METHOD FOR DETERMINING A THERMAL RUNOUT OF AN ELECTRICAL ENERGY STORAGE SYSTEM OF A PARTICULARLY ELECTRICALLY POWERED MOTOR VEHICLE, COMPUTER PROGRAM PRODUCT AND ELECTRONIC COMPUTING DEVICE

Description

[0001] The invention relates to a method for determining a thermal runaway of an electrical energy storage device of an at least partially electrically operated motor vehicle by means of an electronic computing device of the motor vehicle according to the preamble of patent claim 1. Furthermore, the invention relates to a computer program product and an electronic computing device.

[0002] It is already known that if, for example, a traction battery used as an electrical energy storage device in a motor vehicle experiences thermal runaway, the vehicle's occupants must be warned five minutes before a fire breaks out. Currently, a combination of voltage measurement and insulation measurement is used in vehicles. If both an undervoltage and an insulation fault are detected, an alarm is triggered. However, measuring the insulation fault is relatively error-prone. The integration of a dedicated additional sensor, such as a pressure sensor, is also known. However, this leads to higher costs. The cell temperature itself can also be used.However, since not every battery cell has a sensor and, depending on the installation location, may be well shielded from the hot gases, a significant time lag can occur with temperature sensors. Measuring cell voltage alone is unreliable, as this can lead to frequent false alarms. If, for example, a measuring lead breaks, this would lead to a false alarm due to an apparent low voltage without an additional signal for plausibility check.

[0003] EP 3 843 195 A1 relates to a thermal runaway detection device, a battery system, and a method for detecting thermal runaway of the battery system, the thermal runaway detection device comprising: a first measurement module for measuring temperature values ​​of the plurality of cells via at least one temperature sensor; a second measurement module for measuring an output voltage value of the battery system; and a controller for determining validity of the thermal runaway detection based on the temperature value by monitoring data received from the first measurement module, and for detecting thermal runaway of the battery system by selectively monitoring one of the temperature value and the output voltage value according to a result of the validity determination of the thermal runaway detection based on the temperature value.

[0004] The object of the present invention is to provide a method, a computer program product and an electronic computing device by means of which a thermal runaway of an electrical energy storage device can be detected in an improved manner.

[0005] This object is achieved by a method, a computer program product, and an electronic computing device according to the independent patent claims. Advantageous embodiments are specified in the subclaims.

[0006] One aspect of the invention relates to a method for determining thermal runaway of an electrical energy storage device of an at least partially electrically powered motor vehicle by means of an electronic computing device of the motor vehicle. The electrical energy storage device is continuously monitored by means of at least one diagnostic method for determining a current state of the electrical energy storage device based on a diagnostic signal. If an anomaly is detected in the diagnostic signal, a frequency of the anomaly in the diagnostic signal is determined over a predetermined period of time. Furthermore, if an anomaly is detected in the diagnostic signal, a dynamics of the anomaly in the diagnostic signal is determined over a predetermined period of time. A communication line of the electrical energy storage device is continuously monitored by means of a limited anomaly counter.When an anomaly is detected within the communication line, the limited anomaly counter is compared with an unlimited anomaly counter, and a difference signal is generated based on this. The thermal runaway is determined based on the determined frequency and dynamics and the difference signal.

[0007] This makes it possible to better detect thermal runaway within an electrical energy storage device.

[0008] In particular, thermal runaway of a battery cell or electrical energy storage device, especially in the form of a lithium-ion battery, can be robustly detected without additional sensors. Since the cell monitoring electronics are already part of an electrical energy storage device, especially a traction battery in a motor vehicle, appropriate diagnostics are implemented to achieve ASIL safety. This eliminates component costs and also minimizes the need for software expansion. Thus, thermal runaway can be detected with existing systems or methods with reduced effort.

[0009] In particular, the cell voltage measurement is used, the diagnostics for the cell voltage measurement are carried out, the signals derived from the diagnostics and the threshold value binding are calculated and the diagnoses are combined via corresponding AND operations in order to be able to determine the thermal runaway.

