An inner panel of a base plate assembly for a battery frame of a vehicle battery

Abstract

An inner panel 304 of a base plate assembly 300, the inner panel comprises first and second crossmember attachment portions (308a, 308b), and a base plate attachment portion 312 located between the first and second crossmember attachment portions. The base plate attachment portion 312 is spaced from the first crossmember attachment portion and the second crossmember attachment portion in a direction perpendicular to a transverse plane to space a base plate from a transverse plane in a vehicle battery assembly. The inner panel may attach to a base plate to form part of a base plate assembly 300. The base plate assembly may form part of a battery frame of a vehicle battery assembly. The first and second crossmember attachment portions are attachable to first and second crossmembers 202 of the battery frame and the base plate attachment portion is attachable to a base plate 302 of the base plate assembly. The inner panel 304 may be profiled and advantageously provides increased stiffness and improved impact resistance for a vehicle battery assembly.

Description

The present disclosure relates to a vehicle battery assembly, particularly fora battery electric vehicle. Aspects of the invention relate to an inner panel of a base plate assembly for a battery frame of a vehicle battery assembly, to a base plate assembly for a battery frame of a vehicle battery assembly, to a battery frame of a vehicle battery assembly, to a vehicle battery assembly, and to a vehicle. BACKGROUND It is known to provide a vehicle battery assembly for a battery electric or hybrid vehicle. The vehicle battery assembly includes a battery frame that houses battery cells for providing electric power to the vehicle. The battery frame includes a base plate assembly forming a base of the battery frame. The battery frame is mounted to the underside of the vehicle and the base plate is exposed on the underside of the vehicle during use. The battery frame provides a watertight enclosure for the battery cells and also protects the battery cells from impacts. In particular, the base plate provides protection against impacts on the underside of the vehicle, such as when the vehicle is driven over an uneven surface. There is a need to provide a base plate for a battery frame of a vehicle battery assembly that provides impact protection and watertightness without significantly contributing to the weight of the vehicle battery assembly. It is known to provide a base plate assembly that includes a base plate and an inner panel. The inner panel is spaced from the inner surface of the base plate and provides a watertight barrier. The base plate and inner panel together provide impact resistance. Any impact is first imparted on the base plate, and then on the inner panel if the base plate is deformed to contact the inner panel. It is an aim of the present invention to address one or more of the disadvantages associated with the prior art. SUMMARY OF THE INVENTION Aspects and embodiments of the invention provide an inner panel of a base plate assembly fora battery frame of a vehicle battery assembly, a base plate assembly for a battery frame of a vehicle battery assembly, a battery frame of a vehicle battery assembly, a vehicle battery assembly and a vehicle, as claimed in the appended claims. According to an aspect of the present invention there is provided an inner panel of a base plate assembly for a battery frame of a vehicle battery assembly, the battery frame comprising a crossmember extending across the vehicle battery assembly in a transverse plane. The inner panel has a crossmember attachment portion that is attachable to the crossmember, and a base plate attachment portion attachable to a base plate of the base plate assembly. The base plate attachment portion is spaced from the crossmember attachment portion in a direction perpendicular to the transverse plane to space the base plate from the transverse plane in the vehicle battery assembly. According to an aspect of the present invention there is provided an inner panel of a base plate assembly for a battery frame of a vehicle battery assembly, the battery frame comprising a first crossmember and a second crossmember being spaced from each other and extending across the vehicle battery assembly in a transverse plane, wherein the inner panel comprises: a first crossmember attachment portion attachable to the first crossmember, a second crossmember attachment portion attachable to the second crossmember, and a base plate attachment portion located between the first crossmember attachment portions and the second crossmember attachment portion and being attachable to a base plate of the base plate assembly, wherein the base plate attachment portion is spaced from the first crossmember attachment portion and the second crossmember attachment portion in a direction perpendicular to the transverse plane to space the base plate from the transverse plane in the vehicle battery assembly. Advantageously, the inner panel extends at least partly in a direction perpendicular to the transverse plane and so the stiffness of the inner panel is increased, allowing a thinner and lighter material to be used for the inner panel to reduce the weight of the vehicle battery assembly. Additionally, the attachment between the base plate attachment portion and the base plate in the location between the crossmembers improves the impact resistance of the vehicle battery assembly because the force of an impact is transferred from the base plate into the inner