JP6376003B2 - Charge control device and charge control method - Google Patents

Description

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

  Conventionally, constant current charging (CCCV (Constant Current) charging) is performed by switching to constant voltage charging (CV (Constant Voltage) charging) and then charging. Are known. However, when terminating CV charging, (1) the termination current cannot be completely reduced due to the restrictions of the charger (cannot be charged until the termination current = 0 [A]), (2) Even when the target voltage corresponding to SOC (State of Charge) is reached and charging is terminated, there is a problem that a voltage drop occurs due to the internal resistance of the battery and charging cannot be performed to the target voltage. Therefore, as one of the CCCV charging, the constant voltage applied to the battery in the CV charging is set to a voltage (threshold voltage) higher than the target voltage in consideration of the voltage drop due to the internal resistance after the charging is completed. Overshoot charging is known.

The threshold voltage in overshoot charging is determined by the internal resistance, temperature, and end current of the battery before switching from CC charging to CV charging.
However, since the battery is charged with a large current during CC charging, the battery heat generation increases, and when switching to CV charging, the current is rapidly reduced and the battery heat generation decreases. Therefore, the temperature of the battery during CV charging may be lower than during CC charging. Then, when CV charging ends, that is, when the current is reduced to the end current, the threshold voltage determined before CV charging is not an optimal value, and may not reach the target voltage after charging ends.

As a related technique, a charging control device that switches a target voltage according to a temperature during CV charging of CCCV charging is disclosed. See US Pat.
In addition, as a related technique, a charge control method is disclosed in which the end current is switched according to the temperature during CV charge of CCCV charge. See US Pat.

JP 2010-187472 A JP 2002-058171 A

  An object according to one aspect of the present invention is to perform charge control that improves the accuracy of approaching a target voltage by changing a termination current or a threshold voltage according to the battery temperature during CV charging of CCCV charging using overshoot charging. An apparatus and a charge control method are provided.

  A charge control device that performs constant-current constant-voltage charging using overshoot charging that is one form according to the present invention includes a storage unit and a control unit. The storage unit stores battery characteristic information in which the temperature of the battery is associated with the end current for ending constant voltage charging in constant current constant voltage charging. The control unit acquires the measured battery temperature during constant voltage charging, and determines the termination current with reference to the battery characteristic information.

In addition, the control unit lowers the termination current when the temperature of the battery measured during constant voltage charging decreases.
The storage unit also includes temporary threshold characteristic information that associates the battery temperature, the temporary threshold voltage used for constant voltage charging, and the termination current, the battery temperature, and a limit voltage that indicates a limit at which the battery deteriorates. , Is stored. The control unit acquires the measured battery temperature and end current, refers to the temporary threshold characteristic information and the degradation limit information, and lowers the end current when the temporary threshold voltage is equal to or higher than the limit voltage.

  A charge control device that performs constant-current constant-voltage charging using overshoot charging that is one form according to the present invention includes a storage unit and a control unit. The storage unit stores second battery characteristic information in which an initial end current, a battery temperature, and a threshold voltage that changes according to the temperature are associated with each other. The initial threshold voltage is determined based on the initial cutoff current determined before the constant voltage charging, the measured battery temperature is obtained during the constant voltage charging, and the threshold value is obtained by referring to the second battery characteristic information. Determine the voltage.

  During CV charging of CCCV charging using overshoot charging, the accuracy of approaching the target voltage can be improved by changing the termination current or the threshold voltage according to the battery temperature.

It is a figure which shows one Example of a charging control apparatus. It is a figure which shows the relationship between the electric current at the time of overshoot charge, voltage, temperature, and internal resistance. It is a figure which shows an example of the data structure of 1st battery characteristic information. FIG. 6 is a flowchart showing an example of the operation of the charge control device of the first embodiment. It is a figure which shows the relationship between the electric current at the time of overshoot charge of Embodiment 2, voltage, temperature, and internal resistance. It is a figure which shows the relationship between temperature, end current, and threshold voltage. It is the figure which showed one Example of the data structure of temporary threshold value characteristic information and deterioration limit information. FIG. 10 is a flowchart showing an example of operation of the charge control device of the second embodiment.

