CN118414739A

CN118414739A - Pressure sensing unit for accurate pressure sensing in battery pack

Info

Publication number: CN118414739A
Application number: CN202280083422.2A
Authority: CN
Inventors: A·克雷坦; P·迪马里奥科拉; T·戈尼瓦; L·维特
Original assignee: IEE International Electronics and Engineering SA
Current assignee: IEE International Electronics and Engineering SA
Priority date: 2021-12-15
Filing date: 2022-12-12
Publication date: 2024-07-30
Also published as: LU501378B1

Abstract

A pressure sensing unit (20) for a battery pack (10) including a plurality of linearly stacked battery cells (12, 14, 16) is provided. The pressure sensing unit (20) includes an at least partially liquid filled and fluid resistant flexible pouch container (22) having a plurality of electrical feedthroughs (34), at least one pressure sensitive member (30) including a plurality of electrical pins (32) disposed within the flexible pouch container (22), and a plurality of electrical wires (38) electrically connecting the plurality of electrical feedthroughs (34) and the plurality of electrical pins (32). A battery pack (10) is provided that includes a plurality of linearly stacked battery cells (12, 14, 16) and at least one such pressure sensing cell (20). A method for detecting at least one of impending thermal runaway, supporting a safety state assessment thereof, and supporting a health state assessment thereof of a battery pack (10) comprising a plurality of linearly stacked battery cells (12, 14, 16) employs at least one such pressure sensing unit (20).

Description

Pressure sensing unit for accurate pressure sensing in battery pack

Technical Field

The present invention relates to a pressure sensing unit for use in a battery pack comprising a plurality of linearly stacked battery cells, a battery pack comprising a plurality of linearly stacked battery cells and at least one such pressure sensing unit, and a method for at least one of detecting an impending thermal runaway of such a battery pack, supporting an assessment of its safety state and supporting an assessment of its health state.

Background

Modern batteries are widely used in various technical fields. For example, batteries are currently used in electrical equipment, vehicles, or large industrial facilities. Typically, a plurality of cells (each of which is a battery cell) are disposed in a case of a battery pack, for example, a pouch unit (pouch cell).

In view of the current mobile related technology, such battery packs are key elements for storing and providing energy for Electric Vehicles (EVs), hybrid Electric Vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and New Energy Vehicles (NEVs).

During its service life, the battery is not only subjected to highly demanding environmental influences (e.g. heat, cold and humidity), but also to highly demanding reaction kinetics, such as the frequency and number of charging and discharging processes. These aspects all have an effect on the overall life and remaining life of the battery pack and the status. Thus, the cells and battery packs may undergo aging and degradation processes, which may increase the occurrence of "swelling" or "gassing".

The term "gassing" generally refers to a phenomenon caused by the generation of gas inside a battery (cell). Gassing may be due to decomposition of electrolyte inside the cell and/or caused by overheating and/or overcharging of the cell. The gassing cell may expand, rupture or even explode. "expansion" generally refers to the change in volume of the cell. Expansion may be caused, for example, by storage and removal processes of lithium ions in and/or on the electrode. Expansion may also be caused by gassing. The expansion results in mechanical deformation of the battery cells, which can create pressure within and/or on the housing of the battery cells and/or battery pack. To compensate for the expansion, battery manufacturers typically use rigid structures, such as metal or hard plastic housings, that counteract the expansion of the housing. In addition, cell manufacturers typically include an elastic material (e.g., foam) in the stack to absorb this expansion.

The expansion caused by the pressure generated during the expansion (displacement or expansion, respectively) may be related to the so-called "state of health" (SOH) of the battery. "state of health" generally refers to the state of aging of a battery pack, and thus represents a measure (i.e., an indicator) of the ability of the battery pack to store and deliver electrical energy as compared to a new battery pack. The expansion may also be used to determine and/or predict end of life (EOL) of the battery. EOL is generally used to determine the period of time that a battery pack can safely charge and discharge. Like SOH, EOL may also be used as an indicator of the remaining run time (i.e., the remaining service life) of the battery pack.

