Heat: High temperatures can cause a car battery to degrade more quickly. When exposed to excessive heat, the battery's electrolyte (a mixture of water and sulfuric acid) can evaporate, leading to a decrease in the battery's capacity and performance. Heat can also cause the battery's internal components to corrode and deteriorate, reducing its overall lifespan. Additionally, heat can increase the self-discharge rate of the battery, causing it to lose charge faster when not in use.
Cold: Extreme cold temperatures can also adversely affect car batteries. Cold weather reduces the battery's ability to produce power, which can make it harder for the battery to start the engine. The electrolyte in the battery can also become thicker and more resistant to flow, making it difficult for the battery to deliver the required power to start the engine. Cold weather can also increase the internal resistance of the battery, further reducing its ability to provide adequate power.