sailing yacht electric propulsion

HYBRID AND ELECTRIC MARINE POWER AND PROPULSION SYSTEMS

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THE FACTS ABOUT ELECTRIC POWER, BATTERIES AND PROPULSION

Today's electric motor technology has already moved from

the open road to the open ocean.

Instant High Torque

Electric motors are in constant ‘stand by’ mode; you can engage the control lever at any time for instant forward or reverse propulsion.

Electric motors achieve instant torque with Electromotive Force while internal combustion engines need to build RPMs gradually by increasing piston firing frequency.

Hydro Generation

At sailing speeds over 6 knots Oceanvolt systems are able to generate significant power for recharging the battery bank by activating at the touch of a button.

Power regeneration increases exponentially with each additional knot of speed.

Lithium Ion batteries are superior to other battery storage technology; highest storage capacity, high effective current delivery, high charge capacity resiliency and wide temperature range performance. In today's digital age, where everything is just a click away, 1xbet mobile takes a significant chunk of the online casino services sector. Starting as an online casino service in 2007, 1xBet expanded its services in 2014 to include sports betting. Fast forward to 2018, and they marked their entry into the Indian market. Their app and website, designed in a calming blue and white hue, are not just a treat for the eyes but are also super intuitive. With a support interface that covers 50 languages, including Hindi, the platform ensures that language is no barrier to placing your bet.

Oceanvolt highly skilled technical team ensures proper installation and system-optimization.  Only the highest quality Li-Ion batteries are used - to ensure performance and safety.

For those interested in a hybrid solution, generators are a highly efficient way to extend range while at sea.

DC generators have the advantage of rapid recharging capability.

AC generators are, generally, smaller and even portable which means that the generator can be aboard only in situations where longer motoring might be required.

Battery recharging is accomplished with shore connection, hydro generation (an integrated part of all Oceanvolt systems) and/or solar panels.

In Hybrid solutions , a generator (either AC or DC) can be used to recharge batteries / extend motoring range.

Integrated components

It is essential that all system components are properly selected and installed.

Our team of highly skilled technicians ensure that all components are compatible and that system management software is optimized.

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The Promises and Pitfalls of an All-Electric Yacht

• By Tim Murphy
• Updated: November 8, 2021

This past October, I saw one of the most interesting exhibits in more than 500 new cruising sailboats I’ve reviewed over two decades. It was the Arcona 435Z, built in Sweden and introduced by Graham Balch of Green Yachts in San Francisco. Balch describes his business as “a new brokerage dedicated to the electric revolution on the water,” and it was the “Z” in the boat’s name, which stands for “zero emissions,” that made this boat so interesting. This was the first electric propulsion system—not hybrid but all-electric —I’d ever seen on a cruising sailboat.

Electric propulsion isn’t new. Since 1879, electric motors have propelled boats; a fleet of some four-dozen electric launches transported visitors around the 1893 Colombian Exposition in Chicago. But cruising sailboats are not launches, and the open sea is not a protected canal. When we’re using cruising boats as they’re meant to be used, they seldom end their day plugged into a shore-power outlet. Cruising boats comprise many devices —stove, refrigerator, freezer, windlass, winches, autopilot, radar, lights—whose power typically comes from a tank of fossil fuel. And today’s cruising sailors are accustomed to using diesel auxiliary power to motor through lulls or punch into headwinds and seas.

Starting about 15 years ago, we saw a wave of diesel-electric and hybrid propulsion systems on production and custom cruising boats ( see “Perpetuated Motion,” CW , March 2005 ). Both of those systems ultimately start with an onboard internal-combustion engine. A diesel-electric propulsion system relies on a running genset to directly power the electric motor that turns the propeller. A hybrid system relies on batteries to power the electric motor, plus an internal-combustion genset to recharge the batteries. One of the promises of a hybrid system is the ability to regenerate electrical power. Regeneration means using boatspeed under sail to turn the propeller, whose spinning shaft sends electrons from the electric motor back through an electronic controller to recharge the batteries. In such a system, the boat’s propeller is both an electrical load (when running under power) and a charging source (when sailing in regeneration mode).

The Arcona 435Z was different from both of these systems: It incorporates no onboard fossil-fuel engine at all. Instead, it has a bank of lithium batteries, several solar panels, and a proprietary propulsion leg that looks like a saildrive. “This boat,” Balch said, “has the very first production unit in the world of Oceanvolt’s newest electric propulsion system, called the ServoProp.”

For our sea trial, Balch was joined by Derek Rupe, CEO of Oceanvolt USA. “If you can sail the boat and you have some solar, you can go anywhere in the world, and you can make all your power underway while you go,” Rupe said. When we spoke in October 2020, he touted three high-profile sailors who were using the Oceanvolt electric propulsion system: Alex Thomson, for his Hugo Boss Open 60 Vendée Globe program; Jimmy Cornell, for his Elcano 500 expedition; and Riley Whitelum and Elayna Carausu, who had been teasing their new boat for months on their popular Sailing La Vagabonde YouTube channel.

The efficiency of Oceanvolt’s ServoProp and the regeneration from it is the promised game-changer in each of these boats. The ServoProp is a leg with a ­feathering propeller that can be set for optimal pitch in three modes: forward, reverse and regeneration.

“You don’t need fuel,” Rupe said. “You don’t need to dock; you can go anywhere you want to go and always have the power for living and propulsion.”

That’s the promise. But are there also pitfalls?

Innovation and Risk

Marine electric propulsion is an emerging technology. Compared with the mature and settled technology of diesel engines and lead-acid batteries, electric-propulsion systems—with their electronic controllers and lithium batteries—are in a stage of development best described as adolescent. Every sailor has his or her own tolerance for technical innovation. For the promise of fewer ­seconds per mile, grand-prix-racing sailors willingly trade a high risk of expensive damage to the sails, rig or the boat’s structure itself; cruising sailors, by contrast, tend to favor yearslong reliability in their equipment as they seek miles per day.

Folks who identify as early adopters take special joy in the first-wave discoveries of a new technology; if they’re clear-eyed about supporting an ongoing experiment, they see themselves as partners with the developers, accepting failures as opportunities for learning. Sailors motivated primarily by changing the trajectory of climate change might be especially willing to modify their behavior to limit their own output of greenhouse gases. Investing in any emerging technology asks you to start with a clear assessment of your own risk tolerance. We’ll return to this theme with one or two real-life examples.

The American Boat and Yacht Council, founded in 1954, sets recommended standards for systems installed on recreational boats. For decades, ABYC has published standards related to installations of diesel and gasoline engines, as well as electrical systems based around lead-acid batteries. By contrast, it was only three years ago that ABYC came out with its first electric-propulsion standard (revised July 2021). And only last year it published its first technical-information report on lithium batteries (a technical-information report is an early step toward a future standard). The takeaway is that if you need help servicing your diesel engine or electrical system built around lead-acid batteries, you can pull into any reasonable-size port and find competent technicians to help you. With electric propulsion and lithium batteries, that pool of skilled talent is significantly scarcer.

To say that a technology is mature simply means that we’ve learned to live with it, warts and all, but that it holds few remaining surprises. Certainly, diesel-propulsion and lead-acid-battery technologies each leave plenty of room for improvement. When a charge of fuel ignites in the combustion ­chamber of a diesel engine, some three-quarters of the energy is lost in heat and the mechanical inefficiencies of converting reciprocating motion to rotation. Lead-acid batteries become damaged if we routinely discharge more than half of their capacity. During charging, they’re slow to take the electrons we could deliver.

Lithium batteries are comparatively full of promise. Their power density is far greater than that of lead-acid batteries, meaning they’re much lighter for a given capacity. They’re capable of being deeply discharged, which means you can use far more of the bank’s capacity, not merely the first half. And they accept a charge much more quickly; compare that to several hours a day running an engine to keep the beers iced down.

But the pitfalls? Let’s start with ABYC TE-13, Lithium Ion Batteries. Some of its language is bracing. “Lithium ion batteries are unlike lead-acid batteries in two important respects,” the report says. “1) The electrolyte within most lithium ion batteries is flammable. 2) Under certain fault conditions, lithium ion batteries can enter a condition known as thermal runaway, which results in rapid internal heating. Once initiated, it is a self-perpetuating and exothermic reaction that can be difficult to halt.”

Thermal runaway? Difficult to halt? Self-perpetuating?

“Typically, the best approach is to remove heat as fast as possible, which is most effectively done by flooding the battery with water,” TE-13 continues, “although this may have serious consequences for the boat’s electrical systems, machinery, buoyancy, etc.”

If you were following the news in January 2013, you might remember the ­story of Japan Airlines Flight 008. Shortly after landing at Boston’s Logan Airport, a mechanic opened the aft ­electronic equipment bay of the Boeing 787-8 to find smoke and flames billowing from the auxiliary-power unit. The fire extinguisher he used didn’t put out the flames. Eventually Boston firefighters put out the fire with Halotron, but when removing the still-hissing batteries from the plane, one of the ­firefighters was burned through his ­professional protective gear.

Samsung Galaxy cellphones, MacBook Pro laptops, powered skateboards—in the past decade, these and other devices have been recalled after their lithium batteries burned up. In that period, several high-end custom boats were declared a total loss following failures from lithium batteries. In March 2021, a 78-foot Norwegian hybrid-powered tour boat, built in 2019 with a 790 kW capacity battery bank, experienced thermal runaway that kept firefighters on watch for several days after the crew safely abandoned the ship.

Yes, experts are learning a lot about how to mitigate the risks around lithium batteries. But we’re still on the learning curve.

ABYC’s TE-13 “System Design” section starts, “All lithium-ion battery ­systems should have a battery ­management system (BMS) installed to prevent damage to the battery and provide for battery shutoff if potentially dangerous conditions exist.” It defines a bank’s “safe operating envelope” according to such parameters as high- and low-voltage limits, charging and discharging temperature limits, and charging and ­discharging current limits.

Graham Balch takes these safety recommendations a step further: “To our knowledge, the BMS has to monitor at the cell level. With most batteries, the BMS monitors at the module level.” The difference? “Let’s say you have 24 cells inside the battery module, and three of them stop working. Well, the other 21 have to work harder to compensate for those three. And that’s where thermal events occur.”

Balch followed the story of the Norwegian tour boat this past spring. He believes that the battery installation in that case didn’t meet waterproofing standards: “The hypothesis is that due to water intrusion, there was reverse polarity in one or more of the cells, which is worse than cells simply not working. It means that they’re actively working against the other cells. But if the BMS is monitoring only at the module level, you wouldn’t know it.”

On the Green Yachts website, Graham lists five battery manufacturers whose BMS regimes monitor at the cell level. “If I were sailing on an electric boat, whether it be commercial or recreational, I would feel comfortable with having batteries from these five companies and no other,” he said.

