Electric vehicle

Abstract

An electric vehicle (10, 120) includes: a power storage pack (15, 80, 90, 100, 110) provided with a cell group (22) including a plurality of power storage cells (21); an electric heater (30, 81) connected in parallel to at least a part of the cell group; a switch (32) provided between the cell group and the electric heater; a charging inlet (17, 124) connected to the power storage pack via an energization line; and a control system (50) provided with a processor and a memory communicably connected to each other. When charging connectors (20, 125) extending from external power sources (18, 127) are connected to the charging inlet and the temperature of the power storage pack is lower than a threshold value, the control system executes heater energization control for controlling the switch into an ON state and supplying power from the power storage pack to the electric heater.

Description

Electric vehicle

[0001] The present disclosure relates to an electric vehicle.

[0002] Electric vehicles and plug-in hybrid vehicles include a battery pack formed of a lithium ion battery or the like, that is, an electricity storage pack (see Patent Documents 1 to 4). Further, as a method for charging the electricity storage pack using an external power source, there are a charging method using an external charger installed outside the vehicle, and a charging method using an on-board charger mounted inside the vehicle.

[0003] Japanese Patent Application Laid-Open No. 2022-81897, Japanese Patent Application Laid-Open No. 2021-34271, Japanese Patent Application Laid-Open No. 2012-252907, Japanese Patent Application Laid-Open No. 2023-32426

[0004] By the way, since the internal resistance of the electricity storage pack increases as the temperature decreases, it is necessary to warm the electricity storage pack to efficiently charge the electricity storage pack in a low-temperature environment.

[0005] According to the present disclosure, the electric vehicle includes: an electricity storage pack including a cell group formed of a plurality of electricity storage cells; an electric heater connected in parallel to at least a part of the cell group; a switch provided between the cell group and the electric heater; a charging inlet connected to the electricity storage pack via a current-carrying line; and a control system including a processor and a memory communicably connected to each other. The control system, when a charging connector extending from an external power source is connected to the charging inlet and the temperature of the electricity storage pack is lower than a threshold value, controls the switch to an on state to execute heater energization control that supplies electric power from the electricity storage pack to the electric heater.

[0006] According to the present disclosure, not only can the electricity storage pack be warmed by the electric heater, but also the electricity storage pack can be warmed by self-heating accompanying discharge of the electricity storage pack.

[0007] Figure 1 shows an electric vehicle which is one embodiment of the present disclosure. Figure 2 shows an example of a battery pack and its peripheral equipment included in an electric vehicle. Figure 3 shows an example of the basic structure of an electronic control unit. Figure 4 is a flowchart showing an example of the execution procedure for battery charging control. Figure 5 is a flowchart showing an example of the execution procedure for flag setting control which is performed in parallel with battery charging control. Figure 6 shows the execution status of heater energization control. Figure 7 shows the execution status of external charging control. Figure 8 is a timing chart showing an example of the execution status of battery charging control. Figure 9 shows a battery pack of Modification 1 included in an electric vehicle. Figure 10 shows a battery pack of Modification 1 included in an electric vehicle. Figure 11A shows a battery pack of Modification 2. Figure 11B shows a battery pack of Modification 3. Figure 11C shows a battery pack of Modification 4. Figure 12 shows an example of a battery pack and its peripheral equipment included in an electric vehicle of Modification 5.

[0008] Embodiments of this disclosure will be described in detail below with reference to the drawings. In the following description, identical or substantially identical components and elements will be denoted by the same reference numerals, and repeated descriptions will be omitted.

[0009] <Electric Vehicle> Figure 1 is a diagram showing an electric vehicle 10 which is one embodiment of the present disclosure. As shown in Figure 1, the electric vehicle 10 has an electric axle 13 consisting of an electric motor 11 and a differential mechanism 12. The electric vehicle 10 also has a battery pack (energy storage pack) 15 connected to the electric motor 11 via an inverter 14, and a charging inlet 17 connected to the battery pack 15 via power lines 16p and 16n. The battery pack 15 mounted on the electric vehicle 10 can be charged using an external power source 18, which is a commercial power source, i.e., external charging. When performing this external charging, a charging connector 20 extending from an external charger 19 installed outside the vehicle is connected to the charging inlet 17. When the charging connector 20 is connected to the charging inlet 17 in this way, the external charger 19 converts the AC power from the external power source 18 into DC power, and the external charger 19 supplies DC power to the battery pack 15.

[0010] <Battery Pack> Figure 2 shows an example of a battery pack 15 and its peripheral equipment provided in an electric vehicle 10. As shown in Figure 2, the battery pack 15 has a cell group 22 consisting of a plurality of battery cells (energy storage cells) 21. The positive electrode 22p of the cell group 22 is connected to the positive terminal 15p via the positive electrode line 23p, and the negative electrode 22n of the cell group 22 is connected to the negative terminal 15n via the negative electrode line 23n. The battery pack 15 also has a main relay 24 provided on the positive electrode line 23p and a main relay 25 provided on the negative electrode line 23n. The battery pack 15 shown has one cell group 22, but is not limited to this, and may have multiple cell groups connected in series with each other, or multiple cell groups connected in parallel with each other.

