Battery diagnostic method, battery diagnostic device for performing the same, and battery pack

Abstract

To provide a battery diagnosis method, a battery diagnosis device and a battery pack executing the same.SOLUTION: A battery diagnosis device includes: a detection device that detects a cell voltage of a battery cell; and a diagnosis device that calculates a rate of voltage decrease over time of the cell voltage if a negligence test of the battery cell is initiated, detects an inflection point at which the rate of voltage decrease changes from a decreasing trend to an increasing trend, and diagnoses the battery cell as an abnormal battery cell if the inflection point is detected.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a battery diagnostic method, and a battery diagnostic device and battery pack for performing the method. [Background technology]

[0002] Secondary batteries differ from primary batteries, which only provide for the irreversible conversion of chemicals into electrical energy, in that they can be repeatedly charged and discharged.

[0003] Generally, a secondary battery cell includes an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive and negative electrodes, a case that houses the electrode assembly, and electrode terminals that are electrically connected to the electrode assembly. An electrolyte solution is injected into the case to enable charging and discharging of the battery cell through electrochemical reactions between the positive electrode, the negative electrode, and the electrolyte solution. The shape of the case, such as cylindrical or rectangular, varies depending on the application of the battery cell.

[0004] In secondary battery cells, internal short circuits can occur when the separator loses its function, causing a short circuit between the positive and negative electrodes inside the battery cell.Internal short circuits in secondary battery cells can occur due to deformation caused by external impact, metallic foreign matter introduced during the manufacturing process, or the formation of lithium or copper dendrites due to electrochemical reactions.

[0005] Such an internal short circuit in the secondary battery cell can cause safety issues such as thermal runaway. Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present disclosure is to provide a battery diagnostic method for detecting a battery cell that is expected to have an internal short circuit, and a battery diagnostic device and a battery pack that perform the method. [Means for solving the problem]

[0007] According to one embodiment of the present invention, a battery diagnostic device for solving the above problem may include a detection device for detecting a cell voltage of a battery cell, and a diagnostic device for calculating a voltage decrease rate of the cell voltage over time when a storage test of the battery cell is started, detecting an inflection point at which the voltage decrease rate changes from a decreasing trend to an increasing trend, and diagnosing the battery cell as an abnormal battery cell when the inflection point is detected.

[0008] The diagnostic device may operate in a standby test mode to perform the standby test in a state where the battery cell's SOC (state of charge) is charged to a predetermined value or more, and the predetermined value may be 80%.

[0009] When the inflection point is detected, the diagnostic device classifies the battery cell into an internal short circuit risk group, and when the voltage decrease rate in the time period after the inflection point satisfies a predetermined condition, the diagnostic device can finally determine the battery cell as an abnormal battery cell.

[0010] The diagnostic device may finally determine the battery cell as an abnormal battery cell if the voltage decrease rate in the time period after the inflection point is 0.7 mV / h or more.

[0011] A battery pack according to an embodiment may include the battery diagnostic device and a battery including at least one battery cell.

[0012] A battery diagnosis method for a battery pack according to one embodiment may include entering a storage test mode for a battery cell, detecting a cell voltage of the battery cell, calculating a voltage decrease rate of the cell voltage according to time, detecting an inflection point at which the voltage decrease rate changes from a decreasing trend to an increasing trend, and determining the battery cell as an abnormal battery cell when the inflection point is detected.

[0013] The battery diagnosis method may further include, before the entering step, charging the battery cell so that the SOC of the battery cell is equal to or greater than a predetermined value, where the predetermined value may be 80%.

[0014] The determining step may include classifying the battery cell into an internal short circuit risk group when the inflection point is detected, and finally determining the battery cell as an abnormal battery cell when the voltage decrease rate satisfies a predetermined condition in a time period after the inflection point.

[0015] The final determination may include determining the battery cell as an abnormal battery cell if the voltage decrease rate in the time period after the inflection point is equal to or greater than 0.7 mV / h. [Effects of the Invention]

[0016] According to the present disclosure, by detecting abnormal battery cells that are likely to have an internal short circuit through advance diagnosis, it is possible to protect the battery from thermal runaway, fire, etc. [Brief explanation of the drawings]

[0017] [Figure 1] 1 illustrates a schematic diagram of a battery pack according to one embodiment. [Figure 2] 1 shows an example of a change in cell voltage of a battery cell measured during a storage test. [Figure 3] 1 illustrates a battery diagnostic method according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Hereinafter, functions and effects of embodiments of the present invention and methods for realizing the same will be described with reference to the accompanying drawings. In the drawings, the same reference numerals indicate the same elements, and redundant description will be omitted. However, the present invention may be embodied in various forms and should not be construed as being limited to the embodiments shown herein. Rather, these embodiments are provided as examples so that this disclosure will be thorough and complete, and will fully convey aspects and features of the present invention to those skilled in the art.

