Solar fuse confusion, what size do I need?

[chaostactics]

I have paid for two of these wiring diagrams and every diagram calls for a different amperage fuse. I've not been able to get answers from the place where I purchased the diagram.

I am going to be running 600 watts of solar pair with a 300 Ah battery the MPPT will be a 100|50 model. The wiring between MPPT and the lynx bus bar calls for 6 AWG.
One diagram called for 70a fuses, one called for 80a fuses, and a calculator calls for 75a fuses. I already bought 80a fuses but now I'm not sure if I need something else. I'm anxious to get this system running.

[Persistent]

6 awg should be safe using an 80 amp fuse in an RV. How much current will the wire being protected carry? What will it be doing.

Which wire are you trying to protect, the panel wire to the solar controller or the main connection to the battery bank?

I cannot read the brand names or model numbers on the diagram you posted. The installation manual for the equipment is your best source for recommendations.

See attached file for recommendations for use with an inverter. Wire size is chosen in this case to minimize voltage loss at different distances. The wire can actually carry more than shown safely. Post make and model of the solar controller for better advice.

Battery charging and inverting require large wire to minimize voltage drop. Other applications are more tolerant.

Wire size is chosen to safely carry the needed current.
Fuse size is chosen to safely protect the wire.
120/240 volt residential wiring is usually tested and codified in a national standard. Localities then adopt the national standard or not.

Automotive standards are not as clearly defined. Different automotive companies determine wire size needed by themselves. Different applications have different needs. You may get different recommendations from different sources.

Yes, the fuse and wire size for RV 12 volt systems is vague. If the wire or connections get hot, go to larger wire size.

[chaostactics]

Hopefully, this is zoomed in enough to solve some confusion. Its a trailer so I'm not using the DC/DC & alternator circuit. The wire I was protecting is the one from the MPPT to the Lynx. I ended up buying a couple of 70 amp mega fuses but I can carry the 80's I already bought as well. I just need to get this project done so having some redundant fuses is better than waiting for info and having to order more.

Inverter is the Victron Multiplus 12V/2000VA/80A AC transfer capacity 50Amp, inverter 120V

The solar charger is Victron MPPT 100|50

Originally Posted by Persistent

6 awg should be safe using an 80 amp fuse in an RV. How much current will the wire being protected carry? What will it be doing.

Which wire are you trying to protect, the panel wire to the solar controller or the main connection to the battery bank?

I cannot read the brand names or model numbers on the diagram you posted. The installation manual for the equipment is your best source for recommendations.

See attached file for recommendations for use with an inverter. Wire size is chosen in this case to minimize voltage loss at different distances. The wire can actually carry more than shown safely. Post make and model of the solar controller for better advice.

Battery charging and inverting require large wire to minimize voltage drop. Other applications are more tolerant.

Wire size is chosen to safely carry the needed current.
Fuse size is chosen to safely protect the wire.
120/240 volt residential wiring is usually tested and codified in a national standard. Localities then adopt the national standard or not.

Automotive standards are not as clearly defined. Different automotive companies determine wire size needed by themselves. Different applications have different needs. You may get different recommendations from different sources.

Yes, the fuse and wire size for RV 12 volt systems is vague. If the wire or connections get hot, go to larger wire size.

[Persistent]

Victron makes a SmartSolar MPPT 100/30 & 100/50.

A 70 or 80 amp fuse is an excellent choice for use with 6 gage wire. The SmartSolar manual says to use 55 to 70 amp fuse for the 50 amp version. This is the best recommendation.

The MPPT 30 will output 30 amps. Use 35 to 40 amp fuse with 8 gage wire.

Conservative fuse and wire size:
30 amp current, 35 amp fuse, 10 gage wire
50 amp current, 55 amp fuse, 8 gage wire
50 amp current, 70 amp fuse, 6 gage wire

Shorter and larger size wire is always better for battery charging.

See previously posted table for recommendations.

See page 9 in manual:
https://www.victronenergy.com/upload...ual-pdf-en.pdf

[chaostactics]

Thank you so much for taking the time to provide such a detailed response. I went ahead and got some 70 amp fuses.

Originally Posted by Persistent

Victron makes a SmartSolar MPPT 100/30 & 100/50.

A 70 or 80 amp fuse is an excellent choice for use with 6 gage wire. The SmartSolar manual says to use 55 to 70 amp fuse for the 50 amp version. This is the best recommendation.

The MPPT 30 will output 30 amps. Use 35 to 40 amp fuse with 8 gage wire.

Conservative fuse and wire size:
30 amp current, 35 amp fuse, 10 gage wire
50 amp current, 55 amp fuse, 8 gage wire
50 amp current, 70 amp fuse, 6 gage wire

Shorter and larger size wire is always better for battery charging.

See previously posted table for recommendations.

See page 9 in manual:
https://www.victronenergy.com/upload...ual-pdf-en.pdf