Battery cell diagnostic device and method

Abstract

The present invention relates to an apparatus and method for diagnosing an increase in resistance of a battery cell lead, and a battery cell diagnosis method according to one embodiment of the present invention includes: a first voltage measurement step of measuring a voltage for each unit cell of a battery pack when the battery pack is in an open-circuit voltage state; a second voltage measurement step of measuring a voltage for each unit cell along a predetermined current flowing through the battery pack when the battery pack is in a charging or discharging state; and a step of comparing the voltage measured in the first voltage measurement step with the voltage measured in the second voltage measurement step for each unit cell to detect whether or not there is an abnormality in the unit cell.

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims the benefit of priority based on Korean Patent Application No. 10-2019-0052154, filed May 3, 2019, and all contents disclosed in the documents of this Korean patent application are incorporated herein by reference.

[0002] The present invention relates to an apparatus and method for diagnosing resistance increases in battery cell leads. [Background technology]

[0003] Generally, when a plurality of unit cells are connected in series and / or parallel to form a high-voltage battery, the resistance of the leads at both ends of the unit cells, which are contact points, increases due to corrosion or poor contact.

[0004] When the resistance of the lead portion of such a unit cell increases, the increased resistance generates heat during charging and discharging of the battery, accelerating the deterioration of the unit cell. Furthermore, there is a problem that the voltage applied to the resistance portion causes measurement errors when measuring the cell voltage. Furthermore, there is also a problem that the heat generated can lead to the battery catching fire. Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made to solve the above problems, and an object of the present invention is to provide a battery cell diagnosis device and method that can quickly diagnose resistance present in leads of unit cells during charging and discharging when a battery includes at least a plurality of unit cells connected in series, thereby improving battery stability. [Means for solving the problem]

[0006] A battery cell diagnostic device according to an embodiment of the present invention includes a voltage measuring unit that measures a voltage across each unit cell of a battery pack; a current measuring unit that measures a current of the battery pack; and a detection unit that detects whether or not there is an abnormality in a unit cell by comparing a first voltage, which is a voltage measured for each unit cell when the battery pack is in an open-circuit voltage state, with a second voltage, which is a voltage measured for each unit cell along with a predetermined current flowing through the battery pack when the battery pack is in a charging or discharging state.

[0007] For example, the voltage measurement unit may include a multiplexer (MUX) having measurement terminals connected to leads between the unit cells and to leads of both last unit cells for at least a plurality of unit cells connected in series, and outputting a measurement voltage from the measurement terminals at both ends of one unit cell according to a preset measurement condition; and an ADC (Analog to Digital Converter) for analog-to-digital conversion of the measurement voltage output from the multiplexer.

[0008] The detection unit detects whether or not there is an abnormality by determining whether a voltage difference between the first voltage and the second voltage exceeds a predetermined standard for each unit cell. When an abnormality is detected in a unit cell, the detection unit may determine that a resistance equal to or greater than a predetermined standard exists in some of the leads at both ends of the unit cell.

[0009] For example, when an abnormality in a unit cell is detected, the detector may generate a notification signal for the unit cell.

[0010] In addition, the battery cell diagnostic device according to an embodiment of the present invention may further include a memory that stores at least one of the first voltage and the second voltage.

[0011] A battery cell diagnosis method according to an embodiment of the present invention may include a first voltage measurement step of measuring a voltage for each unit cell of a battery pack when the battery pack is in an open-circuit voltage state; a second voltage measurement step of measuring a voltage for each unit cell along a predetermined current flowing through the battery pack when the battery pack is in a charging or discharging state; and a step of detecting whether or not there is an abnormality in the unit cell by comparing the first voltage measured in the first voltage measurement step with the second voltage measured in the second voltage measurement step for each unit cell.

[0012] The detecting step detects whether or not an abnormality exists by determining whether a voltage difference between the first voltage and the second voltage exceeds a predetermined standard for each unit cell. For example, if an abnormality is detected in a unit cell, it may be determined that a resistance equal to or greater than a predetermined standard exists in some of the leads at both ends of the unit cell.

