A Guide to Choosing the Right Battery for a Trolling Motor

Importance of selecting the correct battery for a trolling motor.

How the right battery can significantly impact your fishing experience.

Marine enthusiasts understand the importance of choosing the right battery for your vehicle. Choosing the wrong one can result in a bad time, especially if you’re right in the middle of beating your fish-catching record.

Choosing the right marine battery for your trolling motor is crucial to ensuring the longevity of your marine vehicle. With all the available options out there, it’s important to take the time and learn the differences between the different types of marine batteries so you can make the most informed choice.

What is a Marine Starting Battery?

A Marine Starting Battery is designed specifically for starting boat engines. It provides a high burst of current in a short time to ensure the engine starts smoothly. It’s used in a variety of boats, from small fishing boats to large yachts.

Key Features of a Marine Starting Battery:

• High Instant Current Output: A starting battery's main role is to deliver a large current quickly (usually within 30 seconds) to start the boat’s engine. This is referred to as Cranking Amps (CA). In cold conditions, it’s called Cold Cranking Amps (CCA).

  • Cranking Amps (CA): CA measures how much current the battery can deliver at 32°F (0°C) for 30 seconds while maintaining a voltage of at least 7.2V (for a 12V system). It shows the battery’s ability to start the engine in normal temperatures.

  • Cold Cranking Amps (CCA): CCA measures the current the battery can deliver at 0°F (-18°C) for 30 seconds, also while keeping the voltage above 7.2V. CCA is more critical as it indicates how well the battery performs in cold environments, where performance tends to drop.

• Fast Recharge Recovery: After starting the engine, the battery quickly recharges, ready for the next use.

• Durability and Vibration Resistance: Built tough to withstand marine conditions, including vibrations and moisture, ensuring it lasts longer in harsh environments.

• Cold Start Capability: Even in cold weather, it provides enough current to reliably start the engine.

Power Requirements for Different Types of Boats:

• Small Boats (e.g., fishing boats, leisure boats)
  These boats have smaller engines and require lower starting power, typically needing 400-700 amps of starting current.

• Medium Boats (e.g., cruisers, sailboats)
  With larger engines, these boats need a higher current, usually around 700-1000 amps.

• Large Boats (e.g., yachts, commercial vessels)
  Large boats have the most demanding engines, needing 1000-1200 amps or more to ensure a smooth start.

Each type of boat requires a battery with the right cranking power to ensure reliable engine starts under various conditions.

Overview of Battery Types

As you’re looking for a battery for a trolling motor, it’s recommended that you limit your search to batteries that are designed for deep-cycle use. Deep-cycle batteries are designed to provide a short burst of power over long periods of time. This means they’re able to start your motor while also running several electronics, offering a wider array of flexibility.

Some of the most common deep-cycle battery types are lead-acid batteries, absorbent glass mat (AGM) batteries, and lithium-iron phosphate (LiFePO4) batteries. Each battery is designed for deep-cycle use; however, there are stark differences between the different batteries. Understanding the differences can help you make a better-informed decision.

1. Lead-Acid Batteries

Lead-acid batteries are common batteries used for trolling motors on marine vehicles. These batteries are affordable and reliable, being found in most places that sell batteries. As reliable as they are, however, there are a few caveats that can affect buyers.

For starters, they have a vastly shorter lifespan when compared to other deep-cycle batteries. Depending on the quality of the battery, they’re only rated to last between 2-3 years before they need to be replaced. During that time, they will need constant maintenance including filling the batteries with water to operate properly. Because of their makeup (lead plates and water), these batteries are much heavier than others, weighing in around 80 pounds.

Another concern to take into consideration is spillage. Lead-acid batteries are prone to vibrations which can cause the acid inside the battery to spill during refills or use (if not properly done).

2. AGM (Absorbent Glass Mat) Batteries

AGM batteries are completely sealed and more stable than flooded batteries. One big thing about these batteries is that a fiberglass mat sits between the positive and negative plates inside the panel. As such, this absorbs the battery acid, reducing any maintenance required for these batteries.

Because of their more advanced build and reduced maintenance costs, AGM batteries are more expensive than lead-acid batteries. With the added fiberglass plates to help absorb the battery acid and prevent vibrations, they are heavier than most other batteries on the market.

