Why do Car Batteries Die in the Winter?

Extreme cold can affect your battery, even if it is a new battery. Cold slows the chemical process that builds voltage in your battery. If the temperature is low enough, the chemical process is slowed enough to deny the amperage necessary to start your engine.
Your battery is the sole source of the current needed to start your vehicle. The amount of amperage needed to crank your vehicle increases considerably during cold temperatures due to the thickening of your oil through which the crank moves.