Battery pack, vehicle

Abstract

Battery pack (100), comprising: a battery group (10) comprising several individual cells stacked in succession (11); a front plate (20) which is provided along a stacking direction of the individual cells (11) at one end of the battery group (10); a monitoring structure (30) which is provided on a side surface parallel to the end plate (20) of at least one of the individual cells (11) and is designed to monitor an expansion-deformation value of the individual cells (11); and a battery management system, BMS (40) which is electrically connected to the monitoring structure (30) and is designed to calculate a deformation rate and a deformation speed in a specified time according to the expansion-deformation value in order to determine, according to the deformation rate and the deformation speed, whether the battery pack (100) is in thermal runaway.

Description

Technical field

[0001] The present application relates to the technical field of batteries and in particular to a battery pack, a vehicle and a monitoring method for thermal runaway. State of the art

[0002] The battery pack is a core component of a new energy vehicle and provides the energy for its operation. During use, thermal runaway can occur in the battery pack due to manufacturing defects or in extreme cases such as severe impacts, causing the batteries within the pack to expand and deform.

[0003] To ensure passenger safety, a thermal runaway warning signal must be emitted 5 minutes before the thermal runaway reaches the passenger compartment, giving passengers sufficient time to escape. Generally, monitoring of a temperature or voltage signal is used in the thermal runaway monitoring methods for the battery pack. Disclosure of the application; Technical problem to be solved

[0004] In related technologies, a negative temperature coefficient (NTC) thermistor is used to detect temperature signals and is susceptible to environmental influences. Alternatively, a pressure signal can change significantly when a vehicle is driven from a low to a high altitude, which can lead to a false alarm. Technical solutions

[0005] In a first aspect, the present application provides a battery pack comprising: a battery group comprising several single cells stacked in succession; an end plate provided along a stacking direction of the single cells at one end of the battery group; a monitoring structure provided on a side surface parallel to the end plate of at least one of the single cells and designed to monitor an expansion-deformation value of the single cells; and a battery management system (BMS) electrically connected to the monitoring structure and designed to calculate a deformation rate and a deformation rate in a predetermined time according to the expansion-deformation value in order to determine, based on the deformation rate and the deformation rate, whether the battery pack is in thermal runaway.

[0006] In a second aspect, the present application provides for a vehicle comprising a body and the aforementioned battery pack, the battery pack being mounted on the body.

[0007] In a third aspect, the present application provides a monitoring method for thermal runaway of a battery pack, comprising: obtaining an expansion-deformation value ΔL of an individual cell in a battery pack by a monitoring structure, and calculating a deformation rate ε of the individual cell and a deformation rate F(t) in a predetermined time t based on the expansion-deformation value ΔL by a BMS (40); determining whether the deformation rate ε is within a first predetermined range and whether the deformation rate F(t) is within a second predetermined range; and confirming that the battery pack is in thermal runaway, provided that the determination result is yes. Beneficial effects

[0008] Since the individual cells expand to a large area during thermal runaway, the monitoring structure is located on the side surface of the individual cells parallel to the end plate. This structure monitors the expansion-deformation value of the individual cells after expansion during thermal runaway. The expansion-deformation value is transmitted to the BMS, which then calculates the deformation rate and rate over a specified time. This allows the BMS to determine whether the battery pack is experiencing thermal runaway based on the deformation rate and rate. If thermal runaway is confirmed, the BMS can then trigger an alarm.With this setting, monitoring the expansion-deformation value of the individual cells in the battery pack after expansion during thermal runaway provides a basis for determining whether the battery pack is experiencing thermal runaway. Compared to a method for monitoring a temperature change or a pressure change of the battery pack, the patented method is less influenced by the environment and has higher accuracy. Brief description of the drawings Fig. Figure 1 is a schematic structure diagram of a battery pack according to an embodiment of the present application; Fig. Figure 2 is a schematic structure diagram of a battery pack made of Fig. 1 in normal working order; Fig. Figure 3 is a schematic structure diagram of a battery pack made of Fig. 1 during a thermal runaway; Fig. 4 is a schematic structure diagram of a single cell made up of Fig. 1 during a thermal runaway; Fig. Figure 5 is a schematic structure diagram of a monitoring structure. Fig. 2; and Fig. Figure 6 is a schematic flowchart of a monitoring procedure for thermal runaway of a battery pack according to another embodiment of the present application. Reference symbol:

[0009] 100-Battery pack; 10-Battery group; 11-Single cell; 20-End plate; 30-Monitoring structure; 31-Strain gauge film; 32-Insulating protection element; 40-Battery management system, BMS; 50-Insulating sheet. Designs

[0010] In relation to Fig. 1 to Fig. In one embodiment of the present application, a battery pack 100 is provided comprising a battery group 10, an end plate 20, a monitoring structure 30 and a battery management system BMS 40.

