JP2015207371A - State estimation device for lithium secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an erroneous determination of high-rate deterioration when estimating the high-rate deterioration of a lithium secondary battery on the basis of a surface pressure change of a battery cell.SOLUTION: A state estimation device 200 includes: a surface pressure acquisition section 210 for acquiring a surface pressure of a battery cell 110 of a lithium secondary battery (secondary battery 100); and a control section 240 configured to control a residual capacitance (SOC) of the lithium secondary battery (secondary battery 100) and estimates a deterioration state of the lithium secondary battery (secondary battery 100) on the basis of the surface pressure acquired by the surface pressure acquisition section 210, a discharge current and the SOC of the lithium secondary battery (secondary battery 100). When estimating the deterioration state, in the case where the SOC is equal to or more than a predetermined value, the control section 240 controls the SOC in such a manner that the SOC becomes less than the predetermined value.

Description

  The present invention relates to a state estimation device for a lithium secondary battery.

  One of the secondary batteries is a lithium ion secondary battery (hereinafter simply referred to as “lithium secondary battery”). One of the indexes indicating the deterioration of the lithium secondary battery is the size of the internal resistance of the battery cell. When the internal resistance increases, the output performance of the lithium secondary battery decreases and the lithium secondary battery deteriorates.

  The increase in internal resistance is caused, for example, by a bias in the lithium salt concentration in the non-aqueous electric field solution during charging / discharging of the lithium secondary battery. When the internal resistance increases, for example, the influence of the internal resistance becomes obvious during charging / discharging at a large current (high rate), and the performance of the lithium secondary battery deteriorates. Such a decrease in the performance of the secondary battery due to the increase in internal resistance is sometimes called high-rate deterioration.

  For example, Japanese Patent Laying-Open No. 2013-122907 proposes to estimate high-rate deterioration of a lithium secondary battery based on the surface pressure of the battery cells constituting the lithium secondary battery.

JP2013-122907A

  The inventors of the present application have made extensive studies and have found that the change in the surface pressure of the battery cell depends on the remaining capacity (SOC: State Of Charge) of the lithium secondary battery. For example, when the SOC increases, the change in the surface pressure of the battery cell decreases. On the other hand, when the SOC decreases, the change in the surface pressure of the battery cell increases. For example, when the change in the surface pressure of the battery cell is small because the SOC is large, the change in the surface pressure of the battery cell is not accurately detected. As a result, there is a risk of misjudgment of the high rate deterioration of the lithium secondary battery.

  Further, the change in the surface pressure of the battery cell also depends on the current (discharge current or the like) of the lithium secondary battery. For example, when the discharge current increases, the change in surface pressure of the battery cell increases. Conversely, when the discharge current is reduced, the change in the surface pressure of the battery cell is reduced. Even when such a relationship between the discharge current and the change in surface pressure is not taken into account, there is a risk of misjudgment regarding the high-rate deterioration of the lithium secondary battery.

  An object of the present invention is to suppress misjudgment of high rate deterioration when estimating high rate deterioration of a lithium secondary battery based on a change in surface pressure of a battery cell.

  In one aspect, the present invention is a state estimation device for a lithium secondary battery. The state estimation device is configured to be capable of controlling the surface pressure of the lithium secondary battery, and the surface pressure acquired by the surface pressure acquisition unit. And a controller that estimates a deterioration state of the lithium secondary battery based on the discharge current and the remaining capacity of the lithium secondary battery. When estimating the deterioration state, the control unit estimates the deterioration state after controlling the remaining capacity so that the remaining capacity is less than the predetermined value if the remaining capacity is equal to or greater than a predetermined value.

