Lead Acid Batteries – State Of Charge versus Freezing Temperature

Yes, A frozen lead acid battery is a damaged or ruined lead acid battery. But under what circumstances will a lead acid battery freeze?

Putting it simply… A dead lead acid battery will freeze at 32 degrees-F.

However, a well or moderately charged battery will not freeze. (Sort of)

A little more detail… A fully charged (lead acid) battery will freeze. But not until temperatures drop to 94 below zero (-70 °C)! That’s pretty much not going to happen anywhere here on earth!

But >> Important >> The less charge on the battery, the more susceptible it is to freezing.

I built a chart that cross references battery state-of-charge with the approximate temperature at which the battery will freeze. This is for lead acid type batteries. Car batteries, for example. Or those which typically install in lawn tractors, ATV’s, snowmobiles, etc..

Chart: Lead Acid Battery – Approximate Freezing Temperature

As you can see, if your battery is only half charged, it could freeze solid at -4 degrees F.

Or, if it’s down to just 30% charge, the battery will freeze at 13 degrees F.

I lost two 12-volt batteries a few years ago in my 5th-wheel. I forgot to disconnect the batteries for the winter. As it turns out, there was a parasitic load constantly drawing down the batteries. Since I wasn’t charging them, they eventually went dead. And then they froze. It was an expensive mistake that I will never make again.

Since that time I installed a high current DC ON-OFF switch directly at the battery compartment location. I also make sure to FULLY CHARGE the batteries before winter sets in.

You can leave a lead acid battery installed and/or outside during the winter. But only if the battery is in good condition, there is no parasitic load, and the battery is fully charged.

This is the 12-volt Battery Trickle Charger that I have been using for years. Love it…

>> Battery Tender Plus Trickle Charger

I hope this helps some of you who may come across this post.

data sources include:
Math Encounters Blog – Battery Freezing Math

Here’s another short article that may help in the battery department:

[ Read: Battery State-Of-Charge Chart ]

Sort of related… One reason I chose AGM batteries for my off-grid solar power system was so I could keep them indoors. It gets very cold during the winters here. I knew that lead acid batteries can be a problem out in the cold (depending). And I knew that colder temperatures reduce the effective energy capacity in reserve. AGM’s are safe for indoors (no off-gassing of hydrogen). So that’s what I did.

Since then, Lithium battery technology has become popular. I might consider that option when my present battery bank reaches end-of-life.

For those interested in this, and the other choices for battery bank energy storage, I recommend that you check out who specializes in this area:



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