Systems and methods for controlling battery connections in electric vehicles

Abstract

A system and method for controlling the battery connection of an electric vehicle are disclosed. The system for controlling the battery connection of an electric vehicle includes: a battery cell comprising multiple battery packs; a power relay assembly (PRA) for electrically connecting or disconnecting the battery cell and an inverter, and for changing the connection configuration of the multiple battery packs to one of a series connection mode and a parallel connection mode via multiple relays; and a controller for switching the connection configuration to a series connection mode via the PRA in response to a driver's request to increase motor output, and for switching the connection configuration to a parallel connection mode via the PRA in response to a driver's request to increase driving range.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority and benefit to Korean Patent Application No. 10-2021-0143513, filed with the Korean Intellectual Property Office on October 26, 2021, the entire contents of which are incorporated herein by reference. Background of the Invention

[0003] (a) Field of Invention

[0004] This invention relates to a system and method for controlling the battery connection of an electric vehicle, and more specifically, to a system and method for controlling the battery connection of an electric vehicle by being able to change the connection structure of the battery pack according to the driver's needs.

[0005] (b) Description of related technologies

[0006] Electric vehicles (EVs) are vehicles powered by electric motors that use electricity and are equipped with high-voltage battery packs for storing electrical energy.

[0007] Unlike conventional internal combustion engine vehicles, electric vehicles obtain their driving force through an electric motor, thus increasing the battery's charging capacity to increase range or improve output performance.

[0008] However, currently mass-produced electric vehicles use battery packs with fixed driving ranges and fixed connection methods. For example, depending on the model of the electric vehicle, the battery consists of a basic type (e.g., 58kWh) and a long-range type (e.g., 73kWh), and each type has a specified standard driving range. Therefore, the problem is that it is impossible to extend the output and driving range of the electric vehicle according to the user's needs.

[0009] The information disclosed above in this background section is only intended to enhance the understanding of the background of the present invention, and therefore may contain information that does not constitute prior art known to those skilled in the art in this country. Invention Overview

[0010] This invention aims to provide systems and methods for controlling the battery connections of electric vehicles. These systems and methods can improve the output performance of the electric vehicle's batteries or increase the electric vehicle's driving range by changing the connection structure of multiple battery packs installed in series or parallel in the electric vehicle according to the driver's needs.

[0011] An exemplary embodiment of the present invention provides a system for controlling the battery connection of an electric vehicle, the system comprising: a battery cell including a plurality of battery packs; a power relay assembly (PRA) for electrically connecting or disconnecting the battery cell and an inverter, and for changing the connection configuration of the plurality of battery packs to one of a series battery cell mode and a parallel battery cell mode via the plurality of relays; and a controller for switching the connection configuration to a series battery cell mode via the PRA in response to a driver's request to increase motor output, and for switching the connection configuration to a parallel battery cell mode via the PRA in response to a driver's request to increase driving range.

[0012] Each of the multiple battery packs can be an independent structure and can be configured to have the same voltage and capacity as each other.

[0013] The PRA may include a connection mode switching-type circuit, which includes: a series relay for connecting or disconnecting multiple battery packs in series; a parallel relay for connecting or disconnecting multiple battery packs in parallel; and an output relay for ultimately outputting the voltage applied from the series or parallel relays.

[0014] The PRA may also include a circuit breaker for connecting the connection mode switching type circuit to the main relay circuit for connection to the inverter, or disconnecting the connection mode switching type circuit.

[0015] PRA can improve the motor's output performance by increasing the voltage via a series configuration of battery cells used to connect multiple battery packs in series, based on control signals applied from the controller.

[0016] PRA can increase the motor's range by increasing capacity through a parallel mode of battery cells used to connect multiple battery packs in parallel, based on control signals applied from the controller.

[0017] The system may also include a selector switch for inputting a request signal based on the driver's operation, which requests switching the connection structure to either a series connection mode or a parallel connection mode for battery cells.

[0018] The switch can be formed by a hardware operating system installed in the central dashboard area or by a software button displayed on the vehicle navigation system.

[0019] When the driver inputs a changeover switch to increase motor output, the controller can selectively control either the battery cell series mode or the battery cell parallel mode via PRA.

