AGM Battery Health vs PV to the Grid

[mexsudo]

AGM Battery Health vs PV to the Grid

Not sure where to start.
this is a typical sunny day, as soon as the sun gets bright it switches to charging the battery at the expense of uploading to the grid.

sunny all day.png (7.34 KiB) Viewed 5759 times

I am concerned that the battery is being pounded unnecessarily. at night it idles at about 51.6 volts, then jumps to 57.2 or so.
I want the batteries to last "forever" but I also want my power bills to go down.

I am using a 48 volt system, with 8 AGM batteries.

Data sheet for the Batteries: https://duravolt.com.mx/wp-content/uplo ... ravolt.pdf

any ideas where to start?
basic settings using my Mate3s ?
Thanks, Peter

[mexsudo]

PS: If anyone would like to review my opticsre settings I will gladly provide the invite.

My original installer has been in the solar business for Ten Years, but his experience is with Off Grid and Grid Tie systems.
This "hybrid" as he calls it is Not in his realm of expertise.
when he finished up last year I believe he said that mine was his second ever.
that combined with a language barrier has made it difficult for me.

[raysun]

I'm off-grid so don't have direct experience with your setup and issue. However, once the battery is fully charged, the PV harvest should feed house loads and sell excess to the grid if the system is properly configured. To help assure that happens, the Sell voltage should be 1-1.5V lower than the battery Float voltage.

[mexsudo]

I'm off-grid so don't have direct experience with your setup and issue. However, once the battery is fully charged, the PV harvest should feed house loads and sell excess to the grid if the system is properly configured. To help assure that happens, the Sell voltage should be 1-1.5V lower than the battery Float voltage.

Thanks

the float is 54.5 I don't know if that is "proper" or not
sell Was 52.0
Reset sell to 53.2 54.5 - 53.2 = 1.3 ... (target 1.0 to 1.5)

let's see how it acts with this for the remainder of today

Peter

[mexsudo]

I'm off-grid so don't have direct experience with your setup and issue. <snip>

@ Raysun I do consider you my battery expert.
can you have a look at the data sheet I linked above? It's all Greek to me. Is that Float voltage at 54.5 OK?
Thanks

=============
History:
the additional set of 4 batteries were installed about a month ago ... (we had shipping delays caused by Virus alarms)
They have been thru several bulk charging cycles, so they must be as "conditioned" as they will get...
We have had several night time blackouts and they held a good charge for 8 or 10 hours, looking much better!

[raysun]

I'm off-grid so don't have direct experience with your setup and issue. <snip>

@ Raysun I do consider you my battery expert.
can you have a look at the data sheet I linked above? It's all Greek to me. Is that Float voltage at 54.5 OK?
Thanks

=============
History:
the additional set of 4 batteries were installed about a month ago ... (we had shipping delays caused by Virus alarms)
They have been thru several bulk charging cycles, so they must be as "conditioned" as they will get...
We have had several night time blackouts and they held a good charge for 8 or 10 hours, looking much better!

I've seen that spec sheet now in Spanish and Chinese, most of it is Greek to me. ;)

From what I can discern this is a fairly typical AGM battery. Holding too high an Aborb or Float voltage can lead to grid corrosion as well as loss of electrolyte. I'd tend toward the low end of their recommended range for Float - 54V.

You're going to want to watch the Absorb cycle closely to determine the best voltage and time. The low end of the Absorb voltage (called Cycle Voltage) in the spec sheet is 57.6V. I'd use that setting. Ideally the Bulk charge cycle would switch to Absorb around 85% SoC, and Absorb would complete the last 15% of the charge. As Absorb executes, the voltage will be held constant and the charging current will slowly decline. When the charge current reaches about 3% of the total battery AmpHour capacity at the C20 rate (115 × 2 × 0.03 = 7A) the battery can be considered fully charged. However, you might want to leave Absorb to run a bit longer to see if this minimum charge current, called Charged Return Amps in Outback parlance, declines further. I'm guessing an Absorb Time of 2 hours will be about right, but 3 hours or more may be needed depending on charging efficiency.

Only after Absorb is completed should the charge transition to Float.

[mexsudo]

I'm off-grid so don't have direct experience with your setup and issue. <snip>

@ Raysun I do consider you my battery expert.
can you have a look at the data sheet I linked above? It's all Greek to me. Is that Float voltage at 54.5 OK?
Thanks

=============
History:
the additional set of 4 batteries were installed about a month ago ... (we had shipping delays caused by Virus alarms)
They have been thru several bulk charging cycles, so they must be as "conditioned" as they will get...
We have had several night time blackouts and they held a good charge for 8 or 10 hours, looking much better!

I've seen that spec sheet now in Spanish and Chinese, most of it is Greek to me. ;)

From what I can discern this is a fairly typical AGM battery. Holding too high an Aborb or Float voltage can lead to grid corrosion as well as loss of electrolyte. I'd tend toward the low end of their recommended range for Float - 54V.
**1

You're going to want to watch the Absorb cycle closely to determine the best voltage and time. The low end of the Absorb voltage (called Cycle Voltage) in the spec sheet is 57.6V. I'd use that setting.
**2

Ideally the Bulk charge cycle would switch to Absorb around 85% SoC, and Absorb would complete the last 15% of the charge.
**3

As Absorb executes, the voltage will be held constant and the charging current will slowly decline. When the charge current reaches about 3% of the total battery AmpHour capacity at the C20 rate (115 × 2 × 0.03 = 7A) the battery can be considered fully charged. However, you might want to leave Absorb to run a bit longer to see if this minimum charge current, called Charged Return Amps in Outback parlance, declines further. I'm guessing an Absorb Time of 2 hours will be about right, but 3 hours or more may be needed depending on charging efficiency.

