Quick Summary: For your trolling motor, choose a deep-cycle marine battery, ideally a Group 24 or 31 size, offering ample power and long lifespan for fishing trips. AGM batteries are low-maintenance and spill-proof, while flooded lead-acid batteries are a budget-friendly option but require more care.
What Battery For Trolling Motor: Your Essential Guide
Navigating the waters with your trolling motor is one of the great joys of fishing. But when that motor sputters or refuses to start, it can quickly turn a relaxing day into a frustrating one. The heart of your trolling motor is its battery, and picking the right one is key to uninterrupted fun. Many folks get a little turned around when looking for the perfect battery, but don’t worry! I’m here to guide you through it, just like a trusty mechanic showing you the ropes.
We’ll break down what makes a good trolling motor battery, explore the different types available, and help you figure out exactly what you need. No confusing jargon, just clear, practical advice to get you back on the water with confidence. Ready to power up your next fishing adventure?
Why Your Trolling Motor Battery Matters
Your trolling motor battery isn’t just any old battery; it’s designed for a specific job. Unlike the battery in your car, which is built to deliver a quick jolt of power to start the engine and then recharge, a trolling motor battery needs to provide a steady, consistent stream of power for extended periods. This is often called “deep cycling.” Drawing too much power too quickly or letting a car battery drain too low can seriously damage it and shorten its life.
Think of it this way: your car battery is like a sprinter, giving a burst of energy. Your trolling motor battery is more like a marathon runner, sustaining its effort over a long distance. Getting this right means more time fishing and less time worrying about power.
Understanding Trolling Motor Battery Types
When you start looking for a trolling motor battery, you’ll notice a few main types. Each has its own pros and cons, so let’s make sense of them.
1. Flooded Lead-Acid Batteries (Wet Cell)
These are the most traditional and often the most affordable type of deep-cycle battery. They’re also commonly known as “wet cell” batteries because they contain liquid electrolyte (a mix of sulfuric acid and water) above lead plates.
- Pros: Lower upfront cost, widely available, can often be revived if deeply discharged (though not recommended).
- Cons: Require regular maintenance (checking and topping up electrolyte levels), can be spill-prone and emit gasses during charging (requiring good ventilation), heavier than other types, sensitive to vibration.
If you’re on a tight budget and don’t mind a bit of regular upkeep, a flooded lead-acid battery can be a solid choice. Just be sure to handle them with care and ensure your boat has proper ventilation when charging. You can find more details on proper battery maintenance on FuelEconomy.gov, which offers general automotive maintenance tips applicable to battery care.
2. Sealed Lead-Acid Batteries (SLA)
These batteries are “sealed” to prevent the electrolyte from spilling or gassing. There are two main sub-types:
a) Gel Batteries
In gel batteries, the electrolyte is mixed with a silica-based gelling agent, giving it a jelly-like consistency. This makes them very spill-proof and maintenance-free.
- Pros: Spill-proof, maintenance-free, good performance in a wide range of temperatures, less sensitive to vibration than flooded batteries.
- Cons: More expensive than flooded batteries, can be sensitive to overcharging (which can permanently damage them), may offer slightly less cranking power than flooded types.
b) Absorbed Glass Mat (AGM) Batteries
AGMs are currently the most popular choice for trolling motors. They use a fine fiberglass mat between the lead plates to absorb the electrolyte. This makes them extremely robust and virtually spill-proof.
- Pros: Low maintenance (no watering needed), highly spill-proof and vibration-resistant, faster charging times than flooded batteries, can deliver high starting currents, good performance in cold weather.
- Cons: More expensive than flooded lead-acid batteries, can be damaged by overcharging or charging with the wrong charger.
For most users, especially those who want a reliable, low-maintenance option, AGM batteries are tough to beat. They offer a great balance of performance, durability, and ease of use.
3. Lithium-Ion Batteries (LiFePO4)
Lithium-ion, specifically Lithium Iron Phosphate (LiFePO4) which is the safest and most stable type for these applications, are the newest and most advanced option. They use lithium compounds to store energy.
- Pros: Extremely lightweight (up to 70% lighter than lead-acid), much longer lifespan (thousands of charge cycles), can be discharged more deeply without damage, fast charging capability, consistent voltage output, built-in Battery Management System (BMS) for safety.
- Cons: Significantly higher upfront cost, may require a specialized lithium charger, performance can be reduced in very cold temperatures (though many have built-in low-temperature protection).
