Battery cell heat transfer loops incorporating battery mounts and related methods of manufacture

Abstract

The invention relates to a battery support comprising a base (1) and a heat transfer circuit (2) comprising a first conduit and a second conduit wherein a first end of the first conduit allows for receiving a heat transfer liquid and a first end of the second conduit allows for discharging the heat transfer liquid, the first and second conduits are connected together by the second ends of the first and second conduits, the first and second conduits being delimited on the one hand by the base (1) and on the other hand by a set of walls, the first and second conduits sharing a common wall. The cross-section of the wall of the heat transfer circuit (2) is W-shaped, and the heat transfer circuit is produced by additive manufacturing.

Description

Technical Field

[0001] The technical field of the present invention is the protection of multi-cell batteries, and more specifically the protection of such batteries from thermal runaway. Background Art

[0002] The electrochemical cells of a battery are typically assembled within a housing in contact with a heat transfer circuit in which a heat transfer fluid circulates.

[0003] Such a housing typically includes a tray or base and a bell-shaped member that mates with the base to define an enclosed volume in which the cells of the battery are disposed.

[0004] The heat transfer circuit is in contact with the base and is in the form of a set of welded tubes that are typically connected in parallel. When the set of welded tubes is connected in this way, the flow rate of the heat transfer fluid through each tube is substantially equal. However, such a configuration creates a thermal gradient between the input and output of the circuit.

[0005] In some configurations, not all cells can be cooled in parallel. The heat transfer circuit then includes tubes connected in parallel and tubes connected in series. Combined with the temperature gradient in the parallel regions, this has the effect of not subjecting all cells to the same temperature of the heat transfer fluid. The temperature of some cells is higher than that of other cells. This is also the case when a large number of cells are cooled by a parallel circuit, with the cells closer to the inlet of the heat transfer circuit having a lower temperature than the cells closer to the outlet.

[0006] This situation is harmful because the temperature of the cells directly affects their lifespan, and more specifically, affects the aging of the cells. In a battery including multiple cells, the differential aging of the cells is problematic because it can lead to premature failure of the cells experiencing the highest temperature. Such a failure requires specific maintenance operations.

[0007] In addition, the heat transfer circuit is typically independent of the base, which facilitates its manufacture, control, and maintenance.

[0008] The disadvantages of this are an increase in the weight of the components, an increase in the number of parts to be managed, and the need to use a thermal interface between the base and the heat transfer circuit to compensate for the mechanical gap between the two parts and enhance heat exchange. The thermal interface is typically produced in the form of a thermal pad, which affects the weight and cost of the components.

[0009] There is a need to reduce the weight of the battery and its heat transfer system, especially from the perspective of aviation applications.

[0010] There is also a need to reduce the temperature gradient between individual cells. Summary of the Invention

[0011] The object of the present invention is a battery support, which comprises a base and a heat transfer circuit. The heat transfer circuit includes a first pipe and a second pipe. The first end of the first pipe allows the reception of a heat transfer liquid, and the first end of the second pipe allows the discharge of the heat transfer liquid. The first pipe and the second pipe are connected together through the second ends of the first pipe and the second pipe. The first pipe and the second pipe are bounded on one hand by the base and on the other hand by a set of walls, and the first pipe and the second pipe share a common wall.

[0012] The cross-section of the wall of the heat transfer circuit may be in the shape of an "E".

[0013] The cross-section of the wall of the heat transfer circuit may be in the shape of a "W".

[0014] Another object of the present invention is a battery, which comprises at least one battery cell. The at least one battery cell is arranged on the battery support as described above. These battery cells are arranged on one side of the base, and the heat transfer circuit is arranged on the other side of the base so as to extend opposite to each battery cell.

[0015] The heat transfer liquid may be selected from refrigerants, ethylene glycol water or gases, especially air.

[0016] Another object of the present invention is a method for manufacturing the battery support as described above. The method comprises the following steps:

[0017] - Manufacturing the base and the heat transfer circuit,

[0018] - Arranging the heat transfer circuit on the base,

[0019] - Subsequently attaching a holding tool to the base so that it extends above the heat transfer circuit,

[0020] - Then adjusting the pressure exerted by the holding tool on the heat transfer circuit so as to reduce the distance between the wall of the heat transfer circuit and the base,

[0021] - Performing laser welding on the wall of the heat transfer circuit and the base,

[0022] - Removing the holding tool,

[0023] - Closing the holes that may be arranged in the base for attaching the holding tool by the following method: arranging and welding a shoulder washer or a metal pad for each hole.