[0011] In relation to Fig. 1 to Fig. The battery group 10 comprises a plurality of individual cells 11 stacked sequentially. The end plate 20 is provided along a stacking direction of the individual cells 11 at one end of the battery group 10. The monitoring structure 30 is provided on a side surface of at least one individual cell 11 parallel to the end plate 20 and is configured to monitor an expansion-deformation value ΔL of the individual cell 11. The BMS 40 is electrically connected to the monitoring structure 30 and is configured to calculate a deformation rate ε and a deformation rate F(t) within a predetermined time t according to the expansion-deformation value ΔL in order to determine whether the battery pack 100 is in thermal runaway according to the deformation rate ε and the deformation rate F(t).

[0012] Since in the previous battery pack 100 the individual cells 11 expand to a large area during thermal runaway, the monitoring structure 30 is provided on the side surface of the individual cells 11 parallel to the end plate 20 in order to monitor the expansion-deformation value ΔL of the individual cells 11 after expansion by the monitoring structure 30 during thermal runaway. The expansion-deformation value ΔL is transmitted to the BMS 40, and the deformation rate ε and the deformation rate F(t) within the specified time are obtained by the BMS 40 according to the expansion-deformation value ΔL, so that the BMS 40 determines whether the battery pack 10 is in thermal runaway according to the deformation rate ε and the deformation rate F(t). The BMS 40 can then subsequently perform an alarm action under the condition that a determination result is yes.With such a setting, monitoring the expansion-deformation value ΔL of the individual cells 11 in the battery group 10 after expansion during thermal runaway provides a basis for determining whether the battery pack 100 is experiencing thermal runaway. Compared to a method for monitoring a temperature change or a pressure change of the battery pack 100, the patented method is less influenced by the environment and has higher accuracy.

[0013] In some embodiments, the individual cells 11 are square cells. When the square cells form the battery pack 100, they have one side surface parallel to the end plate 20, with the side surface representing a large area of ​​the square cells. When the square cell is subjected to thermal runaway, the expansion deformation of the cell towards the large area occurs in an extremely short time. Therefore, the expansion deformation of the individual cell 11 during thermal runaway can be monitored by the monitoring structure 30. The BMS 40 is configured to monitor the cell's condition to prevent overcharging or over-discharging, thereby extending the cell's service life, and is also configured to detect thermal runaway to ensure the cell's safety during use.

[0014] In particular, the monitoring structure 30 in some embodiments includes a strain gauge 31. The strain gauge 31 is a device for measuring the strain of an object and comprises an insulating substrate and a metal-sensitive grid. During measurement, the strain gauge 31 is connected to a surface of the object, for example, by being glued to the large area of ​​the individual cell 11. The sensitive grid also deforms when the individual cell 11 expands and deforms due to thermal runaway, so that the resistance value of the sensitive grid changes accordingly. By detecting even a slight change in the resistance of the sensitive grid, it can be converted into an actual strain value of the individual cell 11, so that the expansion-deformation value ΔL of the individual cell 11 can be obtained.

[0015] In relation to Fig. For example, protrusions may occur at the weld feet, partially on the strain gauge film 31, due to the arrangement of a cable bundle of the strain gauge film 31 when the strain gauge film 31 adheres to the large surface of the individual cell 11. To prevent the protrusions from damaging the surface of the individual cell 11, the battery pack 100 in some embodiments further includes an insulating protective element 32 with which the outside of the monitoring structure 30 is encased. In this way, the insulating protective element 32 can wrap around the protrusions by positioning the insulating protective element 32 outside the strain gauge film 31, thus avoiding the risk of scratching a protective film of the individual cell 11 when the strain gauge film 31 adheres to the surface of the individual cell 11, since the protrusion position is in direct contact with the surface of the individual cell 11.

