vehicle battery system and method of estimating aging deterioration for the battery

专利摘要:
The present invention relates to a battery system (10) including: a battery (12); a voltage detector (22) that detects a battery voltage (12) as a detected voltage value (vb); a current detector (20) which detects a current flowing through the battery (12) as a detected current value (ib); and an electronic control unit (14). the electronic control unit (14) is configured to estimate an aging deterioration of the battery (12) based on an open circuit voltage value (vo; vo1, vo2) which is calculated from the detected voltage value and a integrated current value (¿ah; ¿ah12) calculated from the detected current value, and estimate the aging deterioration of the battery (12) based on the open circuit voltage value (vo; vo1, vo2) and the value integrated current ratings (¿ah; ¿ah12) that are calculated when a battery charge level (12) is in the non-hysteresis region.
公开号:BR102018007917A2
申请号:R102018007917-4
申请日:2018-04-19
公开日:2018-11-21
发明作者:Kenji Takahashi；Kazushi AKAMATSU；Kiyohito Machida
申请人:Toyota Jidosha Kabushiki Kaisha；
IPC主号:

专利说明:

(54) Title: BATTERY SYSTEM IN VEHICLE AND METHOD OF ESTIMATING DETERIORATION IN AGING FOR THE BATTERY (51) Int. Cl .: G01R 31/36; H01M 10/48.
(30) Unionist Priority: 04/27/2017 JP 2017-088148.
(71) Depositor (s): TOYOTA JIDOSHA KABUSHIKI KAISHA.
(72) Inventor (s): KENJI TAKAHASHI; KAZUSHI AKAMATSU; KIYOHITO MACHIDA.
(57) Summary: The present invention relates to a battery system (10) which includes: a battery (12); a voltage detector (22) that detects battery voltage (12) as a detected voltage value (Vb); a current detector (20) that detects a current flowing through the battery (12) as a detected current value (Ib); and an electronic control unit (14). The electronic control unit (14) is configured to estimate a deterioration in battery aging (12) based on an open circuit voltage value (Vo; Vol, Vo2) that is calculated from the detected voltage value and a integrated current value (<j, Ah; cAhl2) calculated from the detected current value, and estimate the aging deterioration of the battery (12) based on the value of the open circuit voltage (Vo; Vol, Vo2) and the integrated current value (<j, Ah; óAhl2) which are calculated when a battery charge level (12) is in the non-hysteresis region.
1/60
Descriptive Report of the Patent of Invention for BATTERY SYSTEM IN VEHICLE AND METHOD OF ESTIMATION OF DETERIORATION IN AGING FOR THE BATTERY.
BACKGROUND OF THE INVENTION
1. Field of the Invention [001] The present specification discloses a battery system that is equipped in a vehicle, which includes a battery capable of being charged and discharged, and which has a function to estimate deterioration in aging of the battery, and a aging deterioration estimation method for a battery.
2. Description of the related technique [002] An electrically powered vehicle that is equipped with a rotating electrical machine as a driving source is widely known. This electrically driven vehicle is equipped with a battery system that includes a secondary battery that can be charged and discharged. The secondary battery supplies electrical power to the rotating electrical machine when the rotating electrical machine is driven like an electric motor and stores electrical energy generated when the rotating electrical machine is driven like an electrical generator. The battery system controls the charge and discharge of the secondary battery so that the charge level of the secondary battery, that is, the so-called charge state (SOC) does not exceed a prescribed upper limit (which is sufficiently less than 100%) and it does not fall below a prescribed lower limit (which is sufficiently above 0%). In order to carry out such a control, in the battery system, it is desirable to estimate the charge level of the secondary battery exactly.
[003] Generally, the charge level of the secondary battery is calculated by referring to a SOC-OCV curve previously stored, the total charge capacity of the secondary battery, or something similar. OCV is an abbreviation for Circuit Voltage
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2/60
Open and means open circuit voltage. The SOC-OCV curve is a curve that indicates the open circuit voltage (OCV) value of the secondary battery in relation to the charge level. For example, when the secondary battery open circuit voltage value can be acquired, the battery system estimates the current charge level by checking the open circuit voltage value against the SOCOCV curve. As another type, the battery system calculates the integrated current value that is input and output from the secondary battery, and estimates the amount of change in the charge level and the current charge level based on the comparison between the value of integrated current and full load capacity.
[004] Since the charge level of the secondary battery is estimated by reference to the SOC-OCV curve or the total charge capacity in this way, it is desirable that the stored SOC-OCV curve or the total charge capacity indicate exactly the status of the secondary battery at the current time, to accurately estimate the charge level. However, the full charge capacity of the secondary battery and the characteristic of changing the open circuit voltage in relation to the charge level gradually change with the deterioration in aging of the secondary battery. Consequently, in order to accurately estimate the charge level, it is desirable to estimate the aging deterioration of the secondary battery and modify the SOC-OCV curve and the total charge capacity, depending on the result of the estimate, where appropriate. [005] To estimate the aging deterioration of the secondary battery, conventionally, several technologies have been proposed. For example, Japanese Patent Application Publication No. 2015121444 (JP 2015-121444 A) discloses a technology in which the total load capacity is estimated based on the open circuit voltage value and the integrated current value. Specifically, in JP 2015121444 A, the open circuit voltage value is detected twice
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3/60 in the middle of the secondary battery charge and the current value integrated between the detections is acquired. Then, in the disclosed technology, SOCs at the time of detection are evaluated as a first SOC and a second SOC, based on the open circuit voltage value, and a value resulting from dividing the integrated current value by a difference value between the first SOC, and the second SOC is calculated as the total load capacity.
[006] Japanese Patent No. 5537236 discloses a technology in which three deterioration parameters that indicate an open circuit voltage characteristic, which is a characteristic of changing the open circuit voltage in relation to the total charge capacity of the secondary battery, is evaluated in a search mode. Specifically, in Japanese Patent No. 5537236, a measured value of the open circuit voltage characteristic is acquired by measuring the open circuit voltage value of the secondary battery and the integrated current value, and three deterioration parameters corresponding to the measured open circuit voltage.
SUMMARY OF THE INVENTION [007] As described above, in most of the related art, the aging deterioration of the secondary battery is estimated from the relationship between the actually measured open circuit voltage value and the integrated current value. On the other hand, some secondary batteries have significant hysteresis in which there is a certain amount or more of difference in the open circuit voltage value in relation to the charge level between a time after a continuous charge and a time after a continuous discharge, in a partial charge level range. For example, in the case of a secondary lithium-ion battery that has an active negative electrode material that contains a silicon material (for example, Si or SiO) and graphite, it is known that there is a
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4/60 difference between the open circuit voltage value after a continuous charge and an open circuit voltage value after a continuous discharge, even in the same SOC, in a low SOC region. As described above, in estimating aging deterioration, the measured value of the open circuit voltage value is used, and when the open circuit voltage value is acquired over a load level range in which significant hysteresis appears, it is difficult to uniquely identify aging deterioration from the open circuit voltage value.
[008] Thus, the present specification discloses a battery system and an aging deterioration estimation method for a battery, which makes it possible to estimate aging deterioration easily and exactly, even in the case of the battery in which significant hysteresis appears in a partial charge level range. [009] As an exemplary aspect of the present invention is a battery system that is equipped in a vehicle. The battery system includes: a battery configured to be charged and discharged, the battery being equipped in the vehicle, a battery charge level range including a hysteresis region and a non-hysteresis region, the hysteresis region being a battery charge level where significant hysteresis occurs, significant hysteresis being hysteresis in which open circuit voltage values in relation to a battery charge level after continuing charging and after continuing discharging are different from each other by a predetermined value or more, the region of non-hysteresis being a battery charge level range where significant hysteresis does not occur; a voltage detector configured to detect a battery voltage as a detected voltage value, a current detector configured to detect a current flowing through the battery
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5/60 as a detected current value; and an electronic control unit configured to control battery charge and discharge. The electronic control unit is configured to estimate deterioration in battery aging based on an open circuit voltage value that is calculated from the detected voltage value and an integrated current value that is calculated from the current value detected. The electronic control unit is configured to estimate the aging deterioration of the battery based on the open circuit voltage value and the integrated current value, which are calculated when the battery charge level is in the non-hysteresis region.
[0010] In the battery system, the open circuit voltage value and the integrated current value that are used to estimate the aging deterioration of the battery are acquired when the charge level is in the non-hysteresis region. Therefore, it is possible to estimate deterioration in aging without any influence from significant hysteresis. As a result, it is possible to estimate aging deterioration with ease and accuracy.
[0011] The open circuit voltage value can include a first open circuit voltage value and a second open circuit voltage value that are acquired in the non-hysteresis region, the integrated current value can be a value resulting from integrating the current value detected until the open circuit voltage value changes to the second open circuit voltage value after the open circuit voltage value becomes the first open circuit voltage value, and the electronic control unit can be configured to estimate, as a characteristic that indicates aging deterioration, at least one of the battery's full charge capacity at a current time and a characteristic of changing the open circuit voltage value in relation to the charge level, with based on first value
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6/60 open circuit voltage, the second open circuit voltage value and the integrated current value.
[0012] The battery's total charge capacity and the characteristic of changing the open circuit voltage value in relation to the charge level are used to estimate the battery charge level. When estimating the values that are used to estimate the charge level, it is possible to accurately estimate the charge level of the battery.
[0013] The battery system can also include a charger configured to charge the battery while the vehicle is stopped. The electronic control unit can be configured to temporarily stop the battery charge with the charger when the battery charge level reaches a first charge level or a second charge level in the non-hysteresis region in the middle of the battery charge with the charger, and acquire the detected voltage value that is obtained during a load stop period, as one of the first open circuit voltage value and the second open circuit voltage value.
[0014] Adopting such a configuration, it is possible to safely acquire the open circuit voltage value and the integrated current value that are used to estimate the aging deterioration of the battery.
[0015] The electronic control unit can be configured to acquire two values of open circuit voltage that are acquired in moments when the battery charge level is in the non-hysteresis region and the values of open circuit voltage are acquirable, as the first open circuit voltage value and the second open circuit voltage value, during a vehicle energization.
[0016] Adopting such a configuration, it is possible to acquire the open circuit voltage value and the integrated current value that are used to estimate the aging deterioration of the battery, even during the energization of the vehicle.
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7/60 [0017] The electronic control unit can be configured to control the charge and discharge of the battery, such that the battery charge level transitions to the non-hysteresis region and acquires the first open circuit voltage value, the second open circuit voltage value and the integrated current value, when a time elapsed since the last aging deterioration estimate is equal to or greater than a prescribed reference time.
[0018] By adopting such a configuration, it is possible to safely acquire the open circuit voltage value and the integrated current value that are used to estimate the aging deterioration of the battery.
[0019] The electronic control unit can be configured to: estimate at least one characteristic of changing the open circuit voltage value with respect to the load level, as a characteristic that indicates deterioration in aging; estimate the load level range that is the non-hysteresis region based on the estimated change characteristic of the open circuit voltage value with respect to the load level; and update the non-hysteresis region based on the estimated charge level range.
[0020] Adopting such a configuration, it is possible to constantly obtain the non-hysteresis region corresponding to the state of the battery at the current moment.
[0021] The electronic control unit can be configured to update the load level at the time of acquiring the open circuit voltage value and the integrated current value that are used for an estimate of aging deterioration and a range of load level together with the update of the non-hysteresis region.
[0022] By adopting such a configuration, it is possible to acquire the open circuit voltage value and the integrated current value that are used
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8/60 to estimate battery aging deterioration at a more appropriate time, it is possible to further improve an estimation property for aging deterioration, and it is possible to obtain an opportunity to estimate aging deterioration more safely .
[0023] The battery may be a secondary lithium-ion battery that has an active negative electrode material that contains at least one material of silicon and graphite, and the charge level range of the non-hysteresis region may be greater at the level load than a load level range in the hysteresis region.
[0024] When using such a battery, it is possible to increase the capacity. [0025] The battery can be a secondary lithium ion battery that has an active negative electrode material that contains at least one material of silicon and lithium titanate, and the charge level range of the non-hysteresis region can be more higher in the load level than a load level range of a hysteresis region.
