Electric work machine and control method for electric work machine

Abstract

To efficiently perform charging even when a sufficient charge time cannot be secured.SOLUTION: An electric working machine comprises: a plurality of battery packs; an operation apparatus that operates by electric power supplied from the battery packs; a battery monitoring device that detects the remaining capacity of each battery pack; and a control device that controls charging and discharging of the plurality of battery packs on the basis of the remaining capacity of each battery pack. In a discharge mode for supplying electric power to the operation apparatus, the control device determines one of the plurality of battery packs to be a battery pack for discharging that supplies electric power to the operation apparatus, and causes electric power to be supplied from the battery pack for discharging to the operation apparatus. In a charge mode for charging the battery packs, the control device determines preferentially a battery pack whose remaining capacity is large among the plurality of battery packs to be a battery pack for charging and causes the determined battery pack for charging to be charged.SELECTED DRAWING: Figure 1

Description

Technical Field

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[0001] The present invention relates to a power-operated work machine that operates on battery power and a control method for the power-operated work machine.

Background Art

[0002] Patent Document 1 discloses an electric construction machine that mounts a plurality of battery packs (battery systems) and selects any one of the battery packs for discharging or charging.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] [[ID=三十五]]However, in the technology of Patent Document 1, since the battery pack with the least remaining capacity among the plurality of battery packs is determined as the charging battery pack and charged, optimal charging may not be performed depending on the usage situation of the power-operated work machine.

[0005] For example, in a power-operated work machine in which output limitation is performed when the remaining capacity of the discharge battery pack drops below a threshold value, if sufficient charging time cannot be ensured, charging the battery pack with the least remaining capacity as the charging battery pack may only charge up to the remaining capacity near the threshold value, and output limitation may be performed immediately after charging, and the power charged in the charging time may not be efficiently utilized. More specifically, for example, in a power-operated work machine in which output limitation is applied when the remaining capacity of the battery becomes less than 20%, when the remaining capacity of the battery is charged from 10% to 30%, output limitation is applied only by operating for 10% after charging. In this case, although it is charged by 20%, only 10% of the work can be performed without output limitation after charging.

[0006] Furthermore, even if output limits are not imposed based on remaining capacity, if a battery pack with low remaining capacity is used as a charging battery pack and then subsequently used as a discharging battery pack, the remaining capacity of that battery pack may be depleted prematurely if sufficient charging time is not provided. This can lead to a decrease in work efficiency, such as the need to switch battery packs.

[0007] This invention was made to solve the problems of the prior art, and aims to enable efficient charging even when sufficient charging time cannot be secured. [Means for solving the problem]

[0008] An electric work machine according to one aspect of the present invention comprises a plurality of battery packs, an operating device that operates using power supplied from the battery packs, and the remaining capacity of each battery pack. and the temperature of each of the aforementioned battery packs The system includes a battery monitoring device that detects the remaining capacity of each battery pack, and a control device that controls the charging and discharging of a plurality of battery packs based on the remaining capacity of each battery pack, wherein in the discharge mode, the control device determines one of the plurality of battery packs to be the discharge battery pack that supplies power to the operating device, and causes the discharge battery pack to supply power to the operating device, and in the charging mode, among the plurality of battery packs, The remaining capacity is less than a predetermined first remaining capacity threshold and the temperature is less than a predetermined temperature threshold, Remaining capacity most Large battery pack to fill The battery pack for power supply has been selected, and the selected battery pack for charging has been put into operation. In the charging mode, if the temperature of the charging battery pack exceeds the temperature threshold, the charging battery pack is switched to the battery pack with the largest remaining capacity among the other battery packs whose remaining capacity is less than the first remaining capacity threshold and whose temperature is below the temperature threshold. If a battery pack is detected whose remaining capacity is less than the first remaining capacity threshold and whose temperature is below the temperature threshold, and whose remaining capacity is greater than the remaining capacity of the charging battery pack, the charging battery pack is switched to that battery pack. [Effects of the Invention]

[0009] With the above configuration, charging can be performed efficiently even if sufficient charging time cannot be secured. [Brief explanation of the drawing]

[0010] [Figure 1]This is an electrical block diagram of an electric work machine in the first embodiment. [Figure 2] This is a hydraulic circuit diagram of an electric work machine in the first embodiment. [Figure 3] This is a hydraulic circuit diagram of an electric work machine in a modified example of the first embodiment. [Figure 4] This diagram illustrates the series of discharge control steps of the control device according to the first embodiment. [Figure 5] This diagram illustrates a series of steps in the charge control of the control device according to the first embodiment. [Figure 6] This figure illustrates a series of steps in the charge control of the control device in a modified example of the first embodiment. [Figure 7] This is an electrical block diagram of an electric work machine in the second embodiment. [Figure 8] This is an example showing the relationship between the elapsed time, the remaining capacity of the charging battery pack, and the magnitude of the DC power output to the charging battery pack (charging current value) when constant current charging is performed. [Figure 9] Figure 1 illustrates a series of steps in the charge control of the control device according to the second embodiment. [Figure 10] Figure 2 illustrates a series of steps in the charge control of the control device according to the second embodiment. [Figure 11] Figure 3 illustrates the sequence of charge control steps of the control device according to the second embodiment. [Figure 12] This is an overall side view of the electric work machine. [Modes for carrying out the invention]

[0011] One embodiment of the present invention will be described below with reference to the drawings. [First Embodiment] First, let me explain the overall configuration of the electric work machine 1.

[0012] FIG. 12 is an overall side view of the power working machine 1. The power working machine 1 is a backhoe and includes a body (swing body) 2, a traveling device 10, a working device 20, and the like. On the body 2, a driver's seat 4 on which an operator sits and a protection mechanism 6 for protecting the driver's seat 4 from the front, rear, left, right, and above are provided.

[0013] In the following description, the direction in which the operator sitting on the driver's seat 4 faces (the direction of arrow A1 in FIG. 12) is referred to as the front, and the opposite direction (the direction of arrow A2 in FIG. 12) is referred to as the rear. Also, the left side of the operator (the front side in FIG. 12) is referred to as the left, and the right side of the operator (the back side in FIG. 12) is referred to as the right. Further, the horizontal direction, which is the direction orthogonal to the front-rear direction (the body front-rear direction), will be described as the body width direction.

[0014] The protection mechanism 6 shown in FIG. 12 has a configuration (cab specification) in which the driver's seat 4 is disposed within the protection mechanism 6. Note that the protection mechanism 6 is not limited to the cab specification, and may have a configuration (canopy specification) in which the upper part of the driver's seat 4 is covered with a roof (canopy), or may have a configuration in which the front-rear direction, the body width direction, and the upper part of the driver's seat 4 are open to the outside. The protection mechanism 6 of the cab specification partitions the space around the driver's seat 4 from the outside. That is, a driver's cab 4R having the driver's seat 4 is formed by the protection mechanism 6.

[0015] An operation device 5 for operating the power working machine 1 is provided around the driver's seat 4 inside the protection mechanism 6 (the driver's cab 4R).

[0016] The traveling device 10 is a device for traveling the body 2 and has a traveling frame (track frame) 11 and a traveling mechanism 12. The traveling frame 11 is a structure that attaches the traveling mechanism 12 around it and supports the body 2 on the upper part.

[0017] The traveling mechanism 12 is, for example, a crawler-type traveling mechanism. The traveling mechanisms 12 are provided on the left side and the right side of the traveling frame 11, respectively. The traveling mechanism 12 has idlers 13, drive wheels 14, a plurality of tumbler wheels 15, an endless crawler belt 16, and traveling motors ML, MR.

[0018] The idler 13 is located at the front of the running frame 11. The drive wheel 14 is located at the rear of the running frame 11. Multiple road wheels 15 are provided between the idler 13 and the drive wheel 14. The crawler belt 16 is wrapped around the idler 13, the drive wheel 14, and the road wheels 15.

[0019] The left-hand drive motor ML is included in the drive mechanism 12 located on the left side of the drive frame 11. The right-hand drive motor MR is included in the drive mechanism 12 located on the right side of the drive frame 11. These drive motors ML and MR are hydraulic motors. In each drive mechanism 12, the drive wheels 14 are rotated by the power of the drive motors ML and MR, causing the crawler belt 16 to circumferentially move around.

[0020] The aircraft body 2 is rotatable around the pivot axis X via the pivot bearing 3 on the running frame 11. It is supported by a motor. Inside the aircraft body 2, there is a slewing motor MT. The slewing motor MT consists of a hydraulic motor (hydraulic actuator). The aircraft body 2 rotates around the slewing axis X using the power of the slewing motor MT.

[0021] The working device 20 is supported at the front of the machine body 2. The working device 20 includes a boom 21, an arm 22, a bucket (working tool) 23, a dozer device 25, and hydraulic cylinders (hydraulic actuators) C1 to C5. The base end of the boom 21 is pivotally attached to a swing bracket 24 so as to be rotatable around a horizontal axis (an axis extending in the width direction of the machine body 2). As a result, the boom 21 can swing up and down (vertically). The arm 22 is pivotally attached to the tip of the boom 21 so as to be rotatable around a horizontal axis. As a result, the arm 22 can swing in the front-rear direction or up and down direction. The bucket 23 is provided at the tip of the arm 22 so as to be able to perform scooping and dumping operations.

[0022] The electric work implement 1 can be fitted with other work tools (hydraulic attachments) that can be driven by a hydraulic actuator, either in place of or in addition to the bucket 23. Examples of these other work tools include hydraulic breakers, hydraulic crushers, angle brooms, earth augers, pallet forks, sweepers, mowers, and snow blowers.

[0023] The swing bracket 24 swings from side to side by the extension and retraction of the swing cylinder C1 located inside the machine body 2. The boom 21 swings up and down (forward and backward) by the extension and retraction of the boom cylinder C2. The arm 22 swings up and down (forward and backward) by the extension and retraction of the arm cylinder C3. The bucket 23 performs scooping and dumping operations by the extension and retraction of the bucket cylinder (work tool cylinder) C4. The swing cylinder C1, boom cylinder C2, arm cylinder C3, and bucket cylinder C4 are composed of hydraulic cylinders (hydraulic actuators).

[0024] The dozer device 25 is mounted on the front of the traveling device 10. The dozer device 25 swings up and down by the extension and retraction of the dozer cylinder C5. The dozer cylinder C5 is attached to the traveling frame 11. The dozer cylinder C5 consists of a hydraulic cylinder (hydraulic actuator).

[0025] The electric work machine 1 moves using a travel device 10 having the aforementioned travel motors ML and MR, and performs work using a work device 20 having hydraulic cylinders C1 to C5 and a slewing motor MT. In other words, the slewing motor MT can be considered a work device 20 for which the electric work machine 1 performs work. Furthermore, in the following explanation, the travel motors ML and MR may be referred to as the hydraulic actuators of the travel system, and the hydraulic cylinders C1 to C5 and the slewing motor MT may be referred to as the hydraulic actuators of the work system.

[0026] Next, the electrical configuration of the electric work machine 1 will be described. Figure 1 is an electrical block diagram of the electric work machine 1 in the first embodiment. As shown in Figure 1, the electric work machine 1 includes a control device 30, a storage device 31, a battery unit 40, a charging port 42, a charger 43, a junction box 44, an inverter 45, an electric motor 46, a DC / DC converter 47, and a low-voltage battery 48.

[0027] The control device 30 is located inside the machine body 2 or the protection mechanism 6 and is composed of electrical and electronic circuits, a CPU, a program stored in memory, etc. The control device 30 controls various devices connected to the vehicle network N of the electric work machine 1. The control device 30 controls the operation of each part of the electric work machine 1, as shown in Figure 1.

[0028] For example, the control device 30 can perform discharge control (discharge control) to supply power (discharge) to various parts of the electric work machine 1 from the battery unit 40, and charge control (charge control) to charge the battery unit 40. The control device 30 can switch between a discharge mode, which supplies power to the powered operating equipment E (for example, the electric motor 46 described later), and a charge mode, which charges the battery unit 40, performing discharge control in the discharge mode and charge control in the charge mode.

[0029] At least some of the operating components of the operating device 5 of the electric work machine 1 are connected to the control device 30 in a manner that allows communication. The control device 30 controls the operation of each part of the electric work machine 1 based on the operation signals output from the operating device 5. As shown in Figure 1, the operating device 5 controls The device 30 has an operating lever 5a and an operating switch 5b as operating members connected to it. The operating lever 5a and the operating switch 5b can be operated by an operator seated in the driver's seat 4. In Figure 1, for convenience, the operating lever 5a and the operating switch 5b are each shown as a single block, but in reality, there are multiple operating levers 5a and operating switches 5b.

[0030] As shown in Figure 1, the operation switch 5b includes a mode selector switch 5b1. The mode selector switch 5b1 is a switch for inputting an instruction to switch between the discharge mode and the charge mode of the control device 30.

[0031] A starter switch 32 is connected to the control device 30. The starter switch 32 is located inside the protection mechanism 6 and can be operated by an operator seated in the driver's seat 4. The starter switch 32 is operated to start and stop the electric work implement 1. The control device 30 starts the various parts of the electric work implement 1 in response to the ON operation of the starter switch 32, and stops the various parts of the electric work implement 1 in response to the OFF operation of the starter switch 32.

