Battery charging method and battery system providing the same

Abstract

The present invention relates to a battery charging method and a battery system providing the same. The battery system of the present invention is a battery system for charging a plurality of battery packs connected in parallel with power from a charger, the battery system including a battery including a plurality of battery packs, each including a battery module including a plurality of battery cells and a voltage sensor for measuring a pack voltage, which is a voltage across the battery module, and a master BMS for setting a plurality of voltage intervals using a minimum pack voltage value and a reference voltage value among the plurality of pack voltages, classifying each of the plurality of battery packs into a voltage interval to which it belongs among the plurality of voltage intervals, classifying the plurality of battery packs into a plurality of charging groups, and controlling charging of the battery packs belonging to the plurality of charging groups in the order from the charging group with a low voltage range to the charging group with a high voltage range.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of priority based on Korean Patent Application No. 10-2021-0152520 dated November 8, 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 charging a plurality of battery packs connected in parallel and a battery system which provides such a method. [Background technology]

[0003] In general, a lithium-ion battery charger safely charges a battery using a constant current (CC) / constant voltage (CV) charging method. For example, when the battery voltage is below a reference voltage level (Vref) (e.g., 4.2V), the battery is charged with a constant current (CC) of a preset intensity (I1) (e.g., 1.5C-rate), and when the battery voltage reaches the reference voltage level (Vref), the battery is charged with a constant voltage (CV) of the reference voltage level (Vref) (e.g., 4.2V).

[0004] Constant current (CC) charging is to charge the battery with a constant current strength. When constant current (CC) charging is performed, the battery voltage gradually increases. Even if the battery voltage reaches the reference voltage level (Vref) (e.g. 4.2V) during constant current (CC) charging, the battery is not in a buffer state. Once the battery voltage reaches the reference voltage level (Vref), the charger can switch to constant voltage (CV) charging to fully charge the battery without damaging the battery's performance.

[0005] Meanwhile, when the pack voltage difference between multiple battery packs connected in parallel is equal to or greater than a predetermined reference value, if the switches connected to each battery pack (hereinafter, pack switches) are turned on simultaneously for charging, the amount of current (hereinafter, compensation current) flowing between the battery packs may be large and the pack switches may be damaged.

[0006] In addition, if the relay unit that electrically connects the battery system to an external device (e.g., a charger) does not include a pre-charge resistor, when the relay unit is turned on for charging, the amount of current (hereinafter, charging current) flowing from the charger to the battery system may be large (inrush current), and the relay unit may be damaged. Furthermore, if the charger does not have a constant voltage (CV) charging function, the relay unit may be damaged when it is turned off after charging is completed. Specifically, there is a high risk of damage if the relay unit is turned off while a current (especially an overcurrent) is flowing.

[0007] Therefore, when charging multiple battery packs connected in parallel, a method is required that can charge the battery packs without damaging the pack switches and / or relays even when the battery system is not equipped with a pre-charge resistor and / or when charging with a charger that does not have a constant voltage (CV) charging function. Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention provides a battery charging method capable of charging a plurality of battery packs without damaging a plurality of pack switches that respectively connect the battery packs in parallel to the battery system, even when the voltage difference between the plurality of battery packs connected in parallel is large, and a battery system that provides the method.

[0009] The present invention provides a battery charging method capable of charging a battery without damaging a main relay even in a battery system without a pre-charge resistor, and a battery system providing the method.

[0010] The present invention provides a battery charging method capable of charging a battery without damaging a main relay even when an external charger that does not have a constant voltage (CV) charging function and only has a constant current (CC) charging function is used, and a battery system that provides this method. [Means for solving the problem]

[0011] According to one aspect of the present invention, a battery system charges a plurality of battery packs connected in parallel with power from a charger, the battery system including a battery including a plurality of battery packs, each including a battery module including a plurality of battery cells and a voltage sensor measuring a pack voltage, which is a voltage across the battery module, and a master BMS that sets a plurality of voltage intervals using a minimum pack voltage value and a reference voltage value among the plurality of pack voltages, classifies each of the plurality of battery packs into a voltage interval to which it belongs among the plurality of voltage intervals, and divides the plurality of battery packs into a plurality of charging groups, and controls charging of the battery packs belonging to the plurality of charging groups in the order from the charging group with a low voltage range in the voltage interval to the charging group with a high voltage range in the voltage interval.

[0012] The master BMS may set the plurality of voltage intervals by adding a multiple of the reference voltage value to the lowest pack voltage value.

