METHOD FOR DETERMINING THE AGING STATE OF A BATTERY, COMPUTER PROGRAM, MEMORY, CONTROL UNIT AND VEHICLE

Description

[0001] The present invention relates to a method for determining the aging state of a battery that is provided for the energy supply of an electric motor of a vehicle for propelling the vehicle. The invention further relates to a computer program for determining the aging state of a battery, a storage medium with a computer program stored thereon for determining the aging state of a battery, a control unit with a computer program installed thereon for determining the aging state of a battery, and a vehicle with such a control unit.

[0002] For electric vehicles, knowing the state of health (SOH) of the vehicle battery, or traction battery, which supplies energy to the electric motor to propel the vehicle, is crucial. However, determining the state of health is a challenging task due to the complex processes involved in charging and discharging the battery. Current production vehicles typically only implement estimation systems for determining the battery's state of health, and their accuracy is insufficient for many applications.

[0003] One way to estimate or determine the state of aging is impedance spectroscopy. In this method, various sinusoidal frequencies are applied to the current in the vehicle battery cells. The voltage response of these frequencies can then be used to determine the impedance of the vehicle battery or individual battery cells. Impedance is a parameter that expresses the aging of the battery cell. Currently, performing such impedance spectroscopy requires a complex measurement setup with separate, high-quality sensors. This results in high costs and is only conditionally applicable to mobile systems such as electric vehicles.

[0004] Therefore, solutions are currently being sought to enable impedance spectroscopy to be performed in mobile applications of electric vehicles with reasonable effort. These solutions are mostly based on the development of methods for additionally exciting the battery during driving or charging.

[0005] US patent application US 2011 / 0208452 A1 proposes a non-invasive method for determining the electrical impedance of an electric vehicle battery. Specifically, it proposes utilizing the sensors already available in the electric vehicle to determine the impedance of the battery or its individual cells. For this purpose, operating parameters of the battery, such as voltage and current, are measured and transformed into defined frequency ranges. Subsequently, the impedances of the battery cells are calculated within these frequency ranges, and the battery's state of aging is determined based on these calculated impedances. However, this approach does not yet achieve the desired accuracy in determining the battery's state of aging.Further systems and methods for determining the aging state of a battery are described in US 4 678 998 A and EP 1 892 536 A1.

[0006] The object of the present invention is to at least partially address the aforementioned problem. In particular, the object of the present invention is to provide a method, a computer program, a storage medium, a control unit, and a vehicle with a control unit for the cost-effective, mobile, and / or most accurate possible determination of the aging state of a battery, especially a vehicle battery.

[0007] The aforementioned problem is solved by the claims. In particular, the aforementioned problem is solved by the method according to claim 1, the computer program according to claim 6, the storage medium according to claim 7, the control unit according to claim 8, and the vehicle according to claim 9. Further advantages of the invention will become apparent from the dependent claims, the description, and the figures. Features described in connection with the method naturally also apply in connection with the computer program, the storage medium, the control unit, and the vehicle according to the invention, and vice versa, so that the disclosure of the individual aspects of the invention always makes, or can make, reciprocal references.

[0008] According to a first aspect of the present invention, a method for determining the aging state of a battery, in particular a vehicle battery, which is provided for supplying energy to an electric motor, in particular an electric motor for driving a vehicle, is provided. The method comprises the following steps: Determining the operating voltage (and operating current) of the battery in real time during vehicle operation, checking the determined operating voltage (10) and operating current of the battery for sinusoidal curve sections of different frequencies if sinusoidal curve sections are detected, extracting the detected sinusoidal curve sections of different frequencies, calculating the battery impedance using impedance spectroscopy based on the sinusoidal curve sections, and determining the battery's state of aging based on the calculated impedance.

[0009] Within the scope of the present invention, it was discovered that by selectively filtering the sinusoidal curve segments for subsequent impedance spectroscopy, the results for determining the aging state of the battery, particularly a vehicle battery, can be significantly improved in a simple manner. This eliminates the need for the previously required additional imprinting of sinusoidal oscillations by external system components. In other words, the proposed method can be carried out using only the vehicle's existing sensors and power electronics. Consequently, the method can be implemented in a particularly cost-effective, mobile, and highly flexible manner.

[0010] In the inventive method, the sinusoidal curve segments are stored as soon as they have been identified or recognized. Once a frequency spectrum necessary for impedance spectroscopy has been completely acquired, an impedance can be calculated. The calculated impedance can then be converted into a health-related value using physical aging models and / or mathematical models.

