Auto Service World
Feature   September 1, 2002   by Auto Service World

Countertalk For the Counterperson: ASE Parts Specialist Test – Vehicle System Review: Battery Rating Systems

There is a saying in the automotive battery business that summer wounds batteries, but winter kills them. That’s one reason why the first cold snap brings with it a rapid upswing in sales. And with those sales will probably come questions about why one battery costs more than another, has a longer warranty than another, and what those different numbers mean.

Since batteries are still one of the most popular DIY items, it is advisable to know the differences that can exist among batteries that can fit into the same hole. Knowing how to handle questions about quality and longevity are important aspects of dealing with customers, of both the consumer and the trade variety.

If a customer asks you why one battery costs this much and another costs less, you would probably know to begin talking about Cold Cranking Amp ratings, but do you know what these are and how they differ from Cranking Amps? How about Reserve Capacity?

Here’s a brief rundown on how batteries are rated, both in terms of capacity and type.

The CCA number stands for Cold Cranking Amps. This number, which can range from somewhere in the 500s to more than 900, is how much power that battery can deliver at minus 18C. This is what gets you started on those cold winter nights. The number below this one, CA or Cranking Amps, is the power delivered at 0C. This number will always be higher than the CCA rating, so don’t confuse the two. A battery’s ability to supply power is halved by every 10 drop in the temperature. Of course, at colder temperatures you need more power to turn that engine over. When those two demands intersect–the battery’s reduced ability to supply power becomes less than the starter needs to turn the engine over quickly enough–roadside assistance gets the call.

Usually, there are several CCA rated batteries available for a given Battery Council International (B.C.I.) Group Size (e.g. 41).

The third number is Reserve Capacity (RC). This may not be on the battery but it should be in your supplier’s catalog. This number is particularly important for anyone who may have a large accessory power drain on their vehicle. This could be extra lights or a large stereo that can increase the demand on the battery substantially. Reserve Capacity is the number of minutes that a fully charged battery at 80F can be continually discharged at a 25 ampere load (this is substantial) and still maintain a voltage of 10.5.

While that last number may not be too critical for the everyday user, it is important for the car owner who needs more power. So, if a customer is in the market for a battery, they should be advised that the higher the CCA number the better and, if they have a large stereo or accessory lights system, to opt for more Reserve Capacity.

Marine Batteries are required to withstand special conditions, such as the jarring associated with boating, and are constructed to include an accessory hookup. Another number used on marine batteries is Marine Cranking Amps (MCA). This is similar to the CA rating but is a rating of the discharged load (in amperes) for a new fully-charged battery at 80F for 30 seconds and still maintain a voltage of 1.2 volts per cell or higher. Usually, the cranking power of a marine starting battery is lower than that of automotive batteries.

Marine Deep Cycle batteries must undergo severe discharge before being recharged. Often these batteries are specified in Amp Hours (AH) rather than RC.

You may not be selling too many marine batteries over the winter, of course, but the last few months of the boating season subject them to the same drop in temperature that automotive batteries do, so you should be aware of this potential demand.

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