All auto batteries aren't created equal, according to test results recently published by Consumer Reports magazine. In fact, the longest-lived batteries lasted nine times as long as those that failed early in comparative tests, the publication reported in its October 2002 issue.
CR said the Sears Roebuck and Co.'s Diehard batteries lived up to their name by consistently delivering longer service across most of the battery sizes tested.
Shortest lived were the size-35 Champion and Duralast Gold models designed for smaller vehicles. Not surprisingly, larger batteries tended to outlast smaller ones over all.
The publication evaluated 34 batteries in five group sizes for cars and light trucks, namely group sizes 75, 65, 35, 34 and 34/78. Because some brands sell northern and southern variations for cooler and warmer climates, CR said it tested both models when available.
Testers placed the batteries in water heated to 167 degrees Fahrenheit to approximate the underhood environment of a typical vehicle. They then cycled the batteries back and forth between four minutes of 25-amp discharging and 10 minutes of 25-amp recharging for a period of 100 hours to simulate the demands of stop-and-go driving.
After a 60-hour rest, the batteries then were checked to determine whether they delivered their rated cold-cranking amps for 30 seconds at 167 degrees. Those units whose output fell below 7.2 volts-an industry standard-were considered to have failed.
Batteries also were tested for reserve capacity, the length of time a fully charged battery can run the vehicle's electrical system. Reserve capacity ranged from 60 to 147 minutes among the units tested, with batteries in the larger-sized, group-65 and -75 batteries demonstrating the greatest capacity. However, even the 60-minute reserve capacity of the smaller batteries tested ought to be sufficient to allow most passenger cars to reach the nearest service outlet, the magazine said.
Likewise, those batteries with even the lowest listed cold cranking amps (CCA) should start most vehicles during frigid weather. For that reason, ``buying more CCA than specified for your vehicle is a waste of money and can result in shorter battery life,'' the publication advised.
CR said that among group size 75 batteries, which fit most four- and six-cylinder General Motors Corp. vehicles, the Diehard WeatherHandler (South) 30375, priced at $60, offers ``lots of reserve capacity'' while achieving the highest overall life-test score.
Also worth considering, the publication said, is the NAPA Legend 75 Professional Line 7575, priced at $60, which scored lower in the life test but higher for CCA and reserve capacity,
Among group size 65 batteries which fit most large six- and eight-cylinder Ford Motor Co. vehicles, the Sears' Diehard Gold (South) 33165, at $80, was recommended for use in warmer climates and the Exide NASCAR Select 65-84N, at $90, for cooler areas of the country.
Few among the group size 35 batteries (mostly for newer Hondas, Nissans and Toyotas), fared well in the life-expectancy test, CR said. However, the top-rated Sears Diehard WeatherHandler (South) 30335, at $60, and the Exide NASCAR Select 35-84N, at $80, offered good balance of life-test and other performance features, CR said.
Sears Diehard WeatherHandler North (30034) and South (30334) were the only two models tested in size 34 which fits most DaimlerChrysler-made vehicles. Both did well in all three key performance areas, CR said.
The publication said southern motorists also can obtain similar overall performance with a top-scoring 34/78-sized battery that will fit the same vehicles. Batteries in the 34/78 size group have both top- and side-mounted terminals and can replace size-34 batteries in Chrysler and size-78 batteries in GM vehicles.
Top-rated models in that category included the Motorcraft Test Tough Max BXT-3478 at $80, Optima Red Top 34/78-1050 at $140, Duralast Gold (North) 34DT-DGN, at $75, and the NAPA 75XDT800 at $100.
Most automotive batteries in North America are produced by just three manufacturers. Delphi Corp. makes General Motors' ACDelco brand and some EverStart batteries (sold by Wal-Mart Stores Inc.). Exide Technologies produces Exide, Champion, NAPA and some EverStart brand batteries. Johnson Controls Inc. makes Sears' Diehard, Duralast (sold by AutoZone Inc.), Interstate, Costco Wholesale Corp.'s Kirkland, Ford Motor Co.'s Motorcraft and some EverStart models, the publication said.