Battery system and pack connection method using the same

Abstract

The present invention relates to a battery system and a pack connection method using the same. The battery system includes a battery device including a plurality of battery packs connected in parallel, a plurality of switches connected in series to one of both ends of each of the plurality of battery packs, and a battery management system (BMS) that divides the plurality of battery packs into a plurality of pack groups, determines at least one battery pack belonging to each of the plurality of pack groups, determines one pack group from the plurality of pack groups to be subjected to a discharging operation, and transmits a switch control signal to turn on at least one switch from the plurality of switches connected to the one pack group and to turn off the remaining switches from the plurality of switches except for the at least one switch, and each of the plurality of battery packs includes a plurality of battery cells each containing metallic phase lithium in a negative electrode material.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0183601 dated December 23, 2022 and Korean Patent Application No. 10-2023-0124691 dated September 19, 2023, and all contents disclosed in the documents of said Korean patent applications are incorporated herein by reference.

[0002] The present disclosure relates to a battery system and a pack connection method using the same. [Background technology]

[0003] When the battery cells included in the battery system are secondary batteries, the anode material is as important as the cathode material in the battery. Lithium metal can be used for the anode of the battery.

[0004] In a battery system including a battery cell with a lithium metal anode, when the battery is discharged at a low discharge rate, the battery life is inferior to when the battery is discharged at a high discharge rate. Therefore, methods for improving the battery life are being discussed. Summary of the Invention [Problem to be solved by the invention]

[0005] To provide a battery system and a pack connection method using the same, which enable a battery device including a plurality of battery packs to discharge at a higher discharge rate than the discharge rate of the battery device by using only some of the plurality of battery packs during the discharging operation of the battery device. [Means for solving the problem]

[0006] According to one feature of the invention, a battery system includes a battery device including a plurality of battery packs connected in parallel, a plurality of switches connected in series to one of both ends of each of the plurality of battery packs, and a battery management system (BMS) that divides the plurality of battery packs into a plurality of pack groups, determines at least one battery pack belonging to each of the plurality of pack groups, determines one pack group among the plurality of pack groups to be subjected to a discharging operation, and transmits a switch control signal to turn on at least one switch among the plurality of switches connected to the one pack group and to turn off the remaining switches of the plurality of switches except for the at least one switch, wherein each of the plurality of battery packs includes a plurality of battery cells including metallic phase lithium in each negative electrode material.

[0007] A discharge rate of the battery device for supplying power required by a load connected to the battery device is a first discharge rate, and each of the plurality of pack groups can discharge at a second discharge rate greater than the first discharge rate.

[0008] The BMS can determine the number of the plurality of pack groups by dividing a reference discharge rate for each of the plurality of battery packs by a discharge rate of the battery device, and can determine the number of the plurality of battery packs belonging to each of the plurality of pack groups by dividing the number of the plurality of battery packs by the number of the plurality of pack groups.

[0009] The BMS can determine a plurality of discharge patterns that constitute the discharge pattern cycle for the plurality of pack groups so that a difference between an average pre-discharge rest time of any one of the plurality of pack groups and an average pre-discharge rest time of any other of the plurality of pack groups is small.

[0010] The positive electrode material of each of the plurality of battery cells contains elemental sulfur, and the plurality of discharge patterns include a first discharge pattern in which a first pack group and a second pack group are discharged in that order among the plurality of pack groups, and the BMS performs a discharge operation on the first pack group and monitors whether at least one of the pack voltages of each of at least one first battery pack belonging to the first pack group is equal to or lower than a predetermined lower discharge voltage limit.

[0011] If at least one of the pack voltages of each of the at least one first battery pack is below a predetermined lower discharge limit voltage, the BMS can turn off a switch connected to each of the at least one first battery pack, discharge the second pack group, and monitor whether at least one of the pack voltages of each of the at least one second battery pack belonging to the second pack group is below a predetermined lower discharge limit voltage.

[0012] The BMS can turn off the multiple switches when all of the multiple pack groups include a battery pack whose voltage is equal to or lower than a predetermined lower discharge limit voltage.

[0013] According to another aspect of the present invention, a pack connection method of a battery system including a battery device including a plurality of battery packs connected in parallel includes the steps of: a battery management system (BMS) connected to the battery device divides the plurality of battery packs into a plurality of pack groups; determining at least one battery pack belonging to each of the plurality of pack groups; determining one pack group to be subjected to a discharge operation from among the plurality of pack groups; and transmitting a switch control signal to turn on at least one switch among the plurality of switches connected to the one pack group and to turn off the remaining switches among the plurality of switches except for the at least one switch, and each of the plurality of battery packs may include a plurality of battery cells including metallic phase lithium in their negative electrode material.

[0014] A discharge rate of the battery device for supplying power required by a load connected to the battery device is a first discharge rate, and each of the plurality of pack groups can discharge at a second discharge rate greater than the first discharge rate.

[0015] The method may further include determining the number of the plurality of pack groups by dividing a reference discharge rate for each of the plurality of battery packs by a discharge rate of the battery device, and determining the number of the plurality of battery packs belonging to each of the plurality of pack groups by dividing the number of the plurality of battery packs by the number of the plurality of pack groups.

[0016] The step of determining one of the plurality of pack groups to perform a discharge operation may include a step of determining a plurality of discharge patterns that constitute the discharge pattern cycle for the plurality of pack groups such that a difference between an average pre-discharge pause time of any one of the plurality of pack groups and an average pre-discharge pause time of another of the plurality of pack groups is small in a discharge pattern cycle for the plurality of pack groups.

[0017] The positive electrode material of each of the plurality of battery cells includes elemental sulfur, the plurality of discharge patterns include a first discharge pattern in which a first pack group and a second pack group are arranged in that order among the plurality of pack groups, and the step of transmitting the switch control signal may include the step of discharging the first pack group and monitoring whether at least one pack voltage of each of at least one first battery pack belonging to the first pack group is equal to or lower than a predetermined lower discharge limit voltage.

[0018] The method may further include turning off a switch connected to each of the at least one first battery pack and discharging the second pack group if at least one of the pack voltages of each of the at least one first battery pack is equal to or lower than a predetermined lower discharge voltage limit, and monitoring whether at least one of the pack voltages of each of the at least one second battery pack belonging to the second pack group is equal to or lower than a predetermined lower discharge voltage limit.

[0019] The method may further include turning off the switches when all of the pack groups include battery packs whose voltages are equal to or lower than a predetermined lower discharge limit voltage. Effect of the Invention

[0020] According to the present disclosure, by discharging a plurality of battery packs including lithium metal batteries at a discharge rate higher than the discharge rate of a battery device for supplying the power required by a load, it is possible to suppress the formation of lithium dendrites that may occur when the battery packs are discharged at a low discharge rate, and to prevent early degradation of each of the plurality of battery packs.

