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How to Charge Trolling Motor Battery While on the Water

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One early morning, I launched my small fishing boat just before sunrise, excited for a full day on the lake. The water was calm, and everything seemed perfect. I spent hours trolling slowly, enjoying the stillness, casting my line, and waiting for bites.

But by late afternoon, my trolling motor began slowing down. Then it just stopped. I hadn’t realized how much power I was using, and I didn’t have any way to recharge the battery out there.

I had to paddle back, exhausted. That day was a turning point. I decided I would never go out again without knowing how to charge my trolling motor battery while still on the water.

If you’re like me and love long, quiet days on the water, you’ll need to learn how to avoid that situation. In this article, I’ll guide you through each method of charging a trolling motor battery while you’re still out on the lake or river—using simple language and practical steps.

Why On-the-Water Charging Is Essential

A trolling motor is an electric motor designed to give you smooth and quiet control while boating or fishing. Most trolling motors run on deep-cycle marine batteries.

These batteries are made to release energy slowly over long periods, but they’re not infinite. If you use your trolling motor for hours without giving it a chance to recharge, it will eventually stop working.

Being able to charge the battery while you’re still on the water means:

  • You can stay out longer
  • You reduce the risk of getting stranded
  • You won’t need to carry backup batteries
  • You’ll get the most out of your battery’s life

It adds comfort, reliability, and safety to your time on the water.

Can You Really Charge a Trolling Motor Battery on the Water?

Yes, you definitely can. Many boaters already use these techniques. Some setups require equipment installed beforehand, while others are portable solutions you can bring along.

The main charging methods include:

  • Solar charging setups
  • Onboard marine battery chargers
  • Outboard motor alternator power
  • Portable generators or lithium power stations
  • Hydrogenerators (for large vessels)

Let’s look at each option in full detail.

Method 1: Charging with Solar Panels

How Solar Charging Works

Solar panels convert sunlight into electricity. This energy is sent through a charge controller, which protects the battery from overcharging. The controller then sends the correct amount of electricity to your trolling motor battery.

Items You Need:

  • Marine-Grade Solar Panel (100W or more for faster charging)
  • Charge Controller (preferably MPPT for better efficiency)
  • Marine-Grade Wiring and Connectors
  • Mounting Hardware (like suction cups, clamps, or adhesive pads)

Step-by-Step Setup:

  1. Mount the solar panel on a flat area of your boat where it gets full sunlight.
  2. Connect the panel to a charge controller.
  3. Connect the controller to your battery’s terminals.
  4. Monitor the charge level to avoid draining the panel’s efficiency.

Benefits:

  • Silent and eco-friendly
  • Great for slow charging or maintaining battery levels
  • No moving parts and low maintenance

Limitations:

  • Charging is slow and depends on sun availability
  • Works best on sunny days with direct sunlight

Table: Typical Solar Setup

ComponentDetails
Panel Size100W or 200W Flexible Marine Panel
Charge ControllerMPPT 10A–20A
Battery Type12V Deep-Cycle AGM or Lithium
Output in Sunlight5–8 Amps

Method 2: Using an Onboard Marine Battery Charger

What Is It?

An onboard charger is installed inside your boat and directly wired to your trolling motor battery. It recharges the battery when connected to an external power source like shore power or a generator.

Installation Process:

  1. Mount the charger securely in a dry area inside the boat.
  2. Connect the charger leads to the battery terminals.
  3. Plug into power source when available (dock outlet or generator).
  4. Let the charger run automatically—it’s usually smart enough to stop when full.

Ideal Features:

  • Waterproof housing
  • Multi-bank charging (for multiple batteries)
  • Smart technology for safer charging

Tip:

Pairing an onboard charger with your outboard motor or generator gives you a strong, reliable system.

Method 3: Alternator Charging from Your Outboard Motor

What It Does:

If your outboard motor has an alternator, it produces electricity while the motor runs. You can use this to recharge your trolling battery.

