Rebound voltage control device and control method

Abstract

The present invention relates to a rebound voltage control device and a control method, and more specifically, to a rebound voltage control device and a control method that can prevent secondary safety accidents such as heat generation, ignition, and explosion during the dismantling and crushing process by controlling the rebound voltage that occurs after the completion of discharge, and at the same time minimize damage to the positive electrode active material. According to the present invention, by stably controlling the voltage rebound that occurs after the discharge of a waste battery is completed, secondary safety accidents such as localized heating, ignition, and explosion during the dismantling and crushing process can be effectively prevented. In addition, by calculating the value of the external resistor according to the series and parallel structure and number of battery cells, precision in current control is ensured, and it can be widely applied to various types of battery cells, modules, and packs.

Description

Technology Field

[0001] The present invention relates to a rebound voltage control device and a control method, and more specifically, to a rebound voltage control device and a control method that can prevent secondary safety accidents such as heat generation, ignition, and explosion during the dismantling and crushing process by controlling the rebound voltage that occurs after the completion of discharge, and at the same time minimize damage to the positive electrode active material. Background Technology

[0002] As the adoption of electric vehicles in Korea increases rapidly, it is expected that more than 100,000 used batteries will be generated by 2030, and these discharged electric vehicle batteries are classified as subjects for reuse or recycling through performance evaluation before removal.

[0003] At this time, batteries classified as reusable are utilized in low-speed vehicles such as energy storage systems (ESS) or electric forklifts.

[0004] On the other hand, batteries classified for recycling are processed through discharge, disassembly, sorting, and refining to extract valuable metals such as cobalt, nickel, and lithium.

[0005] At this stage, a complete discharge is performed, which is a battery residual voltage control process that is essential before the metal recovery stage. The discharge process is broadly divided into wet discharge and dry discharge.

[0006] The above wet discharge method consumes residual electricity by immersing the battery in a brine solution to induce a short circuit between the electrodes. While it has the characteristics of a simple process and the ability to completely discharge electrical energy, it has an environmental limitation in that secondary wastewater treatment is required.

[0007] In contrast, dry discharge reduces the battery voltage using a power converter and has the advantage of allowing precise control of the discharge rate and termination voltage; however, voltage rebound may occur even after discharge is complete, which is attributed to the redistribution of residual energy within the cell.

[0008] Such a resurgence of voltage can cause secondary safety accidents, such as localized heating and explosions, during the dismantling and crushing process after the discharge is judged to be complete, making it difficult to ensure the safety of workers and the work site.

[0009] In addition, a secondary discharge method using a resistor after discharge has been used to control voltage rebound, but this can lead to heat generation and electrode damage, resulting in a decrease in metal recovery rate and a decrease in the quality of the recovered metal.

[0010] Therefore, there is a need for voltage rebound control technology that can increase metal recovery efficiency without electrode damage while ensuring safety during the discharge, dismantling, and crushing stages of waste batteries.

[0011] Therefore, the present invention aims to provide a control method and apparatus for solving the above-mentioned problems. Prior art literature

[0012] (Prior Art 1) Korean Published Patent No. 10-2025-0013023 The problem to be solved

[0013] Therefore, the present invention has been devised to resolve the aforementioned conventional problems,

[0014] The objective of the present invention is to provide a method for controlling the rebound voltage that occurs when disconnecting a waste battery after discharge within a safe range.

[0015] To this end, the present invention aims to provide a waste battery voltage control method capable of stably controlling rebound voltage without heat generation by calculating and connecting the resistance value of an external resistor suitable for the number of battery cells and the series / parallel structure.

[0016] Another objective of the present invention is to provide a method that ensures the safety of workers and the working environment by preventing localized heating, explosions, and ignition that may occur due to rebound voltage during the dismantling and crushing process after discharge, while simultaneously minimizing damage to the anode material.

[0017] Furthermore, the objectives of the present invention are not limited to those mentioned above, and other unmentioned objectives will be clearly understood from the description below. means of solving the problem

[0018] To achieve the above objective, the method for controlling the rebound voltage after discharge of a waste battery according to the present invention is,

[0019] A discharged waste battery preparation step (S100) for preparing a discharged waste battery;

[0020] A rebound voltage / temperature measurement step (S200) for measuring the rebound voltage and temperature of the discharged waste battery;

[0021] An external resistor resistance value calculation step (S300) for calculating the resistance value of an external resistor based on the above-mentioned measured voltage and a series-parallel structure including the number of series cells (Sn) and the number of parallel cells (Pn) of the waste battery cells;

[0022] A rebound voltage control step (S400) in which the above-calculated external resistor is connected to the waste battery, and the discharge current of the waste battery is controlled by controlling the ON / OFF of the circuit breaker to control the rebound voltage;

[0023] It includes a waste battery dismantling step (S500) for dismantling the waste battery in which the rebound voltage is controlled.

[0024] Meanwhile, the rebound voltage control device for controlling the rebound voltage after discharge of a waste battery according to the present invention is,

[0025] An external resistor (100) connected to a discharged waste battery (10);

[0026] A circuit breaker (200) that controls the connection between the above external resistor and the waste battery;

[0027] Voltage sensor (300) for measuring the voltage of the waste battery;

[0028] A temperature sensor (400) for measuring the temperature of the waste battery; and

[0029] It includes a control unit (500) that receives measurement values ​​from the voltage sensor and temperature sensor, calculates the resistance value of an external resistor based on the number of series cells (Sn) and parallel cells (Pn) of the waste battery, and controls the ON / OFF of the circuit breaker. Effects of the invention

[0030] The rebound voltage control device and control method of the present invention provide the following remarkable effects.

[0031] First, by stably controlling the voltage rebound that occurs after the discharge of the waste battery is complete, secondary safety accidents such as localized heating, ignition, and explosion during the dismantling and crushing process can be effectively prevented.

[0032] Second, by calculating the value of the external resistor according to the series and parallel structure and number of battery cells, the precision of current control is ensured, and it can be widely applied to various types of battery cells, modules, and packs.

[0033] Third, the voltage control method according to the present invention provides the effect of not requiring excessive power consumption or additional large-scale charging and discharging equipment when performing voltage control on a number of waste batteries.

[0034] In other words, since voltage rebound can be controlled with a simple procedure of connecting the waste battery, which is separated from the device after discharge is completed using the charging and discharging device, to an external resistor, the process configuration is simplified and operating costs can be significantly reduced.

[0035] Fourth, by applying an external resistor with excellent heat resistance, the present invention minimizes safety issues caused by heat that may occur during voltage control and ensures stability even under long-term current control and storage conditions.

[0036] Fifth, by suppressing heat generation during the rebound voltage control process, damage to the electrodes (anode material and current collector) can be minimized, and as a result, the recovery rate and quality of the recovered metal in the metal recovery process can be improved.

[0037] Therefore, the present invention can be economically and practically applied to a recycling process for processing a large number of waste batteries, and has the effect of significantly improving safety and recycling efficiency. Brief explanation of the drawing

[0038] FIG. 1a is a flowchart illustrating a method for controlling the rebound voltage after discharge of a waste battery according to an embodiment of the present invention. Figure 1b is a schematic diagram showing the voltage range in which the rebound voltage after discharge can be controlled by an external resistor. Figure 2a is a graph showing the change in discharge voltage of each cell of the module to which the voltage control method of Figure 1 is applied. Figure 2b is a graph showing the change in discharge voltage of each cell of the pack to which the voltage control method of Figure 1 is applied. Figure 3a is a graph showing the changes over time of the total voltage, each cell temperature, and the temperature of the connected resistor of a module to which the voltage control method of Figure 1 is applied. Figure 3b is a graph showing the changes over time of the total voltage of the pack, the temperature of each module, and the temperature of the connected resistor to which the voltage control method of Figure 1 is applied. Figure 4 is an image showing the temperature change before and after module crushing. Figure 5 is a graph showing the voltage recovery (rebound) characteristics of the module and pack units. Figure 6 is a graph showing the recovery process of the rebound voltage and the temperature change of each cell after the discharge is completed. Figure 7 is a graph illustrating an example of rebound voltage control after discharge for different battery configurations (3P10S, 3P9S, 2P6S, 3P4S). Figure 8 is a graph showing the experimental results of controlling the rebound voltage by connecting a 330 Ω external resistor to a battery pack. FIG. 9 is a conceptual diagram showing a rebound voltage control device for controlling the rebound voltage after discharge of a waste battery according to an embodiment of the present invention. Specific details for implementing the invention

[0039] The following description merely illustrates the principles of the present invention. Therefore, those skilled in the art may invent various devices that embody the principles of the present invention and are included within the concept and scope of the present invention, even though they are not explicitly described or illustrated in this specification.

[0040] Furthermore, all conditional terms and embodiments listed in this specification are, in principle, explicitly intended only for the purpose of enabling an understanding of the concept of the invention and should be understood not as being limited to the embodiments and conditions specifically listed as such.

[0041] A method for controlling the rebound voltage after discharge of a waste battery according to one embodiment of the present invention is,

[0042] A discharged waste battery preparation step (S100) for preparing a discharged waste battery;

[0043] A rebound voltage / temperature measurement step (S200) for measuring the rebound voltage and temperature of the discharged waste battery;

[0044] An external resistor resistance value calculation step (S300) for calculating the resistance value of an external resistor based on the above-mentioned measured voltage and a series-parallel structure including the number of series cells (Sn) and the number of parallel cells (Pn) of the waste battery cells;

[0045] A rebound voltage control step (S400) in which the above-calculated external resistor is connected to the waste battery, and the discharge current of the waste battery is controlled by controlling the ON / OFF of the circuit breaker to control the rebound voltage;

[0046] It is characterized by including a waste battery dismantling step (S500) for dismantling the waste battery in which the rebound voltage is controlled.

