Auto Service World
Feature   September 1, 2003   by Auto Service World

ASE Parts Specialist Test Preparation: Batteries and Battery Rating Systems

While it has become more complex to some degree, the starting and charging system on today’s cars is probably the least changed of the systems located under the hood since the days when the starting power came courtesy of the driver’s forearm and a hand crank.

The Starting System Circuit is made up of the starter motor and solenoid assembly — whether together or separate, the battery, the starter or ignition switch, and the wiring that connects it all.

The lead-acid Battery is the keystone component of the starting system. It provides the all-important stored electrical energy to start the engine. Until such time as automotive systems move to a higher voltage standard–36 volt or 48 volt–the conventional battery will continue to be the “12 volt” battery. Actually, it is a 12.6-volt battery, since each automotive starting battery is made up of six cells generating 2.1 volts each. Bathed in an acid bath, they are linked in series to provide the customary voltage. The number of plates in each of these cells helps determine the total amps that the battery can provide at this voltage; the more plates, the more amps. As these become damaged, the ability of the battery to provide its rated amperage diminishes, even though it may still maintain 12.6 volts.

It is a general misconception that cold weather damages batteries, but it is really heat. The reason they so often fail in winter is the increased demand that cold-weather cranking places on a battery. An old saying in the battery business says that summer weakens a battery, winter kills it.

As temperatures decline, battery output declines with it. At the same time, the energy required to wind the starter and turn over the engine can increase-particularly on cars in less-than-perfect condition.

Everybody has long recognized this in the battery business, and it is why a standard method of measuring battery output was devised years ago. Actually, there are several methods of measuring battery performance, which could lend to some confusion if you aren’t fluent in the language of battery rating systems.

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 Cold Cranking Amps, or CCA, number can range from somewhere in the 500s to more than 900, and 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 the ability of the battery to supply power is exceeded by the needs of the starter to turn over the engine 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 his vehicle. This could be accessory 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 the RC 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 cool mornings during the last few months of the recreational boating season can subject them to the same drop in temperature that automotive batteries experience, so you should be aware of this potential demand. And it is always wise to remember that there is no roadside assistance in the middle of a lake.

Back on dry land, higher underhood temperatures, alternators designed to keep a battery charged only if it is in good order, and more demand from electrical accessories place increasingly high loads on the trusty lead-acid battery.

Overall, batteries are under a greater demand these days than ever, so quality should be high on your list of selling features. And you should avoid selling battery options that do not fulfil the specific demands of the vehicle, lest your customer come back to lodge a complaint–on foot.

Sample Questions

1) A customer comes into your store looking for a new battery for his car. You offer two options for this customer’s vehicle. Battery A is a 60-month battery with a price of $85. Battery B is a 40-month battery with a price of $65. Which battery would offer the best value, and what is the cost per month?

A) Battery A, the 60-month battery, cost $1.41 per month.

B) Battery A, 60-month battery, cost $1.56 per month.

C) Battery B, the 40-month battery, cost $0.60 per month.

D) Battery B, the 40-month battery, cost $1.60 per month.

2) Using the same example as above, if Battery A, the 60-month battery, generated a 25% margin, and Battery B, the 40-month battery, had a 50% markup, which would generate a higher profit and what would it be?

A) Battery A, profit $21.25

B) Battery B, profit $21.75

C) Battery A, profit $22.50

D) Battery B, profit $32.50

3) A young customer comes into your store and orders a high-output alternator. Parts Specialist A says that you should tell him to make sure his battery is charged. Parts Specialist B says that you should ask him about his stereo. Who is correct?

A) Parts Specialist A only

B) Parts Specialist B only

C) Both Parts Specialist A and B

D) Neither Parts Specialist A nor B

4) All of the following are true about battery ratings, EXCEPT:

A) CCA and CA both measure battery output.

B) RC and MCA are similar ratings.

C) CCA is always lower than CA.

D) Marine batteries are measured in Amp Hours.

5) Parts Specialist A says that batteries can last indefinitely as long as the alternator keeps it charged. Parts Specialist B says that maintenance-free type batteries are completely sealed units. Who is correct?

A) Parts Specialist A only

B) Parts Specialist B only

C) Both Parts Specialist A and B

D) Neither Parts Specialist A nor B

Answers: 1) A; 2) B; 3) C; 4) B; 5) D.

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