Electrolyte freezes at different temps depending on it's charge
due to the fact that it's specific gravity changes depending on that charge.

From the Trojan Battery web site, a fully charged battery is good to -92
degrees.
At 40% state of charge, it will freeze at 16 degrees.

I've left flooded Rolls Batteries through the winter with no problem.
I'm in Maryland, so you're looking at typical winter temps of 20 to 40
degrees night/day
with an occasional cold snap getting into the single digits for a couple of
days.
(At 280 lbs each, I refuse to wrestle them on and off every winter!)

I don't think you'll have a problem.

T.O.


"Roger Long" wrote in message
...
Larry (or whoever else jumps in),

I know there was a recent thread on this but Google didn't turn up the
clear answer I'm looking for.

I know it's theoretically better to keep batteries on a trickle charge and
warm over the winter but it costs me $70 to have them taken out of the
boat and stored by the yard. (Nevermind the reasons why I don't want to
take them out myself and home to my basement.)

I've got a good three stage charger in the boat. If I put a good charge
on my two AGM's just before the shrink wrap goes on and leave them till
early spring with no further attention, will I have reduced their life and
strength enough that the $70 would have been a good investment? If the
difference between warm, charged, and dead, cold storage is just around
the theoretical margins, I'm inclined to leave them in place this year.

I'm in Maine which isn't quite as cold as people think, at least on the
coast. These two year old batteries get pretty light use with a 15 hp
diesel, a few lights, and frequent dockside charging from shore power. I
don't leave the charger on all the time so they don't micro cycle but they
seldom get pulled down very far either.

--

Roger Long