Battery rack and battery rack management method

Abstract

The present invention relates to a battery rack for increasing a cell balancing speed of a newly replaced battery pack in an ESS rack system, and a method for cell balancing of a battery pack included in a battery rack. The battery rack according to an embodiment of the present invention comprises: a plurality of battery packs each including an electrochemical impedance spectroscopy (EIS) measurement unit; a state-of-charge (SOC) monitoring unit that monitors the SOC of each of the battery packs; and a rack control unit that, when the SOC of a selected first battery pack among the plurality of battery packs differs from the average SOC of the other battery packs or the SOC of another arbitrary battery pack by a predetermined reference value or more, controls the EIS measurement unit of the first battery pack to perform EIS measurement.

Description

Battery Rack and Battery Rack Management Methods

[0001] The present invention relates to an Energy Storage System (ESS) rack system, and more specifically, to a battery rack for balancing a new battery pack replaced in an ESS rack system and a battery rack management method for balancing a battery pack constituting the battery rack.

[0002] Currently commercialized rechargeable batteries include nickel-cadmium batteries, nickel-hydrogen batteries, nickel-zinc batteries, and lithium-ion batteries. Among these, lithium-ion batteries are gaining attention for their advantages over nickel-based batteries, such as the ability to freely charge and discharge due to almost no memory effect, a very low self-discharge rate, and high energy density.

[0003] These lithium secondary batteries primarily use lithium-based oxides and carbon materials as the positive and negative active materials, respectively. The lithium secondary battery comprises an electrode assembly in which a positive plate and a negative plate, each coated with the positive and negative active materials, are arranged with a separator in between, and an outer casing that seals and houses the electrode assembly together with an electrolyte, namely a battery pouch casing.

[0004] Recently, rechargeable batteries are being widely used not only in small devices such as portable electronic devices but also in medium-to-large devices such as automobiles and power storage systems. When used in these medium-to-large devices, a large number of rechargeable batteries are electrically connected to increase capacity and output. In particular, pouch-type rechargeable batteries are frequently used in these devices due to the advantage of being easy to stack.

[0005] Meanwhile, with the recent increase in the need for large-capacity structures, including their utilization as energy storage sources, there is a growing demand for battery racks equipped with multiple secondary batteries electrically connected in series and / or parallel, as well as battery modules housing these secondary batteries and battery management systems (BMS).

[0006] An Energy Storage System (ESS) rack system consists of multiple battery packs. If a problem occurs with one of the battery packs in the ESS rack system, the entire rack is not repaired; instead, only the faulty battery pack is replaced with a new one.

[0007] At this time, the newly replaced battery pack may have a lower State of Health (SOH) compared to the existing battery pack. In other words, since the existing battery packs have not experienced SOH degradation, the State of Charge (SOC) may not be balanced with the newly replaced battery pack. Therefore, to balance the SOC, a cell balancing operation must be performed to discharge the capacity of the newly replaced battery pack.

[0008] The cell balancing operation of the conventional technology utilizes cell balancing elements including balancing resistors and balancing switches to perform full cell balancing operations on each cell through balancing resistors connected to each battery cell inside the battery pack, thereby discharging battery energy to achieve SOC balance with existing battery packs.

[0009] However, conventional cell balancing operations have the problem that the balancing speed is significantly slow because the cell balancing current is in the mA range. In particular, there is a problem that the battery energy discharged due to cell balancing is simply burned away as heat energy through the balancing resistor.

[0010] Prior art documents include (Patent Document 1) Korean Published Patent Application No. 10-2024-0001366 (published Jan 3, 2024) and (Patent Document 2) Korean Published Patent Application No. 10-2022-0075024 (published June 7, 2022).

[0011] The present invention aims to provide a battery rack and a battery rack management method for increasing the balancing speed of a new battery pack replaced in an ESS rack system.

[0012] The present invention aims to provide a battery rack and a battery rack management method that enable the discharge of a battery pack necessary for battery pack balancing to be performed simultaneously with the discharge of a battery pack occurring during the EIS measurement of a battery pack.