[0019] Therefore, processes, elements, and techniques that are not considered necessary for those skilled in the art to fully understand the aspects and features of the present invention may not be described. In the drawings, the relative sizes of elements, layers, and regions may be exaggerated for clarity.

[0020] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. Also, when describing embodiments of the present invention, the use of "may" means "one or more embodiments of the present invention." In the following description of embodiments of the present invention, terms in the singular form can include the plural form unless the context clearly dictates otherwise.

[0021] Although terms including ordinal numbers such as "first," "second," and "third" are used to describe various elements, it should be understood that these elements should not be limited by these terms. These terms are used only to distinguish one element from another. For example, a first element may be named a second element, and similarly, a second element may be named a first element without departing from the scope of the present invention. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. Phrases such as "at least one" preceding a list of elements modify the entire list of elements, not the individual elements of the list.

[0022] As used herein, the terms "substantially," "about," and similar terms are used as terms of approximation, not as terms of degree, and are intended to describe inherent deviations in measured or calculated values ​​that can be recognized by those of ordinary skill in the art. Also, when the term "substantially" is used in conjunction with a characteristic that can be expressed using a numerical value, the term "substantially" indicates a range of + / - 5% of the value centered on that numerical value.

[0023] When a component or layer is described as being "on," "connected," or "bonded" to another component or layer, "on," "connected," and "bonded" include being formed directly or via one or more other components or layers. Also, when a component or layer is described as being "between" two components or layers, it should be understood that it may be the only component or layer between the two components or layers, or that there may be one or more intervening components or layers.

[0024] Electrically connecting two components includes not only directly connecting the two components but also connecting the two components via another component between them. The other component may include a switch, a resistor, a capacitor, etc. In describing the embodiments, the expression "connected" means electrically connecting unless there is an expression "directly connected."

[0025] Hereinafter, a battery diagnostic method according to an embodiment, and a battery diagnostic device and a battery pack for performing the same will be described in detail with reference to the accompanying drawings.

[0026] FIG. 1 illustrates a schematic diagram of a battery pack according to one embodiment.

[0027] Referring to FIG. 1, a battery pack 1 according to an embodiment may include a battery 10 and a battery diagnostic device 20.

[0028] The battery 10 may include at least one battery cell. When the battery 10 includes multiple battery cells, the multiple battery cells may be electrically connected to each other in series and / or parallel.

[0029] The battery diagnostic device 20 continuously detects the status information of the battery 10 and, based on the detected status information, can diagnose whether or not there is an abnormality in the battery 10. The battery diagnostic device 20 may include a detection device 21 and a diagnosis device 22.

[0030] The detection device 21 can detect the state information of the battery 10, that is, the state information of the battery cells that make up the battery 10 (cell voltage, temperature, current, etc.).

[0031] The diagnostic device 22 monitors the state information of the battery cells constituting the battery 10 through the detection device 21, and can diagnose whether or not the battery 10 has an abnormality.

[0032] A storage test may be performed to evaluate the long-term storage performance of the battery pack 1 before use. The storage test may be performed by charging the battery 10 to a predetermined state and then storing the battery 10 in a rest state without charging or discharging for an extended period of time while monitoring changes in its state. For example, the storage test may be performed after charging the battery 10 until the state of charge (SOC) of the battery cells constituting the battery 10 reaches a range of 80% or more. FIG. 2 illustrates changes in the cell voltage of the battery cells measured during the storage test, showing results obtained after storing a battery cell with a 100% SOC for 10 hours. Referring to FIG. 2, the battery cell (Flat#3) with an internal short circuit exhibits a gradual decrease in its cell voltage decrease rate over time (i.e., the amount of cell voltage decrease per unit time) similar to other normal battery cells during the initial storage period. However, after six hours of storage, the battery cell (Flat#3) exhibits abnormal behavior, exhibiting a gradual increase in its cell voltage decrease rate, unlike other normal battery cells.

