The AGM do a good job of holding their charge so this should be much
of a problem. I have two AGM starting batteries and I discovered last
year that they were not getting combined, so one ran most of the
summer without ever getting charged. And the loads from the GPS and
VHF are (probably) pretty small, so in fact you would recover a full
day's use in 10 or 20 minutes of running the engine.

However, it would be prudent to have a panel to make sure the pump
will continue to run, and the engine can be started. There are nice
flexible panels that are convenient - I used one for a few seasons.
They can be toss on the deck, the seat or draped over the boom. You
just want to try to avoid shading. If there's a good spot for a solid
panel, that would put out 2-3 times the power for the price, but the
flexi is more convenient.

The only problem is that they are a bit pricey - the smaller ones that
list around $100 don't have much output. However, it you look on eBay
you might find the same panel that West sells for $200 for half the
price. A 10 Watt panel should do a reasonable job of keeping the
batteries topped off while you're not there.



* Roger Long wrote, On 3/19/2007 6:03 AM:
I knew that there is no way solar would keep up with my cruising loads.
Cruising in Maine, where the wind usually doesn't come up unitl noon,
usually involves enough motoring to keep the batteries charged. It's the
periods when we're not cruising and just daysailing that I'm concerned
about.

I won't be running the anchor light on the mooring and I just bought one of
the new low draw LED units anyway. My old one was a combination bow/mast
light with two bulbs and was a real hog but it was the only one I could get
when I found that the original was toast the day before the mast was to go
up. The only daysailing draw will be the GPS, radio which I seldom
transmit on (for which I have been already soundly berated on this group),
instruments, and a bit of fresh water pumping.

I also don't expect to keep up entirely with the loads. It's more a matter
of balancing the cost of a modest solar rig against the extension of battery
life and capacity. Maybe just buying new batteries every 2 - 3 years makes
more sense. I get my AGM's cheap enough from a non-marine source that a set
every year would just be a blip in the cost of boat ownership.

Wind is the way to go but location and foundation support are an issue on my
boat.

I'd still like to know if there is a panel that you think makes sense for
this application.

--
Roger Long