[0032] Furthermore, as shown in Figure 1, a state detection device 35 is connected to the control device 30 to detect the state of the electric work implement 1. The state detection device 35 outputs the detected state of the electric work implement 1 as a detection signal to the control device 30. The state detection device 35 includes, for example, a rotation sensor 35a. The rotation sensor 35a is a sensor that detects the rotation speed of the electric motor 46, and the control device 30 calculates the rotation speed of the electric motor 46 based on the detection signal input from the rotation sensor 35a.

[0033] The storage device 31 is a storage medium such as an SSD (Solid State Drive) or HDD (Hard Disk Drive), and stores various information related to the electric work machine 1.

[0034] The battery unit 40 is a structure that can store electricity and discharge (output) the stored power. The battery unit 40 has multiple battery packs 41. All of the battery packs 41 have the same specifications (same discharge capacity, etc.). In the example shown in Figure 1, the battery unit 40 is provided with, for example, two battery packs 41. Note that the number of battery packs 41 in the battery unit 40 is not limited to two, and may be three or more. Also, the discharge capacities of the multiple battery packs 41 do not have to be the same.

[0035] Multiple battery packs 41 supply power to the operating equipment E. Each battery pack 41 is a secondary battery (storage battery) such as a lithium-ion battery, composed of at least one battery. When each battery pack 41 is composed of multiple batteries, these multiple batteries are electrically connected in series and / or parallel (at least one of series and parallel). Furthermore, each battery constituting each battery pack 41 has multiple cells inside, and these multiple cells are electrically connected in series and / or parallel. The multiple battery packs 41 have a discharge capacity that allows each part of the electric work machine 1 to operate for a predetermined time. The multiple battery packs 41 are connected in parallel to each other.

[0036] Furthermore, each of the multiple battery packs 41 is equipped with a BMU (battery management unit; battery monitoring device) 41a. The BMU 41a is located inside the corresponding battery pack 41. Note that the BMU 41a may be built into the corresponding battery pack 41 or installed on the outside of the battery pack 41.

[0037] The BMU41a controls the corresponding battery pack 41. The BMU41a controls the opening and closing of relays located inside the battery pack 41 to control the start and stop of power supply from the battery pack 41. The BMU41a also detects (monitors) the status of each corresponding battery pack 41. The BMU41a detects the temperature (measured temperature, actual temperature), voltage, current, or terminal voltage of the internal cells of the battery pack 41.

[0038] Furthermore, the BMU41a detects the remaining capacity (charge rate) of each battery pack 41 by a voltage measurement method, for example, based on the terminal voltage of the cells inside the battery pack 41. In this embodiment, the BMU41a detects the remaining capacity of the battery pack 41 as a percentage.

[0039] Furthermore, the method for detecting the remaining capacity of the battery pack 41 is not limited to the voltage measurement method, but also includes the coolant. Other methods such as the meter counter method, battery cell modeling method, and impedance track method may also be used. In addition, a capacity detection unit for detecting the remaining capacity of the battery pack 41 may be provided separately from the BMU 41a.

[0040] The charging port 42 has a connector (not shown) into which a charging cable (not shown) is fitted, and a connection detection device (connection detection sensor) 42a. An external power source (commercial power supply, etc.) is connected to the charging port 42 via the charging cable.

[0041] In addition to or instead of the mode switching switch 5b1 on the operating device 5, the charging port 42 may be provided with a connection detection device 42a that detects whether or not an external power supply is connected. The connection detection device 42a has a sensor or the like that detects when a charging cable is fitted into the charging port 42 and an external power supply is connected. Therefore, the control device 30 switches to charging mode when the connection detection device 42a detects that a charging cable is connected to the charging port 42, and switches to discharge mode when the connection detection device 42a detects that a charging cable is not connected to the charging port 42.

[0042] Furthermore, the control device 30 may switch between discharge mode and charge mode not by the mode switching switch 5b1 and the connection detection device 42a, but as another example, the control device 30 may switch to discharge mode when the starter switch 32 is turned ON (starting operation of the electric work machine 1), or switch to charge mode when the ON operation is not performed, or it may switch to discharge mode or charge mode based on the operation status of the operation lever 5a or operation switch 5b that operates the travel device 10 or work device 20.

[0043] The charger 43 is electrically connected to the charging port 42 and the junction box 44, and converts the three-phase AC power input from an external power source via the charging cable and charging port 42 into DC power, and supplies the DC power to the junction box 44. The charger 43 has a rectifier (not shown) that converts the three-phase AC power into DC power, and an electronic circuit (not shown) that adjusts the current and voltage of the DC power supplied to the junction box 44.

[0044] The electronic circuit is composed of, for example, switching elements, diodes, resistors, and electrolytic capacitors. In this embodiment, the charger 43 adjusts the current and voltage of the DC power supplied to the junction box 44 using the electronic circuit to charge the battery pack 41 with constant current charging and constant voltage charging. The control device 30 switches between constant current charging and constant voltage charging according to the remaining capacity of the battery pack 41. The current and voltage of the DC power used when performing constant current charging and constant voltage charging are defined by a predetermined table stored in the storage device 31. The charger 43 may also charge the battery pack 41 using only constant current charging.

[0045] The junction box 44 is electrically connected to the battery unit 40, the charger 43, the inverter 45, and the DC / DC converter 47. The junction box 44 outputs power input from the charger 43 to the battery unit 40. The junction box 44 also outputs power output from the battery unit 40 to the inverter 45 and the DC / DC converter 47.

[0046] The inverter 45 is electrically connected to the electric motor 46 and the junction box 44. It converts the DC power input from the battery unit 40 via the junction box 44 into three-phase AC power and supplies this three-phase AC power to the electric motor 46. The inverter 45 can also arbitrarily adjust the frequency and voltage of the power supplied to the electric motor 46.

[0047] The electric motor 46 is powered by the battery pack 41 and is driven by the supplied power to generate power. The electric motor 46 is electrically connected to the inverter 45 and is driven by the power supplied from the battery unit 40 (battery pack 41) via the inverter 45. The electric motor 46 is the drive source of the electric work machine 1 and is composed of, for example, a permanent magnet embedded type three-phase AC synchronous motor. The electric motor 46 has a rotatable rotor and a stator that generates the force to rotate the rotor.

[0048] The rotational speed of the electric motor 46 is controlled by the rotational speed control tool 5c, which is the operating device 5. As shown in Figure 1, the rotation speed control device 5c is connected to the control device 30 and outputs an operation signal to the control device 30. The rotation speed control device 5c is, for example, a dial-shaped switch such as a selector switch with multiple switching positions, and target values ​​for the rotation speed of the electric motor 46 are assigned to the multiple switching positions. The rotation speed control device 5c can set the target value of the rotation speed of the electric motor 46 within the range of 1500 to 2600 rpm / min.

[0049] The control device 30 transmits an instruction signal to the inverter 45 in response to the operation signal output from the rotation speed control device 5c. The inverter 45 adjusts the frequency and voltage of the power supplied to the electric motor 46 in response to the instruction signal output from the control device 30, thereby changing the motor speed of the electric motor 46.

[0050] The electric motor 46 may be any other type of synchronous motor, and may be either an AC motor or a DC motor. Furthermore, the rotational speed of the electric motor 46 is not limited to the rotational speed control device 5c, but may be controlled by other components of the control device 5. For example, the rotational speed of the electric motor 46 may be controlled based on a preset table according to the amount of operation of the control device 5.

[0051] The DC / DC converter 47 is a voltage converter that converts the voltage of the DC power input from the battery unit 40 via the junction box 44 to a different voltage. In this embodiment, the DC / DC converter 47 is a step-down converter that converts the high voltage of the battery unit 40 to a predetermined low voltage corresponding to the electrical components of the electric work machine 1. After voltage conversion, the DC / DC converter 47 supplies power to the low-voltage battery 48. The electrical components are operating devices E that are powered by the power supplied from the battery unit 40 via the DC / DC converter 47 and the low-voltage battery 48. The electrical components include, for example, a control device 30, a fan motor 50a of the radiator 50, a fan motor 52a of the oil cooler 52, an air conditioning unit 55, and various lamps (interior lights, work lights, headlights, signal lights, lights for operating members, etc.) 58.

[0052] The low-voltage battery 48 is a storage battery with a lower voltage than the battery unit 40. The low-voltage battery 48 is charged by power supplied from the DC / DC converter 47. The low-voltage battery 48 supplies power to the electrical components of the electric work machine 1.

[0053] The control device 30 controls the charging and discharging of multiple battery packs 41 based on the remaining capacity of each battery pack 41. The control device 30 determines and switches between the discharge battery packs that supply power to the operating device E in discharge mode and the charging battery packs that charge in charge mode. As a result, the control device 30 causes the discharge battery packs to supply power to the operating device E and the charging battery packs to be charged. As shown in Figure 1, the control device 30 has a control unit 30a that performs discharge control and charge control. The control unit 30a consists of a CPU, a program stored in memory, etc.

[0054] The control unit 30a switches between the connected state and the disconnected state of the connection switching device provided by the electric work machine 1 to determine and switch between the discharge battery pack in discharge mode and the charge battery pack in charge mode. The connection switching device includes a connection switching unit 41b of the battery pack 41 and a junction box 44. The connection switching unit 41b is composed of, for example, a relay or a switch, and is switchable between a connected state and a disconnected state.

[0055] In discharge mode, the control unit 30a determines one of the multiple battery packs 41 to be used for discharge, or switches the discharge battery pack to another battery pack. In discharge mode, the control unit 30a switches one of the connection switching units 41b to the connected state and the other connection switching unit 41b to the disconnected state. As a result, the control unit 30a causes one of the multiple battery packs 41 to output power to the junction box 44, and stops the output of power from the other battery pack 41. The control unit 30a controls the junction box 44 to connect the inverter 45 and DC / DC converter 47 to each battery pack 41, and disconnects the charger 43 (charging port 42) to each battery pack 41.

[0056] Furthermore, in charging mode, the control unit 30a selects one of the multiple battery packs 41. The control unit 30a determines which battery pack to charge, or switches the charging battery pack to another battery pack. In charging mode, the control unit 30a switches one of the connection switching units 41b to the connected state and the other connection switching unit 41b to the disconnected state. The control unit 30a controls the junction box 44 to disconnect the inverter 45 and DC / DC converter 47 for each battery pack 41, and connect the charger 43 (charging port 42) to each battery pack 41. As a result, the control unit 30a outputs power input from the junction box 44 to one of the battery packs 41, and stops power input to the other battery pack 41.

[0057] As described above, the control unit 30a controls the input and output of power to the multiple battery packs 41.

[0058] The following describes an example of an electrical component powered by a low-voltage battery 48, or an equipment in which such an electrical component is installed: a radiator 50, an oil cooler 52, and an air conditioning system 55.

[0059] The radiator 50 cools the cooling water used to cool high-heat-generating electrical equipment such as the battery unit 40, inverter 45, electric motor 46, and DC / DC converter 47. High-heat-generating electrical equipment refers to electrical equipment that generates more heat than other electrical equipment in the electric work machine 1 due to its operation using electricity. The cooling water is not just water, but is composed of a liquid that will not freeze even in cold climates.

[0060] The radiator 50 includes a fan motor 50a, a radiator fan (not shown) and a heat exchange section (not shown) that are rotationally driven by the power of the fan motor 50a. The fan motor 50a is driven by power supplied from a low-voltage battery 48.

[0061] The cooling pump 51 is installed in a cooling water passage (not shown) located within the machine body 2, together with the radiator 50 and the high-heat-generating electrical equipment mentioned above. The cooling pump 51 discharges and circulates cooling water into the cooling water passage.

[0062] The oil cooler 52 cools the hydraulic fluid that has passed through the hydraulic actuators ML, MR, MT, C1-C5 mentioned above, as well as the hydraulic pumps P1, P2 and control valve V described later. The oil cooler 52 includes a fan motor 52a, an oil cooler fan (not shown) and a heat exchange section (not shown) that are rotationally driven by the power of the fan motor 52a. The fan motor 52a is powered by the low-voltage battery 48.

[0063] The air conditioning system 55 is powered by the low-voltage battery 48 and provides air conditioning around the driver's seat 4 (driver's cab 4R). The air conditioning system 55 can provide at least one of heating or cooling of the driver's cab 4R. In this embodiment, the air conditioning system 55 includes an electric heating system 56 for heating and an electric cooling system 57 for cooling.

[0064] The electric heating device 56 operates using power from the low-voltage battery 48 to heat the inside of the protection mechanism 6. The electric heating device 56 is, for example, an electric heater. The electric heating device 56 has a heating element 56a, a fan motor 56b, and a heating fan (not shown). The heating element 56a generates high heat when energized. The fan motor 56b rotates the heating fan. The heating fan blows the ambient air heated by the heating element 56a into the inside of the protection mechanism 6. The fan motor 56b is powered by the low-voltage battery 48.

