Negative pressure system for cooling a battery and associated cooling method

Abstract

The invention relates to a system for cooling a battery (2), which system comprises: - a main circuit (4) comprising the battery and a pump (5) for circulating a dielectric fluid arranged between a main outlet (BS1) and a main inlet (BE1) of the battery; - a degassing circuit (7) comprising an expansion tank (8) and at least one tank of variable volume, which degassing circuit is connected to the main circuit by a first tapping (10) adjacent to the main outlet (BS1) of the battery or positioned on a secondary outlet (BS2) of the battery, and by a second tapping (11) positioned downstream of the main outlet; and - a three-way valve (12) a first flow path whereof is connected to the expansion tank, a second flow path whereof is connected to the second tapping of the main circuit and a third flow path whereof is connected to a third tapping (14) positioned downstream of the pump and upstream of the main outlet.

Description

[0001] DESCRIPTION

[0002] TITLE: Cooling system for a battery with negative pressure operation and associated cooling method

[0003] 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.

[0004] In particular, the invention relates to a battery cooling system, to a motor vehicle incorporating such a cooling system and to a method of cooling a battery from such a cooling system.

[0005] It is a known method to cool a battery using a dielectric fluid circulating in direct contact with its constituent cells. The large surface area for heat exchange between the cells and the fluid makes this a highly efficient solution. In fact, the surface area ensuring this exchange is three to ten times larger than the surface area for heat exchange between the cells and a cooling circuit consisting of a cooling plate positioned under the battery and traversed by a refrigerant.

[0006] However, this large surface area requires a substantial volume of dielectric fluid, on the order of 20 to 40 liters, representing three to eight times the volume of a cooling system with a cooling plate.

[0007] 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. Additionally, the volume of the cells increases with time and 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."

[0008] However, increasing cell volume reduces the volume occupied by the dielectric fluid within the battery. Given the significant total volume occupied by all the cells in a battery, the expansion of the dielectric fluid, and the increase in the volume of each cell, a solution is needed to store the resulting volume of dielectric fluid.

[0009] To cope with these volume variations, it is known to use an expansion tank connected to the battery.

[0010] However, its required volume is on the order of three times the variation in the volume of the dielectric liquid to be stored, so it is difficult to find space to house it, especially in a motor vehicle.

[0011] 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.

[0012] 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.

[0013] However, in order to ensure the mechanical integrity of the battery casing and to prevent its deformation, it is important that the pressure inside the battery be as low as possible.

[0014] Therefore, there is a need to further reduce the pressure within the battery.

[0015] In parallel, it is necessary that the cooling system has a degassing function to expel air bubbles present in the dielectric liquid.

[0016] The invention therefore aims to overcome these drawbacks and to provide a battery cooling system, particularly for motor vehicles, incorporating a dielectric fluid circulating in contact with the battery cells and reducing the pressure inside the battery while maintaining a degassing function for the dielectric fluid. A battery cooling system using a dielectric fluid intended to circulate in contact with the battery's energy storage components is thus proposed. The cooling system comprises: a main circuit for circulating the dielectric fluid on which the battery is placed, a pump for circulating the dielectric fluid between a main outlet and a main inlet of the battery, and a heat exchanger for cooling the dielectric fluid.and a dielectric fluid degassing circuit on which are arranged an expansion vessel and at least one variable volume reservoir connected to the expansion vessel, the degassing circuit being connected to the main circuit by a first branch connected 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, a three-way valve of which a first port is in fluidic connection with the expansion vessel, a second port is in fluidic connection with the second branch of the main circuit and a third port 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.

[0017] In one embodiment, the third tap can be positioned upstream of the battery, adjoining the main inlet of the battery.

[0018] In another embodiment, the third connection can be positioned on the battery.

[0019] Advantageously, the battery may comprise a casing containing the energy storage components, the casing comprising an upper wall, a lower wall opposite the upper wall, and first, second, third, and fourth side walls, the first and third side walls being opposite each other and the second and fourth side walls being opposite each other. Advantageously, the main inlet and main outlet of the battery may be positioned on the first side wall, with the third outlet positioned on the opposite third side wall.

