Battery diagnostic device, battery diagnostic method, battery pack, and automobile

Abstract

A battery diagnostic device according to an embodiment of the present invention includes a voltage sensing circuit configured to generate a voltage signal indicating a cell voltage of a battery cell, a recording medium configured to record time-series data of the cell voltages, and a control circuit operatively coupled to the voltage sensing circuit and the recording medium. The control circuit is configured to (i) receive the voltage signal and record the time-series data of the cell voltages on the recording medium, (ii) select a set of cell voltages measured at k-th, k+1-th, and k+2-th cell voltages from the time-series data as diagnostic data (where k is an index indicating the order of cell voltage measurements, is a natural number greater than or equal to 1, and is assigned multiple values), (iii) determine a first voltage difference between the k-th cell voltage and the k+1-th cell voltage, and a second voltage difference between the k+1-th cell voltage and the k+2-th cell voltage, and (iv) diagnose a battery cell as having an abnormal voltage if a count of a cell voltage set for which a normal diagnosis condition, that is, the pth power of the first voltage difference (p is a natural number greater than or equal to 1) is greater than the pth power of the second voltage difference, is equal to or greater than a reference value.

Description

Technical Field

[0001] The present invention relates to a technique for diagnosing voltage abnormalities of a battery.

[0002] This application claims priority based on Korean Patent Application No. 10-2022-0117336 filed on September 16, 2022, and all the contents disclosed in the specification and drawings of the application are incorporated into this application.

Background Art

[0003] In recent years, the demand for portable electronic products such as notebook computers, video cameras, and mobile phones has grown rapidly. As the development of electric vehicles, energy storage systems, robots, artificial satellites, etc. has become full-scale, research on high-performance rechargeable batteries has been actively conducted.

[0004] Currently commercially available batteries include nickel-cadmium batteries, nickel-metal hydride batteries, nickel-zinc batteries, lithium batteries, etc. Among them, lithium batteries have attracted attention because they can be charged and discharged freely because they hardly have a memory effect compared to nickel-based batteries, have a very low self-discharge rate, and have a high energy density.

[0005] In recent years, energy storage systems and electric vehicles that require high voltage have become widely popular. Along with this, the need for a diagnostic technique to accurately detect voltage abnormalities of each of a plurality of battery cells connected in series in a battery pack has been increasing.

[0006] The voltage abnormality of a battery cell means a failure state in which the cell voltage abnormally drops and / or rises due to an internal short circuit, an external short circuit, a failure of a voltage sensing line, a poor connection with a charge / discharge line, etc.

[0007] Traditionally, a simple method was used to diagnose battery cell voltage abnormalities by determining whether the difference between cell voltages measured at two different points in time exceeded a critical value. This method has the advantage of not requiring a high-performance processor because it does not involve a large amount of data processing.

[0008] However, since the voltage of a battery cell also depends on the temperature, current, and / or State of Health (SOH), simply comparing the voltage difference and critical value of battery cells measured at different points in time makes it difficult to accurately diagnose a voltage anomaly in a battery cell.

[0009] Furthermore, even if the voltage difference between battery cells is below the critical value, there is a limitation in that the abnormality in the cell voltage cannot be detected if the voltage slope of the battery cells exhibits abnormal behavior, for example, if lithium plating occurs at the negative electrode of a lithium battery. [Overview of the project] [Problems that the invention aims to solve]

[0010] This invention was devised to solve the above-mentioned problems, and aims to provide a battery diagnostic device, a battery diagnostic method, a battery pack, and an automobile for efficiently and accurately diagnosing battery cell voltage abnormalities using the trend of the slope of voltage change in battery cells.

[0011] Other objects and advantages of the present invention can be understood from the following description and will be more clearly shown by the embodiments of the present invention. Furthermore, the objects and advantages of the present invention can be realized by the means and combinations thereof set forth in the claims. [Means for solving the problem]

[0012] To achieve the above objective, a battery diagnostic device according to one aspect of the present invention includes a voltage sensing circuit configured to generate a voltage signal indicating the cell voltage of a battery cell, a recording medium configured to record time-series data of the cell voltage, and a control circuit operably coupled to the voltage sensing circuit and the recording medium.

[0013] The control circuit may be configured to (i) receive the voltage signal input and record time-series data of the cell voltage on a recording medium, (ii) select the k-th, k+1-th and k+2-th cell voltage sets measured from the time-series data as diagnostic data (k is an index indicating the measurement order of the cell voltages, which is a natural number of 1 or more and can be assigned multiple values), (iii) determine the first voltage difference between the k-th cell voltage and the k+1-th cell voltage, and the second voltage difference between the k+1-th cell voltage and the k+2-th cell voltage, and (iv) diagnose a voltage abnormality in a battery cell if the count of cell voltage sets for which the normal diagnostic condition that the first voltage difference raised to the power of p (p is a natural number of 1 or more) is greater than the second voltage difference raised to the power of p is exceeded by a reference value.

[0014] The aforementioned p can be 1 or a natural number greater than or equal to 2.

[0015] The aforementioned reference value may be 1 or two or more natural numbers.

[0016] The control circuit may be configured to select a plurality of cell voltage sets from the time-series data of the cell voltages while increasing k by 1 from 1 to n-2 (where n is the number of voltage data points included in the time-series data).

[0017] The control circuit may be configured to perform the control logic described in (i) to (iv) above when the operating state of the battery cell is switched from a charging or discharging state to an unloaded state.

[0018] The diagnostic device may further include an interface unit that is operably coupled with the control circuit to support communication with an external device.

[0019] The control circuit may be configured to transmit the diagnostic result to an external device via the interface unit if the battery cell is diagnosed with a voltage abnormality.

[0020] The diagnostic device may further include an interface unit operably coupled to the control circuit and an output device operably coupled to the interface unit.

[0021] The control circuit may be configured to output the diagnostic result visually or audibly through the output device when the battery cell is diagnosed with a voltage abnormality.

[0022] The above objectives can also be achieved by a battery pack including the aforementioned battery diagnostic device and an automobile including the battery pack.

