Electric bicycle, battery switching device, and battery switching method

Abstract

To suppress generation of current from a drive unit to a battery when a discharge battery is switched.SOLUTION: A control device 38 sets a second current control switch 31B to an intermediate state in a process of switching a discharge battery, which supplies current to a drive unit 10, from a first battery 41A to a second battery 41B. Thereafter, when a relative relation between a potential of a smoothing capacitor 16 and a potential of a second battery 41B satisfies a condition for terminating the intermediate state, the control device 38 sets the second current control switch 31B to a bidirectional conduction state. The intermediate state is a state in which current flowing from the batteries 41A and 41B to a drive unit 10 is permitted and current flowing from the drive unit 10 to the batteries 41A and 41B is restricted. The bidirectional conduction state is a state in which current flowing from the batteries 41A and 41B to the drive unit 10 and current flowing from the drive unit 10 to the batteries 41A and 41B are both permitted.SELECTED DRAWING: Figure 6A

Description

[Technical field]

[0001] The present disclosure relates to an electric bicycle, a battery switching device, and a battery switching method. [Background technology]

[0002] Patent Document 1 discloses an electric bicycle that can be equipped with two batteries. This bicycle has a switching unit between the battery and a drive unit that includes an electric motor, for switching the battery that supplies power to the electric motor. The switching unit is composed of a field effect transistor (FET). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2004-359032 A Summary of the Invention [Problem to be solved by the invention]

[0004] The output potential of a battery (the voltage at the positive terminal) generally decreases as the remaining battery power decreases. In an electric bicycle with two batteries, when the battery supplying power to the driving unit is switched from a battery with a higher output potential to a battery with a lower output potential, the potential of the driving unit may temporarily become higher than the potential of the battery after the switch. In that case, a current is generated from the driving unit to the battery. Such a current may have a detrimental effect on the battery. [Means for solving the problem]

[0005] (1) An example of an electric bicycle proposed in this disclosure includes a first battery, a second battery, a drive unit including an electric motor, and a battery switching device disposed between the first battery, the second battery, and the drive unit. The battery switching device includes a first current control switch disposed between the first battery and the drive unit, a second current control switch disposed between the second battery and the drive unit, and a control device that controls the first current control switch and the second current control switch. Each of the first current control switch and the second current control switch has a bidirectional conduction state that allows both a current flowing from the battery to which the current control switch is connected to the drive unit and a current flowing from the drive unit to the battery, an intermediate state that allows a current flowing from the battery to which the current control switch is connected to the drive unit and restricts a current flowing from the drive unit to the battery, and a bidirectional restriction state that restricts both a current flowing from the battery to which the current control switch is connected to the drive unit and a current flowing from the drive unit to the battery. The control device sets the second current control switch to the intermediate state in the process of switching the battery supplying current to the driving unit from the first battery to the second battery, and thereafter sets the second current control switch to the bidirectional conductive state when the relative relationship between the potential of the driving unit and the potential of the second battery satisfies a predetermined condition. With this electric bicycle, it is possible to suppress the generation of current from the driving unit to the second battery.

[0006] (2) The electric bicycle of (1) may have a current detection unit for detecting a current flowing between the second battery and the drive unit. The control device may determine whether or not the relative relationship between the potential of the drive unit and the potential of the second battery satisfies the predetermined condition based on an output of the current detection unit.

[0007] (3) The electric bicycle of (1) may have a battery voltage detection unit for detecting the potential of the second battery and a drive unit voltage detection unit for detecting the potential of the drive unit. The control device may determine whether the relative relationship between the potential of the drive unit and the potential of the second battery satisfies the predetermined condition based on an output of the battery voltage detection unit and an output of the drive unit voltage detection unit.

[0008] (4) In the electric bicycle of (3), the predetermined condition may be that the difference between the electric potential of the drive unit and the electric potential of the second battery is smaller than a threshold value. This makes it possible to shorten the time required for the predetermined condition to be satisfied.

[0009] (5) In the electric bicycle described in any one of (1) to (3), the specified condition may be that the electric potential of the second battery is the same as or higher than the electric potential of the drive unit.

[0010] (6) In an electric bicycle described in any one of (1) to (5), the control device changes the first current control switch from the bidirectional conduction state to the intermediate state, and changes the second current control switch from the bidirectional restriction state to the intermediate state, in the process of switching the battery supplying current to the drive unit from the first battery to the second battery.

[0011] (7) In the electric bicycle described in any one of (1) to (6), the drive unit may have a motor drive device that supplies current to the electric motor, and a smoothing capacitor connected in parallel with the motor drive device. This makes it possible to reduce fluctuations in the current supplied to the motor drive device.

[0012] (8) The electric bicycle described in any one of (1) to (7) may have an input unit for user operation. The control device may switch the battery supplying current to the drive unit between the first battery and the second battery based on a signal input from the input unit. This makes it easy for the user to use, for example, one battery preferentially and reduce the remaining battery charge to an amount suitable for charging.

[0013] (9) In the electric bicycle described in any one of (1) to (8), each of the first current control switch and the second current control switch includes a first field effect transistor (first FET) that allows a current to flow from a battery to which the current control switch is connected to the drive unit in an on state, and a second field effect transistor (second FET) that allows a current to flow from the drive unit to the battery to which the current control switch is connected in an on state, and the first FET and the second FET may be arranged in series such that the forward directions of their body diodes are opposite to each other. This allows the intermediate state to be realized by utilizing the body diodes of the FETs, thereby reducing the number of parts.

[0014] (10) A battery switching device proposed in the present disclosure includes a first current control switch disposed between a first battery and the drive unit, a second current control switch disposed between a second battery and the drive unit, and a control device that controls the first current control switch and the second current control switch. Each of the first current control switch and the second current control switch has a bidirectional conduction state that allows both a current flowing from the battery to which the current control switch is connected to the drive unit and a current flowing from the drive unit to the battery, an intermediate state that allows a current flowing from the battery to which the current control switch is connected to the drive unit and restricts a current flowing from the drive unit to the battery, and a bidirectional restriction state that restricts both a current flowing from the battery to which the current control switch is connected to the drive unit and a current flowing from the drive unit to the battery. When the battery supplying current to the drive unit is switched from the first battery to the second battery, the control device sets the second current control switch to the intermediate state, and thereafter sets the second current control switch to the bidirectional conductive state when the relative relationship between the potential of the drive unit and the potential of the second battery satisfies a predetermined condition. This battery switching device can suppress the generation of current from the drive unit to the second battery.

