Power supply system for electric vehicle

Abstract

The present invention provides a power supply system for an electric vehicle, the system capable of appropriately improving the charging capacity of a battery. The power supply system for an electric vehicle comprises: a battery that stores power for traveling; a charging connector that receives charging power from a charging facility outside the vehicle body; and a control circuit. The charging facility is configured to transmit the charging power outputted from a charging device to the charging connector via a charging cable, and the control circuit measures the resistance value of the charging cable.

Description

Power system for electric vehicle

[0001] The present invention relates to a power system for an electric vehicle.

[0002] Patent Document 1 discloses measuring a resistance value of a bus bar connected to a plurality of battery modules in an electric vehicle. When the resistance value is equal to or higher than a threshold value, the control device determines that the battery is abnormal.

[0003] Japanese Unexamined Patent Application Publication No. 2020-161315

[0004] In an electric vehicle, if a charging facility can supply a large current to a battery and a charging power line, the charging capacity of the battery can be improved, and charging of a large amount of power can be completed in a short time. On the other hand, since a power line has a slight resistance, heat is generated when a large current flows therethrough.

[0005] An object of the present invention is to provide a power system for an electric vehicle that can appropriately improve the charging capacity of a battery.

[0006] A power system for an electric vehicle according to one aspect of the present invention comprises: a battery that stores electric power for traveling; a charging connector that receives charging power from a charging facility outside a vehicle body; and a control circuit, wherein the charging facility is configured to transmit charging power output from a charging device to the charging connector via a charging cable, and the control circuit measures a resistance value of the charging cable.

[0007] According to the present invention, a power system for an electric vehicle that can appropriately improve the charging capacity of a battery can be provided.

[0008] FIG. 1 is a block diagram showing an electric vehicle equipped with a power system according to an embodiment of the present invention. FIG. 2 is a block diagram showing a power system according to an embodiment of the present invention. FIG. 3 is a diagram explaining each section of a power line. FIG. 4 is a diagram explaining each section of a power line. FIG. 5 is a flowchart showing a procedure of first resistance value measurement processing according to an embodiment. FIG. 6 is a first part of a flowchart showing a procedure of second resistance value measurement processing according to an embodiment of the present invention. FIG. 7 is a second part of a flowchart showing a procedure of second resistance value measurement processing according to an embodiment of the present invention. FIG. 8 is a diagram explaining a resistance value of a power line acquired by resistance value calculation processing.

[0009] Hereinafter, each embodiment of the present invention will be described in detail with reference to the drawings. Figure 1 is a block diagram showing an electric vehicle 1 equipped with a power supply system 20 according to an embodiment of the present invention. The electric vehicle 1 in Figure 1 includes drive wheels 2, an electric motor 3 that drives the drive wheels 2, a driver-operated control device 5, and a vehicle control circuit 6 that receives an operation signal from the driver-operated control device 5 and outputs an operation command for the electric motor 3. The electric vehicle 1 further includes a power supply system 20.

[0010] As shown in Figure 1, the power supply system 20 includes a battery (for example, two batteries 21A and 21B) for storing power for driving, a battery management circuit (for example, two battery management circuits 25A and 25B) for managing the batteries, a motor control circuit 22 for controlling the drive of the electric motor 3, and a control circuit 28 for managing the power lines. The motor control circuit 22 includes an inverter 221 (see Figure 2) for driving the electric motor 3. Furthermore, the power supply system 20 includes a charging connector (for example, a charging inlet) 291 for taking in DC charging power from charging equipment 500 outside the vehicle, and a charging control circuit 293 for controlling charging.

[0011] Batteries 21A and 21B output a high voltage, for example, 100V or more to 800V or more. Batteries 21A and 21B are, for example, lithium-ion secondary batteries or nickel-metal hydride secondary batteries, but various other types of secondary batteries may be used. One of the batteries, 21A, may be called the first battery. The other battery, 21B, may be called the second battery.

[0012] The vehicle control circuit 6 is an ECU (Electronic Control Unit) that executes a control program and controls the driving of the electric vehicle 1. The vehicle control circuit 6 communicates with and cooperates with other ECUs. Communication is carried out via a communication network NE, such as a CAN (Controller Area Network). The same applies to communication between ECUs as described below. The driving control device 5 includes steering members 5a such as a steering wheel, acceleration members 5b such as an accelerator pedal, and braking members 5c such as a brake pedal. The vehicle control circuit 6 receives signals from the driving control device 5. The vehicle control circuit 6 calculates the torque and other parameters required for the electric motor 3 according to these signals. Then, the vehicle control circuit 6 sends a command to the motor control circuit 22 so that the torque and other parameters are realized. The motor control circuit 22 drives the inverter 221 based on the above command to operate the electric motor 3 in a powered or regenerative mode. Through this control, the electric vehicle 1 is driven according to the driving operation. Note that the driving control device 5 may be operated by an automatic driving system instead of a driver.