The broader takeaway for today’s sailors is that lithium batteries bring their own sets of problems and solutions, which are different from those of conventional propulsion and power-supply technologies. A reasonably skilled sailor could be expected to change fuel filters or bleed a diesel engine if it shuts down in rough conditions. With lithium-ion batteries aboard, an operator needs to understand the causes and remedies of thermal runaway, and be ready to respond if the BMS shuts down the boat’s power.

Real-World Electric Cruising Boats

When we met Oceanvolt’s Derek Rupe a year ago, he and his wife had taken their all-electric boat to the Bahamas and back the previous season. Before that, he’d been installing electric-propulsion packages for six years on new Alerion 41s and other refit projects. “My real passion is on the technical side of things—installations, really getting that right. That’s half the picture. The technology is there, but it needs to be installed correctly.”

When talking to Rupe, I immediately encountered my first learning curve. I posed questions about the Oceanvolt system in amps and amp-hours; he responded in watts and kilowatt-hours. This was yet another example of the different mindset sailors of electric boats need to hold. Why? Because most cruising boats have just one or two electrical systems: DC and AC. The AC system might operate at 110 or 220 volts; the DC side might operate at 12 or 24 volts. On your own boat, that voltage is a given. From there we tend to think in terms of amps needed to power a load, and amp-hours of capacity in our battery banks. Going back to basics, the power formula tells us that power (watts) equals electrical potential (volts) times current (amps). If your boat’s electrical system is 12 volts and you know that your windlass is rated at 400 watts, it follows that the windlass is rated to draw 33 amps.

But an all-electric boat might comprise several systems at different voltages. A single battery bank might supply cabin lights at 12 volts DC; winches and windlasses at 24 volts DC; the propulsion motor at 48 volts DC; and an induction stove, microwave and television at 110 volts AC. A DC-to-DC power converter steps the voltage up or down, and an inverter changes DC to AC. Instead of translating through all those systems, the Oceanvolt monitor (and Derek Rupe) simply reports in watts coming in or going out of the bank.

“We keep all our thoughts in watts,” Rupe said. “Watts count in the AC induction. They count in the DC-to-DC converter. They count the solar in. They count the hydrogeneration in. And the ­power-management systems tracks it that way for shore-power in.

“On a boat like this, maybe I have 500 watts coming in the solar panels,” he continued. “So then I can think: ‘Well, my fridge is using 90 watts. My boat has an electric stove. When I cook a big meal, I can see that for every hour we cook, we lose about 10 to 12 minutes of our cruising range.’”

During his Bahamas cruising season, Rupe observed that on days that they were sailing, the combination of solar panels and hydroregeneration supplied all the power he and his wife needed. “When we weren’t sailing,” he said, “we found that we were losing 8 percent each day, in the difference from what the sun gave us to what we were using for the fridge, lights, charging our laptops, and all that stuff.”

Rupe’s solution? “Twice in Eleuthera and once outside Major’s, we went out and sailed laps for a couple of hours because the batteries were below 30 percent of capacity. It was good sailing, and the wind was coming over the shore, so we didn’t have any sea state. We did a couple of hot laps on nice beam reaches, and generated about 700 watts an hour.”

Of the three sailors Rupe touted in October 2020—Alex Thomson, Jimmy Cornell and the Sailing La Vagabonde couple—only Cornell can report back on his all-electric experiences with Oceanvolt. Alex Thomson ended his circumnavigation abruptly last November, just 20 days after the Vendée Globe start, when Hugo Boss collided with an object in the South Atlantic. And at press time in early fall 2021, Riley and Elayna had just recently announced the build of their new Rapido trimaran; keep an eye on their YouTube channel for more about their experiences with the Oceanvolt propulsion system.

As for Cornell—circumnavigator, World Cruising Routes author, creator of the transoceanic rally, and veteran of some 200,000 ocean miles—he suspended his planned Elcano 500 round-the-world expedition solely because of the Oceanvolt system in his new Outremer catamaran. His Aventura Zero Logs on the Cornell Sailing website, particularly the Electric Shock article posted on December 2, 2020, are essential reading for any sailor interested in sailing an electric boat. “Sailing around the world on an electric boat with zero emissions along the route of the first circumnavigation was such a tempting opportunity to do something meaningful and in tune with our concern for protecting the environment that my family agreed I should do it,” Cornell wrote. “What this passage has shown was that in spite of all our efforts to save energy, we were unable to regenerate sufficient electricity to cover consumption and top up the batteries.”

Cornell’s experience in that article is raw, and his tone in that moment bitterly disappointed. We recommend it as essential reading—not as a final rejection of the electric-boat concept or of Oceanvolt’s system, or even as an endorsement of Cornell’s own decision that the system didn’t work. I suspect that I may have arrived at the same conclusion. Yet given the same boat in the same conditions, one imagines that a new breed of sailor—a Graham Balch or a Derek Rupe—may have responded differently to the constraints imposed by an all-electric boat, as nearly every cruising sailor today habitually responds to the inconvenient constraints of diesel engines and lead-acid batteries.

“If you bring electric winches, electric heads and an induction stove, and then sail into a high-pressure system, you’ll set yourself up for failure,” Balch said. “You have to balance your power inputs and your power outputs.

“Sailing an electric boat is a return to the tradition of sailing that the crutch of a diesel engine has gotten us away from,” he added. “Magellan’s fleet got all the way around the world, and they didn’t have a diesel engine.”

Tim Murphy is a Cruising World editor-at-large and ­longtime Boat of the Year judge.

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This New Electric Sailing Yacht Can Charge Its Own Batteries While Cruising

The 49-footer can generate 3.5 kw of clean, green energy when sailing at speeds greater than 8 knots., rachel cormack.

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It’s no easy feat to incorporate a next-gen electric propulsion system into an elegant sloop. X- Yachts appears to have pulled it off, though.

The Danish yacht maker, which has spent more than 40 years in the game, just launched a futuristic new sailing yacht that looks to be as stylish as it is sustainable. Christened the X49E , the 49-footer is the very first electric sailboat to be made by the yard.

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The 12-ton newcomer is based on the existing X49 model , but eschews the traditional diesel engines in favor of two of Oceanvolt’s 10 kW electric motors. The pods are mounted on each side of the traditional engine compartment, below the aft cabin bunks. The space which used to hold the engines now houses a 28.8 kWh lithium battery bank and an onboard DC generator with a capacity of 11 kW.

The X49E’s solar panels generate energy to power the hotel load.  X-Yachts

Range with pure electric power depends on the boat speed, wind and sea state, but X-Yachts estimates in calm conditions the yacht can travel 22.7 nautical miles at 5 knots. Of course, the diesel generator can be used to run the boat if more range is required.

X49E can also produce up to 3.5 kW when sailing at speeds greater than 8 knots. That means if you sail for roughly eight hours, the batteries will charge from empty to full. The best part is the “full tank” is 100 percent green and free of cost.

To top it off, the X49E is fitted with solar panels that will generate clean energy to power the hotel load. That is the lights, navigation systems, appliances and so on.

The first hull was built for a discerning yachtsman.  X-Yachts

”We didn’t want to be first movers on this area, but preferred to wait until technology and knowledge had matured properly”, Kraen Nielsen, CEO of X-Yachts, said in a statement . “And I’m really happy to say that the time finally is right to present the first X-Yacht with electric propulsion.”

The first hull was built for discerning yachtsman John Haurum, who has a passion for sailing both recreationally and in competition.

“My plans for the X49 are primarily to use it for long-distance cruising, but it has also been specified with performance sailing in mind and I intend to participate in challenges like Around Denmark Race and, eventually, the ARC Cross Atlantic,” Haurum adds.

Looks like you’ll see the X49E tearing it up on the ocean before too long.

Rachel Cormack is a digital editor at Robb Report. She cut her teeth writing for HuffPost, Concrete Playground, and several other online publications in Australia, before moving to New York at the…

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Arcona 415 Unveiled: The Sailing Yacht With Electric Propulsion As Standard

The Arcona 415 is the first series produced sailing yacht with electric propulsion as standard. Electric propulsion is already available across all the Arcona fleet as an upgrade option and Arcona Yachts has the largest fleet of electric ‘zero emissions’ yachts on the water, the first being the Arcona 380Z launched in 2015.

Arcona performance cruisers will always sail beautifully but in light winds, when you need to use the engine, electric propulsion is the way forward. The sleek and light hull design works well with electric propulsion.

In response to customer demand, the Arcona 415 has the option of a three or two cabin version with an additional en suite in the owner´s cabin.

The Arcona 415, with her modern hull shape, open transom, more accessible stowage space and increased light, continues the tradition of Arcona 410 as a quality performance cruiser, built with attention to detail. In terms of power, the Arcona 415 is equipped with an Oceanvolt Servoprop 15kW electric propulsion system, with variable pitch propeller technology. It has a 19kWh battery pack as standard. A 15kW electric motor is the equivalent of a 50hp diesel engine on our 40-43ft yachts.

For the propulsion system, Arcona works with Oceanvolt. The lightweight system uses hydro regeneration via the propeller to regenerate power whilst sailing, storing it in the propulsion battery pack for later use. Regeneration depends on sailing speed, however our customers have seen the hydro regeneration commence when the yacht is sailing at a speed as low as 3.3knots.

The benefits of electric propulsion are numerous; not having an exhaust and the elimination therefore of emissions, the ongoing cost saving vs. fuelling up with diesel, the minimised operating noise and vibrations, the increased space for living, the complete power management, the ease of use and maintenance, and having an overall lighter weight thus increased performance.

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The Bootswerft Heinrich-built 13m Yamila uses an Oceanvolt electric motor rather than a diesel engine. Photo: Peter Minder

Every sailor is familiar with the wet cough of the diesel engine, and the acrid smell of its exhaust. For some it’s the sign that an adventure is starting, for others it is the reassurance that all is well on board the boat. The traditional engine is perhaps your boat’s most important safety feature, but its days may be numbered.

The electric sailing revolution is coming – and though adoption in the marine sector is proving much slower than in the automotive world ashore, progress is being made.

The market is still relatively small. Clear market leader Torqeedo had sales of €25m last year, most of which was in ferries and compact outboards. It also offers a range of saildrive and pod drive motors for yachts displacing from 2 to 50 tonnes, or roughly 20-60ft LOA.

But sailors have been slow on the uptake, and for one good reason: if you’re planning to cross an ocean or take on tough conditions offshore, you rely on your engine to help you outrun danger or motor through the doldrums – sometimes for days at a time.

Oceanvolt AXC series is a modular shaft drive system (10kW to 40kW) that will fit in place of a tradition diesel engine

Even with the current crop of advanced lithium-ion boat batteries , the range of an electric system is measured in tens of miles, not hundreds. So a 35ft monohull with 10kWh of lithium battery (four units weighing 96kg in total) would have a range of just 24 nautical miles at 3.8 knots, or less than 16 nautical miles at full throttle.

