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Car Battery Buying Guide
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Consumer Reports offers in-depth vehicle reports for every model tested - to help you make the right purchasing decision on your next car or truck.
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The two most crucial factors in choosing a battery are its "group size" and "cold-cranking amps."
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 | | The time to think about buying a new auto battery is before the old one fails. Photo: Digital Vision | |
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The time to think about buying a new auto battery is before the old one fails. Once you're stranded by a dead battery, you probably won't want to spend time shopping around for another. At the first sign that your current battery is growing weaker, have a garage perform a "load test" to see if it's holding a charge properly. If it isn't, find a new battery.
All car batteries aren't created equal. A battery's size, rated capacity, and age help determine how it will perform.
WHAT'S AVAILABLE
Most auto batteries are made by just three manufacturers, Delphi, Exide, and Johnson Controls Industries. Each makes batteries sold under several different brand names. Delphi makes ACDelco and some EverStart (Wal-Mart) models. Exide makes Champion, Exide, Napa, and some EverStart batteries. Johnson Controls makes Diehard (Sears), Duralast (AutoZone), Interstate, Kirkland (Costco), Motorcraft (Ford), and some EverStarts.
Service centers such as Firestone, Goodyear, Pep Boys, and Sears tend to have a large, fresh inventory and relatively low prices. They also handle installation. Stores such as Kmart, Target, Trak Auto, and Wal-Mart may have the lowest prices, but not all of them can install a battery for you. Installing a battery yourself is not technically difficult, but it can be cumbersome, and you have to dispose of the old battery properly. Service stations and tune-up shops sell batteries as well, and they offer convenient and comprehensive service, but their selection tends to be limited and their stock may not be fresh. For cars and trucks still under warranty, a franchised dealer is your first choice, particularly if the vehicle warranty covers the battery. For older vehicles, though, a dealership is probably the last resort—it's the most expensive service venue. The two most crucial factors in choosing a battery are its "group size" and "cold-cranking amps," or CCA.
Group Size. A group size defines the battery's outside dimensions and the placement of the terminals on them. For instance, group size 75 fits mainly General Motorscars. Size 65 applies to most large Ford, Lincoln, and Mercury products. Newer Hondas, Nissans, and Toyotas use size 35. Most Chryslers use 34. You'll also see combinations like 34/78, which has two sets of terminals and will fit either Chryslers or some GM models. Choose the group size recommended by your car's manufacturer. (Reference guides at battery retailers can tell you which group size your car needs.) The wrong size might not fit securely.
Cold-cranking amps. CCA is a measure of a battery's ability to start a car in cold weather, when thickened engine oil and slowed chemical reactions make starting hardest. CCAs denote how much current the battery can deliver to the starter at 0° F. Don't confuse CCA with CA, which stands for cranking amps. That's a measure taken at 32° instead of 0° and is typically much higher than the CCA rating.
Key considerations
Reserve capacity is another important measure of battery quality. It indicates how many minutes your car might run using the battery alone, should the car's alternator fail. You may have to check product literature rather than the battery's labeling to find the reserve capacity.
Buy a fresh battery—one manufactured less than six months earlier. Batteries are stamped with a date code, either on the battery's case or an attached label. The vital information is usually in the first two characters—a letter and a digit. Most codes start with the letter indicating the month: A for January, B for February, and so on. The digit denotes the year: 0 for 2000, say. For example, B3 stands for February 2003.
Warranties. Like CA ratings, battery warranties can sound better than they are. You'll see two numbers: one for the total warranty period and one for the free-replacement period (usually three months to three years). The free-replacement period is key. If the old battery fails after this period expires, you get only a prorated credit toward a new battery.
How to choose
Performance differences. Our tests of batteries regularly show wide variations between and within brands. See below for details on how to obtain Ratings and additional battery information.
What you can do. Check the battery group size and CCA for your vehicle. Not every brand comes in every CCA level. To get the brand you want, you may need to go a bit above your car's CCA requirements.
Steer clear of batteries with a CCA rating below the one specified for your vehicle, as well as those rated 200 amps or more higher than the specified rating. It's a waste of money to go too high. Buy a battery with the longest reserve capacity you can find. If it's not printed on the battery (and it usually isn't), ask store personnel or check product literature. Should your car's charging system fail, a longer capacity can make the difference between driving to safety and getting stuck.
Read our complete Ratings report and related information on car batteries (available to ConsumerReports.org subscribers).
The full Ratings and recommendations for more than 200 vehicles, along with the latest information on thousands of other products and services, are available to ConsumerReports.org subscribers. Find out how to subscribe today.
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