24 cell 12 volt module?

littleharbor2
littleharbor2 Solar Expert Posts: 2,102 ✭✭✭✭✭
in General Solar Power Topics #1
Can somebody help me to understand how these low cell count modules put out a 12 volt nominal voltage? Haven't we all been accustomed to 36 cell = 12volt nominal and 72 cell = 24 volt nominal? Sorry about the large format, I don't see a way to decrease the size.

2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

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  • softdown
    softdown Solar Expert Posts: 3,897 ✭✭✭✭
    edited October 2016 #2
    Parallel wiring versus serial wiring? That's my guess and I bet a nickel on it.

    Fried my brains on taxes last night though.
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #3
    That is a picture from an EBay listing for a Natural Current PWP-140 panel, I think?

    http://www.ebay.com/itm/Natural-Current-140W-Solar-Panel-/291822895354 (EBay links do go away quickly--Will likely not be accessible in a few months from now)

    As far as I can see, that should be a Vmp~12.0 volt panel, not a Vmp~18 volt panel (only 24 cells that I can see, not the typical 36 cell needed for a Vmp~18 volts for charging a 12 volt battery bank).

    I think you are correct--There appears to be no way that this can be divided up into a 36 cell string with this configuration.

    Leaving us with either the wrong picture or an incorrect data plate (that has no brand/mfg. listed).

    We have seen an incorrectly marked panel here before (I guess it was marked wrong at the factory, then sold on the secondary market for really low prices).

    -Bill

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,102 ✭✭✭✭✭
    #4
    Bill, you are right about this being a eBay listing. I have seen many different low cell count panels like this on ebay. Not sure the pic is miss placed but maybe so. The 140 watt rating seems rather high for 24 cells too.

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

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  • softdown
    softdown Solar Expert Posts: 3,897 ✭✭✭✭
    #5
    They moved from 5" cells to 6" cells a couple years ago....just an idea.

    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #6
    Large cells just have more current (Imp rating). Vmp per cell (for silicon panels) is still ~0.5 volts per cell (standard test conditions) regardless of size.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • softdown
    softdown Solar Expert Posts: 3,897 ✭✭✭✭
    #7
    I was addressing the 140 watt figure that little harbor was discussing. My brain is toast today...

    Doing taxes once a year is not often enough to get good at it. Somehow....TurboTax was unable to access the data, on this computer, from previous years. So....starting over again and losing the principal reason to use TurboTax.

    I'm sure that Ingsoc took TurboTax over. It is what authoritarian governments do.
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    edited October 2016 #8
    Fun Stuff! Did a quick search, found a PWP-140w solar panel at Amazon, that is a 72 cell panel, also with messed up spec's!


    Spec's claim;

    Model No: PWP-140W
    Watts Peaks(Pm): 140W
    Short Circuit current (Isc): 4.43A
    Open circuit voltage (Voc): 33.8V
    Optimum operating current (Imp): 5.1A
    Optimum power voltage (Vmp): 27.4V

    Also found a company called "Natural Current" that does some solar applications including pool pumps.

    I'd wonder if they had a 140 watt pump running on solar, that panel was later labeled incorrectly... Just one theory, I'd stay away from it!
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #9
    For What it's worth, if you are looking for inexpensive 12 volt nominal panels, Amazon does sell a 165 watt panel for @$200 delivered or 2 for $380...


    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,102 ✭✭✭✭✭
    #10
    Photowhit said:
    Fun Stuff! Did a quick search, found a PWP-140w solar panel at Amazon, that is a 72 cell panel, also with messed up spec's!


    Spec's claim;

    Model No: PWP-140W
    Watts Peaks(Pm): 140W
    Short Circuit current (Isc): 4.43A
    Open circuit voltage (Voc): 33.8V
    Optimum operating current (Imp): 5.1A
    Optimum power voltage (Vmp): 27.4V

    Also found a company called "Natural Current" that does some solar applications including pool pumps.

    I'd wonder if they had a 140 watt pump running on solar, that panel was later labeled incorrectly... Just one theory, I'd stay away from it!

    Exactly my point. I get uncomfortable thinking about these oddball uncomforming modules opposed to the warm and fuzzy feeling when things make sense, i.e, 36 cell, 12 volt, 60 cell grid tie and 72 cell 24 volt/grid tie. LOL

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

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  • softdown
    softdown Solar Expert Posts: 3,897 ✭✭✭✭
    edited October 2016 #11
    Photowhit said:
    For What it's worth, if you are looking for inexpensive 12 volt nominal panels, Amazon does sell a 165 watt panel for @$200 delivered or 2 for $380...


    Made in the USA: "the solar panel assembly was done in the Silicon Valley, California" Why do they use labor in Silicone Valley? Call me sentimental or whatever...I think we need a strong manufacturing base to be viable in the long term.

    Amazon must get amazing prices on boxes and shipping. I ordered 12 spatulas since my dogs sometimes like to chew on them when I am gone...plus they had/have a great deal on Cuisinart spatulas. They used four good sized boxes...very strange. I have a fear of not having a good spatula.

    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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