Winter Battery Charging

[raycullum]

I store my boat in my yard and able to plug in and charge my batteries all winter. Is it okay to keep them on a float charge continually, or should they be taken off the charge now and then.

[garyfdl]

I do and have do so for years - and not just for the boat (lawn equipment, tractors, etc are also kept on maintainer/float chargers).

Just make sure that if they are lead/acid batteries, and the cells have removable caps, that they are topped up with distilled water, and that the tops of the batteries are clean.

[boatpoker]

No need to do that. Make sure they are topped up (if LA) and fully charged. Disconnect the negative cable and they will be fine for the whole winter just like 10's of thousands of other boats on the Great Lakes.

[S/V Illusion]

Some charge them over the cold season; others don’t. And both choices work.

The only real difference is the unlikely possibility of an electrical problem with the charger. Why take that chance for no good reason?

[rslifkin]

They don't necessarily need to be kept on a float charge, but constant float at an appropriate voltage is just fine and possibly better for the batteries (lead acid batteries hate being even slightly less than fully charged).

[smac999]

Originally Posted by S/V Illusion

Some charge them over the cold season; others don’t. And both choices work.

The only real difference is the unlikely possibility of an electrical problem with the charger. Why take that chance for no good reason?

bigger chance the boat floods with rain / snow and you need the charger on to keep the bilge pumps going.... then the charger failing in a way that causes a problem to the boat.

[GordMay]

At a temperature of 80° F, a flooded lead acid [FLA] battery will self-discharge, at a rate of approximately 3 - 4% a week [±12%/month].
In cold weather, flooded batteries will take longer to discharge.

My question is:
What self-discharge compensation factor [% per 10°F below 80° F] should one apply, for temperatures below 80° F?

Can we extrapolate from the specific gravity temperature compensation adjustment?

A typical, fully charged, flooded battery, will have an electrolyte density around 1.265 as measured on a hydrometer, at battery temperature of 80° F. To compensate for winter temperatures, subtract 0.004 for every ten degrees below 80° F [26.6º C].

Trojan is no help.
“Deep-Cycle Battery Storage” ~ Trojan Battery White Paper
➥ https://www.trojanbattery.com/pdf/WP...orage_0512.pdf