[0065] The electric cooling device 57 is powered by the low-voltage battery 48 and cools the inside of the protection mechanism 6. The electric cooling device 57 is, for example, an air conditioner.

[0066] Next, the hydraulic circuit K provided in the electric work machine 1 will be described. Figure 2 is a hydraulic circuit diagram of the electric work machine 1 in the first embodiment. As shown in Figure 2, the hydraulic circuit K is equipped with hydraulic equipment such as hydraulic actuators C1 to C5, ML, MR, MT, control valve V, hydraulic pumps P1, P2, hydraulic oil tank T, oil cooler 52, operating valves PV1 to PV6, unload valve 66, and oil passage 60.

[0067] Of the multiple hydraulic pumps P1 and P2, one is an operating hydraulic pump P1, and the other is a control hydraulic pump P2. These hydraulic pumps P1 and P2 are driven by the power of an electric motor 46.

[0068] The hydraulic pump P1 draws hydraulic fluid stored in the hydraulic fluid tank T and controls The hydraulic fluid is discharged to valve V. In Figure 2, for convenience, one hydraulic pump P1 is shown, but it is not limited to this, and any number of hydraulic pumps P1 may be provided to supply hydraulic fluid to each hydraulic actuator C1~C5, ML, MR, MT as appropriate.

[0069] The control hydraulic pump P2 outputs hydraulic pressure for signaling or control purposes by discharging hydraulic fluid from the hydraulic fluid tank T. In other words, the control hydraulic pump P2 supplies (discharges) pilot oil. The number of control hydraulic pumps P2 can be provided as needed.

[0070] The control valve V has multiple control valves V1 to V8. Each control valve V1 to V8 controls (adjusts) the flow rate of hydraulic fluid output from hydraulic pumps P1 and P2 to each hydraulic actuator C1 to C5, ML, MR, and MT. The swing control valve V1 controls the flow rate of hydraulic fluid supplied to the swing cylinder C1. The boom control valve V2 controls the flow rate of hydraulic fluid supplied to the boom cylinder C2. The arm control valve V3 controls the flow rate of hydraulic fluid supplied to the arm cylinder C3. The bucket control valve V4 controls the flow rate of hydraulic fluid supplied to the bucket cylinder C4. The dozer control valve V5 controls the flow rate of hydraulic fluid supplied to the dozer cylinder C5. The left travel control valve V6 controls the flow rate of hydraulic fluid supplied to the left travel motor ML. The right travel control valve V7 controls the flow rate of hydraulic fluid supplied to the right travel motor MR. The slewing control valve V8 controls the flow rate of hydraulic fluid supplied to the slewing motor MT.

[0071] The control valves PV1 to PV6 operate in response to the operation of various control levers 5a provided on the control device 5. In proportion to the amount of operation (operation) of each control valve PV1 to PV6, pilot oil acts on each control valve V1 to V8, causing the spools of each control valve V1 to V8 to move. Then, an amount of hydraulic fluid proportional to the amount the spools of each control valve V1 to V8 are moved is supplied to the controlled hydraulic actuators C1 to C5, ML, MR, and MT. Furthermore, each hydraulic actuator C1 to C5, ML, MR, and MT is driven in accordance with the amount of hydraulic fluid supplied from each control valve V1 to V8.

[0072] In other words, when the operating lever 5a is operated, the hydraulic fluid (pilot oil) acting on the control valves V1 to V8 is adjusted, thereby controlling the control valves V1 to V8. Then, the amount of hydraulic fluid supplied from the control valves V1 to V8 to the hydraulic actuators C1 to C5, ML, MR, and MT is adjusted, thereby controlling the driving and stopping of the hydraulic actuators C1 to C5, ML, MR, and MT.

[0073] The oil passage 60 is a passage that connects the various parts of the hydraulic circuit K and supplies hydraulic fluid or pilot oil to each part. The oil passage 60 includes a first oil passage 61, a second oil passage 62, a first suction oil passage 63, a second suction oil passage 64, and a limiting oil passage 65.

[0074] The first suction oil passage 63 is a passage through which the hydraulic oil drawn by the operating hydraulic pump P1 from the hydraulic oil tank T flows. The second suction oil passage 64 is a passage through which the hydraulic oil drawn by the control hydraulic pump P2 from the hydraulic oil tank T flows.

[0075] The first oil passage 61 is a flow path that directs the hydraulic fluid discharged by the operating hydraulic pump P1 towards the control valves V1 to V8 of the control valve V. The first oil passage 61 branches into multiple paths within the control valve V and is connected to each of the control valves V1 to V8.

[0076] The second oil passage 62 is a flow path that directs the hydraulic fluid that has passed through control valves V1 to V8 toward the hydraulic fluid tank T. The hydraulic fluid tank T stores the hydraulic fluid. The second oil passage 62 includes a reciprocating oil passage 62a and a discharge oil passage 62b.

[0077] Multiple reciprocating oil passages 62a are provided to connect each control valve V1 to V8 to the controlled hydraulic actuators C1 to C5, ML, MR, and MT in pairs. The reciprocating oil passages 62a are the flow paths that supply hydraulic fluid from the connected control valves V1 to V8 to the hydraulic actuators C1 to C5, ML, MR, and MT, and return hydraulic fluid from the hydraulic actuators C1 to C5, ML, MR, and MT to the control valves V1 to V8. One end of the discharge oil passage 62b branches into multiple sections, each connected to one of the control valves V1 to V8. The other end of the discharge oil passage 62b is connected to the hydraulic fluid tank T.

[0078] A portion of the hydraulic fluid that flows through the first oil passage 61 to one of the control valves V1 to V8 passes through the control valves V1 to V8 and through one of the reciprocating oil passages 62a, and is supplied to the controlled hydraulic actuators C1 to C5, ML, MR, and MT. The hydraulic fluid discharged from ML, MR, and MT returns to the connected control valves V1 to V8 through the other end of the reciprocating oil passage 62a, passes through the control valves V1 to V8, and flows through the discharge oil passage 62b.

[0079] Furthermore, the remaining hydraulic fluid that has flowed through the first oil passage 61 to one of the control valves V1 to V8 is not supplied to the hydraulic actuators C1 to C5, ML, MR, and MT, but instead passes through the control valves V1 to V8 and flows into the discharge oil passage 62b. An oil cooler 52 is provided in the discharge oil passage 62b. The oil cooler 52 cools the hydraulic fluid that has flowed from one of the control valves V1 to V8 through the discharge oil passage 62b.

[0080] The hydraulic fluid cooled by the oil cooler 52 returns to the hydraulic fluid tank T through the discharge oil passage 62b. As described above, the oil passages 61, 62, and 63 are arranged to circulate the hydraulic fluid to the hydraulic fluid tank T, the hydraulic pump P1, the control valves V1 to V8 of the control valve V (and some of the hydraulic fluid also goes to the hydraulic actuators C1 to C5, ML, MR, and MT).

[0081] The restricting oil passage 65 is a passage that carries the hydraulic fluid discharged by the control hydraulic pump P2 to the control valves PV1 to PV6. One end of the restricting oil passage 65 is connected to the control hydraulic pump P2, and the other end branches into multiple passages, each connected to the primary port of the control valves PV1 to PV6.

[0082] An unload valve 66 is provided in the restricted oil passage 65. The unload valve 66 shuts off the supply of hydraulic fluid from the operating hydraulic pump P1 to the hydraulic actuators C1-C5, ML, MR, and MT, thereby preventing the driving of the hydraulic actuators C1-C5, ML, MR, and MT, i.e., the driving of the travel device 10 and the work device 20.

[0083] The unload valve 66 is switched between a supply position and a shut-off position in response to an instruction signal from the control device 30. The control device 30 switches between demagnetizing and energizing the unload valve 66 based on an operation signal output from the unload lever (not shown) included in the operation lever 5a. The unload valve 66 is biased by a spring in the direction that switches it to the shut-off position (unload position), and is set to the shut-off position when the solenoid is demagnetized, and switched to the supply position when the solenoid is energized. The unload valve 66 is energized when the unload lever is lowered and demagnetized when the unload lever is raised.

[0084] When the unload valve 66 switches to the supply position, the hydraulic fluid discharged from the control hydraulic pump P2 into the limiting oil passage 65 is supplied to the operating valves PV1 to PV6, enabling the operation of the control valves V1 to V8. This also enables the operation of the hydraulic actuators C1 to C5, ML, MR, MT, the travel device 10, and the work device 20. The hydraulic fluid discharged from the operating valves PV1 to PV6 returns to the hydraulic fluid tank T through another discharge oil passage (not shown).

[0085] On the other hand, when the unload valve 66 is switched to the shut-off position, the hydraulic fluid discharged from the control hydraulic pump P2 into the restricting oil passage 65 is discharged into the hydraulic fluid tank T, and is no longer supplied to the operating valves PV1 to PV6 (supply stop), thus prohibiting the operation of the control valves V1 to V8. In addition, this also prohibits the operation of the hydraulic actuators C1 to C5, ML, MR, MT, the work device 20, and the travel device 10.

[0086] In the above-described embodiment, the electric motor 46 is driven by power supplied from the battery pack 41, the hydraulic pumps P1 and P2 are driven by the power of the electric motor 46, the hydraulic actuators C1 to C5, ML, MR, and MT are driven by the hydraulic fluid discharged from the hydraulic pumps P1 and P2, and the traveling device 10 and the working device 20 are driven by the power of the hydraulic actuators C1 to C5, ML, MR, and MT. However, the configuration is not limited to this. For example, the traveling device 10 and the working device 20 may be driven by power supplied from the battery pack 41, and some or all of the actuators provided on the traveling device 10 and the working device 20 may be made of electric actuators, and these electric actuators may be driven by power from the battery pack 41, and the traveling device 10 and the working device 20 may be driven by the power of these electric actuators.

[0087] The following describes in detail the discharge control and charge control methods of the electric work machine 1.

[0088] The control unit 30a (control device 30) determines the battery pack to be discharged in accordance with the operation of the selection tool 5d as a discharge control. The selection tool 5d selects any of the multiple battery packs 41. It is an operating member that accepts one selection operation. In this embodiment, the selection tool 5d is provided on a meter panel that displays the status of the electric work machine 1 (for example, the rotation speed of the electric motor 46 or the remaining capacity of the battery pack 41). The meter panel is a display device and has a display screen that is either a liquid crystal panel, a touch panel, or another type of panel. The meter panel can display the status of the electric work machine 1 as an image, and the selection tool 5d is the display image displayed on the display screen. The display device is connected to the control device 30 so as to be communicative, and the operation signal of the selection tool 5d is output to the control device 30 (control unit 30a). Based on the operation signal output from the selection tool 5d, the control unit 30a determines one of the multiple battery packs 41 to be used as the discharge battery pack.

[0089] Furthermore, in discharge mode, the control device 30 acquires the remaining capacity of each battery pack 41 detected by the BMU 41a and performs discharge control based on the remaining capacity. As part of the discharge control, the control device 30 performs a limiting process to limit the power supplied from the discharge battery pack to the operating equipment E if the remaining capacity of the discharge battery pack is less than a predetermined first threshold. The operating equipment E includes an electric motor 46 that is powered by the discharge battery pack. The operating equipment E can be any equipment that operates using the power supplied from the battery pack 41, and may include equipment driven by the power generated by the electric motor 46 powered by the battery pack 41 (for example, a travel device 10 and a work device 20). The operating equipment E may also include equipment that operates using the power supplied from a low-voltage battery 48 that is powered by the battery pack 41 (for example, a radiator 50, an oil cooler 52, an air conditioning system 55, or various lamps 58).

[0090] As shown in Figure 1, the control device 30 has a limiting processing unit 30b. The limiting processing unit 30b obtains the remaining capacity of the discharge battery pack from the BMU 41a and determines whether the remaining capacity is less than a first threshold. The first threshold is a predetermined value pre-stored in the storage device 31, for example, defined as 20%. Note that the first threshold is not limited to 20%, but may be 15% or 25%. Furthermore, the first threshold may be changed to any value by operating an input device (for example, a display device, not shown) connected to the control device 30 and which inputs information. In addition, the first threshold may be defined within a predetermined range of values ​​including an upper limit and a lower limit in order to suppress chattering.

[0091] The limiting processing unit 30b performs a predetermined limiting process when it determines that the remaining capacity of the discharge battery pack is below a first threshold. The limiting processing unit 30b consists of a CPU, a program stored in memory, etc. The limiting process performed by the limiting processing unit 30b is a process that suppresses the consumption of power output from the discharge battery pack to the operating device E.

[0092] For example, the limiting process includes a process (first limiting process) that limits the upper limit of the rotational speed of the operating device E (electric motor 46) when the remaining capacity of the discharge battery pack is less than a first threshold. The limiting processing unit 30b calculates the rotational speed of the electric motor 46 based on the detection signal obtained from the rotation sensor 35a. In addition, regardless of the operation signal output from the rotational speed control device 5c, the limiting processing unit 30b corrects the instruction signal output to the inverter 45 and limits the rotational speed of the electric motor 46 to less than a predetermined upper limit. The upper limit is a predetermined value, defined as, for example, 1400 rpm. Note that the upper limit is not limited to 1400 rpm, but may be 1300 rpm or 1500 rpm. Furthermore, the upper limit may be changed to any value by operating the input device. Furthermore, the upper limit may be defined within a predetermined range of values ​​including an upper limit and a lower limit in order to suppress chattering.