[0013] The battery pack may further include a pack switch that connects the battery modules in parallel to the battery system, and a slave BMS that communicates with the master BMS to transmit a message indicating a pack voltage value, receive a signal to control the pack switch, and control the pack switch.

[0014] The master BMS may select a charging group having the lowest voltage range in a corresponding voltage section from among a plurality of charging groups not being charged, control the slave BMS to turn on a pack switch of a battery pack belonging to the selected charging group, and transmit a current increase request signal to the charger requesting that a charging current supplied by the charger be increased from a predetermined lower limit current amount to a predetermined upper limit current amount for a predetermined preparation time.

[0015] When the pack voltage value of the battery module being charged reaches a maximum voltage value of a voltage section corresponding to the selected charging group, the master BMS may transmit a current reduction request signal to the charger requesting that the charging current be reduced from the upper limit current amount to the lower limit current amount for a predetermined end time.

[0016] The master BMS may transmit the current reduction request signal to the charger if a pack voltage value of the battery modules reaches an upper charging voltage limit while the battery modules are being charged.

[0017] According to another aspect of the present invention, a battery charging method is a method in which a master BMS charges a plurality of battery packs connected in parallel with power of a charger, the method including: a grouping step of setting a plurality of voltage intervals using a lowest pack voltage value and a reference voltage value among pack voltages of each of the plurality of battery packs, classifying each of the plurality of battery packs into a voltage interval among the plurality of voltage intervals, and classifying the plurality of battery packs into a plurality of charging groups; and a charging step of controlling charging of the battery packs belonging to the plurality of charging groups in the order from a charging group with a low voltage range in the voltage interval to a charging group with a high voltage range in the voltage interval.

[0018] The grouping step may set the plurality of voltage intervals by adding a multiple of the reference voltage value to the lowest pack voltage value.

[0019] The charging step may include a step of selecting a charge group having a lowest voltage range of a voltage section from among a plurality of uncharged charge groups, turning on pack switches of battery packs belonging to the selected charge group to connect the battery packs belonging to the selected charge group in parallel to a battery system, and a step of transmitting a current increase request signal to the charger to request that a charging current supplied by the charger be increased from a predetermined lower limit current amount to a predetermined upper limit current amount for a predetermined preparation time, thereby starting charging.

[0020] The method may further include, after the step of starting charging, transmitting a current reduction request signal to the charger to request that the charging current be reduced from the upper limit current amount to the lower limit current amount for a predetermined termination time, when a pack voltage value of the battery module being charged reaches a maximum voltage value of a voltage range corresponding to the selected charging group, thereby temporarily suspending charging.

[0021] After the step of temporarily pausing the charging, the method may include determining whether there are a plurality of charging groups that are not being charged; if there is only one charging group, turning on pack switches of battery packs that belong to a final charging group to connect the battery packs that belong to the final charging group in parallel to a battery system; and transmitting a current increase request signal to the charger to charge the plurality of battery modules.

[0022] If a pack voltage value of the battery modules reaches a charging upper limit voltage after charging the battery modules, the current reduction request signal may be transmitted to the charger to terminate charging. Effect of the Invention

[0023] The present invention groups a plurality of battery packs connected in parallel based on the pack voltage into a plurality of charging groups that are divided into predetermined voltage intervals, and controls the charging of the battery packs belonging to each charging group in the order from the charging group with the lowest voltage value in the voltage interval to the charging group with the highest voltage value in the voltage interval, thereby making it possible to charge a plurality of battery packs without damaging the pack switches.

[0024] In the present invention, the master BMS communicates with an external charger to control the amount of charging current so that the charging current gradually increases in the charging start section and gradually decreases in the charging end section, thereby making it possible to charge the battery without damaging the main relay. [Brief description of the drawings]

[0025] [Figure 1] FIG. 1 is a diagram illustrating a battery charging system according to an embodiment. [Diagram 2] FIG. 2 is a block diagram illustrating the battery system of FIG. 1 in detail. [Diagram 3] FIG. 3 is a block diagram illustrating the battery of FIG. 2 in greater detail. [Figure 4] 4 is a flowchart illustrating a battery charging method according to an embodiment. [Diagram 5] FIG. 5 is an exemplary diagram illustrating the grouping step S200 of FIG. [Figure 6] 5 is a flow chart illustrating in detail the charging stage S300 of FIG. 4; [Figure 7] 5 is an exemplary diagram illustrating a change in the amount of charging current in the process of charging a plurality of battery packs by the charging method of FIG. 4. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] Hereinafter, the embodiments disclosed herein will be described in detail with reference to the attached drawings, and the same or similar components are denoted by the same or similar 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 writing only, and do not have any meaning or role that is different from each other. In addition, when describing the embodiments disclosed herein, if it is determined that a specific description of such known technology may obscure the gist of the embodiments disclosed herein, the detailed description thereof will be omitted. Furthermore, the attached drawings are merely for the purpose of making the embodiments disclosed herein easily understandable, and it should be understood that the attached drawings do not limit the technical ideas disclosed herein, and include all modifications, equivalents, or alternatives within the ideas and technical scope of the present invention.

