What Size LiFePo4 Battery For Trolling Motor?

When choosing the right lithium battery for a trolling motor, the first thing to consider is the motor's voltage. Trolling motors rated below 55 lb of thrust typically run on a 12V system, while higher-thrust motors usually require 24V or 36V.

In terms of capacity, a 50Ah battery is generally sufficient if you're only fishing on a small pond for one or two hours. However, if you plan to spend a full day on the water or regularly run the motor against wind and waves, a 100Ah battery is a much better choice.

Compared with lead-acid batteries, LiFePO4 batteries are far more user-friendly. The most noticeable advantages are their lighter weight and the fact that the motor does not lose power as the battery discharges. To estimate runtime, simply divide the battery capacity by the motor's current draw. Today, most saltwater and bass anglers prefer 100Ah LiFePO4 batteries because they provide reliable all-day runtime without adding excessive weight to the boat.

LiFePO4 Battery Size Chart for Trolling Motors

How Trolling Motor Thrust Affects Battery Size?

The higher the motor thrust, the faster it consumes power. So if you upgrade to a higher-thrust motor and want to maintain the same fishing time, you'll need a higher-capacity LiFePO4 trolling motor battery.

1. Amp Draw

The greater the thrust (lbs), the more current the motor pulls from the battery at high speeds.

• Low Thrust (e.g., 30–45 lbs): Draws approximately 30–40A at full speed.
• High Thrust (e.g., 55–80+ lbs): Can draw 50A or more at full speed.

Formula: Runtime (hours) = Battery Capacity (Ah) ÷ Current Draw (A). Example: A 100Ah lithium battery running a 50A motor at full speed lasts about 2 hours; running a 30A motor, it lasts about 3.3 hours.

2. Capacity (Ah) Thresholds

• Entry Level (50Ah): Suitable for low-thrust motors or short trips (2–4 hours) in calm water.
• Standard Level (100Ah): The "go-to" choice for most anglers. It provides enough power for mid-to-high thrust motors for a full day (6–10 hours) of mixed-speed fishing.
• Professional Level (150Ah+): Necessary for extreme thrust requirements or for staying in place (Spot-Lock) against strong winds and heavy currents.

3. The Role of Voltage Systems

To prevent excessive heat and efficiency loss from high current, high-thrust motors use higher voltages (24V or 36V):

• Efficiency: For the same amount of power, a 24V system draws fewer Amps than a 12V system. This higher efficiency helps the battery last longer while providing more pushing power.

If your motor has a high thrust (e.g., 55 lbs or more), it is highly recommended to use at least a 100Ah LiFePO4 battery to ensure you have enough reserve power for full-speed bursts or fighting heavy weather.

12V vs 24V vs 36V LiFePO4 Batteries for Trolling Motors

Additional Notes:

• Space Savings: Using a single high-voltage battery (e.g., one 24V unit) saves more deck space and simplifies wiring compared to connecting multiple 12V batteries in series.
• Charging: For series setups, it is best to use a multi-bank charger or a dedicated voltage charger to ensure all battery cells remain balanced.
• The Lithium Edge: Regardless of the voltage, LiFePO4 batteries maintain a high, steady output until nearly empty, unlike lead-acid batteries which lose power as they discharge.

related article:  Parallel Batteries With Different Capacities: Safety Tips

How Long Will a LiFePO4 Battery Run a Trolling Motor?

The runtime of a LiFePO4 battery depends on its Amp-hour rating and how much current the motor draws. You can use this simple formula to get an estimate:

Quick Reference: How long will a 100Ah Lithium battery last?

Using the most common 12V 100Ah LiFePO4 battery as an example:

• Full Throttle: Most motors draw about 50A at max speed, giving you roughly 2 hours.
• Medium Speed (50% Throttle): Current draw drops to around 20–25A, lasting about 4–5 hours.
• Low Speed/Trolling (25% Throttle): Current draw is only about 5–10A, which can last over 10 hours.

Why does Lithium last longer than Lead-Acid?

Even if the Ah rating is the same, LiFePO4 outperforms traditional batteries in two ways:

• Depth of Discharge (DoD): Lithium can safely use nearly 100% of its capacity, whereas lead-acid batteries shouldn't be discharged past 50%. This means a 100Ah Lithium battery provides as much usable power as a 200Ah Lead-Acid battery.
• Flat Voltage Curve: Lithium stays at a high voltage (near 13V) until it is nearly empty, keeping your motor at full power. Lead-acid voltage drops steadily, causing the motor to lose thrust as the battery drains.

Estimated Runtime Table

Note: Factors like headwind, heavy currents, and boat weight will increase the Amp draw and reduce total runtime.

Want to know exactly how long your setup will last on the water? Send Copow your motor's thrust and battery specs, and we will calculate the runtime for you.

Single Battery vs Series Configuration for Trolling Motors

If you're using a 24V or 36V trolling motor, you can either buy a single high-voltage battery or connect multiple 12V batteries in series. A single battery saves space and simplifies wiring, while a series setup offers more flexibility for handling and future replacement. You can choose the option that best fits the available space on your boat.

