Charging systems, vehicles
The charging system addresses long charging times by switching from series to parallel charging based on battery voltage, optimizing power usage and preventing voltage overload, thus reducing overall charging duration.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- TOYOTA JIDOSHA KK
- Filing Date
- 2023-08-09
- Publication Date
- 2026-07-07
AI Technical Summary
Existing charging systems require longer charging times when the maximum charging voltage of the power source is lower, as parallel charging receives less power than series charging, leading to extended charging durations.
A charging system that switches from series charging to parallel charging when the battery voltage reaches a predetermined value during series charging, utilizing a control device to manage the transition and maintain optimal charging power.
This approach significantly reduces charging time by allowing higher power charging initially, while preventing voltage overload, and enables charging with both high- and low-voltage equipment.
Smart Images
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Abstract
Description
Technical Field
[0001] The present disclosure relates to a charging system and a vehicle.
Background Art
[0002] Japanese Patent No. 7006263 (Patent Document 1) discloses a charging system including a power 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 able to switch between a first state in which a 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 from a power source outside the vehicle to the power storage device. When a plug-in operation for charging the power storage device is performed, the control device controls the switching relay to the first state. Further, when the maximum charging voltage of the power source is smaller 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
Summary of the Invention
Problems to be Solved by the Invention
[0004] By the way, in the charging of the power storage device in the second state (parallel charging), the power (charging power) received by the power storage device is smaller than that in the charging of the power storage device in the first state (series charging). Therefore, parallel charging tends to take longer charging time (time required to complete charging) than series charging. In the charging system described in Patent Document 1 above, parallel charging is executed when the maximum charging voltage of the power source is smaller than a threshold value, so it is considered that the charging time becomes long.
[0005] The present disclosure has been made to solve the above problems, and an object thereof is to shorten the charging time. [Means for solving the problem]
[0006] A charging system according to one embodiment of the present disclosure comprises an energy storage device including a first battery and a second battery, and a control device for controlling the charging of the energy storage device. The energy storage device is configured to perform series charging, in which the first battery and the second battery are connected in series, and parallel charging, in which the first battery and the second battery are connected in parallel. The control device is configured to switch the charging method from series charging to parallel charging and continue charging the energy storage device after the voltage of the energy storage device reaches a predetermined value during series charging.
[0007] In another form of this disclosure, a vehicle equipped with the above-described charging system is provided. [Effects of the Invention]
[0008] According to this disclosure, it will be possible to shorten the charging time. [Brief explanation of the drawing]
[0009] [Figure 1] This figure shows a charging system according to an embodiment of the present disclosure. [Figure 2] This flowchart shows a charging method according to an embodiment of the present disclosure. [Figure 3] This figure shows a comparison of the state changes of an energy storage device charged by the charging method according to each of the examples and modified examples. [Figure 4] This figure shows the charging data measured for each of the examples and modified versions of the charging method. [Figure 5] Figure 2 is a flowchart showing a modified example of the charging method. [Figure 6] This figure shows a modified version of the charging system shown in Figure 1. [Modes for carrying out the invention]
[0010] Embodiments of this disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and their descriptions will not be repeated.
[0011] Figure 1 shows a charging system according to an embodiment of the present disclosure. Referring to Figure 1, the charging system according to this embodiment includes a vehicle 100 and an EVSE 300. The EVSE 300 receives power from a power grid PG. EVSE stands for Electric Vehicle Supply Equipment. The power grid PG is a power network constructed by transmission and distribution equipment. Multiple power plants (not shown) are connected to the power grid PG. The power grid PG receives power from these power plants. In this embodiment, the power grid PG supplies AC power.
[0012] The EVSE300 incorporates a power supply circuit 310 and a charging cable 320. The power supply circuit 310 is electrically connected to the power grid PG. The charging cable 320 has a connector 320a (plug) at its end and contains communication lines and power lines internally. One wire may serve as both a communication line and a power line. The power supply circuit 310 converts the power supplied from the power grid PG into power suitable for supplying power to the vehicle 100 and outputs the converted power to the charging cable 320. The EVSE300 outputs AC power from the connector 320a.
