Battery cooling system and method for preparing such a cooling system

Abstract

A cooling system for a battery (2) using a dielectric fluid intended to circulate in contact with the energy storage components of the battery (2), the cooling system (1) comprising the battery (2), a pump (5) for circulating the dielectric fluid between a main outlet (BS1) and a main inlet (BE1) of the battery (2), a heat exchanger (6) for cooling the dielectric fluid, an expansion vessel (8), at least one variable-volume reservoir (9a, 9b) connected to the expansion vessel (8), and an isolation valve (16) adapted for the selective passage of dielectric fluid between the expansion vessel (8) and the variable-volume reservoir (9a, 9b). Figure for the abstract: Fig 1

Description

Title of the invention: Battery cooling system and method for preparing such a cooling system

[0001] The present invention relates, in general, to the cooling of a battery by a dielectric fluid and the management of the resulting pressure variations within the battery.

[0002] In particular, the invention relates to a battery cooling system, to a motor vehicle incorporating such a cooling system and to a method for preparing such a cooling system.

[0003] It is known to cool a battery using a dielectric fluid circulating in direct contact with the cells that compose it. The large exchange surface area between the cells and the fluid makes this an efficient solution. Indeed, the surface area ensuring this exchange is three to ten times larger than the exchange surface area between the cells and a cooling circuit formed by a cooling plate positioned under the battery and through which a refrigerant fluid flows.

[0004] However, this large surface area requires a substantial volume of dielectric liquid, on the order of 20 to 40 liters, representing three to eight times the volume of a cooling system by a cooling plate.

[0005] Furthermore, several parameters cause variations in the volume of the dielectric fluid and the volume of the battery cells. During vehicle operation, the volume of the dielectric fluid increases with its temperature. In addition, the volume of the cells increases with time, their temperature, and varies according to their state of charge. A discharged cell is smaller than a charged cell. This phenomenon of cell swelling is known as "cell swelling."

[0006] However, increasing the volume of the cells results in reducing the volume occupied by the dielectric liquid within the battery.

[0007] Given the large total volume occupied by all the cells in a battery, the expansion of the dielectric liquid and the increase in the volume of each of the cells, it is necessary to provide a solution to store the volume of the dielectric liquid resulting from the sum of these increases.

[0008] To deal with these volume variations, it is known to use an expansion vessel connected to the battery.

[0009] However, its required volume is on the order of three times the variation in the volume of the dielectric liquid to be stored, so that it is difficult to find space to house it, especially in a motor vehicle.

[0010] In addition, the pressure in the expansion tank increases with the arrival of the liquid, and this increase in pressure poses problems with regard to the sealing of the battery and its mechanical strength.

[0011] To further compensate for volume variations, one solution is to add at least one variable volume reservoir, classically in the form of a flexible bag, connected to the vessel, allowing the pressure in the vessel to be maintained close to atmospheric pressure.

[0012] The preparation of the cooling system is carried out in the factory, on an assembly line intended for the preparation of the motor vehicle.

[0013] The preparation classically includes a vacuum pulling step using a vacuum pulling device in order to remove air from within the cooling system.

[0014] When a vacuum is reached, the vacuum pumping device, connected to the expansion vessel, is switched to a filling mode for filling the cooling system with dielectric liquid.

[0015] During its stages, when the variable volume reservoir is positioned below the expansion vessel, part of the filling liquid escapes towards the flexible pockets.

[0016] However, the variable volume reservoir must remain empty at the factory in order to reserve its volume for the dielectric liquid that it must contain after the irreversible decrease in the available volume inside the battery after a certain period of cell use, linked to the swelling phenomenon.

[0017] The invention therefore aims to remedy these drawbacks and to propose a battery cooling system, in particular for motor vehicles, incorporating a dielectric liquid circulating in contact with the battery cells and allowing to preserve all the functions of the variable volume reservoir during the preparation of the cooling system before its use and during maintenance operations, regardless of its position relative to the expansion tank.

