Picking a Trolling Motor Battery

Trolling Motor Battery Selection: How To Pick The Correct Battery For Your Trolling Motor

Whether you are replacing existing batteries or installing a new trolling motor, there are a few things you will want to consider: Battery type, amperage hour rating, size/weight and your budget.

Battery Types

For many years, there were two primary types of deep-cycle 12-volt batteries recommended for use with trolling motors: Lead Acid (flooded) and AGM (Absorbent Glass Mat) Batteries.

The term "Deep-cycle" means that the batteries are designed for discharging smaller amounts of current (amperage) over a longer period of time.

Although lead acid and AGM batteries are still the most popular trolling motor batteries, Lithium (LiFePO4) batteries are catching on!

Flooded Lead Acid Batteries:

Flooded lead acid batteries are common and affordable deep cycle batteries for trolling motors. They can handle frequent draining and re-charging associated with trolling motor use. Depending on quality, lead acid batteries will last between 2-3 years. These batteries can be purchased for less than $100 and are readily available in a variety retail outlets. The downside of lead acid batteries is that they can require occasional maintenance – topping off the water – and they are also prone to vibration and potential spillage.

AGM (Absorbent Glass Matt) Batteries:

AGM Batteries are advanced lead acid batteries that are completely sealed and more stable than flooded lead acid batteries. AGM batteries contain glass fiber mats which separate the positive and negative plates inside the battery and help absorb the battery acid.

AGM batteries also tend to provide a slightly longer run time and life-span relative to flooded lead acid batteries. While a flooded lead acid battery might last approximately 2-3 years, an AGM deep cycle battery can last up to 4 years.

Due to their more advanced technology and maintenance-free construction, AGM's are often a bit more expensive than flooded lead acid batteries and may not be an option for those on a tight budget. Although they are pricier, the safety, stability and performance benefits of deep-cycle AGM's may be worthwhile investment as the power source for your trolling motor. 

Lithium Batteries:

"LiFePO4" (lithium iron phosphate) is the technical term for the lithium batteries used with trolling motors. These lithium batteries are becoming increasingly popular choice for a variety of reasons:

Only One Battery Required -  Single lithium batteries are available in 12v, 24v, 36v and 48v. So even if you have a 36v trolling motor, you only need one 36v lithium battery instead of three 12v lead-acid or AGM batteries.  

Significantly Longer Run Time - Depending on the amp hour rating, lithium batteries can significantly increase your time out on the water compared to flooded lead acid and AGM batteries. 

Extremely Lightweight - For the smaller boats or boats where weight can be a considerable factor, lithium batteries offer a 70% average reduction in weight compared to traditional batteries. If you have a 24v or 36v motor you are cutting down even more weight because you would only require a single 24v or 36v battery. 

Longer Overall Battery Life - Depending on the brand, Lithium (LiFePO4) batteries can last up to 20 years whereas lead acid wet-cell and AGM batteries have an average life span of 2-4 years.

Cost Savings - Even though there is a higher up-front cost, purchasing a lithium battery for your trolling motor can save you money in the long run. If you calculate the cost of replacing your batteries every 2-4 years compared to the much longer lifespan of lithium batteries, you'll most likely be spending less on batteries when all is said and done. 

100% Depth of Discharge - This essentially means that you'll have full power no matter how charged they have left. Traditional batteries tend to lose power and capacity as their charge is depleted. By the way, the new Minn Kota Precision chargers are compatible with lithium batteries but they can only charge 12v lithiums; they are unable to charge the 24v or 36v models.

More Power - Due to the consistent, sudden fluctuation in speeds, trolling motors require a fair amount of cranking torque (aka thrust). Lithium batteries supply more power due to their negligible voltage drop when rapid acceleration is required.

Ultimately, good quality batteries with the right specs (see below), will provide adequate power for a full day of fishing.

We now sell BioennoPower and LBP (Lithium Battery Power) LiFePO4 Batteries.

