Battery system thermal event detection method and battery system using the same

Abstract

A battery system includes: a battery pack containing a plurality of battery cells; a pressure sensor located in the battery pack to measure the internal pressure of the battery pack at each sampling time interval; and a battery management system that updates a reference pressure as an average of the internal pressures measured at each sampling time interval, calculates a pressure change as the difference between the internal pressure measured at each sampling time interval and the reference pressure, and determines that a thermal event has occurred in the battery pack if the internal pressure measured at each sampling time interval increases at least twice consecutively when the pressure change is greater than or equal to a predetermined threshold pressure.

Description

Technical Field

[0001] Cross-references to related applications

[0002] This application claims the benefit of Korean Patent Application No. 10-2020-0132500, filed with the Korean Intellectual Property Office on October 14, 2020, the disclosure of which is incorporated herein by reference in its entirety.

[0003] This disclosure relates to a method for detecting thermal events in a battery system and a battery system using the method. Background Technology

[0004] Recently, with the increasing demand for electric vehicles, fires involving electric vehicles have also increased. These fires can be caused by battery damage. To prevent battery damage that could lead to fires in electric vehicles, technologies have been developed to diagnose battery damage by measuring factors such as cell voltage, cell temperature, and insulation resistance.

[0005] However, if the battery management system operates in coasting mode when the vehicle is parked, it is impossible to measure cell voltage, cell temperature, insulation resistance, etc., and therefore, it is impossible to diagnose whether the battery is damaged. In electric vehicles, approximately 21% of battery-related fires actually occur while the vehicle is parked. Therefore, battery diagnostics are necessary not only when the electric vehicle is in motion but also when it is parked. Summary of the Invention

[0006] Technical issues

[0007] This invention aims to provide a method for detecting thermal events in a battery and a battery system using the method.

[0008] Technical solution

[0009] An exemplary embodiment of the present invention provides a battery system comprising: a battery pack containing a plurality of battery cells; a pressure sensor located inside the battery pack to measure the internal pressure of the battery pack in each sampling cycle; and a battery management system that updates a reference pressure based on the average value of the internal pressure measured in the sampling cycles during a sampling period, calculates a pressure fluctuation based on the difference between the internal pressure measured in each sampling cycle and the reference pressure, and determines that a thermal event has occurred in the battery pack if the internal pressure measured in each sampling cycle increases at least twice consecutively when the pressure fluctuation is greater than or equal to a predetermined threshold pressure.

[0010] When the battery management system is in sleep mode, the pressure sensor can update the reference pressure based on the average value of the internal pressure measured in the sampling cycle during the sampling period, calculate a first pressure fluctuation based on the difference between the internal pressure measured in each sampling cycle and the reference pressure, and wake up the battery management system when the first pressure fluctuation is greater than or equal to a predetermined threshold pressure.

[0011] After the battery management system is activated, if the internal pressure measured in each sampling cycle increases at least twice consecutively, the battery management system can determine that the battery pack is abnormal.

[0012] After a thermal event has been determined, the battery management system can measure the voltage and temperature of multiple battery cells and the insulation resistance between the battery pack and ground. If at least one of the voltage, temperature, and insulation resistance of the multiple battery cells is abnormal, the battery pack is determined to be abnormal.

[0013] The battery management system can determine that the battery pack is abnormal if at least one of the following conditions is met: a first condition that at least one of the voltages of the plurality of battery cells is greater than or equal to a threshold voltage; a second condition that at least one of the temperatures of the plurality of battery cells is greater than or equal to a threshold temperature; and a third condition that the insulation resistance between the battery pack and the ground is less than or equal to a predetermined threshold resistance.

[0014] The battery system may further include relays that connect the battery pack and the output terminals of the battery system to each other, and the battery management system may disconnect the relays when the battery pack is determined to be malfunctioning.

[0015] The battery management system can notify the vehicle's battery pack of abnormalities, including the battery system itself.

[0016] The battery system may also include an auxiliary power supply for powering the pressure sensor.