[0013] The battery cell diagnosis method according to an embodiment of the present invention may further include generating a notification signal for the unit cell when an abnormality in the unit cell is detected.

[0014] The present invention may also be embodied in a battery pack. The battery pack according to one embodiment of the present invention includes a battery module including at least a plurality of unit cells connected in series; and a battery management system for controlling charging and discharging of the battery module, the battery management system including a voltage measurement unit for measuring a voltage across each unit cell, a current measurement unit for measuring a current through the battery module, and a detection unit for detecting whether or not there is an abnormality in the unit cell by comparing a first voltage, which is a voltage measured for each unit cell when the battery module is in an open-circuit voltage state, with a second voltage, which is a voltage measured for each unit cell according to a predetermined current flowing through the battery module when the battery module is in a charging or discharging state. [Effects of the Invention]

[0015] According to the present invention, the resistance present in the lead portion of the unit cell can be quickly diagnosed during charging and discharging, thereby improving the stability of the battery.

[0016] The effects of the present invention will be further explained with reference to the following embodiments. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 2 is a block diagram illustrating a schematic configuration of a battery pack. [Figure 2] 1 is a block diagram for explaining the configuration of a battery cell diagnostic device according to an embodiment of the present invention; [Figure 3] FIG. 3 is an exemplary diagram specifically showing the configuration of a voltage measurement unit in FIG. 2. [Figure 4] 10 is an exemplary diagram illustrating a case where there is no lead resistance in a battery cell during battery cell diagnosis; FIG. [Figure 5] 10 is an exemplary diagram illustrating a case where lead resistance exists in a battery cell during battery cell diagnosis; FIG. [Figure 6] 3 is a flowchart illustrating a battery cell diagnostic method according to an embodiment of the present invention. [Figure 7] 3 is a flowchart illustrating a battery cell diagnostic processing method according to an embodiment of the present invention. [Figure 8] 1 is a block diagram showing a hardware configuration of a battery management system (BMS) according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, various embodiments of the present invention will be described with reference to the drawings. However, it should be understood that this is not intended to limit the present invention to the specific embodiments, but rather includes various modifications, equivalents, and / or alternatives of the embodiments of the present invention. In describing the drawings, similar reference numerals may be used for similar components.

[0019] The terms used in this document are merely used to describe particular embodiments and are not intended to limit the scope of other embodiments. The singular term includes the plural term unless the context clearly dictates otherwise. All terms used herein, including technical and scientific terms, may have the same meaning as commonly understood by a person of ordinary skill in the art of the present invention. Terms defined in commonly used dictionaries may be interpreted as having the same or similar meaning as the meaning they have in the context of the relevant art, and unless explicitly defined in this document, they should not be interpreted in an idealized or overly formal sense. In some cases, even terms defined in this document may not be interpreted to exclude embodiments of the present invention.

[0020] Furthermore, when describing components of an embodiment of the present invention, terms such as first, second, A, B, (a), (b), etc. are used. Such terms are used only to distinguish the component from other components, and do not limit the nature, procedure, or order of the components. When a component is described as being "coupled," "coupled," or "connected" to another component, it should be understood that the component may be directly coupled or connected to the other component, but that other components may also be "coupled," "coupled," or "connected" between each component.

[0021] The configuration of the battery pack will be described with reference to Fig. 1. Fig. 1 is a block diagram that schematically shows the configuration of the battery pack.

[0022] As shown in FIG. 1, the battery pack (B) includes a rechargeable battery module 1 made up of one or more battery cells, a switching unit 2 connected in series to the positive terminal side or the negative terminal side of the battery module 1 to control the flow of charge / discharge current of the battery module 1, and a battery management system 3 (hereinafter also referred to as "BMS") that monitors the voltage, current, temperature, etc. of the battery pack (B) and controls and manages it to prevent overcharging and over-discharging, etc.

[0023] Here, the switching unit 2 is a mechanical switching element or a semiconductor switching element for controlling the flow of current for charging or discharging the battery module 1, and for example, at least one mechanical relay or MOSFET may be used.