1. Single High-Voltage Battery

Pros:

• Simpler Wiring: Only two main cables (positive and negative), reducing the risk of loose connections or corrosion.
• Space Efficient: Usually more compact than multiple batteries, freeing up valuable storage space on your boat.
• Automatic Balancing: The internal Battery Management System automatically balances all cells within the single unit.

Cons:

• Concentrated Weight: While still lighter than lead-acid, one large battery is heavier to lift than separate smaller ones.
• Lower Redundancy: If the single battery fails, your entire propulsion system is down.

2. Multiple 12V Batteries in Series

Pros:

• Weight Distribution: You can place batteries in different compartments to balance the boat's center of gravity.
• Easier Replacement: If one battery fails, you only need to replace that specific unit, which can be more cost-effective.
• Versatility: Individual 12V batteries can be used for camping, emergency jumps, or other 12V electronics when not fishing.

Cons:

• Complex Wiring: More jumpers and terminals mean more points of potential failure or resistance.
• Imbalance Issues: Over time, the charge levels of the batteries may drift; it is highly recommended to use a multi-bank charger to keep them balanced.

Do You Need a Dedicated Trolling Motor Battery?

For trolling motors, it is essential to use a dedicated deep-cycle battery, rather than an automotive or marine engine starting battery. This is because a trolling motor requires a steady, continuous current over long periods, while starting batteries are designed to deliver a short burst of very high current to start an engine. If a starting battery is used to power a trolling motor, it will quickly suffer permanent damage due to repeated deep discharges.

LiFePO4 deep-cycle batteries are currently the ideal choice for trolling motors. They allow you to use nearly the full capacity without shortening battery life, while maintaining a stable voltage throughout the discharge cycle.

This ensures consistent motor thrust from launch to return. In contrast, combining starting and propulsion duties in a single battery not only severely limits runtime but can also leave you stranded on the water if the battery is depleted and the engine can no longer start. For both fishing efficiency and on-water safety, using a dedicated, purpose-built LiFePO4 battery bank for your trolling motor is the best solution.

Common LiFePO4 Battery Sizing Mistakes for Trolling Motors

For beginners choosing a LiFePO4 battery for a trolling motor, it's easy to run into problems like insufficient power or even damaging the equipment if a few common pitfalls aren't avoided. Let's take a look at how to steer clear of these most common mistakes.

Undersizing Capacity (Insufficient Ah)

While lithium batteries offer more usable power than lead-acid, many users choose 20Ah or 30Ah models to save money or weight. These often fail to provide enough runtime for a full day of fishing, especially when fighting strong winds or heavy currents.

Ignoring BMS Continuous Current Limits

Every lithium battery has an internal Battery Management System. If the battery's continuous discharge limit (e.g., 50A) is lower than the motor's draw at full speed, the BMS will trigger an overload protection and shut down the motor unexpectedly.

Mixing Different Battery Specs

Using batteries of different brands, capacities, or ages when wiring in series for 24V or 36V systems is a major mistake. This creates an imbalance where one battery discharges faster than the others, significantly shortening the lifespan of the entire bank.

Neglecting Cold Weather Performance

Standard LiFePO4 batteries cannot be charged below 0°C (32°F). If you fish in cold climates but buy a battery without "Low-Temperature Charging Protection" or an "Auto-Heating" function, you risk damaging the battery or being unable to recharge it.

Using Incompatible Chargers

Reusing old lead-acid chargers can be dangerous. The charging profiles for lead-acid (like desulfation modes) can damage a lithium BMS. You must use a charger specifically designed for LiFePO4.

Conclusion

Installing the right lithium battery for trolling motor is one of the most important steps to enhance your on-water experience. As long as the battery voltage matches your motor's thrust and you choose the capacity based on your planned outing time, you can enjoy full power all day. Whether for casual fishing or competitive tournaments, LiFePO4 batteries deliver far greater thrust and stability compared to lead-acid batteries.

Key Takeaways

Before making your final decision, keep these three essential factors in mind:

• Voltage Consistency: Always match your battery setup voltage to your motor's specific requirements to prevent equipment damage.
• Capacity Needs: While 50Ah works for short trips, 100Ah remains the gold standard for all-day reliability across most mid-to-high thrust motors.
• Configuration Choice: Decide between a single high-voltage unit for a clean and space-saving installation or multiple 12V batteries for better weight distribution and versatility.

Final Recommendation

Investing in a dedicated LiFePO4 deep-cycle battery will completely solve power drop issues and significantly reduce your boat's weight, letting you focus on fishing without constantly monitoring the battery. As long as you choose the right capacity and pair it with a compatible charger, this power system can serve you reliably for many years.

FAQ

Is 100Ah lithium enough for a trolling motor?

For most anglers, a 100Ah lithium battery is the gold standard for full-day, moderate-to-high intensity use, providing roughly 6 to 10 hours of runtime at mixed speeds.

What size battery do I need for a 24 volt trolling motor?

For a 24V trolling motor, you typically need a capacity of 60Ah to 100Ah, though a 100Ah LiFePO4 battery is highly recommended to ensure reliable, all-day runtime.

Is A12V 20Ah lithium good for a trolling motor?

A 12V 20Ah lithium battery is generally too small for a trolling motor and is only suitable for very short trips on small kayaks; in normal fishing conditions, it will likely run out of power quickly or shut down due to BMS protection limits.