Auto Service World
Feature   September 1, 2005   by Auto Service World

Standard Battery Sizes Hiding Changing Power Delivery Ratings

Customers who opt to add accessories that draw more power, such as this show vehicle, should be steered toward battery options that will meet their needs. Other customers may not know just how extreme even standard demands can be.


Following the trend of other electrical components, particularly the alternator, batteries have been put under increasing pressure to increase capacity as a result of increasing electrical loads.

According to battery suppliers, battery capacity continues to increase due to larger engines, more electrical demands and more creature comforts.

The way that vehicle manufacturers have dealt with these increasing demands is not consistent across the board. While some have specified larger battery sizes for their vehicles, others have moved to higher cold cranking amp (CCA) batteries in the same size.

While GM continues to standardize on Group 75 and 78 as their primary batteries, Ford continues to use group 65 as its main OE battery with 650 to 850 CCA. Some new Global Ford vehicles are using a DIN-style battery with recessed post and a lower CCA. DaimlerChrysler continues to use Group 34 in passenger cars, but has continued moving into the Group 65 in Ram trucks. Honda, not surprisingly, has not settled on any given battery option, choosing from among Group 51, 51R, 35, and 24F sizes depending on the application. Following suit, though with less variation, is Toyota, which opts for Group 35 and 24F batteries, except where its luxury line Lexus comes in, where the selected sizes are from Group 24F and 27F.

Batteries are among the more common do-it-yourself items, and for jobbers and their counterpeople this may require employing some communication skills.

A number of battery sizes are available in a variety of CCA ratings. Naturally the lower-rated batteries will be priced at a lower cost and jobbers should make sure that customers do not unwittingly choose a battery with a CCA rating lower than required.

In general terms, however, jobbers can get away with stocking the highest CCA rating for most sizes that will be commonly called for. Those in charge of stock orders should note carefully that some sizes come in CCA ratings beyond the needs of most consumers, however. Stocking only the highest CCA ratings for all sizes may put your offering in a non-competitive position within the marketplace from a price standpoint. If, however, your local market requires significant cold starting capability–extremely cold conditions combined with vehicles being parked outside such as would be the case for vehicles used on worksites–it is important to have them at hand. It is also important to note that older vehicles often require more power for starting than the originally-specified CCA rating may account for. An upgrade is an advisable option.

In addition, batteries with a higher Reserve Capacity (RC) should be recommended where high loads are applied to the battery over an extended period of time. If you have customers who install auxiliary lighting for appearance only or as a work requirement, or customers who have stereo systems designed to wake the dead, counterpeople should be talking to them about RC ratings.

Most consumers will not be aware of this rating as it is rarely noted on the battery, and it may take a bit of explaining, but it is a case of keeping the customer happy and on the road longer.

Ultimately, any customer will be better served by being encouraged to purchase a battery that even slightly exceeds their needs than one that falls short. In the long run, they will not remember the few dollars they saved, but they will never forget it if you sold them a battery that let them down.

Special thanks to East Penn/Power Battery Sales and Exide Technologies for information used in the creation of this article.

Inventory Mix Important for Market Success

Jobbers should ensure they have the right battery size and rating mix on hand and should schedule some time to review that mix at least yearly.

Your battery vendor should be able to provide trend information for the more popular group sizes, as well as which CCA levels to stock, but you may have specific, special circumstances that can cause your ideal mix and quantity to differ. Be prepared to have a proper discussion with the battery vendor’s representative regarding any of these situations as well as any premature battery failures you may have come across.

On the whole, however, this is what the general activity in the marketplace indicates:

* The two most popular group sizes remain the group 75 (small to mid-sized GM engines) and the group 65 (larger Ford engines). However, total volume for both group sizes is now starting to drop.

* The Group 78 (large GM engines and heavy accessory loads) has been growing significantly over the past several years, and total annual volume is now approaching the group 65 levels.

* The group 51R (some Acura, Honda, Hyundai, and Mistubishi models) popularity has been steadily increasing since 1994, and should now be an important part of your inventory mix. However, since 450 is the maximum CCA requirement, you probably only need to stock one rating of this size.

* The group 58R (some Fords and Mazda) had been growing steadily since 1994 until it was discontinued as OE in 1998. Replacement use has peaked and is now starting to trend down. You should only need to stock this battery size at the 580 CCA rating.

* The group 36R (Ford Taurus/Mercury Sable), which was introduced in 1998, has grown to the point where it is now a viable stocking option. It is advisable to stock the 650 CCA rated battery in the group size.

Battery Ratings Provide Selling Points

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?

The CCA number stands for Cold Cranking Amps. This number, which can range from 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 mornings. 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 (BCI) 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 catalogue. 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 deliver 10.5 volts.

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, he should be advised that the higher the CCA number the better, and if he has 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 hook-up. 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 while still maintaining 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.


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1 Comment » for Standard Battery Sizes Hiding Changing Power Delivery Ratings
  1. Lorne says:

    What is the difference between a smaller battery and a larger battery with the same CCA? For Example, the difference between a battery that fits a Chevy Cavalier versus a battery that fits a Ford Explorer. More importantly, can I use that Cavalier battery in an Explorer with good performance, assuming universal posts on the battery.

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