Thermal management system for electrical energy storage devices

Abstract

The invention relates to a thermal treatment system (100) for an electrical energy storage device comprising electrical energy storage means (22), the thermal treatment system (100) comprising the electrical energy storage device and a dielectric liquid circuit comprising: - at least one channel (24) for circulating a dielectric liquid between at least a portion of the electrical energy storage means (22) of the storage device; - a dielectric liquid circulation pump (3); - a heat exchanger (5) configured for thermally treating the dielectric liquid, the thermal treatment system (100) being characterized in that the dielectric liquid circuit comprises an expansion tank (1) and in that the thermal treatment system (100) comprises a variable volume tank (14) connected to the expansion tank (1).

Description

Technical Field

[0001] This invention relates to the fields of thermodynamics and electricity, and more specifically to a cooling and / or heating system for energy storage devices such as batteries, which has specific applications in the automotive industry. Background Technology

[0002] Electric or hybrid vehicles are equipped with high-voltage batteries, which are necessary to power the electric motors connected to the wheels of these vehicles to ensure traction or propulsion. To ensure that such vehicles have sufficient range without affecting the available volume in the vehicle, the trend is to increase the power density of these batteries (which typically use lithium-based technology).

[0003] However, these batteries have a maximum open-circuit voltage of approximately 200 V to 800 V, requiring a highly efficient cooling system. In fact, their energy storage cells tend to heat up, especially during rapid discharge or charging. Their temperature must be kept within a certain range to prevent combustion under conditions of intense heat and peak vehicle power consumption.

[0004] Available cooling solutions use cooling plates (e.g., allowing ethylene glycol-water to flow through them) or phase change materials (PCMs). Cooling plates can only contact the battery's insulating walls, resulting in a small exchange surface area with the storage cells, making this type of cooling relatively ineffective. PCMs can directly contact the storage cells, but this solution is complex and expensive, especially when the battery comprises multiple modules (each module grouping multiple cells together). To avoid imbalances in the state of the PCMs between modules, this solution requires a closed loop for each module.

[0005] Another cooling solution involves immersing the battery's energy storage cells in a dielectric fluid, which is itself cooled by an exchanger circulating, for example, water-glycol. However, this solution requires a large amount of dielectric (approximately 20 liters) and a very large and highly pressure-resistant battery casing to maintain its tightness during changes in the volume of the dielectric fluid. This is because the storage cells increase in volume during charging and / or aging, and the dielectric fluid itself increases in volume at high temperatures. Therefore, the casing must have a large-volume expansion tank to compensate for these volume changes. Even with a large-volume tank, the pressure inside the tank varies and can reach an absolute pressure of 2.5 bar during high temperatures and battery charging. Summary of the Invention

[0006] Therefore, there is still a need for a simple and compact, efficient cooling system for batteries with energy storage cells.

[0007] The present invention aims to overcome at least part of the above-mentioned disadvantages by providing a heat treatment system for an energy storage device and a method for injecting a dielectric liquid into the dielectric circuit of such a heat treatment system, which allows the dielectric liquid to circulate in contact with the energy storage components of the storage device while no pressure changes occur in its housing during the life cycle of the storage device.

[0008] Therefore, the present invention proposes a heat treatment system for an energy storage device, the energy storage device including an energy storage component, and the heat treatment system including the energy storage device and a dielectric liquid circuit, the dielectric liquid circuit including: - At least one channel for circulating a dielectric liquid between at least a portion of the energy storage components of the storage device. - Dielectric liquid circulation pump, - A heat exchanger configured for heat treatment of the dielectric fluid. The heat treatment system is characterized in that the dielectric liquid circuit includes an expansion tank, and is further characterized in that the heat treatment system includes a variable volume tank connected to the expansion tank.

[0009] Energy storage devices, such as high-voltage batteries in electric or hybrid vehicles, are provided with a heat treatment system according to the invention that allows for cooling or heating of the high-voltage battery depending on the vehicle's operating environment.

[0010] The energy storage components of the storage device are, for example, energy storage battery cells, such as cylindrical lithium-ion battery cells, prismatic lithium battery cells, or pouch battery cells.

[0011] In the heat treatment system according to the invention, a dielectric liquid circulates between these components, and the circulation channels can be formed by the entire housing of the storage device, provided that inlets and outlets for the dielectric liquid are provided on the housing. However, preferably, several circulation channels are provided in the storage device to better guide the dielectric liquid, which may be, for example, oil or any other dielectric liquid capable of cooling the components of the storage device.

[0012] The heat treatment system is configured to maintain the dielectric liquid in a liquid state, i.e., there is no vapor or solid phase of the dielectric liquid in the dielectric liquid circuit during operation. In particular, a suitable selection of the dielectric liquid enables it to remain liquid within the operating temperature range of the storage device.

