BATTERY PACK ASSEMBLY

A clamshell plate for a battery pack is configured to facilitate connection via adhesive to a plurality of battery cells. The clamshell plate includes: an exterior surface; a recess within the clamshell plate for accommodating a battery cell therein; a channel extending around at least a portion of an inner diameter of the recess in which adhesive can be accommodated to secure the clamshell plate to the battery cell; a manifold opening into the channel; and a vent hole from the channel to the exterior surface of the clamshell plate. A battery pack and a method can employ the clamshell plate.

TECHNICAL FIELD

The present invention relates to apparatus and methods for a battery pack.

BACKGROUND

There is much interest in developing battery-powered vehicles. These applications often require that the battery cells be mechanically coupled together. This is problematic, especially with large numbers of battery cells.

If the technology is to be applied to aircraft, consideration also has to be given to minimize weight and to ensure resistance to shock and vibration failures.

SUMMARY OF THE INVENTION

In accordance with a broad aspect of the present invention, there is provided a clamshell plate for a battery pack, comprising: an exterior surface; a recess within the clamshell plate for accommodating a battery cell therein; an channel extending around at least a portion of an inner diameter of the recess in which adhesive can be accommodated to secure the clamshell plate to the battery cell; a manifold opening into the channel; and a vent hole from the channel to the exterior surface of the clamshell plate.

In accordance with another broad aspect of the present invention, there is provided a battery pack comprising: a battery cell; and a clamshell plate including: an exterior surface; a recess within the clamshell plate for accommodating the battery cell therein; an channel extending around at least a portion of an inner diameter of the recess in which adhesive can be accommodated to secure the clamshell plate to the battery cell; a manifold opening into the channel; and a vent hole from the channel to the exterior surface of the clamshell plate.

In accordance with another broad aspect of the present invention, there is provided a method for manufacturing a battery pack comprising: inserting a battery into each recess of a plate that is in communication with a manifold enclosed within the plate and having conduit connections to an channel extending along at least a portion of an inner diameter around each recess; injecting adhesive into an inlet port to the manifold such that the adhesive flows through the manifold, through each of the conduit connections and into the channels around the recesses; and continuing to inject the adhesive until an indicator on the plate indicates that the adhesive has flowed around the channel.

It is to be understood that other aspects of the present invention will become readily apparent to those skilled in the art from the following detailed description, wherein various embodiments of the invention are shown and described by way of illustration. As will be realized, the invention is capable of other and different embodiments and its several details are capable of modification in various other respects, all within the present invention. Furthermore, the various embodiments described may be combined, mutatis mutandis, with other embodiments described herein. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not as restrictive.

DETAILED DESCRIPTION OF EMBODIMENTS

The detailed description set forth below in connection with the appended drawings is intended as a description of various embodiments of the present invention and is not intended to represent the only embodiments contemplated by the inventor. The detailed description includes specific details for providing a comprehensive understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without these specific details.

An apparatus and method have been invented relating to a battery pack10. The battery pack includes multiple battery cells12held together by at least one clamshell plate. In the illustrated embodiment, there are two clamshell plates: an upper plate14aand a lower plate14b. While six battery cells are shown in the embodiments illustrated herein, there may be any number of battery cells secured together with one or more plates in the battery pack. It is noted that clamshell plate is a term in the art and such a plate can have various shapes. For example, as illustrated, a clamshell plate of the type used in a battery pack assembly need not have a concave clamshell shape and need not come together with other plates in a clamshell arrangement. At the same time, however, the clamshell of the present invention need not be shaped only like that illustrated. For example, the clamshell plate of the present need not be flat and need not be rectangular or square.

Useful battery cells12are each often cylindrically housed/shaped. For example, D-cell batteries are often used and they have a cylindrical shape with a diameter dcthat is known or can be readily determined. The assembly will include a plurality of battery cells12. The battery cells are all of a similar shape and are arranged side by side, with their lengthwise dimensions substantially in parallel. The clamshell plates14a,14bare installed adjacent (i.e. on or near) the ends of the arrangement of battery cells. In particular, each clamshell plate has a plurality of recesses18. While the illustrated recesses are holes passing fully through the plate, a recess could be an indent that is closed at one end or a tapered hole. Each recess18is sized to accommodate an end of one battery cell12. Therefore, each battery cell has at least one of its ends disposed in a recess a clamshell plate. As illustrated, each battery cell could have (i) its upper end installed in a recess of a top clamshell plate and (ii) its lower end installed in a recess of a lower clamshell plate14b.

To hold the battery pack together, adhesive20is applied to secure the battery cells12to the plates14a,14b. Adhesive20resides between each battery cell and each plate. In the illustrated embodiment, there is a ring of adhesive20between the circumference of each battery cell and the inner diameter of the recess.

