Car Battery Ratings Explained
There are three main car battery ratings used to identify a battery and define where and how it can be used. The first of these is the warranty period. Typically this will be either 60 or 72 months. The other two, which will usually vary from battery to battery, are cold cranking power or amps, and reserve capacity.
Cold Cranking Amps
Cold cranking amps is a description of how much current a car battery is capable of supplying at a constant 12 volts for 30 seconds at zero degrees ambient temperature, and still be able to provide a usable amount of power afterward. Larger and higher performance engines require more energy to turn over when starting. New engine controls and accessories create a larger drain on the battery during starting, which means the battery will need a higher cold cranking amp rating. The higher the number, the more current the battery will be capable of supplying.
Reserve capacity describes how long the battery is able to supply a constant 12 volt, 25 amp load at 80 degrees ambient temperature. The higher the number, the longer your battery will be able to keep your engine running if the alternator belt breaks or the alternator stops generating power.
Usually, a battery with a high cold cranking amp rating will also have a higher reserve capacity rating. Typically, you're going to want to buy the battery of the proper Group Size with the highest set of ratings that you can afford.