[0027] Terms including ordinal numbers such as first, second, etc. may be used to describe various components, but the components are not limited by the terms. The terms are used only to distinguish one component from another.

[0028] 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 that there may be other components in between. In contrast, 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.

[0029] It should be understood that in this application, terms such as "comprise" or "have" are intended to specify the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0030] FIG. 1 is a diagram illustrating a battery charging system according to one embodiment, FIG. 2 is a block diagram illustrating the battery system of FIG. 1 in detail, and FIG. 3 is a block diagram illustrating the battery bank of FIG. 2 in detail.

[0031] Referring to FIG. 1, the charging system includes an external charger A and an automobile system B.

[0032] The automobile system B includes a battery system 100 and a host controller 200. Referring to Fig. 1, the battery system 100 is electrically connected to an external charger A and is charged with power from the external charger A. In addition, the battery system 100 can communicate with the external charger A via the host controller 200 to transmit and receive various signals and data.

[0033] Specifically, the master BMS 40 described below controls the battery system 100 overall, and can communicate with the external charger A via the upper controller 200 to transmit and receive various signals and data. However, the present invention is not limited thereto, and the master BMS 40 can include a communication module capable of directly communicating with the external charger A without going through the upper controller 200. In this case, the upper controller 200 can include an ECU (Electronic Control Unit) that controls the automobile system B overall.

[0034] The external charger A is electrically connected to the battery system 100 and can supply power to the battery system 100 to charge the battery system 100. According to an embodiment, the external charger A can include a charger that is not equipped with a constant current (CC) function and is equipped with only a constant voltage (CV) charging function. Even if the external charger A is not equipped with a constant current (CC) function, when charging the battery 10 according to the charging method described below with reference to FIG. 4, it is possible to prevent a main relay SW described below from being damaged by a charging current supplied from the external charger A at a charging end stage.

[0035] Referring to FIG. 2, the battery system 100 includes a battery 10, a relay unit 20, a current sensor 30, and a master BMS (Battery Management System) 40.

[0036] The battery 10 may include a plurality of battery packs 1-N connected in parallel. Hereinafter, when referring to a specific battery pack among the plurality of battery packs 1-N, reference numeral "j" will be used, and reference numerals "j1", "j3", "j5", and "PSWj" will be used to refer to the battery modules, voltage sensors, slave BMSs, and pack switches included in the battery pack j, respectively.

[0037] Referring to Fig. 3, the battery pack j may include a battery module j1, a voltage sensor j3, a slave BMS j5, and a pack switch PSWj. In Fig. 3, the pack switch PSWj includes a positive pack switch PSWj(+) and a negative pack switch PSWj(-), but is not limited thereto. For example, the pack switch PSWj may include only a positive pack switch PSWj(+). In addition, the battery pack j may further include a pack current sensor (not shown) that measures a pack current flowing through the battery module j1.

[0038] The battery module j1 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 FIG. 3 illustrates a battery module j1 including three battery cells connected in series, the battery module j1 may include various numbers of battery cells.

[0039] Each of the battery cells is electrically connected to the slave BMSj5 via a wire. The slave BMSj5 can transmit various information related to the battery cells, including information related to the battery cells, to the master BMS40. The slave BMSj5 can control charging and discharging of the battery cells under the control of the master BMS40.

[0040] The voltage sensor j3 is connected in parallel with the battery module j1. The voltage sensor j3 measures a pack voltage, which is a voltage across the battery module j1, and transmits the measurement result to the slave BMS j5.

[0041] The slave BMSj5 can communicate with the master BMS40 to transmit data including various information about the battery cells and information about the pack voltage, and receive various commands.

[0042] According to one embodiment, the slave BMSj5 can control the switching operation of the pack switch PSWj under the control of the master BMS 40. For example, the slave BMSj5 can generate switching control signals PSC[j1], PSC[j2] of an on level to control the pack switch PSWj to be turned on. At this time, the switching operation of the pack switch PSWj can include turn-on (turn-on, close) or turn-off (turn-off, open).

[0043] The pack switch PSWj can electrically connect or disconnect the battery module j1 to the battery system 100. For example, when the pack switch PSWj is turned on, the battery module j1 is connected to the battery system 100 in parallel.

