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How to Pick the Best Battery for Your Boat

Power - by Bryan Veldboom - updated on 5/22/2020

2 children looking out of the back of a red boat

Summer is made for boating. Whether you can’t get enough of fishing, or just love racing along on the waves, boats allow you to make the most of the season. Before you head out onto the open water though, it’s important to determine the best marine battery for your needs.

Boat Battery Basics

Let’s start with the basics. There are three marine battery types: starter, deep cycle and dual-purpose. Starter batteries (also known as cranking batteries) are designed to deliver short bursts of power like what is needed to start your inboard or outboard engine. A deep cycle battery, on the other hand, is designed to provide a continuous source of power over a longer period of time. They are ideal for trolling motors, or for powering depth finders, sonar and other boat accessories. A dual purpose marine battery splits the different, by doing a little bit of everything. They offer the initial burst of power you need to start an engine, while providing the sustained power needed to operate your accessories.

So which battery is right for you? That depends entirely on your needs. Start off by asking a few basic questions. How powerful is your motor? Do you need additional power for things like radios, running lights, sonar or fish locators?

If you’re using a smaller boat with minimal accessories, you may be able to get away with just a single starting battery. Larger motors and boats with multiple accessories, however, will require more power. That may mean using both a starting and deep cycle battery together, or opting for a dual purpose battery. Check out the chart below for help determining your boat battery power needs.

Starting Power

  • Moderate Needs Motors of 100 horsepower or less
  • Heavy Needs Motors greater than 100 horsepower

Deep Cycle

  • Moderate Needs Radio, sonar, fish locator, running lights, etc.
  • Heavy Needs Trolling motor, refrigerator, portable tvs, inverters, multiple low drain devices, etc.

Which type of battery will be able to adequately handle your specific power needs?

Starting Needs Deep Cycle Needs Starting Battery Deep Cycle Battery Dual Purpose Battery Dual Purpose AGM Battery
Moderate None x x x
Moderate Moderate x x x
Moderate Heavy x
Heavy None x x x
Heavy Moderate x
Heavy Heavy x x

Flooded vs Sealed Batteries

Okay, let’s talk chemistry. Boats run on lead acid batteries. There are two separate types of lead acid options, flooded and sealed. This is true for starting, deep cycle and dual-purpose types. Lead acid batteries have lead plates inside them along with an electrolyte liquid made of water and sulfuric acid. Flooded batteries are your most affordable option, however, they require you to regularly add distilled or deionized water in order to protect the lead plates from deterioration.

The Duracell Group 31 12 volt Deep Cycle Marine Battery is perfect for deep cycling applications like trolling motors, GPS systems and radios. For starting batteries, we suggest the Duracell Ultra BCI Group 24M High CCA Starting Marine Battery. This flooded battery provides a starting power of 800 CCA (Cold Cranking Amps), making it ideal for larger engines.

Sealed batteries, as their name implies, are completely sealed off. They require no maintenance whatsoever and are both maintenance-free and spill proof. The oxygen produced on the positive plates of these batteries is absorbed by the negative plates, which, in turn, produce water. Because of this, the owner doesn’t have to add water to these batteries. The most effective type of sealed marine batteries are AGM types.

An AGM (Absorbed Glass Mat) battery uses a special glass mat to absorb the electrolyte between the battery plates. The thin plates create high reserve capacity, enabling it to run more accessories, while the pure calcium makeup of the plates offers increased cranking power and a longer battery life. In addition, AGM batteries are resistant to vibration and stand up well to extreme temperatures, both of which you’re likely to encounter on a boat. Plus, AGM batteries are easy to install, easy to charge and recharge at a faster rate.

The Duracell Ultra Platinum AGM BCI Group 24M Dual Purpose Battery combines strong starting power with a deep cycle capacity of 78Ah (amp hours). The Group 24 AGM 12 volt Dual Purpose Battery from X2Power is another great AGM dual purpose option, providing 76Ah of deep cycling capacity, along with high starting power.

Regardless of the type of battery you decide on, it’s important that you use only one type of battery chemistry (flooded or AGM) for all of the batteries on your boat. Each battery type requires specific charging voltages and mixing different battery types can result in under- or overcharging, both of which can be fatal to your battery.

As you can see, batteries play a crucial role in your boat’s performance. A little forethought can help prevent you from being stranded and provide you with a worry-free day on the water. If you have questions, the associates at your neighborhood Batteries Plus Bulbs will be happy to help, or shop our selection of marine batteries online.