EP4695860A1

EP4695860A1 - Battery pack servicing

Info

Publication number: EP4695860A1
Application number: EP24719488.9A
Authority: EP
Inventors: Matthew ALBRECHT
Original assignee: Jaguar Land Rover Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2023-04-12
Filing date: 2024-04-08
Publication date: 2026-02-18
Also published as: WO2024213519A1; CN121241464A; GB2628996A; GB202305351D0

Abstract

Aspects of the present invention relate to a method (1000) of releasing a first component (100) of a battery pack (1) from the battery pack (1), to a battery pack (1), and to a vehicle (50). The first component (100) being secured to a second component (100) of the battery pack (1) by an adhesive bond (120). The method (1000) comprises: applying a load to the first component (100) in a direction away from the second component (200) and flowing a thermally-conditioned fluid through a cavity (300) of the battery pack (1) to generate a temperature gradient between the first component (100) and the second component (200) such that the adhesive bond (120) is weakened. The first component (100) is separated from the second component (100) by means of the applied load.

Description

BATTERY PACK SERVICING

TECHNICAL FIELD

The present disclosure relates to battery pack servicing. Aspects of the invention relate to a method of releasing a first component of a battery pack from the battery pack, to a battery pack, and to a vehicle.

BACKGROUND

Battery packs are used in electrified vehicles such as a battery electric vehicles, hybrid electric vehicles, plugin hybrid electric vehicles and fuel-cell electric vehicles. Such battery packs typically contain large numbers of individual electrical cells (‘cells’) which may be in the form of prismatic, pouch or cylindrical cells. Cells may comprise rechargeable cells and/or capacitors. Cells are typically arranged in cell subassemblies (‘modules’ or ‘stacks’) within the battery pack. It is known to secure the components of a battery pack by various fixings such as clips, rivets, screws, nuts and bolts, and also by various types of adhesive bond formed of structural and semi-structural adhesives. In so-called ‘cell-to-pack’ arrangements which have little or no intermediate modular structure, the application of structural and semi-structural adhesives to cells provides a distributed stiffening benefit to the battery pack which is not achievable by the use of discreet fixings alone, such as rivets and screws. Such battery packs are expected to be serviceable so that a malfunctioning battery pack is recoverable to a functional state after one or more cells have malfunctioned and need to be replaced. However, when battery packs need to be serviced, adhesives are not as easy to disassemble as are discreet fixings.

It is desirable to service a battery pack by only removing the malfunctioning components, cells or cell subassemblies, and for the remaining components of the battery pack to be undamaged during the servicing operation. Current methods of servicing battery packs in which adhesives are used rely on separating malfunctioning components by mechanically loosening them from the rest of the battery pack. Methods include peeling and chiselling adhesive from the cells, and this may be difficult to achieve when the adhesive bond to be loosened is not readily accessible. It is desirable to provide a battery pack and method of servicing where some adhered cells may be separated from the battery pack without causing damage to the rest of the battery pack.

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 a method, a battery pack and a vehicle as claimed in the appended claims.

According to an aspect of the present invention there is provided a method of releasing a first component of a battery pack from the battery pack, the first component secured to a second component of the battery pack by an adhesive bond, the method comprising: applying a load to the first component in a direction away from the second component; flowing a thermally-conditioned fluid through a cavity of the battery pack to generate a temperature gradient between the first component and the second component such that the adhesive bond is weakened; and separating the first component from the second component by means of the applied load.

The method is useful in servicing battery packs where removal of one or more components or subassemblies is required. The method provides a means of inducing adhesive failure of the adhesive bond due to a differential thermal expansion of at least the first component and second component, and also of the adhesive. Advantageously this will weaken or loosen adhesive bonds so that components are removable from the battery pack. This method is useful for weakening adhesive bonds that are inaccessible by mechanical methods. Also, provision of a temperature gradient at the adhesive bond does not necessitate application of high temperatures to other components of the battery pack which are not being removed. Applying load before the heat provides for separation occurring as soon as the adhesive bond is weakened. Heating before applying load, or heating and applying load simultaneously are also useful in loosening joints.

