Device for heating and cooling a battery pack and vehicle traction battery assembly

Abstract

Device (18) for heating and cooling a battery pack (12), in particular a vehicle traction battery pack with several battery cells (15), comprising a heating device (22) comprising at least one heating element (26) and a cooling device (20) comprising at least one cooling element (24) through which a cooling fluid flows for the removal of heat energy, wherein the at least one heating element (26) is in direct contact with the cooling element (24) or directly with a side of the battery pack (12) on which the at least one cooling element (24) is also in contact, characterized in that two superimposed heating elements (26) are provided which form a unit, wherein an elastic material (46) is provided between the two heating elements (26).

Description

[0001] The invention relates to a device for heating and cooling a battery pack, in particular a vehicle drive battery pack with multiple battery cells. Furthermore, the invention relates to a vehicle drive battery assembly with such a heating and cooling device.

[0002] Due to the environmental impact of vehicles with purely internal combustion engines, the development of vehicle drive systems is increasingly moving toward electric drives, which at least partially replace conventional combustion engines. Electric drives typically feature a drive battery assembly through which the electric drive generates its power. The drive battery assembly comprises at least one battery pack, which is composed of at least one battery module containing several battery cells. The battery packs or battery modules used are high-voltage batteries, which can have voltages ranging from 130 to 360 V.

[0003] Because batteries release heat during charging and discharging, they typically require cooling via cooling devices to maintain optimal performance. However, batteries must also be heated at colder ambient temperatures, as otherwise the batteries could be damaged if subjected to heavy loads below 0°C, for example. To prevent damage, the batteries are controlled in such a way that they can only provide partial power. As the diagram in Fig. As shown in Figure 9, the voltage and capacity of the battery are significantly reduced at higher temperatures. Fig. Table 10 specifies the maximum permissible charging and discharging power at different temperatures for lithium-ion batteries and NiMH batteries. The maximum permissible charging and discharging power decreases with decreasing temperatures. For example, at temperatures below 0 °C, charging or accelerating the vehicle is not possible in normal traffic situations because less than 40% of the rated power is available.

[0004] Therefore, it is known from the prior art to attach heating devices to the battery packs to heat the battery pack in order to provide full power. However, since cooling the battery cells is the primary goal, the cooling device is arranged at a location within the battery pack that offers the best thermal contact area, so that the battery cells are cooled efficiently and effectively. In contrast, the heating devices are arranged at positions within the battery pack that have poorer thermal contact and thus lower efficiency. For example, the heating devices are attached to the outer sides of the battery pack, which, however, only heats the outer battery cells.

[0005] Devices for cooling a battery pack are also known from EP 2 388 851 A1, EP 2 343 769 A1 and US 2010 / 0 151 307 A1.

[0006] The object of the invention is to provide a device that enables both the cooling and heating of a battery pack in an efficient manner.

[0007] The object of the invention is achieved by a device for heating and cooling a battery pack, in particular a vehicle drive battery pack with multiple battery cells, comprising a heating device comprising at least one heating element, and a cooling device comprising at least one cooling element through which a cooling fluid flows to dissipate thermal energy. The at least one heating element bears directly against the cooling element or directly against a side of the battery pack against which the at least one cooling element also bears. Two superimposed heating elements are provided, forming a unit, with an elastic material being provided between the two heating elements.

[0008] The sandwich unit thus formed has two opposing heating surfaces, which can be used to heat, for example, two battery modules that are positioned opposite each other with their sides to be heated or cooled. A unit formed in this way can also be referred to as a heating laminate. The elastic material sandwiched between them can be an elastic foam material.

[0009] Alternatively, it can also be provided that the elastic material is only loosely stored, whereby no unit is present.

