JP2013213684A - Power storage system and charging state estimation method - Google Patents

Power storage system and charging state estimation method Download PDF

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JP2013213684A
JP2013213684A JP2012083000A JP2012083000A JP2013213684A JP 2013213684 A JP2013213684 A JP 2013213684A JP 2012083000 A JP2012083000 A JP 2012083000A JP 2012083000 A JP2012083000 A JP 2012083000A JP 2013213684 A JP2013213684 A JP 2013213684A
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internal resistance
value
power storage
voltage
storage device
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JP2012083000A
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Masaru Kimura
優 木村
Akio Ishioroshi
晃生 石下
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Toyota Motor Corp
トヨタ自動車株式会社
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    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00Enabling technologies or technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10Energy storage
    • Y02E60/12Battery technologies with an indirect contribution to GHG emissions mitigation

Abstract

PROBLEM TO BE SOLVED: To estimate SOC of a battery with high accuracy.SOLUTION: A power storage system is mounted on a vehicle with a power storage device that performs charging/discharging. The power storage system includes a controller that calculates an open circuit voltage on the basis of a closed-circuit voltage to be detected by a voltage sensor, a first voltage change value due to internal resistance in accordance with a charging/discharging current value to be detected by a current sensor, and a second voltage change value due to polarization, and calculates a charging state on the basis of OCV-SOC characteristics where correspondence relation between the open circuit voltage and the charging state of the power storage device is defined in advance. The controller calculates internal resistance of the power storage device on the basis of the charging/discharging current value and the closed-circuit voltage, calculates a first correction value corresponding to the first voltage change value in accordance with a change in internal resistance calculated for a reference value of the internal resistance of the power storage device, and a second correction value corresponding to the second voltage change value, and calculates the open circuit voltage by correcting the first voltage change value and the second voltage change value.

Description

  The present invention relates to a technique for estimating a charging state of a secondary battery or the like, and more particularly to a technique for calculating an open circuit voltage (OCV) of a secondary battery or the like for estimating a charging state.

  The state of charge (SOC) of the secondary battery is detected by integrating the charging / discharging current of the secondary battery, or the open circuit voltage (OCV) corresponding to the SOC. , Hereinafter referred to as OCV).

  In Patent Document 1, when calculating OCV from a closed circuit voltage (CCV) of a secondary battery (hereinafter referred to as CCV), voltage fluctuation due to polarization is taken into consideration, so that the correspondence between SOC and OCV is It describes that the SOC of a secondary battery can be detected with high accuracy.

JP 2000-258514 A

  The secondary battery is known to deteriorate due to aging, and the internal resistance of the secondary battery changes with the deterioration. However, Patent Document 1 does not consider the secular change of internal resistance of the secondary battery (deviation from the internal resistance in the initial state). For this reason, the voltage fluctuation due to the battery internal resistance and the voltage fluctuation due to polarization cannot be accurately grasped according to the secular change of the internal resistance, the OCV calculation accuracy is lowered, and the SOC may not be estimated accurately.

  A power storage system mounted on a vehicle including a power storage device that performs charging / discharging according to the first invention of the present application is based on OCV-SOC characteristics that predefine a correspondence relationship between an open circuit voltage and a charge state of the power storage device. A controller for calculating the state of charge is provided. Based on the closed circuit voltage detected by the voltage sensor, the first voltage fluctuation value due to the internal resistance corresponding to the charge / discharge current value detected by the current sensor, and the second voltage fluctuation value due to polarization, the controller Is calculated. At this time, the controller calculates the internal resistance of the power storage device from the charge / discharge current value and the detected closed circuit voltage, and the first voltage fluctuation according to the calculated change in the internal resistance with respect to the reference value of the internal resistance of the power storage device A first correction value corresponding to the value and a second correction value corresponding to the second voltage fluctuation value are respectively calculated, and the first voltage fluctuation value and the second voltage fluctuation value are corrected to calculate the open circuit voltage.

  According to the first invention of the present application, the first voltage fluctuation (for example, voltage drop) due to the internal resistance of the power storage device corresponding to the charge / discharge current from the closed circuit voltage and the second voltage fluctuation due to polarization are taken into account, and the open circuit of the power storage device When calculating the voltage, the first voltage fluctuation and the second voltage fluctuation are corrected using the correction value corresponding to the secular change of the internal resistance of the power storage device, and the open circuit voltage is calculated. Therefore, the voltage varies with the secular change. The open circuit voltage of the power storage device can be accurately calculated according to the internal resistance, and the SOC detection accuracy is improved.

  The controller has a first variation that predefines a correspondence relationship of the first voltage variation value by the second internal resistance according to the charge / discharge current value based on the second internal resistance that is lower than the first internal resistance of the power storage device in the initial state. The first voltage fluctuation value can be calculated based on the characteristics, and the first correction value can be calculated based on the resistance change rate of the internal resistance calculated using the first internal resistance as a reference value.

  The controller predetermines a correspondence relationship between the second voltage fluctuation values based on the second internal resistance that is lower than the first internal resistance of the power storage device in the initial state according to the charge / discharge current value and the past charge / discharge history. The second voltage fluctuation value can be calculated based on the second fluctuation characteristic, and the second correction value can be calculated based on the resistance change rate of the internal resistance calculated using the first internal resistance as a reference value. Can do.

  The first internal resistance can be an upper limit value in the variation error of the internal resistance at the time of manufacturing the power storage device.

  Moreover, the charge / discharge state estimation method of the power storage device that performs charge / discharge according to the second invention of the present application is based on the OCV-SOC characteristic in which the correspondence between the open circuit voltage of the power storage device and the charge state is defined in advance. calculate. At this time, the closed circuit voltage of the power storage device detected by the voltage sensor, the first voltage fluctuation value due to the internal resistance of the power storage device and the second voltage fluctuation value due to polarization according to the charge / discharge current value detected by the current sensor are calculated. To do. Then, based on the rate of change of the internal resistance calculation value of the power storage device calculated from the charge / discharge current value and the closed circuit voltage with respect to the reference value of the internal resistance of the power storage device, the first correction value corresponding to the first voltage fluctuation value and A second correction value corresponding to the second voltage fluctuation value is calculated. Using the calculated first correction value and second correction value, the first voltage fluctuation value and the second voltage fluctuation value are corrected, and based on the closed circuit voltage, the corrected first voltage fluctuation value, and the second voltage fluctuation value. An open circuit voltage of the power storage device is calculated. The second invention of the present application can also obtain the same effects as those of the first invention of the present application.

