How To Choose The Right Battery For Your Fish Finder (5 Things You Need To Know)

PUBLISHED 10 FEBRUARY 2022

by Robert Ceran

Are you wondering how to choose a battery for your fish finder?

This is a challenging question because you have to decide whether to get a separate battery for your fish finder, as well as the type and size of battery that is best for your fish finder. 

In this article we’ll walk you through everything you need to know about fish finder batteries, to help you decide what battery setup to choose for your fish finder. 

Do you need a separate battery for your fish finder?

No, you don’t need a separate battery for your fish finder, and can definitely hook it up to your starting battery or trolling motor battery instead.

However, it’s usually better to use a separate battery for your fish finder, as that helps to avoid common issues such as interference from the trolling motor, or the starting battery getting drained by the fish finder (more on that below).

See also: What is the best battery for fish finders?

Can you connect your fish finder to a trolling motor battery?

Yes, you can definitely connect your fish finder to a trolling motor battery, and this is a common practice among anglers. As long as the voltage of the trolling motor battery is between 12 and 24 volts, the battery should be able to power your fish finder, as that is the voltage required by the majority of fish finders.

One thing to keep in mind, though, is that running a trolling motor and a fish finder with a large display from the same battery can drain the battery faster than expected, which means you might run out of battery power before you’re done fishing. 

The best way to avoid this problem is to use separate batteries for your fish finder and trolling motor, and only use the same battery for both as a backup option. 

Can you run a fish finder and trolling motor on the same battery?

Yes, you can run a fish finder and trolling motor on the same battery, but if you do this, be aware that a common problem caused by this setup is electromagnetic interference caused by the trolling motor. 

If you run into this problem, you’ll notice interference patterns on your fish finder screen whenever you turn on the trolling motor. In some cases, you can even trigger interference simply by rotating the trolling motor with an electric steer foot pedal. 

In order to avoid interference from the trolling motor, it’s essential to wire your fish finder directly to the battery, and avoid using any hubs or switchboards. That way you’ll get a direct connection between the fish finder and the battery, and in most cases that’s sufficient to avoid interference. 

Also, when you wire the fish finder to the battery, make sure that you choose the right gauge wire (which depends on the length of wire you need to use), and make sure to solder the connections. 

Can you connect your fish finder to a starting battery?

Yes, you can connect a fishfinder to a starting battery, and this option is used by many anglers. However, if you do this, a common problem caused by this setup is that the fish finder turns off when you start your outboard motor. 

Again, the best way to avoid this problem is to wire your fish finder directly to the starting battery, without using any switchboards or hubs.

Also, if you use your cranking battery for your fish finder, another issue to be aware of is that you may end up draining the starting battery if you use it to run your fish finder for many hours at a time.

This issue is especially significant if you’re using a fish finder with a large display requiring a lot of power, or if you’re using several fish finders at the same time. This problem also gets worse when your starting battery gets old, while it’s less of an issue with a brand new battery. 

What kind of battery do you need for a fish finder?

You can use either a deep cycle or a starting battery for your fish finder, as long as it has a voltage between 12 and 24 volts.

While a starting battery isn’t the ideal option, since it’s designed for strong bursts of discharge over a short period of time, instead of a slow steady discharge, it will still work adequately to power a fish finder. 

Also, you can use either a lithium or a sealed lead acid battery for a fish finder. Lithium batteries come with the advantage of having a longer runtime, as well as a longer overall lifespan compared to lead acid models, but they are also significantly more expensive. 

Do you need a deep cycle battery for a fish finder?

No, it’s not essential to use a deep cycle battery for a fish finder, as you can also run it with a starting battery.

However, a deep cycle battery is definitely the best option for a fish finder, since this battery type is designed for a slow and steady discharge of power over a long period of time, which is exactly what you want for a fish finder. 

Can you run a fish finder off a car battery?

Yes, you can run a fish finder off a car battery, but this isn’t ideal, since a car battery is a starting battery designed for short, strong bursts of discharge required to crank an engine, instead of a slow steady discharge required to run a fish finder.

So if you use a car battery for your fish finder, you’ll drain the car battery faster than you would a deep cycle battery, and this kind of use will also reduce the lifespan of the car battery dramatically. Because of this, it’s best to use a car battery for your fish finder only as a last resort, if you have no other options. 

What size battery do you need to run a fish finder?

The ideal size battery for a fish finder is a 12V with 7 to 18Ah (amp hours). This battery size is small enough to be readily portable and stowable, while providing enough power to run a fish finder for a whole day or even longer. 

However, if you plan to power a bunch of different boat electronics from the same battery as your fish finder, it may be better to get a larger capacity battery, with 24 or even 36Ah. 

Will a 6 volt battery run a fish finder?

No, a 6 volt battery is not able to run most fish finders. The  voltage required for the majority of fish finders is between 10 and 20 volts, with 12 volts being ideal (though you can go up to 24 volts in most cases).

How long does a fish finder battery last?

In order to determine how long your fish finder battery will last, you need to divide the battery amp hours by the amp draw of your fish finder.

For example, a Lowrance Elite FS unit is listed as drawing 0.9 amps at maximum screen brightness. So if you have a battery with 10Ah capacity, this will give you 11.1 hours of run time in theory. 

However, since real run times can differ by up to 25% from theoretical run times (due to host of other factors that play into this), it’s best to shave off 25% from the result, and assume that your run time is going to be about 8.3 hours, which puts you on the safe side. 

How do you charge your fish finder battery?

If you’re using a deep cycle battery for your fish finder, you need to recharge it with a compatible charging device after use. A lithium battery requires a lithium battery charger, while a sealed lead acid battery requires an SLA battery charger.

On the other hand, if you’re using your starting battery for your fish finder, it will be automatically recharged when you run the outboard motor.

How long does it take to charge a fish finder battery?

The exact time to charge a fish finder battery depends on the amp hour capacity of your battery, as well as the amperage provided by the charger. But a standard 10Ah battery takes about 3 to 5 hours to recharge when charged by a 2 Amp charger. 

See also: How many hours does it take to charge a deep cycle battery?