The amperage capacity of a car battery is measured in two different ways: amp hours or cold cranking amperage, or CCA rating. The measurements mean two different things. Most automobile batteries have a capacity of between 45 and 50 amp hours. For most passenger cars, the battery CCA will fall between 400 and 600.
Amp hours capacity refers to the amperage delivered during a number of hours when the battery is fully charged. In the case of 45 amp hours, for example, this means that the battery can delivery 1 amp for 45 hours, 2 amps for 22.5 hours and so on.
The CCA rating indicates how well the battery can start up in cold temperatures. Specifically, it measures the amount of current the battery is able to deliver for 30 seconds at a temperature of 32 degrees Fahrenheit. For larger vehicles such as light trucks it may run between 700 and 1000.