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Marine Battery vs. Car Battery: What Are the Differences?

Know the differences between a marine battery and a car battery so that you can boat safely.

The “marine battery versus car battery” discussion is one that’s been had by anyone shopping for a battery for their boat. Being tempted by the easily available automotive power units is only natural, but it’s important to understand that there are key differences between the two that can have a significant impact on their utility.

Let’s take a look at why marine and car batteries are in two different sections of the store.

Different Tasks

When examining these two types of batteries, it helps to understand the fundamental role each plays in its respective electrical ecosystem.

Car batteries play a very specific role: Provide enough amperage to turn over a gasoline or diesel engine, regardless of how high or low temperatures outside might be. This means that these batteries are designed to discharge big amps in a short period of time, and then to let the vehicle’s alternator charge them back up again.Three small boats tied to a dock

Marine batteries, however, are asked to perform a more diverse set of tasks. While yes, they are often required to start engines (albeit typically smaller ones than those in the average automobile), their job continues after firing things up. These batteries need to provide enough juice to keep the lights running, the gauges functioning and any pumps or other boat accessories fully operational. This means that they must offer a long draw-down on power before emptying out.

Behind the Scenes

The designs of marine and car batteries reflect this key difference in mission statement. Marine units feature thicker internal lead plates than their automotive counterparts, which allow them to discharge energy over a longer period of time. Their housings are also typically larger than an equivalent car battery, with extra plastic protection because boating environments aren’t nearly as smooth as on-road driving.

Finally, you can identify a marine battery by its use of “marine cranking amps,” or MCA rating, instead of the standard automotive “cold cranking amps” (CCA). Boat batteries have their MCA capability tested right at the freezing point, rather than below it as for CCA, because it’s rare that a pleasure boat will be out fording icy waters.

Keep the above differences in mind, and avoid the temptation to choose an automotive battery instead of a marine battery for your boat. Using the right one means you’ll be safe and sound out on the lake, all season long.

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 the marine battery, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

Photo courtesy of Flickr.


Benjamin Hunting View All

Having been bitten by the car bug at a young age, I spent my formative years surrounded by Studebakers at car shows across Quebec and the northeastern United States. Over ten years of racing, restoring, and obsessing over automobiles lead me to balance science writing and automotive journalism full time.  I currently contribute as an editor to several online and print automotive publications, and I also write and consult for the pharmaceutical and medical device industry.

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