Installing a new converter and need advice on cable size

I am most surprised at the fantastic response I received. It sounds like the majority is saying to run 4 gauge wire. I have no problem running new wire as it is a simple run for me, 15 feet straight run under the camper. I will probably run #4 or maybe even #2 cable and be done with it. Thank you for reminding me about the fuse, I will replace that also.