[0023] To achieve the above objective, a battery diagnostic method according to another aspect of the present invention includes the steps of: (a) receiving a voltage signal input indicating the cell voltage of a battery cell from a voltage sensing circuit and recording time-series data of the cell voltage on a recording medium; (b) selecting the k-th, k+1-th, and k+2-th cell voltage sets measured from the time-series data as diagnostic data (where k is an index indicating the measurement order of the cell voltage, and is a natural number of 1 or more, to which multiple values ​​may be assigned); (c) determining a first voltage difference between the k-th cell voltage and the k+1-th cell voltage, and a second voltage difference between the k+1-th cell voltage and the k+2-th cell voltage; and (d) diagnosing a battery cell as having a voltage abnormality if the count of cell voltage sets for which the normal diagnostic condition that the first voltage difference raised to the power of p (where p is a natural number of 1 or more) is greater than the second voltage difference raised to the power of p is not met exceeds a reference value.

[0024] The aforementioned p can be 1 or a natural number greater than or equal to 2.

[0025] The aforementioned reference value may be 1 or two or more natural numbers.

[0026] Multiple sets of the cell voltages can be selected from the time-series data of the cell voltages by increasing k by 1 from 1 to n-2 (where n is the number of cell voltages included in the time-series data).

[0027] The steps (a) to (d) described above may be performed when the operating state of the battery cell is switched from a charging or discharging state to a no-load state.

[0028] The diagnostic method may further include a step of transmitting the diagnostic result to an external device if the battery cell is diagnosed with a voltage abnormality.

[0029] The diagnostic method may further include the step of outputting the diagnostic result visually or audibly through an output device if the battery cell is diagnosed with a voltage abnormality. [Effects of the Invention]

[0030] According to one aspect of the present invention, a battery cell experiencing a voltage anomaly can be easily diagnosed by analyzing the trend of the slope of cell voltages between continuously measured cell voltages using simple mathematical calculations.

[0031] Furthermore, according to one aspect of the present invention, since the calculation method used for diagnosing the battery is not complex, a high-spec processor is not required.

[0032] Furthermore, according to one aspect of the present invention, the reliability of voltage anomaly diagnosis can be improved by using mathematical operations that can amplify the trend of the slope of the cell voltage.

[0033] Furthermore, according to one aspect of the present invention, even if the difference between voltages measured at different points in time is not large, battery cells exhibiting abnormal voltage behavior can be reliably identified.

[0034] The effects of the present invention are not limited to those described above, and other effects of the present invention not mentioned herein will be clearly understood by those skilled in the art from the claims.

[0035] The following drawings accompanying this specification illustrate preferred embodiments of the invention and, together with the detailed description of the invention, serve to further illustrate the technical idea of ​​the invention; therefore, the invention should not be construed as being limited solely to what is shown in the drawings. [Brief explanation of the drawing]

[0036] [Figure 1] This diagram illustrates the configuration of an automobile according to one embodiment of the present invention. [Figure 2a] In an embodiment of the present invention, when a battery cell being charged is switched to an unloaded state, the graph shows a portion of the cell voltage profile exhibited by a normal battery cell, and is a diagram for deriving a mathematical formula used to diagnose voltage abnormalities. [Figure 2b] In an embodiment of the present invention, this is a graph of a portion of the cell voltage profile exhibited by a normal battery cell when a battery cell in the process of discharge is switched to an unloaded state, and is a diagram for deriving a mathematical formula used to diagnose voltage abnormalities. [Figure 3a] This graph shows an example of time-series data for the cell voltage of a battery cell with a normal voltage, according to an embodiment of the present invention. [Figure 3b] This graph shows an example of time-series data for the cell voltage of a battery cell experiencing a voltage anomaly, according to an embodiment of the present invention. [Figure 4a] In another embodiment of the present invention, this graph shows an example of time-series data for the cell voltage of a battery cell with a normal voltage. [Figure 4b] In another embodiment of the present invention, this graph shows an example of time-series data for the cell voltage of a battery cell where a voltage anomaly has occurred. [Figure 5] This flowchart illustrates a battery diagnostic method according to one embodiment of the present invention. [Modes for carrying out the invention]

[0037] Preferred embodiments of the present invention will now be described in detail with reference to the attached drawings. Prior to this, terms and words used herein and in the claims shall not be interpreted in their usual and dictionary sense, but rather in a sense and concept that corresponds to the technical idea of ​​the present invention, in accordance with the principle that the inventor himself may appropriately define the concept of terms in order to best describe the invention.

[0038] Therefore, the embodiments and configurations shown in the drawings described herein represent only one of the most preferred embodiments of the present invention and do not represent the entire technical concept of the invention. It should be understood that there are various equivalents and modifications that can be substituted for these at the time of filing this application.

[0039] Terms that include ordinal numbers, such as "1st," "2nd," etc., are used to distinguish one of several components from others, and these terms do not limit the components themselves.

[0040] Throughout the specification, when a part of it "includes" a component, this does not exclude other components unless otherwise specified, but rather means that it may include other components. Furthermore, terms such as "[control unit]" in the specification mean a unit that processes at least one function or operation, and can be embodied in hardware, software, or a combination of hardware and software.

[0041] Furthermore, when a part of the specification is described as being "connected" to another part, this includes not only "direct connections" but also "indirect connections" mediated by other elements.

[0042] Figure 1 is a diagram illustrating the configuration of an automobile according to one embodiment of the present invention.

[0043] Referring to Figure 1, the automobile 1 includes a battery pack B, an inverter 3, an electric motor 4, and a vehicle controller 5.

[0044] Automobile 1 means a vehicle driven by a motor using electrical energy provided by battery pack B. For example, automobile 1 may be an electric vehicle, a plug-in hybrid vehicle, or a hybrid vehicle.

[0045] Battery pack B includes cell group CG, switch 6, and battery management system 100.

[0046] Cell group CG can be coupled to inverter 3 through a pair of power terminals provided on battery pack B. Cell group CG consists of multiple battery cells BC1~BC connected in series. N This includes the number of battery cells, where N is a natural number greater than or equal to 2. i The type of battery cell is not particularly limited, as long as it is capable of repeated charging and discharging, such as a lithium-ion battery cell. i is an index for identifying the battery cell. i is a natural number, between 1 and N.

[0047] Switch 6 is connected in series with the cell group CG. Switch 6 is located in the current path for charging and discharging the cell group CG. Switch 6 is controlled to turn on or off in response to a switching signal from the battery management system 100. Switch 6 may be a mechanical relay that is turned on or off by the magnetic force of a coil, or a semiconductor switch such as a MOSFET (Metal Oxide Semiconductor Field Effect Transistor).