[0016] In particular, the insulating protection element 32 is, in some embodiments, a mica roll. The mica roll is an insulating material formed by resin bonding and drying a mica paper as the base material and a glass or ceramic fiber as the reinforcing material. Furthermore, an adhesive can be applied to the surface of the mica roll, which can directly cause the strain-measuring foil 31 to adhere to the surface of the individual cell 11, thus facilitating the mounting of the strain-measuring foil 31.

[0017] In particular, in some embodiments, the thickness of the strain gauge 31 with the mica paper wrapped around its outer surface is in the range of 0.2 mm to 0.3 mm. By setting a relatively small thickness, it is possible to prevent the assembly of the entire battery pack 100 from being affected and to avoid increasing the length of the battery pack 100 in any stacking direction of the individual cells 11, thus keeping the length of the battery pack 100 within a reasonable range. For example, the thickness of the strain gauge 31 with the mica paper can be set to correspond to the thickness of various individual cells 11, such as 0.2 mm, 0.22 mm, 0.24 mm, 0.26 mm, 0.28 mm, or 0.3 mm, which is not limited here.

[0018] In relation to Fig. 2 and Fig. 3 In some embodiments, when adjusting the monitoring structure 30 within the battery group 10 to ensure the safety and service life of the battery group 10 along the stacking direction of the individual cells 11, the monitoring structure 30 is provided on an individual cell 11 at one end of the battery group 10 and on a side of the individual cell 11 facing the end plate 20. Fig. Figure 2 is a schematic diagram of battery group 10 in normal operating condition. Fig. Figure 3 is a schematic diagram of battery group 100 in a thermal runaway after expansion in the service condition.

[0019] In particular, with reference to Fig. 1. Since an insulating plate 50 is provided between the end plate 20 and the battery group 10, the monitoring structure 30 is provided between the insulating plate 50 and the battery group 10. The monitoring structure 30 is positioned at one end of the battery group 10 to prevent normal expansion of the entire battery group 10 during use, thus ensuring the service life and safety of the battery group 10 during use. Since the monitoring structure 30 also needs to be electrically connected to the BMS 40, positioning the monitoring structure 30 at one end of the battery group 10 can reduce the installation costs of the monitoring structure 30 and facilitate the electrical connection between the cable bundle and the BMS 40 after the cable bundle has been wrapped.

[0020] In this way, by means of the assembly of the above-mentioned monitoring structure 30, when a single cell 11 in the battery group 10 expands during a thermal runaway, e.g., when the single cell 11 located in a central area expands, the large area of ​​the single cell 11 is subjected to expansion and deformation, which are sequentially transmitted to the single cell 11 at one end, so that the monitoring structure 30 located at one end can monitor the expansion-deformation value ΔL of the single cell 11.

[0021] To more accurately monitor thermal runaway of the battery group 10 during use, a monitoring structure 30 is provided at each individual cell 11 at both ends of the battery group 10. This allows for more precise monitoring of the expansion of the individual cell 11 throughout the battery group 10, enabling more accurate transmission of control commands via the BMS 40. In some embodiments, provided that the individual cell 11 expands normally and the assembly costs of the monitoring structure 30 can be reduced, a monitoring structure 30 can be mounted along the stacking direction of the individual cells 11 every 1 / 3, 1 / 4, or 1 / 5 of the way. This allows for more accurate monitoring of cell 11 deformations after expansion and also reduces the setup costs of the monitoring structure 30 accordingly.

[0022] A normal operating condition of the individual cells 11 is in Fig. 1 and a state after the expansion of the individual cells 11 during a thermal runaway is indicated by the dashed lines in Fig. 3 and Fig. 4 shown.

[0023] Whether thermal runaway occurs in battery group 10 is determined by the deformation rate ε and the deformation velocity F(t) according to the expansion-deformation value ΔL. For example, with respect to Fig. Figure 4 shows that the initial thickness L1 of the single cell 11 is 25 mm. The thickness L1 = 25 mm increases to L2 = 30 mm within a predetermined time, for example t = 3 s, when the single cell 11 undergoes thermal expansion. For example, the dashed lines in Figure 4 indicate the thermal expansion of the individual cell 11. Fig. 3 and Fig. 4. The state of thermal expansion is defined as follows: the expansion-deformation value ΔL of individual cell 11 is 5 mm, the deformation rate ε = (L2 - L1) / L1 = 2%, and the deformation rate F(t) = ε / t = 2% / 3 = 0.67%. Provided that the deformation rate of 2% and / or the deformation rate of 0.67% falls within the specified range for thermal runaway, it is indicated that thermal runaway has occurred in individual cell 11.

