Modular removable battery system and method for powering an electric watercraft

Abstract

System for powering an electric watercraft comprising a removable modular battery comprising a plurality of removable rechargeable battery stacks. The battery stacks are arranged inside one or more battery frames in order to facilitate the removal of depleted and / or damaged battery stacks and their replacement with charged ones. Also provided is a method for powering an electric watercraft using the modular variable capacity electric power system disclosed herein. Said system and method are particularly suitable for watercrafts operating journeys consisting of one or more intermediate stops such as ferryboats.

Description

[0001] MODULAR REMOVABLE BATTERY SYSTEM AND METHOD FOR POWERING AN ELECTRIC WATERCRAFT

[0002] TECHNICAL FIELD

[0003] The present invention is directed to a system for powering electric watercrafts equipped with rechargeable battery powered electric motors. The system is particularly suitable for watercrafts operating journeys consisting of one or more intermediate stops such as ferryboats, performing regular scheduled or chartered journeys over open water / sea carrying persons or / and cargo for commercial purposes. It also relates to a method for powering an electric watercraft using the modular variable capacity electric power system disclosed herein.

[0004] BACKGROUND OF THE INVENTION

[0005] At present, electric watercrafts are widely accepted to be suited to a circular economy because of the low or zero CO2emissions, high endurance of the electric motors and gradual dominance of rechargeable batteries, thus having a smaller footprint on the environment. With the continuous improvement of international ship emission regulations and the continuous maturity of ship power batteries and hybrid power technologies, the acceptance of the electric ship market is also continuously improving, The electric ship is poised to become a key point for the development of the ship industry in the future. Besides reducing the emission, the running cost of the electric ship is obviously lower than that of a diesel- and LNG-powered ship, the structure of the electric ship is simple, the number of rotating parts is small, and meanwhile, the maintenance cost is also lower.

[0006] Electric ships perform journeys that comprise of one or more intermediate stops. Due to the high energy needs that result from moving with speeds comparable to traditionally powered watercrafts, the batteries of electric ship deplete quickly, making long journeys impossible. One of the solutions provided in prior art is to recharge at intermittent points throughout the journey. However, due to low recharging rate of the rechargeable batteries, recharging times are long, making the overall journey cumbersome and ultimately expensive.

[0007] Another important consideration which is particularly relevant for watercrafts, whether docked or at mid sea, is that they should always have power supply to operate essential systems. In case of a power system failure, redundancy should inherently be present in the design of the watercraft.

[0008] Therefore, a need remains to provide a means for powering electric watercrafts which would render them able to cover distances and speeds comparable to traditionally powered (i.e. diesel, other fuels) watercrafts while at the same time securing a safe journey.

[0009] SUMMARY OF THE INVENTION

[0010] The invention described herein provides a system according to claim 1 that solves the problems of the prior art. Specifically, the present invention provides a system for powering an electric watercraft arranged in the interior of said watercraft, said system comprising: a removable battery comprising a plurality of removable rechargeable battery stacks, wherein each battery stack comprises a plurality of electrically-coupled battery modules; wherein said battery stacks are arranged inside one or more battery frames configured to support said battery stacks; wherein each battery stack is electrically connected to a battery management system (BMS) configured to monitor a status of said battery stack and to manage the charging and discharging of said battery modules; a battery controller configured to electrically connect or disconnect said battery stacks to or from said system, wherein said controller is also configured to selectively electrically connect or disconnect one or more battery stacks to or from the system; and a non-removable rechargeable battery arranged to continuously provide power to nonmotor watercraft power consumers.

[0011] Said system is particularly suitable for powering electric watercrafts operating journeys consisting of one or more intermediate stops such as ferryboats. Replacing depleted or partially depleted battery modules with charged ones would solve the issue of long battery recharging times associated with prolonged stays in the harbor, thus making longer journeys with short intermediate stop possible. In addition, during the battery exchange process (i.e., replacing depleted battery stacks at intermediate stops) the disclosed system always provides power to essential elements of the watercraft, with the use of a modular battery with replaceable and non-replaceable elements.

[0012] The present invention also provides a method for powering an electric watercraft using the modular variable capacity electric power system disclosed herein, the method comprising the following steps in this order: a) determining the required electric capacity for a planned journey of said watercraft, based on the desired speed and the remaining distance to the next stop and / or final destination of the journey; b) placing said watercraft in data communication with external battery exchange apparatus at an intermediate stop, the battery exchange apparatus being configured to install battery frames with charged battery stacks into said watercraft and to remove battery frames with depleted and / or damaged battery stacks from said watercraft; c) at the intermediate stop removing, using the external battery exchange apparatus, one or more battery frames with depleted and / or damaged stacks from the watercraft; and d) installing, using the external battery exchange apparatus, one or more battery frames with charged battery stacks into said variable-capacity electric power system so as to additively provide at least said required electric capacity.

[0013] Other aspects and benefits of the present invention will become apparent from the detailed description to follow.