It is a figure which shows the structure of the battery system mounted in a vehicle. It is a figure which shows the relationship between OCV and CCV of an assembled battery. It is a figure which shows an example of IR characteristic data. It is a figure which shows an example of Vdyn characteristic data. It is a figure which shows the relationship between each CCV and OCV at the time of the initial stage of an assembled battery, and deterioration. It is a figure which shows the relationship between OCV and SOC of an assembled battery. It is a figure which shows an example of the resistance change rate of an assembled battery (unit cell). It is a figure which shows an example of the correction gain map according to the internal resistance calculation value of an assembled battery. It is a figure which shows an example of the correction gain (Ca) corresponding to the voltage fluctuation (1st voltage fluctuation value) by internal resistance according to the relationship between the temperature of an assembled battery, and internal resistance calculation value. It is a figure which shows an example of the correction | amendment gain (Cb) corresponding to the voltage fluctuation (2nd voltage fluctuation value) by polarization according to the relationship between the temperature of an assembled battery, and internal resistance calculation value. It is a figure which shows an example of IV plot of an assembled battery. It is a flowchart which shows the calculation process of OCV and SOC of an assembled battery.

  Examples of the present invention will be described below.

Example 1
A battery system (corresponding to a power storage system) that is Embodiment 1 of the present invention will be described. FIG. 1 is a diagram showing the configuration of the battery system of this example. The battery system of the present embodiment can be mounted on a vehicle. Vehicles include hybrid cars and electric cars. The hybrid vehicle includes an engine or a fuel cell as a power source for running the vehicle, in addition to the assembled battery described later. An electric vehicle includes only an assembled battery as a power source for the vehicle.

  The assembled battery 10 (corresponding to a power storage device) has a plurality of unit cells 11 connected in series. The number of the single cells 11 constituting the assembled battery 10 can be set as appropriate based on the required output. The assembled battery 10 may include a plurality of unit cells 11 connected in parallel. As the cell 11, a secondary battery such as a nickel metal hydride battery or a lithium ion battery can be used. An electric double layer capacitor (capacitor) can be used instead of the secondary battery.

  The unit cell 11 can be configured by housing a power generation element that performs charging and discharging inside a battery case that forms a cylindrical or rectangular exterior (not shown). The power generation element is an element that performs charge and discharge, and includes a positive electrode plate, a negative electrode plate, and a separator disposed between the positive electrode plate and the negative electrode plate. The positive electrode plate includes a current collector plate and a positive electrode active material layer formed on the surface of the current collector plate. The negative electrode plate has a current collector plate and a negative electrode active material layer formed on the surface of the current collector plate. The positive electrode active material layer includes a positive electrode active material and a conductive agent, and the negative electrode active material layer includes a negative electrode active material and a conductive agent.

When a lithium ion secondary battery is used as the single battery 11, for example, the current collector plate of the positive electrode plate can be formed of aluminum, and the current collector plate of the negative electrode plate can be formed of copper. As the positive electrode active material, for example, LiCo 1/3 Ni 1/3 Mn 1/3 O 2 can be used, and as the negative electrode active material, for example, carbon can be used. An electrolyte solution is infiltrated into the separator, the positive electrode active material layer, and the negative electrode active material layer. Instead of using the electrolytic solution, a solid electrolyte layer may be disposed between the positive electrode plate and the negative electrode plate.

  The assembled battery 10 is connected to the boost converter 41 via a connection line. A system main relay 31 is provided between the positive terminal of the assembled battery 10 and the boost converter 41, and a system main relay 32 is provided between the negative terminal of the assembled battery 10 and the boost converter 41. The system main relays 31 and 32 are switched between ON (connected state) and OFF (blocked state) in response to a control signal from the controller 50.

  Boost converter 41 boosts the output voltage of battery pack 10 and outputs the boosted power to inverter 42. Boost converter 41 steps down the output voltage of inverter 42 and outputs the stepped down power to assembled battery 10. The step-up converter 41 can be composed of, for example, a chopper circuit. Boost converter 41 operates in response to a control signal from controller 50.

  Inverter 42 converts the DC power output from boost converter 41 into AC power, and outputs the AC power to motor generator (MG) 43. As the motor generator 43, for example, a three-phase AC motor can be used. The inverter 42 converts the AC power output from the motor / generator 43 into DC power, and outputs the DC power to the boost converter 41.

  Motor generator 43 receives AC power from inverter 42 and generates kinetic energy for running the vehicle. The motor / generator 43 is connected to wheels, and the kinetic energy generated by the motor / generator 43 is transmitted to the wheels. When the vehicle is decelerated or stopped, the motor / generator 43 converts kinetic energy generated during braking of the vehicle into electric energy (AC power). The AC power generated by the motor / generator 43 is output to the inverter 42. Thereby, regenerative electric power can be stored in the assembled battery 10.

  In the battery system of the present embodiment, the motor / generator 43 can be used as a load that operates by receiving electric power from the assembled battery 10. Further, the boost converter 41 can be omitted. That is, the assembled battery 10 can be connected to the inverter 42.

  The voltage sensor 20 is connected to the controller 50, detects the voltage between the terminals of the assembled battery 10, and outputs the detection result to the controller 50. Further, the voltage sensor 20 can also detect the voltage of each of the unit cells 11 connected in series that constitutes the assembled battery 10.

  The current sensor 21 detects the charging / discharging current of the assembled battery 10 that performs charging / discharging, and outputs the detection result to the controller 50. For example, when the battery pack 10 is being discharged, a positive value can be used as the current value detected by the current sensor 21. Further, when the battery pack 10 is being charged, a negative value can be used as the current value detected by the current sensor 21.

