Charging control device, vehicle, charging control method, and control program

Abstract

To perform equalization processing even in a battery pack that cannot be separated from a load.SOLUTION: A monitoring ECU 14 as a charge control device comprises: a control unit that controls charging of a plurality of battery cells 32 constituting an auxiliary machine battery 30; a measurement unit that measures CCV (Closed Circuit Voltage) of the plurality of battery cells 32 in a case where a voltage value of a battery cell 32 having highest voltage of the plurality of battery cells 32 is more than or equal to a threshold value and a current value is less than or equal to a setting value, during charging by control of the control unit; and an execution unit that executes discharge processing such that a potential difference is resolved, for the battery cell 32 in which a potential difference between its voltage and the voltage of the battery cell 32 having the lowest measured CCV is more than or equal to a predetermined value.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a charge control device, a vehicle, a charge control method, and a control program.

Background Art

[0002] Patent Document 1 discloses a charge rate equalization device that equalizes the charge rates of each battery cell constituting a battery pack, which is a lithium-ion battery. In this equalization device, in the charging process, a plurality of battery cells are charged together, and when a certain battery cell reaches the maximum voltage, the OCV (Open Circuit Voltage) after a predetermined time has elapsed is acquired, and the equalization of the battery cells is performed based on the acquired OCV.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Even if the equalization device of Patent Document 1 attempts to be applied to an auxiliary battery of a vehicle that needs to constantly supply power, it is difficult to apply because the auxiliary battery and the vehicle load cannot be disconnected by a relay to acquire the OCV.

[0005] An object of the present invention is to provide a charge control device, a vehicle, a charge control method, and a control program capable of performing equalization processing even in a battery pack that cannot be disconnected from a load.

Means for Solving the Problems

[0006] The charging control device according to claim 1 includes a control unit that controls the charging of a plurality of battery cells constituting a battery pack, and during charging under the control of the control unit, when the voltage value of the battery cell with the highest voltage among the plurality of battery cells is equal to or higher than a threshold value and the current value is equal to or lower than a set value, a measurement unit that measures the CCV (Closed Circuit Voltage) of the plurality of battery cells, and an execution unit that executes a discharging process so as to eliminate the potential difference for a battery cell whose potential difference from the voltage of the battery cell with the lowest measured CCV is equal to or higher than a predetermined value.

[0007] When the control unit of the charging control device according to claim 1 performs charging of the battery cells, the measurement unit measures the CCV of each battery cell when the voltage value of the battery cell with the highest voltage during charging is equal to or higher than a threshold value and the current value is equal to or lower than a set value. Then, in the charging control device, the execution unit executes a discharging process so as to eliminate the potential difference for a battery cell whose potential difference from the voltage of the battery cell with the lowest measured CCV is equal to or higher than a predetermined value. According to the charging control device, by executing the discharging process of the battery cells with a potential difference based on the CCV, equalization processing can be performed even in a battery pack that cannot be disconnected from the load.

[0008] The charging control device according to claim 2 is the charging control device according to claim 1, wherein the control unit controls to perform charging until a predetermined time elapses in a region where the voltage during charging becomes a high voltage.

[0009] In the charging control device according to claim 2, the control unit performs charging so as to maintain a state where the SOC (State Of Charge) of the battery pack is high. Thereby, even in a battery pack having a flat region with little change in OCV in an SOC-OCV curve such as a lithium iron phosphate ion battery, equalization processing of the battery cells can be performed in a region where the voltage fluctuates with respect to the SOC.

[0010] The charging control device according to claim 3 is the charging control device according to claim 1 or 2, wherein the measurement unit measures the CCV when a state where the current value is equal to or lower than the set value has elapsed for a specific time.

[0011] In the charging control device according to claim 3, when the measurement unit measures the CCV when the state where the current value is equal to or less than the set value has elapsed for a specific time, it is possible to eliminate polarization in the battery cell as much as possible and measure the CCV in a state close to the OCV. Thereby, even when using CCV, it is possible to perform the equalization process of the battery cells with high accuracy.

[0012] The vehicle according to claim 4 includes the charging control device according to any one of claims 1 to 3 and a charging device that charges the assembled battery.

