Battery system and battery pack connection method using same

Abstract

The invention relates to a battery system and a battery 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 the two terminals 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 battery pack groups, determines at least one battery pack belonging to each of the plurality of battery pack groups, determines one battery pack group to be subjected to a discharge operation from among the plurality of battery pack groups, and performs a discharge operation on the battery pack group. And transmitting a switching control signal for turning on at least one switch connected to one battery pack group from among a plurality of switches and turning off the remaining switches other than the at least one switch from among the plurality of switches, in which the plurality of battery packs each include metal lithium in a negative electrode material thereof.

Description

Technical Field

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to and the benefit of Korean Patent Application No. 10-2022-0183601 filed in the Korean Intellectual Property Office on December 23, 2022, and Korean Patent Application No. 10-2023-0124691 filed in the Korean Intellectual Property Office on September 19, 2023, the entire contents of which are incorporated herein by reference.

[0003] The present disclosure relates to a battery system and a battery pack connection method using the battery system. Background Art

[0004] When the battery cell included in the battery system is a secondary battery, the negative electrode material is as important as the positive electrode material in the battery. For the negative electrode of the battery, lithium metal can be used.

[0005] In a battery system including a battery cell having lithium metal as a negative electrode, the life of the battery may be shorter when the battery is discharged at a low discharge rate than when it is discharged at a high discharge rate. Therefore, measures to improve the battery life are discussed. Summary of the invention

[0006] Technical issues

[0007] The present disclosure is directed to a battery system and a method of connecting battery packs using the same, which allows the battery packs to be discharged at a discharge rate higher than the discharge rate of the battery device by using only some of the battery packs in a discharge operation of a battery device including the plurality of battery packs.

[0008] Technical Solution

[0009] A battery system according to one feature of the present invention includes: a battery device, the battery device including a plurality of battery packs connected in parallel; for each of the plurality of battery packs, a plurality of switches connected in series to one of the two ends of each battery pack; and a battery management system (BMS), the BMS being used to divide the plurality of battery packs into a plurality of battery groups, determine at least one battery group belonging to each of the plurality of battery groups, determine one battery group to be discharged among the plurality of battery groups, and send a switch control signal for turning on at least one switch connected to the one battery group among the plurality of switches, and turning off the remaining switches among the plurality of switches except the at least one switch, wherein each of the plurality of battery packs includes a plurality of battery cells including metallic phase lithium in their respective negative electrode materials.

[0010] A discharge rate of the battery device for supplying power required by a load connected to the battery device may be a first discharge rate, and each of the plurality of battery groups may perform a discharge operation at a second discharge rate greater than the first discharge rate.

[0011] The BMS may determine the number of the plurality of battery groups by dividing a reference discharge rate for each of the plurality of battery groups by a discharge rate of the battery device, and determine the number of battery groups belonging to each of the plurality of battery groups by dividing the number of the plurality of battery groups by the number of the plurality of battery groups.

[0012] The BMS may determine a plurality of discharge modes configured for discharge mode cycles of the plurality of battery groups so that a difference between an average value of rest time before discharge of any one of the plurality of battery groups and an average value of rest time before discharge of any other of the plurality of battery groups is smaller.

[0013] The positive electrode material of each of the multiple battery cells may include elemental sulfur, and the multiple discharge modes may include a first discharge mode that is a sequence of a first battery group and a second battery group among the multiple battery groups, and the BMS may cause the first battery group to perform a discharge operation and monitor whether at least one of the battery group voltages of at least one first battery group belonging to the first battery group is equal to or less than a predetermined discharge voltage lower limit.

[0014] When at least one of the battery pack voltages of the at least one first battery pack is equal to or less than the predetermined discharge voltage lower limit, the BMS can turn off the switch connected to each of the at least one first battery pack, so that the second battery pack group performs a discharge operation, and monitor whether at least one of the battery pack voltages of the at least one second battery pack belonging to the second battery pack group is equal to or less than the predetermined discharge voltage lower limit.

[0015] The BMS may turn off the plurality of switches when the plurality of battery pack groups all include battery packs having a voltage equal to or less than the predetermined discharge voltage lower limit.

[0016] According to another feature of the present invention, a battery pack connection method for a battery system includes a battery device having a plurality of battery packs connected in parallel, and the method includes the following steps: a battery management system (BMS) connected to the battery device divides the plurality of battery packs into a plurality of battery groups; determines at least one battery pack belonging to each of the plurality of battery groups; determines a battery group to be discharged among the plurality of battery groups; and sends a switch control signal to turn on at least one switch among the plurality of switches connected to the one battery group, and turns off the remaining switches among the plurality of switches except the at least one switch; wherein each of the plurality of battery groups includes: a plurality of battery cells, and the plurality of battery cells include metallic phase lithium in each negative electrode material.

[0017] A discharge rate of the battery device for supplying power required by a load connected to the battery device may be a first discharge rate, and each of the plurality of battery groups may perform a discharge operation at a second discharge rate greater than the first discharge rate.

[0018] The battery pack connection method may further include the following steps: determining the number of the multiple battery groups by dividing a reference discharge rate for each of the multiple battery packs by a discharge rate of the battery device; and determining the number of battery packs belonging to each of the multiple battery groups by dividing the number of the multiple battery packs by the number of the multiple battery groups.

[0019] The step of determining one battery group to be discharged among the multiple battery groups may include: determining multiple discharge modes configured for the discharge mode cycles of the multiple battery groups so that the difference between the average value of the rest time before discharge of any one of the multiple battery groups and the average value of the rest time before discharge of any other battery group among the multiple battery groups is smaller.

[0020] The positive electrode material of each of the multiple battery cells may include elemental sulfur, and the multiple discharge modes may include a first discharge mode, the first discharge mode is the order of a first battery group and a second battery group among the multiple battery groups, and the step of sending the switch control signal may include: causing the first battery group to perform a discharge operation, and monitoring whether at least one of the battery group voltages of at least one first battery group belonging to the first battery group is equal to or less than a predetermined discharge voltage lower limit.

[0021] The battery pack connection method may also include the following steps: when at least one of the battery pack voltages of the at least one first battery group is equal to or less than the predetermined discharge voltage lower limit, turning off the switch connected to each of the at least one first battery group so that the second battery group performs a discharge operation; and monitoring whether at least one of the battery pack voltages of the at least one second battery group belonging to the second battery group is equal to or less than the predetermined discharge voltage lower limit.

[0022] The battery pack connection method may further include the step of turning off the plurality of switches when the plurality of battery pack groups all include battery packs having a voltage equal to or less than the predetermined discharge voltage lower limit.

[0023] Beneficial Effects

[0024] According to the present disclosure, the formation of lithium dendrites that may occur when the battery pack is discharged at a low discharge rate can be suppressed, and premature degradation of each of the multiple battery packs can be prevented by discharging multiple battery packs including lithium metal batteries at a discharge rate higher than the discharge rate of a battery device used to provide power required by a load.

