Control method, program, control system, and work machine

Abstract

To provide a technique capable of appropriately using a plurality of batteries connected in parallel.SOLUTION: An exemplary control method is a method of controlling a plurality of batteries connected in parallel with a controller via a relay provided for every battery thereof. The method comprises the steps of: detecting being in a discharging mode where it is possible to make the batteries be discharged; and performing discharge processing by which a maximum value in voltage difference among the plurality of batteries is made to be within a voltage threshold value, by switching the relay from turn-off to turn-on for some of the plurality of batteries, when being in the discharging mode.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a technique for controlling a plurality of batteries connected in parallel. [Background technology]

[0002] 2. Description of the Related Art Conventionally, there is known an electric working machine capable of operating a working device by driving an electric motor (see, for example, Patent Document 1).

[0003] Patent Document 1 discloses that an electric work machine includes an electric motor and a battery unit that supplies power to the electric motor. In Patent Document 1, the battery unit includes a plurality of batteries that are connected in parallel to each other. The electric work machine also includes a connection switching unit that switches the power supply path from the batteries to the electric motor between a connected state and a cut-off state for each battery. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-80703 Summary of the Invention [Problem to be solved by the invention]

[0005] In an electric work machine having multiple batteries connected in parallel, if there is a voltage difference between the batteries, and the connection switching units of the batteries are simultaneously connected, an unintended current may flow, which may cause damage to the equipment.

[0006] An object of the present invention is to provide a technique that enables appropriate use of multiple batteries connected in parallel. [Means for solving the problem]

[0007] An exemplary control method of the present invention is a method of controlling multiple batteries connected in parallel by a control device via a relay provided for each of the batteries, and includes detecting a discharge mode in which the batteries can be discharged, and, when the batteries are in the discharge mode, switching the relays from off to on for some of the multiple batteries to perform a discharge process such that the maximum value of the voltage differences between the multiple batteries is within a voltage threshold. Effect of the Invention

[0008] The exemplary invention allows for the appropriate use of multiple batteries connected in parallel. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a side view showing a schematic configuration of a work machine; [Diagram 2] A block diagram showing a schematic configuration of a work machine. [Diagram 3] Schematic diagram showing the circuit configuration of the control system [Figure 4] Schematic diagram showing the state of the control system when an electric motor is used [Diagram 5] Schematic diagram showing the state of the control system during discharge processing to balance between parallel circuits [Figure 6] Schematic diagram showing the state of the control system during charging processing with parallel balancing [Figure 7A] 1 is a flowchart showing a part of the flow of a control process executed by a control system. [Figure 7B] 11 is a flowchart showing another part of the flow of the control process executed by the control system. [Figure 7C] 7B is a flowchart showing another part of the flow of the control process executed by the control system; [Figure 8] Schematic diagram for explaining a discharge process for achieving parallel balance [Figure 9] FIG. 13 is a schematic diagram showing an example of a screen of a display device provided in the control system; [Figure 10] Schematic diagram for explaining a charging process for balancing parallel circuits DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference characters and description thereof will not be repeated.

[0011] <1. Working Machinery> Fig. 1 is a side view showing a schematic configuration of a work machine 100 according to an embodiment of the present invention. In Fig. 1, the X direction is the front-rear direction, the Y direction is the left-right direction, and the Z direction is the up-down direction. In the X direction, the side toward which the arrow points is the front side, and the opposite side is the rear side. In the Y direction, the front side of the paper is the left side, and the rear side of the paper is the right side. In the Z direction, the side toward which the arrow points is the top side, and the opposite side is the bottom side.

[0012] Specifically, the work machine 100 is a backhoe. The work machine 100 includes a crawler-type running body 101, a rotating body 102 disposed above the running body 101, and a working device 103 attached to the rotating body 102.

[0013] The traveling body 101 includes a pair of left and right crawlers 101a and a pair of left and right traveling motors 102b. Each traveling motor 102b is a hydraulic motor. The traveling motors 102b may be electric motors. The left and right traveling motors 102b drive the left and right crawlers 101a, respectively, to move the work machine 100 forward and backward.

[0014] The rotating body 102 is mounted on the traveling body 101 so as to be rotatable about a central axis extending in the vertical direction. The rotating body 102 is driven by a rotation motor (not shown) configured as a hydraulic motor. The rotation motor may be an electric motor. The rotating body 102 is provided so as to be capable of rotating right and left.

[0015] Here, the working device 103 will be described on the assumption that the rotating body 102 is facing forward as shown in Fig. 1. The working device 103 includes a boom 103a, an arm 103b, and a bucket 103c. The boom 103a, the arm 103b, and the bucket 103c are provided so as to be able to operate independently, thereby enabling excavation work of earth and sand, etc. to be performed.

[0016] The boom 103a is provided so as to be swingable in the forward and backward directions by a boom cylinder 103d that is provided so as to be extendable. The arm 103b is provided so as to be rotatable in a vertical plane by an arm cylinder 103e that is provided so as to be extendable. The bucket 103c is provided so as to be rotatable in a vertical plane by a bucket cylinder 103f that is provided so as to be extendable. The working device 103 is provided so as to be swingable in the left and right directions by a swing cylinder (not shown). The boom cylinder 103d, the arm cylinder 103e, the bucket cylinder 103f, and the swing cylinder are constituted by hydraulic cylinders.

[0017] Fig. 2 is a block diagram showing a schematic configuration of the work machine 100. As shown in Fig. 2, the work machine 100 is equipped with a control system 1. The work machine 100 also includes an inverter device 2, an electric motor 3, a pilot pump 4, a main pump 5, a solenoid valve 6, a remote control valve 7, a control valve 8, and a hydraulic actuator 9. Note that reference numeral 200 in Fig. 2 denotes an AC power source. In this embodiment, the AC power source 200 is a commercial power source. The AC power source 200 is not a component of the work machine 100 in this embodiment.

[0018] The control system 1 is a system that performs control related to a battery 121 (see FIG. 3 etc.), which will be described in detail later. The control system 1 includes a power supply device 11, a battery unit 12, and a control device 13.

[0019] The power supply device 11 is provided so as to be able to supply power from the AC power supply 200. The power supply device 11 is provided so as to be able to be connected to the AC power supply 200 by, for example, a cable (not shown), and is supplied with power from the AC power supply 200 by the connection of the cable. The power supply device 11 converts an AC voltage of the AC power supply 200 into a DC voltage, and supplies the power to, for example, the battery unit 12. The power supply device 11 may also supply power to the inverter device 2.

[0020] As described in detail below, the battery unit 12 includes a plurality of batteries 121 (see FIG. 3, etc.) that are provided so as to be capable of being charged and discharged. Each battery 121 is provided so as to be capable of being charged by receiving power from the power supply device 11. Each battery 121 is also provided so as to be capable of supplying stored power to the electric motor 3. The batteries 121 are, for example, secondary batteries such as lithium ion batteries or lead storage batteries.

