EP4725066A1

EP4725066A1 - A rechargeable battery pack

Info

Publication number: EP4725066A1
Application number: EP24733687.8A
Authority: EP
Inventors: Riser FREDERIC
Original assignee: Fortescue Zero Ltd
Current assignee: Fortescue Zero Ltd
Priority date: 2023-06-12
Filing date: 2024-06-12
Publication date: 2026-04-15
Also published as: GB202308751D0; WO2024256814A1; GB2630934A; CN121359278A; AU2024303816A1

Abstract

A rechargeable battery pack comprising: a battery housing, at least two battery modules, each comprising a plurality of battery cells, the battery modules being located inside the housing, at least one closed loop channel within the housing that extends along a vertical direction from a region at or adjacent an upper end of the battery pack to a region at or adjacent to a lower end of the battery pack, the closed loop channel being partially filled with a phase change material which at a first temperature has a liquid form and lies towards the bottom of the channel and at a second higher temperature has a gaseous form and rises towards the top of the channel, a heat sink located above the battery modules and in contact with an upper portion of the closed loop channel.

Description

A RECHARGEABLE BATTERY PACK

This invention relates to rechargeable battery packs, in particular high voltage battery packs which can be rapidly recharged.

Batteries are increasingly being used in vehicles of all kinds as a replacement or a supplement to a traditional internal combustion engine. With ever increasing development in battery pack technology, in particular energy density and weight, it has become feasible to operate those vehicles over long distances or for long operating times between recharging, something that had previously been a barrier to the technology becoming widely adopted.

To make battery power attractive to users familiar with internal combustion engine vehicles it is desirable that the battery pack can be recharged rapidly. This process is limited by the battery cell technology and also in the case of high voltage battery packs by the need to limit the temperature increase in the battery pack when recharging. Similarly, care must be taken to limit heat build-up in the battery pack when it is placed under high energy loads, for instance to provide maximum acceleration to a vehicle that is fully laden and travelling up an incline. To ensure the batteries of the battery pack are not damaged it is standard practice to provide a battery pack with a sophisticated thermal management system that can monitor the temperature of the batteries in the pack, sometimes at the level of individual battery cells, and to control the discharge and charging of the cells accordingly.

It is also known to actively cool the battery cells in a battery pack. In the cases of a high-power battery pack for an electric vehicle the cooling system typically uses liquid cooling in the same way that is used to cool an internal combustion engine. Channels are formed within the battery pack that weave their way around the battery and carry cooling fluid. Ancillaries including a pump and often a compressor and expansion vessel are also required to push the liquid through the channels. While normal passenger electric vehicle batteries do not require fast cooling during road operation due to the mild driving conditions temperature rises would be high if fast charging options where to be used. The battery thermal management system may monitor the temperature of the liquid that is being circulated through the battery pack and in the event of a potential overheating of the battery pack may alter the flow of the liquid or limit the rate of charging or discharging of the battery pack or both.

The applicant has appreciated that liquid cooling as used in the prior art is not always appropriate. For example, in the case of a racing car the use of a liquid, most commonly a water/glycol mix, flowing within/ between battery cells in a battery pack may be prohibited due to safety issues. Alternative liquid coolants that are safer are available but are either heavily polluting or unsustainable and very expensive. Even in situations where water/liquids may be permitted, intricacies in the battery packing mean complicated piping, large pressure drops, maintenance issues, etc.

According to a first aspect the invention provides a rechargeable battery pack comprising: a battery housing, at least two battery modules, each comprising a plurality of battery cells, the battery modules being located inside the housing, at least one closed loop channel within the housing that extends along a vertical direction from a region at or adjacent an upper end of the battery pack to a region at or adjacent to a lower end of the battery pack, the closed loop channel being partially filled with a phase change material which at a first temperature has a liquid form and lies towards the bottom of the channel and at a second higher temperature has a gaseous form and rises towards the top of the channel, and a heat sink located above the battery modules and in contact with an upper portion of the closed loop channel.