[0011] The battery pack 15 has an electric heater 30, such as a film heater, connected in parallel to the cell group 22. This electric heater 30 is located near the cell group 22. The positive electrode 30p of the electric heater 30 is connected to the positive electrode line 23p via the positive electrode line 31p, and the negative electrode 30n of the electric heater 30 is connected to the negative electrode line 23n via the negative electrode line 31n. In other words, the positive electrode 30p of the electric heater 30 is connected to the positive electrode terminal (positive electrode) 15p via the positive electrode lines 23p and 31p, and the negative electrode 30n of the electric heater 30 is connected to the negative electrode terminal (negative electrode) 15n via the negative electrode lines 23n and 31n. The battery pack 15 also has a heater switch (switch) 32 provided on the positive electrode line 31p. In other words, the heater switch 32 is provided between the cell group 22 and the electric heater 30. Furthermore, the battery pack 15 includes a battery sensor 33 for detecting charge / discharge current and terminal voltage, and a temperature sensor 34 for detecting the temperature of the cell group 22.

[0012] A battery control unit 40, which is an electronic control unit, is connected to the battery pack 15. The battery control unit 40 has the function of monitoring the charging and discharging of the battery pack 15 and controlling the main relays 24 and 25 and the heater switch 32. The battery control unit 40 also has the function of calculating the State of Charge (SOC) of the battery pack 15 based on the charging and discharging current and terminal voltage of the battery pack 15. The SOC of the battery pack 15 is a value that indicates the remaining amount of stored energy in the battery pack 15, and is the ratio of the amount of stored energy to the full charge capacity of the battery pack 15. For example, when the battery pack 15 is charged to its upper limit capacity, the SOC is calculated as 100%, and when the battery pack 15 is discharged to its lower limit capacity, the SOC is calculated as 0%.

[0013] <Charging Inlet> As shown in Figure 2, the battery pack 15 and the inverter 14 are connected to each other via power lines 41p and 41n. A power line 16p extending from the charging inlet 17 is connected to power line 41p, and a power line 16n extending from the charging inlet 17 is connected to power line 41n. In other words, the charging inlet 17 is connected to the battery pack 15 via power lines 16p, 16n, 41p, and 41n. The charging inlet 17 has a positive terminal 17p connected to power line 16p, a negative terminal 17n connected to power line 16n, and a communication terminal 17s connected to the charging control unit 42. The charging connector 20 connected to the charging inlet 17 has a positive terminal 20p that can be connected to the positive terminal 17p, a negative terminal 20n that can be connected to the negative terminal 17n, and a communication terminal 20s that can be connected to the communication terminal 17s.

[0014] As mentioned above, the communication terminal 17s of the charging inlet 17 is connected to the charging control unit 42, which is an electronic control unit. In other words, when the charging connector 20 is connected to the charging inlet 17, the external charger 19 and the charging control unit 42 are connected in a way that allows them to communicate with each other. The charging control unit 42 then transmits signals such as the target charging voltage and target charging current to the controller 19a of the external charger 19, and controls the DC power supplied from the external charger 19 to the battery pack 15.

[0015] <Control System> As shown in Figure 2, the electric vehicle 10 has a control system 50 consisting of a plurality of electronic control units. The electronic control units that make up the control system 50 include the battery control unit 40 and the charging control unit 42 mentioned above. In addition, the vehicle control unit 51 that outputs control signals to each of the aforementioned control units 40 and 42 is also an electronic control unit that makes up the control system 50. These control units 40, 42 and 51 are connected to each other so as to be able to communicate with one another via an in-vehicle network 52.

[0016] The electric vehicle 10 has a select lever 53 operated by the driver when switching the driving range, and a power switch 54 operated by the driver when switching the power mode of the control system 50. The select lever 53 and the power switch 54 are communicated to the vehicle control unit 51. The vehicle control unit 51 sets the operating targets for the battery pack 15 and the external charger 19 based on input signals from the various control units 40, 42, the select lever 53, and the power switch 54. The vehicle control unit 51 also generates control signals according to the operating targets for the battery pack 15 and the external charger 19, and outputs these control signals to the battery control unit 40 and the charging control unit 42.

[0017] Figure 3 shows an example of the basic structure of electronic control units 40, 42, and 51. As shown in Figure 3, the electronic control units 40, 42, and 51 have a microcontroller 72 into which a processor 70 and main memory (memory) 71 are incorporated. A predetermined program is stored in the main memory 71, and the program is executed by the processor 70. The processor 70 and the main memory 71 are connected to each other so as to be able to communicate with each other. Note that the microcontroller 72 may incorporate multiple processors 70, and the microcontroller 72 may also incorporate multiple main memory 71.

