How To Charge A Trolling Motor Battery with Solar Panels?

As an avid mariner who values eco-friendly power solutions, I have learned that charging with solar panels is the most cost-effective method in the long term.

Sure, it’ll take a while for the investment to pay off, but considering the lifespan of a panel is roughly 25 years, there’s plenty of time to do so.

Charging a trolling motor with a solar panel is really straightforward. If you want to charge your trolling motor battery without shore power, then this is your guide to going solar-electric!

🔩 Installation and Setup

Installing and setting up a solar power system for charging a trolling motor battery involves several steps, such as selecting the right solar panel, mounting it, and wiring it to the battery.

Solar Panel Mounting

When choosing a solar panel for my trolling motor battery, I consider the power output and size of the panel.

A 50W solar panel is a reasonable choice, as it requires around 24 hours of sunshine to charge a 1,200Wh battery.

Solar panels come in various sizes and mounting options, so I select one that fits my boat’s dimensions and mounting area.

To mount the solar panel, I typically follow these steps:

1️⃣ Choose a suitable location on my boat with minimal shading and ample space for the solar panel.

2️⃣ If necessary, use a mounting kit designed for solar panels to secure the panel to my boat. Some kits include adjustable brackets to optimize the angle of the panel for maximum sunlight exposure.

3️⃣ Ensure the panel is securely fastened to avoid damage from wind, waves, or vibrations during boat operation.

Wiring the Solar Panel to the Battery

To wire the solar panel to my trolling motor battery, I carefully follow these instructions:

1️⃣ Confirm the solar panel’s voltage output matches the battery system (12V or 24V).

2️⃣ Locate the positive (black wire) and negative (red wire) leads coming from the solar panel.

3️⃣ Attach an appropriate solar charge controller to the solar panel leads, which will regulate the power output and prevent overcharging of the battery.

4️⃣ Connect the charge controller’s output wires to the battery’s terminals. Attach the positive (red) wire to the battery’s positive terminal and the negative (black) wire to the battery’s negative terminal.

Here is a thirty-second video showing you how to connect your solar panel and solar charge controller to the battery.

For small boats with limited space, I recommend using a compact PV (Photovoltaic) system that can be easily integrated without obstructing the boat’s functions. 

A properly installed and maintained solar panel system will provide an eco-friendly, efficient, and cheap energy source for charging the trolling motor’s battery.

If you decide to go the whole nine yards with solar, the process of hooking up your boat’s battery to solar is similar.

Charging Process and Optimization

Next, we need to discuss optimal charging conditions, charging multiple batteries, trickle charging and managing parasitic loads.

Optimal Charging Conditions

To get the best charging performance from solar, pay close attention to the following factors:

  • Sunlight exposure: Ensuring that my solar panel is placed in a spot with maximum sunlight exposure throughout the day is essential.
  • Panel angle: Adjusting the solar panel angle according to the sun’s position helps me achieve better efficiency.
  • Panel cleanliness: In saltwater environments, regular cleaning of the panel surface is crucial for maintaining optimal charging rates and preventing debris from blocking sunlight

Charging Multiple Batteries

As someone with a 24v trolling motor, I typically use two 12v deep cycle batteries connected in series. To charge both batteries with a single panel, I use a solar charger with multiple outputs and follow these steps:

  1. Connect each battery to the solar charger, ensuring that the wire colors match (red to red, black to black).
  2. Connect the solar panel to the charger.

This setup allows me to charge both batteries simultaneously and maintain an even battery capacity.

Trickle Charging

Trickle charging is a great way to maintain a trolling motor battery’s charge without overcharging it. By using a solar panel with a lower wattage, you can gently add power to the battery, extending the time between recharging sessions and prolonging battery life.

Parasitic Loads

Parasitic loads are unintended electrical draws when not actively using the motor. To prevent unnecessary power loss, follow these practices:

  • Turning off all unused devices connected to the battery
  • Installing a power switch between the battery and the trolling motor to ensure it won’t consume power when not in use

By following these guidelines, I’ve managed to make my trolling motor battery charging process eco-friendly and efficient while catering to my power needs as an angler.

⚠️ Important Considerations

Energy Requirements and Solar Panel Size

As a boat owner wanting to use solar to charge my trolling motor battery, I first needed to understand the energy requirements of the trolling motor, the solar power requirements of the entire boat, and the solar panel size. 

To figure out the ideal panel size for your rig, begin by calculating the trolling motor’s energy requirement. 

Solar panels come in various sizes, like 10-watt, 12-watt, etc. For instance, a 70-watt solar panel might take 2-3 days to recharge a 50% depleted trolling motor battery.

In contrast, a 100-watt to 150-watt panel may do so in a day or two, depending on sunlight availability.

Battery Sizing for Best Performance

Battery size is another essential factor in ensuring the best charging performance. So select a solar panel with a wattage rating that is at least equal to the battery’s amp-hour rating.

Furthermore, you must make sure you are using deep-cycle marine batteries, as they’re specifically designed to withstand the harsh marine environment and can provide consistent power.

🔑 Key Takeaways

1️⃣ It is important to understand the energy requirements of your trolling motor and choose an appropriately sized solar panel to meet these needs. Depending on sunlight availability, a 70-watt solar panel might take 2-3 days to recharge a 50% depleted trolling motor battery, while a 100-watt to 150-watt panel may do so in a day or two.

2️⃣ Selecting the correct battery size is vital for the best charging performance. The solar panel’s wattage rating should be at least equal to the battery’s amp-hour rating. Deep-cycle marine batteries are recommended for their durability and consistent power supply.

Nice to e-meet you. I’m Justin, a seasoned sailing journalist and communications pro with more than 25 years of extensive industry experience. And a track record of successfully promoting teams and events on the global stage.