Method for determining swelling of a battery cell

Abstract

The invention relates to a method for determining a swelling of a battery cell, comprising the following steps: - causing a flow of a fluid (9) around the battery cell; - detection of sound caused by the flowing fluid (9); and - Determination of swelling using the detected sound.

Description

[0001] The present invention relates to a method for determining a swelling of a battery cell according to claim 1 and a device for determining a swelling of a battery cell according to claim 7. In the context of this description, a battery cell is understood to mean, in particular, a pouch cell. The swelling can also be referred to as "swelling."

[0002] From DE 10 2020 112 169 A1 a method is known for measuring deformations of a battery tray of a motor vehicle using structure-borne sound.

[0003] In contrast, the object of the invention is to provide a way to assess the condition of a battery cell.

[0004] This object is achieved by a method according to claim 1, by a device according to claim 7 and by a system according to claim 10. Embodiments of the invention are specified in the dependent claims.

[0005] The method for determining swelling of a battery cell involves causing a fluid to flow around the battery cell. The fluid can flow directly around the battery cell. It is also possible for the battery cell to be part of a battery or battery module, with the battery or battery module comprising multiple battery cells around which the fluid flows.

[0006] The flowing fluid generates sound, which is detected. During detection, measurement data can be recorded, for example. The swelling is determined using the detected sound. This is particularly possible because the flow cross-section available for the fluid depends on the swelling. The more the battery cell swells, the smaller the flow cross-section becomes. This results in characteristic flow noises that can be detected as sound. This can be structure-borne sound, in particular, but also airborne sound.

[0007] The method is advantageous because the swelling can be determined without opening a housing in which the battery cell may be located. By determining the swelling, conclusions can also be drawn about the condition of the battery cell. For example, it can be determined whether the battery cell should be replaced, since battery cells typically swell when their quality declines, for example, due to their age or frequency of use as an energy source.

[0008] According to one embodiment of the invention, the fluid can be a cooling liquid used during operation of the battery cell to transport heat away from the battery cell. In this case, the fluid thus fulfills two functions: It is used as a cooling liquid and for determining swelling.

[0009] According to one embodiment of the invention, the flow can be caused by a predetermined pressure, a predetermined volume flow, and / or a predetermined temperature of the fluid. In the context of this description, this is understood in particular to mean that the pressure, the volume flow, and / or the temperature for detecting the sound are predetermined. For example, it can be a pressure, a volume flow, and / or a temperature at which sound measurements have already been carried out on a non-swollen battery cell, so that the detected sound can be compared with these measurements. Preferably, this pressure, this volume flow, and / or this temperature is / are always used when the swelling is to be determined. For this purpose, for example, a workshop mode of the cooling system can be used, which is designed to determine the swelling of the battery cell.This ensures that the sound is always detected under the same conditions.

[0010] According to one embodiment of the invention, the sound can be structure-borne sound. This is often easier to measure and comparable with other sound measurement data, since coupling of the sound from the battery housing into the air is not absolutely necessary.

[0011] According to one embodiment of the invention, a state of charge and / or an internal resistance can also be used to determine the swelling. This can be the state of charge and the internal resistance of the battery cell or of a battery module of which the battery cell is a component. The state of charge and the internal resistance are further parameters that allow conclusions to be drawn about the condition of the battery cell. In combination with the detected sound, it may be possible to determine whether the swelling is unusual and whether the battery cell should be replaced. This can be the case, for example, if the state of charge and / or the internal resistance indicate that the swelling is less severe than that determined using the detected sound. In this case, the determination of the swelling also includes an assessment of the swelling determined using the detected sound.

[0012] According to one embodiment of the invention, when determining the swelling, the detected sound can be compared with sound measurement data of a fluid flowing around the battery cell. This fluid can be the same fluid used to detect the sound or a different fluid. Preferably, the sound measurement data were recorded using another intact battery cell without swelling. Such a comparison can be used to determine the extent of the swelling of the battery cell.