3. Lithium Iron Phosphate (LiFePO4) Batteries

Lithium batteries are relatively new to the battery market, yet they are taking off particularly. Although they have an initial higher cost than some of the other types of batteries, their popularity has surged for a number of reasons, including:

• Longer runtime
• Lightweight
• Longer battery life
• 100% deeper discharge
• Larger power
• Smaller footprint

There are different lithium battery types for your trolling motor, each with its own benefits, such as lithium iron phosphate batteries, or lithium batteries with internal heaters for colder temperatures.

Shop 12.8V 100Ah LifePO4 Battery for Trolling Motor

Selecting the Right Battery Capacity and Size

Calculating the required runtime to ensure the battery can provide adequate power for a full day of fishing.

When you figure out the type of battery you want to use for your marine trolling engine, the next step is to select the correct size and capacity of the battery. Just picking the battery with the largest capacity won’t work as more capacity means more components in the battery which adds to the size and weight. Depending on the size of your boat and engine, this can negatively impact your battery and the engine itself.

Some factors to consider when choosing the size of your battery include:

• Boat Size: Larger boats will require batteries with a large capacity that can handle larger loads to prevent your engine from shorting or stalling.
• Battery Weight: Factoring in the weight of the battery can affect the performance of your overall engine. Lighter weights are another reason why lithium batteries are so popular, as they are lighter than other batteries.
• Vehicle usage: The higher the thrust of the engine, the more energy is required from your battery. Same with the ignition; if you don’t have enough amperage, you could end up stalling the engine.
• Boating Conditions: Whether it’s fishing in a creek or constantly moving, the battery you choose can be affected by these conditions.

Finding the Motor Trolling Time

Picking the right size and capacity of your new trolling motor battery involves calculating the motor run time. This is so you can figure out the length of time your motor will run on the water. To find this out, you need two things: the amp hour (Ah) rating of your battery and the amperage draw of your trolling motor. When you do, you can divide the two as follows.

Ah Rating/Motor Amp Draw = Use Time

For example, if your battery is rated as having 100Ah and your trolling motor at a lower speed is rated to pull 5 amps, you would have about 20 hours' worth of power.

100Ah / 5A = 20 hours

It’s not an exact science, but doing this can help you understand how long your battery can keep powering your engine.

Considerations

There are several other things to take into account when deciding on your new battery. On top of the more obvious considerations such as weight and battery capacity, you need to consider the following:

• Durability: Marine vehicles are bound to be on the move. Finding a battery that can withstand the uncertainty of the water is crucial to being long-lasting.
• Lifespan: Choosing a battery suitable for deep-cycle use can save you thousands of dollars in the long run.
• Battery Maintenance: Understanding how to properly maintain the battery to extend its lifespan, such as how to store and clean it.
• Temperature Tolerance: Performance of different battery types in extreme temperatures.

Installation and Configuration

Important installation considerations, such as wiring methods, and when to use parallel vs. series connections.

Ensuring consistency when using multiple batteries (same type, age, and size).

If you already have a battery and are looking to expand, there are some other considerations to take into account. One of the most important things to factor into your decision is using the same type of battery. If you have a Lithium iron phosphate battery (LiFePO4) and want to expand, it’s highly recommended to use the same type, in this instance a LiFePO4 battery.

It doesn’t stop there, though; if you are expanding, then it would be safest to be consistent in your battery choice, meaning that you should use the same size and capacity as your initial battery. If you can, you should have a battery that’s the same age, so that one isn’t detrimental to the others.

Series or Parallel Connection

How you wire the batteries together can also affect your battery performance. There are two methods to wiring your batteries: in series or in parallel. Each presents its own benefits and disadvantages that can affect your overall engine performance.

• Series

Wiring your batteries in series is simple enough: you use a battery cable to connect one battery’s positive terminal, to the next battery’s negative terminal, and so on, until your desired connection is achieved. Connecting batteries in this configuration results in a higher voltage output of the battery.

• Parallel

Parallel wiring of batteries connects the batteries in parallel. So the first battery’s positive cell is connected to the next battery’s positive cell, which in turn is connected to the positive cell of the next battery, and so on. The same is done to the negative cells, until all are connected. This increases the capacity of the entire battery, as each cell equally shares the load of the next.

Finding the right battery for your trolling motor is an important decision with many factors that need to be considered. Using the wrong size can negatively impact your engine, and truly ruin your fishing trip. As such, it’s crucial to take all considerations into account, such as capacity, weight, size, and type, so you can find the marine battery that’s right for you.