Electric battery pack with immersion thermoregulation system and improved sealing device

Description

DESCRIPTION of the industrial invention entitled: “Electric battery pack with immersion thermoregulation system and improved sealing device”, by: CRF Società Consortile per Azioni, Italian nationality, Strada Torino 50, 10043 Orbassano (TO). Designated Inventors: RICCO Raffaele; VURRO Luca; LORUSSO Eligio; THIRTY-TWO Maurizio. Filed on: **** DESCRIPTION TEXT Field of invention The present invention relates to the field of electric batteries, in in particular to electric batteries for powering electric traction motors for electric or hybrid vehicles. More specifically, the invention relates to battery packs of the type where the battery cells are in direct contact with a flow of a liquid temperature regulator, typically a dielectric oil, which runs through the battery pack in order to maintain the battery cells in a temperature range predetermined, so as to ensure correct and safe operation of the package battery in all operating and environmental conditions. Background of the invention The Applicant has already proposed several solutions in the field of thermoregulation for electric battery packs. See for example the Italian patent applications 102023000022692, 102023000022698, 102023000022704, 102023000025884, 102024000002776, 102024000002779, 102024000004423, 102024000007807, 102024000007813, 102024000007816, 102024000007828, 102024000013039, 102024000013492, 102024000014308, 102024000014314, 102024000014326, 102024000015637, 102024000016354, 102024000016933, all still not publicly available at the priority date of the present invention. Figure 1 of the attached drawings shows an example of a battery module. 1 of a type known per se, to which the present invention is applicable. The module of battery 1 comprises an aligned array of battery cells 2 of the type prismatic illustrated in figure 2. This type of battery cell includes a casing with a top wall 2A, from which the positive and negative poles or "tabs" protrude negative 3P and 3N of cell 2, two main walls 2B (only one of which is visible in figure 2), two end walls 2C (only one of which is visible in figure 2) and a 2D bottom wall. In battery modules of the type described above, the battery cells 2 are placed inside an airtight container 4 and are immersed in a flow of a liquid dielectric thermoregulator, for example oil. Container 4 defines its inside an inlet collector chamber 5 (illustrated schematically in the figure 3) arranged below the cells 2, and an output collector chamber 6 (also illustrated schematically in figure 3) arranged above the cells 2. Container 4 has a 5A input and a 6A output for the liquid thermoregulator, communicating respectively with the entrance collector chamber 5 and with the output collector chamber 6. P and N indicate the positive pole and the negative pole of battery module 1. Generally, the 5A input is always placed under the 2 cells, while The 6A output is arranged above the 2 cells, to allow any air bubbles formed within the liquid can be collected in the collecting chamber upper. However, this layout is not the only possible one. Entrance and exit they can be inverted between them when an inlet pressure can be guaranteed designed to avoid any form of evaporation of the liquid. Battery modules of the type illustrated in figure 1 are used for to produce battery packs intended to power electric traction motors Hybrid electric vehicles. In use, the thermoregulating fluid enters the chamber input collector 5, arranged below the battery cells 2, and reaches the output collector chamber 6, arranged above the battery cells 2, passing through a plurality of passages 7, arranged between the battery cells 2. In figure 3, the dimensions of the passages 7, arranged between the battery cells 2, have been exaggerated for clarity. In general, it is of fundamental importance to ensure that during the use of the electric vehicle, the battery cells are always at a temperature contained within a predetermined range, typically between a minimum threshold of 20°C and a maximum threshold of 55°C. The battery cells used in electric vehicles are typically lithium-ion battery cells, which tend to develop heat as a result of the chemical reaction that takes place inside the battery cells during operation, and also for the effect Joule due to the passage of current inside the battery. With the term "battery operation" here means both the charging process of the battery, both the discharge process, which typically occurs while driving of the vehicle. It is necessary to consider that the most critical conditions of battery operation are those related to the fast charging process, that is, charging the battery in less than an hour. During normal operating conditions of the battery pack, the fluid the thermoregulator must have a cooling action, to counteract the increase in temperature due to the heat that develops in the cells for the reasons above. To this end, the thermal regulation system includes a circuit external to the battery module (not shown in Figure 1), including one or more heat exchangers configured to cool the hot liquid coming from from the 6A output, before it is powered again, via a pump (not shown) to the 5A input. However, under extreme operating conditions, in especially