Question on wiring two solar panels

RedNeckSolarMan
RedNeckSolarMan Solar Expert Posts: 34 ✭
in Solar Beginners Corner #1
Hello everyone, I have a question, currently I have 20 watt solar panel and I plan to add 60 watt solar panel (got great for it). I would like to wire up both solar panels up parallel to get better amps. My question is, how to wire them up to my charge controller. I seen online about using a electrical box, is that possible with two solar panels. If anyone has a idea, feel free to reply and thank you everyone.
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #2
    Re: Question on wiring two solar panels

    What are the voltage ratings of the panels? Too big a spread between the two will be a no go. If they're fairly close in voltage, you can wire them + to + and - to -, then to the single controller, IF the controller can handle the extra power, and IF the lead wires between the panels and the controller are thick enough to handle the extra power.
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  • RedNeckSolarMan
    RedNeckSolarMan Solar Expert Posts: 34 ✭
    #3
    Re: Question on wiring two solar panels

    20 & 60 watt solar panels voltage are close about 17.2 & 17.3
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #4
    Re: Question on wiring two solar panels
    RedNeckSolarMan wrote: »
    20 & 60 watt solar panels voltage are close about 17.2 & 17.3

    Well you've got it made then. Just have to make sure the cables to the controller can handle the extra current. Likewise the controller and the cables from the controller to the batteries must be heavy enough to handle the extra power.
    You might also consider a fuse in line with the 20 watt panel, in case it were to short out and not be able to handle the current that would then be dumped into it from the 60 watter without catching fire.
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  • RedNeckSolarMan
    RedNeckSolarMan Solar Expert Posts: 34 ✭
    #5
    Re: Question on wiring two solar panels

    Ok, thanks for info
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #6
    Re: Question on wiring two solar panels

    it might be a good idea to put a fuse on the smaller pv so if there's a problem the big pv can't blow out the smaller pv.
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  • RedNeckSolarMan
    RedNeckSolarMan Solar Expert Posts: 34 ✭
    #7
    Re: Question on wiring two solar panels

    Thats a good idea to put a fuse on smaller pv. One thing I found online is and seen alot of people are doing this is make a combiner box. And couple websites recommend using a Schottky diode to stop electric going back into solar panels but direct the flow of electric to charge controller/battery. My question will be do I install the Schottky diode on positive wire for each solar panel or put Schottky diode on the terminal block.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #8
    Re: Question on wiring two solar panels

    The diode in question is a blocking diode, to prevent reverse current flow at night that can drain the battery through the panel. Schottky refers to a type of diode which has a very low V-drop across it so that it doesn't reduce the charge Voltage significantly.

    Many, but not all, panels have such a blocking diode built in. If you are using a good charge controller it becomes irrelevant because the circuitry within will perform the same function.
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  • RedNeckSolarMan
    RedNeckSolarMan Solar Expert Posts: 34 ✭
    #9
    Re: Question on wiring two solar panels

    If my memory serves correct, there is a diode on 20 watt panel and I would have to look at 60 watt panel when I get this week. I am using Morningstar PS-30 charge controller (no complaints on my end on this charge controller). I like the combiner box because if I would like to add another solar panel, I got the terminals to add another one. I may add fuse to 20 watt panel just in case 60 watt panel acts up.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #10
    Re: Question on wiring two solar panels
    RedNeckSolarMan wrote: »
    If my memory serves correct, there is a diode on 20 watt panel and I would have to look at 60 watt panel when I get this week. I am using Morningstar PS-30 charge controller (no complaints on my end on this charge controller). I like the combiner box because if I would like to add another solar panel, I got the terminals to add another one. I may add fuse to 20 watt panel just in case 60 watt panel acts up.

    As Niel suggested, fusing the small panel (based on its Isc) is a good idea. Should the small panel short, the large one is capable of pushing enough current through it to start a fire. The 20 Watt panel would probably produce about 1.2 Amps and the 60 Watt about 3.5 Amps. The Isc on the 20 Watt is probably less than 2 Amps, which as you can see the larger panel is easily able to exceed.
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  • RedNeckSolarMan
    RedNeckSolarMan Solar Expert Posts: 34 ✭
    #11
    Re: Question on wiring two solar panels

    Ok, fire is the last thing I don't need, specially where I live. Let me get this straight and I do apologize if I sound dumb, still learning on this. But pretty much put a fuse on 20 watt solar panel and fuse amp be 2 or 3, and install the fuse on positive wire.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #12
    Re: Question on wiring two solar panels
    RedNeckSolarMan wrote: »
    Ok, fire is the last thing I don't need, specially where I live. Let me get this straight and I do apologize if I sound dumb, still learning on this. But pretty much put a fuse on 20 watt solar panel and fuse amp be 2 or 3, and install the fuse on positive wire.

    You've got it.
    A panel can take its short-circuit current indefinitely, but it can't take more than that. Roughly a 2 Amp fuse on the positive lead of the 20 Watt panel should be all that's necessary. If you add another panel you'll be in a situation where each panel will need its own fuse.
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  • RedNeckSolarMan
    RedNeckSolarMan Solar Expert Posts: 34 ✭
    #13
    Re: Question on wiring two solar panels

    Cool, thank you for info and help.
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