ELECTRICAL MODULE COMPRISING A MULTIPLE BATTERY CELLS IMMERSED IN A DIELECTRIC FLUID

Abstract

The invention relates to an electrical module comprising a plurality of battery cells immersed in a dielectric fluid. The module further comprises an electronic battery management circuit immersed in said dielectric fluid.

Description

Scope of the invention The present invention relates to a battery pack with an optimized thermal management system in which a temperature-controlled fluid comes into direct contact with the battery cells. It is particularly, but not exclusively, applicable to the automotive field. For example, it applies to traction batteries in electric vehicles (EVs) and hybrid electric vehicles (HEVs). A lithium-ion (Li-ion) electrochemical battery module undergoes regular charging and discharging cycles, resulting in significant heating. This electrochemistry also has a narrow operating temperature range, typically between 0 and 45°C for charging and -20°C and 60°C for discharging. Cell aging accelerates when the cell temperature deviates from an ideal operating temperature, typically 25°C. It is therefore necessary to cool it efficiently in order to maintain its performance level and limit its aging. The power density of these batteries tends to increase to meet the demands for range and fast charging. Liquid cooling, usually with glycol water, meets these needs. However, since water is also a good electrical conductor, a drawback of this type of solution is that safety constraints, particularly to prevent any risk of short circuits, for example in the event of an impact, make them very complex to implement. Thus, the water is typically contained in a plate, itself placed in contact with the electrochemical cells. The contact between the cells and the water is therefore indirect and local, thus reducing the system's efficiency. Water can sometimes be replaced by dielectric thermal fluids. State of the art Patent application W02014176320A2 discloses a known battery comprising a chamber partially filled with a liquid-vapor phase change material (LV, such as water or alcohol) and hermetically sealed under vacuum. Prismatic electrochemical cells are arranged vertically at the bottom of the chamber, such that one edge of each cell is immersed in the liquid phase change material. The outer shell of each cell is coated with a fine hydrophilic structure that allows the liquid phase change material to saturate the entire shell by capillary action. The phase-change material transitions from liquid to vapor through heating within the hydrophilic structure during cell operation (charging and discharging). Various solutions are proposed to recondense the phase-change material, causing it to fall back onto the cells coated by the hydrophilic structure in droplets. This allows the cells to be "bathed" in liquid phase-change material despite the small amount of material present in the chamber. Disadvantage of prior art The major drawback of prior art solutions lies in the need to maintain the air gap in The enclosure must remain airtight for the entire battery life, which is very difficult to guarantee given the numerous cables. Indeed, if air enters the enclosure, the pressure increases, hindering the evaporation / condensation processes of the phase-change material and reducing cooling performance. Therefore, the system must be designed to be doubly airtight: preventing air from entering when cold and preventing vapor from escaping when hot. Another drawback of current technology lies in the mechanical strength of the enclosure: a battery pack is bulky, generally flat to facilitate integration, and has a large surface area on the upper part of its external walls. Consequently, a pressure differential between the inside and outside generates stress and potentially significant deformation. Therefore, the enclosure walls must be sufficiently thick and rigid to prevent deformation, which increases the pack's weight. Finally, a last drawback of the current state of the art concerns the cooling of peripherals such as busbars, connectors, and the battery management electronics circuit, particularly the resistors in the battery cell voltage balancing circuit. When operating at high amperages, these components heat up and limit battery utilization. Furthermore, calibrating electronic circuits at various temperatures is a lengthy and expensive step in their development. Maintaining electronic circuits within a limited temperature range is also desirable to reduce their aging. Solution provided by the invention The solutions implemented in the invention consist of including all the peripheral components of the battery cells inside the sealed enclosure, in by immersing them in a dielectric fluid. This cools the electronic circuits, busbars, and connectors. Furthermore, the number of interfaces with the outside of the enclosure is significantly reduced, simplifying the sealing of the enclosure. The developed connectors are particularly hermetic to both liquids and gases. Furthermore, the system implemented in the invention features an expansion vessel equipped with a deformable membrane. The side not in contact with the dielectric fluid defines a chamber whose pressure is controlled by a valve. This valve either equalizes the chamber pressure with atmospheric pressure or connects the chamber to a vacuum pump. Once activated, the vacuum pump removes the air from the chamber to reduce its pressure below the saturation pressure of the dielectric fluid at its operating temperature. Consequently, it is possible to maintain a pressure equal to atmospheric pressure during system shutdowns, for example, to limit air ingress into the system.It is also possible to control the subcooling of the dielectric fluid between a minimum value, which is the subcooling required for the proper functioning of the dielectric fluid circulation pump, and a maximum value corresponding to the temperature differences that are allowed between the different battery cells. Furthermore, the dielectric fluid used can be chosen to have a saturation temperature at atmospheric pressure outside the operating temperature range, specifically above it, so that the difference between