Transport vehicle and charging system

Abstract

To provide a transport vehicle and a charging system capable of charging a battery pack provided in a transport vehicle using a single charger with a fixed output voltage.SOLUTION: A transport vehicle 10 includes a first assembled battery 11 composed of a plurality of secondary batteries charged by a charger 30 which is an external device, a second assembled battery 12 composed of another plurality of secondary batteries charged by the charger 30, and a connection method changeover switch 15 which switches the connection method of the first assembled battery 11 and the second assembled battery 12. The connection method changeover switch 15 changes the connection method of the first assembled battery 11 and the second assembled battery 12 from a series connection to a parallel connection when the first assembled battery 11 and the second assembled battery 12 are being charged.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a rechargeable transport vehicle and a charging system for charging the rechargeable transport vehicle.

Background Art

[0002] Conventionally, in a factory production line or the like, a rechargeable transport vehicle such as an automatic guided vehicle (AGV) that transports various loads has been used. The rated voltage of each battery pack provided in such a transport vehicle may differ depending on the operating voltage of the devices provided in the transport vehicle. Therefore, when the rated voltages of the battery packs differ for a plurality of transport vehicles, in order to charge the battery packs provided in these transport vehicles, a charger capable of outputting a voltage corresponding to the rated voltage of each battery pack of each transport vehicle must be prepared for each transport vehicle. Alternatively, on the charger side, the output voltage must be switched according to the various rated voltages of the battery packs of each transport vehicle.

[0003] Regarding this point, Patent Document 1 discloses a battery pack including a plurality of secondary battery cells and a control circuit. The plurality of secondary battery cells are connected in series during discharge and in parallel during charging under the control of the control circuit. The control circuit measures the voltage of each secondary battery cell before charging, and charges the other secondary battery cells in parallel while electrically disconnecting the secondary battery cells whose measured voltage value is below a predetermined value from the other secondary battery cells.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the battery pack disclosed in Patent Document 1, it is not possible to charge the assembled batteries of various voltages provided in the transport vehicle using a single charger with a fixed output voltage.

[0006] The present disclosure has been made to solve such problems, and an object thereof is to provide a transport vehicle and a charging system capable of charging an assembled battery provided in a transport vehicle using a single charger with a fixed output voltage.

Means for Solving the Problems

[0007] A transport vehicle provided with an assembled battery charged by a charger which is an external device according to the present disclosure includes a first assembled battery composed of a plurality of secondary batteries charged by the charger, a second assembled battery composed of other plurality of secondary batteries charged by the charger, a connection method switching switch for switching the connection method of the first assembled battery and the second assembled battery, a first charge control circuit connected to the first assembled battery, and a second charge control circuit connected to the second assembled battery, The connection method switching switch switches the connection method of the first assembled battery and the second assembled battery from series connection to parallel connection when charging the first assembled battery and the second assembled battery, The first charge control circuit sets the voltage applied to the first assembled battery during charging to be equal to or lower than a predetermined first upper limit voltage corresponding to the first assembled battery, The second charge control circuit sets the voltage applied to the second assembled battery during charging to be equal to or lower than a predetermined second upper limit voltage corresponding to the second assembled battery.

[0008] In addition, the transport vehicle may include a vehicle device that operates by the power supplied from the first assembled battery and the second assembled battery, and a first assembled battery switching switch that is selectively connected to the positive electrode sides of the first assembled battery and the second assembled battery and allows the current output from one of the first assembled battery and the second assembled battery to flow to the vehicle device.

[0009] The transport vehicle also includes a second battery switching switch that is selectively connected to the negative electrode sides of the first battery pack and the second battery pack. The second battery switching switch allows the current output from the first battery pack via the vehicle device to flow back to the first battery pack. The second battery switching switch allows the current output from the second battery pack via the vehicle device to flow back to the second battery pack.

[0010] The connection method switching switch can switch the connection method of the first battery pack and the second battery pack from parallel connection to series connection when the first battery pack and the second battery pack are discharging.

[0011] The first charge control circuit includes a first charge stop means for stopping the charging of the first battery pack. The second charge control circuit may include a second charge stop means for stopping the charging of the second battery pack.

