Battery system

Abstract

To provide a battery system capable of suppressing voltage fluctuations in a secondary battery. [Solution] The battery system 1 comprises a plurality of first secondary batteries 11A to 11D connected in series, a first switch SW1 positioned between two branching points B1 and B2 located between two adjacent battery blocks 11B and 11C, a second switch SW2 and a second secondary battery 20 positioned to branch from the two branching points B1 and B2, and a control device 10 that controls the charging and discharging of the first secondary batteries 11A to 11D and the second secondary battery 20. When the power value of the power supply target device 3 is less than a predetermined lower power threshold, the control device 10 turns off the first switch SW1 and turns on the second switch SW2 to connect the first secondary batteries 11A to 11D and the second secondary battery 20 in series, and electrically connects the first secondary batteries 11A to 11D and the second secondary battery 20 to the power supply target device 3.

Description

Technical Field

[0001] The present disclosure relates to a battery system including a secondary battery.

Background Art

[0002] Conventionally, various battery systems including secondary batteries have been proposed. Due to the influence of its internal resistance, the voltage of a secondary battery tends to vary significantly during charging and discharging. When such voltage fluctuations cause a voltage to be applied that exceeds the voltage range tolerated by the power supply target device, which is the target of power supply, there is a possibility of damaging the power supply target device.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Regarding this point, Patent Document 1 discloses a battery control device including a battery circuit in which a plurality of batteries are connected in series, a plurality of bypass circuits that exclude each of the plurality of batteries from the battery circuit, a plurality of switches that switch to connect each of the plurality of batteries in series or to connect to a bypass circuit and exclude it from the battery circuit, a deterioration detection unit that detects the deterioration of each of the plurality of batteries, and a switch control unit that controls the switches to exclude a battery with greater deterioration from the battery circuit and connect batteries with less deterioration in series. However, this battery control device has a problem in that it cannot suppress voltage fluctuations of the secondary battery included in the battery system.

[0005] The present disclosure addresses such problems and aims to provide a battery system capable of suppressing voltage fluctuations of a secondary battery.

Means for Solving the Problems

[0006] The generator that supplies power according to this disclosure and the battery system electrically connected to the power supply target device to which the power is supplied are: Multiple battery blocks consisting of multiple first secondary batteries connected in series, A first switch is positioned between two branching points located between two adjacent battery blocks, A second switch arranged to branch from two branching points and at least one second secondary battery, The system includes a control device for controlling the charging and discharging of a first secondary battery and a second secondary battery. The orientation of the positive and negative electrodes of the second secondary battery is the same as the orientation of the positive and negative electrodes of the first secondary battery. The control device is A switch control unit that controls the on and off states of the first switch and the second switch, It includes a power value acquisition unit that acquires a power value indicating the output power of the power supply target device, The switch control unit, when the power value is below a predetermined lower power threshold, turns off the first switch and turns on the second switch to connect the first and second secondary batteries in series, and electrically connects the first and second secondary batteries to the power supply device.

[0007] The second secondary battery is located in the center of the multiple battery blocks.

[0008] Furthermore, the battery system includes a temperature determination unit that determines whether the measured temperatures of the first secondary battery and the second secondary battery are below a predetermined temperature threshold. When the switch control unit determines that the measured temperature is below a predetermined temperature threshold and the power value is below a predetermined lower power threshold, it turns off the first switch and turns on the second switch to connect the first secondary battery and the second secondary battery in series, and electrically connects the first secondary battery and the second secondary battery to the power supply target device.

[0009] The control device is An SOC difference determination unit that determines whether the SOC difference, which is the difference between the SOC (State of Charge) of the first secondary battery and the SOC of the second secondary battery, is greater than or equal to a predetermined difference threshold, The system includes an SOC determination unit that determines whether the SOC of the second secondary battery is equal to or greater than a predetermined SOC threshold if it is determined that the SOC difference is equal to or greater than a predetermined difference threshold. When the power value is above a predetermined lower power threshold and below a predetermined upper power threshold Pc, and the switch control unit determines that the SOC of the second secondary battery is below a predetermined SOC threshold, it turns off the first switch and turns on the second switch to connect the first and second secondary batteries in series and electrically connect the first and second secondary batteries to the generator.

[0010] The generator that supplies power according to this disclosure and the battery system electrically connected to the power supply target device to which the power is supplied are: Multiple battery blocks consisting of multiple first secondary batteries connected in series, A first switch is positioned between two branching points located between two adjacent battery blocks, A second switch arranged to branch from two branching points and at least one second secondary battery, The system includes a control device for controlling the charging and discharging of a first secondary battery and a second secondary battery. The orientation of the positive and negative electrodes of the second secondary battery is opposite to that of the positive and negative electrodes of the first secondary battery. The control device is A switch control unit that controls the on and off states of the first switch and the second switch, It includes a power value acquisition unit that acquires a power value indicating the output power of the power supply target device, When the power value exceeds a predetermined upper power threshold, the switch control unit turns off the first switch and turns on the second switch to connect the first and second secondary batteries in series, and electrically connects the first and second secondary batteries to the power supply device.

[0011] A generator that supplies power according to the present disclosure and a battery system electrically connected to a power supply target device to which power is supplied are as follows: A plurality of battery blocks each composed of a plurality of first secondary batteries connected in series; A first switch disposed between two branch points located between two adjacent battery blocks; A second switch and at least one second secondary battery disposed so as to branch from the two branch points; A third switch disposed between two other branch points located between two adjacent battery blocks; A fourth switch and at least one third secondary battery disposed so as to branch from the two other branch points; A control device that controls charging and discharging of the first secondary battery, the second secondary battery, and the third secondary battery; The directions of the positive and negative electrodes of the second secondary battery are the same as those of the positive and negative electrodes of the first secondary battery; The directions of the positive and negative electrodes of the third secondary battery are opposite to those of the positive and negative electrodes of the first secondary battery; The control device A switch control unit that controls on and off of the first switch, the second switch, the third switch, and the fourth switch; A power value acquisition unit that acquires a power value indicating the output power of the power supply target device; When the power value is less than a predetermined lower power threshold value, the switch control unit turns off the first switch, turns on the second switch, turns on the third switch, and turns off the fourth switch, so as to connect the first secondary battery and the second secondary battery in series and electrically connect the first secondary battery and the second secondary battery to the power supply target device.

Advantages of the Invention

[0012] According to the present disclosure, a battery system capable of suppressing voltage fluctuations of a secondary battery can be provided.

Brief Description of the Drawings

[0013] [Figure 1]It is a diagram showing the relationship between the battery system according to the present disclosure, the generator, and the power supply target device. [Figure 2] It is a diagram showing the time-series change of the output power of the battery system, the generator, and the power supply target device according to the present disclosure. [Figure 3] It is a diagram showing an example of the hardware configuration of the battery system according to the first embodiment. [Figure 4] It is a diagram showing an example of the configuration of the control device according to the first embodiment. [Figure 5] It is a diagram showing an example of the process executed by the control device according to the first embodiment. [Figure 6] It is a diagram showing an example of the process executed by the control device according to the first embodiment. [Figure 7] It is a diagram showing an example of the time-series change of the output power of the power supply target device 3, the output current of the generator 2, the total output current of the first secondary battery and the second secondary battery, and the total voltage of the first secondary battery and the second secondary battery according to the first embodiment. [Figure 8] It is a perspective view showing a battery pack formed of a plurality of secondary batteries arranged in the thickness direction. [Figure 9] It is a diagram showing an example of the temperature of a plurality of secondary batteries arranged in the thickness direction. [Figure 10] It is a diagram showing an example of the hardware configuration of the battery system according to the second embodiment. [Figure 11] It is a diagram showing an example of the process executed by the control device according to the second embodiment. [Figure 12] It is a diagram showing an example of the process executed by the control device according to the second embodiment. [Figure 13] It is a diagram showing an example of the time-series change of the output power of the power supply target device 3, the output current of the generator 2, the total output current of the first secondary battery and the second secondary battery, and the total voltage of the first secondary battery and the second secondary battery according to the second embodiment. [Figure 14] It is a diagram showing an example of the hardware configuration of the battery system according to the third embodiment. [Figure 15]This figure shows an example of a process performed by the control device according to the third embodiment. [Figure 16] This figure shows an example of a process performed by the control device according to the third embodiment. [Figure 17] This figure shows an example of a process performed by the control device according to the third embodiment. [Figure 18] This figure shows an example of the time-series changes of the output power of the power supply device 3, the output current of the generator 2, the total output current of the first and second secondary batteries, and the total voltage of the first and second secondary batteries according to the third embodiment. [Modes for carrying out the invention]

[0014] <First Embodiment> Figure 1 shows the relationship between the battery system 1, the generator 2, and the power supply device 3 according to this disclosure. The battery system 1, the generator 2, and the power supply device 3 are connected by a power line 4.

[0015] The battery system 1 is a system that supplies power to an external device or receives power from an external device. In this embodiment, the battery system 1 supplies power to the power supply target device 3. A specific example of the battery system 1 is a secondary battery pack, etc. Details of the battery system 1 will be described later.

[0016] Generator 2 is a device that generates electricity. Generator 2 supplies power to battery system 1 and power supply target device 3.