[0025] According to the present disclosure, in the case of a lithium-sulfur secondary battery among lithium metal batteries, dissolution of lithium polysulfide into an electrolyte can be suppressed by allowing the battery to be discharged to the end without pausing in the middle of the discharge operation, thereby improving the life of multiple battery packs.

[0026] According to the present disclosure, the premature degradation phenomenon occurring at a low discharge rate when lithium metal is used as the negative electrode can be solved by a BMS without making any changes to the materials or cell technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a block diagram schematically illustrating a battery system according to an exemplary embodiment.

[0028] Figure 2 is a diagram illustrating the shape of the lithium metal surface according to the difference in the peeling rate of the lithium metal battery.

[0029] Figure 3 This is a graph illustrating the relationship between the discharge rate and life of a battery cell using lithium metal as a negative electrode.

[0030] Figure 4 is a flowchart of a battery pack connection method using a battery system according to an exemplary embodiment.

[0031] Figure 5 yes Figure 4 Detailed flowchart of operation S100. DETAILED DESCRIPTION

[0032] Hereinafter, the exemplary embodiments disclosed in this specification will be described in detail with reference to the accompanying drawings, and regardless of the figure numerals, the same or similar constituent elements are represented by the same figure numerals, and their repeated description will be omitted. The suffixes "module" and "unit" of the constituent elements used in the following description are given or mixed only in consideration of the ease of writing the specification, and the suffixes themselves do not have a distinguishing meaning or role. In addition, when describing the exemplary embodiments disclosed in this specification, when it is determined that the detailed description related to the well-known function or configuration may make the subject matter of the exemplary embodiments disclosed in this specification unnecessarily obscure, the detailed description will be omitted. In addition, the accompanying drawings are provided to help easily understand the exemplary embodiments disclosed in this specification, and the technical spirit disclosed in this specification is not limited by the accompanying drawings, and it should be understood that the present invention includes all modifications, equivalents and substitutes contained in the spirit and technical scope of the present invention.

[0033] Terms including general numbers such as first and second are used to describe various constituent elements, but the constituent elements are not limited by the terms. The terms are used only to distinguish one constituent element from another constituent element.

[0034] In the present application, it should be understood that the terms "including" and "having" are intended to indicate the existence or a combination of the characteristics, quantities, steps, operations, constituent elements and components described in the specification, and do not exclude the possibility of pre-existing or adding one or more other characteristics, quantities, steps, operations, constituent elements and components or a combination thereof.

[0035] A program implemented as a set of instructions for implementing a control algorithm required to control another configuration may be installed in a configuration for controlling another configuration under specific control conditions among the configurations according to the exemplary embodiment. The control configuration may process input data and stored data according to the installed program to generate output data. The control configuration may include a non-volatile memory for storing the program and a memory for storing data.

[0036] Figure 1 is a block diagram schematically illustrating a battery system according to an exemplary embodiment.

[0037] 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 to SW6 .

[0038] The battery device 100 may include a plurality of battery packs 101 to 106 connected in parallel. Each of the plurality of battery packs 101 to 106 may be implemented as 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. Figure 1 , the number of battery packs 101 to 106 and the number of switches SW1 to SW6 are illustrated as six, but the present invention is not limited thereto, and the battery system 1 may include two or more battery packs and two or more switches.

[0039] One end of each of the relays 300 and 301 is connected to the battery device 100, and the other end of each of the relays 300 and 301 is connected to at least one configuration of the external device 2. Closing and opening of the relays 300 and 301 may be controlled according to relay control signals RSC1 and RSC2 provided from the BMS 200.

[0040] The battery system 1 can be connected to an external device 2. The external device 2 may 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 can be connected to the charger and charged by receiving power from the charger. Hereinafter, when the external device 2 is a charger, both ends P+ and P- of the battery system 1 are connected to the charger to receive power from the charger and are charged, which is referred to as a "charging operation".

[0041] When the external device 2 is a load, both ends P+ and P- of the battery system 1 are connected to the load so that the power provided by the battery device 100 can be discharged through the load. Hereinafter, the operation of supplying power from the battery device 100 to the load and reducing the charge of the battery device 100 is referred to as a "discharging operation".

[0042] In an exemplary embodiment, each of the plurality of battery cells included in each of the plurality of battery packs 101 to 106 may be a lithium metal battery using lithium (Li) metal as a negative electrode. Specifically, the negative electrode material of each of the plurality of battery cells included in each of the plurality of battery packs 101 to 106 may include lithium in a metallic phase.

[0043] During the discharge process of the lithium metal battery, an oxidation reaction occurs in which lithium metal contained in the negative electrode material of the lithium metal battery is stripped and moves to the positive electrode through the electrolyte.

[0044] When lithium metal is stripped from a specific position on the lithium metal of the negative electrode material, the position where the lithium metal has been stripped, the corner of the lithium deposit, the high curvature point in the lithium deposit, etc. may be in a state where another lithium metal ion is easily stripped. In addition, in a lithium metal battery discharged at a low discharge rate, the stripping from the surface of the lithium metal is not uniform compared to a lithium metal battery discharged at a high discharge rate, and the metal ions may be stripped at a position that is easy to strip.

[0045] During the charge and discharge process of lithium metal batteries, irregular lithium ions on the negative electrode surface due to irregular deposition of lithium metal or irregular stripping of lithium ions may lead to the formation of lithium dendrites pointing from the negative electrode surface to the positive electrode surface. When the lithium metal battery is repeatedly charged and discharged, these lithium dendrites may accumulate excessively and penetrate into the separator, resulting in an internal short circuit between the negative electrode and the positive electrode.

[0046] In the following, reference will be made to Figure 2 The lithium stripping operation of lithium metal batteries based on the difference in discharge rate is described.

[0047] Figure 2 is a diagram illustrating the shape of the lithium metal surface according to the difference in the peeling rate of the lithium metal battery.

[0048] Figure 2 (A) in the figure may represent the shape of lithium deposits irregularly deposited on lithium metal by charging of a lithium metal battery. Figure 2 (A), the irregular deposition of lithium metal may include narrow points 21.

[0049] When lithium metal is removed from Figure 2 When the lithium deposit illustrated in (A) is stripped, the lithium metal can be returned to the Figure 2 The shape illustrated in (A1) is such that most of the irregular deposits of lithium metal have been removed.

[0050] In contrast, when lithium metal is removed from Figure 2 When the lithium deposit illustrated in (A) is stripped, stripping actively occurs at the corners or points of high curvature of the lithium deposit (e.g. Figure 2 shape shown in (A2)), and the irregular deposits of lithium metal may be peeled off more irregularly.