in cold weather conditions, the thermoregulating liquid must perform a heating function. For this purpose, the external circuit can comprising a heater exchanger and / or a heating device by electrical resistance. With reference to the configuration illustrated as an example in the figure 3, experiences conducted on batteries of this type show that the temperature within the battery module varies greatly from cell to cell, as the 2 cells that are furthest from the 5A input of the thermoregulating liquid are subjected to less cooling, both inside each cell, where the temperature distribution tends to be higher where the lines of currents are denser, for example near the poles. Numerous studies have shown that: - to reduce the aging process of the single cell battery it is advisable to reduce the temperature gradient inside the cell itself within 5° C; - to avoid a "thermal runaway" phenomenon, destructive for the battery, it is necessary to maintain the maximum temperature of each single cell below 55°C. It is therefore desirable not only to maintain the temperature of the cell battery within a predetermined temperature range, but also try to to make the temperature of the different battery cells as uniform as possible and the temperature inside each cell. In order to solve this problem, solutions of the type have already been proposed: illustrated schematically in figure 4. This figure is a perspective view of a group of battery cells, with one of the cells removed to reveal an element 8 forming part of a spacer frame placed between adjacent cells. In the solutions of this type, each spacer element 8 comprises one or more relatively narrow passages (indicated by 9 in figure 4) that put in communication between adjacent cells with the entrance collector chamber 5. The narrow passages 9 are configured and sized so as to oppose the flow of the thermoregulating liquid with sufficient resistance to prevent the thermoregulatory liquid tends to flow more in the spaces between the cells which are closer to the 5A input opening and / or the 6A output opening. In this case way, it is obtained that the flow rate of the thermoregulating liquid through the different spaces between cells are substantially uniform. Furthermore, as illustrated in the figure 4, each spacer element 8 includes a plurality of narrow passages distributed along the width of the cells, which also allows for uniformity the thermoregulation action between the center and the sides of each individual cell. In developing solutions of this type, the Applicant has however noted the need to solve a further problem, linked to the risk of leaks of the thermoregulating liquid between the contact surfaces of the cells and elements spacers placed between the cells. In case of leaks of this type, it is lost control of the flow of the thermoregulating liquid through the passages restricted, which jeopardizes the achievement of the above-mentioned benefits. To reduce the risk of leaks can be increased by the force with which the different cells are pressed together along the X direction, with the help of tie rods applied to the pack of cells. However, this solution has limitations, linked to the need not to damage the structure of the cells. Another need that is found in solutions of this type is to ensure that the narrow passage section is strictly maintained unchanged over time, to avoid losing control of the liquid flow thermoregulator through said passages. There is therefore a need for further improvements in this field. Purpose of the invention It is therefore an object of the present invention to make a battery pack of the type indicated at the beginning of this document description, which is equipped with a highly efficient thermoregulation system and reliable, and free from the above-mentioned drawbacks. In particular, it is an object of the invention to provide a battery pack of the type indicated above, in which the flow rate of the liquid thermoregulator through the different spaces between the battery cells both substantially uniform, without the risk of unwanted leakage of the liquid thermoregulator which affect the control of the flow through the above mentioned narrow passages. A further object of the invention is to realize all of the above objectives with extremely simple and low-cost means. Summary of the invention In order to achieve one or more of the above-mentioned purposes, the invention has for object an electric battery pack, comprising one or more groups of cells battery arranged inside a battery pack container, where each battery cell group comprises an array of batteries arranged side by side along a horizontal direction and kept spaced from each other by respective spacer frames, where the battery pack container is configured to be crossed by a flow of a thermoregulating liquid that comes into contact directly with the battery cells to keep them within a temperature range predetermined, wherein the battery pack includes a liquid distribution system temperature controller, including: an inlet opening for the thermoregulating liquid, communicating with an entrance collector chamber, located below the row of cells drums, an outlet opening for the thermoregulating liquid, communicating with a output collector chamber arranged above the battery cell array, where the inlet collector