GB2568957A

GB2568957A - An electricity storage system, a vehicle, a method and an electronic control means

Info

Publication number: GB2568957A
Application number: GB1720136.9A
Authority: GB
Inventors: John Greenwood Jeremy; Clarke Chris; White David
Original assignee: Jaguar Land Rover Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2017-12-04
Filing date: 2017-12-04
Publication date: 2019-06-05
Anticipated expiration: 2037-12-04
Also published as: GB2568957B; GB201720136D0

Abstract

An electricity storage system 101comprises a plurality of cells 102 electrically connected together to form a battery 104 and located within a container 105. The electricity storage system also includes a pressure adjustment means 106 configured to adjust pressure in a fluid 201 surrounding the cells within the container and a sensing means 107 configured to sense a pressure in the fluid. The fluid may be a gas such as air or carbon dioxide. A control means 108 is configured to control the pressure adjustment means to adjust pressure in the fluid surrounding the cells according to the sensed fluid pressure. The pressure adjustment means may comprise a tank 601 configured to provide fluid to the container. The tank may also be configured to receive fluid from the container, the fluid may then be pressurized by a pump 301 and returned to the container. The pressure adjustment means may comprise a valve 304. The control means may be configured to control the pressure adjustment based on a detected rate of charging or discharging of the cells. The control means may be configured to maintain the pressure within a predetermined range of pressures.

Description

AN ELECTRICITY STORAGE SYSTEM, A VEHICLE, A METHOD AND AN ELECTRONIC CONTROL MEANS

TECHNICAL FIELD

The present disclosure relates to an electricity storage system, a vehicle, a method and an electronic control means. In particular, but not exclusively it relates to an electricity storage system, in a vehicle such as a road vehicle.

Aspects of the invention relate to electricity storage system, a vehicle, a method and an electronic control means.

BACKGROUND

Lithium ion pouch cells are typically pressurized in order to maintain a high charge capacity. To achieve the pressurization the cells are typically arranged side by side to form a block and mechanically pressed together. One disadvantage with such an arrangement is that pressure applied to the cells fluctuates under electrical load, due to the arrangement not being able to accommodate cell expansion and contraction. This can adversely affect the life of the cells.

There is evidence that the optimum applied pressure varies with the electrical load state, and a second disadvantage is that the pressure applied cannot be adjusted in order to optimize it.

A third disadvantage is that the space provided for the cells has to accommodate the blocks of cells that are mechanically pressed together.

It is an aim of the present invention to address these disadvantages.

SUMMARY OF THE INVENTION

Aspects and embodiments of the invention provide electricity storage system, a vehicle, a method and an electronic control means as claimed in the appended claims.

According to an aspect of the invention there is provided an electricity storage system comprising: a container; a plurality of cells located within the container, the cells being electrically connected together to form a battery; a pressure adjustment means configured to adjust pressure in a fluid surrounding the cells within the container; a sensing means configured to provide a first signal indicative of a pressure in the fluid; and a control means configured to control the pressure adjustment means to adjust pressure in the fluid surrounding the cells, in dependence on the first signal received from the sensing means.

This provides the advantage that the container does not have to be designed to accommodate cells pressed together by a mechanical device, and the cells may be positioned to optimize use of the space within the container. It also enables the pressure applied to the cells to be kept relatively constant even when some change in dimensions of the cells occurs during charging or discharging, and/or it enables pressure applied to be temporarily adjusted in dependence on electrical load on the cells.

In some embodiments the cells are lithium-ion cells.

In some embodiments the pressure adjustment means is configured to generate a pressure in the fluid of at least 50kPa above ambient atmospheric pressure.

In some embodiments the pressure adjustment means comprises a pump; the sensing means comprises a pressure sensor configured to sense pressure within the fluid; and the control means comprises a controller.

In some embodiments the pressure adjustment means comprises a valve means controllable by the control means.

In some embodiments the valve means is configured to release pressure of the fluid in the container.

In some embodiments the control means comprises an electronic control unit.

In some embodiments the control means is configured to receive a second signal indicative of a rate of charging or discharging of the cells of the battery and to control the pressure adjustment means in dependence on the second signal. This provides the advantage of enabling the pressure applied to the cells to be adjusted over time to optimize power output or rate of charging or life of the cells.

In some embodiments the control means is configured to control the pressure adjustment means to maintain pressure of fluid in the container within a predefined range of pressures.

In some embodiments the control means is configured to: control the pressure adjustment means to reduce pressure in the container to a first pressure and subsequently provide a flow of fluid into the container; monitor pressure, or rate of increase of pressure, in the container during said flow of fluid into the container; and provide an output signal indicating a faulty cell in dependence on detecting a temporary reduction in the rate of increase of pressure in the container during said flow of fluid into the container. This provides the advantage of enabling a faulty cell to be detected before it catastrophically fails.

In some embodiments the control means is configured to: control the pressure adjustment means to maintain a pressure in the fluid surrounding the cells between a lower limit and an upper limit; monitor pressure, or rate of increase of pressure, in the container; and control the pressure adjustment means to reduce pressure in the container to below said lower limit in dependence on detecting a rate of increase of pressure above a predefined rate. This provides the advantage of enabling the fumes expelled from a failing cell to escape from the container in a less explosive manner than they would if a burst disc were used.

In some embodiments the control means is configured to: control the pressure adjustment means to maintain a pressure in the fluid surrounding the cells between a lower limit and an upper limit; monitor pressure, or rate of increase of pressure, in the container; and provide an output signal indicating a faulty cell in dependence on detecting a rate of increase of pressure above a predefined rate. This provides the advantage that a user of the vehicle, or a system of the vehicle, may be notified that a cell has, or is about to, catastrophically fail.

