Vehicle battery unit

Abstract

The present disclosure relates to a battery unit for a vehicle. The battery unit includes a battery tray made of a composite material that defines an interior space configured to receive a battery including one or more battery cells. The interior space is further bounded by a bottom wall and one or more side walls. Additionally, the battery unit includes a top cover configured to close the battery tray and an integrated cooling system for cooling the battery. The present disclosure also relates to a battery system and a vehicle including one or more battery units.

Description

[Technical Field]

[0001] This application claims the benefit of European Patent Application No. 22 382 941.7, filed October 6, 2022. This disclosure relates to a battery unit for a vehicle. More particularly, this disclosure relates to a battery unit comprising a battery tray made of a composite material and a top cover including a cooling system. This disclosure also relates to a battery system including one or more battery units, and a vehicle including such a battery system. [Background technology]

[0002] Vehicles, such as cars, incorporate a structural skeleton designed to withstand all the loads the vehicle may be subjected to during its lifetime. The structural skeleton, or "body-in-white" (BIW), is further designed to withstand and absorb impacts (e.g., in the event of a collision with another vehicle). The structural skeleton is also designed to be as lightweight as possible to reduce the emission of pollutants (e.g., CO2) into the environment or to reduce power consumption in electric vehicles.

[0003] The structural skeleton or BIW of an automobile may include, for example, bumpers, pillars (e.g., A-pillars, B-pillars, C-pillars), side impact beams, and rocker panels. These and other structural members may have one or more regions with a substantially U-shaped (also known as a "hat" shaped) cross section. These structural members may be manufactured in a variety of ways and from a variety of materials. For example, rocker panels may be made of steel, particularly ultra-high strength steel (UHSS), and may be manufactured by press hardening.

[0004] Ultra-high strength steels (UHSS) are optimized for maximum strength per unit of weight and advantageous forming properties in the automotive industry for at least some of the structural frameworks of vehicles or their components. In the present disclosure, UHSS may be considered to be steels with an ultimate tensile strength (after hot stamping) of at least 1000 MPa, preferably up to about 1500 MPa, or up to 2000 MPa or more. An example of UHSS used in the automotive industry is boron steel, such as 22MnB5 steel.

[0005] The processing of vehicle components can involve forming metal plates, especially steel plates, to give them a desired shape. One process that is particularly used in the automotive industry is Hot Forming Die Quenching (HFDQ). In the HFDQ process, a steel blank is heated above the austenitizing temperature, above Ac1, or above Ac3. After heating above the austenitizing temperature, the blank is placed in a hot forming press. The blank is deformed and quenched (rapidly cooled) at the same time. The cooling can usually be performed at a rate higher than the so-called critical cooling rate.

[0006] The rapid development of electric vehicles (EVs) and hybrid vehicles is forcing the industry to design new vehicle components, particularly to reduce weight to increase vehicle range, and to house and protect the new vehicle components. To achieve safety and lightweighting goals, structural components with new geometries and alternative materials are being manufactured and integrated into EVs. While reference is made generally to electric vehicles or EVs herein, hybrid vehicles are expressly intended to be covered as well.

[0007] Traction batteries are an essential part of EVs and are configured to power the vehicle's electric motor. Due to their electronic and chemical properties, batteries are particularly sensitive to high mechanical loads, such as crash impacts, and high operating temperatures. To extend battery life, the automotive industry has made considerable efforts to provide battery enclosures and load-bearing structures suitable for EVs that combine battery protection and battery cooling. Thus, various battery components have been designed and developed over the past few years to house and protect (mechanically and thermally) traction batteries.

[0008] For this purpose, steel battery boxes or trays have been developed. Polymer (plastic) or composite materials are also known. Plastic and composite materials can be lighter than metal components, but they must be designed and dimensioned to protect against severe impacts. Furthermore, they must be provided with an appropriate cooling system to keep the battery temperature within acceptable limits while reducing the overall weight of the battery system.

[0009] The present disclosure aims to provide an improved structure for protecting automotive batteries.

[0010] overview In a first aspect, a battery unit for a vehicle is provided. The battery unit includes a battery tray made of a composite material. The battery tray defines an interior space configured to receive a battery including one or more battery cells. The battery tray is bounded by a bottom wall and one or more side walls. The battery unit also includes a top cover configured to close the battery tray. Additionally, a cooling system for cooling the battery is integrated with the top cover.

