Why battery ? even if I put 20 batteries in there, if the current demand is higher than the input current, eventually I will run out of juice...
My boat has three battery banks, three 125 Ah batteries on one bank, two 125 Ah batteries on another bank and one 125 Ah batteries on the last bank. I have a mechanical switch that can short the two multiple-battery banks together.
My largest current draw is my custom Oasis XD3000 air compressor at about 180A.
My second largest current draw is my custom 2,500W sound system, that pulls about 100A in the typical high-volume mode.
The current is replenished by the two engines, each with a 90A generator and also when the boat is plugged into shore power or when the gasoline-powered generator is running an on-board 70A charger is providing current to offset the draw.
When all else fails the lone 125 Ah battery has one single function, to start the gasoline powered generator that will then power that 70A charger, plus everything else on the boat.
My experience is that extended periods of air usage and also extended periods of loud music, both very high current draws, are satisfied by the multiple batteries and the chargers. So a large reservoir is a good option to handle periods of excessive draw, even when they exceed the charger rate.