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, filed December 23, 2022, and Korean Patent Application No. 10-2023-0124691, filed 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 just 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 enables 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 when the battery device performs a discharge operation. [Means for solving the problem]

[0006] According to one aspect 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 end 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 perform a discharging operation, and transmits switch control signals 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, wherein each of the plurality of battery packs includes a plurality of battery cells each containing metallic phase lithium in a negative electrode material.

[0007] The discharge rate of the battery device for supplying the power required by the 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 the difference between the average pre-discharge rest time of any one of the plurality of pack groups and the average pre-discharge rest time of another of the plurality of pack groups is small.

[0010] The positive electrode material of each of the plurality of battery cells contains elemental sulfur, 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 can discharge the first pack group and monitor 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 equal to or lower than a predetermined lower discharge limit voltage, the BMS can turn off a switch connected to each of the at least one first battery pack, cause the second pack group to perform a discharge operation, 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 equal to or lower than a predetermined lower discharge limit voltage.

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

[0013] According to another aspect of the present invention, a pack connection method is a pack connection method for a battery system including a battery device including a plurality of battery packs connected in parallel, the method including the steps of: a battery management system (BMS) connected to the battery device dividing 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 from the plurality of pack groups to perform a discharging operation; and transmitting 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, wherein each of the plurality of battery packs includes a plurality of battery cells each containing metallic phase lithium in a negative electrode material.

[0014] The discharge rate of the battery device for supplying the power required by the 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 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 another of the plurality of pack groups is small in the 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 sequentially discharged among the plurality of pack groups, and the step of transmitting the switch control signal may include a 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 plurality of pack groups include battery packs whose discharge voltage is equal to or lower than a predetermined lower limit voltage. [Effects 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 the battery device for supplying the power required by the 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 completion 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 negative electrode can be overcome by using BMS without any changes in materials or cell technology. [Brief explanation of the drawings]

[0023] [Figure 1] FIG. 1 is a block diagram that schematically illustrates a battery system according to one embodiment. [Figure 2] FIG. 1 shows the morphology of the lithium metal surface as a function of different stripping rates in a lithium metal battery. [Figure 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] 1 is a flowchart of a pack connection method using a battery system according to an embodiment. [Figure 5] 5 is a detailed flowchart of step S100 in FIG. 4. DETAILED DESCRIPTION OF THE INVENTION

[0024] Hereinafter, the embodiments disclosed herein will be described in detail with reference to the accompanying drawings. Identical or similar components will be designated by the same or similar drawing numbers, and redundant descriptions thereof will be omitted. The suffixes "module" and / or "section" for components used in the following description are given or used interchangeably solely for the convenience of writing the specification, and do not have any distinct meanings or functions. Furthermore, when describing the embodiments disclosed herein, if it is determined that a detailed description of such well-known technology may obscure the gist of the embodiments disclosed herein, the detailed description will be omitted. Furthermore, the accompanying drawings are merely intended to facilitate understanding of the embodiments disclosed herein, and it should be understood that the accompanying drawings do not limit the technical concept disclosed herein, and all modifications, equivalents, or alternatives within the concept and technical scope of the present invention are included.

[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, the use of terms such as "comprise" or "have" is intended to specify the presence of a feature, number, step, operation, component, part, or combination thereof stated in the specification, but does not preclude the possible presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0027] According to an embodiment, a component that controls another component under a specific control condition is provided with a program implemented by a set of commands that embody a control algorithm required to control the other component. The control component can process input data and stored data using the provided program to generate output data. The control component can include a non-volatile memory that stores the program and a memory that stores data.

[0028] FIG. 1 is a block diagram that schematically 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 each including two or more battery cells connected in parallel, or two or more battery cells connected in parallel. While FIG. 1 illustrates 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 or 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, the operation of connecting both ends P+ and P- of the battery system 1 to the charger and receiving power from the charger to be charged will be referred to as a "charging operation."

[0033] When the external device 2 is a load, both terminals 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 decreases will be 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 using lithium (Li) metal as an anode. Specifically, the anode material of each of the battery cells included in each of the battery packs 101-106 may include metallic phase lithium.

[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 location in the lithium metal anode material, other lithium metal ions are likely to be stripped from locations where lithium metal has already been stripped, such as corners of the lithium deposits and points of large curvature in the lithium deposits. Furthermore, in a lithium metal battery discharged at a low discharge rate, lithium metal stripping from the surface is less uniform than in a lithium metal battery discharged at a high discharge rate, and metal ions are stripped at locations where they are more likely to be stripped.