[0011] Composite battery trays can provide a lightweight structure for battery units. Furthermore, composite materials can be selected to provide tailored mechanical strength; for example, composite materials can be stronger in one direction than another. Additionally, the introduction of a top cover with an integrated cooling system allows for efficient cooling of the battery while simultaneously reducing the overall weight of the battery unit by eliminating redundant layers of material. Thus, the provided battery unit benefits from the light weight of composite or polymeric units while including a cooling system integrally located within the battery unit in a weight-saving configuration. Furthermore, composite battery trays can integrate several functions into one single component, for example, facilitating the integration of different components within a single mold through a composite manufacturing process. In some instances, composite battery trays can fully replace welded steel subassemblies.

[0012] Throughout this disclosure, "electric vehicle" or "hybrid vehicle" may be understood to encompass any vehicle having a traction battery configured at least in part to power the vehicle's electric powertrain.

[0013] Also, throughout this disclosure, references to "mechanical properties of a structure" may be understood as the mechanical properties of the material forming said structure. Thus, unless stated otherwise, comparisons of mechanical properties of structures, components, or other structures are directed to the material and not to its geometry or other particularities.

[0014] In some examples, the composite material used to form the battery tray may include fiberglass, although other materials, such as carbon fiber or aramid fiber, may also be used.

[0015] In some examples, the battery trays can be made from sheet molding compound, which is a composite material that comes in sheet form. The sheets are typically made by spreading a resin paste onto a surface and distributing chopped fibers on top. Another layer of resin is then added on top of the chopped fibers, and the sheet is compressed and stored while it cures.

[0016] In some examples, the battery tray may include cross-members configured to separate the battery cells. Furthermore, the cross-members can increase the strength of the battery tray, for example, against bending loads. In addition, the cross-members can help provide stability to the battery cells during installation of the battery cells in the battery tray. For example, cross-members positioned offset along the battery tray for separate groups of battery cells (e.g., five or more cells) can facilitate positioning of the battery cells per group.

[0017] In some examples, the battery tray includes brackets configured to connect the battery tray to the vehicle framework. The brackets may be located on the side walls, may be integrally manufactured with the battery tray, or may be inserted afterward, for example, using fasteners, welding, or adhesives, among others. In some examples, brackets may be located on two opposing side walls of the battery tray to provide stability to the connection with the vehicle framework.

[0018] In some examples, the top cover is configured to at least partially seal the battery tray. For example, the top cover may be configured to limit the ingress of liquid into the battery tray and / or the egress of liquid from the battery tray. In this manner, the top cover can protect the battery from the ingress of foreign particles and liquid that may damage the battery cells, and can contain any liquid that may be present within the battery. Thus, the top cover can function as a cooling element and a sealing plate, and can reduce the number of components of the battery unit and the associated weight.

[0019] In some examples, the top cover may include a seal that substantially follows the periphery of the top cover. Further, the seal may be or include an adhesive that adheres to at least one of the top cover and the battery tray. Additionally, the seal may have a thermal resistance of 1 W m -1 ·K -1 Thermal conductivity above 1.5 W m -1 ·K -1 In a further example, the top cover may include a seal on substantially all of the interior surface of the top cover. For example, the seal may form a thin film between the top cover and the battery tray and between the battery cells within the battery tray.

[0020] In some examples, the cooling system includes one or more cooling channels configured to contain a liquid coolant. The cooling channels may each have an input port for introducing the coolant at a relatively low temperature and an output port for extracting the coolant at a relatively high temperature. The heated coolant may be cooled again by a heat exchanger before being reintroduced into the battery box for cooling.

[0021] The composition of the coolant can be selected to obtain a coolant with a high specific heat capacity (i.e., a high heat capacity per unit of mass) or a coolant with a high latent heat (i.e., a high heat absorption capacity during phase transformation) and a phase transition close to the operating temperature of the battery unit. Thus, a cooling system with cooling channels can keep the operating temperature of the battery below a critical temperature at which the battery may experience thermal runaway.

[0022] Thermal runaway can be understood as a chemical chain reaction that occurs within a battery cell after a critical temperature is reached. This type of chain reaction is generally complex to control once initiated, and therefore components and devices must be provided to control the battery temperature.

[0023] In some examples, the top cover may be made of aluminum, which provides good heat transfer characteristics in a relatively lightweight component. Multiple cooling channels through which liquid coolant circulates may be formed, for example, within the extruded aluminum profile or between two aluminum plates or sheets.