internal and external pressure does not change sign, remaining negative (under negative pressure in the enclosure). This simplifies the sealing solutions required for the enclosure. Finally, such an enclosure, always under negative pressure, experiences a pressure differential limited to 1 barG, thus reducing the enclosure's structural load. Object of the invention The invention, in its most general sense, relates to an electrical module comprising a plurality of battery cells immersed in a dielectric fluid, characterized in that it further comprises an electronic battery management circuit immersed in said dielectric fluid. According to variants, the module according to the invention further has one or more of the following additional features, taken individually or in combination: the module casing has on its inner wall a housing immersed in said dielectric fluid, said battery management electronic circuit being disposed in said housing. - the plurality of battery cells is assembled to form a block, the said battery management electronic circuit being fixed to said block. - the electronic battery management circuit is arranged so that the normal to the plane defined by said electronic circuit is substantially horizontal. - the electronic battery management circuit is connected to an external socket via a waterproof connector passing through the wall of the module's housing. - the module includes at least two electrical terminals passing through the wall of the module's housing in a sealed manner, the inner part of said electrical terminals being immersed in said dielectric fluid. - the module includes a switch for switching off said battery, said switch being immersed in said dielectric fluid. the module includes at least one temperature sensor immersed in said dielectric fluid. - The module includes a current sensor immersed in said dielectric fluid. - the module includes busbars immersed in said dielectric fluid. the electronic circuit includes a battery cell voltage balancing circuit immersed in said dielectric fluid. Detailed description of a non-limiting example of the invention The present invention will be better understood upon reading the detailed description of a non-limiting example of the invention that follows, with reference to the accompanying drawings where: - Figure 1 represents an exploded view of an example of an embodiment of a battery module according to the invention. - Figure 2 shows a cross-sectional view of the module. Figures 3 and 4 show top and bottom views of the lid respectively. Figure 5 shows a detailed view of the cover with an added heat exchanger. - Figures 6 and 7 represent a variant of the module for which the housing is made up of a flexible envelope. - Figure 8 represents a variant embodiment of the module containing pocket cells. Figures 9, 10, 11 and 12 represent the Schematic diagrams of cooling loops. - Figure 13 represents the integration of one of the thermal management systems of a battery with other thermal management functions. - Figure 14 shows a detailed cross-sectional view of a hermetic electrical connector. - Figure 15 represents a variant of the cell assembly using prismatic cells. - Figure 16 represents a variant embodiment of the module with the dielectric fluid circulating. General architecture and operating principle The module (1) described in figure 1 consists of an enclosure made up of three main parts: - a rigid case (100) - a lid (200) - a base (300). Inside this case (100) is arranged a block of batteries (400) arranged horizontally, on two parallel planes, offset by half a step. The module (1) forms a hermetically sealed enclosure, defining a free internal volume (i.e., the internal volume of the enclosure subtracted from the volume of the battery pack (400)) divided into: a lower part, filled exclusively with the liquid phase of a dielectric fluid (140), an upper part (150) exclusively filled with gas. The enclosure forms a rigid and robust component, which includes: - electrical power connectors (110, 120) for power connection, - one or more electrical data connectors (130) for connecting a link to one or more battery management systems, - Fittings at the hydraulic inlet and outlet ports (210, 220) for connecting supply and outlet pipes of a heat transfer fluid (145). The fluid The heat transfer fluid (145) circulates through a heat exchanger (236 or 237) contained within the module (1) to control the temperature inside the module. In Figure 1, this heat exchanger (236) is contained within the cover (200). Alternatively, in Figure 5, it is a separate component (237). Alternatively, in Figure 16, the heat exchanger is located outside the module (1), and the dielectric fluid (140) flows from the module (1) to a heat exchanger. In this configuration, the hydraulic inlet and outlet ports (210, 220) are used for the circulation of the dielectric fluid (140). The dielectric fluid (140) has the following characteristics: - zero ozon depletion potential, low global warming potential, preferably less than 150, or even less than or equal to 1. - low flammability, below A2L according to the classification by European Directive 2003 / 632 / EC - breakdown voltage greater than 20 kV / mm in liquid and gaseous phases, - electrical resistivity greater than 10E8 Ohm.cm density less than 1600 kg / m3 preferably, latent heat greater than 80 kJ / kg preferably. Furthermore, the product's operating range is characterized by a minimum (Tmin) and maximum (Tmax) temperature, typically -40°C and 60°C respectively. The dielectric fluid (140) can exhibit a boiling point at atmospheric pressure (Tsat(Patm)) that varies: - Tmin <Tsat(Patm)<Tmax : il existe une température d'ébullition pour laquelle le fluide est à pression atmosphérique dans la plage d'utilisation du produit. Ainsi la Fluid saturation pressure varies below and above atmospheric pressure depending on the temperature. If the only fluid present in module (1) is the dielectric fluid (140), then at thermodynamic equilibrium, the interior of module (1) is either under negative pressure or positive pressure, depending on the temperature. It can then be advantageous to have a deformable balloon (160) inside module (1), connected