[0024] An object of the present invention is a method for manufacturing the battery support as described above, wherein the heat transfer circuit is directly produced on the base by additive manufacturing. Description of the Drawings

[0025] With reference to the accompanying drawings, other objects, features and advantages of the present invention will become apparent from the following description, which is provided by way of non-limiting example only, in which:

[0026] - Figure Figure 1 shows a first embodiment of a heat transfer circuit,

[0027] - Figure Figure 2 shows a cross-sectional view of the heat transfer circuit,

[0028] - Figure Figure 3 shows a cross-sectional view of a section of the heat transfer circuit,

[0029] - Figure Figure 4 shows a holding tool for holding the heat transfer circuit on the base during welding,

[0030] - Figure Figure 5 shows the main steps of a method for manufacturing a heat transfer circuit according to the first embodiment,

[0031] - Figure Figure 6 shows a cross-sectional view of a section of a heat transfer circuit according to a second embodiment, and

[0032] - Figure Figure 7 shows a second embodiment of the heat transfer circuit. Detailed Description

[0033] The battery housing according to the present invention includes a bell-shaped member and a base, and the heat transfer circuit is welded to the surface of the base. Figure Figure 1 shows the base 1 and the heat transfer circuit 2.

[0034] The heat transfer circuit includes a first pipe 2a and a second pipe 2b, and the liquid received in the circuit flows in the first pipe, and the liquid discharged from the heat transfer circuit 2 flows in the second pipe. The heat transfer fluid is received in the first pipe through the first end of the first pipe 2a. The heat transfer liquid is also discharged from the second pipe through the first end of the second pipe 2b. The heat transfer liquid is selected from refrigerant liquids, ethylene glycol water, or even gases (such as air).

[0035] The two pipes are connected together through the second ends of the two pipes.

[0036] In order to make the temperature between the battery cells uniform, the inventors thought of sharing a wall between the two pipes. Figure Figure 2 shows a cross-sectional view according to a plane passing through the central axis of each pipe.

[0037] In order to reduce the weight of the battery housing and improve the heat transfer efficiency, the inventors thought of removing the wall of the heat transfer circuit 2 that contacts the base. Thus, cost can be saved on the wall of the heat transfer circuit at the interface with the base 1. Accordingly, the weight of the assembly and the thermal inertia of the assembly are reduced, facilitating heat transfer. Fig. Figure 3 shows a cross-sectional view perpendicular to the axis of each pipe. Fig. Figure 2 's cutting plane A-A', as well as the base 1, the first pipe 2a and the second pipe 2b are shown.

[0038] From this removal, it can be seen that the heat transfer circuit 2 includes an open face and an E-shape. Thus, the pipes 2a, 2b can only receive the heat transfer liquid when fixed to the base 1.

[0039] It should be noted that the E-shape of the heat transfer circuit corresponds to the requirements in terms of thermal management of the battery cells, especially in terms of heat transfer. Given the heat capacity of the heat transfer fluid used and the amount of heat energy to be dissipated, the required flow rate of the heat transfer fluid can be determined. Given the capacity of the on-board circulation pump, the required cross-section of the pipes of the heat transfer circuit can be determined. The cross-section of the heat transfer circuit can be modified, especially in terms of aspect ratio, to take into account the structural limitations of the pipes. In particular, the height of the coil can be adjusted according to the bending or torsional resistance.

[0040] Based on the above considerations, both the first pipe where the received liquid flow is located and the second pipe where the discharged liquid flow is located are in contact with the same components, especially the same battery cells. Combined with the common wall, this has the advantage of equalizing the temperature between the received heat transfer liquid and the discharged heat transfer liquid, thereby reducing the temperature gradient. In addition, removing the wall of the pipe that contacts the base can prevent the double interface generated due to the contact between the pipe wall and the base. The thermal inertia is reduced, which further reduces the temperature gradient.

[0041] In a specific embodiment, the heat transfer circuit is designed to be in contact with the electrical connector of the battery.

[0042] Now a method for manufacturing the above heat transfer circuit will be described.

[0043] Fig. Figure 3 's E-shaped cross-section of the heat transfer circuit shows the limited accessibility of the central wall of the heat transfer circuit 2 when welded to the base 1.

[0044] In a first embodiment, the heat transfer circuit is welded to the base by laser welding. This welding is carried out in a transparent manner, such that the limited accessibility of the central wall does not pose a problem. Another advantage of it is that no additional metal needs to be added, so the weight is not increased.

