Battery module for a motor vehicle

Abstract

The invention relates to a battery(3) module (7) comprising a housing (8) enclosing electrical energy storage cells (9) and a device (19) for monitoring a characteristic of the fluid contained in the housing (8) of the module (7) other than the temperature in order to diagnose the deterioration of at least one of the electrical energy storage cells (9) enclosed in the housing (8) of the module (7).

Description

Battery module for automotive vehicle Technical field of the invention

[0001] The invention relates to the field of batteries and, more specifically, to battery modules for a motor vehicle. Technical background

[0002] Motor vehicles increasingly require electrical energy storage capacity, particularly due to anti-pollution standards imposed by local legislation. While the use of a battery does indeed allow an electric motor to replace all or part of a combustion engine and the pollution associated with its combustion, it does not allow it to be replaced under the same operating conditions.

[0003] A major drawback lies in the risk of thermal runaway of the electrical energy storage cells, particularly for lithium-ion batteries. In concrete terms, if the temperature increases too much, a chain reaction inside the electrical energy storage cell ends up vaporizing the electrolyte, which leads to internal overpressure in the electrical energy storage cell. In the most severe cases, several or even all of the electrical energy storage cells are subject to thermal runaway, which can lead to a fire in the battery and, incidentally, in the components surrounding the battery, i.e. in particular all or part of the motor vehicle in which the battery is mounted.

[0004] This drawback has already been raised in documents WO 2021 / 001108, EP 3 910 349, DE 10 2020 109269, FR 3 112 028, US 2012 / 003515, EP 3 166 175 and the article “A survey of methods for monitoring and detecting thermal runaway of lithium-ion batteries”, journal of power sources, Elsevier edition, vol. 436, July 20, 2019, ISSN: 0378-7753.

[0005] To make matters worse, the higher the current consumed by the battery, the greater the power discharged by the battery (the Joule effect increasing according to the square of the discharge current) and the more the user is encouraged to use a fast charging terminal (the Joule effect increasing according to the square of the charging current), which makes the risk of thermal runaway even more frequent.

[0006] It therefore appears that thermal regulation of the battery is becoming a major issue for motor vehicles designed to comply with ever more drastic pollution standards.

[0007] The invention aims in particular to propose a battery module capable of detecting as early as possible the risk of thermal runaway of the electrical energy storage cells contained in the battery module.

[0008] To this end, the invention relates to a battery module for a motor vehicle comprising a housing enclosing electrical energy storage cells, characterized in that the battery module comprises a device for monitoring a characteristic of a fluid contained in the housing of the module in order to diagnose deterioration of at least one of the electrical energy storage cells enclosed in the housing of the module),in that the monitoring device comprises at least one detection element mounted on the module housing and intended to determine the presence of a pollution fluid escaping from at least one of the electrical energy storage cells different from the fluid contained in the module housing and in that the detection element comprises an electrical conductivity sensor in order to measure a variation in electrical conductivity in the fluid contained in the module housing generated by the pollution fluid escaping from at least one of the electrical energy storage cells.,

[0009] According to the invention, it is provided that the battery is formed of several modules electrically connected in parallel or in series, which has several advantages. First of all, it is simpler to thermally regulate several battery modules than a single volume comprising the same number of electrical energy storage cells. It is also simpler to install several battery modules in the motor vehicle than a single volume comprising the same number of electrical energy storage cells. Finally, it is simpler to be able to replace a module comprising faulty electrical energy storage cells rather than replacing the entire battery for only a small portion of faulty electrical energy storage cells.It is therefore understood that the diagnosis of the monitoring device will allow any faulty electrical energy storage cells to be quickly checked, already knowing the battery module to be checked.

[0010] Furthermore, advantageously, each module can, according to the invention, detect the deterioration of at least one of its electrical energy storage cells in order to manage the stopping of the thermal runaway of the battery as soon as possible. The obvious solution to solve a thermal runaway problem would be to monitor the temperature of the electrical energy storage cells. However, this is not the solution followed by the invention because, effectively, the increase in temperature takes place very shortly before the fire.