[0044] In the case where the pack switch PSWj includes a positive pack switch PSWj(+) and a negative pack switch PSWj(-), when the positive pack switch PSWj(+) and the negative pack switch PSWj(-) are turned on, the battery module j1 is connected in parallel to the battery system 100. When at least one of the positive pack switch PSWj(+) and the negative pack switch PSWj(-) is turned off, the battery module j1 is electrically isolated from the battery system 100.

[0045] The relay unit 20 can electrically connect or disconnect the battery system 100 and the external charger A. Specifically, when the relay unit 20 electrically connects the battery system 100 and the external charger A, the battery 10 is charged with power from the external charger A.

[0046] 2, the relay unit 20 may include a pre-charge relay SWp, a pre-charge resistor Rp, and a main relay SW. At this time, the pre-charge relay SWp may perform a switching operation according to a pre-charge switching control signal SC[1] transmitted by the master BMS 40. The main relay SW may perform a switching operation according to main switching control signals SC[2] and SC[3] transmitted by the master BMS 40.

[0047] When the pre-charge relay SWp is turned on, the amount of charging current supplied from the external charger A is reduced through the pre-charge resistor Rp, and the reduced minute current is supplied to the battery 10. Thereafter, when a predetermined time has elapsed since the main relay SW was turned on, the pre-charge relay SWp is turned off. This makes it possible to prevent the main relay SW from being damaged by an inrush current supplied from the external charger A.

[0048] According to an embodiment, the relay unit 20 may not include the precharge relay SWp and the precharge resistor Rp. Even if the battery system 100 does not include the precharge relay SWp and the precharge resistor Rp, when charging the battery 10 by the charging method described below with reference to Fig. 4, the main relay SW can be prevented from being damaged by an inrush current supplied from the external charger A at the start of charging.

[0049] The main relay SW can electrically connect or disconnect the battery system 100 and the external charger A. Although a first main relay SW1 connecting the positive electrode (+) of the battery system 100 and the external charger A and a second main relay SW2 connecting the negative electrode (-) of the battery system 100 and the external charger A are shown in Fig. 1, the present invention is not limited thereto. For example, the main relay SW may include only the first main relay SW1 connecting the positive electrode (+) of the battery system 100 and the external charger A.

[0050] The current sensor 30 is connected in series to a current path between the battery 10 and the external charger A. The current sensor 30 can measure a battery current flowing through the battery 10, that is, a charging current Icc or a discharging current, and transmit the measurement result to the master BMS 40.

[0051] The master BMS 40 can control charging of a plurality of battery packs 1-N connected in parallel by communicating with the external charger A via the upper controller 200. Hereinafter, it will be described that the master BMS 40 communicates with the external charger A, which may include a first method of communicating with the external charger A via the upper controller 200 and a second method of directly communicating with the external charger A.

[0052] According to one embodiment, the master BMS 40 groups a plurality of battery packs 1-N into a plurality of charging groups based on pack voltage values, and controls charging of a battery pack j belonging to a plurality of charging groups according to a voltage range of the charging group. As a result, when a plurality of battery packs 1-N are connected in parallel, it is possible to prevent the pack switch PSWj from being damaged by an overcurrent flowing between the plurality of battery packs 1-N. A more detailed description will be given below with reference to Figs. 4 to 7.

[0053] FIG. 4 is a flowchart illustrating a battery charging method according to one embodiment, FIG. 5 is an example diagram illustrating the grouping step S200 of FIG. 4, FIG. 6 is a flowchart illustrating the charging step S300 of FIG. 4 in detail, and FIG. 7 is an example diagram illustrating a change in the amount of charging current during charging of a plurality of battery packs according to the charging method of FIG. 4.

[0054] Referring to FIG. 4, first, the master BMS 40 receives a charging preparation signal from the external charger A (S100).

[0055] The master BMS 40 can communicate with the external charger A via the upper controller 200. Alternatively, the master BMS 40 can be equipped with a communication module capable of communicating with the external charger A and can communicate directly with the external charger A. Hereinafter, the master BMS 40 and the external charger A will be described as communicating with each other, but this may be via the upper controller 200 or direct communication between them.

[0056] When the external charger A is ready to charge, it can transmit a charge preparation signal to the master BMS 40. The charge preparation signal is a signal indicating a state in which charging is possible when the external charger A and the battery system 100 are electrically connected after completing a physical connection between them. For example, the state in which charging is possible when electrically connected is a state in which the connection terminals for charging are physically connected and the battery 10 can be charged when only the relay unit 20 is turned on.

