whether to winter-charge AGM batteries?

M

MitchM

.
Jan 20, 2005
1,031
Nauticat 321 pilothouse 32 Erie PA
In May 2012, we invested in 2 expensive Lifeline XT31's (135 aH each) as house batteries. In the first year of winter storage, we left these batteries installed on the boat but did not drive to the boat for 6 hours each month to plug in a charger . (The main reason that we were willing to go with the Lifeline is their claim that the Lifelines lose only a very small amount of voltage while in storage, as opposed to the old wet cells.) I've become curious as to whether putting a winter charge on AGMs is necessary or advisable. What are the opinions of my fellow owners about whether you charge your AGM bank during winter storage? (Note that for us it is very difficult to get the batteries out of the boat and then reinstall them each year. The alternative is to leave them installed and do a 6 hour drive once a month in terrible winter weather to plug into the storage yard's power post to power the boat's 3 stage Mastervolt charger to top up the batteries. The other alternative i could see is to install a solar panel system with appropriate charge controller to keep the batteries topped up year round.

thanks in advance for your thoughts,

Eagleswing, port of Erie PA
 
woodster

woodster

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Sep 15, 2009
6,244
S2 9.2a Fairhope Al
my understanding is that if you disconnect them over the winter they will hold a good charge...but you have to top them off before disconnecting them Mainsail did an article on this iirc.....
 
Brezzin

Brezzin

.
Sep 20, 2006
155
Hunter 49 Mystic CT
Leave them on board but take the cables off. There may be a small drain on them. On my boat I have smoke detectors and co2 detectors that are wired to the batteries. The link 1000 I have also will have a draw.
My AGMs barely lose anything after 6 months on the hard.
 
Jerry Clark H356 SV Persi

Jerry Clark H356 SV Persi

.
Mar 3, 2003
710
Hunter 356 Grand Rivers
I have Lifelines (2-4D house and Group 24 starting) and during our winter layover in the water, usually three months, I go to the boat once a month and charge for about 6 hours. I have a small draw from the bilge pump but leave everything else off and still will lose some charge in a month. Six hours usually gets them about most of the way up but I don't get back to 100% until I de-winterize and charge overnight. There are years when I have been on the hard for 3 months in the winter and haven't charged. My lifelines lasted 8 seasons, but I rarely discharged them over 50%.
 
Maine Sail

Maine Sail

.
Feb 6, 1998
11,759
Canadian Sailcraft 36T Casco Bay, ME
MitchM said:
In May 2012, we invested in 2 expensive Lifeline XT31's (135 aH each) as house batteries. In the first year of winter storage, we left these batteries installed on the boat but did not drive to the boat for 6 hours each month to plug in a charger . (The main reason that we were willing to go with the Lifeline is their claim that the Lifelines lose only a very small amount of voltage while in storage, as opposed to the old wet cells.) I've become curious as to whether putting a winter charge on AGMs is necessary or advisable. What are the opinions of my fellow owners about whether you charge your AGM bank during winter storage? (Note that for us it is very difficult to get the batteries out of the boat and then reinstall them each year. The alternative is to leave them installed and do a 6 hour drive once a month in terrible winter weather to plug into the storage yard's power post to power the boat's 3 stage Mastervolt charger to top up the batteries. The other alternative i could see is to install a solar panel system with appropriate charge controller to keep the batteries topped up year round.

thanks in advance for your thoughts,

Eagleswing, port of Erie PA
Click to expand

Charge to full, then 1 hour at 15.5V, then 100% disconnect them and come back in the spring..
 
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