How to Choose the Best Trolling Motor Battery

With all the available battery models and brands on the market, finding a suitable trolling motor battery often can be a daunting task, but it shouldn't be.

But before getting a new battery or battery pack, one should first write down a few things, including the size and weight of the boat, motor strength, required trolling time, and of course, the funds allocated for the new trolling motor battery.

Updated: October 29, 2021.

On This Page:

Size and Weight of the Boat Electric Trolling Motor Thrust vs. Power What Type of Battery Do I Need For My Trolling Motor? Little Bit of Math BCI Group 31 Batteries 100Ah Lithium Batteries 200Ah Lithium Batteries Frequently Asked Question - FAQ Few Final Words

Size and Weight of the Boat

Electric motor power is rated in "pounds of thrust" (or "kg of thrust") which is not the most correct measure of force, but it gives a rough picture of the electric motor's ability to provide means of propulsion for the boat.

Also, when choosing the right electric trolling motor, it is a good idea to over-dimension both the electric motor and the battery for safety reasons.

The following table lists the most common sizes and weights of small boats and pontoons commonly used for trolling:

Boat Weight	Boat Length	Minimum Recommend Thrust	Recommended Thrust With Power Reserve
2000 lbs (906 kg)	<16 feet (~4.9 m)	40 lbs ~18 kg	60 lbs ~27 kg
2500 lbs (1132 kg)	~17 feet (~5.2 m)	50 lbs ~23 kg	70 lbs ~32 kg
3000 lbs (1360 kg)	~18 feet (~5.5 m)	60 lbs ~27 kg	80 lbs ~36 kg
3500 lbs (1586 kg)	~19 feet (~5.8 m)	70 lbs ~32 kg	90 lbs ~41 kg
4000 lbs (1812 kg)	~20 feet (~6.1 m)	80 lbs ~36 kg	100 lbs ~45 kg
5000 lbs (2265 kg)	21+ feet (6.4+ m)	>100 lbs >45 kg	>120 lbs >54 kg

Note that the actual required thrust depends on other things too, for example:

- water and weather conditions: calm water and no wind require no additional motor power. On the other hand, strong currents and wind can help the vessel sail faster down the current and wind, but if one has to sail up the current and wind, much more power and larger thrust are required.

- height of the boat: kayaks and most of the inflatable boats are low in the water with a relatively modest area of the boat that can act as the sail, requiring very little extra power. However, some pontoon boats and catamarans/trimarans are very tall, requiring extra power and thrust in windy conditions.

- presence of seagrass or similar vegetation: subsurface vegetation increases the vessel's resistance requiring more power and thrust to keep the required trolling speed. Also, the vegetation can wrap around the propeller shaft, greatly increasing the motor load and even causing the circuit breaker to go off.

So, feel free to choose the required electric trolling motor strength according to the table, just have in mind all (or most of) other possible situations, too.

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Electric Trolling Motor Thrust vs. Power

Thrust achieved by electric trolling motor roughly equals to the water mass flow in the unit of time, multiplied by the water speed difference.

In order to stay away from the math as much as possible, just have in mind that an electric trolling motor with a larger thrust requires more electric power.

The following table lists some of the common electric trolling motors, their maximum thrust, nominal voltage, maximum current, and nominal maximum power:

Note: Amazon affiliate links in the table open in the new windows, feel free to check them for the most up-to-date offers and prices.

In order to keep maximum currents at acceptable levels (at most 50-60 Amps), stronger electric trolling motors operate at 24, 36, or even at 48 volts.

For example, electric trolling motors with thrust up to 60-70 pounds operate at 12 V, trolling motors with a thrust between 70-100 pounds operate at 24 volts, while electric trolling motors with thrust levels of 100 or more pounds, usually operate at 36 V, although there are models that operate at 48 or even more volts.

Of course, there are exceptions. For example, Minn Kota Riptide EM 160 operates at 24V with a maximum of 116 Amps. However, this is a double motor electric drive consisting of two 80 pounds electric motors, requiring 58 Amps each - hence the 116 Amps max. 

