Charging system

Abstract

Charge the battery until it is fully charged. [Solution] The ECU performs the following steps when plug-in charging is started (YES in S100): performing CC charging with current value Ia (S102); performing CV charging with voltage value Va when the voltage reaches threshold Va (YES in S104) (S106); performing CC charging with current value Ib when the current value reaches threshold Ib (YES in S108) (S110); performing CV charging with voltage value Vb when the voltage value reaches threshold Vb (YES in S112) (S114); and stopping charging when charging is completed (YES in S116) (S118).

Description

Technical Field

[0001] The present disclosure relates to a charging system.

Background Art

[0002] Japanese Patent Application Laid-Open No. 2023-127623 (Patent Document 1) discloses CCCV charging in which the magnitude of the charging current is maintained until the voltage of the battery reaches the upper limit value to perform CC (Constant Current) charging, and then CV (Constant Voltage) charging is performed while maintaining the voltage of the battery.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When performing the above-described CCCV charging on a battery composed of, for example, an LFP battery (lithium iron phosphate ion battery) with a lower SOC (State Of Charge) estimation accuracy than others, it is required to set the charging voltage low enough that lithium does not precipitate when switching from CC charging to CV charging. As a result, there may be cases where the battery cannot be charged until it reaches the fully charged state (SOC is 100%).

[0005] The present disclosure has been made to solve the above-described problems, and an object thereof is to provide a charging system that charges a battery until it reaches the fully charged state.

Means for Solving the Problems

[0006] A charging system relating to a certain aspect of this disclosure is a charging system equipped with a control device that controls the charging of a battery, including a lithium iron phosphate battery. The control device charges the battery at a first current value when charging of the battery is started, charges the battery while maintaining the first voltage value when the battery charging voltage reaches a first voltage value, charges the battery at a second current value when the charging current becomes a second current value lower than the first current value, and charges the battery while maintaining the second voltage value when the charging voltage becomes a second voltage value higher than the first voltage value.

[0007] In this way, the battery can be charged by increasing the voltage value in two stages. For example, the battery can be charged while suppressing lithium deposition at the first voltage value, and then the battery can be continued to be charged until it is fully charged by performing forced charging while suppressing lithium deposition at the second current value.

[0008] In one embodiment, the control device performs temperature-raising control to raise the temperature of the battery when charging the battery with a second current value.

[0009] In this way, the battery can be continued to charge at the second current value while suppressing lithium deposition by raising the battery's temperature.

[0010] Furthermore, in one embodiment, the first voltage value includes a voltage value that can suppress the deposition of lithium.

[0011] In this way, the battery can be charged while suppressing lithium deposition at the first voltage value.

[0012] Furthermore, in one embodiment, the second current value includes a current value that can suppress lithium deposition even when the battery is charged until it is fully charged.

[0013] In this way, even when charging above the first voltage value, the battery can be charged at the second current value, thereby suppressing lithium deposition and allowing the battery to continue charging.

[0014] In one further embodiment, the second voltage value includes a voltage value capable of charging the battery to a fully charged state.

[0015] By doing this, the battery can be fully charged by maintaining the second voltage value and continuing the charging process. [Effects of the Invention]

[0016] According to this disclosure, a charging system can be provided that charges a battery until it is fully charged. [Brief explanation of the drawing]

[0017] [Figure 1] This is a diagram showing an example of a charging system configuration. [Figure 2] This flowchart shows an example of a process performed by the ECU. [Figure 3] This figure shows an example of a map illustrating the relationship between temperature and current value Ib. [Figure 4] This is a timing chart showing an example of ECU operation. [Figure 5] This flowchart shows an example of the processing performed by the ECU in a modified example. [Modes for carrying out the invention]

[0018] The embodiments of this disclosure will be described in detail below 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.