The battery pack may include a cooling means for actively cooling the heat sink.

The battery pack according to invention uses closed loop channels, such as microchannels, microtubes, etc. which contain a small volume of liquid. The liquid is ideally one with a low boiling point, preferably dielectric. A part of the channel is in thermal contact with the heat source, in this case, a battery pack. This part is ideally the lower section of the channel, wherein the small liquid volume is contained. The liquid boils absorbing heat from the battery and the vapour rises to the top section of the channel. The top section is in thermal contact with the heatsink. This may be actively cooled by flowing a fluid such as air across the heatsink or through at least one channel within the heatsink for instance providing a heat sink in the form of a cooling plate(s) containing a circulating volume of fluid, such as gas, air, water or appropriate coolant. This condenses the vapour which then returns to the bottom section thus completing the thermal cycle. Such closed loop channels are often described as heat pipes.

The closed loop channel may comprise a sealed pipe or tube the heat pipe is partially filled with a working fluid. The working fluid mass is chosen so that the heat pipe contains both vapor and liquid over the operating temperature range of the battery pack. The space that is not filled with working fluid at a temperature where no working fluid has evaporated may be filled with an inert gas such as Nitrogen.

The working fluid may comprise water, or an alcohol such as ethanol. The choice of working fluid will depend on the expected temperature conditions within the battery pack, with a requirement that the freezing point of the fluid is below the operating range. The working fluid may be selected to operate over a range of 15 degrees C to 70 degrees C, and most preferably optimised to work over a temperature range of 20 degrees C to 45 degrees C.

The invention provides a self-priming system that allows extraction of heat from within a battery arrangement without being in contact with the circulating water, using phase changing closed loop channels. This ensures safety as well as removes need for complicated plumbing.

The volumes of water required for the cooling operation is also minimal, as only the sink plate has to be cooled and there is no circulation into the main battery volume.

The battery pack may include a more than two battery modules, and each battery module may be in thermal contact with at least one closed loop channel.

The closed loop channels may extend downward from a point located in a plane that is above the upper end of each battery cell.

There may be at least one closed loop channel for each battery module.

At least one closed loop channel may extend downward in a space between adjacent battery modules. At least one close loop channel may extend downward in a space between adjacent battery cells within a battery module.

At least one closed loop channel may be in direct mechanical contact with at least one battery cell of at least one of the battery modules.

Mechanical contact may be achieved by clamping of each closed loop channel directly onto a battery module. A thermally conductive paste may be provided to enhance the transfer of heat energy from the battery module to the closed loop channel.

The contact region may be located outside of an adiabatic region of the closed loop channel to maximise the rate of movement of heat energy upwards to the cooling plate. The adiabatic region is typically surrounded by a thermal insulator meaning that little heat transfer from the batteries to the channel will occur in that region.

The battery pack may comprise two or more battery modules arranged in a N by M grid pattern, where N and M may take a value of 1 or higher. For instance, they may be arranged in a 6 by 2 grid, or a 6 by 4 grid.

Battery modules may be arranged in at least two grids, one spatially located above another.

Where the battery modules are arranged in two or more layers, at least one of the closed loop channels may pass from the top of the battery modules through every layer. Every closed loop may pass through every layer.

Each battery module may include a sub-housing for a set of battery cells of the module which is thermally conductive and which is in thermal contact with at least one of the closed loop channels.

Where the battery modules are arranged in multiple layers, one or more of the closed loop cooling channels may pass through only the upper most layer, or one or more upper layers without passing vertically lower than the top of the bottom layer or only part way down through bottom layer. There may be a mix of closed loop cooling channels that have different lengths and each pass through one or more layers.

The cooling channels may each form a separate closed loop with the phase change material inside each channel unable to mix with the phase change material in other channels.

Alternatively, a manifold may be provided that connects at least two channels so that the phase change material can mix between the two channels.