chamber and the outlet collector chamber communicate with each other through the spaces defined between the battery cells by said frames spacers, wherein each of said spaces defined between the battery cells communicates with the input collector chamber, located below the battery cells, via a or more relatively narrow passages, configured to oppose the flow of liquid thermoregulator with sufficient resistance to prevent a tendency of the liquid thermoregulator to flow more in the spaces between the battery cells which are closest to said inlet opening and / or said outlet opening, wherein the battery cells have lower portions adjacent to said chamber inlet manifold, between which respective sealing elements are placed, where each sealing element is in sealing contact with both battery cells between which the sealing element is interposed, and in which the aforementioned relatively narrow passages for communication between the input collector chamber and the spaces between the battery cells are defined by one or more rigid tubular elements which are embedded in each of said elements sealing elements that are placed between the battery cells. Thanks to the above mentioned features, in the battery pack according to the invention any risk of unwanted leaks of the thermoregulating liquid in the contact areas between the sealing elements and the cells it is avoided. Each of the above sealing elements is made of an elastomer material, such as example of a silicone material that is electrically non-conductive and resistant to high temperatures temperatures. Each sealing element has an elongated body that extends across the entire transverse dimension of the battery cells, orthogonal to the direction along which the cells are placed side by side. In a preferred embodiment, the elongated body of each element sealing has a cross-section T, so that it includes a portion central one which is placed between the facing surfaces of the lower portions of two adjacent cells, and a head portion, orthogonal to the central portion, which is in sealing contact with the lower surfaces of the aforementioned cells. In a further for example, the elongated body of each sealing element has two walls of ends orthogonal to the longitudinal direction of the sealing element, which are in sealing contact with opposite end surfaces of the battery cells. According to the invention, within the elastically deformable body of each sealing element are embedded rigid tubular elements (e.g. metal) defining the narrow passages for the thermoregulating liquid. It can be foreseen that the wall of each battery cell is fixed a layer of plastic material, such as PTFE, in the contact area with the sealing element. During operation of the above preferred form of embodiment with sealing elements having a T-shaped cross-section, the flow of the liquid thermoregulator through the narrow passages gives rise to an increase in pressure upstream of the narrow passages, which tends to press the head portion of each sealing element against the lower surfaces of the cells, which further ensures the seal. At the same time, the rigid tubular elements embedded in the elements of seals ensure a predefined flow rate of the thermoregulating liquid, which remains unchanged over time, despite the tendency of battery cells to undergo the so-called swelling or "swelling" phenomenon due to the effect of the gases that produce inside the casing of each cell during charging cycles and download. The sealing elements provided in the solution according to the invention allow for high adaptability to cell deformation. Each sealing element is configured to allow for dimensional variations of the cells of battery, due to "swelling" or "breathing" phenomena. This ensures that the integrity of the seal is maintained throughout the life cycle of the battery, unlike what happens in conventional solutions. A further advantage of the invention is that it ensures the maintenance of the passage section over time in the aforementioned passages restricted. The invention allows to maintain a constant predetermined value of the section of such narrow passages, which ensures uniform cooling and efficient of all battery cells and in particular of the cell poles, which It is crucial for battery performance and longevity. The solution according to the invention also allows to avoid that the sealing elements can be deformed or extruded through the spaces between the cells due to the pressure to which they are subjected. In a preferred example, this it is obtained thanks to the mutual commitment of the material constituting each element sealing (e.g. silicone material) and a layer of synthetic material (e.g. PTFE) which is applied on the surface of the cells, in the area of contact with the sealing element. Finally, the solution according to the invention has a high resistance at high temperatures, thanks to the possibility of using sealing materials (for example (e.g. silicone materials) having excellent resistance to high temperatures temperatures. This makes it possible to apply the invention in cases where the Thermal stability is critical. As indicated, the materials chosen for the sealing elements are materials non-electrically conductive, which ensures that the sealing elements do not interfere with the electrical performance of battery