[0093] The limiting process does not need to be limited to a first limiting process that limits the rotational speed of the electric motor 46, but rather any process that suppresses the consumption of power output from the discharge battery pack. For example, the limiting processing unit 30b may, as a limiting process, perform a process to limit the output of heating or cooling from the operating device E (air conditioner 55) (for example, the temperature of the air blown from the air conditioner 55 around the driver's seat 4, or the upper limit of the set temperature) when the remaining capacity of the discharge battery pack is less than the first threshold (second limiting process). In the second limiting process, the limiting processing unit 30b may limit the output of heating and / or cooling (at least one of heating and / or cooling) or cut off the power supply to the air conditioner 55. This limits the heating or cooling output of the air conditioning unit 55.

[0094] Furthermore, the limiting processing unit 30b may, as a limiting process, perform a process to limit the upper limit of the rotational speed of the operating device E (fan motor 50a) when the remaining capacity of the discharge battery pack is less than the first threshold (third limiting process). In the third limiting process, the limiting processing unit 30b reduces the rotational speed of the fan motor 50a or limits the rotational speed of the fan motor 50a to zero by cutting off the power supply to the fan motor 50a, compared to the case where the third limiting process is not performed.

[0095] Furthermore, the limiting processing unit 30b may, as a limiting process, perform a process to limit the upper limit of the rotational speed of the operating device E (fan motor 52a) when the remaining capacity of the discharge battery pack is less than the first threshold (fourth limiting process). In the fourth limiting process, the limiting processing unit 30b reduces the rotational speed of the fan motor 52a or limits the rotational speed of the fan motor 52a to zero by cutting off the power supply to the fan motor 52a, compared to the case where the fourth limiting process is not performed.

[0096] Furthermore, the limiting processing unit 30b may perform a limiting process if the remaining capacity of the discharge battery pack is less than the first threshold (fifth limiting process). In the fifth limiting process, the limiting processing unit 30b limits the power supplied from the low-voltage battery 48 to the lamp 58 and reduces the illuminance of the lamp 58.

[0097] Furthermore, the limiting processing unit 30b may perform a limiting process to restrict the operation of the operating equipment E (traveling device 10 and working device 20) when the remaining capacity of the discharge battery pack is less than the first threshold (sixth limiting process). In the sixth limiting process, the limiting processing unit 30b switches the unload valve 66 to the shut-off position to restrict the operation of the traveling device 10 and working device 20.

[0098] In the above-described embodiment, as shown in Figure 2, a single unload valve 66 is provided in the restricting oil passage 65, and when the unload valve 66 is switched to the shut-off position, the supply to all operating valves PV1 to PV6 is cut off. However, as shown in the modified example in Figure 3, the restricting oil passage 65 branches into multiple branches downstream, and multiple unload valves 66 are provided downstream. The restricting processing unit 30b performs a process to restrict the driving of the traveling device 10 and the driving of the working device 20 separately as a restricting process. Figure 3 is a hydraulic circuit diagram of the electric work machine 1 in a modified example of the first embodiment.

[0099] First, the restricting oil passage 65 and unload valve 66 in the modified example will be described. As shown in Figure 3, in the modified example, the restricting oil passage 65 branches downstream into multiple parts, and has a first part 65a connected to operating valves PV1 and PV2, and a second part 65b connected to operating valves PV3 to PV6. The first part 65a is provided with a first unload valve 66A, and the second part 65b is provided with a second unload valve 66B.

[0100] When the first unload valve 66A is switched to the supply position, hydraulic fluid is supplied to the control valves PV1 and PV2, enabling the operation of the travel device 10. On the other hand, when the first unload valve 66A is switched to the shut-off position, hydraulic fluid is no longer supplied to the control valves PV1 and PV2, and the operation of the hydraulic actuators of the travel system is prohibited. Therefore, by changing the switching position of the first unload valve 66A, it is possible to change whether the drive of the travel device 10 is prohibited or permitted.

[0101] When the second unload valve 66B is switched to the supply position, hydraulic fluid is supplied to the control valves PV3 to PV6, enabling operation of the hydraulic actuators of the work system. On the other hand, when the second unload valve 66B is switched to the shut-off position, hydraulic fluid is no longer supplied to the control valves PV3 to PV6, and operation of the hydraulic actuators of the work system is prohibited. Therefore, by changing the switching position of the second unload valve 66B, it is possible to change whether the operation of the work device 20 is prohibited or permitted.

[0102] Next, the limiting process in a modified version of the first embodiment will be described. In the modified version, the limiting processing unit 30b performs a limiting process to restrict the operation of the operating device E (travel device 10) when the remaining capacity of the discharge battery pack is less than the first threshold (seventh limiting process). In the seventh limiting process, the limiting processing unit 30b switches the first unload valve 66A to the shut-off position to restrict the operation of the travel device 10.

[0103] Furthermore, the limiting processing unit 30b performs a limiting process where the remaining capacity of the discharge battery pack is the first threshold. If the value is less than the specified value, the operation of the actuator E (working device 20) is restricted (8th restriction process). In the 8th restriction process, the restriction processing unit 30b switches the second unload valve 66B to the shut-off position to restrict the operation of the working device 20.

[0104] In the modified example, when the sixth limiting process is performed, the limiting processing unit 30b switches both the first unload valve 66A and the second unload valve 66B to the shut-off position, thereby limiting the driving of the traveling device 10 and the working device 20.

[0105] Furthermore, in the sixth to eighth limiting processes, the limiting processing unit 30b only needs to limit the driving of at least the traveling device 10 and / or the working device 20 (at least one of the traveling device 10 and the working device 20), and the method of limiting is not limited to the method described above. For example, if the operating valves PV1 to PV6 are composed of solenoid valves that change their opening degree in response to instruction signals from the control device 30, and the control device 30 outputs instruction signals to the operating valves PV1 to PV6 based on the operation signals input from the operating member (e.g., the operating lever) and a predetermined table that associates the operation signals with instruction signals, the limiting processing unit 30b may limit the driving of the traveling device 10 and / or the working device 20 by correcting the operation signals and the instruction signals based on the table so that the opening degree of the operating valves PV1 to PV6 becomes smaller.

[0106] Furthermore, the limiting processing unit 30b may perform a combination of any of the first to eighth limiting processing as a limiting process, or it may perform a different combination of processing depending on the remaining capacity of the discharge battery pack.

[0107] Furthermore, the limiting processing unit 30b may perform a predetermined limiting process not only when it determines that the remaining capacity of the discharge battery pack is less than the first threshold, but also when it determines that the temperature of the discharge battery pack is above a predetermined value (the fifth threshold). In this embodiment, the limiting processing unit 30b obtains the temperature of the discharge battery pack from the BMU 41a and determines whether the temperature is above the fifth threshold. The fifth threshold is a predetermined value pre-stored in the storage device 31, for example, defined as 45°C. In this embodiment, if the limiting processing unit 30b determines that the temperature of the discharge battery pack is above the fifth threshold, it performs the first limiting process.

[0108] Furthermore, the fifth threshold is not limited to 45°C, but may be 40°C or 50°C. Also, the fifth threshold may be changed to any value by operating the input device. Additionally, the fifth threshold may be defined within a predetermined range of values, including an upper and lower limit, in order to suppress chattering.

[0109] Furthermore, the control unit 30a (control device 30), as part of the charging control, prioritizes selecting the battery pack 41 with the largest remaining capacity from among the multiple battery packs 41 whose remaining capacity is less than the second threshold (which is greater than the first threshold) as the battery pack for charging. In addition, the control unit 30a prioritizes the battery pack 41 with the largest remaining capacity from among the battery packs 41 whose remaining capacity is less than the second threshold, by selecting them as the battery pack for charging in order from the battery pack 41 with the largest remaining capacity.

[0110] The control unit 30a obtains the remaining capacity of each battery pack 41 from the BMU 41a and determines whether the remaining capacity is less than a second threshold. The second threshold is the target value for completing the charging of the battery pack 41. The second threshold is a predetermined value pre-stored in the storage device 31, for example, defined as 100%.

[0111] Furthermore, the second threshold is not limited to 100%, but may be 90% or 95%. The second threshold may also be changeable to any value by operating the input device. Additionally, the second threshold may be defined within a predetermined range of values, including upper and lower limits, to suppress chattering.

[0112] Furthermore, the conditions under which the control unit 30a determines the battery pack to be charged are not limited to the remaining capacity of each battery pack 41, but may also be determined based on other conditions. For example, the control unit 30a may determine the battery pack to be charged based on the temperature of each battery pack 41 in addition to the remaining capacity of each battery pack 41. In charging mode, the control unit 30a determines the battery pack 41 with the largest remaining capacity among the battery packs 41 whose remaining capacity is less than a second threshold and whose temperature is less than a predetermined third threshold as the battery pack to be charged.

[0113] The control unit 30a obtains the temperature of each battery pack 41 from the BMU 41a and determines whether the temperature is below a third threshold. The third threshold is the maximum temperature when the charging efficiency of the battery pack 41 is relatively stable. The third threshold is a predetermined value pre-stored in the storage device 31, for example, defined as 45°C.

[0114] Furthermore, the third threshold is not limited to 45°C; it may be 40°C or 50°C. Also, the third threshold may be changed to any value by operating the input device. Additionally, the third threshold may be defined within a predetermined range of values, including an upper and lower limit, to suppress chattering.

[0115] Furthermore, as a condition for determining the battery pack to be charged, the control unit 30a may, for example, if there are multiple battery packs 41 with the largest remaining capacity, determine the battery pack 41 with the lowest temperature among them as the battery pack to be charged.

[0116] Next, we will explain how the control unit 30a switches the charging battery pack when the charging battery pack is being charged. In charging mode, when the temperature of the charging battery pack exceeds the third threshold, the control unit 30a switches the charging battery pack to the battery pack 41 with the largest remaining capacity among the other battery packs 41 whose remaining capacity is less than the second threshold and whose temperature is less than the third threshold.

[0117] Furthermore, in charging mode, if the temperature of the charging battery pack is below the third threshold and the remaining capacity of the charging battery pack reaches the second threshold, the control unit 30a switches the charging battery pack to the battery pack 41 with the largest remaining capacity among the other battery packs 41 whose remaining capacity is below the second threshold and whose temperature is below the third threshold.

[0118] In other words, using the battery unit 40 shown in Figure 1 as an example, the control unit 30a switches the charging battery pack (one battery pack 41A) to the other battery pack 41 (the other battery pack 41B) if the temperature of the charging battery pack (one battery pack 41A) rises and exceeds the third threshold. However, if the temperature of the other battery pack 41B is below the third threshold, the charging battery pack is not switched until the remaining capacity reaches the second threshold. In other words, in such a case, even if the temperature of one battery pack 41A drops below the third threshold, the other battery pack 41B continues to be charged.

[0119] Furthermore, if there are multiple battery packs 41 with the highest remaining capacity, the control unit 30a may switch the charging battery pack to the one with the lowest temperature among the battery packs 41.

[0120] Furthermore, in charging mode, if the temperature of all battery packs 41 whose remaining capacity is less than the second threshold is above a predetermined third threshold, the control unit 30a determines or switches the charging battery pack to the battery pack 41 with the largest remaining capacity among the battery packs 41 whose remaining capacity is less than the second threshold and whose temperature is above the third threshold.

[0121] However, when the control unit 30a determines or switches to a battery pack 41 whose remaining capacity is less than the second threshold and whose temperature is above the third threshold as the battery pack for charging, it limits the magnitude of the current in constant current charging (charging current value). The control unit 30a outputs an instruction signal to the charger 43, and the charger 43 adjusts the current and voltage of the DC power output to the battery pack 41 using an electronic circuit to lower the charging current value.

[0122] The following describes the series of discharge control and charge control steps in the control method of the electric work machine 1 in this embodiment, using Figures 4 and 5. Figure 4 is a diagram illustrating the series of discharge control steps of the control device 30 in the first embodiment. Figure 5 is a diagram illustrating the series of charge control steps of the control device 30 in the first embodiment. The series of processes shown in Figures 4 and 5 are executed by the CPU based on a software program pre-stored in the memory of the control device 30. Also, in Figures 4 and 5, for convenience, the battery pack 41 is shown as "BP", the discharge battery pack is shown as "discharge BP", and the charge battery pack is shown as "charge BP".

[0123] First, using Figure 4, we will explain the series of steps in the discharge control of the control device 30. The control unit 30a determines whether the current mode of the control device 30 is discharge mode or charge mode (S1). The control unit 30a determines whether or not a charging cable is connected to the charging port 42. Accordingly, or depending on the state of the mode selector switch 5b1 used by the operator to switch between discharge mode and charge mode, the control device 30 determines whether the current mode is discharge mode or charge mode.

