Battery system, battery control device, vehicle, and recording medium having computer program recorded thereon

Abstract

A battery system is provided that can suppress degradation as much as possible with a lightweight and low-cost battery structure while avoiding a significant drop in battery voltage. The battery system disclosed herein includes: a battery pack comprising a first battery group and a second battery group, the first battery group being composed of multiple cells connected in series, and the second battery group being composed of a different number of cells connected in series than the first battery group, and setting the voltage value of the first battery group in a low SOC state as an upper limit voltage; a switching mechanism capable of switching at least to a first connection mode connecting the first battery group to a load, or a second connection mode connecting the first battery group and the second battery group in parallel to the load; and a battery control device that controls the switching mechanism, wherein when the first battery group is in a low SOC state, the battery control device switches from the first connection mode to the second connection mode via the switching mechanism.

Description

Technical Field

[0001] This disclosure relates to a battery system, a battery control device for controlling the battery system, a vehicle equipped with the battery system, and a recording medium containing a computer program for controlling the battery system. Background Technology

[0002] As a rechargeable and discharging energy storage device installed in a vehicle, a non-aqueous electrolyte secondary battery (hereinafter also simply referred to as "non-aqueous secondary battery") is known. Lithium-ion secondary batteries, as an example of this non-aqueous secondary battery, can achieve very high energy density and have therefore been developed for automotive applications. In such automotive battery systems, it is desirable to maintain the voltage required by the vehicle independently of the battery's state of charge (SOC).

[0003] Regarding this, for example, Patent Document 1 discloses the following: when the charge SOC (MB) is determined to be below a predetermined value A2, the main control unit 62 switches the power supply path by using the power from the auxiliary battery SB instead of the main battery MB to drive the electric generator MG2. Similarly, in the battery control device disclosed in Patent Document 2, it is described that when there is no remaining capacity of more than a predetermined amount in the main battery, control is performed by outputting power from the auxiliary battery.

[0004] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2007-129799 Patent Document 2: Japanese Patent Application Publication No. 2011-024322 Summary of the Invention

[0005] Technical issues However, existing technologies, including the aforementioned patent documents, do not yet meet market demands and suffer from the following problems. Generally, in a low-SOC state (low state of charge) battery, the internal resistance increases, resulting in a significant decrease in battery output. Regarding this, as proposed in Patent Document 1, switching from the main battery to the auxiliary battery when the main battery is in a low SOC state can avoid this significant voltage drop. However, this simple switching method from the main battery to the auxiliary battery cannot effectively utilize the main battery's capacity, causing the auxiliary battery's charging rate to drop immediately as well. Therefore, a larger-capacity auxiliary battery must be used, leading to increased vehicle weight and cost, and thus, efficiency is not considered good.

[0006] This disclosure was made in view of the above-mentioned problems as an example, and provides a battery system, etc., in a vehicle equipped with a battery pack consisting of a first battery pack and a second battery pack connected in series with different numbers of cells, which can suppress battery degradation as much as possible with a lightweight and low-cost battery structure while avoiding a large voltage drop from the cells.

[0007] Technical solution To address the aforementioned problems, according to one aspect of this disclosure, a battery system is provided, comprising: a battery pack consisting of a first battery group and a second battery group, wherein the first battery group is composed of multiple units connected in series, and the second battery group is composed of a different number of units connected in series than the first battery group, and the voltage value of the first battery group in a low SOC state is set as an upper limit voltage. A switching mechanism capable of switching at least to a first connection mode connecting the first battery pack to a load and a second connection mode connecting the first battery pack and the second battery pack in parallel to the load; and a battery control device controlling the switching mechanism, wherein the battery control device switches from the first connection mode to the second connection mode via the switching mechanism when the first battery pack is in the low SOC state.

