Heat treatment system for an electrical energy storage device

Abstract

Thermal treatment system for an electrical energy storage device The present invention relates to a thermal treatment system (100) for an electrical energy storage device comprising electrical energy storage elements (22), the thermal treatment system (100) comprising the electrical energy storage device, and a dielectric fluid circuit comprising: - at least one circulation channel (24) for the dielectric fluid between at least a part of the electrical energy storage elements (22) of the storage device, - a circulation pump (3) for the dielectric fluid, - a heat exchanger (5) configured to thermally treat the dielectric fluid, the thermal treatment system (100) being characterized in that the dielectric fluid circuit comprises an expansion vessel (1) and in that the thermal treatment system (100) comprises a variable volume reservoir (14) connected to the expansion vessel (1).(Figure 1).

Description

Title of the invention: Heat treatment system for an electrical energy storage device

[0001] The present invention relates to the fields of thermodynamics and electricity, and more specifically concerns a cooling and / or heating system for an energy storage device such as a battery, finding particular application in the automotive industry.

[0002] Electric or hybrid vehicles are equipped with high-voltage batteries, necessary to power electric motors coupled to the wheels of these vehicles, to provide traction or propulsion. In order to ensure sufficient driving range for such a vehicle without impacting the available space within it, the trend is towards increasing the power density of these batteries, which often use lithium-based technology.

[0003] However, such batteries, with a maximum open-circuit voltage of approximately 200 to 800V, require an efficient cooling system. Indeed, their energy storage cells tend to heat up, particularly during rapid charging or discharging. Their temperature must be maintained within a range that prevents combustion in the event of high heat and peak electrical consumption by the vehicle.

[0004] Available cooling solutions use cooling plates, for example through glycol water, or phase-change materials. Cooling plates can only be made in contact with insulated battery walls, and therefore have a small surface area for heat exchange with the storage cells, making this type of cooling device relatively inefficient. Phase-change materials can be placed directly in contact with the storage cells, but this solution is complex and expensive, especially when the battery comprises several modules, each containing multiple cells. This solution requires a closed circuit for each module to avoid imbalances in the state of the phase-change material from one module to another.

[0005] Another cooling solution consists of immersing the battery's energy storage cells in a dielectric liquid, itself cooled by a heat exchanger through which, for example, glycol water circulates. However, this solution requires a large volume of dielectric, on the order of 20 liters, and a very large battery casing that is highly resistant to pressure, in order to maintain its seal during variations in the volume of the dielectric liquid. Indeed, the storage cells Batteries increase in volume when charged and / or age, and the dielectric fluid itself expands when hot. Therefore, the housing must have a large expansion tank to compensate for this volume change. Even with a large tank, the pressure inside the tank varies and can reach 2.5 bar absolute when hot and when the battery is charged.

[0006] There therefore remains a need for an efficient cooling system for a battery of energy storage cells, which is not very complex and compact.

[0007] The present invention aims to remedy at least in part the aforementioned drawbacks by providing a heat treatment system for an electrical energy storage device and a method for filling a dielectric circuit of such a heat treatment system with dielectric liquid, which allows a dielectric liquid to circulate in contact with the energy storage elements of the storage device, without generating pressure variations in the housing of the storage device during its life cycle.

[0008] To this end, the invention proposes a heat treatment system for an electrical energy storage device comprising electrical energy storage elements, the heat treatment system comprising the electrical energy storage device, and a dielectric liquid circuit comprising: - at least one channel for circulating the dielectric fluid between at least some of the electrical energy storage components of the storage device, - a dielectric fluid circulation pump, - a heat exchanger configured to thermally treat the dielectric liquid, the heat treatment system being characterized in that the dielectric liquid circuit includes an expansion vessel and in that the heat treatment system includes a variable volume tank connected to the expansion vessel.

[0009] The energy storage device is, for example, a high-voltage battery of an electric or hybrid vehicle, the thermal treatment system according to the invention allowing the high-voltage battery to be cooled or heated depending on the context of use of the vehicle.

[0010] The electrical energy storage components of the storage device are, for example, energy storage cells, for example cylindrical Lithium-ion cells, or prismatic Lithium cells, or even pouch cells also called "pouch cells" in English.

[0011] The dielectric fluid circulates in the heat treatment system according to the invention between these components, the circulation channel being able to be formed by the entire housing of the storage device, provided with a dielectric fluid inlet and outlet. Preferably, however, several circulation channels are provided in the storage device to better channel the dielectric liquid, which is for example oil or any other dielectric liquid that can cool the components of the storage device.

[0012] The heat treatment system is configured to keep the dielectric fluid in a liquid state; that is, there is no vapor or solid phase of the dielectric fluid in the operating dielectric fluid circuit. In particular, a suitable choice of dielectric fluid ensures that it remains liquid within the operating temperature range of the storage device.

