JP5687584B2 - Lithium-ion battery condition measurement device - Google Patents

Description

  The present invention relates to a state measuring apparatus for a secondary battery. In particular, the present invention relates to a state measuring apparatus capable of measuring a deterioration state of a secondary battery.

  It has been conventionally known that a salt concentration distribution is generated between electrodes and within an electrode surface when a secondary battery is discharged or charged, thereby increasing the internal resistance of the secondary battery. Furthermore, it is known that this salt concentration distribution becomes conspicuous during large current discharge or large current charge, and the internal resistance increases remarkably. This phenomenon is hereinafter referred to as “high-rate degradation” because the internal resistance is remarkably increased by charging and discharging with a large current.

  It is known that this high rate degradation is reversible and can be eliminated. For example, when high-rate deterioration occurs due to large current discharge, it is known that high-rate deterioration can be eliminated by large current charging. Therefore, for example, in Patent Document 1, the degree of high-rate deterioration is estimated, and the progress of high-rate deterioration is suppressed or the processing for eliminating high-rate deterioration is performed according to the degree of progress of high-rate deterioration.

  For example, Patent Document 1 uses a battery model that models the behavior of an active material and ions of a secondary battery in estimating the progress of high-rate degradation. In the battery model in Patent Document 1, various formulas are established under the assumption that (1) the influence of the salt concentration distribution is small, and (2) no parameter change occurs due to aging, and the secondary order is based on this formula. The terminal voltage value and current value of the battery are estimated. An estimated voltage value is obtained by substituting the measured current value of the secondary battery into this battery model. Further, the difference between the estimated voltage value and the measured voltage value of the secondary battery is obtained. FIG. 29 shows a voltage characteristic 100 during a large current discharge by a battery model (hereinafter simply referred to as a voltage characteristic by a battery model) and, in other words, when a large current discharge is repeatedly performed on a secondary battery in an initial state. A voltage characteristic 102 when high-rate deterioration occurs is shown. There is a difference between the two voltage values, and this difference is considered to be caused by high-rate deterioration. Therefore, it is possible to estimate the progress of the high rate deterioration based on this difference. In Patent Document 1, estimation based on a current error is also possible.

  Here, a comparison between a battery model and a secondary battery that has passed a predetermined period from the initial state will be considered. The deterioration of the secondary battery is caused not only by the high rate deterioration but also by so-called aging deterioration. Aging deterioration, also called wear deterioration, refers to a phenomenon in which internal resistance increases with the passage of the secondary battery's usage period, and is basically irreversible (difficult to resolve) unlike high-rate deterioration. It is. Since the battery model described above assumes a secondary battery in which parameter change due to aging does not occur, the difference between the estimated voltage value by the battery model and the measured voltage value of the aging secondary battery is a high rate. In addition to deterioration, it is thought to be caused by aging. Therefore, in Patent Document 1, a correction process considering aging deterioration is performed on the battery model to separate the aging deterioration from the high rate deterioration, and then the degree of progress of the high rate deterioration is estimated.

  Referring again to FIG. 29, there is almost no difference between the voltage drop pattern 100 by the battery model and the voltage drop pattern 102 at the time of large current discharge immediately after the start of discharge, and the difference between the two as the discharge time elapses. It is understood that it will open. In other words, at the initial stage of discharge, the influence of high rate deterioration is so small that it can be ignored.

  On the other hand, the influence of aging deterioration appears remarkably from the initial stage of discharge. As shown in FIG. 30, in the voltage drop pattern 104 when the large current discharge is repeatedly performed on the aged battery, the voltage drop starts from a position where the voltage drop pattern 100 falls below the voltage drop pattern 100 by the battery model. . This difference in depression is thought to be due to aging.

  Based on the difference in behavior between the high rate deterioration and the aging deterioration at the initial stage of the discharge, in Patent Document 1, a process for removing the influence of the aging deterioration according to the difference at the initial stage of the discharge is performed as shown in FIG. ing. Specifically, the resistance change rate corresponding to the difference between the voltage drop due to the battery model and the measured voltage drop of the secondary battery at the initial stage of discharge is obtained, and the resistance change rate is reflected in the process of calculating the estimated voltage value of the battery model. ing. The rate of change in resistance is updated each time the battery model and the actual voltage value of the secondary battery are plotted. When the discharge further progresses and the voltage drop of the actual secondary battery becomes steep, the update of the resistance change rate is stopped because the influence of the high rate deterioration starts to appear.

JP 2010-60406 A

  Incidentally, some secondary batteries show a voltage drop pattern different from those shown in FIGS. FIG. 32 shows the voltage drop pattern 106 estimated by the battery model, the voltage drop pattern 108 at the time of large current discharge for a secondary battery that has deteriorated over time, and the large current discharge for a secondary battery in which high-rate deterioration has occurred simultaneously with the deterioration over time. A voltage drop pattern 110 at the time is illustrated. Comparing the three, the degree of voltage drop differs between the three at the initial stage of discharge, and thereafter the voltage drops while drawing an almost equal curve. Therefore, it is difficult to distinguish whether the voltage drop pattern 110 has further deteriorated over time with respect to the voltage drop pattern 108 or whether high-rate deterioration has occurred. That is, when a difference occurs between the battery model and the actual measurement value, it is difficult to determine whether the cause of the difference is due to aging deterioration or high rate deterioration. When such a secondary battery is used as a measurement target, if the aging deterioration correction is performed under the condition that the voltage drop is corrected from the initial stage of discharge until the voltage drop becomes steep as in the conventional case, the high rate deterioration is added in addition to the aging deterioration component. In some cases, components are corrected, and it is difficult to accurately estimate high-rate degradation. Accordingly, an object of the present invention is to provide a state measuring apparatus for a secondary battery that can accurately estimate high-rate degradation even for a voltage effect pattern in which the influence of high-rate degradation appears from the beginning of discharge.

The present invention relates to measuring apparatus of the lithium-ion蓄 batteries. The apparatus includes a measuring unit for measuring a terminal voltage and current values of the lithium ion蓄 battery, the internal resistance increase rate due to aging and high-rate deterioration of the lithium ion蓄 battery based on the battery model for the lithium-ion蓄 batteries a calculation unit calculating for, and the internal resistance increase rate of the calculating unit is determined, pre-acquired from the difference between the measured value of the internal resistance increase rate due to aging of lithium-ion蓄 battery, the internal resistance increase rate due to high-rate deterioration A correction unit to be obtained.

The present invention relates to measuring apparatus of the lithium-ion蓄 batteries. The apparatus calculator for determining a measurement unit that measures a terminal voltage value and the current value of the lithium ion蓄 battery, the internal resistance increase rate due to aging and high-rate deterioration of the lithium-ion battery from the current value and the terminal voltage value And, from the difference between the internal resistance increase rate obtained by the calculation unit and the measured value of the internal resistance increase rate due to aging of the lithium ion storage battery obtained in advance, a correction unit for obtaining the internal resistance increase rate due to high rate deterioration, Is provided.

The present invention relates to measuring apparatus of the lithium-ion蓄 batteries. The apparatus includes a measuring unit for measuring a terminal voltage and current values of the lithium ion蓄 battery, a calculation unit for determining the internal resistance due to aging and high-rate deterioration of the lithium-ion battery from the current value and the terminal voltage value A correction unit that obtains an internal resistance value due to high-rate degradation from a difference between the internal resistance value obtained by the calculation unit and a measured value of the internal resistance of the lithium ion storage battery that is obtained in advance due to deterioration over time .

The present invention relates to measuring apparatus of the lithium-ion蓄 batteries. The apparatus calculates for calculating a measurement unit that measures a terminal voltage value and the current value of the lithium ion蓄 battery, the internal resistance increase rate due to aging and high-rate deterioration of the lithium-ion battery from the current value and the terminal voltage value And a determination value based on an actually measured value of the internal resistance increase rate of the lithium ion storage battery due to aged deterioration determined in advance, and whether or not the internal resistance increase rate determined by the calculation unit exceeds the determination value A determination unit for determining whether or not .

The present invention relates to measuring apparatus of the lithium-ion蓄 batteries. The apparatus calculating unit for calculating a measurement unit that measures a terminal voltage value and the current value of the lithium ion蓄 battery, the internal resistance due to aging and high-rate deterioration of the lithium-ion battery from the current value and the terminal voltage value And a determination value is set based on an actually measured value of the internal resistance of the lithium ion storage battery due to aged deterioration determined in advance, and it is determined whether the internal resistance value calculated by the calculation unit exceeds the determination value. A determination unit .