[0024] In addition, the BMS 3 is connected to the battery module 1 to monitor the voltage, current, temperature, etc. of the battery pack (B), and can receive data on the voltage, current, temperature, etc. In addition, for example, if the switching unit 2 is a semiconductor switching element, it can measure or calculate the voltage and current of the gate, source, drain, etc. of the semiconductor switching element, and can also measure the current, voltage, temperature, etc. of the battery module 1 using various sensors 4 provided in contact with the semiconductor switching element. The BMS 3 is an interface that receives input of measured values ​​of the various parameters described above, and can include a plurality of terminals and circuits connected to these terminals for processing the input values.

[0025] In addition, the BMS 3 can control the ON / OFF of the switching unit 2 and can monitor the state of the battery module 1 by being connected to the battery module 1.

[0026] The BMS 3 may also be connected to a host controller 7. The BMS 3 may transmit information related to the battery state and control to the host controller 7, or may control the operation of the battery pack (B) based on a control signal applied from the host controller 7. The BMS 3 may transmit and receive various signals and data to and from the host controller 7 via wire and / or wirelessly. Here, the battery pack (B) may be, for example, an automobile battery pack, and the host controller 7 may be a microcontroller (MCU) of an automobile system. Alternatively, the battery pack (B) may be, but is not limited to, a battery pack of an energy storage system (ESS).

[0027] The battery cell diagnostic device according to one embodiment of the present invention may be provided between the battery module 1 and the battery management system 3, or may be a part of the battery management system 3.

[0028] Next, a battery cell diagnostic device according to an embodiment of the present invention will be described with reference to Figures 2 and 3. Figure 2 is a block diagram illustrating the configuration of a battery cell diagnostic device according to an embodiment of the present invention. Figure 3 is an exemplary diagram specifically illustrating the configuration of a voltage measurement unit in Figure 2.

[0029] First, as shown in FIG. 2, a battery cell diagnostic device according to an embodiment of the present invention may include a voltage measuring unit 10, a current measuring unit 20, and a detecting unit 30.

[0030] The voltage measuring unit 10 is configured to measure the voltage across each unit cell of the battery pack (ie, each unit cell of a plurality of unit cells connected in series within a battery module).

[0031] 3, the voltage measurement unit 10 may include a multiplexer 11 in which measurement terminals (T1 to T9) are connected to leads between the unit cells and to leads of both last unit cells for at least a plurality of unit cells (Cell 1 to Cell 18) connected in series, and which outputs a measurement voltage from the measurement terminals at both ends of one unit cell according to preset measurement conditions; and an ADC 13 that performs analog-to-digital conversion of the measurement voltage output from the multiplexer 11. Here, the preset measurement conditions may be set in various ways according to the measurement environment, and may be set, for example, to measure Cell 1 to Cell 18 in sequence at a regular interval.

[0032] The current measuring unit 20 is configured to measure the current of the battery pack. For example, the current measuring unit 20 may be connected in series to a charge or discharge line to measure the amount of current when the battery pack is in a charge or discharge state. Techniques for measuring the amount of current of a battery pack in a charge or discharge state are well known, and therefore, detailed description thereof will be omitted.

[0033] The detection unit 30 is configured to detect whether or not a unit cell is abnormal by comparing a first voltage, which is a voltage measured for each unit cell when the battery pack is in an open-circuit voltage state, with a second voltage, which is a voltage measured for each unit cell according to a predetermined current flowing through the battery pack when the battery pack is in a charging or discharging state. That is, the detection unit 30 detects whether or not a unit cell is abnormal by comparing the voltage when the battery pack is in an open-circuit voltage state with the voltage when the battery pack is in a charging or discharging state. Here, the first voltage when the battery pack is in the open-circuit voltage state is a reference value for comparison, and may be measured once and used repeatedly. To this end, the battery cell diagnosis device according to an embodiment of the present invention may further include a memory (not shown) that stores at least one of the first voltage and the second voltage.