Optionally, the temperature of the thermally-conditioned fluid is higher than the temperature of the battery pack such that the temperature of the adhesive bond is raised as the fluid flows through the cavity. This provides a means of inducing a cohesive failure as well as adhesive failure of the adhesive bond. Advantageously adhesive bonds that are inaccessible to chiselling may be further weakened by cohesive failure as well as adhesive failure.

Optionally, the flow of thermally-conditioned fluid is controlled to maintain a temperature of the battery pack within a predetermined limit. Controlling the temperature provides protection for remaining cells in the pack. Advantageously the rest of the battery pack is reusable.

Optionally, applying the load to the first component comprises applying the load to a load attachment point extending from a first end of the first component to peel the first component away from the second component. This provides a way of transferring a single load to one or more cells of a cell subassembly. Advantageously multiple cells may be removed in a single operation. This method also initiates a peeling action which is a controlled way of removing a component from a battery pack. The method provides a separating force at an edge of the adhesive bond. Peeling loads are lowerthan the loads that induce a sudden detachment (cleavage) of the entire first component.

Optionally, the adhesive bond lies substantially within an adhesion plane between the first component and the second component, and wherein the load is applied to the load attachment point in a direction approximately perpendicular to the adhesion plane. Advantageously, applying load perpendicularly provides an efficient way of separating components with a lower load than if the load were applied obliquely or in the plane.

Optionally, the cavity is formed using an external jig applied to a surface of the battery pack. The cavity is only provided during servicing and is not part of the structure of the battery during battery use. This may simplify the battery design. It may also provide a cavity that is entirely external to the battery pack. Alternatively, the cavity is formed as a channel within the second component. This provides a simple means of providing a cavity since the channel may also form part of a structural section such as a box section or a part of an extrusion, i.e. the channel may be provided for the purposes of structural stiffness and also have a further use as the cavity of the invention. Advantageously a single component comprising a channel may be used for more than one purpose. Also, there is no need to manufacture a bespoke cavity if a cavity having a second purpose in the second component is used for receiving the thermally-conditioned fluid.

Alternatively, the battery pack comprises a third component arranged to be in thermal contact with the second component and the cavity is formed as a channel within the third component. This provides a simple means of using a channel as the cavity, since the channel may be provided within a structural section of the third component. The structural section may be a box section or a part of an extrusion that is in thermal contact with the second component. Advantageously the third component comprising a channel may be used for more than one purpose. Also, there is no need to manufacture a bespoke cavity for receiving the thermally-conditioned fluid if a cavity in a third component is used.

Optionally, the battery pack comprises a baseplate arranged to be in thermal contact with the second component and the cavity is formed as a channel within the baseplate. This provides a simple means of using a channel as the cavity, since the channel may be within a structural section of the baseplate, such as a box section or a part of an extrusion that is in thermal contact with the second component. Advantageously the baseplate comprising a channel may be used for more than one purpose. Also, there is no need to manufacture a bespoke cavity for receiving the thermally-conditioned fluid if a cavity in a baseplate is used.

Optionally, the thermally-conditioned fluid is flowed into the cavity via one or more entrance ports and out of the cavity via one or more exit ports. This provides a means of flowing fluid through the cavity. Advantageously the flow rate may be controlled by the size of the ports. Optionally the one or more entrance ports and/or one or more exit ports may be formed by drilling into the cavity.

Optionally, the thermally-conditioned fluid is a hot gas, such as hot air.

According to another aspect of the invention, there is provided a battery pack for containing electrical cells within a sealed internal volume of the battery pack, the battery pack comprising: a first component and a second component, the first component secured to the second component by an adhesive bond; and a battery plate, the battery plate arranged to be in thermal contact with the second component, wherein the battery plate comprises a cavity external to the sealed internal volume of the battery pack, such that a thermally-conditioned fluid may be flowed through the cavity of the battery plate to generate a temperature gradient between the first component and the second component for weakening the adhesive bond during servicing of the battery pack. In this way the entrance ports and/or exit ports may be drainage ports in a wet area. The wet area of a vehicle is known to be a dirty area and so, advantageously, is sealed from the internal regions of the vehicle and particularly those regions which contain sensitive components such as the internal volume of a battery pack. The cavity in a baseplate may be a wet area. Advantageously drilling ports into a cavity that is external to the sealed internal volume of the battery (such as a wet area cavity) will not allow swarf to enter the sensitive internal parts of the battery pack.

