Battery Voltage vs SOC

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warren
warren Registered Users Posts: 21 ✭
in General Solar Power Topics #1
When printing out a spreadsheet for Voltages & SG, referenced to battery State of Charge I found 2 very different tables. The difference relates mainly to what the voltage of a cell when discharged. The Wind & Sun table is much different from 2 others I found. The W&S table does state that it is for batteries having been at rest for 3 or more hours. By implication does that mean the other tables (which agree) are for real time use? Comments appreciated.
Thanks

W&S table http://www.windsun.com/Batteries/Battery_FAQ.htm

1st Ref http://www.marine-electronics.net/techarticle/battery_faq/b_faq.htm#3

2nd Ref http://www.batteryfaq.org/
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  • boB
    boB Solar Expert Posts: 1,030 ✭✭✭✭
    #2
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    Re: Battery Voltage vs SOC

    From my experience, your table looks to be right on the money.
    (or, right on the voltage)... :D

    At least at the top and the bottom. I bet the middle numbers are correct too.

    boB
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  • warren
    warren Registered Users Posts: 21 ✭
    #3
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    Re: Battery Voltage vs SOC

    Thanks for the reply boB, but which table are you saying you agree with ..... the W&S table or one of the reference sites, both of which are quite different from the W&S table.

    Thanks Again
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  • boB
    boB Solar Expert Posts: 1,030 ✭✭✭✭
    #4
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    Re: Battery Voltage vs SOC
    warren wrote: »
    Thanks for the reply boB, but which table are you saying you agree with ..... the W&S table or one of the reference sites, both of which are quite different from the W&S table.
    Thanks Again

    I just looked at your table, but I also based my opinion on recollection of other company's documented Volts per cell.

    The only thing I would have expected was maybe 100% to be 12.6 Volts rather than 12.7 Volts. There may be other 0.1 volt differences but
    in general, close enough for battery work.

    Big enough to worry about or change ? Probably not.

    I will take a look at the others.

    boB
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  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    #5
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    Re: Battery Voltage vs SOC

    Ref #2 is Bill Darden's up-to-date battery FAQ website. Ref #1 appears to me to be a knock-off of ref #2.

    Darden does indicate that a battery should be at rest for four hours (no charging or discharging) or have the surface charge dissipated before testing.

    There are SOC vs voltage differences between flooded-cell batteries and VRLA types. Here are some additional quality reference links:

    Trojan Battery: http://www.trojanbattery.com/BatteryMaintenance/Testing.aspx
    East Penn Battery (Deka and MK): http://www.eastpenn-deka.com/assets/base/0139.pdf

    HTH,
    Jim / crewzer
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  • boB
    boB Solar Expert Posts: 1,030 ✭✭✭✭
    #6
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    Re: Battery Voltage vs SOC

    Another thing that can possibly be done instead of waiting 3 or 4 hours is to just load the battery down for a few seconds.... (I think ?)... :confused:


    boB :D
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #7
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    Re: Battery Voltage vs SOC

    windsun.com/Batteries/Battery_FAQ.htm 77F * voltage measurements are only approximate

    marine-electronics.net 80F

    batteryfaq.org
    http://jgdarden.com/batteryfaq/SoC.xls
    Temp corrected table: .xls spreadsheet

    Also note that the maint free battery types have a different chemistry, which produces a different voltage chart [12.65 vs 12.80 @ 80F]
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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  • nigtomdaw
    nigtomdaw Solar Expert Posts: 705 ✭✭
    #8
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    Re: Battery Voltage vs SOC

    boB r u applying the best guess (BHSF) alogarithium as...look Im in the cr.p need an answer like real quick r my batteries cooooked. It usually provides an accurate lead to final prognosis. Dont u just love logs :p

    BHSF ..Battery Health Syndrome Formula.

    We are all missing the point the most expensive purchase with a limited life is your batteries. Battery monitors are real cheap compared to new batteries. I have a XMB from X best buy I ever made. My friends have dying batteries and a tale to tell. I have a XBM and a quality DC Clamp meter, but Im a nerd:D

    U pays a lot of money u makes your choice, clever people by a Battery Monitor, daft people buy new batteries.:cry:

    Guess I havent lost the soft English touch.

    How much for new batteries:confused:
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  • nigtomdaw
    nigtomdaw Solar Expert Posts: 705 ✭✭
    #9
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    Re: Battery Voltage vs SOC

    I still think we need a real good VFM battery monitor from an independant which can be fitted to Xantrex, OB, Magnum,Studer,SMA or any third party or Chinese Products, a mountable unit including wiring, shunt for $100 with alarm alerts like the XBM. Doesnt need fancy PC Software,

    Just allows simple Joe to have an idea that hes killing his batteries and can address the issue b4 we call the Coroner?

    Ive been on this Soap Box B4 and expect to be on it again.

    Time for bed I guess:p
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