JP2020041977A - Device and method for estimating full charge capacity - Google Patents

Abstract

To increase the accuracy of estimating a full charge capacity.SOLUTION: A power source system includes a vehicle and a charge/discharge device. The vehicle includes a battery and a vehicle-side controller. The vehicle-side controller includes a battery ECU and a DC charge ECU. The battery ECU can estimate a full charge capacity from the charge rate of the battery before the battery is charged, the charge rate of the battery after the battery is charged, and the current integrated value of the charge current while the battery is charged. The DC charge ECU causes a charge/discharge device to charge or discharge the battery before the charge rate of the battery before the battery is charged is estimated.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a full charge capacity estimation device and a full charge capacity estimation method.

  The full charge capacity of a lithium ion secondary battery decreases due to deterioration due to repeated charging and discharging and aging. The decrease in the full charge capacity may cause a difference between the estimated value of the charging rate and the actual charging rate. Therefore, in Patent Literature 1, the full charge capacity is estimated based on the current integrated value of the charging current between the charging rate before charging the lithium ion secondary battery and the charging rate after charging. The charging rate of the lithium ion secondary battery can be estimated from the correspondence between the open circuit voltage and the charging rate of the lithium ion secondary battery.

JP 2018-85278 A

  By the way, it is known that the correspondence between the open circuit voltage and the charging rate of the lithium ion secondary battery has a hysteresis characteristic according to the charge / discharge state of the lithium ion secondary battery. Therefore, the open circuit voltage differs depending on whether the lithium ion secondary battery is charged or discharged, even if the charging rate is the same. For this reason, due to the hysteresis characteristic of the lithium ion secondary battery, the accuracy of estimating the charging rate may decrease, and the accuracy of estimating the full charge capacity may decrease.

  An object of the present invention is to provide a full charge capacity estimation device and a full charge capacity estimation method that can improve the estimation accuracy of the full charge capacity.

  A full charge capacity estimating apparatus that solves the above-described problem, by controlling a charging device that charges a lithium ion secondary battery, a charging unit that charges the lithium ion secondary battery from a preset charging start time. A voltage acquisition unit that acquires a measurement value from a voltage detection unit that detects an open circuit voltage of the lithium ion secondary battery, and a relationship between the open circuit voltage and a charging rate of the lithium ion secondary battery. An estimation unit for estimating a charging rate of the ion secondary battery, a current acquisition unit for acquiring a measurement value from a current detection unit for detecting a charging current flowing to the lithium ion secondary battery, and the lithium before charging by the charging unit. The charging rate of the ion secondary battery, the charging rate of the lithium ion secondary battery after charging by the charging unit, and the charging while charging the lithium ion secondary battery A full charge capacity estimating unit for estimating the full charge capacity of the lithium ion secondary battery from the integrated current value of the current, wherein the full charge capacity estimation device electrically connects the lithium ion secondary battery and a load. Discharge of the lithium ion secondary battery by controlling the connected device that causes the lithium ion secondary battery to discharge by connecting to the charging of the lithium ion secondary battery by controlling the charging device A charging / discharging unit that performs the charging / discharging start time, which is a time before the charging start time, wherein the voltage acquiring unit is configured to perform the discharging and charging of the lithium ion secondary battery by the charging / discharging unit. And obtains a measurement value from the voltage detection unit before the charging start time, and charges the charging rate of the lithium ion secondary battery estimated using the measurement value by the charging unit. Above using as the charging rate of the lithium ion secondary battery, the full charge capacity estimating unit estimates the full charge capacity.

  The present inventor repeated experiments to reduce the effect of hysteresis that occurs in the correspondence between the open circuit voltage and the charging rate.As a result, the effect of hysteresis was reduced by performing both discharging and charging of the lithium ion secondary battery. I learned that I can do it. Based on this, discharging and charging are performed before estimating the charging rate of the lithium ion secondary battery, and then the charging rate of the lithium ion secondary battery is estimated from the obtained open circuit voltage. Thereby, the charging rate can be estimated from the open circuit voltage in which the influence of the hysteresis is reduced, and the accuracy of estimating the charging rate of the lithium ion secondary battery can be improved. The full charge capacity estimating unit estimates the full charge capacity using the charging rate with the improved estimation accuracy. Therefore, the estimation accuracy of the full charge capacity can be improved.

  For the full charge capacity estimating device, after discharging and charging of the lithium ion secondary battery by the charging and discharging unit, the lithium ion secondary battery of the lithium ion secondary battery for a predetermined time or more before the charging start time The voltage acquiring unit may include a regulating unit that regulates discharging and charging, and the voltage acquiring unit may acquire a measured value from the voltage detecting unit after the lapse of the predetermined time and before the charging start time.

  According to this, polarization caused by discharging and charging of the lithium ion secondary battery by the charge / discharge unit can be eliminated within a predetermined time. Therefore, the estimation accuracy of the charging rate of the lithium ion secondary battery can be further improved, and the estimation accuracy of the full charge capacity can be further improved.

  In the full charge capacity estimating device, the charging device and the connection device can charge the lithium ion secondary battery with electric power supplied from a system power supply, and cooperate with the system power to load the lithium ion secondary battery. And a charging / discharging device capable of supplying power to the lithium ion secondary battery.

According to this, the electric power of the lithium ion secondary battery can be used to drive the load.
In the full charge capacity estimating device, the charge / discharge unit may include a discharge current amount due to a discharge performed before the discharge and charging of the lithium ion secondary battery, or a discharge and charge of the lithium ion secondary battery. The larger the amount of charging current due to the charging performed before the operation is performed, the greater the amount of electric power by discharging and charging the lithium ion secondary battery may be.

