Question about Wiring?

System
System Posts: 2,511 admin
in General Solar Power Topics #1
My Solar Panels are wired using #10 from the Roof down the Fridge Chimney to the Controller set in the wall above the fridge and then on to the 12 Volt Fridge connector and I presume to the Batteries! The wire size that connects to the Controller looks to be 18 Gauge. Is there Something Wrong with the way this setup is wired?

It seems to work , but It doesn't make sense to Me that the Controller is in series in the Middle of the Circuit and has these thin Wires! Doesn't this create a Huge Voltage Drop ?
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #2
    Re: Question about Wiring?

    i would think the frig should be located after the controller's regulation because the high and low dc voltages from the pvs would not be good for the frig to run on. i am not sure of your wiring and it would depend on how far the wires go at what gauge and with what current. i don't know if you know this information or not. i would venture to say lengths of #18 would or could be used on the smallest of setups with very short wire runs, but it isn't that expensive to upgrade from #18, that's for sure as #16 speaker wire isn't out of site yet. for most everybody i personally would not recommend using anything small and you should check into the sticky here in the general section on the basic voltage drop calculator. if you don't want to do the calcs yourself and have the info i can figure it for you.
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  • System2
    System2 Posts: 6,290 admin
    #3
    Re: Question about Wiring?

    The fridge is after the controller! My question is regarding the wire size that connects the controller to the pv panel and the fridge!

    It seems to me that IF the panel was wired ALL the way with #10 or #8 Wire the Batteries would get the Full Charge . The way they are now connected throught the Controller using these Small # 18 or 16 Wires there must be a considerable Voltage Drop at the Controller!

    After all the Controller IS wired in Series with the PV Panels and the Batteries!
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  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    #4
    Re: Question about Wiring?

    There might be a considerable voltage drop in the 18 AWG wire. It depends on the length of the wire and how much current is running though it. You can calulate the voltage drop using this formula: V = IR. V= voltage (drop), I = current, and R= wire resistance.

    For RV systems, the wire guage from the controller to the battery(ies) is typically the same size, or even larger, as the wire from the PV module(s) to the controller.

    Assuming a PWM controller, some voltage drop between the module(s) and the controller is OK, as the battery voltage plus the wiring voltage drop plus the controller voltage drop combine to set the array voltage. As long as that total is below the actual available array voltage (almost always less than STC Vmp), you're OK.

    However, since the controller sets the target battery charging voltages at its battery connection terminals, you do want to minimize the voltage drop between the controller and the battery. So, within reason, bigger cable here is better.

    You should also look into moving the fridge DC connection from between the controller and battery to downstream from the battery. It's easier to fuse and distribute DC power brom the battery to your loads this way.

    This fused distribution block might be helpful: http://bluesea.com/category/5/21/productline/125

    HTH,
    Jim / crewzer
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #5
    Re: Question about Wiring?

    jim,
    i think what he may be saying is that it has #18 pigtails coming out of the controller to connect with the other wiring rather than a junction box type arrangement. if this is the case the wire is probably too short to give a large voltage drop, but i wouldn't like it because it would be the weak link in a system.
    robatthlake,
    what brand and model controller is it?
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  • System2
    System2 Posts: 6,290 admin
    #6
    Re: Question about Wiring?

    The Controller is by GO Electric as are the 2 75 Watt PV Panels ( Shell )!

    It "Is" the Pig tails that concern Me ,even though they are only a couple of Inches long! It seems that it would make more sense to have the Heavier Wire attach directly to Terminals on the Controller Board!
    I Have another Controller , that is connected to a 3rd 75 Watt PV Panel which goes to another Battery Bank. It Too has very Small Pigtails! I'm going to have to rethink the Entire Setup when I Change to a Newer Motorhome Next Spring!

    Incidently I Run with 6 Golf Cart Batteries in Total so likely could get away without a Controller at all or Maybe I will have to Spring for a Bigger more Hi Tech device in the future!

    Like I stated on My First Post the system seems to be working , I Just think that I could get More out of those Panels if the wiring wasn't so cheezy!
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #7
    Re: Question about Wiring?

    i would not be overly concerned with it as a few inches of smaller wire will not do much of anything to hinder your power collection abilities. if they are not under warranty you may be able to go inside of the controller removing the smaller wire and add a larger sized wire to the controller's + and - if it can be added. if the original wire is multistranded and soldered straight to a pc board, you may want to rethink going with very large wire as it could strain the pc board especially if solid wire. if you do it anyway, it may be possible to attach a small junction box to the controller just as many pvs have such boxes attached to them. it would take any stresses of wires being attached that way.
    as i said before it will not degrade your power collection ability worth going through all of that trouble to change it over to larger wire. i do advise not going straight to the batteries with the pvs, as in eliminating the controller, for the pvs can overcharge the batteries. i learned that lesson years ago the hard way.
    if you feel you aren't getting as much from your system then please tell us more about your system and why you believe it's not right.
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  • System2
    System2 Posts: 6,290 admin
    #8
    Re: Question about Wiring?

    Thanks Niel,
    If you think that what I Have will continue providing good service I will leave it alone. I appreciate your taking the time to listen!

    Next question I will ask concerns Wire sizes for Additional Battery Banks!

    I'll start another thread.

    Thanks again Rob
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