Patent Description:
An increasing number of vehicles are being manufactured, wherein the vehicle uses electric energy from a battery installed in the vehicle as an energy source. The vehicle could be an electric vehicle or a hybrid vehicle. Vehicles may be domestic vehicles or high power, lightweight vehicles such as supercars. It is desirable to manufacture a battery configurable to be installed in vehicles of all dimensions and shapes. Examples of such batteries may be found in patent literature <CIT>, <CIT> and <CIT>.

The cavity to contain the battery in some vehicles may be positioned behind one or more seats of the vehicle. Vehicle seats comprise a seat floor and a seat back, the seat floor being substantially parallel to the vehicle floor. Vehicle seats are designed to allow a driver or passenger in the vehicle to sit comfortably and hence the seat back of the vehicle seat is often not positioned orthogonally to the vehicle floor. Vehicle seat backs are often positioned obliquely to the vehicle floor so that a person sitting in the seat may be seated in an at least slightly reclined position. Batteries of the conventional shape of a cube or cuboid thus are unable to fit into a cavity behind a vehicle seat whilst utilising all the space available within the cavity.

The cavity to contain the battery in another type of vehicle may be a more regular shape of a cube or cuboid.

Hence it is desirable for a battery to be capable of being installed into a vehicle in a cavity behind one or more vehicle seats or into a cuboidal cavity.

According to a first aspect of the present invention there is a provided a battery comprising a plurality of battery modules, each battery module being according to appended claim <NUM>.

The battery module may comprise first and second fixings, the fixings protruding from the end structure in a direction away from the cell cavity, each fixing comprising a tab defining a connection hole.

The connection hole is preferably configured to receive a fixing element for securing the battery module to another battery module.

The battery module is preferably secured to a similar battery module by one or more fixing elements.

The back wall may extend orthogonally between the first and second external walls and orthogonally between two other walls.

The cells may be held in a cell tray located in the cell cavity. The cell tray may be configured to act as a fluid partition, the fluid partition dividing the cell cavity into a first region and a second region, the inlet opening providing an aperture in the first region and the outlet opening providing an aperture in the second region.

A portion of the cell tray nearest the end structure may comprise through-holes and the battery module may be configured so that coolant enters the first region through the said inlet opening, flows through the first region, passes through the through-holes into the second region, flows through the second region and exits the second region through the said outlet opening.

The through-holes nearest the top exterior wall may have a first diameter, the through holes nearest the bottom exterior wall may have a second diameter greater than the first diameter and the remaining through-holes having diameters which increase with the perpendicular distance between the top exterior wall and the respective through-hole.

The exterior walls of the battery module may be composed of exterior faces of the cell tray and exterior faces of the housing.

The housing may enclose all faces of the cell tray.

The battery module may have the form of a trapezoidal prism.

The battery module may nest with a similar battery module to form a battery module block. The battery module block may have the form of a cuboid.

The following description is presented to enable any person skilled in the art to make and use the invention, and is provided in the context of a particular application. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art.

<FIG> shows a battery <NUM> which may comprise a number of identical battery modules <NUM>. The battery modules may be arranged in a row. The battery may comprise any number of battery modules <NUM>. In the example depicted in <FIG>, one battery module <NUM> is shown for clarity, but in a preferred example there may be thirteen modules.

The battery may be installed in a vehicle. <FIG> shows the battery <NUM> fixed to a battery floor 1a. The battery floor 1a may be structurally integral to the vehicle in which the battery is installed. For example, the battery floor may be a load bearing component of a vehicle chassis. The battery floor 1a may be configured to be removably fitted to the vehicle so that the battery <NUM> can be removed from the vehicle. For example, for maintenance or replacement of the battery <NUM>.

The battery <NUM> may further comprise a battery control unit <NUM> which protrudes from the row of battery modules. The battery control unit <NUM> may be electrically connected to one or more module control units 12a. Each battery module <NUM> may comprise an attached module control unit 12a. The battery control unit <NUM> may control each battery module control unit 12a. Each battery module control unit 12a may control the activity of the respective attached battery module. Each battery module control unit 12a may receive information concerning the operation of the respective attached battery module. The battery module control units 12a may process that information and feed that information to battery control unit <NUM>.

The battery modules and battery control unit <NUM> may be enclosed by the battery floor 1a and a battery housing 1b.