According to this, the influence of the hysteresis can be further reduced.
In the full charge capacity estimating device, the charging / discharging unit may control the lithium ion secondary battery so that a discharge current amount due to discharging the lithium ion secondary battery and a charging current amount due to charging of the lithium ion secondary battery are the same. The secondary battery may be discharged and charged.

According to this, the influence of the hysteresis can be further reduced.
A method of estimating a full charge capacity that solves the above-described problem includes a charging step of charging the lithium ion secondary battery from a preset charging start time by controlling a charging device that charges the lithium ion secondary battery. The charging rate of the lithium ion secondary battery before charging in the charging step, the charging rate of the lithium ion secondary battery after charging in the charging step, and during charging of the lithium ion secondary battery. A full charge capacity estimating step of estimating a full charge capacity of the lithium ion secondary battery from a current integrated value of a charge current, wherein the full charge capacity estimation method comprises: Discharge of the lithium ion secondary battery by controlling a connected device that causes the lithium ion secondary battery to perform discharge by connecting the battery and controlling the charging device Charging and discharging of the lithium-ion secondary battery by performing a charging and discharging step from a charging and discharging start time that is a time before the charging start time, and in the full charge capacity estimating step, the charging and discharging step Using the charge rate of the lithium ion secondary battery after the discharge and charge of the lithium ion secondary battery and before the charge start time as the charge rate of the lithium ion secondary battery before the charge, Estimate full charge capacity.

  In the full charge capacity estimation step, the full charge capacity is estimated using the charge rate with the improved estimation accuracy. Therefore, the estimation accuracy of the full charge capacity can be improved.

  According to the present invention, it is possible to improve the estimation accuracy of the full charge capacity.

FIG. 2 is a schematic configuration diagram of a power supply system. FIG. 3 is an interaction diagram of a vehicle-side control unit and a charge / discharge control unit. 5 is a time chart showing a correspondence between a battery voltage and a battery charging rate when the full charge capacity estimation method is performed. FIG. 4 is a schematic diagram illustrating an example of a hysteresis characteristic of a lithium ion secondary battery. The schematic block diagram which shows the full charge capacity estimation apparatus of a modification.

Hereinafter, an embodiment of a full charge capacity estimation device and a full charge capacity estimation method will be described.
As shown in FIG. 1, the power supply system 10 includes a vehicle 11 and a charging / discharging device 31.
The vehicle 11 includes a battery 12, a monitoring unit 14, a current detection unit 15, a vehicle-side control unit 16, and a vehicle-side connector 23 connected to the charging / discharging device 31.

  The battery 12 includes a plurality of lithium ion secondary batteries 13. The battery 12 has a plurality of lithium ion secondary batteries 13 connected in series. The battery 12 may be a battery in which a plurality of lithium ion secondary batteries 13 are connected in parallel, or a battery in which a plurality of lithium ion secondary batteries 13 are connected to form a module, which are connected in series or connected in parallel.

  The battery 12 is a power source of a traveling motor that drives the vehicle 11. The vehicle 11 is an electric vehicle or a plug-in hybrid vehicle that can run using the power of the battery 12.

  As the monitoring unit 14, an integrated circuit for voltage detection is used. The monitoring unit 14 has a plurality of ports, and the positive and negative electrodes of each lithium ion secondary battery 13 are connected to the ports by voltage detection lines. Adjacent lithium ion secondary batteries 13 share a voltage detection line and a port with the electrodes connected to each other. The monitoring unit 14 measures the voltage of each lithium ion secondary battery 13.

The current detector 15 is connected to the battery 12 in series. The current detection unit 15 measures a charging current of the battery 12 and a discharging current of the battery 12.
The vehicle-side control unit 16 includes a battery ECU 17 and a DC charging ECU 20. The battery ECU 17 is an electronic control unit that includes a CPU 18 and a storage unit 19 including a RAM and a ROM. The DC charging ECU 20 is an electronic control unit including a CPU 21 and a storage unit 22 including a RAM and a ROM. Each of the ECUs 17 and 20 has a timer function such as a timer. Each of the ECUs 17 and 20 may include dedicated hardware for executing at least a part of various processes, for example, an application-specific integrated circuit (ASIC). Each of the ECUs 17 and 20 may be configured as one or more processors operating according to a computer program, one or more dedicated hardware circuits such as an ASIC, or a circuit including a combination thereof. The processor includes a CPU and a memory such as a RAM and a ROM. The memory stores program codes or instructions configured to cause the CPU to execute processing. Memory, or computer readable media, includes anything that can be accessed by a general purpose or special purpose computer.

  The battery ECU 17 can acquire a measurement value of the monitoring unit 14. The battery ECU 17 can acquire the measurement value of the current detection unit 15. The battery ECU 17 can estimate the state of charge (SOC) of the battery 12 from the open circuit voltage (OCV). The storage unit 19 of the battery ECU 17 stores information indicating the correspondence between the charging rate of the battery 12 and the open circuit voltage. For example, the battery ECU 17 opens a switch (not shown) connected in series with the battery 12 when the vehicle 11 is not traveling, and acquires the measurement value of the monitoring unit 14 in a state where the battery 12 and the traveling motor are disconnected. By doing so, the open circuit voltage can be obtained. Note that the open circuit voltage may be estimated from the closed circuit voltage. The monitoring unit 14 functions as a voltage detection unit. The battery ECU 17 functions as a voltage acquisition unit that acquires a measurement value of the monitoring unit 14. The battery ECU 17 functions as a current acquisition unit that acquires a measurement value of the current detection unit 15. The battery ECU 17 functions as an estimating unit that estimates a charging rate of the battery 12 by executing a predetermined program.

