How to Charge a Trolling Motor Battery: Expert Guide

Trolling motors have become an essential tool for anglers who want to navigate their boats in a quiet and efficient manner. These electric motors require a reliable power source to …

Trolling motors have become an essential tool for anglers who want to navigate their boats in a quiet and efficient manner. These electric motors require a reliable power source to function, and that’s where trolling motor batteries come in. However, charging a battery for your trolling motor can be a confusing process, especially for beginners.

That’s why we have created this expert guide. We will provide you with the step-by-step process on how to properly charge your trolling motor’s battery plates, the different types of charging methods available, and provide some tips to help extend battery life expectancies.

What Type of Battery Charger Do You Need?

The type of trolling battery charger you need for your trolling motor battery depends on the type of battery you have and the charging method you prefer. There are three main types of battery chargers for trolling motor batteries.

Onboard Chargers

These are chargers that are built into the boat and can charge multiple batteries simultaneously. They are typically designed to be mounted permanently and can provide a convenient charging solution.

Portable Chargers

These are standalone chargers that can be carried with you and used to charge your battery wherever you go. They are usually smaller and more lightweight than an onboard charger but can be excellent for kayakers due to their smaller size and portability.

Solar Chargers

These chargers use solar panels to convert sunlight into electricity and charge your battery. They are a great option for anglers who spend a lot of time in remote locations where electrical outlets are not available such as kayakers or canoeists that travel to natural mountain lakes.

How to Charge a Lead Acid Trolling Motor Battery

Trolling motor battery sealed lead acid battery
Lead acid trolling motor batteries need ventilation, a suitable charger, secure connections, and regular monitoring to prevent overheating.

Choose a Well-Ventilated Area

Lead-acid batteries can produce hydrogen gas during charging, which can be dangerous in a poorly ventilated area. Make sure to choose a well-ventilated area before you start.

Choose a Suitable Charger

Select a battery charger that is compatible with your lead-acid battery. Make sure to choose a charger that matches the voltage and amperage of your battery. Most lead-acid trolling motor batteries are 12 volts, but always check the manufacturer’s information for the specific type.

Connect the Charger to the Battery

Connect the positive (red) charger cable to the positive terminal on the battery and the negative (black) cable to the negative terminal. Ensure that the connections are tight and secure to prevent any sparks or electrical arcs.

Check the Battery Periodically

While the battery is charging, check it periodically to ensure that it is not overheating. If the battery becomes hot or starts to emit a foul odor, turn off the charger and let the battery cool down before continuing the charging process.

How to Charge an AGM Trolling Motor Battery

Trolling motor battery AGM batter
Charge AGM batteries correctly by using a compatible charger, connecting the cables properly, and regularly checking for overcharging.

Choose a Suitable Charger

AGM batteries require a specific type of charger designed to work with AGM batteries. Make sure to choose a charger that is compatible with AGM batteries and matches the voltage and amperage of your battery.

Connect the Charger to the Battery

Connect the positive charger cable to the positive terminal on the battery and the negative cable to the negative terminal. Be sure the connections are not reversed since this could cause sparks, fire, or even explosions when the charger is turned on.

Turn on the Charger

Turn on the charger and allow the batteries to start charging. AGM batteries typically charge faster than traditional lead-acid batteries, so check the batteries periodically to prevent overcharging. Many AGM chargers have a “float” or “maintenance-free” mode, which keeps the battery topped off without overcharging it.

How to Charge a Lithium Trolling Motor Battery

Trolling motor battery Lithium Iron Phosphate battery
To avoid battery problems, use the correct charger, connect it properly, and monitor the charging process with a safe charger for lithium batteries.

Use the Right Charger

Lithium batteries have their own special charger, so be sure the charger you have is able to be used with a lithium battery. Using the wrong charger can cause a number of problems, including failing to turn on, failing to battery charge, rapid overcharging, overheating, and more.

Connect the Charger to the Battery

Just as mentioned in the previous two sections, connect the battery system to the charger by making sure the red charging cable connects to the positive battery terminal and the black charging cable connects to the negative battery terminal.

Monitor the Charging Process

Lithium batteries can charge extremely quickly, so while the battery is charging, monitor it closely to ensure that it is charging properly. A lithium battery is sensitive to overcharging, so it’s important to choose a charger with built-in safety features like overcharge protection and cell balancing.

Average Trolling Motor Battery Life

A lead-acid battery used for a trolling motor typically lasts between two to three years, although with proper maintenance and charging, it can last up to five years. 

An AGM (absorbent glass mat) battery generally has a longer lifespan and can last for up to five years or more, depending on usage and maintenance.

A well-maintained lithium battery can last up to ten years or more, depending on usage and charging practices, since overcharging can severely reduce its overall lifespan

When to Charge

Knowing when to charge your trolling motor’s battery is essential to ensure that it is always ready when you need it. Here are some factors to consider when determining when to charge your batteries:

Battery Voltage

You can check the voltage of your batteries using a voltmeter. A fully charged 12-volt battery should have a voltage reading between 12.6 to 12.8 volts, while 24-volt batteries should read between 25.2 to 25.6 volts.