[0012] The first charge control circuit determines whether the remaining capacity of the first battery pack is less than or equal to a predetermined remaining capacity. If it is determined that the remaining capacity of the first battery pack is less than or equal to the predetermined remaining capacity, the first battery pack is charged. If it is determined that the remaining capacity of the first battery pack exceeds the predetermined remaining capacity, the first battery pack is not charged. The second charge control circuit determines whether the remaining capacity of the second battery pack is less than or equal to a predetermined remaining capacity. If it is determined that the remaining capacity of the second battery pack is less than or equal to the predetermined remaining capacity, the second battery pack is charged. If it is determined that the remaining capacity of the second battery pack exceeds the predetermined remaining capacity, the second battery pack is not charged.

[0013] The charging system according to the present disclosure includes a charger for charging a secondary battery at a predetermined voltage and a transport vehicle. The transport vehicle includes a first battery pack composed of a plurality of secondary batteries charged by the charger, and A second battery pack composed of a plurality of other secondary batteries charged by a charger, A connection method switching switch for switching the connection method of the first battery pack and the second battery pack, A first charge control circuit connected to the first battery pack, And a second charge control circuit connected to the second battery pack, The connection method switching switch switches the connection method of the first battery pack and the second battery pack from series connection to parallel connection during charging of the first battery pack and the second battery pack, The first charge control circuit sets the voltage applied to the first battery pack during charging to be equal to or lower than a predetermined first upper limit voltage corresponding to the first battery pack, The second charge control circuit sets the voltage applied to the second battery pack during charging to be equal to or lower than a predetermined second upper limit voltage corresponding to the second battery pack.

Advantages of the Invention

[0014] According to the present disclosure, it is possible to provide a transport vehicle and a charging system capable of charging a battery pack provided in a transport vehicle using a single charger with a fixed output voltage.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0016] FIG. 1 is a diagram showing an example of a charging system 1 according to the present disclosure. The charging system 1 includes a transport vehicle 10 and a charger 30. Note that FIG. 1 shows a state in which the transport vehicle 10 and the charger 30 are electrically connected.

[0017] The transport vehicle 10 is a vehicle for transporting various goods. Specific examples of the transport vehicle 10 include an automated guided vehicle and the like. The transport vehicle 10 includes a first battery pack 11, a second battery pack 12, a charge control circuit 13, a charge control circuit 14, a connection method switching switch 15, a vehicle device 16, a drive device 17, a battery pack switching switch 18, backflow prevention elements 19 to 22, and a battery pack switching switch 23. These components are electrically connected via an electric wire 24.

[0018] The first battery pack 11 is a battery composed of a plurality of secondary batteries. The first battery pack 11 is charged by a charger 30 which is an external device of the transport vehicle 10.

[0019] The second battery pack 12 is a battery composed of a plurality of secondary batteries. The second battery pack 12 is charged by the charger 30.

[0020] The charge control circuit 13 is a circuit that controls the voltage applied to the first battery pack 11 during charging, and is connected in series to the first battery pack 11. The charge control circuit 13 corresponds to the first charge control circuit. Specifically, the charge control circuit 13 sets the voltage applied to the first battery pack 11 during charging to be equal to or lower than a predetermined first upper limit voltage corresponding to the first battery pack. The first upper limit voltage defines the maximum charging voltage of the first battery pack 11.

[0021] The charge control circuit 14 is a circuit that controls the voltage applied to the second battery pack 12 during charging, and is connected in series to the second battery pack 12. The charge control circuit 14 corresponds to the second charge control circuit. Specifically, the charge control circuit 14 sets the voltage applied to the second battery pack 12 during charging to be equal to or lower than a predetermined second upper limit voltage corresponding to the second battery pack. The second upper limit voltage defines the maximum charging voltage of the second battery pack 12.

[0022] The charge control circuit 13 and the charge control circuit 14 each have a charge stop means for stopping the charging of the first battery pack 11 and the second battery pack 12, respectively. The charge stop means corresponds to the first charge stop means and the second charge stop means.