[0013] A battery rack according to an embodiment of the present invention comprises: a plurality of battery packs including an EIS (Electrochemical Impedance Spectroscopy) measuring unit; an SOC monitoring unit for monitoring the SOC of each of the plurality of battery packs; and a rack control unit for controlling the operation of EIS measurement in the EIS measuring unit of the first battery pack when the SOC of a selected first battery pack among the plurality of battery packs differs from the average SOC value of other battery packs or the SOC of any other battery pack by more than a predetermined reference value.

[0014] Each of the above battery packs further includes: a battery module having one or more battery cells; a cell balancing unit that forms a cell balancing path connected to (+)(-) for each battery cell constituting the battery module through which a cell balancing current flows and selectively discharges each cell; and a pack control unit that controls the operation of the cell balancing unit and the EIS measuring unit within the battery pack under the control of the rack control unit.

[0015] The rack control unit controls the EIS measuring unit of the first battery pack to operate EIS measurement when the SOC of the first battery pack differs from the average SOC of all other battery packs or the SOC of any other battery pack by more than a predetermined reference value, and stops the EIS measurement operation of the EIS measuring unit of the first battery pack when the difference between the SOC of the first battery pack and the average SOC of all other battery packs or the SOC of any other battery pack falls within a predetermined reference value, and controls the battery cells of the first battery pack to be balanced with the cells of other battery packs through the cell balancing unit of the first battery pack.

[0016] The cell balancing unit comprises: a balancing resistor formed in a cell balancing path through which cell current flows by connecting the (+) and (-) terminals of each battery cell to generate a cell potential difference due to the cell current flowing in the cell balancing path; and a balancing switch (B_SW) formed in the cell balancing path to perform a cell balancing operation by turning the cell balancing path on / off, wherein the balancing switch (B_SW) is controlled to be on / off by a control signal of the rack control unit.

[0017] The above EIS measuring unit comprises: an EIS measuring resistor that connects the (+) and (-) terminals of a battery module having one or more battery cells to form an EIS measuring path through which an EIS current (AC current for EIS measurement) flows, and generates an EIS potential difference due to the EIS current flowing in the EIS measuring path; and an EIS current switch (EIS_SW) formed in the EIS measuring path, which turns the EIS measuring path on / off at a predetermined period to discharge the battery module simultaneously with the EIS measurement operation of the battery module, wherein the EIS current switch (EIS_SW) is selectively controlled on / off by a control signal of the rack control unit.

[0018] The rack control unit controls the cell balancing unit and the EIS measuring unit to operate selectively when a pack balancing operation is required.

[0019] The rack control unit is characterized by being a means for controlling the on / off of the balancing switch (B_SW) of the cell balancing unit and the EIS switch (EIS_SW) of the EIS measuring unit based on a control signal transmitted from the MCU or BMIC of the BMS, or by the MCU / BMIC being configured as the rack control unit or being provided outside the BMS to control the on / off of the balancing switch (B_SW) and the EIS switch (EIS_SW).

[0020] A cell balancing method for battery packs constituting a battery rack according to an embodiment of the present invention comprises, in a balancing method for a plurality of battery packs constituting a battery rack, an SOC monitoring step in which the SOC of each battery pack is monitored in an SOC monitoring unit; an EIS measurement step in which, as a result of the monitoring, the difference between the SOC of a first battery pack selected among the plurality of battery packs and the SOC of the entire battery pack or the SOC of any other battery pack is greater than or equal to a predetermined reference value, in which a rack control unit controls the operation of EIS measurement in the first battery pack; and a cell balancing step in which, as a result of the monitoring, the difference between the SOC of the first battery pack and the SOC of the entire battery pack or the SOC of any other battery pack falls within a predetermined reference value, in which the rack control unit stops the EIS measurement operation of the first battery pack and controls it to be balanced with the cells of the other battery pack through discharge through a cell balancing unit.

[0021] The cell balancing step above performs balancing with any battery cells of any other battery pack by discharging each cell of the first battery pack through the cell balancing part of the first battery pack.

[0022] The above EIS measurement step extracts an AC current for EIS measurement from the first battery pack to measure the EIS of the first battery pack and discharges the first battery pack.

[0023] The cell balancing step above discharges each cell provided in each cell balancing path through which a cell current flows, formed by connecting the (+)(-) of each battery cell constituting the battery module included in the first battery pack.