Taking into account the incredible wastage of combustion engines, which dissipate more energy as heat and noise than they provide in propulsion, diesel is still ten times more energy dense than batteries.

Full-carbon luxury daysailer Yamila uses an Oceanvolt SD8 8kW electric saildrive system. Photo: Tobias Stoerkle

“When you look at bluewater cruisers, of course you will have a diesel,” says Torqeedo’s founder and CEO, Dr Christoph Ballin. “And it’s right that not many coastal sailors opt for pure electric.”

But that doesn’t mean that electric has no interest for cruising sailors – far from it. The more common route for ‘normal’ sailors will be to combine diesel and electric in a hybrid sailing system.

Under this model, the engine is replaced by an electric motor, hooked up to a bank of lithium batteries. This can be charged via hydrogeneration – when the speed under sail turns the propeller and puts charge back into the batteries – and solar or wind. But when extended periods under power are required a standalone DC generator, which can be installed anywhere on board, supplies the electricity.

This is the set-up recommended by Finland’s Oceanvolt, which has focused on the cruising sailing market with a range of shaft and sail drive motors from 3.7kW to 15kW (roughly 10hp to 45hp in diesel engine terms).

“In the case of the round-the-world cruiser, we recommend a hybrid system with a backup genset to support continuous drive when/if needed,” says Oceanvolt CEO Markus Mustelin. “A regenerating prop, which spins while sailing and recharges the batteries (sacrificing 0.2-0.4 of a knot, depending on the boat and conditions) makes it possible to be almost independent of the genset and use it only for backup.”

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This system has the advantage that the generator is only needed on longer passages, so the boat still manoeuvres silently in and out of ports and anchorages.

And a well-designed, correctly sized generator is much more efficient at turning diesel into electricity than an engine not originally designed for the job. Some sailors opt for an in-line hybrid system, like those offered by Hybrid-Marine, which bolts onto the existing diesel.

These are easier to retrofit, with many of the same characteristics as the full hybrid system, but there’s the disadvantage of still having an engine boxed away somewhere near the middle of the boat.

Electro magnetism

Until now, most business has been done through retrofitting existing yachts. But an increasing number of yacht builders are looking to include electric propulsion as original equipment. The world’s third largest boatbuilder, Hanse Yachts , is perhaps the most advanced – offering its entry-level Hanse 315 with an electric rudder-drive option.

The system takes up less space than the standard diesel, is much quieter and vibration- and emissions-free. But Hanse admits take up has been disappointing.

The technology has found more interest among lake sailors. Innovative young German brand Bente has been fitting Torqeedo motors to its successful 24ft model, originally designed for Germany’s ‘Green Lakes’.

Closer to home, dinghy specialist RS Sailing has decided to fit a retractable electric drive to its new RS21 keelboat. Already christened the ‘invisible gennaker’, the system is based on Torqeedo’s Travel 1003 outboard motor.

Bigger race boats have also been attracted by the lure of low-weight propulsion. Just look at Malizia , an IMOCA 60 being prepared for the 2020 Vendée Globe with a lightweight Torqeedo system.

“Emissions-free round the world under race conditions, while simultaneously producing your own energy, is a thoroughly inspirational concept,” said Malizia skipper Boris Herrmann.

Electric has also been successful at the luxury end of the market, where lithium-ion batteries account for a smaller share of the boat’s overall cost. A 50ft Privilege 5 catamaran and a carbon fibre Gunboat 60 have both been retrofitted with Torqeedo kit, while Oceanvolt appears on a Swan 57 and an all-carbon Agile 42.

Overview of the Torqeedo Deep Blue propulsion system installed in the Gunboat Moonwave

The Gunboat Moonwave has two 25kW Deep Blue saildrives both capable of regenerating under sail. There is still a generator on board to extend battery range offshore, but “they no longer use the generator – it’s just for emergency,” says Torqeedo’s Ballin.

Spirit Yachts is also designing electric propulsion into its Spirit 111  flagship, due for launch this summer. With four big 40kW lithium batteries aboard and a 100kW motor, the yacht will be able to operate silently for hours, although it also has 100kW of diesel generator capacity.

“The real focus is not the propulsion,” explains Spirit director Nigel Stuart, “but that everything works in harmony, from galley equipment and hot water to heating, air conditioning, hydraulics etc.” The British yard is also building a 65-footer using Oceanvolt hybrid technology and a new 44-footer that is pure electric.

With racing on one hand and high-end cruisers on the other, there is something of a gap in the middle. By Torqeedo’s own admission, the cruising sailor hasn’t been a big focus of the electric revolution, but all that is about to change. “We started a bit late with sailing,” Ballin admits, “but in the next five to eight years it will be addressed big time.”

Fully integrated electric drive system will power the new 111ft Spirit Yachts flagship

What does that really mean? Well, in the first instance, it means system integration. If that doesn’t sound revolutionary, then imagine a set-up on board where solar panels, hydrogenerators, batteries, generators and motors all worked seamlessly together to keep the yacht supplied with ample power around the clock. “That’s what people are willing to pay for: plenty of energy with heating or air-con through the night,” says Ballin.

The future of hybrid sailing

In the near future, Torqeedo is planning a new range-extending DC generator specifically for hybrid sailing boats. Its existing unit is built by WhisperPower and provides 25kW, which is too much power for boats using the pod drive system.

The genset will be designed to operate at optimum revolutions, while clever DC to DC conversion decouples the battery voltage from the charging voltage, for much greater efficiency.

With boats, just as with cars, the breakthrough that will make all the difference is around battery capacity. Until range under electric power can match that of diesel, there will be many sceptics. And that isn’t likely to happen for a decade or more, according to Ballin.

“Theoretically, they’ve tested batteries in labs that are ten times more efficient than lithium,” he explains. “And if that comes through, then gasoline is done. But we are trying to combine long-term vision with short-term mindset.”

In the meantime, the prevalent technology is based on lithium-manganese-cobalt, and a process of steady development is making this 5-8% better each year. For example, BMW has just announced its next generation i3 battery, used by Torqeedo’s Deep Blue system, will be able to hold 40kWh of power – an increase of 33% for the same size, weight and nearly the same cost.

Torqeedo Cruise 2.0 FP Pod Drive is suitable for small yachts up to 4 tonnes – a folding prop can also be fitted

The other area of development is around the propeller. Most cruising systems use a folding or feathering prop designed for diesel engines. But Torqeedo’s own research shows that the consistently high torque of an electric motor is best utilised by props with variable pitch.

And yet it is Oceanvolt that has addressed this issue specifically for electric motors with its Servo Prop system, which it claims to be 30% more efficient ahead, 100% better astern and 300% more efficient in regeneration mode.

Oceanvolt says that this prop can pump around 500W into the batteries at just 5 knots – the average pace of a 30ft monohull. At 6 knots that rises to around 800W, and at a very manageable 7 knots for a larger ocean cruiser you get 1.2kW.

“A new technology can rarely compete in price with an established one in its initial growth phase,” says Mustelin. “However, we have passed this and today electric systems are offered at a quite competitive price. When you add to that the fact the electric system is almost service free, the total cost of ownership is turning in favour of electric.”

So, you may not hear them approach, but expect to see more and more electric-powered boats on the water as the revolution continues.

A question of torque

A key part of the viability of electric propulsion rests on the notion that a smaller motor can achieve the same work as a bigger diesel. There are two elements to this. First, a diesel engine is not an efficient converter of chemical energy into thrust, creating a lot of heat and noise in the process. Second, the torque characteristics of electric are much better than diesel.

Mustelin says that Oceanvolt’s 10kW motor “easily outperforms” a 30hp diesel. “Typically, maximum boat speed will be somewhat lower (0.5kt-1.0kt) than with a comparable diesel engine, but at the same time the boat will maintain the speed better in heavy seas and headwind due to higher torque. Manoeuvrability is much better in confined marina spaces.”

That’s because combustion engines only reach peak power (and maximum torque) over a small range of speeds. Torque is a measure of turning power – at the propeller in the case of a boat.

A diesel engine develops optimum torque between 1,800-2,000rpm, while electric motors deliver it from 0 to around 2,000rpm. This allows electric motors to use higher efficiency propellers that are slimmer and more steeply pitched.

Engine-driven: The ‘alternator on steroids’

It has taken years of development and over $10m of funding, but renowned boat systems expert Nigel Calder has helped design an alternator so powerful that it eliminates the need for a generator on board.

Mounted on the engine, on the second alternator position, the Integrel can produce five to ten times more power. Sitting behind the system is at least 10kWh of lead acid batteries (lithium is also an option), and Victron chargers and inverters.

“If you crank the engine it’ll charge the batteries; if you’re running with the engine in neutral, it’ll know it’s in standalone generator mode and switch to that algorithm,” explains Calder. “It will likely be cheaper than a generator installation, and eliminates the issue of the through-hulls, the cooling circuits, the long running hours, the maintenance.”

The system allows you to run all sorts of creature comforts on board that would normally require a generator: from hot water on-demand to coffee makers and freezers. “We honestly believe that this system is going to supplant generators on almost all boats that currently have, or would like to have, a generator,” adds Calder.

With the engine in gear and at low revs, tests show how the Integrel can produce some 2kW of power without increasing fuel consumption or reducing speed – simply utilising the engine’s wasted capacity. This means it will work with the yacht’s existing engine – no need to overspec – and it has already been successfully installed on a new Southerly 480, a Malo 46 and a similar-sized Hallberg-Rassy.

Case study: Dufour 382 Alcyone

Built by Dufour in 2016, Alcyone was immediately retrofitted professionally with Oceanvolt’s SD15 saildrive motor, supplied by a 14kWh lithium battery bank. Owners Michael Melling and Diana Kolpak also specced an 8kWh DC generator for range extension. The fit out cost €30,600 for the motor and battery system, plus an additional €13,744 for the generator, and installation costs were around €8,000.

They charter the boat out near Vancouver, for exploring Desolation Sound and the surrounding area where silent, clean propulsion is a selling point. “Nothing spoils the joy of sailing – or a secluded anchorage – more than the noise and smell of diesel engines,” they explained. “Installing an Oceanvolt system in our new boat has freed us from that. It’s the way of the future.”

Charter manager Merion Martin said the conversion has also been popular with charter customers, adding: “The main advantage of the system is that it consistently uses around 40% less fuel than a standard diesel engine over the course of a week’s charter. But understanding the power management system takes a bit of getting used to, and the many components involved in the system can make troubleshooting a challenge.”

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How to convert a yacht to electric propulsion

• Duncan Kent
• May 22, 2024

Thinking about changing your ageing diesel engine for a new all-electric propulsion system? Duncan Kent offers advice on the pros and cons

There are hundreds, if not thousands of yachts still sailing with 40-year-old diesel engines emitting smoke and pollutants, so is now the time to replace them with a clean, low maintenance, pure electric propulsion instead?