[0013] The device according to claim 7 comprises a clamping means, a sound sensor, and an evaluation unit. The clamping means is designed to press the sound sensor with a clamping force against a housing of a battery with the battery cell. It should be noted that, in the context of this description, this also means that the sound sensor is pressed indirectly against the housing, for example by arranging a measuring adapter between the sound sensor and the housing. However, it is also possible for the sound sensor to be pressed directly against the housing. The sound sensor is designed to detect sound within the housing. The evaluation unit is designed to evaluate sound detected by the sound sensor. The device is designed to carry out a method according to one embodiment of the invention. For example, the evaluation unit can also be designed to determine the swelling.

[0014] According to one embodiment of the invention, the device can comprise a measuring adapter designed for direct, flat contact with the housing. In the context of this description, this particularly means that the measuring adapter is designed to bear directly against the housing with a contact surface. Such a contact surface can, in particular, differ from a linear or point-shaped contact. Such a measuring adapter is advantageous for particularly good sound detection and easy adaptability of the device to different batteries.

[0015] According to one embodiment of the invention, the clamping means can comprise a screw. The screw can be designed to be screwed into a screw opening in the housing and, when screwed in, to press the measuring adapter and the sound sensor against the housing. The measuring adapter can be pressed directly against the housing, and the sound sensor can be pressed indirectly. Attaching both the measuring adapter and the sound sensor using the screw is advantageous because it saves components and installation space. Furthermore, the attachment process is simplified.

[0016] The system according to claim 10 comprises a device according to an embodiment of the invention and the battery. The battery cell can in particular have a drain opening for the fluid. This drain opening can, for example, be designed to drain the fluid from the battery cell. A thread, in particular an internal thread, can be arranged in the drain opening, for example, so that the screw can be screwed into the drain opening. In this way, the drain opening can be used both to drain the fluid and to attach the device to the battery. The drain opening can therefore be the screw opening.

[0017] Further features and advantages of the present invention will become clear from the following description of preferred embodiments with reference to the accompanying drawings. The same reference numerals are used for identical or similar features and for features with identical or similar functions. Fig. 1 is a schematic flow diagram of a method according to an embodiment of the invention; and Fig. 2 a schematic sectional view of a system according to an embodiment of the invention.

[0018] The swelling behavior V of the battery cell depends on the battery cell's state of charge (SoC) and its wear level (a), see Figure 1. The wear level (a) depends on the battery cell's use and age. The swelling behavior V can thus be represented in a three-axis diagram with curves depending on the state of charge (SoC) and the wear level (a). The more the battery cell swells, the smaller the flow cross-section A available for the fluid flowing around the battery cell becomes, see Figure 3. This results in characteristic flow noise, which can be detected as structure-borne sound (db(A)) of the battery casing through which the fluid flows, see Figure 4.

[0019] To detect this flow noise as structure-borne sound dB(A), the battery's cooling circuit is set into a mode that circulates the fluid and generates the flow noise. Preferably, in this mode, the fluid is set in flow at a predetermined pressure, a predetermined volume flow, and / or a predetermined temperature, thus creating reproducible conditions for sound detection. The detected sound is stored as sound data set 5.

[0020] The sound data set 5 and other input variables 6, such as the state of charge and / or internal resistance of a cell module, of which the battery cell is a component, are fed to an evaluation unit 7, which determines the swelling of the battery cell. Fourier transformations and other statistical evaluation and data processing functions can be used. The data can also be compared with sound measurement data from an intact battery cell. If differences between the sound measurement data and the sound data set are too great, it can be determined that the swelling is too great. If abnormal and / or excessive swelling is detected, for example, depending on the state of charge or wear of the battery cell, it can be recommended that the battery cell be replaced to reduce safety risks.

[0021] The Fig. The system shown in Figure 2 comprises a battery with a housing 8. Within the housing 8, a fluid 9 is present, which is designed to flow directly around the battery cell within the housing 8 and to dissipate heat generated by the battery cell during operation. A screw opening 10 is provided in the housing 8. The screw opening 10 can be an opening designed to drain the fluid 9 from the battery. An internal thread 11 is arranged in the screw opening 10. This can be, for example, a nut that is fastened to the housing 8 via a welded connection 12.