[0048] The inverter 3 is provided to convert the DC current from the cell group CG into AC current in response to commands from the battery management system 100 or the vehicle controller 5. The electric motor 4 may be, for example, a three-phase AC motor. The electric motor 4 is driven by the AC power provided by the inverter 3.

[0049] The battery management system 100 is provided to be responsible for the overall control related to the charging and discharging of the cell group CG during the operation of the vehicle 1. Here, the operation of the vehicle 1 may include driving the vehicle 1, stopping while moving, parking, etc.

[0050] The battery management system 100 includes a battery diagnostic device 200. The battery management system 100 may further include at least one of a current sensor 310, a temperature sensor 320, and an interface unit 330.

[0051] The battery diagnostic device 200 detects multiple battery cells BC1~BC during the operation of the vehicle 1. N It is provided to diagnose individual voltage anomalies. The battery diagnostic device 200 includes a voltage sensing circuit 210 and a control circuit 220.

[0052] The voltage sensing circuit 210 senses multiple battery cells BC1~BC through multiple voltage sensing lines. N It is connected to the individual positive and negative electrodes. The voltage sensing circuit 210, under the control of the control circuit 220, checks each battery cell BC at regular time intervals while the vehicle 1 is in operation. i The voltage sensing circuit 210 is configured to measure the cell voltage across both ends of the battery and generate a voltage signal indicating the measured cell voltage. The voltage sensing circuit 210 may include a conventional voltage measurement circuit known in the industry. The voltage measurement circuit may include a multiplexing circuit that can sequentially select battery cells to be measured at time intervals, a filter circuit that removes noise from the voltage measurement signal, and an amplification circuit that amplifies the voltage measurement signal.

[0053] The current sensor 310 is connected in series to the cell group CG through a current path. The current sensor 310 is configured to detect the battery current flowing through the cell group CG at regular time intervals under the control of the control circuit 220 while the vehicle 1 is in operation, and to generate a current signal indicating the detected battery current. The current sensor 310 may be a conventional sensor known in the industry, such as a sense resistor or a Hall sensor. The current flowing through the cell group CG may be a charging current or a discharging current.

[0054] The temperature sensor 320 is configured to detect the temperature of the cell group CG at regular time intervals under the control of the control circuit 220 while the vehicle 1 is in operation, and to generate a temperature signal indicating the detected temperature. The temperature sensor 320 may be a conventional sensor known in the industry, such as a thermocouple. The temperature sensor 320 is configured to detect the temperature of each battery cell BC i Multiple points within the battery pack B may be provided to allow for independent measurement of the temperature.

[0055] The control circuit 220 can be implemented in hardware using at least one of the following: ASICs (application-specific integrated circuits), DSPs (digital signal processors), DSPDs (digital signal processing devices), PLDs (programmable logic devices), FPGAs (field programmable gate arrays), microprocessors, or other electrical units for performing functions.

[0056] The control circuit 220 may have a recording medium 221. The recording medium 221 may be at least one form of recording medium from among flash® memory, hard disk, SSD (Solid State Disk), SDD (Solid Disk Drive), multimedia microcard, RAM (Random Access Memory), SRAM (Static RAM), ROM (Read Only Memory), EEPROM (Electrically Erasable Programmable ROM), and PROM (Programmable ROM). The recording medium 221 may record data and programs required for the calculation operations of the control circuit 220. The recording medium 221 may cumulatively record data indicating the results of the calculation operations of the control circuit 220, for example, diagnostic results, along with a timestamp.

[0057] The control circuit 220 may be operably coupled to the voltage sensing circuit 210, the temperature sensor 320, the current sensor 310, the interface unit 330, and / or the switch 6. The control circuit 220 may collect sensing signals from the voltage sensing circuit 210, the current sensor 310, and the temperature sensor 320 at regular time intervals while the vehicle 1 is in operation. The sensing signals include voltage signals, current signals, and / or temperature signals. The voltage signals, current signals, and / or temperature signals may be collected in a synchronized measurement manner. The control circuit 220 may convert the voltage signals, / or current signals, and / or temperature signals into digital data and accumulate and record them on the recording medium 221 in order to generate time-series data regarding the voltage and / or current and / or temperature of the battery cells. Thus, the recording medium 221 contains data for each battery cell BC. i Time-series data regarding the cell voltage, current flowing through battery pack B, and temperature can be accumulated and recorded.

[0058] Time-series data for voltage may include a number of voltage data points corresponding to the number of voltage measurements. Each voltage data point includes the measurement time and the measured voltage value. Time-series data for current may include a number of current data points corresponding to the number of current measurements. Each current data point includes the measurement time and the measured current value. Time-series data for temperature may include a number of temperature data points corresponding to the number of temperature measurements. Each temperature data point includes the measurement time and the measured temperature value.

[0059] The control circuit 220 can identify whether the battery cell is charging, discharging, or in an unloaded state by referring to the magnitude and sign of the current measured through the current sensor 310.

[0060] Specifically, the control circuit 220 can identify that the battery cell is in an unloaded state when the magnitude of the current measured through the current sensor 310 is 0. Furthermore, the control circuit 220 can identify that the battery cell is discharging when the magnitude of the current measured through the current sensor 310 is greater than 0 and the sign of the current value is positive. Also, the control circuit 220 can identify that the battery cell is charging when the magnitude of the current measured through the current sensor 310 is greater than 0 and the sign of the current value is negative.

[0061] The interface unit 330 may include a communication circuit configured to support wired or wireless communication between the control circuit 220 and the vehicle controller 5 (for example, an electronic control unit (ECU)). Wired communication could be, for example, CAN (Controller Area Network) communication, and wireless communication could be, for example, Zigbee® or Bluetooth® communication. Of course, the type of communication protocol is not particularly limited as long as it supports wired or wireless communication between the control circuit 220 and the vehicle controller 5.

[0062] The interface unit 330 can be operably coupled to an output device 331 that provides information received from the vehicle controller 5 and / or the control circuit 220 in a form recognizable by the user. The output device 331 may include a display 331a and a speaker 331b.

[0063] The interface unit 330 may include a video I / O interface and an audio I / O interface to output the diagnostic result visually or audibly through the output device 331.

