Field of Invention

This invention relates to battery packs. More specifically, the invention relates to configurations of battery cells in battery packs, clamping devices for supporting those cells, and thermal management of those cells.

Background

Battery packs are typically constructed from a number of connected modules, each module comprising a group of battery cells. Typically, each cell in the battery pack is connected to a busbar. Constructing battery packs in this way introduces a significant number of additional mechanical and electrical components to the battery pack which do not contribute to the storage of energy (for example module casings for holding the groups of battery cells, mountings for retaining the modules in the battery pack or for mechanically interconnecting modules, and electrical connectors for electrically connecting modules together).

These additional components are problematic because they take up space within a battery pack and add weight to a battery pack, thereby reducing the amount of energy that can be stored by the battery pack per unit volume or per unit weight of the overall battery pack (the ‘volumetric’ and ‘gravimetric’ energy densities of the battery pack respectively). Furthermore, the modular construction of battery packs introduces additional electrical and mechanical connections between cells within modules and between separate modules, with each joint generating additional electrical resistance within the battery pack and also representing a potential point of failure in the electric circuit.

Battery cells generate heat when charging and discharging. Excessive heat can cause the cells to deteriorate and can lead to irreversible effects on the cell chemistry. This results in reduced cell performance and a reduced product life. Additionally, low ambient temperatures impact cell performance by limiting power output. In most existing battery packs, systems for transferring heat away from cells are separate from any systems for transferring heat into cells. Also, in existing battery packs, electrical connection of and between battery cells in a battery pack is facilitated by a system independent from the system that provides thermal management. This results in surplus components which reduce the volumetric and gravimetric energy density of the battery pack.

The present invention aims to ameliorate some of the above problems. Summary of the Invention

Aspects and embodiments of the present invention are set out in the claims. These and other aspects and embodiments of the invention are also described herein.

According to at least one aspect described herein, there is provided a battery pack comprising a plurality of battery cells, wherein: each cell is a substantially planar and comprises a pair of flat terminal tabs located at opposing ends of the cell, each tab extending from an edge of the cell substantially in the same plane as the cell; and wherein the plurality of cells are electrically connected in series and configured such that each cell in the series is electrically connected to an adjacent cell in the series via an electrical coupling between terminal tabs of adjacent cells. Connected battery cells tab-to-tab in this way reduces the number of electrical connections required in the circuit thus reducing the potential points of failure in the circuit and reducing the electrical resistance in the circuit.

Preferably, the electrical coupling comprises a direct electrical contact between the terminal tabs of adjacent cells in the series. Connected the cells via a direct tab-to-tab connection, instead of indirectly connecting via another component such as a busbar, reduces the number of non-energy storing components required in the battery pack thus increasing the volumetric and gravimetric energy density of the battery pack.

Preferably, the direct electrical contact comprises a face to face contact between overlapping terminal tabs of adjacent cells in the series. The face-to-face contact between the terminal tabs maximises the area of the electrical connection between the adjacent cells which reduces the electrical resistance across the connection. This results in reduced energy loses across the connection.

Preferably, the terminal tabs of adjacent cells are maintained in direct electrical contact via a clamping device. The use of a clamping device ensures that the terminal tabs are secured and remain in electrical contact thereby reducing the risk of a failure in the connection between battery cells.

Preferably, the terminal tabs of adjacent cells are bonded together. The bonding of terminal tabs of adjacent cells provides further securement of the terminal tabs together, further reducing the risk of a failure.

Preferably, the bonding comprises at least one weld. For example, a spot well or a laser weld. The tabs may alternatively become welded in use. The welding secures the terminal tabs together to reduce the risk that the electrical connection between terminal tabs becomes broken. Preferably, the plurality of cells comprises groups of cells, wherein all cells in a group are mounted in the battery pack in substantially the same plane and electrically coupled end to end. The groups form rows in a configuration of battery cells. The end-to-end and tab-to-tab coupling of the cells reduces the number of components required to connect the battery cells in series, thereby reducing the number of electrical connections and increasing the gravimetric energy density. This coupling also enables more densely packed arrangements of battery cells thereby increasing the volumetric energy densities of the cell.

According to another aspect described herein, there is provided a battery pack comprising a plurality of battery cells, each cell being substantially planar and having a longitudinal axis along its length, wherein: the plurality of cells are configured in at least two rows, each row comprising at least two cells; the cells in a row lie in the same plane and are oriented such that their longitudinal axes are aligned; and the direction of orientation of cells in adjacent rows is antiparallel. This antiparallel configuration results in the polarity of the terminal tabs are the ends of adjacent rows being opposite, therefore only a short electrical connection is required to connect the ends of the adjacent rows which reduces the size of the connecting components, thus allowing for more tightly packed cells and increasing the volumetric and gravimetric energy densities of the battery pack.

Preferably, a cell at the end of each row is electrically coupled to a cell at the end of an adjacent row such that the cells are electrically connected in series. Connecting the cells in series provides a high-voltage power source when the string of cells is connected into an external circuit.

Preferably, the electrical coupling between cells at the ends of adjacent rows comprises a direct electrical contact between terminal tabs of those cells. For example, the terminal tabs of the cells at the ends of adjacent rows may be bent together so as to touch. The direct electrical contact means that there is no need for a separate component to electrically connect the cells thereby increasing the volumetric and gravimetric energy density of the battery pack and reducing the number points of electrical connection.

Alternatively, the battery pack further comprises a conductive bridge element arranged to provide an indirect electrical contact between the cell at the end of each row and the cell at the end of an adjacent row. Preferably, the indirect electrical contact is between terminal tabs of the cells. The indirect electrical connection (via the bridge element) means that the terminal tabs at the ends of adjacent cells need not be deformed in order to be connected.

Preferably, every cell in the battery pack is electrically connected in series to every other cell in the battery pack to form a continuous string of cells. Alternatively, the battery pack may comprise a number of separate strings of cells, wherein every cell within a string of cells is electrically connected in series, and the strings are electrically connected in parallel. Alternatively, there may be no electrical connection between the strings; in this case each string of cells is able to provide a separate power source, for example to power separate electrical circuits or components.

According to another aspect described herein, there is provided a clamping device for supporting battery cells in a battery pack, the battery cells having flat terminal tabs each extending along an edge of the cell, the clamping device comprising: a thermally conductive body having a longitudinal axis; and at least one slot in the thermally conductive body, the slot being aligned along or parallel to the longitudinal axis of the thermally conductive body; wherein the at least one slot is adapted to receive a terminal tab of a battery cell thereby to clamp the terminal tab of the battery cell within the slot. The clamping device grips the terminal tab held within the slot thereby to retain the battery cell in the battery pack. The clamping device is thermally conductive and therefore provides a thermal connection to and from the battery cell, via the clamped terminal tab. In this way, a single component - the clamping devices - has both the function of providing thermal management for the battery cells but also for facilitating electrical connection from one cell to another (rather than independent components or systems carrying out these functions separately).

Preferably, the term “thermally conductive”, or a related term, is used here (for example, in relation to the thermally conductive body of the clamping device above) to mean a material that provides a pathway for heat transfer. For example, the thermally conductive body of the clamping devices provides a pathway for heat transfer to or from the battery cells. Examples of good metallic thermal conductors include aluminium, silver, copper and gold. These good thermal conductors have thermal conductivity rates in the range of about 225 W/mK (Watts per meter-Kelvin) to about 430 W/mK. Other acceptable thermally conductive materials include other metallic thermal conductors - such as stainless steel and titanium which have thermal conductivity rates in the range of about 13 W/mK to about 20 W/mK - and Thermal Plastics such as Celanese Cool Poly E3603 PPA which has a thermal conductivity rate of about 20 W/mK. Such Thermal Places are advantageous because they can be more easily moulded and shaped for different uses compared to metals. Generally, materials having a thermal conductivity rate of more than about 10 W/mK would be acceptable for use in the present invention.

Preferably, the slot is adapted to receive the terminal tab of a battery cell via an interference fit. The interference fit secures the tab within the slot such that it is (removably) fixed within the slot. This retains the battery cell, whose terminal tab is clamped, within the battery pack. Preferably, the at least one slot is located between resilient walls biased to close the slot thereby to clamp the battery terminal tab between the walls. The walls biased walls exert a clamping force on the terminal tab. As the walls are biased, the force is automatically exerted without need for a user input (such as a user tightening the clamp).

Preferably, the clamping device further comprise means for securing the device to a housing of the battery pack thereby to secure a battery cell clamped by the device to the housing of the battery pack. The battery cell is clamped by the clamping device which in turn is secured to the battery pack, thereby to secure the cell within the battery pack.

Preferably, the clamping device further comprises one slot adapted to receive a first terminal tab from a first cell and a second terminal tab from a second cell, and wherein the clamping device is arranged to electrically couple the first and second tabs within the slot. The electrical coupling is either indirect such that the terminal tabs are held within the slot but not overlapping, and electrically connected via the clamping device, or direct in that the clamping device clamps the first and second terminal tabs in overlapping face-to-face contact.

Preferably, the clamping device further comprises an electrical connector, such as a plate with a through-hole for receiving a busbar, adapted to electrically connect the clamping device (and in use the battery cell whose terminal tab is in use clamped within the slot) to a circuit. Preferably a battery pack comprises two such clamping device: one connected to the first battery cell in a series and one connected to the last battery cells in the series.

