Charging system and vehicle

Abstract

The invention relates to a charging system and a vehicle. A charging system includes an electricity storage device including a first battery and a second battery, and a control device that performs charging control of the electricity storage device. The power storage device is configured so as to be able to perform serial charging in a state in which the first battery and the second battery are connected in series, and parallel charging in a state in which the first battery and the second battery are connected in parallel. The control device is configured so as to continue the charging of the power storage device by switching the charging method from serial charging to parallel charging after the voltage of the power storage device during serial charging reaches a predetermined value.

Description

Technical Field

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

[0002] Japanese Patent No. 7006263 discloses a charging system, which includes a power storage device including a plurality of batteries and a switching relay, and a control device for controlling the switching relay. The switching relay is configured to be able to switch 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 power storage device from a power source outside the vehicle. When an insertion operation for charging the power storage device is performed, the control device controls the switching relay to the first state. In addition, when the maximum charging voltage of the power source is less than a threshold value, the control device changes the switching relay from the first state to the second state. Summary of the invention

[0003] Incidentally, in the charging of the power storage device in the second state (parallel charging), the power received by the power storage device (charging power) becomes smaller than that in the charging of the power storage device in the first state (serial charging). Therefore, the parallel charging tends to have a longer charging time (time taken until charging is completed) than the serial charging. In the charging system described in the above-mentioned Japanese Patent No. 7006263, parallel charging is performed when the maximum charging voltage of the power supply is less than the threshold value, so it is considered that the charging time becomes longer.

[0004] The present disclosure has been made to solve the above-mentioned problems, and an object of the present disclosure is to shorten the charging time.

[0005] A charging system according to one embodiment of the present disclosure includes a power storage device including a first battery and a second battery, and a control device for controlling the charging of the power storage device. The power storage device is configured to be capable of performing serial charging and parallel charging, wherein serial charging is charging in a state where the first battery and the second battery are connected in series, and parallel charging is charging in a state where the first battery and the second battery are connected in parallel. The control device is configured to switch the charging mode from serial charging to parallel charging and continue charging the power storage device after the voltage of the power storage device during serial charging reaches a predetermined value.

[0006] According to another aspect of the present disclosure, a vehicle including the above-mentioned charging system is provided.

[0007] According to the present disclosure, it is possible to shorten the charging time. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, in which like reference numerals represent like elements, and in which:

[0009] Figure 1 is a diagram showing a charging system according to an embodiment of the present disclosure;

[0010] Figure 2 is a flow chart showing a charging method according to an embodiment of the present disclosure;

[0011] Figure 3 is a diagram showing, by comparison, the transition of states of the power storage device charged by the respective charging methods of the embodiment and the modified example;

[0012] Figure 4 is a diagram showing charging data measured by the charging methods of each of the embodiment and the modified example;

[0013] Figure 5 Yes means Figure 2 A flowchart of a variation of the charging method shown; and

[0014] Figure 6 Yes means Figure 1 A diagram of a modified example of the charging system shown. DETAILED DESCRIPTION

[0015] The embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and their description will not be repeated.

[0016] Figure 1 2 is a diagram showing a charging system according to an embodiment of the present disclosure. Figure 1 The charging system of this embodiment includes a vehicle 100 and an EVSE 300. The EVSE 300 receives power supply from a power system PG. EVSE refers to Electric Vehicle Supply Equipment. The power system PG is a power grid constructed by power transmission and distribution equipment. The power system PG is connected to a plurality of power stations (not shown). The power system PG receives power supply from these power stations. In this embodiment, the power system PG supplies AC power.

[0017] EVSE 300 has a built-in power supply circuit 310 and 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 the front end, and includes a communication line and a power line inside. One wire can also serve as both a communication line and a 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. EVSE 300 outputs AC power from the connector 320a.

[0018] The vehicle 100 is provided with an inlet 60 to which a connector 320a can be attached and detached. 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 vehicle 100 in the parked state, whereby the vehicle 100 is electrically connected to the power system PG via the EVSE 300 (hereinafter also referred to as the "plugged in state"). On the other hand, for example, while the vehicle 100 is traveling, the vehicle 100 is not electrically connected to each of the EVSE 300 and the power system PG (hereinafter also referred to as the "unplugged state").