[0017] The power supply target device 3 is a device that receives power from the battery system 1 and / or the generator 2. The power supply target device 3 controls the charging and discharging power of the battery system 1 and the generator 2. Specific examples of the power supply target device 3 include inverter circuits that convert direct current to alternating current. However, the power supply target device 3 is not limited to inverter circuits; it also includes other devices that supply power from the battery system 1 and / or the generator 2 to devices other than the battery system 1 and / or the generator 2.

[0018] Figure 2 shows the time-series changes in the output power of the battery system 1, generator 2, and power supply device 3. As shown in Figure 2, when generator 2 is started, the output power of generator 2 is small, so power supply device 3 consumes the power of battery system 1. As the output power of generator 2 gradually increases, power supply device 3 begins to consume the power supplied by generator 2, and the power consumption of battery system 1 begins to decrease. When generator 2 is able to supply the power required by power supply device 3 on its own, power consumption of battery system 1 by power supply device 3 stops. After this, when power consumption by power supply device 3 ends, the power supplied by generator 2 gradually decreases. During this time, the secondary battery in battery system 1 is charged by the power supplied by generator 2. When the output power of generator 2 becomes 0, charging of the secondary battery ends.

[0019] Figure 3 shows an example of the hardware configuration of the battery system 1 according to the first embodiment. The battery system 1 comprises a plurality of battery blocks 11A to 11D, a first switch SW1, a second switch SW2, at least one second secondary battery 20, a control device 10, a positive terminal, and a negative terminal.

[0020] Multiple battery blocks 11A to 11D consist of multiple first secondary batteries connected in series. Each first secondary battery in battery blocks 11A to 11D is arranged with the positive and negative terminals facing the same direction. The first switch SW1 is located between two branching points B1 and B2, which are situated between two adjacent battery blocks 11B and 11C. The second switch SW2 and the second secondary battery 20 are arranged to branch from branching points B1 and B2. In the example shown in Figure 3, the second switch SW2 is connected to branching point B1 and the second secondary battery 20 is connected to branching point B2. Alternatively, the second switch SW2 may be connected to branching point B2 and the second secondary battery 20 may be connected to branching point B1.

[0021] The second secondary battery 20 is positioned so that its positive and negative terminals are oriented in the same direction as the first secondary battery. The number of second secondary batteries 20 is less than the number of first secondary batteries. For example, the number of second secondary batteries 20 can be the same as the number of first secondary batteries that make up one battery block. The second secondary batteries 20 are positioned in the center of a plurality of battery blocks 11A to 11D.

[0022] The control device 10 is a device that controls the charging and discharging of the battery system 1. Figure 4 is a diagram showing an example of the configuration of the control device 10. Specific examples of the control device 10 include an ECU (Electronic Control Unit). The control device 10 comprises at least one arithmetic unit 100, a storage device 120, and a communication interface (I / F) 130. Specific examples of the arithmetic unit 100 include a processor such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit). The arithmetic unit 100 realizes the functional means shown in Figure 4 by executing instructions contained in a program stored in the storage device 120. Note that integrated circuits such as FPGAs (Field-Programmable Gate Arrays) or ASICs (Application Specific Integrated Circuits) may perform the processing executed by the control device 10. Integrated circuits such as processors, MPUs, FPGAs, and ASICs are equivalent to computers.

[0023] The storage device 120 stores various information such as programs executed by the arithmetic unit 100 and data processed by the arithmetic unit 100.

[0024] The communication interface 130 is an interface for data communication between the control device 10 and other devices such as the power supply target device 3.

[0025] The arithmetic unit 100 includes a switch control unit 101, a battery information acquisition unit 102, a temperature determination unit 103, a SOC calculation unit 104, an SOC difference calculation unit 105, an SOC difference determination unit 106, an SOC determination unit 107, a power value acquisition unit 108, a power determination unit 109, and a request transmission unit 110. These functional means can be implemented by a program.

[0026] The switch control unit 101 controls the on and off states of the first switch SW1 and the second switch SW2.

[0027] The battery information acquisition unit 102 acquires measurement information of the first secondary batteries 11A to 11D and the second secondary battery 20. Specifically, the battery information acquisition unit 102 acquires the measured temperature Tb of the first secondary batteries 11A to 11D and the second secondary battery 20 from temperature sensors (not shown) located near each of the first secondary batteries 11A to 11D and the second secondary battery 20 in each of the battery blocks 11A to 11D. The battery information acquisition unit 102 also acquires the measured voltage Vb of the first secondary batteries 11A to 11D and the second secondary battery 20 from voltage sensors (not shown) electrically connected to each of the first secondary batteries 11A to 11D and the second secondary battery 20 in each of the battery blocks 11A to 11D. Furthermore, the battery information acquisition unit 102 acquires the measured current Ib from a current sensor (not shown). This current sensor detects the current input from the generator 2 to the secondary batteries 11A and 11B, and the current output from the secondary batteries 11A and 11B to the power supply device 3.

[0028] The temperature determination unit 103 determines whether the measured temperature Tb is below the temperature threshold Tb_th. Generally, the charge and discharge capacity of a secondary battery decreases as the temperature decreases. The temperature threshold Tb_th is set to be below the temperature at which the charge and discharge capacity of secondary batteries 11A and 11B decreases.

[0029] The SOC calculation unit 104 calculates the State of Charge (SOC) of secondary batteries 11A and 11B using the measured current Ib, measured voltage Vb, and measured temperature Tb of secondary batteries 11A and 11B. Specifically, the SOC calculation unit 104 calculates the charge / discharge amount (Ah) of secondary batteries 11A and 11B by integrating the measured current Ib. Next, the SOC calculation unit 104 calculates the SOC of secondary batteries 11A and 11B based on the fully charged capacity of secondary batteries 11A and 11B and the calculated charge / discharge amount. Then, the SOC calculation unit 104 identifies the internal resistance of secondary batteries 11A and 11B corresponding to the measured temperature Tb, based on the known correspondence between the measured temperature of secondary batteries 11A and 11B and the internal resistance of secondary batteries 11A and 11B. Next, the SOC calculation unit 104 calculates the open-circuit voltage (OCV) of secondary batteries 11A and 11B by subtracting the product of the measured current Ib and the internal resistance from the measured voltage Vb of secondary batteries 11A and 11B. Then, based on the known relationship between SOC and open-circuit voltage, the SOC calculation unit 104 derives the SOC corresponding to the calculated open-circuit voltage. Finally, the SOC calculation unit 104 can calculate the SOC of secondary batteries 11A and 11B by correcting the SOC obtained by integrating the measured current Ib using the SOC based on the open-circuit voltage.

[0030] The SOC difference calculation unit 105 calculates the SOC difference, which is the difference between the SOC of each of the first secondary batteries in battery blocks 11A to 11D and the SOC of the second secondary battery 20.

[0031] The SOC difference determination unit 106 determines whether each SOC difference calculated by the SOC difference calculation unit 105 is greater than or equal to a predetermined difference threshold. The predetermined difference threshold can be any value, for example, 5%.

[0032] The SOC determination unit 107 determines the State of Charge (SOC) of the second secondary battery 20 calculated by the SOC calculation unit 104. Specifically, the SOC determination unit 107 compares the calculated SOC values ​​of the second secondary battery 20 with a predetermined SOC threshold. The SOC threshold can be any value. For example, the SOC threshold can be 60%.

[0033] The power value acquisition unit 108 acquires a power value Pout from the power supply target device 3, which indicates the output power of the power supply target device 3.

[0034] The power determination unit 109 uses the upper power threshold Pc and the lower power threshold Pd to determine whether the power value Pout is within the range of the discharge warning area, the charge warning area, or the normal range. The discharge warning area is the range of power below the lower power threshold Pd. The charge warning area is the range of power exceeding the upper power threshold Pc. The normal range is the range of power above the lower power threshold Pd and below the upper power threshold Pc. The upper power threshold Pc and the lower power threshold Pd are power values ​​within the range that the output power of the power supply target device 3 can take. The upper power threshold Pc is a value greater than the lower power threshold Pd. For example, the upper power threshold Pc can be a power value corresponding to 80-90% of the maximum output power of the power supply target device 3. The lower power threshold Pd can be a power value corresponding to 10-20% of the maximum output power of the power supply target device 3. Note that these values ​​are examples, and other arbitrary values ​​can be adopted.

[0035] The request transmission unit 110 transmits a charge request to the power supply target device 3, requesting that the battery system 1 be charged, and a discharge request to request that the battery system 1 be discharged. When the power supply target device 3 receives a charge request, it increases the power output of the generator 2, and power from the generator 2 is supplied to the battery system 1. This allows the battery system 1 to be charged. When the power supply target device 3 receives a discharge request, it decreases the power output of the generator 2. This allows the battery system 1 to be discharged.

[0036] Figures 5 and 6 are flowcharts illustrating an example of a process performed by the control device 10 according to the first embodiment. In step S1, the switch control unit 101 turns on the first switch SW1 and turns off the second switch SW2. This electrically disconnects the second secondary battery 20.

