Charging control device, vehicle, charging control method, and recording medium

Abstract

The present invention provides a charging control device, a vehicle, a charging control method, and a recording medium containing a control program. The charging control device includes: a control unit that controls the charging of a plurality of cells constituting a battery pack; a measuring unit that, during charging under the control of the control unit, measures the CCV (Closed Circuit Voltage) of the plurality of cells when the voltage value of the cell with the highest voltage among the plurality of cells is greater than a threshold value and the current value is less than a set value; and an execution unit that performs a discharge process on a cell whose voltage difference from the cell with the lowest measured CCV is greater than a predetermined value, in order to eliminate the potential difference.

Description

Technical Field

[0001] The present disclosure relates to a charging control device, a vehicle, a charging control method, and a recording medium having a control program recorded thereon. Background Art

[0002] Japanese Patent Application Laid-Open No. 2018-129958 discloses a charging rate balancing device that balances the charging rates of individual cells that make up a lithium-ion battery, or battery pack. This balancing device charges multiple cells collectively during the charging process. When a cell reaches its maximum voltage, the OCV (open circuit voltage) is measured after a predetermined period of time. Based on the measured OCV, the cells are then balanced.

[0003] Even if the balancing device disclosed in Japanese Patent Application Laid-Open No. 2018-129958 is applied to an auxiliary battery of a vehicle that requires constant power supply, it is difficult to use the device because it is impossible to disconnect the auxiliary battery from the vehicle load using a relay to obtain OCV. Summary of the Invention

[0004] An object of the present disclosure is to provide a charging control device, a vehicle, a charging control method, and a recording medium recording a control program that can perform a balancing process even in a battery pack that cannot be disconnected from a load.

[0005] The first embodiment is a charging control device comprising: a control unit for controlling the charging of a plurality of cells constituting a battery pack; a measuring unit for measuring the CCV (Closed Circuit Voltage) of the plurality of cells when, during charging under the control of the control unit, the voltage value of the cell having the highest voltage among the plurality of cells is greater than or equal to a threshold value and the current value is less than or equal to a set value; and an execution unit for performing a discharge process on a cell having a voltage difference greater than or equal to a specified value from the cell having the lowest measured CCV, in order to eliminate the potential difference.

[0006] In the charge control device of the first embodiment, when the control unit charges the cells, the measurement unit measures the CCV of each cell when the voltage value of the cell with the highest voltage during charging is greater than or equal to a threshold value and the current value is less than or equal to a set value. Furthermore, in this charge control device, the execution unit performs a discharge process on the cell whose voltage has a voltage difference greater than or equal to a predetermined value from the cell with the lowest measured CCV, thereby eliminating this potential difference. This charge control device, by performing a discharge process on cells with a potential difference based on the CCV, enables equalization even in a battery pack that cannot be disconnected from the load.

[0007] The charge control device of the second aspect is implemented based on the charge control device of the first aspect, wherein the control unit performs control so that charging is performed in a region where the voltage during charging is high until a predetermined time has elapsed.

[0008] In the second embodiment of the charge control device, the control unit charges the battery pack to maintain a high SOC (State of Charge). This allows for cell balancing in the region where voltage fluctuates relative to SOC, even for battery packs such as iron phosphate lithium-ion batteries, which have a flat region in the SOC-OCV curve with minimal OCV variation.

[0009] A charge control device according to a third aspect is provided in addition to the charge control device according to the first or second aspect, wherein the measuring unit measures the CCV when the current value remains below the set value for a predetermined period of time.

[0010] In the charge control device of the third embodiment, the measuring unit measures the CCV when a specific period of time has elapsed while the current value remains below the set value. This allows the polarization in the cell to be eliminated as much as possible, allowing the CCV to be measured close to the OCV. This allows for highly accurate cell balancing even when using the CCV.

[0011] A fourth aspect is a vehicle comprising: the charge control device according to any one of the first to third aspects; and a charging device for charging the battery pack.

[0012] According to the vehicle of the fourth aspect, even if the battery pack is an auxiliary machine battery that cannot cut off the supply of electric power and constantly supplies electric power to auxiliary machines, it is possible to perform the cell balancing process.