[0010] In particular, the cell monitoring electronics are designed to measure cell voltages and cell temperatures. Since these values ​​are used to meet safety targets with an ASIL rating, they are checked for correct function using diagnostics anyway. These diagnostics are triggered when such a fault / anomaly occurs. In a thermal runaway, which is also known as thermal runaway, many of these faults occur, sometimes simultaneously. The challenge now is to separate thermal runaway from an actual fault. To make matters worse, some hardware faults, especially non-existent thermal runaway, trigger multiple diagnostics.In order to achieve better differentiation, the dynamics of the errors or anomalies as well as the number of errors or anomalies occurring simultaneously are taken into account.

[0011] Furthermore, thermal runaway also results in frequent communication errors occurring during transmission via a so-called daisy chain, which in this case corresponds to the communication line and can be implemented as a CAN bus, for example. In implementations using an ASIC of analog functional components, these errors are counted using a PEC (Packet Error Counter). This PEC corresponds to the unlimited anomaly counter. However, since multiple packets can be corrupted even under normal circumstances, for example when switching contactors, an investigation is also carried out here. For this purpose, the PEC is dynamically limited using a rate limiter, in other words the limited anomaly counter, and the difference to the actual PEC, which corresponds to the unlimited anomaly counter, is then determined. If this difference signal exceeds a threshold, this indicates thermal runaway.

[0012] Thus, the combination of the dynamics of the anomaly, the number of simultaneously occurring anomalies, and the difference signal allows conclusions to be drawn about thermal runaway without, in particular, obtaining false detections.

[0013] According to an advantageous embodiment, an interruption in a cell voltage line is monitored using the diagnostic method. In particular, this diagnostic method is a diagnostic method already installed in the motor vehicle for monitoring the cell voltage measuring line. This diagnostic method can then be used to check whether an anomaly exists and to monitor its dynamics and frequency. This method is, in particular, a so-called open-wire method.

[0014] It has also proven advantageous if the diagnostic method is used to monitor the switching state of a balancing semiconductor element. The balancing semiconductor element is, in particular, a so-called balancing FET element. In particular, it can be checked whether, for example, this semiconductor element is not switching or is permanently switched on. This diagnostic method is also a diagnostic method already installed in the motor vehicle for monitoring the electrical energy storage device.

[0015] A further advantageous embodiment provides that the diagnostic method is used to monitor a short circuit between adjacent pins on a circuit board of the electronic computing device. This also involves a method already installed in motor vehicles for monitoring the electrical energy storage device or the electronic computing device. In particular, it involves checking whether a short circuit is detected between adjacent GPIOs (general purpose input / output), i.e., the pins on the ASIC to which, for example, the temperature sensor is connected.

[0016] Furthermore, it can be provided that a deviation from a second reference voltage source is monitored using the diagnostic method. This also represents a method already installed in the motor vehicle for monitoring electrical components, in particular battery cells, which allows thermal runaway to be easily determined.

[0017] It has also proven advantageous if the diagnostic method monitors a total voltage across a circuit board of the electronic computing device. In particular, the total voltage is monitored via the ASIC, especially to determine whether it is different from the summed individual voltages. This method is also already installed in motor vehicles or in electrical energy storage systems, allowing for reliable and simple detection of thermal runaway.

[0018] A further advantageous embodiment provides that the difference signal is only generated when a predetermined threshold value between the limited anomaly counter and the unlimited anomaly counter is exceeded. For example, the rate of the limited anomaly counter can be limited to four errors per second. If the threshold value is then above 20, for example, this can be taken as an indication that an error / anomaly is present.

[0019] According to an advantageous embodiment, when a potential thermal runaway is determined, a warning message is output to a passenger in the motor vehicle on an output device of the motor vehicle. In particular, this warning message is output at least five minutes before the thermal runaway. The output device can be a haptic output device, a visual output device, or an acoustic output device. In particular, different warning messages, for example, an acoustic warning signal, a visual warning signal, and a haptic warning signal, can be output simultaneously.

[0020] The presented method is a computer-implemented method. Therefore, a further aspect of the invention relates to a computer program product with program code means that cause an electronic computing device, when the program code means are processed by the electronic computing device, to perform a method according to the preceding aspect. In particular, the method is carried out by means of the electronic computing device. The computer program product can also be referred to as a computer program.

[0021] A further aspect of the invention therefore also relates to a computer-readable storage medium with the computer program product.

[0022] Furthermore, the invention also relates to an electronic computing device for determining thermal runaway of an electrical energy storage device of an at least partially electrically powered motor vehicle, wherein the electronic computing device is designed to carry out a method according to the preceding aspect. In particular, the method is carried out by means of the electronic computing device.

