Electric work equipment and method for starting electric work equipment

Abstract

To provide an electric work machine that can prevent battery packs from breaking down by connecting a plurality of battery packs in parallel.SOLUTION: The electric work machine includes an electric device 20, an electric circuit 21, a plurality of battery packs 22, etc., and a control unit 23. The electric circuit is electrically connected to the electric device 20. The plurality of battery packs are connected to the electric device 20 via the electric circuit 21. In a drive mode, if a voltage difference between the plurality of battery packs 22, 22 exceeds a preset reference value, the control unit 23 connects the battery pack 22 with the highest voltage among the plurality of battery packs 22, etc. to the electric device 20.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present invention relates to a power-operated work machine that operates with power supplied from a plurality of battery packs.

Background Art

[0002] Conventionally, power-operated work machines that operate with power supplied from a plurality of battery packs (assembled batteries) have been provided. This type of power-operated work machine includes an electric device, an electric circuit electrically connected to the electric device, and a plurality of battery packs connected in parallel to the electric device via the electric circuit. In this type of power-operated work machine, by electrically connecting a plurality of battery packs in parallel, the current value of each battery pack is reduced to supply power to the electric device (see, for example, Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, when multiple battery packs are connected in parallel, the voltage difference between the battery packs can cause them to malfunction. Specifically, a battery pack is a battery pack containing multiple individual cells connected in series, and therefore, the individual characteristics (output performance) of each battery pack are affected by the individual differences of each of the individual cells that make up the battery pack. As a result, the voltage (power supply voltage) differs for each battery pack, and when multiple battery packs are connected in parallel, electricity flows from the battery pack with the higher voltage to the battery pack with the lower voltage. In this case, if the current value of the electricity flowing into the battery pack with the lower voltage exceeds the allowable value, the internal circuit of the battery pack may be damaged, and as a result, the battery pack may malfunction.

[0005] Therefore, the object of the present invention is to provide an electric work machine and a method for starting an electric work machine that can prevent battery pack failures caused by the parallel connection of multiple battery packs. [Means for solving the problem]

[0006] The electric work machine according to the present invention comprises an electrical device, an electrical circuit electrically connected to the electrical device, and a connection to the electrical device via the electrical circuit. Three or more The system comprises a battery pack and a control unit, the control unit having a drive mode for driving the electrical equipment with power supplied from the battery pack and a charge mode for charging the battery pack. The voltages of the three or more battery packs are compared with each other to calculate the voltage difference between the battery packs of the combination being compared, and if at least one of the calculated voltage differences exceeds a preset reference value, the drive mode is activated. , the above Three or more Of the battery packs, only the battery pack with the highest voltage is connected to the electrical device to power it.

[0007] The electric work machine according to the present invention comprises an electrical device, an electrical circuit electrically connected to the electrical device, and a connection to the electrical device via the electrical circuit. Three or moreThe system comprises a battery pack and a control unit, the control unit having a drive mode for driving the electrical equipment with power supplied from the battery pack and a charge mode for charging the battery pack. The voltages of the three or more battery packs are compared with each other to calculate the voltage difference between the battery packs of the combination being compared, and if at least one of the calculated voltage differences exceeds a preset reference value, in the charging mode, The aforementioned Three or more Of the battery packs, only the one with the lowest voltage will be charged.

[0008] The method for starting an electric work machine according to the present invention comprises an electrical device, an electrical circuit electrically connected to the electrical device, and a connection to the electrical device via the electrical circuit. Three or more A battery pack is provided, and the electrical equipment is powered by the power supplied from the battery pack. A method for starting an electric work machine having a drive mode and a charging mode for charging the battery pack, The voltages of the three or more battery packs are compared with each other to calculate the voltage difference between the battery packs of the combination being compared, and if at least one of the calculated voltage differences exceeds a preset reference value, in the drive mode, The aforementioned Three or more Of the battery packs, only the battery pack with the highest voltage is connected to the electrical device to power it.

[0009] The charging method for an electric work machine according to the present invention comprises an electrical device, an electrical circuit electrically connected to the electrical device, and a connection to the electrical device via the electrical circuit. Three or more A charging method for an electric work machine comprising a battery pack and a drive mode for driving the electrical equipment with power supplied from the battery pack, and a charging mode for charging the battery pack, The voltages of the three or more battery packs are compared with each other to calculate the voltage difference between the battery packs of the combination being compared, and if at least one of the calculated voltage differences exceeds a preset reference value, in the charging mode, The aforementioned Three or more Of the battery packs, only the one with the lowest voltage will be charged. [Effects of the Invention]

[0010] According to the present invention, battery pack failure can be prevented by connecting multiple battery packs in parallel. [Brief explanation of the drawing]

[0011] [Figure 1]FIG. 1 is a side view of a power working machine according to an embodiment of the present invention. [Figure 2] FIG. 2 is a schematic system diagram of a hydraulic system and an electrical system of the power working machine according to the same embodiment. [Figure 3] FIG. 3 is an electrical system diagram of the power working machine according to the same embodiment. [Figure 4] FIG. 4 is a processing flowchart of parallel connection availability diagnosis of a battery pack of the power working machine according to the same embodiment. [Figure 5] FIG. 5 is a processing flowchart of parallel connection processing of a battery pack of the power working machine according to the same embodiment. [Figure 6] FIG. 6 is a list of diagnosis conditions and results in each diagnosis process in the opening / closing operation diagnosis of an internal relay of a battery pack of the power working machine according to the same embodiment. [Figure 7] FIG. 7 is a processing flowchart of failure diagnosis of the power working machine according to the same embodiment. [Figure 8] FIG. 8 is a processing flowchart of single connection processing of a battery pack of the power working machine according to the same embodiment. [Figure 9] FIG. 9 is a processing flowchart of a charging mode for charging a battery pack of the power working machine according to the same embodiment.

MODE FOR CARRYING OUT THE INVENTION

[0012] Hereinafter, a power working machine according to an embodiment of the present invention will be described with reference to the drawings.

[0013] As shown in FIG. 1, the power working machine 1 is a self-propelled riding-type working machine and includes a traveling device 10.

[0014] The traveling device 10 has a traveling frame 100 and a traveling mechanism 101. The traveling frame 100 is a structure to which the traveling mechanism 101 is attached.

[0015] The running mechanism 101 is provided on the left and right sides of the running frame 100, respectively. That is, the running mechanism 101 is located in the left-right width direction perpendicular to the forward and backward directions. They are arranged in pairs.

[0016] In this embodiment, the travel mechanism 101 is a crawler-type travel mechanism. Specifically, the travel mechanism 101 comprises an idler 102, a drive wheel 103, a plurality of road wheels 104, an endless annular crawler belt 105, and a travel motor 106.

[0017] The idler 102 is located at the front of the running frame 100, on the leading side in the forward direction. The drive wheel 103 is located at the rear of the running frame 100, on the leading side in the reverse direction. Multiple road wheels 104 are provided between the idler 102 and the drive wheel 103. The crawler belt 105 is wrapped around the idler 102, the drive wheel 103, and the road wheels 104.

[0018] The travel motor 106 rotates the drive wheels 103. In this embodiment, a hydraulic motor is used for the travel motor 106. Each of the pair of left and right travel mechanisms 101 rotates the crawler belt 105 by rotating the drive wheels 103.

[0019] The electric work machine 1 according to this embodiment includes a work device 11 for performing a predetermined task. The electric work machine 1 also includes a turntable 12 fixed to a travel frame 100, a machine body 13 supported by the turntable 12, and a cabin 14 supported by the machine body 13.

[0020] In this embodiment, the electric work machine 1 includes a dozer device 11a and a shovel device 11b as the work device 11.

[0021] The dozer device 11a is mounted in front of the traveling device 10. Specifically, the dozer device 11a comprises a dozer plate 110a, a support arm 111a to which the dozer plate 110a is connected at its tip, the support arm 111a being connected to the traveling frame 100 via a laterally extending shaft and capable of swinging vertically around the shaft, and a hydraulic cylinder 112a for swinging the support arm 111a.

[0022] The shovel device 11b comprises a boom 110b, an arm 111b, a bucket 112b which is a work tool, and hydraulic cylinders 113b, 114b, and 115b.

[0023] The boom 110b has a base end and a tip end. The base end of the boom 110b is pivotally connected to a swing bracket 130, which will be described later, via a first axis S1 that extends in a direction perpendicular to the vertical direction. As a result, the boom 110b rotates (rotates) around the first axis S1, allowing the tip end to swing in the vertical direction.

[0024] The arm 111b has a base end and a tip end. The base end of the arm 111b is pivotally connected to the tip end of the boom 110b via a second axis S2 that extends in a direction perpendicular to the vertical direction. As a result, the arm 111b rotates (rotates) around the second axis S2, allowing the tip end to swing in the forward / backward or vertical direction. The bucket 112b is connected to the tip end of the arm 111b so as to enable scooping and dumping operations.

[0025] The electric work machine 1 includes, as hydraulic cylinders for the work device 11, a boom cylinder 113b for swinging the boom 110b, an arm cylinder 114b for swinging the arm 111b, and a bucket cylinder 115b for performing scooping and dumping operations on the bucket 112b. The electric work machine 1 also includes, as a hydraulic cylinder, a swing cylinder 131 for swinging the swing bracket 130.

[0026] The turntable 12 is a turntable bearing having an inner ring and an outer ring, and either the inner ring or the outer ring A travel frame 100 is connected to one of the inner or outer rings, and the machine body 13 is connected to the other of the inner or outer rings. The turntable 12 meshes a pinion attached to the output shaft of a slewing motor 120 (see Figure 2), which is fixed to either the machine body 13 or the travel frame 100, with an annular gear provided on the inner circumference of the inner ring or the outer circumference of the outer ring, which is connected to the other of the machine body 13 or the travel frame 100. As a result, the turntable 12 rotates the inner and outer rings relative to each other around an axis that extends vertically when driven by the slewing motor 120, and rotates the machine body 13, which is connected to the other of the inner or outer ring, around an axis that extends vertically. In this embodiment, a hydraulic motor is used for the slewing motor 120.

[0027] A swing bracket 130 is connected to the front of the machine body 13, which is the leading edge in the forward direction. Specifically, the swing bracket 130 is pivotally connected to the machine body 13 via an axis that extends in the vertical direction. This allows the swing bracket 130 to rotate (rotate) around the axis that extends in the vertical direction. In other words, the swing bracket 130 swings from side to side by the extension and retraction of the swing cylinder 131. The machine body 13 supports the cabin 14, which houses a seat 140 in which an operator sits, an operating means 141 for operating the electric work machine 1, a start switch for activating the electric work machine 1 (traveling device 10 and work device 11), and a monitor 142 (see Figure 2) as a means of notifying the operator of the operating status, etc.

[0028] As shown in Figure 2, the electric work machine 1 is equipped with multiple hydraulic actuators such as hydraulic cylinders 112a, 113b, 114b, 115b, 131 and hydraulic motors 106, 120, and the travel device 10 (travel mechanism 101), work device 11 (dozer device 11a and shovel device 11b), and turntable 12, and is equipped with a hydraulic pump 15 that supplies hydraulic fluid to multiple hydraulic actuators 106, 112a, 113b, 114b, 115b, 120, 131. In this embodiment, a multi-cylinder hydraulic pump 15 is used for the hydraulic pump 15 in order to supply hydraulic fluid to multiple hydraulic actuators 106, 112a, 113b, 114b, 115b, 120, 131.

[0029] The hydraulic pump (multi-unit hydraulic pump) 15 is electrically powered. That is, the electric work machine 1 is equipped with an electric motor 16 that drives the hydraulic pump 15.

[0030] The electric work machine 1 according to this embodiment comprises, based on the above configuration, an electrical device 20, an electrical circuit 21 electrically connected to the electrical device 20, a plurality of battery packs 22... sequentially connected in parallel to the electrical device 20 via the electrical circuit 21, and a control unit 23. Furthermore, the electric work machine 1 comprises a junction box 24 that houses all or part of the electrical circuit 21. In Figure 2, the electrical circuit 21 is shown by a dashed line, the signal system for sending and receiving control signals is shown by a dashed line, and the hydraulic system is shown by a double dashed line.

[0031] In this embodiment, the electric work machine 1 is equipped with a plurality of electrical devices 20. Specifically, the electric work machine 1 is equipped with an inverter 20a for driving an electric motor 16 as an output electrical device 20. That is, the electric work machine 1 is equipped with electrical devices 20 for driving work devices 11 (in this embodiment, a dozer device 11a and a shovel device 11b) for performing a predetermined task.

[0032] The electric work machine 1 is equipped with other electrical equipment 20 for output, such as a DC / DC converter 20b and a heater 20c for heating the cabin 14. Note that the other electrical equipment 20 for output described here is an example and may be added depending on the specifications and functions of the electric work machine 1.

[0033] The electric work machine 1 is equipped with a charging inlet that connects to an external charging device (e.g., a rapid charger) as an input electrical device 25. In this embodiment, a 12V battery 26 is connected to the DC / DC converter 20b in addition to the battery pack 22.

[0034] As shown in Figure 3, the electrical devices 20 and 25 each have a positive terminal PE and a negative terminal NE, both for input and output.

[0035] The electrical circuit 21 includes a plurality of external relays 211, each corresponding to a plurality of battery packs 22, etc. Specifically, the electrical circuit 21 includes a plurality of primary circuits 210, each electrically and physically connected to a plurality of battery packs 22, etc., each of which is electrically connected to an output electrical device 20 (inverter 20a, DC / DC converter 20b, heater 20c) and an input electrical device, a charging inlet 25, and a plurality of external relays 211, etc., which switch each of the plurality of primary circuits 210, etc.

[0036] In this embodiment, the electric work machine 1 includes, as described above, multiple output electrical devices 20 (inverter 20a, DC / DC converter 20b, heater 20c) and an input electrical device, a charging inlet 25. Accordingly, the electrical circuit 21 includes multiple secondary circuits 212... that are electrically and physically connected to the multiple output electrical devices 20 (inverter 20a, DC / DC converter 20b, heater 20c) and the input electrical device (charging inlet) 25.

[0037] Specifically, the electrical circuit 21 includes a plurality of primary circuits 210... connected to each of the plurality of battery packs 22, a common circuit 213 to which the plurality of primary circuits 210... are electrically and physically connected, and a plurality of secondary circuits 212... electrically and physically connected to the common circuit 213, each of which is connected to a separate output electrical device 20 (inverter 20a, DC / DC converter 20b, heater 20c) and an input electrical device, a charging inlet 25.

[0038] The electrical circuit 21 connects multiple battery packs 22... in parallel by connecting multiple primary circuits 210... to a common circuit 213. More specifically, the electrical circuit 21 includes multiple positive primary circuits 210a... connected to the positive output terminals (positive-side external terminals) 223a of each of the multiple battery packs 22..., and multiple negative primary circuits 210b... connected to the negative output terminals (negative-side external terminals) 223b of each of the multiple battery packs 22....

[0039] Furthermore, the electrical circuit 21 includes a common circuit 213, which is a positive common circuit 213a to which a plurality of positive primary circuits 210a... are connected, and a negative common circuit 213b to which a plurality of negative primary circuits 210b... are connected. In addition, the electrical circuit 21 includes a plurality of secondary circuits 212..., which are a plurality of positive secondary circuits 212a... connected to the positive common circuit 213a, each connected to the positive connection terminal PE of a separate output electrical device 20 (inverter 20a, DC / DC converter 20b, heater 20c) and an input electrical device (charging inlet) 25, and a plurality of negative secondary circuits 212b... connected to the negative common circuit 213b, each connected to the negative connection terminal NE of a separate output electrical device 20 (inverter 20a, DC / DC converter 20b, heater 20c) and an input electrical device (charging inlet) 25.

