Method for determining an electrical property of at least one battery cell of an electrical energy storage device, computer program product, computer-readable storage medium, and battery management system

Abstract

The invention relates to a method for determining an electrical property (18) of at least one battery cell (14) of an electrical energy storage device (12) for an at least partially electrically powered motor vehicle (10) by means of a battery management system (16) for the electrical energy storage device (12), comprising the steps of: - predefining a stiffness model (26) for the battery cell (14) depending on the electrical property (18) by means of an electronic computing device (20) for the battery management system (16); - detecting an actual stiffness (24) of the battery cell (14) by means of a detection device (22) for the battery management system (16); - comparing the actual stiffness (24) with the stiffness model (26) by means of the electronic computing device (20); and - determining the electrical property (18) depending on the comparison by means of the electronic computing device (20). The invention also relates to a computer program product, a computer-readable storage medium, and a battery management system (16).

Description

[0001] Method for determining an electrical property of at least one battery cell of an electrical energy storage device, computer program product, computer-readable storage medium and battery management system

[0002] The invention relates to a method for determining an electrical property of at least one battery cell of an electrical energy storage device of an at least partially electrically operated motor vehicle by means of a battery management system of the electrical energy storage device according to the applicable patent claim 1. Furthermore, the invention relates to a computer program product, a computer-readable storage medium and a battery management system.

[0003] In the current state of the art, the so-called state of charge (SOC), which can also be referred to as the state of charge, can be determined using a stored open-circuit voltage (OCV) characteristic curve. However, the battery voltage must relax for a long time to establish the open-circuit voltage and allow the state of charge to be read. Furthermore, the open-circuit voltage and thus the state of charge can only be determined when no current is flowing, which is therefore only possible with corresponding estimation errors, especially when the vehicle is in motion.

[0004] DE 102021 005 418 A1 relates to a method for determining a

[0005] Aging state of a battery cell of an electrical energy storage device by means of a monitoring device of the electrical energy storage device, in which a cell thickness of the battery cell, which changes in thickness depending on a charge state of the battery cell, is detected by means of a detection device of the monitoring device and the aging state is determined depending on the detected cell thickness, wherein the detected cell thickness is compared with the current charge state of the battery cell with a reference thickness at a current charge state and the aging state is determined depending on the comparison. The object of the present invention is to create a method, a computer program product, a computer-readable storage medium and a battery management system by means of which an electrical property of a battery cell can be determined in an improved manner.

[0006] This object is achieved by a method, a computer program product, a computer-readable storage medium, and a battery management system according to the independent patent claims. Advantageous embodiments are specified in the subclaims.

[0007] One aspect of the invention relates to a method for determining an electrical property of at least one battery cell of an electrical energy storage device of an at least partially electrically powered motor vehicle by means of a battery management system of the electrical energy storage device. A stiffness model of the battery cell is specified as a function of the electrical property by means of an electronic computing device of the battery management system. The current stiffness of the battery cell is detected by means of a detection device of the battery management system. The current stiffness is compared with the stiffness model by means of the electronic computing device, and the electrical property is determined as a function of the comparison by means of the electronic computing device.

[0008] This makes it possible to determine the electrical properties of the battery cell more effectively.

[0009] In particular, it is intended that the electrical property, such as the state of charge or the state of aging, can be determined from the mechanical properties of the battery cell by defining a corresponding stiffness characteristic. This allows the electrical property to be determined even during vehicle operation, or when current is flowing and the battery voltage is not relaxed.

[0010] This improves, for example, the state of charge estimation in motor vehicles, as additional information can be used to estimate the state of charge. The state of charge is determined more accurately, especially during ferry operation, and thus also during current flow, which has a positive effect on the accuracy of the range forecast with the current battery charge. In the best case, the range with the current battery charge also increases. In addition to determining the state of charge during ferry operation, as already mentioned, the state of health can also be determined more accurately during ferry operation, and a more accurate range forecast can be realized based on the determined state of health.