[0034] The detection unit 30 detects whether an abnormality exists by determining whether the voltage difference between the first and second voltages for each unit cell exceeds a predetermined threshold. Thus, when an abnormality is detected in a unit cell, the detection unit 30 can determine that a resistance above a certain threshold exists in some of the leads at both ends of the unit cell. Furthermore, since the present invention determines an increase in resistance component based on the voltage across each unit cell, it can detect whether an abnormality exists not only in the resistance at the leads at both ends but also in an increase in the internal resistance of each unit cell, thereby comprehensively diagnosing whether an abnormality exists due to the resistance of the battery cell. Furthermore, detecting whether an abnormality exists by comparing the voltage difference between each unit cell under predetermined conditions, as in the present invention, can more accurately diagnose an increase in resistance than detecting whether an abnormality exists by comparing the voltage difference between unit cells. This is because a voltage difference may exist between unit cells due to manufacturing design.

[0035] As an embodiment, a diagnosis process by a battery cell diagnosis device will be described with reference to Fig. 4 and Fig. 5. Fig. 4 is an exemplary view illustrating a case where there is no lead resistance in a battery cell during battery cell diagnosis, and Fig. 5 is an exemplary view illustrating a case where there is lead resistance in a battery cell during battery cell diagnosis.

[0036] First, in FIGS. 4 and 5, it is assumed that each unit cell of the battery pack is designed to have a voltage of 3 V. As shown in FIG. 4, assuming that the battery cells have almost no lead resistance, when there is no charge / discharge current, i.e., when the battery pack is in an open-circuit voltage state, the voltage of each unit cell measured by the multiplexer 11 and ADC 13 of the voltage measurement unit is, for example, approximately 3 V. Then, the battery is discharged to pass a current through the battery cells. At this time, for example, the discharge current measured by the current measurement unit 20 is 100 A, and the measured voltage of each unit cell is approximately 2.9 V. In this case, the voltage difference between the voltage measured when each unit cell is in an open-circuit voltage state and the voltage measured when the battery pack is discharged at 100 A is approximately 0.1 V.

[0037] However, as shown in Fig. 5, if unit cell Cell 5 has a resistance value, for example, 10 mΩ, that cannot be ignored as lead resistance, when the battery pack is in an open-circuit voltage state, the voltage of each unit cell measured by multiplexer 11 and ADC 13 of the voltage measurement unit will still be approximately 3 V. However, when the battery is subsequently discharged and a current flows through the battery cells, when the discharge current measured by current measurement unit 20 is 100 A, the measured voltage of each unit cell will be approximately 2.9 V for unit cells Cell 1 to Cell 4 and Cell 6 to Cell 8, but approximately 2.9 V for unit cell Cell 5. 1.9 Voltage at V (i.e., cell voltage 2.9V) -The figure shows the difference in voltage between the open circuit voltage and the 100A discharge voltage for each unit cell. For unit cells Cell 1 to Cell 4 and Cell 6 to Cell 8, the difference is 0.1V. For unit cell Cell 5, the difference is 0.1V. 1.1 V. Therefore, the detection unit 30 can determine that a resistance exists in the lead portion of the unit cell Cell 5.

[0038] Furthermore, when an abnormality in a unit cell is detected, the detection unit 30 may generate a notification signal for the unit cell. As a result, for example, when the notification signal is generated, the battery management system may limit the charge / discharge operation of the battery or transmit the notification signal to a higher-level controller or a manager terminal to display a warning, thereby enabling a quick response when an abnormality due to an increase in resistance of the unit cell occurs and preventing further accidents.

[0039] According to the present invention, the resistance present in the lead portion of the unit cell can be quickly diagnosed during charging and discharging, thereby improving the stability of the battery.

[0040] Next, a battery cell diagnostic method according to an embodiment of the present invention will be described with reference to Fig. 6. Fig. 6 is a flowchart showing a battery cell diagnostic method according to an embodiment of the present invention.

