Battery diagnosis device, battery diagnosis method, battery pack, and electric vehicle

Abstract

A battery diagnostic device according to the present application includes a voltage sensor that generates a voltage signal indicating a battery voltage of a battery, a current sensor that generates a current signal indicating a battery current of the battery, and a control circuit. A capacity curve indicating a relationship between the battery voltage and a charge capacity in a set voltage range is determined based on the voltage signal and the current signal collected per unit time during a constant current charging period. The control circuit determines a differential curve indicating a relationship between the battery voltage and a differential capacity in the set voltage range based on the capacity curve. The control circuit determines whether a lithium precipitation abnormality has occurred in the battery based on an approximate straight line of the differential curve by using a linear approximation algorithm.

Description

Technical Field

[0001] This application claims the benefit of Korean Patent Application No. 10-2020-0185703, filed with the Korean Intellectual Property Office on December 29, 2020, the disclosure of which is incorporated herein by reference in its entirety.

[0002] This disclosure relates to techniques for detecting lithium deposition in batteries. Background Technology

[0003] Recently, demand for portable electronic products such as laptops, cameras and mobile phones has increased rapidly, and with the widespread development of electric vehicles, energy storage devices, robots and satellites, there is a lot of research being done on high-performance batteries that can be repeatedly recharged.

[0004] Currently, commercially available batteries include nickel-cadmium batteries, nickel-metal hydride batteries, nickel-zinc batteries, and lithium-ion batteries. Among them, lithium-ion batteries have little or no memory effect, and therefore they receive more attention than nickel-based batteries. The advantages of lithium-ion batteries are that they can be recharged whenever convenient, have a very low self-discharge rate, and high energy density.

[0005] A lithium-ion battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. It is a secondary battery that can be charged / discharged as lithium ions move through the electrolyte between the positive and negative electrodes.

[0006] Lithium-ion batteries degrade slowly during repeated charge / discharge cycles. In particular, the likelihood of lithium deposition increases when the negative electrode structure deteriorates from its factory fresh condition. During lithium deposition, some lithium ions that migrate from the positive to the negative electrode through the electrolyte during charging fail to embed in the negative electrode and deposit as metallic lithium on its surface. Lithium deposition is a major cause of reduced charge / discharge performance and shortened lithium-ion battery life, and it also increases the risk of fire due to short circuits between the positive and negative electrodes caused by metallic lithium. Summary of the Invention

[0007] Technical issues

[0008] The inventors recognized that the relationship between battery voltage and charging capacity of a charged battery changes significantly depending on the presence or absence of lithium deposition. This disclosure relates to providing battery diagnostic equipment, battery diagnostic methods, battery packs, and electric vehicles, wherein capacity curves and differential curves of a battery deteriorating from its factory condition are obtained sequentially through a constant current charging process; information related to lithium deposition is extracted from the approximate straight line of the differential curve; and the presence or absence of lithium deposition in the battery is determined based on the extracted information.

[0009] These and other objects and advantages of this disclosure will be understood from the following description and will be apparent from embodiments of this disclosure. Furthermore, it will be readily understood that the objects and advantages of this disclosure can be achieved by the means set forth in the appended claims and combinations thereof.

[0010] Technical solution

[0011] A battery diagnostic device according to one aspect of this disclosure includes: a voltage sensor configured to measure a battery voltage across a battery and generate a voltage signal indicating the measured battery voltage; a current sensor configured to measure a battery current flowing through the battery and generate a current signal indicating the measured battery current; and a control circuit configured to collect the voltage signal and the current signal at each unit time. The control circuit is configured to: determine a capacity curve indicating the relationship between the battery voltage and charging capacity within a predetermined set voltage range based on the voltage signal and the current signal collected at each unit time during a constant current charging period of the battery. The charging capacity indicates the cumulative value of the battery current. The control circuit is configured to determine a differential curve indicating the relationship between the battery voltage and differential capacity within the set voltage range based on the capacity curve. The differential capacity is the ratio of the change in charging capacity per unit time to the change in battery voltage per unit time. The control circuit is configured to use a linear approximation algorithm to determine an approximate straight line of the differential curve. The control circuit is configured to determine the presence of lithium deposition in the battery based on the approximate straight line.