[0023] Specifically, when the charging method is constant voltage (CV) charging, the charging stop means measures the voltage of the battery packs 11 and 12 during charging, and stops charging the battery packs 11 and 12 when the measured voltage of the battery packs 11 and 12 reaches a predetermined voltage. The predetermined voltage can be any voltage value.

[0024] Also, when the charging method is minus delta V (-ΔV) charging, the charging stop means measures the voltage of the battery packs 11 and 12 during charging, and stops charging the battery packs 11 and 12 when the measured voltage of the battery packs 11 and 12 drops by a predetermined value from the maximum reachable voltage. This utilizes the property that the voltage drops when the battery is fully charged. The predetermined value can be any voltage value.

[0025] Furthermore, when the charging method is timer charging, the charging stop means measures the charging time, and stops charging the battery packs 11 and 12 when the measured charging time reaches a predetermined time. The predetermined time can be any time.

[0026] Furthermore, when the charging method is temperature control charging, the charging stop means obtains the temperature of the battery packs 11 and 12 per a certain time interval from a temperature sensor that detects the temperature of the battery packs 11 and 12. Next, the charging stop means calculates a change amount indicating the temperature change of the battery packs 11 and 12 per a certain time interval based on the obtained temperature. Then, the charging stop means determines whether or not the calculated change amount is equal to or higher than a predetermined temperature. The predetermined temperature can be any temperature. When it is determined that the calculated change amount is equal to or higher than the predetermined temperature, the charging stop means stops charging the battery packs 11 and 12.

[0027] Furthermore, when the charging method is temperature control charging, the charging stop means obtains the temperature of the battery packs 11 and 12 from a temperature sensor that detects the temperature of the battery packs 11 and 12. Next, the charging stop means determines whether or not the temperature of the battery packs 11 and 12 is equal to or higher than a predetermined temperature based on the obtained temperature. The predetermined temperature can be any temperature. When it is determined that the temperature of the battery packs 11 and 12 is equal to or higher than the predetermined temperature, the charging stop means stops charging the battery packs 11 and 12.

[0028] In addition, the charge control circuits 13 and 14 can distribute the charging current to the battery packs 11 and 12 according to the power consumption of each battery pack 11 and 12. There may be a difference in power consumption between the battery packs 11 and 12 depending on how they are used. For example, when only the vehicle device 16 is operating and the drive device 17 is stopped during maintenance of the transport vehicle 10, power is consumed by either one of the battery packs 11 and 12. When the transport vehicle 10 attempts to resume operation in this state, the remaining capacity of either the battery pack 11 or the battery pack 12 may be insufficient for the power required for the operation of the drive device 17. In such a case, the charge control circuits 13 and 14 can charge only the battery pack with insufficient remaining capacity. Thereby, the charging time can be shortened.

[0029] Specifically, the charge control circuit 13 determines whether the remaining capacity of the first battery pack 11 is less than or equal to a predetermined remaining capacity. The predetermined remaining capacity can be, for example, the SOC (State Of Charge) required to drive the drive device 17. When it is determined that the remaining capacity of the first battery pack 11 is less than or equal to the predetermined remaining capacity, the charge control circuit 13 charges the first battery pack 11. On the other hand, when it is determined that the remaining capacity of the first battery pack 11 exceeds the predetermined remaining capacity, the charge control circuit 13 does not charge the first battery pack 11.

[0030] In addition, the charge control circuit 14 determines whether the remaining capacity of the second battery pack 12 is less than or equal to a predetermined remaining capacity. When it is determined that the remaining capacity of the second battery pack 12 is less than or equal to the predetermined remaining capacity, the charge control circuit 14 charges the second battery pack 12. On the other hand, when it is determined that the remaining capacity of the second battery pack 12 exceeds the predetermined remaining capacity, the charge control circuit 14 does not charge the second battery pack 12.

