Patent Publication Number: US-2021194072-A1

Title: Thermal runaway detection system and battery system

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of European Patent Application No. 19218474.5, filed on Dec. 20, 2019, and Korean Patent Application No. 10-2020-0177630, filed on Dec. 17, 2020, the entire content of each of which is incorporated herein by reference. 
     BACKGROUND 
     1. Field 
     Aspects of embodiments of the present disclosure relate to a thermal runaway detection system and a battery system including the same. 
     2. Description of Related Art 
     A rechargeable (or secondary) battery differs from a primary battery in that it is designed to be repeatedly charged and discharged, while the latter is designed to provide an irreversible conversion of chemical to electrical energy. Low-capacity rechargeable batteries may be used as power supplies for small electronic devices, such as cellular phones, notebook computers, and camcorders, while high-capacity rechargeable batteries may be used as power supplies for hybrid vehicles and the like. 
     In general, rechargeable batteries include an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive and negative electrodes, a case receiving (or accommodating) the electrode assembly, and an electrode terminal electrically connected to the electrode assembly. An electrolyte solution is injected into the case to enable charging and discharging of the battery via an electrochemical reaction of the positive electrode, the negative electrode, and the electrolyte solution. The shape of the case, such as cylindrical or rectangular, may be selected or determined based on the battery&#39;s intended purpose. 
     Rechargeable batteries may be used as a battery module formed of a plurality of unit battery cells coupled to each other in series and/or in parallel to provide a high energy density for, as an example, motor driving of a hybrid vehicle. For example, the battery module may be formed by interconnecting the electrode terminals of the plurality of unit battery cells depending on a desired amount of power and to realize a high-power rechargeable battery for, as an example, an electric vehicle. 
     Battery modules may be constructed either in block design or in modular design. In the block design, each battery cell is coupled to a common current collector structure and a common battery management system. In the modular design, pluralities of battery cells are connected to each other to form submodules, and several submodules are connected to each other to form the battery module. Battery management functions may be realized either on the module or submodule level and, thus, interchangeability of the components is improved. One or more battery modules may be mechanically and electrically integrated, equipped with a thermal management system, and configured to communicate with one or more electrical consumers to form a battery system. 
     A casing (or housing) may be provided either at the battery submodule level, at the battery module level, or at the battery system level to enclose all the components constituting the respective unit (or level). To provide thermal control of the enclosed components, a thermal management system may be used to efficiently emit, discharge, and/or dissipate heat generated within the casing. If such a thermal management system is omitted or the heat removal (or drain) from the casing is not sufficiently performed, an increase in the internal temperature can lead to abnormal reactions occurring therein. An example of such abnormal operation condition is a thermal runaway of a battery cell that may occur due to overheating or overcharging the lithium ion cell. Thermal runaway is a self-accelerating chemical reaction inside the cell, which produces high amounts of heat and gas, until all available material is exhausted. Due to high amounts of hydrogen and carbon monoxide within the produced gas, the produced gases may be toxic and flammable. 
     A thermal runaway will likely cause a thermal propagation along the battery cells of a battery module, which might eventually lead to a fire in the battery module. Hence, early detection of a thermal runaway in a battery module is important for the timely initiation of countermeasures and/or the timely output of warning signals, for example, to the passengers of an electric vehicle. So far, the detection of thermal runaway is usually based on internal cell measurements, for example, on measurements of cell voltage, cell current, and/or cell temperature. In other words, so far the thermal runaway itself is not detected but rather secondary effects related to a thermal runaway are detected within a battery module. Further, to avoid false warnings, trigger thresholds are usually set which relate to (or indicate) thermal propagation across at least two cells, for example, by detecting abnormal cell voltages, currents, and/or temperatures of at least two cells. However, these trigger thresholds are often based on specific battery system models, and hence, might not be suitable for all battery modules irrespective of geometry. 
     SUMMARY 
     Aspects of the present disclosure overcome or at least reduce the disadvantageous of the prior art and solve at least one of the problems existing in the prior art to at least some extent. 
     Aspects of embodiments of the present disclosure overcome or reduce at least some of the drawbacks of the prior art and provide thermal runaway detection that provides reliable detection of thermal runaway itself rather than detecting its secondary effects. 