[0013] Of course, the heat treatment system according to the invention may include more components, particularly several heat exchangers, several expansion tanks or variable volume tanks, but this would complicate the system without any additional advantages.

[0014] Although the housing of the storage device is preferably airtight and the storage components are immersed in oil in direct contact with the housing, as a variation, the oil is confined in one or more airtight containers containing the storage components, and the housing leaves space between these containers and their walls to accommodate other components of the heat treatment system, such as expansion tanks, variable volume tanks, heat exchangers, and pumps.

[0015] In this variant, the dielectric liquid circuit is entirely confined within the housing of the storage device, but the housing may include outlets and inlets for the heat transfer liquid or refrigerant through a heat exchanger. For example, ethylene glycol water circulates through the heat exchanger and in one or more cooling loops, thereby cooling not only the storage device but also the power electronics modules.

[0016] Due to the expansion tank and variable volume tank, this invention ensures that the housing volume of the storage device is no larger than, for example, a cooled storage device with cooling plates, and maintains the pressure within the storage device at near atmospheric pressure, i.e., within the pressure drop of the channel system, approximately one bar. This is because the variable volume tank allows for the absorption of a volume change of approximately 3 liters without causing an increase in pressure within the tank, thus limiting the pressure inside the storage device housing. This invention is also suitable for adding dielectric fluid to a heat treatment system, which is performed under vacuum on an assembly line. In practice, since absolute vacuum cannot be guaranteed, a certain volume of air always remains in the heat treatment system after it has been assembled.

[0017] Preferably, the expansion chamber is made of a rigid material, and the variable volume chamber is made of a flexible material. For example, they are made of PVC (polyvinyl chloride), but other types of materials can certainly be used. The expansion chamber can be made of several materials, but it must be able to contain dielectric fluid and air within a fixed volume, and the expansion chamber must be able to degas the dielectric fluid present in the dielectric fluid circuit. The chamber can also be made of several materials that allow the chamber volume to decrease or increase.

[0018] The variable-volume container can take the form of a flexible bag, which can be easily accommodated in the underframe of a vehicle containing storage equipment, or within the storage equipment itself. This embodiment allows the shape of the variable-volume container to adapt to constrained spaces of various shapes, even when the container is full.

[0019] In addition, the expansion chamber allows the dielectric fluid circulating between storage devices to be discharged into the air bubbles in the expansion chamber (which is partially filled with dielectric fluid and partially filled with air), thereby maintaining effective heat exchange between the dielectric fluid and the storage components of the storage devices.

[0020] In one embodiment of the invention, in the heat treatment system according to the invention, the energy storage components of the storage device are grouped together into modules, each of which includes at least one dielectric fluid circulation channel. The dielectric fluid circuit includes a dielectric fluid inlet manifold connecting the inlets of the modules to each other and a dielectric fluid outlet manifold connecting the outlets of the modules to each other. The expansion tank 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 circulation of the dielectric liquid.

[0022] In this embodiment of the invention, the expansion tank thus receives a portion of the dielectric fluid flow from the outlet manifold, while the dielectric fluid leaving the expansion tank flows into the main dielectric fluid circulation upstream of the circulation pump. Therefore, one branch of the dielectric fluid circuit connects the expansion tank to the outlet manifold, and another branch of the dielectric fluid circuit connects the expansion tank to the circulation pump inlet or to yet another branch of the dielectric fluid circuit that connects the outlet manifold to the circulation pump inlet.

[0023] In another embodiment of the invention, in the heat treatment system according to the invention, the energy storage components of the storage device are grouped together into modules, each of which includes at least one dielectric fluid circulation channel. The dielectric fluid circuit includes a dielectric fluid inlet manifold connecting the inlets of these modules to each other, a first dielectric fluid outlet manifold connecting the outlets located in the upper portions of these modules to each other, and a second dielectric fluid outlet manifold connecting the outlets located in the lower portions of these modules to each other. The expansion tank is connected to the first outlet manifold on one side and to the second outlet manifold on the other side.

[0024] In this other embodiment of the invention, the upper portion of each module is higher than the lower portion of the module. In other words, the first outlet manifold is positioned higher relative to the second outlet manifold, and the terms "top" and "bottom" refer here to the vertical direction in which the heat treatment system is intended to be positioned during operation. The cross-section of the first manifold is much smaller than that of the second manifold because the function of the first manifold is to capture 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 additionally positioned to receive dielectric liquid from the circulation channel, i.e., the lightest (and therefore containing air bubbles) dielectric liquid circulating in the circulation channel leaves the module via the first outlet manifold, while the heaviest (and therefore purged of air) dielectric liquid circulating in the circulation channel leaves the module via the second outlet manifold.

