So, just some follow-up.
I think I am comfortable leaving the batteries in the boat for the winter, but, out of curiosity, I got out my copy of Calder's "Boatowner's Mechanical and Electrical
Manual." He clearly belives in removing the batteries. In the Winterizing checklist, he says:
"Unless the batteries are being properly float-charged (via solar
panel or battery charger
with float regulation), remove them from the boat and store in a cool, dry place. Bring wet-cell batteries to a full charge once a month."
In the section on battery maintenance
, there are numerous charts
that depict discharge rates at different temperatures for batteries left standing as well as freezing point charts
. These charts would lead me to believe that it is ok to leave the batteries in the boat so long as the temperatures are reasonably low. Even at 68 deg F/20 deg C, the battery only loses about 20% of its charge in 6 months.
I guess the ideal solution is to leave the batteries in the boat and purchase
a small solar
panel to keep them topped up.