[0021] According to the present disclosure, in the case of a lithium-sulfur secondary battery among lithium metal batteries, discharging is performed to the end without pausing the discharge operation, thereby preventing lithium polysulfide from dissolving in the electrolyte, thereby improving the lifespan of multiple battery packs.

[0022] According to the present disclosure, the premature degradation phenomenon at low discharge rates observed when using lithium metal as the anode can be overcome by using BMS without any changes in materials or cell technology. [Brief description of the drawings]

[0023] [Figure 1] FIG. 1 is a block diagram illustrating a battery system according to one embodiment. [Diagram 2] FIG. 1 shows the morphology of the lithium metal surface as a function of different stripping rates in a lithium metal battery. [Diagram 3] 1 is a graph illustrating the relationship between discharge rate and life of a battery cell using lithium metal as a negative electrode. [Figure 4] 4 is a flowchart of a pack connection method using a battery system according to an embodiment. [Diagram 5] 5 is a detailed flowchart of step S100 in FIG. 4. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Hereinafter, the embodiments disclosed herein will be described in detail with reference to the attached drawings, and the same or similar components will be given the same or similar drawing numbers, and duplicated descriptions thereof will be omitted. The suffixes "module" and / or "part" for components used in the following description are given or mixed for the sake of ease of specification writing only, and do not have any meaning or role that is different from each other by themselves. In addition, when describing the embodiments disclosed herein, if it is determined that a specific description of such known technology may obscure the gist of the embodiments disclosed herein, the detailed description will be omitted. Furthermore, the attached drawings are merely for the purpose of making the embodiments disclosed herein easily understandable, and it should be understood that the attached drawings do not limit the technical ideas disclosed herein, and include all modifications, equivalents, or alternatives included in the ideas and technical scope of the present invention.

[0025] Terms including ordinal numbers such as first, second, etc. may be used to describe various components, but the components are not limited by the terms. The terms are used only to distinguish one component from another.

[0026] It should be understood that in this application, terms such as "comprise" or "have" are intended to specify the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0027] In one embodiment, a configuration for controlling another configuration under a specific control condition is provided with a program implemented by a set of commands embodying a control algorithm required to control the other configuration. The control configuration can process input data and stored data by the provided program to generate output data. The control configuration can include a non-volatile memory for storing the program and a memory for storing data.

[0028] FIG. 1 is a block diagram that illustrates a battery system according to one embodiment.

[0029] The battery system 1 may include a battery device 100, a battery management system (BMS) 200, relays 300 and 301, and a plurality of switches SW1-SW6.

[0030] The battery device 100 may include a plurality of battery packs 101-106 connected in parallel. Each of the plurality of battery packs 101-106 may be realized by two or more battery cells connected in series, a plurality of battery cells in which two or more battery cells connected in parallel are connected in series, or two or more battery cells connected in parallel. Although FIG. 1 shows six battery packs 101-106 and six switches SW1-SW6, the invention is not limited thereto, and the battery system 1 may include two or more battery packs and two or more switches.

[0031] One end of the relays 300, 301 is connected to the battery device 100, and the other end of the relays 300, 301 is connected to at least one component in the external device 2. The closing and opening of the relays 300, 301 can be controlled by relay control signals RSC1, RSC2 supplied from the BMS 200.

[0032] The battery system 1 can be connected to an external device 2. The external device 2 can include a load such as an inverter and a converter, and a charging device. When the external device 2 is a charger, both ends P+ and P- of the battery system 1 are connected to the charger and receive power from the charger to be charged. Hereinafter, when the external device 2 is a charger, an operation in which both ends P+ and P- of the battery system 1 are connected to the charger and receive power from the charger to be charged is referred to as a "charging operation."

[0033] When the external device 2 is a load, both ends P+ and P- of the battery system 1 are connected to the load, and the power supplied by the battery device 100 is discharged through the load. Hereinafter, the operation in which power is supplied from the battery device 100 to the load and the charge of the battery device 100 is reduced is referred to as a "discharging operation."

[0034] In one embodiment, each of the battery cells included in each of the battery packs 101-106 may be a lithium metal battery that uses lithium (Li) metal as a negative electrode. Specifically, the negative electrode material of each of the battery cells included in each of the battery packs 101-106 may include lithium in a metal phase.

[0035] During the discharge process of a lithium metal battery, an oxidation reaction occurs in which the lithium metal contained in the negative electrode material of the lithium metal battery is stripped and moves to the positive electrode through the electrolyte.

[0036] When lithium metal is stripped from a specific position of the lithium metal anode material, other lithium metal ions are likely to be stripped again from positions where lithium metal has already been stripped, corners of the lithium deposit, points of large curvature of the lithium deposit, etc. Furthermore, in a lithium metal battery discharged at a low discharge rate, lithium metal is stripped from the surface less uniformly than in a lithium metal battery discharged at a high discharge rate, and metal ions are stripped at positions where they are likely to be stripped.

[0037] During the charge and discharge process of a lithium metal battery, lithium ions become irregular on the surface of the negative electrode due to irregular deposition of lithium metal or irregular stripping of lithium ions, and lithium dendrites are formed by pointing in a direction from the negative electrode surface to the positive electrode surface. When a lithium metal battery is repeatedly charged and discharged, such lithium dendrites accumulate excessively and may permeate the separator, causing an internal short circuit between the negative electrode and the positive electrode.

[0038] Hereinafter, the lithium stripping operation according to the difference in discharge rate of the lithium metal battery will be described with reference to FIG.

[0039] FIG. 2 shows the morphology of the lithium metal surface as a function of different stripping rates in a lithium metal battery.

[0040] 2A shows the shape of a lithium deposit that occurs when irregular deposition occurs on lithium metal during charging of a lithium metal battery. Referring to FIG. 2A, the irregular deposition of lithium metal can include narrow points 21.

[0041] If lithium metal is stripped at a fast rate from the lithium deposit shown in FIG. 2A, the highly reversible shape can return to a shape with most of the irregular lithium metal deposits removed, such as the shape shown in FIG. 2A1.

[0042] In comparison, if lithium metal is stripped at a relatively slow rate from the lithium deposit shown in FIG. 2A, stripping will occur more actively at corners or points of high curvature of the lithium deposit, as in the shape shown in FIG. 2A2, and the irregular deposit of lithium metal will be stripped more irregularly.

[0043] Referring to FIG. 2A2, the irregular deposits of slow stripped lithium metal can include narrow spots 22.

[0044] The narrow point 22 in Fig. 2A2 is narrower than the narrow point 21 in Fig. 2A, and thus the area 23 in the lithium deposit that is separated from the narrow point 22 is separated from the lithium deposit. Also, the irregular surface makes it easier for lithium dendrites to form.