[0051] Reference Figure 2 (A2), the irregular deposition of lithium metal with slow exfoliation may include a narrow point 22.

[0052] Included in Figure 2 The narrow point 22 in (A2) is included in Figure 2 The narrow point 21 in (A) is further narrowed, so that the region 23 separated from the lithium deposit by the narrow point 22 can be separated from the lithium deposit. In addition, lithium dendrites can also be easily formed due to the irregular surface.

[0053] As the discharge rate of the lithium metal battery increases, the stripping rate of the lithium metal contained in the lithium metal battery can become fast and uniform. In contrast, when the lithium metal battery is discharged at a low discharge rate below a predetermined level, the stripping of the lithium metal (or the deposit of lithium metal) contained in the lithium metal battery from the surface is unlikely to be uniform, and the possibility of lithium dendrites forming on the surface of the lithium metal is high.

[0054] Specifically, the irregular growth of lithium metal may be mainly caused by the change of current density on the surface, and when the lithium metal battery is operated in an environment with a slower stripping rate than the deposition rate on the lithium metal, there is a possibility that lithium fragments may be disconnected from the irregularly grown lithium metal. The formation of such lithium fragments can increase the degradation rate that reduces the overall capacity of the lithium metal battery cell.

[0055] In this way, when the lithium metal battery is discharged at a low discharge rate less than a predetermined level, premature degradation of the lithium metal battery cell may occur. When the first discharge rate is less than the second discharge rate, each of the plurality of battery packs 101 to 106 is more likely to experience premature degradation when discharged at the first discharge rate than when discharged at the second discharge rate. In other words, a higher discharge rate is advantageous in terms of degradation of the lithium metal battery. Based on this, the BMS 200 according to the exemplary embodiment can control the discharge of the plurality of battery packs 101 to 106 so that the plurality of battery packs 101 to 106 are discharged at a high discharge rate equal to or greater than a predetermined level.

[0056] Alternatively, in some exemplary embodiments, each of the plurality of battery cells included in each of the plurality of battery groups 101 to 106 may be a lithium-sulfur secondary battery. Specifically, the negative electrode material of each of the plurality of battery cells included in each of the plurality of battery groups 101 to 106 may include lithium in a metallic phase, and the positive electrode material of each of the plurality of battery cells may include elemental sulfur (e.g., S8) or a sulfur-containing complex having a sulfur-sulfur bond as a positive electrode active material.

[0057] During the discharge process of the lithium-sulfur secondary battery, sulfur (e.g., S 8 ) and the continuous oxidation reaction of the metallic lithium contained in the negative electrode occur within each electrode and the electrolyte. As the continuous oxidation / reduction reactions occur, a variety of lithium polysulfides (LiPS) can be formed in the electrolyte and move between the electrodes, and the final solid lithium sulfide (Li 2 S) can be deposited on the negative electrode.

[0058] However, in the process of forming lithium polysulfide by continuous oxidation / reduction reaction, a part of lithium polysulfide dissolved in the electrolyte may have a side reaction with the negative electrode, etc., which may be a factor that reduces the life characteristics of the lithium-sulfur secondary battery.

[0059] Therefore, the frequency of side reactions caused by a portion of the lithium polysulfide dissolved in the electrolyte and the negative electrode increases as the discharge time is longer. In other words, 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 the lithium-sulfur secondary battery cell enters a rest state during discharge and is then discharged again, the total discharge time increases compared to the case where the lithium-sulfur secondary battery cell does not have a rest state. This may increase the frequency of side reactions. Therefore, increasing the discharge rate of the lithium-sulfur secondary battery cell to achieve a shorter discharge time may be advantageous in terms of the life of the lithium-sulfur secondary battery.

[0060] Therefore, when any one of the plurality of battery groups is in a discharge operation, the BMS 200 can monitor the battery pack voltage to ensure that the lithium-sulfur secondary battery cell is discharged with a shorter discharge time during discharge without pausing until it is fully discharged. Hereinafter, the battery pack voltage refers to the battery pack voltage of at least one battery pack connected to a turned-on switch among the plurality of switches SW1 to SW6.

[0061] Based on the characteristics of the above-described lithium metal battery and lithium-sulfur secondary battery, the operation of the battery system 1 will be described below.

[0062] The BMS 200 may divide the plurality of battery packs 101 to 106 into a plurality of battery groups, and determine at least one battery group to be discharged among the plurality of battery groups. The BMS 200 may control the supply of power to the load from at least one determined battery group. The BMS 200 may determine the number of battery groups to be discharged among the plurality of battery groups based on the discharge rate of the battery device 100 for providing the power required by the load (hereinafter referred to as “the discharge rate of the battery device 100 required by the load”) and the reference discharge rate of the battery pack. The reference discharge rate of the battery pack may be a range of discharge rates of each of the plurality of battery packs 101 to 106 that is less sensitive to the degradation of each of the plurality of battery packs 101 to 106.

[0063] When supplying power to a load, the BMS 200 may discharge only some of the battery groups at a high discharge rate (C rate) instead of discharging all of the battery groups in the plurality of battery 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 may be determined by the maximum power of the load.

[0064] Assume that the number of battery packs included in the battery device 100 is m (where m is a natural number equal to or greater than 2), and m=n*p (where n and p are natural numbers equal to or greater than 1). When the m battery packs are grouped in units of "P", "n" may be the number of battery groups. The BMS 200 may divide the m battery packs into n battery groups and discharge each of the n battery groups in sequence. Each of the n battery groups includes p battery packs.

[0065] When one of the n battery groups is in a discharging operation, a discharge rate of each of the p battery groups in the discharging-operating battery group may be n times a discharge rate of the battery device 100 required by the load.

[0066] For example, when the discharge rate of the battery device 100 required by the load is 0.1C, and the number n of battery groups is 3, the BMS 200 may determine that the discharge rate of each of the three battery groups is 0.3C when discharging one of the three battery groups in sequence, and control the discharge rate of each of the battery packs belonging to each battery group to 0.3C.

[0067] In some exemplary embodiments, the number n of battery groups may be pre-stored in the BMS 200. In an exemplary embodiment, the BMS 200 may determine the number n of battery groups based on a discharge rate of the battery device 100 required by a load and a reference discharge rate of the battery pack.

[0068] In an exemplary embodiment, the BMS 200 may pre-store the discharge rate of the battery device 100 required for the load and the reference discharge rate of the battery pack. The BMS 200 may derive the number n of battery groups based on the pre-stored discharge rate of the battery device 100 required for the load and the pre-stored reference discharge rate of the battery pack. In addition, based on the derived number n of battery groups and the number m of multiple battery packs 101 to 106, the BMS 200 may derive the number p of battery packs belonging to each of the n battery groups, and discharge each of the n battery groups in turn. The BMS 200 may also determine the p battery packs belonging to each of the n battery groups. In this case, each of the n battery groups may perform a discharge operation at a discharge rate that falls within the reference discharge rate.