Hereinafter, embodiments will be described in detail with reference to the drawings.
<Embodiment 1>
FIG. 1 shows the configuration of the charge control device. FIG. 1 is a diagram illustrating an embodiment of a charge control device. The charge control device 1 that performs CCCV charging using overshoot charging 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 7 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 control unit 3 acquires the measured temperature of the battery 4 during the CV charge of the CCCV charge using the overshoot charge, and associates the temperature of the battery 4 with the termination current for terminating the CV charge in the CCCV charge. Control for determining the end current is performed with reference to the battery characteristic information. When the temperature of the battery 4 measured during CV charging decreases, the control unit 3 performs control to lower the termination current. The battery characteristic information is obtained in advance by experiments or simulations. The control unit 3 is a circuit using, for example, a CPU (Central Processing Unit), a multi-core CPU, and a programmable device (FPGA (Field Programmable Gate Array), PLD (Programmable Logic Device), etc.). 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 8 stores battery characteristic information. The storage unit 8 is a memory such as a ROM (Read Only Memory) or a RAM (Random Access Memory), and may be provided separately from the control unit 3.

The operation of the charge control device will be described.
Since the battery 4 is charged with a large current during CC charging, the heat generation of the battery 4 (current I ² × internal resistance R) increases. Further, during the CC charging, the temperature of the battery 4 increases and the internal resistance decreases due to the heat generation of the battery 4.

  FIG. 2 is a diagram showing the relationship between current, voltage, temperature, and internal resistance when overshoot charging is performed. The vertical axis shows current, voltage, temperature, and internal resistance, and the horizontal axis shows time. . From time t0 to t1 (during CC charging) shown in FIG. 2, the current curve 201 (broken line) of the conventional overshoot charging and the current curve 202 (solid line) of the overshoot charging of the present invention are similarly constant currents. Since charging is performed at I1, the voltage curve 204 (broken line) corresponding to the current curve 201 and the voltage curve 203 (solid line) corresponding to the current curve 201 are similarly threshold voltages V1 higher than the target voltage V2. Go up until. At this time, the battery 4 generates heat, the temperature of the battery 4 rises as shown by the temperature curve 205 in FIG. 2, and the internal resistance falls as shown by the resistance curve 206 in FIG. The target voltage V2 is, for example, a voltage corresponding to full charge, but is not limited thereto.

  Subsequently, when the voltage reaches the threshold voltage V1 (initial threshold voltage) and switches from CC charging to CV charging at time t1 and shifts to CV charging, the current curve 201 and the voltage in FIG. As shown by a curve 204, CV charging is started at a constant voltage V1 from time t1, and CV charging is performed until the end current becomes I2, that is, until time t2. After the end of charging, the voltage drop (IR drop) and polarization due to the internal resistance disappear from time t2 to t4, and should approach the target voltage V2. However, in the conventional overshoot charging, current is rapidly reduced and heat generation is reduced during CV charging, the temperature of the battery 4 decreases as shown by the temperature curve 205, and the internal resistance increases as shown by the resistance curve 206. For this reason, the threshold voltage V1 determined before CV charging is not an optimum value at the time t2 when CV charging ends. Therefore, the voltage of the battery 4 may not reach the target voltage at time t4.

