Charging system, and vehicle

Abstract

To reduce charging time.SOLUTION: A charging system comprises: a power storage device including a first battery and a second battery; and a controller that performs charging control of the power storage device. The power storage device is executable of series charging being charging in a state in which the first battery and the second battery are connected in series, and parallel charging being charging in a state in which the first battery and the second battery are connected in parallel. The controller continues charging of the power storage device by switching a charging system from series charging to parallel charging after voltage of the power storage device during series charging reaches a predetermined value.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a charging system and a vehicle. [Background technology]

[0002] Japanese Patent No. 7006263 (Patent Document 1) discloses a charging system including an electricity storage device including a plurality of batteries and a switching relay, and a control device that controls the switching relay. The switching relay is configured to be switchable between a first state in which the plurality of batteries are connected in series and a second state in which the plurality of batteries are connected in parallel. In this charging system, power for charging is supplied to the electricity storage device from a power source external to the vehicle. When a plug-in operation is performed to charge the electricity storage device, the control device controls the switching relay to the first state. Furthermore, when the maximum charging voltage of the power source is lower than a threshold value, the control device changes the switching relay from the first state to the second state. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7006263 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, when the power storage device is charged in the second state (parallel charging), the power (charging power) received by the power storage device is smaller than when the power storage device is charged in the first state (series charging). For this reason, parallel charging tends to have a longer charging time (time required to complete charging) than series charging. In the charging system described in Patent Document 1, parallel charging is performed when the maximum charging voltage of the power source is lower than a threshold value, which is thought to result in a longer charging time.

[0005] The present disclosure has been made to solve the above-mentioned problems, and has an object to shorten the charging time. [Means for solving the problem]

[0006] A charging system according to an embodiment of the present disclosure includes a power storage device including a first battery and a second battery, and a control device that controls charging of the power storage device. The power storage device is configured to be capable of series charging, which is charging with the first battery and the second battery connected in series, and parallel charging, which is charging with the first battery and the second battery connected in parallel. The control device is configured to switch the charging method from series charging to parallel charging and continue charging of the power storage device after the voltage of the power storage device during series charging reaches a predetermined value.

[0007] According to another aspect of the present disclosure, there is provided a vehicle including the charging system described above. Effect of the Invention

[0008] According to the present disclosure, it is possible to shorten the charging time. [Brief description of the drawings]

[0009] [Figure 1] 1 is a diagram showing a charging system according to an embodiment of the present disclosure. [Diagram 2] 4 is a flowchart illustrating a charging method according to an embodiment of the present disclosure. [Diagram 3] 11 is a diagram showing, in comparison, transitions in state of an electricity storage device charged by the charging methods according to an embodiment and a modification example. FIG. [Figure 4] FIG. 11 is a diagram showing charging data measured for the charging methods according to the embodiment and the modified examples. [Diagram 5] 3 is a flowchart showing a modification of the charging method shown in FIG. 2. [Figure 6] FIG. 2 is a diagram showing a modification of the charging system shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present disclosure will now be described in detail with reference to the accompanying drawings, in which the same or corresponding parts are designated by the same reference characters and will not be described repeatedly.

[0011] FIG. 1 is a diagram illustrating a charging system according to an embodiment of the present disclosure. With reference to FIG. 1, the charging system according to this embodiment includes a vehicle 100 and an EVSE 300. The EVSE 300 receives power supply from a power system PG. EVSE stands for Electric Vehicle Supply Equipment. The power system PG is a power grid constructed by power transmission and distribution equipment. A plurality of power plants (not shown) are connected to the power system PG. The power system PG receives power supply from these power plants. In this embodiment, the power system PG supplies AC power.

[0012] The EVSE 300 incorporates a power supply circuit 310 and includes a charging cable 320. The power supply circuit 310 is electrically connected to the power system PG. The charging cable 320 has a connector 320a (plug) at its tip, and includes a communication line and a power line inside. A single electric wire may serve as both the communication line and the power line. The power supply circuit 310 converts the power supplied from the power system PG into power suitable for supplying power to the vehicle 100, and outputs the converted power to the charging cable 320. The EVSE 300 outputs AC power from the connector 320a.