<FIG> shows a battery module <NUM> with a trapezoidal prism shape. The battery module depicted in <FIG> comprises a cell tray <NUM> and a two-part housing 3a, 3b. In <FIG>, the battery module <NUM> and the cell tray <NUM> share a common longitudinal axis.

An exemplary cell tray <NUM> is shown in <FIG>. The cell tray depicted in <FIG> comprises cell holes <NUM> for holding cells (not shown). Each cell hole <NUM> may extend through the cell tray in a direction perpendicular to the longitudinal axis of the cell tray. The cell tray may be formed of electrically insulating material.

The cell tray may further comprise a fixing hole <NUM> configured to receive a fixing element (not shown) for securing the cell tray <NUM>, and hence the battery module <NUM>, to the battery floor (not shown). As shown in <FIG>, the fixing hole may extend through the cell tray. The fixing hole may extend through the entire length of the cell tray. The fixing hole may extend through the entire height of the cell tray. The fixing hole may extend through the entire cell tray in a direction perpendicular to the direction in which each cell hole extends through the cell tray. The fixing hole may extend through the entire cell tray in a direction perpendicular to the longitudinal axis of the cell tray.

<FIG> shows the cell tray <NUM> comprising two fixings <NUM>, each fixing comprising a tab 9a, the tab forming a connection hole 9b. Both fixings are generally positioned in the same plane as the cell tray. Each connection hole 9b may extend through its respective tab 9a in a direction parallel to the direction in which the cell holes <NUM> extend through the cell tray <NUM>. The cell tray may comprise more than two fixings. The cell tray may comprise a single fixing. Fixings on multiple battery modules may receive one or more common elements so that the battery modules can be secured to one another.

<FIG> shows a number of cells <NUM> being held in the cell holes <NUM> of the cell tray <NUM>. The cell tray may be configured to hold any number of cells. In the example depicted in <FIG> there are forty-eight cells held in respective cell holes <NUM>. Each cell hole may hold one cell.

Resin may be poured into a recessed side of the cell tray. The resin may harden around cells placed in the cell tray so as to secure the cells in the cell tray. Alternatively, each cell <NUM> may be held in a cell hole <NUM> by an interference fit between the cell tray <NUM> surrounding the cell hole and the cell inserted into the respective cell hole.

Each cell hole may extend through the cell tray in a direction perpendicular to the longitudinal axis of the cell tray. In the example cell tray depicted in <FIG>, each cell hole is cylindrical so as to accommodate cylindrical cells. In other examples, each cell hole may be prismatic so as to accommodate prismatic cells.

The length of each cell may be greater than the length of each cell hole. Each cell <NUM> comprises a positive terminal and negative terminal. When a cell <NUM> is inserted into a cell hole <NUM>, a length of the cell <NUM> comprising the positive terminal of the cell may protrude from the cell hole on one side of the cell tray <NUM> whilst a length of the cell <NUM> comprising the negative terminal protrudes from the cell hole on the other side of the cell tray. The portion of the cell <NUM> comprising the positive terminal and the portion of the cell <NUM> comprising the negative terminal may protrude from opposite sides of the cell tray. The protruding length of the portion of the cell comprising the cell's positive terminal and the protruding length of the portion of the cell comprising the cell's negative terminal may be equal.

The battery module <NUM> shown in <FIG> comprises a two-part module housing 3a, 3b. The housing 3a, 3b may form two enclosed regions which contain the cells <NUM> held in the cell tray <NUM>. In <FIG>, one part of the module housing 3a encloses the portions of cells protruding on one side of the cell tray. The second part of the module housing 3b encloses the portions of the cells protruding on the opposite side of the cell tray.

In <FIG>, the exterior faces of the battery module <NUM> comprise faces of the cell tray <NUM> and the housing 3a, 3b. Alternatively, the housing 3a, 3b may enclose the entirety of the cell tray. In this case, the exterior faces of the battery module would comprise faces of the housing 3a, 3b.

<FIG> shows busbars <NUM> contacting the terminals of multiple cells to form electrical connections between the multiple cells <NUM>. The busbars <NUM> are formed of electrically conductive material. The busbars <NUM> may be formed of metal, for example copper or aluminium.

As above, the cell tray <NUM> (not shown in <FIG>) fixedly holds cells <NUM>, each cell having a positive terminal and a negative terminal. The busbars <NUM> may link the cell terminals of any number of cells.

