By Cecil Hoge – President, Sea Eagle® Boats, Inc.

I have been testing electric motors with solar panels on inflatable boats for over 15 years and while I have made steady improvements in using solar panels with electric motors and inflatable boats, I have not been able to reach, until recently, the Holy Grail of using solar power with electric motors. What is the Holy Grail of Solar Power with electric motors? It is simply to have the ability to motor without limits perpetually without ever having to recharge the battery with a plug-in battery charger.

The solar powered inflatable boat above recharges itself by converting sunlight into electrical current and charging the battery whenever there is some sunlight. That is accomplished by the 4 175-watt Renogy flexible solar panels shown on the custom canopy. With the Cruise 2 Torqeedo® electric motor the FastCat™ 14.4 can go perpetually, as long as there is sunlight, at 4 to 5 miles an hour without using any battery power. The top speed of this solar boat configuration at max throttle power is only 6 to 7 mph. So, in truth, there is not much difference between cruising strictly on sunlight and going at full throttle and using some battery power.

This FastCat™ 14.4 has been tied up to a dock at my house for the last five months and I have been testing this special Solar Powered Boat configuration literally four to six days a week. I am lucky in that I live on a tidal bay called Little Bay. It is appropriately named because it is little – only about 1/2 a mile across and 3/4 quarters of a mile long. Little Bay leads out to Setauket Harbor and that leads into Port Jefferson Harbor. If you go left when you come out of Setauket Harbor and follow that for about a mile, you can take another left into Conscience Bay. The point I want to make here is that I have direct access to four different bays and Long Island Sound beyond.

Now living on a tidal bay is often not understood by folks not familiar with the coming and going of tides. The actual fact is that my entire bay completely empties twice a day, which means that my boat is either floating in water or sitting on mud. I am fond of saying that I have 9 feet of water or 9 feet of mud. In truth, since the tide is always coming or going, the level of the water or the lack of water is always changing and depends completely on where the tide is. At my house the tide is generally out for 3 and half hours twice a day and in for 8 and a half hours twice a day. That allows plenty of time to go boating.

I have now gotten to test and use this boat configuration for over 5 months and I can say that the combination of 4 175-watt Renogy flexible solar panels, the Cruise 2 Torqeedo® Motor, a Torqeedo® Solar Controller, and FastCat™ 14.4 really works in what I would call a “Holy Grail” manner. That is, this boat can be powered perpetually as long as there is sunlight and that allows you to motor it wherever you wish without ever having to charge it yourself.

I consider this a lifetime dream of practical, perpetual solar power come true. And while I have tested numerous other configurations of solar panels, electric motors, and inflatable boats, this is the first solar boat configuration that delivers “perpetual solar power”.

Let me count the ways this is wonderful:

1. You never have to charge the battery because the solar panels do that for you. So this is a boat that literally powers itself.
2. An electric motor under power is far quieter than a gas motor. In my case, I carry on board a small bluetooth speaker to listen to music. Because the electric motor is incredibly quiet, you can really listen to the music as you and any family or friends cruise the different waterways.
3. There is no smell of gas or oil fumes and no pollution created by motoring with this solar boat configuration no matter how far you go.
4. You do not need to worry about filling up a gas tank or having gas and oil spills because electric motors do not use gas or oil. So not only is an electric motor far quieter and less odorous, it costs zero for gas and it is far less messy.
5. Starting an electric motor is far easier – turn the master switch on, push the power button on, turn and twist the throttle – away you go!
6. Because solar panels automatically charge the battery, there is no need to drag the battery to a 110-volt outlet to plug in an electronic charger. And for those of you who do not know, batteries tend to be heavy (the Torqeedo® lithium battery weighs 62 lbs.), so moving a battery involves strong arms, strong legs, and a strong back. Having the battery in the boat with solar panels automatically charging the battery eliminates the need to move the battery to a place to plug the electronic into an electrical outlet.
7. Of course, I have to admit this is only practical if you already live on a lake or bay where you can moor your boat or have it tied up to a dock. However, it is also practical to leave solar panels on a boat that you either trailer back and forth to the water or park outside on a lawn where there is sunlight.
8. Perhaps the most important benefit is the fact that you can, if you have to, go hundreds of miles for hours on end with no cost for fuel or electrical power.
9. If one compares the cost of a solar powered boat to a gas powered boat, generally the initial cost is far lower for a gas powered boat, but when one compares the long-term need to continually fill up a gas powered boat and the yearly upkeep to tune-up a gas motor and keep it in good repair, solar power does pay off within several years.

