I agree that a single battery bank (i.e. no separate windlass battery)
is the best option if you can accomodate it. (read on for the 'if's).
Note that you do _not_ save much money if you install a separate
battery: The wiring from the new battery to the windlass may be
shorter and smaller, but consider this text, quoted from "Wiring 12
Volts for Ample Power":
"...if your alternator is puny...then #10 wire to a windlass battery
woudl work. But wire to a windlass battery must be sized for the
maximum rating of the alternator!" To that I'd add that your charging
source may not be the alternator but your shorepower charger as well.
If your charging source is 100A (yous aid you have a charger), then
you'll have to rate your wiring to 100A to your windlass battery. Note
that if you go directly from the breaker panel, the wiring to the
breaker panel shoudl be big enough to support all appliances running on
the breaker panel, including the windlass charging. The best option,
IMHO, is to run wiring from the main battery bus. (Note: Do not wire
directly to the battery--the battery ON/OFF switch should control all
electronics as much as that's possible. Wiring to your distribution
bus is the goal, but make sure all wiring to/from the distribution bus
is big enough as well. You say you have #4 to the breaker, which,
depending on the windlass draw, may not be enough. How big is the wire
to the battery on/off, or battery selector switch if you have one?)

If possible! Sometimes it's not. Here is an example: I recently
replaced the motor of my windlass. The company used to make a 1000 W
model and a 1200W model. Now they only make the 1200W model. The
bigger model, however, allows a smaller space between the motor and the
case, meaning that the largest size wire you can fit in there is #0.
If your round-trip length is long enough, then you may not be able to
fit a suitable sized wire in the case, and thus a second battery may be
necessary.


Good luck; let us know how it goes.

cheers.
mickey