[0021] The control device 13 controls the power supply device 11 and the battery unit 12. In this embodiment, the control device 13 controls various control elements in addition to the above. The control device 13 controls the inverter device 2 and the solenoid valve 6, for example.

[0022] The control device 13 is a so-called computer device, and includes a controller 131 and a memory 132. The controller 131 includes an arithmetic device such as a processor or a microprocessor. The memory 132 is a main storage device such as a read only memory (ROM) and a random access memory (RAM). The memory 132 may further include an auxiliary storage device such as a hard disk drive (HDD) or a solid state drive (SSD). The memory 132 stores various programs 132a and data. The controller 131 constituting the control device 13 performs various functions by reading the program 132a from the memory 132 and executing arithmetic processing according to the program.

[0023] The control device 13 may be configured as one piece of hardware, or may be configured as multiple pieces of hardware that can communicate with each other. The functions of the controller 131 may be realized by executing arithmetic processing according to a program, that is, by software, or may be realized by other methods. At least some of the functions of the control device 13 may be realized, for example, by using an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array). That is, at least some of the functions of the control device 13 may be realized by hardware using a dedicated IC or the like. At least some of the functions of the control device 13 may be realized by using both software and hardware.

[0024] The inverter device 2 converts the power supplied from the battery unit 12 from DC to AC and supplies it to the electric motor 3. That is, the work machine 100 is equipped with the electric motor 3 supplied with power from a plurality of batteries 121. Note that the inverter device 2 may be supplied with power from an AC power source 200 via a power feeder 11. The electric motor 3 driven via the inverter device 2 is a three-phase AC motor whose rotational speed is determined by a rotating magnetic field. The electric motor 3 operates hydraulic pumps 4, 5, thereby supplying pressure oil to the hydraulic actuator 9.

[0025] The electric motor 3 drives two hydraulic pumps, a pilot pump 4 and a main pump 5. The pilot pump 4 is a displacement type pump, and supplies hydraulic oil toward a remote control valve 7 provided on a work operation lever corresponding to each hydraulic actuator 9. The main pump 5 is a variable displacement type pump, and supplies hydraulic oil toward the hydraulic actuator 9. A control valve 8 that switches the hydraulic oil flow path by pilot pressure supplied from the remote control valve 7 is interposed between the main pump 5 and the hydraulic actuator 9. In addition, a solenoid valve 6 is interposed between the pilot pump 4 and the remote control valve 7.

[0026] The hydraulic actuator 9 is used as a general term for actuators powered by hydraulic oil pumped from the hydraulic pumps 4 and 5. In this embodiment, the hydraulic actuator 9 includes a boom cylinder 103d, an arm cylinder 103e, a bucket cylinder 103f, and a swing cylinder (not shown). That is, the work machine 100 is equipped with a work device 103 that is driven by the electric motor 3. In this embodiment, the hydraulic actuator 9 also includes the above-mentioned travel motor (not shown) and swing motor (not shown).

[0027] The control device 13 controls the rotation speed of the electric motor 3 via the inverter device 2, thereby controlling the amount of hydraulic oil discharged by the hydraulic pumps 4 and 5. Furthermore, the rotation speed of the electric motor 3 is detected by an encoder and fed back to the control device 13. In this way, the control device 13 realizes high-precision operation of the electric motor 3. Furthermore, the control device 13 controls the operation of the hydraulic actuator 9 by controlling the opening and closing of the solenoid valve 6. For example, the control device 13 closes the solenoid valve 6 to block the supply of hydraulic oil to the pilot port of the control valve 8 via the remote control valve 7, thereby stopping the operation of the hydraulic actuator 9.

[0028] In this embodiment, the work machine 100 equipped with the control system of the present invention is a backhoe, but this is an example. The work machine 100 equipped with the control system of the present invention may be a construction machine other than a backhoe, an agricultural machine, or the like. The control system of the present invention is also applicable to machines other than work machines, and is widely applicable to devices equipped with multiple batteries connected in parallel, such as automobiles, railway vehicles, and ships.

[0029] <2. Control system> Next, the control system 1 of the present embodiment will be described in detail.

[0030] FIG. 3 is a schematic diagram showing a circuit configuration of a control system 1 according to an embodiment of the present invention. In order to facilitate understanding of the configuration of the control system 1, FIG. 3 also includes elements other than the components of the control system 1. The elements other than the components of the control system 1 include an AC power source 200, an inverter device 2, an electric motor 3, and auxiliary machinery 10. However, at least some of these may be included in the control system 1. The auxiliary machinery 10 may be composed of one device or multiple devices. For example, the auxiliary machinery 10 includes the above-mentioned solenoid valve 6, a display device (not shown), and the like. The display device is a device having a monitor that shows various kinds of guidance to the operator of the work machine 100.

[0031] In Fig. 3, the thick solid line L1 indicates a high-voltage power transmission line (hereinafter referred to as a high-voltage power line). The thin solid line L3 indicates a control signal line for transmitting a control signal. The solid line L3 (middle line L3) of a thickness between the thick solid line and the thin solid line indicates a low-voltage power transmission line (hereinafter referred to as a low-voltage line).

[0032] As shown in Fig. 3, the batteries 121 included in the battery unit 12 are connected in parallel to each other. That is, the control system 1 includes the batteries 121 connected in parallel. Note that, although the number of batteries 121 is two in the example shown in Fig. 3, the number of batteries 121 may be three or more.

[0033] The battery unit 12 includes a plurality of batteries 121, a relay 122, and a battery management unit (BMU) 123.

[0034] The relay 122 is provided for each battery 121. That is, the control system 1 includes a relay 122 provided for each battery 121. Each relay 122 is connected in series to each battery 121. The relay 122 switches between a state (on state) in which the battery 121 is connected to a charge / discharge path and a state (off state) in which the battery 121 is disconnected from the charge / discharge path. That is, the relay 122 is turned on and off. In the example shown in FIG. 3, the first relay 122a is connected in series to the first battery 121a. Also, the second relay 122b is connected in series to the second battery 121b. The relay 122 may be a contact relay (mechanical relay) or a contactless relay (MOS FET relay, etc.).

[0035] The BMU 123 monitors and controls the multiple batteries 121. The BMU 123 manages, for example, the temperature and voltage of each battery 121. Each battery 121 is provided with a measuring means (not shown) for measuring the temperature and voltage. The BMU 123 switches each relay 122 on and off as necessary. In this embodiment, the BMU 123 may turn the relay 122 on and off in response to an instruction from the control device 13. That is, the control device 13 controls the on and off of the relay 122. By controlling the on and off of the relay 122, the charging and discharging of the battery 121 can be controlled. Therefore, it can be said that the control system 1 of this embodiment includes the control device 13 that controls the multiple batteries 121 via the relay 122.

[0036] As shown in Fig. 3, the control system 1 includes a DC / DC converter 14 and a control battery 15 in addition to the above-mentioned power supply device 11, battery unit 12, and control device 13. The DC / DC converter 14 converts a high-voltage DC voltage into a low-voltage DC voltage. The control battery 15 supplies power supply power to the control board. The control battery 15 is formed of a secondary battery such as a lead-acid battery or a lithium-ion battery.