Alternatively, the thermally conductive body may comprise two prongs spaced apart, each prong comprising a slot, wherein the slot of the first prong is adapted to receive a terminal tab of a first cell and the slot of the second prong is adapted to receive a terminal tab of a second cell. The clamping device provides a bridge between the cell whose terminal tab is clamped in the slot of the first prong and the other cell whose terminal tab is clamping in the slot of the second prong.

Preferably, the slots of the first and second prongs are arranged in parallel thereby to receive terminal tabs from first and second battery cells arranged in parallel. Therefore, the distance spanned by the clamping device is minimised in order to reduce the size of the clamping device to increase the volumetric and gravimetric energy density of the battery pack.

Preferably, the clamping device further comprises an electrically conductive bridge for electrically coupling the terminal tab of the first cell received within the slot of the first prong and the terminal tab of the second cell received within the slot of the second prong. Preferably, the conductive bridge comprises a first electrically conductive lining within the slot of the first prong and a second electrically conductive lining within the slot of the second prong, and an electrical connection between the first and second conductive linings. This means that the external surface of the clamping devices can be electrically and thermally insulating which may make it safer to touch.

According to another aspect described herein, there is provided a battery pack as aforementioned comprising: first clamping devices with one slot as aforementioned disposed between each cell in a row, each first clamping device arranged to receive, within the slot, terminal tabs of adjacent cells in the row thereby to electrically couple those terminal tabs; and second clamping devices with two slots as aforementioned (electrically) connected between each row, each of the second clamping devices arranged to receive, within the slot of the first prong and the slot of the second prong respectively, a terminal tab from a cell at the end of a first row and a terminal tab from a cell at the end of a second row between which the second clamping device is connected, thereby to electrically couple those terminal tabs. This clamping devices comprise thermally conductive bodies and also provide or facilitate electrical connection between the cells. Therefore, the device performs a dual function of electrical connection and thermal management, rather than having independent components or systems performing there functions separately. Therefore, the number of non-energy storing components is reduced which enables a more compact configuration of battery cells with increase gravimetric and volumetric energy density.

According to another aspect described herein there is provided a kit of parts comprising a plurality of clamping devices as aforementioned, and a clasp, the clasp comprising: a clasp body and a plurality of teeth; wherein the teeth are distributed along the clasp body with spaces between; and wherein the spaces between the teeth are sized so as to each accommodate one of the clamping devices. The accommodation is preferably via an interference fit. The clasp and the clamping devices mesh so that the clasp provides structural support to the clamping devices.

Preferably, the clasp body comprises means for engaging part of a housing of the battery pack thereby to secure the clasp to the housing. The clasp, when meshing with the clamping devices and secured to the battery pack housing, also secures the clamping devices to the battery pack housing. The battery pack housing may be a base plate or a frame on or within which the battery cells are mounted.

Preferably, the plurality of clamping devices are arranged in a row with spaces between, and wherein the spaces between the clamping devices are sized so as to each accommodate one of the teeth of the clasp. Preferably, the accommodation is via an interference fit. The spaces between the clamping devices therefore mesh with the teeth of the clasp, and the spaced between the teeth of the clasp mesh with the clamping devices. The clasp provides structural support to the clamping devices.

Preferably, the teeth of the clasp are inserted within the spaces between the clamping devices, the teeth exert a force on the clamping device which acts to close the slot thereby to clamp a battery cell terminal tab received within the slot. The clamping device may already exert a clamping force on the terminal tab (for example it may be biased closed) however the lateral force exerted by the clamping device may act to further clamp the terminal tab.

Preferably, the clasp, when secured to the housing of the battery pack, exerts a force on the clamping devices to secure the clamping devices to the housing of the battery pack. The force is a (vertical) force towards the housing of the battery pack.

According to another aspect described herein there is provided a battery pack comprising: a plurality of battery cells, each cell having a pair of terminal tabs; and a plurality of thermally conducting clamping devices; wherein the clamping devices are arranged to clamp the terminal tabs of the cells thereby to electrically couple cells within the battery pack; and wherein the clamping devices are arranged to provide a path for heat transfer to or from the battery cells via the terminal tabs. The clamping devices therefore perform the dual function of facilitating thermal management of the cells as well as facilitating electrical coupling of the cells. Having a single component perform these dual functions, rather than separate systems dedicated to each function, reduces the number of non-energy storing components in the battery pack thereby increasing the volumetric and gravimetric energy densities of the battery pack.

Preferably, each of the clamping devices is arranged to clamp a positive terminal tab of one cell and a negative terminal tab of an adjacent cell. The clamping facilitates an electrical coupling between the terminal tabs of the adjacent cells.

Preferably, the battery pack further comprises a heat sink or heat source, wherein the plurality of thermally conducting clamping devices are arranged to provide a heat flow path between the terminal tabs of the battery cells and the heat sink or heat source. The thermally conducting clamping devices therefore provide a bridge through which heat can flow out of the battery cells via the terminal tabs to the heatsink, thereby to cool the battery cells. Similarly, the devices provide a bridge for heat to flow into the cells via the terminal tabs from the heat source. Thermal management of the cells, either by heating the cells or cooling the cells, enables control of the temperature of the cells to maintain the cells at the optimum temperature to optimise the performance of the cells. Preferably, the heat sink or heat source comprises a cooling duct carrying a circulation of coolant within the battery pack. The coolant absorbs heat from the battery cells, via the terminal tabs and the clamping devices, to cool the battery cells. Equally, the coolant may give out heat to the battery cells via the clamping devices and the terminal tabs to heat the battery cells. In this way the coolant maintains the cells at their optimum temperature.

Preferably, the thermally conducting clamping devices are arranged in a row, and wherein the cooling duct follows a path along and/or between the clamping devices thereby to facilitate heat transfer between the clamping devices and the coolant. In this way, the path of the coolant sticks closely to the clamping devices so as to more effectively absorb heat from or give out heat to the clamping devices. The coolant duct may be in physical contact with a part of the clamping device so as to facilitate effective heat conduction between the clamping device and the coolant. Alternatively, the coolant duct may follow a path close to but not touching the clamping device.

Preferably, the cooling duct follows a winding path between the clamping devices. The winding path extends the total length of the path of the duct along the clamping devices thereby to increase the amount of coolant in close proximity to the clamping devices. This enables more heat to be absorbed by or give out from the coolant flowing through the coolant duct.

Preferably, the cooling duct runs along a base plate of the battery back, and wherein the clamping devices are secured to the base plate. The bate plate provides a foundation on which the duct is mounted. The base plate may also be heat conducting and therefore heat may be conducted from the battery pack to the base plate, and from the base plate to the cooling ducts running along the base plate.

Preferably, the coolant is thermally conductive but electrically insulating. The coolant is thermally conducting so as to absorb heat from or give out heat to the clamping devices. However, the coolant is preferably electrically insulting to prevent any conduction of electricity into the coolant from the (electrically conductive) clamping devices.

Alternatively, the coolant comprises a first coolant flow in close proximity to, or in direct contact with, the clamping devices, and a second coolant flow in close proximity to the first coolant flow (but separated from the clamping devices). Preferably, the first coolant flow is adapted for heat transfer between the clamping devices and the first coolant. Preferably, the second coolant flow is adapted for heat transfer between the first and second coolant. Preferably, one or both of the coolants is electrically insulating, thereby to electrically isolate the second coolant from the battery cells and/or the clamping devices and prevent the coolants conducting electricity away from the battery cells and/or clamping devices. For example, the first coolant could be electrically insulating while the second coolant is electrically conductive, or the second coolant could be electrically insulating while the first coolant is electrically conductive. This arrangement is advantageous because it is possible to choose from a wider group of coolants (both electrically conductive and electrically insulating coolants) when selecting one of the two coolants. Preferably, the electrically conductive coolant is water or an aqueous solution.

The coolant is described above as a coolant flow, however in another example the coolant may instead be a coolant bath. The clamping devices and/or battery cells in this example are in thermal contact with the coolant bath, for example part of the clamping devices and/or battery cells are immersed in the coolant bath. In this example, the coolant may comprise two separate coolant baths; a first coolant bath in thermal contact with the clamping devices and/or battery cells for transferring heat between the first coolant bath and the clamping devices and/or cells, and a second coolant bath in thermal contact with the first, for transferring heat between the first and second coolant baths. One or both of the coolant baths may contain an electrically insulating coolant so as not to conduct electricity away from the clamping devices and/or battery cells via the two coolants.

Preferably, the thermally conducting clamps are clamping devices as aforementioned.

Preferably, the battery cells are solid-state cells or liquid (liquid electrolyte) cells, such as lithium ion cells, or a combination thereof. Preferably, the battery pack comprises a plurality of solid-state cells each connected in series as aforementioned, and a separate plurality of liquid cells, such as lithium ion cells, each connected in series as aforementioned. Preferably, the solid-state cell series and the liquid cell series power separate circuits.

Any apparatus feature as described herein may also be provided as a method feature, and vice versa. As used herein, means plus function features may be expressed alternatively in terms of their corresponding structure.

