How to wire 3-275 Watt Panels

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jalbers
jalbers Registered Users Posts: 13 ✭
in Off Grid Solar & Battery Systems #1
Hello,

I am lost and confused (?) I have 3-275 watt panels that I want to use to charge 8-6 volt T-105 batteries. These will be a 48 volt system and I'm using an Outback 60 charge controller. How do I wire the panels? Do I need a combiner box and a breaker for each panel? I want/ need these to be series/parallel?

Thanks for the help

Jerry
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,447 admin
    #2
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    Re: How to wire 3-275 Watt Panels

    Exactly what panels by name and model number and/or what is their Vmp, Voc, Imp, Isc ratings?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • jalbers
    jalbers Registered Users Posts: 13 ✭
    #3
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    Re: How to wire 3-275 Watt Panels

    OK here is what we have: Green Brilliance, 275 watt, Operating voltage is 37.2, VOC 44.78, Rated current is 7.54, Isc is 8.05.

    Thanks for the reply
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #4
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    Re: How to wire 3-275 Watt Panels

    Do you want the bad news or the bad news? :cry:

    Your three panels can not be configured for a 48 Volt system. The reasons being that the Vmp per panel is too low for 48 Volt charging so you can't put them all in parallel and the Voc is so high that if you put them all in series it will exceed the OB's maximum input level (depending on the exact model - it's pretty dicey over 130 Volts).

    But the other bad news comes with good news: you don't have enough panel to recharge that battery bank. Add one more and you might come in at around 6% charge rate, not including losses to loads.

    Ideally those Trojans would want double the amount of panel you've got. The rough calculation:

    22.5 Amps charge rate (Trojan's 10% recommendation) @ 59.2 Volts (again Trojan's #) = 1332 watts. Less "typical" efficiency derating of 77% = 1730 Watt array. You could probably get away with six of those 275 Watt panels, given a spot of good weather.

    Handing out bad news all the time is getting me down. :cry:
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  • jalbers
    jalbers Registered Users Posts: 13 ✭
    #5
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    Re: How to wire 3-275 Watt Panels

    Hi, No issues on the "bad news". Are thoughts are mirroring yours so we were prepared.

    So, Ok, we do have 6 of those 275 watt panels. Please tell me if we hooked two in series, then two in series then two in series then to a combiner box with 3 breakers would that work to our OB60 controller? We figure this way would be approximately 90 volts on a string then parallel 3 strings of 2 panels (to keep the volts the same but increasing the amps)to get at least 22.5 amps to the 48 volt battery bank.

    Pleeeeease tell this would work???? :)

    I hope you can understand my thoughts!!!

    Thank you,

    Mrs. Jerry Albers
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #6
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    Re: How to wire 3-275 Watt Panels

    Yes; three parallel strings of two in series.
    Voc will be about 90, Vmp about 74 - the Outback can definitely handle that. Mine does.
    The Imp will be about 23 and Isc about 24.15. Each string will need its own fuse or circuit breaker of about 10 Amps.

    Yes I'm doing the math in my head so the numbers aren't precise; please check before proceeding.
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  • jalbers
    jalbers Registered Users Posts: 13 ✭
    #7
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    Re: How to wire 3-275 Watt Panels

    Hello again, You have given us exactly what we need to know. We have a combiner box we can use with the rated fuses and we are going to proceed with caution as you suggested. Thank you for your advice and GOOD NEWS!!! :)

    Theresa
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  • jalbers
    jalbers Registered Users Posts: 13 ✭
    #8
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    Re: How to wire 3-275 Watt Panels

    All is going well with new setup!!!!! Thanks again.

    jalbers wrote: »
    Hello again, You have given us exactly what we need to know. We have a combiner box we can use with the rated fuses and we are going to proceed with caution as you suggested. Thank you for your advice and GOOD NEWS!!! :)

    Theresa
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,447 admin
    #9
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    Re: How to wire 3-275 Watt Panels

    Glad to hear that everything is working OK. :D

    Let us know how your system works out.

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