lead acid battery freezing point

Lead Acid Batteries Freezing Point & State Of Charge

Yes, A lead acid battery has a freezing point. It could become damaged or ruined. But under what circumstances will a lead acid battery freeze? I’ve included a lead acid battery freeze chart below…

Putting it simply, a dead lead acid battery will freeze at 32 degrees-F.

However, a well or moderately charged battery will not freeze in practical use. Well, actually, there’s still a point of freezing, depending on the temperature. But, those temperatures (versus battery state of charge) are pretty cold and you likely will not experience that cold (see chart below).

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

But >> Important >> The less charge on the lead acid 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..

Lead Acid Battery Freeze Chart – Temperature vs State of Charge

Lead acid battery freeze chart

As you can see, if your battery is only half charged (50% SOC), it could freeze solid at -4 degrees F. This scenario is entirely plausible. I often see temperatures below zero during the coldest winter months. The coldest I’ve experienced here was 32 below. Typically we always see some early morning temperatures around 20 below at times throughout the winter.

An aging car battery may not hold the charge that it once used to. And it could become damaged when it’s that cold.

Another example… If the battery is really low, say 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 camper. I forgot to physically disconnect the batteries for the winter. As it turned out, there was a small parasitic drain constantly drawing down the batteries (propane gas detectors and a few other things). The batteries 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 battery disconnect switch directly at the battery compartment location. I also make sure to FULLY CHARGE the batteries before winter sets in.

Battery Switch
(amzn)

12 - 48 volt battery disconnect switch

How do you know if a lead acid battery has frozen?

A likely indicator of a battery having previously frozen. Bulged out sides. It could also cause a crack and some or all the battery acid will leak out of that cell.

What about the 12 volt batteries on your tractor, lawn mowers, ATV’s, etc.. during winter?

Some people remove them and store inside where it’s warm during the winter. This is a good idea. Better safe than sorry, right?

However, you can leave a lead acid battery installed during the winter. But only if the battery is in good condition, there is no parasitic load slowly draining the battery, and the battery is fully charged.

I periodically trickle charge my lead acid batteries with the following charger. This is the 12-volt Battery Trickle Charger that I have been using for years. Love it…

Battery Tender Plus Trickle Charger
(amzn)

data sources include:
Math Encounters Blog – Battery Freezing Math

[ Read: Battery State-Of-Charge Chart ]

6 Comments

  1. Several snow bird neighbors that go south each year hook their batteries up to trickle chargers. After several years, I have not heard about any failures/freezing. My next door friend who is now in AZ fishing (I should unfriend him) has his side-by-side, boat, hunting trailer, second vehicle, generator, tractor, … all on small trickle chargers.

  2. Timely subject. I was just going to start looking for a trickle charger. Is there much difference between chargers? i see a fairly big price range and came here to see what was new before i started looking at them.

    1. Country,
      In my neck of the woods Schumacher brand is sold. There are trickle chargers, chargers with booster and jumping capabilities, and also with trickle and 6v charging ( for 6 volt tractor batteries). I also bought cheap Chinese 7 Amp trickle (online) charger with “repair mode” which actually is a pulsing voltage circuit to de-sulfanate lead acid batteries, which seems to work well for the price ($26). Most important to clean and grease battery connections for good connection, so charger and alternator can maintain battery charge while driving. Good luck.

      1. – Schumacher is good stuff. I have several of their items and have not been disappointed with any and some I have used for over a decade. Just asking, where did you get the Chinese model?
        – Papa S.

  3. on my troybilt riding mower, i just always take off battery and store in garage for winter, so far it works good, though i usually charge it in spring before i put back on mower.

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