[0013] Vehicle 100 is equipped with 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, vehicle 100 becomes electrically connected to the power grid PG via the EVSE 300 (hereinafter also referred to as the "plugged-in state"). On the other hand, for example, when vehicle 100 is in motion, vehicle 100 becomes electrically disconnected from both the EVSE 300 and the power grid PG (hereinafter also referred to as the "plugged-out state").
[0014] Vehicle 100 further comprises a battery 11, an SMR (System Main Relay) 12, an MG (Motor Generator) 20, a PCU (Power Control Unit) 22, and an ECU (Electronic Control Unit) 150. The ECU 150 includes a processor 151, a RAM (Random Access Memory) 152, and a storage device 153. The storage device 153 is configured to store stored information. The storage device 153 stores programs as well as information used by the programs (e.g., maps, mathematical formulas, and various parameters). In this embodiment, the processor 151 executes the programs stored in the storage device 153, thereby performing various controls by the ECU 150 (e.g., battery 11 charging control). However, these processes may be performed solely by hardware (electronic circuits) without the use of software. The ECU 150 and battery 11 in this embodiment correspond to examples of the "control device" and "energy storage device" according to this disclosure, respectively.
[0015] Vehicle 100 is configured to run using electricity stored in battery 11. Vehicle 100 is, for example, an electric vehicle (BEV) without an engine (internal combustion engine). However, it is not limited to this, and vehicle 100 may be a PHEV (plug-in hybrid vehicle) equipped with an internal combustion engine, or another electric vehicle (xEV).
[0016] Battery 11 includes battery B1 (first battery), battery B2 (second battery), and three relays R1, R2, and R3. In this embodiment, batteries B1 and B2 are each a battery pack. A battery pack is composed of multiple secondary batteries (generally also called "cells") electrically connected to each other. Multiple cells in a battery pack are connected in series, for example. However, the connection configuration of cells in a battery pack is not limited to series and may include parallel connections. Also, batteries B1 and B2 may each be single secondary batteries instead of a battery pack.
[0017] Relay R1 is provided on the electric wire EL1 that connects the positive electrode of battery B1 and the positive electrode of battery B2. Relay R2 is provided on the electric wire EL2 that connects the positive electrode of battery B1 and the negative electrode of battery B2. Relay R3 is provided on the electric wire EL3 that connects the negative electrode of battery B1 and the negative electrode of battery B2. The electric wire EL1 and the electric wire EL2 are connected to each other at node N1. The electric wire EL2 and the electric wire EL3 are connected to each other at node N2. The positive terminal T1 and the negative terminal T2 of the battery 11 are provided on the electric wires EL1 and EL3, respectively. Relay R1 is located between the positive terminal T1 and the node N1. Relay R3 is located between the negative terminal T2 and the node N2. When relays R1, R2, and R3 are OFF, ON, and OFF, respectively, batteries B1 and B2 are in a state of being connected in series (series state). When relays R1, R2, and R3 are ON, OFF, and ON, respectively, batteries B1 and B2 are in a state of being connected in parallel (parallel state). As the switching relay (relays R1, R2, and R3) for switching between the series state / parallel state, an electromagnetic mechanical relay can be adopted. However, instead of this, semiconductor relays such as thyristors, triacs, and transistors may be adopted as the switching relay.
[0018] The battery 11 is provided with a BMS (Battery Management System) 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 (for example, voltage, current, and temperature) of the battery 11 and a monitoring IC (integrated circuit) to which detection signals from the various sensors are input. The temperature control 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 control 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, it is not limited to this, and each of the voltage sensor and the temperature sensor may be provided one by one for each of a plurality of cells, or only one may be provided for one battery pack. The monitoring IC generates a signal indicating the state of the battery 11 (hereinafter, also referred to as "BMS signal") using the detection signals from the various sensors described above, 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 charge amount, and is, for example, a ratio of the current charge amount to the charge amount in the fully charged state, expressed as 0 to 100%. The monitoring IC may have a function of equalizing the cell voltages.