[0026] Therefore, the expansion tank receives the dielectric liquid containing air bubbles from the first outlet manifold, while the dielectric liquid flows out of the expansion tank after the air has been expelled, enters the second outlet manifold, and then enters the circulation pump.

[0027] The branch of the dielectric liquid circuit may optionally connect to the first outlet manifold and the second outlet manifold so as to allow the air-free dielectric liquid to settle into the second outlet manifold by gravity.

[0028] In these embodiments of the invention, the module is, for example, a compartment of the housing of a storage device, each compartment including a plurality of energy storage battery units immersed in a dielectric liquid within each of the compartments.

[0029] Preferably, in this invention, the variable volume tank is directly connected to the expansion tank. Therefore, there is a single pipe connecting the expansion tank to the variable volume tank, and no other connection exists between the variable volume tank and the dielectric liquid circuit.

[0030] If the expansion tank is located outside the battery housing (i.e., the storage device) and is vertically positioned above the battery housing, the connection between the outlet manifold and the expansion tank inlet can be vertically positioned at any level within the expansion tank. Conversely, if the tank is integrated into the battery housing, or if the tank is located below the battery housing, the piping must connect to the lower portion of the expansion tank, i.e., the area where liquid is always present. This prevents air from rising from the expansion tank into the outlet manifold.

[0031] When the expansion tank inlet is located in the lower part of the expansion tank, a fluid flow obstruction can be placed between the inlet and the expansion tank outlet, with one outlet connected to a variable volume tank and the other outlet connected to another outlet manifold or circulation pump (depending on the embodiment of the invention). This prevents air bubbles traveling from the expansion tank inlet to the expansion tank outlet from being sucked in.

[0032] The expansion tank can be housed in the empty space of the battery casing or integrated into one of the battery modules.

[0033] Furthermore, according to an optional and advantageous feature of the invention, the expansion tank has a filling port cover. This cover allows for the addition of dielectric fluid to the circuit or the drainage of the dielectric fluid.

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

[0035] For example, the expansion tank can hold 0.5 liters to 2 liters of dielectric liquid, and the variable volume tank can hold 2 liters to 8 liters of dielectric liquid. Preferably, the expansion tank can hold 1 liter to 1.5 liters of dielectric liquid, and the variable volume tank can hold 3 liters to 6 liters of dielectric liquid.

[0036] The present invention also relates to a method for adding dielectric liquid to the dielectric liquid circuit of a heat treatment system according to the present invention, the method comprising the following steps: - Remove any air present in the dielectric liquid circuit. - Introduce a predetermined amount of dielectric liquid into the dielectric liquid circuit. - Activate the circulation pump, - The amount of first dielectric liquid present in the variable volume tank is compared with a first predetermined amount, and the amount of second dielectric liquid present in the expansion tank is compared with a second predetermined amount, and where the first dielectric liquid amount and the second dielectric liquid amount correspond to the first predetermined amount and the second predetermined amount, respectively. - The dielectric liquid circuit is sealed by fitting the filling port cap onto the expansion tank.

[0037] This filling process is performed, for example, when installing the storage device into a vehicle or when draining the dielectric fluid circuit for fluid replacement.

[0038] Air is expelled from the dielectric fluid circuit, for example, by vacuum suction using an ejector or vacuum pump connected to an opening in the dielectric fluid circuit formed by previously opening the filler cap. Additionally, activating the circulation pump degassing the dielectric fluid allows control over the amount of dielectric fluid in the expansion tank and variable volume tank, representing the amount present in these containers during vehicle operation.

[0039] When the first dielectric liquid amount is equal to the first predetermined amount within a tolerance of approximately 0.1 liters, and when the second dielectric liquid amount is equal to the second predetermined amount within a tolerance of approximately 0.1 liters, the first dielectric liquid amount and the second dielectric liquid amount correspond to the first predetermined amount and the second predetermined amount, respectively.

[0040] When this correspondence is not achieved, if the first dielectric fluid quantity and the second dielectric fluid quantity are less than the first predetermined quantity and the second predetermined quantity, respectively, dielectric fluid is introduced into the dielectric fluid circuit in small, frequent amounts until these first predetermined quantities and the second predetermined quantity are reached after a new step of activating the circulation pump. Conversely, if the first dielectric fluid quantity and the second dielectric fluid quantity are greater than the first predetermined quantity and the second predetermined quantity, respectively, dielectric fluid is withdrawn from the dielectric fluid circuit in small amounts until these first predetermined quantities and the second predetermined quantity are reached after a new step of activating the circulation pump.

[0041] For example, the first predetermined amount is between 1 liter and 3 liters at an ambient temperature of 20°C.

[0042] The present invention also relates to an electric or hybrid vehicle comprising a heat treatment system for an energy storage device according to the present invention.