[0024] In particular, in some embodiments the range of the deformation rate ε and the deformation speed F(t) of the individual cell 11 during thermal runaway is specified as follows: 2%<ε<8%; and / or 0.4% / s <F(t)<2% / s.

[0025] Provided that the deformation rate ε and the deformation rate F(t), which are calculated by the BMS 40 based on the expansion-deformation value ΔL of the single cell 11 monitored by the monitoring structure 30, fall within the aforementioned range, this indicates that the battery pack 100 is in thermal runaway and the BMS 40 must subsequently perform an alarm action.

[0026] By configuring the monitoring structure 30 in battery group 10 to monitor the expansion-deformation value ΔL of the individual cell 11, the expansion-deformation value ΔL is transmitted to the BMS 40 in the above battery pack 100, and the deformation rate ε and the deformation rate F(t) are calculated by the BMS 40. Provided that both the deformation rate ε and the deformation rate F(t) reach the specified range of the individual cell 11 during thermal runaway, this indicates that the individual cell 11 has undergone thermal runaway, and the BMS 40 can then send an alarm signal to ensure the safe evacuation of the occupants.

[0027] In a second embodiment of the present application, with reference to Fig.6 a monitoring procedure for the thermal runaway of the aforementioned battery pack 100 is provided, comprising the following steps:

[0028] Step S21: Obtaining an expansion-deformation value ΔL of a single cell 11 in a battery pack 100 by a monitoring structure 30, and calculating a deformation rate ε of the single cell 11 and a deformation rate F(t) in a given time t based on the expansion-deformation value ΔL, where an initial thickness of the single cell is L1, a thickness of this single cell after expansion during thermal runaway is L2, the expansion-deformation value ΔL = L2 - L1, the deformation rate ε of the single cell 11 is ε = (L2 - L1) / L1 * 100% and the deformation rate F(t) = ε / t.

[0029] Prior to the aforementioned step, a monitoring structure 30 and a battery pack 100 are provided. The battery pack 100 comprises individual cells 11 and an end plate 20 provided at one end of the individual cells 11 in the stacking direction, which is parallel to the large surface area of ​​each of the individual cells 11. The individual cell 11 can be a square cell. The square cell can be an aluminum-cased cell and can also be a secondary battery, such as a blade cell. If one or more of the individual cells 11 in the battery pack 10 are subjected to thermal expansion, the expansion occurs on the large surface area of ​​the individual cells 11, and there is a transfer between the individual cells 11, causing the surrounding individual cells 11 to expand. In this way, the monitoring structure 30, arranged at one end, is able to monitor a thermal runaway of the battery pack 10.

[0030] In some embodiments, the monitoring structure 30 comprises a strain gauge film 31 and an insulating element 32, which encases the outer surface of the strain gauge film 31. The resistance value of the strain gauge film 31 changes accordingly when the individual cell 11 expands and deforms due to thermal runaway. The resulting resistance change can be converted into an actual strain value, thus allowing the expansion-deformation value ΔL of the individual cell 11 to be determined. Even when the outer surface of the strain gauge film 31 is encased in a layer of insulating element 32, protrusions may occur on the strain gauge film 31, for example, due to the arrangement of the cable bundle at the welded feet.To prevent the protrusions from damaging the surface of the individual cells 11, the battery pack 100 in some embodiments further includes an insulating protection element 32 with which the outside of the monitoring structure 30 is encased, thereby avoiding the risk of scratching a protective film of the individual cell 11 when the strain gauge film 31 adheres to the surface of the individual cell 11, since the protrusion position is in direct contact with the surface of the individual cell 11.

[0031] In particular, in some embodiments the insulating protection element 32 is a glow-in-the-dark paper. An adhesive is provided on the back of the glow-in-the-dark paper to facilitate direct adhesion of the entire monitoring structure 30 to the surface of the battery.