Cells <NUM> may be arranged in the cell tray <NUM> so that positive and negative cell terminals protrude from opposite sides of the cell tray. In this way, a current flow path may be created through cells and busbars. For example, the current flow path may "snake" through the battery module. The current flow path may repeatedly intersect the cell tray. The current flow path may repeatedly intersect the longitudinal axis of the battery module. At least some of the cells may be connected in parallel by the busbars <NUM>, meaning that the current flow path passes through multiple cells as the current flow path intersects the cell tray.

Module terminals <NUM> are shown in <FIG>. The module terminals <NUM> are positioned on the back of the battery module and may be integral to the cell tray <NUM> (not shown in <FIG>). Module terminals <NUM> of neighbouring battery modules may be electrically connected, for example, by module to module busbars. The module terminals <NUM> allow a supply of current to and/or from the cells <NUM> of the battery module <NUM>.

The busbars <NUM> may be integrated with a flexible printed circuit board (not shown in <FIG> shows the flexible printed circuit board <NUM> of a battery module. A portion of the flexible printed circuit board <NUM> is located in the region enclosed by the module housing and another portion of the flexible printed circuit board <NUM> is wrapped around the exterior faces of both parts of the two-part module housing 3a, 3b, also shown in <FIG>.

The busbars <NUM> shown in <FIG> may be integrated with the flexible printed circuit board <NUM>. The busbars <NUM> may be configured to conduct a high level of current between the cells of the module and the module terminals <NUM>.

The flexible printed circuit board <NUM> shown in <FIG> may further comprise sense wires. The sense wires may be configured to conduct a low current signal. The sense wires in the flexible printed circuit board may be attached to voltage sensors. Each voltage sensor may be capable of determining the voltage at a point on the busbar. Each voltage sensor may be capable of determining the voltage being drawn from a cell. Each voltage sensor may be capable of inferring the voltage being drawn from a cell from a measurement taken of the voltage being drawn from a busbar <NUM>. Each sense wire in the flexible printed circuit board may be capable of communicating voltage measurements from a voltage sensor to a module control unit 12a, shown in <FIG>. The module control unit 12a may be capable of adapting the activity of the battery module in response to the voltage measurements provided by the sense wire. Each sense wire may be capable of communicating voltage measurements to the battery control unit. The module control unit 12a may be capable of communicating voltage measurements to the battery control unit. The battery control unit <NUM>, also shown in <FIG>, may be capable of adapting the activity of the battery module in response to the voltage measurements. The battery control unit <NUM> may be capable of adapting the activity of the battery in response to the voltage measurements.

The sense wires of the flexible printed circuit board <NUM> may be attached to one or more temperature sensors. A temperature sensor may be capable of determining the temperature of a part of the battery module. Each sense wire may be capable of communicating temperature measurements from a temperature sensor to the module control unit. The module control unit may be capable of adapting the activity of the battery module in response to the temperature measurements provided by the sense wire. Each sense wire may be capable of communicating temperature measurements to the battery control unit. The module control unit may be capable of communicating temperature measurements to the battery control unit. The battery control unit may be capable of adapting the activity of the battery module in response to the temperature measurements. The battery control unit may be capable of adapting the activity of the battery in response to the temperature measurements.

The sense wires may be attached to other types of sensors, for example current sensors, and/or fluid flow sensors.

<FIG> also show terminal tabs <NUM>, <NUM> which each of which connect either a positive or a negative end of the busbar to the respective positive or negative module terminal.

It is known to supply coolant to regulate the temperature of batteries. In typical batteries, the coolant is confined within coolant jackets or pipes. In such batteries, cells are cooled in areas of the cell which make contact with the jacket or pipe containing the coolant. This is a slow and inefficient cooling method.

In other typical batteries, coolant is not confined by coolant jackets or pipes, but makes direct contact only with the body/centre portion of each cell. In such batteries, the cell terminals are protected so that coolant does not make contact with the cell terminals. Such contact is avoided as it would typically lead to electrical shorting. This is also an inefficient method because the cell terminals, being electrically connected, are often the hottest parts of the cell and yet they are not directly cooled by the coolant.

By contrast, in the battery module described herein, coolant supplied to the battery module <NUM> makes direct contact with cell terminals, flexible printed circuit board <NUM>, busbars <NUM>, and cell body. The entirety of the cell and connected conducting parts are bathed in coolant. That is, the entirety of the portions of each cell which protrude from the cell tray are configured to be directly contacted by coolant. The coolant used is a dielectric oil. Dielectric oils have insulating properties. Cells drenched in dielectric oil are insulated from one another preventing short circuiting between cells. This is an efficient method of regulating cell temperature. Such efficient cooling enables the cells to operate at a higher power and for longer. This means that fewer and/or smaller cells are required to generate the same power as batteries utilising the previously mentioned cooling methods.