to a reference pressure, for example, open to the atmosphere, so that the balloon inflates in case of negative pressure in module (1) to avoid negative pressure operation and maintain a pressure approximately equal to atmospheric pressure. This is achieved by ensuring that the liquid volume of the dielectric fluid (140) is equal to the internal volume of module (1) minus the volume of the inflated balloon (160). In this case, the internal pressure of module (1) is between atmospheric pressure and the saturation pressure at the maximum operating temperature. If, in addition to the dielectric fluid (140), another gas is present in the module (1), for example air or nitrogen, then the pressure in the module is the sum of the partial pressure of the gas and the saturation pressure of the dielectric fluid (140). It is then possible to adjust the partial pressure of the gas during the filling of the module (1) to maintain overpressure throughout the operating range, particularly at Tmin. The internal pressure of the module is then between a lower limit, equal to the saturation pressure at the minimum operating temperature plus the pressure of the gas mass at the minimum operating temperature and the volume of the upper gaseous portion (150), and an upper limit equal to the saturation pressure at the maximum operating temperature plus the pressure of the gas mass at the maximum operating temperature and the volume of the upper gaseous portion (150). - Tsat(Patm)>Tmax: The saturation pressure of the fluid when using the product is always less than atmospheric pressure. In the case where the only fluid present in module (1) is the dielectric fluid (140), then the pressure inside module (1) is always less than atmospheric pressure and equal to the saturation pressure of the dielectric fluid at the operating temperature. During operation, the battery cells (414) heat up due to the Joule effect. When subjected to a current, their internal resistance produces heat, the power of which is equal to the internal resistance multiplied by the square of the current. Consequently, the dielectric fluid (140) inside the module (1) undergoes an isochoric heating and cooling cycle. In contact with the operating battery cells (414), it heats up, thus cooling the cells (414). It then transfers this heat to the heat exchanger (236 or 237). In the first case, the dielectric fluid (140) remains in the liquid phase. It rises (vertically upwards) towards the heat exchanger (236 or 237) by natural convection, its density being lower than that of the cold dielectric fluid. If it reaches the heat exchanger, it cools and descends towards the bottom of the module (1), thus forming a convection cell. In a second case, it evaporates upon contact with the cells (414). The bubbles formed move from the lower to the upper part (150) due to buoyancy. The gaseous phase of the dielectric fluid (140) condenses upon contact with the cooler heat exchanger (236 or 237). Droplets form on the internal surface of the heat exchanger (236 or 237) and fall back into the lower liquid section. Depending on the temperature and pressure, the ratio between the lower volume, the upper volume (150) and the volume of the possible balloon (160) varies, the cumulative volume, representing the interior of the module (1), remaining unchanged. The housing does not allow any circulation of the liquid phase of the dielectric fluid (140) to the outside of this enclosure, except during the filling phases, nor any circulation of the gaseous phase of the dielectric fluid (140). The liquid phase of the dielectric fluid (140) is generally static, without movement of the liquid phase under the effect of a pump or any means of mixing or forced circulation. The only movements of the liquid phase are those resulting from the natural phenomena of convection and circulation of bubbles in the gaseous phase and from vibrations caused by the support of the module (1). It may be advantageous to work only under vacuum to reduce the maximum pressure difference seen by the module (1), which allows for a lighter housing structure. Non-exhaustive examples of usable dielectric fluids are detailed below: - SF33 from Chemours (trade names) which boils at 33°C at IbarA and at 60°C at 2.45barA - Novec 649 from the company 3M (trade names) which boils at 49°C in IbarA - Novec 7100 from the company 3M (trade names) which boils at 61°C in IbarA - Novec 7200 from the company 3M (trade names) which boils at 76°C in IbarA - dielectric oils (boiling temperature typically > 200°C, leading to negligible saturation pressures at the envisaged operating temperatures). Detailed description of the case (100) The housing (100) consists of a hollow profile, preferably made of aluminum, optionally featuring reinforcing ribs to optimize the thickness (and therefore the weight) in relation to resistance to pressures or depressions forming inside the enclosure. It features mounting lugs (170) with tapped holes, in the example described, for screwing on the cover (200) and the base (300). The upper edge (171) and the lower edge (172) have grooves (173, 174) respectively for receiving a gasket (175, 176) ensuring a seal with the cover (200) and the base (300) respectively. This gasket can be an O-ring or a flat gasket. The base (300) is formed by a sheet of aluminum or stainless steel that hermetically seals the lower part of the housing (100). Alternatively, the housing (100) could also directly integrate the base (300) into a single piece, the housing then being produced by a casting process, for example. This solution eliminates the need for the O-ring (176) and the base fixing lugs. Alternatively, the housing (100) can be made of plastic or composite material. The enclosure shown in the example features four mounting tabs (180) for attaching to the module bracket (1), and two handles (190, 191) for handling the module. These handles (190, 191) are taller than the connectors (110, 120) to provide mechanical protection for them. The enclosure also features four threaded holes (181) on the front panel for attaching to the module bracket or for mounting the module (1) in a bay, for example, a 19-inch bay. The electrical connectors (110, 120, 