Battery state estimation method and battery state estimation device

Abstract

To provide a battery state estimation method and a battery state estimation device with which, even in a case where a secondary battery is quickly charged, the full charge capacity of the secondary battery can be highly precisely estimated.SOLUTION: In a battery state estimation method for estimating the full charge capacity of a secondary battery, the correspondence between the AC impedance of the secondary battery and the full charge capacity of the secondary battery is changed based on the quick charging history of the secondary battery, and the full charge capacity is estimated from the correspondence changed due to the history of quick charging and a measurement value of the AC impedance.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a battery state estimation method and a battery state estimation device. [Background technology]

[0002] Patent Document 1 discloses a technique for estimating the full charge capacity of a secondary battery based on the correspondence relationship among the temperature history, input / output resistance, and full charge capacity of the secondary battery. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-132369 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, with the technology of Patent Document 1, when a secondary battery is subjected to rapid charging, it becomes difficult to accurately estimate the full charge capacity of the secondary battery.

[0005] An object of the present invention is to provide a battery state estimating method and device that are capable of estimating the full charge capacity of a secondary battery with high accuracy even when the secondary battery is subjected to rapid charging. [Means for solving the problem]

[0006] A battery state estimation method according to the present invention is a battery state estimation method for estimating the full charge capacity of a secondary battery. This estimation method changes the correspondence between the AC impedance of the secondary battery and the full charge capacity of the secondary battery based on the history of rapid charging of the secondary battery, and estimates the full charge capacity from the correspondence changed due to the history of rapid charging and the measured value of the AC impedance. Effect of the Invention

[0007] According to the present invention, the full charge capacity of a secondary battery can be estimated with high accuracy even when the secondary battery is subjected to rapid charging. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a block diagram of a battery state estimating device according to the present embodiment. [Diagram 2] FIG. 2 is a diagram showing a calibration curve used when estimating the full charge capacity of a secondary battery in the battery state estimating device of this embodiment. [Diagram 3] FIG. 3 is a control flow of the battery state estimating device of this embodiment. [Figure 4] FIG. 4 is a map showing the relationship between the number of quick charges and the shift amount of the calibration curve. [Diagram 5] FIG. 5 is a map showing the relationship between the number of quick charges, the full charge capacity, and the shift amount of the calibration curve. [Figure 6] FIG. 6 is a map showing the relationship between the number of quick charges, the magnitude of the charging current, and the shift amount of the calibration curve. [Figure 7] FIG. 7 is a map showing the relationship between the temperature of the secondary battery and the correction amount of the calibration curve. [Figure 8] FIG. 8 is a map showing the relationship between the temperature of the secondary battery and the corrected value of the AC impedance. [Figure 9] FIG. 9 is a map showing the relationship between the charge amount of the secondary battery and the correction amount of the calibration curve. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0010] [Basic configuration of this embodiment] Fig. 1 is a block diagram of a battery state estimating device 1 of this embodiment. As shown in Fig. 1, the battery state estimating device 1 of this embodiment estimates the full charge capacity of the secondary battery 100 based on the temperature history, AC impedance, and quick charge history of the secondary battery 100.

[0011] Here, the secondary battery 100 is, for example, a lithium ion battery, in which the negative electrode uses, for example, a mixture of a Si active material and a conductive additive (carbon, etc.), and the positive electrode uses, for example, a transition metal oxide containing lithium ions.

[0012] The battery state estimation device 1 includes a temperature detection unit 2 that detects the temperature of the secondary battery 100, an AC impedance detection unit 3 that detects the AC impedance of the secondary battery 100, and a current detection unit 4 that detects the charging current flowing into the secondary battery 100.

[0013] The battery state estimation device 1 also includes a temperature history recording unit 5 that records the history of the temperature input from the temperature detection unit 2, and a quick charge history recording unit 6 that generates and records quick charge history information from the current input from the current detection unit 4.