The manifold may be located at the bottom of the battery modules. It may occupy a space between a lower end of the battery modules and a base of the battery housing.

Each closed loop channel may comprise an elongate hollow channel such as microchannels, microtubes, etc. which contain a small volume of liquid. The liquid is ideally one with a low boiling point, preferably dielectric.

The heat sink, which may take the form of a cooling plate, may be located outside of the battery housing. It may form a lid of the battery housing. It may be indirectly in contact with the top of the closed loop channel or channels through an intermediate component such as a lid of the housing or a fixed wall of the housing. It may have at least one connector that extends down from the underside of the plate and is connected to an end of a respective closed loop channel.

Alternatively, the closed loop channels may be rigidly connected to the heat sink by welding or other means in the manner of spines. Where the heat sink is located outside of the battery housing these may project through holes in a lid of the housing into the battery housing.

The heat sink may form a lid of the housing and a seal such a polymeric seal may be provided between the cooling plate and an upper opening of the battery pack housing.

The heat sink may include a cooling means comprising at least one internal channel having an inlet end for receiving cooling fluid and an outlet end for outputting fluid that has flowed through the channels. At least one channel may include a cooling fluid. This may be water, either potable water or even sea water or river water. Because this water does not flow through the battery modules there is little to no need to regulate what is used. If the water contains sediment that clogs up the channel or channels in the cooling it can be easily removed and replaced or cleaned and refitted.

Actively cooling the heat sink speeds up the transfer of heat energy from the gas in the top of the closed loop channel which then turns to a liquid and drops under gravity to the bottom of the channel, where the heat transfer cycle can start again.

The heat sink may be planar and may lie in a generally horizontal plane above the battery modules and may be releasable without a need to open the battery housing for easy servicing or replacement.

The apparatus may include a compressor and an expansion vessel that are placed in a closed loop, with a pump for circulating fluid through the closed loop, the fluid in the loop passing through the closed channel of the cooling plate or through a heat exchanger which is in series with the cooling channel in the cooling plate.

The apparatus may include an inlet port and an outlet port for connection to an external cooling circuit that is at a fixed location. This allows cooling fluid to be pumped through the cooling plate from the external circuit from a fixed cooling circuit.

The heat sink may be provided, as an alternative to cooling channels or in addition, with a plurality of fins through which heat in the cooling plate will radiate into the surrounding atmosphere.

The fins may be provided on an upper face of the cooling plate that extend away from the battery modules.

The battery pack may be constructed without any liquid flowing through or around the battery modules, liquid only flowing through the cooling plate where optionally provided. The primary source of cooling will then be the closed loop channels, and the heat sink into which heat is fed from the channels. The heat sink may be a flat plate. This plate may be located outside of a main body of the housing that contains the battery modules, safely isolating the modules from any liquid used to cool the plate.

The heat sink may include one or more fins that project from a body of the heat sink. In the case of a plate these may be connected at one end to the plate and extend with a radial component away from the plate. Providing a heat sink with fins is an effective way to give a high surface area in a limited volume of space from which heat can be radiated into the surrounding air.

The battery may comprise a removable part of a vehicle such as an automobile, for instance a passenger car, or a truck, or a specialist mobile equipment. The battery may comprise a rechargeable electric vehicle battery that in use provides the power to the electric motor or motors that provide propulsion to the vehicle.

The battery cells may comprise cylindrica cells. These may be arranged in a grid within a battery module and closely packed with a closed loop channel extending down the space inevitably left between adjacent cells.

The battery cells may comprise prismatic cells having a rigid rectangular outer casing. These can be more closely packed than cylindrical cells. A closed loop channel may be sandwiched in between adjacent cells or adjacent modules of cells.

The battery cells may be Li-ion battery cells.

The battery pack may comprise a rechargeable battery of a hybrid vehicle that has both an internal combustion engine and at least one electric motor that together are configured to provide propulsion.

