Ventilation system

Abstract

An aircraft battery ventilation system 200 comprising a first battery module 212, a first battery container (220, Fig. 5) housing the module, and a first flow path extending from a coolant source 250

Description

FIELD OF THE INVENTION

[0001] The present invention relates to a battery ventilation system and to an aircraft comprising the same. BACKGROUND OF THE INVENTION

[0002] In modern aircraft, batteries are often used during pre-flight modes to supply power to various devices present on-board the aircraft.

[0003] Currently, Nickel-Cadmium batteries tend to be used for powering the various electrical and avionics systems on-board modern aircraft. However, in recent years, the aircraft industry has started to explore the use of alternative battery technologies, such as Lithium Ion (or Li-Ion) batteries.

[0004] One drawback with current Li-Ion battery technologies is that they are prone to overheating, particularly when the battery becomes over-charged or structurally damaged, which can lead to the generation of heat and gases which may cause neighbouring batteries to also overheat and fail.

[0005] The claimed invention aims to provide a solution to this issue. SUMMARY OF THE INVENTION

[0006] According to an first aspect of the present invention there is provided an aircraft battery ventilation system comprising a first battery module, a first battery container for housing said first battery module and a first flow path extending from a coolant source to an exhaust port of the aircraft, wherein the first flow path passes at least partially through the first battery container such that coolant passing from the coolant source to the exhaust port imparts a cooling effect on the first battery module.

[0007] Advantageously, by placing the first battery module in the flow path between the coolant source and the exhaust port, the flow of coolant from the coolant source to the exhaust port can be used to cool the battery module during use, thereby helping to prevent said battery module from overheating. more, since the first flow path is fluidly connected to the aircraft exhaust port, the aforementioned system is also able to jettison unwanted gases which may be generated by the battery module during use, which may otherwise potentially hamper the normal working of the battery module.

[0009] In exemplary embodiments, the coolant source is held at a first pressure, said first pressure being, greater than an ambient pressure.

[0010] Advantageously, the provision of a pressurised coolant source creates a differential pressure across the first battery container due to the difference in pressure between the coolant source and the ambient (low pressure) air on the outside of the aircraft. This provides a passive means for driving the flow of coolant across the first battery container and hence the system can be operated without having to draw power directly from the aircraft.

[0011] In exemplary embodiments, the coolant source is held at a pressure between 0.7 atm and 1 atm.

[0012] In exemplary embodiments, the coolant source is an air source.

[0013] In exemplary embodiments, the air source is air from a compartment of the aircraft (e.g., the avionics bay).

[0014] Advantageously, using air from a compartment of the aircraft allows the battery ventilation system to be implemented without requiring a dedicated coolant supply.

[0015] In exemplary embodiments, the system comprises a first check valve provided between the first battery container and the exhaust port, said first check valve being configured so as to prevent ambient air from flowing into the first battery container via the exhaust port.

[0016] Advantageously, the aforementioned check valve helps to prevent ambient air, and / or other unwanted gases, from flowing back up the outlet ducts into the first battery container.

[0017] In exemplary embodiments, the system comprises a second check valve provided between the first battery container and the coolant source. ageously, the provision of the aforementioned check valve helps to prevent unwanted gasses from the first battery container from flowing into compartments of the aircraft.

[0019] In exemplary embodiments, the system further comprises a second battery module, a second battery container for housing said second battery module, and a second flow path extending from the coolant source to the exhaust port of the aircraft, wherein the second flow path passes at least partially through the second battery container such that coolant passing from the coolant source to the exhaust port imparts a cooling effect on the second battery module.

[0020] Advantageously, the provision of a second flow path helps to further prevent the second battery module from overheating during use. Furthermore, providing first and second battery modules in separate containers helps to prevent heat generated during operation of the first battery module from passing to the second battery module (and vice versa).

[0021] In exemplary embodiments, the system comprises a third check valve provided between the second battery container and the exhaust port, said third check valve being configured so as to prevent ambient air from flowing into the second battery container via the exhaust port.

[0022] Advantageously, the aforementioned check valve helps to prevent ambient air, and / or other unwanted gases, from flowing back up the outlet duct into the second battery container.

