In article ,
Jim Cate wrote:

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


We just got a 11 watt panel for about the same purposes. From others'
experience, it'll be enough to top the batteries up during the week
(possibly 50-60 amp hours), or if we blow battery management while
cruising, give us enough charge to start the diesel after a few hours'
exposure with everything else off (aka belts and suspenders).

The 1-2 peak amps shouldn't hurt a fully charged battery and I'm hoping
that being better charged more of the time will keep the batteries
healthier.

A good alternator and regulator would be nice to have, but are probably
tough to put on an outboard. We could mount them on our diesel, but for
various reasons I opted for solar first. One of them was the cheap
Walmart charger: though it seemed to work to spec, it didn't charge at a
much higher rate than our current alternator.

--
Jere Lull
Xan-a-Deux ('73 Tanzer 28 #4 out of Tolchester, MD)
Xan's Pages: http://members.dca.net/jerelull/X-Main.html
Our BVI FAQs (290+ pics) http://homepage.mac.com/jerelull/BVI/