Charging control device and charging control method

Abstract

A charge control device according to the present disclosure includes: a voltage sensor configured to detect a voltage of a battery cell; and a controller configured to execute an intermittent charging process to alternately repeat a charging mode and a rest mode of the battery cells. In a case where a charging mode is switched to a rest mode while performing an intermittent charging process, the controller is configured to perform: an operation of determining an internal resistance of the battery cell based on a change amount of a voltage of the battery cell in a rest period in which the rest mode continues; and an operation of recording the internal resistance in association with the SOC of the battery cell.

Description

Technical Field

[0001] The present disclosure relates to techniques for controlling charging of battery cells.

[0002] This application is based on and claims the benefit of priority from Korean Patent Application No. 10-2023-0065907 filed on May 22, 2023, Korean Patent Application No. 10-2024-0032180 filed on March 6, 2024, and Korean Patent Application No. 10-2024-0061358 filed on May 9, 2024, in the Korean Intellectual Property Office, the disclosures of which are incorporated herein by reference in their entireties. Background Art

[0003] In recent years, as the demand for portable electronic products such as notebook computers, camcorders, and portable phones has rapidly increased, and as the development of battery systems, energy storage batteries, robots, and satellites has firmly begun, research on high-performance batteries that are repeatedly chargeable and dischargeable is being actively conducted.

[0004] Currently commercialized batteries include, for example, nickel-cadmium batteries, nickel-metal hydride batteries, nickel-zinc batteries, and lithium batteries, etc. Among them, lithium batteries have attracted much attention due to their advantages over nickel-based batteries in that they contain almost no memory effect, result in free charge and discharge, have a very low self-discharge rate, and have a high energy density.

[0005] In recent years, as the demand for high-capacity and high-output battery cells continues to increase, technology for charging the battery cells as quickly as possible in order to shorten the charging time has been proposed. Summary of the invention

[0006] Technical issues

[0007] The present disclosure provides an apparatus and method for calculating an internal resistance of a battery for each rest mode while alternately repeating a charging mode and a rest mode depending on a charging progress condition of a battery cell, and monitoring a history of a change in the internal resistance due to multiple executions of the rest mode.

[0008] In addition, the present disclosure provides an apparatus and method for deriving a depth of charge (DOC) of a battery cell capable of avoiding lithium plating according to a history of changes in internal resistance under a specific charging schedule condition.

[0009] Other uses and advantages of the present disclosure can be understood from the following description and will be more clearly recognized from the embodiments of the present disclosure. In addition, it will be easily understood that the uses and advantages of the present disclosure can be achieved by the features set forth in the claims and their combinations.

[0010] Technical Solution

[0011] A charging control device according to one aspect of the present disclosure includes: a voltage sensor configured to detect a voltage of a battery cell; and a controller configured to perform an intermittent charging process to alternately repeat a charging mode and a rest mode of the battery cell. In the case where switching from the charging mode to the rest mode is performed while the intermittent charging process is performed, the controller is configured to perform: an operation of determining an internal resistance of the battery cell based on an amount of change in the voltage of the battery cell during a rest period during which the rest mode lasts; and an operation of recording the internal resistance in association with a state of charge (SOC) of the battery cell.

[0012] The charging mode may be a mode in which a charging current having a predetermined current rate is supplied to the battery cell.

[0013] The controller may be configured to control the intermittent charging process to switch from the charging mode to the rest mode when a duration of the charging mode reaches a first reference period of time or when an increase in the SOC of the battery cell due to the charging mode reaches a reference increase.

[0014] The controller may be configured to control the intermittent charging process to switch from the rest mode to the charging mode when a duration of the rest mode reaches a second reference time period.

[0015] The controller may be configured to: determine a reference frequency according to a complex impedance curve of the battery cell obtained in advance using an electrochemical impedance spectroscopy (EIS) device; and determine the second reference time period based on the reference frequency.

[0016] The controller may be configured to determine the second reference time period to have a predetermined negative corresponding relationship with the reference frequency.

[0017] The controller may be configured to determine the DOC of the battery cell by analyzing a resistance time series data set representing a history of changes in internal resistance within a charging control period from initiation to termination of the intermittent charging process.

[0018] The controller may be configured to: perform curve fitting on the resistance time series data set to generate a resistance profile representing a relationship between the SOC and the internal resistance of the battery cell; and determine the DOC based on a pattern of the resistance profile.

[0019] The controller may be configured to determine that the DOC is equal to a predetermined end-of-charge SOC when only a continuous increase pattern of the internal resistance is identified in the resistance profile.

[0020] When a transition of the internal resistance from an increasing pattern to a decreasing pattern is identified in the resistance profile, the controller may be configured to determine the DOC based on a boundary SOC between the increasing pattern and the decreasing pattern.

[0021] When only a continuous decreasing pattern of the internal resistance is identified in the resistance profile, the controller may be configured to determine the DOC based on the SOC at which the second derivative of the resistance profile becomes zero.

[0022] A battery pack according to another aspect of the present disclosure includes the charge control device.

[0023] A battery system according to another aspect of the present disclosure includes the charging control device.

[0024] A charging control method according to another aspect of the present disclosure includes performing an intermittent charging process to alternately repeat a charging mode and a rest mode of a battery cell. The charging control method further includes: determining an internal resistance of the battery cell based on an amount of change in voltage of the battery cell during a rest period in which the rest mode continues; and recording the internal resistance in association with the SOC of the battery cell. These steps are performed under the condition that switching from the charging mode to the rest mode is performed while performing the intermittent charging process.

[0025] The charging control method may further include determining the DOC of the battery cell by analyzing a resistance time series data set representing a history of changes in internal resistance within a charging control period from initiation to termination of the intermittent charging process.

[0026] A charging control method according to another aspect of the present disclosure includes: connecting a voltage sensor to a battery cell; performing an intermittent charging process to alternately repeat a charging mode and a rest mode of the battery cell; measuring an internal resistance of the battery cell in the rest mode; recording the measured internal resistance in association with an SOC of the battery cell; and discerning a pattern of the internal resistance based on the recorded internal resistance and SOC-related data and determining a DOC of the battery cell based on the pattern.

[0027] The charging control method may further include, after recording the internal resistance in association with the SOC of the battery cell, performing curve fitting and differentiation of the internal resistance with respect to the SOC.

[0028] Beneficial Effects

[0029] According to at least one of the embodiments of the present disclosure, while the charging mode and the rest mode are alternately repeated depending on the charging progress condition of the battery cell, the internal resistance of the battery cell in each rest mode can be estimated, and the history of the change of the internal resistance due to the multiple execution of the rest mode can be monitored. Since the history of the change of the internal resistance of the battery cell reflects the sign or presence or absence of lithium plating, DOC, which is the SOC at which the battery cell can be charged while substantially suppressing the possibility of lithium plating, can be identified from the history of the change of the internal resistance.

[0030] In addition, according to at least one of the embodiments of the present disclosure, an appropriate duration of the rest mode is set based on electrochemical impedance spectroscopy (EIS) data of the battery, and an estimate of the internal resistance is calculated based on the amount of change in the voltage of the battery in the rest mode. Therefore, it is possible to prevent the accuracy of the DOC from being reduced due to an excessively short or long duration of the rest mode.

