Method for determining a critical state of an electrical energy storage device, computer program product and monitoring device

Abstract

The invention relates to a method for determining a critical state of an electrical energy storage device (12) of an at least partially electrically powered motor vehicle (10) by means of a monitoring device (20), comprising the steps of: detecting an alternating current component (34) of the electrical energy storage device (12) by means of a detection unit (22) of the monitoring device (20); analyzing the detected alternating current component (34) and assigning the detected alternating current component (34) to a critical state of the electrical energy storage device (12) by means of an electronic computing unit (24) of the monitoring device (20); and determining the critical state as a function of the assignment by means of the electronic computing unit (24). The invention further relates to a computer program product and a monitoring device (20).

Description

[0001] The following invention relates to a method for determining a critical state of an electrical energy storage device of an at least partially electrically powered motor vehicle, by means of a monitoring device according to claim 1. The invention further relates to a corresponding computer program product and a corresponding monitoring device.

[0002] The timely identification of critical conditions in an electrical energy storage system, particularly in high-voltage lithium-ion batteries such as traction batteries, is crucial for improving road safety. Critical conditions arise especially when a battery cell experiences thermal runaway, creating a risk of thermal propagation. This condition detection is often referred to as "TP detection."

[0003] According to current technology, TP (Torque Boost) detection is usually achieved through the combined evaluation of the following sensor data signals: individual voltages, temperature measurements, and pressure measurements. The disadvantage of this approach is that it requires complex and project-specific data analysis as well as an active battery management system. These systems may be inactive, for example, when the vehicle is parked. Furthermore, a reliable pressure signal is necessary.

[0004] German patent DE 11 2020 002 115 T5 describes a battery monitoring device for monitoring the condition of a rechargeable battery comprising an electrolyte and a plurality of electrodes. The device includes a signal control unit configured to instruct the output of a predetermined alternating current signal, a response signal input unit configured to receive a response signal from the rechargeable battery to the alternating current signal, and a calculation unit configured to calculate a complex impedance of the rechargeable battery based on the response signal. The signal control unit is configured to cause the monitored rechargeable battery, acting as a power source, to output the predetermined alternating current signal.

[0005] DE10 347 110 B3 describes a device and a method for measuring individual cell voltages of the cells in a cell stack of an energy storage device, wherein a series connection of two diodes is arranged in parallel to each cell, wherein the connection points of these diodes are connected via a capacitor to a differential amplifier via a switch and an alternating current of a certain frequency and amplitude is fed into these capacitors, which generates an alternating voltage corresponding to the cell voltage, which after rectification becomes a ground-referenced DC voltage value for the cell voltage.

[0006] The object of the present invention is to create a method, a computer program product and a monitoring device by means of which a critical state of an electrical energy storage device can be reliably determined.

[0007] This problem is solved by a method, a computer program product, and a monitoring device according to the independent claims. Advantageous embodiments are specified in the dependent claims.

[0008] One aspect of the invention relates to a method for determining a critical state of an electrical energy storage device of an at least partially electrically powered motor vehicle using a monitoring device. An alternating current component of the electrical energy storage device is detected by means of a sensing unit of the monitoring device. The detected alternating current component is analyzed and assigned to a critical state of the electrical energy storage device by means of an electronic computing unit of the monitoring device. The critical state is determined by the electronic computing unit based on this assignment.

[0009] In particular, the invention utilizes the fact that the AC component of the total battery voltage can be used to detect critical battery cell conditions. A battery cell in thermal runaway generates AC voltage components that differ from typical vehicle electrical system fluctuations. Detection can be achieved, for example, by frequency-selective pattern comparison using artificial intelligence. This allows for continuous monitoring of the battery's AC voltage throughout its lifespan. In the event of a critical condition, the monitoring device can trigger appropriate responses. Furthermore, when the vehicle is stationary, especially in an inactive vehicle without interfering vehicle electrical system components, the sensitivity to undesirable behavior can be significantly increased.