[0024] The above EIS measurement step is such that when the SOC of the first battery pack differs from the SOC of another battery pack by more than a predetermined reference value, cell balancing through the cell balancing unit is not operated and only EIS measurement is operated, and the above cell balancing step is such that when the difference between the SOC of the first battery pack and the SOC of another battery pack falls within a predetermined reference value, the EIS measurement operation is stopped and cell balancing through the cell balancing unit is operated.

[0025] According to an embodiment of the present invention, the balancing speed of a new battery pack replaced in an ESS rack system can be increased, thereby compensating for economic losses incurred during the balancing process of the battery pack.

[0026] In addition, the present invention utilizes the discharge of the battery pack generated during the EIS measurement of the battery pack for the discharge required for battery pack balancing, thereby allowing the discharge energy of the battery pack, which was previously wasted by conventional cell balancing, to be utilized for extracting EIS measurement data, thus having the effect of increasing energy efficiency.

[0027] The features and advantages of the present invention can be better understood by referring to the following attached drawings together with the detailed description of embodiments of the present invention that follows, and among said drawings:

[0028] FIG. 1 is a diagram showing the configuration of a battery rack according to an embodiment of the present invention.

[0029] FIG. 2 is a detailed diagram showing the configuration of the battery pack of FIG. 1.

[0030] FIG. 3 is a drawing for explaining a method for managing a battery rack according to an embodiment of the present invention.

[0031] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. However, the present invention is not limited to the embodiments disclosed below but may be implemented in various different forms, and the embodiments of the present invention are provided merely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention. To explain the invention in detail, the drawings may be exaggerated, and like reference numerals in the drawings refer to like elements.

[0032] FIG. 1 is a diagram showing the configuration of a battery rack according to an embodiment of the present invention, and FIG. 2 is a diagram showing the configuration of a battery pack of FIG. 1 in detail.

[0033] Referring to FIG. 1, a battery rack according to an embodiment of the present invention comprises a plurality of battery modules (110: 111, 112, 113) each having one or more battery cells, a plurality of battery packs (100) each comprising an EIS measuring unit (131) for EIS measurement, a SOC monitoring unit (200) for monitoring the SOC of each battery pack (100), and a rack control unit (300) for controlling the operation of EIS (Electrochemical Impedance Spectroscopy) measurement in the EIS measuring unit (131) of the first battery pack (100) when the SOC (State of Charge) of the first battery pack (100) selected among the plurality of battery packs (100) differs from the SOC of another battery pack by more than a predetermined reference value. The battery rack (300) further comprises a charge / discharge switch or relay (10) for opening and closing a connection with an external device (400), such as a charger or a load.

[0034] At this time, the external device (400) may include a load and a charging device such as an inverter or a converter. If the external device (400) is a charger, both ends of the battery rack are connected to the charger so that power is supplied from the charger and charged. If the external device (400) is a load, both ends of the battery rack are connected to the load so that the power supplied by the battery rack can be discharged through the load.

[0035] And one end of the switch or relay (10) is connected to a battery rack, and the other end of the switch or relay (10) is connected to at least one configuration in an external device (400). The closing and opening of the switch or relay (10) can be controlled according to a relay control signal supplied from a Battery Management System (BMS).

[0036] A battery pack (100) comprises a battery module (111) having one or more battery cells, a cell balancing section (121) that forms a cell balancing path connected to (+)(-) for each battery cell constituting the battery module (111) to allow cell balancing current to flow and discharges each cell, an EIS measuring section (131) that forms an EIS measuring path connected to (+)(-) of the battery module (111) to allow EIS current to flow and discharges the battery module through an EIS measuring operation of the battery module (111), and a pack control section (140) that controls the operation of the cell balancing section (121) and the EIS measuring section (131) within the battery pack (100) under the control of a rack control section (300).

[0037] At this time, FIG. 1 is illustrated as including battery cells in which a plurality of battery modules (111) are connected in series, but is not limited thereto and may be configured in parallel or a combination of series and parallel. Additionally, a pack control unit (140) is included in each battery pack.