[0022] The system also includes a device with a screw 13, a measuring adapter 14 and a sound sensor 15. The screw 13 is screwed into the screw opening 10 using the internal thread 11 and clamps the measuring adapter 14 and the sound sensor 15 against the housing 8. The measuring adapter 14 is arranged between the housing 8 and the sound sensor 15. The measuring adapter 14 is in direct contact with the housing 8. The sound sensor 15 is connected to the evaluation unit 7 (in Fig. 2 not shown).

[0023] The fluid 9 flowing within the housing 8 generates structure-borne sound, which is transmitted via an active contact 16 between the housing 8 and the measuring adapter 14 to the measuring adapter 14, and from the measuring adapter 14 to the sound sensor 15. The active contact 16 is therefore essential for high-quality transmission of the structure-borne sound signal. For particularly good transmission of the structure-borne sound from the housing 8 to the measuring adapter 14, the contact surface between the housing 8 and the measuring adapter 14 should be particularly flat, and the measuring adapter 14 should lie flat against the housing 8.

[0024] The measuring adapter 14 is also an important link for transmitting the structure-borne sound from the housing 8 to the sound sensor 15. To achieve particularly low attenuation of the structure-borne sound, a particularly rigid material, such as metal, can be used for the measuring adapter 14. Furthermore, the mass of the measuring adapter 14 should be kept low, which can be achieved by a low installation height 17 and the selection of a lightweight material, such as titanium.

[0025] During operation, a flow of fluid 9 is caused, which, depending on the flow cross-section available for the flow, causes structure-borne noise in the housing 8. The flow cross-section depends on the swelling of the battery cell arranged within the housing 8, which is directly surrounded by the fluid 9. The structure-borne noise is transmitted from the housing via the active contact 16 to the measuring adapter 14 and from there to the sound sensor 15. The sound sensor 15 detects the sound and generates a sound data set from the detected sound, which is transmitted via the data connection 18 to the evaluation unit 7. The swelling is then determined in the evaluation unit 7, as exemplified with reference to Fig. 1 was described. QUOTES CONTAINED IN THE DESCRIPTION

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

[0000] DE 10 2020 112 169 A1

[0002]

Claims

[1] A method for determining swelling of a battery cell, comprising the following steps: - causing a flow of a fluid (9) around the battery cell; - detection of sound caused by the flowing fluid (9); and - Determination of swelling using the detected sound. [2] Method according to claim 1, characterized by that the fluid (9) is a cooling liquid which is used during operation of the battery cell to transport heat away from the battery cell. [3] Method according to one of the preceding claims, characterized by that the flow is caused by a predetermined pressure, a predetermined volume flow and / or a predetermined temperature of the fluid. [4] Method according to one of the preceding claims, characterized by that the sound is structure-borne sound. [5] Method according to one of the preceding claims, characterized bythat a state of charge and / or an internal resistance is also used to determine the swelling. [6] Method according to one of the preceding claims, characterized by that when determining the swelling, the detected sound is compared with sound measurement data of a fluid flowing around the battery cell. [7] Device for determining a swelling of a battery cell, wherein the device comprises a clamping means (13), a sound sensor (15) and an evaluation unit (7), wherein the clamping means (13) is designed to press the sound sensor (15) with a clamping force against a housing (8) of a battery with the battery cell, wherein the sound sensor (15) is designed to detect sound within the housing (8), wherein the evaluation unit (7) is designed to evaluate sound detected by the sound sensor (15), and wherein the device is designed to carry out a method according to one of the preceding claims. [8] Device according to the preceding claim, characterized by in that the device comprises a measuring adapter (14), wherein the measuring adapter (14) is designed for a flat direct contact with the housing (8), wherein the clamping means (13) is designed to press the measuring adapter (14) directly against the housing (8), wherein in the state of the measuring adapter (14) and the sound sensor (15) pressed against the housing (8), the measuring adapter (14) is arranged between the housing (8) and the sound sensor (15). [9] Device according to the preceding claim, characterized by in that the clamping means (13) comprises a screw, wherein the screw is designed to be screwed into a screw opening (10) of the housing (8) and to press the measuring adapter (14) and the sound sensor (15) against the housing (8) in the screwed-in state. [10] System comprising a device according to any one of the preceding three claims and the battery.