Battery module anomaly detection device

Abstract

In a battery module with multiple batteries connected in parallel, a break in the connection can be detected in a short time. [Solution] The battery module has multiple batteries connected in parallel. The battery ECU calculates a first voltage value Uocv(k) corresponding to the OCV of the battery module from the terminal voltage VB and input / output current IB of the battery module (S10), and subtracts the previous first voltage value Uocv(k-1) to obtain the first voltage change ΔUocv (S11). Using the SOC-OCV characteristics from the SOC estimated by the Coulomb counting method, the second voltage value OCV(k) is calculated (S12), and subtracts the previous second voltage value OCV(k-1) to obtain the second voltage change ΔOCV (S13). When the difference between the first voltage change ΔUocv and the second voltage change ΔOCV is greater than or equal to a threshold α, it is determined that a break has occurred in the battery module (S15, S16).

Description

Technical Field

[0001] The present disclosure relates to an abnormality detection device for a battery module, and particularly to an abnormality detection device for a battery module in which a plurality of batteries are connected in parallel.

Background Art

[0002] Japanese Patent Application Laid-Open No. 2018-73708 (Patent Document 1) discloses a disconnection detection system for a secondary battery in which a plurality of battery cells are connected in parallel. In this disconnection detection system, a salt concentration difference in a salt concentration distribution between the positive and negative electrodes of a battery cell is calculated, and when the salt concentration difference is greater than a determination salt concentration difference, disconnection detection by a resistance method is permitted. Thereby, it is said that false detection can be suppressed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In Patent Document 1, when the salt concentration difference of a battery cell is greater than the determination salt concentration difference, disconnection detection is performed. It takes time until a salt concentration difference occurs as the resistance of the battery cell increases. Therefore, there is a concern that the disconnection detection device of Patent Document 1 takes time until disconnection can be detected after disconnection occurs.

[0005] An object of the present disclosure is to detect disconnection in a short time in a battery module in which a plurality of batteries are connected in parallel.

Means for Solving the Problems

[0006] The abnormality detection device of this disclosure is an abnormality detection device for a battery module in which multiple batteries are connected in parallel. The abnormality detection device comprises: a first calculation means that estimates a first voltage value of the battery module based on the terminal voltage of the battery module and calculates a first voltage change amount, which is the amount of change in the first voltage value over a predetermined period; a second calculation means that estimates a second voltage value of the battery module based on the current flowing through the battery module and calculates a second voltage change amount, which is the amount of change in the second voltage value over the predetermined period; and a determination unit that determines that a wire break has occurred when the difference between the first voltage change amount and the second voltage change amount is greater than or equal to a threshold.

[0007] In this configuration, the abnormality detection device includes a determination unit that determines whether there is a break in the ionization module, which consists of multiple batteries connected in parallel. The determination unit determines that a break has occurred when the difference between the first voltage change and the second voltage change is greater than or equal to a threshold.

[0008] The first calculation means estimates a first voltage value based on the terminal voltage of the battery module and calculates a first voltage change, which is the amount of change in the first voltage value over a predetermined period. The first voltage value may be the open circuit voltage (OCV) of the battery module estimated from the terminal voltage of the battery module. The predetermined period may be, for example, the calculation period for calculating the first voltage value, and the difference between the first voltage value calculated previously and the first voltage value calculated this time is calculated as the first voltage change.

[0009] The second calculation means estimates a second voltage value based on the current flowing through the battery module and calculates a second voltage change, which is the amount of change in the second voltage value over the predetermined period. The second voltage value may be the OCV of the battery module, obtained from the State of Charge (SOC)-OCV characteristics (SOC-OCV curve) of the battery module. The SOC is estimated based on the current flowing through the battery module using the Coulomb counting method. Using the estimated SOC, the OCV is determined from the SOC-OCV characteristics and the second voltage value is calculated. The calculation periods for the second voltage value and the first voltage value may be the same; for example, the difference between the second voltage value calculated previously and the second voltage value calculated this time is calculated as the second voltage change.