[0015] (11) In the battery switching method proposed in the present disclosure, the second current control switch transitions from a bidirectional restrictive state in which both the current flowing from the second battery to the drive unit and the current flowing from the drive unit to the second battery are restricted to an intermediate state in which the current flowing from the second battery to the drive unit is permitted and the current flowing from the drive unit to the second battery is restricted. Then, when the relative relationship between the potential of the drive unit and the potential of the second battery satisfies a predetermined condition, the second current control switch transitions from the intermediate state to a bidirectional conductive state in which both the current flowing from the second battery to the drive unit and the current flowing from the drive unit to the second battery are permitted.

[0016] The electric bicycle proposed in this disclosure may be a bicycle that runs by combining the force applied by the rider to the pedals and the force output from the electric motor, or it may be a bicycle that can run solely on the force applied by the rider to the pedals or solely on the force output from the electric motor, depending on the rider's choice. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a left side view showing an example of an electric bicycle proposed in the present disclosure. [Diagram 2] FIG. 2 is a block diagram showing hardware of the electric bicycle. [Diagram 3] FIG. 2 is a diagram showing a current control switch included in the battery switching device. [Figure 4] 3 is a block diagram showing functions of a control device included in the battery switching device; FIG. [Diagram 5] FIG. 4 is a flow diagram showing an example of processing executed by a control device (switching execution unit). [Figure 6A] 4 is a diagram for explaining a process of switching a battery (discharging battery) that supplies current to a drive unit from a first battery to a second battery. FIG. [Figure 6B] FIG. 4 is a diagram for explaining a process of switching a discharging battery from a first battery to a second battery. [Figure 6C] FIG. 4 is a diagram for explaining a process of switching a discharging battery from a first battery to a second battery. [Figure 6D] FIG. 4 is a diagram for explaining a process of switching a discharging battery from a first battery to a second battery. [Figure 6E] FIG. 4 is a diagram for explaining a process of switching a discharging battery from a first battery to a second battery. [Figure 7A] FIG. 13 is a diagram illustrating another example of a battery switching device. [Figure 7B] FIG. 13 illustrates yet another example of a battery switching device. [Figure 8] FIG. 11 is a diagram illustrating another example of the process executed by the control device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] An example of an electric bicycle proposed in this disclosure will be described below. Fig. 1 is a left side view of an electric bicycle 1, which is an example of an electric bicycle proposed in this disclosure. Fig. 2 is a block diagram showing the hardware of the electric bicycle 1.

[0019] As shown in FIG. 1, the electric bicycle 1 has a front wheel 2, a front fork 5 supporting the front wheel 2, a handlebar 6 fixed to the upper part of the front fork 5, a body frame 5 having a saddle 4 and a saddle post 5a supporting the saddle 4, and a rear wheel 7.

[0020] [Drive unit] The electric bicycle 1 has a drive unit 10 including an electric motor 12 (see FIG. 2) and a reduction mechanism that reduces the speed of rotation from the electric motor 12 and outputs the reduced speed. The drive unit 10 is disposed, for example, below the saddle post 5a. The position of the drive unit 10 is not limited to the example shown in the figure. The drive unit 10 is provided with a crankshaft. A crank arm 19 is connected to the crankshaft. A pedal 13 is attached to the tip of the crank arm 19. The drive unit 10 combines a force (pedal force) applied to the pedal 13 and a force output by the electric motor 12. For example, the force (pedal force) applied to the pedal 13 and the force output by the electric motor 12 are input to a rotating shaft that constitutes the reduction mechanism, thereby combining the two forces. The output (rotation) of the drive unit 10 is transmitted to the rear wheel 7 via a transmission member such as a chain, a belt, or a shaft.

[0021] 2, the drive unit 10 has, in addition to the electric motor 12 described above, a motor drive device 15 and a smoothing capacitor 16. The electric bicycle 1 also has a plurality of batteries 41A-41B, a battery switching device 30, and a motor control device 20. The battery switching device 30 is disposed between the plurality of batteries 41A-41B and the motor drive device 15, and the current of the batteries 41A-41B is supplied to the motor drive device 15 through the battery switching device 30.

[0022] The batteries 41A and 41B store power to be supplied to the electric motor 12. The batteries 41A and 41B may be, for example, lithium ion batteries or nickel-metal hydride batteries. The number of batteries 41A and 41B is, for example, two as shown in the figure, but may be three or more. In the following description, when it is necessary to distinguish between the two batteries 41A and 41B, the battery 41A will be referred to as the "first battery" and the battery 41B will be referred to as the "second battery."

[0023] The batteries 41A and 41B may be separately detachable from the electric bicycle 1. In other words, while the first battery 41A is mounted on the electric bicycle 1, only the second battery 41B may be removed from the electric bicycle 1, or conversely, while the second battery 41B is mounted on the electric bicycle 1, only the first battery 41A may be removed from the electric bicycle 1. The batteries 41A and 41B may be chargeable via a charger when removed from the electric bicycle 1.

[0024] 1, the second battery 41B is disposed along the rear side of the saddle post 5a, and the first battery 41A is disposed in front of the saddle post 5a. At the positions where the batteries 41A, 41B are disposed, receptacles to which the batteries 41A, 41B are detachable and having terminals for establishing electrical connection with the batteries 41A, 41B may be disposed. The arrangement of the batteries 41A, 41B is not limited to the example shown in FIG. 1, and may be changed as appropriate.

[0025] Each of the batteries 41A and 41B may have a temperature detector for monitoring the temperature of the battery cells therein, a voltage detector for detecting the voltage of the battery cells, a current detector for detecting the charging and discharging current, and a control device (not shown) for monitoring the temperature, voltage, current, and remaining battery capacity based on the outputs of these devices. The batteries 41A and 41B may have a communication module for communicating with the battery switching device 30.

[0026] Motor drive device 15 supplies to electric motor 12 a current corresponding to a command value input from motor control device 20. Motor drive device 15 includes, for example, an inverter circuit, and converts DC current supplied from batteries 41A and 41B into AC current and supplies it to electric motor 12.

[0027] Smoothing capacitor 16 is connected in parallel with motor drive device 15. When current is supplied to motor drive device 15 from batteries 41A and 41B via battery switching device 30, charge is stored in smoothing capacitor 16. Smoothing capacitor 16 reduces fluctuations in the current supplied to motor drive device 15.

