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

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Discussion Overview

The discussion centers on the challenges of starting a car battery in winter compared to summer, exploring the underlying chemical and physical principles involved. Participants examine the role of temperature, electrolyte behavior, and reaction rates in this context.

Discussion Character

  • Homework-related
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions the applicability of the Nernst equation, suggesting that since the electrolyte is the same for both electrodes in a lead sulfate battery, the reaction quotient Q should always be 1, implying temperature has no effect on voltage.
  • Another participant advises to focus on temperature rather than Q in the context of battery performance.
  • A different participant disputes the initial claim about the uniqueness of the lead sulfate battery, stating that the Nernst equation does not encompass all factors, particularly the resistance of the electrolyte.
  • One participant asserts that a decrease in temperature leads to a decrease in the rate of reaction, resulting in slower movement of the electrolyte and reduced battery performance.
  • Another participant emphasizes the importance of considering multiple factors, noting that the final effect on battery performance is likely a combination of various influences, including the battery's ability to deliver high current in cold conditions.

Areas of Agreement / Disagreement

Participants express differing views on the factors affecting battery performance in cold temperatures, with no consensus reached on the relative importance of temperature, electrolyte behavior, and resistance.

Contextual Notes

Some assumptions about the behavior of the electrolyte and the applicability of the Nernst equation remain unresolved, and the discussion highlights the complexity of the interactions involved in battery performance.

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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.
 
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Ignore Q... focus on T.
 
Hockeystar said:
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.

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

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