[0024] In some examples, the aluminum profile, plate, or sheet may be configured to contact the battery cells via a particularly high thermal conductivity interface material, such as a high thermal conductivity sealant or filler material.

[0025] In some examples, the battery includes a bus bar that electrically connects the battery cells. Further, the bus bar can be configured to be at least partially located within the battery tray. In some examples, the bus bar can be positioned almost completely within the battery tray. In some examples, the bus bar can have a substantially U-shape, the U-shape including a first side member electrically connected to the positive terminals of the battery cells and a second side member electrically connected to the negative terminals of the battery cells, each connected to an electrical joint that can be located near the center plane.

[0026] Additionally, in some examples, the battery unit includes a layer over the top cover configured to provide flame retardant protection.

[0027] In another aspect, a battery system is provided that includes one or more battery units as disclosed above, such that individual battery units of the battery system can be replaced, for example in the event of a malfunction, while other components of the battery system remain unaffected / unaltered.

[0028] In some examples, each battery unit of a battery system may include or be connected to a separate battery management system (BMS). A BMS is an electronic system that manages the battery by protecting it from operating outside of its safe operating range. For example, a BMS may monitor, among other things, the voltage, temperature, and current of the battery and battery cells, the cooling system, and the balance status of the cells. Separate BMSs result in a battery system with battery units that can operate completely independently of each other.

[0029] In some examples, the battery system includes a bottom cover or bottom cover component configured to cover the battery units. In this way, a single bottom cover (component) protects all battery units from external impacts, dust, stones, bollards, etc. Furthermore, the bottom cover may be designed to have a substantially flat bottom so that the drag coefficient of the vehicle can be reduced. This may also improve the driving range of the electric vehicle.

[0030] In yet another aspect, a vehicle including the disclosed battery system is provided.

[0031] In some examples, the battery units are connected to the vehicle framework via removable fasteners. Again, this allows the battery system to be disassembled without requiring permanent modifications to the vehicle or the battery units. Because each unit may be substantially independent with its own cooling system, its own busbars, etc., replacing one unit with a new one may be relatively simple.

[0032] In some examples, a vehicle may include a battery system including two or more battery units. Further, the vehicle may include at least three coupling structures configured to receive removable fasteners. The first and second coupling structures may be positioned on first and second sides of the battery system, respectively. Further, the third coupling structure may be positioned between the battery units and configured to receive removable fasteners from both battery units.

[0033] This vehicle configuration allows for a compact design in which two battery units can be independently mounted and connected to the vehicle. The battery units can be positioned, for example, to lower the center of gravity of the vehicle and can be distributed substantially symmetrically about the vehicle's central longitudinal axis. A coupling structure can provide suitable connection areas between the battery units and the vehicle and can be integrated into or coupled to the vehicle.

[0034] Non-limiting examples of the present disclosure are described below with reference to the accompanying drawings. [Brief explanation of the drawings]

[0035] [Figure 1] 1 shows a schematic exploded view of an example battery unit according to the present disclosure. [Figure 2] 1 illustrates a schematic exploded view of an example battery system according to the present disclosure. [Figure 3] 3 shows a schematic bottom perspective view of the battery system of FIG. 2 in a vehicle according to the present disclosure. [Figure 4] A cross section across the plane A-A' in FIG. 3 is shown diagrammatically. [Figure 5] A cross section across the plane B-B' in FIG. 3 is shown diagrammatically.

[0036] These drawings refer to example implementations and are used only as an aid in understanding the claimed subject matter and are not to be used to limit the subject matter in any way.

[0037] Detailed explanation of the example FIG. 1 schematically illustrates a battery unit 100 for a vehicle. The battery unit 100 includes a battery tray 10 made of a composite material. The battery tray 10 defines an interior space configured to receive a battery 20 including one or more battery cells. The battery tray 10 is bounded by a bottom wall 11 and at least one side wall 12. The battery unit 100 further includes a top cover 50 configured to close the battery tray 10. A cooling system 53 for cooling the battery 20 is integrated into the top cover 50.

[0038] The battery tray 10 is made of a composite material (e.g., a fiber-reinforced polymer), which can be selected and tailored to provide specific mechanical properties to the battery tray 10. For example, the composite material can include layers of biaxial or triaxial fibers to increase the tray's mechanical properties in a particular direction. Additionally, the fiber and resin materials can be selected to obtain a final product, i.e., the battery tray 10, with specific mechanical and physical properties. For example, the fibers can include glass fiber, carbon fiber, or aramid fiber, among others. By selecting the appropriate polymer and fiber, the battery can be electrically insulated from the rest of the vehicle.