[0019] The vehicle 100 also 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 store stored information. In addition to the program, the storage device 153 also stores information used in the program (for example, mapping, mathematical formulas, and various parameters). In this embodiment, the processor 151 executes the program stored in the storage device 153, thereby performing various controls of the ECU 150 (for example, charging control of the battery 11). However, these processes can also be performed only by hardware (electronic circuit) without using software. The ECU 150 and the battery 11 of this embodiment are respectively equivalent to an example of the "control device" and the "power storage device" of the present disclosure.

[0020] The vehicle 100 is configured to travel using the power stored in the battery 11. The vehicle 100 is, for example, a battery electric vehicle (BEV) without an engine (internal combustion engine). However, the present invention is not limited thereto, and the vehicle 100 may be a plug-in hybrid electric vehicle (PHEV) with an internal combustion engine or another electric vehicle (xEV).

[0021] The battery 11 includes a battery B1 (first battery), a battery B2 (second battery) and three relays R1, R2, and R3. In this embodiment, batteries B1 and B2 are battery packs, respectively. A battery pack is composed of a plurality of secondary batteries (also generally referred to as "battery cells") electrically connected to each other. The plurality of battery cells in a battery pack are connected in series, for example. However, the connection method of the battery cells in the battery pack is not limited to series connection, but may also include parallel connection. In addition, batteries B1 and B2 may each be a single secondary battery instead of a battery pack.

[0022] Relay R1 is provided on wire EL1 connecting the positive electrode of battery B1 with the positive electrode of battery B2. Relay R2 is provided on wire EL2 connecting the positive electrode of battery B1 with the negative electrode of battery B2. Relay R3 is provided on wire EL3 connecting the negative electrode of battery B1 with the negative electrode of battery B2. Wire EL1 and wire EL2 are connected to each other at node N1. Wire EL2 and wire EL3 are connected to each other at node N2. Positive terminal T1 and negative terminal T2 of battery 11 are provided on wires EL1 and EL3, respectively. Relay R1 is located between positive terminal T1 and node N1. Relay R3 is located between negative terminal T2 and node N2. When relays R1, R2, and R3 are disconnected, connected, and disconnected, respectively, batteries B1 and B2 are connected in series (series state). When relays R1, R2, and R3 are connected, disconnected, and connected, respectively, batteries B1 and B2 are connected in parallel (parallel state). As the switching relays (relays R1, R2, R3) for switching between the series state and the parallel state, an electromagnetic mechanical relay can be used, but instead, a semiconductor relay such as a thyristor, a triac, or a transistor may be used as the switching relay.

[0023] The battery 11 is provided with a battery management system (BMS) 11a for monitoring the state of the battery 11 and a temperature control system 11b for adjusting the temperature of the battery 11. The BMS 11a includes various sensors for detecting the state of the battery 11 (e.g., voltage, current, and temperature), and a monitoring IC (integrated circuit) for inputting detection signals obtained by the various sensors. The temperature control system 11b includes at least one of a heater and a cooling device. The cooling method may also be water cooling or oil cooling. The temperature control system 11b is controlled by the ECU 150.

[0024] In this embodiment, a voltage sensor and a temperature sensor are provided for each battery cell constituting the battery 11 (battery pack). However, the present invention is not limited thereto, and each of the voltage sensor and the temperature sensor may be provided one for each of the plurality of battery cells, or only one for one battery pack. The monitoring IC generates a signal indicating the state of the battery 11 (hereinafter also referred to as a "BMS signal") using the detection signals obtained by the various sensors, and outputs the generated BMS signal to the ECU 150. Based on the BMS signal, the ECU 150 obtains, for example, the temperature, current, voltage, and state of charge (SOC) of the battery 11. The SOC indicates the remaining power, and for example, 0 to 100% is used to indicate the ratio of the current power storage amount to the power storage amount in the fully charged state. The monitoring IC may also have a function of equalizing the voltage of the battery cells.

[0025] The vehicle 100 further includes a charger 61 and a charging relay 62. The charger 61 and the charging relay 62 are located between the inlet 60 and the battery 11. The charger 61 and the charging relay 62 are controlled by the ECU 150, respectively. In this embodiment, a charging line including the inlet 60, the charger 61, and the charging relay 62 is connected between the SMR 12 and the PCU 22. However, this is not limited to this, and the charging line may be connected between the battery 11 and the SMR 12.

