1. Don’t buy an old battery. Look for a date code printed on a sticker on the side of the battery. Always check to make sure you get the newest one on the shelf. When batteries sit, they can start losing their charge. Here’s how to decipher the code: A battery made in October 2015 will have a numeric code of 10-5 or an alphanumeric code of K-5. “A” is for January, “B” is for February, and so on (the letter “I” is skipped). We instruct our shoppers to buy batteries that are no older than six months—preferably three months or newer.

2. Take your old battery to the store so that it can be recycled. Don’t just throw it in the trash! That is important because batteries contain lead and must be disposed of properly. If you don’t have your old battery with you at time of purchase, you may be charged a “core charge,” or a deposit of $5 to $25.

3. Don’t focus too much on cold-cranking-amp (CCA) claims. Modern cars with fuel-injected engines controlled by computers take no more than a few seconds to start. They don’t need the highly inflated CCA numbers that manufacturers like to put on the packaging and marketing materials. We keep this in mind when weighing this measure against the others in our tests.  

See our complete car battery buying advice and ratings.

Tester John Banta offers expert car battery tips
To find out how long a battery lasts, we charge and discharge it thousands of times over a 15-week period in a 167° F water bath.

Editor's Note: This article also appeared in the January 2016 issue of Consumer Reports magazine.