Battery management device

Abstract

To attain appropriate management of a battery including a battery cell by accurately discriminating whether a detected abnormality of the battery cell is deterioration of a connection state between the battery cell and a bus bar or deterioration of the battery cell.SOLUTION: A battery management device 12 is a system for managing states of a plurality of battery cells 14 constituting a battery 11. Terminals 18a and 18b of the battery cells 14 are mutually connected by bus bars 19. The battery management device comprises: a temperature detection section 17 capable of detecting a temperature Tp of a connection part 20a between one terminal 18a of the battery cell 14 and the bus bar 19 and a temperature Tc in a central part 21a between both the terminals 18a and 18b in a sheath body 21 of the battery cell 14; and a connection abnormality determination section 15 which determines the presence / absence of a connection abnormality between the battery cell 14 and the bus bar 19 based on a comparison result of the temperature Tp of the connection part 20a and the temperature Tc in the central part 21a of the sheath body 21, the temperatures being detected by the temperature detection section 17.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a battery management device, and more particularly to a technique for enabling appropriate monitoring of the connection state between battery cells and bus bars that constitute a battery. [Background technology]

[0002] Conventionally, devices called BMS (battery management systems) are used to manage the status of batteries, also known as secondary batteries, in order to extend their lifespan and ensure their safety. The BMS mainly monitors the voltage, current, temperature, etc. of the entire battery, and also monitors the voltage, current, etc. of the battery cells that make up the battery, making it possible to detect abnormalities in the battery cells.

[0003] For example, Patent Document 1 proposes a method for detecting the current and voltage of each unit cell of a battery pack, estimating the internal resistance of each unit cell based on the detected current and voltage values, and diagnosing the presence or absence of degradation of each unit cell based on the usable capacity and usable output derived from the estimated internal resistance. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2011-257372 A Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, this type of battery cell abnormality may be caused not only by the deterioration of the battery cell due to the increase in internal resistance described above, but also by a deterioration in the connection between each electrode terminal of the battery cell and the bus bar (connection abnormality). That is, with continued use of the battery cell, the bolts fastening the bus bar to the battery cell may loosen, or a part of the joint joining the bus bar to the battery cell may peel off, and this deterioration in the connection may be a factor in fluctuations in parameters such as the current value and temperature. Therefore, by simply monitoring each parameter in the conventional manner, it is difficult to determine whether the fluctuation in the parameter is due to the deterioration of the battery cell or the occurrence or progression of a connection abnormality between the battery cell and the bus bar.

[0006] In view of the above circumstances, the technical problem to be solved in this specification is to make it possible to accurately determine whether a detected abnormality in a battery cell is due to a deterioration in the connection between the battery cell and the bus bar or due to deterioration of the battery cell, thereby enabling appropriate management of the battery including the battery cell. [Means for solving the problem]

[0007] The above-mentioned problems are solved by a battery management device according to the present invention. That is, the battery management device is a system for managing the states of a plurality of battery cells constituting a battery, in which terminals of the battery cells are connected to each other by a bus bar, and is characterized in that it includes a temperature detection unit capable of detecting the temperature of a connection between one terminal of the battery cell and the bus bar and the temperature of a central portion between both terminals of an exterior body of the battery cell, and a connection abnormality determination unit that determines the presence or absence of a connection abnormality between the battery cell and the bus bar based on a result of comparing the temperature of the connection detected by the temperature detection unit with the temperature of the central portion of the exterior body.

[0008] The inventors focused on the difference in temperature change between the connection between the terminal of each battery cell and the bus bar and the temperature at the center of the battery cell's exterior body between the two terminals, and discovered that by comparing the two temperatures, it is possible to determine whether a detected abnormality in a battery cell is due to a deterioration in the connection with the bus bar or deterioration of the battery cell. The present invention was made based on the above findings, and detects the temperature of the connection between one terminal of the battery cell and the bus bar, and the temperature at the center of the battery cell's exterior body between the two terminals, and determines the presence or absence of a connection abnormality between the battery cell and the bus bar based on a comparison result between the temperature of the connection obtained thereby and the temperature at the center of the exterior body. For example, when the battery is in discharge mode, if the temperature of the center of the exterior body of the battery cell is always higher than the temperature of the connection between the terminal of the battery cell and the bus bar, and if the manner of temperature change of the center of the exterior body according to the discharged current is constant and the temperature of the connection between the terminal of the battery cell and the bus bar exceeds the temperature of the center of the exterior body, it can be considered that the connection between the terminal of the battery cell and the bus bar is excessively heated, which in turn reduces the connection area of ​​the connection, and it can be determined that a connection abnormality has occurred in the connection.On the other hand, if, for example, the temperature difference between the temperature of the connection and the temperature of the center of the exterior body when a predetermined voltage drop is observed in the battery cell does not change (is roughly constant) before and after the voltage drop, it can be determined that the battery cell has deteriorated due to an increase in the internal resistance of the battery cell.

