What Size Battery Do I Need for a Trolling Motor?

When you’re out on the water, whether for a leisurely day of fishing or a more serious adventure, the last thing you want is for your trolling motor to run out of power. Choosing the right battery size for your trolling motor is essential to ensure you have enough juice to navigate smoothly and efficiently for the duration of your trip. However, with so many options available, selecting the perfect battery can feel overwhelming. In this guide, we’ll walk you through the key factors to consider when matching a battery to your trolling motor, from understanding thrust and voltage to calculating the correct battery capacity. By the end of this post, you’ll have all the knowledge you need to make an informed decision and ensure your next outing is powered for success!

Understanding Trolling Motors

What is a Trolling Motor?

A trolling motor is a small, electric-powered motor used to propel boats at slow speeds. Unlike the main engine, which is used for faster speeds, a trolling motor is designed for precise maneuverability and quiet operation. It’s primarily used for fishing, allowing boaters to navigate through waters without disturbing the fish. Trolling motors are typically mounted on the bow or stern of the boat and can be operated via a hand tiller or a foot pedal, depending on the model.

The key advantage of a trolling motor is its ability to provide consistent and controlled movement at a slow speed, which is ideal for fishing. This gives anglers the ability to maintain their position in the water, drift with the current, or maneuver around obstacles without spooking fish.

Types of Trolling Motors

Electric Trolling Motors The most common type of trolling motor is electric. These motors are powered by batteries and are known for being quiet and efficient. Electric trolling motors are available in different voltages (12V, 24V, and 36V) and thrust ratings, allowing boaters to choose the right motor for their boat size and specific needs.
- 12V Trolling Motors: These are the most common and are typically used for smaller boats or kayaks. They are generally less powerful but still provide ample thrust for smaller vessels.
- 24V and 36V Trolling Motors: These motors offer more power and are used for larger boats or those that need to cover larger distances. They require two or three batteries, respectively, and can provide better performance, especially in windy conditions or strong currents.
Electric trolling motors are highly favored for their ease of use and low maintenance requirements. They can operate for long hours, depending on the battery capacity, and are environmentally friendly since they don’t produce emissions like gas-powered motors.
Gas-Powered Trolling Motors While less common today, gas-powered trolling motors are still used by some boaters. These motors run on gasoline and offer a higher level of power, making them suitable for larger boats or situations where longer-range and more power are needed. They do tend to be noisier and less efficient than electric motors, but they have the advantage of not relying on battery power, which can be important on longer fishing trips.Gas trolling motors are often more complicated to maintain and can be less maneuverable than their electric counterparts, which is why they are used less frequently for precise, slow-speed navigation.

Common Uses for Trolling Motors

Fishing The primary use of trolling motors is for fishing. Whether you’re a recreational angler or a professional, having a trolling motor allows you to quietly move through the water while maintaining a steady speed, keeping your fishing lines in the water. For many anglers, a trolling motor is an essential piece of equipment, especially for bass fishing, fly fishing, or any situation where you need to move slowly and precisely.Trolling motors are perfect for controlling the boat’s drift, helping anglers position themselves in the best spots without disturbing the fish. They’re also great for navigating around underwater obstacles or over shallow waters where larger boat engines might be impractical.
Small Boats and Kayaks Trolling motors are often used on small boats and kayaks, where the space is limited, and the need for speed is minimal. In these cases, a trolling motor provides the necessary propulsion without taking up too much room or requiring a lot of maintenance. Electric trolling motors are especially popular for kayaks, as they are lightweight and easy to install.For kayakers, a trolling motor can greatly improve the experience by allowing them to travel longer distances, conserve energy, and focus on fishing instead of paddling. It also makes it easier to navigate against currents or wind without much physical effort.
Pontoons and Small Fishing Boats Many small fishing boats, including pontoons, often use trolling motors for slow, controlled movement. This is especially true for boats that don’t need to travel at high speeds but require precise maneuvering to fish in specific locations or drift along shores. A trolling motor can keep the boat in position and can be operated with ease, even by beginners.For pontoon boats, trolling motors are often used in conjunction with a main engine for fishing trips, allowing boaters to take advantage of both speed and quiet navigation when needed.

Factors that Affect Battery Size for Trolling Motors

Motor Power (Thrust)

One of the most important factors to consider when choosing a battery for your trolling motor is the motor’s thrust rating. Thrust is the measure of a trolling motor’s power to push or pull a boat through the water. It is usually measured in pounds (lbs) of thrust, and typical ratings range from 30 lbs to 100+ lbs for larger motors. The higher the thrust rating, the more power the motor has to move the boat.