[0013] The vehicle 100 includes an inlet 60 to which a connector 320a can be attached and detached. When the connector 320a of the charging cable 320 connected to the main body of the EVSE 300 is connected to the inlet 60 of the parked vehicle 100, the vehicle 100 is electrically connected to the power grid PG via the EVSE 300 (hereinafter also referred to as a "plugged-in state"). On the other hand, for example, while the vehicle 100 is traveling, the vehicle 100 is not electrically connected to either the EVSE 300 or the power grid PG (hereinafter also referred to as a "plugged-out state").

[0014] The vehicle 100 further includes a battery 11, a system main relay (SMR) 12, a motor generator (MG) 20, a power control unit (PCU) 22, and an electronic control unit (ECU) 150. The ECU 150 includes a processor 151, a random access memory (RAM) 152, and a storage device 153. The storage device 153 is configured to be able to save stored information. In addition to programs, the storage device 153 stores information used in the programs (e.g., maps, formulas, and various parameters). In this embodiment, the processor 151 executes the programs stored in the storage device 153, thereby executing various controls (e.g., charging control of the battery 11) by the ECU 150. However, these processes may be executed only by hardware (electronic circuits) without using software. The ECU 150 and the battery 11 according to this embodiment correspond to examples of a "control device" and a "power storage device" according to the present disclosure, respectively.

[0015] Vehicle 100 is configured to be capable of running using electric power stored in battery 11. Vehicle 100 is, for example, an electric vehicle (BEV) that does not have an engine (internal combustion engine). However, the vehicle 100 is not limited to this, and may be a PHEV (plug-in hybrid vehicle) that has an internal combustion engine, or another type of electric vehicle (xEV).

[0016] Battery 11 includes a cell B1 (first cell), a cell B2 (second cell), and three relays R1, R2, and R3. In this embodiment, each of cells B1 and B2 is a battery pack. A battery pack is formed by electrically connecting a plurality of secondary cells (generally also referred to as "cells") to each other. The cells in the battery pack are connected in series, for example. However, the connection of the cells in the battery pack is not limited to series and may include parallel connection. Also, each of cells B1 and B2 may be a single secondary battery instead of a battery pack.

[0017] The relay R1 is provided on the wire EL1 connecting the positive electrode of the battery B1 and the positive electrode of the battery B2. The relay R2 is provided on the wire EL2 connecting the positive electrode of the battery B1 and the negative electrode of the battery B2. The relay R3 is provided on the wire EL3 connecting the negative electrode of the battery B1 and the negative electrode of the battery B2. The wires EL1 and EL2 are connected to each other at a node N1. The wires EL2 and EL3 are connected to each other at a node N2. The positive terminal T1 and the negative terminal T2 of the battery 11 are provided on the wires EL1 and EL3, respectively. The relay R1 is located between the positive terminal T1 and the node N1. The relay R3 is located between the negative terminal T2 and the node N2. When the relays R1, R2, and R3 are OFF, ON, and OFF, respectively, the batteries B1 and B2 are connected in series (series state). When relays R1, R2, and R3 are ON, OFF, and ON, respectively, batteries B1 and B2 are connected in parallel (parallel state). Electromagnetic mechanical relays can be used as the switching relays (relays R1, R2, and R3) that switch between the series and parallel states. However, instead of this, semiconductor relays such as thyristors, triacs, and transistors may also be used as the switching relays.

[0018] The battery 11 is provided with a BMS (Battery Management System) 11a that monitors the state of the battery 11, and a temperature adjustment system 11b that adjusts the temperature of the battery 11. The BMS 11a includes various sensors that detect the state of the battery 11 (e.g., voltage, current, and temperature), and a monitoring IC (integrated circuit) to which detection signals from the various sensors are input. The temperature adjustment system 11b includes at least one of a heater and a cooling device. The cooling method may be a water-cooling type or an oil-cooling type. The temperature adjustment system 11b is controlled by the ECU 150.