  In the state estimation device configured as described above, when the deterioration state is estimated, the control unit controls the remaining capacity so that the remaining capacity becomes less than the predetermined value when the remaining capacity of the lithium secondary battery is equal to or larger than the predetermined value. Thereby, the deterioration state of the lithium secondary battery is estimated based on the surface pressure acquired when the remaining capacity is less than the predetermined value, that is, based on a relatively large surface pressure change. By estimating the deterioration state of a lithium secondary battery based on such a large change in surface pressure, it is possible to estimate the deterioration state of the lithium secondary battery rather than estimating the deterioration state of the lithium secondary battery based on a small change in surface pressure. Is accurately estimated. The predetermined value is determined in consideration of, for example, a surface pressure acquisition (measurement) error.

  Moreover, in the state estimation device having the above configuration, the deterioration state of the lithium secondary battery is estimated in consideration of not only the surface pressure of the battery cell but also the discharge current and remaining capacity of the lithium secondary battery. Thereby, the judgment of high rate deterioration is made appropriately.

  According to the present invention, when the high-rate deterioration of the lithium secondary battery is estimated based on the change in the surface pressure of the battery cell, erroneous determination of the high-rate deterioration is suppressed.

It is a figure for demonstrating the state estimation apparatus which concerns on embodiment of this invention. It is a figure for demonstrating an example of the structure of the secondary battery for acquiring the surface pressure of a battery cell. It is a flowchart for demonstrating the process performed for estimation of high-rate degradation. It is a graph which shows the acquired experimental data for demonstrating the relationship between discharge current and surface pressure in each SOC. It is a figure for demonstrating the relationship between SOC, a discharge current, and the surface pressure of a battery cell when a secondary battery is discharged. It is a diagram for illustrating setting of the threshold value [Delta] P _th respect to the surface pressure change [Delta] P. If the discharge current is 180A, the rate of increase in the internal resistance of the battery is a diagram for explaining a determination example of a surface pressure decrease amount [Delta] P _drop of the battery _cells, and high-rate deterioration. It is a figure for demonstrating another example of the structure of the secondary battery for acquiring the surface pressure of a battery cell.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

  FIG. 1 is a diagram for explaining a state estimation apparatus 200 for a lithium secondary battery according to an embodiment of the present invention. The state estimation device 200 is mounted on the vehicle 1 and used to estimate the state of the secondary battery 100 mounted on the vehicle 1, for example.

  As shown in FIG. 1, vehicle 1 includes a secondary battery 100, a state estimation device 200, a power converter 300, and a rotating electrical machine 400.

  Secondary battery 100 constitutes a chargeable / dischargeable power storage device. Secondary battery 100 includes, for example, a lithium ion battery. The secondary battery 100 may include a plurality of battery cells 110 to obtain desired characteristics. Secondary battery 100 may include a storage element such as a nickel hydride battery, a lead storage battery, or an electric double layer capacitor in addition to the lithium ion battery.

  The state estimation device includes a surface pressure acquisition unit 210, a secondary battery monitoring unit 220, a storage unit 230, and a control unit 240.

  The surface pressure acquisition unit 210 acquires (measures) the surface pressure of the battery cell of the secondary battery 100. The acquired surface pressure information is sent to the control unit 240. Details of the acquisition of the surface pressure will be described later.

  The secondary battery monitoring unit 220 monitors the secondary battery 100. The secondary battery monitoring unit 220 monitors, for example, charge / discharge power of the secondary battery 100 (voltage or current may be used instead of power), the SOC of the secondary battery 100, the temperature of the secondary battery 100, and the like. . Information such as the SOC value of the secondary battery 100 monitored by the secondary battery monitoring unit 220 is sent to the control unit 240.

  The storage unit 230 stores various information necessary for the operation of the state estimation device 200. For example, the storage unit 230 stores the surface pressure of the battery cell of the secondary battery 100 acquired by the above-described surface pressure acquisition unit 210, the SOC value of the secondary battery 100 monitored by the secondary battery monitoring unit 220, and the like. . In addition, the storage unit 230 can also store a predetermined value determined for the SOC of the secondary battery 100 described later, a threshold value determined for a change in the surface pressure of the battery cell, and the like.

  The control unit 240 is an ECU (Electronic Control Unit) that controls each element of the vehicle 1. The control is realized using, for example, a control signal or a communication signal between the control unit 240 and each element of the vehicle 1.