[0028] The motor control device 20 includes a storage device such as a RAM (Random Access Memory) or a ROM (Read Only Memory), and a calculation device such as a CPU (Central Processing Unit). The motor control device 20 controls the electric motor 12 by executing a program stored in the storage device in the calculation device. Specifically, the motor control device 20 calculates a command value according to the speed of the electric bicycle 1 and the force (pedal force) applied to the pedal 13, and outputs this command value to the motor drive device 15. A vehicle speed sensor 29 and a pedal force sensor 28 may be connected to the motor control device 20. The motor control device 20 may be configured with an FPGA (Field-Programmable Gate Array).

[0029] [Battery switching device] As shown in FIG. 2, the battery switching device 30 has power lines P1 and P2 that connect the batteries 41A and 41B to the motor drive device 15. The power lines P1 and P2 are respectively connected to two receptacles (not shown) to which the two batteries 41A and 41B are detachably attached. The receptacles may be provided with terminals for the power lines P1 and P2 and a terminal for a communication line (not shown). The battery switching device 30 also has a connection point Px to which the power lines P1 and P2 are connected. The battery switching device 30 may have a connector for electrically connecting to the drive unit 10. The connector may be provided with a terminal common to the two power lines P1 and P2 that is connected to the connection point Px.

[0030] The battery switching device 30 switches the battery that discharges to the drive unit 10 between the batteries 41A and 41B according to an instruction from a user (passenger) and the driving environment. Hereinafter, the battery that is in a state to discharge to the drive unit 10 is referred to as the "discharging battery."

[0031] 2, the battery switching device 30 includes current control switches 31A and 31B, switch drive circuits 32A and 32B, and a control device 38. The battery switching device 30 may also include voltage detection units 34A, 34B, and 34C, an indicator 35, a communication unit 36, and an input unit 37.

[0032] The first current control switch 31A is located between the first battery 41A and the drive unit 10, and is connected in series with the first battery 41A. The first current control switch 31A controls the current flowing between the first battery 41A and the drive unit 10 in response to a command from the control device 38. Similarly, the second current control switch 31B is located between the second battery 41B and the drive unit 10, and is connected in series with the second battery 41B. The second current control switch 31B controls the current flowing between the second battery 41B and the drive unit 10 in response to a command from the control device 38.

[0033] FIG. 3 is a diagram showing the configuration of the current control switches 31A and 31B. As shown in the figure, the first current control switch 31A has, for example, a first field effect transistor (first FET) 33A and a second field effect transistor (second FET) 33B. In the first current control switch 31A, the two FETs 33A and 33B are connected in series, and the forward directions of their body diodes 33a and 33b are opposite to each other. In the example shown in the figure, the drain of the first FET 33A is connected to the drain of the second FET 33B. Alternatively, the source of the first FET 33A may be connected to the source of the second FET 33B. Similarly, the second current control switch 31B has a first FET 33C and a second FET 33D. In the second current control switch 31B, the two FETs 33C and 33D are connected in series, and the forward directions of their body diodes 33a and 33b are opposite to each other. In the example shown in the figure, the FETs 33A to 33D are N-channel FETs, but they may also be P-channel FETs.

[0034] The switch drive circuit 32A (see FIG. 2) controls the gate voltages of the FETs 33A and 33B connected to the first battery 41A in accordance with a signal input from the control device 38. Similarly, the switch drive circuit 32B controls the gate voltages of the FETs 33C and 33D connected to the battery 41B in accordance with a signal input from the control device 38.

[0035] The control device 38 includes a storage device such as a RAM or a ROM, and an arithmetic device such as a CPU. The motor control device 20 controls the current control switches 31A and 31B by executing a program stored in the storage device in the arithmetic device. The processing executed by the control device 38 will be described in detail later. The control device 38 may be configured with an FPGA.

[0036] The indicator 35 may include, for example, a plurality of light-emitting elements (for example, LEDs). The control device 38 controls the indicator 35 to indicate the status of the batteries 41A and 41B. For example, the control device 38 may use the indicator 35 to indicate the battery (discharging battery) supplying current to the drive unit 10, or to indicate the operating status of the batteries 41A and 41B. The operating status of the batteries 41A and 41B may be, for example, the remaining charge, voltage, or temperature abnormality of the batteries 41A and 41B.

[0037] The communication unit 36 ​​may be a communication module for communicating with control devices built into the batteries 41A and 41B. The control device 38 of the battery switching device 30 may receive information on the batteries 41A and 41B, such as the voltages (positive electrode potentials) of the batteries 41A and 41B, the temperatures of the battery cells, the discharge current, and the remaining battery capacity, from the batteries 41A and 41B via the communication unit 36.

[0038] Furthermore, the communication unit may include a communication module capable of communicating with the motor control device 20. The control device may transmit information about the batteries 41A and 41B to the motor control device 20 through the communication unit .

[0039] In this way, the battery switching device 30 may relay transmission and reception of information about the batteries 41A, 41B between the batteries 41A, 41B and the motor control device 20. The battery switching device 30 may be connected to the motor drive device 15 via a terminal (a terminal on the drive unit 10 side of the connection point Px) common to the two power lines P1, P2. In this way, the battery switching device 30 can operate as an adapter device that causes the multiple batteries 41A, 41B to function as if they were a single battery. The battery switching device 30 may be housed in a housing separate from the batteries 41A, 41B and the drive unit 10.

[0040] The input unit 37 shown in FIG. 2 is, for example, a switch that can be manually operated by the user. The user may be able to input a battery switching instruction through the input unit 37. That is, when the first battery 41A is used as a discharging battery, the user may be able to instruct the control device 38 to switch to the battery 41B by operating the input unit 37. Conversely, when the second battery 41B is used as a discharging battery, the user may be able to instruct the control device 38 to switch to the battery 41A by operating the input unit 37. The electric bicycle 1 may be capable of mounting three or more batteries. In this case, the user may be able to select the discharging battery from among these three or more batteries by operating the input unit 37. That is, the input unit 37 may be able to input a battery selection instruction to the control device 38.

[0041] The voltage detection unit 34A is a circuit that outputs a signal corresponding to the output voltage (e.g., the potential of the positive terminal) of the first battery 41A. The voltage detection unit 34B is a circuit that outputs a signal corresponding to the output voltage (e.g., the potential of the positive terminal) of the second battery 41B. The voltage detection unit 34C is a circuit that outputs a signal corresponding to the potential of the drive unit 10 (the potential of the positive terminal of the drive unit 10, or the positive potential of the smoothing capacitor 16 in this embodiment).