[0057] Next, the master BMS 40 groups the multiple battery packs 1-N into multiple charging groups based on the pack voltage values ​​and the reference voltage values ​​(S200).

[0058] The master BMS 40 can receive pack voltage values ​​from the slave BMS j5. The master BMS 40 can extract the lowest pack voltage value from among the pack voltage values ​​of each of the multiple battery packs 1-N. The master BMS 40 can set multiple voltage intervals by adding a multiple of a reference voltage value to the lowest pack voltage value. The master BMS 40 can classify each of the multiple battery packs 1-N into the voltage interval to which it belongs from among the multiple voltage intervals, and group the multiple battery packs 1-N into multiple charging groups Group1-GroupN.

[0059] The reference voltage value can be determined to be a voltage value at which the pack switch PSWj is not damaged by the balancing current. For example, when battery packs having a voltage difference of 10 V or less are connected in parallel, the balancing current flowing between the battery packs is not high, and therefore the pack switch PSWj is not damaged.

[0060] For example, if the reference voltage value is 10 V, the master BMS 40 can group the battery packs 1-N into integer multiples of 10 V. Then, the voltage difference between the battery packs belonging to each charging group is 10 V or less, and even if the battery packs belonging to the charging group are connected in parallel by the method described below, the pack switches of the battery packs belonging to the charging group will not be damaged by the balancing current.

[0061] 5, for example, it is assumed that the pack voltage values ​​of the first to ninth battery packs 1-9 are (1) (240V), (2) (244V), (3) (247V), (4) (251V), (5) (253V), (6) (256V), (7) (258V), (8) (267V), and (9) (269V). The master BMS 40 can extract the lowest pack voltage value (240V, (1)) from the nine pack voltage values ​​(1)-(9). The master BMS 40 can then add a multiple (e.g., an integer multiple) of a reference voltage value (e.g., 10V) to the lowest pack voltage value (240V, (1)) to set first to third voltage sections, and determine first to third charging groups Group1-Group3 corresponding to the first to third voltage sections, respectively.

[0062] The first voltage range may include a voltage range set by adding one time the reference voltage value (e.g., 10V) to the lowest pack voltage value (240V, (1)). For example, as shown in FIG. 5, the first voltage range may include a voltage range of 240V or more and less than 250V. The second voltage range may include a voltage range calculated by adding twice the reference voltage value (e.g., 10V) (e.g., 20V) to the lowest pack voltage value (240V, (1)). In this case, the master BMS 40 may set the second voltage range so as not to include a range that overlaps with the first voltage range. For example, as shown in FIG. 5, the second voltage range may include a voltage range of 250V or more and less than 260V. The third voltage range may include a voltage range calculated by adding three times the reference voltage value (e.g., 10V) (e.g., 30V) to the lowest pack voltage value (240V, (1)). In this case, the master BMS 40 may set the third voltage section so as not to include a section overlapping with the first and second voltage sections. For example, as shown in FIG 5, the third voltage section may include a voltage section of 260V or more and less than 270V.

[0063] Referring to FIG. 5, the first charging group Group1 can include the first to third battery packs 1-3. Here, the pack voltage values ​​(1), (2), and (3) of the first to third battery packs 1-3 are included in the first voltage section (240V or more and less than 250V). The second charging group Group2 can include the fourth to seventh battery packs 4-7. Here, the pack voltage values ​​(4), (5), (6), and (7) of the fourth to seventh battery packs 4-7 are included in the second voltage section (250V or more and less than 260V). The third charging group Group3 can include the eighth and ninth battery packs 8 and 9. Here, the pack voltage values ​​(8), (9) of the eighth and ninth battery packs 8 and 9 are included in the third voltage section (260V or more and less than 270V).

[0064] Next, the master BMS 40 controls the charging of the battery packs belonging to the multiple charging groups in the order from the charging group with the lowest voltage range in the voltage section to the charging group with the highest voltage range in the voltage section (S300).

[0065] Referring to FIG. 6, in step S300, the master BMS 40 selects a charging group having the lowest voltage range of the voltage section from among the multiple charging groups Group1-GroupN, and connects at least one battery pack j belonging to the selected charging group to the battery system 100 (S310).

[0066] The master BMS 40 may control the slave BMS j5 to turn on the pack switch PSWj of the battery pack j belonging to the selected charging group. For example, when the slave BMS j5 of at least one or more battery packs j belonging to the selected charging group turns on the pack switch PSWj, at least one or more battery packs j belonging to the selected charging group are connected in parallel to the battery system 100. At this time, self-balancing is performed between the parallel-connected battery packs j, and the pack voltage values ​​of the respective battery packs j may be the same within a predetermined error range.