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What Type of Battery Do I Need For My Trolling Motor?

When looking for a new trolling motor battery, be sure to check battery chemistry, voltage, capacity (Ah or Amp Hour Rating), type, Reserve Capacity,  maximum continuous discharge current, maximum surge current, number of charging/discharging cycles, etc.

Trolling motor batteries must be able to withstand regular deep discharge operations and cyclic use. Also, from time to time, these batteries are left unattended for weeks or even for months, with local temperatures being sometimes very low (winter) or very hot (summer).

Common starting/cranking car/boat batteries should not be discharged regularly below 50% of their capacity, or their operating life can be significantly reduced.

Thus, for an electric trolling motor battery, one should choose a dual-purpose or preferably deep-cycle lead-acid or lithium marine or general-purpose battery. Such batteries have limited cranking currents, but that is not what they are designed for - they can easily withstand regular deep discharges down to 20-30% without adverse effects on their operating life.

Lead-Acid or Lithium Batteries?

Lead-acid batteries have been in use for a long time and will continue to be used for various purposes.

Lead-acid batteries may be wet/flooded lead-acid batteries, Absorbent Glass Mat (AGM) Sealed Lead-Acid (SLA) batteries, or Gel-Cell SLA batteries.

Lead-acid batteries are rather affordable and reliable batteries that can be recharged using various lead-acid battery chargers, preferable advanced battery chargers that also include battery diagnostics.

On the other hand, lead-acid batteries are heavy, they support a relatively small number of charging/discharging cycles, they don't tolerate well deep discharge applications, they suffer from capacity loss when discharged via strong currents, and similar.

Lithium rechargeable batteries initially cost more and are sensitive to charging and discharging conditions, but lithium batteries come with the built-in Battery Management Systems (BMS) that monitor the battery's condition and if required, they protect the batteries from unwanted situations like low/high temperature, low/high voltage, over-current, short-circuit, and similar.

Also, in order to prolong the lithium battery operating life, BMS usually monitors individual cells and if required, it balances them.

Lithium rechargeable batteries come as starting (being able to provide huge currents but for a limited time) and as deep cycle batteries (having limited maximum allowed currents, but great capacity). Also, some brands offer dual-purpose lithium batteries which are able to provide strong currents and which tolerates deep discharge conditions well.

Lithium batteries cost perhaps 3-5x times more than lead-acid batteries, but they often can withstand 5-10x more charging and discharging cycles and are 3-4x lighter than lead-acid batteries. So, in the long run, they are actually cheaper (check warranty conditions!) and save plenty of weight.

Although there are several lithium battery chemistries on the market today, lithium deep-discharge rechargeable batteries that are used as trolling motor batteries are almost exclusively Lithium Iron Phosphate (LiFePO₄) batteries, featuring a nominal voltage of 3.2V per cell and are able to provide ~1C current continuously and sometimes 2-5C currents for a very short period of time.

Lithium Iron Phosphate (LiFePO₄) batteries are the safest lithium battery chemistry, but they also must have protective BMS - better safe than sorry. Also, these batteries are true non-spillable and maintenance-free batteries, that are able to operate at any position.

Battery Voltage

Most batteries are offered as 12V models, but there are lithium batteries that are offered as 12V, 24V, 36V, 48V, etc. batteries.

While lead-acid batteries may be connected in series and parallel freely (some rules do apply!), lithium batteries may be connected in series and parallel only if explicitly allowed/recommended by the battery manufacturer.

After picking "the best" trolling motor, check its voltage and maximum current.

Note: some electric trolling motors feature battery charge indicators that are calibrated for lead-acid batteries - such battery charge indicators are inaccurate when the lithium batteries are used!

Battery Capacity

Battery capacity is given in Amp Hours (Ah) and is the ability of the battery to provide the current at certain conditions.

In most cases, the battery capacity of the lead-acid batteries is given for the period of 20h - the battery is discharged with 0.05C current.