[0023] In exemplary embodiments, the second flow path comprises a fourth check valve provided between the second battery container and the coolant source.

[0024] Advantageously, the provision of the aforementioned check valve helps to prevent unwanted gasses from the second battery compartment from flowing into compartments of the aircraft.

[0025] In exemplary embodiments, the first flow path comprises a first outlet duct arranged so as to provide a fluid connection between an outlet of the first battery container and the exhaust port, and the second flow path comprises a second outlet duct to provide a fluid connection between an outlet of the second battery container and the exhaust port.

[0026] Advantageously, the provision of first and second outlet ducts helps to prevent the system from becoming overloaded in the unlikely event of both first and second battery modules simultaneously overheating.

[0027] In exemplary embodiments, the first and second flow paths share a common inlet duct arranged so as to provide a fluid connection between respective inlets of the first and second battery containers and the coolant source.

[0028] Advantageously, the provision of a common inlet duct helps to reduce the amount of ducting required to implement the claimed system. This provides a weight saving benefit and also helps to reduce the cost and complexity of the system.

[0029] In exemplary embodiments, the first and second battery modules comprise constituent parts of the same battery unit.

[0030] In exemplary embodiments, the first and second battery modules comprise constituent parts of different battery units.

[0031] In exemplary embodiments, the first and / or second battery container comprises a thermally insulating material.

[0032] Advantageously, this provision helps to prevent heat generated from the first battery module during use from passing to the second battery module. Consequently, in the event that the first battery module starts to overheat, this feature helps to prevent neighbouring modules (such as the second battery module) from also overheating.

[0033] In exemplary embodiments, the first and / or second battery modules comprise a plurality of battery cells.

[0034] In exemplary embodiments, the plurality of battery cells are Lithium Ion (Li-ion) battery cells.

[0035] According to a second aspect of the present invention, there is provided an aircraft comprising the aircraft battery ventilation system according to the first aspect of the present invention. ing to a third aspect of the invention, there is provided a ventilation system for an aircraft battery comprising a battery module and a battery casing for housing said battery module, wherein the battery casing comprises an inlet fluidly connected to a coolant source, said inlet being configured so as to permit the ingress of coolant from the coolant source into the battery casing, and wherein the battery casing further comprises an outlet fluidly connected to the ambient atmosphere, said outlet being configured to permit the egress of coolant and / or other gases from the battery casing to the ambient atmosphere.

[0037] We consider the term “check valve” to be defined as a valve which allows the flow of fluids in only a single direction across the valve.

[0038] We consider the term “pressurised” to be defined as having a pressure which is greater than an ambient pressure at a given altitude.

[0039] We consider the term “thermally insulating material” to be defined as a material having a thermal conductivity of 0.1 W nr1 K d or less.

[0040] We consider the term “fluid” to encompass both liquids and gases. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Embodiments of the invention will now be described with reference to the accompanying drawings, in which:

[0042] Figure 1 is a plan view of an aircraft to which the battery ventilation system of the present invention may be applied;

[0043] Figure 2 is a side view of the aircraft depicted in Figure 1;

[0044] Figure 3 is a schematic view of a battery ventilation system according to an embodiment of the present invention;

[0045] Figure 4 is a perspective view of a battery unit of the battery ventilation system depicted in Figure 3; and

[0046] Figure 5 is an exploded view of a battery module and battery container of the battery unit depicted in Figure 4. ESCRIPTION OF EMBODIMENT(S)

[0047] Figures I and 2 illustrate a fixed wing aircraft 100 which is an example of one potential type of aircraft to which the battery ventilation system according to the present invention may be applied.

[0048] The fixed wing aircraft 100 depicted in Figures 1 and 2 has a port wing 102 and a starboard wing 103 carrying engines 104a, 104b on pylons.

[0049] Each wing 102, 103 of the aircraft 100 has a cantilevered structure with a length extending in a span-wise direction from a root to a tip, the root being joined to an aircraft fuselage 106. The fuselage 106 has a nose 107 and a tail 108, which forms the empennage of the aircraft 100, where respective vertical 109 and horizontal 110a,b stabilisers of the aircraft 100 are located.