     According to an embodiment of the present disclosure, a thermal runaway detection system is provided that includes a venting device and a thermal runaway detection circuit. The venting device has a sealing body that is disposed in a venting passage (e.g., in a passage or opening) that is configured to let pass (to vent) venting gases in (or during) a thermal runaway of a battery cell. The sealing body is configured to close the venting passage in a first position of the sealing body and is configured to open the venting passage in a second position of the sealing body that is different from the first position. In the context of the present disclosure, a position of the sealing body refers to a spatial position of the sealing body without a change of state of the sealing body. Thus, the sealing body remains unaltered in the first and second position. 
     The thermal runaway detection system according to an embodiment of the present disclosure further includes a thermal runaway detection circuit that is configured to monitor a position of the sealing body and to output a signal corresponding to the position of the sealing body. The monitoring of the position of the sealing body is performed by the selective closing and opening (e.g., setting conductive and non-conductive) of a conductive circuit based on a position of the sealing body as described in more detail below. However, the position of the sealing body may also be measured by using optical and/or mechanical devices. For example, a laser may be selectively interrupted based on a position of the sealing body and may be detected by a photodiode when it is not interrupted. Hence, a signal output by the photodiode may be used to monitor the position of the sealing body. Also, a capacitive measurement may be carried out to determine the position of the sealing body, and the sealing body may be configured as a movable plate of a capacitor. However, the present disclosure is not limited to these examples, and a mechanical device, such as a gear rack or the like, may be used to determine the position of the sealing body. Depending on the method or device used to determine the position of the sealing body, corresponding circuitry may be used to output the signal. 
     Generally, a battery cell has a vent opening to allow (e.g., to selectively allow or permit) gas produced in the battery cell during an abnormal operation condition to be released from the cell when a reference overpressure and/or a reference temperature inside the cell is exceeded. The vent opening is usually covered (e.g., sealed) by a membrane that bursts open when a pressure inside the battery cell exceeds a reference pressure threshold. In other embodiments, the vent opening is covered by a notched portion of a cap plate to allow the portion of the cap plate to burst open when a pressure inside the battery cell exceeds a reference pressure threshold. Thus, once the vent opening opens, it cannot close (or seal) the cell housing again and the battery cell can no longer be used and usually has to be disposed. 
     The casing of a battery submodule, battery module, or battery system usually also encloses the components therein in an essentially gas tight manner, and thus, an opening in the submodule, module, or system casing (e.g., housing) is often included to prevent damage to the casing and its sealing due to highly increased interior pressure. Such an opening also allows for venting away (or expelling) the venting gases safely to protect persons from dangerous fumes and gases that may occur during thermal runaway or other dysfunctions of battery cells within the casing. For fast venting of vent gases, the opening should be configured to open at a reference pressure inside the casing. 
     According to embodiments of the present disclosure, the sealing body in such an opening is configured to affect the opened state or the closed state of the opening is used to determine a thermal runaway of at least one battery cell within the casing (housing). Hence, according to embodiments of the present disclosure, a thermal runaway of, for example, a battery submodule, battery module, or battery system disposed within the housing can be determined almost immediately (e.g., with a very quick response time) as the pressure rises immediately during a venting event of a battery cell within the housing. Further, the detection of the thermal runaway is independent of internal battery measurements, such as measurements of voltage or temperature of a battery cell, which might be impaired by thermal propagation. Further, utilizing the opening state of a venting device for thermal runaway detection provides a low risk of false warnings of thermal runaway, as common venting devices are configured to open only due to a sufficient overpressure inside the casing. 
     In one embodiment, the thermal runaway detection circuit of the thermal runaway detection system has a first detection node that is connected to the venting device and a second detection node that is connected to the venting device. Thus, a conductive path is formed between the first and second detection nodes of the thermal runaway detection circuit, respectively, and the venting device. The venting device includes first and second contact nodes (e.g., contact pads) to enable the contact to the detection nodes. 