In some embodiments the cells are configured to: provide electrical energy to an electrically powered device; and receive charge via a connection means.

In some embodiments the connection means comprises a connector for conductively connecting to an electricity supply or an electrically conductive coil for inductively receiving an electric current.

In some embodiments the pressure adjustment means comprises a tank for containing fluid, the tank having an outlet configured to provide fluid to the container to increase pressure of fluid within the container. This provides the advantage that the tank may be used to store fluid at high pressure, ready to be supplied to the container, or used to store fluid to be pumped into the container, in which case it may be arranged to receive fluid previously released from the container.

In some embodiments, the tank has an inlet configured to receive fluid from the container, and the pressure adjustment means comprises a pump configured to: pressurize fluid received from the tank; and provide pressurized fluid to the container. This provides the advantage of enabling the fluid to be retained in a sealed system and reused.

In some embodiments, the pressure adjustment means comprises a pump configured to provide pressurized fluid to the tank for supply to the container. This provides the advantage of enabling the pressure applied to the cells to be increased by releasing fluid from the tank into the container. In which case, the pressure in the container may be increased at a time when the pump is not energized or it is possible that the pressure in the container may be increased more rapidly than would be possible using the pump.

In some embodiments the fluid comprises a gas. The gas may comprise air or carbon dioxide. The use of air provides the advantage of a readily available supply of fluid and exhausted fluid may be released to atmosphere. Carbon dioxide provides the advantage of being relatively inert and incombustible.

In some embodiments the fluid comprises a non-conductive liquid. This provides the advantage that it may provide improved transfer of heat from the cells by conduction and convection, or by pumping fluid through the container.

According to another aspect of the invention there is provided a vehicle comprising an electricity storage system according to any one of the previous paragraphs.

In some embodiments the vehicle comprises an electric motor for driving the vehicle, wherein the plurality of cells forms at least a portion of a battery for powering the electric motor.

According to further aspect of the invention there is provided a method of controlling pressure applied to cells in an electric battery, comprising: receiving a first signal indicative of a pressure of pressurized fluid surrounding the cells; and causing adjustment of the pressure of the pressurized fluid in dependence on the first signal.

In some embodiments causing adjustment of the pressure comprises controlling a pump or a valve to increase pressure of fluid surrounding the cells and/or controlling a valve to release pressure of fluid surrounding the cells.

In some embodiments the method comprises receiving a second signal indicative of a rate of charging or discharging of the cells of the battery and the causing adjustment of the pressure is in dependence on the second signal.

According to yet another aspect of the invention there is provided an electronic control means configured to: receive an input signal providing an indication of a pressure of fluid surrounding cells of an electric battery; and, in dependence on the indication of pressure, provide to a pressure adjustment means an output signal for causing adjustment to the pressure of the fluid.

In some embodiments the electronic control means is configured to: receive a second signal indicative of a rate of charging or discharging of the cells of the battery; and provide the output signal in dependence on the second signal.

In some embodiments the electronic control means comprises: electronic memory device having instructions stored therein; and an electronic processor electrically coupled to the electronic memory device and configured to access the memory device and execute the instructions stored therein.

According to yet another aspect of the invention there is provided an electricity storage system comprising: a container; a plurality of cells located within the container, the cells being electrically connected together to form a battery; a fluid within the container surrounding the cells; a pump configured to adjust pressure in the fluid; a sensor configured to provide a first signal indicative of a pressure in the fluid; and an electronic controller configured to control the pressure adjustment means to adjust the pressure of fluid surrounding the cells, in dependence on the first signal received from the sensing means.

According to a further aspect of the invention there is provided an electronic control unit configured to: receive an input signal providing an indication of a pressure of fluid surrounding cells of an electric battery; and, in dependence on the indication of pressure, produce an output signal to cause adjustment to the pressure of the fluid by a pump and/or a valve.

According to yet a further aspect of the invention there is provided an electronic control unit comprising: an electronic memory device having instructions stored therein; and an electronic processor electrically coupled to the electronic memory device and having an electrical input configured to receive input signal providing an indication of a pressure of fluid surrounding cells of an electric battery, wherein the electronic processor is configured to access the memory device and execute the instructions stored therein such that it is operable to, in dependence on the indication of pressure, produce an output signal to cause adjustment to the pressure of the fluid by a pump and/or a valve.

According to yet another aspect of the invention there is provided a system for controlling pressure applied to cells of an electric battery, the system comprising: a container for containing a plurality of electrochemical cells; a pressure adjustment means configured to adjust pressure in a fluid within the container; a sensing means configured to provide a first signal indicative of a pressure in the fluid; and a control means configured to control the pressure adjustment means to adjust the pressure in the fluid within the container in dependence on the first signal received from the sensing means.

According to a further aspect of the invention there is provided a system for controlling pressure applied to cells of an electric battery, the system comprising: a container for containing a plurality of cells connected together to form an electric battery; a pressure adjustment means configured to adjust pressure applied to the cells of the electric battery; a control means for controlling the pressure adjustment means in dependence on a received signal indicative of a rate of charging or discharging of the cells.

According to yet a further aspect of the invention there is provided an electricity storage system comprising: a container; a plurality of cells located within the container, the cells being electrically connected together to form a battery; a pressure adjustment means for adjusting pressure applied to the cells; a sensing means configured to provide a first signal indicative of a pressure applied to the cells; and a control means configured to control the pressure adjustment means to adjust pressure applied to the cells, in dependence on the first signal received from the sensing means.