Usage

If you use your trolling motor frequently, you should charge the batteries after each use or at least every two to three uses. If you only use your trolling motor or outboard motor occasionally, you should charge the battery every few weeks to keep it in good condition with trickle chargers, onboard battery chargers, a solar charger, or standard charger to prevent a dead battery.

How Long to Charge

A typical lead-acid marine or car battery may take 8-10 hours to charge fully using a standard 10-amp charger. However, some higher-capacity batteries may take longer to charge.

An AGM battery will typically charge faster than lead-acid batteries and may take 6-8 hours to charge fully using a standard 10-amp charger.

A lithium battery can charge much faster than lead-acid or AGM, and some lithium-specific battery chargers can charge a battery in as little as 1-2 hours.

How to Solar Charge a Trolling Motor Battery

Solar battery charging your trolling motor’s battery can be a great way to keep it charged without the need for an electrical outlet or generator. Here are the steps to solar charge a trolling motor battery:

Choose the Right Solar Panel

Select a solar panel with enough power to charge your trolling motor’s battery. The panel should have a wattage rating that is at least equal to the battery’s amp-hour rating.

Install the Solar Panel

Mount the solar panel on a flat surface that receives direct sunlight as much as possible throughout the day. Make sure to connect the panel to a charge controller, which regulates the battery charging algorithm and prevents overcharging.

Connect the Charge Controller

Connect the charge controller to the batteries using the provided cables just as you would with a normal charger; red to positive, black to negative.

How to Use On-Board Chargers

An onboard battery charger is a convenient and efficient way to charge more than one battery while out on the water. Here are the steps to use an on-board charger:

Select the Right Charger

Choose an onboard charger that is compatible with your trolling motor or outboard motor battery’s voltage and capacity. The smart charger amperage rating should be suitable for the battery’s capacity.

Install the Charger

Follow the manufacturer’s instructions to install the smart charger on your boat. The charger should be mounted in a dry, well-ventilated location that is away from direct sunlight, moisture, and heat sources.

Connect the Charger

Connect the charger’s cables to the motor or boat battery’s terminals so positive connects to positive, and negative connects to negative.

Plug in the Charger

Once the charger is connected, plug it into a power source such as a dockside outlet or generator, or allow it to be powered by your boat’s electrical system. Make sure the power source is rated for the charger’s amperage and voltage requirements.

How to Use Portable Chargers

Portable chargers are a convenient option for charging trolling motor batteries when you’re away from a power source or on the go. Here are the steps to use a portable charger:

Select the Right Charger

Make sure the portable battery charger you select is compatible with your trolling motor battery’s voltage and capacity requirements in how it can deliver power.

Connect and Turn On

Connect the cables to the marine battery terminals in the red-to-red and black-to-black configuration. Press the power button to turn on the charger.

Recharge the Charger

Once the marine battery is fully charged and has been disconnected, recharge the portable charger using a power source such as a wall outlet, boat outlet, or solar panel.

FAQs

What to Do When Your Trolling Motor Battery Doesn’t Last?

If your trolling motor’s or outboard motor battery is not lasting as long as it used to, there could be several reasons for this, including:
Age
Overuse
Undercharging
Over-discharging

Can You Use an AGM or Lead Acid Charger With a Lithium Battery?

No. Lithium requires a specific type of battery charger that is designed to meet its unique charging requirements. Using an AGM or lead-acid charger on a lithium battery can damage the battery and potentially cause a fire or explosion.

What Is a Deep Cycle Battery?

A deep cycle is a boat battery type designed to provide a steady amount of power over a long period of time. Unlike a traditional starting battery which is designed to provide a short burst of power to start an engine and then be recharged by an alternator, a deep cycle battery is designed to be discharged and recharged repeatedly over its lifespan.

Float vs Trickle Charging?

A trickle charge and float charging are two methods of maintaining the charge of batteries, but they are different in terms of their purpose and charging voltage.

A float charger is a way of charging batteries at a constant voltage to maintain the charge level. Once the batteries are fully charged, the float chargers will reduce the voltage to a lower level, typically around 13 volts for lead-acid batteries, to prevent overcharging. The purpose of float charging is to keep the batteries fully charged and ready for use without damaging the batteries by overcharging them.

Trickle is a method of charging batteries at a very low rate with precision chargers, typically at 1/20th of the battery’s amp-hour capacity, to maintain its charge level over a longer period of time. The purpose of a trickle charger is to compensate for the self-discharge of the battery’s power over time, which can occur even when the batteries are not being used.

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Jeff Knapp is an expert fisherman, guide and outdoor writer whose work is widely published across a range of sites including Tackle Village. Jeff is based in Pennsylvania and loves exploring the waterways of that state in pursuit of smallmouth bass, largemouth, panfish and trout.
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