Battery safety system

Abstract

There is provided a system for improving the safety of a battery. The system is directed towards a first passive cooling system that comprises a support structure and a cooling circuit that comprises a plurality of cooling plates arranged in parallel. The support structure comprises a chassis member that houses a plurality of battery modules and a thermal bridge member that is in thermal communication with the chassis member and cooling plates. Accordingly, thermal energy emitted by a battery module is removed by the first passive cooling system without propagating to neighbouring battery modules.

Description

[0001] BATTERY SAFETY SYSTEM

[0002] FIELD OF INVENTION

[0003] The present disclosure generally relates to battery technology for use with yachts, sailboats, ships, and other waterborne vessels. In particular, the present disclosure relates to ensuring the safety of such batteries.

[0004] BACKGROUND OF THE INVENTION

[0005] Recent advances in electricity-powered transport systems and portable devices have led to increased use of batteries. For example, Lithium-ion (Li-ion) batteries have been a popular choice in many fields of technologies as they advantageously provide high energy density, low self-discharge rate, no memory effect, and high number of charge-discharge cycles.

[0006] However, an increasing use of batteries for marine applications, such as powering waterborne vessels, has also led to increased level of safety concerns. In particular, high energy density batteries are susceptible to overheating due to chemical heat generation and joule heating from the internal resistance of battery cells. Unchecked, this may lead to thermal runaway where an exothermic reaction triggers a chain reaction of further exothermic reactions in other areas of the battery. Thermal runaway may be initiated if a battery undergoes mechanical, electrical and / or thermal abuses, and may ultimately result in fire, explosion, and / or off-gas generation.

[0007] Accordingly, batteries and battery packs for use in the marine and automotive industries typically undergo rigorous testing. For example, marine battery packs must pass a strict thermal propagation test to ensure that a battery cell undergoing thermal runaway does not transfer excessive thermal energy to neighbouring cells, and thus prevents neighbouring battery cells from also undergoing thermal runaway. It is typically difficult to pass this test when using high energy density battery cells due to the volatile chemical composition of the cell.

[0008] Existing solutions address the above problems using one or more of: cylindrical cell technologies and thermal interface materials; fresh water flooding, or water / glycol pressurized filling; immersion cooling; the use of low energy density materials, and / or complex active cooling systems. However, each of these solutions has disadvantages. For example, the use of cylindrical cells presents extreme technical challenges when manufacturing large capacity battery packs, due to the large number of cell interconnects, manufacturing complexities, and lack of durability. The use of fresh water flooding for marine applications bears a significant weight penalty, thus affecting the performance of the waterborne vessel. The use of low energy density materials results in the size of the battery pack being much larger. Finally, more complex solutions, such as active cooling systems, may be prohibitively expensive to implement across a fleet of vehicles.

[0009] It is therefore desirable to provide a battery safety system that passively mitigates thermal energy propagating throughout a battery pack, for example during a thermal runaway event.

[0010] SUMMARY OF THE INVENTION

[0011] The invention is defined by the claims to which reference should now be made. Preferred features are outlined in the dependent claims.

[0012] According to a first aspect of the invention, there is provided a battery safety system comprising a first passive cooling system, the first passive cooling system comprising a support structure and a cooling circuit, the support structure comprising one or more chassis members and one or more thermal bridge members, the one or more chassis members at least partially defining a plurality of enclosures, each enclosure for housing a respective battery module, the cooling circuit comprising a plurality of cooling plates arranged in parallel, each cooling plate extending under one or more of the plurality of enclosures, and the one or more thermal bridge members being in thermal communication with each chassis member and each cooling plate. Embodiments according to the first aspect of the invention advantageously reduce thermal energy from propagating between neighbouring battery modules such that a first battery module entering thermal runaway does not cause a chain reaction in neighbouring battery modules. Advantageously, each chassis member is in thermal communication with each of the plurality of cooling plates via the thermal bridge members. This advantageously increases the cooling capability of the battery safety system significantly.

[0013] An embodiment of the invention further comprises a second passive cooling system comprising a respective vent gate for each of the plurality of enclosures and an exhaust duct in communication with each of the respective vent gates. This advantageously allows hot gasses, which may be produced by a battery module leading up to thermal runaway and which may contain substantial amounts of thermal energy, to be expelled from the battery module enclosure and directed away from other battery modules.

[0014] In another embodiment, each vent gate is configured to open at a threshold pressure and / or temperature. This advantageously ensures each battery module enclosure remains sealed unless and until the built up gasses within the battery module enclosure contain enough kinetic energy to be released. Advantageously, the threshold at which each vent gate opens may be configured such that thermal energy is vented from the battery module enclosure before the battery module enters thermal runaway. Ensuring the vent gates remain sealed up to a threshold pressure and / or temperature advantageously reduces thermal energy from outside the battery module enclosure from propagating into the battery module enclosure.

