Battery storage for winter

Another subject that seems to have different opinions...

What should I do with my battery during winter ?

1- Leave it fully charged in the boat where it will freeze

or

2- Remove it and store it in my house (fully charged) at ambient temperature ?

Number 2.

Re: Battery storage for winter

A fully charged lead-acid battery will not freeze until the temps drop to around -90F (pretty cold...). A battery that is only half charged will freeze somewhere around -20F to -25F (not as cold).

But what really kills a battery is heat. That said, if a battery is left for too long, the electrolyte will start to stratify and that can lead to sulfation, prematurely killing a battery by dramatically reducing its capacity. Regardless where you leave the battery for the winter, charge it at least once every 2 months to "stir up" the electrolyte (some prefer to leave it at a float charge for long periods, but even when doing that, you should really "top it off" (provide an equalizing charge) at regular intervals. When charging, ensure the area is well ventilated.

Worst killer of lead-acid batteries, part from heat, is to leave a very small "parasite" current on the battery (like an alarm, a clock, blinking LEDs, small supply current to keep radio stations in memory, etc).

Re: Battery storage for winter

I do the #1 ( left in the boat outside ). I charge them up fully before closing things up. If there is a break in the weather during the winter, I'll charge them again. In the spring they still have good life in them.

Re: Battery storage for winter

Supertaz said:

Another subject that seems to have different opinions...

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No big issues with battery storage.

Wellcraft's explanation is right on. The only thing I would add is if you store it out of the boat do not set it on a concrete surface. The concrete aids in the discharge of the battery. Also clean the battery. A dirty battery top will also aid in discharge.

Re: Battery storage for winter

Why would storing a battery on concrete cause it to discharge any more than setting it on anything else? The battery case is an effective insulator (by design). If the battery was dirty there might be a current path to ground from the posts through the contamination, but if it is clean there should be no way for the current to discharge by that route.

The only thing I can think of is that concrete is an effective heat sink and this might cool the battery more than if it was sitting on something else.

Re: Battery storage for winter

ssobol said:

Why would storing a battery on concrete cause it to discharge any more than setting it on anything else? The battery case is an effective insulator (by design).

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You are correct. I have just dated myself. Much of our farm equipment and vehicles had older batteries. Those batteries had soft/rubber cases. It just became a habit to keep them off the concrete.
However surface discharge on a dirty battery can still be a problem.

Re: Battery storage for winter

Good info...Thanks !!

Since my boat will be stored for the next 7 months :facepalm: I might keep it inside in a cool spot of the house and recharge it every 2 months as suggested !!!

Good idea.