[0012] The upper limit of the set voltage range can be equal to the preset charging end voltage of the battery. The lower limit of the set voltage range can be equal to a voltage that is lower than the upper limit by a reference voltage.

[0013] The linear approximation algorithm is the least squares method.

[0014] The control circuit can be configured to determine the presence of lithium deposition in the battery when the slope of the approximate straight line is greater than a reference slope.

[0015] The control circuit can be configured to determine the reference slope based on the cumulative usage capacity of the battery.

[0016] The control circuit can be configured to determine the presence of lithium deposition in the battery when the coefficient between the differential curve and the approximate straight line is less than a reference determination coefficient.

[0017] The control circuit can be configured to determine the reference determination factor based on the cumulative usage capacity of the battery.

[0018] According to another aspect of this disclosure, the battery pack includes battery diagnostic equipment.

[0019] According to another aspect of this disclosure, an electric vehicle includes a battery pack.

[0020] A battery diagnostic method according to another aspect of this disclosure can be performed by a battery diagnostic device. The battery diagnostic method includes the following steps: determining a capacity curve indicating the relationship between the battery voltage and charging capacity within a set voltage range based on voltage and current signals collected per unit time during a constant current charging period of the battery; determining a differential curve indicating the relationship between the battery voltage and the differential capacity within the set voltage range based on the capacity curve; determining an approximate straight line of the differential curve using a linear approximation algorithm; and determining the presence of lithium deposition in the battery based on the approximate straight line.

[0021] Beneficial effects

[0022] According to at least one embodiment of this disclosure, the presence of lithium deposition in the battery can be determined based on information related to lithium deposition extracted from an approximate straight line of the differential curve after obtaining capacity and differential curves of the battery deteriorated from its factory condition in a continuous sequence through a constant current charging process.

[0023] According to at least one embodiment of this disclosure, at least one parameter (hereinafter referred to as 'reference voltage', 'reference slope', 'reference determination coefficient') for diagnosing lithium deposition in the battery can be determined based on the battery's cumulative charge / discharge capacity.

[0024] The effects of this disclosure are not limited to those described above, and those skilled in the art will clearly understand, based on the appended claims, these and other effects not mentioned herein. Attached Figure Description

[0025] The accompanying drawings illustrate preferred embodiments of the present disclosure and are used together with the detailed description of the present disclosure described below to provide a further understanding of the technical aspects of the present disclosure, and therefore the present disclosure should not be construed as being limited to the drawings.

[0026] Figure 1 This is a schematic diagram illustrating an electric vehicle according to the present disclosure.

[0027] Figure 2 It shows through Figure 1 The diagram shows a capacity curve obtained by constant current charging of the battery.

[0028] Figure 3 It is shown that... Figure 2The diagram shows a differential curve related to the capacity curve.

[0029] Figure 4 This is an exemplary flowchart illustrating a battery diagnostic method according to a first embodiment of the present disclosure.

[0030] Figure 5 This is an exemplary flowchart illustrating a battery diagnostic method according to a second embodiment of the present disclosure. Detailed Implementation

[0031] In the following, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Before the description, it should be understood that the terms or words used in the specification and appended claims should not be construed as limited to their general and dictionary meanings, but rather as interpreted based on their meanings and concepts corresponding to the technical aspects of the present disclosure, in accordance with the principle that the inventors are permitted to appropriately define terms for the best interpretation.

[0032] Therefore, the embodiments described herein and the illustrations shown in the accompanying drawings are merely the most preferred embodiments of this disclosure, but are not intended to fully describe the technical aspects of this disclosure. It should be understood that various other equivalents and modifications may be made thereto when filing the application.

[0033] Terms that include ordinal numbers (such as "first", "second", etc.) are used to distinguish one element from another among various elements, but are not intended to limit the elements to the terms.

[0034] Unless the context clearly indicates otherwise, it will be understood that the term "comprising" as used in this specification specifies the presence of the stated elements, but does not exclude the presence or addition of one or more other elements. Additionally, as used herein, the term "control unit" refers to a processing unit that performs at least one function or operation and may be implemented individually or in combination by hardware and software.

[0035] Furthermore, as will be further understood throughout the specification, when an element is referred to as being “connected to” another element, it may be directly connected to the other element, or there may be an intermediate element present.

[0036] Figure 1 This is a schematic diagram illustrating an electric vehicle according to the present disclosure.

