The propulsion of an electric surfboard comes from several key components. The electric motor has a power of 5-15 kilowatts, with 10 kilowatts being common; the battery has a capacity of 2-4 kilowatt-hours, with a range of 45 minutes to 2 hours; the jet system has a power of 3-15 kilowatts; the battery accounts for 30%-50% of the total cost, and the electric motor accounts for 35%-45%.
Electric Motor
Market analysis shows that the range of motor power in mainstream electric surfboards falls within a range of 5 kW to 15 kW. The 10 kW is the most conventional model, quite enough to provide a drive on water at a speed of 30 to 40 km/h.
In electric surfboards, brushless DC motors are the most operational technology; their efficiency reaches 90% or higher. The typical efficiency of classical brushed motors is below 75%. It follows from this that such a cooling system can support the operating temperature of the motor below 70°C approximately 20% lower than in the traditional air cooling system.
A 2 kWh lithium battery with a 10 kW motor can give around 40 minutes to 1 hour of range, while a 4 kWh would give 1.5 hours. The cost of the electric motor accounts for about 35% to 45% of the total budget for manufacturing the surfboard.
It is a well-known brand that uses anodized aluminum casing and IP68 waterproof design. The life of the motor can reach 5,000 hours, which is about 8 to 10 years for normal usage. While ordinary motors need to be replaced after 2,000-3,000 hours, this difference makes a big distinction in the cost of long-time use.
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Battery Capacity
Most electric surfboards offer a range of 45 minutes to 2 hours at distances from 2 kWh to 4 kWh, respectively. In case one chooses a higher capacity battery—for instance, a 5 kWh, the range can be extended to 2.5 hours—but normally this is usually accompanied by a higher price and longer charging time.
A 2 kWh battery weighs about 10 kg, while a 4 kWh battery is more than 18 kg. Indeed, it follows from the data that an electric surfboard equipped with a 2.5 kWh battery weighs a total of 27 kg, while its 4 kWh version weighs 35 kg. A 3 kWh battery can support the surfboard to run at 40 km/h for 1 hour, while a 2 kWh battery under the same conditions only provides a range of 40 minutes.
The cost of the battery generally takes 30% to 50% of the total cost of the electric surfboard. For example, a 4 kWh high-performance battery usually costs between 2,000 to 4,000 USD, while a 2 kWh battery costs between 1,000 to 2,000 USD.
This would generally take 2 to 3 hours for a 2 kWh battery, while a 4 kWh would take roughly 4 to 6 hours. With the fast charge technology of some brands, one could even charge to 80% in 1 hour. The wave environment can also raise the battery's energy use by up to 20 or 30% under similar conditions.
Some new types of batteries make use of silicon anode technology, which assures 20-30% higher energy density compared with traditional lithium-ion batteries. A 4 kWh battery using silicon anode technology weighs only 15 kg, which is about 3 kg lighter than traditional batteries.
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Hydrodynamic Design
Generally, the lengths of mainstream electric surfboards in the market range between 1.5 meters and 2.2 meters, with widths ranging from 50 cm to 70 cm. Some high-end models use V-shaped hull designs to reduce drag by more than 15% when passing through the water. The weight of an electric surfboard usually ranges between 20 kg to 35 kg, and the weight is focused on the central hull to enhance stability by a great margin.
The children's electric surfboard, for the most part, has a length from 1.2 meters to 1.5 meters and has no more than 15 kilograms in weight. Children's boards are about 18% more stable compared to the adult ones. For example, the double-layer hollow-structured surfboard can increase its buoyancy by 30%. This kind of board can bear 150kg at the stationary state, which is 50% higher compared with the single-layer structure.
The carbon fiber composite materials of most high-end surfboards sold in the market today have a density of 1.6 grams per cubic centimeter, 25% lower than that of traditional fiberglass materials. On average, carbon fiber surfboards can be used for 8 to 10 years, while those made of fiberglass can only last 5 to 7 years.
Jet Propulsion System
The power range of mainstream jet propulsion systems generally falls between 3 kW and 15 kW; the more powerful, the stronger the thrust. For example, an electric surfboard jet propulsion system can generate 200 newtons of thrust, enough to support the user in gliding at 50 km/h on the water.
When the speed in the water approaches 15 meters per second, the efficiency of the jet propulsion system can be higher than 85%. Some high-performance models use an optimized impeller design, and the rotational speed reaches 20,000 RPM. Optimizing the systems of a jet can increase the speed by around 10% with the same power, for instance, from 40 km/h to 44 km/h.
The weight of a standard jet propulsion system is around 8 kg, the length - 50 cm. Depending on water quality and frequency of use, the lifespan of the jet system varies from 500 to 800 hours. In fresh water, its service life is about 20% longer than in sea water. Given the annual usage time of 100 h, the average maintenance cost for a jet system can range from US$150 to 300 per year, mainly towards wear parts replacements and lubrication.
