Don't freeze out your car battery

Modern electrical and fuel systems can start a car with minimal cranking, so you might not know that your battery needs replacing until it's too late.

That's why Consumer Reports recommends having your car's battery tested annually by a qualified mechanic as part of regular maintenance, when it's 2 years old if you live in a warmer climate or 4 years old if you're in a colder climate. Hot temperatures tax batteries more than cold weather, but a battery weakened by summer's heat is more likely to fail once freezing weather arrives.

And with winter just around the corner, now is the time to have your car's battery checked. Not only is it inconvenient and potentially dangerous to be stranded in freezing weather, but an emergency is no time to shop for the best replacement battery or the best price.

Highlights from CR's testing

CR tested the latest car batteries and included 60 batteries in its ratings, including seven CR Best Buys. Here are some of its findings:

* Walmart's EverStart batteries are very good overall choices; prices are low and performance rivals that of CR's top scorers.

* Bosch batteries, which CR tested for the first time, are now tops in two of the group sizes in which they were tested. They're sold exclusively through Pep Boys stores.

* Some absorbed glass-mat, or AGM, batteries are top performers. But they can be twice the cost of competitive conventional models and might not be worth the money for most buyers.

A battery's service life is the most important consideration, CR believes, so the ratings put more weight on life-test results than reserve capacity and cold-cranking performance. For cold-weather climates, CR's recommendations include the Kirkland Signature 12866, $75, a CR Best Buy; the EverStart Maxx-65N (North), $75; and the NAPA Legend Premium 8434/78, $95. For more temperate climates, recommendations include the Kirkland Signature 12866, $75, a CR Best Buy; the EverStart Maxx-65S (South), $75; and the Autocraft Titanium 34/78-4, $85, a CR Best Buy.

How to choose

First check your car's owner's manual or an in-store fit guide to determine the size you need and whether your battery uses top- or side-mounted terminals. The wrong size might not fit securely or provide sufficient power to start your car, and battery cables might not reach if the terminals are in the wrong place. Next consider the factors below and check CR's ratings for the battery that best meets your needs and budget.

* Consider maintenance. You don't have to check electrolyte levels or occasionally add distilled water with maintenance-free batteries. Many of them are sealed. Some non-AGM models are maintenance free and offer comparable performance but don't cost any more than models that require maintenance.

* Consider your climate. Choose a battery that scored well in CR's life testing, particularly if you make a lot of short trips, which doesn't allow much time for your electrical system to recharge the battery. Extreme hot and cold climates are also tough on battery life. High temperatures increase corrosion of plates and vaporize the electrolyte faster. Cold temperatures sap a battery's energy and thicken motor oil, making it harder for the engine to turn over.

* A handle comes in handy. An attached plastic loop eases carrying and lifting. Because the average weight of CR's tested batteries is 40 pounds, this helps if you install or remove the battery yourself.

* Fresh is best. All batteries lose their strength over time, even new models that are just sitting on a shelf. Look for one that's no more than six months old.

* Dispose of your old battery safely. Batteries contain toxic lead and acid, but can be easily recycled. Some retailers will install a new battery free and dispose of the old one for you, but other outlets charge for the services. Check before you buy.

Visit the Consumer Reports website at www.consumerreports.org.