[0020] 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. Each of the charger 61 and the charging relay 62 is controlled by the ECU 150. 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, it is not limited to this, and a charging line may be connected between the battery 11 and the SMR 12.
[0021] The charger 61 charges the battery 11 using the power input from outside the vehicle to the inlet 60. The charger 61 includes a power conversion circuit (for example, 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 the connection / disconnection of the circuit 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 (for example, a current sensor and a voltage sensor) that detect the state of the charger 61, and outputs the detection result to the ECU 150.
[0022] In the plugged-in vehicle 100, external charging (i.e., charging of the battery 11 with power from outside the vehicle) becomes possible. Power for external charging is supplied, for example, from the power grid PG to the inlet 60 via the 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] MG20 is, for example, a three-phase AC motor generator. MG20 functions as a drive motor for vehicle 100. MG20 is driven by PCU22 and rotates the drive wheels of vehicle 100. MG20 also performs regenerative power generation and outputs the generated electricity to battery 11. The number of drive motors in vehicle 100 is arbitrary.
[0024] The PCU22 includes a circuit that drives the MG20 using power supplied from the battery 11. The SMR12 switches the connection / disconnection of the electrical circuit from the battery 11 to the PCU22. The PCU22 includes, for example, an inverter and a converter. Both the SMR12 and the PCU22 are controlled by the ECU150. The SMR12 is closed (connected) when the vehicle 100 is running. The SMR12 is also closed when power is exchanged between the battery 11 and the inlet 60 (and thus outside the vehicle).
[0025] As described above, battery 11 is equipped with a series / parallel connection switching mechanism. Battery 11 is configured to be able to be charged in series and in parallel. However, in parallel charging, the power received by battery 11 (energy storage device) is less than in series charging. When batteries B1 and B2 are connected in parallel and charging is performed (parallel charging), the current and voltage of battery B1 and the current and voltage of battery B2 are each halved compared to when batteries B1 and B2 are connected in series and charging is performed (series charging). Furthermore, the total power received by batteries B1 and B2 connected in parallel in parallel charging is halved compared to the total power received by batteries B1 and B2 connected in series in series charging. For this reason, the charging time (time required to complete charging) tends to be longer in parallel charging than in series charging.
[0026] Therefore, the ECU 150 according to this embodiment performs a series of processes shown in Figure 2, which will be described below, and after the voltage of the battery 11 during series charging reaches a predetermined value, it switches the charging method from series charging to parallel charging and continues charging the battery 11.
[0027] Figure 2 is a flowchart illustrating the charging method according to this embodiment. In the flowchart, "S" represents a step. The process shown in this flowchart is executed by the ECU 150 in the plugged-in vehicle 100. The process flow shown in Figure 2 is started when predetermined charging start conditions are met for the vehicle 100. For example, the charging start conditions may be met when the vehicle 100 is plugged in. Alternatively, the charging start conditions may be met when the vehicle 100 is plugged in and a charging start operation is performed by the user on the EVSE 300 or the vehicle 100.
[0028] Referring to Figure 2 in conjunction with Figure 1, in S10, the ECU 150 acquires equipment information regarding the EVSE 300 (power supply equipment that supplies power to the battery 11) from the EVSE 300 connected to the vehicle 100. The equipment information includes the equipment upper limit voltage (hereinafter referred to as "Vc") which indicates the maximum charging voltage of the EVSE 300, and the equipment upper limit current (hereinafter referred to as "Ic") which indicates the maximum charging current of the EVSE 300. If the charging voltage or charging current of the battery 11 exceeds Vc or Ic, the EVSE 300 will not be able to charge the battery 11.