Any feature in one aspect may be applied to other aspects, in any appropriate combination. In particular, method aspects may be applied to apparatus aspects, and vice versa. Furthermore, any, some and/or all features in one aspect can be applied to any, some and/or all features in any other aspect, in any appropriate combination. It should also be appreciated that particular combinations of the various features described herein can be implemented and/or supplied and/or used independently. As used herein, means plus function features may be expressed alternatively in terms of their corresponding structure. One or more aspects will now be described, by way of example only and with reference to the accompanying drawings having I ike- reference numerals, in which:

Figure 1 is a perspective view of an exemplary battery cell;

Figure 2 is a perspective view of two electrically connected battery cells;

Figure 3 is an electrical connection between two battery cells;

Figure 4 is a plan view of a plurality of battery cells electrically connected in series;

Figures 5 is a plan view of a battery pack comprising a plurality of battery cells electrically connected in series;

Figure 6 is a perspective view of a battery pack having a base plate and thermal management system;

Figure 7 is a perspective view of a battery cell clamping arrangement including a plurality of clamping devices;

Figure 8 is a perspective view of a first type of such clamping devices;

Figure 9 is a perspective view of a second type of such clamping devices;

Figure 10 is a perspective view of a third type of such clamping devices;

Figure 11 is a perspective view of the battery pack of Figure 6 comprising a plurality of battery cells clamped by the clamping devices, and clasps;

Figures 12a and 12b show a first and second type of clasp respectively;

Figure 13 shows a perspective view of the interaction between a clasp, the clamping devices, and the battery cells;

Figure 14 shows a cross sectional view of the interaction between a clasp, the clamping devices, and the battery cells;

Figure 15 shows a battery pack comprising a plurality of battery cells with the clasps in place; and

Figures 16a, 16b, and 16c show alternative embodiments of the clasp with cooling channels.

Detailed Figure 1 is a perspective view of an exemplary battery cell 100. The battery cell has a cuboidal cell body 102 having a length (L) and a width (W) that are substantially longer than its thickness (T). Therefore, the cell body 102 is substantially planar, being arranged in the length-width plane as shown in Figure 1 . The cell 100 has a positive terminal tab 104a (+) and a negative terminal tab 104b (-) located at opposing ends of the cell body 102. In this example the opposing ends are at either end of the length of the cell 100, therefore the cell 100 has an axis from the positive terminal tab 104a, along the length of the cell body 102, to the negative terminal tab 104b (as indicated by the dashed line A in Figure 1 and referred to herein as the ‘longitudinal axis’ of the cell). The terminal tabs 104a, 104b are substantially flat, thin strips such that each tab two opposing faces, one on each side of the strip, facing in opposite directions and facing perpendicular to the longitudinal axis of the cell 100. The terminal tabs 104a, 104b are formed from an electrically and thermally conductive material. The terminal tabs 104a, 104b in this example each extend along the entire width the cell body 102 (however the terminal tabs in other embodiments may extend only part-way along a side of the cell body 102). The flat terminal tabs 104a, 104b protrude from the cell body 102 in the same plane as each other, and in the same plane as the plane of the cell body 102. In other embodiments, the terminal tabs may protrude in planes parallel to each other and parallel to the plane of the cell body (for example, the negative terminal tab may extend from the rear face of the cell body 102 whereas the positive terminal tab may extend from the front face of the cell body 102 or vice versa). The terminal tabs 104a, 104b provide positive and negative terminals for electrically connecting the cell 100 into an electrical circuit, optionally in series with other such cells.

Figure 2 is a perspective view of a first battery cell 100a and a second battery cell 100b (each having a cell body 102a, 102b and terminal tabs 104a, 104b as described with reference to Figure 1). The cells 100a, 100b are electrically coupled together in series. The two cells 100a, 100b are connected end-to-end such that the cells are substantially aligned along the longitudinal axes (A) along the lengths of the cells.

The battery cells 100a, 100b are in direct electrical contact via the positive terminal tab 104a of the first battery cell 100a and the negative terminal tab 104b of the second battery cell 100b. The flat faces of the terminal tabs 104a, 104b are overlapping such that the terminal tabs are in direct face-to-face contact thereby to provide an electrical connection between the battery cells 100a, 100b. In this example, the cells 100a, 100b are simply positioned so as to be in contact via the terminal tabs 104a, 104b, however the terminal tabs are not bonded together. In other examples the terminal tabs are bonded together (such as in the example shown in Figure 3) and/or the terminal tabs may be secured together in electrical contact, for example by a clamp. The size of the overlapping area of the terminal tabs 104a, 104b is preferably maximised because maximising the area of the electrical contact between the terminal tabs minimises the electrical resistance at the contact between the terminal tabs. Minimising the electrical resistance at the contact between the cells 100a, 100b reduces the electrical energy losses between electrically connected cells which increases the efficiency and longevity of battery pack comprising such cells connected in this way. Thus, the terminal tabs 104a, 104b preferably overlap across substantially the entire area of their faces.

Figure 3 shows in more detail an electrical connection between a first battery cell 100a and a second battery cell 100b. In this example, the positive terminal tab 104a of the first battery cell 100a overlaps with the negative terminal tab 104b of the second battery cell 100b such that the terminal tabs are electrically connected together face-to-face. The terminal tabs 104a, 104b in this example are bonded together by a series of six bonding points 300 so as to ensure that the terminal tabs remain in electrical contact and do not become separated. The bodying points 300 are preferably welds which may be formed for example by spot welding, laser welding, or by any other appropriate method. Alternatively, the terminal tabs 104a, 104b of the cells may begin unbonded but become bonded when the cells 100a, 100b are electrically connected in series and the electrical current flowing across the terminal tabs causes the tabs to heat up to the point that they become bonded.

Figure 4 is a plan view of a plurality of battery cells electrically connected in series arranged in a configuration 400. The plurality of cells are arranged in at least two rows with each row comprising at least two cells (in the example shown in Figure 4 there are thirty cells arranged in six rows with each row comprising five cells). Within a particular row, every cell in that row is arranged in the same direction of orientation, and the cells 100 within a particular row are arranged end-to-end. Therefore, the longitudinal axes (A) of every cell within a particular row are aligned. The cells (as described with reference to Figure 1) are substantially planar, therefore all of the cells in a particular row are also arranged in substantially the plane, and the plane of one row is parallel to the plane of the next row. The cells within a particular row are electrically coupled via the terminal tabs located at opposing ends of the cells. For example, as shown in Figure 4, a first cell 100a is electrically coupled to a second cell 100b via a direct electrical contact between the negative terminal tab 104b of the first cell 100a and the positive terminal tab 104a of the second cell 100b. Each cell within a row is electrically coupled to the two cells on either side of it in the row (other than the cells located at the beginning and end of each row, which have only one adjacent cell within the row, and which are described below). Therefore, a cell in a particular row, located between two other cells in the row, will be electrically coupled to the positive terminal tab of the adjacent cell on one side and to the negative terminal tab of the adjacent cell on the other side in the row. While the direction of orientation of all cells within a particular row is the same, the direction of orientation of cells in reversed from one row to the next row. Therefore, the longitudinal axes of the cells in the first row are antiparallel to the longitudinal axes of the cells in the second row (as shown by the antiparallel axes Ai and A2 in Figure 4). In addition, the longitudinal axes of the cells in the first and third rows are parallel (as shown by the parallel axes A1 and A3 in Figure 4) and so on. Thus, the direction of orientation of the cells zigzags from the first to the last row in the arrangement 400.

The cells within a particular row are electrically coupled via a direct electrical contact between the terminal tabs of adjacent cells in the row. The direct electrical contact in the example shown in Figure 4 is provided by a clamping device 402 which forces the terminal tabs of adjacent cells into face-to-face electrical contact. (An exemplary such clamping device is described below with reference to Figure 8.) The terminal tabs of adjacent cells in the row may be bonded together, for example by welds as described with reference to Figure 3, either instead of being secured together by the clamping device 402 or in addition to being secured by the clamping device 402. As mentioned above, the terminals tabs may begin unbonded (and merely secured together by the clamp 402) but in use, when a current flows between the terminal tabs thereby heating the tabs, the tabs may become bonded.

Adjacent rows of cells are also electrically coupled. The electrical coupling between rows is provided via a cell at the end of one row and another cell at the same end of an adjacent row. For example, as shown in Figure 4, a cell 100c at the right-hand end of the first row is electrically coupled to another cell 100d at the same end of the second row, thereby to electrically couple the first row to the second row. Another cell at the opposite end (i.e. the left-hand end) of the second row is coupled electrically coupled to a cell at the same end of the third row thereby to electrically couple the second and third rows, and so on. The electrical coupling between the cells at the ends of adjacent rows is between the end-most terminal tabs of those cells (i.e. the end of the cell which is not coupled to an adjacent cell in the same row). For example, as shown in Figure 4, the cell 100c at the end of the first row is coupled to the cell 100d at the end of the second via the negative terminal tab 104c of the first cell 100c and the positive terminal tab 104d of the second cell 100d.

The electrical coupling between the cells at the end of adjacent rows may be achieved via a direct electrical contact between terminal tabs, or via an indirect electrical connection. In the example shown in Figure 4, the cells at the ends of adjacent rows are indirectly electrically connected via conductive bridge elements 404. (An exemplary conductive bridge element is described below with reference to Figure 9.) The conductive bridge elements 404 simultaneously clamp the negative terminal tab of one cell at the end of a row and the positive terminal tab of another cell at the end of an adjacent row and provide an electrical connection therebetween so as to provide a route for current to flow between the adjacent rows of cells.