[0037] refer to Figure 1 The electric vehicle 1 includes a battery pack 2, an inverter 3, an electric motor 4, a charging module 5, and a vehicle controller 6.

[0038] Battery pack 2 includes battery B, switch SW and battery management system 100.

[0039] Battery B can be connected to converter 3 and / or charging module 5 via a pair of power terminals located in battery pack 2. Battery B is a rechargeable battery and can be, for example, a lithium-ion battery.

[0040] The converter 3 is configured to convert direct current (DC) from battery B into alternating current (AC) in response to a command from the battery management system 100. The electric motor 4 can be, for example, a 3-phase AC motor. The electric motor 4 operates using AC power from the converter 3.

[0041] Switch SW is connected in series with battery B. Switch SW is installed in the charging / discharging current path of battery B. Switch SW is turned on / off in response to a switching signal from battery management system 100. Switch SW can be a mechanical relay that is turned on / off by the magnetic force of a coil or semiconductor switching device (such as a metal-oxide-semiconductor field-effect transistor (MOSFET)).

[0042] The charging module 5 is provided to adjust the charging power of battery B in response to commands from control circuit 230. This adjustment is made when the battery voltage of battery B is equal to or lower than the lower limit V of a set voltage range as described below. L At this time, the control circuit 230 can command the charging module 5 to perform constant current charging. The charging module 5 can be hardware, a DC-DC converter, a constant current circuit, or a combination thereof.

[0043] A battery management system 100 is provided to be responsible for overall control related to the charging / discharging of battery B. The battery management system 100 includes a battery diagnostic device 200. The battery management system 100 may also include at least one of a temperature sensor 310 or a communication circuit 320. Hereinafter, it is assumed that the battery management system 100 includes the battery diagnostic device 200, the temperature sensor 310, and the communication circuit 320.

[0044] The battery diagnostic device 200 includes a voltage sensor 210, a current sensor 220, and a control circuit 230.

[0045] Voltage sensor 210 is connected in parallel to battery B and is configured to detect the battery voltage across battery B and generate a voltage signal indicating the detected battery voltage.

[0046] Current sensor 220 is connected in series to battery B via a current path. Current sensor 220 is configured to detect the battery current flowing through battery B and generate a current signal indicating the detected battery current.

[0047] Temperature sensor 310 is configured to detect the temperature of battery B and generate a temperature signal indicating the detected temperature.

[0048] The communication circuit 320 may include communication circuitry configured to support wired or wireless communication between the control circuit 230 and the vehicle controller 6 (e.g., an electronic control unit (ECU)). Wired communication may be, for example, Controller Area Network (CAN) communication, and wireless communication may be, for example, Zigbee or Bluetooth communication. The communication protocol is not limited to a specific type and may include any communication protocol used to support wired / wireless communication between the control circuit 230 and the vehicle controller 6.

[0049] The communication circuit 320 may include output devices (e.g., a display, a speaker) to provide information in an identifiable form received from the vehicle controller 6 and / or control circuit 230. The vehicle controller 6 may control the converter 3 based on battery information (e.g., voltage, current, temperature, SOC) collected via communication with the battery management system 100.

[0050] The control circuit 230 may be implemented in hardware using at least one of an application-specific integrated circuit (ASIC), a digital signal processor (DSP), a digital signal processing device (DSPD), a programmable logic device (PLD), a field-programmable gate array (FPGA), a microprocessor, or an electrical unit for performing other functions.

[0051] The control circuit 230 may have a storage device. The storage device may include at least one type of storage medium selected from, for example, flash memory, hard disk, solid-state drive (SSD), silicon disk drive (SDD), multimedia card micro, random access memory (RAM), static random access memory (SRAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), or programmable read-only memory (PROM). The storage device may store data and programs required for calculations by the control circuit 230. The storage device may also store data indicating the calculation results of the control circuit 230.

[0052] Control circuit 230 can be operationally connected to switch SW, charging module 5, voltage sensor 210, current sensor 220, temperature sensor 310, and / or communication circuit 320. Operational connection means being connected to send and receive signals in one or both directions. Control circuit 230 can collect sensing signals periodically or aperiodically in a repetitive manner. Sensing signals indicate synchronously detected voltage, current, and / or temperature signals.