[0013] The fifth method is a charging control method in which a computer performs the following processing: charging multiple single cells that constitute a battery pack, during charging, when the voltage value of the single cell with the highest voltage among the multiple single cells is greater than a threshold value and the current value is less than a set value, the CCV (Closed Circuit Voltage) of the multiple single cells is measured, and a discharge process is performed on the single cell whose voltage has a potential difference of greater than a specified value from the single cell with the lowest measured CCV, so as to eliminate the above-mentioned potential difference.

[0014] In the fifth embodiment of the charging control method, while charging the cells, the computer measures the CCV of each cell when the voltage of the cell with the highest voltage during charging is above a threshold and the current is below a set value. The computer then discharges the cells whose voltage difference from the cell with the lowest measured CCV is greater than a predetermined value to eliminate this potential difference. This charging control method, by discharging cells with potential differences based on their CCV, enables equalization even in battery packs that cannot be disconnected from the load.

[0015] A sixth aspect is a non-transitory recording medium having a control program recorded thereon. The control program causes a computer to execute processing for charging a plurality of cells constituting a battery pack. When the voltage value of the cell with the highest voltage among the plurality of cells during charging is greater than or equal to a threshold value and the current value is less than or equal to a set value, the CCV (Closed Circuit Voltage) of the plurality of cells is measured, and a discharge process is performed on the cell having a voltage difference greater than or equal to a predetermined value from the cell with the lowest measured CCV, in order to eliminate the voltage difference.

[0016] The control program in the sixth embodiment causes a computer to execute the following processing. While charging the cells, if the voltage of the cell with the highest voltage during charging is above a threshold and the current is below a set value, the computer measures the CCV of each cell. Furthermore, the computer discharges cells whose voltage difference from the cell with the lowest measured CCV is greater than a predetermined value to eliminate this potential difference. This control program, by discharging cells with potential differences based on their CCVs, enables balancing even in battery packs that cannot be disconnected from the load.

[0017] According to the present disclosure, balancing can be performed even on a battery pack that cannot be disconnected from a load. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] An exemplary embodiment of the present invention is described in detail based on the following figures, in which:

[0019] Figure 1 It is a schematic configuration diagram of a vehicle and a power supply system according to an embodiment.

[0020] Figure 2 This is a block diagram showing the hardware configuration of the monitoring unit according to the embodiment.

[0021] Figure 3 This is a block diagram showing the functional configuration of a CPU in the monitoring unit according to the embodiment.

[0022] Figure 4 This is a flowchart showing the flow of equalization processing in the embodiment.

[0023] Figure 5 The SOC-OCV relationship of an iron phosphate lithium-ion battery is shown. DETAILED DESCRIPTION

[0024] An example embodiment of the present disclosure is described in detail below with reference to the accompanying drawings. The charging control device of the present disclosure is installed in a vehicle power supply system. The charging control device performs a process (hereinafter referred to as "balancing process") to equalize the SOC (State of Charge) of each cell in an iron phosphate-based lithium-ion battery.

[0025] Figure 5 The SOC-OCV relationship of an iron phosphate lithium-ion battery is shown in FIG. Figure 5 As shown, in iron phosphate lithium-ion batteries, both the charge-side OCV (OCV) representing the OCV during charging and the discharge-side OCV (OCV) representing the OCV during discharging have a flat range with minimal OCV variation between 35% and 95% SOC. Furthermore, iron phosphate lithium-ion batteries exhibit hysteresis between charge and discharge, as indicated by the voltage difference between the charge-side OCV and the discharge-side OCV. Therefore, the SOC-OCV relationship is unique, making it difficult to perform the same OCV-based balancing process as is used for ternary lithium-ion batteries, which exhibit virtually no hysteresis between charge and discharge.

[0026] Furthermore, in the case of batteries that constantly supply power to auxiliary machines, such as auxiliary batteries, it is not possible to disconnect the load from the auxiliary battery using a relay, making it difficult to measure OCV. Therefore, the charge control device of the present disclosure implements balancing processing by monitoring CCV.