[0064] The vehicle controller 5 may control the inverter 3 based on battery information (e.g., voltage, current, temperature, SOC (State of Charge)) collected through communication with the battery management system 100.

[0065] During the operation of the automobile 1, the control circuit 220 records the time-series data of the cell voltage of each battery cell BC measured by the voltage sensing circuit 210 in the recording medium 221, and can diagnose whether the battery cell has a voltage abnormality using the time-series data. i Specifically, the control circuit 220 selects a set of cell voltages V measured at the k-th, k + 1-th, and k + 2-th as diagnostic data from the time-series data of the cell voltages recorded in the recording medium 221. Here, k is an index indicating the measurement order of the cell voltages, and is a natural number from 1 to n. n is the total number of cell voltages included in the time-series data. For the sake of convenience of explanation, the voltage value measured at the k-th is denoted as V.

[0066] When k = 1, the control circuit 220 selects a set of cell voltages V1, V2, and V3 from the time-series data of the cell voltages. When k = 2, the control circuit 220 selects a set of cell voltages V2, V3, and V4 from the time-series data of the cell voltages. When k is an arbitrary m, the control circuit 220 selects a set of cell voltages V, V, and V from the time-series data of the cell voltages. k for description.

[0067] When k = 1, the control circuit 220 selects a set of cell voltages V1, V2, and V3 from the time-series data of the cell voltages. When k = 2, the control circuit 220 selects a set of cell voltages V2, V3, and V4 from the time-series data of the cell voltages. When k is an arbitrary m, the control circuit 220 selects a set of cell voltages V, V, and V from the time-series data of the cell voltages. m V m+1 and Vm+2 Select the option where m is a natural number between 3 and n-2.

[0068] The control circuit 220 also determines the first voltage difference between the k-th cell voltage and the (k+1)-th cell voltage, and the second voltage difference between the (k+1)-th cell voltage and the (k+2)-th cell voltage.

[0069] The control circuit 220 determines whether the normal diagnostic condition is met for each cell voltage set selected from the time-series data of cell voltages, where the first voltage difference raised to the power of p (where p is a natural number greater than or equal to 1) is greater than the second voltage difference raised to the power of p. The control circuit 220 then counts the number of cell voltage sets selected from the time-series data that do not satisfy the normal diagnostic condition.

[0070] The control circuit 220 diagnoses a battery cell as having a voltage abnormality if the number of cell voltage sets that do not meet the normal diagnostic conditions exceeds a certain threshold.

[0071] The reference value can be set to a natural number greater than or equal to 1. In applications requiring a high level of diagnostic sensitivity, the reference value may be set low, for example, between 1 and 3. On the other hand, in applications requiring a normal level of diagnostic sensitivity, the reference value may be set higher, for example, to 4 or above.

[0072] Preferably, in applications to which the present invention is applied, the appropriate level of the reference value can be determined through trial and error.

[0073] In one configuration, the reference value can be increased in applications where voltage noise is easily introduced into the voltage sensing circuit 210. This is because if the accuracy of cell voltage measurement is reduced due to voltage noise, a small reference value may lead to a misdiagnosis of a voltage abnormality even in battery cells exhibiting normal voltage behavior.

[0074] In other configurations, the reference value can be reduced if the voltage sensing circuit 210 is designed to be robust against voltage noise.

[0075] The diagnostic logic of the control circuit 220 described above is preferably executed after the battery cell has switched from a charging or discharging state to an unloaded state. An unloaded state means a state in which the magnitude of the charging current or discharging current is substantially zero. An unloaded state may include cases in which the magnitude of the charging current or discharging current is very small. The diagnostic logic of the control circuit 220 may also be executed while the battery cell is charging or discharging.

[0076] Figures 2a and 2b are diagrams used to derive mathematical formulas that represent the normal diagnostic conditions for battery cells, using the voltage behavior of battery cells without voltage abnormalities.

[0077] The voltage profile shown in Figure 2a corresponds to a portion of the cell voltage profile shown by a normal battery cell without voltage abnormalities when the battery cell being charged is switched to an unloaded state in an embodiment of the present invention.

[0078] The voltage profile shown in Figure 2b corresponds to a portion of the cell voltage profile shown by a normal battery cell without voltage abnormalities when a battery cell that is discharging is switched to an unloaded state in an embodiment of the present invention.

[0079] As shown in Figures 2a and 2b, when a battery cell without voltage abnormalities transitions from charging or discharging to a no-load state, the electrode polarization relaxes, and the cell voltage stabilizes to a stable voltage (V). OCV It tends to gradually converge to the stabilized voltage (V) immediately after the battery cell goes from charging to an unloaded state. OCV It gradually decreases and converges to (V). Conversely, when a battery cell goes from being discharged to a no-load state, the cell voltage immediately after becoming no-load will stabilize at (V). OCV It gradually increases and converges to ). Here, the stabilization voltage (V OCV IR refers to the open-circuit voltage corresponding to the current charge state of the battery cell. Also, in the initial stages of a no-load state, the IR voltage of the battery cell is 0, so the range of change in cell voltage is relatively large.

[0080] Referring to Figures 2a and 2b, an arbitrary set of cell voltages V selected from the time-series data of cell voltages for a battery cell in an unloaded state. k , V k+1 , V k+2 This can be represented by three points O1, O2, and O3 on the cell voltage profile.

[0081] Continuously measured cell voltage V k , V k+1 , V k+2 The measurement points are t k t k+1 t k+2 Therefore, the measurement period of the cell voltage is constant with respect to Δt. The measurement period of the cell voltage can range from a few milliseconds to a few seconds.

[0082] When a battery cell in an unloaded state exhibits normal voltage behavior as shown in the cell voltage profiles of Figures 2a and 2b, the slope of the line segment L1 connecting two points O1 and O2 is relatively larger than the slope of the line segment L2 connecting two points O2 and O3, for any given set of cell voltages.

[0083] The cell voltage profile of a battery cell without voltage abnormalities is the regulated voltage (V OCV The stabilizing voltage (V) gradually increases or gradually decreases toward ) OCV This is because it tends to converge to ). This characteristic can be expressed by the following equation 1.

[0084] [Formula 1] |(V k+1 - V k )| / |Δt| > | (V k+2 - V k+1 )| / |Δt|

[0085] Furthermore, by multiplying the right-hand and left-hand equations of equation 1 by |Δt|, equation 1 can be expressed as equation 2.

