I have some questions. I recently woke up to a dead battery. It's been below zero lately so it's not surprising as it's not an every day driver. Yesterday when I opened the hood to check the battery cell water levels I noticed multiple things.

There is frost on the outside of the battery, but it's not showing any bulging at initial glance.

There is also frost on the outside of the coolant reservoir (though the coolant is not frozen), as well as some of the metal pipes under the hood. I have not checked the rest of the fluids nor the other pipes as my main interest was the battery.

Is this normal? The day I drove it, it was snowing and the road was wet.

My other questions are, should I even try to charge the battery or should I go get a new one? If there is frost on the outside of the battery covers side, do I need to thaw it out? Stories of exploding batteries have me concerned. Thanks!

  • Welcome to Motor Vehicle Maintenance & Repair! Jan 6 '19 at 15:48

The freezing point of the acid inside a battery depends on how fully charged it is.

A completely flat battery might freeze at about -10C (+14F) if you are unlucky, but a fully charged battery won't freeze until about -60C (-76F).

So long as the battery terminals are covered in grease (to keep water away from the terminals themselves) frost and water condensation on the outside of a battery isn't a problem. The heat from the engine will soon dry it when you start driving the car.

Obviously the cooling system should be filled with the correct amount of antifreeze for the weather conditions where you live. Antifreeze doesn't "wear out" over time. If you are losing coolant and keep topping up the system with water (not with the correct antifreeze/water mixture) you will dilute the antifreeze and raise the freezing temperature, but the best way to avoid that is fix the leak instead of repeatedly topping up the level.

Batteries only "explode" if they are maltreated and start to produce a lot of gas, which is an explosive mixture of hydrogen and oxygen while it is trapped inside the battery and not diluted by mixing with the air. It also needs something like a spark or a flame to set off the explosion. A battery which is charged and working properly won't generate any gas. "Explosions" do happen but they are usually caused by people doing dumb things while trying to fix problems - for example by trying to jump start the car with another battery and connecting it the wrong way round.

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