In order to improve the safety and reliability of a battery pack in its operating environment, a Battery Management System (BMS) is generally used to determine or estimate the state of charge (SOC), and SOH and EOL of each battery cell of the battery pack. "state of charge" generally refers to the available capacity, which may be expressed or expressed as a percentage of its predetermined capacity. In other words, SOC, EOL, and SOH are indicators determinable by the BMS.

The BMS may also be configured to measure and/or determine other parameters of the battery pack and/or the battery cells, such as temperature values and/or voltages of the battery cells. The BMS may also access predetermined and stored specific cell characteristic data and measurements taken from the reference cells and/or the reference battery pack. For example, based on these data, the BMS may compare stored and/or measured values of the cells with reference values in order to more accurately determine the different metrics. The BMS may be further configured to monitor functions of the respective units and charge and discharge processes. Thus, the BMS can identify defective cells and turn off the cells. In most cases, the unit must be replaced when it is identified as defective; typically, the entire module or group is replaced.

The useful life of the battery (i.e., the service life time or the remaining run time) may be limited by the maximum pressure exerted on the mechanical housing (i.e., shell) of the battery pack. In general, the value of the maximum sustainable pressure is known to the manufacturer. A pressure (force) exceeding a predetermined maximum withstand pressure may cause failure of the battery cell, the case, or the entire battery pack. For example, a pressure caused by swelling of the battery cell and exceeding a predetermined maximum sustainable pressure value may cause rupture of the battery cell. To this end, the battery management system may also be configured to detect swelling.

To detect swelling, common battery management systems use algorithms or complex mechanical devices to estimate the current condition (i.e., state) of the battery cells and/or the battery pack. The use of such algorithms may be more or less based on or dependent on the correct estimation of EOL, SOC or SOH indicators. In addition, in order to determine the state of the battery, the BMS may accept a test environment in, for example, a laboratory or a test stand. In this case, the battery pack would be detected by or connected to a complex mechanical measuring device.

For example, US2014/0107949 A1 describes a battery management system for use with a battery under test conditions. The system includes a container configured to hold a battery. The system also includes a stress/strain sensor. The container is configured to hold the battery in a fixed relationship relative to the stress/strain sensor. The processor is coupled to the stress/strain sensor, wherein the processor is configured to measure stress/strain on the battery and determine a state of health (SOH) of the battery based on the measured stress/strain and previously stored SOH relationship data for the battery. The processor may be configured to determine a state of charge (SOC) of the battery based on the measured stress/strain, SOH of the battery, and previously stored SOC relationship data for the battery.

Furthermore, DE 10 2012 209 271 A1 describes at least one battery cell having a cell housing and an electrode winding arranged in the cell housing. The battery management system includes battery status detection. The electrode windings of the battery cells are at least partially covered by a pressure sensitive film sensor. The battery state detection means are designed to read a measured value provided by the pressure-sensitive film sensor or a variable derived from the measured value and to use the measured value or the variable as an evaluation parameter for determining the battery state. The battery state detection mechanism is configured to determine an expansion force from expansion of the electrode windings due to their state of charge using a measurement or derivative variable provided by the pressure sensitive film sensor. The expansion force is used to further determine the state of charge (SOC) or state of health (SOH) of the battery cell.

In a battery pack having linearly stacked battery cells, one or more compression pads stacked between adjacent battery cells are used to ensure slight compression in the newly built state and further to allow for expansion and contraction during charge, discharge and aging, as is known in the art. Typical values for the coverage of the compression pad are several percent of the length of the battery during its lifetime. For materials used in such compression pads, it is desirable that the stress-strain curve exhibit low compressive stress over a wide range of compressive strains. Furthermore, such materials should exhibit as low compression set as possible, especially in the upper region of the normal operating range of the battery under conditions of high relative humidity and temperature. A known example of such a material is microcellular polyurethane foam.

