Portable solar install Q. How flexible is 8/2 a cord?

I am planning on putting together a 200w - 12v portable solar system for my motor home.  I want to go about 30 feet.  My primary camping site is in the shade, so I need to move out that far.   The wiring tables indicate needing 8awg wire.  So I'm looking at getting a 8/2 SOOW cord and using Anderson 50a connectors.   Is this going to be a reasonable outdoor cable?  Meaning will it hold up, will I be able to coil it up and put in storage with the panels or will I hate it?    

Comments

  • Raj174Raj174 Posts: 639Solar Expert ✭✭✭✭
    edited March 2016 #2
    Hi tbearkline,

    I don't have experience with this particular cable but the following information from the manufacturer indicates that it would very likely meet your needs.

    Applications:

    SOOW Flexible Cord applications include portable tools and equipment, portable appliances, small motors and associated machinery

    Features:

    Excellent resistance to oil and moisture. Good tensile strength, elongation and aging characteristics. High flexibility. Excellent abrasion resistance. Sunlight-resistant. Temperature range: -40ºC to +90ºC

    Something else to consider might be grounding the array, however I am not familiar with the grounding rules for RVs. Someone else may comment on that.
    I would recommend a Midnite lightning arrestor on the PV line.    
    3600W PV, MNE175DR-TR epanel modified, MN Classic 150, Outback Radian GS4048A, Mate3, 54.4V 207AH LiFePO4 no BMS, 4500W genset.
  • BB.BB. Posts: 27,780Super Moderators admin
    Watch the Anderson to SO cord connections. Generally Anderson connectors are soldered by folks... And soldered connections subjected to flexing will break the copper strands right where the solder ends.

    You could also look at commercial large amperage AC connectors--May not be any cheaper, but their bolt up the connections and strain relief to SO cord connection will have a longer life.

    Both standard and twist lock connectors will work--But for an RV application you may prefer straight blade connections. If you "drive away" and forget the cord/array--A twist lock will hold onto the cable until something else fails--Not pretty.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • tbearklinetbearkline Posts: 2Registered Users
    I like the idea of using AC connectors.  If I get 200w or now thinking maybe 300w in panels, amps at 12v would be a little less than 15.  Would a 15a 120v straight blade connector be heavy enough for the load?  Just thinking I would then make or buy 10/3 extension cables.
  • BB.BB. Posts: 27,780Super Moderators admin
    In general, in North America, you should derate wiring/breakers/fuses/plugs by 0.80 (NEC derating).

    So, if you want to have 15 amps (DC) continuous, then your plug/wiring should be rated:
    • 15 amps / 0.80 NEC derating = 18.75 Amps minimum ~ 20 amp plug/wiring.
    Of course you have to worry about voltage drop... 15 amps on 50 amp 10 awg cord:

    http://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=3.277&voltage=17.5&phase=dc&noofconductor=1&distance=50&distanceunit=feet&amperes=15&x=80&y=10

    Voltage drop: 1.50
    Voltage drop percentage: 8.57%
    Voltage at the end: 16

    That is a pretty high voltage drop... We try, in solar, to keep to 3% drop or not.

    Another way to address the issue is to run Vmp~24/35 to 100 volts (panels in series) and a MPPT type charge controller. Can take high voltage/low current and efficiently down convert to low voltage/high current needed by the battery bank.

    MPPT controllers are more expensive--But allowing to you to use much smaller awg/diameter copper wiring can be a huge saver in costs and weight/cable management.

    -Bill


    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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