[0013] The heat treatment system according to the invention can of course contain more elements, in particular several heat exchangers, several expansion vessels or variable volume tanks, but this complicates the system without additional advantage.

[0014] Although preferably the housing of the storage device is hermetically sealed, with the oil bathing the storage elements being in direct contact with the housing, alternatively the oil is confined in one or more hermetically sealed containers containing the storage elements, and the housing has spaces between these containers and its walls to accommodate other elements of the heat treatment system such as the expansion vessel, the variable volume tank, the heat exchanger and the pump.

[0015] In this embodiment, the dielectric fluid circuit is entirely confined within the housing of the storage device, which may nevertheless include an inlet and outlet for a heat transfer fluid or refrigerant, passing through the heat exchanger. For example, the heat exchanger is traversed by glycol water, which circulates in one or more cooling circuit loops, enabling the cooling of power electronics modules in addition to the storage device.

[0016] Thanks to the expansion vessel and the variable-volume reservoir, the invention avoids oversizing the storage device's housing volume compared to a storage device cooled with a cooling plate, for example, and maintains the pressure within the storage device at a pressure close to atmospheric pressure, i.e., approximately one bar, excluding pressure drop in the pipes. Indeed, the variable-volume reservoir can absorb a volume variation of approximately 3 liters without increasing the pressure in the reservoir, thus limiting the pressure inside the storage device's housing. Furthermore, the invention is suitable for filling the heat treatment system with dielectric liquid under vacuum on the assembly line. Since absolute vacuum is not guaranteed, a volume of air always remains in the heat treatment system after its assembly.

[0017] Preferably, the expansion vessel is made of rigid material and the variable volume reservoir of flexible material. For example, they are made of PVC (polychloride). vinyl), but other types of materials are of course usable. The expansion vessel can be made of several materials, but they must be capable of containing a fixed volume of dielectric fluid and air. The expansion vessel allows for the degassing of the dielectric fluid present in the dielectric fluid circuit. The reservoir can also be made of several materials, allowing its volume to decrease or increase.

[0018] The variable-volume reservoir takes, for example, the form of a flexible pouch easily housed in the underbody of a vehicle incorporating the storage device, or within the storage device itself. Such a design makes the shape of the variable-volume reservoir, even when filled, adaptable to confined spaces and various shapes.

[0019] In addition, the expansion vessel allows the dielectric fluid circulating between the storage elements to discharge as air bubbles into the expansion vessel which is partly filled with dielectric fluid and partly with air, and thus to maintain an efficient heat exchange between the dielectric fluid and the storage elements of the storage device.

[0020] In one embodiment of the invention, in the heat treatment system according to the invention, the electrical energy storage elements of the storage device are grouped into modules, each of the modules includes at least one dielectric fluid circulation channel, the dielectric fluid circuit includes a dielectric fluid inlet manifold connecting the inlets of the modules and a dielectric fluid outlet manifold connecting the outputs of the modules, and the expansion vessel is connected on one side to the outlet manifold and on the other side to a point in the dielectric fluid circuit located downstream of the outlet manifold and upstream of the circulation pump.

[0021] In this application, the terms "upstream" and "downstream" refer of course to the direction of flow of the dielectric liquid.

[0022] In this embodiment of the invention, the expansion vessel receives a portion of the dielectric fluid flow from the outlet manifold, and the dielectric fluid exiting the expansion vessel joins a main dielectric fluid circuit upstream of the circulation pump. One branch of the dielectric fluid circuit thus connects the expansion vessel to the outlet manifold, and another branch of the dielectric fluid circuit connects the expansion vessel to an inlet of the circulation pump, or yet another branch of the dielectric fluid circuit connects the outlet manifold to an inlet of the circulation pump.

[0023] In another embodiment of the invention, in the heat treatment system according to the invention, the electrical energy storage elements of the storage device are grouped into modules, each module comprising at least one dielectric fluid circulation channel, the dielectric fluid circuit includes a dielectric fluid inlet manifold connecting the module inlets together, a first dielectric fluid outlet manifold connecting the outputs located in the upper part of the modules together and a second dielectric fluid outlet manifold connecting the outputs located in the lower part of the modules together, the expansion vessel being connected on one side to the first outlet manifold and on the other side to the second outlet manifold.

[0024] In this other embodiment of the invention, the upper part of each module is higher than the lower part of the module. In other words, the first outlet manifold is located higher than the second outlet manifold, the terms "upper" and "lower" referring here to the vertical direction in which the heat treatment system is intended to be positioned during operation. The first manifold has a much smaller cross-section than the second manifold because its function is to capture air bubbles at the top of each module, and its flow rate is much lower than that of the second manifold.