     According to embodiments of the present disclosure, a conductive (e.g., conductible) path between the first detection node and the second detection node is set conductive via the sealing body in one of the first position and the second position. Hence, the conductive path between the first and second detection nodes is set non-conductive in the other one of the first position and the second position of the sealing body. For example, the conductivity of the conductible path depends on whether or not the sealing body is opened or closed (i.e., seals) the venting passage. Hence, the conductivity of the conductive path indicates whether or not the venting passage is open or closed. 
     The thermal runaway detection circuit according to an embodiment of the present disclosure further includes a controller that is configured to detect the conductivity of the conductive path and to output a signal corresponding to the conductivity of the conductive path. The controller may be configured to measure a voltage and/or current on the conductive path or is configured to control a device to measure a voltage and/or current on the conductive path. The controller is further configured to determine the conductivity of the conductive path based on the obtained measurement signals. The signal corresponding to the conductivity of the conductive path generated by the controller takes different values for different conductivity states of the conductive path. For example, a value of the signal may correspond to the conductivity in absolute numbers (e.g., may be a measure of the conductivity). In other embodiments, the signal may take a first value for a conductivity below a reference threshold and a second value for a conductivity above a reference threshold. Further, one of the first and second values may be zero. 
     In an embodiment of the present disclosure, the sealing body is moveable from the first position to the second position in a reversible manner. Hence, once the pressure drops below the reference pressure threshold, the sealing body transfers (or reverts) back to the first position to close the venting passage. Hence, during a normal operation state, the venting device closes the venting passage to ensure protection from environmental influences. Hence, even if the sealing body moves to the second position to allow vent gases to be emitted via the venting passage, the thermal runaway detection system can be reused afterwards. 
     In an embodiment, the venting device is disposed in a housing, such as the housing of a battery submodule, a battery module, or a battery system. According to this embodiment, the venting device is configured to transition from the first position to the second position when a pressure within the housing exceeds a reference (or predefined) pressure threshold. Hence, because the venting device is reversibly transferable between the first and second positions, the casing (housing) can even be used after the occasion of a venting event of at least one battery cell within the housing. Also, the sealing body protects the inside of the casing (housing) from environmental influences while it is in the first state (e.g., when the venting passage is closed). 
     In an embodiment of the present disclosure, the conductive path between the first detection node and the second detection node is set conductive via the sealing body being in the first position. For example, when the sealing body closes the venting passage, the sealing body provides an electric closure to the conductive path. For example, the conductible path is set non-conductive when the sealing body is in the second position. 
     According to this embodiment, contact areas between the sealing body and a corresponding sealing surface against which the sealing body abuts to seal the venting passage may be formed as electric contacts. Further, the sealing body is electrically conductive or includes an electrically conductive path. Hence, when the sealing body seals the venting passage and abuts against the contact areas, it closes the conductive path between the first and second detection nodes. In one embodiment, the sealing body is a valve plate, and the venting device further includes a spring to push (or bias) the valve plate into the second (closed) position. Further, the sealing body is an electrically conducting part of the conductible path, at least while the sealing body is in the first position to close the venting passage. In other words, the sealing body electrically closes the conductive path while it is in the first position. 
     Further, the thermal runaway detection circuit has a first power input connected to a first cell terminal of at least one battery cell and a second power input connected to a second cell terminal of at least one battery cell. In one embodiment, at least one battery cell is the same battery cell, the venting of which effects a transition of the sealing body from the first position into the second position. In other words, according to this embodiment, the thermal runaway detection circuit, particularly the controller thereof, is self-supplied by the at least one battery cell that is supervised by the thermal runaway detection system. That is, the controller is connected to the first power input and to the second power input, and the controller is powered via the at least one battery cell. 
     Further, the first detection node of the circuit is connected to the first power input, and the second detection node of the circuit is connected to the second power input. The first detection node of the circuit may be connected to the first power input via the controller or independently of the controller. The second detection node of the circuit may be connected to the second power input via the controller or independently of the controller. The first detection node differs from the first power input, and the second detection node differs from the second power input. In some embodiments, the controller is supplied with power via the first power input and second power input and is independent of the conductivity state of the conductive path. In other words, the controller and the conductive path (i.e., the venting device with the sealing body) are connected in parallel to each other with respect to the at least one battery cell operating as power supply. 