[0026] The charger 61 charges the battery 11 using the power input from the outside of the vehicle to the inlet 60. The charger 61 includes a power conversion circuit (e.g., an inverter) and is configured to adjust the charging current. The power conversion circuit performs DC (direct current) / AC (alternating current) conversion. The charging relay 62 switches the connection / disconnection of the circuit from the inlet 60 to the battery 11. The vehicle 100 also 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.

[0027] In the vehicle 100 in the plugged-in state, external charging (i.e., charging of the battery 11 with power from outside the vehicle) can be performed. Power for external charging is supplied to the inlet 60 from the power system PG through the charging cable 320 of the EVSE 300, for example. 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 in a closed state (connected state), and when external charging is not performed, the charging relay 62 is in an open state (disconnected state).

[0028] MG 20 is, for example, a three-phase AC motor generator. MG 20 functions as a driving motor of vehicle 100. MG 20 is driven by PCU 22 to rotate the drive wheels of vehicle 100. In addition, MG 20 performs regenerative power generation and outputs the generated power to battery 11. It should be noted that the number of driving motors provided in vehicle 100 is arbitrary.

[0029] The PCU 22 includes a circuit for driving the MG 20 using the power supplied from the battery 11. The SMR 12 switches the connection / disconnection of the circuit 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 controlled by the ECU 150, respectively. The SMR 12 is in a closed state (connected state) when the vehicle 100 is traveling. In addition, when the battery 11 and the inlet 60 (and thus the outside of the vehicle) are exchanged with each other, the SMR 12 is also in a closed state.

[0030] As described above, the battery 11 is provided with a switching mechanism for series / parallel connection. The battery 11 is configured to be able to perform charging of the battery 11 in a series state (serial charging) and charging of 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) becomes smaller than in serial charging. When charging is performed in a state where the batteries B1 and B2 are connected in parallel (parallel charging), the current and voltage of the battery B1 and the current and voltage of the battery B2 are respectively reduced to one-half compared to the case where charging is performed in a state where the batteries B1 and B2 are connected in series (serial charging). Furthermore, the total power received by the batteries B1 and B2 connected in parallel in parallel charging is one-half of the total power received by the batteries B1 and B2 connected in series in serial charging. Therefore, there is a tendency for the charging time (the time taken until charging is completed) to be longer in parallel charging compared to serial charging.

[0031] Therefore, the ECU 150 of this embodiment executes the following steps: Figure 2 In the series of processes shown, after the voltage of the battery 11 during serial charging reaches a predetermined value, the charging method is switched from serial charging to parallel charging to continue charging the battery 11 .

[0032] Figure 2 1 is a flowchart showing the charging method of this embodiment. "S" in the flowchart represents a step. The processing shown in the flowchart is executed by ECU 150 in vehicle 100 in the plug-in state. Figure 2The processing flow shown 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 plugged in. Alternatively, the charging start condition may be satisfied when the vehicle 100 is plugged in and the user performs a charging start operation on the EVSE 300 or the vehicle 100.

[0033] Reference Figure 1 and Figure 2 In S10, the ECU 150 obtains device information related to the EVSE 300 from the EVSE 300 (power supply device that supplies power to the battery 11) connected to the vehicle 100. The device information includes a device upper limit voltage (hereinafter referred to as "Vc") indicating the maximum charging voltage of the EVSE 300 and a device upper limit current (hereinafter referred to as "Ic") indicating the maximum charging current of the EVSE 300. When the charging voltage or charging current of the battery 11 exceeds Vc or Ic, the EVSE 300 cannot charge the battery 11.

[0034] In the next S11, the ECU 150 sets the relays R1, R2, and R3 to be disconnected, connected, and disconnected, respectively, so that the battery 11 is in a series state, and sends a charging instruction for serial charging to the charger 61. The charger 61 that receives the charging instruction 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 instruction. In this way, the external charging of the battery 11 is performed. The ECU 150 determines a target charging current value below 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 set as the target charging current value.

