Series and Parallel question

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System
System Posts: 2,511 admin
in Advanced Solar Electric Technical Forum #1
Can I wire panels of different wattages together? I have an 85 watt panel already and would like to add one additional panel. The cost difference between an 85 and 135 watt panel isn't much. Obviously I want to get the most power for the buck. As long as my charge controller is able to handle the resulting watts and amps I shouldn't have a problem right? As you can probably tell...........when it come to electricity I need stick figure and crayon drawings! LOL

PS These are on a 12 volt system!
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
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    Re: Series and Parallel question

    As long as the Vmp of the panels is close (within 10% or so) then paralleling different wattage panels isn't too big of a problem.

    Although Solar Guppy is the true expert on this sort of thing, not I!
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #3
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    Re: Series and Parallel question

    Yep--a god estimate is to parallel panels that have Vmp within 10% of each other.

    And to connect panels that are within 10% of Imp.

    The other thing to add--if you get more than two panels in parallel, you need series a protection fuse for each series string. This protects a shorted panel from overheating by being fed from the other "good panels" (the approximate fuse rating should be larger than Isc and less than ~2xIsc -- if the panel spec. sheet does not list the value of the series protection fuse).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • System2
    System2 Posts: 6,290 admin
    #4
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    Re: Series and Parallel question

    Thanks for the answers! Of course now I have to print this out and do lots of checking when I get back to the house in 2 weeks.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #5
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    Re: Series and Parallel question

    actually it wouldn't be a bad idea to fuse both pvs or at least one of them in case it gets wired baclwards. this is cheap insurance and it doesn't just protect the wiring all of the time as wiring backwards can damage one or both pvs.
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