[0037] The high-voltage line L1 connects the power supply device 11 and each battery 121 via the relay 122. The high-voltage line L1 also connects the power supply device 11 and the inverter device 2. The high-voltage line L1 also connects each battery 121 and the inverter device 2 via the relay 122. The high-voltage line L1 also connects each battery 121 and the DC / DC converter 14 via the relay 122.

[0038] The low-voltage line L3 connects the control battery 15 to the inverter device 2, the auxiliary devices 10, the control device 13, the DC / DC converter 14, and the BMU 123. That is, the control battery 15 supplies power source power to the multiple elements connected by the low-voltage line L3. The low-voltage line L3 also connects the power supply device 11 to the control device 13 and the BMU 123. The power supply device 11 is provided so as to be able to supply power source power to the control device 13 and the BMU 123 when connected to the AC power source 200. Note that even when the power supply device 11 is connected to the AC power source 200, the control battery 15 may be configured to supply power source power to the control device 13 and the BMU 123.

[0039] The control signal line L2 connects the control device 13 to the inverter device 2, the power supply device 11, and the BMU 123. That is, the control device 13 is provided so as to be able to control the multiple elements connected by these control signal lines L2.

[0040] Fig. 4 is a schematic diagram showing the state of the control system 1 when the electric motor 3 is used. Note that the electric motor 3 is assumed to be used, for example, when the work machine 100 performs work using the work implement 103. Also, in Fig. 4, the parts indicated by dashed lines are not used.

[0041] As shown in Fig. 4, when the electric motor 3 is in use, each relay 122 of the multiple batteries 121 is turned on, and power is supplied from each battery 121 to the inverter device 2. The inverter device 2 converts the supplied DC power into AC power and supplies it to the electric motor 3, thereby driving the electric motor 3. When the electric motor 3 is in use, the control device 13 receives source power from the control battery 15 and controls the inverter device 2 and the BMU 123. The control battery 15 also supplies source power to the inverter device 2, the accessories 10, and the BMU 123.

[0042] The electric motor 3 can also be driven by supplying power from the AC power supply 200 to the inverter device 2, but this embodiment does not assume such a usage method under normal circumstances. Also, the electric motor 3 can be driven by using only some of the multiple batteries 121, but this embodiment does not assume such a usage method under normal circumstances.

[0043] Although not shown, when the multiple batteries 121 are charged, the relays 122 of the multiple batteries 121 are turned on and power is supplied from the power supply device 11 to each battery 121. This charges each battery 121. When charging, the control device 13, which receives power from the power supply device 11, controls the power supply device 11 and the BMU 123. The power supply device 11 also supplies power to the BMU 123.

[0044] Note that the control battery 15 may also be charged when the multiple batteries 121 (battery units 12) are being charged. However, the control battery 15 may be configured to be charged by another method. For example, in the case where the work machine 100 is a hybrid work machine equipped with an electric motor 3 and an engine, the control battery 15 may be configured to store electric power supplied from a generator driven by the engine. Also, the control battery 15 may be configured to be charged using regenerative energy.

[0045] Incidentally, if there are batteries 121 among the parallel-connected batteries 121 whose voltage difference exceeds a voltage threshold (a predetermined voltage range), a current will be generated when the relays 122 of all the batteries 121 are turned on at the same time. The voltage difference exceeding the voltage threshold corresponds to the voltage difference being outside the voltage threshold. The voltage difference being equal to or less than the voltage threshold corresponds to the voltage difference being within the voltage threshold. The generation of a current when the relays 122 are turned on may cause a breakdown of the device. The voltage threshold is determined according to the battery 121 and the circuit configuration around it. In the battery unit 12, the internal resistance of the battery 121 and the resistance of the peripheral circuit tend to be small, and the voltage threshold tends to be relatively small. That is, in the battery unit 12 having the parallel-connected batteries 121, a current based on the above-mentioned voltage difference is likely to be generated, and measures against this are important. This measure will be described below.

[0046] In this embodiment, during normal use, it is unlikely that any of the multiple batteries 121 will have a voltage difference outside the voltage threshold (exceeding the voltage threshold). Such a battery 121 will occur, for example, when the battery is left for a long period of time with the relays 122 turned off. In addition, such a battery 121 will also occur when an abnormal usage state is executed, for example, when the relays 122 of only some of the multiple batteries 121 are turned on and the electric motor 3 is driven using only some of the batteries 121.

[0047] In this embodiment, when the control device 13 is in a discharge mode in which the battery 121 can be discharged, the control device 13 switches the relay 122 from off to on for some of the multiple batteries 121. Then, the control device 13 performs a discharge process in which the maximum value of the voltage difference between the multiple batteries 121 is within the voltage threshold. The maximum value of the voltage difference between the multiple batteries 121 is obtained by subtracting the voltage value (maximum value-minimum value) between the battery 121 with the maximum voltage value and the battery 121 with the minimum voltage value among the multiple batteries 121. Setting the maximum value of the voltage difference within the voltage threshold corresponds to setting the maximum value of the voltage difference equal to or less than the voltage threshold. Among the multiple batteries 121, there may be only one battery 121 with the maximum voltage value or there may be multiple batteries 121. Among the multiple batteries 121, there may be only one battery 121 with the minimum voltage value or there may be multiple batteries 121.

[0048] In more detail, the discharge process is executed when it is determined that there is a battery 121 whose maximum voltage difference among the multiple batteries 121 is outside the voltage threshold. The discharge process here is a process for balancing the voltages of the batteries 121 connected in parallel to reduce the voltage difference between them (parallel balancing process). The discharge mode in which discharge is possible (dischargeable mode) corresponds to a case other than the charge mode in which the battery 121 is charged. Before the start of the discharge process, all the relays 122 are turned off.

[0049] By performing such a discharge process for achieving parallel balance, it is possible to reduce the voltage difference between the multiple batteries 121 connected in parallel, and then turn on the relays 122 of all the batteries 121. In other words, it is possible to prevent a situation in which an unintended current occurs and equipment failure occurs when the relays 122 of all the batteries 121 are turned on.

[0050] Fig. 5 is a schematic diagram showing a state of the control system 1 during a discharge process for achieving parallel balance. In the example shown in Fig. 5, the maximum value of the voltage difference among the multiple batteries 121 corresponds to the voltage difference between two batteries 121. In the example shown in Fig. 5, the difference between the voltage of the first battery 121a and the voltage of the second battery 121b exceeds the voltage threshold (outside the voltage threshold).