[0040] The external relay 211 is placed in each of the multiple positive primary circuits 210a... or in each of the multiple negative primary circuits 210b.... In this embodiment, the external relay 211 is placed in each of the multiple negative primary circuits 210b.... The external relay 211 is a normally open (a) contact relay switch. That is, the external relay 211 is a relay switch that normally maintains the electrical circuit 21 in an open (disconnected) state and closes the electrical circuit 21 in an open (connected) state when activated. Yes, there is. The external relay 211 operates in response to instructions from the control unit 23 (ECU 23a) and opens and closes the electrical circuit 21.

[0041] As a result, multiple external relays 211... can open and close the circuits (electrical systems) connecting multiple battery packs 22... to output electrical equipment 20 (inverter 20a, DC / DC converter 20b, heater 20c). In addition, multiple external relays 211... can also open and close the circuits (electrical systems) connecting multiple battery packs 22... to the input electrical equipment, the charging inlet 25.

[0042] Each of the multiple battery packs 22... has an internal circuit 222 and an internal relay 220 that opens and closes the internal circuit 222. Each of the multiple battery packs 22... also has a battery cell (single cell) 221. Specifically, each of the multiple battery packs 22... has multiple battery cells 221... In other words, the battery pack 22 is a so-called battery pack. Accordingly, each of the battery packs 22... has an internal circuit 222 that includes multiple battery cells 221... connected in series. That is, the internal circuit 222 is a series circuit in which multiple battery cells 221... and the internal relay 220 are connected in series.

[0043] The battery pack 22 has positive and negative external terminals 223a and 223b that terminate the internal circuit 222. That is, the battery pack 22 has a positive output terminal 223a and a negative output terminal 223b as external terminals. The positive output terminal 223a is electrically connected to the positive terminal of a battery cell 221 at one end of a plurality of battery cells 221... connected in series, and the negative output terminal 223b is electrically connected to the negative terminal of a battery cell 221 at the other end of a plurality of battery cells 221... connected in series.

[0044] Specifically, the internal circuit 222 includes a plurality of battery cells 221... connected in series, a first circuit 222a connecting the positive terminal and positive output terminal 223a of a battery cell 221 at one end of the plurality of battery cells 221... connected in series, and a first internal relay 220a on the positive side, which serves as the internal relay 220, and a second circuit 222b connecting the negative terminal and negative output terminal 223b of a battery cell 221 at the other end of the plurality of battery cells 221... connected in series, and a second internal relay 222b on the negative side, which serves as the internal relay 220.

[0045] The internal relays 220 (first internal relay 220a and second internal relay 220b) are relay switches with normally open (a) contacts. In other words, the internal relays 220 (first internal relay 220a and second internal relay 220b) are relay switches that normally keep the internal circuit 222 open and close the internal circuit 222 when activated.

[0046] In this embodiment, the internal circuit 222 includes a precharge circuit 224 connected in parallel to the first internal relay 220a of the first circuit 222a. The precharge circuit 224 is a circuit connected to the first circuit 222a, which is on the primary side (upstream) and secondary side (downstream) of the first internal relay 220a, and includes a precharge resistor 224a and a precharge relay 224b that opens and closes the precharge circuit 224. The precharge relay 224b is a normally open relay switch. That is, the precharge relay 224b is a relay switch that normally keeps the precharge circuit 224 open and closes the precharge circuit 224 when activated. In the precharge circuit 224, the precharge resistor 224a and the precharge relay 224b are connected in series. In other words, the pre-charge resistor 224a and the pre-charge relay 224b form a series connection circuit, and the pre-charge circuit 224, which includes this series connection circuit (pre-charge resistor 224a and pre-charge relay 224b), is connected in parallel to the first internal relay 220a.

[0047] The battery pack 22 (internal circuit 222) includes a discharge circuit 225. The discharge circuit 225 is connected to the first circuit 222a and the second circuit 222b. Specifically, the discharge circuit 225 is a so-called discharge circuit, and it spans the downstream side of the first internal relay 220a in the first circuit 222a and the upstream side of the second internal relay 220b in the second circuit 222b. Here, "upstream side" and "downstream side" are expressions based on the direction of current (flow of electricity) relative to the multiple battery cells 221... (multiple battery cells 221... connected in series) that constitute the internal circuit 222 of the battery pack 22.

[0048] The discharge circuit 225 includes a discharge resistor 225a and a discharge relay 225b that opens and closes the discharge circuit 225. The discharge relay 225b is a normally open (a) contact relay switch. That is, the discharge relay 225b is a relay switch that normally keeps the discharge circuit 225 open (disconnected) and closes (connects) the discharge circuit 225 when activated. In the discharge circuit 225, the discharge resistor 225a and the discharge relay 225b are connected in series.

[0049] The control unit 23 controls the opening and closing of the electrical circuit 21 and the internal circuit 222 of the battery pack 22. Specifically, in addition to the external relay 211 in the electrical circuit 21, the control unit 23 operates the opening and closing of the internal relays 220 (first internal relay 220a and second internal relay 220b), the pre-charge relay 224b, and the discharge relay 225b in the internal circuit 222 of the battery pack 22. The control unit 23 has a drive mode in which it drives the electrical equipment 20 with power supplied from the battery pack 22, and a charge mode in which it charges the battery pack 22. More specifically, as shown in Figure 2, the electric work machine 1 includes an electronic control unit (hereinafter referred to as ECU) 23a as the control unit 23 that controls the entire electric work machine 1. In this embodiment, as a battery pack 22, which is a battery pack, is used as the power supply source, the electric work machine 1 includes a battery management system (hereinafter referred to as BMS) 23b as the control unit 23 that monitors and controls the battery pack 22. Accordingly, in this embodiment, the ECU23a and BMS23b, which constitute the control unit 23, operate the opening and closing of relay switches (external relay 211 in the electrical circuit 21, internal relays 220 (first internal relay 220a and second internal relay 220b) in the internal circuit 222 of the battery pack 22, pre-charge relay 224b, and discharge relay 225b). Specifically, the ECU23a issues instructions for opening and closing the relay switches, and the BMS23b, in response to the instructions from the ECU23a, executes the opening and closing of the relay switches.

[0050] In this embodiment, the ECU 23a sequentially connects a plurality of battery packs 22... to the electrical equipment 20. Accordingly, the plurality of battery packs 22... include a first battery pack 22, which is the battery pack set to be connected first to the electrical equipment 20, and a second battery pack 22, which is the battery pack set to be connected second or later to the electrical equipment 20. Specifically, the plurality of battery packs 22 are connected sequentially to the electrical equipment 20 and are ultimately connected in parallel, so that all of them supply power to the electrical equipment 20.

[0051] Accordingly, in this document, among multiple battery packs 22, the battery pack 22 that is first connected to the electrical equipment 20 is referred to as the first battery pack, and the battery packs 22 that are second or later connected to the electrical equipment 20 are referred to as second battery packs. If there are two battery packs 22, there will be one first battery pack 22 and one second battery pack 22. However, if there are three or more battery packs 22, there will be one first battery pack 22 and two or more second battery packs 22.

[0052] Based on this premise, the ECU23a is connected to the second battery pack of the electrical equipment 20. The ECU 23a is configured to allow specifying whether or not to diagnose the opening and closing operation of the internal relay 220 of the 22. The ECU 23a is also configured to allow specifying whether or not to perform precharging in the precharge circuit 224 of the second battery pack 22. Furthermore, when connecting the second battery pack 22 to the electrical equipment 20 (when performing the first downstream processing described later), the ECU 23a is configured to allow specifying whether or not to simultaneously close the first internal relay 220a and the second internal relay 220b, which are internal relays 220.

[0053] For these specifications, the ECU23a's memory unit either stores pre-set information (unchangeable standard information) or stores information entered via the input device (changeable information). The input device may be a device dedicated to input, but for example, the monitor 142, which serves as a notification means, may be configured as a touch panel, and input may be performed via the monitor 142.

[0054] In this embodiment, the above specifications are stored in the memory unit of the ECU23a, which contains pre-set information (unchangeable specification information). Specifically, the memory unit of the ECU23a stores a specification (instruction) indicating that diagnosis is not required regarding whether or not diagnosis of the opening and closing operation of the internal relay 220 of the second battery pack 22 is required. The memory unit of the ECU23a also stores a specification (instruction) indicating that precharging is not required regarding whether or not precharging is required in the precharge circuit 224 of the second battery pack 22. Furthermore, the memory unit of the ECU23a stores a specification (instruction) indicating that the first internal relay 220a and the second internal relay 220b should be closed simultaneously when connecting the second battery pack 22 to the electrical equipment 20 (when performing the first downstream processing described later).

[0055] The electric work machine 1 is equipped with a start switch, and is started and stopped by an ON / OFF operation of the start switch. In this embodiment, when the start switch is turned ON, the control unit 23 (ECU 23a) executes a drive mode in which the electrical equipment 20 is driven by power supplied from the battery pack 22. That is, the ECU 23a performs the start process when the start switch is turned ON.

[0056] The BMS23b is a control device specifically for the battery pack 22, while the ECU23a is a higher-level control device than the BMS23b. In other words, the BMS23b performs control such as opening and closing of the internal relays 220 (220a, 220b), but it is under the control of the ECU23a and follows instructions and commands from the ECU23a.

[0057] A BMS23b is provided for each battery pack 22 and monitors (measures) the overall temperature, current, and voltage of the corresponding battery pack 22. The overall current and voltage refer to the current and voltage between the positive output terminal 223a and the negative output terminal 223b, which are external terminals of each battery pack 22. In this embodiment, the BMS23b is intended to monitor (measure) the entire battery pack 22, but in addition to monitoring (measuring) the entire battery pack, it may also monitor (measure) the temperature, voltage, and current of the multiple battery cells 221... housed inside.

[0058] Although not shown in the diagram, the junction box 24 is a housing with an openable and closable door, and houses the electrical circuit 21. In this embodiment, the junction box 24 houses the downstream portion of a plurality of primary circuits 210 (210b, 210a), the common circuit 213 (213b, 213a), and the upstream portion of a plurality of secondary circuits 212 (212b, 212a). That is, the junction box 24 contains the connection portions of the plurality of primary circuits 210 (210b, 210a) to the common circuit 213 (213b, 213a), and the connection portions of the plurality of secondary circuits 212 (212b, 212a) to the common circuit 213 (213b, 213a).

[0059] Furthermore, the junction box 24 also houses external relays 211 that are installed on the primary circuits 210 (210b, 210a). Accordingly, multiple external relays 211... are installed at intermediate positions in multiple primary circuits 210 (negative primary circuit 210b) and housed in the junction box 24.

[0060] In this embodiment, the electrical circuit 21 includes a negative primary circuit 210b and a positive primary circuit 210a as the primary circuit 210, and the external relay 211 is provided only in the negative primary circuit 210b. Accordingly, the external relay 211 is provided at an intermediate position in the negative primary circuit 210b so that it fits inside the junction box 24.

[0061] The external relay 211 is replaceable. That is, the external relay 211 is detachably mounted to the junction box 24 and can be replaced in the event of a failure.

[0062] In this explanation of the electrical circuit 21, "upstream side" refers to the battery pack 22 side (closer to the battery pack 22 than the reference point) with respect to any point on the electrical circuit connecting the battery pack 22 to the electrical equipment 20, and "downstream side" refers to the electrical equipment 20 side (closer to the electrical equipment 20 than the reference point) with respect to any point on the electrical circuit connecting the battery pack 22 to the electrical equipment 20.

[0063] The electric work machine 1 according to this embodiment is as described above. In the execution of the drive mode (startup process), the control unit 23 supplies power to the electrical equipment 20 (inverter 20a, DC / DC converter 20b, heater 20c) in the following procedure, and the electrical equipment 20 (inverter 20a, DC / DC converter 20b, heater 20c) performs its function. That is, among the multiple electrical equipment 20 (inverter 20a, DC / DC converter 20b, heater 20c), the inverter 20a, which is the electrical equipment 20 that operates the work device 11 (dozer device 11a, shovel device 11b), drives the electric motor 16 when powered, and the electric motor 16 operates the hydraulic pump 15.

[0064] To explain in more detail, when executing the above drive mode (startup process), first, when the operator turns ON the start switch, the control unit 23 (ECU 23a) determines whether or not multiple battery packs 22... can be connected in parallel (parallel connection feasibility diagnosis). Specifically, as shown in Figure 4, the BMS 23b measures the total voltage of the battery packs 22 and sends the result to the ECU 23a (S1). The ECU 23a compares the voltages of each of the multiple battery packs 22... and calculates the voltage difference between the battery packs 22, 22 (two battery packs 22, 22) that are being compared (S2). In this embodiment, since the electric work machine 1 is equipped with only two battery packs 22, 22, the ECU 23a has only one combination to compare and calculates the voltage difference between the two battery packs 22, 22.

[0065] The ECU23a determines whether the calculated voltage difference matches a preset reference value (S3). The "reference value" here is a value that does not cause any problems even if electricity flows between battery packs 22,22 due to the voltage difference between them when multiple battery packs 22,22 are connected in parallel. In this embodiment, the "reference value" is set within a range between an upper threshold and a lower threshold (between the two thresholds) (stored in the ECU23a), and if it is within the range of the two thresholds, it is treated as a match. Note that the reference value does not need to have a range (between the two thresholds), and may be a single threshold.

[0066] Note that the flowchart shown in Figure 4 also assumes the case where there are three or more battery packs 22..., and in the case where there are three or more battery packs 22..., there are three or more possible combinations for comparison. Accordingly, the ECU 23a calculates the voltage difference between the battery packs 22, 22 for three or more combinations and determines whether each voltage difference matches the reference value.

[0067] If the ECU 23a determines that the voltage difference between the two battery packs 22, 22 being compared matches the reference value (YES in S3), it decides to connect the battery packs 22 of that combination (the two battery packs 22, 22) in parallel (S4). In other words, if there are three or more combinations to compare, and the ECU 23a determines that the voltage difference in each combination matches the reference value, it decides to connect all three or more battery packs 22... in parallel (S4).

[0068] On the other hand, if the ECU 23a determines that the voltage difference between the two battery packs 22, 22 being compared does not match the reference value (NO in S3), the ECU 23a determines whether there is any other combination of two battery packs 22, 22 being compared in which the voltage difference matches the reference value (S5). If there is any other combination of two battery packs 22, 22 being compared in which the voltage difference matches the reference value (YES in S5), the ECU 23a decides to connect the battery packs 22, 22 in the combination in which the voltage difference matches the reference value in parallel (S4).

[0069] If there are no other combinations of battery packs 22,22 whose voltage difference matches the reference value (NO in S5), ECU 23a decides to use the battery pack 22 with the higher voltage among the two battery packs 22,22 that were compared as the power source (S6). In other words, if the voltage difference between the battery packs 22,22 being compared exceeds the reference value (or exceeds the upper threshold if the reference value has an upper and lower threshold), ECU 23a decides that the voltage difference between the battery packs 22,22 is too large and decides to connect the battery pack 22 with the highest voltage among the multiple battery packs 22... to the electrical equipment 20 (S6).

[0070] If there are three or more possible combinations, and none of the combinations match the standard value, the ECU 23a decides to use the battery pack 22 with the highest voltage among the three or more battery packs 22... as the power source (S6). In conjunction with this decision, the ECU 23a displays "Charging Required" on the monitor 142 inside the cabin 14, notifying the worker to charge the battery (S7, END).

[0071] As described above, in this embodiment, since only two battery packs 22, 22 are provided, if the voltage difference between the two battery packs 22, 22 matches the reference value (YES in S3), the ECU 23a decides to connect the two battery packs 22, 22 in parallel (S4). On the other hand, if the voltage difference between the two battery packs 22, 22 does not match the reference value (NO in S3), the ECU 23a determines that there are no combinations that can be connected in parallel (NO in S5), and decides to use the battery pack 22 with the higher voltage among the two battery packs 22, 22 that were compared as the power source (S6). In conjunction with this decision, the ECU 23a displays "Charging required" on the monitor 142 inside the cabin 14, and notifies the worker to charge (S7, END).