[0014] Furthermore, the battery state estimating device 1 includes a correspondence relationship storage unit 7 in which information on the correspondence relationship between the AC impedance and the full charge capacity of the secondary battery 100 is stored.

[0015] The battery state estimating device 1 includes a full charge capacity estimating unit 8 that estimates the full charge capacity of the secondary battery 100 based on the temperature history input from the temperature history recording unit 5, the AC impedance input from the AC impedance detection unit 3, and the quick charge history information input from the quick charge history recording unit 6, while referring to the correspondence stored in the correspondence storage unit 7.

[0016] The temperature detection unit 2 detects the temperature of the secondary battery 100 as described above, and is preferably capable of measuring the temperature of the electrolyte of the secondary battery 100 with high accuracy.

[0017] The AC impedance detection unit 3 applies a high frequency (for example, 1 [kHz]) to the secondary battery 100 (positive electrode, negative electrode) and measures the AC impedance. The AC impedance mainly reflects the impedance of the electrolyte.

[0018] The quick charge history recording unit 6 chronologically records information about the charging current detected by the current detection unit 4. The quick charge history recording unit 6 also records, as quick charge history information, information that is highly correlated with changes in the full charge capacity of the secondary battery 100, such as the average current during quick charge in a predetermined period (e.g., one month), the average value of the maximum current during charging (the charging current at the start of charging), and the number of times (the number of quick charges) that the predetermined current (the charging current recognized as quick charging) was exceeded.

[0019] The temperature history recording unit 5 chronologically records the temperatures detected by the temperature detection unit 2. The temperature history recording unit 5 also records, as temperature history information, information that is highly correlated with changes in the full charge capacity of the secondary battery 100, such as the average temperature during quick charging in the specified period (e.g., one month), the average temperature when the maximum current (charging current at the start of charging) flows during quick charging, and the number of times the reference temperature (temperature that changes the AC impedance) is exceeded.

[0020] The full charge capacity estimation unit 8 estimates the current full charge capacity of the secondary battery 100 based on the AC impedance input from the AC impedance detection unit 3 and the correspondence relationship between the AC impedance and the full charge capacity stored in the correspondence storage unit 7 (a calibration curve 9 described later).

[0021] At that time, the full charge capacity estimating unit 8 corrects the correspondence relationship (calibration curve 9 described later) between the AC impedance and the full charge capacity based on the rapid charge history input from the rapid charge history recording unit 6. The correction of the correspondence relationship (calibration curve 9 described later) takes into consideration the number of rapid charges of the secondary battery 100, the magnitude of the charging current during rapid charge, the full charge capacity of the secondary battery 100, the SOC (charge amount) of the secondary battery 100, the temperature of the secondary battery 100 during rapid charge, etc. In addition, the full charge capacity estimating unit 8 corrects the input AC impedance based on the temperature history input from the temperature history recording unit 5.

[0022] Here, quick charging refers to applying a high voltage (about 400-500[V]) DC voltage from a quick charger (for example, installed at a station along the road) using a three-phase AC (200[V] or 400[V]) power source to the secondary battery 100 in the vehicle via the vehicle's quick charging port, thereby charging the secondary battery 100. The charging current is 100[A] or more, and the output is several tens of kW to several hundred tens of kW.

[0023] Moreover, normal charging (low-speed charging) refers to connecting a single-phase AC (200 [V] or 100 [V]) power source from a general household power source to the secondary battery 100 via a normal charging port and an on-board charger of the vehicle, changing the AC to DC in the on-board charger and boosting the voltage to apply the voltage to the secondary battery 100, thereby charging the secondary battery 100. The charging current is about 10 to 20 [A], and the output is about several [kW].

[0024] [AC impedance and full charge capacity] Fig. 2 is a diagram showing a calibration curve 9 used when the battery state estimating device 1 of this embodiment estimates the full charge capacity of the secondary battery 100. In Fig. 2, the horizontal axis represents AC impedance [mΩ], and the vertical axis represents full charge capacity [%]. Here, the full charge capacity is represented by the ratio between the full charge capacity of the secondary battery 100 when it is not in use and the full charge capacity after repeated charging and discharging.