[0124] When the control unit 30a determines that the current mode of the control device 30 is discharge mode (S1: Yes), it acquires the operation signal output from the selection tool 5d to the control device 30 (S2). The control unit 30a then selects a battery pack for discharge from the multiple battery packs 41 according to the acquired operation signal from the selection tool 5d (S3).

[0125] The control unit 30a controls the connection switching unit 41b and the junction box 44 to supply (discharge) power from the discharge battery pack to the inverter 45 and the DC / DC converter 47 (S4). The control device 30 controls the DC / DC converter 47 to supply power from the DC / DC converter 47 to the low-voltage battery 48, thereby charging the low-voltage battery 48 as needed (S5).

[0126] Next, the BMU 41a detects the status of each battery pack 41, and the limiting processing unit 30b obtains the remaining capacity and temperature of the discharge battery pack from the BMU 41a (S6), and determines whether the remaining capacity is less than the first threshold (S7). If the limiting processing unit 30b determines that the remaining capacity of the discharge battery pack is less than the first threshold (S7: Yes), it performs a predetermined limiting process (for example, one of the first to eighth limiting processes) (S8).

[0127] If the limiting processing unit 30b determines that the remaining capacity of the discharge battery pack is not below the first threshold (S7: No), it determines whether the temperature of the discharge battery pack is above the fifth threshold (S9). If the limiting processing unit 30b determines that the temperature of the discharge battery pack is above the fifth threshold (S9: Yes), it performs the first limiting process (S10).

[0128] If the limiting processing unit 30b performs a predetermined limiting process in S8 (S8), if the limiting processing unit 30b determines in S9 that the temperature of the discharge battery pack is not above the fifth threshold (S9: No), or if the limiting processing unit 30b performs the first limiting process in S10 (S10), the control unit 30a acquires an operation signal output from the selection tool 5d to the control device 30 and determines whether the selection tool 5d has been operated (S11). If the control unit 30a determines that the selection tool 5d has been operated based on the acquired operation signal from the selection tool 5d (S11: Yes), it switches the discharge battery pack to one of the multiple battery packs 41 based on the acquired operation signal from the selection tool 5d (S12) and proceeds to the process in S4.

[0129] Furthermore, if the control unit 30a determines, based on the acquired operation signal of the selection tool 5d, that the selection tool 5d has not been operated (S11: No), it proceeds to process S6 without switching the discharge battery pack.

[0130] Furthermore, the flowchart showing the discharge control of the electric work machine 1 in Figure 4 is just one example and is not limited to the flow described above. For example, in Figure 4, the control unit 30a determines the discharge mode or the charge mode before deciding on the discharge battery pack or the charge battery pack, but conversely, it may determine the discharge mode or the charge mode after deciding on the discharge mode or the charge battery pack.

[0131] Next, the sequence of charge control operations of the control device 30 will be explained using Figure 5. In S1, if the control unit 30a determines that the current mode of the control device 30 is the discharge mode (S1: No), it obtains the remaining capacity and temperature of each battery pack 41 from the BMU 41a (S13).

[0132] The control unit 30a determines whether there is a battery pack 41 among the multiple battery packs 41 whose remaining capacity is less than the second threshold (S14). If the control unit 30a determines that there is no battery pack 41 whose remaining capacity is less than the second threshold (S14: No), it terminates the series of processes.

[0133] On the other hand, if the control unit 30a determines that there is a battery pack 41 among the multiple battery packs 41 whose remaining capacity is less than the second threshold (S14: Yes), it determines whether there is a battery pack 41 among those battery packs 41 whose temperature is less than the third threshold (S15).

[0134] When the control unit 30a determines that there is a battery pack 41 whose temperature is below the third threshold, ( S15: Yes), the battery pack 41 with the largest remaining capacity among these battery packs 41 is determined to be the battery pack for charging (S16). For this reason, when the system is switched to charging mode, the control unit 30a determines the battery pack for discharging based on the detection results of the state of each battery pack 41 obtained from the BMU 41a. The control unit 30a controls the connection switching unit 41b and the junction box 44 to charge the battery pack for charging with power input to the charger 43 from an external power source via the charging cable and charging port 42 (S17).

[0135] Furthermore, in S15, if the control unit 30a determines that there are no battery packs 41 whose temperature is below the third threshold among the battery packs 41 whose temperature is below the second threshold (S15: No), it selects the battery pack 41 with the largest remaining capacity among the battery packs 41 whose remaining capacity is below the second threshold as the battery pack for charging (S18). The control unit 30a controls the connection switching unit 41b and the junction box 44 and outputs an instruction signal to the charger 43 to charge the battery pack for charging with a limited current (a low set charging current value) (S19).

[0136] When the control unit 30a charges the rechargeable battery pack in S17 and S19 (S17, S19), it obtains the remaining capacity and temperature of the rechargeable battery pack from the BMU 41a (S20). The control unit 30a determines whether the remaining capacity of the rechargeable battery pack is below the second threshold (S21).

[0137] If the control unit 30a determines that the remaining capacity of the charging battery pack is below the second threshold (S21: Yes), it determines whether the temperature of the charging battery pack is below the third threshold (S22). If the control unit 30a determines that the temperature of the charging battery pack is below the third threshold (S22: Yes), it proceeds to the process in S20.

[0138] On the other hand, if the control unit 30a determines that the temperature of the charging battery pack is above the third threshold (S22: No), it obtains the remaining capacity and temperature of the other battery packs 41 other than the charging battery pack from the BMU 41a (S23).

[0139] The control unit 30a determines whether there is a battery pack 41 among the other battery packs 41 whose remaining capacity is less than the second threshold (S24). If the control unit 30a determines that there is a battery pack 41 among the other battery packs 41 whose remaining capacity is less than the second threshold (S24: Yes), it determines whether there is a battery pack 41 among those battery packs 41 whose temperature is less than the third threshold (S25).

[0140] If the control unit 30a determines that there is a battery pack 41 whose temperature is below the third threshold among the battery packs 41 whose remaining capacity is below the second threshold (S25: Yes), it selects the battery pack 41 with the largest remaining capacity among these battery packs 41 as the battery pack for charging (S26) and proceeds to the process in S17.

[0141] Furthermore, if the control unit 30a determines in S24 that there are no other battery packs 41 whose remaining capacity is less than the second threshold (S24: No), and if it determines in S25 that there are no battery packs 41 whose temperature is less than the third threshold among the battery packs 41 whose remaining capacity is less than the second threshold (S25: No), it will not switch the charging battery pack and will perform the process in S19.

[0142] Furthermore, if the control unit 30a determines in S21 that the remaining capacity of the charging battery pack is equal to or greater than the second threshold (S21: No), it obtains the remaining capacity and temperature of other battery packs 41 other than the charging battery pack from the BMU 41a (S27).

[0143] The control unit 30a determines whether there is a battery pack 41 among the other battery packs 41 whose remaining capacity is less than the second threshold (S28). If the control unit 30a determines that there is no battery pack 41 whose remaining capacity is less than the second threshold (S28: No), it terminates the series of processes.

[0144] On the other hand, in S28, if the control unit 30a determines that there is a battery pack 41 whose remaining capacity is less than the second threshold (S28: Yes), it determines whether there is a battery pack 41 among the battery packs 41 whose remaining capacity is less than the second threshold whose temperature is less than the third threshold (S29). If the control unit 30a determines that there is a battery pack 41 among the battery packs 41 whose remaining capacity is less than the second threshold whose temperature is less than the third threshold (S29: Yes), then in S26 Perform the following process.

[0145] Furthermore, if the control unit 30a determines that there are no battery packs 41 whose temperature is below the third threshold (S29: No), it switches the charging battery pack to the battery pack 41 with the largest remaining capacity among these battery packs 41 (S30) and performs the process in S19.

[0146] As described above, according to the control method (charging control) for the electric work machine 1 in this embodiment, using the battery unit 40 shown in Figure 1 as an example, even if, for instance, the remaining capacity of one battery pack 41A is 10% and the remaining capacity of the other battery pack 41B is 40%, and charging time cannot be secured, resulting in only 20% charging of one of the battery packs 41, the control unit 30a will determine the other battery pack 41B, which has a larger remaining capacity, to be the battery pack to be charged. As a result, the electric work machine 1 can charge the other battery pack 41B to 60%.

[0147] Here, if one of the battery packs 41A is used as the charging battery pack, it can only be charged to 30%. In other words, if the control unit 30a determines that one of the battery packs 41A is the discharging battery pack, the electric work machine 1 can only use 20% of its remaining capacity until the limiting processing unit 30b performs the limiting process.

[0148] Therefore, in the control method (charging control) of the electric work machine 1 in this embodiment, in the above case, the other battery pack 41B can be charged to 60%, and if the other battery pack 41B is determined to be the discharge battery pack, 40% of the remaining capacity can be used until the limiting processing unit 30b performs the limiting processing.

[0149] In the above-described embodiment, if the temperature of the charging battery pack is below the third threshold in the charging mode, the control unit 30a continues charging until the remaining capacity of the charging battery pack reaches the second threshold (S20-S22). However, the control unit 30a only needs to prioritize selecting the battery pack 41 with the largest remaining capacity among the battery packs 41 whose remaining capacity is below the second threshold as the charging battery pack. For this reason, the control unit 30a may adopt a configuration in which, even if the remaining capacity of the charging battery pack is below both the second and third thresholds while the charging battery pack is being charged in the charging mode, if it detects a battery pack 41 with a larger remaining capacity than the charging battery pack, it switches the charging battery pack to that battery pack 41.

[0150] Using the battery unit 40 shown in Figure 1 as an example, and assuming that one of the battery packs 41A is for charging, in the modified example, if the temperature of the charging battery pack (one of the battery packs 41A) rises and the temperature exceeds the third threshold, the control unit 30a switches the charging battery pack to the other battery pack 41 (the other battery pack 41B). On the other hand, if the other battery pack 41B is a charging battery pack and is being charged, and the temperature of the one battery pack 41A drops below the third threshold, the control unit 30a switches the original one battery pack 41A back to the charging battery pack until the remaining capacity of the other battery pack 41B reaches the second threshold or the temperature reaches the third threshold.

[0151] The following describes the sequence of charging control of the electric work machine 1 in a modified example of the first embodiment using Figure 6. Note that the flowchart of the charging control in this modified example differs from the flowchart of the charging control in the first embodiment shown in Figure 5 because the processing after the control unit 30a determines in S22 that the temperature of the charging battery pack is below the third threshold (S22: Yes) is different. Therefore, the processing from S40 to S44, which are the differences, will be explained.

[0152] As shown in Figure 6, in S22, if the control unit 30a determines that the temperature of the charging battery pack is below the third threshold (S22: Yes), it obtains the remaining capacity and temperature of the other battery packs 41 other than the charging battery pack from the BMU 41a (S40).

[0153] The control unit 30a determines whether there is a battery pack 41 among the other battery packs 41 whose remaining capacity is less than the second threshold (S41). If the control unit 30a determines that there is a battery pack 41 whose remaining capacity is less than the second threshold (S41: Yes), it determines whether there is a battery pack 41 among those battery packs 41 whose temperature is less than the third threshold (S42).

[0154] When the control unit 30a determines that there is a battery pack 41 whose temperature is below the third threshold, ( S42: Yes), it is determined whether the remaining capacity of the battery pack 41 with the largest remaining capacity among these battery packs 41 is greater than the remaining capacity of the charging battery pack (S43).

[0155] If the control unit 30a determines that the remaining capacity of the battery pack 41 with the largest remaining capacity is greater than the remaining capacity of the charging battery pack (S43: Yes), it switches the charging battery pack to the battery pack 41 (S44) and proceeds to the process in S17.

[0156] Furthermore, if the control unit 30a determines in S41 that there are no other battery packs 41 whose remaining capacity is less than the second threshold (S41: No), if it determines in S42 that there are no battery packs 41 whose temperature is less than the third threshold (S42: No), or if it determines in S43 that the remaining capacity of the battery pack 41 with the largest remaining capacity is less than the remaining capacity of the charging battery pack (S43: No), it will not switch the charging battery pack and will proceed to the process in S20.

[0157] Furthermore, the control unit 30a may adopt, in addition to the condition that the temperature of the battery pack 41 is below the third threshold, a condition that the temperature is above a predetermined fourth threshold that is below the third threshold as a condition for determining or switching the battery pack for charging. The fourth threshold is the lowest temperature at which the charging efficiency of the battery pack 41 is relatively stable. The fourth threshold is a predetermined value pre-stored in the storage device 31, for example, defined as 0°C. The fourth threshold is not limited to 0°C, and may be -5°C or 5°C. Also, the fourth threshold may be changed to any value by operating the input device. In addition, the fourth threshold may be defined within a predetermined range of values ​​including an upper limit and a lower limit in order to suppress chattering.

[0158] Furthermore, the series of steps for controlling the charging of the electric work machine 1 in the modified example described above can be understood by replacing the descriptions of "less than the third threshold" in S15, S22, S25, and S29 in the charging control flowchart of the first embodiment shown in Figure 5, and the descriptions of "less than the third threshold" in S22 and S42 in the charging control flowchart of the modified example of the first embodiment shown in Figure 6, with "greater than or equal to the fourth threshold and less than the third threshold," so a detailed explanation is omitted.

