being serious,,,, Throw it in the bin and do it manually ( well set absorb times yourself) Maybe keep it as a "pretty display" But do not trust it any more than you would a rabid dog with your roast beef dinner ](*,)

Tim
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Re: Drastic SOC Change

Post by JRHill » Mon Jan 30, 2017 10:17 am

blackswan555 wrote:
Throw it in the bin and do it manually ? But being serious,,,, Throw it in the bin and do it manually
An addition to the old phrase "'Close' only counts in horseshoes, hand grenades and FNDC calcs."

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Re: Drastic SOC Change

Post by blackswan555 » Mon Jan 30, 2017 11:37 am

I wear a watch that stopped some years ago,,,, At least it is right twice a day :smile:
Tim
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Re: Drastic SOC Change

Post by timmartin » Mon Jan 30, 2017 11:38 am

JRHill wrote:So, the FNDC is reset to full batteries in their current state/age but after the draw down and recharge, SOC seems "stuck" at 100%. The unit is totally confused. At this point I'm not sure what next steps should be taken. I suppose I'll watch to see what happens for the next few days but I'm thinking it'll take another extended absorb while checking SGs, FNDC reset, and start again.
You probably realize this, but all this work with absorbing, EQing, and SG is all great, but the FNDC doesn't behave any different/better. It's a very simple thing really, it just measures the current leaving the batteries and measure the current entering the batteries and does the math. It has bugs and issues, but most importantly it doesn't know squat about the actual state of your batteries.

So if it's "stuck" at 100%, there are very few possible issues:
1) it's installed incorrectly and not properly measuring your battery usage
2) you're experiencing a bug in the FNDC software where it's not doing the math properly.

Any time it's "stuck" you could disconnect it from power and reconnect it. It'll start at 100% every time you do that, but it should start falling immediately after being reset if the problem is because of a bug in the FNDC.

Here's a perfect example... I ran the generator for a long time charging the batteries, in the meantime it got dark outside. The FNDC allowed the net amp-hours to climb well into the positive range and when the generator was turned off it STILL didn't reset to zero. Thus SOC was pegged at 100 all night long:
stuck_at_100.jpg
Then the next morning when the charge controllers came online it triggered the FNDC to reset the net amp-hours to zero and resume proper operation, albeit with a massively incorrect SOC.
reset.jpg

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Re: Drastic SOC Change

Post by blackswan555 » Mon Jan 30, 2017 12:00 pm

It's a very simple thing really, it just measures the current leaving the batteries and measure the current entering the batteries and does the math.
Too simple, Sadly it (none of them do though, not just FNDC) does not take into account Mr Peukerts law,
A reasonable description from someone else :smile: https://www.solarpaneltalk.com/forum/of ... es-and-you

Tim
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Re: Drastic SOC Change

Post by JRHill » Mon Jan 30, 2017 3:25 pm

blackswan555 wrote:
Mr Peukerts law
Makes complete sense to - I perform in a similar way. All those times I was told to "Get the lead out" now come back to me.

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Re: Drastic SOC Change

Post by SandyP » Mon Jan 30, 2017 10:29 pm

blackswan555 wrote:
It's a very simple thing really, it just measures the current leaving the batteries and measure the current entering the batteries and does the math.
Too simple, Sadly it (none of them do though, not just FNDC) does not take into account Mr Peukerts law,
A reasonable description from someone else :smile: https://www.solarpaneltalk.com/forum/of ... es-and-you

Tim
I had hoped that, as descibed in their manual, the Victron BMV battery monitors did allow you to calculate a Peukert Factor (exponent) for your batteries and this is then used in the calculation of SoC.

Pages 29-30 : https://www.victronenergy.com/upload/do ... -PT-IT.pdf

Yes, I own and use a Victron BMV and feel confident of what it is showing (yes, I have SLA batteries so cannot check the SGs). After a stretch of days without returning to fully charged you can expect that the BMV will be around 3-5% out however this will easily reset when the charge voltage and amps settings are reached.

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Re: Drastic SOC Change

Post by blackswan555 » Tue Jan 31, 2017 3:36 am

I had hoped that, as descibed in their manual, the Victron BMV battery monitors did allow you to calculate a Peukert Factor (exponent) for your batteries and this is then used in the calculation of SoC.
Calculate no, Guess yes, Peukerts changes constantly with load, also temperature and state of charge will affect the number counting of the "device" non of them are accurate for any length of time,,,,,,
Victron say so themselves,
2.2 Synchronizing the BMV
For a reliable readout, the state of charge as displayed by the battery
monitor has to be synchronized regularly with the true state of charge of
the battery.
This is accomplished by fully charging the battery.
In case of a 12V battery, the BMV resets to ÔÇÿfully chargedÔÇÖ when the
following ÔÇÿcharged parametersÔÇÖ are met: the voltage exceeds 13.2V and
simultaneously the (tail-) charge current is less than 4.0% of the total
battery capacity (e.g. 8A for a 200Ah battery) during 4 minutes.
And then if you actually look at what they are suggesting as charged over 13.2v,,,4% current for 4 mins, ](*,)

14.4v ( and that is on the low side by most manufacturers these days) 1 to 2 % ,,,, but that is a bit variable & 1/2 hr minimum (FLA) would be a better place to start

