Array wattage just beyond controller limit

rgk1
rgk1 Solar Expert Posts: 135 ✭✭✭
in General Solar Power Topics #1
Getting ready to test new array consisting of used panels.  I just realized nameplate wattage is 1285 watts total and my controller shows maximum array size for 24v as 1200 watts.  With the panels not being new and adding in inherent losses, would this be ok or is a new CC going to be required to use this array with all 4 panels? 
4-Risen 320 watt in series/parallel, 8-215ah 6 volt GC2 batteries in series, Exeltech 1100 watt/48 volt inverter, Tristar 45 MPPT controller.
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #2
    In general you should be fine. I haven't read the abut the MPPT Tristar TS-45, Believe the MPPT TS-60 can be over paneled very high without damage. 

    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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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    #3
    One of the best resources for Morningstar is their calculator, http://string-calculator.morningstarcorp.com if there are any concerns with results, contact tech support, they are extremely helpful. With the calculator don't  use extreme temperatures, use average highs and lows, for the most part being slightly over shouldn't be too much of an issue, pass it by support for confirmation they usually respond without any delay, based on my experience.
    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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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #4
    Generally, an array will only produce about 80% of nameplate.  The few times it exceeds that, most robust MPPT controllers will simply throttle back to safe limits.  it's when you greatly exceed the limits, the controller is unable to compensate well.  You should be fine with slight over paneling.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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  • rgk1
    rgk1 Solar Expert Posts: 135 ✭✭✭
    #5
    Thanks for the replies!  I did get a chance to do a temporary swap in of a pair of the panels and 80% of nameplate is what I got - 504 watts according to CC.
    4-Risen 320 watt in series/parallel, 8-215ah 6 volt GC2 batteries in series, Exeltech 1100 watt/48 volt inverter, Tristar 45 MPPT controller.
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  • NANOcontrol
    NANOcontrol Registered Users Posts: 273 ✭✭✭
    #6
    I have over 1500W of panels on a 500W controller.  And it is not even a good controller.
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  • mike_s
    mike_s Registered Users Posts: 156 ✭✭
    #7
    It's right there in the TS-MPPT manual:

    The TriStar MPPT 150V will limit battery current to the Maximum Battery Current rating. An over-sized solar array will not operate at peak power. The solar array should be less than the TriStar MPPT 150V Nominal Maximum Input Power rating for optimal performance... power levels refer to the maximum wattage each of the TS-MPPTs can process at a certain system voltage. Higher power arrays can be used without damaging a controller, but array cost-benefits will be reduced at power levels much beyond the nominal ratings.
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  • rgk1
    rgk1 Solar Expert Posts: 135 ✭✭✭
    #8
    Thanks Mike_S for pointing that out.  I did not see it 3 years ago when I first installed the controller as there was no way I was going exceed the limit back then.  Only looked at the quick general specs this time, but you are correct, there it is in the manual.
    4-Risen 320 watt in series/parallel, 8-215ah 6 volt GC2 batteries in series, Exeltech 1100 watt/48 volt inverter, Tristar 45 MPPT controller.
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  • 706jim
    706jim Solar Expert Posts: 519 ✭✭✭✭
    #9
    Or you could do what I just did; point half of the panels southeast and the other half southwest. Kind of like a rigid tracker.
    Island cottage solar system with appriximately 2500 watts of panels, 1kw facing southeast 1.3kw facing southwest 170watt ancient Arco's facing due south. All panels in parallel for a 24 volt system. Trace DR1524 MSW inverter which has performed flawlessly since 1994. Outback Flexmax 80 MPPT charge controller four 467A-h AGM batteries. Insignia 11.5 cubic foot electric fridge 1/4hp GSW piston pump. My 31st year.
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  • jrcent
    jrcent Registered Users Posts: 47 ✭✭
    #10
    Morningstar sunsaver suggests that you can oversize PV the controller as long as you don't exceed the max voltage. The power will be clipped in full sun but the harvest bandwidth will be greater in low light and cloudy conditions . Quote from MS MPPT technology primer

    "Q5. Can I use a 240 Watt (60 Cell / Vmp≅ 30V) PV module with a SunSaver MPPT™
    controller? 
    Yes. Even though the SunSaver MPPT™ controller in a 12V system is nominally rated for a 200W PV array, you 
    can use a larger PV module e.g. a 240W PV module. 
     For 12V systems the SunSaver MPPT controller is an acceptable option due to its ability to convert the 
    module voltage down and charge a 12V battery very effectively. (Fact: all Morningstar MPPT controllers 
    are buck converters—they can convert voltage down but not up, which is known as a boost 
    converter. For this reason, the Vmp of the module must be above the battery voltage at all times or 
    charging will cease). 
     For 24V systems the use of this module with a SunSaver MPPT controller is not an option since the 
    voltage (Vmp≈30V) is too low for a single module to charge correctly (Vmp too low) and Voc is too high 
    for two modules in series—as this would exceed the controllers 75Voc maximum.

    "Q6. Can I oversize other brands of MPPT Controllers?
    Morningstar’s TriStar MPPT™ & SunSaver MPPT controllers are the only controllers that will always limit the 
    output current regardless of input power levels. Morningstar’s patented TrakStar Technology is capable of 
    limiting the output current, while other manufacturers’ MPPT controllers will operate above their maximum 
    current ratings at higher power levels. 
    Morningstar’s MPPT controllers can operate with an oversized array that is several times larger than the 
    maximum Nominal Solar PV ratings, while still limiting the maximum battery current to the controller’s 
    maximum current rating. Many other MPPT controllers on the market cannot react quickly enough for fast 
    changes in solar conditions. Even at the published maximum power levels, these controllers are known to exceed 
    their maximum output current ratings and can trip the overcurrent protection fault shutting off the controller 
    during high power conditions."

    I would imagine MS isn't the only controller capable of doing that. 
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