     Further, the controller of the thermal runaway detection system, for example, of the thermal runaway detection circuit, is configured to output the signal while the conductive path is set conductive. According to this embodiment, when the controller detects a property of the conductive path (e.g., a voltage or current along the conductive path), a high signal corresponding to this property may be in the controller (e.g., the controller may detect a property of the conductive path as a high signal). Such a high signal in the controller is then output or at least used to output the signal indicative of the conductivity of the conductive path. For example, the controller according to this embodiment may detect a signal corresponding to the conductivity of the conductive path to determine this conductivity and at the same time outputs this signal corresponding to the conductivity of the conductive path. In this embodiment, the circuitry of the controller might be relatively simple. 
     In another embodiment, the controller is configured to output the signal when a current across the conductive path falls below a reference (or predetermined) current threshold. According to such embodiment, the controller is configured to detect a current across the conductive path and is further configured to compare this measured current with a reference (or preset) current. Such a comparison may be performed by using a comparator or the like. According to this embodiment of the present disclosure, the thermal runaway detection system further includes a shunt resistor that is interconnected between the first power input and the first detection node or between the second power input and the second detection node. For example, the shunt resistor may be integrated into an extension of the conductive path on the thermal runaway detection circuit, for example on a substrate carrier carrying this circuit. According to this embodiment, the controller is further configured to detect a voltage drop over the shunt resistor and to determine a current along the conductive path based on the voltage drop detected over the shunt resistor. In this embodiment, the controller may be connected to a node upstream of the shunt to tap a voltage upstream of the shunt and to another node downstream of the shunt resistor in order to tap a voltage downstream of the shunt. 
     The electronic or electric devices and/or any other relevant devices or components according to embodiments of the present disclosure may be implemented utilizing any suitable hardware, firmware (e.g., ASIC), software, or a combination of software, firmware, and hardware. For example, the various components of these devices may be formed on one integrated circuit (IC) chip or on separate IC chips. Further, the various components of these devices may be implemented on a flexible printed circuit film, a tape carrier package (TCP), a printed circuit board (PCB), or formed on one substrate. Further, the various components of these devices may be a process or thread, running on one or more processors, in one or more computing devices, executing computer program instructions and interacting with other system components for performing the various functionalities described herein. 
     The computer program instructions are stored in a memory which may be implemented in a computing device by using a standard memory device, such as, for example, a random access memory (RAM). The computer program instructions may also be stored in other non-transitory computer readable media, such as, for example, a CD-ROM, flash drive, or the like. Also, a person of skill in the art should recognize that the functionality of various computing devices may be combined or integrated into a single computing device, or the functionality of a particular computing device may be distributed across one or more other computing devices without departing from the scope of the embodiments of the present disclosure. 
     Another embodiment of the present disclosure relates to a battery submodule that includes a plurality of aligned battery cells. The battery submodule further includes a submodule housing that encloses the plurality of aligned battery cells. The battery submodule further includes the claimed thermal runaway detection system as described above, and the venting device is disposed in the venting passage of the battery submodule housing. Some embodiments of the battery submodule correspond to the embodiments of the thermal runaway detection system as described above. For example, the venting passage of the thermal runaway detection system of the present disclosure connects the interior of the battery submodule housing with the exterior of the battery submodule housing depending on the position of the sealing body being one of the first or second position. 
     Another embodiment of the present disclosure relates to a battery module that includes a plurality of battery submodules, each battery submodule including a plurality of aligned battery cells. The battery module includes a plurality of battery submodules according to an embodiment of the present disclosure as described above. The battery module further includes a module housing enclosing the battery submodules and the thermal runaway detection system according to an embodiment of the present disclosure as described above. Therein, the venting device is disposed in the venting passage of the battery module housing. In other words, the venting passage of the thermal runaway detection system of the present disclosure connects the interior of the battery module housing with the exterior of the battery module housing depending on the position of the sealing body being one of the first or second position. Embodiments of the battery module correspond to or include the thermal runaway detection system according to embodiments as described above. 