[0018] A system for cooling a battery by means of a dielectric fluid intended to circulate in contact with energy storage components of the battery is therefore proposed, the cooling system comprising the battery, a pump for circulating the dielectric fluid between a main outlet and a main inlet of the battery, a heat exchanger intended to cool the dielectric fluid, an expansion vessel, at least one variable volume tank connected to the expansion vessel, and an isolation valve adapted for the selective passage of dielectric fluid between the expansion vessel and the variable volume tank.

[0019] Preferably, the isolation valve is a manual valve.

[0020] In one embodiment, the expansion vessel may include a dielectric fluid inlet and a first outlet in fluidic connection with the reservoir with variable volume, the isolation valve can be positioned under the expansion vessel, between the first outlet of the expansion vessel and the variable volume tank.

[0021] In another embodiment, the isolation valve can be positioned directly on the first outlet of the expansion vessel.

[0022] Advantageously, the first outlet can be positioned on the bottom of the expansion vessel.

[0023] In one embodiment, the cooling system may include:

[0024] a main circuit for circulating the dielectric fluid on which are arranged the battery, the pump for circulating the dielectric fluid between a main outlet and a main inlet of the battery, and the heat exchanger intended to cool the dielectric fluid,

[0025] a dielectric fluid degassing circuit on which are arranged the expansion vessel and the variable volume reservoir connected to the expansion vessel, the degassing circuit being connected to the main circuit by a first branch adjacent to the main outlet of the battery or positioned on a secondary outlet of the battery and by a second branch positioned downstream of the main outlet of the battery and upstream of the pump, and

[0026] a three-way valve, the first of which is in fluidic connection with the expansion vessel, the second of which is in fluidic connection with the second branch of the main circuit, and the third of which is in fluidic connection with a third branch positioned on the main circuit downstream of the pump and upstream of the main outlet of the battery.

[0027] The invention also relates to a method for preparing a cooling system as previously described, comprising the following steps:

[0028] a vacuum pulling step (to remove at least partially the air contained within the cooling system, and

[0029] a step of filling the cooling system with dielectric fluid,

[0030] the isolation valve being closed to isolate the variable volume tank from the expansion vessel during the vacuum pulling and filling steps.

[0031] Preferably, the isolation valve is opened after the vacuum pulling and filling steps to fluidly connect the variable volume tank to the expansion vessel.

[0032] Advantageously, the preparation process may include a step of degassing the dielectric fluid of the cooling system, the isolation valve being opened at the beginning of the degassing step or after the degassing step to fluidly connect the variable volume tank to the expansion vessel.

[0033] The invention also relates to a motor vehicle comprising at least one cooling system as described above. Brief description of the drawings

[0034] Other purposes, advantages and features will become apparent from the following description, given for illustrative purposes only and with reference to the accompanying drawings on which:

[0035] [Fig.1] represents a cooling system according to a first embodiment of the invention.

[0036] [Fig.2] illustrates a method of preparing a cooling system as illustrated in [Fig.1] according to an embodiment of the invention.

[0037] [Fig.3] illustrates the cooling system shown in [Fig.1] in positive pressure operation.

[0038] [Fig.4] illustrates the cooling system shown in [Fig.1] in negative pressure operation.

[0039] [Fig.5] represents a cooling system according to a second embodiment of the invention.

[0040] [Fig.6] represents a cooling system according to a third embodiment of the invention.

[0041] [Fig.7] is a top cross-sectional view of the cooling system battery shown in [Fig.6].

[0042] [Fig.8] represents a cooling system according to a fourth embodiment of the invention. Detailed description

[0043] In what follows, the bounds of a domain of values ​​are included in that domain, in particular in the expression "between".

[0044] Furthermore, the expression "at least one" used in this description is equivalent to the expression "one or more".

[0045] Fig. 1 illustrates a cooling system 1 for a battery 2 according to an embodiment of the invention.

[0046] In the illustrated example, battery 2 is a high-voltage battery from an electric or hybrid vehicle but is not limited to such use.

[0047] Advantageously, the battery 2 comprises a sealed case 3 containing electrical energy storage components.

[0048] In the illustrated example, the housing 3 is substantially parallelepiped-shaped and comprises an upper wall 3a, a lower wall 3b opposite the upper wall 3a, and a plurality of side walls, in particular the first, second, third, and fourth side walls 3c, 3d, 3e, and 3f. The first and third side walls 3c and 3d are opposite and the second and fourth lateral walls 3e and 3f are opposite.