[0045] When the discharge rate of a lithium metal battery is increased, the stripping rate of the lithium metal contained in the lithium metal battery is fast and uniform. In contrast, when a lithium metal battery is discharged at a low discharge rate below a predetermined level, the stripping from the surface of the lithium metal (or lithium metal deposits) contained in the lithium metal battery is not uniform, and lithium dendrites are likely to form on the surface of the lithium metal.

[0046] Specifically, the irregular growth of lithium metal is mainly initiated by the change in surface current density, and when the lithium metal battery is operated in an environment where the stripping rate is slower than the deposition rate of lithium metal, lithium debris may break off from the irregularly grown lithium metal. The formation of such lithium debris may increase the degradation rate, which reduces the total capacity of the lithium metal battery cell.

[0047] In this way, when the lithium metal battery is discharged at a low discharge rate below a predetermined level, early deterioration of the lithium metal battery cells may occur. When the first discharge rate is lower than the second discharge rate, each of the battery packs 101-106 is more likely to deteriorate early when discharged at the first discharge rate than when discharged at the second discharge rate. In other words, in terms of the deterioration degree of the lithium metal battery, the higher the discharge rate, the more advantageous it is. Based on this, the BMS 200 according to an embodiment may control the discharge of the battery packs 101-106 so that the battery packs 101-106 are discharged at a high discharge rate equal to or higher than a predetermined level.

[0048] Alternatively, in one embodiment, each of the battery cells included in each of the battery packs 101-106 may be a lithium-sulfur secondary battery. Specifically, the negative electrode material of each of the battery cells included in each of the battery packs 101-106 may include metallic phase lithium, and the positive electrode material of each of the battery cells may include elemental sulfur (e.g., S8) having a Sulfur-Sulfur Bond (SS bond) or a sulfur-containing complex as a positive electrode active material.

[0049] During the discharge process of a lithium-sulfur secondary battery, continuous reduction reactions of sulfur (e.g., S8) contained in the positive electrode and continuous oxidation reactions of metallic phase lithium contained in the negative electrode occur in each electrode and electrolyte. As a result of these continuous oxidation / reduction reactions, multiple types of lithium polysulfides (LiPS) are formed in the electrolyte and can move between the electrodes, and the final solid-state lithium sulfide (Li2S) can accumulate on the negative electrode.

[0050] However, during the process of forming lithium polysulfide through the continuous oxidation / reduction reaction, some of the lithium polysulfide dissolved in the electrolyte may undergo side reactions with the negative electrode, which may be one of the factors that reduces the life characteristics of lithium-sulfur secondary batteries.

[0051] Thus, the frequency of side reactions occurring between some of the lithium polysulfide dissolved in the electrolyte and the negative electrode increases as the discharge time becomes longer. That is, in order to reduce the frequency of side reactions, it is necessary to control the discharge rate by shortening the discharge time of the lithium-sulfur secondary battery cell. When a lithium-sulfur secondary battery cell goes into a rest state during discharge and then discharges again, the overall discharge time increases compared to when there is no rest state. This can increase the frequency of side reactions. Therefore, increasing the cell discharge rate of the lithium-sulfur secondary battery and discharging it for a shorter discharge time is advantageous in terms of the life of the lithium-sulfur secondary battery.

[0052] Therefore, if any one of the plurality of pack groups is in a discharging operation, the BMS 200 can monitor the on-pack voltage so that the lithium-sulfur secondary battery cells are discharged in a short discharge time without pausing until the lithium-sulfur secondary battery cells are fully discharged during discharging. Hereinafter, the on-pack voltage refers to the pack voltage of at least one battery pack in which a coupled switch among the plurality of switches SW1-SW6 is turned on.

[0053] Based on the above-mentioned characteristics of the lithium metal battery and the lithium-sulfur secondary battery, the operation of the battery system 1 will be described below.

[0054] The BMS 200 can divide the multiple battery packs 101-106 into multiple pack groups and determine at least one pack group to be discharged from among the multiple pack groups. The BMS 200 can control so that power is supplied to the load from the determined at least one pack group. The BMS 200 can determine the number of pack groups to be discharged from among the multiple pack groups based on the discharge rate of the battery device 100 for supplying power required by the load (hereinafter, "discharge rate of the battery device 100 required by the load") and a reference discharge rate of the battery packs. The reference discharge rate of the battery packs may be within a range of discharge rates for each of the multiple battery packs 101-106 that has little effect on the degree of degradation of each of the multiple battery packs 101-106.

[0055] When supplying power to a load, the BMS 200 is capable of discharging only some of the pack groups at a high discharge rate (C-rate) without discharging all of the pack groups. Hereinafter, the discharge rate of the battery device 100 required by the load is referred to as the load discharge rate, and the unit of the discharge rate (C-rate) is "C". The power required by the load can be determined by the maximum power of the load.

[0056] Assume that the number of battery packs included in the battery device 100 is m (m is a natural number equal to or greater than 2), and m=n*p (n and p are natural numbers equal to or greater than 1). "n" may be the number of pack groups when m battery packs are grouped into units of "p". The BMS 200 can divide the m battery packs into n pack groups and sequentially perform a discharge operation on each of the n pack groups. Each of the n pack groups includes p battery packs.

[0057] If one of the n pack groups performs a discharging operation, the discharge rate of each of the p battery packs included in the pack group performing the discharging operation may be n times the discharge rate of the battery device 100 required by the load.

[0058] For example, if the discharge rate of the battery device 100 required by the load is 0.1C and the number of pack groups (n) is 3, the BMS 200 can determine the discharge rate of each of the three pack groups to be 0.3C when sequentially discharging one of the three pack groups, and control the discharge rate of each battery pack belonging to each pack group to 0.3C.

[0059] In an embodiment, the number (n) of pack groups may be pre-stored in the BMS 200. In one embodiment, the BMS 200 can determine the number (n) of pack groups based on the discharge rate of the battery apparatus 100 required by the load and the reference discharge rate of the battery packs.

[0060] In one embodiment, the BMS 200 may store in advance the discharge rate of the battery device 100 required by the load and the reference discharge rate of the battery packs. The BMS 200 can derive the number (n) of pack groups based on the discharge rate of the battery device 100 required by the load and the reference discharge rate of the battery packs stored in advance. Furthermore, based on the derived number (n) of pack groups and the number (m) of the multiple battery packs 101-106, the BMS 200 can derive the number (p) of battery packs belonging to each of the n pack groups, and sequentially perform a discharge operation on each of the n pack groups. Furthermore, the BMS 200 can determine p battery packs belonging to each of the n pack groups. At this time, each of the n pack groups can perform a discharge operation at a discharge rate belonging to the reference discharge rate.

