this may be dumb but...

[44'cruisingcat]

80 amps isn't really a problem for most decent size (the kind of size you would find in a car for instance) batteries. Batteries usually have a CCA rating (cold cranking Amps) on them, which is measured when the battery is very cold and usually CCA ratings are in the 500 - 700 range. So the battery should handle 80 amps no problem, as long as it's not for long enough to drain it.
(actually, for long life, most people reccommend not draining a deep cycle battery below 50%, and less than that for a start battery)

[Lynx]

The windless has been a source of fires on boats because of wrong size wires, bad conenctions bad installation ect..... With an 80 amp draw is a lot on a boat. It is very wise to consult specialist unless you are trained. Even better to have a pro install it.