How to wire PV Array

nschizzano
nschizzano Registered Users Posts: 38 ✭✭
in General Solar Power Topics #1
How do I get 18 individual 100w panels at 7A and 21V to, together achieve 135v-450v(best at 450v) and max of 15A

And what gauge cables would it need at 75 feet. 

Im plugging my own array into a Large Jackery power station they are having huge deals and its nearly the best route with time and money and quality that I can find
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,714 admin
    #2
    What is your location? I.e., lowest temperature--To figure out Vmp-array-cold does not exceed Vmax-array-input voltage...

    What is the max input voltage for your controller? Typically the high voltage max input is 600 VDC...

    450 VDC is that the max input voltage, or the max/optimum Vmp-array input voltage?

    What is the max power (Watts) and/or Current input to the charge controller?

    Your 18x 100 Watt panels, is Vmp-std ~ 17.5 volts?

    I do have a question--Why 100 Watt panels? Why not 400-450 Watt panels? 1/4 the electrical connections? And probably a viable warranty. Are the 100 Watt panels used?

    Just to make a quick calculation. Lets say you want a 400 Vmp-array-std (allowing for cold weather)...

    400 Vmp-input / 17.5 Vmp-std = 22.9 "panels"... ~ 22-23x panels in series

    16 panels / 4 panels per string = 4 parallel strings
    100 Watt panels / 17.5 volts Vmp = 5.71 amps per string
    17.5 volts Vmp * 18 panels per string (what you have) = 315 Vmp-array-std
    21 Volts Voc * 18 panels series = 378 Voc-array-std (should be no "cold weather" issue with Voc-array-cold)
    1 series string of 18 panels * 5.71 amps = 5.71 Imp-array
    5.71 Amps Imp * 1.25 NEC Derating for continuous current = 7.1 Amps minimum solar circuit current rating/fuse/breaker (if used)
    14 AWG is rated for a (typical) 15 Amps max current

    Using NEC cable amperage ratings:

    https://usawire-cable.com/wp-content/uploads/nec-ampacities.pdf

    And for 75 Feet (one way run) of cable using a voltage drop calculator for 315 Volts @ 5.71 amps, single phase:

    http://wiresizecalculator.net/calculators/voltagedrop.htm

    14 AWG:
    Voltage Drop2.69 V
    Voltage at Load312.31 V
    Percentage Drop0.85 %

    1%-3% is typically the maximum drop in voltage you would like to see... 0.85% is just fine for your needs.

    Your thoughts/questions?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • cleancurrent002
    cleancurrent002 Registered Users Posts: 10 ✭✭
    #3
    That’s a solid setup idea! To reach around 450V, you’d likely want to wire most or all of your panels in series since voltage adds up in series. With 18 panels at 21V each, wiring all 18 in series gives about 378V (close to your target). Just make sure your Jackery’s input voltage limit supports that. For the 75-foot run, 10-gauge wire should handle it safely, but if you want to minimize voltage drop, you might consider 8-gauge.
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  • MGar
    MGar Registered Users Posts: 20 ✭✭
    edited October 7 #4

    this one?


    Jackery Explorer 5000 Plus

    https://ca.jackery.com/products/jackery-explorer-5000-plus?variant=44766101504181#product_tab_1
    135V-450V⎓15A Max
    About 134.5 lbs (61 kg)

    A nice way to learn ...

    Panels will output MORE power when COLD that includes a cloudy
    day with wind my 100 watt panels normally around 2400 watts but
    if a dark cloud and it'd windy can reach 3600 watts when very cold.
     
    30% de-rate (if it gets -40) as your panels don't have the temp coefficient marked? 

    Two strings of 9, if it gets to -40. #10 solar cable.
    I got 36 100 watt panels two strings of 18 into a 550 V [600max]
    controller.

    put one panel in the sun perpendicular and see what the VOC is.
    it should be marked in the panel. 


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  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,171 ✭✭✭✭✭
    #5
    MGar said:

    this one?


    put one panel in the sun perpendicular and see what the VOC is.

    it should be marked in the panel. 


    Unless the panel is cold your VOC will be lower than the data on the panel. Panels warm up in the sun pretty quick the cell temperature will likely be higher than 25° C

    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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