[0011] According to an advantageous embodiment, the current state of charge of the battery cell is determined as the electrical property. In particular, a variety of stiffnesses of the battery cell can be specified in the stiffness model depending on a variety of states of charge. In particular, the cell stiffness depends on the state of charge, and this dependency is characteristic of cell parameters such as the cell chemistry, for example the anode, cathode, or electrolyte material, or the cell housing type, for example pouch or hardcase cell. The stiffness is increased or decreased at a higher state of charge compared to a lower state of charge. In particular, based on simple compression measurements of the battery cells at different states of charge, a clear state of charge dependency results. The cell stiffness can be characterized in particular via the state of charge and stored in the vehicle as a characteristic curve.By determining the stiffness during ferry operation, the loading state can be estimated or the data can be used to optimize existing estimation mechanisms.

[0012] Furthermore, it has proven advantageous to determine the current health status of the battery cell as an electrical property. In this case, it can also be provided that a variety of battery cell stiffnesses are specified in the stiffness model depending on a variety of health statuses. In particular, the cell stiffness is higher in aged battery cells than in unaged battery cells. Degradation mechanisms in the electrodes and cell thickness growth change the mechanical structure and mechanical properties of the cell. This includes, in particular, layer thickness growth, but also particle decontacting or cracking, as well as electrolyte consumption, which particularly influences viscosity, and corresponding gassing.In particular, cell stiffness can be characterized based on the state of health and stored as a characteristic curve in the vehicle. The stiffness determined during vehicle operation can be used to estimate the state of health, or the data can be used to optimize existing estimation methods. A further advantageous embodiment provides for the range of the vehicle to be determined depending on the determined electrical property. In particular, a remaining range is determined depending on, for example, the state of charge and the state of health. In particular, a more precise remaining range can thus be displayed to a vehicle user, allowing them to plan their route more effectively.

[0013] Furthermore, it has proven advantageous to measure the current stiffness using a pressure-measuring film as the detection device and / or a laser measuring device as the detection device. In particular, this allows the stiffness to be measured using different detection devices. This allows the current stiffness to be reliably determined and thus the current electrical properties to be determined.

[0014] The method presented is, in particular, a computer-implemented method. Therefore, a further aspect of the invention relates to a computer program product with program code means that, when the program code means are processed by the electronic computing device, cause an electronic computing device to perform a method according to the preceding aspect.

[0015] Furthermore, the invention also relates to a computer-readable storage medium with a computer program product according to the preceding aspect.

[0016] Yet another aspect of the invention relates to a battery management system for determining an electrical property of at least one battery cell 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 battery management system is configured to carry out a method according to the preceding aspect. In particular, the method is carried out by means of the battery management system.

[0017] The electronic computing device comprises, for example, processors, circuits, in particular integrated circuits, and other electronic components to enable the corresponding method steps to be carried out. Furthermore, the invention also relates to an electrical energy storage device with at least one battery management system according to the preceding aspect.

[0018] Yet another aspect of the invention also relates to a motor vehicle with an electrical energy storage device according to the preceding aspect. The motor vehicle can be designed as an at least partially electrically powered motor vehicle or as a fully electrically powered motor vehicle.

[0019] Advantageous embodiments of the method are to be regarded as advantageous embodiments of the battery management system, the electrical energy storage device, and the motor vehicle. The battery management system, the electrical energy storage device, and the motor vehicle have material features for this purpose in order to be able to carry out corresponding method steps.

[0020] Further advantages, features, and details of the invention will become apparent from the following description of preferred embodiments 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 figures, can be used not only in the respective specified combinations, but also in other combinations or on their own, without departing from the scope of the invention.

[0021] Showing:

[0022] Fig. 1 is a schematic side view of an embodiment of a motor vehicle with an embodiment of an electrical energy storage device with an embodiment of a battery management system; and

[0023] Fig. 2 is a schematic block diagram according to an embodiment of a battery management system.

[0024] In the figures, identical or functionally equivalent elements are provided with the same reference numerals. Fig. 1 shows a schematic side view of an embodiment of a motor vehicle 10. The motor vehicle 10 is at least partially electrically operated or also fully electrically operated. For this purpose, the motor vehicle 10 has at least one electrical energy store 12. The electrical energy store 12 has at least one battery cell 14, in particular a plurality of battery cells 14. Furthermore, in particular a battery management system 16 of the electrical energy store 12 is provided. The battery management system 16 is designed to determine an electrical property 18 (Fig. 2). For this purpose, the battery management system 16 has at least one electronic computing device 20 and a detection device 22.The detection device 22 can be designed, for example, in the form of a pressure measuring film and / or in the form of a laser measuring device.