130) have a hermetically sealed base to prevent fluid from entering dielectric (140) to be able to escape from the module (1) in case of overpressure or to allow air to enter the module (1) in case of depression. Detailed description of the balloon (160) It is advantageous that the pressure differential between the inside of the module (1) and the atmosphere does not change sign. Indeed, it is more complex to design a module that is hermetic under both negative and positive pressure. If the dielectric fluid (140) used has a Tsat(Patm) within its operating range, then it may be advantageous to use a variable-volume balloon (160). In Figure 1, the module (1) comprises a flexible balloon (160) immersed in the lower part of the fluid (140). The balloon (160) has an opening (161) connected to the outside. Since the opening (161) is always open during the operation of the module (1), the inside of the balloon (160) is constantly exposed to the external pressure. Consequently, the balloon (160) inflates when the internal pressure of the module (1) decreases, which occurs when the internal temperature drops below Tsat(Patm). As it inflates, the upper gaseous part (150) is reduced to zero, so there is no longer liquid-vapor equilibrium in the module (1), and the pressure of the liquid—which is then subcooled—is maintained approximately equal to atmospheric pressure. Conversely, the balloon (160) deflates when the internal pressure of the module (1) increases, for example, during a heating of the inside of the module (1). Its volume is then reduced to zero.Therefore, the balloon (160) constitutes, to some extent, a means of regulating the internal pressure of the module (1) with respect to the outside. This pressure regulation improves the hermeticity of the housing, as the seals are less stressed by pressure variations. The balloon (160) also simplifies the procedure for filling the module (1) with fluid (140), eliminating the need to evacuate the module (1) before filling. Indeed, to prevent any degradation of the dielectric fluid (140) by water and oxygen from the air, the module (1) must not contain any air. To achieve this, during the filling phase, the balloon (160) is kept inflated by an external pressure source. The module (1) is then completely filled to its highest point with the dielectric fluid (140), as the upper volume (150) of this fluid is not present in its gaseous phase. The module (1) is then hermetically sealed, and the pressure inside the balloon (160) is released. At this stage, that is, when the cells (414) are not heating up and there is therefore no evaporation, the balloon (160) remains inflated and the upper volume (150) does not exist. There is therefore no air in the module (1).When the cells (414) begin to heat up and the dielectric fluid (140) starts to evaporate, the pressure rises, the balloon (160) deflates, and the upper volume (150) of gas increases. The lid (200) then acts as a condenser, with the cooling fins (235) in contact with the gas. The volume of the balloon (160) is at least equal to the volume of gas contained at the level of the cooling fins (235). Consequently, when the balloon (160) is completely deflated, the upper volume (150) is such that the cooling fins (235) are entirely within the volume of gas. The efficiency of this cooling system is then maximized. Detailed description of the lid (200) Figures 3 and 4 show detailed views of the lid, respectively in exploded top view and bottom view. Figure 5 shows a detailed view of the cover with an added heat exchanger. The cover (200) consists of a solid block (230) of aluminum obtained by machining or casting. This block (230) has cooling fins (235) arranged longitudinally on its underside, along the longest axis of the cover (200). These fins (235) have a thickness of between 2 and 5 millimeters. They are regularly spaced at least 5 millimeters apart to prevent the formation of liquid bridges between two fins during the condensation of the dielectric fluid. The height of the fins (235) is between 5 and 15 millimeters. These fins (235) define heat exchange surfaces with the heat transfer fluid (145) on the one hand, and the gaseous phase present in the upper volume (150) on the other hand. The heat exchanger (236) of the cooling circuit is formed on the opposite surface of the solid block (230). It consists of a machined section forming a serpentine opening onto a hydraulic inlet port (210) and leading into a hydraulic outlet port (220). The upper surface of this coil is closed by a sheet metal plate (239) screwed around its periphery onto said solid block (230). Alternatively, this sheet metal plate (239) can be welded to the edges of the coil, or glued. Alternatively, in Figure 5, the previously described cooling circuit (236) can be replaced by a heat exchanger (237) between the heat transfer fluid (145) and the dielectric fluid (140), the heat transfer fluid (145) then circulating in a heat exchanger (237), which can be of the finned or brazed plate type. In this variant, the sheet metal (239) is still necessary to close the module (1) and ensure its airtightness. Advantageously, said heat exchanger (237) can be integral with said sheet (239), in particular in the case of a brazed plate heat exchanger and an aluminium sheet. The cover (200) has a through-hole housing a safety valve (240) or a rupture disc, which opens in the event of overpressure within the enclosure to release a portion of the gaseous phase (150) of the dielectric fluid (140) as well as any gases produced, for example, during battery thermal runaway, thus preventing the risk of module (1) explosion. In the event of overheating that triggers the opening of the safety valve (240), a temperature sensor near the valve (240) detects the overheating and transmits the information to the battery management module, which will prevent the module from being used until it is repaired. In the event of thermal runaway, the dielectric fluid will first evaporate, absorbing the heat emitted by the faulty cell, and then be expelled through the valve. The significant amount of energy contained in the evaporation of the fluid will prevent the temperature from rising further and spreading to