[0011] Thus, it has been found that to avoid deformations of each electrical energy storage cell and therefore deterioration of the organs surrounding the electrical energy storage cell, an exhaust valve is generally provided, often formed by a frangible part intended to break from a predetermined internal pressure, to allow the excess pressure to communicate to the outside of the electrical energy storage cell. Once the exhaust valve is open, the electrical energy storage cell is therefore no longer functional.

[0012] The invention therefore takes advantage of this observation to, not monitor the temperature of each electrical energy storage cell, but to monitor at least one other characteristic than the temperature of the fluid present in the battery module such as the electrical conductivity and, possibly in addition, the composition, pressure or transparency to determine whether a polluting fluid such as a gas has escaped from at least one of the electrical energy storage cells of the module in order to diagnose possible thermal runaway as early as possible.

[0013] Indeed, it is expensive and complex to mount a temperature sensor on each electrical energy storage cell and the single temperature measurement in the housing does not allow thermal runaway of one of the electrical energy storage cells to be detected with certainty and sufficiently early. In a different manner according to the invention, an anomaly is detected after the destruction of at least one of the electrical energy storage cells. Thus, the thermal runaway is located immediately among the battery modules and sufficiently early (in particular earlier than by temperature monitoring) to prevent it from spreading to the other electrical energy storage cells of the battery module and / or to the other battery modules. Finally, advantageously according to the invention, the monitoring device is compatible with a wide variety of types of thermal regulation systems.

[0014] Advantageously according to the invention, the detection element can be mounted both inside and outside the housing of each module depending on the location or type of battery. Of course, several identical detection elements (same detected characteristic of the fluid present in the battery module) and / or different (several different detected characteristics of the fluid present in the battery module) can be present on the same module in order to improve the diagnosis.

[0015] An electrical conductivity sensor is preferred because it is more reliable in detecting its characteristic in the fluid compared to other characteristics. Thus, it is less sensitive to other characteristics of the fluid (e.g. color, transparency, etc.) that could interfere / change the measurements of the characteristic. In other words, an electrical conductivity sensor provides fewer false measurements than other types of sensors in the context of the invention.

[0016] Advantageously according to the invention, as soon as a variation in the conductivity (or conversely the resistivity) of the fluid in the module is outside predetermined thresholds (such as the average conductivity of the other battery modules, a deviation from a normal conductivity at a given temperature or a deviation from a predetermined conductivity), the monitoring device will be able to diagnose a possible thermal runaway.

[0017] Advantageously according to the invention, in the particular case where the fluid is air, an electrical conductivity sensor can also detect an increase in the humidity level in the air which can lead to a short circuit (air breakdown) which generally precedes thermal runaway. In other words, an electrical conductivity sensor not only diagnoses thermal runaway, but can also prevent it. No other type of sensor such as a temperature sensor or a pressure sensor can do this.

[0018] The invention may also include one or more of the following optional features, taken alone or in combination.

[0019] The detection element may further comprise a concentration sensor in order to measure the concentration of pollution fluid escaping from at least one of the electrical energy storage cells in the fluid contained in the module housing. It is therefore understood that as soon as a tiny proportion of pollution fluid is present, the monitoring device will be able to diagnose a possible thermal runaway.

[0020] The detection element may further comprise a pressure sensor in order to measure a pressure variation in the fluid contained in the housing of each module generated by the pollution fluid escaping from at least one of the electrical energy storage cells. Advantageously according to the invention, as soon as a variation in the pressure of the fluid in the module is above a predetermined threshold (such as the average pressure of the other battery modules, a deviation from a normal pressure at a given temperature or a deviation from a predetermined pressure), the monitoring device will be able to diagnose a possible thermal runaway.

[0021] The detection element may further comprise an optical sensor in order to measure a variation in light transmission in the fluid contained in the housing of each module generated by the pollution fluid escaping from at least one of the electrical energy storage cells. Advantageously according to the invention, as soon as a variation in brightness of the fluid in the module is outside predetermined thresholds (such as the average brightness of the other battery modules or a deviation from a predetermined brightness), the monitoring device will be able to diagnose a possible thermal runaway. It is noted that this latter type of sensor allows other additional detections. Thus, if a fire is starting in the module, the monitoring device will be able to detect smoke by the decrease in brightness or, on the contrary, flames by the increase in brightness.In addition, in case of liquid fluid in the module, the monitoring device will be able to detect gas bubbles escaping from electrical energy storage cells by the variation in brightness.