As noted, the clamshell plates illustrated herein include recesses formed as holes, where each hole is configured for accepting the end of one of a plurality of battery cells. The clamshell plate is secured to the plurality of battery cells by injecting adhesive into an annular space between the circular surface that is the recess hole inner diameter and each battery circumference orthogonal to its long axis. The adhesive is selected to be injectable such as anywhere from a flowable paste to a pourable liquid.

To provide a good adhesion and to facilitate operations, it has been found that the adhesive should be substantially continuous about approximately one half of, and possibly about the full, circumference of each battery cell and the adhesive should be neatly contained in the annular space. The decision on the degree to which the adhesive extends around the battery cell may be dependent on any of the desired weight, adhesive cost, expected need for greater adhesion, etc.

To accomplish these goals, each battery recess has a groove around at least one half of its inner diameter, which can accommodate and retain adhesive. The grooves are formed within the thickness of the clamshell plate. In the illustrated embodiment, each recess18includes an annular groove defined between an upper rim18aand a lower rim18b. Upper rim18ahas a diameter drmjust slightly larger than the diameter dcof the battery cell that is to be received in the recess and lower rim18bhas a diameter similar to and centred on the upper rim. Between the upper rim and the lower rim is a groove that forms a channel18c,18c′ that extends at least partly around the recess. The channel has a diameter drcthat is larger than the diameters of the rims such that a groove with a depth is formed around the recess in the thickness of the plate. There is an channel18c,18c′ open on the inner diameter of each recess hole. As shown inFIG.7, channel18c′ extends only part way, approximately 180° around the inner circumference of its recess hole. InFIGS.1-5, the channel is an annular channel18cthat extends around the entire inner circumference of each recess hole.

When the battery cell is positioned in its recess18, the upper rim18aand the lower rim18bare in close contact with the sides of the battery and the channel18c,18c′ is open to the circumference of the outer surface of the battery cell. There is a space, therefore, between the depth of the channel and the inner edges of the rims, which is where the outer surface of the battery cell12will bear. The channel can accommodate the adhesive20therein and the rims can, by close fit against the battery cell outer surface, prevent the adhesive from leaking out of the channel.

While adhesive could be introduced into the channel grooves by various means, a manifold arrangement24may be employed to direct and feed adhesive to a plurality of battery recesses simultaneously. Therefore, in one embodiment, between a plurality of the battery recesses, there is a manifold24(shown in dashed lines) that opens to a plurality of annular channels. The manifold is a conduit formed and enclosed within the thickness of the clamshell plate. The manifold has conduit connections to all of the annular channels that it is to service.

Looking at the illustrated embodiment ofFIG.4, for example, the four recesses18on the left hand side are accessed through one manifold and the two recesses on the right hand side are accessed through a separate manifold between them. It is to be appreciated that a manifold can open into any number of recesses, not just two or four.

The interconnected manifold24and plurality of annular channels18callow an applicator to dispense adhesive in one location: into the manifold12. As the adhesive is injected, it flows from injection site through the manifold to the multiple annular channels in communication via connections25to the manifold. The adhesive is, therefore, introduced around the circumferences of the plurality of the battery cells. Using basic tools, multiple battery cells can be glued to a plate simultaneously, reducing labor cost as well as capital equipment costs.

Adhesive can be introduced to the manifold via various means. In one embodiment, if the clamshell material is penetrable by a needle, the adhesive can be injected via a needle to the manifold. For example, if the clamshell material is soft or meltable, a needle injector can be inserted through the clamshell material to access the manifold and then the adhesive can be injected. In another embodiment, the clamshell plate can include an inlet port. The inlet port extends from an outer surface of the clamshell plate to the manifold. The inlet port can extend from a side edge or from one of the planar upper or lower surfaces of the plate to open into the manifold.

In the illustrated embodiment, there are inlet ports26from the exterior, planar surface of the plate to manifolds24. Looking at the illustrated embodiment ofFIG.4, for example, the manifold for the four recesses18on the left hand side is accessed via the left hand side port26and the manifold for the two recesses on the right hand side is accessed via port26on the right hand side.

Adhesive injected at an inlet port26flows through its manifold and out through the plurality of annular channels18ctowards the recesses. The port26, of course, only extends through one side planar surface of the plate, so that the injected adhesive is forced to move through the path.

To ensure that the adhesive properly migrates partially or fully around the battery cells, indicators on the clamshell plate provide visual verification that glue has been injected and flowed into the groove of every recess. The indicator can be a window, a colour changing patch, or a vent hole. There may be more than one indicator per recess. In one embodiment, the indicator is one or more vent holes28. A vent hole is a physical hole through the rim that extends from the channel18cto an outer surface of the plate. Each annular channel18caround each cell recess18can have a vent hole28. When adhesive begins to emerge from that channel's vent hole, this provides a visual indication that the adhesive has flowed a selected distance around the entire channel.