[0023] The electronic computing device comprises, for example, processors, circuits, in particular integrated circuits, as well as other electronic components in order to be able to carry out corresponding process steps.

[0024] The invention also relates to an at least partially electrically operated or even a fully electrically operated motor vehicle.

[0025] Advantageous embodiments of the method are to be regarded as advantageous embodiments of the computer program product, the electronic computing device, and the motor vehicle. The electronic computing device and the motor vehicle, in particular, have features enabling the execution of corresponding method steps.

[0026] 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 the features and combinations of features mentioned below in the description of the figures and / or shown alone in the single figure, can be used not only in the respective specified combination, but also in other combinations or on their own, without departing from the scope of the invention.

[0027] The only figure shows a schematic block diagram according to an embodiment of the method.

[0028] In the figure, identical or functionally identical elements are provided with the same reference numerals.

[0029] The figure shows a schematic block diagram according to an embodiment of an electronic computing device 10 for determining a thermal runaway of an electrical energy storage device 12 of an at least partially electrically powered motor vehicle. In the present exemplary embodiment, a flowchart is shown in particular. In particular, the electrical energy storage device 12 is continuously monitored by means of at least one diagnostic method 14 for determining a current state of the electrical energy storage device 12 based on a diagnostic signal 16. Upon detection of an anomaly 44 in the diagnostic signal 16, a frequency 18 of the anomaly 44 in the diagnostic signal 16 is determined over a predetermined period of time 20. Furthermore, upon detection of the anomaly 44 in the diagnostic signal 16, a dynamic range 22 of the anomaly 44 in the diagnostic signal 16 is determined over the predetermined period of time 20.Furthermore, a communication line 24 of the electrical energy storage device 12 is continuously monitored by means of a limited anomaly counter 26. When the anomaly 44 is detected within the communication line 24, the limited anomaly counter 26 is compared with an unlimited anomaly counter 28 and, depending thereon, a difference signal 30 is generated. The thermal runaway is then determined in turn as a function of the determined frequency 18, the determined dynamics 22 and the difference signal 30.

[0030] For this purpose, it can be provided in particular that a threshold value comparison is carried out. For example, a first threshold value 32 of greater than 100 can be provided for the measure of frequency 18. In other words, only when more than or equal to 100 anomalies 44 are detected can this lead to a warning signal 34 for thermal runaway. Furthermore, a second threshold value 36 can be provided, which in turn describes the dynamics. For example, the dynamics can relate to an absolute value of the derivative of the number of set bits and, for example, comprise a second threshold value 36 of ≥ 10. A third threshold value 38 can be provided, which in turn describes the measure of the noticeably frequently occurring communication errors, which can be regarded as > 20, for example.Only when all three threshold comparisons are classified as positive, i.e., when thresholds 32, 36 have been exceeded, are they combined in an AND operation 40. If all three thresholds 32, 36, 38 are exceeded, a warning message 34 is generated. The warning message 34 can, for example, be output via an output device 42 of the motor vehicle. For example, the output device 42 can be configured as a display device, loudspeaker device, or haptic device.

[0031] For example, the period 20 can refer to 20 seconds or another time period, such as 40 seconds.

[0032] As already mentioned, it is shown here that an AND operation 40 is provided. An alternative implementation is, for example, that instead of thresholding before the AND operation 40, an addition with weighting is performed and only then the thresholding is performed.

[0033] In particular, the figure shows that the cell monitoring electronics are responsible for measuring the cell voltage and the cell temperature. Since these values ​​are used to meet safety targets with a corresponding ASIL classification, correct function is checked using diagnostic methods 14. Such diagnoses include, for example, an interruption in the cell voltage measuring line, a so-called open wire diagnosis. Furthermore, diagnostic methods 14 can also be used which monitor, for example, a balancing semiconductor switching element. For example, it can be checked whether this semiconductor element is not switching or is permanently switched on. This can also be referred to as a balancing FET stuck. Furthermore, a short circuit between adjacent boards, so-called general purpose input / output, can also be checked.In particular, this checks whether the corresponding pins on the ASIC, to which the temperature sensor is connected, for example, are short-circuited. Furthermore, a deviation from a second reference voltage source can also be used for monitoring. Furthermore, the total voltage via the ASIC can also be checked, for example, whether it is different from the summed individual voltages.

