Outback FNDC State Of Charge resets to 100% incorrectly

RandomJoe · September 2013

I have been running my subpanel 24x7 on the inverter, to sort of emulate Chris' pattern of not charging to 100% each day. When I do this, the system doesn't make it all the way to float but often (especially when I'm at work all day) still hits absorb for at least a little bit. Because of that I had figured the 100% SOC readings were just that - the system put back as many AH as were taken out but that's not actually *completely* charged.

Today, though, I noticed the system never made it to absorb (some clouds) and just happened to be watching when it jumped from 94% SOC to 100% SOC!

I'm going to have to reread the Outback docs, see if I can find anything that might be causing this, but wanted to ask if anyone else might remember right off. It's been a few years since I was into the programming at that level.

Some part of the FNDC does know a full charge hasn't taken place, as Charge Parameters Met is No and Days Since Full is currently 4.2. Unfortunately I was using the SOC number to determine when to do certain things programmatically, if it isn't reliable I'm going to have to figure something else out. For instance, right now I show 90% SOC but if that jump was invalid, I'm actually down closer to 84% SOC (the jump happened close to sunset).

Anyone else experienced this and found a way to correct it?

unicornio · September 2013

Re: Outback FNDC State Of Charge resets to 100% incorrectly

I think what you get is normal. 100% SOC is reached in the FlexNetDC when accounting for the battery system retrieves all wasted kwh (compensating yields and loses)

another thing is that the system does not reach the state of "meet charge parameters " until it meets the factor of "return amps", that does not mean that the battery is at 100%, but much more, that the battery is fully charged and electrolyte densities are at their nominal value.

carefully adjusting the charge parameters in the flexnetdc can be obtained more accurately the actual status of the battery and more realistic indication of the SOC

this in my configuration,
i am working with a 760Ah C20 24V batt,
that having 8 years age when i put the flexnet dc to work. now battery have working 10 years.

Return Amps:10.0 ADC
Full Voltage:28.6 VDC
Time At Charged Parameters:1 Minutes
Charge Efficiency Factor:93 %

i do not know how many time i spend to make flexnetdc working properly, but i thing maybe some months.
meanwhile, I think this is normal for all battery monitors if we want it to work well, especially with a some years used (and abused) batteries.

vtmaps · September 2013

Re: Outback FNDC State Of Charge resets to 100% incorrectly

RandomJoe wrote: »

Anyone else experienced this and found a way to correct it?

read these:
http://www.outbackpower.com/forum/viewtopic.php?f=28&t=6046
http://www.outbackpower.com/forum/viewtopic.php?f=28&t=5787

also, this might be of interest to you:
http://www.outbackpower.com/forum/viewtopic.php?f=28&t=7035

--vtMaps

RandomJoe · September 2013

Re: Outback FNDC State Of Charge resets to 100% incorrectly

Well, phooey. Thanks for the links vtMaps! That's what I was afraid of. I had also already run across the spurious readings from the Mate, those have been programmed around. Looks like now I get to figure out a workaround for the inaccurate SOC readings.

I'll have to check my logs and see if the Daily Totals (AH In/Out) jump as well or if they are left alone. If they don't jump perhaps I can use those to keep a daily running total of AH in/out. Or I could perhaps track Net AH In/Out and only accept single-digit changes. As someone else mentioned on the Outback forum, for the price of the FNDC I sure expected better!

I suppose their excuse is that for *most* people it doesn't matter - long as you have excess solar capacity most days, the system still continues to charge fully even if the FNDC resets early. That was certainly my case, this only became an issue when I started trying to draw down the bank and run in the 70-90% SOC range. Long as I have an *accurate* reading of SOC that's no problem but now I'm wondering if - right now, after 5 days without completing charge - I'm actually at 84% SOC or I might actually be down to 70% or lower.

Might have to look into home brewing a monitor too, that could be a fun little project. Been thinking about adding a Midnite CC anyway so won't be 100% through the Mate anymore.

unicornio · September 2013

Re: Outback FNDC State Of Charge resets to 100% incorrectly

perhaps I have not explained very well.
I will try to say it again, thanks!...;-)

in my system, when the day before it has reached the condition of "meet charge parameters" and flexnetdc is properly adjusted, the indication of SOC 100% matches exactly in time with "meet charge parameters" and "return amps" ...

if for several days you have not reached the condition of "meet charge parameters", then the indication of SOC reaches 100% soon and in a sudden such as 96% to 100% ... the more the difference in the jump farther the battery to be charged in truth and right the densities ...

all this can be seen today (please, change day if you see it is on another date), here:
monitor solar on-line del taller ecologico los unicornios

after yesterday reaching "meet charge parameters", today the 100% SOC and "meet charge parameters" are completely synchronized ...this means FlexNet DC is properly configured and accurate...

since I have installed the FlexNet DC with 3 shunts have achieved the following:

1) when my system reaches the condition of "meet charge parameters", is exactly that densities in my battery are perfect, and logically, the battery fully charged and healthy. Occasionally I go back to check and is accurate.

2 º) I never have had to re-make an EQ, even reaching 50% of SOC, after several days with good harvest sunlight and a couple of days with long absorptions time (4 hours) back to achieve the condition of "meet charge parameters" and densities are perfect even after 20 days without reaching "meet charge parameters", several absorptions, everything is ok! ...

