METHOD FOR ESTIMATING BATTERY RESISTANCE AND BATTERY SYSTEM PROVIDED WITH THE METHOD - Patent application

Abstract

The present invention relates to a method for estimating battery resistance and a battery system providing the same. The battery system of the present invention includes a battery including a new battery pack having a known internal resistance value and a target battery pack whose internal resistance needs to be estimated, and a master BMS (Battery Management System) that estimates a target resistance value of the target battery pack based on 1) a current value of a first compensation current that flows when the new battery pack and the target battery pack are connected in parallel, 2) a new resistance value of the new battery pack, and 3) a current value of a second compensation current corresponding to a first pack voltage difference value between the new battery pack and the target battery pack, a first reference resistance value, and a second reference resistance value.

Description

[Technical field]

[0001] Cross-reference to related application(s) This application claims the benefit of priority based on Korean Patent Application No. 10-2021-0155537 dated November 12, 2021, and all contents disclosed in the documents of that Korean patent application are incorporated herein by reference.

[0002] The present invention relates to a method for estimating the resistance of a battery and a battery system providing the method. [Background technology]

[0003] Batteries, which can be repeatedly charged and discharged, are gaining attention as an alternative to fossil energy. Batteries were mainly used in traditional handheld devices such as mobile phones, video cameras, and power tools. However, recently, their application areas have been gradually increasing, including electrically driven vehicles (EV, HEV, PHEV), large-capacity energy storage systems (ESS), and uninterruptible power supplies (UPS).

[0004] In the case of a battery, as the capacity decreases, the resistance increases, which causes more electrical energy to be lost as heat. Therefore, when the capacity of a battery decreases below a critical value, the performance of the battery drops significantly, the amount of heat generated increases, and the battery requires inspection or replacement.

[0005] Meanwhile, in a battery system (A) including a plurality of parallel-connected battery packs, when replacing some of the battery packs whose performance has deteriorated, the degree of deterioration (SOH: State Of Health) may differ between a battery pack that has already been installed and used for a certain period of time (hereinafter, referred to as an "Old Battery Pack") and a newly installed battery pack (New Battery Pack).

[0006] In this case, only when the degree of deterioration of the old battery pack is accurately known can an operation strategy be planned for the efficient use of the newly installed new battery pack and the old battery pack. Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention provides a method for estimating battery resistance, which estimates direct current internal resistance (DCIR), which is one of the factors indicating the degree of deterioration of a battery pack, and a battery system which provides such a method. [Means for solving the problem]

[0008] A battery system according to one aspect of the present invention includes a battery including a new battery pack whose internal resistance value is known and a target battery pack whose internal resistance value needs to be estimated, and a master Battery Management System (BMS) that estimates a target resistance value of the target battery pack based on 1) a current value of a first compensation current that flows when the new battery pack and the target battery pack are connected in parallel, 2) a new resistance value of the new battery pack, and 3) a current value of a second compensation current corresponding to a first pack voltage difference value between the new battery pack and the target battery pack, a first reference resistance value, and a second reference resistance value.

[0009] The second compensation current is a compensation current that flows when a first reference battery pack and a second reference battery pack having a second pack voltage difference value that is the same voltage value as the first pack voltage difference value are connected in parallel, the first reference resistance may be an internal resistance of the first reference battery pack, and the second reference resistance may be an internal resistance of the second reference battery pack.

[0010] The battery system may further include a memory in which a look-up table is stored in which 1) a current value of a second compensation current and 2) a first reference resistance value and a second reference resistance value corresponding to each of a plurality of second pack voltage difference values ​​are mapped and recorded.

[0011] The master BMS may select a second pack voltage difference value having the same voltage value as the first pack voltage difference value from among the plurality of second pack voltage difference values, and extract a current value of the second compensation current, the first reference resistance value, and the second reference resistance value mapped to the second pack voltage difference value, to estimate a target resistance value of the target battery pack.

[0012] The master BMS controls the first compensation current (I m ) current value, the new resistance value (R new ), the second compensation current (I d ) current value, the first reference resistor (R ref_1 ) value, and the second reference resistor (R ref_2 ) value into the following formula (1) to obtain the target resistance (R old_t ) values ​​to estimate the battery system.

