GB2594916A

GB2594916A - Battery module

Info

Publication number: GB2594916A
Application number: GB2003903.8A
Authority: GB
Inventors: Eswaran Vishnuprasad; Trojak Krzysztof; Kovaichelvan Deepak
Original assignee: Cummins Inc
Current assignee: Cummins Inc
Priority date: 2020-03-18
Filing date: 2020-03-18
Publication date: 2021-11-17
Also published as: CN214706154U; GB202003903D0; CN215008506U

Abstract

A battery module 12 for a battery pack (10, Figure 1) has stackable cells 24. Each cell is of one of two types, each type having a different configuration of electrical terminals. A battery module having stacked cells is held together by bands 28. A battery module formed of stacked cells has at least one hole (80, Figures 16-17) cooperating with a location pin (56, Figures 8, 14A-15 and 18) to restrict movement of the module in two directions and at least one slot (82, 83, Figures 16-17) cooperating with a location pin to restrict movement in one of the two directions and allow movement in the other. A clamping arrangement for clamping a module in a battery pack has a frame (20, Figure 1); a plurality of cross members (15, Figures 1, 8 and 9-13); and a clamping plate (52, Figures 8-11 and 13) attached to two adjacent cross members. A method of reconfiguring a battery module having stackable cells electrically connected in series and/or parallel using a busbar 42 involves changing a stack up order of the cells and/or the busbar. A method of assembling a battery module involves stacking cells, compressing the cells and fastening the stack using module bands.

Description

BATTERY MODULE

The present invention relates to a battery module for use in a battery pack, and in particular a battery module which is configurable and easily serviceable. The present invention also relates to techniques for retaining battery modules in a battery pack. The present invention has particular, but not exclusive, application in battery packs for use in mobile applications such as electric or hybrid electric vehicles, construction equipment, and so forth.

Electric vehicles and hybrid electric vehicles, such as cars, buses, vans and trucks, typically use battery packs that are designed with a high ampere-hour capacity in order to give power over sustained periods of time. A battery pack typically comprises a large number of individual electrochemical cells connected in series and parallel to achieve the total voltage and current requirements. To assist in manufacturing, assembly and servicing, the cells in a battery pack may be grouped into modules. The modules may include a support structure and a battery management unit to manage cell charge and discharge.

In order to help with packing efficiency, some known battery modules use pouch cells. Pouch cells provide energy dense electrical storage in the form of a relatively thin and generally flat pouch. Typically, a number of pouch cells are stacked together inside a support structure to form a battery module. The cells in the module are connected in series and parallel to achieve the target voltage. This is normally achieved by welding terminal blocks to the cell terminals and connecting busbars to the terminal blocks to achieve the required configuration.

In practice, it may be desirable to produce battery packs which can be used for a variety of different applications. Therefore it may be desirable to produce battery modules which can be reconfigured to achieve different target voltages.

However, existing battery modules are not easily reconfigurable to achieve different output voltages.

During use of the battery pack, it is possible for one of the cells to become damaged or otherwise compromised. In existing battery packs, this would typically require the whole module to be replaced. However, this may be inefficient in terms of cost and material usage.

Battery packs for electric vehicle applications tend to degrade during use and are typically designed for approximately ten years of life. When the battery packs no longer meet electric vehicle performance standards they may need to be replaced. However, the replaced battery packs may be reused in second life (typically stationary) applications. This can reduce the amount of waste and help reduce the cost of ownership.

Before reusing a battery pack in a second life application, it may need to be refurbished, as different cells may have degraded at different rates. However existing battery packs are not normally constructed with second use applications in mind. Thus, existing battery packs are not easy to reconfigure or refurbish for second life applications.

It would therefore be desirable to provide a battery module which is readily configurable to achieve different target voltages. It would also be desirable to provide a battery module which is easily serviceable, and which can be readily refurbished for second life uses.

In order to assist with servicing of the battery pack, the battery modules may be exchangeable. In this case it is necessary to ensure that the removable battery modules are adequately restrained within the battery pack. This may be achieved using some form of clamping arrangement.

When using exchangeable battery modules, the battery modules themselves typically do not contribute to the structure of the battery pack. As a consequence, it may be necessary to provide the battery pack with structural features to ensure that it has sufficient overall strength. These (and other) requirements can make it difficult to achieve a high energy density pack with regards to total pack volume and mass of the pack, which are critical parameters in mobile battery pack applications.

Therefore, it would also be desirable to provide battery module assemblies which can help to ensure structural rigidity and module constraint and/or help to reduce battery pack volume and weight.

According to one aspect of the present invention there is provided a battery module for a battery pack, the battery module comprising a plurality of stackable battery cell units, wherein each battery cell unit is of one of two types, each type having a different configuration of electrical terminals.

The present invention may provide the advantage that, by arranging the battery cell units to be one of two types, each type having a different configuration of electrical terminals, reconfiguration of the battery module may be facilitated. In particular, it may be possible to reconfigure the battery pack to achieve a different series and/or parallel configuration of the battery cells. This may be achieved for example by changing the order of battery cell units in the battery pack, and/or changing a busbar used to connect the battery cell units.

The electrical terminals are preferably terminals which are used to connect the battery cell units to other components such as a busbar.

Preferably the electrical terminals of one type of battery cell unit are in a different position on the battery cell unit from the electrical terminals of the other type. This may help with reconfiguration of the battery module.

For example, each battery cell unit may comprise positive and negative terminals, and the positive and negative terminals of one type of battery cell unit may be on opposite sides of the battery cell unit to the positive and negative terminals of the other type. Thus, the positive terminal of one type of battery cell unit may be on the same side of the battery cell unit as the negative terminal of the other type of battery cell unit, and vice versa.

