I have an onboard charging system on my boat. It charges both the Cranking battery and the trolling motor battery. My question is this. Can I leave the boat plugged in all Winter to keep the batteries in check? Or should I go with my usual procedure of putting them on a Trickle charger in the base ment for the Winter? I live in New Hampshire. So it will get cold.

Personally in your climate , they would go in the basement. JMHO

I beleive there is info on the battiers for storing temp.  When you purchase them there is a tag full of information.  If you don't have it I would go look up the battery were you got it to see what is recomended.

They should be fine.  You don't take the batteries from your car to bed with you every night and they don't even have a charger on them.

Anne Marie,

Since most of us start our car every day or so, I'm assuming that's only OK to leave your batteries in your boat if they have a trickle charger on them, correct?  

leave my batteries in both of my boats (7 batteries in all) all stay on the onboard chargers 24/7/365 outside up here in Pittsburgh pa and temps get low and freeze and never have any problems with mine

leave my batteries in both of my boats (7 batteries in all) all stay on the onboard chargers 24/7/365 outside up here in Pittsburgh pa and temps get low and freeze and never have any problems with mine

SOLD!!! Thanks to all for the replies. Looks like I am going to go with this route, I'll just make sure that the batteries are topped off with Distilled Water before I have her Shrink Wrapped. :'(

The higher the charge the lower temperature they can stand so charging fully then leaving a trickle charge or regular top-ups are helpful.

Do not add distilled water before leaving them for the winter.  The water is much lighter than the acid and it will stratify and sit on top.  This low acid water layer can freeze and do physical damage.  If you add distilled water, always do an equalizing charge where you get some bubbling in the liquid to mix the water uniformly with the acid.

If they are low on liquid level you would be better off waiting until summer to top them off.  The higher acid concentration will lower the freezing temperature and avoid the stratification problem.