Patent Publication Number: US-2011074214-A1

Title: Battery apparatus and electric vehicle

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a battery apparatus and an electric vehicle including the same. 
     2. Description of the Background Art 
     Electric vehicles such as electric bicycles have conventionally been equipped with battery apparatuses including batteries. The battery apparatus includes a control circuit for controlling charge/discharge of the battery (hereinafter referred to as a battery control circuit). The battery control circuit is connected to communicate with a control circuit of another module provided in the electric vehicle. For example, the battery control circuit and a control circuit of a user interface (hereinafter referred to as a UI control circuit) displaying remaining capacity of the battery and so on are connected to communicate with each other. In this case, various types of information (e.g., the remaining capacity of the battery) is transmitted and received between the battery control circuit and the UI control circuit. 
     In recent years, a controller area network (CAN) has been used as a form of communication among a plurality of control circuits (see JP 2002-101109 A, for example). In communication using the CAN, two termination resistors are usually connected to a communication bus for impedance matching. 
     In the electric bicycles and the like, the termination resistors are provided in any of the plurality of modules having the control circuits. However, a connection state among the plurality of modules is optionally changed by users. The battery apparatus and the user interface are connected to each other during driving of the electric bicycle, and the battery apparatus is separated from the user interface and connected to a charger during the charge of the battery of the battery apparatus, for example. This makes it difficult to properly connect the two termination resistors to the communication bus. 
     BRIEF SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a battery apparatus capable of properly connecting a termination resistor to a communication bus and an electric vehicle including the same. 
     (1) According to an aspect of the present invention, a battery apparatus arranged to form a communication bus when being connected to another module includes a control circuit arranged to have a communication function for communicating with the another module through the communication bus, a battery arranged to supply electric power to the another module when the another module is connected to the battery apparatus, a first termination resistor arranged to be switchable between a first state where the first termination resistor is connected to the communication bus and a second state where the first termination resistor is separated from the communication bus, a detection circuit configured to be able to detect that the another module is connected to the battery apparatus, and a switch circuit arranged to determine whether or not the another module is connected to the battery apparatus based on detection performed by the detection circuit, and selectively switches the first termination resistor between the first state and the second state based on a result of determination. 
     The communication bus is formed when the another module is connected to the battery apparatus. The control circuit communicates with the another module through the communication bus. 
     When the another module is connected to the battery apparatus, the electric power is supplied from the battery to the another module, and the detection circuit detects that the another module is connected to the battery apparatus. The switch circuit determines whether or not the another module is connected to the battery apparatus based on the detection performed by the detection circuit. Based on the result of the determination, the switch circuit selectively switches the first state where the first termination resistor is connected to the communication bus and the second state where the first termination resistor is not connected to the communication bus. 
     Thus, the number of termination resistors connected to the communication bus can be adjusted depending on a connection state between the battery apparatus and the another module. This allows a state where two termination resistors are properly connected to the communication bus to be maintained even though a user optionally changes the connection state between the battery apparatus and the another module. This results in good communication between the battery apparatus and the another module through the communication bus. 
     (2) The another module may include first and second modules, the battery may supply electric power to the first and second modules when the first and second modules are connected to the battery apparatus, the detection circuit may be configured to be able to feed back a voltage based on the electric power supplied to each of the first and second modules and detect the voltage fed back from each of the first and second modules when the first and second modules are connected to the battery apparatus, and the switch circuit may determine whether or not each of the first and second modules is connected to the battery apparatus based on the voltage detected by the detection circuit, and selectively switch the first termination resistor between the first state and the second state based on a result of determination. 
     In this case, the first termination resistor is selectively switched between the first state and the second state depending on a connection state between the battery apparatus and the first module and a connection state between the battery apparatus and the second module. Thus, the number of termination resistors connected to the communication bus can be adjusted depending on the respective connection states between the battery apparatus and the first and second modules. 
     This allows the state where two termination resistors are properly connected to the communication bus to be maintained even though the user optionally changes the respective connection states between the battery apparatus and the first and second modules. This results in good communication between the battery apparatus and the first and second modules through the communication bus. 
     (3) When determining that the another module is connected to the battery apparatus, the switch circuit may further determine whether or not the another module that is connected to the battery apparatus has a termination resistor based on the voltage detected by the detection circuit, and selectively switch the first termination resistor between the first state and the second state based on a result of determination. 
     In this case, the first termination resistor is selectively switched between the first state and the second state depending on whether or not the another module connected to the battery apparatus has the termination resistor. Accordingly, the number of the termination resistors connected to the communication bus can be accurately adjusted in any of the cases where the another module having the termination resistor is connected to the battery apparatus and where the another module not having the termination resistor is connected to the battery apparatus. 
     (4) The battery apparatus may further include a second termination resistor connected to the communication bus, wherein the switch circuit may determine whether or not two termination resistors are connected to the communication bus based on the voltage detected by the detection circuit, and switch the first termination resistor between the first state and the second state based on a result of determination such that two termination resistors are connected to the communication bus. 
     In this case, a state where the second termination resistor is connected to the communication bus is maintained. Therefore, a state where two termination resistors are connected to the communication bus can be reliably maintained by bringing the first termination resistor into the second state when the another module having the termination resistor is connected to the battery apparatus and bringing the first termination resistor into the first state when the another module not having the termination resistor is connected to the battery apparatus. 
     (5) The another module may include a third module, the third module may have a third termination resistor arranged to be switchable between a third state where the third termination resistor is connected to the communication bus and a fourth state where the third termination resistor is separated from the communication bus, the switch circuit may determine whether or not two termination resistors are connected to the communication bus based on the voltage detected by the detection circuit, and switch the third termination resistor between the third state and the fourth state based on a result of determination such that two termination resistors are connected to the communication bus. 
     In this case, the first termination resistor of the battery apparatus is switched between the first and second states, and the third termination resistor of the third module is switched between the third and fourth states. Thus, the number of the termination resistors connected to the communication bus can be more accurately adjusted depending on the connection state between the battery apparatus and the another module. 
     (6) According to another aspect of the present invention, an electric vehicle includes the battery apparatus according to the one aspect of the present invention, a motor driven by electric power supplied from the battery of the battery apparatus, and a drive wheel that is rotated by a torque generated by the motor. 
