Charge control device and charge control method

Abstract

A charge control device and a charge control method are provided. The charge control device according to the present invention includes a voltage sensor that detects the voltage of a battery cell, and a control unit configured to perform an intermittent charging process that alternately repeats a charging mode and a sleep mode for the battery cell. The control unit is configured to perform, on a condition that the charging mode is switched to the sleep mode during the intermittent charging process, 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 sleep period in the sleep mode, and an operation of recording the internal resistance in association with a SOC of the battery cell, on the basis of an amount of change in voltage of the battery cell during a sleep period in the sleep mode.

Description

[Technical Field]

[0001] The present invention relates to a technique for controlling the charging of battery cells.

[0002] This application claims priority to 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, and the contents disclosed in the specifications and drawings of those applications are incorporated herein in their entirety. [Background technology]

[0003] Recently, the demand for portable electronic products such as laptops, video cameras, and mobile phones has increased dramatically, and the development of battery systems, energy storage batteries, robots, satellites, etc. has gained momentum. As a result, research into high-performance batteries that can be repeatedly charged and discharged is being actively conducted.

[0004] Currently commercially available batteries include nickel-cadmium batteries, nickel-metal hydride batteries, nickel-zinc batteries, and lithium batteries. Of these, lithium batteries are attracting attention due to their advantages over nickel-based batteries, such as almost no memory effect, allowing for free charging and discharging, a very low self-discharge rate, and a high energy density.

[0005] Recently, as the demand for high-capacity and high-power battery cells has been gradually increasing, various technologies have been proposed to charge battery cells as quickly as possible in order to shorten the charging time. Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention provides an apparatus and method for alternately repeating a charging mode and a sleep mode according to the charging progress conditions of a battery cell, calculating the internal resistance of a battery for each sleep mode, and monitoring the change history of the internal resistance due to multiple sleep modes.

[0007] The present invention also provides an apparatus and method for deriving a depth of charge of a battery cell that can avoid lithium deposition from a history of changes in internal resistance under specific charging conditions.

[0008] Other uses and advantages of the present invention will become apparent from the following description and will become more clearly understood by the embodiments of the present invention. In addition, it will be readily apparent that the uses and advantages of the present invention can be realized by the means recited in the claims and their combinations. [Means for solving the problem]

[0009] A charge control device according to one aspect of the present invention includes a voltage sensor that detects a voltage of a battery cell, and a control unit that is configured to perform an intermittent charging process that alternately repeats a charging mode and a sleep mode for the battery cell, wherein the control unit is configured to perform, on condition that the charging mode is switched to the sleep mode during execution of the intermittent charging process, 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 sleep period in which the sleep mode continues, and an operation of recording the internal resistance in association with a State Of Charge (SOC) of the battery cell.

[0010] The charging mode may be a mode in which a charging current at a predetermined current rate is supplied to the battery cell.

[0011] The control unit may be 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 or an increase in SOC of the battery cell due to the charging mode reaches a reference increase.

[0012] The control unit may control the intermittent charging process such that the sleep mode is switched to the charging mode when the duration of the sleep mode reaches a second reference time.

[0013] The control unit may be configured to determine a reference frequency from a complex impedance curve of the battery cell acquired in advance using an electrochemical impedance spectroscopy (EIS) device, and to determine the second reference time based on the reference frequency.

[0014] The control unit may be configured to determine the second reference time to have a predetermined negative correspondence relationship with the reference frequency.

[0015] The control unit may be configured to determine a depth of charge of the battery cell by analyzing a resistance time series data set indicating a history of changes in the internal resistance over a charge control period from a start point to an end point of the intermittent charging process.

[0016] The control unit may be configured to curve fit the resistance time series data set to generate a resistance profile indicating a relationship between a SOC and an internal resistance of the battery cell, and determine the depth of charge based on a pattern of the resistance profile.

[0017] The control unit may be configured to determine that the state of charge is equal to a predetermined end-of-charge SOC when only a pattern of a sustained increase in the internal resistance is identified in the resistance profile.

[0018] The control unit may be configured to, when a switch from an increase pattern to a decrease pattern of the internal resistance is identified in the resistance profile, determine the depth of charge based on a boundary SOC between the increase pattern and the decrease pattern.

[0019] The control unit may be configured to determine the depth of charge based on an SOC at which a second derivative of the resistance profile becomes zero when only a sustained decrease pattern of the internal resistance is identified in the resistance profile.

[0020] A battery pack according to another aspect of the present invention includes the above-described charge control device.

[0021] A battery system according to still another aspect of the present invention includes the charge control device.

[0022] According to another aspect of the present invention, a charge control method includes performing an intermittent charging process in which a charge mode and a rest mode are alternately repeated for a battery cell, and the charge control method further includes, on a condition that the charge mode is switched from the charge mode to the rest mode during the intermittent charging process, determining an internal resistance of the battery cell based on an amount of voltage change of the battery cell during a rest period in the rest mode, and recording the internal resistance in association with a SOC of the battery cell.

[0023] The charge control method may further include determining a depth of charge of the battery cell by analyzing a resistance time series data set indicating a history of changes in the internal resistance over a charge control period from a start point to an end point of the intermittent charging process.

[0024] A charge control method according to another aspect of the present invention includes the steps of connecting a voltage sensor to a battery cell, performing an intermittent charging process on the battery cell by alternately repeating a charging mode and a resting mode for the cell, measuring an internal resistance of the battery cell in the resting mode, recording the measured internal resistance in association with a SOC of the battery cell, and recognizing a pattern of the internal resistance based on the recorded internal resistance and SOC-related data, and determining a state of charge of the battery cell based on the pattern.

[0025] The charging control method may further include, after the step of recording the internal resistance in association with the SOC of the battery cell, performing curve fitting and differentiating the internal resistance with respect to the SOC. [Effects of the Invention]

[0026] According to at least one of the embodiments of the present invention, a charging mode and a sleep mode are alternately repeated according to the charging progress conditions of the battery cell, the internal resistance of the battery cell for each sleep mode is calculated (estimated), and the history of changes in the internal resistance due to the sleep mode being repeated multiple times can be monitored. Since the history of changes in the internal resistance of the battery cell reflects signs and the presence or absence of lithium deposition, the depth of charge, which is the SOC at which the battery cell can be charged, can be identified from the history of changes in the internal resistance while significantly reducing the possibility of lithium deposition occurring.

[0027] Furthermore, according to at least one of the embodiments of the present invention, by setting an appropriate duration of the sleep mode from EIS (electrochemical impedance spectroscopy) data of the battery and calculating an estimated value of the internal resistance based on the amount of change in the battery voltage in the sleep mode, it is possible to prevent a decrease in accuracy of the depth of charge due to an insufficient or excessive duration of the sleep mode.

[0028] The effects of the present invention are not limited to the above effects, and effects not mentioned will be clearly understood by those skilled in the art from the description of the claims.