The combustion engine may drive one or more road wheel of the vehicle alongside the electric motor or may drive an alternator that charges the battery with only the electric motor providing propulsion. The vehicle may comprise a passenger car, or a racing car. It may comprise a truck for use on the road or a specialist commercial vehicle for use off road such as a mining truck. The possible uses of the battery pack in terms of the type of vehicle are endless.

The battery pack may comprise a part of a helicopter, or an airplane. Where the battery pack forms a part of a helicopter or airplane, it is desirable to provide cooling fins on the cooling plate and to locate this in a region of high airflow when the airplane of helicopter is in forward flight. Providing an air cooled battery with no requirement to circulate cooling fluid can be considerable lighter than a conventional liquid cooled battery pack.

The battery pack may comprise a part of a river faring or sea faring vessel such as a boat, yacht, ship, jetski or speedboat. The battery pack may be located so that the cooling plate is submerged within the water that the vessel floats in or has one face in contact with that water. It may form a part of a hull of the vessel or be fixed to an underside of the hull of the vessel. The river or sea water flowing over the plate and optionally through a channel in the cooling plate remove heat energy from the battery pack.

The battery pack may comprise a part of a satellite for positioning in space or in a near space region of the earth’s atmosphere or part of a lunar rover for use on a planet other than the earth.

The battery bank may comprise a power bank for storing electrical energy at a domestic or commercial premises.

According to a second aspect the invention provides a recharging station for an electric vehicle having a battery pack in accordance with the first aspect comprising;

A source of chilled fluid,

A connector for connecting the source of chilled fluid to a fluid channel within the cooling plate of the battery pack when the vehicle is at the recharging station and for extracting fluid that has circulated through the plate, and

A source of electrical energy that is connectable to a charging port located on the vehicle for charging the battery. There will now be described by way of example only several embodiments of the present invention with reference to and as illustrated in the accompanying drawings of which:

Figure 1(a) is a schematic elevational view of a first embodiment of a battery pack in accordance with an aspect of the invention;

Figure 1(b) is a schematic elevational view of an alternative embodiment of a battery pack in accordance with an aspect of the invention;

Figure 2 is a cross sectional plan view of the first embodiment of a battery pack in accordance with an aspect of the invention where the cross section is part way up the battery pack;

Figure 3 is a schematic diagram showing how the cooling plate can be integrated into a circuit for flowing cooling fluid through the plate;

Figure 4 is diagram showing a single closed loop channel in elevational cross section with the fluid inside the channel visible in both the liquid and gaseous states;

Figure 5 is a schematic elevational view of a second embodiment of a battery pack in accordance with an aspect of the invention;

Figure 6 is a cross sectional plan view of the second embodiment of a battery pack in accordance with an aspect of the invention where the cross section is part way up the battery pack;

Figure 7 is a schematic elevational view of a third embodiment of a battery pack in accordance with an aspect of the invention

Figure 8 is a cross sectional plan view of the third embodiment of a battery pack in accordance with an aspect of the invention where the cross section is part way up the battery pack; Figure 9 is a cross sectional plan view of a fourth embodiment of a battery pack in accordance with an aspect of the invention where the cross section is part way up the battery pack;

Figure 10 is a cross sectional plan view of the fifth embodiment of a battery pack in accordance with an aspect of the invention where the cross section is part way up the battery pack;

Figure 11 is a perspective view of a single closed loop channel, or heat pipe, that is used in the first to fifth embodiments; and

Figure 12 is a perspective view of a heat sink arranged as a cooling plate that may be used in the first to fifth embodiments; and

Figure 13 shows an alternative heat sink that includes a set of fins suitable for cooling of the heat sink by air blown across the fins.