[0037] During the charge and discharge process of a lithium metal battery, irregular deposition of lithium metal or irregular stripping of lithium ions causes irregular lithium ions on the surface of the negative electrode, forming lithium dendrites that point from the negative electrode surface toward the positive electrode surface. When a lithium metal battery is repeatedly charged and discharged, these lithium dendrites accumulate excessively and may penetrate the separator, causing an internal short circuit between the negative and positive electrodes.

[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 depending on the different stripping rates of a lithium metal battery.

[0040] 2A shows the shape of a lithium deposit that occurs when irregular lithium metal deposits occur during charging of a lithium metal battery. Referring to FIG. 2A, the irregular lithium metal deposits may include narrow spots 21.

[0041] If lithium metal is stripped from the lithium deposit shown in FIG. 2(A) at a high rate, the irregular lithium metal deposit can return to a shape with almost no deposit, as shown in FIG. 2(A1), due to high reversibility.

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

[0043] Referring to FIG. 2(A2), the irregular deposit 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 this separates the area 23 in the lithium deposit from the narrow point 22. The irregular surface also facilitates the formation of lithium dendrites.

[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, irregular lithium metal growth primarily originates from variations in surface current density, and when a 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] As such, when a lithium metal battery is discharged at a low discharge rate below a predetermined level, early degradation of the lithium metal battery cells may occur. When the first discharge rate is lower than the second discharge rate, each of the plurality of battery packs 101-106 is more likely to degrade early when discharged at the first discharge rate than when discharged at the second discharge rate. In other words, a higher discharge rate is more advantageous in terms of the degree of degradation of the lithium metal battery. Based on this, the BMS 200 according to one embodiment may control the discharge of the plurality of battery packs 101-106 so that the plurality of battery packs 101-106 are discharged at a high discharge rate equal to or higher than a predetermined level.

[0048] Alternatively, in some embodiments, 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, as a positive electrode active material, elemental sulfur (e.g., S) having a sulfur-sulfur bond (SS bond) or a sulfur-containing complex.

[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 lithium contained in the negative electrode occur within each electrode and electrolyte. As these continuous oxidation / reduction reactions occur, various 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 lithium polysulfide formation through the continuous oxidation / reduction reaction, some of the lithium polysulfide dissolved in the electrolyte may undergo side reactions with the anode, which may be one of the factors that reduce the life characteristics of lithium-sulfur secondary batteries.

[0051] As such, the frequency of side reactions, in which some of the lithium polysulfide dissolved in the electrolyte reacts with the negative electrode, increases with increasing discharge time. In other words, to reduce the frequency of side reactions, it is necessary to shorten the discharge time of the lithium-sulfur secondary battery cell and control the discharge rate. When a lithium-sulfur secondary battery cell enters 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 shortening the discharge time are advantageous in terms of the lifespan 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 they are fully discharged. Hereinafter, the on-pack voltage refers to the pack voltage of at least one battery pack having a connected switch among the plurality of switches SW1-SW6 turned on.

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

[0054] The BMS 200 can divide the multiple battery packs 101-106 into multiple pack groups and determine at least one pack group from the multiple pack groups to discharge. 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 from the multiple pack groups to discharge based on the discharge rate of the battery device 100 for supplying power required by the load (hereinafter referred to as the "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 can discharge only some of the pack groups at a high discharge rate (C-rate) without discharging all of the multiple 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 be 0.3C.

[0059] In one embodiment, the number of pack groups (n) may be pre-stored in the BMS 200. 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.

[0060] In one embodiment, the BMS 200 may pre-store 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 of pack groups (n) based on the pre-stored discharge rate of the battery device 100 required by the load and the reference discharge rate of the battery packs. Furthermore, based on the derived number of pack groups (n) and the number (m) of the plurality of 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 discharge 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 discharge at a discharge rate corresponding 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 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 such that 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 the 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 plurality of battery cells included in each of the plurality of battery packs 101-106 is a lithium-sulfur secondary battery, the BMS 200 may cause p battery packs included in a pack group that has started a discharging operation among n pack groups to maintain a discharging state until the discharging is completed without pausing in between, thereby improving the lifespan of the plurality of battery cells undergoing the discharging operation.

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

[0065] In the specification, completion of discharge may refer to 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 discharge voltage. The predetermined lower limit discharge voltage may be a predetermined value or a predetermined range that indicates that the battery pack is fully discharged. For example, in one embodiment, the predetermined lower limit discharge voltage may be 1.5 to 1.9 V, and in another embodiment, the predetermined lower limit discharge voltage may be 1.8 V.

