SYSTEM FOR DETECTING THERMAL EVENTS IN A BATTERY SYSTEM

Abstract

A system for detecting thermal events in a battery system comprises a detection circuit functionally connected to the battery system, wherein the battery system comprises a plurality of sets of battery cells, the detection circuit comprises a plurality of resistors, each resistor of the plurality of resistors being located near a respective set of battery cells, the plurality of resistors being connected in parallel to a conductor.The system also includes a detector electrically connected via the conductor to the plurality of resistors, the detector being configured to detect an electrical signal from the detection circuit, the electrical signal being based on the resistance of each resistor, and a processor configured to receive a value of the electrical signal during operation of the battery system and to identify a thermal event based on the electrical signal, the thermal event causing a change in the resistance of at least one resistor.

Description

INTRODUCTION The subject matter of the invention relates to batteries and in particular a system according to the preamble of claim 1 for detecting thermal events in a battery system, as is known essentially from DE 10 2023 120 980 A1. Further details of the state of the art can be found in DE 10 2019 109 539 A1. Vehicles, including gasoline and diesel-powered vehicles as well as electric and hybrid electric vehicles, have battery storage systems to supply power to electric motors, electronics, and other vehicle subsystems. Monitoring the battery system's health is a critical aspect of battery operation. Thermal events can lead to battery system malfunctions. It is desirable to provide methods and systems that address the improved detection and mitigation of undesirable thermal events. SUMMARY According to the invention, a system for detecting thermal events in a battery system is presented, characterized by the features of claim 1. In addition to one of the features described herein, the deformable substrate is configured to rest on a surface of each of the sets of battery cells. In addition to one or more of the features described herein, the thermal event includes a set of battery cells that exceed a threshold temperature. In addition to one or more of the features described herein, the change in resistance of the at least one resistor is based on a separation of the at least one resistor due to the thermal event. In addition to one or more of the features described herein, the system includes a reference resistor connected to the sensing circuit, wherein the reference resistor has a fixed resistance at a given input voltage. In addition to one or more of the features described herein, the electrical signal is an output voltage of the sensor circuit, and the processor is configured to detect the thermal event based on the output voltage being greater than a reference voltage. In addition to one or more of the features described herein, the processor is configured to determine the origin of the thermal event based on the electrical signal. Furthermore, a method for detecting a thermal event in a battery system is described. The method comprises monitoring a detection circuit functionally connected to the battery system, wherein the battery system comprises a plurality of sets of battery cells, the detection circuit comprises a plurality of resistors, each resistor of the plurality of resistors being arranged near a respective set of battery cells, and the plurality of resistors being connected in parallel to a conductor.The method also includes receiving an electrical signal at a detector that is electrically connected via the conductor to the plurality of resistors, wherein the electrical signal is based on a resistance of each resistor, and identifying a thermal event based on the electrical signal, wherein the thermal event causes a change in the resistance of at least one resistor. In addition to one or more of the features described herein, the majority of the resistors are arranged on a deformable substrate. In addition to one or more of the features described herein, the thermal event includes a set of battery cells that exceed a threshold temperature. In addition to one or more of the features described herein, the change in resistance of the at least one resistor is based on a separation of the at least one resistor due to the thermal event. In addition to one or more of the features described herein, the electrical signal is an output voltage of the detection circuit, and identifying the thermal event involves comparing the output voltage with a reference voltage to determine whether the output voltage matches the reference voltage. In addition to one or more of the features described herein, identifying the thermal event based on the output voltage not matching the reference voltage includes determining an origin of the thermal event based on the output voltage. In addition to one or more of the features described herein, determining the origin includes comparing the output voltage with a plurality of output voltage reference values, each output voltage reference value specifying a set of battery cells in which the thermal event is initiated. Furthermore, a vehicle system is described. The vehicle system comprises a memory containing computer-readable instructions and a processing device for executing the computer-readable