Disclosure of Invention

Object of the invention

It is therefore an object of the present invention to provide a battery-compatible detection unit for use in a battery pack comprising a plurality of linearly stacked battery cells, in particular pouch cells, for reliably sensing the current compressive load present in the battery pack in support of detecting an impending thermal runaway of the battery pack and/or evaluating its state of safety (SOS) and/or its state of health (SOH).

General description of the invention

In one aspect of the present invention, the object of the present invention is achieved by a pressure sensing unit for use in a battery pack including a plurality of linearly stacked battery cells. The pressure sensing unit includes a flexible bag container, at least one pressure sensitive member, and a plurality of electrical wires. The flexible pouch container is at least partially filled and fluid-proof and has a plurality of electrical feedthroughs. At least one pressure sensitive member includes a plurality of electrical pins and is disposed within the flexible bag container. The plurality of wires connects the plurality of electrical feedthroughs and the plurality of electrical connectors.

One insight of the present invention is that the compressive load exerted on the flexible pouch container is proportional to the forces present in the stacked battery cells when mounted in the battery pack, and may be sensed by at least one pressure sensitive member disposed within the flexible pouch container.

Since the compression load rise is one of the initial symptoms of impending thermal runaway of the battery pack, the proposed pressure sensing unit can achieve early detection of the occurrence of thermal runaway and can support taking measures for potential prevention by accurately sensing the current compression load. Furthermore, the proposed pressure sensing unit provides a prerequisite for continuous monitoring of the compressive load within the battery pack, and thus the state of health of the battery cells can be evaluated by applying one of the well known suitable evaluation methods.

Thermal runaway is known to be one of the most serious failure modes of rechargeable traction batteries. Details are described, for example, in Koch, sascha et al, "fast thermal runaway detection of lithium Ion Batteries in large traction Batteries (FAST THERMAL Runaway Detection for Lithium-Ion CELLS IN LARGE SCALE Traction Batteries)" (Batteries 2018,4 (2), 16; DOI:10.3390/Batteries 4020016). Thermal runaway of individual cells in large lithium ion batteries is a well known risk that, if countermeasures are not taken, may lead to critical situations in current lithium ion traction batteries for Battery Electric Vehicles (BEVs), plug-in hybrid electric vehicles (PHEVs), and Hybrid Electric Vehicles (HEVs). Therefore, the rapid and reliable detection of a faulty cell within a lithium ion battery that is subject to thermal runaway is a critical factor in the battery design for overall passenger safety.

The pressure sensing unit according to the invention is particularly advantageously applicable to a battery pack of an automobile. The term "car" as used in this patent application is to be understood in particular as being applicable to vehicles including passenger cars, trucks, semi-trucks and buses.

The present invention still further contemplates that the proposed pressure sensing unit(s) may be used in addition to or instead of compression pads used in conventional battery packs.

It will be appreciated that flexible bag containers according to the present invention are preferably made of a suitable flexible film material that is sealed at each boundary to form a fluid-resistant bag. One example of a suitable material for the flexible bag container is a sandwich laminate comprising aluminum and Polyethylene (PE) and/or polypropylene (PP). Preferably, the dimensions of the flexible pouch container in a virtual plane transverse to the stacking direction of the battery pack are adapted to the respective dimensions of the battery cells. The flexible pouch container may in particular have similar dimensions as the battery cell or the battery pouch. In this way, the entire cross-sectional area of the battery pack may be included in the sensing of the compressive load, and any rise in the compressive load may be captured by the pressure sensing unit, as the compressive load propagates uniformly in the fluid of the flexible bag container.

In a preferred embodiment, the pressure sensing unit comprises a dielectric carrier member to which at least the wires of the plurality of wires are fixedly attached. In this way, a compact and mechanically stable solution for the electrical wires of the pressure sensing unit can be provided, enabling a high degree of operational reliability.

Similar advantages may be achieved if the pressure sensing unit comprises a dielectric carrier member to which at least one pressure sensitive member is fixedly attached. A mechanically stable and reliable configuration of the pressure sensing unit can be achieved in particular if both the electrical wire and the at least one pressure sensitive member are fixedly attached to the same dielectric carrier member.

