Battery system

Abstract

To make it possible to efficiently increase a total capacity of a battery after replacement even when the number of replaced batteries is reduced.SOLUTION: A battery system (10) comprises a plurality of batteries (21) connected to a load (25) of a device (11) so as to be capable of supplying an electric power thereto and fixed to the device (11). The plurality of batteries (21) include a first battery (21A) and a second battery (21B). At least the first battery (21A) is detachably fixed to the device (11), and includes: a measurement part that measures a stored voltage of the plurality of batteries 21; and a control part (23) that controls charging and discharging of the plurality of batteries (21) based on the stored voltage measured by the measurement part, and the control part (23) controls charging and discharging of the first battery (21A) and the second battery (21B) such that the stored voltage of the second battery (21B) becomes higher than that of the first battery (21A) after a predetermined time elapses.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a battery system. [Background technology]

[0002] In recent years, efforts to realize a low-carbon or carbon-free society have become more active, and research and development is being conducted on technologies to extend the driving range of electric vehicles in order to reduce CO2 emissions and improve energy efficiency. One such technology has been proposed, which has a main battery pack and an extended-range battery pack, and when the voltage of the main battery pack is higher than that of the extended-range battery pack, discharge is controlled until the voltage of the main battery pack matches that of the extended-range battery pack or so that the voltage difference is within an acceptable range; and when the voltage of the main battery pack is lower than that of the extended-range battery pack, discharge is controlled so that the voltage of the extended-range battery pack matches that of the main battery pack or so that the voltage difference is within an acceptable range (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Chinese Patent Application Publication No. 106627188 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the technology of increasing the remaining battery capacity by replacing the battery and extending the driving range or the usage time of the device, there is a need to reduce the number of battery replacements as much as possible. However, because conventional technology balances the voltages of the two batteries, the remaining capacity of each battery is almost the same, so replacing one battery may not fully increase the total capacity of all batteries. Therefore, reducing the number of battery replacements may result in a situation where the driving range or the usage time of the equipment cannot be fully extended. The present invention has been made in view of the above circumstances, and aims to enable efficient increase in the total capacity of batteries after replacement even when the number of battery replacements is reduced, thereby contributing to improvement of energy efficiency. [Means for solving the problem]

[0005] Provided is a battery system comprising a plurality of batteries connected to a load of an equipment so as to be able to supply power to the equipment and fixed to the equipment, the plurality of batteries including a first battery 21A and a second battery, at least the first battery being detachably fixed to the equipment, a measuring unit that measures the storage voltage of the plurality of batteries, and a control unit that controls charging and discharging of the plurality of batteries (21) based on the storage voltage measured by the measuring unit, and the control unit controls the charging and discharging of the first battery and the second battery so that the storage voltage of the second battery becomes higher than that of the first battery after a predetermined time has elapsed. [Effects of the Invention]

[0006] To efficiently increase the total capacity of batteries after replacement even when the number of battery replacements is reduced. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a diagram schematically showing an electric vehicle equipped with a battery system according to an embodiment of the present invention; [Figure 2] FIG. 1 is a diagram illustrating a battery system. [Figure 3] FIG. 2 is a diagram showing a circuit configuration of a battery system. [Figure 4] 10 is a flowchart illustrating a basic operation of an example of battery control. [Figure 5] 10 is a flowchart showing a basic operation of another example of battery control. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1 is a diagram schematically showing an electric vehicle 11 equipped with a battery system 10 according to this embodiment. The electric vehicle 11 is an electric vehicle (EV) that runs on an electric motor 12 driven by electric power from the battery system 10. The electric vehicle 11 to which the present invention is applicable may be any vehicle that is driven by power supplied from a battery for traveling, such as not only four-wheeled vehicles but also saddle-ride type two-wheeled vehicles, three-wheeled vehicles, and even power-assisted bicycles. The electric vehicle 11 may also be a hybrid electric vehicle (e.g., HEV) equipped with an internal combustion engine that uses fuel such as a diesel engine or a gasoline engine as an energy source.