Each vent is positioned at the point where the adhesive is intended to at least reach. For example with reference toFIG.7, if the manufacture process requires that the adhesive reach at least half of the full circumference, then a vent hole may be positioned about 90° around the recess, from where the manifold connection25opens into the channel18c′. In such an embodiment, there may be two vent holes28a,28bdiametrically opposite each other across the recess and each about 90° around the recess, from where the manifold connection opens into the annular channel.

As another example with reference toFIGS.1-5, if the manufacture process indicates that the adhesive should fully encircle the battery cell, then vent hole28may be positioned across the recess, such as diametrically opposite across the recess, from where the manifold connection opens into the annular channel.

Vent holes28,28a,28bcan each be a distinct hole spaced from the rim edge of the recess or they can each be a notch in the rim (FIG.7). All the vent holes may be on the same side of the plate, so they can all be observed at the same time. Typically, the vent holes28,28a,28bare open on the same side of the plate on which the port26opens. This is generally the planar side of the plate that forms an exterior surface of the battery pack, so that the vents are easily visible from the environment around the battery pack.

It is noted above that this illustrated embodiment has recesses18formed as holes through the clamshell plates. In particular, in this embodiment, each battery recess18is a hole that extends fully through its plate such that the upper end of each battery cell protrudes up through the plate. The annular channels are formed between an upper end of the hole, which is upper rim18a, and a lower end of the hole, which is lower rim18b. The upper and lower ends of each hole have a diameter that closely fits against the outer diameter of the battery cell to be installed therein. As such, the close tolerance fit between the hole upper and lower rims and the battery exterior surface creates a seal to prevent leakage of adhesive from the annular channels during the injection process. At the same time, the holes permit the clamshell plate to be used on any shape battery terminal end surface and the hole leaves the battery terminal ends exposed for connection to contacts, etc.

If it is found that leakage of adhesive does occur, for example, from between the plate and the battery cell outer surface a sealant can be applied about the interface between the plate and the battery cell. For example, a liquid sealant such as LOCKTITE™ can be applied to the edge of the recess from the exterior surface prior to introducing the adhesive. The liquid sealant dries to form a seal about the rim and the battery outer surface, which will deter the adhesive from leaking out.

While an embodiment is described where recess18is a hole passing fully through the plate, it is to be appreciated that the present invention of annular channels and indicators can be used even where the recesses are indents on one side of the plate or are tapered holes with one rim18aor18bsmaller in diameter than the other rim. In such an embodiment, the adhesive seal from the battery cell may be positioned in whole or in part against an upper end or shoulder of the battery cell, rather than just against the side surface as described above.

In aircraft applications, weight is an important consideration. Therefore, the amount of adhesive applied can be controlled by the size of the annular channels. It has been found that channels of less than 3 mm depth and height are more than adequate to hold the battery pack together. The plates may be only slightly thicker than the annular channel and therefore may be less than 5 mm. With such a thin plate, advantageously most of the battery cell, such as a D-cell battery, is left exposed and open for airflow therepast. Therefore, the channels maintain the adhesive within the thickness of the plate. In one embodiment, the annular channel has a depth of less than 2 mm.

While the clamshell plate may be constructed by various methods, in one embodiment (FIGS.6A,6B) the clamshell plate may be constructed as a laminate of at least three plate layers. A middle layer can include cutouts that form the manifold lateral shape, the communication conduits and the recesses with diameter drcdefining the depth of the annular channels. A top and bottom layer can be attached, as by adhesives or polymeric welding, onto an upper surface and a lower surface, respectively of the middle layer. Each of the top and bottom layer can include holes of diameter drmthat can be positioned over the middle layer cutouts with diameter drcand with a solid portion to close in the manifold cutout. The holes of diameter drmwill define the rims18a,18bof the recesses. One of the top or the bottom layers can further include the input ports26positioned in alignment with any manifold cutouts in the middle layer. One of the top or the bottom layers can also include the holes or notches28to create the vent holes. One of the top or the bottom plates generally has both the ports26and the holes or notches28.

A method for manufacturing a battery pack, may include: inserting a battery into each recess of a plate that is in communication with a manifold enclosed within the plate and having conduit connections to an annular channel around each of the recesses. The method may then proceed by injecting adhesive into an inlet port that is in fluid communication with the manifold. In this step, the adhesive flows through the manifold, then through each of the conduit connections and then into the annular channels around the recesses. The injecting step continues until an indicator on the plate indicates that the adhesive has flowed entirely around the annular channels, to surround the batteries. In one embodiment, the indicator is a vent hole opening from the annular channel in a position across the recess from the conduit connection opening to that annular channel and the injecting step continues until adhesive is visible through, and possibly emerges from, the vent hole.