[0017] Another exemplary embodiment of the present invention provides a method for detecting thermal events in a battery system, the battery system comprising: a battery pack including a plurality of battery cells; a pressure sensor located within the battery pack; and a battery management system, the method comprising: measuring the internal pressure of the battery pack in each sampling cycle using the pressure sensor; updating a reference pressure based on the average value of the internal pressure measured in the sampling cycles during the sampling period; calculating a pressure fluctuation based on the difference between the internal pressure measured in each sampling cycle and the reference pressure; determining whether the pressure fluctuation is greater than or equal to a predetermined threshold pressure; and determining that a thermal event has occurred in the battery pack if the internal pressure measured in each sampling cycle increases at least twice consecutively when the pressure fluctuation is greater than or equal to the threshold pressure.

[0018] When the battery management system is in sleep mode, the pressure sensor can perform the updating of the reference pressure, the calculation of the pressure fluctuation, and the determination of whether the pressure fluctuation is greater than or equal to the threshold pressure.

[0019] The thermal event detection method may also include: when the battery management system is in sleep mode, if the pressure fluctuation is greater than or equal to the threshold pressure, waking up the battery management system via a pressure sensor.

[0020] After the battery management system is activated, it can determine the occurrence of thermal events in the battery pack.

[0021] Determining the occurrence of a thermal event in the battery pack may include: calculating a pressure difference by subtracting the internal pressure measured in a previous sampling cycle from the internal pressure measured in the current sampling cycle; determining whether the calculated pressure difference is greater than or equal to 0; and if the calculated pressure difference is greater than or equal to 0, determining that the internal pressure has increased.

[0022] Beneficial effects

[0023] A method for detecting thermal events in a battery and a battery system using the method are provided. Attached Figure Description

[0024] Figure 1 This is a diagram illustrating a battery system according to an exemplary embodiment.

[0025] Figure 2 and Figure 3 Each of these is a flowchart illustrating a method for determining the occurrence of a thermal event according to an exemplary embodiment. Detailed Implementation

[0026] In the following description, exemplary embodiments disclosed in this specification will be described in detail with reference to the accompanying drawings; however, identical or similar components will be indicated by identical or similar reference numerals, and overlapping descriptions thereof will be omitted. The terms "module" and / or "unit" used for components in the following description are for ease of explanation only. Therefore, these terms do not inherently have a meaning or function that distinguishes them from each other. Furthermore, detailed descriptions of related known technologies will be omitted when it is determined that a detailed description of the exemplary embodiments disclosed in this specification might unnecessarily obscure the essential points of the exemplary embodiments disclosed in this specification. Moreover, the accompanying drawings are provided only to aid in the easy understanding of the exemplary embodiments disclosed in this specification, and the spirit of the disclosure in this specification is not limited by the drawings. It should be understood that the spirit and scope of the invention include all modifications, equivalents, and substitutions.

[0027] Terms such as first and second ordinal numbers may be used to describe various components, but these components are not limited by these terms. These terms are used only for the purpose of distinguishing one component from another.

[0028] It should be understood that when a component is referred to as "connected to" another component, a component can be directly connected to another component, or connected to another component with an intermediary component in between. On the other hand, it should be understood that when a component is referred to as "directly connected to" another component, a component can be connected to another component without an intermediary component in between.

[0029] It should be understood that the terms "comprising," "having," etc., used in this application specify the presence of features, numbers, steps, operations, components, parts, or combinations thereof mentioned in the specification, but do not preclude the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0030] Figure 1 This is a diagram illustrating a battery system according to an exemplary embodiment.

[0031] The battery system 1 can be installed on the vehicle and connected to a power supply unit 3 for generating various power sources required to operate the vehicle and charge the battery system 1. The electronic control unit (ECU) 2 that controls the operation of the vehicle can send / receive information to / from the battery management system 20 via controller area network (CAN) communication.

[0032] The battery system 1 may include a battery pack 10, a battery management system (BMS) 20, a relay 30, a current sensor 40, a pressure sensor 50, a temperature sensor 60, and an insulation resistance calculation circuit 70.

[0033] Battery pack 10 includes multiple battery cells 11 to 15 connected in series with each other. Although in Figure 1 The diagram shows a battery pack 10 comprising five battery cells 11 to 15, but this is only an example and the invention is not limited thereto.