[0014] BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The present invention will now be described with reference to certain embodiments thereof which are illustrated in the accompanying drawings. It should be noted that the accompanying drawings illustrate preferred embodiments of the invention, therefore should not be considered as limiting the scope of the invention. It is also understood that the illustrations may include optional features which are not necessary in any embodiment.

[0016] Fig. 1 is a schematic presentation of the cross-sectional side view of a conventional electric watercraft according to the prior art. The watercraft is serviced by an external electric supply or charging station or internally via an Internal Combustion Engine (ICE) and carries a sizeable electrical energy storage unit or battery, encased in a sealed frame.

[0017] Fig. 2 is a schematic presentation of the cross-sectional side view of a watercraft bearing the system of the present invention.

[0018] Fig. 3 is a schematic presentation of a top view of a ship bearing the system of the present invention.

[0019] Fig. 4 is a schematic presentation of a top view of a battery frame disclosed herein.

[0020] Fig. 5 is a schematic presentation of a top view of a battery stack disclosed herein.

[0021] Fig. 6 is a schematic presentation of a cross sectional side view of a battery stack disclosed herein.

[0022] DETAILED DESCRIPTION OF THE INVENTION

[0023] The present disclosure provides a modular battery system comprising both removable and non-removable battery elements suitable for powering electric watercrafts. It also discloses a method for powering an electric watercraft using the modular variable capacity electric power system described herein.

[0024] The term “watercraft” as used throughout the description and claims refers to any vessel used in or on water as well as underwater, including ships, hydrofoils, ferries, hovercrafts, boats and submarines.

[0025] Electric watercrafts perform journeys that comprise one or more intermediate stops. Currently, electric watercrafts (Figure 1) are serviced by an external electric supply or charging station or internally via an Internal Combustion Engine (ICE) and carry a sizeable electrical energy storage unit or battery, encased in a sealed frame. Due to the high energy needs that result from moving at speeds comparable to traditionally powered watercrafts, the prior art batteries used to power electric watercrafts deplete quickly, making long journeys impossible. One of the solutions provided in prior art is to recharge at intermittent points throughout the journey. However, due to slow recharging rate of the rechargeable batteries, recharging times are long making the overall journey cumbersome and ultimately expensive. In addition, watercrafts used in the conditions mentioned above, usually carry people and / or other important cargo, meaning that the electric power system of the watercraft needs to always power essential systems, because a power failure in watercrafts has serious consequences such as inability to navigate, risk of collision, contact damage with a shore structure or running aground. Thus, the watercraft while in operation over the length of the journey including intermittent stops should always be powered from the battery system.

[0026] The inventor has found that by replacing the conventional watercraft batteries (1) with a system arranged in the interior of said watercraft (Figures 2 and 3) and comprising a modular removable battery (2) comprising one or more removable rechargeable battery stacks (3), the depleted battery stacks (3) can be exchanged with charged ones at intermediate stops, for instance at a harbour. An advantage of this system over the traditional watercraft batteries is that the depleted stacks (3) can be exchanged with charged ones at intermittent points throughout the journey at a fraction of the time needed to recharge non removable batteries.

[0027] Thus, according to the present invention, a system is provided for powering an electric watercraft arranged in the interior of said watercraft, said system comprising a battery with removable components comprising a plurality of removable rechargeable battery stacks (3), preferably at least two battery stacks (3). The number of stacks (3) that will provide enough energy for the watercraft to cover the minimum distance to the next service point can be easily determined by a person skilled in the field. Each battery stack (3) comprises a plurality of electrically-coupled battery modules (4). The chemical compositions for storing energy of the battery modules (4) may be chosen from LiFePO4, LCO (Lithium Cobalt Aluminum Oxide), Sodium-Ion, Lithium-Ion or other available types. A typical number of serially connected LIFePO4modules per battery stack is between 16 and 200, but other battery technologies will require adjustments to these values. The exact number of battery modules (4) is dependent upon the voltage level of the power bus (9) which in turn is determined by the power level and efficiency of the electric motor(s) (11).

[0028] The battery stacks (3) are arranged inside one or more battery frames (5) configured to support the battery stacks (3), so that multiple stacks (3) can be exchanged at the same time, further reducing the time needed to complete the battery exchange process. Thus, the removable battery (2) of the invention extends across multiple battery frames (5), each arranged to accommodate a plurality of loading configurations so that the battery frame (5) may be loaded on demand with a variable number of battery stacks (3), depending on the planned journey of said watercraft. Preferably, the battery frames (5) have a grid or cage-like structure.

[0029] Because watercrafts operate in unstable environmental conditions, the removable battery system (2) should be securely positioned in the interior of the watercraft. Preferably, each battery frame (5) is positioned inside a battery placeholder (15) as shown in the embodiment of Figure 2, each battery placeholder (15) being an integral part of the watercraft, with dimensions capable of securely admitting a battery frame (5).