panel in an improved manner. In particular, the impact force is transferred into the inner panel and onto the crossmembers, providing greater impact resistance. Further, the impact force would be resisted by elastic and plastic deformation of the base plate and the inner panel, and also by the force required to detach the base plate from the base plate attachment portion, which further improves the impact resistance of the vehicle battery assembly. In examples, the inner panel comprises a first angled portion between the first crossmember attachment portion and the base plate attachment portion. The first angled portion may extend partly in the direction perpendicular to the transverse plane. In examples, the inner panel comprises a second angled portion between the second crossmember attachment portion and the base plate attachment portion. The second angled portion may extend partly in the direction perpendicular to the transverse plane. Advantageously, an impact force on the base plate would be transferred into the first and / or second angled portion(s) and onto the first and second crossmembers, providing greater impact resistance. In examples, the first angled portion and / or the second angled portion extend at an angle of between about 20 degrees and about 50 degrees to the transverse plane. More specifically, the first angled portion and / or second angled portion extend at an angle of about 25 degrees to about 35 degrees to the transverse plane, more specifically between about 30 degrees and about 35 degrees to the transverse plane. Advantageously, the angles of the first and second angled portions are selected to provide improved stiffness of the inner panel and improved impact resistance. In examples, the base plate attachment portion comprises a planar face attachable to the base plate, for example the planar face is attachable to the base plate by adhesive and / or welding. Advantageously, the planar face enables a strong attachment to be formed between the base plate attachment portion and the base plate and provides a surface area for transfer of impact forces from the base plate to the inner panel. Advantageously, a combination of adhesive and welding joining the base plate attachment portion to the base plate provides a strong attachment force, which increases the impact force required to delaminate the base plate and the base plate attachment portion, increasing impact resistance. Further, welding, in particular spot welding, and / or adhesive ensures that the base plate maintains a watertight barrier as no opening is formed through the base plate. In examples, the inner panel comprises a spacer portion aligned with the first crossmember and arranged to space the base plate from the first crossmember. Optionally, the inner panel comprises a second spacer portion aligned with the second crossmember. In examples, the or each spacer portion may abut the base plate but not be attached to the base plate. Alternatively, the or each spacer portion may be attached to the base plate, for example by welding (spot welding) and / or adhesive. In examples, the or each spacer portion divides the respective crossmember attachment portion into a first part and a second part. Advantageously, the spacer portion(s) contribute to the stiffness of the inner panel and provide impact resistance for impacts on the base plate that are aligned with the crossmembers. In examples, the base plate attachment portion is a first base plate attachment portion, and wherein the inner panel comprises a third crossmember attachment portion for attachment to a third crossmember of the battery frame. The third crossmember may be adjacent to, and spaced from, the second crossmember. In such examples, the inner panel may comprise a second base plate attachment portion located between the second crossmember attachment portion and the third crossmember attachment portion. Advantageously, the inner panel may therefore be attached to the base plate between the first and second crossmembers and between the second and third crossmembers, providing impact resistance over a substantial part of the base of the vehicle battery assembly. In examples, the inner panel comprises a webbing portion extending between the first and second crossmember attachment portions in the transverse plane. The webbing portion may extend perpendicular to the crossmembers, crossmember attachment portions, and base plate attachment portion(s). Advantageously, the webbing portion improves the torsional stiffness of the inner panel. This helps the inner panel maintain the desired shape during manufacture, for example when stamping, and during assembly with the battery frame and base plate. In examples, the inner panel comprises an aluminium sheet. The aluminium sheet may have a thickness of between about 1 mm and about 4 mm, for example about 2 mm or about 3 mm. Optionally, the inner panel is formed by stamping (it is stamped). Advantageously, aluminium provides a lightweight inner panel with good impact resistance, structural rigidity, and corrosion resistance. According to a further aspect of the invention, there is provided a base plate assembly for a battery frame of a vehicle battery assembly, the vehicle battery assembly comprising a first crossmember and a second crossmember extending across the vehicle battery assembly in a transverse plane, the first crossmember being spaced from the second crossmember, wherein the base plate assembly comprises: a base plate, and the inner panel described above, wherein the base plate is attached to the inner panel at the base plate attachment