In a preferred embodiment, the pressure sensing unit further comprises at least one temperature sensor arranged within the flexible bag container. The electrical contacts of the at least one temperature sensor are electrically connected to the plurality of electrical feedthroughs by a plurality of electrical wires.

In addition to providing the current compressive load in the battery, the current temperature present in the battery is also provided so that further independent information can be used to detect impending thermal runaway of the battery and/or to evaluate the state of health or safety of the battery in an improved manner.

Preferably, the at least one temperature sensor is arranged in a virtual plane perpendicular to the stacking direction, in relation to the middle third of the size of the flexible bag container. In this way, the temperature sensed by the at least one temperature sensor may be representative of the stack temperature that is not affected by boundary or geometric effects, and thus may be considered a characteristic stack temperature.

In a preferred embodiment of the pressure sensing unit, the dielectric carrier member is mostly made of a planar foil of a plastic material selected from the group of plastic materials formed by: polyethylene terephthalate (PET), polyimide (PI), polyetherimide (PEI), polyethylene naphthalate (PEN), polyoxymethylene (POM), polyamide (PA), polyphthalamide (PPA), polyetheretherketone (PEEK) and combinations of at least two of the foregoing plastic materials, and the wires of the plurality of wires comprise a cured conductive ink.

The term "majority" as used in the present application is to be understood in particular as being equal to or greater than 70%, more preferably greater than 80% and most preferably greater than 90% by volume and shall include a portion of 100%, i.e. the dielectric carrier member is made entirely of the selected plastic material.

These plastic materials may allow for easy manufacturing and in this way provide a durable, cost-effective dielectric carrier member with low manufacturing tolerances. The use of a planar foil of plastic material allows a particularly compact design of the assembly, in particular in a direction perpendicular to the surface of the dielectric carrier member.

By making the wires of the plurality of wires from the conductive ink, high precision manufacturing methods (e.g., screen printing and ink jet printing) can be conveniently applied, thereby reducing production tolerances and reducing material waste.

In a preferred embodiment of the pressure sensing unit, the dielectric carrier member is mostly made of a glass fiber reinforced epoxy laminate, and the wires of the plurality of wires are formed of etched copper tracks. In this way, a dielectric carrier member can be provided which is light in weight and mechanically stable and which can be manufactured using well known methods of manufacturing printed circuit boards.

In another aspect of the present invention, a battery pack is provided that includes a plurality of linearly stacked battery cells and at least one possible embodiment of the pressure sensing unit disclosed herein. In the battery pack, the flexible pouch container of the pressure sensing unit is arranged in mechanical contact with at least one battery cell. The advantages described in terms of the pressure sensing unit are maximally applicable to the proposed battery pack.

In particular, the battery cells of the battery pack may be designed as pouch cells, as known in the art.

Preferably, the flexible pouch container of the at least one pressure sensing unit has a material with an ultimate tensile strength exceeding the ultimate tensile strength of the pouch material. In this way, the operability of the pressure sensing unit is ensured at least before one cell of the battery pack fails.

In another aspect of the present invention, a method for detecting at least one of an impending thermal runaway of a battery pack, supporting a safety state assessment thereof, and supporting a health state assessment thereof is provided, wherein the battery pack comprises a plurality of linearly stacked battery cells.

The proposed method comprises at least the following steps:

Providing a pressure sensing unit of at least one possible embodiment disclosed herein,

Arranging at least one pressure sensing unit in the battery pack, arranging the flexible pouch container in mechanical contact with the at least one battery unit,

Providing electrical connection from the plurality of electrical feedthroughs to at least one electrical receiving circuit,

-Receiving, by at least one electrical receiving circuit, an electrical signal representative of the current compression load or representative of the current compression load and the current battery cell temperature, and

-Evaluating at least one of the state of impending thermal runaway, the safe state and the state of health of the battery pack from the electrical signal received by the electrical receiving circuit.