[0034] Relay 30 is connected between the positive terminal and the output terminal P+ of battery pack 10, and is opened or closed under the control of BMS 20. For example, relay 30 can be closed according to an on-level relay control signal (RCS) received from BMS 20, and can be opened according to an off-level relay control signal (RCS). Although in Figure 1Only one relay is shown, but this is merely an example, and the invention is not limited thereto. Another relay may be connected between the negative terminal of battery pack 10 and the output terminal P-.

[0035] The current sensor 40 can sense the current flowing through the battery pack 10 (hereinafter referred to as battery current), and the current sensor 40 can transmit a signal indicating the sensed current to the BMS 20.

[0036] Pressure sensor 50 may be located within battery pack 10 to measure the internal pressure of battery pack 10 in each sampling cycle and transmit the measured pressure to BMS 20. When the vehicle is parked, BMS 20 may enter sleep mode. During sleep mode, BMS 20 does not measure the voltage, temperature, insulation resistance, etc. of the cells in battery pack 10. During sleep mode of BMS 20, pressure sensor 50 may update the reference pressure based on the average value of the internal pressure measured in the sampling cycle during the sampling period, calculate a first pressure fluctuation based on the difference between the internal pressure measured in each sampling cycle and the reference pressure, and wake up BMS 20 when the first pressure fluctuation is greater than or equal to a predetermined threshold pressure.

[0037] In the vehicle's operating mode, the BMS 20 can receive the internal pressure measured by the pressure sensor 50, update the reference pressure based on the average value of the internal pressure measured in a sampling cycle during the sampling period, calculate a first pressure fluctuation based on the difference between the internal pressure measured in each sampling cycle and the reference pressure, and determine that a thermal event has occurred in the battery pack 10 when the first pressure fluctuation is equal to or greater than a predetermined threshold pressure. A thermal event means that heat is generated within the battery pack 10, which indicates a risk of fire, explosion, etc. The heat generated inside the battery pack 10 causes an increase in internal pressure. Therefore, in an exemplary embodiment, the occurrence of a thermal event can be detected by measuring the internal pressure of the battery pack 10.

[0038] The reference pressure is updated via BMS 20 in active mode or via pressure sensor 50 in sleep mode by averaging the internal pressure measured in sampling cycles during the sampling period. The sampling period is set from a time point prior to the current sampling time point to the current sampling time point. The reference voltage can be updated by BMS 20 in active mode or by pressure sensor 50 in sleep mode during each sampling period. Therefore, the reference pressure can be updated for each sampling cycle. Since the reference pressure is updated based on the average value of the sampling period, the influence of noise, which causes the internal pressure to be measured with peaks, can be reduced.

[0039] Even when the BMS 20 is in sleep mode, the pressure sensor 50, which needs to operate, is powered by the auxiliary power supply 4 instead of the battery pack 10. The auxiliary power supply 4 can be located separately in the battery system or in the vehicle.

[0040] Temperature sensor 60 can be installed within battery pack 10 to measure the temperature of each of the plurality of battery cells 11 to 15. Temperature sensor 60 can send a signal indicating the measured temperature of each of the plurality of battery cells 11 to 15 to BMS 20.

[0041] The BMS 20 can be connected to multiple battery cells 11 to 15 to measure the voltage of the multiple battery cells 11 to 15 and the voltage of the battery pack 10. It receives information including battery current, the temperature of the multiple battery cells 11 to 15, and the internal pressure of the battery pack 10. Based on the voltage and battery current of the multiple battery cells 11 to 15, it controls the charging / discharging current of the battery pack 10 and controls the cell balancing operation of the multiple battery cells 11 to 15.

[0042] To control the charging or discharging of the battery pack 10, the BMS 20 controls the relay 30 to open or close. The BMS 20 can generate and provide control signals (RCS) for controlling the opening or closing of the relay 30.

[0043] The BMS 20 controls the insulation resistance calculation circuit 70 to calculate the insulation resistance using the measurement voltages V1 and V2 required for the calculation. Figure 1 The diagram shows the insulation resistance RL1 between the positive terminal of battery pack 10 and ground, and the insulation resistance RL2 between the negative terminal of battery pack 10 and ground, connected to each other. This is an example used to describe the insulation resistances RL1 and RL2, and the invention is not limited thereto.