[0031] The effects of the present disclosure are not limited to the above-mentioned effects, and other effects not mentioned above will be clearly understood by those skilled in the art from the description of the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The accompanying drawings illustrate embodiments of the present disclosure and are used together with the detailed description of the present disclosure to be described later to further understand the technical concept of the present disclosure. Therefore, the present disclosure should not be understood as being limited to the contents shown in the drawings.

[0033] Figure 1 is a view illustrating a configuration of a battery system according to the present disclosure.

[0034] Figure 2a and Figure 2b is a flowchart illustrating a charging control method according to the first embodiment of the present disclosure.

[0035] Figures 3 to 7 Is a description Figure 2a and Figure 2b The view that is referenced when the method is called.

[0036] Figure 8 is a flowchart illustrating a charging control method according to a second embodiment of the present invention.

[0037] Figures 9 to 13 The diagram is describing Figure 8 The resistance profile diagram used as a reference when performing the method.

[0038] Figures 14 to 16 is a graph to be referred to when describing the relationship between lithium plating and impedance during battery charging.

[0039] Fig.17 and Fig.18 is a view illustrating the structure of a test jig for a battery charging test.

[0040] Fig.19 and Fig. 20 In describing the use Fig.17 and Fig.18 The test fixture shown is a view to refer to when the results of the charging test are shown.

[0041] Fig.21 is a flow chart illustrating a method of measuring DOC of a battery cell of the present disclosure.

[0042] In some of the drawings, corresponding components are given the same reference numerals. It will be appreciated by those of ordinary skill in the art that the drawings simply and clearly illustrate the elements and are not necessarily drawn to scale. For example, to aid in understanding the various embodiments, the dimensions of some elements illustrated in the drawings may be exaggerated relative to other elements. In addition, elements that are useful or essential in commercially implementable embodiments but are known in the art may not generally be described to avoid hindering the understanding of the spirit of the various embodiments of the present disclosure. DETAILED DESCRIPTION

[0043] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Prior to this, the terms and words used in the specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted based on the principle that the inventor can appropriately define the concepts of the terms in order to best explain his or her invention using the meanings and concepts that are consistent with the technical ideas of the present disclosure.

[0044] Therefore, since the embodiments described in this specification and the configurations shown in the accompanying drawings are merely some exemplary embodiments of the present disclosure and do not represent all technical ideas of the present disclosure, it should be understood that when submitting this application, there may be various equivalents and modifications that can replace the embodiments.

[0045] Terms including ordinal numbers such as first and second are used to distinguish one of the various components from the rest, rather than to limit the components by such terms.

[0046] Throughout the specification, when a part is described as "comprising" a certain component, this means that other elements are not excluded, but other components may be further included unless otherwise explicitly stated. In addition, terms such as "controller" described in the specification refer to a unit that processes at least one function or operation, and the controller can be implemented in hardware, software, or a combination of hardware and software.

[0047] In addition, throughout the specification, when a component is described as being “connected” to another component, this includes not only a case where the components are “directly connected” but also a case where the components are “indirectly connected” with another element interposed therebetween.

[0048] When charging a battery, fast charging using a high-rate charging current can significantly reduce the charging time compared to slow charging using a low-rate charging current, but has the disadvantage of causing significant damage to the battery cells, thereby shortening the life of the battery.

[0049] Higher charging currents may more easily lead to so-called "Li-plating", in which lithium ions inside the battery cell accumulate on the surface of the negative electrode as lithium metal. The amount of lithium ions that can participate in the charging and discharging reactions is reduced by the amount of lithium plating, and the potential imbalance between the positive and negative electrodes becomes more serious. In addition, the overgrown lithium metal may also tear the separator, thereby increasing the possibility of internal short circuit failure, and such internal short circuit failure increases the risk of explosion and fire of the battery cell.

[0050] The present disclosure proposes a method for deriving a fast charging protocol, which makes it possible to obtain battery cell characteristic information related to the possibility of lithium plating of the battery cell throughout its life after manufacture (for example, the relationship between SOC and internal resistance) without manufacturing a separate test cell (for example, a three-electrode single cell), and to avoid lithium plating by obtaining a fast charging DOC using the obtained information.

[0051] For example, when medium to large-sized pouch cells applied to electric vehicles are repeatedly used, lithium metal deposits are generated on the surface of the negative electrode, and the resistance of the lithium metal deposits is combined in parallel with the resistance on the surface of the negative electrode. As a result, when lithium metal deposits are generated, the total resistance on the surface of the negative electrode of the battery cell may be reduced. In this case, the impedance of the battery cell changes, and the changed impedance diagram can be used to determine the reference frequency to correspond to the charging progress conditions when the intermittent charging process is initialized using, for example, electrochemical impedance spectroscopy (EIS). Once the reference frequency of the intermittent charging process is determined, an appropriate rest period given during the intermittent charging process can be obtained, and during the appropriate rest period, for example, the voltage change and resistance change due to the internal resistance of the battery cell (BC) can be observed, and the voltage change and resistance change can be used to obtain the DOC of the battery cell. The theoretical background of lithium plating and surface resistance of battery cells and the method of obtaining an appropriate rest period will be introduced in more detail below.

[0052] Figure 1 is a view illustrating a configuration of a battery system according to an embodiment of the present disclosure. A battery system 1 described below can obtain, for example, necessary battery cell characteristic information by being connected to a commercial secondary battery via a test jig or directly connected to a secondary battery without a test jig.

[0053] refer to Figure 1 , the battery system 1 includes a system controller (electronic control unit (ECU)) 2, a battery pack 10, a relay 20, an inverter 30, and an electric motor 40. The term battery system 1 may encompass not only an electrical system using a battery as a power source, such as in an electric vehicle, but also a test system for confirming / verifying electrical characteristics of a battery.

[0054] The charging and discharging terminals P+ and P- of the battery pack 10 may be electrically coupled to the inverter 30 and / or the charger 3 via a charging cable, etc. The charger 3 may be included in the battery system 1 or provided in a charging station provided outside the battery system 1 .

[0055] The system controller 2 is configured to send a key start signal to the charge control device 100 in response to a start button (not shown) provided in the battery system 1 being switched to the on position by a user. The system controller 2 is configured to send a key off signal to the charge control device 100 in response to a start button being switched to the off position by a user. The charger 3 communicates with the system controller 2 to provide charging power to the battery 11 via the charging and discharging terminals P+ and P- of the battery pack 10 according to at least one charging protocol (e.g., constant current charging, constant voltage charging, and / or constant power charging).

[0056] The battery pack 10 includes a battery 11 and a charge control device 100. The charge control device 100 may also function as a battery management system (BMS).

[0057] The battery 11 includes a cell group 12 and a case 13. The case 13 defines the overall appearance of the battery 11 and provides an internal space in which the cell group 12 can be placed. The case 13 is fixedly fastened to a battery chamber provided in the battery system 1 using, for example, bolts.

[0058] The cell group 12 is disposed (housed) in an internal space provided by the case 13 and includes at least one battery cell BC. The type of the battery cell BC is not particularly limited as long as it can be repeatedly charged and discharged, such as a lithium ion cell, for example.