When the battery is being used for powering trolling motors, one must calculate discharge time when the trolling motor is pushed to its maximum in order to find the shortest time that a new, fully charged battery, is able to power such trolling motor.

When the discharge current of the lead-acid battery is increased, the actual capacity is decreased - when the lead-acid battery is discharged for one hour, the battery's actual capacity drops down to 50-70% of the nominal capacity!

Lithium batteries don't suffer from such capacity loss - most of the lithium batteries support 1C currents continuously for almost an hour.

Number of Charging/Discharging Cycles

When the deep-cycle lead-acid batteries are discharged down to 80-100% DoD (Depth of Discharge), they support 150-300 charging/discharging cycles.

When the Lithium Iron Phosphate batteries are discharged down to 80-100% DoD, they support up to 2000-4000 charging/discharging cycles.

Also, Lithium Iron Phosphate batteries tolerate charging currents in the 0.33-1.0C range and can be cycled much quicker than lead-acid batteries.

Battery Weight

Relative battery weight can be easily calculated by dividing nominal energy stored in the battery (usually given in the Wh) by the weight of the battery (given in pounds or kilograms).

The problem with that calculation is that for lead-acid batteries one uses nominal capacity (rated for 20h constant current discharge) and not the actual capacity when the battery is used for powering trolling motor (or some other similar application).

When the lead-acid battery is discharged, for example, for 90 minutes, the actual capacity is just 70-80% of the nominal capacity, which increases the battery's relative weight even more.

On the other hand, lithium batteries tolerate very well discharge currents up to 1C, with almost no capacity loss, causing the relative battery weight difference between lead-acid and lithium batteries to be even larger.

On average, a good lead-acid deep-discharge battery is 3-6x heavier than the lithium deep-discharge battery - and that is a lot.

Connecting the Batteries in Series and Parallel

If your trolling motor operates at 12 V, you need one large or a pair of two smaller batteries connected in parallel.

If your motor operates at 24V, you need a pair of larger batteries connected in series or four smaller batteries connected in parallel and series.

If your motor operates at 36V, you need three larger batteries connected in series or six smaller batteries connected in parallel and series to achieve desired performances.

In order to keep the number of connections to the minimum, one can also go for 24V, 36V, or 48V lithium batteries - if the capacity is too low, go for the models that allow connecting the batteries in parallel and add enough batteries to create the battery pack according to your own needs and preferences.

In real life, one rarely uses an electric trolling motor at full throttle all the time - most of the time, power is reduced down to 30-50%, while the maximum power is used only in emergencies or when changing fishing locations and similar.

If you do use your trolling motor at full throttle most of the time, perhaps it is underpowered for your application, and getting a stronger motor (or one more) with more powerful/larger batteries will increase your safety. 

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Little Bit of Math

Unfortunately, in order to pick the best trolling motor battery, some math is required.

Lead-acid batteries are known as being very tolerant when operating connected in series (for larger voltage) and in parallel (for larger capacity). When connecting batteries in series and/or parallel, always try to obtain the same batteries from the same manufacturer, preferably from the same manufacturing batch.

Why? Well, even the slightest differences among the batteries can cause one battery to be under larger stress/load, leading to imbalances within the battery pack and ultimately to the battery pack failure. And that can be costly!

Example: If you need/have an electric trolling motor that draws 55-60 Amp at maximum power and you want at least 90 minutes of operation at full throttle, you need at least 150-160 Ah battery.

60 A x 1.5 h = 90 Ah

Since we don't want to fully discharge the lead-acid battery, we will discharge it down to 20%:

90 Ah / 0.8 = 112 Ah

The nominal capacity of lead-acid batteries drops when they are being discharged faster. On average, when such batteries are discharged within a 1.5 h period, their capacity drops down to ~70-80% of nominal capacity. Just to be safe, let's assume that our battery capacity drops down to 70% of nominal capacity when being drained at such rate:

112 Ah / 0.7 = 160 Ah
112 Ah / 0.8 = 140 Ah

Although this is the calculation for the 'worst-case scenario', it is also a calculation for the real-life situation!

