What Size Battery Should Be Used with a Trolling Motor?

Trolling motors are an excellent tool to add to your boat - but finding the right type of battery with the dimensions and voltage you need isn't so easy.

If you’re a bass angler, you know this to be absolutely true:

Largemouth bass fishing requires anglers to be precise in everything they do.

Without a doubt, this includes equipment selection and where they cast their lures.

One of the most important components of achieving this level of precision is the orientation of the boat to the cover that is being fished. A trolling motor is a critical piece of equipment to achieve proper boat placement and orientation to the cover that holds record largemouth bass. 

However, it’s not easy to know which size battery should be selected for a trolling motor. There are a variety of factors involved and no two boats are alike.

To make matters worse, some of the electrical principles can be very confusing to the uninitiated. Understanding the dynamics of selecting the best trolling motor battery can be incredibly confusing and intimidating.

Let’s dive into all the different factors you’ll need to consider when choosing the right battery for your particular trolling motor, boat, and fishing goals.

Different Battery Types Explained 📖

Understanding the proper charging methods and techniques for your trolling motor is crucial to getting the most out of your trolling motor battery. To prevent trolling motor battery failure, selecting a deep cycle marine battery with the appropriate amp hour ratings for the motor it will be attached to and charging it properly is essential.

Batteries are inherently complicated. There are many different types and each type is affected differently by the environment they are subjected to.

However, to make the best decision for your trolling motor battery, you must first understand the different types of batteries. This will allow you to make informed decisions as to their individual strengths and weaknesses and how it applies to your particular application.

Lead Acid Wet Cell 🔋

The most classic example of a trolling motor battery is the lead acid wet cell battery. For many years these batteries were the only type that was on the market. Essentially, they are just a car battery.

Certain types of lead acid wet cells are optimized for deep cycle marine use, but they are not really different from a standard car battery. While these are the most widely available batteries on the market, they are also the most technologically outdated. There are far better options available today.

If you are choosing a lead acid wet cell battery for your trolling motor battery, there are concerns you should note before purchase and installation. Installing a lead acid wet cell battery should be done with caution and in the correct sequence.

The acid that must be placed in the cells with distilled water can spill out and create a very real hazard for yourself, the boat, and the environment. While these are cheap and effective, they are discouraged for use in general but specifically for use on boats for this reason.

AGM Batteries 🔋

Absorbent Glass Matt or AGM batteries are the most common marine battery on the market currently. They work just like lead acid batteries but are not spillable as they are completely enclosed.

The key difference between a lead acid battery and an AGM battery is its internal components. Where lead acid uses hydrochloric acid and lead, AGM batteries use glass matt and a gel to create the needed chemical reaction to store electrical power. The result is a safe, non-spillable battery that is safe to use in nearly all applications. 

When you consider the water and humidity that comes with fishing for bass in rainy conditions, having a completely sealed battery is critical. The long-term health and safe operation of the battery hinges on the ability of the battery to keep the appropriate balance of its internal chemicals. 

Where a lead acid battery can leak if one of the cell caps is loose, an AGM battery has no such weakness. This feature alone has led to AGM batteries to be widely adopted by the public.

Lithium Batteries 🔋

While still very expensive, lithium batteries are the direction trolling motor batteries are going. They are extremely powerful, extremely lightweight, and their power discharge curve is flat allowing 100% power until the battery is completely depleted.

When you consider a standard battery only weighs six pounds and can be tucked into a very small compartment, lithium is the obvious choice for trolling motor batteries. They come in a wide range of sizes and different amp hours allowing the boat owner to select the best battery for his vessel.

They do have their limitations. Most chargers, to include popular onboard boat chargers, can only charge them to 80% capacity. In addition to being expensive, they can also explode if damaged or exposed to direct sunlight for a prolonged period of time.

If this happens, they will produce a fire that cannot be extinguished with water. Therefore, lithium batteries should never be discarded in your household garbage or stored in exposed sunlight.

Despite their limitations, one of the best kayak fishing tips you will receive concerning trolling motors and their batteries is to use a lithium battery. They take up almost no space and their weight is so small that they provide a negligible impact to the boat’s performance.

This makes the lithium battery the best possible choice for the kayak fisherman. If they can be afforded, then lithium is the type of battery you should select for your kayak setup. Generally speaking, the top trolling motors for kayaks are equipped with lithium batteries. 

