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How to Charge Your Trolling Motor Battery Step-by-Step Guide

Mike Smith
Mike Smith
—
20/03/2023

Are you tired of your trolling motor battery running out of juice in the middle of a fishing trip? Don't let a dead battery cut your day short. Learning how to properly charge your deep cycle trolling motor battery is essential for maximizing its lifespan and ensuring you have reliable power when you need it most. This guide will walk you through the process step-by-step, covering preparation, charging methods, and crucial best practices. Let's dive in!

Section 1: Why Proper Charging Matters for Your Trolling Motor Battery

Trolling motors typically use deep cycle batteries (like Lead-Acid, AGM, or Lithium LiFePO4). Unlike car batteries that provide a short burst of power, deep cycle batteries deliver steady power over a long time. However, they need specific care during charging to perform their best.

Properly charging your trolling motor battery:

  • Extends its lifespan: Correct charging prevents damage and helps you get more seasons out of your battery.
  • Ensures reliable performance: A fully and correctly charged battery delivers the power you expect.
  • Prevents damage: Overcharging, undercharging, or using the wrong charger can permanently harm your battery.

Section 2: Preparing to Charge Your Trolling Motor Battery

Before you plug anything in, a little preparation goes a long way.

1. Know Your Battery Type:

Identify whether you have a Flooded Lead-Acid (Wet-Cell), AGM (Absorbed Glass Mat), or Lithium (LiFePO4) battery. This is crucial because different types require different charging profiles. Read on the Types of Trolling Motor Batteries for detailed comparison.

2. Select the Right Charger:

  • Compatibility is Key: Always use a charger specifically designed for your battery type (Lead-Acid, AGM, Lithium). Many modern chargers have selectable modes. Using the wrong type can damage the battery.
  • Charger Types: You might use a portable charger (versatile, use anywhere) or an onboard charger (installed on the boat, often charges multiple batteries).
  • Consider a Smart Charger: These automatically adjust the charging process, prevent overcharging, and often have modes for different battery types, ensuring a safe and optimal charge. (For example, LiFePO4 battery chargers like those from LiTime offer multi-stage charging and safety protections like reverse polarity).

proection the litime lifepo4 lithium battery chargers offer

3. Safety First:

  • Wear safety glasses and gloves.
  • Ensure the charging area is well-ventilated, especially for lead-acid batteries which can release gas.
  • Keep sparks, flames, and metal objects away from battery terminals.

Section 3: How to Charge Your Trolling Motor Battery (Step-by-Step)

Here’s the core process for charging your trolling motor battery using a standard portable or onboard charger:

1. Turn Off Power: Ensure the trolling motor and any other accessories connected to the battery are turned OFF. If using an onboard charger, turn off the boat's main power breaker if applicable.

2. Connect the Charger:

  • Connect the RED (positive, +) clamp from the charger to the RED (positive, +) terminal on the battery.
  • Connect the BLACK (negative, -) clamp from the charger to the BLACK (negative, -) terminal on the battery.
  • Ensure clamps have a solid, clean connection.

connect charger to charge lithium trolling motor battery

3. Set Charger Parameters:

If your charger has settings, select the correct mode for your battery type (Flooded/Wet, AGM, or Lithium/LiFePO4). Select the appropriate voltage (12V, 24V, 36V) if needed.

4. Start Charging

Plug in the charger and turn it ON (if it has a power switch). The charger should indicate that it's charging (lights, display).

5. Monitor Progress

Check the charger periodically. Smart chargers will typically reduce the current as the battery fills and may indicate when charging is complete. Avoid letting lead-acid batteries get excessively hot.

6. Disconnect the Charger:

  • IMPORTANT: Turn the charger OFF or unplug it from the power source first.
  • Remove the BLACK (negative, -) clamp from the battery terminal.
  • Remove the RED (positive, +) clamp from the battery terminal. (Removing negative first minimizes the risk of sparks).

7. Store Properly (If Applicable)

If you've removed the battery for charging, store it in a cool, dry place once fully charged.

Section 4: Charging On-the-Go: Alternative Methods

Need to charge your trolling motor battery away from shore power?

Charging with Solar:

A solar panel setup can maintain or recharge your battery on the water. You'll need:

  • A suitably sized solar panel.
  • A solar charge controller (connects between the panel and battery to regulate voltage and prevent overcharging). 
  • Secure mounting for the panel in direct sunlight.
  • Proper connections from the controller to the battery.