[0037] In step S2, the power value acquisition unit 108 acquires the power value Pout of the power supply target device 3. In step S3, the power determination unit 109 determines whether the power value Pout is greater than or equal to the lower power threshold Pd and less than or equal to the upper power threshold Pc. If it is determined that the power value Pout is not greater than or equal to the lower power threshold Pd and less than or equal to the upper power threshold Pc (NO), the process branches to step S4.

[0038] In step S4, the battery information acquisition unit 102 acquires the measured temperatures Tb of the first secondary batteries 11A to 11D and the second secondary battery 20 of each of the battery blocks 11A to 11D. In step S5, the temperature determination unit 103 determines whether the measured temperatures Tb of the first secondary batteries 11A to 11D and the second secondary battery 20 of each of the battery blocks 11A to 11D are less than or equal to the temperature threshold Tb_th. If it is determined that all measured temperatures Tb exceed the temperature threshold Tb_th (NO), the process returns to step S1.

[0039] On the other hand, if it is determined that the measured temperature Tb of at least one of the first secondary batteries 11A to 11D and the second secondary battery 20 of the battery blocks 11A to 11D is less than or equal to the temperature threshold Tb_th (YES), the process branches to step S6.

[0040] In step S6, the power determination unit 109 determines whether the power value Pout is less than the lower power threshold Pd. If it is determined that the power value Pout is not less than the lower power threshold Pd (NO), in other words, if the power value Pout exceeds the upper power threshold Pc, the process returns to step S1. Therefore, if the output power of the power supply target device 3 is within the range of the charge warning area, the process returns to step S1.

[0041] On the other hand, if it is determined that the power value Pout is less than the lower power threshold Pd (YES), the process branches to step S7. In other words, if the output power of the power supply target device 3 is within the range of the discharge warning area, the process branches to step S7. In step S7, the switch control unit 101 turns off the first switch SW1 and on the second switch SW2, and the process returns to step S2. As a result, the second secondary battery 20 is electrically connected, and the first secondary batteries 11A~11D and the second secondary battery 20 are connected in series.

[0042] If it is determined in step S3 that the power value Pout is greater than or equal to the lower power threshold Pd and less than or equal to the upper power threshold Pc (YES), the process branches to step S8. In other words, if the output power of the power supply target device 3 is within the normal range, the process branches to step S8. If the output power of the power supply target device 3 is within the normal range, the SOC of each of the first secondary batteries and / or the second secondary battery 20 of the battery blocks 11A to 11D is adjusted as described later.

[0043] In step S8, the battery information acquisition unit 102 acquires the measured current Ib, measured voltage Vb, and measured temperature Tb of each of the first secondary batteries 11A to 11D and the second secondary battery 20 in battery blocks 11A to 11D. In step S9, the SOC calculation unit 104 uses the measured current Ib, measured voltage Vb, and measured temperature Tb of each of the first secondary batteries 11A to 11D and the second secondary battery 20 in battery blocks 11A to 11D to calculate the SOC of each of the first secondary batteries in battery blocks 11A to 11D and the SOC of the second secondary battery 20.

[0044] In step S10, the SOC difference calculation unit 105 calculates the SOC difference between the SOC of each of the first secondary batteries in battery blocks 11A to 11D and the SOC of the second secondary battery 20. In step S11, the SOC difference determination unit 106 determines whether the SOC difference calculated in step S11 is greater than or equal to a predetermined difference threshold. If it is determined that the SOC difference is less than the difference threshold (NO), the process returns to step S1. In this case, no adjustment is made to the SOC of each of the first secondary batteries 11A to 11D in battery blocks 11A to 11D and the second secondary battery 20. On the other hand, if it is determined that the SOC difference is greater than or equal to a predetermined difference threshold (YES), the process branches to step S12.

[0045] In step S12, the SOC determination unit 107 determines whether the SOC of the second secondary battery 20 is equal to or greater than a predetermined SOC threshold. If it is determined that the SOC of the second secondary battery 20 is less than the SOC threshold (NO), in step S13, the switch control unit 101 turns off the first switch SW1 and turns on the second switch SW2. As a result, the second secondary battery 20 is electrically connected, and the first secondary batteries 11A~11D and the second secondary battery 20 are connected in series. In step S14, the request transmission unit 110 sends a charge request to the power supply target device 3, and processing returns to step S2. As a result, the first secondary batteries 11A~11D and the second secondary battery 20 can be charged with power supplied by the generator 2.

[0046] On the other hand, if it is determined that the State of Charge (SOC) of the first secondary batteries 11A to 11D and the second secondary battery 20 is equal to or greater than the SOC threshold (YES), in step S15, the switch control unit 101 turns on the first switch SW1 and turns off the second switch SW2. This electrically disconnects the second secondary battery 20. In step S16, the request transmission unit 110 sends a discharge request to the power supply target device 3, and the process returns to step S2. As a result, the second secondary battery 20 is not discharged, and the first secondary battery becomes dischargeable.

[0047] Figure 7 shows an example of the time-series changes of the output power of the power supply target device 3, the output current of the generator 2, the output current of the battery system (BS) 1, and the voltage of the battery system 1 according to the first embodiment.

[0048] At time 0, the output power of the power supply target device 3 is below the lower power threshold Pd, in other words, within the discharge warning range. Therefore, the control device 10 of the battery system 1 turns off the first switch SW1 and turns on the second switch SW2. As a result, the second secondary battery 20 is connected in series with the first secondary battery, and the voltage of the battery system 1 increases as shown by the white arrow in Figure 7. Assume that the SOC of the first secondary battery and the SOC of the second secondary battery 20 at time 0 are 60%.

[0049] Next, when the power supply target device 3 attempts to consume power equivalent to the maximum output power, the first secondary batteries 11A to 11D and the second secondary battery 20 discharge, and the generator 2 begins supplying power. At this time, the voltage of the battery system 1 decreases to its minimum voltage due to the discharge. Assume that during this process, the SOC of the first secondary battery and the SOC of the second secondary battery 20 decrease to 55%.

[0050] Then, when the output power of the power supply target device 3 falls within the range of the charging warning area, at time T1, the control device 10 of the battery system 1 turns on the first switch SW1 and turns off the second switch SW2. As a result, the second secondary battery 20 is electrically disconnected, and the voltage of the battery system 1 drops.

[0051] When the output power of the power supply target device 3 becomes 0, the output current of the generator 2 gradually decreases, and the output current of the generator 2 charges the first secondary batteries 11A to 11D. At this time, the voltage of the battery system 1 reaches its maximum voltage. During this process, the SOC of the first secondary battery increases to 60%, while the SOC of the second secondary battery 20 remains at 55%.

[0052] Then, because the output power of the power supply target device 3 is within the range of the discharge warning area, at time T2, the control device 10 of the battery system 1 turns off the first switch SW1 and turns on the second switch SW2.

[0053] Next, when the power supply target device 3 attempts to consume power corresponding to the output power within the normal range, the first secondary batteries 11A~11D and the second secondary battery 20 discharge, and then the generator 2 starts supplying power. During this process, assume that the SOC of the first secondary battery decreases to 58% and the SOC of the second secondary battery 20 decreases to 53%. Here, assume that this SOC difference is above the difference threshold. Also, assume that the SOC of the second secondary battery 20 (53%) is below the SOC threshold. In this case, the state in which the first switch SW1 is off and the second switch SW2 is on is maintained.

[0054] Then, when the output power of the power supply target device 3 falls within the normal range, at time T3, the control device 10 of the battery system 1 turns off the first switch SW1 and turns on the second switch SW2. As a result, the first secondary batteries 11A~11D and the second secondary battery 20 are electrically connected, and the first secondary batteries 11A~11D and the second secondary battery 20 become ready for charging. As a result, the first secondary batteries 11A~11D and the second secondary battery 20 are charged by the power supplied by the generator 2, and the SOC of the first secondary battery increases to 65%, and the SOC of the second secondary battery 20 increases to 60%. Here, the SOC of the second secondary battery 20 (60%) is assumed to be above the SOC threshold.

[0055] At time T4, the control device 10 of the battery system 1 turns on the first switch SW1 and turns off the second switch SW2. As a result, the second secondary battery 20 is electrically disconnected, and only the first secondary battery remains electrically connected. In this state, the control device 10 sends a discharge request, and if the output current of the generator 2 becomes insufficient, discharge from the first secondary battery begins.

[0056] As described above, the battery system 1 comprises a plurality of battery blocks 11A to 11D, a first switch SW1, a second switch SW2, and at least one second secondary battery 20, and a control device 10. The first switch SW1 is positioned between two branching points B1 and B2 located between two adjacent battery blocks. The second switch SW2 and at least one second secondary battery 20 are positioned to branch from the two branching points B1 and B2. The orientation of the positive and negative electrodes of the second secondary battery 20 is the same as the orientation of the positive and negative electrodes of the first secondary battery. The power determination unit 109 of the control device 10 determines whether the power value indicating the output power of the power supply target device 3 is less than a predetermined lower limit power threshold Pd. If the switch control unit 101 determines that the power value is less than a predetermined lower power threshold Pd, it turns off the first switch SW1 and turns on the second switch SW2 to connect the first secondary batteries 11A to 11D and the second secondary battery 20 in series, and electrically connects the first secondary batteries 11A to 11D and the second secondary battery 20 to the power supply target device 3.