[0010] This enables lifelong and continuous monitoring of an electrical energy storage system without the need for additional components. A simple analysis concept based on a single signal parameter, specifically the AC component of the total battery voltage, eliminates the need for sensor wiring within the actual electrical energy storage device. This allows for battery-independent and project-spanning analysis concepts, regardless of the design or number of cells in the electrical energy storage system.

[0011] In particular, the invention utilizes the fact that during thermal runaway of a battery cell, an exothermic reaction occurs, which strongly heats the battery cell and usually destroys it. During this process, an alternating current component can be generated, caused by the failure of the battery cell's internal resistance. However, this alternating current component also depends on various factors, such as the battery type, the extent of the thermal runaway, and the corresponding measurement conditions.

[0012] According to an advantageous embodiment, the electronic computing device is provided as a microcontroller. The microcontroller is preferably an ASIC (Automatic Integrated Circuit). This is a simple electronic computing device that can be operated independently of a battery management system. Thus, the critical state can be determined in a simple manner.

[0013] It has also proven advantageous if the analysis and classification are performed by the electronic computing unit independently of the battery management system of the electrical energy storage device. In other words, the electronic computing unit can be provided separately from the actual battery management system. Thus, regardless of, for example, the control or power supply of the battery management system, the electrical energy storage device can reliably analyze the critical event and, in particular, classify it accordingly.

[0014] It has also proven advantageous to determine the critical state during a period of vehicle inactivity. Inactivity can refer, for example, to an inactive vehicle, such as when parked or stationary. In particular, the battery management system is not receiving power during this time. However, the electronic control unit can still monitor the AC current even during periods of inactivity. This allows for monitoring of the electrical energy storage system without significant energy consumption and independent of driving conditions.

[0015] Furthermore, it has proven advantageous to define a potential thermal runaway of the electrical energy storage device as a critical condition. Thermal runaway is also known as "thermal runaway." It is a dangerous process that can occur in battery cells when they overheat. This process involves an exothermic reaction that further heats the battery cell and ultimately destroys it. Thermal runaway typically begins with a small temperature increase caused by an overload, a short circuit, or other faults. As the temperature rises, the reaction rate within the cell also increases, leading to a further temperature increase. This positive feedback loop accelerates the process and can ultimately result in thermal runaway.Thermal conductivity poses a serious safety hazard that must be considered when using battery cells. It is therefore important to ensure that the battery cells are charged and discharged correctly to avoid overloads or short circuits. Furthermore, suitable safety measures should be taken to minimize the risk of fires or explosions if thermal conductivity occurs. The method according to the invention now allows potential thermal conductivity to be detected at an early stage and thus prevented, or countermeasures to be initiated.

[0016] It is also advantageous if a warning message is generated when a critical condition is identified. In particular, an occupant can be warned accordingly. Furthermore, it is also possible to warn external parties, uninvolved individuals, and those affected. Critical components can also be shut down as needed. Thus, safety can be increased in the event of a potentially critical incident.

[0017] It is also advantageous if the battery management system of the energy storage device is activated when the critical state is determined. In particular, this allows, for example, a wake-up signal to be generated for the battery management system. The battery management system can then also perform further subsequent actions. Thus, monitoring can be carried out independently of the battery management system, and the battery management system can be activated accordingly, which in turn can trigger appropriate subsequent actions.

[0018] In a further advantageous embodiment, the alternating current component is captured as a superimposed signal of a direct current supplied by the electrical energy storage device. Specifically, the electrical battery storage device provides a corresponding direct current. This superimposed alternating current signal, as the alternating current component, can be used, in particular, to perform the necessary analysis to determine the critical state. Since the critical state is independent of the direct current component, the superimposed alternating current signal is used to determine the critical state.

[0019] The presented method is, in particular, a computer-implemented method. Therefore, a further aspect of the invention relates to a computer program product with program code means which, when the program code means are executed by the electronic computing device, cause it to carry out a method according to the preceding aspect.

[0020] Furthermore, the invention also relates to a computer-readable storage medium containing at least the computer program product according to the preceding aspect.