When the plurality of cells 100 are incorporated into a battery pack, the clamping device 402 and the conductive bridge element 404 may be secured to a frame or base plate of the battery pack. Therefore, the clamping of the terminal tabs by the clamping device 402 or the conductive bridge element 404 acts to mechanically retain the cells 100 within the battery pack. Furthermore, the clamping device 402 and conductive bridge element 404 are thermally conductive. Therefore, when the clamping device 402 and conductive bridge element 404 are secured to a frame or base plate of the battery pack (and clamp the terminal tabs of the cells 100), they provide a pathway for heat transfer between the cells 100 and frame or baseplate of the battery pack thereby to facilitate heat transfer into or out of the battery cells 100 (via the terminal tabs of the battery cells). There, the clamping devices and conductive bridge elements provide a dual function of electrically connecting the cells as well as transferring heat in or out of the cells. The removes the need for two independent components or systems (one for electrical connection and one for thermal management) thus increasing the volumetric and gravimetric energy densities of the battery pack.

The thirty cells shown in Figure 4 form one continuous string of cells connected in series. The five cells in the first row are each connected in series end-to-end (with their longitudinal axes aligned running left to right in Figure 4) via the terminal tabs of adjacent cells in the row (the tabs being secured together by the clamping devices 402 and/or a bonding between the tabs). The first row is then electrically connected to the second row via a conductive bridge element 404, and the cells in the second row are connected end-to-end and tab-to-tab with their axes aligned running right to left in Figure 4. The second row is electrically connected to the third row by another conductive bridge element 404, and so on.

At one end of the thirty-cell string is a positive end terminal 406a and at the other end of the string is a negative end terminal 406b. The end terminals 406a, 406b provide points of electrical connection whereby the entire string of cells 100 can be connected into an electrical circuit. The positive end terminal 406a clamps onto the positive terminal tab of the cell at the beginning of the string of cells (as shown at the upper left-hand corner of Figure 4) and the negative end terminal 406b clamps onto the negative terminal tab of the cell at the end of the string of cells (as shown at the lower left-hand corner of Figure 4). The end terminals 406a, 406b also comprises a connection point for electrically coupling the terminals tabs that they clamp to another component. For example, the end terminals 406a, 406b may comprise a connection point for electrically coupling to a busbar. (An exemplary end terminal clamping device is described below with reference to Figure 10.) The configuration described above provides a more compact arrangement of battery cells for a battery pack thereby increasing the gravimetric and volumetric energy density of the battery pack. This is achieved by reducing or minimising the space and weight taken up by mechanical and electrical connections. For example, using the configuration described above, there is no need to include a separate component for electrically connecting the cells within rows as they are directly connected tab to tab. In addition, the antiparallel configuration of cells in adjacent rows means that the electrical connection between the terminal tabs at the ends of adjacent rows (e.g. tabs 104c and 104d in Figure 4) requires only a short bridging connection (thus reducing the space and weight taken up by that connection). If the cells 100c and 100d were aligned in the same direction of orientation, the bridging element 404 would need to extend along the entire length of the cells in order to connect their respective positive and negative terminals.

Figures 5a is a plan view of a battery pack 500 comprising a plurality of battery cells electrically connected in series. The cells in the battery pack are configured in accordance with the principles described above with reference to Figure 4.

The plurality of battery cells (which are indicated in Figure 4 by cross hatching) are arranged in series in one continuous string. Each cell in the string is connected to other cells either by clamping devices 502 or by conductive bridge elements 504 depending on their location within the string. The clamping devices 502 (which are equivalent to the clamping devices 402 described with reference to Figure 4) electrically couple cells that are adjacent in a row by clamping the positive terminal tab of one cell and the negative terminal tab of an adjacent cell in a row in face-to-face contact. The conductive bridge elements 504 (which are equivalent to the conductive bridge elements 404 described with reference to Figure 4) electrically couple cells are the ends of adjacent rows. At the ends of the continuous string are an end positive terminal 506a and an end negative terminal 506b by which the string can be connected into an electrical circuit, such as to a busbar. A continuous series connection can be traced from the end positive terminal 506a, through every one of the plurality of cells, and through every clamping device 502 and every conductive bridge element 504, to the end negative terminal 506b.

The plurality of cells shown in Figure 5 are conceptually divided into groups 508 as denoted by the dashed lines to indicate how a battery back can be constructed. (The divisions are only conceptual because, as mentioned above, the cells form a single continuous series of cells rather than a set of discrete modules.) The groups 508 in this example consist of either five cells or six cells. For the five-cell groups, the direction of orientation of the first cell in the group (i.e. the cell in the upper most row in the group) is antiparallel to the direction of orientation of the last cell in the group (i.e. the lower most row in the group), because the direction of orientation alternates between rows and there are an odd number of rows in the group. For the six-cell groups, the direction of orientation of the first cell is parallel to the direction of orientation of last cell because there is an even number of cells in the group. Therefore, for a group with an odd number of cells, the polarity of the of the terminal tab at the upper left-hand corner of the group will be opposite of the polarity of the terminal tab at the lower right-hand corner of the group. For a group with the even number of cells, the polarity of the terminals is the same. This principle can be used to construct a tightly packed configuration of the cells (maximising the volumetric and gravimetric energy densities) by minimising the distance between a cell at the end of one row and a cell at the beginning of the next row, and thereby minimising the amount of connective material that is required to span that distance.

The cells in this example are also configured so as to leave a space 510 where there are no groups of cells. This space 510 can be used to accommodate other electronic components within the battery pack, such as contactors of fuses.

Figure 6 shows a battery pack 600 having a base plate 602 and a thermal management system 604 which carries a fluid coolant. The fluid coolant is thermally conductive but electrically insulating. The base plate 602 provides a foundation or on which the battery pack is assembled and may form part of a wider housing of the battery pack 600. The thermal management system 604 comprises a cooling circuit 606 comprising a series of heatsink ducts 608 disposed between a coolant distribution duct 610 and a coolant collection duct 612. The distribution duct 610 is connected to an inlet of each of the heatsink ducts 608 and acts to distribute the fluid coolant even between the series of heatsink ducts 608. The example shown in Figure 6 has three such heatsink ducts 608. The coolant collection duct 612 is connected at the opposite end of the heatsink ducts 608 to an outlet of each of the heatsink ducts 608 and collects coolant that has passed through the heatsink ducts.

As the coolant runs through the heatsink ducts 608, and absorbs heat from items, such as battery cells, assembled above the ducts 608, the coolant will increase in temperature and some of the coolant will evaporate and become gaseous. Therefore, while the liquid component of the coolant continues through to the coolant collection duct 612, the gaseous component may be released from the cooling circuit 606 via an off-gassing duct 614. The release of the gas via the off-gassing duct 614 prevents a build-up of pressure within the cooling circuit 606. The off-gassing duct 614 may have a pressure release valve configured to trigger off-gassing when the pressure within the cooling circuit 606 exceeds a threshold level. The battery pack of the example shown in Figure 6 also has an additional cooling circuit 616 with components analogous to those described above.

The heatsink ducts 608 are arranged substantially in parallel and spaced apart evenly by a distance equal to the length of a battery cell which in use (as is described below with reference to Figure 11) sits on top of the thermal management system 604. Each of the heatsink ducts 608 is formed in a serpentine shape to as to provide close contact with items (such as the clamping devices described below) assembled in the gaps between the turns of the serpentine heatsink ducts 608. In addition, the serpentine shape increases the length of the heatsink duct (and therefore the amount of coolant) present between the distribution duct 610 and the collection duct 612. In this way, the amount of heat that can be absorbed by the coolant from battery cells assembled above the heatsink ducts is increased. In other examples, the heatsink ducts may be formed in alternative winding shapes, such as in the shape of a square wave having right-angle turns. In other examples, the heatsink ducts may instead be formed as a straight line between the distribution and collection ducts, or a series of parallel straight- line ducts between the distribution and collection ducts.

In operation, coolant is piped from the distribution duct 610 which acts to collect the coolant and evenly distribute the coolant into the heatsink ducts 608. The coolant is piped along the heatsink ducts such that it is able to absorb heat from objects (such as battery cells) placed above the heatsinks ducts so that the coolant increases in temperature. The liquid heated coolant is collected in the collection duct 612 once it has passed through the heatsink ducts, and any evaporated gas is released via the off-gassing duct 614.

While this example has been described with reference to the coolant absorbing heat from items, such as battery cells, placed above the heatsink ducts 608, the coolant may also be used to provide heat to such items placed above the ducts. The heated coolant is, for example, coolant from other systems in a machine in which the battery pack 600 is installed. For example, if the battery pack 600 is installed in a vehicle, the coolant may be used to absorb heat from the engine or motor thereby to cool the engine or motor, and then piped through the cooling circuit 606. The heated coolant acts to heat battery cells placed above the heatsink ducts 608, thereby preventing the battery cells becoming too cold which can be detrimental to the cell’s performance and power output.