[0009] The battery system 10 includes a plurality of batteries 21 (eight in this embodiment), and each battery 21 is detachably fixed to the electric vehicle 11. Each battery 21 is a secondary battery, such as a lithium-ion battery. The battery 21 in this embodiment is a portable battery housed in a battery case that can be easily held by a user, and is also called an MPP (Mobile Power Pack), which can be easily removed from the electric vehicle 11 and replaced by a user of the electric vehicle 11, etc.

[0010] The electric motor 12 is a motor that provides driving force to the electric vehicle 11, and can also be called a traction motor or a rotating electric machine. The electric motor 12 of this embodiment is also used as a regenerative brake. Regenerative braking operates the electric motor 12 as a generator when the electric vehicle 11 decelerates or stops, and recovers the generated power to the battery 21, thereby improving the energy efficiency of the electric vehicle 11. Note that a known configuration can be appropriately adopted as the configuration for recovering the generated power of the electric motor 12 to the battery 21. Furthermore, the electric motor 12 can be any suitable motor that can be mounted on the electric vehicle 11, and is not limited to a single motor, but may be multiple motors, and the electric motor 12 may be equipped with a motor dedicated to regeneration (which can also be called a generator or rotating electric machine) in addition to a driving motor.

[0011] In the electric vehicle 11, a PDU (Power Drive Unit) 22 converts DC power supplied from each battery 21 into AC power for driving the motor and outputs it to the electric motor 12. The electric motor 12 is driven by the PDU 22, and for example, the rotation speed and torque of the electric motor 12 are controlled. The PDU 22 is formed of, for example, an AC-DC converter.

[0012] The electric motor 12 and the PDU 22 are examples of loads to which power is supplied from the battery system 10, and in other words, constitute part of the load of the electric vehicle 11. In the following description, when there is no need to particularly distinguish between the electric motor 12 and the PDU 22, they will be simply referred to as the load 25.

[0013] In the electric vehicle 11, an ECU (Electronic Control Unit) 23 functions as a control unit (which can also be called a control device) that controls each part of the electric vehicle 11. The ECU 23 is made up of one or more CPUs and peripheral circuits. The configuration of the ECU 23 is not particularly limited, but the ECU 23 of this embodiment includes a load ECU 23a that controls the PDU 22 and a battery ECU 23b that controls the battery system 10, as shown in FIG.

[0014] 1 and 2 show an example in which the ECU 23 is provided outside the battery system 10, but the present invention is not limited to this configuration. For example, the battery ECU 23b may be provided in the battery system 10. 1 and 2 also show communication lines L1, L2, and L3 that form part of the LAN. The ECU 23 can communicate with each part of the electric vehicle 11 using these communication lines L1, L2, and L3.

[0015] 2, the plurality of batteries 21 are assigned to either a first battery 21A or a second battery 21B other than the first battery 21A. The first battery 21A and the second battery 21B are connected to a load 25 in parallel. In this embodiment, half (four) of the batteries 21 are assigned to the first battery 21A, and all of the remaining (four) batteries 21 are assigned to the second battery 21B. The specifications of each battery 21 are common, such as the same rated voltage and rated capacity (which can also be referred to as rated power). Therefore, the rated capacity of the first battery 21A is the same as the rated capacity of the second battery 21B.

[0016] In the electric vehicle 11 of this embodiment, all batteries 21 are replaceable, but the first battery 21A is treated as the battery that is given priority for replacement. The first battery 21A can be referred to as the sub-battery that is given priority for replacement, and the second battery 21B can be referred to as the main battery.

[0017] It is preferable that the specifications of the batteries 21 are the same, but the specifications of the batteries 21 may be different. For example, a plurality of batteries 21 having a common rated voltage but different rated capacities may be mounted. Furthermore, the number of batteries 21 assigned to each of the first battery 21A and the second battery 21B may be changed as appropriate, and the number of batteries may differ between the first battery 21A and the second battery 21B.

[0018] Each battery 21 is equipped with a battery management unit (hereinafter referred to as BMU) and has a function of transmitting information detected by the BMU to the ECU 23. The BMU has a function of detecting the voltage, current, temperature, etc. of the battery 21, a monitoring function of monitoring the battery 21 based on the detection results, and a communication function of outputting the detection results and monitoring results to the outside as data. A widely available BMU can be used as the BMU.

