JP2016093030A - Device and method for charge control - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method suable for measuring internal resistance for use to determine a threshold voltage in constant-voltage charge of constant-current constant-voltage charge.SOLUTION: A charge control device 1 includes: a measuring unit 7 which measures the internal resistance of a battery 4 when the measured voltage of the battery 4 approaches a target voltage set in the constant-voltage constant-current charge; and a determination unit 8 which, after the measurement of the internal resistance, determines a threshold voltage for use in the constant-voltage charge performed in the constant-voltage constant-current charge to a higher voltage than a target voltage, according to the measured internal resistance.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a charge control device and a charge control method for controlling charging of a battery.

  Constant current constant voltage charging is known in which charging is performed by switching to constant voltage charging after performing constant current charging as battery charging. As one of constant current and constant voltage charging, the constant voltage applied to the battery in constant voltage charging is raised to a threshold voltage higher than a target voltage corresponding to a target SOC (State of Charge), and the threshold voltage is used. A method of performing constant voltage charging is known.

  However, as the battery deteriorates, there is a problem that even if constant voltage charging is performed using the initial threshold voltage, the target voltage is not reached. Therefore, a proposal has been made to determine the threshold voltage according to the deterioration of the battery, and perform charging at a constant voltage using the determined threshold voltage, so that charging can be performed up to the target voltage even in the case of deterioration. Yes. See, for example, US Pat.

  However, when determining the threshold voltage, it is necessary to accurately detect battery deterioration. The deterioration of the battery can be detected from the measured internal resistance of the battery, for example. Cited Document 2 proposes to measure internal resistance based on the increase / decrease width of the battery voltage by repeating charging and discharging.

  Moreover, according to the cited documents 1 and 3, the proposal which changes the threshold voltage used for charge of a battery according to the magnitude | size of internal resistance is made.

International Publication No. 2012/043744 JP 2004236363 A JP 2011-061947 A

However, the above proposal does not disclose a method suitable for measuring the internal resistance used for determining the threshold voltage.
An object of one aspect of the present invention is to provide a method suitable for measuring an internal resistance used for determining a threshold voltage in constant voltage charging of constant current constant voltage charging.

The charge control device which is one aspect of the present invention includes a measurement unit and a determination unit.
A measurement part measures the internal resistance of a battery, when the measurement voltage of a battery approaches the target voltage set in constant current constant voltage charge.

After determining the internal resistance, the determination unit determines a threshold voltage used for constant voltage charging performed in constant current and constant voltage charging to be a voltage higher than the target voltage in accordance with the measured internal resistance.
The measuring unit may measure the internal resistance by charging for a predetermined time after the constant voltage charging.

Further, the measurement unit may measure the internal resistance from the change of the measurement voltage after constant voltage charging.
In addition, the measurement unit stops charging before shifting from constant current charging to constant voltage charging in constant current constant voltage charging, measures the internal resistance from the change in the measured voltage, and the determination unit responds to the measured internal resistance. The threshold voltage used for the constant voltage charge after the transition may be determined.

  According to the embodiment, it is possible to measure the internal resistance used for determining the threshold voltage, which is suitable for constant voltage charging of constant current constant voltage charging.

FIG. 1 is a diagram illustrating an embodiment of the charging control apparatus. FIG. 2 is a diagram illustrating a relationship between current and voltage in constant current and constant voltage charging according to the first embodiment. FIG. 3 is a flowchart showing an embodiment of the constant current and constant voltage charging operation. FIG. 4 is a diagram illustrating a relationship between current and voltage in constant current and constant voltage charging according to the second embodiment. FIG. 5 is a diagram illustrating a relationship between current and voltage in constant current and constant voltage charging according to the third embodiment. FIG. 6 is a flowchart illustrating an example of the operation of constant current constant voltage charging according to the third embodiment.

