How to maintain a Marine Battery

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Marine Battery Care & Maintenance

The right care is essential to maximise the life of your Marine battery

If your passion is boating, then knowing what you need to ensure your boat is safe, enjoyable and comfortable is important. Whether you’re planning a day on the water or a longer sailing trip, one of the most vital components for ensuring safety and performance is your marine battery or batteries. If your batteries are in a low state of charge you could find yourself left stranded on the water in a boat that won’t start, which can be dangerous on the water.

People often think when they’re not using their boats that the battery or batteries will remain charged and be ready for when you next use them. The truth is batteries will discharge even when you’re not using them. That’s why you should always take precautions to ensure they are regularly tested and kept topped up with charge, using the correct battery charger, so your next outing or holidays don’t start with the disappointment of flat batteries or worse still, dead batteries.

When it comes to marine battery maintenance, you will first want to establish what type of battery or batteries you have? For instance, do you have a wet flooded battery? Or perhaps you have an AGM sealed battery, maybe even a Lithium option. While the basics are similar, we will help establish a basis for you to maintain these battery options. Another important thing to remember is your boat, yacht or watercraft will, in most cases, have a starting battery or batteries for the engines and also the domestic batteries for powering lighting, air-conditioning, fridges, radio’s and much more besides.

Regularly checking the level of charge in your batteries is good practice to ensure safety and to also achieve the best possible battery life.

Wet Flooded Battery

Your standard wet flooded battery is one that is filled with electrolyte (acid) and depending on whether your battery is open vented or fully sealed, will vary the level of maintenance required. During your scheduled maintenance of the battery you would want to keep the battery clean and make sure the terminals are free of any corrosion, as this can lead to many problems. If you need to clean your battery and the terminals, as well as the battery tray, then a mixture of water and baking soda is ideal. We advise you to regularly check the charge level in your batteries and charge as required, if you’re using your boat, yacht or watercraft regularly or you are hooked up to the marina mains power then it is likely you will have sufficient charge in your batteries but it is always prudent to check the charge level regularly. If you have an open vented battery, this means you have six screw in caps where you can access the inside of the battery to top up the electrolyte as and when required, it is important that you also regularly check the electrolyte level in your battery, and add distilled water when it’s needed, making sure there’s enough to cover the battery plates.

If you use your boat, yacht or watercraft all year round then sticking to the above will help get the most out of your batteries, however if you are planning on storing your boat, yacht or watercraft over the winter or for an extended period then please see storing your marine batteries.

AGM Battery

When it come to maintaining your boat, yacht or watercraft marine batteries that has AGM technology, you’ll be pleased to know there isn’t as much maintenance to do as with a wet flooded battery. This is because AGM (Absorbed Glass Mat) batteries are fully sealed and so once they have been activated from new, they are closed and as such they don’t require any electrolyte or water. All of that said, you will still need to regularly check the charge level in your battery and charge as required. Also keeping your battery and terminals clean and free of corrosion will prevent many problems from occurring, especially important when around sea water due to it’s corrosive nature. When cleaning your battery, terminals or the battery tray then using water and baking soda is a great solution.

Lithium Battery

As with the AGM battery, there is relatively little maintenance to do on Lithium batteries unlike the wet flooded lead-acid battery. It is true that Lithium batteries can be stored (when not connected to an application) for long periods of time without seeing the drop in voltage you would see with lead-acid batteries, however, this is when they are disconnected from onboard equipment. If you have your Lithium batteries connected to your boat, yacht or watercraft, then just like lead-acid batteries, you will see a parasitic drain over time from the connected onboard equipment and as such you must make sure you regularly check the charge level of the batteries and charge as required. When storing Lithium-ion batteries, disconnect the batteries from the vessel and immediately charge the batteries on a Lithium battery charger, the batteries can then be happily stored for up to a year. When you wish to use the batteries after storing them, put them on charge again to make sure you have full power prior to use. Also keeping your battery and terminals clean and free of corrosion will prevent many problems from occurring especially important when around sea water due to it’s corrosive nature. When cleaning your battery, terminals or the battery tray then using water and baking soda is a great solution.

