The only thing I would add to this thread is the difference between voltage and amperage. Just because you have adequate voltage doesn't mean you have the right amount of amps getting trough. You refer not working leads me to believe that may be an issue. Usually caused by corrosion somewhere in the system usually at the battery posts or broken wire strands due to chafing, or loose or corroded wire butt splices. But since you change batteries frequently I would suspect a bad ground somewhere or one off the other conditions I mentioned. If your batteries pass a load test I would try to equalize them first and check and clean all connections. If the batteries are bad I would defiantly go with 2 6 v GC batteries, they will last much longer than your 12 v batteries. I like your idea of two battery banks and was considering adding a separate bank of 2 more 6v GC batteries but after many years of dry camping have never needed the extra power.
