My batteries went flat over the winter! Why?

[garmstro55]

For the first time in 2 years we wintered our MS400 on the hard in the marina parking lot. Went I went to the marina in February to check on things it seems both 8D batteries went flat, both below 5 volts. I had turned off both battery switches before I left in the fall. It was shrink-wrapped and there was no water in the bilge (so the pump couldn't have been running) and I just can't figure out what drained the batteries. I did winter on the hard in 2020-21 with no issues. Both batteries are less than 2 years old. Any ideas what I should look for?

Note: Flooded cell batteries in NE Maryland.

 

[SteveK]

In an attempt to avoid to have everyone repeat themselves, read this thread from March 3, 2024

 

[DavidM]

You have to be well below 50% SOC for batteries to freeze in that part of Maryland. The question is, how did they get so low.

David

 

[garmstro55]

In an attempt to avoid to have everyone repeat themselves, read this thread from March 3, 2024

Read it Steve, I can't believe that's the reason. They were fully charged at the end of November. Something must have drained them low enough to freeze, if that's what happened.

 

[Bmarler]

Flooded batteries self discharge, but I don’t know exactly how long you were off the charger.
Has this strategy of disconnect and shrink wrap been successful in the past?
With the battery switches off, I take it the bilge pump circuit is still live. Are the pumps the style that auto start every now and then to rest for water? What else bypasses the battery switches? Starter maybe? Possible there’s some leakage there?
Is there any other parasitic load that bypasses the battery switches? With the switches off, try placing an amp meter between the negative post and the cable to see if there’s some draw you weren’t aware of.
Hopefully, if the batteries weren’t at low voltage for very long you might be able to bring them back into service. Hard to say if they’ll be ok, but it’s worth trying.
Impossible to tell if they froze, but it wasn’t mentioned in the first post.

 

[SteveK]

Gary, we know it happened to you, so now we look for the reason.
As shown in the other thread already weak batteries left without charge maintenance will freeze. I think it is due to diluted fluid from topping up over time. Any batteries I have replaced would charge to 100% but would discharge to 50% well before 50% rated Ah out was used. Left alone without a load they would discharge.
If that was your batteries before they went on the hard then you have your answer.

 

[Bacchus]

Turning off batty switches is not sufficient.
There are "always on" loads besides bilge pumps... CO2 sensors for one, that can run battys down in a couple weeks.
Best to FULLY CHARGE then disconnect main leads for storage.pulling the bilgevdrain plug incase there us V water intrusion.

It sometimes takes more than one cycle of chargers as sometimes chargersvwill time out and switch to float before battys are up to 100% SOC. If the yard runs the boat & winterizes frequently battys are veliwv100% SOC when they block it. Best to top off yourself to confirm 100% SOC.
I measure V again in spring before reconnecting to see how they have faired over winter. I then gauge useful life based on how well they survived storage and whether replacement us getting closer.

 

[BruceK]

That you did the same in 2020-2021, successfully,presumably with inferior batteries, doesn`t seem well explored.
Were there any possible added/changed loads this time? Were there any known loads last time? Something added directly on the batteries not covered by the main switch?
Whatever the cause,let`s hope they come with charging, but it`s a low voltage with FLA`s.

 

[Iggy]

Sorry to here about your batteries! I just had to change out my starting battery and add to 2 new batteries when I upgraded my bow thruster last month with a bigger one and went to 24V. After buying 4 batteries, I replaced the genset battery too. Five total.

Around 2005 I went to AGM type batteries. More money but lasted 3 times longer if not more. Plus I want a good dependable battery being out on the water. Flooded will self discharge 3 to 5% per month where AGMs is more like 1 to 2% and will freeze, brand dependent -25 to -50.

I don't understand, why use flooded? Yes, less money but the advantages of AGMs are far greater.

True story and maybe hard to believe. My last boat had 5 AGMs from Odyssey. Two of them lasted 7 yrs and the other three lasted at least 12yrs. Than I sold the boat, at that time all five were good.

 

[kthoennes]

We've kept our boats on the hard, jackstands, shrink wrapped, since 2011 but with the battery cables disconnected. No trickle chargers. FLA. The current boat has six batteries and we've never lost one due to winter storage, even though our winter runs Nov - March and we always get at least a week or two at 25 below zero or so. They do only last about 4-5 years, but it's always a slow degrade with age, not freezing. I think thousands of farmers who store their farm equipment overwinter with no maintainers on their batteries would be amused by these threads. Anyway, in summary, I think disconnecting the cables at layup is a better way to go, no mystery drains.

 

[garmstro55]

Turning off batty switches is not sufficient.
There are "always on" loads besides bilge pumps... CO2 sensors for one, that can run battys down in a couple weeks.
Best to FULLY CHARGE then disconnect main leads for storage.pulling the bilgevdrain plug incase there us V water intrusion.