[0013] The battery management circuit 25A may be a BMC (Battery Management System) that monitors the voltage, temperature, and other conditions of multiple battery cells of one battery 21A and maintains the voltage balance of the multiple battery cells. Alternatively, the battery management circuit 25A may be a BCU (Battery Control Unit) that estimates the SOC (State of Charge) and SOH (State of Health) of one battery 21A, and manages the output power and input power of one battery 21A. Alternatively, the battery management circuit 25A may be a BMC equipped with the functions of a BCU. The other battery management circuit 25B is a circuit that has similar functions for the other battery 21B. The one battery management circuit 25A may be called the first battery management circuit. The other battery management circuit 25B may be called the second battery management circuit.

[0014] Figure 2 is a block diagram of the power supply system 20. Figures 3A and 3B are diagrams illustrating each section of the power line 31. The power supply system 20 comprises the two batteries 21A and 21B, the two battery management circuits 25A and 25B, the motor control circuit 22, the charging connector 291, the charging control circuit 293, and the control circuit 28, as described above.

[0015] In Figure 2, the anode terminal 291p and cathode terminal 291n of the charging connector 291 are depicted separately, but in reality, they are located close together and constitute a single charging connector 291. The same applies to the power supply connector 503. The charging connector 291 can be connected to the charging cable 502 via the power supply connector 503 (e.g., a charging gun). In Figure 2, the anode and cathode of the charging cable 502 are depicted separated partway through, but in reality, the charging cable 502 is bundled together from the charging device 501 to the power supply connector 503.

[0016] The power supply system 20 further includes a power line 31, two main relays 26Ap, 26An, 26Bp, and 26Bn, and two charging relays 295Ap, 295An, 295Bp, and 295Bn.

[0017] The power line 31 includes a pair of first power lines 311p, 311n (shown as short dashed lines in Figure 11A) that transmit power between one battery 21A and the inverter 221, and a pair of second power lines 312p, 312n (shown as short dashed lines in Figure 11B) that transmit power between the other battery 21B and the inverter 221. Furthermore, the power line 31 includes a pair of first charging power lines 313p, 313n (shown as dashed lines in Figure 11B) that transmit power between one battery 21A and the charging connector 291 (291p, 291n), and a pair of second charging power lines 314p, 314n (shown as dashed lines in Figure 11A) that transmit power between the other battery 21B and the charging connector 291 (291p, 291n). Here, "a pair" means a pair of anode and cathode lines.

[0018] Figure 2 shows the resistance R1 of the first charging power lines 313p and 313n, and the resistance R2 of the second charging power lines 314p and 314n. In Figure 2, resistances R1 and R2 are shown on a portion of the power line 31, but the actual resistance R1 represents the total resistance of the pair of first charging power lines 313p and 313n on the anode and cathode sides. The actual resistance R2 represents the total resistance of the pair of second charging power lines 314p and 314n on the anode and cathode sides.

[0019] The first power lines 311p and 311n and the second power lines 312p and 312n include overlapping sections 316p and 316n. The first power lines 311p and 311n, the second power lines 312p and 312n, the first charging power lines 313p and 313n, and the second charging power lines 314p and 314n include overlapping sections 317p, 317n, 318p, and 318n. Each of the overlapping sections 316p to 318p and 316n to 318p is composed of a single power line.

[0020] The main relays 26Ap and 26An of the first system are provided to disconnect a pair of first power lines 311p and 311n, respectively. The main relays 26Bp and 26Bn of the second system are provided to disconnect a pair of second power lines 312p and 312n, respectively. The cathode side may include the main relays 26An and 26Bn, a relay Re for switching between disconnecting and connecting the power lines, and a pre-charge relay PRe for slowly supplying current through a pre-charge resistor Rp when connecting the power lines.

[0021] The first charging relays 295Ap and 295An are configured to disconnect the first charging power lines 313p and 313n, respectively. The second charging relays 295Bp and 295Bn are configured to disconnect the second charging power lines 314p and 314n, respectively. The first charging relays 295Ap and 295An may also be called the first charging relays. The second charging relays 295Bp and 295Bn may also be called the second charging relays.