[0008] To address the aforementioned problems, according to another aspect of this disclosure, a battery control device is provided. This battery control device controls a battery pack, which comprises a first battery group and a second battery group. The first battery group is composed of multiple units connected in series, and the second battery group is composed of a different number of units connected in series than the first battery group. The voltage value of the first battery group in a low SOC state is set as an upper limit voltage. The battery control device includes a processor and a memory. The memory stores a program executed by the processor. The program contains instructions that cause the processor to detect the SOC of the first battery group and, when the first battery group is in the low SOC state, connect the first battery group and the second battery group in parallel with a load via a switching mechanism.

[0009] To address the aforementioned problems, according to another aspect of this disclosure, a recording medium is provided, the recording medium recording a computer program applicable to a battery system mounted in a vehicle, comprising a first battery pack and a second battery pack, the first battery pack being composed of multiple cells connected in series, the second battery pack being composed of a different number of cells connected in series than the first battery pack, and setting the voltage value of the first battery pack in a low SOC state as an upper limit voltage, the computer program causing one or more processors to perform processes including: a process for detecting the SOC of the first battery pack; and a process for connecting the first battery pack and the second battery pack in parallel via a switching mechanism when the first battery pack is in the low SOC state.

[0010] Technical effect According to this disclosure, while maintaining the vehicle's driving range with a lightweight and low-cost battery structure, it is possible to suppress battery degradation as much as possible for loads such as the vehicle's electric motor, and achieve more stable battery output. Attached Figure Description

[0011] Figure 1 This is a schematic diagram illustrating an example configuration of a vehicle equipped with the battery system of this disclosure.

[0012] Figure 2 This is a schematic diagram illustrating an example configuration of a battery system including a switching mechanism according to the present disclosure.

[0013] Figure 3 This is a schematic diagram illustrating the discharge rate characteristics of a unit cell constituting the first battery pack in the battery system of this disclosure.

[0014] Figure 4 This is a schematic diagram illustrating a first connection method of the battery system of this disclosure relative to a load.

[0015] Figure 5 This is a schematic diagram illustrating a second connection method of the battery system of this disclosure relative to a load.

[0016] Figure 6 This is a schematic diagram illustrating a third connection method of the battery system of this disclosure relative to the load.

[0017] Figure 7 This is a schematic diagram illustrating a fourth connection method of the battery system of this disclosure relative to the load.

[0018] Figure 8 This is a schematic diagram illustrating the discharge characteristics of a battery pack obtained by combining a first battery pack and a second battery pack in the battery system of this disclosure.

[0019] Figure 9This is a functional block diagram of the battery control device of the battery system disclosed herein.

[0020] Figure 10 This is a flowchart illustrating the control method of the battery system executed by the battery control device according to the present disclosure.

[0021] Symbol Explanation 10: Battery pack; 10A: First battery pack; 10B: Second battery pack; 20: Switching mechanism; 20A: First switch; 20B: Second switch; 20C: Third switch; 30: Battery control device; 100: Battery system; 200: Vehicle. Detailed Implementation

[0022] Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. It should be noted that in this specification and the drawings, constituent elements having substantially the same function are omitted from repeated description by using the same reference numerals. Furthermore, regarding structures other than those described in detail below, for example, known technologies, including those in the aforementioned patent documents, and vehicle configurations may be appropriately applied.

[0023] Reference Figures 1-7 Examples of the configuration of the battery system 100 and the vehicle 200 according to embodiments of the present disclosure will be described. Figure 1 This is a schematic diagram of a vehicle 200, which is equipped with an onboard load 50 and a battery system 100 capable of supplying power to the load 50. As an example, such a load 50 can be an example of a known electric motor that receives power from the battery system 100 via a known inverter 22 and is driven by it.

[0024] Hereinafter, as an example of vehicle 200, an electric vehicle (BEV) equipped with a known electric motor is illustrated. It should be noted that vehicle 200 in this embodiment is not limited to the electric vehicle described above, but may be a hybrid electric vehicle (HEV) that uses a known engine (internal combustion engine), or an electric vehicle equipped with other known power generation devices such as a gas turbine.

[0025] <Battery System> exist Figure 2 An example configuration of the battery system 100 of this embodiment is shown.

[0026] according to Figure 2 It is understood that the battery system 100 is configured to include a battery pack 10, a switching mechanism 20, and a battery control device 30.