[0018] The electronic control units 40, 42, and 51 each include an input circuit 73, a drive circuit 74, a communication circuit 75, an external memory 76, and a power supply circuit 77. The input circuit 73 converts signals input from various sensors into signals that can be input to the microcontroller 72. The drive circuit 74 generates drive signals for devices such as the main relays 24 and 25 and the heater switch 32 based on signals output from the microcontroller 72. The communication circuit 75 converts signals output from the microcontroller 72 into communication signals destined for other electronic control units, etc. The communication circuit 75 also converts communication signals received from other electronic control units, etc., into signals that can be input to the microcontroller 72. Furthermore, the power supply circuit 77 supplies power voltage to the microcontroller 72, the input circuit 73, the drive circuit 74, the communication circuit 75, and the external memory 76, etc. The external memory 76, which consists of non-volatile memory, stores programs and various data.

[0019] <Battery Charging Control: Flowchart> The following describes the battery charging control for performing external charging. Figure 4 is a flowchart of an example of the execution procedure for battery charging control. Figure 5 is a flowchart of an example of the execution procedure for flag setting control, which is performed in parallel with battery charging control. Note that each step described in the flowcharts of Figures 4 and 5 is a step performed by the processor 70 that constitutes the control system 50.

[0020] As indicated by the symbol α in Figure 4, battery charging control is initiated in conjunction with a charging operation performed by an operator. Here, a charging operation performed by an operator refers to an operation performed on the electric vehicle 10 in order to perform external charging. For example, a charging operation performed by an operator may include operating the select lever to set the electric vehicle 10 to the parking range, operating the power switch to set the power mode of the control system 50 to the off mode, and connecting the charging connector 20 to the charging inlet 17. The off mode of the control system 50 is the power mode set when stopping the starting of the electric vehicle 10, and is a power mode in which external charging of the battery pack 15 is permitted.

[0021] As described above, when the electric vehicle 10 is set to the parking range, the power mode of the control system 50 is set to the off mode, and the charging connector 20 is connected to the charging inlet 17, the control system 50 proceeds to step S10 and starts charging preparation control. In step S10, the control system 50 establishes bidirectional data communication with the external charger 19 and transmits charging parameters such as the maximum charging voltage and maximum charging current to the external charger 19. After executing the charging preparation control in step S10, the control system 50 proceeds to step S11 and determines whether the temperature of the cell group 22, i.e., the battery pack 15 (hereinafter referred to as battery temperature), detected by the temperature sensor 34, falls below the threshold T1.

[0022] If the control system 50 determines in step S11 that the battery temperature is below the threshold T1, it proceeds to step S12 to determine whether the State of Charge (SOC) of the battery pack 15 is above the threshold S1. If the control system 50 determines in step S12 that the SOC is above the threshold S1, it proceeds to step S13 to determine whether the normal flag FL, described later, is set. Here, the normal flag FL is a flag that is set when data communication between the control system 50 and the external charger 19 is normal and no error signals related to external charging are emitted from the electric vehicle 10 and the external charger 19. In other words, the situation in which the normal flag FL is set is a situation in which external charging using the external power supply 18 is possible and it is possible to transition to external charging control normally.

[0023] Next, the flag setting control for setting the normal flag FL will be described. The control system 50 performs flag setting control in parallel with battery charging control after data communication with the external charger 19 is established. As shown in Figure 5, the control system 50 proceeds to step S20 and determines whether the data communication between the control system 50 and the external charger 19 is normal. In step S20, the control system 50 sends a communication test request signal to the external charger 19 and determines that bidirectional data communication is normal when it receives a communication test response signal from the external charger 19.

[0024] If the control system 50 determines in step S20 that data communication is normal, it proceeds to step S21 and determines the reception status of error signals that may be transmitted from the electric vehicle 10 and the external charger 19. The charging control unit 42 and battery control unit 40 of the electric vehicle 10 periodically perform checks for open circuits in the charging path and welding of various contacts, and if an abnormality such as an open circuit is detected, it transmits an error signal to the vehicle control unit 51. Similarly, the external charger 19 connected to the electric vehicle 10 periodically performs checks for open circuits in the charging path and welding of various contacts, and if an abnormality such as an open circuit is detected, it transmits an error signal to the control system 50.

[0025] If the control system 50 determines in step S21 that it has not received an error signal, it proceeds to step S22 and sets the normal flag FL. In other words, if the control system 50 determines that bidirectional data communication is normal and that it has not received an error signal, it proceeds to step S22 and sets the normal flag FL (FL = 1). On the other hand, if the control system 50 determines in step S20 that data communication is abnormal, or if it determines in step S21 that it has received an error signal, it proceeds to step S23 and clears the normal flag FL (FL = 0). Thus, the flag setting control for setting the normal flag FL corresponds to the charging determination control that determines whether or not external charging using the external power supply 18 is possible. In other words, the situation in which the normal flag FL is set by the flag setting control is a situation in which it is determined that external charging using the external power supply 18 is possible.