[0019] Hereinafter, an example of the configuration of the charging system 1 according to the present embodiment will be described. FIG. 1 is a diagram showing an example of the configuration of the charging system 1. As shown in FIG. 1, the charging system 1 is mounted on the vehicle 200. The vehicle 200 may be any vehicle equipped with a battery that can be charged using electric power supplied from an external power source (for example, a charging stand 10 which is an external power supply facility), and for example, it may be an electric vehicle or a plug-in hybrid vehicle.

[0020] The vehicle 200 includes an ECU (Electronic Control Unit) 100 which is a control device, a battery 214, an inverter 216, an MG (Motor Generator) 218, an inlet 220, and a charging device 222. The charging system 1 according to the present embodiment is composed of the ECU 100, the battery 214, and the charging device 222.

[0021] The battery 214 includes a secondary battery such as a lithium-ion battery having a liquid electrolyte or a solid electrolyte. In the present embodiment, the battery 214 includes a lithium iron phosphate ion secondary battery that can be recharged.

[0022] The inverter 216 is configured to be able to convert the DC power of the battery 214 and the AC power of the MG 218 bidirectionally according to a control signal from the ECU 100.

[0023] The MG 218 is a drive source for driving the drive wheels of the vehicle 200 and is composed of, for example, a three-phase AC rotating electric machine or the like. The MG 218 has a function as an electric motor (motor) for driving the vehicle 200 using the power of the battery 214 and a function as a generator for generating power (for example, regenerative power) for charging the battery 214.

[0024] The inlet 220 has a shape to which the connector 17 of the charging stand 10 can be attached. The inlet 220 is electrically connected to the battery 214 via the charging device 222.

[0025] The charging device 222 is configured to charge the battery 214 by converting the AC power supplied from the charging station 10 into DC power. The charging power (current and voltage) supplied from the charging device 222 to the battery 214 is controlled by the ECU 100.

[0026] Sensors 102, 104, and 106 are connected to the ECU 100 to acquire the voltage V, current I, and temperature TB of the battery 214. The ECU 100 includes a CPU (Central Processing Unit) and memory (neither of which are shown). Based on the signals received from each sensor, as well as information such as maps and programs stored in the memory, the ECU 100 controls each device (such as the inverter 216 and the charging device 222) so that the vehicle 200 reaches a desired state.

[0027] The ECU 100 has the function of sequentially calculating the State of Charge (SOC) of the battery 214 based on the detection values ​​of each sensor 102, 104, and 106. Various known methods can be used to calculate the SOC, such as a method using current value integration (Coulomb count) or a method using open circuit voltage (OCV) estimation. The ECU 100 is configured to communicate with the communication unit 13 of the charging station 10, which will be described later.

[0028] The charging stand 10 includes a communication unit 13, a control unit 14, a transmission unit 15, a cable 16, and a connector 17.

[0029] The communication unit 13 communicates with the ECU 100 of the vehicle 200 via cable 16 when the connector 17 is connected to the inlet 220 of the vehicle 200. Wired communication includes, for example, power line communication, CAN (Control Area Network) communication, or LAN communication. The communication unit 13 may also communicate with the ECU 100 of the vehicle 200 using, for example, wireless communication of various standards (for example, Wi-Fi).

[0030] The control unit 14 controls the operation of the transmission unit 15. The control unit 14 includes, for example, a CPU and memory (neither of which are shown). The control unit 14 controls the transmission unit 15 based on information received from the vehicle 200 using the communication unit 13 (such as the requested current value described later) and information such as maps and programs stored in memory. When the connector 17 is attached to the inlet 220, the control unit 14 uses the communication unit 13 to acquire information about the battery 214 (for example, information about the SOC, charging voltage, requested current value, and information about power transmission requests) and to transmit information about the charging station 10 (for example, information about the available time, the minimum charging power that can be supplied, and the lower limit of the output current).

[0031] One end of the cable 16 is connected to the transmission unit 15. The other end of the cable 16 is connected to a connector 17. The transmission unit 15 transmits AC power from the grid power supply 400 to the destination of the connector 17 in accordance with the control signal from the control unit 14.