[0019] In this embodiment, a voltage sensor and a temperature sensor are provided for each cell constituting the battery 11 (battery pack). However, the present invention is not limited to this, and each of the voltage sensor and the temperature sensor may be provided for each of a plurality of cells, or only one for each battery pack. The monitoring IC generates a signal indicating the state of the battery 11 (hereinafter also referred to as a "BMS signal") using detection signals from the various sensors, and outputs the generated BMS signal to the ECU 150. The ECU 150 acquires, for example, the temperature, current, voltage, and SOC (State Of Charge) of the battery 11 based on the BMS signal. The SOC indicates the remaining amount of electricity, and is, for example, the ratio of the current amount of electricity to the amount of electricity in a fully charged state, expressed as 0 to 100%. The monitoring IC may have a function of equalizing cell voltages.

[0020] Vehicle 100 further includes a charger 61 and a charging relay 62. Charger 61 and charging relay 62 are located between inlet 60 and battery 11. Each of charger 61 and charging relay 62 is controlled by ECU 150. In this embodiment, a charging line including inlet 60, charger 61, and charging relay 62 is connected between SMR 12 and PCU 22. However, this is not limited thereto, and a charging line may be connected between battery 11 and SMR 12.

[0021] The charger 61 charges the battery 11 using power input to the inlet 60 from outside the vehicle. The charger 61 includes a power conversion circuit (e.g., an inverter) and is configured to be able to adjust the charging current. The power conversion circuit performs DC (direct current) / AC (alternating current) conversion. The charging relay 62 switches between connection / disconnection of the electrical path from the inlet 60 to the battery 11. The vehicle 100 further includes a detector 61a that monitors the state of the charger 61. The detector 61a includes various sensors (e.g., a current sensor and a voltage sensor) that detect the state of the charger 61, and outputs the detection results to the ECU 150.

[0022] With the vehicle 100 in a plugged-in state, external charging (i.e., charging of the battery 11 with power from outside the vehicle) becomes possible. Power for external charging is supplied to the inlet 60, for example, from the power system PG through a charging cable 320 of the EVSE 300. The charger 61 converts the AC power received by the inlet 60 into DC power suitable for charging the battery 11, and outputs the DC power to the battery 11. When external charging is performed, the charging relay 62 is set to a closed state (connected state), and when external charging is not performed, the charging relay 62 is set to an open state (disconnected state).

[0023] The MG 20 is, for example, a three-phase AC motor generator. The MG 20 functions as a traction motor for the vehicle 100. The MG 20 is driven by the PCU 22 to rotate the drive wheels of the vehicle 100. The MG 20 also performs regenerative power generation and outputs the generated power to the battery 11. The number of traction motors provided in the vehicle 100 is arbitrary.

[0024] The PCU 22 includes a circuit that drives the MG 20 using power supplied from the battery 11. The SMR 12 switches between connection and disconnection of an electric path from the battery 11 to the PCU 22. The PCU 22 includes, for example, an inverter and a converter. The SMR 12 and the PCU 22 are each controlled by the ECU 150. The SMR 12 is set in a closed state (connected state) when the vehicle 100 is traveling. The SMR 12 is also set in a closed state when power is exchanged between the battery 11 and the inlet 60 (and thus, the outside of the vehicle).

[0025] As described above, the battery 11 has a mechanism for switching between series and parallel connections. The battery 11 is configured to be capable of charging the battery 11 in a series state (series charging) and charging the battery 11 in a parallel state (parallel charging). However, in parallel charging, the power (charging power) received by the battery 11 (power storage device) is smaller than in series charging. When charging is performed with the batteries B1 and B2 connected in parallel (parallel charging), the current and voltage of the battery B1 and the current and voltage of the battery B2 are each half compared to when charging is performed with the batteries B1 and B2 connected in series (series charging). The total power received by the batteries B1 and B2 connected in parallel in parallel charging is half the total power received by the batteries B1 and B2 connected in series in series charging. For this reason, parallel charging tends to require a longer charging time (time required to complete charging) than series charging.

[0026] Therefore, the ECU 150 according to this embodiment executes a series of processes shown in FIG. 2, which will be described below, to switch the charging method from series charging to parallel charging and continue charging the battery 11 after the voltage of the battery 11 during series charging reaches a predetermined value.