[0047] At this time, the discharge in the discharge waste battery preparation step (S100) is,

[0048] It is characterized by being performed at a C-rate of 0.1 C to 0.3 C and discharging to 0.1V to 0.5V per cell.

[0049] At this time, the voltage measurement in the rebound voltage / temperature measurement step (S200) is performed within a range of 0.1V to 2V based on the cell, and after discharge, when the temperature of the waste battery is less than 60℃, the process proceeds to the external resistor resistance value calculation step (S300).

[0050] At this time, the method is characterized by the fact that, after the discharge is completed in the rebound voltage / temperature measurement step (S200), if the temperature of the waste battery is 60℃ or higher, the method proceeds to the next step if the temperature stabilizes below 60℃ after waiting 6 hours in a natural cooling state, and if the temperature does not drop below 60℃ even after 6 hours, the waste battery is excluded from the application of the control method.

[0051] At this time, the above external resistor is,

[0052] It is characterized by being a cement resistor or a metalclad resistor.

[0053] At this time, in the step of calculating the resistance value of the external resistor (S300), the resistance value (R) of the external resistor satisfies the following equation.

[0054] R = (Sn / Pn)ㆍR1cell

[0055] Here, Sn is the number of series cells, Pn is the number of parallel cells, and R1cell is the single-cell reference resistance value.

[0056] At this time, the single cell reference resistance value is,

[0057] It is characterized by being set to approximately 10 Ω.

[0058] At this time, the allowable power of the external resistor is characterized by being set with a 10% margin of power calculated by the following formula.

[0059] P = I·Vmax = I·(2V·Sn)

[0060] Here, I is the current of the module or pack, Vmax is the maximum voltage, and Sn is the number of series cells.

[0061] At this time, in the rebound voltage control step (S400), the wire connected to the calculated external resistor and circuit breaker is,

[0062] It is characterized by having a conductor cross-sectional area with a margin of 120 to 130% corresponding to the magnitude of the calculated total current.

[0063] At this time, in the rebound voltage control step (S400),

[0064] In the case of a single cell, turn on the circuit breaker when the cell voltage is 2.0V or lower, and

[0065] In the case of a module or pack, it is characterized by turning on the circuit breaker when the total voltage is Sn × 2.0V or less.

[0066] At this time, in the rebound voltage control step (S400),

[0067] It is characterized by generating a warning when the minimum voltage per cell reaches 0.1V, turning off the circuit breaker to terminate control when the minimum voltage per cell reaches 0V, and continuing voltage control for the remaining cells excluding the cell when a reverse voltage of -0.1V or higher occurs.

[0068] At this time, in the rebound voltage control step (S400),

[0069] The rebound voltage control time is characterized by being set to 12 hours for a single cell, 14 hours for a module of 12 V or less, 16 hours for a module of 40 V or less, and 20 to 24 hours for a pack of 196 V or less, depending on the battery configuration.

[0070] At this time, in the rebound voltage control step (S400),

[0071] The voltage control is terminated by turning off the circuit breaker when the change in each cell voltage becomes 0.05V / cell or less for 2 hours, assuming the voltage has stabilized.

[0072] In this case, if the above waste battery is in pack units,

[0073] The method is characterized by selecting and removing modules in which the temperature rise has intensified during the discharge process in the rebound voltage / temperature measurement step (S200), and then performing voltage control using an external resistor on an individual module basis for the remaining modules.

[0074] At this time, the waste battery dismantling step (S500) is,

[0075] The waste battery, having completed voltage control, is dismantled and crushed to recover the cathode material, and is characterized by the extraction of valuable metals including lithium, nickel, cobalt, and manganese from the recovered cathode material, and the absence of impurities (e.g., copper, etc.).

[0076] At this time, in the waste battery dismantling step (S500),

[0077] It is characterized by maintaining the surface temperature of the waste battery at 60℃ or lower so that localized heating, ignition, or explosion does not occur.

[0078] Meanwhile, a rebound voltage control device for controlling the rebound voltage after discharge of a waste battery according to an embodiment of the present invention is,

[0079] An external resistor (100) connected to a discharged waste battery (10);

[0080] A circuit breaker (200) that controls the connection between the above external resistor and the waste battery;

[0081] Voltage sensor (300) for measuring the voltage of the waste battery;

[0082] A temperature sensor (400) for measuring the temperature of the waste battery; and

[0083] It is characterized by including a control unit (500) that receives measurement values ​​from the voltage sensor and temperature sensor, calculates the resistance value of an external resistor based on the number of series cells (Sn) and parallel cells (Pn) of the waste battery, and controls the ON / OFF of the circuit breaker.

[0084] At this time, the voltage sensor (300) is,

[0085] It is characterized by a measurement range of -1V to 200V, an accuracy of ±0.05% or ±0.01V whichever is greater, and a response speed of within 1 second.

[0086] At this time, the temperature sensor (400) is,

[0087] It is a K-type thermocouple, characterized by a measurement range of -40℃ to 150℃, an accuracy of ±1℃, and a response speed of within 5 seconds.

[0088] At this time, the control unit (500) is,

[0089] For a single cell, R1Cell = 10 Ω is used as the standard, and for a module or pack, the resistance value of an external resistor is calculated using the formula R = (Sn / Pn)ㆍR1cell, and the allowable power is set by leaving a 10% margin on the calculated power.

[0090] At this time, the rebound voltage control device for controlling the rebound voltage after discharge of the waste battery according to an additional aspect is,

[0091] LED indicator (600) that displays real-time voltage status and abnormal conditions;

[0092] It is further characterized by including an alarm unit (700) that provides a notification when reverse voltage occurs and when minimum voltage is reached.

[0093] Hereinafter, the rebound voltage control device and control method according to the present invention will be described in detail through embodiments.

[0094] FIG. 1a is a flowchart illustrating a method for controlling the rebound voltage after discharge of a waste battery according to an embodiment of the present invention.

[0095] As illustrated in FIG. 1a, the method for controlling the rebound voltage after discharge of a waste battery according to the present invention is,

[0096] A discharged waste battery preparation step (S100) for preparing a discharged waste battery;

[0097] A rebound voltage / temperature measurement step (S200) for measuring the rebound voltage and temperature of the discharged waste battery;

[0098] An external resistor resistance value calculation step (S300) for calculating the resistance value of an external resistor based on the above-mentioned measured voltage and a series-parallel structure including the number of series cells (Sn) and the number of parallel cells (Pn) of the waste battery cells;

[0099] A rebound voltage control step (S400) in which the above-calculated external resistor is connected to the waste battery, and the discharge current of the waste battery is controlled by controlling the ON / OFF of the circuit breaker to control the rebound voltage;

[0100] It is characterized by including a waste battery dismantling step (S500) for dismantling the waste battery in which the rebound voltage is controlled.

[0101] To explain in detail, the discharge waste battery preparation step (S100) is a basic step for applying the voltage control method of the present invention, and is a step of preparing the waste battery to an appropriate discharge state.

[0102] Preferably, the recovered waste battery is connected to a charging and discharging device to perform discharge at a constant current level, wherein the discharge current is set to a C-rate of 0.1C to 0.3C relative to the battery capacity so that the voltage per cell decreases to 0.1V to 0.5V.

[0103] For example, in the case of a single cell with a capacity of 60Ah, it is discharged with a current of 6A to 18A to control the cell voltage to reach a range of 0.1V to 0.5V.

[0104] At this time, the discharge process can be performed in two stages. In the first discharge stage, the SOC is discharged to 0% (approx. 2.8V) with a current of approximately 0.3C of the rated capacity. In the second discharge stage, the cell voltage is lowered to the range of 0.1V to 0.5V with a current of 0.1C, and then maintained in constant voltage (CV) mode for approximately 4 hours.

[0105] This two-stage discharge method can contribute to minimizing voltage rebound after discharge is complete by consuming the charge inside the battery more uniformly.

[0106] In addition, for module or pack units, the discharge current is determined by converting the C-rate calculated based on a single cell to the total capacity.

[0107] For example, in the case of a module with a 3 parallel 10 series (3P10S) structure (total 180Ah), "I = C-Rate x battery capacity is calculated, where I = 1 / 10 x 180Ah = 18A" and the total voltage is controlled to reach the range of 1V to 5V (0.1V to 0.5V per cell × 10 series).

[0108] In addition, in the case of a pack unit, discharge is performed by connecting to a charging / discharging device through an HV (High Voltage) connector, and after discharge is completed, the OCV (Open Circuit Voltage) is measured to check the condition of each cell. If, during this process, the temperature of a specific module rises abnormally or the voltage deviation is significantly large, the module in question is selected, removed from the pack, and managed separately, thereby ensuring safety.

[0109] In addition, the rebound voltage / temperature measurement step (S200) is a process for measuring the rebound voltage and temperature of the discharged waste battery, and is a step for determining whether to proceed to the next step by monitoring the degree of voltage recovery (rebound) and temperature of the discharged waste battery in real time.

[0110] In other words, immediately after discharge is complete, a rebound phenomenon occurs in which the voltage rises again due to the redistribution of residual charge within the battery cell; accurately measuring this rebound voltage is the core of this invention.