[0022] Battery management circuit 25A manages one battery 21A. This battery management circuit 25A includes a battery current sensor 251A that detects the input and output current of one battery 21A, and a battery voltage sensor 252A that detects the voltage across the terminals of one battery 21A. The other battery management circuit 25B manages the other battery 21B. This battery management circuit 25B includes a battery current sensor 251B that detects the input and output current of the other battery 21B, and a battery voltage sensor 252B that detects the voltage across the terminals of the other battery 21B.

[0023] The motor control circuit 22 includes an inverter 221 that drives the electric motor 3, an inverter current sensor 222 that detects the input current of the inverter 221, an inverter voltage sensor 223 that detects the input voltage of the inverter 221 (i.e., the voltage between input terminals tp1 and tn1), and an inverter control circuit 224 that controls the inverter 221. The inverter control circuit 224 is an ECU that executes a control program and communicates with the vehicle control circuit 6.

[0024] The charging control circuit 293 (see Figure 1) has a communication circuit 294 that communicates with the charging equipment 500, and sends commands related to charging to the charging equipment 500 through this communication. The charging equipment 500 transmits the charging power output from the charging device 501 to the charging connector 291 via the charging cable 502 and the power supply connector 503. The charging control circuit 293 can receive the value of the output voltage VC of the charging device 501 from the charging equipment 500 through the above communication.

[0025] The control circuit 28 (see Figure 2) is an ECU that executes a control program stored in the storage device 28a. The storage device 28a is, for example, a non-volatile memory. The control circuit 28 communicates with and cooperates with other ECUs. The control circuit 28 manages the power line 31 and the charging cable 502. Specifically, the control circuit 28 measures the resistance of the power line 31 and the resistance of the charging cable 502 and diagnoses whether there is an abnormality or deterioration. Furthermore, the control circuit 28 has a function to limit the charging power according to the resistance value, and a function to adjust the magnitude of the charging power according to the resistance value. If the resistance is small, the amount of heat generated can be suppressed even if a large current is passed, so it is possible to set it to transmit a large amount of power.

[0026] In this embodiment, a configuration is shown that includes a dedicated control circuit 28 for managing the power lines 31. However, the control circuit 28 may be integrated into, for example, the vehicle control circuit 6, or into another ECU. Furthermore, the control circuit 28 may include multiple ECUs, and the processing of the control circuit 28 may be realized by the cooperation of multiple ECUs.

[0027] <Resistance Measurement Process> In the power supply system 20 of this embodiment, the control circuit 28 measures the resistance of the power line that transmits charging power based on the output voltage VC of the charging device 501 received from the charging equipment 500 and the voltage and current values ​​measured at each part of the power line 31. The resistance of the power line includes the resistance of the charging cable 502 located outside the vehicle. With this configuration, the control circuit 28 can accurately estimate the amount of heat generated by the charging cable 502 during charging. Therefore, even if there are individual differences in the resistance of the charging cable 502, it is possible to perform appropriate charging processing that brings out the capabilities of each individual charging cable 502. Furthermore, the control circuit 28 can detect abnormalities in the charging cable 502 that increase its resistance.

[0028] Next, an example of the resistance measurement procedure will be described. The resistance measurement procedure includes a first resistance measurement procedure that measures the total resistance "R1 + R2" of the first charging power lines 313p, 313n and the second charging power lines 314p, 314n, and a second resistance measurement procedure that measures the resistance of each part, including the resistance of the external charging cable 502 extending from the charging equipment 500. In the following, even if the control circuit 28 receives measured values ​​or information via communication with other ECUs, and even if the control circuit 28 performs operational control such as relay switching via communication with other ECUs, mention of the involvement of other ECUs will be omitted.

[0029] Figure 4 is a flowchart showing the procedure for the first resistance measurement process according to an embodiment of the present invention. The control circuit 28 starts the resistance measurement process when a system shutdown request occurs for the electric vehicle 1. A shutdown request is a request to switch the main relays 26Ap to 26Bn to the open state and to shut down each ECU, for example, when the electric vehicle 1 is stopped and the user turns off the power button or the ignition key.

[0030] When a pause request is received and the resistance measurement process begins, the control circuit 28 determines whether the potential difference between the two batteries 21A and 21B is below a threshold (step S1). This threshold is set to a value such that an abnormally large current does not flow even when the two batteries 21A and 21B are connected in parallel.

