Charge / discharge control device, dual battery pack system, electric vehicle, and charge / discharge control method

Abstract

A charge / discharge control device, a dual battery pack system, an electric vehicle, and a charge / discharge control method are provided. The charge / discharge control device according to the present invention is for controlling the charge and discharge of a dual battery pack system including a first battery pack and a second battery pack, and includes a first relay connected between the first battery pack and a load, a second relay connected between the second battery pack and the load, a DC / DC converter connected between the second battery pack and the load, a voltage measuring unit for measuring the first pack voltage of the first battery pack and the second pack voltage of the second battery pack, and a control unit for controlling the first relay, the second relay, and the DC / DC converter. The control unit controls the DC / DC converter to a turned-on state during a voltage adjustment period in which a reduction in the voltage difference between the first pack voltage and the second pack voltage is required while operating in a discharge sequence control mode.

Description

[Technical Field]

[0001] The present invention relates to a technology for controlling the charging and discharging of a dual battery pack system, and more specifically, to an apparatus and method for controlling the charging and discharging of a dual battery pack system by utilizing a DC / DC converter, provided as a power transmission channel between the auxiliary battery pack and the load (one of two battery packs provided for power supply to the load), as a temporary voltage regulator to suppress the voltage difference between the main battery pack and the auxiliary battery pack, or the voltage difference between the auxiliary battery pack and the output side of the DC / DC converter.

[0002] This application claims priority based on Korean Patent Application No. 10-2023-0096260, filed on 24 July 2023, and all contents disclosed in the specification and drawings of said application are incorporated into this application. [Background technology]

[0003] Recently, demand for portable electronic products such as laptops, video cameras, and mobile phones has increased dramatically, and with the full-scale development of electric vehicles, energy storage batteries, robots, and satellites, research into high-performance batteries capable of repeated charging and discharging is becoming increasingly active.

[0004] Currently available commercially include nickel-cadmium batteries, nickel-metal hydride batteries, nickel-zinc batteries, and lithium batteries. Among these, lithium batteries are attracting attention because they have advantages such as virtually no memory effect compared to nickel-based batteries, allowing for flexible charging and discharging, a very low self-discharge rate, and high energy density.

[0005] As the demand for higher capacity batteries, such as those required for long-distance driving, increases daily for electric vehicles and other applications, the demand for so-called "dual battery pack systems," which include two battery packs that can be connected in parallel, is also expanding.

[0006] In a dual battery pack system, one of the two battery packs can be used as the main battery pack, and the other as the auxiliary battery pack. The auxiliary battery pack is used to supplement the output of the main battery pack when the main battery pack alone is insufficient to supply power to the electrical load.

[0007] On the other hand, if one of the two battery packs is electrically connected to a load on its own, and the other battery pack is then electrically connected to the load, an excessive voltage difference between the two battery packs may cause an inrush current to flow between them. In this case, the inrush current could damage not only the two battery packs but also the surrounding circuitry. Therefore, it is necessary to adjust the voltage before connecting the two battery packs in parallel, and a DC / DC converter or similar device can be used for this purpose.

[0008] Conventionally, dual battery pack systems using the so-called active topology shown in Figure 8, or the semi-active topology shown in Figure 9, have been primarily used.

[0009] Referring to Figure 8, the active topology is a method that allows for more active use of the two battery packs by connecting one DC / DC converter to each of the main and auxiliary battery packs. Referring to Figure 9, the semi-active topology is a method in which a DC / DC converter is connected only to the power transfer path between the auxiliary battery pack and the load, and the DC / DC converter is constantly operating while power from the auxiliary battery pack is supplied to the load.

[0010] Both active and semi-active topologies involve supplying power to the load after the output voltage of the auxiliary battery pack is regulated via a DC / DC converter. Therefore, there is a constraint that the DC / DC converter must be kept running at all times while power from the auxiliary battery pack is being supplied to the load.

[0011] This means that the output and efficiency of the DC / DC converter will have a significant impact on the performance of the dual battery pack system.

[0012] Specifically, increasing the output of a DC / DC converter leads to an increase in its volume, so using a high-output DC / DC converter results in a decrease in the overall capacity of the battery pack. Furthermore, the high-efficiency DC / DC converters required for semi-active and active systems are expensive, leading to increased costs for the battery pack system. Active topologies also increase costs due to the use of two DC / DC converters and make dual battery pack systems difficult to control. In particular, among the various types of dual battery pack systems, hybrid dual battery pack systems, which include two different types of battery packs with complementary electrical performance characteristics, are even more difficult to operate and control effectively compared to other types of dual battery pack systems that include two identical battery packs.

[0013] Therefore, there is a need for charge / discharge control technology that can overcome the aforementioned drawbacks associated with conventional active and semi-active topologies. [Overview of the project] [Problems that the invention aims to solve]

[0014] The present invention has been made to solve the above problems and aims to provide a charge / discharge control device, a dual battery pack system, an electric vehicle, and a charge / discharge control method that can utilize a DC / DC converter, provided as a power transmission channel between the auxiliary battery pack and the load (of two battery packs provided for power supply to a load), as a temporary voltage regulator to suppress the voltage difference between the main battery pack and the auxiliary battery pack, or the voltage difference between the auxiliary battery pack and the output side of the DC / DC converter.

[0015] Other objectives and advantages of the present invention can be understood from the following description and will be understood more clearly from the embodiments of the present invention. Furthermore, it will be readily understood that the objectives and advantages of the present invention can be achieved by the means and combinations thereof set forth in the claims. [Means for solving the problem]

[0016] A charge / discharge control device according to one aspect of the present invention is for a dual battery pack system including a first battery pack and a second battery pack, and includes a first relay connected between the first battery pack and a load, a second relay connected between the second battery pack and the load, a DC / DC converter connected between the second battery pack and the load, a voltage measuring unit for measuring a first pack voltage which is the voltage across both ends of the first battery pack and a second pack voltage which is the voltage across both ends of the second battery pack, and a control unit for controlling the first relay, the second relay and the DC / DC converter based on at least one of the first pack voltage and the second pack voltage.

[0017] In response to a discharge start command received from the vehicle controller, the control unit enters a discharge sequence control mode, and during operation in the discharge sequence control mode, the control unit may be configured to control the DC / DC converter to be in an on state during a voltage adjustment required period in which reduction of the voltage difference between the first pack voltage and the second pack voltage is required.

[0018] During operation in the discharge sequence control mode, the control unit determines whether the first pack voltage is equal to or higher than a first reference voltage. When the first pack voltage is equal to or higher than the first reference voltage, the control unit may be configured to execute a first discharge stage of controlling the first relay to be in an on state so that the output power of the first battery pack is supplied to the load via the first relay.