[0031] The connection method switching switch 15 is a switch that switches the connection method of the first battery pack 11 and the second battery pack 12. When the first battery pack 11 and the second battery pack 12 are discharging, the connection method switching switch 15 is turned on, and the first battery pack 11 and the second battery pack 12 are connected in series. On the other hand, when the first battery pack 11 and the second battery pack 12 are charging, the connection method switching switch 15 is turned off, and the first battery pack 11 and the second battery pack 12 are connected in parallel. Therefore, in the circuit shown in FIG. 1, by turning the connection method switching switch 15 from on to off when the first battery pack 11 and the second battery pack 12 are charging, the connection method of the first battery pack 11 and the second battery pack 12 switches from series connection to parallel connection. On the other hand, by turning the connection method switching switch 15 from off to on when the first battery pack 11 and the second battery pack 12 are discharging, the connection method of the first battery pack 11 and the second battery pack 12 switches from parallel connection to series connection.

[0032] The vehicle device 16 is a device provided in the transport vehicle 10 and operates by the electric power supplied by the first battery pack 11 and the second battery pack 12. Specific examples of the vehicle device 16 include a controller such as a PLC (Programmable Logic Controller), a light, and the like. The vehicle device 16 is selectively connected to one of the first battery pack 11 and the second battery pack 12. Therefore, an electric current output from one of the first battery pack 11 and the second battery pack 12 flows through the vehicle device 16.

[0033] The drive device 17 is a device for rotating a wheel (not shown) provided in the transport vehicle 10 and operates by the electric power supplied by both the first battery pack 11 and the second battery pack 12. Specific examples of the drive device 17 include a motor and the like. The drive device 17 is connected to both the first battery pack 11 and the second battery pack 12. Therefore, electric currents output from both the first battery pack 11 and the second battery pack 12 flow through the drive device 17.

[0034] The battery pack switching switch 18 is a switch that switches the battery pack that supplies power to the vehicle device 16. The battery pack switching switch 18 is selectively connected to the positive electrode sides of the first battery pack 11 and the second battery pack 12, and allows the current output from one of the first battery pack 11 and the second battery pack 12 to flow to the vehicle device 16. In the present embodiment, as shown in FIG. 1, the battery pack switching switch 18 is connected to the positive electrode sides of the first battery pack 11 and the second battery pack 12. Further, the battery pack switching switch 18 is disposed between the first battery pack 11 and the second battery pack 12 and the vehicle device 16. The battery pack switching switch 18 corresponds to the first battery pack switching switch.

[0035] The backflow prevention elements 19 to 22 are elements for preventing the backflow of current in the electric circuit provided in the transport vehicle 10. Specific examples of the backflow prevention elements 19 to 22 include diodes and the like.

[0036] As shown in FIG. 1, the backflow prevention element 19 is disposed between the charge control circuit 13 and the positive electrode side of the first battery pack 11. By disposing the backflow prevention element 19 at this position, the direction of the current flowing into the charge control circuit 13 can be restricted to one direction.

[0037] As shown in FIG. 1, the backflow prevention element 20 is disposed between the charge control circuit 14 and the negative electrode side of the second battery pack 12. By disposing the backflow prevention element 20 at this position, the direction of the current flowing into the charge control circuit 14 can be restricted to one direction.

[0038] As shown in FIG. 1, the backflow prevention element 21 is disposed between the vehicle device 16 and the positive electrode side of the second battery pack 12. By disposing the backflow prevention element 21 at this position, the direction of the current flowing into the vehicle device 16 can be restricted to one direction.

[0039] As shown in FIG. 1, the backflow prevention element 22 is disposed between the vehicle device 16 and the negative electrode side of the second battery pack 12. By disposing the backflow prevention element 22 at this position, the direction of the current flowing into the vehicle device 16 can be restricted to one direction.

[0040] The battery pack switching switch 23 is a switch that switches the current output from the vehicle device 16. The battery pack switching switch 23 is disposed between the vehicle device 16 and the first battery pack 11 and the second battery pack 12, and is selectively connected to the negative electrode sides of the first battery pack 11 and the second battery pack 12. The battery pack switching switch 23 performs a switching operation in conjunction with the battery pack switching switch 18. The battery pack switching switch 23 corresponds to the second battery pack switching switch.

[0041] Specifically, the battery pack switching switch 23 causes the current output from the first battery pack 11 via the vehicle device 16 to flow to the first battery pack 11. Further, the battery pack switching switch 23 causes the current output from the second battery pack 12 via the vehicle device 16 to flow to the second battery pack 12.