[0057] By adopting this configuration, the first secondary batteries 11A to 11D and the second secondary battery 20, whose positive and negative terminals are oriented in the same direction, are connected in series, and as shown in Figure 7, the minimum voltage of the battery system 1 increases. Therefore, the voltage fluctuation range between this minimum voltage and the maximum voltage of the battery system 1 is reduced, and voltage fluctuations can be suppressed. Note that the conventional voltage fluctuation and voltage fluctuation range shown in Figure 7 are those of a battery system without a second secondary battery.

[0058] Furthermore, the second secondary battery 20 is positioned in the center of the multiple battery blocks 11A to 11D. The second secondary battery 20 is connected in series with the first secondary battery only in predetermined cases, specifically when the power value Pout is less than the lower power threshold Pd, or when the SOC of the second secondary battery 20 is less than the SOC threshold. As a result, the frequency of use of the second secondary battery 20 is reduced, and the temperature rise of the second secondary battery 20 is suppressed. As shown in Figure 8, when a secondary battery pack is formed by arranging multiple first secondary batteries 11A to 11D and the second secondary battery 20 in the thickness direction, the secondary battery positioned in the center tends to have a higher temperature than secondary batteries positioned elsewhere. Therefore, by positioning the second secondary battery 20, whose temperature rise is suppressed, in the center of the multiple battery blocks 11A to 11D, the temperature difference between multiple secondary batteries arranged in the thickness direction can be reduced, as shown in Figure 9.

[0059] Furthermore, the temperature determination unit 103 determines whether the measured temperatures of the first secondary batteries 11A to 11D and the second secondary battery 20 are below a predetermined temperature threshold Tb_th. When the switch control unit 101 determines that the measured temperatures are below the predetermined temperature threshold Tb_th and that the output power of the power supply target device 3 is below a predetermined lower limit power threshold Pd, it turns off the first switch SW1 and turns on the second switch SW2 to connect the first secondary batteries 11A to 11D and the second secondary battery 20 in series, and electrically connects the first secondary batteries 11A to 11D and the second secondary battery 20 to the power supply target device 3.

[0060] By adopting this configuration, voltage fluctuations of the secondary batteries in the battery system 1 can be suppressed at temperatures where the charge and discharge capabilities of the first secondary batteries 11A to 11D and the second secondary battery 20 decrease. Generally, the internal resistance of secondary batteries increases at low temperatures, so if the same current as at room temperature is attempted to flow, the voltage fluctuations of the secondary batteries become large, potentially damaging the power supply device 3. However, by adopting the above configuration, voltage fluctuations of the secondary batteries can be suppressed, allowing the power supply device 3, such as an inverter, to be used at maximum power even at low temperatures.

[0061] Furthermore, the SOC difference determination unit 106 determines whether the SOC difference, which is the difference between the SOC of the first secondary battery and the SOC of the second secondary battery, is greater than or equal to a predetermined difference threshold. If it is determined that the SOC difference is greater than or equal to the predetermined difference threshold, the SOC determination unit 107 determines whether the SOC of the second secondary battery is greater than or equal to a predetermined SOC threshold. The power determination unit 109 determines whether the power value is greater than or equal to a predetermined lower power threshold Pd and less than or equal to an upper power threshold Pc. When the power value is determined to be greater than or equal to a predetermined lower power threshold Pd and less than or equal to an upper power threshold Pc, the switch control unit 101 determines that the SOC of the second secondary battery is less than a predetermined SOC threshold, turns off the first switch and turns on the second switch to connect the first secondary batteries 11A to 11D and the second secondary battery 20 in series, and electrically connects the first secondary batteries 11A to 11D and the second secondary battery 20 to the generator 2.

[0062] By adopting this configuration, when the output power of the power supply target device 3 is above a predetermined lower power threshold Pd and below a predetermined upper power threshold Pc, in other words, within the normal range, and it is determined that the SOC of the second secondary battery 20 is below a predetermined SOC threshold, the second secondary battery 20 can be made rechargeable, enabling adjustment of the SOC. This prevents the voltage of the battery system 1 from exceeding the upper voltage limit of the power supply target device 3 due to fluctuations in the output power of the generator 2, and also prevents it from falling below the lower voltage limit of the power supply target device 3.

[0063] <Second Embodiment> Figure 10 shows an example of the hardware configuration of the battery system 5 according to the second embodiment. The differences from the first embodiment will be explained below.

[0064] In the second embodiment, the second secondary battery 20 is arranged such that the orientation of its positive and negative electrodes is opposite to the orientation of the positive and negative electrodes of the first secondary battery in the battery blocks 11A to 11D. The number of second secondary batteries 20 is less than the number of first secondary batteries.

[0065] Figures 11 and 12 are flowcharts showing an example of a process performed by the control device 10 according to the second embodiment. In step S21, the switch control unit 101 turns on the first switch SW1 and turns off the second switch SW2. This electrically disconnects the second secondary battery 20.

[0066] In step S22, the power value acquisition unit 108 acquires the power value Pout of the power supply target device 3. In step S23, the power determination unit 109 determines whether the power value Pout is greater than or equal to the lower power threshold Pd and less than or equal to the upper power threshold Pc. If it is determined that the power value Pout is not greater than or equal to the lower power threshold Pd and less than or equal to the upper power threshold Pc (NO), the process branches to step S24.

[0067] In step S24, the battery information acquisition unit 102 acquires the measured temperatures Tb of the first secondary batteries 11A to 11D and the second secondary battery 20 of each of the battery blocks 11A to 11D. In step S25, the temperature determination unit 103 determines whether the measured temperatures Tb of the first secondary batteries 11A to 11D and the second secondary battery 20 of each of the battery blocks 11A to 11D are less than or equal to the temperature threshold Tb_th. If it is determined that all measured temperatures Tb exceed the temperature threshold Tb_th (NO), the process returns to step S21.

[0068] On the other hand, if it is determined that the measured temperature Tb of at least one of the first secondary batteries 11A to 11D and the second secondary battery 20 of the battery blocks 11A to 11D is less than or equal to the temperature threshold Tb_th (YES), the process branches to step S26.

[0069] In step S26, the power determination unit 109 determines whether the power value Pout exceeds the upper power threshold Pc. If it is determined that the power value Pout does not exceed the upper power threshold Pc (NO), in other words, if the power value Pout is less than the lower power threshold Pd, the process returns to step S21. Therefore, if the output power of the power supply target device 3 is within the range of the charge warning area, the process returns to step S21.

[0070] On the other hand, if it is determined that the power value Pout exceeds the upper power threshold Pc (YES), the process branches to step S27. In other words, if the output power of the power supply target device 3 is within the range of the charging warning area, the process branches to step S27. In step S27, the switch control unit 101 turns off the first switch SW1 and on the second switch SW2, and the process returns to step S22. As a result, the second secondary battery 20 is electrically connected, and the first secondary batteries 11A~11D and the second secondary battery 20 are connected in series.

[0071] If it is determined in step S23 that the power value Pout is greater than or equal to the lower power threshold Pd and less than or equal to the upper power threshold Pc (YES), the process branches to step S28. In other words, if the output power of the power supply target device 3 is within the normal range, the process branches to step S28. If the output power of the power supply target device 3 is within the normal range, the SOC of each of the first secondary batteries and / or the second secondary battery 20 of the battery blocks 11A to 11D is adjusted as described later.

[0072] In step S28, the battery information acquisition unit 102 acquires the measured current Ib, measured voltage Vb, and measured temperature Tb of each of the first secondary batteries 11A to 11D and the second secondary battery 20 in battery blocks 11A to 11D. In step S29, the SOC calculation unit 104 uses the measured current Ib, measured voltage Vb, and measured temperature Tb of each of the first secondary batteries 11A to 11D and the second secondary battery 20 in battery blocks 11A to 11D to calculate the SOC of each of the first secondary batteries and the SOC of the second secondary battery 20.

[0073] In step S30, the SOC difference calculation unit 105 calculates the SOC difference between the SOC of each of the first secondary batteries in battery blocks 11A to 11D and the SOC of the second secondary battery 20. In step S31, the SOC difference determination unit 106 determines whether the SOC difference calculated in step S31 is greater than or equal to a predetermined difference threshold. If it is determined that the SOC difference is less than the difference threshold (NO), the process returns to step S21. In this case, no adjustment is made to the SOC of each of the first secondary batteries 11A to 11D in battery blocks 11A to 11D and the second secondary battery 20. On the other hand, if it is determined that the SOC difference is greater than or equal to a predetermined difference threshold (YES), the process branches to step S32.

[0074] In step S32, the SOC determination unit 107 determines whether the SOC of the second secondary battery 20 is equal to or greater than a predetermined SOC threshold. If it is determined that the SOC of the second secondary battery 20 is less than the SOC threshold (NO), in step S33, the switch control unit 101 turns off the first switch SW1 and turns on the second switch SW2. As a result, the second secondary battery 20 is electrically connected, and the first secondary batteries 11A to 11D and the second secondary battery 20 are connected in series. In step S34, the request transmission unit 110 transmits a discharge request to the power supply target device 3, and processing returns to step S22. The discharge request in the second embodiment requests that the battery system 5 as a whole be discharged. As a result, the discharge of the first secondary battery begins, and the second secondary battery 20 becomes capable of charging.