[0067] 5, the master BMS 40 selects the first charging group Group1 having the lowest voltage range in the voltage section, and controls the first to third slave BMSs 15, 25, and 35 to turn on the first to third pack switches PSW1, PSW2, and PSW3 corresponding to the first to third battery packs 1-3 belonging to the first charging group Group1. Then, the first to third battery packs 1-3 are connected in parallel to the battery system 100.

[0068] If the selected charging group is the first, the master BMS 40 controls the slave BMS j5 so that at least one battery pack j belonging to the selected charging group is connected in parallel to the battery system 100, and then controls the relay unit 20 so that the battery system 100 is electrically connected to an external device.

[0069] 5, when the selected charging group is the first charging group Group1, the master BMS 40 controls the first to third slave BMSs 15, 25, 35 to turn on the first to third pack switches PSW1, PSW2, PSW3 corresponding to the first to third battery packs 1-3, respectively, and then controls the relay unit 20 to be turned on. This can prevent the relay unit 20 from being damaged by an overcurrent of the charger.

[0070] In step S300, the master BMS 40 transmits a current increase request signal to the external charger A to start charging (S320).

[0071] The current increase request signal is a signal that requests that the charging current Icc be gradually increased from a predetermined lower limit current amount to a predetermined upper limit current amount during a predetermined preparation time. For example, the lower limit current amount may indicate 0 A. The upper limit current amount may be a current amount Ia optimized for charging the battery 10. Then, the external charger A can supply the charging current Icc to the battery system 100 such that the charging current Icc is gradually increased from the predetermined lower limit current amount to the predetermined upper limit current amount.

[0072] 7, the external charger A supplies the charging current Icc to the battery system 100 so that the amount of current gradually increases during a predetermined preparation time Tr, and when the amount of the charging current Icc reaches an upper limit current amount Ia, the external charger A supplies the charging current Icc at a constant amount of current corresponding to the upper limit current amount Ia to the battery system 100. In other words, when the amount of the charging current Icc reaches the upper limit current amount Ia, the external charger A can charge the battery 10 by a constant current (CC) charging method.

[0073] In step S300, if the pack voltage of the battery pack j being charged reaches the maximum voltage value of the voltage section corresponding to the selected charging group, the master BMS 40 transmits a current reduction request signal to the external charger A to temporarily suspend charging (S330).

[0074] The master BMS 40 can receive pack voltage values ​​from the multiple slave BMSs 15-N5 at a predetermined cycle or in real time. For example, if the pack voltage value of the battery pack being charged reaches the maximum voltage value of the voltage section corresponding to the selected charging group, the master BMS 40 can transmit a current reduction request signal to the external charger A. At this time, the maximum voltage value of the voltage section corresponding to the selected charging group can correspond to the minimum voltage value of the voltage section corresponding to the charging group selected next in order.

[0075] The current reduction request signal is a signal that requests that the charging current Icc be gradually reduced from the upper limit current amount to the lower limit current amount for a predetermined end time. Then, the external charger A can supply the charging current Icc, which gradually reduces from the upper limit current amount Ia to the lower limit current amount, to the battery system 100.

[0076] 5, for example, during the charging process of the first to third battery packs 1-3 included in the first charging group, if the pack voltage values ​​of the first to third battery packs 1-3 reach 250V, the maximum voltage value of the first charging group Group1, or approach a predetermined voltage difference, the master BMS 40 may transmit a current reduction request signal to the external charger A. In this case, the maximum voltage value (250V) of the first charging group Group1 may correspond to the minimum voltage value (250V) of the voltage section corresponding to the second charging group Group2, which is selected next in order.

[0077] 7, the external charger A supplies the charging current Icc to the battery system 100 so that the amount of current gradually decreases during a predetermined end time Tf, and suspends charging when the amount of the charging current Icc reaches a lower limit current amount (e.g., 0 A). Referring to the current pattern during the charging process for the first charging group Group1 in FIG 7, when the amount of change in the charging current Icc gradually increases and reaches a predetermined upper limit current amount Ia, it is maintained constant at the upper limit current amount Ia, and when it approaches a predetermined time difference (e.g., end time Tf) at the charging suspension time point t1, it gradually decreases and reaches the lower limit current amount (0 A).

[0078] In step S300, the master BMS 40 determines whether there are a plurality of charging groups that are not being charged (S340).