If you don't wish to connect the batteries in parallel in order to achieve desired capacity, good choices for such requirements are batteries of the BCI Group 8D, with capacities of 200 or even more Ah.

However, if you don't mind connecting batteries in parallel, the list of potential batteries is much longer (you just need a pair of them) - practically a pair of any deep cycle batteries with at least 75-80 Ah will be enough.

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BCI Group 31 Batteries

BCI Group 31 batteries are a very popular battery group size used in many automotive, marine, off-the-grid, and industrial applications.

Group 31 batteries come in various chemistries including lead-acid wet/flooded, AGM, Gel-cell, enhanced wet, lithium, etc.

The best trolling motor group 31 batteries feature 12V nominal voltage and nominal capacity of 100-135 Ah, with some models featuring Reserve Capacity of up to 240+ minutes, especially the lithium 100Ah 12V batteries.

The following comparison chart lists some of the most popular group 31 batteries, with their most important features and specifications:

Note: Amazon affiliate links ('Model' column) open in the new windows, feel free to check them for the most up-to-date offers and prices. Also, we have really tried to verify every sling bit of information in this table (and the rest of our site), but things change over time without prior notice ...

For occasional use of an electric trolling motor, one should go for an affordable, general-purpose, deep-cycle, sealed lead-acid battery (AGM or Gel-Cell) with a nominal capacity of 100+ Ah.

Such batteries are easy to maintain, they tolerate vibrations very well, have good capacity when discharged with currents up to 0.5C.

For frequent use, but with costs in mind, one should go for a strong and durable AGM or Gel-Cell battery that tolerates cycling applications rather well, like Odyssey, NorthStar, Optima, and VMAXTANKS batteries.

However, even such batteries cannot be compared with the Group 31 lithium batteries in terms of lightweight design and number of charging/discharging cycles - and yes, these batteries cost more, but in the long run, lithium batteries save money!

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100Ah Lithium Batteries

100Ah lithium batteries are a very popular category of deep-cycle lithium batteries ranging in voltage from 12V to 48V.

Although these batteries have limited maximum discharge currents to mostly 1C (100 Amps), this is still strong enough for most trolling motors on the market (max. current up to 60 Amps).

The following comparison chart lists some of the most popular 100Ah lithium batteries, with their most important features and specifications:

Most 12V 100Ah lithium batteries belong to the BCI group 31, although the batteries with higher voltages tend to be 4D (6D) batteries.

Note: Many batteries are labeled as 4D batteries, but they actually have dimensions closer to BCI 6D battery group.

100Ah deep-cycle lithium batteries cannot be used as starting/cranking batteries, but that is not their intended use - they are designed for applications that require currents up to 1C, from the lightweight batteries that support a large number of charging/discharging cycles.

When connecting lithium batteries in parallel and/or series, always connect them as recommended by their manufacturer.

And if You are looking for lithium batteries of even larger capacity, check 200Ah lithium batteries.

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200Ah Lithium Batteries

200Ah lithium batteries are made as 4D (6D) or even larger batteries, ranging in voltage from 12V to 48V.

The following comparison chart lists some of the most popular 200Ah lithium batteries, with their most important features and specifications:

The use of such large batteries reduces the number of connections between the batteries, simplifying their use.

For example, Ampere Time 12V 200Ah Plus (Amazon link, link opens in the new window) battery weighs only 52.3 pounds (23.7 kg), can provide 200 Amps continuously, 400 Amps for 5 seconds, and supports connecting in parallel/series (up to 4).

Single such battery is able to power 12V 50 Amps electric trolling motor for ~4 hours at full throttle (if it doesn't overheat in the meantime), or 6+ hours when the motor is throttled down to ~33 Amps.

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Frequently Asked Question - FAQ

These are the most common questions about electric trolling motors and their batteries. Some of them can be answered with a simple yes or no, but some of them require much more elaborate answers.