[0032] In some embodiments, the monitoring structure 30 is mounted on a side surface of at least one single cell 11 that is parallel to the end plate 20 before the measurement.

[0033] When installing the monitoring structure 30 in the battery group 10, the monitoring structure 30 is provided on a single cell 11 located at one end of the battery group 10 and on a side surface of the single cell 11 facing the end plate 20, in order to ensure the safety and service life of the battery group 10 along a stacking direction of the individual cells 11. To monitor thermal runaway in the battery group 10 more accurately during use, in some embodiments the individual cells 11 at both ends of the battery group 10 are each provided with a monitoring structure 30. In this way, the expansion of the individual cell 11 within the entire battery group 10 can be monitored more accurately, so that control commands can be sent more precisely via the BMS 40.In some embodiments, provided that the individual cell 11 can expand normally and the assembly costs of the monitoring structure 30 can be reduced, a monitoring structure 30 can be mounted every 1 / 3, 1 / 4, or 1 / 5 of the way along a stacking direction of the individual cells 11. In this way, the deformation of the individual cell 11 after expansion can be monitored more accurately, and the setup costs of the monitoring structure 30 can be reduced accordingly.

[0034] After the assembly of the battery pack 100 is complete, the expansion-deformation value ΔL of the individual cell 11 is obtained by the monitoring structure 30 in this step. That is, the deformation rate ε and the deformation velocity F(t) in a given time are obtained from ΔL and used for further determination.

[0035] The expansion-deformation value ΔL in the present step refers to the expansion-deformation quantity of the individual cell 11 after the actual expansion, which can be monitored by the monitoring structure 30 when expansion occurs in the individual cell 11. For example, if the initial thickness L1 of the individual cell 11 is 25 mm, and the thickness of the individual cell 11 is increased from 25 mm to L2 = 30 mm within a predetermined time, e.g., t = 3 s, then the expansion-deformation value ΔL of the individual cell 11 is 5 mm, the deformation rate ε = (L2-L1) / L1 = 2%, and the deformation rate F(t) = ε / t = 2% / 3 = 0.67%. If the initial thickness L1 of the single cell 11 is 25 mm and the thickness of the single cell 11 is increased from 25 mm to L2 = 35 mm within a given time t, e.g. t = 4 s, then the expansion-deformation value ΔL of the single cell 11 is 10, the deformation rate ε = (L2-L1) / L1 = 10 / 25 = 4%, and the deformation rate F(t) = ε / t = 4% / 4 = 1% / s.Provided that at least one of the deformation rate and deformation rate falls within the specified range, it is indicated that the battery pack 100 is undergoing thermal runaway. To ensure the accuracy of the determination, it is necessary to obtain not only the deformation rate ε but also the deformation rate F(t), since the individual cell 11 can expand during normal use due to environmental influences or self-heating during long-term use, and an incorrect determination may occur if only the deformation rate ε is monitored. The individual cell 11 can expand relatively quickly during thermal runaway.Provided that the monitored deformation rate F(t) meets the specified condition and is used jointly as a basis for determining the subsequent steps, a more accurate determination can be made as to whether thermal runaway occurs, thereby avoiding incorrect determinations.

[0036] Step S22: Determine whether the deformation rate ε lies within a first specified range and whether the deformation velocity F(t) lies within a second specified range.

[0037] The deformation rate ε and deformation velocity F(t) of the single cell 11 obtained in the previous step are used in the present step and in the specified area for determination.

[0038] In particular, the first specified range is: 2% < ε < 8%; and the second specified range is: 0.4% / s < F(t) < 2% / s.

[0039] Step S23: Confirmation that the battery pack is in thermal runaway, provided the determination result is yes.

[0040] In the above-mentioned step, it is noted that, provided that the obtained deformation rate ε is in the range of 2% < ε < 8%, and / or the obtained deformation rate F(t) is in the range of 0.4% / s < F(t) < 2% / s,

[0041] that the battery pack 100 is experiencing thermal runaway.

[0042] The square cells have varying thicknesses. The thicker the square cell, the greater the deformation. Therefore, the deformation is set to be within the range of 2% < ε < 8%, and the deformation rate is set to 0.4% / s < F(t) < 2% / s. If either the deformation rate ε or the deformation rate F(t) falls within the specified range, it is indicated that thermal runaway occurs in the individual cells 11 of battery pack 100, meaning the battery pack 100 is experiencing thermal runaway. Furthermore, if both the deformation rate ε and the deformation rate F(t) fall within the specified ranges, it can be precisely determined that the battery pack 100 is experiencing thermal runaway, thus reducing the possibility of error detection.

