Battery system, vehicle, control method for battery system, and program

Abstract

To secure a power storage amount of a high-voltage battery even if charging rate characteristics of the high-voltage battery are changed.SOLUTION: A battery system 30 comprises a low-voltage battery 31, a high-voltage battery 32 and a CPU 41. The CPU 41 executes: determining whether or not a power storage amount of the low-voltage battery 31 exceeds a determinative power storage amount; and, if it is determined that the power storage amount of the low-voltage battery 31 exceeds the determinative power storage amount, controlling charging of the high-voltage battery 32 so as to charge the high-voltage battery 32 with a predetermined quantity of electricity from the low-voltage battery 31.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a battery system, a vehicle, a control method for a battery system, and a program. [Background technology]

[0002] Patent Document 1 discloses an example of a battery system including a low-voltage battery and a high-voltage battery having a higher rated voltage than the low-voltage battery. In this battery system, the high-voltage battery is charged from the low-voltage battery until the charging rate of the high-voltage battery reaches a predetermined charging rate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent No. 10,052,967 Summary of the Invention [Problem to be solved by the invention]

[0004] The charging rate characteristics of a high-voltage battery may change due to factors such as the progression of battery deterioration. The charging rate characteristics are characteristics that indicate the relationship between the amount of charge stored in the high-voltage battery and the charging rate. If the charging rate characteristics of a high-voltage battery change, even if the high-voltage battery is charged up to a predetermined charging rate, the amount of charge stored in the high-voltage battery may not reach the desired amount. [Means for solving the problem]

[0005] A battery system for solving the above problem includes a low-voltage battery, a high-voltage battery having a higher rated voltage than the low-voltage battery, and a processing circuit for controlling charging from the low-voltage battery to the high-voltage battery. The processing circuit determines whether the amount of electricity stored in the low-voltage battery exceeds a determined amount of electricity, and, if it determines that the amount of electricity stored in the low-voltage battery exceeds the determined amount of electricity, controls charging of the high-voltage battery so that a predetermined amount of electricity is charged from the low-voltage battery to the high-voltage battery.

[0006] A vehicle that solves the above problem includes the above battery system and a traction motor that is driven by power supplied from the high-voltage battery. A control method for a battery system for solving the above problem includes a low-voltage battery and a high-voltage battery having a rated voltage higher than that of the low-voltage battery, the control method including: causing a determination unit to determine whether the amount of electricity stored in the low-voltage battery exceeds a determined amount of electricity; and, when the determination unit determines that the amount of electricity stored in the low-voltage battery exceeds the determined amount of electricity, causing a control unit to control charging of the high-voltage battery so that a predetermined amount of electricity is charged from the low-voltage battery to the high-voltage battery.

[0007] A program for solving the above problem is a program executed by a processing circuit when a high-voltage battery having a higher rated voltage than a low-voltage battery is charged from a low-voltage battery, the program causing the processing circuit to determine whether the amount of electricity stored in the low-voltage battery exceeds a determined amount of electricity, and, if it is determined that the amount of electricity stored in the low-voltage battery exceeds the determined amount of electricity, to control charging of the high-voltage battery so that a predetermined amount of electricity is charged from the low-voltage battery to the high-voltage battery. [Effects of the Invention]

[0008] Even if the charging rate characteristics of the high voltage battery change, the amount of charge stored in the high voltage battery can be ensured. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a block diagram showing an outline of a vehicle equipped with a battery system according to an embodiment. [Figure 2] FIG. 2 is a block diagram showing a functional configuration of a control device provided in the battery system of FIG. [Figure 3] FIG. 3 is a flowchart showing a series of processes executed by the control device when charging the high-voltage battery in the battery system of FIG. [Figure 4] FIG. 4 is a diagram showing the relationship between the capacity and the amount of electricity of the low-voltage battery provided in the battery system of FIG. [Figure 5] FIG. 5 is a flowchart showing a series of processes executed by the control device when setting the lower limit guard in the battery system of FIG. [Figure 6] FIG. 6 is a flowchart showing a series of processes executed by the control device when setting a predetermined amount of electricity in the battery system of FIG. [Figure 7] FIG. 7 is a diagram showing a change in the amount of stored electricity in the high-voltage battery when charging is performed from the low-voltage battery in the battery system of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of a battery system, a vehicle, a control method for a battery system, and a program will be described with reference to FIGS. <Vehicle configuration> 1 shows a vehicle 10 equipped with a battery system 30. The vehicle 10 further includes a solar power generation system 20, at least one traction motor 11, and a plurality of accessories 13. The traction motor 11 functions as a power source for the vehicle 10. The plurality of accessories 13 includes an air conditioning device, an audio device, a display device, and the like.

[0011] The solar power generation system 20 includes a solar panel 21 and a solar converter 25. The solar panel 21 has a plurality of solar cells 22 that generate electricity when irradiated with sunlight. For example, the solar panel 21 is installed on the roof of the vehicle 10. The solar converter 25 converts the voltage of the DC power generated by the solar panel 21. The solar converter 25 then outputs the converted DC power to the battery system 30.

[0012] <Battery system configuration> The battery system 30 includes a low-voltage battery 31 and a high-voltage battery 32 . The low-voltage battery 31 is a secondary battery. An example of the low-voltage battery 31 is a lithium-ion battery. The rated voltage of the low-voltage battery 31 is, for example, about 12 V to 48 V. The low-voltage battery 31 supplies DC power to the above-mentioned auxiliary equipment 13 and the like.

[0013] The low-voltage battery 31 is charged by being supplied with DC power from the solar power generation system 20. That is, the low-voltage battery 31 is charged by being supplied with DC power output from the solar converter 25.