portion. Advantageously, the inner panel extends at least partly in a direction perpendicular to the transverse plane and so the stiffness of the base plate assembly is increased, allowing a thinner material to be used for the inner panel and base plate and reducing the weight of the vehicle battery assembly. Additionally, the attachment between the base plate attachment portion and the base plate in the location between the crossmembers improves the impact resistance of the vehicle battery assembly because the force of an impact is transferred from the base plate into the inner panel in an improved manner. In particular, the impact force is transferred into the inner panel and onto the crossmembers, providing greater impact resistance. Further, the impact force would be resisted by elastic and plastic deformation of the base plate and the inner panel, and also by the force required to detach the base plate from the base plate attachment portion, which further improves the impact resistance of the vehicle battery assembly. In examples, the base plate is attached to the base plate attachment portion of the inner panel by a weld. Optionally, the weld comprises a plurality of spot welds arranged in one or more lines. Optionally, the plurality of spot welds are arranged in two lines. Advantageously, the weld (e.g., spot weld(s)) provides a strong attachment between the inner panel and the base plate and the base plate maintains a watertight barrier as no opening is formed through the base plate. In examples, the base plate is attached to the base plate attachment portion of the inner panel by an adhesive, in particular by a strip of adhesive. Optionally, the base plate is attached to the base plate attachment portion by adhesive and welding. Advantageously, the adhesive provides a strong attachment between the inner panel and the base plate, and the base plate maintains a watertight barrier. In examples, the base plate assembly comprises a strip of adhesive attaching the base plate and the base plate attachment portion of the inner panel, the strip of adhesive overlying the weld. In particular, the base plate may be attached to the base plate attachment portion of the inner panel by a line of adhesive and a plurality of spot welds formed in the adhered area. More than one line of adhesive and spot welds may be provided. Advantageously, the combination of the weld (e.g., spot welds) and the adhesive provides a strong attachment between the inner panel and the base plate and the base plate maintains a watertight barrier because no opening is formed through the base plate. In examples, the base plate is planar where it underlies the first crossmember and the second crossmember. Advantageously, this reduces the likelihood of damage as the vehicle is driven (e.g., because there are no edges or protrusions to catch on the road surface). In addition, it provides a planar surface for attachment of the inner panel. In examples, the base plate comprises a raised edge such that the base plate is dish-shaped. Advantageously, the raised edge may include fixing points for mounting the base plate to the battery frame. The dish-shape of the base plate may improve the sealing of the vehicle battery assembly. The raised edge may be welded or otherwise joined to the inner panel and / or to the battery frame. The raised edge may be sealed to the battery frame, for example by welding, so that the base plate assembly provides a sealed enclosure on the base of the vehicle battery assembly. In examples, the base plate comprises an aluminium sheet. The aluminium sheet may have a thickness of between about 1 mm and about 4 mm, for example about 2 mm or about 3 mm. Optionally, the base plate is formed by stamping (it is stamped). Advantageously, aluminium provides a lightweight inner panel with good impact resistance, structural rigidity, and corrosion resistance. According to a further aspect of the invention, there is provided a battery frame of a vehicle battery assembly, the battery frame comprising: a first crossmember and a second crossmember spaced from each other and extending parallel to each other in a transverse plane of the vehicle battery assembly, and the base plate assembly described above, wherein the first crossmember attachment portion is attached to the first crossmember and the second crossmember attachment portion is attached to the second crossmember. Advantageously, as described above, the base plate assembly provide improved stiffness, reducing the weight of the vehicle battery assembly. Additionally, the attachment between the base plate attachment portion and the base plate in the location between the crossmembers improves the impact resistance of the vehicle battery assembly. In examples, the first crossmember attachment portion and the second crossmember attachment portion are attached to the first crossmember and the second crossmember, respectively, by rivets. Optionally the rivets are self-piercing rivets (SPRs). Advantageously, the rivets (SPRs) provide a strong attachment of the inner panel to the first and second crossmembers, which improves the stiffness and impact resistance of the base plate assembly as more force can be transferred from the inner panel to the crossmembers. Optionally, the first crossmember and the second crossmember each comprise a T-shaped beam having a central section and two flanges extending in the transverse plane. The first and second crossmember attachment portions of the inner panel may be attached to a flange of the respective first and second crossmembers. Advantageously, the flanges of the crossmembers