Jim,
You should work out an "energy budget," conservatively estimating your usage.
Although your boat gear (autopilot, VHF,GPS, etc) might seem to be the worst,
their usage will likely be limited, and often used while your engine is running.
Creature comforts can be much worse, especially if you hang out for extended
periods at an anchorage (like a rainy day) while the kids watch videos, you
listen to the ball game, and someone forgets to turn off a light.

BTW, your Bigfoot has a 10 amp alternator, so it will easily keep up with usage
while running, but it will take a long time charge a depleted battery. If this
is really an issue for you, the best bet might be a small, portable generator,
which could be had for under $500 and might have other uses.




"Jim Cate" wrote in message
...


David&Joan wrote:
Jim:

A 10 watt solar panel is only good for maintaining a charge on your
batteries, not recharging in a short time. A 10 watt panel doesn't need a
controller. A rule of thumb is that if the charging current is less than 2%
of the amphour capacity of your batteries, then you don't need a charger.
For even a single group 27 battery you will be below this threshold for a 10
watt panel.

As you note, for a 3-4 day cruise it isn't worth installing a big solar
array to keep your batteries charged up. It would take 100-200 watts to
begin to keep up with refrigeration and other demands of extended cruising.

I would first install a high output alternator and a good regulator- Balmar
sells a package for $600 which will keep you going on a limited cruise
duration. You may have to run your engine for an hour or two each day, but
for occaisional use, it's ok.

David


Thanks for the suggestions. This is a small (26-ft) boat with a 50 hp
outboard, but I plan to use it for bay and coastal cruising, on trips
normally less than 5 days or so. The boat will not have refrigeration,
AC, hot-plates, windlass, etc., but I would be using the second battery
to power the autosteering unit, depth finder, GPS chartplotter, VHF
radio, lights, etc., and possibly radar. Also, I would like to use the
solar panel in trickle charge mode to keep the batteries charged when
the boat is not being used.

Jim