[0027] The battery pack 10 comprises a first battery group 10A consisting of multiple units connected in series and a second battery group 10B consisting of a different number of units connected in series with the first battery group 10A. It should be noted that, as units assembled in the battery pack 10 of this embodiment, a known lithium-ion secondary battery, for example, is suitable with a positive electrode made of a ternary material with nickel, manganese, and cobalt as the main components and a negative electrode made of carbon material.

[0028] The following example illustrates a battery pack 10 comprising a battery array consisting of lithium-ion secondary batteries connected in series as described above. However, the battery pack 10 can also be constructed using other known secondary batteries besides lithium-ion secondary batteries, such as lithium-ion secondary batteries with iron phosphate cathodes or nickel-metal hydride batteries. Furthermore, the following description focuses on a battery pack 10 having a first battery array 10A and a second battery array 10B, but it is not limited to this example; the battery pack 10 may also have three or more battery arrays.

[0029] The first battery pack 10A is composed of multiple cells connected in series. The cells constituting the first battery pack 10A can be, for example, known lithium-ion secondary batteries made of ternary cathode materials and carbon-based anode materials with an open-circuit voltage (OCV) of approximately 4.0 to 4.2 V. In this embodiment, the output voltage from the battery system 100 is specified as 350V to 360V; therefore, as an example, the first battery pack 10A can also be configured with a rated voltage of 3.7V and 96 of the aforementioned cells connected in series.

[0030] The second battery pack 10B operates at a first threshold V under the low SOC state of the first battery pack 10A. th1 This is the upper limit voltage.

[0031] Here, as Figure 3 As shown, "low SOC state" refers to the cell's charge rate state when, although it exists in the common region of the cell's discharge curve (i.e., without significant cell degradation), a relatively large voltage drop occurs during cell discharge due to increased internal resistance. As an example, in this embodiment, when the aforementioned lithium-ion secondary battery is used, the voltage drop occurs around 20% SOC. Therefore, in this embodiment, the state where the cell's SOC is 10% to 20% is defined as the low SOC state. It should be noted that the charge rate representing the "low SOC state" can be envisioned as being in the range of approximately 10% to 20%, but the specific "low SOC state" charge rate can also be predetermined through experiments or simulations depending on the type of secondary battery.

[0032] As an example, the upper limit voltage of the second battery pack 10B can be based on the first threshold voltage V of the cell in the low SOC state of the first battery pack 10A described above.th1 The voltage is specified as 3.3V. Therefore, when the upper limit voltage of the cells constituting the second battery pack 10B is set to 4.2V, 75 (3.3 × 96 / 4.2) of the aforementioned cells can be connected in series. Thus, in the battery pack 10 of this embodiment, the upper limit voltage of the second battery pack 10B is consistent when the voltage of each cell in the first battery pack 10A reaches 3.3V. Furthermore, in the battery pack 10 of this embodiment, the number of cells constituting the first battery pack 10A is set to be greater than the number of cells constituting the second battery pack 10B.

[0033] like Figure 2 As shown, the switching mechanism 20 is configured to include a first switch 20A that controls the connection between the first battery pack 10A and the load 50, a second switch 20B that controls the connection between the second battery pack 10B and the load 50, and a third switch 20C that controls at least the electrical connection between the second battery pack 10B and the boost circuit 21.

[0034] More specifically, the switching mechanism 20 is configured to switch the power supply from the battery to a first connection mode that connects the first battery pack 10A to the load 50 by controlling the connection mode of the first switch 20A to the third switch 20C (see reference). Figure 4 And a second connection method that connects the first battery pack 10A and the second battery pack 10B in parallel to the load 50 (see reference). Figure 5 ).

[0035] Furthermore, the switching mechanism 20 of this embodiment can also disconnect the first battery pack 10A and connect the second battery pack 10B to the load 50 in a third connection method (see [reference]). Figure 6 Switch.

[0036] Furthermore, the switching mechanism 20 of this embodiment can also disconnect the first battery pack 10A and connect the second battery pack 10B to the load 50 in a fourth connection manner (see [reference]) by boosting the voltage through the boost circuit 21. Figure 7 Switch.