[0020] The controller can combine vehicle driving modes that reflect the driver's driving intentions and selectively control the entry into either battery cell series mode or battery cell parallel mode via PRA.

[0021] When the vehicle is in Sport mode, the controller can operate in series battery cell mode, while when the vehicle is in Eco mode, the controller operates in parallel battery cell mode.

[0022] The controller can collect the state of charge (SOC) of the battery cells, and when the current SOC is equal to or less than a threshold, the controller can restrict the switching to battery cell series mode via PRA.

[0023] Another exemplary embodiment of the present invention provides a method for controlling the battery connection of an electric vehicle equipped with a power relay assembly (PRA) capable of connecting battery cells comprising multiple battery packs connected in series or in parallel via multiple relays, the method comprising: a) inputting a changeover switch according to a driver's request to increase motor output during operation of the electric vehicle; b) controlling the battery cells to be in a battery cell series mode by applying a control signal to the PRA; c) inputting a changeover switch according to a driver's request to increase driving range while controlling the battery cells to be in the battery cell series mode; and d) applying a control signal to the PRA to switch the battery cell series mode to a battery cell parallel mode.

[0024] Controlling the battery cells to be in series mode can include connecting the (+) terminal of the first battery pack and the (-) terminal of the second battery pack in series by turning on the series relay of PRA and turning off the parallel relay.

[0025] Controlling the battery cells to be in series mode may also include: outputting the voltage of the (+) terminal of the first battery pack to the main relay by activating the output relay of the PRA, the voltage being the upper voltage of the battery cell; charging the inverter capacitor with a current reduced by the pre-charge resistor by activating the pre-charge relay of the PRA; finally outputting the voltage of the (+) terminal of the first battery pack to the (+) terminal of the inverter by activating the (+) terminal of the main relay of the PRA; and finally outputting the voltage of the (-) terminal of the first battery pack to the (-) terminal of the inverter by activating the (-) terminal of the main relay of the PRA.

[0026] Switching from a series battery cell mode to a parallel battery cell mode can include connecting the (-) terminals of the first battery pack and the second battery pack in parallel by turning on the parallel relay of the PRA and turning off the series relay.

[0027] Switching from series battery cell mode to parallel battery cell mode may include: connecting the (+) terminals of the first battery pack and the second battery pack in parallel by activating the output relay of the PRA; charging the inverter capacitor with a current reduced by the pre-charge resistor by activating the pre-charge relay of the PRA; finally outputting the voltage of the (+) terminal of the first battery pack to the (+) terminal of the inverter by activating the (+) terminal of the main relay of the PRA; and finally outputting the voltage of the (-) terminal of the first battery pack to the (-) terminal of the inverter by activating the (-) terminal of the main relay of the PRA.

[0028] The method may further include: between step a) and step b), determining whether the current SOC of the battery cell is equal to or less than a set threshold; and when the SOC is equal to or less than the set threshold, restricting the switching to the battery cell series mode.

[0029] The method may further include: after step b), determining whether the current SOC of the battery collected during operation in battery cell series mode is equal to or less than a set threshold; and forcibly switching the battery cell series mode to battery cell parallel mode.

[0030] According to an exemplary embodiment of the present invention, by configuring a PRA that can change the connection structure of multiple battery packs installed on an electric vehicle to a series structure and a parallel structure, it is possible to improve the output performance of the battery or increase the driving range according to the driver's request.

[0031] Furthermore, based on the driver's request to improve output performance, the battery series mode is supported to the maximum extent. However, when the battery's SOC is insufficient, the switch to battery series mode is restricted. Additionally, when the SOC is insufficient during operation in series mode, the series mode is automatically switched to parallel mode, thereby achieving the effect of stable battery management. Brief description of the attached diagram

[0032] Figure 1 This is a block diagram schematically illustrating the configuration of a system for controlling the battery connection of an electric vehicle according to an exemplary embodiment of the present invention.

[0033] Figure 2 This is a diagram illustrating the connection structure of a battery cell according to an exemplary embodiment of the present invention.

[0034] Figure 3This is a flowchart illustrating a method for controlling the battery connection of an electric vehicle according to an exemplary embodiment of the present invention.