[0061] For example, if the reference discharge rate of the battery pack is 0.3C to 1C, the number of the battery packs constituting the battery device 100 is six, and the discharge rate of the battery device 100 required by the load is 0.2C, the BMS 200 can calculate n, a natural number in which 0.2C*n is within the range of 0.3 to 1 and is divisible by 6. Through the calculation, n may be one of 2 and 3. In other words, the BMS 200 can divide the six battery packs into two or three groups.

[0062] Alternatively, in one embodiment, the BMS 200 may receive a signal indicating a discharge rate of the battery device 100 required by the load from the external device 2, determine the discharge rate of the battery device 100 based on the received signal, and derive the number of pack groups (n) based on the determined discharge rate of the battery device 100 and a reference discharge rate of the battery packs.

[0063] In one embodiment, if each of the battery cells included in each of the battery packs 101-106 is a lithium-sulfur secondary battery, the BMS 200 can improve the lifespan of the battery cells undergoing the discharging operation by causing p battery packs included in a pack group that has started a discharging operation among the n pack groups to maintain the discharging state until the discharging is completed without pausing in between.

[0064] In this case, the discharge operation of each of the n pack groups by the BMS 200 may include an operation of discharging one of the n pack groups, and then discharging another of the n pack groups when the discharging is completed, thereby sequentially discharging the m battery packs in units of p battery packs by repeating the operation. The operation of the BMS 200 discharging one pack group may refer to an operation of discharging each of the p battery packs by turning on switches connected to each of the p battery packs belonging to one pack group.

[0065] In the specification, the completion of discharge may indicate a state in which at least one of the pack voltages of each of the p battery packs is equal to or lower than a predetermined lower limit voltage of discharge. The predetermined lower limit voltage of discharge may be a predetermined value or a predetermined range indicating that the battery pack is fully discharged. For example, in one embodiment, the predetermined lower limit voltage of discharge may be 1.5 to 1.9V, and in another embodiment, the predetermined lower limit voltage of discharge may be 1.8V.

[0066] When a pack group belonging to one of the multiple pack groups is performing a discharging operation, BMS200 does not pause until each of the p battery packs belonging to the pack group performing the discharging operation reaches a lower discharge limit voltage, and when the pack voltage of at least one of the p battery packs reaches the lower discharge limit voltage, BMS200 can terminate discharging of the pack group performing the discharging operation and start the discharging operation of another pack group of the multiple pack groups.

[0067] The BMS 200 can determine a pack group to perform a discharging operation among the plurality of pack groups, and can turn on a switch connected to the determined pack group among the plurality of switches SW1-SW6. Then, the corresponding battery pack can be connected to the node N1. The discharging operation can include an operation for supplying power to the outside. Here, when at least one battery pack to perform a discharging operation among the plurality of battery packs 101-106 is two or more, the battery packs can be connected in parallel to each other.

[0068] One end of each of the multiple switches SW1-SW6 is connected to one another at a node N1, and the other end of each of the multiple switches SW1-SW6 is connected in series to one end of each of the multiple battery packs 101-106.

[0069] 1 shows that the battery packs 101-106 include a plurality of battery cells and that the switches SW1-SW6 are connected to the battery packs 101-106 connected in parallel, this is for convenience of explanation, and in some embodiments, the switches SW1-SW6 may be connected to each battery cell. When the switches SW1-SW6 are connected to each battery cell, the description of the battery system 1 in this specification regarding the packs may be substituted for the description of the cells and may be applied.

[0070] One end of the switch SW1 is connected to the relay 300 at the node N1, and the other end of the switch SW1 is connected to the positive terminal of the battery pack 101. One end of the switch SW2 is connected to the relay 300 at the node N1, and the other end of the switch SW2 is connected to the positive terminal of the battery pack 102. One end of the switch SW3 is connected to the relay 300 at the node N1, and the other end of the switch SW3 is connected to the positive terminal of the battery pack 103. One end of the switch SW4 is connected to the relay 300 at the node N1, and the other end of the switch SW4 is connected to the positive terminal of the battery pack 104. One end of the switch SW5 is connected to the relay 300 at the node N1, and the other end of the switch SW5 is connected to the positive terminal of the battery pack 105. One end of the switch SW6 is coupled to the relay 300 at the node N1, and the other end of the switch SW6 is coupled to the positive terminal of the battery pack 106.

[0071] The BMS 200 can turn on a switch connected to a battery pack performing a discharging operation among the battery packs 101-106 and monitor the voltage of the battery pack performing a discharging operation. The BMS 200 can receive a plurality of voltage measurement signals VS1-VS6 from one end of each of the battery packs 101-106. The BMS 200 is connected to one end of each of the battery packs 101-106 via a plurality of wirings LN1-LN6.

[0072] The BMS 200 may include a plurality of terminals P1-P6. Each of the plurality of terminals P1-P6 is coupled to one end of each of the plurality of battery packs 101-106 via a respective one of a plurality of wires LN1-LN6. The BMS 200 may receive a plurality of voltage measurement signals VS1-VS6 via the plurality of terminals P1-P6.

[0073] The positive electrode terminal of the battery pack 101 is connected to the terminal P1 via a wire LN1, and the BMS 200 can acquire a voltage measurement signal VS1 measured from the positive electrode terminal of the battery pack 101 via the terminal P1. The positive electrode terminal of the battery pack 102 is connected to the terminal P2 via a wire LN2, and the BMS 200 can acquire a voltage measurement signal VS2 measured from the positive electrode terminal of the battery pack 102 via the terminal P2. The positive electrode terminal of the battery pack 103 is connected to the terminal P3 via a wire LN3, and the BMS 200 can acquire a voltage measurement signal VS3 measured from the positive electrode terminal of the battery pack 103 via the terminal P3. The positive electrode terminal of the battery pack 104 is connected to the terminal P4 via a wire LN4, and the BMS 200 can acquire a voltage measurement signal VS4 measured from the positive electrode terminal of the battery pack 104 via the terminal P4. The positive terminal of the battery pack 105 is coupled to the terminal P5 via a wire LN5, and the BMS 200 can acquire a voltage measurement signal VS5 measured from the positive terminal of the battery pack 105 via the terminal P5. The positive terminal of the battery pack 106 is coupled to the terminal P6 via a wire LN6, and the BMS 200 can acquire a voltage measurement signal VS6 measured from the positive terminal of the battery pack 106 via the terminal P6.

[0074] The BMS 200 can derive the pack voltages of each of the battery packs 101-106 from the voltage measurement signals VS1-VS6. The BMS 200 can thus monitor the pack voltages of the battery packs connected to the closed switches of the switches SW1-SW6 among the battery packs 101-106.