Storing Marine Batteries Over The Winter

Once you have finished using the your boat, yacht or watercraft for the season and it’s time to put it away for the winter, there are some things you want to do to make sure your vessel is in the best possible condition for storage, this includes your batteries. Firstly you’ll have wanted to thoroughly wash and dry your vessel also cleaning and removing any salt or dirt that has built up around the batteries, keeping this area clean will help increase battery life as salt water is extremely corrosive. Next you will have to prepare for the winterisation and you may have your local dealer taking care of this for you, but if you’re doing it yourself then part of that process is preparing the batteries and below we have some great tips to ensure you don’t have to purchase another battery or batteries for next season. When removing your batteries from your vessel store them in a cool dry place, we would highly recommend carefully reading the owners manual, this will let you know the tools that you’ll need and the correct process they recommend as this may vary from model to model.

Frequently Asked Questions

Several factors could affect the lifespan of a marine battery, what type of battery you have, how you use it and how well you maintain it. Generally speaking, a marine battery can last anywhere from 1 to 6 years, and some high-quality batteries last even longer.

Lead-acid batteries are the most common type of marine battery and they typically last between 3 and 5 years, this can however vary depending on the usage and maintenance. Gel batteries and AGM (Absorbed Glass Mat) batteries are also available and have a longer lifespan, lasting anywhere up to 7 years or more with proper maintenance. Lithium batteries are becoming more popular now, these are much lighter than the lead-acid equivalent and last far longer. Go Batteries stock a wide range of marine batteries covering all technologies and brands, ask a member of our team if you’re unsure of which would suit you.

Dual-purpose marine batteries can be a good choice depending on your needs and planned usage. They are designed to provide both starting power and deep-cycling capabilities, meaning they are a popular choice among boaters as they can handle both turning the engine over and powering any onboard electrical equipment, essentially a two-in-one battery. They are also generally less costly and more compact and lighter than traditional deep-cycle batteries, meaning they are easier to install and manoeuvre on boats with limited space. However, they are not a good choice for any boaters that run high-powered electronics for extended periods or those with a larger boat or yacht as a larger engine may require more starting power.

How often you should add distilled water to your batteries depends on the type of battery you have and how often you use it. We recommend checking the water level at least once a month, or after every use, to ensure that the water level is within the manufacturer’s recommended range.

Yes, it is a good idea to charge your marine batteries after every use, especially if it has been discharged significantly. Lead-acid batteries, which are the most common type of marine batteries, can be damaged if they are allowed to remain discharged for an extended period. By charging your marine batteries after every use, you help prevent this hardening of lead sulphate and extend the batteries lifespan. It’s also important to keep in mind that if the batteries are not fully charged, they may not have enough power to start the engine or power onboard equipment on your next outing. Dual-purpose or deep-cycle marine batteries may not need as much charging, you should consult the manufacturer’s recommendations of how often your batteries will need charging.

Again, this depends on the type of battery, its age and the temperature at which you store it. A fully charged lead-acid marine battery can sit unused for around 6 to 12 months, depending on the conditions. If the battery is not fully charged when it’s stored, its lifespan can be significantly reduced. If a battery is stored in a warm location, it may lose its charge quicker than if it were stored in a cooler location.  If a battery is not charged and maintained regularly, this can lead to decreased performance and greatly reduce the lifespan.

The short answer is, yes, you can overcharge marine batteries. This can cause a lot of damage. Excessive heat and gas could build up inside which can not only damage the battery and the surrounding equipment. Thankfully most new marine battery chargers have an automatic shut-off feature that prevents overcharging. Make sure that you use a charger that is designed for your specific battery type and size and follow any recommendations for charging. If you are using a manual charger, monitor the battery’s voltage and current throughout the charging process to avoid overcharging.

Following these tips on how to properly maintain your marine battery is crucial to ensure your boat functions properly. Regular maintenance can help prevent costly repairs and ensure a safe and enjoyable boating experience.


Checking The Charge Level

Most modern boats, yachts and watercraft have a built-in battery monitor, however some of the older models may not. We recommend checking your battery charge levels with a voltmeter or multi-meter, below we have a quick reference chart to assist your checks.

Prior to taking the readings, ensure all electrical appliances and systems are switched off.

Meter Reading               Approximate Charge Level

12.7V or above              100%
12.5V                               75%
12.4V                               50%
12.2V                               25%
12V or less                     Discharged

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