Oversizing an array with mppt controller

ayurtdweller
ayurtdweller Registered Users Posts: 26 ✭✭
in Off Grid Solar & Battery Systems #1
Let's say we you have a 40 amp mppt controller rated for 500 watts input at 12v. 1000 at 24v.
What would. The result be if you were to exceed the max watt input while remaining within max voltage input?
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    #2
    Controllers generally can tolerate over paneling, the amount by which is different between manufacturers, the maximum  current capacity is usually a fixed value, so the only advantage will be in less than full sunlight. Before considering over paneling check with the manufacturers recommendations, those with string a calculator will let you know if the amount exceeds limitations.
    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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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #3
    There are a lot of variables, but as a general proposition you can hook up more wattage, within reason (say 30% more), of pv without problems This can be quite useful in getting some meaningful charging current on lightly overcast days.

    Generally speaking, charge controllers won't put out more than rated, so overpanelling within reason is okay. In an extreme situation (like 2-3x overpanelling), it's conceivable that the controller couldn't react fast enough to an edge of cloud sort of situation to limit output, but otherwise the panels simply won't put out more wattage than the controller calls for.
    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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  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,113 ✭✭✭✭✭
    #4


    Here's what EPever says about their Tracer MPPT controllers.

    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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  • boB
    boB Solar Expert Posts: 1,032 ✭✭✭✭
    #5
    One reason that way too high of input power is hard on MPPT controllers is that when they limit, they usually have to run at a higher input voltage to do the limiting.  This makes them (typically) run hotter at that voltage.
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