[0050] Although not shown in Figures 1 and 2, one or more batteries are provided onboard the aircraft 100 for providing power to the various electrical and avionics systems on-board the aircraft 100 during pre-flight phases, for starting one or more of the aircraft engines 104a,b and / or for starting the auxiliary power unit (not shown).

[0051] In some embodiments, the one or more batteries may be located within the avionics bay 120 of the aircraft 100, which is a compartment of the fuselage 106 located proximal to the nose 107 of the aircraft, typically situated below the flight deck 124 and above the nose landing gear 126. However, it shall be appreciated that in other embodiments, the one or more batteries may be provided in other locations about the aircraft 100.

[0052] A battery ventilation system 200 according to an embodiment of the present invention shall now be described with reference to Figure 3.

[0053] The battery ventilation system 200 has a first battery unit 210 which is made up of a first battery module 212, a second battery module 214 and a first battery control unit (or BCU) 216, which is electrically connected to the first 212 and second 214 battery modules. As such, the first 212 and second 214 battery modules and the first battery control unit 216 are constituent parts of the first battery unit 210.

[0054] The battery ventilation system 200 also features a second battery unit 310, which is arranged in parallel to the first battery unit 210. ond battery unit 310 is made up of a third battery module 312, a fourth battery module 314 and a second battery control unit (or BCU) 316, which is electrically connected to the third 312 and fourth 314 battery modules. As such, the third 314 and fourth 314 battery modules and the second battery control unit 316 are constituent parts of the second battery unit 310.

[0056] The first, second, third and fourth battery modules are each made up of a plurality of battery cells which store chemical energy and, when required, convert said chemical energy into electrical energy which can be used to power the various electrical and avionics systems provided on-board the aircraft 100. The number of battery cells which make up each module is selected based on the energy demand of the aircraft 100 or based on the energy demand of the application for which the battery unit is intended.

[0057] In the illustrated embodiment, the battery modules are lithium-ion battery modules and hence the first, second, third and fourth battery modules are each made up of a plurality of lithium-ion battery cells. However, it shall be appreciated that in other embodiments, the battery ventilation system according to the present invention made be used with battery modules made up of different types of cells.

[0058] It shall also be appreciated that whilst the illustrated embodiment depicts a system comprising a pair of battery units which are made up of two battery modules, it shall be appreciated that in other embodiments, the battery ventilation system may have a different number of battery units such a 1, 3, 4, 5, 6, 7, 8,9, 10 etc. and the respective battery units may have a different number of battery modules such as 1, 3, 4, 5, 6, 7, 8, 9, 10, etc.

[0059] The first battery unit 210 is illustrated in greater detail in Figure 4.

[0060] As shown in Figure 4, the first 212 and second 214 battery modules (which make up the first battery unit 210) are housed within respective first 220 and 230 second battery containers.

[0061] The first 220 and second 230 battery containers are configured to thermally isolate the first battery module 212 from the second battery module 214 such that heat generated by the first battery module 212 is not passed to the second battery module 214 (or vice versa). ’h not shown in Figure 4, the third 312 and fourth 314 battery modules (which make up the second battery unit 310) are also housed within their own respective containers which are configured to thermally isolate the third battery module 312 from the fourth battery module 314. As such, heat generated by the third battery module 312 is not passed to the fourth battery module 314 (or vice versa).

[0063] Furthermore, since each of the first, second, third and fourth battery modules are housed within their own respective containers, the first 212 and second 214 battery modules of the first battery unit 210 are also thermally isolated from the third 312 and fourth 314 battery modules of the second battery unit 310. As such, heat generated by the first 212 or second 214 battery modules is not passed to the third 312 or fourth 314 battery modules (and vice versa).

[0064] The first battery container 220 shall now be described in greater detail with reference to Figure 5.

[0065] It shall also be appreciated that the battery containers used for housing the second, third and fourth battery modules are of a substantially identical construction to that of the first battery container 220 and so, for the sake of conciseness, the second, third and fourth battery containers shall not be described in further detail.

[0066] As shown in Figure 5, the first battery container 220 has an outer casing 222 having a hollow body which defines a cavity 222a for receiving the first battery module 212 and a lid 226 for fluidly sealing the cavity 222a defined by the outer casing 222.