[0049] Advantageously, the housing 3 of the battery 2 can contain one or more battery modules, each comprising one or more electrical energy storage elements.

[0050] According to an alternative, the electrical energy storage organs can be arranged in the housing 3 without compartmentalization in battery modules.

[0051] As shown in [Fig.6], electrical energy storage organs can be flexible pouch cells C, also known as "pouch" cells.

[0052] Alternatively, the electrical energy storage organs C can, for example, be prismatic cells or cylindrical cells.

[0053] Preferably, a dielectric fluid completely fills the available volume of the battery, in particular the sealed case 3, circulating in each module when the battery 2 is compartmentalized, around the electrical energy storage elements so that the electrical energy storage elements are bathed in the dielectric fluid.

[0054] The dielectric fluid is, for example, a dielectric liquid such as oil.

[0055] The cooling system 1 includes a main circuit 4 for circulating the dielectric fluid.

[0056] The illustrated battery 2 has a main inlet BEI of the dielectric fluid, a main outlet BS1 and a secondary outlet BS2 of the dielectric fluid.

[0057] Advantageously, the main inlet BEI of the dielectric fluid, the main outlet BS1 and the secondary outlet BS2 of the dielectric fluid can be carried by the housing 3.

[0058] Preferably, the main inlet BEI of the dielectric fluid and the main outlet BS1 are positioned on one of the side walls, in particular the first side wall 3c, and the secondary outlet BS2 of the dielectric fluid is carried by the upper wall 3a of the housing 3.

[0059] In the illustrated example, the main outlet BS1 is advantageously arranged in a plane higher than the main inlet BEI of the dielectric fluid.

[0060] The main circuit 4 includes the battery 2, a pump 5 for circulating the dielectric fluid along the main circuit 4, between the main inlet BEI and the main outlet BS1 of the battery 2, and a heat exchanger 6 for cooling the dielectric fluid passing through it.

[0061] Preferably, the heat exchanger 6 is positioned downstream of the pump 5, between the pump 5 and the main inlet BEI of the battery.

[0062] The battery cooling system 1 allows the dielectric fluid to circulate in contact with the energy storage components of the battery 2 in order to cool them.

[0063] The main circuit 4 comprises a plurality of pipes fluidly connecting the different elements of the circulation circuit 4. A first main pipe 41 fluidly connects the main outlet BS1 of the battery 2 to the pump 5, a second main pipe 42 fluidly connects the pump 5 to the heat exchanger 6 and a third main pipe 43 fluidly connects the heat exchanger 6 to the main inlet BEI of the battery 2.

[0064] The cooling system 1 further includes a degassing circuit 7 for the dielectric fluid.

[0065] In the illustrated example, the degassing circuit 7 includes an expansion vessel 8 and two variable volume tanks 9a and 9b, fluidly connected to the expansion vessel 8. The first variable volume tank 9a is connected to the expansion vessel 8 and the second variable volume tank 9b is only connected to the first variable volume tank 9a.

[0066] In the illustrated example, each of the variable volume reservoirs 9a and 9b is a flexible pouch.

[0067] In the illustrated example, the expansion vessel 8 comprises a lower wall 8a forming a base, at least one side wall 8b and an upper wall 8c opposite the lower wall 8a and having a dielectric fluid filling opening closed by a plug B.

[0068] The illustrated expansion vessel 8 further includes a dielectric fluid inlet VE1, a first dielectric fluid outlet VS1 and a second outlet VS2.

[0069] The expansion vessel 8 comprises a lower half including the bottom 8a and an upper half including the upper wall 8c.

[0070] Preferably, and as illustrated, the first outlet VS1 of the expansion vessel 8 is positioned on the lower half, under the expansion vessel, on the bottom 8a of the expansion vessel 8.

[0071] Preferably, the second outlet VS2 of the expansion vessel 8 is positioned on the lower half, under the expansion vessel, on the bottom 8a of the expansion vessel 8.

[0072] Preferably, the dielectric fluid inlet VE1 is arranged in a plane above the first and second dielectric fluid outlets VS1 and VS2. Advantageously, the VE1 inlet is positioned on the lower half and can be located on the side wall 8b.