  Further, the current sensor 21 detects an external charging current flowing through the assembled battery 10 via the charger 60 and outputs a detection result to the controller 50. The current sensor 21 of the present embodiment is provided in the current path of the external charging current output from the charger 60 to the assembled battery 10, and the system main relays 31 and 32 are in the off state, that is, the connection between the assembled battery 10 and the load. Is provided in a current path through which the external charging current flows to the assembled battery 10 in a state where is interrupted. A current sensor that detects an external charging current flowing through the battery pack 10 via the charger 60 and a current sensor that detects a current flowing through the battery pack 10 in charge / discharge control of the battery pack 10 are provided separately. Alternatively, the current may be detected.

  The temperature sensor 22 detects the temperature of the assembled battery 10. The temperature sensor 22 is connected to the controller 50 and outputs a detection result to the controller 50. The temperature sensor 22 can be configured to be included in the voltage sensor 20, and can be configured as a monitoring IC that detects the voltage and temperature of the assembled battery 10, for example.

  The charger 60 is connected to the assembled battery 10. The charger 60 boosts an AC / DC converter (not shown) that converts AC power supplied from the external power supply 70 into DC power, or an external charging current (DC current) output from the external power supply 70 or AC / DC converter. Thus, a DC / DC converter that outputs to the assembled battery 10 can be included. The external power source 70 is a power source provided separately from the vehicle outside the vehicle. As the external power source, for example, a commercial power source can be used.

  A charging relay 61 is provided on the current path between the charger 60 and the positive terminal of the assembled battery 10, and a charging relay 62 is provided on the current path between the charger 60 and the negative terminal of the assembled battery 10. It has been. The charge relays 61 and 62 are switched between ON (corresponding to a connected state) and OFF (corresponding to a cut-off state) in response to a control signal from the controller 50.

  The charger 60 is connected to an inlet 63 provided on a side portion of a vehicle on which the battery system of this embodiment is mounted. A charging cable 72 having a connection plug 71 connected to an external power source 70 is connected to the inlet 63.

  The controller 50 is a control device that performs charge / discharge control of the assembled battery 10. The controller 50 is a discharge control that outputs the electric power of the assembled battery 10 to a load based on a vehicle output request, and a charging control that charges the assembled battery 10 with regenerative power during vehicle braking when the vehicle decelerates or stops. I do. The controller 50 according to the present embodiment includes an SOC estimation unit 51, a full charge capacity calculation unit 52, a charge control unit 53, and a memory 54.

  After the ignition switch of the vehicle is turned on and charge / discharge control is started (IG-ON), the controller 50 continues until the ignition switch is turned off and charge / discharge control ends (IG-OFF). The inter-terminal voltage of the assembled battery 10 detected at 1), the current value detected by the current sensor 21 and the battery temperature detected by the temperature sensor 22 are acquired at a predetermined timing and at a predetermined time interval, and the assembled CCV is acquired from the acquired CCV. An OCV calculation process and an SOC estimation process for calculating the OCV of the battery 10 are performed. Values and detection values calculated in each process are used for charge / discharge control and stored in the memory 54.

  Further, the controller 50 can perform a process of integrating the charge / discharge current during the charge / discharge control, and store the charge / discharge current integrated value in the memory 54 as the charge / discharge history. For example, in the detection value detected by the current sensor 21, the charge / discharge current integrated value can be calculated by integrating the discharge current as positive and the charge current as negative.

  When the ignition switch of the vehicle is switched from ON to OFF, the controller 50 ends the charge / discharge control of the battery system, ends the OCV calculation process and the SOC estimation process, and stores the calculated value, the detected value, etc. It is stored in the memory 54 as a discharge history.

  The memory 54 stores a program for operating the controller 50 and various kinds of information, and stores correspondence data (OCV-SOC map) between the OCV and SOC of the assembled battery 10 and various characteristic data described later. .

  The SOC estimation unit 51 calculates the OCV of the assembled battery 10 from the voltage between the terminals of the assembled battery 10 detected by the voltage sensor 20, and displays the SOC corresponding to the calculated OCV in the OCV-SOC map stored in the memory 54. Calculate (estimate) based on this.

  The SOC of the assembled battery 10 indicates the current charging capacity ratio (charging state) with respect to the fully charged capacity of the assembled battery 10. FIG. 6 is a diagram illustrating an example of a correspondence relationship between the OCV and the SOC of the assembled battery 10.

  The OCV (open circuit voltage) of the assembled battery 10 is a voltage between terminals detected by the voltage sensor 20 in a state where the assembled battery 10 is not connected to a load, that is, a terminal of the assembled battery 10 in a state where no current flows through the assembled battery 10. Voltage. In this embodiment, after the ignition switch is switched from OFF to ON, each of the system main relays 31 and 32 is turned from OFF to ON (a state where the assembled battery 10 is connected to a load and can be charged / discharged). The voltage between the terminals when the current flowing through the assembled battery 10 is 0 can also be included as the OCV.

  The CCV (closed circuit voltage) of the assembled battery 10 is a voltage between terminals detected by the voltage sensor 20 in a state where a load is connected to the assembled battery 10, that is, in a state where a current is flowing while the assembled battery 10 is connected to the load. The voltage between the terminals of the assembled battery 10 of FIG. The CCV at the time of discharge becomes a value lower than the OCV corresponding to the voltage fluctuation of the voltage drop due to the internal resistance of the assembled battery 10, and the CCV becomes smaller as the discharge current increases (the voltage fluctuation value of the voltage drop due to the internal resistance becomes larger). . On the other hand, the CCV at the time of charging is a value higher than the OCV because the voltage fluctuation of the voltage drop due to the internal resistance of the assembled battery 10 is opposite to that at the time of discharging, and the CCV increases as the charging current increases.

FIG. 2 is a diagram showing the relationship between the CCV and OCV of the assembled battery 10 during discharge, with the vertical axis representing voltage and the horizontal axis representing time. As shown in FIG. 2, there is a relationship of the following formula (1) between CCV and OCV of the assembled battery 10 in a state where a current is flowing.
(Formula 1) OCV = CCV-IR-Vdyn
Here, IR is a voltage fluctuation value with respect to the current I due to the internal resistance R of the assembled battery 10, and Vdyn is a voltage fluctuation value due to polarization.