[0072] Through the above process, the ECU23a diagnoses whether multiple battery packs 22… can be connected in parallel. If there is a combination of battery packs 22… that can be connected in parallel, it performs the parallel connection process for the battery packs 22…. If there is no combination of battery packs 22… that can be connected in parallel, it performs the connection process for a single battery pack 22 (single connection). Perform the processing.

[0073] When performing parallel connection processing of battery packs 22..., as shown in Figure 5, the ECU 23a checks the number of times the external relay 211 corresponding to the battery pack 22 to be connected in parallel has been switched (S10). That is, the ECU 23a cumulatively stores the number of times the external relay 211 corresponding to the battery pack 22 has been switched and checks the current total number of times it has been switched at startup (S10). Then, based on the number of times the external relay 211 has been switched, the ECU 23a determines the order in which to connect the multiple battery packs 22... to the electrical circuit 21 (S11). In this embodiment, the ECU 23a sets the order of the battery packs 22 corresponding to the external relay 211 in descending order of the number of times the external relay 211 has been switched. That is, when the order in which to connect the multiple battery packs 22... to the electrical circuit 21 is determined (S11), the battery packs 22... connected to the external relay 211 that has a high number of times it has been switched as the external relay 211 corresponding to the second battery pack 22 are assigned an earlier order (set in descending order from first).

[0074] As will be described in detail later, in this embodiment, the external relay 211 corresponding to the first battery pack 22 is not (or is less likely to be) damaged by the inrush current caused by switching. On the other hand, the external relay 211 corresponding to the second battery pack 22 is damaged by the inrush current when switching, and the damage accumulates (cumulative) according to the number of switching cycles.

[0075] Therefore, by setting the connection order of the battery pack 22 to the external relay 211 that is most damaged (has the most switching cycles) as the external relay 211 corresponding to the second battery pack 22 as the first connection, the effect (damage) of inrush current on the external relay 211 that has suffered the most damage (accumulated damage) is reduced, and the damage received by each of the multiple external relays 211 is equalized.

[0076] Since the electric work machine 1 of this embodiment is equipped with only two battery packs 22, 22, at the time of the first startup, one of the battery packs 22 is set as the first (first battery pack), and the other battery pack 22 is set as the second or later (second battery pack). However, at the time of the second and subsequent startups, the battery pack 22 that is set as the first battery pack (set as the first) will alternate.

[0077] As described above, once the first battery pack 22 is determined, the ECU 23a performs a connection process to connect the first battery pack (battery pack) 22 to the electrical equipment 20. In this connection process, the ECU 23a performs a diagnostic process for battery packs 22 that are specified to require a diagnostic process for the switching operation of the internal relay 220, and omits the diagnostic process for battery packs 22 that are specified not to require a diagnostic process for the switching operation of the internal relay 220. In this embodiment, once the first battery pack 22 is determined, the ECU 23a performs a diagnostic process for the switching operation of the internal relay 220 of the first battery pack 22 (S12). In other words, the control unit 23, or ECU 23a, is configured to perform a diagnostic process for the opening and closing operation of the internal relay 220 for the first battery pack 22, which is the first battery pack connected to the electrical equipment 20 among the multiple battery packs 22..., and is configured to specify whether or not to perform a diagnostic process for the opening and closing operation of the internal relay 220 for the second battery pack 22, which is the second or later battery pack connected to the electrical equipment 20 among the multiple battery packs 22.... In this embodiment, the control unit 23, or ECU 23a, is configured to omit (omit) the diagnostic process for the opening and closing operation of the internal relay 220 for the second battery pack 22.

[0078] Accordingly, as described above, once the first battery pack 22 is determined, the ECU 23a performs a diagnostic process for the opening and closing operation of the internal relay 220 (S12).

[0079] The control unit 23, which is the ECU 23a, determines whether or not the internal relay 220 should operate in the diagnostic process for the switching operation of the internal relay 220, based on the switching state of the internal relay 220 and the change in the output voltage state of the first battery pack 22 that accompanies the switching of the internal relay 220.

[0080] In this embodiment, since the battery pack 22 has a pre-charge relay 224b and a discharge relay 225b in addition to the internal relay 220 as relay switches, the ECU 23a determines whether there is a malfunction in each relay switch based on the open / closed state of the internal relay 220 (first internal relay 220a, second internal relay 220b), the pre-charge relay 224b, and the discharge relay 225b located in the battery pack 22, and the change (presence or absence) of the output voltage of the battery pack 22 associated with the opening and closing of the relay switches.

[0081] In other words, in the diagnostic process for the internal relay 220, the ECU 23a assumes that the relay switch in the battery pack 22 is a normally open (a) contact switch, and identifies the faulty (stuck) relay switch (internal relay 220 (first internal relay 220a, second internal relay 220b), pre-charge relay 224b) based on the combination of opening and closing of the relay switch in the battery pack 22 and the output voltage state of the battery pack 22 corresponding to the opening and closing state (combination of opening and closing) of the relay switch.

[0082] To explain in more detail, the external relay 211, internal relays 220 (first internal relay 220a, second internal relay 220b), pre-charge relay 224b, and discharge relay 225b are normally open switches. However, in the diagnostic process for the opening and closing operation of the internal relays 220, etc., the ECU 23a instructs the external relay 211, internal relays 220 (first internal relay 220a, second internal relay 220b), pre-charge relay 224b, and discharge relay 225b to either open or close.

[0083] Based on the instructions from ECU23a, BMS23b controls the opening and closing of the external relay 211, internal relays 220 (first internal relay 220a, second internal relay 220b), pre-charge relay 224b, and discharge relay 225b. However, here we will omit the description of the instructions from ECU23a and the actions taken by BMS23b, and simply explain based on the open / closed states of the external relay 211, internal relays 220 (first internal relay 220a, second internal relay 220b), pre-charge relay 224b, and discharge relay 225b.

[0084] As shown in Figure 6, first, the external relay 211 is closed, and the first internal relay 220a, the second internal relay 220b, the pre-charge relay 224b, and the discharge relay 225b are opened. In this state, if there is an output voltage of the battery pack 22 (there is a voltage rise), the ECU 23a determines that one of the first internal relay 220a, the second internal relay 220b, or the pre-charge relay 224b is stuck in the closed state (first diagnosis).

[0085] In this state, the second internal relay 220b is closed, and if there is an output voltage from the battery pack 22 (voltage rise) in this state, the ECU 23a determines that either the first internal relay 220a or the pre-charge relay 224b is stuck in the closed state (second diagnosis).

[0086] Then, when the second internal relay 220b is opened and the pre-charge relay 224b is closed, and in this state there is an output voltage from the battery pack 22 (there is a voltage rise), the ECU 23a determines that the second internal relay 220b is stuck in the closed position (third diagnosis).

[0087] Next, the second internal relay 220b is closed, and then the first internal relay 220a is closed. When the second internal relay 220b is closed, the output voltage of the battery pack 22 rises. Using this rise in output voltage as a reference, if there is no rise in the output voltage of the battery pack 22 (no voltage rise) when the first internal relay 220a is closed, the ECU 23a determines that the second internal relay 220b or the pre-charge relay 224b is stuck in the open position, or that the discharge relay 225b is stuck in the closed position (fourth diagnosis).

[0088] Then, the pre-charge relay 224b is opened, and in this state, if the output voltage of the battery pack 22 does not rise (change) from the output power referenced in the fourth diagnosis, the ECU 23a determines that the first internal relay 220a is stuck in the open state (fifth diagnosis).

[0089] Furthermore, if the discharge relay 225b is closed after the first internal relay 220a is opened, and in this state the output voltage of the battery pack 22 does not drop below the output power referenced in the fourth diagnosis, the ECU 23a determines that the first internal relay 220a or the second internal relay 220b is stuck in the closed position, or that the discharge relay 225b is stuck in the open position (sixth diagnosis).

[0090] Next, the second internal relay 220b and the discharge relay 225b are opened. If the output voltage of the battery pack 22 does not drop at this time, the ECU 23a determines that the discharge relay 225b is stuck in the open position, the discharge resistor 225a has melted, or the first internal relay 220a or the second internal relay 220b is stuck in the closed position (seventh diagnosis).

[0091] In this way, the diagnostic process for the opening and closing operation of the relay switch (internal relay 220) can diagnose (determine) whether there is an abnormality in the relay switches 220, 224b, and 225b (internal circuit 222) based on the voltage state (change) of the battery pack 22 that occurs when there is an abnormality in one of the multiple relay switches (internal relay 220 (first internal relay 220a, second internal relay 220b), pre-charge relay 224b, and discharge relay 225b) inside the battery pack 22.

[0092] Furthermore, the diagnostic process for switching operations according to this embodiment detects abnormalities in relay switches based on the combination of the switching states of multiple relay switches (internal relay 220 (first internal relay 220a, second internal relay 220b), pre-charge relay 224b, discharge relay 225b) within the battery pack 22 and the output voltage state of the battery pack 22 at that combination. This makes it possible to identify the faulty relay switch from among the multiple relay switches.

[0093] Then, as described above, a diagnostic process is performed on the opening and closing operation of the relay switches (internal relays 220 (first internal relay 220a, second internal relay 220b), pre-charge relay 224b, discharge relay 225b) of the first battery pack 22. If it is determined that there is an abnormality in the relay switches (internal relays 220 (first internal relay 220a, second internal relay 220b), pre-charge relay 224b, discharge relay 225b) the drive mode (startup process) is canceled, or a single battery pack connection process (single connection process: see Figure 8) is performed on the battery pack 22 as the second battery pack 22. In this case, the drive mode (startup process) is canceled, and consequently, the notification means (monitor) 142 is displayed to notify the operator that there is an abnormality in the battery pack 22.

[0094] Returning to Figure 5, as described above, ECU 23a performs a diagnostic process for the opening and closing operation of the relay switches of the first battery pack 22 (internal relays 220 (first internal relay 220a, second internal relay 220b), pre-charge relay 224b, discharge relay 225b). If it determines that there is no abnormality in the relay switches (internal relays 220 (first internal relay 220a, second internal relay 220b), pre-charge relay 224b, discharge relay 225b), it changes the external relay 211 corresponding to the first battery pack 22 from the open state to the closed state (S13: first pre-processing (second connection processing)). In other words, ECU 23a changes the external relay 211 on the primary circuit 210 connected to the first battery pack 22 from the open state to the closed state (S13: first pre-processing (second connection processing)). In this embodiment, the ECU 23a changes the external relay 211 on the negative primary circuit 210b connected to the first battery pack 22 from an open state to a closed state (S13: First pre-processing (second connection processing)).

[0095] ECU23a waits until the external relay 211 of the primary circuit 210 (negative primary circuit 210b) connected to the first battery pack 22 is closed (S14). When the external relay 211 on the primary circuit 210 (negative primary circuit 210b) is closed (YES in S14), ECU23a instructs the pre-charge relay 224b of the first battery pack 22 to switch from the open state to the closed state (S15: second pre-processing). In addition, ECU23a instructs the internal relay 220 of the first battery pack 22 to be closed at the same time as closing the pre-charge relay 224b (S15: third pre-processing (first connection processing)). Accordingly, BMS23b corresponding to the first set battery pack 22 closes the internal relay 220 and the pre-charge relay 224b (S15: second pre-processing, third pre-processing).

[0096] In this embodiment, the battery pack 22 includes a first internal relay 220a and a second internal relay 220b as internal relays 220, and since the precharge circuit 224 is connected in parallel with the first internal relay 220a, when the BMS 23b changes the internal relay 220 of the first battery pack 22 from the open state to the closed state, it first changes the second internal relay 220b and the precharge relay 224b from the open state to the closed state (after precharging in the precharge circuit 224 is completed), and then changes the first internal relay 220a, which is in parallel with the precharge relay 224b, from the open state to the closed state (S15: third pre-processing). That is, with the first internal relay 220a, which is connected in parallel with the precharge circuit 224, being the last to close, the entire internal circuit 222 becomes closed (conductive), and the first battery pack 22 is electrically connected to the electrical circuit 21 (electrical equipment 20) (S15: third pre-processing).

[0097] Normally, the inrush current (starting current) that would act on the first internal relay 220a when it closes passes through the pre-charge circuit 224 connected in parallel to the first internal relay 220a, and is absorbed by the pre-charge resistor 224a on the pre-charge circuit 224. Therefore, damage to the internal relays 220 (220a, 220b) of the first battery pack 22 due to the inrush current is suppressed.

[0098] The ECU 23a waits until the internal relays 220 (first internal relay 220a and second internal relay 220b) of the first battery pack 22 are closed (S16). Although not shown in the flowchart of Figure 5, when precharging is performed by the precharge circuit 224, after precharging is complete and the internal circuit 222 is closed, the first internal relay 220a, which is in parallel with the precharge relay 224b, ensures continuity of the internal circuit 222. Therefore, with the first internal relay 220a in the closed state, the precharge relay 224b is opened.

[0099] Then, when the entire internal circuit 222 of the first battery pack 22 becomes conductive (the internal relays 220 (first internal relay 220a and second internal relay 220b) are closed) (YES in S16), the ECU 23a extracts the battery pack 22 that will be connected next (the battery pack to be connected) from among the second and subsequent battery packs 22 (S17). In this embodiment, the ECU 23a extracts the other battery pack 22 as the next target for connection (S17).

[0100] When ECU23a extracts the second battery pack 22 (S17), it instructs whether or not to perform fault diagnosis (external relay diagnosis process, switching relay diagnosis process) on the discharge relay 225b and the external relay 211 of the electrical circuit 21 of the second battery pack 22 (the second and subsequent battery packs 22 to be connected). In other words, if ECU23a is set to perform fault diagnosis (YES in S18), it performs fault diagnosis (S24), and if it is set not to perform fault diagnosis (NO in S18), it does not perform fault diagnosis and proceeds to the next step (S19).

[0101] In this embodiment, regarding the diagnostic process for the switching operation of the internal relay 220 of the battery pack 22, as described above, it is set to be performed for the first battery pack 22 but omitted (not performed) for the second battery pack 22, so the determination of whether or not the diagnostic process for the switching operation of the internal relay 220 of the second battery pack 22 is necessary is omitted. In addition to diagnosing the internal relay 220 of the battery pack 22, the diagnostic process for the switching operation of the discharge relay 225b was included in addition to diagnosing the internal relays 220 (first internal relay 220a, second internal relay 220b), but the fault diagnosis (switching relay diagnostic process) here is specialized for the discharge relay 225b.

[0102] The presence or absence (or necessity) of fault diagnosis for the discharge relay 225b and the external relay 211 is specified in the memory of the ECU 23a, and the ECU 23a follows the contents stored in the memory.

[0103] In this embodiment, the system is configured to perform fault diagnosis (external relay diagnostic processing, switching relay diagnostic processing). Accordingly, the ECU23a performs fault diagnosis (external relay diagnostic processing, switching relay diagnostic processing) (YES in S18, S24). As shown in Figure 7, when the ECU23a performs fault diagnosis (external relay diagnostic processing, switching relay diagnostic processing), it first monitors (measures) the external terminals of the second battery pack 22 (positive output terminal 223a, negative output terminal 223b) and the voltage of the discharge circuit 225 (voltage across the discharge circuit 225) (S30). Since the discharge circuit 225 is located inside the battery pack 22, the BMS23b monitors (measures) the voltage of the discharge circuit 225 (voltage across the discharge circuit 225) and transmits the monitoring (measurement) result to the ECU23a.

[0104] Based on this, ECU23a determines whether there is voltage at the external terminals (positive output terminal 223a, negative output terminal 223b) of the battery pack 22 (S31). If the voltage at the external terminals (positive output terminal 223a, negative output terminal 223b) is above a threshold (YES in S31), ECU23a determines that the external relay 211 on the primary circuit 210 is connected (fixed connection by welding) and that there is an abnormality in the external relay 211 in the electrical system of the battery pack 22 to which it is connected (S37). On the other hand, if the voltage at the external terminals (positive output terminal 223a, negative output terminal 223b) is below the threshold (NO in S31), ECU23a changes the external relay 211 on the primary circuit 210 from the open state to the closed state (S32). The threshold used as the basis for this determination is set to the power supply voltage value in the specifications of the battery pack 22.