Hereinafter, embodiments will be described in detail with reference to the drawings.
The first embodiment will be described.
FIG. 1 is a diagram illustrating an embodiment of a charge control device. The charge control device 1 shown in FIG. 1 is, for example, a battery pack. In this example, the charging control device 1 includes an assembled battery 2 having one or more batteries 4, a control unit 3 that controls the charging control device 1, a voltmeter 5 that measures the voltage of the battery 4, and a current flowing through the assembled battery 2. It has the ammeter 6 to measure, and the thermometer 10 to measure the temperature of the assembled battery 2 or the battery 4 or the ambient temperature. The battery 4 is a secondary battery such as a lithium ion battery or a storage element. The thermometer 10 may not be provided.

  The control unit 3 includes a measurement unit 7, a determination unit 8, and a storage unit 9. Also. The control unit 3 may be, for example, a circuit using a CPU (Central Processing Unit), a multi-core CPU, or a programmable device (FPGA (Field Programmable Gate Array), PLD (Programmable Logic Device), etc.). Or the program which controls each part of the charging control apparatus 1 memorize | stored in the memory | storage part 9 provided outside is read and executed. In this example, the control unit 3 is used for description. However, the control executed by the control unit 3 may be performed by, for example, one or more ECUs (Electronic Control Units) mounted on the vehicle. .

  The storage unit 9 is a memory such as a ROM (Read Only Memory) or a RAM (Random Access Memory), and may store data such as parameter values and variable values, or may be used as a work area at the time of execution. The storage unit 9 may be provided separately from the control unit 3.

  The measurement unit 7 is a target for terminating the constant voltage charging (CV charging) set in the constant current constant voltage charging (hereinafter referred to as CCCV charging) by the measured voltage of the battery 4 measured using the voltmeter 5. When the voltage approaches, the internal resistance of the battery 4 is measured. In the measurement part 7 of Embodiment 1, it charges for predetermined time after CV charge, and measures internal resistance. Here, the target voltage is OCV (Open Circuit Voltage). The target voltage is a voltage corresponding to the SOC indicated by the fully charged voltage or the set target value, and is a voltage in a state where there is no voltage drop due to internal resistance and the polarization is eliminated in the battery 4 after charging.

  The determination unit 8 determines a threshold voltage used for CV charging performed in CCCV charging according to the internal resistance of the battery 4. However, the timing for obtaining the internal resistance and the timing for determining the threshold voltage are not the same. The determination unit 8 according to the first embodiment obtains a threshold voltage according to the measured internal resistance at the time of CCCV charging after the next time, and uses the threshold voltage for CV charging.

A method for obtaining the internal resistance in CCCV charging will be described.
FIG. 2 is a diagram illustrating a relationship between current and voltage in constant current and constant voltage charging according to the first embodiment. The vertical axis represents current and voltage, and the horizontal axis represents time. In the period from time t0 to time t1 in FIG. 2, constant current charging (CC charging) is performed on the battery 4. In CC charging, the constant current I1 is supplied to the assembled battery 2 until the voltage of the battery 4 reaches the threshold voltage V1. The threshold voltage V1 is higher than the target voltage V2, and is a voltage determined according to the internal resistance Ra indicating the deterioration of the battery 4.

  In the period from time t1 to time t2 in FIG. When a constant voltage (= threshold voltage V1) is applied to the battery 4 and the measured current flowing through the assembled battery 2 measured using the ammeter 6 reaches a predetermined current I2 (= end current I2) (time t2), CV charging is performed. finish.

  After the end of CV charging at time t2 in FIG. 2, after the time t3 has elapsed, that is, when the measured voltage of the battery 4 approaches the target voltage V2, measurement of the internal resistance Ra is started. In this example, when the measured voltage of the battery 4 measured by the voltmeter 5 reaches the set voltage V3 (V2 <V3 <V1) set to obtain the internal resistance Ra indicating that the target voltage V2 has been approached, The measurement of the resistance Ra is started.

  In the period (predetermined time) from time t3 to time t4 in FIG. 2, the battery 4 is charged by flowing a constant current. For example, a constant current I1 may be passed through the battery 4 for 10 seconds. However, the time for flowing the constant current is not limited to 10 seconds. The constant current is not limited to I1. However, it is desirable that the time and the constant current be such that the internal resistance Ra can be accurately measured.