[0027] (structure)

[0028] like Figure 1 As shown, the power supply system 10 of this embodiment is mounted on a vehicle 12. Vehicle 12 can be exemplified by an EV (Electric Vehicle) or an HEV (Hybrid Electric Vehicle). Vehicle 12 of this embodiment is supplied with power by the power supply system 10. Vehicle 12 includes auxiliary machines 26, which are devices that operate various components of vehicle 12, and a control ECU 28 that controls various components of vehicle 12, including auxiliary machines 26.

[0029] The power supply system 10 is configured to include a monitoring ECU 14 as a charging control device, a high voltage battery 22, a DC / DC converter 24, and an auxiliary battery 30 as an auxiliary battery. Figure 1 In FIG, reference symbol G represents the earth. The monitoring ECU 14 will be described in detail later.

[0030] The high-voltage battery 22 is a high-voltage battery used to operate a driving motor for driving the vehicle 12 , and is composed of a rechargeable secondary battery such as a lithium-ion battery or a nickel-metal hydride battery. The high-voltage battery 22 is connected to a DC-DC converter 24 .

[0031] The DC-DC converter 24 supplies power output from the high-voltage battery 22 to the auxiliary battery 30 and auxiliary equipment 26 serving as loads. The high-voltage battery 22 is connected to the input side of the DC-DC converter 24, and the auxiliary battery 30 and auxiliary equipment 26 are connected to the output side. When supplying power, the DC-DC converter 24 steps down the output voltage of the high-voltage battery 22, which serves as input voltage, to a predetermined voltage based on instructions from the control ECU 28, and then outputs the voltage to the auxiliary battery 30 and auxiliary equipment 26. The DC-DC converter 24 of this embodiment is an example of a charging device.

[0032] Control ECU 28 is constituted by, for example, a microcomputer and has a function of controlling DCDC converter 24 , thereby supplying electric power from high-voltage battery 22 to auxiliary battery 30 and auxiliary devices 26 via DCDC converter 24 .

[0033] The auxiliary battery 30 is a battery capable of operating the auxiliary machinery 26. In this embodiment, the auxiliary battery 30 is a rechargeable iron phosphate lithium-ion battery. Furthermore, the auxiliary battery 30 is a battery pack composed of a plurality of cells 32. The auxiliary battery 30 is connected to the DC-DC converter 24 and can receive power from the DC-DC converter 24. Furthermore, the auxiliary battery 30 is connected to the auxiliary machinery 26 of the vehicle 12 and supplies power to the auxiliary machinery 26.

[0034] The monitoring ECU 14 is configured to include a monitoring unit 14A and a discharging unit 14B. The monitoring unit 14A includes a monitoring unit 20, which is configured as a microcomputer; multiple voltmeters 34, provided for each cell 32; and an ammeter 35, which is provided on the wiring of the auxiliary battery 30. The discharging unit 14B includes multiple discharging units 36, which are provided for each cell 32. The discharging units 36 are configured to include, for example, a discharging resistor connected to the cell 32 and a switch that controls the flow of current from the cell 32 to the resistor.

[0035] like Figure 2As shown, the monitoring unit 20 includes a CPU (Central Processing Unit) 20A, a ROM (Read Only Memory) 20B, a RAM (Random Access Memory) 20C, an input / output interface 20D, and a communication interface 20E. The CPU 20A, ROM 20B, RAM 20C, the input / output interface 20D, and the communication interface 20E are interconnected via an internal bus 20F so as to be able to communicate with each other.

[0036] The CPU 20A is a central processing unit that executes various programs and controls various components. Specifically, the CPU 20A reads programs from the ROM 20B and executes the programs using the RAM 20C as a work area.

[0037] The ROM 20B stores various programs and various data. In the embodiment, the ROM 20B stores a control program 100 .

[0038] Control program 100 is a program for controlling monitoring unit 20 . Monitoring unit 20 , which is controlled by control program 100 , controls charging and discharging of auxiliary battery 30 .

[0039] The RAM 20C serves as a work area for temporarily storing programs or data.

