Best breakers for solar.

[Solar Buddy]

Good day. I have a question for my system design. I am in the process of installing 10 X 160watt solar panels on my travel trailer. Already have installed 4 X 400AH Lithium iron phosphate batteries for my battery bank. Using a 4000 Watt 12 volt inverter for powering the 30 amp service to the trailer. Question is what are the best breakers available to protect the battery bank and the charge controller. The trailer will not be drawing more than 3600 watts in total so figuring that a 300amp breaker should work. Anyone have tried and true dependable breakers for a system this size? New to solar so need to do this right. Thanks.

 

[SolarForU2]

As your inverter is only 85% efficient at best, the supply current will be near 350 amps, not accounting for appliance surges during switch on. Suggest you use a 400A fuse and an isolation switch.
With that sort of power, its too high for a 12v setup to be reliable, better going to 24V.

 

[Solar Buddy]

Thanks for the reply. Yes I am regretting not going to minimum 24 volts. But already have the batteries and inverter so changing everything out is not an option. But I agree with your response about 400amp fuse/breaker and kill switch.

 

[SolarForU2]

I have a similar smaller 12V test setup here at home, that uses 4 x 400AH Calb Lifepo4 cells, been running past 4 years with a 3500W inverter, powering my office and a fridge + Freezer; I design and build PV controllers and sometimes use it for testing them out.

For fuse\Isolation of battery I use a 400A ceramic fuse that fits inside an isolator with manual opening pull handle, its actually a 3 phase device, just using one of the fused phases. Cables back to the battery are less than 1 meter long, 50mm^2, average power draw is 400 - 500 watts so quite low.

You may be able to get something like this DC MCCB, to work and bolt it next to your battery, then to a low voltage heavy duty truck isolation switch.

Mike