The electricity storage system may be for providing electricity to an electric motor for driving a vehicle.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Fig. 1 shows a schematic diagram of a vehicle comprising an electricity storage system embodying the present invention;

Fig. 2 shows a schematic diagram of the electricity storage system of Fig. 1;

Fig. 3 shows an embodiment of the electricity storage system shown in Fig. 2;

Fig. 4 illustrates an alternative electricity storage system embodying the present invention;

Fig. 5 illustrates a further alternative electricity storage system embodying the present invention;

Fig. 6 illustrates a further alternative electricity storage system embodying the present invention;

Fig. 7 illustrates yet another alternative electricity storage system embodying the present invention;

Fig. 8 shows a flowchart illustrating a method of controlling pressure applied to cells in an electric battery 104;

Fig. 9 shows a flowchart illustrating a more specific embodiment of the method shown in Fig. 8;

Fig. 10 shows a flowchart illustrating another more specific embodiment of the method shown in Fig. 8;

Fig. 11 shows a flowchart illustrating another embodiment of the method;

Fig. 12 shows a flowchart illustrating additional processes that may be included in a method embodying the present invention;

Fig. 13 shows an alternative electricity storage system embodying the present invention; and Fig. 14 shows a side view of the vehicle 100.

DETAILED DESCRIPTION

A vehicle 100 embodying the present invention is shown in the schematic diagram of Fig. 1 and the side view of Fig. 14. As shown in Fig. 14, the vehicle 100 is a road vehicle in the form of a car. As shown in Fig. 1, the vehicle 100 comprises an electricity storage system 101. The electricity storage system 101 comprises a plurality of electrochemical cells 102 (referred to below simply as cells 102) that are electrically connected together by connectors 103 to form a battery 104. The cells 102 are located within a container 105.

The electricity storage system 101 also comprises a pressure adjustment means 106 for adjusting pressure applied to the cells 102 and a sensing means 107 configured to provide a first signal, to a pressure control means 108, that is indicative of a pressure applied to the cells 102. The pressure control means 108 is configured to control the pressure adjustment means 106 in dependence on the first signal received from the sensing means 107.

The battery 104 is arranged to supply electrical energy for energizing an electric motor 109 used to drive the vehicle 100. Supply of electrical energy to the motor 109 is controlled by a motor controller 110 in response to signals received from a vehicle speed controller 111, such as an accelerator pedal.

In order to recharge the battery 104, the vehicle 100 has a connection means 112, such as an electric connector for conductively connecting to an electric power supply, or a coil for inductively connecting to an electric power supply. The vehicle 100 also comprises a battery management system 113 configured to control charging of the battery 104 when the connection means 112 is connected to a power supply. As well as monitoring electric current supplied to the battery 104 from the connection means 112, the battery management system 113 may also be arranged to monitor electric current supplied to the motor controller 110, the temperature of the cells 102 of the battery 104, and other parameters as in known in the art.

The pressure control means 108 may comprise a separate electronic control unit that is dedicated to controlling the pressure applied to the cells 102 of the battery 104, but alternatively, the pressure control means 108 may comprise a controller embodied in software within the same electronic control unit as the battery management system 113.

In the present embodiment, during charging of the battery 104, the battery management system 113 is arranged to provide a signal to the pressure control means 108 indicative of the current being supplied to the battery 104, i.e. indicative of the rate of charging of the battery 104. The vehicle speed controller 111, the motor controller 110, or the battery management system 113 may be arranged to provide a signal to the pressure control means 108 indicative of the electric current that is currently being supplied by the battery 104 during operation of the motor 109.

In the present embodiment, the cells 102 are pouch cells 102 comprising electrodes and electrolyte within a sealed foil pouch. The cells 102 are lithium-ion cells, but in alternative embodiments they may be of another type known for use to power an electric vehicle. The life of such cells 102 is dependent upon pressure applied to them, and the control means 109 is configured to monitor the applied pressure and generally control the pressure adjustment means 106 to apply a selected pressure for providing the cells 102 with a long life. For example, the pressure control means 106 may be configured to maintain the pressure applied to the cells 102 within a predefined range, such as between 50 kilopascals (kPa) and 90 kPa above atmospheric pressure, or between 60 and 80 kPa above atmospheric pressure, or between 65 and 75 kPa above atmospheric pressure. However, in the present embodiment, the pressure control means 106 is configured to also control the pressure adjustment means 106 in dependence on the signals received from the battery management system 113 and/or the motor controller 110 or the vehicle speed controller 111 indicative of a rate of charging or discharging of the cells 102 of the battery 104. For example, the pressure applied to the cells 102 may be temporarily increased or decreased from the predefined range during times when charging or discharging of the battery 104 is above a threshold rate. For example, when the construction of the cells 102 is such that they may temporarily provide increased power if pressure applied to them is reduced, the pressure control means 108 is configured to control the pressure adjustment means 106 to temporarily reduce the pressure applied to the cells when it receives a signal indicating that power consumption by the motor 109 has exceeded a threshold value.

In the embodiment of Fig. 1, the vehicle 100 also comprises a user output device 114 for providing information to a user of the vehicle 100. The user output device 114 may comprise a display device, such as a liquid crystal display, or an audio device for presenting audio signals to the user. In dependence on signals received from the pressure control means, the user output device 114 is configured to present information to the user indicative of a failure of one or more of the cells 102, as will be described below, with reference to Figs. 11 and 12.