  Note that the functions of the surface pressure acquisition unit 210, the secondary battery monitoring unit 220, and the storage unit 230 may also be realized by the ECU.

  The power converter 300 converts the power from the secondary battery 100 into power for operating the rotating electrical machine 400. Further, the power converter 300 converts the power from the rotating electrical machine 400 into the charging power for the secondary battery 100.

  The rotating electrical machine 400 receives power from the power converter 300 and generates power for traveling the vehicle 1. In this case, the secondary battery 100 is discharged, and the SOC of the secondary battery 100 decreases.

  The rotating electrical machine 400 receives power from an engine (not shown) to generate power, and sends the generated power to the power converter 300. In this case, the secondary battery 100 is charged and the SOC of the secondary battery 100 increases. The rotating electrical machine 400 can also generate power using regenerative energy associated with the braking operation of the vehicle 1 and send the generated power to the power converter 300.

  For example, charge / discharge of the secondary battery 100 is controlled by the control unit 240 being appropriately controlled by the power converter 300 and the rotating electric machine 400. Thereby, the SOC of the secondary battery 100 is controlled. That is, the control unit 240 is configured to be able to control the SOC of the secondary battery 100.

  In the embodiment, the deterioration state of the secondary battery 100 is estimated. The deterioration state of the secondary battery 100 is, for example, a state where the internal resistance of the secondary battery 100 is increased. Specifically, the deterioration state of the secondary battery 100 is, for example, a state in which the internal resistance is increased due to a bias in the lithium salt concentration in the non-aqueous electric field solution due to charge / discharge of the secondary battery, that is, so-called Indicates that the high-rate deterioration has occurred.

  In a secondary battery such as a lithium ion battery, there is a predetermined relationship between the surface pressure of the battery cell and the high rate deterioration of the secondary battery. For example, when the secondary battery is discharged, the surface pressure of the battery cell decreases from the surface pressure during non-discharge. In the embodiment, this amount of decrease is defined as “change in surface pressure”. As the high-rate deterioration progresses, the difference (surface pressure change) between the surface pressure during discharge and the surface pressure during non-discharge tends to decrease.

  If attention is paid to the change in surface pressure, high-rate deterioration of the secondary battery can be estimated. For example, if the change in surface pressure is equal to or greater than a threshold value, it can be determined that the secondary battery has deteriorated. If the change in surface pressure is less than the threshold value, it can be determined that the secondary battery has not deteriorated.

  The inventors of the present application have conducted intensive studies and have found that, in actual surface pressure measurement, the change in the surface pressure of the battery cell of the secondary battery depends on the SOC of the secondary battery. For example, when the SOC of the secondary battery 100 shown in FIG. 1 increases, the surface pressure change of the battery cell 110 decreases. Conversely, when the SOC of the secondary battery 100 is relatively small, the change in the surface pressure of the battery cell 110 becomes large. Then, for example, when the surface pressure change of the battery cell 110 is small because the SOC of the secondary battery 100 is large, the surface pressure change of the battery cell 110 is not accurately detected. As a result, there is a risk of misjudging the high rate deterioration of the secondary battery 100.

  That is, the surface pressure change is calculated, for example, by the surface pressure acquisition unit 210 acquiring (measuring) the surface pressure of the battery cell of the secondary battery 100, but the surface pressure value acquired by the surface pressure acquisition unit 210 is calculated. Includes an error (surface pressure error). If the change in surface pressure is small, the surface pressure value may not be obtained accurately due to the effect of surface pressure error. If the surface pressure difference is calculated based on the surface pressure that is not accurately acquired and the deterioration of the secondary battery 100 is estimated, the high rate deterioration characteristic may be erroneously determined.