[0013] According to the vehicle according to claim 4, even if the assembled battery is a auxiliary battery that cannot cut off the power supply and constantly supplies power to auxiliary devices, it is possible to perform the equalization process of the battery cells.

[0014] The charging control method according to claim 5 charges a plurality of battery cells constituting an assembled battery, and during charging, when the voltage value of the battery cell with the highest voltage among the plurality of battery cells is equal to or higher than a threshold value and the current value is equal to or less than a set value, the CCV (Closed Circuit Voltage) of the plurality of battery cells is measured, and a computer executes a process of performing a discharge process so as to eliminate the potential difference with respect to a battery cell whose potential difference between the measured CCV and the voltage of the battery cell with the lowest CCV is equal to or greater than a predetermined value.

[0015] In the charging control method according to claim 5, when the computer charges the battery cells, it measures the CCV of each battery cell when the voltage value of the battery cell with the highest voltage during charging is equal to or higher than a threshold value and the current value is equal to or less than a set value. Then, the computer executes a discharge process so as to eliminate the potential difference with respect to a battery cell whose potential difference between the measured CCV and the voltage of the battery cell with the lowest CCV is equal to or greater than a predetermined value. According to this charging control method, by performing the discharge process of the battery cells having a potential difference based on CCV, it is possible to perform the equalization process even in an assembled battery that cannot be disconnected from the load.

[0016] The control program according to claim 6 charges a plurality of battery cells constituting a battery pack, and during charging, when the voltage value of the battery cell with the highest voltage among the plurality of battery cells is equal to or higher than a threshold value and the current value is equal to or lower than a set value, it measures the CCV (Closed Circuit Voltage) of the plurality of battery cells, and for a battery cell whose potential difference from the voltage of the battery cell with the lowest measured CCV is equal to or higher than a predetermined value, it causes a computer to execute a discharge process so as to eliminate the potential difference.

[0017] The control program according to claim 6 causes a computer to execute the following process. When the computer charges a battery cell, it measures the CCV of each battery cell when the voltage value of the battery cell with the highest voltage during charging is equal to or higher than a threshold value and the current value is equal to or lower than a set value. Then, the computer executes a discharge process so as to eliminate the potential difference for a battery cell whose potential difference from the voltage of the battery cell with the lowest measured CCV is equal to or higher than a predetermined value. According to the control program, by executing a discharge process on a battery cell with a potential difference based on CCV, an equalization process can be performed even on a battery pack that cannot be disconnected from a load.

Advantages of the Invention

[0018] According to the present invention, an equalization process can be performed even on a battery pack that cannot be disconnected from a load.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Best Mode for Carrying Out the Invention

[0020] Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings. The charge control device of the present invention is incorporated in a power supply system in a vehicle. This charge control device performs processing (hereinafter referred to as "equalization processing") for equalizing the SOC (State Of Charge) of each battery cell in a lithium iron phosphate-based lithium ion battery.

[0021] FIG. 5 illustrates the correspondence between the SOC and OCV of a lithium iron phosphate-based lithium ion battery. As shown in FIG. 5, in a lithium iron phosphate-based lithium ion battery, both the charging-side OCV indicating the OCV during charging and the discharging-side OCV indicating the OCV during discharging have a flat region where the change in OCV is small when the SOC is between 35% and 95%. Further, the lithium iron phosphate-based lithium ion battery has hysteresis between charging and discharging as indicated by the voltage difference between the charging-side OCV and the discharging-side OCV. Therefore, there is uniqueness in the SOC-OCV correspondence, and it is difficult to perform equalization processing based on OCV, which is the same equalization processing as that of a ternary lithium ion battery with almost no hysteresis between charging and discharging.

[0022] Also, in the case of a battery that constantly supplies power to auxiliary equipment, such as an auxiliary battery, it is not possible to cut off the load from the auxiliary battery by a relay, and it is difficult to measure the OCV. Therefore, the charge control device of the present invention realizes equalization processing by monitoring using CCV.