[0045] However, one of the main limitations of laser welding is the distance between the components to be welded, which in this case is the distance between the wall and the base. With current technology, this distance should be less than 0.2 mm.

[0046] To ensure that this constraint between the wall of the heat transfer circuit and the base is respected, a holding tool has been developed. Fig. Figure 4 shows this holding tool 3, which comprises a metal plate 4 provided with a first set of blind tapped holes 5 arranged opposite the base 1 and a second set of through tapped holes 6 arranged above the heat transfer circuit 2.

[0047] A set of holes 7 is produced in the base 1, which is opposite the first set of blind tapped holes 5. Subsequently, the tool and the base are fixed by means of spacers 8 adjusted to the height of the heat transfer circuit 2 and screws 9. Alternatively, threaded rods and nuts are used instead of the screws 9.

[0048] The second set of holes 6 is provided with additional screws 10, by screwing which pressure can be exerted on the heat transfer circuit 2. This pressure makes it possible to reduce the distance between the wall of the heat transfer circuit 2 and the base 1 below the limit distance for laser welding.

[0049] The manufacturing process is shown in Fig. Figure 5 The manufacturing process comprises a first step 101: during this step, the heat transfer circuit 2 is placed on the base 1. Subsequently, the holding tool 3 is attached to the base 1 so that it extends above the heat transfer circuit 2 and the screw 10 comes into contact with the heat transfer circuit 2. Then the pressure on the heat transfer circuit 2 is adjusted by adjusting the screwing of the screw 10 in order to reduce the distance between the wall of the heat transfer circuit 2 and the base 1.

[0050] During a second step 102, laser welding is carried out. During a third step 103, the holding tool is removed. During a fourth step 104, each threaded hole 7 arranged in the base 1 and allowing the attachment of the holding tool is subsequently provided with a shoulder washer or a metal washer, which is also welded by laser welding.

[0051] The layout of the first assembly 5 and the choice of the number of holes depend on the length of the heat transfer circuit 2, its shape and the deformation of the base 1, etc.

[0052] It should be noted that laser welding can weld parts made of titanium, which is a material with very good mechanical resistance. The construction of the titanium heat transfer circuit is of particular interest because it is subject to mechanical stresses during the cooling or heating of the battery cells and because of the stiffness that the heat transfer circuit 2 imparts to the base 1. Finally, for the same dimensions, titanium is lighter than stainless steel.

[0053] In another embodiment of the manufacturing method, the heat transfer circuit is produced directly on the base by additive manufacturing. To take into account the constraints specific to this additive manufacturing, the E-shape is replaced by a W-shape in which each pipe 2a, 2b is triangular. Fig. Figure 6 shows the W-shape of the heat transfer circuit 2, while Fig. Figure 7 is a top view of the heat transfer circuit 2 formed on the base 1 by additive manufacturing.

[0054] The above description shows the cooling of the battery cell. However, it is known that heating such a cell is also beneficial, especially in the context of low-temperature charging. Such an embodiment is also included within the scope of the present invention, since it differs only in that the heat input is effected by a circulating heated heat transfer liquid instead of the heat removal effected by the circulating cooled heat transfer liquid described above.

Claims

1. A battery support, the battery support comprising a base (1) and a heat transfer circuit (2), the heat transfer circuit (2) comprising a first pipe (2a) and a second pipe (2b), a first end of the first pipe (2a) being adapted to receive a heat transfer liquid, a first end of the second pipe (2b) being adapted to discharge the heat transfer liquid, the first pipe (2a) and the second pipe (2b) being connected together by second ends of the first pipe and the second pipe, the battery support being characterized in that the first pipe (2a) and the second pipe (2b) are delimited on the one hand by the base (1) and on the other hand by a set of walls, the first pipe (2a) and the second pipe (2b) sharing a common wall, a cross-section of the walls of the heat transfer circuit (2) being in the shape of a W, and the heat transfer circuit being produced by additive manufacturing.

2. A battery, the battery comprising at least one battery cell, the at least one battery cell being disposed on the battery support according to claim 1, the battery cell being disposed on one side of the base (1), and the heat transfer circuit (2) being disposed on the other side of the base (1) so as to extend opposite each battery cell.

3. The battery according to claim 2, wherein The heat transfer liquid is selected from a refrigerant, ethylene glycol water or a gas, in particular air.

4. A method for manufacturing the battery support according to claim 1, during the manufacture of the battery support, the heat transfer circuit is produced directly on the base by additive manufacturing.

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