Help, I have battery confusion and or a circuit or stater problem. My Beneteau First 285 has two 12 volt batteries #1 and #2 with a switch to use either. There is a charger to keep both charged. When I bought the boat seeveral months ago either would start the engine(a VolvoPenta). Then one day #1 would not start the engine and eventually was even to weak to run the house. The previous owner thought there might be a problem either with a weak battery or defective charger so through in a new charger. Even though the old #1 battery tested fair I replaced it as it would not hold a charge. I also put in the new charger. I bought an off the shelf 12 volt at local store and low and behold it also would not start the engine, yet the good old #2 battery continues to start the engine either in the #1 or #2 position, just for yuks I pulled the battery out of my Dakota pickup and it also would not start the engine, not even a good growl. Testing the battery while cranking yields just a minimum(not even a 1 volt)drop in either the 1 or 2 position. What is majic about the good old #2 battery (it is an Autozone cold crank rated 500amps--625 at 32 degrees). Is this all a signn of resistance someplace? Cables and conections all look good. Is my starter about to go? Hellllllllp!