  Further, the reason why the internal resistance Ra is obtained in the period from time t3 to time t4 is that the accuracy of the internal resistance Ra for determining the threshold voltage V1 is closer to the target voltage V2 than immediately after the start of charging. Because it is expensive. That is, it is better to determine the threshold voltage V1 using the internal resistance Ra at a high SOC. Note that the measured voltage after the end of CV charging is OCV.

  At time t4 in FIG. 2, the measurement voltage V4 measured using the voltmeter 5 is acquired. Subsequently, a differential voltage dV (= V4−V3) corresponding to a rise from the set voltage V3 for measuring the preset internal resistance Ra to the measured voltage V4 is obtained. Then, the internal voltage Ra (= dV / I1) is obtained by dividing the differential voltage dV by the constant current I1. The obtained internal resistance Ra includes resistance due to IR drop and polarization.

An example of a method for determining the threshold voltage will be described.
After determining the internal resistance Ra, the determination unit 8 determines the threshold voltage V1 used for CV charging performed in CCCV charging to be higher than the target voltage V2 in accordance with the measured internal resistance Ra. The threshold voltage V1 is obtained using, for example, the internal resistance Ra, the end current I2, and the temperature. In this example, the internal resistance Ra is a value obtained after charging. The end current I2 is a value determined at the time of subsequent charging. The temperature is a value measured during charging. That is, since the temperature changes during charging, for example, the temperature is obtained before changing from CC charging to CV charging, and the threshold voltage V1 is obtained using the temperature at that time, the internal resistance Ra, and the end current I2. The reason for using the termination current I2 is that the voltage drop (= Ra × I2) due to the internal resistance Ra and the voltage drop due to polarization change depending on the current I2 immediately before the end of CV charging.

The operation of the first embodiment will be described.
FIG. 3 is a flowchart showing an embodiment of the constant current and constant voltage charging operation.
In step S1, the control unit 3 starts a constant current charging process. In the constant current charging process, CC charging is performed with the constant current I1 until the measured voltage of the battery 4 reaches the threshold voltage V1, and when the measured voltage of the battery 4 reaches the threshold voltage V1, the CC charging is shifted to CV charging.

  In step S2, the control unit 3 starts a constant voltage charging process. The constant voltage charging process performs CV charging at a constant voltage (= threshold voltage V1) until the current flowing through the assembled battery 2 reaches the predetermined current I2, and when the measured current flowing through the assembled battery 2 reaches the predetermined current I2, the CV charging is performed. finish.

  In step S3, the control unit 3 starts an internal resistance measurement process. In the internal resistance measurement process, when the measured voltage of the battery 4 approaches the target voltage V2 (becomes the set voltage V3), the battery pack 2 is charged by flowing a constant current for a predetermined time (from time t3 to time t4). Subsequently, the set voltage V3, which is the voltage at time t3, and the measured voltage V4 measured at time t4 are acquired, and the differential voltage dV is obtained. Then, the internal resistance Ra is obtained using the differential voltage dV and a constant current (I1 in this example) flowing through the assembled battery 2.

  In step S4, after measuring the internal resistance Ra, the threshold voltage V1 used for CV charging performed in CCCV charging is determined to be higher than the target voltage V2 in accordance with the measured internal resistance Ra. That is, when a new CCCV charge is started, the control unit 3 starts a threshold voltage determination process in order to determine the threshold voltage V1 to be used for the CV charge of the CCCV charge. In the threshold voltage determination process, the threshold voltage V1 determined using the internal resistance Ra, the end current I2, and the temperature is stored in the storage unit 9.

  According to the first embodiment, the internal resistance Ra used for determining the threshold voltage V1 suitable for CV charging of CCCV charging can be measured. The battery may be discharged for a predetermined time after being charged for a predetermined time after charging. Even after charging for a predetermined time to obtain the internal resistance Ra after charging to the full charge voltage by CCCV charging, overcharging can be prevented by discharging for a predetermined time.