An embodiment of the electricity storage system 101 of Fig. 1 is shown in the schematic diagram of Fig. 2. For the purposes of illustration, relatively few cells 102 are shown connected by connectors 103 to form the battery 104, but it will be understood that in reality the battery 104 may contain many hundreds of cells 102. In the embodiment of Fig. 2, the cells 102 are disposed within a container 105 that also contains a fluid 201 held at a pressure above atmospheric pressure.

The pressure sensing means 107 of Fig. 2 comprises a fluid pressure sensor 107 capable of measuring the pressure of the fluid 201 within the container 105 and providing a signal indicative of the fluid pressure to the pressure control means 108. The pressure control means 108 is configured to control the pressure adjustment means 106 to adjust the pressure in the fluid 201 within the container 105 to apply the required pressure to the cells 102.

Because pressure is applied to the cells 102 by the fluid surrounding them, the cells 102 may be located in an irregularly shaped container 105 and oriented and positioned relative to each other in a way that optimizes the packing of the cells within the container 105. Additionally, the container is not required to contain a mechanical clamping device for applying the pressure to the cells 102.

In the present embodiment, the signal received from the sensing means 107 comprises a value indicative of the fluid pressure in the container. The control means 108 comprises an electronic processor 202 electrically coupled to an electronic memory device 204 and configured to access the memory device 204 and execute instructions 205 stored therein. Execution of the instructions 205 configures the processor 202 to provide an output signal in dependence on the value indicative of the fluid pressure. In the present embodiment, the processor 202 compares the received value to a predefined range of values and if the received value is below or above the predefined range then it provides a signal to the pressure adjustment means 106 to respectively increase or decrease the pressure in the container 105.

In the present embodiment, the control means 108 is also configured to receive second signals 203 indicating a charging rate during charging of the battery 104 or a rate of discharging of the battery 104 due to use of the motor 109. The processor 202 is configured to determine a required pressure or range of pressures in the container 105 in dependence on the received second signal 203. In the present embodiment this is achieved by retrieving one or more pressure values corresponding to the received second signal from a look-up table stored in the electronic memory device 204. In other embodiments the one or more pressure values are calculated from the received second signal using a predefined algorithm or formula. After determining a required range of pressures for the fluid 201, the processor 202 is configured to compare the value received from the sensing means 107 with the required range to determine whether to control the pressure adjustment means 106 to increase or decrease the fluid pressure in the container 105.

Signals provided between the sensing means 107, the control means 108 and the pressure adjustment means 106 may be electrical signals provided over dedicated cables, a network bus, such as a CAN bus, or signals provided over a wireless link.

In some embodiments the fluid comprises a gas, but in alternative embodiments, the fluid comprises a non-conductive liquid such as an oil. The term “gas” as used herein refers to both pure gases and mixtures of gases. For example, in some embodiments the gas comprises air, but in other embodiments the gas is carbon dioxide.

In an alternative embodiment, to that of Fig. 2, the pressure adjustment means comprises a mechanical clamping arrangement in which blocks of cells 102 are located between a pair of clamping plates connected by a screw mechanism and an electric motor arranged to adjust the pressure applied to the cells 102 by tightening or loosening the screw mechanism. A sensing means, such as a load cell, monitors the pressure applied to the cells and provides a signal indicative of the pressure to the pressure control means. The pressure control means then provides an output signal to control the electric motor to adjust the applied pressure in dependence on the signal received from the sensing means.

An embodiment of the electricity storage system 101 shown in Fig. 2 is shown in the schematic diagram of Fig. 3. In this embodiment, during operation the container 105 contains air 201 at a pressure that is above the ambient atmospheric pressure, in order to apply a required pressure to the cells 102. The sensing means 107 comprises a gas pressure sensor configured to provide a signal to the control means 108, and the signal comprises a value indicative of air pressure within the container 105.

The pressure adjustment means 106 comprises a pump 301 configured to receive atmospheric air and, in dependence on signals received from the control means 108, pump air through an inlet 305 into the container 105 to increase pressure within it. An air filter 302 and/or a dehumidifier 303 may be positioned at the inlet to the pump 301. The pump 301 may be provided with a check valve 307 (or one-way valve) at its outlet to ensure that air cannot escape from the container 105 through the pump 301.

The pump 301 may be electrically powered, or, in an embodiment in which the vehicle 100 is a hybrid vehicle, it may be driven by the operation of the engine of the vehicle. The pump 301 may be dedicated to the function of increasing air pressure within the container 105, or the pump 301 may provide one or more other functions. For example, in an embodiment in which the vehicle is a hybrid vehicle, the pump 301 may be a turbocharger associated with the internal combustion engine.

The pressure adjustment means 106 also comprises a valve means 304 configured to enable air to escape through an outlet 306 from the container 105 in dependence on signals received from the control means 108. In some embodiments, the valve means 304 comprises a single electrically operable valve that is controlled to open only when a reduction in air pressure in the container 105 is required. In other embodiments, the valve means 304 may comprise a valve capable of providing a relatively slow flow of air, such that operation of the pump 301 while the valve is open enables a required pressure in the container to be achieved while allowing a flow of air through the container 105. This provides the advantage of enabling heat generated by cells 102 to be extracted from the battery 104.

The control means 108 is configured to process a signal received from the sensing means 107 and any second signals 203 indicative of charging rate or discharging rate of the battery

104 as described above with regard to Fig. 2, to determine if the pressure in the container

105 is within a required range. In dependence on the determination, the control means 108 provides a signal to the pump 301 to increase the pressure or to the valve means 304 to reduce the pressure, as required.