[0026] As an exemplary aspect of the present invention is a method of estimating aging deterioration for a battery system. A battery charge level includes a hysteresis region and a non-hysteresis region, the hysteresis region being a range of the battery charge state where significant hysteresis occurs, significant hysteresis being hysteresis in which open circuit voltage values in relation to a charge level of the battery charge after continuing charging and after continuing discharging are different from each other by a predetermined value or more, the non-hysteresis region being a battery charge level where significant hysteresis is does not occur. The battery system includes an electronic control unit. The aging deterioration estimation method includes: acquiring, through the electronic control unit, parameters from which
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9/60 open circuit at two points and an integrated current value between the two points are calculated when the battery charge level is in the region of non-hysteresis; and estimate, by means of the electronic control unit, a deterioration in battery aging based on the acquired open circuit voltage values and the acquired integrated current value.
[0027] In the aging deterioration estimation method, the open circuit voltage value and the integrated current value that are used to estimate the aging deterioration of the battery are acquired when the charge level is in the non-hysteresis region . Therefore, it is possible to estimate deterioration in aging without any influence from significant hysteresis. As a result, it is possible to estimate aging deterioration with ease and accuracy.
[0028] In the battery system and the aging deterioration estimation method for the battery, which are disclosed in this specification, the open circuit voltage value and the integrated current value that are used to estimate aging deterioration of the battery are acquired when the charge level is in the non-hysteresis region. Therefore, it is possible to estimate deterioration in aging without any influence from significant hysteresis. As a result, it is possible to estimate aging deterioration with ease and accuracy.
BRIEF DESCRIPTION OF THE DRAWINGS [0029] Characteristics, advantages and technical and industrial significance of the exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which equal numbers indicate similar elements and in which:
FIG. 1 is a diagram showing a configuration of an electrically driven vehicle equipped with a battery system;
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10/60 to FIG. 2 is a diagram showing an example of a SOC-OCV curve;
FIG. 3 is a flowchart showing an example of an aging deterioration estimation process for a battery;
FIG. 4A is a flow chart showing part of an example of a parameter acquisition routine;
FIG. 4B is a flowchart showing an example part of a parameter acquisition routine;
FIG. 5 is a diagram showing an exemplary operation of the parameter acquisition routine in FIGS. 4A and 4B;
FIG. 6 is a flow chart showing another example of the parameter acquisition routine;
FIG. 7 is a diagram showing an exemplary operation of the parameter acquisition routine in FIG. 6;
FIG. 8A is a flow chart showing part of another example of the parameter acquisition routine;
FIG. 8B is a flow chart showing part of another example of the parameter acquisition routine;
FIG. 9 is a diagram showing an exemplary operation of the parameter acquisition routine in FIGS. 8A and 8B;
FIG. 10 is a flow chart showing an example of a deterioration estimation routine;
FIG. 11 is a flow chart showing another example of the deterioration estimation routine;
FIG. 12 is a diagram showing a characteristic of changing an open circuit voltage in relation to a change in the local charge level in a secondary lithium ion battery;
FIG. 13 is a diagram showing a change in poPetition 870180031862, from 04/19/2018, p. 122/219
11/60 open circuit potential of a positive electrode associated with a decrease in the capacity of the positive electrode and a change in the open circuit potential of a negative electrode associated with a decrease in the capacity of the negative electrode in the secondary lithium ion battery;
FIG. 14 is a diagram to describe a gap in the composition correspondence between the positive and negative electrodes of the secondary lithium-ion battery;
FIG. 15 is a diagram to describe a gap in the composition correspondence due to the deterioration of the secondary lithium ion battery;
FIG. 16 is a diagram showing a change (open circuit voltage curve) in open circuit voltage in relation to the battery capacity of the secondary lithium ion battery;
FIG. 17 is an explanatory diagram for an AV voltage error;
FIG. 18 is a diagram to describe a change in the point of appearance of hysteresis associated with the deterioration of the secondary lithium ion battery; and FIG. 19 is a flow chart showing an example of a non-hysteresis region estimation routine.
DETAILED DESCRIPTION OF THE MODALITIES [0030] From now on, the configuration of a battery system will be described with reference to the drawings.
[0031] FIG. 1 is a diagram showing a schematic configuration of an electrically driven vehicle 100 equipped with the battery system 10. The electrically driven vehicle 100 is a hybrid vehicle that includes two rotating electric machines MG1, MG2 and an engine 104 as sources of dynamic energy . The battery system 10, disclosed in the present specification, can be equipped in another type of electrically driven vehicle. For example, the
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12/60 battery 10 can be equipped in an electric vehicle that includes only a rotating electric machine as a source of dynamic energy.
[0032] Motor 104 is connected to a dynamic energy dividing mechanism 106 that includes planetary gear and the like. The planetary gear splits and transmits dynamic energy from motor 104 to a driving wheel 108 and the first rotating electric machine MG1. Each of the two rotating electric machines MG1, MG2 works as an electric motor and, in addition, it works as an electric generator. An output shaft of the second rotating electric machine MG2 is hinged to the driving wheel 108. The second rotating electric machine MG2 functions primarily as an electric motor, and provides driving torque to the driving wheel 108 when the vehicle travels. When the vehicle brakes, the second rotating electric machine MG2 works as an electric generator that generates electricity using braking energy. The first rotating electric machine MG1, which is hinged to the dynamic energy splitting mechanism 106, receives excess dynamic energy from the engine 104 and generates electricity. The first rotating electric machine MG1 also functions as a starting motor that starts engine 104. Since the electrically driven vehicle 100 disclosed in the present specification includes motor 104 in this way, the electrically driven vehicle 100 can charge a battery 12 that uses excess dynamic energy from engine 104, even while the vehicle is traveling. In addition, a fuel cell or the like can be fitted instead of the engine.
[0033] An inverter 102 converts direct current energy to alternating current energy and converts alternating current energy to direct current energy. Specifically, inverter 102 converts direct current energy supplied from battery 12, described later, into alternating current energy and outputs alternating current energy for the first and second electrical machines
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13/60 rotary MG1, MG2 that are driven as electric motors. In addition, inverter 102 converts alternating current energy generated by the first and second rotating electrical machines MG1, MG2 that are driven as electric generators, into direct current energy and supplies direct current energy to the battery 12. Between inverter 102 and battery 12, a transformer for increasing or decreasing electrical power can be provided. Drives of inverter 102, rotary electrical machine MG1, MG2, motor 104 and the like are controlled by a control device 14.
[0034] Battery system 10 includes battery 12 that can be charged and discharged. Battery 12 is a secondary battery that provides electrical energy to drive the rotating electrical machines MG1, MG2 and which stores electrical energy generated by the rotating electrical machines MG1, MG2. Battery 12 includes a plurality of electrical cells connected in series or in parallel. Like battery type 12, several types are possible. In the modality, a secondary lithium ion battery is used, in which a complex containing a material of silicon and graphite is used as active material of negative electrode. In the event that a complex containing a silicon and graphite material is used as the active negative electrode material, the battery 12 has partly significant hysteresis in a characteristic of changing an open circuit voltage value Vo relative to a level load Cb. This will be described later. The charge level Cb is a value (%) of multiplying the ratio of a charge capacity at the current time to a total FCC charge capacity of the battery of 12 by 100%, and is a value that is generally called the charge state. (SOC).
[0035] The battery system 10 is equipped with a current sensor
20, a voltage sensor 22, a temperature sensor 24 and similarityPetition 870180031862, of 19/04/2018, p. 125/219
14/60 tes, to identify the status of the battery 12. The current sensor (current detector) 20 detects a current value that is input to or output from the battery 12. The detected current value is input to the control device 14 , as a detected current value Ib. The voltage sensor (voltage detector) 22 detects a voltage value between the battery terminals 12. The detected voltage value is entered for the control device (electronic control unit) 14 , as a detected voltage value Vb. Typically, battery 12 is an assembled battery that has a plurality of cells connected in series or in parallel. Therefore, voltage sensor 22 can be provided for each cell, or it can be provided for each block made up of a plurality of cells. Only one voltage sensor 22 can be supplied for the assembled battery pack. The temperature sensor 24 detects the temperature of the battery 12. The detected temperature is entered into the control device 14 as a battery temperature Tb. A temperature sensor 24 can be provided, or a plurality of temperature sensors 24 can be provided. In the case where a plurality of voltage sensors 22 or temperature 24 is provided, a statistical value of detected values from the plurality of temperature sensors voltage 22 or temperature sensors 24, for example, average value, maximum value, minimum value or the like, can be treated as the detected voltage value Vb or the battery temperature Tb.
[0036] The battery system 10 also includes a charger 16 and a connector 18 for external battery charge 12. The external charge is a battery charge 12 with electrical energy from an external power source (for example, a source commercial power supply) supplied outside the electrically driven vehicle 100. Connector 18 can be connected to a connector (a so-called charging plug) on the external power source. Charger 16 converts external electrical energy
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15/60 (alternating current energy) supplied through connector 18, in direct current energy, and supplies direct current energy to battery 12. Battery system 10 may include a charging mechanism other than the charging mechanism external, provided that battery 12 can be charged while vehicle 100 is stationary. For example, battery system 10 may include a solar panel and the like, which generate electricity using sunlight, instead of or in addition to charger 16 and the like for external charging. For some situations, battery system 10 does not need to include the charging mechanism to charge battery 12 while vehicle 100 is stopped.
[0037] Control device 14 controls drives from drive sources such as the rotating electric machines MG1, MG2, motor 104 and the like, and controls battery charging and discharging 12. Control device 14 includes a sensor interface 26 , a memory 28, a CPU 30 and the like. The sensor interface 26 is connected with the respective sensors 20, 22, 24. The sensor interface 26 outputs control signals to the respective sensors 20, 22, 24 and converts input data from the respective sensors 20, 22, 24 to a signal format that allows processing by CPU 30. Memory 28 stores various control parameters and programs. CPU 30 performs various information and computation processes. The sensor interface 26, the CPU 30 and the memory 28 are connected to each other via a data bus 44. In FIG. 1, the control device 14 is illustrated as a block, but the control device 14 can consist of a plurality of devices (a plurality of CPUs 30, a plurality of memories 28 and the like). Some functions of the control device 14 can be performed by an external device that is provided outside the vehicle and that can communicate wirelessly with the control device.
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16/60 control provided in the vehicle.
[0038] The control device 14 controls the charging and discharging of the battery 12 in such a way that a charge level Cb of the battery 12 does not exceed a prescribed upper and lower limit. For this control, the control device 14 estimates and periodically monitors the charge level Cb of the battery 12. The control device 14 estimates the charge level Cb of an open circuit voltage value Vo of the battery 12 or of a integrated current value AAh. The integrated current value AAh is an integrated current value that is input to or is output from battery 12, and is typically evaluated by AAh = Z (lbxAt) / 3600 when a sampling period for the detected current value Ib is At. Here, when the battery is used so that the load is greater, AAh is a value that increases the capacity of the battery (increases the SOC). When the battery is used so that the discharge is greater, AAh is a value that decreases the capacity of the battery (decreases the SOC).
[0039] The charge level estimate Cb will be specifically described. In memory 28, the total FCC load capacity of battery 12 and a SOC-OCV curve are stored. The SOC-OCV curve is a curve that indicates a change in the open circuit voltage value Vo in relation to the battery charge level Cb 12. FIG. 2 shows an example of the SOC-OCV curve. The control device 14 estimates the charge level Cb by checking the open circuit voltage value Vo of the battery 12 against the SOC-OCV curve. The open circuit voltage value Vo is a voltage between the terminals of battery 12 in a state where battery 12 is not polarized (in a relaxed state). The open circuit voltage value Vo that is used for various computations can be a measured value or it can be an estimated value. Therefore, when the charging and discharging of the battery 12 is interrupted for a certain period of time and the polarization is eliminated, the detected voltage value Vb detected by the voltage sensor 22 can be treated
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17/60 as the open circuit voltage value Vo. In addition, even during polarization, if the current flowing through the battery 12 is very low and a polarization component can be estimated accurately, a value resulting from correcting the detected voltage value Vb detected by the voltage sensor 22 under consideration the influence of polarization can be treated as the open circuit voltage value Vo.
[0040] As another method, the control device 14 estimates the charge level Cb at the current time by calculating a quantity of change ACb of the charge level Cb from the integrated current value AAh and adding the quantity of change ACb to the level of load Cb at the last moment. The amount of change ACb of the load level Cb is the relationship between the integrated current value AAh and the total load capacity FCC and is obtained by computing ACb = (AAh / FCC) x100.