[0023] (Configuration) As shown in FIG. 1, the power supply system 10 of the present embodiment is mounted on a vehicle 12. The vehicle 12 is exemplified by an EV (Electric Vehicle) or an HV (Hybrid Vehicle). The vehicle 12 of the present embodiment is supplied with power by the power supply system 10. This vehicle 12 includes auxiliary equipment 26 that is equipment for operating each part of the vehicle 12, and a control ECU 28 that controls each part of the vehicle 12 including the auxiliary equipment 26.

[0024] The power supply system 10 includes a monitoring ECU 14 as a charge control device, a high-voltage battery 22, a DCDC converter 24, and an auxiliary battery 30 as an auxiliary machine battery. In FIG. 1, the symbol G indicates the ground. Details of the monitoring ECU 14 will be described later.

[0025] The high-voltage battery 22 is a high-voltage battery for operating a traveling motor or the like related to the drive of the vehicle 12, and is composed of a rechargeable secondary battery such as a lithium-ion battery or a nickel-metal hydride battery, for example. The high-voltage battery 22 is connected to the DCDC converter 24.

[0026] The DCDC converter 24 has a function of supplying the power output from the high-voltage battery 22 to the auxiliary battery 30 and the auxiliary devices 26. The DCDC converter 24 has the high-voltage battery 22 connected to its input side, and the auxiliary battery 30 and the auxiliary devices 26 connected to its output side. When supplying power, the DCDC converter 24 steps down the output voltage of the high-voltage battery 22, which is the input voltage, to a predetermined voltage based on an instruction from the control ECU 28, and outputs it toward the auxiliary battery 30 and the auxiliary devices 26. The DCDC converter 24 of the present embodiment is an example of a charging device.

[0027] The control ECU 28 is composed of, for example, a microcomputer and has a function of controlling the DCDC converter 24. Thereby, the control ECU 28 supplies power from the high-voltage battery 22 to the auxiliary battery 30 and the auxiliary devices 26 via the DCDC converter 24.

[0028] The auxiliary battery 30 is a battery that can operate the auxiliary devices 26. The auxiliary battery 30 of the present embodiment is a rechargeable lithium iron phosphate-based lithium-ion battery. Further, the auxiliary battery 30 is a battery pack composed of a plurality of battery cells 32. The auxiliary battery 30 is connected to the DCDC converter 24 and can receive power supply from the DCDC converter 24. Also, the auxiliary battery 30 is connected to the auxiliary devices 26 of the vehicle 12 and supplies power to the auxiliary devices 26.

[0029] The monitoring ECU 14 is configured to include a monitoring unit 14A and a discharging unit 14B. The monitoring unit 14A includes a monitoring section 20 composed of a microcomputer, a plurality of voltmeters 34 provided for each battery cell 32, and an ammeter 35 provided on the wiring of the auxiliary battery 30. The discharging unit 14B includes a plurality of discharging sections 36 provided for each battery cell 32. The discharging section 36 is configured to include, for example, a discharging resistor connected to the battery cell 32 and a switch for controlling energization from the battery cell 32 to the resistor. As shown in FIG. 2, the monitoring section 20 is configured to include a CPU (Central Processing Unit) 20A, a ROM (Read Only Memory) 20B, a RAM (Random Access Memory) 20C, an input / output I / F (Interface) 20D, and a communication I / F 20E. The CPU 20A, the ROM 20B, the RAM 20C, the input / output I / F 20D, and the communication I / F 20E are communicatively connected to each other via an internal bus 20F.

[0030] The CPU 20A is a central processing unit that executes various programs and controls each part. That is, the CPU 20A reads a program from the ROM 20B and executes the program using the RAM 20C as a working area.

[0031] The ROM 20B stores various programs and various data. The control program 100 is stored in the ROM 20B of the embodiment.

[0032] The control program 100 is a program for controlling the monitoring section 20. The monitoring section 20 controlled by the control program 100 controls the charging and discharging of the auxiliary battery 30.

[0033] The RAM 20C temporarily stores a program or data as a working area. The input / output I / F 20D is an interface for electrically connecting the monitoring unit 20 to each of the voltmeter 34, the ammeter 35, and the discharge unit 36.