<FIG> shows a supply coolant conduit portion <NUM> and a drain coolant conduit portion <NUM>. In the exemplary configuration shown in <FIG>, the supply coolant conduit portion <NUM> is positioned in a lower position and the drain coolant conduit portion <NUM> is positioned in an upper position. Such a configuration reduces the risk of air locks occurring during filling. Alternatively, the supply coolant conduit portion may be positioned in an upper position and the drain coolant conduit portion may be positioned in a lower position.

In order to fill the battery module with coolant so that components of the module can be bathed in coolant, air is first displaced. Each battery module may thus comprise an outlet for allowing air to leave the battery module. The air outlet may be referred to as a bleed port.

Both coolant conduit portions may extend along the battery module in a direction orthogonal to the longitudinal axis of the battery module. Both coolant conduit portions may extend along the battery module in a direction orthogonal to the direction in which the fixing hole <NUM> extends through the cell tray <NUM>. Both coolant conduit portions may extend along the battery module in a direction parallel to the direction in which the cell holes <NUM> extend through the cell tray <NUM>.

As shown in <FIG>, the supply coolant conduit portion <NUM> is linked to an inlet <NUM> in the battery module so that coolant may be supplied to a region enclosed by the housing of the battery module. The drain coolant conduit portion <NUM> is linked to an outlet <NUM> so that coolant may be drained from a region enclosed by the housing of the battery module. Inlet <NUM> and outlet <NUM> are openings formed in the module housing. The inlet may be located in an upper position and the outlet in a lower position. Alternatively, the outlet may be located in an upper position and the inlet in a lower position. The coolant may be supplied to one of the two regions enclosed by the housing and be drained from the other of the two regions enclosed by the housing, one region being on an opposite side of the longitudinal axis of the cell tray to the other region. The cell tray <NUM> may comprise through-holes <NUM> to <NUM> for allowing the passing of coolant from a respective one of the said regions to the other of the said regions. The through-holes may be located in the cell tray <NUM> at the end of the cell tray <NUM> remote from the inlet <NUM> and outlet <NUM>. The through-holes may be shaped to promote even fluid flow over the cells.

As shown in <FIG>, battery <NUM> contains a number of battery modules <NUM> arranged in a row. When battery modules <NUM> are positioned in a row, a coolant conduit portion <NUM> of one battery module aligns with a coolant conduit portion of a neighbouring battery module. The two coolant conduit portions may be connected to one another by a coupler <NUM>, shown in <FIG>. Couplers <NUM> form liquid tight connections between coolant conduit portions so that coolant may flow from portion to portion. When supply coolant conduit portions <NUM> of the battery modules in the row of battery modules are connected by couplers <NUM>, they form a supply coolant conduit 14a which extends along the length of the row of battery modules. When drain coolant conduit portions <NUM> of the battery modules in the row of battery modules are connected by couplers <NUM>, they form a drain coolant conduit 15a which extends along the length of the row of battery modules. Alternatively, adjacent coolant conduit portions may be integral to one another such that couplers joining portions are not required. Multiple coolant conduit portions may form longer conduits which once installed cannot be split into conduit portions. A row of battery modules <NUM> may comprise a supply coolant conduit which extends along the length of the row of battery modules and is not divided into individual portions. A row of battery modules <NUM> may comprise a drain coolant conduit which extends along the length of the row of battery modules and is not divided into individual portions.

As shown in <FIG>, the longitudinal axes of all the battery modules <NUM> in the row of battery modules of the battery <NUM>, may be parallel to one another. Both coolant conduits 14a, 15a may extend along the row of battery modules in a direction orthogonal to the longitudinal axes of the battery modules in the row of battery modules. Both coolant conduits may extend along the row of battery modules in a direction orthogonal to the direction in which the fixing hole <NUM> extends through the cell tray <NUM> of each battery module. Both coolant conduits may extend along the row of battery modules in a direction parallel to the direction in which the cell holes <NUM> extend through the cell tray <NUM> of each battery module.