[0032] The connector 17 has a shape that allows it to be attached to the inlet 220. When the connector 17 is attached to the inlet 220, power can be supplied from the transmission unit 15 to the charging device 222 based on the control signal received by the control unit 14 from the ECU 100.

[0033] For example, when the connector 17 is connected to the inlet 220 of a stationary vehicle 200, the charging station 10 supplies AC power from the grid power supply 400 to the charging device 222 via the transmission unit 15. The ECU 100 requests the charging station 10 to supply AC power from the transmission unit 15 when the connector 17 is connected to the inlet 220 of a stationary vehicle 200. The control unit 14 of the charging station 10 controls the transmission unit 15 to supply AC power from the grid power supply 400 to the charging device 222 in response to the power supply request from the ECU 100. When the power is supplied to the charging device 222 from the transmission unit 15, the ECU 100 charges the battery 214 using the charging device 222 if the State of Charge (SOC) of the battery 214 is below a threshold. When the State of Charge (SOC), calculated using the detection values ​​of each sensor 102, 104, and 106, exceeds a threshold value during charging of the battery 214, the ECU 100 requests the charging station 10 to stop charging using the charging device 222 and to stop the power supply from the transmission unit 15. The control unit 14 of the charging station 10 controls the transmission unit 15 to stop the power supply to the charging device 222 in response to the request from the ECU 100 to stop the power supply.

[0034] When charging begins, the ECU 100 controls at least one of the charging current and / or charging voltage to continue charging the battery 214 until it reaches a predetermined state (for example, a fully charged state). For example, the ECU 100 performs CCCV charging, which involves maintaining the magnitude of the charging current until the voltage of the battery 214 reaches an upper limit, and then performing CV charging while maintaining the voltage of the battery 214.

[0035] When performing CCCV charging as described above on a battery 214 composed of an LFP battery (lithium iron phosphate battery) whose estimated SOC is lower than others, it is necessary to set the charging voltage low enough to prevent lithium deposition when switching from CC charging to CV charging. As a result, it may not be possible to charge the battery to a fully charged state (SOC of 100%).

[0036] Therefore, in this embodiment, the ECU 100 operates as follows when it starts charging the battery 214. Specifically, the ECU 100 controls the charging device 222 to charge the battery 214 with a first current value (Ia). Subsequently, when the charging voltage of the battery 214 reaches a first voltage value (Va), the ECU 100 controls the charging device 222 to maintain the first voltage value (Va) and charge the battery 214. Then, when the charging current becomes a second current value (Ib) which is lower than the first current value (Ia), the ECU 100 controls the charging device 222 to charge the battery 214 with the second current value (Ib). Subsequently, when the charging voltage becomes a second voltage value (Vb) which is higher than the first voltage value (Va), the ECU 100 controls the charging device 222 to maintain the second voltage value (Vb) and charge the battery 214.

[0037] In this way, the battery 214 can be charged by increasing the voltage value in two stages. For example, the battery 214 can be charged while suppressing lithium deposition at the first voltage value (Va), and then forced charging can be performed while suppressing lithium deposition at the second current value (Ib), allowing charging to continue until the battery 214 is fully charged.

[0038] The following describes an example of the processes performed in the ECU100, with reference to Figure 2. Figure 2 is a flowchart showing an example of the processes performed in the ECU100. The series of processes shown in this flowchart are repeatedly executed at predetermined intervals.

[0039] In step 100 (hereinafter referred to as S), the ECU 100 determines whether or not to start plug-in charging. For example, the ECU 100 determines to start plug-in charging if the charging start conditions are met. The charging start conditions include at least one of the following: the vehicle 200 is stopped, the connector 17 is connected to the inlet 220, power can be supplied from the transmission unit 15, and the state of charge (SOC) of the battery 214 is below the threshold set for starting charging. If it is determined that plug-in charging should be started (YES in S100), the process moves to S102. If it is determined that plug-in charging should not be started (NO in S100), the process ends.