[0067] In the illustrated embodiment, a layer of thermally insulating material 224 is disposed around a circumference of the cavity 222a to provide the first battery container 220 with the requisite insulating properties required to thermally isolate the battery module 212 contained therein from neighbouring battery modules.

[0068] However, it shall be appreciated that in other embodiments, the outer casing 222 may itself be formed from a thermally insulating material and hence, in some embodiments, the provision of a separate layer of thermally insulating material provided within the cavity may be omitted.

[0069] In the illustrated embodiment, the lid 226 is formed from the same material as that which is used for the layer of a thermally insulating material thereby further helping t from escaping the first battery container 220. However, it shall be appreciated that in other embodiments, the lid 226 may be made from a different material, and a layer of thermally insulating material may instead be arranged on an underside of the lid 226.

[0070] The first battery container 220 is provided with an inlet 221, which is configured to permit the ingress of fluid into the cavity 222a defined by the outer casing 222, and an outlet 223, which is configured to permit the egress of fluid from within the cavity 222a to a location external to the cavity 222a.

[0071] The first battery container 220 also features an electrical connector 225 for facilitating electrical connection between the first battery module 214 (housed within the cavity 222a) and the first battery control unit 216.

[0072] In the illustrated embodiment, the inlet 221, the outlet 223 and the electrical connector 225 are provided on the lid 226. However, it shall be appreciated that in other embodiments, the inlet 221, the outlet 223 and the electrical connector 225 may be provided at different locations about the first battery container 220.

[0073] The first, second, third and fourth battery containers are provided with respective inlets to facilitate cooling of the battery modules contained therein during normal operation as shall be described in greater detail below. This helps to prevent the battery modules of the present invention from overheating during use.

[0074] The first, second, third and fourth battery containers are provided with respective outlets to allow used coolant and / or other unwanted gases, which may be generated during operation of the respective battery modules, to be jettison from the aircraft as shall also be described in greater detail below. This helps to prevent such gases, which would otherwise be stored within the respective battery containers, from potentially hampering the normal operation of the battery modules.

[0075] Referring back to the battery ventilation system 200 illustrated in Figure 2, the inlet 221 of the first battery container 220 is fluidly connected to a coolant source 250 via an inlet duct 240.

[0076] In the illustrated embodiment, the coolant source 250 is a source of pressurised air. More particularly, the coolant source 250 is pressurised air taken from an internal )f the aircraft fuselage 106, in this instance the avionics bay 120. However, it shall be appreciated that in other embodiments, the coolant source may be pressurised air from a different compartment of the aircraft, may be pressurised air provided from a cannister or may be a different type of fluid.

[0077] The inlet duct 240 has a common inlet 242, which is fluidly connected to the coolant source 250, and a plurality of outlets 244a-d which branch off from the inlet 242. Each of the plurality of outlets 244a-d are fluidly connected to an inlet of a respective one of the first, second, third or fourth battery containers. The first outlet 244a is fluidly connected to the inlet 221 of the first battery container 220, the second outlet 244b is fluidly connected to the inlet of the second battery container 230, the third outlet 244c is fluidly connected to the inlet of the third battery container and the fourth outlet 244d is fluidly connected to the inlet of the fourth battery container.

[0078] In the illustrated embodiment, the first 210 and second 310 battery units have a total of four battery modules, and hence the inlet duct 240 has four outlets, one for each battery container. However, it shall be appreciated that in other embodiments featuring a different number of battery modules, a different number of outlets may be provided.

[0079] Advantageously, the provision of a common inlet duct helps to reduce the amount of ducting required to implement the battery ventilation system of the present invention, thereby achieving a cost and weight saving benefit.

[0080] However, it shall be appreciated that in other embodiments, separate inlet ducts may be provided for fluidly coupling each battery container to the coolant source. Furthermore, in some embodiments, separate coolant sources may be provided for each battery container.

[0081] A series of check valves 261-264 are provided at each outlet 244a-d of the inlet duct 240.