While the initial investment is higher, the longevity and performance benefits of lithium batteries can make them more cost-effective over time. If weight is a major concern or you plan on heavy usage, lithium is worth strong consideration.
Key Battery Specifications to Consider
Now that you know the types, let’s look at the numbers and terms that matter when choosing a battery.
1. Voltage
Trolling motors typically run on 12V, 24V, or 36V systems. This voltage is determined by how many batteries you connect in series (positive to negative). Your motor’s specifications will tell you what voltage it requires. Most anglers start with a 12V system for smaller boats or lighter motors, moving up to 24V or 36V for more power and longer run times on larger boats.
2. Ampere-Hour (Ah) Rating
This is probably the most important number. Ampere-hour (Ah) tells you how much capacity the battery has – essentially, how long it can deliver a certain amount of power. A higher Ah rating means longer run time.
- Example: A 100Ah battery can theoretically deliver 10 amps for 10 hours (10A x 10h = 100Ah) or 5 amps for 20 hours (5A x 20h = 100Ah).
How much Ah do you need? It depends on your motor’s amp draw (check the motor’s manual) and how long you typically fish. A good rule of thumb is to get a battery with at least double the Ah you think you might need to avoid constantly running it down too low, which shortens its life.
3. Reserve Capacity (RC)
Reserve Capacity (RC) is measured in minutes. It tells you how long a new, fully charged battery can deliver 25 amps at 80°F (27°C) before dropping below 10.5 volts. This is useful for understanding how long your battery can run at a moderate load.
4. Cold Cranking Amps (CCA) and Marine Cranking Amps (MCA)
While important for car batteries, CCA and MCA are less critical for trolling motor batteries. They measure a battery’s ability to start an engine in cold weather. Trolling motors don’t need this kind of high burst power, so focus more on Ah and RC.
5. Battery Size and Group Numbers
Batteries come in standard sizes, often referred to by a “Group Number.” Common sizes for trolling motors include:
- Group 24: A popular, versatile size. Usually around 80-100Ah.
- Group 27: Slightly larger than Group 24, offering more capacity, typically 100-120Ah.
- Group 31: One of the largest and most common for deep-cycle marine applications, offering significant capacity, often 100-150Ah or more.
Always check the physical dimensions of the battery and compare them to the battery compartment on your boat to ensure a proper fit.
Choosing the Right Battery Size for Your Needs
The “best” battery isn’t one-size-fits-all. It depends on your boat, your motor, and your fishing habits.
Factors to Consider:
- Boat Size and Weight: Larger, heavier boats require more power to move, meaning a higher amp draw.
- Trolling Motor Amperage Draw: Check your motor’s manual. A 55-pound thrust motor might draw 40-50 amps at full power, while a 112-pound thrust motor could draw 100+ amps.
- Duration of Use: Do you fish all day without returning to shore? Or are you making short runs?
- Water Type: Strong currents or windy conditions will require you to run your motor at higher speeds for longer periods.
- Budget: As we discussed, lithium is the most expensive upfront, good quality AGMs are mid-range, and flooded lead-acid are the most budget-friendly.
Example Scenarios:
Let’s say you have a 55 lb thrust trolling motor that draws about 50 amps at full power. You typically fish for 6 hours a day and want to avoid draining your battery below 50% (to prolong its life).
Calculation:
- Total amps needed: 50 amps x 6 hours = 300 Ah.
- To only use 50% capacity: 300 Ah / 0.50 = 600 Ah needed.
This is a very high estimate to show how much capacity you’d theoretically need for extreme conditions. In reality, you might not run your motor at full blast for 6 hours straight. A more realistic draw might be 25 amps average over 6 hours, leading to 150 Ah needed. Doubling that for a safety buffer and shallower discharge: 150 Ah x 2 = 300 Ah. A 100Ah battery would likely get you through a decent day, but two 100Ah batteries in parallel (giving you 200Ah) would offer much more security.
For most casual anglers with a 12V system and a 50-70 lb thrust motor, a single 100Ah to 120Ah deep-cycle battery (like a Group 27 or Group 31 AGM) is often sufficient for a full day of fishing.
Connecting Batteries for More Power
If you need more power or longer run times than a single battery can provide, you can connect multiple batteries.
