Cranked Up: How Battery Cranking Amps Are Calculated And Used

An ignition system requires power from a battery to do its job, but do you know about the cranking amps the battery produces to help start the engine? You’ll see a lot of numbers thrown around when it comes to cranking amps, but this rating is more than just a number.

The measurement of cranking amps is defined by the Battery Council International (BCI) so battery manufacturers can apply a specific number based on the outcome of a test. Jim Mcllvaine from OPTIMA Batteries explains how this test works.

“In the test for cranking amps, the BCI puts a battery in a somewhat cold environment, 32°F, and measures the discharge load in amperes that a new, fully-charged battery can deliver for 30 seconds, while still maintaining terminal voltage equal to or higher than 1.20 volts per cell. The results allow consumers to make an apples-to-apples comparison of the performance of various battery options relative to these standardized measurements.”

When vehicles come from the manufacturer, they have a battery installed that provides enough cranking amps for the OEM engine. The battery requirements are determined by engineers, based on what electronics the vehicle uses, and how much power is needed to start the engine. High-performance engines have a different set of needs based on how they’re built to crank over.

“While specifications like cranking amps and cold cranking amps are measured at relatively cold temperatures (32°F and 0°F, respectively) that many high-performance engines will not encounter, there are a variety of factors that make it harder to start an engine, and colder temperatures are definitely one of those factors. Thicker oil, higher compression engines (especially diesel engines, which often use two batteries), larger cylinders, and other factors all require more energy to get these engines started,” Mcllvaine states.

You can get lost in a hurry shopping for batteries to fire up your high-performance engine — OPTIMA offers several different battery types that will work for just about every application under the sun.

“OPTIMA batteries offer the REDTOP, YELLOWTOP, and even BLUETOP batteries that people could use for a high-horsepower engine. We’ll use the group 34 battery as an example to explain the differences. The Group 34 REDTOP weighs just under 38 pounds and offers 1,000 cranking amps, but is not designed or warrantied for deep-cycle use, so it should not be run in an application with significant electrical accessories, underdrive pulleys, or no charging system. The Group 34 YELLOWTOP weighs just under 43 pounds and offers 870 cranking camps, but is designed and warrantied for deep-cycle use. We also have BLUETOP versions of those batteries (34M & D34M, respectively) that are slightly heavier, but also have additional threaded top post terminals,” Mcllvaine says.

If you’re looking for a battery or want to learn more about what will work for your specific application make sure you check out OPTIMA’s website right here.

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About the author

Brian Wagner

Spending his childhood at different race tracks around Ohio with his family’s 1967 Nova, Brian developed a true love for drag racing. When Brian is not writing, you can find him at the track as a crew chief, doing freelance photography, or beating on his nitrous-fed 2000 Trans Am.
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