[0029] The following drawings attached to this specification illustrate preferred embodiments of the present invention and, together with the detailed description of the invention, serve to further understand the technical concepts of the present invention. Therefore, the present invention should not be interpreted as being limited to only the matters described in the drawings. [Brief explanation of the drawings]

[0030] [Figure 1] 1 is a diagram illustrating an example of a configuration of a battery system according to the present invention; [Figure 2a] 1 is a flow chart illustrating an example of a charge control method according to a first embodiment of the present invention; [Figure 2b] 1 is a flow chart illustrating an example of a charge control method according to a first embodiment of the present invention; [Figure 3] FIG. 3 is a reference diagram for explaining the method of FIGS. 2a and 2b. [Figure 4] FIG. 3 is a reference diagram for explaining the method of FIGS. 2a and 2b. [Figure 5] FIG. 3 is a reference diagram for explaining the method of FIGS. 2a and 2b. [Figure 6] FIG. 3 is a reference diagram for explaining the method of FIGS. 2a and 2b. [Figure 7] FIG. 3 is a reference diagram for explaining the method of FIGS. 2a and 2b. [Figure 8] 5 is a flowchart illustrating an example of a charge control method according to a second embodiment of the present invention. [Figure 9] 9 is a graph showing an exemplary resistance profile referenced to explain the method of FIG. 8. [Figure 10] 9 is a graph showing an exemplary resistance profile referenced to explain the method of FIG. 8. [Figure 11] 9 is a graph showing an exemplary resistance profile referenced to explain the method of FIG. 8. [Figure 12]9 is a graph showing an exemplary resistance profile referenced to explain the method of FIG. 8. [Figure 13] 9 is a graph showing an exemplary resistance profile referenced to explain the method of FIG. 8. [Figure 14] FIG. 1 is a reference diagram for explaining the relationship between lithium deposition and impedance during charging of a battery. [Figure 15] FIG. 1 is a reference diagram for explaining the relationship between lithium deposition and impedance during charging of a battery. [Figure 16] FIG. 1 is a reference diagram for explaining the relationship between lithium deposition and impedance during charging of a battery. [Figure 17] FIG. 10 is a diagram illustrating an example of the structure of a test fixture for a battery charging test. [Figure 18] FIG. 10 is a diagram illustrating an example of the structure of a test fixture for a battery charging test. [Figure 19] FIG. 19 is a reference diagram for explaining the results of a charging test using the test jig shown in FIGS. 17 and 18. [Figure 20] FIG. 19 is a reference diagram for explaining the results of a charging test using the test jig shown in FIGS. 17 and 18. [Figure 21] 3 is a flowchart illustrating a method for measuring the state of charge of a battery cell according to the present invention.

[0031] In some of the accompanying drawings, corresponding components are designated by the same reference numerals. Those skilled in the art will appreciate that the drawings illustrate elements simply and clearly and are not necessarily drawn to scale. For example, to facilitate understanding of the various embodiments, the dimensions of some elements illustrated in the drawings may be exaggerated relative to other elements. Furthermore, elements of the publicly known art that are useful or essential to commercially viable embodiments are often not depicted so as not to obscure the spirit of the various embodiments of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0032] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, the terms and phrases used in the specification and claims should not be construed as being limited to their ordinary and dictionary meanings, but should be construed as having meanings and concepts corresponding to the technical ideas of the present invention, in accordance with the principle that the inventors themselves can appropriately define the concepts of terms in order to best describe the invention.

[0033] Therefore, it should be understood that the configurations shown in the embodiments described in this specification are merely the most desirable embodiments of the present invention and do not represent the entire technical idea of ​​the present invention, and that there may be various equivalents and modifications that can be substituted for them at the time of this application.

[0034] Terms including ordinal numbers such as first, second, etc. are used to distinguish one of the various components from the rest, and are not used to limit the components by those terms.

[0035] Throughout the specification, when a part "comprises" a certain element, this does not mean that it excludes other elements, but that it may further include other elements, unless otherwise specified. Furthermore, terms such as "controller" in the specification refer to a unit that processes at least one function or operation, and can be realized by hardware, software, or a combination of hardware and software.

[0036] Throughout this specification, when a part is said to be "connected" to another part, this includes not only the case where the part is "directly connected" to another part, but also the case where the part is "indirectly connected" via another element between them.

[0037] 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 it has the disadvantage of causing significant damage to the battery cells and shortening the battery's lifespan.

[0038] The higher the charging current, the more likely it is that lithium ions inside the battery cell will deposit as lithium metal on the surface of the negative electrode, a phenomenon known as "lithium plating." The amount of lithium plating reduces the amount of lithium ions available for charge-discharge reactions, exacerbating the potential imbalance between the positive and negative electrodes. Furthermore, excessive lithium metal buildup can damage the separator, increasing the likelihood of an internal short circuit, which can increase the risk of battery cell explosion and fire.

[0039] The present invention provides a method for deriving a fast charging protocol that can avoid lithium precipitation by obtaining characteristic information (e.g., SOC-internal resistance relationship) of a battery cell regarding the possibility of lithium precipitation throughout the entire life of the battery cell after its manufacture without producing a separate test cell (e.g., a three-electrode mono cell) and using the information to determine the depth of charge of fast charging.

[0040] For example, in the case of medium- to large-sized pouch cells used in electric vehicles, lithium metal deposits form on the surface of the negative electrode with repeated use. The resistance of the lithium metal deposits is compounded in parallel with the resistance of the negative electrode surface. As a result, the formation of lithium metal deposits can reduce the total resistance of the negative electrode surface of the battery cell. In this case, the impedance of the battery cell changes, and a reference frequency can be determined corresponding to the charging conditions at the start of the intermittent charging process using electrochemical impedance spectroscopy (EIS) or other methods based on the changed impedance graph. Once the reference frequency for the intermittent charging process is determined, an appropriate rest period to be applied during the intermittent charging process can be determined. During the appropriate rest period, changes in voltage and resistance, for example, due to the internal resistance of the battery cell BC, can be observed, and the depth of charge of the battery cell BC can be determined using this data. The theoretical background of lithium deposition and the surface resistance of battery cells and a method for determining the appropriate rest period are described in more detail below.

[0041] 1 is a diagram illustrating an example of the configuration of a battery system according to an embodiment of the present invention. The battery system 1 described below can be connected to a commercially available secondary battery via a test jig or directly to the secondary battery without using a test jig to acquire required battery cell characteristic information.

[0042] 1, a 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 battery system 1 can be a term that encompasses not only an electrical system in which a battery is used as a power source, such as an electric vehicle, but also a test system used to check / verify the electrical characteristics of a battery.

[0043] The charging and discharging terminals (P+, P-) of the battery pack 10 may be electrically coupled to the inverter 30 and / or the charger 3 via a charging cable or the like. The charger 3 may be included in the battery system 1 or may be provided in a charging station located outside the battery system 1.