  Therefore, in the embodiment, the high rate deterioration characteristic is estimated in a state where the SOC of the secondary battery 100 is less than a predetermined value. When the SOC of the secondary battery 100 is greater than or equal to a predetermined value, the high rate deterioration characteristic is estimated after the SOC of the secondary battery 100 is controlled so that the SOC of the secondary battery 100 is less than the predetermined value. The predetermined value is set to a value so that high-rate deterioration is not erroneously determined due to the influence of the surface pressure error. For this reason, when the high-rate deterioration of the lithium secondary battery is estimated based on the change in the surface pressure of the battery cell, erroneous determination of the high-rate deterioration is suppressed.

  In the embodiment, the threshold for the change in surface pressure of battery cell 110 is determined based on the discharge current and SOC of secondary battery 100. This will be further described later with reference to FIGS.

Next, the measurement of the surface pressure of the battery cell will be described with reference to FIG.
FIG. 2 is a diagram for explaining an example of the configuration of the secondary battery for obtaining the surface pressure of the battery cell.

  As shown in FIG. 2, secondary battery 100 </ b> A includes a plurality of battery cells 110. The battery cells 110 are stacked via the resin frame 120 to form a stack 160.

  Support members 150-1 and 150-2 support restraint plates 140-1 to 140-3 so that the distance between restraint plates of restraint plates 140-1 to 140-3 can be changed.

  The stack 160 is disposed between the restraint plate 140-1 and the restraint plate 140-2. The restraint plate 140-1 and the restraint plate 140-2 restrain the stack 160. The surface pressure of the battery cells included in the stack 160 is transmitted to the restraining plates 140-1 and 140-2.

  A load cell 170 is disposed between the restraint plate 140-2 and the restraint plate 140-3. The restraint plate 140-2 and the restraint plate 140-3 restrain the load cell 170. Thereby, the load cell can detect the pressure received from the restraint plate 140-2 and the restraint plate 140-3. Thereby, the load cell 170 can detect the surface pressure of the battery cell 110 via the restraining plate 140-2. The pressure detected by the load cell 170 can be appropriately compensated to indicate the surface pressure of the battery cell 110.

  The pressure (P) of the battery cell 110 acquired by the load cell 170 is sent to the surface pressure acquisition unit 210 shown in FIG. 1, for example. In this way, the surface pressure of the battery cell 110 is acquired. In addition, with reference to FIG. 8 later, another example of the structure of the secondary battery for acquiring the surface pressure of a battery cell is demonstrated.

  As described above, with the configuration described with reference to FIGS. 1 and 2, the state estimation device 200 can estimate the high rate deterioration of the secondary battery 100.

  FIG. 3 is a flowchart for explaining processing executed for estimating high-rate deterioration.

  Referring to FIGS. 1 and 3, first, in step S1, traveling by high-rate energization is started. In traveling by high-rate energization, the secondary battery 100 is discharged at a high rate, and the vehicle 1 travels using the discharged power.

  In step S2, it is determined whether or not a decrease in the output of the secondary battery 100 is detected on-board, that is, in the running vehicle 1. For example, when the voltage drop of the secondary battery 100 becomes significant during discharge at a high rate and the voltage falls below a predetermined voltage, it is detected that the output of the secondary battery 100 is lowered. If the output of secondary battery 100 is decreasing (YES in step S2), the process proceeds to step S3. If not (NO in step S2), the process returns to step S1.

  In step S3, diagnosis of the secondary battery 100, that is, estimation of the deterioration state of the secondary battery 100 is started. A specific process is performed after step S4.

  In step S4, it is determined whether or not the SOC of the secondary battery 100 is less than a predetermined value. The predetermined value is, for example, 72%. This will be described later with reference to FIG. If the SOC is less than the predetermined value (YES in step S4), the process proceeds to step S6. If not (NO in step S4), the process proceeds to step S5.

  In step S5, the SOC of the secondary battery 100 is controlled so that the SOC of the secondary battery 100 is less than a predetermined value. For example, when the secondary battery 100 is not charged and the discharge is maintained, the SOC of the secondary battery 100 decreases and becomes less than a predetermined value.