[0019] The battery system 10 has a converter 31 connected between the first battery 21A and the load 25. The converter 31 is an electrical component that converts the power of the first battery 21A, and in this embodiment, is a transformer that converts the voltage of the DC power of the first battery 21A. The converter 31 can convert the voltage of the power from the first battery 21A to a predetermined voltage that allows the second battery 21B to be charged with the power from the first battery 21A. The predetermined voltage may be set to any appropriate value, but is set to at least a value higher than the voltage of the second battery 21B. The converter 31 is configured, for example, by a DC-DC converter.

[0020] FIG. 3 is a diagram showing the circuit configuration of the battery system 10. As shown in FIG. 3, the positive electrode of the output side of converter 31 is connected to the positive electrode of load 25 via first switch SW1. The negative electrode of the output side of converter 31 is connected to the negative electrode of load 25. The positive electrode of second battery 21B is connected to the positive electrode of load 25 via second switch SW2. The negative electrode of second battery 21B is connected to the negative electrode of load 25. According to this circuit configuration, by switching on the first switch SW1 and the second switch SW2 and setting the output voltage of the converter 31 to a voltage higher than the voltage of the second battery 21B, it is possible to supply power from the first battery 21A to the second battery 21B, as shown by the symbol α in Figure 2, and charge the second battery 21B with the power of the first battery 21A.

[0021] 2 indicates a junction box disposed between the second battery 21B and the load 25. The junction box 32 is a component that aggregates wiring that connects the battery 21 of the second battery 21B to the PDU 22 and the converter 31.

[0022] The ECU 23 performs control relating to the electric motor 12 (hereinafter referred to as load control) and control relating to the battery 21 (hereinafter referred to as battery control). The load ECU 23a receives, as an input signal related to load control, a sensor detection signal indicating the operation of an operator operated by a user (for example, an accelerator pedal and a brake pedal), and controls the PDU 22 based on the sensor detection signal. As a result, when the accelerator pedal is operated, for example, the ECU 23 controls the current supplied from the battery system 10 to the electric motor 12 by the PDU 22, and performs operation control of the electric motor 12 (which can also be called powering control or powering operation). Also, for example, when the brake pedal is operated and a predetermined regeneration condition is met, the ECU 23 converts the AC power generated by the electric motor 12 into DC power with a voltage higher than the voltage of the second battery 21B using the PDU 22, and performs control (which can also be called regenerative control or regenerative operation) to charge the battery system 10 with the regenerative power.

[0023] As battery control, the battery ECU 23b controls the supply of power from the first battery 21A to the second battery 21B so that the stored voltage of the second battery 21B is higher than that of the first battery 21A. Here, the stored voltage means the voltage of the battery in a charged state, but can also be simply referred to as the voltage of the battery. Generally, the stored voltage is proportional to the remaining capacity of a battery, so by making the stored voltage of the second battery 21B higher than that of the first battery 21A, the remaining capacity of the second battery 21B can be made greater than that of the first battery 21A.

[0024] 4 is a flowchart showing a basic operation of an example of battery control performed by the battery ECU 23b. The battery control shown in FIG. 4 is appropriately referred to as battery control of a first embodiment. In the battery control of the first embodiment, the battery ECU 23b receives signals from the BMU of each battery 21 as input signals related to the battery control, and thereby identifies the voltage of each battery 21 at predetermined time intervals (step S1). If the battery 21 does not have a communication function, the battery ECU 23b may acquire the voltage of each battery 21 at predetermined time intervals using a voltage sensor that detects the voltage of each battery 21. In other words, the BMU, the voltage sensor, and at least a part of the battery ECU 23b that uses them function as an example of a "measurement unit that measures the stored voltage of the battery 21" of the present invention.