instructions, wherein the computer-readable instructions control the processing device to perform a procedure. The procedure comprises monitoring a detection circuit functionally connected to the battery system, wherein the battery system comprises a plurality of sets of battery cells, the detection circuit comprises a plurality of resistors, each resistor of the plurality of resistors being arranged near a respective set of battery cells, and the plurality of resistors being connected in parallel to a conductor.The method also includes receiving an electrical signal at a detector that is electrically connected via the conductor to the plurality of resistors, wherein the electrical signal is based on a resistance of each resistor, and identifying a thermal event based on the electrical signal, wherein the thermal event causes a change in the resistance of at least one resistor. In addition to one or more of the features described herein, the electrical signal is an output voltage of the detection circuit, and identifying the thermal event involves comparing the output voltage with a reference voltage to determine whether the output voltage matches the reference voltage. In addition to one or more of the features described herein, identifying the thermal event based on the output voltage not matching the reference voltage includes determining an origin of the thermal event based on the output voltage. In addition to one or more of the features described herein, determining the origin includes comparing the output voltage with a plurality of output voltage reference values, each output voltage reference value specifying a set of battery cells in which the thermal event is initiated. The aforementioned features and advantages, as well as other features and advantages of the invention, are readily apparent from the following detailed description in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Further features, advantages, and details are listed by way of example only in the following detailed description, the detailed description referring to the drawings, wherein: Fig. 1 is a top view of a motor vehicle comprising a battery system, according to an exemplary embodiment; Fig. 2 shows a thermal event detection system, according to an exemplary embodiment; Fig. 3 is a circuit diagram showing a sensor circuit, according to an exemplary embodiment; Fig. 4 is a flowchart of a method for detecting thermal events, according to an exemplary embodiment; Fig. 5 is a circuit diagram showing a section of a detection circuit and aspects of an example of a thermal event; and Fig. 6 shows a computer system according to an exemplary embodiment. DETAILED DESCRIPTION Devices, systems, and methods for monitoring a battery system and detecting thermal events are provided. One embodiment of a thermal event detection system comprises a sensing circuit having a plurality of resistors connected in parallel to each other and to a detector. Each resistor is located near a respective set of cells in a battery system (e.g., a single battery cell, a group of cells, a battery module, etc.) such that a thermal event at the respective set of cells can displace the resistor or cause the resistor to disconnect from the sensing circuit, thereby changing the resistance of the sensing circuit. The detection system is configured to monitor the battery system and the sensing circuitry during operation and to detect or identify a thermal event, which includes an event or condition in which one or more sets of cells reach a temperature above a threshold temperature. The thermal event can be identified or detected by comparing an electrical output of the sensing circuitry to a reference value. The electrical output can also be used to determine the origin of the thermal event. For example, the detection system compares an output voltage with a reference output voltage and determines that a thermal event has occurred if the output voltage does not match the reference voltage. When a thermal event is detected, the detection system can compare the output voltage with reference data to determine which set of cells is the source of the thermal event. The embodiments described herein offer numerous advantages and technical benefits. They provide effective detection and diagnosis of thermal events. Furthermore, they offer more efficient thermal event detection that requires fewer components than existing systems. For existing battery management systems, accurately detecting and tracking the origin of thermal events in battery cells is often difficult. These systems typically rely on complex circuitry and multiple detection channels, which can lead to increased noise. The proposed embodiments address these limitations by providing a streamlined and efficient method for detecting thermal events that requires fewer components than existing systems. For example, external sensors such as gas, pressure, or ambient temperature sensors can be replaced by less complex and less resource-intensive designs using resistors (e.g., surface-mount (SMD) chip resistors). Additionally, the detection time can be significantly improved by configuring the resistors to be directly affected by gases produced during a thermal event. The embodiments also provide effective means to define which specific cell or group of cells initially undergoes a thermal event (i.e., which cell or group of cells is the origin of the event). This