Right On. People don't understand fuses. They blow due to heat. The environments temperature effects the AMP rating. Fuses are self heating per watts law: W=A*A*R. With R being the fuses resistance.
BTW My DC-DC Watts was based on it's 93% efficiency rating.
I don't trust it.
Know your batteries! The DC-DC has a set output voltage. It could over or under charge. Ditto for the wrong charger or charger setting.
13.8V worked just fine for me. PHX AZ to the Rim Country (mountains) is a 4 hour run. It's 1000 miles to see my grand kids.