  The DC charging ECU 20 controls external charging, which is charging by electric power supplied from outside the vehicle 11. The DC charging ECU 20 and the battery ECU 17 can communicate with each other using a communication protocol such as CAN (Controller Area Network) or LIN (Local Interconnect Network). Further, the DC charging ECU 20 can control the charging / discharging device 31 by transmitting the information of the battery 12 acquired from the battery ECU 17 to the charging / discharging device 31 or giving a command to the charging / discharging device 31.

  The vehicle connector 23 includes positive and negative input / output terminals 24 and 25 and a communication terminal 26. The positive input / output terminal 24 is connected to the positive electrode of the battery 12. The negative input / output terminal 25 is connected to the negative electrode of the battery 12. The communication terminal 26 is connected to the DC charging ECU 20.

  The charging / discharging device 31 is used for both charging the battery 12 from the system power supply SP and supplying power from the battery 12 to the load L in the building. The charging / discharging device 31 is a system cooperation power supply device capable of supplying power to the load L from the battery 12 in cooperation with the system power supply SP. The charging / discharging device 31 is, for example, a device that performs charging conforming to the CHAdeMO (registered trademark) standard and discharging conforming to the electric vehicle charging / discharging system guidelines.

  The charging / discharging device 31 is installed outside a building such as a parking place of the vehicle 11, for example. The building is a building, such as a house, an office building, a factory, and a store, on which a load L supplied from the system power supply SP can be installed. A distribution board B and a plurality of loads L are installed in the building. The distribution board B is supplied with commercial AC power from the system power supply SP. This AC power is supplied to each load L in the building through the distribution board B.

  The charge / discharge device 31 includes a bidirectional inverter 32, a charge / discharge control unit 35 for controlling the charge / discharge device 31, and a charge / discharge connector 38 connected to the vehicle-side connector 23. The bidirectional inverter 32 includes a DC / AC converter 33 and a DC / DC converter 34. The DC / AC converter 33 is connected to the distribution board B. When charging the battery 12, the DC / AC conversion unit 33 converts AC power supplied from the system power supply SP into DC power and outputs the DC power to the DC / DC conversion unit 34. When charging the battery 12, the DC / DC converter 34 boosts the DC power output from the DC / AC converter 33 and outputs the boosted voltage. The DC / DC converter 34 converts the voltage of the DC power output from the battery 12 to a predetermined voltage and outputs it to the DC / AC converter 33 when discharging from the battery 12 to the load L. The DC / AC converter 33 converts the DC power output from the DC / DC converter 34 into AC power and outputs the AC power when discharging from the battery 12 to the load L. That is, when the battery 12 is discharged, the battery 12 and the load L are electrically connected by the DC / AC converter 33 and the DC / DC converter 34, and the battery 12 is discharged. . The charging / discharging device 31 can perform both charging and discharging of the battery 12. Therefore, it can be said that the charging / discharging device 31 functions as a charging device and a connection device.

  The charge / discharge control unit 35 includes a CPU 36 and a storage unit 37 including a RAM, a ROM, and the like. The storage unit 37 stores a program for controlling the charge / discharge device 31. The charge / discharge control unit 35 charges / discharges the battery 12 by controlling the bidirectional inverter 32. More specifically, the charge / discharge control unit 35 can charge / discharge the battery 12 by performing a predetermined charging sequence or discharging sequence.

  The input device ID is connected to the charge / discharge control unit 35. The input device ID is a device used by the user to operate the charge / discharge device 31. The input device ID includes an operation unit O and a control unit C. The operation unit O is, for example, a touch panel or a button. The control unit C receives an input from the operation unit O. The user can cause the charging / discharging device 31 to perform a desired operation by operating the operation unit O. For example, by operating the operation unit O, a charge start, a charge stop, a charge start time designation, a charge end time designation, a peak shift in which the battery 12 is charged at night and the battery 12 is discharged during the day, or the like is performed. Can be set. Starting charging means starting charging of the battery 12 when the operation unit O is operated, and stopping charging means stopping charging of the battery 12. The control unit C transmits an input from the operation unit O to the charge / discharge control unit 35. The input device ID may be provided inside the building, or may be provided outside the building together with the charging / discharging device 31.

  The charge / discharge connector 38 includes input / output terminals 39 and 40 and a communication terminal 41. The positive / negative input / output terminals 39 and 40 are connected to the DC / DC converter 34. The input / output terminals 39 and 40 of the charge / discharge connector 38 can be connected to the input / output terminals 24 and 25 of the vehicle-side connector 23. The communication terminal 41 of the charging / discharging connector 38 can be connected to the communication terminal 26 of the vehicle-side connector 23. The connection between the charge / discharge connector 38 and the vehicle-side connector 23 allows the charge / discharge device 31 to charge and discharge the battery 12. Further, the DC charging ECU 20 and the charging / discharging control unit 35 can communicate with each other using a communication protocol such as CAN, so that information necessary for charging / discharging the battery 12 can be transmitted / received.