[0037] It should be noted that, as a specific example of the boost circuit 21, there are no particular limitations as long as the battery voltage can be boosted to any value; for example, a known DC-DC converter can also be used. Thus, the battery system 100 of this embodiment may also include the boost circuit 21, which is connected to the second battery pack 10B via the switching mechanism 20 and is capable of boosting the voltage between the terminals of the second battery pack 10B.

[0038] The battery control device 30 is configured to have the function of controlling the switching mechanism 20. Such a battery control device 30 is also called a BMU (Battery Management Unit), and is configured to include, for example, one or more processors such as a CPU (Central Processing Unit), and one or more memories such as RAM (Random Access Memory) or ROM (Read Only Memory) communicatively connected to the processor.

[0039] In this way, the battery control device 30 executes a computer program via one or more processors, thereby enabling the switching mechanism 20 to change the power supply method from the battery pack 10 to the load 50. This computer program is used to cause the processor to execute the battery control method that the battery control device 30 should perform (see [reference]). Figure 10 The computer program executed by the processor may be recorded on a recording medium that functions as a storage unit (memory) in the battery control device 30, or on other known recording media that can be externally placed in the battery control device 30.

[0040] Recording media for computer programs can be magnetic media such as hard disks, floppy disks, and magnetic tapes; optical recording media such as CD-ROMs (Compact Disk Read Only Memory), DVDs (Digital Versatile Disk), and Blu-rays (registered trademark); magneto-optical media such as optical disks; storage elements such as RAM and ROM; flash memory such as USB (Universal Serial Bus); SSDs (Solid State Drives); and other media capable of storing programs.

[0041] <One of the switching controls performed by the battery control device> Figure 8 The discharge characteristics of the battery pack 10, which combines a first battery pack 10A and a second battery pack 10B, are shown. In the figure, the vertical axis represents the voltage (V) of the battery pack 10, and the horizontal axis represents the capacity (Ah) of the battery pack 10. Figure 8 As an example, the voltage values ​​of the first battery pack 10A (containing 96 cells connected in series) and the second battery pack 10B (containing 75 cells connected in series) of this embodiment are shown. More specifically, in Figure 8 In the example of the battery pack shown, the upper limit voltage is set to 403V (4.2 × 96), which is related to the first threshold voltage. th1The corresponding voltage was set to 317V (3.3 × 96), which is the second threshold voltage. th2 The corresponding voltage is set to 288V (3.0×96), and the lower limit voltage is set to 240V (2.5×96).

[0042] The battery control device 30 is configured such that when the first battery pack 10A is in a low SOC state (as an example, the voltage of the cell becomes a first threshold V), the battery control device 30 is configured to control the battery pack 10A. th1 When the SOC is 20%, the switching mechanism 20 is used to switch from the first connection method ( Figure 4 To the second connection method ( Figure 5 Switching between ( ). That is, such as Figure 8 As shown, when the SOC of the first battery pack 10A is less than 20%, the first battery pack 10A and the second battery pack 10B are connected in parallel to the load 50.

[0043] Therefore, the degradation of the first battery pack 10A, which is in a low SOC state where it is prone to deterioration, can be suppressed as much as possible, and compared with the case where current is drawn from only the second battery pack 10B, the capacity of the first battery pack 10A can be utilized while a stable battery output is performed to the load 50.

[0044] <Switch control via battery control device, part two> Furthermore, the battery control device 30 of this embodiment can also be configured to switch from the second connection method described above via the switching mechanism 20 when the first battery pack 10A is below the commonly used lower limit of SOC. Figure 5 ) to the third connection method ( Figure 6 The switching of ) . Thus, as Figure 8 As shown, it is able to suppress battery degradation when using the first battery pack 10A in the SOC region where a significant voltage drop of the battery occurs, and it is able to perform battery output from the second battery pack 10B to the load 50.