other cells. Optionally, the cover (200) also has perforations (290) opening into the bottom of the coil (236). These perforations (290) are sealed by fusible plugs at a temperature above 80°C. If these plugs melt during overheating due to thermal runaway, the coolant escapes from the cooling circuit to fill the enclosure and thus provide additional cooling to the thermally runaway cell (414) to prevent contagion to other cells. Detailed description of electrical components The casing encloses the battery pack (400), which is fully immersed in the liquid phase of the dielectric fluid (140). The battery cells (414) are connected in series, parallel, or series-parallel by busbars (401), made of a conductive material that may be locally coated with an insulating layer. They are held in a cage formed by two frames (411, 412) connected by spacers (413). Because the busbars (401) are immersed in the liquid dielectric fluid (140), they benefit from the same type of evaporative cooling as the cells (414). Consequently, these busbars can be undersized as they are not susceptible to excessive heating, which is advantageous for the module's compactness, weight, and cost. Depending on the stresses applied to the module (1), the battery pack (400) can be secured in the housing using plates (260, 261) that encircle the frames (411, 412) from above and are fixed with screws. The battery pack (400) can also be secured at its base via plates (262 to 264) fixed to the bottom (300) of the module (1). The housing also contains an electronic circuit (420) for battery management, which is also fully immersed in the liquid phase of the dielectric fluid (140). Immersion of this electronic circuit (420) allows for its cooling, and in particular the cooling of the balancing resistors used during cell charging (414). These resistors can then easily accept a much higher balancing current to reduce the duration of the final charging phase of the cells (414). Alternatively, the battery management electronic circuit (420) can be mounted outside the module (1), and therefore outside the dielectric fluid (140). In this case, the temperature and voltage information for the cells (414) must be transmitted through a sealed bulkhead connector. The housing can also contain other peripheral components: electrical connectors, temperature and pressure sensors, contactors, current sensors, and various cables, all immersed in the liquid phase of the dielectric fluid (140) to ensure their cooling. The assembly formed by the battery pack (400), the busbars (401), the electronic circuits (420), and all the aforementioned peripheral components is called the cell assembly (402). Figure 15 illustrates a variant of this cell assembly (402) using prismatic cells. Figure 8 shows only the battery pack (400) with pouch-type cells (414). Detailed description of electrical connectors The electrical connectors (110, 120, 130) have a hermetically sealed base to prevent the dielectric fluid (140) from escaping from the module (1) in case of overpressure or air from entering the module (1) in case of depression. The airtightness of these connectors (110, 120, 130) can be ensured by overmolding the metal parts. In this case, the material used for this overmolding is chosen from among those compatible with the dielectric fluid used. For example, if the chosen fluid is 3M Novec 7100, the preferred materials for overmolding are epoxy resins. The airtightness of these connectors (110, 120, 130) can also be ensured by an O-ring located inside the connector. In this case, the material used for this seal is chosen from among those compatible with the dielectric fluid used. For example, if the chosen fluid is the SF33 from Chemours, the preferred materials for the seal are those based on EPDM (ethylene-propylene-diene monomer). These types of electrical connectors are generally very expensive and complex when they must remain airtight under pressure differences, due to the use of pins embedded in an insulating glass sleeve, for example. Therefore, a sealing cap (111) can be fitted inside standard power connectors (110, 120), which are not gas-tight in particular. This sealing cap consists of a cylindrical piece made of a conductive material (112), which is screwed directly onto the male pin (121) of the electrical connector (110, 120). In the example shown in Figure 14, this male pin (121) is directly overmolded into the body of the base (122) made of insulating material. Current flow is ensured by an annular contact surface (117) located between the conductive cylindrical piece (112) and the male pin (121).This annular surface (117) also serves as a mechanical stop when screwing the conductive part (112) onto the pin (121). The contact pressure and the contact surface are chosen to obtain a very low electrical contact resistance to prevent voltage drop and heating at this point. A typical value not to be exceeded is 2 mOhms. The cylindrical conductive part (112) includes a threaded portion (118) around which the internal connector is screwed. The cap (111) also includes a cylindrical insulating piece (113) that keeps the cylindrical conductive part (112) away from the housing wall (100) and prevents any risk of electrical arcing. The insulating piece (113) also includes two O-rings (114, 115) to ensure the cap (111) remains airtight under significant internal pressure. The casing contains several blocks of insulating material (250 to 256), typically ranging in thickness from 3 mm to 20 mm. These blocks provide electrical insulation between the battery pack (400) and the metal parts of the casing. They also help to secure the battery pack (400) in the event of an impact. The volume of these blocks (250 to 256) is maximized to reduce the free volume, particularly where the presence of the dielectric fluid (140) is not required. Indeed, some of the free volume of dielectric fluid is due to manufacturing and assembly constraints of the module, which limit the achievable shapes. Components requiring cooling have a typical spacing of 1 to 5 mm from the blocks (250 to 256) to allow the dielectric fluid (140) to pass through. Therefore, the inner faces of the blocks (250 to 256) are shaped to best fit the