[0039] In some examples, the composite battery tray 10 can be manufactured using compression molding or sheet molding compound. In this case, sheet molding compound (SMC) can be cut into appropriately sized sheets and placed in a heated die of a mold. In some examples, the temperature of the heated die can be 130-160°C. One or more dies of the mold are then closed together and a pressure of 30-120 bar is applied. As the viscosity of the material decreases, the SMC flows and fills the mold cavity. It should be noted that other techniques can be used in which the pressure applied to the SMC is significantly lower, i.e., less than 30 bar.

[0040] Glass fiber SMC can cure in 30 to 150 seconds after starting the molding process, allowing for an overall manufacturing cycle as fast as 80 seconds, reducing material costs and enabling mass production.

[0041] The composition of the SMC can be tailored to yield composites with improved properties. For example, carbon fiber can be introduced into the SMC to increase the strength-to-weight and stiffness-to-weight ratios. Additionally, other additives can be provided to prevent surface microcracking due to outgassing.

[0042] In other examples, the composite battery tray 10 can be manufactured by hand layup, for example, by manually placing layers of dry fabric onto a tool (mold) to form a laminate stack. Resin can then be applied to the dry fabric by, for example, resin infusion or pouring using RTM. In further examples, prepreg (fabric pre-impregnated with resin) can be used. After the prepreg is laid, it can be heated to cure.

[0043] In other cases, the manufacturing process may involve laying down fabrics that have already been coated with resin, and then debulking the stack, which may be done manually using rollers or using vacuum-bagging techniques.

[0044] Note that the battery tray 10 in the example of FIG. 1 also includes cross-members 13 between the sidewalls 12 configured to separate battery cells or groups of battery cells. The cross-members thus function as "spacers" or "separators." When multiple electrical cells comprising the battery 20 are mounted within the tray, the spacers may help separate the cells from one another and stabilize the cells during assembly. The cross-members 13 may also be designed to provide rigidity to the tray 10.

[0045] In some examples, the battery cells may be secured to the bottom wall 11 of the battery tray 10 using a (structural) adhesive, with the cross-member providing additional stability to the assembly. A structural adhesive herein may be considered a high strength adhesive capable of bonding components together in a load-bearing structure.

[0046] The cross member 13 in this example may be integrally formed with the battery tray 10. For example, the mold used to manufacture the battery tray 10 may include this geometry, and the cross member 13 may be formed from a composite material. In other examples, the cross member 13 may be made from a different material, such as another composite material, or for example, a suitable polymer material.

[0047] The cross members may extend from the bottom wall 11 to the top of the battery tray 10 or may leave a clearance gap. Such clearance gap can facilitate airflow circulation and cooling of the battery. Furthermore, the number of cross members 13 and their separation can be adapted according to several battery parameters, such as the number of battery cells, the width of the battery cells, and the structural requirements of the battery tray.

[0048] 1, the battery tray 10 may include brackets 14 configured to connect the battery tray 10 to the vehicle framework. The brackets may also be integrally formed with the battery tray 10 or may be joined to the battery tray 10 after formation. In this example, the battery tray 10 includes fourteen brackets 14, seven on two opposing sides of the battery tray 10, although other numbers of brackets 14 and other arrangements about the periphery of the battery tray 10 may be used.

[0049] 1 also shows that the battery cells of the battery 20 can be electrically connected using bus bars 30. In this example, the bus bars 30 have a substantially U-shape. Thus, a first side member 31 of the bus bar 30 is electrically connected to the positive terminals of the battery cells, and a second side member 32 is electrically connected to the negative terminals of the battery cells. Each side member 31, 32 can be connected to an electrical junction, i.e., a main electrical connector of the battery unit. The main electrical connector can be positioned substantially longitudinally about the center of the unit.

[0050] 1 further illustrates that the top cover 50 is configured to at least partially seal the battery tray 100. In this example, the top cover 50 includes a seal 40 that substantially follows the perimeter or peripheral edge of the top cover 50. This promotes a substantially uniform seal around the entire perimeter of the battery tray 10, reducing the risk of liquid ingress or egress.