An alternative electricity storage system 101 embodying the present invention is illustrated in Fig. 4. The electricity storage system 101 of Fig. 4 is like that of Fig. 3, and it has a sensing means 107, a pressure control means 108 and a pressure adjustment means 106 comprising a pump 301 and a valve 304. However, the valve means 304 of Fig. 4 comprises a three-port valve 304 having a first port 401 connected to the pump 301, a second port 402 connected to a port of the container 105 and a third port 403 open to atmosphere. The three port valve 304 is moveable between three positions. In a first of the three positions the valve 304 enables air to flow from the pump 301 to the container 105, in a second position it prevents any flow of air through the valve 304 and in the third position it enables a flow of air from the container 105 to atmosphere. Thus, under the control of the pressure control means 108, the pump 301 is energized and the valve 304 opened to enable air to be pumped into the container 105, or the pump 301 is switched off and the valve 304 closed to prevent air from leaking out of the container 105, or the pump 301 is switched off and the valve 304 is opened to allow air to escape from the container 105 to atmosphere.

A further alternative electricity storage system 101 embodying the present invention is illustrated in Fig. 5. The electricity storage system 101 of Fig. 5 has a sensing means 107, a pressure control means 108 and a pressure adjustment means 106 comprising a pump 301 and a three-port valve 304 for controlling flow of air into and out of the container 105, in a similar arrangement to that of Fig. 4. However, the electricity storage system 101 of Fig. 5 differs from that of Fig. 4 in that it comprises a tank 501 for containing air at high pressure. The tank 501 has an inlet configured to receive air from the pump 301, so that the pump 301 is able to be periodically operated to provide compressed air for storage within the tank 501. The tank 501 has an outlet arranged to provide air to the container 105, via the valve 304, to increase air pressure within the container 105. This arrangement has the advantage that pressure applied to the cells 102 of the battery 104 may be increased rapidly when required simply by opening the valve 304 to enable air stored within the tank 501 to flow to the container 105.

In addition, in embodiments of the invention, the pressure control means 108 monitors pressure within the container 105 at all times, even when the vehicle 100 is not in use. The electricity storage system 101 of Fig. 5 provides the advantage that, when pressure within the container 105 needs to be increased, the pressure control means 108 of Fig. 5 is able to increase the pressure within the container 105, simply by operation of the valve 304, rather than having to energize the pump 301.

A further alternative electricity storage system 101 embodying the present invention is illustrated in Fig. 6. The electricity storage system 101 of Fig. 6 has a sensing means 107, a pressure control means 108 and a pressure adjustment means 106 comprising a pump 301 and a three-port valve 304 for controlling flow of air into and out of the container 105, in a similar arrangement to that of Fig. 4. However, the electricity storage system 101 of Fig. 6 differs from that of Fig. 4 in that it comprises a tank 601 for containing fluid released from the container 105 via the third port 403 of the valve 304.

In the embodiment of Fig. 6, the three-port valve 304 is moveable between three positions. In the first position it allows fluid to be pumped by the pump 301 into the container 105. In the second position all flow of fluid through the valve 304 is prevented. In the third position, the valve 304 enables fluid to flow from the container 105 to the tank 601. The tank 601 has an outlet connected to the inlet of the pump 301, so that fluid released from the container 105 is stored within the tank 601 for reuse by the pump 301. The arrangement of Fig. 6 therefore comprises a sealed system in which fluid is retained within the electricity storage system 101. The arrangement of Fig. 6 is therefore suitable when the fluid that is used is a gas other than air, or a liquid. It also provides the advantage that the fluid stored in the tank 601 has a pressure that is above atmospheric pressure and therefore the pump 301 is required to do less work when increasing the pressure in the container 105.

Yet another alternative electricity storage system 101 embodying the present invention is illustrated in Fig. 7. The electricity storage system 101 of Fig. 7 has all of the features of the electricity storage system 101 of Fig. 6, which are similarly labelled. In addition, the electricity storage system 101 includes a second tank 501, like that of Fig. 5, having an inlet for receiving fluid from the pump 301 and an outlet for providing fluid to the container 105 via the valve 304. Thus, under the control of the pressure control means 108, the pump 301 may be occasionally operated to pump fluid from the first tank 601 into the second tank 501 where it is stored at a higher pressure than pressures required within the container 105.

When a signal received from the sensing means 107 indicates that the pressure within the container 105 is below a required pressure, the pressure control means 108 provides an output signal to the valve 304 to enable a flow of fluid from the second tank 501 to the container 105 until a signal from the sensing means 107 indicates that the pressure within the container 105 is as required, e.g. within a required range. The pressure control means 108 then provides a further signal to the valve 304 to cause it to close.

When a signal received from the sensing means 107 indicates that the pressure within the container 105 is above a required pressure, the pressure control means 108 provides an output signal to the valve 304 to enable a flow of fluid from the container 105 to the first tank 601 until a signal from the sensing means 107 indicates that the pressure within the container 105 is as required, e.g. within a required range. The pressure control means 108 then provides a further signal to the valve 304 to cause it to close.

A method 800 of controlling pressure applied to cells 102 in an electric battery 104, which embodies the present invention, is illustrated in the flowchart of Fig. 8. The method 800 may be performed by an electronic control unit such as the control means 108 of Fig. 2. The method 800 comprises, at block 801, receiving a first signal indicative of a pressure of pressurized fluid surrounding the cells 102. For example, the signal may be supplied by a fluid pressure sensor 107 arranged to measure fluid pressure with the container 105. The method 800 further comprises, at block 802, causing adjustment of the pressure of the pressurized fluid in dependence on the first signal. For example, the first signal may comprise a value indicative of the pressure surrounding the cells 102 of the battery 104, and the value may be compared to a defined range to determine if the pressure of the fluid should be increased or decreased. Alternatively the value may be compared to a single reference value to determine whether it is within a tolerance of the reference value and if not, then the pressure is increased or decreased as required.