I am not particularly bashing the FNDC, Installed and set up correctly it is probably about the best battery monitor of the lot ( read the manual, word by word,, twice, and then read it again,,, twice,,,) But and it is a big BUT, non of them can accurately count amps in and out of your batteries over a period of time & then to make it more fun your batteries change their capacity as they go along (regular servicing helps combat, But most do not do it) Also throw into the mix that most people are way to conservative on their charge regime but as their battery monitor is telling them all is fine,,,, Well it has to be "the battery monitor says so" followed some months later with "the battery monitor says they are full but they are flat" eg, if you are under by 1% on your "full" calculation & charge every day, in 100 days monitor will still be saying 100% but batteries will be 0%,

Tim
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Re: Drastic SOC Change

Post by blackswan555 » Tue Jan 31, 2017 4:43 am

Think of trying to use your car for months with the fuel gauge disconnected and instead using your milage to decide how much fuel to put in it.
For example, you do 40 miles a day to work and back & "you know" it does 40mpg, 1 gallon a day, Most days it does do 40mpg ,,, but on Wednesdays & Fridays you have to give your rather bulky workmates a lift so it only does 35mpg, you do not take this into consideration when adding your standard 1 gallon of fuel every day & soon would be on the side of the road telling the RAC man "well the mileometer says we have fuel"
The point of this comment ? Well there are too many variables to say "that car does 40mpg" all day,, every day,,everywhere with any load, so use that figure to add the exact amount of fuel to do the job every day, Batteries & battery meters are similar, They are counting a theoretical number with too many variables not taken into consideration to get even close in my opinion, Resulting in many getting a false sense of security from them , (thats what bugs me about battery meters, people trust them to much)

Tim
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Re: Drastic SOC Change

Post by JRHill » Tue Jan 31, 2017 9:16 am

Hopefully, as others read through this thread they will get a better perspective of what the FNDC *can* do and the precautions as well. Other than timmarten's reference to a s/w "bug" in the FNDC, which may have been the culprit, I still have no idea what triggered the SOC to change so radically a week ago.Then again, why that day? I follow the same usage/charging pattern every day.

So here's my take away on all this: normal maintenance like battery watering, connections, etc. is the easy part. But I try to never dismiss an event or symptom without understanding the cause. If I can't confirm the cause its time to dive deeper. Checking SG readings, to borrow a line from Firesign Theater, is akin to "...picking lint off the wall" (or was it the dog?) in my book but it has to be done and logged. With flooded batteries, the periodic extended absorb cycle is needed to fully charge the batteries and reset the FNDC. Again for flooded batteries, a periodic deep cycle and full recharge. I'm tardy with the charging stuff as I didn't want to do it in the middle of the winter on generator power but when it's nice out it doesn't get done due to other pressing chores. 16 months has been too long for resetting the FNDC.

As for the FNDC overall, the gas gauge analogy is pretty good. The FNDC is what triggered my recent maintenance catch-up and I'm glad I added it to the system. This morning I awoke to a 85% SOC. A week ago it would've been ~5 points lower.

Thanks, folks, for your input. As always, I learned some new things.

Best,
Jim

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Re: Drastic SOC Change

Post by blackswan555 » Tue Jan 31, 2017 9:57 am

Sorry to be pedantic but
I follow the same usage/charging pattern every day
Bit like saying my car does 40mpg EVERY day,,, Hot or cold, uphill or down,, Get it 1% wrong and 99 days later, well you are not on the side of the road, you are looking at you next bank of batteries :mrgreen:
Tim
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Re: Drastic SOC Change

Post by SandyP » Tue Jan 31, 2017 4:46 pm

blackswan555 wrote:.......getting a false sense of security from them , (thats what bugs me about battery meters, people trust them to much)

Tim
As long as system owners / users understand that the battery meters are just a "meter" then all should be OK. The control of your solar system / battery charging is best left to equipment made for this purpose with the proviso that the charging parameters have been set properly and the system is regularly monitored. Nothing with RE systems is fool proof and requires human monitoring to detect when something is "wrong".
I installed the Victron to allow non techy people to "see" what the system was doing when they are using the cabin and also to provide 24/7 data logging which I can access remotely.
SP_Log.jpg

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Re: Drastic SOC Change

Post by blackswan555 » Wed Feb 01, 2017 3:14 am

I do not dispute they are "useful" in the right situation, But most seem to get it out the box and trust it is correct from day one (usually without charging batteries to 100% first,,,, or reading & UNDERSTANDING manual :smile: )

Tim

To add, you could do with another couple of hours on your absorb, You want to see your amps flatline for about half hr before ending absorb, on that graph, about 16.30
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Re: Drastic SOC Change

Post by SandyP » Wed Feb 01, 2017 1:30 pm

blackswan555 wrote:......
To add, you could do with another couple of hours on your absorb, You want to see your amps flatline for about half hr before ending absorb, on that graph, about 16.30
I have my absorb set to terminate when the charging current drops to 1% (5a) of the battery capacity. Whilst I have heard about waiting until it flatlines in my case this would be when the charging current is less than 1a.
Given these are GEL batteries I am happy to stay with what is recommended by the manufacturer.

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