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[0013] Each of the new battery pack and the target battery pack may include a battery module including a plurality of battery cells, a voltage sensor that measures a pack voltage which is a voltage across the battery module, a current sensor that measures a pack current flowing within the battery module, a pack switch that connects the battery module in parallel to the battery system when turned on, and a slave BMS that communicates with the master BMS to transmit measurement results of the voltage sensor and the current sensor and receive a control signal that controls a switching operation of the pack switch.

[0014] The master BMS may receive a first pack voltage value of the new battery pack and a second pack voltage value of the target battery pack measured before the new battery pack and the target battery pack are connected in parallel, and a current value of the first compensation current measured after the new battery pack and the target battery pack are connected in parallel, and may calculate the first pack voltage difference value which is a difference between the first pack voltage value and the second pack voltage value.

[0015] According to another aspect of the present invention, there is provided a battery resistance estimating method for estimating an internal resistance value of a target battery pack in a battery system including a new battery pack having a known internal resistance value and a plurality of existing battery packs for which an internal resistance value needs to be estimated, the method including the steps of: selecting the target battery pack from the plurality of existing battery packs according to a predetermined criterion; connecting the new battery pack and the target battery pack in parallel; receiving a current value of a first compensation current flowing between the new battery pack and the target battery pack connected in parallel, a first pack voltage value of the new battery pack, and a second pack voltage value of the target battery pack; and estimating a target resistance value of the target battery pack based on 1) the current value of the first compensation current, 2) a new resistance value of the new battery pack, and 3) a current value of a second compensation current corresponding to a first pack voltage difference value between the new battery pack and the target battery pack, a first reference resistance value, and a second reference resistance value.

[0016] the second compensation current is a compensation current that flows when a first reference battery pack and a second reference battery pack having a second pack voltage difference value that is the same voltage value as the first pack voltage difference value are connected in parallel, the first reference resistance is an internal resistance of the first reference battery pack, and the second reference resistance is an internal resistance of the second reference battery pack.

[0017] The step of estimating the target resistance value of the target battery pack may include the steps of: calculating the first pack voltage difference value, which is a difference value between the first pack voltage value and the second pack voltage value; and extracting, from a lookup table, a current value of the second compensation current, the first reference resistance value, and the second reference resistance value, which correspond to a second pack voltage difference value, which is the same voltage value as the first pack voltage difference value.

[0018] The step of estimating a target resistance value of the target battery pack includes, after the step of extracting from the look-up table, calculating the first compensation current (I m ) current value, the new resistance value (R new ), the second compensation current (I d ) current value, the first reference resistor (R ref_1 ) value, and the second reference resistor (R ref_2 ) value into the following formula (1) to obtain the target resistance (R old_t ) values ​​can be estimated.

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[0019] The receiving step may include receiving a first pack voltage value of the new battery pack and a second pack voltage value of the target battery pack measured before the new battery pack and the target battery pack are connected in parallel, and a current value of the first compensation current measured after the new battery pack and the target battery pack are connected in parallel. Effect of the Invention

[0020] The present invention can estimate the internal resistance (DCIR) of an old battery pack that has already been installed in a battery system (A) and used for a certain period of time in a simple manner without removing the old battery pack.

[0021] The present invention can accurately estimate the internal resistance (DCIR) of each of the old battery packs even when there are a plurality of old battery packs. [Brief description of the drawings]