The more I’ve looked at sailing yachts that have been converted from diesel to electric auxiliary drive, the more I wonder why you wouldn’t do it, especially now that the cost of hi-tech boat batteries and solar charging has dropped dramatically.

The immediate advantage of changing to marine pure electric drive (PED) systems is that they’re clean, quiet, smell-free and require minimal maintenance, all of which is very appealing if you’ve ever owned a boat with an ancient, clunky diesel. PEDs offer other benefits too. Their reaction to the throttle is instant, which is a boon when berthing in a cramped marina, and once you’re sailing at a decent lick you can generate free ‘fuel’ from the prop.

The disadvantages are the initial cost of the system (largely due to the batteries) and range issues. On a typical 10m cruising yacht it’s just not possible to store enough energy to motor at full tilt for 10 hours a day, so if you’re planning to make long offshore passages regularly then you’ll either need a lot of patience or enough solar and wind generation to power a small village.

But for coastal cruising, often from marina berth to marina berth (what 85% of today’s boat owners do anyway), a PED system is far more viable, especially once your old iron topsail has reached the point where it’s just so much ballast.

If there’s even a little bit of you that would rather not get your hands dirty tinkering with a temperamental diesel, then electric may just be for you. Photo: Fernhurst Books

The devil you know

A diesel engine can provide heaps of grunt when you mistime the tides and want to escape an oncoming storm, provided, of course, that choppy seas haven’t stirred up the inevitable gloop at the bottom of your diesel tank and blocked up your fuel filters.

It’s also fairly simple tech, so, if you’re mechanically minded and have all the tools and spares on board, you can usually keep it turning over. Fuel can also be carried in jerries too, so if it takes a bit longer to thrash your way back into port you can top it up along the way.

You can also leave the boat for months, even years, on end without much harm coming to it and without needing an umbilical cord permanently attached to the shore to keep the expensive power pack in optimum condition.

A spare charged battery, a pair of jump leads, some fresh fuel and bingo, you’re away. But if there’s just a little bit of you that would love to never have to lift the engine box lid and prefer to start your annual cruise with clean fingernails, then sliding soundlessly out of your berth in the early hours must sound appealing.

Range currently remains an issue with battery capacity the limiting factor, but things are improving all the time

Range anxiety

Just as with electric cars, whenever anyone whose vessel is equipped with a conventional diesel falls into a conversation about electric propulsion for boats, the first question is almost always, ‘How far will it go on a charge?’

Well, the answer I’m afraid is simply, ‘It depends.’ How far do you want it to go? Are you willing to toddle along at four knots, or do you want to charge around from port to port like a Greek charter yacht?

I get that it’s not for everyone and, being a mature seafarer myself, I dread to think about losing all power whilst halfway through the Portland Race in the dark. But as with pretty much anything to do with navigating a vessel, you just need to plan things out carefully in advance.

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There are those that say having a finite source of auxiliary propulsion teaches you to sail better, which in many ways is true. The introduction of the powerful modern marine engine has made us all lazy with our tidal planning, knowing, as we do, that you can always resort to the donk to get you home if the log drops below 4 knots or that extra pint in the pub has made you late for the tidal gate.

So, let’s look at some facts. The typical electric propulsion system for a 10m, 6-tonne cruising yacht will usually be designed to provide around five to six hours of gentle cruising in fairly neutral currents at around 4 knots, or maybe 10 hours of motor-sailing, before requiring a charge.

Unlike a car, however, a boat can have solar panels on its deck, coachroof and arch, that can extend this range by another couple of hours, maybe, in the summer.

And then there’s the possibility of regeneration.

Oceanvolt electric ServoProp propeller has electrically controlled pitch which auto adjusts for your speed, or for regeneration

Hydro-regeneration

Nearly all electric motors used in marine propulsion have the capability to turn into a hydro-generator when your speed under sail goes above 4.5 knots or so and the prop/motor is allowed to rotate in reverse.

Regeneration doesn’t make a massive contribution, at best around 750W at 7 knots boat speed per prop, but at 48V (typical electric drive voltage) that’s another useful 15A or so going back into the battery bank.

There are some systems – Oceanvolt’s ServoProp for instance – that incorporate a variable pitch prop. These are capable of a more decent output at lower speeds but are currently seriously expensive.

Either way, I believe solar and hydro-regen should be treated as a bonus when planning your system, not as a given.

If you are unlucky enough to have a few days of no sun or wind you will be back to relying solely on the energy reserves held in your battery bank.

For those who really can’t get over the nagging worry of running out of drive power on a passage, there’s always the option of installing a hybrid system, in which a standby diesel engine is always on hand to get you out of an emergency.

Oceanvolt’s award-winning HighPower ServoProp 25 electric saildrive

Variable pitch props

A normal fixed propeller is designed for propelling the boat and not for generating power as with a hydro-generator. However, Oceanvolt’s DAME award-winning ServoProp saildrive, suitable for monohulls and multihulls from 35-90ft LOA, features a variable pitch prop that combines a high efficiency saildrive with a powerful hydro-generator.

With its unique ability to rotate its propeller blades through more than 180°, ServoProp’s control software adjusts the pitch of the propeller blades to automatically optimise all hydro-generation and propulsion needs.

Oceanvolt claims that a normal fixed propeller generates less than half the power of ServoProp, which it states can produce more than 1kW at 6-8 knots, and 5kW at 10 knots.

It also estimates a 30% increase in forward propulsion, +100% in reverse, and +300% in hydro-generation mode.

Renowned marine propeller supplier, Bruntons, has also launched its Autoprop Eco*Star, designed specifically to propel the rapidly growing number of hybrid and pure electric craft, both motor and sail.

Autoprops are highly efficient because of their ability to auto-pitch depending on engine speed and sea conditions, in order to provide optimum thrust at all times. But with electric propulsion the advantages provided by the new Eco*Star propellers are further extended.

Electric motors provide a constant torque from zero to maximum rpm. Using its auto-pitching ability, the Eco*Star can match its own efficiency curve with that of the electric motor, resulting in more boat speed with less energy.

Eco*Star can spin when under sail allowing the motor to become a generator for recharging the batteries.

Battery setup in an Oceanvolt electric propulsion unit

Drive types

Shaft drive – In most cases it’s possible to retain the shaft and stern gland from an existing shaft drive ICE system, although you’ll probably need a new shaft bearing and coupler unless it is a direct-drive system. The propeller will also probably need to be changed if you want regeneration when sailing.

Saildrive – In many ways electric saildrive units are easier than shaft drives because, as with pods, they come as a complete package with the correct propeller for optimum regeneration. They’re also more efficient at regeneration as the propshaft can be aligned horizontally, unlike shafts, which are usually angled slightly downwards. Some owners choose to convert from a shaft to a saildrive for this reason.

Pod drive – Electric drive pods are similar to saildrives, except they have a direct-drive motor at the bottom of the leg, which allows them to benefit from automatic cooling. Electric drive pods also only require a few small holes in the hull, usually two to four for mounting the unit and one for the routing of the power cable. Pod props and motors are also designed with optimum regeneration in mind.

Most PED systems on small to medium-sized yachts utilise a 48V battery bank. Although there are some that still use deep-cycle AGM battery technology, the only realistic battery chemistry currently available for marine PED systems is lithium-ion.

The safest of the li-ion group is lithium iron phosphate (LiFePO4). While not the most energy dense of the lithium-ion group, they have been proven to be the safest type of li-ion cells to install into a boat, where a battery fire would be catastrophic.

Originally, many professionally built and installed marine electric drive systems utilised other, more volatile types of li-ion batteries such as nickel manganese cobalt (NMC) or lithium manganese oxide (LMO).

System displays can give real time readouts of battery capacity, power usage and remaining range

These types of li-ion are commonly used in the automotive industry for their high capacity, but are wholly reliant on their highly sophisticated battery management system (BMS) to keep them operating within safe parameters.

Apart from preventing a fire risk, the problem with relying on a BMS to monitor the batteries is what happens if something triggers a safety shutdown, causing your boat to lose power completely. A battery shutdown isn’t as drastic as having a lithium battery fire on board, but the total loss of propulsion isn’t ideal, even on a sailing boat.

It’s worse, of course, if you use the same power bank for your house power. Then the loss of your navigation and communications facilities at the same time can be extremely dangerous. For this reason, I would always recommend keeping motor and house banks entirely separate from each other.

If you’re happy to have the more volatile batteries on board or are forced to in order to achieve the desired range, then I highly recommend you have your system professionally designed, installed and commissioned.

Yes, it’ll be expensive, but you’ll sleep at night!

The battery monitoring system will control charge from all sources

Charging a motor bank

Having a much lower internal resistance, li-ion batteries will charge more rapidly than lead-acid batteries because they can accept a much higher rate of charge.

A good quality battery can usually accept a charge up to its own capacity, meaning a 100Ah battery can be charged at 100A. This is called a capacity acceptance rate (CAR) of 1C, and is important when it comes to charging overnight, with the intention of continuing your cruise early the next day.

It also enables various different methods of charging to be accepted simultaneously, provided the combined charge doesn’t exceed 1C, so you can be using solar to its max while also charging from shore power. Another advantage of using li-ion over lead-acid batteries is the BMS can be networked to all charging sources to provide control over the charging regime, plus the data can provide power monitoring at a glance.

Costs of converting

The cost of installing a complete pure electric drive system on a yacht depends on how far and how fast you want to motor between battery charges. The greater the range or faster the speed required, the more battery capacity you’ll need.

A typical 40hp diesel replacement will cost close to £20k including all the parts and installation. A DIY-installed PED replacement would cost £15-£25k, depending on the number of batteries specified, whereas a professionally designed and installed pure electric drive system is more likely to be in the region of £30-£45k.

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Solar power

Electric boats.

• electric boat

I drove a rare solar-electric yacht to test clean-sea propulsion, here’s how it went

While we at Electrek often tend to focus on electric vehicles taking over roads, it’s important to remember that our inevitable abandonment of fossil fuels stems to all modes of transportation, whether it’s by land, air, or even the sea . I recently had the opportunity to set sail on Sunwater Marine’s Ramblin’ Rose , a 40-foot sailing yacht powered by solar panels and electric propulsion. It’s one of the only vessels of its kind on the West Coast.

Sunwater Marine is a San Diego-based nautical transportation company with a keen focus on spreading the benefits of renewable energy and electric propulsion to sea dwellers.

It was founded by president James Richmond in 2020, amid the global pandemic. Richmond had a little more free time to search for a boat for blue water cruising to which he could add solar.

James has been sailing for over 50 years, and has nearly 40 years of experience in the renewable and energy-efficiency industry.

He soon found a 2015 Leopard 40 Catamaran and initially planned to simply add solar panels for an electric range and an energy-efficient water maker.