[0159] Furthermore, in the embodiment described above, the control unit 30a was shown as an example in which it determines or switches the battery pack to be charged based on the temperature (actual temperature) of each battery pack 41 detected by the BMU 41a in charging mode. However, the determination of whether or not the temperature of the battery pack 41 is below the third threshold is not limited to the actual temperature. In other words, the control device 30 may calculate the expected temperature of a battery pack 41 when it is charged for a predetermined time (e.g., 15 minutes or 30 minutes) for a battery pack 41 whose remaining capacity is below the second threshold and whose temperature is below a predetermined third threshold, and the control unit 30a may determine or switch the battery pack to be charged based on this expected temperature. The storage device 31 stores a calculation map showing the relationship between the actual temperature of the battery pack 41 and the charging time, and the control device 30 calculates the expected temperature based on the temperature (actual temperature) of each battery pack 41 detected by the BMU 41a and the calculation map. As a result, the control device 30 (control unit 30a) determines or switches to the battery pack 41 with the largest remaining capacity among the battery packs 41 whose predicted temperature is below the third threshold as the battery pack for charging.

[0160] Furthermore, in the above-described embodiment, the limiting processing unit 30b was described as performing the first limiting process when it determined that the temperature of the discharge battery pack was above the fifth threshold. However, the third threshold may be used as the fifth threshold.

[0161] The electric work machine 1 and the control method for the electric work machine 1 according to the first embodiment described above have the following effects.

[0162] The above-described electric work machine 1 comprises a plurality of battery packs 41, an operating device E that operates using power supplied from the battery packs 41, a battery monitoring device 41a that detects the remaining capacity of each battery pack 41, and a control device 30 that controls the charging and discharging of the plurality of battery packs 41 based on the remaining capacity of each battery pack 41. In the discharge mode, the control device 30 determines one of the plurality of battery packs 41 as the discharge battery pack that supplies power to the operating device E, and has the operating device E supplied with power from the discharge battery pack. In the charging mode, the control device 30 prioritizes the battery pack 41 with the largest remaining capacity among the plurality of battery packs 41 for charging. The system was selected for repacking, and the selected battery pack was to be charged.

[0163] Furthermore, the control method for the electric work machine 1 is a control method for the electric work machine 1 which is equipped with a plurality of battery packs 41 and an operating device E that operates using power supplied from the battery packs 41. In the discharge mode, one of the plurality of battery packs 41 is selected as the discharge battery pack that supplies power to the operating device E, and power is supplied from the discharge battery pack to the operating device E. In the charging mode, the battery pack 41 is charged, and the battery pack 41 with the largest remaining capacity is selected as the charging battery pack, and the selected charging battery pack is charged.

[0164] According to the above-described electric work implement 1 and control method for the electric work implement 1, by prioritizing the charging of the battery pack 41 with the largest remaining capacity, charging can be performed efficiently so that work can be carried out properly after charging, even if sufficient charging time cannot be secured.

[0165] Furthermore, in discharge mode, if the remaining capacity of the discharge battery pack is less than a predetermined first threshold, the control device 30 performs a limiting process to limit the power supplied from the discharge battery pack to the operating device.

[0166] With the above configuration, even if sufficient charging time cannot be secured, it is possible to suppress the output limitation that occurs immediately after charging.

[0167] Furthermore, in charging mode, the control device 30 prioritizes selecting battery packs with a larger remaining capacity from among the battery packs whose remaining capacity is less than a second threshold (which is set to a value greater than the first threshold) as the battery pack for charging.

[0168] With the above configuration, even if sufficient charging time cannot be secured, charging can be performed efficiently so that work can be carried out properly after charging.

[0169] Furthermore, in charging mode, the control device 30 prioritizes selecting the battery pack 41 with the largest remaining capacity among the battery packs 41 whose remaining capacity is less than the second threshold as the battery pack for charging.

[0170] According to the above configuration, by prioritizing the charging of the battery pack 41 with the largest remaining capacity, the battery pack 41 is sufficiently charged to the first threshold. This allows for efficient charging even when sufficient charging time cannot be secured.

[0171] Furthermore, the battery monitoring device 41a detects the temperature of each battery pack 41 in addition to the remaining capacity of each battery pack 41, and the control device 30, in charging mode, determines the battery pack 41 with the largest remaining capacity among the battery packs 41 whose remaining capacity is below a second threshold and whose temperature is below a predetermined third threshold as the battery pack for charging.

[0172] According to the above configuration, while the charging efficiency of battery pack 41 decreases when its temperature rises above a predetermined temperature, the overall charging efficiency of the work machine can be improved by prioritizing the charging of battery pack 41 with a relatively lower temperature.

[0173] Furthermore, in charging mode, if the temperature of the charging battery pack exceeds the third threshold, the control device 30 switches the charging battery pack to the battery pack 41 with the largest remaining capacity among the other battery packs 41 whose remaining capacity is less than the second threshold and whose temperature is less than the third threshold.

[0174] According to the above configuration, the charging efficiency of the battery pack 41 decreases when its temperature rises above a predetermined temperature. However, by switching to a battery pack 41 with a relatively lower temperature for charging, the overall charging efficiency of the work machine can be improved.

[0175] Furthermore, in charging mode, if the temperature of the charging battery pack is below the third threshold and the remaining capacity of the charging battery pack reaches the second threshold, the control device 30 switches the charging battery pack to the battery pack 41 with the largest remaining capacity among the other battery packs 41 whose remaining capacity is below the second threshold and whose temperature is below the third threshold.

[0176] According to the above configuration, even when charging of a predetermined battery pack (charging battery pack) 41 is complete, the battery pack 41 with a large remaining capacity and a relatively low temperature is continued to be charged preferentially, thereby improving the work efficiency of the work machine and the overall charging efficiency of the work machine.

[0177] Furthermore, in charging mode, the control device 30 checks when the remaining capacity is below the second threshold and the temperature is below the third threshold. If a battery pack 41 is detected that is less than the specified value and has a remaining capacity greater than the remaining capacity of the charging battery pack, the charging battery pack is switched to the battery pack 41.

[0178] According to the above configuration, even when another battery pack 41 is being charged in place of a battery pack 41 whose temperature has risen above a predetermined temperature, if the temperature of the battery pack 41 whose temperature has risen decreases and the remaining capacity of this battery pack 41 is still large, the battery pack 41 can be charged preferentially, thereby improving the work efficiency of the work machine and the overall charging efficiency of the work machine.

[0179] Furthermore, in charging mode, the control device 30 calculates the expected temperature of a battery pack 41 when it is charged for a predetermined time if the battery pack 41 has a remaining capacity below a second threshold and a temperature below a predetermined third threshold, and determines the battery pack 41 with the largest remaining capacity among the battery packs 41 whose expected temperature is below the third threshold to be used for charging.

[0180] According to the above configuration, the temperature of the battery pack 41 will not exceed the third threshold immediately after charging, thus preventing the immediate switching of the charging battery pack.

[0181] Furthermore, in discharge mode, the control device 30 performs a limiting process to restrict the power supplied from the discharge battery pack to the operating device E if the temperature of the discharge battery pack is above the third threshold.

[0182] The above configuration makes it possible to suppress the shortening of the lifespan of the discharge battery pack.

[0183] Furthermore, the operating device E includes an electric motor 46, and in discharge mode, the control device 30 limits the upper limit of the rotational speed of the electric motor 46 as a limiting process when the remaining capacity of the discharge battery pack is less than a first threshold.

[0184] According to the above configuration, when the remaining capacity of the discharge battery pack becomes relatively low and power is continuously supplied from the discharge battery pack to the electric motor 46 to drive the electric motor 46, it is possible to suppress a rapid decrease in the remaining capacity of the discharge battery pack. [Second Embodiment] Figure 7 is an electrical block diagram of the electric work machine 1 in the second embodiment.Hereinafter, the electric work machine 1 and the control method of the electric work machine 1 in the second embodiment will be described, focusing on the configurations that differ from the above-described embodiment (first embodiment), and the same reference numerals will be used for configurations common to the first embodiment, and detailed explanations will be omitted.In the first embodiment, the control device 30 (control unit 30a) determined the battery pack 41 with the largest remaining capacity among the battery packs 41 whose remaining capacity is less than the second threshold and whose temperature is less than a predetermined third threshold to be the battery pack for charging, and switched the battery pack for charging to another battery pack 41 when the battery pack for charging reached the second threshold or when its temperature became above the third threshold, etc.In the second embodiment, the control unit 30a determines and switches the battery for charging based on different conditions, either in lieu of or in addition to the above conditions.

[0185] Specifically, the control unit 30a selects one of the multiple battery packs 41 whose remaining capacity is less than the first target value as the battery pack to be charged, and charges the selected battery pack with a constant current until its remaining capacity reaches the first target value (first charging process). When the remaining capacity of the battery pack to be charged reaches the first target value, the control unit 30a switches the battery pack to one of the other battery packs 41 whose remaining capacity is less than the first target value, and charges the switched battery pack with a constant current until its remaining capacity reaches the first target value (second charging process). In other words, the control unit 30a switches the battery packs to be charged and charges the battery packs 41 whose remaining capacity is less than the first target value until the remaining capacity of all of the multiple battery packs 41 provided in the battery unit 40 reaches the first target value.

[0186] Furthermore, if there are no battery packs 41 among the multiple battery packs 41 whose remaining capacity is less than the first target value, the control unit 30a determines one of the battery packs 41 whose remaining capacity is less than a predetermined second target value which is greater than the first target value to be used for charging, and charges the selected charging battery pack with a constant current until its remaining capacity reaches the second target value (third charging process). When the charging battery pack is being charged, the control unit 30a determines when the remaining capacity of the charging battery pack moves from less than the first target value to the first target value. If no battery pack 41 has reached the target value and is below the first target value, the charging battery pack is continuously charged with a constant current.

[0187] Then, when the remaining capacity of the charging battery pack reaches the second target value, the control unit 30a switches the charging battery pack to one of the other battery packs 41 whose remaining capacity is less than the second target value, and charges the switched charging battery pack with a constant current until its remaining capacity reaches the second target value (fourth charging process).

[0188] Therefore, if the last battery pack 41 among the multiple battery packs 41 whose remaining capacity is less than the first target value is being charged, when the remaining capacity of that battery pack 41 reaches the first target value, the control unit 30a continues to charge that battery pack 41 with a constant current without switching the charging battery pack. The control unit 30a also switches the charging battery packs until the remaining capacity of each battery pack 41 reaches the second target value.

[0189] In the second embodiment, the control device 30 (control unit 30a) outputs an instruction signal to the charger 43 in charging mode, and the charger 43 adjusts the DC power current and voltage using an electronic circuit to charge the battery pack 41 using only constant current charging.

[0190] Next, the first target value and the second target value will be described. The first target value is a predetermined value pre-stored in the memory device 31, for example, which is greater than the first threshold and less than full charge. Preferably, the first target value is defined (set) based on the remaining capacity at which the charging efficiency by constant current charging decreases.

[0191] Figure 8 shows an example of the relationship between elapsed time, remaining capacity of the charging battery pack, and the magnitude of the DC power output to the charging battery pack (charging current value) when constant current charging is performed. As shown in Figure 8, due to the characteristics of the batteries constituting each battery pack 41, when charging with constant current, it is necessary to set the charging current value output to the charging battery pack to a lower value as it approaches full charge. For this reason, in the example shown in Figure 8, the control unit 30a gradually lowers the charging current value after the remaining capacity of the charging battery pack reaches 80% or more. That is, when the remaining capacity of the charging battery pack is 80% or more, the charging speed of the charging battery pack decreases. In this embodiment, the first target value pre-stored in the storage device 31 is defined as, for example, 80%.

[0192] Note that the relationship between the elapsed time, the remaining capacity of the charging battery pack, and the charging current value output to the charging battery pack when constant current charging is performed, as shown in Figure 8, is merely illustrative. Furthermore, the first target value may be defined within a predetermined range of values, including an upper limit and a lower limit, in order to suppress chattering.

[0193] Furthermore, the first target value is set (defined) by the target value setting process. The target value setting unit 30c of the control device 30 performs the target value setting process and sets the first target value. The target value setting unit 30c is composed of a program stored in the CPU, memory, etc. Based on the information acquired by the acquisition unit 30d, the target value setting unit 30c arbitrarily sets the first target value within a range less than full charge. Based on the operation signal of the setting operation tool 5e acquired by the acquisition unit 30d, the target value setting unit 30c arbitrarily sets the first target value within a range less than full charge.

[0194] The acquisition unit 30d acquires information for setting a first target value for charging the battery pack 41 in charging mode. The acquisition unit 30d consists of a program stored in the CPU, memory, etc.

[0195] As shown in Figure 7, the electric work machine 1 is equipped with an operating device (setting device) 5e that can be operated to set a first target value, and the acquisition unit 30d acquires the operation signal output from the setting device 5e. The setting device 5e is, for example, a display image displayed on a display screen such as a meter panel. The setting device 5e has a first operating device 5e1 for increasing the first target value and a second operating device 5e2 for decreasing the first target value. In addition, the display screen may display a display unit (not shown) that displays the first target value set by the setting device 5e.