[0009] As described above, according to the battery management device of the present invention, when an abnormality in a battery cell is detected by a conventional voltage monitoring method, it is possible to determine with high accuracy whether the abnormality is a connection abnormality in the connection between the terminal of the battery cell and the bus bar. Therefore, it is possible to perform appropriate processing on the target connection and to avoid unnecessary replacement of the battery cell based on a misidentification of the battery cell as deterioration, thereby reducing the cost of parts (replacement cost) and labor required for the battery cell. Of course, by detecting an abnormality in the connection, it is possible to discover the risk of an external short circuit at an early stage, and therefore to prevent accidents before they occur.

[0010] In addition, the battery management device of the present invention may further include a potential difference detection unit capable of detecting the potential difference between the positive electrode side of the battery cell and the outer casing, and the potential difference between the negative electrode side and the outer casing, and the connection abnormality determination unit may select the connection between the bus bar and the terminal on the electrode side where a predetermined potential difference is detected between the electrode cell and the outer casing, as the target for comparing the temperature with the center of the outer casing.

[0011] Whether the terminals of the positive electrode side and the negative electrode side of the battery cell have the same potential with respect to the exterior body is determined by the structure of the battery cell (particularly, whether an insulating member is arranged on either the positive electrode side or the negative electrode side, or on both sides). Therefore, for example, if the battery cell is designed in-house, there is no problem, but if not, it is necessary to confirm in advance which of the positive electrode side and the negative electrode side of the battery cell has the same potential with respect to the exterior body. In this configuration, since it is possible to detect the potential difference between the positive electrode side of the battery cell and the exterior body and the potential difference between the negative electrode side and the exterior body, it is possible to detect which of the positive electrode side and the negative electrode side of the battery cell has the same potential with the exterior body. Therefore, by comparing the temperature of the connection between the terminal on the electrode side where a potential difference is found with the exterior body and the bus bar with the temperature of the center part of the exterior body, it is possible to determine the presence or absence of a connection abnormality in the connection between the terminal on the side where a connection abnormality may occur and the bus bar. Therefore, it is possible to expand the application range of the present invention and improve the versatility of the battery management device according to the present invention. Effect of the Invention

[0012] As described above, the battery management device of the present invention can accurately determine whether a detected abnormality in a battery cell is due to a deterioration in the connection between the battery cell and the bus bar or due to deterioration of the battery cell, thereby enabling proper management of the battery including the battery cells. [Brief description of the drawings]

[0013] [Figure 1] 1 is a diagram showing an overall configuration of a battery system according to an embodiment of the present invention; [Diagram 2]2 is a diagram conceptually showing a connection state of a temperature detection unit shown in FIG. 1 to a battery cell. [Diagram 3] 11 is a perspective view of a battery pack according to an example of a selection criterion for battery cells that are targets of detection by a temperature detection unit; FIG. [Figure 4] 13 is a perspective view of a battery pack according to another example of the selection criteria for battery cells to be detected by the temperature detection unit; FIG. [Diagram 5] 4 is a flowchart showing an example of a method for detecting a connection abnormality using the battery management device shown in FIG. [Figure 6] 13 is a graph showing an example of the temperature history of the connection portion and the temperature history of the center portion of the exterior body when the connection state between the terminal of the battery cell and the bus bar is normally maintained during the discharge mode. [Figure 7] 13 is a graph showing an example of the temperature history of the connection portion and the temperature history of the center portion of the exterior body when the connection state between the terminal of the battery cell and the bus bar deteriorates during the discharge mode. [Figure 8] 13 is a graph showing another example of the temperature history of the connection portion and the temperature history of the center portion of the exterior body when the connection state between the terminal of the battery cell and the bus bar deteriorates during the discharge mode. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A battery management device according to an embodiment of the present invention and a method for detecting an abnormal connection between a battery cell and a bus bar using the battery management device will be described below with reference to the drawings.

[0015] 1 shows the overall configuration of a battery system 10 according to one embodiment of the present invention. This battery system 10 includes a battery 11, a battery management device 12 that manages the state of the battery 11, and an external power source 13. In this embodiment, a description will be given of an example in which the battery system according to the present invention is applied to a vehicle powered by a motor. Note that the vehicle powered by a motor includes not only an electric vehicle that does not have an internal combustion engine, but uses only a motor as a power source and supplies power to the motor from a chargeable and dischargeable battery (corresponding to the battery 11 in this embodiment), but also a hybrid vehicle that uses both an internal combustion engine and a motor as a power source and supplies power to the motor from a chargeable and dischargeable battery.