Further, according to the first embodiment, it is possible to cope with a change in internal resistance due to temperature, so that a more accurate threshold voltage can be obtained.
Embodiment 2 will be described.

  In the second embodiment, the measurement unit 7 measures the internal resistance Rb from the change in the measurement voltage after CV charging, and the determination unit 8 obtains a threshold voltage according to the measured internal resistance, and the threshold voltage is used for the subsequent CV charging. Use.

A method for obtaining the internal resistance in CCCV charging will be described.
FIG. 4 is a diagram illustrating a relationship between current and voltage in constant current and constant voltage charging according to the second embodiment. The vertical axis represents current and voltage, and the horizontal axis represents time. In the period from the time t0 to the time t1 in FIG.

  In the period from time t1 to time t2 in FIG. When a constant voltage (= threshold voltage V1) is applied to the battery 4 and the measured current flowing through the assembled battery 2 measured by the ammeter 6 reaches a predetermined current I2 (time t2), the CV charging is terminated.

  The voltage of the battery 4 is measured in the period from time t2 to time ta in FIG. 4, that is, for a predetermined time after the end of CV charging. For example, it is conceivable to measure the voltage of the battery 4 for 10 seconds. However, the time during which the constant current is applied is not limited to 10 seconds, and it is desirable that the internal resistance can be accurately measured.

  When the time ta in FIG. 4 is reached, a change in the measured voltage of the battery 4 in a predetermined time is obtained. In the example of FIG. 4, a differential voltage dVa (= V1−Va) corresponding to a voltage drop from the measured voltage (= threshold voltage V1) at time t2 to the measured voltage Va after a predetermined time has elapsed is obtained.

Subsequently, the differential voltage dVa is divided by a predetermined current I2 to obtain an internal resistance Rb (= dVa / I2). The obtained internal resistance Rb includes resistance due to IR drop and polarization.
Further, the reason why the internal resistance Rb is obtained during the period from the time t2 to the time ta is that the accuracy of the internal resistance Rb for determining the threshold voltage V1 is closer to the target voltage V2 than immediately after the start of charging. Because it is expensive. That is, it is better to determine the threshold voltage V1 using the internal resistance Rb at a high SOC. Note that the measured voltage after the end of CV charging is OCV.

An example of a method for determining the threshold voltage will be described.
After determining the internal resistance Rb, the determination unit 8 determines the threshold voltage V1 used for CV charging performed in CCCV charging to be higher than the target voltage V2 according to the measured internal resistance Rb. The threshold voltage V1 is obtained using, for example, the internal resistance Rb, the end current I2, the temperature, and the like. In this example, the internal resistance Rb is a value obtained after charging. The end current I2 is a value determined at the time of subsequent charging. The temperature is a value measured during charging. That is, since the temperature changes during charging, for example, the temperature is obtained before changing from CC charging to CV charging, and the threshold voltage V1 is obtained using the temperature at that time, the internal resistance Rb, and the end current I2. The reason for using the end current I2 is that the voltage drop due to the internal resistance Rb (= Rb × I2) and the voltage drop due to polarization change depending on the current I2 immediately before the end of CV charging.

The operation of the second embodiment will be described.
The operation of CCCV charging according to the second embodiment will be described with reference to FIG. In the second embodiment, steps S1 and S2 in FIG. 3 are the same as those in the first embodiment, and a description thereof will be omitted.

  In step S3 of the second embodiment, the control unit 3 starts the internal resistance measurement process of the second embodiment. In the internal resistance measurement process, the voltage of the battery 4 is measured for a predetermined time (from time t2 to time ta in FIG. 4) after the end of CV charging, and after the predetermined time has elapsed (when time ta in FIG. 4 is reached), A change in the measurement voltage at a predetermined time is obtained. In the example of FIG. 4, after a predetermined time has elapsed, the differential voltage dVa (= V1−Va) corresponding to the voltage drop at the measurement voltage (= threshold voltage V1) at time t2 to the measurement voltage Va is obtained. Then, the obtained differential voltage dVa is divided by a predetermined current I2 to obtain an internal resistance Rb (= dVa / I2).

