How to Check the Size of a Car Battery

by Don Bowman

Before replacing a car battery, the owner's manual should be consulted to ascertain the battery group pertaining to size, the cold cranking amps recommended and the reserve capacity. Many cars have the ability to accept several sizes of batteries, but not all. The free replacement period, the warranty area, and whether the battery is prorated after the free period should be addressed before purchase.

Get the battery group size from the owner's manual or from a battery distributor. The battery group number relates to the size of the battery that will fit in the vehicle. It is always shown on the label on the top of the battery.

Check the cold cranking amp (CCA) rating on the battery. The CCA rating relates to how many amps the battery can put out for 30 seconds at 0 degrees Fahrenheit before dropping too low in amps and voltage to be useful. For example, a 650 CCA battery can put out 650 amps for 30 seconds before it dies. This is exceptionally important in cold climates.

Check the reverse capacity (RC) rating. This indicates how long the battery can put out an average of 25 amps before the battery voltage drops below 10.5 volts. This is important; if the vehicle experiences an alternator failure, the vehicle will need to run on the battery alone to get to a service station. The higher the RC rating, the safer the battery is during an alternator failure.

Look at the side of the battery, and check the manufacture date. This is obviously important, since a 4-year battery is good for that period of time from the time it was first charged. In the past, the batteries came dry, and came with the electrolyte separately. This was better for getting all the life of the battery, but proved to be a hassle for the stores, so they discontinued this practice. If a battery is purchased that sat on the shelf for the past year, it will not likely last an additional 4 years. The code starts with a letter to designate the month. For example, A is for January, and B is for February and so on. The letter code will be followed by a number. The number is the year such as 9 for 2009.

Check the AH rating if a deep cycle battery is being purchased. This relates to how many amps the battery can put out, and how long it can maintain them before needing a recharge. To determine which one is needed, add the watts or amps for each appliance together, then multiply by the number of hours to be operated. Add 20 percent for "fudge factor." This is the AH rating needed.

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About the Author

Don Bowman has been writing for various websites and several online magazines since 2008. He has owned an auto service facility since 1982 and has over 45 years of technical experience as a master ASE tech. Bowman has a business degree from Pennsylvania State University and was an officer in the U.S. Army (aircraft maintenance officer, pilot, six Air Medal awards, two tours Vietnam).