[0035] As described above, when the predetermined charging start condition is satisfied in a state where the EVSE 300 (power supply equipment outside the vehicle) and the vehicle 100 are electrically connected to each other, the ECU 150 starts serial charging of the battery 11 using the power supplied from the EVSE 300 (S11). However, in the case where the predetermined charging end condition is satisfied in S11, Figure 2 The processing flow shown ends. The charging end condition is satisfied, for example, when the storage capacity of the battery 11 reaches the target value. The target value can be set automatically by the ECU 150 or the EVSE 300, or by the user. The state of the battery 11 (such as the voltage and SOC) is measured by the BMS 11a. In addition, for example, the charging end condition can also be satisfied based on an instruction from the user to stop charging. If the charging end condition is satisfied during serial charging, the switch to parallel charging (S18) is not performed. Figure 2 The shown processing flow ends.

[0036] In the next S12, the ECU 150 measures the voltage (hereinafter referred to as "Vs") of the battery 11 during the serial charge. 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 referred to as "OCV (open circuit voltage)". The ECU 150 may also use the map pre-stored in the storage device 153 to obtain the internal resistances of the batteries B1 and B2, respectively, based on the SOC and temperature of the batteries B1 and B2 measured by the BMS11a. The ECU 150 may also calculate the no-load voltage, charging current, and internal resistance of the battery 11 based on 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 the serial charge. The ECU 150 may also calculate Vs according to the formula "Vs = no-load voltage + Is × internal resistance" related to the battery 11. According to such a method, it is easy to calculate the voltage of the battery 11 during the serial charge with high accuracy.

[0037] In the next S13, the ECU 150 determines whether Vs is greater than or equal to Vc. If Vs is less than Vc ("No" in S13), the process returns to S11 and the serial charging is continued. The voltage (Vs) of the battery 11 increases by the serial charging (S11). Then, when Vs reaches Vc ("Yes" in S13), the process proceeds to S14.

[0038] In S14, the ECU 150 sends a current suppression command for reducing the charging current of the battery 11 to the charger 61. The current suppression command indicates a target charging current value for making the voltage (Vs) of the battery 11 consistent with Vc. The charger 61 that receives the current suppression command controls the charging current of the battery 11 in such a way that the voltage (Vs) of the battery 11 is maintained at Vc while reducing the charging current of the battery 11. Thus, the serial charging continues. However, the control method of the serial charging is switched from constant current charging to constant voltage charging.

[0039] In S15, the ECU 150 measures the charging power (hereinafter referred to as "Ws") of the battery 11 during serial 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 equation "Ws = Vc x (Vc - no-load voltage) / internal resistance" related to the EVSE 300 and the battery 11.

[0040] Next, the ECU 150 predicts the charging power (hereinafter referred to as "Wp") of the battery 11 when the charging method is switched from serial charging to parallel charging in S16. The ECU 150 calculates Wp using Ic, for example. The ECU 150 may also calculate Wp according to the formula "Wp = (2 × no-load voltage + Ic × internal resistance) × Ic / 4" related to the EVSE 300 and the battery 11. Wp is an example of the "parallel charging power" of the present disclosure.

[0041] Next, the ECU 150 determines in S17 whether Ws is less than a reference value determined based on Wp. In this embodiment, a value obtained by adding a predetermined margin (hereinafter referred to as "Wx") to Wp (=Wp+Wx) is used as the reference value. Wx can be set arbitrarily. Wx can be a power value greater than 0 or 0.

[0042] When Ws is greater than the reference value ("No" in S17), the process returns to S14 and the serial charging is continued. The power (Ws) of the battery 11 is reduced by the current suppression command (S14). When Ws reaches the reference value ("Yes" in S17), the process proceeds to S18.

[0043] In S18, the ECU 150 switches the charging mode from serial charging to parallel charging and continues charging the battery 11. Specifically, the ECU 150 sets the relays R1, R2, and R3 to be on, off, and on, respectively, so that the battery 11 is in a parallel state, and sends a charging instruction for parallel charging to the charger 61. The charger 61 that receives the charging instruction controls the charging current of the battery 11 in such a way that the charging current of the battery 11 approaches the target charging current value indicated by the charging instruction. Thus, parallel charging of the battery 11 is performed. The ECU 150 determines a target charging current value below Ic / 2, and after reducing the charging current of the battery 11 to the target charging current value, constant current charging is performed at the target charging current value. In this embodiment, Ic / 2 (the value obtained by dividing Ic by 2) is used as the target charging current value. The parallel charging started in S18 can also be continued until the predetermined charging end condition is met.

