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How Often Should I Replace My Boat Battery?

How Often Should I Replace My Boat Battery?

Are you wondering if it’s time to replace your boat battery? Have you had your boat battery for several years and you want to get the most out of it but you also don’t want to run out of power while you’re out on the water?

Understanding how boat batteries work and what they are usually used for can help you understand when to change your battery. It can also help you know how to extend the life of your battery.

If you’re wondering about boat batteries, here’s what you need to know.

Types of Boat Batteries

Two main types of batteries get used on boats. These are starting batteries and deep cell batteries.

Starting batteries are similar to what you would use in your car. They are designed to expend a lot of power all at once, then to recharge quickly from the engine.

Optima Batteries 8020-164 35 RedTop Starting Battery

Deep cell batteries are different. They are designed to expend small amounts of power over longer periods. These are the batteries you should get when using things like trolling motors.

You can use starting batteries and deep cell batteries interchangeably, especially in an emergency. However, using them for purposes they weren’t designed for will shorten their lifespans.

ML35-12 - 12 Volt 35 AH SLA Battery- Mighty Max Battery Brand Product

How Long Should My Boat Battery Last?

For most purposes on a boat, you will want one (or more, depending on your setup) starting battery. These can last 3-4 years, though they may last up to 6 years under certain conditions.

Many people replace their boat batteries every 2-3 years. After all, it’s worth the investment to avoid getting stuck out on the water. No one wants to be towed in.

How Many Years Should a Trolling Motor Battery Last?

This is a complex question because it involves several factors, including:

In general, deep cycle trolling motor batteries last 2-4 years. Get the most out of your battery by making sure you charge it occasionally, even if you aren’t using it on your boat.

How Do I Know if My Trolling Motor Battery is Bad?

voltmeter checking boat battery voltage

Start by inspecting the battery visually. If anything is broken or discolored, or if there are breaks or bulges in the case, the battery has gone bad.

Next, check the voltage. If it doesn’t get higher than 10.5 volts, at least one cell has been damaged. If the charger says that it is fully charged but it won’t go past 12.4 volts, it has been damaged.

You cannot restore a battery after the damage has been done. The best thing to do is to replace the battery with a new one.

If you’re still not sure, take your battery to a local marine shop and ask them to load test it for you. They will let you know if the battery is working properly or if it has gone bad.

How Can I Make My Trolling Motor Battery Last Longer?

There are a few things you can do to extend the life of your trolling motor battery. These include:

  • Charge the battery regularly – at least every 6 months – even when you aren’t using it on your boat.
  • Understand how your battery works and how much power your boat draws so you can use it confidently.
  • Use the trolling motor mostly in calm water. The more chop and wind you have to fight, the harder it will be on your battery.
  • Don’t overtax your trolling motor by making too many sharp turns or by abruptly changing speed. This will also overtax your battery.
  • Charge your battery to 100% every time.
  • Make sure you don’t charge your battery until it is 50-80 percent discharged.
  • Store your battery fully charged.
  • Charge your battery as slowly as possible. Rapid chargers can be useful but they will limit the lifespan of the battery.

Why Does My Boat Battery Keep Dying?

low boat battery keeps dying

There are many reasons why your boat battery may keep dying. Your battery may not be producing enough voltage. In that case, it needs to be replaced.

However, this is not always the case. Check to see if any lights or other things got left on. These draw power from the battery and may make it die regularly.

You may also want to check the rectifier on your engine (or have a marine mechanic do it for you). This part is supposed to recharge the battery. If it goes bad, your battery will not get more power and will eventually die.


Most boat batteries last 3-4 years, though you can extend that lifespan if you use the battery wisely and treat it well.

If you need a new boat battery or you think yours is close to dying, replace it soon. Then, get back out on the water and enjoy yourself again!