[0042] The battery switching device 30 may have voltage detection units 34A, 34B, and 34C in a housing that accommodates the power lines P1 and P2, the control device 38, etc. This can reduce the time required for the control device 38 to obtain information on the potential.

[0043] Unlike the example shown in the figure, the voltage detection units 34A and 34B may be mounted on the batteries 41A and 41B, instead of on the battery switching device 30. In this case, the control device 38 may receive information on the output voltages of the batteries 41A and 41B from the batteries 41A and 41B via the communication unit 36. Similarly, the voltage detection unit 34C may be provided in the drive unit 10, and the control device 38 may receive information on the potential of the drive unit 10 (the potential of the positive terminal of the smoothing capacitor 16) from the drive unit 10 (or the motor control device 20) via the communication unit 36.

[0044] [Battery switching device control device] Fig. 4 is a block diagram showing functions of the control device 38. As shown in the figure, the control device 38 has, as its functions, a switching timing detection unit 38a and a switching execution unit 38c.

[0045] [Switching timing detection section] The switching timing detector 38a detects the timing for switching the discharging battery (the battery that supplies current to the drive unit 10) from one of the plurality of batteries 41A and 41B to another one.

[0046] The switching timing detection unit 38a may detect the timing to switch the discharge battery based on, for example, a signal (battery switching instruction) input from the input unit 37. The user may be allowed to switch the discharge battery at any timing. For example, when the remaining charge of the current discharge battery becomes low, the user may be able to switch the discharge battery to a battery with a large remaining charge through the input unit 37. Conversely, the user may be able to switch the discharge battery from a battery with a large remaining charge to a battery with a small remaining charge. In addition, the above-mentioned communication unit 36 ​​may be capable of communicating with a mobile terminal owned by the user. In this case, the control device 38 may receive a battery switching instruction from the mobile terminal.

[0047] Furthermore, the switching timing detection unit 38a may detect the timing to switch the discharging battery based on information on the batteries 41A and 41B received from the communication unit 36. For example, when the remaining battery charge falls below a threshold value or when the temperature of the battery cell becomes abnormal, the switching timing detection unit 38a may determine that the time has come to switch the discharging battery.

[0048] [Switching Execution Section] When the switching timing detector 38a detects the timing to switch the discharge battery, the switching execution unit 38c operates the current control switches 31A and 31B to switch the discharge battery from one of the batteries 41A and 41B to another one. Each of the current control switches 31A and 31B has a bidirectional conduction state, an intermediate state, and a bidirectional restriction state. In the process of switching the discharge battery, the switching execution unit 38c transitions the state of the current control switches 31A and 31B to these three states in order.

[0049] In a bidirectional conduction state, the first current control switch 31A allows both a current flowing from the first battery 41A to the drive unit 10 and a current flowing from the drive unit 10 to the first battery 41A. For example, as shown in Fig. 6A, when two FETs 33A and 33B are both in the on state, the bidirectional conduction state is realized. Similarly, the bidirectional conduction state of the second current control switch 31B is realized, for example, when two FETs 33C and 33D are both in the on state.

[0050] In the bidirectional regulation state, the first current control switch 31A regulates both the current flowing from the first battery 41A to the drive unit 10 and the current flowing from the drive unit 10 to the first battery 41A. For example, as shown in Figures 6D and 6E, the bidirectional regulation state is realized when both of the two FETs 33A and 33B are in the off state. Similarly, the bidirectional regulation state of the second current control switch 31B is realized, for example, when both of the two FETs 33C and 33D are in the off state.

[0051] In the intermediate state, the first current control switch 31A allows a current (discharge) flowing from the first battery 41A to the drive unit 10 and regulates a current (charge) flowing from the drive unit 10 to the first battery 41A. For example, as shown in FIG. 6B, this intermediate state is realized when the first FET 33A, whose forward direction of the body diode 33a is the direction from the battery 41A to the drive unit, is turned off and the second FET 33B, whose forward direction of the body diode 33b is the direction from the drive unit 10 to the battery 41A, is turned on. In this state, the current from the first battery 41A to the drive unit 10 flows through the body diode 33a in the first FET 33A and flows through the channel in the second FET 33B. The intermediate state is also realized for the current control switch 31B when the first FET 33C is turned off and the second FET 33D is turned on.

[0052] In the process of switching the discharging battery, the potential of the drive unit 10 side may temporarily become higher than that of the batteries 41A and 41B. In the example shown in the figure, this may be the cause of the smoothing capacitor 16 of the drive unit 10. The output voltage of a battery generally decreases when the remaining battery charge becomes low. The smoothing capacitor 16 stores a charge according to the output voltage of the current discharging battery (the discharging battery before switching). When the discharging battery is switched from a battery with a higher potential to a battery with a lower potential, the potential of the smoothing capacitor 16 temporarily becomes higher than that of the discharging battery (the battery after switching). In this state, if the current control switch connected to this discharging battery is in a bidirectional conductive state, a current flows from the drive unit 10 to the discharging battery. This may have an adverse effect on the batteries 41A and 41B. For example, it may have an adverse effect on the life and discharge performance of the batteries 41A and 41B.

[0053] Furthermore, in the electric bicycle 1, the user can switch the discharging battery from a battery with a large remaining battery power (e.g., the first battery 41A) to a battery with a small remaining battery power (e.g., the second battery 41B) by operating the input unit 37. By such switching, the user can preferentially use the battery with a small remaining battery power (e.g., the battery 41B) and reduce the remaining battery power to an amount suitable for charging. When such switching is performed, the discharging battery is switched from the battery with a high potential (battery 41B in the above example) to the battery with a low potential (battery 41A in the above example). As a result, the potential of the smoothing capacitor 16 becomes temporarily higher than that of the discharging battery (the battery after switching, battery 41A in the above example).

[0054] Therefore, the switching execution unit 38c temporarily sets the second current control switch 31B to an intermediate state (FIG. 6C) during the process of switching the discharging battery from the first battery 41A to the second battery 41B. Thereafter, when the relative relationship between the potential of the drive unit 10 and the potential of the second battery 41B (the battery after switching) satisfies a predetermined condition, the switching execution unit 38c sets the second current control switch 31B to a bidirectional conductive state. This makes it possible to prevent current from flowing from the potential of the drive unit 10 to the second battery 41B. The switching execution unit 38c also performs a similar process when switching the discharging battery from the second battery 41B to the first battery 41A. Hereinafter, this predetermined condition will be referred to as an "intermediate state ending condition."