[0073] In the first embodiment illustrated in [Fig. 1], the degassing circuit 7 is connected to the main circuit 4 by a first branch 10 positioned on the outlet secondary BS2 of battery 2, and by a second branch 11 positioned downstream of the main outlet BS1 of battery 2 and upstream of pump 5.

[0074] Preferably, the first tap 11 is positioned at a distance less than or equal to 6 cm from the main output BS1 of the battery 2, preferably less than or equal to 5 cm.

[0075] The cooling system 1 further includes a three-way valve 12, the first of which is in fluidic connection with the expansion vessel 8 and the second of which is in fluidic connection with the second branch 11 of the main circuit 4.

[0076] The degassing circuit 7 comprises a plurality of lines fluidly connecting the various elements of the degassing circuit 7. A first degassing line 71 fluidly connects the secondary outlet BS2 of the battery 2 and the inlet VE1 of the expansion vessel 8, a second degassing line 72 fluidly connects the second outlet VS2 of the expansion vessel 8 to the first port of the three-way valve 12, and a third degassing line 73 fluidly connects the second port of the three-way valve 12 to the second branch IL

[0077] A filling line 13 fluidly connects the first outlet VS1 of the expansion vessel 8 to the first variable volume reservoir 9a.

[0078] The second branch 11 connects the third degassing line 73 and the first main line 4L

[0079] In addition, the cooling system 1 includes a third branch 14 on the main circuit 4 intended for the operation of the cooling system 1 at negative pressure.

[0080] The third branch 14 is positioned downstream of the pump 5, in particular downstream of the heat exchanger 6, and upstream of the main outlet BS1 of the battery 2.

[0081] In the first embodiment illustrated in [Fig.1], the third branch 14 is positioned between the pump 5 and the main inlet BEI of the battery 2, upstream of the battery, and adjacent to the main inlet BEI of the battery 2.

[0082] Preferably, the third tap 14 is positioned at a distance less than or equal to 6 cm from the main BEI inlet of battery 2, preferably less than or equal to 5 cm.

[0083] An additional conduit 15 fluidly connects a third way of the three-way valve 12 to the third branch 14.

[0084] The third branch 14 connects the additional pipe 15 and the third main pipe 43.

[0085] The three-way valve 12 thus allows for the fluid connection, in a selective manner, of either the expansion vessel 8 with the main circuit 4 upstream of the pump 5 via the second branch 11 for pressure operation positive of operating system 1, i.e. the expansion vessel 8 with the main circuit 4 downstream of the pump 5 via the third branch 14 for negative pressure operation of operating system 1.

[0086] The operating system 1 may include a control device, connected to the three-way valve 12, adapted to control the selective opening and closing of the second and third ways, and thus adapted to control the transition from positive pressure operation to negative pressure operation, and vice versa.

[0087] Preferably, the three-way valve 12 is positioned directly downstream of the expansion vessel 8.

[0088] Preferably, the diameter of the first degassing line 71 is less than the diameter of the first main line 41, the second main line 42, the third main line 43, the second degassing line 72, the third degassing line 73 and the additional line 15.

[0089] Advantageously, the diameter of the first degassing pipe 71 is between 4 and 8 mm.

[0090] Advantageously, the diameter of the filling pipe 13 is also between 4 and 8 mm.

[0091] Advantageously, the diameter of the first main pipe 41, the second main pipe 42, the third main pipe 43, the second degassing pipe 72, the third degassing pipe 73 and the additional pipe 15 is between 10 and 35 mm.

[0092] Preferably, the cooling system 1 also includes an isolation valve 16 adapted for the selective passage of dielectric fluid between the expansion vessel 8 and the first and second variable volume tanks 9a, 9b.

[0093] The first and second variable volume reservoirs 9a, 9b can be positioned at a different level than that of the expansion vessel 8. The isolation valve 16 thus allows the first and second variable volume reservoirs 9a, 9b to be isolated from the expansion vessel 8 when the plug B is opened, in order to prevent the dielectric fluid contained in the expansion vessel 8 from emptying into the first and second variable volume reservoirs 9a, 9b when the latter are positioned below the expansion vessel 8. According to another embodiment, the first and second variable volume reservoirs can be arranged above the expansion vessel 8; the isolation valve 16 can then prevent the dielectric fluid contained by the first and second variable volume reservoirs 9a, 9b from returning to the expansion vessel 8 when the plug B of the expansion vessel 8 is opened.