[0051] As shown in FIG. 5, in the discharge process, the relay 122a is turned on for the first battery 121a, which is one of the multiple batteries 121a and 121b. That is, the relay 122a of the first battery 121a, which has a higher voltage among the multiple batteries 121a and 121b, is turned on, and the relay 122b of the second battery 121b, which has a lower voltage, is turned off. As a result, only the first battery 121a, which has a higher voltage, is discharged. The voltage of the first battery 121a decreases due to the discharge and approaches the voltage of the second battery 121b, so that the voltage difference between the first battery 121a and the second battery 121b falls within the voltage threshold (below the voltage threshold). When the voltage difference falls within the voltage threshold, the discharge of the first battery 121a is stopped.

[0052] In this embodiment, the battery 121 is discharged in the discharge process by utilizing the DC / DC converter 14 that converts the voltage down. In detail, the first battery 121a is discharged to supply power to a battery for another purpose connected to the DC / DC converter 14. The battery for another purpose is charged by the power supply. In this embodiment, the battery for another purpose is the control battery 15.

[0053] With this configuration, parallel balancing can be performed while charging a battery for another purpose (control battery 15). As a result, the possibility that the battery for another purpose (control battery 15) falls into an over-discharge state can be reduced. Furthermore, since discharging for parallel balancing is performed using the DC / DC converter 14, the discharge process can be controlled with a small current. As a result, parallel balancing can be performed with high accuracy.

[0054] In this embodiment, a part of the discharged power is also used as power supply power for the control device 13 and the BMU 123.

[0055] In the present embodiment, the control device 13 switches the relays 122 from off to on for some of the batteries 121 when in a charging mode in which the batteries 121 are charged. The control device 13 then performs a charging process to set the maximum value of the voltage difference between the batteries 121 within the voltage threshold (below the voltage threshold). In particular, the charging process is performed when it is determined that there is a battery 121 whose maximum value of the voltage difference between the batteries 121 is outside the voltage threshold. The charging process here is a process of balancing the voltages between the batteries 121 connected in parallel to reduce the voltage difference between them (a process of balancing between parallel batteries). Before the charging process starts, all the relays 122 are off. Charging in the charging mode is performed by the power supply device 11 using the AC power source 200.

[0056] By performing such a charging process for achieving parallel balance, it is possible to reduce the voltage difference between the multiple batteries 121 connected in parallel, and then turn on the relays 122 of all the batteries 121. In other words, it is possible to prevent a situation in which an unintended current is generated and equipment failure occurs when the relays 122 of all the batteries 121 are turned on.

[0057] Fig. 6 is a schematic diagram showing a state of the control system 1 during charging processing for parallel balancing. In the example shown in Fig. 6, the maximum value of the voltage difference among the multiple batteries 121 corresponds to the voltage difference between two batteries 121. In the example shown in Fig. 6, the difference between the voltage of the first battery 121a and the voltage of the second battery 121b exceeds the voltage threshold (outside the voltage threshold).

[0058] As shown in FIG. 6, in the charging process, the relay 122b is turned on for the second battery 121b, which is one of the multiple batteries 121a and 121b. That is, the relay 122b of the second battery 121b, which has a lower voltage among the multiple batteries 121a and 121b, is turned on, and the relay 122a of the first battery 121a, which has a higher voltage, is turned off. As a result, only the second battery 121b, which has a lower voltage, is charged by the power supplied from the power supply device 11. The voltage of the second battery 121b increases due to charging and approaches the voltage of the first battery 121a, so that the voltage difference between the first battery 121a and the second battery 121b falls within the voltage threshold (below the voltage threshold). When the voltage difference falls within the voltage threshold, the charging of the second battery 121b is stopped.

[0059] According to this configuration, the parallel balancing process is performed while power is being supplied from the power supply device 11, so that the parallel balancing process can be performed without reducing the charge capacity of the battery 121 constituting the battery unit 12 and the control battery 15. During the charging process for parallel balancing, the power supply device 11 supplies power to the control device 13 and the BMU 123.

[0060] <3. Specific examples of control methods> Next, a specific example will be described of a control method (control process) executed by the control system 1. The control method described below is a method in which a plurality of batteries 121 connected in parallel are controlled by the control device 13 via a relay 122 provided for each battery 121.

[0061] Fig. 7A is a flowchart showing a part of the flow of the control process executed by the control system 1. Fig. 7B is a flowchart showing another part of the flow of the control process executed by the control system 1. Fig. 7C is a flowchart showing another part of the flow of the control process executed by the control system 1, different from Fig. 7B.

[0062] The flowcharts shown in Figs. 7A to 7C can be realized by a computer device executing arithmetic processing according to a computer program. In this embodiment, the computer program is a program that causes a computer (controller 131) to execute a control method for controlling a plurality of batteries 121 connected in parallel via a relay 122 provided for each battery 121. The computer program is provided by being stored in various non-volatile recording media that can be read by a computer. The computer program may be composed of only one program, or may be composed of a plurality of programs that work together.

[0063] In step S1 (see FIG. 7A), the control device 13 monitors whether or not the key switch is turned on. The key switch is provided in the work machine 100. The key switch may be configured, for example, so that a key is inserted into a so-called key cylinder and an electric signal (a key-on signal and a key-off signal) is generated by a rotating action. However, the key switch may also be configured to generate an electric signal when authentication is obtained using an electronic key equipped with an immobilizer, or to generate an electric signal by a push button. Key-on is an instruction to start the electric motor 3, and is realized by the action of the operator of the work machine 100. If the key is turned on (Yes in step S1), processing proceeds to the next step S2. If the key is not turned on (No in step S1), processing proceeds to step S7 (see FIG. 7B).

[0064] In this embodiment, the key-on state is not a charge mode in which the battery 121 is charged, but is one form of a discharge mode in which the battery 121 can be discharged. Therefore, the process of step S1 can be said to be a process of detecting the discharge mode. That is, the control method of this embodiment includes detecting that the vehicle is in the discharge mode. Also, the program of this embodiment causes the computer to function as a means for executing the detection of the vehicle in the discharge mode.

[0065] In step S2, the control device 13 judges whether each of the plurality of batteries 121 is within the remaining charge threshold. Within the remaining charge threshold means that the remaining charge of the battery 121 is equal to or greater than the remaining charge threshold. The remaining charge threshold can be set, for example, for the SOC (State Of Charge) or voltage (cell voltage) of the battery 121. The remaining charge threshold is, for example, a value obtained by adding a margin to a value such as SOC when the battery 121 is in a state in which it should not be discharged. The state in which the battery 121 should not be discharged is determined, for example, by the battery specifications. In this embodiment, if the SOC or voltage value of any one of the plurality of batteries 121 is smaller than the remaining charge threshold, it is judged that the remaining charge is not within the remaining charge threshold. If the remaining charge is not within the remaining charge threshold (No in step S2), the process proceeds to step S3. If the remaining charge is within the remaining charge threshold (Yes in step S2), the process proceeds to step S4.

[0066] In step S3, the control device 13 performs a notification process for requesting the operator to charge the battery 121. The notification process may be, for example, a process of displaying a notification requesting charging on a display device (monitor). The notification process may also be a process of outputting sound from a sound output device (speaker) instead of or in addition to the process of displaying on a display device. When the notification process requesting charging of the battery 121 is completed, the process returns to step S1. In this case, the operator normally charges the battery 121 in accordance with the charge request. For this reason, the key is turned off in step S1, and the process proceeds to step S7 (see FIG. 7B).

