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How to Tell What Kind of Marine Battery You Have?

to identify marine battery you have

Visions of exciting boating adventures are dancing in your head, and there is one thing you are certain of: you want a dependable marine battery that will help to make those adventures happen.

As with any marine product, you know that marine batteries are not all the same.

There are different types of marine batteries, each of which is ideal for a particular use. Once you have decided what aspect is most important to you, you can select the best one for your needs. 

If you already have a marine battery, you will want to know what kind it is. That way, you can know its advantages.

So, let’s take a look at the different marine battery types and see how you can determine which type your battery is.

Marine Battery Categories

Choosing the Right Marine Battery | ACDelco Garage

There are two basic categories of marine batteries: starting and deep-cycle.

The first category is starting batteries . Starting batteries are used to get the engine started, similar to your car battery. Once the engine starts, the starting battery yields to its friend, the alternator. The alternator takes over and keeps the boat engine going.

So, the job of the starting battery is simply to create a big push to get the engine going. Then it rests until the time comes to start the engine again.

The starting battery has thin plates. These plates are kept inside of an electrolyte, which allows electrical current to flow within the battery. High amperages are output very quickly.

It is this quick output of high amperage that produces the spark that jolts the battery to start the engine. Then you are free to shove off, enjoy your day and load your tub with bass, marlin, trout, or whatever else you find.

But let’s say your boat has a lot of devices that need power. You may have lights, a radio, a television and other devices. How can you keep them going if your battery stops putting out power once the engine is started?

VMAX MR127 12 Volt 100Ah AGM Deep Cycle Maintenance Free Battery

That is where the second marine battery category, deep cycle batteries , come in.

Deep cycle batteries are thicker than starting batteries. They can discharge half-way and still bounce back for further use. They produce electricity steadily for a long time. 

While a deep cycle battery is more powerful, a starting battery does have advantages. A starting battery is normally lower priced. And, since deep cycle batteries do not produce a large burst of power, they are much less successful for starting engines. 

Ideally, it is wise to have both. A starting battery will get you going and get you back home, and a deep cycle battery will keep all of your devices powered.

That way, your fishing excursion will be more enjoyable and carefree.

Marine Battery Types 

Within these categories, there are four marine battery types. Since each type has its advantages, it is best to determine what is most important to you when choosing your battery.

1. Flooded Marine Batteries

Marine Battery Replaces D27M 8027-127 Group 27

Flooded marine batteries use liquid sulfuric acid. When a flooded battery is charging, it releases hydrogen and oxygen. A vent in the battery allows the gases to get out. It is important to keep an eye on a flooded battery to be sure it has enough distilled water.

A drawback is that flooded batteries can not handle a lot of vibration. This creates a challenge when you are boating at high speeds. You must also be careful when dealing with wake.

Still, if you want a battery that can handle overcharge, the flooded battery is the best choice.

2. Gel Batteries

Neptune 12V 100AH Rechargeable Deep Cycle Hybrid GEL Battery

The second type of marine batteries are gel batteries. These combine sulfuric acid, fumed silica, pure water and phosphoric acid. The resulting gel is how this battery gets its name. 

The biggest advantage of gel batteries is they are not prone to leaking. The gel provides a wall to protect the battery from seepage.

So, like the flooded batteries, you can enjoy your outing without having to constantly monitor your battery. That way, you can relax and search for a hot spot.

3. AGM Batteries

VMAX MR137-120 12V 120Ah AGM Deep Cycle Marine Battery

The third type of marine battery is the Absorbed Glass Mat, or AGM, battery. This battery uses pressure valves to push oxygen from the positive to the negative plate. The oxygen then combines with hydrogen to create water.

AGM batteries have many advantages.

They need very little maintenance, they’re great for starting, and they recharge well. One of its biggest advantages is that it handles vibrations flawlessly. This makes it a favorite of many boaters.

So if you plan on heading for rough waters, you may wish to consider using an AGM.

4. Lithium Batteries

12V Battery, HWE 12V 100Ah Lithium Battery

The most popular marine battery may be lithium batteries. They are lightweight, making them easy to install. They offer the most charge to discharge cycles, and they can handle discharge at eighty to one-hundred percent and bounce back without a problem.

Although lithium batteries are typically the highest priced, they are usually the longest lasting marine battery. Most importantly, water does not affect it, so splashing and rain are not a concern.

Which Marine Battery Type Do You Have?

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If you already have a marine battery, how can you tell which type you have?

Flooded batteries are easy to identify. If your battery was inexpensive, the chances are that you have a flooded battery.

Flooded batteries also require a lot of maintenance. If you need to check the water level often, it is probably a flooded battery.

If it needs charging even without use, that is an excellent clue as well. But the easiest way to identify a flooded battery is to check to see if it has lead plates. 

Identifying an AGM battery is slightly more difficult, but there are some sure fire identifiers.

Check the instructions to see if venting is emphasized, as all AGM batteries must be vented. Look for mats that are squeezed between two plates. It will resemble a sandwich. This is the most visible physical characteristic. AGM batteries are often block shaped, as well.

Lithium batteries also have common traits. If your battery charges quickly, it is most likely a lithium battery. Most lithium batteries top off in charge in a couple of hours.

If the instructions mention a BMS, or Battery Monitoring System, it could be a lithium battery. A BMS system is necessary to protect the battery from overcharging. This is critical to maintaining a lithium battery.

Endurance is the hallmark of a gel battery. If you have been able to charge your battery hundreds of times, you probably have a gel battery.

If you are still not certain which marine battery you have, look at the sticker on the battery. Look for designations such as “Gel Deep Cycle,” or simply “Lithium.” If the name on the label does not clearly identify the type, read the fine print, as well. 

12V 18AH Gel Deep Cycle Battery ExpertPower

If you are still unsure, you can simply uninstall the battery and take it to a Marine store. The customer service representative will be happy to identify the battery type for you.

Knowing your marine battery type is as important as knowing the type of boat that you have. That way, you can properly care for the battery and have confidence that you will be able to get back to the dock safely.


There are four types of marine batteries. These include the flooded, gel, AGM, and lithium batteries.

If you are concerned about battery overcharge, consider the flooded battery. If you need a battery that won’t die out due to constant charging, the gel battery is a wise selection.

If you want your battery to charge fast, the Absorbed Glass Mat, or AGM battery, is ideal.

If you want maximum battery life, and you don’t mind paying a higher price, the lithium battery is a great choice.

Whichever marine battery you choose, you can identify it by examining its shape, reading its label, or by checking with a marine store representative.

So choose your marine battery wisely, and enjoy your boating adventures!