[0044] Figure 3 1 is a diagram showing the state transition of the battery 11 charged by the charging method of the embodiment and the modified example. Figure 2 The charging method described above is shown in the figure. The charging method of the modified example is a method of switching the charging method from serial charging to parallel charging when the voltage of the battery 11 during serial charging reaches a predetermined value (e.g., Vc). Regardless of which method is used, the charging method is switched from serial charging to parallel charging after the voltage of the battery 11 during serial charging reaches a predetermined value (e.g., Vc).

[0045] exist Figure 3 In FIG. 1 , lines L1 , L2 , L3 , and L4 respectively represent the charging current, the load voltage, the no-load voltage, and the charging power of the battery 11 . Figure 3 "VB" in the figure represents the voltage of the battery 11 (the upper limit voltage of the battery) when the battery 11 is fully charged in the series state by the serial charging control (S11) without the current suppression (S14). When Vc is higher than VB, the serial charging (fast charging) can be continued until the charging is completed. The period T10 represents the period from when the voltage of the battery 11 in the serial charging reaches a predetermined value (for example, Vc) to when the charging method of the battery 11 is switched to parallel charging. The period T10 is equivalent to an example of the "switching judgment period" of the present disclosure. In the period T10, the charging power of the charging method of the embodiment becomes larger than that of the charging method of the variant. Therefore, the charging power amount in the charging method of the embodiment is greater than the charging power amount in the charging method of the variant. Figure 3 The amount of electrical power shown is dW.

[0046] Figure 4 FIG. 2 is a graph showing charging data measured by the charging method of the embodiment and the modified example. Figure 4 In the figure, lines L11, L12, L14, L15, L31, and L32 respectively represent the SOC, charging current, maximum battery cell temperature, minimum battery cell temperature, voltage, and power of the battery 11 in the charging method of the embodiment. Lines L21, L22, L24, L25, L41, and L42 respectively represent the SOC, charging current, maximum battery cell temperature, minimum battery cell temperature, voltage, and power of the battery 11 in the charging method of the modified example. Lines L13 and L23 respectively represent the maximum charging current (equipment upper limit current) of the power supply device that supplies power to the battery 11. Lines L51 and L52 respectively represent the maximum charging voltage (equipment upper limit voltage) and the maximum charging power (equipment upper limit power) of the power supply device.

[0047] exist Figure 4 In the example shown, charging is performed until the SOC of the battery 11 changes from about 15% to about 80%. In addition, when the maximum battery cell temperature (the temperature of the battery cell with the highest temperature in the battery 11) becomes 50°C or higher during the charging of the battery 11, the temperature control system 11b uses the power supplied from the above-mentioned power supply equipment (e.g., EVSE 300) to perform cooling of the battery 11. Based on the obtained data, it is confirmed that the charging time of the charging method of the embodiment is shorter than that of the charging method of the modified example. In one example of the data, the charging time for the battery 11 to reach 78% from 15% is shorter by 0.3 minutes in the charging method of the embodiment.

[0048] As described above, the charging method of this embodiment includes Figure 2 In the charging system of this embodiment, the ECU 150 (control device) is configured to switch the charging method from serial charging to parallel charging and continue charging the battery 11 after the voltage of the battery 11 during serial charging reaches a predetermined value.

[0049] According to the serial charging, the battery 11 can be charged with a larger charging power than the parallel charging. The larger the charging power, the higher the charging speed. However, as the charging of the battery 11 proceeds, the storage amount of the battery 11 increases, and the no-load voltage of the battery 11 becomes higher. The voltage of the battery 11 during the serial charging becomes a value obtained by adding the voltage rise amount (IR amount) caused by the charging current to the no-load voltage. If the voltage of the battery 11 during the serial charging becomes too high, it may not be possible to continue charging depending on the specifications of the device that supplies power to the battery 11. On the other hand, during the period when the voltage of the battery 11 during the serial charging is low, by continuing the serial charging, the charging speed of the battery 11 can be increased. Therefore, in the above-mentioned charging system, the serial charging of the battery 11 is continued during the period when the voltage of the battery 11 during the serial charging does not reach the predetermined value. Thus, the charging time (the time taken until the charging is completed) is shortened. Then, after the voltage of the battery 11 during the serial charging reaches the predetermined value, the charging method is switched from the serial charging to the parallel charging. By switching the charging method from the serial charging to the parallel charging, the voltage of the battery 11 is reduced. This can prevent the voltage of the battery 11 from becoming excessively high during charging of the battery 11 .