[0051] In some examples, the seal 40 may include an adhesive; for example, the seal may be glued to the top cover 50 and then press-fit into a recess in the battery tray 10. In other examples, the seal may be glued to both the top cover 50 and the battery tray 10. Furthermore, in some cases, the connection between the top cover 50 and the battery tray 10 may be achieved through a combination of geometric interference (e.g., press-fitting the seal 40 into a recess) and an adhesive. Additionally, other fastening elements, such as removable fasteners, may be used to mechanically secure the connection between the top cover 50 and the battery tray 10.

[0052] In some examples, the seal 40 may be positioned, for example, by adhesively bonding to a majority of the inner surface of the top cover 50. Additionally, the seal 40 may also be bonded to the battery tray 10. A thermally conductive adhesive may be used to connect the battery cells to the top cover and improve thermal control for the battery cells. Thus, the adhesive in this example may provide sealing, structural adhesion, and thermal conductivity.

[0053] In further examples, the battery tray 10 and top cover 50 may define a substantially labyrinthine interphase to further impede liquid ingress / egress.

[0054] Additionally, the top cover 50 may be made of a metal with a relatively high thermal conductivity and a relatively low density, such as aluminum, although other materials or combinations of materials, such as aluminum alloys, may be used for this purpose.

[0055] Additionally, the top cover 50 may include a cooling system 53 having one or more cooling channels configured to receive a liquid coolant. The cooling system may be formed by controlled atmosphere brazing (CAB). In addition, the cooling system may be manufactured according to any other suitable manufacturing process, such as machining a blank, soldering a curved section to a flat plate, metal forming, deforming a plate (e.g., an aluminum plate) to define open cooling channels, and joining an additional plate (either deformed or flat) to close the cooling channel.

[0056] Any suitable coolant may be used, such as water, or a more complex composition (e.g., a composition including ethylene glycol). In a particular example, a composition including 50% glycol and 50% water may be used.

[0057] As previously mentioned, the composition of the coolant can be selected to obtain a coolant with a high specific heat capacity (i.e., a high heat capacity per unit mass) or a high latent heat (i.e., a high heat absorption during phase transformation) and a phase transition close to the operating temperature of the battery unit. Furthermore, the coolant can have low electrical conductivity or electrical insulating properties. In some examples, the coolant can be a dielectric coolant. Thus, a cooling system with cooling channels can maintain the temperature of the battery at an appropriate operating temperature, i.e., a temperature at which the battery will operate efficiently and without problems. Thus, a cooling system with cooling channels can maintain the temperature of the battery at an appropriate operating temperature, i.e., a temperature at which the battery will operate efficiently and without problems. In either case, the cooling system can ensure that the temperature is maintained below a critical temperature at which the battery may experience thermal runaway.

[0058] In some examples, a cooling system can also be used to heat the cell to an appropriate operating temperature. For example, the cooling system can heat the cell during an initial warm-up process and then cool the cell after it reaches the desired operating temperature.

[0059] Additionally, the cooling channels may have an inlet port 51 for introducing coolant at a relatively low temperature and an outlet port 52 for extracting coolant at a relatively high temperature, respectively. The inlet and outlet ports 51, 52 may be connected to a heat exchanger and a pressurization system. As shown in FIG. 1, each battery unit 100 may have its own cooling system and its own thermal management system. That is, the thermal management of a unit 100 may be independent from the thermal management of adjacent units in the same vehicle. If a unit is damaged or requires repair, it can simply be replaced without affecting the functionality of other units in the same vehicle.

[0060] Furthermore, the example of the battery unit 100 shown in FIG. 1 illustrates that the battery unit 100 may also include a layer 60 on the top cover 50 to provide flame retardant protection and at least partially isolate the battery unit 100 from other vehicle components. The layer 60 may be molded to at least partially match the geometry of the top cover 50 into which the cooling channels 53 are integrated. Indeed, in this example shown in FIG. 1, the layer 60 may be formed by spraying an epoxy-containing composition. The composition can thus be adapted to the geometry of the top cover before curing, resulting in a layer with a substantially constant material thickness.

[0061] The layer that provides the flame retardancy can generally be made of a coating material. The coating material can be an epoxy-containing composition that can be cured at room temperature or at a higher temperature to accelerate the curing process. In some instances, other materials (such as fiber cloth or mica plates) can be used to provide flame retardant protection.

[0062] 2 is a schematic diagram of a battery system 1000 including two battery units 100. In other examples, the battery system may include any other number of battery units, for example, three or more battery units.