Amperage Hour Rating

You can think of a battery's amperage hour rating as being similar to the gas tank of a car. With all else equal, a battery with a 115 amp hour rating will last longer than a 100 amp hour rated battery. A 100 amp hour rated battery can deliver 100 amp hours of current to a trolling motor but that does not mean that you will get 100 hours of run time.

If your motor is running at a very low speed and pulling 4 amps, the battery should provide approximately 25 hours of run time (100 amp hour rating / 4 amps = 25 hours). Similarly, if the motor is running on a high speed and pulling 40 amps, the battery would last for 2.5 hours (100 amp hour rating / 40 amps = 2.5 hours). For more information on understanding battery run times, please see our guide on Calculating Trolling Motor Run Time.

For trolling motor use, we recommend a battery with AT LEAST a 100 amp hour rating, a Group 27 rating and 175 minutes of Reserve Capacity (RC). We do not sell flooded lead acid lead or AGM batteries at TrollingMotors.net. However, both types listed above should be widely available in most areas.

For LiFePO4 (lithium) batteries, we recommend 50 amp hour rating or higher. A 50 amp hour rating may seem low compared to a lead acid battery but it's important to remember that LiFePO4 batteries are able to discharge 100% of their charge capacity whereas lead acid can only output 50% of their charge capacity. High quality lithium batteries also have better power density and more efficient voltage stability which increases capacity and run time. 

Amp Hour Rating Considerations For Lithium (LiFePO4) Batteries 

There are a tons of lithium battery brands out there with a wide scope of prices. For the most part, you get what you pay for with lithium batteries. Don't skimp and purchase a $100 battery made in China sold on Amazon; batteries are the beating heart of your trolling motor setup.

Lithiums contain Battery Management Systems (aka BMS); which act as the brains of the battery controlling thermal regulation, discharge rates and other important battery functions. When you hear about issues with lithium batteries getting hot, swelling or even catching fire, those are likely cheap batteries with a poor BMS. 

It's also important to read the fine print on warranties to determine the actual details of coverage. Make sure that the battery has at least a 8-10 year warranty and full replacement coverage. 

Battery Tips

• Never mix battery types or old batteries with new batteries. 
• Charge batteries as soon as possible after each use – leaving batteries in a discharged state will decrease their longevity and performance.
• If using flooded wet-cell batteries check fluid levels and top-off as needed 
• Check terminal connectors periodically for signs of corrosion – clean with a paste of baking soda and water. 
• Store batteries in a cool, dry place in the off-season and maintain with a trickle charger

In our opinion, high-quality LiFePO4 batteries are the best power source for trolling motors because they are safe, lightweight and can provide significantly longer run time; all from one battery! However, If you'd rather not spend the cash that's understandable, an AGM from a trusted brand will do just fine as well. 

 

Trolling Motor Battery FAQ

What type of battery is best for a trolling motor?

Trolling motors require deep-cycle batteries because they are designed to provide steady power over long periods of time. Unlike starting (aka cranking) batteries, deep cycle batteries are built to handle repeated discharge and recharge cycles commonly experienced during fishing trips.

Definition: Deep Cycle Battery
A deep cycle battery is designed to provide steady power over long periods of time and withstand repeated discharge and recharge cycles. This makes it ideal for trolling motors and other marine electronics that require continuous power throughout the day.

Can I use a car battery for a trolling motor?

No. Using a standard automotive starting battery for a trolling motor is not recommended. Car batteries are designed for short bursts of power to start an engine, not continuous discharge over several hours.

Does a trolling motor need its own dedicated power supply?

Yes, a trolling motor should have its own dedicated battery system separate from the engine starting battery and onboard electronics. Trolling motors draw significant continuous power, especially in wind, current or when using GPS anchoring features like Spot-Lock. Using a dedicated battery bank helps prevent voltage drops, protects sensitive electronics and ensures you still have sufficient power available to start the outboard at the end of the day.

What are the differences between lithium and lead-acid batteries for use with a trolling motor?