[0059] When the cell group 12 includes a plurality of battery cells, the battery cells may be connected to each other in series, in parallel, or in a mixture of series and parallel.

[0060] The relay 20 is electrically connected in series to the battery 11 via a power supply path interconnecting the battery 11 and the inverter 30. Figure 1 , the relay 20 is illustrated as being connected between the positive terminal of the battery 11 and the charge and discharge terminal P+. The relay 20 is controlled to be turned on / off in response to a switching signal from the charging control device 100. According to an embodiment of the present disclosure, the relay 20 may be a mechanical contactor that is turned on / off by the magnetic force of a coil, or a semiconductor switch such as a metal oxide semiconductor field effect transistor (MOSFET).

[0061] The inverter 30 is provided to convert the DC current from the cell group 12 into AC current in response to a command from the charging control device 100 or the system controller 2 .

[0062] The electric motor 40 is driven using AC power from the inverter 30. As the electric motor 40, for example, a three-phase AC electric motor can be used.

[0063] The charging control device 100 includes a voltage sensor 111, a current sensor 113, a temperature sensor 115, a controller 130, and a memory 140. The charging control device 100 may further include an outdoor temperature sensor 117. The charging control device 100 may further include a communication circuit 150. The charging control device 100 may be configured as follows: Figure 1 The illustrated embodiment is included in the battery pack 10, but is not limited thereto. The charging control device 100 may be included in the battery system 1 independently of the battery pack 10. The voltage sensor 111 is connected in parallel with the battery 11 and is configured to detect a battery voltage, which is a voltage across opposite terminals of the battery 11, and generate a voltage signal representing the detected battery voltage.

[0064] The voltage sensor 111 may be connected to the positive and negative terminals of each battery cell BC included in the battery 11 to detect a cell voltage, which is a voltage across opposite terminals of each battery cell BC, and may output an additional voltage signal representing the cell voltage to the controller 130 .

[0065] The current sensor 113 is connected in series to the battery 11 via a current path between the battery 11 and the inverter 30. The current sensor 113 is configured to detect a battery current, which is a current flowing through the battery 11, and to generate a current signal representing the detected battery current. The current sensor 113 can be implemented using one of known current detection elements, or a combination of two or more, such as a shunt resistor and a Hall effect element.

[0066] The temperature sensor 115 is configured to detect the battery temperature and generate a temperature signal representing the detected battery temperature. The temperature sensor 115 may be disposed within the housing 13 to detect a temperature close to the actual temperature of the battery 11. For example, the temperature sensor 115 may be attached to the surface of at least one battery cell BC included in the cell group 12, and may detect the surface temperature of the battery cell BC as the battery temperature. For reference, what is simply described as a "temperature detection value" herein may refer to a detected battery temperature value.

[0067] The voltage sensor 111 , the current sensor 113 , and the temperature sensor 115 may each be referred to as a “sensing unit”.

[0068] The outdoor temperature sensor 117 is configured to detect an outdoor temperature (ambient temperature), which is a temperature at a predetermined location spaced apart from the battery 11, and generate a temperature signal representing the detected outdoor temperature. The outdoor temperature sensor 117 may be placed at a predetermined location outside the housing 13 where heat exchange occurs between the battery 11 and the outdoor air.

[0069] Each of the temperature sensor 115 and the outdoor temperature sensor 117 may be implemented using one of temperature detection elements such as a thermocouple, a thermistor, a bimetal strip, or a combination of two or more thereof.

[0070] The communication circuit 150 is configured to support wired or wireless communication between the controller 130 and the system controller 2. The wired communication may be, for example, a controller area network (CAN) communication, and the wireless communication may be, for example, Zigbee or Bluetooth communication. The type of communication protocol is not particularly limited as long as it supports wired and wireless communication between the controller 130 and the system controller 2. The communication circuit 150 may include an output device (e.g., a display or a speaker) that provides information received from the controller 130 and / or the system controller 2 in a form discernible to a user.

[0071] The controller 130 is operably coupled to the relay 20, the voltage sensor 111, the current sensor 113, the temperature sensor 115, the outdoor temperature sensor 117, and the communication circuit 150. When two components are described as being operably coupled, it means that the two components are directly or indirectly connected to be able to send and receive signals unidirectionally or bidirectionally.

[0072] The controller 130 may collect a voltage signal from the voltage sensor 111, a current signal from the current sensor 113, a temperature signal from the temperature sensor 115 (which may be referred to as a “battery temperature signal”), and / or a temperature signal from the temperature sensor 117 (which may be referred to as an “outdoor temperature signal”). The controller 130 may convert each of the analog signals collected from the sensors 111, 113, 115, and 117 into a digital value using an analog-to-digital converter (ADC) provided therein, and record the converted digital value.

[0073] The controller 130 may be referred to as a “control circuit” or a “battery controller” and may be implemented in hardware using 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, and electrical units for performing other functions.

[0074] The memory 140 may include at least one type of storage medium selected from among a flash memory type, a hard disk type, a solid state drive (SSD) type, a silicon disk drive (SDD) type, a multimedia card micro type, a random access memory (RAM) type, a static random access memory (SRAM) type, a read-only memory (ROM) type, an electrically erasable programmable read-only memory (EEPROM) type, and a programmable read-only memory (PROM) type. The memory 140 may store data and programs required for the controller 130 to perform computing operations. The memory 140 may store data representing the results of the computing operations performed by the controller 130. Although Figure 1 The memory 140 is illustrated as being physically independent from the controller 130 , but the memory may also be built into the controller 130 .

[0075] The controller 130 may turn on the relay 20 in response to a key start signal. The controller 130 may turn off the relay 20 in response to a key off signal. The key off signal is a signal that induces switching from a cycle state, which is a state in which the battery 11 is being charged / discharged, to a rest state, which is a state in which the charging / discharging of the battery 11 is stopped. Alternatively, the system controller 2 may be responsible for the on / off control of the relay 20 instead of the controller 130.

[0076] When the inverter 30 or the charger 3 is operated while the relay 20 is turned on, the battery 11 is switched to a circulation state. On the contrary, when the relay 20 is turned off, or the operation of the inverter 30 and the charger 3 is stopped, the battery 11 is in a rest state.

[0077] Meanwhile, when the battery 11 is described as being in a cycle state or a rest state, this means that each battery cell BC included in the battery 11 is also in a cycle state or a rest state.

[0078] While the battery cell BC is in a cycling state and / or a resting state, the controller 130 may determine a voltage detection value, a current detection value, a battery temperature detection value, and an outdoor temperature detection value based on the voltage signal, the current signal, the battery temperature signal, and the outdoor temperature signal, and then determine (estimate) the state of charge (SOC) of the battery cell BC based on the voltage detection value, the current detection value, and / or the outdoor temperature value.

[0079] When the charger 3 operates in a constant current charging mode, the current rate of the charging current supplied to the battery cell BC (which may be referred to as a "C rate") has a pre-known constant value, and when estimating the SOC of the battery cell BC, the value of the constant current output from the charger 3 may be used instead of the current detection value obtained using the current sensor 113.