cells. The inclusion of rigid tubular elements within the sealing elements gives result in additional mechanical resistance, which improves robustness overall and reliability of the seal. This ensures the integrity of the seal. in all operating conditions and throughout the life of the battery pack. An additional advantage of the invention is that it can be reduced significantly the force with which the cells must be pressed against each other inside the battery pack. Detailed description of the invention Further features and advantages of the invention will result from the description that follows with reference to the attached drawings, provided for information purposes only non-limiting example, where: Figure 1 is a schematic perspective view of a battery module which the present invention is applicable, Figure 2 is a perspective view of a prismatic type battery cell, used in a battery module to which the invention is applicable, Figure 3 is a further longitudinal sectional view of the battery module of figure 1, and Figure 4 is a further simplified perspective view of the module. battery of figures 1, 3, Figure 5 is a longitudinal sectional view of a battery module according to the invention, Figure 6 is an enlarged scale view of a detail of Figure 5, Figure 7 is a partial perspective view of a sealing element used in the battery pack according to the invention, Figure 8 is a variant of Figure 6, and Figure 9 illustrates a further embodiment. Figures 1-4 have already been described above. In the following description of embodiments of the battery pack according to the invention, parts corresponding to those illustrated in figures 1-4 are indicated with the same reference numbers. Figure 5 is a schematic sectional view substantially corresponding to that of figure 3. The main difference of the solution illustrated in figure 5 compared to the one illustrated in figure 4 lies in the fact that, in the case of the present invention, the spacer elements interposed between the lower portions of the cells of battery 2 are sealing elements 10 made, for example, of material elastomer, especially silicone material, in which elements are embedded rigid tubes 11, for example made of metal material, defining the narrow passages 9 of predetermined size. Naturally, in addition to the sealing elements 10, it is possible to foresee spacer frames of any known type, placed between the upper portions of the battery cells, to keep them spaced apart and allow at the same time time a swelling of the central portions of the cells due to the phenomenon of “swelling” that occurs during battery pack operation. With reference also to figures 6, 7, in the preferred form of implementation which is described herein, each sealing element 10 has an elongated body, extending across the entire length of the battery cells 2 in the Y direction (see figure 1), orthogonal to the horizontal direction X along which they are place the battery cells side by side 2. In the illustrated example, each sealing element 10 has a body elongated with a T-shaped cross-section, so that the sealing element 10 includes a central portion 10A, interposed between the facing surfaces of two adjacent cells, and a portion of head 10B, orthogonal to the central portion 10A, defining two wings in contact with the lower surfaces of cells 2. In this way, the overpressure that is created in the collector chamber of entrance 5 due to the resistance opposed by the narrow passages 9 tends to press the wings of the head portion 10B of each sealing element 10 against the lower surfaces of the cells, ensuring a perfect seal. In the example shown in figure 7, each sealing element 10 It also has two end walls 12 (only one of which is visible in the figure 7) orthogonal to the longitudinal direction of the sealing element and configured to make sealing contact with opposite end surfaces, orthogonal to the Y direction, of the cells 2. Preferably, on the surfaces of the cells 2 which are in contact with the sealing elements 10 are applied layers of synthetic material, preferably PTFE, which are in contact with the sealing elements 10, thus increasing further guaranteeing a perfect seal. Figure 8 shows a variant of Figure 6, where each element metal tube 11 is made with a T-head, so as to prevent that element 11 can disengage from the body of the sealing element 10, for example due to overpressure in the thermo-regulating liquid. As already indicated, the narrow passages 9 give rise to an increase in pressure in the thermo-regulating liquid upstream of steps 9, which is proportional to the flow rate of the thermo-regulating liquid and which tends to push the cells 2 upwards, i.e. towards the battery pack cover, generating a oscillatory vertical movement of the cells whenever an increase occurs of pressure in the environment under the cells. To overcome this problem, in the embodiment illustrated in figure 9 includes spacer elements 13 interposed between the upper surfaces of the cells and the upper cover14 of the battery pack container. Naturally, without prejudice to the principle of the invention, the details of construction and forms of implementation may vary widely from as described and illustrated purely by way of example, without thereby departing within the scope of the present invention, as defined in the appended claims.