[0035] Figure 4 This is a diagram illustrating the operation sequence in the battery cell series mode (battery cell series mode operation sequence) according to an exemplary embodiment of the present invention.

[0036] Figure 5 This is a diagram illustrating the operating sequence (battery cell parallel mode operating sequence) in the battery cell parallel mode according to an exemplary embodiment of the present invention.

[0037] Figure 6 This is a flowchart illustrating a method for controlling the battery connection of an electric vehicle according to an additional exemplary embodiment of the present invention.

[0038] Detailed description of exemplary embodiments

[0039] In the following detailed description, only certain exemplary embodiments of the invention are illustrated and described by way of illustration only. Those skilled in the art will recognize that the described embodiments can be modified in various different ways without departing from the spirit or scope of the invention. Accordingly, the drawings and description are to be considered illustrative in nature rather than restrictive. Throughout the specification, the same reference numerals denote the same elements.

[0040] Throughout this specification, unless explicitly stated otherwise, the word "comprise" and variations such as "comprises" or "comprising" will be understood to imply inclusion of the stated elements, but not exclusion of any other elements. Furthermore, the terms "-er," "-or," and "module" as described in this specification refer to a unit for performing at least one function and operation, and can be implemented by hardware components or software components and combinations thereof.

[0041] Throughout this specification, the terms first, second, A, B, (a), (b), etc., may be used when describing the structural elements of the present invention, but the structural elements shall not be limited by these terms. Such terms are only used to distinguish one structural element from another and do not limit the essential characteristics.

[0042] Throughout this specification, it should be understood that when a structural element is referred to as being "coupled to" or "connected to" another structural element, a structural element may be directly coupled to or connected to the other structural element, but there may also be intermediate elements. Conversely, when a structural element is "directly coupled to" or "directly connected to" another structural element, it should be understood that there are no intermediate elements.

[0043] The terminology used in this specification is for describing particular embodiments only and is not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise.

[0044] In this application, it should be understood that the terms “comprising” and “having” are intended to indicate the presence of the features, quantities, steps, operations, structural elements, and components described in the specification, or combinations thereof, and do not preclude the possibility of the presence or addition of one or more other features, quantities, steps, operations, structural elements, and components, or combinations thereof.

[0045] All terms used herein, including technical or scientific terms, have the same meaning as commonly understood by those skilled in the art, unless they are defined differently in this specification. Terms defined in general dictionaries should be interpreted as having meanings that match those meanings in the context of the relevant art, and should not be interpreted in an ideal or overly formal sense unless they are explicitly defined in this application.

[0046] A system for controlling the battery connection of an electric vehicle according to an exemplary embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

[0047] Figure 1 This is a block diagram schematically illustrating the configuration of a system for controlling the battery connection of an electric vehicle according to an exemplary embodiment of the present invention. Figure 2 This is a diagram illustrating the connection structure of a battery cell according to an exemplary embodiment of the present invention.

[0048] refer to Figure 1 and Figure 2 A system 100 for controlling the battery connection of an electric vehicle according to an exemplary embodiment of the present invention includes: a battery cell 110 including a plurality of battery packs; a power relay assembly (PRA) 120 electrically connecting or disconnecting the battery cell 110 and an inverter 130 to change the connection structure of the plurality of battery packs to a series structure and a parallel structure via a plurality of relays; and a controller 150 capable of switching the PRA 120 in series in response to a driver's (user's) request to increase motor output, and switching the PRA 120 in parallel in response to a driver's request to increase driving range.

[0049] Battery cell 110 includes a first battery pack 111 and a second battery pack 112 configured independently of each other. In the following description, for ease of description, battery cell 110 will be described as assuming that battery cell 110 includes two battery packs 111 and 112, but the number of battery packs 111 and 112 is not limited to two and can be further increased.

[0050] RPA 120 may also include a connection mode switching circuit, which includes a series relay 121 for connecting or disconnecting multiple battery packs 111 and 112 configured in battery cell 110 in series, a parallel relay 122 for connecting or disconnecting multiple battery packs 111 and 112 in parallel, and an output relay 123 that ultimately outputs the voltage applied from the series relay 121 or the parallel relay 122. RPA 120 may also include a circuit breaker 124 for connecting the connection mode switching circuit to or disconnecting the connection mode switching circuit from the main relay of the general PRA 120 circuit.