[0067] In step S4, the control device 13 performs an existence / non-existence determination as to whether or not there is a battery among the plurality of batteries 121 whose maximum voltage difference among the plurality of batteries 121 is outside the voltage threshold value. In detail, the difference in voltage value (maximum value-minimum value) is obtained between the battery 121 with the maximum voltage value and the battery 121 with the minimum voltage value among the plurality of batteries 121. If the difference value is greater than the voltage threshold value, it means that there is a battery whose maximum voltage difference among the plurality of batteries 121 is outside the voltage threshold value. If it is determined that there is a battery by the existence / non-existence determination (Yes in step S4), the process proceeds to step S5. If it is determined that there is no battery by the existence / non-existence determination (No in step S4), the process proceeds to step S6.

[0068] The following can be said from the processing content of step S4. The control method of this embodiment includes determining, in the discharge mode, whether or not there is a battery for which the maximum value of the voltage difference among the plurality of batteries 121 is outside the voltage threshold. Furthermore, the program of this embodiment causes the computer to function as a means for executing the determination of whether or not there is a battery for which the maximum value of the voltage difference among the plurality of batteries 121 is outside the voltage threshold.

[0069] In step S5, the control device 13 performs the above-mentioned parallel balancing process (discharge process). That is, the control method of this embodiment includes performing a discharge process in which, in a discharge mode, the relays 122 are switched from off to on for some of the batteries 121, so that the maximum value of the voltage difference between the batteries 121 is within the voltage threshold. The program of this embodiment also causes the computer to function as a means for performing a discharge process in which, in a discharge mode, the relays 122 are switched from off to on for some of the batteries 121, so that the maximum value of the voltage difference between the batteries 121 is within the voltage threshold. With this configuration, it is possible to reduce the voltage difference between the batteries 121 connected in parallel, and then perform discharging by turning on the relays 122 of all the batteries 121. That is, when discharging is performed by turning on the relays 122 of all the batteries 121, it is possible to prevent a situation in which an unintended current is generated and equipment failure occurs.

[0070] In the above-described discharge process for achieving parallel balance, which has been described with reference to Fig. 5, the number of batteries 121 is two. An example of a discharge process for achieving parallel balance when the number of batteries 121 is more than two will be described with reference to Fig. 8. Fig. 8 is a schematic diagram for explaining a discharge process for achieving parallel balance.

[0071] In Fig. 8, as an example, the plurality of batteries 121 are nine batteries, namely, first to ninth batteries 121a to 121i. The left side of Fig. 8 shows the voltage relationship of the plurality of batteries 121a to 121i at the start of the discharge process. The right side of Fig. 8 shows the voltage relationship of the plurality of batteries 121a to 121i in the middle of the discharge process.

[0072] Among the multiple batteries 121a to 121i, the voltage value obtained by subtracting the voltage threshold Vth from the voltage value of the battery (maximum voltage battery) having the maximum voltage is the voltage value Va. The voltage threshold Vth is the same as the voltage threshold used in the processing of step S4, and is a constant value. When the voltage value of the maximum voltage battery fluctuates, the voltage value Va fluctuates. A battery having a voltage value lower than the voltage value Va corresponds to a low-voltage battery whose voltage difference with the maximum voltage battery is outside the voltage threshold (exceeds the voltage threshold). A battery having a voltage value equal to or higher than the voltage value Va corresponds to a battery whose voltage difference with the maximum voltage battery is within the voltage threshold (below the voltage threshold) (sometimes referred to as an within-threshold battery in the explanation related to FIG. 8).

[0073] The number of maximum voltage batteries may be more than one. Also, the maximum voltage battery may be a different battery during the discharge process from the battery at the start of the discharge. However, in FIG. 8, the first battery 121a is always the maximum voltage battery.

[0074] In the discharge process for achieving parallel balancing, the relays 122 of the within-threshold batteries among the multiple batteries 121a to 121i are turned on. These within-threshold batteries with their relays 122 turned on supply power to the control battery 15 via the DC / DC converter 14. The relays 122 of the low-voltage batteries are kept off. In the example shown in FIG. 8, at the start of the discharge process, the first to fourth batteries 121a to 121d are within-threshold batteries, and their relays 122 are turned on to perform discharge. The fifth to ninth batteries 121e to 121i are low-voltage batteries, and their relays 122 are kept off.

[0075] The first to fourth batteries 121a to 121d that have started discharging have their voltage values ​​reduced by discharging. In response to the reduction in voltage, the voltage value Va also drops, so that the batteries that were low-voltage batteries at the start of the discharging process become within-threshold batteries (i.e., no longer low-voltage batteries). The fifth to seventh batteries 121e to 121g that were low-voltage batteries at the start of the discharging process (see the left diagram of FIG. 8) become within-threshold batteries (no longer low-voltage batteries) in the right diagram of FIG. 8. The batteries that are no longer low-voltage batteries have their relays 122 switched from off to on to perform discharging. The discharging may be started when the batteries are no longer low-voltage batteries, or may be started after a predetermined time has elapsed since the batteries were no longer low-voltage batteries. By performing the discharging process as described above, all of the first to ninth batteries 121a to 121i can be within-threshold batteries. That is, the maximum value of the voltage difference between the multiple batteries 121 can be made within the voltage threshold. The discharge process for achieving parallel balancing is terminated when all of the first to ninth batteries 121a to 121i have become within-threshold batteries (when there is no low-voltage battery).

[0076] As can be seen from the above description, in the discharge process of this embodiment, the relays 122 of the batteries 121 other than the low-voltage battery whose voltage difference with the battery having the maximum voltage falls outside the voltage threshold are turned on. Also, in the discharge process of this embodiment, the relays 122 of the batteries that have ceased to be low-voltage batteries are changed from off to on. The discharge process may be performed, for example, by discharging the batteries 121 one by one in order starting from the battery with the highest voltage, so that the maximum voltage difference between the batteries 121 connected in parallel falls within the voltage threshold. However, if the configuration is such that the low-voltage battery is eliminated while the batteries other than the low-voltage battery are discharged simultaneously as in the above-described embodiment, the process of balancing between parallel batteries can be efficiently performed without complicating the process.

[0077] 7A, when the discharge process for achieving parallel balancing in step S5 is completed, the process returns to step S1. After the discharge process for achieving parallel balancing is completed, it is unlikely that there exists a battery 121 whose maximum voltage difference is outside the voltage threshold in step S4, and the process normally proceeds to step S6.

[0078] In step S6, the control device 13 performs a process of turning on all the relays 122. That is, all the batteries 121 are electrically connected in parallel. At this time, since the maximum value of the voltage difference between the multiple batteries 121 is within the voltage threshold value, no unintended current flows. By turning on all the relays 122, the electric motor 3 is started.