The thrust rating directly correlates to the size and weight of the boat. Larger boats or those with more weight (such as loaded fishing gear, passengers, or equipment) will require a motor with a higher thrust rating. For example, a 30 lb thrust motor might be sufficient for a small, lightweight boat like a kayak or a small jon boat, but a larger boat will need a motor with 55 lbs or more of thrust to ensure it can move effectively through the water.

Motor efficiency is also tied to thrust. A motor with too little thrust may struggle to move a heavier boat, causing it to work harder and drain the battery faster. On the other hand, a motor with more thrust than necessary will use more power than needed, reducing the efficiency of your setup. Therefore, it’s important to match the thrust rating to the size and weight of your boat to optimize both performance and battery life.

Voltage Requirements

Trolling motors typically operate on three common voltages: 12V, 24V, and 36V. The voltage of the trolling motor is a key factor in determining the type of battery you’ll need. Generally, higher voltage motors are more powerful, and they provide longer run times at higher speeds, making them ideal for larger boats or those requiring greater power.

12V Motors: These are the most common and are typically used for smaller boats (like kayaks or small fishing boats). A 12V system generally requires one battery and offers moderate power, suitable for lighter loads and shorter trips.
24V Motors: These motors provide more power than 12V systems and are generally used for medium to large boats. A 24V trolling motor requires two 12V batteries connected in series. They are great for boats that need more thrust and longer operation times without overloading the system.
36V Motors: These motors are typically used for large boats that require maximum thrust. They are more efficient for large, heavy boats or in windy and rough conditions. A 36V trolling motor requires three 12V batteries. While they provide the highest thrust and best efficiency, they are also more costly and require more battery maintenance.

The choice of voltage not only impacts the motor’s power but also the capacity and configuration of the battery system. Higher voltage motors generally offer better performance and longer operational time, but they also require a greater number of batteries, which affects your overall setup and maintenance needs.

Boat Size and Weight

The size and weight of your boat are critical factors in determining the necessary battery size for your trolling motor. A larger, heavier boat will need a motor with greater thrust to move efficiently, which in turn requires a more powerful battery. Smaller boats, like kayaks or dinghies, can operate well with a 12V system, while medium to large boats may need a 24V or 36V system for adequate power.

The weight of the boat, including any gear or passengers, can impact the motor’s performance. A heavily loaded boat will put more strain on the motor, which can lead to reduced efficiency and shorter battery life. This is why understanding your boat’s weight and choosing the right thrust rating is so important to ensure that you select the right size battery.

Additionally, consider how the weight distribution in your boat may affect the trolling motor’s performance. If your boat is unevenly loaded, it may require more power to maintain speed and stability, which will increase the strain on both the motor and the battery.

Duration of Use

The length of time you plan to use your trolling motor is another critical factor in determining battery size. The longer you intend to run the motor, the more battery capacity you’ll need. Trolling motors draw a significant amount of power, especially when operated at higher speeds or against currents.

Battery capacity is measured in amp-hours (Ah), and it refers to how long a battery can provide power before it needs recharging. A 12V battery with a higher Ah rating will provide more power for a longer period. For example, a 12V 100Ah battery will allow for a longer runtime compared to a 12V 50Ah battery.

If you plan to fish for several hours or take long trips, it’s essential to choose a battery with sufficient capacity to meet your needs. If you anticipate shorter outings or only using the trolling motor occasionally, a smaller battery may suffice. It’s also important to consider how often you’ll need to charge the battery and whether you have access to charging facilities during your trips.

Water Conditions

The type of water you are boating in—saltwater or freshwater—can affect the performance and battery life of your trolling motor. Saltwater can be harsher on both the motor and the battery due to the corrosive nature of salt, which can degrade electrical components over time. Additionally, saltwater is denser than freshwater, which means it can create more resistance for the motor, requiring more power and thus draining the battery faster.

Freshwater, on the other hand, is generally less demanding on the motor, and you may find that your battery lasts longer under these conditions. However, you should still factor in the water conditions when determining your battery needs. If you are using your trolling motor in saltwater, consider opting for a marine-grade battery that is designed to resist corrosion and withstand the harsher environment.

Choosing the Right Battery Size for Your Trolling Motor

Amp-Hour (Ah) Rating

The Amp-Hour (Ah) rating is a key metric when selecting the right battery for your trolling motor. Amp-Hours measure the battery’s capacity to supply current over a specific period. It refers to how much power the battery can provide for a given amount of time. For instance, a battery rated at 100Ah can supply 1 amp of current for 100 hours or 10 amps for 10 hours, and so on. Essentially, the higher the Ah rating, the longer the battery can power your trolling motor before needing a recharge.

The Amp-Hour rating is directly related to how long you plan to use the trolling motor. If you expect to use your trolling motor for extended periods, especially at higher speeds or in tough conditions, you’ll need a battery with a higher Ah rating to ensure you don’t run out of power too quickly. For example, a boat that requires a 30 lb thrust trolling motor and will be used for short trips may only need a 50Ah battery, while a 36V system with a larger motor may require 100Ah or more to ensure a full day of use.