[0069] For example, when the reference discharge rate of the battery pack is 0.3C to 1C, the number of the plurality of battery packs configuring the battery device 100 is six, and the discharge rate of the battery device 100 required by the load is 0.2C, the BMS 100 can calculate that 0.2C*n is within the range of 0.3 to 1, and n is a natural number that can be divided by 6. According to the calculation, n can be 2 or 3. That is, the BMS 100 can divide the six battery packs into two groups or three groups.

[0070] Alternatively, in some exemplary embodiments, the BMS 200 may receive a signal from the external device 2 indicating the discharge rate of the battery device 100 required by the load, determine the discharge rate of the battery device 100 based on the received signal, and derive the number n of battery group groups based on the determined discharge rate of the battery device 100 and a reference discharge rate of the battery pack.

[0071] In an exemplary embodiment, when each of the multiple battery cells included in each of the multiple battery groups 101 to 106 is a lithium-sulfur secondary battery, BMS200 can improve the life of the multiple battery cells in the discharge operation by ensuring that the p battery groups included in the battery group group that has started the discharge operation among the n battery groups remain in the discharge state until the discharge is completed without pausing in the middle of the discharge.

[0072] In this case, the operation of the BMS 200 to discharge each of the n battery groups may include the following operation: discharging one of the n battery groups, and after the discharging is completed, sequentially repeating the discharging operation of discharging another of the n battery groups, thereby sequentially discharging p of the m battery groups. The operation of the BMS 200 to discharge one battery group may mean that the BMS 200 discharges each of the p battery groups by turning on a switch connected to each of the p battery groups belonging to one battery group.

[0073] In the specification, full discharge may refer to a state in which at least one of the battery pack voltages of the corresponding p battery packs is equal to or less than a predetermined discharge voltage lower limit. The predetermined discharge voltage lower limit may be a predetermined value or a predetermined range indicating that the battery pack is fully discharged. For example, in an exemplary embodiment, the predetermined discharge voltage lower limit may be 1.5V to 1.9V, and in some exemplary embodiments, the predetermined discharge voltage lower limit may be 1.8V.

[0074] When a battery group belonging to one of the multiple battery groups is in a discharge operation, BMS200 does not stop the battery group until each of the p battery groups belonging to the discharge operation battery group reaches a discharge voltage lower limit, and when at least one of the battery group voltages of the p battery groups reaches the discharge voltage lower limit, BMS200 can terminate the discharge of the discharge operation battery group and start the discharge operation of another battery group among the multiple battery groups.

[0075] The BMS 200 may determine which of the plurality of battery groups performs a discharge operation, and may turn on a switch connected to the determined battery group among the plurality of switches SW1 to SW6. The corresponding battery group may then be connected to the node N1. The discharge operation may include an operation of supplying power to an external power source. Here, when the number of at least one battery group performing a discharge operation among the plurality of battery groups 101 to 106 is two or more, the battery groups may be connected in parallel to each other.

[0076] One end of each of the plurality of switches SW1 to SW6 may be connected to each other at a node N1 , and the other ends of the plurality of switches SW1 to SW6 may be connected in series to one ends of the plurality of battery packs 101 to 106 , respectively.

[0077] exist Figure 1 In the embodiment, the plurality of battery packs 101 to 106 are illustrated as including a plurality of battery cells, and the plurality of switches SW1 to SW6 are connected in parallel to the plurality of battery packs 101 to 106, but this is for convenience of illustration, and in some exemplary embodiments, the plurality of switches SW1 to SW6 may be connected to the battery cells, respectively. When each of the plurality of switches SW1 to SW6 is connected to a corresponding battery cell, the description of the battery pack in the description of the battery system 1 in this specification may be replaced by the description of the battery cell.

[0078] 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 connected to the relay 300 at the node N1, and the other end of the switch SW6 is connected to the positive terminal of the battery pack 106.

[0079] The BMS 200 may turn on a switch connected to a battery pack to be discharged among the plurality of battery packs 101 to 106, and monitor the voltage of the discharge operation battery pack. The BMS 200 may receive a plurality of voltage measurement signals VS1 to VS6 from one end of the plurality of battery packs 101 to 106, respectively. The BMS 200 is connected to each of the plurality of battery packs 101 to 106 through a plurality of wires LN1 to LN6, respectively.

[0080] The BMS 200 may include a plurality of terminals P1 to P6. The plurality of terminals P1 to P6 are respectively connected to one ends of the plurality of battery packs 101 to 106 through a plurality of wires LN1 to LN6. The BMS 200 may receive a plurality of voltage measurement signals VS1 to VS6 through the plurality of terminals P1 to P6.

[0081] The positive terminal of the battery pack 101 may be connected to the terminal P1 through the wire LN1, and the BMS 200 may obtain the voltage measurement signal VS1 measured from the positive terminal of the battery pack 101 through the terminal P1. The positive terminal of the battery pack 102 may be connected to the terminal P2 through the wire LN2, and the BMS 200 may obtain the voltage measurement signal VS2 measured from the positive terminal of the battery pack 102 through the terminal P2. The positive terminal of the battery pack 103 may be connected to the terminal P3 through the wire LN3, and the BMS 200 may obtain the voltage measurement signal VS3 measured from the positive terminal of the battery pack 103 through the terminal P3. The positive terminal of the battery pack 104 may be connected to the terminal P4 through the wire LN4, and the BMS 200 may obtain the voltage measurement signal VS4 measured from the positive terminal of the battery pack 104 through the terminal P4. The positive terminal of the battery pack 105 may be connected to the terminal P5 through the wire LN5, and the BMS 200 may obtain the voltage measurement signal VS5 measured from the positive terminal of the battery pack 105 through the terminal P5. The positive terminal of the battery pack 106 may be connected to the terminal P6 through a wire LN6 , and the BMS 200 may obtain a voltage measurement signal VS6 measured from the positive terminal of the battery pack 106 through the terminal P6 .

[0082] The BMS 200 may derive the battery pack voltages of the plurality of battery packs 101 to 106 from the plurality of voltage measurement signals VS1 to VS6, respectively. The BMS 200 may monitor the battery pack voltages of battery packs among the plurality of battery packs 101 to 106 connected to closed switches among the plurality of switches SW1 to SW6.

[0083] When at least one of the battery pack voltages of at least one battery pack in a discharge operation battery pack group as a result of monitoring is equal to or less than a predetermined discharge voltage lower limit, BMS200 can turn off the switch connected to each battery pack in the discharge operation battery pack group, and turn on the switch connected to each battery pack in the battery pack group to be discharged next.

[0084] In the charging operation, the BMS 200 transmits on-level switch control signals SS1 to SS6 to the plurality of switches SW1 to SW6 , and when the plurality of switches SW1 to SW6 are closed, the plurality of battery packs 101 to 106 may be charged.