[0019] During execution of the first discharge stage, when the difference between the first pack voltage and a predetermined second reference voltage lower than the first reference voltage becomes equal to or less than a first predetermined value, the control unit sets the target value of the output voltage of the DC / DC converter to be the same as the second reference voltage, and then may be configured to execute a second discharge stage of controlling the DC / DC converter to be in an on state so that the output power of the second battery pack is supplied to the load via the DC / DC converter.

[0020] When the execution time of the second discharge stage reaches a first set time, the control unit may be configured to execute a third discharge stage of controlling the first relay to be in an off state so that power supply from the first battery pack to the load is cut off.

[0021] During execution of the third discharge stage, when the difference between the output voltage of the DC / DC converter and the second pack voltage becomes equal to or less than a second predetermined value, the control unit may be configured to execute a fourth discharge stage of controlling the second relay to be in an on state so that the output power of the second battery pack is supplied to the load via both the DC / DC converter and the second relay.

[0022] The control unit may be configured to execute a fifth discharge stage, which controls the DC / DC converter to a turn-off state so that the power supply from the second battery pack to the load via the DC / DC converter is cut off when the execution time of the fourth discharge stage reaches a second set time.

[0023] The control unit may be configured to execute a sixth discharge stage, in which, if the voltage difference between the second pack voltage and the first pack voltage falls below a third predetermined value during the execution of the fifth discharge stage, the first relay is switched from the off state to the on state so that the parallel circuit of the first battery pack and the second battery pack is connected to the load.

[0024] The control unit may be configured to enter a charging sequence control mode in response to a charging start command received from the vehicle controller, identify the charging procedure between the first battery pack and the second battery pack, control the first relay to the turn-on state when the charging procedure for the first battery pack arrives until the voltage of the first pack reaches the target voltage, and control the second relay to the turn-on state when the charging procedure for the second battery pack arrives until the voltage of the second pack reaches the target voltage.

[0025] The control unit may be configured to prioritize the charging procedure for the first battery pack over the charging procedure for the second battery pack if the voltage of the first battery pack at the time of receiving the charging start command is less than or equal to the voltage of the second battery pack, and to prioritize the charging procedure for the second battery pack over the charging procedure for the first battery pack if the voltage of the first battery pack at the time of receiving the charging start command is greater than the voltage of the second battery pack.

[0026] Another aspect of the present invention includes a dual battery pack system that includes the charge / discharge control device.

[0027] An electric vehicle according to yet another aspect of the present invention includes the dual battery pack system.

[0028] A charge / discharge control method according to yet another aspect of the present invention can be executed by the charge / discharge control device. The charge / discharge control method may include the steps of: entering the discharge sequence control mode in response to a discharge start command received from the vehicle controller; and controlling the first relay, the second relay, and the DC / DC converter based on at least one of the first pack voltage and the second pack voltage while operating in the discharge sequence control mode.

[0029] The steps of controlling the first relay, the second relay, and the DC / DC converter may include at least one discharge process that controls the DC / DC converter to a turned-on state for a period of voltage adjustment required to reduce the voltage difference between the first pack voltage and the second pack voltage.

[0030] The steps of controlling the first relay, the second relay, and the DC / DC converter may further include: determining whether the first pack voltage is equal to or greater than a first reference voltage; and, if the first pack voltage is equal to or greater than the first reference voltage, performing a first discharge stage that controls the first relay to a turned-on state so that the output power of the first battery pack is supplied to the load via the first relay.

[0031] The steps of controlling the first relay, the second relay, and the DC / DC converter may further include, during the execution of the first discharge stage, if the difference between the first pack voltage and a predetermined second reference voltage less than the first reference voltage becomes less than or equal to a first predetermined value, the steps of controlling the DC / DC converter to a turn-on state such that the output power of the second battery pack, along with the output power of the first battery pack, is supplied to the load via the DC / DC converter, after setting the target value of the output voltage of the DC / DC converter to be the same as the second reference voltage.

[0032] The steps of controlling the first relay, the second relay, and the DC / DC converter may further include the step of performing a third discharge stage that controls the first relay to a turn-off state so that when the execution time of the second discharge stage reaches a first set time, the power supply from the first battery pack to the load is cut off.

[0033] The steps of controlling the first relay, the second relay, and the DC / DC converter may further include a step of performing a fourth discharge stage in which, during the execution of the third discharge stage, when the difference between the output voltage of the DC / DC converter and the voltage of the second pack falls below a second predetermined value, the output power of the second battery pack is supplied to the load via both the DC / DC converter and the second relay.

[0034] The steps of controlling the first relay, the second relay, and the DC / DC converter may further include the step of performing a fifth discharge stage, which controls the DC / DC converter to a turn-off state such that when the execution time of the fourth discharge stage reaches a second set time, the power supply from the second battery pack to the load via the DC / DC converter is cut off. [Effects of the Invention]

[0035] According to at least one embodiment of the present invention, among the two battery packs provided for supplying power to a load, the DC / DC converter provided as a power transmission channel between the auxiliary battery pack and the load is utilized for temporary voltage adjustment to suppress the voltage difference between the main battery pack and the auxiliary battery pack, or the voltage difference between the auxiliary battery pack and the output side of the DC / DC converter. This eliminates the need to constantly drive the DC / DC converter while power from the auxiliary battery pack is being supplied to the load, and allows power from the auxiliary battery pack to be supplied directly to the load via a relay without going through the DC / DC converter.

[0036] This eliminates the need for a high output from the DC / DC converter, allowing for the use of a smaller DC / DC converter. As a result, the overall pack capacity of the dual battery pack system can be increased. Furthermore, since a high-efficiency DC / DC converter is not required, a less expensive DC / DC converter can be used. Consequently, the overall cost of the dual battery pack system can be reduced. In addition, because the power from the auxiliary battery pack is output directly through a relay without going through a DC / DC converter, the overall capacity efficiency of the dual battery pack system can be improved.

[0037] Furthermore, according to at least one embodiment of the present invention, when configuring a dual battery pack system, if there is a difference in voltage between the battery packs during charging, the lower-voltage battery pack is charged preferentially, and after the voltages of the two packs become approximately equal, both battery packs can be charged simultaneously. This ensures safety because a large current does not flow from the higher-voltage battery pack to the lower-voltage battery pack. In addition, the charging time can be shortened when charging two battery packs simultaneously compared to charging each battery pack at different times.

[0038] The effects of the present invention are not limited to those mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description of the claims.