parts they surround, while maintaining this spacing. This maximization of the volume of the blocks (250 to 256) is motivated by the reduction of the volume of dielectric fluid (140) in order to minimize weight, as the material constituting the blocks (250 to 256) is advantageously lighter than the dielectric fluid (140) it replaces.This maximization is also motivated by cost, as the dielectric fluid (140) is more expensive than the blocks (250 to 256). These blocks (250 to 256) are chosen from a material compatible with the dielectric fluid (140). In the example described, polyurethane-based expanded foam blocks are preferred. The materials are also closed-cell, so that they do not absorb the dielectric fluid (140). Alternatively, a resin may be used to provide electrical insulation between the battery pack (400) and the metal parts of the case. Alternatively, the foam can be deposited in the module (1) by a foaming process using a counter-mold: • The first step involves positioning the counter-form within the electrical module enclosure, • A second step consists of injecting the still-liquid foam into the defined internal space between the electrical module enclosure and the counter-mold, • A third step involves removing the counter-mold once the foam has hardened (250 to 256), • a fourth step consists of positioning the cell assembly (402), composed of a battery pack (400), busbars (401), connectors (110, 120, 130), sensors and electronic circuits (420), in the assembly composed of the module (1) and the hardened foam (250 to 256). In this process, the mold is shaped so that the cell assembly (402), consisting of a battery pack (400), busbars (401), connectors (110, 120, 130), sensors, and electronic circuits (420), can be positioned during the fourth step. This positioning also maintains a space between the cell assembly (402) and the foam (250 to 256), typically 1 to 5 mm thick, except for areas of mechanical contact between the cell assembly (402) and the enclosure (100, 200, 300). Ideally, the mold occupies all the free volume of the dielectric fluid not required for cooling. In practice, however, constraints related to mounting the cell assembly in the enclosure limit the shape of this mold. The heat transfer fluid (145) circulating in the heat exchanger (236) of the cover's (200) cooling circuit absorbs the heat generated in the module (1) and dissipates it using a cooling system. The cooling system consists of a cold source, a circulation pump (704) for the heat transfer fluid (145) circulating in a closed circuit, supplying one or more modules (1) with the cooled heat transfer fluid (145). The heat transfer fluid (145) can be a 50% mixture of deionized water and ethylene glycol to prevent freezing at low temperatures while maintaining good thermal properties. Alternatively, any non-flammable heat transfer fluid (145) with high sensible heat capacity and low viscosity may be used: propylene glycol, special oils. In a first embodiment shown in Figure 9, the cold source is a radiator (701), preferably cooled by a fan (702), capable of dissipating heat from the heat transfer fluid (145) into the ambient air. This embodiment is suitable for applications where the ambient air temperature does not exceed approximately 30°C, and preferably 25°C, in order to limit the temperature of the cells (414) in the module (1), for example, to around 40°C maximum. Furthermore, with this type of solution, the temperature of the cooling circuit is highly dependent on the power dissipated in the module (1) and the ambient temperature, resulting in its preferred use in applications with relatively stable battery power to avoid thermal cycling. The supply of several modules (1) by the heat transfer fluid loop (145) can be carried out in series or in parallel, or by a combination of both. Preferably, the number of modules (1) in series will be chosen, on the one hand, equal to a minimum of 2 in order to limit the required flow rate of the pump (704), and on the other hand, equal to a maximum of 3 in order to limit the required pressure of the pump (704) and the heating of the heat transfer fluid (145) as it passes through the modules (1). The number of modules in parallel will preferably be between 2 and 8. The heat transfer fluid (145) circulation pump (704) can advantageously be regulated in rotation speed and controlled to the cooling requirements of the modules (1) in order to improve the energy efficiency of the complete system. Similarly, the radiator (701) can advantageously be equipped with a fan (702) with regulated rotation speed, with the same energy efficiency objective as described previously. In a second embodiment shown in Figure 10, the cold source consists of the evaporator (708) of a vapor compression refrigeration system (703), of the type used for air conditioning the passenger compartment of vehicles. This type of system consists of an evaporator (708), a compressor (705), a condenser (706), and an expansion valve (707) connected by pipes that allow the circulation of a refrigerant (709) in a closed loop. This refrigerant (709) can be, for example, an HFC such as R134a, or an HFO such as R1234yf, R1234ze, or R1233zd. The cooling produced by the evaporator (708) is used to lower the temperature of the heat transfer fluid (145), if necessary to a value lower than that of the ambient air, which makes it possible to control the temperature in the module (1) to a predetermined value, and in particular to limit it - for example to a maximum of 40°C - regardless of the fluctuations in power dissipated in the module and the ambient temperature of the application. The refrigeration system (703) can also be reversible. In heating mode, it can thus provide heat to warm the modules (1) whose performance under load is affected, in particular, at temperatures typically below 0°C. For embedded applications where mass must be minimized, the compressor (705) of the refrigeration system will advantageously be chosen from among the air conditioning compressors used in electric vehicles, which are made primarily of aluminum alloys and are designed to be directly powered by direct current from a battery. Since these compressors are equipped with