[0038] When the rack control unit (300) differs from the average SOC of all other battery packs monitored by the SOC monitoring unit (200) or the SOC of any other battery pack by more than a predetermined reference value, the rack control unit (300) controls the EIS measurement unit (130) of the first battery pack (100) to operate the EIS measurement through the pack control unit (140).

[0039] At this time, the first battery pack (100) may be a new battery pack in which a battery pack that has a problem, such as a failure, among a plurality of battery packs configured in a battery rack has been replaced. For example, the battery pack that has been replaced with a new one has less State of Health (SOH) degradation, whereas the normal battery packs that are currently in use (not replaced) may have SOH degradation. Therefore, the SOC balance between the replaced battery pack and the battery packs that have not been replaced may not be correct.

[0040] Referring together with FIG. 2, the cell balancing section (120) of the battery pack (100) includes a balancing resistor (121a) formed in a cell balancing path through which cell current flows by connecting the (+) and (-) terminals of each battery cell to generate a cell potential difference due to the cell current flowing in the cell balancing path, and a balancing switch (B_SW) formed in the cell balancing path to perform pack balancing operation by turning the cell balancing path on / off. At this time, the balancing switch (B_SW) is selectively turned on / off by a control signal from the rack control section (300).

[0041] Additionally, the EIS measuring unit (130) of the battery pack (100) includes an EIS measuring path through which an EIS current (AC current for EIS measurement) flows by connecting the (+) and (-) terminals of a battery module (110) having one or more battery cells, an EIS measuring resistor (131a) that generates an EIS potential difference due to the EIS current flowing in the EIS measuring path, and an EIS current switch (EIS_SW) formed in the EIS measuring path that turns the EIS measuring path on / off at a predetermined cycle to discharge the capacity of the battery module (110) simultaneously with the EIS measurement operation of the battery module (110). At this time, the EIS current switch (EIS_SW) is selectively turned on / off by a control signal from the rack control unit (300) through the pack control unit (140).

[0042] The cell balancing unit (120) and the EIS measurement unit (130) may be included in the BMS. The cell balancing unit (121) and the EIS measurement unit (131) are used in a configuration that can reduce the capacity (pack balancing operation) of at least one battery pack that is not balanced with the SOC of any other battery pack among a plurality of battery packs (100) provided inside the ESS rack.

[0043] When pack balancing operation is required, for example, when the first battery module (111) differs from the SOC average of all other battery modules (110) monitored by the SOC monitoring unit (200) or the SOC of any other battery module by a predetermined reference value or within a predetermined reference value, the rack control unit (300) controls either the cell balancing unit (120) or the EIS measurement unit (130) to selectively perform pack balancing.

[0044] When the rack control unit (300), based on the monitoring result of the SOC monitoring unit (200), determines that the SOC of the first battery pack (100) differs from the average SOC of all other battery packs or the SOC of any other battery pack by more than a predetermined reference value, the cell balancing unit (121) of the first battery pack (100) is not operated, and only the EIS measurement unit (131) of the first battery pack (100) is operated first (EIS measurement operation). That is, AC current for EIS measurement is extracted from the first battery pack (100) that requires pack balancing, and the EIS of the first battery pack (100) is measured while the first battery pack (100) is discharged. At this time, since the EIS measurement operation is performed in units of A (Ampere), the balancing speed can be significantly faster compared to the cell balancing of the cell balancing unit (120) which is operated in units of mA.

[0045] When the rack control unit (300), based on the monitoring result of the SOC monitoring unit (200), determines through the EIS measurement operation that the difference between the SOC of the first battery pack (100) and the average SOC of all other battery packs or the SOC of any other battery pack falls within a predetermined reference value, it stops the EIS measurement operation of the EIS measurement unit (131) of the first battery pack (100) and controls the battery cells of the first battery pack to be balanced with the cells of other battery packs through the cell balancing unit (120) of the first battery pack (100). That is, it discharges each cell provided in each cell balancing path through which the cell current formed by connecting the (+)(-) of each battery cell constituting the battery module (111) included in the first battery pack (100) that requires pack balancing flows. At this time, the cell balancing operation through the cell balancing unit (120) is slow because the cell balancing current is in the mA unit, but precise cell balancing is possible.