[0040] In S102, ECU100 performs CC charging with a current value Ia. That is, ECU100 charges battery 214 so that the charging current for battery 214 is maintained at a current value Ia. The current value Ia is a predetermined value that is determined through experimentation or other means. The process then moves to S104.

[0041] In S104, the ECU100 determines whether the voltage value has reached the threshold Va. For example, the ECU100 determines that the threshold Va has been reached when the voltage value of the battery 214 is equal to or greater than the threshold Va. The threshold Va is set by fitting a voltage at which Li deposition does not occur through experiments or other means. If it is determined that the voltage value has reached the threshold Va (YES in S104), the process moves to S106.

[0042] In S106, ECU100 performs CV charging at voltage value Va. That is, ECU100 charges battery 214 so that the voltage value Va is maintained as the charging voltage. The process then moves to S108.

[0043] In S108, the ECU100 determines whether the current value has reached the threshold Ib. For example, the ECU100 determines that the threshold Ib has been reached when the current value of the battery 214 falls below the threshold Ib. The current value threshold Ib is the current at which Li deposition is suppressed even when the battery 214 is charged until its SOC reaches 100%, and is a value that is fitted through experiments, etc. The current value threshold Ib changes with temperature. The ECU100 sets the current value threshold Ib using the temperature TB of the battery 214 and a map, etc. Figure 3 is a diagram showing an example of a map that shows the relationship between temperature and current value Ib. As shown in Figure 3, for example, in a temperature range of -30°C to 30°C for the temperature TB of the battery 214, I(0), I(1), I(2), I(3), I(4), I(5), and I(6) are set correspondingly for every 10°C interval. The map shown in Figure 3 is set by fitting through experiments, etc. The ECU 100 sets a threshold value Ib corresponding to the battery temperature TB of the battery 214, which is obtained by linear interpolation or the like using the battery temperature TB and the map. If it is determined that the current value has reached the threshold value Ib (YES in S108), the process moves to S110.

[0044] In S110, ECU100 performs CC charging with current value Ib. That is, ECU100 charges battery 214 so that the charging current for battery 214 is maintained at current value Ia. The process then moves to S112.

[0045] In S112, the ECU 100 determines whether the voltage value has reached the threshold Vb. For example, the ECU 100 determines that the threshold Vb has been reached when the voltage value of the battery 214 is equal to or greater than the threshold Vb. The threshold Vb includes the voltage value that can charge the battery 214 to a fully charged state. The ECU 100 may set the threshold Vb according to the degradation state of the battery 214. If it is determined that the voltage value has reached the threshold Vb (YES in S112), the process moves to S114.

[0046] In S114, ECU100 performs CV charging at voltage value Vb. That is, ECU100 charges battery 214 so that the voltage value Vb is maintained as the charging voltage. The process then moves to S116.

[0047] In S116, the ECU 100 determines whether or not to terminate charging. The ECU 100 determines to terminate charging if the conditions for terminating charging are met. The conditions for terminating charging may include, for example, the condition that the battery 214 has reached a predetermined state. The predetermined state may include, for example, a fully charged state (SOC is 100%). Alternatively, the conditions for terminating charging may include, in place of or in addition to the condition regarding SOC, the condition that the charging duration exceeds a threshold. The threshold may be set by the available time of the charging station 10, etc. If it is determined to terminate charging (YES in S116), the process moves to S118.

[0048] In S118, the ECU 100 stops charging. That is, the ECU 100 stops the operation of the charging device 222. The ECU 100 may also send a request to the charging station 10 to stop the power supply. If it is determined that plug-in charging will not start (NO in S100), this process is terminated. If it is determined that the voltage value has not reached the threshold Va (NO in S104), the process returns to S104. Furthermore, if it is determined that the current value has not reached the threshold Ib (NO in S108), the process returns to S108. Furthermore, if it is determined that the voltage value has not reached the threshold Vb (NO in S112), the process returns to S112. Furthermore, if it is determined that charging will not be terminated (NO in S116), the process returns to S116.