[0063] In the illustrated example, the battery system 1000 includes two battery units 100 that are substantially similar, but in other examples, the battery system 1000 may include battery units 100 with different specifications (including number of cells, battery capacity, battery dimensions, etc.).

[0064] In the illustrated example of the battery system 1000, each battery unit 100 includes a separate battery management system 400. Note that the battery management system is shown schematically and the connections between the batteries and the battery management system are not shown. As discussed above, the battery management system may be configured to monitor, among other things, the voltage, temperature, and current of the battery and battery cells, as well as the cooling system and the balance status of the cells. Additionally, the battery management system may be configured to send control signals to other electronic components of the battery unit to change any of the aforementioned parameters or other parameters.

[0065] Thus, the battery system 1000 may comprise more than one battery unit 100 which may be considered as independent units, i.e. a battery unit may operate the vehicle without affecting other battery units, particularly in terms of electrical operation (power, voltage, current, etc.) and cooling.

[0066] Furthermore, the battery system 1000 may include a lower cover 200 configured to cover the battery unit 100. The lower cover 200 can protect the battery unit 100 from an impact from below the vehicle. The lower cover 200 may be a metal component, for example, a hot-stamped metal component.

[0067] In some examples, the lower cover 200 may be made of boron steel, such as 22MnB5 steel (e.g., Usibor® 1500, commercially available from ArcelorMittal), or 37MnB5 steel (e.g., Usibor® 2000), with or without a protective coating, or any martensitic steel, or ultra-high strength steel (UHSS).

[0068] Usibor® 1500 and similar 22MnB5 steels are typically supplied in the ferrite-pearlite phase. This is a fine-grained structure distributed in a homogeneous pattern. The mechanical properties are related to this structure. After heating, the hot stamping process, and subsequent quenching, a martensitic microstructure is produced. As a result, the tensile strength and yield strength are significantly increased.

[0069] The composition of Usibor® 1500 is summarized below in weight percentages (the balance being iron (Fe) and impurities): ·Carbon (C) (%): max. 0.25 Silicon (Si) (%): Max 0.4 Manganese (Mn) (%): Max 1.4 Phosphorus (P) (%): Max 0.03 ·Sulfur (S) (%): Maximum 0.01 Aluminum (Al) (%): 0.01 to 0.1 Titanium (Ti) (%): Max 0.05 Niobium (Nb) (%): Max 0.01 ·Copper (Cu) (%): Maximum 0.20 Boron (B) (%): Max 0.005 Chromium (Cr) (%): Max 0.35

[0070] Usibor® 2000 is another boron steel with even higher strength. After the hot stamping, die-quenching process, Usibor® 2000's yield strength can be greater than 1300 MPa, and its ultimate tensile strength can exceed 1800 MPa.

[0071] The composition of Usibor® 2000 is summarized below in weight percentages (the balance being iron (Fe) and impurities): ·Carbon (C) (%): max. 0.36 Silicon (Si) (%): Max 0.8 Manganese (Mn) (%): Max 0.8 Phosphorus (P) (%): Max 0.03 ·Sulfur (S) (%): Maximum 0.01 Aluminum (Al) (%): 0.01-0.06 Titanium (Ti) (%): Max 0.07 Niobium (Nb) (%): Max 0.07 ·Copper (Cu) (%): Maximum 0.20 Boron (B) (%): Max 0.005 Chromium (Cr) (%): Max 0.50 Molybdenum (Mb) (%): Max 0.50

[0072] 22MnB5 may be coated with an aluminum-silicon coating to prevent decarburization and scale formation during the forming process. Several 22MnB5 steels with similar chemical compositions are commercially available. However, the exact amounts of each component in 22MnB5 steel may vary slightly depending on the manufacturer. Other ultra-high strength steels include BTR 165, commercially available from Benteler.

[0073] Additionally, the lower cover 200 may be made of other high-strength steel materials. For example, Fortiform® steel may also be used to manufacture the lower cover 200 by cold forming. A lower cover 200 made of Fortiform® may provide additional weight savings compared to a component made of DP steel with similar mechanical properties. Furthermore, Fortiform® steel exhibits excellent fatigue properties due to its very high mechanical strength. Fortiform® steel is commercially available from ArcelorMittal.

[0074] In some examples, the lower cover 200 may be made of Fortiform®, for example, the lower cover 200 may be made of Fortiform® 1180 (HF1180Y850) (tensile strength 1180-1330 MPa). In other examples, the lower cover 200 may be made of Fortiform® S1270 (tensile strength 1270-1400 MPa).