Optionally, the first component comprises a cell subassembly, the cell subassembly comprising: at least one electrical cell; a flexible cell carrier having a first side secured to each of the at least one electrical cell, and having a second side secured to the second component by the adhesive bond; and a load attachment point extending from a first end of the cell carrier, such that when a load is applied to the load attachment point the flexible cell carrier is peeled from the second component commencing at the first end.

The cell carrier provides flexibility of cell subassembly for peeling. Advantageously cell subassemblies may be removed easily from the battery pack.

Optionally, the battery pack further comprises drainage ports for draining the cavity in use, and the drainage ports are configured for flowing thermally-conditioned fluid therethrough during servicing of the battery pack. The entrance ports and/or exit ports may be drainage ports in a wet area. The wet area of a vehicle is known to be a dirty area and so, advantageously, is sealed from the internal regions of the vehicle and particularly those regions which contain sensitive components such as the internal volume of a battery pack. Advantageously drilling or enlarging ports into a cavity sealed from the internal volume of a battery pack will not allow swarf to enter the sensitive internal parts of the battery pack.

According to a further aspect of the invention, there is provided a vehicle comprising the battery pack.

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 any way 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 is a schematic view of components in a battery pack;

Figure 2 shows an example of the steps of a method of releasing a first component of a battery pack from the battery pack;

Figure 3 shows an example battery pack;

Figure 4 shows the battery pack of Figure 3 with the lid and electrical cells removed;

Figure 5 shows a schematic view of a vertical section through part of a battery pack;

Figure 6 shows a vertical section through part of a battery pack;

Figure 7 shows a detailed view of the components of Figure 6;

Figure 8 shows a cell carrier with a load attachment point; and

Figure 9 shows an example of a vehicle.

DETAILED DESCRIPTION

A battery pack 1 and a method of releasing a first component from the battery pack in accordance with an embodiment of the present invention is described herein with reference to the accompanying Figures.

Figure 1 illustrates a battery pack 1 comprising a first component 100 and a second component 200 adhered together by an adhesive bond 120. A cavity 300 is present within the second component 200. Alternatively, the cavity may be associated with other components of the battery pack 1 . The first component 100 and/or the second component 200 may each comprise a module of cells, an individual cell, a structural component, a lid, a plate, a cooling component, a busbar, a sensor, a circuit board, a valve, a pump or any other component or subassembly of the battery pack 1 . In this example, the first component 100 comprises a stack of cells and the second component 200 comprises a structural component. The first component 100 may comprise a subassembly of malfunctioning electrical cells which need to be replaced during servicing of the battery pack 1 .

The servicing of malfunctioning battery packs 1 requires adhesive bonds 120 to be de-bonded, perhaps by mechanically loosening or some other means. In Figure 1 the adhesive bond 120 is not readily accessible for mechanical loosening because it lies underneath the first component 100.

One method of de-bonding is the use of heat sensitive adhesives. However, such heat sensitive adhesives de-bond at temperatures within the operating range of the battery pack 1 (i.e. less than approximately 30 to 45°C depending on the cell chemistry employed for charge storage). Therefore, such heat sensitive adhesives would not be suitable since they would de-bond during normal vehicle use.

Another method of de-bonding is to use adhesives which de-bond at temperatures higher than the operating range of the battery pack 1 . However, heating electrical cells to a high temperature may chemically age the cells and so reduce their energy capacity. Providing heat into the internal volume of the battery pack 1 would heat many components other than those being serviced, including electrical cells within the internal volume. Heating of the internal volume may thus cause heat-damage to those electrical cells which are not being removed as part of the servicing operation. It is within this context that the following inventive method has been developed.