[0085] Figure 3 is a graph illustrating the relationship between the discharge rate and life of a lithium metal battery.

[0086] Reference Figure 3 , the following describes the cycle life of the battery according to the C rate representing the discharge rate of the battery under the condition that the remaining life retention rate is 80%. When the discharge rate (C rate) is 0.1C, the cycle life of the battery is 90 cycles, and when the discharge rate (C rate) is 0.3C., the cycle life of the battery is 147 cycles. Therefore, when the C rate is tripled from 0.1C to 0.3C, the cycle life of the battery increases by 63.33% from 90 cycles to 147 cycles.

[0087] In an exemplary embodiment, the BMS 200 may divide the plurality of battery packs 101 to 106 into n battery pack groups for discharge operation so that only a portion of the plurality of battery packs 101 to 106 performs a discharge operation. The discharge rate of the battery device 100 may be a value obtained by dividing the sum of the discharge rates of the discharge operation battery packs by the number of battery packs 101 to 106. For example, when each of the plurality of battery packs 101 to 106 has a discharge rate of 0.3C and only two of the six battery packs 101 to 106 are allowed to discharge, the discharge rate of the battery device 100 is 0.3*2 / 6=0.1C. Therefore, in an exemplary embodiment, the discharge rate of each of the plurality of battery packs 101 to 106 may be higher than the discharge rate of the battery device 100, so that a battery system 1 that is advantageous in terms of the life of each of the plurality of battery packs 101 to 106 may be provided.

[0088] Figure 4 is a flowchart of a battery pack connection method using a battery system according to an exemplary embodiment.

[0089] Hereinafter, redundant description of the above-mentioned battery system 1 may be omitted.

[0090] When the battery system 1 starts the discharge operation, the BMS 200 may divide the plurality of battery packs 101 to 106 into a plurality of battery groups (S100). In the BMS 200, information about the number n of battery groups may be pre-stored, or the BMS 200 may determine the number of the plurality of battery groups based on the discharge rate of the battery device 100 required by the load and the reference discharge rate of the battery group. The BMS 200 may determine at least one battery group belonging to each of the plurality of battery groups. The BMS 200 may discharge each of the plurality of battery groups in sequence.

[0091] The BMS 200 may discharge only at least one battery pack belonging to one battery pack group among the plurality of battery packs 101 to 106, and place the remaining battery packs in a rest state. Therefore, when the number of the plurality of battery pack groups is n, each of the plurality of discharge-operating battery packs 101 to 106 may be discharged at a discharge rate that is n times the discharge rate of the battery device 100.

[0092] For example, when the BMS 200 divides the plurality of battery packs into two battery groups (n=2), each of at least one battery group in the battery group in the discharge operation may have a discharge rate that is twice the discharge rate of the battery device 100, that is, 100% increase based on the discharge rate of the battery device 100. When the BMS 200 divides the plurality of battery packs into three battery groups (n=3), each of at least one battery group in the battery group in the discharge operation may have a discharge rate that is three times the discharge rate of the battery device 100, that is, 200% increase based on the discharge rate of the battery device 100. When the BMS 200 divides the plurality of battery packs into four battery groups (n=4), each of at least one battery group in the battery group in the discharge operation may have a discharge rate that is four times the discharge rate of the battery device 100, that is, 300% increase based on the discharge rate of the battery device 100. This allows the battery system 1 to increase the discharge rate of each of the plurality of battery packs 101 to 106, thereby improving the life of the lithium metal battery.

[0093] Hereinafter, for convenience of description, it is assumed that the number of battery packs included in the battery device 100 is referred to as m = 6, the number of battery pack groups is referred to as n = 3, and the number of battery packs included in each of the three battery pack groups is referred to as p = 2. In addition, each of the plurality of battery packs 101 to 106 may be a first battery pack to a sixth battery pack.

[0094] The BMS 200 may divide the six battery packs 101 to 106 into three battery groups. The BMS 200 may divide the plurality of battery packs 101 to 106 into three battery groups, that is, the first battery group to the third battery group, and determine the battery group belonging to each of the three battery groups. For example, the BMS 200 may generate a first battery group including the first battery group 101 and the second battery group 102, a second battery group including the third battery group 103 and the fourth battery group 104, and a third battery group including the fifth battery group 105 and the sixth battery group 106.

[0095] When multiple battery groups are discharged in a predetermined discharge cycle, the BMS 200 may determine the order in which the multiple battery groups are discharged in each cycle (hereinafter, "multiple discharge orders"). Here, the discharge cycle may refer to the number of times the battery device 100 is discharged from a fully charged state to a fully discharged state. Here, the state in which the battery device 100 is fully charged may represent a state in which all battery group voltages of the multiple battery groups 101 to 106 are equal to or greater than a predetermined upper limit of the charging voltage, and the state in which the battery device 100 is fully discharged may represent a state in which all n battery groups include battery groups that are equal to or less than a lower limit of the discharge voltage. The predetermined upper limit of the charging voltage may be a predetermined value or a predetermined range indicating that the battery group is fully charged.

[0096] BMS200 can determine multiple discharge modes so that the average value of the rest time before discharge and / or the average value of the rest time after discharge are uniform in the discharge mode cycles of multiple battery groups. A discharge mode cycle refers to a cycle of executing multiple discharge modes of multiple battery groups. For example, the first discharge mode of multiple battery groups is the order of the first battery group, the second battery group, and the third battery group; the second discharge mode is the order of the second battery group, the third battery group, and the first battery group; and the third discharge mode is the order of the third battery group, the first battery group, and the second battery group. A discharge mode cycle may include a first discharge mode, a second discharge mode, and a third discharge mode, and the discharge mode cycle may be repeated.

[0097] The BMS 200 may calculate an average value of the rest time before discharge of one battery group by dividing a value obtained by summing the rest time before discharge of one battery group in each of the plurality of discharge modes in the discharge mode cycle of the one battery group by the number of the plurality of discharge modes.

[0098] The BMS 200 may determine a plurality of discharge modes so that the difference between the average value of the rest time before discharge of any one of the plurality of battery groups and the average value of the rest time before discharge of any other of the plurality of battery groups is smaller. The BMS 200 may determine a plurality of discharge modes so that the difference between the average value of the rest time after discharge of any one of the plurality of battery groups and the average value of the rest time after discharge of any other of the plurality of battery groups is smaller.

[0099] Hereinafter, it is assumed that the number of the plurality of discharge modes is n.

[0100] The BMS 200 may determine n different discharge modes corresponding to one discharge mode cycle.