  In step S <b> 6, the surface pressure change ΔP is calculated and stored in the storage unit 230. The calculation of the surface pressure change ΔP is obtained by acquiring the surface pressure of the battery cell at the current time when the vehicle 1 is traveling by high-rate energization, and further, the surface pressure of the battery cell in a state where the secondary battery 100 is not discharged. This is done by calculating the difference between The surface pressure of the battery cell in a state where the secondary battery 100 is not discharged is stored in the storage unit 230 in advance, for example.

In step S7, it is determined whether or not the surface pressure change ΔP is less than the threshold value ΔP _th . If ΔP is less than ΔP _th (YES in step S7), the process proceeds to step S8. If not (NO in step S7), the process returns to step S1. The threshold value ΔP _th will be further described later with reference to FIG.

In step S8, it is determined that the secondary battery 100 has deteriorated at a high rate.
In step S9, it is determined that traveling by high-rate energization is not possible. If it is determined that traveling by high-rate energization is not possible, for example, the discharge power of the secondary battery 100 is limited. At this time, the user may be notified that the discharge power of the secondary battery 100 has deteriorated. The notification to the user can be performed, for example, by being displayed on a display unit (not shown) included in the vehicle 1 (for example, a display of a navigation system).

After the process of step S9 is completed, the process of the flowchart ends.
According to the flowchart shown in FIG. 3, the SOC of secondary battery 100 is controlled to a relatively low value (for example, less than 72%), for example, at step S5. Thereby, the high rate deterioration state of the secondary battery 100 is estimated based on the relatively large surface pressure change ΔP of the battery cell 110. As a result, erroneous determination of high rate degradation is suppressed.

  4 and 5 are diagrams for explaining the relationship among the SOC, the discharge current, and the surface pressure of the battery cell when the secondary battery is discharged.

  FIG. 4 is a graph showing acquired experimental data for explaining the relationship between the discharge current and the surface pressure in each SOC. The horizontal axis of the graph represents time, and the vertical axis represents surface pressure.

  Referring to FIG. 4, after time t1 and before time t2, the relationship between the discharge current and the surface pressure in a state where the SOC is about 36% is shown. Specifically, changes in surface pressure when the discharge current is 60A, 130A, and 180A are shown. The surface pressure decreases due to the discharge current. The amount of decrease in surface pressure is illustrated as a surface pressure change ΔP. As shown in FIG. 4, the surface pressure change ΔP increases as the discharge current increases.

  After time t2, the relationship between the discharge current and the surface pressure when the SOC is about 56% is shown. At this time, as in the case where the SOC is about 36%, the surface pressure change ΔP increases as the discharge current increases.

Further, as shown in FIG. 4, the smaller the SOC, the larger the surface pressure change ΔP.
FIG. 5 is a graph showing the relationship between the SOC and the surface pressure change ΔP when the discharge current is used as a parameter. The horizontal axis of the graph indicates SOC (%), and the vertical axis indicates the surface pressure change ΔP.

  As shown in FIG. 5, for example, even when the discharge current is about 130 A, the magnitude of the surface pressure change ΔP varies depending on the SOC. Specifically, as the SOC decreases, the surface pressure change ΔP increases. Similarly, in any case where the discharge current is about 10 A, about 60 A, or about 180 A, the surface pressure change ΔP increases as the SOC decreases.

  Further, when the discharge current is relatively large (for example, when the discharge current is about 180 A), the surface pressure change ΔP becomes larger than when the discharge current is relatively small (for example, when the discharge current is 60 A).

In the graph of FIG. 5, “ΔP _error ” shown on the vertical axis indicates the maximum value of an error that can occur when measuring the surface pressure change ΔP. In order to accurately measure the surface pressure change ΔP, it is desirable to measure the surface pressure when the surface pressure change ΔP is larger than ΔP _error . The magnitude of ΔP _error is caused by, for example, the measurement accuracy of the load cell 170 in FIG.