Alternatively or in addition, the electrical terminals of one type of battery cell unit may be displaced from an edge of the battery cell unit by a different amount than the electrical terminals of the other type. Thus, the terminals of one type may be closer to the edge of the battery cell unit that the terminals of the other type. This may help to ensure that, when two battery cell units of different types are stacked adjacent to each other, there is sufficient electrical separation between the negative terminals and the positive terminals of the respective battery cell units.

Preferably each battery cell unit comprises a pouch cell and a cell tray. Use of pouch cells may help to provide energy dense electrical storage.

Preferably the cell tray comprises a cell frame which surrounds an edge of the pouch cell. This may help to support the pouch cell, while minimising weight.

Furthermore, where pressure is applied to the pouch cell through compression foam, the use of a cell frame which surrounds an edge of the pouch cell may help to ensure that the pressure is applied evenly to all of the pouch cells in the stack, and may help to prevent over compression of the foam. This in turn may help to extend the life of the pouch cells.

Each battery cell unit may further comprise a cell cover arranged to clamp the pouch cell. Thus, the pouch cell may be clamped between the cell frame and the cell cover. This may facilitate assembly, and may also allow the battery cell unit to be readily disassembled. Preferably the cell cover is provided along one edge of the battery cell unit (for example the same edge as the electrical terminals), although other arrangements are also possible.

The battery cell units are preferably arranged such that they can be disassembled. For example, the battery cell unit may be disassembled by separating the cell frame from the cell cover. This may allow parts of the battery cell unit to be easily replaced. For example, if an individual pouch cell has failed, then it may be possible to replace that pouch cell without requiring the whole module to be replaced.

The electrical terminals may comprise terminal blocks, which may be used to connect the battery cell units in the required series and/or parallel configuration, for example using a busbar. The terminal blocks are preferably attached to the electrical terminals of the pouch cell for example by welding. Where the battery cell unit comprises a cell cover, then the cell cover may be arranged to clamp the terminal blocks between the cell cover and the cell tray. This may facilitate assembly of the two different types of battery cell unit.

The terminal blocks of one type of battery cell unit may be different from the terminal blocks of the other type of batter cell unit. For example, the terminal blocks of one type of battery cell unit may have their electrical terminals in different positions on the battery cell unit from the terminal blocks of the other type. Thus, even when the pouch cells have their electrical terminals in the same positions, it may be possible for the battery cell units of different types to have their electrical terminals in different positions.

Preferably the terminal blocks comprise holes for removably connecting electrical connectors such as busbars. The holes may be threaded in order to receive threaded pins. This may facilitate connection and/or reconfiguration of the battery module.

The battery module may further comprise a busbar unit for electrically connecting the plurality of battery cells. The busbar unit may comprise a plurality of busbars. The busbars may be, for example, laminated between layers of insulating sheets.

This may facilitate connection of the battery module in the required series and/or parallel configuration. Furthermore, reconfiguration of the battery module may be easily achieved by changing the busbar unit and/or the stack-up order of the battery cell units.

Preferably the busbar unit is replaceable in order to reconfigure the battery module. Thus, the battery module may be reconfigured by replacing the busbar unit with a different busbar unit having a different configuration of busbars, in order to reconfigure the electrical connections of the battery cells.

Thus it will be appreciated that the plurality of battery cell units may be connected in series and/or parallel using a busbar unit, and the module may be arranged such that the series and/or parallel connections can be changed by changing a stack-up order of the battery cell units and/or the busbar. This may allow easier reconfiguration of the battery module than previous arrangements, which typically involved disconnecting and reconnecting welded joints.

The battery cell units are preferably arranged such that they can only be stacked in one orientation. For example, each battery cell unit may comprise a location feature such as a protrusion on one side and a recess on the other side, with a protrusion on one side being arranged to engage with a corresponding recess in an adjacent battery cell unit. This may help to ensure that the battery cell units can only be stacked in the correct orientation, which help to ensure that only the correct electrical connections can be made.

The battery cell module may comprise a stack of battery cell units and at least one end plate. Preferably two end plates are provided, one at each end of the stack of battery cell units. The end plates may act as a structural support, to help retain the size and shape of the battery module. Furthermore, the end plates may be used to apply pressure to the pouch cells in the battery cell units.

The battery module may further comprise an expansion pad between each of the battery cell units. The expansion pad may be for example a layer of compressible foam. This may help to ensure that, when the battery module is compressed, a suitable pressure is applied to the cells. This may help to extend the life of the cells.

Preferably the battery module is held together by module bands. For example, where the battery cell module comprises a stack of battery cell units and two end plates, the module bands may pass around each end plate. This may help to keep the stack of battery cell units and the end plates in the desired shape, while at the same time minimising the size and weight of the battery module.

The module bands may be made from a metal such as steel or any other appropriate material such as fibre or plastic based materials. The module bands may be provided as strips which are wrapped around the module while it is under compression. The ends of the strips may then be fastened together, for example by crimping or any other suitable fastening method.

An advantage of using such module bands is that the module can be easily assembled. For example, the module can be assembled by stacking together the battery cell units, adding the end plates to the stack, compressing the stack, and then adding the module bands while the stack is under compression. This may also provide the advantage that the module band can keep the stack of battery cell units in compression, which may help to ensure that a suitable pressure is applied to the cells. Furthermore, it may be easy to reconfigure the battery module by removing the module bands. Once the module has been reconfigured, it may be compressed and new module bands added.

This aspect of the invention may also be provided independently. Thus, according to another aspect of the invention there is provided a battery module for a battery pack, the battery module comprising a plurality of stacked battery cell units, wherein the battery module is held together by module bands.

Preferably the module bands apply a compressive force to the battery module.

For example, the module bands may be under tension. This may help to maintain the size and shape of the module, and may compress a foam expansion pad between the cells to ensure that a suitable pressure is applied to the cells.