  According to the present invention, it is possible to estimate high-rate degradation with high accuracy even for voltage effect patterns in which high-rate degradation appears from the beginning of discharge.

It is a figure which illustrates the state measuring device of the secondary battery concerning this embodiment. It is a functional block diagram of a control part. It is a figure explaining the generation | occurrence | production principle of salt concentration distribution. It is a figure explaining the generation | occurrence | production principle of salt concentration distribution. It is a figure explaining the salt concentration distribution which generate | occur | produces in an electrode surface. It is a figure which illustrates the relationship between salt concentration distribution and internal resistance. It is a figure which illustrates an aged deterioration map. It is a figure explaining the estimation method of the resistance component by high-rate degradation. It is a figure explaining the estimation method of the resistance component by high-rate degradation. It is a figure explaining the calculation method of internal resistance and its increase rate using a battery model. It is a figure explaining the calculation method of internal resistance and its increase rate using a battery model. It is a figure explaining the calculation method of internal resistance and its increase rate using a battery model. It is a figure explaining the calculation method of internal resistance and its increase rate using a battery model. It is a figure explaining the calculation method of internal resistance and its increase rate using a battery model. It is a figure explaining the calculation method of internal resistance and its increase rate using a battery model. It is a figure explaining the calculation method of internal resistance and its increase rate using a battery model. It is a figure explaining the calculation method of internal resistance and its increase rate using a battery model. It is a figure explaining the calculation method of internal resistance and its increase rate using a battery model. It is a figure explaining the estimation method of the resistance component by high-rate degradation. It is a figure which illustrates the flowchart for performing the current limiting control of a secondary battery. It is a figure explaining a charging / discharging excessive parameter | index. It is a figure explaining the setting method of the upper limit of a current limitation. It is a figure explaining the setting method of the threshold value which performs an electric current limitation. It is a figure explaining the setting method of the threshold value which performs an electric current limitation. It is a figure explaining the setting method of the threshold value which performs an electric current limitation. It is a figure explaining the setting method of the threshold value which performs an electric current limitation. It is a figure explaining the setting method of the upper limit of a current limitation. It is a figure which illustrates the flowchart for performing the current limiting control of a secondary battery. It is a figure which illustrates the voltage characteristic of a secondary battery. It is a figure which illustrates the voltage characteristic of a secondary battery. It is a figure which illustrates the voltage characteristic of a secondary battery. It is a figure which illustrates the voltage characteristic of a secondary battery.

  A state measuring apparatus for a secondary battery according to this embodiment is illustrated in FIG. The state measuring device 10 includes a control unit 12, a voltage sensor 16, a current sensor 18, and a temperature sensor 20. The control unit 12 is electrically connected to the connection target 22, and the voltage sensor 16, the current sensor 18, and the temperature sensor 20 are electrically connected to the secondary battery 14.

  The state measuring apparatus 10 and the secondary battery 14 shown in FIG. 1 are mounted on a device that uses the secondary battery 14 as a power source. For example, it is mounted on a hybrid vehicle (HV), a plug-in hybrid vehicle (PHV), an electric vehicle (EV), or the like that uses the power of the secondary battery 14 as a drive source. In this case, the connection target 22 includes, for example, a DC / DC converter or an inverter that performs power conversion of the secondary battery 14 and supplies power to a rotating electrical machine (not shown).

The voltage sensor 16 is directly or indirectly connected to the positive output side and the negative output side of the secondary battery 14 and measures the terminal voltage of the secondary battery 14. The measured terminal voltage value V _b is sent to the control unit 12. The current sensor 18 is connected between the secondary battery 14 and the connection target 22 and measures the discharge current or the charge current of the secondary battery 14. The measured current value I _b is sent to the control unit 12. The temperature sensor 20 measures the temperature of the secondary battery 14 and sends the measured temperature _Tb to the control unit 12. The temperature measurement location may be one location or a plurality of locations. For example, when the secondary battery 14 is composed of a stack of a plurality of cells, the temperature of a predetermined number of cells may be measured and the average value may be sent to the control unit 12.

  The control unit 12 includes an arithmetic processing unit for calculating information and a storage unit for storing information. The arithmetic processing unit may be any device that can receive voltage value, current value, and temperature as input information and perform arithmetic processing, and includes, for example, a microcomputer. This microcomputer can be composed of, for example, an electronic control unit (ECU) mounted on a hybrid vehicle. Further, the storage unit may be any device capable of storing input information such as a high-rate deterioration estimation program, an aging deterioration map, and a voltage value, current value, and temperature, which will be described later. For example, ROM, RAM, EPROM, hard disk device, and the like. One or a plurality of combinations of these can be used.

  In estimating the high rate deterioration, the control unit 12 executes a plurality of functions. A schematic diagram showing the control unit 12 as a set of a plurality of functional blocks is shown in FIG. The control unit 12 includes a calculation unit 24, a correction unit 28, and a determination unit 30. A method of estimating the high rate deterioration by each of these functional blocks will be described later.

Moreover, the secondary battery 14 should just be a chemical battery which can be charged / discharged, for example, is comprised from a nickel hydride storage battery or a lithium ion storage battery. Here, the high rate deterioration of the secondary battery 14 will be described with reference to FIG. In FIG. 3, a lithium ion storage battery is used as an example of the secondary battery 14. LiPF ₆ is used as an example of the electrolytic solution. The electrolytic solution may be an organic electrolytic solution in which a lithium salt is dissolved. For example, LiBF ₄ may be used. FIG. 3 shows a schematic diagram in which solvation and the like are omitted in order to simplify the description.

  By generating a lithium salt concentration distribution within and between the electrodes of the secondary battery 14, the internal resistance of the secondary battery 14 increases. The occurrence of the salt concentration distribution is mainly caused by ion migration (transport number) when the secondary battery 14 is conducted. FIG. 3 shows a schematic diagram of the secondary battery 14 before conduction. Before conduction, the cations 34 and the anions 36 in the electrolytic solution 32 are distributed almost uniformly.

FIG. 4 illustrates the charging of the secondary battery 14. When the secondary battery 14 becomes conductive, cations 34 are released from the positive electrode 38 and the cations 34 are occluded in the negative electrode 40. Here, since the release amount of the cation 34 at the positive electrode 38 and the occlusion amount of the cation 34 at the negative electrode 40 are theoretically equal if the side reaction or the like is ignored, the amount of LiPF ₆ in the electrolytic solution 32 is the same as when the conduction is cut off. It doesn't change at the time of conduction. At this time, a salt concentration distribution (salt concentration gradient) is generated in the electrolytic solution 32 in accordance with the transport number. Further, the salt concentration distribution is generated not only between the electrodes but also within the surface of the electrode 39 as shown in FIG. In FIG. 5, the salt concentration at the end of the electrode 39 wound in a cylindrical shape is relatively high, and the salt concentration at the center of the electrode 39 is relatively low.

  The relationship between the salt concentration and the internal resistance of the secondary battery 14 is shown in FIG. As shown in this figure, the internal resistance varies depending on the salt concentration, and there exists an optimum concentration where the internal resistance takes the lowest value. In response to this, it is conceivable to adjust the concentration of the electrolytic solution to the optimum concentration. However, as described above, when the secondary battery becomes conductive, a salt concentration distribution is generated, and a region deviating from the optimum concentration is generated in the electrolytic solution. As a result, the internal resistance in the electrolyte increases. In this embodiment, this phenomenon of increase in internal resistance accompanying the occurrence of salt concentration distribution is called high-rate degradation.

  As understood from the fact that the salt concentration distribution is caused by ion migration (transport number), the salt concentration distribution is noticeable during large current discharge or large current charge (salt concentration gradient becomes steep). As a result, the progress of the high rate deterioration of the secondary battery 14 becomes remarkable, and the internal resistance increases. On the other hand, the salt concentration distribution is eliminated by flowing a current in the direction opposite to the current flow direction that caused the salt concentration distribution, and high-rate deterioration can be reduced. For example, when high rate deterioration occurs due to large current discharge, high rate deterioration can be eliminated by performing large current charging.

  Therefore, it is possible to suppress the increase in internal resistance by appropriately detecting and eliminating the high rate deterioration, and to suppress the voltage drop of the terminal voltage of the secondary battery 14. On the other hand, as described above, the increase in the internal resistance of the secondary battery 14 is caused not only by high-rate deterioration but also by aging deterioration. Aged deterioration refers to a phenomenon in which internal resistance increases with the passage of the use period of the secondary battery 14, and is caused by partial collapse (structural change) of the active material. Unlike the high-rate deterioration, the aging deterioration is an irreversible (difficult to solve) deterioration accumulated with the use of the secondary battery 14. The control unit 12 measures the internal resistance of the secondary battery 14 and estimates what percentage of the increase in the internal resistance is due to the high-rate deterioration, and performs a high-rate deterioration suppression process or a cancellation process according to the estimation result. It is determined whether or not to perform.