[0080] SOC is the ratio of the remaining capacity of a battery cell BC to the fully charged capacity (maximum capacity), and is usually processed as a range of 0 to 1 or 0 to 100%. For example, the SOC can be determined using an ampere counting method, an open circuit voltage (OCV)-SOC curve, or a Kalman filter.

[0081] The battery system 1 may further include an EIS device 4. The EIS device 4 is provided to apply an AC signal to the battery cell BC and measure the response characteristics of the battery cell BC to the applied AC signal. Figure 1 , the EIS device 4 is illustrated as being connected in parallel to the battery 11, but is not limited thereto. For example, the EIS device 4 may be selectively connected to each battery cell BC through a separate switch circuit.

[0082] A process of obtaining battery cell characteristic information in a rest mode of an intermittent charging process while performing an intermittent charging process by connecting the above-mentioned battery system 1 to a commercial secondary battery (e.g., a medium to large-sized pouch cell applied to an electric vehicle) via a test jig or the like and applying the above-mentioned appropriate rest period will be described.

[0083] Figure 2a and Figure 2b is a flowchart illustrating a charging control method according to a first embodiment of the present disclosure, and Figures 3 to 7 is describing Figure 2a and Figure 2b The view to refer to when using the method.

[0084] Figure 2a The method can be Figure 1 The charging control device 100 shown in the figure executes. Figure 2a The set of steps S210 to S250 included in may be collectively referred to as control steps of an “intermittent charging process”. Figure 2a The method may be repeatedly performed until the SOC of the battery cell BC reaches a predetermined lower limit SOC (which may be referred to as a “charge initialization SOC”) from a predetermined upper limit SOC (which may be referred to as a “charge termination SOC”).

[0085] Each of the lower limit SOC and the upper limit SOC may depend on Figure 2a The charging mode of the method uses the magnitude of the charging current (e.g., current rate) and the initialization Figure 2a The method is set according to the battery temperature.

[0086] For example, when the current rate and the battery temperature are 0.5°C and 25°C, respectively, the lower limit SOC and the upper limit SOC may be set to 88% and 97%, respectively, and when the current rate and the battery temperature are 2°C and 25°C, respectively, the lower limit SOC and the upper limit SOC may be set to 68% and 77%, respectively. The relationship data between the lower limit SOC and the upper limit SOC of the current rate and the battery temperature (or the outdoor temperature) may be pre-recorded in the memory 140 in the form of a lookup table and / or a function.

[0087] refer to Figure 1 , Figure 2a and Figure 2b In step S210, the controller 130 controls the charger 3 to be in a charging mode for supplying a charging current to the battery cell BC. For example, the controller 130 sends a charging request signal to the charger 3 via the communication circuit 150, and the charger 3 operates in the charging mode in response to the charging request signal and supplies a charging current having a required current rate to the battery cell BC. Here, the charging mode may be, for example, a constant current charging mode in which the battery cell BC is charged with a charging current having a predetermined current rate.

[0088] In step S220, the controller 130 determines whether a first switching condition for switching from the charging mode to the rest mode is satisfied. The first switching condition may be a time-based condition or an SOC-based condition. As an example, in response to the duration of the charging mode (e.g., the time elapsed from the initialization time of the charging mode) reaching a first reference time period, it may be determined that the first switching condition is satisfied. As another example, in response to the increase in the SOC of the battery cell BC due to the charging mode (e.g., the difference between the SOC when the current charging mode is initialized and the current SOC) reaching a reference increase (e.g., 0.5%), it may be determined that the switching condition is satisfied. When the value of step S220 is "No", step S220 may be repeatedly repeated. When the value of step S220 is "Yes", that is, when it is determined in S220 that the first switching condition is satisfied, the process proceeds to step S230.

[0089] In step S230, the controller 130 controls the charger 3 to be in the rest mode. Therefore, the intermittent charging process is switched from the charging mode to the rest mode. For example, when the controller 130 sends a charging stop signal to the charger 3 via the communication circuit 150, the charger 3 enters the rest mode in response to the charging stop signal. In the rest mode, the supply of the charging current from the charger 3 to the battery cell BC is blocked. The controller 130 may record the SOC of the battery cell BC when switching from the charging mode to the rest mode in the memory 140.

[0090] In step S240, the controller 130 determines whether a second switching condition for switching from the rest mode to the charging mode is satisfied. The second switching condition may be a time-based condition. As an example, in response to the duration of the rest mode (i.e., the time elapsed from the time the rest mode is initialized) reaching a second reference time period, it may be determined that the second switching condition is satisfied. The second reference time period may be a predetermined fixed time period, or a variable time period adjusted by the controller 130 based on the electrochemical characteristic data of the battery cell BC. The adjustment of the second reference time period may refer to the second reference time period. Fig.14 When the value of step S240 is "No", that is, when the duration of the rest mode has not reached the second reference time period, step S240 may be repeatedly performed again. When the value of step S240 is "Yes", that is, when the duration of the rest mode has reached the second reference time period, the process may proceed to step S250.

[0091] In step S250, the controller 130 determines whether the SOC of the battery cell BC reaches the charge termination SOC. When the value of step S250 is "No", the process may return to step S210. For example, the intermittent charging process may switch from the rest mode to the charging mode to repeat the charging mode and the rest mode until the SOC of the battery cell BC reaches the charge termination SOC. Meanwhile, when the value of step S250 is "Yes", for example, when the SOC of the battery cell reaches the charge termination SOC, the intermittent charging process may be terminated. Figure 2a method.

[0092] As mentioned above, this can be done by Figure 2a Repeat the charging mode and rest mode in steps to obtain Figure 3 Shown is a graph of cell voltage (V) versus time (minutes). Figure 3 The portion indicated by the fill pattern in FIG. 1 schematically illustrates the rest period of the intermittent charging process, as shown in FIG. Figure 4 Picture.

[0093] Figure 2b The method can be Figure 2a The decision value in step S240 is "yes". Figure 2b In the method, when the second switching condition is met in step S240, step S260 to be described below may be performed before proceeding to step S250.

[0094] In step S260 , the controller 130 calculates the internal resistance of the battery cell BC based on the amount of change in the voltage of the battery cell BC in the rest state, and records the internal resistance calculated in step S270 in association with the SOC of the battery cell.

[0095] Figure 3is a diagram illustrating the history of changes in the cell voltage of the battery cell BC during the charging control period in which the intermittent charging process is performed. Figure 3 As can be seen in FIG. 1 , the voltage of the battery cell BC shows an overall rising trend throughout the charging control period, and as shown by the fill pattern in the figure, the voltage rising section in which the charger 3 operates in the charging mode and the voltage falling section in which the charger 3 operates in the rest mode are repeated alternately.

[0096] Figure 4 This is the voltage drop section in rest mode The enlarged view of the voltage drop section is Figure 3 The area marked by the dotted line. Figure 4 In, t r1 represents the time when the charger 3 is requested to switch from the charging mode to the rest mode (or the time when the switching event from the charging mode to the rest mode occurs), t r2 represents the time when the charger 3 is requested to switch from the rest mode to the charging mode (or the time when a switching event from the rest mode to the charging mode occurs), represents the duration in rest mode (the length of the rest period), V r1 Indicates t r1 The cell voltage at r2 Indicates t r2 The cell voltage at Indicates the voltage change in rest mode. That is, V r1 represents the single cell voltage detected before switching from charging mode to rest mode, and V r2 Indicates the cell voltage detected before switching from rest mode to charge mode. ,and .