[0025] The first and second outlet manifolds are further positioned so as to receive dielectric liquid from the circulation channels, that is to say that the lighter dielectric liquid, therefore charged with air bubbles, circulating in the circulation channels, exits the modules through the first outlet manifold, while the heavier dielectric liquid, therefore discharged with air, circulating in the circulation channels, exits the modules through the second outlet manifold.

[0026] The expansion vessel therefore receives dielectric fluid charged with bubbles from the first outlet manifold, and the dielectric fluid exits the expansion vessel discharged of air to enter the second outlet manifold and then enter the circulation pump.

[0027] A branch of the dielectric fluid circuit optionally connects the first outlet manifold and the second outlet manifold, in order to allow the air-free dielectric fluid to flow down by gravity into the second outlet manifold.

[0028] In these embodiments of the invention, the modules are, for example, compartments of the housing of the storage device, each comprising several energy storage cells immersed in the dielectric liquid in each of these compartments.

[0029] Preferably in the invention, the variable volume reservoir is directly connected to the expansion vessel. A pipe therefore connects the expansion vessel to the variable volume reservoir, which has no other connection to the dielectric fluid circuit.

[0030] If the expansion tank is located outside the battery case (i.e., the storage device), and if it is located vertically at a level above the battery case, the connection to the expansion tank of the line connecting the manifold The outlet and inlet of the expansion tank can be located vertically at any level of the tank. However, if the tank is integrated into the battery box, or if it is located below the battery box, the line must be connected to a lower portion of the expansion tank where there is always coolant. This prevents air from the expansion tank from rising towards the outlet manifold.

[0031] When the inlet of the expansion vessel is located in the lower portion of the expansion vessel, a flow barrier may be placed in the expansion vessel between this inlet and the outlets of the expansion vessel, one being connected to the variable volume reservoir and the other to another outlet manifold or to the circulation pump, depending on the embodiment of the invention. This prevents air bubbles arriving through the inlet of the expansion vessel from being drawn towards the outlets of the expansion vessel.

[0032] The expansion vessel can be housed in an empty volume of the battery case, or integrated into one of the battery modules.

[0033] Furthermore, according to an optional and advantageous feature of the invention, the expansion vessel includes a filler cap. This cap allows the dielectric fluid circuit to be filled or drained.

[0034] According to another optional and advantageous feature of the invention, the dielectric fluid circuit includes a safety valve. This is, for example, connected to an outlet manifold of the dielectric fluid circuit, or arranged on the filling cap of the expansion tank.

[0035] By way of example, the expansion vessel is suitable for holding 0.5 to 2 liters of dielectric fluid, and the variable volume reservoir is suitable for holding 2 to 8 liters of dielectric fluid. Preferably, the expansion vessel is suitable for holding 1 to 1.5 liters of dielectric fluid, and the variable volume reservoir is suitable for holding 3 to 6 liters of dielectric fluid.

[0036] The invention also relates to a method for filling the dielectric liquid circuit of a heat treatment system according to the invention with dielectric liquid, comprising the steps of: - evacuation of air present in the dielectric fluid circuit, - introduction of a predetermined quantity of dielectric fluid into the dielectric fluid circuit, - activation of the circulation pump, - comparison of a first quantity of dielectric fluid present in the variable volume tank with a first predetermined quantity, and comparison of a second quantity of dielectric fluid present in the expansion vessel with a second predetermined quantity, and, if the first and second quantities of dielectric fluid correspond respectively to the first and second quantities predetermined - airtight closure of the dielectric fluid circuit by mounting the filling plug on the expansion tank.

[0037] This filling process is carried out for example when installing the storage device in the vehicle, or when draining the dielectric fluid circuit to renew it.

[0038] Air is removed from the dielectric fluid circuit, for example, by drawing a vacuum using an ejector or a vacuum pump connected to the opening in the dielectric fluid circuit formed by first opening the filler cap. Furthermore, activating the circulation pump allows the dielectric fluid to be degassed, thus enabling the quantities of dielectric fluid in the expansion tank and the variable-volume reservoir to be controlled and representative of the quantities present in these containers during vehicle operation.

[0039] The first and second quantities of dielectric liquid correspond to the first and second predetermined quantities when the first quantity of dielectric liquid is equal to the first predetermined quantity to within a tolerance of the order of 0.1 liter, and when the second quantity of dielectric liquid is equal to the second predetermined quantity to within a tolerance of the order of 0.1 liter. When this correspondence is not achieved, if the first and second quantities of dielectric fluid are less than the predetermined first and second quantities, more dielectric fluid is introduced into the dielectric fluid circuit in small quantities until these predetermined first and second quantities are reached after a further activation of the circulation pump. Conversely, if the first and second quantities of dielectric fluid are greater than the predetermined first and second quantities, dielectric fluid is withdrawn in small quantities from the dielectric fluid circuit until these predetermined first and second quantities are reached after a further activation of the circulation pump.