  Next, a method for estimating the full charge capacity of the battery 12 will be described. In the present embodiment, the estimation of the full charge capacity of the battery 12 is performed by the cooperation of the battery ECU 17, the DC charge ECU 20, and the charge / discharge control unit 35. Therefore, the vehicle-side control unit 16 and the charge / discharge control unit 35 function as the full charge capacity estimation device 50. The estimation of the full charge capacity in the present embodiment is performed when charging is started from a predetermined charging start time. When the charge start is input by the input device ID, the full charge capacity estimation in the present embodiment is not performed. On the other hand, when the charging start time is specified by the input device ID, when the charging end time is specified, or when the peak shift is performed, the full charge capacity is estimated. Although these are described as an example of the charging mode of the charging / discharging device 31, the full charging capacity is estimated even in other charging modes as long as the charging mode is a charging mode in which the charging start time is set.

  As shown in FIGS. 2 and 3, in step S11, the charging / discharging control unit 35 sets the charging start time t11 based on the input from the input device ID and the information on the battery 12. When the charging start time t11 is input by the input device ID, the input charging start time t11 is set. When the charging end time is input by the input device ID, the time required for charging is calculated based on information such as the charging rate of the battery 12, and the time obtained by subtracting the time required for charging from the charging end time is the charging start time t11. Is set as When the peak shift is performed, the charging start time t11 is set so that the charging ends at midnight when the power demand decreases.

  Next, in step S12, the charging / discharging control unit 35 transmits the charging start time t11 set in step S11 to the DC charging ECU 20. Next, in step S13, the charge / discharge control unit 35 supplies power to the load L by controlling the bidirectional inverter 32. The distribution board B is supplied with both the AC power from the system power supply SP and the AC power from the charging / discharging device 31 to perform system cooperation operation. The discharging of the battery 12 by the charging / discharging device 31 is performed according to the power demand of the load L.

  In step S21, the DC charging ECU 20 calculates a charging / discharging start time t12 from the charging start time t11. The charge / discharge start time t12 is a time before the charge start time t11. Next, in step S22, the DC charging ECU 20 transmits a charging / discharging start command to the charging / discharging control unit 35 at the charging / discharging start time t12.

  As shown in FIG. 3, the discharge of the battery 12 is performed over a discharge time T1, which is a period until a charge / discharge start command is received. During the discharging time T1, the charging rate of the battery 12 decreases due to the discharging of the battery 12 by the charging / discharging device 31.

  As shown in FIG. 2, when receiving the charge / discharge command in step S <b> 14, the charge / discharge control unit 35 starts discharging and charging the battery 12 by controlling the bidirectional inverter 32. Step S14 is a charge / discharge step. The discharging and charging of the battery 12 may be performed in the order of discharging → charging, or may be performed in the order of charging → discharging. However, if the discharging is performed before performing the process of step S14, the charging is performed. It is preferable to perform the discharge in the order of discharge, and if the charge is performed before performing the processing in step S14, it is preferable to perform the discharge in the order of charge. In the present embodiment, since the battery 12 has been discharged before performing the processing in step S14, the charge / discharge control unit 35 performs discharge and charge in the order of charge → discharge. The charge / discharge control unit 35 alternately repeats charging and discharging.

  As shown in FIG. 3, the discharging and charging of the battery 12 are performed over a charging / discharging time T2. The charge / discharge control unit 35 performs the discharge and the charge such that the discharge current amount [Ah] by the discharge of the battery 12 and the charge current amount [Ah] by the charge of the battery 12 are the same. Note that “same” here is not limited to the case where the charge current amount and the discharge current amount completely match, but allows an error that may occur due to the discharge and charge of the battery 12. The battery ECU 17 acquires a charging current and a discharging current by acquiring a measurement value from the current detecting unit 15. The battery ECU 17 calculates the amount of charging current by integrating the product of the charging current and the predetermined period for each predetermined period. Battery ECU 17 calculates the amount of discharge current by integrating the product of the discharge current and the predetermined cycle at each predetermined cycle. The charge / discharge control unit 35 acquires the charge current amount and the discharge current amount of the battery 12 via the DC charge ECU 20. Thereby, the charge / discharge control unit 35 can perform the discharge and the charge while grasping the charge current amount and the discharge current amount.

  Here, since the charge / discharge control unit 35 causes the battery 12 to discharge according to the power demand of the load L, the discharge power of the battery 12 depends on the power demand, and the discharge power cannot be controlled. . Accordingly, the charge / discharge control unit 35 grasps the amount of discharge current of the battery 12 discharged according to the power demand, and controls the bidirectional inverter 32 so that the amount of discharge current and the amount of charge current are the same. 12 is discharged and charged.

  In addition, the charge / discharge control unit 35 increases the power amount [Wh] by discharging and charging the battery 12 as the discharge current amount due to the discharge performed before performing the processing in step S14 is large. Here, the discharge current amount due to the discharge performed before performing the processing in step S14 may be an integrated value of the current discharged over the discharge time T1. In addition, as can be understood from FIG. 3, the discharge and the stop of the discharge are repeated during the discharge time T1, and it can be said that the discharge of the battery 12 is performed intermittently. The discharge current amount due to the discharge performed before performing the processing in step S14 may be an integrated value of the current discharged by the last discharge among the discharges intermittently performed during the discharge time T1.