In the example described above with reference to Figure 6, the thermal management system utilises one coolant that circulates through the heatsink ducts 608. However, in an alternative example, the thermal management system may comprise more than one coolant flow. In particular, the thermal management system may comprise a first coolant flow which passes in close proximity to (or even in direct contact with) the battery cells and/or the battery cell clamping devices. The first coolant must therefore be thermally conductive but electrically insulating so as to be able to exchange heat with the battery cells and clamping devices but avoid conducting electricity away from the battery cells and clamping devices. Preferably, the first coolant is a heat-transfer fluid. The thermal management system of this alternative example also comprises a second coolant flow which does not pass in close proximity to the battery cells or clamping devices and which is arranged to exchange heat with the first coolant flow. Since the second coolant flow does not pass in close proximity to the battery cells or clamping devices (and is separated from the battery cells and clamping devices by the insulating first coolant) it need not be electrically insulating as there is not the risk of the second coolant conducting electricity away from the battery cells or clamping devices. Therefore, the second coolant could be an electrically conductive fluid. This alternative thermal management system may include a heat exchanger between the first and second coolant flows to facilitate efficient heat transfer between the two coolants. This arrangement provides the advantage that it is possible to choose from a wider group of coolants (both electrically conductive and electrically insulating coolants) when selecting an appropriate coolant for the second coolant. Therefore, the most efficient coolant can be used regardless of its electrical conductivity properties.

Figure 7 shows a battery cell clamping arrangement 700. The arrangement 700 is intended to be fitted in the battery pack 600 described above with reference to Figure 6.The clamping arrangement 700 comprises a plurality of clamping devices arranged in three parallel columns 701a, 701b, 701c that are evenly spaced apart by the length of a battery cell. The clamping devices are configured to clamp, in use, a plurality of battery cells in rows electrically connected in series.

The central column 701b consists of clamping devices of a first type 702 which are configured to clamp battery cell terminal tabs of adjacent battery cells arranged end-to-end. The first type of clamping device 702 performs the function of the clamping devices 402 and 502 described above with reference to Figures 4 and 5. The right-hand column 701c consists of clamping devices of a second type 704 which are configured to clamp terminal tabs of battery cells at the ends of adjacent rows in the battery pack. The second type of clamping device 704 performs the function of the conductive bridge elements 404 and 504 described above with reference to Figures 4 and 5. The left-hand column 701a consists of clamping devices of the second type 704 except for the clamping devices 706a, 706b at either end of the column which are clamping devices of a third type. One of the third type of clamping devices 706a is a positive end terminal clamp and the other of the third type of clamping device 706b is a negative end terminal clamp (however, the polarity of the clamps could be reversed in other examples). The clamping devices 706 clamp the terminals tabs of the battery cells at the beginning and end of the string of cells electrically connected in series and provide a point of contact to electrically connect the string of cells into an external circuit (such as to a busbar). The third type of clamping devices 706a, 706b therefore perform the function of the positive and negative end terminals 406a, 406b, 506a, 506b described about with reference to Figures 4 and 5.

When the clamping arrangement 700 is installed onto the base plate 602 of the battery pack 600 described above, the columns of clamping devices are positioned above the heatsink ducts 608 of the thermal management system 604 and are aligned along the path of the heatsink ducts between the distribution and collection ducts. The clamping devices are made from heat conducting material, preferably aluminium, such that the clamping devices are capable of transferring heat between the battery cells that they clamp, in use, and the coolant that runs through the heatsink ducts. Therefore, in use, the clamping devices act as a pathway for heat to flow out of the battery cells (via the terminal tabs clamped by the clamping devices) to the coolant in order to cool the battery cells. Alternatively, the clamping devices could act as a pathway for heat to flow into the battery cells (via the terminal tabs clamped by the clamping devices) from the coolant to warm the battery cells (for example when the battery pack is first switched on) in order to increase the performance of the battery cells.

The battery cells are secured to the base plate 602 of the battery pack 600 via a mat 708. The mat 708 is secured to the base plate 602 or formed as part of the base plate. The mat 708 comprises a lower layer 710 and an upper layer 712 positioned on top of the lower layer. The heatsink ducts of the thermal management system are sandwiched between the lower layer 710 and the upper layer 712 of the mat 708. The clamping devices 702, 704, 706 comprise legs (not shown) which pass through openings of the upper layer 712, and feet which are sandwiched between the lower layer 710 and upper layer 712. In this way, the clamping devices are secured to the mat 708 which in turn is secured to the base plate 602 of the battery pack.

Figure 8 shows the first type of clamping device 702. The clamping device 702 has a body 800 which has a thin slot 802 at its upper end. The slot divides that upper end of the clamp body 800 such that the body has two opposing walls 804 forming the slot 802. The slot is sized so as to receive the terminal tabs of adjacent battery cells (for example the terminal tabs 104a, 104b of the battery cell 100 described above with reference to Figure 1). The clamping device body 800 is substantially planar, having a height and width substantially larger than its thickness. The slot 802 is formed in the upper end of the device in same plane at the body 800 of the device, and the slot extends along the entire width of the body 800 but not along the entire height of the body 800. In use, the clamping device 702 is positioned between two such battery cells arranged end- to-end and receives within the slot 802 a positive terminal tab from one battery cell and a negative terminal tab from the other battery cell. The terminal tabs may be overlapping within the slot such that they are electrically coupled via a face-to-face contact between the terminal tabs. The gap between the walls 804 is narrow enough that two overlapping face-to-face terminal tabs fit within the slot 802 between the walls 804 via an interference (friction) fit. Therefore, the width of the slot 802 is just smaller than twice the width of the terminal tabs of the battery cells. Alternatively, or additionally, the walls 804 are resilient such that they can be elastically deformed in order to open the slot 802 to fit the overlapping terminal tabs within the slot 802, with the walls 804 being biased together such that the walls 804 exert a clamping force on the terminal tabs held within this slot 802. It should be understood that while the clamping devices 702, 704, 706 are described herein as being slotted, so as to grip the terminal tabs within the slot, the clamping devices could operate in any other way so long as they are capable of gripping a terminal tab (for example, clamping device could utilise hinged clips, or screw clamps).

The clamping device 702 also comprises a leg 806 protruding from the lower end of the clamping device (the end opposite the upper end which has the slot 802). The leg 806 extends in substantially the same plane as the device body 800. The leg 806 is adapted to be secured to the battery pack in which the clamping device 702 is installed as described above.

In the example shown in Figure 8, the entire clamping device 702 is made from electrically conductive material, preferably aluminium. When a positive terminal tab of a battery cell and a negative terminal tab of another battery cell are clamped within the slot 802, there will be a face-to-face electrical contact between the terminal tabs, but there will also be an electrical contact between the other, outer faces of the terminal tabs and the interior faces of the walls 804 within the slot 802. Therefore, current will flow between the terminal tabs not only across the point of direct (face-to-face) contact between the terminal tabs but also through the electrically conductive clamping device itself. Maximising the area of electrical contact across the connection between the battery cells reduced the electrical resistance across the connection.

In the example shown in Figure 8, the entire clamping device 702 is also made from thermally conductive material. Electrical connection between two battery cells will tend to cause the battery cells to heat up. When terminal tabs of adjacent battery cells are held in electrical contact within the slot 802, the thermally conductive clamping device 702 will act as a pathway for outflow of heat from the battery cells, via the terminal tabs clamped within the slot 802, to a heatsink, such as the coolant flowing through the heatsink ducts of the thermal management system described above with reference to Figures 6. The thermally conductive clamping device 702 can also act as pathway for inflow of heat to the battery cells, via the terminal tabs clamped within the slot 802, from a heat source such as a warm coolant flowing through the heatsink ducts of the thermal management system. The clamping device 702 therefore can be used to heat battery cells clamped by the clamping device to improve the performance of the battery cells (for example when the battery pack is first turned on).

In other examples, the clamping device 702 may not be entirely electrically and/or thermally conductive but may instead comprise an electrically and/or thermally conductive component. For example, the clamping device 702 may comprises an electrically and/or thermally conductive core contained within an electrically and/or thermally insulating body. In this case, the exterior of the clamping device body is electrically and thermally insulating, however the interior of the slot 802 (such as a lining on the interior of the slot), an interior of the body 800 electrically connected to that lining, and the leg 806 form a thermally conductive core (they must be thermally conductive in order to carry heat from the battery cell terminal tabs to the heatsink duct of the thermal management system) and the interior of the slot 802 is also electrically conductive to increase the area of the electrical connection. If the exterior of the clamping device is electrically and thermally insulating, the risk of injury (burns or electrocution) from a person touching the device is reduced.

Figure 9 shows the second type clamping device 704. The clamping device 704 has a forked body 900 having two prongs 900a, 900b. The first prong 900a has a first thin slot 902a at its upper end which divides the upper end of that prong into two first opposing walls 904a which form the first slot 902a therebetween. The second prong 900b has a second thin slot 902b at its upper end which divides the upper end of that prong into two second opposing walls 904b which form the second slot 902b therebetween.

The slots 902a, 902b are sized so as to receive the terminal tabs of battery cells (for example the terminal tabs 104a, 104b of the battery cell 100 described above with reference to Figure 1) at the ends of adjacent rows in an arrangement of a plurality of cells so as to electrically couple those cells. Each of the prongs 900a. 900b is substantially planar, having a height and width substantially larger than its thickness. The slots 902a, 902b are formed in the upper end of the device in same plane at the prongs of the body 900, and the slots extend along the entire width of their respective prongs but not along the entire height of the prongs.