[0015] In another embodiment, each vent gate is configured to seal a respective one of the plurality of enclosures when in a closed configuration. Ensuring the vent gates remain sealed advantageously reduces thermal energy from outside the battery module enclosure from propagating into the battery module enclosure.

[0016] In another embodiment, each vent gate is integrally formed with the support structure. This advantageously simplifies the manufacturing process.

[0017] In another embodiment, the support structure has a thermal conductivity greater than 200 W / (mK). This advantageously enables the support structure to quickly and effectively conduct thermal energy away from each battery module.

[0018] In another embodiment, the support structure is formed of aluminium, gold, silver or copper. This advantageously enables the support structure to quickly and effectively conduct thermal energy away from each battery module.

[0019] In another embodiment, the one or more chassis members are formed of a first high thermal conductivity material, and the one or more thermal bridge members are formed of a second high thermal conductivity material. This advantageously enables the rate at which thermal energy is conducted away from each battery module by the chassis members and the thermal bridge members to be configurable.

[0020] In another embodiment, the one or more chassis members at least partially define the plurality of enclosures and, when in use, act as a heatsink to reduce propagation of thermal energy between the one or more adjacent battery modules. This advantageously ensures that each battery module is at least partially enclosed by a chassis member that conducts thermal energy away from each battery module before the thermal energy is able to propagate to an adjacent battery module.

[0021] In another embodiment, the thermal bridge members support the one or more chassis members and the plurality of cooling plates to provide a rigid structure. This advantageously provides a suitable housing for securely containing a plurality of battery modules.

[0022] In another embodiment the support structure comprises one or more strengthening elements. This advantageously enables the support structure to securely contain a plurality of battery modules.

[0023] In another embodiment, the support structure further defines one or more enclosures for housing electrical equipment. This advantageously prevents thermal energy from propagating to electrical circuitry for controlling the one or more battery modules housed by the support structure.

[0024] In another embodiment, the one or more cooling plates cooperate with the support structure to define the plurality of enclosures. This advantageously ensures that each battery module is at least partially enclosed by a cooling plate for conducting thermal energy away from the battery module.

[0025] In another embodiment, the cooling circuit contains a coolant, the cooling circuit being configured to provide the coolant to one or more battery modules to thereby decrease the temperature of the one or more battery modules. This advantageously increases the amount of thermal energy that may be removed from each battery module.

[0026] In another embodiment, the coolant is a liquid coolant or a gaseous coolant. This advantageously enables different types of coolant to be used, and provides a configurable rate at which thermal energy may be removed from a battery module.

[0027] An embodiment further comprises a fire suppressant module configured to provide a first fire suppressant material. This advantageously enables a fire to be prevented or extinguished. Another embodiment further comprises one or more dry break couplings configured to provide a second fire suppressant material. This advantageously enables a fire to be prevented or extinguished using a material provided external to the battery.

[0028] In a second aspect of the invention there is provided a battery system comprising the battery safety system according to the first aspect, and a plurality of battery modules, wherein each of the plurality of enclosures houses a respective one of the plurality of battery modules. Advantages of the second aspect of the invention are as described above for the first aspect of the invention.

[0029] In an embodiment of the invention, the plurality of cooling plates are in direct thermal communication with a contact surface of one or more of the battery modules. This advantageously increases the efficiency of thermal energy transfer from the battery modules to the cooling plates.

[0030] In another embodiment, each of the plurality of battery modules comprises at least one Li- ion battery cell. This advantageously reduces the manufacturing cost and complexity of the battery system.

[0031] BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The invention will be described in more detail, by way of example, with reference to the accompanying drawings, in which:

[0033] Figure 1 is a schematic diagram of an example waterborne vessel that incorporates aspects of the invention;

[0034] Figure 2 is a schematic diagram of an example electrical energy storage and distribution system suitable for implementing on a waterborne vessel;

[0035] Figure 3A is a schematic diagram of a battery pack;

[0036] Figure 3B is another schematic diagram of a battery pack;

[0037] Figure 4 is a schematic diagram of removing thermal energy from a battery pack using a first passive cooling system according to aspects of the invention;

[0038] Figure 5 is a schematic diagram of an end view of a battery pack, showing a plurality of vent gates; and

[0039] Figure 6 is a schematic diagram of removing thermal energy from a battery pack using a second passive cooling system according to aspects of the invention. The above figures are included to provide illustration and a further understanding of the various aspects and embodiments, and are incorporated in and constitute a part of this specification, but are not intended as a definition of the limits of the invention. In the figures, each identical or nearly identical component that is illustrated in various figures is represented by a like numeral. For purposes of clarity, not every component may be labelled in every figure.

[0040] DETAILED DESCRIPTION

[0041] It is to be appreciated that embodiments of the systems and methods discussed herein are not limited in application to the details of construction and the arrangement set forth in the following description or illustrated in the accompanying drawings. The systems and methods are capable of implementation in other embodiments and of being practiced or of being carried out in various ways. Examples of specific implementations are provided herein for illustrative purposes only and are not intended to be limiting. Also, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use herein of “including,” “comprising,” “having,” “containing,” “involving,” and variations thereof is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. References to “or” may be construed as inclusive so that any terms described using “or” may indicate any of a single, more than one, and all of the described terms.

