Things to consider before buying a battery

Daily Press (Newport News, Va.) (MCT) - If your car engine won't rev up after a proper jump start, you may need to purchase a new battery. Since you'll be in a hurry when your car is sitting cold in the parking lot, you should do a little research before the crisis. Here are some issues to consider.

Be able to read the code. Auto part stores will have a guide to help you pick the correct battery size. First, you'll need to look up the year, make and model of your car in the battery guide for a group number. Sometimes the size of the car engine also will make a difference in which group number is assigned to your car. That group number (Example: 58-600) tells you what size battery you'll need to purchase.

The second number you need to pay attention to is the cold-cranking amps number. This is the measure of a battery's ability to start a car in cold weather. Your car manual will tell you what CCA rating is best (Example: 460). Consumer Reports recommends steering clear of batteries with a CCA rating below the specified rate for your car, or a battery with a CCA rating 200 amps higher than what's recommended in the manual. A high rating will give the car a little more power, but it's a waste of money to go too high.

Age is key. You need to know how long the battery has been on the shelf before you buy it. The manufacture date will be labeled in one of several forms. Some dates are simply written out, other dates are written in a letter and digit code. The letter will indicate the month, A for January, B for February, etc., and the digit denotes the year, 0 for 2000. The code A5, for example, means January 2005. Dave Kruger, manager of an auto mechanic store in Newport News, Va., says batteries should be less than a year old, and Consumer Reports recommends a shelf life of less than 6 months.

It should run on its own. Reserve capacity, the number of minutes a battery can run on its own if the alternator fails, is another measure of battery quality. Consumer Reports suggests buying a battery with the longest reserve capacity you can find. You'll need to consult the battery's manual to find this information.

You're paying for the warranty. Batteries typically run from $60-$200 (except for hybrid batteries, which are in a whole different league). Kruger says the cheaper batteries run for less time, with the least expensive batteries only lasting about 2 years. You can get a sense of how long the battery is expected to last by what type of manufacturer's warranty comes with it. Consumer Reports says to pay attention to the "free replacement period" in the warranty. If your battery fails after that period, you'll only get a prorated credit toward a new battery.

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Test the alternator first. Kruger recommends performing a test on the battery and alternator before purchasing a new battery. In his experience, about 50 percent of cars that won't start have a bad alternator. Auto stores such as AutoZone and Advance Auto will perform these tests for free.

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© 2008, Daily Press (Newport News, Va.).