Size of breaker needed

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JeffF
JeffF Registered Users Posts: 2 ✭
in Solar Beginners Corner #1
This is for a houseboat. I have 1200 Watts in solar panels which run to an 80 amp Epever charge controller.  From the controller I have 6 AWG wire running to the batteries.  I have 6 6 volt batteries which have about 2400 amp hours total which lead to a 3000 watt inverter.  

My question is what size breaker do I need from the controller to the batteries.  I have an 80 amp and it keeps popping.  Thanks
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  • Photowhit
    Photowhit Solar Expert Posts: 6,003 ✭✭✭✭✭
    #2
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    Well it's a thermal problem I suspect. 6 gauge wire isn't rated for 80 amps. So you have 1200 watts going to your 80 amp charge controller, if it's a MPPT type you could output 80 amps when the battery is well rundown and you are well angled to catch the sun.

    If you have a power center with 1 set of wires going to the inverter, you could draw 3000 watts at 12 volts or 3000/12=250 amps through the wire. You would want 4/0 or larger wire for that load.

    Lots of info you are saying, ...
    A MPPT type charge controller?
    A 12 volt system?
    6 - 400 amp 6 volt batteries, so a 1200 amp 12 volt battery bank?
    A central power center, with 1 set of wires going to your battery bank, 6 gauge?




    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • softdown
    softdown Solar Expert Posts: 3,822 ✭✭✭✭
    #3
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    12V system? Somebody else will have to do the math after they wake up. Guessing 120A breaker at 5:15am.
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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  • softdown
    softdown Solar Expert Posts: 3,822 ✭✭✭✭
    #4
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    On thing you may have overlooked - assuming 12V system here. Panels are feeding well over 12V - likely closer to 20V and perhaps more. So the 80A controller is proving adequate.

    But the controller drops the voltage down for the batteries - which drives the amps up, Something like this may be taking place:
    Incoming to CC:
    30V @ 60amps
    Leaving the CC to batteries:
    15V @ 120amps

    Note that I plucked those numbers for their ease in translating to lower voltage and resulting higher amps.

    Just an idea'r. 
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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  • Photowhit
    Photowhit Solar Expert Posts: 6,003 ✭✭✭✭✭
    #5
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    softdown said:
    Leaving the CC to batteries:
    15V @ 120amps
    No! Charge controller are rated on their output, an 80 amp shouldn't output more than 80 amps.

    With PWM this sometimes isn't true...

    Something else which should be addressed is if the Breaker is DC rated! But as I've said, the breaker is already too large for the wire. Breakers are designed to protect wiring.


    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • softdown
    softdown Solar Expert Posts: 3,822 ✭✭✭✭
    #6
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    Larger wires will increase the current to the breaker.
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
    · Share on Twitter

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