[0042] Aspects and embodiments described herein generally relate to a battery safety system and method for use with yachts, sailboats, ships, and other waterborne vessels.

[0043] Figure 1 shows a waterborne vessel in the form of a monohulled vessel 100 provided with a hydrofoil system. The hydrofoil system comprises a controller 120 located within the hull 140 of vessel 100. A battery system 160 in accordance with the present invention is located adjacent controller 120, and in electrical communication with the controller 120. A foil 180 is located on the outer surface of the foil hull below the floating waterline 110. The foil 180 is connected to the hull 140 of vessel 100 by means of a vertical shaft 182, and a propeller 184 is mounted on the foil 180 for driving the vessel 100 through the water during travel.

[0044] The foil 180 may comprise a plurality of adjustment members operable to vary the lift characteristics of the vessel 100 during travel. Each adjustment member comprises a flap and associated actuator. Actuators can be either electric or hydraulic and may be integrated within foil 180 (as shown in figure 1) or may be located within the vessel 100 itself depending on the vessel size and associated foil size. Actuators operate to control the position of associated flaps to control the ship in heave (i.e. the ride height 130 relative to the floating water line 110), as well as the pitch, roll and thrust. Ride height 130 is shown in figure 1 and is based on the distance between the water surface (floating water line 110) and the foiling water line 120. Foiling water line refers to where the water free surface sits, relative to the foils / hull, while the boat is airborne. When the boat is floating, the water line is defined by how much the hull needs to sink to obtain the volume of displacement (under Archimedean hydrostatic force). When foiling, the foiling water line is the optimum between minimum foil immersion (the vertical part “shaft”) to reduce drag without having the elevator ventilating because of the free surface proximity.

[0045] Figure 2 shows a schematic diagram of an electrical energy storage and distribution system 200 that may form part of the waterborne vessel of Figure 1. As shown in Figure 2, the electrical energy storage and distribution system 200 may comprise: one or more battery packs 210; one or more battery modules 220; a power distribution unit (PDU) 230; an inverter 240; and a motor 250. Each battery module 220 includes a plurality of battery cells 222, and a battery management system (BMS) 224.

[0046] In the example shown in Figure 2, the PDU 230 controls and distributes the electrical power stored in the battery packs 210. This may be achieved by the PDU 230 interfacing with battery module 220A and battery module 220B in order to distribute the electrical power to an electrical motor 250 for driving propellor 184 via an inverter 240, which converts the DC power supply from the battery modules 220 into an AC power supply.

[0047] In some embodiments, the PDU 230 may also distribute electrical power to other electrical systems such as electrical displays, climate control systems, navigation and steering systems, etc. In some embodiments the PDU 230 may also provide protection against short circuits and current leaks.

[0048] A plurality of battery cells 222 may be combined to provide a battery module 220, and a plurality of battery modules may be combined to provide the battery pack 210.

[0049] Preferably, the battery cells 222 are Nickel-Cobalt-Manganese (NCM) Lithium-Ion pouch cells. However, it will be appreciated that any high energy density battery cell may be used. For example, the battery cell may have an energy density of at least 200 Wh / kg. In preferred embodiments, each battery module may comprise 24 pouch battery cells and has a nominal operating voltage of 44V. However, it will be appreciated that other battery module configurations may be used as part of the claimed invention. For example, each battery module may comprise 12 battery cells having two pieces of six cells in series (i.e. a 6s2p configuration) that has a nominal operating voltage of 21.6 V. The battery module may further comprise a plurality of sensors (not shown) that interface with a slave battery management system (BMS). The slave BMS receives data relating to the battery cells and battery module, for example cell voltage and cell temperature, and communicates the data to a master BMS 224 for the battery pack.

[0050] Preferably, the battery modules may be combined in a scalable mannerwithin a battery pack. In some embodiments, a battery pack may comprise 15 battery cells having one piece of fifteen cells in series (i.e. a 15s1p configuration). Preferably, such battery packs have a maximum capacity of approximately 103 kWh and a nominal voltage output of 660V.

[0051] In some embodiments, the BMS 224 is configured to receive sensor data relating to a battery module or battery cell, including the voltage, current and temperature. The BMS 224 may then calculate one or more parameters based on the sensor data, including electrical parameters and / or temperature parameters that are each associated with at least one battery module. Electrical parameters may include one or more of: a state of charge (SOC); a state of health (SOH); a state of function (SOF); power availability; total power cycles; energy throughput; and cell impedance. Temperature parameters may include the battery core temperature for each battery module. In some embodiments, the sensor data and calculated parameters may be stored in a database. The BMS 224 may also calculate power limits for each battery module given the current power usage and battery cell conditions.