[0041] As is obvious from the description above, in the estimation of the load level Cb, the control device 14 refers to the SOCOCV curve or the total load capacity FCC. Consequently, in order to accurately estimate the charge level Cb at the current time, the SOCOCV curve or FCC total charge capacity stored in memory 28 needs to accurately reflect the state of battery 12 at the current time. The SOC-OCV curve or the FCC total charge capacity gradually changes with the aging deterioration of the battery 12. Therefore, in order to accurately estimate the current charge level Cb it is desirable to estimate the aging deterioration of the battery 12 as needed, and modify and update the SOC-OCV curve or the FCC full load capacity stored in memory 28 as needed. Therefore, the control device 14 estimates the aging deterioration of the battery 12 as needed. In the following, an aging deterioration estimate for battery 12 will be described
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18/60 in detail.
[0042] Normally, the aging deterioration of the battery 12 is estimated based on the open circuit voltage values Vo at a plurality of points away from each other and the integrated current value AAh between the plurality of points. As described above, for battery 12 in the modality, the SOC-OCV curve partially has significant hysteresis. This will be described with reference to FIG. 2. FIG. 2 is a diagram showing an example of the SOC-OCV curve of battery 12. In FIG. 2, the abscissa axis indicates the load level Cb (SOC) and the ordinate axis indicates the open circuit voltage value Vo. In addition, in FIG. 2, the solid line is a SOC-OCV curve that is obtained in the process in which the battery 12 is charged after the battery 12 is completely discharged. In other words, the solid line is a SOC-OCV curve after a continuous charge. Thereafter, this curve is referred to as an OCV or OCVch load. The alternating long and short dash line is a SOC-OCV curve that is obtained in the process in which the battery 12 is discharged after the full charge of the battery 12. In other words, the alternating long and short dash line is a SOC curve. -OCV after continuous discharge. Thereafter, this curve is referred to as an OCV or OCVdis discharge.
[0043] As is obvious from FIG. 2, in a high SOC region where the Cb load level is relatively high, there is little difference between OCV ch and OCV dis and there is no significant hysteresis in the region. On the other hand, in a region of low SOC in which the load level Cb is relatively low, there is a certain amount or more of difference between OCV dis and OCV ch, and there is significant hysteresis. Thereafter, the region in which significant hysteresis does not appear is referred to as a non-hysteresis region. In addition, the region in which significant hysteresis appears is referred to as a hysteresis region. In addition, the level of charge at the border between the non-hysteresis region and the
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19/60 hysteresis region is referred to as a Cb_b load limit level. When Vch [n] is a voltage indicated by OCV ch in the case of the load level Cb = n, Vdis [n] is a voltage indicated by OCV dis in the case of the load level Cb = n and AVdef is a prescribed threshold, the region non-hysteresis is a satisfying region (| Vch [n] - Vdis [n] | <AVdef), and the hysteresis region is a satisfying region (| Vch [n] - Vdis [n] |> AVdef). [0044] In the non-hysteresis region, it can be imagined that a charge level Cb after continuous discharge, and a charge level Cb after continuous charge, are equivalent in the case of an identical open circuit voltage value Vo. In other words, it can be said that the open circuit voltage value Vo obtained in the non-hysteresis region indicates only the state of the battery 12. On the other hand, in the hysteresis region, a charge level Cb after continuous discharge and a load level Cb after continuous load are different, even in the case of an identical open circuit voltage value Vo. For example, in the case of the open circuit voltage value Vo = Va, the charge level Cb after continuous discharge is Co, and the charge level Cb after continuous charge is Ci. In addition, in the case where the charge and the discharge are repeated alternately, the charge level Cb sometimes has a value between Co and Ci, even in the case of the open circuit voltage value Vo = Va. Consequently, the open circuit voltage value Vo obtained in the region of hysteresis cannot exclusively indicate the state of the battery 12.
[0045] In the case of using the open circuit voltage value Vo which cannot exclusively indicate the state of battery 12 in this way, it is difficult to estimate only the deterioration in aging of battery 12. Thus, to solve this problem, the system of battery 10 published in the specification estimates the deterioration using only the open circuit voltage value Vo and integrated current value AAh adPetition 870180031862, from 04/19/2018, p. 131/219
20/60 quiridos in the region of non-hysteresis, to estimate the deterioration in aging easily and accurately.
[0046] FIG. 3 is a flowchart showing the most basic flow of an aging deterioration estimation process for battery 12. Control device 14 estimates aging deterioration by performing the flowchart shown in FIG. 3 periodically or at specific times.
[0047] The aging deterioration estimation process is roughly divided into a parameter acquisition routine (S10) and a deterioration estimation routine (S20). In the parameter acquisition routine, the control device 14, in the non-hysteresis region, acquires a first open circuit voltage value Vo1, a second open circuit voltage value Vo2 and an integrated current value AAhi2 resulting from integrating the detected current value Ib until the open circuit voltage value Vo changes to the second open circuit voltage value Vo2 after the open circuit voltage value Vo becomes the first open circuit voltage value Vo1. The first open circuit voltage value Vo1 and the second open circuit voltage value Vo2 are not particularly limited, as long as the first open circuit voltage value Vo1 and the second open circuit voltage value Vo2 are voltage values of open circuit Vo acquired when the load level Cb is in the region of non-hysteresis (Cb_b <Cb <100). However, in view of the accuracy of the battery deterioration estimate 12, it is preferable that the first open circuit voltage value Vo1 and the second open circuit voltage value Vo2 deviate from each other to some degree. In any case, it can be said that the first and second open circuit voltage values Vo1, Vo2 and integrated current value AAhi2 acquired in the non-hysteresis region are parameters that uniquely indicate the state of the battery 12 at the current time.
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21/60 [0048] In the deterioration estimation routine (S20), the control device 14 estimates the aging deterioration of the battery 12, using the parameters acquired in the parameter acquisition routine (S10). Specifically, the control device 14 estimates at least one of the total FCC load capacity of the battery 12 at the present time and the SOC-OCV curve, using the acquired parameters. As an estimation method, several methods are possible. This will be described later in detail. In any estimation method, using the parameters acquired in the non-hysteresis region, it is possible to estimate exactly the state of the battery 12 at the current moment, without the influence of hysteresis.
[0049] Next, a specific example of the parameter acquisition routine will be described. FIGS. 4A and 4B are a flow chart showing an example of the parameter acquisition routine. In the example illustrated in FIGS. 4A and 4B, the first and second open circuit voltage values Vo1, Vo2 and the integrated current value AAhi2 are acquired in the timing of the external battery charge 12. In the example illustrated in FIGS. 4A and 4B, to acquire the parameters, a first load level Cb1 and a second load level Cb2 are previously stored in memory 28.
[0050] The first load level Cb1 and the second load level Cb2 are each values in the non-hysteresis region, and values that deviate sufficiently from each other (see FIG. 2). The first and second load levels Cb1, Cb2 can be fixed values, or they can be variable values. Here, the non-hysteresis region and the Cb_b boundary charge level change with the deterioration in battery aging 12. Consequently, in the case where the first and second charge levels Cb1, Cb2 are fixed values, the first and second levels load values Cb1, Cb2 are set to values that are maintained in the non-hysteresis region, even when the non-hysteresis region increases or decreases
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22/60 with battery aging deterioration 12. In the case where the first and second charge levels Cb1, Cb2 are variable values, the first and second charge levels Cb1, Cb2 can be varied together with the increase or decrease in the region of non-hysteresis associated with deterioration in battery aging 12.
[0051] In the example illustrated in FIGS. 4A and 4B as already described in the parameter acquisition routine, the control device 14 acquires the parameters in the external load timing and, therefore, monitors if there is an external load instruction (S110). When there is an external load instruction, the control device 14 initiates the external load (S112).
[0052] During the execution of the external load, the control device 14 checks whether the load level Cb has reached the first load level Cb1 stored in memory 28 (S114). Here, the load level Cb at the current moment is estimated from the open circuit value Vo or the integrated current value AAh. During the execution of the external load, the detected voltage value Vb includes the polarization component and, therefore, it is necessary to estimate the open circuit voltage value Vo by subtracting the polarization component from the detected voltage value Vb. However, the low SOC region (hysteresis region) has an influence on hysteresis. Consequently, it is difficult to identify the load level Cb exclusively from the open circuit voltage value Vo, without considering a history of past charges and discharges. Therefore, in the hysteresis region, it is preferable to estimate the load level Cb with a predetermined period, mainly from the integrated current value AAh, both during external load and during travel.
[0053] When the load level Cb reached the first load level
Cb1, the control device 14 interrupts the external load (S116).
During the stop period, the control device 14 checks whether the
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23/60 polarization has been eliminated, with a predetermined period (S118). When the verification result shows that the polarization has been eliminated, the control device 14 measures the detected voltage value Vb at the time point, as the first open circuit voltage value Vo1 (S120).
[0054] After acquiring the first open circuit voltage value Vo1, the control device 14 restarts the external load (S122). In addition, the control device 14 starts calculating the integrated current value AAhi2 (S124). The control device 14 carries out the external load until the load level Cb reaches the second load level Cb2 stored in memory 28 (until the determination of Yes is made in S126). When the load level Cb has reached the second load level Cb2, the control device 14 stops the load and waits until the polarization is eliminated (S128). When the polarization has been eliminated (Yes in S130), the control device 14 measures the detected voltage value Vb at the time point as the second open circuit voltage value Vo2 (S132). In addition, the control device 14 acquires the integrated current value AAhi2 from the measurement of the first open circuit voltage value Vo1 until the measurement of the second open circuit voltage value Vo2 (S124, S133).
[0055] After the acquisition of the second open circuit voltage value Vo2, the control device 14 restarts the external load (S134). Then, when the load level Cb has reached a predetermined target load level (for example, 90%), the control device 14 determines that the load has been completed (S136), and the external load ends (S138). With that, the parameter acquisition routine is finished. Here, when the target load level is in the non-hysteresis region, the target load level can be defined as the second load level Cb2. In this case, since the load is finished at step S133, step S134 and step S136 are unnecessary.
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24/60 [0056] FIG. 5 is a diagram showing an exemplary operation of the parameter acquisition routine. In FIG. 5, the abscissa axis indicates time, and the ordinate axis indicates the load level Cb. In FIG. 5, when the external charge is started at time t1, the charge level Cb gradually increases. Then, when the load level Cb reaches the first load level Cb1 at time t2, the control device 14 interrupts the external load. As a result, a period in which loading and unloading is not carried out continues. By continuing the charge-discharge stop period, battery 12 polarization is gradually eliminated. Then, when the polarization influence disappears at time t3, the control device 14 acquires the detected voltage value Vb at time t3, as the first open circuit voltage value Vo1.
[0057] After the acquisition of the first open circuit voltage value Vo1, the control device 14 restarts the external load. Due to the external load, the load level Cb gradually increases. Then, when the load level Cb reaches the second load level Cb2 at time t4, the control device 14 interrupts the external load again and waits. Then, when the polarization influence disappears at time t5, the control device 14 acquires the detected voltage value Vb at time t5, as the second open circuit voltage value Vo2. In addition, the control device 14 acquires the integrated value of the detected current value Ib from time t3 to time t5, as the integrated current value AAhi2. After the acquisition of the second open circuit voltage value Vo2, the control device 14 starts the external load again. Then, when the charge level Cb reaches the desired charge level at time t6, the control device 14 interrupts the external charge.
[0058] As is obvious from the description above, in the parameter acquisition routine, the open circuit voltage values Vo1, Vo2
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25/60 and the integrated current value AAhi ₂ are acquired in the region of non-hysteresis. In other words, it can be said that the acquired open circuit voltage values Vo1, Vo2 and integrated current value AAhi2 are values that are not influenced by hysteresis. By estimating aging deterioration based on such values, it is possible to estimate aging deterioration easily and accurately. Here, the parameter acquisition routine shown in FIGS. 4A and 4B are based on the external charge, but another type of charge can be adopted as long as battery 12 can be charged while the vehicle is stationary. For example, battery 12 can be charged with electrical energy generated by a solar panel.
