Most sailors are tired of replacing their boat’s batteries every few years. Lead-acid, sealed gel, and AGM batteries don’t last that long, but they’ve been the only option to power trolling motors or onboard electronics and small appliances. However, lithium batteries are gaining traction in the marine community.

Lithium batteries offer several advantages over these older types of batteries, including better performance, cost savings over time, no maintenance, faster charging, and more. However, the most significant benefit of lithium batteries is that they last a lot longer than lead-acid batteries.

How long? While the exact length of time varies based on your setup and usage, let’s talk about the life of a lithium battery.

The Cycle Life of Lithium Batteries

When determining how long a lithium battery will last, you need to understand how it works. Every battery has a cycle life, which is the number of times you can charge and discharge it before it starts to lose its performance capabilities.

If you charge your battery to 100% and then wholly deplete it to 0%, that is a complete cycle. If you don’t charge entirely or don’t discharge completely, that would be considered a partial cycle. When you’re using a battery, you’re usually using partial cycles, which affects the total number of cycles you’ll get.

So, how do manufacturers come up with their cycle numbers for batteries? They run tests. But, they only use partial cycles. For example, a manufacturer may say that their battery gets 500 charge/discharge cycles. The company charged the battery 625 times in their testing, but they only charged it to 80%. Then, they use this data to calculate the full cycle life of their batteries. In this case, 80% of 625 equals 500 full cycles.

What does this all mean? Let’s get into the numbers. Lead-acid batteries generally get between 500 and 1,000 life cycles. On the other hand, lithium batteries typically get between 2,000 to 5,000 cycles, and some can reach upwards of 7,000. Whether you fully comprehend what these cycle lives mean, what you can take away from this is that lithium batteries last at least three to five times longer than lead-acid batteries.

If your current lead-acid boat battery needs to be replaced every few years, an equivalent lithium battery likely will last closer to ten years.

The Lifespan of Lithium Batteries

How long any battery actually lasts depends on a variety of other factors, but again, lithium batteries excel over traditional marine batteries.

As you likely already know, charging lead-acid batteries can be a pain. They can’t be depleted past 50% and need to be charged to 100% to prevent damage. This is because of Peukert's law, which shows that voltage output decreases in a lead-acid battery as it is discharged.

Lithium batteries don’t suffer from this problem. They maintain their voltage capacity at any level of discharge. Also, they don’t have to be charged fully. You can charge a lithium battery to 80%, which results in faster charge times, and will reduce the number of charge cycles. In turn, this lengthens the battery’s overall lifespan.

When you’re using lead-acid batteries, proper maintenance can extend the life of your battery. Maintenance includes checking acid levels, adding water, and cleaning corrosion. If you’re not caring for your battery, it won’t last as long. On the other hand, lithium batteries don’t require any maintenance, which means you don’t have to worry about a decreasing lifespan resulting from improper care.

Lastly, how often you use your boat affects the battery’s lifespan. If you’re living on a houseboat or spend the majority of your time on the water, this may not affect you. However, if you leave your boat sitting around unused during the offseason, you’ll want to be mindful of how it affects your batteries. Lead-acid batteries lose around 33% of their charge in a month when they’re left sitting. Lithium batteries only lose 2-3% in that same time block.

What this means is that you’ll likely have to use a charge cycle or two to keep your lead-acid battery in working condition, even if you’re not using your boat for months. But lithium batteries could be left for a year without charging and still be able to power your boat when you’re ready, prolonging their lifespan.

Are Lithium Batteries Worth It?

If you’re tired of replacing your lead-acid batteries every few years, consider making the switch to lithium batteries. Although you’ll pay more upfront, you’ll end up saving money over time, and you won’t have to worry about buying replacements for at least ten years or more.

If you still have any questions, you can check out our 5 Most Common Questions About Marine Batteries blog post or give Patriot Power Source a call at 888-287-2864.