Car Battery vs Marine Battery: What Are The Differences?

Posted by David Lee

Last Updated February 1, 2023

While car and marine batteries have some basic functionality in common, there are many differences you should know when deciding on a car battery vs marine battery.

Cranking vs Multipurpose Usage

The largest difference between these two batteries is their basic purpose.

A car battery is used to start the engine. After the engine is running smoothly, the battery is not used for much else. The engine is responsible for charging the battery and all of the other electrical components.

A car battery is used only to start or “crank” the engine. It is similar to a lighter’s spark in that it does one job and only that job.

In comparison, a marine battery has much larger tasks to manage, as it outputs was the initial spark of energy and then continues providing power to other needed components on the boat.

This constant energy is output in small amounts so no damage will happen to the appliances on the boat. If the first jolt of power used to start the engine were used instead, most of the appliances would be destroyed.

The constant output of energy given by a marine battery is called a deep cycle. Unlike a lighter’s spark, a marine battery is like our heartbeats, continuously pumping blood throughout our bodies.

Discharge Measurements for Car Batteries and Marine Batteries

Multipurpose batteries are common for boats as they need to rely on the battery for starting and maintaining power. Different measurements must be used for each type of battery.

To determine the highest discharge for a marine or car battery, automotive experts use “cold cranking amps” (CCA) as their unit of measurement. The higher this number is, the more powerful the marine or car battery is. More power offers a greater likelihood that it can start the engine.

Marine batteries are rated in CCAs, amp hours (Ah), and “marine cranking amps.” To ensure the battery is discharging enough energy over time, amp hours are measured over a 20-hour period. A good marine battery will reach 10.5 volts over 20 hours when the temperature is 80F.

Marine cranking amps are used to determine the maximum discharge when temperatures reach freezing levels 32F.

It is recommended to check your marine battery’s discharge rate before going into the water to ensure it will provide enough power during hot and cold weather.

Variations in Design

Car batteries have thin plates inside because they do not need to discharge energy over a period of time. After their one-time starting jolt, they remain inactive.

Marine batteries, on the other hand, have thicker plates so they can safely provide different discharge amounts. Besides, the battery’s housing area is usually made of thick plastic so it can withstand vibrations and possible impacts. This helps the battery last longer and saves money because fewer replacements are needed.

Should You Use A Car Battery In Your Boat?

No. Car and marine batteries are specifically made to support either a car or a boat. While a marine battery can be expensive, it is better to think of it as an investment in the health of your boat.

These are some of the differences you should consider when choosing a car battery vs a marine battery.

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