‘Waratah’ will have a main electrical system which is 24 VDC. There is some equipment, like the navigation equipment, which is only available in 12 VDC. So this equipment will have it’s own power supply through a 24/12 VDC converter, via a 12 VDC battery, which also acts as a UPS.
And then there will be a 24 VDC/ 220 VAC converter, for the electric water heater, outlets for laptop and other 220 VAC equipment.
The main house bank is about 450 Ah, and will be charged by a Balmar marine alternator, which has been added to the Yanmar engine. The engine has it’s own 12 VDC starting battery, with matching alternator which came with the engine.
The Balmar alternator is rated at 140 Ah at 24 VDC, and that is about as big as you can fit safely on my Yanmar engine, without putting too much stress on the non-drive end bearing. The two pictures show the arrangement.