[0027] FIG. 2 is a flowchart showing a charging method according to this embodiment. In the flowchart, "S" means a step. The process shown in this flowchart is executed by the ECU 150 in the vehicle 100 in a plugged-in state. The process flow shown in FIG. 2 is started when a predetermined charging start condition is satisfied for the vehicle 100. For example, the charging start condition may be satisfied when the vehicle 100 is in a plugged-in state. Alternatively, the charging start condition may be satisfied when the vehicle 100 is in a plugged-in state and a charging start operation is performed by a user on the EVSE 300 or the vehicle 100.

[0028] 2 together with Fig. 1, in S10, ECU 150 acquires equipment information related to EVSE 300 from EVSE 300 (power supply equipment that supplies power to battery 11) connected to vehicle 100. The equipment information includes an equipment upper limit voltage (hereinafter referred to as "Vc") indicating the maximum charging voltage of EVSE 300, and an equipment upper limit current (hereinafter referred to as "Ic") indicating the maximum charging current of EVSE 300. If the charging voltage or charging current of battery 11 exceeds Vc or Ic, EVSE 300 cannot charge battery 11.

[0029] In the next step S11, the ECU 150 sets the battery 11 in a series state by turning relays R1, R2, and R3 OFF, respectively, and transmits a charging command for series charging to the charger 61. The charger 61 that receives the charging command controls the charging current of the battery 11 so that the charging current of the battery 11 approaches the target charging current value indicated by the charging command. In this way, external charging of the battery 11 is performed. The ECU 150 determines a target charging current value equal to or less than Ic, and after increasing the charging current of the battery 11 to the target charging current value, performs constant current charging at the target charging current value. In this embodiment, Ic is the target charging current value.

[0030] As described above, when a predetermined charging start condition is satisfied while the EVSE 300 (power supply equipment outside the vehicle) and the vehicle 100 are electrically connected to each other, the ECU 150 starts series charging of the battery 11 using power supplied from the EVSE 300 (S11). However, when a predetermined charging end condition is satisfied in S11, the process flow shown in FIG. 2 ends. The charging end condition is satisfied, for example, when the amount of stored power in the battery 11 reaches a target value. The target value may be set automatically by the ECU 150 or the EVSE 300, or may be set by a user. The state of the battery 11 (for example, voltage and SOC) is measured by the BMS 11a. Also, the charging end condition may be satisfied in response to, for example, an instruction to stop charging from a user. When the charging end condition is satisfied during series charging, the process flow shown in FIG. 2 ends without switching to parallel charging (S18).

[0031] In the next S12, the ECU 150 measures the voltage (hereinafter referred to as "Vs") of the battery 11 during series charging. Specifically, the ECU 150 calculates Vs using the no-load voltage, charging current, and internal resistance of each of the batteries B1 and B2. The no-load voltage is generally also referred to as "OCV (open circuit voltage)". The ECU 150 may obtain the internal resistance of each of the batteries B1 and B2 from the SOC and temperature of the batteries B1 and B2 measured by the BMS 11a using a map stored in advance in the storage device 153. The ECU 150 may calculate the no-load voltage, charging current, and internal resistance of the battery 11 from the no-load voltage, charging current, and internal resistance of each of the batteries B1 and B2. The charging current of the battery 11 obtained here corresponds to the current (hereinafter referred to as "Is") of the battery 11 during series charging. The ECU 150 may calculate Vs according to the formula "Vs = no-load voltage + Is × internal resistance" for the battery 11. According to this method, it becomes easier to calculate the voltage of the battery 11 during series charging with high accuracy.

[0032] In the next step S13, the ECU 150 determines whether Vs is equal to or greater than Vc. If Vs is less than Vc (NO in S13), the process returns to S11, and series charging continues. The voltage (Vs) of the battery 11 increases due to series charging (S11). Then, when Vs reaches Vc (YES in S13), the process proceeds to S14.