[0111] Specifically, after discharge is complete, the open-circuit voltage (OCV) of the cell is measured at 1-minute intervals for about 3 hours to observe the trend of voltage change. For a single cell, the voltage measurement range is 0.1V to 2V based on the cell, and for a module or pack, the measurement is performed within a voltage range multiplied by the number of series cells (Sn) (for example, 1V to 20V for a 10S module).

[0112] At this time, the voltage sensor can be configured with specifications that have a measurement range of -1V to 200V, an accuracy of ±0.01V, and a response speed of within 1 second to ensure precise voltage measurement.

[0113] In this case, temperature measurement serves as an important indicator for verifying battery safety; therefore, a thermocouple K-type temperature sensor is attached to the center of the battery cell or module to monitor the surface temperature in real time.

[0114] Preferably, the measurement range of the temperature sensor is -40℃ to 150℃, the accuracy is ±1℃, and the response speed is set to within 5 seconds to enable rapid detection of temperature changes.

[0115] In addition, after discharge is complete, when the temperature of the waste battery is less than 60℃, the process proceeds to the external resistor resistance value calculation step (S300), and if the temperature is 60℃ or higher, it waits for about 6 hours in a natural cooling state without a separate forced cooling or repeated cooling procedure.

[0116] At this time, if the temperature stabilizes below 60℃ after 6 hours, the process proceeds to the next step. However, if the temperature does not drop below 60℃ even after 6 hours, the battery is determined to have a problem within it, such as an internal short circuit, and is excluded from the application of this control method and managed separately.

[0117] In particular, in the case of a pack unit, if the temperature rise of a specific module becomes severe during the discharge process, that module is selected and removed, and voltage control using external resistors is performed on the individual module basis for the remaining modules, thereby ensuring both safety and efficiency simultaneously.

[0118] And, the external resistor resistance value calculation step (S300) is a step of calculating the resistance value of the external resistor based on the measured voltage and a series-parallel structure including the number of series cells (Sn) and the number of parallel cells (Pn) of the waste battery cells, wherein the number of series cells (Sn) and the number of parallel cells (Pn) of the waste battery are verified, and the total resistance value (R) is calculated based on the single cell reference resistance value (R1cell).

[0119] Specifically, the size of the external resistor is calculated based on the series-parallel configuration and the number of cells of the battery module and pack, and the resistance value of the entire module and pack is determined based on approximately 10 Ω for a single cell, and the calculated resistance value can be set to satisfy the following Equations 1 and 2.

[0120] I 1cell = V r / R 1cell = 2V / 10Ω = 0.2A <Equation 1>

[0121] The above Equation 1 represents the current (I₁cell) flowing when an external resistor (R₁cell) is connected based on a single cell.

[0122] Here, cell voltage V r Calculate the current using the resistor R₁cell, and as an example, V r If we apply = 2V and R₁cell = 10Ω, I₁cell = 0.2 A, which becomes the basis value for calculating the total module current based on the current of a single cell.

[0123] R = V total / I = SnㆍV r / PnㆍI cell = (Sn / Pn)ㆍR1 cell <Formula 2>

[0124] Here, Sn is the number of series cells, Pn is the number of parallel cells, R1cell is the single-cell reference (or internal) resistance value, V r represents the single-cell recovery voltage.

[0125] Equation 2 above represents a method for calculating the total resistance R by considering the single cell current and the series-parallel configuration of the module and pack (Sn: number of series cells, Pn: number of parallel cells). The total resistance is calculated by adjusting the single cell resistance according to the module configuration ratio, based on the series and parallel structure of the module and pack, thereby enabling the prediction of the total current and voltage of the module and pack during discharge.

[0126] I = Vmax / R = (2V·Sn) / R <Equation 3>

[0127] Equation 3 above is a formula for calculating the current flowing at the maximum voltage (Vmax) based on the calculated total resistance, where Vmax is calculated by multiplying the single cell voltage by the number of series cells Sn, and dividing this by the total resistance to obtain the current in the module and pack units.

[0128] P = IㆍVmax = Iㆍ(2VㆍSn) <Equation 4>

[0129] Here, I represents the current of the module or pack, Vmax represents the maximum voltage, and Sn represents the number of series cells. Equation 4 above is a formula for calculating the power (P) consumed by the module during discharge, calculated by multiplying the calculated current by the maximum voltage.

[0130] This allows for the evaluation of the power level generated when the module discharges under resistance connection conditions, and since it is related to the heat generated in the resistor when an external resistor is connected, the allowable power can be set with a margin of about 10% of the calculated power.

[0131] In addition, the external resistor is characterized as being a cement resistor or a metal-clad resistor. Specifically, the external resistor is made of a material resistant to temperature, and it is preferable to use a cement resistor (allowable temperature -40℃ to 155℃) or a metal-clad resistor (allowable temperature -55℃ to 200℃).

[0132] At this time, cement resistors are suitable for battery modules (rebound maximum voltage: ~40V), while metal-clad resistors have the advantage of being able to stably handle high power in battery pack units (rebound maximum voltage: ~200V).

[0133] And, the rebound voltage control step (S400) is a step of controlling the rebound voltage by connecting the calculated external resistor to the waste battery and controlling the ON / OFF of the circuit breaker to regulate the discharge current of the waste battery.

[0134] First, the condition for turning on the circuit breaker is determined. In the case of a single cell, the circuit breaker is turned on when the cell voltage is 2.0V or less, and in the case of a module or pack, the circuit breaker is turned on when the total voltage is Sn × 2.0V or less.

[0135] For example, in the case of a module composed of 10 series (10S), when the total voltage is 20V or less, the circuit breaker is turned ON to start discharge through an external resistor. This is to ensure sufficient time to stably connect the external resistor at a time when the voltage rise rate is fast during the initial stage of voltage recovery (about 2 to 3 hours after discharge is complete).

[0136] In addition, after the circuit breaker is turned ON, a discharge current continuously flows through an external resistor, thereby gradually reducing the rebound voltage. The voltage and temperature are monitored in real time, and the measurement cycle can be set from 1 second to 30 seconds. All measurement data, including time, voltage, temperature, and battery ID, can be stored in a CSV or log file format to ensure traceability.

[0137] In addition, the rebound voltage control time varies depending on the battery configuration, and the recommended control time is as follows.

[0138] That is, the standard is set to 12 hours for a single cell (2V), 14 hours for modules below 12V (2P6S, 3P4S, etc.), 16 hours for modules below 40V (3P9S, 3P10S, etc.), and 20 to 24 hours for a pack below 196V (3P98S).

[0139] However, the control time can be adjusted according to the initial rebound size, and it is desirable to set it to 12 hours when the rebound is 0.3V or less per cell, 16 hours when it is 0.3 to 1.0V, and 20 hours or more when it is greater than 1.0V.

[0140] In addition, voltage control is completed by measuring the voltage in 1-minute intervals, and when the change in each cell voltage becomes 0.05V / cell or less for 2 hours, it is determined that the voltage has stabilized and the circuit breaker is turned OFF to terminate the voltage control.

[0141] This completion criterion means that a stable state has been reached where voltage rebound is sufficiently suppressed and no further rapid voltage rise occurs.

[0142] In addition, a monitoring method for preventing reverse voltage can be applied, which generates a warning when the minimum voltage per cell reaches 0.1V and terminates control by turning off the circuit breaker when the minimum voltage per cell reaches 0V.

[0143] If a reverse voltage of -0.1V or higher occurs, the corresponding cell is monitored separately, and voltage control is continued for the remaining cells excluding the one with the reverse voltage. This ensures that safe voltage control of the entire battery can be maintained even if reverse voltage occurs in some cells.

[0144] In addition, depending on the additional aspect, it displays real-time voltage status and abnormal situations via an LED indicator, and provides immediate notification via voice alerts or alarms when reverse voltage occurs or minimum voltage is reached.

[0145] In addition, all data, such as each cell voltage, reverse voltage detection, and monitoring after the circuit breaker is turned off, are recorded in the system log and utilized for safety management and analysis of subsequent preprocessing processes.

[0146] And, in the rebound voltage control step (S400) above, the wire connected to the calculated external resistor and circuit breaker is,

[0147] It is characterized by having a conductor cross-sectional area with a margin of 120 to 130% corresponding to the magnitude of the calculated total current.

[0148] Specifically, the total resistance value (R) and maximum voltage (Vmax) calculated in the external resistor resistance value calculation step (S300) are used to calculate the current (I) expected to flow, and a wire having an allowable current greater than or equal to the value obtained by multiplying this current value by 1.2 to 1.3 is selected.

[0149] For example, if the calculated current is 0.5A, use a wire capable of reliably withstanding an allowable current of 0.6A (0.5A × 1.2) to 0.65A (0.5A × 1.3) or more.

[0150] To explain more specifically based on actual experiments, in the rebound voltage control step (S400) of the present invention, when determining the specifications of the wire connecting the external resistor (100) and the circuit breaker (200), the conductor cross-sectional area corresponding to the calculated total current magnitude was calculated.

[0151] Specifically, the expected current (I) is first calculated using the total resistance value (R) and maximum voltage (Vmax) calculated in the external resistor resistance value calculation step (S300), and a wire having an allowable current capacity greater than the value obtained by multiplying this current value by a margin of 1.2 to 1.3 times is selected.

[0152] This is intended to prevent wire overheating and insulation damage in preparation for instantaneous current rises or voltage fluctuations that may occur during the actual control process.

[0153] For example, when the calculated current is 0.5 A, a wire capable of stably withstanding an allowable current of 0.6 A (0.5 A × 1.2) to 0.65 A (0.5 A × 1.3) or more was used, and the wire used was selected by comprehensively reviewing the voltage rating, cross-sectional area, insulation heat resistance characteristics, etc.