[0026] As shown in Figure 4, when the control system 50 determines in step S13 that the normal flag FL is set, it proceeds to step S14 and executes heater energization control to supply power from the cell group 22 of the battery pack 15 to the electric heater 30. In this way, when the battery temperature falls below the threshold T1, that is, when the internal resistance of the battery pack 15 is high, the control system 50 executes heater energization control to raise the battery temperature using the electric heater 30 before starting external charging, from the viewpoint of lowering the internal resistance of the battery pack 15 and improving charging efficiency. In other words, when the battery temperature falls below the threshold T1, the SOC is above the threshold S1, and the normal flag FL is set, the control system 50 executes heater energization control to discharge the battery pack 15 and generate heat in the electric heater 30.

[0027] When the control system 50 starts heater power supply control in step S14, it returns to step S11 and determines whether all the execution conditions for heater power supply control are met. In other words, if the control system 50 determines, after going through steps S11 to S13, that the battery temperature is below the threshold T1, the SOC is above the threshold S1, and the normal flag FL is set, it proceeds to step S14 and executes heater power supply control. On the other hand, if the control system 50 determines in steps S11 and S12 that the execution conditions are not met, it proceeds to step S15 and stops the heater power supply control and executes external charging control to charge the battery pack 15. Also, if the control system 50 determines in step S13 that the execution conditions are not met, it stops the heater power supply control and exits the routine.

[0028] In other words, if the control system 50 determines in step S11 that the battery temperature is above the threshold T1, it proceeds to step S15, stopping the heater power control and executing external charging control, because the battery temperature has risen due to the heater power control. Also, if the control system 50 determines in step S12 that the SOC is below the threshold S1, it proceeds to step S15, stopping the heater power control and executing external charging control, because it is difficult to continue the heater power control that involves discharging the battery pack 15. Furthermore, if the control system 50 determines in step S13 that the normal flag FL has been cleared, it stops the heater power control and exits the routine, because it is difficult to transition from heater power control to external charging control.

[0029] When the control system 50 performs heater power supply control, a situation may occur where external charging control is not started for a predetermined period of time while the charging connector 20 is connected to the charging inlet 17. This situation, where external charging control is not started for a predetermined period of time, can cause the external charger 19 to mistakenly determine that some kind of abnormality has occurred. Therefore, the control system 50 performs heater power supply control and simultaneously sends a standby signal to the external charger 19 to prevent the external charger 19 from making an incorrect abnormality determination. In other words, the external charger 19 is designed to stop determining abnormalities while it is receiving the standby signal.

[0030] <Heater Power Supply Control and External Charging Control> Figure 6 shows the status of heater power supply control. As shown in Figure 6, when the control system 50 performs heater power supply control, it controls the main relays 24 and 25 to the off state (open) and the heater switch 32 to the on state (connected). As a result, as indicated by arrow P1 in Figure 6, power is supplied from the cell group 22 to the electric heater 30, so the electric heater 30 can be controlled to a heating state, and the electric heater 30 can warm the cell group 22, i.e., the battery pack 15. Furthermore, because power is supplied from the cell group 22 to the electric heater 30, the cell group 22, i.e., the battery pack 15 can be warmed by self-heating due to the discharge of the cell group 22.

[0031] Figure 7 shows the execution status of external charging control. As shown in Figure 7, when the control system 50 executes external charging control, it controls the main relays 24 and 25 to the ON state (connected) and the heater switch 32 to the OFF state (open). As a result, as indicated by arrow P2 in Figure 7, DC power from the external charger 19 can be supplied to the cell group 22 of the battery pack 15, and the cell group 22 of the battery pack 15 can be charged. Even when this external charging control is executed in a low-temperature environment, the aforementioned heater energization control is executed before external charging, which raises the battery temperature and lowers the internal resistance of the battery pack 15, thereby increasing the charging efficiency during external charging and shortening the charging time.

[0032] Furthermore, as shown in Figure 6, in heater power control, power is supplied from the battery pack 15 to the electric heater 30. This allows the electric heater 30 to warm the battery pack 15, as well as the battery pack 15 to warm itself through self-heating caused by discharge. In other words, the electric heater 30 warms the cell group 22 from the outside, and the self-heating caused by discharge warms the cell group 22 from the inside, allowing the temperature of the battery pack 15 to rise rapidly.

[0033] This allows the battery temperature to rise quickly during heater power control, thus shortening the execution time of heater power control and enabling a rapid transition to external charging control. Furthermore, if the battery cells 21 are composed of lithium-ion batteries, the execution of heater power control allows the battery pack 15 to be discharged with a large current, which is expected to eliminate dendrites that cause battery degradation.

[0034] <Battery Charging Control: Timing Chart> Next, the aforementioned battery charging control will be explained using a timing chart. Figure 8 is a timing chart showing an example of the execution status of battery charging control. As shown in Figure 8, at time t11, the operator performs a charging operation such as connecting the charging connector 20 to the charging inlet 17. At time t11, the control system 50 performs charging preparation control such as establishing data communication with the external charger 19 (reference numeral a1), and terminates the charging preparation control at time t12. Furthermore, when data communication is established upon the start of charging preparation control, the control system 50 performs flag setting control to set the normal flag FL (reference numeral b1).

