Wiring Size - Panels to Charge Controllers/Battery Bank

mjp24cohomjp24coho Solar Expert Posts: 104 ✭✭✭
I'm hoping you guys can help me with some remidial confusion on wiring and voltage loss. To get the best unobstructed sunlight, I'm thinking of mounting my panels ~130 ft from my charge controller and battery bank. I'm planning on (2) 205W Kyocera panels, wired in series to be 48V (8.5 amps). These panels require the MC4 connectors, so I was planning on buying 130' of 10 AWG MC4 wiring from our forum's sponsor. I'm concerned, though, as to whether I would have too much voltage loss. I used the voltage drop calculator on this forum, and it would appear that I would be under 3% loss at 130' (assuming I entered everything correctly). However, do I need to enter my distance as 260', since it's twice the length from the panels to the charger/batteries? If it should be 260', I would be over 5%, which would be too much, I assume. However, MC4 wiring isn't available at anything less than 10 AWG. If that were the case, would I need to use MC4 wiring to run to a combiner box near the panels, and then run 6 AWG wiring from the combiner box to the charger/batteries? It's obviously a big jump in wiring prices over 130', if I go from the MC4 10 AWG wiring to 6 AWG wiring. Any thoughts would be appreciated.

Comments

  • mikeomikeo Solar Expert Posts: 386 ✭✭✭
    Re: Wiring Size - Panels to Charge Controllers/Battery Bank
    However, MC4 wiring isn't available at anything less than 10 AWG

    I would locate a fused combiner box near the panels and run the larger wire, either #6 or preferably #4 to your charger controller and allow for some expansion. This would give you the least amount of loss over 130 ft. The cost shouldn't be too much different if you shop around. Are you running in conduit, or do you need UF wire to get to your controller?
  • mjp24cohomjp24coho Solar Expert Posts: 104 ✭✭✭
    Re: Wiring Size - Panels to Charge Controllers/Battery Bank

    Thanks for the advice. I hadn't yet decided on whether I would run in conduit or not - whichever gave me the cheapest net cost for the wiring. It probably makes sense to go to 4 AWG wiring, to allow for expansion.
  • audredgeraudredger Solar Expert Posts: 272 ✭✭
    Re: Wiring Size - Panels to Charge Controllers/Battery Bank

    #6 wire will give you 1.9% drop ... #4 will give you 1%

    I have a similar situation... 125' one way to one array and 135' to two other arrays. Run the voltage as high as the weather and your charge controller will allow. Do, put the wire in an oversize conduit and run a messenger (pull rope) with your wire .... you can add more later.
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Wiring Size - Panels to Charge Controllers/Battery Bank

    mjp24coho,
    anytime the distance (run) is x number of feet you will have twice that distance in wire (2x) because of there being 2 wires, one being + and one being -. your 130ft distance equates to 260ft of wire and that is what is used in the calculator.
  • audredgeraudredger Solar Expert Posts: 272 ✭✭
    Re: Wiring Size - Panels to Charge Controllers/Battery Bank

    If you are going to expand... I would recommend #2.

    On both of my arrays I used #2 welding cable.. Array 1; 19.08 amps @ 103.8 volts, Array 2; 14.31 amps @ 69.2 volts. Both < 1% drop. In the old days, <2% was considered acceptable ..... many shoot for <1% now!

    You paid ~$3 per watt on the solar panels, does it not make cents to spend the extra buck or two to maximize that investment?
  • mjp24cohomjp24coho Solar Expert Posts: 104 ✭✭✭
    Re: Wiring Size - Panels to Charge Controllers/Battery Bank

    Good advice - thanks everyone for your input
  • mjp24cohomjp24coho Solar Expert Posts: 104 ✭✭✭
    Re: Wiring Size - Panels to Charge Controllers/Battery Bank

    Finally getting around to buying my wiring. I'm looking at either 6 or 4 AWG. Any suggestions on best wiring to buy. Ideally, I'd like to buy wire that is two conductor, but I don't think that's possible for under 8 AWG. So I assume I'll need to get two separate wires. Any suggestions on the best, cost efficient wire? I'm planning on burying it in conduit. Would it be THHN wiring? I don't see any of that for sale on our sponsor's website - any suggestions on where to buy? Thanks.
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