[0034] These diagnostic procedures 14 are triggered when such an error / anomaly 44 occurs. In a thermal runaway, many of these errors occur, sometimes simultaneously. The challenge now lies in separating thermal runaway from an actual error. Further complicating matters is that some hardware errors that do not correspond to thermal runaway trigger multiple diagnostic procedures 14. To achieve better differentiation, the dynamics 22 and the frequency 18 of the anomaly 44 are taken into account.

[0035] Furthermore, thermal runaway also results in frequent communication errors occurring during transmission over the communication line 24, particularly in the so-called daisy chain. In the ASIC implementation of analog devices, these errors are counted using a so-called unlimited anomaly counter 28 (Packet Error Counter - PEC). However, since multiple packets can be corrupted even under normal circumstances, for example, when switching contactors, a distinction is also made here. For this purpose, the dynamic range of the PEC is limited using a limited anomaly counter 26, a so-called rate limiter, and the difference to the actual PEC is then determined. If this difference signal 30 exceeds a threshold, in particular the third threshold 38 in this case, this indicates a thermal runaway.

[0036] The limited anomaly counter 26 can, for example, perform a rate limitation of four errors or anomalies 44 per second.

[0037] If the frequency 18, the dynamics 22 as well as the difference signal 30 exceed the corresponding threshold value 32, 36, 38, the thermal runaway is detected on the basis of the AND operation 40 and the warning signal 34 is generated. List of reference symbols

[0038] 10electronic computing device 12electrical energy storage device 14diagnostic procedure 16diagnostic signal 18frequency 20period 22dynamics 24communication line 26limited anomaly counter 28unlimited anomaly counter 30differential signal 32first threshold 34warning message 36second threshold 38third threshold 40and operation 42output device 44anomaly

Claims

1. Method for determining a thermal runaway of an electrical energy storage device (12) of an at least partially electrically operated motor vehicle by means of an electronic computing device (10) of the motor vehicle, comprising the steps of: - continuously monitoring the electrical energy storage device (12) by means of at least one diagnostic method (14) for determining a current state of the electrical energy storage device (12) on the basis of a diagnostic signal (16); - if an anomaly (44) is detected in the diagnostic signal (16), determining a frequency (18) of the anomaly (44) in the diagnostic signal (16) over a predetermined period of time (20); - if an anomaly (44) is detected in the diagnostic signal (16), determining a dynamic range (22) of the anomaly (44) in the diagnostic signal (16) over a predetermined period of time (20); - continuously monitoring a communication line (24) of the electrical energy storage device (12) by means of a limited anomaly counter (26); - if an anomaly (44) is detected within the communication line (24), comparing the limited anomaly counter (26) with an unlimited anomaly counter (28) and generating a difference signal (30) on the basis of the comparison; and - determining the thermal runaway (44) on the basis of the determined frequency (18) and the determined dynamic range (22) and the difference signal (30).

2. Method according to claim 1, characterized in that a break in a cell voltage measuring line is monitored by means of the diagnostic method (14).

3. Method according to claim 1 or claim 2, characterized in that a switching state of a balancing semiconductor element is monitored by means of the diagnostic method (14).

4. Method according to any of the preceding claims, characterized in that a short circuit between adjacent pins on a circuit board of the electronic computing device (10) is monitored by means of the diagnostic method (14).

5. Method according to any of the preceding claims, characterized in that a deviation of a second reference voltage source is monitored by means of the diagnostic method (14).

6. Method according to any of the preceding claims, characterized in that a sum voltage across a circuit board of the electronic computing device (10) is monitored by means of the diagnostic method (14).

7. Method according to any of the preceding claims, characterized in that the difference signal (30) is only generated when a predetermined threshold value between the limited anomaly counter (26) and the unlimited anomaly counter (38) is exceeded.

8. Method according to any of the preceding claims, characterized in that upon determining a potential thermal runaway, a warning message (34) for an occupant in the motor vehicle is output on an output device (42) of the motor vehicle.

9. Computer program product comprising program code means which cause an electronic computing device (10) to carry out a method according to any of claims 1 to 8 when the program code means are processed by the electronic computing device (10).

10. Electronic computing device (10) for determining a thermal runaway of an electrical energy storage device (12) of an at least partially electrically operated motor vehicle, wherein the electronic computing device (10) is designed to carry out a method according to any of claims 1 to 8.