[0035] At time t12, when the charge preparation control is completed, the control system 50 executes heater energization control to discharge the battery pack 15 and generate heat in the electric heater 30 because the battery temperature has fallen below threshold T1 (code c1), the SOC has risen above threshold S1 (code d1), and the normal flag FL is set (code e1). As this heater energization control is executed, the battery temperature gradually rises (code c2), and the SOC of the battery pack 15 gradually decreases (code f1). Then, at time t13, the control system 50 stops the heater energization control (code f2) and executes external charge control (code g1) because the battery temperature has reached threshold T1 or higher (code c3).

[0036] <Summary> As explained above, the control system 50 controls the heater switch 32 to the ON state and performs heater power supply control to supply power from the battery pack 15 to the electric heater 30 when the charging connector 20 extending from the external power supply 18 is connected to the charging inlet 17 and the temperature of the battery pack 15 falls below the threshold T1. In other words, when performing external charging of the battery pack 15 in a low-temperature environment, the external charging control is not started immediately, but rather the heater power supply control is performed to warm up the battery pack 15 first, and then the external charging control is performed to supply power from the external power supply 18 to the battery pack 15. This makes it possible to increase the charging efficiency of the battery pack 15 even in a low-temperature environment and shorten the charging time of the battery pack 15.

[0037] Furthermore, in heater power control, power is supplied from the battery pack 15 to the electric heater 30. This allows the electric heater 30 to warm the battery pack 15, as well as the battery pack 15 to warm itself through self-heating caused by discharge. In other words, the electric heater 30 warms the cell group 22 from the outside, while the self-heating from discharge warms the cell group 22 from the inside, allowing the temperature of the battery pack 15 to rise rapidly.

[0038] In the example shown in Figure 4, the control system 50 executes heater power supply control when it determines that the battery temperature is below threshold T1, the SOC is above threshold S1, and the normal flag FL is set, but it is not limited to this. For example, the control system 50 may execute heater power supply control when it determines that the charging connector 20 extending from the external power supply 18 is connected to the charging inlet 17 and the battery temperature is below threshold T1. Alternatively, the control system 50 may execute heater power supply control when it determines that the charging connector 20 extending from the external power supply 18 is connected to the charging inlet 17, the battery temperature is below threshold T1, and the SOC is above threshold S1. Alternatively, the control system 50 may execute heater power supply control when it determines that the charging connector 20 extending from the external power supply 18 is connected to the charging inlet 17, the battery temperature is below threshold T1, and the normal flag FL is set.

[0039] In the example shown in Figure 4, when the battery temperature exceeds the threshold T1 due to heater power supply control, the control system 50 controls the heater switch 32 to the off state to stop the heater power supply control and performs external charging control, supplying power to the battery pack 15 from the external power supply 18. In other words, the control system 50 stops the heater power supply control and performs external charging control when the temperature of the battery pack 15 exceeds the threshold T1 due to the execution of heater power supply control, but is not limited to this. For example, the control system 50 may stop the heater power supply control and perform external charging control when the temperature of the battery pack 15 exceeds a threshold higher than the threshold T1 due to the execution of heater power supply control.

[0040] <Modification 1> In the example shown in Figure 2, one electric heater 30 is connected in parallel to the cell group 22, but this is not the only option, and multiple electric heaters 30 may be connected in parallel to the cell group 22. Here, Figures 9 and 10 show the battery pack 80 of Modification 1 provided in the electric vehicle 10. Figure 9 shows the execution status of heater power supply control, and Figure 10 shows the execution status of external power supply control.

[0041] As shown in Figure 9, the battery pack (energy storage pack) 80 has an electric heater 81 connected in parallel to the cell group 22. The electric heater 81 comprises a first heater section 82 connected in parallel to a part of the cell group 22, and a second heater section 83 connected in parallel to a part of the cell group 22. The positive electrode 82p of the first heater section 82 is connected to the positive terminal (positive electrode) 80p of the battery pack 80 via positive electrode lines 84p and 23p. The negative electrode 82n of the first heater section 82 is connected to a potential point 85 with a different potential from the negative terminal (negative electrode) 80n of the battery pack 80 via a current line 84n. The positive electrode 83p of the second heater section 83 is connected to a potential point 85 with a different potential from the positive terminal 80p of the battery pack 80 via a current line 86p. The negative electrode 83n of the second heater unit 83 is connected to the negative electrode terminal 80n of the battery pack 80 via negative electrode lines 86n and 23n.

[0042] The battery pack 80 includes a heater switch 32 provided on the positive electrode line 84p, a discharge switch 87 provided on the current line 84n, and a discharge switch 88 provided on the current line 86p. The discharge switch 87 includes a discharge contact 87a connected to the potential point 85 and a normal contact 87b that is away from the potential point 85. Similarly, the discharge switch 88 includes a discharge contact 88a connected to the potential point 85 and a normal contact 88b that is away from the potential point 85. The discharge switches 87 and 88 are operable to a discharge position in which the movable contacts 87c and 88c are connected to the discharge contacts 87a and 88a, and a normal position in which the movable contacts 87c and 88c are connected to the normal contacts 87b and 88b. The normal contacts 87b and 88b of the discharge switches 87 and 88 are connected to each other.