     Another embodiment of the present disclosure relates to a battery system that includes at least one battery module and a system controller configured to operate the at least one battery module. The system controller may be is a battery management system configured to detect states of the battery cells of the battery module, perform balancing of the cells, and/or to establish a communication connection with external loads or the like. The battery module may include at least one battery submodule, and each battery submodule has a plurality of aligned battery cells stacked together. The battery system further includes a system housing and the thermal runaway detection system according to an embodiment of the present disclosure as described above. Therein, the venting device is disposed in the venting passage of the battery system housing. In other words, the venting passage of the thermal runaway detection system of the present disclosure connects the interior of the battery system housing with the exterior of the battery system housing depending on the position of the sealing body being one of the first or second position, such as the first position. Embodiments of the battery system correspond to embodiments of the thermal runaway detection system as described above. 
     Another embodiment of the present disclosure is directed to a vehicle that includes a battery submodule as described above, a battery module as described above, and/or a battery system as described above and further includes at least one vehicle control unit that is configured to receive the signal that is output from the controller and corresponds to the conductivity state of the conductive path. The vehicle includes at least one output means (e.g., an output device configured to output a signal), and the vehicle control unit is further configured to output a warning to a passenger based on the received signal. The vehicle may include a display for outputting a visual warning to a passenger. Alternatively or additionally, the vehicle may include a speaker for outputting an audible warning to a passenger for warning the passenger. Above that, the vehicle may provide a haptic warning to a passenger, such as a vibration. 
     Another embodiment of the present disclosure relates to a method for detecting a thermal runaway of at least one battery cell of a plurality of battery cells disposed within a housing in which a venting device with a sealing body is disposed in a venting passage of the housing. Therein, the sealing body is configured to close the venting passage in a first position and to open the venting passage in a second position different from the first position in response to a reference (or predefined) pressure within the housing. Further, the sealing body is configured to set a conductive path conductive in one of the first state and the second state and to set the conductive path non-conductive in the other state. The method according to embodiments of the present disclosure includes detecting, via a controller that is configured to detect a conductivity of the conductive path, a conductive state of the conductive path and outputting a first signal. The method of the present disclosure further includes detecting, via the controller, a non-conductive state of the conductive path and outputting a second signal. Therein, one of the first and second signals indicates a thermal runaway of a battery cell. 
     In one embodiment, the method according to embodiments of the present disclosure further includes outputting a warning and/or performing at least one countermeasure in response to the signal indicating a thermal runaway. As described above with respect to the vehicle of the present disclosure, the warning may be output via at least one output device of, for example, an electric vehicle. The countermeasure may include shutting down at least one up to and including all of the plurality of battery cells and/or emitting a fire extinguishing (and or cooling) substance to one up to and including all of the plurality of battery cells. Further, the countermeasure may include increasing the cooling performance of a cooling system of the at least one battery cell and/or activating a device to increase thermal conductivity between the plurality of battery cells by, for example, activating additional ventilation devices, such as ventilation fans. The method according to embodiments of the present disclosure further includes stopping the output of the warning and/or the performance of the countermeasure in response to the other signal that does not indicate a thermal runaway. Therein, the warning and/or the countermeasure is one of those warning and countermeasures as described above. 
     Another embodiment of the present disclosure relates to a computer program including instructions which, when the program is executed by a controller of a thermal runaway detection system as described above, cause the controller to carry out the method according to embodiments of the present disclosure as described above. Therein, the controller may control other elements of the thermal runaway detection system for carrying out the method. Other aspects and features of the system and method according to embodiments of the present disclosure may be learned by the following description of the drawings and the dependent claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Aspects and features of the present disclosure will become apparent to those of ordinary skill in the art by describing, in detail, exemplary embodiments with reference to the attached drawings, in which: 
         FIG. 1  is a schematic illustration of a battery module according to an embodiment; 
         FIG. 2  is a schematic illustration of a thermal runaway detection circuit according to an embodiment; 
         FIG. 3  is a schematic illustration of a venting device according to a first embodiment; and 
         FIG. 4  is a schematic illustration of a venting device according to a second embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made, in detail, to embodiments, examples of which are illustrated in the drawings, and aspects and features of the embodiments will be described with reference to the accompanying drawings. In the drawings, like reference numerals denote like elements, and redundant descriptions of same reference elements may be omitted. Aspects and features of the inventive concept and methods of accomplishing the same may be understood more readily by reference to the following detailed description of embodiments and the accompanying drawings. The present disclosure, however, may be embodied in various different forms and should not be construed as being limited to the illustrated embodiments. 