[0075] The composition of Fortiform® 1180 is summarized below in weight percentages (the balance being iron (Fe) and impurities): ·Carbon (C) (%): max. 0.23 Silicon (Si) (%): Max 2.0 Manganese (Mn) (%): Max 2.9 Phosphorus (P) (%): Max 0.040 ·Sulfur (S) (%): Maximum 0.010 Aluminum (Al) (%): 0.015-1.0 Titanium + Niobium (Ti + Nb) (%): Max 0.15 Niobium (Nb) (%): Max 0.10 ·Copper (Cu) (%): Maximum 0.20 Boron (B) (%): Max 0.005 Chromium + Molybdenum (Cr+Mo)(%): Max 0.60

[0076] The composition of Fortiform® S1270 is summarized below by weight percentage (the balance being iron (Fe) and impurities): ·Carbon (C) (%): Maximum 0.21 Silicon (Si) (%): Max 1.5 Manganese (Mn) (%): Max 4.1 Phosphorus (P) (%): Max 0.04 ·Sulfur (S) (%): Maximum 0.01 Aluminum (Al) (%): 0.015-1.0 Titanium + Niobium (Ti + Nb) (%): Max 0.15 Niobium (Nb) (%): Max 0.10 ·Copper (Cu) (%): Maximum 0.2 Chromium + Molybdenum (Cr+Mo)(%): Max 0.6

[0077] Steels suitable for hot forming and also for cold forming with other material compositions may be used to manufacture the lower cover 200 .

[0078] Additionally, the lower cover 200 may have an electrical adapter for connecting the battery unit 100 to other components of the vehicle. The electrical adapter may have multiple ports. In some examples, the ports may be configured to provide different electrical outputs, i.e., the maximum voltage and / or current provided by each port may be different.

[0079] In some examples, the bottom cover 200 may include additional ports (not shown), for example, to allow battery gases to escape to the atmosphere. Additional vent devices configured for the same purpose may also be used in the battery tray 10.

[0080] 2 also shows vehicle coupling structures 300, 310. The coupling structures 300, 310 are configured to receive removable fasteners so that the battery system can be coupled to the vehicle. These structures are described in more detail in conjunction with FIGS. 3-5.

[0081] 3 is a schematic bottom perspective view of an example vehicle framework 1500 of a vehicle according to the present disclosure. Note that other vehicle components not mechanically coupled to the battery system 1000 are not shown for simplicity.

[0082] The vehicle in this example is equipped with a battery system 1000 that includes two battery units covered by a lower cover 200. In this example, the lower cover 200 also includes other openings configured to receive an electrical adapter 210 and inlet and outlet ports 51 and 52 of a cooling system.

[0083] 3, the lower cover 200 may have a substantially flat bottom, so that the underbody of the vehicle may remain substantially flat, thereby improving the aerodynamic performance of the vehicle. In other examples, the lower cover 200 may be adapted to gradually adjust to the underbody diffuser of the vehicle.

[0084] Figure 4 shows a schematic cross section across the plane A-A' of Figure 3. In this figure, only half of the vehicle framework 1500 and the battery system 1000 are shown.

[0085] FIG. 4 shows that the battery tray 10 can be connected to the coupling structures 300, 310 through removable fasteners 141. In this example, the brackets 14 of the battery tray 10 are elements of the battery tray 10 configured to receive the fasteners 141 and hold the battery tray 10 in place. Additionally, the lower cover 200 can also include flanges configured to receive the removable fasteners 241 and connect the lower cover 200 to the vehicle framework 1500. Thus, if a qualified operator needs access to the interior of the battery system 1000, the operator can remove the fasteners 241 of the lower cover 200, remove the lower cover 200, and disassemble the particular battery unit 100 from the rest of the vehicle. The battery unit 100 can be replaced with another battery unit as needed. The operation of adjacent battery units is substantially independent of the new battery unit (in terms of electrical control and cooling) and therefore substantially unaffected.

[0086] 4 also shows that the bottom wall 11 of the battery tray 10 can be separated from the lower cover 200. Thus, an impact received by the lower cover 200 is not directly transmitted to the battery tray 10. In other examples, an intermediate cushioning layer, for example, with a foam or honeycomb material, can be positioned between the lower cover 200 and the lower wall 11 of the battery tray 10.