[0196] In other words, when the operator operates the first operating tool 5e1, the first target value displayed on the display unit increases, and when the operator operates the second operating tool 5e2, the first target value displayed on the display unit decreases. The operation signal of the setting operating tool 5e is output to the control device 30, and the target value setting unit 30 c sets (updates) the first target value stored in the storage device 31 based on the operation signal. The target value setting unit 30c acquires the first target value corresponding to the operation signal, for example, based on a table stored in the storage device 31 and the acquired operation signal.

[0197] As described above, the control device 30 can arbitrarily set the first target value within a range less than full charge based on the operation of the operating tool 5e.

[0198] The setting device 5e only needs to be able to set the first target value, and may be a dial-shaped switch such as a selector switch with multiple switching positions.

[0199] In this embodiment, the target value setting unit 30c can continuously set a first target value in the range of 50% or more and less than 100% based on an operation signal. The range in which the target value setting unit 30c can set the first target value is at least the range in which the remaining capacity of the charging battery pack is less than fully charged, and is preferably defined as a range that includes the remaining capacity before the charging efficiency decreases (e.g., 70%), the remaining capacity when the charging efficiency tends to decrease (e.g., 80%), and the remaining capacity after the charging efficiency decreases (e.g., 90%), based on the relationship between the elapsed time and the remaining capacity of the charging battery pack when constant current charging is performed as shown in Figure 8. In such a case, the control device 30 (control unit 30a) can be said to set the charging current value used for constant current charging when the remaining capacity of the charging battery pack is equal to or greater than the first target value to be less than the charging current value used for constant current charging when the remaining capacity is less than the first target value.

[0200] Furthermore, the range of the first target value set by the target value setting unit 30c is not limited to the range of 50% or more and less than 100%, but may also be, for example, 30% or more and less than 90%, or 60% or more and less than 95%.

[0201] Furthermore, the target value setting unit 30c may arbitrarily set the first target value within a range less than full charge, and it is not necessary to be able to set the value continuously. That is, the target value setting unit 30c may set the first target value based on a plurality of default values. The storage device 31 stores a plurality of default values ​​that can be candidates for the first target value, for example, 40%, 50%, 60%, 70%, and 80%, and the setting operation tool 5e accepts a selection operation of the plurality of default values ​​stored in the storage device 31.

[0202] The second target value is, for example, a predetermined value stored in the memory device 31 beforehand, and for example, the second target value is defined as 100% as the remaining capacity when the battery pack 41 is fully charged.

[0203] Furthermore, the second target value may be set to any value by operating the input device. Also, the second target value may be defined within a predetermined range of values, including an upper and lower limit, in order to suppress chattering. In such a case, if the second target value (full charge) is defined to 80% or 85%, the degradation of the battery pack 41 due to repeated charging and discharging can be suppressed.

[0204] Accordingly, in this embodiment, the control unit 30a charges one of the battery packs 41 (first charging process), and when the remaining capacity of one of the battery packs 41 reaches a first target value, it switches the charging battery pack to the other battery pack 41 (second charging process). When the remaining capacity of the other battery pack 41 reaches a first target value, the control unit 30a does not switch the charging battery pack from the other battery pack 41, but continues to charge the other battery pack 41 (third charging process). When the remaining capacity of the other battery pack 41 reaches a second target value, the control unit 30a switches the charging battery pack back to one of the battery packs 41 and charges that one battery pack 41 until its remaining capacity reaches the second target value (fourth charging process).

[0205] The following describes the sequence of charge control of the electric work machine 1 in the second embodiment using Figures 9, 10, and 11. Figure 9 is the first diagram illustrating the sequence of charge control of the control device 30 in the second embodiment. Figure 10 is the second diagram illustrating the sequence of charge control of the control device 30 in the second embodiment. Figure 11 is the third diagram illustrating the sequence of charge control of the control device 30 in the second embodiment.

[0206] If the control unit 30a determines in S1 or S11 that the current mode of the control device 30 is discharge mode (S1: Yes, S11: Yes), the acquisition unit 30d acquires the operation signal output by the setting tool 5e to the control device 30 (S50). The target value setting unit 30c acquires The unit 30d refers to the operation signal it has acquired and the first target value stored in the storage device 31 to determine whether or not to update (set) the first target value (S51). If the target value setting unit 30c determines that it should update the first target value (S51: Yes), it updates the first target value stored in the storage device 31 to set the first target value (S52).

[0207] If the target value setting unit 30c updates the first target value (S52), and if the target value setting unit 30c determines in S51 that it will not update the first target value (S51: No), the control unit 30a obtains the remaining capacity and temperature of each battery pack 41 from the BMU 41a (S53). The control unit 30a determines whether there is a battery pack 41 among the multiple battery packs 41 whose remaining capacity is less than the first target value (S54).

[0208] If the control unit 30a determines that there is a battery pack 41 among the multiple battery packs 41 whose remaining capacity is less than the first target value (S54: Yes), it determines whether there is a battery pack 41 among the battery packs 41 whose remaining capacity is less than the first target value whose temperature is less than the third threshold (S55).

[0209] If the control unit 30a determines that there is a battery pack 41 whose temperature is below the third threshold (S55: Yes), it selects the battery pack 41 with the largest remaining capacity among these battery packs 41 as the battery pack for charging (S56). The control unit 30a controls the connection switching unit 41b and the junction box 44 to charge the battery pack for charging (S57).

[0210] Furthermore, if the control unit 30a determines in S55 that there are no battery packs 41 whose temperature is below the third threshold (S55: No), it selects the battery pack 41 with the largest remaining capacity among the battery packs 41 whose remaining capacity is below the first target value as the battery pack for charging (S58). The control unit 30a controls the connection switching unit 41b and the junction box 44, outputs an instruction signal to the charger 43, and causes the battery pack for charging to be charged with a limited current (a low set charging current value) (S59).

[0211] As shown in Figure 10, when the control unit 30a charges the charging battery pack in S57 and S59 (S57, S59), the target value setting unit 30c refers to the operation signal acquired by the acquisition unit 30d and the first target value stored in the storage device 31 to determine whether or not to update (set) the first target value (S60).

[0212] If the target value setting unit 30c determines that the first target value should be updated (S60: Yes), it updates the first target value stored in the storage device 31 and sets the first target value (S61).

[0213] If the target value setting unit 30c updates the first target value (S61), or if the target value setting unit 30c determines that it will not update the first target value (S60: No), the control unit 30a obtains the remaining capacity and temperature of the charging battery pack from the BMU 41a (S62). The control unit 30a determines whether the remaining capacity of the charging battery pack is less than the first target value (S63).

[0214] If the control unit 30a determines that the remaining capacity of the charging battery pack is less than the first target value (S63: Yes), it determines whether the temperature of the charging battery pack is below the third threshold (S64). If the control unit 30a determines that the temperature of the charging battery pack is below the third threshold (S64: Yes), it proceeds to process S60.

[0215] On the other hand, if the control unit 30a determines that the temperature of the charging battery pack is above the third threshold (S64: No), it obtains the remaining capacity and temperature of the other battery packs 41 other than the charging battery pack from the BMU 41a (S65).

[0216] The control unit 30a determines whether there is a battery pack 41 among the other battery packs 41 whose remaining capacity is less than the first target value (S66). If the control unit 30a determines that there is a battery pack 41 whose remaining capacity is less than the first target value (S66: Yes), it determines whether there is a battery pack 41 among those battery packs 41 whose temperature is less than the third threshold (S67). If the control unit 30a determines that there is a battery pack 41 whose temperature is less than the third threshold (S67: Yes), it selects the battery pack 41 with the largest remaining capacity among these battery packs 41 as the battery pack for charging (S68) and proceeds to the process in S57.

[0217] Furthermore, in S66, the control unit 30a determines that there are no other battery packs 41 whose remaining capacity is less than the first target value (S66: No), and S In step 67, if it is determined that there are no battery packs 41 with a remaining capacity below the first target value whose temperature is below the third threshold (S67: No), the charging battery pack is not switched, and the process in S59 is performed.

[0218] Furthermore, if the control unit 30a determines in S63 that the remaining capacity of the charging battery pack is equal to or greater than the first target value (S63: No), it obtains the remaining capacity and temperature of the other battery packs 41 other than the charging battery pack from the BMU 41a (S69).

[0219] The control unit 30a determines whether there is a battery pack 41 among the other battery packs 41 whose remaining capacity is less than the first target value (S70). If the control unit 30a determines that there is a battery pack 41 whose remaining capacity is less than the first target value (S70: Yes), it determines whether there is a battery pack 41 among those battery packs 41 whose temperature is less than the third threshold (S71). If the control unit 30a determines that there is a battery pack 41 whose temperature is less than the third threshold (S71: Yes), it performs the process in S68.

[0220] On the other hand, if the control unit 30a determines that there are no battery packs 41 whose temperature is below the third threshold (S71: No), it selects the battery pack 41 with the largest remaining capacity among these battery packs 41 as the battery pack for charging (S72), and performs the process in S59.

[0221] As shown in Figure 11, if the control unit 30a determines in S54 that there are no battery packs 41 with a remaining capacity less than the first target value (S54: No), and if it determines in S70 that there are no battery packs 41 with a remaining capacity less than the first target value (S70: No), it determines in S75 whether there is a battery pack 41 among the multiple battery packs 41 with a remaining capacity less than the second target value. If the control unit 30a determines that there are no battery packs 41 with a remaining capacity less than the second target value (S75: No), it terminates the series of processes.

[0222] If the control unit 30a determines that there is a battery pack 41 whose remaining capacity is less than the second target value (S75: Yes), it determines whether there is a battery pack 41 among those battery packs 41 whose temperature is below the third threshold (S76). If the control unit 30a determines that there is a battery pack 41 whose temperature is below the third threshold (S76: Yes), it determines that the battery pack 41 among these battery packs 41 has the largest remaining capacity to be used as the charging battery pack (S77). The control unit 30a controls the connection switching unit 41b and the junction box 44 to charge the charging battery pack (S78).

[0223] Furthermore, if the control unit 30a determines in S76 that there are no battery packs 41 whose temperature is below the third threshold (S76: No), it selects the battery pack 41 with the largest remaining capacity among the battery packs 41 whose remaining capacity is below the second target value as the battery pack for charging (S79). The control unit 30a controls the connection switching unit 41b and the junction box 44, outputs an instruction signal to the charger 43, and causes the battery pack for charging to be charged with a limited current (a low set charging current value) (S80).

[0224] When the control unit 30a charges the rechargeable battery pack in S78 and S80 (S78, S80), it obtains the remaining capacity and temperature of the rechargeable battery pack from the BMU 41a (S81). The control unit 30a determines whether the remaining capacity of the rechargeable battery pack is less than the second target value (S82).

[0225] If the control unit 30a determines that the remaining capacity of the charging battery pack is less than the second target value (S82: Yes), it determines whether the temperature of the charging battery pack is below the third threshold (S83). If the control unit 30a determines that the temperature of the charging battery pack is below the third threshold (S83: Yes), it proceeds to the process in S81.

[0226] Furthermore, if the control unit 30a determines that the temperature of the charging battery pack is above the third threshold (S83: No), it obtains the remaining capacity and temperature of the other battery packs 41 other than the charging battery pack from the BMU 41a (S84).

[0227] The control unit 30a determines whether there is a battery pack 41 among the other battery packs 41 whose remaining capacity is less than the second target value (S85). If the control unit 30a determines that there is a battery pack 41 among the other battery packs 41 whose remaining capacity is less than the second target value (S85: Yes), it determines whether there is a battery pack 41 among those battery packs 41 whose temperature is less than the third threshold (S86). The control unit 30a determines whether there is a battery pack 41 whose temperature is less than the third threshold If it is determined that there is a battery pack 41 (S86: Yes), the battery pack 41 with the largest remaining capacity among these battery packs 41 is selected as the battery pack for charging, and the process proceeds to (S87) S78.

[0228] Furthermore, if the control unit 30a determines in S85 that there are no other battery packs 41 whose remaining capacity is less than the second target value (S85: No), and if it determines in S86 that there are no battery packs 41 whose temperature is below the third threshold among the battery packs 41 whose remaining capacity is less than the second target value (S86: No), it performs the process in S80.

[0229] Furthermore, if the control unit 30a determines in S82 that the remaining capacity of the charging battery pack is equal to or greater than the second target value (S82: No), it obtains the remaining capacity and temperature of the other battery packs 41 other than the charging battery pack from the BMU 41a (S88).

[0230] The control unit 30a determines whether there is a battery pack 41 among the other battery packs 41 whose remaining capacity is less than the second target value (S89). If the control unit 30a determines that there is no battery pack 41 whose remaining capacity is less than the second target value (S89: No), it terminates the series of processes.

[0231] On the other hand, in S89, if the control unit 30a determines that there is a battery pack 41 whose remaining capacity is less than the second target value (S89: Yes), it determines whether there is a battery pack 41 among those battery packs 41 whose temperature is below the third threshold (S90). If the control unit 30a determines that there is a battery pack 41 whose temperature is below the third threshold (S90: Yes), it performs the process in S87.