[0022] [Figure 1] 1 is a diagram illustrating a battery system (A) for estimating a battery resistance according to an embodiment. [Diagram 2] 2 is a diagram illustrating in detail the configuration of the battery pack of FIG. 1. [Diagram 3] 1 is a conceptual diagram illustrating a method for measuring the internal resistance of a new battery pack among a plurality of battery packs by connecting a new battery pack and one of the existing battery packs in parallel. FIG. [Figure 4] 1 is a conceptual diagram illustrating a method for measuring the internal resistance of a new battery pack among a plurality of battery packs by connecting a new battery pack and one of the existing battery packs in parallel. FIG. [Diagram 5] 1 is a conceptual diagram illustrating a method for measuring the internal resistance of a new battery pack among a plurality of battery packs by connecting a new battery pack and one of the existing battery packs in parallel. FIG. [Figure 6] 4 is a diagram illustrating a method for estimating a battery resistance according to an embodiment; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Hereinafter, the embodiments disclosed in the present specification will be described in detail with reference to the attached drawings, and the same or similar components are given the same or similar drawing reference numerals, and the duplicated description thereof will be omitted. The suffixes "module" and / or "part" for components used in the following description are given or mixed for the sake of ease of specification preparation only, and do not have any meaning or role that is different from each other by themselves. In addition, when describing the embodiments disclosed in the present specification, if it is determined that a detailed description of related known technology may make the gist of the embodiments disclosed in the present specification unclear, the detailed description thereof will be omitted. In addition, the attached drawings are merely for the purpose of making the embodiments disclosed in the present specification easily understandable, and the technical ideas disclosed in the present specification are not limited by the attached drawings, and it should be understood that the drawings include all modifications, equivalents, or alternatives included in the idea and technical scope of the present invention.

[0024] Terms including ordinal numbers such as first, second, etc. may be used to describe various components, but the components are not limited to the terms. The terms are used only to distinguish one component from another.

[0025] When a component is said to be "coupled" or "connected" to another component, it should be understood that it may be directly coupled or connected to the other component, but there may also be other components in between. Conversely, when a component is said to be "directly coupled" or "directly connected" to another component, it should be understood that there are no other components in between.

[0026] In this application, the terms "comprise" or "have" and the like are intended to specify the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, but should be understood as not precluding the presence or additional possibility of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0027] FIG. 1 is a diagram illustrating a battery system (A) for estimating the resistance of a battery according to one embodiment, FIG. 2 is a diagram illustrating in detail the configuration of the battery pack of FIG. 1, and FIGS. 3 to 5 are conceptual diagrams illustrating a method of measuring the internal resistance of an existing battery pack by connecting a new battery pack and one of the existing battery packs in parallel among a plurality of battery packs.

[0028] Referring to FIG. 1, a battery system (A) includes a battery 10, a relay 20, and a master battery management system (BMS) 30.

[0029] The battery 10 includes a plurality of battery packs 1-N and a plurality of pack switches SW1-SWN that connect each of the plurality of battery packs 1-N in parallel to the battery system (A). Hereinafter, when a specific battery pack among the plurality of battery packs 1-N is designated, reference numeral "j" is used, and the battery modules, voltage sensors, slave BMSs, and pack switches included in the battery pack j are designated by reference numerals "j1," "j3," "j5," and "PSWj," respectively. In addition, when a specific pack switch that connects a specific battery pack j in parallel to the battery system (A) among the plurality of pack switches SW1-SWN is designated, reference numeral "SWj" is used.

[0030] 2, a battery pack j may include a battery module 100j, a voltage sensor 200j, a current sensor 300j, a slave BMS 400j, and a pack switch SWj. In FIG. 1, the battery pack j is illustrated as not including a pack switch SWj, but this is not limited thereto, and a pack switch SWj corresponding to any battery pack j may be included in the battery pack j.

[0031] The battery module 100j may include a plurality of battery cells connected in series and / or parallel. In some embodiments, the battery cells may be rechargeable secondary batteries. Although the battery module 100j includes three battery cells Cell1-Cell3 connected in series in FIG. 2, the battery module 100j may include various numbers of battery cells.

[0032] The voltage sensor 200j is connected in parallel to the battery module 100j. The voltage sensor 200j measures a pack voltage Vj, which is a voltage across the battery module 100j, and transmits the measurement result to the master BMS 30 through the slave BMS 400j.

[0033] The current sensor 300j is connected in series with the battery module 100j. The current sensor 300j measures a pack current Ij flowing through the battery module 100j and transmits the measurement result to the master BMS 30 through the slave BMS 400j.

[0034] The slave BMS 400j can communicate with the master BMS 30 to transmit data including various information on the battery cells, information on the pack voltage Vj, and the pack current Ij, and receive various commands. For example, the slave BMS 400j can receive a control signal that controls the switching (on / off) operation of the pack switch SWj.