What Are The Limitations Of A Solar Powered Boat?

• Outfitting electric motors & batteries with solar panels generally works best with smaller electric motors and that generally restricts your maximum speed to under 10 miles per hour. I would expect that to change as solar panels, batteries and electric motors become more powerful and more efficient. In the future it will be more practical to recharge larger electric motors and that will deliver higher speeds.
• It is also true that mating solar panels with smaller electric motors will provide the best economic comparison to gas outboards in terms of overall cost.
• In outfitting a boat with solar panels, you have to have a convenient, out of the way place to put solar panels. That is why we made an aluminum frame canopy to hold the panels – the panels sit above the passengers, they do not get in the way of needed space and they provide a shelter from sun and rain. A true win, win. That is also why we offer solar panels that conveniently fit on our sun/rain canopies.
• A solar powered boat will provide unlimited power AS LONG AS THE SUN IS OUT at a slow speed, depending on the solar panels used. As mentioned earlier, the FastCat™ 14.4 will cruise just on sunlight at 4 or 5 miles per hour indefinitely as long as the sun is out.
• However, if it is cloudy or early in morning or late in the afternoon when the sun is at a low angle, solar power is greatly reduced. And that is even more true if it is raining for one or more days.
• In the times that the sun is not recharging the battery, you will be using up battery power when motoring, and that will naturally limit your range.
• So, while solar panels can provide perpetual power that can allow you to go really long distances if the sun is not shining, you will have to rely on power in the battery or you will have to recharge it using an electrical charger plugged into an electrical outlet.

With the present Custom Solar Configuration for FastCat™ 14.4 that I am showing in this blog story, there are inherent drawbacks. The Cruise 2 Torqeedo® electric motor only goes 7 mph at max speed, so if you have a need for speed, you are out of luck. I would note here that the Cruise 2 Torqeedo® has now been replaced with a newer model, the Cruise 3 Torqeedo®. The newer motor goes a little faster, about 8.5 mph with our FastCat™ 14.4, and the battery now has about 1/3 more power, so that also enhances the distances you go when your use exceeds the power of incoming sunlight. The new battery weighs 62 lbs. and the Cruise 3 motor weighs 38 lbs., so on a weight only basis it is about the same as a gas 9.9 outboard. Being under 100 lbs., both are reasonably easy for one person to manage, but having the motor and battery separate certainly makes it easier to put on and off of a boat.

However, cost-wise, electric motors are far more expensive to buy. The Cruise 3 motor (the new model that replaces the Cruise 2 we are using) costs $4299 for the motor and $2999 for the battery. We sell a far more powerful 9.9 Honda for $3,079. It will motor 3 people on the FastCat™ 14.4 at 14 miles per hour, so it is not only way cheaper to buy, it pushes that boat far faster. So, if you choose a Cruise 3 motor, you have to love the benefits of electric power because economically it is going to take a long time for your investment to pay off.

My own conclusion is that solar power does not presently make economic sense for higher power electric motors, especially when combined with the very reasonable costs of inflatable boats. That said, I must also say that the landscape for electric outboards is changing rapidly, There are presently only a few companies offering higher power electric motors, but Mercury and many other outboard brands are rushing electric motor models to the marketplace and no doubt, pricing, electric motor propulsion, battery efficiency and the efficiency of solar panels will all get better in the near future.

I can say that the custom model boat configuration that we have made up and described here is a totally practical use of solar power with electric motors. It is fairly expensive to do this with a 6 hp electric outboard. And if cost is the main consideration, the best immediately available benefit is with smaller electric trolling motors like the WaterSnake® Asp 24, Venom 34, Advance 70 and Minnkota® 30, and Minnkota® 55 motors that we sell. At the bottom of this story, you will find a link to the present solar boat packages we offer.

As a company, we presently sell all those models in Solar Boat Packages with PowerFilm 50 and 110 watt solar panels. The advantage of those packages is that they are still reasonable in price and you can hook up that Powerfilm Solar Panels to any 12 volt lead acid, AGM, Gel or Lithium battery (in the case of our Advance 70 WaterSnake® electric motor) on a “plug and play” basis. That is one solar panel with one electric motor with built-in solar controller and built-in fuse.