provide a convenient mounting point forthe inner panel and provide high stiffness to the crossmembers. Additionally, battery cells can be supported on the flanges. In examples, the battery frame comprises a third crossmember. In such examples the inner panel of the base plate assembly may comprise a third crossmember attachment portion attached to the third crossmember. In such examples, the inner panel may comprise a second base plate attachment portion located between the second crossmember attachment portion and the third crossmember attachment portion. The second base plate attachment portion may be attached to the base plate. Advantageously, the inner panel may therefore be attached to the base plate between the first and second crossmembers and between the second and third crossmembers, providing impact resistance over a substantial part of the base of the vehicle battery assembly. According to a further aspect of the invention, there is provided a vehicle battery assembly comprising the battery frame described above and a battery cell, the battery cell being supported by, and extending between, the first crossmember and the second crossmember. The battery cell may be a secondary battery cell. The vehicle battery assembly may comprise a plurality of (secondary) battery cells. Advantageously, as described above, the base plate assembly provides improved impact resistance to improve protection of the battery cells. According to a further aspect of the invention, there is provided a vehicle comprising a vehicle body and the vehicle battery assembly described above, wherein the vehicle battery assembly is attached to the vehicle body. Advantageously, as described above, the base plate assembly provides improved impact resistance to improve protection of the battery cells, particularly when the vehicle is driven over an uneven surface. In examples, the base plate assembly, in particular the base plate, may form an outer (bottom) surface of the vehicle. The base plate assembly advantageously provides sealing and impact resistance as described above. In examples, the vehicle is a battery electric vehicle, or a hybrid vehicle (e.g., a plug-in hybrid vehicle or a mild hybrid vehicle). The vehicle battery assembly may be a primary or secondary energy source for vehicle propulsion. The vehicle battery assembly may be a traction battery of the vehicle. Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and / or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and / or features of any embodiment can be combined in anyway and / or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and / or incorporate any feature of any other claim although not originally claimed in that manner. BRIEF DESCRIPTION OF THE DRAWINGS One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a vehicle; Figure 2 shows a schematic cross-section through a vehicle battery assembly of the vehicle of Figure 1; Figure 3A shows a base plate assembly of the vehicle battery assembly of Figure 2, and three crossmembers of a battery frame of the vehicle battery assembly of Figure 2; Figure 3B shows the base plate assembly of Figure 3A; Figure 4A shows a simplified cross-section through the base plate assembly and crossmembers of the battery frame; Figure 4B shows a magnified view of part of the cross-section of Figure 4A; Figure 4C shows a top view of the base plate assembly illustrating how the base plate is attached to the inner panel; Figure 5 shows a magnified view of a part of the inner panel; and Figure 6 shows the base plate in isolation, all the foregoing according to embodiments of the invention. DETAILED DESCRIPTION A vehicle 100 in accordance with an embodiment of the present invention is shown in Figure 1. Figure 2 shows a schematic cross-section through a vehicle battery assembly 200 of the vehicle 100. The cross-section is taken through a plane extending longitudinally through the vehicle, vertically from a front of the vehicle to a rear of the vehicle. The vehicle battery assembly 200 is installed on an underside of the vehicle 100. The vehicle battery assembly 200 includes a plurality of fixings 210 for mounting the vehicle battery assembly 200 to the underside of the vehicle 100. The fixings 210 may attach to various parts of the underside of the vehicle 100, for example parts of a chassis and / or monocoque and / or other structural members of the vehicle 100. The vehicle battery assembly 200 houses a plurality of battery cells 206. The battery cells 206 may be secondary cells of the vehicle battery assembly 200. The vehicle battery assembly 200 may also house battery monitoring systems, control systems, cooling systems, and other sub-assemblies (not illustrated). In some examples the vehicle battery assembly 200 is a traction battery. The vehicle 100 may be a battery electric vehicle, a hybrid vehicle (e.g., a plug-in hybrid vehicle, or a mild hybrid vehicle). The vehicle battery assembly 200 may be a primary or secondary energy source for vehicle propulsion. The vehicle battery assembly 200 shown in Figure 2 includes a battery frame 208. The battery frame 208 includes crossmembers 202 that extend transversely across the vehicle battery assembly 200. In this example, the battery frame 208 includes four crossmembers 202, but in various examples the battery frame 208 may comprise two or more crossmembers 202. The battery frame 208 also includes end members 212 at each end of the battery frame 208. The end members 212 are similar to the crossmembers 202. In some examples the vehicle battery assembly 200 may include end sections 212 and no crossmembers 202. The