[0050] Due to the evolution of standards in recent years, the voltage of vehicle-mounted batteries and power supply equipment has been continuously developed. However, under the current situation, there are still low-voltage power supply equipment. In this regard, according to the above-mentioned charging system, the battery 11 that becomes high voltage by series connection is switched to parallel connection during charging, thereby enabling the battery 11 to be charged not only by high-voltage equipment but also by low-voltage equipment (old or household power supply equipment).

[0051] In the above embodiment, the ECU 150 switches the charging method of the battery 11 to parallel charging during the switching determination period (for example, from when the voltage of the battery 11 during serial charging reaches a predetermined value) until the charging method of the battery 11 is switched to parallel charging. Figure 3 The charging current of the battery 11 in the serial charging is reduced (period T10 shown in the figure). By reducing the current of the battery 11 in the serial charging in this way, the voltage rise caused by the charging current is suppressed. In the charging system of the above-mentioned embodiment, by such current control, it is possible to suppress the voltage of the battery 11 from becoming too high during the serial charging of the battery 11. Therefore, it is easy to extend the period (switching judgment period) during which the serial charging of the battery 11 continues.

[0052] In the charging method of the embodiment, after the voltage of the battery 11 in serial charging becomes equal to or greater than a predetermined value, the charging method of the battery 11 is switched from serial charging to parallel charging when the charging power of the battery 11 in serial charging becomes equal to or less than a reference value determined based on Wp (parallel charging power). According to such a method, the effect of shortening the charging time is increased (see Figure 3 and Figure 4 ). Specifically, during period T10( Figure 3 ), serial charging of the battery 11 is performed, and the current of the battery 11 decreases during the serial charging. Moreover, as the charging current decreases, the charging power decreases. If the serial charging of the battery 11 is continued even if the charging power of the battery 11 decreases, it will soon become possible to obtain a larger charging power by switching to parallel charging than by continuing the serial charging. If the serial charging of the battery 11 is continued until such a situation occurs, the charging time of the battery 11 will be prolonged. Therefore, in the charging system of 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. As a result, the charging method can be switched to parallel charging at an appropriate time.

[0053] In the above embodiment, Vc is used as the above predetermined value (voltage value for switching the charging mode). Then, during the period T10 ( Figure 3 ) controls the current of the battery 11 in such a way that the voltage of the battery 11 is consistent with the upper limit voltage (Vc) of the device. During the period T10 (switching judgment period), the charging power decreases as the charging current decreases, but by maintaining the voltage of the battery 11 high, the decrease in the charging power of the battery 11 can be suppressed. The above-mentioned predetermined value can be changed appropriately. A voltage value with a predetermined margin lower than Vc can also be used as the above-mentioned predetermined value.

[0054] ECU 150 can also replace Figure 2 The processing flow shown is executed Figure 5 The processing flow shown. Figure 5 Yes means Figure 2 Flowchart of a variation of the charging method shown. Figure 5 The processing flow shown in the figure replaces S14 to S17 ( Figure 2 ) and use other than S14A, S14B, S17A, and Figure 2 The processing flow shown is the same. S14A, S14B and S17A will be described below.

[0055] Reference Figure 5In this modification, when Vs reaches Vc in the serial charging of the battery 11 based on the processing of S11 ("Yes" in S13), the ECU 150 measures the time after Vs reaches Vc (hereinafter referred to as "Tc") in S14A. Next, the ECU 150 sends a current suppression instruction to the charger 61 in S14B for reducing 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 also increase the current throttling amount as Tc increases. The charger 61 that receives the current suppression instruction controls the charging current of the battery 11 in such a manner that the charging current of the battery 11 is reduced according to the current throttling amount indicated by the current suppression instruction. It should be noted that the current throttling amount during the switching judgment period may also be a fixed value.