[0016] The battery 11 is, for example, a battery cell 14 connected in series, and is a secondary battery suitable for vehicle use, such as a lithium ion battery. 0 The electromotive force of the battery 11 formed by connecting a plurality of these battery cells 14 in series is on the order of 10 1 ~10 2 V order (e.g. 10 1 If it is V order, it is 40~50V, 10 2 Therefore, depending on the required electromotive force of the battery 11, a number ranging from several to several tens of battery cells 14 are connected in series.

[0017] The battery management unit 12 has a monitoring unit 15 that monitors the state of the battery 11. This monitoring unit 15 corresponds to a connection abnormality determination unit according to the present invention. Although not shown in the drawings, the battery management unit 12 may further have elements other than the monitoring unit 15, such as a cell balance circuit for leveling the voltages among the multiple battery cells 14, as necessary.

[0018] The monitoring unit 15 is configured to monitor the state of the battery 11, and when it is determined to be necessary based on the monitoring result, to transmit a predetermined command to the ECU 16 of the vehicle (not shown) in which the battery management device 12 is mounted. Specifically, the monitoring unit 15 has various detection units including the temperature detection unit 17 shown in FIG. 2, and an MCU (both not shown) serving as a host computer. The monitoring unit 15 detects various parameters indicating the state of the battery 11, such as the voltage, current, and temperature of the entire battery 11, by the various detection units including the temperature detection unit 17, analyzes the various detected parameters by the MCU, and determines whether any abnormality has occurred in the battery 11. When it is determined that any abnormality has occurred, the monitoring unit 15 transmits a command according to the content of the abnormality to the ECU 16. The monitoring unit 15 also detects and analyzes various parameters indicating the state of each of the multiple battery cells 14 constituting the battery 11, such as the temperature, voltage, and current, and determines whether any abnormality has occurred in each of the battery cells 14. When it is determined that an abnormality has occurred, the monitoring unit 15 transmits a command according to the content of the abnormality to the ECU 16 (details will be described later). The monitoring of the battery 11 by the monitoring unit 15 described above is mainly performed when the battery 11 is being charged or discharged, but may also be performed when the battery 11 is on standby (when neither charging nor discharging is being performed).

[0019] 2 conceptually illustrates a connection between the temperature detection unit 17 of the monitoring unit 15 and each battery cell 14 of the battery 11. As illustrated in FIG. 2, the temperature detection unit 17 is configured to be able to detect a temperature Tp of a connection portion 20a between the positive terminal 18a of the battery cell 14 and the bus bar 19, a temperature Tn of a connection portion 20b between the negative terminal 18b of the battery cell 14 and the bus bar 19, and a temperature Tc of a central portion 21a between the two terminals 18a, 18b of the exterior body 21 of the battery cell 14.

[0020] As will be described later, when it is known in advance which terminal 18a, 18b in the battery cell 14 to be detected has a potential difference between it and the exterior body 21, the temperature detection unit 17 may be configured to detect only the temperature Tp of the connection between the electrode side terminal where the potential difference occurs and the bus bar 19 (in FIG. 2, the connection 20a between the positive electrode side terminal 18a and the bus bar 19) and the temperature Tc of the central part 21a of the exterior body 21.

[0021] As shown in FIG. 2, when the temperature detection unit 17 detects the temperature of a specific battery cell 14 among the multiple battery cells 14, the battery cell 14 to be detected can be any battery cell in principle. On the other hand, as shown in FIG. 3 and FIG. 4, when the multiple battery cells 14 are modularized, it is preferable to detect the temperature of the battery cell 14 arranged in a position that is less susceptible to the surrounding environment, such as the outside air, among the multiple battery cells 14 constituting each module 22a, 22b. For example, when the module 22a is configured as shown in FIG. 3, it is preferable to detect the temperature of the battery cell 14 (14a) in the center surrounded by the multiple battery cells 14. Alternatively, when the module 22b is configured as shown in FIG. 4, it is preferable to detect the temperature of the battery cell 14 (14b) sandwiched on both sides by the battery cells 14 and located at the center in the direction in which the multiple battery cells 14 are arranged in parallel.

[0022] The battery cell 14 to be detected does not have to be one per battery 11 (module 22a), and for example, two or more battery cells 14 may be targets for temperature detection.