[0053] Control circuit 230 can determine the state of charge (SOC) of battery B based on sensing signals at predetermined time intervals during the charging / discharging of battery B. Well-known algorithms such as ampere counting, SOC open-circuit voltage (OCV) curve 20, and Kalman filtering can be used to determine SOC.

[0054] Figure 2 It shows through Figure 1 The diagram shows a capacity curve obtained by constant current charging of the battery. Figure 3 It is shown that... Figure 2 The diagram shows a differential curve related to the capacity curve. Figure 2 and Figure 3 Each curve shown, 201, 202, 301, 302, can be considered as a type of signal (time series).

[0055] Figure 2 The two capacity curves were obtained by constant current charging of two sample batteries manufactured with the same electrochemical specifications as battery B and having the same state of health (SOH). Figure 2 The figure shows the discharge end voltage V for each sample battery. D to the predetermined end voltage V C Constant current charging within the total voltage range. Charging end voltage V C The maximum voltage to which battery B can be charged can be given, and the discharge end voltage V. D It can be given as the minimum voltage to which battery B is allowed to discharge.

[0056] refer to Figure 2 Capacity curve 201 indicates the relationship between battery voltage and charging capacity over the total voltage range, obtained by constant current charging of a sample battery without lithium deposition. Capacity curve 202 indicates the relationship between battery voltage and charging capacity over the total voltage range, obtained by constant current charging of a sample battery with lithium deposition.

[0057] The charging capacity used in this paper is the result of accumulating the battery current measured by the current sensor 220 at each unit time during charging, starting from a specific time (i.e., the cumulative value of the battery current). Therefore, the charging capacity continues to increase during charging.

[0058] refer to Figure 3 The differential curve 301 can be derived from... Figure 2 The dataset obtained from the capacity curve 201 indicates the set voltage range V. L ~V U The relationship between (i) battery voltage V and (ii) the differential capacity dQ / dV of capacity curve 201 is shown in Figure 302. Differential curve 302 can be seen from... Figure 2 The dataset obtained from the capacity curve 202 indicates the set voltage range V. L ~V U The relationship between (i) battery voltage and (ii) the differential capacity of capacity curve 202.

[0059] A constant current charging event occurs when the battery voltage reaches the lower limit V of the set voltage range. L Time until the battery voltage reaches its upper limit V U The process of charging battery B with a predetermined current rate (e.g., 0.1C rate) during a constant current period of time. Upper limit V U (For example, 4.3V) equals the charging end voltage V. C Lower limit V L It can be equal to the upper limit V U Low reference voltage V ref (e.g., 0.3V) voltage (e.g., 4.0V). That is, the width of the set voltage range is equal to the reference voltage V. ref .

[0060] The differential capacity dQ / dV is the ratio of the change in charging capacity Q (dQ) per unit time to the change in battery voltage V (dV) per unit time. In one example, control circuit 230 can determine an approximate capacity curve by curve fitting. Figure 2 The relationship between battery voltage and charging capacity in capacity curve 201 is fitted to a polynomial function. Since capacity curve 201 is converted to an approximate capacity curve, noise components present in capacity curve 201 are removed. Subsequently, as a result of differentiating capacity curve 201 with respect to the approximate capacity curve with battery voltage as the input variable, control circuit 230 can obtain differential curve 301. Similarly, as a result of differentiating approximate capacity curve 202 with respect to battery voltage, control circuit 230 can obtain differential curve 302.

[0061] In the sample battery with lithium deposition, some lithium ions that have moved to the negative electrode during charging do not embed themselves into the negative electrode and instead deposit as metallic lithium on the negative electrode surface. Therefore, to increase the sample battery with and without lithium deposition to the same battery voltage, an additional charging current equal to the amount of lithium ions deposited as metallic lithium is required. (Reference) Figure 3 Within the set voltage range, as the battery voltage decreases from the lower limit V... L Rise to the upper limit V U The differential capacity of differential curve 301 gradually decreases approximately linearly. In contrast, differential curve 302 exhibits a nonlinear increase in differential capacity over a certain portion of the set voltage range due to lithium deposition.

[0062] In the following text, it is assumed that the capacity curve and differential curve of battery B are the same as capacity curve 202 and differential curve 302, respectively.