[0046] Meanwhile, the rack control unit (300) is configured to operate as a master BMS and the pack control unit (140) as a slave BMS, thereby enabling efficient management and data integration through measurement and control of the battery system.

[0047] Through this, the rack control unit (300) is a higher-level control device that manages the entire battery rack system. Accordingly, the rack control unit (300) can collect status data of multiple battery packs (100), synchronize between battery packs (100) and maintain the balance of the entire rack, control charging and discharging and safety management at the system level, and communicate with external systems (e.g., power grid, energy management system, etc.). That is, the rack control unit (300) coordinates the operation of the entire system and controls the flow of power by communicating with the outside. The rack control unit (300) may be a Rack Control Unit (RCU).

[0048] Additionally, the pack control unit (140) is a sub-control unit that manages the status of individual battery packs. By doing so, it monitors the voltage, current, temperature, etc. of the cells and modules inside the battery pack, performs cell-to-cell balancing, and can transmit status data to the master control unit (rack control unit (300)). The pack control unit (140) may be a Pack Control Unit (PCU) or a slave BMS.

[0049] Accordingly, when the pack control unit (140) collects detailed data of each battery pack (e.g., cell voltage, temperature, etc.) and transmits it to the rack control unit (300), the rack control unit (300) comprehensively analyzes this and issues a control command to the pack control unit (140) if necessary.

[0050] The rack control unit (300) may be a means for controlling the on / off of the balancing switch (B_SW) of the cell balancing unit (120) and the EIS switch (EIS_SW) of the EIS measurement unit (130) based on a control signal transmitted from the MCU or BMIC of the BMS through the pack control unit (140), or the MCU / BMIC may be configured as the rack control unit (300) or provided outside the BMS to control the on / off of the balancing switch (B_SW) and the EIS switch (EIS_SW).

[0051]

[0052] Hereinafter, a method for managing a battery rack according to an embodiment of the present invention will be described. The method for managing a battery rack according to an embodiment of the present invention may be a method for processing a received signal using the aforementioned battery rack, and since the aforementioned details regarding the battery rack can be applied as is, the description of redundant details may be omitted.

[0053] FIG. 3 is a drawing for explaining a method of managing a battery rack according to an embodiment of the present invention.

[0054] Referring to FIG. 3, a method for balancing battery packs constituting a battery rack according to an embodiment of the present invention first monitors the SOC of each battery pack in an SOC monitoring unit (200) (S10).

[0055] When, based on the monitoring result (S10), the difference between the SOC of the first battery pack (100) selected among the plurality of battery packs and the SOC of the entire battery pack or any other battery pack is greater than a predetermined reference value (S20), the rack control unit (300) controls the EIS measurement to be performed on the first battery pack (100) through the pack control unit (140) (S30).

[0056] The above EIS measurement operation extracts an AC current for EIS measurement from a first battery pack (100) that requires pack balancing, measures the EIS of the first battery pack (100), and discharges the first battery pack (100). At this time, since the EIS measurement operation is performed in units of A (Ampere), the balancing speed can be significantly faster compared to the cell balancing of the cell balancing unit (120) which is operated in units of mA.

[0057] Additionally, if, based on the monitoring result (S10), the difference between the SOC of the first battery pack (100) and the average SOC of all other battery packs or the SOC of any other battery pack falls within a predetermined reference value (S20), the EIS measurement operation of the first battery pack (100) is stopped (S40), and control is made to balance with the cells of other battery packs through discharge via the cell balancing unit (120) (S50). At this time, although the balancing speed is slow because the cell balancing current through the cell balancing unit (120) is in the mA unit, precise cell balancing is possible.

[0058] The pack balancing operation through the cell balancing unit (120) is provided for each battery cell constituting the battery module (111) included in the first battery pack (100) that requires pack balancing, and discharges each cell. For example, by discharging each cell of the first battery pack (100) through the cell balancing unit (121) of the first battery pack (100), it refers to performing balancing with any battery cells of any other battery pack.

[0059] At this time, the first battery pack (100) may be a new battery pack in which a battery pack that has a problem, such as a failure, among a plurality of battery packs configured in a battery rack has been replaced. For example, the battery pack that has been replaced with a new one has less State of Health (SOH) degradation, whereas the normal battery packs that are currently in use (not replaced) have SOH degradation, so the SOC balance between the replaced battery pack and the battery packs that have not been replaced may not be balanced.