[0040] The input / output I / F 20D is an interface for electrically connecting the monitoring unit 20 to the voltmeter 34 , the ammeter 35 , and the discharge unit 36 ​​.

[0041] Communication I / F 20E is an interface for connecting to various ECUs such as control ECU 28 . This interface can use, for example, a communication standard based on the CAN protocol. Monitoring unit 20 controls DCDC converter 24 via control ECU 28 connected to communication I / F 20E, thereby controlling charging of auxiliary battery 30 .

[0042] The monitoring unit 20 may include a memory as a storage unit in addition to the ROM 20B or may include a memory as a storage unit instead of the ROM 20B. The memory may be composed of, for example, a HDD (Hard Disk Drive) or an SSD (Solid State Drive).

[0043] like Figure 3 As shown, in the monitoring unit 20 of the present embodiment, the CPU 20A functions as the control unit 200 , the measuring unit 210 , and the executing unit 220 by executing the control program 100 .

[0044] The control unit 200 has a function of controlling the charging of the auxiliary battery 30. The control unit 200 of this embodiment controls the charging of each cell 32 so that the voltage during charging is in a high voltage region until a predetermined time has elapsed. Here, the "high voltage region" is a region where the SOC is higher than the flat region and the voltage of the cell 32 changes relative to the SOC (see Figure 5 ). In addition, the "predetermined time" refers to the time until at least the current value and the voltage value stabilize.

[0045] The measuring unit 210 has the function of measuring the voltage of each cell 32 using the voltmeter 34 and the current of the auxiliary battery 30 using the ammeter 35. During the charging of the auxiliary battery 30, when the voltage value of the cell with the highest voltage among the plurality of cells 32 is greater than a threshold value and the current value is less than a set value, the measuring unit 210 of this embodiment measures the CCV of the plurality of cells 32. Here, the voltage "threshold" is set to a flat region (see Figure 5 ) or above the voltage of the battery cell 32. Specifically, the threshold value is the voltage value of the battery cell 32 voltage change relative to the SOC. Furthermore, the "set value" of the current is set to a current value that allows for a voltage drop associated with the internal resistance of the battery cell 32.

[0046] Furthermore, when the current value remains below the set value for a predetermined time, the measuring unit 210 measures the CCV. Here, the "predetermined time" is set to at least the time required for polarization in the cell 32 to be eliminated.

[0047] The execution unit 220 has a function of discharging each cell 32 via the discharge unit 36. In this embodiment, the execution unit 220 performs a discharge process on cells whose voltage difference from the cell with the lowest measured CCV is greater than or equal to a predetermined value, thereby eliminating this potential difference. Here, the "predetermined value" is set to a value obtained by converting the errors of sensors such as the voltmeter 34 and the ammeter 35 into voltage values ​​and integrating them.

[0048] (Control process)

[0049] use Figure 4 The flow of the equalization process as the charging control method executed by the monitoring unit 20 in this embodiment will be described using the flowchart of FIG. The equalization process in the monitoring unit 20 is implemented by the CPU 20A functioning as the control unit 200, the measuring unit 210, and the executing unit 220 described above.

[0050] exist Figure 4In step S100, CPU 20A starts charging. CPU 20A continues charging until the voltage of auxiliary battery 30 reaches a high voltage range, and maintains each cell 32 in a high voltage range. CPU 20A maintains charging for at least the time required for the current and voltage values ​​to stabilize.

[0051] In step S101, the CPU 20A determines whether the voltage value of the highest-voltage cell 32 is above a threshold value and the current value is below a set value. If the voltage value of the highest-voltage cell 32 is determined to be above the threshold value and the current value is below the set value ("YES" in step S101), the CPU 20A proceeds to step S102. On the other hand, if the voltage value of the highest-voltage cell 32 is determined to be above the threshold value and the current value is not below the set value ("NO" in step S101), the CPU 20A terminates the balancing process.

[0052] In step S102, CPU 20A determines whether a specific time has passed. If it is determined that the specific time has passed (if "Yes" in step S102), CPU 20A proceeds to step S103. On the other hand, if it is determined that the specific time has not passed (if "No" in step S102), CPU 20A repeats step S102.