[0079] If the determination in step S300 is that there is more than one (Yes in S340), the master BMS 40 repeats from step S310. For example, when charging for the first charging group Group1 is completed and charging is temporarily suspended, the charging groups that have not been charged are the second charging group and the third charging group. Since there are more than one charging group that have not been charged, the master BMS 40 can select the second charging group as the next charging target. At this time, the master BMS 40 can perform steps S310, S320, and S330 for the second charging group.

[0080] Specifically, referring to Figures 5 and 7, the master BMS 40 controls the fourth to seventh slave BMSs 45, 55, 65, and 75 to turn on the fourth to seventh pack switches PSW4, PSW5, PSW6, and PSW7 corresponding to the fourth to seventh battery packs 4-7, respectively, at charging start time t1 for the second charging group Group2, and transmits a current increase request signal to the external charger A (S320).

[0081] When the first to third pack switches PSW1, PSW2, and PSW3 are on and the fourth to seventh pack switches PSW4, PSW5, PSW6, and PSW7 are turned on, the first to seventh battery packs 1-7 are connected in parallel to the battery system 100. Referring to Fig. 5, when the pack voltage values ​​of the first to seventh battery packs 1-7 reach the maximum voltage value (260V) of the voltage section corresponding to the second charging group Group2, the master BMS 40 transmits a current reduction request signal to the external charger A (S330).

[0082] 7, the second charging group is shown, which means that the second charging group is newly added to the charging process, and in the voltage section corresponding to the second charging group, the first to seventh battery packs 1-7 belonging to the first charging group and the second charging group are actually charged. Referring to the current pattern in the charging process for the second charging group, the amount of change in the charging current Icc gradually increases and when it reaches a predetermined upper limit current Ia, it is maintained constant at the upper limit current Ia, and when it approaches a predetermined time difference (e.g., the end time Tf) at the charging interruption time t2, it gradually decreases and reaches the lower limit current (0 A).

[0083] In step S300, if the number of battery packs is one (S340, No), the master BMS 40 controls at least one battery pack j belonging to the final charging group that remains uncharged to be connected to the battery system 100 (S350).

[0084] For example, in a state in which the first to seventh battery packs belonging to the first charging group Group1 and the second charging group Group2 are connected to the battery system 100, the master BMS 40 selects the eighth and ninth battery packs 8, 9 belonging to the third charging group Group3 that remain uncharged. Then, the master BMS 40 can control the eighth and ninth slave BMSs 85, 95 so that the eighth and ninth pack switches PSW8, PSW9 are turned on. Then, the first to ninth battery packs 1-9 are connected in parallel with each other, and self-balancing is performed between the first to ninth battery packs 1-9 connected in parallel. As a result, the pack voltage values ​​of the first to ninth battery packs 1-9 may be the same within a predetermined error range.

[0085] In step S300, the master BMS 40 transmits a current increase request signal to the external charger A (S360).

[0086] If the pack voltages of the battery packs 1-N being charged reach the upper charge voltage limit in step S300, the master BMS 40 transmits a current reduction request signal to the external charger A (S370).

[0087] The charging upper limit voltage is the maximum voltage to which the battery 10 can be charged without being dangerous, and can be set in advance according to a predetermined standard. For example, assume that the charging upper limit voltage is 290V. Referring to FIG. 5, unlike step S330, the master BMS 40 does not end charging even if the pack voltages of the first to ninth battery packs 1-9 reach the maximum voltage value (270V) of the voltage section corresponding to the third charging group Group3. The master BMS 40 maintains charging until the pack voltages of the first to ninth battery packs reach the charging upper limit voltage (290V), and when the pack voltages of the first to ninth battery packs reach the charging upper limit voltage (290V), it can transmit a current reduction request signal to the external charger A. For example, in FIG. 7, the pack voltage values ​​of the first to ninth battery packs at charging interruption time point t3 for the third charging group Group3 may be 290V.

[0088] In FIG. 7, the third charging group Group3 is shown, which means that the third charging group Group3 is newly added to the charging process, and the first to ninth battery packs 1-9 belonging to the first charging group Group1, the second charging group Group2, and the third charging group Group3 are actually charged in that voltage section.

[0089] Next, the master BMS 40 transmits a charging end signal to the external charger A (S400).

[0090] The charge end signal is a signal that requests that charging be terminated because there are no more battery packs to be charged. At this time, the master BMS 40 can turn off the relay unit 20 when, before, or after transmitting the charge end signal.

[0091] 4 and 6, steps S370 and S400 are distinguished, but the present invention is not limited thereto. For example, the master BMS 40 may transmit a current reduction request signal for the third charging group Group3 to the external charger A (S370), and then transmit a charging end signal (S400). As another example, the master BMS 40 may transmit a charging end signal to the external charger A together with the current reduction request signal for the third charging group Group3.