fixings 210 may be attached to the crossmembers 202 and / or end members 212 for mounting the vehicle battery assembly 200 to the vehicle. The battery frame 208 includes a battery lid 214 that is attached to the top of crossmembers 202 and end members 212. The battery frame 208 includes a base plate assembly 300 mounted to the bottom of the crossmembers 202 and end members 212. The base plate assembly 300 forms the bottom of the vehicle battery assembly 200. The base plate assembly 300 may be exposed below the vehicle 100 and provide sealing and protection for the battery cells 206 within the vehicle battery assembly 200. The battery frame 208, in particular the crossmembers 202 and end members 210, provide internal mounting for the battery cells 206 and other sub-assemblies. For example, a stack of battery cells 206 may be supported by the crossmembers 202 as illustrated. Figure 3A shows the base plate assembly 300 of the vehicle battery assembly 200. Figure 3A also shows some of the crossmembers 202 of the battery frame 208 described with reference to Figure 2. In this example three crossmembers 202 are shown, but as described above the battery frame 208 may include two or more crossmembers 202, for example two, three, four, five or six crossmembers 202. As described with reference to Figure 2, the crossmembers 202 extend in a transverse direction across the vehicle battery assembly 200, from one side of the vehicle 100 towards the other when installed on the vehicle 100 of Figure 1. The crossmembers 202 each comprise a T-shaped profile having a central web portion 204 and two flanges 206a, 206b extending from the central web portion 204 in opposite directions. The two flanges 206a, 206b extend in a transverse plane. The flanges 206a, 206b of two or more of the crossmembers 202 may be arranged (aligned) in the same transverse plane. The crossmembers 202 may be metal, for example aluminium. The flanges 206a, 206b may have a thickness of between about 1 mm and about 4 mm, for example about 3 mm. As described further hereinafter, the base plate assembly 300 is attached to the battery frame 208 at the crossmembers 202. Specifically, the base plate assembly 300 is attached to the crossmembers 202. The base plate assembly 300 includes a base plate 302 and an inner panel 304. The base plate 302 forms the outermost (bottommost) part of the base plate assembly 300, with the inner panel 304 disposed on an inner side of the base plate 302. The inner panel 304 is attached to the crossmembers 202 and to the base plate 302. The base plate 302 and the inner panel 304 may be metal, for example aluminium, e.g., aluminium sheet. The base plate 302 may comprise a thickness of about 2 mm in some examples. The inner panel 304 may comprise a thickness of about 2 mm in some examples. Figure 3B shows the base plate assembly 300 in isolation. As shown, the inner panel 304 comprises a profiled form, described in detail below. The profiled form provides a plurality of crossmember attachment portions 308 that are attached to the crossmembers 202 shown in Figure 3A. The profiled form also provides a plurality of base plate attachment portions 312 that are attached to the base plate 302. As shown in Figure 3B, the profiled form does not extend fully across the inner panel 304 and is only formed in some parts of the inner panel 304. In particular, an edge of the inner panel 304 may be planar and may be attached to the battery frame (208, see Figure 2), in particular to the end members 212 and / or any side members of the battery frame (208, see Figure 2). In examples the inner panel 304 is adhered and / or riveted to the battery frame (208, see Figure 2). In examples, the base plate 302 may be welded to the battery frame (208, see Figure 2). In particular, an edge of the base plate 302 may protrude past the end of the inner panel 302 and may be welded to the battery frame (208, see Figure 2), in particularthe end sections (212, see Figure 2) and any side members. Such welding of the base plate 302 to the battery frame provides a sealed attachment and retains the inner panel 304 between the battery frame and the base plate 302. In addition, the inner panel 304 may include webbing portions as described in more detail below with reference to Figure 6. Figures 4A and 4B show simplified partial cross-sections through the base plate assembly 300 and two crossmembers 202 of the battery frame (208, see Figure 2). The cross-sections of Figures 4A and 4B are taken through the plane 328 shown in Figure 3A. Figure 4B shows the area indicated in Figure 4A. As illustrated, the inner panel 304 is attached to the crossmembers 202, and the base plate 302 is attached to the inner panel 304. That is, the inner panel 304 is sandwiched between the base plate 302 and the crossmembers 202. As shown, the profiled form of the inner panel 304 acts to space the base plate 302 from the crossmembers 202. In particular, the profiled form of the inner panel 304 acts to space the base plate 302 from a transverse plane 306 defined by the flanges 206a, 206b of the crossmembers 202. The spacing between the base plate 302 and the crossmembers 202 provides a deformation zone in which the base plate 302 and inner panel 304 can deform when subject to an impact without displacing the crossmembers 202. As illustrated, for each crossmember 202 the inner panel 304 comprises a crossmember attachment portion 308. Each crossmember attachment portion 308 includes a first part 308a that is attached to the first flange 206a of the corresponding crossmember 202, and a second part 308b is attached to the