Each year Consumer Reports testers put car batteries through, well, a battery of tests. The batteries are continuously drained and recharged until they can't start a car, chilled to zero degrees, and even subjected to more than 160-degree heat, all to see which ones work best. Consumer Reports tested almost two dozen car batteries with names such as DieHard, NAPA, and Duralast. This traditional battery cost $70, while this new type called an absorbed glass-mat battery, or AGM, cost $180.

Why is it so much more expensive? Those batteries contain absorbent fibrous glass material that can make them last longer. They're also sealed and spill-proof, which can make them safer than conventional batteries. Most of the AGM batteries outperformed traditional batteries. Another plus with the AGM batteries: They're maintenance-free. You don't have to refill them with distilled water like you do with some regular batteries. That's particularly important if your battery is tough to get to. More and more cars have batteries in hard-to-reach places.

When getting a new battery, it's important to check the manufacturing date. You don't want to buy a battery that's more than six months old because batteries lose strength when they're sitting on the shelf. Some batteries have an obvious manufacturing date. Others use a letter for the month, for example "A" for January, followed by the year. And it's a good idea to get your battery tested at least every four years so you're sure it's got enough power to get you where you're going.

Consumer Reports says be aware, there are a number of things that can shorten the life of your car battery. For instance, if most of your driving is short trips, the battery doesn't get enough time to recharge. And living in a hot climate is tough on auto batteries.

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