[0021] A further aspect of the invention relates to a monitoring device for determining a critical state of an electrical energy storage device of an at least partially electrically powered motor vehicle, comprising at least one detection device and an electronic computing device, wherein the monitoring device is configured to carry out a method according to the preceding aspect. In particular, the method is carried out by means of the monitoring device.

[0022] Furthermore, the invention also relates to an electrical energy storage device with at least one monitoring device according to the preceding aspect.

[0023] The invention also relates to a motor vehicle with at least one electrical energy storage device as described above. In particular, the motor vehicle is designed as either a partially or fully electric vehicle.

[0024] An advantageous embodiment of a method can be considered an advantageous embodiment of the computer program product, the computer-readable storage medium, the monitoring device, the electrical energy storage device, and the motor vehicle. The monitoring device, the electrical energy storage device, and the motor vehicle possess specific features to enable the execution of the corresponding method steps.

[0025] Further advantages, features, and details of the invention will become apparent from the following description of a preferred embodiment and from the drawings. The features and combinations of features mentioned above in the description, as well as those mentioned below in the figure description and / or shown in the figures alone, can be used not only in the combinations specified, but also in other combinations or individually, without departing from the scope of the invention.

[0026] This shows: Fig. 1 A schematic side view according to an embodiment of a motor vehicle with an embodiment of an electrical energy storage device with an embodiment of a monitoring device; Fig. 2 a schematic block diagram according to an embodiment of a monitoring device; and Fig. 3 a further schematic block diagram according to an embodiment of an electronic computing device of a monitoring device according to the invention.

[0027] In the figures, identical or functionally equivalent elements are provided with the same reference symbols.

[0028] Fig. Figure 1 shows a schematic side view of a motor vehicle 10. The motor vehicle 10 has an electrical energy storage device 12. The motor vehicle 10 is designed as either a partially or fully electric motor vehicle 10. The electrical energy storage device 12 can, for example, provide electrical energy for a drive unit 14 of the electric motor vehicle 10. The electrical energy storage device 12 has a plurality of battery cells 16. Furthermore, the electrical energy storage device 12 has a battery management system 18.

[0029] According to the invention, a monitoring device 20, designed separately from the battery management system 18, is provided. The monitoring device 20 comprises at least one detection device 22, for example for detecting the voltage and / or current of the battery cells 16, and an electronic computing device 24. The electronic computing device 24 is preferably designed as a microcontroller, in particular as an ASIC.

[0030] The Fig. Figure 1 further shows that a functional unit 26 is shown. The functional unit 26 can, for example, be considered to be in the form of a warning device for a person inside or outside the motor vehicle 10.

[0031] Fig. Figure 2 shows a schematic circuit diagram of an embodiment of the electrical energy storage device 12. In particular, corresponding high-voltage outputs 28 and 30 are shown, with high-voltage output 28 representing a positive terminal and high-voltage output 30 representing a negative terminal. Furthermore, four battery cells 16 are shown in the following exemplary embodiment, which are essentially connected in series. The battery management system 18 is also shown, which can, for example, control switching elements 32 accordingly. The monitoring device 20 is also shown.

[0032] In particular, it is thus provided that a critical state of the electrical energy storage device 12 can be determined by means of the monitoring device 20. An alternating current component 34 ( Fig. 3) The electrical energy storage device 12 is detected by means of the detection device 22. The detected AC component 34 is analyzed and assigned to a critical state of the electrical energy storage device 12. The critical state is then determined accordingly by means of the electronic computing device 24.

[0033] As already mentioned, the electronic computing unit 24 is specifically designed as a microcontroller. Furthermore, it can be provided that the analysis and assignment are carried out by the electronic computing unit 24 independently of the battery management system 18 of the electrical energy storage device 12. It can also be provided that the determination of the critical state is carried out during a period of inactivity of the vehicle 10, for example, when the vehicle 10 is stationary. This can, of course, also be done during operation. A potential thermal runaway of the electrical energy storage device 12 can be defined as a critical state. Furthermore, it can be provided that, for example, a warning message is generated when the critical state is determined, for example, by activating the warning device 26.