[0105] In this state, ECU23a determines whether there is voltage across the external terminals (positive output terminal 223a, negative output terminal 223b) and the discharge circuit 225 (S33, S34). As a result, if the voltage across the external terminals (positive output terminal 223a, negative output terminal 223b) is not above a threshold (NO in S33), ECU23a determines that the external relay 211 on the primary circuit 210 is faulty (it has not changed from the open state to the closed state) (S37).

[0106] On the other hand, if the voltage at the external terminals (positive output terminal 223a, negative output terminal 223b) is above a threshold (YES in S33), it can be inferred that the external relay 211 on the primary circuit 210 has properly changed from an open state to a closed state, and the ECU 23a determines whether there is voltage across the discharge circuit 225 (S34). Here, the voltage across the discharge circuit 225 refers to the voltage on both sides of the discharge relay 225b (one side and the other side of the discharge relay 225b).

[0107] If there is a voltage across the discharge circuit 225 and that voltage is below a threshold (NO in S34), ECU23a determines that the discharge relay 225b is faulty (not in the open state) (S38). On the other hand, if the voltage across the discharge circuit 225 is higher than the threshold (YES in S34), ECU23a determines that the discharge relay 225b on the discharge circuit 225 is in the open state and that the connected battery pack 22 and its electrical system (discharge relay 225b and external relay 211) are normal (normal) (S35).

[0108] Here, the reason why the voltage across the discharge circuit 225 when the discharge relay 225b is open is greater (higher) than the voltage across the discharge circuit 225 when the discharge relay 225b is closed is that the potential state on both sides of the discharge relay 225b changes depending on the open / closed state of the discharge relay 225b. Specifically, when the discharge relay 225b is closed, current flows from the positive side to the negative side, and there is no difference (potential difference) between the potential on the positive side and the potential on the negative side. On the other hand, when the discharge relay 225b is open, there is potential on the positive side, while the negative side is ground, so the potential on the negative side is zero.

[0109] This creates a potential difference between the positive and negative terminals on both sides of the discharge relay 225b. Therefore, the voltage (potential difference) across the discharge circuit 225 when the discharge relay 225b is open is greater (higher) than the voltage (potential difference) across the discharge circuit 225 when the discharge relay 225b is closed.

[0110] Then, if ECU23a determines that the discharge relay 225b is functioning correctly (S35), it returns the external relay 211 to the open state (S36) and terminates the diagnosis (END).

[0111] Returning to Figure 5, if the ECU 23a determines, as a result of the fault diagnosis, that there is an abnormality in the second battery pack 22 and the external relay 211 (YES in S25), it determines whether there is another second battery pack 22 (S23). If there is no other second battery pack 22 (YES in S23), it does not connect the second battery pack 22 that was determined to be abnormal (it does not connect subsequent battery packs 22 in order) and terminates the battery parallel connection process (END). In other words, the ECU 23a instructs that power be supplied only by the first battery pack 22. On the other hand, if there is another second battery pack 22 (YES in S23), the ECU 23a extracts (determines) the battery pack 22 to be connected to the electrical equipment 20 next from the other second battery packs 22 (S17), and makes a determination as necessary regarding fault diagnosis, etc., in the same way as with the previous second battery pack 22 (S18~S25).

[0112] If the second battery pack 22 and the external relay 211 are determined to be normal (NO in S25), the ECU 23a performs a connection process to connect the second battery pack (battery pack) to the electrical equipment 20. In this connection process, the ECU 23a performs a diagnostic process for battery packs 22 that are specified to require a diagnostic process for the switching operation of the internal relay 220, as with the first battery pack 22, and omits the diagnostic process for battery packs 22 that are specified not to require a diagnostic process for the switching operation of the internal relay 220. In this embodiment, the second battery pack (battery pack) is specified not to require a diagnostic process for the switching operation of the internal relay 220, and therefore the diagnostic process is omitted for the second battery pack 22.

[0113] Specifically, in this embodiment, based on instructions stored in the memory unit, the ECU 23a instructs that the internal relay 220 of the battery pack 22 be closed from the open state, eliminating the need to diagnose the opening and closing operation of the internal relay 220 of the second battery pack 22 and eliminating the need to perform precharging by the precharge circuit 224 (S19: first subsequent processing (first connection processing)). That is, unlike the connection order of the first battery pack 22, the ECU 23a instructs that the internal relay 220 of the second battery pack 22 be closed from the open state without using the precharge circuit 224 (S19: first subsequent processing (first connection processing)). Accordingly, the BMS 23b closes the internal relay 220 from the open state (S19: first subsequent processing (first connection processing)).

[0114] In this embodiment, the ECU 23a simultaneously closes the first internal relay 220a and the second internal relay 220b based on instructions stored in the memory unit (S19: first post-processing). Specifically, the battery pack 22 is equipped with a first internal relay 220a and a second internal relay 220b as internal relays 220, but with respect to the second battery pack 22, the ECU 23a instructs, based on instructions stored in the memory unit, to simultaneously close the first internal relay 220a and the second internal relay 220b from the open state, without assigning a priority to the first internal relay 220a and the second internal relay 220b (S19: first post-processing (first connection processing)). Accordingly, the BMS 23b simultaneously closes the first internal relay 220a and the second internal relay 220b from the open state (S19: first post-processing (first connection processing)).

[0115] ECU23a waits for the internal relays 220 (first internal relay 220a, second internal relay 220b) to change from the open state to the closed state (S20). Once the internal relays 220 (first internal relay 220a, second internal relay 220b) have changed from the open state to the closed state (YES in S20), ECU23a changes the external relay 211 corresponding to the second battery pack 22 (external relay 211 on the primary circuit 210 connected to the battery pack 22) from the open state to the closed state (S21: second post-processing).

[0116] Then, when the external relay 211 corresponding to the second battery pack 22 is closed (YES in S22), the ECU 23a checks whether there is a subsequent battery pack 22 (the remaining second battery pack 22 to be connected) (S23). If it determines that there is a subsequent battery pack 22 (NO in S23), it extracts the next battery pack 22 in order and repeats the above procedure (S17~S23).

[0117] In contrast, if it is determined that there is no subsequent battery pack 22 (YES in S23), all of the battery packs 22, 22 that were connected in parallel are connected to the electrical circuit 21 and supply power to the electrical equipment 20.

[0118] Here, with respect to the second battery pack 22, in order to change the internal relay 220 from the open state to the closed state, and then change the external relay 211 on the primary circuit 210 from the open state to the closed state, the inflow of current due to the starting current and the voltage difference with the previously connected battery pack 22 acts as an inrush current on the external relay 211, but damage to the internal relay 220 of the battery pack 22 can be avoided. Also, unlike the internal relay 220 of the battery pack 22, the external relay 211, which is installed in the junction box 24 in a replaceable manner, will be damaged by the inrush current, so even if the external relay 211 is damaged, it can be easily restored by replacement.

[0119] The process for parallel connection of multiple battery packs 22... is as described above. If, in the parallel connection feasibility diagnosis, the ECU 23a decides not to connect multiple battery packs 22... in parallel (i.e., it decides to use the battery pack 22 with the most remaining charge as the power source), the ECU 23a performs a single connection process for the battery pack 22. Specifically, as shown in Figure 8, the ECU 23a changes the external relay 211 on the primary circuit 210 (210b) connected to the first battery pack 22 from the open state to the closed state (S40). The ECU 23a changes the external relay 211 on the negative primary circuit 210b connected to the first battery pack 22 from the open state to the closed state.

[0120] The ECU23a waits until the external relay 211 of the primary circuit 210 (negative primary circuit 210b) connected to the first battery pack 22 is closed (S41). Once the external relay 211 on the primary circuit 210 (negative primary circuit 210b) is closed (YES in S41), the ECU23a instructs the pre-charge relay 224b and internal relay 220 of the first battery pack 22 to be closed (S42). Accordingly, the BMS23b corresponding to the first set battery pack 22 closes the pre-charge relay 224b and internal relay 220 (S42).

[0121] Specifically, ECU23a instructs the first battery pack 22 to switch the pre-charge relay 224b from the open state to the closed state (second pre-processing). In conjunction with this, ECU23a instructs the first battery pack 22 to close the internal relay 220 (third pre-processing). Consequently, BMS23b closes the internal relay 220 and the pre-charge relay 224b corresponding to the first battery pack 22 (second pre-processing, third pre-processing).

[0122] In this embodiment, the battery pack 22 is equipped with a first internal relay 220a and a second internal relay 220b as internal relays 220, and since the precharge circuit 224 is connected in parallel with the first internal relay 220a, when the BMS 23b changes the internal relay 220 of the first battery pack 22 from the open state to the closed state, it changes the second internal relay 220b and the precharge relay 224b from the open state to the closed state (after precharging by the precharge circuit 224 is completed), and then changes the first internal relay 220a, which is in parallel with the precharge relay 224b, from the open state to the closed state (third pre-processing).

[0123] In this way, the first internal relay 220a, which is connected in parallel with the pre-charge circuit 224, is the last to close, causing the entire internal circuit 222 to close (conductive), and the first battery pack 22 is electrically connected to the electrical circuit 21 (electrical equipment 20) (third pre-processing).

[0124] Ideally, when the first internal relay 220a is finally closed, the inrush current (starting current) acting on the first internal relay 220a will pass through the pre-charge circuit 224 connected in parallel to the first internal relay 220a, and will be absorbed by the pre-charge resistor 224a on the pre-charge circuit 224. Therefore, damage to the internal relays 220 (220a, 220b) of the first battery pack 22 due to the inrush current is suppressed.

[0125] Then, ECU23a waits until the internal relays 220 (first internal relay 220a and second internal relay 220b) of the first battery pack 22 are closed (S43). When the internal relays 220 (first internal relay 220a and second internal relay 220b) of the first battery pack 22 are closed (YES in S43), ECU23a terminates the single connection process for the battery packs 22, and the battery pack 22 with the highest voltage is connected to the electrical equipment 20 to drive the electrical equipment 20. Although not shown in the flowchart of Figure 8, when the battery pack 22 is connected to the electrical equipment 20, ECU23a instructs the pre-charge relay 224b of the pre-charge circuit 224 of the first battery pack 22 to change from closed to open. Accordingly, BMS23b changes the pre-charge relay 224b of the pre-charge circuit 224 of the first battery pack 22 from closed to open.

[0126] In the parallel connection feasibility diagnosis described above, if the system notifies that charging is required and the operator charges the battery pack 22 accordingly, the charging cable connected to the charging device (e.g., a fast charger) is connected to the charging inlet 25.

[0127] When a charging cable is connected to the charging inlet 25, the ECU23a detects the connection and executes a charging mode to charge the battery pack 22.

[0128] As shown in Figure 9, in charging mode, the ECU 23a sets the battery pack 22 with the lowest voltage as the target for charging (S50). In this embodiment, the battery pack 22 that was not selected for connection to the electrical circuit 21 in the parallel connection feasibility diagnosis (the battery pack 22 with the lowest voltage) is set as the target for charging (S50). In other words, the ECU 23a sets the battery pack 22 with the lowest remaining charge among the multiple battery packs 22... as the target for charging.

[0129] Accordingly, the ECU 23a changes the external relay 211 on the primary circuit 210 (210b) connected to the battery pack 22 that is being charged from the open state to the closed state, and keeps the external relay 211 on the primary circuit 210 (210b) connected to the battery pack 22 that is not being charged (the battery pack 22 with a large remaining charge) in the open state.

[0130] As a result, the electrical connection between the battery pack 22 with a high remaining charge and the charging inlet 25 is disconnected, while the charging inlet 25 and the battery pack 22 with a low remaining charge are connected in a way that allows power to flow.

[0131] When charging begins for a battery pack 22 with a low voltage (a battery pack 22 with low remaining charge) (YES in S51), the ECU 23a measures the voltage of each of the multiple battery packs (all battery packs) 22..., including the battery pack 22 that is not being charged (S52). Based on this, the ECU 23a compares the voltages of each of the multiple battery packs 22... (S53). That is, the ECU 23a calculates the voltage difference between the battery packs 22 (two battery packs 22, 22) that are being compared (S53). In this embodiment, since the electric work machine 1 is equipped with only two battery packs 22, 22, there is only one combination that is being compared, and the ECU 23a calculates the voltage difference between the two battery packs 22, 22 (S53).

[0132] The ECU23a compares the voltages of the battery packs 22 and determines whether the voltage of the battery pack 22 being charged has become equivalent to the voltage of the battery pack 22 that is not being charged (the battery pack 22 with the higher voltage) (the voltage difference is approximately zero with the battery pack 22 with the higher voltage as the reference: reference value) (S54). In this embodiment, based on the calculation of the voltage difference in S53, which is the voltage comparison, the ECU23a determines that the voltage of the battery pack 22 being charged has become equivalent to the voltage of the battery pack 22 that is not being charged when the voltage difference of the battery packs 22 being compared becomes zero or approximately zero (YES in S54).

[0133] When ECU23a determines that the voltage of the battery pack 22 being charged has become equivalent to the voltage of the battery pack 22 that is not being charged (YES in S54), it changes the external relay 211 on the primary circuit 210 connected to the battery pack 22 that was not being charged (the battery pack 22 with the most remaining charge) from the open state to the closed state (S55). In other words, when the voltages of the battery packs 22 being compared match or nearly match, all the battery packs being compared are connected in parallel and charged until fully charged (S55).

[0134] As a result, when the voltage difference is within the standard range (no voltage difference between battery packs 22, or a small voltage difference), each of the multiple battery packs 22 is charged to full capacity (S56). If there are three or more battery packs 22, the battery packs 22 that were not being charged are charged sequentially, provided that their voltages match or nearly match.

[0135] By doing so, at startup, there is no voltage difference, or only a small voltage difference, between the multiple battery packs 22..., thus reducing damage to the external relay 211, which is the last to be closed when connected in parallel. In addition, since the multiple battery packs 22... are fully charged, long operating times are possible.

[0136] In this embodiment, when stopping the electric work machine 1, the start switch is turned OFF, causing the ECU 23a to switch the internal relay 220 of the battery pack 22 and the external relay 211 on the primary circuit 210 from a closed state to an open state, thereby disconnecting the electrical system and cutting off the power supply from the battery pack 22 to the electrical equipment 20.

[0137] The electric work machine 1 according to this embodiment is as described above, and the electric work machine 1 encompasses multiple inventions (groups of inventions), each of which performs its own unique function and effect.

[0138] Specifically, in the above embodiment, the electric work machine 1 comprises an electrical device 20, an electrical circuit 21 electrically connected to the electrical device 20, a plurality of battery packs 22... each having an internal relay 220 that opens and closes an internal circuit 222, a plurality of battery packs 22... sequentially connected to the electrical device 20 via the electrical circuit 21 and connected in parallel, and a control unit 23, wherein the electrical circuit 21 comprises a plurality of external relays 211... corresponding to each of the plurality of battery packs 22... that open and close the circuit connecting the corresponding battery pack 22 and the electrical device 20 The control unit 23 includes a number of external relays 211... and with the first battery pack 22, which is the first battery pack 22 among the multiple battery packs 22... to be connected to the electrical equipment 20, electrically connected to the electrical equipment 20, performs a first downstream process (S19) to close the internal relay 220 of the second battery pack 22, which is the second or later battery pack 22 among the multiple battery packs 22... and a second downstream process (S21) to close the external relay 211 corresponding to the second battery pack 22 whose internal relay 220 has been closed.

[0139] According to the above configuration, the electrical circuit 21 includes multiple external relays 211, each corresponding to one of the multiple battery packs 22, which open and close the circuit connecting the corresponding battery pack 22 to the electrical equipment 20. Therefore, when the multiple external relays 211 are closed in sequence, the multiple battery packs 22 are connected to the electrical equipment 20 (electrical circuit 21) in sequence. When all of the multiple external relays 211 are closed, the multiple battery packs 22 are connected to the electrical equipment 20 (electrical circuit 21) in a parallel configuration.