[0034] The communication I / F 20E is an interface for connecting to each ECU such as the control ECU 28. For this interface, for example, a communication standard based on the CAN protocol is used. The monitoring unit 20 can control the DCDC converter 24 via the control ECU 28 connected to the communication I / F 20E and control the charging of the auxiliary battery 30.

[0035] Note that the monitoring unit 20 may include a storage as a storage unit in addition to or instead of the ROM 20B. This storage is constituted by, for example, an HDD (Hard Disk Drive) or an SSD (Solid State Drive).

[0036] As shown in FIG. 3, in the monitoring unit 20 of the present embodiment, the CPU 20A functions as a control unit 200, a measurement unit 210, and an execution unit 220 by executing the control program 100.

[0037] The control unit 200 has a function of controlling the charging of the auxiliary battery 30. The control unit 200 of the present embodiment controls the charging of each battery cell 32 so as to perform charging until a predetermined time elapses in a region where the voltage during charging becomes a high voltage. Here, the "region where the voltage becomes a high voltage" is a region where the SOC is higher than the flat region and the voltage of the battery cell 32 with respect to the SOC changes (see FIG. 5). Also, the "predetermined time" is at least the time until the current value and the voltage value become stable.

[0038] The measurement unit 210 has a function of measuring the voltage of each battery cell 32 with a voltmeter 34 and the current of the auxiliary battery 30 with an ammeter 35. During the charging of the auxiliary battery 30, the measurement unit 210 in the present embodiment measures the CCV of the plurality of battery cells 32 when the voltage value of the battery cell with the highest voltage among the plurality of battery cells 32 is equal to or higher than a threshold value and the current value is equal to or lower than a set value. Here, the "threshold value" for the voltage is set to a value equal to or higher than the voltage of the battery cell 32 in the flat region (see FIG. 5). That is, the threshold value is a voltage value at which the voltage of the battery cell 32 with respect to the SOC changes. The "set value" for the current is set to a current value at which the voltage drop due to the internal resistance of the battery cell 32 can be tolerated.

[0039] In addition, the measurement unit 210 measures the CCV when a state where the current value is equal to or lower than the set value has elapsed for a specific time. Here, the "specific time" is set to at least the time when the polarization in the battery cell 32 is eliminated.

[0040] The execution unit 220 has a function of discharging each battery cell 32 by the discharge unit 36. The execution unit 220 in the present embodiment performs a discharge process on a battery cell whose potential difference from the voltage of the battery cell with the lowest measured CCV is equal to or higher than a predetermined value so as to eliminate the potential difference. Here, the "predetermined value" is set to a value obtained by adding up the errors of sensors such as the voltmeter 34 and the ammeter 35 converted into voltage values.

[0041] (Flow of control) The flow of the equalization process as a charging control method executed in the monitoring unit 20 of the present embodiment will be described with reference to the flowchart of FIG. 4. The equalization process in the monitoring unit 20 is realized by the CPU 20A functioning as the control unit 200, the measurement unit 210, and the execution unit 220 described above.

[0042] In step S100 of FIG. 4, CPU 20A starts the charging process. CPU 20A performs the charging process until the voltage of the auxiliary battery 30 reaches a high voltage region, and holds the region where each battery cell 32 reaches a high voltage. Here, CPU 20A holds the charging process until at least the current value and the voltage value become stable.

[0043] In step S101, CPU 20A determines whether the voltage value of the battery cell 32 with the highest voltage is equal to or higher than the threshold value and the current value is equal to or lower than the set value. When CPU 20A determines that the voltage value of the battery cell 32 with the highest voltage is equal to or higher than the threshold value and the current value is equal to or lower than the set value (YES in step S101), it proceeds to step S102. On the other hand, when CPU 20A determines that the voltage value of the battery cell 32 with the highest voltage is equal to or higher than the threshold value and the current value is not equal to or lower than the set value (NO in step S101), it ends the equalization process.

[0044] In step S102, CPU 20A determines whether a specific time has elapsed. When CPU 20A determines that a specific time has elapsed (YES in step S102), it proceeds to step S103. On the other hand, when CPU 20A determines that a specific time has not elapsed (NO in step S102), it repeats step S102.

