How Long Do Boat Batteries Last? (The Average Lifespan)

• For example, let’s say, you used the boat battery for a total of 5 months per year; then we can assume that the battery will be subjected to around 50 cycles.

A standard medium-duty battery will last you 200 to 300 cycles. If 50 cycles/year is your consistent frequency of use, with minimal deviations, then it will likely last between 3 and 6 years.

• It’s a different story for boats that hit the water regularly with only a few breaks. You may accumulate 200 or more cycles yearly, so if that’s the case, the deep cycle battery lifespan, assuming it’s the same make, will likely only last you 1 to 2 years.

• Starting – Starts boat engines using a powerful burst of energy. They need to be recharged by the engine’s alternator and can’t handle continuous use.
• Deep-cycle – These are the opposite of starting batteries in that they discharge slowly and continuously to power up the engine and other components like windlasses, audio systems, fish finders, etc.
• Dual-Purpose – These batteries are versatile enough to function as both starting and deep-cycle batteries. They have become close to permanent presences on boats running on a trolling motor due to this reason.

• AGM (Absorbent Glass Mat) Batteries

Despite being heavier and having a lower capacity than most, these batteries don’t leak and have a lower self-discharge rate. They also require little to no maintenance.

• Flood Lead Acid (FLA) Batteries

These are generally considered old, heavy, and require water to be maintained, but are more economical compared to newer types.

• Gel Batteries

These also don’t spill and are low maintenance, with a lower self-discharge rate than FLA batteries. They’re also hefty, though, and have a relatively low capacity.

• Lithium-ion Batteries

Favored for being long-lasting and fast-charging, li-ion batteries also stand out because of their safety, low maintenance, remote monitoring, and capability to provide consistent output. They are premium choices price-wise, though.

• Type of battery – as the tables above prove, certain types have more longevity, with lithium-ion being supreme powerhouses, as they can work for a decade or two.

This is made even more apparent if we compare them to their lead-acid, deep-cycle counterparts that need to supply power continuously, which may not even last more than two years. 

• Climate and extreme temperatures – climates with regular and drastic temperature shifts may not be too amenable to your battery’s lifespan. The same rings true for humid and rainy locales where corrosion remains a constant risk.

• Usage and charging rate – frequent use and charging of boat batteries often mean a shortened lifespan. However, the opposite is just as bad—we’ll explore this in deeper detail below.

• Maintenance – it’s simple, really: proper marine battery maintenance and storage extends its life. 

• Corrosion – this leads to sulfation that may drain the battery’s life and impair its ability to hold a charge. Try to clean its terminals regularly and apply a corrosion inhibitor afterward. Also, keep the battery dry at all times.

• Infrequent or zero usage – if you leave your boat dormant for months or years, that spells bad news since the battery may self-discharge. You can use a maintenance charger to prevent this from happening.

• Parasitic draw – leaving any boat appliance or compartment that draws electricity on will drain the battery, enough to affect its longevity. Therefore, always unplug all the wires connected to the battery’s terminals when the boat is not in use.

• Overcharging and undercharging – doing either regularly has been proven to cause marine batteries to die earlier than the average lifespan. 

To circumvent the issue, always charge the battery with a suitable charger until it’s full, at which point you should immediately unplug the unit.

• The boat constantly fails to start or takes longer than usual to turn over.

The battery may no longer have enough power to meet the engine’s current needs, particularly when starting it. Don’t underestimate this, as this has led to many stranded boaters.

• Clear physical damage.

Acid built-ups, sulfation, bulges, cracks, corrosion, and heat damage are but some signs that your battery has gone through significant abuse and may be failing.

• Electronics not working as they should.

If you notice lights turning off suddenly and the GPS malfunctioning, these could be signs that the battery can’t handle their respective loads anymore.

• Stay on top of signs of damage and other symptoms above.
• Stop completely discharging the battery. You should recharge the battery whenever it drops below 20%.
• Use the right battery for your needs.
• Use power responsibly. Just by minimizing parasitic draw, you’re already lessening their burden.
• Charge them properly. You can keep them hooked to a maintenance charger, for instance, but be sure you’re using it correctly.
• Rely on other sources of power, such as renewable energy.