specific spot information can enable more in-depth investigations, for example, by tracing the serial number of a cell or a structural or thermal management defect when multiple cells or sets of cells are affected by a thermal event. The embodiments are not limited to use with a specific vehicle and can be applicable in various contexts. For example, the embodiments can be used in motor vehicles, trucks, aircraft, construction machinery, agricultural equipment, automated factory plants, and / or any other device or system that uses rechargeable energy storage systems. Fig. 1 shows an embodiment of a motor vehicle 10 comprising a vehicle body 12 that forms at least a portion of a passenger compartment 14. The vehicle body 12 also carries various subsystems of the vehicle, including a drive system 16, and other subsystems for supporting functions of the drive system 16 and other vehicle components, such as a brake subsystem, a suspension system, a steering subsystem, a fuel injection subsystem, an exhaust subsystem, etc. The vehicle 10 can be a vehicle with an internal combustion engine, an electric vehicle (EV), or a hybrid vehicle. In one embodiment, the vehicle 10 is a hybrid vehicle comprising an internal combustion engine system 18 and at least one electric motor arrangement. In another embodiment, the drive system 16 comprises an electric motor 20 and can include one or more additional motors mounted at different locations. The vehicle 10 can also be a fully electric vehicle comprising one or more electric motors. The vehicle 10 comprises a battery system 22, which can be electrically connected to the motor 20 and / or other components, such as the vehicle electronics. The battery system 22 can be configured as a rechargeable energy storage system (RESS). In one embodiment, the battery system 22 comprises a high-voltage battery pack 26, which has a plurality of battery modules 26. The battery system 22 can also include a monitoring unit 28, such as a battery management system (BMS) controller, which includes components such as a processor, memory, an interface, a bus and / or other suitable components. In one embodiment, a “battery system” refers to a group of battery cells (i.e., two or more cells). For example, the battery system may be the battery pack 24, a battery module 26, or a group of cells within a module 26. Additionally, a “battery module” may comprise a single cell or a group of cells that form a subset of the battery system and is not limited to the specific configurations described herein. The battery system 22 is electrically connected to components of the drive system 16. The drive system may also include an inverter module 30 and a DC-DC converter module 32. The inverter module 30 (e.g., a traction inverter or TPIM) converts direct current (DC) from the battery system 22 into multiphase alternating current (AC) (e.g., three-phase, six-phase, etc.) to drive the motor 20. The vehicle 10 can include various control modules (electronic control modules or ECUs). For example, it can include an on-board charger module (OBCM) 34, which connects the battery system 22 to a charging port 36 and controls aspects of charging the battery system 22 (e.g., from a charging station, a power grid, or another vehicle) and / or providing charge to an external system. The battery system 22 comprises a thermal event detection system 40, which includes or is connected to at least one sensing circuit 42. Each sensing circuit 42 includes a resistor 44 located near a set of cells (i.e., one or more cells). In one embodiment, a resistor 44 is located near one of the battery modules 26 (each resistor 44 is located near a respective battery module 26). The detection system 40 is not limited in this respect, as a resistor may be located near a single cell, a group of cells, or any other set of cells. The resistors 44 are connected in parallel to each other and to a processor, such as the monitoring unit 28. Each resistor 44 is configured such that a thermal event, in which one or more components of the battery system 22 exceed the temperature threshold, causes a change in the resistance of one or more resistors 44. The change in resistance can be caused, for example, by material expansion, an increase in atmospheric pressure, and / or gases produced that act on a resistor and / or cause the resistor 44 to disconnect from the sensing circuit 40. In one embodiment, the thermal event occurs when the temperature in a battery cell reaches a point that triggers a chemical reaction within the cell. This reaction produces more heat, leading to a rapid temperature rise and potentially causing malfunction. A thermal event in one cell or module can affect other cells and modules by causing a temperature increase in adjacent cells or modules. The vehicle 10 also includes a computer system 60, which comprises one or more processing units 62 and a user interface 64. The various processing units and devices can communicate with each other via a communication device or system, such as a Controller Area Network (CAN) or Transmission Control Protocol (TCP) bus. The computer system 60 can be configured to perform aspects of the procedures described herein, for example, in conjunction with the monitoring unit 28. Fig. 2 shows an embodiment of the thermal event detection system 40 as connected to an example of the battery module 26. In this example, the battery module 26 comprises a series