[0040] By way of example, the first predetermined quantity is between 1 and 3 liters at an ambient temperature of 20°C (degrees Celsius).

[0041] The invention also relates to an electric or hybrid vehicle comprising a heat treatment system according to the invention of an electrical energy storage device.

[0042] The vehicle and the method according to the invention have advantages similar to those of the heat treatment system according to the invention.

[0043] Other features and advantages of the invention will become apparent from the following description on the one hand, and from several examples of embodiments given by way of illustration and not limitation with reference to the attached schematic drawings on the other hand, on which:

[0044] [Fig. 1] illustrates a heat treatment system according to the invention of an electrical energy storage device, in a first embodiment of the invention,

[0045] [Fig. 2] illustrates a heat treatment system according to the invention of an electrical energy storage device, in a second embodiment of the invention,

[0046] [Fig. 3] is a cross-sectional view of a heat treatment system according to the invention of an electrical energy storage device, in a variant of the first embodiment of the invention, at the beginning of the life of the electrical energy storage device, the latter being discharged with electricity, at a temperature of approximately 20°C,

[0047] [Fig.4] is a cross-sectional view of the heat treatment system of [Fig.3], at the end of the life of the energy storage device, at the end of an electrical charge, and at a relatively high temperature,

[0048] [Fig.5] is a cross-sectional view of the heat treatment system of [Fig.3], at the beginning of the life of the energy storage device, with a low electrical charge and an ambient temperature of -30°C, and

[0049] [Fig.6] represents steps of a filling process according to the invention of a heat treatment system according to the invention of an electrical energy storage device, in an embodiment of the invention.

[0050] According to a first embodiment of the invention shown in [Fig. 1], a heat treatment system 100 according to the invention comprises an electrical energy storage device, which is here a high-voltage battery from an electric or hybrid vehicle. The storage device comprises a sealed housing 9, for example made of aluminum.

[0051] The housing 9 of the storage device is divided into four modules 2, each containing several electrical energy storage elements 22, here prismatic energy storage cells, which may alternatively be pouch cells, or cylindrical cells. In [Fig. 1], not all the elements 22 are shown to avoid cluttering the figure, but each module 2 contains more than two elements, for example, ten elements. Similarly, the storage device in [Fig. 1] only has four modules to make the various elements of the heat treatment system 100 more easily visible, but it is understood that the invention applies to storage devices that can contain far more than four modules.

[0052] The organs 22 are immersed in a dielectric liquid, for example oil, in each module 2, the dielectric liquid completely filling the available volume in each module around the organs 22.

[0053] The heat treatment system 100 also includes a liquid circuit di The electrical current circulates the dielectric fluid, particularly within the modules 2, which form channels for the dielectric fluid. In each module 2, the dielectric fluid circulates between the components 22 and the walls of the module 2, but also between the components 22 themselves. Since the components 22 are oblong and parallelepiped-shaped, a natural circulation channel 24 is formed between two adjacent components 22 within the same module 2.

[0054] In this first embodiment of the invention, each module 2 comprises a dielectric liquid inlet 62, proximal to one end of a circulation channel 24 of the module 2 under consideration, and two dielectric liquid outlets 42, 82 proximal to the other end of the circulation channel 24.

[0055] The unreferenced arrows in Figures 1 and 2 show the direction of flow of the dielectric liquid.

[0056] A first output 82 of the two outputs is located in the upper part of module 2, and a second output 42 of the two outputs is located in the lower part of module 2, that is to say that the first output 82 is arranged in height relative to the second output 42 when the heat treatment system 100 is integrated into the vehicle and is operating normally.

[0057] The dielectric fluid circuit includes an inlet manifold 6 which takes the form of a pipe along a first wall 92 of the housing 9, transverse to the modules 2, the pipe having four fluidic connections to the four inlets 62 of dielectric fluid of the modules 2 on the first transverse wall 92 of the housing 9.

[0058] The dielectric liquid circuit also includes a first outlet manifold 8, arranged at the top of a second wall 94 of the housing 9, transverse to the modules 2, the second wall 94 being opposite to the first wall 92 with respect to the housing 9. The first outlet manifold 8 similarly takes the form of a pipe running along the second wall 94, and which includes four fluidic connections to the four outlets 82 of dielectric liquid located in the upper part of the modules 2.

[0059] The dielectric fluid circuit also includes a second outlet manifold 4, located at the bottom of the second wall 94 of the housing 9. The second outlet manifold 4 takes the form of a pipe running along the second wall 94, and includes four fluid connections to the four dielectric fluid outlets 42 located in the lower part of the modules 2.

[0060] The first outlet manifold 8 is therefore arranged in height relative to the second outlet manifold 4. It allows to collect a part of the dielectric liquid charged with air bubbles at the outlet of the modules 2, while the second outlet manifold 4 allows to collect a part of the dielectric liquid devoid of air at the outlet of the modules 2, this part devoid of air being heavier than the part charged with air bubbles.