In use, the clamping device 704 is used to electrically couple two rows of battery cells. The clamping device 704 is positioned such that the first prong 900a is aligned in the same plane as one row of battery cells in the arrangement, and the second prong 900b is aligned in the same plane as the next row of battery cells in the arrangement. The flat positive terminal tab of the cell at the end of the first row is received within the first slot 902a and the flat negative terminal tab of the cell at the end of the next row is received within the second slot 902b. The slots 902a, 902b are each narrow enough that a single terminal tab fits within it via an interference (friction) fit, and/or the walls 904a, 904b may be resilient and biased to clamp a terminal tab slotted between the walls as described above. The prongs 900a, 900b are spaced apart, with a gap 905 between the prongs, such that the distance between the slots 902a, 902b is more than or equal to the thickness of the body of the battery cell with which the clamping device 704 is use. This is so that the cells can be arranged in parallel rows with at least a small air gap between the cells of adjacent rows.

At the lower end of the clamping device body 900 the prongs are joined such that the forked body 900 is formed as a single piece. The clamping device 704 also comprises a pair of legs 906 protruding from the lower end of the clamping device body 900 (the end opposite end having the slots 902a, 902b). Each of the legs 906 extends in substantially the same plane as one of the prongs. The legs 906 are adapted to be secured to the battery pack in which the clamping device 704 is installed as described above. While in the example shown in Figure 9 has two legs 906, the clamping device 704 may instead have more or fewer legs; for example the device may have just one leg protruding centrally from the lower end of the body 900 in a plane between and parallel to the planes of the planar prongs

In the example shown in Figure 9, the entire clamping device 704 is made from electrically conductive material, preferably aluminium. Therefore, when a positive terminal tab of a battery cell at the end of one row of cells is clamped within the first slot 902a and a negative terminal tab of a battery cell at the end of the next row of cells is clamped within the second slot 902b, the cells are electrically coupled via the device 704. Thus, the device 704 forms an electrically conductive bridge between two rows of cells.

In the example shown in Figure 9, the entire clamping device 704 is also made from thermally conductive material so that the device 704 acts are a thermal bridge between the battery cells that are clamped within the slots 902a, 902b and a heatsink such as a coolant running through ducts of the thermal management system of a battery pack. The clamping device 704 therefore provides a pathway for outflow or inflow of heat to the cells that it clamps in use, thereby to cool or to heat those cells.

In other examples, the clamping device 704 may not be entirely electrically and/or thermally conductive but may instead comprise an electrically and/or thermally conductive component. For example, the body 900 of the clamping device 704 may comprises an electrically conductive core running from an electrically conductive lining on the interior of the first slot 902, through an electrically conductive core of the body 900 (down the first prong and up into the second prong), to an electrically conductive lining on the interior of the second slot 902b. In this case, the exterior of the clamping device body 900 is electrically insulating. Similarly, the clamping device 704 may comprise a thermally conductive core, within a thermally insulating exterior, joining the interior of the slots 902a, 902b to the legs 906 via the interior of the device body 900. Such an arrangement makes the device safer as described above.

Figure 10 shows the third type of clamping device 706. The third type of clamping device 706 has a body 1000 which has a thin slot 1002 at its upper end. The slot 1002 is sized so as to receive the terminal tab of a battery cell (for example a terminal tab of the battery cell 100 described above with reference to Figure 1) at the beginning or end of a string of such cells connected in series. The clamping device body 1000 is substantially planar, having a height and width substantially larger than its thickness. The slot 1002 is formed in the same plane as the body 100 of the device.

In use, the clamping device 706 is positioned at an end of a battery cell at the beginning or end of a string of battery cells connected in series. The device 706 receives within the slot 802 a terminal tab the battery cell which is not connected to an adjacent cell in the series. The slot 1002 is narrow enough that the terminal tab fits within the slot 1002 via an interference (friction) fit. Therefore, the width of the slot 1002 is just smaller than the width of the terminal tabs of the battery cells. Alternatively, or additionally, the body 1000 is resilient such that it can be elastically deformed in order to open the slot 1002 to fit the terminal tab within the slot 1002, with the walls of the slot being biased together such that a clamping force is exerted on the terminal tabs held within the slot 1002.

The clamping device 706 also comprise an electrical connector 1004 which is adapted to provide a point of electrical connection between a battery cell clamped by the clamping device (via its terminal tab in the slot 1002) and an electric circuit. In the example shown in Figure 10, the electrical connector 1004 is a flat plate protruding from a side of the clamping device 706 in the same plane as the clamping device. The plate has a hole adapted to receive a busbar for electrically coupling the battery cell clamped by the clamping device to the busbar. In other examples, the electrical connector 1004 is another means for providing an electrical connection, such as a clip or clamp.

The clamping device 706 also comprises a leg 1006 protruding from the lower end of the clamping device (the end opposite the upper end which has the slot 1002). The leg 1006 extends in substantially the same plane as the device body 1000. The leg 1006 is adapted to be secured to the battery pack in which the clamping device 706 is installed as described above. In the example shown in Figure 10, the entire clamping device 706, including the connector 1004, is made from electrically conductive material, preferably aluminium. Therefore, when a terminal tab of a battery cell is clamped within the slot 1002, the clamping device 706 provides a pathway for current for flow between the battery cell clamped by the device and the electrical connector 1004 (and thus between the battery cell and the external electrical circuit to which the connector 1004 is connected). In addition, in the example shown in Figure 10, the entire clamping device 706 is also made from thermally conductive material. Electrical connection between battery cell clamped by the device 706 and an external circuit will tend to cause the battery cell to heat up. The thermally conductive clamping device 706 therefore acts as a pathway for outflow of heat from the battery cell, via the terminal tab clamped within the slot 1002, to a heatsink. The thermally conductive clamping device 706 can also act as pathway for inflow of heat to the battery cell, via the terminal tabs clamped within the slot 1002, from a heat source to enable heating of the battery cell clamped by the clamping device to improve its performance.

In other examples, the clamping device 706 may not be entirely electrically and/or thermally conductive but may instead comprise an electrically and/or thermally conductive component. For example, the clamping device 706 may comprises an electrically and/or thermally conductive core contained within an electrically and/or thermally insulating body. In this case, the exterior of the clamping device body is electrically and thermally insulating, however the interior of the slot 1002 (such as a lining on the interior of the slot), a core of the body 1000, and the leg 1006 form a thermally conductive core. In addition, an electrically conductive interior of the slot 1002 is connected to the electrical connector 1004 to provide an electrical coupling between a terminal tab held within the slot 1002 and the connector 1004.

The clamping devices described above with reference to Figures 8 to 10 may optionally also include integrated sensors to measure conditions at the clamping device. For example, the clamping devices may each comprises a temperature sensor for measuring the temperature at the clamping device. Alternatively, or additionally, the clamping device may comprise a voltage sensor (voltmeter) to measure the voltage across an electrical connection (such as between adjacent cells in a row, or cells at the ends of adjacent rows). Such sensors could identify faults in the circuit such as a disconnection or a short-circuit.

Figure 11 shows the battery pack 600 described above with reference to Figure 6 (not showing the thermal management system) including a plurality of battery cells 100. The battery cells 100 are arranged in a plurality of parallel rows, with two cells in each row. The cells in each row are arranged end-to-end in the configuration described with reference to Figure 4. The battery cells 100 are electrically connected in series using the clamping devices 702, 704, 706. The first cell in the series 100a is connected to a clamping device of the third type 706a (as described above with reference to Figure 10). The clamping device 706a receives, within the slot in its upper end, the left-hand terminal tab of the first cell 100a in the series. In this example the cell 100a is oriented such that the left-hand terminal tab of that cell is the positive terminal tab. Therefore, the clamping device 706a acts as a positive end terminal for the string of cells and provides a point of electrical contact for connecting the positive end of the string of cells to an external circuit.

The negative terminal tab at the right-hand end of the first cell 100a is electrically connected to the positive terminal tab at the left-hand end of the second cell 100b in the series. Thus, the first cell 100a and the second cell 100b have their longitudinal axes aligned. The negative terminal tab of the first cell 100a and the positive terminal tab of the second cell 100b are received within the slot at the upper end of one of the first type of clamping devices 702. In the example shown in Figure 11, the tabs do not overlap in face-to-face contact but instead are electrically coupled via the electrically conductive clamping device 702. Thus, the first cell 100a and the second cell 100b are electrically connected in series.