[0033] In S14, the ECU 150 transmits a current suppression command to the charger 61 to reduce the charging current of the battery 11. The current suppression command indicates a target charging current value that makes the voltage (Vs) of the battery 11 equal to Vc. The charger 61 that has received the current suppression command controls the charging current of the battery 11 so that the voltage (Vs) of the battery 11 is maintained at Vc while reducing the charging current of the battery 11. This allows series charging to continue. However, the control method for series charging switches from constant current charging to constant voltage charging.

[0034] In S15, the ECU 150 measures the charging power (hereinafter, referred to as "Ws") of the battery 11 during series charging. The ECU 150 obtains Ws based on the state of the battery 11 measured by the BMS 11a. The ECU 150 may calculate Ws according to the formula "Ws = Vc × (Vc - no-load voltage) / internal resistance" for the EVSE 300 and the battery 11.

[0035] Next, in S16, the ECU 150 predicts the charging power (hereinafter, referred to as "Wp") of the battery 11 when the charging method is switched from series charging to parallel charging. The ECU 150 obtains Wp by using Ic, for example. The ECU 150 may calculate Wp according to a formula related to the EVSE 300 and the battery 11, "Wp = (2 x no-load voltage + Ic x internal resistance) x Ic / 4." Wp corresponds to an example of "parallel charging power" according to the present disclosure.

[0036] Next, in S17, the ECU 150 determines whether or not Ws has become equal to or less than a reference value determined based on Wp. In this embodiment, the reference value is set to a value (=Wp+Wx) obtained by adding a predetermined margin (hereinafter, referred to as "Wx") to Wp. Wx can be set arbitrarily. Wx may be a power value greater than 0, or may be 0.

[0037] If Ws is greater than the reference value (NO in S17), the process returns to S14 and series charging continues. The power (Ws) of the battery 11 is reduced by the current suppression command (S14). Then, when Ws reaches the reference value (YES in S17), the process proceeds to S18.

[0038] In S18, the ECU 150 switches the charging method from series charging to parallel charging and continues charging the battery 11. Specifically, the ECU 150 sets the battery 11 in a parallel state by turning the relays R1, R2, and R3 ON, OFF, and ON, respectively, and transmits a charging command for parallel charging to the charger 61. The charger 61 that receives the charging command controls the charging current of the battery 11 so that the charging current of the battery 11 approaches the target charging current value indicated by the charging command. In this way, the parallel charging of the battery 11 is performed. The ECU 150 determines a target charging current value equal to or less than Ic / 2, reduces the charging current of the battery 11 to the target charging current value, and then performs constant current charging at the target charging current value. In this embodiment, Ic / 2 (a value obtained by dividing Ic by 2) is set as the target charging current value. The parallel charging started in S18 may be continued until a predetermined charging end condition is satisfied.

[0039] Fig. 3 is a diagram showing a comparison of state transitions of battery 11 charged by charging methods according to the embodiment and the modified example. The charging method according to the embodiment corresponds to the charging method described above and shown in Fig. 2. The charging method according to the modified example is a method in which the charging method is switched from series charging to parallel charging at the timing when the voltage of battery 11 during series charging reaches a predetermined value (e.g., Vc). In either method, the charging method is switched from series charging to parallel charging after the voltage of battery 11 during series charging reaches a predetermined value (e.g., Vc).

[0040] In FIG. 3, lines L1, L2, L3, and L4 respectively indicate the charging current, the load voltage, the no-load voltage, and the charging power of the battery 11. B " indicates the voltage (battery upper limit voltage) of the battery 11 when the battery 11 is fully charged in series by series charging control (S11) without current suppression (S14). BIf the charging voltage Vc is higher than 10 V, series charging (fast charging) can be continued until charging is completed. Period T10 indicates the period from when the voltage of battery 11 during series charging reaches a predetermined value (e.g., Vc) to when the charging method of battery 11 is switched to parallel charging. Period T10 corresponds to an example of a "switching determination period" according to the present disclosure. In period T10, the charging power is greater in the charging method according to the embodiment than in the charging method according to the modified example. Therefore, the amount of charging power in the charging method according to the embodiment is greater than the amount of charging power in the charging method according to the modified example by the amount of power dW shown in FIG. 3.