[0042] The charger 30 is a device that charges the battery pack provided in the transport vehicle 10. The charger 30 can be electrically connected to the battery pack of the transport vehicle 10 via connection means (not shown) such as connection terminals and cables. The charger 30 may charge the battery pack of the transport vehicle 10 by wireless charging. The charger 30 can charge the battery pack by applying an output voltage corresponding to the upper limit voltage that the charger 30 can output to the battery pack of the transport vehicle 10. In the present embodiment, a charger 30 with an arbitrary output voltage can be employed. Note that it is preferable to employ a charger 30 having an output voltage equal to or higher than the maximum upper limit voltage among the upper limit voltages of the battery packs provided in the transport vehicle 10.

[0043] As described above, when the first battery pack 11 and the second battery pack 12 are discharging, as shown in FIGS. 2 and 3, the connection method switching switch 15 is turned on. In this state, when the battery pack switching switch 18 is connected to the positive electrode side (B1) of the first battery pack 11 and the battery pack switching switch 23 is connected to the negative electrode side (B1) of the first battery pack 11, as shown in FIG. 2, only the current output from the first battery pack 11 flows to the vehicle device 16 via the battery pack switching switch 18, and the current output from the second battery pack 12 does not flow to the vehicle device 16.

[0044] When one side, the battery pack switching switch 18 is connected to the positive electrode side (B2) of the second battery pack 12, and the battery pack switching switch 23 is connected to the negative electrode side (B2) of the second battery pack 12, as shown in FIG. 3, only the current output from the second battery pack 12 flows through the battery pack switching switch 18 to the vehicle device 16, and the current output from the first battery pack 11 does not flow to the vehicle device 16.

[0045] Also, as shown in FIGS. 2 and 3, during discharge, the current output from the first battery pack 11 and the second battery pack 12 does not flow through the charge control circuit 13, the charge control circuit 14, the backflow prevention element 19, and the backflow prevention element 20. Therefore, in the circuits shown in FIGS. 2 and 3, the charge control circuit 13, the charge control circuit 14, the backflow prevention element 19, and the backflow prevention element 20 do not reduce the voltage supplied from the first battery pack 11 and the second battery pack 12.

[0046] In the above-described embodiment, the transport vehicle 10 includes a first battery pack 11 composed of a plurality of secondary batteries charged by a charger 30, a second battery pack 12 composed of other plurality of secondary batteries charged by the charger 30, and a connection method switching switch 15 that switches the connection method of the first battery pack 11 and the second battery pack 12. The connection method switching switch 15 switches the connection method of the first battery pack 11 and the second battery pack 12 from series connection to parallel connection during charging of the first battery pack 11 and the second battery pack 12.

[0047] For example, when the upper limit voltage of the first battery pack 11 and the second battery pack 12 of the transport vehicle 10 is 12V, when these battery packs are connected in series, it is necessary to charge these battery packs using a charger 30 with an output voltage of 24V. On the other hand, in the invention according to the present disclosure, since the connection method of the first battery pack 11 and the second battery pack 12 is parallel connection during charging, these battery packs can be charged using a charger 30 with an output voltage of 12V. In other words, these battery packs can be charged using a charger with a lower output voltage. Therefore, the output voltage of the charger required to charge the plurality of battery packs provided in the transport vehicle 10 can be reduced.

[0048] Also, in the above-described embodiment, the transport vehicle 10 includes a first charge control circuit 13 connected to the first battery pack 11 and a second charge control circuit 14 connected to the second battery pack 12. The first charge control circuit 13 sets the voltage applied to the first battery pack 11 during charging to be equal to or lower than a predetermined first upper limit voltage corresponding to the first battery pack 11. The second charge control circuit 14 sets the voltage applied to the second battery pack 12 during charging to be equal to or lower than a predetermined second upper limit voltage corresponding to the second battery pack 12.