Another method 800A, providing a more specific example of the method 800 of Fig. 8, is illustrated in the flowchart of Fig. 9. In this embodiment, a first signal indicative of a pressure of pressurized fluid surrounding the cells 102 of a battery is received at block 801. At block 802A, in dependence on the received signal, a pump 301 and/or a valve 304 is controlled to increase pressure of fluid surrounding the cells 102 or a valve 304 is controlled to release pressure of fluid surrounding the cells 102.

Another method 800B, providing a more specific example of the method 800 of Fig. 8, is illustrated in the flowchart of Fig. 10. At block 801 of the embodiment of Fig. 10, the method 800 comprises receiving a first signal indicative of a pressure of pressurized fluid surrounding the cells 102. At block 1001 the method 800 comprises receiving a second signal indicative of a rate of charging or discharging of the cells 102 of the battery 104. For example, the second signal may be received from a motor controller 110 arranged to provide electrical energy to an electric motor 109 of the vehicle 100, or the second signal may be received from a battery management system 113 arranged to monitor electric charge flowing to and from the battery 104.

At block 802B, the method comprises causing adjustment of the pressure of the pressurized fluid in dependence on the first signal and the second signal. For example, pressure applied to the cells 102 may be generally kept at a predefined pressure, or within a predefined range of pressures, that is believed to provide a long life for the cells 102. However, the second signal may be processed in order to determine whether that predefined pressure should be used or if a different pressure is required, for example, due to a high rate of charging or discharging of the battery 104 at the present time. Having determined from the second signal what pressure is required to be applied to the cells 102, this may be compared to the currently applied pressure determined from a first signal received from a fluid pressure sensor 107. When the comparison indicates that the currently applied pressure is not the required pressure, or within a required range of pressures, the applied pressure is caused to be adjusted at block 802B. As indicated in block 802A of Fig. 9, the adjustment at block 802B of Fig. 10 may comprise controlling a pump 301 and/or a valve 304 to increase pressure of fluid surrounding the cells 102 or controlling a valve 304 to release pressure of fluid surrounding the cells 102.

Another method 1100, providing another example of the method 800 of Fig. 8, is illustrated in the flowchart of Fig. 11. The method 1100 includes a process for controlling the pressure in fluid surrounding the cells 102 at instances when a cell fails catastrophically causing a sudden increase in pressure.

At block 1101 of the method 1100, the pressure adjustment means 106 is controlled to maintain a pressure in fluid surrounding the cells 102 between a lower limit and an upper limit. For example, the process of block 1101 may comprise the method 800 or 800A described above and the pressure may be controlled to be between 65 kPa and 75 kPa. Alternatively, the process of block 1101 may comprise the method 800B described above and the pressure may be controlled to be between limits determined in dependence on the second signal received from the motor controller 110 or the battery management system 113.

At block 1102 of the method 1100, pressure, or increase in pressure, in the fluid surrounding the cells 102 in the container 105 is monitored. For relatively small increases in pressure, or relatively small rates of increase in pressure, the pressure adjustment means 106 may be controlled to maintain the pressure in the fluid between the lower limit and the upper limit referred to in regard to block 1101. However, at block 1103, in dependence on detecting a rate of increase of pressure that is above a predefined rate, the pressure adjustment means 106 is controlled to reduce pressure in the container 105 to a pressure below the lower limit. For example, the valve means 304 of the pressure adjustment means 106 may include a dump valve for enabling the fluid in the container 106 to be released to atmosphere. By enabling the fluid to escape in this manner enables it to be released at a lower pressure than existing systems that may comprise a mechanical burst disc that bursts under excessive pressure. Therefore the method 1100 allows a less explosive release of fumes than a system that relies on a burst disc.

In some embodiments, the reduction in pressure at block 1103 may additionally be in dependence on a receiving a signal, for example from the battery management system 113, indicative of a rise in temperature above a threshold level or a rate of rise in temperature above a threshold rate.

Optionally, at block 1104, in dependence on detecting the rate of increase of pressure that is above a predefined rate, an output signal is provided indicating that a cell 102 has, or is about to, catastrophically fail. The output signal may be provided to a user output device 114 (shown in Fig. 1), such as visual display device or an audio device, configured to provide an output to a user. In addition, or alternatively, the output signal may be provided to another system of the vehicle 100, such as the vehicle traction controller, which may be arranged to reduce power demand or even stop the vehicle in response.

The method 800, 800A, 800B or 1100 may include additional processes such as the process 1200 outlined in the flowcharts of Fig. 12. The process 1200 shown in Fig. 12 is a process that may be performed intermittently to determine if any of the cells 102 are faulty causing them to create gas within their foil pouch. For example, the process 1200 may be performed periodically, or at the start of each use of the vehicle 100. At block 1201 of the process 1200 the adjustment means 106 is controlled to reduce pressure of the pressurized fluid surrounding the cells 102 in the container 105, so that the pressure attains a predefined value for the process 1200. The pressure is chosen to be sufficiently low to allow any faulty cells 102 to swell due to the internal pressure caused by the internally created gas. In an embodiment, the pressure of the fluid surrounding the cells 102 is reduced to atmospheric pressure at block 1201.