As shown in plan view in Figure la and in cross section taken at midway up the battery pack in Figure 2, a battery pack comprises a housing having a rectangular base and four side walls 2a, 2b, 2c, 2d to form an open ended space. Note that only two of the walls 2b and 2d can be seen in Figure 1. Within this space are two battery modules 3, 4 arranged in an N by M grid where N equals 1 and M equals 2. Each battery module 3,4 comprises a set of 4 prismatic shaped lithium Ion (Li-Ion) battery cells 5 arranged in a two by two grid. The two sets of battery cells 5 are located and held in place in each battery module by a respective thermally conductive housing 6,7 or support frame. Each battery cell consists of a negative anode and the positive cathode separated by an electrolyte. The battery pack is charged by connecting to a high voltage source which causes ions in the electrolyte to move towards and coat the negative electrode, and when the battery is discharging into a load the reverse happens. It is this movement that generates unwanted heat within the battery pack.

The cells 5 each have a relatively low voltage of perhaps 4v and are connected in series in a module to give an overall module voltage of 16v. The two modules are also connected in series to give an overall battery pack voltage of 32v but may also be connected in parallel. The skilled person will appreciate that in practice there may be many more cells 5 and modules 3 to give a much higher voltage and a higher energy storage capacity. For example, the widely used Tesla ® battery pack used to power their battery electric vehicles contains 7, 104 battery cells which each have a 4.2v rating. These are arranged as a grid of 16 4 cell modules that each contain 444 battery cells. More recent Tesla ® battery packs at the time of writing had a higher number of cells in each module to provide more energy storage.

The battery pack includes a battery management system 12, one function of which is to monitor the temperature of various parts of the battery pack. A set of temperature sensors 10 indicated by the solid circle shapes in Figure la may be provided that measure the temperature of each module or cell and may also measure the temperature of the cooling fluid. The battery management system uses data from these sensors to limit the rate of charging and discharging of the battery.

The battery pack housing includes a lid 13 or clamp plate that seals the top of the battery housing. A peripheral seal 14 is provided between an upper edge of the housing and an underside of the rim of the lid 13. This lid 13 supports a heat sink comprising a cooling plate 15 which can be seen in perspective in Figure 12. The cooling plate comprises a solid plate 16 of thermally conductive material such as aluminium. In this example the plate includes a single serpentine internal cooling channel 17 that has in input port 18 through which a coolant such as a mix of water and glycol may enter and an output port 19 from which the coolant can flow out of the channel in the cooling plate.

The coolant is circulated using a pump that may be located remote from the battery pack of part of the pack, and optionally cooled using a condenser and an evaporator as is well known in the field of refrigeration technology. The cooling plate 15 is included in a cooling circuit such as the one shown schematically in Figure 3 which may form a part of the battery pack of may be provided remotely. The cooling circuit may take many forms. In this example the fluid flows around a loop which includes an expansion device 20, a condenser 21 and a compressor 22. 1 It is notable that the cooling fluid that passes through the cooling plate is isolated from the internals of the battery housing which ensures that there is limited opportunity for the fluid to contact the battery cells in the event of an accident. Whilst this shows a refrigeration loop to cool the fluid that is not essential to the invention. Chilled fluid could be provided from a remote source such as a supply line from a tank of chilled fluid as an alternative option and in that case a continuous supply of fluid cooled be used as opposed to recirculating a small volume of fluid as shown in Figure 3.

An alternative design of heat sink 15a is shown in Figure 13. This comprises a plate 16 that optionally has the cooling channels but also includes fins 16a that extend out from the plate 16 to increase the surface area of the heat sink within a relatively small volume of space. Heat may be removed from the heat sink by passing air over these fins. In the case of a moving vehicle such as a car or truck this moving air can be readily obtained by directly the airflow over the vehicle across these fins.

Connected to an underside of the cooling plate 15 and extending downwards through openings in the lid Marc a set of closed loop cooling channels 23,24. As shown in Figure 2 there are two closed loop cooling channels, each one in thermal contact with a respective sub-housing of each module 3,4, Each closed loop cooling channel 8,9 comprises an inverted L-shaped heat pipe as shown in Figure 11. In the embodiment shown in Figures 1 and 2 there are two closed loop cooling channels 8, 9 which each have a depending portion that extends vertically down from the cooling plate 15 to the bottom of the battery modules 3,4. The depending portion f the channels 8,9 do not need to be straight as shown and can bend through multiple turns as required to weave down through spaces towards the bottom of the battery modules. The top horizontal portion contacts the underside of the cooling plate along its entire length to provide a highly effective level of heat transfer from the pipe into the cooling plate.