Figure 2 illustrates an effective method 1000 for releasing the first component 100 from the battery pack 1 . The method 1000 is useful when the first component 100 is secured to one or more second component 200 of the battery pack by an adhesive bond 120 and needs to be separated from the one or more second component 200.

In the first step 1100 a load L is applied to the first component 100 which is to be removed from the battery pack 1 , the load L being applied in a direction away from the second component 200.

In step 1200 a thermally-conditioned fluid is flowed through the cavity 300 of the battery pack 1 to generate a temperature gradient between the first component 100 and the second component 200 such that the adhesive bond 120 is weakened. A thermally-conditioned fluid is a fluid whose temperature has been controlled to be different to the temperature of the first component 100 and second component 200. For example the battery pack 1 may have previously been left to stabilise at room temperature so that the temperatures of the first component 100 and the second component 200 are the same. The thermally- conditioned fluid is either hotter or colder than the temperature of the first component 100 and the second component 200.

When either a hot fluid or a cold fluid is flowed through the cavity, a temperature differential is thus generated between the first component 100 and the second component 200 due to the difference in the thermal path between the cavity and the first component 100 and the second component 200. For example, the cavity may be in much closer thermal contact with the first component 100 than the second component 200. The temperature differential provides a temperature gradient between the first component 100 and the second component 200. It is desirable to change the temperature of the adhesive bond 120 quickly in order to achieve a temperature gradient across the adhesive bond 120. Heating the adhesive bond 120 slowly would result in a shallower temperature gradient. Thermally-conditioned gas is useful for rapidly generating a temperature gradient between the first component 100 and the second component 200 without unduly influencing the bulk temperature of the rest of the battery pack 1 .

The temperature gradient generates a differential thermal expansion of the first component 100, the adhesive bond 120 and the second component 200. The degree of differential thermal expansion depends on the thermal expansion coefficients of the materials used. Differential expansion gives rise to stress within the adhesive bond which leads to weakening of the adhesive bond and so results in adhesive failure. Adhesive failure is an interfacial bond failure between the adhesive and the substrate, that is between the adhesive and one or both of the first component 100 and second component 200.

When the thermally-conditioned fluid is a relatively hot fluid compared to the temperature of the first component 100 and the second component 200 then it not only provides the temperature gradient leading to adhesive failure between the first component 100 and the second component 200, but also leads to a heating of the adhesive bond 120. When the adhesive bond is heated this promotes a cohesive failure of the adhesive bond 120. Cohesive failure is a failure within the adhesive itself (otherwise known as adhesive splitting) leaving some adhesive on each of the first component 100 and second component 200. For the method to succeed in separating the first and second components the adhesive does not need to melt in the manner of a heat-sensitive adhesive, but only to weaken so that under the action of the applied load L a failure of the adhesive bond 120 occurs through adhesive failure, cohesive failure, or a combination of both adhesive failure and cohesive failure.

For this reason, the use of hot fluid as the thermally-conditioned fluid is preferred in some applications where the adhesive weakens with the application of heat, but the use of cold fluid may be preferred in other applications where a differential thermal expansion is required and where some of the components of the battery pack are more vulnerable to thermal-ageing effects at higher temperatures.

In some examples the flow of thermally-conditioned fluid is controlled so that a temperature of battery pack components is maintained within predetermined temperature limits. This may be achieved by control of the temperature and/or the flow rate of the fluid. By this means the total heat energy and power that flows into the cavity 300 is controlled, which ensures that the degree of heating or cooling of the components of the battery pack 1 is controlled. The likelihood of heat damage to components of the battery pack 1 is then reduced by limiting the upper temperature of the components of the battery pack 1. The temperature limit may be predetermined by experiment or by computer-modelling of heat flow within the battery pack 1 , or by some other estimation method. The temperature value that is being sensed is preferably a temperature of the components that are not being removed from the battery pack 1 , or a surrogate of such.