[0023] Next, an example of a method for detecting a connection abnormality according to the present invention using the battery management device 12 (monitoring unit 15) configured as described above will be described mainly with reference to the flowchart shown in FIG.

[0024] First, in the monitoring method (detection method) according to this embodiment, the discharge mode of the battery system 10 is started by an operator (step S1). Then, for example, during the discharge mode, the voltage and current of each battery cell 14 constituting the battery 11 are detected at predetermined time intervals by a voltage detection unit and a current detection unit (not shown), and the presence or absence of an abnormality in each battery cell 14 is determined based on the magnitude of the detected voltage and current (step S2). Here, for example, if the detected voltage drops beyond an allowable range, it is determined that some abnormality has occurred in the battery cell 14 to be detected.

[0025] In this case, the temperature detection unit 17 then detects the temperature of the target battery cell 14, in this case the temperature Tp of the connection 20a between the electrode side terminal (here the positive electrode side terminal 18a) where a predetermined potential difference occurs between the outer casing 21 and the bus bar 19, and the temperature Tc of the central part 21a of the outer casing 21 of the battery cell 14 in question.

[0026] Thereafter, the detected temperature Tp of the connection part 20a is compared with the temperature Tc of the central part 21a of the exterior body 21, and the presence or absence of an abnormality (connection abnormality) in the connection part 20a is determined based on the comparison result (step S3). In this embodiment, the magnitude relationship between the temperature Tp of the connection part 20a and the temperature Tc of the central part 21a is compared. Then, if the magnitude relationship between the temperature Tp and the temperature Tc coincides with the magnitude relationship between the temperature Tp and the temperature Tc during the discharge mode in the normal state (see FIG. 6), that is, if the detected temperature Tc of the central part 21a is higher than the temperature Tp of the connection part 20a, it is determined that there is no connection abnormality in the connection part 20a. In this case, if it is determined in step S2 that some abnormality has occurred in the target battery cell 14, it is determined that the battery cell 14 has deteriorated due to an increase in internal resistance (step S4).

[0027] In this case, the discharge mode continues without being stopped, and the monitoring unit 15 transmits a command to the ECU 16 to replace the target battery cell 14, for example.

[0028] Alternatively, in step S3, if the magnitude relationship between temperatures Tp and Tc is reversed from the magnitude relationship between temperatures Tp and Tc during normal discharge mode (see FIG. 6), that is, if the detected temperature Tp of connection part 20a is greater than the temperature Tc of central part 21a (see FIG. 7), it is determined that connection part 20a has generated excessive heat and that a connection abnormality has occurred between positive terminal 18a and bus bar 19 (step S5).

[0029] In this case, the discharge mode continues without being stopped, and the monitoring unit 15 transmits a command to the ECU 16 to, for example, limit the current output or to issue a warning.

[0030] The above-described series of steps S1 to S5 are repeatedly executed while the discharge mode continues, which allows not only deterioration of each battery cell 14 but also the occurrence of an abnormal connection between each battery cell 14 and the bus bar 19 to be detected early.

[0031] As described above, the battery management device 12 according to this embodiment detects the temperature Tp of the connection 20a between one terminal (here, the positive terminal 18a) of the battery cell 14 and the bus bar 19, and the temperature Tc at the center 21a between the two terminals 18a, 18b of the exterior body 21 of the battery cell 14, and can thus determine with high accuracy whether the abnormality of the battery cell 14 is due to deterioration of the battery cell 14 or due to an abnormal connection with the bus bar 19. Therefore, appropriate processing can be performed on the target connection 20a, and unnecessary replacement of the battery cell 14 based on a misidentification of deterioration can be avoided, thereby reducing the cost of parts (replacement cost) and labor required for the battery cell 14. Of course, by detecting an abnormality in the connection 20a, the risk of an external short circuit can be discovered early, making it possible to prevent accidents before they occur.

[0032] Although one embodiment of the present invention has been described above, the battery management device and the method for detecting a fastening abnormality according to the present invention can also adopt configurations other than those described above without departing from the spirit thereof.

[0033] For example, in the above embodiment, with regard to a method of detecting a connection abnormality using the battery management device 12, a comparison is made between the detected temperature Tp of the connection part 20a and the temperature Tc of the central part 21a of the outer casing 21, and the presence or absence of an abnormality (connection abnormality) in the connection part 20a is determined based on the comparison result of the magnitude relationship (step S3). However, this is not limited to this.