[0035] The relay 20 can electrically connect or disconnect the battery system (A) and the external device (B). Specifically, if the relay 20 electrically connects the battery system (A) and the external device (B), the battery 10 can be charged with power from the external device (B) or supply power to the external device (B). The external device (B) can be a charger in a charge mode in which the battery 10 is charged, or a load (e.g., a vehicle motor, etc.) in a discharge mode in which the battery 10 is discharged.

[0036] 3 to 5, the relay 20 may be turned off while the master BMS 30 estimates the internal resistance (DCIR) of the battery pack j. In this way, the master BMS 30 can accurately estimate the internal resistance (DCIR) of the battery pack j without being affected by the external device (B).

[0037] When the master BMS 30 communicates with a higher-level controller (not shown) and receives a message instructing that a new battery pack is to be installed in the battery system (A), the master BMS 30 can select a target battery pack whose internal resistance (DCIR) needs to be estimated from among a plurality of old battery packs.

[0038] 1, the master BMS 30 may include a memory 31 in which a look-up table is stored in which a plurality of second compensation current values ​​and a reference resistance value corresponding to each of a plurality of second pack voltage difference values ​​are mapped and recorded. For example, the look-up table may be stored in the memory 31 in the form of Table 1 described below.

[0039] 3 to 5, for example, it is assumed that the first battery pack 1 is a new battery pack that has been replaced, and the second to fourth battery packs 2 to 4 are old battery packs. The new battery pack may be a battery pack that has not been used and has a known internal resistance value. The existing battery pack may be a battery pack that has already been installed in the battery system (A) and used for a certain period of time and has an unknown internal resistance value.

[0040] According to an embodiment, the master BMS 30 may select a target battery pack for estimating an internal resistance value from among the second to fourth battery packs 2-4, which are a plurality of existing battery packs, according to a predetermined criterion. The master BMS 30 may turn on each pack switch SWj so that the target battery pack and the new battery pack are connected in parallel. The master BMS 30 may estimate the internal resistance (DCIR) of the target battery pack based on each pack voltage Vj of the target battery pack and the new battery pack and the current value of the compensation current (Im) flowing between the target battery pack and the new battery pack connected in parallel. More detailed information will be described below with reference to FIGS. 3 to 6.

[0041] FIG. 6 is a diagram illustrating a method for estimating a battery resistance according to an embodiment.

[0042] Hereinafter, a battery resistance estimation method and a battery system that provides the method will be described with reference to FIGS.

[0043] Referring to FIG. 6, first, when the master BMS 30 communicates with a higher-level controller (not shown) and receives a message instructing that a new battery pack is to be installed in the battery system (A), the master BMS 30 performs an internal resistance (DCIR) estimation logic for the old battery pack (S100).

[0044] 3 to 5, it is assumed that the first battery pack 1 is a new battery pack that has been replaced, and the second to fourth battery packs 2 to 4 are old battery packs. However, the present invention is not limited to this, and the battery 10 may include various numbers of old battery packs and new battery packs.

[0045] Next, the master BMS 30 selects a target battery pack from among the multiple existing battery packs 2-4 according to a predetermined criterion (S200).

[0046] For example, if the internal resistance (DCIR) values ​​of each of the second to fourth battery packs 2-4 are required, the master BMS 30 may select the target battery pack in the order of the second battery pack 2, the third battery pack 3, and the fourth battery pack 4. However, without being limited thereto, the master BMS 30 may apply various criteria, such as randomly selecting the second to fourth battery packs 2-4 as the target battery pack.

[0047] Next, the master BMS 30 connects the new battery pack 1 and the target battery pack j in parallel (S300).

[0048] For example, referring to FIG. 3, the master BMS 30 can turn on the first pack switch SW1 of the first battery pack 1, which is a new battery, and the second pack switch SW2 of the second battery pack 2, which is the target battery pack, to connect the first battery pack 1 and the second battery pack 2 in parallel.

[0049] As another example, when the internal resistance (DCIR) estimation for the second battery pack 2 is completed (step S500 described below), the third battery pack 3, which is the next target battery pack, can be connected in parallel with the first battery pack 1, which is a new battery. Referring to Fig. 4, the master BMS 30 can turn on the first pack switch SW1 and the third pack switch SW3 to connect the first battery pack 1 and the third battery pack 3 in parallel.

