I am totally confused with the above. My humble physical knowledge says
P(in watt) = U (in volt) * A (Amp)
If the solar panel is 789 W (seems to me very very high) and the boat is 12 V, it should generate 789/12= 65 A. This is what my alternator
is generating out of 40 HP engine
From what I see, the new panels are rated 75-125 W each. If you put 3 or max 4 (on a large cat) makes about 400 W / 12 = 33 A max. On a average day this should give roughly 180-200 Ah.
In a long passage
chart ploter 2 A * 24= 48 Ah,
frigo 5 A for 12 hours =60 Ah
autopilote 2 A *24 = 48 Ah
Stereo 2 A * 4 hours = 8 Ah
Lights (assuming LED) 0,2*10 hours= 2 Ah
factor = 20 Ah
Total= 186 Ah.
That means you 4X 100 w solar panel will keep you off from starting yr engine
or genset to keep charged yr batteries. With 50% charging
ratio, you would need 400 Ah batteries.
I would suggest you add one wind generator
to cover the cloudy days to make 100% sure..
Am I missing anything ??