[0030] As shown in Figures 4 and 5, each battery stack (3) has a battery management system (BMS) (6) installed inside it, wherein said BMS (6) is configured to monitor a status of the battery stack (3), such as temperature, voltage and current among others. The BMS (6) also manages the charging and discharging of battery modules (4). The BMS monitors in real time battery modules status (temperature, voltage, current etc.) and guarantees uniform use of battery modules (4) within the stack (3).

[0031] The system disclosed in the present invention also comprises a battery controller (7) shown in Figure 2, configured to electrically connect or disconnect the battery stacks (3) to or from said system. More specifically, the battery controller (7) selectively electrically connects a number of battery stacks (3) to the system, based on the battery supply needs of the watercraft and power needs of the electric motor(s) (11). Depending on the length of the journey, the battery controller (7) engages the needed stacks (3), based on the information provided by the BMS (6), that will provide enough energy to reach the destination or the next intermediate stop.

[0032] As shown in Figures 1 and 2, power from battery stacks reaches the engines via a Power Management Module (16). This module is responsible for receiving the power produced by the batteries in DC and transforming it to the form that will be used in the electric motor(s) (11). For example, in the specific design, the DC current from the batteries is transformed into AC with varying frequency in order to feed the AC motors and control the speed of rotation of the engines and connected propellers.

[0033] According to the present invention, the system disclosed is configured to always provide power to essential elements of the watercraft other than the motor(s) (11), such as but not limited to radio, navigation instruments, lights, heating, air conditioning, other passenger power needs, even during the battery exchange process. This is achieved with the use of a non-removeable rechargeable battery (8), shown in the embodiments of Figures 2 and 3, arranged to continuously provide power to non-motor watercraft power consumers. According to an embodiment, the non-removable battery (8) is charged either by the removable batteries during the journey or by external means during intermediate stops or by photovoltaic panels placed on the watercraft. In another embodiment, the nonremovable battery (8) is located in a separate watertight compartment of the ship, such that any water splashes created during the battery exchange process at the intermediate stop, such as from waves, cannot reach the non-removable battery (8) which is operating at all times.

[0034] Thus, a second advantage of the present system comprising both replaceable and non- replaceable rechargeable modules (4) is that it safely meets all watercraft energy demands by providing amounts of power / energy to electric engines and to other auxiliary needs of the watercraft in all situations, i.e. during the journey as well as during the battery exchange process at the intermediate stop.

[0035] The system described herein is applicable to all watercrafts and is particularly suitable for ships, hydrofoils, ferries, and more particularly useful for light watercrafts, such as hydrofoils and other planing hull watercrafts which move over the water and not by displacing it, due to the lower energy needs inherently needed to cover long distances. Said battery may be targeted to perform at least the equivalent level of 300 HP gas / diesel engines and higher; however, lower power levels are also possible. The present invention is applicable to electric motors across all power ranges but is particularly adapted for use in the upper end of the power range for high performance watercrafts, generally in the range of 30 HP to 10000 HP. The term “electric motor” as used herein includes both the electrical and the electronic equipment needed for the conversion of electrical power to watercraft propulsion. Power delivery from the motor to the propeller is outside the scope of this invention and can be achieved by any means already used, such as propellers or waterjets.

[0036] Upon reaching the destination or an intermediate stop, the used stacks (3) are removed from the ship and replaced with charged ones. Optionally, additional stacks (3) may be installed depending on the length of the planned journey ahead. Alternatively, upon reaching the destination or an intermediate stop, one or more unused stacks (3) may be removed from the watercraft and not replaced with charged ones, if the power needs to the next stop are lower than the power needs to arrive to the current stop. Thus, in said embodiments, each battery frame (5) is configured to accommodate a plurality of loading configurations so that each battery frame (5) can be loaded on demand with a variable number of said battery stacks (3).

[0037] In a separate embodiment, upon reaching an intermediate stop, one or more battery frames (5) may be removed from the watercraft if the power needs to the next stop are lower than the power needs to arrive to the current stop. In this way, the watercraft carries less weight. Thus, in said embodiment, the removable battery system (2) is configured to accommodate a plurality of loading configurations so that said battery system (2) can be loaded on demand with a variable number of battery frames (5).

[0038] According to another embodiment, in order to easily detach and attach battery frames (5) from / to the watercraft at the dock, each battery frame (5) may comprise integrated frame motors that move the battery frames (5) towards the outside of the ship hull, such that the frame (5) is easily reachable from an external battery exchange apparatus. For instance, the integrated frame motors may lift up the frame(s) (5), in the cases where the entrance to the battery compartment is on deck level, or push the frame(s) (5) to the side of the watercraft, in the cases where the entrance to the battery compartment is on a side wall of the watercraft. The battery frame(s) (5) can then be picked up by the battery exchange apparatus on the dock. By the reverse method, the new frame(s) are loaded on the ship: the frame(s) (5) are placed to the battery placeholder (15) and the integrated frame motors lower the frame(s) (5) inside the watercraft, or, in the cases where the entrance to the battery compartment is on a side wall of the watercraft, the external battery exchange apparatus will push the battery frame (5) into the placeholder (15) until it reaches the operational zone of the integrated frame motors. The external battery exchange apparatus may comprise a crane or other battery stack moving equipment. The alignment of the external battery exchange apparatus with the battery placeholder (15) for the loading and unloading to the watercraft is preferably achieved by the use of guides which are also an integral part of the battery placeholder(s) (15).