[0031] If the result of the determination in step S1 is YES, the control circuit 28 proceeds with the resistance value measurement process. On the other hand, if it is NO, the control circuit 28 does not perform the resistance value measurement process and notifies the vehicle control circuit 6, which then performs the normal pause transition process (step S2). The electric vehicle 1 then transitions to the pause state.

[0032] If the determination result in step S1 is YES and the resistance measurement process proceeds, the control circuit 28 outputs a full ON command to close all of the two charging relays 295Ap to 295Bn. Furthermore, the control circuit 28 outputs a command to open the first main relay 26Ap and 26An and close the second main relay 26Bp and 26Bn (step S3). Then, the control circuit 28 causes the two battery management circuits 25A and 25B and the motor control circuit 22 to measure the current and voltage (step S4).

[0033] By switching the relay in step S3, the two batteries 21A and 21B and the inverter 221 are connected in parallel via the first charging power lines 313p and 313n, the second charging power lines 314p and 314n, and the second power lines 312p and 312n. As a result, current flows between the two batteries 21A and 21B, between one battery 21A and the inverter 221, and between the other battery 21B and the inverter 221.

[0034] Then, in step S4, the combined current of the three currents is measured at three locations. Furthermore, in step S4, the control circuit 28 calculates the difference between the voltages measured at the three locations. As a result, the control circuit 28 determines the voltage applied to the first charging power lines 313p, 313n and the second charging power lines 314p, 314n, the voltage applied to the first charging power lines 313p, 313n, the second charging power lines 314p, 314n and the second power lines 312p, 312n, and the voltage applied to the second power lines 312p, 312n. Here, the voltage applied to the power lines means the sum of the voltage across both ends of the anode-side power line and the voltage across both ends of the cathode-side power line. Then, the control circuit 28 derives a system of equations based on the superposition theorem from the above current and voltage, and solves these equations to calculate the total resistance value "R1 + R2" of the first charging power lines 313p, 313n and the second charging power lines 314p, 314n, and the resistance values ​​of the second power lines 312p, 312n (step S5).

[0035] Next, the control circuit 28 outputs a full-on command to close both of the two charging relays 295Ap to 295Bn. Furthermore, the control circuit 28 outputs a command to close the first main relay 26Ap and 26An and to open the second main relay 26Bp and 26Bn (step S6). Then, the control circuit 28 causes the two battery management circuits 25A and 25B and the motor control circuit 22 to measure the current and voltage (step S7).

[0036] By switching the relay in step S6, the two batteries 21A and 21B and the inverter 221 are connected in parallel via the first charging power lines 313p and 313n, the second charging power lines 314p and 314n, and the first power lines 311p and 311n. As a result, current flows between the two batteries 21A and 21B, current flows between one battery 21A and the inverter 221, and further current flows between the other battery 21A and the inverter 221.

[0037] Then, in step S7, the combined current of the three currents is measured at three locations. Furthermore, in step S7, the control circuit 28 calculates the difference between the voltages measured at the three locations. As a result, the control circuit 28 determines the voltage applied to the first charging power lines 313p, 313n and the second charging power lines 314p, 314n, the voltage applied to the first charging power lines 313p, 313n and the second charging power lines 314p, 314n and the first power line 311p, 311n, and the voltage applied to the first power line 311p, 311n. Here, the voltage applied to the power line means the sum of the voltage across both ends of the anode-side power line and the voltage across both ends of the cathode-side power line. Then, the control circuit 28 derives a system of equations based on the superposition theorem from the above current and voltage, and solves these equations to calculate the total resistance value "R1 + R2" (corresponding to the first resistance value) of the first charging power lines 313p, 313n and the second charging power lines 314p, 314n, and the resistance values ​​of the first power lines 311p, 311n (step S8). Note that steps S6 to S8 may be omitted.

[0038] Once the resistance values ​​of the first charging power lines 313p, 313n and the second charging power lines 314p, 314n, the resistance values ​​of the first power lines 311p, 311n, and the resistance values ​​of the second power lines 312p, 312n have been calculated, the control circuit 28 stores the resistance values ​​of each section in the storage device 28a based on these values ​​(step S9).

[0039] Then, the control circuit 28 notifies the vehicle control circuit 6, which then performs the normal pause transition process (step S10), and the electric vehicle 1 transitions to the pause state.