[0086] [Formula 2] |(V k+1 - V k )| > |(Vk+2 - V k+1 )|

[0087] In equation 2, |(V k+1 -V k )| is the cell voltage V measured at the kth cell. k and the cell voltage V measured at the (k+1)th cell k+1 This corresponds to the absolute difference between and the first voltage difference ΔV 1,k It can be defined as follows.

[0088] Similarly, |(V k+2 -V k+1 )| is the cell voltage V measured at the (k+1)th cell. k+1 and the cell voltage V measured at the (k+2)th cell k+2 This corresponds to the absolute difference with the second voltage difference ΔV 2,k It can be defined as follows.

[0089] Depending on the definitions of the first voltage difference and the second voltage difference, equation 2 can be expressed as equation 3 below.

[0090] [Formula 3] ΔV 1,k > ΔV 2,k

[0091] The inequality in equation 3 can still be maintained even if the first voltage difference and the second voltage difference are both raised to the power of p, as shown in equation 4 below.

[0092] [Equation 4] ΔV 1,k p > ΔV 2,k p (Here, p is a natural number greater than or equal to 1)

[0093] Equation 4 is an arbitrary set of cell voltages V selected from the cell voltage profile for the battery cells. k , V k+1 , V k+2 When diagnosing whether a battery cell voltage is abnormal, this can be used as a normal diagnostic condition.

[0094] In equation 4, p is a natural number greater than or equal to 1. Preferably, p may be 2 or greater. When p is 2 or greater, if the first voltage difference and / or the second voltage difference have a value greater than 1, that value may be amplified even more. Also, when p is 2 or greater, if the first voltage difference and / or the second voltage difference have a value less than 1, that value may be attenuated even more. Therefore, when p is 2 or greater, the possibility of errors occurring in the process of determining whether or not the inequality of equation 4 is satisfied can be reduced. Values ​​greater than 1 are amplified even more, and values ​​less than 1 are attenuated even more, resulting in the first voltage difference (ΔV 1,k ) and the second voltage difference (ΔV 2,k This is because the difference with ) becomes large.

[0095] When the time-series data contains a total of n cell voltages, the total number of selectable cell voltage sets from the time-series data is n-2. Therefore, the control circuit 220 can determine whether the normal diagnostic conditions of Equation 4 are met for the total of n-2 cell voltage sets, and can accumulate and count the number of cell voltage sets that do not meet the normal diagnostic conditions.

[0096] The control circuit 220 may also record the counting results of cell voltage sets that do not meet the normal diagnostic conditions on the recording medium 221. Furthermore, if the number of cell voltage sets that do not meet the normal diagnostic conditions exceeds a standard value, the control circuit 220 may diagnose the battery cell as having a voltage abnormality and record the diagnostic result on the recording medium 221. The diagnostic result may include the time when the voltage abnormality of the battery cell was diagnosed, and identification information (such as a serial number) of the battery cell in which the voltage abnormality appeared.

[0097] The control circuit 220 can also output the diagnostic results visually or audibly through an output device 331 operably coupled to the interface unit 330.

[0098] As an example, the control circuit 220 may output the diagnostic results via a graphical user interface through the display 331a. As another example, the control circuit 220 may output the diagnostic results audibly through the speaker 331b. Preferably, the diagnostic results may include a warning message indicating that a thorough inspection of the battery pack B is required. When the diagnostic results are output visually or audibly, only the warning message may be output.

[0099] The control circuit 220 can also transmit diagnostic results to an external device via wireless communication supported by the interface unit 330.

[0100] For example, the external device could be a vehicle controller 5. When the vehicle controller 5 receives the diagnostic results, it can output a warning message via a graphical user interface through the integrated display panel mounted on the vehicle 1. In this case, the driver can take the vehicle 1 to a service center for a thorough inspection of the battery pack B. If a battery cell with a voltage abnormality is identified through the thorough inspection, that battery cell can be replaced with another battery cell.

[0101] As another example, the external device may be an on-board diagnostic device (not shown) connected via the interface unit 330. The on-board diagnostic device is a device that checks the condition of various parts included in the automobile 1. When the on-board diagnostic device is connected via the interface unit 330, the control circuit 220 can read the diagnostic results regarding voltage abnormalities of the battery cells recorded on the recording medium 221 and transmit them to the on-board diagnostic device side via the interface unit 330. Then, the operator can recognize the diagnostic results output through the display of the on-board diagnostic device and perform a detailed inspection of the battery pack B. In addition, if a battery cell with a voltage abnormality is identified, the operator can replace that battery cell with another battery cell.

[0102] The onboard diagnostic device may execute the diagnostic logic of the control circuit 220 described above. In this case, the onboard diagnostic device may receive time-series data of the cell voltage for each battery cell recorded on the recording medium 221 from the control circuit 220. The time-series data of the cell voltage may be measured after the battery pack B has switched from a charged or discharged state to an unloaded state. The onboard diagnostic device may generate and output the results of voltage anomaly diagnosis for each battery cell via a display.

[0103] Figure 3a is a graph showing an example of time-series data for the cell voltage of a battery cell with a normal voltage in an embodiment of the present invention.

[0104] Figure 3b is a graph showing an example of time-series data for the cell voltage of a battery cell where a voltage anomaly occurred, according to an embodiment of the present invention.

[0105] The cell voltage profiles in Figures 3a and 3b may appear when the battery cell switches from a charged state to an unloaded state. Alternatively, the cell voltage profiles in Figures 3a and 3b may appear during the discharge of the battery cell.

[0106] Referring to Figure 3a, the cell voltage of a battery cell with normal voltage gradually decreases over time without exhibiting any unusual behavior. Therefore, from the time-series data of cell voltage, an arbitrary set of cell voltages V k , V k+1 , V k+2 Even if this option is selected, the cell voltage set still satisfies the normal diagnostic conditions in Equation 4. Therefore, when the time-series data of the cell voltages shows a profile like that in Figure 3a, the count of cell voltage sets that do not satisfy the normal diagnostic conditions can be 0.