[0043] For example, according to the two examples listed above, ε = 2%, F(t) ≈ 0.67% correspond to the ranges of 2% < ε < 8% and 0.4% / s < F(t) < 2% / s; and ε = 4%, F(t) = 1% also correspond to the ranges 2% < ε < 8% and 0.4% / s < F(t) < 2% / s, indicating that the battery pack 100 is in thermal runaway.

[0044] To ensure the accuracy of the determination, the monitoring procedure for the thermal runaway of the battery pack 100, prior to the step of obtaining the deformation rate ε of the individual cell 11 and the deformation velocity F(t) in the specified time t by the monitoring structure 30, further includes:

[0045] Maintaining a voltage and temperature of the battery pack 100;

[0046] Determine whether a ratio x of a voltage drop value in a given time t' to an initial voltage value lies within a third given range and whether a temperature rise rate y lies within a fourth given range in the given time t';

[0047] Performing the step to obtain the expansion-deformation value ΔL of the single cell 11 by the monitoring structure 30 under the condition of a determination result of yes.

[0048] To avoid incorrect determinations, before obtaining the deformation rate ε and the deformation rate F(t), it is also necessary to determine the voltage and temperature within the battery pack 100 and to ascertain whether the voltage drop and temperature rise rate within the given time t' are within their respective predefined ranges. The subsequent step to obtain the expansion-deformation value ΔL of the individual cell 11 is only performed if the voltage drop and temperature rise rate within the given time t' also meet the conditions, thus ensuring the accuracy of the determination of whether the battery pack 100 is experiencing thermal runaway.

[0049] The initial voltage of the battery pack is V1, the voltage at the given time t' is V2, the voltage drop is ΔV = (V2-V1), and the ratio of the voltage drop to the initial voltage is x = ΔV / V1 * 100%. The initial temperature of the battery pack is T1, the temperature at the given time t' is T2, and the temperature rise rate is y = (T2-T1) / t * 100%.

[0050] In particular, in some embodiments the specified time t' ≥ 3 s; the third specified range relates to the range in which the voltage drop value is located and is x ≥ 25 %, and the fourth specified range relates to the temperature rise rate y ≥ 1°C / s.

[0051] For example, the initial voltage of the battery pack is 100 V1 = 100 V. When the voltage drops to V2 = 70 V, the voltage drop is ΔV = V2 - V1 = 100 - 30 = 30 V, and the ratio of the voltage drop to the initial voltage is x = 30 / 100 * 100% = 30%, 30% > 25%, which satisfies the third specified range. Also, if the initial temperature of the battery pack is T1 = 60°C, then the temperature of the battery pack reaches T2 = 70°C within the time t' = 3 s, and the temperature increase rate in between is y = (T2 - T1) / t' * 100% = 10 / 3 = 3.33°C / s, which satisfies the fourth specified range. Both the voltage drop value and the temperature rise rate of the battery pack 100 correspond to their respective specified ranges.In some embodiments, it is possible to determine, in combination with the deformation rate ε and the deformation speed F(t), whether the battery pack 100 is in a thermal runaway, thereby avoiding incorrect determinations.

[0052] It should be noted that when adopting the monitoring method for thermal runaway of the battery pack 100, in some embodiments, if the individual cell 11 is in a high state of charge (SOC) or a low state of health (SOH), the individual cell 11 may be in a swollen state due to cyclic gas production. In such a case, there is a higher risk of thermal runaway of the individual cell 11. Therefore, it is more accurate to monitor the thermal runaway of the individual cell 11 by monitoring the end-of-line (EOL) via the strain gauge 31, which can avoid false alarms.

[0053] In another embodiment of the present application, a vehicle is further provided, the vehicle comprising a body and a battery pack 100 mentioned above, and the battery pack 100 is mounted on the body.