Since the compressive load rise is one of the initial symptoms of impending thermal runaway of the battery, the proposed method can ensure early detection of the occurrence of thermal runaway and can provide support for potential preventive action by accurately sensing the current compressive load. Furthermore, the proposed method also provides continuous monitoring of the compression load within the battery pack and thus enables an assessment of the safety and/or health status of the battery cells by applying one of the well known suitable assessment methods.

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

It should be noted that the features and measures individually specified in the foregoing description may be combined with each other in any technically meaningful way and show further embodiments of the invention. The present invention has been described and illustrated with particular reference to the accompanying drawings.

Drawings

Further details and advantages of the invention will be apparent from the following detailed description of non-limiting embodiments with reference to the attached drawings, in which:

Fig. 1 schematically shows an embodiment of a battery pack according to the invention, in a perspective partial ghost view, the battery pack being mounted in a battery electric vehicle,

Fig. 2 is a perspective partial schematic view of one of the battery packs according to fig. 1, including an exploded view of one embodiment of a pressure sensing unit according to the present invention stacked between battery cells of the battery pack,

Figure 3 is a schematic front view of one embodiment of a pressure sensitive member fixedly attached to an alternative embodiment of a dielectric carrier member forming part of the pressure sensing unit according to figure 2 seen in the stacking direction,

Figure 4 is a schematic side sectional view of the pressure sensing unit according to figure 2,

Figure 5 is a schematic view in front cross-section of the pressure-sensitive unit according to figure 2 seen in the stacking direction,

FIG. 6 is a schematic diagram of one embodiment of a pressure sensing unit with a pressure sensor in a secondary container, an

Fig. 7 is a flowchart of a method of detecting at least one of an impending thermal runaway, supporting an assessment of a safe state, and supporting an assessment of a healthy state using the pressure sensing unit according to fig. 2.

In the different figures, identical components are always denoted by identical reference numerals or numerals, respectively. Therefore, it is generally described only once.

Detailed Description

Fig. 1 schematically illustrates a battery pack 10 according to the present invention comprising two modules installed in a battery electric vehicle 42 in a perspective partial double-view. In this particular embodiment, the vehicle 42 may be designed as a passenger car, but in other embodiments, multiple battery packs 10 may be installed in a truck or bus.

Fig. 2 is a schematic perspective partial view of one of the battery packs 10 according to fig. 1, which is exemplarily shown for all battery packs 10. The battery pack 10 includes a plurality of battery cells 12, 14, 16, which are stacked linearly in a stacking direction 18, and which may be formed of pouch cells, in particular. In the present embodiment, the stacking direction 18 is arranged in parallel with the width direction of the vehicle 42.

The battery pack 10 further includes a plurality of pressure sensing cells 20. Fig. 2 schematically illustrates one embodiment of one of the pressure sensing cells 20 according to the present invention used in the battery pack 10 in an exploded view. The pressure sensing unit 20 is stacked between the two battery cells 14, 16 of the battery pack 10.

Fig. 4 is a cross-sectional side view schematic of the pressure sensing unit 20 according to fig. 2. Fig. 5 is a schematic front cross-sectional view of the pressure-sensitive unit 20 according to fig. 2, seen in the stacking direction 18.

The pressure sensing unit 20 includes a fluid-proof flexible bag container 22 formed substantially as a hollow rectangular block. One example of a suitable material for flexible bag container 22 is a sandwich laminate comprising aluminum and Polyethylene (PE) and/or polypropylene (PP). As shown in fig. 2, the dimensions of the flexible pouch container 22 in a virtual plane transverse to the stacking direction 18 of the battery pack 10 are compatible with the respective dimensions of the battery cells 12, 14, 16. Depending on the particular application, the flexible bag container 22 may be partially filled with a fluid 28 (fig. 4), such as a gas (e.g., air) or a gel. Another portion of the volume of the flexible bag container 22 may be occupied by foam, such as microcellular polyurethane foam.