[0039] In an alternative embodiment, in order to easily remove and attach battery frames (5) from / to the watercraft at the dock, the system may comprise one or more motors attached to the watercraft interior and configured to move said one or more battery frames (5) towards the exterior of the watercraft, such that the frame (5) is easily reachable from an external battery exchange apparatus. For instance, the motors may lift up the frame(s) (5), in the cases where the entrance to the battery compartment is on deck level, or push the frame(s) (5) to the side of the watercraft, in the cases where the entrance to the battery compartment is on a side wall of the watercraft. The battery frame (5) can then be picked up by the battery exchange apparatus on the dock. By the reverse method the new frame(s) (5) are loaded on the ship: each frame (5) is placed to the battery placeholder and the motors lower the frame(s) (5) inside the watercraft or, in the cases where the entrance to the battery compartment is on a side wall of the watercraft, the external battery exchange apparatus will push the battery frame (5) into the placeholder (15) until it reaches the operational zone of the motors attached to the watercraft interior.

[0040] In a preferred embodiment, the battery frames (5) have an aerodynamic shape or comprise aerodynamic design elements that facilitate battery frame (5) loading and unloading in strong wind environments, thus reducing the turbulence and excess movement resulting from strong winds. Optionally, the battery stacks (3) also have an aerodynamic shape or comprise aerodynamic design elements. The term "aerodynamic shape" refers to the shape of an object configured to pass through air such that not as much turbulence and / or air resistance is generated around the object. Examples of such shapes are teardrop shape, spindle shape, cylindrical or spherical shape to name a few. Preferably, said shape is a spindle shape or a cylindrical shape, as schematically illustrated in Figure 4.

[0041] In a preferred embodiment, the system disclosed herein comprises at least one electrical power bus (9) configured to coupling said battery stacks (3), in parallel via their electrical connectors (latches), to the electric watercraft drive system. Each power bus (9) is electrically connected to the stack(s) (3) by means of one or more metal connectors provided on each battery stack (3). In a more preferred embodiment, the system comprises at least two power buses.

[0042] Turning to the embodiment of Figure 6, each battery stack (3) may be provided with watertight BMS latches (12) and watertight power bus latches (13). The role of these latches (12, 13) is to provide to the battery stack (3) a secure data and power connection, respectively, in an environment of high mechanical stress and humidity. The power bus latches (13) are metal connectors that connect the battery stacks (3) to a power bus (9). They have distinct polarity (plus or minus) and are capable of resisting strong vibration and shock. Preferably, the power bus latches (13) are also configured to operate in an environment prone to high water moisture, as will be explained below. The watertight BMS latches (12) are data connectors / adaptors providing data connectivity between the BMS (6) and battery controller (7). They also allow for secure locking and unlocking from the data network in a humid environment of high vibrations and shocks.

[0043] For the modular battery of the present invention to function properly, it is important to ensure that it operates in a watertight environment in order to achieve safe operation and prolong battery life. This may be achieved for instance by making the battery compartment watertight, e.g., by making the entrance to the battery compartment close in a watertight fashion. However, this only ascertains that water does not enter the compartment during the journey; moisture such as water droplets and water spray may enter the battery compartment during loading and unloading of the frames (5). Thus, in certain embodiments, each battery stack (3) is configured to operate in an environment prone to high water moisture. In certain preferred embodiments, the battery stacks (3) are coated with plastic or other water resistant material or with an electrically non conducting material such as non conductive ceramics (e.g aluminium oxide). Alternatively or in addition, the power bus latches (13) are configured to operate in an environment prone to high water moisture. In one embodiment, said power bus latches (13) are protected with a housing made from an electrically non conducting material (such as plastic) which is designed to allow metal to metal connection to the power bus. As another alternative, the power bus latches (13) are covered by a watertight housing which permits the movement of the latch during locking or unlocking from the power bus (9) while maintaining connectivity. As a separate alternative, the power bus latches (13) of each battery stack (3) may be coated with a thin layer of electrically conductive corrosion resistant material, such as the coatings described in PCT application WO 1998027620 Al. Preferably, each battery stack (3) is designed to withstand at least Ingress Protection Testing IPX3 based on the IEC 60529 standard.

[0044] Battery modules (4) have strict requirements on operating temperature limits. Temperature in each battery module is monitored by the stack BMS (6). During operation, heat that is emitted by the battery modules (4) has to be removed from the battery stacks (3). This is achieved depending on the cooling needs of the modules (4) either by:

[0045] 1. Placing holes through the body of the battery stacks (3). In this way, air is used to cool down battery modules by means of non forced air circulation.