  The OCV of the assembled battery 10 changes according to the state of charge. For example, the OCV when the SOC is 80% is larger than the OCV when the SOC is 20%, and the discharge continues as in the example of FIG. As the SOC decreases, the OCV also decreases.

  When a current flows through the assembled battery 10, a voltage drop occurs due to the internal resistance R of the assembled battery 10, and a voltage fluctuation corresponding to the current I flowing through the assembled battery 10 and the internal resistance R occurs. This voltage fluctuation corresponds to the IR term in equation (1). The voltage fluctuation value due to the internal resistance R of the assembled battery 10 is defined as a first voltage fluctuation value. The first voltage fluctuation value is a negative voltage fluctuation with respect to the OCV during discharging, and is a positive voltage fluctuation during charging. The internal resistance R is a predetermined initial value of the internal resistance of the assembled battery 10, and is a fixed value that can be obtained in advance by measurement or calculation.

  Next, when a current flows through the assembled battery 10, polarization occurs and the voltage of the assembled battery 10 fluctuates. For example, when the battery pack 10 is discharged, a polarization voltage is generated in a negative (negative) direction, and a negative voltage fluctuation occurs with respect to the OCV. When the battery pack 10 is charged, a polarization voltage is generated in a positive (positive) direction, and a positive voltage fluctuation occurs with respect to the OCV. When the charging / discharging of the battery pack 10 is stopped, the voltage fluctuation due to the polarization is gradually eliminated with the passage of time (the polarization voltage gradually approaches 0). The voltage fluctuation value due to this polarization is a voltage drop that grows with a time constant depending on the flowing current, and corresponds to the Vdyn term in equation (1). The voltage fluctuation value due to the polarization of the battery pack 10 is set as the second voltage fluctuation value.

  Polarization is voltage fluctuation that dynamically changes depending on the charge / discharge history. The assembled battery 10 generates an electromotive force (corresponding to OCV) due to the chemical change of the electrode active material in each unit cell 11, but the chemical reaction of the electrode active material is likely to occur near the surface, and the reaction inside the electrode Causes a delay time for diffusion. For this reason, due to imbalance (polarization) between the inside of the electrode and the surface portion, a difference in electromotive force occurs even with the same SOC.

  For example, when the discharge continues, the polarization voltage increases in the minus (decrease) direction, and when switching from discharge to charge thereafter, the polarization voltage that has increased in the minus direction fluctuates so as to increase in the plus direction.

  The magnitude of voltage fluctuation due to polarization at a certain time during charge / discharge can be determined according to the past charge / discharge history and the magnitude of the charge / discharge current at that time. As described above, polarization occurs due to the flow of the discharge or charge current. Therefore, the voltage fluctuation due to the polarization at a certain time point is greatly influenced by the most recent charge / discharge history, and becomes larger as the current value of the charge / discharge current increases. .

The voltage fluctuation value Vdyn due to polarization in this embodiment can be obtained by the following equation (2).
(Expression 2) Vdyn (t) = Vdyn (t−1) × attenuation rate + F (I (t)) × (Δt / τ (I (t))
Here, τ (I (t)) is the speed at which polarization proceeds (unit is seconds), F (I (t)) is the current dependence of the polarization voltage, and I (t) is the charge / discharge current (unit) at time t. [A]). Δt / τ (I (t)) is a time constant, and the attenuation rate is the reciprocal of the exponential function {exp (Δt / τ (I (t)))} of the time constant.

  According to Equation 2, a voltage fluctuation value (unit: [V]) due to polarization at an arbitrary time point t can be obtained. Δt can be set to 1 second, for example, and thus Vdyn can be calculated every second. As Vdyn (t = 0), a preset initial value can be used.

  F (I (t)), which is the current dependency of the polarization voltage, represents the magnitude of polarization corresponding to the magnitude of the charge / discharge current at an arbitrary time point t. The polarization voltage in the case where the current is constant in the above formula 2 becomes constant when a sufficient time has passed, and therefore the polarization voltage depends only on F (I (t)). Therefore, F (I (t)) can be measured in advance based on the detection result in constant current discharge or constant current charge at each current value.

  As described above, since CCV and OCV have the relationship of Formula (1), for example, the OCV (corresponding relationship between OCV and SOC shown in the example of FIG. 6) with respect to the internal resistance R and a predetermined SOC flows through the assembled battery 10. From the current value and the CCV detected by the voltage sensor 20, F (I (t)) (= Vdyn) can be obtained. F (I (t)), which is the current dependence of the polarization voltage, can be calculated in advance by acquiring CCV for each of a plurality of types of constant currents (discharge or charge).

  Also, as described above, CCV for each of a plurality of types of constant current (discharge or charge) is acquired for each different SOC, and a change in F (I (t)) between different SOCs is measured in advance. Thus, F (I (t)) for an arbitrary SOC can also be calculated from F (I (t)), which is the current dependency of the polarization voltage with respect to the predetermined SOC.

  In the formula (1), each characteristic data corresponding to each of the IR term and the Vdyn term can be created in advance. The controller 50 can calculate the IR term and the Vdyn term using the current value I detected from each characteristic data stored in the memory 54, and can calculate the OCV from the CCV detected by the voltage sensor 20.

  For example, since the internal resistance R can be grasped in advance, the correspondence between the current value and the IR term (first voltage fluctuation value) can be created in advance as IR characteristic data (first fluctuation characteristic data). Similarly, the polarization voltage Vdyn can be calculated using F (I (t)) as a variable as shown in Equation 2, and the current value can be obtained by grasping the time constant, the attenuation rate, and the previous value in advance. And Vdyn term (second voltage fluctuation value) can be created in advance as Vdyn characteristic data (second fluctuation characteristic data). Each of these characteristic data can be created for each battery temperature of the assembled battery 10, and FIG. 3 is a diagram showing an example of IR characteristic data in the initial value of the internal resistance R. Associated with. FIG. 4 is a diagram showing an example of Vdyn characteristic data in the initial value of the internal resistance R, and is associated with the charge / discharge current and the battery temperature.

  In calculating the SOC of the battery pack 10 in a state where current flows in this way, the first voltage fluctuation value due to the internal resistance R of the battery pack 10 and the second voltage fluctuation value due to polarization are calculated, and the OCV of the battery pack 10 is calculated. Can be requested.