[0014] The high-voltage battery 32 is, for example, a battery for propelling the vehicle 10. That is, the high-voltage battery 32 supplies DC power to the propulsion motor 11. The rated voltage of the high-voltage battery 32 is higher than the rated voltage of the low-voltage battery 31. The rated voltage of the high-voltage battery 32 is, for example, about 200 [V] to 250 [V].

[0015] The battery system 30 includes a bidirectional DC / DC converter 35 and a switch circuit 36. The bidirectional DC / DC converter 35 is a circuit that converts the voltage of DC power input thereto and outputs the converted power. For example, when the low-voltage battery 31 charges the high-voltage battery 32, the bidirectional DC / DC converter 35 boosts the voltage of the DC power output from the low-voltage battery 31, thereby supplying the DC power output from the low-voltage battery 31 to the high-voltage battery 32. When the high-voltage battery 32 charges the low-voltage battery 31, the bidirectional DC / DC converter 35 lowers the voltage of the DC power output from the high-voltage battery 32, thereby supplying the DC power output from the high-voltage battery 32 to the low-voltage battery 31.

[0016] The switch circuit 36 ​​is installed, for example, on a power line connecting the bidirectional DC / DC converter 35 and the high-voltage battery 32. Turning the switch circuit 36 ​​off cuts off the current flow between the high-voltage battery 32 and the bidirectional DC / DC converter 35. Turning the switch circuit 36 ​​on allows the current flow between the high-voltage battery 32 and the bidirectional DC / DC converter 35.

[0017] The battery system 30 includes a control device 40 that controls the entire system. An example of the control device 40 is an electronic control device. In this case, the control device 40 includes a CPU 41, a first memory 42, and a second memory 43. The CPU 41 corresponds to the "processing circuit." The first memory 42 stores a control program executed by the CPU 41. The second memory 43 stores the results of calculations by the CPU 41, etc. The CPU 41 controls charging from the low-voltage battery 31 to the high-voltage battery 32 by executing the control program in the first memory 42.

[0018] <Functional section> 2, the CPU 41 functions as various functional units by executing a control program in the first memory 42. The various functional units shown in Fig. 2 are functional units for controlling charging from the low-voltage battery 31 to the high-voltage battery 32. The various functional units include a determination unit 101, a control unit 102, a guard setting unit 103, and an electricity quantity setting unit 104.

[0019] <Judgment part> The determination unit 101 determines whether the stored power amount AES1 of the low-voltage battery 31 exceeds the determined stored power amount AES1th. The "stored power amount" here refers to the amount of electricity currently stored in the battery. The amount of electricity is the time integral of the amount of power. The determined stored power amount AES1th is a criterion for determining whether the stored power amount AES1 is sufficient when supplying power from the low-voltage battery 31 to the high-voltage battery 32. If the stored power amount AES1 is equal to or less than the determined stored power amount AES1th, it can be considered that the stored power amount AES1 of the low-voltage battery 31 is not large. If the stored power amount AES1 exceeds the determined stored power amount AES1th, it can be considered that the stored power amount AES1 of the low-voltage battery 31 is large.

[0020] The determination unit 101 determines whether the stored power amount AES2 of the high-voltage battery 32 is equal to or greater than the upper limit amount AES2L. If the maximum stored power amount AES2max is the amount of power stored when the high-voltage battery 32 is fully charged at that time, the determination unit 101 sets the upper limit amount AES2L to a stored power amount slightly smaller than the maximum stored power amount AES2max. If the stored power amount AES2 exceeds the upper limit amount AES2L, a value at which it can be determined that the high-voltage battery 32 is likely to deteriorate is set as the upper limit amount AES2L. For example, the product of the maximum stored power amount AES2max and a predetermined rate may be set as the upper limit amount AES2L. In this case, the upper limit amount AES2L decreases as the maximum stored power amount AES2max decreases.

[0021] <Control unit> The control unit 102 controls the charging of the high-voltage battery 32 so that a predetermined quantity of electricity QE is charged from the low-voltage battery 31 to the high-voltage battery 32. At this time, the control unit 102 operates the bidirectional DC / DC converter 35 with the switch circuit 36 ​​turned on, thereby charging the high-voltage battery 32 with the predetermined quantity of electricity QE from the low-voltage battery 31. Hereinafter, the control of operating the bidirectional DC / DC converter 35 to charge the high-voltage battery 32 from the low-voltage battery 31 with the switch circuit 36 ​​turned on will be referred to as "charging control."

[0022] The control unit 102 performs charging control when it is determined that the stored power amount AES1 of the low-voltage battery 31 exceeds the determined stored power amount AES1th. In other words, the control unit 102 does not perform charging control when it is determined that the stored power amount AES1 is equal to or less than the determined stored power amount AES1th.

[0023] The control unit 102 performs charging control when it is determined that the stored power amount AES2 of the high-voltage battery 32 is less than the upper limit amount AES2L. In other words, the control unit 102 does not perform charging control when it is determined that the stored power amount AES2 is equal to or greater than the upper limit amount AES2L.

[0024] When the control unit 102 performs charging control, the amount of stored power AES2 of the high-voltage battery 32 increases. As the amount of stored power AES2 increases, the high-voltage battery voltage VB2, which is the voltage of the high-voltage battery 32, increases. The high-voltage battery voltage VB2 is the voltage across the battery cells of the high-voltage battery 32. If the high-voltage battery voltage VB2 becomes too high, the amount of stored power AES2 may significantly exceed the upper limit amount AES2L during charging control. Therefore, a voltage for determining whether the amount of stored power AES2 has significantly exceeded the upper limit amount AES2L is set to a specified voltage VB2th. Then, when the high-voltage battery voltage VB2 becomes higher than the specified voltage VB2th during charging control, the control unit 102 stops the charging control. That is, the control unit 102 stops the charging control before a predetermined amount of electricity QE is charged to the high-voltage battery 32.