[0045] In step S103, CPU 20A measures the CCV. That is, CPU 20A measures the voltage of each battery cell 32 by each voltmeter 34.

[0046] In step S104, the CPU 20A determines whether there is a battery cell 32 whose CCV is equal to or higher than the sum of the voltage value of the battery cell 32 with the lowest voltage and a predetermined value. In other words, it determines whether there is a battery cell 32 whose potential difference from the voltage of the battery cell 32 with the lowest CCV is equal to or higher than the predetermined value. When the CPU 20A determines that there is a battery cell 32 whose CCV is equal to or higher than the sum of the voltage value of the battery cell 32 with the lowest voltage and the predetermined value (YES in step S104), it proceeds to step S105. On the other hand, when the CPU 20A determines that there is no battery cell 32 whose CCV is equal to or higher than the sum of the voltage value of the battery cell 32 with the lowest voltage and the predetermined value (NO in step S104), it ends the equalization process.

[0047] In step S105, the CPU 20A starts the discharge process. Specifically, it starts the discharge process for the battery cell 32 whose potential difference from the voltage of the battery cell 32 with the lowest CCV is equal to or higher than the predetermined value.

[0048] In step S106, the CPU 20A determines whether a certain period of time has elapsed. When the CPU 20A determines that a certain period of time has elapsed (YES in step S106), it proceeds to step S107. On the other hand, when the CPU 20A determines that a certain period of time has not elapsed (NO in step S106), it repeats step S106. Here, the "certain period of time" may be set to the time when the voltage imbalance between the battery cells 32 is eliminated.

[0049] In step S107, the CPU 20A ends the discharge process. Note that if the CCV is measured again and there is still a battery cell 32 whose potential difference from the voltage of the battery cell 32 with the lowest CCV is equal to or higher than the predetermined value, the discharge process may be executed again for the battery cell 32. Then, the equalization process ends.

[0050] (Summary of the Embodiment) When the control unit 200 charges the battery cell 32, the monitoring unit 20 of the present embodiment measures the CCV of each battery cell 32 when the voltage value of the battery cell 32 with the highest voltage during charging is equal to or higher than the threshold value and the current value is equal to or lower than the set value. Then, the execution unit 220 executes a discharge process so that the potential difference between the measured CCV and the voltage of the battery cell 32 with the lowest CCV is eliminated for the battery cell 32 with a potential difference equal to or higher than the predetermined value. According to the present embodiment, by executing the discharge process of the battery cell 32 with a potential difference based on the CCV, an equalization process can be performed even in the auxiliary battery 30 that cannot be disconnected from the auxiliary devices 26 by the relay.

[0051] In addition, in the present embodiment, the control unit 200 performs charging so as to maintain a state where the SOC of the auxiliary battery 30 is high. Thereby, according to the present embodiment, even in a battery pack having a flat region with little change in OCV in the SOC-OCV correspondence relationship such as a lithium iron phosphate ion battery (see FIG. 5), an equalization process of the battery cell 32 can be performed.

[0052] Furthermore, in the present embodiment, the measurement unit 210 measures the CCV when a state where the current value is equal to or lower than the set value has elapsed for a specific time, thereby eliminating polarization in the battery cell 32 as much as possible and measuring the CCV in a state close to the OCV. Thereby, according to the present embodiment, even when using the CCV, an equalization process of the battery cell 32 can be performed with high accuracy.

[0053] [Remarks] In the above embodiment, the monitoring ECU 14 corresponding to the charge control device includes the voltmeter 34, the ammeter 35, and the discharge unit 36, but this is not the case. The monitoring ECU 14 only needs to have the monitoring unit 20, and the voltmeter 34, the ammeter 35, and the discharge unit 36 may be separate from the monitoring ECU 14, respectively.

[0054] Also, the equalization process in the above embodiment may be executed either during the running of the vehicle 12 or when an external charger is connected during parking.