Therefore, in the overshoot charging of the present invention, (1) the end current is changed according to the temperature during CV charging (first processing), or (2) the threshold voltage is changed according to the temperature during CV charging ( Second processing). Alternatively, (3) changing the termination current based on the measured temperature and the threshold voltage corresponding to the measured temperature (third process).
(1) In the first process, the temperature of the battery 4 is measured using the thermometer 7 even after shifting to CV charging, and the end current is changed during CV charging according to the measured temperature of the battery 4. As shown in the current curve 202 in FIG. 2, the end current is decreased from I2 to I3 as the temperature of the battery 4 decreases from time t1. In the case of the first processing, the threshold voltage is not changed and the threshold voltage V1 is maintained. Moreover, the determination of the termination current during CV charging in the first process is performed, for example, for each termination current (initial termination current) determined before CV charging, and the temperature of the battery 4 measured during CV charging and CV charging. The end current is determined with reference to the first battery characteristic information having the end current associated with the previously determined threshold voltage. The first battery characteristic information is obtained in advance through experiments or simulations.

FIG. 3 is a diagram illustrating an example of a data structure of the first battery characteristic information. In the example of FIG. 3, the first battery characteristic information 300a to 300c corresponding to three types of initial cutoff currents are included. For example, the first battery characteristic information 300a corresponds to the initial end current Ib. In addition, the first battery characteristic information 300a includes an “initial stop current” 301 that stores “Ib” indicating an initial stop current, and a table 302 that determines a stop current during CV charging. In table 302, information indicating the temperature of the battery 4 (eg, “Tem0” to “Tem7”) and information indicating the threshold voltage (eg, “V10” to “V18”) are changed during CV charging. Each termination current is stored. For example, when the temperature during CV charging is “Tem0” and the threshold voltage determined before CV charging is “V10”, the end current associated with “Tem0” and “V10” is selected. In addition, you may obtain | require using a calculation formula etc. instead of the table as shown in the table 302.
(2) In the second process, even after shifting to CV charging, the temperature of the battery 4 is measured using the thermometer 7, and the measured temperature of the battery 4 is used to measure the CV according to the temperature during CV charging. The threshold voltage is changed during charging. As shown in the voltage curve 203 of FIG. 2, the threshold voltage is raised from V1 to V3 as the temperature of the battery 4 decreases from time t1. In the case of the second process, the end current is not changed, and the end current I2 is kept unchanged. The threshold voltage during CV charging in the second process is determined by referring to the second battery characteristic information that associates the temperature of the battery 4 with the threshold voltage that changes according to the temperature for each initial end current. Then, the threshold voltage is determined. For example, the second battery characteristic information that associates the initial end current, the temperature of the battery 4, and the threshold voltage that changes according to the temperature is stored in the storage unit 8. The initial threshold voltage is determined based on the initial cutoff current determined in step (b), the measured temperature of the battery 4 is acquired during CV charging, and the threshold voltage is determined with reference to the second battery characteristic information.

The second battery characteristic information is obtained in advance by experiments or simulations. Further, the relationship between the temperature and the threshold voltage in the second battery characteristic information may be expressed using a table, or may be expressed using a calculation formula or the like.
(3) In the third process, even after shifting to CV charging, the temperature of the battery 4 is measured using the thermometer 7, and the measured temperature of the battery 4 and the threshold voltage changed in accordance with the measured temperature Based on the above, the termination current is changed during CV charging. As shown in the voltage curve 203 of FIG. 2, from time t1 to time t3, as the temperature of the battery 4 decreases, the threshold voltage V1 is increased to V3, and based on that, the end current is also decreased from I2 to I3. Further, the threshold voltage and the end current during CV charging in the third process are determined by referring to the second battery characteristic information, for example, and then referring to the first battery characteristic information. Then, the end current is determined.

The operation of the control unit will be described.
FIG. 4 is a flowchart illustrating an example of the operation of the charge control device according to the first embodiment.
In step S1, the control unit 3 acquires an initial end current. That is, the end current determined before switching to CV charging is acquired. From time t0 to t1 in FIG. 2, the initial end current I2 is acquired.

  In step S2, the control unit 3 shifts to CV charging. That is, when the voltage of the battery 4 reaches the threshold voltage V1, the CC charging is switched to the CV charging. At time t1 in FIG. 2, switching to CV charging is performed.