The pressure sensing unit 20 further comprises a pressure sensitive member 30 comprising a plurality of electrical pins 32. The electrical pins 32 are only shown in fig. 3, fig. 3 being a schematic view of the pressure sensitive member 30 of an alternative embodiment fixedly attached to the dielectric carrier member 36'. The pressure sensitive member 30 may be formed of an IC-based capacitive sensor device or a piezoresistive sensor having micromachined features. Such sensors are currently commercially available. They are particularly configured for automotive applications and are also well known in the art. Some of these sensors convert absolute pressure into an analog output signal provided at their plurality of electrical pins 32. The pressure sensitive member 30 is disposed within the flexible bag container 22. Since the flexible bag container 22 is filled with fluid, any force externally applied to the flexible bag container 22 is transferred to the pressure sensitive member 30.

The fluid-tight flexible pouch container 22 is equipped with a plurality of electrical feedthroughs 34 located on the container side 26 (fig. 5). The pressure sensing unit 20 includes a dielectric carrier member 36 and a plurality of electrical wires 38.

In this particular embodiment (fig. 4 and 5), the dielectric carrier member 36 is largely made of a planar foil of plastic material, such as Polyimide (PI), which may have a thickness of about 50 μm to provide mechanical strength as well as sufficient flexibility. The wires 38 of the plurality of wires 38 of the pressure sensing unit 20 are fixedly attached to the dielectric carrier member 36 and may be produced by dispensing conductive ink (e.g., by screen printing or ink jet printing) on the dielectric carrier member 36 and then performing a curing process.

In alternative embodiments (not shown) having different applications of requirements, the dielectric carrier member 36 may be made mostly of a glass fiber reinforced epoxy laminate, and the wires 38 of the plurality of wires 38 may be formed by etching copper tracks.

The pressure sensitive member 30 is fixedly attached to the dielectric carrier member 36 by connecting (e.g., by soldering) the electrical pins 32 with a plurality of electrical wires 38. Note that the ICs may also be connected by an "adhesive" technique using an anisotropic conductive adhesive. In addition, glue may also be used to adhere the pressure sensitive member 30 to the dielectric carrier member 36. At an end facing away from the pressure sensitive member 30, an electrical wire 38 of the plurality of electrical wires 38 is electrically connected with the plurality of electrical feedthroughs 34.

Referring to fig. 2, a pressure sensing unit 20 is stacked between two battery cells 14, 16 of the battery pack 10, with a flexible pouch container 22 configured to be in mechanical contact with the two battery cells 14, 16. The ultimate tensile strength of the material of the flexible pouch receptacle 22 of the pressure sensing unit 20 exceeds the ultimate tensile strength of the pouch material of the battery cells 12, 14, 16, for example, by selecting a greater material thickness. It will be appreciated that the sealing joint of the flexible bag container 22 is an important factor in addition to the strength of the material of the flexible bag container. In fact, the seal must be properly configured to withstand the pressure levels prescribed by the flexible bag container 22.

The dielectric carrier member 36 extends from the container side 26 to the central region 24 of the flexible bag container 22, shown in phantom in fig. 5. The pressure sensing unit 20 is also equipped with a temperature sensor 40, which may be formed, for example, by an NTC (negative temperature coefficient) temperature sensor. The temperature sensor 40 is fixedly attached to the end of the dielectric carrier member 36 facing away from the electrical feedthrough 34. The electrical contacts of the temperature sensor 40 are electrically connected to the feedthroughs 34 of the plurality of electrical feedthroughs 34 by wires 38 of the plurality of wires 38.

The temperature sensor 40 is thus arranged in the flexible pouch container 22, and more specifically in the central region 24 of the flexible pouch container 22, which central region may be defined by the middle third of the size relative to the flexible pouch container 22 in a virtual plane perpendicular to the stacking direction 18, in order to obtain a temperature that may be considered to be characteristic of the battery pack temperature. In fig. 5, the virtual plane coincides with the drawing plane.