[0140] Each of the multiple battery packs 22... has an internal relay 220. When the internal relay 220 is open, the internal circuit 222 is also open, and when the internal relay 220 is closed, the internal circuit 222 is also closed. Therefore, as described above, when the internal relays 220 of the multiple battery packs 22... are closed, and all of the multiple external relays 211... are also closed, the multiple battery packs 22... are electrically connected in parallel to the electrical equipment 20. This reduces the electrical load on each battery pack 22, thereby suppressing the occurrence of power supply problems (failures) in the electric work machine 1.

[0141] In the above configuration, multiple battery packs 22... are connected sequentially to the electrical equipment 20. Here, the first battery pack 22 is electrically connected to the electrical equipment 20 when its internal relay 220 is closed and the corresponding external relay 211 is closed.

[0142] Based on this state, the control unit 23 performs a first post-processing step (S19) to close the internal relay 220 of the second battery pack 22, and a second post-processing step (S21) to close the external relay 211 corresponding to the second battery pack 22 whose internal relay 220 is closed. As a result, the battery pack 22 is connected to the electrical equipment 20 without any inrush current acting on the internal relay 220 of the battery pack 22.

[0143] In other words, after closing the internal relay 220 of the battery pack 22 in the first downstream process (S19), and then closing the external relay 211 in the second downstream process (S21), an inrush current acts on the external relay 211, which was the last to be closed. That is, the external relay 211, which is outside the battery pack 22, receives an inrush current.

[0144] Therefore, according to the electric work machine 1 of the above embodiment, even if multiple battery packs 22... are connected in parallel, it is possible to suppress the failure of the battery packs 22 due to the inrush current when starting up the electrical equipment 20.

[0145] Furthermore, at least the first battery pack 22 has a first internal relay 220a as an internal relay 220, and a pre-charge circuit 224 in which a series connection circuit of a pre-charge resistor 224a and a pre-charge relay 224b is connected in parallel to the first internal relay 220a. When the control unit 23 connects the first battery pack 22 to the electrical equipment 20, it performs a first pre-processing step to close the external relay 211 corresponding to the first battery pack 22, a second pre-processing step to close the pre-charge relay 224b of the first battery pack 22, and a third pre-processing step to close the first internal relay 220a of the first battery pack 22 after the first and second pre-processing steps.

[0146] In this way, when the external relay 211 is closed in the first pre-processing stage (S13), the electrical circuit 21 becomes closed (conductive), but in this state, the internal circuit 222 of the battery pack 22 is open, so no inrush current acts on the external relay 211. Also, in the second pre-processing stage (S15), when the pre-charge relay 224b of the pre-charge circuit 224 is closed, the pre-charge circuit 224 connects the circuit with the internal relay 220 spanning over it.

[0147] Accordingly, the first pre-processing (S13) is performed before or after the second pre-processing (S15), and the external relay 211 corresponding to the first battery pack 22 is closed, causing the internal circuit 222 and electrical circuit 21 of the battery pack 22 to conduct. As a result, an inrush current is generated due to the power supply from a single battery pack 22, but since the pre-charge circuit 224 is in a closed state and pre-charging is being performed (the pre-charge resistor 224a of the pre-charge circuit 224 absorbs the inrush current), damage to the internal circuit 222 and electrical circuit 21 (external relay 211) is reduced.

[0148] Then, in the third pre-processing stage (S15), by closing the internal relay 220 (first internal relay 220a) which is in parallel with the pre-charge circuit 224 of the first battery pack 22, the circuit configuration can be made such that no load is placed on the pre-charge resistor 224a of the pre-charge circuit 224 (the normal circuit configuration when energized).

[0149] Each of the multiple battery packs 22... has a battery cell 221 and an internal relay 220, which includes a first internal relay 220a located on the path 222a on one pole side of the battery cell 221 and arranged in parallel with the pre-charge circuit 224, and a second internal relay 220b located on the path 222b on the other pole side of the battery cell 221. In the second pre-processing stage, the control unit 23 keeps the first internal relay 220a open and closes the second internal relay 220b and the pre-charge relay 224b.

[0150] In this way, when the second internal relay 220b and the pre-charge relay 224b are closed in the second pre-processing stage, the internal circuit 222 becomes conductive via the pre-charge circuit 224. However, since the pre-charge circuit 224 contains a pre-charge resistor 224a, power is consumed by this pre-charge resistor 224a. As a result, even when the first internal relay 220a is closed in the third pre-processing stage (S15), the inrush power acting on the first internal relay 220a is small, and the shock and other effects acting on the first internal relay 220a are reduced.

[0151] In the above embodiment, the electric work machine 1 further includes a junction box 24 that houses part or all of the electrical circuit 21, and a plurality of external relays 211... are housed in the junction box 24 in a replaceable manner. In this way, even if an external relay 211 fails, it can be easily restored by replacing the failed external relay 211 with a new one.

[0152] In the above embodiment, the electric work machine 1 further comprises a work device 11 that performs a predetermined task, and the electrical equipment 20 directly or indirectly drives the work device 11. In this way, the electrical equipment 20 drives the work device 11 by receiving power from a battery pack 22 that has not been damaged in its internal circuit 222 (internal relay 220, etc.). That is, since the battery pack 22 is connected to the electrical equipment 20 after the above startup process, damage to the internal relay 220 during the startup process is suppressed, and therefore, power supply malfunctions when the electrical equipment 20 drives the work device 11 are suppressed.

[0153] The control unit 23 sets the battery pack 22 corresponding to the external relay 211… with the highest cumulative number of switching operations among the multiple external relays 211… as the first battery pack 22. In this way, the damage received by each of the multiple external relays 211… can be equalized.

[0154] Specifically, the damage to the external relay 211 varies depending on the number of times it is switched on or off. That is, as the number of times the external relay 211 is switched on and off increases, the damage it receives due to the switching of the circuit increases, while as the number of times it is switched on and off decreases, the damage it receives due to the switching of the circuit decreases. In the above embodiment, the external relay 211 corresponding to the first battery pack 22 connected to the electrical equipment 20 is closed first in the entire electrical system including the battery pack 22, and is therefore not affected (or is less affected) by the inrush current. On the other hand, the external relay 211 corresponding to the second battery pack 22 connected to the electrical equipment 20 is closed last in the entire electrical system, and is therefore affected by the inrush current and suffers significant damage. In particular, the damage to the external relay 211 corresponding to the battery pack 22 that is set (connected second or later) more often accumulates and becomes large.

[0155] However, in the above embodiment, the battery pack 22 corresponding to the external relay 211 with the most cumulative switching counts is set as the first (set as the first battery pack 22), thus reducing the damage to the external relay 211, which would otherwise suffer significant damage. Furthermore, each time the electrical device 20 is started, the first battery pack 22 connected to the electrical device 20 (electrical circuit 21) is changed, so that the external relay 211 is the first to be closed. Since the same changes are made, the damage received by each of the multiple external relays 211... can be equalized. This makes it possible to prevent a specific external relay 211 from failing.

[0156] In the above embodiment, the starting method for the electric work machine 1 comprises an electrical device 20, an electrical circuit 21 electrically connected to the electrical device 20, and a plurality of battery packs 22... each having an internal relay 220 that opens and closes an internal circuit 222, wherein the plurality of battery packs 22... are sequentially connected to the electrical device 20 via the electrical circuit 21 and connected in parallel, and the electrical circuit 21 comprises a plurality of external relays 211... corresponding to each of the plurality of battery packs 22..., which open and close the circuit connecting the corresponding battery pack 22 and the electrical device 20. In a method for starting an electric work machine 1 that includes internal relays 211..., with the first battery pack 22, which is the first battery pack 22 in the sequence of being connected to the electrical equipment 20 among the multiple battery packs 22..., electrically connected to the electrical equipment 20, a first downstream process is performed to close the internal relay 220 of the second battery pack 22, which is the second or later battery pack 22 in the sequence among the multiple battery packs 22..., and a second downstream process is performed to close the external relay 211 corresponding to the second battery pack 22 whose internal relay 220 has been closed.

[0157] In the above startup method, a first post-processing step (S19) is performed to close the internal relay 220 of the second battery pack 22, and a second post-processing step (S21) is performed to close the external relay 211 corresponding to the second battery pack 22 whose internal relay 220 is closed. As a result, the battery pack 22 is connected to the electrical equipment 20 without any inrush current acting on the internal relay 220 of the battery pack 22.

[0158] In other words, after closing the internal relay 220 of the battery pack 22 in the first downstream process (S19), and then closing the external relay 211 in the second downstream process (S21), an inrush current acts on the external relay 211, which was the last to be closed. That is, the external relay 211, which is outside the battery pack 22, receives an inrush current.

[0159] Therefore, according to the above method for starting the electric work machine 1, even if multiple battery packs 22... are connected in parallel, it is possible to suppress the failure of the battery packs 22 due to the inrush current when starting the electrical equipment 20.

[0160] Furthermore, in the above embodiment, the electric work machine 1 comprises an electrical device 20, an electrical circuit 21 electrically connected to the electrical device 20, a plurality of battery packs 22... each having an internal relay 220 that opens and closes an internal circuit 222, a plurality of battery packs 22... sequentially connected to the electrical device 20 via the electrical circuit 21 and connected in parallel, and a control unit 23. The electrical circuit 21 includes a plurality of external relays 211... corresponding to each of the plurality of battery packs 22..., a plurality of external relays 211... that open and close a circuit connecting the corresponding battery pack 22 to the electrical device 20, and the control unit 23 is configured to specify whether or not a diagnostic process for the opening and closing operation of the internal relay 220 of the battery pack 22 is necessary for each battery pack 22. When connecting the battery pack 22 to the electrical device 20, the diagnostic process is performed for the battery pack 22 that is specified as requiring a diagnostic process for opening and closing operation, and the diagnostic process is omitted for the battery pack 22 that is specified as not requiring a diagnostic process for opening and closing operation.

[0161] According to the above configuration, the battery pack 22, which is designated to require diagnostic processing for opening and closing operations, will undergo diagnostic processing, allowing power to be supplied to the electrical equipment 20 without any internal problems (such as problems with the internal relay 220) in the battery pack 22.

[0162] In contrast, regarding the battery pack 22, which is specified as not requiring diagnostic processing for opening and closing operations: Since diagnostic processing is omitted, the connection time of the battery pack 22 to the electrical equipment 20 can be shortened.

[0163] The control unit 23 specifies that a diagnostic process should be performed for the first battery pack 22, which is the first battery pack 22 connected to the electrical equipment 20 among the multiple battery packs 22..., and specifies that the diagnostic process should be omitted for the second battery pack 22, which is the second or later battery pack 22 connected to the electrical equipment 20 among the multiple battery packs 22....

[0164] In this way, the control unit 23 specifies that diagnostic processing should be omitted for the second and subsequent battery packs 22 among the multiple battery packs 22. By omitting diagnostic processing depending on the situation, the connection time of the battery packs 22 can be shortened.

[0165] The control unit 23 diagnoses the switching operation of the internal relay 220 based on the switching instruction status for the internal relay 220 and the change in the output voltage of the battery pack 22 associated with the switching instruction for the internal relay 220. In this way, it is possible to identify not only whether the internal relay 220 is malfunctioning or not, but also which internal relay 220 is malfunctioning.

[0166] Based on the above processing, each of the multiple battery packs 22... has a pre-charge circuit 224 in which a series connection circuit of a pre-charge resistor 224a and a pre-charge relay 224b is connected in parallel to an internal relay 220. The control unit 23 is configured to specify for each battery pack 22 whether or not to perform pre-charging, which involves closing the pre-charge relay 224b before closing the internal relay 220. When connecting a battery pack 22 that is specified to require pre-charging to the electrical equipment 20, a first connection process (third pre-stage process) S15 is performed to close the internal relay 220 of the battery pack 22 after pre-charging. When connecting a battery pack 22 that is specified to not require pre-charging to the electrical equipment 20, the first connection process (first post-stage process) S19 is performed without pre-charging.

[0167] In this way, when connecting a battery pack 22, which is designated to require precharging, to electrical equipment 20, the first connection process (third pre-processing) S15 is performed after precharging, so that the battery pack 22 can be connected to electrical equipment 20 without any internal problems (such as problems caused by the inrush current affecting the internal relay 220).

[0168] In contrast, when connecting a battery pack 22, which is designated as not requiring precharging, to an electrical device 20, precharging is omitted, thus shortening the connection time of the battery pack 22 to the electrical device 20.

[0169] In the above embodiment, the electric work machine 1 comprises an electrical device 20, an electrical circuit 21 electrically connected to the electrical device 20, a plurality of battery packs 22... each having an internal relay 220 that opens and closes an internal circuit 222, a plurality of battery packs 22... sequentially connected to the electrical device 20 via the electrical circuit 21 and connected in parallel, and a control unit 23, wherein the electrical circuit 21 includes a plurality of external relays 211... corresponding to each of the plurality of battery packs 22..., a plurality of external relays 211... that open and close a circuit connecting the corresponding battery pack 22 and the electrical device 20, and each of the plurality of battery packs 22... has a pre-charge resistor 224a connected to the internal relay 220 The battery pack 224 has a pre-charge circuit 224 which connects a series connection circuit of the pre-charge relay 224b in parallel. The control unit 23 is configured to specify for each battery pack 22 whether or not to perform pre-charging, which involves closing the pre-charge relay 224b before closing the internal relay 220. When connecting a battery pack 22 which is specified to require pre-charging to the electrical equipment 20, the control unit 23 performs a first connection process (third pre-processing) S15 which closes the internal relay 220 of the battery pack 22 after pre-charging. When connecting a battery pack 22 which is specified to not require pre-charging to the electrical equipment 20, the control unit 23 omits pre-charging and performs a first connection process (first post-processing) S19.

[0170] According to the above configuration, when connecting a battery pack 22, which is designated to require precharging, to electrical equipment 20, the first connection process (third pre-processing) S15 is performed after precharging. This allows the battery pack 22 to be connected to electrical equipment 20 without any internal problems (such as problems caused by inrush current affecting the internal relay 220).

[0171] In contrast, when connecting a battery pack 22, which is designated as not requiring precharging, to an electrical device 20, precharging is omitted, thus shortening the connection time of the battery pack 22 to the electrical device 20.

[0172] Each of the multiple battery packs 22... has an internal relay 220, which is a first internal relay 220a located on the positive side and a second internal relay 220b located on the negative side. The control unit 23 is configured to specify whether or not to close the first internal relay 220a and the second internal relay 220b simultaneously in the first connection process (first subsequent process) S19. If it is specified that the first internal relay 220a and the second internal relay 220b be closed simultaneously, the first internal relay 220a and the second internal relay 220b are closed simultaneously in the first connection process (first subsequent process) S19. In this way, even if the battery pack 22 has multiple relay switches (first internal relay 220a, second internal relay 220b) as internal relays 220, specifying that they be closed simultaneously shortens the operating time of the internal relays 220 and allows the battery pack 22 to be connected to the electrical equipment 20.

[0173] The control unit 23 specifies that precharging should be performed on the first battery pack 22, which is the first battery pack 22 connected to the electrical device 20 among the multiple battery packs 22..., and that precharging should be omitted for the second battery pack 22, which is the second or later battery pack 22 connected to the electrical device 20 among the multiple battery packs 22.... In this way, even if multiple battery packs 22 are connected to the electrical device 20 sequentially, precharging is omitted for the second battery pack 22, which is the second or later battery pack 22 connected to the electrical device 20. As a result, the processing time required for precharging of the second and subsequent battery packs 22 is shortened, enabling a shorter startup time.

[0174] When connecting a battery pack 22 to an electrical device 20 for pre-charging, the control unit 23 performs a first pre-processing S13 that closes the external relay 211 corresponding to the battery pack 22, a second pre-processing S15 that closes the pre-charging relay 224b of the battery pack 22, and a third pre-processing S15 that closes the internal relay 220 of the battery pack 22 after the first pre-processing S13 and the second pre-processing S15.