[0052] The BMS 224 may configure one or more battery cells in the battery module based on the sensor data and calculated parameters in order to balance the relative voltage and SOC of each battery cell. This enables the BMS 224 to identify battery cells that are, or are at risk of becoming, over-charged or under-charged. When the BMS 224 identifies an imbalance between battery cells, the BMS 224 may enable cell-to-cell balancing to be performed. This may be achieved passively, for example using shunt resistors to expend excess charge stored in a battery cell. In other embodiments, the BMS 224 communicates with a battery charger that recharges the battery cells in order to configure the flow of charge to the battery. This may enable additional charge to be provided to under-charged battery cells or to prevent excess charge from being provided to over-charged battery cells.

[0053] Known battery systems in use in the marine industry suffer from a number of problems. Marine vessels with electric propulsion systems typically require a high voltage power supply that occupies minimal onboard space. Accordingly, many battery modules are typically connected together as a compact battery pack to provide power for the electric propulsion system. Additionally, multiple battery packs may be connected together to form a battery unit. However, it is well known such battery configurations are susceptible to overheating, which can lead to thermal runaway.

[0054] Typically, when a battery module overheats there are two different stages where thermal energy is released by the battery module. In a first stage, the battery module undergoes an exothermic reaction where the battery module rapidly heats up and emits off-gasses. In a second stage, the battery module releases the thermal energy generated during the exothermic reaction which is then often absorbed by neighbouring battery modules. Accordingly, the close proximity of the battery components (e.g. battery cell(s), battery module(s), battery pack(s), and / or battery unit(s)) means that it is even more difficult to adequately address the risk of thermal runaway in a first battery module from causing a chain reaction in neighbouring battery modules. This proximity amplifies the challenge of containing thermal runaway events within individual battery modules.

[0055] To mitigate this heightened risk, various known battery designs incorporate thermal barriers or insulating thermal bridge members between individual battery modules. These measures aim to impede the spread of thermal energy between neighbouring modules to reduce the likelihood that a thermal runaway event in a first battery module will trigger an adjacent, or neighbouring, module into also entering thermal runaway.

[0056] Nevertheless, batteries and battery packs for use in the marine and automotive sectors undergo rigorous testing to determine what effect a thermal runaway event within in a first battery module has on the battery pack as a whole. For example, the acceptance criterion for the VDA (Verband der Automobilindustrie) standard requires that when half of all cells within a test battery module experience thermal runaway, no adjacent battery modules enter thermal runaway. In other words, the propagation of heat energy between cells is prevented such that no neighbouring battery modules heat up to such an extent that they also enter thermal runaway. Importantly, the VDA standard requires the internal temperature of each battery module adjacent to the module experiencing thermal runaway to remain at or below 90°C. This test is then repeated three times to validate consistency and reliability.

[0057] Accordingly, aspects of the invention provide a battery pack configured to regulate the propagation of thermal energy between adjacent battery modules, such that a thermal runaway event does not propagate within the battery pack. More particularly, aspects of the invention relate to a battery safety system comprising a first passive cooling system that includes a support structure made of high thermal conductivity material and a cooling circuit in thermal communication with the support structure. When in use, thermal energy emitted by a battery module is transported to the cooling system via the support structure such that propagation of thermal energy within the battery pack, particularly to adjacent battery modules, is minimised.

[0058] Figure 3A shows an example of a battery pack 300 that includes a battery safety system in accordance with embodiments of the claimed invention. The battery pack 300 shown in Figure 3A is made up of a plurality of battery modules (not shown) enclosed within the battery pack, and includes a battery support structure 320, an exhaust duct 340 and a cooling circuit 360.

[0059] Figure 3B shows the battery pack 300 of Figure 3A without a battery pack casing, and thus illustrates the internal structure of the battery pack 300 in more detail.

[0060] Figure 3B shows that the battery pack 300 includes a plurality of battery modules

[0061] 350. Fifteen battery modules 350 are shown in the example battery pack of Figure 3B. As shown in the example of Figure 3B, the battery modules 350 may have a column- and / or row-oriented configuration such that the battery modules 350 are arranged in one or more columns by one or more rows. However, it will be understood that, in other embodiments, the battery modules 350 may be arranged in any other configurations resulting in one or more of the battery modules 350 having at least one neighbouring battery module 350.

[0062] Battery Support Structure

[0063] Figure 3B also shows that the battery support structure 320 preferably comprises a plurality of elements. The battery support structure 320 provides at least part of a chassis that encloses and supports the plurality of battery modules 350. More particularly, in preferred embodiments the support structure 320 comprises one or more chassis members 320A extending in a first direction and one or more thermal bridge members 320B extending in a second planar direction. In such cases, the one or more thermal bridge members 320B may be in thermal communication with the one or more chassis members 320A and the cooling circuit 360. The one or more thermal bridge members 320B are configured to support the chassis members 320A and one or more cooling plates of the cooling circuit such that the chassis members, cooling plates and thermal bridge members form a rigid structure. The thermal bridge members 320B may be configured to extend perpendicularly to the one or more chassis members 320A.