  The correction unit 28 (see FIG. 2) of the control unit 12 stores an actual measurement value of the increasing tendency of the internal resistance of the secondary battery 14 due to deterioration over time. Specifically, the correction unit 28 stores the transition of the internal resistance value and the internal resistance increase rate with respect to the total time (total time) from the initial state of the secondary battery 14 as a function or a map (table). Note that the initial state refers to a reference time point for detecting high-rate deterioration of the secondary battery 14. For example, measurement of a new state of the secondary battery 14 and voltage, current, and temperature of the secondary battery 14 is started. It points to the time. Also, instead of taking the total usage time of the secondary battery 14 on the time axis, the reduction rate of the fully charged capacity of the secondary battery 14, the temperature history of the secondary battery 14, the accumulated current amount of the secondary battery 14, etc. It may be used.

  Here, acquisition of a map (hereinafter referred to as an aging deterioration map) stored in the correction unit 28 in which an actual measurement value of an increase tendency of internal resistance due to aging deterioration is recorded will be described. When acquiring an aged deterioration map, the high-rate deterioration is not caused, or the increase in internal resistance due to the high-rate deterioration is negligible compared to when the secondary battery 14 is actually used in a vehicle. The internal resistance of the secondary battery 14 is measured in advance. For example, the internal resistance of the secondary battery 14 is measured without performing a large current discharge and a large current charge. Specifically, when the capacity at the time of full charge of the secondary battery in the initial state is expressed by C [Ah], charging and discharging with a constant current is performed at a discharge rate of 1 C [A] or less, for example, 0.1 C [A]. . Alternatively, when charging / discharging with a large current, large current charging and large current discharging are performed equally. For example, when discharging at 2C [A] is performed for 30 seconds, similarly charging at 2C [A] is performed for 30 seconds. As a matter of course, the secondary battery 14 for obtaining the aged deterioration map is of the same type as the secondary battery 14 mounted on the vehicle.

  One discharge and one charge are regarded as one cycle, and IV characteristics are obtained over a plurality of cycles. For example, a cycle (for example, 5000 cycles) until the end of the life of the secondary battery 14 is divided into a plurality of cycle periods (for example, 100 cycles), an endurance test is performed for each cycle period, and IV characteristics are obtained each time. The IV characteristic is the slope of the approximate line or the rate of increase of the approximate curve when the current value and the voltage value are plotted on a plane composed of the current value axis and the voltage value axis, and is regarded as the internal resistance of the secondary battery 14. be able to. Therefore, the increase rate of the internal resistance can be obtained by obtaining the increase rate of the IV characteristic. In calculating the internal resistance increase rate, the increase rate from the initial state may be obtained, or the increase rate from an arbitrary time point may be obtained.

  Further, when using the accumulated current amount [Ah] instead of the total usage time of the secondary battery 14 as the time axis of the aging deterioration map, the accumulated current amount is divided into a plurality of sections, for example, every 0.5 Ah. It is preferable that the IV characteristic is obtained by dividing into ranges and plotting the current value and the voltage value in each section. Similarly, it is preferable that the capacity reduction rate [%] at full charge is similarly divided into a plurality of sections to obtain IV characteristics in the sections.

  The temperature history is calculated as follows, for example. The secondary battery 14 has temperature characteristics, and it is known that the degree of progress of deterioration changes depending on the temperature. Therefore, a temperature with a relatively slow progress (for example, 25 ° C.) is converted into a temperature parameter with a relatively small weight (for example, 1), and a temperature with a relatively fast progress of the degraded state (for example, 40 ° C.). The temperature parameter is converted into a relatively heavy temperature parameter (for example, 10), and the internal resistance of the secondary battery 14 with respect to the integrated value of the temperature parameter from the initial state is measured. Even in this case, it is preferable to divide the integrated value of the temperature parameter into a plurality of sections and obtain the IV characteristics in the section.

  Since the internal resistance of the secondary battery 14 varies depending on the temperature and the charging rate (SOC), the sampling point of the current value-voltage value as described above is used in the total use time section, the capacity reduction rate section at full charge, or the temperature parameter. After grouping for each section, the sampling points of current value-voltage value in each section are further divided into predetermined temperature sections and predetermined SOC sections, and the IV characteristics and the rate of increase are divided for each group of distributed sampling points. Is preferably obtained. In calculating the increase rate, it is preferable to use the IV characteristics in the initial state in the same section as the SOC section and the temperature section in which the IV characteristics are calculated. FIG. 7 shows a plurality of aging deterioration maps according to usage time, temperature, and SOC of the secondary battery 14. In addition, although the resistance increase rate is shown in the aging deterioration map shown in FIG. 7, the internal resistance value (IV characteristic value) itself may be stored instead of or in addition to this. Further, instead of storing in the state of the map (table), a relational expression may be acquired by the least square method or the like and stored in the correction unit 28.

  The high rate deterioration component in the internal resistance of the secondary battery 14 is estimated using the aged deterioration map acquired as described above. As the high-rate deterioration estimation means, mainly (1) the internal resistance value or internal resistance increase rate calculated based on the voltage drop from the relaxed state of the secondary battery 14 and the internal resistance value or internal resistance increase rate in the aging deterioration map (2) Comparison between internal resistance value or internal resistance increase rate calculated based on current value and voltage value of secondary battery 14 in operation and internal resistance value or internal resistance increase rate in the aging deterioration map ( 3) There are three types of means: comparison between the internal resistance value or internal resistance increase rate calculated by the battery model and the internal resistance value or internal resistance increase rate in the aging deterioration map. Each means will be described below. Further, unless otherwise specified in the following description, the aging deterioration map assumes the total elapsed time (total use time) from the initial state of the secondary battery 14 on the time axis.

(1) Comparison between the internal resistance value or internal resistance increase rate calculated based on the voltage drop from the relaxed state of the secondary battery 14 and the internal resistance value or internal resistance increase rate in the aging deterioration map 24 acquires the voltage value V _b from the voltage sensor 16 and the current value I _b from the current sensor 18. In this means, the temporal change of the current value and the voltage value is measured from the state where the secondary battery 14 is relaxed, that is, the state where the current is not flowing and the voltage value is stable (for example, when the vehicle is stopped). By measuring the open voltage (OCV) when the secondary battery 14 is completely relaxed and then measuring the voltage drop when the secondary battery 14 starts to flow a constant value from the fully relaxed state for a predetermined time. , IV characteristics can be measured with high accuracy. In addition, when the vehicle is a so-called plug-in hybrid vehicle, the IV characteristics can be obtained with high accuracy by passing a constant current of a desired pattern during charging or the like and measuring a change in voltage value with time. Is possible.

Furthermore, the calculation unit 24 groups the acquired voltage value V _b and current value I _b . Specifically, the sampling points of the current value-voltage value are assigned for each predetermined SOC interval and temperature interval within a predetermined time interval. The distribution based on the time interval is performed based on a timer (not shown) that can transmit time information to the calculation unit 24. Further, the sorting based on the SOC section is performed based on the accumulated current amount of the secondary battery 14 or the like. Further sorting based on the temperature interval is based on the temperature T _b sent from the temperature sensor 20.

  The calculation unit 24 obtains IV characteristics, that is, internal resistance values from sampling points in a specific time interval, SOC interval, and temperature interval. When taking the internal resistance increase rate as a reference, the internal resistance value in the initial state of the secondary battery 14 corresponding to the SOC interval and the temperature interval for which the internal resistance value is obtained is stored in the storage unit in the control unit 12 over time. Called from the deterioration map, and calculates the internal resistance increase rate from the initial state. Here, instead of the initial state, an arbitrary time point may be set as the reference time for calculating the increase rate.

  The internal resistance value or the internal resistance increase rate calculated by the calculation unit 24 (hereinafter referred to as the internal resistance value or the internal resistance increase rate by the calculation unit) is sent to the correction unit 28. The correction unit 28 calls the aging deterioration map from the storage unit of the control unit 12. Further, the correction unit 28 includes an internal resistance value corresponding to the time interval, SOC interval, and temperature interval of the internal resistance value by the calculation unit, or an internal resistance corresponding to the time interval, SOC interval, and temperature interval of the internal resistance increase rate by the calculation unit. The increase rate is extracted from the aging deterioration map.