As described above, in the embodiment, the high rate deterioration of the secondary battery is estimated based on the surface pressure change ΔP of the battery cell. Therefore, if the value of the surface pressure change ΔP is accurate, there is a possibility that the high-rate deterioration of the secondary battery is erroneously determined. For example, in the example shown in FIG. 5, when the SOC exceeds about 72%, the surface pressure change ΔP becomes smaller than ΔP _error (becomes buried in an error), and the surface pressure change ΔP cannot be measured accurately. Conversely, if the SOC is about 72% or less, the change in surface pressure ΔP can be measured with high accuracy. Therefore, the predetermined value for the SOC described above is set to 72% as an example (see step S4 in FIG. 3).

As described above with reference to FIGS. 4 and 5, the surface pressure change ΔP depends on the SOC and the magnitude of the discharge current. Therefore, threshold value ΔP _th is set for each SOC and discharge current.

FIG. 6 is a diagram for explaining the setting of the threshold value ΔP _th (see step S7 in FIG. 3 and the like) for the surface pressure change ΔP described above. FIG. 6 is a graph showing, as an example, a threshold value ΔP _th set for each SOC when the discharge current is 180 A. The horizontal axis of the graph indicates SOC (%), and the vertical axis indicates the change in surface pressure ΔP.

A broken line indicated as “initial surface pressure change” in FIG. 6 represents a surface pressure change with respect to the SOC in the secondary battery before high-rate deterioration. As the high-rate deterioration progresses, the surface pressure change ΔP becomes smaller, so the threshold value ΔP _th is set smaller than the initial surface pressure change. For example, the threshold value ΔP _th is set to half the initial surface pressure change (that is, 50%).

Further, in FIG. 6, the amount by which the change in the surface pressure is reduced (decreased) from the change in the initial surface pressure is illustrated as a surface pressure decrease amount ΔP _drop (%). In the example shown in FIG. 6, when the surface pressure decrease amount ΔP _drop exceeds 50%, the surface pressure change ΔP falls below the threshold value ΔP _th .

FIG. 7 is a diagram for explaining a determination example of high-rate deterioration based on the surface pressure decrease amount ΔP _drop . More specifically, FIG. 7 is a table showing an example of determining the rate of increase of the internal resistance of the battery, the amount of decrease in the surface pressure ΔP _{drop of} the battery cell, and the high rate deterioration when the discharge current is 180A. “Resistance increase rate (times)” in the table indicates the ratio of the size of the internal resistance increased by the high rate deterioration to the size of the internal resistance before the high rate deterioration. When both magnitudes are equal, the resistance increase rate is 1. The larger the “resistance increase rate” is, the higher the internal resistance is, and the higher the rate of deterioration is.

As the high-rate deterioration progresses and the resistance increase rate increases, the surface pressure decrease amount ΔP _drop (see FIG. 6) increases. In the example shown in FIG. 7, when the resistance increase rate is 1.1, ΔP _drop is 10%. When the resistance increase rate is 1.2, ΔP _drop is 35%. When the resistance increase rate is 1.3, ΔP _drop is 55%. When the resistance increase rate is 1.5, ΔP _drop is 65%.

For example, as described above with reference to FIG. 6, when threshold ΔP _th is set to 50% of the initial surface pressure change, there is no high rate deterioration when resistance increase rate is 1.1 and 1.2 (no deterioration) ), And when the resistance increase rate is 1.3 and 1.5, it is determined that there is high-rate deterioration (deterioration).

In the above, with reference to FIG. 6 and FIG. 7, when the discharge current is 180 A, the threshold value ΔP _th set for each SOC and the determination of the presence or absence of high-rate deterioration based on the threshold value ΔP _th have been described. On the other hand, for discharge currents having a magnitude different from 180A, similarly, a threshold value ΔP _th is set for each SOC, and the presence or absence of high-rate deterioration is determined based on the threshold value ΔP _th . That is, the threshold value ΔP _th is set for each discharge current and SOC. Such information of the threshold value ΔP _th is used as map data, for example. The map data is stored, for example, in the storage unit 230 in FIG.

