So...when I bought my boat last winter, the House bank was pretty pitiful...One 31 case battery, one similar for the Start system. Both 4 years old but still showing a good resting voltage. Too good to toss. Envisioning some cruising this summer, I combined those two into the start bank and found the room (Barely) for (4) 6V Crown GC batteries for a 440 amp hour house bank.. Should keep the beer cold during those nights on the hook! The rest of my on-board 12V systems are very simple so this may be overkill...But, by my way of thinking you can't have too much battery capacity when running a fridge etc. Installed today with a Victronix battery monitor. Also ordered a Flow-rite battery watering system as access is not great here!