New electric boat motor uses wind and water to recharge its batteries at sea

It may not offer infinite range, but it’s close. The new Oceanvolt ServoProp saildrive has a regeneration feature that efficiently charges up an electric boat’s batteries while sailing.

Many people think of sailboats as being purely wind powered. While smaller sailboats usually are, most decently sized sailboats have a motor for maneuvering in a marina or when the winds die down.

Saildrive motors are an innovative propulsion system commonly found on modern sailboats, offering a compact and efficient alternative to traditional shaft-driven inboard engines.

Designed with a sleek, low-drag profile, saildrives are integrated into the hull and consist of an engine mounted directly above a drive leg that extends through the hull, with a propeller at the lower end. This configuration not only reduces vibrations and noise but also minimizes the complexity of installation and maintenance.

Saildrive motors offer smooth, efficient power delivery and extra maneuverability. Their streamlined design contributes to enhanced sailing performance by reducing drag. As a result, saildrives have become a popular choice for contemporary sailing enthusiasts seeking a balance between performance, ease of use, and reduced environmental impact.

Electric saildrive motors have the benefit of offering hydro-regeneration – a unique advantage that can help recharge an electric sailboat’s batteries. When sailing under wind power, the electric motor is actually forced backwards by the water moving over the propellor. That turns the motor into a generator that can send energy back into the batteries to be used later.

Oceanvolt is widely seen as a leader in the field of hydro-regenerating motors, having racked up awards for their motors going back years, according to Plugboats. The company’s saildrives use propellors with variable pitch blades, which when combined with the motor’s ability to rotate 360 degrees, creates the most efficient environment for both propulsion and hydro-regeneration.

The company’s newest HighPower ServoProp 25 is the most powerful model in its lineup, capable of regenerating 5 kW of power while traveling at around 10 knots. According to company, future software updates that will tweak the saildrive’s performance will allow it to produce even higher power with greater efficiency.

Controlled from within the cockpit, the ServoProp 25 can switch from regeneration to propulsion with the push of a button. A readout for the operator shows the saildrive’s current operation mode, generated power, RPM, and time remaining until the 48V batteries have been recharged.

Beyond the obvious advantages over combustion engines, such as quieter operation and lack of noxious emissions, the entire system is digitally controlled to make installation simple. The water-cooling system, motor controller, and blade controller are all built into the unit, further simplifying the installation process.

When back in propulsion mode, the motor can output 25 kW continuously, though it has a peak power rating of 30 kW for 15 minutes. As is usual with electric boat motors, their lower power figure is equivalent to a much more powerful combustion engine. In this case, Oceavolt says that the 25 kW nominal power is similar in performance to a 75 kW (100 hp) combustion engine drive.

The instant torque and 5,000 newton (approximately 1,100 lb.) thrust force are major advantages of the electric setup.

The 419 lb. (190 kg) saildrive is suitable as a propulsion motor for boats up to 70 ft. in length and weighing up to 27.5 US tons (25 metric tons).

It can also be used as a hydro-regenerator alone in considerably larger vessels. Deliveries of the new saildrive are expected to begin by the end of this year.