     In the electric vehicle, the motor is driven by the electric power supplied from the battery of the battery apparatus. The drive wheel is rotated by the torque generated by the motor, thereby causing the electric vehicle to move. 
     The communication bus is formed when the another module is connected to the battery apparatus. The control circuit communicates with the another module through the communication bus. 
     When the another module is connected to the battery apparatus, the electric power is supplied from the battery to the another module, and the detection circuit detects that the another module is connected to the battery apparatus. The switch circuit determines whether or not the another module is connected to the battery apparatus based on the detection performed by the detection circuit. Based on the result of the determination, the switch circuit selectively switches the first state where the first termination resistor is connected to the communication bus and the second state where the first termination resistor is not connected to the communication bus. 
     Thus, the number of termination resistors connected to the communication bus can be adjusted depending on a connection state between the battery apparatus and the another module. This allows a state where two termination resistors are properly connected to the communication bus to be maintained even though a user optionally changes the connection state between the battery apparatus and the another module. This results in good communication between the battery apparatus and the another module through the communication bus. Accordingly, driving performance of the electric vehicle can be improved. 
     According to the present invention, the number of termination resistors connected to the communication bus can be adjusted depending on the connection state between the battery apparatus and the another module. This allows the state where two termination resistors are properly connected to the communication bus to be maintained even though a user optionally changes the connection state between the battery apparatus and the another module. This results in good communication between the battery apparatus and the another module through the communication bus. 
     Other features, elements, characteristics, and advantages of the present invention will become more apparent from the following description of preferred embodiments of the present invention with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a schematic diagram showing the configuration of an electric bicycle according to an embodiment of the present invention; 
         FIG. 2  is a block diagram showing the configurations of a user interface, a vehicle body controller, a battery apparatus and a charger in a simplified manner; 
         FIG. 3  is a schematic diagram showing the detailed configuration of the battery apparatus; 
         FIG. 4  is a flowchart showing operation of a microcomputer circuit; 
         FIG. 5  is a schematic diagram for explaining switching of the state of a termination resistor; 
         FIG. 6  is a schematic diagram for explaining switching of the state of the termination resistor in the battery apparatus when the termination resistor is not provided in the charger; 
         FIG. 7  is a diagram showing an example in which a capacitor is provided in the charger; 
         FIG. 8  is a schematic diagram showing another example of connection of detection resistors in the vehicle body controller, the battery apparatus and the charger; 
         FIG. 9  is a diagram showing an example in which a capacitor is provided in the charger of  FIG. 8 ; 
         FIG. 10  is a schematic diagram showing a modification of the battery apparatus and the changer; 
         FIG. 11  is a schematic diagram showing an example of switching of the state of the termination resistor; 
         FIG. 12  is a schematic diagram showing another modification of the battery apparatus; 
         FIG. 13  is a schematic diagram showing an example of switching of the state of the termination resistor in the battery apparatus of  FIG. 12 ; and 
         FIG. 14  is a side view of a two-wheeled electric vehicle including the battery apparatus. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Description will be made of a battery apparatus and an electric vehicle including the same according to embodiments of the present invention while referring to the drawings. In the following description, an electric bicycle is described as an example of the electric vehicle. 
     (1) Electric Vehicle 
       FIG. 1  is a schematic diagram showing the configuration of an electric bicycle according to an embodiment of the present invention. 
     In the electric bicycle  100  of  FIG. 1 , a front fork  103  is provided at the front end of a main frame  101  so as to be rotatable within a given angular range around its axis in an up-and-down direction. A front wheel  104  is rotatably supported at the lower end of the front fork  103 . A motor MO for rotating the front wheel  104  is attached to the front wheel  104 . 
     A handle  105  is provided at the upper end of the front fork  103 . A user interface  200  is arranged at the handle  105 . Details of the user interface  200  will be described below. 
     A crank  108  is rotatably provided at the center of the main frame  101 . A pedal  107  is attached to the tip of the crank  108 . A saddle  110  is attached to an upper portion of the main frame  101 , and a rear wheel  109  is rotatably supported at the rear end of the main frame  101 . 
     A user rotates the pedal  107  and the crank  108  in an integrated manner. A torque generated by the crank  108  is transmitted to the rear wheel  109  through a chain (not shown). This causes the rear wheel  109  to rotate. 
     A vehicle body controller  300  is provided near the crank  108 . The vehicle body controller  300  is electrically connected to the user interface  200  while being electrically connected to the motor MO attached to the front wheel  104 . The vehicle body controller  300  detects the torque generated by the crank  108 , and controls the motor MO based on the torque. 
     A battery attachment portion  300   a  is electrically connected to the vehicle body controller  300 . A battery apparatus  400  including a battery is attached to the battery attachment portion  300   a  in a detachable manner. The battery apparatus  400  is attached to the battery attachment portion  300   a , thereby causing the battery apparatus  400  and the vehicle body controller  300  to electrically connected to each other. 
     Electric power is supplied from the battery apparatus  400  to the user interface  200 , the vehicle body controller  300  and the motor MO. The torque of the front wheel  104  is converted into regenerated electric power by the motor MO during deceleration using a brake (not shown) and driving downhill. The battery apparatus  400  is supplied with the regenerated electric power, thus being subjected to regenerative charge. 
     A plug socket  400   a  is provided in the battery apparatus  400 . A plug  500   a  of a charger  500  is inserted in the plug socket  400   a . This causes the charger  500  and the battery apparatus  400  to be electrically connected to each other. A plug  500   b  of the charger  500  is inserted in an outlet of a commercial power supply that is not shown. The charger  500  performs AC-DC (alternating current-direct current) conversion on electric power supplied from the commercial power supply and supplies the converted electric power to the battery of the battery apparatus  400 . This causes the battery of the battery apparatus  400  to be charged. 
     In the present embodiment, the vehicle body controller  300  is an example of a first module, and the charger  500  is an example of a second module. 
     (2) The User Interface, the Vehicle Body Controller, the Battery Apparatus and the Charger 
     Next, description is made of the configurations of the user interface  200 , the vehicle body controller  300 , the battery apparatus  400  and the charger  500  in a simplified manner.  FIG. 2  is a block diagram showing the configurations of the user interface  200 , the vehicle body controller  300 , the battery apparatus  400  and the charger  500  in a simplified manner.  FIG. 2  shows the user interface  200 , the vehicle body controller  300 , the battery apparatus  400  and the charger  500  that are connected to one another. 