[0022] The monitoring device may comprise at least one guide element mounted on the module housing and intended to divert the pollution fluid escaping from at least one of the electrical energy storage cells towards the detection element in order to make the detection more reliable and limit the number of detection elements. It is understood that the guide element may form a part of the upper cover of the housing of each module to impose a passage of the pollution fluid in front of each detection element. The guide element may thus form a collector forcing all the pollution fluids to pass in front of each detection element.

[0023] The fluid contained in the module housing may be air in the gaseous phase or a dielectric heat transfer fluid in the liquid phase intended to thermally regulate at least part of the electrical energy storage cells included in the battery module.

[0024] The invention also relates to a thermal regulation system for a battery module for a motor vehicle as presented above, characterized in that the regulation system comprises a control unit electrically connected to the device for monitoring the fluid contained in the module housing in order to selectively control the operation of the thermal regulation system as a function of the diagnosed deterioration of at least one of the electrical energy storage cells enclosed in the module housing.

[0025] Finally, the invention relates to a motor vehicle characterized in that it comprises a thermal regulation system as presented above. Brief description of the figures

[0026] Other features and advantages of the invention will emerge clearly from the description given below, for information purposes only and in no way limiting, with reference to the appended drawings, in which:

[0027] is a schematic top view of an example of a vehicle in which a thermal regulation system of a battery module according to the invention is mounted;

[0028] is a schematic perspective view of an example of battery modules according to a first embodiment of the invention;

[0029] is a schematic sectional view of an example of a battery module according to a second embodiment of the invention. Detailed description

[0030] In all that follows, the orientations are the orientations of the figures. In particular, the terms "upper", "lower", "left", "right", "above", "below", "forward" and "backward" are generally understood in relation to the direction in which the figures are represented.

[0031] The invention applies to any type of thermal regulation system 1 for battery 3, in particular those intended to equip a motor vehicle 4 of the passenger car type, SUV (“Sport Utility Vehicles”), two-wheelers (in particular motorcycles), airplanes, industrial vehicles chosen from vans, “Heavy Goods Vehicles” - that is to say metro, buses, road transport vehicles (trucks, tractors, trailers), off-road vehicles such as agricultural or civil engineering vehicles -, or other transport or handling vehicles.

[0032] The motor vehicle 4 may be of the electric type, i.e. with at least one electric motor powered by at least one battery, or of the hybrid type, i.e. with at least one internal combustion engine powered by at least one fuel (gasoline, liquefied petroleum gas, diesel, natural gas for vehicles, biofuel such as, for example, ethanol obtained from plant material, etc.) and assisted by at least one electric motor powered by at least one battery and / or the on-board network of the motor vehicle 4, of the fuel cell type, i.e. at least one electric motor powered by at least one battery and / or by a fuel cell powered by dihydrogen (such as that coming from a pressurized tank) and dioxygen (such as that coming from the ambient air), or of the rechargeable hybrid type, i.e. at least one internal combustion engine powered by at least one fuel (gasoline, liquefied petroleum gas, diesel, natural gas for vehicles, biofuel such as, for example, ethanol obtained from plant material, etc.) and at least one electric motor powered by the on-board network of the motor vehicle 4 and / or at least one rechargeable battery by connection with an electrical network external to the motor vehicle 4.Of course, the invention is not limited to the above examples of motor vehicles 4 but applies to any type of motor vehicle 4 comprising at least one battery without departing from the scope of the invention.

[0033] By "thermal regulation system 1" is meant all types of systems 1 for managing the flow, temperature and pressure of a heat transfer fluid intended, by moving said heat transfer fluid around a portion of the electrical energy storage cells 9 of a battery 3 (exchange by immersion in a dielectric heat transfer fluid, exchange by pulsed air, exchange by air - exchanger), to exchange thermally with all or part of the electrical energy storage cells 9 in order to control its temperature, that is to say typically to heat and / or cool, according to a predetermined control, all or part of the electrical energy storage cells 9 present in at least one module 7 of battery 3.