  In step S4, after measuring the internal resistance Rb, the threshold voltage V1 used for CV charging performed in CCCV charging is determined to be higher than the target voltage V2 in accordance with the measured internal resistance Rb. That is, when a new CCCV charge is started, the control unit 3 starts the threshold voltage determination process of the second embodiment in order to determine the threshold voltage V1 to be used for the CV charge of the CCCV charge. In the threshold voltage determination process, the threshold voltage V1 determined using the internal resistance Rb, the end current I2, and the temperature is stored in the storage unit 9.

According to the second embodiment, the internal resistance Rb used for determining the threshold voltage V1 suitable for CV charging of CCCV charging can be measured.
Further, according to the second embodiment, it is possible to cope with a change in internal resistance due to temperature, so that a more accurate threshold voltage can be obtained.

A third embodiment will be described.
The measuring unit 7 of the third embodiment stops charging before shifting from CC charging to CV charging in CCCV charging, and measures the internal resistance Rc from the change in the measured voltage. The determining unit 8 responds to the measured internal resistance Rc. Then, the threshold voltage V1 is obtained, and the threshold voltage V1 is used for CV charging after the transition.

A method for obtaining the internal resistance Rc in CCCV charging will be described.
FIG. 5 is a diagram illustrating a relationship between current and voltage in constant current and constant voltage charging according to the third embodiment. The vertical axis represents current and voltage, and the horizontal axis represents time. In the period from time t0 to time tf in FIG. However, when the voltage of the battery 4 approaches the target voltage V2 or reaches the target voltage V2, CC charging is temporarily stopped (time tc), CC charging is restarted after a predetermined time (time td), and the CC charging is continued until the threshold voltage V1 is reached. Charge (time te). For example, the predetermined time may be 10 seconds. However, the predetermined time is not limited to 10 seconds, and is preferably a time during which the internal resistance Rc can be accurately measured.

  In the period from time te to time tf in FIG. When a constant voltage (= threshold voltage V1) is applied to the battery 4 and the measured current flowing through the assembled battery 2 measured by the ammeter 6 reaches a predetermined current I2 (time tf), the CV charging is terminated.

  In the third embodiment, the voltage of the battery 4 during the period from time tc to time td in FIG. 5 is measured, and the difference voltage dVc (= V2−Vc) corresponding to the drop from the measurement voltage V2 to the measurement voltage Vc after a predetermined time has elapsed. Ask for. Note that the measurement voltage during the period from time tc to time td is CCV (Close Circuit Voltage).

  Subsequently, the internal voltage Rc (= dVc / I1) is obtained by dividing the differential voltage dVc by the constant current I1 during CC charging. The obtained internal resistance Rc includes resistance due to IR drop and polarization.

  The reason why the internal resistance Rc during the period from time tc to time td is obtained is that the accuracy of the internal resistance Rc for determining the threshold voltage V1 is closer to the target voltage V2 than immediately after the start of charging. Because it is expensive. That is, it is better to determine the threshold voltage V1 using the internal resistance Rc at a high SOC.

An example of a method for determining the threshold voltage will be described.
After determining the internal resistance Rc, the determination unit 8 determines the threshold voltage V1 used for CV charging performed in CCCV charging to be higher than the target voltage V2 in accordance with the measured internal resistance Rc. The threshold voltage V1 is obtained using, for example, the internal resistance Rc, the end current I2, the temperature, and the like. In this example, the internal resistance Rc is a value obtained before shifting from CC charging to CV charging. The end current I2 is a value determined at the time of subsequent charging. The temperature is a value measured during charging. That is, since the temperature changes during charging, for example, the temperature is obtained before changing from CC charging to CV charging, and the threshold voltage V1 is obtained using the temperature at that time, the internal resistance Rc, and the end current I2. The reason for using the end current I2 is that the voltage drop due to the internal resistance Rc (= Rc × I2) and the voltage drop due to polarization change depending on the current I2 immediately before the end of CV charging.