However, James soon discovered viable options for electric propulsion, and began researching the possibility of converting his new yacht to be be solar-electric.

The result is the Ramblin’ Rose , a catamaran that can haul 12 passengers and sleep up to nine. It also happens to be one of the only solar-electric yachts in the West Coast.

I got the chance to take the solar-electric yacht out of beautiful Coronado and test the technology out myself.

The Ramblin’ Rose solar-electric yacht

As previously mentioned, Sunwater Marine’s Ramblin’ Rose is centered around a Leopard 40 catamaran, built by Robertson & Caine in South Africa. Richmond then put an additional $100k into a renewable energy conversion, equipping the yacht with solar panels, and electric motors.

While the original catamaran came with some traditional solar panels, Richmond’s experience in renewable energy told him that would not suffice for his solar-electric yacht.

He added lighter and more flexible solar technology from Sunflare , the first company to successfully mass-produce thin, durable CIGS (copper indium gallium selenide) solar panels.

The Sunflare panels on the Ramblin’ Rose operate individually with their own bypass diode, so if one is shaded (by the sail for example), the rest still work.

Richmond also separated the solar panels into three separate zones, so if one side of the boat is shaded, the other two are still harnessing the sun’s power back into the boat’s batteries.

He also showed me how durable these advanced solar panels were, as I was able to walk around on top of them without worrying about breaking any glass or ruining them.

The panels help charge the electric yacht’s battery packs while out sailing and indicate to the captain when they are doing so.

Electric propulsion and battery packs

To help power this vessel in and out of the marina and on the sea, Sunwater Marine’s president researched electric propulsion systems around the world, and decided that OCEANVOLT was the best option.

The solar-electric yacht now features two OCEANVOLT 15 kW ServoProp sail drives , utilizing unique propeller blades that can change pitch to optimize efficiency and even regenerate power.

The software controlled variable system adjusts the pitch of each of the propeller blades automatically, so that the power generation and output are always optimal. This is much more efficient than traditional fixed propellers.

The electric propulsion is powered by a 48 volt system, meaning it’s safe to touch without electrical shock (an ideal situation for maritime fun).

Each electric motor on the yacht is powered by a bank of 12 Lithium Iron Phosphate (LFP) batteries on each side, 24 total. The batteries provide 21 kWh of power on each side of the vessel, 42 kWh in total.

Richmond explained that he positioned each battery pack eight inches off the bottom of the boat, too, so if any water were to come in, the batteries would still be OK. Furthermore, the captain showed me backup storage of eight additional batteries should anything go awry at sea.

The status of each and every battery is monitored 24/7 by a supervisory battery management system (BMS) that will shut the battery bank down, should any individual battery begin to malfunction. Fire is not something you want on a boat, despite being surrounded by water.

Additionally, the system was implemented to safely operate minimal electric functions under any conditions, so if the electric yacht were to tip over, there would still be power to send a distress signal.

Thoughts on the future of electric propulsion

After manning the helm of the the Ramblin’ Rose , there is a lot to be excited about for the future of electric propulsion at sea , especially on a gorgeous yacht.

The ride itself was eerily smooth and quiet compared to diesel motors, with zero vibration throughout the boat. If you didn’t look back and see the wake of the electric motors, you might not even notice the yacht was being propelled.

There is a lot of potential in electric propulsion, especially as it pertains to propellers than can remotely change their angle like the OCEANVOLT ServoProps. This makes reversing the electric yacht in particular, much easier for captains compared to fixed props built to push forward.

The ability to set sail and regenerate power from the propellers is also a huge perk and pairs nicely with the advanced solar panels. Plus, you always have shore power as a backup when you’re in a pinch.

From what I’ve seen, the biggest hurdle looking ahead will be battery capacity, and providing enough stored energy to power the electric propulsion systems on the yacht.

The solar panels do help a lot, but it’s a relatively slow process. Smaller, lighter battery options will be crucial for longer distances at higher speeds at sea someday. In the meantime however, we still have sun and wind to pick up the slack.

Currently, the range and top speed are still limited by this lack of surplus energy below deck. We didn’t take the Ramblin’ Rose above 7.5 knots (~8.6 mph) because we didn’t want to burn through all our battery life (that was also in respect to the charter setting sail after us that day).

The solar-electric yacht still has diesel motors onboard for emergencies, but Sunwater Marine’s founder agreed with me that we’d like to see a day when those motors are not needed at all. Unfortunately, the technology is not quite there yet.

Luckily, people like Richmond and Sunwater Marine are using their knowledge and resources (and personal funds) to figure this stuff out for the masses, while spreading the word about electric propulsion. It has become a genuinely viable option at sea, even if it is only in support of other forms of propulsion like sailing for now.

If you’re ever visiting the San Diego area, I highly recommend reaching out to Sunwater Marine and chartering the Ramblin’ Rose , or one of the other solar-electric yachts Captain Richmond is working on.

FTC: We use income earning auto affiliate links. More.

Scooter Doll is a writer, designer and tech enthusiast born in Chicago and based on the West Coast. When he’s not offering the latest tech how tos or insights, he’s probably watching Chicago sports. Please send any tips or suggestions, or dog photos to him at [email protected]

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Electric Propulsion: Solomon Technologies’ High-Wire Act

It's powerful and quiet. it's renewable, and sometimes even free. it doesn't pollute. it's simple enough to understand. how severe are the drawbacks that depends on several of your thresholds..

As much as we like to believe that we’re purists when it comes to sailing, the auxiliary engine is obviously very important to most of us, whether inboard or outboard, gasoline- or diesel-powered. We rely on the engine to get us in and out of the marina, get us off a lee shore, charge the batteries, dig in the anchor, and provide us with power for all sorts of electrical needs. 

We have standard and virtually universal complaints about auxiliary engines: They’re noisy, often unreliable, difficult and expensive to service, and they require a lot of space, spares, and tools to stay running happily. They need oil and fuel and coolants and filters. They require holes to be drilled through the bottom of the boat. All the moving parts, alignments, plumbing, cooling, exhausts, filters, etc. work together to make the auxiliary both high-cost and high-maintenance. Additionally, access to all the parts that need servicing is usually cramped and miserable.

Nothing says that an auxiliary has to be a fossil-fuel driven system. Indeed, boats have been using electric motors with storage batteries for propulsion for over 100 years (both on top of and under the water). However, the reasons for the popularity of the fossil-fuel driven auxiliary are similar to the reasons that gas engines are still so popular in cars—given their high power output (or “power density”), they’re extremely economical. Put another way, you get a lot of bang for the buck. While this has been true enough for decades, there are times when innovation—often in the form of old ideas updated with modern techniques— becomes viable enough to be lucrative. Witness the increasing popularity of electric-hybrid cars from Honda and Toyota.

In the world of sailing, we’ve seen a gathering ground-swell of interest in the electric auxiliary system designed and installed by Solomon Technologies of Benedict, MD. The company has exhibited its “Electric Wheel™” at many boat shows in recent years, and a number of PS readers have sent letters asking what we know about the system. Until recently, all we knew was that the device reminded us of an article in NASA’s Tech Briefs back in the ’80s, describing an electric motor design that was small, highly efficient, and suitable for installing at each wheel of an electric vehicle. Motors of this type have not yet made it to the consumer automotive market, but they’ve made it to Mars, and now they’re making it into a few sailboats.

After studying what we could about Solomon Technologies via their website, we called the number and asked if we could come for a visit.

The Company Solomon Technologies is located on the shores of the Patuxent River, about 13 miles from the Patuxent Naval Air Station and the Chesapeake Bay. The company’s offices are in an older house; the testing, developing, and manufacturing are done in an adjacent barn. Across the street is a small marina that serves as the working yard for installing Solomon Technologies Motors and on-the-water testing.

We met with David Tether, inventer, CEO, and motive force behind the company’s products, and with John Finnerty, the company’s marketing director.

Tether was a contractor for the US Navy for 14 years. He invented simulators for thermo-nuclear explosions, and was a specialist in electro-magnetic signatures. He’s a high-energy personality, and in fact can get so carried away with preaching the gospel of electric auxiliary power as represented by his products that it can be difficult for his questioner to get the facts straight. This is where John Finnerty comes in handy.

The first facts that needed straightening, as far as we were concerned, had to do with what, exactly, an “Electric Wheel” is. Solomon Technologies’ website and literature use the term to describe all their products, yet it had seemed to us on boatshow and website visits that there were at least two different bits of machinery that shared the name under the same umbrella. This, as it turns out, is true.

All of Solomon Technologies’ products use a proprietary DC brushless motor. We’ll refer to this motor as an ST Motor. There is also the Electric Wheel, which refers to the ST Motor as the power source, combined with a proprietary internal planetary gear system—the ingenious turning gizmo vaunted at the ST boatshow booth.

The ST Motor Most of us are familiar with the simple electric trolling motor, in which the motor itself is submerged along with the propeller it drives.

The Solomon Technologies motor is not—by a long shot—a trolling motor. It’s a brushless DC motor with the windings on the stator, and neodymium iron boron permanent magnets on the rotor. The power take-off shaft connects to the rotor.

The ST Motor works by switching the current through the windings, which “pulls” the permanently magnetized rotor along with the switching magnetic fields. The motor shaft has a Delrin  coupling.

The ST Gear Assembly The planetary gear assembly on display at boatshows is composed of sun and ring gears made of Delrin, and planet gears made of bronze. A demonstration version of the ST58 Electric Wheel, without the case and windings, makes both its operation and the cleverness behind the assembly readily apparent. The operation is a little complicated to explain, but it becomes obvious once you see it in action.

Assume that you’re driving the boat forward and looking at the front of the motor, which points to the bow. In the ST58, one ST Motor drives the ring gear and another ST Motor drives the sun gear. The planetary gear carrier connects to the drive shaft (PTO).

At motor speeds below 600 RPM, the sun gear turns counterclockwise (CCW), the ring gear freewheels, and the planetary gears drive the shaft clockwise (CW). The gear ratio is 2.6:1. Above 600 RPM, a controller switches the drive gears—the ring gear drives CW and the sun gear freewheels. Again, the planetary gear assembly continues driving the shaft CW, though at a ratio of 1.6:1. When the motor speed exceeds 650 RPM, the controller switches both sun and ring gears to drive CW, and the gear ratio becomes 1:1.

Products Presently, Solomon Technologies sells three different propulsion systems: the ST37, the ST58, and the ST74. (The number in the product name indicates the motor’s torque in foot-pounds.) All systems use the ST Motor as the power source. The ST58 and the ST74 use two ST37 ST Motors combined into one housing. The motors have a water-resistant cast aluminum case. All the motors are 13″ in diameter.