  The amount of power by discharging and charging the battery 12 is an integrated value of the power charged and discharged during the charging and discharging time T2 when the discharging and charging of the battery 12 are performed. In order to increase the amount of power charged / discharged by discharging and charging the battery 12, for example, the number of repetitions of discharging / charging is increased, the charging / discharging time T2 is increased, and the current and voltage during discharging and charging are increased. And increasing the size. The discharging and charging of the battery 12 by controlling the bidirectional inverter 32 are executed by the DC charging ECU 20 transmitting a charge / discharge command. Therefore, it can be said that the DC charging ECU 20 functions as a charging / discharging unit that discharges and charges the battery 12 by executing a predetermined program.

  As shown in FIG. 2, in step S23, the DC charging ECU 20 transmits a charge / discharge stop command to the charge / discharge control unit 35. The charge / discharge stop command is transmitted, for example, when the number of times the battery 12 is discharged and charged, or when the charge / discharge time T2 reaches a predetermined value.

  In step S15, upon receiving the charge / discharge stop command, the charge / discharge control unit 35 stops discharging and charging the battery 12. When receiving the charge / discharge stop command, the charge / discharge control unit 35 regulates the discharge and charge of the battery 12. It can be said that the DC charging ECU 20 functions as a regulating unit that regulates charging and discharging of the battery 12 by executing a predetermined program and transmitting a charging / discharging stop command to the charging / discharging control unit 35.

  As shown in FIG. 3, the charging and discharging of the battery 12 is restricted over the idle time T3. The leaving time T3 is a time from the charging / discharging time T2 to the charging start time t11. The leaving time T3 is a time equal to or longer than a predetermined time during which the polarization of the lithium ion secondary battery 13 can be eliminated. When the battery 12 is charged and discharged, polarization occurs in the lithium ion secondary battery 13. There are two types of polarization: charge polarization that occurs during charging and discharge polarization that occurs during discharging. Charging polarization refers to a phenomenon in which the voltage of the lithium ion secondary battery 13 is higher than in the case where no polarization occurs. Discharge polarization refers to a phenomenon in which the voltage of the lithium ion secondary battery 13 is lower than when no polarization occurs. Therefore, the open circuit voltage differs depending on whether the lithium ion secondary battery 13 has been charged or discharged, even if the charging rate is the same, and the open circuit voltage also changes depending on the amount of discharge and the amount of charge. Polarization caused by charging / discharging of the battery 12 is eliminated over time by leaving the battery 12 without charging / discharging.

  By discharging and charging the battery 12 during the charge / discharge time T2, discharge polarization is generated in the lithium ion secondary battery 13 by the last performed discharge. By regulating charging and discharging of the battery 12 for a predetermined time, the discharge polarization of the lithium ion secondary battery 13 is eliminated.

  As shown in FIG. 2, in step S24, the battery ECU 17 acquires the measured value of the open circuit voltage from the monitoring unit 14 a predetermined time after the regulation of the charging and discharging of the battery 12 is started, and The charging rate of the battery 12 is estimated. That is, after the discharge polarization of the lithium ion secondary battery 13 is eliminated, the battery ECU 17 acquires the measured value from the monitoring unit 14. Battery ECU 17 temporarily stores the estimated charging rate of battery 12 in a rewritable storage area.

  As shown in FIG. 3, the open circuit voltage is obtained at a time t13 which is a predetermined time later and is a time within the leaving time T3. Since the leaving time T3 is performed before the charging start time t11, the time t13 at which the open circuit voltage is obtained is a time after a predetermined time and before the charging start time t11.

  The charge / discharge start time t12 is a time obtained by subtracting the charge / discharge time T2 and the idle time T3 from the charge start time t11. Therefore, it can be said that the charge / discharge start time t12 calculated in step S21 is calculated by subtracting the charge / discharge time T2 and the idle time T3 from the charge start time t11.

  As shown in FIG. 2, in step S16, the charge / discharge control unit 35 controls the bidirectional inverter 32 at the charging start time t11 to charge the battery 12. Therefore, step S16 is a charging step. In the present embodiment, constant-current charging is performed until the voltage of the battery 12 reaches the predetermined voltage, and charging is performed by so-called CCCV charging in which constant-voltage charging is performed after the voltage of the battery 12 exceeds the predetermined voltage. The charging method is not limited to CCCV charging, and may be changed as appropriate. It can be said that the charge / discharge control unit 35 functions as a charging unit that charges the battery 12 by executing a predetermined program.

  In step S25, the DC charging ECU 20 acquires the voltage value and the current value of the battery 12 from the battery ECU 17, and transmits a charge stop command to the charge / discharge control unit 35 when the battery 12 is fully charged. In step S17, when receiving the charge stop command, the charge / discharge control unit 35 stops charging the battery 12.

As shown in FIG. 3, charging is performed from a charging start time t11 to a charging time T4, and the battery 12 is fully charged.
As shown in FIG. 2, in step S26, the battery ECU 17 acquires the measured value of the open circuit voltage from the monitoring unit 14 after a predetermined time, and estimates the charging rate of the battery 12. Here, the predetermined time is a time required for eliminating polarization caused by charging of the battery 12. The predetermined time in step S24 and the predetermined time in step S26 may be different times. The predetermined time in step S24 is a time for eliminating the polarization caused by the last discharge of the discharge and the charge performed during the charge / discharge time T2. On the other hand, the predetermined time in step S26 is a time for eliminating polarization due to charging performed during the charging time T4. The charge current amount due to the charging performed during the charging time T4 is larger than the discharge current amount due to the last discharging performed between the discharging performed during the charging and discharging time T2 and the charging, and it takes time to eliminate the polarization. Therefore, the predetermined time in step S26 may be longer than the predetermined time in step S24.

