How do you leave the batteries?

[J Clark H356]

We are in Kentucky Lake and I move to Tennessee for 3 months each winter. I don't leave the boat plugged into shore power at my home port or in Tennessee for the winter 3 months. I shut everything off and go to the boat for a day each in January and February, plug in, and recharge. I use a ceramic heater to keep the boat modestly warm when on it myself, other times it is not heated and just sits in ambient temperature but winterized - and unplugged.

Around the first of March we get to the boat around midday and start de-winterizing. We plug in on arrival and start recharging. We have to move to a dock where I use 100 feet of hose to reach a frost free hydrant and start de-winterizing the water system after we have done the HVAC system.. We do that into late evening and run the generator. By morning we are fully charged and our batteries never get below 50% charge during the month while we are absent. We stay on the water dock and do a final flush in the early morning, then head back north 7 hours to Lighthouse Landing where we spend the summer. Instead of hauling in the winter, we do our major haul out work now - when it is high 90's and 100's. We don't sail from just after the 4th of July until mid to late August when the weather breaks.

We got 7 years on our last set of Lifeline batteries. We are on year 3 on the ones we have now and these spent a winter in Florida. That season, we left everything running when we returned to Tennessee. We spent 50% of our time on the boat and 50% at home that 6 month period. We left everything running during that period either on generator while not at the dock or shore power when in a marina. We don't depend much on batteries, but have 2 4D house and one Group 24 starting battery - all Lifeline AGM. We run our generator full time when not at the dock.


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[sailorboy1]

Originally Posted by J Clark H356

We run our generator full time when not at the dock.

WOW! Do you really have a sailboat or do you have a large cruise ship?

[savoir]

Maybe their icemaker gets a real workout. Could be a fun boat.

[MarkSF]

Originally Posted by Guy

I just turn everything off for 5 months. However there might be a very slight drain through the batt switches. Bilge pump is direct so it would stop after 7 batts died but our boat is dry so not really a concern.

After 5 months your batteries will will have self-discharged to about 80% at 20C, so you will have lost 20% capacity to sulphation. That gets expensive with 7 batteries.

[model 10]

Originally Posted by MarkSF

After 5 months your batteries will will have self-discharged to about 80% at 20C, so you will have lost 20% capacity to sulphation. That gets expensive with 7 batteries.

Crap. How about AGM's at 60 deg C during the day?

[MarkSF]

Is that really 60C, or 60F?

Here is a data sheet from Victron. It states 2% a month for AGMs at 20C, doubling for every 10C.

https://www.victronenergy.com/upload...tteries-EN.pdf

[model 10]

[QUOTE=MarkSF;2181078]Is that really 60C, or 60F?

Arg! No it's 140deg during the day on the hard in Guatemala. From that chart it sounds terrible whether they were still connected or not.
What a dumb ass I am. Last year we left the boat on the hard and when I got back several batts were toast and it did get that hot inside the boat. I put it down to a mysterious voltage drop or cheap AGM's only lasting 3 years. From the chart it looks like only a few years life is to be expected at best. This year the boat is in the water so it should only be about 90deg F inside.

[quandary]

In the water, I switch off batteries at isolator but leave a solar panel connected to trickle charge. I disconnect shorepower to try and reduce galvanic corrosion. In winter (UK) I run an extension cord from shorepower into the boat for dehumidifier and heater ie I don't connect shorepower to the boat systems and earthing to limit galvanic corrosion.
On the hard under a cover (ie no solar trickle) I find it best to disconnect batteries at the terminals. They easily hold charge for 3+months.

[John_Trusty]

First Dr. D: Congratulations on your new (to you) Jeanneau -- cool cruiser!

I'm not an expert at battery life and loss, but I have read someone who is: MaineSail Welcome To MarineHowTo.com Photo Gallery by Compass Marine How To at pbase.com He's actually published tests of the effects of too much discharge and leaving batteries in cold conditions over the winter. Based on that advice, as summarized by LeftBrain's "Batteries like to be charged", while my boat is in the slip and I'm around, I keep it plugged in to top the batteries up. I'm more concerned with the many AC shore power problems outlined above than perhaps some loss of life in a partially discharged battery.

[a64pilot]

If you have a very good Solar system, one that is capable of keep the batteries fully charged and you have your fridge on, your still cycling your batteries,1 cycle every day.
If you have a good Solar system and have your shore power connected and the charger on, you do not cycle your batteries.
Since one limit on battery life is number of cycles and right now I only use the boat on weekends, I leave it plugged in and not cycling, plus my interior thanks me for running the AC as a dehumidifier and keeping the interior temps down to about 80 F or so.

Now I'm sniveling, but I have I think about $1,800 in batteries, so I'm going to do my best to keep them if I can.

[sailorboy1]

Originally Posted by a64pilot

If you have a very good Solar system, one that is capable of keep the batteries fully charged and you have your fridge on, your still cycling your batteries,1 cycle every day.

If that were a battery cycle my batteries would have died years ago.

[a64pilot]

Oh, it's a cycle alright, not a deep cycle, but a cycle is nothing more than a discharge and a charge, does not have to be to 50%, and of course the shallower the cycle, the more you get.
Age of course does play into battery life and temps and other factors, it's not just cycles.

[Dr. D]

Thanks for your many inputs and comments!

I believe the statement in the owner's manual is legal CYA. I'll keep the batteries charging somehow.