[0043] As shown in Fig. 9, when executing the heater energization control described above, the control system 50 controls the main relays 24 and 25 to an on state, controls the heater switch 32 to an on state, and controls the discharge switches 87 and 88 to a discharge position. At this time, the control system 50 transmits a target charging voltage slightly higher than the terminal voltage of the battery pack 80 to the external charger 19. Accordingly, as indicated by an arrow Pa3 in Fig. 9, power is supplied from a part of the cell group 22 to the first heater unit 82, and as indicated by an arrow Pb3, power is supplied from a part of the cell group 22 to the second heater unit 83. Further, as indicated by an arrow Pc3, power can be supplied from the external charger 19 to the battery pack 80 with a small current.

[0044] Accordingly, the first heater unit 82 and the second heater unit 83 can be controlled to a heat-generating state, and the cell group 22, that is, the battery pack 80 can be warmed by the electric heater 81. Furthermore, since power is supplied from the cell group 22 to the first heater unit 82 and the second heater unit 83, the cell group 22, that is, the battery pack 80 can be warmed by self-heating caused by discharge of the cell group 22. Furthermore, current can be continuously supplied from the external charger 19 to the battery pack 80 even during execution of the heater energization control. Accordingly, even if the specifications of the external charger 19 are such that abnormality determination is performed based on charging stoppage over a predetermined period of time, abnormality determination of the external charger 19 caused by the heater energization control can be prevented.

[0045] Next, as shown in Fig. 10, when executing the external charging control described above, the control system 50 controls the main relays 24 and 25 to an on state, controls the heater switch 32 to an off state, and controls the discharge switches 87 and 88 to a normal position. Accordingly, as indicated by an arrow P4 in Fig. 10, DC power from the external charger 19 can be supplied to the cell group 22 of the battery pack 80, and the cell group 22 of the battery pack 80 can be charged. Even when this external charging control is executed in a low-temperature environment, the heater energization control described above is executed before external charging, so the temperature of the battery pack 80 can be increased to lower the internal resistance, and charging efficiency during external charging can be improved to shorten the charging time.

[0046] <Modifications 2, 3, 4> In the example shown in FIG. 2, the positive electrode 30p of the electric heater 30 is connected to the positive electrode terminal 15p of the battery pack 15, and the negative electrode 30n of the electric heater 30 is connected to the negative electrode terminal 15n of the battery pack 15; however, the present invention is not limited thereto. That is, although the electric heater 30 shown in FIG. 2 is configured to be connected in parallel to the entire cell group 22, the configuration is not limited thereto, and the electric heater 30 may be configured to be connected in parallel to a part of the cell group 22. Here, FIG. 11A is a diagram showing a battery pack 90 of Modification 2, FIG. 11B is a diagram showing a battery pack 100 of Modification 3, and FIG. 11C is a diagram showing a battery pack 110 of Modification 3.

[0047] As shown in FIG. 11A, the battery pack 90 includes the electric heater 30 connected in parallel to the cell group 22. The positive electrode 30p of the electric heater 30 is connected to a positive electrode terminal (positive electrode) 90p of the battery pack 90 via positive lines 91p and 23p. The negative electrode 30n of the electric heater 30 is connected via a negative line 91n to a potential point 92 having a different potential from that of a negative electrode terminal (negative electrode) 90n of the battery pack 90. As described above, the electric heater 30 may be configured to be connected in parallel to a part of the cell group 22.

[0048] As shown in FIG. 11B, the battery pack 100 includes the electric heater 30 connected in parallel to the cell group 22. The positive electrode 30p of the electric heater 30 is connected via a positive line 101p to a potential point 102 having a different potential from that of a positive electrode terminal (positive electrode) 100p of the battery pack 100. The negative electrode 30n of the electric heater 30 is connected to a negative electrode terminal (negative electrode) 100n of the battery pack 100 via negative lines 101n and 23n. As described above, the electric heater 30 may be configured to be connected in parallel to a part of the cell group 22.

[0049] As shown in Figure 11C, the battery pack 110 has an electric heater 30 connected in parallel to the cell group 22. The positive electrode 30p of the electric heater 30 is connected via a positive electrode line 111p to a potential point 112 that is at a different potential from the positive electrode terminal (positive electrode) 110p of the battery pack 110. The negative electrode 30n of the electric heater 30 is connected via negative electrode lines 111n and 23n to a potential point 113 that is at a different potential from the negative electrode terminal (negative electrode) 110n of the battery pack 110. Thus, the electric heater 30 may be configured to be connected in parallel to a portion of the cell group 22.

[0050] <Modification 5> In the example shown in Figure 2, the configuration uses an external charger 19 installed outside the vehicle for external charging, but it is not limited to this, and the configuration may also use an onboard charger installed inside the vehicle for external charging. Figure 12 shows an example of the battery pack 15 and its peripheral equipment included in the electric vehicle 120 of Modification 5.