a variable speed drive, they allow, on the one hand, for improved energy efficiency by adjusting the cooling capacity of the refrigeration system (703) to the precise needs of the modules (1), and on the other hand, for achieving high maximum capacities by operating at maximum speed. Furthermore, the temperature range targeted for the thermal regulation of the batteries makes it possible to raise the evaporation temperature level beyond 15°C, or even up to 30°C, and thus increase the cooling capacity developed by the compressor (705) compared to conventional use in air conditioning: specific powers of the order of 1.5 kW cooling per kilogram of compressor can thus be achieved. Similarly, to minimize the mass of the system, an evaporator (708) made of aluminum alloy can be used, preferably of the brazed plate type in order to reduce the internal volume on the heat transfer fluid side (145). The heat transfer fluid loop (145) is adapted to distribute to the modules (1) the cooling power generated at the level of the evaporator (708), in particular when several modules of a battery pack need to be powered and are located at a certain distance from it. Alternatively, in Figure 11, for more compact systems, the heat transfer fluid loop (145) can be omitted, with the module's cooling circuit (236) then serving directly as an evaporator (708) for the refrigeration system (703). This type of arrangement is particularly suitable for cooling a single module (1), or a limited number of modules (1) to be cooled, in order to limit the required refrigerant charge (709) and the complexity associated with managing multiple evaporators in parallel within a refrigeration system (703). Alternatively, for more energy-efficient systems, the energy consumption of the refrigeration system (703) can be limited by connecting it in parallel with the radiator (701) of the heat transfer fluid loop (145). It is also possible to eliminate the heat transfer fluid loop (145) as shown in Figure 12 by circulating the dielectric fluid (140) from the module(s) (1) to the radiator (701). The parallel refrigeration system (703) then preheats the dielectric fluid (140) before it enters the radiator (701), thus facilitating its cooling by increasing the temperature difference with the air. It also cools the dielectric fluid (140) to the desired temperature immediately after the radiator (701).This configuration allows the refrigeration system (703) to activate only when a threshold temperature on the return line of the dielectric fluid (140) is exceeded, thus reducing the energy consumption of the refrigeration system (703) when the battery's power consumption is low, when it has time to cool down between uses, or when the ambient temperature is low. Eliminating the heat transfer fluid loop (145) also eliminates the accumulation of temperature differentials between the cold source and the cells, which impairs the energy efficiency of the cooling. This solution is preferable for [the following applications]. demanding embedded applications that must be self-sufficient in cooling due to their weight and energy efficiency. In order to circulate the dielectric fluid (140), a module variant is shown in Figure 16. In this variant, the heat exchanger (236) is removed and the hydraulic inlet and outlet ports (210 and 220) are used by the dielectric fluid (140). Finally, Figure 13 shows the integration of one of the thermal management systems of a battery with other thermal management functions, for example those of the electronics (712), electric motors (711) and the heating, ventilation and air conditioning system (710) of the cabin of a vehicle. The electronics (712) can consist of the battery safety management system (BMS) but also the power electronics supplying an electric motor. The heating, ventilation and air conditioning system (710) is connected to a second evaporator (7080) in parallel with the evaporator (708) which is connected to the dielectric fluid loop (140). The flow rate in this second evaporator (7080) is controlled by a second expansion valve (7070). Figure 13 also illustrates two actuator control systems for this system. The refrigeration system (703) is servo-controlled to regulate subcooling at the inlet of the pump (704) to prevent cavitation and minimize the use of the refrigeration system (703) to limit its energy consumption. To achieve this, a pressure sensor (P) and a temperature sensor (T) positioned upstream of the pump are required. A typical target subcooling is less than 5°C below the saturation temperature at the measured pressure. The second control algorithm servo-controlled the rotational speed of the fan (702) such that the difference between the fluid temperature (T2) and the fan speed is maintained. dielectric (140) at the outlet of the radiator (702) and the ambient temperature (T3) is less than a value varying between 1 and 8°C depending on the use case of the application, for example charging or discharging, vehicle moving or stationary, etc.Also illustrated is a system for reducing the vacuum in the dielectric fluid loop (140), particularly when the system is not operating. This system is used especially when a fluid with a Tsat(Patm) lower than the maximum temperature seen by the system is used. An expansion vessel (713) with an internal diaphragm is connected to the dielectric fluid circuit (140). This expansion vessel (713) is controlled by an air pressure regulated by a valve (714). When the air pressure is lower than the pressure in the dielectric fluid circuit (140), the diaphragm is pressed against the bottom of the vessel (713) and the dielectric fluid is drawn into the vessel (713). Conversely, when the air pressure is higher than the pressure in the dielectric fluid circuit (140), the diaphragm expands and forces the fluid (140) out of the vessel (713).To regulate an air pressure lower than atmospheric pressure, a vacuum pump (715) is connected to one of the two inlets of the valve (714). The valve (714) thus allows the pressure to be regulated between 0 bar absolute and atmospheric pressure. To prevent a vacuum at standstill, the valve supplies air pressure equal to atmospheric pressure, which fills the fluid circuit with