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Not long ago, the notion of electric powered catamarans was limited to sketches due to the lack of credibility exhibited by marine battery manufacturers. Sailors feared being stuck offshore with the limited range and severe depletion of electric boat batteries against the water’s high drag. However, technological advancements made to the underlying concept of electric boat batteries overtime, forever changed the future of sustainable yachting.

The Mechanism of Electric Powered Catamarans

Bringing physics into the mix, the relationship between energy and power determines how much of each is required to move the weight of an electric powered catamaran against the force and resistance of water. This in turn controls the speed and distance travelled onboard.

The energy stored in electric boat batteries is transferred to mechanical energy to move the propellers, which causes them to exert force against the waters to move the electric powered catamaran. Sunreef Yachts currently deploys 700V electric boat batteries for all its sailing and power models.

Types of Electric Boat Batteries

The emphasizes on e-mobility in the nautical industry led to the development in energy-storage technology. While several variants may exist, there are three primary types of electric boat batteries on the market:

  • AGM

Absorbent Glass Mat (or AGM) batteries are notably the most common types of lead-acid batteries viewed as a safe choice for electric boat batteries. They consist of clean cells, minus the electronics to monitor, prompting a robust system for contemplating how long the batteries should last depending on the usage. However, typically AGM batteries need replacing every six to 10 years.

A prominent advantage of this type of lead battery was the simple technology in use and significantly lower purchase price. Despite this, the technologically advanced lithium-ion electric boat batteries quickly put AGM batteries out of business since they would take longer hours to recharge, offer poor running time even at high power outputs, and weighed significantly more.

  • Lead Carbon

Like AGM, these are yet another form of lead batteries that consist of pure cells. However, they have better performance than AGM at partial charge with higher efficiency, increased cycles, and reduced sulfation. On a lower charging voltage, the positive plates of the lead carbon batteries experience less corrosion with greater efficiencies, resulting in an improved lifecycle.

Nonetheless, lead carbon batteries recently went out of fashion since they lacked the circuitry that the latest technology lithium batteries encompassed to ensure safety over the years.

  • Lithium

Lithium boat batteries have secured a prominent place in the marine market in today’s day and age because of their exceptional performance alongside internal combustion engines. These are the most popular rechargeable electric boat batteries that use lithium-ion as a crucial element. While some may argue that these electric boat batteries are pricier, it is notable that they are easier to place and install, weigh three times lighter for the same amount of energy, and are near indestructible.

While lead batteries have been a part of the marine world for longer, lithium-ion batteries were deemed more favorable as they are less polluting and more economical. Apart from superior capacity, lithium batteries also have an efficiency of 98 percent, compared to the 80 percent of acid batteries. Likewise, the lifespan of lithium batteries is four times longer than that of its opponent for an identical usage.

The capacity and performance of lithium batteries emerged as the single greatest determining factor for the future of sustainable technology. Last but not least, lithium batteries are less likely to adversely affect the environment as the alkaline (that composes the lithium) is far less reactive to the living organisms in water as compared to acid in case of direct exposure.

Factors Determining a Successful Implementation

Choosing the correct electric boat batteries is vital as it is a critical and costly component that effects the electric powered catamaran’s performance. It is of utmost importance that the electric boat batteries of choice are deemed compatible with the electric motors enabling full adaptation to a boater’s needs. Additionally, it must live up to a rational number of cycles at nearly 80 percent depth of discharge, without decreasing the performance (i.e., the condition of the batter when used in extreme temperature environments).

Another important criterion for the success of electric boat batteries is their power density (weight-to-energy ratio). Because a significantly reduced battery weight accounts for less drag, hence, lesser energy is consumed whilst propulsion. Unlike lead-acid batteries, lithium-ion batteries are relatively small, provide great energy efficiency, and are nearly have the mass. In a real-world scenario, an electric powered catamaran possessing two 280 kilowatts main engines will require electric boat batteries of at least 380 kilowatts as to not overstress the batteries in use.

Today, lithium-ion batteries are placed at the centre of clean energy transition; however, determining the efficiency of electric boat batteries is heavily reliant upon their chemical composition. Typically, the anode of lithium-ion batteries is made from graphite whereas the cathode contains lithium alongside the minerals which largely regulate the power, performance, safety, cost, capacity, and lifespan of the battery. As a result of the mineral composition of the cathode changing, the batteries chemistries also differ. There are six major lithium-ion technologies in-use.

1.    NMC Batteries

The primary reason as to why Lithium Nickel Manganese Cobalt Oxide (LiNiMnCoO2) batteries have gained popularity in recent times is that they have high specific energy, i.e., the energy content per unit of mass of the battery by weight. Additionally, they offer faster charging performance in cold climates and enable longer ranges.

