C10 C13 12v vs 24v

unyalli
unyalli Solar Expert Posts: 121 ✭✭
in Advanced Solar Electric Technical Forum #1
Thanks to all the great learning I have experienced here I understand "in general" I charge 12 volt nominal Flooded Lead Acid (FLA) batteries at 10% of the total bank capacity. 100ah bank limit charge amps to 10. I also understand "in general" AGM batteries can go 13%

What about 24 volt bank? I can't find literature or threads where this is discussed.

- Jeff
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,623 admin
    #2
    AH rating and 10%-etc. is current... A 100 AH 12 volt bank @ 10 amps. And a 100 AH 24 volt bank @ 10 amps.

    Note that Power=Voltage*Current... so a:
    • 12 volt * 100 AH = 1,200 Watt*Hours of stored energy
    • 24 volt * 100 AH = 2,400 Watt*Hours of stored energy
    And the 24 volt @ 100 AH battery bank will be ~2x heavier than a 12 volt @ 100 AH battery bank.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #3
    > @unyalli said:
    > Thanks to all the great learning I have experienced here I understand "in general" I charge 12 volt nominal Flooded Lead Acid (FLA) batteries at 10% of the total bank capacity. 100ah bank limit charge amps to 10. I also understand "in general" AGM batteries can go 13%
    >
    > What about 24 volt bank? I can't find literature or threads where this is discussed.
    >
    > - Jeff

    Those would be pretty conservative limits. A flooded deep cycle battery should be able to take ~15-20% of capacity in bulk, an AGM ~20-25ish. Always check manufacturers recommendation though, as they vary. Starting type batteries can take higher rates.

    I'm wondering if the numbers you quote are battery charging limits, or the rule of thumb numbers for economic sizing of pv arrays, for which we use 10-13% for a full-time off-grid application?
    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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  • Marc Kurth
    Marc Kurth Solar Expert Posts: 1,170 ✭✭✭✭
    edited August 2017 #4
    Sorry. I deleted info not directly related to question.

    Marc
    I always have more questions than answers. That's the nature of life.
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  • unyalli
    unyalli Solar Expert Posts: 121 ✭✭
    #5
    The question was do I change the bulk amp limit when going 24 volt. According to Bill, no. Thanks Bill. The reason for the question was not to discuss what the charge limit should be but will it change.

    Thanks guys

    - Jeff
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  • unyalli
    unyalli Solar Expert Posts: 121 ✭✭
    edited August 2017 #6
    Update, I have the east penn (decka) doc for the agm batteries i'm looking at and it says 30% so one of these 12 volt 105 ah batteries would like around 30 amps bulk. Two in parallel wants 60 but two in series is still 30.

    - Jeff
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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #7
    Yup.
    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
    · Share on Twitter

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