[0053] In step S103 , the CPU 20A measures the CCV. Specifically, the CPU 20A measures the voltage of each cell 32 using each voltmeter 34 .

[0054] In step S104, the CPU 20A determines whether there is a cell 32 whose voltage value is equal to or greater than the sum of the voltage value of the cell 32 with the lowest CCV and a predetermined value. In other words, it determines whether there is a cell 32 whose voltage difference with the cell 32 with the lowest CCV is equal to or greater than the predetermined value. If it is determined that there is a cell 32 whose voltage value is equal to or greater than the sum of the voltage value of the cell 32 with the lowest CCV and the predetermined value (if "YES" in step S104), the process proceeds to step S105. On the other hand, if it is determined that there is no cell 32 whose voltage value is equal to or greater than the sum of the voltage value of the cell 32 with the lowest CCV and the predetermined value (if "NO" in step S104), the CPU 20A terminates the balancing process.

[0055] In step S105 , the CPU 20A starts the discharge process. Specifically, the discharge process starts for the battery cell 32 whose voltage potential difference from the battery cell 32 having the lowest CCV is equal to or greater than a predetermined value.

[0056] In step S106, the CPU 20A determines whether a predetermined time has elapsed. If it is determined that the predetermined time has elapsed ("YES" in step S106), the CPU 20A proceeds to step S107. On the other hand, if it is determined that the predetermined time has not elapsed ("NO" in step S106), the CPU 20A repeats step S106. The "predetermined time" can be set to the time required for the voltage imbalance of each battery cell 32 to be eliminated.

[0057] In step S107, CPU 20A terminates the discharge process. Alternatively, the CCV may be measured again, and if a cell 32 remains whose voltage difference from the cell 32 with the lowest CCV is greater than or equal to a predetermined value, the discharge process is repeated for that cell 32. The balancing process then terminates.

[0058] (Summary of Implementation Methods)

[0059] In the monitoring unit 20 of this embodiment, when the control unit 200 charges the cells 32, the measuring unit 210 measures the CCV of each cell 32 when the voltage of the cell 32 with the highest voltage during charging is greater than or equal to a threshold value and the current is less than or equal to a set value. Furthermore, the executing unit 220 performs a discharge process on the cell 32 whose voltage difference from the cell 32 with the lowest measured CCV is greater than or equal to a predetermined value, thereby eliminating this potential difference. According to this embodiment, by performing a discharge process on cells 32 with a potential difference based on the CCV, it is possible to perform a balancing process even on auxiliary batteries 30 that cannot be disconnected from the auxiliary equipment 26 via a relay.

[0060] In addition, in the present embodiment, the control unit 200 charges the auxiliary battery 30 so as to maintain a high SOC. Therefore, according to the present embodiment, even a lithium-ion battery such as an iron phosphate battery has a flat region with little change in OCV in the SOC-OCV correspondence relationship (see Figure 5 ) battery pack can also perform balancing processing on the single cells 32.

[0061] Furthermore, in this embodiment, by measuring the CCV when the current value remains below a set value for a specified period of time, the measurement unit 210 can minimize polarization in the cells 32 and measure a CCV close to the OCV. Thus, according to this embodiment, even when using the CCV, balancing of the cells 32 can be performed with high accuracy.

[0062] [Remark]

[0063] Furthermore, in the above embodiment, the monitoring ECU 14, which corresponds to the charging control device, includes the voltmeter 34, the ammeter 35, and the discharge unit 36. However, this is not limiting. The monitoring ECU 14 only needs to include the monitoring unit 20, and the voltmeter 34, the ammeter 35, and the discharge unit 36 ​​may be independent of the monitoring ECU 14.

[0064] Furthermore, the equalization process in the above-described embodiment may be executed while the vehicle 12 is traveling, or may be executed when the vehicle 12 is parked and connected to an external charger.