When the battery modules are assembled in the battery pack, it is necessary to ensure that they are properly located and that they are constrained. However, expansion of the cells during use and tolerance build up may make this difficult to achieve.

In a preferred embodiment, the battery module comprises features which are arranged to locate the battery module and to restrict its movement. For example, the battery module may comprise a plurality of apertures which are arranged to receive location pins. Where the battery module comprises a stack of battery cell units and two end plates, the apertures may be provided in the end plates. This may avoid the need to provide location features in other parts of the battery module, and thus may help to provide a compact and lightweight module.

The apertures may comprise at least one hole which is arranged to cooperate with a location pin to restrict movement of the module in two (perpendicular) directions. The apertures may further comprise at least one slot which is arranged to cooperate with a location pin to restrict movement in one of the two directions and to allow movement in the other direction. This may allow for some tolerance in the battery module, for example due to slight variations in the stack of battery cell units. Furthermore, this may allow for some expansion or reduction in the size of the module during use, for example due to expansion of the pouch cells.

According to another aspect of the invention there is provided a battery module for a battery pack, the battery module comprising a plurality of stacked battery cell units, the battery module further comprising at least one hole arranged to cooperate with a location pin to restrict movement of the module in two directions and at least one slot arranged to cooperate with a location pin to restrict movement in one of the two directions and to allow movement in the other direction.

The battery module may also comprise a pad for engagement with a support pin. This may help to ensure that the module is correctly positioned in a vertical direction, while allowing for some tolerance or expansion in horizontal directions.

The above arrangements may help to ensure more accurate positioning of the module than would otherwise be the case. Accurate module positioning may help to ensure uniform pressure on the cooling system, reducing the risk of pressure drop, and may help to achieve better flexibility in module placement.

The battery module may be arranged for use with a clamping arrangement for clamping the battery module. In one embodiment, the clamping arrangement comprises means for applying a clamping force to the battery module, preferably such that the battery module maintains contact with a cooling system, and support means for supporting the battery module, the support means comprising a compression stop. This may allow the battery module to maintain thermal contact with the cooling system, while ensuring that any additional forces are transferred through the support means rather than through the cooling system. The compression stop may be for example in the form of a shoulder on a location pin.

In one embodiment, the battery pack comprises a frame and a plurality of cross members. The cross members may be provided on either side of the battery module, or a row of battery modules. In this case, the clamping arrangement may comprise a clamping plate attached to two adjacent cross members (preferably cross members on either side of the battery module). The clamping plate may be arranged to apply the clamping force to the battery module. This may help to ensure that an even pressure is applied to the battery module, helping to ensure even contact with the cooling system. Furthermore, by attaching the module clamping plate to adjacent cross members, the structural rigidity of the battery pack may be improved.

According to another aspect of the invention there is provided a clamping arrangement for clamping a battery module in a battery pack, the battery pack comprising a frame and a plurality of cross members, the clamping arrangement comprising a clamping plate attached to two adjacent cross members.

This aspect of the invention may provide the advantage that the clamping plate can apply an even pressure to the battery module, helping to ensure even thermal contact with a cooling system. Furthermore, by attaching the module clamping plate to adjacent cross members, the structural rigidity of the battery pack may be improved. This may allow the battery pack to have a lower weight than would otherwise be the case. Module clamps that do not connect cross-members will not contribute to the pack rigidity as much as this design.

A gap may be provided between the clamping plate and the cross members. This may help to ensure that the clamping plate is able to provide the required clamping force.

The clamping plate may be arranged to apply a clamping force to the battery module such that the battery module maintains thermal contact with the cooling system.

Preferably means are provided for providing a counter force to the cooling system. The means for providing a counter force may be, for example, compression foam, or any other suitable elastic material. For example, in one embodiment, a counter clamping part includes a layer of foam on the opposite side of the cooling system to the battery module. In this case, the size, type and/or compression curve of the foam may be selected, together with other parameters of the clamping arrangement, to provide the required counter force to ensure that thermal contact is maintained between the battery module and the cooling system.

The counter force is preferably less than the clamping force applied to the battery module. This may help to ensure that the battery module maintains contact with the cooling system and with the compression stop. This in turn may help to ensure that dynamic loads are passed through the support means rather than the cooling system.

The clamping arrangement may further comprise support means for supporting the battery module. The support means may comprise a compression stop. For example, the clamping arrangement may comprise a plurality of pins, which may include a plurality of location pins arranged to locate and to support the battery module. The location pins may have a shoulder which may act as the compression stop.

Corresponding method aspects may also be provided. Thus, according to another aspect of the invention, there is provided a method of reconfiguring a battery module comprising a plurality of stackable battery cell units electrically connected in series and/or parallel using a busbar, the method comprising changing a stack-up order of the battery cell units and/or the busbar.

According to another aspect of the invention, there is provided a method of assembling a battery module, the method comprising stacking a plurality of stackable battery cell units, compressing the battery cell units, and fastening the stack of battery cell units with module bands.

According to a further aspect of the invention there is provided a method of clamping a battery module in a battery pack, the battery pack comprising a frame and a plurality of cross members, the method comprising attaching a clamping plate to two adjacent cross members so as to provide a clamping force to the battery module.

Features of one aspect of the invention may be used with any other aspect. Any of the apparatus features may be provided as method features and vice versa.

Further details of the battery pack, battery module and clamping arrangement may be, for example, as disclosed in co-pending UK patent applications entitled "Battery Module Clamping Arrangement", 'Battery Antipropagation Techniques" and "Battery Pack' in the name of the present applicant, the subject matter of each of which is incorporated herein by reference.