second flange 206b of the corresponding crossmember 202. In examples, the crossmember attachment portions 308 may be attached to the crossmembers 202 (specifically to the first and second flanges 206a, 206b) by welding and / or adhesive. In some examples, the crossmember attachment portions 308 may be attached to the crossmembers 202 (specifically the first and second flanges 206a, 206b) by rivets, in particular self-piercing rivets (SPRs). A plurality of SPRs may be provided along the first and second flanges 206a, 206b. During manufacture, the inner panel 304 can be riveted to the battery frame 208 (in particular the crossmembers 202) before attachment of the base plate 302. The base plate 302 can then attached (welded) to the inner panel 304 and to the battery frame 208. Between the first and second parts 308a, 308b of the crossmember attachment portions 308 the inner panel 304 comprises a spacer portion 310. Each spacer portion 310 extends away from the transverse plane 306 and spaces the base plate 302 from the crossmember 202 in a position aligned with the crossmembers 202. In some examples each spacer portion 310 may be attached to the base plate 302 (e.g., adhered and / or spot welded), or each spacer portion 310 may only abut the base plate 302 (i.e., not be attached). Each spacer portion 310 may comprise a curved profile that curves downwards from the transverse plane 306 under the first flange 206a, inflexes at the base plate 304, and curves back to the transverse plate 306 under the second flange 206b. Such a curved profile may provide resistance against impacts to the base plate that are aligned with the crossmembers 202. As also illustrated in Figures 4A and 4B, the inner panel 304 comprises a base plate attachment portion 312 that is attached to the base plate 302. The base plate attachment portion 312 is laterally spaced from the crossmember attachment portions 308 so that the base plate attachment portion 312 is located between the adjacent crossmember attachment portions 308 and corresponding crossmembers 202, for example equidistant from the adjacent crossmembers 202. The base plate attachment portion 312 has a planar face that is parallel to the inner surface of the base plate 302 (and parallel with the transverse plane 306). The base plate attachment portion 312 is attached to the base plate 302 by welding (in particular spot welding) and / or adhesive. The base plate attachment portion 312 can be advantageously attached to the base plate 302 by a non-fastener attachment, thereby avoiding the need for an opening through the base plate 302 that may compromise sealing of the vehicle battery assembly 200. Examples of non-fastener attachment is by welding or the use of adhesive. In some examples, the base plate attachment portion 312 is attached to the base plate 302 along a line extending along the base plate attachment portion 312. In particular, the base plate attachment portion 312 may be attached to the base plate 302 by one or more lines of spot welds extending along the base plate attachment portion 312 parallel to the crossmembers 202. A line of adhesive may attach the base plate attachment portion 312 to the base plate 302 along the base plate attachment portion 312 parallel to the crossmembers 202. Spot welds may be formed in the adhered area. Figure 4C shows a top view of a portion of the base plate assembly 300 from the side of the inner panel 304. The base plate 302 is underneath the inner panel 304 in this view. As shown, the base plate attachment portion 312 extends across the inner panel 312, parallel to the cross member attachment portions 308. As shown, the base plate attachment portion 312 is here attached to the base plate 302 by two strips of adhesive 320 extending along the base plate attachment portion 312 parallel to the crossmember attachment portions 308, and by a plurality of spot welds 322 provided in the adhered area. One or more strips of adhesive 320 may be provided, and one or more lines of spot welds 322. Advantageously, the adhesive 320 acts to hold the base plate 302 and the inner panel 304 in position while the spot welds 322 are formed, and this form of attachment does not compromise the sealing provided by the base plate 302 because no hole is formed through the base plate 302. As illustrated in Figures 4A and 4B, the base plate attachment portion 312 is offset from the crossmember attachment portions 308 in a direction perpendicular to the transverse plane 306. Accordingly, the base plate 302 is spaced from the transverse plate 306 and the crossmembers 202. In particular, as illustrated in Figures 4A and 4B, between each of the crossmember attachment portions 308 and an adjacent base plate attachment portion 312 the inner panel 304 comprises an angled portion 314a, 314b. Specifically, between a first crossmember attachment portion 308 and the base plate attachment portion 312 the inner panel 304 includes a first angled portion 314a, and between a second crossmember attachment portion 308 (which is attached to the adjacent crossmember 202) and the next base plate attachment portion 312 the inner panel 304 includes a second angled portion 314b. The first angled portion 314a extends from the first crossmember attachment portion 308 in a direction at least partly perpendicular to the transverse plane 306 to the base plate attachment portion 312 (i.e., having a directional component perpendicular to the transverse plane 306). Similarly, the second angled portion 314b extends from the second crossmember attachment portion 308 in a direction at least partly perpendicular to the transverse