[0101] BMS200 can determine the discharge mode cycle so that the average value of the rest time before discharge of any one of the multiple battery groups in each discharge mode is the same as the average value of the rest time before discharge of any other one of the multiple battery groups in each discharge mode and / or the average value of the rest time after discharge of any one of the multiple battery groups in each discharge mode is the same as the average value of the rest time after discharge of any other one of the multiple battery groups in each discharge mode.

[0102] For example, assume that in the first discharge mode cycle, the discharge time of each battery group is 1 hour, and here, in the first discharge mode cycle, for multiple battery groups, the first discharge mode is the order of the first battery group, the second battery group and the third battery group; the second discharge mode is the order of the second battery group, the third battery group and the first battery group; and the third discharge mode is the order of the third battery group, the first battery group and the second battery group.

[0103] Each battery group can be determined to be resting while the other battery groups are in discharge. For the first discharge mode to the third discharge mode, the rest time before discharge of the first battery group is 0 hours, 2 hours and 1 hour respectively, so the average rest time before discharge of the first battery group in the first discharge mode cycle is 1 hour. For the first discharge mode to the third discharge mode, the rest time before discharge of the second battery group is 1 hour, 0 hours and 2 hours respectively, so the average rest time before discharge of the second battery group in the first discharge mode cycle is 1 hour. For the first discharge mode to the third discharge mode, the rest time before discharge of the third battery group is 2 hours, 1 hour and 0 hours respectively, so the average rest time before discharge of the third battery group in the first discharge mode cycle is 1 hour. Therefore, the average rest time before discharge of any one of the multiple battery groups in each discharge mode is the same as the average rest time before discharge of any other battery group in the multiple battery groups in each discharge mode.

[0104] Similarly, for the first discharge mode to the third discharge mode, the rest time after discharge of the first battery group is 2 hours, 0 hours and 1 hour, respectively, so the average value of the rest time after discharge of the first battery group in the first discharge mode cycle is 1 hour. In addition, for the first discharge mode to the third discharge mode, the rest time after discharge of the second battery group is 1 hour, 2 hours and 0 hours, respectively, so the average value of the rest time after discharge of the second battery group in the first discharge mode cycle is 1 hour. Similarly, for the first discharge mode to the third discharge mode, the rest time after discharge of the third battery group is 0 hours, 1 hour and 2 hours, respectively, so the average value of the rest time after discharge of the third battery group in the first discharge mode cycle is 1 hour. Therefore, the average value of the rest time after discharge of any one of the multiple battery groups in each discharge mode is the same as the average value of the rest time after discharge of any other battery group in the multiple battery groups in each discharge mode.

[0105] When the BMS 200 determines a plurality of discharge modes in a discharge mode cycle, the BMS 200 may sequentially perform discharge operations on a plurality of battery groups according to the discharge mode cycle.

[0106] Hereinafter, when the BMS 200 determines a first discharge mode in order of the first, second, and third battery groups, an operation of the BMS 200 to sequentially discharge each of the plurality of battery groups according to the first discharge mode will be described with reference to operations S101 to S109 .

[0107] The BMS 200 may discharge the first battery group according to the first discharge mode (S101). The BMS 200 may turn on switches SW1 and SW2 connected to the first battery group 101 and the second battery group 102 belonging to the first battery group through a plurality of switches SW1 to SW6, and turn off switches SW3 to SW6 connected to the third battery group 103 to the sixth battery group 106.

[0108] The BMS 200 can close the switches SW1 and SW2 by sending on-level switch control signals SS1 and SS2 to the switches SW1 and SW2. The BMS 200 can open the switches SW3 to SW6 by sending off-level switch control signals SS3 to SS6 to the switches SW3 to SW6. Here, the turned-off third to sixth battery packs 103 to 106 can be considered to be in a dormant state.

[0109] The BMS 200 may monitor the battery pack voltage (S102). The battery pack voltage in operation S102 and operation S103 includes the battery pack voltage of each of the first battery pack 101 and the second battery pack 102. The BMS 200 may derive the battery pack voltage from the voltage measurement signals VS1 and VS2.

[0110] The BMS 200 may determine whether at least one of the voltages on the battery pack has reached a predetermined discharge voltage lower limit ( S103 ).

[0111] Hereinafter, determining whether at least one of the voltages on the battery pack has reached a predetermined discharge voltage lower limit is intended to ensure that the lithium-sulfur secondary battery cell as described above becomes dormant during discharge, and then the discharge-operating battery pack is discharged to the discharge voltage lower limit without being discharged again to be advantageous in terms of the life of the lithium-sulfur secondary battery.

[0112] The BMS 200 may also monitor the battery pack voltage of each of the plurality of battery packs 101 to 106 to determine whether the plurality of battery pack groups all include battery packs having a voltage equal to or less than the discharge voltage lower limit. When the plurality of battery pack groups all include battery packs having a voltage equal to or less than the discharge voltage lower limit, the BMS 200 may terminate the discharge operation.

[0113] When the voltage on at least one battery pack does not reach the predetermined discharge voltage lower limit in operation S103, operation S102 may be repeated.

[0114] When the voltage on at least one battery pack reaches a predetermined discharge voltage lower limit in operation S103, the BMS 200 may turn off the switch connected to each of the battery packs belonging to the first battery pack group in the discharge operation, and enable the second battery pack group as the next discharge sequence according to the first discharge mode to perform the discharge operation (S104). The BMS 200 may turn on the switch SW3 and the switch SW4 connected to the third battery pack 103 and the fourth battery pack 104 belonging to the second battery pack group through a plurality of switches SW1 to SW6, and turn off the switches SW1, SW2, SW5, and SW6 connected to the first battery pack 101, the second battery pack 102, the fifth battery pack 105, and the sixth battery pack 106.

[0115] The BMS 200 may send on-level switch control signals SS3 and SS4 to the switches SW3 and SW4 to close the switches SW3 and SW4. The BMS 200 may send off-level switch control signals SS1, SS2, SS5, and SS6 to the switches SW1, SW2, SW5, and SW6 to turn off the switches SW1, SW2, SW5, and SW6. Here, the first battery pack 101, the second battery pack 102, the fifth battery pack 105, and the sixth battery pack 106 that are turned off may be considered to be in a dormant state.

[0116] The BMS 200 may monitor the battery pack voltage (S105). The battery pack voltage in operations S105 and S106 includes a battery pack voltage of each of the third battery pack 103 and the fourth battery pack 104. The BMS 200 may derive the battery pack voltage from the voltage measurement signal VS3 and the voltage measurement signal VS4.

[0117] The BMS 200 may determine whether at least one of the voltages on the battery pack has reached a predetermined discharge voltage lower limit ( S106 ).

[0118] The BMS 200 may also monitor the battery pack voltage of each of the plurality of battery packs 101 to 106 to determine whether the plurality of battery pack groups all include battery packs having a voltage equal to or less than the discharge voltage lower limit. When the plurality of battery pack groups all include battery packs having a voltage equal to or less than the discharge voltage lower limit, the BMS 200 may terminate the discharge operation.