Inlet <NUM> and outlet <NUM> may be configured to allow coolant to enter and leave the battery module <NUM>. Inlet <NUM> and outlet <NUM> may further act as passages through which the flexible printed circuit boards <NUM> pass between the interior and exterior of the battery module, as shown in <FIG>. The inlet <NUM> and outlet <NUM> may be the only openings in the two-part housing 3a, 3b of the battery module <NUM>. Alternatively, the battery module may comprise other inlets and outlets, for example a bleed port used to allow air to leave the battery module. <FIG> shows sealant <NUM> around the inlet <NUM> and outlet <NUM>. Sealant <NUM> ensures that coolant inside the battery module does not leak from the battery module into other parts of the battery.

The method of direct cell cooling described herein also has further advantages in the case that excessive pressure builds up inside a cell. Each cell may comprise a cell vent port. In the case that excessive pressure builds up inside the cell, the cell vent port may be activated, allowing fluids within the cell to escape the cell. The cell vent port may be configured to expel cell fluids in the event that pressure within the cell exceeds a threshold. Upon leaving the cell, the fluids are quenched by the surrounding coolant.

A battery of a modular design is beneficial. Battery modules can be arranged in a variety of configurations to enable the battery to fit into cavities of different shapes and sizes. Hence the same battery modules may be used in a number of different vehicles, for example, different vehicle models in a manufacturers range of vehicles.

The battery pack described herein comprises a plurality of battery modules. The battery modules are shaped such that the battery pack is configurable. The battery modules described herein negate the need for different batteries to be designed and manufactured for installation in different types of vehicles.

<FIG> shows a battery module <NUM>. In the example shown, the end structure <NUM> of the battery module comprises a single flat face extending obliquely between the top exterior wall <NUM> and bottom exterior wall <NUM>. The end structure may extend obliquely between two other walls. The end structure may comprise a single face or multiple faces. Each face may have the form of a curved face. Each face may have the form of a convex face. Each face may have the form of a concave face. The end structure may comprise a face with convex portions. The end structure may comprise a face with concave portions. The end structure may have the form of a stepped structure comprising multiple faces. The end structure may comprise multiple faces, one or more of the faces being orthogonal to the top exterior wall and the bottom exterior wall.

The end structure extending between the top wall and the bottom wall defines an end of the housing in a first direction. The end structure may be inclined with respect to the top and bottom walls such that the cell cavity extends in the first direction beyond the furthest extent of the top wall. The end structure may comprise a single flat face extending obliquely between the top exterior wall and bottom exterior wall. The battery module may further comprise a back wall. The back wall may extend orthogonally between the top and bottom exterior walls and orthogonally between two other walls. The battery module may have the form of a trapezoidal prism, as depicted in <FIG>. In the battery module shown in <FIG>, a back wall <NUM> extends orthogonally between the top and bottom exterior walls <NUM>, <NUM> and orthogonally between two other walls. Alternatively, the back wall may extend obliquely between the top and bottom exterior walls. The back wall may extend obliquely between two other walls. The back wall may be a curved wall. The back wall may be a convex wall. The back wall may be a concave wall. The back wall may comprise a wall with convex portions. The back wall may comprise a wall with concave portions.

The exterior walls of the battery module <NUM> shown in <FIG> are composed of exterior faces of the cell tray <NUM> and exterior faces of the housing 3a, 3b. The housing is a two-part housing 3a, 3b. In another example, the housing <NUM> may enclose the entirety of the cell tray.

<FIG> is a schematic view of a battery module <NUM> positioned in a vehicle cavity behind a vehicle seat. The battery module <NUM> may represent a row of battery modules. The bottom exterior wall <NUM> is substantially parallel to the vehicle floor. The end structure <NUM> is substantially parallel to the vehicle seat back. In the example battery module shown in <FIG>, the end structure comprises a single flat face extending obliquely between the top exterior wall and bottom exterior wall. Alternatively, the end structure may have the form of a curved face. A battery module comprising a curved end structure may be installed in a vehicle cavity behind a vehicle seat with a curved vehicle back.

<FIG> is a schematic depicting pairs of nested battery modules <NUM> in a cuboidal vehicle cavity. Each battery module <NUM> shown in <FIG> may represent a row of battery modules. There may be multiple rows of nested battery modules. In each pair of nested battery modules, the end structure of one battery module overlaps the end structure of the similar battery module in a direction perpendicular to the top exterior wall of the battery module.