[0029] In the subsequent step S11, the ECU 150 connects the batteries 11 in series by switching relays R1, R2, and R3 OFF, ON, and OFF respectively, and sends a charge command for series charging to the charger 61. Upon receiving the charge command, the charger 61 controls the charging current of the battery 11 so that it approaches the target charging current value indicated in the charge command. This enables external charging of the battery 11. The ECU 150 determines a target charging current value less than or equal to Ic, increases 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 is the target charging current value.
[0030] As described above, when the EVSE 300 (external power supply equipment) and the vehicle 100 are electrically connected and the predetermined charging start conditions are met, the ECU 150 starts series charging of the battery 11 using the power supplied from the EVSE 300 (S11). However, if the predetermined charging end conditions are met in S11, the processing flow shown in Figure 2 ends. The charging end conditions are met, for example, when the amount of charge stored in the battery 11 reaches a target value. The target value may be automatically set by the ECU 150 or EVSE 300, or it may be set by the user. The state of the battery 11 (e.g., voltage and SOC) is measured by the BMS 11a. In addition, the charging end conditions may be met, for example, in response to a charging stop instruction from the user. If the charging end conditions are met during series charging, the processing flow shown in Figure 2 ends without switching to parallel charging (S18).
[0031] In the subsequent S12, the ECU 150 measures the voltage of battery 11 during series charging (hereinafter referred to as "Vs"). Specifically, the ECU 150 calculates Vs using the no-load voltage, charging current, and internal resistance of batteries B1 and B2, respectively. The no-load voltage is also commonly referred to as "OCV (open circuit voltage)". The ECU 150 may also use a map pre-stored in the memory device 153 to determine the internal resistances of batteries B1 and B2 from the SOC and temperature of batteries B1 and B2 measured by the BMS 11a. The ECU 150 may also calculate the no-load voltage, charging current, and internal resistance of battery 11 from the no-load voltage, charging current, and internal resistance of batteries B1 and B2, respectively. The charging current of battery 11 obtained here corresponds to the current of battery 11 during series charging (hereinafter referred to as "Is"). The ECU150 may also calculate Vs according to the formula for battery 11, "Vs = no-load voltage + Is × internal resistance". This method makes it easier to calculate the voltage of battery 11 during series charging with high accuracy.
[0032] In the following step S13, the ECU150 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 series charging continues. The series charging (S11) increases the voltage (Vs) of battery 11. When Vs reaches Vc (YES in S13), the process proceeds to S14.
[0033] In S14, the ECU 150 sends 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 will make the voltage (Vs) of the battery 11 match Vc. Upon receiving the current suppression command, the charger 61 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 ECU150 measures the charging power (hereinafter referred to as "Ws") of the battery 11 during series charging. The ECU150 determines Ws based on the state of the battery 11 measured by the BMS11a. The ECU150 may also calculate Ws according to the formula "Ws = Vc × (Vc - no-load voltage) / internal resistance" relating to the EVSE300 and the battery 11.
[0035] Next, in S16, the ECU150 predicts the charging power of the battery 11 (hereinafter referred to as "Wp") when the charging method is switched from series charging to parallel charging. The ECU150 calculates Wp using, for example, Ic. The ECU150 may also calculate Wp according to the formula "Wp = (2 × no-load voltage + Ic × internal resistance) × Ic / 4" relating to the EVSE300 and the battery 11. Wp corresponds to an example of "parallel charging power" as described in this disclosure.
[0036] Next, in S17, the ECU150 determines whether Ws has fallen below a reference value determined based on Wp. In this embodiment, the reference value is the value obtained by adding a predetermined margin (hereinafter referred to as "Wx") to Wp (=Wp+Wx). Wx can be set arbitrarily. Wx may be a power value greater than 0, or it may be 0.