  As shown in FIG. 8, the correction unit 28 subtracts the internal resistance value due to aging from the internal resistance value by the calculation unit or the internal resistance increase rate due to aging from the internal resistance increase rate by the calculation unit. FIG. 8 illustrates a state in which the internal resistance increase rate 42 according to the aging deterioration map is subtracted from the internal resistance increase rate 41 by the calculation unit. As described above, the internal resistance value (or internal resistance increase rate) by the calculation unit overlaps the internal resistance value (or internal resistance increase rate) due to aging degradation and the internal resistance value (or internal resistance increase rate) due to high-rate degradation. It is thought that. On the other hand, it is considered that the internal resistance value (or internal resistance increase rate) based on the aging deterioration map mainly indicates the internal resistance value (or internal resistance increase rate) due to aging deterioration. Therefore, by obtaining the difference between the internal resistance value by the calculation unit and the internal resistance value by the aging deterioration map, or the difference between the internal resistance increase rate by the calculation unit and the internal resistance increase rate by the aging deterioration map, The rate of increase in internal resistance can be estimated.

  In addition, when using the battery capacity reduction rate at the time of full charge instead of using the total time of the secondary battery 14 as the horizontal axis, an accurate battery capacity reduction rate is obtained from the accumulated current amount of the secondary battery 14 by the current sensor 18 or the like. It can be difficult. For example, the battery capacity [Ah] at the time of full charge can be obtained from the accumulated current amount from the time of full charge to the end-of-discharge voltage, and therefore the reduction rate of the battery capacity at the time of full charge can be obtained. During driving of the vehicle, charging may be started before reaching the final discharge voltage, or discharging may be started before reaching full charge. In such a case, it is possible to estimate by using a model formula of a full charge capacity as described in, for example, Japanese Patent Application Laid-Open No. 2010-60384.

(2) Comparison of internal resistance value or internal resistance increase rate calculated based on current value and voltage value of secondary battery 14 in operation and internal resistance value or internal resistance increase rate in aging deterioration map (1 ), The internal resistance value and the rate of increase in internal resistance are obtained with the secondary battery 14 in a relaxed state as a base point. Instead, the internal resistance value and the internal resistance value are calculated from the current value and voltage value of the operating secondary battery 14. The internal resistance increase rate may be obtained. The calculation unit 24 measures the current value and the voltage value of the secondary battery 14 during the period when the secondary battery 14 is charged / discharged, such as when the vehicle is running, and determines the IV characteristic (internal resistance) from the measured current value and voltage value. Value). In calculating the IV characteristic, the current value and the voltage value in the time interval, the SOC interval, and the temperature interval determined as in (1) are extracted, and the IV characteristic is obtained based on the extracted current value and voltage value. The correction unit 28 calls the internal resistance value of the aging deterioration map in the time interval, SOC interval, and temperature interval corresponding to the calculated IV characteristic. Further, as shown in FIG. 9, the correction unit 28 obtains a difference between the IV characteristic 44 (internal resistance value) by the calculation unit and the internal resistance value 46 in the aging deterioration map. Specifically, the difference between the slopes of the respective straight lines is obtained. Since this difference in inclination is considered to represent high-rate deterioration, it is possible to grasp the increasing tendency of high-rate deterioration by monitoring the difference in inclination by the determination unit 30.

  Further, instead of comparing the internal resistance value by the calculation unit and the internal resistance value by the aging deterioration map, the internal resistance increase rate by the calculation unit and the internal resistance increase rate of the aging deterioration map may be compared in the same manner as in (1). Good. That is, the internal resistance value in the initial state (or any time point) of the secondary battery 14 corresponding to the time interval, the SOC interval, and the temperature interval for which the internal resistance value is obtained by the calculation unit is stored in the storage unit in the control unit 12. The internal resistance increase rate is calculated by calling from the aged deterioration map and dividing the internal resistance value by the calculation unit by the internal resistance value in the initial state. On the other hand, the internal resistance increase rate corresponding to the SOC interval and the temperature interval for which the internal resistance value is obtained by the calculation unit is extracted from the aging deterioration map. Furthermore, the respective internal resistance increase rates obtained are compared.

(3) Comparison of the internal resistance value or internal resistance increase rate calculated by the battery model and the internal resistance value or internal resistance increase rate in the aging deterioration map This model models the behavior of active materials and ions in the secondary battery Use the same battery model. FIG. 10 is a conceptual diagram illustrating an outline of the internal configuration of the secondary battery expressed by a battery model. Secondary battery 14 includes a negative electrode 40, a separator 114, and a positive electrode 38. The separator 114 is configured by, for example, infiltrating an electrolytic solution into a resin provided between the negative electrode 40 and the positive electrode 38.

Each of the negative electrode 40 and the positive electrode 38 is composed of an assembly of spherical active materials 118. When the secondary battery 14 is discharged, a chemical reaction that releases lithium ions Li ⁺ and electrons e ⁻ is performed on the interface of the active material 118 of the negative electrode 40. On the other hand, a chemical reaction that absorbs lithium ions Li ⁺ and electrons e ⁻ is performed on the interface of the active material 118 of the positive electrode 38. When the secondary battery 14 is charged, a reaction opposite to the above reaction is performed with respect to the emission and absorption of the electron e ⁻ .

The negative electrode 40 is provided with a current collector 113 that absorbs electrons e ⁻ , and the positive electrode 38 is provided with a current collector 116 that emits electrons e ⁻ . The negative current collector 113 is typically made of copper, and the positive current collector 116 is typically made of aluminum. The current collector 113 is provided with a negative electrode terminal, and the current collector 116 is provided with a positive electrode terminal. By the exchange of lithium ions Li ⁺ through the separator 114, the secondary battery 14 is charged and discharged, and a charging current or a discharging current is generated.

  That is, the charge / discharge state inside the secondary battery varies depending on the lithium concentration distribution in the active material 118 of the electrodes (the negative electrode 40 and the positive electrode 38). This lithium corresponds to a reaction participating substance in the lithium ion battery.

Pure electric resistance (pure resistance) Rd against the movement of electrons e ⁻ at the negative electrode 40 and the positive electrode 38 and a charge transfer resistance (reaction resistance) Rr that acts equivalently as an electric resistance when a reaction current is generated at the active material interface. The combination is equivalent to the internal resistance (DC resistance) when the secondary battery 14 is viewed macroscopically. This macro internal resistance is also referred to as DC resistance Ra below. Further, the diffusion of lithium Li in the active material 118 is governed by the diffusion coefficient D _s . That is, the diffusion coefficient D _s is a parameter indicating the magnitude of the diffusion resistance.

  Next, an example of the battery model 125 will be described. In the battery model described here, a model that ignores the influence is constructed in consideration of the small influence of the electric double layer capacitor at normal temperature. Furthermore, the battery model is defined as a model per unit electrode plate area of the electrode. By using a model per unit electrode plate area of the electrode, the model can be generalized to the design capacity.

  First, the battery voltage V that is the output voltage of the secondary battery 14 is as follows using the battery temperature T, the battery current I, the open circuit voltage (OCV) U, and the macro DC resistance Ra of the entire secondary battery 14 described above. (1) (voltage equation) is established. Here, the battery current I represents a current value per unit electrode plate area. That is, when the battery current flowing through the positive and negative terminals (current value measurable by an ammeter) is Ib and the double-sided electrode plate area of the battery is S, the battery current I is defined as I = Ib / S. Hereinafter, “current” and “current estimation value” described in the battery model refer to the current per unit electrode plate area unless otherwise specified.

θ ₁ and θ ₂ represent local SOC on the surface of the positive electrode active material and local SOC on the surface of the negative electrode active material, respectively. The open circuit voltage OCV is expressed as a potential difference between the positive electrode open potential U ₁ and the negative electrode open potential U ₂ .

As shown in FIG. 11, the positive electrode open-circuit potential U ₁ and the negative electrode open-circuit potential U ₂ each have a characteristic that varies depending on local SOC [theta] ₁ and local SOC [theta] _1. Therefore, in the initial state of the secondary battery 14, by measuring the relationship between the local SOC θ ₁ and the positive electrode open potential U ₁ and the relationship between the local SOC θ ₂ and the negative electrode open potential U ₂ , the local SOC θ ₁ it is possible to create a positive open-circuit potential U ₁ (θ ₁₎ variation characteristics and characteristic map that prestores change characteristics of negative electrode open-circuit potential U ₂ (θ ₂₎ with respect to changes in the local SOC [theta] ₂ of the relative change.