[0043] The vehicle and method according to the invention have similar advantages to the heat treatment system according to the invention. Attached Figure Description

[0044] Other features and advantages of the invention will become more apparent, on the one hand, from the following description, and on the other hand, from the various non-limiting exemplary embodiments shown in the accompanying drawings, in which: [ Figure 1 This illustrates a heat treatment system for an energy storage device according to the invention, as shown in a first embodiment. [ Figure 2 The second embodiment of the invention illustrates a heat treatment system for an energy storage device according to the invention. [ Figure 3 [This is a cross-sectional view of the heat treatment system for an energy storage device according to the invention in a variant embodiment of the first embodiment, at the early stage of the energy storage device's lifespan, when the device is in a discharge state and the temperature is approximately 20°C.] [ Figure 4 ]yes Figure 3 Cross-sectional views of the heat treatment system at the end of the lifespan of the energy storage device, at the end of charging, and at relatively high temperatures. [ Figure 5 ]yes Figure 3 A cross-sectional view of the heat treatment system at the beginning of the lifespan of the energy storage device, when the energy storage device is slightly charged and the ambient temperature is -30°C, and [ Figure 6 The following illustrates the steps of a method according to the invention for charging a heat treatment system for an energy storage device according to the invention, in one embodiment of the invention. Detailed Implementation

[0045] according to Figure 1 The first embodiment of the invention shown includes a heat treatment system 100 comprising an energy storage device, which in this case is a high-voltage battery for an electric or hybrid vehicle. The storage device includes a sealed housing 9, for example, made of aluminum.

[0046] The housing 9 of the storage device is divided into four modules 2, each module including multiple energy storage components 22, here prismatic energy storage battery cells; as a variation, these energy storage battery cells can be pouch cells or cylindrical battery cells. Figure 1 To avoid making the accompanying drawings too complex, not all components 22 are shown, but each module 2 includes more than two components, for example, ten components. Similarly, in Figure 1 In this invention, the storage device includes only four modules to make the various components of the heat treatment system 100 more visible, but it should be clearly understood that the invention is applicable to storage devices that may contain far more than four modules.

[0047] Component 22 is immersed in a dielectric liquid (e.g., oil) in each module 2, the dielectric liquid completely filling the available volume around component 22 in each module.

[0048] The heat treatment system 100 also includes a dielectric liquid circuit that allows the dielectric liquid to circulate specifically within modules 2, which form dielectric liquid circulation channels. In each module 2, the dielectric liquid circulates between the member 22 and the wall of the module 2, and also circulates between the members 22. Since the members 22 are rectangular and parallelepiped in this case, natural circulation channels 24 are formed, particularly between two adjacent members 22 within the same module 2.

[0049] In this first embodiment of the invention, each module 2 includes a dielectric liquid inlet 62 near one end of the circulation channel 24 of the module 2 under discussion and two dielectric liquid outlets 42, 82 near the other end of the circulation channel 24.

[0050] Figure 1 and Figure 2 The arrows not mentioned in the text depict the circulation direction of the dielectric liquid.

[0051] The first outlet 82 of the two outlets is located in the upper part of module 2, and the second outlet 42 of the two outlets is located in the lower part of module 2. In other words, when the heat treatment system 100 is integrated into the vehicle and is operating normally, the first outlet 82 is positioned higher than the second outlet 42.

[0052] The dielectric liquid circuit includes an inlet manifold 6, which is in the form of a conduit extending transversely to the first wall 92 of the module 2 along the housing 9, and the conduit includes four fluid connections to four dielectric liquid inlets 62 of the module 2 on the first transverse wall 92 of the housing 9.

[0053] The dielectric liquid circuit also includes a first outlet manifold 8 disposed at the top of a second wall 94 of the housing 9, which is transverse to the second wall 94 of the module 2, opposite the first wall 92 relative to the housing 9. The first outlet manifold 8 similarly takes the form of a conduit extending along the second wall 94, and the conduit includes four fluid connections to four dielectric liquid outlets 82 located in the upper portion of the module 2.

[0054] The dielectric fluid circuit also includes a second outlet manifold 4 disposed at the bottom of the second wall 94 of the housing 9. The second outlet manifold 4 takes the form of a pipe extending along the second wall 94 and includes four fluid connections to four dielectric fluid outlets 42 located in the lower portion of the module 2.

[0055] Therefore, the first outlet manifold 8 is positioned higher than the second outlet manifold 4. This allows a portion of the dielectric fluid containing air bubbles to be collected at the outlet of module 2, while the second outlet manifold 4 allows a portion of the dielectric fluid without air to be collected at the outlet of module 2, the air-free portion being heavier than the portion containing air bubbles.