[0061] The dielectric fluid circuit further comprises a circulation pump 3 and a heat exchanger 5, through which the dielectric fluid flows on one side and a heat transfer fluid 55, such as glycol water or a refrigerant, on the other, allowing the dielectric fluid to be cooled or heated according to the operating mode of the heat treatment system 100. The glycol water or the refrigerant circulates inside another circuit, not shown.

[0062] The heat exchanger 5 has a dielectric fluid outlet connected by a branch 65 of the dielectric fluid circuit to the inlet of the inlet manifold 6, arranged at one end of its pipe shape. The circulation pump 3 has a dielectric fluid outlet connected, by a branch 53 of the dielectric fluid circuit, to the dielectric fluid inlet of the heat exchanger 5, and a dielectric fluid inlet connected by a branch 34 of the dielectric fluid circuit to the outlet of the second outlet manifold 4 located at one end of its pipe shape.

[0063] The terms "connected" or "connection" in this application refer of course to a fluid connection, the branches of the dielectric fluid circuit being sealed pipes.

[0064] The dielectric liquid circuit further comprises a rigid expansion vessel 1, for example made of high-density polyethylene (HDPE), equipped with a filling plug 16.

[0065] The expansion vessel 1 has an inlet located in its lower portion, so as to always open into the dielectric fluid present in the expansion vessel 1 under the nominal operating conditions of the heat treatment system 100. This inlet is connected by a branch 18 of the dielectric fluid circuit to the first outlet manifold 8, which allows it to receive air bubbles in its upper part. The expansion vessel 1 also has an outlet located in its lower part, connected by a branch 41 of the dielectric fluid circuit to the second outlet manifold 4.Thus, with the expansion vessel 1 filled in its lower part with dielectric fluid and in its upper part with air, the dielectric fluid present in the expansion vessel 1 can flow towards the second outlet manifold 4, without encountering a significant air pocket between these two elements of the dielectric fluid circuit.

[0066] Finally, the dielectric fluid circuit includes a variable-volume reservoir 14, in the form of a flexible synthetic material bag, for example PVC. The variable-volume reservoir 14 is connected by a pipe 10 to another opening in the expansion vessel 1, located in its lower part. It can advantageously be positioned in an available empty space near the modules 2; this space can be of any shape as long as it has the maximum volume occupied by the variable volume tank 14, provided for during operation of the heat treatment system 100.

[0067] Thus, when the circulation pump 3 is started, the dielectric fluid exiting it reaches the heat exchanger 5, then enters the inlet manifold 6, which carries the dielectric fluid to each of the modules 2 through their inlets 62. The dielectric fluid passes through each of the modules 2, with some of the dielectric fluid containing air exiting through the outlets 82 located at the top of the modules 2 to enter the first outlet manifold 8, and some of the dielectric fluid free of air exiting through the outlets 42 located at the bottom of the modules 2 to enter the second outlet manifold 4. The dielectric fluid in the second outlet manifold 4 returns to the inlet of the circulation pump 3, while the dielectric fluid in the first outlet manifold 8 is carried by branch 18 of the dielectric fluid circuit to the expansion vessel 1 to be degassed.The dielectric fluid, once degassed in the expansion vessel 1, is drawn, by the suction of the circulation pump 3, into branch 41 of the dielectric fluid circuit.

[0068] The expansion vessel 1 has a degassing function and, to a lesser extent, a function of limiting the pressure rise of the dielectric liquid circuit when this circuit is hot and the dielectric liquid expands.

[0069] The variable volume reservoir 14 absorbs the variations in volume of the dielectric liquid and of the components 22, due to variations in temperature and / or the charged or discharged state of the components 22, and therefore allows the pressure in the expansion vessel 1 to be kept close to atmospheric pressure.

[0070] In this first embodiment of the invention, a safety valve 30 is nevertheless arranged on the first outlet manifold 8. Alternatively, this safety valve is arranged elsewhere on the cooling circuit, for example it is arranged in the filler cap 16.

[0071] For guidance purposes, the volume occupied by the components 22 is approximately 130 liters at the beginning of the storage device's service life, with the components 22 uncharged. This volume increases by two liters at the end of the storage device's service life, with the components 22 charged. The volume of the dielectric fluid is approximately twenty liters in the housing 9 of the storage device. The expansion vessel 1 has a capacity of 1 to 1.5 liters, and the variable-volume reservoir 14 has a capacity of 3 to 6 liters.

[0072] A heat treatment system 102 for an electrical energy storage device is now described in a second embodiment of the invention, in connection with [Fig. 2]. This second embodiment of the invention includes many elements common to the first embodiment of the invention, which are referenced in the same way. In particular, the storage device includes a casing 9 divided into four modules 2 each containing a set of energy storage organs 22, which are immersed in dielectric liquid, here oil, in each module 2.