In step S <b> 3, the control unit 3 acquires the temperature of the battery 4. The temperature of the battery 4 is measured using the thermometer 7.
In step S4, the control unit 3 determines a threshold voltage during CV charging. In step S5, the control unit 3 determines an end current during CV charging.

  However, when the first process is performed, the process of step S4 may not be executed. After performing the process of step S3, it transfers to step S5 and determines a termination current with reference to 1st battery characteristic information.

  Moreover, when implementing a 2nd process, the process of step S5 does not need to be performed. After performing the process of step S3, it transfers to step S4 and determines a threshold voltage with reference to 2nd battery characteristic information.

  Moreover, when implementing a 3rd process, the process of step S4, S5 is performed. After performing the process of step S3, it transfers to step S4 and determines a threshold voltage, and it transfers to step S5 and determines final current.

  In step S6, the current measured by the ammeter 6 is acquired, and the control unit 3 determines whether or not the acquired current is a termination current. If the acquired current is the termination current (Yes), the CV charging is terminated. If it is not the termination current (No), the process proceeds to step S3.

According to the first embodiment, it is possible to determine the threshold voltage or the end current according to the temperature during CV charging. As a result, since the threshold voltage or the termination current can be set to the optimum value even during CV charging, the battery 4 is more than after the conventional overshoot charging is terminated after the voltage drop and polarization due to the internal resistance are resolved after the charging is terminated. The accuracy with which the voltage is brought close to the target voltage can be improved.
<Embodiment 2>
In the second embodiment, when the process described in the first embodiment is executed, when the threshold voltage reaches a limit voltage at which the battery 4 deteriorates, the threshold voltage is determined so as not to exceed the limit voltage. Moreover, the process which changes a termination current according to the threshold voltage is performed.

The configuration of the second embodiment will be described.
Since the configuration of the second embodiment is the same as the configuration of the first embodiment, only the configuration different from the first embodiment will be described. The storage unit 8 according to the second embodiment includes the temporary threshold characteristic information that associates the temperature of the battery 4, the temporary threshold voltage used for CV charging, and the termination current, the temperature of the battery 4, and the limit at which the battery 4 deteriorates. Degradation limit information that associates the limit voltage indicating Here, the temporary threshold voltage is a threshold voltage that is temporarily used before determining a threshold voltage that is actually used during CV charging, and is used for comparison with a limit voltage. The temporary threshold voltage is determined by the temperature of the battery 4 and the end current.

  Further, the control unit 3 according to the second embodiment acquires the measured temperature and end current of the battery 4, refers to the temporary threshold characteristic information and the deterioration limit information, and the temporary threshold voltage is equal to or higher than the limit voltage. , Lower the end current.

The operation of the charge control device will be described.
FIG. 5 is a diagram illustrating a relationship among current, voltage, temperature, and internal resistance when overshoot charging is performed according to the second embodiment. The vertical axis represents current, voltage, temperature, and internal resistance, and the horizontal axis represents time. Further, the current curve 201 (broken line), voltage curve 204 (broken line), temperature curve 205, and resistance curve 206 shown in FIG. 5 are the same as those described in FIG.

  Since charging is performed with a constant current I1 from time t0 to t1 (during CC charging) shown in FIG. 5, a voltage curve 502 (solid line) corresponding to the overshoot charging current curve 501 of the second embodiment is a voltage curve. As in the case of 204, the voltage is raised until the threshold voltage V1 is higher than the target voltage V2.

  Subsequently, when the voltage of the battery 4 reaches the threshold voltage V1 (the initial threshold voltage) and switches from CC charging to CV charging at time t1 and shifts to CV charging, any one of the first processing to the third processing is performed. Start one process. At this time, when the threshold voltage reaches the limit voltage at which the battery 4 deteriorates, in FIG. 5, when the threshold voltage reaches the limit voltage at time t2, the threshold voltage or the stop current is set so as not to exceed the limit voltage from time t2. Decide.