[0107] Referring to Figure 3b, a battery cell experiencing a voltage anomaly exhibits peculiar behavior (see C1) in a specific time interval. For example, if the battery cell is a lithium-ion battery, lithium plating occurring at the negative electrode will cause the cell voltage slope to exhibit peculiar behavior. That is, while the magnitude of the cell voltage slope is gradually decreasing, there will be a section where it actually increases. Therefore, in the time interval in which the abnormal change pattern of the cell voltage appears, the cell voltage set V k , V k+1 , V k+2 If this is selected, the cell voltage set in question does not satisfy the normal diagnostic conditions of Equation 4. Therefore, when the time-series data of the cell voltage shows a profile like that in Figure 3b, the count of cell voltage sets that do not satisfy the normal diagnostic conditions may be 1. Of course, if abnormal changes in the cell voltage appear at multiple points in the cell voltage profile, the count of cell voltage sets that do not satisfy the normal diagnostic conditions may increase by the number corresponding to those multiple points.

[0108] Figure 4a is a graph showing an example of time-series data for the cell voltage of a battery cell with a normal voltage, in another embodiment of the present invention.

[0109] Figure 4b is a graph showing an example of time-series data for the cell voltage of a battery cell where a voltage anomaly has occurred, in another embodiment of the present invention.

[0110] The cell voltage profiles in Figures 4a and 4b may appear when the battery cell switches from a discharged state to an unloaded state. Alternatively, the cell voltage profiles in Figures 4a and 4b may appear during the charging of the battery cell.

[0111] Referring to Figure 4a, the cell voltage of a battery cell with normal voltage gradually increases over time without exhibiting any unusual behavior. Therefore, from the time-series data of cell voltage, an arbitrary set of cell voltages V k , V k+1 , V k+2Even if this option is selected, the cell voltage set still satisfies the normal diagnostic conditions in Equation 4. Therefore, when the time-series data of the cell voltages shows a profile like that in Figure 4a, the count of cell voltage sets that do not satisfy the normal diagnostic conditions can be 0.

[0112] Referring to Figure 4b, a battery cell experiencing a voltage anomaly exhibits peculiar behavior (see C2) in a specific time interval. For example, when the battery cell is a lithium-ion battery, if lithium plating occurs at the negative electrode or if an electrode tab breaks, the cell voltage slope exhibits peculiar behavior. That is, while the magnitude of the cell voltage slope is gradually decreasing, there is an interval in which it actually increases. Therefore, in the time interval in which the abnormal change pattern of the cell voltage appears, the cell voltage set V k , V k+1 , V k+2 If this is selected, the cell voltage set in question does not satisfy the normal diagnostic conditions of Equation 4. Therefore, when the time-series data of the cell voltage shows a profile like that in Figure 4b, the count of cell voltage sets that do not satisfy the normal diagnostic conditions may be 1. Of course, if abnormal changes in the cell voltage appear at multiple points in the cell voltage profile, the count of cell voltage sets that do not satisfy the normal diagnostic conditions may increase by the number corresponding to those multiple points.

[0113] The control circuit 220 can periodically execute the diagnostic logic for voltage abnormalities in the battery cells described above for all battery cells included in the battery pack B. In addition, when executing the diagnostic logic for all battery cells, the control circuit 220 can independently execute the diagnostic logic for each battery cell in a predetermined order.

[0114] The control circuit 220 can also execute the aforementioned diagnostic logic regarding battery cell voltage anomalies in real time in conjunction with the measurement of cell voltages, before acquiring time-series data for a preset number of cell voltages.

[0115] Specifically, when the control circuit 220 begins diagnosing a voltage anomaly in the battery cells, it can determine whether the normal diagnostic conditions of Equation 4 are met for the cell voltage sets V1, V2, and V3 when the first, second, and third cell voltages V1, V2, and V3 are measured. The measurement period for the cell voltages is the same as Δt. Furthermore, when the fourth cell voltage V4 is measured, it can determine whether the normal diagnostic conditions of Equation 4 are met for the cell voltage sets V2, V3, and V4. This process can be repeated each time a cell voltage is measured. That is, the k+2th cell voltage V k+2 When measured, the cell voltage set V k , V k+1 , V k+2 It is possible to determine whether the normal diagnostic conditions in Equation 4 are met. This diagnostic process can be repeated until the last cell voltage Vn is measured. The total number of cell voltages to be measured can be predetermined.

[0116] The battery diagnostic device 200 according to an embodiment of the present invention may be included in a battery management system 100, a load device control system (not shown), or a diagnostic system installed in a service center for automobile 1 or battery pack B.

[0117] In the present invention, the control circuit 220 may selectively include processors, ASICs (Application-Specific Integrated Circuits), other chipsets, logic circuits, registers, communication modems, data processing devices, etc., known in the industry, in order to execute the various control logics described above.

[0118] Furthermore, when the control logic is implemented as software, the control circuit 220 can be replaced by a processor that executes a set of program modules. In this case, the program modules can be recorded in memory and executed by the processor. The memory can be located inside or outside the processor and can be connected to the processor by a variety of well-known computer components. The memory can also be included in the recording medium 221. Moreover, the term "memory" is a general term for any device on which information is recorded, regardless of the type of device, and does not refer to a specific memory device.

[0119] Furthermore, at least one of the various control logics of the control circuit 220 can be combined, and the combined control logic can be created in a computer-readable code system and recorded on a computer-readable recording medium. The type of recording medium is not particularly limited as long as it is accessible by a processor included in a computer. As an example, the recording medium includes at least one selected from the group including ROM, RAM, registers, CD-ROM, magnetic tape, hard disk, floppy disk, and optical data recording device. Furthermore, the code system can be distributed, recorded, and executed on computers connected via a network. In addition, functional programs, codes, and code segments for realizing the combined control logic can be easily inferred by programmers in the art to which this invention belongs.

[0120] The following describes in detail a battery diagnostic method using the battery diagnostic device 200 of the present invention as described above. In one embodiment, the battery diagnostic method may be performed by the battery diagnostic device 200 while the automobile 1 is in operation. In another embodiment, the battery diagnostic method may be performed by the battery diagnostic device 200 while the automobile 1 is being charged at a charging station. In yet another embodiment, the battery diagnostic device 200 may be included in the charging station, and the battery diagnostic method may be performed by the battery diagnostic device 200 included in the charging station while the automobile 1 is being charged at the charging station. The battery diagnostic device 200 included in the charging station may receive time-series data of cell voltage to the battery cells from the control circuit 220.

[0121] The operation of the control circuit 220 will be described in more detail in various embodiments of the battery diagnostic method.