[0040] Figures 5 and 6 are flowcharts illustrating the procedure for the second resistance measurement process. The second resistance measurement process is initiated during DC charging via the charging connector 291. Once the process begins, the control circuit 28 first determines whether the State of Charge (SOC) of one of the batteries 21A is below a first threshold requiring charging (step S21). If the result is YES, the control circuit 28 closes the first charging relays 295Ap and 295An, leaves the second charging relays 295Bp and 295Bn open, and requests charging power from the charging equipment 500 to begin charging one of the batteries 21A (step S22).

[0041] Next, the control circuit 28 acquires the output voltage VC of the charging device 501 during the charging process, and further measures the input voltage V1 and charging current i1 of the battery 21A during charging (step S23). Based on the acquired and measured values ​​from step S23, the control circuit 28 calculates the total resistance value "Rc + R1" (corresponding to the second resistance value) of the charging cable 502 and the first charging power lines 313p and 313n (step S24). Next, the control circuit 28 waits for the SOC of the battery 21A to reach the charging completion value (step S25). Once the charging completion value is reached, the control circuit 28 switches the charging relays 295Ap and 295An to the open state, ending the charging of one of the batteries 21A (step S26).

[0042] Then, when charging of one battery 21A is completed, the control circuit 28 determines whether the SOC of the other battery 21B is equal to or higher than a second threshold value indicating that the battery is fully charged (step S27). As a result, if the determination is NO, the control circuit 28 keeps charging relays 295Bp and 295Bn of the second system in a closed state, keeps charging relays 295Ap and 295An of the first system in an open state, and requests charging power from the charging facility 500, thereby starting charging of the other battery 21B (step S28).

[0043] Subsequently, during the above charging, the control circuit 28 acquires the value of the output voltage VC of the charging device 501, and further measures the input voltage V2 and charging current i2 of the battery 21B being charged (step S29). Then, based on the acquired value and measured value in step S28, the control circuit 28 calculates the total resistance value "Rc+R2" (corresponding to a third resistance value) of the charging cable 502 and the second charging power lines 314p and 314n (step S30). Subsequently, the control circuit 28 waits until the SOC of the battery 21B reaches a charging end value (step S31). Then, when the SOC reaches the charging end value, the control circuit 28 switches the charging relays 295Bp and 295Bn to an open state, and ends the charging of the other battery 21B (step S32).

[0044] Subsequently, when the charging of the other battery 21B is completed, the control circuit 28 determines whether the SOC of the one battery 21A is equal to or higher than the second threshold value indicating that the battery is fully charged (step S33). As a result, if the determination is NO, the control circuit 28 executes the processing from step S22.

[0045] After charging the two batteries 21A and 21B, the control circuit 28 performs the determination process in step S26 or step S31. If the determination result is YES, the process proceeds to the next step. The control circuit 28 then uses the resistance values ​​"Rc + R1" (corresponding to the second resistance value) and "Rc + R2" (corresponding to the third resistance value) calculated in steps S24 and S30, and the total resistance value "R1 + R2" (corresponding to the first resistance value) of the first charging power lines 313p and 313n and the second charging power lines 314p and 314n, calculated in the first resistance value measurement process, as a system of simultaneous equations. The control circuit 28 then solves these equations to calculate the value of resistance R1 of the first charging power lines 313p and 313n, the value of resistance R2 of the second charging power lines 314p and 314n, and the value of resistance Rc of the charging cable 502 (step S34).

[0046] Once the values ​​of resistors R1, R2, and Rc are calculated, the control circuit 28 learns the values ​​of resistors R1, R2, and Rc based on these values ​​and stores the learned values ​​in the memory device 28a (step S35). The values ​​to be stored may be the calculated values ​​themselves. Alternatively, the values ​​to be stored may be values ​​that have undergone a learning process to reduce measurement errors, based on the values ​​of resistors R1, R2, and Rc that have been calculated and stored at multiple timings in the past, and the current values. This learning process may include statistical processing to reduce measurement errors. In step S35, it was explained that the memory device 28a learns and stores the values ​​of resistors R1, R2, and Rc, but these resistance values ​​may also be learned and stored by each ECU that performs control using these resistance values. For example, the value of resistor R1 may be learned and stored by the battery management circuit 25A. The value of resistor R2 may be learned and stored by the battery management circuit 25B. The value of resistor Rc may be learned and stored by the charging control circuit 293. Alternatively, as mentioned above, a configuration in which these multiple ECUs operate in cooperation with each other may be considered as the control circuit 28.