[0175] In this way, the internal relay 220 is closed while precharging is being performed, so even if the internal relay 220 in the battery pack 22 is closed last, the effect of the inrush current is suppressed. In other words, the inrush current that acts when the internal relay 220 closes is absorbed by the precharging resistor 224a, so damage to the internal relay 220 is suppressed and damage to the battery pack 22 is prevented.

[0176] If the electric work machine 1 is further equipped with a work device 11 that performs a predetermined task, and the electrical equipment 20 drives the work device 11 directly or indirectly, the startup time of the work device 11 will be shortened because diagnostic processing and precharging are omitted when connecting the battery pack 22 to the electrical equipment 20.

[0177] In the method for starting the electric work machine 1 according to the above embodiment, the electric work machine 1 comprises an electrical device 20, an electrical circuit 21 electrically connected to the electrical device 20, and a plurality of battery packs 22... each having an internal relay 220 that opens and closes an internal circuit 222, and a plurality of battery packs 22... sequentially connected to the electrical device 20 via the electrical circuit 21 and connected in parallel, wherein the electrical circuit 21 comprises a plurality of external relays 211... corresponding to each of the plurality of battery packs 22..., and a plurality of external relays 211... that open and close a circuit connecting the corresponding battery pack 22 and the electrical device 20, the method for starting the electric work machine 1 includes a step of specifying for each battery pack 22 whether or not a diagnostic process is required for the opening and closing operation of the internal relay 220 of the battery pack 22, and a connection step of connecting the battery packs 22 to the electrical device 20, wherein in this connection step, a diagnostic process is performed for the battery packs 22 that are specified as requiring a diagnostic process, and the diagnostic process is omitted for the battery packs 22 that are specified as not requiring a diagnostic process.

[0178] According to the above method, in the step of specifying whether or not a diagnostic process for the switching operation of the internal relay 220 of the battery pack 22 is necessary, for battery packs 22 that are specified to require a diagnostic process for the switching operation, the diagnostic process is performed in the connection step of connecting the battery pack 22 to the electrical equipment 20. Therefore, the battery pack 22 can be connected to the electrical equipment 20 without any internal problems (such as problems with the internal relay 220) in the battery pack 22.

[0179] In contrast, in the step of specifying whether or not a diagnostic process for the switching operation of the internal relay 220 of the battery pack 22 is necessary, for battery packs 22 that are specified as not requiring a diagnostic process for the switching operation, the diagnostic process is omitted in the connection step of connecting the battery pack 22 to the electrical equipment 20, thereby shortening the connection time of the battery pack 22 to the electrical equipment 20.

[0180] In the starting method for the electric work machine 1 according to the above embodiment, the electric equipment 20 comprises an electrical device 20, an electrical circuit 21 electrically connected to the electric equipment 20, and a plurality of battery packs 22... each having an internal relay 220 that opens and closes an internal circuit 222, and a plurality of battery packs 22... sequentially connected to the electric equipment 20 via the electrical circuit 21 and connected in parallel, wherein the electrical circuit 21 includes a plurality of external relays 211... corresponding to each of the plurality of battery packs 22..., and a plurality of external relays 211... that open and close a circuit connecting the corresponding battery pack 22 and the electric equipment 20, and each of the plurality of battery packs 22... has a pre-charge resistor 224a and a pre-charge relay 224b connected to the internal relay 220 In a starting method for an electric work machine 1 having a pre-charge circuit 224 that connects series circuits in parallel, the method includes a step of specifying for each battery pack 22 whether or not to perform pre-charging, which involves closing the pre-charge relay 224b before closing the internal relay 220, and a connection step of connecting the battery packs 22 to the electrical equipment 20. In this connection step, for battery packs 22 that are specified to require pre-charging, a first connection process (third pre-processing) S15 is performed to close the internal relay 220 of the battery pack 22 after pre-charging, and for battery packs 22 that are specified to not require pre-charging, the first connection process (first post-processing) S19 is performed without pre-charging.

[0181] According to the above method, in the step of specifying whether or not precharging is required for the battery pack 22, for battery packs 22 that are specified to require precharging, the first connection process (third pre-processing) S15 is performed after precharging in the connection step of connecting the battery pack 22 to the electrical equipment 20. This ensures that the battery pack 22 can be connected to the electrical equipment 20 without any internal problems (such as problems caused by the inrush current affecting the internal relay 220).

[0182] In response to this, the necessity of pre-charging the battery pack 22 is determined by the battery pack For battery packs 22 that are specified as not requiring precharging in each specified step, precharging is omitted in the connection step of connecting the battery pack 22 to the electrical equipment 20, thereby shortening the connection time of the battery pack 22 to the electrical equipment 20.

[0183] Furthermore, in the above embodiment, the electric work machine 1 comprises an electrical device 20, an electrical circuit 21 electrically connected to the electrical device 20, a plurality of battery packs 22... having positive and negative external terminals, which are sequentially connected to the electrical device 20 via the electrical circuit 21 and connected in parallel, and a control unit 23, wherein the electrical circuit 21 includes a plurality of external relays 211... corresponding to each of the plurality of battery packs 22... which open and close the circuit connecting the corresponding battery pack 22 and the electrical device 20, and the control unit 23 controls the battery pack 2 before it is connected to the electrical device 2 With the internal circuit 222 of the battery pack 22 open, an external relay diagnostic process is performed to diagnose whether the contacts of the external relay 211 corresponding to the battery pack 22 are stuck. In the external relay diagnostic process, the internal circuit 222 of the battery pack 22 to be diagnosed is opened, and with the external relay 211 corresponding to the battery pack 22 opened, if the voltage between the positive and negative external terminals 223a and 223b of the battery pack 22 is above a threshold, it is determined that the contacts of the external relay 211 are stuck. If the voltage between the positive and negative external terminals 223a and 223b of the battery pack 22 is below the threshold, it is determined that the contacts of the external relay 211 are normal.

[0184] According to the above configuration, multiple battery packs 22... are connected in parallel by sequentially connecting to the electrical equipment 20, so that electricity flows into the circuits connected to battery pack 22 from other battery packs 22. However, when the external relay 211 corresponding to battery pack 22 is open, the positive and negative external terminals 223a, 223b of that battery pack 22 are not affected by electricity from other battery packs 22, and the voltage between the positive and negative external terminals 223a, 223b becomes lower than the threshold.

[0185] In contrast, if the contacts of the external relay 211 are stuck (welded), the external relay 211 will be in a closed state (conductive state). When the external relay 211 corresponding to the battery pack 22 is in a closed state (conductive state), the positive and negative external terminals 223a and 223b of the battery pack 22 will be affected by electricity from another battery pack 22, and the voltage between the positive and negative external terminals 223a and 223b will exceed a threshold.

[0186] Therefore, without activating the external relay 211, the presence or absence of contact sticking of the external relay 211 can be properly diagnosed simply by comparing the voltage and threshold between the positive and negative external terminals 223a and 223b of the battery pack 22. As a result, with the electric work machine 1 configured above, damage to the internal circuit 222 of the battery pack 22 due to the inrush current during startup can be prevented. Furthermore, it is possible to properly determine whether or not multiple battery packs 22 can be connected sequentially.

[0187] The control unit 23 connects the first battery pack 22, which is the first battery pack among the multiple battery packs 22... to the electrical equipment 20, to the electrical equipment 20 without performing the external relay diagnostic process for the external relay 211 corresponding to the first battery pack 22. For the second battery pack 22, which is the second or later battery pack among the multiple battery packs 22..., it performs the external relay diagnostic process for the external relay 211 corresponding to the second battery pack 22 before connecting it to the electrical equipment 20.

[0188] According to the above configuration, the first battery pack 22 is electrically connected to the electrical equipment 20 without performing external relay diagnostic processing on the corresponding external relay 211. As a result, when the external relay diagnostic processing is performed on the external relay 211 corresponding to the second battery pack 22, electricity flows into the electrical circuit 21 from the first battery pack 22. However, when the second battery pack 22 and the corresponding external relay 211 are open, the electricity from the first battery pack 22 does not affect the positive and negative external terminals 223a and 223b of the second battery pack 22, and the voltage between the positive and negative external terminals 223a and 223b of the second battery pack 22 becomes lower than the threshold.

[0189] In contrast, if the contacts of the external relay 211 are stuck (welded), the external relay 211 will be in a closed state (conductive state). When the external relay 211 corresponding to the second battery pack 22 is in a closed state (conductive state), the positive and negative external terminals 223a and 223b of the second battery pack 22 are affected by the electricity from the first battery pack 22, and the voltage between the positive and negative external terminals 223a and 223b of the second battery pack 22 will be above a threshold.

[0190] Therefore, without activating the external relay 211, the presence or absence of contact sticking of the external relay 211 can be properly diagnosed simply by comparing the voltage and threshold between the positive and negative external terminals 223a and 223b of the second battery pack 22. As a result, with the electric work machine 1 configured above, damage to the internal circuit 222 of the battery pack 22 due to the inrush current during startup can be prevented. Furthermore, it is possible to properly determine whether or not multiple battery packs 22 can be connected sequentially.

[0191] In the above embodiment, if the control unit 23 determines in the external relay diagnostic process that the contacts of the external relay 211 are stuck, it discontinues the electrical connection of the battery pack 22 corresponding to the external relay 211 to the electrical equipment 20. In this way, power is not supplied to the electrical equipment 20 from the battery pack 22 corresponding to the external relay 211 with stuck contacts, thereby preventing electrical accidents.

[0192] The battery pack 22 has a discharge circuit 225 that connects the positive terminal side and the negative terminal side of the internal circuit 222, and includes a discharge resistor 225a and a discharge relay 225b connected in series. The control unit 23, when it determines in the external relay diagnostic process that the contacts of the external relay 211 are normal, performs a discharge relay diagnostic process to diagnose whether the contacts of the discharge relay 225b of the battery pack 22 are stuck, and in the discharge relay diagnostic process, operates the external relay 211, which was determined to be normal in the external relay diagnostic process, to a closed state. Furthermore, if the discharge relay 225b of the battery pack 22 is opened and the voltage between the positive and negative external terminals 223a and 223b of the battery pack 22 is above the threshold, and the voltage across the discharge circuit 225 is below the threshold, it is determined that the contacts of the discharge relay 225b of the discharge circuit 225 are stuck. If the voltage between the positive and negative external terminals 223a and 223b of the battery pack 22 is above the threshold, and the voltage across the discharge circuit 225 is higher than the threshold, it is determined that the contacts of the discharge relay 225b of the discharge circuit 225 are normal.

[0193] Since the discharge circuit 225 connects the positive external terminal 223a and the negative external terminal 223b of the internal circuit 222, when the discharge relay 225b of the discharge circuit 225 is closed, the internal circuit 222 becomes a closed circuit, and if power is applied in this state, there is a risk that the discharge resistor 225a may be damaged or the internal circuit 222 may be damaged.

[0194] However, in the above embodiment, in the switching relay diagnostic process, in order to determine whether or not the contacts of the discharge relay 225b of the discharge circuit 225 are stuck, This prevents damage to the charge resistor 225a and the internal circuit 222.

[0195] More specifically, as described above, when the battery pack 22 and the corresponding external relay 211 are in a closed state (conductive state), the positive and negative external terminals 223a and 223b of the battery pack 22 are affected by electricity from another battery pack 22, and the voltages of the positive and negative external terminals 223a and 223b become above a threshold.

[0196] Since the discharge circuit 225 connects the positive external terminal 223a and the negative external terminal 223b of the internal circuit 222, when the discharge relay 225b is closed, the voltage across the discharge circuit 225 decreases. In other words, when the discharge relay 225b is closed, current flows and the potential difference across the discharge circuit 225 decreases (or disappears), resulting in the voltage across the discharge circuit 225 falling below a threshold.

[0197] In contrast, when the discharge relay 225b of the discharge circuit 225 is opened, the voltage across the discharge circuit 225 increases (the voltage rises). That is, when the discharge relay 225b of the discharge circuit 225 is opened, the discharge circuit 225 is disconnected, resulting in a voltage (potential difference) being generated on both sides of the discharge relay 225b (positive and negative sides). In other words, when the discharge relay 225b is open, the voltage (potential difference) across the discharge circuit 225 increases and becomes greater than (higher than) the threshold.

[0198] In this way, based on the voltages across the external terminals 223a and 223b and the discharge circuit 225, it is possible to properly diagnose whether or not the contacts of the discharge relay 225b of the discharge circuit 225 are stuck, thereby preventing damage to the internal circuit 222 and the discharge circuit 225 (discharge resistor 225a).

[0199] In the above embodiment, the electric work machine 1 comprises an electrical device 20, an electrical circuit 21 electrically connected to the electrical device 20, a plurality of battery packs 22... having positive and negative external terminals, the plurality of battery packs 22... sequentially connected to the electrical device 20 via the electrical circuit 21 and connected in parallel, and a control unit 23, the electrical circuit 21 includes a plurality of external relays 211... corresponding to each of the plurality of battery packs 22..., which open and close the circuit connecting the corresponding battery pack 22 and the electrical device 20, the battery pack 22 has a discharge circuit 225 connecting the negative external terminal side and the positive external terminal side of the internal circuit 222, which includes a discharge resistor 225a and a discharge relay 225b connected in series, and the control unit 23 connects the battery pack 22 to the electrical device 20, A discharge relay diagnostic process is performed to diagnose whether the contacts of the discharge relay 225b of the battery pack 22 are stuck. In the discharge relay diagnostic process, the external relay 211 corresponding to the battery pack 22 to be diagnosed is operated to the closed state, and the discharge relay 225b of the battery pack 22 is operated to the open state. If the voltage between the positive and negative external terminals 223a and 223b of the battery pack 22 is above a threshold, and the voltage across the discharge circuit 225 is below a threshold, it is determined that the contacts of the discharge relay 225b of the discharge circuit 225 are stuck. If the voltage between the positive and negative external terminals 223a and 223b of the battery pack 22 is above a threshold, and the voltage across the discharge circuit 225 is higher than the threshold, it is determined that the contacts of the discharge relay 225b of the discharge circuit 225 are normal.

[0200] In the above configuration, the external relay 211 corresponding to the battery pack 22 is in a closed state (conductive state). In this state, the positive and negative external terminals 223a and 223b of the battery pack 22 are affected by electricity from another battery pack 22, and the voltages of the positive and negative external terminals 223a and 223b exceed a threshold.

[0201] Since the discharge circuit 225 connects the positive external terminal 223a and the negative external terminal 223b of the internal circuit 222, when the discharge relay 225b is closed, the voltage across the discharge circuit 225 decreases. In other words, when the discharge relay 225b is closed, current flows and the potential difference across the discharge circuit 225 decreases (or disappears), resulting in the voltage across the discharge circuit 225 falling below a threshold.

[0202] In contrast, when the discharge relay 225b of the discharge circuit 225 is opened, the voltage across the discharge circuit 225 increases (the voltage rises). That is, when the discharge relay 225b of the discharge circuit 225 is opened, the discharge circuit 225 is disconnected, resulting in a voltage (potential difference) being generated on both sides of the discharge relay 225b (positive and negative sides). In other words, when the discharge relay 225b is open, the voltage (potential difference) across the discharge circuit 225 increases and becomes greater than (higher than) the threshold.

[0203] In this way, based on the voltages across the external terminals 223a and 223b and the discharge circuit 225, it is possible to properly diagnose whether or not the contacts of the discharge relay 225b of the discharge circuit 225 are stuck, thereby preventing damage to the internal circuit 222 and the discharge circuit 225 (discharge resistor 225a).

[0204] In the above embodiment, if the control unit 23 determines in the discharge relay diagnostic process that the contacts of the discharge relay 225b are stuck, it discontinues the electrical connection of the battery pack 22 equipped with the discharge relay 225b that is determined to be stuck to the electrical equipment 20. In this way, power is not supplied to the electrical equipment 20 from the battery pack 22 having the discharge relay 225b with stuck contacts, thereby preventing an electrical accident.