[0073] The heat treatment system 102 comprises an inlet manifold 6 arranged on a first wall 92 of the housing 9, supplying the dielectric fluid to each of the modules 2, but includes a single outlet manifold 8, arranged on a second wall 94 of the housing 9, opposite the first wall 92 of the housing 9 with respect to the latter. As in the first embodiment of the invention, the outlet manifold 8 is positioned against an upper portion of the module 2 so as to receive the dielectric fluid containing air bubbles, and to be able to degas it in a rigid expansion vessel 1, identical to that of the first embodiment of the invention. The outlet manifold 8 is further equipped with a safety valve 30.

[0074] A variable volume reservoir 14 allows the absorption of volume variations of the dielectric liquid during the life of the storage device.

[0075] The heat treatment system 102 also includes a heat exchanger 5 and a circulation pump 3.

[0076] The dielectric fluid outlet of the heat exchanger 5 is connected by a branch 65 of the dielectric fluid circuit, to the inlet of the inlet manifold 6. The outlet of the circulation pump 3 is connected by a branch 53 of the dielectric fluid circuit, to the dielectric fluid inlet of the heat exchanger 5, and the inlet of the circulation pump 3 is connected by a branch 38 of the dielectric fluid circuit to an outlet of the outlet manifold 8.

[0077] The expansion vessel 1 has an inlet located in its lower portion, opening into the dielectric fluid present in the expansion vessel 1. This inlet is connected by a branch 18 of the dielectric fluid circuit to the outlet manifold 8, allowing it to receive air bubbles in its upper part. The expansion vessel 1 also has an outlet located in its lower part, connected by a branch 31 to the branch 38 of the dielectric fluid circuit. An obstacle (not shown in [Fig. 2]) with a diameter 2 to 5 times that of the branch 18 is optionally positioned directly opposite its outlet to prevent air bubbles from being drawn directly into the two outlets of the expansion vessel 1 connected to the pipe 10 and the branch 31.With the expansion vessel 1 filled in its lower part with dielectric fluid and in its upper part with air, the dielectric fluid present in the expansion vessel 1 can flow towards the circulation pump 3, without encountering a significant air pocket between these two elements of the dielectric fluid circuit.

[0078] The variable volume reservoir 14, identical to that of the first embodiment, is connected by pipe 10 to another opening of the expansion vessel 1, located in the lower part of it.

[0079] Thus, when the circulation pump 3 is started, the dielectric fluid exiting it reaches the heat exchanger 5, then enters the inlet manifold 6, which carries the dielectric fluid to each of the modules 2 through their inlets 62. The dielectric fluid passes through each of the modules 2, then enters, laden with air (during a degassing phase after draining and then refilling with dielectric fluid during after-sales service or on the vehicle assembly line), the outlet manifold 8. Part of the dielectric fluid then passes through branch 18 to the expansion tank 1 where it is degassed, then returns to the circulation pump 3 via branches 31 and 38 of the dielectric fluid circuit, while another part of the dielectric fluid arrives directly from the outlet manifold 8 into the circulation pump 3 via branch 38 of the dielectric fluid circuit.

[0080] Figures 3 to 5 illustrate an alternative embodiment of the first embodiment, in which the elements identical to those in the first embodiment are referenced in the same way. This alternative differs from the first embodiment primarily in the arrangement of the variable-volume reservoir 14, which is here a flexible plastic bag placed on the modules 2 of the storage device, and in that a housing 90 of the storage device is separate from the walls of the modules 2. In this alternative embodiment, the housing 90 integrates all the elements of the dielectric fluid circuit. The housing nevertheless includes, in one wall, an inlet and outlet for the heat transfer fluid or refrigerant, allowing it to circulate in the heat exchanger 5. For clarity, only the lower wall of the housing 90 is shown in Figures 3 to 5.

[0081] Figure 3 illustrates the state of the heat treatment system according to the invention, where the pouch 14 is placed on top of the modules. In this embodiment, at an ambient temperature of 20°C and at the beginning of the life of the storage device, i.e., the energy storage components 22, which are not yet charged with electricity, the dielectric circuit has been filled with 22.4 liters of dielectric fluid. The variable-volume reservoir 14 contains 2 liters of dielectric fluid, while the expansion vessel 1 contains 0.7 liters of dielectric fluid and 0.3 liters of air. This initial filling of the storage device prevents a vacuum from forming in the dielectric fluid circuit when the temperature in this circuit drops to very low temperatures, for example, -30°C. At this temperature, the volume of the dielectric fluid contracts considerably.