[0059] Next, another example of the parameter acquisition routine will be described. FIG. 6 is a flow chart showing another example of the parameter acquisition routine. In the example illustrated in FIG. 6, when the vehicle is started after the external load is completed, the first and second open circuit voltage values Vo1, Vo2 and the integrated current value AAhi ₂ are acquired when the load level Cb decreases. That is, typically, in the electrically driven vehicle 100, as needed, the electrical energy generated by the rotating electrical machines MG1, MG2 is stored or electrical energy is supplied to the rotating electrical machines MG1, MG2 to drive the rotating electrical machines MG1, MG2. Therefore, the charge level Cb of battery 12 is maintained at an intermediate value Cb_c (for example, about 30%) which is relatively low and which is in the hysteresis region. Consequently, when the vehicle is started after the external charge is completed, the control device 14 decreases the charge level Cb of battery 12 to approximately the intermediate value Cb_c. In the example illustrated in FIG. 6, the necessary parameters for the estimation of deterioration in aging are acquired in the timing when the load level Cb decreases from the total load.
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26/60 [0060] In the example illustrated in FIG. 6, to acquire the parameters, an integrated current reference value AAhdef and an elapsed time reference tdef are previously stored. In the flow chart in FIG. 6, the first and second open circuit voltage values Vo1, Vo2 are acquired for the deterioration estimate. To ensure the accuracy of the deterioration estimate, it is preferable that the absolute value | AAhi2 | of the integrated current value between the acquisition of the first open circuit voltage value Vo1 and the acquisition of the second open circuit voltage value Vo2 is a large value to some degree. The integrated current reference value AAhdef has a magnitude of the absolute value | AAhi2 | of the integrated current value necessary to maintain the accuracy of the deterioration estimate. When an elapsed time ti2 from the acquisition of the first open circuit voltage value Vo1 to the acquisition of the second open circuit voltage value Vo2 is excessively large, an integrated error component included in the integrated current value | AAhi2 | it may increase due to the influence of current sensor errors and may cause a decrease in the accuracy of the deterioration estimate. The elapsed reference time tdef is a time that allows the integrated error of the integrated current value AAhi2 to be suppressed to a certain value or less. The value of the integrated reference current AAdef and the elapsed time of reference tdef can be fixed values, or they can be variable values that vary depending on the degrees of deterioration of the battery 12 and the current sensor 20, the ambient temperature and the like.
[0061] The parameter acquisition routine in FIG. 6 starts when the external charge of battery 12 is completed. When the external load is completed, the control device 14 monitors whether the open circuit voltage value Vo is acquirable (S140). Here, the state where the open circuit voltage value Vo is acquirable includes a
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27/60 state in which the polarization of battery 12 has been eliminated and where the detected voltage value Vb itself can be treated as the open circuit voltage value Vo. Consequently, for example, it can be said that, upon completion of the external load, the open circuit voltage value Vo is obtainable immediately after the vehicle is energized, that is, immediately after a so-called ignition on. In addition, the state in which the open circuit voltage value Vo is achievable includes a state in which the bias component can be accurately estimated, although a very low current flows through the battery 12. In this case, the control device 14 acquires a value resulting from correcting the detected voltage value Vb in consideration of an influence of the estimated polarization component, such as the open circuit voltage value Vo at the time point. Consequently, for example, even when the vehicle is traveling, it can be said that the open circuit voltage value Vo is acquirable in a period when the vehicle temporarily stops at a traffic light, and in a period when the vehicle is traveling only with motor 104 (a period in which the rotating electric machines MG1, MG2 are not running).
[0062] In the case where the control device 14 determines that the open circuit voltage value Vo is acquirable, the control device 14 checks whether the load level Cb at the time point is in the non-hysteresis region (S142) . The load level Cb, in this case, can be estimated mainly based on the open circuit voltage value Vo, or it can be estimated mainly based on the integrated current value ΔΑ. In the case where the load level Cb is not in the non-hysteresis region, the control device 14 returns to step S140. On the other hand, in the case where the load level Cb is in the non-hysteresis region, the control device 14 acquires the voltage value
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28/60 open circuit Vo at the time point, as the first open circuit voltage value Vo1 (S144).
[0063] After acquiring the first open circuit voltage value Vo1, the control device 14 starts calculating the integrated current value AAhi2 and counting the elapsed time ti2 (S146). Thereafter, the control device 14 compares the elapsed time ti2 with the elapsed reference time tdef (S148). In the event that the elapsed time ti2 is exceeding the elapsed reference time tdef, as a result of the comparison (Not in S148), the control device 14 determines that the integrated current error is more than the certain value. In this case, the control device 14 returns to step S140, and starts the acquisition of the first open circuit voltage value Vo1 again. On the other hand, in the case where the elapsed time ti2 is equal to or less than the elapsed reference time tdef (Yes in S148), the control device 14 then compares the integrated current value AAhi2 with the value of integrated reference current AAhdef (S150) .In the case of | AAhi2 | <AAhdef as a result of the comparison (Not on S150), control device 14 returns to step S148. On the other hand, in the case of | AAhi2 | ^ AAhdef (Yes in S150), control device 14 checks whether the value of the open circuit voltage Vo is achievable and whether the load level Cb at the current time is in the non-hysteresis region (S152, S154). In the event that at least one condition is not satisfied as a result of the check (Not in S152 or Not in S154), the control device 14 returns to step S148. On the other hand, in the case where the open circuit voltage value Vo is obtainable and the load level Cb is in the region of non-hysteresis (Yes in S152 and Yes in S154), the control device 14 acquires the voltage value open circuit voltage Vo at the point in time, as the second open circuit voltage value Vo2 (S156).
[0064] At the point in time when the second voltage value of
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29/60 open circuit Vo2 has been acquired, control device 14 finishes calculating the integrated current value AAhi2 and counting the elapsed time ti2 (S158). Thus, the parameter acquisition routine is finished. In the example of FIG. 6, the integrated current value AAhi2 and the elapsed time ti2 are monitored when acquiring the second open circuit voltage value Vo2, but the monitoring of the integrated current value AAhi2 and the elapsed time ti2 can be excluded. That is, in FIG. 6, step S148 and step S150 can be excluded.
[0065] FIG. 7 is a diagram showing an exemplary operation of the parameter acquisition routine. In FIG. 7, the abscissa axis indicates time, and the ordinate axis indicates the load level Cb. In the example of FIG. 7, the elapsed reference time tdef is sufficiently longer than the time period from time t1 to time t5. The exemplary operation in FIG. 7 starts in a state where the charge level Cb of battery 12 is a level (for example, 90%) close to the full charge after the external charge of battery 12 is completed. At time t1, the electrically driven vehicle 100 is energized , and the control device 14 starts the routine in FIG. 6. Immediately after the electrically driven vehicle 100 is energized, the polarization state of battery 12 has been eliminated, and it can be said that the open circuit voltage value Vo is achievable. Consequently, the control device 14 acquires the detected voltage value Vb at time t1 immediately after the electrically driven vehicle 100 is energized, as the first open circuit voltage value Vo1. In addition, the control device 14 starts calculating the integrated current value AAhi2 and counting the elapsed time ti2.
[0066] Thereafter, the control device 14 controls the charge and discharge of the battery 12 in such a way that the discharge is greater (for example, an EV traveling), until the charge level Cb reaches an interPetition value 870180031862, of 19/04/2018, p. 141/219
30/60 predetermined median Cb_c (for example, about 30%). Here, suppose that, in a period from time t2 to time t3, the vehicle, for example, stops at a traffic light, the amount of charge and the amount of discharge from battery 12 decreases and a low charge state continues. In this case, it is possible to acquire the open circuit voltage value Vo at time t3, removing the estimated polarization component from the detected voltage value Vb. However, at time t3, the absolute value | AAhi ₂ | of the integrated current value is less than the integrated reference current value AAhdef and, therefore, the control device 14 continues the process of acquiring the second open circuit voltage value Vo2.
[0067] Next, suppose that, in a period from time t4 to time t5, the vehicle, for example, stops again at a traffic light, the amount of charge and the amount of discharge from battery 12 decrease and a state of low charge continues. In this case, it is possible to acquire the open circuit voltage value Vo at time t5, removing the estimated polarization component from the detected voltage value Vb. Also, suppose that, at time t5, the absolute value | AAhi ₂ | the value of the integrated current is greater than the value of the integrated reference current AAhdef, the elapsed time ti2 is less than the elapsed reference time tdef and the charge level Cb is in the non-hysteresis region. In this case, the control device 14 acquires the open circuit voltage value Vo at time t5, as the second open circuit voltage value Vo2, and ends the parameter acquisition routine.
[0068] As is obvious from the description above, also in the parameter acquisition routine shown in FIG. 6, the first and second open circuit voltage values Vo1, Vo2 and the integrated current value AAhi ₂ are acquired in the non-hysteresis region. In other words, it can be said that the acquired open circuit voltage values Vo1, Vo2 and the integrated current value AAhi ₂ are values that
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31/60 are not influenced by hysteresis. By estimating aging deterioration based on such values, it is possible to estimate aging deterioration easily and accurately.
[0069] Next, another example of the parameter acquisition routine will be described with reference to FIGS. 8A and 8B. FIGS. 8A and 8B are a flow chart showing another example of the parameter acquisition routine. In the example illustrated in FIGS. 8A and 8B, the time for the acquisition of the parameters is necessarily generated by the control of the charge and discharge of the battery 12. That is, as already described, in the electrically driven vehicle 100, typically, the charge level Cb of the battery 12 is maintained in the intermediate value Cb_c (for example, about 30%) which is relatively low and which is in the hysteresis region. If this state continues for a long time, it is not possible to acquire the parameters that are used to estimate aging deterioration. Therefore, when a time elapsed since the last aging deterioration estimation process is equal to or greater than a prescribed reference time t_def2, the control device 14 forcibly increases the battery charge level Cb 12 for the region non-hysteresis, and acquires the necessary parameters for the estimation of deterioration in aging. The reference time value t_def2 is not particularly limited since the reference time t_def2 depends on the speed of battery deterioration and, for example, is a value from several weeks to several months.
[0070] In the example illustrated in FIGS. 8A and 8B, to acquire the parameters, a first charge level Cb1 and a second charge level Cb2 are previously stored in memory 28. The first and second charge levels Cb1, Cb2 are almost equal to the first and second charge levels Cb1, Cb2 described in FIGS. 4A and 4B. The first and second load levels Cb1, Cb2 can each be values
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32/60 fixed or can be variable values as long as the first and second load levels Cb1, Cb2 are in the non-hysteresis region.
[0071] To execute the parameter acquisition routine, the control device 14 has a normal mode, a higher load mode and a load-discharge limitation mode, such as control modes of the electrically driven vehicle 100. The control mode Higher charge is a control mode in which the battery charge amount 12 is greater than the discharge amount. For example, in the highest load mode, control device 14 starts engine 104 in such a way that engine 104 outputs a dynamic energy equal to or greater than a dynamic energy that is necessary for the vehicle to travel, and causes that the first rotary electric machine MG1 generates electricity using dynamic energy surplus from engine 104. At this time, the control device 14 for the second rotary electric machine MG2, allows only electrical generation using braking energy and prohibits the drive as an electric motor .
[0072] The charge-discharge limitation mode is a mode in which both the charge and discharge of battery 12 are limited. For example, in the load-unload limiting mode, the control device 14 controls the engine 104 in such a way that the engine 104 produces the dynamic energy necessary for the vehicle to travel and limits as much as possible the activation of the first and second rotary electric machine MG1, MG2. That is, the control device 14 also limits the electrical generation of the first and second rotating electrical machines MG1, MG2. The normal mode is a control mode that is neither the highest charge mode nor the charge-discharge limitation mode. As needed, the control device 14 can perform an electrically driven trip in which the vehicle travels with only the dynamic energy of the second rotating electric machine MG2, or it can play a hybrid vehicle in which the vehicle travels with the dynamic energy of the
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33/60 second rotary electric machine MG2 and engine 104.
[0073] In the parameter acquisition routine in FIGS. 8A and 8B, the control device 14 counts the time elapsed since the last estimation process for aging deterioration and monitors whether the elapsed time t is equal to or greater than the prescribed reference time t_def2 (S160). When the elapsed time is equal to or greater than the reference time t_def2, the control device 14 changes the vehicle's control mode to the highest load mode (S162). As a result, the charge level Cb of battery 12 gradually increases from the intermediate value Cb_c (for example, about 30%) in the hysteresis region and reaches the non-hysteresis region.