     As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Further, the use of “may” when describing embodiments of the present disclosure refers to “one or more embodiments of the present disclosure.” It will be understood that although the terms “first” and “second” are used to describe various elements, these elements should not be limited by these terms. These terms are used to distinguish one element from another element. For example, a first element may be named a second element and, similarly, a second element may be named a first element. 
     Spatially relative terms, such as “beneath,” “below,” “lower,” “under,” “above,” “upper,” and the like, may be used herein for ease of explanation to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or in operation, in addition to the orientation depicted in the figures. 
     It will be understood that when an element or layer is referred to as being “on,” “connected to,” or “coupled to” another element or layer, it can be directly on, connected to, or coupled to the other element or layer, or one or more intervening elements or layers may be present. In addition, it will also be understood that when an element or layer is referred to as being “between” two elements or layers, it can be the only element or layer between the two elements or layers, or one or more intervening elements or layers may also be present. 
     Unless otherwise defined, all terms (also technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art. It will be further understood that terms, such as those defined in common dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and/or the present specification, and should not be interpreted in an idealized or overly formal manner. 
       FIG. 1  is a perspective view illustrating a battery module  50  according to an embodiment. The battery module  50  illustrated in  FIG. 1  may be a battery module  50  as utilized in an electric vehicle. The battery module  50  includes a housing  53  having a plurality of (e.g., four) lateral exterior walls and a single linearly extended partition wall  54  arranged at a center of the housing  53 . The housing  53  may be closed by a top cover and is an essentially gastight housing. 
     The partition wall  54  divides the housing  53  in two submodule compartments. Battery submodules  20  are arranged in both of the submodule compartments. Each of the battery submodules  20  includes a plurality of (e.g., ten) aligned battery cells  10  that are stacked in a stacking direction with their wide side surfaces facing each other. The stacking direction of the battery submodules  20  is also the longitudinal direction of the battery module  50  along which the battery module  50  has its largest extension (e.g., its longest extension length). The battery submodules  20  are positioned in the submodule compartments with their longitudinal direction essentially parallel to the partition wall  54 . In the following description, a first battery submodule  20   a  is primarily described, the configuration of which is identical or substantially similar to the second battery submodule  20   b , which also forms part of battery module  50 . 
     The first battery submodule  10   a  includes a plurality of (e.g., ten) battery cells  10 , and each of the battery cells  10  of the first battery submodule  10   a  includes an electrode assembly accommodated in a case  16  together with an electrolyte. The case  16  of each battery cell  10  may have a substantially cuboidal or prismatic shape and may be formed of a metal, such as aluminum. Each battery cell  10  may further include a cap assembly  14  for sealing an opening of the case  16 . Each cap assembly  14  includes a cap plate for covering an opening in the case  16 , a first cell terminal  11  (e.g., a positive terminal), and a second cell terminal  12  (e.g., a negative terminal). The cell terminals  11 ,  12  protrude from the cap assembly  14 . The cap assembly  14  includes a vent  13  which has a vent opening that is covered by a membrane or has a notch (e.g., a notch in the cap assembly  14 ). The membrane or notched portion of the cap assembly  14  is configured to open in response to a certain overpressure within the battery cell  10 . 
     The battery cells  10  of the first battery submodule  20   a  are connected to each other via busbars  15  in, for example, a 2p5s configuration. The battery cells  10  of the second battery submodule  20   b  are connected to each other via busbars  15  in the same configuration. However, in other embodiments, the battery cells in the different battery submodules  20   a ,  20   b  may be respectively connected to each other in different configurations. Each busbar  15  connects two first cell terminals  11  of first battery cells  10   a  with two second cell terminals  12  of second battery cells  10   b . That is, each busbar  15  may connect a total of four cell terminals  11 ,  12  to each other. 
