Why is it harder to start a car battery in winter?

[Hockeystar]

Homework Statement

Why is it harder to start a battery in winter rather then summer?

Homework Equations

Nerst Equation

Ecell = Ecell - RT/zf(lnQ)

The Attempt at a Solution

Isn't the lead sulfate bettery unique such that the electroyte for the anode and cathode is the same Pb(SO₄). Shouldn't that mean that Q should always be 1 therefore ln(1) is 0. This would mean temperature has no affect on voltage. I'm confused though because I know cars are harder to start during the winter.

 

[chemisttree]

Ignore Q... focus on T.

 

[Borek]

Isn't the lead sulfate bettery unique such that the electroyte for the anode and cathode is the same Pb(SO₄).

No.

And Nernst equation doesn't tell whole story, there is also other part - resistance of the electrolyte.

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methods

 

[Hockeystar]

So the short answer is just a Temperature decrease will decrease the rate of reaction. Electrolyte has less energy and therefore moves slower.

 

[Borek]

I don't think it makes sense to ignore other factors, final effect is a combination of all. Could be one of them is more important that the others, but it is hard to say without trying to find and compare some numbers.

When starting the engine you need to draw high current, cold battery is not able to deliver it.