Also, DC resistance R _a is local SOC (θ _1), having a characteristic that varies according to changes in the local SOC (θ ₂₎ and battery temperature. That is, the DC resistance _Ra is shown as a function of the SOC (more specifically, the local SOC (θ ₁ , θ ₂ )) and the battery temperature T. Thus, based on the measured experimental results in the initial state of the secondary battery 14, it is possible to pre-create the initial state value map 131 of DC resistance R _a as shown in FIG. 13.

Referring to FIG. 13, in initial state value map 131, the SOC range obtained by dividing 0 (%) to 100 (%) into a plurality of temperatures, and the temperature range obtained by dividing −Ty (° C.) to Tx (° C.) into a plurality of for each region defined by the combination of the initial state value of the DC resistance R _a is stored. Since these plural regions coincide with the learning category of the parameter change rate described later, they are also referred to as “learning regions”.

Referring to FIG. 10 again, as described above, in the spherical active material models of the negative electrode 40 and the positive electrode 38, the local SOC θ _i (i = 1, 2) on the active material surface (interface with the electrolyte) is It is defined by the following equation (2). As in the case of the local SOC θ _i , in the following description, the subscript represented by i is defined as a positive electrode when 1 and a negative electrode when 2.

In the formula (2), c _{se, i} is the average lithium concentration at the active material interface, and c _{s, i, max} is the critical lithium concentration in the active material.

In the active material handled by the spherical model, the lithium concentration c _{s, j} has a distribution in the radial direction. That is, the lithium concentration distribution in the active material assumed to be spherical is defined by the diffusion equation of the polar coordinate system shown in the following equation (3).

In the formula (3), D _{s, i} is a diffusion coefficient of lithium in the active material. As shown in FIG. 14, the diffusion coefficient D _{s, i} has a characteristic that varies depending on the SOC and the battery temperature. Hereinafter, when D _{s, i} (i = 1, 2) is generically referred to, it is also simply referred to as a diffusion coefficient D _s .

For the diffusion coefficient D _s, as with DC resistance R _a of the above, based on the measured experimental results in the initial state of the secondary battery 14, it is possible to pre-create the initial state value map 132 as shown in FIG. 14 .

Referring to FIG. 14, in the initial state value map 132, the initial state value of the diffusion coefficient D _s is stored for each learning region divided in common with the initial state value map 131. The initial state value map 131 shown in FIG. 13 and the initial state value map 132 shown in FIG. 14 are stored in the storage unit of the control unit 12, for example.

  The boundary conditions of the diffusion equation (3) are set as shown in the following expressions (4) and (5).

  Equation (4) indicates that the concentration gradient at the center of the active material is zero. In the formula (5), the change in lithium concentration at the electrolyte interface of the active material means that it changes as lithium enters and leaves from the active material surface.

In equation (5), r _{s, i} represents the active material radius, ε _{s, i} represents the volume fraction of the active material, and as _{, i} represents the active material surface area per unit electrode volume. These values are determined from the results measured by various electrochemical measurement methods. F is a Faraday constant.

Furthermore, j ^Li in the equation (5) is the amount of lithium produced per unit volume and time, and for the sake of simplicity, assuming that the reaction is uniform in the electrode thickness direction, the electrode thickness L _i and the unit electrode Using the battery current I per plate area, the following equation (6) is used.

  By inputting the battery current I or the battery voltage V and solving these equations (1) to (6) simultaneously, the internal state of the secondary battery 14 is estimated while calculating the estimated voltage value or estimated current value. Thus, the charging rate can be estimated.

  By using this battery model, for example, it is possible to estimate the charging rate of the secondary battery with the battery voltage V as an input. When the battery voltage V is input, the charging rate is calculated using a map showing the relationship between the average lithium concentration in the active material model and the charging rate as shown in FIG. That is, the current SOC can be estimated from the average lithium concentration in the active material model calculated by the battery model formula according to the map of FIG.

  Here, the control processing procedure of the state estimation of the secondary battery using the battery model described above will be described with reference to FIG. The process shown in FIG. 15 is executed by the control unit 12 at predetermined calculation cycles.

FIG. 15 shows control processing procedures for both state estimation and parameter change rate learning of the secondary battery. In step S < _b > 100, the control unit 12 measures the battery voltage V _b using the voltage sensor 16. Control unit 12 in step S110, measuring the battery temperature T _b by the temperature sensor 20. The battery voltage V _b and the battery temperature T _b in the current calculation cycle are used as the battery voltage V and the battery temperature T in the battery model formula, respectively. The control unit 12 is collected also battery current I _b obtained by the measurement.

In step S120, the controller 12 calculates the local SOC θ _i (θ ₁ and θ ₂ ) on the active material surface based on the lithium concentration distribution c _{se, j} in the previous calculation cycle according to the equation (2).

Further, the control unit 12 in step S130, as shown in FIG. 11, the characteristic map of open-circuit potential U _i (θ _i) with respect to the local SOC [theta] _i, and calculates the open-circuit potential U _i (U ₁ and U ₂₎ Then, an open-circuit voltage estimated value U # is calculated as the potential difference between the calculated open-circuit potentials U ₁ and U ₂ .

Further, the control unit 12, in step S140, based on local SOC [theta] _i and measured battery temperature T calculated in step S130, obtains the DC resistance R _a. For example, the DC resistance _Ra is determined according to the initial state value map 131.

Control unit 12 further in step S150, the battery voltage V (= V _b), calculated open-circuit voltage using the estimated value U # and DC resistance R _a, the battery current based on the following equation (7) Estimated value _Ite is calculated.

Next, in step S160, the control unit 12 substitutes the estimated battery current value I _te into the battery current I in the equation (6) to calculate the lithium generation amount j ^Li per unit volume / time. The lithium concentration distribution in the active material of each of the positive and negative electrodes is determined by solving the diffusion equation of equation (3) using the lithium generation amount j ^Li per unit volume and time as the boundary condition of equation (5). . Note that the diffusion coefficient D _{s, i} in equation (3) is also determined based on the SOC and battery temperature. For example, the diffusion coefficient D _{s, i} is determined according to the initial state value map 132.

When solving the diffusion equation (3), the control unit 12 updates the lithium concentration distribution c _{s, i, k} (t + Δt) inside the active material using the diffusion equation discretized by the position and time. (Step S170). Here, Δt represents a discrete time step and corresponds to a calculation execution cycle. K represents a discrete position number discretized in the radial direction. Since the method of discretizing the diffusion equation by position and time is well known, detailed description will not be repeated here.

Next, the control part 12 calculates the average lithium density _| concentration c _save inside an active material according to the following (8) Formula by step S180. However, in the formula (8), N is the number of divisions when the spherical active material is discretized in the radial direction.

Then, in step S190, the control unit 12 stores a pre-stored map showing the relationship between the average lithium concentration c _save in the active material and the charging rate (SOC) of the secondary battery 14 as shown in FIG. Is used to calculate the SOC.

In this way, the control unit 12 determines the charge rate (SOC) of the secondary battery 14, the estimated open-circuit voltage U #, and the unit electrode plate area from the battery voltage V _b and the battery temperature T _b measured by the sensor. The estimated value of the battery current can be calculated. Further, the estimated value of the current flowing through the entire battery can be calculated by multiplying the estimated current value per unit electrode plate area by the double-sided electrode plate area of the battery, from the above-described formula of the battery current I.

  In the above battery model formula, a corresponding separate spherical active material model was set for each of the negative electrode 40 and the positive electrode 38. However, in order to reduce the calculation load of the control unit 12, a single spherical model having the averaged characteristics of the negative electrode 40 and the positive electrode 38 may be used as an active material model common to the positive electrode and the negative electrode.

Next, parameters in the battery model will be described. Some of the plurality of parameters of the battery model formula change due to deterioration of the battery accompanying the use of the secondary battery. For example, the DC resistance R _a is increased gradually due to the deterioration of the battery. When the difference between the direct current resistance _Ra (initial state value) in the initial state (typically when new) and the actual direct current resistance _Ra (current parameter value) is large, the SOC estimation error is It tends to occur.

  Similarly, due to the deterioration of the battery, the diffusion rate of the reaction-participating substance in the active material decreases (that is, the diffusion coefficient decreases), and as a result, the so-called diffusion resistance increases. The increase in the diffusion resistance has a great influence on the battery performance and the current-voltage characteristics, particularly in the case where charging / discharging with a large current is continued. Therefore, in an electric vehicle (hybrid vehicle or electric vehicle) that charges or discharges a battery with a large current, it is preferable to estimate a change in diffusion resistance, that is, a change in diffusion coefficient in the active material.