[0045] Here, "common lower limit of SOC" refers to the lower end of the common region where the discharge curve of the cell illustrated in the steady region has a gentle slope, corresponding to the lower limit of the aforementioned low SOC state, which is the second threshold V that produces a significant voltage drop. th2 A comparable SOC state. As an example, in this embodiment, the aforementioned second threshold V is... th2 The value is specified as 3.0V, which will be compared with the second threshold V. th2The equivalent SOC is defined as "10%". In other words, in this embodiment, if the SOC of the first battery pack 10A exceeds 20%, the required current is supplied from the first battery pack 10A to the load 50 via the switching mechanism 20 in a first connection manner. Furthermore, if the SOC of the first battery pack 10A is in the range of 10% to 20%, the current is supplied to the load 50 from both the first battery pack 10A and the second battery pack 10B in parallel via the switching mechanism 20 in a second connection manner.

[0046] <Part Three: Switching Control by Battery Control Device> As described above, if the SOC of the first battery pack 10A is less than 10%, the required current is supplied from the second battery pack 10B to the load 50 via the switching mechanism 20 in a third connection manner. At this time, the battery control device 30 can also switch from the second connection manner (…) via the switching mechanism 20. Figure 5 ) to the fourth connection method ( Figure 7 The switching of the second battery pack 10B. That is, the battery control device 30 can boost the voltage output by the second battery pack 10B via the boost circuit 21.

[0047] That is, such as Figure 8 As shown, when the first battery pack 10A is disconnected from the load 50 and the second battery pack 10B continues to supply power to the load 50, the output from the battery pack 10 will decrease slightly. In contrast, if the switching mechanism 20 switches from the second connection mode to the fourth connection mode, the voltage is boosted to, for example, the rated voltage of the first battery pack 10A, enabling a stable power supply from the second battery pack 10B to the load 50.

[0048] <Functional blocks of the battery control unit> Figure 9 The functional blocks of the battery control device 30 in this embodiment are shown.

[0049] The battery control device 30 is composed of one or more processors such as CPUs, and includes a voltage value acquisition unit 31, a SOC monitoring unit 32, a switch control unit 33, and a prompt control unit 34. These components of the battery control device 30 are functions implemented by executing programs based on the aforementioned processor. However, some of the voltage value acquisition unit 31, SOC monitoring unit 32, switch control unit 33, and prompt control unit 34 may also be composed of known analog circuits. As described later, the battery control device 30 of this embodiment can perform processes such as detecting the SOC of the first battery pack 10A, and connecting the first battery pack 10A and the second battery pack 10B in parallel with the load via the switch mechanism 20 when the first battery pack 10A is in a low SOC state.

[0050] like Figure 9As shown, the battery control device 30 can also be configured to communicate with a vehicle control device 40, which is composed of other known ECUs on the vehicle. It should be noted that the vehicle control device 40 may, for example, have the function of controlling the drive of the vehicle 200 based on the detection values ​​of known vehicle state sensors, including vehicle speed sensors, acceleration sensors, angular velocity sensors, steering angle sensors, accelerator pedal sensors, and brake pedal sensors.

[0051] In addition, the battery control device 30 can also be configured to communicate with a known external network such as the Internet via a known in-vehicle communication device CD.

[0052] The storage unit MD can also be configured as a known memory such as RAM for temporary storage of information, or a known recording device such as a hard disk or SSD capable of storing programs. In this embodiment, the storage unit MD can store not only the program executed by the battery control device 30 and various parameters for executing the program, but also acquired data, calculation results, and the like.

[0053] (Voltage value acquisition unit) The voltage acquisition unit 31 performs the process of acquiring the voltage values ​​of each battery pack in the battery pack 10 installed in the vehicle 200. Specifically, the voltage acquisition unit 31 has the function of detecting the voltage values ​​of the first battery pack 10A and the second battery pack 10B in the vehicle 200 when it is in motion or parked, by means of a known voltage sensor SR1 installed in the battery system 100 (such as within the battery pack 10). It should be noted that the battery control device 30 of this embodiment detects the voltage values ​​of the first battery pack 10A and the second battery pack 10B by means of the voltage sensor SR1, but the state values ​​of the batteries (current value, voltage value, etc.) can also be detected by means of the known current sensor SR2, which acquires the current value flowing in the first battery pack 10A and the second battery pack 10B.