The thermally-conditioned fluid, as discussed, may be a hot fluid provided by a heating system which heats the fluid and also pumps it into the cavity 30. The heating system may be connected to a controller (not shown) which controls the temperature and/or flow rate of fluid. A temperature sensor is configured to measure a temperature of a component of the battery pack, and the output of the temperature sensor is connected to the controller so that the heating system is controlled according to the temperature measurement. The temperature sensor may be provided within the adhesive bond 120 or it may be associated with the cells, the cell stack or the cell module. The temperature sensor may be built into the battery pack 1 when manufactured or may be applied during a servicing operation on the battery pack 1 . The temperature sensor may be a thermistor, or other such temperature sensor know to the skilled person.

In an example, the hot fluid is hot air and the heating system is a heat gun and the control of the temperature is managed manually by the operator. An example temperature of the adhesive bond 120 at which separation occurs is 50°C, and an example adhesive is polyurethane. Other adhesives are useful such as mastic. Other separation temperatures may occur for other adhesives, such as mastic.

An example heat gun has a maximum power rating of 1800 watts, having three different temperature settings of 50°C, 300°C and 600°C, and three different flowrates of 200l/min, 350l/min and 500l/min. By controlling the flowrate and/or temperature the temperature is managed by the operator. Hot air is introduced to the cavity 300 through entrance ports and hot air leaves the cavity through exit ports. Other types of hot fluid may be a hot gas such as an inert gas or nitrogen, which may be used instead of hot air. In step 1300 the first component 100 is separated from the second component 200 under the action of the applied load L. The load L is applied at any location on the first component 100 and the load L is arranged so as to pull the first component 100 in a direction away from the second component 200 so that the first component 100 and second component 200 become separate. In some examples the application of the load L to a load attachment point 440 at a first end of the first component 100 facilitates a peeling action of the first component 100 away from the second component 200. It will be understood that the application of the load L in step 1100 continues throughout steps 1200, 1300 of the method 1000 until the first component 100 is separated from the second component 200. Step 1100 may occur before step 1200 as shown in Figure 2, in which case the separation of components occurs as the adhesive bond 120 is weakened. Alternatively step 1200 may precede step 1100.

The battery pack 1 has a large mass and so effectively resists the load L by gravity, but in some embodiments step 1100 may also include securing the battery pack 1 so as to resist the load L applied to the first component 100.

An example of a battery pack from a battery electric vehicle is shown in Figure 3, the battery pack 1 having a lid 2 on its upper surface. In Figure 4 the same battery pack 1 is shown with the lid 2 and a cell subassembly removed. The cell subassembly is a stack, or module, of electrical cells, and is an example of the first component 100 in the method 1000. As shown in Figure 4, the battery pack 1 includes a battery frame 4 comprising structural components 20a, 20b either side of a central bay 5 for receiving cells. Other bays for receiving cells 6 are shown either side of the central bay 5. In this example, the battery pack 1 includes five bays 5, 6 in total. However, it will be appreciated that in other examples the battery pack 1 may include any number of bays 5, 6 as appropriate for the desired energy capacity of the battery pack 1 .

Figure 5 shows a simplified schematic section of the bay 5 in the XZ plane, with a cell subassembly 10 assembled into the bay 5 and secured on its underside to the structural components 20a, 20b by an adhesive bond 12a, 12b. The cell subassembly 10 comprises a stack of prismatic rechargeable electrical cells. The structural components 20a, 20b are formed by extrusion and comprise internal cavities 22, 24. The adhesives 12a and 12b are not accessible for mechanical loosening because of the cell subassembly 10 itself blocking access to the adhesive bonds 12a, 12b. In this example, the adhesive bond 12a, 12b in the form of two strips of adhesive are an example of the adhesive bond 120 in the method 1000. The cell subassembly 10 is an example of the first component 100 and the structural components 20a, 20b are examples of the second component 200.