[0046] 2. In cases where heat dissipation via non forced air circulation is not enough to cool down certain or all modules (4), a fan or multiple fans located at the bottom of each stack (3) will force air through the stack (3). 3. In cases where forced air circulation is not enough to keep temperatures within the operating limits in a specific module (4), a group of modules (4) or the totality of the modules (4) within a stack (3), an air-to-air heat exchanger can be placed on said battery module(s) (4).

[0047] 4. In case where all methods above do not achieve the heat dissipation needed, a liquid cooled heat exchanger will be used on each concerned module (4).

[0048] If needed, all of the above methods can be used together in the same stack (3).

[0049] Another important consideration for ensuring safe journey conditions for electric watercrafts is systems redundancy, that is, the watercraft while in operation over the length of the journey should have redundant power and control systems and the ability to switch between them in case of need. In addition, the watercraft while in operation over the length of the journey should be designed in way to limit the spread of faults and failures of either power or control systems with the aim of securing a safe journey.

[0050] Thus, in one embodiment, the system disclosed herein comprises a minimum number of battery stacks (3) to provide sufficient electric power supply for the watercraft to complete its planned journey and further includes at least one additional battery stack (3) to provide extended mileage for the watercraft.

[0051] Alternatively or in addition, the system disclosed herein comprises at least two electrical power buses (9) configured to coupling one or more battery stacks (3) to the electric motor(s) (11) of said watercraft via the Power Management Module (16). In this embodiment, in case of a short-circuit or failure of a power bus (9), power can be transmitted to the electric watercraft drive system via a separate power bus (9). Through this means, redundancy can be achieved while providing power from the battery stacks (3) to the motor(s) (11). Preferably, specific design elements such as physically separated power buses (9) as well as physically separated battery poles / latches that prohibit the mitigation of a fault to other systems are also utilized. As one can see in the embodiment of Figure 3, two separate power buses (9) are connected to physically separated groups of battery stacks (3), and the power buses (9) follow separate routes throughout the length of the watercraft. In this way any short-circuit or any other fault that may occur in any part of the one power bus (9) does not affect the other power bus(es) (9). This is very important for keeping the ship under power under any circumstances and ascertain a safe journey. Preferably, the battery controller (7) controls the connection of each battery stack (3) to one of the power buses (9), such that, in case of a short-circuit or other failure of a power bus (9), the battery controller (7) may disconnect the battery stack(s) (3) from one power bus (9) and connect them to another. The battery controller communicates with the Power Management Module (16) in order to efficiently delivery the energy from the batteries to the electric motor(s) (11).

[0052] Alternatively or in addition, the battery controller (7) is configured to connect to the BMS (6) of each battery stack (3), such that, based on the battery health status information received from the BMS (6), the battery controller (7) connects or disconnects one or more battery stacks (3) to the appropriate power bus (9). For instance, if certain stack(s) are damaged, under-performing or depleted, the battery controller (7) disconnects said battery stacks (3) from the power bus (9). In this embodiment, the battery controller (7) is able to connect and disconnect elements of the system with the scope of providing a safe journey even in a case of an element failure.

[0053] In the embodiments where the system disclosed herein comprises at least two electrical power buses (9), the battery controller (7) may be configured to connect to the BMS (6) of each battery stack (3), such that, based on status data received from each BMS (6), such as temperature, voltage and current among others, the battery controller (7) selectively connects to an appropriate power bus (9) or disconnects from a power bus (9) one or more battery stacks (3) in order to achieve optimization of power transmission.

[0054] In the embodiments where the system includes at least two power buses (9), a plurality of battery modules (4) of different types / chemical compositions can be accommodated concurrently, such as LiFePO4, LCO (Lithium Cobalt Aluminum Oxide), Sodium-Ion, Lithium-Ion, to name a few. That means that the watercraft can accommodate multiple different battery technologies or chemical compositions to achieve the most effective and efficient way to reach the next stop of the voyage. For example, in order to reach more distant destinations, the watercraft may use more energy-dense type batteries such as Lithium Cobalt Aluminum Oxide batteries which are more expensive and provide fewer recharging cycles while on shorter legs other battery types can be used, such as LiFePO4which provide more recharging cycles but lower energy density. Each power bus (9) can accommodate one type / chemical composition of battery at a given time. The number of different types / chemical compositions of the battery modules (4) accommodated may be at least as many as the power buses (9) included in the system. Thus, in the embodiments where the system includes at least two power buses (9), a first power bus (9) can be coupled to one type of battery type / chemical composition at a given time, and a second power bus (9) can be coupled to a different type. In this case, by selecting the first or the second power bus (9), the most suited type / chemical composition of battery module (4) available can be chosen for each part of the journey so as to optimize the energy consumption during the whole journey.

[0055] According to certain embodiments, the system of the present invention comprises at least one data network (10). A data network (10) is the means for the battery controller (7) to reach all elements of the watercraft defined in this invention. The connection between the BMS (6) of each battery stack (3), the battery controller (7), the Power Management Module (16) (if present) and the electric motor(s) (11), may be achieved via a data network, such as wired or wireless network. Optionally, the connection between the battery controller (7) and the integrated frame motors may also be achieved via a data network, such as wired or wireless network.