[0075] On the other hand, if it is determined that the State of Charge (SOC) of the first secondary batteries 11A to 11D and the second secondary battery 20 is equal to or greater than the SOC threshold (YES), in step S35, the switch control unit 101 turns on the first switch SW1 and turns off the second switch SW2. This electrically disconnects the second secondary battery 20. In step S36, the request transmission unit 110 sends a charge request to the power supply target device 3, and the process returns to step S22. The charge request in the second embodiment requests that the battery system 5 be charged as a whole. As a result, the first secondary batteries are charged. At this time, the second secondary battery 20 is not discharged.

[0076] Figure 13 shows an example of the time-series changes of the output power of the power supply target device 3, the output current of the generator 2, the output current of the battery system (BS) 5, and the voltage of the battery system 5 according to the second embodiment.

[0077] At time 0, the output power of the power supply target device 3 is below the lower limit power threshold Pd, in other words, within the discharge warning range. Therefore, the control device 10 of the battery system 5 turns on the first switch SW1 and turns off the second switch SW2. Assume that the SOC of the first secondary battery and the SOC of the second secondary battery 20 at time 0 are 60%.

[0078] Next, when the power supply target device 3 attempts to consume power equivalent to the maximum output power, the first secondary battery discharges, and the generator 2 begins supplying power. At this time, the voltage of the battery system 5 decreases due to the discharge to its minimum voltage. In this process, let's assume that the State of Charge (SOC) of the first secondary battery decreases to 55%.

[0079] Then, when the output power of the power supply target device 3 falls within the range of the charging warning area, at time T1, the control device 10 of the battery system 5 turns off the first switch SW1 and turns on the second switch SW2. As a result, the second secondary battery 20 is connected in series with the first secondary battery, and the voltage of the battery system 5 decreases, as shown by the white arrow in Figure 13.

[0080] When the output power of the power supply target device 3 becomes 0, the output current of the generator 2 gradually decreases, and the output current of the generator 2 charges the first secondary batteries 11A to 11D. At this time, the voltage of the battery system 5 reaches its maximum voltage. On the other hand, since the positive and negative terminals of the second secondary battery 20 are oriented in the opposite direction to those of the first secondary battery, a discharge-direction current flows into the second secondary battery 20. As a result, the voltage and SOC of the second secondary battery 20 decrease. In this process, assume that the SOC of the first secondary battery increases to 60%, and the SOC of the second secondary battery 20 decreases to 55%.

[0081] Then, because the output power of the power supply target device 3 is within the range of the discharge warning area, at time T2, the control device 10 of the battery system 5 turns on the first switch SW1 and turns off the second switch SW2.

[0082] Next, when the power supply target device 3 attempts to consume power corresponding to the output power within the normal range, the first secondary battery discharges, and then the generator 2 begins supplying power. During this process, the SOC of the first secondary battery decreases to 58%, while the SOC of the second secondary battery 20 remains at 55%. Here, the difference in SOC between the first secondary battery and the second secondary battery 20 is assumed to be above the difference threshold. Also, the SOC of the second secondary battery 20 (55%) is assumed to be below the SOC threshold.

[0083] Then, when the output power of the power supply target device 3 falls within the normal range, at time T3, the control device 10 of the battery system 5 turns off the first switch SW1 and turns on the second switch SW2. As a result, the first secondary batteries 11A~11D and the second secondary battery 20 are electrically connected, making the first secondary batteries ready for discharge and the second secondary battery 20 ready for charging. When the control device 10 sends a discharge request in this state, the entire battery system 5 begins to discharge. As a result, the first secondary batteries 11A~11D are discharged and the second secondary battery 20 is charged. During this process, the SOC of the first secondary batteries decreases to 53%, and the SOC of the second secondary battery 20 increases to 60%. Here, the SOC of the second secondary battery 20 (60%) is assumed to be above the SOC threshold.

[0084] At time T4, the control device 10 of the battery system 5 turns on the first switch SW1 and turns off the second switch SW2. This electrically disconnects the second secondary battery 20, leaving only the first secondary battery electrically connected. When the control device 10 sends a charge request in this state, the first secondary batteries 11A to 11D are charged.

[0085] As described above, in the second embodiment, the orientation of the positive and negative electrodes of the second secondary battery 20 is opposite to the orientation of the positive and negative electrodes of the first secondary battery. The power determination unit 109 of the control device 10 determines whether the power value Pout of the power supply target device 3 exceeds a predetermined upper limit power threshold Pc. If the switch control unit 101 determines that the power value Pout exceeds a predetermined upper limit power threshold Pc, it turns off the first switch SW1 and turns on the second switch SW2 to connect the first secondary batteries 11A to 11D and the second secondary battery 20 in series, and electrically connects the first secondary batteries 11A to 11D and the second secondary battery 20 to the power supply target device 3.

[0086] By adopting this configuration, the first secondary batteries 11A to 11D and the second secondary battery 20, whose positive and negative terminals are oriented in opposite directions, are connected in series. As a result, the maximum voltage of the battery system 5 decreases, as shown in Figure 13. Therefore, the voltage fluctuation range between the maximum voltage and the minimum voltage of the battery system 5 is reduced, and voltage fluctuations can be suppressed. Note that the conventional voltage fluctuation and voltage fluctuation range shown in Figure 13 are those of a battery system without a second secondary battery.

[0087] Furthermore, when the switch control unit 101 determines that the measured temperature Tb of the first secondary batteries 11A to 11D and the second secondary battery 20 is below a predetermined temperature threshold Tb_th, and that the power value Pout exceeds a predetermined upper limit power threshold Pc, it turns off the first switch SW1 and turns on the second switch SW2 to connect the first secondary batteries 11A to 11D and the second secondary battery 20 in series, and electrically connects the first secondary batteries 11A to 11D and the second secondary battery 20 to the power supply target device 3.

[0088] By adopting this configuration, voltage fluctuations in the secondary batteries of the battery system 5 can be suppressed at temperatures where the charge and discharge capabilities of the first secondary batteries 11A to 11D and the second secondary battery 20 decrease. Therefore, the power supply target device 3 can be used at maximum power even at low temperatures.

[0089] Furthermore, when the switch control unit 101 determines that the power value Pout is greater than or equal to a predetermined lower power threshold Pd and less than or equal to a predetermined upper power threshold Pc, and that the SOC of the second secondary battery 20 is less than a predetermined SOC threshold, it turns off the first switch SW1 and turns on the second switch SW2 to connect the first secondary batteries 11A to 11D and the second secondary battery 20 in series. The number of first secondary batteries is greater than the number of second secondary batteries 20.

[0090] By adopting this configuration, the first secondary batteries 11A to 11D and the second secondary battery 20, whose positive and negative terminals are oriented in opposite directions, are connected in series. In this state, when the overall discharge of the battery system 5 begins, the second secondary battery 20 can be charged.

[0091] <Third Embodiment> Figure 14 shows an example of the hardware configuration of the battery system 6 according to the third embodiment. The differences from the first embodiment will be explained below.

[0092] The battery system 6 comprises a plurality of battery blocks 11A to 11D, a first switch SW1, a second switch SW2, at least one second secondary battery 20, a third switch SW3, a fourth switch SW4, at least one third secondary battery 30, a control device 10, a positive terminal, and a negative terminal.

[0093] The third switch SW3 is positioned between two branching points B3 and B4, which are located between two adjacent battery blocks 11B and 11C. The fourth switch SW4 and the third secondary battery 30 are positioned to branch from branching points B3 and B4. In the example shown in Figure 14, the fourth switch SW4 is connected to branching point B3 and the third secondary battery 30 is connected to branching point B4. Alternatively, the fourth switch SW4 may be connected to branching point B4 and the third secondary battery 30 may be connected to branching point B3.

[0094] The third secondary battery 30 is positioned so that its positive and negative terminals are oriented opposite to those of the first secondary battery. The number of third secondary batteries 30 is less than the number of first secondary batteries. For example, the number of third secondary batteries 30 can be the same as the number of first secondary batteries that make up one battery block. The third secondary batteries 30 are positioned in the center of the multiple battery blocks 11A to 11D.

[0095] Figures 15 to 17 are flowcharts illustrating an example of processing performed by the control device 10 according to the third embodiment. In step S41, the switch control unit 101 turns on the first switch SW1, turns off the second switch SW2, turns on the third switch SW3, and turns off the fourth switch SW4. As a result, the second secondary battery 20 and the third secondary battery 30 are electrically disconnected.

[0096] In step S42, the power value acquisition unit 108 acquires the power value Pout of the power supply target device 3. In step S43, the power determination unit 109 determines whether the power value Pout is greater than or equal to the lower power threshold Pd and less than or equal to the upper power threshold Pc. If it is determined that the power value Pout is not greater than or equal to the lower power threshold Pd and less than or equal to the upper power threshold Pc (NO), the process branches to step S44.