[0082] It should be noted that the use of the variable volume reservoir 14 offers many advantages. Indeed, this use avoids a pressure increase in the dielectric fluid circuit, which would be very significant with a conventional expansion vessel of the same capacity. In particular, a variable volume reservoir The variable-volume reservoir 14, with a capacity of 4 to 6 liters, can absorb an increase in the total volume of the dielectric fluid circuit of approximately 3 liters. Furthermore, its placement on the modules 2 does not create a significant difference in static pressure, as the housing 90 is typically only about ten centimeters high. In the proposed embodiment, the pressure in the variable-volume reservoir 14 and the expansion vessel 1 remains close to atmospheric pressure.

[0083] Figure 4 illustrates the state of the heat treatment system according to the invention, in this embodiment, at a temperature of the storage elements 22 and the dielectric fluid well above 20°C, for example at 60°C at the end of rapid charging and at the end of the storage device's life, i.e., the energy storage elements 22 have undergone a very large number of charging and discharging cycles. Furthermore, in this Figure 4, the energy storage elements 22 are electrically charged. Under these conditions, the volume of the dielectric fluid contained in the modules is minimal, and the variable-volume reservoir receives the maximum amount of dielectric fluid.

[0084] Due to the aging of the energy storage components 22, and the recharging of the storage device causing thermal expansion, the volume of the storage components 22 is increased by two liters compared to the state of the heat treatment system in [Fig. 3]. The volume occupied by the dielectric fluid in the storage device is therefore reduced by two liters, which are expelled into the expansion vessel 1 and the variable volume reservoir 14. Since the dielectric fluid itself expands by approximately one liter, the modules 2 are filled with 20 liters of dielectric fluid, the variable volume reservoir 14 contains approximately 5 liters of dielectric fluid, and the air volume in the expansion vessel is expanded from 0.3 liters to 0.34 liters.

[0085] Figure 5 illustrates the state of the heat treatment system according to the invention, in this embodiment, where the volume of the dielectric liquid contained in the modules is at its maximum, where the temperature of the storage elements 22 and the dielectric liquid is at -30°C, and at the beginning of the life of the storage device, the energy storage elements 22 being discharged with electricity.

[0086] Due to this very low temperature, the volume of the energy storage components 22 contracts, as do the envelopes of the modules 2. The volume occupied by the dielectric fluid in the modules 2 increases if the reduction in the volume of components 22 is greater than the reduction in the envelopes of the modules 2. The modules 2 therefore draw in the dielectric fluid present in the variable volume reservoir 14, which initially contained a volume of 2 liters of dielectric fluid. The dielectric fluid itself also contracts. The air in the expansion vessel 1 also contracts, decreasing from a volume of 0.3 liters to 0.22 liters, which means that the expansion vessel 1 also draws in dielectric fluid from the variable volume reservoir 14. The volume of dielectric fluid in the expansion vessel 1 therefore increases to 0.78 liters, the one in the variable volume tank 14 is close to 0 liters.

[0087] During the cooling of the heat treatment system, thanks to the flexible bag, the pressure in the expansion vessel 1 remains at atmospheric pressure, whereas with a rigid container, it would be the liquid in the container that would be drawn in, there would be a vacuum created in the container, this vacuum can be significant if the volume of air is not sufficient, the safety valve could open to let air in in order to limit this vacuum, which could create a mechanical problem and a problem of sealing of the circuit.

[0088] A method for filling the dielectric fluid circuit of one of the heat treatment systems 100 or 102 described above is now described in relation to [Fig. 6]. In the application described here, this filling with dielectric fluid takes place at a temperature of 20°C and at the beginning of the storage device's service life, before the energy storage components 22 are electrically charged. In other words, this filling is carried out at the factory before the storage device is installed in an electric or hybrid vehicle.

[0089] A first step 202 of the filling process 200 is the opening of the dielectric liquid circuit by unscrewing the filling plug 16 of the expansion vessel 1. This first step is of course optional if the heat treatment system is supplied for filling with the expansion vessel already open.

[0090] A second step 204 of the filling process 200 is a vacuuming by opening the expansion vessel 1, by connecting for example a vacuum pump to this opening, so as to evacuate the air from the dielectric liquid circuit.

[0091] A third step 206 of the filling process 200, is the introduction of a predetermined quantity of dielectric liquid into the dielectric liquid circuit, here 22.4 liters.

[0092] A fourth step 208 of the filling process 200 is the activation of the circulation pump 3 in order to degas the dielectric liquid in the dielectric liquid circuit, with the air escaping through the opening of the expansion vessel 1. In a fifth step 210 of the filling process 200, it is verified that the volume of dielectric liquid present in the variable volume tank 14 is approximately 2 liters and that the volume of dielectric liquid present in the expansion vessel 1 is approximately 0.7 liters, plus or minus 0.1 liters.

