When summer and fall boating season is unfortunately over, many owners will say goodbye to their boats for the winter. During storage, its important to know the do’s and don’ts of storing boat batteries in winter and charging them in winter. Storage for boat batteries doesn’t have to be daunting, though, especially if they are lithium batteries. Let’s take a closer look at leaving batteries in a boat over winter and why you may want to avoid it. 

Keep Your Batteries Alive Through Winter

As anyone who’s owned a battery knows, they aren’t invulnerable to the elements. Just about all varieties will be affected by very cold or very hot temperatures. This is true not only of traditional auto batteries but also marine batteries for boats. 

And there are few things more disappointing than arriving back at the marina ready for the first boat trip of the spring only to find a completely dead battery. These issues can range from a minor hassle to an expensive replacement or repair in some cases. That’s why it’s so crucial to ensure your boat and batteries are stored and maintained properly all year round. So, can you safely leave batteries in your boat over winter?

What Happens If Your Marine Batteries Freeze?

Ever heard the myth about storing your batteries in the freezer to make them last longer? It’s just that: a myth.

It’s not common, but in certain situations, lead-acid marine batteries can completely freeze in cold temperatures. This happens when the battery drains almost entirely of energy. This may cause a chemical process that dilutes the electrolyte liquid in the batteries. 

The diluted liquid is more prone to freezing, which will damage the battery cells and potentially even crack the battery case due to expansion. Different types of lead-acid batteries will have different freezing points, but all face this issue to some extent.

pier with boats in freezing winter temperatures with snow

On the other hand, lithium-ion battery users will most likely not worry about a freeze under most conditions. In fact, Battle Born lithium marine batteries won’t face any freezing or other issues related to cold temperatures until the temperature drops to -15 degrees Fahrenheit. 

Can You Leave Marine Batteries on Your Boat in Freezing Temperatures?

Technically, leaving your batteries in the boat during very cold winter weather is permissible. However, it’s generally not recommended due to the potential for damage or extra maintenance. Extreme cold can lead to a cracked or entirely drained lead-acid marine battery. You may need to make regular trips to your boat during winter to ensure things are staying safe. 

Also, those using traditional lead-acid batteries should use a battery maintainer or battery tender. These protect your battery by keeping them charged and preventing a freeze-up. These devices connect to batteries and supply a small trickle of energy over time. This is just enough to counteract the natural energy loss incurred by cold weather.

Battery maintainers also include smart technology to help avoid overcharging batteries. Even when using a maintainer, batteries should be disconnected from all wiring in the boat.

snowy marina in winter with sunrise over buildings

Removing and Storing Your Marine Batteries in the Winter

Most boaters find it is not worth leaving batteries in a boat over winter if it means freezing temperatures and the possibility of ruining them.

At a minimum, you should disconnect your batteries from the electrical system. Most boaters or other marine battery users may have a battery disconnect switch within their boat. These can cut power to the battery. This may cut off some systems, but others deemed essential (like emergency sensors or carbon monoxide alarms) may still draw power. This is why it’s important to fully disconnect marine batteries during periods of extended inactivity. It helps avoid a slow and steady draining of energy.

The best way to store marine batteries in cold weather is by removing them completely and keeping them above freezing, if possible.

Removing batteries also helps ensure they remain at proper temperatures throughout the winter and stay safe from any potential severe weather. It also allows you to store them in an area that is easier to keep a trickle charger on them. Keep in mind that lead-acid batteries can off-gas and need to be stored in a well-vented area and not in the living space.

With Battle Born lithium marine batteries, however, you don’t need to remove them as long as you fully charge them and hit the battery disconnect switch. The cold temperature will not affect them as long as they aren’t being used. If you expect temperatures below -15F, however, we still recommend removing them and keeping them climate-controlled. They can be stored indoors because they will not off-gas and are non-toxic and non-spillable.

Charging Your Marine Batteries in the Winter

As we mentioned, no one likes finding a dead battery when they’re ready to get out on the water in the spring. That’s why it’s crucial to know how to keep your batteries charged over the winter (and whether users need to do anything at all). Lead-acid batteries will need a battery maintainer.

Boats moored by pier at harbor against mountains

This is yet another situation where lithium battery users will avoid the issue altogether. Lithium batteries don’t generally experience the steady, gradual loss of energy over time that lead-acid ones do. That means users can store them for winter without any battery maintainer or other technology and without fearing they’ll be dead come spring.

If your batteries get low during the winter and you need to completely recharge them, we recommend warming the batteries above freezing before charging. Charging batteries at below-freezing temperatures can damage them and reduce their lifespan. Although Battle Born lithium batteries’ internal BMS automatically prevents charging if the internal temperature is too low to avoid damage, it’s still important to keep this in mind.

Want to learn the truth about Lead-Acid Vs. Lithium in the cold? We have tested our lithium-ion batteries extensively in the cold against lead-acid batteries. Learn more about it here: Lead is Dead White Paper: Cold Charging Study

Battle Born Batteries offers an easy winterizing process for storage for a battery in a boat. Simply bring the battery to a full charge and then disconnect it from the electrical system. They can stay in place or, if you feel like moving them, owners should then store the battery in any dry place with temperatures between -10 degrees Fahrenheit and 140 degrees Fahrenheit. This is an easier task thanks to lithium batteries weighing half of what deep-cycle lead-acid batteries weigh.

Even with six months in storage, users will typically find 75-80% of the battery capacity remaining when they reinstall the battery next season. Generally, these batteries will lose just 2-3% charge per month. 

Avoid Leaving Batteries in Your Boat Over Winter, If Possible

Charging, maintaining, and storing boat batteries in winter isn’t a complicated process in most cases. But it can be a crucial step in ensuring boat owners are ready to get out on the water with a working power system come spring. Generally speaking, leaving batteries in your boat over winter is just going to cost you money and time in the long run.

Follow these simple guidelines, and no matter how long or cold winter may be, your boat’s marine battery will make it through safely.

Want To Learn More About Electrical Systems and Lithium Batteries?

We know that building or upgrading an electrical system can be overwhelming, so we’re here to help. Our Reno, Nevada-based sales and customer service team is standing by at (855) 292-2831 to take your questions!

Also, join us on Facebook, Instagram, and YouTube to learn more about how lithium battery systems can power your lifestyle, see how others have built their systems, and gain the confidence to get out there and stay out there.

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