[0097] In step S44, the battery information acquisition unit 102 acquires the measured temperatures Tb of the first secondary batteries, the second secondary battery 20, and the third secondary battery 30 of each of the battery blocks 11A to 11D. In step S45, the temperature determination unit 103 determines whether the measured temperatures Tb of the first secondary batteries, the second secondary battery 20, and the third secondary battery 30 of each of the battery blocks 11A to 11D are less than or equal to the temperature threshold Tb_th. If it is determined that all measured temperatures Tb exceed the temperature threshold Tb_th (NO), the process returns to step S41.

[0098] On the other hand, if it is determined that the measured temperature Tb of at least one of the first secondary battery, the second secondary battery 20, and the third secondary battery 30 of the battery blocks 11A to 11D is less than or equal to the temperature threshold Tb_th (YES), the process branches to step S46.

[0099] In step S46, the power determination unit 109 determines whether the power value Pout is less than the lower power threshold Pd. If it is determined that the power value Pout is less than the lower power threshold Pd (YES), the process branches to step S47. In other words, if the output power of the power supply target device 3 is within the range of the discharge warning area, the process branches to step S47. In step S47, the switch control unit 101 turns off the first switch SW1, turns on the second switch SW2, turns on the third switch SW3, and turns off the fourth switch SW4, and the process returns to step S42. As a result, the second secondary battery 20 is electrically connected, and the first secondary batteries 11A~11D and the second secondary battery 20 are connected in series. On the other hand, the third secondary battery 30 is not electrically connected.

[0100] On the other hand, if it is determined that the power value Pout is not less than the lower power threshold Pd (NO), in other words, if the power value Pout exceeds the upper power threshold Pc, the process branches to step S48. In step S48, the switch control unit 101 turns on the first switch SW1, turns off the second switch SW2, turns off the third switch SW3, and turns on the fourth switch SW4, and the process returns to step S42. As a result, the third secondary battery 30 is electrically connected, and the first secondary battery and the third secondary battery 30 are connected in series. Meanwhile, the second secondary battery 20 is not electrically connected.

[0101] If it is determined in step S43 that the power value Pout is greater than or equal to the lower power threshold Pd and less than or equal to the upper power threshold Pc (YES), the process branches to step S49. In other words, if the output power of the power supply target device 3 is within the normal range, the process branches to step S49. If the output power of the power supply target device 3 is within the normal range, the SOC of the first secondary battery, the second secondary battery 20 and / or the third secondary battery 30 of the battery blocks 11A to 11D are adjusted as described later.

[0102] In step S49, the battery information acquisition unit 102 acquires the measured current Ib, measured voltage Vb, and measured temperature Tb of the first secondary battery, the second secondary battery 20, and the third secondary battery 30 of each of the battery blocks 11A to 11D. In step S50, the SOC calculation unit 104 uses the measured current Ib, measured voltage Vb, and measured temperature Tb of the first secondary battery, the second secondary battery 20, and the third secondary battery 30 of each of the battery blocks 11A to 11D to calculate the SOC of the first secondary battery, the second secondary battery 20, and the third secondary battery 30.

[0103] In step S51, the SOC difference calculation unit 105 calculates the SOC difference between the SOC of each of the first secondary batteries in battery blocks 11A to 11D and the SOC of the third secondary battery 30. In step S52, the SOC difference determination unit 106 determines whether the SOC difference calculated in step S51 is greater than or equal to a predetermined difference threshold. If it is determined that the SOC difference is greater than or equal to the predetermined difference threshold (YES), the process branches to step S53.

[0104] In step S53, the SOC determination unit 107 determines whether the SOC of the third secondary battery 30 is equal to or greater than a predetermined SOC threshold. If it is determined that the SOC of the third secondary battery 30 is less than the SOC threshold (NO), in step S54, the switch control unit 101 turns on the first switch SW1, turns off the second switch SW2, turns off the third switch SW3, and turns on the fourth switch SW4. As a result, the first secondary battery and the third secondary battery 30 are connected in series. On the other hand, the second secondary battery 20 is not electrically connected. In step S55, the request transmission unit 110 sends a discharge request to the power supply target device 3, and processing returns to step S42. The discharge request in the third embodiment requests that the battery system 6 as a whole be discharged. As a result, the third secondary battery 30 becomes rechargeable. Therefore, the SOC of the third secondary battery can be increased.

[0105] On the other hand, in step S53, if it is determined that the SOC of the first secondary battery and the third secondary battery 30 is equal to or greater than the SOC threshold (YES), in step S56 the switch control unit 101 turns on the first switch SW1, turns off the second switch SW2, turns on the third switch SW3, and turns off the fourth switch SW4. As a result, the first secondary batteries 11A to 11D and the second secondary battery 20 are connected in series. Meanwhile, the third secondary battery 30 is not electrically connected. In step S57, the request transmission unit 110 transmits a charge request to the power supply target device 3, and processing returns to step S42. The charge request in the third embodiment requests that the battery system 6 be charged as a whole. As a result, the power supplied by the generator 2 makes it possible to charge the first secondary battery. Therefore, the SOC of the first secondary battery can be increased and brought closer to the SOC of the third secondary battery 30.

[0106] In step S52, if it is determined that the SOC difference calculated in step S51 is less than the difference threshold (NO), the process branches to step S58. In step S58, the SOC difference calculation unit 105 calculates the SOC difference between the SOC of each of the first secondary batteries in battery blocks 11A to 11D and the SOC of the second secondary battery 20. In step S59, the SOC difference determination unit 106 determines whether the SOC difference calculated in step S58 is greater than or equal to a predetermined difference threshold. If it is determined that the SOC difference is greater than or equal to the difference threshold (YES), the process branches to step S60.

[0107] In step S60, the SOC determination unit 107 determines whether the SOC of the second secondary battery 20 is equal to or greater than a predetermined SOC threshold. If it is determined that the SOC of the second secondary battery 20 is less than the SOC threshold (NO), in step S61, the switch control unit 101 turns off the first switch SW1, on the second switch SW2, on the third switch SW3, and off the fourth switch SW4. As a result, the first secondary batteries 11A to 11D and the second secondary battery 20 are connected in series. On the other hand, the third secondary battery 30 is not electrically connected. In step S62, the request transmission unit 110 sends a charge request to the power supply target device 3, and processing returns to step S42. As a result, the second secondary battery 20 can be charged by the power supplied by the generator 2. Therefore, the SOC of the second secondary battery can be increased.

[0108] On the other hand, in step S60, if it is determined that the SOC of the first secondary batteries 11A to 11D and the second secondary battery 20 is equal to or greater than the SOC threshold (YES), in step S63 the switch control unit 101 turns on the first switch SW1, turns off the second switch SW2, turns on the third switch SW3, and turns off the fourth switch SW4. In step S64, the request transmission unit 110 sends a discharge request to the power supply target device 3, and the process returns to step S42. As a result, the first secondary battery is discharged, and the SOC of the first secondary battery can be reduced.

[0109] Figure 18 shows an example of the time-series changes of the output power of the power supply target device 3, the output current of the generator 2, the output current of the battery system (BS) 6, and the voltage of the battery system 6 according to the third embodiment.

[0110] At time 0, the output power of the power supply target device 3 is below the lower limit power threshold Pd, in other words, within the discharge warning range. Therefore, the control device 10 of the battery system 6 turns off the first switch SW1, turns on the second switch SW2, turns on the third switch SW3, and turns off the fourth switch SW4. As a result, the second secondary battery 20 is connected in series with the first secondary battery, and the voltage of the battery system 6 increases as shown by the white arrow in Figure 18. Assume that the SOC of the first secondary battery and the SOC of the second secondary battery 20 at time 0 are 60%.

[0111] Next, when the power supply target device 3 attempts to consume power equivalent to the maximum output power, the first secondary batteries 11A to 11D and the second secondary battery 20 discharge, and the generator 2 begins supplying power. At this time, the voltage of the battery system 6 decreases to its minimum voltage due to the discharge. Assume that during this process, the SOC of the first secondary battery and the SOC of the second secondary battery 20 decrease to 55%.

[0112] Then, when the output power of the power supply target device 3 falls within the range of the charging warning area, at time T1, the control device 10 of the battery system 6 turns on the first switch SW1, turns off the second switch SW2, turns off the third switch SW3, and turns on the fourth switch SW4. As a result, the second secondary battery 20 is electrically disconnected, and the third secondary battery 30, which has its positive and negative terminals oriented in the opposite direction to the first secondary battery, is connected in series with the first secondary battery. Therefore, as shown by the white arrow in Figure 18, the voltage of the battery system 6 drops.

[0113] When the output power of the power supply target device 3 becomes 0, the output current of the generator 2 gradually decreases, and the first secondary batteries 11A to 11D are charged by the output current of the generator 2. At this time, the voltage of the battery system 6 reaches its maximum voltage. On the other hand, the voltage of the third secondary battery 30 decreases. In this process, the SOC of the first secondary battery increases to 60%, and the SOC of the third secondary battery decreases to 55%. The SOC of the second secondary battery 20 remains at 55%.

[0114] Since the output power of the power supply target device 3 is within the discharge warning range, at time T2, the control device 10 of the battery system 6 turns off the first switch SW1, turns on the second switch SW2, turns on the third switch SW3, and turns off the fourth switch SW4.