As shown in fig. 2, the pressure sensing unit 20 may be stacked between two battery cells 14, 16 of the battery pack 10. In the present embodiment, the pressure sensing unit 20 includes a fluid-proof flexible pouch container 22 disposed between two battery cells and a pressure-sensitive member 30 disposed inside the fluid-proof flexible pouch container 22 at a position between the two battery cells 14, 16. While this embodiment allows for a compact structure outside of the cell area, it is apparent that such an embodiment requires a thicker flexible pouch container 22 or pouch to achieve a good pressure ratio between the uncompressed and compressed states.

It will be appreciated that the pressure sensitive member 30 (i.e., the IC-based sensor) need not be geometrically arranged in a plane between two adjacent battery cells. Indeed, in one possible embodiment, schematically represented in FIG. 6, the fluid-resistant flexible bag container 22 may include a primary bag 44 and a secondary bag 46 fluidly connected by a connecting channel 48. In such an embodiment, the primary pouch 44 of the flexible pouch container 22 would be disposed in the space between the cells, while the secondary pouch 46 could be disposed outside of the cells, such as on the lateral side of the battery pack. The pressure sensitive member 30, i.e., the IC-based sensor, is preferably disposed in a secondary bag 46 that is in fluid connection with the primary bag 44. Due to the fluid connection between the primary bag 44 and the secondary bag 46, the pressure increase within the flexible bag container 22 may be reliably detected by the pressure sensitive member 30 disposed within the secondary bag. It will be appreciated that in this embodiment, this allows the main pouch 44 to be reduced in thickness since the IC-based sensor is located outside the space between the battery cells.

Hereinafter, one embodiment of a method for detecting at least one of an impending thermal runaway of the battery pack 10 (which includes a plurality of linearly stacked battery cells 12, 14, 16), supporting an evaluation of a safety state thereof, and supporting an evaluation of a health state thereof using the pressure sensing unit 20 according to fig. 5 will be described with reference to fig. 7 (which shows a flowchart of the method).

Referring to fig. 2 and 7, in step 100 of the method, a pressure sensing unit 20 is provided, and in another step 200 the pressure sensing unit 20 is arranged in the battery pack 10 such that the flexible pouch container is in mechanical contact with both battery cells 14, 16 of the battery pack 10.

Then, in a further step 300, electrical connections are provided from the plurality of electrical feedthroughs 34 to an electrical receiving circuit (not shown). For example, the electrical receiving circuit may form part of a battery management system or an electronic control unit of the vehicle 42. In another step 400 of the method, the electrical receiving circuit receives an electrical signal from the pressure sensitive member 30 representative of the current compression load and an electrical signal from the temperature sensor 40 representative of the current cell temperature.

In another step 500, at least one of a state of impending thermal runaway, a state of safety (SOS), and a state of health (SOH) of the battery pack 10 is evaluated using the electrical signal received by the electrical receiving circuit as an evaluation parameter.

It is noted herein that the drawings in the present application generally cannot be regarded as scale drawings unless explicitly described otherwise.

While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments.

Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality, the plural being means an amount of at least two. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims shall not be construed as limiting the scope.

List of reference symbols

10 Battery pack

12 Cell unit

14 Cell unit

16 Battery unit

18 Stacking direction

20 Pressure sensing unit

22 Flexible bag container

24 Center region (middle third)

26 Container side

28 Fluid

30 Pressure sensitive member

32 Electric pins

34 Electrical feed-through

36 Dielectric carrier member

38 Electric wire

40 Temperature sensor

42 Vehicle

44 Main bag

46 Auxiliary bags

48 Connection channels

100 Provides a pressure sensing unit

200 Configuring a pressure sensing cell in a battery pack

300 Provide electrical connection from an electrical feedthrough to an electrical receiving circuit

400 Receives electrical signals from a pressure sensitive member and a temperature sensor

500 Evaluate a state of impending thermal runaway and/or SOS and/or SOH.

Claims

1. A pressure sensing unit (20) for use in a battery pack (10) comprising a plurality of linearly stacked battery cells (12, 14, 16), characterized by

An at least partially liquid-filled and fluid-proof flexible pouch container (22) having a plurality of electrical feedthroughs (34),

-At least one pressure sensitive member (30) comprising a plurality of electrical pins (32) arranged within the flexible bag container (22), and

-A plurality of wires (38) electrically connecting the plurality of electrical feedthroughs (34) and the plurality of electrical pins (32).