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

[0067] The BMS 200 determines a pack group to perform a discharging operation from among the plurality of pack groups and turns on a switch connected to the determined pack group from among the plurality of switches SW1-SW6. This allows the corresponding battery pack to be connected to the node N1. The discharging operation may include an operation for supplying power to the outside. Here, if there are two or more battery packs among the plurality of battery packs 101-106 that perform a discharging operation, the battery packs may be connected in parallel to each other.

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

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

[0070] One end of switch SW1 is connected to relay 300 at node N1, and the other end of switch SW1 is connected to the positive terminal of battery pack 101. One end of switch SW2 is connected to relay 300 at node N1, and the other end of switch SW2 is connected to the positive terminal of battery pack 102. One end of switch SW3 is connected to relay 300 at node N1, and the other end of switch SW3 is connected to the positive terminal of battery pack 103. One end of switch SW4 is connected to relay 300 at node N1, and the other end of switch SW4 is connected to the positive terminal of battery pack 104. One end of switch SW5 is connected to relay 300 at node N1, and the other end of switch SW5 is connected to the positive terminal of battery pack 105. One end of the switch SW6 is coupled to the relay 300 at 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 which is coupled to one end of each of the battery packs 101-106 via a plurality of wires LN1-LN6, respectively. The BMS 200 may receive a plurality of voltage measurement signals VS1-VS6 via the plurality of terminals P1-P6.

[0073] The positive terminal of battery pack 101 is connected to terminal P1 via wiring LN1, and the BMS 200 can acquire a voltage measurement signal VS1 measured from the positive terminal of battery pack 101 via terminal P1. The positive terminal of battery pack 102 is connected to terminal P2 via wiring LN2, and the BMS 200 can acquire a voltage measurement signal VS2 measured from the positive terminal of battery pack 102 via terminal P2. The positive terminal of battery pack 103 is connected to terminal P3 via wiring LN3, and the BMS 200 can acquire a voltage measurement signal VS3 measured from the positive terminal of battery pack 103 via terminal P3. The positive terminal of battery pack 104 is connected to terminal P4 via wiring LN4, and the BMS 200 can acquire a voltage measurement signal VS4 measured from the positive terminal of battery pack 104 via terminal P4. The positive terminal of the battery pack 105 is connected 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 connected 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 voltage of each of the battery packs 101-106 from the voltage measurement signals VS1-VS6, and can monitor the pack voltage of the battery pack connected to the closed switch among 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 battery pack belonging to the pack group performing the discharging operation is connected, and then turn on the switches to which each battery pack 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 at an on level to the switches SW1-SW6, and when the switches SW1-SW6 are closed, the battery packs 101-106 are charged.

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

[0078] Below, we will explain the battery life (cycle life) according to the C-rate, which indicates the battery discharge rate, when the remaining life capacity (retention) is 80%, with reference to Figure 3. When the discharge rate (C-rate) is 0.1C, the battery life is 90 cycles, and when the C-rate is 0.3C, the battery life is 147 cycles. Therefore, when the C-rate increases threefold from 0.1C to 0.3C, the battery 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 discharging operation on each of them, thereby discharging only some of the battery packs 101-106. The discharge rate of the battery device 100 is calculated by dividing the total discharge rate of the battery packs performing the discharging operation by the number of battery packs 101-106. For example, if the discharge rate of each of the battery packs 101-106 is 0.3 C and only two of the six battery packs 101-106 are performed a discharging operation, the discharge rate of the battery device 100 is 0.3*2 / 6=0.1 C. 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, thereby providing a battery system 1 that is advantageous in terms of the lifespan of each of the battery packs 101-106.

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

[0081] Hereinafter, duplicated explanations 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 plurality of battery packs 101-106 into a plurality of pack groups (S100). The BMS 200 may have information about the number of pack groups (n) stored in advance, or the BMS 200 may determine the number 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. The BMS 200 can determine at least one battery pack belonging to each of the plurality of pack groups. The BMS 200 can sequentially perform a discharge operation on each of the plurality of pack groups.