     Further, the first battery submodule  20   a  is connected to the second battery submodule  20   b  via an interconnector (e.g., a busbar)  17 , and the interconnector  17  interconnects first terminals (e.g., two first terminal)  11  of the second battery submodule  20   b  with second terminals (e.g., two second terminals)  12  of the first battery submodule  20   a . Further, first terminals (e.g., two first terminals)  11  of the first battery submodule  20   a  are connected to a first module terminal (e.g., a positive terminal)  51  via a first terminal connector  18 , and second terminals (e.g., two second terminals)  12  of the second battery submodule  20   b  are connected to a second module terminal (e.g., a negative terminal)  52  via a second terminal connector  19 . A high current path is formed by the busbars  15 , the interconnector  17 , and the terminal connectors  18 ,  19 . This high current path extends from the first module terminal  51  along the battery cells  10  of the battery submodules  20   a ,  20   b  to the second module terminal  52 . 
     According to an embodiment, the battery module  50  further includes a thermal runaway detection system. For example, the battery module  50  may include a venting device (e.g., a vent)  55  that is disposed in a lateral exterior wall of the housing  53  of the battery module  50 . The battery module  50  may further include a thermal runaway detection circuit  60 . The thermal runaway detection circuit  60  has a first power input  61  connected to first terminals of cells of the second battery module  20   b  and a second power input  62  connected to second terminals of cells of the first battery module  20   a . Hence, power is supplied to the thermal runaway detection circuit  60  at least by part of the battery module  50 . The thermal runaway detection circuit  60  further includes a first detection node  63  connected to the venting device  55  and a second detection node  64  also connected to the venting device  55 . The venting device  55  includes a sealing body (e.g., a seal) configured to seal a venting passageway in the exterior lateral wall of the battery module  50  depending on its positions. Further, the thermal runaway detection circuit  60  is configured to monitor the position of the sealing body via the first detection node  63  and the second detection node  64 . Based on the monitored (or determined) position of the sealing body, the thermal runaway detection circuit  60  outputs a signal that is indicative of the position of the sealing body. Thus, based on the signal output by thermal runaway detection circuit  60 , a thermal runaway is reliably detected. 
     An embodiment of the thermal runaway detection circuit  60  is schematically illustrated in  FIG. 2 , and embodiments of the venting device  55  are schematically illustrated in  FIGS. 3 and 4 . These embodiments are described below with respect to the integration in the battery module  50  shown in  FIG. 1 . However, the embodiments of the thermal runaway detection circuit  60  and the venting device  55  described herein may also be used independently of the battery module  50  shown in  FIG. 1  (e.g., in a battery system). 
     As schematically illustrated in  FIG. 2 , the thermal runaway detection circuit  60  has a conductive path (shown as dashed line) that connects the first power input  61  and the first detection node  63 . The thermal runaway detection circuit  60  also includes another conductive path (also shown as dashed line) that connects the second power input  62  and the second detection node  64 . Further, a controller  65  is interconnected between these conductive paths and, thus, is connected to the first and second power inputs  61 ,  62 . Thus, power is supplied to the controller  65  by the second battery submodule  20   b  shown in  FIG. 1 . Further, a shunt resistor  67  is disposed in the conductive path between the first power input  61  and the first detection node  63 . The controller  65  is connected to a first voltage measurement node downstream of the shunt resistor  67  and to a second voltage measurement node upstream of the shunt resistor  67 . The controller  65 , thus, taps a first voltage downstream of the shunt resistor  67  and a second voltage upstream of the shunt resistor  67  and is configured to determine a voltage drop over (or through) the shunt resistor  67 . Based on a known (or set or reference) resistivity of the shunt resistor  67 , the controller  65  determines a current through the shunt resistor  67  and, thus, a current through the first detection node  63 . Because the first detection node  63  and the second detection node  64  are connected via the venting device  55  as illustrated in  FIG. 1 , the current through the first detection node  63  is also indicative for the current through the venting device  55  and can be used to monitor (or determine) a position of the sealing body in the venting device  55 . This will be explained in more detail with respect to the embodiments shown in  FIGS. 3 and 4 . 