  As shown in FIG. 3, the open circuit voltage is obtained at time t14, which is the time after the polarization has been eliminated. The open circuit voltage may be acquired at any time after the predetermined time and before the charging and discharging of the battery 12 is performed.

  As shown in FIG. 2, in step S27, the battery ECU 17 estimates the full charge capacity [Ah] of the battery 12. Step S27 is a full charge capacity estimation step. The full charge capacity of the battery 12 is the charging rate of the battery 12 before charging estimated from the open circuit voltage acquired at time t13, and the charging of the battery 12 after charging estimated from the open circuit voltage acquired at time t14. It can be calculated from the rate and the integrated current value of the charging current while the battery 12 is being charged at the charging time T4. Specifically, the full charge capacity of the battery 12 is estimated from the following equation (1).

It can be said that the battery ECU 17 functions as a full charge capacity estimation unit that estimates the full charge capacity of the battery 12 by executing a predetermined program.

  When estimating the full charge capacity, the battery ECU 17 updates the full charge capacity stored in the storage unit 19 from the estimated full charge capacity. The battery ECU 17 may store the estimated full charge capacity as a new full charge capacity in the storage unit 19, or may use the estimated full charge capacity as a learning value to calculate the full charge capacity stored in the storage unit 19. Updates may be made. When using the estimated full charge capacity as a learning value, the full charge capacity is updated using the estimated full charge capacity and the previously estimated full charge capacity. For example, the full charge capacity may be updated by adding or subtracting a fixed value to the full charge capacity stored in the storage unit 19 according to whether the estimated full charge capacity is lower than the past full charge capacity. .

The operation of the embodiment will be described.
As shown in FIG. 4, the SOC-OCV characteristic indicating the correspondence between the charging rate of the lithium ion secondary battery 13 and the open circuit voltage has a hysteresis characteristic that varies between charging and discharging. FIG. 4 shows an example of the hysteresis characteristic of the SOC-OCV.

  When charging and discharging are performed, the SOC-OCV characteristics fluctuate. The polarization is eliminated over time by leaving the lithium-ion secondary battery 13 without charging and discharging. However, in the lithium ion secondary battery 13, it is known that hysteresis remains even after a time longer than the time in which the polarization can be eliminated. If an attempt is made to eliminate the difference in open circuit voltage due to hysteresis by regulating the charge and discharge of the lithium ion secondary battery 13, a longer time is required than the time required to eliminate the polarization.

  In FIG. 4, a line L1 is an SOC-OCV characteristic when there is no influence by hysteresis, a line L2 is an SOC-OCV characteristic when there is influence by hysteresis due to discharge, and a line L3 is a case where hysteresis due to charge is affecting. 5 shows the SOC-OCV characteristics of the sample.

  Hysteresis due to discharge of the lithium ion secondary battery 13 acts to lower the voltage of the lithium ion secondary battery 13. Hysteresis due to charging of the lithium ion secondary battery 13 acts to increase the voltage of the lithium ion secondary battery 13. Therefore, if the open circuit voltage is acquired in a state where the influence of the hysteresis remains, it is understood that the accuracy of estimating the charging rate is reduced.

  Note that the hysteresis characteristic generated in the SOC-OCV characteristic depends on the material used for the electrode of the lithium ion secondary battery 13. When silicon is used as the active material of the negative electrode of the lithium ion secondary battery 13 or when a layered solid solution compound is used as the active material of the positive electrode of the lithium ion secondary battery 13, the hysteresis characteristics are remarkably exhibited.

  The present inventor repeated experiments to reduce the effect of hysteresis occurring in the correspondence between the open circuit voltage and the charging rate. As a result, the effect of the hysteresis was reduced by performing both discharging and charging of the lithium ion secondary battery 13. It was found that it can be reduced. In the present embodiment, discharging and charging are performed before estimating the charging rate of the lithium ion secondary battery 13, and then the charging rate of the lithium ion secondary battery 13 is estimated from the obtained open circuit voltage. Therefore, the estimation accuracy of the charging rate of the lithium ion secondary battery 13 before charging is improved. Therefore, the estimation of the full charge capacity by the battery ECU 17 is performed using the charge rate in which the influence of the hysteresis is reduced.

The effects of the embodiment will be described.
(1) The battery ECU 17 estimates the charging rate before charging from the open circuit voltage of the lithium ion secondary battery 13 in which the influence of hysteresis is reduced by performing discharging and charging. Since the influence of the hysteresis is reduced, the accuracy of estimating the charging rate of the lithium ion secondary battery 13 is improved. Since the battery ECU 17 can estimate the full charge capacity by using the charging rate with the improved estimation accuracy, the estimation accuracy of the full charge capacity can be improved.

  (2) The charge and discharge of the lithium ion secondary battery 13 are regulated for a predetermined time or more after the discharge and charge of the lithium ion secondary battery 13 are completed. Thereby, polarization caused by discharging and charging of the lithium ion secondary battery 13 can be eliminated. Accordingly, the accuracy of estimating the charging rate of the lithium ion secondary battery 13 can be further improved, and the accuracy of estimating the full charge capacity can be further improved.

  (3) The charge and discharge device 31 capable of system cooperation discharges and charges the lithium ion secondary battery 13. Therefore, the lithium ion secondary battery 13 can be discharged by supplying power to the load L in cooperation with the system power supply SP. The load L can be driven by the power from the discharge of the lithium ion secondary battery 13.