[0049] An example of the operation of the ECU 100 based on the structure and flowchart described above will be explained with reference to Figure 4. Figure 4 is a timing chart showing an example of the operation of the ECU 100. LN1 in Figure 4 shows the time change of the voltage V of the battery 214. LN2 in Figure 4 shows the time change of the current I flowing through the battery 214.

[0050] For example, when the connector 17 is attached to the inlet 220 of the vehicle 200, AC power is supplied to the vehicle 200 from the transmission unit 15 of the charging station 10 in response to a request from the ECU 100. At time T(0), if it is determined that the charging start condition is met, it is determined that plug-in charging will start (YES in S100), and CC charging is performed at a current value Ia as shown in LN2 of Figure 4 (S102). As a result, the battery 214 is charged so that the current value Ia is maintained. At this time, the voltage V of the battery 214 increases over time from the voltage at the start of charging, as shown in LN1 of Figure 4, and the SOC increases.

[0051] At time T(1), as shown in LN1 of Figure 4, when the voltage V of battery 214 reaches the threshold Va (YES in S104), CV charging is performed at the voltage value Va (S106). Therefore, battery 214 is charged so that the voltage value Va is maintained. At this time, as shown in LN2 of Figure 4, the current I of battery 214 decreases from the current value Ia as time passes, and the SOC increases. In addition, because CV charging is performed at the voltage value Va, lithium deposition during charging is suppressed.

[0052] At time T(2), as shown in LN2 of Figure 4, when the current I of the battery 214 reaches a threshold Ib set according to the temperature of the battery 214 using the map shown in Figure 3 (YES in S108), CC charging is performed at the current value Ib (S110). Therefore, the battery 214 is charged so that the current value Ib is maintained. At this time, the voltage V of the battery 214 increases from the voltage value Va as time passes, and the SOC increases. In addition, because CC charging is performed at the current value Ib, lithium deposition during charging is suppressed.

[0053] At time T(3), as shown in LN1 of Figure 4, when the voltage V of battery 214 reaches the threshold Vb (YES in S112), CV charging is performed at the voltage value Vb (S114). Therefore, battery 214 is charged so that the voltage value Vb is maintained. At this time, the current I of battery 214 decreases from the current value Ib as time passes, as shown in LN2 of Figure 4, and the SOC increases. Since battery 214 is charged with a current lower than the current value Ib, lithium deposition during charging is suppressed.

[0054] Subsequently, when the battery 214 reaches a fully charged state, the conditions for ending charging are met, and it is determined that charging should be terminated (YES in S116), and charging is stopped (S118).

[0055] As described above, the charging system 1 according to this embodiment allows the battery 214 to be charged by increasing the voltage value in two stages. Therefore, by CV charging the battery 214 while suppressing lithium deposition at a voltage value Va, and then CC charging while suppressing lithium deposition at a current value Ib, charging can be continued while suppressing lithium deposition until the battery 214 is fully charged. Thus, a charging system that charges the battery until it is fully charged can be provided.

[0056] Furthermore, since the voltage value Va is a voltage value that can suppress lithium deposition, lithium deposition can be suppressed by charging the battery 214 while maintaining a voltage value below Va.

[0057] Furthermore, since the current value Ib is sufficient to suppress lithium deposition even when charging the battery 214 until it is fully charged, lithium deposition can be suppressed by maintaining a current of Ib or less while charging the battery 214, even when charging above the voltage value Va.

[0058] Furthermore, by maintaining the voltage value Vb and continuing to charge, the battery 214 can be brought to a fully charged state.