liquid and maintains it as a subcooled liquid at approximately atmospheric pressure. During operation, the dielectric fluid (140) is drawn back into the vessel (713), reducing the control pressure of the vessel (713) to a pressure close to the saturation pressure of the dielectric fluid at its measured temperature (T), thus allowing space for a vapor phase. The system is sized to have a reduced volume of vapor phase, for example, one-third of the volume of the pipe between the module (1) and the [unclear - possibly "the other component"]. radiator (702), which allows for a relatively small vessel (713). If a dielectric fluid with a Tsat(Patm) value higher than the maximum temperature seen by the system is used, then the valve (714) and the vacuum pump (715) could be omitted. The expansion vessel (713) is then simply brought to atmospheric pressure. It is even possible to do without a membrane if the dielectric fluid (140) is not susceptible to oxidation or hydrolysis by oxygen and ambient humidity. Removing the pressure control upstream of the circulation pump (704) simplifies the system but results in uncontrolled and very high subcooling, which hinders evaporation on the cells. Consequently, the heat transfer coefficients at the cell interface are lower, and the temperature differences between cells are greater. The use of such a fluid then becomes less advantageous. Implementation variations In the figures shown, the module is displayed with cylindrical cells (414) with a diameter of 66mm and a length of 160mm, using lithium titanate (LTO) electrochemistry, similar to Yinlong's 40Ah LTO cells. However, the same type of dielectric fluid cooling (140) is not limited to these cells (414) and can be used for other types of cells, such as 18650 cells, for example, with LG's HG2 electrochemistry, or "thin rectangular pocket" cells, for example, from Xalt or Kokam, or prismatic cells, for example, measuring 139x22x56mm from Toshiba. In the case of the variant with "pocket" format cells mentioned earlier, it should be noted that the plates The interlayers (601) between the cells have a design specific to the evaporative cooling system. Indeed, as shown in Figure 8, these plates have substantially vertical passages (602) intended to allow the flow of evaporated fluid to rise towards the exchanger (237). In cases where the dielectric fluid (140) used has a Tsat(Patm) outside its operating range, for example, Novec 7100 from 3M (trade names), which boils at 61°C at IbarA, it may be advantageous to fill the module after first evacuating it with a liquid volume of dielectric fluid less than its free volume, in order to maintain a gaseous headspace at a pressure below atmospheric pressure. In this case, the use of a balloon (160) is not required. Also, since the internal pressure does not exceed IbarA, the housing can be made of a flexible casing (502), as shown in Figures 8 and 9. This flexible casing (502), preferably made of plastic, is hermetically sealed using a joint (503), which can be a weld between the two parts of the casing (502).As shown in Figure 7, the lower internal pressure compared to the external pressure, combined with the flexibility of the casing (502), means that the casing adheres very closely to the cells (414), thus reducing the volume of dielectric fluid (140) present in the module (1). This type of flexible-casing module operates similarly to that described for a rigid casing; as shown in Figure 6, it also has insulating filler blocks (250), a volume of dielectric fluid (140) in liquid and gaseous phases (150), and a heat exchanger (237) with hydraulic inlet and outlet ports (210 and 220). The hydraulic outlets (210 and 220) are hermetically sealed to the casing (502) by welded joints (604) to ensure the airtightness of the module (1).

Claims

Demands 1 - Electrical module comprising a housing (100) containing a plurality of battery cells immersed in a dielectric fluid (140), and an electronic battery management circuit (420) immersed in said dielectric fluid (140), characterized in that it further comprises at least one heat exchanger (236 or 237) through which a heat transfer fluid (145) circulates, and in that said housing (100) encloses several blocks of insulating material (250 to 256) to ensure electrical insulation between the battery block (400) and the metallic parts of the housing (100) and to hold the battery block (400) in place in case of shock. 2 --- Electrical module according to claim 1, characterized in that said exchanger (236) is integrated into the cover (200) of said housing (100). 3 - Electrical module according to claim 1, characterized in that said electronic battery management circuit (420) is arranged so that the normal to the plane defined by said electronic circuit (420) is substantially horizontal. 4 - Electrical module according to claim 1, characterized in that said electronic battery management circuit (420) is connected to an external socket via a waterproof connector (110, 120, 130) passing through the wall of the housing (110) of said module. 5 - Electrical module according to claim 1, characterized in that it comprises at least two electrical terminals (110, 120, 130) passing through the wall of the housing in a sealed manner (100) of said module, the inner part of said electrical terminals (110, 120, 130) being immersed in said dielectric fluid (140). 6 - Electrical module according to claim 1, characterized in that it comprises a switch for switching off said battery, said switch being immersed in said dielectric fluid (140). 7 - Electrical module according to claim 1, characterized in that it comprises at least one temperature sensor immersed in said dielectric fluid (140). 8 - Electrical module according to claim 1, characterized in that it comprises a current sensor immersed in said dielectric fluid. 9 - Electrical module according to claim 1, characterized in that it comprises busbars (401) immersed in said dielectric fluid (140). 10 - Electrical module according to claim 1, characterized in that said electronic circuit (420) comprises a battery cell voltage balancing circuit immersed in said dielectric fluid (140).

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