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Increasing the run range of electric boats

24 January 2023

What if you could change the boat design to achieve double or triple the run times from the same battery?

One of the first questions we get asked is how long does the electric outboard motor run for?

This isn't really a question about the electric outboard motor - which can run all day. It is really a question about the boat's design, how fast do you want the boat to go – and of course how much energy you are carrying in batteries - it's no more complex than deciding the capacity of your fuel tank.

At Eclass Outboards we use a guide of 1kWh per kW of engine power to give one hour at wide open throttle (WOT) or two to three hours at mixed speeds.

One hour at WOT is plenty for the typical electric boat outing. Especially as research has shown that most leisure boats spend around 40% of their time on the water at idle – which with electric outboard motors means no amps are drawn during idle.

And with instant torque available to get the boat moving we find that very little time is spent at WOT with an electric outboard. With an ICE engine, the full HP is not developed until the RPMs reach 5/6000 RPM, so again in the low to mid-range RPMs the electric outboard will outperform the ICE engine, conserving battery.

That said, Lithium-Ion batteries are not currently as energy-dense as fossil fuels. This will change as there are literally billions of $ being spent on R&D in this area.

However, for those wanting longer range times, who don’t have the budget for more kWh in batteries or their boat can’t carry the weight of more batteries, or who don’t want to wait until batteries are more energy dense – what if you could change the boat design to get the run time?

Hydro foiling electric boats.

The first response to a longer and faster run time was the hydro-foiling electric boat. This puts the boat out of the water while planing, dramatically reducing the energy required to propel the boat.

The most spectacular example is the European luxury electric boat maker Candela. The C-8 model makes a claim that with Polestar EV car batteries they will have the longest range in the world. The Candela C-8 will have a range of up to 57 nautical miles, or 105 km, at a cruising speed of 22 knots, or 40 km per hour, which equates to around 2.6 hours of run time at Wide Open Throttle (WOT). Candela says the C-8’s performance puts it on par with powerboats using internal combustion engines.

Eclass Outboards have had a couple of approaches from companies wanting to build hydro foiling boats in Australia. This technology is very expensive as not only is the boat a completely different design, but the computer technology required for stabilization is very sophisticated. However, we are ready to meet the challenge with our Australian-made and affordable electric outboard motors when asked.

Air-cushioned hulls for electric boats

The newest exciting electric motor run time solution, again from Europe, is the air-cushioned hull.

Using technology that has been around for a couple of decades, SES-X Norway has announced they are ready to commercialize an air-cushioned hull. (pictured above: Source PlugBoats) Conceptually this is a cross between a hydro-foiling boat and a hovercraft, reducing the friction between a boat and the water by raising the boat’s hull above the water's surface.

SES-X system hull is a combination of a catamaran and monohull, using the best features of both.

Boat volume provides space for the fans creating the air cushion as well as the batteries necessary for the fans and electric propulsion motors. Sensors collect data as the boat is in motion to adjust the air output from the fan.

These hulls can have any topside installed, so they can be applied to leisure boats, water taxis, work boats, and passenger ferries, however, due to early costs it is expected that ferries, workboats, and luxury 8m leisure craft will be the first vessels with this technology.

This technology could be very exciting as it could be used as an amphibious craft. Again, Eclass would be up for the challenge as we have already been approached by Hovercraft owners and have talked through a solution with them.

Because planing boats powered by our Australian-made electric outboard motors get on the plane early due to the instant torque it is pleasant to cruise at 10 knots on the plane using very little energy and, in some states, don’t require a license to operate at 10 knots or under.

If you have a boat design concept that needs a custom marine electric engine, please get in contact here

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