How to Charge a Trolling Motor Battery with Solar Panels

With solar power being used on everything from mobile devices, appliances, RVs to houses, it’s only natural that anglers and fishermen ask the question, can solar power charge a trolling motor battery? It is a good question, but there is no clear cut answer given the many possible scenarios that can arise.

A 6W or 12W solar panel is enough to trickle charge a trolling motor and ensure it remains full even when not in use. A 10 watt solar panel that generates 1 to 2 amps will keep the battery from discharging. .

What Solar Panel Size Do I Need to Charge a Trolling Motor Battery?

We need to clarify some points here. By maintaining, we mean the battery is 100% charged and the solar panel will be used to maintain this charged state. We will assume you are not using the boat since the battery is not being utilized. A 10 to 12 watt solar panel is enough for trolling motor batteries.

That is a very small power requirement, so even a portable solar panel like the Eco Worthy 10W Solar Panel can handle that. Small solar panels produce750mA to 5A a day. That is more than enough to keep the trolling motor charged, but this assumes no battery parasitic load, otherwise you have to double the solar panel size requirement.

There are several portable solar panels designed for marine batteries. The only thing you have to consider is the power output. If it is more than 12 watts it should be able to top off the battery. While you can buy specially designed solar panels for marine batteries, regular solar panels will be enough.

While we are talking about solar panels, you can achieve the same results with a portable solar generator. Because the power required is low, a handheld solar power station will be enough. No need for large generators here. Even if there is sufficient space in your boat, there is no need to put a large solar power station or solar panel there if a small system will do.

How to Recharge Trolling Motor Batteries with Solar Panels

As we pointed out, it is possible to charge a trolling motor battery with solar power after you’re done using it. However most people find this impractical for various reasons, but mainly it has to do with the solar panel size required.

The bottom line is you will need a fairly large solar panel to recharge a trolling battery. Whereas a solar panel is easy to mount on an RV, it’s a different matter on a boat. There is not enough space on the average boat for the solar panel. This doesn’t mean you cannot recharge with solar power. It is possible, but space might be an issue.

If there is plenty of room on your boat, recharging with solar is a good idea. Most trolling motors use AGM or lead acid, both of which have a 50% depth of discharge (DOD), meaning it needs to be recharged when the battery level drops to 50%. With a 50% DOD, the solar panel must provide 50 to 65A. A more depleted battery will require a large solar panel or longer recharge time. Recharging at 60% or higher means a less solar power will be needed.

But aside from the solar panel size, the charging time is another factor. If you’re done for the day, you probably think it doesn’t matter. Just let the solar panel take its time and the battery should be ready tomorrow. In fact, charge time is crucial for several reasons.

One, long charging times force the battery to remain inactive. Too long of a period might lead to battery sulfation and shorten its lifespan. Two, what if something comes up and you need to use your boat? Can you wait hours for the charge to finish? Finally, you never know when a sudden downpour will occur. It could be bright and sunny one moment and torrential the next. With a fast solar panel you can complete the charge faster.

What is the Right Solar Panel Size to Charge Trolling Motor Batteries?

A12W solar panel is sufficient to trickle charge a trolling motor. But what if you need to recharge the battery/

A 75ah-120ah trolling motor battery needs a 12V 70W solar panel, with 100W-150W recommended. A 70W solar panel produces 16-24A every day in ideal weather. A 100W solar panel generates 20A-30A, and a 150W PV module good for 30A-50A. So how do these figures translate into real time charging?

A 70W solar panel requires 2-3 days to recharge a 50% depleted trolling motor battery. A 100W-150W may be able to do it in a day or two depending on how much sunlight is available. Before you decide what solar panel size to use, factor in the time it will take. If you have to use your boat every day, a 70W solar panel will not be enough to recharge the battery.

The figures above are for 12V trolling motor batteries. If your boat has 24V batteries, you need to use 24V solar panels, and you need twice the power needed by 12V modules. That is why a lot of people don’t like to recharge trolling batteries with solar. It takes a lot of time and a lot of space.

If space is not a problem, you can charge and recharge trolling motors. That is really the only hindrance. Provided you have a sizeable boat you can mount a solar panel to recharge your motor.

Can You Run a Trolling Motor Battery with Solar Power?

If it is difficult to recharge a trolling battery with solar power, it’s even more so to run it continuously on solar panels alone. A small trolling motor battery is in the 25ah-50ah range, which is 300W-600W. A high end 12V 100ah trolling motor needs 1200W, something only large solar panels can generate.

If you own a small boat and still want to use solar power, you should use a small trolling motor battery or use solar panels to top off the battery. Better yet, buy a solar generator. There are 1000W solar generators available that take up less space than solar panels. These generators have multiple inputs and outputs so you can find one that works with a marine battery.

The Benefits of Solar Charging Trolling Motor Batteries

Charging trolling motor batteries with solar power presents challenges, but the benefits far outweigh the disadvantages. If you are still undecided whether to go solar on not, here are the advantages you may have overlooked.

Limitless Energy

Solar energy is limitless. You can use it for as long as the sun is out shining. That is probably the biggest benefit here in terms of cost. Yes you have to pay for the solar panel, but prices have gone down so it is not much of an issue. And it is the only thing you have to pay for.

Once you have the solar panel, you can charge the battery as often as needed. And with solar panel warranties good for ten years or more, it is a good investment. The even better news is solar panels are becoming more powerful and more compact, so space will not be an issue in the future.

Safe to Use

Solar panels do not have any moving parts and you don’t need an inverter in this case, just the PV modules. You don’t have to worry about anything breaking or wearing down, though you may want to buy solar panel covers for protection when not in use, but that’s about it.

Compared to other trolling battery options, solar is safer to use. It will give you peace of mind and you can focus on other tasks. Just let the solar panel or generator recharge the battery while you go about your business.

Convenient

Whether it is a solar panel or solar generator, expect ease of use. Basically you just connect the battery to the PV module and the sun will do the rest. No need to mess around with various controls or buttons. A solar power system includes a monitor system so you will know the charge status.

There are a lot of accessories you can buy to enhance a solar power system, but even the basic one will do fine for a trolling motor. The point is you will find it more convenient to use than other types of chargers, and it is cheaper too.

Eco-Friendly

Solar power has taken off because it is eco-friendly. Doing your part to keep the environment clean and green won’t hurt. In fact it’s going to help as a clean environment enhances marine life, and that is something anglers and fishermen will definitely appreciate.

Conclusion

Running a boat requires a lot of power, so it’s no surprise more people are looking at alternative sources. While solar panels can run trolling motor batteries, the logistics are difficult for small boats. Of course if you have a large vessel, you can install a good size solar panel and charge until there’s full power.