The second cell 100b is electrically connected to the third cell 100c in the series (which is the right-hand cell in the second row) via a clamping device of the second type 704 (which is occluded by a clasp 1102b which is described below). The direct of orientation of the third cell 100c is reversed as compared to the first cell 100a and second cell 100b, such that the longitudinal axis of the third cell 100c is antiparallel to the longitudinal axis of the second cell 100b. Therefore, the positive terminal tab of the third cell 100c is on the right-hand side of the cell. The negative terminal tab of the second cell 100b is clamped within the slot of the first prong of the clamping device 704 and the positive terminal tab of the third cell 100c is clamped within the slot of the second prong to the same clamping device 704. The tabs are electrically coupled via the clamping device 704 which acts as a conductive bridge between the first and second rows of cells. The negative terminal tab on the left-hand end of the third cell 100c is connected to a fourth cell (the left-hand cell in the second row) via a clamping device of the first type 702 in the same way that the first and second cells are connected. The fourth cell is electrically connected to a fifth cell (the left-hand cell in the third row) via a clamping device of the second type 704 in the same way that the second and third cells. The rest of the cells are connected as described above such that the cells are connected in series in a continuous zigzagging string. The last cell in the series (the left-hand cell in the last row, which is not shown) is connected to a clamping device of the third type 706b. The clamping device 706b received the negative terminal tab of the last cell so that the device 706b acts as a negative end terminal for the string of cells and provides a point of electrical contact for connecting the positive end of the string of cells to an external circuit.

The clamping devices are secured to the mat by their feet which are sandwiched between the lower layer 710 of the mat and the upper later of the mat (not shown). The clamping devices are further secured via clasps laid over the clamping devices and clipped onto the mat. The clasps are either double-sided clasps 1100 which are for securing the first type of clamping devices to the mat (situated between two battery cells) or single-sided clasps 1102a, 1102b for securing the second or third types of clamping devices to the mat (situated at the ends of the rows of cells). The clasps are described in more detail below with references to Figures 12a to 15b.

Figure 12a shows the double-sided clasp 1100 and Figure 12b shows the single-sided clasp 1102. The clasps 1100, 1102 comprise clasp bodies 1200 which have a plurality of teeth 1202 distributed along the length of the clasp body with spaces 1204 between. The clasps have arms 1206 are either end of the clasp bodies 1200 for securing the clasps to the mat. The arms 1206 secure the clasps 1100, 1102 to the mat via latches 1208 located at their lower ends. The teeth 1202 are substantially planar, being arranged in a plane perpendicular to a direction along the length of the clasp bodies 1200.

The spaces 1204 between the teeth 1202 are sized so as to each accommodate the bodies of the first and third types of clamping devices, or one of the prongs of the second type of clamping device. Therefore, when the clasp 1100, 1102 is secured over a plurality of clamping devices (arranged with spaced between them), the clamping devices mesh with the spaces 1204 between the teeth 1202 of the clasps, and the teeth 1202 of the clasps mesh with the gaps between the clamping devices.

On the double-sided clasp 1100, the planar teeth 1202 extend, transverse to the length of the clasp body 1200, out on both sides of the clasp body 1200. In contrast, on the single-sided clasp 1102, the planar teeth 1202 extend only on one side (the left-hand side in Figure 12b) of the clasp body 1200. This is because the double-sided clasp 1100 is for use with the first type of clamping device 702 which connects adjacent cells in row, and as such the clasp 1100 is adapted to accommodate a cell on either side of the clasp body 1200. The single-sided clasp however is for use with the second and third types of clamping devices 704, 706 which connects cells at the ends of rows and as such the clasp 1102 need only be adapted to accommodate cells on one side of the clasp body 1200.

Figure 13 shows a simplified embodiment of the clasp described above. The clasp 1300 shown in Figure 13 is similar to the clasps 1100, 1102 described above in that it has a body 1302 and teeth 1304 with gaps between them. However, in the clasp 1300 of Figure 13 the teeth 1304 do not extend transverse to the clasp body 1302.

The clasp 1300 secures clamping devices, which in the example shown in Figure 13 are clamping devices of the first kind 702 (as described with reference to Figure 8), within a battery pack. Each clamping device 702 receives part of the terminal tab 104 of a battery cell 100 within the slot of the clamping device 702 thereby to clamp the tab. In this example, the terminal tabs 104 of the cells 100 have a tab casing 1305 extending from the cell body in the same plane as the cell body and extending from the entire width of the cell body. The tab casing 1305 is preferably electrically insulating and encases the electrically conductive part of the tab which extends out from the casing 1305 (but which does not extend along the entire width of the cell body - just along a central portion of the width). The electrically conductive part of the tab 104 is clamped within the slot of one of the camping devices 702 (and is therefore not visible). The whole terminal tab 104, including the casing 1305 and the electrically conductive part extending out of the casing to be clamped, is therefore substantially T-shaped. The clamping devices 702 are positioned in line and distributed equally spaced apart with gaps between the device 702.

The clasp 1300 is position over the clamping devices 702 such that the gaps between the teeth 1304 of the clasp 1300 accommodate the clamping devices 702, and the gaps between the clamping devices 702 accommodate the teeth 1304. Thus, the clasp 1300 meshes with the clamping devices. The arms 1306 of the clasp 1300 extend down the outer side of the end most clamping devices 702, and the latches 1308 at the ends of the arms engage the mat thereby to secure the clasp 1300 to the mat and thus to the base plate of the battery pack.

When secured in placed, the clasp body 1302 exerts a vertical force down on the clamping devices 702 holding them against the mat to secure them in place. The teeth 1304 when fit within the gaps between the clamping devices 702 via an interference fit exert a horizontal force on the upper part of the clamping devices 702. This horizontal force acts to bias (or further bias if the walls of the slot are also resiliency biased) the slots of the clamping devices 702 to a closed position thereby to tightly clamp the terminal tabs 104 of the battery cells 100. The clasp 1300 also provides structural stability to the set of clamping devices 702 and, for example, maintains the devices 702 in an upright position and prevents the devices 702 from leaning over.

The clamping devices comprises feet 1310 at the bottom of legs which extend from the bottom of the bodies of the clamping devices 702 through the upper Iayer 712 of the mat as previously described. The feet 1310 contact the lower layer 710 of the mat to provide a foundation on which the clamping devices 702 stand. The feet 1310 also provide a stop to prevent the legs of the clamping devices 702 being withdrawn through the upper later 712 of the mat so that the clamping devices are secured to the mat and thus to the battery pack.

The lower layer 710 and upper layer 712 of the mat also sandwich the heatsink ducts 608 of the thermal management system 604 of the battery pack as described previously. The heatsink ducts 608 carry fluid coolant from a distribution duct 610 to a collection duct 612 along a winding serpentine path. The serpentine path of the heatsink ducts winds back and forth between the feet of the clamping devices 702 so as to be in close proximity to the feet (or in direct contact with the feet) thereby to facilitate heat exchange between the thermally conductive clamping devices and the coolant running through the heatsink ducts 608. The winding path of the heatsink ducts 608 between the feet maximises the length of duct that is in close proximity or direct contact with the clamping devices 702. Heat from the battery cells is thus transferred from the cells, through the terminal tabs, through the clamping device body to the legs and feet of the clamping device and into the coolant running through the heatsink ducts. This pathway can be used in reverse to transfer heat from the coolant to the cells via the terminal tabs.

Figure 14 shows the interaction between the clasp and clamping devices in cross section. In the example shown in Figure 14, the set of clamping devices represents the left-hand column 701a of clamping devices as described above with reference to Figure 7. Thus, the set of clamping devices comprises two clamping devices of the third kind 706, which are positive and negative end terminals for the string of cells, with the rest of clamping devices being of the second kind 704 for providing a conductive bridge between cells at the ends of adjacent rows. The clasp therefore it a single-side clasp 1102 as described with reference to Figure 12b.

The clamping devices 704, 706 are spaced apart such that the slots of the devices are equally spaced apart. Thus, the separation between the first and second prong of the same clamping device 704 is equal to the separation between a prong of one clamping device 704 and the prong of an adjacent device 704, which is also equal to the separation between the end clamping devices 706 and the nearest prong of the adjacent clamping devices 704. These spaces are sized so as to receive the teeth 1202 of the clasp 1102 via an interference fit. Similarly, the thickness of the prongs of the second type of clamping device 704 and the thickness of the body of the third type of clamping device 706 are sized so as to be received within the gaps between the teeth 1202 of the clasp via an interference fit. Thus, the clamping devices and the clasp mesh. The arms 1206 of the clasp 1102 extend down the outer side of the end clamping devices 706, and the latches 1208 at the ends of the arms engage the lower later 710 of the mat thereby to secure the clasp 1102 to the mat and thus to the base plate of the battery pack.

When secured in placed, the clasp body 1200 exerts a vertical force down on the clamping devices 704, 706 holding them against the mat to secure them in place. The teeth 1202 exert a horizontal force on the upper parts of the clamping devices 704, 706 which acts to further bias the slots of the clamping devices 704, 706 to a closed position thereby to tightly clamp the terminal tabs held within the slots. The cross-sectional path of the heatsink ducts 608 between the lower layer 710 and upper layer 712 of the mat is also shown winding back and forth between the feet of the clamping devices 704, 706 in a similar way as described above with reference to Figure 13.

The clasps described above with reference to Figures 11 to 14 may optionally also include integrated sensors to measure conditions at the clamp. For example, each fork may comprise a temperature sensor for measuring the temperature between two clamping devices. Alternatively, or additionally, the forks may each comprise a voltage sensor (voltmeter) to measure the voltage across between adjacent clamping devices. Such voltage sensors could identify faults in the circuit such as a disconnection or a short-circuit.