Boat Weight and Thrust 🚤

The weight of your boat is likely the biggest factor you need to consider to select the right size trolling motor. Once you have selected the correct trolling motor, then the manufacturer will dictate what size battery you need for that particular motor. The chart below denotes how different weights of vessels require different levels of thrust at a minimum. 

However, it is common practice among many anglers to get an oversized trolling motor and operate it on the lower end of its capability spectrum. This allows you to have the ability to fight wind and waves, and operate as a secondary propulsion method if needed. While this increases the weight and expense of the boat, it is a recommended practice as it increases your flexibility and capability on the water. 

While weight is a large determining factor in your trolling motor size and therefore battery, it is only one factor. You must ask yourself difficult questions about what you can expect in the waters you normally operate in.

If you have a lightweight boat in open water, you may want to increase the size of the trolling motor you mount on your vessel. That will require much more battery capacity.

However, if you are operating in low current, low wind, enclosed areas, it may make much more sense to get the minimum recommended trolling motor. However, in no case should you run the risk of underpowering your vessel by going under its weight class. 

How Hull Design Impacts Thrust 💡

The greatest factor to consider when looking at different boat hulls in terms of trolling motor effectiveness is their hull design. The deeper the hull extends into the water, the more the trolling Jontor has to work to turn the boat.

If the boat sits on top of the water with very little depth like a jon or pontoon boat, it is very easy to simply push the boat across the surface of the water. However, with modified and deep v hulls, a trolling motor will have to work much harder to overcome the resistance of the increased surface area of the hull extended into the water to get the boat to turn.

This is another area where the fishing kayaks excel at trolling motor efficiency and effectiveness. With advanced hull designs fishing kayaks have very little displacement and virtually sit on the skin of the water.

This allows paddling, pedaling, and trolling motoring hull design to be done very efficiently. Higher speeds can be achieved with less battery power being expended since the resistance against the motor is minimized. 

However, there is a catch. Lighter craft with low levels of hull displacement are much more susceptible to forces acting on the boat. This means wind and waves have much more of an effect on the hull. This translates to more frequent and heavier use of the trolling motor to keep the boat in place. 

Voltage and Thrust ⚡️

While many things are complicated concerning this topic, the relationship between voltage and thrust is pretty straight forward. The higher the voltage the motor, the more thrust can be produced.

This is simply because the trolling motor can turn the prop faster and result in more revolutions of the prop through the water. Therefore a 36VDC trolling motor, given being attached to the same hull, will go much faster than a 12VDC trolling motor.

Additionally, the higher voltage trolling motors are often more efficient and last longer than the lower voltage trolling motors at lower speeds. This is a feature that makes them desirable provided you can compensate for the extra battery weight and space in the boat. 

Amp Hour Rating and Amperage Draw 📊

When you are selecting a battery, the term “amp-hour” will be frequently talked about. While this concept can be confusing at first, it is very simple to understand. It only takes some getting used to.

An amp hour is simply the power capacity of the battery. It denotes how many amps can be supplied over one hour. Therefore, if it is a 100 AH battery, it can supply 100 amps over 1 hour or 25 amps for four hours. 

“Amperage” is another term that needs to be understood in this arena. The classic metaphor to understand amperage and voltage is a water hose. Voltage is the diameter of the hose. The more voltage, the larger the water hose you have in your hand. Amperage is the speed in which water flows out of that hose.

Therefore you could have a high amperage, low voltage circuit which is very powerful in the same way a car wash water sprayer is powerful. However, you could also have a very large hose that only trickles water much like a garden hose. 

The “amperage draw” is merely the speed at which electricity flows through your trolling motor system. The higher the amperage draw, the faster the trolling motor is likely to propel the boat, but it will die sooner. The lower the amperage draw, the slower, but longer it will go through the day. Therefore, to get the most out of your battery, you need to have the most efficient fishing setup possible. 

If you can keep your weight, drag, displacement, and exposure to wind down, your battery will last longer. It is a general rule of thumb not to operate your trolling motor above 30% unless you need to to counteract wind or current. This is typically the sweet spot between speed and efficiency and will let you get the most out of the trolling motor battery. 