[0075] If the monitoring results show that at least one of the pack voltages of at least one battery pack belonging to the pack group performing the discharging operation is equal to or lower than a predetermined lower discharge limit voltage, BMS200 can turn off the switches to which each of the battery packs belonging to the pack group performing the discharging operation is connected, and then turn on the switches to which each of the battery packs belonging to the pack group performing the discharging operation is connected.

[0076] In a charging operation, the BMS 200 transmits switch control signals SS1-SS6 of an on level to the multiple switches SW1-SW6, and when the multiple switches SW1-SW6 are closed, the multiple battery packs 101-106 are charged.

[0077] FIG. 3 is a graph illustrating the relationship between discharge rate and life of a lithium metal battery.

[0078] Hereinafter, the battery cycle life according to the C-rate, which indicates the discharge rate of the battery, will be described with reference to Fig. 3, under the condition that the remaining life capacity (retention) is 80%. When the discharge rate (C-rate) is 0.1C, the battery cycle life is 90 cycles, and when the C-rate is 0.3C, the battery cycle life is 147 cycles. Therefore, when the C-rate increases threefold from 0.1C to 0.3C, it can be seen that the battery cycle life increases by 63.33%, from 90 cycles to 147 cycles.

[0079] In one embodiment, the BMS 200 divides the battery packs 101-106 into n pack groups and performs a discharge operation, thereby discharging only some of the battery packs 101-106. The discharge rate of the battery device 100 is a value obtained by dividing the total discharge rate of the battery packs performing the discharge operation by the number of the battery packs 101-106. For example, if the discharge rate of each of the battery packs 101-106 is 0.3C and only two battery packs out of the six battery packs 101-106 are performed a discharge operation, the discharge rate of the battery device 100 is 0.3*2 / 6=0.1C. Therefore, in one embodiment, the discharge rate of each of the battery packs 101-106 is higher than the discharge rate of the battery device 100, and a battery system 1 that is advantageous in terms of the life of each of the battery packs 101-106 can be provided.

[0080] FIG. 4 is a flowchart of a pack connection method using a battery system according to one embodiment.

[0081] Hereinafter, any overlapping description of the above-mentioned battery system 1 may be omitted.

[0082] When the battery system 1 starts a discharge operation, the BMS 200 can divide the multiple battery packs 101-106 into multiple pack groups (S100). The BMS 200 stores information regarding the number (n) of pack groups in advance, or the BMS 200 can determine the number of multiple pack groups based on the discharge rate of the battery device 100 required by the load and the reference discharge rate of the battery packs. The BMS 200 can determine at least one battery pack belonging to each of the multiple pack groups. The BMS 200 can sequentially perform a discharge operation on each of the multiple pack groups.

[0083] The BMS 200 can cause at least one battery pack belonging to one pack group among the battery packs 101-106 to perform a discharging operation, and can put the remaining battery packs in a hibernation state. Therefore, when the number of pack groups is n, each of the battery packs 101-106 performing a discharging operation is discharged at a discharging speed that is n times the discharging speed of the battery device 100.

[0084] For example, when the BMS 200 divides the battery packs into two pack groups (n=2), the discharge rate of each of at least one battery pack belonging to the pack group performing the discharge operation can be twice as fast as the discharge rate of the battery device 100, which is increased by 100% based on the discharge rate of the battery device 100. When the BMS 200 divides the battery packs into three pack groups (n=3), the discharge rate of each of at least one battery pack belonging to the pack group performing the discharge operation can be three times as fast as the discharge rate of the battery device 100, which is increased by 200% based on the discharge rate of the battery device 100. When the BMS 200 divides the battery packs into four pack groups (n=4), the discharge rate of each of at least one battery pack belonging to the pack group performing the discharge operation can be four times as fast as the discharge rate of the battery device 100, which is increased by 300% based on the discharge rate of the battery device 100. In this way, the battery system 1 can increase the discharge rate of each of the battery packs 101-106 to improve the life of the lithium metal batteries.

[0085] For ease of explanation, it is assumed below that the number of battery packs included in the battery device 100 is m=6, the number of pack groups is n=3, and the number of battery packs included in each of the three pack groups is p=2. It is also assumed that the multiple battery packs 101-106 are the first to sixth battery packs, respectively.

[0086] The BMS 200 can divide the six battery packs 101-106 into three pack groups. The BMS 200 can divide the multiple battery packs 101-106 into three pack groups, i.e., first to third pack groups, and determine the battery packs that belong to each of the three pack groups. For example, the BMS 200 can generate a first pack group including the first and second battery packs 101, 102, a second pack group including the third and fourth battery packs 103, 104, and a third pack group including the fifth and sixth battery packs 105, 106.

[0087] When multiple pack groups are discharged in a predetermined discharge cycle, the BMS 200 can determine an order in which the multiple pack groups are discharged in each cycle (hereinafter, "multiple discharge orders"). Here, the discharge cycle can indicate the number of times the battery device 100 is discharged from a fully charged state to a fully discharged state. Here, the fully charged state of the battery device 100 can indicate a state in which all of the pack voltages of the multiple battery packs 101-106 are equal to or higher than a predetermined charging upper limit voltage, and the fully discharged state of the battery device 100 can indicate a state in which all of the n pack groups include battery packs whose voltages are equal to or lower than a discharge lower limit voltage. The predetermined charging upper limit voltage can be a predetermined value or a predetermined range that indicates that the battery packs are fully charged.

[0088] The BMS 200 can determine multiple discharge patterns such that the average pre-discharge pause time and / or the average post-discharge pause time are uniform in a discharge pattern cycle for multiple pack groups. The discharge pattern cycle refers to a cycle in which multiple discharge patterns are performed for multiple pack groups. For example, the first discharge pattern for the multiple pack groups is in the order of the first pack group, the second pack group, and the third pack group, the second discharge pattern is in the order of the second pack group, the third pack group, and the first pack group, and the third discharge pattern is in the order of the third pack group, the first pack group, and the second pack group. One discharge pattern cycle includes the first discharge pattern, the second discharge pattern, and the third discharge pattern, and the discharge pattern cycle is repeated.

[0089] BMS200 can calculate the average pre-discharge rest time by adding up the time that a pack group rests before discharging in each of multiple discharge patterns belonging to a discharge pattern cycle for one pack group and dividing the sum by the number of discharge patterns.

[0090] BMS200 can determine multiple discharge patterns such that a difference between an average pause time before discharge of any one of the multiple pack groups and an average pause time before discharge of another one of the multiple pack groups is small. BMS200 can also determine multiple discharge patterns such that a difference between an average pause time after discharge of any one of the multiple pack groups and an average pause time after discharge of another one of the multiple pack groups is small.