How long will a 100ah battery run a trolling motor?

This depends on the actual battery capacity and the actual trolling motor current draw.

Lead-acid batteries discharged within one hour feature actual capacity in the 55-70% nominal capacity range - for example, 12V 75Ah AGM battery may provide 40-50 Amps for one hour. If You have an electric trolling motor that draws 50 Amps max. and You intend to use it at maximum throttle, You can expect such battery to last up to 45-50 minutes (60 minutes at most, if a high-quality battery is used) under such conditions.

The best course of action is to check the battery's actual constant current discharge table and compare it with the planned electric motor use/current draw.

Can you use a lithium battery for a trolling motor?

Yes, You can. But, lead-acid batteries feature a nominal voltage of 12V with actual voltage ranging from 12.8-13.2V down to 10.5 or even fewer volts. On the other hand, lithium batteries feature a nominal voltage of 12.8 volts which is very constant during the discharge.

If the trolling motor features a battery charge indicator, it is probably calibrated for lead-acid batteries and it can provide inaccurate readings for lithium batteries.

How to charge trolling motor battery?

Easily - connect the battery to the suitable battery charger and let it do its job.

Wet/flooded, AGM and Gel-Cell batteries should be charged using currents in the 0.1-0.2C range (model dependent) using smart/advanced lead-acid battery chargers that allow the user to set the battery type (wet, AGM, Gel) and that feature temperature sensor for temperature compensation.

Lithium batteries should be charged using chargers for lithium batteries (or at least with the chargers that feature lithium battery charging mode) using currents in the 0.2-1.0C range (model dependent).

Does a 24-volt trolling motor need 2 batteries?

A 24-volt electric trolling motor requires a single 24-volt battery or 24-volt battery pack consisting of two 12V batteries connected in series.

Will a car battery work for a trolling motor?

Yes, it will. But, if such battery is discharged too low, it will not be able to crank the car's engine until it is fully recharged again.

Also, car batteries are starting batteries, which are not intended for deep-discharge applications - if You want to test the electric trolling motor using a car's battery, go for it for a few minutes.

For example, if 50 Amps trolling motor is run for 5 minutes using a 12V starting battery, the battery will be discharged by ~4.2 Ah - that is less than 10% capacity for a 42Ah battery.

Will a car battery hurt a trolling motor?

No, the car battery will not hurt your trolling motor, but your trolling motor may harm your car's battery which is starting battery and not a deep-cycle battery.

How long can a car battery run a trolling motor?

This depends on the battery capacity and average trolling motor current.

For example, a 12V 50 Amps electric trolling motor discharges the 12V battery by ~0.84 Ah per minute. If You have a good 12V 75Ah lead-acid battery that is able to provide 50 Amps for 1h (actual 1h capacity is 50Ah!), powering the electric trolling motor for 30 minutes will discharge such battery down to 50% DoD (50% SoC) - such battery is still able to crank petrol and even diesel engines, but not as good as when the battery was fully charged.

Are lithium batteries worth it for trolling motors?

When lithium batteries are cycled often, yes, they are well worth it.

Also, for applications where the lightweight battery is a "must-have", lithium batteries must be used, regardless of how often they cycle!

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Few Final Words

When choosing "the best" battery for an electric motor, go for the model or models that best suit your needs and preferences.

For a very small electric trolling motor (<30 pounds, <30 Amps), one may go for lighter and smaller AGM/Gel-Cell batteries that are also cheaper - just be aware that lead-acid batteries lose their capacity when discharged using strong currents.

Lithium batteries must be recharged using dedicated lithium battery chargers or at least with advanced AGM battery chargers with the dedicated lithium battery charging mode, but they offer big weight savings and support so much larger number of charging/discharging cycles that they save money in the long run.

Maximum capacity/ stored energy and the maximum power of electric trolling motor should also feature some "reserve" for emergencies (strong current, bad weather, etc.) - it does add some additional weight and additional costs, but it also increases safety.

Again, whatever You do, stay safe!