[0034] For example, in step S3, the presence or absence of a connection abnormality in connection portion 20a may be determined based on the magnitude of the difference Tp-Tc (the absolute value of the difference) between the detected temperature Tp of connection portion 20a and the temperature Tc of central portion 21a of exterior body 21. In this case, even if the magnitude relationship between the temperature Tp of connection portion 20a and the temperature Tc of central portion 21a is not reversed, it can be determined that a connection abnormality has occurred in connection portion 20a when, for example, the magnitude of the difference Tp-Tc of the detected temperatures described above becomes equal to or smaller than a predetermined value set in advance (see FIG. 8).

[0035] In the above embodiment, the presence or absence of a connection abnormality in the connection part 20a is determined based on the comparison result between the temperature Tp of the connection part 20a between the positive terminal 18a and the bus bar 19 and the temperature Tc of the central part 21a of the exterior body 21, but of course this is not limited to this. For example, although not shown, if the battery cell 14 has a structure in which a predetermined potential difference occurs between the negative terminal 18b and the exterior body 21, the presence or absence of a connection abnormality in the connection part 20b may be determined based on the comparison result between the temperature Tn of the connection part 20b between the negative terminal 18b and the bus bar 19 and the temperature Tc of the central part 21a of the exterior body 21.

[0036] Alternatively, although not shown, the monitoring unit 15 may be further provided with a potential difference detection unit capable of detecting the potential difference between the positive electrode side of the battery cell 14 and the exterior body 21 and the potential difference between the negative electrode side and the exterior body 21, and the monitoring unit 15 as a connection abnormality determination unit may be configured to select the connection part 20a (20b) between the bus bar 19 and the terminal 18a (18b) on the electrode side where a predetermined potential difference is detected with the exterior body 21, as a comparison target for temperature with the central part 21a of the exterior body 21. In this case, the temperature Tp (Tn) of the selected connection part 20a (20b) may be detected by the temperature detection unit 17 and used in the method of detecting a connection abnormality by the monitoring unit 15 (detection step S3).

[0037] With the above-mentioned configuration, even for a battery cell 14 whose insulation structure is unknown, it is possible to detect in advance which of the positive and negative terminals has the same potential as the exterior body 21. Therefore, by comparing the temperature of the connection portion 20a (20b) between the terminal 18a (18b) on the electrode side where a potential difference is found with the exterior body 21 and the bus bar 19 with the central portion 21a of the exterior body 21, it is possible to determine the presence or absence of a connection abnormality for the connection portion 20a (20b) between the terminal 18a (18b) on the side where a connection abnormality may occur and the bus bar 19. This makes it possible to expand the scope of application of the present invention and increase the versatility of the battery management device 12 according to the present invention.

[0038] In the above embodiment, the temperature detection unit 17 detects the temperature Tp (Tn) of only the connection part 20a (20b) which is to be judged as having a connection abnormality. However, it is of course possible to detect the temperatures Tp, Tn of both connection parts 20a, 20b and use them to detect a connection abnormality.

[0039] In the above description, the present invention is applied to a motor drive battery of a vehicle driven by a motor, such as an electric vehicle, but the present invention is not limited to this. For example, the present invention may be applied to an in-vehicle battery that supplies power to a power load other than the drive motor. Alternatively, the battery management device or the connection abnormality detection method according to the present invention may be applied to any battery application that requires continuous and stable battery operation, not limited to in-vehicle use. [Explanation of symbols]

[0040] 10 Battery System 11 Battery 12 Battery Management Unit 13 External power supply 14, 14a, 14b Battery cells 15 Monitoring Department 16 ECU 17 Temperature detection section 18a Terminal (positive side) 18b terminal (negative side) 19 Busbar 20a Connection (positive side) 20b Connection part (negative side) 21 Exterior body 21a Central part Module 22a, 22b Tp Temperature of the connection (positive side) Tn Temperature of the connection (negative side) Tc Temperature of the exterior body (center)

Claims

1. A system for managing the states of a plurality of battery cells that constitute a battery, comprising: The terminals of the battery cells are connected to each other by a bus bar, a temperature detection unit capable of detecting a temperature of a connection portion between one terminal of the battery cell and the bus bar and a temperature of a central portion between both terminals of an exterior body of the battery cell; a connection abnormality determination unit that determines whether or not there is a connection abnormality between the battery cell and the bus bar based on a comparison result between the temperature of the connection portion detected by the temperature detection unit and the temperature of the central portion of the exterior body.

2. a potential difference detector capable of detecting a potential difference between a positive electrode side of the battery cell and the exterior body, and a potential difference between a negative electrode side of the battery cell and the exterior body, The battery management device of claim 1, wherein the connection abnormality determination unit selects a connection between the bus bar and an electrode side terminal at which a predetermined potential difference is found between the electrode side terminal and the outer casing as a comparison target for temperature with respect to a center of the outer casing.

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