[0097] The controller 130 may calculate (estimate) the internal resistance for each rest period using Formula 1 below.

[0098] (Formula 1)

[0099]

[0100] In the above formula 1, I CC represents the charging current (e.g., a constant current with a predetermined current rate), and R CT Indicates internal resistance.

[0101] In step S270, the controller 130 records the internal resistance obtained in step S260 in association with the SOC of the battery cell BC in the memory 140. The SOC associated with the internal resistance may be the SOC of the battery cell BC when switching from the charging mode to the rest mode is performed (eg, the execution time of step S230).

[0102] like Figure 3 As shown, during charging of the SOC range of interest (e.g., from the lower limit SOC to the upper limit SOC), the rest mode may be performed multiple times (e.g., multiple rest periods are sequentially provided during the charging control period), and the estimated values ​​of the internal resistance during the rest period occurring each time the rest mode is advanced may be sequentially recorded in the memory 140 in chronological order.

[0103] Therefore, when the SOC of the battery cell BC reaches the upper limit SOC, a resistance time series data set representing the history of the change of the internal resistance over time (which may be referred to as an “internal resistance map”) may be recorded in the memory 140. Each data point in the resistance time series data set may represent a related pair of the internal resistance and the SOC determined at a specific rest period within the charging control period.

[0104] Figures 5 to 7 500, 600 and 700 are diagrams illustrating three typical patterns of resistance time series data sets obtained by repeating the intermittent charging process using three different charging schedule conditions. For example, the general shapes of the charge transfer resistance obtained from the evaluation of the present disclosure can be classified as Figure 5 , Figure 6 and Figure 7 The three cases shown in the figure will be described below. Each figure illustrates the evaluation conditions and environment. However, the measurement does not necessarily have to be performed under these conditions, and intermittent charging can be performed under conditions other than those shown below for evaluation purposes. In the following description, when the DOC is Figure 5 , Figure 6 and Figure 7 As the order of decrease (the charge transfer resistance of the battery is reduced), the DOC can be identified more accurately.

[0105] Figure 5 A resistance time series dataset 500 obtained by performing an intermittent charging process under a first charging schedule condition in which the current rate of the charging current is 0.5C and the battery temperature (eg, the temperature measured at the first initialization of the intermittent charging process) is 25°C is illustrated. An SOC range of interest (eg, 88% to 97%) in the resistance pattern associated with a first charging schedule condition is represented.

[0106] Figure 6A resistance time series dataset 600 obtained by performing an intermittent charging process under a second charging schedule condition in which the current rate of the charging current is 2C and the battery temperature (eg, the temperature measured at the first initialization of the intermittent charging process) is 25°C is illustrated. An SOC range of interest (eg, 68% to 77%) in the resistance pattern associated with a second charging schedule condition is represented.

[0107] Figure 7 A resistance time series dataset 700 obtained by performing an intermittent charging process under a third charging schedule condition in which the current rate of the charging current is 2C and the battery temperature (eg, the temperature measured at the first initialization of the intermittent charging process) is 10°C is illustrated. An SOC range of interest (eg, 63% to 72%) in the resistance pattern associated with a third charging schedule condition is represented.

[0108] The upper limit of each SOC range of interest may be referred to as the charge limit SOC.

[0109] Compare Figure 5 and Figure 6 , the first charging schedule condition has the same battery temperature as the second charging schedule condition, but the first charging schedule condition has a lower current rate than the second charging schedule condition. Therefore, since the first charging schedule condition is less harsh on the battery cells than the second charging schedule condition, it is illustrated that the upper limit SOC (97%) associated with the first charging schedule condition is set higher than the upper limit SOC (77%) associated with the second charging schedule condition.

[0110] Compare Figure 6 and Figure 7 , the second charging schedule condition has the same current rate as the third charging schedule condition, but the third charging schedule condition has a lower temperature than the second charging schedule condition, and the electrochemical reaction of the battery cell BC may be relatively slower under the second charging schedule condition than under the third charging schedule condition. Therefore, the upper limit SOC (72%) associated with the third charging schedule condition is illustrated as being lower than the upper limit SOC (77%) associated with the second charging schedule condition.

[0111] Figures 5 to 7 Each illustrates the history of changes in the internal resistance (reflecting the charge transfer resistance) in a wider range than the SOC range of interest corresponding to each charging schedule condition. However, this is only to help understanding, and in reality, it is sufficient to obtain the history of charging in the internal resistance only in the SOC range of interest corresponding to each charging schedule condition.

[0112] Figure 8is a flowchart illustrating a charging control method according to a second embodiment of the present disclosure, and Figures 9 to 13 The diagram is describing Figure 8 The method should refer to the resistance profile diagram. Figure 2a and Figure 2b After the charging control method of the first embodiment acquires the resistance time series data set during the charging control period, the following steps can be performed: Figure 8 method.

[0113] refer to Figure 8 In step S810, the controller 130 performs curve fitting on the resistance time series data set to generate a resistance profile indicating the relationship between the SOC and the internal resistance of the battery cell BC (which may be referred to as an "internal resistance profile"). Curve fitting may refer to a process or logic of approximating an input data set to a polynomial of a predetermined order. That is, the resistance profile may be a function whose input is the SOC and whose output is the internal resistance.

[0114] Figures 9 to 11 It is shown that by Figures 5 to 7 The three resistance time series data sets 500, 600 and 700 described are respectively obtained by curve fitting with a 9th order polynomial to obtain three resistance profiles 900, 1000 and 1100. To help understand, the three resistance profiles 900, 1000 and 1100 are each illustrated from below three SOC ranges of interest ( , , ) in the range of SOC (50%) to the upper limit SOC of the lower limit SOC of each.

[0115] In step 820 , the controller 130 determines the DOC of the battery cell BC based on the pattern of the resistance profile. The DOC represents the maximum SOC that can be charged without lithium plating occurring (which may be within the SOC range of interest).

[0116] First, we will describe the Figure 5 The time series data set is obtained by curve fitting Fig. 9 The resistance profile 900 identifies the operation of the DOC. Fig. 9 , in the SOC range of interest ( ), the internal resistance continues to increase without decreasing. Fig. 9 As shown in the figure, when a pattern of continuous increase of internal resistance as SOC increases is identified, the controller 130 may set the end point P on the resistance profile 900 to A SOC at Z A ) is determined as DOC (Z A ). That is, in Fig. 9In the case of the pattern shown in the figure, DOC (Z A ) is determined to be equal to the SOC range of interest ( ). An increasing pattern in a profile (or curve) may mean that the first derivative of the profile is positive.