[0047] Subsequently, the control circuit 28 determines whether the resistance Rc of the charging cable 502 is equal to or greater than a threshold value indicating an abnormality as a cable (step S36). If the determination result is YES, the control circuit sets a power limit such that the charging power is reduced during the next charging from the charging facility 500, and sends a notification prompting an inspection to an administrator of the charging facility 500 (e.g., a management company, etc.) (step S37). On the other hand, if the determination result in step S36 is NO, the control circuit sets power such that charging is performed with a larger charging power corresponding to the lower resistance Rc during the next charging from the charging facility 500 (step S38).

[0048] When charging using the charging facility 500 is performed, the charging control circuit 293 receives identification information for identifying each individual charging facility 500, and stores the identification information. Therefore, the control circuit 28 associates the identification information of the charging facility 500 with information on the magnitude of the charging power set in step S37 or S38, and notifies the charging control circuit 293 of the information. Thereby, when charging is performed next time at the charging facility 500, the charging control circuit 293 can control the charging power requested from the charging facility 500 based on the information on the magnitude described above.

[0049] Next, the control circuit 28 determines whether the resistance R1 of the first charging power lines 313p and 313n is equal to or greater than a threshold value indicating an abnormality as a power line (step S39). If the determination result is YES, the control circuit sets a power limit such that the charging power supplied to one battery 21A is reduced during the next charging, and sends a notification prompting an inspection to an administrator of the electric vehicle 1 (e.g., a user) (step S40). On the other hand, if the determination result in step S39 is NO, the control circuit sets power such that charging is performed with a larger charging power corresponding to the lower resistance R1 during the next charging of the battery 21A (step S41).

[0050] Next, the control circuit 28 determines whether the resistance R2 of the second charging power lines 314p and 314n is above a threshold indicating an abnormality in the power lines (step S42). If the result is YES, the control circuit sets a power limit so that the charging power sent to one of the batteries 21A is reduced during the next charging cycle, and also notifies the manager of the electric vehicle 1 (e.g., the user) to perform an inspection (step S43). On the other hand, if the result of the determination in step S42 is NO, the control circuit 28 sets the power so that the next time battery 21B is charged, it is charged with a large charging power corresponding to the low resistance R2 (step S44). Then, the second resistance value measurement process is completed.

[0051] The program for the first resistance measurement process and the program for the second resistance measurement process are stored in a non-transient storage medium, such as the storage device 28a of the control circuit 28. The control circuit 28 may be configured to read a program stored in a portable non-transient recording medium and execute the program. The portable non-transient storage medium may store the program for the first resistance measurement process or the program for the second resistance measurement process described above.

[0052] <Advantages of Resistance Measurement> Figure 7 illustrates the resistance values ​​of the first charging power lines obtained by the second resistance value calculation process. The vertical axis of the bar graph in Figure 7 shows the resistance R1 values ​​of the first charging power lines 313p and 313n. The horizontal axis shows the worst values ​​such as the specification values ​​and the measured values ​​for each of the three identical electric vehicles 1, "Vehicle A" to "Vehicle C".

[0053] As shown in Figure 7, the measured resistance R1 of the first charging power lines 313p and 313n is lower than the worst-case value such as the specification value (resistance R1 of "Vehicle A" to "Vehicle C"). Furthermore, even with the same type of electric vehicle 1, the resistance R1 may vary from one electric vehicle 1 to another ("Vehicle A" to "Vehicle C"). Therefore, by actually measuring, the control circuit 28 can grasp the value of the resistance R1 of the first charging power lines 313p and 313n with little error. On the other hand, if the resistance R1 is not measured, the charging control circuit 293 will apply the worst-case value as the value of resistance R1. In this case, due to errors A to C between the actual value of resistance R1 and the measured value, when managing the heat generation and temperature of the first charging power lines 313p and 313n, the estimated heat generation and temperature will be larger than the actual case. Therefore, even if the charging power can be set higher within a range where the heat generation or temperature does not become abnormal, the charging power will be limited with an excessive safety margin.

[0054] On the other hand, by using the value of resistance R1 measured for each individual electric vehicle, it becomes possible to estimate the amount of heat generated and the temperature with less error. Therefore, if the charging power can be increased within a range where the amount of heat generated or the temperature does not become abnormal, the safety margin can be reduced, and as a result, the appropriate charging capacity can be achieved.