Thus, in this embodiment, the DC resistance R _a and the diffusion coefficient D _s in the formula (3) in the formula (1), by sequentially estimating the parameters rate of change, and updates the parameter value.

First, a description will be given parameter change rate of the DC resistance R _a. For DC resistance R _a, the parameter rate of change from the initial state value R _an, (DC resistance change rate) gr is defined by the following formula (9).

Control unit 12, a parameter change rate gr of DC resistance R _a, estimated using the recursive least-square method with forgetting factor to be described below. First, the sequential least square method with a forgetting factor will be described.

  According to the sequential least square method, in the system represented by the linear regression model represented by the following equation (10), the parameter Θ in the equation (10) is a time update equation represented by the equations (11) to (13). Is sequentially estimated by the initial conditions of the equations (14) and (15). In each equation, the estimated value of the parameter Θ is indicated by Θ #.

In equations (11) and (13), λ is a forgetting factor, and is usually λ <1.0. Further, P is a covariance matrix, and an initial value P (0) of the equation (15) is a matrix obtained by multiplying a diagonal element of the unit matrix I by a constant γ, and γ is usually a large value of about 10 ² to 10 ^3. Use the value. The initial value Θ # ₀ of the parameter Θ # is usually a zero vector.

Using such a sequential least square method with a forgetting factor, the DC resistance change rate gr is estimated as follows. That is, the DC resistance R _a of the secondary battery that has aged (deteriorated) from the new state can be expressed as R _a = gr · R _an by the definition of the equation (9), and this is substituted into the equation (1). When rewritten in the form of equation (10), equation (16) is obtained as a linear regression model equation based on the battery model equation.

While the secondary battery 14 is in use (on-line), the value estimated in the process of the charge rate estimation process is used for the open circuit voltage U (θ) on the left side of equation (16), and V is the measured battery voltage. By using V _b , Y can be calculated. For the right side of the equation (16), the initial state value R _an of the DC resistance is obtained by referring to the initial state value map 131 using the battery temperature T _b and the local SOCs θ ₁ and θ ₂ as arguments. As the battery current I, by substituting the current value per unit plate area calculated from the current of the battery current (measured value) I _b, can be calculated Z.

Thus by using the computed Y and Z, (11) to (15) of the forgetting factor with recursive least square method, as estimated parameter theta, it is sequentially estimating the parameters change rate gr of DC resistance R _a It becomes possible. It is also possible to apply a least square method of another method such as a collective least square method.

Next, estimation of the parameter change rate of the diffusion coefficient D _s will be described. Also for the diffusion coefficient D _s , the parameter change rate gd of the diffusion coefficient is defined as the change rate with respect to the initial state parameter value (D _sn ) according to the following equation (17).

The control unit 12 repeatedly acquires data on the battery voltage V _b , the battery current I _b, and the battery temperature T _{b at} a predetermined period in a time range in which the influence of the diffusion resistance is greatly expressed in the battery voltage.

Further, the control unit 12 uses the battery data in the range to obtain an estimated value I _te of the battery current based on the battery model when the parameter change rate is a certain candidate value, and to determine an error from the actual battery current I _b. An evaluation function for evaluating is calculated. Further, for example, by using the well-known GSM method (golden section method), the parameter change rate that minimizes the evaluation function can be searched by executing the above process a predetermined number of times while switching the parameter change rate. it can.

  The GSM method is a kind of bisection method, and has an advantage that an optimum value satisfying the allowable error can be obtained with a known search function by determining the search range and the allowable error. The lithium diffusion coefficient in the active material of a lithium ion battery after a certain use condition and period of use can be determined in advance by a deterioration test or the like, and to what extent the diffusion coefficient changes compared to the initial state to the maximum Can be predicted in advance.

  Therefore, by setting the range of the change rate that can change to the maximum as the search range, there is an advantage that the calculation time required for estimating the diffusion coefficient change rate can be predicted in advance. This is suitable for application to a secondary battery mounted on a hybrid vehicle or an electric vehicle. Since details of the GSM method are known, detailed description is omitted here.

In the present embodiment, the parameter rates of change, learning is performed for each predetermined learning region defined by a combination of the SOC and the battery temperature T _b of the secondary battery 14. Figure 16 is for storing the parameter rate of change in DC resistance R _a, it is a conceptual diagram illustrating a schematic configuration of a change rate map 141.

  Referring to FIG. 16, in change rate map 141, learning value grl of parameter change rate gr defined by equation (9) is stored for each learning region set in common with initial state value maps 131 and 132. The The initial value of the parameter change rate learning value grl is 1.0 in each learning region. When a predetermined learning condition is satisfied, the control unit 12 calculates a map value (parameter change rate learned value grl) based on the estimated value of the parameter change rate gr in the learning region corresponding to the SOC and the battery temperature at that time. Update.

  For example, a new learning value g11 is calculated according to the following equation (18) based on the map value g10 before update and the estimated value g of the parameter change rate when the learning condition is satisfied. Note that the change in the learning value is smoothed by the coefficient α (0 <α <1) in the equation (18).

FIG. 17 is a conceptual diagram illustrating a schematic configuration of the change rate map 142 for storing the parameter change rate learned value gdl of the diffusion coefficient D _s . In the change rate map 142, the learning value gdl of the parameter change rate gd defined by the equation (17) is stored for each learning region set in common with the initial state value maps 131 and 132 and the change rate map 141. The initial value of the parameter change rate learning value gdl is 1.0 in each learning region. When a predetermined learning condition is satisfied, control unit 12 updates the map value (parameter change rate learned value gdl) based on the estimated value of parameter change rate gd in the learning region corresponding to the SOC and battery temperature at that time. To do. The learning value can be updated according to the above equation (18).

  FIG. 18 is a conceptual diagram illustrating a variation regarding the update of the learning value in the change rate map. It is assumed that the learning condition for the parameter change rate is satisfied in the learning area AR1. At this time, at least the map value of the learning area AR1 is updated according to the above equation (18).

  Furthermore, the map value may be updated for at least a part of the learning areas AR2 to AR8 adjacent to the learning area AR1. At this time, it is preferable to set the coefficient α in the equation (18) to a small value as compared with the update of the map value in the learning area AR1. In this way, when the learning condition is satisfied, the learning result can be reflected even in a similar SOC and / or battery temperature region.

  Next, a control processing procedure for parameter change rate learning in the secondary battery evaluation system according to the present embodiment will be described. Referring to FIG. 15, in parallel with steps S <b> 100 to S <b> 190, control unit 12 performs the parameter change rate gr and gd estimation processes described above. In step S200, the control unit 12 determines whether a learning condition for the parameter change rate is satisfied.

DC resistance R _a is preferably estimated in a region where the battery voltage to the battery current changes linearly. Therefore, when the charging / discharging condition of the secondary battery 14 is established, the learning condition can be set so that step S200 is determined as YES for learning of the parameter change rate gr.

The diffusion coefficient D _s indicates the degree of diffusion of lithium in the active material after the once generated battery current becomes zero. Therefore, after the secondary battery 14 is charged and discharged, the diffusion coefficient is calculated based on the change in the battery voltage after the battery current becomes zero. Therefore, the learning condition can be set so that step S200 is determined as YES for learning of the parameter change rate gd when the battery current = 0 period continues to some extent.

Thus, the parameter change rate gr of DC resistance R _a, the parameter change rate gd of the diffusion coefficient D _s, it is preferred to learn independently. That, also the processing of steps S200, S210, are performed separately for each of the DC resistance R _a and the diffusion coefficient D _s.

  When the learning condition is satisfied (when YES is determined in S200), the control unit 12 updates the map value stored in the change rate map 141 or 142 for the parameter change rate for which the learning condition is satisfied in step S210. Thereby, at least the parameter change rate learning value in the learning region corresponding to the SOC and the battery temperature when the learning condition is satisfied is updated.

  On the other hand, when the learning condition is not satisfied (when NO is determined in S200), the control unit 12 skips the process of step S210. Therefore, the map value of the parameter change rate stored in the change rate map 141 or 142 is maintained.

As described above, in the secondary battery deterioration evaluation system according to the present embodiment, when the secondary battery 14 is used, the predetermined parameters (typically, the DC resistance _Ra and the diffusion coefficient D _s ) in the battery model are initially set. It is assumed that the change to the state value (parameter change rate) is estimated online. Then, based on the estimated parameter change rate, using the change rate maps 141 and 142 shown in FIGS. 16 and 17, the parameter change rate for each predetermined learning category defined by the combination of the SOC and the battery temperature. Has been learned.