[0117] Next, we will describe the Figure 6 The time series data set is obtained by curve fitting Fig.10 The resistance profile 1000 identifies the operation of the DOC. Fig.10 , resistance profile 1000 and Fig. 9 The illustrated resistance profile 900 differs in that the rate of increase of the internal resistance is greater over the SOC range of interest ( ), and then gradually decreases from a certain SOC. Fig.10 As shown, when the increasing section and the decreasing section of the internal resistance are adjacent to each other, the controller 130 can obtain a differential resistance profile by first-order differentiation of the resistance profile 1000 with respect to the SOC. Fig.12 The differential resistance profile 1200 is shown as Fig.10 The controller 130 can determine the depth of charge (Z B ) is equal to the SOC at the boundary point in the differential resistance profile 1200, and the differential resistance value at the boundary point (dR CT / dSOC) changes from positive to negative as SOC increases, that is, the differential resistance value (dR CT / dSOC) is 0 (P B ).according to Fig.12 The DOC (Z B ) can be determined to be equal to Fig.10 The SOC at the boundary point between the increase pattern and the decrease pattern of the internal resistance in the resistance profile 1000. For reference, a decrease pattern in a certain profile (or curve) may mean that the first-order derivative of the profile is negative.

[0118] Next, we will describe the Figure 7 The time series data set is obtained by curve fitting Fig.11 The resistance profile 1100 identifies the operation of the DOC. Fig.11 , resistance profile 1100 and Fig. 9 The resistance profile line is 900 and Fig.10 The resistance profile 1000 differs in that the internal resistance in the SOC range of interest ( ) continues to decrease without increasing the segment. Fig.11When only the decreasing pattern is shown in the range of interest of SOC, the controller 130 can obtain the following equation by taking the second order derivative of the resistance profile 1100 with respect to SOC: Fig.13 The differential resistance profile 1300 is shown. For reference, the differential resistance profile 1300 is different from the differential resistance profile 1200 in that the differential resistance profile 1300 is the result of the second-order differentiation of the resistance profile 1100 , while the differential resistance profile 1200 is the result of the first-order differentiation of the resistance profile 1000 .

[0119] The controller 130 can set the charging depth (Z C ) is determined to be equal to the second order differential resistance value (d 2 R CT / dSOC 2 ) changes from positive to negative as the SOC increases, that is, at the point where the second-order differential resistance value (d 2 R CT / dSOC 2 ) is 0 feature point (P C ) at the characteristic point (P C ) may be the point in the resistance profile 1100 where the absolute value of the resistance change rate is the largest.

[0120] Figures 9 to 13 The depth of charge (Z A , Z B , Z C ) respectively represent the SOC at which the battery cell BC can be charged without lithium plating during constant current charging at a current rate associated therewith (e.g., 2C). For example, when charging is continued under the same charging schedule even though the SOC of the battery cell BC has reached the DOC, lithium plating may occur on the negative electrode surface of the battery cell BC.

[0121] The controller 130 may record the DOC determined for a specific charging schedule condition in the memory 140. In the future, when charging of the battery cell BC is initiated under the same charging schedule condition (e.g., the current rate and battery temperature are 0.5°C and 25°C, respectively), the controller 130 may obtain the DOC associated with the charging schedule condition (e.g., Z A ), and only allows charging of the battery cell BC until the SOC of the battery cell BC reaches the obtained DOC (e.g., Z A ). That is, when the SOC of the battery cell BC reaches the obtained DOC, the controller 130 may control the relay 20 to be turned off or send a request to stop charging to the charger 3.

[0122] A method may be performed for each charging event of the battery 11. Figure 2a ,2b and Figure 8 Alternatively, the method may be performed under the condition that a predetermined diagnosis requiring event occurs, for example, when the state of health (SOH) of the battery 11 decreases by a predetermined value or more than the previous SOH.

[0123] Figures 14 to 16 is a graph to be referred to when describing the relationship between lithium plating and impedance during battery charging.

[0124] first, Fig.14 Schematic diagram showing the formation of lithium metal deposits on the negative electrode of a battery cell BC. Fig.14 During charging under certain charging schedule conditions, lithium ions may be plated as lithium metal on the surface of the negative electrode of the battery cell BC. When the lithium metal deposit is formed, lithium insertion and lithium plating are simultaneously performed on the surface of the negative electrode of the battery cell BC, and thus the movement path of the charging current can be expanded compared to the case where there is no lithium metal deposit.

[0125] Fig.15 is a graph to be referred to when exemplarily describing that the impedance of the battery cell BC changes depending on the presence or absence of lithium plating in the battery cell BC. Fig.15 Each of the two complex impedance curves 1510 and 1520 illustrated in FIG. 1 can be obtained by repeating the process of measuring the impedance of each battery cell when applying an AC signal to a battery cell with lithium plating and a battery cell without lithium plating respectively using the EIS device 4 under the same environmental conditions. For example, Fig.15 It may be a Nyquist diagram showing that the impedance of the battery cell changes depending on the change in the frequency of the AC signal. Since the process of obtaining the complex impedance curve of the battery cell BC is performed once before the intermittent charging process of the battery cell BC is initiated, and the AC signal from the EIS device 4 is applied to the battery cell BC only for a short period of time, the battery cell is substantially not damaged.

[0126] According to an embodiment, a complex impedance curve 1510 may be obtained for a battery cell before lithium plating occurs, and a complex impedance curve 1520 may be obtained for a battery cell after lithium plating occurs.

[0127] Symbol R S Represents the electrolyte resistance of the battery cell, which is hardly affected by the presence or absence of lithium plating. Symbol R p_i and R p_f The symbol R represents the interface resistance of a battery cell without lithium plating and a battery cell with lithium plating. A and R B The internal resistances of the battery cells without lithium plating and the battery cells with lithium plating are respectively represented, wherein and .

[0128] The interfacial resistance is the total resistance due to the solid electrolyte interface (SEI), charge transfer, and double layer, and is greatly affected by the charge accumulation on the surface of the positive and negative electrodes of the battery cell.

[0129] As mentioned above Fig.14 As described above, the resistance of the lithium metal deposit on the surface of the negative electrode is combined in parallel with the resistance on the surface of the negative electrode. As a result, when the lithium metal deposit is generated, the total resistance on the surface of the negative electrode of the battery cell may decrease. Fig.15 It can be seen that R p_f Less than R p_i , and it can be said that the resistance difference between them ( ) has a positive corresponding relationship with the amount of lithium metal deposits generated.

[0130] Meanwhile, the controller 130 may determine the reference frequency from the complex impedance curve 1510. For example, the complex impedance curve 1510 may be divided into a convex section and a sloping section. Here, the convex section may be related to the interface resistance (R p_i ) related segments. The oblique segment is a segment with a linear general shape extending to the right side of the convex segment and represents the diffusion resistance (R diff At the boundary points between these convex and oblique segments (reference R A ) can be determined as the reference frequency.

[0131] The inventors of the present disclosure have recognized that during the intermittent charging process, the SOC of the battery cell BC gradually increases, and the frequency at the boundary point between the convex section and the inclined section gradually increases as the SOC increases. When the reference frequency is determined to correspond to the charging progress condition when the intermittent charging process is initialized, the rest period provided during the intermittent charging process can last for an appropriate period of time required to observe the voltage change due to the internal resistance of the battery cell BC. Therefore, it is possible to prevent the accuracy of the internal resistance from being reduced due to the rest period being set too short or too long.