[0055] The advantages described above can be similarly obtained for the resistance R2 of the second charging power lines 314p and 314n by measuring the resistance R2. Furthermore, in multiple charging facilities, there may be variations in the resistance Rc of individual charging cables 502. Even in such cases, by measuring the resistance Rc of each individual charging cable 502, a small safety margin corresponding to the resistance value of each charging cable 502 can be applied, thereby enabling the appropriate charging capacity to be achieved.

[0056] As described above, according to the power supply system 20 of the electric vehicle 1 of this embodiment, the control circuit 28 measures the resistance Rc of the charging cable 502 of the charging equipment 500 located outside the vehicle. Therefore, even if there is variation in the resistance values ​​of individual charging cables 502 in multiple charging equipment 500, the control circuit 28 can determine the resistance Rc value of each individual charging cable 502. Thus, as mentioned above, a small safety margin corresponding to the resistance value of each individual charging cable 502 can be applied as a safety margin when adjusting the magnitude of the charging power, thereby enabling the vehicle to exhibit appropriate charging capacity. Furthermore, the power supply system 20 can diagnose abnormalities or deterioration of the charging cable 502 based on the measured resistance Rc value.

[0057] Furthermore, according to the power supply system 20 of the electric vehicle 1 of this embodiment, the control circuit 28 obtains the output voltage VC of the charging device 501 through communication with the charging equipment 500 via the communication circuit 294. In addition, the control circuit 28 measures the voltage and current of batteries 21A and 21B. Then, the control circuit 28 calculates the resistance value of the charging cable 502 from these acquired and measured values. Thus, it is possible to obtain the resistance value of the charging cable 502 by reusing the existing sensor and the existing communication circuit 294.

[0058] Furthermore, various methods may be applied to calculate the resistance value of the charging cable 502. For example, the power supply system 20 may have a voltage sensor that measures the terminal voltage of the charging connector 291 and a current sensor that measures the input current from the charging connector 291. The control circuit 28 may then calculate the voltage across both ends of the charging cable 502 from the terminal voltage and the output voltage VC of the charging device 501 obtained through the above-mentioned communication. Furthermore, the resistance Rc of the charging cable 502 may be calculated based on this voltage and the above-mentioned input current. In addition, the power supply system 20 may have a voltage sensor or current sensor that measures at one or more locations of the power line 31 in the electric vehicle 1, and the control circuit 28 may calculate the resistance value of the charging cable 502 by combining the measured values ​​of these voltage sensors or current sensors. The voltage sensor or current sensor may be a configuration that utilizes existing sensors, or it may be a configuration that is specifically provided for resistance measurement.

[0059] Furthermore, according to the power supply system 20 of the electric vehicle 1 of this embodiment, the control circuit 28 notifies the respective administrators of an abnormality if the resistance values ​​of the charging cable 502, the first charging power lines 313p and 313n, and the second charging power lines 314p and 314n exceed a threshold indicating an abnormality. Therefore, if the resistance values ​​become high due to abnormality or deterioration, these can be repaired early.

[0060] Furthermore, the power supply system 20 of the electric vehicle 1 of this embodiment includes batteries 21A and 21B arranged in parallel as batteries, first charging power lines 313p, 313n, and second charging power lines 314p, 314n. The control circuit 28 connects the two batteries 21A and 21B in parallel by closing two sets of charging relays 295Ap, 295An, 295Bp, and 295Bn, and allows current to flow between them. The control circuit 28 then uses this current to calculate the value of the total resistance "R1 + R2" of the first charging power lines 313p, 313n and the second charging power lines 314p, 314n. Thus, by utilizing existing sensors provided in the power supply system 20 having the two batteries 21A and 21B, the control circuit 28 can determine the value of the above resistance "R1 + R2" (referred to as the "first resistance value"). The control circuit 28 can then use this value to calculate the resistance value of the charging cable 502.

[0061] Furthermore, the control circuit 28 obtains the measured values ​​of voltage V1 and current i1 of the battery management circuit 25A measured when one battery 21A is being charged, and the measured values ​​of voltage V2 and current i2 of the battery management circuit 25B measured when the other battery 21B is being charged. From these, the control circuit 28 can calculate the value of the total resistance "R1 + Rc" (referred to as the "second resistance value") of the charging cable 502 and the first charging power lines 313p and 313n. Furthermore, the control circuit 28 can calculate the value of the total resistance "R2 + Rc" (referred to as the "third resistance value") of the charging cable 502 and the second charging power lines 314p and 314n. The control circuit 28 can then use the first to third resistance values ​​to calculate the value of the resistance Rc of the charging cable 502, the value of the resistance R1 of the first charging power lines 313p and 313n, and the value of the resistance R2 of the second charging power lines 314p and 314n. Thus, the control circuit 28 can use existing sensors in the power supply system 20, which has two batteries 21A and 21B, to obtain the values ​​of the three resistances R1, R2, and Rc that are involved in adjusting and managing the magnitude of the charging power.