What You’ll Need:

  • Outboard with at least 10A alternator
  • Battery Isolator or Automatic Charging Relay (ACR)
  • Marine-grade cables and fuse block

How to Set It Up:

  1. Connect the alternator to the isolator/relay.
  2. Wire the isolator to both the starter battery and the trolling battery.
  3. As the motor runs, excess power charges the trolling battery.

Important Notes:

  • Make sure your outboard can handle the extra load
  • Monitor the battery voltage to prevent under or overcharging

Method 4: Using a Portable Generator or Lithium Power Station

Portable Generator Option:

  • Quiet inverter generator (ideal for boats)
  • Plug in your marine battery charger
  • Recharge your trolling battery while anchored

Lithium Power Station Option:

  • Portable lithium battery (like Jackery or Bluetti)
  • Direct 12V DC output or AC outlet for your charger
  • Lighter, silent, and safer to use on small boats

Safety Tips:

  • Never use gas-powered generators inside enclosed spaces
  • Keep lithium stations out of direct sun and dry at all times

This method is very useful when you need a fast power boost and don’t have time to rely on the sun or motor alone.

Method 5: Hydrogenerator Systems (Advanced Users)

Hydrogenerators spin a turbine in the water as your boat moves. This spinning motion generates electricity. They are often used on sailboats or yachts that travel long distances.

Why It’s Rare:

  • Very expensive to install
  • Requires consistent boat movement
  • Not ideal for small fishing boats or kayaks

If you’re a serious sailor or planning a long expedition, it’s a backup worth considering. Otherwise, focus on the first four methods.

Combine Multiple Charging Methods for Best Results

Smart boaters don’t rely on just one system. They mix two or more methods to make sure they always have power. Here’s a perfect combo setup:

  • Solar Panel: Keeps a trickle charge going all day
  • Outboard Alternator: Charges while cruising
  • Onboard Charger or Power Station: Provides full recharges

This approach makes sure your trolling battery gets power during every part of your trip.

How to Take Better Care of Your Trolling Motor Battery

Taking care of your battery will make every charging method more effective:

  • Avoid draining your battery below 50%
  • Charge it fully after every trip
  • Store it in a cool, dry place when not in use
  • Check terminals for rust or loose connections
  • Use a voltmeter or monitor to track performance

Routine care will make your battery last longer and charge more quickly.

Mistakes to Avoid

Avoiding a few simple errors can save you a lot of money and frustration:

  • Don’t mix battery types (AGM, Gel, Lithium) in the same setup
  • Never connect solar panels without a charge controller
  • Don’t ignore wiring quality—cheap wires can melt or catch fire
  • Avoid using automotive chargers on marine batteries
  • Don’t leave batteries exposed to rain or waves

Stick with marine-rated tools and follow proper installation steps.

Frequently Asked Questions (FAQs)

Can I charge my trolling battery while using it?
Yes, especially with solar panels or alternator support. The charge may not fully keep up with heavy usage, but it helps extend battery life.

Is it safe to leave the solar panel connected all day?
Yes, as long as you use a charge controller. It regulates the current and prevents overcharging.

What size generator should I use?
A 2000-watt inverter generator is enough for most marine chargers.

How long does a solar panel take to charge a trolling battery?
A 100W panel in full sun can add about 5–6 amps per hour. To fully charge a 100Ah battery from 50%, it may take 8–10 hours.

Can a lithium power station recharge a deep-cycle battery?
Yes, if it has a high enough output. Check the specs before buying.

Final Thoughts

Learning how to charge a trolling motor battery while you’re on the water gives you control, confidence, and freedom. You no longer have to worry about getting stranded or ending your day early.

From solar panels and onboard chargers to alternator systems and lithium power stations, you now have several ways to keep your battery alive. Choose the methods that work best for your boating style and always carry backup charging gear just in case.

The peace of mind I have now, compared to that stressful day on the lake, is worth every bit of effort I put into learning this. And now, you can have that same confidence on your next trip too.

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