[0205] In the above embodiment, the method for starting the electric work machine 1 comprises an electrical device 20, an electrical circuit 21 electrically connected to the electrical device 20, and a plurality of battery packs 22... having positive and negative external terminals, which are sequentially connected to the electrical device 20 via the electrical circuit 21 and connected in parallel, wherein the electrical circuit 21 includes a plurality of external relays 211... corresponding to each of the plurality of battery packs 22..., which open and close circuits connecting the corresponding battery packs 22 and the electrical device 20, and the method for starting the electric work machine 1 includes a plurality of external relays 211... before the battery pack 22 is connected to the electrical device 20, the battery pack With the internal circuit 222 of 22 in an open state, an external relay diagnostic process is performed to diagnose whether the contacts of the external relay 211 corresponding to the battery pack 22 are stuck. In the external relay diagnostic process, the internal circuit 222 of the battery pack 22 to be diagnosed is operated to an open state, and with the external relay 211 corresponding to the battery pack 22 operated to an open state, if the voltage between the positive and negative external terminals 223a and 223b of the battery pack 22 is above a threshold, it is determined that the contacts of the external relay 211 are stuck. If the voltage between the positive and negative external terminals 223a and 223b of the battery pack 22 is below the threshold, it is determined that the contacts of the external relay 211 are normal.

[0206] According to the premise of the above method, multiple battery packs 22... are connected in parallel by sequentially connecting to the electrical equipment 20, so that electricity from another battery pack 22 flows into the circuit connected to the battery pack 22. However, the external relay corresponding to the battery pack 22 When 211 is open, the positive and negative external terminals 223a and 223b of that battery pack 22 are not affected by electricity from another battery pack 22, and the voltage between the positive and negative external terminals 223a and 223b becomes lower than the threshold.

[0207] In contrast, if the contacts of the external relay 211 are stuck (welded), the external relay 211 will be in a closed state (conductive state). When the external relay 211 corresponding to the battery pack 22 is in a closed state (conductive state), the positive and negative external terminals 223a and 223b of the battery pack 22 will be affected by electricity from another battery pack 22, and the voltage between the positive and negative external terminals 223a and 223b will exceed a threshold.

[0208] Therefore, according to the above method, without activating the external relay 211, it is possible to properly diagnose whether or not the contacts of the external relay 211 are stuck simply by comparing the voltage and threshold value between the external terminals 223a and 223b of the positive and negative terminals of the battery pack 22. As a result, with the electric work machine 1 configured above, it is possible to prevent damage to the internal circuit 222 of the battery pack 22 due to the inrush current during startup. Furthermore, it is possible to properly determine whether or not multiple battery packs 22 can be connected sequentially.

[0209] In the above embodiment, the method for starting the electric work machine 1 comprises an electrical device 20, an electrical circuit 21 electrically connected to the electrical device 20, and a plurality of battery packs 22... having positive and negative external terminals, which are sequentially connected to the electrical device 20 via the electrical circuit 21 and connected in parallel, wherein the electrical circuit 21 includes a plurality of external relays 211... corresponding to each of the plurality of battery packs 22..., which open and close circuits connecting the corresponding battery packs 22 and the electrical device 20, and the battery pack 22 has a discharge circuit 225 connecting the negative external terminal side and the positive external terminal side of an internal circuit 222, which includes a discharge resistor 225a and a discharge relay 225b connected in series, and the method for starting the electric work machine 1 comprises connecting the battery pack 22 to the electrical device 20. At that time, a discharge relay diagnostic process is performed to diagnose whether or not the contacts of the discharge relay 225b of the battery pack 22 are stuck. In the discharge relay diagnostic process, the external relay 211 corresponding to the battery pack 22 to be diagnosed is operated to the closed state, and the discharge relay 225b of the battery pack 22 is operated to the open state. If the voltage between the positive and negative external terminals 223a and 223b of the battery pack 22 is above a threshold, and the voltage across the discharge circuit 225 is below a threshold, it is determined that the contacts of the discharge relay 225b of the discharge circuit 225 are stuck. If the voltage between the positive and negative external terminals 223a and 223b of the battery pack 22 is above a threshold, and the voltage across the discharge circuit 225 is higher than the threshold, it is determined that the contacts of the discharge relay 225b of the discharge circuit 225 are normal.

[0210] In the configuration assumed by the above method, when the battery pack 22 and the corresponding external relay 211 are in a closed state (conductive state), the positive and negative external terminals 223a and 223b of the battery pack 22 are affected by electricity from another battery pack 22, and the voltages of the positive and negative external terminals 223a and 223b become greater than or equal to a threshold.

[0211] Since the discharge circuit 225 connects the positive external terminal 223a and the negative external terminal 223b of the internal circuit 222, when the discharge relay 225b is closed, the voltage across the discharge circuit 225 decreases. In other words, when the discharge relay 225b is closed, current flows and the potential difference across the discharge circuit 225 decreases (or disappears), resulting in the voltage across the discharge circuit 225 falling below a threshold.

[0212] In contrast, when the discharge relay 225b of the discharge circuit 225 is opened, the voltage across the discharge circuit 225 increases (the voltage rises). That is, when the discharge relay 225b of the discharge circuit 225 is opened, the discharge circuit 225 is disconnected, resulting in a voltage (potential difference) being generated on both sides of the discharge relay 225b (positive and negative sides). In other words, when the discharge relay 225b is open, the voltage (potential difference) across the discharge circuit 225 increases and becomes greater than (higher than) the threshold.

[0213] Thus, the above configuration allows for proper diagnosis of whether the contacts of the discharge relay 225b of the discharge circuit 225 are stuck based on the voltages across the external terminals 223a and 223b and the discharge circuit 225, thereby preventing damage to the internal circuit 222 and the discharge circuit 225 (discharge resistor 225a).

[0214] In the above embodiment, the electric work machine 1 comprises an electrical device 20, an electrical circuit 21 electrically connected to the electrical device 20, a plurality of battery packs 22... connected to the electrical device 20 via the electrical circuit 21, and a control unit 23. The control unit 23 has a drive mode for driving the electrical device 20 with power supplied from the battery packs 22 and a charge mode for charging the battery packs 22. In the drive mode, if the voltage difference of the plurality of battery packs 22... exceeds a preset reference value, only the battery pack 22 with the highest voltage among the plurality of battery packs 22... is connected to the electrical device 20 to drive the electrical device 20.

[0215] According to the above configuration, in the drive mode, if the voltage difference between multiple battery packs 22 exceeds a reference value, that is, if multiple battery packs 22... are connected in parallel, and it is anticipated that the flow of electricity between the battery packs 22, 22 will exceed an allowable value, the battery pack 22 with the highest voltage is connected to the electrical equipment 20 to drive the electrical equipment 20. This prevents battery packs 22... with large voltage differences from being connected in parallel, prevents damage to the battery packs 22, and ensures power supply to the electrical equipment 20. In other words, the electric work machine 1 with the above configuration can prevent battery pack 22 from failing due to the parallel connection of multiple battery packs 22....

[0216] The control unit 23 initially connects only the battery pack 22 with the highest voltage to the electrical device 20 to start driving the device 20. Then, when the voltage difference between the battery pack 22 and the other battery packs 22 falls below a reference value, it connects the battery pack 22 and the other battery packs 22 to the electrical device 20 to drive the device 20. In this way, the multiple battery packs 22 supply power to the electrical device 20 when the voltage difference between the multiple battery packs 22... is small (or even eliminated). As a result, power can be efficiently supplied to the electrical device 20 without electricity flowing between the battery packs 22, 22 due to the voltage difference between them.

[0217] The electric work machine 1 is further equipped with a notification means 142 for notifying the worker, and the control unit 23 causes the notification means 142 to notify that charging of the battery packs 22 is necessary if the voltage difference between the multiple battery packs 22 exceeds a reference value.

[0218] With the above configuration, the notification means 142 can prompt charging of the battery pack 22, thus enabling early charging of the battery pack 22. In particular, by providing a notification prompting charging via the notification means 142, the timing of charging is accelerated, allowing the battery pack 22 with a low voltage to recover sooner.

[0219] When the control unit 23 is in charging mode and the voltage difference between the multiple battery packs 22... exceeds a preset reference value, it selects only the battery pack 22 with the lowest voltage among the multiple battery packs 22... and performs the charging process. In this way, only the battery pack 22 with the lowest voltage is charged, so the voltage of only that battery pack 22 becomes higher. As a result, the voltage difference between the battery pack 22 that is being charged and the other battery packs 22 that are not being charged becomes smaller (or disappears). This suppresses the flow of electricity between the battery packs 22, 22 when multiple battery packs 22... are connected in parallel to supply power to the electrical equipment 20, and power is supplied to the electrical equipment 20 efficiently.

[0220] In the above embodiment, the electric work machine 1 comprises an electrical device 20, an electrical circuit 21 electrically connected to the electrical device 20, a plurality of battery packs 22... connected to the electrical device 20 via the electrical circuit 21, and a control unit 23. The control unit 23 has a drive mode for driving the electrical device 20 with power supplied from the battery packs 22, and a charge mode for charging the battery packs 22. In the charge mode, if the voltage difference of the plurality of battery packs 22... exceeds a preset reference value, the control unit 23 performs a charge process on only the battery pack 22 with the lowest voltage among the plurality of battery packs 22....

[0221] According to the above configuration, in charging mode, only the battery pack 22 with the lowest voltage is charged, so the voltage of only that battery pack 22 becomes higher. As a result, the voltage difference between the battery pack 22 being charged and the other battery packs 22 that are not being charged becomes smaller (or disappears). This suppresses the flow of electricity between battery packs 22, 22 when multiple battery packs 22... are connected in parallel to supply power to the electrical equipment 20, and power is supplied to the electrical equipment 20 efficiently.

[0222] The control unit 23 starts the charging process targeting only the battery pack 22 with the lowest voltage. Then, when the voltage difference between the battery pack 22 and the other battery packs 22 falls below a reference value, it starts the charging process targeting both the battery pack 22 and the other battery packs 22. In this way, the charging process causes the voltage of the battery pack 22 with the lowest voltage to rise and approach the voltage of the other battery packs 22.

[0223] As a result, when the voltage difference between the battery packs 22 falls below a standard value, the voltage difference becomes small or disappears. In this state, the other battery packs 22 are also charged, so that multiple battery packs 22... are charged with no (small) voltage difference. Therefore, when multiple battery packs 22... are connected to the electrical equipment 20, power is efficiently supplied to the electrical equipment 20 from the multiple battery packs 22... while suppressing the flow of electricity between the battery packs 22, 22.

[0224] The electric work machine 1 further comprises a charging inlet 25 connectable to a charging device, and the charging inlet 25 is electrically connected to a plurality of battery packs 22... via an electrical circuit 21, and the control unit 23 executes a charging mode when a charging device is connected to the charging inlet 25. In this way, the machine automatically switches to charging mode without the operator having to switch modes.

[0225] The electrical circuit 21 includes a plurality of external relays 211, each corresponding to a plurality of battery packs 22, which open and close the circuit connecting the corresponding battery pack 22 to the charging inlet 25. In charging mode, the control unit 23 closes the external relay 211 corresponding to the battery pack 22 to be charged and opens the external relay 211 corresponding to the battery pack 22 that is not to be charged. This allows the power supply path from the battery pack 22 to the electrical device 20 to be used as a charging path, and also enables charging only the battery pack 22 that is being charged.

[0226] As described above, the electric work machine 1, which has a drive mode and a charging mode, further comprises a work device 11 that performs a predetermined task, and the electrical equipment 20 directly or indirectly drives the work device 11. In this way, power is supplied to the electrical equipment from at least a high-voltage (high-charge) battery pack, so stable operation for a long period of time can be achieved.

[0227] In the above embodiment, the method for starting the electric work machine 1 comprises an electrical device 20, an electrical circuit 21 electrically connected to the electrical device 20, and a plurality of battery packs 22... connected to the electrical device 20 via the electrical circuit 21, and has a drive mode in which the electrical device 20 is driven by power supplied from the battery packs 22, and a charge mode in which the battery packs 22 are charged. In the drive mode, if the voltage difference of the plurality of battery packs 22... exceeds a preset reference value, only the battery pack 22 with the highest voltage among the plurality of battery packs 22... is connected to the electrical device 20 to drive the electrical device 20.

[0228] According to the above method, in the driving mode, if the voltage difference between the multiple battery packs 22 exceeds a reference value, that is, if it is anticipated that an electric current will flow between the battery packs 22, 22 when the multiple battery packs 22... are connected in parallel and that this current will exceed an allowable value, the battery pack 22 with the highest voltage is connected to the electrical equipment 20 to drive the electrical equipment 20.

[0229] This prevents the parallel connection of battery packs 22... with large voltage differences, thereby preventing damage to the battery packs 22, and also ensures power supply to the electrical equipment 20. In other words, the electric work machine 1 with the above configuration can prevent battery pack 22 from failing due to the parallel connection of multiple battery packs 22....

[0230] In the above embodiment, the method for starting the electric work machine 1 comprises an electrical device 20, an electrical circuit 21 electrically connected to the electrical device 20, and a plurality of battery packs 22... connected to the electrical device 20 via the electrical circuit 21, and has a drive mode in which the electrical device 20 is driven by power supplied from the battery packs 22, and a charge mode in which the battery packs 22 are charged. In the charge mode, if the voltage difference of the plurality of battery packs 22... exceeds a preset reference value, only the battery pack 22 with the lowest voltage among the plurality of battery packs 22... is charged and the charging process is performed.

[0231] According to the above method, in charging mode, only the battery pack 22 with the lowest voltage is charged, so the voltage of only that battery pack 22 becomes higher. As a result, the voltage difference between the battery pack 22 being charged and the other battery packs 22 that are not being charged becomes smaller (or disappears). As a result, when multiple battery packs 22... are connected in parallel to supply power to the electrical equipment 20, the flow of electricity between the battery packs 22, 22 is suppressed, and power is supplied to the electrical equipment 20 efficiently.

[0232] It should be noted that the present invention is not limited to the embodiments described above, and modifications can be made as appropriate without departing from the spirit of the invention.

[0233] In the above embodiment, two battery packs 22... were connected in parallel, but the invention is not limited to this. For example, the electric work machine 1 may have three or more battery packs 22... Multiple battery packs 22… may be connected in parallel to supply power to the electrical equipment 20. In other words, multiple battery packs 22… can be connected in parallel with the aim of lowering the current value per battery pack 22, and the number of battery packs 22 is not limited.

[0234] In this case as well, the control (processing) of the first battery pack 22 and the control (processing) of the second battery pack 22 are the same as in the above embodiment.

[0235] In the above embodiment, the control unit 23 sets the battery pack 22 corresponding to the external relay 211 with the most switches on and off as the external relay 211 corresponding to the second battery pack 22, based on the cumulative number of switches on and off for each of the multiple external relays 211..., as the first battery pack 22 (the battery pack 22 that is connected first in the connection order). However, the control unit 23 is not limited to this. For example, the control unit 23 may sequentially change the battery pack 22 set as the first battery pack 22 each time the system is started up (each time a process is performed to connect the multiple battery packs 22... to the electrical equipment 20). In this way, similar to the above embodiment, the damage received by each of the multiple external relays 211... can be equalized.

[0236] Specifically, the damage to the external relay 211 varies depending on the number of times it is switched on and off. That is, as the number of times the external relay 211 is switched on and off increases, the damage it receives from the circuit switching increases, while as the number of times it is switched on and off decreases, the damage it receives from the circuit switching decreases. Therefore, by sequentially changing the first battery pack 22 connected to the electrical equipment 20 (electrical circuit 21) each time the electrical equipment 20 is started, the first external relay 211 to be closed is also changed, thus equalizing the damage received by each of the multiple external relays 211... This makes it possible to prevent a specific external relay 211 from failing.

[0237] In the above embodiment, a crawler-type running mechanism was used as the running mechanism 101, but it is not limited to this. For example, the running mechanism 101 may be a wheel (tire) type running mechanism having a pair of wheels at the front and rear. In this case, both the front and rear wheels may be driven, or either one of the front or rear wheels may be driven.