[0020] Advantageously, the battery may include a central outlet manifold for the dielectric fluid connected to the main outlet of the battery and extending between the first and third side walls and equidistant from the second and fourth side walls, the third branch being positioned opposite the outlet manifold, on the opposite side from the main outlet.

[0021] Preferably, the first connection should be positioned on the upper wall of the battery.

[0022] Preferably, the degassing circuit also includes an isolation valve suitable for the selective passage of the dielectric fluid between the expansion vessel and the variable volume tank. More preferably, the isolation valve is a manual isolation valve.

[0023] The invention also relates to a method of cooling a battery by a dielectric fluid circulating in a cooling system as described above, comprising opening the first and third ways and closing the second way of the three-way valve for the activation of a negative pressure cooling system operation, the dielectric fluid circulating in the main circuit from the main outlet of the battery to the main inlet of the battery, and circulating from the third tap to the first tap through the expansion tank, preferably when the isolation valve is present, the isolation valve is open.

[0024] Preferably, the cooling method comprises opening the first and second ports and closing the third port of the three-way valve to initiate positive pressure cooling system operation. The dielectric fluid circulates in the main circuit from the main battery outlet to the main battery inlet, and from the first port to the second port through the expansion tank, preferably when the isolation valve is present and open. The invention also relates to a motor vehicle comprising at least one cooling system as described above.

[0025] Brief description of the drawings

[0026] Other goals, advantages, and characteristics will become apparent from the following description, given for illustrative purposes only and with reference to the attached drawings, on which:

[0027] [Fig 1] represents a cooling system according to a first embodiment of the invention.

[0028] [Fig 2] illustrates a method for preparing a cooling system as shown in Figure 1 according to one embodiment of the invention. [Fig 3] illustrates the cooling system shown in Figure 1 operating under positive pressure.

[0029] [Fig 4] illustrates the cooling system shown in figure 1 in negative pressure operation.

[0030] [Fig 5] represents a cooling system according to a second embodiment of the invention.

[0031] [Fig 6] represents a cooling system according to a third embodiment of the invention.

[0032] [Fig 7] is a top cross-sectional view of the cooling system battery shown in Figure 6.

[0033] [Fig 8] represents a cooling system according to a fourth embodiment of the invention.

[0034] Detailed description

[0035] In what follows, the boundaries of a domain of values ​​are included in that domain, in particular in the expression "between".

[0036] Furthermore, the expression "at least one" used in this description is equivalent to the expression "one or more".

[0037] Figure 1 illustrates a cooling system 1 for a battery 2 according to an embodiment of the invention. In the illustrated example, the battery 2 is a high-voltage battery from an electric or hybrid vehicle, but the invention is not limited to such use.

[0038] Advantageously, battery 2 has a sealed case 3 containing electrical energy storage components.

[0039] In the illustrated example, the casing 3 is substantially parallelepiped-shaped, and comprises an upper wall 3a, a lower wall 3b opposite the upper wall 3a, and a plurality of lateral walls, in particular the first, second, third and fourth lateral walls 3c, 3d, 3e and 3f. The first and third lateral walls 3c and 3d are opposite and the second and fourth lateral walls 3e and 3f are opposite.

[0040] Advantageously, the housing 3 of the battery 2 can contain one or more battery modules, each containing one or more electrical energy storage components.

[0041] According to an alternative, the electrical energy storage components can be arranged in the housing 3 without compartmentalization in battery modules.

[0042] As shown in Figure 6, electrical energy storage devices can be flexible pouch cells C, also known as "pouch" cells.

[0043] Alternatively, the electrical energy storage organs C can, for example, be prismatic cells or cylindrical cells.

[0044] Preferably, a dielectric fluid completely fills the available volume of the battery, including the sealed casing 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.

[0045] The dielectric fluid is, for example, a dielectric liquid such as oil.

[0046] The cooling system 1 includes a main circuit 4 for circulating the dielectric fluid. The illustrated coil 2 has a main inlet BEI of the dielectric fluid, a main outlet BS1 and a secondary outlet BS2 of the dielectric fluid.