  (4) The amount of power for charging and discharging the lithium ion secondary battery 13 is made different according to the amount of charging current by charging performed before discharging and charging the lithium ion secondary battery 13. The effect of hysteresis increases with the amount of discharge current due to the discharge of the lithium ion secondary battery 13. Therefore, the influence of hysteresis can be further reduced by increasing the amount of electric power for charging and discharging the lithium ion secondary battery 13 according to the amount of discharge current, and the accuracy of estimation of the charging rate can be further improved. it can.

  (5) When discharging and charging the lithium ion secondary battery 13, the discharge current amount and the charge current amount are set to be the same. As a result of an experiment conducted by the present inventors, it has been found that the effect of hysteresis can be reduced by making the discharge current amount and the charge current amount the same as compared with the case where the discharge current amount and the charge current amount are made different. Was done. Therefore, by making the amount of discharge current and the amount of charge current the same, the effect of hysteresis can be further reduced.

  (6) The discharging and charging of the battery 12 are performed in the order of charging → discharging if the discharging is performed before performing the processing in step S14, and the discharging is performed if the charging is performed before performing the processing in step S14. → Perform charging in the order. When discharging is performed before performing the processing of step S14, discharge polarization occurs in the lithium ion secondary battery 13, and when charging is performed before performing the processing of step S14, The secondary battery 13 has a charge polarization. The polarization can be canceled by making the discharge and the charge different from those before performing the process of step S14.

The embodiment can be modified and implemented as follows. The embodiment and the following modified examples can be implemented in combination with each other within a technically consistent range.
○ The charging device and the connection device may be separate devices. For example, as shown in FIG. 5, the charging device may be the on-board charger 61 and the connected device may be the power conversion unit 71. As shown in FIG. 5, the vehicle 11 includes a vehicle-mounted charger 61 and a charging ECU 64 that controls the vehicle-mounted charger 61. A system power supply SP is connected to the vehicle-mounted charger 61. The on-vehicle charger 61 includes an AC / DC converter 62 that converts AC power from the system power supply SP into DC power, and a DC / DC converter 63 that performs voltage conversion. The charging ECU 64 is an electronic control unit including a CPU 65 and a storage unit 66 including a RAM and a ROM. The charging ECU 64 can charge the battery 12 by controlling the in-vehicle charger 61. The charging ECU 64 functions as a charging unit.

  The vehicle 11 includes a power conversion unit 71, a discharge ECU 72 that controls the power conversion unit 71, and a load 80. The load 80 is an in-vehicle load driven by the electric power of the battery 12, and is, for example, a driving motor or a motor for driving an electric compressor used for air conditioning. The power conversion unit is an inverter that converts DC power into AC power or a DC / DC converter that performs voltage conversion. The discharge ECU 72 is an electronic control unit including a CPU 73 and a storage unit 74 including a RAM and a ROM. The discharge ECU 72 can discharge the battery 12 by controlling the power conversion unit 71. For example, when supplying electric power to the traveling motor, the discharge ECU 72 can discharge the battery 12 without rotating the traveling motor by performing vector control on the inverter. More specifically, the inverter is vector-controlled so that the q-axis current component for generating torque in the traveling motor is 0 and only the d-axis current component for generating magnetic flux flows.

  In this case, charging and discharging of the battery 12 are performed by sequentially performing charging by the on-board charger 61 and discharging by the power conversion unit 71. Therefore, the charging ECU 64 and the discharging ECU 72 function as a charging / discharging unit.

  The resistance of a cell balance circuit used for passive cell balance may be used as a load, and a switch of the cell balance circuit may be used as a connection device. In other words, the load only needs to be able to consume the power of the battery 12, and the connected device needs only to be capable of electrically connecting and disconnecting the battery 12 from the load.

  (Circle) the charge current amount by charge of the battery 12 performed in the charge / discharge time T2 may differ from the discharge current amount by discharge. Even in this case, the effect of hysteresis can be reduced as compared with the case where the battery 12 is not discharged and charged.

  The battery 12 may be charged before the battery 12 is discharged and charged. In this case, as the amount of charging current by charging before the discharging and charging of the battery 12 is increased, the amount of power by discharging and charging the battery may be increased.

  The regulation of the charging and discharging of the battery 12 performed after the discharging and charging of the battery 12 may not be performed. In this case, the open circuit voltage obtained before the battery 12 is charged is obtained immediately after the battery 12 is discharged and charged. Even in this case, in addition to the effect of hysteresis being reduced by discharging and charging the battery 12, the discharging polarization and the charging polarization are canceled by performing the discharging and charging, and the polarization is canceled. The effect due to the influence is also reduced. Therefore, the accuracy of estimating the charging rate of the battery 12 can be improved and the accuracy of estimating the full charge capacity can be improved as compared with the case where the battery 12 is not discharged and charged.

  The charging of the battery 12 by the charge / discharge control unit 35 may be performed by the DC charge ECU 20 transmitting a charge command to the charge / discharge control unit 35. In this case, the DC charging ECU 20 that transmits the charging command functions as a charging unit. Therefore, the battery ECU 17 and the DC charge ECU 20 constitute a full charge capacity estimation device.

  The charge / discharge control unit 35 may discharge and charge the battery 12 without receiving a charge / discharge command. In this case, the charge / discharge control unit 35 calculates the charge / discharge start time t12 from the charge start time t11. The charge / discharge control unit 35 functions as a charge / discharge unit.