Charging from Your Outboard:

Some boats are equipped with systems (like DC-to-DC chargers or Voltage Sensitive Relays/Combiners) that allow the outboard engine's alternator to charge the trolling motor batteries while the main engine is running. This depends heavily on your boat's specific wiring setup.

Read on Methods to Charge Batteries While on the Lake for more solutions.

Section 5: Trolling Motor Battery Charging: Best Practices & Mistakes to Avoid

Follow these tips to maximize battery life and safety:

What Should Do

  • DO charge your battery fully after each use, even if only slightly discharged.
  • DO use a charger specifically compatible with your battery chemistry (Lead-Acid, AGM, Lithium).
  • DO charge in moderate temperatures (ideally 50-86°F / 10-30°C). Avoid extreme heat or freezing conditions during charging.

What Should Not Do

  • DON'T overcharge. Use a smart/automatic charger or monitor the process carefully if using a manual charger. (Lithium batteries have a Battery Management System (BMS) for protection, but using the right charger is still vital).
  • DON'T consistently undercharge. This leads to sulfation in lead-acid batteries, reducing capacity.
  • DON'T deeply discharge your batteries unnecessarily, especially Lead-Acid and AGM (aim to keep above 50% charge). Lithium batteries handle deep discharge better due to their BMS.
  • DON'T leave a non-automatic ("dumb") charger connected indefinitely, especially during long-term storage.
  • DON'T charge a visibly damaged or frozen battery.

Section 6: Charging Time & Storage Charging

How Long Does it Take?

Fully charging a trolling motor battery can take anywhere from 4 to 12+ hours. This depends on:

  • Battery size (Amp-hour rating).
  • How deeply it was discharged.
  • Charger output (Amps).
  • Battery type (Lithium often charges faster than lead-acid).

For example, chargin a 100Ah lithium battery fully with 20A charger, it would take around 5 hours.

100Ah ÷ 20A =5h

charging time of trolling motor batteries

Charging Batteries in Storage:

If storing your boat/batteries for months:

  • Charge the batteries at 50% SOC before storage.
  • Disconnect them to prevent parasitic drains.
  • For lead-acid/AGM, check the voltage every 1-3 months. If below ~12.4V, give them a top-up charge. Lithium batteries have very low self-discharge and may only need checking every 6 months.

Section 7: FAQs About Charging Trolling Motor Batteries

Can I charge a marine battery inside?

Yes, provided it's in a well-ventilated area, especially for lead-acid types. Charging in moderate indoor temperatures (50-86°F) is often ideal.

Is it OK to leave my boat battery on the charger all winter?

It is generally not recommended to leave a battery connected to a standard charger for long-term use. Over time, standard chargers may overcharge the battery, potentially causing damage. The best practice is to fully charge the battery, disconnect it for storage, and periodically top it up as needed.

Can I use one charger for multiple trolling motor batteries (e.g., a 24V or 36V system)?

Yes, you can use a multi-bank onboard charger designed to charge each 12V battery independently, or charge each battery individually with a portable charger. You can also use a dedicated 24V or 36V charger if your batteries are permanently wired in series or parallel and the charger matches the total system voltage and battery chemistry.

lifepo4 battery charging voltage chart 

Section 8: Considering Lithium? Charging Advantages

If you're thinking about upgrading, Lithium (LiFePO4) batteries offer several charging-related benefits:

  • Faster Charging: They can typically accept charge current much faster than lead-acid, reducing recharge time significantly.
  • No Memory Effect: Charge them anytime regardless of their current charge level without harm.
  • BMS Protection: An internal Battery Management System (BMS) protects against overcharging, over-discharging, and short circuits, adding a layer of safety.
  • Lighter Weight: While not a charging feature itself, their lighter weight makes handling batteries for charging or removal much easier.

(Consider LiTime LiFePO4 batteries for these benefits. See the Trolling Motor Battery series for options.)

Conclusion

Knowing how to charge your trolling motor battery correctly is a fundamental part of boat and battery maintenance. It's not complicated, but paying attention to your battery type, using the right charger, following the steps carefully, and practicing good habits will ensure your battery performs reliably for many seasons. Charge smart, stay safe, and enjoy more worry-free time on the water!

Mike Smith
Mike Smith
Mike Smith is a marine energy expert with 15+ years of experience and a Master’s in Electrical Engineering from Stanford. Passionate about lithium battery integration, he also enjoys sailing and exploring coastal waters in his free time.

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