[0051] In addition, the general-purpose PRA 120 may include a main relay (+) 125 connected to the inverter (+) terminal, a main relay (-) 126 connected to the inverter (-) terminal, a pre-charge relay 127 (which is used to initially charge the inverter 130 before the relay is driven to prevent damage caused by high-voltage surge current), and a pre-charge resistor 128.

[0052] Inverter 130 converts the direct current (DC) power supplied from battery cell 110 into three-phase alternating current (AC) voltage to generate drive torque for motor (not shown).

[0053] The first battery pack 111 and the second battery pack 112 of the battery cell 110 are each independent structures and are configured to have the same voltage and capacity by encapsulating battery modules in which multiple batteries are stacked in the required number.

[0054] For example, each of the battery packs 111 and 112 of battery cell 110 may have a voltage of 400V and a capacity of 120Ah.

[0055] PRA 120 can increase the voltage to increase the motor output by connecting the first battery pack 111 and the second battery pack 112 in series according to the control signal applied from the controller 150 (hereinafter referred to as "battery cell series mode"). (e.g., battery cell series mode specification: 800V / 120Ah).

[0056] Furthermore, the PRA 120 can increase the capacity to increase the motor's range by connecting the first battery pack 111 and the second battery pack 112 in parallel according to the control signal applied from the controller 150 (hereinafter referred to as "battery cell parallel mode"). (For example, the parallel mode specification of the battery cells is 400V / 240Ah.)

[0057] On the other hand, the system 100 for controlling the battery connection of the electric vehicle also includes a selector switch 140, which is used to input a request signal to switch to either a series mode or a parallel mode based on the driver's operation. The selector switch 140 can be configured as a hardware operating system configured in the central dashboard area or as a software button displayed on the vehicle's navigation system.

[0058] The controller 150 controls the overall operation of the system 100 for controlling the battery connection of an electric vehicle according to an exemplary embodiment of the present invention, and includes at least one program and data for this purpose.

[0059] The controller 150 can selectively implement either the battery cell series mode or the battery cell parallel mode by controlling the PRA 120 according to the driver's request signal received from the selector switch 140. At this time, if either mode is being operated during the operation of the electric vehicle, the controller 150 can switch the mode to the other mode according to the input of the selector switch 140.

[0060] Furthermore, the controller 150 can selectively implement either a series battery cell mode or a parallel battery cell mode, in conjunction with the vehicle's driving mode that reflects the driver's driving intentions. For example, when the vehicle is operating in Sport mode (i.e., Power mode), the PRA 120 is controlled in series battery cell mode, while when the vehicle is operating in Energy Saving mode (i.e., Fuel Saving mode), the PRA 120 can be controlled in parallel battery cell mode.

[0061] In addition, the controller 150 can collect the state of charge (SOC) from the battery management system (BMS) or the BMS's sensors, and when the current SOC is equal to or less than a threshold, the controller 150 can restrict the PRA 120 from entering the battery cell series mode.

[0062] The controller 150 may be implemented as one or more processors operating according to a set program, and the set program may be programmed to perform each operation of the method for controlling the battery connection of an electric vehicle according to an exemplary embodiment of the present invention.

[0063] The method for controlling the battery connection of electric vehicles will now be described in more detail with reference to the accompanying drawings.

[0064] Figure 3 This is a flowchart illustrating a method for controlling the battery connection of an electric vehicle according to an exemplary embodiment of the present invention.

[0065] refer to Figure 3 According to an exemplary embodiment of the present invention, the controller 150 of the system 100 for controlling battery connection turns on the power of the electric vehicle and then starts operation (S10), and operates in battery cell parallel mode via PRA 120 (S20). In this case, the controller 150 may be set to default to operating in battery parallel mode when the vehicle starts operating, or may recall the mode last stored in a previous operation.

[0066] When no input changeover switch 140 is used during operation in the parallel battery cell mode (no in S30), the controller 150 maintains the current mode.