     As shown in  FIG. 2 , the user interface  200  includes en operation display  202 , a user interface control circuit (hereinafter abbreviated as a UI control circuit)  201 , a termination resistor R 12  and terminals  211  to  214 . 
     A communication path T 5  is connected to the terminal  211 , and a communication path T 6  is connected to the terminal  212 . The termination resistor R 12  is connected between the communication paths T 5 , T 6 . An electric power path E 1  is connected to the terminal  213 , and an electric power path E 2  is connected to the terminal  214 . The UI control circuit  201  is connected to the communication paths T 5 , T 6  and the electric power paths E 1 , E 2 , and the operation display  202  is connected to the electric power paths E 1 , E 2 . The UI control circuit  201  and the operation display  202  are connected to each other. 
     The UI control circuit  201  controls operation of the operation display  202 . The operation display  202  displays information relating to a state of the electric bicycle  100  (e.g., remaining capacity of the battery  402  of the battery apparatus  400 ). The user can set the state of the electric bicycle  100  (e.g., ON/OFF of a power supply) via the operation display  202 . 
     The vehicle body controller  300  includes a vehicle body control circuit  301  and terminals  311  to  319 . The terminals  311 ,  315  are connected to each other through a communication path T 3 , and the terminals  312 ,  316  are connected to each other through a communication path T 4 . The terminals  313 ,  318  are connected to each other through an electric power path E 3 , and the terminals  314 ,  319  are connected to each other through an electric power path E 4 . The vehicle body control circuit  301  is connected to the communication paths T 3 , T 4  and the electric power paths E 3 , E 4 . 
     The terminals  211 ,  212  of the user interface  200  are connected to the terminals  311 ,  312  of the vehicle body controller  300  through communication lines C 1 , C 2 , respectively, and the terminals  213 ,  214  of the user interface  200  are connected to the terminals  313 ,  314  of the vehicle body controller  300  through electric power lines D 1 , D 2 , respectively. 
     The user interface  200  and the vehicle body controller  300  are fixed to the electric bicycle  100  of  FIG. 1  while being connected to each other through the communication lines C 1 , C 2  and the electric power lines D 1 , D 2 . 
     The battery apparatus  400  includes a battery control circuit  401 , the battery  402 , a termination resistor R 11 , a switch S 1  and terminals  411  to  420 . The terminals  411 ,  416  are connected to each other through a communication path T 1 , and the terminals  412 ,  417  are connected to each other through a communication path T 2 . The termination resistor R 11  and the switch S 1  are connected in series between the communication paths T 1 , T 2 . 
     The battery control circuit  401  is connected to the communication paths T 1 , T 2 . The battery  402  is connected to the terminals  414 ,  415 ,  419 ,  420 . The battery control circuit  401  and the battery  402  are connected to each other. 
     The battery apparatus  400  is attached to the battery attachment portion  300   a  of  FIG. 1 , so that the terminals  411 ,  412  of the battery apparatus  400  are connected to the terminals  315 ,  316  of the vehicle body controller  300  through communication lines C 3 , C 4 , respectively, and the terminal  413  of the battery apparatus  400  is connected to the terminal  317  of the vehicle body controller  300  through a detection line K 1 . The terminals  414 ,  415  of the battery apparatus  400  are connected to the terminals  318 ,  319  of the vehicle body controller  300  through electric power lines D 3 , D 4 . The switch S 1  is controlled by a microcomputer circuit  410  that will be described below referring to  FIG. 3 . 
     The charger  500  includes a charge control circuit  501 , an AC-DC conversion circuit  502 , a termination resistor R 13  and terminals  511  to  515 . A communication path T 7  is connected to the terminal  511 , and a communication path T 8  is connected to the terminal  512 . The termination resistor R 13  is connected between the communication paths T 7 , T 8 . 
     The charge control circuit  501  is connected to the communication paths T 7 , T 8  and the terminals  514 ,  515 . The AC-DC conversion circuit  502  is connected to the terminals  514 ,  515  and the plug  500   b.    
     The plug  500   a  ( FIG. 1 ) of the charger  500  is inserted in the plug socket  400   a  ( FIG. 1 ) of the battery apparatus  400 , so that the terminals  511 ,  512  of the charger  500  are connected to the terminals  416 ,  417  of the battery apparatus  400  through communication lines C 5 , CS, and the terminal  513  of the charger  500  is connected to the terminal  418  of the battery apparatus  400  through a detection line K 2 . The terminals  514 ,  515  of the charger  500  are connected to the terminals  419 ,  420  of the battery apparatus  400  through electric power lines D 5 , D 6 , respectively. 
     In the electric bicycle  100  according to the present embodiment, a communication bus is constituted by part or all of the communication lines C 1  to C 6  and the communication paths T 1  to T 8 , and controller area network (CAN) communication is performed among the UI control circuit  201 , the vehicle body control circuit  301 , the battery control circuit  401  and the charge control circuit  501  through the communication bus. 
     The electric power is supplied from the battery  402  of the battery apparatus  400  to the vehicle body controller  300  and the user interface  200  through the electric power lines D 1  to D 4 . Also, the electric power is supplied from the commercial power supply to the battery  402  of the battery apparatus  400  through the AC-DC conversion circuit  502  of the charger  500  and the electric power lines D 5 , D 6 . 
     (3) Control of the Switch of the Battery Apparatus 
     Next, description is made of control of the switch S 1  of the battery apparatus  400 .  FIG. 3  is a schematic diagram showing the detailed configuration of the battery apparatus  400 .  FIG. 3  does not show the UI control circuit  201 , the operation display  202 , the vehicle body control circuit  301 , the battery control circuit  401 , the charge control circuit  501  and the AC-DC conversion circuit  502  of  FIG. 2 . 
     As shown in  FIG. 3 , the battery apparatus  400  includes the microcomputer circuit  410  and detection resistors R 21 , R 22 . The microcomputer circuit  410  includes a microcomputer chip and its peripheral circuit, and connected to the terminals  413 ,  418  and the switch S 1 . Voltages of the terminals  413 ,  418  are given to the microcomputer circuit  410 . The microcomputer circuit  410  controls the switch S 1  based on the voltages of the terminals  413 ,  418 . Details of operation of the microcomputer circuit  410  will be described below. 