[0010] The detection unit determines that a disconnection has occurred in the battery module when the difference between the first voltage change and the second voltage change is greater than or equal to a threshold. When a disconnection occurs in one of the paths of batteries connected in parallel, the current flowing through the undisconnected path increases. As a result, the discrepancy between the amount of change in the first voltage value estimated based on the terminal voltage (first voltage change) and the amount of change in the second voltage value estimated based on the current flowing through the battery module (second voltage change) becomes large. Therefore, when the difference between the first voltage change and the second voltage change is greater than or equal to a threshold, it can be determined that a disconnection has occurred in the battery module. Since the disconnection is determined from the discrepancy between the first voltage change and the second voltage change, it is possible to detect the disconnection in a short time. [Effects of the Invention]

[0011] According to this disclosure, a battery module in which multiple batteries are connected in parallel can detect a disconnection in a short amount of time. [Brief explanation of the drawing]

[0012] [Figure 1] This is a schematic overall configuration diagram of the battery module abnormality detection device according to this embodiment. [Figure 2] This flowchart shows an example of a wire break detection process performed by the battery ECU. [Figure 3] This is a diagram illustrating the equivalent circuit model of a battery module. [Modes for carrying out the invention]

[0013] The embodiments of this disclosure will be described in detail below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and their descriptions will not be repeated.

[0014] Figure 1 is a schematic overall configuration diagram of the abnormality detection device S for the battery module 100 according to this embodiment. The battery module 100 includes a plurality of batteries 10 connected in parallel. The number of batteries 10 can be any number, as long as it is two or more. The battery 10 may be configured by connecting a plurality of single cells 10A in series. Alternatively, the battery 10 may consist of a single cell. The single cell 10A may be, for example, a lithium-ion battery.

[0015] Multiple battery modules 100 are connected in series to form a battery pack 1. The number of battery modules 100 constituting the battery pack 1 can be arbitrary. In this embodiment, n battery modules 100 are connected in series to form the battery pack 1. The battery pack 1 is used, for example, as a drive battery for an electric vehicle and is configured to be rechargeable (externally charged) by power from a charging facility (not shown). Furthermore, when the electric vehicle is braked, the battery pack 1 (drive battery) may be charged by regenerative power.

[0016] The monitoring module 20 detects the terminal voltage VB of the battery module 100, the current IB input and output to the battery module 100, the temperature TB of the battery module 100, etc. For example, the terminal voltage VB is detected by the voltage sensor 21, and the current IB is detected by the current sensor 22. The sign of the current IB differs depending on the direction of current flow; it has a positive (+) sign when the battery module 100 is being charged, and a negative (-) sign when the battery module 100 is being discharged. The monitoring module 20 estimates the state of charge (SOC) of the battery module 100 using the Coulomb count method by integrating the current IB. The monitoring module 20 outputs the terminal voltage VB, current IB, temperature TB, SOC, etc. to the battery ECU (Electronic Control Unit) 30. The monitoring module 20, battery ECU 30, etc. correspond to an example of the "abnormality detection device" in this disclosure.

[0017] Figure 2 is a flowchart showing an example of the wire break detection process performed by the battery ECU 30. This flowchart is executed for each battery module 100 and is repeated at predetermined intervals. In step 10 (hereinafter, steps are abbreviated as "S"), the first voltage value Uocv(k) is calculated from the terminal voltage VB and current IB. The first voltage value Uocv(k) is the OCV of the battery module 100, estimated based on the terminal voltage VB.

[0018] Figure 3 is a diagram illustrating the equivalent circuit model of the battery module 100. The equivalent model in this embodiment is an equivalent circuit model in which multiple batteries 10 connected in parallel are treated as a single cell. Voltage changes during battery charging and discharging involve a mixture of fast reactions due to electrolyte resistance and charge transfer resistance, etc., and slow reactions due to the increase in diffusion resistance. The equivalent circuit model in Figure 3 is a well-known model that approximates the fast reactions with a resistive component Ra and represents the diffusion phenomenon inside the electrodes with a parallel circuit of Rb and Cb. In this equivalent circuit model, the approximation formulas (identification formulas) (1) to (5) shown within the dashed lines in Figure 3 hold true. VB(k) is the current terminal voltage VB, and VB(k-1) is the previous terminal voltage VB. IB(k) is the current IB, and IB(k-1) is the current IB mentioned above. Ts is the calculation period (operation period). Uocv is the OCV of the single cell in the equivalent circuit model and corresponds to the first voltage value Uocv. For example, the unknown parameters (b0, b1, a1, f) in approximation equations (1) to (5) can be estimated using the least squares method with a forgetting factor, and by performing sequential calculations, Uocv can be calculated from approximation equation (5) as "Uocv = f / (1 + a1)". In S10, Uocv is calculated from the terminal voltage VB and current IB using the equivalent circuit model in Figure 3, and this is the first voltage value Uocv(k) in this case.

[0019] In the subsequent S11, the absolute value of the value obtained by subtracting the previous first voltage value Uocv(k−1) (the previously calculated Uocv) from the current first voltage value Uocv(k) is calculated as the first voltage change amount ΔUocv (ΔUocv = |Uocv(k)−Uocv(k−1)|). The first voltage value Uocv(k−1) is stored in the memory of the battery ECU 30. The first voltage value Uocv(k−1) is read from the memory, and the first voltage change amount ΔUocv is calculated.