[0079] As can be seen from the above description, the control method of this embodiment includes switching the relays 122 of all of the batteries 121 from off to on without performing a discharge process when the maximum voltage difference between the batteries 121 is within the voltage threshold value in the discharge mode. Then, when the relays 122 of all of the batteries 121 are turned on, the batteries 121 are provided so as to be able to supply power to the electric motor 3 without going through the DC / DC converter 14. When a discharge process for achieving parallel balancing is not necessary, this fact can be appropriately determined, and high-voltage power can be supplied from the batteries 121 to the load.

[0080] As can be seen from the process of step S2 described above, the control method of this embodiment includes determining whether or not to execute a discharge process (a discharge process for achieving parallel balance) based on the remaining charge of the multiple batteries 121. In detail, the discharge process is not executed when the remaining charge is low. This makes it possible to protect the batteries 121.

[0081] If it is determined in step S4 above that there is a battery 121 whose maximum voltage difference is outside the voltage threshold, a discharge process (step S5 process) is performed to balance the parallel connections, and therefore the electric motor 3 does not start immediately even though the key is turned on. In this case, the operator may feel uneasy. Therefore, in this embodiment, as shown in FIG. 9, the control system 1 is provided with a display device 10a that displays that the control system 1 is on standby due to the discharge process. FIG. 9 is a schematic diagram showing an example of a screen of the display device 10a provided in the control system 1. The standby state may be notified by voice in addition to or instead of the display.

[0082] Referring to Fig. 7B, in step S7, the control device 13 determines whether or not a charging switch provided on the work machine 100, for example, has been turned on. The charging switch may be a switch operated by an operator, and such a switch may be a hardware switch such as an operation button or a software switch displayed on a touch panel. The charging switch may also be a switch that is automatically turned on by connecting a cable that supplies AC power source 200 to the power feeder 11. If the charging switch is on (Yes in step S7), processing proceeds to the next step S8. If the charging switch is off (No in step S7), processing proceeds to step S11 (see Fig. 7C).

[0083] In this embodiment, the state in which the charging switch is on corresponds to a charging mode in which the battery 121 is charged. Therefore, the process of step S7 can be said to be a process of detecting the charging mode. That is, the control method of this embodiment includes detecting the charging mode.

[0084] In step S8, the control device 13 performs an existence / non-existence determination as to whether or not there is a battery among the plurality of batteries 121 whose maximum voltage difference value among the plurality of batteries 121 is outside the voltage threshold value. This process is the same as that of step S4 described above. If it is determined that there is a battery (Yes in step S8), the process proceeds to step S9. If it is determined that there is no battery (No in step S8), the process proceeds to step S10.

[0085] The following can be said from the processing content of step S8. The control method of this embodiment includes determining, in the charging mode, whether or not there is a battery for which the maximum value of the voltage difference between the multiple batteries 121 is outside the voltage threshold. The program of this embodiment also causes the computer to function as a means for executing the determination, in the charging mode, of whether or not there is a battery for which the maximum value of the voltage difference between the multiple batteries 121 is outside the voltage threshold.

[0086] In step S9, the control device 13 performs the above-mentioned parallel balancing process (charging process). That is, the control method of this embodiment includes performing charging process in which the relays 122 are switched from off to on for some of the batteries 121 in the charging mode, and the maximum value of the voltage difference between the batteries 121 is within the voltage threshold. The program of this embodiment also causes the computer to function as a means for performing charging process in which the relays 122 are switched from off to on for some of the batteries 121 in the charging mode, and the maximum value of the voltage difference between the batteries 121 is within the voltage threshold. With this configuration, it is possible to reduce the voltage difference between the batteries 121 connected in parallel, and then charge all the batteries 121 with the relays 122 turned on. That is, it is possible to prevent a situation in which an unintended current is generated and the device breaks down when charging all the batteries 121 with the relays 122 turned on.

[0087] In the charging process for achieving parallel balance described above with reference to Fig. 6, the number of batteries 121 is two. An example of the charging process for achieving parallel balance when the number of batteries 121 is more than two will be described with reference to Fig. 10. Fig. 10 is a schematic diagram for explaining the charging process for achieving parallel balance.

[0088] 10, as an example, the plurality of batteries 121 are nine batteries, namely, first to ninth batteries 121a to 121i. The left side of Fig. 10 shows the voltage relationship of the plurality of batteries 121a to 121i at the start of the charging process. The right side of Fig. 10 shows the voltage relationship of the plurality of batteries 121a to 121i in the middle of the charging process.

[0089] Among the multiple batteries 121a to 121i, the voltage value obtained by adding the voltage threshold Vth to the voltage value of the battery (minimum voltage battery) having the minimum voltage is the voltage value Vb. The voltage threshold Vth is the same as the voltage threshold used in the processing of steps S4 and S8, and is a constant value. When the voltage value of the minimum voltage battery fluctuates, the voltage value Vb fluctuates. A battery having a voltage value higher than the voltage value Vb corresponds to a high-voltage battery whose voltage difference with the minimum voltage battery is outside the voltage threshold (exceeds the voltage threshold). A battery having a voltage value equal to or less than the voltage value Vb corresponds to a battery whose voltage difference with the minimum voltage battery is within the voltage threshold (below the voltage threshold) (sometimes referred to as an within-threshold battery in the explanation related to FIG. 10).

[0090] The number of minimum voltage batteries may be more than one. Also, the minimum voltage battery may be a different battery during the charging process from the battery at the start of charging. However, in FIG. 10, the ninth battery 121i is always the minimum voltage battery.

[0091] In the charging process for achieving parallel balancing, the relays 122 of the within-threshold batteries among the multiple batteries 121a to 121i are turned on. These within-threshold batteries with their relays 122 turned on are supplied with power from the power supply device 11 and charged. The relays 122 of the high-voltage batteries are kept off. In the example shown in FIG. 10, at the start of the charging process, the seventh to ninth batteries 121g to 121i are within-threshold batteries, and their relays 122 are turned on to charge them. The first to sixth batteries 121a to 121f are high-voltage batteries, and their relays 122 are kept off.

[0092] The seventh to ninth batteries 121g to 121i that have started charging have their voltage values ​​increased by charging. In response to the increase in the voltage, the voltage value Vb also increases, so that the batteries that were high-voltage batteries at the start of the charging process become within-threshold batteries (i.e., no longer high-voltage batteries). The fifth and sixth batteries 121e and 121f that were high-voltage batteries at the start of the charging process (see the left diagram of FIG. 10) become within-threshold batteries (no longer high-voltage batteries) in the right diagram of FIG. 10. The batteries that are no longer high-voltage batteries are charged by switching the relay 122 from off to on. The charging may be started when the batteries are no longer high-voltage batteries, or may be started after a predetermined time has elapsed since the batteries were no longer high-voltage batteries. By performing the charging process as described above, all of the first to ninth batteries 121a to 121i can be within-threshold batteries. That is, the maximum value of the voltage difference between the multiple batteries 121 can be made within the voltage threshold. The charging process for achieving parallel balancing is terminated when all of the first to ninth batteries 121a to 121i have become within-threshold batteries (when the high-voltage battery runs out).