[0094] Preferably, the isolation valve 16 is a manual valve.

[0095] According to one feature, the isolation valve 16 can be positioned under the expansion vessel 8, between the first outlet VS1 of the expansion vessel 8 and the first and second variable volume tanks.

[0096] Alternatively, the isolation valve 16 can be positioned directly on the first outlet VS1 of the expansion vessel 8.

[0097] In the illustrated example, the first outlet VS1 is positioned on the bottom 8a of the expansion vessel 8.

[0098] Preferably, the cap B of the expansion vessel 8 includes at least one safety valve.

[0099] Preferably, the maximum pressure value Pmax of the safety valve of the cap B is configured according to the position of the first and second variable volume tanks 9a and 9b relative to the expansion vessel 8. In this way, the hydrostatic pressure exerted by the fluid contained in the first and second variable volume tanks 9a and 9b and in the filling line 13 on the safety valve never exceeds a safety opening threshold value.

[0100] Advantageously, the safety valve can be set so that the maximum pressure Pmax, beyond which the safety valve opens, is 0.15 bar above atmospheric pressure.

[0101] The invention also relates to a method of preparing the cooling system 1, illustrated in [Fig.2], in particular carried out on an assembly line of a motor vehicle incorporating the cooling system 1.

[0102] Figure 1 illustrates the cooling system 1 before its use, and in particular before it is filled with dielectric fluid. The variable-volume reservoirs 9a and 9b in the form of flexible pouches are advantageously mounted folded and evacuated of air.

[0103] The preparation process includes a first vacuum evacuation step 100. The plug B is removed to open the expansion vessel 8. The first and third ports of the three-way valve 12 are opened and the second port is closed. A vacuum evacuation device is connected to the expansion vessel 8 to remove the air from the entire cooling system 1.

[0104] When the vacuum created in the cooling system 1 is sufficient, preferably between 0 and 0.95 bar below atmospheric pressure, a second filling step 200 of the cooling system 1 is carried out. A valve of the vacuum pump is switched from vacuum pump mode to filling mode, and the pressurized dielectric fluid is injected into the cooling system 1.

[0105] When a predetermined quantity of injected dielectric fluid is reached, the vacuum pulling device is disconnected from the expansion vessel 8 and the plug B is repositioned on the expansion vessel 8.

[0106] In order that the capacities of the variable volume tanks 9a and 9b to contain dielectric fluid can be reserved to respond to the volume variations associated with the swelling of the energy storage elements during the operation of the battery 2, the isolation valve 16 is preferably closed during the vacuum pulling 100 and filling 200 steps and the variable volume tanks 9a and 9b thus isolated from the degassing circuit 7.

[0107] The preparation process then includes a third degassing step 300 of the cooling system 1 in order to purge the residual air.

[0108] The third port of the three-way valve 12 is closed, the first and second ports of the three-way valve 12 are open, and the pump 5 is started. The dielectric fluid and the air bubbles it contains, set in motion by the pump 5, circulates in the main circuit 4 from the main outlet BS1 of battery 2 to the main inlet BEI of battery 2. Through the first and second connections 10 and 11, the dielectric fluid also circulates from the secondary outlet BS2 of battery 2 to the degassing circuit 7, passing through the expansion vessel 8 where the bubbles rise to the surface of the dielectric fluid contained in the expansion vessel 8. The dielectric fluid enters the expansion vessel 8 through the inlet VE1 and exits through the second outlet VS2, then is routed to the main circuit 4 via the second degassing line 72 and the third degassing line 73.

[0109] Preferably, the isolation valve 16 is opened at the beginning or end of the degassing step 300 so as to connect the variable volume tanks 9a and 9b to the expansion vessel 8, before use of the cooling system 1, and in particular of the battery 2, by a user of the motor vehicle incorporating the cooling system 1.