[0025] Next, the battery ECU 23b uses the voltages of the respective batteries 21 to determine the voltage of the first battery 21A (corresponding to the stored voltage) and the voltage of the second battery 21B (corresponding to the stored voltage) at predetermined time intervals (step S2). For example, the battery ECU 23b may calculate the average voltage or the median of the detected voltages of the respective batteries 21 belonging to the first battery 21A as the voltage of the first battery 21A (corresponding to the stored voltage), and may calculate the average voltage or the median of the detected voltages of the respective batteries 21 belonging to the second battery 21B as the voltage of the second battery 21B (corresponding to the stored voltage). Alternatively, the sum of the voltages of the respective batteries 21 belonging to the first battery 21A may be calculated as the voltage of the first battery 21A (corresponding to the stored voltage), and the sum of the voltages of the respective batteries 21 belonging to the second battery 21B may be calculated as the voltage of the second battery 21B (corresponding to the stored voltage).

[0026] Next, based on the calculated voltages of the batteries 21A and 21B, the battery ECU 23b controls the charging and discharging of the first battery 21A and the second battery 21B so that the voltage (storage voltage) of the second battery 21B becomes higher than that of the first battery 21A after a predetermined time has elapsed (step S3). This allows the storage voltage of the second battery 21B to be higher than that of the first battery 21A.

[0027] A specific example of the process in step S3 will be described. When the electric vehicle 11 is stopped, the battery ECU 23b controls the first switch SW1 and the second switch SW2 shown in Fig. 3 to be on, and makes the output voltage of the converter 31 higher than the voltage of the second battery 21B, thereby supplying power from the first battery 21A to the second battery 21B, as indicated by the symbol α in Fig. 2. This makes it possible to make the stored voltage of the second battery 21B higher than that of the first battery 21A at least after a predetermined time has elapsed.

[0028] Furthermore, when the electric vehicle 11 is in a predetermined operating state 1 (for example, when the demand from the load 25 is small), the battery ECU 23b controls the first switch SW1 to be on and the second switch SW2 to be off, thereby supplying the output power of the converter 31 to the load 25 and not supplying the power of the second battery 21B to the load 25, as indicated by the symbol β in Fig. 2. This allows the stored voltage of the second battery 21B to be higher than that of the first battery 21A.

[0029] Furthermore, when the electric vehicle 11 is in a predetermined operating state 2 (for example, when the demand from the load 25 is large), the battery ECU 23b controls the first switch SW1 to be on and the second switch SW2 to be on, so that the output power of the converter 31 is equal to the output voltage of the second battery 21B. This makes it possible to supply power almost equally from both the first battery 21A and the second battery 21B while meeting the demand from the load 25. Therefore, it is possible to maintain a state in which the stored voltage of the second battery 21B is higher than that of the first battery 21A.

[0030] Furthermore, when a predetermined regeneration condition 1 is satisfied, the battery ECU 23b controls the first switch SW1 to be turned off and the second switch SW2 to be turned on, thereby supplying the electric power generated by the electric motor 12 of the load 25 to the second battery 21B, as indicated by the symbol γ in Fig. 2. This allows the stored voltage of the second battery 21B to be higher than that of the first battery 21A at least after a predetermined time has elapsed.

[0031] In addition, when a predetermined regeneration condition 2 is satisfied, the battery ECU 23b controls the first switch SW1 to be on and the second switch SW2 to be on, thereby supplying the power generated by the electric motor 12 of the load 25 to the first battery 21A and the second battery 21B. Here, Regeneration Condition 2 is set to a condition that anticipates higher regenerative power than Regeneration Condition 1. This allows both the first battery 21A and the second battery 21B to be charged with high regenerative power. Therefore, the storage voltage of both batteries 21A, 21B can be increased while maintaining the storage voltage of the second battery 21B higher than that of the first battery 21A. It should be noted that a wide range of known methods can be applied to determine the state of electric vehicle 11 (whether it is in a stopped state, operating state 1, operating state 2, a state that satisfies regeneration condition 1, and a state that satisfies line condition 2).

[0032] According to the battery control of the first embodiment, it is possible to supply appropriate power to the load 25 in accordance with the state of the electric vehicle 11, while making the stored voltage of the second battery 21B higher than that of the first battery 21A.

