Bat volts low over winter

[Njlarry]

Went down to boat to disconnect the batteries for the winter. The two new group 27s were down to 12.57v but the two older 27s were down to 3.8v. I quess the pumps were running after she was hauled and the AC powered chargers were disconnected.
My question is should I worry about the 3.8v batteries freezing and cracking over winter? They are going to be replaced in the spring regardless with 31s. Would prefer not to have marina staff crawl into shrink wrapped boat just to charge soon tobe recyclables.
Your thoughts, experience?

 

[Nater Potater]

I'd be concerned that the batteries could freeze and swell to the point that the cases crack, leaking battery acid. Now, with the latest batteries, the case material is much better in regards to that than years ago, but it would still make me nervous. YMMV

 

[dvx216]

Disconnected lead acid battery fully charged over a period of time will lose it's charge. There is always a very small amount of resistance between the plates through the Electrolyte/ Acid which over time will discharge your battery. Older / Health of the battery makes this even quicker. Even changes in temperature has an effect in the discharge resistance. This is the down fall of any battery no matter what type over time they will fail. This is another reason EV will fall out of popularity once Hydrogen fuel is perfected.

 

[dvx216]

I'd be concerned that the batteries could freeze and swell to the point that the cases crack, leaking battery acid. Now, with the latest batteries, the case material is much better in regards to that than years ago, but it would still make me nervous. YMMV

Full charged lead acid battery is good to -80 F. so one that is only 50% you will be protected.

 

[Nater Potater]

Full charged lead acid battery is good to -80 F. so one that is only 50% you will be protected.

True, but the OP mentioned that his 27's were down to 3.8 volts. That's a lot lower than 50%.

 

[Pirate Lady]

Those batts are done. I always leave mine in boat all winter. But I am serious hate batts. If they don’t hold a charge for 5 cold months and drop below 11 come spring, they gone. I consider batts like anodes and manifolds, sacrificial parts.
Mine were all new spring of 2020. Don’t care what they read comes spring of 2023, all 3 are getting replaced. Don’t trust past 3 years.

 

[Lazy Daze]

I'd be concerned that the batteries could freeze and swell to the point that the cases crack, leaking battery acid. Now, with the latest batteries, the case material is much better in regards to that than years ago, but it would still make me nervous. YMMV

I agree. I'd rather put a shrink door/zipper in there and get the batteries out than deal with cleaning up acid and/or dealing with whatever the acid may have ate.

 

[BlueYonder]

A fully discharged battery will freeze at 32° F. At 3.8v, your batteries are not only fully discharged, they are most likely ruined. Chances are your charger will not attempt to charge a battery with voltage that low. You should remove those batteries from the boat and replace them in the spring.