what battery rating to buy??

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This might help.  It's the first part of the consumer reports auto battery tests.  The link is the actual test results. 10/2006

Auto batteries: price doesn't equal performance.(SPECIAL AUTO SECTION)(Buyers guide)

COPYRIGHT 2006 Consumers Union of the United States, Inc.

Auto batteries may look identical to you, but under the hood they can perform quite differently from one another.And our tests show that some of the best performers aren't necessarily the more expensive batteries.

With many auto parts stores and bigbox retailers now in the battery business, a great variety is available. Most offer batteries at various prices, with different promises of power and life expectancy. However, most replacement batteries are manufactured by just three different companies: Exide, Johnson Controls, and East Penn, which build them to retailer specifications.

Only one of the 62 batteries we tested rated excellent overall in the Ratings. And even other sizes in that model line didn't earn those high marks. Our tests included sizes that fit many passenger vehicles. Prices ranged from $40 to $100.

Longer life is critical if you take many short trips or do most of your driving in warmer climates. Short trips shorten battery life by not affording a lot of time for the alternator to recharge the battery. High temperatures can also increase oxidation of components and vaporize the electrolyte needed to create current.

Our battery-life test mimics those tough conditions by measuring how many 100-hour drain-and-recharge cycles batteries can handle before their cranking voltage falls below industry standards. Models that excelled in this test endured seven or more of those cycles; the worst performers endured less than two.

HOW TO CHOOSE

You'll find many capable batteries within the five group sizes we tested. Together, they cover many of the foreign and domestic cars and light trucks on the road. See First Things First, below, to determine the correct battery size for your vehicle.Then keep these points in mind:

Fresh is best. Batteries lose strength just sitting on a store shelf. Most are labeled with a shipping-date code. When shopping, look for a month code indicated by a letter ("A" for January, for example) and year ("6" for 2006). It's best to choose a battery no more than six months old.

Insist on real-world performance. Cold-cranking amps (CCAs) are important, especially for those living in cold regions. CCAs are a measure of how much power a battery has at 0[degrees] F, when thickened engine oil makes an engine hardest to start and available battery power drops significantly. Generally, the higher the CCA rating, the greater the starting power of the battery regardless of temperature. In our tests, where batteries are charged at lower, more realistic voltage, we've found that few meet their cold-cranking claims. Only one new model provided the full 30 seconds of cranking power required by our CCA test this year, a decline from last year, when six passed.

Consider manufacturers' CCA claims only as a rough guide, then choose a battery that performed well in our CCA tests.

Also look for a score of good or better in our life and reserve-capacity tests. A battery's reserve capacity indicates how long it will power your car if the charging system fails or if the lights are left on when the engine is off. The models we tested with the best reserve capacity provided power for 120 to 150 minutes, but even models with the shortest reserve, 60 to 90 minutes, should provide sufficient power to get you to safety or start your car.

Pick the best warranty. Other numbers printed on the battery indicate warranty information. A code such as 24/84, for example, indicates a free-replacement period of 24 months and a prorated warranty of 84 months. It's best to pick one with the longest free-replacement period available because the amount of reimbursement in the prorated period usually drops off quickly as the battery ages.

Choose the right battery for your climate. Chilling cold isn't the hardest environment for batteries; hot temperatures actually cause more damage. While starting in frigid climates can be tough on a battery, heat saps more...
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