Using A Car Battery For A Trolling Motor (Here’s What You Need To Know)

UPDATED 31 JULY 2022

by Eric Bartlett

If you want to use a trolling motor, but don’t have a suitable marine battery for the job, it’s tempting to use a regular car battery for this purpose.

And while this is definitely an option, it really isn’t the best solution, since it results in poor trolling motor performance (i.e. a short run time) and a damaged battery.

Want to get the full scoop using an automobile battery to run an electric trolling motor? Read on below!

Can you use a regular car battery for a trolling motor?

Yes you can use a car battery for a trolling motor, but this isn’t the best solution, since a car battery isn’t designed for this task, and should only be used if there’s no marine battery available. 

For a trolling motor, it’s best to use a deep-cycle marine battery with a long discharge time.

This type of battery slowly releases its charge over many hours, allowing the trolling motor to run for a long period of time without problems. 

What is the difference between a car battery and a marine battery?

An automobile battery is designed to provide an intense burst of high amperage electricity in order to get a car engine started.

And after it has done its job and the engine has started, it is then instantly recharged by the alternator.

As a result of this, a car battery never experiences a deep discharge, but only shallow discharges that last for a short time.

This is why car batteries don’t handle deep discharges very well, and if they’re used for deep discharges too often, this significantly shortens their lifespan.

When that happens, a car battery tends to get drained faster and faster every time you use it. In other words, you end up with a short run time for your trolling motor, plus a ruined car battery.

deep cycle marine battery, on the other hand, is designed to release its charge slowly over time, which is ideal for powering a trolling motor for many hours. It also tolerates a deep discharge much better than a car battery.

After it has been discharged, a deep cycle marine battery needs to be gradually recharged with a suitable charging device, and the great thing is that you can repeat this cycle of deep discharge and recharge many times without ruining the battery.

Alternatively, you can also use a portable charging device to recharge the battery while in use.

Why should you use a deep cycle marine battery?

Since trolling motors (and other boat electronics) are usually used over extended periods of time, ranging from several hours to an entire day on the water, it’s best to power them with a deep cycle marine battery.

Especially if you use a 24 or 36 volt battery system, you can expect a runtime that will last the whole day, which is exactly what you need for this purpose.

If you’re thinking about getting a deep cycle marine battery, check out our article on what is the least expensive lithium deep cycle marine battery?

Marine battery vs car battery for trolling motor

While you can use both battery types to power a trolling motor, a marine battery will always outperform a car battery in terms of trolling motor run time.

This can make the difference between running out of power after a couple of hours, or being able the run the motor for a whole day. 

Also, a marine battery will have a much longer lifespan, since it degrades much more slowly when exposed to repeated rounds of deep discharge, since this is what it was designed to do.

A car battery, on the other hand, will deteriorate rapidly if regularly used to power a trolling motor. 

It is also a hassle to recharge the car battery after a deep discharge, since it does not come with a recharging device, and you’ll have to put it back into the car in order to charge it

And last but not least, if you go ahead and use a car car battery for your trolling motor, keep in mind that you may be unable to start your car when you get back, since the battery could be drained before you return it.

So even though both types of batteries are broadly similar (and can be used interchangeably in some instances), they each have a very different purpose, and this means that boat batteries should be used for boats, and car batteries for cars, unless you really have no other choice.

How long will a trolling motor last with a car battery?

A brand new, fully charged car battery can power a 12v trolling motor at low speed for up to 10 hours.

However, if you increase the speed, this will dramatically reduce the battery run time, and you may run out of power after just 1 to 2 hours. 

Also, if the car battery has already been subjected to this kind of deep discharge in the past, this significantly reduces run time.

So if you find yourself in a situation where you have to use a car battery for your trolling motor, it’s usually best to stick to low speed settings in order to conserve power.

Conclusion

In summary, while you can definitely use a car battery for your trolling motor, this damages the battery, resulting in low performance and shortened run times.

This is why I highly recommend using a deep cycle marine battery for your trolling motor if it can be helped.