[0033] 5 is a flowchart showing the basic operation of another example of battery control. The battery control shown in FIG. 5 is appropriately referred to as battery control of a second embodiment. In the battery control of the second embodiment, as shown in FIG. 5, the battery ECU 23b acquires the current and voltage flowing through each battery 21 using at least one of a BMU, a current sensor, and a voltage sensor, and determines the SOC (State Of Charge) indicating the remaining capacity of each battery 21 at predetermined time intervals based on the acquired information (step S1a). A known SOC estimation technique may be used to determine the SOC of each battery 21. For example, a current integration method may be used in which the current flowing through the battery 21 is integrated, the charge / discharge amount is calculated by integrating charge and discharge, and the SOC of each battery 21 is calculated by subtracting the charge / discharge amount from the initial SOC, or a method of calculating the SOC using a Kalman filter may be used.

[0034] Next, the battery ECU 23b determines the SOC indicating the remaining capacity of the first battery 21A and the SOC indicating the remaining capacity of the second battery 21B at predetermined time intervals using the SOC of each battery 21 (step S2a). For example, if the rated capacities of the batteries 21 are the same, the average value of the SOC of the batteries 21 belonging to the first battery 21A is calculated as the SOC of the first battery 21A, and the average value of the SOC of the batteries 21 belonging to the second battery 21B is calculated as the SOC of the second battery 21B. In addition, if the rated capacities of the batteries 21 are different values, the SOC of each battery 21 can be calculated by calculating a total value after weighting the SOC of each battery 21 by the rated capacity of that battery 21, and then dividing this total value by the total rated capacity, thereby calculating the SOC of the first battery 21A and the second battery 21B.

[0035] Thereafter, based on the calculated SOC of each battery 21A, 21B, the battery ECU 23b controls the charging and discharging of the first battery 21A and the second battery 21B so that the voltage (storage voltage) of the second battery 21B becomes higher than that of the first battery 21A after a predetermined time has elapsed (step S3a). The battery control of the second embodiment also makes it possible to make the stored voltage of the second battery 21B higher than that of the first battery 21A.

[0036] By controlling each battery as described above, the stored voltage of the second battery 21B can be made higher than that of the first battery 21A, and therefore the remaining capacity of the second battery 21B can be made higher than that of the first battery 21A. This makes it easier to maintain the second battery 21B in a state close to a fully charged state, for example. Therefore, simply replacing the first battery 21A, or more specifically, simply replacing each battery 21 of the first battery 21A with a charged battery 21, makes it easier to increase the total capacity of the battery consisting of the first battery 21A and the second battery 21B to a state close to a fully charged state.

[0037] As described above, the battery system 10 of this embodiment is connected to the load 25 of the electric vehicle 11 so as to be able to supply power, and includes a plurality of batteries 21 fixed to the electric vehicle 11, each battery 21 including a first battery 21A and a second battery 21B, with at least the first battery 21A being detachably fixed to the electric vehicle 11. The battery system 10 further includes a configuration that functions as a measurement unit that measures the stored voltage of each battery 21, and an ECU 23 that functions as a control unit that controls the charging and discharging of each battery 21 based on the stored voltage measured by the measurement unit. The ECU 23 then controls the charging and discharging of the first battery 21A and the second battery 21B so that the stored voltage of the second battery 21B becomes higher than that of the first battery 21A after a predetermined time has elapsed. According to this configuration, the remaining capacity of the second battery 21B can be made greater than that of the first battery 21A, and the total battery capacity can be efficiently increased simply by replacing the first battery 21A. Therefore, even if the number of battery 21 replacements is reduced, the total capacity of the replaced batteries 21 can be efficiently increased, making it easier to sufficiently extend the cruising distance; in other words, it makes it easier to sufficiently extend the usage time of the electric vehicle 11. Furthermore, since the number of battery 21 replacements can be reduced, the energy consumption required for storing, transporting, and replacing the batteries 21 can be reduced, contributing to improved energy efficiency.

[0038] Furthermore, the ECU 23 controls the power supply from the first battery 21A to the second battery 21B so that the stored voltage of the second battery 21B is higher than that of the first battery 21A, so that the remaining capacity of the second battery 21B can be made greater than that of the first battery 21A. This allows the total battery capacity to be efficiently increased simply by replacing the first battery 21A.