[0067] On the other hand, when the driver inputs the changeover switch 140 during operation in the parallel battery cell mode (yes in S30), the controller 150 switches the parallel battery cell mode to the series battery cell mode via PRA 120 (S40).

[0068] For example, Figure 4 This is a diagram illustrating the operating sequence of battery cells in series mode according to an exemplary embodiment of the present invention.

[0069] refer to Figure 4 The method by which the controller 150 operates the PRA 120 in the battery cell series mode includes: ① connecting the (+) terminal of the first battery pack 111 and the (-) terminal of the second battery pack 112 in series by turning on the series relay 121 and turning off the parallel relay 122; ② outputting the voltage of the (+) terminal of the first battery pack 111 to the main relay by turning on the output relay 123, the voltage being the high voltage of the battery cell; ③ charging the capacitor of the inverter 130 with a current reduced by the pre-charge resistor 128 by turning on the pre-charge relay 127; ④ finally outputting the voltage of the (+) terminal of the first battery pack 111 to the inverter (+) terminal by turning on the main relay (+) 125; and ⑤ finally outputting the voltage of the (-) terminal of the first battery pack 111 to the inverter (-) terminal by turning on the main relay (-) 126.

[0070] Therefore, the controller 150 can selectively control the battery cell 110 in series mode according to the driver's request to increase the voltage supplied to the inverter 130, thereby improving the output performance of the motor.

[0071] On the other hand, when there is no input changeover switch 140 during operation in battery cell series mode (no in S50), controller 150 maintains the current mode.

[0072] On the other hand, when the driver inputs the changeover switch 140 at his request during operation in the battery cell series mode (yes in S50), the controller 150 switches the battery cell series mode to the battery cell parallel mode via PRA 120 (S60).

[0073] For example, Figure 5 This is a diagram illustrating the operating sequence of battery cells in parallel mode according to an exemplary embodiment of the present invention.

[0074] refer to Figure 5 The method by which the controller 150 operates the PRA 120 in the parallel battery cell mode includes: ① connecting the (-) terminal of the first battery pack 111 and the (-) terminal of the second battery pack 112 in parallel by turning on the parallel relay 122 and turning off the series relay 121; ② connecting the (+) terminal of the first battery pack 111 and the (+) terminal of the second battery pack 112 in parallel by turning on the output relay 123; ③ charging the capacitor of the inverter 130 with a reduced current through the pre-charge resistor 128 by turning on the pre-charge relay 127; ④ finally outputting the voltage of the (+) terminal of the first battery pack 111 to the inverter (+) terminal by turning on the main relays (+)(125); and ⑤ finally outputting the voltage of the (-) terminal of the first battery pack 112 to the inverter (-) terminal by turning on the main relay (-) 126.

[0075] As described above, the controller 150 can selectively control the battery unit 110 in parallel mode according to the driver's request, thereby increasing the driving range according to the increase in the capacity of the battery unit 110.

[0076] Subsequently, the switching between battery cell series mode and battery cell parallel mode can be repeated according to the driver's request and ends when the electric vehicle loses power.

[0077] Exemplary embodiments of the present invention have been described above, but the present invention is not limited to the exemplary embodiments described therein, and various other modifications are possible.

[0078] For example, Figure 6 This is a flowchart illustrating a method for controlling the battery connection of an electric vehicle according to an additional exemplary embodiment of the present invention.

[0079] exist Figure 6 The additional exemplary embodiments of the invention shown are similar to those in [the original text]. Figure 3 Exemplary embodiments are described herein. However, according to... Figure 6The additional exemplary embodiments of the invention shown herein control the entry / switching of battery cell series mode and battery cell parallel mode by further considering the battery's SOC. Therefore, descriptions overlapping with the exemplary embodiments of the invention will be omitted, and the main differences will be described.

[0080] refer to Figure 6 The controller 150 can identify the battery's SOC from the BMS in real time when the electric vehicle is being operated.

[0081] When the electric vehicle is operating in parallel battery cell mode, and the driver inputs the switch 140 at his request (yes in S30), the controller 150 determines whether the current battery SOC is equal to or less than the set threshold (S35).