[0020] In S12, the current second voltage value OCV(k) is calculated from the SOC estimated by the monitoring module 20. The monitoring module 20 estimates the SOC of the battery module 100 by the Coulomb counting method at the same operation cycle as the flowchart of FIG. 2. In S12, with the latest SOC as a parameter, OCV is calculated from the SOC-OCV characteristics and used as the current second voltage value OCV(k). The SOC-OCV characteristics of the battery module 100 may be set in advance by experiments or the like.

[0021] In S13, the absolute value of the value obtained by subtracting the previous second voltage value OCV(k−1) (the OCV calculated from the SOC previously) from the current second voltage value OCV(k) is calculated as the second voltage change amount ΔOCV (ΔOCV = |OCV(k)−OCV(k−1)|). The second voltage value OCV(k−1) is stored in the memory of the battery ECU 30. The second voltage value OCV(k−1) is read from the memory, and the second voltage change amount ΔOCV is calculated.

[0022] In S14, the first voltage value Uocv(k) calculated in S10 is stored in the memory as the previous first voltage value Uocv(k−1), and the second voltage value OCV(k) calculated in S12 is stored in the memory as the previous second voltage value OCV(k−1).

[0023] In the subsequent S15, it is determined whether the difference between the first voltage change amount ΔUocv and the second voltage change amount ΔOCV is equal to or greater than the threshold value α. If the difference between the first voltage change amount ΔUocv and the second voltage change amount ΔOCV is equal to or greater than the threshold value α (|ΔUocv - ΔOCV≧α), an affirmative determination is made and the process proceeds to S16. If the difference between the first voltage change amount ΔUocv and the second voltage change amount ΔOCV is less than the threshold value α (|ΔUocv - ΔOCV < α), a negative determination is made and the current routine ends.

[0024] In S16, it is determined that a disconnection has occurred in the battery module 100, and the current routine ends. When a disconnection in the battery module 100 is detected, an alarm of the disconnection may be displayed on the display unit of the HMI (Human Machine Interface) device 40. Also, the MIL (Malfunction Indicator Lamp) may be lit.

[0025] In the battery module 100 in which a plurality of batteries 10 are connected in parallel, when a disconnection occurs in the path of any one of the batteries 10, the current flowing through the non-disconnected path increases. In the present embodiment, the SOC estimated based on the current IB using the Coulomb counting method is calculated from the SOC-OCV characteristics on the premise that no disconnection has occurred even when a disconnection has occurred. Therefore, in the battery module 100, when a disconnection occurs, the change amount of the first voltage value Uocv estimated based on the terminal voltage (terminal voltage) VB (first voltage change amount ΔUocv) and the change amount of the second voltage value OCV estimated based on the current IB flowing through the battery module 100 (second voltage change amount ΔOCV) deviate greatly. Therefore, when the difference between the first voltage change amount ΔUocv and the second voltage change amount ΔOCV is equal to or greater than the threshold α, it can be determined that a disconnection has occurred in the battery module 100. Since the disconnection is determined from the deviation between the first voltage change amount ΔUocv and the second voltage change amount ΔOCV, the disconnection can be detected in a short time. The threshold value α may be set in consideration of the estimation error of the SOC and the estimation accuracy of the equivalent circuit model in FIG. 3.

[0026] Note that S10 and S11 in Figure 2 correspond to an example of the "first calculation means" of this disclosure, and S12 and S13 correspond to an example of the "second calculation means" of this disclosure. S15 and S16 correspond to an example of the "determination unit" of this disclosure.

[0027] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than by the description of the embodiments above, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of symbols]

[0028] 1 battery pack, 10 batteries, 10A single cell (battery cell), 20 monitoring modules, 21 voltage sensor, 22 current sensor, 30 battery ECU, 40 HMI device, S anomaly detection device.

Claims

[Claim 1] An abnormality detection device for a battery module in which multiple batteries are connected in parallel, A first calculation means estimates a first voltage value of the battery module based on the terminal voltage of the battery module and calculates a first voltage change amount, which is the amount of change in the first voltage value over a predetermined period. A second calculation means that estimates a second voltage value of the battery module based on the current flowing through the battery module and calculates a second voltage change amount, which is the amount of change in the second voltage value during the predetermined period, An abnormality detection device for a battery module, comprising: a determination unit that determines that a wire break has occurred when the difference between the first voltage change and the second voltage change is greater than or equal to a threshold; and a determination unit that determines that a wire break has occurred.

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