Storing Batteries on board for the winter

[Tom Metzger]

For the first time this winter I have stored my batteries on board at 44*N latitude, about forty miles south of the Canadian border. Today I drove up to take a look at the boat, check the stands, and charge the batteries.

I had switched off both banks and separated the paralleled house bank on October 21st. The good news is that when I connected them up again prior to charging the house bank read 12.8 volts on the digital voltmeter on the monitor. That's damn close to the fully charged voltage. The starting battery read slightly lower, but that was on the panel meter which is not too precise.

Cold is good!

I now have no concerns about leaving them through the entire winter without charging.

 

[Emerald]

Agree with leaving them on board. Blew out several discs in my neck several years back, so I have great incentive not to contort and do the awkward angle lift to get the batteries off the boat and down the ladder, or over to the pier or whatever. I've never had a problem leaving the batteries on board. I will periodically hook up the shore power while spending a day working on the boat to let the on board 3 stage charger give the batteries any topping they might like.

 

[rwthomas1]

I do the same thing. No reason to remove them just check every few weeks and charge if needed. Cold+no load=very slow discharge. RT

 

[P Abele]

Tom: Be careful - it really wasn't cold this weekend!

I tried going down that path last winter and would charge them every 3-4 weeks, but during one cold snap (high of around 0, low around -15F for a few days), checked on the boat and found the batteries frozen. I then pulled the batteries out that day and took them home to thaw and charge in my basement - if anyting could make the battery removal process less fun, it would be doing it in that sort of cold. They survived that ordeal and seemed to work fine last summer but are in my basement now getting their monthly charge.

 

[NateHanson]

My understanding is that only a discharged battery freezes, so the key to winter on-board storage is to make sure they hold a charge. Disconnect them, as Tom says, and/or have some sort of trickle charge. Mine are onboard, and though my boat is under white shrinkwrap, the solar panel is pointed south, so that may be helping my batteries stay fresh. When I checked them last (a couple weeks ago) they were fully charged.

 

[sleather]

Nate's correct, only a discharged battery will freeze and it's amazing it didn't bust the case(one reason for a battery box).
A "new" to 2-3 year old battery if disconnected will lose little or no charge over the winter. As the battery ages it's wise to either have it on a maintainer or remove and periodically recharge it. My 7 year old Die-Hard finally did.

Emerald, I know your pain!:0305_frow 15 years ago I severely strained a muscle in my back yanking mine out of it's EVIL location in my E23. Had a friend put a new one in in the spring and didn't remove it for 4 years.

Any "longevity" stories out there? I figure 7's about the magic number. My 2001 Grand Cherokee's finally called it quits this week.

 

[Maine Sail]

Batteries naturally self-discharge between 1% to 15% per month while in storage, and lead sulfation will start occurring when the state-of-charge drops below 80%. If left in a boat, disconnecting the negative cable will reduce the level of discharge by eliminating the parasitic load. Cold will slow the self-discharge process down and heat will speed it up. Use the following simple steps to store your batteries:

1) Physically inspect for damaged cases, remove any corrosion, and clean and dry the battery tops.
2) Fully recharge the batteries!
3) Check the electrolyte levels and add distilled water as required, but avoid overfilling.
4) Always fully charge the batteries after adding distilled water.
5) Store in a cold dry place, but avoid temps below 32° F (0° C) when possible.


Depending on the type of battery, it has natural self-discharge or internal electrochemical leakage at between 1% to 15% rate per month that will cause it to become sulfated and eventually, depending on the particular batteries characteristics, fully discharged over time. Again, igher temperatures accelerate this process colder temps slow it. For example a battery stored at 95° F (35° C) will self discharge twice as fast as one at 75° F (23.9° C). Unfortunately temperatures below 0 C or 32 F can also have negative effects.

The bottom line is this. Batteries can and do freeze if not properly charged. A discharged battery will freeze and any battery left in a boat over the winter should carefully maintain a minimum of 80% of charge at all times to avoid plate sulfation and the potential for freezing.

If you can not guarantee that your batteries can maintain a minimum of 80% of charge, and don't rely on a Xantrex Link 10, 20 or XBM for this because they DON'T measure standby loss, then you must have a way of periodically charging them through out the winter. Even a trickle charger plugged in every 5 or six weekends will help tremendously.

Unfortunately, looking at a volt meter tells you nothing about any sort of sulfation damage that may be occurring out of sight and within the batteries case.

Cold weather helps prolong the state of charge but severe cold weather can be as detrimental as extreme heat if the battery does not carry sufficient state of charge going into the cold snap..