[0091] In the following description, it is assumed that the number of the multiple discharge patterns is n.

[0092] The BMS 200 can determine n different discharge patterns corresponding to one discharge pattern cycle.

[0093] BMS200 can determine the discharge pattern cycle so that the average time that any one of the multiple pack groups rests before discharging in each discharge pattern is the same as the average time that any other one of the multiple pack groups rests before discharging in each discharge pattern, and / or so that the average time that any one of the multiple pack groups rests after discharging in each discharge pattern is the same as the average time that any other one of the multiple pack groups rests after discharging in each discharge pattern.

[0094] For example, the first discharge pattern for multiple pack groups is the first pack group, the second pack group, and the third pack group in that order, the second discharge pattern is the second pack group, the third pack group, and the first pack group in that order, and the third discharge pattern is the third pack group, the first pack group, and the second pack group in that order.The description will be given assuming that the discharge time for each pack group in the first discharge pattern cycle is one hour.

[0095] Each pack group is considered to pause while the other pack groups are discharged. The pause times before discharge of the first pack group are 0 hours, 2 hours, and 1 hour in the first to third discharge patterns, respectively, so that the average pause time before discharge of the first pack group in the first discharge pattern cycle is 1 hour. The pause times before discharge of the second pack group are 1 hour, 0 hours, and 2 hours in the first to third discharge patterns, respectively, so that the average pause time before discharge of the second pack group in the first discharge pattern cycle is 1 hour. The pause times before discharge of the third pack group are 2 hours, 1 hour, and 0 hours in the first to third discharge patterns, respectively, so that the average pause time before discharge of the third pack group in the first discharge pattern cycle is 1 hour. Therefore, the average pause time before discharge of any one of the multiple pack groups in each discharge pattern is the same as the average pause time before discharge of another one of the multiple pack groups in each discharge pattern.

[0096] Similarly, the post-discharge downtime of the first pack group is 2 hours, 0 hours, and 1 hour for the first to third discharge patterns, respectively, so the average post-discharge downtime of the first pack group in the first discharge pattern cycle is 1 hour. And, the post-discharge downtime of the second pack group is 1 hour, 2 hours, and 0 hours for the first to third discharge patterns, respectively, so the average post-discharge downtime of the second pack group in the first discharge pattern cycle is 1 hour. Similarly, the post-discharge downtime of the third pack group is 0 hours, 1 hour, and 2 hours for the first to third discharge patterns, respectively, so the average post-discharge downtime of the third pack group in the first discharge pattern cycle is 1 hour. Therefore, the average post-discharge downtime of any one of the multiple pack groups in each discharge pattern is the same as the average post-discharge downtime of any other one of the multiple pack groups in each discharge pattern.

[0097] By determining a plurality of discharge patterns in a discharge pattern cycle, the BMS 200 can sequentially perform a discharge operation on a plurality of pack groups according to the discharge pattern cycle.

[0098] Hereinafter, when the BMS200 determines the first discharge pattern in the order of the first pack group, the second pack group, and the third pack group, the operation of the BMS200 to sequentially discharge each of the multiple pack groups according to the first discharge pattern will be described with reference to steps S101 to S109.

[0099] The BMS 200 can cause the first pack group to perform a discharging operation using a first discharging pattern (S101). The BMS 200 can turn on the switches SW1 and SW2 connected to the first battery pack 101 and the second battery pack 102 belonging to the first pack group via a plurality of switches SW1-SW6, and can turn off the switches SW3-SW6 connected to the third to sixth battery packs 103-106.

[0100] The BMS 200 can transmit switch control signals SS1 and SS2 of an on level to the switches SW1 and SW2 to close the switches SW1 and SW2. The BMS 200 can transmit switch control signals SS3-SS6 of an off level to the switches SW3-SW6 to open the switches SW3-SW6. Here, the turned-off third to sixth battery packs 103-106 are considered to be in a hibernation state.

[0101] The BMS 200 may monitor the on-pack voltage (S102). In steps S102 and S103, the on-pack voltage includes the pack voltages of the first battery pack 101 and the second battery pack 102. The BMS 200 may derive the on-pack voltage from the voltage measurement signals VS1 and VS2.

[0102] The BMS 200 can determine whether at least one of the on-pack voltages has reached a predetermined lower discharge voltage limit (S103).

[0103] Hereinafter, the determination of whether at least one of the on-pack voltages has reached a predetermined lower discharge limit voltage is, as described above, for the purpose of preventing the lithium-sulfur secondary battery cells from discharging again after going into a hibernation state during discharging and for discharging the battery pack during discharging to the lower discharge limit voltage, thereby improving the life of the lithium-sulfur secondary battery.

[0104] In addition, the BMS 200 can monitor the pack voltage of each of the battery packs 101-106 and determine whether all of the pack groups include a battery pack whose voltage is equal to or lower than the lower discharge limit. When all of the pack groups include a battery pack whose voltage is equal to or lower than the lower discharge limit, the BMS 200 can end the discharge operation.

[0105] If at least one of the on-pack voltages does not reach the predetermined lower discharge voltage limit in step S103, step S102 can be repeated.

[0106] If at least one of the on-pack voltages reaches a predetermined lower-limit discharge voltage in step S103, the BMS 200 can turn off the switches connected to the battery packs belonging to the first pack group that is currently discharging, and can discharge the second pack group, which is the next battery pack to be discharged, according to the first discharge pattern (S104). The BMS 200 can turn on the switches SW3 and SW4 connected to the third battery pack 103 and the fourth battery pack 104 belonging to the second pack group via the multiple switches SW1-SW6, and can turn off the switches SW1, SW2, SW5, and SW6 connected to the first, second, fifth, and sixth battery packs 101, 102, 105, and 106.

[0107] The BMS 200 can transmit switch control signals SS3 and SS4 of an on level to the switches SW3 and SW4 to close the switches SW3 and SW4. The BMS 200 can transmit switch control signals SS1, SS2, SS5, and SS6 of an off level to the switches SW1, SW2, SW5, and SW6 to open the switches SW1, SW2, SW5, and SW6. Here, the first, second, fifth, and sixth battery packs 101, 102, 105, and 106 that are turned off are considered to be in a hibernation state.

[0108] The BMS 200 may monitor the on-pack voltage (S105). In steps S105 and S106, the on-pack voltage includes the pack voltages of the third battery pack 103 and the fourth battery pack 104. The BMS 200 may derive the on-pack voltage from the voltage measurement signals VS3 and VS4.

[0109] The BMS 200 can determine whether at least one of the on-pack voltages has reached a predetermined lower discharge voltage limit (S106).