[0044] The system controller 2 is configured to send a key-on signal to the charge control device 100 in response to a start button (not shown) provided on the battery system 1 being switched to an 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 an off position by a user. The charger 3 can communicate with the system controller 2 to supply charging power to the battery 11 via the charging and discharging terminals (P+, P-) of the battery pack 10 by at least one charging protocol (e.g., constant current charging, constant voltage charging, and / or constant power charging).

[0045] The battery pack 10 includes a battery 11 and a charge control device 100. The charge control device 100 can also function as a battery management system (BMS).

[0046] The battery 11 includes a cell group 12 and a case 13. The case 13 defines the overall outer shape of the battery 11 and provides an internal space in which the cell group 12 is disposed. The case 13 is fixed to a battery room provided in the battery system 1 by bolts or the like.

[0047] The cell group 12 is arranged (housed) in the 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.

[0048] When the cell group 12 includes multiple battery cells, the multiple battery cells can be connected in series, in parallel, or in a combination of series and parallel.

[0049] The relay 20 is electrically connected in series with the battery 11 via a power path connecting the battery 11 and the inverter 30. In FIG. 1 , the relay 20 is illustrated as being connected between the positive terminal of the battery 11 and the charge / discharge terminal P+. The relay 20 is controlled to be turned on and off in response to a switching signal from the charge control device 100. According to one embodiment of the present invention, the relay 20 may be a mechanical contactor that is turned on and off by the magnetic force of a coil, or may be a semiconductor switch such as a MOSFET (Metal Oxide Semiconductor Field Effect Transistor).

[0050] The inverter 30 is provided to convert direct current from the cell group 12 into alternating current in response to commands from the charge control device 100 or the system controller 2 .

[0051] The electric motor 40 is driven using AC power from the inverter 30. As the electric motor 40, for example, a three-phase AC motor 40 can be used.

[0052] The charge control device 100 includes a voltage sensor 111, a current sensor 113, a temperature sensor 115, a control unit 130, and a memory 140. The charge control device 100 may further include an outside air temperature sensor 117. The charge control device 100 may further include a communication circuit 150. The charge control device 100 may be included in the battery pack 10 as shown in FIG. 1 , but is not limited to this, and may be included in the battery system 1 independent of the battery pack 10. The voltage sensor 111 is connected in parallel to the battery 11 and is configured to detect a battery voltage, which is a voltage across both ends of the battery 11, and generate a voltage signal indicative of the detected battery voltage.

[0053] Of course, the voltage sensor 111 may be connected to the positive and negative terminals of each battery cell BC included in the battery 11, detect the cell voltage, which is the voltage across both ends of each battery cell BC, and output a further voltage signal indicating the cell voltage to the control unit 130.

[0054] 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 generate a current signal indicative of the detected battery current. The current sensor 113 can be realized by one or a combination of two or more of known current detection elements, such as a shunt resistor and a Hall effect element.

[0055] The temperature sensor 115 is configured to detect the battery temperature and generate a temperature signal indicating the detected battery temperature. The temperature sensor 115 may be disposed inside the case 13 so as 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, anything simply referred to as a "detected temperature value" in this specification may refer to the detected battery temperature value.

[0056] The voltage sensor 111, the current sensor 113, and the temperature sensor 115 can be referred to as a "sensing unit."

[0057] The outside air temperature sensor 117 is configured to detect the outside air temperature (ambient temperature), which is the temperature at a predetermined location separated from the battery 11, and generate a temperature signal indicating the detected outside air temperature. The outside air temperature sensor 117 can be disposed at a predetermined location outside the case 13 where heat exchange between the battery 11 and the outside air takes place.

[0058] Each of the temperature sensor 115 and the outside air temperature sensor 117 can be realized by one or a combination of two or more temperature detection elements such as a thermocouple, a thermistor, a bimetal, or the like.

[0059] The communication circuit 150 is configured to support wired or wireless communication between the control unit 130 and the system controller 2. The wired communication is, for example, CAN (controller area network) communication, and the wireless communication is, for example, ZigBee or Bluetooth (registered trademark) communication. Of course, the type of communication protocol is not particularly limited as long as it supports wired or wireless communication between the control unit 130 and the system controller 2. The communication circuit 150 may include an output device (for example, a display, a speaker) that provides information received from the control unit 130 and / or the system controller 2 in a form that can be recognized by a user.

[0060] The control unit 130 is operably coupled to the relay 20, the voltage sensor 111, the current sensor 113, the temperature sensor 115, the outside air temperature sensor 117, and the communication circuit 150. Two components being operably coupled means that the two components are directly or indirectly connected so as to be able to send and receive signals unidirectionally or bidirectionally.

[0061] The control unit 130 can 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 outside air temperature sensor 117 (which may be referred to as an "outside air temperature signal"). The control unit 130 can use an ADC (Analog to Digital Converter) provided inside it to convert and record each of the analog signals collected from the sensors 111, 113, 115, and 117 into digital values.

[0062] The control unit 130 may be referred to as a "control circuit" or a "battery controller" and may be implemented in hardware using at least one of ASICs (application specific integrated circuits), DSPs (digital signal processors), DSPDs (digital signal processing devices), PLDs (programmable logic devices), FPGAs (field programmable gate arrays), microprocessors, and other electrical units for performing functions.

[0063] The memory 140 may include at least one type of storage medium, such as a flash memory type, a hard disk type, a solid state disk type (SSD type), a silicon disk drive type (SDD type), a micro multimedia card type, a random access memory (RAM), a static random access memory (SRAM), a read-only memory (ROM), an electrically erasable programmable read-only memory (EEPROM), or a programmable read-only memory (PROM). The memory 140 may store data and programs required for calculations performed by the control unit 130. The memory 140 may store data indicating the results of calculations performed by the control unit 130. Although FIG. 1 illustrates the memory 140 as being physically separate from the control unit 130, it may also be embedded within the control unit 130.

[0064] The control unit 130 can turn on the relay 20 in response to a key-on signal. The control unit 130 can 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, in which the battery 11 is being charged or discharged, to a rest state, in which charging or discharging of the battery 11 is stopped. Alternatively, the on / off control of the relay 20 can be performed by the system controller 2 instead of the control unit 130.

[0065] If the inverter 30 or charger 3 operates while the relay 20 is turned on, the battery 11 is in a cycle state. Conversely, if the relay 20 is turned off or the inverter 30 and charger 3 are stopped, the battery 11 is in a rest state.

[0066] Meanwhile, when the battery 11 is in a cycle state or a rest state, it means that each battery cell BC included in the battery 11 is also in a cycle state or a rest state.

[0067] When the battery cell BC is in a cycle state and / or a rest state, the control unit 130 determines a voltage detection value, a current detection value, a battery temperature detection value, and an outside air temperature detection value based on the voltage signal, the current signal, the battery temperature signal, and the outside air temperature signal, and then determines (estimates) the state of charge (SOC) of the battery cell BC based on the voltage detection value, the current detection value, and / or the battery temperature detection value.

