How Many Years Will A Trolling Motor Battery Last? (Explained)

UPDATED 31 JULY 2022

by Eric Bartlett

A good battery is essential to keep your trolling motor running reliably, and it’s incredibly annoying if your trolling motor battery fails while you’re out on the water. 

In order to avoid battery problems, it’s important to know how many years you can expect your trolling motor battery to last, and what you can do to increase its lifespan.

In this article we’ll explain the average lifespan you can expect from different deep cycle battery types, and how to maximize their lifespan with the correct maintenance. 

What is the lifespan of a trolling motor battery?

The average lifespan of a trolling motor battery depends on the type of battery as shown below:

  • Wet lead acid batteries: 2 to 3 years
  • Sealed AGM batteries: 4 to 5 years
  • Gel batteries: 3 to 5 years
  • Lithium batteries: 4 to 6 years

As you can see, wet batteries (which are flooded lead acid batteries) have the shortest lifespan, while lithium batteries have the longest. But keep in mind the maximum lifespan of a deep cycle battery depends a lot on correct maintenance, and especially on regular charging.

For example, if you drain your battery and keep it drained for a long time, this will reduce the lifespan dramatically. And unfortunately, this is exactly what many people do when they stow their batteries for the winter.

So ideally, you should recharge your batteries as soon as possible after each use, and use a trickle charger during the winter. Alternatively, you can just recharge the batteries once a month in winter to maintain the charge.

Another great option is to use an onboard charger, such as the one provided by Minn Kota, and plug it in as soon as you get home after a day’s fishing. This helps to protects them from getting run down below 50% all the time, which is another thing that shortens battery lifespan. 

If you’re currently in the market for a new trolling motor battery, check out our article on what are the cheapest lithium boat batteries?

How to know if your trolling motor battery is bad

When a trolling motor battery nears the end of its lifespan, its performance deteriorates gradually, and this is usually a good sign that the battery is bad.

However, if the trolling motor won’t start at all, it can be hard to tell if it’s because of the batteries or the motor itself. In a case like that you can also use a voltmeter to check your batteries, or you can get them load tested in a repair shop.

Also, you can use another battery, such as your fish finder battery, to test the trolling motor and determine if the problem resides in the motor.

Alternatively, you can also hook up the trolling motor battery in question to another device, and see if it can power that. This is often the fastest way to figure out if your trolling motor battery is bad.

Can you test a trolling motor with a car battery?

Yes, you can definitely use a car battery to test if your trolling motor is working. If you’re not sure if your marine battery is the reason why your trolling motor won’t work, then you can quickly test that by hooking the trolling motor up to a car battery.

However, make sure that you only use the car battery this way for a short period of time, in order to avoid damaging it. Also, if you test the trolling motor at home in your garage, don’t keep it running more than a few seconds, so it doesn’t overheat. Trolling motors are designed to be cooled by water immersion, and overheat very quickly when run out of the water.

When to replace a trolling motor battery?

While you can try to max out the lifespan of your trolling motor battery, and wait until it stops working before you get a new one, it’s generally better to replace it before any issues occur, as that will save you the trouble of the trolling motor losing power during use. 

Generally, I like to replace my AGM batteries every 4 years, which is usually well before they start to slow down. That way I always have full power on the water.

I suggest referring to our list above with the average number of years you can expect your trolling motor battery to run (depending on which type of marine battery you have), and then aim to replace it about 1 year before it reaches its maximum lifespan.

How to extend trolling motor battery life

Here are a few simple things you can do to make sure your deep cycle marine battery lasts as long as possible:

Regularly refill the water in wet batteries

Wet batteries require the most maintenance, since their water level needs to be regularly topped up. If you don’t do this, and let them run dry, they’ll stop working in less than one season. And keep in mind that when you top up the water, it’s important to use distilled water, so you don’t alter the electrolyte concentration.

Because refilling your batteries can be a bit of a hassle, I personally prefer to use sealed batteries that are maintenance free, and don’t require topping up with water.

Keep your batteries dry

While many people assume that marine batteries can tolerate getting wet, this is actually far from the truth. If your batteries get wet, make sure you dry them as soon as possible, and if they’re exposed to saltwater, wipe them off with a moist cloth before you dry them. But both freshwater or saltwater can quickly cause corrosion and malfunction of your batteries.

Keep your batteries fully charged

Even if you’re using deep cycle batteries, it’s important not to let them run down until they are completely empty, and you should definitely avoid keeping them in a deeply discharged state. Doing so dramatically reduces their lifespan.

So, if you use your trolling motor battery all day long on a fishing trip, make sure you recharge it as soon as you get home. And if you only use it sporadically, or for short periods of time, then recharge it at least once a week.

The biggest problem occurs when you store your marine batteries for the winter. If you don’t take them out and charge them regularly (at least once a month), that will ruin them by the end of their first winter. 

A nice way to solve this issue is by using an automatic charging system that detects when the battery is fully charged, and then switches to maintenance mode. Whenever the battery charge drops below a certain threshold, the automatic charger is activated, and keeps the battery fully charged.

This approach allows you to keep your battery hooked up to the charge over the entire winter, which will extend its lifespan by several years. Finally, make sure to store them in a cool dry place in winter, and not on a concrete floor.