[0110] In addition, the BMS 200 can monitor the pack voltage of each of the battery packs 101-106 and determine whether all of the pack groups include a battery pack whose voltage is equal to or lower than the lower discharge limit. When all of the pack groups include a battery pack whose voltage is equal to or lower than the lower discharge limit, the BMS 200 can end the discharge operation.

[0111] If at least one of the on-pack voltages does not reach the predetermined lower discharge voltage limit in step S106, step S105 can be repeated.

[0112] If at least one of the on-pack voltages reaches a predetermined lower-limit discharge voltage in step S106, the BMS 200 turns off the switches connected to the battery packs belonging to the second pack group that are in the discharging operation, and can discharge the third pack group, which is next in the discharging order, according to the first discharging pattern (S107). The BMS 200 can turn on the switches SW5 and SW6 connected to the fifth battery pack 105 and the sixth battery pack 106 belonging to the third pack group via the multiple switches SW1-SW6, and can turn off the switches SW1-SW4 connected to the first to fourth battery packs 101-104.

[0113] The BMS 200 can transmit switch control signals SS5 and SS6 of an on level to the switches SW5 and SW6 to close the switches SW5 and SW6. The BMS 200 can transmit switch control signals SS1-SS4 of an off level to the switches SW1-SW4 to open the switches SW1-SW4. Here, the first to fourth battery packs 101-104 that are turned off are considered to be in a hibernation state.

[0114] The BMS 200 may monitor the on-pack voltages (S108). In steps S108 and S109, the on-pack voltages include the pack voltages of the fifth battery pack 105 and the sixth battery pack 106. The BMS 200 may derive the on-pack voltages from the voltage measurement signals VS5 and VS6.

[0115] The BMS 200 can determine whether at least one of the on-pack voltages has reached a predetermined lower discharge voltage limit (S109).

[0116] In addition, the BMS 200 can monitor the pack voltage of each of the battery packs 101-106 and determine whether all of the pack groups include a battery pack whose voltage is equal to or lower than the lower discharge limit. When all of the pack groups include a battery pack whose voltage is equal to or lower than the lower discharge limit, the BMS 200 can end the discharge operation.

[0117] If at least one of the on-pack voltages does not reach the predetermined lower discharge voltage limit in step S109, step S108 can be repeated.

[0118] If at least one of the on-pack voltages reaches a predetermined lower-limit discharge voltage in step S109, the BMS 200 may end the discharge operation according to the first discharge pattern.

[0119] In an embodiment, if at least one of the on-pack voltages reaches a predetermined lower limit voltage in step S103, S106, or S109, the BMS 200 can monitor the pack voltages of the battery packs 101-106 to determine whether all of the pack groups include a battery pack whose voltage is equal to or lower than the lower limit voltage. If at least one of the on-pack voltages reaches a predetermined lower limit voltage in step S103, S106, or S109, and all of the pack groups include a battery pack whose voltage is equal to or lower than the lower limit voltage, the BMS 200 can terminate the discharge operation according to the first discharge pattern. If at least one of the on-pack voltages reaches a predetermined lower limit voltage in step S103, S106, or S109, and there is a pack group among the pack groups that does not include a battery pack whose voltage is equal to or lower than the lower limit voltage, the BMS 200 can cause the pack groups among the pack groups that do not include a battery pack whose voltage is equal to or lower than the lower limit voltage to perform a discharge operation according to the discharge order of the first discharge pattern.

[0120] If at least one of the on-pack voltages reaches the predetermined lower-limit discharge voltage in step S109, all of the pack groups include battery packs whose voltages are equal to or lower than the lower-limit discharge voltage, and therefore the BMS 200 ends the discharge operation according to the first discharge pattern. When the discharge operation according to the first discharge pattern is ended, the BMS 200 can turn off the switches SW1-SW6.

[0121] When discharging is performed through steps S101 to S109, each of the battery packs 101-106 is in a hibernation state for a period obtained by multiplying the number of pack groups minus 1 by the discharge time of each of the battery packs 101-106. If the number of pack groups is n and the discharge time of each of the battery packs 101-106 is t1 (unit: sec), the hibernation period of each of the battery packs 101-106 is t1*(n-1) (unit: sec).

[0122] For example, assuming that the discharge time of each of the battery packs 101-106 is one hour and the number of pack groups is three, the first battery pack 101 performs a discharge operation during the period corresponding to steps S101 to S103 and goes into a hibernation state during the period corresponding to steps S104 to S109, so that the first battery pack 101 has a hibernation period of only 1(h)*2=2 hours. In this way, each of the battery packs 101-106 can have a hibernation period of several hours.

[0123] In this manner, the BMS 200 can sequentially perform discharge operations on each of a plurality of pack groups using a plurality of discharge patterns in a discharge pattern cycle.

[0124] In one embodiment, the BMS 200 can determine the number of pack groups (n) based on the discharge rate of the battery device 100 required by the load and the reference discharge rate of the battery packs.

[0125] Hereinafter, with reference to FIG. 5, a method in which the BMS 200 divides m battery packs based on the discharge rate of the battery device 100 required by the load and the reference discharge rate of each of the plurality of packs, derives the number (n) of pack groups to be subjected to discharge operation, and determines a discharge pattern cycle in step S100 of FIG. 4 will be described.

[0126] FIG. 5 is a detailed flowchart of step S100 in FIG.

[0127] Hereinafter, any overlapping description of the above-mentioned battery system 1 may be omitted.

[0128] The BMS 200 may store in advance the discharge rate (C_DEVICE) of the battery device 100 required by the load and the reference discharge rate (C_PK) of the battery pack (S201).

[0129] The BMS 200 can determine the number (n) of pack groups by dividing the reference discharge rate (C_PK) of each of the plurality of battery packs 101-106 by the discharge rate (C_DEVICE) of the battery device 100 required by the load (S202).

[0130] For example, if the discharge rate (C_DEVICE) of the battery device 100 required by the load is 0.1 [C] and the reference discharge rate (C_PK) of each of the multiple battery packs 101-106 is 0.3 [C], then the number of pack groups n=C_PK / C_DEVICE=3.

[0131] The BMS 200 can derive the number (p) of battery packs belonging to each of the n pack groups based on the number (n) of pack groups and the number (m) of the plurality of battery packs 101-106 (S203).

[0132] For example, if the number (n) of pack groups is 3 and the number (m) of battery packs 101-106 is 6, then the number of battery packs belonging to each pack group is p=m / n=2.

[0133] BMS200 can determine the battery packs that belong to each of the n pack groups based on the number of pack groups (n), or based on the number of pack groups (n) and the number of battery packs (p) that belong to each of the n pack groups (S204).

