Hterron: Fuse from Charge Controller to Battery Bank

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This discussion was created from comments split from: fuse from charge controller to batteries.
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  • hterron
    hterron Registered Users Posts: 8 ✭✭
    #2
    Hi, Í have 2x250 watt panels in parallel with 60 amp mttp charge controller.. 10awg wire from panels to controller. what size fuse do I need to connect to charge controller to batteries ? I have 230 amp battery .
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,641 admin
    #3
    What voltage battery bank?

    How much power (Watts) or DC Amps do you wish to draw (average worst case, peak surge)?

    How long of wire run from array to charge controller, and how long of wire run from controller to battery bank?

    Do you plan on larger array and or battery back in the future?

    Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #4
    In addition to Bill's questions, what wire size and fuse/breaker size is recommended by the charge controller maker for the battery connection, and what size wire do you expect to install. The fuse/breaker should be sized to protect the lesser of the controller or wire ampacity IMHO, both of which should be well in excess of normal operating currents.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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  • hterron
    hterron Registered Users Posts: 8 ✭✭
    #5
    What voltage battery bank? Is a 12v

    How much power (Watts) or DC Amps do you wish to draw (average worst case, peak surge)?
    Around 1000 watts
    How long of wire run from array to charge controller, and how long of wire run from controller to battery bank?
    From array is about 10 feet. From controller to battery 4 feet
    Do you plan on larger array and or battery back in the future? Yes. It will be good.
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  • hterron
    hterron Registered Users Posts: 8 ✭✭
    #6
    I using size 10 cable
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    #7
    Array to CC #10 is good max fuse "OCP" 20A
    CC to battery I would use #8  OCP  50A 
    Just my thoughts.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #8
    Considering a 1000w inverter, @ nominal12v, could draw sustained 90-100a and surge higher, 8ga and 50a may mean having a lot of spare fuses on hand?
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    #9
    Estragon said:
    Considering a 1000w inverter, @ nominal12v, could draw sustained 90-100a and surge higher, 8ga and 50a may mean having a lot of spare fuses on hand?
    Charge controller to battery, not battery to inverter, not had your morning coffee?  :)
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #10
    Yup, just having it now, and really enjoying it. After a run of 30+° weather, woke to a misty 9°C and an email with the winter storage agreement for the boat. Ugh. :neutral:
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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  • hterron
    hterron Registered Users Posts: 8 ✭✭
    #11
    I have a 2000 watt inverter but I spec to use around 1000 watts
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  • hterron
    hterron Registered Users Posts: 8 ✭✭
    #12
    Is for a refrigerator 2 fan and 6 led light
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,641 admin
    #13
    Heterron,

    I am going to split this into your own thread... Keeps Q&A a bit easier (does not hijack the original poster).... So don't be surprised if you have to look for this moved thread later in the day.

    -Bill "moderator" B.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • hterron
    hterron Registered Users Posts: 8 ✭✭
    #14
    Sorry for that BB. I had the same situation.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,641 admin
    #15
    Not a problem Hterron,

    Sometimes discussions get a bit confused if there is a lot of Q&A between people. Having your own thread usually keeps things addressing just your issues.

    Regarding the wiring... Two issues, the maximum current you plan on running, and the voltage drop. If, you plan on a maximum array of 500 Watts, then:
    • 500 Watts * 1/12 volts * 1.25 NEC derating for continuous current = 52 Amps minimum Branch Circuit+Breaker
    For a 60 Amp MPPT charge controller, I would be suggesting a 60 amp * 1.25 = 75 Amp rounded up to 80 amps for Wiring+Breaker. And a maximum (cost effective) array of:
    • 60 amps * 1/0.77 panel+controller deratings * 14.5 charging voltage = ~1,130 Watt array "cost effective" maximum
    Then there voltage drop... You want a maximum of 0.05 to 0.10 volt drop from charge controller to battery bank... Using a simple voltage drop calculator:

    https://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=0.8152&voltage=14.5&phase=dc&noofconductor=1&distance=4&distanceunit=feet&amperes=57&x=46&y=17

    4 feet of # 4 AWG cable gives you:

    Voltage drop: 0.11
    Voltage drop percentage: 0.78%
    Voltage at the end: 14.39

    And you may find, that you have to trim some strands off to get #4 AWG cable to fit.

    From the NEC wire chart (summary, fairly conservative), 52 amp rating would need #8 wire with high(er) temperature insulation, or #4 with medium temperature insulation if you want to go for 80 Amp current rating:

    https://lugsdirect.com/WireCurrentAmpacitiesNEC-Table-301-16.htm

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • hterron
    hterron Registered Users Posts: 8 ✭✭
    #16
    Thanks
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,641 admin
    #17
    You are very welcome Hterron...

    And to cover all bases, you could shorten the wiring from the charge controller to the battery bank to ~2 feet, and have 1/2 the voltage drop (bit better voltage control for charging battery bank).

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