Why do batteries fail in winter?

Most of us have had that horrible feeling when the car battery suddenly decides to fail, and all we hear is "click, click." Why does it seem more likely in winter?
1. As the temperature decreases, so does the amount of available cranking power
2. Colder temperatures increase the thickness of the engine oil, making the engine harder to turn over

In summer, when the outside temperature is 26.7 C, a fully-charged battery delivers 100% of its cranking power. It is available to start an engine that is easier to turn over because the motor is warmer, making the oil thinner.
So, in winter, when we start the car on a brisk 9 C morning, we have about 34% cranking power available to start a cold engine, which will be harder to turn over because the oil in the engine is considerably cooler and thicker.

So, to start our motor during winter, we have
• Less available cranking power
• More energy required to turn over the engine

Causing a more significant load on the battery and ignition system when starting the vehicle.

So, a battery in fair condition may have quickly started the car in summer, but it is more likely to fail in winter.

When we service your car, we check the battery's charge rate and general condition and clean the terminals to ensure the battery delivers the best cranking power to the vehicle.
Of course, sometimes, the battery is just past its life expectancy.