[0033] The diagnostic device 22 of FIG. 1 can detect such abnormal behavior during a storage test and detect an abnormal battery cell. To this end, when the diagnostic device 22 enters a storage test mode for the battery 10, it can continuously acquire the cell voltages of the battery cells constituting the battery 10 through the detection device 21. The diagnostic device 22 can also monitor the changes in the cell voltages of the battery cells acquired through the detection device 21, continuously calculate a rate of decrease in cell voltage over time, and detect an inflection point at which the rate of decrease in cell voltage over time changes from a decreasing trend to an increasing trend. Here, a decreasing trend in the rate of decrease in cell voltage over time indicates a state in which the amount of decrease in cell voltage per unit time is gradually decreasing, and an increasing trend in the rate of decrease in cell voltage over time indicates a state in which the amount of decrease in cell voltage per unit time is gradually increasing.

[0034] The diagnostic device 22 can also detect inflection points using the second derivative (f"()). Equation 1 below shows a method for detecting inflection points using the second derivative.

[0035] [Formula 1] f”(a+h)×f”(ah)<0 In Equation 1, f"(a+h) and f"(ah) represent second-order derivatives and may be calculated by differentiating the cell voltage slope (dV / dT), which indicates the rate of change in cell voltage over time. Furthermore, a represents the time the battery 10 has been left unused since entering the unused test mode, and h may be selected as a very small value. When an inflection point occurs in the cell voltage slope (dV / dT), the sign of the value obtained by differentiating the cell voltage slope (dV / dT) based on the inflection point changes. Therefore, if an inflection point occurs after the battery 10 has been left unused for a hour, f"(a+h) and f"(ah) have opposite signs, and multiplying the two values ​​may result in a value less than 0. Therefore, when the diagnostic device 22 monitors the cell voltage change of each battery cell and detects a point satisfying Equation 1, it may determine the point as the inflection point.

[0036] When the inflection point is detected, the diagnostic device 22 can classify the battery cell in which the inflection point is detected as an abnormal battery cell in which an internal short circuit has occurred.

[0037] The diagnostic device 22 may perform an additional diagnostic process on a battery cell in which an inflection point has occurred to prevent erroneous diagnosis of a normal battery cell as an abnormal battery cell. When the diagnostic device 22 detects an inflection point, the diagnostic device 22 may first classify the corresponding battery cell into an internal short circuit risk group. Then, the diagnostic device 22 monitors the voltage change after the inflection point for the battery cell classified into the internal short circuit risk group, and if the monitored voltage change meets a predetermined condition, the diagnostic device 22 may finally diagnose the corresponding battery cell as an abnormal battery cell. For example, if the voltage decrease rate (i.e., the amount of cell voltage decrease per unit time) in a time period after the inflection point has occurred is equal to or greater than a critical value (e.g., 0.7 mV / h), the diagnostic device 22 may finally diagnose the corresponding battery cell as an abnormal battery cell.

[0038] When an abnormal battery cell is detected in the battery 10, the diagnostic device 22 can output the detection result through an output device (for example, a display) or transmit it to a higher-level system.

[0039] The diagnostic device 22 may be embodied to be integrated into a battery management system (BMS) mounted on the battery pack 1.

[0040] 3 is a schematic diagram illustrating a battery diagnostic method according to an embodiment of the present invention, which can be performed by the battery diagnostic device 20 of the battery pack 1 described with reference to FIG.

[0041] Referring to FIG. 3, the battery diagnostic device 20 can control the battery 10 to be charged until the SOC of the battery cells constituting the battery 10 meets a predetermined condition (e.g., 80% or more) in order to perform a storage test (S11, S12).

[0042] If the SOC of the battery 10 satisfies a predetermined condition, the battery diagnostic device 20 stops charging the battery 10 and then enters a standby test mode in response to a control input received from the outside (S13). While operating in the standby test mode, the battery diagnostic device 20 can limit the charging and discharging of the battery 10 and maintain the battery 10 in a sleep state.

[0043] While operating in the stand-by test mode, the battery diagnostic device 20 monitors the cell voltage change of the battery cell (S14) and diagnoses whether an inflection point has occurred. That is, the battery diagnostic device 20 monitors the cell voltage change of the battery cell, and when the rate of decrease in the cell voltage of the battery cell over time changes from a decreasing trend to an increasing trend, the battery diagnostic device 20 can detect the corresponding point as an inflection point.