  However, as shown in FIG. 5, the first voltage fluctuation value and the second voltage fluctuation value are generated from the point of time when the discharge is started, and the CCV is lower than the OCV. The first voltage fluctuation value and the second voltage fluctuation value are larger at the time of deterioration, in a state immediately after manufacturing) or in an initial state that is not deteriorated immediately after use and at the time of deterioration after use. This is due to the increase in the internal resistance of the battery pack 10 due to the battery deterioration, and the internal resistance R (fixed predetermined initial value) of the battery pack 10 at the initial stage that has not deteriorated and the time of deterioration. Both the first voltage fluctuation value and the second voltage fluctuation value increase in accordance with the degree of deviation from the internal resistance.

  That is, since the voltage drop at the time of discharge becomes larger than the state of the internal resistance R which has not deteriorated due to the increase of the internal resistance at the time of deterioration, the fluctuation value of the IR term + Vdyn term becomes larger in the equation (1), The increase in internal resistance due to the deterioration of the initial value of the internal resistance R can be regarded as an increase in the fluctuation value of the IR term + Vdyn term.

  As described above, the assembled battery 10 (unit cell 11) is deteriorated due to aging, and the internal resistance of the assembled battery 10 changes from the initial value of the internal resistance R due to the deterioration, but the first voltage fluctuation in the above-described equation (1). The value and the second voltage fluctuation value are calculated on the assumption that the internal resistance R does not always change, and the change in the internal resistance of the assembled battery 10 due to deterioration is not taken into consideration. The characteristic data corresponding to each of the first voltage fluctuation value and the second voltage fluctuation value includes the internal resistance of the assembled battery 10 as a calculation factor. However, since the internal resistance R is an initial value fixed, the battery is actually deteriorated. In other words, the first voltage fluctuation value and the second voltage fluctuation value in the assembled battery 10 in a state where the internal resistance has changed along with the initial value of the internal resistance R are calculated from the IR characteristic data and the Vdyn characteristic data. It will be different from each voltage fluctuation value.

  Therefore, as shown in FIG. 6, the OCV (V1) calculated based on the internal resistance R without considering the secular change is calculated differently from the OCV (V2) at the time of deterioration, and the SOC calculation accuracy is improved. It will decline.

  Therefore, in this embodiment, IR characteristic data and Vdyn characteristic data that do not take into consideration that the internal resistance R of the assembled battery 10 (single battery 11) changes due to aging, that is, a fixed value without taking into account aging. In calculating the OCV of the assembled battery 10 based on the formula (1) using the IR characteristic data and the Vdyn characteristic data created with the internal resistance R as a reference, the calculated internal resistance value of the assembled battery 10 during charging and discharging and the internal By correcting the first voltage fluctuation value and the second voltage fluctuation value according to the deviation from the resistance R (internal resistance change rate), the OCV considering the secular change of the internal resistance of the battery pack 10 to be charged and discharged is obtained. calculate.

Here, the internal resistance R of the assembled battery 10 will be described in detail. A predetermined initial value fixed as described above is used as the internal resistance R, and IR characteristic data and Vdyn characteristic data are created. In this embodiment, the internal resistance R is, for example, the assembled battery 10 (single battery Not the internal resistance R 0 in the initial state that has not deteriorated immediately after the production of the battery 11) (corresponding to the first internal resistance), but the lowest point of the internal resistance of the assembled battery 10 at the stage of starting use (second) Equivalent to internal resistance).

  FIG. 7 is a diagram showing an example of the resistance change rate of the single battery 11. Deterioration is deterioration (so-called wear deterioration) that accompanies the wear of the material constituting the unit cell 11 over time. If the constituent material of the unit cell 11 is worn, the resistance of the unit cell 11 will increase.

A resistance change rate can be used as a parameter for evaluating the deterioration state of the unit cell 11. Resistance change rate Rr can be expressed by the ratio of the resistance of the cell 11 in the initial state Rini (corresponding to R 0), and the resistance value Rc of the single cell 11 after degradation (Rc / Rini).

  In FIG. 7, the vertical axis represents the resistance change rate Rr, and the horizontal axis represents the square root of the elapsed time t. t indicates the elapsed time (days), and can be, for example, the time immediately after the unit cell 11 is manufactured. It is known that the resistance change rate of the single battery 11 is proportional to the square root of the elapsed time t. However, the rate of change in resistance of the unit cell 11 not only increases as the square root of the elapsed time t increases, but the rate of change in resistance of the unit cell 11 may decrease when the unit cell 11 starts to be used. .

  The resistance value Rc of the unit cell 11 after deterioration is a value composed of a decreasing component and an increasing component that decrease the resistance change rate of the unit cell 11 over time. By adding the increase amount of the change rate, the resistance change rate of the single cell 11 can be calculated. When the time t is 0, that is, when the unit cell 11 is in the initial state, the resistance change rate Rr of the unit cell 11 is 1.

  As shown in FIG. 7, the increasing component of the resistance change rate of the unit cell 11 increases as the square root of the elapsed time t increases. On the other hand, at the stage where the unit cell 11 is started to be used, the decreasing component of the resistance change rate decreases as the square root of the elapsed time t increases.

Thus, the resistance change rate of the assembled battery 10 is lower than the internal resistance in the initial state which is not deteriorated immediately after the assembled battery 10 is manufactured at the stage where the unit cell 11 is used. If the internal resistance in the initial state higher than the lowest point of the internal resistance of the battery pack 10 is used, the SOC estimation accuracy decreases. Therefore, the internal resistance R of the assembled battery 10 of the present embodiment uses the internal resistance of the assembled battery 10 which is the lowest point at the stage where the assembled battery 10 lower than the internal resistance R 0 in the initial state is used, and IR Characteristic data and Vdyn characteristic data are created.

FIG. 8 is a diagram illustrating an example of a correction gain map corresponding to the internal resistance of the assembled battery 10 of the present embodiment. In FIG. 8, the vertical axis represents the correction gain, and the horizontal axis represents the internal resistance RL of the assembled battery 10. The internal resistance RL is an internal resistance value calculated based on a charge / discharge current value and a voltage value (closed circuit voltage) detected by each sensor.