[0025] <Guard setting section> When DC power from the low-voltage battery 31 is supplied to the high-voltage battery 32 to charge the high-voltage battery 32, the amount of stored power AES1 in the low-voltage battery 31 decreases. When the amount of stored power AES1 decreases, the voltage between the terminals of the battery cells that make up the low-voltage battery 31 decreases. The voltage between the terminals of the battery cells that make up the low-voltage battery 31 is simply referred to as the "low-voltage battery voltage VB1."

[0026] The capacity CC1 of the low-voltage battery 31 is the maximum amount of electricity that can be stored in the low-voltage battery 31 at this time. As the low-voltage battery 31 deteriorates, the capacity CC1 of the low-voltage battery 31 decreases. It is not desirable for the low-voltage battery voltage VB1 to become too low when the capacity CC1 has decreased.

[0027] Therefore, the guard setting unit 103 sets a lower limit guard VG to prevent the low-voltage battery voltage VB1 from becoming too low due to charging from the low-voltage battery 31 to the high-voltage battery 32. For example, the guard setting unit 103 determines whether the capacity CC1 of the low-voltage battery 31 is equal to or less than a threshold CC1th. If the guard setting unit 103 determines that the capacity CC1 is equal to or less than the threshold CC1th, it sets the lower limit guard VG. If the capacity CC1 is greater than the threshold CC1th, the guard setting unit 103 does not set the lower limit guard VG.

[0028] <Electricity amount setting section> The electricity quantity setting unit 104 sets a predetermined electricity quantity QE. For example, the electricity quantity setting unit 104 sets the predetermined electricity quantity QE according to the state of the high-voltage battery 32. In this case, the electricity quantity setting unit 104 acquires at least one of the state of charge and the degradation state of the high-voltage battery 32 as the state of the high-voltage battery 32. When acquiring the state of charge of the high-voltage battery 32, the electricity quantity setting unit 104 acquires, for example, the stored electricity amount AES2 of the high-voltage battery 32. Then, the electricity quantity setting unit 104 reduces the predetermined electricity quantity QE as the stored electricity amount AES2 of the high-voltage battery 32 increases. When acquiring the degradation state of the high-voltage battery 32, the electricity quantity setting unit 104 acquires, for example, the current capacity CC2 of the high-voltage battery 32. Then, the electricity quantity setting unit 104 reduces the predetermined electricity quantity QE as the capacity CC2 decreases.

[0029] Even if the capacity CC1 of the low-voltage battery 31 decreases due to deterioration of the low-voltage battery 31, if the predetermined quantity of electricity QE is large, there is a risk that the low-voltage battery voltage VB1 will become too low after one charge control. Therefore, the quantity of electricity setting unit 104 determines whether the capacity CC1 of the low-voltage battery 31 is equal to or less than the determination capacity CCth. If the quantity of electricity setting unit 104 determines that the capacity CC1 of the low-voltage battery 31 is equal to or less than the determination capacity CCth, it sets the predetermined quantity of electricity QE to be smaller than when it determines that the capacity CC1 is greater than the determination capacity CCth. In this case, the criterion for determining whether the capacity CC1 has decreased is set as the determination capacity CCth.

[0030] As described above, when the capacity CC1 of the low-voltage battery 31 decreases, the guard setting unit 103 sets the lower limit guard VG. Specifically, when the guard setting unit 103 determines that the capacity CC1 is equal to or less than the threshold CC1th, the guard setting unit 103 sets the lower limit guard VG. When the threshold CC1th is equal to the determined capacity CCth, the electricity quantity setting unit 104 can set the predetermined electricity quantity QE smaller when the lower limit guard VG is set than when the lower limit guard VG is not set. For example, when the guard setting unit 103 sets the lower limit guard VG, the electricity quantity setting unit 104 may set the predetermined electricity quantity QE so that the low-voltage battery voltage VB1 does not fall below the lower limit guard VG. This is because the larger the predetermined electricity quantity QE, the more likely it is that the low-voltage battery voltage VB1 will be lower at the end of charging control.

[0031] In charge control, the bidirectional DC / DC converter 35 and the switch circuit 36 ​​are operated. The more times the bidirectional DC / DC converter 35 and the switch circuit 36 ​​are operated, the more likely they are to deteriorate. Therefore, the electricity quantity setting unit 104 sets the predetermined electricity quantity QE so that when charge control is performed frequently, the predetermined electricity quantity QE is larger than when charge control is performed less frequently. The "frequency of performing charge control" here refers to the number of times charge control is performed within a predetermined time. The more times charge control is performed within a predetermined time, the higher the frequency of performance.

[0032] <High-voltage battery charging process> 3 and 4, the high-voltage battery charging process executed by the CPU 41 will be described. The high-voltage battery charging process is a series of processes for charging the high-voltage battery 32. The CPU 41 repeatedly executes the high-voltage battery charging process.

[0033] In step S11, the CPU 41 determines whether or not the conditions for permitting charging control are met. For example, when the vehicle 10 is running, power is supplied from the high-voltage battery 32 to the traction motor 11. Therefore, it is not preferable to perform charging control when the vehicle 10 is running. Therefore, the conditions for permitting charging should preferably include the vehicle 10 being stopped. If the CPU 41 determines that the conditions for permitting charging are met (S11: YES), the CPU 41 proceeds to step S13. If the CPU 41 determines that the conditions for permitting charging are not met (S11: NO), the CPU 41 temporarily terminates the high-voltage battery charging process.