[0049] By adopting this configuration, the first battery pack 11 and the second battery pack 12 can be charged with voltages equal to or lower than the upper limit voltages corresponding to the first battery pack 11 and the second battery pack 12, respectively. For example, assume that the upper limit voltage of the first battery pack 11 of the transport vehicle 10 is 12V, the upper limit voltage of the second battery pack is 24V, and the output voltage of the charger 30 is 30V. In this case, the first charge control circuit 13 can set the voltage applied to the first battery pack 11 to be 12V or lower. On the other hand, the second charge control circuit 14 can set the voltage applied to the second battery pack 12 to be 24V or lower. Therefore, a single charger with a fixed output voltage can be used to charge a plurality of battery packs with different upper limit voltages provided in a single transport vehicle 10. In other words, the transport vehicle 10 can be provided with battery packs having different upper limit voltages.

[0050] Also, assume that the upper limit voltage of each of the first battery pack 11 and the second battery pack 12 of a certain transport vehicle 10 is 24V, and the upper limit voltage of each of the first battery pack 11 and the second battery pack 12 of another transport vehicle 10 is 12V. In this case, for a certain transport vehicle 10, the first charge control circuit 13 can set the voltage applied to the first battery pack 11 to 12V or less, and the second charge control circuit 14 can set the voltage applied to the second battery pack 12 to 12V or less. On the other hand, for another transport vehicle 10, the first charge control circuit 13 can set the voltage applied to the first battery pack 11 to 24V or less, and the second charge control circuit 14 can set the voltage applied to the second battery pack 12 to 24V or less. Therefore, in the above-described embodiment, it is not necessary to prepare a plurality of chargers with different output voltages according to the upper limit voltages of the first battery pack 11 and the second battery pack 12 provided in the plurality of transport vehicles 10. Also, on the charger side, it is not necessary to switch the output voltage according to the various upper limit voltages of the battery packs of each transport vehicle. In other words, it is possible to charge the battery packs with different upper limit voltages of various transport vehicles 10 using a single charger with a fixed output voltage.

[0051] Furthermore, in the above-described embodiment, the transport vehicle 10 includes a vehicle device 16 that operates by the power supplied from the first battery pack 11 and the second battery pack 12, and a battery pack changeover switch 18. The battery pack changeover switch 18 is selectively connected to the positive electrode sides of the first battery pack 11 and the second battery pack 12, and allows the current output from one of the first battery pack 11 and the second battery pack 12 to flow to the vehicle device 16. As a result, since it is possible to switch between the first battery pack 11 and the second battery pack 12 that supply power to the vehicle device 16, it is possible to suppress the bias in the power consumption of the first battery pack 11 and the second battery pack 12.

[0052] Furthermore, the connection method changeover switch 15 switches the connection method of the first battery pack 11 and the second battery pack 12 from parallel connection to series connection when the first battery pack 11 and the second battery pack 12 are discharging. Thereby, it is possible to supply a high-voltage current from the first battery pack 11 and the second battery pack 12 to the drive device 17 electrically connected to both of these battery packs.

[0053] Furthermore, the first charge control circuit 13 includes a first charge stop means for stopping the charging of the first battery pack 11. Also, the second charge control circuit 14 includes a second charge stop means for stopping the charging of the second battery pack 12. By adopting such a configuration, the charger for charging the transport vehicle 10 does not need to include a charge stop means. Therefore, the transport vehicle 10 can be charged using a charger that does not include a charge stop means.

[0054] In the above example, the program can be stored using various types of non-transitory computer readable media and provided to a computer. Non-transitory computer readable media include various types of tangible storage media. Examples of non-transitory computer readable media include magnetic recording media (e.g., flexible disks, magnetic tapes, hard disk drives), magneto-optical recording media (e.g., magneto-optical disks), CD-ROM, CD-R, CD-R / W, semiconductor memories (e.g., mask ROM, PROM (Programmable ROM), EPROM (Erasable PROM), flash ROM, RAM). Also, the program may be provided to a computer by various types of transitory computer readable media. Examples of transitory computer readable media include electrical signals, optical signals, and electromagnetic waves. Transitory computer readable media can supply the program to a computer via wired communication paths such as electric wires and optical fibers, or wireless communication paths.

[0055] The present disclosure is not limited to the above-described embodiments, and can be appropriately modified without departing from the spirit of the present disclosure.