[0039] Furthermore, when supplying power from each battery 21 to the load 25, the power of the first battery 21A of the first battery 21A and the second battery 21B is supplied to the load 25. This configuration can prevent the remaining capacity of the second battery 21B from decreasing, making it easier to maintain the second battery 21B in a state close to full charge. Therefore, even if a method for reducing the number of battery replacements is adopted in which only the first battery 21A is replaced, the total capacity of the batteries 21 after replacement can be sufficiently increased, making it easier to extend the cruising range and usage time.

[0040] Furthermore, the power supplied from the load 25 is supplied to the second battery 21B of the first battery 21A and the second battery 21B. With this configuration, the remaining capacity of the second battery 21B can be increased by the power supplied from the load, making it easier to maintain the second battery 21B in a state close to full charge. Therefore, even if a method for reducing the number of battery replacements is adopted in which only the first battery 21A is replaced, the total capacity of the batteries 21 after replacement can be sufficiently increased, making it easier to extend the cruising range and usage time.

[0041] As shown in FIG. 3, the inverter has a converter 31 that outputs to a load 25 electric power obtained by changing the voltage of the electric power input from the first battery 21A, and the positive terminal of the output side of the converter 31 and the positive terminal of the second battery 21B are connected to the positive terminal of the load 25, and the negative terminal of the output side of the converter 31 and the negative terminal of the second battery 21B are connected to the negative terminal of the load 25. According to this configuration, by setting the output voltage of the converter 31 to a voltage higher than the voltage of the second battery 21B, power from the first battery 21A can be supplied to the second battery 21B, and the remaining capacity of the second battery 21B can be made greater than that of the first battery 21A.

[0042] [Other embodiments] The above-described embodiment merely shows one aspect of the present invention, and any modifications and applications are possible without departing from the spirit of the present invention.

[0043] In the above embodiment, the case where the multiple batteries 21 are assigned to either the first battery 21A or the second battery 21B other than the first battery 21A has been described, but this is not limiting. In other words, the multiple batteries 21 of the present invention may include the first battery 21A and the second battery 21B. Furthermore, although the present invention is an invention that can reduce the effort required to replace batteries 21 as the number of batteries 21 increases, depending on the number and capacity of batteries 21, the specifications of the electric vehicle 11, and the like, each of the first battery 21A and the second battery 21B may be a single battery 21, which is the smallest unit for replacement.

[0044] Further, the second battery 21B may be configured to be non-detachable by the user, etc. For example, a configuration in which the second battery 21B is a large-capacity battery fixed to the electric vehicle 11 can be realized. In addition, although the first battery 21A and the second battery 21B are used as power sources for the electric motor 12 that provides driving force to the electric vehicle 11 in the above description, the present invention is not limited to this. For example, the first battery 21A and the second battery 21B may be used as power sources for loads other than the electric motor 12 of the electric vehicle 11.

[0045] In the above embodiment, the present invention has been described as being applied to the battery system 10 of the electric vehicle 11, but the present invention may also be applied to the battery system 10 of devices other than the electric vehicle 11. Any device other than the electric vehicle 11 can be applied, and examples thereof include electric mobility other than the electric vehicle 11, a stationary battery, and an outdoor portable power source.

[0046] [Configuration supported by the above embodiment] The above embodiment supports the following configurations.

[0047] (Configuration 1) A battery system comprising a plurality of batteries connected to a load of an equipment so as to be able to supply power to the equipment and fixed to the equipment, the plurality of batteries including a first battery 21A and a second battery, at least the first battery being detachably fixed to the equipment, a measuring unit that measures the storage voltage of the plurality of batteries, and a control unit that controls the charging and discharging of the plurality of batteries (21) based on the storage voltage measured by the measuring unit, the control unit controlling the charging and discharging of the first battery and the second battery so that the storage voltage of the second battery becomes higher than that of the first battery after a predetermined time has elapsed. With this configuration, the total battery capacity can be efficiently increased simply by replacing the first battery, so even if the number of battery replacements is reduced, the total battery capacity after replacement can be increased. Furthermore, since the number of battery replacements can be reduced, the energy consumption required for battery storage and replacement work can be reduced, contributing to improved energy efficiency.

