I am figuring all this out as I go along and utilizing great advise from Main Sail/Compass Marine, but I am still in the "I don't know what I don't know" stage. I am a little foggy on battery size cable. The original configuration was 3 Trojan T-1275 150 AH batteries where one was designated as the starter batter. Two ON/OFF switches, when both are on, the batteries are parallel. All this is wired with AWG 2/0 battery cable even to the engine. The new configuration is combine all 3 into the house bank and add a starter battery ~650 CCA and a third ON/OFF switch as per Maine Sail example. My question is should I wire the whole setup with 2/0 or use 4AWG for starter battery to battery/switch/engine. I will terminal fuse the starter as per M.S. as well. Is there a possibility of burning up the 4AWG if starting from the house bank when the starter battery has failed? I am also not clear on AH vs CCA. In the Bluesea circuit wizard, the option for Battery CCA is CCA or MCA. If a circuit is originating from the house bank, there is no CCA rating only AH. I need to go back and read Calder.