If your car engine won't rev up after a jump-start, you may need a new battery. Because you'll be in a hurry when your car is sitting there, do your research before the crisis. Here's what to consider. McClatchy-Tribune Newspapers
Be able to read the code. Auto parts stores have a guide to help you pick the correct 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 buy.
• The second number you need to pay attention to indicates the battery's cold-cranking amps, or CCA. This measures 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 mechanics store in Newport News, Va., says batteries should be less than a year old, and Consumer Reports recommends a shelf life of less than six months.
You're paying for the warranty. Batteries typically cost $60 to $200 (except for hybrid batteries). Kruger says the cheaper batteries run for less time, with the least expensive batteries lasting only 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 get only a prorated credit toward a new battery.
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. Consult the battery's manual for this information.
Test the alternator first. Kruger recommends testing the battery and alternator before buying a battery. He says about half of cars that won't start have a bad alternator. Auto parts stores such as AutoZone and Advance Auto perform these tests for free.