[0039] The following drawings accompanying this specification illustrate preferred embodiments of the invention and, together with the detailed description of the invention, serve to further illustrate the technical idea of ​​the invention; therefore, the invention should not be construed as being limited solely to what is shown in the drawings. [Brief explanation of the drawing]

[0040] [Figure 1] This diagram illustrates the configuration of an electric vehicle according to the present invention. [Figure 2] This timing chart is referenced to illustrate an example of a discharge sequence for a dual battery pack system executed by a charge / discharge control device according to one embodiment of the present invention. [Figure 3] Figure 2 is a graph illustrating the temporal changes in the first pack voltage, second pack voltage, and DC / DC converter output voltage during the execution period of the discharge sequence shown in Figure 2. [Figure 4a] This is a flowchart illustrating a charge / discharge control method according to one embodiment of the present invention. [Figure 4b] This is a flowchart illustrating a charge / discharge control method according to one embodiment of the present invention. [Figure 5a] This flowchart illustrates a charge / discharge control method according to another embodiment of the present invention. [Figure 5b] This flowchart illustrates a charge / discharge control method according to another embodiment of the present invention. [Figure 6] This flowchart illustrates a charge / discharge control method according to yet another embodiment of the present invention. [Figure 7] This flowchart illustrates a charge / discharge control method according to yet another embodiment of the present invention. [Figure 8]This diagram is referenced to provide a schematic explanation of a dual battery pack system to which an active topology relating to prior art is applied. [Figure 9] This diagram is referenced to provide a schematic explanation of a dual battery pack system to which a semi-active topology relating to prior art is applied. [Modes for carrying out the invention]

[0041] Preferred embodiments of the present invention will be described in detail below with reference to the attached drawings. Prior to this, terms and words used in this specification and in the claims shall not be interpreted in their usual and dictionary sense, but rather in a sense and concept appropriate to the technical idea of ​​the present invention, in accordance with the principle that the inventor himself may appropriately define the concept of terms in order to best describe the invention.

[0042] Therefore, it should be understood that the configurations shown in the embodiments described herein represent only one of the most preferred embodiments of the present invention and do not represent the entire technical concept of the present invention, and that there are various equivalents and modifications that can be substituted therein at the time of filing this application.

[0043] Terms that include ordinal numbers, such as "first," "second," etc., are used to distinguish one of the various components from the rest, and are not used to limit the components by such terms.

[0044] Throughout the specification, when a part of it is said to "include" a certain component, this means, unless otherwise stated, that it may include other components rather than excluding them.

[0045] Furthermore, terms such as "control unit" as described in the specification refer to a unit that processes at least one function or operation, and can be realized by hardware, software, or a combination of hardware and software.

[0046] Furthermore, throughout the specification, when one part is described as being "connected" to another part, this includes not only cases where they are "directly connected," but also cases where they are "indirectly connected" to each other through other elements.

[0047] Figure 1 is a diagram illustrating the configuration of an electric vehicle 1 according to the present invention.

[0048] Referring to Figure 1, the electric vehicle 1 may include a vehicle controller 2, a dual battery pack system 10, a load 20, and a charger 30.

[0049] The vehicle controller 2 (for example, the ECU: Electronic Control Unit) is configured to transmit a key-on signal (sometimes called a "discharge start command") to the dual battery pack system 10 in response to the user switching a start button (not shown) on the electric vehicle 1 to the ON position. The vehicle controller 2 is configured to transmit a key-off signal (sometimes called a "discharge stop command") to the dual battery pack system 10 in response to the user switching the start button to the OFF position. The vehicle controller 2 is configured to transmit a "charge start command" to the dual battery pack system 10.

[0050] The power terminals P+ and P- of the dual battery pack system 10 can be electrically coupled to the charger 30 via a charging cable or the like. The charger 30 can communicate with the vehicle controller 2 and supply constant current or constant voltage charging power via the power terminals P+ and P- of the dual battery pack system 10. The charger 30 is either included in the electric vehicle 1 or installed at an external charging station outside the electric vehicle 1.

[0051] The power terminals P+ and P- of the dual battery pack system 10 can be electrically coupled to the positive and negative terminals of the load 20. The load 20 is a device that can discharge each battery pack by being supplied with power from the dual battery pack system 10.

[0052] The dual battery pack system 10 includes a first battery pack B1, a second battery pack B2, and a charge / discharge control device 100.

[0053] Each of the first battery pack B1 and the second battery pack B2 may contain multiple battery cells connected in series. Each battery cell in the first battery pack B1 and each battery cell in the second battery pack B2 may be of different types.

[0054] The first battery pack B1 may refer to the main battery pack, and the second battery pack B2 may refer to the auxiliary battery pack.

[0055] On the other hand, the battery pack can be configured so that battery cells with relatively small capacity but long lifespan are included in the main battery pack, the first battery pack B1. Conversely, battery cells with relatively short lifespan but large capacity can be included in the auxiliary battery pack, the second battery pack B2.

[0056] Examples of battery cells included in the first battery pack B1 include at least one type of battery cell containing NCM, LFP, etc., as the positive electrode material. Examples of battery cells included in the second battery pack B2 include anode-free battery cell and Li-Si battery cell.

[0057] The charge / discharge control device 100 includes a control unit 110, a first relay R1, a second relay R2, a DC / DC converter 120, a voltage measuring unit 130, a communication unit 140, and a memory 150.

[0058] The first relay R1 is connected between the first battery pack B1 and the load 20. Specifically, the first battery pack B1 and the load 20 are connected via a pair of power lines, and the first relay R1 may be provided on at least one of the pair of power lines.

[0059] The second relay R2 is connected between the second battery pack B2 and the load 20. Specifically, the second battery pack B2 and the load 20 are connected via a pair of power lines, and the second relay R2 may be provided on at least one of the pair of power lines.

[0060] The DC / DC converter 120 is connected between the second battery pack B2 and the load 20. Specifically, the input side IN of the DC / DC converter 120 is connected to the second battery pack B2 via a pair of power lines, and the output side OUT of the DC / DC converter 120 may be connected to the load 20 via another pair of power lines. The DC / DC converter 120 functions as a power transmission channel from the second battery pack B2 to the load 20, independently of the operating state of the second relay R2.

[0061] The voltage measuring unit 130 is operably coupled to the control unit 110. That is, the voltage measuring unit 130 can transmit an electrical signal to the control unit 110 or be connected to the control unit 110 so as to be able to receive an electrical signal from the control unit 110.

[0062] The voltage measurement unit 130 measures the first pack voltage, which is the voltage across both ends of the first battery pack B1, and the second pack voltage, which is the voltage across both ends of the second battery pack B2. Specifically, the voltage measurement unit 130 detects the voltage across both ends of each battery pack using the potential difference between a pair of sensing lines connected to the positive and negative terminals of each battery pack, respectively.

[0063] The communication unit 140 receives a discharge start command, a discharge stop command, a charge start command, and / or a charge stop command from the vehicle controller 2.