[0041] As shown in FIG. 6, in a battery cell diagnosis method according to an embodiment of the present invention, when the battery pack is in an open-circuit voltage state, a voltage measurement unit measures a voltage (i.e., a first voltage) for each unit cell of the battery pack (S10). Then, when the battery pack is in a charging or discharging state, a current measurement unit and a voltage measurement unit measure a voltage (i.e., a second voltage) for each unit cell according to a predetermined current flowing through the battery pack (S20). Next, for each unit cell, the first voltage measured in step S10 is compared with the second voltage measured in step S20 (S30). For example, it is determined whether the difference between the first and second voltages exceeds a predetermined threshold. If the difference between the first and second voltages exceeds the predetermined threshold (Yes) in step S30, the detection unit determines that an abnormality exists in the unit cell (S31). If an abnormality is detected in a unit cell in this way, it can be determined that a resistance above a certain threshold exists in some of the leads at both ends of the unit cell. If the voltage difference between the first voltage and the second voltage does not exceed the predetermined standard (No) in step S30, the detection unit determines that the unit cell is normal (i.e., there is no abnormality) (S33). Next, the detection unit determines whether the determination has been completed for all unit cells (S40). If the determination for the presence or absence of an abnormality has not been completed for all unit cells (No) in step S40, the detection unit returns to step S30 to determine whether the next unit cell has an abnormality. If the determination for the presence or absence of an abnormality has been completed for all unit cells (Yes) in step S40, the detection unit ends the diagnosis procedure. Alternatively, if the determination for the presence or absence of an abnormality has been completed for all unit cells (Yes) in step S40, the detection unit may return to step S10 or step S20 according to a preset cycle and repeat the subsequent procedures.

[0042] Furthermore, the battery cell diagnosis method according to an embodiment of the present invention may further include generating a notification signal for the unit cell when an abnormality in the unit cell is detected.

[0043] As an embodiment, the sequence of a battery cell diagnostic processing method will be described with reference to Fig. 7. Fig. 7 is a flowchart showing a battery cell diagnostic processing method according to one embodiment of the present invention.

[0044] First, the battery cells of the battery pack are diagnosed (S110). For example, as shown in FIG. 6, all unit cells of the battery pack are determined to have an abnormality through steps S10 to S40. Next, it is determined whether an abnormality has been detected in at least one of the unit cells of the battery pack (S120). If no abnormality has been detected in a unit cell (No) in step S120, the process returns to step S110 to diagnose the battery cells. However, if an abnormality has been detected in a unit cell (Yes) in step S120, the detection unit generates a notification signal (i.e., a cell contact resistance increase signal or a cell lead resistance increase signal) for the unit cell in which the abnormality has been detected and transmits the notification signal to a higher-level controller (e.g., an MCU of a battery management system) or a pre-set administrator terminal (S130). Next, the higher-level controller (e.g., a battery management system) limits the battery charge / discharge current and displays a warning signal via a separate output unit (S150).

[0045] Therefore, if an abnormality occurs due to an increase in the resistance of a unit cell, it is possible to quickly deal with the problem and prevent further accidents.

[0046] The present invention may also be embodied in a battery pack. A battery pack according to one embodiment of the present invention includes a battery module including at least a plurality of unit cells connected in series; and a battery management system for controlling charging and discharging of the battery module. The battery management system may include a voltage measurement unit for measuring a voltage across each unit cell; a current measurement unit for measuring a current through the battery module; and a detection unit for detecting an abnormality in a unit cell by comparing a first voltage, which is a voltage measured for each unit cell when the battery module is in an open-circuit voltage state, with a second voltage, which is a voltage measured for each unit cell according to a predetermined current flowing through the battery module when the battery module is in a charging or discharging state. According to the present invention, resistance present in leads of unit cells can be quickly diagnosed during charging and discharging, thereby improving battery stability.

[0047] Meanwhile, the battery management system (BMS) of the battery pack of the present invention may be shown as in Fig. 8. Fig. 8 is a block diagram showing the hardware configuration of the battery management system (BMS) according to one embodiment of the present invention.