Preferred features of the present invention will now be described, purely by way of example, with reference to the accompanying drawings, in which: Figure 1 shows an overview of a battery pack; Figure 2 shows parts of a battery module; Figure 3 is an exploded view of a battery module; Figure 4 shows parts of a battery cell unit in more detail; Figures 5(A) and 5(B) show examples of battery cell units having two different configurations; Figure 6 shows part of a battery module with a plurality of battery cell units stacked together; Figure 7 shows how a battery module can be connected using a laminated busbar; Figure 8 illustrates the basic principles of a module clamping assembly in an embodiment of the invention; Figure 9 shows an example of a module clamp plate; Figure 10 is a cross section through part of the module clamping assembly; Figure 11 shows parts of the clamping assembly in more detail; Figure 12 shows examples of cross members which may be used with a battery pack; Figure 13 shows parts of a battery pack with modules and module clamps in place; Figures 14(A) and 14(B) show examples of a location pin and a support pin; Figure 15 shows schematically positions of the location pins and the support pin relative to a battery module; Figure 16 shows schematically holes in the bottom of the module to receive location pins; Figure 17 shows the bottom of the battery module; and Figure 18 shows schematically part of the clamping arrangement.

Battery pack Figure 1 shows a battery pack of a type with which embodiments of the invention may be used. The battery pack of Figure 1 is designed to be used with electric and hybrid vehicles, particularly in high horsepower applications as buses, trucks, vans, construction equipment, and so forth. However, the principles of the present invention may be applied to any type of battery pack for use in any suitable application.

Referring to Figure 1, the battery pack 10 comprises a plurality of battery modules 12, a plurality of cooling plates 14, cross members 15, a battery management system 16, a module retainer 18, a surround frame 20, a top panel 21 and a bottom panel 22. In this example, fifteen battery modules 12 are provided in five rows of three modules. Each row of three battery modules 12 is located on a corresponding cooling plate 14. The cooling plates 14 are hollow to allow the flow of coolant. Cross members 15 are provided between rows of battery modules. The battery management system 16 is located at one end of the battery pack. In the assembled state, the cross members 15 are attached to the surround frame 20 and span the frame from one side to the other. The top panel 21 and the bottom panel 22 are attached to the top and bottom respectively of the frame 20 and the cross members 15. The battery modules 12, cooling plates 14, battery management system 16 and retainer 18 are housed inside the frame 20 and panels 21, 22. The module retainer 18 is used to hold the battery modules 12 and other components in place.

As will be discussed below, embodiments of the invention relate to battery module assemblies which are configurable, readily serviceable, and which help to ensure structural rigidity and module constraint.

Battery module Figure 2 shows parts of a battery module in an embodiment of the present invention. Referring to Figure 2, in this example the battery module 12 comprises twenty-four battery cell units 24 stacked together side by side. The battery cell units 24 are electrically connected in series and/or parallel to achieve the target pack voltage. End plates 26 are provided on each side of the module. The battery cell units 24 and end plates 26 are held together by steel bands 28. A removable cover 30 is provided at one end of the module. A battery management unit is integrated with the module 12 to monitor and manage cell charge and other aspects of cell operation.

Figure 3 is an exploded view of a battery module. Referring to Figure 3, the battery module 12 is formed by stacking together a plurality of battery cell units 24. A compression foam expansion pad 36 is provided between adjacent cell units. Each of the battery cell units 24 is in the form of a pouch cell 32 held within a cell tray 34. In this example the cell trays 34 are made from a plastic polymer material such as a thermoplastic. Each of the battery cell units 24 includes electrical terminal blocks 38, which are used to make electrical connections to the pouch cell 32. Each of the battery cell units 24 also has a cooling sheet 40 which is used to conduct heat away from the pouch cell 32. The cooling sheets 40 are provided on the rear sides of the cells in Figure 3. Each of the cooling sheets includes tabs 41 which extend around the bottom of the cells. The tabs 41 are designed to contact cooling plates in order to conduct heat away from the cells. The cooling sheets 40 are made from a thermally conductive material such as aluminium or graphite. A thermally conductive electrically insulative film is provided on the cooling sheets.

In the arrangement of Figure 3, a laminated busbar 42 is used to electrically connect the various cell units 24. The laminated busbar 42 is connected to the cell units 24 by means of electrically conducting pins 44. The pins 44 pass through holes in the busbar 42 and into corresponding holes in the terminal blocks 38 of the cell units in order to provide electrical and mechanical connections between the two. The laminated busbar 42 includes electrical conductors which connect the battery cell units 24 in the required series and/or parallel connections to achieve the target voltage. The laminated busbar 42 also connects to positive and negative terminals 45 which provide electrical connections to and from the battery module.

Also shown in Figure 3 is a unified battery management unit 46. The battery management unit 46 is used to monitor and manage cell charge and other aspects of cell operation. The battery management unit 46 is provided on a circuit board, which is mounted on the laminated busbar 42 via an electrically insulating barrier plate 48. A plurality of temperature sensors and voltage sensors are provided on the laminated busbar 42, and are used by the battery management unit 46 to monitor cell temperature and voltage. The battery management unit 46 is protected by removable cover 30. The removable cover is made from a plastic polymer material such as a thermoplastic.

In order to assemble the battery module, the various battery cell units 24 (comprising pouch cell 32, cell tray 34, terminal blocks 38, cooling plate 40, and cell cover 50) are stacked together with a thermally conductive foam expansion pad 36 between each adjacent cell unit. The cell trays include location features such that the cell units can only be stacked in one orientation. The end plates 26 are then added to each side of the stack of cell units. The stack of cell units is then compressed to the required pressure. This ensures that the foam expansion pads 36 provide the required pressure to each of the pouch cells 32. The steel bands 28 are placed around the stack of cells as it is held under pressure. The ends of the steel bands are then crimped together. Thus, the steel bands ensure that the required pressure is maintained against the cells in the module, as well as maintaining the size and shape of the battery module.