plane 306 to the adjacent base plate attachment portion 312 (i.e., having a directional component perpendicular to the transverse plane 306). The angle 324 (see Figure 4B) of the angled portions 314a, 314b with respect to the transverse plane 306 determines, at least in part, the degree of stiffness that the inner panel 304 provides to the base plate assembly 300 and also the impact resistance of the base plate assembly 300. A larger angle will increase the stiffness of the base plate assembly 300 and advantageously allow a thinner and lighter material to be used for the base plate 302 and inner panel 304. A smaller angle will improve the impact resistance of the base plate assembly 300 to an impact on the base plate 302 because more of the material of the angled portions 314a, 314b is in a potential direction of impact (i.e., perpendicular to the base plate 302). An angle of between about 20 degrees and about 50 degrees from the transverse plane 306 provides improved stiffness and improved impact resistance. More specifically, an angle of about 25 degrees to about 35 degrees from the transverse plane 306 is advantageous, more specifically between about 30 degrees and about 35 degrees. Figure 5 shows the inner panel 304 of the base plate assembly 300 in more detail. As shown, the crossmember attachment portions 308 do not extend completely across the inner panel 304 in this example. In particular, a central webbed section 316 is provided in the inner panel 304 and extends perpendicular to the crossmember attachment portions 308. The webbed section 316 thereby divides each of the crossmember attachment portions 308 into two parts. At the webbed section 316 the inner panel 304 is generally level with the base plate 302 and base plate attachment portions 312. The webbed section 316 may improve the torsional stiffness of the inner panel 304, and may prevent deformation (e.g., curling) of the inner panel 304 during manufacture of the inner panel 304, e.g., by stamping. In various examples, more than one webbed section 316 may be provided. Figure 6 shows the base plate 302 in isolation. The base plate 302 in this example has a generally planar inner section 326 that underlies the crossmembers and is spaced from the crossmembers and attaches to the or each base plate attachment portion 312 as described above. The base plate 302 in this example also includes a raised edge 318 extending at least partly, and in some examples fully, about the edge of the base plate 302. The raised edge 318 may be welded to the battery frame 208, the inner panel 304, and / or other parts of the vehicle battery assembly 200. The base plate 302 provides a continuous barrier, without any openings. That is, there is no fastener hole or other opening through the base plate 302. Accordingly, the base plate 302 acts to seal the underside of the vehicle battery assembly 200. In addition, the base plate 302 provides a substantially flat bottom surface of the vehicle battery assembly 200, which reduces the chances of damaging impacts from, for example, uneven road surfaces. As mentioned above, the construction of the base plate assembly 300, with the base plate 302 and the inner panel 304 being spaced from the base plate 302, provides improved stiffness allowing a thinner and / or lighter material to be used when compared with a single base plate. In addition, the construction of the base plate 202 and the inner panel 204 provides for improved impact resistance. One important performance characteristic of the base plate assembly 300 is to protect the vehicle battery assembly 200, in particular the battery cells 206, against impact from the underside of the vehicle. Such an impact may be caused by driving the vehicle over an uneven surface, for example when driving the vehicle 100 offroad. Such impacts are tested by imparting a point impact on the underside of the vehicle battery assembly 200, specifically on the base plate 302. Advantageously, when such a point impact is imparted on the base plate assembly 300 described above the force of the impact is resisted by the inherent stiffness of the base plate 302, and the inherent stiffness of the inner panel 304, which is improved by offsetting the base plate attachment portions 312 from the crossmember attachment portions 308. The inherent resistance from the base plate 302 and inner panel 304 may initially be from elastic deformation of the base plate 302 and the inner panel 304 (particularly the angled portions 314a, 314b and the spacer portions 310). For larger forces the inherent resistance from the base plate 302 and inner panel 304 may initially be from plastic deformation of the base plate 302 and the inner panel 304 (particularly the angled portions 314a, 314b and the spacer portions 310). Additionally, if the point impact is forceful enough to plastically deform the base plate 302 and / or inner panel 304 the attachment of the inner panel 304 to the base plate 302 at the base plate attachment portions 312 provides additional resistance. In particular, further force is required to detach the base plate attachment portions 312 from the inner panel 304 before further plastic deformation can occur, so the delamination force also acts against the impact. Therefore, the construction of the base plate assembly 300 described above, and in particular the profiled form of the inner panel 304, advantageously provides increased stiffness and improved impact resistance. It will be appreciated that various changes and modifications can be made to the present invention without departing from the scope of the present application.