[0082] A first check valve 261 is provided at the first outlet 244a between the inlet of the first battery container 220 and the coolant source 250, a second check valve 262 is provided at the second outlet 244b between the inlet of the second battery container 230 and the coolant source 250, a third check valve 263 is provided at the third outlet 245c between the inlet of the third battery container and the coolant source 250 and a fourth )4 is provided at the fourth outlet 244d between the inlet of the fourth battery container and the coolant source 250.

[0083] The plurality of check valves 261-264 are each configured to permit the flow of fluid from the coolant source 250 into the respective battery containers but are configured to substantially prevent the flow of fluid in the opposite direction (i.e., from the battery containers towards the coolant source). Advantageously, this helps to prevent unwanted gases (which may be generated during operation of the battery modules) from flowing back up the inlet duct 240 and into compartments of the aircraft 100.

[0084] Considering now the downstream portion of the battery ventilation system 200, the outlets of the first 220 and second 230 battery containers are fluidly connected to an exhaust port 280 via a first outlet duct 270.

[0085] The exhaust port 280 is provided in the aircraft fuselage 106 and is configured for jettisoning coolant, or other unwanted fluids, from the aircraft 100 into the external atmosphere.

[0086] In the illustrated embodiment, the first outlet duct 270 is provided in the form of a “T-duct” having a first inlet 272a, which is fluidly connected to the outlet 223 of the first battery container 220, a second inlet 272b, which is fluidly connected to the outlet of the second battery container 230 and an outlet 274, which is fluidly connected to the exhaust port 280.

[0087] In the illustrated embodiment, the first battery unit 210 comprises a total of two battery modules, and hence the first outlet duct 270 has two inlets, one for each battery container. However, it shall be appreciated that in other embodiments featuring a different number of battery modules, a different number of inlets may be provided.

[0088] Advantageously, the provision of a common outlet duct fluidly connecting the outlets of the first 220 and second 230 battery containers to the exhaust port 280 helps to reduce the amount of ducting required to implement the battery ventilation system of the present invention, thereby achieving a cost and weight saving benefit.

[0089] However, it shall be appreciated that in other embodiments, separate outlet ducts may be provided for fluidly coupling the first and second battery containers to the Furthermore, in some embodiments, separate exhaust ports may be provided for each battery container.

[0090] A second outlet duct 290 is also provided for fluidly connecting the respective outlets.

[0091] As with the first outlet duct 270, the second outlet duct 290 is provided in the form of a “T-duct” having a first inlet 292a, which is fluidly connected to the outlet of the third battery container, a second inlet 292b, which is fluidly connected to the outlet of the fourth battery container and an outlet 294, which is fluidly connected to the exhaust port 280.

[0092] In the illustrated embodiment, the second battery unit 310 comprises a total of two battery modules, and hence the second outlet duct 290 has two inlets, one for each battery container. However, it shall be appreciated that in other embodiments featuring a different number of battery modules, a different number of inlets may be provided.

[0093] Advantageously, the provision of a common outlet duct fluidly connecting the outlets of the third and fourth battery containers to the exhaust port 280 helps to reduce the amount of ducting required to implement the battery ventilation system of the present invention, thereby achieving a cost and weight saving benefit.

[0094] Furthermore, the provision of separate outlet ducts for the first 210 and second 310 battery units helps to prevent the battery ventilation system 200 from becoming overloaded in the unlikely event of battery modules in both the first 210 and second 310 battery units simultaneously overheating.

[0095] However, it shall be appreciated that in other embodiments, separate outlet ducts may be provided for fluidly coupling the third and fourth battery containers to the exhaust port. Furthermore, in some embodiments, separate exhaust ports may be provided for each battery container.

[0096] A series of check valves 265-268 are provided at the respective inlets 272a, 272b, 292a, 292b of the first 270 and second 290 outlet ducts.

[0097] A fifth check valve 265 is provided at the first inlet 272a of the first outlet duct 270 between the outlet of the first battery container 220 and the exhaust port 280, a sixth check valve 266 is provided at the second inlet 272b of the first outlet duct 270 between ; second battery container 230 and the exhaust port 280, a seventh check valve 267 is provided at the first inlet 292a of the second outlet duct 290 between the outlet of the third battery container and the exhaust port and a eighth check valve 268 is provided at the second inlet 292b of the second outlet duct 290 between the outlet of the fourth battery container and the exhaust port.