[0044] The insulation resistance calculation circuit 70 is connected between the positive and negative terminals of the battery pack 10 and grounded. The insulation resistance calculation circuit 70 includes two switches SW1 and SW2, four resistors R1 to R4, and a reference voltage source VR. Switch SW1, resistors R1 and R2 are connected between the positive terminal of the battery pack 10 and ground, while switch SW2, resistors R3 and R4, and the reference voltage source VR are connected between the negative terminal of the battery pack 10 and ground. Switch SW1 is switched according to a switch signal SC1 provided from the BMS 20, and switch SW2 is switched according to a switch signal SC2 provided from the BMS 20. The BMS 20 switches SW1 and SW2 on or off by generating each of the switch signals SC1 and SC2 as an on or off level signal.

[0045] The following section describes a method for determining the occurrence of thermal events using pressure sensors.

[0046] Figure 2 This is a flowchart illustrating a method for determining the occurrence of a thermal event according to an exemplary embodiment.

[0047] Figure 2 This is a flowchart illustrating a method for determining the occurrence of thermal events when the BMS 20 is in the active mode of vehicle operation.

[0048] First, pressure sensor 50 measures the internal pressure of battery pack 10 (S1). Pressure sensor 50 measures the internal pressure in each sampling cycle. For example, the sampling cycle can be 0.1 seconds.

[0049] Pressure sensor 50 sends the measured internal pressure to BMS 20. BMS 20 updates the reference pressure Pr based on the received internal pressure and calculates the pressure fluctuation Pde (S2) as the difference between the received internal pressure and the reference pressure. In this case, the reference pressure Pr is the average value of the internal pressure measured during a sampling period from a predetermined time period (e.g., 10 seconds) prior to the current internal pressure measurement time to the current internal pressure measurement time.

[0050] BMS 20 determines whether the pressure fluctuation Pde calculated in step S2 is greater than or equal to the threshold pressure Pth (S3). The threshold pressure can be set as the change in internal pressure of the battery pack, which is configured to identify cell venting when a thermal event occurs. That is, when the fluctuation in internal pressure of the battery pack 10 due to cell venting is greater than or equal to the threshold pressure, there may be a vented cell among the multiple battery cells 11 to 15. The threshold pressure Pth can be obtained experimentally and can be, for example, 1 kPa.

[0051] Pressure sensor 50 measures the internal pressure of battery pack 10 (S4). When the pressure fluctuation Pde is greater than or equal to the threshold pressure Pth as determined in step S3, BMS 20 calculates the pressure difference PDi (where i is a natural number) by subtracting the previously measured internal pressure (e.g., the internal pressure measured in step S1) from the currently measured internal pressure (e.g., the internal pressure measured in step S4) (S5).

[0052] BMS 20 determines whether the pressure difference PDi is greater than or equal to 0 (S6).

[0053] If, as determined in step S6, the pressure difference PDi is greater than or equal to 0, then BMS 20 increments the count value n by 1 (S7). Subsequently, BMS 20 determines whether the count value n is 2 (S8). In the exemplary embodiment, it is described that the pressure difference PDi is determined twice to be greater than or equal to 0 in order to determine whether the internal voltage continues to rise. However, the invention is not limited to this, and the pressure difference PDi may be determined three or more times depending on the design.

[0054] If the count value n, which is the result of the determination in step S8, is not 2, the process is repeated from step S4. If the count value n, which is the result of the determination in step S8, is 2, then BMS 20 determines that a thermal event has occurred (S9).

[0055] If, as determined in step S6, the pressure difference PDi is less than 0, then the process is repeated from step S1. If, as determined in step S3, the pressure fluctuation Pde is less than the threshold pressure Pth, then the process is repeated from step S1.

[0056] Figure 3 This is a flowchart illustrating a method for determining the occurrence of a thermal event according to an exemplary embodiment.

[0057] Figure 3 This is a flowchart illustrating a method for determining the occurrence of a thermal event when the BMS 20 is in a sleep mode where the vehicle is not in operation (such as when the vehicle is parked).