A progressive flow of fluid into the container 105 is then provided at block 1202 and pressure in the container 105, or rate of increase in pressure in the container 105, is monitored during the flow of fluid into the container 105. In general, as the fluid flows into the container 105, the pressure of the fluid in the container 105 rises. If one of the cells 102 has an internal pressure causing it to be swollen, when the pressure of the fluid surrounding the cells 102 reaches that internal pressure, the flow of fluid into the container 105 will cause the cell 102 to shrink. As the volume of the swollen cell is reduced, there will be a temporary reduction in the rate of increase in pressure in the fluid in the container 105. This may be detected from the monitored rate of increase in pressure, or detected as a brief hesitation in the rise of the pressure.

At block 1203 of the process 1200, an output signal is provided indicating a faulty cell 102 in dependence on detecting a temporary reduction in the rate of increase in pressure in the container 105. The output signal may be provided to a user output device 114, such as visual display device or an audio device configured to provide an output to a user. The output signal may be used to recommend or mandate a service action to enable intervention by service, so that the user does not experience a failure of a cell 102. In addition, or alternatively, the output signal may be provided to the traction controller of the vehicle, which may be configured to reduce power demand in response.

An alternative electricity storage system 101 embodying the present invention is shown is Fig. 13. The electricity storage system 101 of Fig. 13 comprises a sensing means 107 configured to provide a signal indicative of a fluid pressure within a container 105 containing cells 102 connected together to form a battery 104. In the embodiment of Fig. 13, the sensing means 107 is a pressure switch 107. The pressure switch 107 is configured to provide a signal while ever the fluid pressure within the container 105 is below a first threshold pressure.

The electricity storage system 101 of Fig. 13 also comprises a pressure adjustment means 106 comprising a pump 301 and a valve means 304.

Additionally, the electricity storage system 101 of Fig. 13 includes a pressure control means 108 in the form of a controller 108 of the pump 301. The controller 108 is configured to energize the pump 301 in dependence on receiving the signal provided by the pressure switch 107. That is, the controller 108 energizes the pump 301 only while it is receiving a signal from the pressure switch 107. In the present embodiment, the controller 108 comprises a relay that provides electrical energy to energize the pump 301 in dependence on receiving the signal from the pressure switch 107.

The valve means 304 of Fig. 13 is a pressure relief valve that has an inlet connected to the container 105 and that is configured to open in dependence on the fluid pressure within the container 105 being above a second threshold pressure. The second threshold pressure is higher than the first threshold pressure.

In operation, the container 105 generally contains fluid at a pressure within the range defined by the first and second threshold pressures. If the pressure within the container 105 falls below the first threshold pressure, the pressure switch 107 provides a signal to the controller 108. In response to receiving the signal, the relay of the controller 108 closes and energizes the pump 301, which pumps air into the container 301, raising the fluid pressure applied to the cells 102. When the pressure within the container 105 has been raised to a sufficiently high value (typically just above the first threshold pressure but below the second threshold pressure) the pressure switch 107 stops providing a signal to the controller 108 and the controller 108 ends its supply of electricity to the pump 301.

If the pressure within the container ever goes above the second threshold pressure, the valve 304 opens to release pressure within the container 105 until the pressure is just below the second threshold pressure but above the first threshold pressure.

For purposes of this disclosure, it is to be understood that the control means or controller(s) described herein can each comprise a control unit or computational device having one or more electronic processors. A vehicle and/or a system thereof may comprise a single control unit or electronic controller or alternatively different functions of the controller(s) may be embodied in, or hosted in, different control units or controllers. A set of instructions could be provided which, when executed, cause said controller(s) or control unit(s) to implement the control techniques described herein (including the described method(s)). The set of instructions may be embedded in one or more electronic processors, or alternatively, the set of instructions could be provided as software to be executed by one or more electronic processor(s). For example, a first controller may be implemented in software run on one or more electronic processors, and one or more other controllers may also be implemented in software run on or more electronic processors, optionally the same one or more processors as the first controller. It will be appreciated, however, that other arrangements are also useful, and therefore, the present disclosure is not intended to be limited to any particular arrangement. In any event, the set of instructions described above may be embedded in a computer-readable storage medium (e.g., a non-transitory computer-readable storage medium) that may comprise any mechanism for storing information in a form readable by a machine or electronic processors/computational device, including, without limitation: a magnetic storage medium (e.g., floppy diskette); optical storage medium (e.g., CD-ROM); magneto optical storage medium; read only memory (ROM); random access memory (RAM); erasable programmable memory (e.g., EPROM ad EEPROM); flash memory; or electrical or other types of medium for storing such information/instructions.

The blocks illustrated in the Figs. 8 to 10 may represent steps in a method and/or sections of code in the computer program 205. The illustration of a particular order to the blocks does not necessarily imply that there is a required or preferred order for the blocks and the order and arrangement of the block may be varied. Furthermore, it may be possible for some steps to be omitted.

Although embodiments of the present invention have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the invention as claimed.

Features described in the preceding description may be used in combinations other than the combinations explicitly described.

Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not.

Although features have been described with reference to certain embodiments, those 5 features may also be present in other embodiments whether described or not.

Whilst endeavoring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features 10 hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

Claims

1. An electricity storage system comprising:

a container;

a plurality of cells located within the container, the cells being electrically connected together to form a battery;

a pressure adjustment means configured to adjust pressure in a fluid surrounding the cells within the container;

a sensing means configured to provide a first signal indicative of a pressure in the fluid; and a control means configured to control the pressure adjustment means to adjust pressure in the fluid surrounding the cells, in dependence on the first signal received from the sensing means.