[0064] The support structure 320 is formed of a material, or a plurality of materials, having high thermal conductivity. In the context of this invention, it will be appreciated that “high thermal conductivity” means having a thermal conductivity of greater than 200 W / (mK). For example, the support structure 320 may be made manufactured of a metal, such as aluminium, gold, silver or copper. The support structure must also be capable of withstanding temperatures in excess of 600°C in order to function when a battery module undergoes a thermal event. In some embodiments, the battery support structure 320 may be made of a plurality of different high thermal conductivity materials. For example, the chassis members 320A may be formed of a first high thermal conductivity material while the thermal bridge members 320B may be formed of a second high thermal conductivity material. In other embodiments, only the thermal bridge members 320B are formed of a high thermal conductivity material. In some embodiments, the battery support structure 320 may further comprise one or more strengthening elements, for example an impact-resistant metal such as steel, which are not formed of a high thermal conductivity material.

[0065] As further described below, the battery support structure provides one or more enclosures for housing a respective one of the plurality of battery modules 350. Alternatively, as shown in the example of Figure 3B, one or more of the enclosures may house electrical components to enable proper functioning of the battery pack. This advantageously enables protection of electrical equipment within the battery pack.

[0066] Cooling Circuit

[0067] The battery pack 300 shown in Figures 3A and 3B further comprises a cooling circuit 360. In preferred embodiments, the cooling circuit 360 comprises a coolant supply path 362, one or more cooling plates 364, and a coolant return path 366. In the example shown in Figure 3B, a cooling plate 364 is provided for each row of battery modules 350 in the battery pack 300. Accordingly, as shown in Figure 3B, four cooling plates are provided in a parallel configuration. This advantageously order ensures that thermal energy is dissipated uniformly throughout the structure of the battery pack 300.

[0068] In some embodiments, the cooling circuit 360 may further comprise a coolant pump that moves a coolant through the cooling circuit.

[0069] It will be appreciated that any suitable coolant may be used in the cooling circuit. For example a liquid coolant, such as water and / or glycol, or a gaseous coolant, such as air or helium, may be used.

[0070] Thermal energy dissipated to the cooling plate 364 is removed by the coolant via the coolant return path and removed from the battery pack, for example via a heat exchanger. Thus, the cooling circuit 360 is configured to remove thermal energy generated by each of the battery modules 350, particularly in the event that a battery module overheats, catches fire, enters thermal runaway, or explodes. Optionally, the cooling circuit 360 further comprises a cooling fan that removes thermal energy from the heated coolant, and a condenser that removes thermal energy from the cooling circuit to prevent the cooling circuit from overheating.

[0071] In some embodiments, each of the cooling plates 364 extends under the battery module enclosures defined by the support structure 320, such that the cooling circuit is in thermal communication with the plurality of battery modules via the support structure. In such cases, the heat transfer between the battery modules 350 and the cooling plates 310 is facilitated by the thermal bridge provided by the high thermal conductivity support structure 320. In other embodiments, the support structure 320 cooperates with the cooling plates 310 to define the battery module enclosures.

[0072] Accordingly, the battery support structure 320 is configured to be in thermal communication with each cooling plate 364. Grounding the entire battery support structure 320, including all shielding between battery module enclosures, results in a very large structural area that surrounds each battery module and maximises the thermal energy transferred to the cold plates 364. Accordingly, both the chassis members 320A and thermal bridge members 320B function as heatsinks that quickly and efficiently transfer thermal energy to the nearest cooling plate 364 through conduction. Thermal energy may be passed from a battery module 350 to an enclosing chassis member 320A and / or thermal bridge member 320B through conduction, convection and / or radiation. Accordingly, the battery support structure 320 is configured to provide a high-conductivity thermal bridge between the battery modules 350 and the cooling circuit 360, thereby enabling thermal energy to be dissipated quickly and efficiently from the battery modules 350 to the cooling circuit 360, and thus away from the battery pack 300.

[0073] Alternatively, each cooling plate may also be in direct thermal communication with a contact surface of one or more respective battery modules 350 to provide direct cooling to the battery modules 350. In such embodiments, the combination of the cooling circuit and the support structure form the battery module enclosures. In embodiments where the cooling plates underlie one or more of the battery modules 350, such as in the example shown in Figure 3B, the cooling plates 364 may form part of the battery module enclosures by supporting and retaining the one or more battery modules 350.

[0074] In preferred embodiments, battery modules can be further thermally isolated from their neighbouring battery modules by ensuring that all structural battery module connections are located on the cold plate, and thus do not contribute to the propagation of thermal energy between neighbouring battery module enclosures.

[0075] First passive cooling system: cooling plates + high conductivity structure

[0076] Figure 4 illustrates how embodiments of the invention are able to regulate the temperature distribution of a battery pack 300 when a first battery module undergoes a thermal event, such as thermal runaway.

[0077] In the example of Figure 4, the temperature of a first battery module 350H rises such that the first battery module 350H undergoes a thermal event, such as thermal runaway, overheating, explosion, or a fire. In the example shown in Figure 4, the temperature of first battery module 350H exceeds 600°C.