The Importance of Reserve Capacity ✅

Reserve capacity is a standardized concept that helps a buyer level set batteries for ease of comparison. It denotes how long a battery can supply 25amps at 80 degrees F until it discharges to 10.5 VDC. Therefore, higher amp-hour batteries will have a higher reserve capacity. Understanding this allows different batteries to be understood and compared simply. 

This is important to understand so that you will know what your battery is capable of and how much electrical power you can store on your boat. If you consider the space available in a battery compartment or place on a kayak, there is only so much room available. Therefore, you should select the battery that will fit, is compatible with your trolling motor, and has the highest reserve capacity to ensure optimal use.

Reserve capacity is important to keep in mind when equipping a kayak with a trolling motor. Depending on the method used to attach the trolling motor, space can come at a premium. 

Therefore, knowing what your minimum reserve capacity is for your battery can drive the space you need to allocate for a battery. If you know the space you need you will know how much room you have available for different mounting options.

Conclusion 🏁

A trolling motor is an essential piece of gear for those that find themselves navigating the habitat maintained by largemouth bass. It allows you to be stealthy and position the boat so that you can make effective presentations to key pieces of cover.

Though selecting a battery for that trolling motor can be daunting at first glace, it is fairly simple. By understanding a few key concepts of both electrical theory and the unique nuances of trolling motors, you can make a good decision with ease.

Determining the Right Battery Dimensions for a Trolling Motor: FAQs

What Size Battery is Best for a Trolling Motor on a Kayak?

The best battery for a trolling motor on a kayak is the one that will get you where you want to go and back safely. The size of the battery should be selected based on the manufacturer’s guidelines for that particular motor.

What Size Battery is Best for a 55lb Thrust Trolling Capacity?

A single 12VDC battery is best for a 55lb thrust trolling capacity trolling motor. For vessels that weigh less than 2500lbs, this will supply more than enough thrust capacity to operate the trolling motor for extended periods at normal levels. However, in the event you need even longer staying power consider getting two batteries and wiring them parallel to one another. 

How Many Amps Does a 55lb Trolling Motor Draw?

A 55lb trolling motor will draw different amperages depending on a variety of factors. The make, model, conditions it is operating in, and the speed it is being operated will all factor into how many amps the trolling motor will draw at any given time. One of the advantages of fishing from a kayak versus a bass boat is that the light weight of the kayak leads the trolling motor to draw far fewer amps and makes the battery last longer. 

How Long Will a 50AH Battery Last with a Trolling Motor?

A 50AH battery will last up to 50 hours if the trolling motor only draws one amp. However, many trolling motors will draw far more than that and will subsequently reduce the length of time that the battery lasts.

The average 55lbs thrust trolling motor operating at full throttle draws 54 amps and will deplete a 50AH battery in less than an hour. It is important to operate your trolling motor, whatever the amp hour rating of your battery, most efficiently and responsibly possible at all times. 

How Long Will a 100AH Battery Last with a Trolling Motor?

A 100AH battery will last with a 55lbs thrust trolling motor operated at full throttle for an hour and fifty-one minutes provided the temperature is around 80 degrees. Any variation from those conditions will lead the battery to last either shorter or longer depending on the adjustment.

The amp hours of a battery are not the determining factor of how long the battery lasts, but rather only what it can produce. The factors surrounding the vessel, the manner it is operated, and the environment it is operated in have a much greater impact on how long the battery lasts. 

What Size Battery is Best for a Trolling Motor on a Canoe?

The best-size battery for a trolling motor on a canoe is the lightest battery that meets the trolling motor manufacturers' requirements and supplies enough reserve capacity to be optimally operated. This requires the operator of the canoe to have the prerequisite boating knowledge to be safe and successful.

What Size Battery Should I Use on a Jon Boat?

You should use the battery that is the appropriate size for the motor you have selected for your Jon boat which will also allow you to operate the vessel in a controlled manner. This is likely a single 12VDC lead acid battery, but if the manufacturer, your boat’s length, or other circumstances calls for it, you could need a larger battery. 

How Long Does a Trolling Motor Battery Last?

A trolling motor battery lasts different times depending on how much it is used, at what intensity it is used, and to what it is connected. For example, a 100AH battery will supply 100 amps for 1 hour or 1 amp for 100 hours.

Therefore, in light of this principle, it is important to attempt to operate your trolling motor at the lowest level possible to achieve the speed you need to maximize your battery's charge. Only run your trolling motor at the highest level if you must.