[0064] The communication unit 140 is configured to support wired or wireless communication between the control unit 110 and the vehicle controller 2. Wired communication may be, for example, CAN (controller area network) communication, and wireless communication may be, for example, Zigbee or Bluetooth communication. Of course, the type of communication protocol is not particularly limited as long as it supports wired or wireless communication between the control unit 110 and the vehicle controller 2. The communication unit 140 may include an output device (e.g., a display, a speaker) that provides information received from the control unit 110 and / or the vehicle controller 2 in a user-recognizable format.

[0065] The memory 150 can include, for example, at least one type of storage medium from among flash memory type, hard disk type, SSD type (Solid State Disk type), SDD type (Silicon Disk Drive type), multimedia card micro type, RAM (random access memory), SRAM (static random access memory), ROM (read-only memory), EEPROM (electrically erasable programmable read-only memory), and PROM (programmable read-only memory). The memory 150 can store data and programs required for the calculation operations performed by the control unit 110. The memory 150 can store data indicating the results of the calculation operations performed by the control unit 110. Although Figure 1 shows the memory 150 as being physically independent of the control unit 110, it can also be incorporated into the control unit 110.

[0066] The control unit 110 can be operably coupled to at least one of the following: the first relay R1, the second relay R2, the DC / DC converter 120, the voltage measuring unit 130, the communication unit 140, and the memory 150. Operatable coupling of two components means that the two components are directly or indirectly connected so that signals can be sent and received in one direction or bidirectionally.

[0067] The control unit 110 can collect voltage signals from the voltage measurement unit 130. The control unit 110 can use an internally installed ADC (Analog to Digital Converter) to convert each analog signal collected from the voltage measurement unit 130 into a digital value and record it.

[0068] The control unit 110 may also be called a "control circuit" or "battery controller," and can be implemented in hardware using at least one of the following: ASICs (application-specific integrated circuits), DSPs (digital signal processors), DSPDs (digital signal processing devices), PLDs (programmable logic devices), FPGAs (field programmable gate arrays), microprocessors, or other electrical units for performing functions.

[0069] The control unit 110 can enter a discharge sequence control mode in response to a discharge start command received from the vehicle controller.

[0070] The control unit 110 may be configured to control the DC / DC converter 120 to a turned-on state during the voltage adjustment period required when a reduction in the voltage difference between the first pack voltage and the second pack voltage is required while operating in discharge sequence control mode.

[0071] The control unit 110 can control the first relay R1, the second relay R2, and the DC / DC converter 120 based on at least one of the first pack voltage and the second pack voltage.

[0072] Specifically, the control unit 110, in response to a discharge start command received from the vehicle controller 2, sets the first pack voltage or the second pack voltage to the first reference voltage V R1 , second reference voltage V R2 Alternatively, it can be compared with the output voltage of the DC / DC converter 120. Depending on the comparison result, the control unit 110 can control the output voltage and operating state of the DC / DC converter 120, and by controlling the states of the first relay R1 and the second relay R2, it can control the electrical connection relationships between the first battery pack B1 and the load 20, and between the second battery pack B2 and the load 20.

[0073] The control unit 110 can identify the charging procedure between the first battery pack B1 and the second battery pack B2 in response to a charging start command received from the vehicle controller 2. Depending on the identified charging procedure, the control unit 110 can control the electrical connection relationships between the first battery pack B1 and the charger 30, and between the second battery pack B2 and the charger 30, by controlling the states of the first relay R1 and the second relay R2.

[0074] Figure 2 is a timing chart referenced to illustrate an example of a discharge sequence for a dual battery pack system executed by a charge / discharge control device according to one embodiment of the present invention, and Figure 3 is a graph illustrating the temporal changes of the first pack voltage, the second pack voltage, and the output voltage of the DC / DC converter 120 during the execution period of the discharge sequence according to Figure 2.

[0075] In FIGS. 2 and 3, t0 is the time when the discharge start command transmitted from the vehicle controller 2 is received by the communication unit 140. In FIG. 3, the voltage curve VC1 shows the temporal change of the first pack voltage, the voltage curve VC2 shows the temporal change of the second pack voltage, and the voltage curve VC3 shows the temporal change of the output voltage of the DC / DC converter 120.

[0076] In response to the discharge start command received from the vehicle controller 2 at time t0, the control unit 110 determines whether the first pack voltage is greater than or equal to the first reference voltage V R1 or not. When the first pack voltage is greater than or equal to the first reference voltage V R1 or more, the control unit 110 executes a first discharge stage of controlling the first relay R1 to the on state so that the power of the first battery pack B1 is supplied to the load 20 via the first relay R1.

[0077] Referring to FIG. 2, while the first discharge stage (t0 to t1 section) is being executed, the first relay R1 is controlled to the on state, and the second relay R2 and the DC / DC converter 120 can be controlled to the off state. As a result, it can be confirmed from FIG. 3 that while the first discharge stage (t0 to t1 section) is being executed, the first pack voltage decreases and the second pack voltage and the output voltage of the DC / DC converter 120 are maintained constant.

[0078] t1 is the time when the difference between the first pack voltage and the second reference voltage V R2 becomes less than or equal to the first predetermined value during the execution of the first discharge stage. Here, the second reference voltage V R2 is less than the first reference voltage V R1 . The second reference voltage V R2 is a predetermined voltage or can also be determined based on the first pack voltage or the second pack voltage at time t0.

[0079] At time t1, the control unit 110 sets the target value of the output voltage of the DC / DC converter 120 to the second reference voltage V R2After setting it to the same state as above, a second discharge stage is executed to control the DC / DC converter 120 to a turned-on state so that the power of the second battery pack B2 is supplied to the load 20 via the DC / DC converter 120.

[0080] Referring to Figure 2, it can be seen that during the second discharge stage (t1-t2 interval), the first relay R1 and the DC / DC converter 120 are controlled to the turn-on state, while the second relay R2 is controlled to the turn-off state. As a result, it can be seen from Figure 3 that during the second discharge stage (t1-t2 interval), the first pack voltage and the second pack voltage decrease, and the output voltage of the DC / DC converter 120 increases.

[0081] t2 is the point at which the execution time of the second discharge stage reaches the first set time. When time t2 arrives, the control unit 110 executes a third discharge stage, which controls the first relay R1 to a turn-off state so that the power supply from the first battery pack B1 to the load 20 is cut off. Meanwhile, the first set time can be set in advance, taking into consideration the durability of the load 20, etc.