[0034] By "heat transfer fluid" is meant a fluid of the thermal regulation system 1 allowing the exchange by contact of the cold and / or the heat of at least a part of the cells 9 for accumulating electrical energy of a battery 3. Typically, the heat transfer fluid can circulate around all or part of the cells 9 for accumulating electrical energy by at least partially filling a module 7 of battery 3.

[0035] By "dielectric heat transfer fluid" is meant a fluid intended to remain in liquid form in the module 7 of battery 3 of the thermal regulation system 1 in order to exchange by contact the cold and / or the heat of at least a part of the cells 9 for storing electrical energy of a battery 3. Typically, the dielectric heat transfer fluid is single-phase, that is to say that it will not change phase (will remain liquid) in the temperature range considered in normal operation such as, for example, between -40°C and 60°C. According to the invention, the heat transfer fluid is dielectric, that is to say it preferably has an electrical resistivity ρ at least equal to 1∙10 9 ohm meters (1 GΩ∙m) at a temperature of 300 kelvins (300 K) or, conversely, an electrical conductivity σ at most equal to 1∙10 - 9 siemens per meter (1 nS∙m - 1) at a temperature of 300 kelvins (300 K), so as not to disturb the electrical connections between in particular the cells 9 present in the same module 7 of battery 3. This type of dielectric heat transfer fluid may be similar to those used for electrical transformers. It will therefore not be described further in the present description because it is known per se. By way of non-limiting example, the dielectric heat transfer fluid may for example be a product of the Novec® 7500 type sold by the company 3M®, of the F18 or F20 type sold by the company Total® or of the DF7 or DFK type sold by the company MiVolt®.

[0036] By "characteristic of a fluid" we mean a physicochemical characteristic of the fluid and not the mass or volume of the fluid.

[0037] By "electrical energy storage cell 9" is meant all types of electrochemical accumulators capable of storing electrical energy and, reversibly, of restoring the stored electrical energy.

[0038] By "battery module 7 3" is meant a housing 8 grouping at least two electrical energy storage cells 9 electrically connected in series or in parallel. In the context of the invention, a circulation of heat transfer fluid is provided in at least one battery module 7 3 in order to thermally regulate at least a portion of the electrical energy storage cells 9 received in the battery module 7 3.

[0039] By “battery 3” is meant all the modules 7 electrically connected in series or in parallel and, incidentally, all the cells 9 for storing electrical energy included in the modules 7.

[0040] By "powertrain 2" is meant the assembly comprising the engine(s) intended to directly or indirectly drive the wheels of the motor vehicle 4 as well as the accessories of each engine such as, for example, the alternator, the cooling system, the gearbox or the lubrication system.

[0041] In the example illustrated in , a thermal regulation system 1 of a battery 3 is mounted in a motor vehicle 4. In this example, an electrical connection element 5 is provided on the body of the motor vehicle 4 to allow the battery 3 to be recharged. As will be explained above, the thermal regulation system 1 and / or the battery 3 can be fluidically and / or electrically connected to the powertrain 2. Advantageously according to the invention, all the technical characteristics and effects of the thermal regulation system 1 make it possible to guarantee optimal operation of the electrical energy exchanges between the battery 3 and the components of the motor vehicle 4, such as, for example, during the running of the motor vehicle or during recharging with electrical energy while the motor vehicle is parked.

[0042] The thermal regulation system 1 may, advantageously according to the invention, be of several types. The heat transfer fluid contained in the housing 8 of the module 7 may be air in the gaseous phase or a dielectric heat transfer fluid in the liquid phase intended to thermally regulate at least a portion of the electrical energy storage cells 9 included in the battery 3 module 7. The battery 3 modules 7 also allow the electrical connection of the electrical energy storage cells 9 to the rest of the motor vehicle 4 in order to guarantee its supply of electrical energy. These electrical connections are made by sealed connectors.The battery modules 7 of 3 each comprise a housing 8 formed of a lower hollow base 8b (receiving the electrical energy storage cells 9) closed by an upper cover 8a in a sealed manner in order to offer protection of the electrical energy storage cells 9 against mechanical incidents (crash, mechanical shocks, etc.) as well as protection in the event of fire (limits the progression of flames external to each battery module 7 of 3 so that the latter do not reach the electrical energy storage cells 9).

