By: Olivia Hudak on February 4th, 2022

Boat Batteries 101: Expert Info Every Boater Needs to Know

Growing up around boats I learned a lot about how they work. A big part of that was learning how to check different functions on the boat to make sure it was operating in tip-top condition. I also learned all about boater’s safety and how to properly drive a boat.

Knowing how to operate a boat and how to drive a boat is one thing, but up until recently I didn’t put much time or effort into learning more about the battery.  Of course, I’ve always known batteries are important as they make the boat run, but I didn’t truly understand the extent of their purpose. I also learned how problematic it can be if you don’t know how to properly maintain them. 

Since I joined the team at Barletta, my eyes were opened to the importance of knowing everything there is to know about boat batteries. I decided to make it easily accessible for everyone by educating myself and putting the info into this article. By the time you finish reading, you will have information on boat batteries that you didn’t even know you needed, but you’ll be glad you have.

What Role does a Boat Battery Play? 

I’ll start by going over exactly what a boat battery is. To explain this in the best way possible, think of a battery as the heart of the boat. That’s because it powers all the functions needed to operate a boat. 

The most important function is that the battery ignites the engine and allows it to start. Equally important, the battery powers all of the electronics inside and outside of the vessel. 

With most boats, there is a wide range of electronics on board, so what all does this include? Components such as lights, the GPS system, fish finder, radio, and any other electrical accessories are all powered by the battery.

Between firing up the engine and running all of the electronics on board, you can see why it is crucial to have a strong and well maintained battery

Different Battery Types 

To understand more about the heart of your boat, you must first know what kind of battery you have, how many batteries your boat needs, and how to maintain the specific type of battery that’s called for. 

There are three different types of batteries which are; cranking, dual-purpose, and deep-cycle batteries.

Cranking batteries are typically what I think of when I think of boat batteries. They are also referred to as starting batteries. Can you guess why they are called that? You probably guessed correctly…they start the boat.

These batteries are similar to the kind of battery you would find in a car. Their sole purpose is to start the engine. Now moving on to dual-purpose batteries. These batteries have two main functions. The functions include starting the engine and powering a small electrical load.

A small electrical load refers to electronics such as the navigation lights on a boat. It must be something that doesn’t draw a ton of electrical power.

Moving on to the last type of boat battery. This is a deep-cycle battery. Another name for these are house batteries. 

Deep-cycle are the batteries that will power heavy electrical loads (within reason, of course). These batteries power boats with a big radio system plus extra lights and other accessories that require a lot of power.

Now that we’ve covered the different types of boat batteries, let’s go over the different makes that are out there. There are also three ways boat batteries are made.

The three makes include flooded, AGM, and lithium batteries. Flooded batteries are more than likely what you think of when you think of batteries. 

Flooded batteries are often used on boats and work relatively well. The problem is that they are susceptible to battery acid leaks caused by vibrations. Flooded batteries have cells that are full of an electrolyte liquid (battery acid). Hence their name--flooded batteries. 

AGM (absorbed glass material) batteries are resistant to vibration which makes them great for boating. These batteries are made up of fiberglass mats that electrolytes are absorbed in. This makes them resistant to leaks which is conducive to boating. 

Finally, we have lithium batteries. These batteries are lightweight and provide a lot of power given their size. They sound great, right? Well, the problem with lithium batteries is that they are highly flammable and can be quite dangerous if you don’t know how to properly maintain them, especially on a boat. 

Now that you know all about what types of batteries are out there and the different ways they are made, let’s go over how you can maintain those batteries to get the most out of them.

Get the Most Out of Your Battery

Always charge your batteries! Think of your boat battery as if it is your phone’s battery. You charge your phone before leaving the house so you don’t have to worry about a dead phone later. The same applies to your boat. 

The best way to maintain a boat battery is to fully charge it and then put it on a trickle charger. The trickle charger evens out the charge in the battery. This is especially important in deep-cycle batteries because they have thicker plates.

Getting in the habit of making sure your battery is fully charged is a great idea. It wouldn’t hurt to practice charging your battery and putting it on a trickle charger during the week if you’re someone who typically only uses their boat on weekends. Although that won’t always happen, it is tremendously important to use a trickle charger when your boat will be sitting for long periods of time. 

You can also use a battery tender or another kind of smart charger. These items will charge your battery when needed but will not overcharge them. Overcharging can lead to damage and ultimately, kill the battery completely. 

Some good information to have as a boater is at what voltage a battery is fully charged. A flooded battery is fully charged at 12.6 Volts. An AGM battery is fully charged at 12.8 Volts. 

Batteries don’t live forever. There’s no way around that. By maintaining your batteries as recommended you will get the most out of them. If you maintain your batteries properly, you should get about five years out of them. 

When that time comes and your battery is dead, check the voltage. No matter what kind of battery it is, it is dead when it reads 11.8 Volts. When this happens, you will need to buy new batteries for your boat.

I recommend turning to your boat dealer as they know what kind of battery your boat will need.  They might even offer to install the new batteries and dispose of the old ones for you which makes your job easy. But, how do you choose the right charger so that you don’t have an unexpected dead battery? 

Battery Chargers

A good bit of knowledge that I had no idea about for the longest time is that the lower the amperage in the charger, the better it is for your battery. This is because higher amps create higher temperatures which can lead to a damaged battery in the long run. 

The problem with lower amp chargers is that they take a longer time to charge. Whatever charger you decide to use, it is important to try to avoid any that are over 20 amps as these can cause quite a bit of damage. 

How to judge how long it will take to charge your battery fully has to do with the amps of the charger. For example, say I have a 5 amp charger. This would charge my battery a total of 5 amps within an hour. A 10 amp charger would charge a battery a total of 10 amps in an hour.

This is good to know in case charging time is important to you in your search for the right battery charger. 

When it comes to battery maintenance and charging tips, there are a few more things to remember.  Letting your battery go below 50% can cause serious damage. You also want to be sure that your connection terminals are clean and tight. Sometimes if a boat is having trouble starting, all it needs is to have the connections tightened. These are easy fixes you should take into consideration if you’re experiencing engine trouble. 

Use Recommended Batteries

You may be looking to replace old batteries and find cheaper/lighter ones that seem like they can do the trick. The truth is they may work for a while but there’s a good chance you will run into problems down the road. 

Boats are manufactured in a certain way that requires a level of power from the batteries. It is important to follow the manufacturers' guidelines when looking to buy new batteries so you don’t end up with issues later on. 

For example, if the factory recommends AGM batteries, that’s what you should be putting in your boat. Those systems are not set up to have different types of batteries such as flooded batteries hooked up. Over time the boat’s system will overcharge the flooded batteries and lead to a very short lifespan.

Some boats require a single battery and some require more. It all depends on the electrical load the batteries are supplying power for. Smaller boats with a smaller number of electrical accessories will typically only require a single battery. Large boats with larger electrical loads will require more batteries.

Boats are set up for specific types of battery systems so it would not be in your best interest to switch to using batteries that are not recommended. Sticking with the manufacturer recommendations will save you time and money in the long run. 

You're a Battery Expert

Learning this information will make your boating life a lot easier. I can say from experience that having the knowledge on how to maintain your boat’s batteries will save you a lot of headache in the long term.  It can save you from being stranded somewhere or ensure that your boat will fire  up before each outing.  

You can now officially call yourself a boat battery expert. Boating should be fun and relaxing but the quickest way to ruin a day out is to have a dead or non-functioning battery.  

I encourage everyone to do their research on anything boat-related whether you are looking to buy a boat or if you’ve been boating your whole life. Regardless it can never hurt to learn more and odds are it will make your life easier in the long run.