     The terminals  414 ,  419  are connected to plus terminals of the battery  402 , and the terminals  415 ,  420  are connected to minus terminals of the battery  402 . The detection resistor R 21  is connected between the terminal  413  and the terminal  414 , and the detection resistor R 22  is connected between the terminal  418  and the terminal  419 . 
     The vehicle body controller  300  includes a detection resistor R 23 . The detection resistor R 23  is connected between the terminal  317  and the terminal  319 . 
     The charger  500  includes a detection resistor R 24 . The detection resistor R 24  is connected between the terminal  513  and the terminal  515 . 
     Next, description is made of the operation of the microcomputer circuit  410  of the battery apparatus  400 .  FIG. 4  is a flowchart showing the operation of the microcomputer circuit  410 . 
     As shown in  FIG. 4 , the microcomputer circuit  410  first determines whether or not the voltage of the terminal  413  ( FIG. 3 ) (hereinafter referred to as the voltage on the vehicle body side) is lower than a prescribed value P 1  (Step S 1 ). 
     Here, a current does not pass through the terminal  413  of the battery apparatus  400  when the terminals  413  to  415  of the battery apparatus  400  and the terminals  317  to  319  of the vehicle body controller  300  are not connected to each other, respectively. Therefore, the voltage on the vehicle body side is equal to the terminal voltage of the battery  402  (the voltage between the plus terminal and the minus terminal). 
     Meanwhile, a series circuit is formed by the battery  402  and the detection resistor R 21  of the battery apparatus  400  and the detection resistor R 23  of the vehicle body controller  300  when the terminals  413  to  415  of the battery apparatus  400  and the terminals  317  to  319  of the vehicle body controller  300  are connected to each other, respectively. In this case, the voltage on the vehicle body side attains a voltage (hereinafter referred to as the divided voltage value) obtained by dividing the terminal voltage of the battery  402  by the detection resistors R 21 , R 23 . 
     The above-mentioned prescribed value P 1  is set to an intermediate value between the terminal voltage of the battery  402  and the divided voltage value caused by the detection resistors R 21 , R 23 . Thus, the voltage on the vehicle body side becomes higher than the prescribed value P 1  when the battery apparatus  400  and the vehicle body controller  300  are not connected to each other, and becomes lower than the prescribed value P 1  when the battery apparatus  400  and the vehicle body controller  300  are connected to each other. 
     When the voltage on the vehicle body side is lower than the prescribed value P 1 , the microcomputer circuit  410  determines that the battery apparatus  400  and the vehicle body controller  300  are connected to each other, and determines whether or not the voltage of the terminal  418  (hereinafter referred to as the voltage on the charger side) is lower than a prescribed value P 2  (Step S 2 ). 
     When the terminals  418  to  420  of the battery apparatus  400  and the terminals  513  to  515  of the charger  500  are not connected to each other, respectively, the current does not pass through the terminal  418  of the battery apparatus  400 . Therefore, the voltage on the charger side is equal to the terminal voltage of the battery  402 . 
     Meanwhile, when the terminals  418  to  420  of the battery apparatus  400  and the terminals  513  to  515  of the charger  500  are connected to each other, respectively, a series circuit is formed by the battery  402  and the detection resistor R 22  of the battery apparatus  400  and the detection resistor R 24  of the charger  500 . In this case, the voltage on the charger side attains a voltage obtained by dividing the terminal voltage of the battery  402  by the detection resistors R 22 , R 24  (hereinafter referred to as a divided voltage value). 
     The above-mentioned prescribed value P 2  is set to an intermediate value between the terminal voltage of the battery  402  and the divided voltage value caused by the detection resistors R 22 , R 24 . Accordingly, the voltage on the charger side becomes higher than the prescribed value P 2  when the battery apparatus  400  and the charger  500  are not connected to each other, and becomes lower than the prescribed value P 2  when the battery apparatus  400  and the charger  500  are connected to each other. 
     When the voltage on the charger side is lower than the prescribed value P 2 , the microcomputer circuit  410  determines that the battery apparatus  400  and the charger  500  are connected to each other, and turns off the switch S 1  (Step S 3 ). This causes the termination resistor R 11  to be electrically separated from the communication paths T 1 , T 2 . In this case, the termination resistors R 12 , R 13  are connected to the communication paths T 1 , T 2 . 
     Meanwhile, when the voltage of the terminal  413  is not less than the prescribed value P 1  in Step S 1 , or when the voltage of the terminal  418  is not less than the prescribed value P 2  in Step S 2 , the microcomputer circuit  410  turns on the switch S 1  (Step S 4 ). This causes the termination resistor R 11  to be electrically connected between the communication paths T 1 , T 2 . In this case, at least one of the termination resistors R 12 , R 13  is not connected to the communication paths T 1 , T 2 . 
     The microcomputer circuit  410  repeats the processes of Steps S 1  to S 4 . This allows for switching between the state where the termination resistor R 11  is electrically connected between the communication paths T 1 , T 2  (hereinafter referred to as the connected state) and the state where the termination resistor R 11  is electrically separated from the communication paths T 1 , T 2  (hereinafter referred to as the non-connected state) depending on a connection state among the vehicle body controller  300 , the battery apparatus  400  and the charger  500 . 
     A step-up circuit or a step-down circuit that raises or drops the voltage applied from the battery  402  of the battery apparatus  400  to the microcomputer circuit  410  may be provided for detecting connection between the vehicle body controller  300  and the battery apparatus  400  and connection between the charger  500  and the battery apparatus  400 . 
       FIG. 5  is a schematic diagram for explaining switching of the state of the termination resistor R 11 . 
     As shown in  FIG. 5  ( a ), the termination resistor R 11  enters the connected state when the battery apparatus  400  is connected to the vehicle body controller  300  and the charger  500  is not connected to the battery apparatus  400 . In this case, the communication paths T 1  to T 6  and the communication lines C 1  to C 4  constitute the communication bus, the termination resistor R 12  of the user interface  200  is connected to one end of the communication bus, and the termination resistor R 11  of the battery apparatus  400  is connected to the other end of the communication bus. 