[0037] If Ws is greater than the above reference value (NO in S17), the process returns to S14 and series charging continues. The current suppression command (S14) reduces the power (Ws) of the battery 11. When Ws reaches the above 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 relays R1, R2, and R3 to ON, OFF, and ON respectively to put the battery 11 into a parallel state and sends a charge command for parallel charging to the charger 61. Upon receiving the charge command, the charger 61 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 charge command. This executes parallel charging of the battery 11. The ECU 150 determines a target charging current value of Ic / 2 or less, 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, the target charging current value is Ic / 2 (the value obtained by dividing Ic by 2). Parallel charging started in S18 may continue until predetermined charging termination conditions are met.
[0039] Figure 3 is a diagram comparing the state changes of the battery 11 being charged by the charging methods according to the embodiment and the modified example. The charging method according to the embodiment corresponds to the charging method described above shown in Figure 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 when the voltage of the battery 11 during series charging reaches a predetermined value (e.g., Vc). In both methods, the charging method is switched from series charging to parallel charging after the voltage of the battery 11 during series charging reaches a predetermined value (e.g., Vc).
[0040] In Figure 3, lines L1, L2, L3, and L4 represent the charging current, load voltage, no-load voltage, and charging power of battery 11, respectively. B This indicates the voltage of battery 11 (battery upper limit voltage) when the battery 11 is fully charged while remaining in series by series charging control (S11) without current suppression (S14). Vc is V BIf the voltage is higher than the specified value, series charging (rapid charging) can be continued until charging is complete. Period T10 represents the period from when the voltage of the battery 11 during series charging reaches a predetermined value (e.g., Vc) until the charging method of the battery 11 is switched to parallel charging. Period T10 corresponds to an example of the "switching decision period" in this disclosure. During period T10, the charging power of the charging method according to the embodiment is greater than that of 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 Figure 3.
[0041] Figure 4 shows the charging data measured for the charging methods according to the embodiment and modified examples. In Figure 4, lines L11, L12, L14, L15, L31, and L32 represent 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, respectively. Lines L21, L22, L24, L25, L41, and L42 represent the SOC, charging current, maximum cell temperature, minimum cell temperature, voltage, and power of the battery 11 in the charging method according to the modified examples, respectively. Lines L13 and L23 each represent the maximum charging current (equipment upper limit current) of the power supply equipment that supplies power to the battery 11. Lines L51 and L52 represent the maximum charging voltage (equipment upper limit voltage) and maximum charging power (equipment upper limit power) of the power supply equipment, respectively.
[0042] In the example shown in Figure 4, the battery 11 was charged from approximately 15% to approximately 80% of its State of Charge (SOC). Furthermore, if the highest cell temperature (the temperature of the hottest cell in the battery 11) exceeded 50°C during charging, the temperature control system 11b used power supplied from the power supply equipment (e.g., EVSE300) to cool the battery 11. The data obtained confirmed that the charging method according to the embodiment resulted in a shorter charging time than the charging method according to the modified example. In one example of the data, the charging time from 15% to 78% of the battery 11's SOC was 0.3 minutes shorter using the charging method according to the embodiment.
[0043] As described above, the charging method according to this embodiment includes the processes shown in Figure 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 reaches a predetermined value during series charging.
[0044] Series charging allows the battery 11 to be charged with greater charging power than parallel charging. Higher charging power results in a faster charging speed. However, as the battery 11 is charged, its stored energy increases, and its no-load voltage rises. During series charging, the battery 11's voltage is the no-load voltage plus the voltage increase due to the charging current (IR component). If the battery 11's voltage becomes too high during series charging, it may become impossible to continue charging depending on the specifications of the equipment supplying power to the battery 11. On the other hand, while the battery 11's voltage is low during series charging, continuing series charging can increase the charging speed of the battery 11. Therefore, in the above charging system, series charging of the battery 11 is continued as long as the battery 11's voltage does not reach a predetermined value. This shortens the charging time (the time it takes to complete charging). After the battery 11's voltage reaches a predetermined value during series charging, the charging method switches from series charging to parallel charging. Switching the charging method from series charging to parallel charging causes the battery 11's voltage to decrease. This prevents the voltage of the battery 11 from becoming too high while it is being charged.