[0051] As shown in Figure 12, the electric vehicle 120 has an on-board charger 122 connected to the battery pack 15 via power lines 121p and 121n, and a charging inlet 124 connected to the on-board charger 122 via power lines 123p and 123n. In other words, the charging inlet 124 is connected to the battery pack 15 via power lines 121p, 121n, 123p, 123n and the on-board charger 122.

[0052] The charging inlet 124 has a positive terminal 124p connected to the power line 123p, a negative terminal 124n connected to the power line 123n, and a communication terminal 124s connected to the charging control unit 42. The charging connector 125 connected to the charging inlet 124 has a positive terminal 125p that can be connected to the positive terminal 124p, a negative terminal 125n that can be connected to the negative terminal 124n, and a communication terminal 125s that can be connected to the communication terminal 124s. The charging cable 126 equipped with the charging connector 125 is connected to an external power supply 127, which is a commercial power supply.

[0053] When the charging connector 125 is connected to the charging inlet 124, the onboard charger 122 converts the AC power from the external power supply 127 into DC power, and the onboard charger 122 supplies DC power to the battery pack 15. In other words, the charging control unit 42, which is communicatively connected to the onboard charger 122, outputs drive signals to the onboard charger 122 according to the target charging voltage and target charging current, and controls the DC power supplied from the onboard charger 122 to the battery pack 15.

[0054] Thus, even when external charging is performed using the on-board charger 122, the control system 50 controls the heater switch 32 to the ON state and performs heater power supply control to supply power from the battery pack 15 to the electric heater 30 when the charging connector 125 extending from the external power supply 127 is connected to the charging inlet 124 and the temperature of the battery pack 15 falls below the threshold T1. In other words, when performing external charging of the battery pack 15 in a low-temperature environment, the external charging control is not started immediately, but rather the heater power supply control is performed to warm up the battery pack 15 first, and then the external charging control is performed to supply power from the external power supply 127 to the battery pack 15. This makes it possible to increase the charging efficiency of the battery pack 15 even in a low-temperature environment and shorten the charging time of the battery pack 15.

[0055] Furthermore, in heater power control, power is supplied from the battery pack 15 to the electric heater 30. This allows the electric heater 30 to warm the battery pack 15, as well as the battery pack 15 to warm itself through self-heating caused by discharge. In other words, the electric heater 30 warms the cell group 22 from the outside, while the self-heating from discharge warms the cell group 22 from the inside, allowing the temperature of the battery pack 15 to rise rapidly.

[0056] In the above description, the control system 50 performs heater power supply control when the charging connector 125 extending from the external power supply 127 is connected to the charging inlet 124 and the temperature of the battery pack 15 is below the threshold T1, but it is not limited to this. For example, the control system 50 may perform heater power supply control when the charging connector 125 extending from the external power supply 127 is connected to the charging inlet 124, the battery temperature is below the threshold T1, and the SOC is above the threshold S1. Alternatively, the control system 50 may perform heater power supply control when the charging connector 125 extending from the external power supply 127 is connected to the charging inlet 124, the battery temperature is below the threshold T1, and the normal flag FL is set.

[0057] Furthermore, the control system 50 may perform heater energization control when it determines that the charging connector 125 extending from the external power supply 127 is connected to the charging inlet 124, the battery temperature is below threshold T1, the SOC is above threshold S1, and the normal flag FL is set. In the case of an electric vehicle 120 that performs external charging using the onboard charger 122, the vehicle control unit 51 performs flag setting control to set the normal flag FL while communicating with the charging control unit 42. In other words, the vehicle control unit 51 sets the normal flag FL when data communication within the control system 50 is normal and no error signals related to external charging are emitted from the electric vehicle 120.

[0058] <Other Modifications> This disclosure is not limited to the embodiments described above, and it goes without saying that various modifications are possible without departing from the spirit of the invention. The illustrated electric vehicles 10 and 120 are electric vehicles equipped with an electric motor 11 as a power source, but are not limited to this, and may be hybrid vehicles equipped with an electric motor and an engine as power sources. In the examples shown in Figures 7 and 10, the control system 50 controls the heater switch 32 to the off state when performing external charging control, but is not limited to this. For example, if the battery temperature falls below a threshold during the execution of external charging control, the heater switch 32 may be controlled to the on state to heat the electric heater 30 using power from the external charger 19 or the onboard charger 122. Also, in the illustrated example, the heater switch 32 is provided on the positive terminal side of the electric heater 30, but is not limited to this, and the heater switch 32 may be provided on the negative terminal side of the electric heater 30.

[0059] In the illustrated example, electric heaters 30, 81 and a heater switch 32 are incorporated into battery packs 15, 80, 90, 100, and 110, but the invention is not limited to this. For example, the electric heaters 30, 81 may be provided outside the housing that forms the outer shell of the battery packs 15, 80, 90, 100, and 110, and the heater switch 32 may be provided outside the housing that forms the outer shell of the battery packs 15, 80, 90, 100, and 110. In the above description, film heaters consisting of an insulating sheet and a resistive heating element are used as electric heaters 30, 81, but the invention is not limited to this, and any electric heater that generates heat when energized may be used.