[0078] In known battery packs, in such instances thermal energy will quickly spread from the first battery module to neighbouring battery modules 350N via conduction, convection and / or radiation. The temperature of the neighbouring battery modules 350N rises until those modules undergo a thermal event. In this way, a chain reaction can be established within the battery pack where thermal energy quickly propagates throughout all of the battery modules within the battery pack. Known solutions to this problem involve mitigating or slowing the propagation of thermal energy between neighbouring battery modules, typically by providing thermally insulating material between each battery module. By contrast, embodiments of the invention prevent thermal energy from propagating between neighbouring battery modules by providing increased conductivity between neighbouring battery modules. Although contrary to intuition, providing a high thermal conductivity path between neighbouring battery modules ensures that thermal energy produced by the affected battery module 350H is rapidly transported to an underlying cold plate 364 due to a high temperature gradient between the cold plate and the battery module 350H. This may be achieved via one or more contact surfaces of the battery module 350H and / or or via the high thermal conductivity structure 320. Accordingly, thermal energy is removed from the battery pack instead of propagating between neighbouring battery modules within the battery pack.

[0079] The high thermal conductivity structure 320 may provide a 2-dimensional and / or 3- dimensional grid structure that contains numerous heat transfer paths to one or more cold plates 364. Consequently, the temperature of the affected battery module 350H can be rapidly decreased during and after a thermal event by providing a number of pathways with high thermal conductance. The quick removal of thermal energy means that the temperature of neighbouring modules 350N does not significantly increase, even though the temperature of an adjacent battery module is extremely high. As shown in the example of Figure 4, the temperature of each of the neighbouring battery modules 350N does not exceed 90°C. Accordingly, embodiments of the invention conform with the requirements set out by the VDA (Verband der Automobilindustrie) standard.

[0080] The battery safety system may further comprise a second passive cooling system, comprising a corresponding vent gate for each of the plurality of battery module enclosures, and an exhaust duct in fluid communication with the vent gates. The vent gates cooperate with the support structure to enclose each of the plurality of battery modules in a corresponding battery module enclosure.

[0081] Vent Gates

[0082] Figure 5 shows a side-view of an example battery pack 300 having a plurality of vent gates 520 disposed in a chassis member 540. As shown in Figure 5, each battery module enclosure is provided with a respective outlet, valve or vent gate 520 to enable the relief of pressure within each battery module enclosure. Each vent gate 520 provides a breakable seal to the respective battery module enclosure. In the event that a particular battery module undergoes a thermal event, such as thermal runaway, overheating, explosion, or a fire then the respective vent gate will be deformed or destroyed at a threshold pressure and / or temperature, thus providing an opening to allow the built up gasses, flame and / or battery cell ejecta to be vented from the battery module enclosure. This advantageously enables significant amounts of thermal energy to be removed from the overheated battery module, and thus the battery pack. The vent gate 520 further advantageously prevents ingress of foreign materials, such as dust, gasses, flames and / or ejecta, into the battery module enclosure during operation.

[0083] Furthermore, the outlets, valves and vent gates 520, once opened, may optionally be configured to remain open permanently or semi-permanently. Accordingly, the vent gates may undergo plastic deformation that advantageously provides a mechanism-free valve that seals each battery module enclosure. This may also be advantageous for post-analysis, forensic, maintenance and repair purposes, as it would enable easy identification of the battery module 350 affected by the thermal event, overheating, explosion, or fire.

[0084] In some embodiments, the vent gates are provided integrally to the chassis member 320A shown in Figure 3B. In other embodiments, chassis member 540 containing the plurality of vent gates 520 is provided as a separate component of the battery pack 300. As shown in the example of Figure 5, the vent gates 520 may be implemented by making cut-outs in a single chassis member 540 forming a side of the battery pack 300. Implementing vent gates 520 integrally with the chassis member 540 enables easy and low-cost manufacturing, as well as making the gate structure more compact. However, it will be understood that, in other embodiments, the vent gates 520 may be implemented as separate parts from the chassis member 540. In such cases, the vent gates 520 may be attached to openings of the battery module enclosures. Optionally, the vent gate 520 may include one or more perforations, or regions of weakness that enable the chassis member 540 to be robust while enabling the vent gate 520 to detach or deform.

[0085] The vent gate 520 may be made of any material that is configured to deform at a threshold pressure and / or temperature, such as a thin metal or plastic. Such materials may be selected from materials that are known to deform and / or be destroyed at or near the temperatures and / or pressures that are indicative of a thermal event, overheating, explosion, or fire. Exhaust Duct

[0086] The battery pack 300 may further comprise an exhaust duct 340 for directing exhaust gasses and ejecta away from the battery pack. When a battery module overheats it is possible for the battery module to undergo outgassing, where the battery electrolyte rapidly evaporates and ignites. This can result in very high amounts of toxic and explosive gasses being generated within the battery cell or battery module, causing the cell or module to burst. The outgasses are then vented into the battery pack. The vented gasses are very hot, reaching temperatures of up to 850°C, and are often combined with other materials ejected from the battery module. Outgassing typically removes 15% of the mass of the battery module, and the remaining 85% of the battery module mass remains at an approximate temperature of 600°C during this time.