[0011] Currents measured during vehicle operation, for example, can be analyzed in real time for existing sinusoidal curve segments, particularly those of different frequencies. This approach makes the process particularly easy to implement in mobile applications, such as while the vehicle is in motion. Real-time operation refers to the operation of a computer system where programs for processing incoming data are constantly available, such that the processing results are available within a predefined timeframe. Depending on the application, the data—in this case, data on the graphical representation or curve of the operating voltage and / or current—can be generated randomly over time or at predetermined intervals.This means that the graphical progression is carried out continuously, at least temporarily, and without significant delays.

[0012] Sinusoidal waveforms can be identified using time series analysis. For example, by determining the similarity between a currently measured current waveform and a reference sinusoidal oscillation, relevant sinusoidal waveforms can be identified. This means that similarity algorithms can be used to detect relevant frequencies or frequency ranges in the battery voltage and current. A corresponding graphical representation of the operating voltage and current is preferably checked or analyzed for sinusoidal waveforms at different frequencies. That is, it is investigated whether at least one sinusoidal waveform can be detected in different frequency ranges of the operating voltage and / or current.

[0013] In this context, the term "battery" or "vehicle battery" can refer to an accumulator, such as a lithium-ion battery, or a fuel cell. Therefore, the process can be implemented in both battery electric vehicles and fuel cell vehicles. The vehicle can be configured as a purely electric vehicle or as a hybrid electric vehicle.

[0014] The term "aging state" can be understood as the health status or state-of-health of the battery, i.e., a characteristic parameter of the battery's functional state.

[0015] The vehicle battery, which supplies energy to the electric motor for propelling the vehicle, is the battery that enables the vehicle to be driven. In other words, the vehicle battery is the electrochemical energy source of the vehicle, providing the electric motor with current and voltage to move the vehicle. The vehicle battery is therefore primarily understood as a corresponding high-voltage battery. However, the method according to the invention should not be considered limited to its application with such a battery. In principle, it is also possible to apply the method to any other battery storage device or accumulator.

[0016] The sinusoidal curve segment preferably refers to a curve segment of the operating voltage and / or a curve segment of the operating current over time, which, after a falling curve, exhibits a rising curve and then another falling curve. The sinusoidal curve segment need not correspond to a perfect sine wave.

[0017] The extraction of sinusoidal curve segments from the determined operating voltage and / or operating current, or from their respective waveforms, means that these sinusoidal curve segments are used for the subsequent calculation of the battery's impedance or the impedance of the battery cells. During the extraction process, the sinusoidal curve segments can be stored. Once a complete frequency spectrum, necessary for impedance spectroscopy, has been stored and recorded, the battery's impedance can be calculated as described above.

[0018] Determining the battery's state of aging based on the calculated impedance can be carried out by determining the battery's state of aging using the calculated impedance, for example by applying physical aging models and / or suitable mathematical models to convert the impedance into the state of aging.

[0019] The battery current and voltage are plotted, particularly over time. Tests conducted within the scope of the present invention have shown that the operating voltage and current are advantageously suited for determining the battery's state of aging. According to the invention, to determine the battery's state of aging, a graph of the battery current over time and a graph of the battery voltage, or the individual battery voltages, over time are determined. Specifically, the graphs of these operating parameters are determined. Additionally, and preferably at least partially simultaneously, the battery's state of charge and / or temperature are determined. These operating parameters can then be used for impedance spectroscopy or for calculating the battery's impedance.In this case, the graphs of the battery current and voltage are then checked for at least one sinusoidal curve segment. Relevant curve segments are extracted and used to calculate the battery impedance. The corresponding state of charge and temperature of the battery—that is, the state of charge and temperature during the acquisition of the respective sinusoidal curve segment—are also preferably used to calculate the impedance.

[0020] Furthermore, it is possible that, in a method, extracted sinusoidal curve segments are stored and classified into similar or comparable temperature ranges of the battery and / or similar or comparable state-of-charge ranges of the battery, with impedance spectroscopy being performed based on the classified sinusoidal curve segments. Experiments conducted within the scope of the present invention have shown that the battery impedance can be temperature- and state-of-charge-dependent. Therefore, it is advantageous if the impedance spectroscopy is performed for similar temperature and / or state-of-charge ranges. Accordingly, in a method, a classification into temperature and / or state-of-charge ranges is performed. The battery's state of aging can thus be determined particularly accurately using this approach. A preferred temperature range, for example, has a temperature window of approximately 10 °C.Sinusoidal curve segments, based on battery temperatures that differ by a maximum of approximately 10 °C, can be classified into predefined temperature ranges. For example, a preferred state-of-charge range has a charge window of approximately 10%. Thus, sinusoidal curve segments, based on battery states that differ by a maximum of approximately 10%, can be classified into correspondingly defined state-of-charge ranges.