  FIG. 8 is a diagram for explaining a configuration example of a secondary battery for obtaining the surface pressure of the battery cell, which is different from the load cell 170 described with reference to FIG.

  As shown in FIG. 8, secondary battery 100 </ b> B includes a plurality of battery cells 110. The battery cells 110 are stacked via the resin frame 120 to form a stack 160A. The stack 160A is disposed between the restraining plates 140-1 and 140-3. The restraining plates 140-1 and 140-3 restrain the stack 160A.

  A surface pressure sensor 180 is disposed between the battery cell 110 and the resin frame 120. The surface pressure sensor 180 detects the surface pressure of the battery cell 110. The pressure detected by the surface pressure sensor 180 can be appropriately compensated to indicate the surface pressure of the battery cell 110. The pressure detected by the surface pressure sensor 180 is sent to, for example, the surface pressure acquisition unit 210 shown in FIG. In this way, the surface pressure of the battery cell 110 can be acquired.

  Finally, embodiments of the present invention will be summarized. Referring to FIG. 1, state estimation device 200 includes a surface pressure acquisition unit 210 that acquires a surface pressure of battery cell 110 of a lithium secondary battery (secondary battery 100), and a lithium secondary battery (secondary battery 100). The remaining capacity (SOC) of the battery is configured to be controllable, and based on the surface pressure acquired by the surface pressure acquisition unit 210 and the discharge current and SOC of the lithium secondary battery (secondary battery 100), the lithium secondary And a control unit 240 that estimates a deterioration state of the battery (secondary battery 100). When estimating the deterioration state, when the SOC is greater than or equal to a predetermined value, control unit 240 estimates the deterioration state after controlling the SOC so that the SOC is less than the predetermined value.

  In state estimation device 200, when estimating the deterioration state, control unit 240 controls the SOC so that the SOC is less than the predetermined value when the SOC of secondary battery 100 is equal to or greater than the predetermined value. Thereby, the deterioration state of secondary battery 100 is estimated based on the surface pressure acquired when SOC is less than a predetermined value, that is, based on a relatively large surface pressure change. By estimating the deterioration state of the secondary battery 100 based on such a large change in surface pressure, the deterioration state of the secondary battery 100 can be estimated rather than estimating the deterioration state of the secondary battery 100 based on a small change in surface pressure. Is accurately estimated. The predetermined value is determined in consideration of, for example, a surface pressure acquisition (measurement) error.

  In the state estimation device 200, not only the surface pressure of the battery cell 110 but also the discharge current and SCO of the lithium secondary battery 100 are considered, and the deterioration state of the lithium secondary battery 100 is estimated. Thereby, the judgment of high rate deterioration is made appropriately.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiment but by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

  DESCRIPTION OF SYMBOLS 1 Vehicle, 100, 100A, 100B Secondary battery, 110 Battery cell, 111 Battery case, 112, 116 External terminal, 113, 117 Terminal board, 114, 118 Volts, 115 Battery cell surface, 119 Gas discharge valve, 120 Resin frame , 140-1 to 140-3, restraint plate, 150-1, 150-2 support member, 160, 160A stack, 170 load cell, 180 surface pressure sensor, 200 state estimation device, 210 surface pressure acquisition unit, 220 secondary battery monitoring Unit, 230 storage unit, 240 control unit, 300 power converter, 400 rotating electric machine.

Claims (1)

A surface pressure acquisition unit for acquiring a surface pressure of the battery cell of the lithium secondary battery;
The lithium secondary battery is configured to be controllable, and based on the surface pressure acquired by the surface pressure acquisition unit, the discharge current of the lithium secondary battery, and the remaining capacity, the lithium secondary battery A controller for estimating the deterioration state of the battery,
The control unit estimates the deterioration state after controlling the remaining capacity so that the remaining capacity is less than the predetermined value when the remaining capacity is greater than or equal to a predetermined value when the deterioration state is estimated. Lithium secondary battery state estimation device.

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