What Size Marine Battery Do I Need for Trolling Motor

When you realize that your old trolling motor marine battery needs to be replaced by a new one. But you are confused about what size marine battery I need for trolling motor, here is my comprehensive advice to guide you through choosing the right battery size.

The marine battery comes in a wide selection of sizes, chemistry, and characteristics. To choose the right battery size you should first consider your boat. Because your boat may be designed for a very specific size of the battery. But you can put a large battery by changing out the battery box or by using the more available space in your boat. For example, If Your boat uses a Group 24 marine battery but has more space to put a Group 27 marine battery then you can think about upgrading to a larger size.

How to Choose the Perfect Size Marine Battery for Trolling Motor

When you get the measurement of your marine battery case for your trolling motor then you should consider your needs for boating. Generally, in the market, you will find three types of marine batteries are:

• Starting battery;
• Deep cycle battery and;
• Dual-purpose battery;

So, first, you should select which type of battery you need. Because each type of battery has a different purpose. Then, connect the trolling motor to the battery.

However, starting batteries are manufactured to deliver a short and high current burst to start an engine like you need when you are starting engine gasoline or diesel. Deep cycling batteries are manufactured to use for a longer period. It puts a small amount of energy for a long period of time like your house bank of batteries and a dual-purpose battery is kind of a balance between Starting batteries and Deep cycle battery

The types of your trolling motor should be in consideration because if the motor is not compatible with the capacity of the battery then it will not work. There are different types of motors available in the market like inboard, outboard, inboard-outboard, or i/o and electric trolling motors. Each type of motor has different requirements for the type of battery. For example, outboard, inboard, and i/o batteries usually require a high amperage battery with plenty of starting power. Generally, people use electric trolling motors for fishing. Fishing boats with trolling motors require long deep power drains that occur before the battery can be recharged.

The capacity of a battery always comes first. Because the more capacity it has the more power it will be able to discharge. The capacity of a battery is measured in two ways, which are ampere and hours. A 12v marine battery with 40 Amp hours can run a 55-pounds motor with 4 people on board for 1 hour at full speed.

So, the more Volt and Amp hours your battery have the more hour it will last. But if you want to know how long it will last without using this method, simply take two batteries one full of charge rated at 12v and another 9v battery out of charge then use a boost converter. Count the time on your watch until it gives you the signal.

So when measuring the right marine battery sizes for your trolling motor you should consider all these above factors. Because you don’t want to waste your money by choosing the wrong batteries.

What Type of Charger Should I Use for My Marine Battery

There are several types of chargers that can be used for a marine battery, but the most common and recommended type is a multi-stage charger.

A multi-stage charger is designed to charge a battery in several stages, such as bulk charging, absorption charging, and maintenance charging. The bulk charge stage delivers a high current to quickly charge the battery, while the absorption stage slows the current down to a steady state, allowing the battery to fully charge without overcharging. The maintenance stage is designed to keep the battery at full charge without overcharging.

Multi-stage chargers also have the ability to sense the state of charge of the battery and adjust the charging accordingly, which helps to prolong the life of the battery. Additionally, most multi-stage chargers are also equipped with a “float” mode which is a special charging mode used to maintain the battery at a full charge.

Another type of charger that can be used for marine batteries is a “smart” charger. Smart chargers are similar to multi-stage chargers, but they have more advanced features such as microprocessor control, temperature sensing and digital displays. These chargers are able to adjust the charging rate based on the temperature of the battery and can provide more precise charge control.

It is important to select a charger that is designed specifically for marine use, as they are built to withstand the harsh marine environment and are sealed to protect against moisture and salt. It is also important to select a charger with a rating that is appropriate for the size and type of battery you are using.

Marine Battery Size Chart for Trolling Motor 

The most common marine battery sizes are 22NF, 24M, 25, 27M, 31M, 34M, 35, and 65 which are acceptable for different kinds of trolling motors. We include here a chart of several boat batteries size and minimum thrust levels and more. 

Battery Size	Battery Types	Boat’s Weight	Thrust Level
12-volt battery	Deep Cycle	1500	30lb
12-volt battery	Deep Cycle	2000	40 to 45lb
12-volt battery	Deep Cycle	2500	50 to 55lb
24-volt battery	Deep Cycle	3000 – 3500	70lb
24-volt battery	Deep Cycle	4000	80lb
36-volt battery	Deep Cycle	4000+	101 to 112lb

If the 12V and 24V battery batteries have a 100 to 120 Ah amp hours rate, they allow you to run for more than three hours. In this case, a higher amp hour rate is good for enjoying more run time of the trolling motor. Don’t forget to charge a deep discharge marine battery timely. Check this article on how to do it.

Conclusion

The size of the marine battery you need for a trolling motor will depend on several factors, including the power of the trolling motor, the length of time you plan to use it, and the number of times you plan to use it in a day. A general rule of thumb is to use a battery with at least 50 amp-hours of capacity for a trolling motor of 50-70 pounds of thrust and a 12-volt system. It’s also important to consider the type of battery you need, such as a deep cycle battery or a starting battery. It’s always recommended to check the manual of your trolling motor or consult with a professional for the exact battery requirement for your specific setup.

Frequently Asked Questions

What size of marine battery do I need to power a trolling motor?

The size of the battery you will need to power a trolling motor depends on the power output of the motor and the length of time you will be running it. Generally, you will need a battery with a minimum rating of 12 volts and at least 35 amp hours of capacity. The larger the trolling motor, the higher the amp hour rating will need to be.

What type of marine battery is best for a trolling motor?

Deep-cycle marine batteries are the best type of marine battery for a trolling motor. These batteries are designed to be regularly discharged and recharged, making them well-suited for use in trolling motors.

How long will a marine battery last when powering a trolling motor?

The life of a marine battery when powering a trolling motor depends on how often it is used and how deep of a discharge it experiences. Generally, a well-maintained battery should last for several years with regular use.