Figure 4 shows in an elevational cross section a depending portion of a single cooling channel 8. The depending portion forms a pipe that has a continuous thin wall 26 of thermally conductive material such as aluminium and is closed at both ends to form a cavity 27. This functions as a heat pipe due to the cavity being partially filled with a phase change liquid under vacuum conditions.

The principle of operation of the closed loop cooling channels 8,9 is to use the process of continuous phase change- evaporation and condensation and then re-evaporation- of a liquid that partially fills the pipe to transfer heat from one point along the pipe to another. In the case of the present invention the heat is transferred from a portion of the pipe that is within or between the modules to the end that contacts the cooling plate. The cooling plate then dissipates this heat into the cooling fluid or to the atmosphere removing it from the battery pack.

Each closed loop channel 8,9 in this example comprises a metallic elongate extrusion with a rectangular cross section that is partially filled with a liquid with the rest of the pipe being evacuated. Aluminium may be used for the channel wall of copper or any other material that has a high thermal transfer capability and will not react with the phase change material. The contents of the pipe that are in liquid form rest at a lower end of the pipe as shown in Figure 4. When heated they turn to a gas that will rise up to the top end of the pipe carrying heat with them. This gas is then cooled and turns back to a liquid with flows back to the bottom of the pipe along the inner wall of the pipe.

The provision of the cooling plate 15 at the top end of each closed loop channel 8,9 helps to rapidly extract heat from the top of the channel which causes the gas that has risen to the top to rapidly condense and fall back to the bottom of the channel.

In the example of Figures 1 to 4, the battery pack 1 comprises a single layer of modules and each of the two closed loop pipes extends substantially vertically from a region above the modules to a region close to the bottom of each module. Figures 5 and 6 shows an alternative in which a battery pack 100 includes battery modules 103a, 103b, 104a, 104b that are arranged in two layers, one above the other. Each layer is identical so in this example there are twice as many modules and cells as Figure 1.

Figure 1(b) shows an alternative battery pack in which the seal 14 contacts an underside of the heatsink rather than the clamping plate 13. An additional seal may also be provided between the clamping plate 13 and the walls of the housing.

In the battery pack of Figures 5 and 6 each module is associated with a respective closed loop cooling channel 110,111, 112,113. The closed loop cooling channels in the embodiment of Figure 5 and Figure 6 have one of two different lengths and are connected at their upper end to the cooling plate 115. Some of the pipes 110, 113 extend down from the cooling plate through both layers and some of the pipes 111, 112 extend down only through the top layer. The reason for this is to ensure that some of the heat pipes contact modules of the upper layer in their axiomatic zone and some of the heat pipes contact modules of the lower layer in a region below their adiabatic region. In the two examples above the heat pipes are thermally in contact with the sub-housings for each module. Figure 7 shows in a view corresponding to Figure 1 a still further alternative in which a battery pack 200 has a cooling plate 215 that forms the lid. This reduces the number of components making up the battery pack. The cooling plate 215 is connected to the housing 202 through a peripheral seal 214. This example uses a single layer of cells but the skilled person will understand it can include multiple layers of cells.

Figure 8 shows a cross sectional view corresponding to the view shown in Figure 2 of a still further alternative battery pack 300 in which closed loop channels 301,302,303,304 extend vertically within each of two battery modules 305,306 and directly contract the individual cells 307 in each battery module. As shown the cells 307are prismatic cells and one heat pipe contacts a pair of cells in each module. Note that a gap filler material is also shown, labelled 301a for the first closed loop channel 301. This ensures a good thermal bridge for conduction of heat from the cells to the closed loop channels. Although not shown, the skilled person will appreciate that this feature can be included in any of the embodiments shown in the accompanying drawings.