Claims

1. An inner panel of a base plate assembly fora battery frame of a vehicle battery assembly, the battery frame comprising a first crossmember and a second crossmember being spaced from each other and extending across the vehicle battery assembly in a transverse plane, wherein the inner panel comprises:a first crossmember attachment portion attachable to the first crossmember,a second crossmember attachment portion attachable to the second crossmember, anda base plate attachment portion located between the first and second crossmember attachment portions and being attachable to a base plate of the base plate assembly,wherein the base plate attachment portion is spaced from the first crossmember attachment portion and the second crossmember attachment portion in a direction perpendicular to the transverse plane to space the base plate from the transverse plane in the vehicle battery assembly.

2. The inner panel of claim 1, wherein the inner panel comprises a first angled portion between the first crossmember attachment portion and the base plate attachment portion, the first angled portion extending partly in the direction perpendicular to the transverse plane.

3. The inner panel of claim 2, wherein the inner panel comprises a second angled portion between the second crossmember attachment portion and the base plate attachment portion, the second angled portion extending partly in the direction perpendicular to the transverse plane.

4. The inner panel of any preceding claim, comprising a spacer portion aligned with the first crossmember and arranged to space the base plate from the first crossmember.

5. The inner panel of any preceding claim, wherein the base plate attachment portion is a first base plate attachment portion, and wherein the inner panel comprises a third crossmember attachment portion for attachment to a third crossmember of the battery frame, and wherein the inner panel comprises a second base plate attachment portion located between the second crossmember attachment portion and the third crossmember attachment portion.

6. A base plate assembly for a battery frame of a vehicle battery assembly, the vehicle battery assembly comprising a first crossmember and a second crossmember extending across the vehicle battery assembly in a transverse plane, the first crossmember being spaced from the second crossmember, wherein the base plate assembly comprises:a base plate, andthe inner panel of any of claims 1 to 5,wherein the base plate is attached to the inner panel at the base plate attachment portion.

7. The base plate assembly of claim 6, wherein the base plate is attached to the base plate attachment portion of the inner panel by a weld.

8. The base plate assembly of claim 7, wherein the weld comprises a plurality of spot welds arranged in lines.

9. The base plate assembly of claim 7 or claim 8, comprising a strip of adhesive attaching the base plate and the base plate attachment portion of the inner panel, the strip of adhesive overlying the weld.

10. A battery frame of a vehicle battery assembly, the battery frame comprising:a first crossmember and a second crossmember spaced from each other and extending parallel to each other in a transverse plane of the vehicle battery assembly, andthe base plate assembly of any of claims 1 to 9, wherein the first crossmember attachment portion is attached to the first crossmember and the second crossmember attachment portion is attached to the second crossmember.

11. The battery frame of claim 10, wherein the first crossmember attachment portion and the second crossmember attachment portion are attached to the first crossmember and the second crossmember, respectively, by rivets.

12. The battery frame of claim 10 or claim 11, comprising a third crossmember, and wherein the inner panel of the base plate assembly comprises a third crossmember attachment portion attached to the third crossmember.

13. The battery frame of claim 12, wherein the inner panel comprises a second base plate attachment portion located between the second crossmember attachment portion and the third crossmember attachment portion, the second base plate attachment portion being attached to the base plate.

14. A vehicle battery assembly comprising the battery frame of any of claims 10 to 13 and a battery cell, the battery cell being supported by, and extending between, the first crossmember and the second crossmember.

15. A vehicle comprising the vehicle battery assembly of claim 14.15

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