[0074] When the charge level Cb of battery 12 becomes the first charge level Cb1 which is a value in the non-hysteresis region (Yes in S164), the control device 14 changes the control mode to the limiting mode load-discharge in which both load and discharge are limited (S166). As a result, the charging and discharging of the battery 12 is limited, and the open circuit voltage value Vo can be acquired. Then, when the open circuit voltage value Vo is acquirable (Yes in S168), the control device 14 acquires the open circuit voltage value Vo at the time point, as the first open circuit voltage value Vo1 (S170 ).
[0075] After the acquisition of the first open circuit voltage values Vo1, the control device 14 changes the control mode of the electrically driven vehicle 100 back to the highest load mode (S172). In addition, the control device 14 starts calculating the integrated current value AAhi2 (S174).
[0076] As a result of switching to the higher load mode, the charge level Cb of battery 12 starts to rise again. Then, when the charge level Cb of the battery 12 becomes the second charge level Cb2 (Yes in S178), the control device 14 changes the charging mode.
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34/60 control for load-discharge limiting mode (S180). Then, when the open circuit voltage value Vo is acquirable (Yes in S182), the control device 14 acquires the open circuit voltage value Vo at the point in time as the second open circuit voltage value Vo2 (S184) . After acquiring the second open circuit voltage value Vo2, the control device 14 finishes the calculation of the integrated current value AAhi2 (S186). After the acquisition of the first and second open circuit voltage values Vo1, Vo2 and the integrated current value AAhi2, the control device 14 changes the control mode of the electrically driven vehicle 100 to the normal mode (S188). In the event that the absolute value | AAhi2 | of the integrated current value is less than a prescribed reference value, the accuracy of the deterioration estimate may decrease. Therefore, it is preferable to perform a control such that the absolute value | AAhi2 | the integrated current value becomes equal to or greater than the prescribed reference value. Similar to the flowchart in FIG. 6, in the example, the control device 14 can check the elapsed time ti2 since the acquisition of the first open circuit voltage value Vo1, immediately before the acquisition of the second open circuit voltage value Vo2. In this case, when the elapsed time ti2 is exceeding a predetermined reference value, the control device 14 operates the electrically driven vehicle 100 in a higher discharge mode, without acquiring the second open circuit voltage value Vo2, and then returns to step S164 to start the acquisition of the first open circuit voltage value Vo1 again.
[0077] FIG. 9 is a diagram showing an exemplary operation of the parameter acquisition routine. In FIG. 9, the abscissa axis indicates time, and the ordinate axis indicates the load level Cb.
The exemplary operation of FIG. 9 starts in a state in which the
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35/60 battery charge level Cb 12 is maintained around the intermediate value Cb_c in the hysteresis region. Typically, the charge level Cb of battery 12 is maintained around the intermediate value Cb_c. Here, suppose that the time elapsed since the last aging deterioration estimation process becomes equal to or greater than the reference time t_def2 at time t1. In this case, the control device 14 changes the vehicle's control mode to the highest load mode. As a result, the charge level Cb of battery 12 goes up. So, suppose that the load level Cb becomes the first load level Cb1 at time t2. In this case, the control device 14 switches the control mode to the load-discharge limiting mode. As a result, after time t2, the change in charge level Cb becomes small. This state continues for a certain time and, at time t3, the open circuit voltage value Vo becomes acquirable. Then, the control device 14 acquires the open circuit voltage value Vo at time t3, as the first open circuit voltage values Vo1.
[0078] After acquiring the first open circuit voltage value Vo1, the control device 14 switches the control mode to the highest load mode again. In addition, the control device 14 starts calculating the integrated current value AAhi ₂ . As a result, after time t3, the charge level Cb of battery 12 increases rapidly. Then, at time t4, the charge level Cb becomes the second charge level Cb2, and the control device 14 changes the control mode to the charge-discharge limiting mode again. The state in which charging and discharging is limited continues for a certain time, and at time t5, the open circuit voltage value Vo becomes acquirable. Control device 14 acquires the open circuit voltage value Vo over time t5 as the second open circuit voltage value Vo2. In addition, the control device 14 acquires the integrated value of the detected current value Ib from time t3 to time
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36/60 t5, as the integrated current value AAhi ₂ . After the acquisition of the first and second open circuit voltage values Vo1, Vo2 and the integrated current value AAhi2, the control device 14 changes the control mode of the hybrid vehicle to normal mode. As a result, the charge level Cb of battery 12 decreases to about intermediate Cb_c.
[0079] As is obvious from the description above, also in the parameter acquisition routine shown in FIGS. 8A and 8B, the first and second open circuit voltage values Vo1, Vo2 and the integrated current value AAhi ₂ are acquired in the non-hysteresis region. In other words, it can be said that the acquired open circuit voltage values Vo1, Vo2 and integrated current value AAhi ₂ are values that are not influenced by hysteresis. By estimating aging deterioration based on such values, it is possible to estimate aging deterioration easily and accurately.
[0080] In the event that aging deterioration is not estimated for a long time, the deviation between the actual state of the battery 12 and the SOC-OCV curve and the FCC total charge capacity stored in memory 28 increases. In this case, the accuracy of the estimate for the battery charge level Cb 12 decreases. In the routine shown in FIGS. 8A and 8B, even in the case where the external load or similar is not carried out for a long time, it is possible to acquire the necessary parameters for the estimation of deterioration in aging, when the time elapsed since the last process of estimation of deterioration in aging becomes equal to or greater than the reference time t_def2. Therefore, it is possible to avoid the problem that the accuracy of the SOC estimate decreases since aging deterioration is not estimated over a long period of time. In the example of FIGS. 8A and 8B, since Cb1 <Cb2, the first open circuit voltage value Vo1 to be acquired for the first moment
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37/60 is less than the second open circuit voltage value Vo2 to be acquired for the second moment. However, by adjusting Cb1> Cb2, the control device 14 can first charge the battery 12 until the charge level Cb reaches the first charge level Cb1, to acquire the first open circuit voltage value Vo1, and then before operating the electrically driven vehicle 100 in such a way that the discharge is greater, to acquire the second open circuit voltage value Vo2 when the charge level Cb has reached the second charge level Cb2 (<Cb1).
[0081] The routine shown in FIGS. 8A and 8B are based on the premise that the battery 12 can be charged while the vehicle is traveling. Therefore, the routine shown in FIGS. 8A and 8B is suitable for electrically driven vehicles that can generate electricity even while the vehicles are traveling. Examples of such electrically powered vehicles include a hybrid vehicle, which includes an engine as a dynamic energy source, in addition to a rotating electrical machine, an electrically powered vehicle equipped with a solar panel that generates electricity using sunlight and an electrically equipped powered vehicle. with a fuel cell that changes the chemical energy of the fuel (hydrogen and the like) to electrical energy.
[0082] Next, the deterioration estimation routine (S20) will be described. The deterioration estimation routine (S20) is not particularly limited, as long as at least one of the SOC-OCV curve and the total FCC load capacity of battery 12 is estimated using the first and second open circuit voltage values Vo1, Vo2 and integrated current value AAhi2 acquired in the parameter acquisition routine (S10). Two types of deterioration estimation routines (S20) will be exemplified below. However, the deterioration estimation routine (S20) is not limited to them, and several conventionally proposed deterioration estimation technologies can be used.
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38/60 [0083] An example of the deterioration estimation routine (S20) will be described with reference to FIG. 10. The deterioration estimation routine in FIG. 10 estimates the total load capacity FCC, based on the relationship between a change value ACb of the load level and the integrated current value AAhi2. Specifically, the control device 14 checks the first and second open circuit voltage values Vo1, Vo2 acquired in the parameter acquisition routine (S10) against the SOC-OCV curve stored in memory 28 and thereby acquires the corresponding load levels. Cb [Vo1], Cb [Vo2] (S210, S212). Then, the control device 14 divides the absolute value | AAhi2 | of the value of the integrated current by the amount of charge level change ACb = | Cb [Vo1] -Cb [Vo2] | and multiplies the resulting value by 100 to calculate the total FCC load capacity (S214). That is, the control device 14 computes FCC = | AAhi2 | / (| Cb [Vo1] -Cb [Vo2] |) x100. After calculating the FCC full load capacity, the control device 14 modifies and updates the FCC full load capacity stored in memory 28, to the FCC calculated total load capacity (S216).
[0084] Next, another example of the deterioration estimation routine (S20) will be described. In the deterioration estimation routine in FIG. 11, three deterioration parameters k1, k2, AQs that indicate a battery state 12 are searched based on the first and second open circuit voltage values Vo1, Vo2 and integrated current value AAhi2 acquired in the parameter acquisition routine. A principle of the deterioration estimation routine will be described before a flow of the deterioration estimation routine is described.
[0085] As already described, battery 12 in the modality is a secondary lithium ion battery. The secondary lithium-ion battery consists of a negative electrode, a separator that contains an electrolyte, and a positive electrode. The negative electrode and the positive electrode, each
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39/60 um, is composed of aggregates of spherical active materials. At the time of discharge of the secondary lithium-ion battery, over an interface of the active material of the negative electrode, a chemical reaction is carried out by which Li ⁺ ions and electrons and ^- are released. On the other hand, on a positive electrode active material interface, a chemical reaction is carried out by which Li ⁺ ions and electrons and ^- are absorbed. At the time of charging the secondary lithium-ion battery, reverse reactions from the above reactions are performed.
[0086] The negative electrode is equipped with a negative electrode current collector that absorbs electrons, and the positive electrode is equipped with a positive electrode current collector that releases electrons. The negative electrode current collector is formed of copper, for example, and is connected to a negative electrode terminal. The positive electrode current collector is formed from aluminum, for example, and is connected to a positive electrode terminal. Lithium ions are transferred between the positive electrode and the negative electrode through the separator, so that secondary lithium ion battery charging and discharging is carried out.
[0087] Here, the charge state inside the secondary lithium ion battery differs depending on the lithium concentration distributions in the positive electrode and negative electrode active materials. The output voltage of the secondary lithium-ion battery is expressed by the following Formula (1).
V = Vo (θι, θ ₂ ) - R x I (1) [0088] Here, R is a resistance of the entire secondary lithium ion battery, and I is a current that flows through the secondary lithium ion battery . Resistance R includes a purely electrical resistance against the movement of electrons between the negative electrode and the positive electrode, and a charge movement resistance that acts
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40/60 equivalent to an electrical resistance when the reaction current is generated on the interfaces of the active material.
[0089] Furthermore, θι is a local charge level on a positive electrode active material surface, and 02 is a local charge level on a negative electrode active material surface. The resistance R has a characteristic to change depending on changes in 01, 02 and the temperature of the battery. In other words, the resistance R can be expressed as a function with 0i, 02 and the temperature of the battery. The local charge levels 0i, 02 are expressed by the following Formula (2).
Oi ⁼ (Cse, i) / (Cs, i, max) (2) [0090] Here, Cse, i is the lithium concentration (average value) of the active material (the positive electrode or the negative electrode) on its interface and C _s , i, max is the limiting lithium concentration of the active material (the positive electrode or the negative electrode). As for index i, 1 indicates the positive electrode and 2 indicates the negative electrode. The limit concentration of lithium is the upper limit of the concentration of lithium in the positive or negative electrode. Each of the local charge levels 0i, 02 of the positive electrode and negative electrode varies in a range from 0 to 1.
[0091] A positive electrode open circuit potential Ui has a characteristic to change depending on the local charge level 0i on the surface of the positive electrode active material, and a negative electrode open circuit potential U2 has a characteristic to change depending on local charge level Θ2 on the surface of the active material of the negative electrode. FIG. 12 shows a relationship of the positive electrode open circuit potential U1 with the local charge level 0i, and a relationship of the negative electrode open circuit potential U2 with the local charge level Θ2, when the secondary lithium ion battery is in an initial state. In battery 12 in the modality, since a complex containing a material of silicon and graphite is used as material
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41/60 active negative electrode, the open circuit potential of negative electrode U2 has, in part, a hysteresis. In FIG 12, the negative electrode open circuit potential U2 shown by the thick line indicates a negative electrode open circuit potential that is obtained in the process in which the battery 12 is charged after the complete discharge of the battery 12 (hereinafter, referred to as a time after a continuous charge), and the negative electrode open circuit potential U2 shown by the thin line indicates a negative electrode open circuit potential that is obtained in the process in which battery 12 is discharged after the battery is fully charged. battery 12 (hereinafter, referred to as time after a continuous discharge). Likewise, the open circuit voltage value Vo shown by the thick line indicates an open circuit voltage after continuous charging and the open circuit voltage value Vo shown by the thin line indicates an open circuit voltage after continuous discharge. From now on, when it is unnecessary to distinguish the time after continuous charging and the time after continuous discharge, the description will be made only for the open circuit potential of negative electrode U2 and for the open circuit voltage value Vo after charging. to be continued.