FIG. 11 is a diagram illustrating an example of an IV plot of the assembled battery 10, and the internal resistance RL can be calculated based on the IV plot of the assembled battery 10. First, a plurality of current values and voltage values flowing through the assembled battery 10 are acquired. As shown in FIG. 11, the relationship between the acquired current value and voltage value is plotted in a coordinate system (IV coordinate diameter) in which the horizontal axis is the current value and the vertical axis is the voltage value. An approximate line L is calculated based on the plotted points, and the slope of the approximate line L is calculated as the internal resistance RL of the battery pack 10.

The controller 50 performs IV plot processing as in the example of FIG. 11 in real time using the current value and voltage value acquired at predetermined time intervals during the charge / discharge control, and the acquired current value and voltage value are Each time the plot is made, the approximate straight line L is drawn again to calculate the internal resistance RL of the battery pack 10. The internal resistance RL of the present embodiment is a learning value calculated while learning a past IV plot (internal resistance value) in real time from the calculation timing.

FIG. 9 is a diagram illustrating an example of the correction gain Ca (corresponding to the first correction value) corresponding to the relationship between the battery temperature of the assembled battery 10 and the internal resistance RL . The correction gain Ca is a correction value corresponding to the first voltage fluctuation value.

The correction gain Ca of the present embodiment is the same as the voltage fluctuation value corresponding to the voltage drop calculated by the internal resistance RL at a certain time point and the charge / discharge current value detected by the current sensor 21, for example. The rate of change between the charge / discharge current value and the voltage fluctuation value corresponding to the voltage drop calculated by the internal resistance R0 (voltage fluctuation rate) can be obtained, and this rate of change can be used as the correction gain Ca. As shown in the example of FIG. 9, the correction gain Ca corresponding to each internal resistance RL is calculated.

The rate of change of voltage fluctuation due to the voltage drop between the internal resistance R L and the internal resistance R 0 is based on the IR term of the equation (1), and the rate of change in resistance between the internal resistance R L and the internal resistance R 0 is Therefore, the correction gain Ca shown in FIG. 9 can be represented by the resistance change rate of the internal resistance RL with respect to the internal resistance R 0 as shown by the solid line in FIG. 8 (first correction gain map). Thus, the correction gain Ca can be calculated based on the rate of change in resistance between the internal resistance R L and the internal resistance R 0, and takes a value of 1 or more.

Subsequently, FIG. 10 shows an example of the correction gain Cb corresponding to the voltage fluctuation (second voltage fluctuation value) due to the polarization of the battery pack 10 according to the relationship between the battery temperature of the battery pack 10 and the internal resistance RL. FIG. As described above, the increase in internal resistance due to deterioration of the battery pack 10, so can be regarded as increasing the amount of IR terms + Vdyn term in equation (1), Vdyn for OCV in the internal resistance R L in the formula (1) The ratio of (1) and the ratio of Vdyn (2) to OCV at the internal resistance R 0 are respectively calculated, the change rate of Vdyn (1) with respect to Vdyn (2) is obtained, and this change rate is calculated as the correction gain Cb. can do.

As with the correction gain Ca, the correction gain Cb shown in FIG. 10 can be expressed by the resistance change rate of the internal resistance RL with respect to the internal resistance R 0 as shown by the solid line in FIG. map). Thus, the correction gain Cb can be calculated based on the resistance change rate between the internal resistance R L and the internal resistance R 0, and the correction gain Cb becomes a value of 1 or more. The gain map shown in FIG. 8 is created individually for each of the correction gains Ca and Cb and stored in the memory 54.

Therefore, as shown in the following formula (3), correction gains Ca and Cb are respectively set in the IR term and the Vdyn term of the formula (1) for calculating the OCV on the basis of the internal resistance R of the assembled battery 10 without considering deterioration. By multiplying, it is possible to calculate the OCV in consideration of the change in the internal resistance of the assembled battery 10 due to deterioration.
(Formula 3) OCV = CCV-Ca * IR-Cb * Vdyn

Here, the correction gains Ca and Cb of this example are not the internal resistance R of the IR characteristic data and the Vdyn characteristic data used in the above-described equation (1), but immediately after the assembled battery 10 (single cell 11) is manufactured. The correction gains Ca and Cb are calculated based on the resistance change rate of the internal resistance RL with the internal resistance R 0 in the initial state that has not deteriorated as a reference value.

In this embodiment, the IR characteristic data and the Vdyn characteristic data used in the expression (3) are the lowest internal resistance R (the lowest internal resistance over time) at the stage of starting use, which is lower than the internal resistance R 0 in the initial state. R) is the initial value. However, as indicated by the two-dot chain line in FIG. 8, when the internal resistance R at the lowest value with time is used as the initial value for obtaining the correction gains Ca and Cb, for example, the time point of the internal resistance R 0 in the initial state that has not deteriorated. Thus, one or more correction gains Ca and Cb are applied, and OCV (SOC) is calculated high.

That is, since the internal resistance R at the lowest value over time is lower than the internal resistance R 0 in the initial state, when the correction gain is applied from the internal resistance R at the lowest value with time whose resistance change rate is less than 1, the initial state is not deteriorated. At this point, the gain is increased by an amount corresponding to the difference between the internal resistance R at the lowest value with time and the internal resistance R0 at the initial state, and the difference between the internal resistance R at the lowest value with time and the internal resistance R0 in the initial state is added. The gain map has a slope as shown by the two-dot chain line in FIG.

For this reason, when the correction gain is calculated from the resistance change rate of the internal resistance RL with respect to the internal resistance R having the lowest value over time, the difference between the internal resistance R having the lowest value with time and the internal resistance R 0 in the initial state is increased. The correction gain is applied, an OCV higher than the actual OCV is calculated, and an incorrect (reversed) SOC is calculated.

