Batteries soc

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mountainman
mountainman Registered Users Posts: 439 ✭✭
in Off Grid Solar & Battery Systems #1
 I'm getting conflicting soc  charts.
After a couple raining days
4 hours Resting voltage at 12.54
Temp compensated S.G. 1.245 on 10 cells and 1.240 on 2.
What is my current soc.
2kw array 6 345 q cells  make sky blue 60 cc
 6 230ah GC @36 volts 
18 amp accusense charger. 3650 champion 
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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #2
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    WAG, ~75%?
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    #3
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    Hard to say definitively if they have been in service for an extended period being under charged, the reading could represent 100% of what capacity remains. On new batteries the reading would be in the 70% neighborhood depending on fill SG value.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
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  • mountainman
    mountainman Registered Users Posts: 439 ✭✭
    #4
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    Batteries are 5 months ~15-20 ℅ daily Discharge. 
    On sunny days by the end of the day S.G. 1.265- 1.270
    Recently got a different c.c. at 1.245 it's saying 70℅. Guess it goes by voltage.
    Was wondering how accurate it was.
    Seems to be about right.

    2kw array 6 345 q cells  make sky blue 60 cc
     6 230ah GC @36 volts 
    18 amp accusense charger. 3650 champion 
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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #5
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    I find my SOC meter (trimetric) and CC (MN Classic) SOC% readings often tend to get increasingly unreliable as the number of partial charge days increases.  Presumably because of different estimating algorithms, they can differ by >10% in %SOC estimates after a few days of gloomy weather.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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  • mountainman
    mountainman Registered Users Posts: 439 ✭✭
    #6
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    Looking for a accurate chart on SOC vs SG anyone?
    2kw array 6 345 q cells  make sky blue 60 cc
     6 230ah GC @36 volts 
    18 amp accusense charger. 3650 champion 
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  • Aguarancher
    Aguarancher Solar Expert Posts: 315 ✭✭✭
    edited December 2019 #7
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    this is the "GENERIC" chart we have been using around here for years, hope it helps.. Please Note: it does Not include the Delta T differential formula..



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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #8
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    FWIW, the SOC may need to be adjusted for temperature.  At about freezing, for example, 1.195 would be closer to 50%SOC.  In a hot shed, it might be closer to 70%.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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  • jonr
    jonr Solar Expert Posts: 1,386 ✭✭✭✭
    #9
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    +1 on what mcgivor suggests - it depends on the battery.  Assuming that a generic chart is correct can cause trouble.

    I am available for custom hardware/firmware development

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  • mountainman
    mountainman Registered Users Posts: 439 ✭✭
    edited December 2019 #10
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    From what I've read my understanding is.
    Eq Batteries  when necessary.  >.030 between cells.
    That SG  reading will be my 100℅ SOC
    Correct?


    2kw array 6 345 q cells  make sky blue 60 cc
     6 230ah GC @36 volts 
    18 amp accusense charger. 3650 champion 
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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #11
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    When SG stops rising between ~1/2 checks in EQ, I consider that cell as full as it gets.  When the weakest cell(s) stop rising, I consider the bank as full as it gets.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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  • mountainman
    mountainman Registered Users Posts: 439 ✭✭
    #12
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    Approximately how many amps required to EQ A 400 ah bank.
    2kw array 6 345 q cells  make sky blue 60 cc
     6 230ah GC @36 volts 
    18 amp accusense charger. 3650 champion 
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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #13
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    The bank should be full before starting the EQ, so not much current needed. 

    There would be a fairly short burst in current at first to get up to EQ voltage.  Once there, it doesn't take much current to hold it.  Seems to me it's on the order of maybe 5-ish amps at my EQ voltage setting.  It's enough to get some good bubbling going, but doesn't heat the bank up much.  Usually 1.5-2hrs will do it but if not I repeat the next day after absorb.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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