[0098] The plurality of check valves 265-268 are each configured to permit the flow of fluid from the respective battery containers towards the exhaust port 280 but are configured to substantially prevent the flow of fluid in the opposite direction (i.c., from the exhaust port 280 into the battery containers). Advantageously, this helps to prevent ambient air, and / or other unwanted gases, from flowing back up the outlet ducts into the battery containers.

[0099] The operation of the battery ventilation system 200 shall now be described with reference to Figure 2. In particular, a series of flow paths are defined by the battery ventilation system 200 which extend between the coolant source 250 and the exhaust port 280 which are used to impart a cooling effect on the respective battery modules during use.

[0100] A first flow path of the battery ventilation system 200 extends from the coolant source 250, along the inlet duct 240 and into the first battery container 220 via the first outlet 244a which is fluidly connected to the inlet 221 of the first battery container 220.

[0101] The first flow path further extends from the first battery container 220, along the first outlet duct 270 (which is fluidly connected to the outlet 223 of the first battery container 220) to the exhaust port 280 provided in the aircraft fuselage 106.

[0102] A second flow path of the battery ventilation system 200 extends from the coolant source 250, along the inlet duct 240 and into the second battery container 230 via the second outlet 244b which is fluidly connected to the inlet of the second battery container 230.

[0103] The second flow path further extends from the second battery container 230, along the first outlet duct 270 (which is fluidly connected to the outlet of the second battery container 230) to the exhaust port 280 provided in the aircraft fuselage 106. flow path of the battery ventilation system 200 extends from the coolant source 250, along the inlet duct 240 and into the third battery container via the third outlet 244c which is fluidly connected to the inlet of the third battery container.

[0105] The third flow path further extends from the third battery container, along the second outlet duct 290 (which is fluidly connected to the outlet of the third battery container) to the exhaust port 280 provided in the aircraft fuselage 106.

[0106] Finally, a fourth flow path of the battery ventilation system 200 extends from the coolant source 250, along the inlet duct 240 and into the fourth battery container via the fourth outlet 244d which is fluidly connected to the inlet of the fourth battery container.

[0107] The fourth flow path further extends from the fourth battery container, along the second outlet duct 290 (which is fluidly connected to the outlet of the fourth battery container) to the exhaust port 280 provided in the aircraft fuselage 106.

[0108] The aircraft battery ventilation system 200 illustrated in Figure 2 is made up of four battery modules and hence four flow paths are provided, each being configured to impart a cooling effect on a respective one of the battery modules. However, it shall be appreciated that in other embodiments (such as where the number of battery modules is less than or more than four) a different number of flow paths may be provided.

[0109] During the cruise flight phase, the internal compartments of the aircraft fuselage 106 are held at a first pressure, which is typically between 0.7 atm. to 1 atm.

[0110] Meanwhile, the external (or ambient) pressure at cruising altitude (generally between 9000m and 1200m above sea level) has a second pressure, typically between 0.2 atm. and 0.3 atm., which is less than the first pressure.

[0111] In the illustrated embodiment, the coolant source is a pressurised compartment of the aircraft (more particularly the avionics bay) and hence is held at a pressure between 0.7 atm. and 1 atm. Meanwhile, the exhaust port 280 is in fluid communication with the ambient atmosphere (having a pressure between 0.2 atm. and 0.3 atm).

[0112] In the illustrated embodiment, the pressure difference between the relatively high-pressure coolant source and the relatively low-pressure ambient atmosphere is le flow of coolant from the coolant source 250 along the respective first, second, third and fourth flow paths.

[0113] As such, the aircraft battery ventilation system 200 of the illustrated embodiment is a passive system and therefore does not place any extra power requirement on the aircraft 100.

[0114] As the coolant passes across the respective battery containers as it flows towards the exhaust port, it imparts a cooling effect on the battery modules contained therein thereby helping to prevent said battery modules from overheating.