[0034] In step S13, the CPU 41 determines whether the stored power amount AES1 of the low-voltage battery 31 exceeds the determination stored power amount AES1th. If the CPU 41 determines that the stored power amount AES1 exceeds the determination stored power amount AES1th (S13: YES), the CPU 41 proceeds to step S15. If the CPU 41 determines that the stored power amount AES1 is equal to or less than the determination stored power amount AES1th (S13: NO), the CPU 41 temporarily terminates the high-voltage battery charging process.

[0035] An example of a process for determining whether the amount of stored power AES1 exceeds the determination amount of stored power AES1th will now be described with reference to Fig. 4. Fig. 4 shows the relationship between the low-voltage battery voltage VB1 and the amount of electricity Ah of the low-voltage battery 31.

[0036] 4, when the quantity of electricity Ah is not very large, i.e., when the quantity of electricity Ah is equal to or greater than the first quantity of electricity Ah1 and less than the second quantity of electricity Ah2, the low-voltage battery voltage VB1 remains substantially constant even when the quantity of electricity Ah changes. On the other hand, when the quantity of electricity Ah is relatively large, i.e., when the quantity of electricity Ah is equal to or greater than the second quantity of electricity Ah2, the low-voltage battery voltage VB1 also increases as the quantity of electricity Ah increases.

[0037] Therefore, the CPU 41 can determine whether the stored energy amount AES1 exceeds the determination stored energy amount AES1th based on the amount of change in the low-voltage battery voltage VB1 when the amount of electricity Ah changes. In this case, the CPU 41 determines that the stored energy amount AES1 exceeds the determination stored energy amount AES1th if the amount of change in the low-voltage battery voltage VB1 when the amount of electricity Ah changes is equal to or greater than the determination value. Conversely, the CPU 41 determines that the stored energy amount AES1 is equal to or less than the determination stored energy amount AES1th if the amount of change in the low-voltage battery voltage VB1 when the amount of electricity Ah changes is less than the determination value.

[0038] Note that a method other than the method described with reference to Fig. 4 may be adopted as the process for determining whether the stored power amount AES1 exceeds the determination stored power amount AES1th. For example, the CPU 41 calculates the stored power amount AES1 of the low-voltage battery 31. Then, when the calculated value of the stored power amount AES1 is larger than the determination stored power amount AES1th, the CPU 41 may determine that the stored power amount AES1 exceeds the determination stored power amount AES1th.

[0039] Returning to FIG. 3, in step S15, the CPU 41 determines whether the stored power amount AES2 of the high-voltage battery 32 is less than the upper limit amount AES2L. For example, the CPU 41 calculates the stored power amount AES2 of the high-voltage battery 32. If the calculated value of the stored power amount AES2 is less than the upper limit amount AES2L, the CPU 41 determines that the stored power amount AES2 is less than the upper limit amount AES2L. If the calculated value of the stored power amount AES2 is equal to or greater than the upper limit amount AES2L, the CPU 41 determines that the stored power amount AES2 is equal to or greater than the upper limit amount AES2L. Then, if the CPU 41 determines that the stored power amount AES2 is less than the upper limit amount AES2L (S15: YES), the CPU 41 shifts the process to step S17. If the CPU 41 determines that the stored power amount AES2 is equal to or greater than the upper limit amount AES2L (S15: NO), the CPU 41 temporarily terminates the high-voltage battery charging process.

[0040] In step S17, the CPU 41 performs charging control. The CPU 41 ends the charging control when either one of the following conditions (A1) and (A2) is met. (A1) A predetermined amount of electricity QE is charged from the low-voltage battery 31 to the high-voltage battery 32.

[0041] (A2) During the execution of charging control, the high-voltage battery voltage VB2 becomes higher than the specified voltage VB2th. When the charging control ends, the CPU 41 temporarily ends the high-voltage battery charging process.

[0042] 3, the processes of steps S11, S13, and S15 are executed by the CPU 41 functioning as the determination unit 101. The process of step S17 is executed by the CPU 41 functioning as the control unit 102.

[0043] <Guard setting process> The guard setting process executed by the CPU 41 will be described with reference to Fig. 5. The guard setting process is a series of processes for setting the lower limit guard VG. The CPU 41 sets the guard setting process when a predetermined condition is met. Examples of the predetermined condition include the user getting into the vehicle 10 and the driving switch of the vehicle 10 being turned on.

[0044] In step S31, the CPU 41 acquires the capacity CC1 of the low-voltage battery 31. In the following step S33, the CPU 41 determines whether the capacity CC1 is equal to or less than a threshold CC1th. If the CPU 41 determines that the capacity CC1 is equal to or less than the threshold CC1th (S33: YES), the CPU 41 proceeds to step S35. If the CPU 41 determines that the capacity CC1 is greater than the threshold CC1th (S33: NO), the CPU 41 ends the guard setting process.

[0045] In step S35, the CPU 41 sets the lower limit guard VG, and then the CPU 41 ends the guard setting process. The CPU 41 functions as the guard setting unit 103 to execute the processes of steps S31, S33, and S35 shown in FIG.

[0046] <Electricity amount setting process> 4 and 6, the electricity quantity setting process executed by the CPU 41 will be described. The electricity quantity setting process is a series of processes for setting a predetermined electricity quantity QE. The CPU 41 sets the electricity quantity setting process for each predetermined control period.