[0010] The basic idea of ​​the invention is to position the heating device in such a way that efficient heating of the battery pack is possible. According to the invention, it is provided that the battery cells have the same thermal contact with the heating device as with the cooling device. This is achieved by either arranging the heating device directly on the side of the battery pack on which the cooling device is also provided, or by the heating device interacting with the corresponding contact side of the battery pack via the cooling device. Since the cooling elements are made of a material with a high heat transfer coefficient, it is ensured that the heat generated by the heating device is transferred to the battery pack via the cooling elements.Furthermore, the integrated design ensures standardization of cooling and heating, as the heating and cooling functions are integrated into one and the same device. This reduces assembly effort, as only one device needs to be coupled to the battery pack to provide heating and cooling for the battery pack. Furthermore, the integrated design increases robustness.

[0011] One aspect of the invention provides that the cooling element and / or the heating element are pressed against the battery pack in a prestressed manner. This prestressing improves contact with the side of the battery pack that is to be cooled or heated, resulting in better thermal contact. This increases the efficiency of heating or cooling.

[0012] Furthermore, the heating element can be arranged between two cooling elements, in particular coupled to two cooling elements. The two cooling elements are arranged, for example, to the sides of the heating element. Alternatively, the two cooling elements and the heating element can also form a stack, so that the heating element interacts with two battery modules via the two cooling elements arranged on opposite sides.

[0013] In particular, the cooling element has multiple channels. This ensures that the cooling element can be operated with the refrigerant R744, as the multiple channels ensure that the cooling element has the required burst pressure. The numerous channels and the associated partition walls create a large internal surface within the cooling element, thereby achieving a greater cooling effect. Furthermore, the partition walls serve to transport heat from the associated heating element, as the cooling element and the partition walls can be made of a material with high thermal conductivity, such as a metal.

[0014] According to a further aspect of the invention, the cooling element is a one-piece, plate-shaped part with channels running through it. This shape ensures that the two main surfaces of the plate-shaped cooling element are used for heat transfer to the battery pack and / or from the heating element, so that the smaller secondary surfaces do not contribute significantly to the heat transfer. This increases efficiency because thermal losses at the secondary surfaces are reduced.

[0015] The cooling element can be an extrusion profile so that the cooling element can be manufactured cost-effectively.

[0016] In particular, the heating element and the cooling element have the same length and / or width. This further increases efficiency by ensuring that the heating elements have the same thermal contact area as the cooling elements or utilize the entire surface of the cooling elements.

[0017] According to one aspect of the invention, the heating element can be an electric heating element. This provides a simple and cost-effective way to heat the electric battery cells. The electric heating elements can, in particular, be designed such that both connection poles are located on one side, thereby reducing the wiring effort. This also facilitates the assembly of the heating and cooling device. The electric heating element can also be a resistance heater surrounded by an electrical insulating material.

[0018] To further reduce wiring effort, the heating device can include a wiring harness to which the individual heating elements are connected. This reduces costs due to a standardized design. The heating device thus has a modular structure.

[0019] The invention further relates to a vehicle drive battery assembly comprising a battery pack having at least one battery module with a plurality of battery cells, and a device for heating and cooling of the type described above.

[0020] According to one aspect of the invention, the cooling element and / or the heating element are / is arranged between two opposite sides of two battery modules. The heating and cooling device according to the invention can thus heat and / or cool two battery modules simultaneously. This significantly reduces costs because, on the one hand, a common heating and cooling device is provided, and, on the other hand, only one such device is required to cool and / or heat two battery modules simultaneously. To further increase efficiency, the cooling element and / or the heating element can be pressed directly between the respective bottom sides of the battery modules.

[0021] A further aspect of the invention provides that the heating element is positioned between two cooling elements provided on two opposing battery modules, creating a sandwich structure. This ensures that the heating element interacts directly with the side of the battery module to be heated or indirectly via the cooling element with the side of the battery module to be heated.

[0022] According to a further aspect of the invention, the heating element is arranged laterally next to and between two laterally spaced cooling elements on the same side of the battery module to which the cooling elements are assigned. This results in a particularly flat design of the heating and cooling device, since the side of the battery module is alternately contacted by a heating element and a cooling element. Furthermore, it is guaranteed that both the heating element and the cooling element are provided on the side of the battery module with which the best thermal contact is possible.