Correcting unit 28, based on the rate of change of the estimated DC resistance R _a of the change rate gr and the diffusion coefficient D _s, calculate the internal resistance (IV resistance) increase rate in the battery model. Specifically, since the internal resistance can be expressed by the sum of the DC resistance and the diffusion resistance, the internal resistance increase rate can be obtained based on the DC resistance change rate and the diffusion coefficient change rate. Furthermore, the correction unit 28 calls the internal resistance increase rate under the same conditions as the SOC, temperature, and total time when the internal resistance increase rate based on the battery model is obtained from the aging deterioration map. Further, as shown in FIG. 19, the internal resistance increase rate 50 according to the aging deterioration map is removed (subtracted) from the internal resistance increase rate 48 obtained by the battery model. As a result, the rate of increase in internal resistance due to high rate degradation can be estimated.

  Further, an internal resistance value may be used instead of the internal resistance increase rate. In this case, the internal resistance value in the initial state under the SOC and temperature conditions when the internal resistance increase rate by the battery model is obtained is called from the aging deterioration map, and the product of the extracted internal resistance value and the internal resistance increase rate by the battery model is obtained. To calculate the internal resistance value according to the battery model. Furthermore, the internal resistance value under the same conditions as the SOC, temperature, and total time when the internal resistance increase rate by the battery model is obtained is called from the aging deterioration map, and this is compared with the internal resistance value by the battery model.

  The determination unit 30 determines whether or not the internal resistance value or the internal resistance increase rate due to the high rate deterioration obtained using the methods (1) to (3) exceeds a predetermined upper limit value. Further, when the determination unit 30 determines that the upper limit value has been exceeded, the control unit 12 performs control for suppressing the progress of the high rate deterioration. A flowchart of this high rate deterioration suppression control is shown in FIG. This flowchart also includes the operations of the calculation unit 24 and the correction unit 28 described above.

  First, the state measuring apparatus 10 measures the current value, voltage value, and temperature by the voltage sensor 16, the current sensor 18, and the temperature sensor 20 (S1). Further, the calculation unit 24 obtains the internal resistance increase rate or the internal resistance value by any of the above-described means (1) to (3) (S2). Furthermore, the internal resistance increase rate or internal resistance value under the same conditions as the internal resistance increase rate or internal resistance value by the calculation unit is extracted from the aged deterioration map (S3). Furthermore, the difference between the internal resistance increase rate by the calculation unit and the internal resistance increase rate by the aging deterioration map or the difference between the internal resistance value by the calculation unit and the internal resistance value by the aging deterioration map, that is, the internal resistance increase rate or internal resistance value by the high rate deterioration Is obtained (S4).

  Further, the determination unit 30 determines whether or not the internal resistance increase rate or the internal resistance value due to high rate deterioration exceeds a predetermined threshold (S5). When the internal resistance increase rate or the internal resistance value due to the high rate deterioration exceeds the threshold value, the determination unit 30 further determines whether the secondary battery 14 is excessively discharged or excessively charged (S6). When it is determined that the discharge is excessive, the control unit 12 restricts the discharge current, that is, limits the upper limit value of the discharge current value (S7). On the other hand, if it is determined that the charging is excessive, the charging current is reduced, that is, the upper limit value of the charging current value is limited (S8). By limiting the amount of charging current and the amount of discharging current, charging / discharging due to a large current can be suppressed, and progress of high-rate deterioration can be suppressed.

  Here, as an index for determining the excessive state of charging or discharging in the step (S6), the control unit 12 preferably uses the following “excessive charging / discharging index”. As shown in FIG. 21, the discharge current value and the charge current value in a predetermined period are plotted, and the average value of the discharge current value is compared with the average value of the charge current value. When the current sensor 18 measures the discharge current as a positive value and measures the charge current as a negative value, the sum of the average value of the discharge current value and the average value of the charge current value becomes an overcharge / discharge index. When this index is positive, it is determined that the battery is excessively discharged, and when it is negative, it is determined that the battery is excessively charged.

  In addition, there is another problem that the output of the rotating electrical machine that uses the power of the secondary battery 14 as a drive source is less than the target value or the charging efficiency of the secondary battery 14 is reduced by performing the control to reduce the current. Arise. Therefore, it is preferable to perform control so as not to limit the current excessively. Specifically, current limiting may be performed in consideration of the contribution rate of high rate deterioration to the overall (aging deterioration + high rate deterioration) internal resistance increase of the secondary battery 14.

For example, consider the ratio R _IR = IR _TOTAL / IR _AGING between the internal resistance increase rate IR _TOTAL due to both aging degradation and high-rate degradation and the internal resistance increase rate IR _AGING due only to aging degradation. It can be said that as the increase rate ratio R _IR is higher, the rate of increase in internal resistance due to high rate deterioration is higher, in other words, high rate deterioration is the main cause of increase in internal resistance of the secondary battery 14. On the other hand, it can be said that the lower the increase rate ratio R _IR is, the smaller the contribution to the increase in the internal resistance of the secondary battery 14 is.

From this, as shown in FIG. 22, when the increase rate ratio R _IR is relatively low (eg, 1.1), that is, the increase in internal resistance due to high rate deterioration is the main cause of the increase in overall internal resistance. If not, the control unit 12 sets the upper limit values 52 and 54 of the current value to be relatively high (relaxing the current limit). On the other hand, when the increase rate ratio R _IR is relatively high (for example, 1.6), that is, when the increase in internal resistance due to high-rate degradation is a major cause of the increase in overall internal resistance, the control unit 12 The upper limit values 52 and 54 of values are set relatively low (strict current limitation). Thus, excessive current limitation can be prevented by performing current limitation in consideration of the contribution of high-rate degradation to the overall increase in internal resistance of the secondary battery 14.

Furthermore, in addition to setting the upper limit value of the current limit, the threshold value for executing the current limit may be changeable. That is, the threshold value may be changed according to the degree of contribution of high rate deterioration to the overall increase in internal resistance of the secondary battery 14. Specifically, as shown in FIG. 23, the threshold IR _TH of the increase rate of the high-rate deterioration resistance that starts current limiting is increased with the increase of the increase rate IR _TOTAL of the internal resistance due to both aging deterioration and high-rate deterioration. Excessive current limitation can be prevented by causing the control unit 12 to set such a threshold value.

Further, instead of using the internal resistance value or the internal resistance increase rate, the DC resistance value _Ra or the DC resistance increase rate gr may be used. In this case, the DC resistance value _Ra has temperature dependence, and generally the value decreases as the temperature increases. Therefore, as when the temperature of the secondary battery 14 is high, the percentage of the DC resistance R _a occupying the internal resistance of the whole secondary battery 14 is considered to be small. For example, when the secondary battery 14 is at a high temperature, even if the direct current resistance _Ra becomes 1.2 times from the initial state, the overall internal resistance may hardly change from the initial state. When such case would set the value of DC resistance R _a or increased rate gr thereof starts current limiting uniformly in, there is a possibility that if the current limit is excessively performed occurs.

Therefore, when it is determined whether or not current limitation is possible based on the DC resistance _Ra or its increase rate gr, when the temperature of the secondary battery 14 is high, the threshold value for starting current limitation is increased and set. Is preferred. For example, as shown in FIG. 24, secondary battery 14 overall in the internal resistance of the (with respect to the initial state) to a temperature different DC resistance R _a rate of increase gr secondary battery 14 when the increase rate is 1.2 times Plot. Further, a threshold value is determined according to the characteristic line generated along this plot. Specifically, the threshold value at the temperature T2 (> T1) of the secondary battery 14 is set to A2 higher than the threshold value A1 at the temperature T1 according to the characteristic line. When performing such current limitation, the control unit 12 acquires the temperature of the secondary battery 14 from the temperature sensor 20, for example, and sets a threshold value of the DC resistance increase rate gr according to this temperature.

  Further, the aging of the secondary battery 14 may be taken into consideration. In this case, as shown in FIG. 24, not only the characteristic line when the increase rate of the internal resistance of the entire secondary battery 14 (relative to the initial state) is 1.2 times, but other increases The rate characteristic line is also used as a reference. FIG. 25 shows 1.1 and 1.3 times characteristic lines in addition to the characteristic line when the internal resistance increase rate is 1.2 times. The controller 12 changes the characteristic line as the secondary battery 14 progresses over time. Specifically, the characteristic line is shifted so that the characteristic line with a higher increase rate becomes a reference.