     In the state shown in  FIG. 5  ( a ), the electric bicycle  100  is driven or stopped while the battery apparatus  400  is attached to the battery attachment portion  300   a  ( FIG. 1 ). 
     In this case, the remaining capacity of the battery  402  ( FIG. 2 ) of the battery apparatus  400  is applied from the battery control circuit  401  ( FIG. 2 ) to the vehicle body control circuit  301  ( FIG. 2 ) and the UI control circuit  201  ( FIG. 2 ), for example. The vehicle body control circuit  301  controls the motor MO ( FIG. 1 ) depending on the remaining capacity of the battery  402 . The UI control circuit  201  displays the remaining capacity of the battery  402  on the operation display  202  ( FIG. 2 ). 
     As shown in  FIG. 5  ( b ), the termination resistor R 11  enters the connected state when the charger  500  is connected to the battery apparatus  400  and the battery apparatus  400  is not connected to the vehicle body controller  300 . In this case, the communication paths T 1 , T 2 , T 1 , T 8  and the communication lines C 5 , C 6  constitute the communication bus, the termination resistor R 11  of the battery apparatus  400  is connected to one end of the communication bus, and the termination resistor R 13  of the charger  500  is connected to the other end of the communication bus. 
     In the state shown in  FIG. 5  ( b ), the battery  402  ( FIG. 2 ) of the battery apparatus  400  is charged by the charger  500  while the battery apparatus  400  is separated from the battery attachment portion  300   a  ( FIG. 1 ). 
     In this case, charged capacity of the battery  402  ( FIG. 2 ) of the battery apparatus  400  is applied from the battery control circuit  401  ( FIG. 2 ) to the charge control circuit  501  ( FIG. 2 ), for example. When the charged capacity of the battery  402  reaches a given value, the charge control circuit  501  stops supply of electric power from the commercial power supply to the battery apparatus  400 . In addition, a signal indicating an occurrence of abnormality of the battery apparatus  400  is applied from the battery control circuit  401  to the charge control circuit  501  ( FIG. 2 ). In the case, the charge control circuit  501  stops the supply of electric power from the commercial power supply to the battery apparatus  400 . 
     As shown in  FIG. 5  ( c ), the termination resistor R 11  enters the non-connected state when the battery apparatus  400  is connected to the vehicle body controller  300  and the charger  500  is connected to the battery apparatus  400 . In this case, the communication paths T 1  to T 8  and the communication lines C 1  to C 6  constitute the communication bus, the termination resistor R 12  of the user interface  200  is connected to one end of the communication bus, and the termination resistor R 13  of the charger  500  is connected to the other end of the communication bus. 
     In the state shown in  FIG. 5  ( c ), the battery  402  of the battery apparatus  400  is charged by the charger  500  while the battery apparatus  400  is attached to the battery attachment portion  300   a  ( FIG. 1 ). 
     In this case, the charged capacity of the battery  402  ( FIG. 2 ) of the battery apparatus  400  is applied from the battery control circuit  401  ( FIG. 2 ) to the charge control circuit  501  ( FIG. 2 ), for example. When the charged capacity of the battery  402  reaches the given value, the charge control circuit  501  stops the supply of electric power from the commercial power supply to the battery apparatus  400 . Moreover, the signal indicating an occurrence of abnormality of the battery apparatus  400  is applied from the battery control circuit  401  to the charge control circuit  501 . In the case, the charge control circuit  501  stops the supply of electric power from the commercial power supply to the battery apparatus  400 . 
     The charged capacity of the battery  402  of the battery apparatus  400  is applied from the battery control circuit  401  to the UI control circuit  201  ( FIG. 2 ). The UI control circuit  201  displays the charged capacity of the battery  402  on the operation display  202  ( FIG. 2 ). 
     A signal for inhibiting the electric bicycle  100  from being driven is applied from the battery control circuit  401  to the vehicle body control circuit  301 . In this case, the vehicle body control circuit  301  lacks rotation of the crank  108  ( FIG. 1 ) using a locking mechanism that is not shown. This prevents a user from erroneously driving the electric bicycle  100 . 
     (4) Effects 
     In the battery apparatus  400  according to the present embodiment, the termination resistor R 11  is switched between the connected state and the non-connected state based on the voltage on the vehicle body side and the voltage on the charger side. In this case, the termination resistor R 11  is connected to the communication paths T 1 , T 2  when the battery apparatus  400  is not connected to at least one of the vehicle body controller  300  and the charger  500 , that is, when at least one of the termination resistors R 12 , R 13  is not connected to the communication paths T 1 , T 2 . Meanwhile, the termination resistor R 11  is not connected to the communication paths T 1 , T 2  when the battery apparatus  400  is connected to the vehicle body controller  300  and the charger  500 , that is, when the termination resistors R 12 , R 13  are connected to the communication paths T 1 , T 2 . 
     Thus, even though the user changes the connection state among the vehicle body controller  300 , the battery apparatus  400  and the charger  500  depending on the situation, the state where the two termination resistors are properly connected to the communication bus is maintained. This allows for good CAN communication among the user interface  200 , the vehicle body controller  300 , the battery apparatus  400  and the charger  500 . 
     (5) Modifications 
     (5-1) 
     While the termination resistor R 13  is provided in the charger  500  in the above-described embodiment, the termination resistor R 13  may not be provided in the charger  500  when the lengths of the communication lines C 5 , C 6  are comparatively short, for example. In the case, the detection resistor R 24  of the charger  500  is set to have a different value from that of the detection resistor R 24  when the termination resistor R 13  is provided in the charger  500 . 
     As described above, when the terminals  418  to  420  of the battery apparatus  400  and the terminals  513  to  515  of the charger  500  are connected to each other, respectively, the voltage on the charger side attains the divided voltage value obtained by dividing the terminal voltage of the battery  402  by the detection resistors R 22 , R 24 . 
     The divided voltage value differs depending on the value of the detection resistor R 24 . Therefore, when the value of the detection resistor R 24  differs depending on whether the termination resistor R 13  is provided or not, the voltage on the charger side also differs depending on whether the termination resistor R 13  is provided or not. 
     In this case, the voltage on the charger side when the termination resistor R 13  is provided in the charger  500 , and the voltage on the charger side when the termination resistor R 13  is not provided in the charger  500  are previously stored in the microcomputer circuit  410  of the battery apparatus  400 . 
