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