How to Calculate the Right Amp-Hour Rating for Your Needs?

To calculate the right Amp-Hour rating, you need to consider several factors, including the motor’s power, the voltage of the motor, and the duration of your trips. Here’s a simplified approach to estimating the battery size needed for your trolling motor:

Determine the motor’s power consumption:
- First, find the power consumption of your trolling motor. This is usually listed on the motor’s label or manual in terms of amps per hour. For example, a 12V motor drawing 10 amps per hour at full speed.
Estimate your usage time:
- Next, estimate how many hours you plan to run the trolling motor at full power. For example, if you plan to run the motor for 5 hours, you’ll need to know the total amp-hours required.
Calculate the total Amp-Hours required:
- Multiply the number of amps the motor uses by the number of hours you expect to use it. For example, if your motor uses 10 amps per hour, and you plan to use it for 5 hours:10 amps x 5 hours = 50Ah.
This means you need a battery with a 50Ah rating to last for 5 hours of continuous use at full speed.

Keep in mind that trolling motors rarely run at full power for the entire duration, so you may want to adjust your calculation if you will be using lower settings for longer trips.

Battery Types

When choosing the right battery for your trolling motor, you’ll primarily be deciding between two main types: Lead-Acid and Lithium-Ion batteries. Each has its advantages and disadvantages, so it’s important to understand the key differences.

Lead-Acid Batteries

Lead-acid batteries are the traditional choice for trolling motors. They have been around for decades and are widely available. There are two main types: flooded lead-acid (FLA) and sealed lead-acid (SLA, including AGM and gel).

Pros of Lead-Acid Batteries:
- Lower upfront cost: Lead-acid batteries are more affordable compared to lithium-ion batteries.
- Readily available: They are easy to find at most marine or automotive stores.
- Durability: They have been proven over time and are generally reliable for the average boater.
Cons of Lead-Acid Batteries:
- Heavier: Lead-acid batteries are significantly heavier than lithium-ion batteries, which can affect boat performance and ease of transport.
- Shorter lifespan: They typically last around 3-5 years, depending on usage, while lithium-ion batteries can last much longer.
- Lower efficiency: Lead-acid batteries are less efficient in their power usage, and their performance decreases as they age.

Lithium-Ion Batteries

Lithium-ion batteries have gained popularity in recent years due to their superior performance. These batteries are lighter, more efficient, and have a longer lifespan.

Pros of Lithium-Ion Batteries:
- Lightweight: Lithium-ion batteries are much lighter than lead-acid batteries, making them easier to transport and reducing the overall weight of the boat.
- Longer lifespan: Lithium-ion batteries can last 10 years or more, depending on usage, significantly outlasting lead-acid alternatives.
- Higher efficiency: Lithium-ion batteries maintain a consistent voltage throughout their discharge cycle, providing better performance until they are almost fully drained.
- Faster charging: These batteries generally charge faster, allowing for quicker turnaround times between trips.
Cons of Lithium-Ion Batteries:
- Higher upfront cost: Lithium-ion batteries are significantly more expensive than lead-acid batteries, though the higher initial cost is often offset by their longer lifespan and better efficiency.
- Specialized charging needs: They require a specific charger to ensure proper maintenance and prevent damage.

Calculating Battery Capacity

To calculate the total battery capacity you need, you should use the following formula:

Battery Capacity (Ah) = Motor Power (Amps) x Duration of Use (Hours)

For example, if you have a 12V trolling motor that uses 15 amps at full power and you plan to run it for 6 hours:

15 amps x 6 hours = 90Ah

This means you will need a 12V battery with a 90Ah rating to run the motor for 6 hours at full power. If you’re using a 24V system, you’d typically need two 12V batteries wired in series to achieve the necessary voltage, but the total capacity would still be 90Ah, and the batteries would each provide 45Ah (assuming they are equally rated).

Example Calculations for Different Motor Sizes

For a 30 lb thrust motor: A small motor like this might draw around 5-10 amps per hour. For a 12V system, if you plan to run it for 4 hours, you would need a battery with a 20-40Ah rating.
For a 55 lb thrust motor: This motor might draw 10-15 amps per hour. For 5 hours of use, you would need a battery with a capacity of around 50-75Ah.
For a 75 lb thrust motor: These motors may draw around 15-20 amps per hour. Running it for 6 hours would require a battery rated at 90-120Ah.

How to Match Battery Size to Trolling Motor?