     Accordingly, the microcomputer circuit  410  of the battery apparatus  400  can determine whether or not the termination resistor R 13  is provided in the charger  500  based on the voltage on the charger side. This allows the microcomputer circuit  410  of the battery apparatus  400  to control the state of the termination resistor R 11  depending on the presence/absence of the termination resistor R 13  in the charger  500 . 
       FIG. 6  is a schematic diagram for explaining switching of the state of the termination resistor R 11  in the battery apparatus  400  when the termination resistor R 13  is not provided in the charger  500 . 
     As shown in  FIG. 6 , when the termination resistor R 13  is not provided in the charger  500 , the termination resistor R 11  enters the connected state while the battery apparatus  400  is connected to the vehicle body controller  300  and the charger  500  is connected to the battery apparatus  400 . 
     In this case, the communication paths T 1  to T 8  and the communication lines C 1  to C 6  constitute the communication bus, and the termination resistor R 12  of the user interface  200  and the termination resistor R 11  of the battery apparatus  400  are connected to the communication bus. That is, the termination resistor R 11  of the battery apparatus  400 , instead of the termination resistor R 13  of the charger  500  in the example of  FIG. 5  ( c ), is connected to the communication bus. Thus, the state where the two termination resistors are connected to the communication bus is maintained. This allows for good CAN communication among the user interface  200 , the vehicle body controller  300 , the battery apparatus  400  and the charger  500 . 
     (5-2 
     A capacitor may be provided in the charger  500  in either one of the case where the termination resistor R 13  is provided in the charger  500  or the case where the termination resistor R 13  is not provided in the charger  500 . 
       FIG. 7  is a diagram showing an example in which a capacitor is provided in the charger  500 . In the example of  FIG. 7 , the termination resistor R 13  is provided in the charger  500 , and the capacitor CN is connected between the terminal  513  and the terminal  514 . 
     When the capacitor CN is connected between the terminal  513  and the terminal  514 , the voltage on the charger side gradually drops from the terminal voltage of the battery  402  to the divided voltage value caused by the detection resistors R 22 , R 24  at the time of connection of the battery apparatus  400  and the charger  500  to each other. Meanwhile, when the capacitor CN is not connected between the terminal  513  and the terminal  514 , the voltage on the charger side instantaneously drops from the terminal voltage of the battery  402  to the divided voltage value caused by the detection resistors R 22 , R 24  at the time of connection of the battery apparatus  400  and the charger  500  to each other. 
     In this case, a drop time of the voltage on the charger side when the termination resistor R 13  is provided in the charger  500  and a drop time of the voltage on the charger side when the termination resistor R 13  is not provided in the charger  500  are previously stored in the microcomputer circuit  410  of the battery apparatus  400 . 
     This allows the microcomputer circuit  410  of the battery apparatus  400  to determine whether or not the termination resistor R 13  is provided in the charger  500  based on the drop time of the voltage on the charger side. Accordingly, as in the examples shown in  FIGS. 5 and 6 , the microcomputer circuit  410  of the battery apparatus  400  can control the state of the termination resistor R 11  depending on the presence/absence of the termination resistor R 13  in the charger  500 . 
     (5-3) 
       FIG. 8  is a schematic diagram showing another example of connection of the detection resistors R 21  to R 24  in the vehicle body controller  300 , the battery apparatus  400  and the charger  500 . The example shown in  FIG. 8  is different from the example of  FIG. 3  in the following points. 
     In the example of  FIG. 8 , the detection resistor R 21  is connected between the terminal  413  and the terminal  415 , and the detection resistor R 22  is connected between the terminal  418  and the terminal  420  in the battery apparatus  400 . In the vehicle body controller  300 , the detection resistor R 23  is connected between the terminal  317  and the terminal  318 . In the charger  500 , the detection resistor R 24  is connected between the terminal  513  and the terminal  514 . 
     When the terminals  413  to  415  of the battery apparatus  400  and the terminals  317  to  319  of the vehicle body controller  300  are not connected to each other, respectively, the current does not pass through the terminal  413  of the battery apparatus  400 . Therefore, the voltage on the vehicle body side attains zero. 
     Meanwhile, when the terminals  413  to  415  of the battery apparatus  400  and the terminals  317  to  319  of the vehicle body controller  300  are connected to each other, respectively, the voltage on the vehicle body side attains the divided voltage value obtained by dividing the terminal voltage of the battery  402  by the detection resistors R 21 , R 23 . 
     When the terminals  418  to  420  of the battery apparatus  400  and the terminals  513  to  515  of the charger  500  are not connected to each other, respectively, the current does not pass through the terminal  418  of the battery apparatus  400 . Therefore, the voltage on the charger side attains zero. 
     Meanwhile, when the terminals  418  to  420  of the battery apparatus  400  and the terminals  513  to  515  of the charger  500  are connected to each other, respectively, the voltage on the charger side attains the divided voltage value obtained by dividing the terminal voltage of the battery  402  by the detection resistors R 22 , R 24 . 
     This allows the microcomputer circuit  410  of the battery apparatus  400  to determine whether or not the battery apparatus  400  and the vehicle body controller  300  are connected to each other based on the voltage on the vehicle body side. Also, the microcomputer circuit  410  of the battery apparatus  400  can determine whether or not the battery apparatus  400  and the charger  500  are connected to each other based on the voltage on the charger side. 
     As a result, the state of the termination resistor R 11  of the battery apparatus  400  can be appropriately switched depending on the connection state among the vehicle body controller  300 , the battery apparatus  400  and the charger  500 , as shown in  FIG. 5 . 
     In the example of  FIG. 8 , the termination resistor R 13  may not be provided in the charger  500 . In the case, the detection resistor R 24  of the charger  500  is set to have the different value from the value of the detection resistor R 24  of the charger  500  when the termination resistor R 13  is provided in the charger  500 . 
     In this case, similarly to the foregoing example, the voltage on the charger side when the termination resistor R 13  is provided in the charger  500  and the voltage on the charger side when the termination resistor R 13  is not provided in the charger  500  are previously stored in the microcomputer circuit  410  of the battery apparatus  400 . 