[0047] 6, in step S51, the CPU 41 determines whether or not charging control is being performed. If the CPU 41 determines that charging control is being performed (S51: YES), the CPU 41 temporarily ends the electricity quantity setting process. If the CPU 41 determines that charging control is not being performed (S51: NO), the CPU 41 proceeds to step S53.

[0048] In step S53, the CPU 41 acquires the execution frequency FC of the charging control. In the following step S55, the CPU 41 acquires the state of charge and the state of deterioration of the high-voltage battery 32.

[0049] In the next step S57, the CPU 41 derives a provisional quantity of electricity QEA, which is a provisional value of the predetermined quantity of electricity QE. The CPU 41 derives the predetermined quantity of electricity QE based on the execution frequency FC of the charging control and the state of the high-voltage battery 32 as the provisional quantity of electricity QEA.

[0050] In the next step S59, the CPU 41 determines whether or not a lower limit guard VG has been set by executing the guard setting process. If the lower limit guard VG has been set (S59: YES), the CPU 41 proceeds to step S61. If the lower limit guard VG has not been set (S59: NO), the CPU 41 proceeds to step S63.

[0051] In step S61, the CPU 41 sets a predetermined quantity of electricity QE by correcting the tentative quantity of electricity QEA so that the low-voltage battery voltage VB1 does not fall below the lower limit guard VG after the end of the charging control. Of course, if the CPU 41 can determine that the low-voltage battery voltage VB1 will not fall below the lower limit guard VG even when the charging control is performed with the tentative quantity of electricity QEA set to the predetermined quantity of electricity QE, the CPU 41 may set the tentative quantity of electricity QEA to the predetermined quantity of electricity QE. Once the CPU 41 has set the predetermined quantity of electricity QE, it temporarily ends the quantity of electricity setting process.

[0052] Here, the dashed line in Fig. 4 shows the relationship between the low-voltage battery voltage VB1 and the amount of electricity Ah when the low-voltage battery 31 is degraded. On the other hand, the solid line in Fig. 4 shows the relationship between the low-voltage battery voltage VB1 and the amount of electricity Ah when the low-voltage battery 31 is not degraded. When the third amount of electricity Ah3 is the amount of electricity that serves as the criterion for determining whether the amount of stored electricity AES1 is large when the low-voltage battery 31 is degraded, the second amount of electricity Ah2 is the amount of electricity that serves as the criterion for determining whether the amount of stored electricity AES1 is large when the low-voltage battery 31 is not degraded. As shown in Fig. 4, the third amount of electricity Ah3 is smaller than the second amount of electricity Ah2.

[0053] Therefore, when the capacity CC of the low voltage battery 31 has decreased to the extent that the lower limit guard VG is set, it is preferable to make the predetermined quantity of electricity QE smaller than when the lower limit guard VG is not set.

[0054] 6, in step S63, the CPU 41 sets the temporary quantity of electricity QEA to a predetermined quantity of electricity QE, and then the CPU 41 temporarily ends the quantity of electricity setting process. <Actions and Effects of This Embodiment> The operation and effect of this embodiment will be described with reference to Fig. 7. The charge amount range RA shown in Fig. 7 is the range of charge amount AES2 of the high voltage battery 32 desired for the system.

[0055] The CPU 41 determines whether the stored power amount AES1 of the low-voltage battery 31 exceeds the determination stored power amount AES1th. When the CPU 41 determines that the stored power amount AES1 exceeds the determination stored power amount AES1th, the CPU 41 performs charging control. In the charging control, the CPU 41 controls charging of the high-voltage battery 32 so that a predetermined quantity of electricity QE is charged from the low-voltage battery 31 to the high-voltage battery 32.

[0056] Fig. 7 shows the change in the amount of stored power AES2 of the high-voltage battery 32 due to the execution of charging control. In detail, Fig. 7 shows the change in the amount of stored power AES2 when the high-voltage battery 32 is new and the change in the amount of stored power AES2 when the high-voltage battery 32 is deteriorated.

[0057] In this embodiment, regardless of whether the high-voltage battery 32 has deteriorated, charging control is performed to charge the high-voltage battery 32 with a predetermined amount of electricity QE. Furthermore, when the stored energy amount AES2 of the high-voltage battery 32 is less than the upper limit amount AES2L, charging control is repeatedly performed if it is determined that the stored energy amount AES1 of the low-voltage battery 31 exceeds the determined stored energy amount AES1th. Therefore, the battery system 30 can ensure the stored energy amount AES2 of the high-voltage battery 32 even if the charging rate characteristics of the high-voltage battery 32 change. In other words, the battery system 30 can make the stored energy amount AES2 greater than the lower limit of the stored energy amount range RA.

[0058] The charging rate characteristic is a characteristic that indicates the relationship between the charge rate and the amount of stored electricity AES2 of the high-voltage battery 32. As the deterioration of the high-voltage battery 32 progresses, the maximum amount of stored electricity AES2max becomes smaller. As a result, as the deterioration of the high-voltage battery 32 progresses, the charging rate characteristic of the high-voltage battery 32 changes.

[0059] In this embodiment, the following effects can be further obtained. (1) The low-voltage battery 31 is charged by DC power supplied from the solar power generation system 20. Therefore, in the battery system 30, both the low-voltage battery 31 and the high-voltage battery 32 can be charged by the power generated by the solar panel 21 of the solar power generation system 20.

[0060] (2) The high-voltage battery 32 can supply power to the traction motor 11. The low-voltage battery 31 can supply power to the auxiliary equipment 13. Therefore, the vehicle 10 equipped with the battery system 30 can run using the power generated by the solar panel 21.