[0043] According to the invention, the regulation system 1 comprises a control unit 11 electrically connected to a device 19 for monitoring the fluid contained in the housing 8 of the module 7 of the battery 3 in order to selectively control the operation of the thermal regulation system 1 as a function of the diagnosed deterioration of at least one of the electrical energy storage cells 9 enclosed in the housing 8.

[0044] In the example illustrated in presenting a first embodiment of the invention, the regulation system 1 may be of the type involving immersion of the electrical energy storage cells 9, that is to say that each module 7 of battery 3 comprises a housing 8 enclosing electrical energy storage cells 9 in dielectric heat transfer fluid. Preferably, the electrical energy storage cells 9 of each module 7 of battery 3 are completely immersed in dielectric heat transfer fluid forming part of a fluid network 6. Preferably, several modules 7 of battery 3 are fluidically connected to the rest of the fluid network 6 by fluid connections to a common input ramp 10 and to a common output ramp 12.In the example illustrated in , three battery modules 7 3 are placed in parallel in the fluid network 6 in order to allow an equitable and homogeneous supply of dielectric heat transfer fluid for each of the battery modules 7 3, thus guaranteeing homogeneous thermal regulation of the electrical energy storage cells 9. This parallel arrangement also allows the reduction of pressure losses in the fluid network 6. In order to homogenize the pressure losses in each of the connections of the battery modules 7 3 (and therefore in order to have similar flow rates in each module), the fluid connection section between the common input ramp 10 and its associated battery module 7 3 is of different size depending on its distance from its connection to the fluid network 6 in order to obtain an equivalent flow rate of dielectric heat transfer fluid between the battery modules 7 3.

[0045] In the example illustrated in thepresenting a second embodiment of the invention, the regulation system 1 may be of the heat exchanger 18 type with the heat transfer fluid included around the electrical energy storage cells 9, that is to say that each battery module 7 3 comprises a housing 8 enclosing electrical energy storage cells 9 and a heat exchanger 18. Preferably, the electrical energy storage cells 9 of each battery module 7 3 are therefore heated or cooled by the heat exchanger 18 forming a part of a fluid network 6 of the thermal regulation system 1 via the heat transfer fluid present in the housing 8. Preferably, several battery modules 7 3 are fluidically connected to the rest of the fluid network 6 by hydraulic connections to a common inlet ramp 10 and to a common outlet ramp 12.In the example illustrated in , the modules 7 of battery 3 (only one in ) are placed in parallel in the fluid network 6 in order to allow an equitable and homogeneous supply of heat transfer fluid for each of the heat exchangers 18 of the modules 7 of battery 3, thus guaranteeing homogeneous thermal regulation of the electrical energy storage cells 9. This parallel arrangement also allows the reduction of pressure losses in the fluid network 6 between the inlet 10' and the outlet 12' of the heat exchanger 18 in the housing 8.

[0046] It is therefore understood that the thermal regulation system 1 according to the invention makes it possible to maintain the electrical energy storage cells 9 at their optimum temperature in order to guarantee optimised operation (maintaining the best energy efficiency) and robust operation (optimal charging and discharging for a longer service life) of the battery 3 whatever the external conditions in which the motor vehicle 4 operates, that is to say even if it is very cold or very hot.

[0047] It is also conceivable in a simpler solution that no heat exchanger 18 is used and that the heat transfer fluid, which can be air at ambient pressure, is sucked into the housing 8 then discharged outside the housing 8 by a fan (third embodiment not shown). It is understood that in the latter case, the heating and cooling potential of the thermal regulation system 1 is much more limited than the first two cases.

[0048] Typically, the example by immersion of the first embodiment is more efficient for heat exchanges because the specific exchange surface is larger and the evacuation outside each module 7 of battery 3 by circulation of the dielectric heat transfer fluid is rapid, which allows high efficiency and reactivity of regulation capable of satisfying both the charging (at a fast charging terminal) and the discharging (electrical consumption of the motor vehicle 4 at high load) of high electrical power of the battery. In addition, the heat exchange is very efficient because it is done directly by convection of the heat transfer fluid on the casing of each cell 9 for accumulating electrical energy. In a related manner, regulation by immersion is also safer against the propagation of possible fire of the battery 3 in the motor vehicle 4.