Therefore, in this embodiment, by calculating each correction gain Ca, Cb based on the resistance change rate of the internal resistance R L for the internal resistance R 0 of the internal resistance R 0 as the reference value of the initial state, the solid line in FIG. 8 A correction gain value that does not add the difference between the internal resistance R at the lowest value over time and the internal resistance R 0 in the initial state as shown in FIG. Ca and Cb are prevented from becoming larger than necessary. Specifically, the first voltage fluctuation value and the second voltage fluctuation value are corrected by the correction gain from the initial state in which the resistance change rate is greater than 1, for example, in the initial state. When the resistance change rate of the internal resistance R L with respect to the internal resistance R 0 is less than 1, the correction gain is defined to be always 1, and it is possible to suppress the calculation of an OCV higher than the actual OCV by the correction gain. SOC estimation is often performed.

As shown in FIG. 8, the initial upper limit value of manufacturing variation can be used as the internal resistance R0 in the initial state when calculating the correction gains Ca and Cb. The internal resistance R 0 of the assembled battery 10 (unit cell 11) at the time of manufacture includes an error due to manufacturing variation, and the assembled battery 10 is manufactured so as to have an internal resistance within this variation error. In the present embodiment, as the internal resistance R 0 in the initial state applied to the correction gain, the upper limit value is used among the lower limit value (R 0 _MIN) and the upper limit value (R 0 _MAX) of the variation error during manufacturing. As shown by the solid line in FIG. 8, the correction gain Ca, Cb, the internal resistance R 0 _MAX associated relative inclination of the resistance change rate of the internal resistance R L for greater internal resistance than the internal resistance R 0 _MAX R L Is defined so that a value of 1 or more is applied, and the correction gains Ca and Cb are always set to 1 when the resistance change rate is less than 1.

Moreover, the internal resistance of the assembled battery 10 can set the upper limit in advance. For example, the internal resistance value assumed after 10 years of use as the use limit can be determined as the upper limit value of the internal resistance of the battery pack 10, and in this case, the resistance change rate is also the upper limit value of the internal resistance with respect to the internal resistance R0 . The rate of change is the upper limit. Therefore, as shown in FIG. 8, the upper limit values of the correction gains Ca and Cb are also limited by the upper limit value of the internal resistance, and when the upper limit value of the internal resistance is exceeded, the correction gains Ca and Cb are set to constant values. Can do.

The memory 54 stores a first correction gain map corresponding to the correction gain Ca and a second correction gain map corresponding to the correction gain Cb as shown in FIG. 8, and the controller 50 calculates the assembled battery to be calculated. The correction gain Ca (first correction value) and the correction gain Cb (second correction value) can be calculated from the ten internal resistances RL using the maps of the first correction gain map and the correction gain map. . Since the correction gains Ca and Cb depend on the battery temperature as shown in FIGS. 9 and 10, the first correction gain map and the first correction gain map are created and held for each battery temperature. It may be.

  FIG. 12 is a diagram showing a flowchart of charge / discharge control of the battery system of the present embodiment. Charge / discharge control of the assembled battery 10 is performed by the controller 50. When the ignition switch of the vehicle is switched from OFF to ON (S101), the battery system is activated, and the controller 50 starts charge / discharge control of the battery system ( S102).

  The controller 50 acquires the CCV, charging / discharging current, and battery temperature of the assembled battery 10 acquired by each of the voltage sensor 20, the current sensor 21, and the temperature sensor 22 at predetermined time intervals (S103). The acquired sensor detection value is stored in the memory 54.

The controller 50 calculates the internal resistance RL of the assembled battery 10 using the acquired CCV and charge / discharge current (S104). As shown in FIG. 9, the controller 50 plots the relationship between the acquired current value and voltage value at the IV coordinate diameter, calculates an approximate straight line L based on a plurality of points including past plots, and approximates the approximate straight line. The slope of L can be calculated as the internal resistance RL of the battery pack 10.

Next, the controller 50 uses the acquired battery temperature and charge / discharge current to calculate a first voltage fluctuation value corresponding to the IR term of Equation (1) from the IR characteristic data stored in the memory 54 ( S105), using the acquired battery temperature and the calculated internal resistance RL , a correction gain Ca is calculated from the first correction gain map stored in the memory 54 (S106).

Further, the controller 50 calculates the second voltage fluctuation value corresponding to the Vdyn term of the equation (1) from the Vdyn characteristic data stored in the memory 54 using the acquired battery temperature and charge / discharge current (S107). ), Using the acquired battery temperature and the calculated internal resistance RL , the correction gain Cb is calculated from the second correction gain map stored in the memory 54 (S108). Note that the steps S105 to S108 can be performed in parallel, and the order in which the values are calculated is arbitrary.

  In step S109, the controller 50 multiplies the first voltage fluctuation value by the correction gain Ca to correct the first voltage fluctuation value, and similarly multiplies the second voltage fluctuation value by the correction gain Cb to obtain the second voltage fluctuation value. Is corrected (see equation (3)).

  In step S110, the controller 50 uses the acquired CCV of the assembled battery 10 that is being charged and discharged and the corrected first voltage fluctuation value and second voltage fluctuation value, respectively, and based on the expression (3), the assembled battery 10 OCV is calculated.

  The controller 50 calculates the SOC of the assembled battery 10 from the calculated OCV and the OCV-SOC map stored in the memory 54 (S111). The calculated SOC is stored in the memory 54 as a charge / discharge history (S112).

  The controller 50 repeats steps S103 to S112 until the ignition switch of the vehicle is switched from ON to OFF, and if it is determined that the ignition switch of the vehicle is switched from ON to OFF (S113), the controller 50 The charge / discharge control of the system is terminated.

  As described above, in this embodiment, when the OCV is calculated in consideration of the first voltage fluctuation due to the internal resistance of the battery pack 10 and the second voltage fluctuation due to polarization according to the charging / discharging current from the CCV of the battery pack 10. Since the OCV of the battery pack 10 is calculated by correcting each value of the first voltage fluctuation and the second voltage fluctuation using the correction value corresponding to the aging change of the internal resistance of the battery 10, the internal that changes with the aging change The OCV of the battery pack 10 can be accurately calculated (estimated) according to the resistance, and the SOC detection accuracy is improved.