     This allows the microcomputer circuit  410  of the battery apparatus  400  to determine whether or not the termination resistor R 13  is provided in the charger  500  based on the voltage on the charger side. Accordingly, the microcomputer circuit  410  of the battery apparatus  400  can control the state of the termination resistor R 11  depending on the presence/absence of the termination resistor R 13  in the charger  500  as in the examples shown in  FIGS. 5 and 6 . 
     In the example of  FIG. 8 , the capacitor may be provided in the charger  500  in either one of the case where the termination resistor R 13  is provided in the charger  500  or the case where the termination resistor R 13  is not provided in the charger  500 . 
       FIG. 9  is a diagram showing an example in which the capacitor is provided in the charger  500  of  FIG. 8 . In the example of  FIG. 9 , the termination resistor R 13  is provided in the charger  500 , and the capacitor CN is connected between the terminal  513  and the terminal  515 . 
     When the capacitor CN is connected between the terminal  513  and the terminal  515 , the voltage on the charger side gradually rises from zero to the divided voltage value caused by the detection resistors R 22 , R 24  at the time of connection of the battery apparatus  400  and the charger  500  to each other. Meanwhile, when the capacitor CN is not connected between the terminal  513  and the terminal  515 , the voltage on the charger side instantaneously rises from zero to the divided voltage value caused by the detection resistors R 22 , R 24  at the time of connection of the battery apparatus  400  and the charger  500  to each other. 
     In this case, a rise time of the voltage on the charger side when the termination resistor R 13  is provided in the charger  500  and a rise time of the voltage on the charger side when the termination resistor R 13  is not provided in the charger  500  are previously stored in the microcomputer circuit  410  of the battery apparatus  400 . 
     This allows the microcomputer circuit  410  of the battery apparatus  400  to determine whether or not the termination resistor R 13  is provided in the charger  500  based on the rise time of the voltage on the charger side. Accordingly, as in the examples shown in  FIGS. 5 and 6 , the microcomputer circuit  410  of the battery apparatus  400  can control the state of the termination resistor R 11  depending on the presence/absence of the termination resistor R 13  in the charger  500 . 
     (5-4) 
       FIG. 10  is a schematic diagram showing a modification of the battery apparatus  400  and the charger  500 . The example shown in  FIG. 10  is different from the example of  FIG. 3  in the following points. 
     In the example of  FIG. 10 , the battery apparatus  400  further includes a terminal  421 . The terminal  421  is connected to the microcomputer circuit  410 . The charger  500  further includes a terminal  516  and a switch S 2 . The switch  52  is connected between the termination resistor R 13  and the communication path T 8 . The terminal  516  is connected to the switch  52 . 
     The terminal  421  of the battery apparatus  400  and the terminal  516  of the charger  500  are connected to each other through a control line SC. The microcomputer circuit  410  of the battery apparatus  400  applies an ON/OFF signal to the switch S 2  of the charger  500  through the control line SC. This allows for switching between the state where the termination resistor R 13  is electrically connected between the communication paths T 1 , T 8  (the connected state) and the state where the termination resistor R 13  is electrically separated from the communication paths T 7 , T 8  (the non-connected state). The charger  500  of  FIG. 10  is an example of a third module. 
       FIG. 11  is a schematic diagram showing an example of switching of the state of the termination resistor R 13 . As shown in  FIG. 11  ( a ), the microcomputer circuit  410  ( FIG. 10 ) of the battery apparatus  400  causes the termination resistor R 13  to enter the connected state when the charger  500  is connected to the battery apparatus  400  and the battery apparatus  400  is not connected to the vehicle body controller  300 . 
     In this case, the communication paths T 1 , T 2 , T 7 , T 8  and the communication lines C 5 , C 6  constitute the communication bus, the termination resistor R 11  of the battery apparatus  400  is connected to one end of the communication bus, and the termination resistor R 13  of the charger  500  is connected to the other end of the communication bus. 
     Meanwhile, as shown in  FIG. 11  ( b ), the microcomputer circuit  410  of the battery apparatus  400  causes the termination resistor R 13  to enter the non-connected state when the battery apparatus  400  is connected to the vehicle body controller  300  and the charger  500  is connected to the battery apparatus  400 . 
     In this case, the communication paths T 1  to T 8  and the communication lines C 1  to C 6  constitute the communication bus, and the termination resistor R 12  of the user interface  200  and the termination resistor R 11  of the battery apparatus  400  are connected to the communication bus. 
     As shown in  FIG. 11  ( c ), the microcomputer circuit  410  of the battery apparatus  400  may cause the termination resistor R 11  of the battery apparatus  400  to enter the non-connected state and cause the termination resistor R 13  of the charger  500  to enter the connected state when the battery apparatus  400  is connected to the vehicle body controller  300  and the charger  500  is connected to the battery apparatus  400 . 
     In this case, the communication paths T 1  to T 8  and the communication lines C 1  to C 6  constitute the communication bus, and the termination resistor R 12  of the user interface  200  and the termination resistor R 13  of the charger  500  are connected to the communication bus. 
     In this manner, the microcomputer circuit  410  of the battery apparatus  400  controls the state of the termination resistor R 13  of the charger  500 , thereby maintaining the state where the two termination resistors are connected to the communication bus even though the connection state among the vehicle body controller  300 , the battery apparatus  400  and the charger  500  is changed. This allows for good CAN communication among the user interface  200 , the vehicle body controller  300 , the battery apparatus  400  and the charger  500 . 
     (5-5) 
       FIG. 12  is a schematic diagram showing another modification of the battery apparatus  400 . The example shown in  FIG. 12  is different from the example of  FIG. 3  in the following points. 
     In the example of  FIG. 12 , the battery apparatus  400  further includes a termination resistor R 11   a . The termination resistor R 11   a  is connected between the communication paths T 1 , T 2  in parallel with a series circuit constituted by the termination resistor R 11  and the switch S 1 . 
       FIG. 13  is a schematic diagram showing an example of switching of the state of the termination resistor R 11  in the battery apparatus  400  of  FIG. 12 . In the example of  FIG. 13 , the termination resistor R 13  is not provided in the charger  500 . 
     As shown in  FIG. 13  ( a ), the termination resistor R 11  enters the non-connected state when the battery apparatus  400  is connected to the vehicle body controller  300  and the charger  500  is not connected to the battery apparatus  400 . In this case, the communication paths T 1  to T 6  and the communication lines C 1  to C 4  constitute the communication bus, the termination resistor R 12  of the user interface  200  is connected to one end of the communication bus, and the termination resistor R 11   a  of the battery apparatus  400  is connected to the other end of the communication bus. 