[0025] Generally, the full charge capacity of the secondary battery 100 decreases as the above-mentioned normal charging is repeated. In addition, there is a correlation between the full charge capacity of the secondary battery 100 and the AC impedance, and the inventors of the present application have found that, for example, when the full charge capacity is between 80[%] and 45[%], a large amount of plot data (not shown) that is almost close to the calibration curve 9A (straight line) shown in Fig. 2 is obtained. Therefore, for example, when the AC impedance is 1.0[mΩ], the full charge capacity can be estimated to be about 63[%] based on the position on the calibration curve 9A.

[0026] Incidentally, when the secondary battery 100 is rapidly charged, lithium ions in the electrolyte are irreversibly incorporated into the negative electrode (Si active material) as a solid electrolyte interface (SEI, e.g., microcrystalline LiO), and the amount of lithium ions that can move through the electrolyte is accordingly reduced, resulting in a decrease in the full charge capacity of the secondary battery 100.

[0027] However, even in this case, the AC impedance does not change or changes very little, so an error will occur if the full charge capacity is estimated based on the calibration curve 9A.

[0028] Therefore, in this embodiment, the calibration curve 9 is shifted along the vertical axis based on the number of times of rapid charging, etc., so that the full charge capacity after rapid charging and the full charge capacity when normal charging is performed thereafter can be estimated with high accuracy.

[0029] In this case, as shown in FIG. 2, the calibration curve 9A is shifted downward along the vertical axis based on the number of times of quick charging, etc., to obtain the calibration curve 9B, and the value on the calibration curve 9B that corresponds to the measured value of the AC impedance is identified, thereby making it possible to estimate the full charge capacity of the secondary battery 100 with high accuracy.

[0030] Furthermore, if the temperature of the secondary battery 100 during rapid charging is higher than a reference temperature (e.g., 25°C), the constituent elements of the positive electrode active material from the positive electrode of the secondary battery 100 irreversibly dissolve into the electrolyte, increasing the electrical resistance of the electrolyte and resulting in an increase in AC impedance. However, even if the AC impedance increases, there is no change in the amount of lithium ions that can move through the electrolyte, and therefore there is no change in the full charge capacity of the secondary battery 100.

[0031] 2, for example, when the current calibration curve 9 is the calibration curve 9C and the measured AC impedance is 1.1 mΩ, the full charge capacity is formally estimated to be about 52%. However, the actual full charge capacity is equal to the full charge capacity when the previous quick charge was performed when the temperature of the secondary battery 100 was equal to or lower than the reference temperature.

[0032] Therefore, in this embodiment, a correction value is calculated based on the temperature of the secondary battery 100 during quick charging, and the actual full charge capacity is estimated using the value obtained by subtracting the correction value from the measured AC impedance and the calibration curve 9 (calibration curve 9C) obtained by performing the previous quick charging.

[0033] In FIG. 2, the correction value is, for example, 0.1 [mΩ], and by identifying the value on the calibration curve 9C corresponding to the corrected AC impedance value, i.e., 1.1-0.1=1.0 [mΩ], the full charge capacity (about 57[%]) of the secondary battery 100 can be estimated with high accuracy.

[0034] When the temperature of the secondary battery 100 falls below a predetermined temperature (e.g., 5°C), the viscosity of the electrolyte increases and the conductivity of lithium ions decreases, resulting in a decrease in the full charge capacity of the secondary battery 100. However, the full charge capacity is restored when the temperature of the secondary battery 100 reaches or exceeds the predetermined temperature. Therefore, in this case, the calibration curve 9 is not shifted, and a correction value for the full charge capacity is calculated based on the temperature of the secondary battery 100 during charging, and the position on the calibration curve 9 corresponding to the measured value of the AC impedance minus the correction value is estimated as the full charge capacity.