of cell groups 25. A series of resistors 44 are arranged along the battery module 26 such that each resistor 44 (designated as resistors R0 to RN) is located directly above or otherwise near a corresponding cell group 25. It should be noted that although the detection circuit 40 is configured to have a resistor 44 for each cell group 25, the detection circuit 40 is not limited in this way. Each resistor 44 can be assigned to any set (i.e., one or more) of cells. For example, a resistor 44 can be arranged relative to each battery module 26 (as shown in Fig. 1), or relative to each individual battery cell in a cell group, module, or pack. Each resistor 44 is located in close proximity to a corresponding battery module (or other set of battery cells). As described herein, a resistor 44 is “close” to a battery cell or battery module because the resistor 44 is positioned such that a thermal event in the battery module directly and immediately affects the resistor 44 and causes a corresponding change in the resistance of the resistor 44, or causes the resistor 44 to be disconnected from the sensing circuit 40 (e.g., by damaging the resistor 44). The resistors 44 are connected in parallel to a conductor 46. The conductor 46 connects a detection device, such as the monitoring unit 28, to the resistors 44. The detection system 40 thus avoids the need for dedicated detection channels for each resistor 44 (e.g., one detection channel for a high and a low side of the resistors 44). Each resistor 44 is positioned such that it is disconnected from the detection circuit 40 when a cell group 25 (or another corresponding group of cells) undergoes a thermal event with a sufficient temperature (i.e., the temperature rises to a value at or above a threshold, and / or it rises at a rate of at least one selected value). This disconnection changes the overall resistance of the detection circuit 40. In one embodiment, the resistors 44 are arranged on a flexible or deformable substrate 48. The substrate 48 can be made of silicone, rubber, or another suitable insulating material. This flexibility allows the substrate 48 to hold each resistor 44 in a fixed position relative to a respective set of cells and to allow each resistor 44 to be relocated or switched off in response to a thermal event. Fig. 3 is a circuit diagram that schematically represents the detection circuit 40. Each of the resistors R0 to RN has an initial resistance value. A reference resistor 50, such as a pull-up resistor Rpull-up, has a fixed resistance value and is used to determine a reference value associated with normal operation. For example, a reference voltage associated with a given current is calculated based on the resistance of the reference resistor 50. The output voltage V of the detection circuit 40 is determined based on the provision of an input voltage and the determination of an output voltage. The output voltage can be used as a reference voltage, which is a function of the resistances of the reference resistor 50 and the resistors 44. The output voltage V can be represented by the following equation, where N is the number of resistors and i is a subscript: In one embodiment, the preceding equation is used to calculate a reference output voltage Vref that correlates with normal operation. The reference output voltage Vref is calculated using the preceding equation, an input voltage, and the initial values ​​of resistors 44 and 50. The input voltage is, for example, approximately 3 volts (V) to approximately 5 V. The reference output voltage Vref is related to the fixed value of the reference resistor 50 and the initial resistances of resistors 44. It should be noted that the input voltage, the reference voltage, and the resistances of the various resistors are not limited to the specific examples described herein. In one embodiment, the detection system 40 is configured to detect a thermal event by comparing a measured output voltage with the reference output voltage Vref. A thermal event is identified, for example, when a measured output voltage exceeds the reference output voltage. Based on the identification that a thermal event has occurred, the detection system 40 can further determine from which group of cells the thermal event originated. In one embodiment, a set of reference values ​​is calculated for different thermal event scenarios (i.e., events that originated from or started in different sets of cells). The measured output voltage can then be compared with the set of reference values ​​to determine where the thermal event started. Table 1 presents an example of a reference voltage and an example of the resistances of the individual resistors 44. The reference resistor 50 has a fixed resistance of 5000 ohms at an input voltage of 3 volts, and the resistances of each individual resistor 44 vary as shown: Table 1 Table 1 Pull-up resistor 5000 ohms R050000 Ohm R130000 Ohm R220000 Ohm R310000 Ohm R45000 Ohm R51000 Ohm Table 2 presents an example of a normal or reference voltage (indicating normal battery operation) and an example of various thermal event scenarios: Table 2 Table 2 Normal 0.37 V First cell (R0) Thermal event 2.73 V Second cell (R1) Thermal event 2.37 V Third cell (R2) Thermal event 1.98 V Fourth cell (R3) Thermal event 1.49 V Fifth cell (R4) Thermal event 0.99 V Each thermal event scenario represents a thermal event originating from a different resistor 44. In the example