The Salish 100
This is my experience on the Salish 100 going all solar on a 13-foot dinghy using a standard EP Carry and it's little 6 lb battery. The battery was recharged in real-time by a 200-watt solar array.
I traveled for 39 hours over 7 days; 120.2 nautical miles (That's equivalent to 480 ship-to-shore trips of ¼ mile each) with almost 100 other small boats of all types.
The Salish 100 is a week-long cruise, 100 nautical miles up the length of the Salish Sea (Puget Sound) from Olympia to Port Townsend. Spring in the Salish- weather was constantly changing. We timed each day with the tides as any sailor should, we saw 25 knot winds with 2 ft chop on the nose, we traveled in 3 ft following steep seas and hit the respectable rips on Point-No-Point. We also had long stretches of calm and we all made new friends. Both Swe’Pea and her solar powered EP Carry system worked flawlessly.
Why do this?
I designed the EP Carry to replace small gasoline outboards for good. It has world-class efficiency with its brushless motor, and lithium battery. But in development, I also wanted to address what no outboard manufacturer yet done; focus on the entire ownership experience. That includes actual boat speeds, boat trim, motor and battery handling, transport, storage, charging, robust plug and play connections, more safety features, ½ the weight, great appearance, no maintenance, impact survivability, corrosion prevention, ergonomics, maneuvering, security, entanglement, and beaching ease.
We illustrate all these usability elements on our website. And users agree that this little EP Carry is the easiest to use and easiest to own motor ever. But we still needed to demonstrate the relevance of our incredible efficiency.
Electric dinghies typically need to be supported by the mothership. Using less electricity lowers the impact of charging on the house system to a point where literally any mothership can charge the EP Carry's battery without running a generator or the auxiliary. You can even recharge the EP Carry's battery one time each day with a 40 watt solar panel, small enough to fit on the seat of a dinghy. But I wanted to drive the point home on how small a solar array needs to be for continuous distance travel using the EP Carry, and I wanted to demonstrate how I rely on the EP Carry even in tough headwinds, continuous running, impacts with debris and groundings, pretty impressive tide rips and lots of salt exposure.
So I decided to put a little skin in the game and commit the motor (production serial No. 6) to a publicized 100-mile springtime cruise from Olympia to Port Townsend — the length of the Salish Sea (Roughly, Salish Sea includes Georgia Strait, Puget Sound, and Strait of Juan de Fuca). If the motor or solar scheme failed, everybody would see. The Salish 100 was an ideal trip to demonstrate the value of our efficiency, and to show how reliable the system is in all conditions.
In one day, our 13-foot dinghy traveled 26.2 nautical miles on a solar array covering just 20% of Swe’Pea's footprint. And I ended that day with a higher battery charge level than at the start even with rough seas and stormy conditions at the end. Using a trolling motor, I would have required four times the solar array size – so efficiency is important. I could not have done this trip without our little EP Carry.
Overview of the rig
We recommend the EP Carry for boats up to 13 ft and 600 lb and this was our loaded state for the trip. We outfitted Swe Pea, our 13-foot wooden dinghy, with a solar pop-top, charge controller, meters, safety and navigation equipment. I outfitted myself with warm waterproof clothing, food, water, a port-a-potty, sleeping pads, tent, pads, cooking things.
Boat: Total dry weight approx. 300 lb. A 1950s hot-molded mahogany jet-14 hull shortened by 1 ft to remove rotted sections, 1-1/2” fir transom and motor well. Shear was raised by 8 inches and a new deck and windshield added in 2001. Forward and aft bench seating. Her photo below shows her with her first electric motor, a converted 2-stroke gasoline unit weighing 40 lb with 140 lb of batteries. She's since gone on quite a diet with her 20 lb EP Carry/battery system.
Motor and battery: Total weight 20.4 lb. From the standard EP Carry system package. I kept a second battery stored onboard for emergency use, but never needed it. The motor was modified for remote steering and throttle control but otherwise it was standard issue. This resulted in the loss of the handy “tiller-pull” raising feature. So beaching, like any other motor, was a pain. Note: Use a high-efficiency motor like EP Carry if you can carry 200 watts (12.3 square ft.) of panels.
Solar panels: (shown in lowered position) 2 ALLPOWERS Solar Panel 100W 18V 12V wired in series. Total weight 16 lb. There are many brands of semi-flex panels using Sunpower cells. This is just the one I happened to purchase because it had the least non-active surface around the edges. These panels are recommended after this trip- good efficiency, no hiccups. Panels were fashioned into a pop-top to act as a rigid Bimini up and away from shadows. It could also be lowered for windage reduction, heavy seas and when trailering. Each panel measures 21” x 42” so the array is 42” x 42” in my arrangement. The panels therefore cover 12.25 square feet. With the pop top up, I was shielded from the sun, and to the rain to some extent.
Solar controller: The EP Carry battery will self-regulate its charge with a direct connection to solar panels under 100 watts but I was using 200 watts of panels so I needed a charge controller; a GreeSonic MPPT Solar Charge Controller 15A 12V/ 24V Waterproof (MPPT1575). I set Swe-Pea's solar system last minute without enough time to obtain the desired controller. But the GreeSonic was available and supposed to be programmable for Lithium charge needs. However, re-programming is not yet possible as it turns out, so this MPPT is not recommended for this application; Stuck with lead acid battery output parameters, the GreeSonic goes to a reduced current mode (float) at voltages corresponding to a state of charge of only 85% - 90% for the lithium battery. So it was best to run the battery down to below 85% state of charge immediately to maximize the solar current into the battery and motor. It however is able to manage the battery charging safely, and to 100% eventually. For this trip, I would recommend instead the Genasun GV-Boost solar charge controller with MPPT for 24V Lithium Batteries, though I have not tested it.