[0054] (SOC Monitoring Department) The SOC monitoring unit 32 performs a process that uses the vehicle-mounted voltage sensor SR1 and current sensor SR2 to detect and monitor the SOC (State of Charge) of the battery packs (first battery pack 10A and second battery pack 10B) mounted on the battery pack 10 in the vehicle 200. It should be noted that the specific SOC detection method performed by the SOC monitoring unit 32 is not particularly limited as long as it does not depart from the spirit of this embodiment. For example, various SOC estimation techniques known to the public, such as Japanese Patent Application Publication No. 2021-68637 and International Publication No. WO2019 / 193471, can also be applied.

[0055] (Switch control unit) The switch control unit 33 performs the process of switching the connection state between the battery system 100 and the load 50. For example, the switch control unit 33 can perform the switching process between the first connection mode and the second connection mode, the switching process between the second connection mode and the third connection mode, and the switching process between the second connection mode and the fourth connection mode through the switch mechanism 20.

[0056] (Prompt Control Department) The prompt control unit 34 processes various information, such as the connection status of the battery system 100 and the load 50, displayed on the prompt device PD. Here, the prompt device PD in this embodiment can be exemplified by, for example, a known in-vehicle display or in-vehicle speaker. It should be noted that the prompt control unit 34 can also control the display of the aforementioned information on an external terminal such as a smartphone held by the passenger.

[0057] It should be noted that the computer program implementing the functions of the battery control device 30 described above is applicable to a battery system consisting of, for example, a first battery pack and a second battery pack. The first battery pack is composed of multiple units connected in series in the vehicle, and the second battery pack is composed of a different number of units connected in series than the first battery pack. The computer program sets the voltage value of the first battery pack in its low SOC state to an upper limit voltage. The computer program allows one or more processors to perform processes including: detecting the SOC of the first battery pack; and, when the first battery pack is in the low SOC state, connecting the first battery pack and the second battery pack in parallel via a switching mechanism. Furthermore, such a computer program can be stored on known recording media such as optical discs or various memory devices, or downloaded to the vehicle 200 from a known server such as the cloud.

[0058] <Other vehicle equipment> The vehicle 200 of this embodiment may also include a vehicle control device 40 that cooperates with the battery control device 30 to control the load 50, the generator, etc.

[0059] Such a vehicle control device 40 is configured, for example, to control the driving of the vehicle 200 based on state information of the vehicle 200 detected from a sensor class SR mounted on the vehicle 200. Specific examples of such a sensor class SR include known acceleration sensors, GPS sensors, angular velocity sensors, etc. The sensor class SR may also include steering angle sensors, accelerator pedal sensors, and brake pedal sensors, etc.

[0060] <Battery System Control Methods> Next, refer to Figure 10The control method of the battery system 100 according to this embodiment will be described in detail. It should be noted that this control method can also be used as an algorithm of a program that can be executed by the battery control device 30. A program having such an algorithm can, for example, be distributed in a downloadable manner via a known network, or distributed in the form of storage on a recording medium.

[0061] The following explanation assumes, for example, that a user enters vehicle 200 and starts driving by turning on the system power. Furthermore, the following explanation will describe an example where the first battery pack 10A in the battery pack 10 is used as the primary main battery, and the second battery pack 10B is used as a secondary battery.

[0062] First, in step 11, the battery control device 30 determines whether the voltage of the normally used main battery (first battery pack 10A) is the aforementioned first threshold V. th1 That's all. More specifically, in this example, the battery control device 30 determines, via the voltage sensor SR1, whether the voltage value detected by the first battery pack 10A is 3.3V or higher (equivalent to 20% or higher using SOC).

