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Can You Charge a Trolling Motor Battery with a Car? 

Can You Charge a Trolling Motor Battery with a Car? 

Trolling motors are used in the waters alongside boats for fishing and navigation.

Trolling motor batteries are important to ensure your motor has a consistent output and sustained performance.

Using a proper portable battery charger or onboard charger is always the best option to charge your trolling motor batteries.

However, if the charger is damaged or isn’t working, can you charge a trolling motor battery with a car?

The short answer is yes.

We’ll cover the types of trolling motor batteries out there and how you can charge it with a car.

Types of Trolling Motor Batteries

When it comes to trolling motor batteries, typically deep cycle batteries are used. These battery types discharge small amounts of currents in a short amount of time.

There are three battery types which are Lead Acid Wet-Cell, AGM and Lithium Ion batteries.

Lead Acid Wet-Cell batteries are the cheapest and oldest form of battery.

Lead Acid battery

That being said, they are inferior to AGM batteries because they require frequent maintenance, experience potentially spilling issues and are less durable.

AGM batteries are spill-proof, last longer and completely maintenance free. The drawback is that their more expensive than Wet-Cell batteries.

Battery Tender AGM Motorcycle Battery

Lithium batteries are the most superior type of battery because its long-lasting, most efficient, lighter and more durable. However, the cost doesn’t justify the value especially for inflatable boaters.

LiFePO4 Deep Cycle Battery - Lithium battery

Amp Hours

Another factor to consider is the amp hour rating of your battery.

The amp hour rating is the amount of charge that the battery can store, which in turn results in how long it can run the motor.

Amp hours of battery

This means you’ll need a higher amp hour rating if you want your trolling motor to last longer.

Also, the amount of amp hours will depend on the thrust level of your trolling motor.

Higher thrust levels and running your motor at faster speeds will require a higher amp hour rating.

How to Charge a Trolling Motor Battery With a Car

Charging a trolling battery with a car

First, make sure that your car battery and trolling motor battery are the same voltage. This ensures that the engine regulators work properly.

In this method, you’ll be using your car’s jumper cables to charge your trolling motor battery.

  1. Connect your car’s jumper cables to both terminals of the marine battery.
  2. Make sure that the positive end of the cable connects to the positive end of the car battery.
  3. Then leave the ground cable disconnected. Also, ensure that the cable is safely stowed away from any metal parts of the car.
  4. Next, start the engine of your car.
  5. Disconnect the ground terminal of the car battery. As a result, the car battery is disconnected from the engine. The car’s engine is now running on the alternator alone.
  6. Connect the ground cable from the deep cycle marine battery to the metal part of the car, completing the circuit and simply letting the car engine run.
  7. The car regulator will stop the charge once the battery reaches near the correct voltage, which is usually 12 volts.

Another way to charge your trolling motor battery is through your car’s alternator. The alternator is an electric generator used in your car to charge your battery and power the vehicle’s electrical system while the engine is running. Attaching the deep cycle and starting the battery in a parallel connection will charge them.

car alternator

Connect the trolling motor battery in parallel with your car’s battery.

The idling engine will charge the deep cycle battery through the car’s alternator, however, it may take several hours.

When the batteries are placed parallel, make sure the positive touches positive, and the negative touches the negative.

Deep Cycle Battery Charging with your Alternator: The 3 Best Options explained [+ Wiring Diagram]

Things to Know About Using Your Car to Charge Your Trolling Motor Battery

Although it’s possible to charge a deep cycle battery using a car, it’s important to note that the battery must be a 12-voltage battery.

12 volt trolling battery

You should also understand how the car alternator works.

Most alternators are designed to meet the demands of their vehicle’s electrical requirements and to top off the battery.

Ideally, you’ll want to know the amount of amps that your alternator is putting out and at what rpm. This will allow you to determine how long it will take for you to fully charge your trolling motor battery.

The best thing to do is add the battery to the system in parallel instead of swapping.

When connecting in parallel, the car battery will drain into the trolling motor battery because high voltage always flows into low voltage.

However, the alternator won’t know that there are two batteries.

The alternator will simply operate as if it was charging one battery except it has a larger amp capacity.

Final Thoughts

Trolling motors batteries should be charged after every trip.

The biggest reason most batteries begin to wear down is that people fail to recharge them promptly or discharge them too deeply.

Understanding how to charge your trolling motor battery with a car is useful especially in emergencies when you don’t have a charger or maybe it stopped working while you were out in the waters.