[0049] Advantageously according to the invention, each module 7 of battery 3 comprises a device 19 for monitoring a characteristic of the fluid contained in the housing 8 of the module 7 other than the temperature in order to diagnose the deterioration of at least one of the electrical energy storage cells 9 enclosed in the housing 8.

[0050] According to the invention, it is provided that the battery 3 is formed of several modules 7 electrically connected in parallel or in series, which has several advantages. First of all, it is simpler to thermally regulate several modules 7 of battery 3 than a single volume comprising the same number of electrical energy storage cells 9. It is also simpler to install in the motor vehicle 4 several modules 7 of battery 3 than a single volume comprising the same number of electrical energy storage cells 9. Finally, it is simpler to be able to change a module 7 of battery 3 comprising faulty electrical energy storage cells 9 rather than changing the entire battery 3 for only a small portion of faulty electrical energy storage cells 9.It is thus understood that the diagnosis of the monitoring device 19 will make it possible to quickly check any faulty electrical energy storage cells 9 by already knowing the module 7 of battery 3 to be checked.

[0051] Furthermore, advantageously, each module 7 of battery 3 can, according to the invention, detect the deterioration of at least one of its electrical energy storage cells 9 in order to manage as soon as possible the stopping of the thermal runaway of the battery 3. The obvious solution for solving a thermal runaway problem would be to monitor the temperature of the electrical energy storage cells 9. However, this is not the solution followed by the invention.

[0052] Thus, it has been found that to avoid deformations of each electrical energy storage cell 9 and therefore deterioration of the organs surrounding each electrical energy storage cell 9, an exhaust valve 21 is generally provided, often formed by a frangible part intended to break from a predetermined internal pressure, to allow the excess pressure to communicate to the outside of the electrical energy storage cell 9. Once the exhaust valve 21 is open, the electrical energy storage cell 9 is therefore no longer functional.

[0053] The invention therefore takes advantage of this observation to, not monitor the temperature of each electrical energy storage cell 9, but monitor at least one other characteristic than the temperature of the fluid present in the battery module 7 3 such as the electrical conductivity and, possibly in addition, the composition, pressure or transparency to determine whether a fluid such as a gas has escaped from at least one of the electrical energy storage cells 9 of the battery module 7 3 in order to diagnose a possible thermal runaway as early as possible. Indeed, it is expensive and complex to mount a temperature sensor on each electrical energy storage cell 9 and the single temperature measurement in the housing 8 does not make it possible to detect with certainty and sufficiently early a thermal runaway of one of the electrical energy storage cells 9.In a different manner according to the invention, an anomaly is detected after the destruction of at least one of the electrical energy storage cells 9. Thus, the thermal runaway is located immediately among the modules 7 of the battery 3 and early enough to prevent it from spreading to the other electrical energy storage cells 9 of the module 7 of the battery 3 and / or to the other modules 7 of the battery 3. Finally, advantageously according to the invention, the monitoring device 19 is compatible with a wide variety of types of thermal regulation systems 1 as explained above.

[0054] The monitoring device 19 comprises at least one detection element 13 mounted on the housing 8 of the module 7 and intended to determine the presence of a pollution fluid escaping from at least one of the electrical energy storage cells 9 different from the fluid contained in the housing 8 of the battery module 7. Advantageously according to the invention, the detection element 13 can be mounted both inside and outside the housing 8 depending on the location or the type of the battery 3. Of course, several identical detection elements 13 (same detected characteristic of the fluid present in the battery module 7) and / or different (several different detected characteristics of the fluid present in the battery module 7) can be present on the same module 7 in order to improve the diagnosis of the control unit 11.

[0055] According to the invention, the detection element 13 comprises at least one electrical conductivity sensor in order to measure a variation in conductivity in the fluid contained in the housing 8 generated by the pollution fluid escaping from at least one of the electrical energy storage cells 9. Advantageously according to the invention, as soon as a variation in the conductivity (or conversely the resistivity) of the fluid in the battery module 7 3 is outside predetermined thresholds (such as the average conductivity of the other battery modules 7 3, a deviation from a normal conductivity at a given temperature or a deviation from a predetermined conductivity), the monitoring device 19 will be able to diagnose a possible thermal runaway. By way of non-limiting example, the electrical conductivity sensor may be an electrode sensor.