[0047] 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.

[0048] 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.

[0049] In the illustrated example, the main outlet BS1 is advantageously arranged in a plane higher than the main inlet BEI of the dielectric fluid.

[0050] The main circuit 4 includes 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 battery 2, and a heat exchanger 6 for cooling the dielectric fluid passing through it.

[0051] Preferably, the heat exchanger 6 is positioned downstream of the pump 5, between the pump 5 and the main BEI inlet of the battery.

[0052] The battery cooling system 1 allows the dielectric fluid to circulate in contact with the energy storage components of battery 2 in order to cool them.

[0053] 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.

[0054] The cooling system 1 further includes a degassing circuit 7 for the dielectric fluid.

[0055] 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.

[0056] In the illustrated example, each of the variable volume reservoirs 9a and 9b is a flexible pouch.

[0057] 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.

[0058] The illustrated expansion vessel 8 further includes a dielectric fluid inlet VE 1, a first dielectric fluid outlet VS 1 and a second outlet VS2.

[0059] The expansion vessel 8 comprises a lower half including the bottom 8a and an upper half including the upper wall 8c.

[0060] Preferably, and as illustrated, the first outlet VS 1 of the expansion vessel 8 is positioned on the lower half, under the expansion vessel, on the bottom 8a of the expansion vessel 8.

[0061] 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.

[0062] Preferably, the dielectric fluid inlet VE 1 is arranged in a plane above the first and second dielectric fluid outlets VS 1 and VS2. Advantageously, the VE 1 inlet is positioned on the lower half, and can be disposed on the side wall 8b.

[0063] In the first embodiment illustrated in Figure 1, the degassing circuit 7 is connected to the main circuit 4 by a first branch 10 positioned on the secondary outlet BS2 of battery 2, and by a second branch 11 positioned downstream of the main outlet BS1 of battery 2 and upstream of the pump 5.

[0064] Preferably, the first connection 11 is positioned at a distance less than or equal to 6 cm from the main outlet BS1 of the battery 2, preferably less than or equal to 5 cm. The cooling system 1 further includes a three-way valve 12, the first port of which is in fluidic connection with the expansion vessel 8 and the second port is in fluidic connection with the second connection 11 of the main circuit 4.

[0065] The degassing circuit 7 comprises a plurality of pipes fluidly connecting the different elements of the degassing circuit 7. A first degassing pipe 71 fluidly connects the secondary outlet B S2 of the battery 2 and the inlet VE 1 of the expansion vessel 8, a second degassing pipe 72 fluidly connects the second outlet VS2 of the expansion vessel 8 to the first way of the three-way valve 12, and a third degassing pipe 73 fluidly connects the second way of the three-way valve 12 to the second branch 1 1.

[0066] A filling line 13 fluidly connects the first outlet VS 1 of the expansion vessel 8 to the first variable volume reservoir 9a.

[0067] The second branch 1 1 connects the third degassing line 73 and the first main line 41.

[0068] 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.

[0069] The third branch 14 is positioned downstream of the pump 5, specifically downstream of the heat exchanger 6, and upstream of the main outlet BS 1 of the battery 2.

[0070] In the first embodiment illustrated in Figure 1, the third branch 14 is positioned between the pump 5 and the main inlet BE I of the battery 2, upstream of the battery, and adjoining the main inlet BE I of the battery 2.

[0071] Preferably, the third spigot 14 is positioned at a distance less than or equal to 6 cm from the main inlet BE I of battery 2, preferably less than or equal to 5 cm.

[0072] An additional conduit 1 5 fluidly connects a third way of the three-way valve 12 to the third branch 1 4.

[0073] The third branch 14 connects the additional line 15 and the third main line 43. The three-way valve 12 thus allows fluid connection, in a selective manner, either the expansion vessel 8 with the main circuit 4 upstream of the pump 5 via the second branch 11 for positive pressure operation of the operating system 1, or the expansion vessel 8 with the main circuit 4 downstream of the pump 5 via the third branch 14 for negative pressure operation of the operating system 1.