[0048] 8, the battery management system 300 may include a microcontroller (MCU) 310 that controls various processes and components, a memory 320 that stores an operating system program and various programs (e.g., a battery pack abnormality diagnosis program or a battery pack temperature estimation program), an input / output interface 330 that provides an input interface and an output interface between the battery cell module and / or a switching unit (e.g., a semiconductor switching element), and a communication interface 340 that can communicate with an external device (e.g., a higher-level controller) via a wired or wireless communication network. Thus, the computer program according to the present invention may be stored in the memory 320 and processed by the microcontroller 310, thereby realizing, for example, a module that performs each of the functional blocks shown in FIGS. 2 and 3.

[0049] Although the present invention has been described above using limited embodiments and drawings, the present invention is not limited thereto, and it is of course possible for a person having ordinary skill in the art to which the present invention pertains to implement various embodiments within the scope of the technical concept of the present invention and the equivalent scope of the claims.

Claims

1. a voltage measuring unit for measuring a voltage across each of at least a plurality of unit cells connected in series in the battery pack; a current measuring unit for measuring a current of the battery pack; a detection unit for detecting whether or not there is an abnormality in the unit cell; a memory that stores a first voltage, which is a voltage measured for each unit cell when the battery pack is in an open-circuit voltage state; The detection unit detects the first voltage and detecting whether or not a unit cell is abnormal by comparing the measured voltage with a second voltage, which is a voltage measured for each unit cell when the battery pack is in a charging or discharging state; the detection unit detects whether or not a voltage difference between the first voltage and the second voltage exceeds a predetermined reference for each unit cell, thereby detecting whether or not an abnormality exists; When an abnormality in the unit cell is detected, the detection unit determines that a resistance equal to or greater than a certain standard exists in a part of the leads at both ends of the unit cell or inside the unit cell, the first voltage is measured once and used repeatedly as a reference value for comparison; The voltage measurement unit a multiplexer, in which measurement terminals are connected to lead portions between the at least plurality of unit cells connected in series and to lead portions of unit cells at both ends of the at least plurality of unit cells connected in series, and which outputs a measurement voltage from the measurement terminals at both ends of one unit cell according to a preset measurement condition; and an ADC that performs analog-to-digital conversion on the measured voltage output from the multiplexer.

2. The battery cell diagnostic device according to claim 1 , wherein the memory stores the second voltage.

3. The battery cell diagnosis device according to claim 1 or 2, wherein the detection unit generates a notification signal for the unit cell when an abnormality in the unit cell is detected.

4. a first voltage measuring step of measuring a voltage across one unit cell according to a preset measurement condition for at least a plurality of unit cells connected in series of the battery pack when the battery pack is in an open circuit voltage state; a second voltage measuring step of measuring a voltage of each of the plurality of unit cells when the battery pack is in a charging or discharging state; and detecting whether or not each of the unit cells is abnormal by comparing the first voltages measured in the first voltage measurement step with the second voltages measured in the second voltage measurement step for each of the unit cells, The detecting step includes: determining whether a voltage difference between the first voltage and the second voltage exceeds a predetermined reference for each unit cell to detect whether or not each unit cell is abnormal; If an abnormality is detected in the unit cell, it is determined that a resistance equal to or greater than a certain standard exists in a part of the leads at both ends of the unit cell or inside the unit cell; each of the first voltages is measured once and repeatedly used as a reference value for comparison; The first voltage measuring step and the second voltage measuring step include: a measurement terminal connected to a lead between each of the at least a plurality of unit cells connected in series and to a lead of a unit cell at both ends of the at least a plurality of unit cells connected in series through a multiplexer, and a measurement voltage from the measurement terminals at both ends of one unit cell is output according to a preset measurement condition.

5. The battery cell diagnosis method of claim 4 , further comprising generating a notification signal for the unit cell when an abnormality in the unit cell is detected.

6. a battery module including at least a plurality of unit cells connected in series; a battery management system that controls charging and discharging of the battery module; The battery management system A battery pack comprising the battery cell diagnostic device according to any one of claims 1 to 3.

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