Usually, NMC batteries possess a combination of 33 percent nickel, manganese, and cobalt at the cathode. However, different manufacturers of the NMC batteries may have contrasting recipes for proportions of the three which causes a gain of specific power (i.e., the ability to deliver high energy or power on demand) but loss of specific energy, and vice versa.

A six points system for lithium batteries rating the aspects of NMC batteries.

Similarly, including more nickel into the mix offers a slightly reduced voltage, but it guarantees a lower cost, longer cycle life, and higher energy density. In most cases, the use of cobalt is often limited due to costing and rising concerns about ethical mining. However, high nickel content can potentially make the battery unstable, hence, cobalt and manganese are introduced to the mix to improve thermal safety and stability.

2.    NCA Batteries

As a result of sharing nickel as a common mineral, the Lithium Nickel Cobalt Aluminum Oxide batteries share the advantages of high energy density and specific power with NMC. However, instead of manganese the primary mineral use to increase stability is aluminum. But research has deduced that NCA cathodes are far more expensive and relatively less safe than other lithium-ion technologies on the market.

3.    LMO Batteries

The Lithium Manganese Oxide batteries (aka manganese spinel batteries) offer improved safety, fast charging, and discharging capabilities. For this reason, the LMO cathode materials are often blended with NMC, presenting both high current upon acceleration and longer driver ranges.

4.    LCO Batteries

While Lithium Cobalt Oxide batteries have higher energy density, they possess limited specific power, low thermal stability, and a short lifespan. For this reason, the LCO batteries have become a popular choice for low-load applications, where smaller bursts of power need to be delivered over longer durations. However, this electric battery type is not deployed in the nautical industry.

5.    LTO Batteries

Unlike the other battery chemistries in question, the Lithium Titanate batteries are the only ones to have a unique anode surface that is made of lithium and titanium oxides. As for the cathode chemistry, a similar one of LMO or NMC batteries may be applied. The LTO batteries perform seamlessly under extreme weather temperatures and exhibit excellent safety; however, they have low capacity and are a little pricier which limits their use in the market at scale. However, they are frequently spotted onboard ferries where their weight does not contribute to the problem.

6.    LFP Batteries

Unlike the other battery chemistries in question, the Lithium Titanate batteries are the only ones to have a unique anode surface that is made of lithium and titanium oxides. As for the cathode chemistry, a similar one of LMO or NMC batteries may be applied. The LTO batteries perform seamlessly under extreme weather temperatures and exhibit excellent safety; however, they have low capacity and are a little pricier which limits their use in the market at scale. However, they are frequently spotted onboard ferries where their weight does not contribute to the problem.

The composition of a lithium iron phosphate battery.

The primary elements in Lithium Iron Phosphate batteries, i.e., lithium, iron, and phosphate are deployed as the cathode material. Alongside, a graphite carbon electrode with a metallic backing is used as the anode. Much like other batteries, these too operate by moving positive and negative electrodes to charge and discharge but because phosphate is a non-toxic material, LFP batteries are well capable of delivering constant voltage at a higher charge cycle.

Other benefits of LFP batteries include its prolonger lifespan, aspects of safety, no active maintenance, improved discharge, upgraded charge efficiency, and lightweightness. While these batteries are readily deployed in the automobile sector, the high energy density and significantly lesser weight of the NMC batteries makes it more favorable for implementation in the nautical sector. Higher energy densities translate to improved acceleration performance because of greater energy being stored in a lighter package.

Sunreef Yachts Eco deploys marine batteries that use lithium-ion as the primary element of their electrochemistry. The best pick for Sunreef’s electric powered catamarans has proved to be the Lithium Nickel Manganese Cobalt Oxide (NMC) electric boat batteries.

What’s Next?

To continue enhancing the experience of consumers, Sunreef Yachts Eco is working alongside its manufacturers for migrating onto solid-state batteries that are a greener, more economical battery with three times longer lifespan. In fact, it is possible to achieve a life cycle of more than 10,000 with its outstanding safety record.

While the basic chemistry remains lithium-ion, the solid-state electric catamaran batteries are sure to offer a more significant return on investment for yachting enthusiasts. But most importantly, the battery incurs no ill effects even in cases where it was punctured with a projectile, heated to extreme values, or overcharged. It can also function without the need for cooling in a broader temperature range, i.e., from 0 to 35°C.

Demand and Supply for Electric Boat Batteries

An experiment found that electric powered catamarans (possessing both marine batteries and generators) consume only a fourth of the fuel that diesel catamarans use. As per an experiment, combining two modes of power generation not only reduces diesel consumption from 800 liters to 200 liters for a week worth of travels, but also allowed for longer durations of noiseless, vibration free, and near zero emission travels.