The ST37 and ST74 systems are direct-drive motor systems. The middle system, the ST58, is the Electric Wheel version—two motors plus gear assembly. Again, it has three speed ranges that automatically change according to the motor’s RPM. It has eight moving parts altogether. With the doubled-up motors, if one motor or its associated gear should break, the other gear may be able to propel the boat, albeit at reduced power. According to David Tether, the Delrin gears are self-lubricating and need no maintenance. He estimates that the Electric Wheel has a lifetime of 80,000 hours.

The Electric Wheel is not, in fact, what ST installs in most sailboats that show up for a power-change operation. Most boats need and receive only the ST Motor. It took us quite a while to understand that, but finally John Finnerty clarified it all for us:

The ST58 was the first electric propulsion device designed by Solomon Technologies for the marine market. According to Finnerty, once they started on- the-water testing with the Electric Wheel, they found that the gearing was of little advantage. The development of the ST37 andST74, capitalizing on the electric motor technology in the ST58, deliveredthe required torque in a simpler package. However, the Electric Wheel gearing may have an advantage with regenerating electricity. Solomon Technologies plans tests in the near future to measure the ST58’s regeneration capabilities.

So, as clever and useful as it may be, the gear assembly is more of a red herring when it comes to auxiliary sailboat applications.

Other Elements In addition to the motor, the propulsion system includes the batteries, the SPMD Panel (Safety, Power Monitoring and Distribution), the controller, the wiring, throttle and shift controls, and house voltage regulators.

The ST Motor requires a higher voltage than what we’re used to on most boats—at least 10 times higher, in fact: The recommended voltage is either 120VDC or 144VDC, with battery banks comprised of 10 or 12 12V batteries wired in series to boost the voltage. After every four batteries in the chain, there’s a circuit breaker to protect the wiring and the boat from a catastrophic battery failure.

The ST Motors use this high DC voltage to minimize power losses in the wiring and the windings, and to reduce the size of the battery cables needed in the installation. In the installations we saw, the battery cables were 4 AWG, much smaller than the 2/0 AWG wire many of us are used to.

To supply the rest of the boat with the 12V power that we’ve come to expect in our vessels, Solomon Technologies uses a DC-DC converter to step the voltage down to 12V. These converters generally have efficiencies better than 90%, so waste heat should not be a problem. Battery size is determined by how much energy you want to carry. One installation we saw used 10 Group-30 batteries.

The SPMD is used for passing the power between the batteries, the controller, and the motor. This is an enclosed wiring panel with bus distribution bars and shunts for measuring current flow both into and out of the batteries.

The brains of the ST Motor are in the controller box. In the box is a commercially available industrial motor controller setup for driving the ST Motor. Additionally, there are two muffin fans for cooling the box. The controller sets the motor’s speed by varying the pulse frequency to the windings. The current flowing through the windings sets the power. You control the motor speed through a potentiometer, which can be coupled to a standard Morse-type throttle control or something similar.

Power Equivalents As you can see from the table on page 14, the horsepower for these motors is not close to the horsepower we’re used to with a standard auxiliary engine. However, for driving a propeller, the torque number is more important and that’s the strength of the ST Motor. For example, a Universal M-40B diesel engine produces 37.5 hp at 3,000 rpm and 73 ft-lb of torque at 2,180 rpm. Compare this to the ST74 with 12 hp at 1,100 rpm and a torque of 74 ft-lb. Also, unlike a diesel or gas engine, the ST Motor has nearly constant torque, even down at 1 rpm.

The ST Motor spins the prop at a slower rate than a fossil-fuel auxiliary. Tether claims that the best efficiency happens at above 600 and below the 1,100 rpm limit. At this rate, he says that the efficiency of the ST37 and ST74 are above 80%. We were not able to verify this figure.

Reversing the motor is simple: The controller pulses the windings in the opposite sequence, causing the rotor to turn in the opposite direction. The efficiency is the same.

Generating Power Because the ST Motor’s efficient rpm range is slower than that of a fossil-fuel auxiliary, it requires the largest diameter prop that clearance will allow. Solomon Technologies recommends a three-bladed prop over a two-bladed prop, both because of the rpm issue and because a three-blader will do better at fulfilling the other big promise of the ST Motor: the generation of electricity while the boat is sailing. (Solomon Technologies calls it “regeneration”—not a bad term, considering that energy is retrieved by exactly the same mechanism that uses it.)

As we know, unless the transmission of an inboard auxiliary engine is locked, the propeller tries to freewheel in the waterflow under the boat. The ST Motor makes use of this tendency: The prop is allowed to spin in the flow, the shaft in turn spins the rotor, and the rotor creates voltage and current flow in the windings. Through the controller, this power can be put back into the batteries as a charging voltage. In simple terms, while sailing, you can replenish the charge in your batteries.

Because of inefficiencies in the charging of storage batteries and other losses throughout the system, including the prop and the ST Motor, the ratio of powering time to recharging time is far from equal. According to Tether, depending on the wind speed, it may take two to four hours to replace the power used during an hour of motoring. A fixed two-blade prop won’t work nearly as well as a three-blader, and a folding or feathering prop won’t work at all, because they won’t spin as the boat moves through the water (unless you have a manual feathering control).

For the best regeneration potential, then, you would use the largest diameter three-bladed prop you could fit—and you’ll have maximum drag going through the water. If you care only about propulsion, and not regeneration , a two-bladed prop will do. Tether says his company has successfully fitted a folding Martec prop and a Maxiprop feathering prop.

Installation From the two installations we saw, repowering a boat with an ST Motor appears very straightforward. The owner must remove the original engine and all of its assorted paraphernalia, such as fuel tanks, filters, drip pan, etc. Also, with everything out, it’s time to clean the bilge. Once all of this is completed, Tether says that it takes two Solomon Technologies installers two days to install an ST Motor, SPMD, controller, and E-Meter. The E-Meter, a stock product from Cruising Equipment, shows the power used and the power remaining. You use it just like a fuel gauge.

The owner is responsible for installing the batteries, AC charger, and the throttle controls. According to Tether, the new installation weight is “usually net-even” compared to a diesel engine, fuel tanks, plumbing, and house and starting batteries.

About half the installations that Solomon Technologies has done include a generator as a backup charging system. The gensets have been in the 4- to 6-KW size. Tether recommends that a boat with a genset use ten batteries (120VDC) in its battery bank, whereas a boat without a genset should use 12 batteries (144VDC). In addition, he points out that one additional 12V battery is needed for the bilge pump and to start the generator.

Motor and shaft alignment are accomplished in a unique way: Since the motor can be spun at any speed with unwavering accuracy, an ST installer can simply bring the motor and prop shaft coupler together into crude alignment, then spin the ST Motor at 4 RPM and watch for wobble, making fine adjustments to alignment until the wobble is completely eliminated. The result is shaft rotation with no noise and minimal friction, while perfect control of the motor’s speed is maintained.

Safety A 120VDC or 144VDC system obviously packs a big wallop, and there are naturally safety concerns about such a high-power system on a pleasure boat. The ST Motor comes with a user’s manual, warning labels, and recommended circuit breakers after every fourth battery to meet UL safety requirements. Although any type of storage battery can be used, all installations so far have used absorbed glass mat (AGM) batteries, which are designed for hardy use at a variety of operating angles, and which don’t require special boxes or pans for containing spilled acid. (Still, you would want to make sure that the battery compartments were well-ventilated.) According to David Tether, ST installations have not caused any new insurance issues for the boat owners.

An interesting by-product of using the ST Motor is that the system needs no winterization. In fact, Tether uses the ST Motor and prop on his boat as a bubbler system to keep his slip ice-free in the winter.

Another good feature is that at least two through-hull fittings upon which an auxiliary engine depends—the raw water intake and the exhaust port— can be shut permanently.

On the Water On our visit to Solomon Technologies, we saw a water tank used for testing each motor before it’s installed on a customer’s boat. We also watched two motor installations and went for a ride on Tether’s cutter.

The 2,000-gallon test tank lives in the workshop. It has a prop in it, with the shaft coming through the tank wall, through a stuffing box, and to a flange, so that new ST Motors can be coupled up and checked before delivery, and new designs checked out in “lab” conditions.

We put an ST37 through some simple testing with the tank. The time it took the motor to spin-up from 0 rpm to full speed was quicker than we could measure—much faster than a diesel or gas engine. Also, we could run the motor at a very slow speed with no unusual jerkiness or hesitation with the motor’s rotation. ST claims that the current usage is around 1.1 amps per foot-pound. Since this number is actually voltage dependent, it’s difficult to verify. However, when we saw the ST37 running at full speed spinning the prop, the current usage via an E-Meter was in the mid 30-amp range, which is close to the claim for a motor with 37 ft-lbs of torque.

The two muffin fans used for cooling the internal electronics in the controller consume around 10 watts with the controller powered. Tether says that most people just leave the controller on all the time, since the 10w draw is very small compared to the 4.5kw or more power that the motor uses. Even so, we’d want the fans switched off until the temperature in the box reached a certain point.

The motor is quiet, but not silent—it does emit a low buzzing sound. Most likely this noise comes from the current pulsing through the windings. The noise is very acceptable, especially when you think about the noise that comes from a diesel or gas engine.

Tether retrofitted his 1939 33-ft. Casey cutter, Seaward, from a 22-hp diesel to an ST37 with 12 batteries (144VDC). He uses this heavy boat as a demonstration platform for his technology. As we boarded Seaward, he goosed it slightly forward, which startled and unbalanced us. There was no engine noise and yet this 19,000 lb. boat moved smartly. We tossed off the docklines and took Seaward out into the Patuxent River.

We powered along at 5 knots with barely any noise. The sound was like the whine of a car’s tires on a highway. According to the E-Meter, at full speed we were drawing 35 amps at 144VDC, which is approximately 5KW. We threw the boat into reverse and stopped in about a boatlength.

We tried to sail to test the regeneration capability, but the light winds, typical of a Chesapeake Bay morning, could only move Seaward at less than two knots, which wasn’t nearly fast enough to get the prop spinning.

The full-keeled Casey had unexpectedly good control in reverse. We attributed this to the very slowly turning prop minimizing the prop torque force that would normally cause our stern to walk to port.

The repeatability of the motor’s operation is “very predictable,” according to Tether. For the same power demands from the controls, you’ll always get the same power out. Also, since the controller sets the speed based on the frequency of the windings switching, the operating speed is also repeatable.

For dockside charging of the batteries, you need to use a specialty charger to handle the 120 or 144VDC. These chargers are supplied by Solomon Technologies as part of the installation package.

Feedback Thus far, Solomon Technologies has installed its electric motors in 32 boats, ranging in size from an Ericson 27 to a Cherubini 44. Reports from the few owners we’ve been able to contact directly have been favorable. John Conser of Conser Catamarans in California says the system is “very, very quiet,” and “absolutely the only way to go.” ST Motor systems are now the standard power plants on the Conser 47—there is no diesel option. Conser believes that the loss of boatspeed to prop drag while regenerating power in 18-knot windspeeds is about a knot. This “one knot” refrain was one we heard several times when looking for specific, quantitative information on the actual speed loss for a medium-sized displacement boat regenerating power in a good breeze with a three-bladed prop: “About a knot.” “One knot.” The owners say it, and Tether says it.