[0056] The dielectric liquid loop additionally includes a circulation pump 3 and a heat exchanger 5, through which the dielectric liquid flows on one side and a heat transfer liquid 55 (such as ethylene glycol water) or a refrigerant fluid flows on the other side, thereby enabling the dielectric liquid to be cooled or heated according to the operating mode of the heat treatment system 100. The ethylene glycol water or refrigerant fluid circulates in another loop (not shown).

[0057] The heat exchanger 5 includes a dielectric liquid outlet connected to the inlet of the inlet manifold 6 via a branch 65 of the dielectric liquid circuit, the inlet of which is located at one end in its pipe form. The circulation pump 3 includes a dielectric liquid outlet and a dielectric liquid inlet, the dielectric liquid outlet connected to the dielectric liquid inlet of the heat exchanger 5 via a branch 53 of the dielectric liquid circuit, the dielectric liquid inlet connected to the outlet of the second outlet manifold 4 located at one end in its pipe form via a branch 34 of the dielectric liquid circuit.

[0058] The term "connected" in this application naturally refers to a fluid connection, where the branch of the dielectric fluid circuit is a sealed conduit.

[0059] The dielectric liquid circuit also includes a rigid expansion tank 1, which is made of, for example, high-density polyethylene (HDPE) and fitted with a filling port cap 16.

[0060] The expansion tank 1 includes an inlet located in its lower portion to ensure constant access to the dielectric fluid present in the expansion tank 1 under the nominal operating conditions of the heat treatment system 100. This inlet is connected to a first outlet manifold 8 via a branch 18 of the dielectric fluid circuit, thereby allowing the inlet to receive air bubbles in its upper portion. The expansion tank 1 also includes an outlet located in its lower portion, which is connected to a second outlet manifold 4 via a branch 41 of the dielectric fluid circuit. Therefore, since the expansion tank 1 is filled with dielectric fluid in its lower portion and air in its upper portion, the dielectric fluid present in the expansion tank 1 can flow to the second outlet manifold 4 without encountering significant cavitation between these two components of the dielectric fluid circuit.

[0061] Finally, the dielectric fluid circuit includes a variable volume box 14 in the form of a bag made of a flexible synthetic material (e.g., PVC). The variable volume box 14 is connected via a conduit 10 to another opening in the expansion tank 1, which is located in the lower portion of the expansion tank. The variable volume box can be advantageously arranged in available free space near module 2, and this space can have any shape, as long as it includes the maximum volume occupied by the variable volume box 14 provided during the operation of the heat treatment system 100.

[0062] Therefore, when the circulation pump 3 is turned on, the dielectric liquid leaving the circulation pump reaches the heat exchanger 5 and then enters the inlet manifold 6, which delivers the dielectric liquid to each of the modules 2 via its inlet 62. As the dielectric liquid passes through each of the modules 2, a portion containing air flows out through outlet 82 in the top portion of the module 2 to enter the first outlet manifold 8, and a portion without air flows out through outlet 42 in the lower portion of the module 2 to enter the second outlet manifold 4. The dielectric liquid present in the second outlet manifold 4 merges into the inlet of the circulation pump 3, while the dielectric liquid present in the first outlet manifold 8 is delivered to the expansion tank 1 via branch 18 of the dielectric liquid circuit for degassing. After degassing in the expansion tank 1, the dielectric liquid is then entrained into branch 41 of the dielectric liquid circuit by the suction of the circulation pump 3.

[0063] The expansion chamber 1 has a degassing function and to a lesser extent limits the pressure rise in the dielectric liquid circuit when it is heated and the dielectric liquid expands.

[0064] The variable volume tank 14 absorbs the volume changes of the dielectric liquid and component 22 caused by temperature changes and / or changes in the charging or discharging state of component 22, thereby enabling the pressure in the expansion tank 1 to be kept close to atmospheric pressure.

[0065] In this first embodiment of the invention, the safety valve 30 is still arranged on the first outlet manifold 8. As a variant, the safety valve is arranged elsewhere in the cooling circuit, for example, on the filler cap 16.

[0066] By way of indication, in the early stages of the storage device's lifespan, when component 22 is in a discharged state, the volume occupied by component 22 is approximately 130 liters, and in the later stages of the storage device's lifespan, when component 22 is in a charged state, this volume increases by two liters. The volume of the dielectric liquid in the housing 9 of the storage device is approximately twenty liters. The expansion tank 1 has a capacity of 1 to 1.5 liters, and the variable volume tank 14 has a capacity of 3 to 6 liters.

[0067] Now we will combine Figure 2 A heat treatment system 102 for an energy storage device according to a second embodiment of the present invention is described. This second embodiment of the invention includes many elements common to the first embodiment of the invention, which are referred to in the same manner. In particular, the storage device includes a housing 9 divided into four modules 2, each module including a set of energy storage components 22 immersed in a dielectric liquid (in this case, oil) in each module 2.

