Marine Battery Charging Guideline: How To Charge A Marine Battery

Does your new marine battery run out of power before it is supposed to?

Running out of power in the middle of a fishing trip can be frustrating and dangerous. It can leave you stranded and ruin your day.

The problem may not be with the battery or the particular brand. Improperly charging your marine battery can lead to this kind of trouble. It can lessen the capacity of your battery to hold a full charge.

You will find the solution in this guide that shows you how to charge a marine battery in the right way. Here are some tips and instructions to help make your battery more reliable for longer. We've also included a section on charging a deep cycle marine battery.

Start With The Right Charger

There are different kinds of battery chargers. For the best results, you need to choose the right one for your boat battery. But you may be wondering how to choose a battery charger that is perfect for you!

Here are four important things to know before you make your choice.

1. Using a car battery charger for your marine battery will lessen its lifespan. Car chargers are not designed for the requirements of a marine battery.

2. Chargers that do not completely shut down when the charge is complete lessen battery life.

3. Chargers with limited charging capacity will shorten your battery life.

4. Multi-stage chargers are the best option for preserving marine battery life.

Choose a charger that is made for marine battery charging. Select one with a full charging capacity and an auto shutoff feature that charges in multiple stages.

The charger is optimal when the charger size is between ten and twenty-five percent of the amp-hour rating of the battery. It allows for faster recharge time.​

Best Way To Charge A Marine Battery​


You can charge Marine battery with an on-board charger or with a portable charger ashore. We're going to cover both ways.​

Here Is How To Use A Portable Marine Battery Charger​

1. Refer to the manufacturer's owner's manual. This is the best way to understand how to operate your marine battery charger. It's also a good resource for troubleshooting.

2. Remove the battery from the boat when not using an on-board charger.

3. Choose a well-ventilated area for charging.

4. Inspect the battery. If the terminals and cables have corrosion on them, clean them. Use rubber gloves and goggles to avoid injury from the chemical buildup particles while cleaning.

5. Wet cell batteries have caps. Open and inspect the fluid levels. Use distilled water to bring them to the proper levels. When needed, fill to just under the top of the ring leaving 1/4 inch of space for expansion. AGM batteries don't require this type of maintenance.

6. Connect the red clamp of the battery charger to the positive battery terminal. It has the + symbol.

7. Connect the black clamp to a bare metal ground. It has the - symbol.

8. Plug in the charger to an AC 120 volt electricity outlet.

9. Select the battery type on the charger. Newer chargers have 12-V standard, 12-AGM and 12-V gel cell options.

10. Allow the battery to charge until the charge light is off.

11. Unplug the charger and disconnect from the battery.​

Charging A Deep Cycle Battery​

Charging Deep Cycle Battery

​Deep cycle batteries may be charged using the same steps recommended for other marine batteries. The one thing to keep in mind is that they must be recharged within 24 hours.

Do not allow deep cycle batteries to become depleted or sit uncharged. It will decrease the quality and longevity of the battery.

I have written another article about charging a deep cycle battery. You may check that out too.

Is It Okay To Use A Trickle Charger?​

Yes it is acceptable to use a trickle charger. It's a way of allowing your marine battery to charge overnight.

It isn't the most highly recommended way, but it is efficient and reduces the chance of overcharging when left on for several hours unsupervised.​

​How To Charge A Marine Battery On The Water

charging a marine battery on the water

On-board marine battery chargers allow you to charge the boat battery while out on the water. You can use it in or out of the boat which makes them dual purpose.​

They are a bit more expensive than portable styles, but they are permanently installed in the boat adding convenience.

​Using a portable marine battery charger requires more effort. This is why on-board chargers are gaining in popularity.

You may bring a portable charger on-board and hook it up, but it's not recommended. The on-board wired in charger only need to be connected to an 110-volt electrical outlet for charging.

How To Charge A Marine Battery Fast​

The traditional method of charging your boat battery using a charger is the most highly recommended way. It helps to extend the life of your battery and make it more reliable.

Marine battery chargers are between 10 and 15 amps. In order to get a quick charge, a charger that delivers more amps is required. Choose a 20 amp charger for faster recharge time.


Make note that quick charging marine batteries on a regular basis will decrease the life of the battery. No more than one charge per day should be given.

The battery should also be allowed to cool off before use. Quick charging can cause extra heating. This makes it vital to avoid overcharging the battery with this method.

There are right ways and wrong ways to charge a marine battery. Safety is the number one consideration. Next, knowing the battery size is important for choosing the right type of battery charger. Here is a video about charging and maintaining a marine battery.

Think about which type would work the best for you before you buy. While on-board are more expensive than portables, they are also more convenient and easy to use.​

​When you follow the proper procedures for charging your battery, it will prolong the life and give you more dependable service. It can help you in avoiding frustration and ruined trips because of a dead battery.

Knowing how to charge a marine battery is necessary for safety and battery reliability. It's an important part of boat maintenance for the serious boater or fisherman.

Be prepared and enjoy your boating experience with fewer disruptions by keeping your batteries in top operating condition.​

Richard C.

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