[0060] In this way, when the difference between the SOC of the first battery pack (100) and the average SOC of all other battery packs or the SOC of any other battery pack exceeds a predetermined reference value, the rack control unit (300) controls the cell balancing unit (120) not to operate and only the EIS measurement unit (130) to operate, thereby measuring the EIS of the first battery pack (100) and discharging the first battery pack (100). Then, when the difference between the SOC of the first battery pack (100) and the average SOC of all other battery packs or the SOC of any other battery pack falls within a predetermined reference value, the EIS measurement operation of the first battery pack (100) is stopped, and each cell is discharged through the cell balancing unit (120).

[0061] This is because, as the EIS measurement operation is performed in units of A, the balancing speed can be significantly faster compared to the pack balancing of the cell balancing unit (120) being performed in units of mA.

[0062] Accordingly, when the SOC of the first battery pack (100) differs from the average SOC of all other battery packs or the SOC of any other battery pack by more than a predetermined reference value, the first battery pack (100) is discharged quickly to increase the speed of pack balancing. Then, when the difference between the SOC of the first battery pack (100) and the average SOC of all other battery packs or the SOC of any other battery pack falls within a predetermined reference value, each cell is discharged through the cell balancing unit (120) to perform pack balancing slowly but precisely. At this time, the discharge of each cell can continue until pack balancing with other battery packs is accurately achieved. That is, instead of the aforementioned predetermined reference value, a smaller reference value is set to perform tight pack balancing.

[0063] That is, according to the configuration of the present invention, when discharging the first battery pack (100) for balancing between packs, the first pack balancing is performed by operating the EIS measuring unit (131) of the first battery pack, which is the battery pack that requires discharge for rapid balancing in the beginning, to perform rapid discharge. Afterwards, the cell balancing unit (121) is operated to perform precise second pack balancing. At this time, a predetermined reference value for determining whether the difference between the SOC of the first battery pack (100) and the average SOC of all other battery packs or the SOC of any other battery pack is greater than a predetermined reference value is applied as a value smaller than that for the first pack balancing in the case of second pack balancing.

[0064] According to the present invention, while the energy lost while balancing the first battery pack (100) in the conventional technology is not utilized anywhere, the present invention has the advantage of utilizing the energy lost by using the discharge energy used for balancing the first battery pack (100) to extract EIS measurement data.

[0065]

[0066] In the foregoing, preferred embodiments of the present invention have been described and illustrated using specific terms, but such terms are intended solely to clarify the present invention, and it is obvious that various modifications and changes may be made to the embodiments and described terms of the present invention without departing from the technical spirit and scope of the following claims. Such modified embodiments should not be understood separately from the spirit and scope of the present invention, but should be considered to fall within the scope of the claims of the present invention.

[0067] Meanwhile, the names of the reference numerals used in the present invention are as follows.

[0068] 10: Charge / Discharge Switch, 100: Battery Pack, 110: Battery Module, 120: Cell Balancing Unit, 121a: Balancing Resistor, 130: EIS Measurement Unit, 131a: EIS Resistor, 140: Pack Control Unit, 200: SOC Monitoring Unit, 300: Rack Control Unit, 400: External Device

Claims

1. A plurality of battery packs including an EIS (Electrochemical Impedance Spectroscopy: EIS) measuring unit; SOC monitoring unit for monitoring the SOC of each of the above battery packs; and A rack control unit that controls the operation of EIS measurement in the EIS measurement unit of the first battery pack when the State of Charge (SOC) of the selected first battery pack among the plurality of battery packs differs from the average SOC value of other battery packs or the SOC of any other battery pack by more than a predetermined reference value; A battery rack including 2. In Paragraph 1, Each of the above battery packs is, A battery module having one or more battery cells; A cell balancing unit that forms a cell balancing path through which a cell balancing current flows, connected to (+)(-) for each battery cell constituting the battery module above, and selectively discharges each cell; and A battery rack further comprising a pack control unit that controls the operation of a cell balancing unit and an EIS measuring unit within the battery pack under the control of the above-mentioned rack control unit.