A battery plate 30 encloses the lower side of the frame 4 on the underside of the battery pack 1 . The battery plate 30 is formed of two metal plates glued together. The lower plate is termed the bashplate 34, and is suitable for protecting the battery from impacts arising from stones and debris underneath the vehicle. The upper plate is termed the baseplate 32 having a corrugated shape for stiffening the battery plate 30. Cavities 36a, 36b are formed between the baseplate 32 and bashplate 34. The two cavities 36a, 36b are isolated from each other by regions in which the baseplate 32 and bashplate 34 are glued together. A further cavity 38 is formed between the upper baseplate 32 and the cell subassembly 10. This cavity is a sealed internal volume of the battery pack 1 in which the electrical cells reside. Adhesives are used in the joining of the baseplate 32 to the structural components 20a, 20b. The cavity 36a, 36b in which the thermally-conditioned fluid flows is a cavity of the battery plate 30 in Figure 5. Other cavities of the battery pack 1 may be suitable provided they are in thermal communication with the adhesive bond to generate a temperature gradient across the adhesive bond 12a, 12b. In some examples the cavity is formed within the second component 20a, 20b, such as the cavities within the extrusion 22, 24. Flowing heated fluid in the cavities within the extrusion 22, 24 provides a more rapid heating effect of the adhesive bond 12a, 12b, but may also heat other components which may be less desirable depending on whether those components comprise parts which are temperature-sensitive. The cavities 36a, 36b of the battery plate 30 provide a particular benefit when used in the method 1000 for at least the reasons described as follows.

The cavities 36a, 36b of the battery plate 30 are suitable for use in the present arrangement because the cavities 36a, 36b are in good thermal contact with the structural components 20a, 20b, and thereby with the adhesive bonds 12a, 12b, but the cavities 36a, 36b of the battery plate 30 are not in good thermal contact with the cell subassembly 10, nor with other cells subassemblies within the battery pack 1 which are not being serviced or replaced. Hence the use of selected cavities 36a, 36b will not generate thermal-ageing of those electrical cells of the battery pack which are intended to be undamaged during the servicing operation.

Furthermore, the cavities 36a, 36b of the battery plate 30 are suitable for use in the present arrangement because they are sealed from the electrical cells such that thermally-conditioned fluid does not enter the sealed internal volume 38 which contains the electrical cells, including those cells which are not being removed and replaced during the servicing operation. The cavities 36a, 36b of the battery plate 30 are examples of wet area cavities, having drainage ports (holes) 39a, 39b in the bashplate 34 for drainage of moisture from the wet area cavity in use. Wet area cavities are those cavities which allow moisture to enter during vehicle use. For example, if the vehicle drives in water then moisture may enter the cavities 36a, 36b of the battery plate through the drainage ports 39a, 39b in the bashplate 34. Wet area cavities are useful cavities in which to flow thermally-conditioned fluid since they are not in continuity with the sealed internal volume 38 of the battery pack 1. A plurality of drainage ports 39a, 39b are available in each of the cavities 36a, 36b, and so one or more of the drainage ports 39a, 39b is used as an entrance port for flowing the thermally-conditioned fluid into the cavity 36a, 36b, and one or more of the drainage ports 39a, 39b is used as an exit port for flowing the thermally-conditioned fluid out of the cavity 36a, 36b. Entrance ports and/or exit ports may be drilled into any cavity used for flowing thermally-conditioned fluid. In order to provide a suitable flowrate of thermally-conditioned fluid additional entrance and/or exit ports may easily be drilled into the wet area cavities 36a, 36b without regard to machining swarf entering the sealed interior volume 38. Drainage ports may be configured for flowing thermally-conditioned fluid therethrough by forming the ports to a required size and/or by providing an adapter for connection of a heating system. If more drainage ports 39a, 39b are provided in the bashplate 34 than are required for the entry and/or exit of thermally-conditioned fluid, then excess drainage ports may be sealed.

Hence, the thermally-conditioned fluid is flowed through the wet area cavity of the battery pack 1 to generate a temperature gradient between the first component 100 and the second component 100 for weakening the adhesive bond 120 during servicing of the battery pack. In some embodiments of the method 1000 the cavity 300 is formed by a jig (not shown) applied to a surface of the battery pack 1 . An interior surface of the cavity 300 is formed by a portion of the surface of the battery pack 1 . Another interior surface of the cavity 300 is formed by a portion of the jig. In this case the cavity is only formed during the servicing operation and is not manufactured into the battery pack 1 and not present in the battery pack 1 during normal use.