It would have been nice to provide, for example, a chart with curves showing boatspeed gain and loss in relation to windspeed and charging rates in a “typical” displacement boat, but the rough data for that doesn’t appear to have been generated yet by owners of the system, much less compiled by Solomon Technologies. Aside from the variables of boatspeed and windspeed there’s the matter of prop type, size, and pitch—so it may be that the hope of perfect data here is fanciful, as it often is in sailing. Still, “about a knot” seems a bit loose-ended…

David Hadfield, owner of the first-ever ST installation in a consumer boat, wrote PS a letter offering to share his thoughts with us when we mentioned in our July 15 issue that we would be looking at Solomon Technologies. Hadfield repowered his 1973 Islander 30 Mk II about two years ago, replacing his Palmer 18-hp engine with an ST Motor (a prototype called the Solo 6).

Here’s an e-mail Q&A session between PS and David Hadfield:

PS: What’s your experience with regenerating power?

DH: At hull speed of roughly 7 knots my 30′ Islander will regenerate at a ratio of approximately 2.5 to 1 hour of motoring. At less than 7 knots, say 4 or 5 knots, the ratio goes to 3.5 or 4 to 1.

PS: Does regenerating offer enough power input to keep the batteries charged?

PS: Does the ST Motor develop enough power for your powering needs? Too much power?

DH: Yes — and at 60 % I am normally at hull speed. Any additional power is wasted in a normal transit while powering.

PS: What’s the range, i.e., time or distance, of the electric propulsion system?

DH: Average, with my ten Group 27 batteries, is 6 to 7.5 hours of range.

PS: Any issues with so many batteries on the boat?

DH: None. Batteries were placed centrally and weight has “centered” the boat.

PS: Any other safety or insurance issues with the electric propulsion system?

DH: No vibration; silent, no smell, no visits to the gas dock. My four-year-old plays down below when powering out of the channel—something he never did before. The security of instant power forward and reverse can not be overstated.

PS: Would you install the motor again?

DH: Yes, without reservation. In the last two years I have had zero maintenance and a building confidence in its viability and versatility as anauxiliary.

Conclusion The ST Motor system, with or without the Electric Wheel gear assembly, looks like a reasonable alternative to the diesel auxiliary. There are the usual trade-offs: In some areas where the tradewinds blow and the sun shines enough to make solar panels reliable sources of energy, it’s quite possible to imagine the system being entirely self-sufficient. In other areas it would certainly be more prudent to carry a small generator, although not necessarily permanently mounted. It’s also easy to see how coastal-sailing marina-dwellers with access to AC shore power would be able to “motor” and sail happily in most circumstances without a fossil-fuel burning device on board.

Obviously, a careful assessment of one’s motoring habits and other DC power needs is called-for, although it seems reasonable to assume that a generator could be added later if energy needs turned out to be overwhelming for the system. (It seems to us that a permanently mounted genset in addition to the ST Motor system simply adds back most of the complication that one is presumably trying to escape in the first place. A smaller generator, stowed elsewhere in case of emergency, is different.)

Other advantages were mentioned earlier: fewer holes in the boat, less pollution, less noise, less smell, greater operating and maintenance simplicity, and so on. Also, since the motor controller and other system parts are built from commercially available sources, the teething pains for a new technology have been minimized: Most parts can be had from other sources if needed.

Disadvantages include at least a moderate boatspeed loss while regenerating power. If “about a knot” covers a typical loss, it’s significant. A knot means a lot to boats with typical cruising speed ranges of 5-7 knots.

We also have some questions about the viability of using a DC-DC converter to step the voltage from 120 or 144VDC down to the 12V that most of our equipment uses. Will the DC-DC converter be capable of supplying power to some of the larger power users in today’s boats, like SSB radios and refrigeration? What about the regulation of the 12V output of the DC-DC converter at low power versus high power? We weren’t able to test for these concerns, so we don’t know whether they’re valid.

Finally, we wonder about the longevity of the battery banks, given the kind of use (and disuse) they’re likely to encounter with this system. It’s one thing to replace a $90 battery every few years; it’s another thing to replace 10 or 12 of them.

For someone considering any of these systems, the best thing that Solomon Technologies could do would be to address questions and concerns of this type with hard data. It’s possible that this small company is on the verge of something big, and it would be a shame for it to stumble by spending too much energy on mere boosterism and not enough on clarity about the quantifiable pros and cons of the products. It would do Solomon Technologies good if the following were widely available:

1. A clear separation of the ST Motor technology from the Electric Wheel technology, and an explanation of the advantages of using the gear system.

2. Graphs or charts comparing the ST Motor to conventional diesel or gas engines. There is a graph on Solomon Technologies’ web site, but the Dynamic Output graph is difficult to understand.

3. Graphs or data comparing torque output to power input. For example, does a slower prop speed mean less power usage?

4. A chart or series of charts (as mentioned earlier) showing regeneration capability versus loss of boatspeed, in relation to windspeed, for a variety of boat types and propeller options.

5. Hard data from present users regarding power usage, presented in an easy to understand format, allowing comparisons between boat size, type, and conditions.

We would welcome more feedback from current owners of ST systems. Please e-mail us with your appraisals.

Contacts- Cruising Equipment Company, 5916 195th Northeast, Arlington, WA 98223; 360/925-5000; www.cruisingequip.com . Electric Boat Assn of the Americas, P.O. Box 4025, Lantana, FL 33465-4025; www.electricboat.com . Solomon Technologies, Inc., 7375 Benedict Ave., P.O. Box 314, Benedict, MD 20612; 301/274-4479; www.solomontechnologies.com .

Also With This Article Click here to view “Electric Wheel Drive Characteristics.” Click here to view “ST Motor Comparisons.”

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VESSEL REVIEW | Sinichka – Electric commuter boats designed for Russia’s Moskva River

A series of three new electric monohull commuter ferries have already begun operational sailings on the Moskva River in the Russian capital Moscow.

Built by Russian shipyard Emperium, sister vessels Sinichka , Filka , and Presnya – all named after rivers in Moscow – are being operated by the Moscow Department of Transport and Road Infrastructure Development (Moscow Deptrans). They are the first units of a planned fleet of 20 vessels that will serve the capital city and other nearby communities. The new ferry system will be the water transport system to be operated on the Moskva River in 16 years.

Each vessel has a welded aluminium hull, an LOA of 21 metres, a beam of 6.2 metres, a draught of only 1.4 metres, a displacement of 40 tonnes, and capacity for 80 passengers plus two crewmembers. Seating is available for 42 passengers on each ferry, and the main cabins are also fitted with USB charging ports, wifi connectivity, tables, toilets, and space for bicycles and scooters. The cabin layout can be rearranged to allow the operator to adjust the distances between the seats and to install armrests of varying widths.

An open upper deck is also accessible to passengers and is the only area on each ferry where smoking is allowed.

The ferries are all of modular construction with each ferry's wheelhouse, main cabin, and other structural elements being built as complete, separate components. This enables the ferries to be easily dismantled for transport to anywhere in Russia by rail and then quickly re-assembled within seven days.

The ferries are also ice-capable. Recently completed operational trials on the Moskva showed that the vessels can also easily navigate under mild winter conditions with broken surface ice, though year-round operations are planned for the entire fleet.

The ferries are each fitted with 500kWh lithium iron phosphate battery packs that supply power to two 134kW motors. This configuration can deliver a maximum speed of 11.8 knots, a cruising speed of just under 10 knots, and a range of 150 kilometres.

Emperium said the transfer of rotation of electric motors to the propeller is carried out by direct drive. As a propulsion installation, a pulling rotary propeller-steering column with double screws is used. The installation of double pulling screws, with similar power, allows an operator to increase the efficiency of the propulsion system to deliver a slightly higher speed or to reduce energy consumption. This arrangement also provides the ferries with enhanced manoeuvrability necessary for navigating in close quarters.

The batteries themselves have projected service lives of 10 to 12 years and are fitted with safety features such as built-in fire extinguishers and gas vents. Quick-disconnect features allow the batteries to be easily removed for replacement or maintenance.

Some of our readers have expressed disquiet at our publication of reviews and articles describing new vessels from Russia. We at Baird Maritime can understand and sympathise with those views. However, despite the behaviour of the country's leaders, we believe that the maritime world needs to learn of the latest developments in vessel design and construction there.

Click here to read other news stories, features, opinion articles, and vessel reviews as part of this month's Passenger Vessel Week.

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Outboard Motor Battery: What Size Do I Need & What’s Best for My Boat?

New to boating and trying to figure out what outboard motor battery you need?

However, you might get overwhelmed by the vast choice of outboard motor batteries in the market.

To name just a few: marine batteries, lithium batteries, lead-acid batteries, AGM batteries, deep cycle batteries, starting or cranking batteries…

And all outboard motor batteries are available in various volts, sizes, brands, etc.

The more you search online, the more confused you might be.

You are not alone! Here we will explain all your confusion in a simple guide.

If you are one of those who are trying to figure out the battery needs for your boat (types, sizes, etc), read this post to find quick answers.

Besides that, you will also learn about outboard motor battery wiring and charging in minutes.

Table of contents:

Outboard Motor Battery Types

Electric boat motor battery sizes, best outboard motor battery, outboard battery wiring, outboard motor battery charging.

• FAQs About Outboard Batteries

What kind of battery do I need for an outboard motor?

You might have seen outboard motor batteries with confusing labels. In fact, they are categorized according to their purposes and chemistry.

2 Types Based on Purposes

Basically, all outboard motor marine batteries serve two purposes: starting the engine or running the electrical load onboard. This divides outboard motor batteries into two types.

• Starting Batteries

As the name implies, a starting battery (or cranking battery) is ultimately designed to start the engine. This kind of outboard motor battery comes with high CCA values, providing high current surges and cranking amps to start your engine.

If using the wrong battery that’s not designed for a starting (or high-power) application, you will have a high chance of starting a fire in the voltage regulator and killing the battery.

• Deep Cycle Batteries

By contrast, a deep cycle battery is made for discharge and supports intensive cycling. It provides rechargeable power for many cycles, ideal for running electric outboard motors, trolling motors, and electronics onboard.

Compared with starting batteries, deep cycle batteries are more expensive and heavy, but they are perfect for powering stuff without an engine running.

Key takeaway:

Basically, the kind of battery you need for an outboard ultimately depends on your purpose.

If you’re looking for a battery for an electric start outboard motor (vs pull start) , the starting battery is what you want. However, if you own an electric outboard or trolling motor, you should use deep cycle batteries ( LiFePO4 is recommended).