[0023] Further advantages and features of the invention will become apparent from the following description and the drawings, to which reference is made. In the drawings: - Fig. 1 is a schematic cross-sectional view of a vehicle drive battery assembly according to a first embodiment, - Fig. 2 is a perspective view of a vehicle drive battery assembly according to a second embodiment, - Fig. 3 the device for heating and cooling Fig. 2 in a plan view, - Fig. 4 is a schematic representation of a vehicle drive battery assembly according to a third embodiment, - Fig. 5 is a vertical cross-sectional view of a vehicle drive battery assembly according to a fourth embodiment, - Fig. 6 is a schematic plan view of a vehicle drive battery assembly according to a fifth embodiment, - Fig. 7 is a schematic cross-sectional view of a heating element, - Fig. 8 is a schematic cross-sectional view of a vehicle drive battery assembly according to a sixth embodiment of the invention, - Fig. 9 Voltage and charge curves of a vehicle drive battery at different temperatures, and - Fig. 10 the maximum permissible charging and discharging power of a battery at different temperatures.

[0024] In Fig. 1, a vehicle drive battery assembly 10 is shown schematically in a sectional view, which comprises a battery pack 12, which in the embodiment shown is formed from a battery module 14 having a plurality of battery cells 15, and a battery outer housing 16.

[0025] The battery cells 15 can be arranged in a so-called “jelly roll” design, whereby they extend over the Fig. 1 and are arranged one behind the other.

[0026] The vehicle drive battery assembly 10 further includes a heating and cooling device 18, which includes a cooling device 20 and a heating device 22.

[0027] In the embodiment shown, the cooling device 20 has two separately formed cooling elements 24, which are arranged laterally next to one another and each have a plurality of parallel channels 25. A cooling fluid flows through the channels 25 to dissipate the heat generated by the batteries of the battery module 14. The cooling elements 24 are, in particular, identically formed.

[0028] In the embodiment shown, the heating device 22 also comprises two separate heating elements 26, which are arranged directly on the cooling elements 24. The heating elements 26 have a contact surface 28 with which the heating elements 26 rest against a first outer surface 30 of the cooling elements 24.

[0029] Furthermore, the cooling elements 24 lie with a second outer surface 32 directly against a flat cooling surface 34 of the battery module 14, more precisely directly against the housing of the module.

[0030] In the embodiment shown, the cooling elements 24 are pressed against the cooling surface 34 of the battery module 14, since a preload unit 36 ​​is provided for each cooling element 24. The preload unit 36 ​​is designed as a spring element and rests at one end on the battery housing 16, thereby creating a preload against the cooling surface 34 of the battery module 14.

[0031] In order to decouple the preload unit 36 ​​from the thermally active cooling element 24, a carrier 38 is provided between the preload unit 36 ​​and the cooling element 24, which is typically formed from a material having a low heat transfer coefficient.

[0032] The carrier 38 also serves to ensure that the clamping force generated by the pretensioning unit 36 ​​is evenly transmitted to the cooling element 24, and so that the cooling element 24 is homogeneously applied against the cooling surface 34.

[0033] The heating elements 26 are further arranged between the carrier 38 and the cooling element 24, so that the heating elements 26 are also uniformly acted upon by the carrier 38 and the pretensioning unit 36 ​​against the cooling element 24, in particular the first outer surface 30.

[0034] Due to the pre-tension, it is ensured that both the heating elements 26 and the cooling elements 24 have good thermal contact with the battery cells of the battery module 14 and efficient heating or cooling of the battery cells is possible.

[0035] This is primarily due to the fact that the cooling elements 24 are designed as plate-shaped elements made of a material with a high heat transfer coefficient, for example, a metal. This ensures that the heat generated by the heating elements 26 is transferred via the structure of the cooling elements 24 to the cooling surface 34 of the battery module 14, whereby the battery module 14 can be heated via the cooling surface 34 if necessary.