Figure 6 shows a vertical section through part of a battery pack 1 . In this sectional view, the cell subassembly 10 can be seen to comprise both a cell 14 and a cell carrier 16. The cell carrier 16 is adhered to the structural component 20a.

Figure 7 shows the interface of the cell subassembly 10 and the structural component 20a with the adhesive bond 12a between the cell carrier 16 and the structural component 20a. The cell carrier 16 runs along the length of the cell subassembly 10.

In Figure 8 the cell carrier 16 can be seen to carry multiple cells 14, with the cells being secured to a first side (not shown) of the cell carrier 16. The adhesive bond 12a is applied between the structural component 20a and a second side (not shown) of the cell carrier 16 of the cell subassembly 10. Each of the cells 14 is adhered to the cell carrier 16. Suitable adhesives for adhering the cells 14 to the cell carrier 16 include epoxy, cyanoacrylate or resins. The cell carrier 16 comprises aluminium sheet formed into an L-shape as shown in the cross section of Figure 6. Other materials such as steel or plastics material are also useful. Other shapes for the cell carrier 16 are also useful, such as a flat plate or a box section. The cell carrier 16 may partially or fully enclose all the cells 14 of the cell subassembly 10.

In this example a first purpose of the cell carrier 16 is to provide a means of keeping a stack of cells together in a subassembly 10 during manufacturing of the battery pack 1 . A second purpose of the cell carrier 16 is to provide a means of keeping a stack of cells together in a subassembly 10 during releasing a cell subassembly 10 from a battery pack 1 .

In the example of Figure 8 the cell carrier 16 is flexible and the cells 14 are spaced apart along the length of the cell carrier 16. This spacing allows the cells 14 to expand during use, and also allows the cell subassembly 10 to flex as the cell carrier 16 flexes during separation of the cell subassembly 10 from the battery pack 1 . Figure 8 shows a lifting eye 42 at a load attachment point 44 at a first end 40 of the cell subassembly 10. In some examples the lifting eye 42 is fitted to the cell subassembly during the removal and servicing operation. In the example of Figure 8 the lifting eye 42 is already built-in to the structure of the cell subassembly 10 during manufacture of the battery pack 1. The lifting eye 42 is integral with the cell carrier 16 and extends beyond the end of the cells 14.

As described, in step 1300 the cell subassembly 10 is separated from the structural component 20a, 20b under the continuing action of the applied load L. The load L is applied by an overhead crane or hoist with the applied load being measured by an inline load cell. A non-conducting strap may be used to apply the load. As the first component separates and moves then the crane or hoist requires adjusting in order to maintain the tension at the required load L. Alternatively the load L may be applied by a weight acting over a pulley in which case the load L remains constant as the first component separates. In the example of Figure 8 the load is applied at the first end of the cell subassembly 10. The load attachment point 44 is configured with a slight bend upwards 46 in the direction of the applied load. This slight bend 46 assists in the initiation of a peeling action of the cell carrier 16 away from the structural component 20a as the load L is applied. Peeling is a useful means of separating the first component 100 from the second component 200. Peeling occurs gradually and in a more controlled manner than an instantaneous fracturing of the entire adhesive bond 12a with an associated rapid release of the first component 100. Peeling typically requires lower loads than an instantaneous fracture of the entire adhesive bond 12a. In Figure 8 the load L is provided at an edge of the adhesive bond 12a.

The lifting eye 42 can take any form such as a hook, captive nut or rivet, so long as it provides a means of attaching a load to the first component. Additional lifting eyes may be provided on the cell subassembly 10. In some examples there is a second lifting eye at a second end of the cell subassembly 10 which allows the cell subassembly 10 to be removed by application of loads at both ends simultaneously, or to be removed in two operations. In such examples the cell carrier 16 may be provided in two or more parts so that the cell subassembly 10 is removable in two or more sections. The load may be distributed along the length of the cell subassembly 10.