[0055] The "potential of the drive unit 10" is, for example, the potential of the positive terminal of the connector that connects the drive unit 10 and the battery switching device 30. In the example shown in the figure, the drive unit 10 has a smoothing capacitor 16. The potential of the positive terminal of the drive unit 10 may be the potential of the positive terminal of the smoothing capacitor 16. The "potential of the second battery 41B" is, for example, the potential of the positive terminal of the connector (receptacle) that connects the second battery 41B and the battery switching device 30. The "potential of the first battery 41A" is, for example, the potential of the positive terminal of the connector (receptacle) that connects the first battery 41A and the battery switching device 30. The "relative relationship between the potential of the drive unit 10 and the potential of the second battery 41B" is the relative relationship between the levels of these two potentials or the difference between them.

[0056] 2, the battery switching device 30 has voltage detection units 34A, 34B, and 34C. The switching execution unit 38c detects the potential (Vb) of the batteries 41A and 41B based on the output signals of the voltage detection units 34A and 34B, and detects the potential (Vd) of the smoothing capacitor 16 based on the output signal of the voltage detection unit 34C. In the process of switching the discharging battery from the first battery 41A to the second battery 41B, the switching execution unit 38c determines that the above-mentioned intermediate state ending condition is satisfied, for example, when the potential (Vb) of the second battery 41B becomes the same as or higher than the potential (Vd) of the smoothing capacitor 16. In the process of switching the discharging battery from the second battery 41B to the first battery 41A, the switching execution unit 38c determines that the above-mentioned intermediate state termination condition is met when the potential (Vb) of the first battery 41A becomes the same as or higher than the potential (Vd) of the smoothing capacitor 16.

[0057] The switching execution unit 38c may determine whether a state in which the potential (Vb) of the batteries 41A and 41B is equal to or higher than the potential (Vd) of the smoothing capacitor 16 continues for a predetermined time. Then, when this state continues for the predetermined time or more, the switching execution unit 38c may determine that the above-mentioned intermediate state ending condition is satisfied.

[0058] The intermediate state end condition does not necessarily have to be "the battery potential (Vb) after switching is the same as or higher than the potential (Vd) of the smoothing capacitor 16", i.e., "the difference (Vb-Vd) between the battery potential (Vb) after switching and the potential (Vd) of the drive unit 10 is 0 or more (Vb-Vd≧0)". For example, the intermediate state end condition may be "the difference (Vb-Vd) between the battery potential (Vb) after switching and the potential (Vd) of the smoothing capacitor 16 is greater than a negative threshold (Vb-Vd>Vth, Vth<0)". This allows the intermediate state end condition to be met early.

[0059] Here, the threshold value Vth may be set based on the backflow current (current flowing into the positive electrodes of the batteries 41A and 41B) tolerated by the batteries 41A and 41B. The threshold value Vth may also be set based on the backflow current (Ia) tolerated by the batteries 41A and 41B and the resistance. For example, Vth=-(R1+R2+R3)×Ia (Ia>0) Here, R 1 is the internal resistance of the batteries 41 A and 41 B, R 2 is the resistance of the power lines connecting the batteries 41 A and 41 B and the drive unit 10 , and R 3 is the internal resistance of the smoothing capacitor 16 .

[0060] Furthermore, the threshold value Vth may be set in consideration of the current flowing from the smoothing capacitor 16 to the motor drive device 15. In this case, the threshold value Vth may be smaller than "(R1+R2+R3)×Ia".

[0061] In addition, when making the determination, the switching execution unit 38c does not need to detect the potential of the smoothing capacitor 16 or the potential of the battery (battery 41A or 41B) after switching. For example, it may be determined whether or not the relative relationship between the potential of the smoothing capacitor 16 and the potential of the battery after switching satisfies the intermediate state ending condition based on the current of the power lines P1·P2. In other words, as long as the switching execution unit 38c can detect a state in which the potential (Vb) of the battery after switching is the same as or higher than the potential (Vd) of the smoothing capacitor 16 based on the current flow, it does not necessarily need to directly detect the potential (Vb·Vd). This process will be described in detail later.

[0062] [Processing flow] Fig. 5 is a flow diagram showing an example of a process executed by the switching execution unit 38c. In the following, with reference to Fig. 5 and Fig. 6A to Fig. 6E, an example of a process executed in the process of switching the discharging battery from the first battery 41A to the second battery 41B will be described.

[0063] When the first battery 41A is selected as the discharge battery (i.e., before the battery switching process begins), the first FET 33A and the second FET 33B of the first current control switch 31A are both in the ON state (bidirectional conduction state), while the first FET 33C and the second FET 33D of the second current control switch 31B are in the OFF state (bidirectional regulation state), as shown in FIG 6A.

[0064] When the switching timing detection unit 38a detects the timing to switch the discharging battery from the first battery 41A to the second battery 41B, the switching execution unit 38c switches the first FET 33A of the first current control switch 31A to the OFF state (S101), as shown in Fig. 6B. Also, the switching execution unit 38c maintains the second FET 33B of the first current control switch 31A in the ON state. That is, the first current control switch 31A transitions from the bidirectional conductive state to the intermediate state.

[0065] As described above, in the first FET 33A, the forward direction of the body diode 33a is the discharge direction of the battery 41A. In the second FET 33B, the forward direction of the body diode 33a is opposite to that of the first FET 33A. Therefore, in the intermediate state of Fig. 6B, the current from the first battery 41A flows through the body diode 33a of the first FET 33A and the channel of the second FET 33B.

[0066] 6C, the switching execution unit 38c switches the second FET 33D of the second current control switch 31B to the ON state (S102). At this time, the switching execution unit 38c maintains the first FET 33A of the second current control switch 31B in the OFF state. That is, the second current control switch 31B transitions from the bidirectional restriction state to the intermediate state.

[0067] In the second FET 33D, the forward direction of the body diode 33a is the charging direction of the second battery 41B. On the other hand, in the first FET 33C, the forward direction of the body diode 33a is the discharging direction of the second battery 41B. Therefore, in the intermediate state of FIG. 6C, the current from the second battery 41B flows through the body diode 33a of the first FET 33C and the channel of the second FET 33D. Note that, in the state shown in FIG. 6C, when the potential of the first battery 41A is higher than the potential of the second battery 41B, the current supply from the first battery 41A to the drive unit 10 continues. On the other hand, when the potential of the second battery 41B is higher than the potential of the first battery 41A, the current supply from the second battery 41B to the drive unit 10 starts.