[0058] First, pressure sensor 50 measures the internal pressure of battery pack 10 (S11). Pressure sensor 50 measures the internal pressure in each sampling cycle. For example, the sampling cycle can be 0.66 seconds. That is, the sampling cycle in sleep mode is longer than the sampling cycle in active mode.

[0059] Pressure sensor 50 updates the reference pressure Pr based on the measured internal pressure and calculates the pressure fluctuation Pde as the difference between the measured internal pressure and the reference pressure (S12). In this case, the reference pressure Pr is the average value of the internal pressure measured during the sampling period from a predetermined period (e.g., 5 minutes) prior to the current internal pressure measurement time to the current internal pressure measurement time. That is, the sampling period in sleep mode is longer than the sampling period in activity mode.

[0060] Pressure sensor 50 determines whether the pressure fluctuation Pde calculated in step S12 is greater than or equal to the threshold pressure Pth (S13).

[0061] Pressure sensor 50 measures the internal pressure of battery pack 10 (S14). When the pressure fluctuation Pde is greater than or equal to the threshold pressure Pth, as determined in step S13, pressure sensor 50 sends a wake-up signal to BMS 20, and BMS 20 is woken up (S15).

[0062] BMS 20 calculates the pressure difference PDi (where i is a natural number) by subtracting the previously measured internal pressure (e.g., the internal pressure measured in step S11) from the currently measured internal pressure (e.g., the internal pressure measured in step S14) (S16).

[0063] BMS 20 determines whether the pressure difference PDi is greater than or equal to 0 (S17).

[0064] If, as a result of the determination in step S17, the pressure difference PDi is greater than or equal to 0, then BMS 20 increments the count value n by 1 (S18). Subsequently, BMS 20 determines whether the count value n is 2 (S19). In the exemplary embodiment, it is described that the pressure difference PDi is determined twice to be greater than or equal to 0 in order to determine whether the internal voltage continues to rise. However, the invention is not limited to this, and the pressure difference PDi may be determined three or more times depending on the design.

[0065] If the count value n, which is the determination result in step S19, is not 2, the process is repeated from step S14. If the count value n, which is the determination result in step S19, is 2, then BMS 20 determines that a thermal event has occurred (S20).

[0066] If, as determined in step S17, the pressure difference PDi is less than 0, then the process is repeated from step S11. If, as determined in step S13, the pressure fluctuation Pde is less than the threshold pressure Pth, then the process is repeated from step S11.

[0067] When a thermal event is determined to have occurred, BMS 20 can determine whether the measured cell voltage is greater than or equal to a predetermined threshold voltage, whether the cell temperature received from temperature sensor 60 is greater than or equal to a predetermined threshold temperature, or whether the insulation resistance measured using insulation resistance calculation circuit 70 is less than or equal to a threshold resistance indicating that the insulation has broken down. When at least one of the following conditions is met—that the measured cell voltage is greater than or equal to the threshold voltage, that the cell temperature is greater than or equal to the threshold temperature, and that the insulation resistance is less than or equal to the threshold resistance—BMS 20 can notify ECU 2 of a risk of fire or explosion, causing relay 30 to be blocked.

[0068] As described above, according to the exemplary embodiment, thermal events can be detected even in the sleep and active modes of the BMS, thereby preventing not only fires in the battery pack, but also fires in the vehicle caused by fires in the battery pack.

[0069] While the invention has been described in conjunction with exemplary embodiments now considered practical, it should be understood that the invention is not limited to the disclosed embodiments. Rather, the invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. A battery system comprising: The battery pack includes multiple battery cells; A pressure sensor is used to measure the internal pressure of the battery pack in each sampling cycle; as well as A battery management system is configured to update a reference pressure based on the average internal pressure measured in each sampling cycle during a sampling period, calculate a pressure fluctuation based on the difference between the internal pressure measured in each sampling cycle and the reference pressure, and determine that a thermal event has occurred in the battery pack if the internal pressure measured in each sampling cycle increases at least twice consecutively when the pressure fluctuation is greater than or equal to a predetermined threshold pressure. Specifically, when the battery management system is in active mode, the reference pressure is updated by the battery management system in each sampling period based on the average value of the internal pressure measured in each sampling cycle during the sampling period, and When the battery management system is in sleep mode, the reference pressure is updated by the pressure sensor in each sampling period based on the average value of the internal pressure measured in each sampling cycle of the sampling period.