[0068] When the charger 3 is operating in constant current charging mode, the current rate (which can be referred to as the "C-rate") of the charging current supplied to the battery cell BC is a predetermined constant value, so when estimating the SOC of the battery cell BC, the current value of the constant current output from the charger 3 can be used instead of the current detection value obtained using the current sensor 113.

[0069] The SOC is the ratio of the remaining capacity to the fully charged capacity (maximum capacity) of the battery cell BC, and is usually calculated in the range of 0 to 1 or 0% to 100%. The SOC can be determined using, for example, an ampere count, an OCV (Open Circuit Voltage)-SOC curve, and / or a Kalman filter.

[0070] 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 cells BC and measure the response characteristics of the battery cells BC to the applied AC signal. While FIG. 1 illustrates the EIS device 4 connected in parallel with the battery 11, this is not limiting. For example, the EIS device 4 may be selectively connected to individual battery cells BC by a separate switching circuit.

[0071] The following describes a process of connecting the above-mentioned battery system 1 to a commercial secondary battery, for example, a medium- to large-sized pouch cell used in an electric vehicle, via a test jig or the like, performing an "intermittent charging process" by applying the appropriate rest period described above, and acquiring characteristic information of the battery cell in the rest mode of the intermittent charging process.

[0072] 2a and 2b are flow charts illustrating an example of a charge control method according to a first embodiment of the present invention, and FIGS. 3 to 7 are reference diagrams for explaining the method of FIGS. 2a and 2b.

[0073] The method of Fig. 2a can be performed by the charge control device 100 shown in Fig. 1. The set of steps S210 to S250 included in Fig. 2a can be commonly referred to as control steps of an "intermittent charging process." The method of Fig. 2a can be repeatedly performed until the SOC of the battery cell BC reaches a predetermined upper SOC (also referred to as "charge end SOC") from a predetermined lower SOC limit (also referred to as "charge start SOC").

[0074] Each of the lower and upper SOC limits may be set depending on the magnitude of the charging current (ie, current rate) used in the charging mode of the method of FIG. 2a and the battery temperature at the start time of the method of FIG. 2a.

[0075] For example, the lower limit SOC and upper limit SOC can be set to 88% and 97% when the current rate and battery temperature are 0.5 C and 25° C., 68% and 77% when the current rate and battery temperature are 2 C and 25° C., and 63% and 72% when the current rate and battery temperature are 2 C and 10° C. Data relating the lower limit SOC and upper limit SOC to the current rate and battery temperature (or outside air temperature) can be pre-recorded in the memory 140 in the form of a look-up table and / or function.

[0076] 1, 2a, and 2b, in step S210, the control unit 130 controls the charger 3 to a charging mode in which a charging current is supplied to the battery cell BC. For example, the control unit 130 transmits 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 current rate determined by the charging request signal 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.

[0077] In step S220, the control unit 130 determines whether a first switching condition for switching from the charging mode to the sleep mode is satisfied. The first switching condition may be a time-based condition or an SOC-based condition. As an example, the control unit 130 may determine that the first switching condition is satisfied when the duration of the charging mode (e.g., the elapsed time from the start time of the charging mode) reaches a first reference time. As another example, the control unit 130 may determine that the first switching condition is satisfied when the SOC increase amount of the battery cell BC due to the charging mode (i.e., the difference between the SOC at the start time of the current charging mode and the current SOC) reaches a reference increase amount (e.g., 0.5%). If the result of step S220 is "No," the control unit 130 repeatedly executes step S220. If the result of step S220 is "Yes," i.e., if the control unit 130 determines that the first switching condition is satisfied in S220, the control unit 130 proceeds to step S230.

[0078] In step S230, the control unit 130 controls the charger 3 to enter the sleep mode. This switches the intermittent charging process from the charge mode to the sleep mode. For example, when the control unit 130 transmits a charge stop signal to the charger 3 via the communication circuit 150, the charger 3 enters the sleep mode in response to the charge stop signal. In the sleep mode, the supply of charging current from the charger 3 to the battery cell BC is cut off. The control unit 130 can record in the memory 140 the SOC of the battery cell BC at the time of switching from the charge mode to the sleep mode.

[0079] In step S240, the control unit 130 determines whether a second switching condition for switching from the sleep mode to the charging mode is satisfied. The second switching condition may be a time-based condition. As an example, the control unit 130 may determine that the second switching condition is satisfied in response to the duration of the sleep mode (i.e., the elapsed time since the start time of the sleep mode) reaching a second reference time. The second reference time may be a predetermined fixed time or a variable period adjusted by the control unit 130 based on electrochemical characteristic data of the battery cell BC. Adjustment of the second reference time will be described later with reference to FIG. 14. If the result of step S240 is "No," i.e., the duration of the sleep mode has not reached the second reference time, step S240 is repeatedly executed again. If the result of step S240 is "Yes," i.e., the duration of the sleep mode has reached the second reference time, the control unit 130 proceeds to step S250.

[0080] In step S250, the control unit 130 determines whether the SOC of the battery cell BC has reached the charging end SOC. If the value of step S250 is "No," the process returns to step S210. For example, the intermittent charging process may switch from a sleep mode to a charging mode, and the charging mode and the sleep mode may be repeated until the SOC of the battery cell BC reaches the charging end SOC. On the other hand, if the value of step S250 is "Yes," for example, if the SOC of the battery cell has reached the charging end SOC, the method according to FIG. 2a ends.

[0081] As described above, by repeating the charging and resting modes through the steps shown in Figure 2a, a graph of cell voltage (V) versus time (minutes) can be obtained, as shown in Figure 3. The comb-like pattern in Figure 3 represents the resting period of the intermittent charging process, as shown in Figure 4.

[0082] The method of Fig. 2b can be performed on the condition that the determination value in step S240 of Fig. 2a is "Yes." For example, if the second switching condition is met in step S240, the method of Fig. 2b can perform step S260, described below, before proceeding to step S250.

[0083] In step S260, the control unit 130 calculates the internal resistance of the battery cell BC based on the amount of change in voltage of the battery cell BC in the rest period, and records the internal resistance calculated in S270 in association with the SOC of the battery cell.

[0084] 3 is a graph showing an example of a change history of the cell voltage of the battery cell BC during a charge control period in which an intermittent charging process is performed. As can be seen from FIG. 3, the voltage of the battery cell BC generally shows an upward trend over the charge control period, and as shown by the comb pattern in the graph, there are alternating voltage rise periods when the charger 3 is operating in the charge mode and voltage drop periods when the charger 3 is operating in the sleep mode.

[0085] Figure 4 shows the voltage drop period S in the sleep mode, which is the area marked by the dotted line in Figure 3. drop 4 is an enlarged graph of t r1 is the time when the charger 3 is requested to switch from the charging mode to the sleep mode (or the time when an event of switching from the charging mode to the sleep mode occurs), t r2 is the time when the charger 3 is requested to switch from sleep mode to charge mode (or the time when an event of switching from sleep mode to charge mode occurs), Δt rest is the duration of the sleep mode (the length of the sleep period), V r1 is t r1 Cell voltage at V r2 is t r2 Cell voltage at ΔV rest and V indicate the voltage change amount in sleep mode. r1 is the cell voltage detected just before switching from charging mode to sleep mode, V r2and Δt respectively represent the cell voltages detected just before switching from rest mode to charging mode. rest =t r2 -t r1 and ΔV rest =V r1 -V r2 is.