[0087] In preferred embodiments, the battery pack casing, chassis members 320A, thermal bridge members 320B and cooling circuit 360 together provide a plurality of enclosed volumes. These enclosed volumes may house a respective one of the plurality of battery modules 350. Accordingly, the battery pack 300 comprises a support structure and cooling circuit that provide a plurality of battery module enclosures that house a plurality of neighbouring battery modules. The battery module enclosures function to both remove thermal energy from a battery module, as described above, and to direct gasses, flames and / or ejecta away from the battery module and out of the battery pack via the exhaust vent 340, as further described below.

[0088] Second passive cooling system: vent gates + exhaust duct

[0089] In the event that the first passive cooling system is unable to prevent the temperature of an affected battery module 350H from exceeding a threshold temperature, and thus undergoing a thermal event such as thermal runaway, embodiments of the invention enable the removal of thermal energy through a second passive cooling system comprising the vent gates 520 and exhaust duct 340 described above. The second passive cooling system is configured to remove thermal energy contained by outgasses, flames and battery cell ejecta that may be released by the battery module during a thermal event. The efficient removal of outgas is important, because significantly more (over 2.5 times) thermal energy is released in the form of outgasses compared to the thermal energy that is retained within the battery module. In preferred embodiments, the vent gate 520 is configured to open in order to allow this thermal energy to be released from the battery module enclosure and directed away from the battery pack into the atmosphere via an exhaust duct as further described below.

[0090] Figure 6 shows a top-down view of the battery pack and battery safety system in operation, where the exhaust duct 340 cooperates with one or more vent gates 520 in order to direct the flow of gasses, flames and / or ejecta away from an overheating battery module 350 and out of the battery pack 300.

[0091] More specifically, Figure 6 shows four battery modules 350 that are each enclosed within respective battery module enclosures 610, which are defined by chassis members 320A, thermal bridge members 320B, and cooling circuit 360. One of the battery modules 350 undergoes a thermal event, such as thermal runaway, such that the battery emits gasses, flames and / or ejecta 620 within the battery module enclosure 610. The gasses, flames and / or ejecta 620 build up within the battery module enclosure 610 until a threshold pressure and / or temperature is reached, at which point the vent gate 520 of the battery module enclosure deforms or ruptures, releasing the emissions 620. The vented gasses, flames and / or ejecta 620 are contained within exhaust duct 340 and transported external to the battery pack, where they are dissipated into the atmosphere 630. Accordingly, the battery module enclosures 610, vent gates 520 and exhaust duct 340 may cooperate to minimise thermal energy transfer from a first battery module to a neighbouring battery module by transporting the gasses, flames and / or ejecta emitted by the first battery module away from the battery pack 300. This advantageously reduces the likelihood of a first thermal runaway event triggering a chain reaction throughout the battery pack 300.

[0092] Therefore, the battery safety system according to various embodiments of the present invention provides one or more passive solutions for containing a thermal event within a battery cell, module or pack.

[0093] However, it will be appreciated that the system described in the examples above may also be used in conjunction with an active cooling system. For example, in some embodiments, active emergency cooling may be provided in conjunction with the passive system described above. Such an active cooling system may be controlled by a dedicated control module.

[0094] Emergency Cooling In some embodiments, the above described passive system may be combined with one or more active systems to provide further measures for preventing thermal propagation within the battery.

[0095] For example, in some embodiments, the battery safety system may be configured to provide an emergency cooling mode. In normal operation, most components of the battery cooling circuit 360 will be run via a low voltage (12V) system with the exception of a refrigerant compressor, which is operated on a high-voltage (HV) DC link. However, when emergency cooling is enabled additional power is diverted to the battery cooling circuit 360. Accordingly, power from some or all of the remaining operable battery packs may be provided to the cooling circuit 360 and in some embodiments a total cooling power in the region of 10 kW may be achieved, even in high ambient temperature conditions.

[0096] In other embodiments, the battery safety system may comprise a first fire suppression system, which may be activated at the same time, or after, one or more battery cells enter thermal runaway. The first fire suppression system may be activated manually or automatically, for example based on temperature sensor data.

[0097] The first fire suppression system may comprise one or more fire suppressant modules that contain a first fire-suppressing material that is released into a battery casing to prevent or extinguish a fire. In embodiments where the fire-suppressing material is an aerosol, 120g of aerosol may be provided for battery packs having a capacity of up to 100 kWh. For battery packs having a capacity of between 100 kWh and 200kWh, 250g of aerosol may be provided.

[0098] However, even with the above additional active systems, it is not uncommon for thermal events within a battery pack to continue for hours or even days if all the latent heat produced cannot be effectively removed. Accordingly, in some embodiments each battery pack includes dry break couplings for receiving a second fire suppressant material that is provided externally to the battery casing.