above, a voltage value of 0.37 V represents normal operation (i.e., no thermal event occurs). A voltage value above the reference value of 0.37 V (or by a certain amount greater than the reference value) is considered indicative of a thermal event. For example, a value of 2.73 V indicates that a first cell group (near resistor R0) is the origin of a thermal event. Table 2 also presents values ​​associated with events originating from a second cell group (near resistor R1), a third cell group (near resistor R2), a fourth cell group (near resistor R3), and a fifth cell group (near resistor R4). Fig. 4 illustrates embodiments of a method 70 for monitoring a battery system (e.g., the battery pack 24) and for detecting thermal events (or other undesired thermal events). Aspects of the method 70 can be performed by one or more processors arranged in the vehicle 10 (e.g., the monitoring unit 28, the computer system 60, etc.). It should be noted that the method 70 is not so limited and can be performed by any suitable processing device or system, or a combination of processing devices. Procedure 70 comprises a series of steps or stages represented by blocks 71-77. Procedure 70 is not limited to the number or order of the steps contained therein, as some of the steps represented by blocks 71-77 may be performed in a different order than described below, or fewer than all of the steps may be performed. In block 71, the detection system 40 determines an initial resistance value for each resistor, including the reference resistor 50 and the resistors 44. The initial resistance value can be determined based on existing information, such as manufacturer specifications, or based on performing an initial resistance measurement. In Block 72, a set of resistance change values ​​is generated or obtained. For example, a resistance change matrix is ​​received or calculated that indicates how the resistance in each resistor 44 changes when a specific thermal event occurs. Block 73 generates a reference value matrix or other data structure that specifies the output voltages for each of several different thermal events. For example, a reference output voltage is calculated for each of a plurality of thermal events, with each event being initiated at a different cell group 25 (or a different set of cells). An example of voltage reference values ​​is shown in Table 2. Additionally, a reference output voltage is determined, which corresponds to normal battery operation. This value is based on a normal voltage output value. In block 74, the battery system 22 is monitored during vehicle operation or during other processes in which the battery system 22 is used (e.g., during charging of the battery system 22 or during discharge to another device or system, such as vehicle-to-vehicle or vehicle-to-grid charging). An output voltage is measured continuously (e.g., at each sampling point) or periodically. The measured output voltage is then compared with the normal voltage output value. The system determines whether the measured output voltage value corresponds to the normal voltage output value (i.e., whether it matches the normal value or lies within a selected range of the normal value). If so, battery monitoring continues. In block 75, if the measured output voltage does not match the normal voltage output value, a thermal event is detected. A warning or other indication that the event has been detected can be provided to a vehicle system (e.g., an autonomous control system) or to a user or driver (e.g., via the user interface 64 of Fig. 1). In block 76, upon detection of a thermal event, monitoring unit 28 compares the measured output voltage with reference voltage values ​​to determine the origin of the thermal event. Monitoring unit 28 then determines which output voltage reference value most closely matches the measured value. In block 77, if the measured output voltage matches a reference voltage value, the monitoring unit 28 determines the specific cell group associated with the reference output voltage value and outputs the cell or group number (or other identification information). Fig. 5 illustrates an example of a thermal event. In this example, the thermal event was initiated near resistor R4, resulting in the interruption of a section 80 of the detection circuit (e.g., by the melting of the resistor and / or sections of conductor 46). Consequently, section 80 of the circuit downstream of resistor R4 is open. A section 82 of the circuit 40 between resistor R4 and the monitoring unit 28 (Fig. 3) now has a different resistance than the initial resistance of the circuit 40. The monitoring unit 28 measures an output voltage of approximately 1.49 V and compares the measured output voltage with a normal output voltage. In this example, the normal output voltage is 0.37 V, and the resistors 44 have the initial resistances shown in Table 1. The monitoring unit 28 determines that a thermal event has occurred. The measured output voltage is then compared with reference voltage data, such as the data shown in Table 2. As a result, the monitoring unit 28 identifies the cell or cell group near resistor R4 as the source. Based on the detection of a thermal event, various actions can be taken. For example, the driver or a vehicle control system can shut down the vehicle (possibly in conjunction with bringing it to a safe stop) or otherwise control vehicle or battery operation. In another