[0238] In the above embodiment, each of the multiple battery packs 22... is equipped with a pre-charge circuit 224, but the embodiment is not limited to this. For example, if a particular battery pack 22 is the first to be connected to the electrical equipment 20 (electrical circuit 21), at least the battery pack 22 that is set first in order may have a pre-charge circuit 224 in which a pre-charge resistor 224a and a pre-charge relay 224b are connected in parallel to an internal relay 220 (220a). However, as in the above embodiment, if the battery pack 22 that is set first is changed, it goes without saying that each of the multiple battery packs 22... must have a pre-charge circuit 224.

[0239] In the above embodiment, the electric work machine 1 includes an ECU 23a that controls the entire electric work machine 1 and a BMS 23b that monitors and controls the battery pack 22, with the ECU 23a performing various processes, but is not limited to this. For example, the BMS 23b may perform (process) parallel connection feasibility diagnosis, parallel connection processing of the battery pack 22, single connection processing of the battery pack 22, fault diagnosis, and charging mode, or the ECU 23a and BMS 23b may share the task of performing (processing). In addition, the control unit 23 may include a dedicated control unit (controller unit) that performs parallel connection feasibility diagnosis, parallel connection processing of the battery pack 22, single connection processing of the battery pack 22, fault diagnosis, and charging mode.

[0240] In the above embodiment, each of the multiple battery packs 22... has a first internal relay 220a and a second internal relay 220b as internal relays 220, but is not limited to this. For example, each of the multiple battery packs 22... may have either the first internal relay 220a or the second internal relay 220b as internal relays 220. In other words, each of the multiple battery packs 22... only needs to have at least one internal relay 220 that opens and closes the internal circuit 222.

[0241] In the above embodiment, assuming that each of the multiple battery packs 22... has an internal relay 220, which includes a first internal relay 220a on the positive (P) side and a second internal relay 220b on the negative (N) side, and also has a pre-charge circuit 224 (pre-charge resistor 224a, pre-charge relay 224b) connected in parallel to the first internal relay 220a on the positive (P) side, when connecting the first battery pack 22 to the electrical equipment 20, the second internal relay 220b on the negative (N) side and the pre-charge relay 224b of the pre-charge circuit 224 are closed together (simultaneously), but the embodiment is not limited to this. For example, when connecting the first battery pack 22 to the electrical equipment 20, the second internal relay 220b on the negative (N) side and the pre-charge relay 224b of the pre-charge circuit 224 may be closed at different timings. However, in this case, it is assumed that the internal relay 220 (the first internal relay 220a on the positive (P) side) which is in parallel with the pre-charge circuit 224 is closed last. Also, if the battery pack 22 has one internal relay 220 that opens and closes the internal circuit 222, and a pre-charge circuit 224 connected in parallel to one internal relay 220, then the pre-charge relay 224b of the pre-charge circuit 224 should be closed first, and then the internal relay 220 should be closed.

[0242] In the above embodiment, the second pre-processing S15 was performed after the first pre-processing S13, but the embodiment is not limited to this. That is, after closing the external relay 211 corresponding to the first battery pack 22 for the electrical equipment 20, the internal relay 220 (first internal relay 220a) in parallel with the pre-charge circuit 224 (pre-charge relay 224b) was closed, but the embodiment is not limited to this. For example, after closing the pre-charge circuit 224 (pre-charge relay 224b) of the first battery pack 22 for the electrical equipment 20, the external relay 211 corresponding to the battery pack 22 may be closed. Alternatively, the pre-charge circuit 224 (pre-charge relay 224b) of the first battery pack 22 and the external relay 211 corresponding to the battery pack 22 may be closed simultaneously for the electrical equipment 20. That is, the order of the first pre-processing S13 and the second pre-processing S15 may be reversed, or they may be performed at the same timing.

[0243] However, in all of the above cases, it is assumed that the internal relay 220 (first internal relay 220a), which is in parallel with the precharge circuit 224 (precharge relay 224b), will be closed after the precharge circuit 224 (precharge relay 224b) has been closed (after precharging has been performed). In other words, it is assumed that the third pre-processing S15 will be performed after the first pre-processing S13 and the second pre-processing S15. Furthermore, in order to ensure that precharging is performed reliably, it goes without saying that, as in the above embodiment, it is preferable to close the precharge circuit 224 (precharge relay 224b) after closing the external relay 211.

[0244] In the above embodiment, the storage unit of the ECU23a, which acts as the control unit 23, stores specifications regarding whether or not to diagnose the opening and closing operation of the internal relay 220 of the second battery pack 22, whether or not to perform precharging in the precharge circuit 224 of the second battery pack 22, and whether or not to close the first internal relay 220a and the second internal relay 220b simultaneously. However, it is not limited to these specifications. For example, the storage unit of the ECU23a may only store specifications regarding whether or not to diagnose opening and closing operations that require processing time when connecting multiple battery packs 22. Also, as described above, the specifications stored in the storage unit may be fixed or changeable.

[0245] In the above embodiment, multiple battery packs 22... and multiple electrical devices 20... are electrically connected via an electrical circuit 21, but this is not limited to this. For example, multiple battery packs 22... and a single electrical device 20 may be connected via an electrical circuit 21. That is, as long as multiple battery packs 22... are connected in parallel, the number of electrical devices 20 (output electrical devices 20) powered by the multiple battery packs 22... is not limited. Needless to say, the secondary circuits 212 of the electrical circuit 21 are provided in a number of systems corresponding to the number of electrical devices 20. Therefore, when a single electrical device 20 is connected to multiple battery packs 22... as described above, the secondary circuit 212 will be one system (a pair of positive secondary circuits 212a and negative secondary circuits 212b).

[0246] In the above embodiment, when connecting the first battery pack 22 to the electrical equipment 20, a diagnostic process for the switching operation of the internal relay 220 is performed, followed by a first preliminary process that closes the external relay 211 corresponding to the first battery pack 22, and then a third preliminary process that closes the internal relay 220 of the first battery pack 22. However, the embodiment is not limited to this. For example, when connecting the first battery pack 22 to the electrical equipment 20, it may be unnecessary (not performed) to specify whether or not to perform the diagnostic process for the switching operation of the internal relay 220.

[0247] Furthermore, when connecting the first battery pack 22 to the electrical equipment 20, a diagnostic process for the opening and closing operation of the internal relay 220 may be performed, followed by a third pre-processing step to close the internal relay 220 of the first battery pack 22, and then a first pre-processing step to close the external relay 211 corresponding to the first battery pack 22. However, if precharging is performed, a second pre-processing step for precharging may be performed between the first and third pre-processing steps to suppress the effect of the inrush current on the relay switch (internal relay 220 or external relay 211) that is closed last.

[0248] In the above embodiment, precharging was performed when connecting the first battery pack 22 to the electrical equipment 20, but the embodiment is not limited to this. For example, when connecting the first battery pack 22 to the electrical equipment 20, it is not necessary to specify whether or not precharging is required (it is not performed), and the first battery pack 22 is connected to the electrical equipment 20. In this case, in order to prevent inrush current from acting on the internal relay 220, similar to the second battery pack 22, the internal relay 220 of the first battery pack 22 may be closed (after the first connection process is performed), and then the external relay 211 corresponding to the first battery pack 22 may be closed (the second connection process is performed).

[0249] In the above embodiment, regarding the opening and closing of the internal relay 220 of the second battery pack 22 when connecting the second battery pack 22 to the electrical equipment 20, the first internal relay 220a and the second internal relay 220b are closed together (simultaneously), but the embodiment is not limited to this. For example, regarding the opening and closing of the internal relay 220 of the second battery pack 22 when connecting the second battery pack 22 to the electrical equipment 20, the second internal relay 220b may be closed first, and then the first internal relay 220a may be closed.

[0250] Furthermore, with respect to the first battery pack 22, the first internal relay 220a and the second internal relay 220b may be closed together (simultaneously). That is, if the internal relay 220 of the battery pack 22 includes a first internal relay 220a and a second internal relay 220b, and the first connection process for closing the internal relay 220 is configured to allow specifying whether or not to close the first internal relay 220a and the second internal relay 220b simultaneously, then the first internal relay 220a and the second internal relay 220b should be closed according to that specification.

[0251] Therefore, in the first connection process that closes the internal relay 220, if it is specified that the first internal relay 220a and the second internal relay 220b should be closed simultaneously, then the first internal relay 220a and the second internal relay 220b should be closed at the same time (together). Conversely, in the first connection process that closes the internal relay 220, if it is specified that the first internal relay 220a and the second internal relay 220b should not be closed simultaneously, then the first internal relay 220a and the second internal relay 220b should be closed at different times. In the above embodiment, as a method for correcting the voltage difference between multiple battery packs 22..., only the battery pack 22 with the lowest voltage is charged, and when the voltage of that battery pack 22 becomes equivalent to the voltage of the battery pack 22 with the highest voltage, charging of the battery pack 22 with the highest voltage is also started. However, for example, the control unit 53 may, after connecting only the battery pack 22 with the highest voltage to the electrical equipment 20 and starting to drive the electrical equipment 20, then, when the voltage difference between the battery pack 20 connected to the electrical equipment 20 (the battery pack supplying power) and the other battery packs (the low-voltage battery packs 22 that are not supplying power) falls below a reference value, connect the battery pack 20 connected to the electrical equipment 20 (the battery pack supplying power) and the other battery packs (the low-voltage battery packs 22 that are not supplying power) to the electrical equipment 20 and start driving the electrical equipment 20.

[0252] In this way, since there is no (or only a small) voltage difference between the multiple battery packs 22, 22, when the multiple battery packs 22... are connected to the electrical equipment 20, the flow of electricity between the battery packs 22, 22 is prevented, and damage to the battery packs 22 can be suppressed.

[0253] Although not specifically mentioned in the above embodiment, the inverter 20a, as an electrical device 20, indirectly drives the work device 11 in order to drive the electric motor 16 that drives the hydraulic pump 15. However, the electrical device 20 that drives the work device 11 is not limited to those that drive the work device 11 indirectly. For example, the electrical device 20 that drives the work device 11 may be an electric actuator that directly drives the work device 11 and is powered directly from the battery pack 22...

[0254] In the above embodiment, the electric work machine 1 includes a shovel device 11b as a work device 11, in which a bucket 112b is connected to the tip of an arm 111b, but is not limited to this. For example, the shovel device 11b may have a bucket 112b as its basic configuration, and the bucket 112b may be interchangeable with other work tools. Alternatively, the work device 11 may be a dedicated work device in which other work tools are connected to the tip of an arm 111b that has the configuration of the shovel device 11b. Examples of other work tools include hydraulic breakers, hydraulic crushers, angle brooms, earth augers, pallet forks, sweepers, mowers, snow blowers, etc.

[0255] In the above embodiment, a construction-type electric work machine 1 equipped with a dozer device 11a and a shovel device 11b was described as the work device 11, but it is not limited to this. For example, it may be a transport-type electric work machine 1 or an agricultural-type electric work machine 1. In other words, the electric work machine 1 is not limited to construction machinery, but may also be transport machinery (e.g., a forklift) or agricultural machinery (e.g., a tractor), etc. [Explanation of Symbols]

[0256] 1: Electric work equipment 20: Electrical equipment (electrical equipment for output) 21: Electrical Circuits 22: Battery Pack 23: Control Unit 24: Junction Box 25: Charging inlet (for electrical devices) 142: Monitor (notification method) 211: External relay 220: Internal relay 220a: First internal relay 220b: Second internal relay 222: Internal circuit 224: Pre-charge circuit 224a: Pre-charge resistor 224b: Pre-charge relay 225: Discharge Circuit 225a: Discharge resistor 225b: Discharge relay

Claims

1. Electrical equipment and, An electrical circuit electrically connected to the aforementioned electrical equipment, Three or more battery packs connected to the electrical equipment via the aforementioned electrical circuit, It comprises a control unit and, The control unit, The system has a drive mode for driving the electrical equipment using power supplied from the battery pack, and a charge mode for charging the battery pack. An electric work machine that compares the voltages of the three or more battery packs to each other, calculates the voltage difference between the battery packs of the combination to be compared, and if at least one of the calculated voltage differences exceeds a preset reference value, in the drive mode, connects only the battery pack with the highest voltage among the three or more battery packs to the electrical equipment to drive the electrical equipment.

2. The control unit, The electric work machine according to claim 1, wherein, after starting to drive the electrical equipment by connecting only the battery pack with the highest voltage to the electrical equipment, if the voltage difference between the battery pack and the other battery packs falls below a reference value, the battery pack and the other battery packs are connected to the electrical equipment to drive the electrical equipment.

3. It is further equipped with a notification means for notifying workers, The control unit, If at least one of the multiple voltage differences exceeds a reference value, the notification means will be notified that charging of the battery pack is necessary. The electric work machine according to claim 1.

4. The electric work machine according to claim 1, wherein, in the charging mode, if at least one of the plurality of voltage differences exceeds a preset reference value, the control unit performs charging processing on only the battery pack with the lowest voltage among the three or more battery packs.

5. Electrical equipment and, An electrical circuit electrically connected to the aforementioned electrical equipment, Three or more battery packs connected to the electrical equipment via the aforementioned electrical circuit, It comprises a control unit and, The control unit, The system has a drive mode for driving the electrical equipment using power supplied from the battery pack, and a charge mode for charging the battery pack. An electric work machine that compares the voltages of the three or more battery packs to each other, calculates the voltage difference between the battery packs of the combination to be compared, and if at least one of the calculated voltage differences exceeds a preset reference value, performs charging processing on only the battery pack with the lowest voltage among the three or more battery packs in the charging mode.

6. The control unit, The electric work machine according to claim 4 or 5, wherein after starting the charging process targeting only the battery pack with the lowest voltage, if the voltage difference between the battery pack and the other battery packs falls below a reference value, the charging process is performed targeting both the battery pack and the other battery packs.

7. A charging inlet connectable to a charging device, further comprising a charging inlet electrically connected to the three or more battery packs via the electrical circuit, The control unit, When the charging device is connected to the charging inlet, The electric work machine according to claim 1 or 5, which performs the charging mode.

8. The aforementioned electrical circuit is A plurality of external relays corresponding to each of the three or more battery packs, including a plurality of external relays that open and close a circuit connecting the corresponding battery pack and the charging inlet, The control unit, The electric work machine according to claim 7, wherein, in the charging mode, the external relay corresponding to the battery pack to be charged is closed, and the external relay corresponding to the battery pack not to be charged is opened.

9. The device further includes a work apparatus for performing a predetermined task, The electric work machine according to claim 1 or 5, wherein the electrical equipment directly or indirectly drives the work device.

10. Electrical equipment and, An electrical circuit electrically connected to the aforementioned electrical equipment, The system comprises three or more battery packs connected to the electrical equipment via the aforementioned electrical circuit, A method for starting an electric work machine having a drive mode for driving the electrical equipment with power supplied from the battery pack and a charge mode for charging the battery pack, A method for starting an electric work machine, comprising comparing the voltages of the three or more battery packs to each other, calculating the voltage difference between the battery packs of the combination to be compared, and if at least one of the calculated voltage differences exceeds a preset reference value, connecting only the battery pack with the highest voltage among the three or more battery packs to the electrical equipment in the drive mode to drive the electrical equipment.

11. Electrical equipment and, An electrical circuit electrically connected to the aforementioned electrical equipment, A charging method for an electric work machine comprising three or more battery packs connected to the electrical equipment via the aforementioned electrical circuit, the method having a drive mode for driving the electrical equipment with power supplied from the battery packs, and a charging mode for charging the battery packs, A charging method for an electric work machine, comprising comparing the voltages of the three or more battery packs to each other, calculating the voltage difference between the battery packs of the combination to be compared, and if at least one of the calculated voltage differences exceeds a preset reference value, in the charging mode, charging only the battery pack with the lowest voltage among the three or more battery packs.

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