[0093] As can be seen from the above description, in the charging process of this embodiment, the relay 122 of the battery other than the high-voltage battery, whose voltage difference with the battery having the minimum voltage is outside the voltage threshold, among the multiple batteries 121, is turned on. Also, in the charging process of this embodiment, the relay 122 of the battery that has ceased to be a high-voltage battery is changed from off to on. The charging process may be performed, for example, by charging the batteries 121 one by one in order starting from the battery with the lowest voltage, so that the maximum value of the voltage difference between the multiple batteries 121 connected in parallel falls within the voltage threshold. However, if the configuration is such that the high-voltage battery is eliminated while simultaneously charging the batteries other than the high-voltage battery as in the above-described embodiment, the parallel balancing process can be performed efficiently without complicating it.

[0094] When the charging process for achieving parallel balancing in step S9 is completed, the process returns to step S1 (see FIG. 7A). After the charging process for achieving parallel balancing is completed, it is unlikely that there is a battery 121 whose maximum voltage difference is outside the voltage threshold in step S8 (see FIG. 7B), and the process normally proceeds to step S10.

[0095] In step S10, the control device 13 performs a process of turning on all the relays 122. That is, all the batteries 121 are electrically connected in parallel. At this time, since the maximum value of the voltage difference between the plurality of batteries 121 is within the voltage threshold value, no unintended current flows. By turning on all the relays 122, all the batteries 121 are charged simultaneously using the power supply device 11.

[0096] As can be seen from the above description, the control method of this embodiment includes switching the relays 122 of all of the batteries 121 from off to on without performing a charging process for achieving parallel balancing when the maximum voltage difference between the batteries 121 is within the voltage threshold value in the charging mode. Then, when the relays 122 of all of the batteries 121 are turned on, the batteries 121 are charged by the supply of power from the power supply device 11. When the charging process for achieving parallel balancing is not necessary, it is possible to appropriately determine this and start simultaneous charging of the batteries 121.

[0097] 7C, in step S11, it is determined whether or not a certain time has passed since the relay 122 of each battery 121 was turned off. The certain time may be a time determined in advance by an experiment or the like, and may be, for example, several tens of days. If the certain time has passed (Yes in step S11), the process proceeds to the next step S12. If the certain time has not passed (No in step S11), the process returns to step S1 (see FIG. 7A).

[0098] In this embodiment, the state in which the process of step S11 is executed is not a charge mode in which the battery 121 is charged, and is therefore a form of a discharge mode in which the battery 121 can be discharged. For this reason, it can be said that the process of step S11 includes a process of detecting the discharge mode.

[0099] In step S12, the control device 13 starts a program in the background for performing processing for achieving parallel balance. After the background start-up, the process proceeds to the next step S13.

[0100] In step S13, the control device 13 judges whether or not each of the multiple batteries 121 is within the remaining capacity threshold. This process is the same as the process in step S2 described above. If the remaining capacity is not within the remaining capacity threshold (No in step S13), the control process shown in Figures 7A to 7C ends. If the remaining capacity is within the remaining capacity threshold (Yes in step S13), the process proceeds to step S14.

[0101] In step S14, the control device 13 performs an existence / non-existence determination as to whether or not there is a battery among the plurality of batteries 121 whose maximum voltage difference value among the plurality of batteries 121 is outside the voltage threshold value. This process is the same as step S4 described above. If it is determined that there is a battery (Yes in step S14), the process proceeds to step S15. If it is determined that there is no battery (No in step S14), the process returns to step S1.

[0102] In step S15, the control device 13 performs processing to achieve parallel balancing (discharging processing). This processing is the same as that in step S5 described above. In this embodiment, when the work machine 100 is in the key-off state and no charging instruction has been issued, discharging processing to achieve parallel balancing is automatically performed. This makes it possible to reduce the possibility that processing to achieve parallel balancing will be performed when the key is on. In other words, the start-up time of the electric motor 3 when the key is on can be shortened.

[0103] In this embodiment, when the process of step S15 is completed, the process returns to step S14. However, when the process of step S15 is completed, the process may return to step S1.

[0104] <4. Things to keep in mind> Various technical features disclosed in this specification may be modified in various ways without departing from the spirit of the technical creation. Furthermore, multiple embodiments and modifications shown in this specification may be combined to the extent possible.

[0105] <5. Notes> An exemplary control method of the present invention may be a method of controlling multiple batteries connected in parallel by a control device via a relay provided for each of the batteries, and may be configured (first configuration) to detect a discharge mode in which the batteries can be discharged, and when the batteries are in the discharge mode, to switch the relays from off to on for some of the multiple batteries and perform a discharge process such that the maximum value of the voltage difference between the multiple batteries is within a voltage threshold.

[0106] The control method of the above first configuration may be configured (second configuration) further including switching the relays of all of the multiple batteries from off to on without performing the discharge process when the discharge mode is in the discharge mode and the maximum value of the voltage difference is within the voltage threshold value.

[0107] In the discharge process in the control method of the above first or second configuration, the relay of a battery other than a low-voltage battery whose voltage difference with the battery having the maximum voltage falls outside the voltage threshold may be turned on (third configuration).

[0108] In the discharge process in the control method of the third configuration, the relay of the battery that has changed from the low-voltage battery to no longer be the low-voltage battery may be switched from off to on (fourth configuration).

[0109] The control method according to any one of the first to fourth configurations may be configured (fifth configuration) further comprising determining whether or not to execute the discharging process based on remaining charge amounts of the plurality of batteries.

[0110] In the control method according to any one of the first to fifth configurations, the battery may be discharged in the discharge process by utilizing a DC / DC converter that converts a voltage down (sixth configuration).

[0111] In the control method of the sixth configuration described above, when the relays of all of the plurality of batteries are turned on, the plurality of batteries may be configured to be able to supply power to the electric motor without going through the DC / DC converter (seventh configuration).

[0112] Furthermore, an exemplary control method of the present invention may be a method of controlling multiple batteries connected in parallel by a control device via a relay provided for each of the batteries, and may be configured (8th configuration) to include the following: when in a discharge mode in which the batteries can be discharged, a discharge process is performed for some of the multiple batteries by switching the relay from off to on, so that the maximum value of the voltage difference between the multiple batteries is within a voltage threshold; and when in a charge mode in which the batteries are charged, a charge process is performed for some of the multiple batteries by switching the relay from off to on, so that the maximum value of the voltage difference is within the voltage threshold.

[0113] The control method of the eighth configuration may be configured (ninth configuration) further including switching the relays of all of the plurality of batteries from off to on without performing the discharge processing when the discharge mode is in the discharge mode and the maximum value of the voltage difference is within the voltage threshold value.