[0061] (3) A bidirectional DC / DC converter 35 is installed in the power line between the low-voltage battery 31 and the high-voltage battery 32. As a result, in the battery system 30, the high-voltage battery 32 can be charged from the low-voltage battery 31 via the bidirectional DC / DC converter 35, and the low-voltage battery 31 can be charged from the high-voltage battery 32 via the bidirectional DC / DC converter 35.

[0062] (4) The CPU 41 sets a predetermined quantity of electricity QE according to the state of the high-voltage battery 32. This makes it possible for the battery system 30 to prevent excessive supply of power to the high-voltage battery 32 due to the execution of charging control.

[0063] For example, the CPU 41 can reduce the predetermined quantity of electricity QE as the stored electricity amount AES2 of the high-voltage battery 32 increases. Furthermore, for example, when the high-voltage battery 32 is deteriorating, the CPU 41 can reduce the predetermined quantity of electricity QE compared to when the high-voltage battery 32 is not deteriorating.

[0064] (5) The more times electronic circuits such as the bidirectional DC / DC converter 35 and the switch circuit 36 ​​operate, the higher the possibility that an abnormality such as a malfunction of the electronic circuits will occur. On sunny days, the amount of power generated by the solar panel 21 is greater than on cloudy or rainy days. Therefore, on sunny days, the period from when the charging control ends until the stored power amount AES1 of the low-voltage battery 31 exceeds the determined stored power amount AES1th is shorter. As a result, the frequency FC of the charging control tends to be higher.

[0065] In this regard, in the battery system 30, the CPU 41 sets the predetermined quantity of electricity QE so that when the execution frequency FC of the charging control is high, the predetermined quantity of electricity QE is larger than when the execution frequency FC is low. This prevents an increase in the number of operations of the bidirectional DC / DC converter 35 and the switch circuit 36 ​​for charging the high-voltage battery 32. Therefore, in the battery system 30, abnormalities are less likely to occur in electronic circuits such as the bidirectional DC / DC converter 35 and the switch circuit 36.

[0066] (6) As the deterioration of the low-voltage battery 31 progresses, the capacity CC1 of the low-voltage battery 31 decreases. Furthermore, the low-voltage battery 31 supplies power to the auxiliary device 13. Therefore, if a large amount of electricity is charged to the high-voltage battery 32 while the capacity CC1 is reduced, the low-voltage battery voltage VB1 becomes too low, which may cause the operation of the auxiliary device 13 to become unstable.

[0067] Therefore, in the battery system 30, when the CPU 41 determines that the capacity CC1 of the low-voltage battery 31 is equal to or less than the threshold capacity CCth, the CPU 41 reduces the predetermined quantity of electricity QE compared to when the CPU 41 determines that the capacity CC1 is greater than the threshold capacity CCth. This prevents the low-voltage battery voltage VB1 from becoming too low due to the execution of the charging control. As a result, in the battery system 30, it is possible to prevent the operation of the auxiliary device 13, to which power is supplied from the low-voltage battery 31, from becoming unstable due to the execution of the charging control.

[0068] For example, the CPU 41 sets the predetermined quantity of electricity QE so that the low-voltage battery voltage VB1 does not fall below the lower limit guard VG. As a result, when the CPU 41 determines that the capacity CC1 of the low-voltage battery 31 is equal to or smaller than the determination capacity CCth, the CPU 41 can reduce the predetermined quantity of electricity QE compared to when the CPU 41 determined that the capacity CC1 was greater than the determination capacity CCth.

[0069] (7) As the degradation of the low-voltage battery 31 progresses, the capacity CC1 of the low-voltage battery 31 decreases. When the CPU 41 determines that the capacity CC1 is equal to or less than the threshold CC1th, it sets the lower limit guard VG. This prevents the low-voltage battery voltage VB1 from becoming too low due to the execution of charging control in the battery system 30 when the degradation of the low-voltage battery 31 progresses.

[0070] On the other hand, when the CPU 41 determines that the capacity CC1 is greater than the threshold CC1th, it does not set the lower limit guard VG. Therefore, when the low-voltage battery 31 is not significantly deteriorated, the CPU 41 can set the predetermined quantity of electricity QE to a relatively large value. This prevents the frequency FC of charge control from becoming too high in the battery system 30 when the low-voltage battery 31 is not significantly deteriorated.

[0071] (8) When the high-voltage battery voltage VB2 becomes higher than the specified voltage VB2th during the charging control, the CPU 41 forcibly terminates the charging control. This prevents excessive power from being supplied to the high-voltage battery 32 in the battery system 30.

[0072] <Example of change> The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other within the scope of technical compatibility.

[0073] The CPU 41 may set the lower limit guard VG regardless of the magnitude of the capacity CC1 of the low-voltage battery 31. In this case, the CPU 41 may vary the lower limit guard VG depending on the magnitude of the capacity CC1. For example, the CPU 41 may set a smaller value as the capacity CC1 increases.

[0074] When the CPU 41 determines that the capacity CC1 of the low-voltage battery 31 is equal to or less than the judgment capacity CCth, the CPU 41 does not need to set the lower limit guard VG if the predetermined quantity of electricity QE can be made smaller than when the capacity CC1 is determined to be greater than the judgment capacity CCth.

[0075] The CPU 41 does not have to vary the predetermined quantity of electricity QE according to the capacity CC1 of the low-voltage battery 31. For example, the CPU 41 may forcibly terminate the charging control if the low-voltage battery voltage VB1 becomes equal to or lower than a reference voltage during the charging control. In this case, it is preferable that the reference voltage be set as a criterion for determining whether the low-voltage battery voltage VB1 has become too low. This allows the CPU 41 to prevent the low-voltage battery voltage VB1 from becoming too low during the charging control.