Some brands make high-end products IP68 waterproof in design, operational at 3 meters depth and continually so. The ordinary product is generally IP65 waterproof grade, preventing water from splashing. Actually tested, the IP68 system has a 30% lower failure rate compared to an IP65 system in high wave conditions.
Low-speed mode, 30% power output; medium-speed mode, 60% power output; high-speed mode, 100% power output. On a windless lake, this will increase the range by 30% when in low-speed mode, while large waves will provide stronger thrust at high speed to ensure safety. Generally, every 10 kW jet propulsion system consumes about 1.5 kWh per hour, while an optimized system consumes only 1.2 kWh under the same conditions.
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Weight Distribution
The total weight of an average electric surfboard weighs about 20 kg to 35 kg, while the battery constitutes 60% to 70% of the total weight. For instance, a 2.5 kWh battery would weigh about 12 kg while the motor system weighs about 8 kg. That happens when the center of gravity is about 60 cm from the front side, and stability will be at its best, hence reducing about 20% tilt angle.
A 70 kg user on an electric surfboard in large waves has 15% lower stability compared to a 50 kg user. Most high-end surfboards use carbon fiber composite materials, which boast a density of 1.6 grams per cubic centimeter, 25% lighter than traditional fiberglass materials. An electric surfboard made of carbon fiber has a center of gravity deviation of only 2%, while fiberglass boards can have a deviation of up to 8%.
For instance, an XYZ central battery-designed surfboard performs 10% better in speed on tranquil lakes, while the rear battery design reduces the probability of flipping over in a wave-laden environment by 15%. A surfboard having its center of gravity at the center of the board accelerates from rest to 30 km/h in 4 s whereas a design that has its center of gravity towards the rear does it in 5 s.
Speed Controllers
Some high-performance electric surfboards have multispeed controllers. The user can set them according to water conditions. Their usual speed starts from low-speed mode at about 30% power output and goes as high as high-speed mode-100% power output. The response time of all top-tier controllers is generally under 0.1 second, while that of ordinary ones is about 0.3 to 0.5 seconds.
A normal speed controller is normally 10 cm × 6 cm × 3 cm in size and weighs about 300 grams. However, for some high-class products, because of more integrated chips and lightweight materials, it can shrink down to 8 cm × 5 cm × 2.5 cm with 200 grams of weight. Ordinary speed controllers on the market are between 100 to 200 USD while high-performance ones are up to 500 USD.
By their own definition, some optimized controllers reduce energy consumption by up to 10-15% and increase battery life. For example, a surfboard with an efficient controller using a 2 kWh battery can increase its range from 50 minutes up to 57 minutes.
In the case of high-loaded operating conditions, the temperature of liquid-cooled controllers remains well below 50°C, while in the case of a traditional air-cooled design, it may rise over 70°C. For this reason, the estimated life of the controller will be more than 5 years for the former and only 3 years for the latter.
Most controllers are designed with an IP67 waterproof rating. Adding sealing designs, some high-end products achieve an IP68 rating, enabling them to operate continuously for over 1 hour at depths of 3 meters. These remote controllers have Bluetooth or Wi-Fi in operation, whose effective range is from 10 to 20 meters, and is good enough for long-distance operation. Some brands have also introduced dual-channel communication technology to reduce the probability of signal interruption to 0.1%.
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Propeller Design
Common propeller diameters range from 10 cm to 25 cm. Although larger diameters produce more thrust, the smaller diameters are superior to go at higher velocities gliding. For example, a 20 cm three-blade propeller can have as much as 200 newtons of thrust at 4,000 RPM to give the surfboard the capability to achieve 45 km/h. For one thing, three-bladed propellers do indeed produce approximately 15 percent more thrust when compared to the two-bladed propellers; they are about 8% less efficient in energy expenditure.
Plastic propellers are cheaper, about 20 to 50 USD, but these propellers are less strong and can only be used in light conditions. The price of the aluminum alloy propellers ranges from 100 to 200 USD. They are stronger and corrosion-resistant. The carbon fiber propellers are more than 300 USD. Its density is as low as 1.6 g/cm³, 30% lighter than the aluminum alloy, and much longer in service life.
Within the range of 15° to 25°, the balance between thrust and efficiency can be achieved, and propulsion efficiency can be higher than 85%. When the angle is less than 15°, the energy consumption will be lower, but it is unable to provide enough thrust. Conventional propellers weigh between 200g and 500g, and some lightweight carbon fiber propellers weigh only 150g. Lightweight propellers can reduce acceleration time by 10%, which shortens the time to accelerate from 0 to 30 km/h to 3 seconds.
Noise for some of the traditional propeller designs