[0074] 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.

[0075] Preferably, the three-way valve 12 is positioned directly downstream of the expansion vessel 8.

[0076] 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.

[0077] Advantageously, the diameter of the first degassing pipe 71 is between 4 and 8 mm.

[0078] Advantageously, the diameter of the filling pipe 13 is also between 4 and 8 mm.

[0079] 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.

[0080] 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.

[0081] The first and second variable volume reservoirs 9a, 9b can be positioned at a different level than 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 cap B of the expansion vessel 8 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 flowing back towards the expansion vessel 8 when the cap B of the expansion vessel 8 is opened.

[0082] Preferably, the isolation valve 16 is a manual valve.

[0083] According to one characteristic, the isolation valve 16 can be positioned under the expansion vessel 8, between the first outlet VS 1 of the expansion vessel 8 and the first and second variable volume tanks.

[0084] Alternatively, the isolation valve 16 can be positioned directly on the first outlet VS 1 of the expansion vessel 8.

[0085] In the illustrated example, the first outlet VS 1 is positioned on the bottom 8a of the expansion vessel 8.

[0086] Preferably, the cap B of the expansion vessel 8 includes at least one safety valve.

[0087] 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.

[0088] 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. The invention also relates to a method for preparing the cooling system 1, illustrated in Figure 2, particularly carried out on an assembly line of a motor vehicle incorporating the cooling system 1.

[0089] 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.

[0090] The preparation process includes a first vacuum evacuation step 100. 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.

[0091] 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.

[0092] When a predetermined quantity of injected dielectric fluid is reached, the vacuum pumping device is disconnected from the expansion vessel 8 and the plug B is repositioned on the expansion vessel 8.

[0093] In order that the capacities of the variable volume tanks 9a and 9b to contain dielectric fluid can be reserved to meet 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.

[0094] The preparation process then includes a third degassing step 300 of the cooling system 1 to purge residual air. The third port of the three-way valve 12 is closed, the first and second ports of the three-way valve 12 are opened, 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 tank 8 where the bubbles rise to the surface of the dielectric fluid contained in the expansion tank 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 through the second degassing line 72 and the third degassing line 73.

[0095] 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.

[0096] 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.

[0097] A manual 16 isolation valve facilitates maintenance operations.

[0098] 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.

[0099] The invention also relates to a method for cooling battery 2. Figure 3 illustrates the cooling system 1 during its operation under positive pressure, particularly during its use within the motor vehicle. The first and second ports of the three-way valve 12 are open, and the third port of 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 BS 1 of battery 2 to the main inlet BE 1 of battery 2, passing through battery 2, and flows from the first outlet 10 to the second outlet 11, passing through the expansion tank 8.

[0100] The isolation valve 16 is open. As 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.

[0101] 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.

[0102] 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.

[0103] With reference to Figure 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.

[0104] The dielectric fluid circulates in the main circuit 4 from the main outlet BS 1 of battery 2 to the main inlet BE I of battery 2, and circulates from the third branch 14 to the first branch 10, passing through the expansion vessel 8.

[0105] A depression is created inside 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 B S2 of 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 battery 2, on the upper wall 3 a.

[0106] 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.

[0107] 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.

[0108] The isolation valve 16 is open, and the variable volume tanks 9a and 9b fill with dielectric fluid as the energy storage organs swell by the phenomenon of swelling.

[0109] Figure 5 illustrates a second embodiment of the cooling system 1 in which the first tapping 10 is, alternatively, arranged to be adjoining the main outlet BS 1 of the battery 2.

[0110] In this second embodiment, battery 2 does not include a secondary output B S2.

[0111] Figure 6 illustrates a third embodiment of the cooling system 1 in which the third connection 14 is, alternatively, positioned directly on the battery 2.

[0112] As shown in the detailed view of battery 2 in figure 7, the third tapping 14 is preferably positioned on the opposite third side wall 3d.

[0113] Battery 2 includes a central outlet manifold 17 of the dielectric fluid connected to the main outlet BS 1 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.