[0056] As one skilled in the relevant art would find apparent from the description, the embodiments described above are only examples of the present invention. Many other configurations or modifications are possible, as discussed in the present disclosure and as could be made by one skilled in the art without departing from the scope of the invention as defined by the claims. For instance, one or more functions of the battery controller (7) may be served by one or more separate controllers.

[0057] The present invention also discloses a method for powering an electric watercraft using the modular variable capacity electric power system described herein. According to an embodiment, said method comprises the following steps in this order: a) determining a required electric capacity for a planned journey of said watercraft. In this step the watercraft determines or estimates the minimum electrical power required to complete the planned journey. For example, a central processor or the battery controller (7) calculates the minimum electrical power required to reach the end of the journey, the first intermediate stop, or the first intermediate stop where a battery exchange station is available, preferably the first intermediate stop where a battery exchange station is available. b) placing said watercraft in data communication with external battery exchange apparatus at an intermediate stop, the battery exchange apparatus being configured to install battery frames (5) with charged battery stacks (3) into said watercraft and to remove battery frames (5) with depleted and / or damaged battery stacks (3) from said watercraft. In this step, the watercraft establishes a data communication link with the battery exchange station located at the intermediate stop, preferably with the external battery exchange apparatus at an intermediate stop, to communicate information regarding a status of each battery frame (5), such as the number of stacks (3) per frame (5), the energy status of each stack (3) and the number of defective or under- performing battery stacks (3). This communication may take place before the arrival to the intermediate stop or at the arrival at the intermediate stop and may be mediated by the central processor of the watercraft or a dedicated processor of the watercraft. Said status information is obtained from the BMS (6) of each battery stack (3). The external battery exchange apparatus configured to install battery frames (5) with charged battery stacks (3) into said watercraft and to remove battery frames (5) with depleted and / or damaged battery stacks (3) from said watercraft may be a crane or other battery stack moving equipment. c) at the intermediate stop removing, using the external battery exchange apparatus, one or more battery frames (5) with depleted and / or damaged stacks (3) from the watercraft. During this step that takes place at the battery exchange station at the intermediate stop, the external battery exchange apparatus removes one or more battery frames (5) that contain one or more battery stacks (3) that are depleted and / or damaged. d) installing, using the external battery exchange apparatus, one or more battery frames (5) with charged battery stacks (3) into said variable-capacity electric power system so as to additively provide at least said required electric capacity. During this step, the one or more battery frames (5) that were removed in step c) are replaced with one or more battery frames (5) that contain fully charged battery stacks (3).

[0058] In a preferred embodiment, the number of installed battery frames (5) in step d) is equal to the number of removed battery frames (5). In an alternative preferred embodiment, the number of installed battery frames (5) in step d) is greater than the number of removed battery frames (5). This might be the case where the power needs to the next stop is greater than the power needs to arrive to the current stop. In yet another alternative preferred embodiment, the number of installed battery frames (5) in step d) is smaller than the number of removed battery frames (5). This might be the case where the power needs to the next stop are lower than the power needs to arrive to the current stop.

[0059] The minimum electrical power required for a planned journey may be calculated using a central watercraft processor or the battery controller (7) using an algorithm, based on the desired speed and the remaining distance to the next stop and / or final destination of the journey. Other relevant parameters that may also be taken into consideration when programming the watercraft processor to determine the required electric capacity for a planned journey are battery technology, current weather conditions, current position and watercraft load, to name a few.

[0060] The exchange of the battery frames (5) may be facilitated by means provided by said system. According to a preferred embodiment, each battery frame (5) comprises integrated frame motors that move the battery frames (5) towards the outside of the ship hull, such that the frame (5) is easily reachable from an external battery exchange apparatus. For instance, the integrated frame motors may lift up the frame(s) (5), in the cases where the entrance to the battery compartment is on deck level, or push the frame(s) (5) to the side of the watercraft, in the cases where the entrance to the battery compartment is on a side wall of the watercraft. The battery frame(s) (5) can then be picked up by the battery exchange apparatus on the dock. By the reverse method, the new frames (5) are loaded on the watercraft: the frame(s) (5) are placed in the battery placeholder (15) and the frame motors lower the frame(s) (5) inside the watercraft. According to another preferred embodiment, the system may comprise one or more motors attached to the watercraft interior and configured to move the battery frames (5) towards the exterior of the watercraft, such that the frame (5) is easily reachable from an external battery exchange apparatus. For instance, the motors may lift up the frame(s) (5), in the cases where the entrance to the battery compartment is on deck level, or push the frame(s) (5) to the side of the watercraft, in the cases where the entrance to the battery compartment is on a side wall of the watercraft. The battery frame(s) (5) can then be picked up by the battery exchange apparatus on the dock. By the reverse method, the new frame(s) (5) are loaded on the ship. The frame(s) (5) are placed in the battery placeholder (15) and the motors lower the frame (5) inside the watercraft.