[0122] Figure 5 is a flowchart illustrating an exemplary battery diagnostic method according to one embodiment of the present invention. The diagnostic method in Figure 5 can be repeatedly performed for each battery cell included in the battery pack B at a diagnostic cycle predetermined by the control circuit 220.

[0123] Referring to Figure 5, once the diagnosis begins, the control circuit 220 controls the voltage sensing circuit 210 in step S10 to repeatedly measure the voltage of the battery cells at regular time intervals (Δt), generates time-series data for the n cell voltages, and records it on the recording medium 221.

[0124] Next, the control circuit 220 repeats steps S20 to S50 a predetermined number of times to determine whether the normal diagnostic conditions of Equation 4 are met for all selectable cell voltage sets from the time-series data of the cell voltages, and accumulates and counts the number of cell voltage sets that do not meet the normal diagnostic conditions.

[0125] First, in step S20, the control circuit 220 sets the cell voltage V from the time-series data of the cell voltage. k , Vk+1 , V k+2 Select the following. Since the current k is 1, the selected cell voltage set is V1, V2, V3.

[0126] Next, in step S30, the control circuit 220 determines whether the normal diagnostic conditions of Equation 4 are met for the current cell voltage set.

[0127] If the judgment in stage S30 is "no", the control circuit 220 increases the number of cell voltage sets that do not meet the normal diagnostic conditions by 1 in stage S40.

[0128] On the other hand, if the judgment in stage S30 is "yes", the control circuit 220 moves the process to stage S50. In stage S50, the control circuit 220 determines whether there are any cell voltage sets remaining to be diagnosed. That is, the control circuit 220 determines whether the current cell voltage set is the last cell voltage set. The last cell voltage set is V when the total number of cell voltages included in the time series data is n. n-2 , V n-1 , V n That is the case.

[0129] If the determination in stage S50 is "yes", the control circuit 220 returns the process to stage S20, selects the cell voltage set to be diagnosed next, and repeats stages S30, S40, and S50. The current cell voltage set is V2, V3, and V4. Stages S30, S40, and S50 are repeated until the determination in stage S50 is "no".

[0130] Once the control circuit 220 has completed the diagnosis for all selectable cell voltage sets from the time-series data of the cell voltages, it moves the process to stage S60. In stage S60, the control circuit 220 determines whether the number of cell voltage sets that were counted as not meeting the normal diagnostic conditions of Equation 4 is equal to or greater than a reference value. The embodiment regarding the setting of the reference value is as described above.

[0131] If the determination in stage S60 is "yes," the control circuit 220 may diagnose a voltage abnormality in the battery cell in stage S70 and record the diagnosis result in the recording medium 221. The diagnosis result may include the time when the voltage abnormality was diagnosed and the identification information of the battery cell.

[0132] The control circuit 220 can perform voltage abnormality diagnosis on each individual battery cell in the battery pack B. Furthermore, the control circuit 220 can execute a post-diagnosis process by referring to the diagnosis results recorded on the recording medium 221.

[0133] In other words, after completing the diagnosis of all battery cells, the control circuit 220 may transmit the diagnostic results recorded on the recording medium 221 to an external device via the interface unit 330. The diagnostic results transmitted to the external device may include identification information of the battery cell where the voltage anomaly occurred, and information regarding the time of the voltage anomaly diagnosis of that battery cell. The diagnostic results transmitted to the external device may further include a warning message indicating that inspection of the battery pack B is required, or a corresponding diagnostic code. Alternatively, the identification information of the battery cell where the voltage anomaly occurred and detailed information regarding the time of the voltage anomaly diagnosis of that battery cell may be excluded from the diagnostic results transmitted to the external device. When the external device is a vehicle controller 5, the vehicle controller 5 may output the diagnostic results to an integrated display panel mounted on the vehicle 1 via a graphical user interface. When the external device is an onboard diagnostic device operably coupled to the interface unit 330, the onboard diagnostic device may output the diagnostic results via a display. In this case, it is preferable that the diagnostic results include a diagnostic code indicating that there is a battery cell in the battery pack where a voltage anomaly has occurred.

[0134] As another example, after the diagnosis of the entire battery cell is complete, the control circuit 220 may visually or audibly output the diagnostic results recorded on the recording medium 221 through an output device 331 operably coupled with the interface unit 330. The diagnostic results output through the output device 331 may include identification information of the battery cell where the voltage anomaly occurred and information about the time of the voltage anomaly diagnosis of that battery cell. Alternatively, the diagnostic results output through the output device 331 may further include a warning message indicating that inspection of battery pack B is required or a corresponding diagnostic code. Another alternative is that the diagnostic results output through the output device 331 may exclude identification information of the battery cell where the voltage anomaly occurred and detailed information about the time of the voltage anomaly diagnosis of that battery cell.

[0135] If diagnostic results are output via the output device 331, the user of vehicle 1 can take vehicle 1 to a service center for a more precise diagnosis of the condition of battery pack B. If phenomena such as lithium plating are actually observed in some of the battery cells contained in battery pack B, battery pack B may be replaced.

[0136] On the other hand, the battery diagnostic method according to the present invention may be modified as follows. That is, the control circuit 220 may perform a diagnostic cycle in real time in conjunction with the measurement of cell voltages before acquiring time-series data for a preset number of n cell voltages.

[0137] Specifically, when the control circuit 220 begins diagnosing a voltage anomaly in the battery cells, it may perform steps S30 and S40 for cell voltage sets V1, V2, and V3 when the first, second, and third cell voltages V1, V2, and V3 are measured. Similarly, when the fourth cell voltage V4 is measured, it may perform steps S30 and S40 for cell voltage sets V2, V3, and V4. This process may be repeated each time a cell voltage is measured. That is, the k+2th cell voltage V k+2 When measured, the cell voltage set V k, V k+1 , V k+2 Stages S30 and S40 may be performed for this. This diagnostic process may be repeated until the last cell voltage Vn is measured. The total number of cell voltages to be measured can be predetermined. The last cell voltage V n After the measurement is complete, steps S60 and S70 may be performed.

[0138] The real-time diagnostic logic of the control circuit 220 can be executed in synchronization with the cell voltage measurement process of each battery cell. Furthermore, once the diagnosis of the entire battery cell is complete, the control circuit 220 can transmit the diagnostic results to an external device through the interface unit 330 as described above, or it can output the diagnostic results visually or audibly through an output device 331 operably coupled to the interface unit 330.