Claims

1. Electric battery pack, comprising one or more groups of battery cells (2), arranged inside a container (4) of the battery pack (1), wherein each group of battery cells (2) comprises an array of battery cells (2), arranged side by side along a horizontal direction (X) and kept spaced from each other by respective spacer frames (8; 10), wherein the container (4) of the battery pack (1) is configured to be crossed by a flow of a thermoregulating liquid which comes into direct contact with the battery cells (2) to maintain them within a predetermined temperature range, wherein the battery pack (1) comprises a distribution system for the thermoregulating liquid, including: an inlet opening (5A) for the thermoregulating liquid, communicating with an inlet collector chamber (5), arranged below the array of battery cells (2),an outlet opening (6A) for the thermoregulating liquid, communicating with an outlet collector chamber (6), arranged above the array of battery cells (2), wherein the inlet collector chamber (5) and the outlet collector chamber (6) communicate with each other via the spaces (7) defined between the battery cells (2) by said spacer frames (8), wherein each of said spaces (7) defined between the battery cells (2) communicates with the inlet collector chamber (5), situated below the battery cells (2) via one or more relatively narrow passages (9), configured to oppose to the flow of the thermoregulating liquid a resistance sufficient to prevent a tendency of the thermoregulating liquid to flow more into the spaces (7) between the battery cells (2) that are closest to said inlet opening (5A) and / or to said outlet opening (6A),wherein the battery cells (2) have lower portions adjacent to said inlet collector chamber (5A) between which respective sealing elements (10) are interposed, - 12 wherein each sealing element (10) is in sealing contact with both battery cells (2) between which the sealing element (10) is interposed, and wherein the said relatively narrow passages (9) for communication between the inlet collector chamber (5A) and the spaces (7) between the battery cells (2) are defined by one or more rigid tubular elements (11), which are embedded in each of said sealing elements (10) which are interposed between the battery cells (9)., 2. Battery pack according to claim 1, characterised in that each of said sealing elements (10) is made of elastomer material.

3. Battery pack according to claim 1, characterised in that each of said sealing elements (10) is made of silicone material.

4. Battery pack according to claim 1, characterised in that each of said sealing elements (10) has an elongated body with a T-shaped cross-section, so as to comprise a central portion (10A) which is interposed between the facing surfaces of the lower portions of two battery cells (10), and a head portion (10B), orthogonal to the central portion (10A), which is in sealing contact with the lower surfaces of said battery cells (2).

5. Battery pack according to claim 1, characterised in that each sealing element (10) is in contact with the surfaces of the battery cells (2) with the interposition of a layer of plastic material, preferably PTFE, applied to said surfaces of the battery cells.

6. Battery pack according to claim 1, characterised in that said rigid tubular elements are made of metallic material.

7. Battery pack according to claim 6, characterised in that said metal tubular elements (11) have a circular section and are embedded by moulding within the body of the respective sealing element (10).

8. Battery pack as claimed in the preceding claims wherein each rigid tubular element (11) has a lower T-head integrated into the body of the respective sealing element (10).

9. Battery pack according to claim 1, characterised in that between the upper walls of the battery cells (2) and an upper cover (14) of the battery pack container there are spacer elements configured to prevent the cells (2) from moving upwards due to an increase in pressure in the inlet collector chamber (5) below the cells (2).