[0021] Furthermore, it is possible to determine the battery's operating voltage and current curves online. This approach makes the procedure particularly easy to perform in mobile applications, for example, while the vehicle is in motion.

[0022] Furthermore, one method allows the battery's operating voltage and / or current waveform to be filtered by a signal filter to reduce signal noise. The filtered or smoothed waveform of the operating voltage and / or current provides a particularly accurate basis for calculating the impedance and determining the battery's state of aging. In this case, a circuit can be used as the filter, modifying the waveform's amplitude and phase depending on the frequency, thereby attenuating or suppressing unwanted signal components.

[0023] According to another embodiment, the sinusoidal curve segments can be extracted to cloud storage, and impedance spectroscopy and / or the determination of the aging state can be performed there. Computing power can be provided outside the vehicle that would be unattainable or only achievable with disproportionate effort within the vehicle. The lower computing power requirements within the vehicle allow for the use of less complex components. This can lead to a lighter vehicle and reduced cooling requirements for the in-vehicle computing unit. This is particularly advantageous for mobile applications or when performing the process on-site.In addition to impedance spectroscopy, other process steps, such as storing and / or extracting the sinusoidal waveforms, classifying them, and / or determining the battery's state of aging, can also be outsourced or performed in the cloud using physical and / or mathematical aging models. In the described scenario, a cloud connection for the vehicle to exchange data is, of course, essential. Results, such as the battery's state of aging, could then be sent back to the vehicle from the cloud or cloud storage.

[0024] According to a further aspect of the present invention, a computer program is provided comprising instructions which, when executed by a control unit, cause the control unit to execute the method described above in detail. Thus, the computer program according to the invention offers the same advantages as those described in detail with reference to the method according to the invention. The computer program can be implemented as computer-readable instruction code in any suitable programming language, such as Java or C++. The computer program can be stored on a computer-readable storage medium, such as a data disk, a removable drive, volatile or non-volatile memory, or an integrated memory / processor. The instruction code can program a computer or other programmable devices, such as the control unit, to execute the desired functions.Furthermore, the computer program can be made available on a network, such as the internet, from which it can be downloaded by a user as needed. The computer program can be implemented using software or as a computer program product, using one or more special electronic circuits (i.e., in hardware), or in any hybrid form (i.e., using both software and hardware components).

[0025] Furthermore, within the scope of the present invention, a storage medium with a computer program stored thereon, configured and designed to carry out a method as described above, is provided. Likewise, a control unit with a computer program installed thereon, as described above, is provided, configured and designed to carry out a method according to the invention. Thus, the storage medium and the control unit according to the invention also offer the advantages described above.

[0026] According to a further aspect of the present invention, a vehicle is provided with a control unit as described above, an electric motor, and a battery for supplying energy to the electric motor for propelling the vehicle. Thus, the vehicle according to the invention also offers the advantages described above. The vehicle is preferably designed as a purely electric vehicle or as a hybrid electric vehicle.

[0027] Further measures improving the invention will become apparent from the following description of various embodiments of the invention, which are schematically illustrated in the figures. All features and / or advantages arising from the claims, the description, or the figures, including design details and spatial arrangements, can be essential to the invention, both individually and in various combinations.

[0028] They each show schematically: Figure 1 is a flowchart to explain a method according to an embodiment of the present invention; Figure 2 is a block diagram to visualize the process described in Figure 1. Figure 1 described method, and Figure 3 shows a vehicle with a control unit and a computer program installed therein according to an embodiment of the present invention.

[0029] Elements with the same function and mode of operation are in the Figures 1 to 3 each provided with the same reference numerals.

[0030] Figure 1Figure 1 shows a flowchart illustrating a method according to the invention for determining the aging state of a battery 10 in the form of a high-voltage vehicle battery, which is provided to supply energy to an electric motor 20 for driving a vehicle 100. According to the method, in a first step S1, the graphical profile of the battery current of the battery 10 is determined. This determination is carried out online and in real time. The same is done for the battery voltage of the battery 10 or of the individual battery cells of the battery 10. The graphical profiles are filtered by a signal filter to reduce signal noise.