[0115] Furthermore, the flow of coolant across the battery containers also aids in driving unwanted gases (which may be generated by the battery modules during normal operation) towards the exhaust port so that they can be jettisoned from the aircraft thereby helping to prevent such gases from lingering within the battery containers where they may hamper the normal operation of the battery modules.

[0116] Furthermore, in the battery ventilation system according to the present invention, the first and second battery units are fully segregated thereby helping to prevent the ventilation system from becoming overloaded in the unlikely event of simultaneous overheating in both the first and second battery units.

[0117] Where the word 'or' appears this is to be construed to mean 'and / or' such that items referred to are not necessarily mutually exclusive and may be used in any appropriate combination.

[0118] Although the invention has been described above with reference to one or more preferred embodiments, it will be appreciated that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims.

Claims

1. An aircraft battery ventilation system comprising:a first battery module;a first battery container for housing said first battery module; anda first flow path extending from a coolant source to an exhaust port of the aircraft, andwherein the first flow path passes at least partially through the first battery container such that coolant passing from the coolant source to the exhaust port imparts a cooling effect on the first battery module.

2. The aircraft battery ventilation system according to claim 1. wherein the coolant source is held at a first pressure, and wherein said first pressure is greater than an ambient pressure, and preferably wherein the coolant source is held at a pressure between 0.7 atm and 1 atm.

3. The aircraft battery ventilation system according to claim 1 or 2, wherein the coolant source is an air source, and preferably wherein the air source is air from a compartment of the aircraft (e.g., the avionics bay).

4. The aircraft battery ventilation system according to any preceding claim, wherein the system comprises a first check valve provided between the first battery container and the exhaust port, said first check valve being configured so as to prevent ambient air from flowing into the first battery container via the exhaust port.

5. The aircraft battery ventilation system according to any preceding claim, wherein the system comprises a second check valve provided between the first battery container and the coolant source.

6. The aircraft battery ventilation system according to any preceding claim, wherein the system further comprises:a second battery module;a second battery container for housing said second battery module; anda second flow path extending from the coolant source to the exhaust port of the aircraft, andwherein the second flow path passes at least partially through the second battery container such that coolant passing from the coolant source to the exhaust port imparts a cooling effect on the second battery module.

7. The aircraft battery ventilation system according to claim 6, wherein the system comprises a third check valve provided between the second battery container and the exhaust port, said third check valve being configured so as to prevent ambient air from flowing into the second battery container via the exhaust port.

8. The aircraft battery ventilation system according to claim 6 or 7, wherein the second flow path comprises a fourth check valve provided between the second battery container and the coolant source.

9. The aircraft battery ventilation system according to any of claims 6 to 8, wherein the first flow path comprises a first outlet duct arranged so as to provide a fluid connection between an outlet of the first battery container and the exhaust port, and wherein the second flow path comprises a second outlet duct arranged so as to provide a fluid connection between an outlet of the second battery container and the exhaust port.

10. The aircraft battery ventilation system according to any of claims 6 to 9, wherein the first and second flow paths share a common inlet duct arranged so as to provide a fluid connection between respective inlets of the first and second battery containers and the coolant source.

11. The aircraft battery ventilation system according to any of claims 6 to 10, wherein the first and second battery modules comprise constituent parts of the same battery unit.

12. The aircraft battery ventilation system according to any of claims 6 to 10, wherein the first and second battery modules comprise constituent parts of different battery units.

13. The aircraft battery ventilation system according to any of claims 6 to 12, wherein the first and / or second battery container comprises a thermally insulating material.

14. The aircraft battery ventilation system according to any preceding claim, wherein the first and / or second battery modules comprise a plurality of battery cells, and preferably wherein said battery cells are Lithium Ion (Li-ion) battery cells.

15. An aircraft comprising the aircraft battery ventilation system according to any preceding claim.

16. A ventilation system for an aircraft battery comprising:a battery module; anda battery casing for housing said battery module,wherein the battery casing comprises an inlet fluidly connected to a coolant source, said inlet being configured so as to permit the ingress of coolant from the coolant source into the battery casing; andwherein the battery casing further comprises an outlet fluidly connected to the ambient atmosphere, said outlet being configured to permit the egress of coolant and / or other gases from the battery casing to the ambient atmosphere.

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