[0115] Next, when the power supply target device 3 attempts to consume power corresponding to the output power within the normal range, the first secondary batteries 11A~11D and the second secondary battery 20 discharge, and then the generator 2 starts supplying power. During this process, the SOC of the first secondary battery decreases to 58%, the SOC of the second secondary battery 20 decreases to 53%, and the SOC of the third secondary battery 30 remains at 55%. Here, the difference between the SOC of the first secondary battery and the SOC of the third secondary battery 30 is assumed to be greater than or equal to the difference threshold. Also, the SOC of the third secondary battery 30 (55%) is assumed to be less than the SOC threshold.

[0116] Then, when the output power of the power supply target device 3 falls within the normal range, at time T3, the control device 10 of the battery system 6 turns on the first switch SW1, turns off the second switch SW2, turns off the third switch SW3, and turns on the fourth switch SW4. As a result, the first secondary battery and the third secondary battery 30 are electrically connected, the first secondary batteries 11A to 11D are discharged, and the third secondary battery 30 is charged. As a result, the SOC of the first secondary battery decreases to 53%, and the SOC of the third secondary battery 30 increases to 60%. The SOC of the second secondary battery 20 remains at 53%.

[0117] Here, we assume that the SOC (60%) of the third secondary battery 30 is above the SOC threshold. Therefore, at time T4, the control device 10 of the battery system 6 turns off the first switch SW1, turns on the second switch SW2, turns on the third switch SW3, and turns off the fourth switch SW4. As a result, the first secondary batteries 11A~11D and the second secondary battery 20 are electrically connected, and the third secondary battery 30 is electrically disconnected. Consequently, the first secondary batteries 11A~11D and the second secondary battery 20 can be charged by the power supplied by the generator 2. In this state, we assume that the first secondary batteries 11A~11D and the second secondary battery 20 are charged, and the SOC of the first secondary battery and the SOC of the second secondary battery 20 have increased to 60%. The SOC of the third secondary battery 30 remains at 60%.

[0118] Then, at time T5, the control unit 10 of the battery system 6 turns on the first switch SW1, turns off the second switch SW2, turns on the third switch SW3, and turns off the fourth switch SW4.

[0119] As described above, in the third embodiment, the orientation of the positive and negative electrodes of the second secondary battery 20 is the same as the orientation of the positive and negative electrodes of the first secondary battery, and the orientation of the positive and negative electrodes of the third secondary battery 30 is opposite to the orientation of the positive and negative electrodes of the first secondary battery. When the power value Pout is less than a predetermined lower power threshold Pd, the switch control unit 101 turns off the first switch SW1, turns on the second switch SW2, turns on the third switch SW3, and turns off the fourth switch SW4 to connect the first secondary batteries 11A to 11D and the second secondary battery 20 in series, and electrically connects the first secondary batteries 11A to 11D and the second secondary battery 20 to the power supply target device 3.

[0120] By adopting this configuration, as shown in Figure 18, the minimum voltage of battery system 1 increases, and the voltage fluctuation range between this minimum voltage and the maximum voltage of battery system 6 decreases. Therefore, the voltage fluctuation of the secondary battery in battery system 6 can be suppressed. Note that the conventional voltage fluctuation range shown in Figure 18 is the voltage fluctuation range of a battery system without a second secondary battery and a third secondary battery.

[0121] Furthermore, if the power value Pout exceeds a predetermined upper power threshold Pc, the switch control unit 101 turns on the first switch SW1, turns off the second switch SW2, turns off the third switch SW3, and turns on the fourth switch SW4 to connect the first secondary battery and the third secondary battery 30 in series, and electrically connects the first secondary battery and the third secondary battery 30 to the power supply target device 3.

[0122] By adopting this configuration, the first secondary battery and the third secondary battery 30, whose positive and negative terminals are oriented in opposite directions, are connected in series. As a result, the maximum voltage of the battery system 6 decreases, as shown in Figure 18. Therefore, the voltage fluctuation range between the maximum voltage and the minimum voltage of the battery system 6 is reduced, and voltage fluctuations can be suppressed.

[0123] Furthermore, the temperature determination unit 103 determines whether the measured temperature Tb of the first secondary battery, the second secondary battery 20, and the third secondary battery 30 is less than or equal to a predetermined temperature threshold Tb_th. When the switch control unit 101 determines that the measured temperature Tb is less than or equal to the predetermined temperature threshold Tb_th, and the power value Pout is less than a predetermined lower power threshold Pd, it turns off the first switch SW1, turns on the second switch SW2, turns on the third switch SW3, and turns off the fourth switch SW4 to connect the first secondary batteries 11A to 11D and the second secondary battery 20 in series, and electrically connects the first secondary batteries 11A to 11D and the second secondary battery 20 to the power supply target device 3.

[0124] By adopting this configuration, voltage fluctuations in the secondary batteries of the battery system 6 can be suppressed at temperatures where the charge and discharge capabilities of the first secondary batteries 11A to 11D and the second secondary battery 20 decrease. Therefore, the power supply target device 3 can be used at maximum power even at low temperatures.

[0125] Furthermore, when the switch control unit 101 determines that the measured temperature Tb is less than or equal to a predetermined temperature threshold Tb_th, and the power value Pout exceeds a predetermined upper power threshold Pc, it turns on the first switch SW1, turns off the second switch SW2, turns off the third switch SW3, and turns on the fourth switch SW4 to connect the first secondary battery and the third secondary battery 30 in series, and electrically connect the first secondary battery and the third secondary battery 30 to the power supply target device 3.

[0126] By adopting this configuration, voltage fluctuations in the secondary batteries of the battery system 6 can be suppressed at temperatures where the charge and discharge capabilities of the first and third secondary batteries 30 decrease. Therefore, the power supply device 3 can be used at maximum power even at low temperatures.

[0127] Furthermore, when the power value Pout is greater than or equal to a predetermined lower power threshold Pd and less than or equal to a predetermined upper power threshold Pc, and the switch control unit 101 determines that the SOC of the second secondary battery 20 is less than a predetermined SOC threshold, it turns off the first switch SW1, turns on the second switch SW2, turns on the third switch SW3, and turns off the fourth switch SW4 to connect the first secondary batteries 11A to 11D and the second secondary battery 20 in series, and electrically connects the first secondary batteries 11A to 11D and the second secondary battery 20 to the generator 2.

[0128] By adopting this configuration, when the output power of the power supply target device 3 is above a predetermined lower power threshold Pd and below a predetermined upper power threshold Pc, in other words, within the normal range, and when it is determined that the SOC of the second secondary battery 20 is below a predetermined SOC threshold, the second secondary battery 20 can be charged.

[0129] Furthermore, the SOC difference determination unit 106 determines whether the SOC difference, which is the difference between the SOC of the first secondary battery and the SOC of the third secondary battery 30, is greater than or equal to a predetermined difference threshold. If the SOC difference is determined to be greater than or equal to the predetermined difference threshold, the SOC determination unit 107 determines whether the SOC of the third secondary battery 30 is greater than or equal to a predetermined SOC threshold. When the power value Pout is greater than or equal to a predetermined lower power threshold Pd and less than or equal to a predetermined upper power threshold Pc, the switch control unit 101 determines that the SOC of the third secondary battery 30 is less than the predetermined SOC threshold, and turns on the first switch SW1, turns off the second switch SW2, turns off the third switch SW3, and turns on the fourth switch SW4 to connect the first secondary battery and the third secondary battery 30 in series. The number of first secondary batteries is greater than the number of third secondary batteries 30.

[0130] By adopting this configuration, a first secondary battery and a third secondary battery 30, whose positive and negative electrodes are oriented in opposite directions, are connected in series. In this state, when the overall discharge of the battery system 5 begins, the third secondary battery 30 can be charged.

[0131] In the above example, the program describing the above-described process can be stored and provided to the computer using various types of non-transitory computer-readable medium. Non-transitory computer-readable mediums include various types of tangible storage mediums. Examples of non-transitory computer-readable mediums include magnetic storage media (e.g., flexible disks, magnetic tapes, hard disk drives), magneto-optical storage media (e.g., magneto-optical disks), CD-ROMs, CD-Rs, CD-R / Ws, and semiconductor memory (e.g., mask ROMs, PROMs (Programmable ROMs), EPROMs (Erasable PROMs), flash ROMs, RAMs). Alternatively, the program may be provided to the computer using various types of transient computer-readable mediums. Examples of transient computer-readable mediums include electrical signals, optical signals, and electromagnetic waves. Transitory computer-readable mediums can supply the program to the computer via wired communication channels such as electric wires and optical fibers, or via wireless communication channels.