[0041] Fig. 4 is a diagram showing charging data measured in relation to the charging method according to the embodiment and the modification. In Fig. 4, lines L11, L12, L14, L15, L31, and L32 respectively indicate the SOC, charging current, maximum cell temperature, minimum cell temperature, voltage, and power of the battery 11 in the charging method according to the embodiment. Lines L21, L22, L24, L25, L41, and L42 respectively indicate the SOC, charging current, maximum cell temperature, minimum cell temperature, voltage, and power of the battery 11 in the charging method according to the modification. Lines L13 and L23 each indicate the maximum charging current (equipment upper limit current) of the power supply facility that supplies power to the battery 11. Lines L51 and L52 respectively indicate the maximum charging voltage (equipment upper limit voltage) and maximum charging power (equipment upper limit power) of the power supply facility.

[0042] In the example shown in Fig. 4, the battery 11 was charged until the SOC of the battery 11 reached approximately 15% to approximately 80%. When the maximum cell temperature (the temperature of the cell with the highest temperature in the battery 11) reached 50°C or higher during charging of the battery 11, the temperature adjustment system 11b cooled the battery 11 using the power supplied from the power supply facility (e.g., the EVSE 300). From the obtained data, it was confirmed that the charging method according to the embodiment had a shorter charging time than the charging method according to the modified example. In one example of the data, the charging time until the SOC of the battery 11 reached 78% from 15% was shorter by 0.3 minutes with the charging method according to the embodiment.

[0043] As described above, the charging method according to this embodiment includes the processes shown in Fig. 2. In the charging system according to this embodiment, the ECU 150 (control device) is configured to switch the charging method from series charging to parallel charging and continue charging the battery 11 after the voltage of the battery 11 during series charging reaches a predetermined value.

[0044] According to series charging, the battery 11 can be charged with a larger charging power than in parallel charging. The larger the charging power, the higher the charging speed. However, as the charging of the battery 11 progresses, the amount of stored electricity in the battery 11 increases, and the no-load voltage of the battery 11 increases. The voltage of the battery 11 during series charging is a value obtained by adding the voltage increase (IR) due to the charging current to the no-load voltage. If the voltage of the battery 11 during series charging becomes too high, charging may not be able to be continued depending on the specifications of the equipment that supplies power to the battery 11. On the other hand, while the voltage of the battery 11 during series charging is low, the charging speed of the battery 11 can be increased by continuing the series charging. Therefore, in the above charging system, the series charging of the battery 11 is continued while the voltage of the battery 11 during series charging does not reach a predetermined value. This shortens the charging time (the time required to complete charging). Then, after the voltage of the battery 11 during series charging reaches a predetermined value, the charging method is switched from series charging to parallel charging. By switching the charging method from series charging to parallel charging, the voltage of the battery 11 drops. This makes it possible to prevent the voltage of the battery 11 from becoming too high while the battery 11 is being charged.

[0045] Due to the evolution of standards in recent years, the voltage of in-vehicle batteries and power supply equipment is becoming higher. However, at present, low-voltage power supply equipment still remains. In this regard, according to the charging system described above, by switching the battery 11, which becomes high-voltage when connected in series, to a parallel connection during charging, it becomes possible to charge the battery 11 not only with high-voltage equipment but also with low-voltage equipment (old-fashioned or home power supply equipment).

[0046] In the above embodiment, the ECU 150 reduces the charging current of the battery 11 during series charging during a switching determination period (e.g., period T10 shown in FIG. 3) from when the voltage of the battery 11 during series charging reaches a predetermined value until the charging method of the battery 11 is switched to parallel charging. By reducing the current of the battery 11 during series charging in this manner, a voltage rise due to the charging current is suppressed. In the charging system according to the above embodiment, such current control prevents the voltage of the battery 11 from becoming too high during series charging of the battery 11. This makes it easier to lengthen the period during which series charging of the battery 11 continues (switching determination period).