2. An electricity storage system according to claim 1, wherein the cells are lithium-ion cells.

3. An electricity storage system according to claim 1 or claim 2, wherein the pressure adjustment means is configured to generate a pressure in the fluid of at least 50kPa above ambient atmospheric pressure.

4. An electricity storage system according to any one of claims 1 to 3, wherein: the pressure adjustment means comprises a pump; the sensing means comprises a pressure sensor configured to sense pressure within the fluid; and the control means comprises a controller.

5. An electricity storage system according to any one of claims 1 to 4, wherein the pressure adjustment means comprises a valve means controllable by the control means.

6. An electricity storage system according to any one of claims 1 to 5, wherein the valve means is configured to release pressure of the fluid in the container.

7. An electricity storage system according to any one of claims 1 to 6, wherein the control means comprises an electronic control unit.

8. An electricity storage system according to any one of claims 1 to 7, wherein the control means is configured to receive a second signal indicative of a rate of charging or discharging of the cells of the battery and to control the pressure adjustment means in dependence on the second signal.

9. An electricity storage system according to any one of claims 1 to 7, wherein the control means is configured to control the pressure adjustment means to maintain pressure of fluid in the container within a predefined range of pressures.

10. An electricity storage system according to any one of claims 1 to 9, wherein the control means is configured to: control the pressure adjustment means to reduce pressure in the container to a first pressure and subsequently provide a flow of fluid into the container; monitor pressure, or rate of increase of pressure, in the container during said flow of fluid into the container; and provide an output signal indicating a faulty cell in dependence on detecting a temporary reduction in the rate of increase of pressure in the container during said flow of fluid into the container.

11. An electricity storage system according to any one of claims 1 to 10, wherein the control means is configured to: control the pressure adjustment means to maintain a pressure in the fluid surrounding the cells between a lower limit and an upper limit; monitor pressure, or rate of increase of pressure, in the container; and control the pressure adjustment means to reduce pressure in the container to below said lower limit in dependence on detecting a rate of increase of pressure above a predefined rate.

12. An electricity storage system according to any one of claims 1 to 10, wherein the control means is configured to: control the pressure adjustment means to maintain a pressure in the fluid surrounding the cells between a lower limit and an upper limit; monitor pressure, or rate of increase of pressure, in the container; and provide an output signal indicating a faulty cell in dependence on detecting a rate of increase of pressure above a predefined rate.

13. An electricity storage system according to any one of claims 1 to 12, wherein the cells are configured to: provide electrical energy to an electrically powered device; and receive charge via a connection means.

14. An electricity storage system according to claim 13, wherein the connection means comprises a connector for conductively connecting to an electricity supply or an electrically conductive coil for inductively receiving an electric current.

15. An electricity storage system according to any one of claims 1 to 12, wherein the pressure adjustment means comprises a tank for containing fluid, the tank having an outlet configured to provide fluid to the container to increase pressure of fluid within the container.

16. An electricity storage system according to claim 15, wherein the tank has an inlet configured to receive fluid from the container, and the pressure adjustment means comprises a pump configured to: pressurize fluid received from the tank; and provide pressurized fluid to the container.

17. An electricity storage system according to claim 15, wherein the pressure adjustment means comprises a pump configured to provide pressurized fluid to the tank for supply to the container.

18. An electricity storage system according to any one of claims 1 to 17, wherein the fluid comprises a gas.

19. An electricity storage system according to claim 18, wherein the gas comprises air or carbon dioxide.

20. An electricity storage system according to any one of claims 1 to 17, wherein the fluid comprises a non-conductive liquid.

21. A vehicle comprising an electricity storage system according to any one of claims 1 to 20.

22. A vehicle according to claim 21 comprising an electric motor for driving the vehicle, wherein the plurality of cells forms at least a portion of a battery for powering the electric motor.

23. A method of controlling pressure applied to cells in an electric battery, comprising: receiving a first signal indicative of a pressure of pressurized fluid surrounding the cells; and causing adjustment of the pressure of the pressurized fluid in dependence on the first signal.

24. A method according to claim 23, wherein the causing adjustment of the pressure comprises controlling a pump or a valve to increase pressure of fluid surrounding the cells or controlling a valve to release pressure of fluid surrounding the cells.

25. A method according to claim 23 or claim 24, wherein the method comprises receiving a second signal indicative of a rate of charging or discharging of the cells of the battery and the causing adjustment of the pressure is in dependence on the second signal.

26. An electronic control means configured to: receive an input signal providing an indication of a pressure of fluid surrounding cells of an electric battery; and, in dependence on the indication of pressure, provide to a pressure adjustment means an output signal for causing adjustment to the pressure of the fluid.

27. An electronic control means according to claim 26, wherein the causing adjustment of the pressure comprises controlling a pump and/or a valve to increase pressure of fluid surrounding the cells or controlling a valve to release pressure of fluid surrounding the cells.

28. An electronic control means according to claim 26 or claim 27, wherein the electronic control means is configured to: receive a second signal indicative of a rate of charging or discharging of the cells of the battery; and provide the output signal in dependence on the second signal.

29. An electronic control means according to any one of claims 26 to 28, wherein the electronic control means comprises: electronic memory device having instructions stored therein; and an electronic processor electrically coupled to the electronic memory device and configured to access the memory device and execute the instructions stored therein.

30. An electricity storage system, a vehicle, a method and an electronic control means as herein described with reference to the accompanying figures.