[0036] The intermediate walls of the many channels 25, which are made of the same material as the cooling elements 24, serve as the heat transfer structure, since the cooling elements 24 can in particular be extrusion profiles.

[0037] The cooling element 24, the heating element 26, and the carrier 38 can form a pre-assembly unit, which simplifies assembly because they can be attached to the battery module 14 in a single assembly step. In particular, it can be provided that the carrier 38 is coupled to the cooling element 24 via a clip connection, whereby the intermediately mounted heating element 26 is securely held.

[0038] Furthermore, the heating element 26, as in Fig. 1, be embedded in the carrier 38.

[0039] In Fig. Figure 2 shows an alternative embodiment of the vehicle drive battery assembly 10, which comprises a battery pack 12 comprising a total of six battery modules 14. The vehicle drive battery assembly 10 can be divided into a first part 10a and a second part 10b, each of which has a different structure, as explained below. The separation into the two parts 10a, 10b is achieved by the cooling fluid main line 39 arranged in the center of the vehicle drive battery assembly 10.

[0040] In this embodiment shown, the battery modules 14 are partly formed in groups of two and partly stand-alone.

[0041] In general, the heating device 22 and the cooling device 20 are adapted to the arrangement of the battery modules 14 so that efficient heating and cooling of the battery modules 14 is possible.

[0042] For example, in the first part 10a, the pair of battery modules 14 interacts with a first heating device section 22a and a first cooling device section 20a, whereas the standalone battery module 14 interacts with a second heating device section 22b and a second cooling device section 20b. The differences between the first and second sections 20a, 20b, 22a, 22b result from the number of cooling elements 24 and heating elements 26, respectively.

[0043] In the first heating device section 22a and in the first cooling device section 20a, eight cooling or heating elements 24, 26 are provided, each cooling element 24 being assigned a heating element 26.

[0044] In the second heating device section 22b and the second cooling device section 20b, only four heating or cooling elements 26, 24 are provided, with each cooling element 24 being assigned a heating element 26. The number of cooling and heating elements 24, 26 in the second sections 20b, 22b is reduced compared to the first sections 20a, 22a, since the battery module 14 formed alone has only half the area compared to the group of two.

[0045] Furthermore, Fig. 2, particularly from the second part 10b of the vehicle drive battery assembly 10, that the ratio of cooling element 24 to heating element 26 does not necessarily have to be 1:1, but can be designed to be variable. The ratio can be adapted, in particular, to the typically expected temperatures, since an excessive number of heating elements 26 is unnecessary in warmer regions. This allows for cost savings, since only the heating elements 26 actually required are installed in the heating and cooling device 18.

[0046] The supports 38 not shown here can also be used, in particular in such a way that a support 38 carries only one cooling element 24.

[0047] In Fig. 3, the device 18 is Fig. 2 is shown schematically in plan view, with the main cooling fluid line 39 not shown. This schematic representation clearly illustrates the electrical interconnection of the individual heating elements 26. The heating elements 26 are shown in dashed lines because, in this view, they are located below the cooling elements 24 and are actually concealed by them.

[0048] A wiring harness 40 is provided, which extends centrally through the vehicle drive battery assembly 10 in a manner analogous to the main cooling fluid line 39 and contacts each of the individual heating elements 26 on a side facing the center. The heating elements 26 are further coupled to each other in pairs via U-connections 42, so that all connections of the heating elements 26 are located on the side facing the wiring harness 40. This minimizes the wiring effort, which simplifies installation and avoids unnecessary power losses due to excessive cable lengths.

[0049] In particular, this results in a standardized wiring of the vehicle drive battery assembly 10, which leads to a modular structure.

[0050] Furthermore, Fig. 3 shows that the cooling elements 24 are coupled at the front to collectors and distributors 43, which control the cooling fluid flow through the individual cooling elements 24. Whether it is a distributor or a collector depends on the flow direction of the cooling fluid. In particular, it can be provided that there are mixing elements that are both collectors and distributors, with the cooling fluid flow being guided accordingly through inner walls.