[0031] During the determination of battery current and voltage, or the corresponding graphs, the battery's temperature and state of charge (SOC) are recorded for these time periods. This means that the temperature and state of charge at a given battery current or voltage are determined.

[0032] Subsequently, in a second step S2, the graphical curves of the current and voltage of battery 10 are checked or analyzed for sinusoidal curve sections of different frequencies.

[0033] After sinusoidal curve segments have been detected, they are extracted in a third step S3 and stored in a memory module in vehicle 100. In a fourth step S4, the impedance of battery 10 is calculated using impedance spectroscopy based on the sinusoidal curve segments, the associated temperature, and the corresponding state of charge. The extracted sinusoidal curve segments are stored and classified into defined temperature and state-of-charge ranges for battery 10, and the impedance spectroscopy is then performed on these classified sinusoidal curve segments.

[0034] In a subsequent fifth step S5, the aging state of battery 10 is determined based on the calculated impedance.

[0035] Figure 2 shows a block diagram to visualize the procedure described above. As in Figure 2As shown, the electric motor 20 is in signal communication with the power electronics 50. The power electronics 50 is in signal communication with the battery 10 and with a sensor 60 of the vehicle 100. The sensor 60 of the vehicle 100 can include components such as a voltage measuring device, a current measuring device, a temperature measuring device, and a state-of-charge measuring device.

[0036] In Figure 2 Furthermore, a computer program 30 is visualized which includes instructions that, when executed by a computer, cause the computer to perform the procedure described above.

[0037] In Figure 3A vehicle 100 is shown, comprising a control unit 40, an electric motor 20, and a battery 10 for supplying energy to the electric motor 20 to propel the vehicle 100. A computer program 30, configured and designed to carry out the described procedure, is installed on the control unit 40.

[0038] The invention allows for further design principles in addition to the embodiments shown. That is to say, the invention should not be considered limited to the embodiments explained with reference to the figures. For example, it is possible to extract the sinusoidal curve segments into cloud storage and to perform the storage, classification, impedance spectroscopy, and determination of the aging state of this data in the cloud storage. The determined aging state can then be transmitted back to the vehicle 100. Reference symbol list

[0039] 10Battery 20Electric motor 30Computer program 40Control unit 50Power electronics 60Sensors 100Vehicle

Claims

1. Method for determining a state of health of a battery (10) which is provided to supply energy to an electric motor (20) of a vehicle (100), having the steps of: - determining a profile of an operating voltage of the battery (10) and of an operating current of the battery (10) in real time during driving operation of the vehicle (100), - checking the determined profile of the operating voltage of the battery (10) and the determined profile of the operating current of the battery (10) for sinusoidal curve sections of different frequencies, - if sinusoidal curve sections are identified, extracting the identified sinusoidal curve sections of different frequencies, - calculating an impedance of the battery (10) by means of impedance spectroscopy on the basis of the sinusoidal curve sections, and - determining the state of health of the battery (10) on the basis of the calculated impedance.

2. Method according to Claim 1, characterized in that extracted, sinusoidal curve sections are stored and in the process classified in the same or similar temperature ranges of the battery (10) and / or the same or similar state-of-charge ranges of the battery (10), wherein the impedance spectroscopy is carried out on the basis of the classified sinusoidal curve sections.

3. Method according to either of the preceding claims, characterized in that the profile of the operating voltage of the battery (10) and / or the profile of the operating current of the battery (10) are / is filtered through a signal filter in order to reduce signal noise.

4. Method according to one of the preceding claims, characterized in that the sinusoidal curve sections are extracted into cloud storage and the impedance spectroscopy and / or the determination of the state of health are / is carried out in the cloud storage.

5. Computer program (30) comprising commands which, when the computer program (30) is executed by a control device (40), cause this to implement the method according to one of Claims 1 to 4.

6. Storage means having a computer program (30) stored thereon, which is configured and designed to carry out a method according to one of Claims 1 to 4.

7. Control device (40) having a computer program (30) according to Claim 5 installed thereon, which is configured and designed to carry out a method according to one of Claims 1 to 4.

8. Vehicle (100) having a control device (40) according to Claim 7, an electric motor (20) and a battery (10) for supplying energy to the electric motor (20) in order to drive the vehicle (100).