[0050] As another example, when the internal resistance (DCIR) estimation for the third battery pack 3 is completed (step S500 described below), the fourth battery pack 4, which is the next target battery pack, can be connected in parallel with the first battery pack 1, which is a new battery. Referring to Fig. 5, the master BMS 30 can turn on the first pack switch SW1 and the fourth pack switch SW4 to connect the first battery pack 1 and the fourth battery pack 4 in parallel.

[0051] Next, the master BMS 30 receives the pack current value and the pack voltage value from each of the new battery pack and the target battery pack (S400).

[0052] 3, the master BMS 30 receives a first pack current (I1) value and a first pack voltage (V1) value from the first battery pack 1. The master BMS 30 also receives a second pack current (I2) value and a second pack voltage (V2) value from the second battery pack 2. At this time, the first pack current (I1) is a first compensation current (Im) flowing between the first battery pack 1 and the second battery pack 2 connected in parallel. The second pack current (I2) is also a first compensation current (Im) flowing between the first battery pack 1 and the second battery pack 2 connected in parallel. That is, when the first compensation current (Im) is measured at the first battery pack 1, it is the first pack current (I1), and when the first pack current (I1) is measured at the second battery pack 2, it is the second pack current (I2).

[0053] Also, the first pack voltage (V1) and the second pack voltage (V2) may be pack voltages measured before the first battery pack 1 and the second battery pack 2 are connected in parallel. When the first battery pack 1 and the second battery pack 2 are connected in parallel, the first compensation current (Im) flows according to the first pack voltage difference value (ΔVs). Then, due to a self-balancing effect, the pack voltage values ​​of the first battery pack 1 and the second battery pack 2 may become the same.

[0054] Next, the master BMS 30 calculates the current value of the first compensation current (Im), the current value of the second compensation current (Id), the resistance value of the new resistor (Rnew), the first reference resistor (R ref_1 ) and the resistance of the second reference resistor (R ref_2 ) resistance, the target battery pack internal resistance (DCIR) is calculated based on the target resistance (R old_t ) is estimated (S500).

[0055] The compensation current is a current generated due to a voltage difference between battery packs, and flows to match the voltage values ​​between battery packs connected in parallel. According to one embodiment, the first compensation current (Im) is a compensation current flowing between a new battery pack and a target battery pack connected in parallel. The second compensation current (Id) is a compensation current flowing between a first and second standard battery pack having a second pack voltage difference value (ΔVd) that is the same voltage value as the first pack voltage difference value (ΔVs) between the new battery pack and the target battery pack.

[0056] In step S500, first, the master BMS 30 calculates a first pack voltage difference value (ΔVs=|V1-V2|). For example, in FIG 3, the master BMS 30 may calculate a first pack voltage difference value (ΔVs) which is a difference value between the first pack voltage (V1) of the first battery pack 1 and the second pack voltage (V2) of the second battery pack 2. In this case, it is assumed that the first pack voltage difference value (ΔVs) is 20V.

[0057] In step S500, the master BMS 30 determines a current value (e.g., 5 A) of a second compensation current (Id) corresponding to a second pack voltage difference value (ΔVd=20 V) that is the same voltage value as the first pack voltage difference value (ΔVs=20 V), a first reference resistor (R ref_1 ) resistance (2Ω), and the second reference resistor (R ref_2 The resistance value (2 Ω) of the resistor 1 can be extracted from a look-up table.

[0058] The first pack voltage difference value (ΔVs) may be a difference value between the pack voltages of the new battery pack and the target battery pack, and the second pack voltage difference value (ΔVd) may be a difference value between the pack voltages of the first standard battery pack and the second standard battery pack.

[0059] The following table 1 shows the second compensation current (I diff ) current through the first reference resistor (R ref_1 ) and the resistance of the second reference resistor (R ref_2 1 is an example of a look-up table in which the resistance values ​​of the resistors 101 and 102 are mapped and recorded.