[0068] The heat treatment system 102 includes an inlet manifold 6 disposed on a first wall 92 of the housing 9 to deliver dielectric fluid to each of the modules 2, but also includes a single outlet manifold 8 disposed on a second wall 94 of the housing 9, which is opposite to the first wall 92 of the housing 9. As in the first embodiment of the invention, the outlet manifold 8 is disposed against the upper portion of the module 2 to receive dielectric fluid containing air bubbles and to degas it in a rigid expansion tank 1 (identical to the rigid expansion tank of the first embodiment of the invention). The outlet manifold 8 is also provided with a safety valve 30.

[0069] The variable volume tank 14 allows for the absorption of volume changes in the dielectric liquid throughout the life of the storage device.

[0070] The heat treatment system 102 also includes a heat exchanger 5 and a circulating pump 3.

[0071] The dielectric liquid outlet of heat exchanger 5 is connected to the inlet of inlet manifold 6 via branch 65 of dielectric liquid circuit. The outlet of circulation pump 3 is connected to the dielectric liquid inlet of heat exchanger 5 via branch 53 of dielectric liquid circuit, and the inlet of circulation pump 3 is connected to the outlet of outlet manifold 8 via branch 38 of dielectric liquid circuit.

[0072] The expansion tank 1 includes an inlet located in its lower portion for access to a dielectric liquid present in the expansion tank 1. This inlet is connected to an outlet manifold 8 via a branch 18 of the dielectric liquid circuit, thereby allowing the inlet to receive air bubbles in its upper portion. The expansion tank 1 also includes an outlet located in its lower portion, which is connected to a branch 38 of the dielectric liquid circuit via a branch 31. Optionally, an obstruction is positioned directly opposite the outlet of the expansion tank. Figure 2 (Not shown in the diagram), the barrier is 2 to 5 times the diameter of branch 18, and is used to prevent air bubbles from being directly drawn into the two outlets of expansion tank 1 that connect to pipe 10 and branch 31. Since expansion tank 1 is filled with dielectric fluid in its lower portion and air in its upper portion, the dielectric fluid present in expansion tank 1 can flow to circulation pump 3 without encountering significant cavitation between these two components of the dielectric fluid circuit.

[0073] The variable volume tank 14 (same as the variable volume tank in the first embodiment) is connected to another opening of the expansion tank 1 via a pipe 10, which is located in the lower part of the expansion tank.

[0074] Therefore, when the circulation pump 3 is turned on, the dielectric fluid leaving the circulation pump reaches the heat exchanger 5 and then enters the inlet manifold 6, which delivers the dielectric fluid to each of the modules 2 via its inlet 62. The dielectric fluid passes through each of the modules 2 and then carries air (during after-sales service or on the vehicle assembly line, during the degassing phase after evacuation and refilling of dielectric fluid) into the outlet manifold 8. Some of the dielectric fluid then reaches the expansion tank 1 via branch 18, where it is degassed and then returned to the circulation pump 3 via branches 31 and 38 of the dielectric fluid circuit, while another portion of the dielectric fluid goes directly from the outlet manifold 8 to the circulation pump 3 via branch 38 of the dielectric fluid circuit.

[0075] Figures 3 to 5 A variant embodiment of the first embodiment is shown, wherein the same elements as in the first embodiment are referred to in the same manner. The main difference between this variant and the first embodiment lies in the arrangement of the variable volume tank 14, which in this example is a flexible plastic bag arranged on the module 2 of the storage device, and the housing 90 of the storage device is separate from the wall of the module 2. In fact, in this variant embodiment, the housing 90 contains all the elements of the dielectric liquid circuit. However, the housing includes inlets and outlets in the walls for the heat transfer liquid or for the refrigerant fluid, thereby allowing the heat transfer liquid or refrigerant fluid to circulate in the exchanger 5. For clarity, in Figures 3 to 5 Only the lower wall of the housing 90 is shown in the image.

[0076] Figure 3The diagram illustrates the state of the heat treatment system according to the invention, wherein the recess 14 is positioned at the top of the module. In this variant embodiment, at an ambient temperature of 20°C and during the early stages of the lifespan of the storage devices (i.e., energy storage components 22), these energy storage components are not yet charged. In this state, 22.4 liters of dielectric fluid are added to the dielectric circuit. The variable volume tank 14 contains 2 liters of dielectric fluid, while the expansion tank 1 contains 0.7 liters of dielectric fluid and 0.3 liters of air. This addition at the early stages of the storage device's lifespan prevents negative pressure from forming in the dielectric fluid circuit when the temperature drops to extremely low temperatures (e.g., -30°C). At this temperature, the volume of the dielectric fluid shrinks significantly.