[0083] The BMS 200 can cause at least one battery pack belonging to one pack group among the plurality of battery packs 101-106 to perform a discharging operation, and can place the remaining battery packs in a dormant state. Therefore, when the number of plurality of pack groups is n, each of the plurality of battery packs 101-106 performing a discharging operation is discharged at a discharging rate that is n times the discharging rate 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 discharging operation can be doubled, that 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 discharging operation can be tripled, that 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 discharging operation can be quadrupled, that 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 plurality of battery packs 101-106 are 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 first and second battery packs 101, 102, a second pack group including third and fourth battery packs 103, 104, and a third pack group including fifth and sixth battery packs 105, 106.

[0087] When multiple pack groups are discharged in a predetermined discharge cycle, the BMS 200 can determine the 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 upper charge voltage limit, 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 lower discharge voltage limit. The predetermined upper charge voltage limit may 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 so that the average pre-discharge rest time and / or the average post-discharge rest time are uniform in a discharge pattern cycle for multiple pack groups. A discharge pattern cycle refers to a cycle in which multiple discharge patterns are performed for multiple pack groups. For example, a first discharge pattern for multiple pack groups is performed in the order of the first pack group, the second pack group, and the third pack group; a second discharge pattern is performed in the order of the second pack group, the third pack group, and the first pack group; and a third discharge pattern is performed 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 rest time before discharge by adding up the time that one pack group rests before discharge in each of multiple discharge patterns belonging to a discharge pattern cycle for one pack group and dividing the sum by the number of multiple discharge patterns.

[0090] The BMS200 can determine multiple discharge patterns so as to reduce the difference between the average pre-discharge rest time of any one of the multiple pack groups and the average pre-discharge rest time of another one of the multiple pack groups. The BMS200 can also determine multiple discharge patterns so as to reduce the difference between the average post-discharge rest time of any one of the multiple pack groups and the average post-discharge rest time of another one of the multiple pack groups.

[0091] The following description will be given on the assumption that the number of 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 order of the first pack group, the second pack group, and the third pack group, the second discharge pattern is the order of the second pack group, the third pack group, and the first pack group, and the third discharge pattern is the order of the third pack group, the first pack group, and the second pack group.The explanation 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 rest while the other pack groups are discharged. The pre-discharge rest time of the first pack group is 0 hours, 2 hours, and 1 hour for the first through third discharge patterns, respectively, so the average pre-discharge rest time of the first pack group in the first discharge pattern cycle is 1 hour. The pre-discharge rest time of the second pack group is 1 hour, 0 hours, and 2 hours for the first through third discharge patterns, respectively, so the average pre-discharge rest time of the second pack group in the first discharge pattern cycle is 1 hour. The pre-discharge rest time of the third pack group is 2 hours, 1 hour, and 0 hours for the first through third discharge patterns, respectively, so the average pre-discharge rest time of the third pack group in the first discharge pattern cycle is 1 hour. Therefore, the average pre-discharge rest time of any one of the multiple pack groups in each discharge pattern is the same as the average pre-discharge rest time of any other of the multiple pack groups in each discharge pattern.

[0096] Similarly, the post-discharge rest periods for the first pack group are 2 hours, 0 hours, and 1 hour for the first to third discharge patterns, respectively, so the average post-discharge rest period for the first pack group in the first discharge pattern cycle is 1 hour. The post-discharge rest periods for the second pack group are 1 hour, 2 hours, and 0 hours for the first to third discharge patterns, respectively, so the average post-discharge rest period for the second pack group in the first discharge pattern cycle is 1 hour. Similarly, the post-discharge rest periods for the third pack group are 0 hours, 1 hour, and 2 hours for the first to third discharge patterns, respectively, so the average post-discharge rest period for the third pack group in the first discharge pattern cycle is 1 hour. Therefore, the average post-discharge rest period for any one of the multiple pack groups in each discharge pattern is the same as the average post-discharge rest period for another 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 switches SW1 and SW2 connected to the first battery pack 101 and the second battery pack 102 belonging to the first pack group via multiple switches SW1-SW6, and can turn off switches SW3-SW6 connected to the third to sixth battery packs 103-106.