[0025] Fig. 2 shows a schematic block diagram according to an embodiment of the battery management system 16. In particular, it is shown that a current cell stiffness 24 is determined by means of the detection device 22. In particular, a stiffness model 26 for battery cells 14 is specified in the electronic computing device 20. The current stiffness 24 is then compared with the stiffness model 26, and the electrical property 18 is determined based on the comparison.

[0026] In particular, Fig. 2 shows that additional information 28 can be provided for estimating the electrical property. Furthermore, a direct determination 30 of the electrical property 18 can also be provided.

[0027] In particular, Fig. 2 shows that cell stiffness can be characterized by both the state of charge 32 and the state of health 34, and can be stored as a characteristic curve in the motor vehicle 10. By determining the stiffness during driving, the state of charge 32 and the state of health 34 can be estimated, or data can be used to optimize existing estimation mechanisms, in particular the estimation model 26. Similar methods utilizing cell thickness are also already known. Cell stiffness enables additional information to be gained.

[0028] The state of the art involves determining the state of charge 32 or the state of health 34 based on a stored resting voltage characteristic curve. However, the battery voltage must relax for a long time to establish the resting voltage and to read the state of charge 32 or the state of health 34. Furthermore, the resting voltage and thus the state of charge 32 or the state of health 34 can only be determined when no current is flowing, which is therefore only possible in ferry operation with corresponding estimation errors.

[0029] According to the invention, it is now provided that the state of charge 32 or the state of health 34 can also be determined by the mechanical properties of the battery cell 14 by storing a corresponding characteristic curve for the stiffness over the state of charge 32 or the state of health 34. Thus, the state of charge 32 and the state of health 34 can also be determined during ferry operation, or when no current is flowing and the battery voltage is not relaxed.

[0030] List of reference symbols

[0031] 10 motor vehicle

[0032] 12 electrical energy storage

[0033] 14 battery cells

[0034] 16 Battery management system

[0035] 18 electrical properties

[0036] 20 electronic computing devices

[0037] 22 Recording device

[0038] 24 current stiffness

[0039] 26 Stiffness model

[0040] 28 Additional information

[0041] 30 direct determination

[0042] 32 Charge level

[0043] 34 State of health

Claims

Patent claims 1. A method for determining an electrical property (18) of at least one battery cell (14) of an electrical energy storage device (12) of an at least partially electrically operated motor vehicle (10) by means of a battery management system (16) of the electrical energy storage device (12), comprising the steps: - specifying a stiffness model (26) of the battery cell (14) as a function of the electrical property (18) by means of an electronic computing device (20) of the battery management system (16); - detecting a current stiffness (24) of the battery cell (14) by means of a detection device (22) of the battery management system (16); - comparing the current stiffness (24) with the stiffness model (26) by means of the electronic computing device (20); and - Determining the electrical property (18) as a function of the comparison by means of the electronic computing device (20).

2. Method according to claim 1, characterized in that a current state of charge (32) of the battery cell (14) is determined as the electrical property (18).

3. Method according to claim 2, characterized in that in the stiffness model (26) a plurality of stiffnesses of the battery cell (14) are specified as a function of a plurality of charge states.

4. Method according to one of the preceding claims, characterized in that a current state of health (34) of the battery cell (14) is determined as an electrical property (18).

5. Method according to claim 4, characterized in that in the stiffness model a plurality of stiffnesses of the battery cell (14) are specified as a function of a plurality of health states.

6. Method according to one of the preceding claims, characterized in that a range of the motor vehicle (10) is determined as a function of the determined electrical property (18).

7. Method according to one of the preceding claims, characterized in that the current stiffness (24) is detected by means of a pressure measuring film as the detection device (22) and / or a laser measuring device as the detection device (22).

8. Computer program product with program code means which cause an electronic computing device (20) to carry out a method according to one of claims 1 to 7 when the program code means are processed by the electronic computing device (20).

9. A computer-readable storage medium comprising a computer program product according to claim 8.

10. Battery management system (16) for determining an electrical property (18) of at least one battery cell (14) of an electrical energy store (12) of an at least partially electrically operated motor vehicle (10), with at least one detection device (22) and an electronic computing device (20), wherein the battery management system (16) is designed to carry out a method according to one of claims 1 to 7.

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