[0092] As shown in FIG. 12, the open circuit voltage value Vo of the lithium-ion secondary battery is shown as the potential difference between the positive electrode open circuit potential U1 and the negative electrode open circuit potential U2- Since the potential negative electrode open circuit U2 partly has a hysteresis as already described, the open circuit voltage value Vo also partly has a hysteresis. The initial state means a state in which the secondary lithium-ion battery is not damaged and, for example, means a state immediately after the secondary lithium-ion battery is produced.
[0093] As shown in FIG. 12, when the local charge level θι
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42/60 of the positive electrode is Θιη (= 1), the open circuit potential of the positive electrode Ui is the minimum (the amount of Li in the positive electrode is maximum). On the other hand, when the local charge level 02 of the negative electrode is 02L (= 0), the open circuit potential of the negative electrode U2 is maximum (the amount of Li in the negative electrode is minimal). Data indicating the characteristics (U1, U2) can be previously stored in memory 28 as a map.
[0094] The open circuit voltage Vo value of the secondary lithium ion battery has a characteristic of decreasing with the discharge from the state of full charge. In addition, in the secondary lithium ion battery after deterioration, the amount of voltage drop in the same discharge time is greater than in the secondary lithium ion battery in the initial state. This means that deterioration of the secondary lithium ion battery causes a decrease in the total charge capacity and a change in the open circuit voltage curve. In the modality, the modeling of the change in the open circuit voltage curve associated with the deterioration of the secondary lithium ion battery is performed based on two phenomena that can occur inside the secondary lithium ion battery in the deteriorated state. The two phenomena are a decrease in the capacity of the single electrode in the positive electrode and the negative electrode, and a gap in the composition correspondence between the positive electrode and the negative electrode.
[0095] The decrease in single electrode capacity shows a decrease in the ability to receive lithium in each of the positive and negative electrodes. The decrease in the capacity to receive lithium means a decrease in the active material and the like that effectively works in loading and unloading.
[0096] FIG. 13 schematically shows a change in the open circuit potential of the positive electrode U1 due to a decrease in the capacity of the positive electrode and a change in potential
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43/60 of the open circuit of the negative electrode U2 due to a decrease in the capacity of the negative electrode. In FIG. 13, Qn_ on the positive electrode capacity axis is a capacity corresponding to the local charge level 0il (= 0) in FIG. 12, in the initial state of the secondary lithium-ion battery. QiH_ini is a capacity corresponding to the local charge level Θιη (= 1) in FIG. 12, in the initial state of the secondary lithium ion battery. In addition, Q2L on the negative electrode capacity axis is a capacity corresponding to the local charge level 02H (= 1) in FIG. 12, in the initial state of the secondary lithium-ion battery, and CteHjni is a capacity corresponding to the local charge level 02L (= 0) in FIG. 12, in the initial state of the secondary lithium-ion battery.
[0097] On the positive electrode, when the capacity to receive lithium decreases, the capacity corresponding to the local charge level θιι_ (= 1) changes from QiHjni to QiH_aft- In addition, on the negative electrode, when the capacity to receive lithium decreases, the capacity corresponding to the local charge level 02l (= 0) changes from CteHjni to Q2H_aft [0098] Here, even when the secondary lithium ion battery deteriorates, the ratio (the ratio shown in figure 12) of the open circuit potential of positive electrode U1 for the local charge level θι does not change. Therefore, when the ratio of the positive electrode open circuit potential U1 to the local charge level θι is converted to a ratio of the positive electrode open circuit potential U1 to the positive electrode capacity, a curve (long alternating line and two short dashes) indicating a relationship of an open circuit potential of the positive electrode U1 _ _to ft to the capacity of the positive electrode in the deteriorated state, as shown in FIG. 13, is a curve shrunk from a curve U1 j _n i (solid line) in the initial state by an amount corresponding to the deterioration of the secondary lithium ion battery.
[0099] Likewise, when the circuit potential ratio
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44/60 open of negative electrode U2 for the local charge level Θ2 is converted to a ratio of the open circuit potential of negative electrode U2 to the capacity of the negative electrode, a curve (long alternating line and two short dashes) that indicates a ratio of a negative electrode open circuit potential U2_aft to the negative electrode capacity in the deteriorated state, as shown in FIG. 13, is a curved curve from an Ihjni curve (solid line) in the initial state by an amount corresponding to the deterioration of the secondary lithium ion battery.
[00100] Next, the composition gap will be described. FIG. 14 schematically shows a gap in composition correspondence between the positive and negative electrodes. The gap in the composition correspondence is a gap in the combination of the positive electrode composition (0i) and the negative electrode composition (02) with the initial state of the secondary lithium ion battery, when charging and discharging are carried out using the positive electrode and negative electrode.
[00101] The curves that indicate the relationships of the open circuit potentials of the positive electrode and negative electrode U1, U2 to the local charge levels Οι, Θ2 of the positive electrode and negative electrode are the same as the curves shown in FIG. 12. Here, when the secondary lithium ion battery deteriorates, the axis of the negative electrode composition Θ2 moves through A2 in the direction of the decrease in the positive electrode composition 0i. Thus, a curve (long dashed alternating line and two short dashes) that indicates a relationship of a negative electrode open circuit potential U2_aft to the axis of the negative electrode composition Θ2 in the deteriorated state, is a curve displaced by ΔΘ2 in the direction of decrease in 0i positive electrode composition from a curve (solid line) that indicates the potential of the open circuit
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45/60 of the negative electrode Ihjni for the composition axis of negative electrode 02 in the initial state.
[00102] As a result, the negative electrode composition corresponding to a Θια _χ composition of the positive electrode is 02fix_ini in the initial state of the secondary lithium ion battery, but it is 02fix_aft after the deterioration of the secondary lithium ion battery.
[00103] In the deterioration estimation routine shown in FIG. 11, the modeling of the two phenomena described above is performed by adopting three deterioration parameters in a battery model. The three deterioration parameters are a positive electrode capacity maintenance ratio ki, a negative electrode capacity maintenance ratio k2 and a positive electrode composition gap capacity negative AQ _S. A method of modeling the two deteriorated phenomena will be described below.
[00104] The maintenance ratio of the positive electrode capacity ki is the relationship between the capacity of the positive electrode in the deteriorated state and the capacity of the positive electrode in the initial state. Here, suppose that the capacity of the positive electrode decreases by an arbitrary amount from the capacity in the initial state, after the secondary lithium ion battery becomes in the deteriorated state. In this case, the capacity maintenance ratio of the positive electrode ki is expressed by the following formula (3).
_{hi =} (Q ,. ₁₁ -A0,) ₍₃₎ ^ 1_ίηϊ [00105] Here, Qij ™ represents the capacity of the positive electrode in the initial state of the secondary lithium-ion battery, and AQi represents the amount of decreased capacity of the positive electrode due to the deterioration of the secondary lithium ion battery. Consequently, the capacity of the positive electrode after the secondary ion battery
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46/60 lithium becoming in the deteriorated state is (Qijni-AQi). In addition, ki decreases from 1, which is the value in the initial state. Here, the capacity of the positive Qijni electrode in the initial state can be previously assessed from the theoretical capacity and amount of preparation of the active material and the like.
[00106] The ratio of maintenance of the negative electrode capacity k ₂ is the ratio between the negative electrode capacity in the deteriorated state and the negative electrode capacity in the initial state. Here, suppose that the negative electrode capacity decreases by an arbitrary amount from the capacity in the initial state, after the secondary lithium-ion battery has become in the deteriorated state. In this case, the capacity maintenance ratio of the negative electrode k ₂ is expressed by the following formula (4).
_{kz =} fe, _i ., - â0 ₂ ) ₍₁₎ [00107] Here, Ctejni represents the capacity of the negative electrode in the initial state of the secondary lithium ion battery, and AQ2 represents the amount of decrease in the capacity of the negative electrode due to the deterioration of the secondary battery of lithium ion. Thus, the negative capacity of the electrode after the secondary lithium ion battery becomes in the deteriorated state is (Q2jni-AQ2). In addition, k ₂ decreases from 1, which is the value in the initial state. Here, the capacity of the negative Q2jni electrode in the initial state can be previously assessed from the theoretical capacity and quantity of preparation of the active material and the like.
[00108] FIG. 15 is a schematic diagram to describe a gap in the composition correspondence between the positive and negative electrodes. In the case where the secondary lithium ion battery is in a deteriorated state, the negative capacity of the electrode when the composition of negative electrode 02 is 1 is (Q2jni-AQ ₂ ). The ability to
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47/60 gap correspondence composition of the negative electrode, positive electrode aq electrode _S is a capacity corresponding to an amount of the composition ΔΘ2 gap shaft negative electrode composition Θ2 relative to the axis of θι positive electrode. With that, the relationship of the following formula (5) is satisfied. The positive electrode-negative electrode composition gap capacity AQ _S indicates an amount of variation in battery capacity due to a change from the initial state in the correspondence relationship between the local charge level θι as the charge level local on the surface of the active material of the positive electrode and the local charge level 02 as the level of local charge on the surface of the active material of the negative electrode.
Δθ ₂ : 1 = AQ _S : (Q ₂ _ini-AQ ₂ ) (5) [00109] The following formula (6) is obtained from Formula (4) and Formula (5).
AQ _S = k2XQ2_ini ΧΔΘ2 (6) [00110] When the secondary lithium ion battery is in the initial state, the composition of the positive electrode θιη _χ corresponds to the composition of the negative electrode 02fixjni. When the secondary lithium ion battery is in a deteriorated state the composition of the positive electrode Θιαχ corresponds to the composition of the negative electrode 02fix_aft.
[00111] In the event that the gap in the composition correspondence between the positive electrode and the negative electrode appears due to the deterioration of the secondary lithium ion battery, the negative electrode composition 02fix_aft after the deterioration of the secondary lithium ion battery has the relation of the following formula (7).
®2fix_aft (1 - 9ifix) ^x x Q _{l ini} x AQ _S ^ 2 ^x Q2_ini (Ό
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48/60 [00112] The meaning of Formula (7) will be described. When lithium is released from the positive electrode by the charge in the deteriorated state of the secondary lithium ion battery, the composition of the positive electrode θι decreases from 1. When the composition of the positive electrode θι decreases from 1 to θιηχ, an F1 amount of lithium that is released from the positive electrode is expressed by the following formula (8).
F1 = (1 - 0fix) x kix Qi_íní (8) [00113] Here, the value of (1 - θιηχ) indicates the amount of decrease in the positive electrode composition Θ1 due to the charge of the lithium ion secondary battery and the value de (kix Qijni) indicates the capacity of the positive electrode after the deterioration of the secondary lithium ion battery. [00114] If all the lithium released from the positive electrode is taken in the negative electrode, the composition of the negative electrode 02fixjni is expressed by the following formula (9).
02fix_ini - (1 - θιπχ) X kl x Q _1Jni k ₂ X Q2.ini (9) [00115] Here, the value of (k2 x Q2jni) indicates the capacity of the negative electrode after the deterioration of the secondary lithium ion battery .
[00116] On the other hand, when the gap (ΔΘ2) in the composition correspondence between the positive electrode and the negative electrode appears, the composition of the negative electrode02fix_aft after deterioration is expressed by the following formula (10).
02fix_aft (1 - θιπχ) X kl XQ _Uni k2 x Q2.ini
-δθ ₂ (10) [00117] The amount of gap Δθ2 in the composition correspondence can be expressed by Formula (6), using the composition correspondence gap capacity of the positive electrode-negative electrode AQ _S. Thus, the composition of the 02fix_aft negative electrode after deterioration is expressed by the formula (7) above.