Lithium batteries are lighter, charge faster and maintain voltage more consistently throughout the discharge cycle. Traditional lead-acid batteries are generally less expensive initially but are heavier and may require more maintenance depending on the battery type. However, lithium batteries are increasingly becoming more affordable and common power sources for trolling motors. Lithiums also have a long lifespan (7-10 years) and do not have to be replaced as often as traditional lead acid batteries (3-4 years) which can save money in the long run.

Is there a particular type of lithium battery that I should be looking for?

For trolling motors, LiFePO4 (Lithium Iron Phosphate) batteries are generally considered the best choice. LiFePO4 batteries are specifically designed for deep cycle marine applications such as trolling motors. When selecting a lithium battery, look for a model with an integrated Battery Management System (BMS), marine-grade construction and sufficient amp hour capacity for your trolling motor voltage and expected run time.

Are lithium trolling motor batteries worth the cost?

For many anglers, yes. Lithium batteries offer longer lifespan, faster charging, reduced weight and more consistent power delivery. They are especially beneficial for anglers who fish frequently, want to reduce overall boat weight and save precious cargo space.

How many batteries do I need for my trolling motor?

The number of batteries required depends primarily on the trolling motor voltage. Most 12v trolling motors use one battery, 24v motors use two batteries and 36v motors require three batteries connected in series. Single lithium batteries are available in 12v, 24v and 36v.

What size battery should I use for my trolling motor?

Battery sizing depends on trolling motor thrust, boat size, fishing conditions and desired run time. Larger boats and higher thrust motors typically benefit from larger capacity batteries with higher amp hour ratings. In general, lead acid and AGM batteries should have a 100+ amp hour (ah) rating and lithium batteries should have at least a 50amp hour rating

What does amp hour (Ah) mean on a trolling motor battery?

Amp hour rating measures battery capacity and indicates how much energy the battery can store. In general, higher amp hour ratings provide longer run times for trolling motors.

How long will a trolling motor battery last on the water?

Run time depends on several factors including battery capacity, trolling motor thrust, boat weight, wind, current and how aggressively the motor is used. Heavy wind, current and continuous use of high power settings will reduce overall run time.

Do GPS anchoring features use more battery power?

Yes and no. GPS features such as Minn Kota's Spot-Lock or Garmin's Anchor Lock continuously adjust the trolling motor's speed and heading to maintain boat position. In calm conditions, the motor will require less steering inputs and throttle to hold a position. In windy or rough conditions, the motor needs to work harder to hold a spot which can use up quite a bit of juice.

Should trolling motor batteries be wired in series or parallel?

Most 24v and 36v trolling motor systems use series wiring to increase voltage. Parallel wiring increases capacity but maintains the same voltage. Whatever your choice may be, follow the trolling motor manufacturer wiring recommendations to avoid serious health risks to yourself and your boat...or both.

What is the best battery chemistry for cold weather fishing?

AGM and lithium batteries generally perform better than flooded lead-acid batteries in colder temperatures. Some lithium batteries include internal battery management systems with low-temperature charging protection.

Can I mix different trolling motor battery brands or sizes?

Mixing battery brands, capacities or ages is generally not optimal in multi-battery systems. Uneven performance between batteries can reduce efficiency and shorten overall battery life.

How often should trolling motor batteries be charged?

Trolling motor batteries should ideally be recharged after every use, even after short trips. Allowing batteries to remain partially discharged for extended periods can reduce performance and battery lifespan. Charging times and cycles also depend on battery chemistry and other specifications so make sure to charge per manufacturer recommendations.

What type of charger should I use for my trolling motor batteries?

Always use a charger compatible with your battery chemistry and voltage system. Lithium batteries often require lithium-compatible chargers, while AGM and flooded lead-acid batteries may use different charging profiles.

How can I make my trolling motor batteries last longer?

Proper charging, avoiding deep over-discharge, using the correct charger and storing batteries properly during the offseason can significantly extend battery life. Keeping battery terminals clean and connections tight also helps maintain performance.