Car Battery Amps: Understanding Car Battery Power and Hour Ratings

January 27, 2012

After series or size, the most important specification of a car battery, amps, is actually divided into two separate specifications. The first and most important specification of a car battery, after the size and shape, (which is defined by series number,) is cold cranking amps, or CCA. The other specification is reserve capacity. The following paragraphs describe these two important specifications of car batteries.

Cold Cranking Amps

Cold cranking amps is the amount of power, in amps, that the car’s battery is able to supply in order to start the car’s engine. The technical definition of CCA is the maximum amount of Amps that a battery is capable of delivering at an ambient temperature of zero degrees Fahrenheit for 30 seconds before the battery is no longer able to supply a usable amount of power. When you start your car, the battery has to supply enough power to the starter to run the motor over with enough speed to start. It must also supply enough power to the ignition system to provide a hot enough spark to make the engine start. Additionally, with newer cars, you will have fuel pumps, injector systems, computers and dash instruments which will all pull power while starting. If your battery isn’t capable of supplying a large enough current punch when starting, it won’t start the car. Car batteries are designed to supply anywhere from 400 cold cranking amps on the smaller batteries all the way up to over 1,500 for some of the larger and more expensive batteries.

Reserve Capacity

The reserve capacity of a battery is how long the battery can maintain a constant 25 amp discharge and still retain enough power to be useful. This reserve capacity is stated in Amp hours for car batteries. The higher the reserve capacity of a battery the more expensive that battery will be. If you like to sit in your car with the engine off and listen to the stereo, you’re going to want to spend the extra money on a battery with a higher reserve capacity to ensure you’re able to start the car after playing the stereo for any extended length of time.

Reserve capacity and cold cranking amps are both increased by the manufacturer. Adding more and thicker, denser lead oxide plates, and larger and thicker lead suspension grids, which hold the lead oxide plates. Indestructible separator plates are also used to increase battery life, and prevent oxide shedding which occurs during deep discharge. If too much lead oxide is shed from the plates, it will settle on the bottom of the battery case and possibly cause the battery to short circuit internally. This type of battery construction will also increase the number of times the battery is able to be fully discharged and recharged, as well as increases the overall useful life of the battery.

When choosing a car battery, it’s important to ensure you choose one that will be able to supply power for all occasions you may encounter, whether it’s sitting with the engine off listening to the radio for an extended length of time before attempting to start the engine, or cold weather starting. The preceding article has given you some information that will help you to understand battery specifications to help you choose the correct battery for your needs.

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