<FIG> show two battery modules forming a battery module block. The two modules are secured to one another by a fixing element <NUM>. In this exemplary embodiment, each battery module <NUM> comprises a cell tray <NUM>. Each cell tray comprises two fixings <NUM> comprising a tab 9a and a connection hole 9b. As shown in <FIG>, one battery module is rotated <NUM> degrees about an axis transverse to the first direction. The connection holes of the fixings of the battery module are colinear with the connection holes of the fixings of the similar battery module. A fixing element <NUM> may be passed through the connection holes of the two battery modules so as to secure the battery modules to one another. The nested battery modules form a battery module block. The battery module block shown in <FIG> has the form of a cuboid.

The battery module block may alternatively have the form of a parallelogram prism. In fact, the battery module block may be any 3D shape.

As mentioned above, each battery module may comprise a bleed port. The bleed port may be configured to allow air to escape the battery module. The bleed port may be used to evacuate the battery module of air as the battery module is filled with coolant. In order for air to leave the battery module through the bleed port when the battery module is being filled with coolant, it is preferable that the bleed port is positioned at the top of the battery module. As the battery module is designed such that it can be installed into a vehicle in two orientations, each battery module may comprise two bleed ports where one bleed port may be used in each orientation. One bleed port may be positioned at the top of the battery module and a second port located at the bottom of the battery module. The two bleed ports may be located in opposite faces of the battery module. For example, one bleed port may be located in exterior wall <NUM> and one in exterior wall <NUM>.

Only one bleed port may be utilised at once. According to one example, when the battery module shown in <FIG> is installed in an orientation with exterior wall <NUM> as its base, a bleed port located on exterior wall <NUM> may be closed (e.g. using a plug) and a bleed port located on exterior wall <NUM> may be left open for use. When the battery module is installed in an orientation with exterior wall <NUM> as its base, a bleed port located on exterior wall <NUM> may be closed (e.g. using a plug) and a bleed port located on exterior wall <NUM> may be left open for use. This has the advantage that the same battery module can be filled effectively with coolant in multiple orientations. Once the battery module is filled with coolant, both bleed ports may be closed. Both bleed ports may be closed when the battery module is installed in a vehicle.

Each battery module may be configured to nest with a similar battery module. When a battery module is nested with a similar battery module, the top exterior wall of that battery module may be parallel to the bottom exterior wall of the similar battery module and the end structure of the battery module may overlap the end structure of the similar battery module in a direction perpendicular to the top exterior wall of the battery module. The battery module block may have the form of a cuboid and may hence be installed into a cuboidal cavity - optimising use of the space within that cavity.

When the space within the cavity is optimised, the number of battery modules that can be installed in the cavity is maximised. This is due the exterior walls of the battery modules being colinear with the interior walls of the cavity allowing the battery modules to take up all available space near the interior walls of the cavity.

As described above, the back wall of the battery module comprises an inlet opening and an outlet opening. Adjoined to the back wall of each battery module may be a supply coolant conduit <NUM> configured to supply coolant to the first region of the battery module through the inlet and a drain coolant conduit <NUM> configured to drain coolant from the second region of the battery module through the outlet.

As described above, depending on the shape and size of the vehicle cavity into which the battery is to be installed, the battery modules may be arranged differently. The battery may comprise a single row of battery modules. The battery may comprise a single row of pairs of nested battery modules. The battery may comprise multiple rows of battery modules. The battery may comprise multiple rows of nested battery modules.

Each row may comprise its own supply coolant conduit and its own drain coolant conduit. Each row of battery modules may be served by its own heat exchanger. Alternatively, multiple rows of battery modules may be served by one heat exchanger.

Claim 1:
A battery module (<NUM>) comprising:
a housing (3a, 3b) defining an internal cell cavity; and
cells (<NUM>) located in the cell cavity;
the housing comprising:
a top exterior wall (<NUM>);
a bottom exterior wall (<NUM>) substantially parallel with the top wall;
an end structure (<NUM>) extending between the top wall and the bottom wall and between two other walls, wherein the end structure:
defines an end of the housing in a first direction;
is inclined with respect to the top and bottom walls such that the cell cavity extends in the first direction beyond the furthest extent of the top wall; and
is configured such that the battery module can nest with a similar battery module that has been rotated about an axis transverse to the first direction with the top wall of the battery module parallel to the bottom wall of the similar battery module and the end structure of the battery module overlapping the end structure of the similar battery module in a direction perpendicular to the top wall of the battery module; and
a back wall (<NUM>) extending between and joining the top and bottom walls and the two other walls, the back wall comprising an inlet opening (<NUM>) and an outlet opening (<NUM>), the said inlet opening being configured for supplying coolant to the battery module and the outlet opening being configured for draining coolant from the battery module.