[0062] Embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. For example, in the above embodiment, an example was shown in which the power supply system 20 has two batteries 21A and 21B, but it may also be configured to have one battery. Alternatively, in the above embodiment, a configuration was shown in which the power supply system 20 drives one electric motor 3, but it may also be configured to drive two electric motors. Furthermore, in the above embodiment, a specific example was shown of calculating the resistance value of the charging cable 502 in a configuration of a power line 31 having two batteries 21A and 21B and driving one electric motor 3, but the calculation of the resistance value can be achieved using various methods. For example, if the number of batteries and the number of electric motors to be driven are different, the connection configuration of the power line 31 will be different. And it is conceivable that the locations of the voltage and current that need to be determined in order to calculate the resistance value of the charging cable 502 or the resistance value of the charging power line will differ depending on the connection configuration of the power line 31. However, in such cases, it is sufficient to measure the voltage and current by providing voltage sensors and current sensors at the above locations. With this configuration, the control circuit 28 can calculate the above-mentioned resistance value based on the measured voltage and current values. Further details shown in the embodiment can be modified as appropriate without departing from the spirit of the invention.

[0063] This invention can be used in power supply systems for electric vehicles.

[0064] 1 Electric vehicle 2 Drive wheels 3 Electric motor 20 Power supply system 21A, 21B Battery 25A, 25B Battery management circuit 28 Control circuit 28a Memory device 31 Power line 291 Charging connector 291p Anode terminal 291n Cathode terminal 293 Charging control circuit 294 Communication circuit 295Ap, 295An, 295Bp, 295Bn Charging relay 313p, 313n First charging power line 314p, 314n Second charging power line 500 Charging equipment 501 Charging device 502 Charging cable 503 Power supply connector R1, R2, Rc Resistor VC Output voltage

Claims

1. A power supply system for an electric vehicle comprising: a battery for storing power for driving; a charging connector for receiving charging power from charging equipment outside the vehicle body; and a control circuit, wherein the charging equipment is configured to transmit charging power output from a charging device to the charging connector via a charging cable, and the control circuit measures the resistance value of the charging cable.

2. A power supply system for an electric vehicle according to claim 1, comprising: a charging power line connecting the battery and the charging connector; a communication circuit for communicating with the charging equipment; and a battery management circuit for measuring the voltage and current of the battery, wherein the control circuit obtains the output voltage value of the charging device by communicating with the charging equipment via the communication circuit, and the control circuit calculates the resistance value of the charging cable and the resistance value of the charging power line using the output voltage value and the measurement result of the battery management circuit.

3. The power supply system for an electric vehicle according to claim 1, wherein the control circuit performs a process to notify the administrator of an abnormality when the resistance value exceeds a threshold.

4. The power supply system for an electric vehicle according to claim 2, wherein the battery includes a first battery and a second battery, the battery management circuit includes a first battery management circuit for measuring the voltage and current of the first battery and a second battery management circuit for measuring the voltage and current of the second battery, the charging power line includes a first charging power line connecting the first battery and the charging connector and a second charging power line connecting the second battery and the charging connector, and further comprises a first charging relay capable of disconnecting the first charging power line and a second charging relay capable of disconnecting the second charging power line, the control circuit closes both the first charging relay and the second charging relay, receives the measurement results of the current and voltage of the first battery management circuit and the measurement results of the current and voltage of the second battery management circuit, and uses the measurement results to calculate a first total resistance value of the first charging power line and the second charging power line.

5. The power supply system for an electric vehicle according to claim 4, wherein the control circuit calculates a second total resistance value of the charging cable and the first charging power line based on the measurement result of the first battery management circuit obtained when the first battery is being charged and the output voltage value of the charging device, calculates a third total resistance value of the charging cable and the second charging power line based on the measurement result of the second battery management circuit obtained when the second battery is being charged and the output voltage value, and calculates the resistance value of the charging cable based on the first resistance value, the second resistance value and the third resistance value.

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