  In the above-described embodiment, the high-rate deterioration component is extracted from the overall internal resistance of the secondary battery 14 using the aging deterioration map. However, instead of this form, the secondary battery is not used. The high-rate deterioration may be estimated directly from the total internal resistance of 14.

The internal resistance increase rate may be used as a criterion for replacing the secondary battery 14. For example, the secondary battery 14 is replaced when the internal resistance increase rate reaches a threshold value (for example, 2.0 times). When this threshold is referred to as a replacement threshold IR _REPLACE, replacement threshold IR _REPLACE it is set in consideration of the deterioration state of the secondary battery 14 due to the increase in the internal resistance.

The main factors that raise the internal resistance increase rate of the secondary battery 14 to the replacement threshold IR _REPLACE are considered to be aged deterioration and high-rate deterioration as described above. From this, when considering the deterioration of the secondary battery 14 due to only aged deterioration, the internal resistance increase rate IR _AGING does not _reach the replacement threshold IR _REPLACE , and there is a difference in the high rate deterioration amount between the two. Become. For example, with respect to the replacement threshold IR _REPLACE = 2.0, the internal resistance increase rate IR _AGING due to aging is about 1.3 at the maximum.

From this, as shown in FIG. 26, an arbitrary value (for example, 1.8) that exceeds the maximum value IR _{AGING # MAX} of the internal resistance increase rate IR _AGING only due to aging and falls below the replacement threshold IR _REPLACE is determined. and sets a value IR _{dETERMINATION,} overall of the secondary battery 14, that is configured to detect occurrence of high-rate deterioration with the increase rate IR _tOTAL of internal resistance due to the aging and high-rate deterioration has exceeded a determination value IR _{dETERMINATION} Is possible.

The controller 12 obtains the overall increase rate of the internal resistance of the secondary battery 14, that is, the internal resistance due to aging deterioration and high-rate deterioration by any one of the above-described means (1) to (3). (1)-(3) The overall (aging deterioration + high rate deterioration) internal resistance increase rate (hereinafter referred to as the internal resistance increase rate by the calculation unit) IR _TOTAL obtained by the means of (3) is monitored and When the resistance increase rate IR _TOTAL exceeds the determination value IR _{DETERMINATION} , the control unit 12 executes current limiting in order to suppress the progress of the high rate deterioration.

In executing the current limit, as shown in FIG. 27, the upper limit value of the current limit is gradually decreased (the limit is tightened) as the internal resistance increase rate IR _TOTAL increases by the calculation unit. Also good. Further, the internal resistance increase rate IR _REPLACE and the determination value IR _{DETERMINATION} at the end of the life are set in accordance with the SOC condition and the temperature condition of the secondary battery 14 and stored in the storage unit of the control unit 12. It is preferable to call appropriately according to the temperature and SOC conditions.

FIG. 28 shows a control flow of this current limit. First, the state measuring apparatus 10 measures the current value, voltage value, and temperature by the voltage sensor 16, the current sensor 18, and the temperature sensor 20 (S10). Further, the calculation unit 24 obtains the overall increase rate IR _TOTAL of the internal resistance by any one of the above-described (1) to (3) (S11). The determination unit 30 acquires the temperature and SOC of the secondary battery 14 when the increase rate IR _TOTAL is obtained in step (S11), and stores the determination value IR _{DETERMINATION} set for the same SOC and temperature. It is determined whether the increase rate IR _TOTAL exceeds the determination value IR _{DETERMINATION} (S12).

Further, when it is determined that the increase rate IR _TOTAL exceeds the determination value IR _{DETERMINATION} , the control unit 12 determines whether the secondary battery 14 is in an excessive discharge state or an excessive charge state (S13). For the determination of excessive discharge or excessive charge, it is preferable to use the excessive charge / discharge index described above. When it is determined that the discharge is excessive, the control unit 12 limits the upper limit value of the discharge current value (S14). On the other hand, when it is determined that the charging is excessive, the upper limit value of the charging current value is limited (S15). In this way, it is possible to estimate high-rate degradation directly from the overall internal resistance of the secondary battery 14 and execute current limit control.

Note that the internal resistance value itself may be used as a reference parameter instead of using the increase rate of the internal resistance as a reference parameter for current limitation. With this case used determination internal resistance value R _{DETERMINATION} multiplied by the internal resistance value of the initial state determination value IR _{DETERMINATION} instead of the aforementioned determination value IR _{DETERMINATION,} instead of increasing rate IR _REPLACE the internal resistance, the above-described ( 1) Use the IV characteristic obtained by any means of (3), that is, the overall (aging deterioration + high rate deterioration) internal resistance value R _TOTAL .

  According to this embodiment, although it is difficult to estimate the progress state of high-rate deterioration alone, it is possible to perform high-rate deterioration estimation and current limit control without having an aging deterioration map. There is an advantage that the load on the storage unit for storing is reduced.

  DESCRIPTION OF SYMBOLS 10 State measuring device, 12 Control part, 14 Secondary battery, 16 Voltage sensor, 18 Current sensor, 20 Temperature sensor, 22 Connection object, 24 Calculation part, 28 Correction part, 30 Judgment part, 32 Electrolyte, 34 Cation, 36 Anion, 38 Positive electrode, 39 electrode, 40 Negative electrode, 41 Internal resistance increase rate by calculation part, 42 Internal resistance increase rate by aging deterioration map, 44 IV characteristic by calculation part, 46 IV characteristic by aging deterioration map, 48 Battery model Internal resistance increase rate by 50, internal resistance increase rate by aging map, 52,54 current upper limit value, 113 negative current collector, 114 separator, 116 positive current collector, 118 active material, 125 battery model, 131 DC resistance Initial state value map, 132 Initial state value map of diffusion coefficient, 141 DC resistance The change rate map, 142 change rate map of the diffusion coefficient.

Claims (5)

A measuring unit for measuring a terminal voltage and current values of the lithium ion蓄 batteries,
A calculation unit for calculating an internal resistance increase rate due to aging and high-rate deterioration of the lithium ion蓄 battery based on the battery model for the lithium-ion蓄 batteries,
And an internal resistance increase rate of the calculating unit is determined, pre-acquired from the difference between the measured value of the internal resistance increase rate due to aging of lithium-ion蓄 battery, a correction unit for obtaining an internal resistance increase rate due to high-rate deterioration,
Measuring apparatus of the lithium-ion蓄 battery, characterized in that it comprises a. A measuring unit for measuring a terminal voltage and current values of the lithium ion蓄 batteries,
A calculation unit for obtaining an internal resistance increase rate due to aging deterioration and high rate deterioration of the lithium ion storage battery from the terminal voltage value and the current value ;
From the difference between the internal resistance increase rate obtained by the calculation unit and the measured value of the internal resistance increase rate due to aging deterioration of the lithium ion storage battery obtained in advance, a correction unit for obtaining the internal resistance increase rate due to high rate deterioration,
Measuring apparatus of the lithium-ion蓄 battery, characterized in that it comprises a. A measuring unit for measuring a terminal voltage and current values of the lithium ion蓄 batteries,
A calculation unit for obtaining an internal resistance value due to aging deterioration and high-rate deterioration of the lithium ion storage battery from the terminal voltage value and the current value ;
From the difference between the internal resistance value obtained by the calculation unit and the measured value of the internal resistance of the lithium ion storage battery that is acquired in advance and caused by aging degradation, a correction unit that obtains the internal resistance value due to high-rate degradation,
Measuring apparatus of the lithium-ion蓄 battery, characterized in that it comprises a. A measuring unit for measuring a terminal voltage and current values of the lithium ion蓄 batteries,
A calculation unit for calculating an internal resistance increase rate due to aged deterioration and high-rate deterioration of the lithium ion storage battery from the terminal voltage value and the current value;
A determination value is set based on an actually measured value of the internal resistance increase rate of the lithium ion storage battery due to aged deterioration determined in advance, and it is determined whether the internal resistance increase rate determined by the calculation unit exceeds the determination value. A determination unit to perform,
Measuring apparatus of the lithium-ion蓄 battery, characterized in that it comprises a. A measuring unit for measuring a terminal voltage and current values of the lithium ion蓄 batteries,
A calculation unit for calculating an internal resistance value due to aged deterioration and high-rate deterioration of the lithium ion storage battery from the terminal voltage value and the current value;
A determination unit that sets a determination value based on an actually measured value of the internal resistance of the lithium ion storage battery due to aged deterioration determined in advance and determines whether or not the internal resistance value calculated by the calculation unit exceeds the determination value When,
Measuring apparatus of the lithium-ion蓄 battery, characterized in that it comprises a.

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