[0132] The controller 130 may determine a second reference time period indicating the duration of the rest mode based on the reference frequency. The reference frequency and the second reference time period may have a predetermined negative correspondence. To determine the second reference time period, relationship data that can be expressed by the following formula 2 may be used.

[0133] (Formula 2)

[0134]

[0135] In the above formula 2, f i-drepresents a reference frequency, w represents a predetermined edge constant (which may be 1 or greater), and ΔtR2 represents a second reference time period. Therefore, the second reference time period may be set equal to or greater than the reference frequency (f i-d ) is multiplied by the marginal constant (w). The second reference time period may be the duration of each rest period required to observe the voltage change due to the internal resistance of the battery cell BC.

[0136] The reference frequency and the lower limit SOC of each charging schedule condition may be pre-recorded in the memory 140. The controller 130 may determine the second reference time period by obtaining the charging schedule condition of the intermittent charging process to be performed on the battery cell BC and the reference frequency associated with the lower limit SOC of the SOC range of interest from the memory 140.

[0137] The memory 140 may store the relationship data among the SOC, the battery temperature and the reference frequency. The relationship data among the SOC, the battery temperature and the reference frequency may be replaced with the relationship data among the SOC, the battery temperature and the second reference time period.

[0138] Fig.16 is a graph to be referred to when describing the relationship between the battery temperature and the reference frequency when the SOC of the battery cell BC is set to a certain value (eg, lower limit SOC 10%).

[0139] refer to Fig.16 , assuming that other factors of the charging progress condition (e.g., current rate and upper limit SOC) are the same, as the battery temperature under the charging progress condition increases, the reference frequency associated therewith may increase. That is, the battery temperature and the reference frequency may have a positive corresponding relationship.

[0140] Referring to Formula 2 above, since the reference frequency and the second reference time period are inversely proportional, when the battery temperature of the battery cell BC is high when the control of the intermittent charging process is initiated, the duration of the rest mode (ie, the second reference time period) may be set short.

[0141] exist Figure 1 In the embodiment, the charging control device 100 is illustrated as being included as a subcomponent of the battery system 1, but is not limited thereto. For example, the charging control device 100 may be used as a subcomponent of a charging performance tester to derive a DOC according to a charging progress condition of a battery cell BC. In this case, the charging performance tester may include the charging control device 100 and the charger 3.

[0142] Fig.17 and Fig.18 is a diagram illustrating the configuration of a test jig for a battery charging test.

[0143] refer to Fig.17 and Fig.18 , the test fixture 1700 includes a first plate 1711, a second plate 1712, and a coupling member 1730. The coupling member 1730 includes one or more bolts 1731 and nuts 1732. The charging control device 100 used as a charging tester may perform the above-mentioned intermittent charging process to derive a fast charging protocol of the battery cell BC coupled to the test fixture 1700. At this time, another charger having a function corresponding to the charger 3 may be separately provided for supplying a charging current.

[0144] The first plate 1711 and the second plate 1712 are disposed at opposite sides (e.g., top and bottom) of the battery cell BC. One or more coupling holes are formed in each of the first plate 1711 and the second plate 1712. The threads of the bolts 1731 pass through the coupling holes formed in each of the second plate 1712 and the first plate 1711, and the nuts 1732 are rotationally coupled to the distal ends of the threads of the bolts 1731, respectively. Fig.17 The diagram shows a state in which six bolts and six nuts are coupled to each other one by one. Therefore, the battery cell BC can be firmly fixed between the first plate 1711 and the second plate 1712.

[0145] The test fixture 1700 may also include one or more foam pads 1751 and 1752. The foam pads 1751 and 1752 may be provided for insulation purposes to prevent heat generated from the battery cell BC during charging from being released to the outside. As an example, the fastening between the test fixture 1700 and the battery cell BC may be completed by inserting the foam pad 1751 between the first plate 1711 and the battery cell BC, and pressing the first plate 1711 and the second plate 1712 on opposite sides using a coupling member in a state where the foam pad 1752 is inserted between the second plate 1712 and the battery cell BC. Note that only one of the two foam pads 1751 and 1752 may be inserted between the first plate 1711 or the second plate 1712 and the battery cell BC, or both foam pads 1751 and 1752 may not be inserted. When only one of the two foam pads 1751 and 1752 is inserted, the heat dissipation from the battery cell BC to the outside is smoother than when the two foam pads 1751 and 1752 are inserted. In addition, when neither of the two foam pads 1751 and 1752 is inserted, heat dissipation from the battery cell BC to the outside is maximized compared to the case where only one of the two foam pads 1751 and 1752 is inserted. For example, by changing the insertion conditions of the two foam pads 1751 and 1752 to change the heat generation environment during charging of the battery cell BC, the DOC can be derived for each heat generation environment.

[0146] Fig.19 and Fig. 20 In describing the use Fig.17 and Fig.18 The figure shown is a reference figure for the results of charging tests performed with the test fixture shown.

[0147] First, refer to Fig.19 , three temperature curves 1911, 1912, 1913 are graphs illustrating changes in the surface temperature of the test fixture 1700 relative to the SOC when the battery cell BC is charged from SOC 0% to SOC 100% at three current rates of 2.25C, 2.5C, and 2.75C in a state where the battery cell BC is fastened to the test fixture 1700 in which both the foam pads 1751 and 1752 are not inserted. The surface temperature of the test fixture 1700 may be measured using a temperature sensor inserted into the test fixture 1700 or placed within a predetermined distance from the test fixture 1700.

[0148] The remaining three temperature curves 1921, 1922, and 1923 are graphs illustrating the change in cell temperature relative to SOC when the battery cell BC is charged from SOC 0% to SOC 100% at three current rates of 2.25C, 2.5C, and 2.75C when the battery cell BC is fastened to the test fixture 1700 in which both foam pads 1751 and 1752 are inserted.

[0149] Comparing temperature curves 1911 , 1912 , 1913 with temperature curves 1921 , 1922 , 1923 , it can be seen that the heat generation environment during charging of the battery cell BC differs depending on whether the foam pads 1751 , 1752 are inserted, and as a result, a temperature difference of about 5° C. occurs in the later charging period.

[0150] Next, refer to Fig. 20 , each of the two SOC curves 2010 , 2020 is a graph showing changes in DOC obtained through charging tests one at a time using a plurality of current rates selected from a range of 0.5C to 2.75C in a state where the battery cell BC is fastened to the test fixture 1700 .

[0151] The SOC curve 2010 illustrates the change in DOC depending on the current rate when the battery cell BC is fastened to the test fixture 1700 in which both the foam pads 1751 , 1752 are not inserted.

[0152] The SOC curve 2020 illustrates the change in DOC depending on the current rate when the battery cell BC is fastened to the test fixture 1700 in which both the foam pads 1751 , 1752 are inserted.

[0153] Comparing the two SOC curves 2010 and 2020, when the foam pads 1751 and 1752 are inserted, the heat generated during charging of the battery cell BC placed inside the test fixture 1700 is insulated by the two foam pads 1751 and 1752, so the battery cell BC is charged at a higher temperature compared to the case where the foam pads 1751 and 1752 are not inserted. It can be seen that due to the insulation effect when the foam pads 1751 and 1752 are inserted, the increase in the surface temperature of the test fixture 1700 is reduced by about 5°C, and the DOC is increased compared to the case where the foam pads 1751 and 1752 are not inserted.