[0061] It will be appreciated that, during the battery exchange process, it is advisable that the removable battery (2) be disconnected from the power supply system for reasons of safety. In that embodiment, before the step of removing the battery frame(s) (5), the method comprises a step where the battery controller (7) sends a command to all removable stacks (3) to disconnect from the one or more power buses (9). During this step as well as in all subsequent battery frame (5) exchange steps taking place at the dock, the electrical power required for all watercraft power needs apart from propellant power is supplied by the non-removable rechargeable battery (8). According to a preferred embodiment, the nonremovable battery (8) is charged either by the removable batteries during the journey or by external means during intermediate stops or by photovoltaic panels placed on the watercraft. According to another preferred embodiment, the non-removable battery (8) is located in a separate watertight compartment of the ship, such that any water splashes created during the battery exchange process at the intermediate stop, such as from waves, cannot reach the non-removable battery (8) which is operating at all times.

[0062] Preferably, the data communication of the watercraft with the external battery exchange apparatus is achieved by establishing data communication between said battery controller (7) and said external battery exchange apparatus. The data transmitted over said link include the number of battery frames (5) to be detached and the number of battery frames (5) to be installed as well as their specific positions on the removable battery (2).

[0063] The watercraft can accommodate multiple different battery technologies or chemical compositions, to achieve the most effective and efficient way to reach the next stop of the voyage. In this configuration, at least one of the plurality of battery stacks (3) of the electric power system comprises battery modules (4) that have a chemical composition that is different from the chemical composition of battery modules (4) carried by other stack(s) (3). In this way, the energy consumption can be optimized during each part of the journey. Thus, according to a preferred embodiment, the method disclosed herein further comprises the step of selecting the battery stack(s) (3) that will be used for a specific part of the journey according to the chemical composition of the battery modules (4) carried by said stack(s) (3). The step of selecting the battery stack(s) (3) according to the chemical composition of their battery modules (4) is achieved by providing said system with at least two electrical power buses (9); coupling at least one of the at least two power buses (9) to one or more battery stacks (3) comprising battery modules (4) having a first chemical composition; and coupling at least one of the other power bus(es) (9) to one or more battery stacks (3) comprising battery modules (4) having a second chemical composition. In other words, each power bus (9) can accommodate one type / chemical composition of battery at a given time; at least one power bus (9) is coupled to battery stacks (3) carrying battery modules (4) having a first type of chemical composition; and at least one of the other power buses is coupled to battery stacks (3) carrying battery modules (4) having a different type of chemical composition.

[0064] As a person skilled in the art will readily appreciate, the above description is meant as an illustration of implementation of the principles this invention. This description is not intended to limit the scope or application of this invention in that the invention is susceptible to modification, variation and change, without departing from the scope of this invention, as defined in the following claims.

Claims

CLAIMS1. A system for powering an electric watercraft arranged in the interior of said watercraft, said system comprising: a removable battery (2) comprising a plurality of removable rechargeable battery stacks (3), wherein each battery stack (3) comprises a plurality of electrically-coupled battery modules (4); wherein said battery stacks (3) are arranged inside one or more battery frames (5) configured to support said battery stacks (3); wherein each battery stack (3) is electrically connected to a battery management system (BMS) (6) configured to monitor a status of said battery stack (3) and to manage the charging and discharging of said battery modules (4); a battery controller (7) configured to electrically connect or disconnect said battery stacks (3) to or from said system, wherein said controller (7) is also configured to selectively electrically connect or disconnect one or more battery stacks (3) to or from the system; and a non-removable rechargeable battery (8) arranged to continuously provide power to nonmotor watercraft power consumers.

2. The system according to claim 1, wherein said one or more battery frames (5) comprise integrated frame motors configured to move said one or more frames (5) towards the exterior of the watercraft, and / or vice versa, for facilitating the loading and / or unloading of said one or more battery frames (5) from the watercraft.

3. The system according to claim 1, further comprising one or more motors attached to the watercraft interior and configured to move said one or more battery frames (5) towards the exterior of the watercraft, and / or vice versa, for facilitating the loading and / or unloading of said one or more battery frames (5) from the watercraft.

4. The system according to any one of claims 1 to 3, wherein said one or more battery frames (5) and optionally the battery stacks (3) are aerodynamically shaped inorder to reduce turbulence resulting from strong winds during the loading or unloading of said one or more battery frames (5) to or from the watercraft.

5. The system according to any one of preceding claims, further comprising at least one electrical power bus (9) configured to coupling one or more battery stacks (3) to the electric watercraft drive system via a Power Management Module (16), said Power Management Module (16) being configured to distribute the power transmitted through the power buses to the electric motor(s) (11) of the watercraft; wherein said at least one power bus (9) is electrically connected to said battery stacks (3) by means of one or more metal connectors provided on each battery stack (3).

6. The system according to claim 5, comprising at least two electrical power buses (9) configured to coupling one or more battery stacks (3) to the electric motor(s) (11) via the Power Management Module (16) and arranged such that, in case of failure of a first power bus (9), power can be transmitted to the electric motor(s) (11) through a second power bus (9).