example, diagnostic information can be provided to an external party such as a technician, a fleet management system, and / or a car dealership. Fig. 6 illustrates aspects of an embodiment of a computer system 140 that can perform various aspects of the embodiments described herein. The computer system 140 comprises at least one processing device 142, which generally includes one or more processors for performing aspects of the methods described herein. Components of the computer system 140 include the processing device 142 (such as one or more processors or processing units), a memory 144, and a bus 146 that connects various system components, including the system memory 144, to the processing device 142. The system memory 144 can be a non-transient, computer-readable medium and can comprise a plurality of computer-readable media. These media can be any available medium that the processing device 142 can access, including volatile and non-volatile media, as well as removable and non-removable media. System memory 144 includes, for example, non-volatile memory 148, such as a hard drive, and may also include volatile memory 150, such as random access memory (RAM) and / or cache memory. The computer system 140 may also include other removable / non-removable, volatile / non-volatile storage media of the computer system. The system memory 144 can comprise at least one program product that has a set (e.g., at least one) of program modules configured to perform functions of the embodiments described herein. For example, the system memory 144 stores various program modules that generally perform the functions and / or procedures of the embodiments described herein. One or more modules 152 can be used to perform functions related to battery monitoring and thermal event detection, as described herein. The system 140 is not so limited, as it can also include other modules.As used herein, the term “module” refers to a processing circuit that may include an application-specific integrated circuit (ASIC), an electronic circuit, a processor (common, dedicated or group) and memory that executes one or more software or firmware programs, a combinational logic circuit and / or other suitable components that provide the functionality described. The processing device 142 can also communicate with one or more external devices 156, such as a keyboard, a pointing device, and / or other devices (e.g., a network card, a modem, etc.), which enable the processing device 142 to communicate with one or more other computing devices. Communication with various devices can take place via the input / output (I / O) interfaces 164 and 165. The processing device 142 can also communicate with one or more networks 166, such as a local area network (LAN), a wide area network (WAN), a bus network, and / or a public network (e.g., the Internet), via a network adapter 168. It is understood that other hardware and / or software components can also be used in conjunction with the computer system 140, even if not shown. Examples include: microcode, device drivers, redundant processing units, external hard disk arrays, RAID systems, data archiving systems, etc.

Claims

System for detecting thermal events in a battery system (22), comprising: a detection circuit functionally connected to the battery system (22), wherein the battery system (22) comprises a plurality of sets (25) of battery cells and the detection circuit (40) comprises a plurality of resistors (44), each resistor (44) of the plurality of resistors (44) being located near a respective set (25) of battery cells; a detector configured to detect an electrical signal from the detection circuit (40); and a processor configured to receive a value of the electrical signal during operation of the battery system (22) and to identify a thermal event based on the electrical signal, wherein the thermal event causes a change in the resistance value of at least one resistor (44);characterized in that the plurality of resistors (44) is connected in parallel to a conductor (46) via which the detector is electrically connected to the plurality of resistors (44); wherein the plurality of resistors (44) is arranged on a deformable substrate (48) made of silicone or rubber; and wherein the electrical signal is an output voltage of the detection circuit (40) based on the resistance value of each resistor (44) and thus on the total resistance of the detection circuit (40), and the processor is configured to determine an origin of the thermal event by comparing the output voltage with a plurality of output voltage reference values, each output voltage reference value indicating a set (25) of battery cells in which the thermal event is initiated. System according to claim 1, wherein the deformable substrate (48) is configured to rest on a surface of each of the sets (25) of battery cells. System according to claim 1, wherein the thermal event comprises the exceeding of a threshold temperature by a set (25) of battery cells. System according to claim 1, wherein the change in the resistance value of the at least one resistor (44) is based on a separation of the at least one resistor (44) due to the thermal event. System according to claim 1, further comprising a reference resistor connected to the detection circuit (40), wherein the reference resistor has a fixed resistance value at a given input voltage.

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