[0044] When an inflection point is detected (S15), the battery diagnostic device 20 may classify the battery cell in which the inflection point is detected into an internal short circuit risk group (S16). Thereafter, the battery diagnostic device 20 determines whether a cell voltage change after the inflection point of the battery cell classified into the internal short circuit risk group satisfies a predetermined condition (S17), and if the predetermined condition is satisfied, may finally determine the battery cell as an abnormal battery cell (S18). For example, when the battery diagnostic device 20 determines that the cell voltage decrease rate of the battery cell classified into the internal short circuit risk group is equal to or greater than a critical value (e.g., 0.7 mV / h) during the time period after the inflection point, the battery diagnostic device 20 may finally determine the battery cell as an abnormal battery cell.

[0045] The battery diagnostic device 20 can diagnose abnormal battery cells by repeatedly performing steps S14 to S18 until the end of the standing test is determined by an external control input (S19).

[0046] 3, steps S16 and S17 are additional steps performed to prevent erroneous diagnosis and may be omitted. For example, when an inflection point is detected through step S15, the battery diagnostic device 20 may determine the battery cell in which the inflection point is detected as an abnormal battery cell without performing additional diagnosis.

[0047] Electronic or electrical devices according to the embodiments described herein and / or any other related devices or components may be implemented using any suitable hardware, firmware (e.g., application-specific integrated circuits), software, or a combination of software, firmware, and hardware. For example, various components of these devices may be formed on a single integrated circuit (IC) chip or on separate IC chips. Also, various components of these devices may be implemented on a flexible printed circuit film, a tape carrier package (TCP), a printed circuit board (PCB), or a single substrate. The electrical connections or interconnections described herein may be implemented, for example, by traces or conductive elements on a PCB or other type of circuit carrier. The conductive elements may include, for example, metallization, such as surface metallizations, and / or pins, and may include conductive polymers or ceramics.

[0048] Additionally, the various components of these devices may be processes or threads running on one or more processors, executing within one or more computing devices, executing computer program instructions, and interacting with other system components to perform the various functions described herein. The computer program instructions are stored in memory, which may be embodied in the computing device using standard memory devices, such as random access memory (RAM). The computer program instructions may also be stored on other non-transitory computer-readable media, such as CD-ROMs, flash drives, etc.

[0049] Additionally, those skilled in the art should recognize that the functionality of various computing devices may be combined or integrated into a single computing device, or the functionality of a particular computing device may be distributed across one or more other computing devices without departing from the scope of exemplary embodiments of the present invention. [Explanation of symbols]

[0050] 1: Battery pack 10: Battery 20: Battery diagnostic device 21:Detection device 22: Diagnostic equipment

Claims

1. a detection device for detecting a cell voltage of the battery cell; and a diagnostic device for diagnosing the battery cell as an abnormal battery cell when the battery cell is left unused for a certain period of time, calculating a voltage decrease rate of the cell voltage according to time when the battery cell is left unused for a certain period of time, detecting an inflection point at which the voltage decrease rate changes from a decreasing trend to an increasing trend, and diagnosing the battery cell as an abnormal battery cell when the inflection point is detected; Including, When the inflection point is detected, the diagnostic device classifies the battery cell into an internal short circuit risk group, and when the voltage decrease rate in the time period after the inflection point is equal to or greater than a critical value, the diagnostic device finally determines the battery cell as an abnormal battery cell.

2. 2. The battery diagnostic device of claim 1, wherein the diagnostic device operates in a standby test mode for performing the standby test in a state where the battery cell is charged with a state of charge (SOC) of a predetermined value or more.

3. 3. The battery diagnostic device according to claim 2, wherein the predetermined value is 80%.

4. A battery diagnostic device as described in claim 3, wherein the critical value is 0.7 mV / h.

5. A battery diagnostic device according to any one of claims 1 to 4, and a battery including at least one of the battery cells; Including battery pack.

6. A battery diagnostic method for a battery pack, comprising: Entering a battery cell standby test mode; detecting a cell voltage of the battery cell; calculating a rate of voltage decrease of the cell voltage over time; detecting an inflection point at which the voltage decrease rate changes from a decreasing trend to an increasing trend; and determining the battery cell as an abnormal battery cell when the inflection point is detected; The determining step comprises: classifying the battery cell into an internal short circuit risk group when the inflection point is detected; and When the voltage decrease rate in the time period after the inflection point is equal to or greater than a critical value, the battery cell is finally determined to be an abnormal battery cell.

7. Before the step of entering, The battery diagnosis method of claim 6 , further comprising charging the battery cell so that the SOC of the battery cell is equal to or greater than a predetermined value.

8. 8. The battery diagnostic method according to claim 7, wherein the predetermined value is 80%.

9. A battery diagnostic method as described in claim 6, wherein the critical value is 0.7 mV / h or more.

Images