Odd Question - Adding Panels

walrus170walrus170 Registered Users Posts: 1
Hi folks - 

I've recently just set up an off-grid system. 24 volt, 780watts of PV (72 cell panels), 500Ah battery bank, TriStar TS-45 (PWM). 

I have two 12v panels going unused at the moment, and two slots open on my roof rack system. Is it possible to series these two panels, and then feed them into the 24v system? Is that ever done, or does everything need to match, more-or-less? The panels laying around are HIGHTEC HS-M-B-150's and I have JAM5(L)-72-195/SI's up there now. 

Thanks.

Comments

  • mcgivormcgivor Solar Expert Posts: 3,065 ✭✭✭✭✭
    edited November 2016 #2
    My experience and experimentation says yes you can series 2 X 12V and feed into 24V, as long as the voltages Vmp, Voc, etc. of the series pair is close to those of the 24V ratings. My small experimental rag and bone system is a collection  of 10 different panels some 6v X 4 in series some 12V X 2 and some 24V feeding a TS60 PWM, it's a don't care if it fails setup used for my espresso machine via a 2Kw inverter and some DC lighting.Been working for a year and a half and seems to be working perfectly. By the way having said the voltages should be about the same, some of my small 6v 10W panels have no data as they were parts from small solar lights that had failed but as said, it is an experimental setup, perhaps you care more. You can always send an email to Morningstar help and get their take on the question.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • arbyarby Solar Expert Posts: 103 ✭✭
    edited November 2016 #3
    My experience is the same. i have 4 X 130watt 12 volt panels coupled to 275 watt 24 volt panels and wired to 72 volts in series. Seems to work just fine. My thinking is the CC only knows what it gets from two wires, the positive and negative. Anything before those two wires is unknown. I tried to keep the wattages close.
    3310 watts panels, Classic 200 controller, 8 Surette S530's, Xantrex 5548 inverter, Honda EX5500 backup Genny.
  • softdownsoftdown Solar Expert Posts: 2,383 ✭✭✭✭
    Such a broad array of opinions to be found here. From MacGivor specialists to California code inspectors requiring that your "screwdriver set being UL approved".

    My main hesitation with MacGivoring things is electrical shock and the lack of a warning when electronics do not mesh properly. *One should should always be aware of fire risks of course.*
    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
  • arbyarby Solar Expert Posts: 103 ✭✭
    Of course the proper wiring and fusing should be used but that goes with any electrcal installation.
    3310 watts panels, Classic 200 controller, 8 Surette S530's, Xantrex 5548 inverter, Honda EX5500 backup Genny.
  • mcgivormcgivor Solar Expert Posts: 3,065 ✭✭✭✭✭
    Three is no suggestion one should violate local electrical codes, especially if one is installing systems as an occupation, the electrical code is written by lawyer's, for lawyer's, should anyone install system and something goes wrong , the electrical code book will be refeered to and liability will be based upon the rationale and intent of the said code. The initial question was could two 12V panels be put in series and combined with a 24V  panel and based on experimental findings the answer is yes it can be done as long as compliance  of relevant electrical codes are adhered to. That being said there are some who experiment outside the structure and boundaries of rules and regulations and although unathodox the findings may be of use to others.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • cupcakecupcake Solar Expert Posts: 254 ✭✭✭
    edited November 2016 #7
    There are no codes or rules, everything is subjective, open to interpretation, and LOOSELY based on science.  Logic and common-sense is all ANYONE has... you can write it on paper, stamp it with some 'official gubament seal' or hang on a moutain... in the end the ONLY thing that matters is adherence to common sense and reasoning...

    It is reasonable to series 12v panels into a 24 volt system so long as the voltages line up in the ballpark.. theres no logical or reasonable saftey issue... thus sayeth the code of logic and reason...

    :)





    ~1.5Kw PV in parallel
    Morningstar MPPT-60 controllers (2) in parallel
    3 Trojan tr-1275's in parallel 450ah total
    Samlex 2,000 watt 12-volt inverter hardwired


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