DC circuit breakers for my solar system.

Re: DC circuit breakers for my solar system.

Welcome to the forum "ginnnts".

Your English is fine... Mine, however, is so. so...

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.

-Bill