[0076] The CPU 41 does not need to vary the predetermined quantity of electricity QE according to the execution frequency FC of the charging control. The state of the high-voltage battery 32 may change depending on the temperature of the high-voltage battery 32 or the ambient temperature around the high-voltage battery 32. Therefore, the CPU 41 may acquire the temperature of the high-voltage battery 32 or the ambient temperature around the high-voltage battery 32 as the state of the high-voltage battery 32. In this case, the CPU 41 may vary the predetermined quantity of electricity QE based on the temperature of the high-voltage battery 32 or the ambient temperature around the high-voltage battery 32.

[0077] The CPU 41 may set the predetermined quantity of electricity QE without taking into account the deterioration state of the high-voltage battery 32, as long as the state of charge of the high-voltage battery 32 is taken into consideration. The CPU 41 may set the predetermined quantity of electricity QE without taking into account the state of charge of the high-voltage battery 32, as long as the state of deterioration of the high-voltage battery 32 is taken into consideration.

[0078] The CPU 41 does not need to vary the predetermined quantity of electricity QE according to the state of the high-voltage battery 32. The CPU 41 may fix the predetermined quantity of electricity QE at a preset value. In this case, the CPU 41 may monitor the states of the high-voltage battery 32 and the low-voltage battery 31 while the charging control is being performed. The CPU 41 may then preferably terminate the charging control even if it is midway depending on the states of the high-voltage battery 32 and the low-voltage battery 31.

[0079] The CPU 41 may use the energy amount [Wh] of the low-voltage battery 31 to determine whether the stored amount AES1 of the low-voltage battery 31 exceeds the determination stored amount AES1th. For example, when the energy amount corresponding to the determination stored amount AES1th is set as the determination energy amount, the CPU 41 may determine that the stored amount AES1 exceeds the determination stored amount AES1th if the energy amount of the low-voltage battery 31 is greater than the determination energy amount. In the charge control, the CPU 41 may control the charging of the high-voltage battery 32 so that a predetermined amount of energy is transferred from the low-voltage battery 31 to the high-voltage battery 32. The "predetermined amount of energy" is a value obtained by converting a predetermined amount of electricity QE into an energy amount.

[0080] The battery system only needs to be configured so that the low-voltage battery 31 can charge the high-voltage battery 32. Therefore, a DC / DC converter capable of boosting the voltage of the DC power of the low-voltage battery 31 needs to be arranged on the power line between the low-voltage battery 31 and the high-voltage battery 32. In other words, a DC / DC converter that does not have the function of lowering the voltage of the DC power of the high-voltage battery 32 may be arranged on the power line instead of the bidirectional DC / DC converter 35.

[0081] The low-voltage battery 31 may be a battery that is charged by power supplied from a power supply source other than a solar power generation system. Examples of power supply sources other than a solar power generation system include a generator that generates regenerative energy when braking the vehicle 10, and a commercial power source.

[0082] The battery system may be embodied as a system other than the battery system 30 mounted on the vehicle 10. The control device 40 is not limited to a device that includes a CPU and a ROM and executes software processing. In other words, the control device 40 may have any of the following configurations (a), (b), and (c):

[0083] (a) The control device 40 includes one or more processors that execute various processes according to a computer program. The processor includes a CPU and memory such as RAM and ROM. The memory stores program code or instructions configured to cause the CPU to execute processes. Memory, i.e., computer-readable media, includes any available media that can be accessed by a general-purpose or special-purpose computer.

[0084] (b) The control device 40 includes one or more dedicated hardware circuits that perform various processes. Examples of dedicated hardware circuits include application-specific integrated circuits (ASICs) or FPGAs. ASIC stands for "Application Specific Integrated Circuit," and FPGA stands for "Field Programmable Gate Array."

[0085] (c) The control device 40 includes one or more processors that execute some of the various processes in accordance with a computer program, and one or more dedicated hardware circuits that execute the remaining processes among the various processes.

[0086] The expression "at least one" used herein means "one or more" of the desired options. As an example, the expression "at least one" used herein means "only one option" or "both of two options" if the number of options is two. As another example, the expression "at least one" used herein means "only one option" or "any combination of two or more options" if the number of options is three or more.

[0087] <Technical philosophy> The technical ideas that can be understood from the above-described embodiment and several modified examples will be described as supplementary notes. [Appendix 1] a low-voltage battery; a high-voltage battery having a rated voltage higher than that of the low-voltage battery; and a processing circuit that controls charging from the low-voltage battery to the high-voltage battery; The processing circuitry determining whether the amount of charge stored in the low-voltage battery exceeds a determination amount of charge; When it is determined that the amount of electricity stored in the low-voltage battery exceeds the determined amount of electricity stored, the battery system controls the charging of the high-voltage battery so that a predetermined amount of electricity is charged from the low-voltage battery to the high-voltage battery.

[0088] [Appendix 2] 2. The battery system of claim 1, wherein the low-voltage battery is charged by power supplied from a solar power generation system.

[0089] [Appendix 3] The battery system is mounted on a vehicle, 3. The battery system according to claim 1, wherein the low-voltage battery and the high-voltage battery are configured to supply power to components mounted on the vehicle.

[0090] [Appendix 4] Equipped with a bidirectional DC / DC converter, The battery system according to any one of appendices 1 to 3, wherein the processing circuit charges the high-voltage battery from the low-voltage battery by boosting the voltage of the DC power output from the low-voltage battery.

[0091] [Appendix 5] 5. The battery system according to claim 1, wherein the processing circuit sets the predetermined amount of electricity according to a state of the high-voltage battery.