Figure 15 shows the battery pack 600 (as described above) now comprising a plurality of battery cells with the clasps in place, and showing other components described above. The battery pack 600 includes the plurality of battery cells arranged in rows of two cells connected end-to-end and tab-to-tab via clamping devices of the first kind between the two cells in a row, clamping devices of the second kind between cells at the ends of rows, and clamping devices of the third kind at the start and end of the continuous sting of cells. In the example of Figure 15, the clamping devices of the third kind, which form positive and negative end terminals of the string of cells, are connected via the electrical connectors 1004 to an external circuit 1500. The clamping devices of the first kind positioned between the cells are occluded by the doublesided clasp 1100, and the clamping devices of the second and third kind positioned at the ends of the rows are occluded by the single-sided clasp 1102 which are oriented such that their teeth extend from the clasp body towards the cells 100.

The thermal management system 604 is shown with the various ducts for carrying coolant. A first cooling circuit runs underneath and is occluded by the arrangement of battery cells 100. A second cooling circuit runs underneath and is occluded by a second arrangement of battery cells 1502. The battery cells 1502 are also arranged in rows of two cells, the cells in a row being connected end-to-end. The battery cells 1502 in this example are solid-state battery cells, whereas the cells 100 described previously are liquid battery cells such as lithium-ion battery cells. The solid-state cells 1502 are structurally similar to the cells 100 in that they are planar and include flat planar terminal tabs extended from either end. It should be understood that all of the description above concerning the battery cells 100 applies equally to the solid- state cells 1502, including the description of the configuration of cells in antiparallel rows and the electrical connection of cells tab-to-tab using clamping devices within and between rows. For example, the solid-state cells 1502 are connected via clamping devices in the same way as the cells 100: clamping devices of the third kind 706 are visible connecting the string of solid-state cells to the external circuit 1500 via electrical connectors 1004; clamping devices of the first kind 702 are visible between the cells in each row; and clamping devices of the second kind 704 are visible at the ends of the rows. The battery pack in this example includes both liquid cells 100 and solid-state cells 1502 which are connected to the electrical circuit 1500. Preferably, the battery cells 100 (which are preferably liquid lithium ion battery cells) power one circuit whereas the solid-state cells 1502 power a separate circuit.

The cells 100 are bound together by flexible straps 1504. One strap binds together the lefthand cells and another strap binds together the right-hand cells. The strap runs perpendicular to the longitudinal axes of the cells 100. Similarly, the solid-state cells 1502 are bound together by flexible straps 1506. One strap binds the left-hand cells, and another binds the right-hand cells, with the straps 1506 also perpendicular to the longitudinal axes of the cells 1502. The straps are flexible so as to provide room to enable to the cells 100, 1502 to expand when they heat up in use.

In the examples described above, the clasps are only for providing structural support for the clamping devices and to secure the clamping devices within the battery pack. However, in other embodiments the clasp also forms part of the thermal management system of the battery pack. This alternative embodiment is shown in Figures 16a, 16b, and 16c.

Figure 16a shows such an alternative embodiment of the double-sided clasp 1600. The clasp 1600 has teeth 1602 having gaps 1604 between them, and arms 1606 at either end of a clasp body 1608. The clasp body 1608 has a first channel 1610a for inlet of coolant into the clasp 1600 and a second channel 1610b for outlet of coolant from the clasp 1600. The coolant flows from the inlet channel 1610a to the outlet channel 1610b through the teeth 1602 of the clasp as shown in Figure 16b.

Figure 16b shows the clasp 1600 side-on and showing the interior of one of the teeth 1602. The inlet channel 1610a and outlet channel 1610b through the clasp body 1608 are shown, and the arrow indicates the path of the coolant flowing from the inlet channel 1610a to the outlet channel 1610b via one of the teeth 1602. Each of the teeth 1602 comprises a dividing wall 1612 which ensures that the fluid coolants flows down into the teeth before flowing out of the teeth into the outlet channel (rather than taking a more direct path across the top of the teeth and avoiding the bottom of the teeth). In the examples shown, the coolant may enter the clasp 1600 via the arms 1606a as shown in Figure 16c. Alternatively, the coolant may enter the clasp body 1608 directly (rather than via an arm), as shown by the arrows 1607a shown in Figures 16a and 16c.

Figure 16c shows the clasp 1600 with arrows indicating the path of the fluid coolant up the left-hand arm 1606a of the clasp and along the inlet channel along the clasp body. The coolant flows down into the teeth 1602 and into the outlet channel (which is not shown) of the clasp body. In the example shown, the coolant then flows out of the clasp body via the right-hand arm 1606b of the clasp. Alternatively, the coolant may flow out of the clasp body 1608 directly (rather than via an arm), as shown by the arrows 1607b shown in Figures 16a and 16c. As the arms of the clasp latch onto the mat of the battery pack, the arms provide a convenient point of inlet and outlet of the coolant through the clasp as the ducts of the thermal management system also pass through the mat; therefore the arms are located close to those ducts. The arm 1606a of the clasp for inlet of coolant is coupled to the distribution duct, preferably at the same point as the beginning of the corresponding heatsink duct which runs underneath the clasp in use. The other arm 1606b for outlet of the coolant is coupled to the collection duct, preferably at the same point as the end of the corresponding heatsink duct which runs underneath the clasp in use. Alternatively, when coolant runs through the clasp, the battery pack need not comprise the additional serpentine heatsink ducts through the mat in addition to the coolant pathway through the clasp. Therefore, in this example the battery pack may not comprise the heatsink ducts through the mat, as the function of the heatsink ducts is replaced by the coolant pathway through the clasp.

Furthermore, the clamping devices are described above as being individual stand-alone components which are assembled in rows into the battery pack and individually fixed in place. However, alternatively, the clamping devices may be moulded into the clasp itself, in the gaps between the teeth of the clasp, so that the clasp and the clamping devices are integrated into a single component. For example, Figure 16c shows between each of the teeth 1602 of the clasp 1600 a slotted clamp 1614. The clasp 1600, the teeth 1602, and the clamps 1614 are moulded from a single piece. Therefore, instead of installing a set of individual clamping devices in a row in the battery pack, the clasp 1600 when attached in the battery pack provides a series of slots (the slotted clamps 1614) for receiving the terminal tabs of the battery cells in the battery pack. The slots of the slotted camps 1614 are positioned where the slots of the clamping devices 702, 704, 706 would be. In this example, the slotted clamp 1614 and the clasp 1600 are both made from a thermally conductive material, preferably the same material. Alternatively, the teeth of the clasp may be wider than those shown in Figure 16c such that there is only a narrow gap between adjacent teeth. In this example, these narrows gaps between the wider teeth form slots for receiving the terminal tabs of the battery cells. Therefore, in this example, the narrow gaps between the teeth of the clasp perform the function of the slots of the clamping devices (or the slots of the slotted clamps) in clamping the terminal tabs of the battery cells between the teeth of the clasp, preferably via an interference fit. Therefore, in this example no separate clamping devices, or slotted clamp inserts such as are shown in Figure 16c, are required.

In this case, the orientation of the entire battery pack could be inverted as compared to the battery pack of, for example, Figure 15. In the inverted battery pack, the base plate of the battery pack is reversed so that the mat is on the underside of the base plate. The clasp 1600 is also inverted and attached to the mat such that the latches at the ends of the arms 1606 latch onto the mat and the arms 1606 and teeth 1602 depend downwardly from the mat to meet clasp body 1608. Alternatively, rather than inverting the entire battery pack, only the orientation of the clasp could be inverted, with the battery pack maintaining the same orientation as is shown in Figure 15. In this case, the clasp body (including the coolant carrying channels) runs along the base plate of the battery pack.

Inverting the clasp or the entire battery pack (including the clasp) in this way promotes the flow of coolant through the clasp. This is because gravity will act to drain the coolant from the teeth (through the outlet channel 1610b) which ensures that there is no dead space at the ends of the teeth 1602 where warm coolant is not continually replaced by fresh coolant flowing in from the inlet channel 1610a. Thus, the clamp more effectively cools the terminal tabs (and thus the cells they are connected to) clamped within the slotted clamps 1614.

In a yet further alternative embodiment, the battery pack does not comprise a clasp. In this case, clamping devices may be moulded from the base plate such that the clamping devices and the base plate are a single piece. Thus, the clamping devices would protrude from the base plate to provide means for gripping the terminal tabs of battery cells within the battery pack. In this case, as the clamping devices are formed as part of the base plate, they need not be secured to the base plate by the clasp. For cooling, the base plate may comprise a channel running through the bodies of the clamping devices protruding from the base plate to facilitate circulation of coolant through the clamping devices themselves. In this way, heat from the battery cells can be transferred to the coolant via the terminal tabs held by the clamping devices. In this embodiment, each clamping device must be electrically isolated from the other clamping devices to prevent short circuiting of the battery cells clamped by the clamping devices. For example, a barrier of electrically insulating material divides the clamping devices from one another. This electrical isolation is provided by the clamp, with the teeth of the clasp between each clamping device providing an electrically insulating barrier between the clamping devices.

It will be understood that the invention has been described above purely by way of example, and modifications of detail can be made within the scope of the invention.

Each feature disclosed in the description, and (where appropriate) the claims and drawings may be provided independently or in any appropriate combination.

Reference numerals appearing in the claims are by way of illustration only and shall have no limiting effect on the scope of the claims.