Hterron: Fuse from Charge Controller to Battery Bank

This discussion was created from comments split from: fuse from charge controller to batteries.

Comments

  • hterronhterron Posts: 8Registered Users ✭✭
    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 .
  • BB.BB. Posts: 27,882Super Moderators, Administrators admin
    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
  • EstragonEstragon Posts: 2,838Registered Users ✭✭✭✭✭
    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
  • hterronhterron Posts: 8Registered Users ✭✭
    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.
  • hterronhterron Posts: 8Registered Users ✭✭
    I using size 10 cable
  • mcgivormcgivor Posts: 2,201Solar Expert ✭✭✭✭✭
    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 bank 

  • EstragonEstragon Posts: 2,838Registered Users ✭✭✭✭✭
    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
  • mcgivormcgivor Posts: 2,201Solar Expert ✭✭✭✭✭
    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 bank 

  • EstragonEstragon Posts: 2,838Registered Users ✭✭✭✭✭
    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
  • hterronhterron Posts: 8Registered Users ✭✭
    I have a 2000 watt inverter but I spec to use around 1000 watts
  • hterronhterron Posts: 8Registered Users ✭✭
    Is for a refrigerator 2 fan and 6 led light
  • BB.BB. Posts: 27,882Super Moderators, Administrators admin
    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
  • hterronhterron Posts: 8Registered Users ✭✭
    Sorry for that BB. I had the same situation.
  • BB.BB. Posts: 27,882Super Moderators, Administrators admin
    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
  • hterronhterron Posts: 8Registered Users ✭✭
    Thanks
  • BB.BB. Posts: 27,882Super Moderators, Administrators admin
    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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