[0114] 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 BS 1. In other words, the third branch 14, the outlet manifold 17 and the main outlet BS 1 are arranged in a common plane.

[0115] Such a position of the tap 14 makes it possible to further reduce the pressure within battery 2. Indeed, in such a configuration, the pressure at the third tap 14 is equal to the average of the pressure at the main inlet BE I of battery 2 and the pressure at the main outlet BS 1 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 Figure 1.

[0116] Figure 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 adjoining the main outlet BS 1 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: a main circuit (4) for circulating the dielectric fluid on which the battery (2) is disposed, a pump (5) for circulating the dielectric fluid between a main outlet (BS1) and a main inlet (BEI) of the battery (2), and a heat exchanger (6) for cooling the dielectric fluid, a degassing circuit (7) for the dielectric fluid on which an expansion vessel (8) and at least one variable volume reservoir (9a, 9b) connected to the expansion vessel (8) are disposed,the degassing circuit (7) being connected to the main circuit (4) by a first branch (10) adjacent to the main outlet (BS1) of the battery (2) or positioned on a secondary outlet (BS2) of the battery (2) and by a second branch (11) positioned downstream of the main outlet (BS1) of the battery (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 battery (2).

2. Cooling system according to claim 1, wherein the third tapping (14) is positioned upstream of the battery (2), adjacent to the main inlet (BEI) of the battery (2).

3. Cooling system according to claim 1, wherein the third tapping (14) is positioned on the battery (2).

4. Cooling system according to claim 3, wherein the battery (2) comprises a housing (3) enclosing the energy storage elements, the housing (3) comprising an upper wall (3a), a lower wall (3b) opposite the upper wall (3a), and first, second, third and fourth side walls (3c, 3d, 3 e , 3f), the first and third side walls (3c, 3d) being opposite and the second and fourth side walls (3e, 3f) being opposite, the main inlet (BEI) and the main outlet (BS1) of battery (2) are positioned on the first side wall (3c), the third tap (14) being positioned on the opposite third side wall (3d).

5. Cooling system according to claim 3, wherein the battery (2) comprises a central outlet manifold (17) of the dielectric fluid connected to the main outlet (BS1) of the battery (2) and extending between the first and third side walls (3c, 3d) and equidistant from the second and fourth side walls (3e, 3f), the third branch (14) being positioned opposite the outlet manifold (17), opposite the main outlet (BS1).

6. Cooling system according to any one of the preceding claims, wherein the battery (2) comprises a housing (3) containing the energy storage elements, the housing (3) comprising an upper wall (3a), a lower wall (3b) opposite the upper wall (3a), the first spigot (10) being positioned on the upper wall (3a) of the battery (2).

7. Cooling system according to any one of the preceding claims, wherein the degassing circuit (7) further comprises an isolation valve (16) adapted for the selective passage of the dielectric fluid between the expansion vessel (8) and the variable volume reservoir (9a, 9b), preferably the isolation valve (16) is a manual isolation valve.

8. Method of cooling a battery (2) by a dielectric fluid circulating in a cooling system (1) according to any one of the preceding claims, comprising opening the first and third ports and closing the second port of the three-way valve (12) for the activation of a negative pressure operation of the cooling system (1), the dielectric fluid circulating in the main circuit (4) from the main outlet (BS1) of the battery (2) to the main inlet (BEI) of the battery (2), and circulating from the third branch (14) to the first branch (10) through the expansion vessel (8), preferably when the isolation valve (16) is present, the isolation valve (16) is open.

9. Cooling method according to claim 8, comprising opening the first and second ways and closing the third way of the three-way valve (12) for the activation of a positive pressure operation of the cooling system (1), the dielectric fluid circulating in the main circuit (4) from the main outlet (BS1) of the battery (2) to the main inlet (BEI) of the battery (2), and circulating from the first branch (10) to the second branch (11) through the expansion vessel (8) preferably when the isolation valve (16) is present, the isolation valve (16) is open.

10. Motor vehicle comprising at least one cooling system (1) according to any one of claims 1 to 7.

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