A successful (comfortable) cruiser understands and manages resources well. One of the most important resources is the Ampere. The cruiser does not live by Amps alone but they are right at the top of the list. All other aspects of a cruiser’s “activities of daily living” are controlled, regulated and/or facilitated by “Amps”. Proper collection, storage and frugal usage of Amps will make an extended cruise a pleasure and are absolutely essential for living aboard. Nothing on a cruising or live aboard boat works without electrical power with the exception of a diesel motor or generator and even those need electrons to power their starters. Extended cruising and living aboard is like living off the “Power Grid” with a chance to drown.
For design and planning purposes the place to start is usually to determine how much of what kind of “juice” you will be using and then work backward to determine your required input. As Millennium Dragon is a real functioning vessel it may be easier to understand the system if we start at the input and follow the flow of electrons to their final use. The Dragon uses 115 volt AC for some devices and 12 volt DC for most. The AC supply has two sources, although only one is, technically, an external source.