[0077] It should be noted that the use of the variable volume tank 14 offers several advantages. In fact, the use of this variable volume tank prevents pressure rises in the dielectric fluid circuit, which would be significant when using a conventional expansion tank of the same capacity. Specifically, the variable volume tank 14, with a capacity of 4 to 6 liters, can absorb approximately 3 liters of total volume increase in the dielectric fluid circuit. Furthermore, its location on module 2 does not create a significant hydrostatic pressure difference, and the height of the housing 90 is typically on the order of approximately ten centimeters. In the proposed variant embodiment, the pressure in both the variable volume tank 14 and the expansion tank 1 remains close to atmospheric pressure.

[0078] Figure 4 The diagram illustrates the state of the heat treatment system according to the invention in this variant embodiment, where the temperature of the storage member 22 and the dielectric fluid is significantly higher than 20°C (e.g., 60°C at the end of a rapid recharge), and the system is nearing the end of its lifespan; that is, the energy storage member 22 has undergone a very large amount of recharging and discharging. Furthermore, in this… Figure 4 In this process, the energy storage component 22 is charged. Under these conditions, the volume of dielectric fluid contained in the module is minimized, and the variable volume tank receives the maximum amount of dielectric fluid.

[0079] Due to the aging of the energy storage component 22 and the thermal expansion caused by the recharging of the storage device, and Figure 3 Compared to the state of the heat treatment system, the volume of storage component 22 has increased by two liters. Therefore, the volume occupied by the dielectric liquid in the storage device has decreased by two liters, which are discharged into expansion tank 1 and variable volume tank 14. Since the dielectric liquid itself has expanded by approximately one liter, module 2 is now filled with 20 liters of dielectric liquid, variable volume tank 14 holds approximately 5 liters of dielectric liquid, and the air volume in the expansion tank has expanded from 0.3 liters to 0.34 liters.

[0080] Figure 5The state of the heat treatment system according to the invention in this variant embodiment is shown, wherein the volume of the dielectric liquid contained in the module is at its maximum, the temperature of the storage member 22 and the dielectric liquid is -30°C, and the energy storage member 22 is in a discharged state at the beginning of the life of the storage device.

[0081] Due to this extremely low temperature, the volume of energy storage component 22 shrinks, and the shell of module 2 also shrinks. If the decrease in volume of component 22 is greater than the decrease in the shell of module 2, the volume that the dielectric fluid in module 2 can occupy increases. Therefore, module 2 draws dielectric fluid from the variable volume tank 14, which initially holds 2 liters of dielectric fluid. The dielectric fluid itself also shrinks. The air volume in expansion tank 1 also shrinks from 0.3 liters to 0.22 liters, causing expansion tank 1 to also draw dielectric fluid from variable volume tank 14. Therefore, the volume of dielectric fluid in expansion tank 1 increases to 0.78 liters, and the volume of dielectric fluid in variable volume tank 14 approaches 0 liters.

[0082] During the cooling process of the heat treatment system, the pressure in expansion tank 1 remains at atmospheric pressure due to the flexible bag. However, for the rigid tank, the liquid in the tank will be drawn in, and a negative pressure will be generated in the tank. If the air volume is insufficient, this negative pressure can be significant. The safety valve will open to allow air to enter in order to limit the negative pressure, which will cause mechanical problems and issues related to the circuit seal.

[0083] Now refer to Figure 6 A method 200 for filling the dielectric fluid circuit of one of the aforementioned heat treatment systems 100 or 102 is described. In the example of use described herein, this dielectric fluid filling is performed at a temperature of 20°C and at the beginning of the lifespan of the storage device (before the energy storage component 22 is charged). In other words, this filling is performed at the factory before the storage device is assembled into an electric or hybrid vehicle.

[0084] The first step 202 of the filling method 200 is to open the dielectric liquid circuit by unscrewing the filling port cap 16 on the expansion tank 1. Of course, this first step is optional if the expansion tank is already open for filling when the heat treatment system is supplied.

[0085] The second step 204 of the filling method 200 is to evacuate the expansion chamber 1 through the opening, for example by connecting a vacuum pump to the opening, so as to remove air from the dielectric liquid circuit.

[0086] The third step 206 of the filling method 200 is to introduce a predetermined amount of dielectric liquid (22.4 liters in this case) into the dielectric liquid circuit.

[0087] The fourth step 208 of the filling method 200 is to activate the circulation pump 3 to degas the dielectric liquid in the dielectric liquid circuit, so that air escapes through the opening of the expansion tank 1.

[0088] In the fifth step 210 of the filling method 200, it is checked whether the volume of the dielectric liquid present in the variable volume tank 14 is approximately 2 liters and whether the volume of the dielectric liquid present in the expansion tank 1 is approximately 0.7 liters to within ±0.1 liters.