[0154] In contrast, when both the foam pads 1751 and 1752 are not inserted, since the heat generated during the charging of the battery cells BC is conducted to the first plate 1711 and the second plate 1712 and rapidly dissipated to the outside, the surface temperature of the test jig 1700 is observed to be relatively high compared to the case where the foam pads 1751 and 1752 are inserted. Therefore, compared to the case where the foam pads 1751 and 1752 are inserted, the temperature increase caused by the heat generation of the battery cells BC is eliminated, and the DOC is reduced.

[0155] Fig.21 is a flow chart illustrating a method of measuring DOC of a battery cell of the present disclosure.

[0156] In S2010, a voltage sensor is connected to the battery cell. Figure 1 In order to measure the DOC of the battery cell BC, the voltage sensor 111 is first connected in parallel to the battery cell BC. Then, in S2020, the intermittent charging process is performed on the battery 11 using the charging control device 100 under preset conditions, such as a set current rate and temperature.

[0157] In S2030, the internal resistance of the battery cell is measured based on the voltage change of the battery cell in the rest mode of the intermittent charging process, and in S2040, the measured internal resistance is recorded in association with the SOC of the battery cell to derive a graph of internal resistance and SOC. For example, the controller 130 can derive the above graph by associating the SOC of the battery cell with the measured internal resistance. Figures 5 to 7 Meanwhile, based on the map derived from S2040 , a differential map may be derived by performing curve fitting based on the map derived at S2040 and differentiating the internal resistance with respect to the SOC.

[0158] In S2050, a pattern of change in internal resistance depending on SOC is identified based on the derived map. Figure 5 The intermittent charging process performed under the conditions of shows a pattern in which the internal resistance decreases when the SOC is in a section of about 50% to 65%, and then increases from 65%.

[0159] In S2060, the DOC is determined based on the identified pattern of the internal resistance. Figure 5 When the pattern is shown, the DOC can be determined to be the same value as the charge limit SOC (the upper limit of the SOC range of interest), for example, about 95%.

[0160] The above-mentioned embodiments of the present disclosure may be implemented not only by devices and methods, but also by programs that implement functions corresponding to the configurations of the embodiments of the present disclosure or recording media having the programs recorded thereon. This may be easily implemented by a person of ordinary skill in the art to which the present disclosure belongs based on the description of the above-mentioned embodiments.

[0161] Although the present disclosure has been described above with reference to several embodiments of the present disclosure, the present disclosure is not limited to these embodiments, and a person skilled in the art to which the present disclosure belongs may make various changes and modifications without departing from the technical spirit and equivalent scope of the present disclosure defined in the appended claims.

[0162] In addition, since ordinary technicians in the field to which the present disclosure belongs can make various replacements, modifications and changes to the above-mentioned present disclosure without departing from the technical spirit of the present invention, the present invention is not limited to the above-mentioned embodiments and drawings, but can selectively combine all or part of the various embodiments, so that various modifications can be made.

Claims

1. A charging control device, comprising: a voltage sensor configured to detect a voltage of a battery cell; as well as a controller configured to perform an intermittent charging process to alternately repeat a charging mode and a rest mode of the battery cell, Wherein, in the case of switching from the charging mode to the rest mode while executing the intermittent charging process, the controller is configured to execute: an operation of determining an internal resistance of the battery cell based on an amount of change in voltage of the battery cell during a rest period during which the rest mode continues; and The operation of the internal resistance is recorded in association with the state of charge of the battery cell.

2. The charging control device according to claim 1, wherein: The charging mode is a mode in which a charging current having a predetermined current rate is supplied to the battery cells.

3. The charging control device according to claim 1, wherein: The controller is configured to control the intermittent charging process to switch from the charging mode to the resting mode when a duration of the charging mode reaches a first reference time period or when an increase in the state of charge of the battery cell due to the charging mode reaches a reference increase.

4. The charging control device according to claim 1, wherein: The controller is configured to control the intermittent charging process to switch from the rest mode to the charging mode when a duration of the rest mode reaches a second reference time period.

5. The charging control device according to claim 4, wherein: The controller is configured to: determine a reference frequency according to a complex impedance curve of the battery cell pre-acquired using an electrochemical impedance spectroscopy device; and The second reference time period is determined based on the reference frequency.

6. The charging control device according to claim 5, wherein: The controller is configured to determine the second reference time period to have a predetermined negative corresponding relationship with the reference frequency.

7. The charging control device according to claim 1, wherein: The controller is configured to determine the depth of charge of the battery cell by analyzing a resistance time series data set representing a history of changes in the internal resistance within a charging control period from initiation to termination of the intermittent charging process.

8. The charging control device according to claim 7, wherein: The controller is configured to: performing curve fitting on the resistance time series data set to generate a resistance profile representing a relationship between the state of charge and the internal resistance of the battery cell; and The depth of charge is determined based on a pattern of the resistance profile.

9. The charging control device according to claim 8, wherein: When only a continuously increasing pattern of the internal resistance is identified in the resistance profile, the controller is configured to determine that the depth of charge is equal to a predetermined end-of-charge state of charge.

10. The charging control device according to claim 8, wherein: When a transition of the internal resistance from an increasing pattern to a decreasing pattern is identified in the resistance profile, the controller is configured to determine the charging depth based on a boundary charging state between the increasing pattern and the decreasing pattern.

11. The charging control device according to claim 8, wherein: When only a continuous decreasing pattern of the internal resistance is identified in the resistance profile, the controller is configured to determine the depth of charge based on the state of charge at which a second-order derivative of the resistance profile becomes zero.

12. A battery pack comprising the charge control device according to claim 1.

13. A battery system comprising the charging control device according to claim 1.

14. A charging control method, comprising: An intermittent charging process is performed to alternately repeat a charging mode and a rest mode of a battery cell, Wherein, in the case of switching from the charging mode to the rest mode while executing the intermittent charging process, the charging control method includes: determining an internal resistance of the battery cell based on an amount of change in voltage of the battery cell during a rest period during which the rest mode continues; and The internal resistance is recorded in association with the state of charge of the battery cell.

15. The charging control method according to claim 14, further comprising: The depth of charge of the battery cell is determined by analyzing a resistance time series data set representing a history of changes in the internal resistance within a charging control period from initiation to termination of the intermittent charging process.

16. A charging control method for a battery cell, the charging control method comprising: connecting a voltage sensor to the battery cell; performing an intermittent charging process to alternately repeat a charging mode and a rest mode of the battery cells; measuring the internal resistance of the battery cell in the rest mode; recording the measured internal resistance in association with a state of charge of the battery cell; as well as A pattern of the internal resistance is discerned based on the recorded internal resistance and state of charge related data, and the depth of charge of the battery cell is determined based on the pattern.

17. The charging control method according to claim 16, further comprising: After the internal resistance has been recorded in association with the state of charge of the battery cell, a curve fit and a differentiation of the internal resistance with respect to the state of charge are performed.

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