2. The pressure sensing unit (20) according to claim 1, wherein the dimensions of the flexible pouch container (22) in a virtual plane transverse to the stacking direction (18) of the battery pack (10) are adapted to the respective dimensions of the battery cells (12, 14, 16).

3. The pressure sensing unit (20) of claim 1 or 2, comprising a dielectric carrier member (36), at least a wire (38) of the plurality of wires (38) being fixedly attached to the dielectric carrier member (36).

4. The pressure sensing unit (20) according to any one of the preceding claims, further comprising a dielectric carrier member (36), the at least one pressure sensitive member (30) being fixedly attached to the dielectric carrier member (36).

5. The pressure sensing unit (20) of any one of the preceding claims, further comprising at least one temperature sensor (40) arranged within the flexible bag container (22) and whose electrical contacts are electrically connected to the plurality of electrical feedthroughs (34) by the plurality of electrical wires (38).

6. The pressure sensing unit (20) of claim 5, wherein the at least one temperature sensor (40) is arranged in a virtual plane perpendicular to the stacking direction (18) at a middle third (24) of a size relative to the flexible bag container (22).

7. The pressure sensing unit (20) according to any one of claims 3 to 6, wherein

-The dielectric carrier member (36) is mostly made of a planar foil of a plastic material selected from the group of plastic materials formed of: polyethylene terephthalate PET, polyimide PI, polyetherimide PEI, polyethylene naphthalate PEN, polyoxymethylene POM, polyamide PA, polyphthalamide PPA, polyetheretherketone PEEK, and combinations of at least two of these plastic materials, and

-The wires (38) of the plurality of wires (38) comprise a cured conductive ink.

8. The pressure sensing unit (20) according to any one of claims 3 to 6, wherein the dielectric carrier member (36) is made mostly of a glass reinforced epoxy laminate, and the wires (38) of the plurality of wires (38) are formed by etching a copper track.

9. The pressure sensing unit (20) according to any of the preceding claims, wherein the fluid-proof flexible bag container (22) comprises a primary bag (44) and a secondary bag (46) fluidly connected by a connecting channel (48), wherein, in operation, the primary bag (44) of the flexible bag container (22) is arranged between adjacent battery cells, while the secondary bag (46) is arranged outside the battery cells, and wherein at least one pressure sensitive member (30) is preferably arranged in the secondary bag (46).

10. A battery pack (10) comprising a plurality of linearly stacked battery cells (12, 14, 16) and at least one pressure sensing unit (20) according to any one of claims 1 to 9, wherein the flexible pouch container (22) is arranged in mechanical contact with at least one battery cell (14, 16), wherein the ultimate tensile strength of the material of the flexible pouch container (22) of at least one pressure sensing unit (20) exceeds the ultimate tensile strength of the pouch material of the battery cell (12, 14, 16).

11. A method for at least one of detecting impending thermal runaway, supporting assessment of a safety condition thereof, and supporting assessment of a health condition thereof of a battery pack (10) comprising a plurality of linearly stacked battery cells (12, 14, 16), the method comprising at least the steps of:

-providing (100) at least one pressure sensing unit (20) according to any one of claims 1 to 9,

-Arranging (200) said at least one pressure sensing unit (20) in said battery pack (10) such that said flexible pouch container (22) is arranged in mechanical contact with at least one of said battery cells (14, 16),

Providing (300) an electrical connection from the plurality of electrical feedthroughs (34) to at least one electrical receiving circuit,

-Receiving (400), by means of the at least one electrical receiving circuit, an electrical signal representative of the current compression load or representative of the current compression load and the current battery cell temperature, and

-Evaluating (500) at least one of a state of impending thermal runaway, a safe state and a state of health of the battery pack (10) from an electrical signal received by the electrical receiving circuit.