Group 48 Duralast Platinum AGM car batteries fall short in Consumer Reports' life test

Absorbent Glass Mat, or AGM, batteries are touted by manufacturers as being more capable of meeting the demanding electrical needs of modern cars—from powering infotainment systems to fuel-saving start-and-stop engine operation at traffic lights. The downside is that AGM batteries typically cost more than old-fashioned "flooded" batteries. And they don't always deliver on their performance promise.

In our latest battery tests, not only did some Duralast Platinum AGM batteries not perform as well as other AGM batteries but they also didn't measure up to less expensive conventional batteries (including those from Duralast). This is even more surprising given that other Duralast batteries have been regular Best Buys in our Ratings. (Duralast batteries are sold only at AutoZone.)

If you're in the market for a new car battery, check our  recenty updated car battery buying guide and Ratings.

One Duralast Platinum AGM battery in the common group 48 size failed our tough life test at just five weeks; another bit the dust after six weeks. To be sure the failures were't anomalies, we tested a few more Duralast Platinum AGM group 48 batteries. One of those failed in three weeks and another lasted 7 weeks. Based on these results, we will not make the latest group 48 Duralast AGM batteries recommended models in our Ratings.

Four Duralast Platinum AGM group 65 batteries also failed before reaching 12 weeks. That's longer than the group 48 models but still disappointing.

—Jim Travers