     As schematically illustrated in  FIG. 3 , the venting device  55  has a venting passage  555  that connects (or extends between) an interior and an exterior of the housing  53 . The venting passage  555  is selectively opened or closed based on the positions of a first sealing body  551  and of a second sealing body  552 . Each of the sealing bodies  551 ,  552  is connected to a lateral wall of the venting passage via a respective torsion spring. 
     The torsion springs are pre-stressed such that the first and second sealing body  551 ,  552  abut against each other to close the venting passage  555  in a first position (or first state) as illustrated in the left part of  FIG. 3 . Further, each of the first and second sealing body  551 ,  552  includes (or is made of) a conductive material, such as aluminum. Further, the first sealing body  551  is connected to the first detection node  63 , and the second sealing body  552  is connected to the second detection node  64 . Hence, when the first and second sealing body  551 ,  552  abut against each other, a conductive path between the first detection node  63  and the first detection node  64  is closed via the first and second sealing bodies  551 ,  552 . 
     When a pressure inside the housing  53  exceeds a reference (or predefined) threshold, the first and second sealing bodies  551 ,  552  move against the spring force exerted by the respective torsion springs into a second position (or second state) as illustrated in the right part of  FIG. 3 . In the second position, the first and second sealing bodies  551 ,  552  do not abut against each other and open the venting passage  555 , thus allow a venting gas  556  emitted by at least one of the battery cells  10  in the housing  53  to exit the housing  53  via the venting passageway  555 . At the same time, the conductive path between the first and second detection nodes  63  and  64  is opened (i.e., set non-conductive), such that the thermal runaway detection circuit  60  (see, e.g.,  FIG. 2 ) can detect the second position of the first and second sealing bodies  551 ,  552  and output a signal  66  that is indicative of the first and second sealing bodies  551 ,  552  being in a second position and that a venting event related to a thermal runaway occurred. 
     Another embodiment of venting device  55  is schematically illustrated in  FIG. 4 . The venting device  55  shown in  FIG. 4  includes a single sealing body  553  that is pressed by a linear spring  554  to contact areas of the venting device  55  to close the venting passage  555 . The venting passage  555  is closed in a first position (or first state) of the sealing body  553  as illustrated in the left part of  FIG. 5 , and a venting gas  556  is blocked from being emitted from the housing  53 . As the same time, a conductive path between the first detection node  63  and the second detection node  64  is closed by the conductive sealing body  553 . 
     However, when the pressure inside the housing  53  exceeds a reference (or predetermined) value and a force exerted by this pressure on the sealing body  553  exceeds a force exerted by the spring  554 , the sealing body  553  moves from the first position (or first state) to a second position (or second state) as illustrated in the right side of  FIG. 4 . In the second position, the venting passage  555  is open and, thus, a venting gas  556  emitted by at least one of the battery cells  10  in the housing  53  can be emitted from the housing  53  via the venting passageway  555 . At the same time, the conductive path between the first and second detection nodes  63  and  64  is open (i.e., set non-conductive), such that the thermal runaway detection circuit  60  (see, e.g.,  FIG. 2 ) can detect the second position of the sealing body  553  and output a signal  66  that is indicative of such second position and that a venting event connected to a thermal runaway has occurred. 
     SOME REFERENCE NUMERALS 
     
         
           10  battery cell 
           11  first cell terminal (e.g., positive cell terminal) 
           12  second cell terminal (e.g., negative cell terminal) 
           13  vent 
           14  cap assembly 
           15  busbar 
           16  housing 
           17  submodule interconnector 
           18  first terminal connector 
           19  second terminal connector 
           20  battery submodule 
           50  battery module 
           51  first module terminal (e.g., positive terminal) 
           52  second module terminal (e.g., negative terminal) 
           53  housing 
           54  partition wall 
           55  venting device 
           551  first swiveling sealing body 
           552  second swiveling sealing body 
           553  movable sealing body 
           554  spring 
           555  venting passage 
           556  venting gas flow 
           60  thermal runaway detection circuit 
           61  first power input 
           62  second power input 
           63  first detection node 
           64  second detection node 
           65  controller 
           66  signal output 
           67  shunt resistor