[0082] Referring to Figure 2, it can be seen that during the third discharge stage (t2-t3 interval), only the DC / DC converter 120 is controlled to the turn-on state, while the first relay R1 and the second relay R2 are controlled to the turn-off state. At predetermined time intervals from time t2, the control unit 110 can set a target value for the output voltage of the DC / DC converter 120 so that the output voltage of the DC / DC converter 120 follows the second pack voltage. As a result, it can be seen from Figure 3 that the voltage difference between the output voltage of the DC / DC converter 120 and the second pack voltage gradually decreases from time t2.

[0083] t3 is the time during the execution of the third discharge stage when the difference between the output voltage of the DC / DC converter 120 and the voltage of the second battery pack becomes less than or equal to a second predetermined value. At time t3, the control unit 110 executes a fourth discharge stage, which controls the second relay R2 to the turn-on state so that the output power of the second battery pack B2 is supplied to the load 20 via both the DC / DC converter 120 and the second relay R2.

[0084] Referring to Figure 2, it can be seen that during the fourth discharge stage (t3-t4 interval), the second relay R2 and the DC / DC converter 120 are controlled to be turned on, while the first relay R1 is controlled to be turned off. As a result, it can be seen from Figure 3 that during the fourth discharge stage (t3-t4 interval), the second pack voltage and the output voltage of the DC / DC converter 120 gradually decrease, while the first pack voltage remains constant.

[0085] The second discharge stage (t1-t2 interval) and the third discharge stage (t2-t3 interval) each correspond to the voltage adjustment period required according to the present invention.

[0086] t4 is the time when the execution time of the fourth discharge stage reaches the second set time. At time t4, the control unit 110 can execute a fifth discharge stage, which controls the DC / DC converter 120 to a turn-off state so that the power supply from the second battery pack B2 to the load via the DC / DC converter 120 is cut off. On the other hand, the second set time can be set considering the durability of the load 20, etc.

[0087] Referring to Figure 2, it can be seen that during the fifth discharge stage (t4-t5 interval), only the second relay R2 is controlled to the turn-on state among the first relay R1, the second relay R2, and the DC / DC converter 120, while the first relay R1 and the DC / DC converter 120 are controlled to the turn-off state. As a result, it can be seen from Figure 3 that during the fifth discharge stage (t4-t5 interval), the second pack voltage gradually decreases, while the first pack voltage remains constant.

[0088] t5 is the time during the execution of the fifth discharge stage when the voltage difference between the second pack voltage and the first pack voltage becomes less than or equal to the third predetermined value. t6 is the time when the control unit 110 receives a discharge stop command (key-off signal) from the vehicle controller 2 via the communication unit 140. At time t5, the control unit 110 can execute the sixth discharge stage, which involves switching the first relay R1 from the turn-off state to the turn-on state so that the parallel circuit of the first battery pack B1 and the second battery pack B2 is connected to the load 20.

[0089] Referring to Figure 2, it can be confirmed that after time t5, the first relay R1 and the second relay R2 are controlled to the turn-on state, and the DC / DC converter 120 is controlled to the turn-off state. Referring to Figure 3, it can be confirmed from Figure 3 that as a result, the first pack voltage and the second pack voltage decrease.

[0090] In the entire discharge period (t0 to t6), the second battery pack B2 is discharged from t3 to t6, while the DC / DC converter 120 is turned on from t1 to t4. In other words, of the periods in which the second relay R2 is turned on, the DC / DC converter 120 is also turned on only from t3 to t4.

[0091] In contrast to conventional technology, which requires the DC / DC converter (see Figures 8 and 9) to remain turned on while the discharge power of the auxiliary battery pack is supplied to the load, the charge / discharge control device 100 according to the present invention can utilize the DC / DC converter 120, provided as a power transmission channel between the second battery pack B2 and the load 20, for temporary voltage adjustment to suppress the voltage difference between the first battery pack B1 and the second battery pack B2, or the voltage difference between the second battery pack B2 and the output side OUT of the DC / DC converter 120.

[0092] Therefore, the charge / discharge control device 100 according to one embodiment of the present invention does not need to keep the DC / DC converter 120 running at all times while the power of the second battery pack B2 is supplied to the load 20, and the power of the second battery pack B2 can be supplied directly to the load 20 via the second relay R2 without going through the DC / DC converter 120. In other words, since a large output specification is not required for the DC / DC converter 120, a DC / DC converter 120 with a small volume can be used, and since a high-efficiency DC / DC converter 120 is not required, an inexpensive DC / DC converter 120 can be used. As a result, the overall pack capacity of the dual battery pack system 10 can be increased, and there is an advantage in that costs can be reduced. In addition, since the power of the second battery pack B2 is output directly through the second relay R2 without going through the DC / DC converter 120, the overall capacity efficiency of the dual battery pack system 10 can be improved.

[0093] The control unit 110 can enter a charging sequence control mode in response to a charging start command received from the vehicle controller 2 and identify the charging procedure between the first battery pack B1 and the second battery pack B2. The control unit 110 may be configured to control the first relay R1 to the turned-on state when the charging procedure for the first battery pack B1 arrives, until the voltage of the first pack reaches the target voltage, and to control the second relay R2 to the turned-on state when the charging procedure for the second battery pack B2 arrives, until the voltage of the second pack reaches the target voltage.

[0094] In other words, by selectively charging each of the two battery packs until they reach their target voltage, a situation where both battery packs are charged simultaneously is prevented.

[0095] The control unit 110 can, if the first pack voltage is less than or equal to the second pack voltage, set the charging procedure for the first battery pack B1 to take precedence over the charging procedure for the second battery pack B2, and if the first pack voltage is greater than the second pack voltage, set the charging procedure for the second battery pack B2 to take precedence over the charging procedure for the first battery pack B1.

[0096] Figures 4a and 4b are flowcharts illustrating a charge / discharge control method according to one embodiment of the present invention. The control unit 110 can enter a discharge sequence control mode in response to receiving a discharge start command from the vehicle controller 2 via the communication unit 140. The methods shown in Figures 4a and 4b can be executed while the control unit 110 is operating in the discharge sequence control mode.

[0097] Referring to Figures 1 to 4b, in step S4000, the control unit 110 acquires a measured value of the first pack voltage. The measured value of the first pack voltage acquired in step S4000 can represent the first pack voltage at time t0 in Figure 3.

[0098] In step S4010, the control unit 110 determines that the first pack voltage is the first reference voltage V R1It is possible to determine whether or not the above is true. First reference voltage V R1 This may be a predetermined minimum voltage at which the first battery pack B1 alone is permitted to drive the load 20, compared to the first battery pack B1 and the second battery pack B2. If the value of step S4010 is "yes", the process can proceed to step S4020. If the value of step S4010 is "no", the method according to Figures 4a and 4b can be terminated or step S4010 can be re-executed.