[0065] The various processes executed by CPU20A reading the software (program) in the above embodiment may also be executed by various processors other than the CPU. As the processor in this case, FPGA (Field-Programmable Gate Array) and other processors with PLD (Programmable Logic Device) and ASIC (Application Specific Integrated Circuit) which can change the circuit structure after manufacturing, which are designed as dedicated circuit structures for executing specific processes, i.e., dedicated circuits, etc. can be exemplified. In addition, each of the above processes may be executed by one of these various processors, or by a combination of two or more processors of the same or different types (for example, multiple FPGAs, and a combination of a CPU and an FPGA, etc.). In addition, the hardware structure of these various processors is more specifically a circuit that combines circuit elements such as semiconductor elements.

[0066] In addition, in the above embodiment, each program is described as being pre-stored (installed) on a computer-readable non-transitory recording medium. For example, the control program 100 in the monitoring unit 20 is pre-stored in the ROM 20B. However, this is not limiting, and each program may also be provided in the form of a non-transitory recording medium such as a CD-ROM (Compact Disc Read Only Memory), a DVD-ROM (Digital Versatile Disc Read Only Memory), or a USB (Universal Serial Bus) memory. Alternatively, the program may be downloaded from an external device via a network.

[0067] The processing flow described in the above embodiment is merely an example, and unnecessary steps may be deleted, new steps may be added, or the processing order may be changed without departing from the spirit of the invention.

Claims

1. A charging control device, wherein: have: a control unit that controls charging of a plurality of cells constituting the battery pack; a measuring unit that measures CCV, or closed circuit voltage, of the plurality of cells when a voltage value of a cell with the highest voltage among the plurality of cells is greater than or equal to a threshold value and a current value is less than or equal to a set value during charging under the control of the control unit; as well as an execution unit that executes a discharge process for a cell having a potential difference of a predetermined value or more from the voltage of the cell with the lowest CCV measured so as to eliminate the potential difference; The battery pack is an iron phosphate lithium ion battery, When the current value is below the set value for a predetermined period of time, the measuring unit measures the CCV. The set value is set to a current value that can allow a voltage drop associated with the internal resistance of the cell. The specific time is set as the time when polarization in the single cell is eliminated.

2. The charging control device according to claim 1, wherein: The control unit performs control so that charging is performed in a region where the voltage during charging becomes a high voltage until a predetermined time has elapsed.

3. A vehicle, wherein: have: The charging control device according to claim 1 or 2; and A charging device is used to charge the battery pack.

4. The vehicle according to claim 3, wherein: A load is provided that receives power from the battery pack and the charging device.

5. The vehicle according to claim 3 or 4, wherein: Processes performed by the control unit, the measurement unit, and the execution unit are executed while the vehicle is traveling.

6. A charging control method, wherein: The following processing is performed by a computer: Charge the multiple cells that make up the battery pack. During charging, when the voltage value of the cell with the highest voltage among the multiple cells is greater than a threshold value and the current value is less than a set value, the CCV, or closed circuit voltage, of the multiple cells is measured. A discharge process is performed on a cell whose potential difference from the cell with the lowest CCV measured is greater than or equal to a predetermined value so as to eliminate the potential difference. The battery pack is an iron phosphate lithium ion battery, When the current value is below the set value for a specific period of time, the CCV is measured. The set value is set to a current value that can allow a voltage drop associated with the internal resistance of the cell. The specific time is set as the time when polarization in the single cell is eliminated.

7. A non-transitory recording medium, wherein: A control program is recorded, which causes the computer to execute the following processing: Charge the multiple cells that make up the battery pack. During charging, when the voltage value of the cell with the highest voltage among the multiple cells is greater than a threshold value and the current value is less than a set value, the CCV, or closed circuit voltage, of the multiple cells is measured. A discharge process is performed on a cell whose potential difference from the cell with the lowest CCV measured is greater than or equal to a predetermined value so as to eliminate the potential difference. The battery pack is an iron phosphate lithium ion battery, When the current value is below the set value for a specific period of time, the CCV is measured. The set value is set to a current value that can allow a voltage drop associated with the internal resistance of the cell. The specific time is set as the time when polarization in the single cell is eliminated.

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