[0060] [Table 1]

[0061] In step S500, the master BMS 30 determines the current value of the first compensation current (Im), the current value of the second compensation current (I diff ), the resistance of the new resistor (Rnew), and the first reference resistor (R ref_1 ) and the resistance value of the second reference resistor (Rref_2) into the following equation (1), the resistance value of the target resistor (Rold_t) can be calculated or estimated.

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[0062] Specifically, formula (1) above can be derived on the premise that formula (2) and formula (3) below are identical. That is, formula (2) below is an equation for the first pack voltage difference value (ΔVs=20V), and formula (3) below is an equation for the second pack voltage difference value (ΔVd=20V).

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[0063] In the above formula (2), the first pack voltage difference value (ΔVs) represents the product of the first compensation current (Im) and the combined internal resistance (Rold_t+Rnew) of the parallel-connected battery packs, where the current value of the first compensation current (Im) is a current value measured in the battery pack, and the resistance value of the new resistor (Rnew) may be a previously known resistance value.

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[0064] In the above formula (3), the second pack voltage difference value (ΔVd) is calculated by multiplying the second compensation current (Id) and the combined internal resistance (R ref_1 +R ref_2 At this time, the current value of the second compensation current (Id) and the first reference resistance (R ref_1 The resistance value of the reference resistor Rref_1 and the resistance value of the second reference resistor Rref_2 may be values ​​that can be found through a look-up table.

[0065] In addition, in the above formula, if the new battery pack, the first reference battery pack, and the second reference battery pack are all new battery packs that have the same performance and have not been used, the internal resistance (DCIR) value of each battery pack may be the same. In this case, the above formula (1) may be rearranged as the following formula (4).

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[0066] For example, if the current value of the first compensation current (Im) is 2A, the current value of the second compensation current (Id) is 5A, the new resistor (Rnew), the first reference resistor (R ref_1 ), and a second reference resistor (R ref_2 ) has a resistance value of 2Ω. Then, the master BMS 30 can estimate the resistance value of the target resistor (Rold_t) to be 8Ω.

[0067] Next, the master BMS 30 determines whether there is an existing battery pack whose internal resistance value needs to be estimated (S600).

[0068] Next, if the determination result indicates that there is a battery pack (S600, Yes), the above-described process is repeated from S200. For example, when the second battery pack 2 is selected as the target battery pack and the estimation of the resistance value of the internal resistance (DCIR) of the second battery pack 2 is completed, the master BMS 30 may select the third battery pack 3 as the target battery pack. Also, when the estimation of the resistance value of the internal resistance (DCIR) of the third battery pack 3 is completed, the master BMS 30 may select the fourth battery pack 4 as the target battery pack.

[0069] Next, if the determination result is that there is no internal resistance (S600, No), the master BMS 30 ends the internal resistance value estimation logic.

[0070] Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by a person having ordinary skill in the field to which the present invention belongs also fall within the scope of the present invention. [Explanation of symbols]

[0071] 1-N Battery Pack 10. Battery 20 Relay 30 Master BMS 31 Memory

Claims

1. A battery including a new battery pack having a known internal resistance value and a target battery pack having a required internal resistance value to be estimated; A master BMS (Battery Management System), 1) a current value of a first compensation current flowing between the new battery pack and the target battery pack when the new battery pack and the target battery pack are connected in parallel; 2) a new resistance value, which is the internal resistance value of the new battery pack; and 3) A current value of the corresponding second compensation current, a first reference resistance value, and a second reference resistance value A master BMS that estimates a target resistance value, which is an internal resistance value of the target battery pack, based on the Including, the second compensation current is a compensation current flowing between the first reference battery pack and the second reference battery pack when a first reference battery pack and a second reference battery pack having a second pack voltage difference value that is the same voltage value as a first pack voltage difference value between the new battery pack and the target battery pack before the new battery pack and the target battery pack are connected in parallel are connected in parallel, The first reference resistance value is an internal resistance value of the first reference battery pack, The second reference resistance value is an internal resistance value of the second reference battery pack.

2. 2. The battery system of claim 1, further comprising a memory in which a look-up table is stored in which 1) a current value of the second compensation current and 2) a first reference resistance value and a second reference resistance value corresponding to each of a plurality of second pack voltage difference values ​​are mapped and recorded.

