Since the operation of a battery is based on a chemical reaction, temperature plays an important role in performance. The ideal operating temperature for an automotive battery is 26.7 C (80 F). This is when the battery operates at maximum efficiency.
It’s getting hot in here: Heat typically accelerates chemical activity, but higher temperatures also speed up internal corrosion within the cells and reduce the life of the battery. This is particularly true of batteries that repeatedly reach high internal temperatures, and once capacity has been damaged by heat, it can’t be restored.
Cold bogs batteries down: Just as heat speeds up chemical reactions, cold temperatures slow them down. That’s why a battery can become sluggish in winter, even though its state of charge may remain unchanged.
At colder temperatures, the battery’s ability to provide sufficient power to start and run a vehicle is diminished. That’s why automotive batteries are rated in CCA (Cold-Cranking Amperage). This is the amount of current a battery can deliver for 30 seconds at -18 C without dropping to a specified cutoff voltage. Obviously, the higher the CCA, the better the battery will perform in adverse conditions.
Batteries can freeze: A fully charged lead-acid battery can survive up to –50 C, but a battery with a low state of charge can freeze at –1 C. When the water in a battery freezes it expands and can cause irreparable damage to the cells.