[0092] Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited to these embodiments, and various modifications and improvements made by those having ordinary skill in the art to which the present invention pertains also fall within the scope of the present invention.

Claims

1. A battery system that charges a plurality of battery packs connected in parallel with power from a charger, comprising: A battery including a plurality of battery packs including a battery module including a plurality of battery cells and a voltage sensor for measuring a pack voltage, which is a voltage across the battery module; a master BMS that sets a plurality of voltage intervals using a lowest pack voltage value and a reference voltage value among a plurality of pack voltages, classifies each of the plurality of battery packs into a voltage interval to which it belongs among the plurality of voltage intervals, and divides the plurality of battery packs into a plurality of charging groups, and controls charging of the battery packs that belong to the plurality of charging groups in the order from the charging group with a low voltage range in the voltage interval to the charging group with a high voltage range in the voltage interval.

2. The master BMS comprises: The battery system according to claim 1 , wherein the plurality of voltage intervals are set by adding a multiple of the reference voltage value to the minimum pack voltage value.

3. The battery pack includes: a pack switch that connects the battery modules in parallel to the battery system; 3. The battery system according to claim 1, further comprising: a slave BMS that communicates with the master BMS to transmit a message indicating a pack voltage value of the battery module, receives a signal to control the pack switch, and controls the pack switch.

4. The master BMS comprises:

4. The battery system of claim 3, further comprising: a charging group having the lowest voltage range in a corresponding voltage section among a plurality of charging groups not being charged; controlling the slave BMS to turn on a pack switch of a battery pack belonging to the selected charging group; and transmitting a current increase request signal to the charger to request that a charging current supplied by the charger be increased from a predetermined lower limit current amount to a predetermined upper limit current amount for a predetermined preparation time.

5. The master BMS comprises:

5. The battery system of claim 4, wherein when a pack voltage value of a battery module being charged reaches a maximum voltage value of a voltage section corresponding to the selected charging group, a current reduction request signal is transmitted to the charger to request that the charging current be reduced from the upper limit current amount to the lower limit current amount for a predetermined termination time.

6. The master BMS comprises: The battery system according to claim 5 , wherein when a pack voltage value of the plurality of battery modules reaches a charging upper limit voltage while the plurality of battery modules are being charged, the current reduction request signal is transmitted to the charger.

7. A battery charging method in which a master BMS charges a plurality of battery packs connected in parallel with power from a charger, comprising: a grouping step of setting a plurality of voltage intervals using a lowest pack voltage value and a reference voltage value among pack voltages of the plurality of battery packs, classifying each of the plurality of battery packs into a voltage interval to which it belongs among the plurality of voltage intervals, and classifying the plurality of battery packs into a plurality of charging groups; a charging stage for controlling charging of battery packs belonging to a plurality of charging groups in the order from the charging group with a low voltage range in the voltage section to the charging group with a high voltage range in the voltage section.

8. The grouping step includes:

8. The method of claim 7, further comprising: setting the plurality of voltage intervals by adding a multiple of the reference voltage value to the minimum pack voltage value.

9. The charging step comprises: selecting a charge group having a lowest voltage range of a voltage section from among a plurality of charge groups not being charged, and turning on pack switches of battery packs belonging to the selected charge group to connect the battery packs belonging to the selected charge group in parallel to a battery system; 9. The battery charging method of claim 7, further comprising: transmitting a current increase request signal to the charger, requesting that the charging current supplied by the charger be increased from a predetermined lower limit current amount to a predetermined upper limit current amount for a predetermined preparation time, thereby starting charging.

10. After the step of initiating charging, 10. The battery charging method of claim 9, further comprising: when a pack voltage value of the battery module being charged reaches a maximum voltage value of a voltage range corresponding to the selected charging group, transmitting a current reduction request signal to the charger to request that the charging current be reduced from the upper limit current amount to the lower limit current amount for a predetermined termination time, thereby temporarily suspending charging.

11. After the step of temporarily suspending charging, determining whether there is a plurality of charging groups that are not being charged; if the number of battery packs is one, turning on a pack switch of a battery pack belonging to a final charging group to connect the battery pack belonging to the final charging group in parallel to the battery system; 11. The method of claim 10, further comprising: transmitting a current increase request signal to the charger to charge a plurality of battery modules.

12. After the step of charging the plurality of battery modules, The battery charging method according to claim 11, further comprising transmitting the current reduction request signal to the charger and terminating charging when the pack voltage value of the plurality of battery modules reaches a charging upper limit voltage.

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