[0119] When the voltage on at least one battery pack does not reach the predetermined discharge voltage lower limit in operation S106, operation S105 may be repeated.

[0120] When the voltage on at least one battery pack reaches a predetermined discharge voltage lower limit in operation S106, the BMS 200 may turn off the switch connected to each of the battery packs belonging to the second battery pack group of the discharge operation, and enable the third battery pack group as the next discharge sequence according to the first discharge mode to perform the discharge operation (S107). The BMS 200 may turn on the switch SW5 and the switch SW6 connected to the fifth battery pack 105 and the sixth battery pack 106 belonging to the third battery pack group through a plurality of switches SW1 to SW6, and turn off the switches SW1 to SW4 connected to the first battery pack 101 to the fourth battery pack 104.

[0121] The BMS 200 may send on-level switch control signals SS5 and SS6 to the switches SW5 and SW6 to close the switches SW5 and SW6. The BMS 200 may turn off the switches SW1 to SW4 by sending off-level switch control signals SS1 to SS4 to the switches SW1 to SW4. Here, the turned-off first to fourth battery packs 101 to 104 may be considered to be in a dormant state.

[0122] The BMS 200 may monitor the battery pack voltage (S108). The battery pack voltage in operations S108 and S109 includes the battery pack voltage of each of the fifth battery pack 105 and the sixth battery pack 106. The BMS 200 may derive the battery pack voltage from the voltage measurement signal VS5 and the voltage measurement signal VS6.

[0123] The BMS 200 may determine whether at least one of the voltages on the battery pack has reached a predetermined discharge voltage lower limit ( S109 ).

[0124] The BMS 200 may also monitor the battery pack voltage of each of the plurality of battery packs 101 to 106 to determine whether the plurality of battery pack groups all include battery packs having a voltage equal to or less than the discharge voltage lower limit. When the plurality of battery pack groups all include battery packs having a voltage equal to or less than the discharge voltage lower limit, the BMS 200 may terminate the discharge operation.

[0125] When the voltage on at least one battery pack does not reach the predetermined discharge voltage lower limit in operation S109, operation S108 may be repeated.

[0126] When at least one of the voltages on the battery packs reaches a predetermined discharge voltage lower limit in operation S109 , the BMS 200 may terminate the discharge operation according to the first discharge mode.

[0127] In some exemplary embodiments, when at least one of the battery pack voltages reaches a predetermined discharge voltage lower limit in operation S103, operation S106, or operation S109, the BMS 200 may monitor the battery pack voltage of each of the plurality of battery packs 101 to 106 to determine whether all of the plurality of battery pack groups include battery packs having a voltage equal to or less than the discharge voltage lower limit. When at least one of the battery pack voltages reaches a predetermined discharge voltage lower limit in operation S103, operation S106, or operation S109 and all of the plurality of battery pack groups include battery packs having a voltage equal to or less than the discharge voltage lower limit, the BMS 200 may terminate the discharge operation according to the first discharge mode. When at least one of the voltages on the battery packs reaches a predetermined discharge voltage lower limit in operation S103, operation S106, or operation S109 and there is a battery group among the multiple battery groups that does not include a battery group having a voltage equal to or less than the discharge voltage lower limit, BMS200 may cause the battery group among the multiple battery groups that does not include a battery group having a voltage equal to or less than the discharge voltage lower limit to perform a discharge operation according to a discharge sequence of a first discharge mode.

[0128] When at least one of the voltages on the battery packs reaches a predetermined discharge voltage lower limit in operation S109, the plurality of battery pack groups all include battery packs having voltages equal to or less than the discharge voltage lower limit, so that the BMS 200 terminates the discharge operation according to the first discharge mode. When the discharge operation according to the first discharge mode is terminated by the mode, the BMS 200 may turn off the plurality of switches SW1 to SW6.

[0129] When the discharge operation is performed through operations S101 to S109, each of the plurality of battery packs 101 to 106 may be in a rest state for a period of time obtained by multiplying a value obtained by subtracting 1 from the number of the plurality of battery packs by the discharge time of each of the plurality of battery packs 101 to 106. When the number of the plurality of battery packs is n, and the discharge time of each of the plurality of battery packs 101 to 106 is t1 (unit: seconds), the rest period of each of the plurality of battery packs 101 to 106 may be t1*(n-1) (unit: seconds).

[0130] For example, assuming that the discharge time of each of the plurality of battery packs 101 to 106 is 1 hour and the number of the plurality of battery pack groups is 3, the first battery pack 101 is in a discharge operation during a period corresponding to operation S101 to operation S103, and is in a rest state during a period corresponding to operation S104 to operation S109, so the first battery pack 101 has a rest period equal to 1 (h) * 2 = 2 hours. Therefore, each of the plurality of battery packs 101 to 106 may have a rest period of several hours.

[0131] Therefore, the BMS 200 may cause each of the plurality of battery groups to sequentially perform a discharge operation according to a plurality of discharge modes in a discharge mode cycle.

[0132] In one exemplary embodiment, the BMS 200 may determine the number n of battery group groups based on a discharge rate of the battery device 100 required by the load and a reference discharge rate of the battery group.

[0133] In the following, reference will be made to Figure 5 Described in Figure 4 In operation S100 , 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 battery packs to derive the number n of battery pack groups to be discharged and determine the discharge mode cycle.

[0134] Figure 5 yes Figure 4 Detailed flowchart of operation S100.

[0135] Hereinafter, redundant description of the above-mentioned battery system 1 may be omitted.

[0136] In the BMS 200 , a discharge rate C_DEVICE of the battery device 100 and a reference discharge rate C_PK of the battery pack required by the load may be stored in advance ( S201 ).

[0137] The BMS 200 may determine a value obtained by dividing a reference discharge rate C_PK of each of the plurality of battery packs 101 to 106 by a discharge rate C_DEVICE of the battery device 100 required by a load as the number n of battery pack groups ( S202 ).

[0138] For example, when 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 to 106 is 0.3 [C], the number of battery pack groups n=C_PK / C_DEVICE=3.

[0139] Based on the number n of battery groups and the number m of the plurality of battery groups 101 to 106 , the BMS 200 may derive the number p of battery groups belonging to each of the n battery groups ( S203 ).

[0140] For example, when the number n of battery group is 3 and the number m of battery groups 101 to 106 is 6, the number of battery groups belonging to each battery group is p=m / n=2.

[0141] The BMS 200 may determine the battery packs belonging to each of the n battery groups based on the number n of battery groups or based on the number n of battery groups and the number p of battery packs belonging to each of the n battery groups ( S204 ).

[0142] The BMS 200 may determine the battery packs belonging to each battery group by any method that ensures that the plurality of battery packs 101 to 106 equally belong to each of the n battery groups.