[0045] Recent advancements in standards have led to higher voltages in vehicle batteries and power supply equipment. However, low-voltage power supply equipment still exists. In this regard, the above charging system allows the battery 11, which becomes high voltage when connected in series, to be switched to a parallel connection during charging, making it possible to charge the battery 11 not only with high-voltage equipment but also with low-voltage equipment (older or household power supply equipment).
[0046] In the above embodiment, the ECU 150 reduces the charging current of the battery 11 during series charging from the time the voltage of the battery 11 reaches a predetermined value until the battery 11 is switched to parallel charging (for example, the period T10 shown in Figure 3). By reducing the current of the battery 11 during series charging in this way, the voltage rise due to the charging current is suppressed. In the charging system according to the above embodiment, this current control prevents the voltage of the battery 11 from becoming too high during series charging. Therefore, it becomes easier to extend the period during which series charging of the battery 11 continues (the switching decision period).
[0047] In the charging method according to this embodiment, after the voltage of the battery 11 during series charging reaches a predetermined value or higher, the charging method of the battery 11 is switched from series charging to parallel charging when the charging power of the battery 11 during series charging falls below a reference value determined based on Wp (parallel charging power). This method significantly reduces the charging time (see Figures 3 and 4). Specifically, during period T10 (Figure 3), series charging of the battery 11 is performed, and the current of the battery 11 decreases during series charging. As the charging current decreases, the charging power also decreases. If series charging of the battery 11 is continued even when the charging power of the battery 11 decreases, eventually it will become possible to obtain greater charging power by switching to parallel charging than by continuing series charging. If series charging of the battery 11 is continued until this situation occurs, the charging time of the battery 11 will actually become 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 (voltage value for switching the charging method). The ECU 150 controls the current of the battery 11 so that the voltage of the battery 11 matches the equipment upper limit voltage (Vc) during period T10 (Figure 3). During period T10 (switching decision period), the charging power decreases as the charging current decreases, but the decrease in the charging power of the battery 11 is suppressed by maintaining a high voltage of the battery 11. However, the predetermined value can be changed as appropriate. A voltage value lower than Vc by a predetermined margin may be adopted as the predetermined value.
[0049] The ECU150 may execute the processing flow shown in Figure 5 instead of the processing flow shown in Figure 2. Figure 5 is a flowchart showing a modified version of the charging method shown in Figure 2. The processing flow shown in Figure 5 is the same as the processing flow shown in Figure 2, except that S14A, S14B, and S17A are used instead of S14 to S17 (Figure 2). S14A, S14B, and S17A will be described below.
[0050] Referring to Figure 5, in this modified example, when Vs reaches Vc during series charging of the battery 11 by the process in S11 (YES in S13), the ECU 150 measures the elapsed time since Vs reached Vc (hereinafter referred to as "Tc") in S14A. Subsequently, in S14B, the ECU 150 sends a current reduction command to the charger 61 to reduce the charging current of the battery 11. In this modified example, the ECU 150 determines the current reduction amount (the slope of the current with respect to time) based on Tc. The ECU 150 may increase the current reduction amount as Tc increases. Upon receiving the current reduction command, the charger 61 controls the charging current of the battery 11 so that the charging current of the battery 11 decreases according to the current reduction amount indicated by the current reduction command. Note that the current reduction amount during the switching decision period may be a fixed value.
[0051] Next, in S17A, the ECU150 determines whether Tc has exceeded a predetermined time (hereinafter referred to as "Tx"). Tx may be a fixed value or may be variable depending on the equipment 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 unit) may select one charging control from the options including the charging control shown in Figure 2 and the charging control shown in Figure 5, and execute the selected charging control. The ECU 150 may also decide which charging control to execute based on equipment information (Vc and / or Ic).