[0154] In addition, in order to verify both the calculated current magnitude and thermal stability conditions, the following wire specifications were applied through actual experiments in this invention.

[0155] 1) Single cell and module experiments

[0156] Rated 450 / 750 V, conductor cross-sectional area 1.5 mm 2 A wire was used, and it was confirmed that the wire could stably withstand a current of up to 24 A.

[0157] In particular, the current during control was about 120% of the calculated current, and no abnormal phenomena such as overheating or discoloration occurred on the wire surface or insulation coating.

[0158] 2) Pack (3P98S) Experiment

[0159] For large pack configurations, 2.5 mm 2 A wire was used, and the wire has an allowable current capacity capable of stably withstanding up to 33 A.

[0160] This design also has a margin of about 120 to 130 percent relative to the calculated current, and no overcurrent or abnormal heating was observed during the actual rebound voltage control process.

[0161] In addition, all wires are made of a material with an insulation heat resistance temperature of 70°C or higher so that they can stably withstand local temperature rise around the control unit (500) and external resistor (100).

[0162] In this way, the present invention was able to fundamentally prevent problems such as wire heating, insulation degradation, and current imbalance during rebound voltage control by simultaneously verifying the allowable current and heat resistance characteristics and applying the optimal wire specifications.

[0163] In summary, the present invention calculates the conductor cross-sectional area based on the calculated current × 1.2 to 1.3, and as a result, 1.5 mm in actual experiments 2 and 2.5 mm 2 By using wires to stably handle currents of 24 A and 33 A, the overcurrent safety factor and thermal stability verification were simultaneously satisfied.

[0164] In other words, by selecting a wire with a conductor cross-sectional area having a margin of 120 to 130 percent relative to the calculated current, it is possible to safely respond to unexpected current fluctuations or degradation caused by long-term operation during the rebound voltage control process, and ensure the safety of workers and the reliability of the system.

[0165] And, the above waste battery dismantling step (S500) is a step of dismantling a waste battery with controlled rebound voltage, wherein the circuit breaker is turned OFF when voltage control is completed, the connection with the external resistor is disconnected, and the surface temperature of the battery is finally checked.

[0166] Before disassembly, remeasure the residual voltage of the battery to check if the voltage per cell is maintained at less than 1V, and check if the surface temperature has stabilized at 25℃ or lower.

[0167] By proceeding with physical dismantling only when these conditions are met, the risk of localized heating, ignition, or explosion is prevented.

[0168] In addition, for a single cell, the outer case and edge are carefully cut with a cutting tool to separate the positive and negative electrodes, and a scraper is used on the surface of the positive electrode to scrape and collect only the positive electrode material, taking care not to damage the aluminum current collector.

[0169] In addition, for modules and packs, the case is opened, the Battery Management System (BMS) and wiring are removed, and the units are disassembled into individual cells to recover the cathode material in the same manner.

[0170] Meanwhile, Fig. 1b is a schematic diagram showing the voltage range in which the rebound voltage after discharge can be controlled by an external resistor. After a certain period of time has elapsed following the completion of discharge, the rebound voltage of the waste battery naturally rises, and the voltage [is based on] the number of cells connected in series (N series 2 V × N in proportion to ) series It is possible to reach that level.

[0171] In the present invention, by connecting an external resistor in this section, the rebound current is controlled, and as time elapses, the voltage stabilizes to 0.1 V × N series It shows a gradual decrease to the level.

[0172] That is, Figure 1b schematically illustrates that safe disassembly is possible by maintaining the rebound voltage in a stable controllable voltage range (2 V ~ 0.1 V / cell) through an external resistor after the discharge ends.

[0173] Hereinafter, the present invention will be described in detail with reference to examples in order to specifically explain the invention. However, the embodiments according to the present invention may be modified in various different forms, and the scope of the present invention should not be interpreted as being limited to the embodiments described below. The embodiments of the present invention are provided to more completely explain the invention to those with average knowledge in the art.

[0174] Example 1: Calculation of External Resistor Size

[0175] In order to verify the validity of the method for calculating an external resistor according to the present invention, the size of the external resistor according to the series-parallel configuration of the battery module and pack was calculated by applying the above Equation 1.

[0176] At this time, the calculation result varies depending on each configuration condition, and specific calculation examples are shown in Application Examples 1 to 4 below.

[0177] 1) Application Example 1: Battery module with 3P10S structure

[0178] Application Example 1 illustrates an example of calculating the total resistance value of external resistors for a battery module with a 3 parallel 10 series (3P10S) structure, and the external resistance value R of a single cell. 1cell Based on 10 Ω, the total resistance value is calculated as follows according to Equations 1 to 4.

[0179] I 1cell = V r / R 1cell = 2V / 10Ω = 0.2A

[0180] R total = V total / I total = (10·V r ) / (3ㆍI 1cell ) = (10 / 3)ㆍ10Ω = 33.3Ω

[0181] I = Vmax / R total = (2Vㆍ10) / 33.3Ω = (20 / 33.3)A = 0.6A

[0182] P = IㆍVmax = (20 / 33.3)Aㆍ(2Vㆍ10) = 12.0W

[0183] 2) Application Example 2: Battery module with 3P4S structure

[0184] Application Example 2 illustrates an example of calculating the total resistance value of external resistors for a battery module with a 3 parallel 4 series (3P4S) structure, and the external resistance value R of a single cell. 1cell Based on 10 Ω, the total resistance value is calculated as follows according to Equations 1 to 4.

[0185] I 1cell = Vr / R 1cell = 2V / 10Ω = 0.2A

[0186] R total = V total / I total = (4ㆍV r ) / (3ㆍI 1cell ) = (4 / 3)ㆍ10Ω = 13.3Ω

[0187] I = Vmax / R total = (2V·4) / 13.3Ω = (8 / 13.3)A = 0.6A

[0188] P = IㆍVmax = (8 / 13.3)Aㆍ(2Vㆍ4) = 4.8W

[0189] 3) Application Example 3: Battery module with 2P6S structure

[0190] Application Example 3 illustrates an example of calculating the total resistance value of external resistors for a battery module with a 2 parallel 6 series (2P6S) structure, and the external resistance value R of a single cell. 1cell Based on 10 Ω, the total resistance value is calculated as follows according to Equations 1 to 4.

[0191] I 1cell = V r / R 1cell = 2V / 10Ω = 0.2A

[0192] R total = V total / I total = (6ㆍV r ) / (2ㆍI 1cell ) = (6 / 2)ㆍ10Ω = 30.0Ω

[0193] I = Vmax / R total = (2V·6) / 30.0Ω = (12 / 30.0)A = 0.4A

[0194] P = IㆍVmax = (12 / 30.0)Aㆍ(2Vㆍ6) = 4.8W

[0195] 4) Application Example 4: Battery pack with 3P98S structure

[0196] Application Example 4 illustrates an example of calculating the total resistance value of external resistors for a battery pack with a 3 parallel 98 series (3P98S) structure, and the external resistance value R of a single cell. 1cell Based on 10 Ω, the total resistance value is calculated as follows according to Equations 1 to 4.

[0197] I 1cell = V r / R 1cell = 2V / 10Ω = 0.2A

[0198] R total = V total / I total = (98ㆍV r ) / (3ㆍI 1cell ) = (98 / 3)ㆍ10Ω = 326.7Ω

[0199] I = Vmax / R total = (2V·98) / 326.7Ω = (196 / 326.7)A = 0.6A

[0200] P = I·Vmax = (196 / 326.7)A·(2V·98) = 117.6W

[0201] Experimental Example 1: Module-unit voltage control

[0202] 1) Experimental Method

[0203] As a result of calculating the theoretical size of the external resistor using Formula 1 according to the present invention, it was derived to be approximately 33.3 Ω based on the module (3P10S).

[0204] At this time, considering the possibility of heat generation in the resistor and a rise in cell temperature during discharge, a safety factor of 10% was applied, and a 40 Ω resistor was used in this experiment.

[0205] In the example, the C-rate calculated based on a single cell was converted to a module (3P10S, 180 Ah) standard to calculate the discharge current, and a module-unit discharge experiment was performed using this. After the module discharge was completed, an external resistor was connected to perform voltage control for 12 hours.

[0206] 2) Experimental Results

[0207] Figure 2a illustrates the voltage control change over time after the discharge of each cell of the module is completed. When an external resistor (40 Ω) is applied, the voltage difference between cells decreases by approximately 60% from 0.178 V at the start of control to 0.077 V after 12 hours, and it was confirmed that the minimum voltage of each cell is maintained at less than 1 V without reverse voltage, allowing for safe disassembly.

[0208] In addition, Table 1 below summarizes the main measurement results.

[0209] division item Maximum voltage (V) Minimum voltage (V) Measured value note Resistance conditions Symme resistance - - 40 Ω Control start point Inter-cell voltage deviation 1.623 1.445 0.178V 12 hours after control Inter-cell voltage deviation 0.476 0.404 0.072V About 60% decrease

[0210] * For 40 Ω, the theoretical value is 33.3 + safety factor 10%.

[0211] In addition, FIG. 3a shows each cell of the module and the external resistor As shown in the graph of temperature change over time, the average temperature of the cell during the voltage control period was 28.9 ℃ and the maximum was 29.5 ℃, and the external resistor was measured at an average of 49.2 ℃ and a maximum of 53.6 ℃, confirming that stable voltage control is possible without excessive heat generation.