[0086] The control unit 130 can calculate (estimate) the internal resistance for each pause period using the following equation 1. <Formula 1>

[0087]

number

[0088] In the above formula 1, I CC is the charging current (e.g., a constant current at a given current rate), and R CT and represent the internal resistances, respectively.

[0089] In step S270, the control unit 130 associates the internal resistance acquired in step S260 with the SOC of the battery cell BC and records it in the memory 140. The SOC associated with the internal resistance may be the SOC of the battery cell BC at the time of switching from the charging mode to the resting mode (i.e., the time of execution of step S230).

[0090] As shown in FIG. 3, during charging in the SOC range of interest (i.e., from the lower limit SOC to the upper limit SOC), the sleep mode is performed multiple times (i.e., multiple sleep periods are applied in sequence during the charge control period), and the estimated internal resistance values ​​during the sleep periods that occur each time the sleep mode is executed can be recorded in chronological order in memory 140.

[0091] Therefore, when the SOC of the battery cell BC reaches the upper SOC limit, a resistance time series data set (also referred to as an "internal resistance map") representing a history of changes in the internal resistance over time may be recorded in the memory 140. Each data point in the resistance time series data set may represent a correlated pair of internal resistance and SOC determined at a particular rest period during the charge control period.

[0092] 5 to 7 are graphs 500, 600, and 700 illustrating three typical resistance time-series data sets obtained by repeatedly performing an intermittent charging process using three different charging conditions. For example, the outline of charge transfer resistance obtained from the evaluation of the present invention is classified into three cases shown in FIGS. 5, 6, and 7, which are described below, and each figure is an example of the evaluation conditions and environment. However, measurements are not necessarily required under these conditions, and intermittent charging can also be performed under conditions other than those listed below for evaluation. In the following description, a more accurate state of charge can be determined when the state of charge decreases (deterioration of the battery's charge transfer resistance) in the order of FIGS. 5, 6, and 7.

[0093] 5 illustrates an example resistance time series data set 500 obtained by performing an intermittent charging process under a first charging progression condition in which the charging current rate is 0.5 C and the battery temperature (e.g., the temperature measured at the initial start of the intermittent charging process) is 25° C. int1 is the range of SOC of interest (e.g., 88% to 97%) in the resistance pattern associated with the first charge progression condition.

[0094] 6 illustrates a resistance time series data set 600 obtained by performing an intermittent charging process under a second charging progression condition in which the current rate of the charging current is 2C and the battery temperature (e.g., the temperature measured at the initial start of the intermittent charging process) is 25°C. int2 is the range of SOC of interest (e.g., 68% to 77%) in the resistance pattern associated with the second charge progression condition.

[0095] 7 illustrates a resistance time series data set 700 obtained by performing an intermittent charging process under a third charging progression condition in which the current rate of the charging current is 2C and the battery temperature (e.g., the temperature measured at the initial start of the intermittent charging process) is 10°C. int3 is the range of SOC of interest (e.g., 63% to 72%) in the resistance pattern associated with the third charge progression condition.

[0096] The upper limit of each SOC range of interest is also referred to as the charging limit SOC.

[0097] 5 and 6, the first and second charging conditions have the same battery temperature, but the first charging condition has a lower current rate than the second charging condition. Therefore, since the first charging condition is less strict on the battery cell BC than the second charging condition, the upper limit SOC (97%) associated with the first charging condition is set higher than the upper limit SOC (77%) associated with the second charging condition.

[0098] 6 and 7, the second and third charging conditions have the same current rate, but the third charging condition is at a lower temperature than the second charging condition, and the electrochemical reaction of the battery cell BC may be relatively slower under the second charging condition than under the third charging condition. Therefore, the upper limit SOC associated with the third charging condition (72%) is lower than the upper limit SOC associated with the second charging condition (77%).

[0099] Figures 5 to 7 show the change history of internal resistance (reflecting charge transfer resistance) in a range wider than the range of SOC of interest corresponding to each charging progress condition, but this is for ease of understanding, and in reality, it is also possible to obtain only the change history of internal resistance limited to the range of SOC of interest corresponding to each charging progress condition.

[0100] Fig. 8 is a flow chart illustrating an example of a charge control method according to a second embodiment of the present invention, and Figs. 9 to 13 are graphs illustrating example resistance profiles referred to in describing the method of Fig. 8. The method of Fig. 8 can be performed after a resistance time series data set for a charge control period is acquired by the charge control method according to the first embodiment described above with reference to Figs. 2a and 2b.

[0101] 8, in step S810, the control unit 130 curve-fits the resistance time-series data set to generate a resistance profile (also referred to as an "internal resistance profile") that indicates the relationship between the SOC and the internal resistance of the battery cell BC. Curve fitting refers to a procedure or logic that approximates an input data set with a polynomial having a predetermined degree. That is, the resistance profile may be a type of function whose input is the SOC and whose output is the internal resistance.

[0102] 9 to 11 illustrate three resistance profiles 900, 1000, and 1100, respectively, obtained by individually curve fitting the three resistance time series data sets 500, 600, and 700 described above with reference to FIGS. 5 to 7 with a ninth-order polynomial. For ease of understanding, the three resistance profiles 900, 1000, and 1100 are plotted over three ranges of SOC of interest, ΔSOC int1 , ΔSOC int2 , ΔSOC int3 The values ​​are shown for the range from the SOC 50% lower than the lower SOC limit to the upper SOC limit.

[0103] In step S820, the control unit 130 determines the charge depth of the battery cell BC based on the pattern of the resistance profile. The charge depth indicates the maximum SOC (which may be within a range of SOC of interest) to which the battery cell BC can be charged without lithium deposition.

[0104] First, we will explain the operation of identifying the depth of charge from the resistance profile 900 shown in Figure 9, which is obtained by curve fitting the time series data set of Figure 5. By examining Figure 9, it is possible to determine the SOC range of interest, ΔSOC int19, when a continuous increase pattern of the internal resistance is identified due to an increase in the SOC, the control unit 130 sets the end point P A SOC(Z A ) to charging depth Z A That is, in the case of the pattern form shown in FIG. 9, the charging depth Z A is the SOC range of interest, ΔSOC int1 The increasing pattern of a profile (or curve) may mean that the first derivative of the profile is a positive number.

