Winter: Remove batteries or not?

Hello,
This is the first time my boat is winterized.
Currently my boat is now on the hard and I noticed that the marina mechanic disconnected one pole from the batteries.
Is it enough or should I bring the batteries back home?
Can they be damaged by our cold winter?

Thank you for any info!

What size batteries do you have? Our 8Ds (150+lbs each) always stayed on the boat during the Winter in New England. I never had any problem with cold or freezing, the key being to ensure the battery stays charged throughout the Winter. This required me to travel to the winterized vessel and top-up the battery charge every month or so. Since the marina would not allow power to be left connected to stored vessels, this meant staying around for hours at a time, not to say that I did not leave them on charge and go home a few times. I did also put together a wind-up (12 hour) timer arrangement to turn off the charger power assuming the marina cops did not disconnect it first!! But, having said all that, if your batteries are small enough and easily removable, I would definitely take them home and put them on a trickle charger. You can get an inexpensive trickle charger from Harbor Freight - I use one to keep my motorcycle battery charged.

I'd leave them on the charger ...

Or take them home and leave them on the charger.

Smart charger of course set for the correct voltage for your battery type.

It is a bit of a gamble to leave them in the boat and do nothing. A battery will freeze at -10 deg F at 50% state of charge (SOC) and -35 at 75% SOC. If you need the lower level of protection then keeping them at 75% or better is dicey over a 6 month long Canadian winter.


So, here are three ways to do it:


Remove and take home and put them on a trickle charger.


Sneak a few hours of charging as the PP does. Doing this a couple of times over the winter should keep them above 75%.


I use a small solar panel to keep them up. But you probably will need to brush off the snow every once in a while.


David

For years I just left the batteries on the boat, with a small solar panel connected to them (5 Watt). Never had a problem. With such a small panel, no charge controller is really necessary. Place the panel vertical, facing south, and snow will not accumulate on it.

Using wet cell batteries i never noticed any difference in life if I took them out or not. As long as the charge is near full they will survive winter OK.

I leave mine on the boat. I do have a 40 watt solar panel that outs out enough to keep the batteries topped up even through the shrink wrap.

The other boat is inside. I leave the batteries on that boat too. I just make sure they are fully charged before it gets cold. No problems yet, but it seldom goes below -25C here.

I made a very costly mistake in not disconnecting the cables from my (four-8D AGM) house bank two winters ago. Parasitic loads reduced their SOC and sub-zero temperatures killed all of them.

This winter, I'm fully charging the new bank (8 J305 AGMs), removing every cable and capping the terminals. (Yes, that's overkill; pulling the negatives ought to protect them; but once bitten . . . ) Fully charged AGMs should be fine over 5-6 months of winter without topping off.

Nice and clean setup angus99!

Yes, AGMs have much lower self discharge rates than flooded cell batteries and should be fine for 5-6 months if fully charged when stored and the negative cable is removed.

FLAs OTOH can self discharge where after 5-6 m months they can be down below 75%. Not all of course, but some can.


David

lol i have no experience with winter. :lol:
if your worried about the batteries freezing. a company called hotstart sells battery heating pads. you can get them the with or with an adjustable thermostat. they do work good. i have never seem a battery i put them on freeze.

Lou
A lot depends on the battery type AND size.
If you have small batteries like type 27 and 31 take them home . If you have 8D then they are too darn big and heavy to move reasonably.
Consider:
Talk to the yard about setting up a charger overnight. Even if you have to go buy a small auto type charger of about 10 -15 amp output. That should bring the batteries up overnight. Even go down early in the day to plug in and then back at night to unplug.

The type of charger I'm suggesting is ONLY for the winter and not to be used while the boat is in the water. They draw little current off the supply so will not overload the yard system.

Needs to be done maybe once monthly. If the batteries freeze the case could split and leak acid and of course will have to be replaced. Once a month should suffice as long as batteries have been isolated from the boat electrical system which you say has been done.

I have Gels 8D and no practical way of removal. I fully charge before winter, ensure all are isolated and they are absolutely fine 4,5 months later. They will stand that.

If you have wet cells then the periodic recharge will likely be required. As other owners what they do.

C-lectric,
Thank you very much for this information.

I think it is a 50/50 shot here in the Mid Atlantic area.

We do get freezing temperatures ro zero or so occasionally, but rare.

I would say that 50 percent of the boaters and yards I know leave batteries in the boat after being fully chsrged, but disconnected, and the others remove (at yards for additional costs).

Most of these people store from Mid October to Mid April so about six months. Some try and get a charger on for a half day or so a couple months before launching when they are down to visit or start working on the boat.

Any fully chsrged battery, disconnected, clean, in good health and out of the weather should tolerate 4 to 5 months without charging. Taking a bit of life out of them? Maybe, but other habits or conditions may be impacting them more than just storage.

What would I do?, I would leave them on the boat with a solar keeper. If it was a big investment in batteries...but too heavy to take out or just too big a PIA....I would go charge them myself...or pay someone to do it mid storage.

When we winter on the hard, we leave our AGMs on board, fully connected... with all loads (including the sometimes hidden loads, like stereo memory and CO detectors and such) off... from roughly late-November to roughly mid-March. Negligible discharge.


-Chris

Another consideration. Self-discharge decreases as temperature decreases. At the temperatures you will have in the winter self discharge won't be a big problem. Just make sure the batteries are fully charged and disconnected before winter and you will be fine. Think of it this way, a car parked outside (and not plugged in) doesn't have battery freezing problems because the battery is fully charged.