[0068] 6D, the switching execution unit 38c switches the second FET 33B of the first current control switch 31A to the OFF state (S103). Also, the switching execution unit 38c maintains the first FET 33A of the first current control switch 31A in the OFF state. That is, the first current control switch 31A transitions from the intermediate state to the bidirectional regulation state. Meanwhile, the second current control switch 31B is maintained in the intermediate state.

[0069] In this way, since the second current control switch 31B is set to the intermediate state before the first current control switch 31A is set to the bidirectional restricting state, it is possible to prevent interruption of the current supply to the drive unit 10. Unlike the example shown in Fig. 5, the switching execution unit 38c may perform the process of S101 and the process of S102 simultaneously, or may perform the process of S102 before the process of S101. Even in this case, it is possible to prevent interruption of the current supply to the drive unit 10.

[0070] Next, the switching execution unit 38c judges whether or not the relative relationship between the potential of the smoothing capacitor 16 and the potential of the second battery 41B (the battery after switching) satisfies the intermediate state ending condition (S104). Specifically, the switching execution unit 38c judges whether or not the potential (Vb) of the second battery 41B is the same as or higher than the potential (Vd) of the smoothing capacitor 16. The switching execution unit 38c may also judge whether or not the difference (Vb-Vd) between the potential (Vd) of the smoothing capacitor 16 and the potential (Vb) of the second battery 41B is greater than a negative threshold (Vth). The switching execution unit 38c repeats the process of S104 until the intermediate state ending condition is satisfied.

[0071] 6D, when the potential (Vd) of the smoothing capacitor 16 is higher than the potential (Vb) of the second battery 41B, a current is supplied from the smoothing capacitor 16 to the motor drive device 15, and the potential of the smoothing capacitor 16 gradually decreases. Then, when the potential of the smoothing capacitor 16 becomes equal to the potential of the second battery 41B, current supply from the second battery 41B to the drive unit 10 starts.

[0072] When the intermediate state ending condition is satisfied in S104, the switching execution unit 38c switches the first FET 33A of the second current control switch 31B to the on state (S105), as shown in Fig. 6E. This causes the second current control switch 31B to transition from the intermediate state to the bidirectional conductive state, and the switching process of the discharging battery is completed.

[0073] 5 and 6A to 6E, the process executed in the process of switching the discharging battery from the first battery 41A to the second battery 41B has been described as an example. However, the same process may be executed in the process of switching the discharging battery from the second battery 41B to the first battery 41A. In this case, the above-mentioned process may be interpreted with "first" and "second" reversed.

[0074] If the intermediate state end condition is not satisfied within a predetermined time, the switching execution unit 38c may end the switching process of the discharging battery midway and return the current control switches 31A and 31B to the state before the switching process started (the state of FIG. 6A in the example of FIGS. 6A to 6E). For example, if a battery switching instruction is input to the control device 38 via the input unit 37 while the electric bicycle 1 is stopped, it takes a long time to discharge the smoothing capacitor 16. In such a case, there is a possibility that the intermediate state end condition is not satisfied within the predetermined time. In this case, the switching execution unit 38c may end the switching process of the discharging battery in S104 and return the current control switches 31A and 31B to the state before the switching process started.

[0075] [Other examples] The present disclosure is not limited to the electric bicycle 1 and battery switching device 30 described above.

[0076] Figures 7A and 7B are block diagrams showing another example of a battery switching device proposed in the present disclosure. Figure 7A shows a battery switching device 130 as another example, and Figure 7B shows a battery switching device 230 as another example. In Figures 7A and 7B, the same reference numerals are used to designate the same parts as the battery switching device 30 described above.

[0077] 7A, battery switching device 130 will be described, focusing on the differences from battery switching device 30. Items not described regarding battery switching device 130 may be the same as battery switching device 30.

[0078] As shown in FIG. 7, the battery switching device 130 has a current detection unit 134 instead of the voltage detection units 34A, 34B, and 34C. The current detection unit 134 is a circuit that outputs a signal corresponding to the current supplied from the batteries 41A and 41B to the drive unit 10. The current detection unit 134 is disposed between the positive electrodes of the batteries 41A and 41B and the positive electrode of the smoothing capacitor 16. The current detection unit 134 may be disposed closer to the smoothing capacitor 16 than the connection point Px between the power lines P1 and P2. The current detection unit 134 outputs a signal corresponding to the current value in both cases where a current flows from the battery 41A to the drive unit 10 and where a current flows from the battery 41B to the drive unit 10.

[0079] The above-mentioned intermediate state end condition is, for example, "the potential of the battery after switching is equal to or higher than the potential of the smoothing capacitor 16." In the state shown in FIG. 6D, the battery after switching supplies current to the drive unit 10 only when the potential of the second battery 41B (the battery after switching) becomes equal to or higher than the potential of the smoothing capacitor 16. Therefore, the switching execution unit 38c may determine whether the intermediate state end condition is satisfied based on the output signal of the current detection unit 134. Then, when the second battery 41B starts supplying current to the drive unit 10, the switching execution unit 38c determines that the above-mentioned intermediate state end condition is satisfied ("Yes" in S104 of FIG. 5), and transitions the second current control switch 31B from the intermediate state to the bidirectional restriction state (S105 of FIG. 6).

[0080] 7B, battery switching device 230 will be described, focusing on the differences from battery switching device 30. Items not described about battery switching device 230 may be the same as battery switching devices 30 / 130.

[0081] The battery switching device 230 has a current detection unit 234. The current detection unit 234 is disposed between the negative electrodes of the batteries 41A and 41B and the ground. In the example shown in the figure, the negative electrodes of the batteries 41A and 41B and the negative electrode of the smoothing capacitor 16 are connected to a common ground. Therefore, similar to the current detection unit 134 shown in FIG. 7A, the current detection unit 234 can output a signal according to the current in both cases where a current flows from the first battery 41A to the drive unit 10 and where a current flows from the second battery 41B to the drive unit 10.

[0082] The switching execution unit 38c determines whether the intermediate state end condition is satisfied based on the output of the current detection unit 234. The switching execution unit 38c determines that the intermediate state end condition is satisfied when it detects a current returning from the ground to the negative pole of the batteries 41A and 41B. In other words, the switching execution unit 38c determines that the potential of the positive pole of the second battery 41B (the battery after switching) has become higher than the potential of the positive pole of the smoothing capacitor 16.