[0056] An electrical conductivity sensor is preferred because it is more reliable in detecting its characteristic in the fluid compared to other characteristics. Thus, it is less sensitive to other characteristics of the fluid (e.g. color, transparency, etc.) that could interfere / change the measurements of the characteristic. In other words, an electrical conductivity sensor provides fewer false measurements than other types of sensors in the context of the invention.

[0057] Additionally, in the special case where the fluid is air, an electrical conductivity sensor can also detect an increase in the humidity level in the air that can lead to a short circuit (air breakdown) that usually precedes thermal runaway. In other words, an electrical conductivity sensor not only diagnoses thermal runaway, but can also prevent it. No other type of sensor, such as a temperature sensor or a pressure sensor, can do this.

[0058] According to a first variant, the detection element 13 may further comprise a concentration sensor in order to measure the concentration of pollution fluid escaping from at least one of the electrical energy accumulation cells 9 in the fluid contained in the housing 8. It is therefore understood that as soon as a tiny proportion is present, the monitoring device 19 will be able to diagnose a possible thermal runaway.

[0059] According to a second variant, the detection element 13 may further comprise a pressure sensor in order to measure a variation in pressure in the fluid contained in the housing 8 generated by the pollution fluid escaping from at least one of the electrical energy storage cells 9. Advantageously according to the invention, as soon as a variation in the pressure of the fluid in the battery module 7 3 is above a predetermined threshold (such as the average pressure of the other battery modules 7 3, a deviation from a normal pressure at a given temperature or a deviation from a predetermined pressure such as the ambient pressure outside the housing 8), the monitoring device 19 will be able to diagnose a possible thermal runaway.

[0060] According to a third variant, the detection element 13 may further comprise an optical sensor in order to measure a variation in light transmission in the fluid contained in the housing 8 generated by the pollution fluid escaping from at least one of the electrical energy storage cells 9. Advantageously according to the invention, as soon as a variation in brightness of the fluid in the battery module 7 3 is outside predetermined thresholds (such as the average brightness of the other battery modules 7 3 or a deviation from a predetermined brightness), the monitoring device 19 will be able to diagnose a possible thermal runaway. It is noted that this latter type of sensor allows other additional detections. Thus, if a start of fire is present in the battery module 7, the monitoring device 19 will be able to detect smoke by the decrease in brightness or, on the contrary, flames by the increase in brightness.Furthermore, in the case of a dielectric heat transfer fluid in the liquid phase in the module 7 of the battery 3, the monitoring device 19 will be able to detect gas bubbles escaping from the electrical energy storage cells 9 by the variation in brightness.

[0061] Advantageously according to the invention, the monitoring device 19 may comprise at least one guide element 17 mounted on the housing 8 and intended to divert the pollution fluid escaping from at least one of the electrical energy storage cells 9 towards the detection element 13 in order to make the detection more reliable and limit the number of detection elements 13. It is understood that the guide element 17 may form a part of the upper cover 8a of the housing 8 to impose a passage of the pollution fluid in front of each detection element 13. The guide element 17 may thus form a collector forcing all the pollution fluids to pass in front of each detection element 13.

[0062] In the example illustrated in , it can be seen that the guide element 17 can thus comprise a deflector 16 above a part of the electrical energy accumulation cells 9 in order to force any pollution fluid generated by one of the electrical energy accumulation cells 9 to pass into the detection zone 14 of the detection element 13 before escaping towards the outlet 15.

[0063] Of course, the guide element 17 can also only force any pollution fluid generated by one of the electrical energy storage cells 9 to escape towards the outlet 15 in order to pass into a detection zone 14 of the detection element 13 positioned outside the housing 8 of the module 7, preferably close to the outlet 15.

[0064] The invention is not limited to the embodiments and variants presented and other embodiments and variants will become clear to those skilled in the art. Thus, the embodiments and variants can be combined with one another without departing from the scope of the invention. By way of non-limiting example, it is possible for another type of detection element 13 to be used to enable the detection of a pollution fluid of one of the electrical energy storage cells 9 without departing from the scope of the invention. Furthermore, a temperature detection element T02 can be used to, for example, thermally weight a sensor such as a pressure sensor and / or an electrical conductivity sensor.