[0099] In step S4020, the control unit 110 can execute the first discharge stage. Specifically, the first discharge stage controls the first relay R1 to the turn-on state so that the output power of the first battery pack B1 is supplied to the load 20 via the first relay R1. That is, in the first discharge stage, only the first battery pack B1 of the two battery packs B1 supplies power to the load 20 on its own.

[0100] In step S4030, the control unit 110 determines the first pack voltage and the first reference voltage V R1 Second reference voltage less than V R2 It is possible to determine whether the difference between the two is less than or equal to the first predetermined value. Second reference voltage V R2 This may be predetermined because parallel operation of the first battery pack B1 and the second battery pack B2 is required to drive load 20. At time t1 in Figure 3, the value of step S4030 may be output as "yes". If the value of step S4030 is "yes", the process can proceed to step S4040. If the value of step S4030 is "no", step S4030 can be re-executed.

[0101] In step S4040, the control unit 110 sets the target value of the output voltage of the DC / DC converter 120 to the second reference voltage V R2 It can be set to be the same as [the other setting].

[0102] In step S4050, the control unit 110 can execute the second discharge stage. Specifically, the second discharge stage controls the DC / DC converter 120 to a turned-on state so that the output power of the second battery pack B2, along with the output power of the first battery pack B1, is supplied to the load 20 via the DC / DC converter 120.

[0103] In step S4060, the control unit 110 can determine whether the execution time of the second discharge stage has reached the first set time. At time t2 in Figure 3, the value of step S4060 may be output as "yes". If the value of step S4060 is "yes", the process can proceed to step S4070. If the value of step S4060 is "no", step S4060 can be re-executed.

[0104] In step S4070, the control unit 110 can execute the third discharge stage. Specifically, the third discharge stage controls the first relay R1 to a turn-off state so that the power supply from the first battery pack B1 to the load 20 is cut off.

[0105] In step S4080, the control unit 110 can determine whether the difference between the output voltage of the DC / DC converter 120 and the second pack voltage is less than or equal to a second predetermined value. At time t3 in Figure 3, the value of step S4080 may be output as "yes". If the value of step S4080 is "yes", the process can proceed to step S4090. If the value of step S4080 is "no", step S4080 can be re-executed.

[0106] In step S4090, the control unit 110 can execute the fourth discharge stage. Specifically, the fourth discharge stage controls the second relay R2 to a turned-on state so that the output power of the second battery pack B2 is supplied to the load 20 via both the DC / DC converter 120 and the second relay R2.

[0107] In step S4100, the control unit 110 can determine whether the execution time of the fourth discharge stage has reached the second set time. At time t4 in Figure 3, the value of step S4100 may be output as "yes". If the value of step S4100 is "yes", the process can proceed to step S4110. If the value of step S4100 is "no", step S4100 can be re-executed.

[0108] In step S4110, the control unit 110 can execute the fifth discharge stage. Specifically, the fifth discharge stage controls the DC / DC converter 120 to a turn-off state so that the power supply from the second battery pack B2 to the load 20 via the DC / DC converter 120 is cut off.

[0109] In step S4120, the control unit 110 can determine whether the voltage difference between the second pack voltage and the first pack voltage is less than or equal to a third predetermined value. At time t5 in Figure 3, the value of step S4120 may be output as "yes". If the value of step S4120 is "yes", the process can proceed to step S4130. If the value of step S4120 is "no", step S4120 can be re-executed.

[0110] In step S4130, the control unit 110 can execute the sixth discharge stage. Specifically, the sixth discharge stage controls the first relay R1 and the second relay R2 to the turn-on state so that the parallel circuit of the first battery pack B1 and the second battery pack B2 is connected to the load 20.

[0111] Figures 5a and 5b are flowcharts illustrating a charge / discharge control method according to another embodiment of the present invention. The method in Figures 5a and 5b can be performed when the control unit 110 receives a discharge start command from the vehicle controller 2 via the communication unit 140 and enters the discharge sequence control mode. The method in Figures 5a and 5b can be performed while the control unit 110 is operating in the discharge sequence control mode.

[0112] Referring to Figures 1 to 3, 5a and 5b, in step S5000, the control unit 110 acquires the measured values ​​of the first pack voltage and the second pack voltage from the voltage measurement unit 130. The measured values ​​of the first pack voltage and the second pack voltage acquired in step S5000 can represent the first pack voltage and the second pack voltage at time t0 in Figure 3.

[0113] In step S5005, the control unit 110 determines the first reference voltage V based on the second pack voltage acquired in step S5000. R1 and the second reference voltage V R2 At least one of the following can be set.

[0114] For example, the first reference voltage V R1 This can be set to be the same as the first ratio (e.g., 90%) of the second pack voltage at time t0, and the second reference voltage V R2 The first ratio can be set to be the same as the second ratio (e.g., 50%) of the second pack voltage at time t0. The first ratio may be greater than the second ratio. Each of the first and second ratios may be predetermined considering the rated output and efficiency of the DC / DC converter 120. Of course, the first reference voltage V R1 and the second reference voltage V R2 Only one of the two may be set based on the second pack voltage, in which case the first reference voltage V R1 and the second reference voltage V R2 The other of these may be predetermined.

[0115] In step S5010, the control unit 110 determines that the first pack voltage is the first reference voltage V R1 It is possible to determine whether or not the value is greater than or equal to the above. If the value in step S5010 is "yes", the process can proceed to step S5020. If the value in step S5010 is "no", the method according to Figures 5a and 5b can be terminated or step S5010 can be re-executed.

[0116] In step S5020, the control unit 110 can execute the first discharge stage. Specifically, the first discharge stage controls the first relay R1 to a turned-on state so that the output power of the first battery pack B1 is supplied to the load 20 via the first relay R1.

[0117] In step S5030, the control unit 110 determines the first pack voltage and the first reference voltage V R1 Second reference voltage less than V R2 It is possible to determine whether the difference between the two values ​​is less than or equal to a first predetermined value. At time t1 in Figure 3, the value of step S5030 may be output as "yes". If the value of step S5030 is "yes", the process can proceed to step S5040. If the value of step S5030 is "no", step S5030 can be re-executed.

[0118] In step S5040, the control unit 110 sets the target value of the output voltage of the DC / DC converter 120 to the second reference voltage V R2 It can be set to be the same as [the other setting].

[0119] In step S5050, the control unit 110 can execute the second discharge stage. Specifically, the second discharge stage controls the DC / DC converter 120 to a turned-on state so that the output power of the second battery pack B2, along with the output power of the first battery pack B1, is supplied to the load 20 via the DC / DC converter 120.

[0120] In step S5060, the control unit 110 can determine whether the execution time of the second discharge stage has reached the first set time. At time t2 in Figure 3, the value of step S5060 may be output as "yes". If the value of step S5060 is "yes", the process can proceed to step S5070. If the value of step S5060 is "no", step S5060 can be re-executed.