House electronics: A K2 12v battery provided house power during the trip. It had its own 35 watt panel. K2 batteries provide their own internal charge control that opens the internal battery circuit when the battery reaches balance and 100% state of charge. That means that when fully charged, the terminals go to the solar panel VOC which might damage electronics. So I was careful to not let the VOC condition occur for my house bank. Electronics were minimal– a depth sounder, bilge pump, nav lights, and a USB charge port for charging the nav tablet, phone and VHF radio.
Meters: On a trip like this, you need to see what's happening to control it properly. There are two critical bits of info needed; power into or out of the battery, and the state of charge in the battery. Everything else is extra info to support geekdom. I used a $45 LCD screen coulomb counter meter (Battery Coulometer TK15) arranged to show the battery's state of charge and charge/discharge rate. It is not robust physically but with care, it worked flawlessly on this trip. This product is recommended if it can be adequately protected from the weather and handling. Other options are to use an ammeter that can show positive and reverse current flow, and a good state of charge meter. Note that unlike with lead acid batteries, voltage meters are not effective or accurate on lithium batteries unless readings are taken in fixed conditions. A true coulomb meter is needed for Lithium.
Safety: Here's the list: (total weight 60 lb)
- Nav lights
- Fire extinguisher
- First aid kit
- 8 lb Danforth with 6 ft chain and 100 ft of rode
- Weems & Plath C-1001 SOS Distress Light with Day Signal Flag
- Throwable and spare wearable PFDs in addition to the Mustang inflatable PFD
- Handheld VHF
- Rule IL280P 12 Volt 280 GPH Inline and Submersible Pump
- 400 lb of flotation in addition to the natural wood construction
Weights (in lb)
- 300 Boat
- 20 Motor and battery
- 15 Solar array and controller
- 60 Safety gear
- 200 Pilot
- 70 Personal gear/food
665 Total weight (lb)
- 120.2 nautical miles traveled
- Average trip speed was 3.1 knots
- Max speed was 5.5 knots at full power through Port Townsend canal and Dana passage, in both cases aided by a 1.5 knot flow. Minimum speed was 2 knots at full power against tides, est 15 knots winds, and wind-chop in Port Madison bay.
- Total travel time was 39 hours.
- Conditions first two days were cloudy. I'd estimate the rest of the trip at 40% sun on average. Most days, departure was at 8:00 AM when I could generate at least 15 watts, climbing to 40 W by 9:00-9:30. All but one morning was under cloud cover. The sunny morning at Blake Island saw 45 watts generated at 8:00 AM raising to 180 watts and higher possibly, mid-day between clouds.
Swe’Pea's power-speed curve
This is a very useful curve as it shows why the EP Carry's efficiency is so valuable on such a trip. For example, to travel 2 knots only requires 25 watts of power ( A trolling motor requires 100 watts to do a lower speed of 1.8 knots).
Performance vs sky conditions for solar position, 48 degrees N, and for time; late June
Power generated.Note this is for the actual panels and conditions as used on my trip. It is a measure of actual performance so this would include both the flat orientation of my panels, and the natural sunlight intensity changes by inclination.
Note that the difference between heavy and light clouds is 38 W vs 64 W and even on heavy overcast days, output varies depending on the thickness of the clouds at that particular time. In full sun, power is almost 5x that under dark skies. So you need to keep on the controls every few minutes to keep up. Just like tending a sail, the throttle needs tending.
Here's how cloudy mornings started: At 8:00 AM I could generate 15 watts under very heavy cloud cover. For 2 knots of speed, I needed only 25 watts into the motor so that's 10 Watts from the battery. Keeping that throttle setting, battery draw would diminish to zero by 9:00 AM when I was collecting all 25 watts from the clouds.
In reality, cloud cover was always changing and I found that 2.5 knots right away was a good choice, relying on the fact that higher collection points would happen later in the day. Even on cloudy days, I ended up at 40-50 Watts (2.5 knots over the water) into the motor mid-day while still charging the battery to overcome the morning deficit. On sunny days the picture was much better as you can see in my log later in this report.
Swe’Pea speeds using only solar power and how they vary through the day depending on the sky state.
This chart combines the solar availability chart above, and Swe’Pea's speed-power curve above. If I were to use the battery, Swe’Pea's speed was 4 knots over the water. In reality, due to good planning on the Salish 100 planning folks, we saw an average tidal lift except for those days I went rogue to visit places and friends from my childhood.
If it's a full sunny day and you travel from 8:00 AM to 6:00 PM using no battery, you can go over 40 miles. That distance is down to 23 miles on a consistently cloudy day.
Every day saw varying conditions. Days would often start with heavy overcast, and switch through all conditions to full-sun and then back to heavy clouds when we saw most of the rain in the afternoon. It requires attending the coulomb meter to assess both the state of charge and charge/ discharge rate to track actual sun-generated power.
On average Swe’Pea did 3.2 knots over the ground each day- some days less if they were mostly overcast and some more if mostly sunny.
Interesting note: It seems that the solar motor arrangement is a good auxiliary option for sailboats; Swe’Pea tended to have more favorable power-generation on the days with little wind. On windy days, the sailboats would outrun me like what happened when we rounded Point-No-Point. So sailing and solar seem to fit well together.