     As shown in  FIG. 13  ( b ), the termination resistor R 11  enters the connected state when the charger  500  is connected to the battery apparatus  400  and the battery apparatus  400  is not connected to the vehicle body controller  300 . In this case, the communication paths T 1 , T 2 , T 7 , T 8  and the communication lines C 5 , C 6  constitute the communication bus, and the termination resistors R 11 , R 11   a  of the battery apparatus  400  are connected to the communication bus. 
     As shown in  FIG. 13  ( c ), the termination resistor R 11  enters the non-connected state when the battery apparatus  400  is connected to the vehicle body controller  300  and the charger  500  is connected to the battery apparatus  400 . In this case, the communication paths T 1  to T 8  and the communication lines C 1  to C 6  constitute the communication bus, and the termination resistor R 12  of the user interface  200  and the termination resistor R 11   a  of the battery apparatus  400  are connected to the communication bus. 
     In this manner, when the termination resistor R 13  is not provided in the charger  500 , the state where the two termination resistors are connected to the communication bus is maintained even though the connection state among the vehicle body controller  300 , the battery apparatus  400  and the charger  500  is changed. This allows for good CAN communication among the user interface  200 , the vehicle body controller  300 , the battery apparatus  400  and the charger  500 . 
     Since the termination resistor R 11   a  is not separated from the communication lines T 1 , T 2  due to malfunctions or the like, the termination resistor R 11   a  is reliably connected to the communication bus during driving of the electric bicycle  100 , that is, in the state of  FIG. 13  ( a ). Accordingly, normal CAN communication among the user interface  200 , the vehicle body controller  300  and the battery apparatus  400  can be reliably performed during driving of the electric bicycle  100 . This results in a further improved level of safety during driving of the electric bicycle  100 . 
     (6) Other Embodiments 
     While the electric bicycle including the battery apparatus  400  is described in the foregoing embodiment, the battery apparatus  400  may be provided in another electric vehicle. 
       FIG. 14  is a side view of a two-wheeled electric vehicle including the battery apparatus  400 . As shown in  FIG. 14 , the two-wheeled electric vehicle  600  includes a vehicle body frame  610 , a front fork  611 , a handle  620 , a main body  630 , a seat  640 , a swing arm  650 , a motor  660 , a front wheel  691  and a rear wheel  692 . In the following description, front, rear, left and right means front, rear, left and right directions seen from a position of a driver seated on the seat  640  of the two-wheeled electric vehicle  600 . 
     The vehicle body frame  610  is of an underbone type, and provided to extend in a front-to-rear direction in a lower portion of the two-wheeled electric vehicle  600 . 
     The front fork  611  is attached to a front end portion of the vehicle body frame  610  so as to swing from side to side. The front wheel  691  is attached to a lower end portion of the front fork  611 . The handle  620  is attached to an upper end portion of the front fork  611 . 
     The main body  630  is attached to a portion from the center to the rear of the vehicle body frame  610 . The seat  640  is provided at an upper end portion of the main body  630 . A main controller  631  and the battery apparatus  400  are provided within the main body  630 . The main controller  631  and the battery apparatus  400  are electrically connected to each other. 
     The swing arm  650  is attached to a rear end portion of the vehicle body frame  610  to extend in the rear direction. In this state, a rear end portion of the swing arm  650  can swing in an up-and-down direction with respect to the vehicle body frame  610 . The motor  660  is provided at a rear end of the swing arm  650 . The rear wheel  692  is attached to a rotation shaft of the motor  660 . 
     The motor  660  is electrically connected to the battery apparatus  400  and the main controller  631 . Electric power is supplied from the battery apparatus  400  to the motor  660 . During operation of the motor  660 , a torque generated by the motor  660  is transmitted to the rear wheel  692  through the rotation shaft. 
     In the two-wheeled electric vehicle  600 , the CAN communication is performed between the main controller  631  and the battery apparatus  400  through the communication bus. During the charge of the battery  402  ( FIG. 2 ) of the battery apparatus  400 , a charging device (not shown) is connected to the battery apparatus  400 . In the case, the CAN communication is performed among the main controller  631 , the battery apparatus  400  and the charging device through the communication bus. 
     Therefore, similarly to the foregoing embodiment, the termination resistor R 11  ( FIG. 3 ) of the battery apparatus  400  is switched between the connected state and the non-connected state depending on a connection state among the main controller  631 , the battery apparatus  400  and the charging device. Accordingly, the state where the two termination resistors are connected to the communication bus is maintained even though the user changes the connection state among the main controller  631 , the battery apparatus  400  and the charging device depending on the situation. This allows for good CAN communication among the main controller  631 , the battery apparatus  400  and the charging device. 
     (7) Still Other Embodiments 
     While the vehicle body controller  300 , the charger  500  and the main controller  631  are each used as a module (a first or second module) connected to the battery apparatus in the foregoing embodiment, the present invention is not limited to this. For example, an accessory for vehicles such as a car navigation system or car audio equipment may be used as a module that is connected to the battery apparatus through the communication bus. 
     (8) Correspondences between Elements in the Claims and Parts in Embodiments 
     In the following paragraph, non-limiting examples of correspondences between various elements recited in the claims below and those described above with respect to various preferred embodiments of the present invention are explained. 
     In the above-described embodiments, the battery control circuit  401  is an example of a control circuit, the connected state is an example of a first state, the non-connected state is an example of a second state, the termination resistor R 11  is an example of a first termination resistor, the detection resistors R 21 , R 22  and the terminals  413 ,  418  are an example of a detection circuit, the microcomputer circuit  410  is an example of a switch circuit, the vehicle body controller  300  or the main controller  631  is an example of a first module, the charger  500  is an example of a second module, the termination resistor R 11   a  is an example of a second termination resistor, the charger  500  is an example of a third module, the termination resistor R 13  is an example of a third termination resistor, and the electric bicycle  100  or the two-wheeled electric vehicle  600  is an example of an electric vehicle. 
     As each of various elements recited in the claims, various other elements having configurations or functions described in the claims can be also used. 
     While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.