[0105] Next, we will explain the operation of identifying the depth of charge from the resistance profile 1000 shown in Figure 10, which is obtained by curve fitting the time series data set of Figure 6. By examining Figure 10, it is possible to determine the SOC range of interest, ΔSOC int2 9 in that the rate of increase in the internal resistance gradually becomes gentler in the initial portion of the resistance profile 1000, and the internal resistance gradually decreases from a specific SOC. As shown in FIG. 10, when the internal resistance increase section and decrease section are adjacent to each other, the control unit 130 can obtain a differential resistance profile by first differentiating the resistance profile 1000 with respect to the SOC. For example, the differential resistance profile 1200 in FIG. 12 is exemplified as a result of first differentiation of the resistance profile 1000 in FIG. 10. The control unit 130 calculates the depth of charge Z B However, the differential resistance profile is 1200 and the differential resistance value dR CT The boundary point where / dSOC switches from a positive number to a negative number due to an increase in SOC, i.e., the differential resistance value dR CT Feature point P where / dSOC is 0 B The depth of charge Z determined from the differential resistance profile 1200 of FIG. Bcan be determined to be equal to the SOC at the boundary point between the increasing and decreasing patterns of the internal resistance in the resistance profile 1000 of Fig. 10. For reference, the decreasing pattern of a certain profile (or curve) may mean that the first derivative value of the profile is a negative number.

[0106] Next, we will explain the operation of identifying the depth of charge from the resistance profile 1100 shown in Figure 11, which is obtained by curve fitting the time series data set of Figure 7. By examining Figure 11, it is possible to determine the SOC range of interest, ΔSOC int3 9 and the resistance profile 1000 of FIG. 10 in that the internal resistance continuously decreases without any increasing sections. When the internal resistance only exhibits a decreasing pattern within the range of the SOC of interest as shown in FIG. 11, the control unit 130 can obtain a differential resistance profile 1300 as shown in FIG. 13 by second-order differentiating the resistance profile 1100 with respect to the SOC. For reference, the differential resistance profile 1300 is distinguished from the differential resistance profile 1200, which is the result of first-order differentiation of the resistance profile 1000, in that the differential resistance profile 1300 is the result of second-order differentiation of the resistance profile 1100.

[0107] The control unit 130 determines the charging depth Z C However, the differential resistance profile is 1300 and the second differential resistance value d 2 R CT / dSOC 2 The point where the value of the second differential resistance d 2 R CT / dSOC 2 Feature point P where C It can be determined that the SOC 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 greatest.

[0108] The charging depth Z shown in Figs. 9 to 13 A , Z B , Z Crepresent the SOC at which the battery cell BC can be charged without lithium deposition during constant current charging at the current rate (e.g., 2C) associated with each of them. For example, if charging continues under the same charging conditions even after the SOC of the battery cell BC reaches the charge depth, lithium deposition may occur on the surface of the negative electrode of the battery cell BC.

[0109] The control unit 130 can record the charge depth determined for a specific charging condition in the memory 140. When charging of the battery cell BC starts under the same charging condition in the future (for example, the current rate and the battery temperature are 0.5C and 25°C, respectively), the control unit 130 can record the charge depth (for example, Z A ) from the memory 140, and the SOC of the battery cell BC is obtained based on the charge depth (for example, Z A ) is allowed to be charged. That is, when the SOC of the battery cell BC reaches the acquired charging depth, the control unit 130 can control the relay 20 to an off state or send a charging stop request to the charger 3.

[0110] 2a, 2b, and 8 can be performed each time a charging event occurs for the battery 11, or can be performed when a predetermined diagnosis-requiring event occurs, such as when the SOH (State Of Health) of the battery 11 drops by a predetermined value or more from the previous SOH.

[0111] 14 to 16 are reference diagrams for explaining the relationship between lithium deposition during battery charging and impedance.

[0112] First, Fig. 14 is a schematic diagram illustrating the formation of lithium metal deposits on the negative electrode of a battery cell BC. Referring to Fig. 14, during charging according to any charging conditions, lithium ions may be deposited as lithium metal on the surface of the negative electrode of the battery cell BC. When lithium metal deposits are formed, lithium intercalation and lithium deposition may occur simultaneously on the surface of the negative electrode of the battery cell BC, which may result in a wider path for the charging current than when there are no lithium metal deposits.

[0113] FIG. 15 is a graph used to exemplarily illustrate the change in impedance of battery cell BC depending on whether or not lithium deposition is present in the battery cell BC. Each of the two complex impedance curves 1510 and 1520 shown in FIG. 15 is obtained by repeatedly measuring the impedance of each battery cell when applying an AC signal using the EIS device 4 to a battery cell without lithium deposition and a battery cell with lithium deposition under the same environmental conditions. For example, FIG. 15 may be a Nyquist plot showing the change in impedance of the battery cell depending on the frequency of the AC signal. The process of obtaining the complex impedance curve of battery cell BC is performed once before the intermittent charging process for battery cell BC is initiated. Because the AC signal applied by the EIS device 4 to the battery cell is applied for only a short time, there is little damage to the battery cell.

[0114] In one embodiment, the complex impedance curve 1510 may be obtained for the battery cell before lithium deposition occurs, and the complex impedance curve 1520 may be obtained for the battery cell after lithium deposition occurs.

[0115] R S represents the electrolyte resistance of the battery cell and is hardly affected by the presence or absence of lithium deposition. R p_i and R p_fR represents the interfacial resistance of the battery cell when lithium deposition does not occur and when lithium deposition occurs, respectively. A and R B represent the internal resistance of the battery cell when lithium deposition does not occur and when lithium deposition occurs, respectively, and R A =R S +R p_i and R B =R S +R p_f is.

[0116] The interfacial resistance is the total resistance due to the SEI (Solid Electrolyte Interphase), charge transfer, and double layer, and is greatly affected by the accumulation of charges on the positive and negative electrode surfaces of a battery cell.

[0117] As described above with reference to Figure 14, the resistance of the lithium metal deposit on the negative electrode surface is combined in parallel with the resistance at the negative electrode surface, and as a result, the occurrence of lithium metal deposits can reduce the total resistance at the negative electrode surface of the battery cell. Therefore, as can be seen in Figure 15, R p_f is R p_i and the resistance difference between them (ΔR p ) is positively correlated with the amount of lithium metal precipitates.

[0118] Meanwhile, the control unit 130 can determine the reference frequency from the complex impedance curve 1510. For example, the complex impedance curve 1510 is divided into a convex section and a slope section. Here, the convex section is a section where the interface resistance R p_i The inclined section is a section with a straight line shape continuing to the right of the convex section, and is a section related to the diffusion resistance R of the battery cell. diff The boundary point between such a convex section and a slope section (R A The frequency of the AC signal applied at the reference frequency can be determined as the reference frequency.

[0119] The inventors of the present invention recognized that the SOC of the battery cell BC gradually increases during the intermittent charging process, and that the frequency at the boundary between the convex section and the inclined section gradually increases as the SOC increases. If the reference frequency is determined to correspond to the charging progress conditions at the start of the intermittent charging process, the rest period given during the intermittent charging process can continue for an appropriate time required to observe the voltage change due to the internal resistance of the battery cell BC. Therefore, it is possible to prevent a decrease in the accuracy of the internal resistance due to the rest period being set too short or long.