Configurability The target voltage of a battery module and/or battery pack may vary depending on the application. However, existing battery modules tend to be produced with a single target voltage. Typically, a battery module has busbars which are welded to the cells in the module. It has been found that such battery modules can be difficult to reconfigure to achieve different output voltages.

In embodiments of the present invention, the battery modules are designed to allow the series/parallel connections of the module to be varied. This can allow the target output voltage of the module to be varied, to achieve a target battery pack voltage.

Figure 4 shows parts of a battery cell unit in more detail. Referring to Figure 4, the battery cell unit 24 comprises pouch cell 32, cell tray 34, terminal blocks 38, cooling sheet 40, and cell cover 50. The pouch cell 32 is an electrochemical cell (typically lithium-ion) provided in a pouch. Such pouch cells are commercially available and therefore not described further. The terminal blocks 38 are made from an electrically conductive material such as copper and are used to make the electrical connections to the pouch cell 32. The terminal blocks 38 are welded to the cell terminals 37, for example using ultrasonic welding. The cell tray 34 frames the cell pouch 32 and is used to hold the pouch cell in place. The cell tray 34 is made from a plastic polymer material such as a thermoplastic. The cooling sheet 40 attaches to the cell tray 34 so as to contact the pouch cell 32. The cooling sheet 40 is made from a thermally conductive material such as aluminium or graphite. Where the cooling sheet is made from a metallic material, it may be coated with a high voltage isolating film. The cooling sheets 40 include tabs 41 which extend around the bottom of the cell tray 34. The tabs 41 are designed to contact cooling plates in order to conduct heat away from the cells. The cell cover 50 attaches to the cell tray 34 such that the terminal blocks 38 and the top of the pouch cell 32 are clamped between the cell cover and the cell tray. The cell cover may be attached to the cell tray 34 using heat staking, although other techniques such as plastic rivets could be used instead.

In embodiments of the invention, two different types of battery cell units 24 are provided. In a first type, the positive and negative terminals of the cell units are arranged in a first configuration, and in a second type, the positive and negative terminals of the cells are arranged in a second configuration.

Figures 5(A) and 5(B) show examples of battery cell units 24 having two different configurations. In each case, the terminal blocks 38 are provided on the top of the pouch cell 32, sandwiched between the cell tray 34 and the cell cover 50, and are attached to the terminals of the pouch cell 32. However, the battery cell units of Figures 5(A) and 5(B) differ in that the positive and negative terminals are on the opposite sides of the cell. Thus, in the arrangement of Figure 5(A), the battery cell unit 24 has its positive terminal on the left-hand side of the cell and its negative terminal on the right-hand side of the cell. On the other hand, in the arrangement of Figure 5(B), the battery cell unit 24' has its negative terminal on the left-hand side and its positive terminal on the right-hand side.

In addition, in the arrangements of Figures 5(A) and 5(B), the two battery cell units have different types of terminal block. The two types differ in the position of the electrical contact which is presented for connection to the laminated busbar.

In the first type of cell unit as shown in Figure 5(A), the terminals blocks 38 have an electrical terminal 39 which is towards the outwards edge of the cell unit. On the other hand, in the second type of cell unit as shown in Figure 5(B), the terminals blocks 38' have an electrical terminal 39' which is closer to the centre of the cell unit than is the case for the first type. If desired, the cell trays 34 may have different colours or be otherwise marked to indicate which configuration of electrical terminals they have.

Figure 6 shows part of a battery module, with a plurality of battery cell units of each of the two configurations stacked together. Referring to Figure 6, it can be seen that the electrical terminals of the cells are arranged in a total of four rows.

In Figure 6, from the top down: the first row comprises the positive terminals of the first type of battery cell unit 24; the second row comprises the negative terminals of the second type of battery cell unit 24'; the third row comprises the negative terminals of the second type of battery cell unit 24'; and the fourth row comprises the negative terminals of the first type of battery cell unit 24. By providing the electrical terminals of the second type of cells more towards the centre than the electrical terminals of the second type of cells, sufficient electrical separation between the various positive and negative terminals is maintained.

The battery cell units also include location features 51 which ensure that they can only be stacked in one orientation. In particular, each battery cell unit comprises a protrusion on one side and a recess on the other side, with a protrusion on one side being arranged to engage with a corresponding recess in an adjacent cell unit. This ensures that the units cannot be misconnected.

An advantage of the arrangement described above is that it is easy to connect the various battery cells in the required series and parallel configuration. For example, two adjacent cell units of the same type can easily be connected in parallel, since their positive and negative terminals are both adjacent to each other. Furthermore, two (or more) adjacent cell units of the opposite type can easily be connected in series, since the positive terminals of the first type are adjacent to the negative terminals of the second type, and vice versa.

Figure 7 shows in more detail how the cells in a battery module are connected using a laminated busbar. Referring to Figure 7, the laminated busbar 42 is connected to the cell units 24 by means of electrically conducting pins 44. The pins pass through holes in the busbar 42, and into corresponding holes in the terminal blocks of the cell units. The ends of the pins are threaded and engage with threads in the holes in the terminal blocks.

The laminated busbar of Figure 7 includes a plurality of busbars held between plastic sheets. In the example of Figure 7, the busbars are arranged to connect two adjacent battery cell units of the same type in parallel. The busbar is also arranged to connect the various (parallel connected) pairs of cell units in series, by connecting the positive terminals of one pair to the negative terminals of an adjacent pair, the negative terminals of that pair to the positive terminals of the next pair, and so forth through the module. Thus, in effect the pairs of cell units are connected in a zigzag through the module. The module terminals are at each end of the busbar.