3º) I saved a lot time in maintenance operations of the battery, and especially, I gained a lot in peace, because I trust the Outback whole system completely handles all process and keep my battery healthy and in the best conditions

NorthGuy · September 2013

Re: Outback FNDC State Of Charge resets to 100% incorrectly

RandomJoe wrote: »

Long as I have an *accurate* reading of SOC that's no problem but now I'm wondering if - right now, after 5 days without completing charge - I'm actually at 84% SOC or I might actually be down to 70% or lower.

You program in the efficiency (returned AH/used AH ratio) into the monitor. But the efficiency depends on many factors, and one of the most important ones is the charging pattern. If you discharge deeper, or if you cycle for a while without doing a full charge, your efficiency will change and you will get somehow biased results. Just look at Unicornio's post for an example. This doesn't mean the monitor is faulty.

unicornio · September 2013

Re: Outback FNDC State Of Charge resets to 100% incorrectly

i know, solar monitor online can be a bit difficult to use at the first time,
as you can choose the data that appear in each window ...
but a picture is worth a thousand words ...
so I capture the screen from my firefox:

Attachment not found.

unicornio · September 2013

Re: Outback FNDC State Of Charge resets to 100% incorrectly

after a while:
(with charge mode color marks)
Attachment not found.

unicornio · September 2013

Re: Outback FNDC State Of Charge resets to 100% incorrectly

NorthGuy wrote: »

You program in the efficiency (returned AH/used AH ratio) into the monitor. But the efficiency depends on many factors, and one of the most important ones is the charging pattern. If you discharge deeper, or if you cycle for a while without doing a full charge, your efficiency will change and you will get somehow biased results. Just look at Unicornio's post for an example. This doesn't mean the monitor is faulty.

I agree wiht this, and too, the temperature factor is a very important thing to keep in mind to get really compensate yields and efficiencies of the battery.

since I do not know a battery monitor that takes into account the temperature in their calculations, but I think that a great progress has been made in this field with battery monitors as FlexNetDC, (is the only one I know in depth) when employed fully integrated into a OutBack system ...

however, I expect that the temperature to be incorporated as a factor in computing algorithms for increased accuracy in all conditions ...

BB. · September 2013

Re: Outback FNDC State Of Charge resets to 100% incorrectly

Xantrex Battery Monitor does have a remote battery temperature sensor (NAWS used to sell--But not at the moment):

http://www.xantrex.com/power-products/power-accessories/linkpro-battery-monitor.aspx

And so does Victron:

http://www.victronenergy.com/battery-monitors/bmv-600s%20and%20bmv-602s/#type-1

-Bill

unicornio · September 2013

Re: Outback FNDC State Of Charge resets to 100% incorrectly

BB. wrote: »

Xantrex Battery Monitor does have a remote battery temperature sensor (NAWS used to sell--But not at the moment):

http://www.xantrex.com/power-products/power-accessories/linkpro-battery-monitor.aspx

And so does Victron:

http://www.victronenergy.com/battery-monitors/bmv-600s%20and%20bmv-602s/#type-1

-Bill

OutBack have a temperature sensor which use is shared for all components of the system...
any minimally serious system uses a temperature sensor to compensate for battery charging voltages, it is essential, and normal ...

but a battery monitor that take into account the temperature in the algorithms to calculate differences in the performance of charge and discharge patterns of a battery, it is more difficult.
for xantrex i do not know, victron yes, i know, and do not use it for now.

RandomJoe · September 2013

Re: Outback FNDC State Of Charge resets to 100% incorrectly

unicornio wrote: »

if for several days you have not reached the condition of "meet charge parameters", then the indication of SOC reaches 100% soon and in a sudden such as 96% to 100% ... the more the difference in the jump farther the battery to be charged in truth and right the densities ...

This is where I have a problem with the FNDC, though. The SOC number is being reset to 100% *before* the battery is really at 100%. IF I continue to absorb until float as most people do, then it'll be at 100% and no problem. However that's not what I'm trying to do, I'm purposefully trying NOT to float. So that last 5-6% never gets put back but the SOC number *claims* the battery is at 100% when in reality it might be 4-5% lower for each day I don't complete the charge cycle.

My automation system then continues running off-grid, potentially letting the SOC drop to what it *thinks* is 70% (that's where I limit out and revert to grid) but in worst-case reality after a week of operation it's possible I'm actually down closer to 45% SOC! (Though I think that would require a whole week of clouds / overcast which hasn't yet happened.)

This might not happen if I didn't get up to 95% SOC, I'm not sure. The reports in the links vtMaps provided all suggest it happens in the mid-90% range. Hopefully if I only get to 88% SOC it won't jump 12%!

According to the discussions on those links there is (or was, at the time I bought my FNDC) a bug in the code somewhere that causes it to reset SOC prematurely or for the wrong reasons. There's even someone who apparently works (worked) for Outback that admits it is an issue on the list for the devs but it wasn't considered a priority. (Probably - as I said earlier - because most people try for full charge every day, in which case it doesn't matter.)

Outback FNDC State Of Charge resets to 100% incorrectly

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