4 Types Based on Chemistry

You will find four kinds of outboard motor batteries if you look at their chemistry inside the cells, namely flooded batteries, gel batteries, AGM batteries (advanced lead-acid batteries), and lithium batteries.

Among them, lithium is a HUGE upgrade in battery technology, and there are a great number of advantages that people run to lithium (especially LiFePO4) for their outboard motors:

You can fully discharge the battery cells every day (almost 100% vs 50% for AGM) without killing them. Moreover, they can recharge 2k-10k times vs 300-800 AGM.

These mean significantly more power capacity, so it can last twice as long on the water.

Not to mention they’re also a lot smaller and lighter than the comparable lead-acid battery, and charge much faster. And you can see the battery state on your phone or via a digital screen.

That’s why all reputable electric outboard motor brands, including ePropulsion , use lithium (or even LiFePO4) batteries as their accompanying batteries.

Further Reading : Why You Should Choose LiFePO4 Batteries

What size battery do I need for an outboard motor? What amp-hour rating should I get?

The electric outboard motor batteries are available in a variety of sizes and power levels.

Here is how to calculate the outboard battery sizes in simple steps:

Method #1. Start with Amps.

Step 1. Get the outboard motor electric consumption in Amps (usually available in the manual). Or calculate with Amps = Watts / Volts.

Step 2. Calculate the Amp hour rating of the outboard motor (Ah = Amps x Time).

This Ah rating indicates the battery size that will be sufficient for your requirements.

For example, if your motor consumes about 60 Amps and you want an outboard motor battery that will last 3 hours, you will need a 180 Ah ( = 60 Amps x 3 hrs) battery.

Method #2. Start with Wattage.

(Use this method if you know the wattage rating of your outboard motor.)

Step 1. Calculate the total watt required for the outboard motor battery (Wh = Watt x Time).

Step 2. Calculate the Ah rating with the given voltage (Ah = Wh / Volts).

For example, if you own a 1 kW outboard motor ePropulsion Spirit Evo and you want to use it for six hours on a 48V boat system (on a single charge), you will need a 125 Ah battery.

Note that the calculation is under full load and max amp draw (meaning you’re running the motor wide open the whole time).

In real life, the amp will be much less. That’s to say, you may get away with a smaller battery if you run at part throttle with intermittent use.

However, always go for a larger battery if you go with AGM/lead-acid deep cycle batteries.

Generally, you don’t want to discharge the battery more than 50% to prevent damage. So half the rated capacity.

Alternatively, lithium batteries can be more fully discharged without damage, so you can use more of the rated capacity, which is a big plus for outboard motor batteries.

Reading this far, I believe you should be able to decide the best outboard motor battery for your boat. If you are still not sure, here is a simple guide to help you make a quick decision.

Essentially, three things to consider:

If you are looking for a small outboard motor battery, the weight should be a top priority.

You will never want an outboard motor battery to sink your small boat and break your back every time you carry it from your car and to the dock.

In that case, the lightweight lithium battery would better fit your needs.

Typically, a 12V 100Ah lead acid battery weighs over 60 lbs. Comparatively, a 100Ah LiFePO4 battery weighs only 25 lbs. So you can easily shave about 35 lbs off the weight in your boat.

Not to mention its larger usable battery capacity and smaller lighter battery cell.

As a Zodiac boat owner reported, his 12V LiFePO4 outboard motor battery lasts 2 times as long as a 120 Ah lead acid that weighs 3 times what the LiFePO4 does.

#2. Battery Life

Outboard motor battery life should be a deciding factor in purchase decisions. You need to make sure the outboard motor battery gets enough juice to do the job.

So choose an outboard motor battery that comes with a larger battery capacity and longer life cycles. And the lithium battery goes a long way in these two aspects, with at least 80% DoD (depth of charge) and 5 times more charge cycles than lead-acid batteries.

However, how long your outboard motor battery can run actually depends on a lot more factors.

One of the key factors is outboard power. The best battery for an 25 HP outboard motor is definitely different from the one for 40 HP, since they are running at different watts.

For example, if your motor runs at 300W and you use it with a 230Wh LiFePO4 battery, you will get 40 to 50 minutes’ continuous usage out of this battery.

Note that throttle power settings also make a great difference in your outboard motor battery life:

When moving a boat through water in displacement mode, to go twice as fast you must increase the power about fourfold. That’s to say, if it theoretically takes 200W to go at 2 knots, it would take 800 watts to go at 4 knots.

At the same time, going at half throttle may quadruple your range, even though you’ll get there half as fast. Many electric boat owners simply go quite slowly to make the cost and physics add up.

Also, you can use a solar panel to help keep your outboard motor battery topped up.

Further Reading: Solar Powered Boat Motors: Easiest Way to Set up Your Solar Boat

The last step to get the best bang for your buck is to compare costs.

And that’s not all about the price tags.

Although the lithium outboard motor battery is more expensive, it can last 10+ years if taken care of properly.

Actually, it becomes cheaper if you plan to use it for many years. By this I mean that it may cost 2 times more upfront, but it will survive roughly 5 times as many cycles.

All in all, a lithium battery would be the best outboard motor battery option nowadays if you want to minimize size and weight and don’t mind a higher upfront cost.

Other than that, lead acid is also a reliable technology, proven and improved over hundreds of years. If you have a tight budget, go for a larger lead-acid battery.

How to wire an outboard motor to its battery?

In fact, it’s easy to hook up your outboard motor battery if you follow the manual. You don’t need to fumble with the outboard motor battery cables to get it plugged in.

Basically, you just need to connect the outboard motor and battery with the provided switch cable and communication cable. Also, the control system should be connected to the battery with communication cables.

Some small outboards come with an integrated battery, making it easy for the battery wiring.

For example, the 3 HP ePropulsion Spirit 1.0 Evo only requires you to place the battery in place (secured by two side slots), and then connect the power cable to the battery.

How to charge an outboard motor battery?

Generally speaking, an outboard motor battery needs to be charged with a specialized charger. And the charger decides the charging efficiency.

Fast chargers are available for some models, or you can also use two or more chargers in parallel connection to speed up the charging.

Does an outboard motor charge the battery itself?

Yes, most outboard motors can charge a battery directly while running just like your car’s motor can charge its battery:

The engines come with an alternator or generator. When you start the engine up, the engine will charge the starting outboard motor battery until full. If there is an aux battery, it will then switch over and charge the aux battery.

More About Outboard Motor Batteries

1. does an outboard motor need a battery.

Yes, your outboard motor will need a battery to work unless it’s a pull start.

2. Can a lithium battery start an outboard motor?

Standard deep-cycle lithium batteries are not designed for starter uses.

However, lithium batteries for starting outboard motors are now available, which are specially designed to meet the strict specifications for marine cranking use.

In fact, some outboard manufacturers, such as Mercury Marine, encourage users to use qualified lithium batteries to start the engine for optimal performance.

3. Does an outboard motor charge the battery when running?

Yes, you can charge a battery from an outboard by burning fuel. For electric outboards, some models (including ePropulsion Navy Evo ) can collect electricity from wind and water and charge themselves via a hydrogeneration function.

4. Can an outboard motor charge a lithium battery?

Unfortunately, most outboard motors can not charge a lithium battery directly. You will need a DC/DC charger to make it possible.

Other than that, you can invest in an electric outboard motor with hydrogeneration function which allows the motor to charge itself while sailing.

Hopefully, this post can help you clear your confusion about outboard motor batteries. If you have other concerns, please leave your question in the comment below and I will get back to you ASAP and add it to the list.

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Classic look hydrofoiling electric boat debuts in Moscow

A team in Russia has developed this sleek hydrofoiling electric boat with a retro-tech classic runabout look, both inside and out.

The boat is called the Molniya – Russian for ‘lightning’ – and uses fixed surface piercing (SP) foils rather than the retractable inverted-T fully submerged (FS) type on boats like the Candela 7 .

The Molniya prototype was built by Artem Markov and a small team he assembled in Moscow. Markov is a graduate of the Moscow Automobile and Road Construction Institute, where he was part of their Formula MADI electric car racing team that competed against other universities from around the world.

Hydrofoiling electric boat idea started in 2016

Like many other electric boat developers he is also a long time sailor and says “ I have never been able to understand what is the beauty of going on motor boats with a lot of vibration and noise. So, I decided I wanted to find a way to transfer the silence and comfort of a sailing yacht to a boat. The idea came to me in 2016, and from that moment I started working on the project .”

He is a big fan of the work that the team at Candela has been doing, and is well versed in their reasonings of why hydrofoiling is the way to reduce drag and increase efficiency and comfort. So he knew foiling was the way to go and began to design his dream boat.

It is one thing to know exactly what one wants, but b udget realities quite often make inventors adapt. So he found a classic fibreglass-and-aluminum hull and went to work redesigning and converting it. The team had to strengthen and reinforce the hull to handle the stresses from the front foils. At the stern of the boat they designed  protruding half-wings that would help lift the boat onto those front SP foils as it accelerated.

80kW motor mounted to stern drive unit 

That gives the 8.9 m • 29 ft boat a cruising speed of about 20 kts • 37 km/h and maximum speed of 36 kts • 66km/h. As for range, the Molniya can go for 135 Nautical miles at 5 kts, 17 Nm at 25 kts and 20 Nm at the top speed. 

For the battery, they have taken stock lithium-ion cells and developed the modules themselves. The size is 160kW and there are some creative and useful ideas incorporated into the charging and battery management systems. One is the ability to connect a warning system to a GPS route so if you are driving at a speed that is taking yo u beyond range of getting back to shore the motor will automatically slow down. When you do get back, a full 0-100% charge takes 3.5 hours and you can check status through SMS.

One of the intriguing things about the Molniya is that all of the electric boat technology has been incorporated into a striking overall retro look. The dashboard looks like it might have been taken from a 1950s luxury car catalogue, but of course the actual meters are all digital. The interior of the entire boat harkens back to an earlier day, appearing ready to whisk 6 passengers off to a swing era supper club.

From prototype to production

Having built and tested the prototype from an existing hull, the goal of Markov and the team is to move to production mode and use the materials he always envisioned in his dream boat. While the aluminum and fibreglass of the original have been useful for testing, speed and range will benefit from materials like much lighter carbon-kevlar.

The adapted stern drive was useful for proving the hydrofoiling electric boat concept, but all of the designers and engineers are keen to see the improved efficiency they will get from a motor, drive and battery system they have designed from scratch for the Molniya. As for the foils themselves, the production model will use lighter, thinner composites instead of stainless steel.

Obviously the spring and summer of 2020 has not provided the best opportunities to introduce the prototype at boat shows and stir up interest with consumers, the trade or investors. It seems, though that the Molniya is the type of boat that should appeal to peopl looking for the same thing Artem wanted for himself: a classic motor boat experience but one that is quiet, odour free…and smooth sailing.

You can find out more on the Molniya website, lightning-foil.com .

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