[0139] According to the embodiment described above, by analyzing the trend of the slope of cell voltages between continuously measured cell voltages using simple mathematical calculations, it is possible to easily diagnose a battery cell in which a voltage anomaly has occurred.

[0140] Furthermore, according to the embodiments of the present invention, since the calculation method used for diagnosing the battery is not complex, a high-spec processor is not required.

[0141] Furthermore, according to embodiments of the present invention, the reliability of voltage anomaly diagnosis can be improved by using mathematical operations that can amplify the trend of the cell voltage slope.

[0142] Furthermore, according to embodiments of the present invention, even if the difference between voltages measured at different points in time is not large, battery cells exhibiting abnormal voltage behavior can be reliably identified.

[0143] In the various embodiments of the present invention, components referred to as "parts" or "circuits" must be understood as functionally distinct elements, not physically distinct elements. Therefore, each component may be selectively integrated with other components, or each component may be divided into sub-components for efficient execution of control logic. However, it will be obvious to those skilled in the art that if the functional identity of the components can be maintained even after integration or division, the integrated or divided components will also be considered within the scope of the present invention.

[0144] As described above, the present invention has been explained with limited embodiments and drawings, but the present invention is not limited thereto, and it goes without saying that various modifications and variations are possible within the equivalent scope of the technical concept and claims of the present invention by persons with ordinary skill in the art to which the present invention pertains.

[0145] Furthermore, the present invention described above can be substituted, modified, and altered in various ways by a person with ordinary skill in the art to which the present invention belongs, without departing from the technical spirit of the invention. Therefore, it is not limited by the embodiments and drawings described above, and it is also possible to selectively combine all or part of each embodiment to create a variety of modifications.

Claims

1. A voltage sensing circuit configured to generate a voltage signal indicating the cell voltage of a battery cell, A recording medium configured to record time-series data of the cell voltage, The voltage sensing circuit and the recording medium are operably coupled to the control circuit, The aforementioned control circuit is (i) Upon receiving the voltage signal input, time-series data of the cell voltage is recorded on the recording medium. (ii) Select the cell voltage sets measured at the kth, k+1th, and k+2nd positions from the time-series data as diagnostic data (where k is an index indicating the measurement order of the cell voltages, and is a natural number of 1 or more, to which multiple values ​​may be assigned), (iii) Determine the first voltage difference between the k-th cell voltage and the (k+1)-th cell voltage, and the second voltage difference between the (k+1)-th cell voltage and the (k+2)-th cell voltage. (iv) A battery diagnostic device configured to diagnose a battery cell as having a voltage abnormality if the count of cell voltage sets for which the normal diagnostic condition that the first voltage difference raised to the power of p (where p is a natural number greater than or equal to 1) is not met is greater than the second voltage difference raised to the power of p exceeds a reference value.

2. The battery diagnostic device according to claim 1, wherein p is 1.

3. The battery diagnostic device according to claim 1, wherein p is a natural number of 2 or more.

4. The battery diagnostic device according to claim 1, wherein the reference value is 1.

5. The battery diagnostic device according to claim 1, wherein the reference value is a natural number of 2 or more.

6. The battery diagnostic device according to claim 1, wherein the control circuit is configured to select a plurality of cell voltage sets from the time-series data of the cell voltages while increasing the k by 1 from 1 to n-2 (where n is the number of voltage data included in the time-series data).

7. The battery diagnostic device according to claim 1, wherein the control circuit is configured to perform the control logic (i) to (iv) above when the operating state of the battery cell is switched from a charging or discharging state to an unloaded state.

8. The system further includes an interface unit which is operably coupled to the control circuit and assists in communication with an external device, The battery diagnostic device according to claim 1, wherein the control circuit is configured to transmit the diagnostic result to an external device through the interface unit when the battery cell is diagnosed with a voltage abnormality.

9. An interface unit operably coupled to the aforementioned control circuit, The interface unit further includes an output device operably coupled to the interface unit, The battery diagnostic device according to claim 1, wherein the control circuit is configured to output the diagnostic result visually or audibly through the output device when the battery cell is diagnosed with a voltage abnormality.

10. A battery pack comprising a battery diagnostic device according to any one of claims 1 to 9.

11. An automobile comprising the battery pack described in claim 10.

12. (a) A step of receiving a voltage signal input from a voltage sensing circuit indicating the cell voltage of a battery cell and recording time-series data of the cell voltage on a recording medium, (b) A step of selecting the cell voltage sets measured at the kth, k+1th, and k+2nd positions from the time-series data as diagnostic data (where k is an index indicating the measurement order of the cell voltages, and is a natural number of 1 or more, to which multiple values ​​may be assigned), (c) A step of determining the first voltage difference between the k-th cell voltage and the k+1-th cell voltage, and the second voltage difference between the k+1-th cell voltage and the k+2-th cell voltage, (d) A battery diagnostic method comprising the step of diagnosing a battery cell as having a voltage abnormality if the count of cell voltage sets for which the normal diagnostic condition that the first voltage difference raised to the power of p (where p is a natural number greater than or equal to 1) is greater than the second voltage difference raised to the power of p is exceeds a reference value.

13. The battery diagnostic method according to claim 12, wherein p is 1.

14. The battery diagnostic method according to claim 12, wherein p is a natural number of 2 or more.

15. The battery diagnostic method according to claim 12, wherein the reference value is 1.

16. The battery diagnostic method according to claim 12, wherein the reference value is a natural number of 2 or more.

17. The battery diagnostic method according to any one of claims 12 to 16, wherein a plurality of cell voltage sets are selected from the time-series data of the cell voltages while increasing the k by 1 from 1 to n-2 (where n is the number of cell voltages included in the time-series data).

18. The battery diagnostic method according to any one of claims 12 to 16, wherein steps (a) to (d) are performed when the operating state of the battery cell is switched from a charging or discharging state to an unloaded state.

19. The battery diagnostic method according to any one of claims 12 to 16, further comprising the step of transmitting the diagnostic result to an external device if the battery cell is diagnosed with a voltage abnormality.

20. The battery diagnostic method according to any one of claims 12 to 16, further comprising the step of outputting the diagnostic result visually or audibly through an output device if the battery cell is diagnosed with a voltage abnormality.

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