A method for determining the threshold voltage will be described.
FIG. 6 is a diagram showing the relationship among temperature, end current, and threshold voltage. In the graph shown in FIG. 6, the vertical axis indicates the threshold voltage, and the horizontal axis indicates the temperature [° C.]. A degradation limit line 601 in FIG. 6 indicates the relationship between the temperature and the voltage at which the battery 4 begins to deteriorate. Further, the deterioration limit line 601 indicates that the battery 4 deteriorates even at a low voltage as the temperature becomes lower. Threshold voltage lines 602 to 604 in FIG. 6 indicate the relationship between the temperature for each end current and the threshold voltage. Note that the final current of the threshold voltage line 604 <the final current of the threshold voltage line 603 <the final current of the threshold voltage line 602.

  One of the threshold voltage lines 602 to 604 corresponding to the cutoff current is selected according to the initial cutoff current determined before CV charging. In the following description, it is assumed that the threshold voltage line 603 has been selected. Subsequently, a threshold voltage on the selected threshold voltage line, that is, a temporary threshold voltage is selected according to the measured temperature. Further, a limit voltage on the deterioration limit line 601 is selected according to the measured temperature. Subsequently, the temporary threshold voltage is compared with the limit voltage, and the threshold voltage actually used during CV charging is determined.

  For example, the threshold is determined by determining whether or not the provisional threshold voltage ≧ the limit voltage. If the provisional threshold voltage is equal to or higher than the limit voltage, the control unit 3 determines the limit voltage to be a threshold voltage used for CV charging. In FIG. 6, when the temperature 15 [° C.] is acquired, the temporary threshold voltage Vs 15 at the temperature 15 [° C.] is obtained with reference to the temporary threshold characteristic information in which information about the temperature and the temporary threshold voltage is stored. Further, the limit voltage Vl15 at the temperature of 15 ° C. is obtained with reference to the deterioration limit information in which information on the temperature and the limit voltage is stored. In FIG. 6, since the temporary threshold voltage Vs15 ≧ the limit voltage Vl15, the control unit 3 determines the limit voltage Vl15 as a threshold voltage used for CV charging.

  When the temporary threshold voltage is less than the limit voltage, the control unit 3 determines the temporary threshold voltage as a threshold voltage used for CV charging. In FIG. 6, when the temperature 30 [° C.] is acquired, the temporary threshold voltage Vs 30 at the temperature 30 [° C.] is obtained with reference to the temporary threshold characteristic information in which information about the temperature and the temporary threshold voltage is stored. Further, the limit voltage Vl30 at the temperature of 30 ° C. is obtained by referring to the deterioration limit information in which information on the temperature and the limit voltage is stored. In FIG. 6, since the temporary threshold voltage Vs30 <the limit voltage Vl30, the control unit 3 determines the temporary threshold voltage Vs30 as a threshold voltage used for CV charging.

  In the threshold voltage line 603, when the temperature drops from 30 [° C.] to 15 [° C.] during CV charging, the threshold voltage line 603 and the degradation limit line 601 intersect when the temperature becomes 20 [° C.]. . That is, the timing at time t2 in FIG.

  FIG. 7 is a diagram showing an example of the data structure of temporary threshold characteristic information and deterioration limit information. In the temporary threshold characteristic information 703 in FIG. 7, information in which the temperature and the temporary threshold voltage are associated with each end current is shown. That is, the temporary threshold voltage is determined by the temperature of the battery 4 and the end current. In the example of FIG. 7, the voltage on the threshold voltage line corresponding to the end current Ib is used as the temporary threshold voltage. The deterioration limit information 704 in FIG. 7 shows information that associates the temperature with the limit voltage. In the example of FIG. 7, the limit voltage on the deterioration limit line 601 shown in FIG. 6 is used. In addition, “initial termination current” 702 that stores information on the termination current in FIG. 7 stores “Ib” corresponding to the threshold voltage line 603 in FIG. The temporary threshold characteristic information 703 in which information related to “temperature” and “temporary threshold voltage” is stored includes information indicating temperature (such as “tem0” to “tem8”) and information indicating temporary threshold voltage (from “Vs0” to “ Vs8 "and the like are stored in association with each other. Degradation limit information 704 in which information on “temperature” and “limit voltage” is stored includes information indicating temperature (such as “tem0” to “tem8”) and information indicating limit voltage (such as “V10” to “Vl8”). Note that it is not necessary to use a table as shown in the temporary threshold characteristic information 703 and the deterioration limit information 704, and it may be obtained using a calculation formula or the like.