Guide for Choosing Battery Size Based on Motor Thrust and Usage

When selecting a battery for your trolling motor, it’s essential to match the motor’s thrust capacity with the appropriate battery size to ensure optimal performance. The thrust rating of your trolling motor, which is typically measured in pounds (lbs) of thrust, will determine how much power the motor requires to propel your boat effectively. Thrust directly impacts how well your boat performs in different conditions, and selecting a battery with an adequate Amp-Hour (Ah) rating ensures that the motor runs efficiently without draining the battery too quickly.

Small boats (under 10 feet): For small boats, such as kayaks or small fishing boats, a trolling motor with 30 lbs of thrust or less is generally sufficient. A 12V battery with an Amp-Hour rating between 50Ah and 75Ah will typically meet your needs, depending on how long you plan to use the motor and the weight of the boat and its occupants. For lighter usage, you might not need the highest capacity, but having a higher Amp-Hour rating will offer extended runtime.
Medium-sized boats (10-20 feet): For medium-sized boats like aluminum or fiberglass fishing boats, a 55 lbs to 70 lbs thrust motor would be more appropriate. For this size of motor, you’ll likely need a 12V or 24V battery system with a higher Amp-Hour capacity—ranging from 75Ah to 120Ah—especially if you plan on extended outings. Choosing a 24V battery system with two 12V batteries will provide better performance for longer trips.
Large boats (over 20 feet): Larger boats or those used in challenging conditions (like in wind or strong currents) will require motors with higher thrust ratings, typically 80 lbs or more. These motors will need a 24V or 36V battery system. A 36V system, for example, may require three 12V batteries, each with an Amp-Hour rating between 100Ah and 150Ah. The larger the boat and the greater the need for sustained high-speed movement, the more powerful the battery needs to be to ensure you can run the motor for extended periods.

Tips on Ensuring You Don’t Over or Under-Power Your Trolling Motor

Selecting the right battery size involves finding a balance between having enough power and not exceeding the necessary capacity for your motor. If the battery is too small, the motor won’t perform well, and you risk running out of power mid-trip. On the other hand, choosing a battery that’s too large can lead to unnecessary weight, cost, and underutilization of the battery’s full potential.

Avoid Under-Powering: If you choose a battery that’s too small for your trolling motor’s thrust, your motor may struggle to deliver the necessary power, leading to poor performance, especially in adverse conditions like strong winds or currents. Underpowered motors also tend to drain batteries much faster, reducing runtime and increasing the frequency of recharges.
Avoid Over-Powering: While it may seem like a good idea to choose the most powerful battery available, going too large can be inefficient. A battery with more capacity than needed may result in excess weight, which can affect your boat’s overall performance. Additionally, using a battery with too much power for the motor will lead to increased costs and unnecessary energy consumption without providing tangible benefits in performance.
Factor in Your Usual Conditions: Consider the typical water conditions you’ll be navigating. If you frequently fish in areas with strong currents, wind, or if your boat is heavily loaded with gear, you’ll want to choose a battery that provides a bit more capacity than you might need for calm, still-water conditions. However, for flat-water fishing in a lightweight boat, a smaller battery may suffice.
Plan for Extra Runtime: It’s always a good idea to plan for a little more capacity than you might think you need. Having extra runtime in reserve ensures that you don’t unexpectedly run out of power, especially if you’re fishing in remote areas or planning longer trips.

Common Recommendations for Popular Trolling Motors

When choosing the right battery size for a trolling motor, it’s helpful to consider the recommendations made by motor manufacturers, as these are often based on optimal performance standards. Here are some general guidelines for popular trolling motors and the battery sizes they require:

Minn Kota Endura C2 (30-55 lbs thrust): These motors are commonly used for small to medium-sized boats. A 12V battery with an Amp-Hour rating of 50Ah to 75Ah is typically recommended for optimal performance. For longer trips, a 12V 100Ah battery may be needed to ensure sufficient runtime.
Motorguide Xi3 (55-70 lbs thrust): For these mid-range trolling motors, a 12V battery is often sufficient for a 55 lbs thrust motor, while a 24V battery system is ideal for a 70 lbs thrust motor. The recommended battery capacity ranges from 75Ah to 120Ah, depending on your expected usage.
Minn Kota Terrova (80-112 lbs thrust): Larger motors like the Minn Kota Terrova, which are used for bigger boats or fishing in more challenging environments, often require a 24V or 36V battery system. For the 80 lbs thrust version, a 24V system with two 12V batteries and a capacity of 100Ah to 120Ah is typically recommended. For the 112 lbs thrust version, a 36V system with three 12V batteries with a combined capacity of 150Ah is ideal.
Motorguide Xi5 (80-105 lbs thrust): These high-powered motors are designed for large boats and offer superior performance in tough water conditions. A 24V battery system with two 12V batteries is ideal for the 80 lbs thrust model, while the 105 lbs thrust model requires a 36V battery system. Battery capacity for both ranges from 100Ah to 150Ah, depending on your expected run times.

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