We are presently in the process of developing solar boat packages for Torqeedo® motors. The first motor we will have a solar boat package on with be the Torqeedo® 1103 Travel Motor. This is a somewhat smaller motor delivering the equivalent of 3 hp. Like other Torqeedo® motors, it is not cheap. Presently, that model costs $2,999. A nice feature of the 1103 is that it weighs a total of 39 lbs. with the built-in lithium battery that comes equipped with a built-in solar controller. We will shortly be offering that model with a 165 watt Solgo solar panel with a special Torqeedo® connector to ensure no problems. This will be a true “plug and play” solar boat package.

In the case of the Custom Solar Boat Package that we constructed for purposes of testing and achieving “My Solar Power Dream”, we are also putting together the same kind of “plug and play” solar boat package for that Cruise 3.

Now, people who wish to make their own solar boat packages can go ahead and recreate a solar boat packages with more solar panels similar to the package I created for this blog story. But they should only do that if they have electrical knowledge and are comfortable with matching up lithium batteries with multiple solar panels and a solar controller. If you decide to do that and you want to use Torqeedo® electric motors, you also should know that Torqeedo® will not warranty their products unless you use a Torqeedo® solar controller.

And then there is the cost to consider: For the purposes of this experiment, we used an old Cruise 2 Torqeedo® motor that we had bought 8 years ago and married that with a 4 year lithium battery.

For solar panels, we bought 4 Renogy 175 watt panels and connected them in a series. Because the Renogy panels were flexible and because they blocked out the sun, I got the bright idea to mount the panels side by side on a special square tube frame. That provided an out of the way place for the panels and a UV proof canopy at the same time.

Now, it must be said, that while this same configuration can be re-created by anyone buying one our Sea Eagle® FastCat™ 14.4s, recreating this particular solar boat package will require the following:

• A custom built canopy frame to hold the 4 solar panels – this would require some skills to build a custom canopy frame, as well as various nuts, bolts, and parts to attach the panel into a single frame. In the near future, that should not be much of a problem because we are planning to offer a larger canopy which can hold 4 solar panels. In the meantime, our wide Sun/Rain Canopy will hold 3 Renogy or similar size solar panels, so with our standard wide canopy, you could have 3 solar panel solution. That might not be as much solar power as the configuration, but surely, it will be more than enough solar power for regular use of a Cruise 3 Torqeedo®.
• The above solution would still leave you with the task of buying flexible, solar panels – you should figure $200 to $300 per solar panel and $1,300 for a Torqeedo® solar controller. As mentioned above, the solar controller is a must if you want Torqeedo to uphold its standard warranties. Torqeedo® does offer a fairly reasonable cost solar controller for the Cruise 3 motor, but that is limited to a single solar panel with an output of 8 amps or less. If you wish to have more solar panels, you have to go for the higher end solar controller which costs a hefty $1299. Strangely, that controller is only rated at IP 51, which means it is not truly waterproof. That means you have to have some way to keep the controller out of direct exposure to rain. My solution to that problem was simple: a $4 plastic wastepaper basket that fits neatly over the controller. That works, but it is not the most beautiful solution. Strangely, the cheaper solar controller for one solar panel / 8 amp max is IP67 rated, so that is completely waterproof.
• Next, you cannot forget the motor and the battery – a Torqeedo® Cruise 3 costs a cool $4299 for the motor only. Then there is the battery. That costs $2999 for the lithium battery. So, when you add all of the above costs, including the cost of our FastCat™ 14.4 you are really in for about $12,000. In short, you have to have a real love of electrical power to choose to create this particular solar boat package. Frankly, no matter how much gas you use on 10 or 20 hp gas motor and how many times you repair or tune-up a gas motor, it will take a long time to justify your purchase of this solar boat configuration just on economics.

In summary, you are probably not going to want to re-create this particular solar boat package. As mentioned in this bog story at the beginning, this was always an experimental solar boat package to give us a true understanding of what can be done with solar boat packages. As such, I believe this configuration has given me a true understanding of what is presently possible.

As mentioned above, we already offer 10 solar boat packages with our Sea Eagle® boats and WaterSnake® electric motors. And yes, because WaterSnake® motors do not draw a lot of electrical power, these solar boat packages do work well and are very reasonable in cost.

For those who wish to use larger electric motors, we will shortly be offering solar boat packages with the Torqeedo® 1103c Travel Motor (the equivalent of 3hp gas motor) and the Torqeedo® Cruise 3 motor (the equivalent of a 6 hp gas motor). Those packages will come with canopies to hold the solar panels and will offer what we think will be the most practical and economic configurations for solar boats.

For more information on solar panels, why to go solar, and how to choose the right one for your Sea Eagle, check out this video.

For those of you interested in the present solar boat pack packages, click here to see them.