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Truly classic “Elysium” becomes hybrid sailing yacht

August 8, 2021
The 56ft sailing yacht "Elysium” will be converted into a hybrid sailing yacht. Read what choices have been made by STOK Electric regarding the conversion of the diesel generator and the adjustments of the energy system and what renovations have been carried out by Hutting Yachts.
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Diesel generator: converting a diesel engine with a dynamo

A diesel generator is composed of a dynamo, diesel motor and a controller to use as a generator. STOK Electric converts a diesel engine to a diesel generator by placing a dynamo on the diesel engine, which allows the batteries to be charged. The alternator is specially made so that it fits on the diesel engine and gives the correct output voltage for the system. The generator is controlled by the associated controller. This system can operate completely autonomously. Depending on the battery status, the generator will start automatically and start charging the batteries. As soon as these are sufficiently charged, the generator turns off again. It is also always possible to operate the generator manually.

Other prefabricated generator solutions have also been considered, but these do not meet the requirements set by STOK Electric. It is important that there is enough power onboard, and that the diesel generator can do its job under any circumstances. In addition, it can happen that the diesel generator runs for a longer time, especially during long sailing trips. Practice shows that these much smaller generators are not intended to operate at high power for long periods of time.

The middle photo shows the electric motor used in the Elysium. The photo on the right is the backup diesel generator.

Electric propulsion

In the image below STOK Electric is testing the 70 kW electric motor on the 350V battery bank. In this test setup they use a motor controller, distribution box and an EMC filter to reduce the transfer of electromagnetic noise between the electromotor and battery bank.

STOK Electric offers a large range of reliable electric motors; they can easily vary the speed and power output of the motor, depending on the application. The electric motors come with a flexible coupling adjusted to fit the propeller shaft.

Distribution box & control box

STOK Electric has also developed and built a prototype of the battery distribution and control box. The battery distribution box distributes the connections from the Main Battery Bank to the rest of the systems. The box is placed close to the electric motor and generator to reduce the amount of high voltage cables required. Besides this, it also houses several safety features.

The Battery Control Box is the brain of the system. It checks if all parts are operating correctly. It has, for example, full control over the main battery bank and checks if they’re all at a good status.

Main battery bank

For the main power source of the system, STOK Electric uses a high-quality battery pack. The use of Lithium Iron Phosphate batteries instead of Li-ion batteries is what makes the battery bank stand out from commonly used batteries in electric vehicles. With this battery technique it’s possible to reach almost the same energy density of Li-ion batteries while also increasing safety. LiFePo4 batteries can be extinguished with (sea)water, which is a big plus for ocean-going vessels.

The battery bank runs at 350V nominal, this can be scaled up and down, depending on the vessel. A higher voltage is necessary for larger vessels to reduce the currents and the risk of fire.

Adapted 24V system

The 24V system has been completely adapted and connected. This system includes solar panels, shore power inverters, and all 24V batteries. These batteries have been given a new place on the ship. These changes were necessary to make room for the hybrid energy system and to be able to easily connect the energy systems to each other.

Refit woodwork exterior

While the hybrid system was being thought out and all necessary parts were ordered, Hutting Yachts carried out an extensive refit of the exterior. For example, the teak deck on the cabin roof has been completely renewed, the damage has been removed and all the woodwork has been repainted.

Yacht painting and antifouling

The entire hull has also been sanded and checked for damage. Minor repairs have been carried out where necessary, the underwater hull has been provided with antifouling and the hull has been repainted. The mast and boom were also inspected and treated after they were repainted as a finishing touch.

More information about making a sailing yacht hybrid

The demand and interest in hybrid and electric sailing yachts is increasing growing. This is not surprising when you look at the developments within the automotive industry. However, making a hybrid sailing yacht involves many aspects and, above all, specific expertise. For example, the energy system must be safe enough for blue ocean sailing, reliable in connection with the, often long, sailing trips, and easy to maintain. It concerns craftsmanship and customization because each sailing yacht requires a different system. The custom-made energy system for sailing yacht 'Elysium’ was developed by STOK Electric, where Hutting Yachts offers all support in the field of renovations and installation.

The goal: full-time living on a hybrid sailing yacht

The owners, Harry and Jill, are a Dutch couple who are realizing their sailing dream: living and working onboard full-time and sailing around the world. Visit their website at The first step was taken in 2019, when they bought this Truly Classic Hoek Design in Lymington, UK. Harry and Jill are convinced that hybrid propulsion will greatly increase the value of their sailing yacht and above all that it will better prepare the yacht for the work and travel life they want to spend onboard indefinitely.