More panels or MPPT controller

97TJ
97TJ Solar Expert Posts: 68 ✭✭
in Off Grid Solar & Battery Systems #1
Haven't been here in a while.  Any suggestions are appreciated.  I have had my system up for about 5 years now.  It's at a cabin in northern Michigan and all in all I'm pretty happy with it.  Located in a pretty wooded area I do plan on taking down a few trees to open the area up a bit more but right now I am looking to improve the system a bit.  Not a lot as the current system generally meets my needs and I have a generator and charger to top off the batteries as needed but winter sun is sparse.  I currently have a 12 volt system with three (3) 200 watt panels.  A 45 amp PWM charge controller and a 450 amp battery bank.  My question is would it be more practical to add a couple of 100 watt panels or switch to a MPPT charge controller?  Thank you in advance.
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  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,102 ✭✭✭✭✭
    #2
    Are those 3-200 watt panels 12 volt? such as Evergreen solar produced?  A 200 watt 12 volt panel is somewhat  rare. The price of solar panels are so cheap these days you would probably end up getting more bang for your buck by adding panels as long as your controller has the available headroom. Adding an MPPT controller to your system and series wiring your panels wouldn't add a whole lot to your output aside from gaining a little power when it's cold out and possibly beginning to charge a little sooner due to higher voltage available, but this would be miniscule with poor sun angles in the early and late hours of the day.

    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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  • 97TJ
    97TJ Solar Expert Posts: 68 ✭✭
    #3
    Yes they are the 12 volt evergreen panels. Adding 2 100 watt panels should get me right to about 45 amps. The controller is a Morningstar rated at 45 amps. Thanks for you input.
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    #4
    Adding 2 more panels may exceed the controllers maximum current capacity, enter your information on the Morningstar string calculator to find out.

    http://string-calculator.morningstarcorp.com/
    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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  • Lumisol
    Lumisol Registered Users Posts: 374 ✭✭✭
    #5
    First get a controller that can handle more panels and then add more panels. Adding a controller and panels with a larger or an additional bank is another possibility.
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  • 97TJ
    97TJ Solar Expert Posts: 68 ✭✭
    #6

    mcgivor said:
    Adding 2 more panels may exceed the controllers maximum current capacity, enter your information on the Morningstar string calculator to find out.

    http://string-calculator.morningstarcorp.com/

    Pretty neat calculator there.  My controller will handle another two 100 watt panels so perhaps I'll do that due to littleharbor2 pointing out that the price for panels is pretty low right now. 
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