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How Are Car Battery Ratings Determined?

Close-up of a newly installed car battery displaying several signs and symbols

If you’re shopping for a new car battery, replacing the original battery with the same one is the easiest option. But even if you’re just swapping it out with a newer version, it’s important to understand car battery ratings — what they mean and how they make a difference.

Check the Label

Located on top of any new car battery is a label with important information such as battery voltage, the part number and CA, CCA, RC and AH amperage ratings. The first bit of information confirms that the battery has a 12-volt rating, while the part number ensures that the battery fits your vehicle. Digital Meter, TrueBlue Jr. BK 7002601 Each of the four amperage ratings indicates a different but important aspect of battery performance.

1. Cranking Amps (CA)

Cold weather makes it more difficult to start a vehicle. This is most apparent following a hot summer where high temperatures evaporate the battery’s liquid and weaken its charge. The CA rating measures amperage at 32 degrees Fahrenheit for 30 seconds while maintaining a voltage of at least 7.2 volts. This rating is important for owners no matter where they live.

2. Cold Cranking Amps (CCA)

One of the most important battery ratings is cold cranking amps. The CCA measures a battery’s ability to start the vehicle in very cold weather. Specifically, it indicates how many amps a 12-volt battery supplies for 30 seconds at zero degrees Fahrenheit while maintaining a minimum voltage of 7.2 volts. This rating is most important for anyone living in a cold climate.

3. Reserve Capacity (RC)

The reserve capacity (RC) is a time-focused rating measuring amperage in minutes, which means how long the battery will supply 25 amps until the voltage drops below 10.5 amps. This rating is ideal for starting batteries used in passenger vehicles, for marine applications and in deep-cycle batteries (used in golf carts, forklifts, off-grid renewable energy and recreational vehicles).

4. Amp Hour (AH)

Also known as C20, the amp hour measures how much energy is stored in a battery. Specifically, it represents the energy a battery can continuously supply for 20 hours at 80 degrees Fahrenheit without dropping below 10.5 volts. This rating is useful for vehicles equipped with multiple technologies and other energy-drawing features that require a robust battery. The higher the rating, the better.

Manufacturer Recommended

The vehicle manufacturer determines the right battery for new models. However, if you choose a different battery, simply ensure the amperage ratings listed on the current battery are matched or exceeded by the replacement battery. Keep in mind that getting a replacement battery today avoids the hassle of purchasing one when your current battery dies unexpectedly.

Test the Battery

Lastly, perform a regular checkup on your battery to ensure it has a proper charge. Twice annually following summer and winter are ideal times to check. Connect the battery to a voltmeter and look for a reading above 12.4 volts. A lower reading means the battery needs to be replaced immediately.

Check out all of the batteries available on NAPA online or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on car battery ratings, chat with a knowledgeable associate at your local NAPA AUTO PARTS store.

Photo courtesy of Pixabay.

Matthew C. Keegan View All

Matt Keegan has maintained his love for cars ever since his father taught him kicking tires can be one way to uncover a problem with a vehicle’s suspension system. He since moved on to learn a few things about coefficient of drag, G-forces, toe-heel shifting, and how to work the crazy infotainment system in some random weekly driver. Matt is a member of the Washington Automotive Press Association and is a contributor to various print and online media sources.

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