[0059] The following describes variations. In the above-described embodiment, it was explained that after CV charging with voltage value Va, CC charging is performed with current value Ib when the current reaches threshold value Ib. However, for example, temperature rise control may be performed when the current reaches threshold value Ib after CV charging with voltage value Va.

[0060] Figure 5 shows an example of the processing performed by ECU100 in the modified example. The same step numbers are assigned to the same processes shown in the flowchart of Figure 2, and therefore the content of these processes is the same, except as described below. For this reason, a detailed explanation will not be repeated.

[0061] If it is determined that the current value has reached the threshold Ib (YES in S108), the process moves to S200. In S200, the ECU 100 performs temperature rise control. The ECU 100 may, for example, operate a heating device such as a heater that heats the battery 214 (not shown) to raise the temperature of the battery 214. The ECU 100 may perform temperature rise control until a predetermined time has elapsed, or until the temperature TB of the battery 214 reaches a predetermined temperature. The process then moves to S110.

[0062] In this way, when CC charging is performed at a current value Ib, the temperature of the battery 214 can be raised to further suppress lithium deposition. The ECU 100 may also perform temperature rise control only when the temperature TB of the battery 214 is lower than the threshold value when the current I reaches the threshold value Ib.

[0063] Furthermore, in the above-described embodiment, the ECU 100 was described as controlling the charging current and charging voltage of the battery 214 using the charging device 222. However, if the AC power is converted to DC power in the transmission unit 15 and charging power is supplied to the battery 214 without going through the charging device 222, the ECU 100 may send a control signal to the transmission unit 15 to control the charging current and charging voltage of the battery 214. Alternatively, the control unit 14 may control the charging current and charging voltage of the battery 214 using the transmission unit 15 in response to a request from the ECU 100.

[0064] Furthermore, although the above-described embodiment was explained as performing CV charging at a voltage value Va and then charging the battery 214 with a current of Ib or less, a lower limit guard may be set for the command value of the charging power so that the charging current is not power-limited below the current value Ib. For example, the lower limit guard for the command value of the charging power may be set as the product of the current value Ib, the smaller of the minimum voltage value of the multiple cells and the target voltage during CV charging, and the number of cells.

[0065] Furthermore, although the above-described embodiment explained the case in which the charging system 1 is mounted on a vehicle 200 as an example, it is not limited to the case in which it is mounted on a vehicle 200. For example, the charging system 1 may include a stationary battery, a charging device for charging the stationary battery, and a control device for controlling the charging device.

[0066] Furthermore, the above-mentioned modifications may be implemented by combining all or part of them as appropriate. The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than by the foregoing description, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of symbols]

[0067] 1 Charging system, 10 Charging station, 13 Communication unit, 14 Control unit, 15 Transmission unit, 16 Cable, 17 Connector, 100 ECU, 102, 104, 106 Sensors, 200 Vehicle, 214 Battery, 216 Inverter, 220 Inlet, 222 Charging device, 400 Power supply system.

Claims

1. A charging system equipped with a control device that controls the charging of a battery including a lithium iron phosphate battery, The control device is When charging of the aforementioned battery is started, the battery is charged with a first current value. When the charging voltage of the battery reaches a first voltage value, the battery is charged while maintaining the first voltage value. When the charging current becomes a second current value that is lower than the first current value, the battery is charged with the second current value. A charging system that charges the battery by maintaining the second voltage value when the charging voltage becomes a second voltage value that is higher than the first voltage value.

2. The charging system according to claim 1, wherein the control device performs temperature rise control to raise the temperature of the battery when charging the battery with the second current value.

3. The charging system according to claim 1, wherein the first voltage value includes a voltage value capable of suppressing lithium deposition.

4. The charging system according to claim 1, wherein the second current value includes a current value capable of suppressing lithium deposition even when the battery is charged until it is fully charged.

5. The charging system according to any one of claims 1 to 4, wherein the second voltage value includes a voltage value capable of charging the battery to a fully charged state.

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