[0120] The control unit 130 can determine a second reference time representing the duration of the sleep mode based on the reference frequency. The reference frequency and the second reference time may have a predetermined negative correspondence relationship. The second reference time can be determined using relationship data expressed by the following Equation 2. <Formula 2>

[0121]

number

[0122] In the above formula 2, f i-d is the reference frequency, w is a predetermined margin constant (which can be greater than or equal to 1), Δt R2 represents the second reference time. Therefore, the second reference time is the reference frequency f i-d The second reference time may be determined to be equal to or greater than the reciprocal of the margin constant w multiplied by the margin constant w. The second reference time may be the duration of each rest period required to observe a voltage change due to the internal resistance of the battery cell BC.

[0123] A reference frequency for each charging progress condition and lower limit SOC may be pre-recorded in the memory 140. The control unit 130 may acquire, from the memory 140, the reference frequency associated with the charging progress condition of the intermittent charging process performed on the battery cell BC and the lower limit SOC of the SOC range of interest, and determine the second reference time.

[0124] The memory 140 may store 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 relationship data among the SOC, the battery temperature, and the second reference time.

[0125] FIG. 16 is a graph referred to for explaining the relationship between the battery temperature and the reference frequency when the SOC of the battery cell BC is set to a specific value (for example, a lower limit SOC of 10%).

[0126] 16, when other elements of the charging condition (e.g., current rate, upper limit SOC) are the same, the higher the battery temperature of the charging condition, the higher the reference frequency associated with the battery temperature. In other words, there may be a positive correlation between the battery temperature and the reference frequency.

[0127] Referring to the above-mentioned equation 2, since the reference frequency and the second reference time are inversely proportional, the higher the battery temperature of the battery cell BC at the time when the control of the intermittent charging process is started, the shorter the duration of the sleep mode (i.e., the second reference time) can be set.

[0128] 1, the charge control device 100 is illustrated as being included as a subordinate component of the battery system 1, but is not limited thereto. For example, the charge control device 100 may be used as a subordinate component of a charge performance test device for deriving a charge depth according to a charging progress condition of the battery cell BC. In this case, the charge performance test device may include the charge control device 100 and the charger 3.

[0129] 17 and 18 are diagrams showing examples of the structure of a test jig for a battery charging test.

[0130] 17 and 18, the test jig 1700 includes a first plate 1711, a second plate 1712, and a coupling member 1730. The coupling member 1730 includes at least one bolt 1731 and a nut 1732. The charge control device 100 used as a charging test device can perform the above-mentioned intermittent charging process to derive a fast charging protocol for the battery cell BC coupled to the test jig 1700. In this case, another charger 3 having a function corresponding to the charger 3 can be separately provided for supplying a charging current.

[0131] The first plate 1711 and the second plate 1712 are disposed on both sides (e.g., the top and bottom) of the battery cell BC. At least one coupling hole is 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 the first plate 1711 and the second plate 1712, respectively, and nuts 1732 are rotatably coupled to the ends of the threads of the bolts 1731. FIG. 17 illustrates an example in which six bolts and six nuts are coupled in a one-to-one relationship. This allows the battery cell BC to be firmly fixed between the first plate 1711 and the second plate 1712.

[0132] The test jig 1700 may further include at least one foam pad 1751, 1752. The foam pads 1751, 1752 may be used for thermal insulation to prevent heat generated in the battery cell BC from being released to the outside during charging. For example, with the foam pad 1751 inserted between the first plate 1711 and the battery cell BC and the foam pad 1752 inserted between the second plate 1712 and the battery cell BC, the first plate 1711 and the second plate 1712 are pressed from both sides by the coupling member 1730 to complete the fastening of the test jig 1700 to the battery cell BC. Of course, only one of the two foam pads 1751, 1752 may be inserted between the first plate 1711 or the second plate 1712 and the battery cell BC, or neither of the two foam pads 1751, 1752 may be inserted. When only one of the two foam pads 1751, 1752 is inserted, heat is released from the battery cell BC to the outside more smoothly than when both of the two foam pads 1751, 1752 are inserted. Furthermore, when neither of the two foam pads 1751, 1752 is inserted, heat is released from the battery cell BC to the outside more efficiently than when only one of the two foam pads 1751, 1752 is inserted. In other words, by varying the insertion conditions of the two foam pads 1751, 1752 to diversify the heat generation environment during charging of the battery cell BC, it is possible to derive a depth of charge that corresponds to the heat generation environment.

[0133] 19 and 20 are reference diagrams for explaining the results of a charging test using the test jig shown in FIGS. 17 and 18. FIG.

[0134] 19, three temperature curves 1911, 1912, and 1913 are graphs showing changes in the surface temperature of test jig 1700 with respect to SOC when battery cell BC is fastened to test jig 1700 without foam pads 1751 and 1752 and charged from 0% to 100% SOC at three current rates of 2.25C, 2.5C, and 2.75C. The surface temperature of test jig 1700 can be measured using a temperature sensor inserted into test jig 1700 or placed within a predetermined distance from test jig 1700.

[0135] The remaining three temperature curves 1921, 1922, and 1923 are graphs showing the change in cell temperature versus SOC when the battery cell BC is fastened to the test jig 1700 with both foam pads 1751 and 1752 inserted and charged from 0% to 100% SOC at three current rates of 2.25C, 2.5C, and 2.75C.

[0136] Comparing the temperature curves 1911, 1912, and 1913 with the temperature curves 1921, 1922, and 1923, it can be seen that there is a difference in the heat generation environment during charging of the battery cell BC depending on whether or not foam pads 1751 and 1752 are inserted, resulting in a temperature difference of approximately 5°C in the later stages of charging.

[0137] Next, referring to FIG. 20, each of the two SOC curves 2010 and 2020 is a graph showing the change in the depth of charge obtained by a charging test using multiple current rates selected from the range of 0.5C to 2.75C once each with the battery cell BC fastened to the test jig 1700.

[0138] The SOC curve 2010 shows the change in depth of charge as a function of current rate when the battery cell BC is fastened to the test fixture 1700 without any of the foam pads 1751, 1752 inserted.

[0139] SOC curve 2020 shows the change in depth of charge as a function of current rate when battery cell BC is fastened to test fixture 1700 with both foam pads 1751, 1752 inserted.

[0140] 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 jig 1700 is insulated by the two foam pads 1751 and 1752, so that the battery cell BC is charged at a higher temperature than when the foam pads 1751 and 1752 are not inserted. Due to the insulating effect of the foam pads 1751 and 1752 inserted, it was confirmed that the rise in surface temperature of the test jig 1700 was about 5°C lower than when the foam pads 1751 and 1752 were not inserted, while the depth of charge was higher.