[0063] Control circuit 230 uses a linear approximation algorithm to determine an approximate straight line 312 for the differential curve 302. A linear approximation algorithm is a type of curve fitting and a method of transforming a curve into a straight line with a single slope. In one example, the least squares method can be used for the linear approximation algorithm. The approximate straight line 312 can be expressed as Equation 1 below.

[0064] Equation 1

[0065] y a (x)=Ax+B

[0066] In Equation 1 above, x is the battery voltage, A is the slope of the approximate line 312, B is the y-intercept of the approximate line 312, and y a (x) is an approximation of the differential capacity when the battery voltage is equal to x.

[0067] The reference voltage V can be given based on the electrochemical specifications of battery B. ref Alternatively, the control circuit 230 can determine the reference voltage V based on the cumulative usage capacity of battery B. ref The cumulative usage capacity can be the cumulative value of the discharge current flowing through battery B during the total usage period from the discharge of battery B to the start of the constant current charging period, or the sum of both. The storage device can pre-record the defined cumulative usage capacity relative to the reference voltage V. ref A lookup table for the predetermined correlation between them. In the lookup table, the reference voltage V... ref It can have a linear or non-linear relationship inversely proportional to the cumulative usage capacity. That is, in the lookup table, a larger cumulative usage capacity can be correlated with a smaller reference voltage. As battery B deteriorates, lithium deposition becomes severe, and therefore, when the reference voltage V... ref As the cumulative usage capacity of battery B decreases, the amount of computation required to determine the approximate straight line 312 can be reduced.

[0068] In one embodiment, control circuit 230 can determine the presence of lithium deposition in battery B when the slope A of the approximate straight line 312 is greater than a reference slope. The reference slope can be given by considering the electrochemical specifications of battery B. Alternatively, control circuit 230 can determine the reference slope based on the cumulative usage capacity of battery B. A storage device can pre-record a lookup table defining a predetermined correlation between cumulative usage capacity and the reference slope. In the lookup table, the reference slope can have a linear or non-linear proportional relationship with the cumulative usage capacity. That is, in the lookup table, a larger cumulative usage capacity can be correlated with a larger reference slope. As battery B deteriorates, lithium deposition becomes more severe, and therefore, lithium deposition can be effectively diagnosed based on the degree of battery B deterioration when the reference slope increases with the cumulative usage capacity of battery B.

[0069] In another embodiment, control circuit 230 can calculate the coefficient of determination of the approximate straight line 312 of differential curve 302, and determine the presence of lithium deposition in battery B when the coefficient of determination is less than a reference coefficient of determination. Typically, the coefficient of determination is indicated as R between 0 and 1. 2 The value of , and in this specification, indicates the descriptive power of the approximate straight line 312 of the differential curve 302. The control circuit 230 can use the following equation 2 to calculate the coefficient of determination between the approximate straight line 312 and the differential curve 302.

[0070] Equation 2

[0071]

[0072] In equation 2, y av It is the average differential capacity of the differential curve 302 within the set voltage range, y m (x i () is when the battery voltage equals x i The differential capacity of the time-differential curve 302, y a (x i () is when the battery voltage equals x i The differential capacity of the approximate straight line 312 is given by R. 2 These are the coefficients of determination of the approximate straight line 312 of the differential curve 302.

[0073] As lithium deposition in battery B becomes more severe, the nonlinearity of differential curve 302 increases, and as the nonlinearity of differential curve 302 increases, the coefficient of determination between the approximate straight line 312 and differential curve 302 decreases to 0.

[0074] A reference coefficient of determination can be provided based on the electrochemical specifications of battery B. Alternatively, control circuit 230 can calculate the reference coefficient of determination based on the cumulative usage capacity of battery B. A storage device can pre-record a lookup table defining a predetermined correlation between the cumulative usage capacity and the reference coefficient of determination. In the lookup table, the reference coefficient of determination can have a linear or non-linear proportional relationship with the cumulative usage capacity. That is, in the lookup table, a larger cumulative usage capacity can be correlated with a larger reference coefficient of determination. As battery B deteriorates, lithium deposition becomes severe, and therefore, when the reference coefficient of determination increases with the increase of the cumulative usage capacity of battery B, lithium deposition can be effectively diagnosed based on the degree of degradation of battery B.