[0114] In the discharge process in the control method of the above 8th or 9th configuration, the relay of a battery other than a low-voltage battery whose voltage difference with the battery having the maximum voltage falls outside the voltage threshold may be turned on (10th configuration).

[0115] In the discharge process in the control method of the tenth configuration, the relay of the battery that has ceased to be the low-voltage battery may be switched from off to on (eleventh configuration).

[0116] The control method according to any one of the eighth to eleventh configurations may be configured (a twelfth configuration) further comprising determining whether or not to execute the discharge process based on remaining charge amounts of the plurality of batteries.

[0117] In the control method according to any one of the eighth to twelfth configurations, the battery may be discharged in the discharge process by utilizing a DC / DC converter that converts a voltage down (a thirteenth configuration).

[0118] In the control method of the 13th configuration above, when the relays of all of the multiple batteries are turned on, the multiple batteries may be configured to be able to supply power to the electric motor without going through the DC / DC converter (14th configuration).

[0119] In addition, an exemplary control method of the present invention may be a method of controlling multiple batteries connected in parallel by a control device via a relay provided for each of the batteries, and may be configured (15th configuration) including: detecting a charging mode in which the batteries are charged; and, when the charging mode is selected, switching the relay from off to on for some of the multiple batteries to perform a charging process in which the maximum value of the voltage differences between the multiple batteries is within a voltage threshold.

[0120] Furthermore, an exemplary program of the present invention may be a program that causes a computer to execute a control method for controlling multiple batteries connected in parallel via a relay provided for each of the batteries, and may be configured to cause the computer to function as a means for detecting that the computer is in a discharge mode in which the batteries can be discharged, and, when the computer is in the discharge mode, switching the relays from off to on for some of the multiple batteries to perform a discharge process in which the maximum value of the voltage differences between the multiple batteries is within a voltage threshold (16th configuration).

[0121] Furthermore, an exemplary control system of the present invention may include a plurality of batteries connected in parallel, a relay provided for each of the batteries, and a control device that controls the plurality of batteries via the relay, and when the control device is in a discharge mode in which the batteries can be discharged, the control device may be configured to switch the relay from off to on for some of the plurality of batteries, and perform a discharge process in which the maximum value of the voltage difference between the plurality of batteries is within a voltage threshold value (17th configuration).

[0122] The control system of the seventeenth configuration may be configured (eighteenth configuration) including a display device that displays that the control system is on standby due to the discharge process.

[0123] In addition, an exemplary work machine of the present invention may be configured (19th configuration) including a control system of the above-mentioned 17th or 18th configuration, an electric motor supplied with power from the multiple batteries, and a work device operated by driving the electric motor. [Explanation of symbols]

[0124] 1. Control System 10a...Display device 13. Control device 3. Control device 5...Storage device 14 DC / DC converter 100...Work machinery 103...Work device 121 Battery 122 Relay 132a···Program

Claims

1. A method for controlling a plurality of batteries connected in parallel by a control device via a relay provided for each of the batteries, comprising: Detecting a discharge mode in which the battery can be discharged; When the battery is in the discharge mode, a discharge process is performed for some of the batteries by switching the relay from off to on, so that a maximum value of a voltage difference between the batteries is within a voltage threshold value. A control method comprising:

2. 2 . The control method according to claim 1 , further comprising: switching the relays of all of the batteries from off to on without performing the discharging process when the maximum value of the voltage differences is within the voltage threshold value in the discharging mode.

3. 3. The control method according to claim 1, wherein in the discharge process, the relays of the batteries other than a low-voltage battery whose voltage difference with a battery having a maximum voltage falls outside the voltage threshold are turned on.

4. The control method according to claim 3 , wherein in the discharging process, the relay of the battery that has ceased to be the low-voltage battery from the low-voltage battery is switched from off to on.

5. The control method according to claim 1 , further comprising determining whether or not to execute the discharge process based on remaining charge amounts of the plurality of batteries.

6. 3. The control method according to claim 1, wherein the battery is discharged in the discharge process by using a DC / DC converter that converts a voltage down.

7. 7. The control method according to claim 6, wherein when the relays of all of the plurality of batteries are turned on, the plurality of batteries are provided so as to be able to supply electric power to the electric motor without passing through the DC / DC converter.

8. A method for controlling a plurality of batteries connected in parallel by a control device via a relay provided for each of the batteries, comprising: When the battery is in a discharge mode capable of being discharged, a discharge process is performed for some of the batteries by switching the relay from off to on so that a maximum value of a voltage difference between the batteries is within a voltage threshold value. When the charging mode is for charging the battery, a charging process is performed for some of the batteries by switching the relay from off to on so that the maximum value of the voltage difference falls within the voltage threshold value. A control method comprising:

9. 9. The control method according to claim 8, further comprising: switching the relays of all of the batteries from off to on without performing the discharging process when the maximum value of the voltage differences is within the voltage threshold value in the discharging mode.

10. 10. The control method according to claim 8, wherein in the discharge process, the relays of the batteries other than a low-voltage battery whose voltage difference with a battery having a maximum voltage falls outside the voltage threshold are turned on.

11. The control method according to claim 10 , wherein in the discharging process, the relay of the battery that has ceased to be the low-voltage battery from the low-voltage battery is switched from off to on.

12. The control method according to claim 8 , further comprising determining whether or not to execute the discharge process based on remaining charge amounts of the plurality of batteries.

13. 10. The control method according to claim 8, wherein the battery is discharged in the discharge process by utilizing a DC / DC converter that converts a voltage down.

14. 14. The control method according to claim 13, wherein when the relays of all of the plurality of batteries are turned on, the plurality of batteries are provided so as to be able to supply electric power to the electric motor without passing through the DC / DC converter.

15. A method for controlling a plurality of batteries connected in parallel by a control device via a relay provided for each of the batteries, comprising: Detecting a charging mode in which the battery is charged; When in the charging mode, a charging process is performed for some of the plurality of batteries by switching the relay from off to on so that a maximum value of a voltage difference among the plurality of batteries is within a voltage threshold value. A control method comprising:

16. A program for causing a computer to execute a control method for controlling a plurality of batteries connected in parallel via a relay provided for each of the batteries, the program comprising: The computer, Detecting a discharge mode in which the battery can be discharged; When the battery is in the discharge mode, a discharge process is performed for some of the batteries by switching the relay from off to on, so that a maximum value of a voltage difference between the batteries is within a voltage threshold value. A program that serves as a means to execute a program.

17. A plurality of batteries connected in parallel; A relay provided for each of the batteries; A control device that controls the plurality of batteries via the relay; Equipped with When the control device is in a discharge mode in which the battery can be discharged, it switches the relay from off to on for some of the multiple batteries, and performs a discharge process such that the maximum value of the voltage difference between the multiple batteries is within a voltage threshold.

18. The control system according to claim 17, further comprising a display device that displays that the discharge process is in standby.

19. A control system according to claim 17 or 18; an electric motor supplied with power from the plurality of batteries; A working device that is driven by the electric motor; and A work machine comprising:

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