[0100] The BMS 200 can transmit on-level switch control signals SS1 and SS2 to the switches SW1 and SW2 to close the switches SW1 and SW2. The BMS 200 can transmit off-level switch control signals SS3-SS6 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 can 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 can 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, determining whether at least one of the on-pack voltages has reached a predetermined lower-limit discharge voltage is, as described above, for the purpose of preventing the lithium-sulfur secondary battery cells from discharging again after entering a hibernation state during discharging and ensuring that the battery pack in discharging operation is discharged to the lower-limit discharge voltage, thereby extending 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. If 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 terminate 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 turns 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 next in the discharge order, according to the first discharge pattern (S104). The BMS 200 can turn on 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 turn off 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 on-level switch control signals SS3 and SS4 to the switches SW3 and SW4 to close the switches SW3 and SW4. The BMS 200 can transmit off-level switch control signals SS1, SS2, SS5, and SS6 to the switches SW1, SW2, SW5, and SW6 to open the switches SW1, SW2, SW5, and SW6. Here, the turned-off first, second, fifth, and sixth battery packs 101, 102, 105, and 106 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. If 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 terminate 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 currently discharging, and can discharge the third pack group, which is next in the discharge sequence, according to the first discharge pattern (S107). The BMS 200 can turn on switches SW5 and SW6 connected to the fifth battery pack 105 and the sixth battery pack 106 belonging to the third pack group via multiple switches SW1-SW6, and turn off switches SW1-SW4 connected to the first through fourth battery packs 101-104.

[0113] The BMS 200 can transmit on-level switch control signals SS5 and SS6 to the switches SW5 and SW6 to close the switches SW5 and SW6. The BMS 200 can transmit off-level switch control signals SS1-SS4 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. If 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 terminate 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 terminate the discharge operation according to the first discharge pattern.

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

[0120] If at least one of the on-pack voltages reaches the predetermined lower-limit discharge voltage in step S109, all of the plurality of 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. After the discharge operation according to the first discharge pattern is ended, the BMS 200 can turn off the plurality of switches SW1-SW6.

[0121] When the discharge operation is performed through steps S101 to S109, each of the battery packs 101-106 is in a dormant 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 dormant 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 enters a sleep state during the period corresponding to steps S104 to S109, so that the first battery pack 101 has a sleep period of 1(h)*2=2 hours. In this way, each of the battery packs 101-106 can have a sleep period of several hours.

[0123] In this way, the BMS 200 can sequentially discharge 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 will be described 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 discharged, and determines the discharge pattern cycle in step S100 of FIG. 4.

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

[0127] Hereinafter, duplicated explanations 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 plurality of 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 of pack groups (n) is 3 and the number of battery packs 101-106 (m) is 6, then the number of battery packs belonging to each pack group is p=m / n=2.

[0133] The 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 plurality of battery packs 101-106 belong evenly to each of the n pack groups.

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

[0136] The BMS 200 can determine one pack group to perform the discharging operation from among the plurality of 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 from the multiple pack groups to perform discharging operation.

[0138] The BMS 200 can determine multiple discharge patterns so that the average pre-discharge rest time and / or the average post-discharge rest time is uniform in discharge pattern cycles for multiple pack groups.

[0139] In the specification, it has been described that each of the plurality of 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 perform a discharge operation on only one of the plurality of battery cells 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 falls within 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 examples, and various modifications and improvements made by those skilled 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 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 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 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 a plurality of battery cells each including metallic phase lithium in an anode material; a discharge rate of the battery device for supplying power required by a load connected to the battery device is a first discharge rate; each of the plurality of pack groups operates to discharge at a second discharge rate greater than the first discharge rate; Battery system.

2. 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 1 .

3. The BMS includes: determining a plurality of discharge patterns constituting 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 another of the plurality of pack groups is small; The battery system of claim 1 .

4. the 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 discharged in this 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 discharge lower limit voltage; The battery system of claim 3 .

5. 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 discharge lower limit voltage; The battery system of claim 4 .

6. The BMS includes: turning off the switches when all of the plurality of pack groups include battery packs whose discharge voltage is equal to or lower than a predetermined lower limit voltage; The battery system of claim 4 .

7. A pack connection method for 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 a plurality of battery cells each including metallic phase lithium in an anode material; a discharge rate of the battery device for supplying power required by a load connected to the battery device is a first discharge rate; each of the plurality of pack groups operates to discharge at a second discharge rate greater than the first discharge rate; Pack connection method.

8. determining the number 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 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 pack connecting method according to claim 7.

9. The step of determining one pack group to perform a discharging operation from among the plurality of pack groups includes: determining a plurality of discharge patterns constituting 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 another of the plurality of pack groups is small, The pack connecting method according to claim 7.

10. the 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 discharged in this 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 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 limit discharge voltage; The pack connecting method according to claim 9.

11. 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 pack voltage 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. The pack connecting method according to claim 10.

12. When all of the plurality of pack groups include battery packs with a predetermined discharge lower limit voltage or less, further comprising turning off the plurality of switches. The pack connecting method according to claim 10.

Images