[0082] At this time, when the current battery SOC is equal to or less than the set threshold (yes in S35), even if there is a request from the driver, the controller 150 can restrict the switching to the battery cell series mode (S37) and notify the driver of the reason for restricting the mode switch (e.g., low battery SOC).

[0083] On the other hand, if the current battery SOC is not equal to or less than the set threshold (no in S35), the controller 150 switches the battery cell parallel mode to the battery cell series mode (S40).

[0084] Subsequently, if the current battery SOC collected during operation in battery cell series mode is not equal to or less than the set threshold (no in S45), the controller 150 maintains the battery cell series mode.

[0085] On the other hand, when the current battery SOC collected during operation in battery cell series mode is equal to or less than the set threshold (yes in S45), the controller 150 can force the switch from battery cell series mode to battery cell parallel mode (S60) and notify the driver of the reason for the forced switch (e.g., low battery SOC).

[0086] As described above, according to an exemplary embodiment of the present invention, it is possible to improve battery output performance or driving range by means of a power relay assembly (PRA) according to the driver's request, the power relay assembly (PRA) being capable of changing the connection structure of multiple battery packs installed in series and parallel in an electric vehicle.

[0087] In addition, based on the driver's request for improved output performance, the battery series mode is supported as much as possible. However, when the battery's SOC is insufficient, the change to the battery series mode is restricted. If the SOC is insufficient when operating in series mode, the series mode is forcibly switched to parallel mode, which has the effect of stabilizing battery management.

[0088] The exemplary embodiments of the present invention can be implemented not only by the above-described devices and / or methods, but also by a program for implementing functions corresponding to the configuration of the exemplary embodiments of the present invention, a recording medium in which the program is recorded, etc., and those skilled in the art can easily implement this implementation based on the description of the exemplary embodiments.

[0089] Although exemplary embodiments of the invention have been described in detail, the scope of the invention is not limited to these exemplary embodiments. Various changes and modifications made by those skilled in the art using the basic concepts of the invention as defined in the appended claims should be interpreted as falling within the scope of the invention.

Claims

1. A system for controlling battery connection of an electric vehicle, the system comprising: The battery unit includes a first battery pack and a second battery pack, each battery pack having a (+) terminal and a (-) terminal; A power relay assembly for electrically connecting or disconnecting the battery cells and the inverter, and for changing the connection structure of the multiple battery packs to one of a series connection mode and a parallel connection mode via multiple relays; and The controller, in response to a driver's request to increase motor output, switches the connection structure to a series connection mode for the battery cells via the power relay assembly, and in response to a driver's request to increase driving range, switches the connection structure to a parallel connection mode for the battery cells via the power relay assembly. in: The power relay assembly includes: A series relay configured to selectively connect the (+) terminal of the first battery pack to the (-) terminal of the second battery pack; A parallel relay configured to selectively connect the (+) terminal of the first battery pack to the (+) terminal of the second battery pack; An output relay is configured to output the voltage of the (+) terminal of the first battery pack or to connect the (+) terminal of the first battery pack in parallel with the (+) terminal of the second battery pack; The main relay (+) terminal is configured to connect to the output terminal of the output relay and selectively connect to the inverter (+) terminal; The main relay (-) terminal is configured to be connected to the (-) terminal of the first battery pack and selectively connected to the inverter (-) terminal; A pre-charge relay is disposed on a pre-charge line, the pre-charge line being connected in parallel with the main relay (+) terminal along the line between the output terminal of the output relay and the inverter (+) terminal, and the pre-charge relay selectively connects or disconnects the pre-charge line; and A pre-charge resistor is disposed on the pre-charge line such that the current flowing through the pre-charge line is lower than the current supplied to the inverter (+) terminal through the main relay (+) terminal.

2. The system according to claim 1, wherein: Each of the first battery pack and the second battery pack is an independent structure and is configured to have the same voltage and capacity as each other.

3. The system according to claim 1, wherein: The power relay assembly also includes a circuit breaker for connecting or disconnecting the output terminal of the output relay and the (+) terminal of the main relay.

4. The system according to claim 1, wherein: The power relay assembly improves the output performance of the motor by increasing the voltage via the series connection mode of the battery cells for connecting the first battery pack and the second battery pack, based on the control signal applied from the controller.