[0034] Furthermore, it can be provided that when the critical state is determined, the battery management system 18 of the electrical energy storage device 12 is woken up, which is represented in particular by a wake-up signal 36.

[0035] Fig.Figure 3 shows a schematic view of the monitoring device 20. In particular, a capacitor 38 and an operational amplifier 40 are shown. A voltage source 42 is also shown. The voltage source 42 can, for example, be directly connected to the battery cells 16 or be powered via an external 12-volt connection. If, for example, the vehicle 10 is active and thus the battery storage system is also active, the battery management system 18 can initiate appropriate subsequent reactions. However, if the electrical energy storage system 12 is deactivated or inactive, for example when the vehicle 10 is parked, the battery management system 18 is activated via the wake-up signal 36 and the potential thermal runaway is communicated to the battery management system 18.If necessary, the “thermal runaway” selection sensitivity can also be increased accordingly, especially when the vehicle is stationary.

[0036] In particular, the figures describe how the AC component 34 of the total battery voltage is analyzed, thereby enabling the selection of critical states of the energy storage device 12. A battery cell 16 in or shortly before thermal runaway generates AC voltage components 34 that can be distinguished from typical vehicle electrical system fluctuations. Detection can be achieved by means of frequency-selective pattern comparison using artificial intelligence. Only the microcontroller, for example the ASIC, is required for this – thus enabling lifetime and, in particular, continuous monitoring of the AC voltage of the battery cell 16 or the electrical energy storage device 12. In the event of a critical state, the monitoring device 20 can trigger subsequent reactions or at least wake up the battery management system 18.Additionally, when stationary, especially when the vehicle is inactive, the sensitivity to undesirable behavior can be significantly increased. Reference symbol list 10 motor vehicle 12 electrical energy storage devices 14 Drive unit 16 battery cells 18 Battery Management System 20 Monitoring device 22 Recording device 24 Electronic computing equipment 26 Functional unit 28 high-voltage output 30 high-voltage output 32 switching element 34 AC component 36 Wake-up signal 38 Capacitor 40 operational amplifiers 42 Voltage source QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 11 2020 002 115 T5

[0004] DE 10 347 110 B3

[0005]

Claims

[1] Method for determining a critical state of an electrical energy storage device (12) of a motor vehicle (10) that is at least partially electrically powered by means of a monitoring device (20), comprising the steps: - Detection of an alternating current component (34) of the electrical energy storage (12) by means of a detection device (22) of the monitoring device (20); - Analyzing the detected AC component (34) and assigning the detected AC component (34) to a critical state of the electrical energy storage device (12) by means of an electronic computing unit (24) of the monitoring device (20); and - Determining the critical state depending on the assignment using the electronic computing device (24). [2] Method according to claim 1, characterized by , that the electronic computing device (24) is provided as a microcontroller [3] Method according to claim 1 or 2, characterized by , that the analysis and allocation is carried out by the electronic computing device (24) independently of a battery management system (18) of the electrical energy storage device (12). [4] Method according to any one of the preceding claims, characterized by , that the determination of the critical condition is carried out during a rest period of the motor vehicle (10). [5] Method according to any one of the preceding claims, characterized by , that a potential thermal runaway of the electrical energy storage device (12) is determined to be a critical condition. [6] Method according to any one of the preceding claims, characterized by , that a warning message is generated when the critical condition is determined. [7] Method according to any one of the preceding claims, characterized by, that when the critical state is determined, a battery management system (18) of the electrical energy storage device (12) is awakened. [8] Method according to any one of the preceding claims, characterized by , that the alternating current component (34) is detected as a superimposed signal of a supplied direct current from the electrical energy storage device (12). [9] Computer program product comprising program code means which cause an electronic computing device (24) to perform a method according to any one of claims 1 to 8 when the program code means are executed by the electronic computing device (24). [10] Monitoring device (20) for determining a critical state of an electrical energy storage device (12) of an at least partially electrically powered motor vehicle (10), comprising at least one detection device (22) and an electronic computing device (24), wherein the monitoring device (20) is configured to carry out a method according to one of claims 1 to 8.

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