[0065] List of references

[0066] 1 - thermal regulation system

[0067] 2 - powertrain

[0068] 3 - battery

[0069] 4 - motor vehicle

[0070] 5 - electrical connection element

[0071] 6 - fluid network

[0072] 7 - battery module

[0073] 8 - Battery module housing

[0074] 8a - top cover of the housing

[0075] 8b - lower hollow base of the case

[0076] 9 - electrical energy storage cells

[0077] 10 - common inlet rail

[0078] 10' - entrance

[0079] 11 - control unit

[0080] 12 - common output rail

[0081] 12' - exit

[0082] 13 - detection element

[0083] 14 - detection zone

[0084] 15 - pollution fluid outlet

[0085] 16 - deflector

[0086] 17 - guide element

[0087] 18 - heat exchanger

[0088] 19 - monitoring device

[0089] 21 - exhaust valve

[0090] T02 - module temperature sensing element

Claims

Battery module (7) (3) for a motor vehicle (4) comprising a housing (8) enclosing electrical energy storage cells (9), characterized in that the battery module (7) (3) comprises a device (19) for monitoring a characteristic of a fluid contained in the housing (8) of the module (7) in order to diagnose a deterioration of at least one of the electrical energy storage cells (9) enclosed in the housing (8) of the module (7),in that the monitoring device (19) comprises at least one detection element (13) mounted on the housing (8) of the module (7) and intended to determine the presence of a polluting fluid escaping from at least one of the electrical energy storage cells (9) different from the fluid contained in the housing (8) of the module (7), and in that the detection element (13) comprises an electrical conductivity sensor in order to measure a variation in electrical conductivity in the fluid contained in the housing (8) of the module (7) generated by the polluting fluid escaping from at least one of the electrical energy storage cells (9). Battery module (7) (3) according to the preceding claim, wherein the sensing element (13) further comprises a concentration sensor for measuring the concentration of pollution fluid escaped from at least one of the electrical energy storage cells (9) in the fluid contained in the housing (8) of the module (7). Battery module (7) (3) according to claim 1 or 2, wherein the sensing element (13) further comprises a pressure sensor for measuring a pressure variation in the fluid contained in the housing (8) of the module (7) generated by the pollution fluid escaping from at least one of the electrical energy storage cells (9). Battery module (7) (3) according to any one of the preceding claims, wherein the sensing element (13) further comprises an optical sensor for measuring a variation in light transmission in the fluid contained in the housing (8) of the module (7) generated by the pollution fluid escaping from at least one of the electrical energy storage cells (9). Battery module (7) (3) according to any one of the preceding claims, wherein the monitoring device (19) includes at least one guide element (17) mounted on the housing (8) of the module (7) and intended to divert the escaping pollution fluid from at least one of the electrical energy storage cells (9) towards the detection element (13) in order to make detection more reliable and limit the number of detection elements (13). Battery module (7) (3) according to any one of the preceding claims, wherein the sensing element (13) is mounted inside the housing (8) of the module (7). Battery module (7) (3) according to any one of claims 1 to 5, wherein the sensing element (13) is mounted outside the housing (8) of the module (7). Battery module (7) (3) according to any one of the preceding claims, wherein the fluid contained in the housing (8) of the module (7) is air. Battery module (7) (3) according to any one of claims 1 to 7, wherein the fluid contained in the housing (8) of the module (7) is a liquid-phase dielectric heat transfer fluid intended to thermally regulate at least a portion of the electrical energy storage cells (9) included in the battery module (7) (3). Thermal regulation system (1) of a battery module (7) (3) for a motor vehicle (4) according to any one of the preceding claims, characterized in that the regulation system (1) comprises a control unit (11) electrically connected to the fluid monitoring device (19) contained in the housing (8) of the module (7) in order to selectively control the operation of the thermal regulation system (1) as a function of the diagnosed deterioration of at least one of the electrical energy storage cells (9) enclosed in the housing (8) of the module (7). Motor vehicle (4) characterized in that it comprises a thermal regulation system (1) according to the preceding claim.

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