[0093] If during this fifth step 210, the conditions on the volumes of dielectric liquid present in the variable volume reservoir and the expansion vessel 1 are met, then (branch Y) we proceed to the sixth step 212 of the process, which is the sealing of the dielectric liquid circuit by screwing the filling plug 16 onto the expansion vessel 1.

[0094] If, on the contrary, during this fifth step 210, the conditions on the volumes of If the dielectric fluid in the variable volume reservoir and expansion vessel 1 is not full, the process proceeds (branch N) to step 211, where dielectric fluid is added or removed so that the volumes of dielectric fluid in the variable volume reservoir 14 and expansion vessel 1 are within the specified ranges. By noting the quantity added and its addition, the total quantity required and its dispersion can be determined. The total quantity required can then be injected in step 206 to avoid the need for correction in step 211 when the process is repeated on another identical vehicle.

[0095] Of course, the invention is not limited to the examples just described, and many modifications can be made to these examples without departing from the scope of the invention. In particular, the characteristics of the different embodiments or variants of the invention envisaged in this application can be combined to carry out the invention, provided that these embodiments or variants are not incompatible with each other.

Claims

Demands

1. Heat treatment system (100, 102) of an electrical energy storage device comprising electrical energy storage elements (22), the heat treatment system (100, 102) comprising the electrical energy storage device, and a dielectric fluid circuit comprising: - at least one circulation channel (24) of the dielectric fluid between at least a part of the electrical energy storage elements (22) of the storage device, - a circulation pump (3) of the dielectric fluid, - a heat exchanger (5) configured to heat treat the dielectric fluid, the heat treatment system (100, 102) being characterized in that the dielectric fluid circuit comprises an expansion vessel (1) and in that the heat treatment system (100, 102) comprises a variable volume tank (14) connected to the expansion vessel (1).

2. Heat treatment system (102) of an electrical energy storage device according to claim 1, wherein the electrical energy storage elements (22) of the storage device are grouped into modules (2), each of the modules (2) having at least one circulation channel (24) of dielectric fluid, the dielectric fluid circuit having an inlet manifold (6) of dielectric fluid connecting the inlets (62) of the modules and an outlet manifold (8) of dielectric fluid connecting the outlets (82) of the modules, the expansion vessel (1) being connected on one side to the outlet manifold (8) and on the other side at a point in the dielectric fluid circuit located downstream of the outlet manifold (8) and upstream of the circulation pump (3).

3. A heat treatment system (100) for an electrical energy storage device according to claim 1, wherein the electrical energy storage elements (22) of the storage device are grouped into modules (2), each module (2) having at least one dielectric fluid circulation channel (24), the dielectric fluid circuit comprising a dielectric fluid inlet manifold (6) connecting the inlets (62) of the modules, a first dielectric fluid outlet manifold (8) connecting the outlets (82) located at the top of the modules, and a second outlet manifold (4) of dielectric liquid connecting together outlets (42) located in the lower part of the modules, the expansion vessel (1) being connected on one side to the first outlet manifold (8) and on the other side to the second outlet manifold (4).

4. Heat treatment system (100, 102) of an electrical energy storage device according to any one of claims 1 to 3, wherein the variable volume tank is directly connected to the expansion vessel.

5. Heat treatment system (100, 102) of an electrical energy storage device according to any one of claims 1 to 4, wherein the expansion vessel (1) has a filling plug (16).

6. Heat treatment system (100, 102) of an electrical energy storage device according to any one of claims 1 to 5, wherein the dielectric liquid circuit includes a safety valve (30).

7. Heat treatment system (100, 102) of an electrical energy storage device according to any one of claims 1 to 6, wherein the expansion vessel (1) is capable of containing 0.5 to 2 liters of dielectric liquid, and the variable volume reservoir (14) is capable of containing 2 to 8 liters of dielectric liquid.

8. Heat treatment system (100, 102) of an electrical energy storage device according to any one of claims 1 to 7, wherein the expansion vessel is made of rigid material and the variable volume tank of flexible material.

9. A method for filling (200) the dielectric fluid circuit of a heat treatment system (100, 102) with dielectric fluid according to any one of claims 1 to 8 taken in dependence on claim 5, comprising the steps of: - evacuating (204) the air present in the dielectric fluid circuit, - introducing (206) a predetermined quantity of dielectric fluid into the dielectric fluid circuit, - activating (208) the circulation pump (3), - comparing (210) a first quantity of dielectric fluid present in the variable volume reservoir (14) with a first predetermined quantity, and comparing a second quantity of dielectric fluid present in the expansion vessel (1) with a second predetermined quantity, and, if the first and second The quantities of dielectric liquid correspond respectively to the first and second predetermined quantities. - sealing (212) of the dielectric liquid circuit by mounting the filling plug (16) on the expansion vessel (1).

10. Electric or hybrid vehicle comprising a heat treatment system (100, 102) according to any one of claims 1 to 8 of an electrical energy storage device.

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