[0051] In addition, Fig. 3 clearly shows that the length and width of the cooling and heating elements 24, 26 can be exactly the same, so that the heating elements 26 extend over the entire first outer surface 30 of the cooling elements 24, provided that a heating element 26 is provided on the corresponding cooling element 24.

[0052] In Fig. 4 shows a further embodiment of the vehicle drive battery assembly 10, which has a battery pack 12 consisting of two battery modules 14 arranged side by side, wherein in the left battery module 14 the battery cells 15 are schematically shown in a “jelly roll” design.

[0053] Each of the two battery modules 14 is assigned two heating elements 26, which extend longitudinally over the battery modules 14.

[0054] The individual battery cells 15 extend transversely to the orientation of the heating elements 26, ensuring that the heating elements 26 interact with each individual battery cell 15. This guarantees that each of the battery cells 15 of a battery module 14 can be heated.

[0055] Since, as already described several times, the heating elements 26 extend parallel to the cooling elements 24, the cooling elements 24 also contact each of the battery cells 15, thereby achieving efficient cooling of all battery cells 15.

[0056] Since both the cooling surfaces 34, which are in particular the bottom surfaces of the battery cells 15, and the cooling elements 24 can be metallic and thus have a high thermal conductivity, it is sufficient if only a portion of the cooling surfaces 34 is contacted by the cooling elements 24. These partial surfaces, or cooling contact surfaces, can in particular have an area between 30% and 70% of the total surface 34.

[0057] Fig. 5 shows a fourth embodiment of the vehicle drive battery assembly 10 in a vertical cross-sectional view, showing two battery modules 14 arranged side by side.

[0058] In the middle between the two battery modules 14 there is a distribution unit 44 which directs the cooling fluid via the cooling fluid main line 39 to the individual cooling elements 24 which are in contact with the cooling surfaces 34.

[0059] Furthermore, Fig. 5 clearly shows that the heating elements 26, the cooling elements 24 and the supports 38 can form a flat pre-assembly unit which is arranged on the cooling surfaces 34.

[0060] Fig. 6 shows a fifth embodiment of the vehicle drive battery assembly 10, which in the embodiment shown comprises a battery pack 12 with a total of six battery modules 14, which are shown in dashed lines.

[0061] In the embodiment shown, the cooling device 20 is formed by eight cooling elements 24, wherein four cooling elements 24 are assigned to three battery modules 14.

[0062] Such a design of the cooling device 20 further reduces costs and assembly effort, since the cooling elements 24 interact with three battery modules 14 simultaneously. The cooling elements 24 extend transversely to the long sides of the battery modules 14. The number of collectors and distributors 43 can also be reduced by this design.

[0063] Furthermore, the Fig. 6 shows that the heating device 22 comprises four heating elements 26, with two heating elements 26 being assigned to three battery modules 14. This also allows the number of connections of the heating elements 26 to be reduced.

[0064] The heating elements 26 are designed such that they each have both connection poles on one side, allowing for a compact design of the wiring harness 40. This simplifies assembly and also reduces costs.

[0065] From the Fig. 6 it can also be seen that the heating elements 26 are designed as resistance heaters, since the course of a heating wire 45 within the heating element 26 is shown schematically.

[0066] A heating element 26 designed as a resistance heater is in Fig. 7 in cross-section. The individual heating wires 45 are spaced apart by a distance D1, with the heating wires 45 being spaced apart by a distance D2 from the contact surface 28. The heat flow can be adjusted by an appropriate density of heating wires 45, in particular by ensuring that the ratio D1 / D2 is greater than 0.5 and less than 3. This guarantees uniform heat distribution at the contact surface 28 and the opposite surface, which can interact with the carrier 38 (not shown here).

[0067] In Fig.8 shows a sixth embodiment of the vehicle drive battery assembly 10, wherein the battery pack 12 comprises two battery modules 14 arranged opposite one another.