It sometimes takes more than one cycle of chargers as sometimes chargersvwill time out and switch to float before battys are up to 100% SOC. If the yard runs the boat & winterizes frequently battys are veliwv100% SOC when they block it. Best to top off yourself to confirm 100% SOC.
I measure V again in spring before reconnecting to see how they have faired over winter. I then gauge useful life based on how well they survived storage and whether replacement us getting closer.

That's good advice, Don. I have had boats in the same marina for 15 years and always followed the same practice of turning off the battery switches with no ill effects, but disconnecting the terminal is certainly a better way to go and I will follow that practice in the future. There must have been some parasitic load to cause the batteries to drain, but for the life of me I can't figure it out. Maybe the CO detectors I suppose, but there has never been a problem before this year. It did get down to 11 degrees F this winter so maybe they did freeze. If that's the case, as least I'll know what the problem is.

 

[Chuck34]

Turning off batty switches is not sufficient.
There are "always on" loads besides bilge pumps... CO2 sensors for one, that can run battys down in a couple weeks.

CO2 sensors are a problem on my boat killing batteries. I have special breakers to turn them off which I do.

 

[Bacchus]

I investigated our secondary 12V panel that included the always on loads and moved the CO detectors from always on to switchedv12V. House supply. In figure if I'm not aboard and switch the hose off I don't need CO the detectors on when not aboard... saves parasitic loads when Sw it off.

 

[Iggy]

That's good advice, Don. I have had boats in the same marina for 15 years and always followed the same practice of turning off the battery switches with no ill effects, but disconnecting the terminal is certainly a better way to go and I will follow that practice in the future. There must have been some parasitic load to cause the batteries to drain, but for the life of me I can't figure it out. Maybe the CO detectors I suppose, but there has never been a problem before this year. It did get down to 11 degrees F this winter so maybe they did freeze. If that's the case, as least I'll know what the problem is.

Yep!

 

[Shrew]

I wouldn't expect FLA batteries, left untended all winter, would have much of a charge in the spring. I'm surprised you had so many years of good luck. I'd be curious what the actual SOC was on the FLA batteries after being laid up all winter.

 

[garmstro55]

Well here is an update, for what it's worth. The marina put their charger on the batteries and they seem to have come up to 12.6V, for now at least. I will be monitoring closely to see if any permanent damage has occurred. I am going to be suspicious of them for a while until they can prove to me everything is ok.

 

[Bacchus]

CO2 sensors are a problem on my boat killing batteries. I have special breakers to turn them off which I do.

Some Mainships have a separate panel for the always on accys. Mine (2008 34HT) is on the aft deck and has some of those "special" breakers that are wired thru the batty switches snd others that are direct to the batty.

 

[Comodave]

Well here is an update, for what it's worth. The marina put their charger on the batteries and they seem to have come up to 12.6V, for now at least. I will be monitoring closely to see if any permanent damage has occurred. I am going to be suspicious of them for a while until they can prove to me everything is ok.

I would get a battery load tester and see how the test. Just because they came up to voltage doesn’t mean they may be good.

 

[HeadedToTexas]

Lots of good examples of parasitic loads already listed. I take all cables off the ground terminal on every battery to be sure. Despite the grounds removed, I arrived at the boat a few years ago to find the Balmar Smartguage flashing an error. Not good. Turned out the Smartgauge wire had made contact with the generator start battery. Make sure every battery is disconnected.

 

[Mac G]

The procedure I have done for years with success is to top off water and fully charge batteries before winter layup.
Then I disconnect the batteries so there is no chance for them to be draining via some unknown current leak somewhere.
Then I visit the boat one weekend every month throughout the winter and hook the batteries back up and charge them while working on other stuff.
Will charge them all day Saturday and test them and charge again on Sunday if necessary.
Then I disconnect them again and let them sit for another month.
There seems to be two schools of thought on battery storage: one is using a constant trickle charge and the other is to let them sit idle and slowly self discharge and then charge them up full again.
I subscribe to the latter.
Plus cannot leave things plugged in 24/7 at our boatyard; so that also dictates the choice.
Follow the same procedure with other batteries for tender and other small boats that we store at home in basement.
Never had problems (knock on wood).

 

[Irish Rambler]

Just my two pen'orth.
Based on my own experience, when we lay up a boat we leave the boat on shore power with a tube radiator in the engine room, a couple of space heaters on 'frost' setting. For the batteries I use a timer switch set to come on during the 'silent hours' for 1 hour and a half connected to a smart battery charger. Each time the battery charger time switch is activated it does a quick check on battery state and then charges at the appropriate rate.
We've never had a problem so far.