[0110] Such an isolation valve 16 allows the variable volume tanks 9a and 9b to be isolated during the vacuum pulling 100 and filling 200 steps, but also during maintenance operations of the cooling system 1, in particular when it is necessary to open the cap B, so that the dielectric fluid of the expansion vessel 8 does not empty when the variable volume tanks 9a and 9b are positioned at a level below the expansion vessel 8.

[0111] Such an isolation valve 16 facilitates the preparation of the cooling system 1 and allows the use of pre-existing factory vacuum pulling and filling tools such as the vacuum pulling device.

[0112] A manual isolation valve 16 facilitates maintenance operations.

[0113] The invention also relates to a method for cooling battery 2.

[0114] Figure 3 illustrates the cooling system 1 during its operation under positive pressure, in particular during its use within the motor vehicle. The first and second ports of the three-way valve 12 are open and the third The three-way valve 12 is closed. The dielectric fluid, set in motion by the pump 5, flows in the main circuit 4 from the main outlet BS1 of battery 2 to the main inlet BEI of battery 2, passing through battery 2, and flows from the first branch 10 to the second branch 11, passing through the expansion vessel 8.

[0115] The isolation valve 16 is open. As the battery 2 is used, the energy storage elements it contains swell. The variable volume reservoirs 9a and 9b, connected to the expansion vessel 8, fill with dielectric fluid as the energy storage elements swell.

[0116] The operation of the positive pressure cooling system 1 also allows the degassing of the dielectric fluid it contains, by passing through the expansion vessel 8.

[0117] When it is desired to further reduce the pressure within the cooling system 1, and in particular within the battery 2, a negative pressure operation of the cooling system 1 can be initiated.

[0118] With reference to [Fig.4], the first and third ways of the three-way valve 12 are open and the second way of the three-way valve 12 is closed.

[0119] The dielectric fluid flows in the main circuit 4 from the main outlet BS1 of battery 2 to the main inlet BEI of battery 2, and flows from the third tap 14 to the first tap 10, passing through the expansion vessel 8.

[0120] A depression is created inside the battery 2 and the direction of circulation of the dielectric fluid is reversed in the degassing circuit 7. Indeed, the pressure at the third tap 14 is greater than the pressure at the secondary outlet BS2 of the battery 2 so that the dielectric fluid flows from the third tap 14 to the expansion vessel 8, and from the expansion vessel 8 to the first tap 10, advantageously positioned, in the illustrated example, in the upper position of the battery 2, on the upper wall 3a.

[0121] The operation of the negative pressure cooling system 1 also allows the degassing of the dielectric fluid it contains, by passing through the expansion vessel 8.

[0122] During the degassing step 300 of the cooling system preparation process 1, the three-way valve 12 is configured so that the dielectric fluid does not circulate in the additional line 15. Any air present in the additional line 15 can be eliminated during the operation of the cooling system 1 under negative pressure.

[0123] The isolation valve 16 is open, and the variable volume tanks 9a and 9b fill with dielectric fluid as the energy storage elements swell by the phenomenon of swelling.

[0124] Fig. 5 illustrates a second embodiment of the cooling system 1 in which the first tapping 10 is, alternatively, arranged to be adjacent to the main outlet BS1 of the battery 2.

[0125] In this second embodiment, battery 2 does not include a secondary output BS2.

[0126] Fig. 6 illustrates a third embodiment of the cooling system 1 in which the third tapping 14 is, alternatively, positioned directly on the battery 2.

[0127] As shown in the detailed view of battery 2 in [Fig.7], the third tapping 14 is preferably positioned on the opposite third side wall 3d.

[0128] Battery 2 includes a central outlet manifold 17 of the dielectric fluid connected to the main outlet BS1 of battery 2. The central outlet manifold 17 extends between the first and third side walls 3c and 3d and is positioned equidistant from the second and fourth side walls 3e and 3f.

[0129] Preferably, the third branch 14 is positioned on the third side wall 3d, opposite the outlet manifold 17, on the opposite side of the main outlet BS1. In other words, the third branch 14, the outlet manifold 17 and the main outlet BS1 are arranged in a common plane.

