DC circuit breakers for my solar system.

Hello everyone.
I'm new here and to solar power, so, please, don't be harsh.

I have a single 200w panel.
Impp 5.39A
Isc 5.87A
Vmpp 37.39V

from it ~5m(16.5ft) 10AWG cable to charge controller
MPPT 12V 25A 300W

charge controller is connected to a single 105AH battery by 1m(3ft) 8AWG wire.

connected to battery is 1000W inverter by 0.5m(1.6ft) 8AWG wire.

I think that I need 3 circuit breakers so it would be possible to disconnect every component.

Between panel and controller 10A? (in panel spec Max return current is 12A so i think breaker should be less)
Controller-battery - 25A? (charge controllers amperage)
Battery - inverter - no idea

Please help me. At a moment, my setup is working without any surge protection, but it's dangerous to leave it that way.
Oh, and sorry for bad language, english is not my native.

Comments

  • BB.BB. Super Moderators, Administrators Posts: 30,629 admin
    Re: DC circuit breakers for my solar system.

    Welcome to the forum "ginnnts".

    Your English is fine... Mine, however, is so. so... :cry:
    ginnnts wrote: »
    Hello everyone.
    I'm new here and to solar power, so, please, don't be harsh.

    I have a single 200w panel.
    Impp 5.39A
    Isc 5.87A
    Vmpp 37.39V

    from it ~5m(16.5ft) 10AWG cable to charge controller
    MPPT 12V 25A 300W

    charge controller is connected to a single 105AH battery by 1m(3ft) 8AWG wire.

    connected to battery is 1000W inverter by 0.5m(1.6ft) 8AWG wire.

    I think that I need 3 circuit breakers so it would be possible to disconnect every component.

    Between panel and controller 10A? (in panel spec Max return current is 12A so i think breaker should be less)
    Controller-battery - 25A? (charge controllers amperage)
    Battery - inverter - no idea

    Please help me. At a moment, my setup is working without any surge protection, but it's dangerous to leave it that way.
    Oh, and sorry for bad language, English is not my native.

    For a single solar panel, you do not need a breaker/fuse from panel to charge controller. If you have 3 or more panels in parallel, you "should" have one series fuse/breaker per parallel panel connection.

    For the Charge Controller to Battery bank, you should size the wire 1.25 times the maximum controller rated output (or maximum output you expect):

    25 amps * 1.25 safety factor = 31.25 amps -- Round up to next standard breaker and wiring (mount fuse/breaker near battery bank)

    For the AC inverter... This will scare/surprise you--It will be very heavy wire and a big breaker. Assuming you want to use 1,000 watts maximum from the inverter:

    1,000 watts * 1/0.85 inverter eff * 1/10.5 inverter cutoff * 1.25 NEC derating = 140 Amp minimum wiring fuse/breaker rating

    My suggestion before you spend a lot of time and money on the system.... Back up a moment and define your needs (average watts, peak watt, Watts*Hours per day=total energy use per day).

    A 105 AH 12 volt battery will have a difficult time driving a 1,000 Watt AC inverter. A 100-300 Watt AC inverter would be a better match.

    And it matters how long you run your loads (100 watts * 2 hours = 200 watt*hours per day; 50 watts * 20 hours = 1,000 WH per day).

    I am a very big believer in: 1) define/measure your loads (with lots of conservation), 2) define the battery bank, 3) define the solar array based on 1&2, 4) start buying hardware.

    So--Even if you design the wiring for 140 amps to the 1kW AC inverter, practically speaking, the "small" battery cannot really supply that amount of power for more than a few minutes before it kills the battery. Basically--how long would your car crank if you disconnected the spark plug wires--A few minutes and the battery is dead (and you may have some overheated wiring and starter motor).

    Sorry for making this much more complex than your original question. :blush:

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • ginnntsginnnts Registered Users Posts: 2
    Re: DC circuit breakers for my solar system.

    Thanks for great answer.

    The thing is, I already have this setup.
    I use it in my cabin for 12v LED lighting(connected directly to controller), some radio, TV, phone charging, laptop etc. so I almost never use all 1000w inverter power.

    Yeah, battery is a little small. I'm planning on buying another one as soon as shop receives a new shipment.
    I'm at my cabin every weekend (2 days) I have almost enough battery power for it. Don't know how long It takes for battery to recharge, but usually it's full when I come.
    Don't know if one panel would be able to charge two batteries.

    So i'm going to buy 32A breaker and thicker wire for inverter.
  • westbranchwestbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: DC circuit breakers for my solar system.

    You are using the old school philosophy on charging, developed when PV was very expensive... By all means buy another panel or 3, especially if you are planning to add more storage capacity. Try to get the same panels if possible. The battery is another question, it depends on what condition the first one is in. If they are too far apart, the old one will drag the new one down fast, and then you will have 2 old batteries, condition wise.

    BUT first come back to the forum and we can review your proposal.

    Circuit breakers are a must have item. It can save your house/cabin, 12V wiring and maybe an inverter or CC.
     
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