7. The system according to claim 6, wherein at least one of the plurality of battery stacks (3) of the electric power system comprises battery modules (4) having a first chemical composition and at least one of the other battery stacks (3) comprises battery modules (4) having a second chemical composition; and wherein at least one of the at least two power buses (9) is configured to electrically connect to one or more battery stacks (3) comprising battery modules (4) having a first chemical composition and at least one of the other power bus(es) (9) is configured to electrically connect to one or more battery stacks (3) comprising battery modules (4) having a second chemical composition, such that the battery module composition that is most suited to the energy needs of the watercraft can be chosen.

8. The system according to anyone of claim 5 to 7, wherein the battery controller (7) is configured to connect to the BMS (6) of each battery stack (3), such that, based on voltage and current status data received from each BMS (6), the battery controller (7)selectively connects to an appropriate power bus (9) or disconnects from a power bus (9) one or more battery stacks (3) in order to achieve optimization of power transmission.

9. The system according to any one of the preceding claims, wherein the battery controller (7) is configured to connect to the BMS (6) of each battery stack (3), such that, based on the battery health status information received from the BMS (6), the battery controller (7) selectively electrically disconnects damaged, under-performing or depleted stacks (3) from the system.

10. The system according to any one of claims 5 to 9, wherein the battery stacks (3) are configured to operate in an environment prone to high water moisture, wherein said battery stacks (3) are coated with an electrically non conducting material and wherein the metal connectors provided on each battery stack (3) are protected with a housing made from an electrically non conducting material and designed to allow for metal-to-metal connection to the power bus (9).

11. The system according to any one of the preceding claims, further comprising at least one data network (10) configured to communicate data between the BMS (6) of each battery stack (3), the battery controller (7) and the electric motor(s) (11), and optionally between the battery controller (7) and the integrated frame motors.

12. A method for powering an electric watercraft using the electric power system of anyone of claims 1 to 10, the method comprising the following steps in this order: a) determining the required electric capacity for a planned journey of said watercraft; b) placing said watercraft in data communication with external battery exchange apparatus at an intermediate stop, the battery exchange apparatus being configured to install battery frames (5) with charged battery stacks (3) into said watercraft and to remove battery frames (5) with depleted and / or damaged battery stacks (3) from said watercraft;c) at the intermediate stop removing, using the external battery exchange apparatus, one or more battery frames (5) with depleted and / or damaged stacks (3) from the watercraft; and d) installing, using the external battery exchange apparatus, one or more battery frames (5) with charged battery stacks (3) into said electric power system so as to additively provide at least said required electric capacity.

13. The method according to claim 12, wherein step c) further comprises moving said battery frame(s) (5) towards the exterior of the watercraft using motors integrated in the battery frames (5) or motors attached to the watercraft interior, in order to facilitate removal of said frame(s) (5) by the external battery exchange apparatus; and / or wherein step d) further comprises lowering said frames (5) towards the interior of the watercraft using motors integrated in the battery frames (5) or motors attached to the watercraft interior, in order to facilitate installation of said frame(s) (5) by the external battery exchange apparatus.

14. The method according to claim 12 or 13, further comprising after step b) the step b’) where, at said intermediate stop, the battery controller (7) sends a command to all removable stacks (3) to disconnect from the power bus(es) (9), and wherein, during step b’) and all subsequent steps, the electrical power for the non-motor watercraft power consumers is supplied by the non-removable rechargeable battery (8).

15. The method according to any one of claims 12 to 14, further comprising the step of using the external battery exchange apparatus to increase or decrease the total number of battery frames (5) installed in the electric power system.

16. The method according to any one of claims 12 to 15, wherein the data communication established during step b) is between the battery controller (7) and the external battery exchange apparatus, and wherein the data transmitted over said link include the number of battery frames (5) to be detached and the number of battery frames (5) to be installed.

17. The method according to any one of claims 12 to 16, further comprising the step of programming a watercraft processor to determine the required electric capacity for a planned journey of said watercraft, based on the required speed and the remaining distance to the next stop and / or final destination of the journey.

18. The method according to any one of claims 12 to 17, wherein, if at least one of the plurality of battery stacks (3) of the electric power system comprises battery modules (4) having a first chemical composition and at least one of the other battery stacks (3) comprises battery modules (4) having a second chemical composition, the method further comprises the step of selecting the battery stack(s) (3) that will be used for a specific part of the journey according to the chemical composition of the battery modules (4) carried by said stack(s) (3), thereby optimizing the energy consumption during said part of the journey.

19. The method according to claim 18, wherein the step of selecting the battery stack(s) (3) according to the chemical composition of their battery modules (4) is achieved by providing said system with at least two electrical power buses (9); coupling at least one of the at least two power buses (9) to one or more battery stacks (3) comprising battery modules (4) having a first chemical composition; and coupling at least one of the other power bus(es) (9) to one or more battery stacks (3) comprising battery modules (4) having a second chemical composition.

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