[0053] In the above embodiments and modifications, the charging control of the battery 11 is performed using a charger 61 mounted on the vehicle 100. However, the invention is not limited to this, and the charging control of the battery 11 may also be performed using a charger mounted on the EVSE. Figure 6 shows a modified example of the charging system shown in Figure 1.
[0054] Referring to Figure 6, the EVSE300A 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 adjust the charging current. The detector 331a includes various sensors (e.g., a current sensor and a voltage sensor) to detect the status of the charger 331 and outputs the detection results to the control device 332. When the connector 320a of the EVSE300A is connected to the inlet 60A of the vehicle 100A, the vehicle 100A enters a plug-in state. 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. During external charging, the charger 331 converts the AC power supplied from the power grid PG into DC power and outputs the DC power to the connector 320a. That is, the EVSE300A outputs DC power. The DC power output from EVSE300A to vehicle 100A is input to inlet 60A and charges battery 11.
[0055] The ECU150A performs external charging of the battery 11 according to the charging method shown in Figure 2 or Figure 5. The ECU150A 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 commands received from the ECU150A. This performs external charging of the battery 11. The control device 332 may also acquire the charging current using the detection result from the current sensor of the detector 331a.
[0056] The processing flows shown in Figures 2 and 5 can be modified as needed. For example, the order of processing may be changed, or unnecessary steps may be omitted, depending on the purpose. Also, the content of any of the processes may be changed. For example, the calculations in S14 to S16 in Figure 2 may be performed in parallel and simultaneously.
[0057] The vehicle configuration is not limited to the configuration described above (see Figure 1). For example, the vehicle may be configured to enable contactless charging. A vehicle performing contactless charging may be considered to be in a state similar to the "plug-in state" described above when the alignment between the power transmission unit (e.g., power transmission coil) on the power supply equipment side and the power receiving unit (e.g., power receiving coil) on the vehicle side is completed.
[0058] The energy storage device may be mounted on a resource other than an automobile. The resource may be a mobile object other than an automobile (railway vehicles, ships, airplanes, drones, walking robots, robotic cleaners, etc.). The resource may also be electrical machinery and appliances (lighting devices, air conditioning equipment, cooking appliances, televisions, refrigerators, washing machines, etc.). The energy storage device being charged may be a stationary energy storage device used in a building (house, factory, etc.) or outdoors.
[0059] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of this disclosure is indicated by the claims rather than by the description of the embodiments above, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [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, The system includes a control device that performs charging control for the aforementioned energy storage device, The energy storage device is configured to perform series charging, in which the first battery and the second battery are connected in series, and parallel charging, in which the first battery and the second battery are connected in parallel. The control device is configured to switch the charging method from series charging to parallel charging and continue charging the energy storage device after the voltage of the energy storage device reaches a predetermined value during series charging. The control device, during the switching decision period from when the voltage of the energy storage device during series charging reaches the predetermined value until the charging method of the energy storage device is switched to parallel charging, reduces the charging current of the energy storage device during series charging. The control device is configured to calculate the voltage of the energy storage device during series charging using the no-load voltage, charging current, and internal resistance of the first and second batteries, respectively. The predetermined value is the equipment upper limit voltage, which indicates the maximum charging voltage of the equipment that supplies power to the energy storage device. The control device controls the charging current of the energy storage device during the switching decision period so that the voltage of the energy storage device during series charging matches a predetermined value.
2. The control device predicts the parallel charging power, which is the charging power of the energy storage device when the charging method is switched to parallel charging during the series charging of the energy storage device. The charging system according to claim 1, wherein the control device is configured to switch the charging method of the energy storage device from series charging to parallel charging when the voltage of the energy storage device during series charging becomes equal to or greater than a predetermined value, and the charging power of the energy storage device during series charging becomes equal to or less than a reference value determined based on the parallel charging power.
3. A vehicle comprising the charging system according to claim 1 or 2, A vehicle in which, when predetermined conditions are met while the vehicle and an external power supply facility are electrically connected to each other, the control device starts the series charging of the energy storage device using the power supplied from the power supply facility.