Where the cells are cylindrical rather than prismatic, a heat pipe may be located in the space that is naturally presented when the cells are closed packed. This is shown in Figure 9. In the battery pack 400 there are two modules 403, 404 that each contain four cells 405 that are cylindrical. These are close packed and a closed loop channel 401, 402 that functions as a heat pipe passes down in the space that is formed between the cells 405. A gap filler material in such an arrangements may comprise a thermally conductive paste that fills the small voids between the cells and heat pipe.

In an alternative the heat pipe may be extruded with a cross section that matches the void. A pair of heat pipes 501,502 of this kind is shown in Figure 10 located in the void formed between four closed packed cylindrical cells 505 in a battery pack 500.

The skilled person will appreciate that it is possible to combine features from each of the embodiments to form a battery pack within the scope of the invention which is defined solely by the claims.

Claims

1. A rechargeable battery pack comprising: a battery housing, at least two battery modules, each comprising a plurality of battery cells, the battery modules being located inside the housing, at least one closed loop channel within the housing that extends along a vertical direction from a region at or adjacent an upper end of the battery pack to a region at or adjacent to a lower end of the battery pack, the closed loop channel being partially filled with a phase change material which at a first temperature has a liquid form and lies towards the bottom of the channel and at a second higher temperature has a gaseous form and rises towards the top of the channel, a heat sink located above the battery modules and in contact with an upper portion of the closed loop channel.

2. A rechargeable battery pack according to claim 1 in which the closed loop channel comprises a sealed pipe that is partially filled with a working fluid and a vacuum.

3. A rechargeable battery pack according to claim 1 or claim 2 in which the closed loop channels extends downward from a point located in a plane that is above the upper end of each battery cell.

4. A rechargeable battery pack according to any preceding claim in which there is at least on closed loop channel for each battery module.

5. A rechargeable battery pack according to any preceding claim in which At least one closed loop channel extends downward in a space between adjacent battery modules.

6. A rechargeable battery pack according to any preceding claim in which at least one close loop channel extends downward in a space between adjacent battery cells within a battery module.

7. A rechargeable battery pack according to any preceding claim in which at least one closed loop channel is in direct mechanical thermal contact with at least one battery cell of at least one of the battery modules.

8. A rechargeable battery pack according to any preceding claim in which two or more battery modules arranged in a N by M grid pattern, where N and M may take a value of 1 or higher.

9. A rechargeable battery pack according to any preceding claim in which the modules are arranged in at least two grids, one spatially located above another, optionally in which at least one of the closed loop channels passes from the top of the battery modules through every layer.

10. A rechargeable battery pack according to claim 9 in which one or more of the closed loop cooling channels pass through only the upper most layer, or one or more upper layers without passing vertically through the bottom layer.

11. A rechargeable battery pack according to any preceding claim in which the cooling channels each form a separate closed loop with the phase change material inside each channel unable to mix with the phase change material in other channels.

12. A rechargeable battery pack according to any one of claims in which a manifold is provided that connects at least two channels so that the phase change material can mix between the two channels.

13. A rechargeable battery pack according to any preceding claim in which the heat sink is located outside of the battery housing or forms a lid of the battery housing.

14. A rechargeable battery pack according to any preceding claim in which the heat sink includes a cooling means comprising at least one internal channel having an inlet end for receiving cooling fluid and an outlet end for outputting fluid that has flowed through the channels and in which the at least one channel may include a cooling fluid.

15. A recharging station for an electric vehicle having a battery pack in accordance with any preceding claim in which the recharging station comprises; A source of chilled fluid,

A connector for connecting the source of chilled fluid to a fluid channel within the cooling plate of the battery pack when the vehicle is at the recharging station and for extracting fluid that has circulated through the plate, and - A source of electrical energy that is connectable to a charging port located on the vehicle for charging the battery cells of the battery pack.