  The charging / discharging control unit 35 may stop the discharging and charging of the battery 12 without receiving the charging / discharging stop command, and regulate the discharging and charging of the battery 12. In this case, the charge / discharge control unit 35 functions as a regulating unit.

The charging unit, the voltage obtaining unit, the estimating unit, the current obtaining unit, the full charge capacity estimating unit, the charging / discharging unit, and the regulating unit may each be configured by a separate ECU.
O The vehicle side control part 16 may be comprised by one ECU. That is, the ECU that performs both the processing performed by the battery ECU 17 and the processing performed by the DC charging ECU 20 may be the vehicle-side control unit 16.

  The full charge capacity estimation device 50 is not limited to the one that estimates the full charge capacity of the lithium ion secondary battery 13 mounted on the vehicle 11, and is used to estimate the lithium ion secondary battery 13 used for any device. It may be.

  The charging and discharging performed during the charging / discharging time T2 may be performed once each.

  SP: system power supply, L: load, 13: lithium ion secondary battery, 14: monitoring unit (voltage detection unit), 15: current detection unit, 17: battery ECU (voltage acquisition unit, estimation unit, current acquisition unit, and Charge capacity estimation unit), 20 DC charging ECU (charge / discharge unit and regulation unit), 31 Charge / discharge device (charging device and connected device), 35 Charge / discharge control unit (charge unit), 50 full charge capacity estimation Apparatus, 61: on-board charger (charging device), 64: charging ECU (charging unit and charging / discharging unit), 71: power conversion unit (connected device), 72: discharging ECU (charging / discharging unit).

Claims (6)

By controlling a charging device that charges the lithium ion secondary battery, a charging unit that charges the lithium ion secondary battery from a preset charging start time,
A voltage acquisition unit that acquires a measurement value from a voltage detection unit that detects an open circuit voltage of the lithium ion secondary battery,
From the correspondence between the open circuit voltage and the charge rate of the lithium ion secondary battery, an estimation unit that estimates the charge rate of the lithium ion secondary battery,
A current acquisition unit that acquires a measurement value from a current detection unit that detects a charging current flowing through the lithium ion secondary battery,
The charging rate of the lithium ion secondary battery before charging by the charging unit, the charging rate of the lithium ion secondary battery after charging by the charging unit, and the charging rate of the lithium ion secondary battery while charging the lithium ion secondary battery A full charge capacity estimating unit for estimating a full charge capacity of the lithium ion secondary battery from a current integrated value of a charge current,
Discharge of the lithium ion secondary battery by controlling a connection device that causes the lithium ion secondary battery to discharge by electrically connecting the lithium ion secondary battery and a load, and control of the charging device Charging and discharging of the lithium ion secondary battery by performing a charging and discharging unit from a charging and discharging start time that is a time before the charging start time,
The voltage acquiring unit acquires a measured value from the voltage detecting unit after the discharging and charging of the lithium ion secondary battery by the charging / discharging unit and before the charging start time, and the measured value The full charge capacity estimating unit estimates the full charge capacity using the charge rate of the lithium ion secondary battery estimated by using the charge rate of the lithium ion secondary battery before charging by the charging unit. Full charge capacity estimation device. A regulating unit that regulates the discharging and charging of the lithium ion secondary battery for a predetermined time or more before the charging start time after the discharging and charging of the lithium ion secondary battery by the charging and discharging unit. With
The full charge capacity estimation device according to claim 1, wherein the voltage acquisition unit acquires a measured value from the voltage detection unit after the predetermined time has elapsed and before the charge start time.   The charging device and the connection device can charge the lithium ion secondary battery with power supplied from a system power supply, and the load of the lithium ion secondary battery is added to the load in cooperation with the system power supply. The full charge capacity estimating device according to claim 1 or 2, which is a charging / discharging device capable of supplying electric power.   The charging / discharging unit is configured to perform a discharge current amount by a discharge performed before the discharging and charging of the lithium ion secondary battery is performed, or to perform the discharging current before the discharging and charging of the lithium ion secondary battery is performed. The full charge capacity estimation device according to any one of claims 1 to 3, wherein the larger the amount of charging current by charging, the larger the amount of power by discharging and charging the lithium ion secondary battery.   The charging / discharging unit performs discharging and charging of the lithium ion secondary battery such that a discharge current amount by discharging the lithium ion secondary battery and a charging current amount by charging of the lithium ion secondary battery are the same. The full charge capacity estimating device according to any one of claims 1 to 4. By controlling a charging device that charges the lithium ion secondary battery, a charging step of charging the lithium ion secondary battery from a preset charging start time,
The charging rate of the lithium ion secondary battery before charging in the charging step, the charging rate of the lithium ion secondary battery after charging in the charging step, and the charging while charging the lithium ion secondary battery A full charge capacity estimating step of estimating a full charge capacity of the lithium ion secondary battery from a current integrated value of a current,
Discharge of the lithium ion secondary battery by controlling a connection device that causes the lithium ion secondary battery to discharge by electrically connecting the lithium ion secondary battery and a load, and control of the charging device Charging and discharging of the lithium ion secondary battery by performing a charge and discharge step from a charge and discharge start time that is a time before the charge start time,
In the full charge capacity estimating step, the charge rate of the lithium ion secondary battery after the discharging and charging of the lithium ion secondary battery in the charging / discharging step and before the charging start time are determined. A full charge capacity estimation method for estimating a full charge capacity using the charge rate of the previous lithium ion secondary battery.