Marine and Boat Battery
Buying Guide

Did you know...
Deep cycle batteries come in both AGM and lithium chemistries.

Deep cycle marine batteries feature a heavy charge and discharge cycle, making them perfect for long-lasting power on fishing boats, kayaks, and any other watercraft using a trolling motor or electric motor.

If you're operating a live well pump, depth finder or fish locator, a deep cycle marine battery generates the reliable, durable energy you need.

Deep cycle, or deep cell batteries are designed with fewer, but thicker plates, which means they can be discharged at a consistent rate for a longer time, at a higher depth of discharge.

It also means they can withstand high temperatures while providing high electrical currents. Deep cycle boat batteries can be drained and recharged many times; starting batteries can't. That's why they're typically used to power electric motors, and other applications, too.

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Dual Purpose

Looking for something that does a little of everything? At the mid-point between starting and deep-cycle batteries you'll find dual purpose batteries.

Dual purpose marine batteries provide the strong starting power you need for your engine, as well as the cycling capacity to keep your accessories running smoothly.

Look no further than the name. If you're looking to save money and space, consider replacing two batteries with one. It'll power your boat's engine and all of your on-board applications at the same time.

Please note that dual purpose batteries are recommended for small-midsize boats that take shorter trips on the water.

Dual purpose batteries, while convenient, don't offer the cranking amps of a dedicated starting battery or the same depth of discharge as a deep cycle battery.

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Starting

Starting batteries provide the fast, strong power you need to take your boating adventures to the top. These batteries are best for powering an inboard/outboard motor, as well as accessories like marine lights and radio communications.

Similar to a car battery, a boat starting battery provides a short, powerful burst of cranking amps to the engine when the key is turned, which then turns over your boat's engine.

The marine starting battery design features a wider surface to accommodate thinner plates, enabling it to provide high currents.

Starting batteries tend to have a relatively low capacity, but that's all they really need to start the boat's engine. And when the engine alternator kicks in, the starting battery is charged back up to its full capacity.

While their wide design is perfect for providing the initial cranking amps, it also limits these batteries' capacity and depth of discharge.

Starting batteries should only be discharged at a small percentage, and shouldn't be counted on to power on-board applications or as a trolling motor battery.

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Often called "wet cell" batteries, flooded batteries use a liquid sulfuric acid electrolyte to fill the case and cover the lead plates. This is where the term "flooded" comes from. Flooded batteries are not as rugged or vibration-resistant as other chemistries and must be mounted vertically to prevent electrolyte spillage. They self-discharge slightly more than other batteries, so you must ensure you charge them periodically in the off-season to keep them healthy.

They offer the lowest initial cost of all the batteries but require routine maintenance to ensure a long life. With proper care, flooded batteries can last several hundred charge cycles.

Every year, more and more boaters are making the switch to AGM batteries to power their boat. AGM, short for Absorbed Glass Mat, batteries use a fine fiberglass mat, tightly packed in between the lead plates and then soaked in a sulfuric acid electrolyte solution. The fiberglass mat provides much more durability than a loose-flowing electrolyte.

AGM batteries have a lower internal resistance, allowing them to provide greater starting power as well as better charge acceptance. They can charge twice as fast as other lead-acid batteries. AGM batteries come in dual-purpose varieties that can handle both starting and deep-cycle operations.

They also feature longer lifespans than flooded batteries, have a lower self-discharge rate in storage and are virtually maintenance-free.

Lithium Iron Phosphate (LiFeO4) batteries are the newest and most advanced marine batteries on the market today. X2 Power LiFePO4 marine batteries are for deep-cycle applications only and are not to be used as starting batteries.

Boasting the highest energy density of all other marine batteries, LiFePO4 batteries pack a tremendous amount of power in a lightweight package. When looking at a BCI Group 24M battery, the AGM version is 57.7 pounds. The lithium? 20.8 lbs. That's a huge weight savings. In addition to the weight savings, lithium batteries have 10x the life of lead-acid batteries, charge 4x faster than AGM and provide the best deep-cycle performance money can buy.

LiFePO4 batteries do have a higher initial cost than most batteries. However, with their long lives, you will no longer have to replace batteries as often, saving money in the long run.