The arrangement described allows the modules to be readily reconfigured to achieve different voltage and/or capacity requirements. For example, if it is desired to connect all cells in series to increase the module voltage, then this can be achieved by alternating single ones of each type of cell unit. On the other hand, if it is desired to decrease the voltage (and increase capacity) then three or more of the same type of cell unit could be provided adjacent to each other and connected in parallel. Thus, for example, the module could be connected with twenty-four cells in series; with the cells of a pair in parallel and twelve pairs in series; with groups of three cells in parallel and eight groups in series; and so forth. In each case, the laminated busbar is changed to achieve the appropriate connections between the cells.

Thus, it will be appreciated that the modules can be easily reconfigured by changing the stack up order of the battery cell units and the laminated busbar design.

Serviceability During use of the battery pack, it is possible for one of the cells to become damaged or otherwise compromised. Furthermore, battery packs for electric vehicle applications tend to degrade during use and are typically designed for approximately ten years of life. When the battery packs no longer meet electric vehicle performance standards, which typically include maintaining 80% of total usable capacity, they may need to be replaced. However, the battery packs may still be usable in second life applications, where the battery pack typically remains stationary.

With the modular design described above, it is possible to service the module up to the cell level. Thus for example an individual cell which has become compromised can be replaced without needing to replace the entire module.

Furthermore, the modular design described above can make it easier to repurpose the module for second life use. Thus, once the module no longer meets electric vehicle performance standards, it can easily be broken down to the cell level. This can be achieved simply by removing the metal band. The cells can then be reassembled for use in other (normally stationary) electrical storage applications. This can reduce the amount of waste material and help reduce the cost of ownership.

Module band The module design described above uses module bands and endplates to fulfil the structural rigidity requirements and to provide the required pressure for the cells, while helping to minimise the size and weight of the module.

The primary function of the module bands is to retain the shape and size of the module and to compress the foam expansion pads to the desired pressure. Applying external pressure to the cells in this way can have a significant benefit on the operation of the cells. In particular, the application of pressure may provide an increase in cell capacity, and a decrease in the discharge ohmic resistance.

The module bands also allow the module to be easily disassembled for servicing or repurposing the battery cells. A disassembled module can be easily reassembled by applying new metal bands.

In a preferred embodiment the module bands are made of a metal such as steel. However other materials, such as plastic or fibre-based materials could be used instead.

Module clamping When the battery modules are assembled in the battery pack, it is necessary to ensure that they are properly retained and that optimal contact with the cooling plate is maintained.

In embodiments of the invention, module clamp plates are used to secure the battery modules in the battery pack. The module clamp plates are attached to battery pack cross members, which run across the width of the surround frame 20 shown in Figure 1. The module clamp plates also connect adjacent cross members to increase the rigidity of the structure. The module clamp plates utilise a designed-in gap between the cross-members and module clamps to apply the required compressive force through support foams for optimal thermal contact of the module cooling sheets with the cooling plate. Epoxy coating may be used for electrical isolation of the module clamp plates from the modules.

Figure 8 illustrates the basic principles of the module clamping assembly. Referring to Figure 8, the clamping assembly comprises module clamp plate 52, battery pack cross members 15, gap pad 54, location pins 56, cooling plate 14, cooling plate support foam 58, and battery pack bottom panel 22. Also shown in Figure 8 are the battery module 12, and the battery pack top panel 21.

In the arrangement of Figure 8, the module clamp plate 52 is connected on each side to a battery pack cross member 15. This applies downward pressure to the battery module 12. Some of this downward pressure is applied from the battery module 12, through the gap pad 54 to the top of the cooling plate 14. Counter pressure is applied from the bottom panel 22 through the support foam 58 to the bottom on the cooling plate. The battery module 12 is located on location pins 56. The location pins 56 are connected to the bottom panel 22 and pass through holes in the cooling plate 14. The tops of the location pins 56 engage with holes in the bottom of the battery module 12. The location pins include shoulders which act as a compression stop. This limits the load which is applied to the cooling plate. The rest of the load is applied through the location pins 58 to the bottom panel 22.

Figure 9 shows an example of a module clamp plate in an embodiment of the invention. Referring to Figure 9, the clamp plate 52 is substantially flat, and has dimensions slightly larger than those of the top of the battery module 12. Slots 60 are provided in the clamp plate to allow air flow and to reduce the weight. The clamp plate includes holes 62, 63 which allow the clamp plate to be connected to the battery pack cross members. In this example the clamp plate 52 is made from a metal with a high strength to weight ratio, such as an aluminium alloy. An epoxy coating is applied for electrical isolation.

Figure 10 is a cross section through part of the module clamping assembly, showing how the module clamp plates are connected to the cross members.

Referring to Figure 10, the module clamp plates 52 are attached to the cross members 15 via module clamp bushes 64. The module clamp plates 52 are attached to module clamp bushes 64 using bolts 65. The module clamp bushes 64 are attached to the cross members 15 using bolts 66, which pass through holes in the bushes 64 and into threaded holes at the top of the cross members 15. Figure 11 shows parts of the clamping assembly around the clamping bush in more detail.

In the arrangement of Figures 10 and 11. the dimensions of the module and the module clamping assembly are such that a small gap 68 is left between the bushes 64 and the cross members 15. This small gap ensures that the clamping plates 52 can apply downward pressure to the modules 12. The amount of downward pressure can be reconfigured by adjusting the machined height of the cross members 15. During assembly, the required pressure can be achieved by tightening the bolts to the required torque.

Figures 12(A) and 12(B) show in more detail two types of cross members which may be used in a battery pack such as that shown in Figure 1. Referring to Figures 12, the cross members 15, 15' are of a generally open construction, and are designed to provide rigidity to the surround frame 20 while minimising weight.