[0212] Experimental Example 2: Pack Unit Voltage Control

[0213] 1) Experimental Method

[0214] As a result of calculating the theoretical size of the external resistor using Formula 1 according to the present invention, it was derived to be approximately 330 Ω based on the pack (3P98S).

[0215] In the example, the C-rate calculated based on a single cell was converted to a module (3P98S) standard to calculate the discharge current, and a pack-unit discharge experiment was performed using this. After the discharge was completed, an external resistor was connected to perform voltage control for 12 hours.

[0216] 2) Experimental Results

[0217] Figure 2b illustrates the voltage control change over time after the discharge of each cell in the pack is completed. When an external resistor (330 Ω) is applied, the voltage difference between cells decreased by approximately 44% from 0.327 V at the start of control to 0.184 V after 12 hours, and it was confirmed that the minimum voltage of each cell was maintained at less than 1 V without reverse voltage, allowing for safe disassembly.

[0218] In addition, Table 2 below summarizes the main measurement results.

[0219] division item Maximum voltage (V) Minimum voltage (V) Measured value note Resistance conditions Metalclad resistor - - 330 Ω Control start point Inter-cell voltage deviation 0.706 0.379 0.327V 12 hours after control Inter-cell voltage deviation 0.285 0.101 0.184V About 44% decrease

[0220] In addition, Figure 3b illustrates the temperature changes of each module and external resistor in the pack over time. During the voltage control period, the temperature of the module was at least 23.5°C and at most 30.1°C, and the external resistor was measured at 50°C or lower, confirming that stable voltage control is possible without excessive heat generation.

[0221] Therefore, it was confirmed that the voltage control conditions of the present invention are applicable even at the pack level.

[0222] Experimental Example 3: Temperature change before and after module crushing

[0223] 1) Experimental Method

[0224] The temperature before and after crushing was checked for a module with completed voltage control that applied an external resistor derived by the resistor size calculation formulas 1 to 4 of the present invention.

[0225] As a result, the temperature of the storage container before crushing was approximately 19.4 ℃, and the surface temperature of the crushed material after crushing was measured to be approximately 20.3 to 20.7 ℃.

[0226] 2) Experimental Results

[0227] Figure 4 shows the temperature before and after module crushing in photographs. Measurement results confirmed that no excessive heat was generated during the crushing process and that the change in surface temperature was minimal, allowing for safe dismantling.

[0228] This supports the fact that it can be reliably applied even in crushing and recycling processes, depending on the voltage control conditions and the calculated resistor size.

[0229] Experimental Example 4: Separation and Recovery of Cathode Material from Waste Batteries

[0230] 1) Examples of the present invention

[0231] The rated voltage of the single cell is 3.73V and the rated capacity is 60 Ah. After connecting the cell to a standard charge / discharge device, the discharge current was set to C-rate C / 3 (approx. 18A) and a first discharge was performed down to SOC 0% (approx. 2.8 V).

[0232] Afterwards, the discharge current was set to C-rate C / 10 (approx. 6A) to discharge the cell voltage to the range of 0.1 to 0.5V, and then maintained in constant voltage (CV) mode for about 4 hours.

[0233] After the discharge ended, the rebound voltage was measured for about 3 hours and set as the final target voltage, and an external resistor (10Ω) was connected based on that voltage to perform voltage control for 24 hours.

[0234] 2) Comparative Example 1

[0235] Comparative Example 1 was conducted on an initial sample (NCM 622 Powder) in a state where discharge treatment was not performed.

[0236] That is, an NCM 622 cathode active material that was not exposed to cell manufacturing or discharge processes was used as a reference sample to evaluate changes in composition before and after discharge based on elemental composition and metal content, and through this, the electrode composition stability and metal leaching inhibition effect according to whether the voltage control method proposed in the present invention was applied were compared and analyzed.

[0237] 3) Comparative Example 2

[0238] After connecting a single cell to a special discharger, the discharge current was set to C-rate C / 10 (approx. 18A) and discharged for 2 hours. Comparative Example 2 is intended to implement a general current-controlled forced discharge condition without applying a voltage control method using an external resistor.

[0239] In particular, by simulating the condition where the cell voltage reaches the reverse voltage region, we intended to verify the difference in electrode damage depending on whether the invention was applied.

[0240] 4) Separation and recovery of cathode material within the battery

[0241] In the above embodiment and comparative example 2 of the present invention, a battery single cell that has undergone discharge treatment is prepared, and the single cell is composed of a positive electrode material, an aluminum current collector, a separator, a negative electrode material, a copper current collector, and an electrolyte.

[0242] At this time, the outer case and edge of the prepared single cell were cut off, and the anode was separated. Then, using a scraper on the separated anode, the anode material was recovered by scraping only the upper part while taking care not to damage the aluminum current collector.

[0243] In addition, the recovered cathode material was subjected to quantitative analysis using an ICP-OES instrument for the embodiment and comparative example 2 of the present invention, and for comparative example 1, the same analysis was performed using the NCM 622 powder itself as a reference sample.

[0244] classification Li(wt%) Ni(wt%) Co(wt%) Mn(wt%) Cu(wt%) Examples 9.97 59.80 14.39 15.84 - Comparative Example 1 10.68 54.46 18.30 16.55 - Comparative Example 2 9.92 53.99 13.18 14.79 8.12

[0245] The experimental results are shown in Table 3, which shows the results of analyzing the metal content (wt %) of Li, Ni, Co, Mn, and Cu using ICP-OES on the cathode material separated and recovered from the batteries of the embodiments and comparative examples 1 and 2 of the present invention.

[0246] At this time, in Comparative Example 1 (NCM 622 powder, pristine), the Ni, Co, and Mn content were confirmed to be 54.46 wt%, 18.30 wt%, and 16.55 wt%, respectively, indicating that it is a reference sample that has not been exposed to battery processes or discharge treatments.

[0247] Meanwhile, in the cathode material applied in the embodiment of the present invention, the Ni content was maintained at 59.80 wt%, which is relatively higher than that of Comparative Examples 1 and 2, and the Co and Mn content were also confirmed to be at a stable level.

[0248] In addition, in the case of Comparative Example 2, 8.12 wt% of Cu was detected, which indicates that Cu ions leached from the negative copper current collector due to over-discharge migrated to the anode and were electrodeposited and contaminated on the anode material.

[0249] Therefore, it was confirmed that when the voltage control method according to the present invention is applied, the metal composition of the anode material is stably maintained and the incorporation of impurities is suppressed.

[0250] Experimental Example 5: Circuit Breaker Control Criteria

[0251] 1) Examples of the present invention

[0252] In the present invention, for a single cell, the circuit breaker is turned ON when the cell voltage is 2.0V or less, and for a module, when the number of series cells is S, the circuit breaker is turned ON when the total voltage of the module is Sn × 2.0V or less.

[0253] For example, in the case of a module composed of 10 series (10S), the circuit breaker is turned ON when the total voltage is 20 V or less.

[0254] In addition, as shown in FIG. 5, the inventors experimentally analyzed the voltage recovery (rebound) characteristics of the module and pack units, and among them, after completely discharging the 3P10S module according to the example, the resistors were connected at voltage recovery of 2 V (10 × 0.2 V, i.e., assuming the voltage when the resistor is immediately connected) and 20 V (10 × 2.0 V, based on the safe voltage when disassembled), respectively.

[0255] As a result, at 0.2 V, the voltage rose rapidly, so there was not enough time to connect the resistor after disconnecting from the charger / discharger, whereas at 19 V, it took about 71.28 hours.

[0256] In addition, at the point where the voltage recovers to about 10 V (after about 2.64 hours), the voltage recovery is in the initial stage (within 3 hours), so at this point, sufficient time is secured to stably connect the external resistor, and it was confirmed that the voltage can be safely controlled throughout the voltage rise range (2 to 20 V range).

[0257] Accordingly, the present invention experimentally confirmed that safe and efficient voltage control within the voltage rise range is possible by connecting an external resistor at the point where voltage recovery occurs after about 3 hours (at the point of recovery to about 10 V).

[0258] Experimental Example 6: Temperature-based method

[0259] 1) Examples of the present invention

[0260] As a result of checking the temperature change of the module and pack units during the discharge process in the present invention, it was confirmed that the maximum temperature during discharge under all experimental conditions (room temperature, high temperature, high humidity, etc.) was about 53.5 ℃, and there were no cases where it exceeded 60 ℃.

[0261] That is, as shown in Fig. 6, when the battery is discharged to the lowest voltage (0.1 V), the temperature reaches its peak due to the heat generated during the discharge process.

[0262] Subsequently, an analysis of temperature changes over approximately 6 hours revealed that after the initial temperature rise, the temperature of each cell within the module gradually converged and stabilized without deviation, which implies that the internal reaction of the battery stabilized sufficiently during the natural cooling process after the discharge ended.

[0263] However, even in the case of a battery discharged under conditions other than the current range and discharge method specified in the present invention, the resistance control principle of the present invention may be applied. When applied, the degree of deterioration may be severe in the rebound voltage / temperature measurement step (S200), causing the temperature to rise above 60℃. Therefore, in this case as well, the present invention is appropriate to proceed to the next step only after waiting for about 6 hours in a natural cooling state without a separate forced cooling or repeated cooling procedure, and the temperature stabilizes below 60℃.

[0264] If the temperature does not drop below 60℃ even after 6 hours, it is highly likely that heat generation and safety issues will occur during the subsequent voltage control process using a resistor, so it is desirable to exclude (dispose of) the battery from the application of the method of the present invention, as safety cannot be ensured during the voltage control process in the case of severely degraded waste batteries.