[0232] Furthermore, if the control unit 30a determines that there are no battery packs 41 whose temperature is below the third threshold (S90: No), it selects the battery pack 41 with the largest remaining capacity among these battery packs 41 as the battery pack for charging (S91) and performs the process in S80.

[0233] The steps corresponding to the target value setting process (S52, S61) are called the "target value setting step," and the steps corresponding to the first charging process (S56, S57, S62, S63:Yes, S64) are called the "first charging step." Furthermore, the steps corresponding to the second charging process (S63:No, S69, S70:Yes, S71:Yes, S68, S57) are called the "second charging step," and the steps corresponding to the third charging process (S70:No, S75:Yes, S76:Yes, S77, S78, S81, S82) are called the "third charging step."

[0234] According to the above configuration, since there is no switching between constant current charging and other charging methods, the charging battery pack can be charged stably. The control device 30 can set a first target value, so when the first target value is set to a value relatively close to full charge, a predetermined charging battery pack can be charged preferentially compared to other battery packs, and when the first target value is set to a value relatively far from full charge, the battery pack 41 that has high charging efficiency with constant current charging is charged preferentially, thereby improving the charging efficiency of each of the multiple battery packs 41.

[0235] Furthermore, the flowchart showing the discharge control of the electric work machine 1 in Figure 9 is just one example and is not limited to the flow described above. For example, when performing the process in S77, the control unit 30a may be configured to determine the battery pack 41 with the lowest temperature among the battery packs 41 whose remaining capacity is less than the second target value and whose temperature is less than the third threshold as the battery pack to be charged. By setting the process to the above, it is possible to charge battery packs 41 whose temperature takes a relatively long time to reach the third threshold. The charging efficiency of multiple battery packs 41 can be further improved.

[0236] The electric work machine 1 and the control method for the electric work machine 1 according to the second embodiment described above have the following effects.

[0237] The electric work machine 1 described above comprises a plurality of battery packs 41, an operating device E that operates using power supplied from the battery packs 41, a battery monitoring device 41a that detects the remaining capacity of each battery pack 41, and a control device 30 that controls the charging of the plurality of battery packs 41 based on the remaining capacity of the plurality of battery packs 41, and the control device 30 controls the battery pack The process involves setting a target value for charging 41, selecting one of the multiple battery packs 41 whose remaining capacity is less than the first target value as the charging battery pack, and performing a first charging process in which the charging battery pack is charged with a constant current until its remaining capacity reaches the first target value, and, once the charging battery pack's remaining capacity reaches the first target value, switching the charging battery pack to one of the other battery packs 41 whose remaining capacity is less than the first target value, and performing a second charging process in which the switched charging battery pack is charged with a constant current until its remaining capacity reaches the first target value. If there are no battery packs 41 among the multiple battery packs 41 whose remaining capacity is less than the first target value, selecting one of the battery packs 41 whose remaining capacity is less than a predetermined second target value greater than the first target value as the charging battery pack, and performing a third charging process in which the charging battery pack is charged with a constant current until its remaining capacity reaches the second target value.

[0238] Furthermore, the control method for the electric work machine 1 is a control method for the electric work machine 1 comprising a plurality of battery packs 41 and an operating device E that operates using power supplied from the battery packs 41, comprising: a first target value setting step of setting a first target value for charging the battery packs 41; a first charging step of determining one of the plurality of battery packs 41 whose remaining capacity is less than the first target value as the charging battery pack, and charging the charging battery pack with a constant current until the remaining capacity of the determined charging battery pack reaches the first target value; and when the remaining capacity of the charging battery pack reaches the first target value, the charging battery pack, The charging method includes: a second charging step of switching to one of the other battery packs 41 whose remaining capacity is less than a first target value, and then constantly charging the charging battery pack until the remaining capacity of the switched charging battery pack reaches the first target value; and a third charging step of, if there are no battery packs 41 among the multiple battery packs 41 whose remaining capacity is less than a first target value, determining one of the battery packs 41 whose remaining capacity is less than a predetermined second target value that is greater than the first target value, and then constantly charging the determined charging battery pack until the remaining capacity of the charging battery pack reaches the second target value.

[0239] According to the above-described electric work machine 1 and control method for electric work machine 1, since constant current charging and other charging methods are not switched, the charging battery pack can be charged stably, and the control can be simplified compared to when switching to other charging methods. In addition, generally, when a battery pack is near full charge, it is necessary to limit the charging current value, which reduces the charging speed. However, with the above configuration, when the charging of the charging battery pack is completed to the first target value, the charging battery pack is switched to another battery pack. This makes it possible to efficiently charge multiple battery packs.

[0240] Furthermore, when the remaining capacity of the charging battery pack reaches the second target value, the control device 30 switches the charging battery pack to one of the other battery packs 41 whose remaining capacity is less than the second target value, and performs a fourth charging process in which it constantly charges the switched charging battery pack until its remaining capacity reaches the second target value.

[0241] With the above configuration, the battery pack 41 with high charging efficiency due to constant current charging is charged first, and then the remaining capacity of all battery packs 41 is charged until it reaches the second target value.

[0242] Furthermore, the electric work machine 1 is equipped with an operating tool 5e that can be operated to set a first target value, and the control device 30 arbitrarily sets the first target value within a range less than full charge based on the operation of the operating tool 5e.

[0243] With the above configuration, the operator can choose to either prioritize charging a predetermined battery pack 41 or improve the charging efficiency of each of the multiple battery packs 41 by simply operating the operating tool 5e.

[0244] Furthermore, if the remaining capacity of the charging battery pack reaches the first target value from below the first target value, and there are no other battery packs 41 with a remaining capacity below the first target value, the control device 30 will continue to charge the charging battery pack with a constant current.

[0245] According to the above configuration, the number of times the charging battery pack needs to be switched can be reduced, and multiple This can improve the charging efficiency of the battery pack 41.

[0246] The second target value is the remaining capacity when the battery pack 41 is fully charged.

[0247] According to the above configuration, when the remaining capacity of multiple battery packs 41 reaches the first target value, the remaining capacity of each battery pack 41 can be charged to full capacity. This improves the charging efficiency of multiple battery packs 41 while allowing each battery pack 41 to be fully charged.

[0248] Furthermore, the control device 30 sets the charging current value used for constant current charging when the remaining capacity of the charging battery pack is equal to or greater than the first target value to be less than the charging current value used for constant current charging when the remaining capacity is less than the first target value.

[0249] According to the above configuration, it is possible to suppress overvoltage in a charging battery pack whose remaining capacity is relatively high and whose charging efficiency has decreased.

[0250] Although the present invention has been described above, the embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than by the foregoing description, and all modifications within the meaning and scope equivalent to the claims are intended to be included.

[0251] In the embodiments described above, an example of applying the present invention to an electric work machine 1 such as a backhoe was explained. However, the application of the present invention is not limited to this, and it may also be applied to other construction machinery such as wheel loaders, compact track loaders, and skid steer loaders, or to agricultural machinery such as tractors, combine harvesters, rice transplanters, and lawnmowers.

[0252] Furthermore, the inventions of the first embodiment and its modified form, and the inventions of the second embodiment and its modified form can be combined as appropriate, and such combinations are not limited to the examples described above. [Explanation of symbols]

[0253] 1 Electric work equipment 30 Control device 41 Battery Packs 41a BMU (Battery Monitoring Unit) 46 Electric motor E Actuating equipment

Claims

1. Multiple battery packs, An operating device that operates using power supplied from the aforementioned battery pack, A battery monitoring device that detects the remaining capacity and temperature of each of the aforementioned battery packs, A control device that controls the charging and discharging of a plurality of battery packs based on the remaining capacity of each battery pack, Equipped with, The control device is In the discharge mode for supplying power to the aforementioned operating device, one of the multiple battery packs is selected as the discharge battery pack for supplying power to the operating device, and power is supplied to the operating device from the discharge battery pack. In the charging mode for charging the battery pack, among the multiple battery packs, the battery pack with the largest remaining capacity, whose remaining capacity is below a predetermined first remaining capacity threshold and whose temperature is below a predetermined temperature threshold, is selected as the battery pack for charging, and the selected battery pack is charged. In the aforementioned charging mode, When the temperature of the charging battery pack exceeds the temperature threshold, the charging battery pack is switched to the battery pack with the largest remaining capacity among the other battery packs whose remaining capacity is less than the first remaining capacity threshold and whose temperature is below the temperature threshold. An electric work machine that switches to a battery pack when it detects a battery pack whose remaining capacity is less than the first remaining capacity threshold and temperature is less than the temperature threshold, and whose remaining capacity is greater than the remaining capacity of the charging battery pack.

2. The electric work machine according to claim 1, wherein, in the charging mode, when the temperature of the charging battery pack is below the temperature threshold and the remaining capacity of the charging battery pack reaches the first remaining capacity threshold, the control device switches the charging battery pack to the battery pack with the largest remaining capacity among the other battery packs whose remaining capacity is below the first remaining capacity threshold and whose temperature is below the temperature threshold.

3. Multiple battery packs, An operating device that operates using power supplied from the aforementioned battery pack, A battery monitoring device that detects the remaining capacity and temperature of each of the aforementioned battery packs, A control device that controls the charging and discharging of a plurality of battery packs based on the remaining capacity of each battery pack, Equipped with, The control device is In the discharge mode for supplying power to the aforementioned operating device, one of the multiple battery packs is selected as the discharge battery pack for supplying power to the operating device, and power is supplied to the operating device from the discharge battery pack. In the charging mode for charging the battery pack, among the multiple battery packs, the battery pack with the largest remaining capacity, whose remaining capacity is below a predetermined first remaining capacity threshold and whose temperature is below a predetermined temperature threshold, is selected as the battery pack for charging, and the selected battery pack is charged. An electric work machine that, in the charging mode, calculates the expected temperature of a battery pack when it is charged for a predetermined time for a battery pack whose remaining capacity is less than the first remaining capacity threshold and whose temperature is less than the temperature threshold, and determines the battery pack with the largest remaining capacity among the battery packs whose expected temperature is less than the temperature threshold as the battery pack for charging.

4. The control device is The electric work machine according to any one of claims 1 to 3, wherein, in the discharge mode, if the remaining capacity of the discharge battery pack is less than a predetermined second remaining capacity threshold, a limiting process is performed to limit the power supplied from the discharge battery pack to the operating device.

5. The electric work machine according to claim 4, wherein the first remaining capacity threshold is greater than the second remaining capacity threshold.

6. The aforementioned operating device includes an electric motor, The electric work machine according to claim 4, wherein the control device, in the discharge mode, limits the upper limit of the rotational speed of the electric motor as the limiting process when the remaining capacity of the discharge battery pack is less than the second remaining capacity threshold.

7. The electric work machine according to any one of claims 1 to 3, wherein the control device performs a limiting process to limit the power supplied from the discharge battery pack to the operating device when the temperature of the discharge battery pack is above the temperature threshold in the discharge mode.

8. A control method for an electric work machine comprising multiple battery packs and actuators that operate using power supplied from the battery packs, In the discharge mode for supplying power to the aforementioned operating device, one of the multiple battery packs is selected as the discharge battery pack for supplying power to the operating device, and power is supplied to the operating device from the discharge battery pack. In the charging mode for charging the battery pack, among the plurality of battery packs, the battery pack with the largest remaining capacity, whose remaining capacity is below a predetermined first remaining capacity threshold and whose temperature is below a predetermined temperature threshold, is selected as the battery pack for charging, and the selected battery pack for charging is charged. In the aforementioned charging mode, When the temperature of the charging battery pack exceeds the temperature threshold, the charging battery pack is switched to the battery pack with the largest remaining capacity among the other battery packs whose remaining capacity is less than the first remaining capacity threshold and whose temperature is below the temperature threshold. A control method for an electric work machine that, when a battery pack is detected whose remaining capacity is less than the first remaining capacity threshold and whose temperature is less than the temperature threshold, and whose remaining capacity is greater than the remaining capacity of the charging battery pack, switches the charging battery pack to the battery pack.

9. A control method for an electric work machine comprising a plurality of battery packs and an operating device that operates using power supplied from the battery packs, In the discharge mode for supplying power to the aforementioned operating device, one of the multiple battery packs is selected as the discharge battery pack for supplying power to the operating device, and power is supplied to the operating device from the discharge battery pack. In the charging mode for charging the battery pack, among the multiple battery packs, the battery pack with the largest remaining capacity, whose remaining capacity is below a predetermined first remaining capacity threshold and whose temperature is below a predetermined temperature threshold, is selected as the battery pack for charging, and the selected battery pack is charged. A control method for an electric work machine, comprising: calculating the expected temperature of a battery pack when it is charged for a predetermined time in the charging mode, provided that the battery pack has a remaining capacity less than the first remaining capacity threshold and a temperature less than the temperature threshold; and determining the battery pack with the largest remaining capacity among the battery packs whose expected temperature is less than the temperature threshold as the battery pack for charging.

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