"Cold Cranking Amp" is another one of those important terms that most people don’t know the meaning of.
In a nutshell, a Cold Cranking Amp (CCA) rating is used to define a battery’s ability to start an engine in cold temperatures. The higher the CCA rating, the better off your engine will be in cold conditions.
This is useful for battery users who live in cold climates, especially where it gets frosty in the mornings. Measuring CCAs are important as it gives customers a good idea of what they can expect from their battery in some of the worst conditions possible for starting a vehicle, just ask anyone who has to start a high mileage diesel truck in freezing conditions.
Manufactures test this by placing a fully charged battery in a cold environment and measuring the discharge load in amps that it can deliver in 30 seconds.