[0265] In addition, for the battery pack unit, the condition of each cell is checked by connecting to the charging / discharging equipment via the HV connector and measuring the OCV (open-circuit voltage) after discharge. Modules with severe temperature rise during the discharge process are selected, removed, and excluded, and for the remaining modules, a voltage control method using an external resistor can be applied on an individual module basis.

[0266] Experimental Example 7: Rebound Control Time (Comparison of 12–24 Hour Control)

[0267] 1) Experimental example of the present invention

[0268] This experimental example shows the results of comparing voltage stabilization characteristics for 12 hours, 16 hours, and 20 to 24 hours of control time by connecting an external resistor after waiting 3 hours after discharge is completed, according to the rebound voltage control method of the present invention.

[0269] All tests were performed under identical discharge conditions (after complete discharge, waiting 3 hours in the natural rebound voltage state), and the temperature was measured in an environment of 25 ± 2 ℃.

[0270] Specifically, as illustrated in Fig. 7, the module experiment results show an example of rebound voltage control after discharge for different battery configurations (3P10S, 3P9S, 2P6S, 3P4S).

[0271] First, in the 3P10S module, the initial rebound voltage was approximately 8.39V, and it gradually decreased to 2.65V after 12 hours of control and to 1.73V after 24 hours. When converted to voltage per cell, it showed a voltage reduction of more than 70%, ranging from 0.839V to 0.266V to 0.173V, respectively, and during this process, the temperature was stably maintained at a maximum of 27℃.

[0272] Next, the 3P9S module started with an initial voltage of 1.37V, decreased to 0.75V after 12 hours of control, and to 0.60V after 24 hours. The voltage change per cell was 0.152V → 0.083V → 0.067V, showing a similar control pattern even under initial conditions where the rebound voltage was relatively low.

[0273] Next, in the 2P6S module, the initial voltage was 5.43V, stabilized at 0.95V after 12 hours of control, and 0.71V after 23 hours of control. Based on the voltage per cell, it showed a change from 0.904V → 0.159V → 0.118V, exhibiting a reduction rate of approximately 80%.

[0274] Finally, the 3P4S module had an initial voltage of 3.76V, was controlled to 0.56V after 12 hours of control and 0.51V after 23 hours, the voltage per cell stabilized from 0.941V → 0.139V → 0.127V, and the temperature was maintained at approximately 20℃.

[0275] The experimental results can be briefly explained as follows.

[0276] (1) 3P10S module

[0277] External resistor: 33.3 Ω (based on R₁cell = 10 Ω)

[0278] Initial rebound voltage: 8.393 V (0.839 V per cell)

[0279] After 12 hours of control: 2.656 V (0.266 V per cell)

[0280] After 24-hour control: 1.732 V (0.173 V per cell)

[0281] Voltage reduction rate: Approx. 79%

[0282] Temperature change: Average 25.7 ℃, maximum 27.1 ℃

[0283] That is, a rapid voltage drop occurred for 12 hours after the discharge ended, entered a gradual stabilization phase after 16 hours, and at the 24-hour mark, the rebound voltage was maintained at approximately 1.7 V and was fully stabilized.

[0284] (2) 3P9S module

[0285] External resistor: 30 Ω

[0286] Initial voltage: 1.366 V (0.152 V per cell)

[0287] After 12 hours of control: 0.748 V (0.083 V per cell)

[0288] After 24 hours of control: 0.604 V (0.067 V per cell)

[0289] Voltage reduction rate: Approx. 56%

[0290] Temperature change: Average 26℃, maximum 33℃

[0291] In other words, for small modules, most stabilization was completed within 12 hours because the initial rebound voltage was low, and after 24 hours, there was minimal additional voltage drop and no temperature rise was observed.

[0292] (3) 2P6S module

[0293] External resistor: 30 Ω

[0294] Initial voltage: 5.426 V (0.904 V per cell)

[0295] After 12 hours of control: 0.951 V (0.159 V per cell)

[0296] After 23 hours of control: 0.709 V (0.118 V per cell)

[0297] Voltage reduction rate: Approx. 87%

[0298] Temperature change: Average 21.3 ℃, maximum 24.8 ℃

[0299] In other words, the rebound control effect was stably confirmed even in cells with high current discharge characteristics, and after a rapid drop within 12 hours, it showed a gradual decrease until 23 hours, and the temperature was maintained at 35 ℃ or lower.

[0300] (4) 3P4S module

[0301] External resistor: 13.3 Ω (4 / 3 x 10 Ω = 13.3 Ω)

[0302] Initial voltage: 3.762 V (0.941 V per cell)

[0303] After 12 hours of control: 0.555 V (0.139 V per cell)

[0304] After 23 hours of control: 0.509 V (0.127 V per cell)

[0305] Voltage reduction rate: Approx. 86%

[0306] Temperature change: Average 15 ℃, maximum 23.3 ℃

[0307] In other words, when controlled for more than 20 hours, there is almost no additional decrease in rebound voltage, and it was confirmed to be the point at which voltage stabilization is complete.

[0308] And, in the case of Fig. 8, experimental results are shown of controlling the rebound voltage by connecting a 330 Ω external resistor to a 3P98S battery pack.

[0309] Specifically, when an external resistor (330 Ω) was connected approximately 3 hours after the discharge ended, the initial rebound voltage was measured at 49.473 V (approx. 0.505 V per cell), and after voltage control was performed for 12 hours, the pack voltage decreased rapidly to 13.352 V (approx. 0.136 V per cell), and at the end of the 24-hour control, it stabilized gradually to 11.728 V (approx. 0.120 V per cell).

[0310] In addition, as can be seen in the graph, the voltage dropped sharply within the first 3 hours and then transitioned to a gradual stable range after about 8 to 10 hours, and the total voltage was reduced by more than 70 to 80% within about 24 hours to reach a stable state, and during this process, the module temperature was maintained in the range of about 25 to 30 ℃, so almost no heat was generated, and both the resistor and the cell secured thermal stability.

[0311] In other words, this experiment proved that even in the case of a high-voltage large pack (3P98S, maximum safety voltage during rebound section: approximately 196 V), if an external resistor of the 330 Ω level is used, the rebound voltage stabilizes below the safety standard within 24 hours, demonstrating that the control formula of the present invention is equally effective at the pack level as well as at the module level.

[0312] The experimental results can be briefly explained as follows.

[0313] (5) 3P98S Pack

[0314] External resistor: 330 Ω

[0315] Initial rebound voltage: 49.473 V (0.505 V per cell)

[0316] After 12 hours of control: 13.352 V (0.136 V per cell)

[0317] After 24-hour control: 11.728 V (0.120 V per cell)

[0318] Voltage reduction rate: Approx. 76%

[0319] Temperature change: Average 25 ℃, maximum 30.1 ℃

[0320] That is, even in a large pack configuration (3P98S), the rebound voltage dropped sharply within 12 hours, reached a gradual stabilization phase during 20 to 24 hours of control, the total voltage was maintained at 11.7 V (0.12 V per cell), and the temperature rise was limited to within 5 ℃, resulting in very stable discharge control.

[0321]

[0322] Table 4 above shows the results of voltage stabilization and temperature change according to the rebound voltage control time.

[0323] In other words, voltage stabilization and thermal safety were confirmed within 24 hours in all experimental groups, and as the number of series cells increased, the time to stabilization tended to increase, proving that the rebound control time interval is experimentally valid.

[0324] In conclusion, as shown in Figures 7 and 8 and Table 4, the rebound control exhibited a two-stage pattern in all configurations, with a rapid voltage drop within the first 12 hours followed by a gradual stabilization period.

[0325] In addition, the stabilization time tended to increase with the number of serial cells, and accordingly, a control time of about 12 hours for a single cell, 16 hours for a 3P10S module, and 20 to 24 hours for a 3P98S pack can be recommended, and the temperature in all samples did not exceed 40 ℃ and was maintained in the average range of 20 to 25 ℃.

[0326] This demonstrates that the external resistor selection criteria and control logic of the present invention simultaneously secure voltage stability and thermal safety.

[0327] Furthermore, based on the aforementioned experiment, a tendency was observed where the time to stabilization increased as the number of serial cells increased; accordingly, recommended control times for each configuration can be proposed as follows.

[0328] 1) Rebound Control Time Guide

[0329] (1) Recommended time by battery configuration (based on experimental results)

[0330] ① Single cell (2 V): 12-hour standard

[0331] ② Module (2P6S, 3P4S, ~12 V): 14-hour standard

[0332] ③ Module (3P9S, 3P10S, ~40 V): Based on 16 hours

[0333] ④ Pack (3P98S, ~196 V): Based on 20 to 24 hours

[0334] In this case, the above ~12 V, ~40 V, and ~196 V are based on the maximum rebound voltage.

[0335] (2) Recommended time based on initial rebound size (as it varies depending on the degree of degradation for the same battery configuration)

[0336] ① Rebound ≤ 0.3 V / cell → 12 hours

[0337] ② Rebound 0.3 ~ 1.0 V / cell → 16 hours

[0338] ③ Rebound > 1.0 V / cell → 20 hours or more

[0339] At this time, the recommended time for each initial rebound size was set based on experimental values ​​of the initial rebound voltage size per cell (0.152 ~ 0.941 V / cell), and it was experimentally confirmed that the higher the voltage, the longer the time required for stabilization.

[0340] 2) Completion Judgment Criteria

[0341] (1) Voltage measurement cycle: 1 minute interval (for the purpose of detecting periods of rapid voltage decrease)

[0342] (2) Completion determination condition: If the voltage change within 2 hours is 0.05 V / cell or less, discharge is determined to be complete.