Only after Absorb is completed should the charge transition to Float.

**1 the float is already at 54V (default is 54.4)

**2 Absorb voltage is at 57.6 ...(default setting)

**3 I can't find a % SoC setting...
"Re-Bulk Voltage" is 48V (default)
... works out to 88.9% SoC
Re-Bulk 45.9, Float 54 ....gets me to 85% SoC
-- I will leave it at the default 48

OK, good enough, just reset the Absorb Time

*** changing Only the Absorb Time, when I press APPLY I get the Error popup, again.

I "corrected" those "errors" by following the prompts and resetting to the defaults.
I think I am good to go, we shall see over the next few days

Thanks once again, Peter

[raysun]

In my simple minded approach, I'd cut off the grid power for 24 hours to be sure I have the battery charging dialed in. Your loads and battery capacity might not allow that though. You should be able to draw the battery down 50%. 115AH X 48V = 5.5kWH, probably 5kWH total to power the loads.

There really isn't SoC settings for charging - it's just a benchmark.

The Grid Connect stuff is above my pay grade. There's a few other folks on this forum with direct experience in that, hopefully one will weigh in. My sense is there's a parameter buried somewhere that's out of whack, but I have no clue where to look without RTFM.

Having said that, the Absorb Time change in itself wouldn't seem to have any bearing on the Grid Zero error. My sense of it is the update routine is sweeping through all the parameters on update and is finding something unrelated out of whack.

I'd ignore the battery charging stuff for now - it's in the range of reason - and dig into the Grid Zero operating theory and parameter set. The errors should guide you to a starting place. Grid Zero DoD (Depth of Discharge) Amps sounds like some amount of Amp Hour draw before some change of state happens. For example, 115AH would be 50% DoD for your battery. That parameter, and the others are going to be explained in the manual.

Glad I'm just a simple-minded peasant living an a rock pile off-grid. This modern life stuff is too much for me any more. ;)

[fcwlp]

The Grid Connect stuff is above my pay grade. There's a few other folks on this forum with direct experience in that, hopefully one will weigh in.

Raysun you under estimate yourself. Peter, I will send you a PM.

[raysun]

The Grid Connect stuff is above my pay grade. There's a few other folks on this forum with direct experience in that, hopefully one will weigh in.

Raysun you under estimate yourself. Peter, I will send you a PM.

I knew the cavalry would ride over the ridge any time now.

[mexsudo]

The Grid Connect stuff is above my pay grade. There's a few other folks on this forum with direct experience in that, hopefully one will weigh in.

Raysun you under estimate yourself. Peter, I will send you a PM.

I got your PM and responded... however my Outbox shows 1 message, maybe it did not get sent.

anyway, I sent you an invite to monitor my opticsre settings.

Thanks for your offer of assistance, Peter

[David LeBow]

I got your PM and responded... however my Outbox shows 1 message, maybe it did not get sent.

FYI: Unlike "real" mail, those PM's stay in your outbox until someone reads it - then it moves.

[mexsudo]

I got your PM and responded... however my Outbox shows 1 message, maybe it did not get sent.

FYI: Unlike "real" mail, those PM's stay in your outbox until someone reads it - then it moves.

Thanks. I also discovered that I can edit that message.
I have not figured out how to attach images, if that is possible.

[mexsudo]

I just came back to give a shout out to both fcwlp and raysun

they both gave excellent advice, and have been real gentlemen about it.

I now feel that my battery is healthy and being properly maintained.

my best to all, Peter

[Sglanger]

ANy concerns about mixing 4 new batteries with the old?

[mexsudo]

ANy concerns about mixing 4 new batteries with the old?

I have Lots. Spending $1,000 for the second set is not chump change for me.

After asking for help here http://www.outbackpower.com/forum/viewt ... =1&t=14717
And after doing some testing I finally gained a bit of a comfort level and decided to roll the dice.

David Ramirez, my original installer, was confident that I would be OK, so I had him return and install the second set.

If I had it to do again I would have started with more than I have now.

since the new set was added we have had a couple significant blackouts. I was amazed at how much longer it was able to retain a useable charge, more than double.

[Sglanger]

the particular concern I had was what Raysun alluded to. Te initial problem you posted in this thread is what I would expect from unbalanced battery behavior

[fcwlp]

the particular concern I had was what Raysun alluded to. Te initial problem you posted in this thread is what I would expect from unbalanced battery behavior

I have been working with Peter on his system. The issue is not related to the batteries but to settings on his system that when changed have improved the situation but still need a few more tweaks.

[mexsudo]

the particular concern I had was what Raysun alluded to. Te initial problem you posted in this thread is what I would expect from unbalanced battery behavior

I have been working with Peter on his system. The issue is not related to the batteries but to settings on his system that when changed have improved the situation but still need a few more tweaks.

Thanks for your assistance, it has been very valuable. We have come a Long way.

I will try to get back into the Mate settings via the panel for the Calibrate functions later today.
We have promise of a good solar day today... I want to see how it is behaving with the last tweaks suggested by fcwlp

* I wish Outback would step in with some documentation and explanations on how to use that $450 lump on my wall.
OpticsRe does not interact correctly, and using it seems to be causing some problems screwing up the settings.
at this point we are fighting trying to reverse engineer by trial and error.