[0121] In step S5070, the control unit 110 can execute the third discharge stage. Specifically, the third discharge stage controls the first relay R1 to a turn-off state so that the power supply from the first battery pack B1 to the load 20 is cut off.

[0122] In step S5080, the control unit 110 can determine whether the difference between the output voltage of the DC / DC converter 120 and the second pack voltage is less than or equal to a second predetermined value. At time t3 in Figure 3, the value of step S5080 may be output as "yes". If the value of step S5080 is "yes", the process can proceed to step S5090. If the value of step S5080 is "no", step S5080 can be re-executed.

[0123] In step S5090, the control unit 110 can execute the fourth discharge stage. Specifically, the fourth discharge stage controls the second relay R2 to a turned-on state so that the output power of the second battery pack B2 is supplied to the load 20 via both the DC / DC converter 120 and the second relay R2.

[0124] In step S5100, the control unit 110 can determine whether the execution time of the fourth discharge stage has reached the second set time. At time t4 in Figure 3, the value of step S5100 may be output as "yes". If the value of step S5100 is "yes", the process can proceed to step S5110. If the value of step S5100 is "no", step S5100 can be re-executed.

[0125] In step S5110, the control unit 110 can execute the fifth discharge stage. Specifically, the fifth discharge stage controls the DC / DC converter 120 to a turn-off state so that the power supply from the second battery pack B2 to the load 20 via the DC / DC converter 120 is cut off.

[0126] In step S5120, the control unit 110 can determine whether the voltage difference between the second pack voltage and the first pack voltage is less than or equal to a third predetermined value. At time t5 in Figure 3, the value of step S5120 may be output as "yes". If the value of step S5120 is "yes", the process can proceed to step S5130. If the value of step S5120 is "no", step S5120 can be re-executed.

[0127] In step S5130, the control unit 110 can execute the sixth discharge stage. Specifically, the sixth discharge stage switches the first relay R1 from the turn-off state to the turn-on state so that the parallel circuit of the first battery pack B1 and the second battery pack B2 is connected to the load 20. That is, in the sixth discharge stage, both the first relay R1 and the second relay R2 are kept in the turn-off state.

[0128] Figure 6 is a flowchart illustrating a charge / discharge control method according to another embodiment of the present invention. The control unit 110 can enter charge sequence control mode in response to receiving a charge start command from the vehicle controller 2 via the communication unit 140. The method of Figure 6 can be executed while the control unit 110 is operating in charge sequence control mode.

[0129] Referring to Figure 6, in step S6010, the control unit 110 can identify the charging procedure between the first battery pack B1 and the second battery pack B2.

[0130] In step S6020, the control unit 110 can determine whether or not the charging procedure for the first battery pack B1 has arrived. If the value of step S6020 is "yes", the process can proceed to step S6030. If the value of step S6020 is "no", step S6020 can be re-executed.

[0131] In step S6030, the control unit 110 can control the first relay R1 to the turn-on state until the first pack voltage reaches the target voltage.

[0132] In step S6040, the control unit 110 can determine whether or not the charging procedure for the second battery pack B2 has arrived. If the value in step S6040 is "yes", the process can proceed to step S6050. If the value in step S6040 is "no", step S6040 can be re-executed.

[0133] In step S6050, the control unit 110 can control the second relay R2 to the turn-on state until the first pack voltage reaches the target voltage.

[0134] Figure 7 is a flowchart illustrating a charge / discharge control method according to another embodiment of the present invention. The control unit 110 can enter charge sequence control mode in response to receiving a charge start command from the vehicle controller 2 via the communication unit 140. The method in Figure 7 can be executed while the control unit 110 is operating in charge sequence control mode.

[0135] Referring to Figure 7, in step S7010, the control unit 110 can set the lower-voltage battery pack of the first battery pack B1 and the second battery pack B2 as the higher-voltage battery pack as the lower-priority battery pack.

[0136] In step S7020, the control unit 110 can control a relay connected to the priority battery pack to be turned on. That is, it can control the charger 30 to be electrically connected to the priority battery pack.

[0137] In step S7030, the control unit 110 can determine whether the voltage of the priority battery pack has reached the voltage of the secondary battery pack. If the value in step S7030 is "yes", the process can proceed to step S7040. If the value in step S7030 is "no", step S7030 can be repeated.

[0138] In step S7040, the control unit 110 can control other relays connected to the later battery pack to be turned on. That is, it can control the charger 30 to be electrically connected to the later battery pack.

[0139] In step S7050, the control unit 110 can determine whether or not there is a battery pack whose pack voltage has reached the target voltage. If the value in step S7050 is "yes", the process can proceed to step S7060. If the value in step S7050 is "no", step S7050 can be repeated.

[0140] In step S7060, the control unit 110 can control the relay connected to the battery pack to a turn-off state. That is, it can disconnect the electrical connection between the battery pack and the charger 30 when the pack voltage reaches the target voltage.

[0141] In step S7070, the control unit 110 can determine whether all relays are in the turned-off state. If the value in step S7070 is "yes", the method according to Figure 7 can be terminated. If the value in step S7070 is "no", step S7050 can be re-executed.

[0142] Figure 8 is a diagram that is referenced to schematically illustrate a dual battery pack system to which a prior art active topology is applied.

[0143] Referring to Figure 8, the active topology is a method in which two DC / DC converters are connected to the main battery pack and one auxiliary battery pack, allowing the two battery packs to be used more actively.

[0144] Figure 9 is a diagram that is referenced to schematically illustrate a dual battery pack system to which a semi-active topology relating to the prior art is applied.

[0145] Referring to Figure 9, the semi-active topology is a method in which a DC / DC converter is connected only to the power transfer path between the auxiliary battery pack and the load, and the DC / DC converter is kept running continuously while power from the auxiliary battery pack is supplied to the load.

[0146] The embodiments of the present invention described above are not limited to apparatus and methods, but can also be realized by a program that implements functions corresponding to the configuration of the embodiments of the present invention, or by a recording medium on which such a program is recorded. Such implementation can be easily carried out by experts in the technical field to which the present invention belongs, based on the description of the embodiments described above.

[0147] Although the present invention has been described above with reference to limited embodiments and drawings, it goes without saying that the present invention is not limited thereto, and various modifications and variations are possible within the equivalent scope of the technical idea of ​​the present invention and the claims described below by persons with ordinary skill in the art to which the present invention pertains.