[0143] For example, the BMS 200 may determine the first and second battery groups 101 and 102 as the first battery group, the third and fourth battery groups 103 and 104 as the second battery group, and the fifth and sixth battery groups 105 and 106 as the third battery group among the plurality of battery groups 101 to 106 .

[0144] The BMS 200 may determine one battery group to be discharged among the plurality of battery groups ( S205 ).

[0145] When determining one battery group to be discharged, the BMS 200 may determine a plurality of discharge modes configured for discharge mode cycles of the plurality of battery groups to determine one battery group to be discharged among the plurality of battery groups.

[0146] The BMS 200 may determine the plurality of discharge modes such that an average value of the rest time before discharge and / or an average value of the rest time after discharge is uniform in the discharge mode cycles of the plurality of battery group groups.

[0147] In the specification, it has been described that a plurality of battery groups include at least one battery group including one or more battery cells, but this is only for convenience of description, and the present invention is not limited thereto.

[0148] In some exemplary embodiments, each of the plurality of battery groups may each represent a battery cell, in which case at least one battery group belonging to each of the plurality of battery groups may be replaced by each battery cell, and the battery group voltage may be replaced by the cell voltage of each battery cell. In other words, the BMS 200 may make the discharge rate of the battery cell performing the discharge operation within the reference discharge rate so that only one cell among the plurality of battery cells is discharged and the switches connected to the remaining plurality of cells are turned off.

[0149] While the present invention has been described in connection with what are presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments.

Claims

1. A battery system, comprising: A battery device, the battery device comprising a plurality of battery packs connected in parallel; For each of the plurality of battery packs, a plurality of switches are connected in series to one of the two ends of each battery pack; as well as a battery management system (BMS), the BMS being configured to divide the plurality of battery packs into a plurality of battery groups, determine at least one battery pack belonging to each of the plurality of battery groups, determine one battery group to be discharged from the plurality of battery groups, and send a switch control signal for turning on at least one switch connected to the one battery group among the plurality of switches, and turning off the remaining switches among the plurality of switches except for the at least one switch, Wherein, each of the plurality of battery packs comprises: A plurality of battery cells including metallic phase lithium in respective negative electrode materials.

2. The battery system according to claim 1, wherein: The discharge rate of the battery device for providing power required by a load connected to the battery device is a first discharge rate, and Each of the plurality of battery groups performs a discharge operation at a second discharge rate greater than the first discharge rate.

3. The battery system according to claim 2, wherein: The BMS determines the number of the plurality of battery groups by dividing a reference discharge rate for each of the plurality of battery groups by a discharge rate of the battery device, and determines the number of battery groups belonging to each of the plurality of battery groups by dividing the number of the plurality of battery groups by the number of the plurality of battery groups.

4. The battery system according to claim 1, wherein: The BMS determines a plurality of discharge modes configured for discharge mode cycles of the plurality of battery groups so that a difference between an average value of rest time before discharge of any one of the plurality of battery groups and an average value of rest time before discharge of any other of the plurality of battery groups is smaller.

5. The battery system according to claim 4, wherein: The positive electrode material of each of the plurality of battery cells comprises elemental sulfur, and The plurality of discharge modes include a first discharge mode, the first discharge mode being a sequence of a first battery group and a second battery group among the plurality of battery groups, and The BMS causes the first battery group to perform a discharging operation, and monitors whether at least one of battery group voltages of at least one first battery group belonging to the first battery group is equal to or less than a predetermined discharge voltage lower limit.

6. The battery system according to claim 5, wherein: When at least one of the battery pack voltages of the at least one first battery pack is equal to or less than the predetermined discharge voltage lower limit, The BMS turns off the switch connected to each of the at least one first battery group so that the second battery group performs a discharge operation, and monitors whether at least one of the battery group voltages of at least one second battery group belonging to the second battery group is equal to or less than the predetermined discharge voltage lower limit.

7. The battery system according to claim 5, wherein: The BMS turns off the plurality of switches when all of the plurality of battery pack groups include battery packs having a voltage equal to or less than the predetermined discharge voltage lower limit.

8. A battery pack connection method of a battery system, the battery system comprising a battery device, the battery device comprising a plurality of battery packs connected in parallel, the battery pack connection method comprising the following steps: dividing the plurality of battery packs into a plurality of battery pack groups by a battery management system (BMS) connected to the battery device; determining at least one battery pack belonging to each of the plurality of battery pack groups; determining a battery group to be discharged among the plurality of battery groups; as well as sending a switch control signal to turn on at least one switch connected to the one battery group among a plurality of switches, and to turn off the remaining switches except the at least one switch among the plurality of switches; Wherein, each of the plurality of battery packs comprises: A plurality of battery cells including metallic phase lithium in respective negative electrode materials.

9. The battery pack connection method according to claim 8, wherein: The discharge rate of the battery device for providing power required by a load connected to the battery device is a first discharge rate, and Each of the plurality of battery groups performs a discharge operation at a second discharge rate greater than the first discharge rate.

10. The battery pack connection method according to claim 8, further comprising the following steps: determining a number of the plurality of battery pack groups by dividing a reference discharge rate for each of the plurality of battery packs by a discharge rate of the battery device; as well as The number of battery packs belonging to each of the plurality of battery groups is determined by dividing the number of the plurality of battery packs by the number of the plurality of battery groups.

11. The battery pack connection method according to claim 8, wherein: The step of determining a battery group to be discharged among the plurality of battery groups comprises: A plurality of discharge modes configured for the discharge mode cycle of the plurality of battery groups are determined so that a difference between an average value of rest time before discharge of any one of the plurality of battery groups and an average value of rest time before discharge of any other of the plurality of battery groups is smaller.

12. The battery pack connection method according to claim 11, wherein: The positive electrode material of each of the plurality of battery cells comprises elemental sulfur, and The plurality of discharge modes include a first discharge mode, the first discharge mode being a sequence of a first battery group and a second battery group among the plurality of battery groups, and The steps of sending a switch control signal include: The first battery group is caused to perform a discharging operation, and at least one of the battery group voltages of at least one first battery group belonging to the first battery group is monitored to be equal to or less than a predetermined discharge voltage lower limit.

13. The battery pack connection method according to claim 12, further comprising the following steps: When at least one of the battery pack voltages of the at least one first battery pack is equal to or less than the predetermined discharge voltage lower limit, turning off a switch connected to each of the at least one first battery group so that the second battery group performs a discharge operation; as well as Whether at least one of the battery pack voltages of at least one second battery pack belonging to the second battery pack group is equal to or less than the predetermined discharge voltage lower limit is monitored.

14. The battery pack connection method according to claim 12, further comprising the following steps: When the plurality of battery pack groups all include battery packs having voltages equal to or less than the predetermined discharge voltage lower limit, The plurality of switches are turned off.

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