[0089] If the condition regarding the volume of dielectric liquid present in the variable volume tank and expansion tank 1 is met during the fifth step 210, then (branch Y) the method proceeds to the sixth step 212, i.e., the dielectric liquid circuit is sealed closed by retightening the filling cap 16 on the expansion tank 1.

[0090] On the other hand, if the conditions regarding the volume of dielectric fluid present in the variable volume tank and expansion tank 1 are not met during the fifth step 210, the method continues (branch N) to step 211, in which dielectric fluid is added or removed such that the volume of dielectric fluid present in the variable volume tank 14 and expansion tank 1 is within the expected range. By recording the amount introduced and the amount remaining, the required total amount and its dispersion can be determined. Therefore, when the method is performed again on another identical vehicle, the required total amount can be injected earlier in step 206 to avoid corrections in step 211.

[0091] Of course, the present 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, features of various embodiments or variations of the invention contemplated in this patent application can be combined to implement the invention, provided that these embodiments or variations are not incompatible with each other.

Claims

1. A heat treatment system (100, 102) for an energy storage device, the energy storage device including an energy storage component (22), the heat treatment system (100, 102) including the energy storage device and a dielectric liquid circuit, the dielectric liquid circuit including: - At least one channel (24) for circulating the dielectric liquid between at least a portion of the energy storage components (22) of the storage device. - Dielectric liquid circulation pump (3). - Heat exchanger (5), which is configured to heat treat the dielectric liquid. The heat treatment system (100, 102) is characterized in that the dielectric liquid circuit includes an expansion tank (1), and is further characterized in that the heat treatment system (100, 102) includes a variable volume tank (14) connected to the expansion tank (1).

2. The heat treatment system (102) for an energy storage device as described in claim 1, wherein, The energy storage components (22) of the storage device are grouped together into modules (2), each of which includes at least one dielectric fluid circulation channel (24). The dielectric fluid circuit includes a dielectric fluid inlet manifold (6) that connects the inlets (62) of these modules to each other and a dielectric fluid outlet manifold (8) that connects the outlets (82) of these modules to each other. The expansion tank (1) is connected to the outlet manifold (8) on one side and to a point in the dielectric fluid circuit located downstream of the outlet manifold (8) and upstream of the circulation pump (3) on the other side.

3. The heat treatment system (100) for an energy storage device as described in claim 1, wherein, The energy storage components (22) of the storage device are grouped together into modules (2), each of which includes at least one dielectric fluid circulation channel (24). The dielectric fluid circuit includes a dielectric fluid inlet manifold (6) that connects the inlets (62) of these modules to each other, a first dielectric fluid outlet manifold (8) that connects the outlets (82) in the upper part of these modules to each other, and a second dielectric fluid outlet manifold (4) that connects the outlets (42) in the lower part of these modules to each other. The expansion tank (1) is connected to the first outlet manifold (8) on one side and to the second outlet manifold (4) on the other side.

4. The heat treatment system (100, 102) for an energy storage device as described in any one of claims 1 to 3, wherein, The variable volume tank is directly connected to the expansion tank.

5. The heat treatment system (100, 102) for an energy storage device as described in any one of claims 1 to 4, wherein, The expansion tank (1) has a filling port cover (16).

6. The heat treatment system (100, 102) for an energy storage device as described in any one of claims 1 to 5, wherein, The dielectric fluid circuit includes a safety valve (30).

7. The heat treatment system (100, 102) for an energy storage device as described in any one of claims 1 to 6, wherein, The expansion tank (1) can hold 0.5 liters to 2 liters of dielectric liquid, and the variable volume tank (14) can hold 2 liters to 8 liters of dielectric liquid.

8. The heat treatment system (100, 102) for an energy storage device as claimed in any one of claims 1 to 7, wherein, The expansion chamber is made of a rigid material, while the variable volume chamber is made of a flexible material.

9. A method (200) for injecting dielectric fluid into the dielectric fluid circuit of a heat treatment system (100, 102) as described in any one of claims 1 to 8, when dependent on claim 5, the method comprising the steps of: - Drain (204) the air present in the dielectric liquid circuit. - Introduce (206) a predetermined amount of dielectric liquid into the dielectric liquid circuit. - Activate (208) the circulation pump (3). - The amount of first dielectric liquid present in the variable volume tank (14) is compared with a first predetermined amount (210), and the amount of second dielectric liquid present in the expansion tank (1) is compared with a second predetermined amount, and when the first dielectric liquid amount and the second dielectric liquid amount correspond to the first predetermined amount and the second predetermined amount, respectively, - The dielectric liquid circuit is sealed (212) by fitting the filling port cap (16) onto the expansion tank (1).

10. An electric or hybrid vehicle, comprising a heat treatment system (100, 102) for an energy storage device as claimed in any one of claims 1 to 8.

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