[0054] According to the aforementioned vehicle, the monitoring structure 30 in the body-mounted battery pack is capable of obtaining the expansion-deformation value ΔL of the individual cell 11 in the battery pack. The expansion-deformation value ΔV is transmitted to the BMS 40. The deformation rate ε and the deformation rate F(t) within the specified time are determined by the BMS 40 based on the expansion-deformation value ΔL. The BMS 40 then determines, based on the deformation rate ε and the deformation rate F(t), whether the battery pack 100 is experiencing thermal runaway. If the result of this determination is positive, the BMS 40 can subsequently initiate an alarm action.By monitoring the expansion deformation value ΔL after expansion during thermal runaway in the individual cell 11 of the battery pack 100, a basis is obtained for determining whether the battery pack 100 is experiencing thermal runaway. Compared to a method for monitoring a temperature change or a pressure change of the battery pack 100, the patented method is less influenced by the environment and is designed with higher accuracy, which leads to an increase in the operational safety of the vehicle.

Claims

[1] Battery pack (100), comprising: a battery group (10) comprising several individual cells stacked in succession (11); a front plate (20) which is provided along a stacking direction of the individual cells (11) at one end of the battery group (10); a monitoring structure (30) which is provided on a side surface parallel to the end plate (20) of at least one of the individual cells (11) and is designed to monitor an expansion-deformation value of the individual cells (11); and a battery management system, BMS (40) which is electrically connected to the monitoring structure (30) and is designed to calculate a deformation rate and a deformation speed in a specified time according to the expansion-deformation value in order to determine, according to the deformation rate and the deformation speed, whether the battery pack (100) is in thermal runaway. [2] Battery pack (100) according to claim 1, wherein the monitoring structure (30) comprises a strain gauge film (31). [3] Battery pack (100) according to claim 2, wherein the monitoring structure (30) further comprises an insulating protection element (32) with which the outside of the strain gauge film (31) is enclosed. [4] Battery pack (100) according to one of claims 1 to 3, wherein the monitoring structure (30) is provided along the stacking direction of the individual cells (11) on an individual cell (11) arranged at one end of the battery group (10) and on a side of the individual cell (11) facing the end plate (20). [5] Battery pack (100) according to one of claims 1 to 4, wherein along the stacking direction of the individual cells (11) the individual cells (11) arranged at two ends of the battery group (10) are each provided with the monitoring structure (30). [6] Battery pack (100) according to any one of claims 1 to 5, wherein a thickness range of the monitoring structure (30) in the stacking direction of the individual cells (11) is 0.2 mm to 0.3 mm. [7] Battery pack (100) according to any one of claims 1 to 6, wherein the monitoring structure (30) is provided to obtain the expansion-deformation value ΔL of the individual cell (11) in the battery pack (100), and the BMS (40) is provided to calculate the deformation rate ε of the individual cell (11) and the deformation rate F(t) in a predetermined time t based on the expansion-deformation value ΔL, wherein it is determined whether the deformation rate ε is within a first predetermined range and whether the deformation rate F(t) is within a second predetermined range, and it is confirmed that the battery pack (100) is in thermal runaway under the condition of a determination result of yes. [8] Battery pack (100) according to claim 7, wherein an initial thickness of the individual cell (11) is L1, a thickness of the individual cell (11) after expansion during thermal runaway is L2, the expansion deformation value ΔL = L2 - L1, the deformation rate of the individual cell (11) is ε = (L2 - L1) / L1*100%, and the deformation rate in the predetermined time t is F(t) = ε / t. [9] Battery pack (100) according to claim 8, wherein the first predetermined range is: 2% < ε < 8%; and / or the second predetermined range is: 0.4% / s < F(t) < 2% / s. [10] Battery pack (100) according to one of claims 7 to 9, wherein the monitoring structure (30) is further provided to obtain a voltage and a temperature of the battery pack (100); wherein whether a ratio x of a voltage drop value in a given time t' to an initial voltage value lies in a third given range and whether a temperature rise rate y lies in a fourth given range in the given time t', and the obtaining of the expansion-deformation value ΔL of the individual cell (11) by the monitoring structure (30) is carried out under the condition of a determination result of yes. [11] Battery pack (100) according to claim 10, wherein the specified time t' ≥ 3s; the third specified range x ≥ 25%; and the fourth specified range y ≥ 1°C / s. [12] Vehicle comprising a body and the battery pack (100) according to any one of claims 1 to 11, wherein the battery pack (100) is mounted on the body.

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