[0047] In the charging method according to the embodiment, after the voltage of the battery 11 during series charging becomes equal to or higher than a predetermined value, the charging method of the battery 11 is switched from series charging to parallel charging at the timing when the charging power of the battery 11 during series charging becomes equal to or lower than a reference value determined based on Wp (parallel charging power). According to such a method, the charging time shortening effect is large (see FIG. 3 and FIG. 4). Specifically, in the period T10 (FIG. 3), the series charging of the battery 11 is executed, and the current of the battery 11 decreases during the series charging. Then, the charging power decreases with the decrease in the charging current. If the series charging of the battery 11 is continued even after the charging power of the battery 11 becomes small, eventually a larger charging power can be obtained by switching to parallel charging than by continuing the series charging. If the series charging of the battery 11 is continued until such a situation is reached, the charging time of the battery 11 will rather be longer. Therefore, in the charging system according to this embodiment, the ECU 150 predicts the charging power (Wp) when the charging method is switched to parallel charging, and switches the charging method to parallel charging according to the predicted charging power. This makes it possible to switch the charging method to parallel charging at the appropriate time.

[0048] In the above embodiment, Vc is used as the predetermined value (the voltage value at which the charging method is switched). Then, the ECU 150 controls the current of the battery 11 during the period T10 (FIG. 3) so that the voltage of the battery 11 coincides with the equipment upper limit voltage (Vc). During the period T10 (switching determination period), the charging power decreases with a decrease in the charging current, but by maintaining the voltage of the battery 11 high, the decrease in the charging power of the battery 11 is suppressed. However, the above predetermined value can be changed as appropriate. A voltage value that is lower than Vc by a predetermined margin may be used as the above predetermined value.

[0049] ECU 150 may execute a process flow shown in Fig. 5 instead of the process flow shown in Fig. 2. Fig. 5 is a flowchart showing a modified example of the charging method shown in Fig. 2. The process flow shown in Fig. 5 is the same as the process flow shown in Fig. 2, except that S14A, S14B, and S17A are adopted instead of S14 to S17 (Fig. 2). S14A, S14B, and S17A will be described below.

[0050] With reference to FIG. 5, in this modification, when Vs reaches Vc during series charging of the battery 11 by the process of S11 (YES in S13), the ECU 150 measures the elapsed time (hereinafter, referred to as "Tc") since Vs reached Vc in S14A. Then, the ECU 150 transmits a current suppression command to the charger 61 in S14B to reduce the charging current of the battery 11. In this modification, the ECU 150 determines the current throttling amount (the slope of the current with respect to time) based on Tc. The ECU 150 may increase the current throttling amount as Tc increases. The charger 61 that has received the current suppression command controls the charging current of the battery 11 so that the charging current of the battery 11 is reduced according to the current throttling amount indicated by the current suppression command. The current throttling amount during the switching determination period may be a fixed value.

[0051] Next, in S17A, ECU 150 determines whether Tc is equal to or greater than a predetermined time (hereinafter, referred to as "Tx"). Tx may be a fixed value, or may be variable according to facility information (Vc and / or Ic). When Tc reaches Tx (YES in S17A), the process proceeds to S18 (switching to parallel charging).

[0052] Before starting external charging of the battery 11, the ECU 150 (control device) may select one charging control from options including the charging control shown in Fig. 2 and the charging control shown in Fig. 5, and execute the selected charging control. The ECU 150 may determine which charging control to execute based on the facility information (Vc and / or Ic).

[0053] In the above-described embodiment and modification, charging control of the battery 11 is performed using a charger 61 mounted on the vehicle 100. However, this is not limited to this, and charging control of the battery 11 may be performed using a charger mounted on the EVSE. Fig. 6 is a diagram showing a modification of the charging system shown in Fig. 1.

[0054] Referring to FIG. 6, the EVSE 300A incorporates a charger 331, a detector 331a, and a control device 332. The charger 331 includes a power conversion circuit (e.g., an inverter) and is configured to be able to adjust a charging current. The detector 331a includes various sensors (e.g., a current sensor and a voltage sensor) that detect the state of the charger 331, and outputs the detection result to the control device 332. The connector 320a of the EVSE 300A is connected to the inlet 60A of the vehicle 100A, so that the vehicle 100A is in a plugged-in state. In the vehicle 100A in the plugged-in state, the ECU 150A executes external charging of the battery 11 while communicating with the control device 332 via the charging cable 320. During external charging, the charger 331 converts AC power supplied from the power system PG into DC power and outputs the DC power to the connector 320a. That is, the EVSE 300A outputs DC power. The DC power output from the EVSE 300A to the vehicle 100A is input to the inlet 60A and is used to charge the battery 11.