[0056] Next, the ECU 150 determines in S17A whether Tc is longer than a predetermined time (hereinafter referred to as "Tx"). Tx can be a fixed value or can be variable according to device information (Vc and / or Ic). When Tc reaches Tx ("Yes" in S17A), the process proceeds to S18 (switching to parallel charging).

[0057] The ECU 150 (control device) may also, before starting external charging of the battery 11, Figure 2 The charging control and Figure 5 One of the charging control options is selected and the selected charging control is executed. ECU 150 may determine which charging control is to be executed based on device information (Vc and / or Ic).

[0058] In the above-described embodiment and modified example, the charging control of the battery 11 is executed using the charger 61 mounted on the vehicle 100. However, the present invention is not limited thereto, and the charging control of the battery 11 may be executed using a charger mounted on an EVSE. Figure 6 Yes means Figure 1 A diagram of a modified example of the charging system shown.

[0059] Reference Figure 6, the EVSE 300A has a built-in 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 the charging current. The detector 331a includes various sensors (e.g., a current sensor and a voltage sensor) for detecting the state of the charger 331, and outputs the detection results to the control device 332. The vehicle 100A is in a plug-in state by connecting the connector 320a of the EVSE 300A to the inlet 60A of the vehicle 100A. In the plug-in state of the vehicle 100A, the ECU 150A performs external charging of the battery 11 while communicating with the control device 332 via the charging cable 320. In external charging, the charger 331 converts the 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 to charge the battery 11.

[0060] ECU 150A passed Figure 2 or Figure 5 The charging method shown performs external charging of the battery 11. The ECU 150A sends a charging instruction and a current suppression instruction to the control device 332. The control device 332 controls the charger 331 according to the instruction received from the ECU 150A. Thus, external charging of the battery 11 is performed. The control device 332 may also obtain the charging current using the detection result of the current sensor obtained by the detector 331a.

[0061] Figure 2 and Figure 5 The processing flow shown can be changed appropriately. For example, the order of processing can be changed according to the purpose, and unnecessary steps can be omitted. In addition, the content of any processing can be changed. For example, Figure 2 The operations in S14 to S16 can also be performed simultaneously in parallel.

[0062] The structure of the vehicle is not limited to the aforementioned structure (see Figure 1 ). For example, the vehicle may also be configured to be capable of contactless charging. Regarding a vehicle that performs contactless charging, when the power transmission unit (e.g., power transmission coil) on the power supply device side and the power receiving unit (e.g., power receiving coil) on the vehicle side are aligned, it may be considered to be in a state corresponding to the aforementioned "insertion state".

[0063] The power storage device may be mounted on resources other than automobiles. The resource may be a mobile object other than automobiles (railway vehicles, ships, airplanes, drones, walking robots, robot cleaners, etc.). The resource may also be an electrical mechanical device (lighting devices, air conditioners, cooking appliances, televisions, refrigerators, washing machines, etc.). The power storage device to be charged may also be a fixed power storage device used in a building (residence, factory, etc.) or outdoors.

[0064] The embodiments disclosed this time should be considered as illustrative in all aspects and not restrictive. The scope of the present disclosure is indicated by the claims rather than the description of the embodiments above, and is intended to include all modifications within the meaning and scope equivalent to the claims.

Claims

1. A charging system, wherein: The charging system has: A power storage device including a first battery and a second battery; and a control device for controlling charging of the power storage device, The power storage device is configured to be capable of performing serial charging and parallel charging, wherein the serial charging is charging in a state where the first battery and the second battery are connected in series, and the parallel charging is charging in a state where the first battery and the second battery are connected in parallel. The control device is configured to switch the charging method from the serial charging to the parallel charging to continue charging the power storage device after the voltage of the power storage device during the serial charging reaches a predetermined value.

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

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

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

5. A vehicle comprising the charging system according to any one of claims 1 to 4, wherein: The control device starts the serial charging of the power storage device using electric power supplied from the power supply facility when a predetermined condition is satisfied in a state where a power supply facility external to the vehicle and the vehicle are electrically connected to each other.

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