However, it is possible to eliminate the need for a generator onboard completely, with the use of alternative methods that replenish the battery banks just as well. Sunreef Yachts Eco’s electric powered catamarans are equipped with advanced propulsion systems that promote power generation from renewable sources of energy.

Sunreef Yachts Eco has unveiled the possibility of generating energy from the rotation of the propellers while the catamaran is navigating under sail. Likewise, the wind turbines mounted atop the bimini of Sunreef’s power catamarans encourages the breeze to turn the propeller-like blades around a rotor, which in turn spins the generator to create electricity.

Integrating the in-house engineered solar panels has also proven to be a viable method for the generation of power for Sunreef Yachts Eco in case of both power and sailing catamarans. These are ultra-thin, flexible solar panels that can by fully integrated into the composite structure of the electric powered catamaran, outperforming the performance of a diesel powered generated both by weight and performance. The latest solar catamaran by Sunreef Yachts Eco, the 80 Sunreef Power, incorporates 200 square meters of solar panels weighing in at 360 kilograms to deliver 40 kilowatts per hour. This setup produces enough energy to that of two diesel generators weighing 800 kilograms.

Power generation capabilities of a solar catamaran by Sunreef Yachts Eco.

The Classification for Electric Boat Batteries

Electric powered catamarans designed and manufactured by Sunreef Yachts Eco are equipped with marine lithium-ion batteries that are 30 percent lighter than the average system deployed in the yachting industry. These are advance, safe NMC chemistry batteries that are custom-made for each yacht model.

The first electric powered catamaran, a Sunreef 50, boasted a smart lithium-ion battery pack of 7kg per kWh. However, advancements in the field have made it a reality to integrate electric boat batteries of densities less than 5.2kg per kWh. Each power unit by Sunreef Yachts Eco is custom-made to rightly accommodate the electricity production-to-consumption ratio for subsequent models within the range.

The energy stored in electric boat batteries performs similar operations to that of an engine, i.e., powering electric propulsion, air conditioning, and onboard home appliances. In an attempt of pursuing greater levels of sustainability, the yachting industry encourages the recharge of these batteries via renewable sources of energy instead of the conventional generators or shore supply. Hence, hydrogeneration systems, solar panels, and wind turbines are often spotted onboard electric powered catamarans by Sunreef Yachts Eco.

Electric boat batteries by Sunreef Yachts Eco

The Lifespan of Electric Boat Batteries

What guarantees a peaceful, long-term ownership of an electric powered catamaran is the battery lifespan. Sunreef Yacht Eco employees electric boat batteries with an extensive lifespan of up to 10 years. In most cases, despite 10 years in service, these lithium-ion batteries retain 80 percent of their original operational capacity, hence, allowing for the deployment of these batteries in other domains. Nonetheless, as standard protocol, electric boat battery systems onboard Sunreef Yachts Eco’s catamarans are always duplicated for safety purposes.

More importantly, the lifespan of electric boat batteries is dependent upon the conditions it is stored under. While the temperature in general should not exceed 35 degrees, it is widely preferred to cap it at 25 degrees for an extended battery life. Additionally, it is recommended to not hasten the process of replenishing the electric boat batteries with ‘super-fast charging.’

Frequently Asked Questions

How do I know what size battery for my boat?

According to experts, the battery pack should be big enough to equal the performance of a motor running on full power for one hour. Sunreef Yachts uses advance, safe NMC chemistry batteries that are custom-made for each of its electric powered catamarans model.

How long do electric boat batteries last?

When stored under favorable conditions, NMC electric boat batteries are capable of lasting up to 10 years. Storing the batteries at 25 degrees prevents the battery from overstressing, hence offering as many as 3000 to 4000 full charge cycles. Despite this, it retains near 80 percent of its original operational capacity.

What batteries are best for boats?

Most yacht manufactures today have migrated to lithium-ion batteries from the former lead battery options due to their light weight. Sunreef Yachts uses advance, safe NMC chemistry batteries that are custom-made for each of its electric powered catamaran.

What is the voltage of electric boat battery?

Voltage, denoted as V, is the unit used to measure electrical energy, which calculates the demand of electrical energy to move the electric powered catamaran from one point to another. Sunreef Yachts utilizes 700V electric boat batteries for all its sailing and power models.

Will lithium batteries make my boat faster?

Sunreef Yachts Eco has carefully handpicked its electric boat batteries to be ones that are consistent and reliable power. The lithium batteries of the NMC kind have a high specific energy (i.e., amount of energy stored by weight), ensuring all boating adventures are smooth sailing and enjoyable.

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Sunreef Yachts Shipyard

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80-718 Gdańsk, Poland

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