[0148] Furthermore, the present invention described above can be substituted, modified, and altered in various ways by a person with ordinary skill in the art to which the present invention belongs, without departing from the technical spirit of the invention. Therefore, it is not limited to the embodiments described above and the accompanying drawings, and all or part of each embodiment can be selectively combined to form various modifications. [Explanation of symbols]

[0149] 1 Electric vehicle 2 Vehicle Controller 10 Dual Battery Pack System 20 load 30 charger 100 Charge / Discharge Control Device 110 Control Unit 120 DC / DC Converter 130 Voltage Measurement Section 140 Communications Department 150 memory

Claims

1. A charge / discharge control device for a dual battery pack system including a first battery pack and a second battery pack, A first relay connected between the first battery pack and the load, A second relay connected between the second battery pack and the load, A DC / DC converter connected between the second battery pack and the load, A voltage measuring unit that measures the first pack voltage, which is the voltage across both ends of the first battery pack, and the second pack voltage, which is the voltage across both ends of the second battery pack, The system includes a control unit that controls the first relay, the second relay, and the DC / DC converter based on at least one of the first pack voltage and the second pack voltage, The control unit, In response to the discharge start command received from the vehicle controller, the system enters discharge sequence control mode. A charge / discharge control device configured to control the DC / DC converter to a turn-on state during a period of voltage adjustment required when a reduction in the voltage difference between the first pack voltage and the second pack voltage is required while operating in the discharge sequence control mode.

2. The control unit, while operating in the discharge sequence control mode, Determine whether the first pack voltage is equal to or greater than the first reference voltage. If the first pack voltage is equal to or greater than the first reference voltage, a first discharge stage is executed to control the first relay to a turned-on state so that the output power of the first battery pack is supplied to the load via the first relay. The charge / discharge control device according to claim 1, wherein, during the execution of the first discharge stage, when the difference between the first pack voltage and a predetermined second reference voltage less than the first reference voltage becomes less than or equal to a first predetermined value, the device is configured to execute a second discharge stage in which the target value of the output voltage of the DC / DC converter is set to be the same as the second reference voltage, and the DC / DC converter is turned on so that the output power of the second battery pack is supplied to the load via the DC / DC converter.

3. The control unit, The charge-discharge control device according to claim 2, configured to execute a third discharge stage that controls the first relay to a turn-off state so that the power supply from the first battery pack to the load is cut off when the execution time of the second discharge stage reaches a first set time.

4. The control unit, The charge-discharge control device according to claim 3, wherein, during the execution of the third discharge stage, if the difference between the output voltage of the DC / DC converter and the voltage of the second battery pack falls below a second predetermined value, the device is configured to execute a fourth discharge stage, which controls the second relay to a turned-on state so that the output power of the second battery pack is supplied to the load via both the DC / DC converter and the second relay.

5. The control unit, The charge / discharge control device according to claim 4, configured to execute a fifth discharge stage that controls the DC / DC converter to a turn-off state so that the power supply from the second battery pack to the load via the DC / DC converter is cut off when the execution time of the fourth discharge stage reaches a second set time.

6. The control unit, The charge-discharge control device according to claim 5, wherein, during the execution of the fifth discharge stage, if the voltage difference between the second pack voltage and the first pack voltage falls below a third predetermined value, the device is configured to execute a sixth discharge stage, which involves switching the first relay from an off state to an on state so that the parallel circuit of the first battery pack and the second battery pack is connected to the load.

7. The control unit, In response to a charge start command received from the vehicle controller, the system enters a charge sequence control mode and identifies the charging procedure between the first battery pack and the second battery pack. When the charging procedure for the first battery pack arrives, the first relay is controlled to the turn-on state until the voltage of the first pack reaches the target voltage. The charge / discharge control device according to claim 1, configured to control the second relay to a turned-on state when the charging procedure for the second battery pack arrives, until the voltage of the second pack reaches a target voltage.

8. The control unit, If the voltage of the first battery pack at the time of receiving the charging start command is less than or equal to the voltage of the second battery pack, the charging procedure for the first battery pack is set to take precedence over the charging procedure for the second battery pack. The charge / discharge control device according to claim 7, wherein if the voltage of the first battery pack at the time of receiving the charge start command is greater than the voltage of the second battery pack, the charging procedure for the second battery pack is set to take precedence over the charging procedure for the first battery pack.

9. A dual battery pack system comprising a charge / discharge control device according to any one of claims 1 to 8.

10. An electric vehicle comprising the dual battery pack system described in claim 9.

11. A charge / discharge control method that can be executed by a charge / discharge control device according to any one of claims 1 to 8, The steps include: entering the discharge sequence control mode in response to a discharge start command received from the vehicle controller; The step of controlling the first relay, the second relay, and the DC / DC converter based on at least one of the first pack voltage and the second pack voltage while operating in the discharge sequence control mode, The steps of controlling the first relay, the second relay, and the DC / DC converter are as follows: A charge / discharge control method comprising at least one discharge process for controlling the DC / DC converter to a turned-on state during a voltage adjustment period in which a reduction in the voltage difference between the first pack voltage and the second pack voltage is required.

12. The steps of controlling the first relay, the second relay, and the DC / DC converter are as follows: A step of determining whether the first pack voltage is equal to or greater than the first reference voltage, If the first pack voltage is equal to or greater than the first reference voltage, the first discharge stage is performed to control the first relay to a turned-on state so that the output power of the first battery pack is supplied to the load via the first relay. The charge / discharge control method according to claim 11, comprising the step of, during the execution of the first discharge stage, if the difference between the first pack voltage and a predetermined second reference voltage less than the first reference voltage becomes less than or equal to a first predetermined value, the second discharge stage is executed, which involves setting the target value of the output voltage of the DC / DC converter to be the same as the second reference voltage, and then controlling the DC / DC converter to a turn-on state so that the output power of the second battery pack, along with the output power of the first battery pack, is supplied to the load via the DC / DC converter.

13. The steps of controlling the first relay, the second relay, and the DC / DC converter are as follows: The charge-discharge control method according to claim 12, further comprising the step of executing a third discharge stage, which controls the first relay to a turn-off state so that the power supply from the first battery pack to the load is cut off when the execution time of the second discharge stage reaches a first set time.

14. The steps of controlling the first relay, the second relay, and the DC / DC converter are as follows: The charge-discharge control method according to claim 13, further comprising the step of performing a fourth discharge stage in which, during the execution of the third discharge stage, if the difference between the output voltage of the DC / DC converter and the voltage of the second pack becomes less than or equal to a second predetermined value, the second relay is turned on so that the output power of the second battery pack is supplied to the load via both the DC / DC converter and the second relay.

15. The steps of controlling the first relay, the second relay, and the DC / DC converter are as follows: The charge / discharge control method according to claim 14, further comprising the step of performing a fifth discharge stage, which controls the DC / DC converter to a turn-off state such that when the execution time of the fourth discharge stage reaches a second set time, the power supply from the second battery pack to the load via the DC / DC converter is cut off.

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