Explanation of Reference Numerals

[0056] 1 Charging system 10 Transport vehicle 11 First battery pack 12 Second battery pack 13 Charging control circuit, first charging control circuit 14 Charging control circuit, second charging control circuit 15 Connection mode switching switch 16 Vehicle device 17 Driving device 18 Battery pack switching switch, first battery pack switching switch 19 Backflow prevention element 20 Backflow prevention element 21 Backflow prevention element 22 Backflow prevention element 23 Battery pack switching switch, second battery pack switching switch 24 Electric wire 30 Charger

Claims

1. A transport vehicle comprising a battery pack charged by a charger which is an external device, a first battery pack composed of a plurality of secondary batteries charged by the charger, a second battery pack composed of other plurality of secondary batteries charged by the charger, a connection method switching switch for switching the connection method of the first battery pack and the second battery pack, a first charge control circuit connected to the first battery pack, and a second charge control circuit connected to the second battery pack, When charging the first battery pack and the second battery pack, the connection method switching switch switches the connection method of the first battery pack and the second battery pack from series connection to parallel connection, The first charge control circuit makes the voltage applied to the first battery pack during charging not exceed a predetermined first upper limit voltage corresponding to the first battery pack, The second charge control circuit makes the voltage applied to the second battery pack during charging not exceed a predetermined second upper limit voltage corresponding to the second battery pack, A transport vehicle.

2. A vehicle device operated by the electric power supplied by the first battery pack and the second battery pack, and a first battery pack switching switch selectively connected to the positive electrode sides of the first battery pack and the second battery pack, for flowing the current output from one of the first battery pack and the second battery pack to the vehicle device. The transport vehicle according to claim 1.

3. comprising a second battery pack switching switch selectively connected to the negative electrode sides of the first battery pack and the second battery pack, The second battery pack switching switch allows the current output from the first battery pack through the vehicle device to flow back to the first battery pack, The second battery pack switching switch allows the current output from the second battery pack through the vehicle device to flow back to the second battery pack. The transport vehicle according to claim 2.

4. The connection method switching switch switches the connection method of the first battery pack and the second battery pack from parallel connection to series connection when the first battery pack and the second battery pack are discharging, for the transport vehicle according to claim 1 or 2.

5. The first charge control circuit includes first charge stop means for stopping the charging of the first battery pack, The second charge control circuit includes second charge stop means for stopping the charging of the second battery pack, for the transport vehicle according to claim 1 or 2.

6. The first charge control circuit, determines whether the remaining capacity of the first battery pack is less than or equal to a predetermined remaining capacity, when it is determined that the remaining capacity of the first battery pack is less than or equal to the predetermined remaining capacity, charges the first battery pack, when it is determined that the remaining capacity of the first battery pack exceeds the predetermined remaining capacity, does not charge the first battery pack, The second charge control circuit, determines whether the remaining capacity of the second battery pack is less than or equal to a predetermined remaining capacity, when it is determined that the remaining capacity of the second battery pack is less than or equal to the predetermined remaining capacity, charges the second battery pack, when it is determined that the remaining capacity of the second battery pack exceeds the predetermined remaining capacity, does not charge the second battery pack, for the transport vehicle according to claim 1 or 2.

7. A charger for charging a secondary battery at a predetermined voltage, and a transport vehicle, The transport vehicle, a first battery pack composed of a plurality of secondary batteries charged by the charger, a second battery pack composed of other plurality of secondary batteries charged by the charger, a connection method switching switch for switching the connection method of the first battery pack and the second battery pack, a first charge control circuit connected to the first battery pack, It includes a second charge control circuit connected to the second battery pack. When charging the first battery pack and the second battery pack, the connection mode switching switch switches the connection mode of the first battery pack and the second battery pack from series connection to parallel connection. During charging, the first charge control circuit makes the voltage applied to the first battery pack not exceed a predetermined first upper limit voltage corresponding to the first battery pack. During charging, the second charge control circuit makes the voltage applied to the second battery pack not exceed a predetermined second upper limit voltage corresponding to the second battery pack. Charging system.

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