3. The master BMS comprises: selecting a second pack voltage difference value having an identical voltage value to the first pack voltage difference value from among the plurality of second pack voltage difference values; 3. The battery system of claim 2, further comprising: extracting a current value of the second compensation current mapped to the second pack voltage difference value, the first reference resistance value, and the second reference resistance value to estimate a target resistance value of the target battery pack.

4. The master BMS comprises: The current value of the first compensation current (I ｍ ), the new resistance value (R ｎｅｗ ), the current value of the second compensation current (I ｄ ), the first reference resistance value (R ｒｅｆ＿１ ), and the second reference resistance value (R ｒｅｆ＿２ ) into the following formula (1) to obtain the target resistance value (R ｏｌｄ＿ｔ 13. The battery system of claim 1, wherein the battery is further configured to estimate a current limit. [0010]

5. Each of the new battery pack and the target battery pack is 2. The battery system of claim 1, comprising: a battery module including a plurality of battery cells; a voltage sensor that measures a pack voltage which is a voltage across the battery module; a current sensor that measures a pack current flowing within the battery module; a pack switch that connects the battery module in parallel to the battery system when turned on; and a slave BMS that communicates with the master BMS to transmit measurement results of the voltage sensor and the current sensor and receive a control signal that controls a switching operation of the pack switch.

6. The master BMS comprises: receiving a first pack voltage value of the new battery pack and a second pack voltage value of the target battery pack measured before the new battery pack and the target battery pack are connected in parallel, and a current value of the first compensation current measured after the new battery pack and the target battery pack are connected in parallel; The battery system of claim 5 , further comprising: calculating the first pack voltage difference value to be a difference value between the first pack voltage value and the second pack voltage value.

7. A method for estimating an internal resistance value of a target battery pack in a battery system including a new battery pack having a known internal resistance value and a plurality of existing battery packs whose internal resistance values ​​need to be estimated, comprising: selecting the target battery pack from the plurality of existing battery packs according to a predetermined criterion; connecting the new battery pack and the target battery pack in parallel; receiving a current value of a first compensation current flowing between the new battery pack and the target battery pack connected in parallel, a first pack voltage value of the new battery pack, and a second pack voltage value of the target battery pack; 1) estimating a target resistance value that is an internal resistance value of the target battery pack based on a current value of the first compensation current, 2) a new resistance value that is an internal resistance value of the new battery pack, and 3) a current value of a second compensation current, a first reference resistance value, and a second reference resistance value; the second compensation current is a compensation current flowing between the first reference battery pack and the second reference battery pack when a first reference battery pack and a second reference battery pack having a second pack voltage difference value that is the same voltage value as a first pack voltage difference value between the new battery pack and the target battery pack before the new battery pack and the target battery pack are connected in parallel are connected in parallel, The first reference resistance value is an internal resistance value of the first reference battery pack, the second reference resistance value is an internal resistance value of the second reference battery pack; A battery resistance estimation method comprising:

8. The step of estimating a target resistance value of the target battery pack includes: calculating a first pack voltage difference value, the first pack voltage difference value being a difference value between the first pack voltage value and the second pack voltage value; and extracting, from a lookup table, a current value of the second compensation current, the first reference resistance value, and the second reference resistance value, the current value of the second compensation current corresponding to a second pack voltage difference value that is the same voltage value as the first pack voltage difference value.

9. The step of estimating a target resistance value of the target battery pack includes: After the step of extracting from the lookup table, The current value of the first compensation current (I ｍ ), the new resistance value (R ｎｅｗ ), the current value of the second compensation current (I ｄ ), the first reference resistance value (R ｒｅｆ＿１ ), and the second reference resistance value (R ｒｅｆ＿２ ) into the following formula (1) to obtain the target resistance value (R ｏｌｄ＿ｔ 9. The method of claim 8, further comprising estimating a resistance of a battery. [0025]

10. The receiving step includes:

8. The battery resistance estimating method of claim 7, further comprising receiving a first pack voltage value of the new battery pack and a second pack voltage value of the target battery pack measured before the new battery pack and the target battery pack are connected in parallel, and a current value of the first compensation current measured after the new battery pack and the target battery pack are connected in parallel.

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