[0141] On the other hand, when neither of the foam pads 1751 nor 1752 is inserted, the heat generated during charging of the battery cell BC is thermally conducted to the first plate 1711 and the second plate 1712 and quickly released to the outside, and it is observed that the surface temperature of the test jig 1700 is relatively higher than when the foam pads 1751 and 1752 are inserted. As a result, the temperature rise due to the heat generated by the battery cell BC is eliminated and the depth of charge is reduced compared to when the foam pads 1751 and 1752 are inserted.

[0142] FIG. 21 is a flowchart illustrating a method for measuring the state of charge of a battery cell of the present invention.

[0143] In step S2010, a voltage sensor is connected to the battery cell. Referring to Fig. 1, in order to measure the state of charge of the battery cell BC, the voltage sensor 111 is first connected in parallel to the battery cell BC. Then, in step S2020, the charge control device 100 performs an intermittent charging process on the battery cell BC under preset conditions, such as a preset current rate and temperature.

[0144] In step S2030, the internal resistance of the battery is measured based on the amount of change in the battery voltage during the sleep mode of the intermittent charging process, and in step S2040, the measured internal resistance is recorded in association with the SOC of the battery, and a graph of the internal resistance versus the SOC is derived. For example, the control unit 130 can associate the measured internal resistance with the SOC of the battery to derive the graphs of Figures 5 to 7 described above. Alternatively, based on the graph derived in S2040, curve fitting and differentiation of the internal resistance with respect to the SOC can be performed to derive a differentiated graph.

[0145] In step S2050, the pattern of internal resistance due to changes in SOC is recognized based on the derived graph. For example, in the case of the intermittent charging process performed under the conditions of Figure 5, the pattern shows that the internal resistance decreases in the range of SOC from about 50% to 65%, and then increases from 65%.

[0146] In step S2060, the state of charge is determined based on the recognized internal resistance pattern. For example, if the pattern shown in Fig. 5 is recognized, the state of charge can be determined to be the same value as the SOC limit (the upper limit of the SOC range of interest), for example, about 95%.

[0147] The above-described embodiments of the present invention can be realized not only by an apparatus and a method, but also by a program that realizes functions corresponding to the configuration of the embodiments of the present invention, or a recording medium on which the program is recorded. Such realization can be easily carried out by an expert in the technical field to which the present invention pertains based on the description of the above-described embodiments.

[0148] Although the present invention has been described above using limited embodiments and drawings, it goes without saying that the present invention is not limited thereto, and various modifications and variations can be made by a person having ordinary knowledge in the technical field to which the present invention pertains within the technical spirit of the present invention and the equivalent scope of the claims.

[0149] Furthermore, the present invention described above is not limited to the above-described embodiments and accompanying drawings, and various substitutions, modifications, and alterations can be made by a person having ordinary knowledge in the technical field to which the present invention pertains, without departing from the technical spirit of the present invention. Instead, the present invention can be configured by selectively combining all or part of each embodiment to allow for various modifications. [Explanation of symbols]

[0150] 1 Battery System 2 System Controller 3 charger 4 EIS device 10 Battery Pack 11 Battery 12 Cell Groups 13 cases 20 Relay 30 inverters 40 Electric Motor 100 Charging control device 111 Voltage Sensor 113 Current Sensor 115 Temperature Sensor 117 Outside air temperature sensor 130 Control Unit 140 memory 150 Communication Circuit 1700 Test Jig 1711 Plate 1 1712 Second Plate 1730 Connecting members 1731 Volts 1732 Nut 1751 Foam Pad 1752 Foam Pad BC Battery Cell

Claims

1. a voltage sensor that detects the voltage of the battery cell; a control unit configured to perform an intermittent charging process that alternates between a charging mode and a resting mode for the battery cells; Including, The control unit, on the condition that the charging mode is switched to the sleep mode during the execution of the intermittent charging process, determining an internal resistance of the battery cell based on a voltage change amount of the battery cell during a rest period in which the rest mode continues; Recording the internal resistance in relation to a SOC of the battery cell; The charging control device is configured to perform the following.

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

3. The control unit 2. The charge control device according to claim 1, wherein the intermittent charging process is controlled so as to switch from the charging mode to the sleep mode when a duration of the charging mode reaches a first reference time or when an increase in SOC of the battery cell due to the charging mode reaches a reference increase.

4. The control unit The charge control device according to claim 1 , further comprising: controlling the intermittent charging process such that the sleep mode is switched to the charging mode when the duration of the sleep mode reaches a second reference time.

5. The control unit determining a reference frequency from a complex impedance curve of the battery cell previously acquired using an EIS device; The charge control device according to claim 4 , wherein the charge control device is configured to determine the second reference time based on the reference frequency.

6. The control unit The charge control device according to claim 5 , wherein the second reference time is determined so as to have a predetermined negative correspondence relationship with the reference frequency.

7. The control unit 7. The charge control device according to claim 1, configured to determine a depth of charge of the battery cell by analyzing a resistance time series data set indicating a history of changes in the internal resistance over a charge control period from a start point to an end point of the intermittent charging process.

8. The control unit curve fitting the resistance time series data set to generate a resistance profile indicating the relationship between SOC and internal resistance of the battery cell; The charge control device according to claim 7 , configured to determine the depth of charge based on a pattern of the resistance profile.

9. The control unit The charge control device according to claim 8 , configured to determine that the state of charge is equal to a predetermined end-of-charge SOC when only a pattern of a sustained increase in the internal resistance is identified in the resistance profile.

10. The control unit 9. The charge control device according to claim 8, wherein when a switch from an increasing pattern to a decreasing pattern of the internal resistance is identified in the resistance profile, the charge depth is determined based on a boundary SOC between the increasing pattern and the decreasing pattern.

11. The control unit 9. The charge control device according to claim 8, wherein when only a sustained decrease pattern of the internal resistance is identified in the resistance profile, the charge depth is determined based on an SOC at which a second derivative value 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 charge control device according to claim 1.

14. performing an intermittent charging process that alternates between a charging mode and a resting mode on the battery cells; The intermittent charging process may be switched from the charging mode to the sleep mode during the intermittent charging process. determining an internal resistance of the battery cell based on a voltage change amount of the battery cell during a rest period in which the rest mode continues; Recording the internal resistance in relation to the SOC of the battery cell; The charging control method further includes:

15. 15. The charge control method of claim 14, further comprising: analyzing a resistance time series data set indicating a history of changes in the internal resistance over a charge control period from a start time to an end time of the intermittent charging process to determine a depth of charge of the battery cell.

16. connecting a voltage sensor to a battery cell; performing an intermittent charging process in which the battery cells are alternately charged and rested; measuring an internal resistance of the battery cell in the rest mode; Recording the measured internal resistance in relation to the SOC of the battery cell; recognizing a pattern of the internal resistance based on the recorded internal resistance and SOC related data, and determining a state of charge of the battery cell based thereon.

17. The method of claim 16, further comprising the steps of: performing curve fitting and differentiating the internal resistance with respect to the SOC after the step of recording the internal resistance in association with the SOC of the battery cell.

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