[0048] (Configuration 2) The battery system according to configuration 1, wherein the control unit controls the power supply from the first battery to the second battery so that the stored voltage of the second battery is higher than that of the first battery. This configuration can prevent the remaining capacity of the second battery from decreasing, making it easier to maintain the second battery close to a fully charged state. Therefore, even if a method for reducing the number of battery replacements is adopted in which only the first battery is replaced, the total capacity of the replaced batteries can be sufficiently increased, making it easier to extend the driving range and usage time.

[0049] (Configuration 3) The battery system according to Configuration 1 or 2, wherein when supplying power from the plurality of batteries to the load, power from the first battery of the first battery and the second battery is supplied to the load. This configuration can prevent the remaining capacity of the second battery from decreasing, making it easier to maintain the second battery close to a fully charged state. Therefore, even if a method for reducing the number of battery replacements is adopted in which only the first battery is replaced, the total capacity of the replaced batteries can be sufficiently increased, making it easier to extend the driving range and usage time.

[0050] (Configuration 4) The battery system according to any one of Configurations 1 to 3, wherein the power supplied from the load is supplied to the second battery of the first battery and the second battery. With this configuration, the remaining capacity of the second battery can be increased by the power supplied from the load, making it easier to maintain the second battery in a state close to full charge. Therefore, even if a method for reducing the number of battery replacements is adopted in which only the first battery is replaced, the total capacity of the replaced batteries can be sufficiently increased, making it easier to extend the driving range and usage time.

[0051] (Configuration 5) A battery system according to any one of configurations 1 to 4, comprising a converter that outputs to the load power obtained by changing the voltage of the power input from the first battery, wherein the positive terminal of the output side of the converter and the positive terminal of the second battery are connected to the positive terminal of the load, and the negative terminal of the output side of the converter and the negative terminal of the second battery are connected to the negative terminal of the load. According to this configuration, by setting the output voltage of the converter to a voltage higher than the voltage of the second battery, power from the first battery can be supplied to the second battery, and the remaining capacity of the second battery can be made greater than that of the first battery. [Explanation of symbols]

[0052] 10 Battery System 11 Electric vehicles (equipment) 12 Electric motor 21 Battery 21A 1st battery (sub-battery) 21B Second battery (main battery) 22 PDU 23 ECU (control unit, measurement unit) 23a Load ECU 23b Battery ECU (control unit, measurement unit) 31 Converter 32 Junction Box

Claims

1. A battery system including a plurality of batteries (21) connected to a load (25) of a device (11) so as to be able to supply power to the load (25) of the device (11), and fixed to the device (11), The plurality of batteries (21) include a first battery (21A) and a second battery (21B), At least the first battery (21A) is detachably fixed to the device (11), a measurement unit for measuring the stored voltage of the plurality of batteries (21); a control unit (23) that controls charging and discharging of the plurality of batteries (21) based on the stored voltage measured by the measurement unit, The control unit (23) controls charging and discharging of the first battery (21A) and the second battery (21B) so that the stored voltage of the second battery (21B) becomes higher than that of the first battery (21A) after a predetermined time has elapsed. Battery system.

2. The control unit (23) controls the power supply from the first battery (21A) to the second battery (21B) so that the stored voltage of the second battery (21B) is higher than that of the first battery (21A). The battery system of claim 1 .

3. When supplying the power of the plurality of batteries (21) to the load (25), the power of the first battery (21A) of the first battery (21A) and the second battery (21B) is supplied to the load (25). The battery system of claim 1 .

4. The power supplied from the load (25) is supplied to the second battery (21B) of the first battery (21A) and the second battery (21B). The battery system of claim 1 .

5. a converter (31) that outputs power obtained by changing the voltage of power input from the first battery (21A) to the load (25); a positive terminal of the output side of the converter (31) and a positive terminal of the second battery (21B) are connected to a positive terminal of the load (25); The negative terminal of the output side of the converter (31) and the negative terminal of the second battery (21B) are connected to the negative terminal of the load (25). The battery system of claim 1 .

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