In the example of Figures 5, 6 and 7 the adhesive bond 120 lies in a plane between the first component 100 and the second component 200. It is preferable to apply the load L in a direction that is perpendicular to that plane so as to efficiently break the adhesive bond 120. It will be understood by the skilled person that an approximately perpendicular direction is also useful, such as within 10 or 20 degrees of perpendicular. In some examples the adhesive bond 120 between the first component 100 and second component 200 lies substantially or predominantly in a primary plane, with some of the adhesive bond 120 lying in a different plane, in which case it is still preferable to apply the load L in a direction that is perpendicular to the primary plane. In some examples the adhesive bond 120 is applied in two or more planes and it is useful to apply the load L at a compound angle that is not exactly perpendicular to either of the two or more planes of adhesive bond 120. For example, if the adhesive bond lies equally in two perpendicular planes then it may be useful to apply the load L at a mid-way angle between the two planes, such as 45°. The angle chosen depends on the relative extent of the two adhesive planes.

Figure 9 illustrates a vehicle 50 which comprises a battery pack 1 as described in the above examples.

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 . A method of releasing a first component of a battery pack from the battery pack, the first component secured to a second component of the battery pack by an adhesive bond, the method comprising: applying a load to the first component in a direction away from the second component; flowing a thermally-conditioned fluid through a cavity of the battery pack to generate a temperature gradient between the first component and the second component such that the adhesive bond is weakened; and separating the first component from the second component by means of the applied load.

2. A method according to claim 1 wherein the temperature of the thermally-conditioned fluid is higher than the temperature of the battery pack such that the temperature of the adhesive bond is raised as the fluid flows through the cavity.

3. A method according to any previous claim wherein the flow of thermally-conditioned fluid is controlled to maintain a temperature of the battery pack within a predetermined limit.

4. A method according to any previous claim wherein applying the load to the first component comprises: applying the load to a load attachment point extending from a first end of the first component 100 to peel the first component away from the second component.

5. A method according to claim 4 wherein the adhesive bond lies substantially within an adhesion plane between the first component and the second component, and wherein the load is applied to the load attachment point in a direction perpendicular to the adhesion plane.

6. A method according to any previous claim comprising forming the cavity using an external jig applied to a surface of the battery pack.

7. A method according to claim 1 to claim 5 wherein the cavity is formed within the second component.

8. A method according to any of claims 1 to claim 5 wherein the battery pack comprises a baseplate arranged to be in thermal contact with the second component and the cavity is formed within the baseplate.

9. A method according to any previous claim comprising flowing the thermally-conditioned fluid into the cavity via one or more entrance ports and out of the cavity via one or more exit ports.

10. A method according to claim 9 comprising forming the one or more entrance ports and/or one or more exit ports by drilling into the cavity.

11. A method according to any preceding claim, wherein the thermally-conditioned fluid is hot air.

12. A battery pack for containing electrical cells within a sealed internal volume of the battery pack, the battery pack comprising: a first component and a second component, the first component secured to the second component by an adhesive bond; and a battery plate, the battery plate arranged to be in thermal contact with the second component, wherein the battery plate comprises a cavity external to the sealed internal volume of the battery pack, such that a thermally-conditioned fluid may be flowed through the cavity of the battery pack to generate a temperature gradient between the first component and the second component for weakening the adhesive bond during servicing of the battery pack.

13. A battery pack according to claim 12 wherein the first component comprises a cell subassembly, the cell subassembly 10 comprising: at least one electrical cell; a flexible cell carrier having a first side secured to each of the at least one electrical cell, and having a second side secured to the second component by the adhesive bond; and a load attachment point extending from a first end of the cell carrier, such that when a load is applied to the load attachment point the flexible cell carrier is peeled from the second component commencing at the first end.

14. A battery pack according to claim 12 or claim 13 wherein the battery pack further comprises drainage ports for draining the cavity in use, and the drainage ports are configured for flowing thermally-conditioned fluid therethrough during servicing of the battery pack.

15. A vehicle comprising the battery pack of any of claims 12 to claim 14.