Subsequently, from time t2 in FIG. 5, using the end current, temperature, and the determined threshold voltage, the end current is lowered without changing the threshold voltage in the first process.
This will be described with reference to FIGS. Since the temperature of the current curve 501 in FIG. 5 decreases from the time t1, the end current is decreased as in the first embodiment. Until the time t2 when the threshold voltage line 603 and the degradation limit line 601 intersect, the provisional threshold voltage is smaller than the limit voltage. Therefore, instead of increasing the threshold voltage along the threshold voltage 603, the end current is decreased from I2 to a value lower than I2. . Then, the temperature decreases after the time t2, but the provisional threshold voltage ≧ the limit voltage at the temperature lower than the point where the threshold voltage line 603 and the deterioration limit line 601 intersect. Therefore, after the time t2, the temperature follows the deterioration limit line 601. Instead of lowering the threshold voltage, the end current is lowered from a value lower than I2 to a lower I4.

That is, when the temporary threshold voltage is equal to or higher than the limit voltage, the end current is lowered. More preferably, when the temporary threshold voltage is equal to or higher than the limit voltage, the end current is also lowered as the temperature decreases.
However, in the case of the first process, the threshold voltage is not changed during CV charging, and the end current is lowered. Therefore, if the threshold voltage has already reached the limit voltage before CV charging, that is, before time t1, The threshold voltage is determined so as not to exceed. In that case, the first process is started using the determined threshold voltage.

In the second process, the threshold voltage is lowered without changing the end current.
This will be described with reference to FIGS. Since the temperature of the voltage curve 502 in FIG. 5 decreases from the time t1, the threshold voltage is increased as in the first embodiment. Until the time t2 when the threshold voltage line 603 and the degradation limit line 601 intersect, the provisional threshold voltage <the limit voltage, so the threshold voltage is increased from V1 to V4 along the threshold voltage 603. Then, the temperature decreases after the time t2, but the provisional threshold voltage ≧ the limit voltage at the temperature lower than the point where the threshold voltage line 603 and the deterioration limit line 601 intersect. Therefore, after the time t2, the temperature follows the deterioration limit line 601. To lower the threshold voltage from V4.

That is, when the temporary threshold voltage is equal to or higher than the limit voltage, the threshold voltage is lowered. More preferably, when the temporary threshold voltage is equal to or higher than the limit voltage, the threshold voltage is also lowered as the temperature decreases.
However, in the case of the second process, the threshold voltage is lowered without changing the termination current during CV charging, so the threshold voltage has already reached the limit voltage before CV charging, that is, before time t1, and does not exceed the limit voltage. When the threshold voltage is determined as described above, the second process is started using the threshold voltage, and thus the threshold voltage is decreased from time t1.

  In the third process, the threshold voltage and the end current are lowered. In the case of the third process, when the threshold voltage has already reached the limit voltage before CV charging, that is, before time t1, and the threshold voltage is determined so as not to exceed the limit voltage, the determined threshold voltage is used. Then, the third process is started.

The operation of the control unit will be described.
FIG. 8 is a flowchart illustrating an example of the operation of the charge control device according to the second embodiment.
Since the processing of steps S1 to S3 and S6 in FIG. 8 is the same as the processing of the control unit 3 described in the first embodiment, it will be briefly described. In step S1, the control unit 3 acquires an initial end current. From time t0 to t1 in FIG. 5, the initial end current I2 is acquired. In step S2, the control unit 3 shifts to CV charging. At time t1 in FIG. 5, switching to CV charging is performed. In step S <b> 3, the control unit 3 acquires the temperature of the battery 4.