[0130] Such a position of the tapping 14 makes it possible to further reduce the pressure within the battery 2. Indeed,

[0131] In such a configuration, the pressure at the third tap 14 is equal to the average of the pressure at the main inlet BEI of battery 2 and the pressure at the main outlet BS1 of battery 2. The pressure inside battery 2 then varies between the negative and positive values ​​of this average, i.e. a pressure twice as close to atmospheric pressure as a third tap 14 positioned on the third main line 43 of the main circuit 4, as illustrated in the first embodiment of [Fig.1].

[0132] Fig. 8 illustrates a fourth embodiment of the cooling system 1 in which the third tap 14 is positioned directly on the battery 2, and the first tap 10 is arranged so as to be adjacent to the main outlet BS1 of the battery 2.

Claims

Demands

1. A cooling system for a battery (2) by means of a dielectric fluid intended to circulate in contact with energy storage components of the battery (2), the cooling system (1) comprising the battery (2), a pump (5) for circulating the dielectric fluid between a main outlet (BS1) and a main inlet (BEI) of the battery (2), a heat exchanger (6) for cooling the dielectric fluid, an expansion vessel (8), at least one variable volume reservoir (9a, 9b) connected to the expansion vessel (8), and an isolation valve (16) adapted for the selective passage of dielectric fluid between the expansion vessel (8) and the variable volume reservoir (9a, 9b).

2. Cooling system according to claim 1, wherein the isolation valve (16) is a manual valve.

3. Cooling system according to claim 1 or 2, wherein the expansion vessel (8) includes a dielectric fluid inlet (VE1) and a first outlet (VS1) in fluidic connection with the variable volume reservoir (9a, 9b), the isolation valve (16) being positioned below the expansion vessel (8), between the first outlet (VS1) of the expansion vessel (8) and the variable volume reservoir (9a, 9b).

4. Cooling system according to claim 1 or 2, wherein the expansion vessel (8) comprises a dielectric fluid inlet (VE1) and a first outlet (VS1), the isolation valve (16) being positioned directly on the first outlet (VS1) of the expansion vessel (8).

5. Cooling system according to claim 3 or 4, wherein the first outlet (VS1) is positioned on the bottom (8a) of the expansion vessel (8).

6. Cooling system according to any one of the preceding claims, comprising: a main circuit (4) for circulating the dielectric fluid on which are disposed the battery (2), the pump (5) for circulating the dielectric fluid between a main outlet (BS1) and a main inlet (BEI) of the battery (2), and the heat exchanger (6) for cooling the dielectric fluid, a dielectric fluid degassing circuit (7) on which are arranged the expansion vessel (8) and the variable volume reservoir (9a, 9b) connected to the expansion vessel (8), the degassing circuit (7) being connected to the main circuit (4) by a first branch (10) adjacent to the main outlet (BS1) of the coil (2) or positioned on a secondary outlet (BS2) of the coil (2) and by a second branch (11) positioned downstream of the main outlet (BS1) of the coil (2) and upstream of the pump (5), and a three-way valve (12) of which a first port is in fluidic connection with the expansion vessel (8), a second port is in fluidic connection with the second branch (11) of the main circuit (4) and a third port is in fluidic connection with a third branch (14) positioned on the main circuit (4) downstream of the pump (5) and upstream of the main outlet (BS1) of the coil (2).

7. A method for preparing a cooling system according to any one of the preceding claims, comprising the following steps: a vacuum pulling step (100) to remove at least partially the air contained within the cooling system (1), and a filling step (200) of the cooling system with dielectric fluid, the isolation valve (16) being closed to isolate the variable volume tank (9a, 9b) from the expansion vessel (8) during the vacuum pulling (100) and filling (200) steps.

8. A preparation method according to claim 7, wherein the isolation valve (16) is opened after the vacuum pulling and filling steps to fluidly connect the variable volume tank (9a, 9b) to the expansion vessel (8).

9. A preparation method according to claim 7 or 8, comprising a degassing step (300) of the dielectric fluid of the cooling system (1), the isolation valve (16) being opened at the beginning of the degassing step or after the degassing step to fluidly connect the variable volume tank (9a, 9b) to the expansion vessel (8).

10. Motor vehicle comprising at least one cooling system (1) according to any one of claims 1 to 6.