Series vs. Parallel Connections:
Parallel Connection: Connects batteries positive-to-positive and negative-to-negative. This increases the total Amp-hour (Ah) capacity while keeping the voltage the same. Two 12V 100Ah batteries in parallel become one 12V 200Ah battery.
Series Connection: Connects the positive terminal of one battery to the negative terminal of another. This increases the voltage while keeping the Ah capacity the same. Two 12V 100Ah batteries in series become one 24V 100Ah battery.
You’ll need a 24V motor for a series connection of two 12V batteries, and a 36V motor for a series connection of three 12V batteries.
Important Note: Always use identical batteries when connecting them in series or parallel (same brand, model, age, and capacity) to avoid damaging them.
Table: Common Trolling Motor Battery Sizes
Here’s a quick reference for some common battery group sizes used for trolling motors. Capacities can vary slightly between manufacturers.
| Group Number | Approximate Dimensions (L x W x H) inches | Typical Reserve Capacity (Minutes) | Typical Amp-Hour (Ah) Rating | Common Applications |
|---|---|---|---|---|
| 24 | 10.2 x 6.6 x 8.9 | 110-140 | 75-100 | Smaller boats, light trolling, 12V systems |
| 27 | 12.1 x 6.7 x 9.1 | 150-170 | 100-120 | Medium boats, moderate trolling, 12V systems |
| 31 | 13.0 x 6.8 x 9.4 | 170-220 | 105-135+ | Larger boats, heavy trolling, 12V and 24V (with multiple batteries) |
Note: Always double-check the specific dimensions and ratings for the battery you are considering.
Battery Maintenance and Care for Longevity
Getting the right battery is only half the battle. Proper care will ensure it lasts as long as possible. For reliable power, treating your battery right is essential.
1. Charging Wisely
- Use the Right Charger: This is critical, especially for AGM and Lithium batteries. Use a charger designed for marine deep-cycle batteries, and specifically one that is compatible with your battery type (e.g., a specific Lithium charger for LiFePO4 batteries). A boat motor charger for a car battery can overload and damage a marine battery, or vice versa.
- Avoid Overcharging: Most modern smart chargers will automatically stop when the battery is full. If you have an older charger, monitor it. Overcharging can damage lead-acid batteries, and is particularly harmful to AGMs and Lithium.
- Avoid Deep Discharges: Try not to drain your lead-acid batteries below 50% of their capacity regularly. For Lithium (LiFePO4), most built-in BMS systems allow for deeper discharges, but still, avoiding excessive draining is good practice.
- Charge After Each Use: The best practice is to fully charge your battery after every outing, even if you didn’t use it much.
If you’re unsure about which charger to use, check out resources like BatteryStuff.com for guides on selecting the right marine charger.
2. Keeping Terminals Clean
Corroded battery terminals can impede the flow of electricity. Regularly check the terminals for any white or blue powdery buildup. Clean them with a wire brush and a mixture of baking soda and water. A thin coating of dielectric grease or petroleum jelly can help prevent future corrosion.
3. Proper Storage
If you’re storing your boat for an extended period (like in the off-season), don’t leave the batteries fully depleted. Charge them fully, then disconnect them if possible. Storing them in a cool, dry place is ideal. Some people use a trickle charger or a smart battery maintainer to keep the charge topped up over long storage periods.
4. Ventilation for Flooded Batteries
As mentioned, flooded lead-acid batteries release hydrogen gas as they charge. Ensure the battery compartment is well-ventilated and located away from any open flames or sparks.
Safety First!
Batteries, especially lead-acid ones, contain corrosive acid and can produce flammable gases. Always follow these safety tips:
- Wear Safety Glasses and Gloves: Protect your eyes and skin from acid.
- Never Smoke or Create Sparks Near Batteries: Hydrogen gas is highly explosive.
- Disconnect the Charger Before Connecting or Disconnecting Batteries: This prevents dangerous sparks.
- Handle Batteries Carefully: They are heavy and can contain hazardous materials.
- Ensure Proper Ventilation: Especially for flooded batteries.
When in doubt, consult your trolling motor manual or a qualified marine technician. Resources like the U.S. Coast Guard’s boating safety tips also offer valuable advice for handling electrical systems on boats.
Frequently Asked Questions
Q1: Can I use a car battery for my trolling motor?
A: No, you generally should not use a standard car battery for a trolling motor. Car batteries are designed for “starting” (short bursts of high power) and are not built for the “deep cycling”