[0060] In the above description, State of Charge (SOC) is used as the value indicating the remaining charge of battery packs 15, 80, 90, 100, and 110, but it is not limited to this, and energy [kWh] may be used as the value indicating the remaining charge of battery packs 15, 80, 90, 100, and 110. In the above description, lithium-ion batteries are given as an example of battery cells 21 constituting the cell group 22, but it is not limited to this, and battery cells made of other batteries such as nickel-metal hydride batteries may be used. Furthermore, capacitor cells made of capacitors may be used as energy storage cells constituting the cell group 22.

[0061] 10...Electric vehicle, 15...Battery pack (energy storage pack), 15p...Positive terminal (positive), 15n...Negative terminal (negative), 16p, 16n...Power lines, 17...Charging inlet, 18...External power supply, 20...Charging connector, 21...Battery cell (energy storage cell), 22...Cell group, 22p...Positive, 22n...Negative, 30...Electric heater, 30p...Positive, 30n...Negative, 32...Heater switch (switch), 41p, 41n...Power lines, 50...Control system, 70...Processor, 71...Main memory (memory), 80...Battery pack (energy storage pack), 80p...Positive terminal (positive), 80n...Negative terminal (negative), 81...Electric heater, 82...First heater section, 82 p...positive electrode, 82n...negative electrode, 83...second heater section, 83p...positive electrode, 83n...negative electrode, 85...potential point, 90...battery pack (energy storage pack), 90p...positive electrode terminal (positive electrode), 90n...negative electrode terminal (negative electrode), 92...potential point, 100...battery pack (energy storage pack), 100p...positive electrode terminal (positive electrode), 100n...negative electrode terminal (negative electrode), 102...potential point, 110...battery pack (energy storage pack), 110p...positive electrode terminal (positive electrode), 110n...negative electrode terminal (negative electrode), 112, 113...potential point, 120...electric vehicle, 121p, 121n, 123p, 123n...power lines, 124...charging inlet, 125...charging connector, 127...external power supply, T1...threshold, S1...threshold

Claims

1. An electric vehicle comprising: a battery pack having a group of multiple energy storage cells; an electric heater connected in parallel to at least a portion of the group of cells; a switch provided between the group of cells and the electric heater; a charging inlet connected to the battery pack via a power supply line; and a control system comprising a processor and memory connected to each other in a manner that enables communication, wherein the control system performs heater power supply control by controlling the switch to an ON state to supply power from the battery pack to the electric heater when a charging connector extending from an external power source is connected to the charging inlet and the temperature of the battery pack falls below a threshold.

2. An electric vehicle according to claim 1, wherein the control system controls the switch to an off state to stop the heater power supply control when the temperature of the energy storage pack exceeds a threshold due to the execution of the heater power supply control, and executes external charging control to supply power to the energy storage pack from an external power source.

3. An electric vehicle according to claim 1, wherein the control system performs the heater energization control when a charging connector extending from the external power supply is connected to the charging inlet, the temperature of the energy storage pack falls below a threshold, and the remaining energy stored in the energy storage pack exceeds a threshold.

4. An electric vehicle according to claim 1, wherein the control system performs heater energization control when a charging connector extending from the external power supply is connected to the charging inlet, the temperature of the energy storage pack falls below a threshold, and it is determined that external charging using the external power supply is possible.

5. An electric vehicle according to claim 1, wherein the positive electrode of the electric heater is connected to the positive electrode of the energy storage pack, and the negative electrode of the electric heater is connected to the negative electrode of the energy storage pack.

6. An electric vehicle according to claim 1, wherein the positive electrode of the electric heater is connected to the positive electrode of the energy storage pack, and the negative electrode of the electric heater is connected to a potential point with a potential different from that of the negative electrode of the energy storage pack.

7. An electric vehicle according to claim 1, wherein the positive electrode of the electric heater is connected to a potential point with a potential different from that of the positive electrode of the energy storage pack, and the negative electrode of the electric heater is connected to the negative electrode of the energy storage pack.

8. An electric vehicle according to claim 1, wherein the positive electrode of the electric heater is connected to a potential point with a different potential from the positive electrode of the energy storage pack, and the negative electrode of the electric heater is connected to a potential point with a different potential from the negative electrode of the energy storage pack.

9. An electric vehicle according to claim 1, wherein the electric heater comprises a first heater section and a second heater section, the positive electrode of the first heater section is connected to the positive electrode of the energy storage pack, the negative electrode of the first heater section is connected to a potential point with a different potential from the negative electrode of the energy storage pack, the positive electrode of the second heater section is connected to a potential point with a different potential from the positive electrode of the energy storage pack, and the negative electrode of the second heater section is connected to the negative electrode of the energy storage pack.

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