Rick's Free Auto Repair Advice

Cranking amps

What’s the definition of cranking amps?

Battery ratings require time and temperature standards

To properly rate a battery’s jumping ability, you have to test it at an industry defined temperature, for an industry defined time period, with an industry defined maximum drop in voltage. Here’s the definition of cranking amps:

Cranking amps definition

Cranking amps (CA) refers to the number of amps a battery can output at 32°F (0°C) for 30-seconds while still maintaining at least 7.2 volts. The reason cranking amps is more important than peak amps is that people usually use a jumper pack to start their car in cold weather. Batteries produce power through a chemical reaction and that reaction slows when it’s cold. So you want a rating that’s based on a set temperature, which peak amps don’t have.

In addition to temperature, you also want to know how long a battery can output the specified number of amps. Think about, what good is a battery that puts out more amps but for such a short period of time that it can’t start your engine.  Finally, when the battery voltage drops below a certain point, it can no longer operate the starter motor. That’s why cranking amps cover total amp output at a set temperature, for a set period of time, all while maintaining a voltage above a set minimum.

Cold cranking amps (CCA) is like CA except that the rating is based on amperage output at 0°F (-17.8°C).

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Posted on by Rick Muscoplat


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