5. The system according to claim 1, wherein: The power relay assembly increases the motor's range by increasing capacity via a parallel mode of battery cells used to connect the first and second battery packs in parallel, based on a control signal applied from the controller.

6. The system according to claim 1, further comprising: A selector switch is used to input a request signal, based on the driver's operation, to switch the connection structure to either the series connection mode or the parallel connection mode of the battery cells.

7. The system according to claim 6, wherein: The switch is formed by a hardware operating system installed in the central dashboard area or a software button displayed on the vehicle navigation system.

8. The system according to claim 6, wherein: When the driver inputs the changeover switch in response to a request to increase motor output, the controller selectively controls either the battery cell series mode or the battery cell parallel mode via the power relay assembly.

9. The system according to claim 1, wherein: The controller, in conjunction with a vehicle driving mode that reflects the driver's driving intentions, selectively controls entry into either the battery cell series mode or the battery cell parallel mode via the power relay assembly.

10. The system according to claim 9, wherein: When the vehicle is in Sport mode, the controller operates with the battery cells connected in series; when the vehicle is in Eco mode, the controller operates with the battery cells connected in parallel.

11. A method for controlling the battery connection of an electric vehicle, the electric vehicle being provided with a power relay assembly, the power relay assembly being capable of connecting battery cells comprising a first battery pack and a second battery pack connected in series or parallel via a plurality of relays, the method comprising: a) During operation of the electric vehicle, a selector switch is input according to the driver's request to increase the motor output; b) By applying a control signal to the power relay assembly, the battery cell is controlled to be in a battery cell series mode; c) While controlling the battery cell to be in the battery cell series mode, input the switching switch according to the driver's request to increase the driving range; and d) Apply a control signal to the power relay assembly to switch the battery cell series mode to the battery cell parallel mode. in, Controlling the battery cells to be in the series connection mode includes: connecting the (+) terminal of the first battery pack and the (-) terminal of the second battery pack in series by turning on the series relay of the power relay assembly and turning off the parallel relay; in Controlling the battery cell to be in the series connection mode further includes: By activating the output relay of the power relay assembly, the voltage of the (+) terminal of the first battery pack is output to the main relay, and the voltage is the high voltage of the battery cell; By activating the pre-charge relay of the power relay assembly, the inverter's capacitor is charged with a reduced current through the pre-charge resistor. By activating the main relay (+) terminal of the power relay assembly, the voltage at the (+) terminal of the first battery pack is ultimately output to the inverter (+) terminal; and By connecting the main relay (-) terminal of the power relay assembly, the voltage of the (-) terminal of the first battery pack is finally output to the inverter (-) terminal.

12. The method according to claim 11, wherein: The switching from the series connection mode of the battery cells to the parallel connection mode of the battery cells includes: connecting the (-) terminal of the first battery pack and the (-) terminal of the second battery pack in parallel by turning on the parallel relay of the power relay assembly and turning off the series relay.

13. The method according to claim 12, wherein: The switching from the series connection mode of the battery cells to the parallel connection mode of the battery cells includes: The (+) terminals of the first battery pack and the second battery pack are connected in parallel by turning on the output relay of the power relay assembly; By activating the pre-charge relay of the power relay assembly, the inverter's capacitor is charged with a reduced current through the pre-charge resistor. By activating the main relay (+) terminal of the power relay assembly, the voltage at the (+) terminal of the first battery pack is ultimately output to the inverter (+) terminal; and By connecting the main relay (-) terminal of the power relay assembly, the voltage of the (-) terminal of the first battery pack is finally output to the inverter (-) terminal.

14. The method of claim 11, further comprising: Between step a) and step b), Determine whether the current SOC of the battery cell is equal to or less than a set threshold; and When the SOC is equal to or less than the set threshold, the switching to the battery cell series mode is restricted.

15. The method of claim 11, further comprising: After step b), Determine whether the current SOC of the battery collected during operation in the battery cell series mode is equal to or less than a set threshold; and When the current SOC of the battery, collected during operation in the battery cell series mode, is equal to or less than a set threshold, the battery cell series mode is forcibly switched to the battery cell parallel mode.

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