[0099] For example, the second fire suppressant material may be provided by emergency responders or other support crew. In preferred embodiments, the second fire suppressant material may be fresh water or a high flow foam fire suppressant. In the above embodiments, the battery casing may have an ingress protection (IP) rating.

[0100] In such embodiments the IP rating is at least IP67, which guarantees complete protection against solids, such as dust, and water when immersed at a depth of up to 1 meter for 30 minutes. Ensuring the battery casing has an IP rating allows improved containment of a thermal event and improves the effectiveness of the fire suppression systems. This advantageously provides crew members with additional time to safely evacuate the vessel in an emergency.

[0101] The above detailed description of embodiments of the invention are not intended to be exhaustive or to limit the invention to the precise form disclosed. For example, while processes or blocks are presented in a given order, alternative embodiments may perform routines having steps, or employ systems having blocks, in a different order, and some processes or blocks may be deleted, moved, added, subdivided, combined, and / or modified. Each of these processes or blocks may be implemented in a variety of different ways. Also, while processes or blocks are at times shown as being performed in series, these processes or blocks may instead be performed in parallel, or may be performed at different times.

[0102] Furthermore, although the example described above relate to a battery safety system configured to improve the safety of a battery pack, it will also be understood that the principles of the present invention may be used to improve the safety of other suitable types of battery components and / or structures. For example, the battery safety system may be scaled down in order to prevent a thermal runaway event in a first battery cell from triggering a chain reaction in other neighbouring cells; or scaled up in order to prevent a thermal runaway event in a first battery pack from triggering a chain reaction in other neighbouring packs.

[0103] The teachings of the invention provided herein can be applied to other systems, not necessarily the system described above. The elements and acts of the various embodiments described above can be combined to provide further embodiments.

[0104] While some embodiments of the inventions have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the disclosure. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms. Furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the disclosure.

Claims

CLAIMS1. A battery safety system comprising: a first passive cooling system, the first passive cooling system comprising a support structure and a cooling circuit; the support structure comprising one or more chassis members and one or more thermal bridge members; the one or more chassis members at least partially defining a plurality of enclosures, each enclosure for housing a respective battery module; the cooling circuit comprising a plurality of cooling plates arranged in parallel, each cooling plate extending under one or more of the plurality of enclosures; and the one or more thermal bridge members being in thermal communication with each chassis member and each cooling plate.

2. The battery safety system of claim 1, further comprising a second passive cooling system comprising a respective vent gate for each of the plurality of enclosures and an exhaust duct in communication with each of the respective vent gates.

3. The battery safety system of claim 2, wherein each vent gate is configured to open at a threshold pressure and / or temperature.

4. The battery safety system of claim 2, wherein each vent gate is configured to seal a respective one of the plurality of enclosures when in a closed configuration.

5. The battery safety system of claim 2, wherein each vent gate is integrally formed with the support structure.

6. The battery safety system of claim 1 , wherein the support structure has a thermal conductivity greater than 200 W / (mK).

7. The battery safety system of claim 1 , wherein the support structure is formed of aluminium, gold, silver or copper.

8. The battery safety system of claim 1 , wherein the one or more chassis members are formed of a first high thermal conductivity material, and the one or more thermal bridge members are formed of a second high thermal conductivity material.

9. The battery safety system of claim 1 , wherein the one or more chassis members at least partially define the plurality of enclosures and, when in use, act as a heatsink to reduce propagation of thermal energy between the one or more adjacent battery modules.

10. The battery safety system of claim 1 , wherein the thermal bridge members support the one or more chassis members and the plurality of cooling plates to provide a rigid structure.

11. The battery safety system of claim 1 , wherein the support structure comprises one or more strengthening elements.

12. The battery safety system of claim 1 , wherein the support structure further defines one or more enclosures for housing electrical equipment.

13. The battery safety system of claim 1 , wherein the one or more cooling plates cooperate with the support structure to define the plurality of enclosures.

14. The battery safety system of claim 1 , wherein the cooling circuit contains a coolant, the cooling circuit being configured to provide the coolant to one or more battery modules to thereby decrease the temperature of the one or more battery modules.

15. The battery safety system of claim 14, wherein the coolant is a liquid coolant or a gaseous coolant.

16. The battery safety system of claim 1 , further comprising a fire suppressant module configured to provide a first fire suppressant material.

17. The battery safety system of claim 1, further comprising one or more dry break couplings configured to provide a second fire suppressant material.

18. A battery system comprising: the battery safety system of claim 1 ; anda plurality of battery modules, wherein each of the plurality of enclosures houses a respective one of the plurality of battery modules.

19. The battery system of claim 16, wherein the plurality of cooling plates are in direct thermal communication with a contact surface of one or more of the battery modules.

20. The battery system of claim 16, wherein each of the plurality of battery modules comprises at least one Li-ion battery cell.

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