[0055] The ECU 150A performs external charging of the battery 11 by the charging method shown in Fig. 2 or 5. The ECU 150A transmits a charging command and a current suppression command to the control device 332. The control device 332 controls the charger 331 according to the command received from the ECU 150A. In this way, the external charging of the battery 11 is performed. The control device 332 may obtain the charging current by using the detection result by the current sensor of the detector 331a.

[0056] The process flows shown in Figures 2 and 5 can be modified as appropriate. For example, the order of the processes can be changed or unnecessary steps can be omitted depending on the purpose. Furthermore, the content of any of the processes can be changed. For example, the calculations in S14 to S16 in Figure 2 can be performed simultaneously in parallel.

[0057] The configuration of the vehicle is not limited to the above-described configuration (see FIG. 1). For example, the vehicle may be configured to be capable of being charged wirelessly. A vehicle that performs wireless charging may be considered to be in a state equivalent to the above-described "plugged-in state" when the alignment between the power transmission unit (e.g., a power transmission coil) on the power supply equipment side and the power receiving unit (e.g., a power receiving coil) on the vehicle side is completed.

[0058] The power storage device may be mounted on a resource other than an automobile. The resource may be a moving body other than an automobile (railroad vehicle, ship, airplane, drone, walking robot, robot cleaner, etc.). The resource may be an electric machine or appliance (lighting device, air conditioner, cooking appliance, television, refrigerator, washing machine, etc.). The power storage device to be charged may be a stationary power storage device used in a building (house, factory, etc.) or outdoors.

[0059] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present disclosure is defined by the claims, not by the description of the embodiments described above, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0060] 11 battery, 61 charger, 100 vehicle, 100A vehicle, 150,150A ECU, 300,300A EVSE, 331 charger, 332 control device, B1,B2 battery, PG power system, R1~R3 ​​relay.

Claims

1. a power storage device including a first battery and a second battery; A control device that controls charging of the power storage device, the power storage device is configured to be capable of series charging, which is charging in a state in which the first battery and the second battery are connected in series, and parallel charging, which is charging in a state in which the first battery and the second battery are connected in parallel, the control device is configured to switch a charging method from the series charging to the parallel charging and continue charging the power storage device after a voltage of the power storage device during the series charging reaches a predetermined value.

2. 2. The charging system according to claim 1, wherein the control device reduces a charging current of the power storage device during the series charging during a switching determination period from when a voltage of the power storage device during the series charging reaches the predetermined value until when a charging method of the power storage device is switched to the parallel charging.

3. the control device is configured to calculate a voltage of the power storage device during the series charging, using a no-load voltage, a charging current, and an internal resistance of each of the first battery and the second battery; the predetermined value is an equipment upper limit voltage indicating a maximum charging voltage of equipment that supplies power to the power storage device, 3 . The charging system according to claim 2 , wherein the control device controls a charging current for the power storage device during the switching determination period so that a voltage of the power storage device being series-charged coincides with the predetermined value.

4. the control device predicts parallel charging power, which is charging power of the power storage device when a charging method is switched to the parallel charging during the series charging of the power storage device; 4. The charging system according to claim 3, wherein the control device is configured to switch a charging method of the power storage device from the series charging to the parallel charging at a timing when a charging power of the power storage device during the series charging becomes equal to or lower than a reference value determined based on the parallel charging power after a voltage of the power storage device during the series charging becomes equal to or higher than the predetermined value.

5. A vehicle equipped with the charging system according to any one of claims 1 to 4, When a predetermined condition is satisfied while a power supply facility external to the vehicle and the vehicle are electrically connected to each other, the control device starts the series charging of the power storage device using power supplied from the power supply facility.

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