[0075] When lithium deposition is detected in battery B, control circuit 230 can execute predetermined safety functions. In one example, control circuit 230 can send a warning message to vehicle controller 6 via communication circuit 320. In another example, control circuit 230 can reduce the maximum permissible value of charging current and / or discharging current. The reduction in the maximum permissible value can be proportional to the difference between the slope of approximate straight line 312 and a reference slope and / or the difference between the coefficient of determination of approximate straight line 312 and the coefficient of determination of differential curve 302 and a reference coefficient of determination.

[0076] Figure 4 This is an exemplary flowchart illustrating a battery diagnostic method according to a first embodiment of the present disclosure. Figure 4 The method can be performed by the battery diagnostic device 200.

[0077] refer to Figures 1 to 4 In step S400, the control circuit 230 commands the charging module 5 to begin a constant current charging period. The constant current charging period is when battery B operates within a set voltage range V. L ~V U The time period during which the device is charged at a predetermined current rate.

[0078] In step S410, the control circuit 230 collects voltage and current signals at each unit time during the constant current charging period. That is, the control circuit 230 generates a time series of the battery voltage and a time series of the battery current during the constant current charging period.

[0079] In step S420, the control circuit 230 determines the indication to be within the set voltage range V based on the voltage and current signals collected during the constant current charging period. L ~V U Capacity curve 202 shows the relationship between battery voltage and charging capacity.

[0080] In step S430, the control circuit 230 determines, based on the capacity curve 202, that the voltage range V is within the set voltage range. L ~V U The differential curve 301 shows the relationship between battery voltage and differential capacity. Differential capacity is the ratio dQ / dV of the change in charging capacity per unit time to the change in battery voltage per unit time.

[0081] In step S440, the control circuit 230 uses a predetermined linear approximation algorithm to determine the approximate straight line 312 of the differential curve 302.

[0082] In step S450, control circuit 230 determines whether the slope of approximate straight line 312 is greater than a reference slope. An approximate straight line 312 with a slope greater than the reference slope indicates the presence of lithium deposition in battery B. When the value of step S450 is "yes", step S460 can be executed.

[0083] In step S460, the control circuit 230 performs a predetermined safety function.

[0084] Figure 5 This is an exemplary flowchart illustrating a battery diagnostic method according to a second embodiment of the present disclosure. Figure 5 The method can be performed by the battery diagnostic device 200.

[0085] refer to Figures 1 to 3 and Figure 5 In step S500, the control circuit 230 commands the charging module 5 to begin a constant current charging period. The constant current charging period is when battery B operates within a set voltage range V. L ~V U The time period during which the device is charged at a predetermined current rate.

[0086] In step S510, the control circuit 230 collects voltage and current signals at each unit time during the constant current charging period. That is, the control circuit 230 generates a time series of battery voltage and a time series of battery current during the constant current charging period.

[0087] In step S520, the control circuit 230 determines the indication to be within the set voltage range V based on the voltage and current signals collected during the constant current charging period. L ~V U Capacity curve 202 shows the relationship between battery voltage and charging capacity.

[0088] In step S530, the control circuit 230 determines, based on the capacity curve 202, that the voltage range V is within the set voltage range. L ~V U The differential curve 301 shows the relationship between battery voltage and differential capacity. Differential capacity is the ratio dQ / dV of the change in charging capacity per unit time to the change in battery voltage per unit time.

[0089] In step S540, the control circuit 230 uses a predetermined linear approximation algorithm to determine the approximate straight line 312 of the differential curve 302.

[0090] In step S542, the control circuit 230 calculates the coefficients of determination of the approximate straight line 312 of the differential curve 302.

[0091] In step S550, control circuit 230 determines whether the determined coefficient of determination is less than a reference coefficient of determination. A coefficient of determination less than the reference coefficient of determination between differential curve 302 and approximate straight line 312 indicates the presence of lithium deposition in battery B. When the value of step S550 is "yes", step S560 can be executed.

[0092] In step S560, the control circuit 230 performs a predetermined safety function.

[0093] The embodiments of the present disclosure described above can be implemented not only by devices and methods, but also by programs that perform functions corresponding to the configuration of the embodiments of the present disclosure or by recording media having programs recorded thereon, and such implementation can be readily implemented by those skilled in the art from the disclosure of the above embodiments.

[0094] Although this disclosure has been described with respect to a limited number of embodiments and accompanying drawings, this disclosure is not limited thereto, and it will be apparent to those skilled in the art that various modifications and changes can be made thereto within the technical aspects of this disclosure and within the equivalent scope of the appended claims.