In particular, the correction gains Ca and Cb of the present embodiment are not the internal resistance R of the assembled battery 10 which is the lowest point at the stage of use used for the IR characteristic data and the Vdyn characteristic data, but the assembled battery 10 (single cell). 11) is calculated based on the resistance change rate of the internal resistance R L with respect to the internal resistance R 0 in the initial state which is not deteriorated immediately after manufacturing. For this reason, it is possible to suppress the correction gains Ca and Cb so that the difference between the internal resistance R and the internal resistance R 0 does not become larger than necessary. Can be prevented from being calculated high. Therefore, the OCV can be calculated with high accuracy.

  Note that the OCV calculation process and the SOC calculation process of the present embodiment can also be applied to the external charging control using the external power supply 70. The external charging operation can be performed by the charging control unit 53. When the charging control unit 53 detects that the connection plug 71 extending from the external power source 70 is connected to the inlet 63, the charging control unit 53 switches the charging relays 61 and 62 from off to on to connect the charger 60 and the assembled battery 10 to each other. Connect and start external charging via the charger 60.

  The controller 50 performs steps S103 to S112 shown in FIG. 12 until the external charging is completed after the external charging is started, and the assembled battery 10 according to the internal resistance that changes with aging. The OCV can be calculated and the SOC detection during external charging can be performed with high accuracy.

In the present embodiment, IR characteristic data and Vdyn characteristic created using the internal resistance of the assembled battery 10 which is the lowest point at the stage where the assembled battery 10 lower than the internal resistance R 0 in the initial state is started. Although an example of calculating the OCV by applying data has been described, the present invention is not limited to this. For example, in the calculation of OCV using IR characteristic data and Vdyn characteristic data created with the internal resistance R 0 in the initial state as the initial value of the internal resistance of the assembled battery 10, the internal resistance R 0 of the assembled battery 10 depends on changes over time. The OCV of the battery pack 10 can also be calculated by correcting each value of the first voltage fluctuation and the second voltage fluctuation using the correction value.

10 assembled battery 11 cell 20 voltage sensor 21 current sensor 22 temperature sensor 41 step-up converter 42 inverter 43 motor generator 50 controller 51 SOC estimation unit 52 full charge capacity calculation unit 53 charge control unit 54 memory 60 charger 70 external power source

Claims (5)

  1. A power storage system mounted on a vehicle, equipped with a power storage device for charging and discharging,
    Based on the closed circuit voltage of the power storage device detected by the voltage sensor, the first voltage fluctuation value due to the internal resistance of the power storage device according to the charge / discharge current value detected by the current sensor, and the second voltage fluctuation value due to polarization. A controller that calculates an open circuit voltage of the power storage device and calculates the state of charge based on an OCV-SOC characteristic that predefines a correspondence relationship between the open circuit voltage and the state of charge of the power storage device;
    The controller calculates an internal resistance of the power storage device from the charge / discharge current value and the closed circuit voltage, and the first voltage according to a change in the calculated internal resistance with respect to a reference value of the internal resistance of the power storage device A first correction value corresponding to a fluctuation value and a second correction value corresponding to the second voltage fluctuation value are calculated, and the first voltage fluctuation value and the second voltage fluctuation value are corrected to calculate the open circuit voltage. A power storage system characterized by that.
  2. The controller predetermines a correspondence relationship of the first voltage fluctuation value by the second internal resistance according to the charge / discharge current value based on a second internal resistance lower than the first internal resistance of the power storage device in an initial state. Based on the specified first fluctuation characteristic, the first voltage fluctuation value is calculated,
    2. The power storage system according to claim 1, wherein the first correction value is calculated based on a resistance change rate of the calculated internal resistance with the first internal resistance as a reference value.
  3. The controller has a correspondence relationship between the second voltage fluctuation values based on a second internal resistance lower than the first internal resistance of the power storage device in an initial state according to the charge / discharge current value and a past charge / discharge history. And calculating the second voltage fluctuation value based on a second fluctuation characteristic preliminarily defined as
    The power storage system according to claim 1, wherein the second correction value is calculated based on a resistance change rate of the calculated internal resistance with the first internal resistance as a reference value.
  4.   4. The power storage system according to claim 2, wherein the first internal resistance is an upper limit value in a variation error of the internal resistance when the power storage device is manufactured.
  5. A charge / discharge state estimation method for a power storage device that performs charge / discharge,
    A closed circuit voltage of the power storage device detected by the voltage sensor, a first voltage fluctuation value by the internal resistance of the power storage device and a second voltage fluctuation value by polarization according to the charge / discharge current value detected by the current sensor are calculated. Steps,
    Calculating an internal resistance of the power storage device from the charge / discharge current value and the closed circuit voltage;
    A first correction value corresponding to the first voltage fluctuation value and a second correction value corresponding to the second voltage fluctuation value based on the calculated change rate of the internal resistance with respect to a reference value of the internal resistance of the power storage device. Calculating steps,
    The first voltage fluctuation value and the second voltage fluctuation value calculated using the first correction value and the second correction value are corrected, and the closed circuit voltage, the corrected first voltage fluctuation value, and the second voltage fluctuation value are corrected. Calculating an open circuit voltage of the power storage device based on
    Calculating the state of charge based on an OCV-SOC characteristic that predefines the correspondence between the open circuit voltage and the state of charge of the power storage device;
    The charging / discharging state estimation method characterized by including.
JP2012083000A 2012-03-30 2012-03-30 Power storage system and charging state estimation method Pending JP2013213684A (en)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2015210991A (en) * 2014-04-28 2015-11-24 古河電気工業株式会社 Device and method for identifying secondary battery
KR20160147963A (en) * 2014-05-29 2016-12-23 애플 인크. Adaptive battery life extension
CN108180937A (en) * 2017-12-19 2018-06-19 四川大唐国际甘孜水电开发有限公司 Sensor safely changes method in a kind of power plant control system observation circuit

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2015210991A (en) * 2014-04-28 2015-11-24 古河電気工業株式会社 Device and method for identifying secondary battery
KR20160147963A (en) * 2014-05-29 2016-12-23 애플 인크. Adaptive battery life extension
KR101940389B1 (en) 2014-05-29 2019-01-18 애플 인크. Adaptive battery life extension
CN108180937A (en) * 2017-12-19 2018-06-19 四川大唐国际甘孜水电开发有限公司 Sensor safely changes method in a kind of power plant control system observation circuit

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