Indeed, you may be a newbie (or not), but the question is a good one. You will need to buy a book on this and read it. You will need to make a power budget
, then figure out how you will be charging
(how often, how inconvenient), and from there decide how much battery capacity to have.
To give you an example -- I have 420 amp/hours of batteries (at 24 volts; equivalent to 840 amp/hours at 12). I charge these with a 6.5kW generator
and a large frame alternator
on the main engine
. I almost never let the batts get below a 50% charge (for the sake of longer life), and since you can't efficiently charge to more than 80% using a generator, I usually have 30% or 126 amp/hours to work with (like 252 amp hours at 12v), when at anchor
for longer periods, or on my mooring
This is about right for my style of life on board, which includes charging
multiple laptops, running microwave and coffeemaker and toaster off an inverter
, running a DVD
player, and when at anchor, running instruments and anchor light all night. It means that I can go 24 hours without charging if the use is not unusually heavy (at anchor with instruments on all night, maybe less than that).
Your own power budget will be different, so you need to work it up. A good book on marine
electrics will help you a lot. Good luck.