Author Topic: Daily charge cycle seems normal, but reported SOC no longer reaches 100%  (Read 243 times)

Jszuckerman

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Hi all, this is probably a very simple question. 

My Classic 150 appears to be operating just fine--approaching two years.   But lately the reported SOC never reaches 100%.  (I.e., today the charge status is FLOAT and SOC is 94%.  Did receive today BULK and ABSORB charges as normal.) 

I do realize that SOC reported by the Classic is an estimate only; I thought I remembered the Classic would automatically reset its SOC estimate to 100%, each day upon transition from ABSORB to FLOAT stage.

But clearly a daily reset of SOC to 100% is no longer happening.  Any thoughts?

[I have a Classic 150V (rev 4) with original firmware (Classic Rev: 2096, Network Rev: 2097).  Whizbang Jr. included.  Demo system: battery bank is very small--pair of T-105 RE's only.]

Best, JohnZ





Matrix

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Are you transitioning to float?

Perhaps you have the End Amp setting set to Zero,  and the absorb time set for more hours than you have day light.   So you never reach float.

Have you made changes to the Battery Efficiency setting in the Classic?

But the bigger questions is ... what about the Specific Gravity of the Battery?   It really does not matter if the SOC reaches 100%,  what matters is did the SG rise to the 100% number?
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Jszuckerman

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Thanks, Matrix, all good questions. 

The odd thing is that I have made no settings changes to the Classic for months, and for months as I recall, I always achieved the reported 100% SOC upon reaching FLOAT.  It is only recently I've noticed that reported SOC fails to hit the 100% mark upon FLOAT.   Just not the behavior that I had grown to expect.

Again, I thought the Classic was designed to simply reset the reported SOC to 100% upon each daily state transition from ABSORB to FLOAT.  Maybe someone can confirm?

Also, good point--I will break out my hydrometer and measure the specific gravity.

JohnZ

P.S. [To your specific questions, my End Amps setting is 3.8 (about 2% of total Ah), but my absorb limiter was set to 2:14 (instead of 2:00).  So I had fiddled with the absorb limiter setting.  Battery efficiency is set to 89% per Trojan specs.]





Matrix

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What is Ur absorb volts?

Also as batteries age efficiency goes down

I would increase my absorb volts if SG didn't show full

Ur time seems low too, so hard to say if Ur ending on amps or time. If Ur trying to end on amps set time to 8 hrs
Grid-Assist Off-Grid
REC TwinPeak 2 285W 3S-3P 2565w-STC 1926w-NMOT Array / Classic 150 / Conext SW 4024 Inverter
Trojan L16H-AC 435Ah bank 4S  with 7' of 4/0 cable
24 volt system /  Need 3200Whs Daily
My System Install

Vic

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Hi John,

Seems possible that the Classic could have reported 100% SOC upon its transition from Absorb to Float,   but,  if there was some reason that there was not enough PV power to maintain Vflt  for some time (heavy load,   passing clouds,  etc),   that  the battery was discharged somewhat.   Then that load/low PV output passed.   The Classic could recover to Vflt (and say Float),   but it could take some time for the SOC to return 100-ish percent.   Normally,  one would expect that Vflt would only be reached when the battery had been fully recharged from an earlier discharge ...   

We assume that you are not using Skip Days in the Classic.

Dunno,    Vic
Off Grid - Two systems -- 4 SW+ 5548s, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 3X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  Thanks MN for Great Products/Service/Support!

Jszuckerman

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Interesting points, Matrix and Vic.  Also (I neglected to mention), this system is housed in a greenhouse, which experiences large daily temperature swings.  Perhaps the reported SOC declines (correctly) with each daily increase in battery temperature--and I wasn't noticing.  The transition to FLOAT is occurring early in the day now (because longer days), before greenhouse warming occurs.  I'll keep a closer eye on things for awhile.

[No, not using skip days feature.  I will also see if absorb limiter is a factor.  Absorb voltage set to 14.7 (temp corrected) per Trojan.  Thanks again for ideas.]

JohnZ

Westbranch

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To your specific questions, my End Amps setting is 3.8 (about 2% of total Ah), but my absorb limiter was set to 2:14 (instead of 2:00).  So I had fiddled with the absorb limiter setting.


what were the changes you made? Did you notice any change in SoC? What are the SG readings?

Have you ever done an EQ &/or commissioning charge?

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Vic

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Interesting points, Matrix and Vic.  Also (I neglected to mention), this system is housed in a greenhouse, which experiences large daily temperature swings.  Perhaps the reported SOC declines (correctly) with each daily increase in battery temperature--and I wasn't noticing.  The transition to FLOAT is occurring early in the day now (because longer days), before greenhouse warming occurs.  I'll keep a closer eye on things for awhile.

[No, not using skip days feature.  I will also see if absorb limiter is a factor.  Absorb voltage set to 14.7 (temp corrected) per Trojan.  Thanks again for ideas.]

JohnZ

Hi John,

One would think that SOC  would only be affected by Ah into/out of the battery.   And,  Remaining Ah might well be changed by changes in temperature.

But,   is the following situation possible for today,
"Seems possible that the Classic could have reported 100% SOC upon its transition from Absorb to Float,   but,  if there was some reason that there was not enough PV power to maintain Vflt  for some time (heavy load,   passing clouds,  etc),   that  the battery was discharged somewhat.   Then that load/low PV output passed.   The Classic could recover to Vflt (and say Float),   but it could take some time for the SOC to return 100-ish percent"?

Did you have variable clouds today?
Were there any relatively large heating,  cooling,  fluid pumping loads occurring while the Classic was in Float?

Thanks,   Vic
Off Grid - Two systems -- 4 SW+ 5548s, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 3X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  Thanks MN for Great Products/Service/Support!

boB

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Can you note at around what SOC% the battery charge state gets to before it goes to Float or
at various times in the charge cycle ?   

And/Or remaining Amp-Hours ?

Does it go up during charge ?

Shouldn't have to rely solely on the Classic going from Absorb to Float to reset to full, necessarily.

That is more of a sanity and calibration point but it certainly should go to 100% at that point.

Or, maybe it actually DOES get to 100% but when you are not looking, the SOC% drops ?  Kinda like Vic mentioned.

boB
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