3. In Paragraph 2, The above rack control unit is, If the SOC of the first battery pack differs from the average SOC of all other battery packs or the SOC of any other battery pack by more than a predetermined reference value, the EIS measuring unit of the first battery pack is controlled to operate EIS measurement, and A battery rack that, when the difference between the SOC of the first battery pack and the average SOC of all other battery packs or the SOC of any other battery pack falls within a predetermined reference value, stops the EIS measurement operation of the EIS measurement unit of the first battery pack and controls the battery cells of the first battery pack to be balanced with the cells of other battery packs through the cell balancing unit of the first battery pack.

4. In Paragraph 3, The cell balancing unit above is, A balancing resistor formed in a cell balancing path through which cell current flows by connecting the (+) and (-) terminals of each of the above battery cells, generating a cell potential difference due to the cell current flowing in the cell balancing path; and It includes a balancing switch (B_SW) formed in the cell balancing path and performing a cell balancing operation by turning the cell balancing path on / off, The above balancing switch (B_SW) is a battery rack that is turned on / off by a control signal from the rack control unit.

5. In Paragraph 3, The above EIS measuring unit is, An EIS measuring resistor that forms an EIS measuring path through which an EIS current (AC current for EIS measurement) flows by connecting the (+)(-) terminals of a battery module having one or more battery cells, and generates an EIS potential difference due to the EIS current flowing in the EIS measuring path; and It includes an EIS current switch (EIS_SW) formed in the EIS measurement path, which turns the EIS measurement path on / off at a predetermined period to discharge the battery module simultaneously with the EIS measurement operation of the battery module. The above EIS current switch (EIS_SW) is a battery rack that is selectively turned on / off by a control signal from the rack control unit.

6. In Paragraph 2, The above rack control unit controls the battery rack so that either the cell balancing unit or the EIS measuring unit is selectively operated when a pack balancing operation is required.

7. In Paragraph 1, A battery rack characterized in that the rack control unit is a means for controlling the on / off of the balancing switch (B_SW) of the cell balancing unit and the EIS switch (EIS_SW) of the EIS measuring unit based on a control signal transmitted from the MCU or BMIC of the BMS, or the MCU / BMIC is configured as the rack control unit or is provided outside the BMS to control the on / off of the balancing switch (B_SW) and the EIS switch (EIS_SW).

8. A method for balancing a plurality of battery packs constituting a battery rack, In the SOC monitoring unit, an SOC monitoring step for monitoring the SOC of each battery pack; An EIS measurement step in which, based on the monitoring result above, if the difference between the SOC of a selected first battery pack among the plurality of battery packs and the SOC average of all other battery packs or the SOC of any other battery pack differs by more than a predetermined reference value, the rack control unit controls the operation of EIS measurement in the first battery pack; and A battery rack management method comprising a cell balancing step in which, as a result of the above monitoring, if the difference between the SOC of the first battery pack and the average SOC of all other battery packs or the SOC of any other battery pack falls within a predetermined reference value, the rack control unit stops the EIS measurement operation of the first battery pack and controls it to be balanced with the cells of other battery packs through discharge via the cell balancing unit.

9. In Paragraph 8, The cell balancing step described above is, A method for managing a battery rack that performs balancing with any battery cells of another arbitrary battery pack by discharging each cell of the first battery pack through the cell balancing section of the first battery pack.

10. In Paragraph 8, The above EIS measurement step is a battery rack management method that extracts an AC current for EIS measurement from the first battery pack, measures the EIS of the first battery pack, and discharges the first battery pack.

11. In Paragraph 8, The cell balancing step is a method for managing a battery rack that discharges each cell provided in each cell balancing path through which a cell current formed by connecting the (+)(-) of each battery cell constituting a battery module included in the first battery pack flows.

12. In Paragraph 8, The above EIS measurement step is, If the SOC of the first battery pack differs from the SOC of another battery pack by more than a predetermined reference value, cell balancing through the cell balancing unit is not operated, and only EIS measurement is operated. The cell balancing step described above is, A battery rack management method that stops the EIS measurement operation and controls cell balancing through the cell balancing unit when the difference between the SOC of the first battery pack and the SOC of another battery pack falls within a predetermined reference value.

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