[00118] As shown in FIG. 15, the circuit voltage value
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49/60 open Vo in the deteriorated state of the secondary lithium ion battery is expressed as the potential difference between the positive electrode open circuit potential Ui _to tt and the negative electrode open circuit potential U2_aft in the deteriorated state. That is, by identifying the three deterioration parameters: the ratio of maintenance of the capacity of the positive electrode ki, the ratio of maintenance of the capacity of the negative electrode k2 and the capacity of the composition matching gap of the positive electrode-negative electrode AQ _S is It is possible to identify the potential of the open circuit of the negative electrode U2_aft in the deteriorated state of the secondary lithium-ion battery, and to calculate the open circuit voltage value Vo as the potential difference between the potential of the negative electrode open circuit U2_after the potential of Uijni positive electrode open circuit.
[00119] That is, since it is possible to previously evaluate the capacity of the positive Qijni electrode and the capacity of the negative Q2jni electrode in the initial state from the theoretical capacities and preparation quantities of the active materials, it is possible to calculate the composition of the negative electrode02fix_aft in the deteriorated state using Formula (7), when it is possible to identify the three deterioration parameters: the positive electrode capacity maintenance index ki, the negative electrode capacity maintenance ratio k2 and the composition matching gap capacity negative-positive electrode AQ _S. In addition, it is possible to calculate the amount of gap Δθ2 in the composition correspondence using Formula (6). From the amount of gap Δθ2, as shown in FIG. 12, it is possible to identify the position of 0 of the axis of the composition of the negative electrode 02 in the deteriorated state that corresponds to the position when the composition of the positive electrode 0i in the deteriorated state is 1, and the composition of the negative electrode 02fix_aft- Then, from the positions of 0 and 02fix2fix_aft, as shown in FIG. 12 it is possible to identify the position of
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50/60 of the negative electrode 02 composition axis in deteriorated state. [00120] The ratio of the open circuit potential of the positive electrode Ui to the local charge level 0i of the positive electrode and the relationship of the open circuit potential of the negative electrode U2 to the local charge level 02 of the negative electrode (the relationships shown in FIG. 12) do not change, even when the secondary lithium ion battery deteriorates. Consequently, when it is possible to identify the positions of 0 and 1 of the composition axis of the negative electrode Θ2 in the deteriorated state that correspond to the positions of 1 and 0 of the composition of the positive electrode 01 in the deteriorated state, a curve that indicates the relationship of the potential of open circuit of the positive electrode U1 for the local charge level 01 of the positive electrode shown in FIG 12 is drawn between 1 and 0 of the positive electrode composition 0i in the deteriorated state, and a curve indicating the ratio of the open electrode potential negative U2 for the local charge level Θ2 of the negative electrode shown in FIG. 12 is drawn between 1 and 0 of the composition of the positive electrode 01 in the deteriorated state, so that the curves become the open circuit potential of the positive electrode U1 and the open circuit potential of the negative electrode U2 in the deteriorated state shown in FIG 12 Thus, it is possible to identify the curves that indicate the open circuit potential of the positive electrode U1 and the open circuit potential of the negative electrode U2 and, therefore, it is possible to calculate the open circuit voltage value of the secondary ion battery lithium in a deteriorated state.
[00121] As described above, it is possible to calculate the open circuit voltage Vo value of the secondary lithium ion battery in the deteriorated state, identifying the three deterioration parameters: the maintenance ratio of positive electrode capacity ki, the maintenance ratio of k2 negative electrode capacity and the gap-matching capacity of positive electrode-negative electrode AQs.
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51/60 [00122] In the secondary lithium ion battery in the initial state, the positive electrode capacity maintenance ratio ki is 1, the negative electrode capacity maintenance ratio k2 is 1, and the corresponding gap capacity positive electrode negative electrode AQ _S is 0. The open circuit voltage value Vo calculated (estimated) as described above coincides with the value (measured value) when the open circuit voltage value Vo of the lithium ion secondary battery in the initial state (a new secondary lithium ion battery) is measured.
[00123] As shown in FIG. 16), the value of open circuit voltage Vo of the secondary battery of lithium ion increases with the increase of the capacity of the battery (AAh), that is to say, with the charge of the secondary battery. From now on, a curve of change in the open circuit voltage value Vo in relation to the battery capacity (AAh) is referred to as an open circuit voltage curve. As shown by the alternating long and short line and broken line in FIG. 16, the open circuit voltage curve moves from the initial state to the left side in the figure, due to the deterioration of the battery 12.
[00124] As described above, it is possible to calculate the open circuit voltage Vo value of the secondary lithium ion battery in the deteriorated state from the three deterioration parameters: the capacity maintenance ratio of the positive electrode ki, the ratio of maintenance of negative electrode capacity k2 and the gap capacity of positive electrode-negative electrode composition AQs and, therefore, it is possible to calculate the open circuit voltage curve for the secondary lithium ion battery, from the relation ki positive electrode capacity maintenance ratio, k2 negative electrode capacity maintenance ratio and the positive electrode composition-negative gap matching capacity.
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52/60 [00125] Therefore, in the deterioration estimation routine shown in FIG. 11, a convergent calculation is performed to search for values of (ki, k2, AQ _S ) allowing the open circuit voltage curve (estimated value) in the deteriorated state calculated based on the three deterioration parameters: the maintenance capacity ratio positive electrode ki, the maintenance ratio of negative electrode capacity k2 and the gap capacity matching positive electrode-negative electrode AQ _S roughly coincide with the open circuit voltage curve (measured value). Thus, it is possible to identify the positive electrode capacity maintenance ratio ki, the negative electrode capacity maintenance ratio k2 and the positive electrode composition gap capacity negative AQ _S in a given deteriorated state, and it is possible to estimate a deterioration in the capacity of the secondary lithium-ion battery.
[00126] Specifically, with reference to FIG. 11, a flow of the deterioration estimation routine will be described. In the deterioration estimation routine shown in FIG. 11, the control device 14, first, plots the first and second open circuit voltage values Vo1, Vo2 and integrated current value AAhi2 acquired in the parameter acquisition routine (S10), and generates the voltage curve of open circuit (measured value) (S220).
[00127] Then, the control device 14 establishes candidates of the deterioration parameters (ki, k2, AQ _S ) to generate the characteristic open circuit voltage (estimated value) (S222). Then, the control device 14 generates the open circuit voltage curve (estimated value), using the established deterioration parameters (S224). The principle of generation has been described with reference to FIG. 12 through FIG. 15. FIG. 16 is a diagram showing an example of the open circuit voltage curve (measured value) and the voltage curve of
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53/60 open circuit (estimated value).
[00128] After obtaining the open circuit voltage curve (measured value) and the open circuit voltage curve (estimated value), the control device 14 calculates an AV voltage error and an AQ capacity error between the open circuit voltage (measured value) and the open circuit voltage curve (estimated value) (S226). For example, the AV voltage error can be an AV voltage error in a given battery capacity a, as shown in FIG. 17, or it can be a mean square or similar value of the voltage error between the two open circuit voltage curves.
[00129] The capacity error AQ can be the absolute value of the difference between a measured capacity Q1 and an estimated capacity Q2, that is, AQ = | Q1 - Q2 |. As measured capacity Q1, the integrated current value AAhi2 acquired by the parameter acquisition routine can be used. Like the estimated capacity Q2, the capacity change value at the time of the change from the first open circuit voltage value Vo1 to the second open circuit voltage value Vo2 in the open circuit voltage curve (estimated value) can be used.
[00130] After obtaining the AV voltage error and the AQ capacity error, the control device 14 then calculates an evaluation function f (AV, AQ) for the AV voltage error and the AQ capacity error ( S228). As the evaluation function f (AV, AQ), for example, a value resulting from the weighting and addition of the AV voltage error and the AQ capacity error can be used.
[00131] In addition, the control device 14 determines whether the calculated evaluation function f (AV, AQ) in question is less than an evaluation function f (AV, AQ) stored in memory 28. When the evaluation function f (AV, AQ) in question is less than the function of
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54/60 evaluation f (Δν, ΔΟ) stored in memory 28, the control device 14 stores the evaluation function f (Δν, ΔΟ) in question, in memory 28, together with the deterioration parameters (ki, k2, AQ _S ) in question. When the evaluation function f (Δν, AQ) in question is greater than the evaluation function f (Δν, ΔΟ) stored in memory 28, the evaluation function f (AV, ΔΟ) stored in memory 28 is kept unchanged.
[00132] In step S230, the control device 14 determines whether the deterioration parameters have been changed over the entire search range (S230). When the deterioration parameters have not been changed over the entire search range, the control device 14 changes the candidate values of the deterioration parameters (ki, k2, AQ _S ) (S229) and returns to step S224.
[00133] On the other hand, when the deterioration parameters have been changed over the entire search range, the control device 14 ends the search. At this time, the deterioration parameters (ki, k2, AQ _S ) that minimize the evaluation function f (AV, ΔΟ) in the search range are stored in memory 28. It can be said that the deterioration parameters (ki, k2, AQ _S ) stored in memory 28 are parameters that indicate the deteriorated state of battery 12 at the current moment. The control device 14 estimates the SOC-OCV curve and the total load capacity FCC based on the identified deterioration parameters (ki, k2, AQ _S ) and stores the estimated values in memory 28 (S232).
[00134] The deterioration estimation routines shown in FIG.
and FIG. 11 are examples, and another routine can be used as long as the deteriorated state of the battery 12 is estimated using the open circuit voltage values Vo1, Vo2 at a plurality of points and the integrated current value AAhi2 between the plurality of points.
[00135] As described above, the battery system 10 disclosed in the
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55/60 present specification estimates deterioration in aging, using the parameters (Vo1, Vo2, AAhi ₂ ) acquired in the region of non-hysteresis. With this, it is possible to estimate exactly the deterioration of the battery 12 without the influence of hysteresis. Constantly, to estimate the deterioration of the battery 12 more accurately, it is desirable that the interval of acquisition of the parameters, that is, the interval between the first open circuit voltage value Vo1 and the second open circuit voltage value Vo2 should be the as possible. Thus, if possible, it is desirable that the first and second open circuit voltage values Vo1, Vo2 are acquired near the upper and lower limit of the hysteresis region.
[00136] However, the range of non-hysteresis increases or decreases with aging deterioration of battery 12. This will be described with reference to FIG. 18. In FIG. 18, negative electrode open circuit potentials U ₂ jni, U _{2 to} ft shown by thick lines indicate negative electrode open circuit potentials after continuous battery charging and negative electrode open circuit potentials U ₂ jni, U _{2 a} tt shown by thin lines indicate negative electrode open circuit potentials after continuous discharge. In addition, a local charge level Θ ₂ β in which the difference between the open circuit potential of the negative electrode (thick line) after continuous charging and the open circuit potential of the negative electrode (thin line) after continuous discharge is makes a certain amount or more of difference, it is referred to as a point of appearance of hysteresis Θ ₂ β.
[00137] As already described, the open circuit voltage value Vo of battery 12 is a difference value between the positive electrode open circuit potential and the negative electrode open circuit potential.
Generally, the charge level Cb when the open circuit voltage value Vo of battery 12 is a prescribed upper limit VH is 100%, and the charge level Cb when the open circuit voltage value Vo is one
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56/60 prescribed lower limit VL is 0%. The FCC full charge capacity is a positive electrode capacity or negative electrode capacity that is obtained when the open circuit voltage value Vo changes from Vo = VL to Vo = VH.
[00138] Suppose, with the deterioration in aging of battery 12, the open circuit potential of the negative electrode changes from the open circuit potential of the negative electrode Ihjn in the initial state to the open circuit potential of the negative electrode U2_after deterioration, as shown in FIG. 18. In this case, it appears that the position of the hysteresis onset point 02b in the range of 02L to 02H (Cb = 0% to Cb = 100%), that is, in the total load capacity FCC, differs between the state initial and deteriorated state. This means that the region of non-hysteresis changes due to deterioration.
[00139] Thus, the real non-hysteresis region increases or decreases with deterioration in battery aging 12. Here, in the parameter acquisition routine, the respective parameters Vo1, Vo2, AAhi2 are acquired in the non-hysteresis region stored in memory 28. When there is a deviation between the non-hysteresis region stored in memory 28 and the actual non-hysteresis region, the parameters can actually be acquired in the hysteresis region. This problem can certainly be avoided by predicting the real change in the region of non-hysteresis associated with deterioration and defining the region of non-hysteresis stored in memory 28 from the beginning. However, in this case, the parameter acquisition range sometimes narrows, and the opportunity for the acquisition of parameters decreases.