The operation of the third embodiment will be described.
The operation of CCCV charging according to the third embodiment will be described with reference to FIG. FIG. 6 is a flowchart illustrating an example of the operation of constant current constant voltage charging according to the third embodiment.

In step S601, the control unit 3 starts the constant current charging process of the third embodiment. CC charging is started to flow a constant current I1 to the assembled battery 2.
In step S602, when the voltage measured by the battery 4 reaches the target voltage V2, the control unit 3 temporarily stops CC charging (time tc), and restarts CC charging after a predetermined time has elapsed (time td). In the internal resistance measurement process of the third embodiment, when it is detected that the measured voltage of the battery 4 has reached the target voltage V2, the measured voltage V2 measured at time tc is acquired, and the measurement measured at time td after a predetermined time has elapsed. The voltage Vc is acquired, and a differential voltage dVc between the measurement voltage V2 and the measurement voltage Vc is obtained. Then, the internal resistance Rc is obtained using the differential voltage dVc and the constant current (I1 in this example) flowing through the assembled battery 2.

  In step S603, the control unit 3 starts the threshold voltage determination process of the third embodiment. In the threshold voltage determination process, the threshold voltage V1 is determined using the internal resistance Rc, the end current I2, and the temperature, and the determined threshold voltage V1 is stored in the storage unit 9 for use as the CV charge after the transition.

In step S604, the control unit 3 ends the constant current charging process of the third embodiment. When the measured voltage of the battery 4 reaches the threshold voltage V1, the CC charging is shifted to the CV charging.
In step S605, the control unit 3 starts the constant voltage charging process of the third embodiment. In the constant voltage charging process, CV charging is performed at a constant voltage V1 (= threshold voltage V1) until the current flowing through the assembled battery 2 reaches the predetermined current I2, and when the measured current flowing through the assembled battery 2 reaches the predetermined current I2, CV charging is performed. Quit and migrate.

According to the third embodiment, the internal resistance Rc used for determining the threshold voltage V1 suitable for CV charging of CCCV charging can be measured.
Further, according to the third embodiment, it is possible to cope with a change in the internal resistance Rc due to temperature, and therefore, a more accurate threshold voltage V1 can be obtained.

The charge control device 1 and the charge control method shown in the first to third embodiments may be used for quick charging.
The present invention is not limited to the first to third embodiments, and various improvements and modifications can be made without departing from the gist of the present invention.

1 charge control device,
2 battery packs,
3 Control unit,
4 batteries,
5 Voltmeter,
6 Ammeter,
7 Measuring unit,
8 decision part,
9 Memory part,
10 thermometer,

Claims (5)

When the measurement voltage of the battery approaches the target voltage set in constant current and constant voltage charging, a measurement unit that measures the internal resistance of the battery,
After measuring the internal resistance, a determination unit that determines a threshold voltage used for constant voltage charging performed in constant current and constant voltage charging to be higher than the target voltage according to the measured internal resistance;
A charge control device comprising: The charge control device according to claim 1,
The measurement unit measures the internal resistance by charging for a predetermined time after the constant voltage charge,
The charge control apparatus characterized by the above-mentioned. The charge control device according to claim 1,
The measurement unit measures internal resistance from a change in the measurement voltage after the constant voltage charge,
The charge control apparatus characterized by the above-mentioned. The charge control device according to claim 1,
The measuring unit stops charging before shifting from constant current charging to the constant voltage charging in the constant current constant voltage charging, measures the internal resistance from the change in the measurement voltage,
The said determination part determines the said threshold voltage used for the said constant voltage charge after transfer according to the measured said internal resistance, The charging control apparatus characterized by the above-mentioned. A charge control method for a charge control device, comprising:
When the measured voltage of the battery approaches the target voltage set in constant current constant voltage charging, the internal resistance of the battery is measured,
After measuring the internal resistance, a threshold voltage used for constant voltage charging performed in constant current constant voltage charging is determined as a voltage higher than the target voltage according to the internal resistance.
The charge control method characterized by the above-mentioned.

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