Extra Battery
Hi Bob;
I have a 96 C30 and it is set up like you want. In the battery compartment under the starboard setee, I have 1 Grp 30 deep cycle that is connected to a second grp 30 under the aft quarter berth in parallel. + to +, - to -. There is a board about 1X12"X15"long. It is glassed into the hull next to the water heater.These 2 group 30's are my house bank on battery psn #1 on the switch.
Psn #2 on the battery switch is a grp 27 "dual purpose" located in the factory battery box next to the group 30 there. I use the group 27 as the starting battery, but actually seldom use it to start the engine.
After 2 days on the hook last weekend with hot temps, using refridgeration and lots of lights, my inverter for coffee and running the microwave and my wifes hair dryer and electric curler, plus a TV for the two nights and an anchor light as appropriate, I had only used 20% of my house banks capacity, and I started the engine on the house bank just fine.
With refridgeration, the two battery house bank gives me plenty of power for anchoring out, which we like to do. I plan on moving every third day, or running the engine for battery charging for about an hour. That gives me another 2 days on the hook of needed.
Fair winds
Dave