[0083] The problem of current flowing from the smoothing capacitor 16 to the batteries 41A and 41B when switching the discharge battery is less likely to occur when switching from a low-potential battery to a high-potential battery. Therefore, the control device of the battery switching device may change the procedure for switching the discharge battery depending on the switching mode of the discharge battery. This process can shorten the time required to switch the discharge battery and reduce heat generation by the body diodes 33a of the first FETs 33A and 33C of the high-potential battery.

[0084] 8 is a block diagram showing the functions of an example of a control device that executes such processing. This control device 338 has a switching execution unit 338c and a switching mode determination unit 338e in addition to the above-mentioned switching timing detection unit 38a.

[0085] When the switching timing detection unit 33a detects the switching timing of the discharging battery, the switching mode determination unit 338e determines whether the switching of the discharging battery to be performed is switching from a high potential battery to a low potential battery, or switching from a low potential battery to a high potential battery.

[0086] The switching execution unit 133e may have two modes as a switching procedure of the discharge battery. The first switching mode is the switching process described with reference to Fig. 5. That is, in the first switching mode, the discharge battery after switching (the second battery 41B in the example of Fig. 5 and Figs. 6A to 6E) is set to an intermediate state, and after the intermediate state ending condition is established in S104, the discharge battery after switching is set to a bidirectional conductive state (S105).

[0087] On the other hand, the second switching mode is a mode in which the discharge battery is switched without going through the judgment process of S104. That is, the switching execution unit 338c sets both the discharge battery before switching and the discharge battery after switching to an intermediate state (S101-S102), and then turns off the second FET (second FET 33B in FIG. 5) of the current control switch connected to the discharge battery before switching (first battery 41A in the example of FIG. 5) (S103), and turns on the first FET (first FET 33C in FIG. 5) of the current control switch connected to the discharge battery after switching (second battery 41B in the example of FIG. 5) (S105). In the second switching mode, S104 is not executed.

[0088] The switching execution unit 338c executes the first switching mode when the discharging battery is switched from a high potential battery to a low potential battery, whereas the switching execution unit 338c executes the second switching mode when the discharging battery is switched from a low potential battery to a high potential battery.

[0089] [summary] (1) In the electric bicycle 1, each of the current control switches 31A and 31B has a bidirectional conductive state that allows both a current to flow from the batteries 41A and 41B to which the current control switch 31A and 31B are connected to the drive unit 10 and a current to flow from the drive unit 10 to the batteries 41A and 41B (the state of the first current control switch 31A in FIG. 6A and the state of the second current control switch 31B in FIG. 6E). Each of the current control switches 31A and 31B has an intermediate state that allows a current to flow from the batteries 41A and 41B to which the current control switch 31A and 31B are connected to the drive unit 10 and restricts a current to flow from the drive unit 10 to the batteries 41A and 41B (the states of the first current control switch 31A and the second current control switch 31B in FIG. 6C). Each of the current control switches 31A and 31B has a bidirectional regulation state that regulates both the current flowing from the batteries 41A and 41B to the drive unit 10 and the current flowing from the drive unit 10 to the batteries 41A and 41B (the state of the first current control switch 31A in FIG. 6E, and the state of the second current control switch 31B in FIG. 6A). The control device 38 sets the second current control switch 31B to an intermediate state in the process of switching the discharge battery that supplies current to the drive unit 10 from the first battery 41A to the second battery 41B. Thereafter, when the relative relationship between the potential of the drive unit 10 (specifically, the potential of the smoothing capacitor 16) and the potential of the second battery 41B satisfies an intermediate state ending condition, the control device 38 sets the second current control switch 31B to a bidirectional conductive state. With this electric bicycle 1, it is possible to suppress the generation of a current from the drive unit 10 to the second battery 41B when switching the discharge battery.

[0090] (2) In the example shown in Figures 7A and 7B, the electric bicycle 1 has current detection units 134 / 234 for detecting the current flowing between the second battery 41B and the driving unit 10. Based on the output of the current detection units 134 / 234, the control device 38 determines whether the relative relationship between the potential of the driving unit 10 and the potential of the second battery 41B satisfies the intermediate state ending condition.

[0091] (3) In the example shown in Fig. 2, the electric bicycle 1 has a voltage detection unit 34B for detecting the potential of the second battery 41B, and a voltage detection unit 34C for detecting the potential of the drive unit 10. The control device 38 determines whether the relative relationship between the potential of the drive unit 10 and the potential of the second battery 41B satisfies the intermediate state ending condition, based on the output of the voltage detection unit 34B and the output of the voltage detection unit 34C.

[0092] (4) The intermediate state end condition is, for example, that the difference between the potential of the drive unit 10 and the potential of the second battery 41B is smaller than a threshold value (Vth). This makes it possible to shorten the time required for the intermediate state end condition to be satisfied.

[0093] (5) The intermediate state ending condition is that the potential of the second battery 41B is higher than the potential of the drive unit 10, for example.

[0094] (6) In the process of switching the discharge battery supplying current to the drive unit 10 from the first battery 41A to the second battery 41B, the control device 38 changes the first current control switch 31A from the bidirectional conductive state to the intermediate state and changes the second current control switch 31B from the bidirectional restricted state to the intermediate state. This makes it possible to prevent the current supply to the drive unit 10 from being interrupted.

[0095] (7) The drive unit 10 may include a smoothing capacitor 16 connected in parallel to the motor drive device 15. This can reduce fluctuations in the current supplied to the motor drive device 15.

[0096] (8) The battery switching device 30 has an input unit 37 for user operation. The control device 38 may switch the discharging battery supplying current to the drive unit 10 between the first battery 41A and the second battery 41B based on a signal input from the input unit 37. This makes it easy for the user to preferentially use one battery, for example, and reduce the remaining battery charge to an amount suitable for charging.

[0097] (9) Each of the current control switches 31A and 31B includes a first FET 33A or 33C that, in an on state, allows a current to flow from the drive unit 10 to the batteries 41A or 41B to which the current control switch 31A or 31B is connected, and a second FET 33B or 33D that, in an on state, allows a current to flow from the batteries 41A or 41B to which the current control switch 31A or 31B is connected, to the drive unit 10. The first FET 33A or 33C and the second FET 33B or 33D may be arranged in series such that the forward directions of their body diodes 33a or 33b are opposite to each other. This allows an intermediate state to be realized by utilizing the body diodes 33a or 33b, thereby reducing the number of components.

[0098] [others] It should be noted that the electric bicycle and battery switching device proposed in this disclosure are not limited to the examples described above.