[0055] In the above embodiment, various processes executed by the CPU 20A by reading and executing software (program) may be executed by various processors other than the CPU. Examples of the processor in this case include a PLD (Programmable Logic Device) whose circuit configuration can be changed after manufacture, such as an FPGA (Field-Programmable Gate Array), and a dedicated electric circuit, which is a processor having a circuit configuration dedicated to executing specific processes, such as an ASIC (Application Specific Integrated Circuit). Further, each of the above-described processes may be executed by one of these various processors, or may be executed by a combination of two or more processors of the same type or different types (for example, a plurality of FPGAs, a combination of a CPU and an FPGA, etc.). More specifically, the hardware structure of these various processors is an electric circuit combining circuit elements such as semiconductor elements.

[0056] Also, in the above embodiment, each program has been described in a mode where it is pre-stored (installed) in a non-transitory recording medium readable by a computer. For example, the control program 100 in the monitoring unit 20 is pre-stored in the ROM 20B. However, it is not limited to this, and each program may be provided in a form recorded on 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. Further, the program may be in a form downloaded from an external device via a network.

[0057] The flow of the processes described in the above embodiment is also an example, and unnecessary steps may be deleted, new steps may be added, or the order of the processes may be changed within a range not departing from the gist.

Explanation of Reference Numerals

[0058] 12 Vehicle 14 Monitoring ECU (Charge control device) 24 DCDC converter (Charging device) 30 Auxiliary battery (Battery pack) 32 Battery cell 100 Control program 200 Control unit 210 Measurement unit 220 Execution unit

Claims

1. A control unit that controls charging of a plurality of battery cells constituting a battery pack, a measuring unit that measures the CCV (Closed Circuit Voltage) of the plurality of battery cells when the voltage value of the battery cell with the highest voltage among the plurality of battery cells is equal to or higher than a threshold value and the current value is equal to or lower than a set value during charging under the control of the control unit, an execution unit that executes a discharging process to eliminate the potential difference for a battery cell in which the potential difference between the measured CCV and the voltage of the battery cell with the lowest CCV is equal to or higher than a predetermined value, comprising: the measuring unit measures the CCV when a state where the current value is equal to or lower than the set value has elapsed for a specific time, the threshold value is set to a value equal to or higher than the voltage of a battery cell in a flat region where the change in OCV (Open Circuit Voltage) with respect to the state of charge (SOC) of the battery cell is small, a charging control device.

2. The charging control device according to claim 1, wherein the control unit controls to perform charging until a predetermined time has elapsed in a region where the voltage during charging becomes a high voltage.

3. A vehicle comprising the charging control device according to claim 1 or 2, and a charging device that charges the battery pack.

4. Charging a plurality of battery cells constituting a battery pack, measuring the CCV (Closed Circuit Voltage) of the plurality of battery cells when the voltage value of the battery cell with the highest voltage among the plurality of battery cells is equal to or higher than a threshold value and the current value is equal to or lower than a set value during charging, executing a discharging process to eliminate the potential difference for a battery cell in which the potential difference between the measured CCV and the voltage of the battery cell with the lowest CCV is equal to or higher than a predetermined value, a computer executes the process, measures the CCV when a state where the current value is equal to or lower than the set value has elapsed for a specific time, the threshold value is set to a value equal to or higher than the voltage of a battery cell in a flat region where the change in OCV (Open Circuit Voltage) with respect to the state of charge (SOC) of the battery cell is small, a charging control method.

5. Charging a plurality of battery cells constituting a battery pack, measuring the CCV (Closed Circuit Voltage) of the plurality of battery cells when the voltage value of the battery cell with the highest voltage among the plurality of battery cells is equal to or higher than a threshold value and the current value is equal to or lower than a set value during charging, executing a discharging process to eliminate the potential difference for a battery cell in which the potential difference between the measured CCV and the voltage of the battery cell with the lowest CCV is equal to or higher than a predetermined value, causing a computer to execute the process, ​ When a state where the current value is less than or equal to the set value has elapsed for a specific time, measure the CCV, The threshold value is set to a value equal to or higher than the voltage of a battery cell in a flat region where the change in OCV (Open Circuit Voltage) with respect to the state of charge (SOC) of the battery cell is small, Control program.

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