[0095] Furthermore, without departing from the technical aspects of this disclosure, many substitutions, modifications, and changes can be made to the disclosure described above by those skilled in the art. This disclosure is not limited to the above embodiments and drawings, and all or some embodiments can be selectively combined to allow for various modifications.

[0096] [Figure Labels]

[0097] 1: Electric vehicles

[0098] 2: Battery pack

[0099] B: Battery

[0100] 100: Battery Management System

[0101] 200: Battery diagnostic equipment

[0102] 210: Voltage sensor

[0103] 220: Current sensor

[0104] 230: Control Circuit

Claims

1. A battery diagnostic device, the battery diagnostic device comprising: A voltage sensor configured to measure the battery voltage across the battery terminals and generate a voltage signal indicating the measured battery voltage; A current sensor configured to measure the battery current flowing through the battery and generate a current signal indicating the measured battery current; as well as A control circuit, configured to collect the voltage signal and the current signal at each unit time, The control circuit is configured as follows: A capacity curve indicating the relationship between the battery voltage and charging capacity within the predetermined voltage range is determined based on the voltage and current signals collected at each unit time during a constant current charging period of the battery within a predetermined voltage range, wherein the charging capacity indicates the cumulative value of the battery current. Based on the capacity curve, a differential curve is determined indicating the relationship between the battery voltage and differential capacity within the set voltage range, wherein the differential capacity is the ratio of the change in charging capacity per unit time to the change in battery voltage per unit time. A linear approximation algorithm is used to determine the approximate straight line of the differential curve, and The presence of lithium deposition in the battery is determined based on the approximate straight line.

2. The battery diagnostic device according to claim 1, wherein, The upper limit of the set voltage range is equal to the preset charging end voltage of the battery, and The lower limit of the set voltage range is equal to the voltage that is lower than the reference voltage by the upper limit.

3. The battery diagnostic device according to claim 1, wherein, The linear approximation algorithm is the least squares method.

4. The battery diagnostic device according to claim 1, wherein, The approximate straight line is represented by the following equation 1. Equation 1 , In Equation 1 above, x is the battery voltage, A is the slope of the approximate straight line, B is the y-intercept of the approximate straight line, and y a (x) is an approximate value of the differential capacity when the battery voltage is equal to x.

5. The battery diagnostic device according to claim 1, wherein, The control circuit is configured to determine the presence of lithium deposition in the battery when the slope of the approximate straight line is greater than a reference slope.

6. The battery diagnostic device according to claim 5, wherein, The control circuit is configured to determine the reference slope based on the cumulative usage capacity of the battery.

7. The battery diagnostic device according to claim 1, wherein, The control circuit is configured to determine the presence of lithium deposition in the battery when the coefficient of determination of the approximate straight line of the differential curve is less than a reference coefficient of determination.

8. The battery diagnostic device according to claim 7, wherein, The coefficients of determination for the approximate straight line of the differential curve are calculated using Equation 2 below. Equation 2 In equation 2, y av It is the average differential capacity of the differential curve within the set voltage range, y m (x) i () is when the battery voltage is equal to x i The differential capacity of the differential curve, y a (x) i () is when the battery voltage is equal to x i The differential capacity of the approximate straight line, and R 2 It is the coefficient of determination of the approximate straight line of the differential curve.

9. The battery diagnostic device according to claim 7, wherein, The control circuit is configured to determine the reference determination factor based on the cumulative usage capacity of the battery.

10. The battery diagnostic device according to claim 1, wherein, When lithium deposition is detected in the battery, the control circuit performs a predetermined safety function.

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

12. An electric vehicle comprising a battery pack according to claim 11.

13. A battery diagnostic method, said battery diagnostic method being executable by a battery diagnostic device according to any one of claims 1 to 10, said battery diagnostic method comprising the following steps: A capacity curve indicating the relationship between the battery voltage and charging capacity within the set voltage range is determined based on the voltage and current signals collected per unit time during a constant current charging period of the battery within a set voltage range. A differential curve indicating the relationship between the battery voltage and the differential capacity within the set voltage range is determined based on the capacity curve; A linear approximation algorithm is used to determine the approximate straight line of the differential curve; as well as The presence of lithium deposition in the battery is determined based on the approximate straight line.

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