[0092] [Appendix 6] 5. The battery system according to claim 1, wherein the processing circuit sets the predetermined amount of electricity based on at least one of a state of charge and a state of deterioration of the high-voltage battery.

[0093] [Appendix 7] The battery system according to any one of appendices 1 to 6, wherein the processing circuit sets the predetermined amount of electricity so that when the frequency of charging from the low-voltage battery to the high-voltage battery is high, the predetermined amount of electricity is larger than when the frequency of charging is low.

[0094] [Appendix 8] The processing circuitry determining whether the capacity of the low-voltage battery is equal to or less than a determination capacity; A battery system as described in any one of Appendix 1 to Appendix 7, which, when it is determined that the capacity of the low-voltage battery is equal to or less than the determined capacity, reduces the specified amount of electricity compared to when it is determined that the capacity is greater than the determined capacity.

[0095] [Appendix 9] 8. The battery system according to claim 1, wherein the processing circuit sets the predetermined amount of electricity so that the voltage of the low-voltage battery does not fall below a lower limit guard.

[0096] [Appendix 10] 10. The battery system of claim 9, wherein the processing circuit sets the lower limit guard when it determines that the capacity of the low-voltage battery is equal to or less than a threshold.

[0097] [Appendix 11] The battery system according to any one of claims 1 to 10, wherein the processing circuit stops charging the high-voltage battery if the voltage of the high-voltage battery becomes higher than a specified voltage while the high-voltage battery is being charged from the low-voltage battery.

[0098] [Appendix 12] A vehicle comprising: the battery system according to any one of Supplementary Note 1 to Supplementary Note 11; and a traction motor that is driven by a supply of electric power from the high-voltage battery. [Explanation of symbols]

[0099] 10...Vehicle 11...Traction motor 13...Auxiliary 20...Solar power generation system 21...Solar panel 30...Battery system 31...Low voltage battery 32...High voltage battery 35...Bidirectional DC / DC converter 36...Switch circuit 40...Control device 41...CPU 101…Judgment section 102...Control unit 103...Guard setting section 104...Electricity amount setting unit

Claims

1. a low-voltage battery; a high-voltage battery having a rated voltage higher than that of the low-voltage battery; and a processing circuit that controls charging from the low-voltage battery to the high-voltage battery; The processing circuitry determining whether the amount of charge stored in the low-voltage battery exceeds a determination amount of charge; When it is determined that the amount of electricity stored in the low-voltage battery exceeds the determined amount of electricity stored, charging of the high-voltage battery is controlled so that a predetermined amount of electricity is charged from the low-voltage battery to the high-voltage battery. Battery system.

2. The low-voltage battery is charged by power supplied from a solar power generation system. The battery system of claim 1 .

3. The battery system is mounted on a vehicle, The low-voltage battery and the high-voltage battery are configured to supply power to components mounted on the vehicle. The battery system of claim 1 .

4. A bidirectional DC / DC converter is provided. The processing circuit charges the high-voltage battery from the low-voltage battery by boosting the voltage of the DC power output from the low-voltage battery. The battery system of claim 1 .

5. The processing circuit sets the predetermined amount of electricity according to the state of the high-voltage battery. The battery system according to any one of claims 1 to 4.

6. The processing circuit sets the predetermined amount of electricity based on at least one of a state of charge and a state of deterioration of the high-voltage battery. The battery system according to any one of claims 1 to 4.

7. The processing circuit sets the predetermined amount of electricity so that when the frequency of charging from the low-voltage battery to the high-voltage battery is high, the predetermined amount of electricity is larger than when the frequency of charging is low. The battery system according to any one of claims 1 to 4.

8. The processing circuitry determining whether the capacity of the low-voltage battery is equal to or less than a determination capacity; When it is determined that the capacity of the low-voltage battery is equal to or less than the determined capacity, the predetermined amount of electricity is reduced compared to when it is determined that the capacity is greater than the determined capacity. The battery system according to any one of claims 1 to 4.

9. The processing circuit sets the predetermined amount of electricity so that the voltage of the low-voltage battery does not fall below a lower limit guard. The battery system according to any one of claims 1 to 4.

10. The processing circuit sets the lower limit guard when it determines that the capacity of the low-voltage battery is equal to or less than a threshold. The battery system of claim 9.

11. The processing circuit stops charging the high-voltage battery when the voltage of the high-voltage battery becomes higher than a specified voltage while the high-voltage battery is being charged from the low-voltage battery. The battery system according to any one of claims 1 to 4.

12. 3. A vehicle comprising: the battery system according to claim 1 or 2; and a traction motor that is driven by power supplied from the high-voltage battery. vehicle.

13. A control method for a battery system including a low-voltage battery and a high-voltage battery having a rated voltage higher than that of the low-voltage battery, comprising: causing a determination unit to determine whether or not the amount of stored power in the low-voltage battery exceeds a determination amount of stored power; When the determination unit determines that the amount of electricity stored in the low-voltage battery exceeds the determined amount of electricity stored, the control unit controls charging of the high-voltage battery so that a predetermined amount of electricity is charged from the low-voltage battery to the high-voltage battery. A method for controlling a battery system.

14. A program executed by a processing circuit when a high-voltage battery having a rated voltage higher than that of the low-voltage battery is charged from the low-voltage battery, The processing circuitry includes: determining whether the amount of charge stored in the low-voltage battery exceeds a determination amount of charge; When it is determined that the amount of electricity stored in the low-voltage battery exceeds the determined amount of electricity stored, charging of the high-voltage battery is controlled so that a predetermined amount of electricity is charged from the low-voltage battery to the high-voltage battery. program.

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