[0068] Between the two cooling surfaces 34 of the battery modules 14, both the cooling device 20 with two cooling elements 24 and the heating device 22 are arranged.

[0069] In the embodiment shown, the heating device 22 has two heating elements 26, which lie directly against the associated cooling surface 34 via their respective contact surface 28.

[0070] In the embodiment shown, the two heating elements 26 are particularly formed as a single unit, which also includes an intermediate elastic material 46. The elastic material 46 can be an elastic foam material that is compressible.

[0071] In the embodiment shown, it can be provided, in particular, that the two battery modules 14 are prestressed against each other, so that the cooling elements 24 and the heating element 26 formed as a unit are pressed between the respective cooling surfaces 34 of the battery modules 14. This achieves good thermal contact between the cooling surfaces 34, which enables efficient heating or cooling of the individual battery cells 15.

[0072] In this embodiment, the two cooling elements 24 each rest on a battery module 14 via their first and second outer surfaces 30, 32, in particular the associated cooling surface 34.

[0073] In an alternative not shown here, a heating element 26 is interposed between two cooling elements 24, each of which rests with its second outer surfaces 32 against the contact surfaces 34 of the battery modules 14, with a heating element 26 being mounted between the first outer surfaces 30 of the opposing cooling elements 24. The battery modules 14 can be prestressed against one another in a similar manner, so that the device 10 is held pressed between the battery modules 14.

[0074] According to the invention, a heating and cooling device 18 and a vehicle drive battery assembly 10 are thus created, which provide efficient cooling and efficient heating for the individual battery cells 15. The integration of the heating and cooling functions within a device 18 also enables a compact design, which reduces costs and assembly effort.

[0075] With the device according to the invention, it is possible to heat or cool the battery pack in such a way that a temperature difference of a maximum of 5 K exists between two battery cells, regardless of their position in the battery module 14.

Claims

[1] Device (18) for heating and cooling a battery pack (12), in particular a vehicle drive battery pack with a plurality of battery cells (15), with a heating device (22) which comprises at least one heating element (26), and a cooling device (20) which comprises at least one cooling element (24) through which a cooling fluid flows to remove thermal energy, wherein the at least one heating element (26) lies directly on the cooling element (24) or directly on a side of the battery pack (12) on which the at least one cooling element (24) also lies, characterized by that two heating elements (26) lying one above the other are provided, which form a unit, wherein an elastic material (46) is provided between the two heating elements (26). [2] Device (18) according to claim 1, characterized by that the cooling element (24) and / or the heating element (26) are pre-tensioned and pressed against the battery pack (12). [3] Device (18) according to one of the preceding claims, characterized by that the heating element (26) is arranged between two cooling elements (24), in particular is coupled to two cooling elements (24). [4] Device (18) according to one of the preceding claims, characterized by that the cooling element (24) has several channels (25). [5] Device (18) according to claim 4, characterized by that the cooling element (24) is a plate-shaped part with the channels (25) running through it. [6] Device (18) according to one of the preceding claims, characterized by that the heating element (26) and the cooling element (24) have the same length and / or width. [7] Device (18) according to one of the preceding claims, characterized by that the heating element (26) is an electric heating element (26). [8] Vehicle drive battery assembly (10) with a battery pack (12) having at least one battery module (14) with a plurality of battery cells (15), and a device (18) for heating and cooling according to one of the preceding claims. [9] Vehicle drive battery assembly (10) according to claim 8, characterized by that the cooling element (24) and / or heating element (26) are arranged pressed between two opposite sides (34) of two battery modules (14). [10] Vehicle drive battery assembly (10) according to claim 8 or 9, characterized by that the heating element (26) is positioned between two cooling elements (24) which are provided on two opposite battery modules (14). [11] Vehicle drive battery assembly (10) according to claim 8 or 9, characterized bythat the heating element (26) is arranged next to and between two laterally spaced cooling elements (24), wherein the heating elements (26) and the cooling elements (24) are assigned to the same side (34) of the battery module (14).

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