[0063] It should be noted that, in this example, based on the above principle, the first threshold V is... th1 The specified voltage is 3.3V (equivalent to 20% using SOC), but the most suitable value can also be predetermined through experiments or simulations based on the type of secondary battery used in the battery pack 10 and the specifications of the battery system 100. Furthermore, in step 11 above, the battery control device 30 determines the state of the first battery pack 10A based on the voltage value detected from the voltage sensor, but it can also use the battery's SOC value instead of the voltage value for this determination.

[0064] In step 11, the voltage in the main battery is the first threshold V. th1 In the above case (yes in step 11), the battery control device 30 moves to step 12A, and executes the setting of the switch to the first connection mode described above via the switching mechanism 20 (see...). Figure 4 The control of the first battery pack 10A is as follows: In this case, the state of charge (SOC) of the first battery pack 10A is 20% or higher, the voltage is near the rated voltage, and the battery capacity is sufficient. Therefore, in this case, the required power is supplied from the first battery pack 10A to the load 50.

[0065] On the other hand, in step 11, when the voltage of the main battery is not the first threshold V th1 In the above case (no in step 11), the battery control device 30 moves to step 12B to determine whether the voltage of the main battery is the aforementioned second threshold V. th2That's all. More specifically, in this example, the battery control device 30 determines, via the aforementioned voltage sensor SR1, whether the voltage value detected by the first battery pack 10A is 3.0V or higher (equivalent to 10% or higher using SOC). It should be noted that this is related to the first threshold V... th1 Similarly, regarding the second threshold V in this example th2 The most suitable values ​​can also be predetermined through experiments or simulations based on the type of secondary battery used in the battery pack 10 and the specifications of the battery system 100.

[0066] In step 12B, when the voltage of the main battery is the second threshold V th2 In the above case (yes in step 12B), the battery control device 30 moves to step 13A, whereby the switching mechanism 20 performs the action of setting the switch to the second connection method described above (see...). Figure 5 The control of the first battery pack 10A is as follows: In this case, the SOC of the first battery pack 10A is between 10% and 20%, and the voltage value enters the region where it decreases as the battery capacity decreases. Therefore, in this case, the first battery pack 10A and the second battery pack 10B are connected in parallel to supply the required power to the load 50. Thus, although some degradation may occur in the first battery pack 10A due to the decrease in voltage and battery capacity, a more stable battery output to the load 50 can be achieved compared to simply switching to the second battery pack 10B.

[0067] On the other hand, in step 12B, when the voltage of the main battery is not the second threshold V th2 In the above case (No in step 12B), the battery control device 30 moves to step 13B, whereby the switching mechanism 20 performs the action of setting the switch to the third connection method described above (see...). Figure 6 ) or fourth connection method (refer to Figure 7 The control of the first battery pack 10A is as follows: In this case, the SOC of the first battery pack 10A is less than 10%, and if it continues to be used, it will enter a region where battery degradation becomes significant. Therefore, the first battery pack 10A is disconnected from the load 50, and the required power is supplied to the load 50 from the second battery pack 10B.

[0068] At this time, the battery control device 30 may determine which connection mode to set to, either the third or the fourth connection mode, based on the power requirements of the battery system 100 for the load 50 and the driving status of the vehicle 200 (e.g., acceleration value, speed value, whether there is an uphill slope, accelerator opening at the time of determination, etc.).

[0069] Therefore, by going through the above-mentioned step 13B, the degradation of the first battery pack 10A can be suppressed, and when the battery control device 30 selects the third connection method, power can continue to be supplied to the load 50 from the second battery pack 10B. When the battery control device 30 selects the fourth connection method, sufficient power equivalent to that of the first battery pack 10A can be supplied to the load 50 from the second battery pack 10B.

[0070] Thus, in the battery system 100 of this embodiment, by using the second battery pack 10B first when the capacity of the first battery pack 10A, which is the main battery, decreases, compared to simply switching to the second battery pack 10B, the capacity of the second battery pack 10B is not made excessive, and weight reduction and cost reduction can be achieved. Furthermore, in the battery system 100 of this embodiment, when the boost circuit 21 is provided along with the battery pack 10, even when the first battery pack 10A is unusable, sufficient power equivalent to that of the first battery pack 10A can be supplied to the load 50 from the second battery pack 10B.