The cross members include bolt holes for connecting the cross member to the surround frame, and bolt holes for connecting battery panels to the cross members. The cross members also include mounting points for the bushes 64 shown in Figures 10 and 11.

Figure 13 shows parts of a battery pack with the modules and module clamps in place. Referring to Figure 13, a module clamp plate 52 is placed over each of the battery modules 12 and attached to the cross members 15 in the way described above.

The clamping arrangement described above can allow uniform pressure to be applied through the battery module 12 to the cooling plate 14. This can help to ensure uniform cooling of the battery cells within the module, which may help to prolong the life of the module. In addition, it has been found that by connecting the battery pack cross members 15 using the module clamp plates 52 the structural stiffness of the battery pack may be improved. In particular, connecting the cross members may improve the torsional stiffness of the battery pack, which may help to prevent twisting of the battery pack in use.

A gap is designed into the clamping arrangement between the module clamping plate and the cross members in order to apply compressive force to ensure thermal contact pressure between the module and the cooling plate.

Module constraint When the battery modules are assembled in the battery pack, it is necessary to ensure that they are properly located, that they are constrained and that optimal contact with the cooling plate is maintained. However, expansion of the cells during use and tolerance build up may make this difficult to achieve.

Referring back to Figure 8, the clamping assembly includes location pins 56, which are used to locate the battery module in the battery pack. The location pins 56 are attached to the bottom panel 22 and pass through holes in the cooling plate 14. The tops of the location pins 56 engage with holes in the bottom of the battery module 14.

In one embodiment, three location pins and one support pin are used to locate and support each module. Figures 14(A) and 14(3) show respectively an example of a location pin and a support pin.

Referring to Figure 14(A), the location pin 56 comprises a base portion 70, a pin portion 72, and a shoulder 74. The bottom of the base portion 70 is designed to fit into a shallow hole in the battery pack bottom panel 22. The top of the base portion 70 is designed to pass through a hole in the battery pack cooling plate 14.

The pin portion 72 is designed to fit into a hole or slot in the battery module 12.

The hole or slot in the battery module is sized such that the battery module sits on the shoulder 74 of the location pin.

Referring to Figure 14(3), the support pin 76 comprises base portion 78 and pin portion 80. The bottom of the base portion 78 is designed to fit into a shallow hole in the battery pack bottom panel 22. The top of the pin portion 80 is at approximately the same height (relative to the bottom panel 22) as the shoulder 74 of the location pin 56.

Figure 15 shows schematically the positions of the location pins and the support pin relative to a battery module. Referring to Figure 15, each location pin 56 is located at one of three corners of the battery module. The support pin 76 is located at the fourth corner of the battery module. The position of the battery module relative to the pins is shown by the dashed line.

Figure 16 shows schematically the holes which are provided in the bottom of the module to receive the location pins. In Figure 16, the x-direction is longitudinal along the battery pack, the y-direction is transversal across the pack and the z-direction is vertical within the pack. Referring to Figure 16, the module comprises one circular hole 82 and two slotted holes 83, 84. The circular hole 82 is used as a positional constraint, to constrict movement of the battery module in both the x and y directions. The slotted hole 82 is used to constrict movement of the battery module in the y-direction but allow some movement in the x-direction. This allows for some end-to-end tolerance in the battery module. The slotted hole 83 is used to constrict movement of the battery module in the x-direction but allow some movement in the y-direction. This allows for some side-to-side tolerance in the battery module. Also shown in Figure 16 is a pad 84 which is provided on the bottom of the battery module 12. The pad 84 is designed to rest on the support pin 76. This helps to ensure even compression of the battery module on the cooling system.

Figure 17 shows the bottom of the battery module in one embodiment. Referring to Figure 17, the battery module 12 comprises a stack of battery cells 24 and two end plates 26 held together by steel bands 28. The circular hole 82 and the slotted hole 83 are provided in one of the end plates 26. The slotted hole 83 and the pad 84 are provided on the other end plate 26.

The arrangement described above helps to improve the thermal conductivity between the module and the cooling system, and also allows for expansion of the cells and tolerance build up.

Figure 18 is a schematic view of part of the clamping arrangement showing how dynamic loading is applied through the location pins. Referring to Figure 18, the location pins 56 (and support pin 76) are attached to the battery pack bottom panel 22. The panel 22 is composed mainly from carbon fibre panels. The battery module 12 sits on the location pins 56 and support pin 76, which pass through holes in the cooling system. The module 12 is being pushed downwards by the module clamp plate described above. The module is stopped on the location pins 56 and support pin 76 with the clamp's force F. Between the module there are, from top to bottom, thermal conductive pad (gap pad) 54, cooling plate 14 and support foam 58. The support foam 58 is attached to the bottom panel 22. The support foam distributed loads from the cooling plate 14 to the bottom panel, so as not to damage the cooling plate. The cooling foam also provided thermal isolation between the cooling plate and the bottom panel.

In the arrangement described above, the amount of load applied to the cooling plate by the battery module can be adjusted based on selection of the thickness of the cooling foam, as well as the properties of the foam such as the foam material and its compression curve. Thus, the pressure which is applied to the cooling plate is that which is required to compress the foam (and gap pad) sufficiently for the battery module 12 to rest on the shoulders of the location pins 56 and on the support pin 76. This pressure is chosen to be large enough to ensure good thermal contact between the module and the cooling plate, but small enough to avoid deforming the cooling plate. Any additional force is transferred through the location pins and the support pin rather than through the cooling plate. Thus, if a dynamic load is produced through shocks or other movement of the battery pack, this dynamic load will be transferred through the pins rather than the cooling system.