In step S801, the control unit 3 uses the temperature of the battery 4 and the end current to refer to the temporary threshold characteristic information and the deterioration limit information to obtain the temporary threshold voltage and the limit voltage.
In step S802, the control unit 3 determines whether or not provisional threshold voltage ≧ limit voltage. If provisional threshold voltage ≧ limit voltage (Yes), the process proceeds to step S803, and provisional threshold voltage <limit voltage. If there is (No), the process proceeds to step S804.

In step S803, since the temporary threshold voltage is equal to or higher than the limit voltage, the control unit 3 sets the threshold voltage used for CV charging to the limit voltage obtained in step S801.
In step S804, since the temporary threshold voltage is less than the limit voltage, the control unit 3 sets the threshold voltage used for CV charging to the temporary threshold voltage obtained in step S801.

In step S805, the control unit 3 determines an end current during CV charging.
However, when the first process is performed, the end current is changed using the temperature of the battery 4 and the determined threshold voltage. Further, when the second process is performed, the process of step S805 may not be executed. When the third process is performed, when the process proceeds from step S803 to step S805, the end current is changed based on the temperature of the battery 4 and the determined threshold voltage (limit voltage). Further, when the process proceeds from step S804 to step S805, the end current is changed based on the temperature of the battery 4 and the threshold voltage (temporary threshold voltage).

  In step S6, the current measured by the ammeter 6 is acquired, and the control unit 3 determines whether or not the acquired current is a termination current. If the acquired current is the termination current (Yes), the CV charging is terminated. If it is not the termination current (No), the process proceeds to step S3.

  According to the second embodiment, when the temporary threshold voltage of the battery 4 reaches the limit voltage, a threshold voltage that does not deteriorate the battery is determined, and the temperature during the CV charging is determined using the temperature of the battery 4 and the determined threshold voltage. A threshold voltage or a cutoff current can be determined according to As a result, the threshold voltage or end current can be set to the optimum value even during CV charging. After the charging is completed, the voltage drop and polarization due to the internal resistance are eliminated, and then the charging is completed more than when the conventional overshoot charging ends. The accuracy with which the voltage of the battery 4 is brought close to the target voltage later can be improved.

  The present invention is not limited to the above-described embodiment, and various improvements and modifications can be made without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 1 Charge control apparatus 2 Battery assembly 3 Control part 4 Battery 5 Voltmeter 6 Ammeter 7 Thermometer 8 Storage part

Claims (3)

A charge control device that performs constant current charging or constant voltage charging using overshoot charging,
A storage unit that stores second battery characteristic information in which an initial end current, a battery temperature, and a threshold voltage that changes according to the temperature are associated;
When the voltage of the battery reaches an initial threshold voltage, the control unit shifts from the constant current charging to the constant voltage charging, and controls the battery voltage to the threshold voltage during the constant voltage charging;
With
The control unit determines the initial threshold voltage based on the initial cutoff current determined before the constant voltage charge, acquires the measured temperature of the battery during the constant voltage charge, and The threshold voltage is determined with reference to second battery characteristic information. The charge control device according to claim 1 ,
The controller is configured to increase the threshold voltage when the temperature of the battery measured during the constant voltage charging decreases. The charge control device according to claim 1 or 2 ,
The storage unit
Temporary threshold characteristic information that associates the temperature of the battery, the temporary threshold voltage used for the constant voltage charging, and the termination current, and the temperature of the battery and a limit voltage that indicates a limit at which the battery deteriorates. Store the associated degradation limit information,
The controller is
Obtain the measured temperature of the battery and the initial cutoff current, and refer to the temporary threshold characteristic information and the deterioration limit information, and if the temporary threshold voltage is equal to or higher than the limit voltage, the threshold voltage is Lower,
The charge control apparatus characterized by the above-mentioned.

Images