[00140] Thus, in each deterioration estimation process for battery 12, the range of the non-hysteresis region can be estimated and updated. Specifically, the open circuit potential of the negative U2_aft electrode after deterioration is assessed using the
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57/60 deterioration (ki, k2, AQ _S ) acquired in the deterioration estimation routine shown in FIG. 11. In this way, it is possible to identify the position of a hysteresis onset point 02b or Θιβ, and also the value of the Cb_b boundary load level on the border between the non-hysteresis region and the hysteresis region. Specifically, the Cb_b boundary load level is expressed by the following formula (11) and formula (12), using θι and 02.
Cb_b = (02B-02L) / (02H-02L) (11)
Cb_b = (0ih-0ib) / (0ih-0il) (12) [00141] Control device 14 updates the non-hysteresis region, storing the identified non-hysteresis region specified by the Cb_b boundary load level in memory 28 as a new region of non-hysteresis. When estimating and updating the region of non-hysteresis at the current moment in each aging deterioration estimate in this way, it is possible to acquire the first and second open circuit voltage values Vo1, Vo2 and the integrated current value AAhi2, at an appropriate time (charge level). As a result, it is possible to further increase the accuracy of the estimate for battery aging deterioration 12, and to obtain the estimation opportunity more safely.
[00142] In Formula (11) and Formula (12), the border load level Cb_b is estimated from the local load level 01 or 02. However, the SOC-OCV curve can be evaluated from the potentials positive and negative open circuit after deterioration, and the Cb_b boundary load level can be assessed from the SOC-OCV curve. [00143] FIG. 19 is a flow chart showing an example of a non-hysteresis region estimation routine. The routine for estimating the non-hysteresis region in FIG. 19 is premised on execution after the deterioration estimation routine shown in FIG. 11. Consequently, the routine of estimating the region of non-hysteresis is
Petition 870180031862, of 04/19/2018, p. 169/219
58/60 is based on the premise that the SOC-OCV curve after the aging deterioration of battery 12 (the SOC-OCV curve at the present time), that is, OCVdis and OCVch after the deterioration was obtained.
[00144] When Vdis [n] is a voltage indicated by OCV dis at the load level Cb = n, Vch [n] is a voltage indicated by OCV ch at the load level Cb = n and AVdef is a prescribed threshold value, the device Control 14 searches for the value of n that satisfies (| Vdis [n] -Vch [n] | <AVdef), while sequentially changing the value of the load level Cb = n (S312, S314). The initial value for the survey can be a value resulting from subtracting a predetermined margin α from the Cb_b boundary load level obtained at the time of the last estimate of the non-hysteresis region (S310). Whether the Cb_b border load level increases or decreases after deterioration depends on the battery's characteristic. Consequently, setting the predetermined margin α to a positive value or a negative value can be determined depending on the battery characteristic. The initial search value is not limited to this and can be another value, for example, a predetermined fixed value. When the value n that satisfies (| Vdis [n] -Vch [n] | <AVdef) is found as a result of the search, the value n is stored in memory 28 as a new boundary load level Cb_b (S316).
[00145] As is obvious from the description above, the battery system 10 disclosed in the present specification acquires the necessary parameters for the estimation of deterioration in aging of the battery 12, in the region of non-hysteresis. As a result, it is possible to estimate the aging deterioration of battery 12 with accuracy and ease, without any influence from hysteresis. As long as the parameters needed to estimate aging deterioration are acquired in the region of non-hysteresis, other constituents can be appropriately modified.
Petition 870180031862, of 04/19/2018, p. 170/219
59/60 [00146] For example, in the description above, only open circuit voltage values Vo1, Vo2 at two points and the integrated current value AAhi2 between the two points are acquired as parameters to be used for the deterioration estimate in aging. However, open circuit voltage values Vo at more points and integrated current values AAh between the most points can be acquired, as long as the parameters are in the non-hysteresis region. [00147] The present specification exemplifies the battery 12 having the active material of the negative electrode that contains a material of silicon and graphite. However, the technology disclosed in the present specification can be applied to another type of secondary battery, provided that the secondary battery partially has significant hysteresis. For example, the technology disclosed in the present specification can be applied to a secondary lithium-ion battery that has a negative electrode active material that contains a material of silicon and lithium titanate. In the case of the secondary lithium-ion battery that contains a material of silicon and lithium titanate, it is known that a hysteresis appears in a region of high SOC. Consequently, in the case of using a secondary lithium ion battery, it is only necessary to establish the region of non-hysteresis for a region of low SOC and to use parameters Vo, AAh acquired in the region of low SOC (region of non-hysteresis) to estimate the deterioration in battery aging. In addition, the technology disclosed in the present specification is not limited to the secondary lithium ion battery and can be applied to another type of secondary battery, such as a nickel-hydrogen secondary battery.
[00148] SOC-OCV hysteresis easily appears in a battery that has an active material that contains a material with a large change in volume (expansion or contraction). Examples of the negative electrode material include lithium alloy compounds, such as
Petition 870180031862, of 04/19/2018, p. 171/219
60/60 silicon (Si, SiO and the like), tin compounds (Sn, SnO and the like), germanium compounds and lead compounds. Generally, the volume change of the graphite to be used as the negative electrode material of the lithium ion battery is approximately 10%. The material with a large change in volume that causes SOC-OCV hysteresis can be considered, for example, as a material with a greater change in volume than graphite (a material with a change in volume greater than 10%).
[00149] Alternatively, a conversion material (for example, CoO, FeO, NiO, Fe2O3 or the like) exemplified in Formula (13) below, can be used as the negative electrode material. In Formula (13), M represents a transition metal and X represents O, F, N, S or similar.
nLi ⁺ + ne '+ M ^{n +} X _m θ M + nLiX _m / n (13) [00150] In addition, a conversion material such as FeF3 can be used on the positive electrode. The present specification exemplifies the case where SOC-OCV hysteresis is caused by the negative electrode material. However, the technology disclosed in the present specification can be applied even in the case where hysteresis is caused by the positive electrode material.
Petition 870180031862, of 04/19/2018, p. 172/219
1/5

权利要求:
Claims (10)
[1]
1. Battery system (10) that is equipped in a vehicle (100), the battery system (10) characterized by the fact that it comprises:
a battery (12) configured to be charged and discharged, the battery (12) being equipped in the vehicle (100), a battery charge level range (12) that includes a hysteresis region and a non-hysteresis region, the hysteresis region being a charge level range where significant hysteresis occurs, with hysteresis being significant hysteresis in which open circuit voltage values in relation to a battery charge level (12) after charging continues and after continuation of discharge are different from each other by a predetermined value or more, the region of non-hysteresis being a range of charge level where significant hysteresis does not occur;
a voltage detector (22) configured to detect a battery voltage (12) as a detected voltage value (Vb);
a current detector (20) configured to detect a current flowing through the battery (12) as a detected current value (Ib); and an electronic control unit (14) configured to control the charge and discharge of the battery (12), the electronic control unit (14) being configured to estimate a deterioration in battery aging (12) based on a value of open circuit voltage (Vo; Vo1, Vo2) which is calculated from the detected voltage value and an integrated current value (AAh; AAhi2) calculated from the detected current value, and the electronic control unit (14) being configured to estimate the aging deterioration of the battery (12) based on the open circuit voltage value (Vo; Vo1, Vo2) and the integrated current value (AAh; AAhi2) that are calculated when the battery charge level ( 12) is in the region of non-hysteresis.
Petition 870180031862, of 04/19/2018, p. 107/219
[2]
2/5
Battery system (10) according to claim 1, characterized in that the open circuit voltage value includes a first open circuit voltage value (Vo1) and a second open circuit voltage value (Vo2) that are acquired in the non-hysteresis region, the integrated current value (AAhi ₂ ) is a value resulting from the integration of the detected current value (Ib) until the open circuit voltage value (Vo) changes to the second value of open circuit voltage (Vo2) after the open circuit voltage (Vo) value becomes the first open circuit voltage value (Vo1), and the electronic control unit (14) is configured to estimate, as a characteristic that indicates aging deterioration, at least one of the battery's full charge capacity (12) at a current time and a characteristic of changing the open circuit voltage value in relation to the charge level, based on the first voltage value open circuit (Vo 1), the second open circuit voltage value (Vo2) and the integrated current value (AAhi ₂ ).
[3]
Battery system (10) according to claim 2, characterized by the fact that it also includes a charger (16) configured to charge the battery (12) while the vehicle (100) is stopped, in which the electronic control unit (14) is configured to temporarily interrupt the battery charge (12) with the charger (16) when the battery charge level (12) reaches a first charge level (Cb1) or a second charge level (Cb2) on non-hysteresis region in the middle of the battery charge (12) with the charger (16) and acquire the detected voltage value that is obtained during a charge stop period, as one of the first open circuit voltage values (Vo1) and the second open circuit voltage value (Vo2).
[4]
4. Battery system (10) according to claim 3,
Petition 870180031862, of 04/19/2018, p. 108/219
3/5 characterized by the fact that the electronic control unit (14) is configured to acquire two open circuit voltage values that are acquired in moments when the battery charge level (12) is in the region of non-hysteresis and the values open circuit voltage values are available as the first open circuit voltage value (Vo1) and the second open circuit voltage value (Vo2) during vehicle energization.
[5]
5. Battery system (10) according to claim 3, characterized in that the electronic control unit (14) is configured to control the battery charge and discharge (12) so that the battery charge level (12) transition to the non-hysteresis region and acquire the first open circuit voltage value (Vo1), the second open circuit voltage value (Vo2) and the integrated current value (AAhi2), when a time has elapsed since a last estimate of deterioration in aging is equal to or greater than a prescribed reference time.
[6]
6. Battery system (10) according to any one of claims 1 to 5, characterized in that the electronic control unit (14) is configured to:
estimate at least one characteristic of the change in the value of the open circuit voltage (Vo) in relation to the load level, as a characteristic that indicates deterioration in aging;
estimate the load level range that is the non-hysteresis region, based on the estimated change characteristic of the open circuit voltage (Vo) value in relation to the load level; and update the non-hysteresis region based on the estimated load range interval.
[7]
7. Battery system (10) according to claim 6,
Petition 870180031862, of 04/19/2018, p. 109/219
4/5 characterized by the fact that the electronic control unit (14) is configured to update the load level in an instant of acquisition of the open circuit voltage value (Vo) and the integrated current value (AAh) that are used for one of the aging deterioration estimates and a load level range, along with the update of the non-hysteresis region.
[8]
Battery system (10) according to any one of claims 1 to 7, characterized in that the battery (12) is a secondary lithium-ion battery that has a negative electrode active material that contains at least one material silicon and graphite; and the charge level range of the non-hysteresis region is higher in the charge level than the charge level range of the hysteresis region.
[9]
Battery system (10) according to one of claims 1 to 8, characterized in that the battery (12) is a secondary lithium-ion battery that has an active negative electrode material that contains at least one silicon and lithium titanate; and the charge level range of the non-hysteresis region is higher in the charge level than a charge level range of a hysteresis region.
[10]
10. Aging deterioration estimation method for a battery system (10), a battery charge level range (12) that includes a hysteresis region and a non-hysteresis region, the hysteresis region being a range of charge where significant hysteresis occurs, significant hysteresis being hysteresis in which the open circuit voltage values in relation to a battery charge level (12) after the charging continues and after the discharge continues are different from one another. predetermined value or more, the non-hysteresis region being a battery charge level range (12) where significant hysteresis does not occur, the system
Petition 870180031862, of 04/19/2018, p. 110/219
5/5 battery (10) including an electronic control unit (14), the aging deterioration estimation method characterized by the fact that it comprises:
acquire through the electronic control unit (14), parameters from which open circuit voltage values at two points (Vo1, Vo2) and an integrated current value between the two points (AAhi ₂ ) are calculated when the level battery charge is in the region of non-hysteresis; and estimate, using the electronic control unit (14), a deterioration in the aging of the battery based on the acquired open circuit voltage values (Vo1, Vo2) and the acquired integrated current value (AAhi ₂ ).
Petition 870180031862, of 04/19/2018, p. 111/219
1/21

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法律状态:
2018-11-21| B03A| Publication of a patent application or of a certificate of addition of invention [chapter 3.1 patent gazette]|

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JP2017-088148|2017-04-27|

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JP2017088148A|JP6939057B2|2017-04-27|2017-04-27|In-vehicle battery system and battery aging estimation method|

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