How to Charge a Trolling Motor Battery from the Outboard Motor (part 2)?

(Last Updated On: May 4, 2022)

Trolling is a perfect way to fish. There is only one minus – a suddenly discharged battery. Have you ever been in such a situation? Being stuck in the open sea far away from the shore with nothing helpful is not funny, isn’t it?

Do you fear long fishing sessions because you cannot rely on your trolling battery? Or, maybe, you still struggle to choose the most convenient way of charging batteries, which work inside a running trolling motor, don’t you? If at least one answer is yes, we are companions in misfortune. 

As a trolling fishing enthusiast, I used to face different problems with a battery. After stopping in the middle of the sea and calling a coast squad for help, I’ve decided to dip into extra charging a battery.

Keeping a spare battery in the boat and changing it in the sea has never been an alternative. I could not take the whole workshop with me. Plus, in the past, I used to rent a dock with no option to charge the battery from the shore. I am sure I am not the only one having this trouble.

Brief research showed that charging a trolling battery while running is not that difficult. There are plenty of variants.

This post is a brief explanation of how to charge a boat battery on the water.

I hope it will give you a clue and open a world of long-term fishing without fears and troubles.

Fishing without fears and troubles
via @lodki21

Charging Trolling Motor Batteries While Running with Combiner 100

Let’s discuss concerns regarding charging a trolling battery with an outboard motor. I’ll describe a method that implies a battery combiner called Combiner 100. It is a perfect choice for those who cannot or do not want to change the cables, dismount, and disassemble the motor. The main advantages of the method are:

  • The device is automatic. All you need to do is to set it to the battery properly (details are below).
  • Combiner 100 covers any voltage differences within 100 amp. In the case of a more powerful motor, a producer recommends Combiner 160.
  • The in-built charge leak protection prevents charge losses after work and during combining. 
  • It’s easy to use and apply: a few diodes, a minimal number of buttons, and an ability to disconnect the device while the motor is working. 
  • In case of an overload, the device turns off automatically
  • It is waterproof, so do not be afraid to use it while running.

In addition, Combiner 100 and similar devices are not that expensive. You risk losing more money without them. How to use Combiner 100?

  1. Choose a convenient place to mount Combiner 100. A producer suggests about two feet from a starting battery. There is no need to cover it unless you see the diode glowing under straight sunlight.
  2. Take one of the red wires of a device and connect it with the positive end of a battery. It does not matter which red wire you choose. Be sure that the second red wire is isolated. 
  3. The second red wire should be connected to the positive end of a trolling battery. You might need to prolong it. 
  4. The negative ends of both batteries should be connected with each other. 
  5. Take the black wire of the device and connect it with the negative end of a starting battery.
  6. Leave the green wire of the device untouched and isolated.

That is it. You’ve connected the batteries, and when you start the motor, the starting battery will charge your trolling battery. It will work while the motor is working.

Pay attention to the device from time to time: a red diode flashing or constantly working shows that the device is overloaded and is going to turn off due to overheating.

In this case, it will cool and make another attempt. The producer recommends checking if everything is OK. 

Magnum Energy ME-SBC Smart Battery Combiner
Source: YouTube

In case you cannot find the exact device, I suggest picking this charger or this combiner. They are designed especially for charging marine motor batteries as well. They come with the instructions, and the main principles of their application do not differ from our instructions. As for me, I’ve chosen using a combiner as the most convenient solution on how to charge a boat battery on the water. 

How to Charge Trolling Motor Battery Without Shore Power (Other Ways)

Besides the alternators, there are several ways to charge a trolling motor battery. The first one is questionable – using solar power. In theory, you just need to buy a specialized solar panel and, maybe, something to hold it on a boat. However, the specialists doubt this method is 100% usable.

Using solar power
via @silent_yachts_headquarters

Here are the reasons:

  • Solar power charging works for batteries of small capacity. It will take too long to charge a powerful one. 
  • It is barely impossible to charge the battery in a sea and while the motor is working. Solar batteries cannot produce enough charge to exceed the charge emissions. In the best situation, you’ll have a supporting source of power. 
  • Solar panels are massive and require proper installation. They are not an option for small or medium boats
  • They will support only a battery: there is no possibility to charge other devices with them simultaneously.

Conclusion: solar panels might be a good answer for the question of how to charge trolling motor batteries without shore power only in a dock and only for short rides. If you are not planning a long trip, where you are 100% your battery will not last long, a solar panel is a considerable choice. Otherwise, I recommend paying attention to other options. Plus, specialized solar panels are quite expensive. 

The second way is making an outboard battery charger by yourself.

Battery charger by yourself
Source: YouTube

You’ll need:

To cut a long story short, watch the video describing the method. There is a variation of the method that implies using a charging coil. Get a video with instructions as well. The final result might be a bit extravagant, but if it works, who cares about appearance?


There are several ways to solve the issue. Some of them are expensive. Some are massive. Not every way is good for in-sea charging. However, each of the ways is not that difficult and is worth your consideration. In the end, you’ll get your battery charged anyway. What do you think about it? It would be awesome to read your suggestions and ways you solve the problem of battery charge. Feel free to leave the comments below.

How to Charge a Trolling Motor Battery from the Outboard Motor-1-1

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