[0343] As a result of the experiment, the voltage change per cell (Δ) in the 12 to 24 hr interval was in the range of 0.012 to 0.092 V, and the 2-hour fluctuation was at the level of 0.002 to 0.015 V, stably satisfying the 0.05 V / cell standard.

[0344] Experimental Example 8: Setting a 10% safety factor

[0345] 1) Experimental example of the present invention

[0346] The total resistance value (R) and maximum voltage (Vmax) calculated in the above external resistor resistance value calculation step (S300) are used to calculate the current (I) expected to flow, and a wire having an allowable current greater than or equal to the value obtained by multiplying this current value by 1.2 to 1.3 is selected.

[0347] For example, if the calculated current is 0.5A, use a wire capable of reliably withstanding an allowable current of 0.6A (0.5A × 1.2) to 0.65A (0.5A × 1.3) or more.

[0348] That is, for single-cell and small module experiments, since the calculated current was in the range of approximately 0.2A to 0.6A, 1.5mm of 450 / 750V rating 2 A wire (maximum allowable current of about 24A) was used.

[0349] This has a current capacity of about 40 times greater than the calculated current, sufficiently exceeding a safety margin of 120 to 130% to secure a safety margin.

[0350] In addition, in the pack (3P98S) unit experiment, the calculated current was approximately 0.6A, so 2.5mm 2 A wire (maximum allowable current of about 33A) was used, and this also ensured a sufficient safety factor with a current capacity of about 55 times the calculated current.

[0351] As mentioned above, the reason for setting a margin of 120 to 130% is as follows.

[0352] First, during the rebound voltage control process, the initial voltage may be higher than the assumed 2V / cell during calculation, and in this case, a larger current may flow instantaneously.

[0353] Second, during the process of continuous current flow for a long time (12 to 24 hours), the increase in contact resistance of the wire or the increase in resistance due to temperature rise must be taken into account.

[0354] Third, when handling multiple batteries simultaneously, an additional safety margin is required because current may concentrate at wiring branch points.

[0355] In addition, the heat resistance of the insulation of the wire is also an important selection criterion. In the present invention, a wire with a heat resistance specification of 70°C or higher is used so that the insulation covering is not damaged even if heat generated from an external resistor is transferred to the wire.

[0356] Since the maximum temperature of the external resistor was measured to be approximately 53.6℃ in the experiment (3P10S module experiment), the 70℃ heat resistance specification provides a temperature margin of approximately 16.4℃ to ensure safety.

[0357] In addition, since the rated voltage of the wire must be higher than the maximum voltage of the battery, it is desirable to use wires rated at 450 / 750V for single cells and battery modules (~40V), and wires rated at 300 / 500V or higher for battery packs (~200V).

[0358] In addition, the length of the wire should be kept as short as possible to minimize voltage drop and resistance loss, and it is generally recommended to limit it to within 1m.

[0359]

[0360] In the case of Table 5 above, the allowable power is set with a margin of about 10% based on the actual calculated power for each battery configuration, thereby ensuring safety.

[0361]

[0362] Table 6 above represents the actual experimental results. The actual resistor ratings used were 3P10S-20 W (cement), 3P9S-15 W, 3P4S·2P6S-5 W, and 3P98S (pack)-400 W (metal-clad). In all configurations, sufficient margin was secured compared to the calculated power, and some exceeded 10% significantly.

[0363] In particular, regarding the allowable temperature range for each resistor, the metal-clad resistor was -55℃ to +200℃ and the cement resistor was -40℃ to +155℃, and the experiment was conducted under the assumption of an ambient temperature of 25℃ and a ventilated environment.

[0364] As a result of the experiment, in the case of the above 3P4S and 2P6S, the calculated margin was approximately 4.17%, but almost no heat was generated during the voltage control experiment (minimal temperature rise), and it was confirmed that it operated safely within the allowable temperature range (40 to +155℃) of the cement resistor used.

[0365] In addition, the entire experiment was conducted in a ventilated environment at an ambient temperature of 25°C, and the surface temperature of the resistors was maintained at 60°C or lower.

[0366] In addition, the pack unit (3P98S) was maintained at a stable temperature of 24.7°C when controlled using a metal-clad resistor (55 to 200°C).

[0367] Therefore, the 10% safety factor of the present invention is a reasonable setting that takes into account both calculated power and actual heat generation characteristics, and it was experimentally confirmed that safe operation is possible in all configurations.

[0368] FIG. 9 is a conceptual diagram showing a rebound voltage control device for controlling the rebound voltage after discharge of a waste battery according to an embodiment of the present invention.

[0369] As illustrated in FIG. 9, the rebound voltage control device of the present invention, which controls the rebound voltage after discharge of a waste battery, is:

[0370] An external resistor (100) connected to a discharged waste battery (10);

[0371] A circuit breaker (200) that controls the connection between the above external resistor and the waste battery;

[0372] Voltage sensor (300) for measuring the voltage of the waste battery;

[0373] A temperature sensor (400) for measuring the temperature of the waste battery; and

[0374] It is characterized by including a control unit (500) that receives measurement values ​​from the voltage sensor and temperature sensor, calculates the resistance value of an external resistor based on the number of series cells (Sn) and parallel cells (Pn) of the waste battery, and controls the ON / OFF of the circuit breaker.

[0375] To explain in detail, the waste battery (10) is a lithium-ion battery recovered after use from an electric vehicle, an energy storage system (ESS), or an industrial battery. In the present invention, it refers to a cell, module, or pack-unit battery in a discharged state. Since the waste battery (10) has the characteristic that a certain voltage rises again immediately after discharge due to a rebound phenomenon, the device is connected to a circuit including an external resistor (100) and a circuit breaker (200) to control the voltage below a safety standard.

[0376] And, the above external resistor (100) is a load element for stably controlling the rebound voltage after discharge is completed, and is composed of a cement resistor or a metal-clad resistor with excellent heat resistance.

[0377] This resistor is selected according to the resistance value (R) calculated by the control unit (500), and is calculated using the formula R = (Sn / Pn) × R₁cell based on the single cell reference resistance value (R₁cell = 10 Ω) and the number of series cells (Sn) and parallel cells (Pn) of the battery, for example, it is calculated to be about 33.3 Ω in the case of a 3P10S module and about 330 Ω in the case of a 3P98S pack, and the rated allowable power of the resistor is set to be about 110% or more of the calculated power consumption value to suppress heat generation.

[0378] At this time, as a result of the experiment, the temperature of the external resistor was maintained at a maximum of less than 50℃, ensuring thermal stability.

[0379] And, the circuit breaker (200) acts as a switch that controls the electrical connection between the external resistor (100) and the waste battery (10). The circuit breaker (200) operates ON / OFF according to a signal from the control unit (500). When the voltage per cell is 2.0 V or lower, it automatically turns ON to start consuming rebound current, and when the voltage per cell is 0 V or a reverse voltage (-0.1 V) or higher is detected, it turns OFF to terminate control.

[0380] This prevents excessive discharge or reverse current inflow, thereby minimizing electrode damage and electrical stress at the cell level.

[0381] And, the voltage sensor (300) measures the terminal voltage of the waste battery (10) in real time and transmits it to the control unit (500). Preferably, a precision digital voltmeter type sensor is used, and the measurement range is -1 V to 200 V, the accuracy is the larger value between ±0.05% or ±0.01 V, the response speed is within 1 second, and the measurement cycle is user-configurable from 1 second to 5 minutes.

[0382] At this time, the voltage sensor records voltage data per cell, thereby allowing real-time monitoring of the decrease trend of the rebound voltage during control, and if the voltage of a specific cell drops below a reference level or a reverse voltage is detected, it immediately transmits a signal to the control unit (500).

[0383] And, the temperature sensor (400) is configured to monitor the surface temperature of the waste battery (10) and the external resistor (100) to prevent overheating, preferably using a K-type thermocouple, and the measurement range is set to -40 ℃ to 150 ℃, the accuracy to ±1 ℃, and the response speed to within 5 seconds.

[0384] At this time, the measured temperature data is transmitted to the control unit (500) to stop control or issue a notification when the temperature is 60°C or higher, and this functions as a safety device to prevent secondary accidents such as explosions or ignition caused by the rise in temperature.

[0385] And, the control unit (500) receives measurement values ​​from the voltage sensor and temperature sensor, calculates the resistance value of an external resistor based on the number of series cells (Sn) and parallel cells (Pn) of the waste battery, and performs the function of controlling the ON / OFF of the circuit breaker.

[0386] Specifically, the control unit (500) performs the following functions.

[0387] First, as a resistance value calculation function, for a single cell, a reference resistance value R₁cell = 10 Ω is used, and for a module or pack, the external resistance value is calculated using the formula R = (Sn / Pn) × R₁cell.

[0388] In addition, the allowable power is set by adding a 10% margin to the calculated power consumption value P = I × Vmax.

[0389] Second, as a circuit breaker control function, it is to turn ON when the cell voltage is 2.0 V or lower, and to turn OFF when the minimum cell voltage is 0 V or the reverse voltage is -0.1 V or higher.

[0390] For example, as a step-by-step transition when the minimum voltage per cell is reached, a warning is issued when Min. Cell V reaches 0.1 V, and as a step-by-step transition when the minimum voltage per cell is reached, the circuit breaker is turned OFF (control terminated) when Min. Cell V reaches 0 V.

