From: John De Armond
Subject: Re: Battery removal during winter
Date: Thu, 04 Nov 1999 03:01:39 EST
Newsgroups: rec.outdoors.rv-travel

John Mitchell wrote:
> 
> I live in B.C. - same problem. I top up the batteries with watter and charge
> them up - slow charge. Then disconnect the + connector. Leave them all winter
> - top up with the charger in the spring and reconnect. I have had rv batteries
> last 8 years this way.
> Hope it helps.
> John Mitchell

It would actually be better to leave the trickle charger on the
battery.  The freezing point of the electrolyte varies directly with
the charge on the battery and therefore the concentration of
sulfuric acid in the electrolyte.  At full charge, the freezing
point is very low, lower than -10 deg F, if my scratchy memory
serves.  As the battery (self) discharges, the acid concentration is
reduced until at full discharge the concentration is very weak and
the freezing point rises to approach the 32 deg F FP of water.  When
the freezing point and the outdoor air temperature intersect, a
frozen and almost always ruined battery results.

Trickle charging does something else useful.  It inputs a small
amount of heat to the battery.  This allows the battery to withstand
even lower temperatures without freezing.  I use the little 1 amp
battery maintainer chargers sold at Wal Mart for my infrequently
used delivery trucks.  Never had a battery freeze plus the trucks
are ready to run even after extended idleness.  Not that we have had
to worry about freezing for the last couple of "toy" winters.  

John