[0134] The BMS 200 can determine the battery packs that belong to each pack group by any method that ensures that the multiple battery packs 101-106 belong evenly to each of the n pack groups.

[0135] For example, the BMS 200 can determine, among the multiple battery packs 101-106, the first and second battery packs 101, 102 as a first pack group, the third and fourth battery packs 103, 104 as a second pack group, and the fifth and sixth battery packs 105, 106 as a third pack group.

[0136] The BMS 200 can determine one pack group to be subjected to a discharging operation from among the multiple pack groups (S205).

[0137] When determining one pack group to perform discharging operation, BMS200 can determine multiple discharge patterns that constitute a discharge pattern cycle for multiple pack groups, and determine one pack group to perform discharging operation from among the multiple pack groups.

[0138] The BMS 200 can determine multiple discharge patterns such that the average pre-discharge downtime and / or the average post-discharge downtime are uniform in the discharge pattern cycle for multiple pack groups.

[0139] In the specification, it has been described that each of the multiple pack groups includes at least one battery pack including one or more battery cells, but this is for convenience of explanation and the invention is not limited to this.

[0140] In one embodiment, each of the plurality of pack groups may represent one battery cell, and in this case, at least one battery pack belonging to each of the plurality of pack groups may be replaced by each battery cell, and the pack voltage may be replaced by the cell voltage of each battery cell. In other words, the BMS 200 may cause only one of the plurality of battery cells to perform a discharge operation, and turn off the switches connected to the remaining plurality of cells, so that the discharge rate of the battery cell performing the discharge operation belongs to the reference discharge rate.

[0141] Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited to these embodiments, and various modifications and improvements made by those having ordinary skill in the art to which the present invention pertains also fall within the scope of the present invention.

Claims

1. A battery device including a plurality of battery packs connected in parallel; a plurality of switches connected in series to one of both ends of each of the plurality of battery packs; a battery management system (BMS) that divides the battery packs into a plurality of pack groups, determines at least one battery pack belonging to each of the plurality of pack groups, determines one pack group to be subjected to a discharging operation from the plurality of pack groups, and transmits a switch control signal to turn on at least one switch connected to the one pack group from the plurality of switches and to turn off the remaining switches from the plurality of switches except for the at least one switch; Including, Each of the plurality of battery packs includes: a plurality of battery cells each including metallic phase lithium in said anode material; Battery system.

2. a discharge rate of the battery device for supplying power required by a load coupled to the battery device is a first discharge rate; each of the plurality of pack groups is operated to discharge at a second discharge rate greater than the first discharge rate; The battery system of claim 1 .

3. The BMS includes: determining the number of the plurality of pack groups by dividing a reference discharge rate for each of the plurality of battery packs by a discharge rate of the battery device, and determining the number of the plurality of battery packs belonging to each of the plurality of pack groups by dividing the number of the plurality of battery packs by the number of the plurality of pack groups; The battery system of claim 2 .

4. The BMS includes: determining a plurality of discharge patterns constituting the discharge pattern cycle for the plurality of pack groups such that a difference between an average of a rest time before discharge of any one of the plurality of pack groups and an average of a rest time before discharge of any other of the plurality of pack groups is small; The battery system of claim 1 .

5. a positive electrode material of each of the plurality of battery cells includes elemental sulfur; the plurality of discharge patterns includes a first discharge pattern in which a first pack group and a second pack group are arranged in that order among the plurality of pack groups, The BMS includes: performing a discharging operation on the first pack group, and monitoring whether at least one of the pack voltages of each of at least one first battery pack belonging to the first pack group is equal to or lower than a predetermined lower limit voltage of discharge; The battery system according to claim 4 .

6. If at least one of the pack voltages of each of the at least one first battery pack is equal to or lower than a predetermined discharge lower limit voltage, The BMS includes: turning off a switch connected to each of the at least one first battery pack, discharging the second pack group, and monitoring whether at least one of the pack voltages of each of the at least one second battery pack belonging to the second pack group is equal to or lower than a predetermined lower limit discharge voltage; The battery system according to claim 5 .

7. The BMS includes: turning off the switches when all of the pack groups include a battery pack whose discharge voltage is equal to or lower than a predetermined lower limit voltage; The battery system according to claim 5 .

8. A method for connecting a battery pack in a battery system including a battery device including a plurality of battery packs connected in parallel, comprising: A battery management system (BMS) connected to the battery device divides the plurality of battery packs into a plurality of pack groups; determining at least one battery pack belonging to each of the plurality of pack groups; determining one pack group to be subjected to a discharging operation from among the plurality of pack groups; transmitting a switch control signal to turn on at least one switch connected to the one pack group among a plurality of switches and to turn off the remaining switches of the plurality of switches except for the at least one switch; Each of the plurality of battery packs includes: a plurality of battery cells each including metallic phase lithium in said anode material; Pack connection method.

9. a discharge rate of the battery device for supplying power required by a load coupled to the battery device is a first discharge rate; each of the plurality of pack groups is operated to discharge at a second discharge rate greater than the first discharge rate; The method for connecting packs according to claim 8.

10. determining a number of the plurality of pack groups by dividing a reference discharge rate for each of the plurality of battery packs by a discharge rate of the battery device; and determining a number of battery packs belonging to each of the plurality of pack groups by dividing the number of the plurality of battery packs by the number of the plurality of pack groups. The method for connecting packs according to claim 8.

11. determining one pack group to be subjected to a discharging operation from among the plurality of pack groups, determining a plurality of discharge patterns constituting the discharge pattern cycle for the plurality of pack groups such that a difference between an average of a pause time before discharge of any one of the plurality of pack groups and an average of a pause time before discharge of any other of the plurality of pack groups is small, The method for connecting packs according to claim 8.

12. a positive electrode material of each of the plurality of battery cells includes elemental sulfur; the plurality of discharge patterns includes a first discharge pattern in which a first pack group and a second pack group are arranged in that order among the plurality of pack groups, The step of transmitting the switch control signal comprises: performing a discharging operation on the first pack group, and monitoring whether at least one of the pack voltages of each of at least one first battery pack belonging to the first pack group is equal to or lower than a predetermined lower limit voltage of discharge; The method of connecting packs according to claim 11.

13. If at least one of the pack voltages of each of the at least one first battery pack is equal to or lower than a predetermined discharge lower limit voltage, turning off a switch connected to each of the at least one first battery pack to discharge the second pack group; and monitoring whether at least one of the pack voltages of each of the at least one second battery pack belonging to the second pack group is equal to or lower than a predetermined lower discharge limit voltage. The method of connecting packs according to claim 12.

14. When all of the plurality of pack groups include a battery pack having a predetermined discharge lower limit voltage or lower, further comprising turning off the plurality of switches. The method of connecting packs according to claim 12.

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