2. The battery system according to claim 1, wherein, When the battery management system is in sleep mode The calculation of the pressure fluctuation and the determination of whether the pressure fluctuation is greater than or equal to the threshold pressure are performed by the pressure sensor.

3. The battery system according to claim 1, wherein When the battery management system is in sleep mode If the pressure fluctuation is greater than or equal to the predetermined threshold pressure, the battery management system is activated via the pressure sensor.

4. The battery system according to claim 3, wherein After the battery management system is activated, if the internal pressure measured in each sampling cycle increases at least twice consecutively, the battery management system determines that the battery pack is abnormal.

5. The battery system according to claim 1, wherein After confirming that the thermal event has occurred, the battery management system measures the voltage and temperature of the plurality of battery cells and the insulation resistance between the battery pack and ground, and If at least one of the voltage of the plurality of battery cells, the temperature of the plurality of battery cells, and the insulation resistance is abnormal, the battery pack is determined to be abnormal.

6. The battery system according to claim 1, wherein The battery management system determines that the battery pack is abnormal if at least one of the following conditions is met: a first condition that at least one of the voltages of the plurality of battery cells is greater than or equal to a threshold voltage; a second condition that at least one of the temperatures of the plurality of battery cells is greater than or equal to a threshold temperature; and a third condition that the insulation resistance between the battery pack and ground is less than or equal to a predetermined threshold resistance.

7. The battery system according to claim 5, further comprising: A relay connects the battery pack to the output terminals of the battery system. When the battery management system determines that the battery pack is malfunctioning, it disconnects the relay.

8. The battery system according to claim 5, wherein The battery management system notifies the vehicle, including the battery system, of a battery pack malfunction.

9. The battery system according to claim 1, further comprising: An auxiliary power supply that supplies power to the pressure sensor.

10. A method for detecting thermal events in a battery system, the battery system comprising a battery pack, a pressure sensor, and a battery management system, the battery pack comprising multiple battery cells, the method for detecting thermal events comprising the following steps: The internal pressure of the battery pack is measured using the pressure sensor in each sampling cycle; The reference pressure is updated based on the average value of the internal pressure measured in each sampling cycle during the sampling period; The pressure fluctuation is calculated based on the difference between the internal pressure measured in each sampling cycle and the reference pressure. Determine whether the pressure fluctuation is greater than or equal to a predetermined threshold pressure; as well as If the pressure fluctuation is greater than or equal to the threshold pressure, and the internal pressure measured in each sampling cycle increases at least twice consecutively, then a thermal event has been determined to have occurred in the battery pack. Specifically, when the battery management system is in active mode, the reference pressure is updated by the battery management system in each sampling period based on the average value of the internal pressure measured in each sampling cycle during the sampling period, and When the battery management system is in sleep mode, the reference pressure is updated by the pressure sensor in each sampling period based on the average value of the internal pressure measured in each sampling cycle of the sampling period.

11. The thermal event detection method according to claim 10, wherein... When the battery management system is in sleep mode The calculation of the pressure fluctuation and the determination of whether the pressure fluctuation is greater than or equal to the threshold pressure are performed by the pressure sensor.

12. The thermal event detection method according to claim 10, further comprising: When the battery management system is in sleep mode, if the pressure fluctuation is greater than or equal to the threshold pressure, the battery management system is woken up by the pressure sensor.

13. The thermal event detection method according to claim 11, wherein... After the battery management system is woken up, the battery management system performs the determination of the occurrence of the thermal event in the battery pack.

14. The thermal event detection method according to claim 13, wherein... Determining the occurrence of the thermal event in the battery pack includes: The pressure difference is calculated by subtracting the internal pressure measured in a previous sampling cycle from the internal pressure measured in the current sampling cycle. Determine whether the calculated pressure difference is greater than or equal to 0; as well as If the calculated pressure difference is greater than or equal to 0, then the internal pressure is determined to have increased.

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