[0132] This disclosure is not limited to the embodiments described above, and may be modified as appropriate without departing from the spirit of this disclosure. [Explanation of Symbols]

[0133] 1: Battery System 10: Control device 11A~11D: First secondary battery, battery block, 20: Secondary battery 30: Third secondary battery 100: Arithmetic device 101: Switch Control Unit 102:Battery information acquisition section 103:Temperature judgment section 104:SOC calculation section 105:SOC difference calculation section 106:SOC difference judgment section 107:SOC judgment section 108: Power Value Acquisition Unit 109: Power judgment section 120: Storage device 130: Communication Interface 2: Generator 3: Devices to which power is supplied 4: Power lines 5: Battery System 6: Battery System B1~B4: Branching point SW1: First switch SW2: The Second Switch SW3: The Third Switch SW4: The Fourth Switch

Claims

1. A battery system electrically connected to a generator that supplies power and a power supply device to which power is supplied, Multiple battery blocks consisting of multiple first secondary batteries connected in series, A first switch is positioned between two branching points located between two adjacent battery blocks, A second switch and at least one second secondary battery are arranged to branch off from the two aforementioned branching points. The system includes a control device for controlling the charging and discharging of the first secondary battery and the second secondary battery, The orientation of the positive and negative electrodes of the second secondary battery is the same as the orientation of the positive and negative electrodes of the first secondary battery. The control device is A switch control unit that controls the on and off states of the first switch and the second switch, The system includes a power value acquisition unit that acquires a power value indicating the output power of the power supply target device, The switch control unit, when the power value is less than a predetermined lower power threshold, turns off the first switch and turns on the second switch to connect the first secondary battery and the second secondary battery in series, and electrically connects the first secondary battery and the second secondary battery to the power supply target device. Battery system.

2. The battery system according to claim 1, wherein the second secondary battery is located in the center of the plurality of battery blocks.

3. The system includes a temperature determination unit that determines whether the measured temperatures of the first secondary battery and the second secondary battery are below a predetermined temperature threshold. The battery system according to claim 1 or 2, wherein when the switch control unit determines that the measured temperature is below a predetermined temperature threshold, and the power value is below a predetermined lower power threshold, it turns off the first switch and turns on the second switch to connect the first secondary battery and the second secondary battery in series, and electrically connects the first secondary battery and the second secondary battery to the power supply target device.

4. The control device is An SOC difference determination unit that determines whether the SOC difference, which is the difference between the SOC (State of Charge) of the first secondary battery and the SOC of the second secondary battery, is greater than or equal to a predetermined difference threshold, If the aforementioned SOC difference is determined to be greater than or equal to a predetermined difference threshold, the system includes an SOC determination unit that determines whether or not the SOC of the second secondary battery is greater than or equal to a predetermined SOC threshold. The battery system according to claim 1 or 2, wherein when the power value is greater than or equal to a predetermined lower power threshold and less than or equal to a predetermined upper power threshold Pc, the switch control unit turns off the first switch and turns on the second switch to connect the first secondary battery and the second secondary battery in series, and electrically connects the first secondary battery and the second secondary battery to the generator.

5. A battery system electrically connected to a generator that supplies power and a power supply device to which power is supplied, Multiple battery blocks consisting of multiple first secondary batteries connected in series, A first switch is positioned between two branching points located between two adjacent battery blocks, A second switch and at least one second secondary battery are arranged to branch off from the two aforementioned branching points. The system includes a control device for controlling the charging and discharging of the first secondary battery and the second secondary battery, The orientation of the positive and negative electrodes of the second secondary battery is opposite to the orientation of the positive and negative electrodes of the first secondary battery. The control device is A switch control unit that controls the on and off states of the first switch and the second switch, The system includes a power value acquisition unit that acquires a power value indicating the output power of the power supply target device, The switch control unit, when the power value exceeds a predetermined upper power threshold, turns off the first switch and turns on the second switch to connect the first secondary battery and the second secondary battery in series, and electrically connects the first secondary battery and the second secondary battery to the power supply target device. Battery system.

6. The battery system according to claim 5, wherein the second secondary battery is located in the center of the plurality of battery blocks.

7. The system includes a temperature determination unit that determines whether the measured temperatures of the first secondary battery and the second secondary battery are below a predetermined temperature threshold. The battery system according to claim 5 or 6, wherein the switch control unit, when it is determined that the measured temperature is below a predetermined temperature threshold, and when it is determined that the power value exceeds a predetermined upper power threshold, turns off the first switch and turns on the second switch to connect the first secondary battery and the second secondary battery in series, and electrically connects the first secondary battery and the second secondary battery to the power supply target device.

8. The control device is An SOC difference determination unit that determines whether the SOC difference, which is the difference between the SOC of the first secondary battery and the SOC of the second secondary battery, is greater than or equal to a predetermined difference threshold, If the aforementioned SOC difference is determined to be greater than or equal to a predetermined difference threshold, the system includes an SOC determination unit that determines whether or not the SOC of the second secondary battery is greater than or equal to a predetermined SOC threshold. The number of the first secondary batteries is greater than the number of the second secondary batteries. The battery system according to claim 5 or 6, wherein the switch control unit, when the power value is greater than or equal to a predetermined lower power threshold and less than or equal to a predetermined upper power threshold, determines that the SOC of the second secondary battery is less than a predetermined SOC threshold, turns off the first switch and turns on the second switch to connect the first secondary battery and the second secondary battery in series.

9. A battery system electrically connected to a generator that supplies power and a power supply device to which power is supplied, Multiple battery blocks consisting of multiple first secondary batteries connected in series, A first switch is positioned between two branching points located between two adjacent battery blocks, A second switch and at least one second secondary battery are arranged to branch off from the two aforementioned branching points. A third switch is positioned between two other branching points located between the two adjacent battery blocks, A fourth switch and at least one third secondary battery are arranged to branch off from the other two branching points. The system includes a control device for controlling the charging and discharging of the first secondary battery, the second secondary battery, and the third secondary battery, The orientation of the positive and negative electrodes of the second secondary battery is the same as the orientation of the positive and negative electrodes of the first secondary battery. The orientation of the positive and negative electrodes of the third secondary battery is opposite to the orientation of the positive and negative electrodes of the first secondary battery. The control device is A switch control unit that controls the on and off states of the first switch, the second switch, the third switch, and the fourth switch, A power value acquisition unit that acquires a power value indicating the output power of the power supply target device, The switch control unit, when the power value is less than a predetermined lower power threshold, turns off the first switch, turns on the second switch, turns on the third switch, turns off the fourth switch, connects the first secondary battery and the second secondary battery in series, and electrically connects the first secondary battery and the second secondary battery to the power supply target device. Battery system.

10. The battery system according to claim 9, wherein the switch control unit turns on the first switch, turns off the second switch, turns off the third switch, and turns on the fourth switch when the power value exceeds a predetermined upper power threshold, thereby connecting the first secondary battery and the third secondary battery in series and electrically connecting the first secondary battery and the third secondary battery to the power supply target device.

11. The battery system according to claim 9 or 10, wherein the second secondary battery and the third secondary battery are arranged in the central part of the plurality of battery blocks.

12. The system includes a temperature determination unit that determines whether the measured temperatures of the first secondary battery, the second secondary battery, and the third secondary battery are below a predetermined temperature threshold. The battery system according to claim 9, wherein when the switch control unit determines that the measured temperature is below a predetermined temperature threshold, and the power value is below a predetermined lower power threshold, it turns off the first switch, turns on the second switch, turns on the third switch, and turns off the fourth switch to connect the first secondary battery and the second secondary battery in series, and electrically connects the first secondary battery and the second secondary battery to the power supply target device.

13. The system includes a temperature determination unit that determines whether the measured temperatures of the first secondary battery, the second secondary battery, and the third secondary battery are below a predetermined temperature threshold. The battery system according to claim 10, wherein when the switch control unit determines that the measured temperature is below a predetermined temperature threshold, and the power value exceeds a predetermined upper power threshold, it turns on the first switch, turns off the second switch, turns off the third switch, and turns on the fourth switch to connect the first secondary battery and the third secondary battery in series, and electrically connects the first secondary battery and the third secondary battery to the power supply target device.

14. The control device is An SOC difference determination unit that determines whether the SOC difference, which is the difference between the SOC of the first secondary battery and the SOC of the second secondary battery, is greater than or equal to a predetermined difference threshold, If the aforementioned SOC difference is determined to be greater than or equal to a predetermined difference threshold, the system includes an SOC determination unit that determines whether or not the SOC of the second secondary battery is greater than or equal to a predetermined SOC threshold. The battery system according to claim 9 or 12, wherein when the power value is above a predetermined lower power threshold and below a predetermined upper power threshold, and the switch control unit determines that the SOC of the second secondary battery is below a predetermined SOC threshold, it turns off the first switch, turns on the second switch, turns on the third switch, and turns off the fourth switch to connect the first secondary battery and the second secondary battery in series, and electrically connects the first secondary battery and the second secondary battery to the generator.

15. The control device is An SOC difference determination unit that determines whether the SOC difference, which is the difference between the SOC of the first secondary battery and the SOC of the third secondary battery, is greater than or equal to a predetermined difference threshold, If the aforementioned SOC difference is determined to be greater than or equal to a predetermined difference threshold, the system includes an SOC determination unit that determines whether or not the SOC of the third secondary battery is greater than or equal to a predetermined SOC threshold. The number of the first secondary batteries is greater than the number of the second secondary batteries. The battery system according to claim 10 or 13, wherein the switch control unit, when the power value is greater than or equal to a predetermined lower power threshold and less than or equal to a predetermined upper power threshold, determines that the SOC of the third secondary battery is less than a predetermined SOC threshold, turns on the first switch, turns off the second switch, turns off the third switch, and turns on the fourth switch to connect the first secondary battery and the third secondary battery in series.

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