[0391] In addition, as a processing function for reverse voltage detection, when a reverse voltage of -0.1 V or higher occurs, the cell is monitored separately, and the remaining cells excluding the cell with the reverse voltage are additionally controlled or terminated by connecting a resistor.

[0392] Third, as a stabilization judgment function, if the change in cell voltage is 0.05 V or less for 2 hours, it is determined that voltage stabilization is complete.

[0393] Fourth, as a data logging and notification linkage function, each measurement value, current flow, circuit breaker status, and the time of warning occurrence are all recorded, and signals are transmitted to the LED indicator (600) and the alarm unit (700).

[0394] In addition, the control unit is implemented based on a microcontroller (MCU) and incorporates non-volatile memory to store control history and log data.

[0395] In this case, the data recording is characterized by including data fields for minimum recording items (time, voltage, temperature), storage format (CSV or log file), and traceability (including battery ID).

[0396] Specifically, the control unit (500) stores the following minimum recording items in real time during the execution of the rebound voltage control step (S400).

[0397] 1) Time: Elapsed time or absolute time since the start of control (yyyy-mm-dd hh:mm:ss format)

[0398] 2) Voltage: Cell voltage and total module / pack voltage (measured to the nearest 0.001 V)

[0399] 3) Temperature: Waste battery surface temperature and external resistor temperature (measured to the nearest 0.1 ℃)

[0400] In addition, the above items are automatically updated and recorded according to the measurement cycle (1 second to 5 minutes), and all data is stored in CSV format or a dedicated log file format.

[0401] In this case, when saved in CSV format, data from each measurement point is accumulated in rows and includes columns such as "time, cell voltage, total voltage, temperature, and circuit breaker status".

[0402] On the other hand, the log file format accumulates data in chronological order within the device's internal memory and supports an export function to external storage devices (USB or network servers).

[0403] In addition, the present invention ensures data traceability by assigning a unique battery identification number (ID) to each data file.

[0404] That is, when control begins, the control unit (500) automatically recognizes the battery ID or receives it manually and includes the corresponding ID in the header and filename of all data files, thereby allowing the voltage history, temperature changes, and circuit breaker operation times of each battery to be tracked in subsequent processes (e.g., dismantling, crushing, metal recovery, etc.).

[0405] These data management functions enable the verification of rebound control stability, quality history management (QA / QC), and post-safety analysis; in particular, the cumulative recording of data per battery can significantly contribute to the standardization and reliability improvement of the entire recycling process.

[0406] Meanwhile, according to an additional aspect, the rebound voltage control device of the present invention for controlling the rebound voltage after discharge of a waste battery is,

[0407] LED indicator (600) that displays real-time voltage status and abnormal conditions;

[0408] It is further characterized by including an alarm unit (700) that provides a notification when reverse voltage occurs and when minimum voltage is reached.

[0409] To explain in detail, the LED indicator (600) is linked with the control unit (500) and performs the function of visually indicating the rebound voltage control status and whether an abnormality has occurred.

[0410] For example, the following states are displayed through LED colors or flashing patterns.

[0411] 1) Green: Under normal control (stable state)

[0412] 2) Yellow: Minimum cell voltage 0.1 V warning status

[0413] 3) Red: Reverse voltage detected or circuit breaker OFF state

[0414] As mentioned above, the LED indicator enables field workers to immediately recognize the progress of battery voltage stabilization, thereby ensuring safety during subsequent dismantling operations.

[0415] In addition, the above alarm unit (700) performs the function of outputting a voice or alarm sound to alert the worker immediately when a voltage abnormality or reverse voltage occurs.

[0416] In particular, when the minimum cell voltage reaches 0.1 V, a warning sound is generated, and when 0 V or reverse voltage occurs, an alarm sound is continuously output to send a signal to the control unit (500) to immediately switch the circuit breaker to the OFF state.

[0417] In addition, the alarm unit (700) also automatically records each alarm event in the system log, and the log is subsequently used for pre-processing safety analysis and quality history management.

[0418] Accordingly, the rebound voltage control device of the present invention according to FIG. 9 collects data from voltage and temperature sensors, controls an external resistor and a circuit breaker through a control unit, and notifies the real-time status through an LED indicator and an alarm unit, thereby enabling safe and precise control of the rebound voltage after discharge of the waste battery.

[0419] The above-described configuration is applicable to various types of batteries, such as modules and packs, and simultaneously provides technical effects such as heat suppression, reverse voltage prevention, and worker safety.

[0420] According to the present invention, by stably controlling the voltage rebound that occurs after the discharge of a waste battery is completed, secondary safety accidents such as localized heating, ignition, and explosion during the dismantling and crushing process can be effectively prevented.

[0421] In addition, by calculating the value of the external resistor according to the series and parallel structure and number of battery cells, precision in current control is ensured, and it can be widely applied to various types of battery cells, modules, and packs.

[0422] Those skilled in the art to which the present invention pertains will understand that the present invention, as described above, may be implemented in other specific forms without altering the technical concept or essential features of the invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

[0423] The scope of the present invention is defined by the claims set forth below rather than by the detailed description above, and all modifications or variations derived from the meaning and scope of the claims and equivalent concepts thereof should be interpreted as being included within the scope of the present invention. Industrial applicability

[0424] The rebound voltage control device and control method according to the present invention can eliminate electrical and thermal risks in advance prior to the dismantling, crushing, and metal recovery processes.

[0425] Accordingly, dismantling work can be safely carried out at waste battery recycling plants, secondary battery material recovery facilities, and medium-to-large ESS dismantling lines without accidents such as explosions, fires, or electric shocks.

[0426] In particular, while conventional processes suppressed rebound voltage by merely waiting for a certain period after discharge, the present invention enables rapid control to below the safety standard (0.1V / cell level) through the connection of an external resistor and real-time voltage management based on a control unit, thereby simultaneously providing the effects of reducing process time and improving work efficiency.

[0427] In addition, since the present invention includes a function to automatically calculate resistance values ​​according to the series and parallel structure of module and pack units, and to record and track temperature and voltage data in real time, it can be utilized as a standardized safe dismantling process in the waste battery processing industry.

[0428] This provides a technical foundation that can be applied as a standard model when establishing related industry standards in the future, such as safety standards for electric vehicle battery recycling or safety management regulations for ESS dismantling.

[0429] Furthermore, the present invention can be utilized as a pretreatment technology for a resource recycling process that recovers positive electrode materials, negative electrode materials, electrolytes, etc., from waste batteries safely dismantled through a rebound voltage control process after discharge.

[0430] In other words, by stably recovering valuable metals such as lithium, nickel, cobalt, and manganese, it improves the economic viability and environmental sustainability of the waste battery recycling industry.

[0431] Therefore, the present invention can be directly applied in various industrial fields such as the waste battery recycling and metal recovery industry, and electric vehicle and ESS dismantling facilities. As a core pretreatment process technology that integrates electrical, chemical, environmental, and safety technologies, it is expected to contribute significantly to the safety standardization and competitiveness of the domestic and international waste battery processing industry. Explanation of the symbols

[0432] 10 : Waste battery 100 : External resistor 200 : Circuit breaker 300: Voltage sensor 400: Temperature sensor 500 : Control unit 600 : LED indicator 700 : Alarm unit

Claims

Claim 1 A rebound voltage control device for controlling the rebound voltage after discharge of a waste battery comprises: an external resistor (100) connected to a discharged waste battery (10); a circuit breaker (200) for controlling the connection between the external resistor and the waste battery; a voltage sensor (300) for measuring the voltage of the waste battery; a temperature sensor (400) for measuring the temperature of the waste battery; and a control unit (500) that receives measured values ​​from the voltage sensor and the temperature sensor, calculates the resistance value of the external resistor based on the number of series cells (Sn) and the number of parallel cells (Pn) of the waste battery, and controls the ON / OFF of the circuit breaker. A rebound voltage control device comprising, wherein the control unit (500) calculates the resistance value (R) of the external resistor according to the following formula, R = (Sn / Pn) × R1cell (wherein Sn is the number of series cells, Pn is the number of parallel cells, and R1cell is the single cell reference resistance value), and controls the circuit breaker (200) to ON when the temperature of the waste battery measured by the temperature sensor (400) is less than 60℃, and when the voltage measured by the voltage sensor (300) is Sn × 2.0V or less. Claim 2 A method for controlling the rebound voltage after discharge of a waste battery, comprising: a discharged waste battery preparation step (S100) for preparing a discharged waste battery; a rebound voltage / temperature measurement step (S200) for measuring the rebound voltage and temperature of the discharged waste battery; an external resistor resistance value calculation step (S300) for calculating the resistance value of an external resistor based on the measured voltage and a series-parallel structure including the number of series cells (Sn) and the number of parallel cells (Pn) of the waste battery cells; and a rebound voltage control step (S400) for connecting the calculated external resistor to the waste battery and controlling the ON / OFF of a circuit breaker to regulate the discharge current of the waste battery and control the rebound voltage. A rebound voltage control method comprising: a waste battery dismantling step (S500) for dismantling the waste battery in which the rebound voltage is controlled; wherein the external resistor resistance value calculation step (S300) is performed when the temperature of the waste battery measured in the rebound voltage / temperature measurement step (S200) is less than 60℃, and the resistance value (R) of the external resistor is calculated according to the following formula, R = (Sn / Pn) × R1cell (where Sn is the number of series cells, Pn is the number of parallel cells, and R1cell is the single cell reference resistance value); and wherein the rebound voltage control step (S400) is characterized by turning on the circuit breaker when the voltage measured in the rebound voltage / temperature measurement step (S200) is Sn × 2.0V or less.

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