[0087] 4 partially illustrates the arrangement of the coupling structures 300, 310. More precisely, FIG. 4 illustrates that the vehicle may include at least three coupling structures 300, 310 (one not shown). The first and second coupling structures 300 may be positioned on first and second sides of the battery system 1000, respectively, and the third coupling structure 310 may be positioned between the battery units 100 of the battery system 1000.

[0088] Thus, both the first and second coupling structures 300 may be configured to secure each battery unit 100 to a side structure (which may be, for example, a rocker, depending on the vehicle framework), and the third coupling structure 310 may be configured to secure both battery units 100 to each other and to the vehicle framework.

[0089] The coupling structure may be configured to receive removable fasteners, allowing the battery system to be assembled and disassembled several times relative to the vehicle without any structural changes to the battery system itself.

[0090] In some examples, the bonded structure may be made from an extruded profile, for example an aluminum extruded profile.

[0091] FIG. 5 shows a schematic cross section across the plane B-B' of FIG.

[0092] The vehicle coupling structure 310 may extend substantially along the entire length of the battery tray 10 to facilitate connection between the battery tray 10 and the vehicle. In other examples, the coupling structure 310 may be substantially shorter than the battery tray 10, and multiple coupling structures 310 may be distributed along the length of the battery tray 10.

[0093] In some examples, the joining structures 300, 310 may be joined to the vehicle framework 1500 by welding, such as spot welding, although other approaches may also be used. For example, the joining structures 300, 310 may be integrally formed within the vehicle framework. Additionally, the joining structures 300, 310 may be made of a metal with high mechanical properties. For example, the joining structures 300, 310 may be made of a suitable steel (boron steel, such as 22MnB5 or 37MnB5, or others), as discussed above in connection with the lower cover 200.

[0094] FIG. 5 also shows that the bottom cover 200 may be adapted to receive other components of the battery system 1000, for example, it may include openings for ports 51, 52 of the cooling system 53 and an opening for an electrical adapter 210.

[0095] While only a number of examples are disclosed herein, there may be other alternatives, modifications, uses, and / or equivalents thereof. Furthermore, all possible combinations of the examples described are also covered. Thus, the scope of the present disclosure should not be limited by the specific examples, but should be determined solely by a fair reading of the following claims.

Claims

1. A battery unit for a vehicle, the battery unit comprising: a battery tray made of a composite material defining an interior space configured to receive a battery including one or more battery cells, the interior space being bounded by a bottom wall and one or more side walls, the battery tray including a cross member configured to separate the battery cells, the cross member being integrally formed with the battery tray; and a top cover configured to close the battery tray; a cooling system for cooling the battery integrated into the top cover, the top cover including a seal at least substantially along a periphery of the top cover, the seal being a thermally conductive seal and positioned in contact with the top cover and the battery cells.

2. The battery unit according to claim 1 , wherein the battery tray is made of a sheet molding compound.

3. The battery unit according to claim 1 or 2, wherein the composite material comprises glass fibers.

4. 4. The battery unit of claim 1, wherein the battery tray comprises a bracket configured to connect the battery tray to a vehicle framework.

5. 5. The battery unit according to claim 1, wherein the top cover is made of aluminum.

6. The battery unit of claim 1 , wherein the seal comprises an adhesive.

7. 7. The battery unit according to claim 1, wherein the battery includes bus bars that electrically connect the battery cells, the bus bars being at least partially located inside the battery tray.

8. 8. The battery unit according to claim 7, wherein the bus bar has a substantially U-shape, the U-shape including a first side member electrically connected to the positive terminal of the battery cell and a side member electrically connected to the negative terminal of the battery cell.

9. A battery system comprising one or more battery units according to any one of claims 1 to 8.

10. The battery system of claim 9 , wherein each battery unit includes a separate battery management system.

11. The battery system according to claim 9 or 10, wherein the battery system comprises a bottom cover configured to cover the battery unit.

12. A vehicle comprising a battery system according to any one of claims 9 to 11.

13. 13. The vehicle of claim 12, wherein the battery unit is connected to the vehicle framework via removable fasteners.

14. 14. The vehicle of claim 13, wherein the battery system includes two battery units, and the vehicle further comprises at least three coupling structures configured to receive the removable fasteners, first and second coupling structures located on a first side and a second side of the battery system, respectively, and a third coupling structure configured to receive removable fasteners from both battery units located between the two battery units.

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