[0071] As explained above, a vehicle 200 with a battery system 100 according to an embodiment of the present disclosure can maintain the vehicle's driving range with a lightweight and low-cost battery structure, while suppressing battery degradation as much as possible for loads such as the vehicle's electric motor, and can achieve more stable battery output.

[0072] The preferred embodiments of this disclosure have been described in detail above with reference to the accompanying drawings, but the technology of this disclosure is not limited to the examples described above. Those skilled in the art to which this disclosure pertains will recognize that various modifications or alterations can be conceived within the scope of the technical concept set forth in the claims, and will understand that these modifications or alterations also fall within the technical scope of this disclosure.

[0073] For example, in the second connection method described above, the battery control device 30 connects the first battery pack 10A and the second battery pack 10B in parallel. However, if the voltage difference between the cells constituting the first battery pack 10A and the cells constituting the second battery pack 10B is greater than a predetermined value (e.g., immediately after rapid vehicle acceleration), it can temporarily disconnect the first battery pack 10A from the load 50. This can suppress unexpected degradation of the first battery pack 10A. It should be noted that the "predetermined value" for the aforementioned voltage difference can be appropriately set through experimentation or simulation.

[0074] Furthermore, in the aforementioned fourth connection method, the battery control device 30 boosts the voltage of the second battery pack 10B via the boost circuit 21. However, this disclosure is not limited to the above method; for example, the boost circuit 21 can also be used to control the voltage of the first battery pack 10A under predetermined conditions. Examples of such "predetermined conditions" include, for instance, uphill roads and accelerator settings.

Claims

1. A battery system, characterized in that, include: The battery pack consists of a first battery pack and a second battery pack. The first battery pack is composed of multiple units connected in series, and the second battery pack is composed of a different number of units connected in series than the first battery pack. The voltage value of the first battery pack in the low SOC state is set as the upper limit voltage. A switching mechanism capable of switching at least to a first connection mode connecting the first battery pack to a load, and a second connection mode connecting the first battery pack and the second battery pack in parallel to the load; and The battery control device controls the switching mechanism. When the first battery pack is in the low SOC state, the battery control device switches from the first connection mode to the second connection mode via the switching mechanism.

2. The battery system according to claim 1, characterized in that, The switching mechanism can also disconnect the first battery pack and switch to a third connection mode that connects the second battery pack to the load. When the first battery pack's state of charge (SOC) is below the commonly used lower limit, the battery control device switches from the second connection mode to the third connection mode via the switching mechanism.

3. The battery system according to claim 2, characterized in that, The battery system also includes a boost circuit, which is connected to the second battery pack via the switching mechanism and is capable of boosting the voltage between the terminals of the second battery pack. The battery control device boosts the voltage of the second battery pack via the boost circuit.

4. A battery control device, characterized in that, This is a battery control device that controls a battery pack, which consists of a first battery group and a second battery group. The first battery group is composed of multiple units connected in series, and the second battery group is composed of a different number of units connected in series than the first battery group. The device sets the voltage value of the first battery group at its low SOC state as the upper limit voltage. The battery control device includes a processor and a memory, the memory being capable of storing programs executed by the processor. The program contains instructions. The instruction causes the processor to detect the SOC of the first battery pack, and when the first battery pack is in the low SOC state, to connect the first battery pack and the second battery pack in parallel with the load via a switching mechanism.

5. A vehicle, characterized in that, The battery system is equipped with any one of claims 1 to 3 or the battery control device as described in claim 4.

6. A recording medium containing a computer program, characterized in that, The computer program is applicable to a battery system consisting of a first battery pack and a second battery pack installed in a vehicle. The first battery pack is composed of multiple cells connected in series, and the second battery pack is composed of a different number of cells connected in series than the first battery pack. The voltage value of the first battery pack at its low SOC state is set as the upper limit voltage. The computer program causes one or more processors to perform the following processes: Processing to detect the SOC of the first battery pack; and When the first battery pack is in the low SOC state, the first battery pack and the second battery pack are connected in parallel via a switching mechanism.

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