[0099] For example, the current control switches 31A and 31B may be configured with other elements such as insulated gate bipolar transistors (IGBTs) instead of the FETs 33A to 33D. In this case, each of the current control switches 31A and 31B may have a diode (a pair of two diodes with opposite forward directions) equivalent to the body diodes 33a and 33b of the FETs 33A to 33D.

[0100] Furthermore, the drive unit 10 does not necessarily have to include the smoothing capacitor 16. Even in this case, the first FETs 33A and 33C connected to the switched discharge battery may be maintained in the off state until the intermediate state ending condition is satisfied. This makes it possible to prevent, for example, the regenerative current from the electric motor 12 from flowing into the switched discharge battery.

[0101] In still another example, the battery switching device 30 may not have the input unit 37 for user operation. In this case, the switching timing detection unit 33a may detect the switching timing of the discharging battery based on the state of the batteries 41A and 41B. [Explanation of symbols]

[0102] 1: electric bicycle, 10: drive unit, 12: electric motor, 15: motor drive device, 16: smoothing capacitor, 20: motor control device, 30: battery switching device, 31A-31B: Current control switch, 32A and 32B: switch drive circuit, 33A and 33C: first FET, 33B and 33D: second FET, 33a and 33b: body diode, 38: control device, 38a: switching timing detection unit, 38c: switching execution unit, 34A, 34B, and 34C: voltage detection unit, 35: indicator, 36: communication unit, 37: input unit, 41A: first battery, 41B: second battery, 130 and 230: battery switching device, 134 and 234: current detection unit, 333: control device, 333c: switching execution unit, 333e: switching mode determination unit.

Claims

1. A first battery; A second battery; A drive unit including an electric motor; a battery switching device disposed between the first battery, the second battery, and the drive unit; the battery switching device includes a first current control switch disposed between the first battery and the drive unit, a second current control switch disposed between the second battery and the drive unit, and a control device that controls the first current control switch and the second current control switch, Each of the first current control switch and the second current control switch is a bidirectional conduction state in which a current flows from a battery to which the current control switch is connected to the drive unit and a current flows from the drive unit to the battery; an intermediate state in which the current control switch allows a current to flow from a battery connected to the drive unit and restricts a current to flow from the drive unit to the battery; a bidirectional regulation state in which the current control switch regulates both a current flowing from the battery to the drive unit and a current flowing from the drive unit to the battery; having The control device sets the second current control switch to the intermediate state in a process of switching the battery supplying current to the drive unit from the first battery to the second battery, and thereafter sets the second current control switch to the bidirectional conductive state when a relative relationship between a potential of the drive unit and a potential of the second battery satisfies a predetermined condition. Electric bicycle.

2. a current detection unit for detecting a current flowing between the second battery and the drive unit; The control device determines whether or not a relative relationship between a potential of the drive unit and a potential of the second battery satisfies the predetermined condition based on an output of the current detection unit.

2. The electric bicycle according to claim 1.

3. a battery voltage detection unit for detecting a potential of the second battery; a drive unit voltage detection unit for detecting a potential of the drive unit; having The control device determines whether a relative relationship between a potential of the drive unit and a potential of the second battery satisfies the predetermined condition based on an output of the battery voltage detection unit and an output of the drive unit voltage detection unit.

2. The electric bicycle according to claim 1.

4. The predetermined condition is that a difference between the potential of the driving unit and the potential of the second battery is smaller than a threshold value.

4. The electric bicycle according to claim 3.

5. The predetermined condition is that the potential of the second battery is the same as or higher than the potential of the drive unit. An electric bicycle as claimed in any one of claims 1 to 3.

6. The control device changes the first current control switch from the bidirectional conducting state to the intermediate state and changes the second current control switch from the bidirectional restricting state to the intermediate state in a process of switching a battery supplying current to the drive unit from the first battery to the second battery. An electric bicycle as claimed in any one of claims 1 to 5.

7. The drive unit includes a motor drive device that supplies a current to the electric motor, and a smoothing capacitor that is connected in parallel with the motor drive device. An electric bicycle as claimed in any one of claims 1 to 6.

8. An input unit for a user to operate, The control device switches a battery that supplies a current to the drive unit between the first battery and the second battery based on a signal input from the input unit. An electric bicycle as claimed in any one of claims 1 to 7.

9. each of the first current control switch and the second current control switch includes a first field effect transistor (first FET) that allows a current to flow from a battery to which the current control switch is connected to the driving unit in an on state, and a second field effect transistor (second FET) that allows a current to flow from the driving unit to the battery to which the current control switch is connected in an on state; The first FET and the second FET are arranged in series such that the forward directions of their body diodes are opposite to each other. An electric bicycle as claimed in any one of claims 1 to 8.

10. A battery switching device disposed between a first battery, a second battery, and a drive unit of an electric bicycle, a first current control switch disposed between the first battery and the driving unit; a second current control switch disposed between the second battery and the driving unit; a control device that controls the first current control switch and the second current control switch; having Each of the first current control switch and the second current control switch is a bidirectional conduction state in which a current flows from a battery to which the current control switch is connected to the drive unit and a current flows from the drive unit to the battery; an intermediate state in which the current control switch allows a current to flow from a battery connected to the drive unit and restricts a current to flow from the drive unit to the battery; a bidirectional regulation state in which the current control switch regulates both a current flowing from a battery connected to the drive unit and a current flowing from the drive unit to the battery; The control device sets the second current control switch to the intermediate state when switching the battery supplying current to the drive unit from the first battery to the second battery, and thereafter sets the second current control switch to the bidirectional conductive state when a relative relationship between a potential of the drive unit and a potential of the second battery satisfies a predetermined condition. Battery switching device.

11. An electric bicycle having a first battery, a second battery, a drive unit including an electric motor, a first current control switch disposed between the first battery and the drive unit, and a second current control switch disposed between the second battery and the drive unit, A method for switching a battery supplying current to the drive unit from the first battery to the second battery, comprising: transitioning the second current control switch from a bidirectional regulation state in which both a current flowing from the second battery to the drive unit and a current flowing from the drive unit to the second battery are regulated to an intermediate state in which a current flowing from the second battery to the drive unit is permitted and a current flowing from the drive unit to the second battery is regulated; When a relative relationship between the potential of the drive unit and the potential of the second battery satisfies a predetermined condition, the second current control switch is transitioned from the intermediate state to a bidirectional conduction state in which a current flows from the second battery to the drive unit and a current flows from the drive unit to the second battery. How to switch batteries.

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