An advantage of the above arrangement is that the cooling plate can be made lighter and thinner than would otherwise be the case, because it does not to absorb dynamic loads. Furthermore, deformation of the cooling plate which might otherwise occur due to dynamic loading may be avoided. In addition, a single cooling plate can be used for one row of battery modules, rather than providing a separate cooling plate for each module. This can lead to further reduction in the weight of the cooling system and/or improvements in the flow of coolant and thus the cooling efficiency.

In this embodiment, the bottom panel 22 acts as a counter clamping part for the exchangeable battery modules. The battery modules sit on the pin and pads, which leads to a uniform pressure distribution between the battery module cooling sheets and cooling plate interfaces. Accurate module positioning helps to keep the cooling plate at the same level, helping to avoid pressure drop in the cooling system. Furthermore, the above arrangement helps to achieve better flexibility in battery placement in a vehicle regarding other packs in a system.

In the above description, preferred features of the invention have been described with reference to various embodiments. It will be appreciated that features of one embodiment may be used with any other embodiment. Furthermore, the invention is not limited to these embodiments, and variations in detail may be made within the scope of the appended claims.

Claims

CLAIMS1. A battery module for a battery pack, the battery module comprising a plurality of stackable battery cell units, wherein each battery cell unit is of one of two types, each type having a different configuration of electrical terminals.
2. A battery module according to claim 1, where the electrical terminals of one type of battery cell unit are in a different position on the battery cell unit from the electrical terminals of the other type.
3. A battery module according to claim 1 or 2, each battery cell unit comprising positive and negative terminals, wherein the positive and negative terminals of one type of battery cell unit are on opposite sides of the battery cell unit to the positive and negative terminals of the other type.
4. A battery module according to any of the preceding claims, wherein the electrical terminals of one type of battery cell unit are displaced from an edge of the battery cell unit by a different amount than the electrical terminals of the other type.
5. A battery module according to any of the preceding claims, wherein each battery cell unit comprises a pouch cell and a cell tray.
6. A battery module according to claim 5, wherein the cell tray comprises a cell frame which surrounds an edge of the pouch cell.
7. A battery module according to claim 5 or 6, wherein each battery cell unit further comprises a cell cover arranged to clamp the pouch cell.
8. A battery module according to claim 7, wherein the battery cell unit can be disassembled by separating the cell frame from the cell cover.
9. A battery module according to any of the preceding claims, wherein the electrical terminals comprise terminal blocks.
10. A battery module according to claim 9, wherein the terminal blocks comprise holes for removably connecting electrical connectors.
11. A battery module according to any of the preceding claims, further comprising a busbar unit for electrically connecting the plurality of battery cells, the busbar unit comprising a plurality of busbars.
12. A battery module according to claim 11, wherein the busbar unit comprises a plurality of busbars laminated between sheets of electrically insulating material.
13. A battery module according to claim 11 or 12, wherein the busbar unit is replaceable in order to reconfigure the battery module.
14. A battery module according to any of the preceding claims, wherein the plurality of battery cell units are connected in series and/or parallel using a busbar unit, and the module is arranged such that the series and/or parallel connections can be changed by changing a stack-up order of the battery cell units and/or the busbar.
15. A battery module according to any of the preceding claims, wherein the battery cell units are arranged such that they can only be stacked in one orientation.
16. A battery module according to any of the preceding claims, wherein the battery module comprises a stack of battery cell units terminated with at least one end plate.
17. A battery module according to any of the preceding claims, further comprising an expansion pad between each of the battery cell units.
18. A battery module according to any of the preceding claims, wherein the battery module is held together by module bands.
19. A battery module for a battery pack, the battery module comprising a plurality of stacked battery cell units, wherein the battery module is held together by module bands.
20. A battery module according to claim 19, wherein the module bands apply a compressive force to the battery module.
21. A battery module according to any of the preceding claims, wherein the battery module comprises a plurality of apertures which are arranged to receive location pins.
22. A battery module according to claim 21, wherein the battery module comprises a stack of battery cell units and two end plates, and the apertures are provided in the end plates.
23. A battery module according to claim 21 or 22, wherein the apertures comprise at least one hole which is arranged to cooperate with a location pin to restrict movement of the module in two directions, and at least one slot which is arranged to cooperate with a location pin to restrict movement in one of the two directions and to allow movement in the other direction.
24. A battery module for a battery pack, the battery module comprising a plurality of stacked battery cell units, the battery module further comprising at least one hole arranged to cooperate with a location pin to restrict movement of the module in two directions and at least one slot arranged to cooperate with a location pin to restrict movement in one of the two directions and to allow movement in the other direction.
25. A battery module according to any of the preceding claims, wherein the battery module is arranged for use with a clamping arrangement comprising: means for applying a clamping force to the battery module; and support means for supporting the battery module, the support means comprising a compression stop.
26. A clamping arrangement for clamping a battery module in a battery pack, the battery pack comprising a frame and a plurality of cross members, the clamping arrangement comprising a clamping plate attached to two adjacent cross members.
27. A clamping arrangement according to claim 26, wherein a gap is provided between the clamping plate and the cross members.
28. A clamping arrangement according to claim 26 or 27, wherein the clamping plate is arranged to apply a clamping force to the battery module such that the battery module maintains thermal contact with a cooling system.
29. A clamping arrangement according to claim 28, further comprising means for applying a counter clamping force to the cooling system.
30. A clamping arrangement according to any of claims 26 to 29, further comprising support means for supporting the battery module, the support means comprising a compression stop.
31. A method of reconfiguring a battery module comprising a plurality of stackable battery cell units electrically connected in series and/or parallel using a busbar, the method comprising changing a stack-up order of the battery cell units and/or the busbar.
32. A method of assembling a battery module, the method comprising stacking a plurality of stackable battery cell units, compressing the battery cell units, and fastening the stack of battery cell units with module bands.