[0035] [Control Flow] Fig. 3 is a control flow of the battery state estimating device 1 of this embodiment. Fig. 4 is a map showing the relationship between the number of quick charges and the shift amount of the calibration curve 9. Fig. 5 is a map showing the relationship between the number of quick charges, the magnitude of the full charge capacity, and the shift amount of the calibration curve 9. Fig. 6 is a map showing the relationship between the number of quick charges, the magnitude of the charging current, and the shift amount of the calibration curve 9. Fig. 7 is a map showing the relationship between the temperature of the secondary battery 100 and the correction amount of the calibration curve 9. Fig. 8 is a map showing the relationship between the temperature of the secondary battery 100 and the correction value of the AC impedance.

[0036] A control flow of the battery state estimating device 1 of this embodiment will be described. The battery state estimating device 1 of this embodiment estimates a full charge capacity in response to quick charging performed during a predetermined period (e.g., one month). The battery state estimating device 1 (current detection unit 4, quick charge history recording unit 6) also records the value of the charging current flowing into the secondary battery 100 in chronological order, and the battery state estimating device 1 (temperature detection unit 2, temperature history recording unit 5) records the temperature of the secondary battery 100 in chronological order. The correspondence storage unit 7 stores information on a calibration curve that indicates the correspondence between the AC impedance used when estimating the full charge capacity last and the full charge capacity.

[0037] In step S101, the battery state estimating device 1 determines whether or not a system startup operation has been received from the driver or the like, and if YES, the process proceeds to step S102, and if NO, the process returns to step S101.

[0038] In step S102, the battery state estimating device 1 determines whether a predetermined period (e.g., one month) has elapsed since the quick charging history and the temperature history were last updated, and if YES, proceeds to step S103, and if NO, proceeds to step S105.

[0039] In step S103, the battery state estimation device 1 (quick charge history recording unit 6) adds information such as the number of quick charges performed within the specified period, the average charging current during quick charging, and the average maximum quick charge current (charging current at the start of quick charging) to the existing quick charge history to update it.

[0040] In step S104, the battery state estimation device 1 (temperature history recording unit 5) adds information such as the average temperature during quick charging performed within the specified period, the average temperature when quick charging has a maximum current (at the start of quick charging), the number of times the reference temperature was exceeded during quick charging, etc. to the existing temperature history to update it.

[0041] In step S105, the battery state estimating device 1 (AC impedance detection unit 3) measures the AC impedance of the secondary battery 100.

[0042] In step S106, the battery state estimation device 1 (full charge capacity estimation unit 8) refers to the quick charge history and calculates the shift amount of the calibration curve 9. The battery state estimation device 1 (full charge capacity estimation unit 8) calculates the shift amount of the calibration curve 9 based on the map shown in Fig. 4, for example. Note that the horizontal axis may represent the number of quick charges within the predetermined period, or may represent the accumulated number of quick charges previously performed on the secondary battery 100. Note that when the number of quick charges is zero, the shift amount of the calibration curve 9 is zero.

[0043] Furthermore, as shown in the map of FIG. 5, the battery state estimating device 1 (full charge capacity estimating unit 8) performs a correction such that the shift amount increases as the last estimated full charge capacity increases, and decreases as the last estimated full charge capacity decreases.

[0044] Furthermore, as shown in the map of FIG. 6, the battery state estimation device 1 (full charge capacity estimation unit 8) performs a correction such that the greater the average charging current during quick charging in the specified period (or during the last quick charging in the specified period) or the greater the average maximum current (current at the start of charging) during quick charging in the specified period (or the last quick charging in the specified period), the greater the shift amount of the calibration curve 9, and conversely, the smaller the average charging current is, the smaller the shift amount is.

[0045] In step S107, the battery state estimation device 1 (full charge capacity estimation unit 8) refers to the temperature history, and calculates a correction value [%] of the full charge capacity based on either information of the average temperature during quick charge in the specified period (or the last quick charge in the specified period) or the average temperature at the maximum current (current at the start of charging) during quick charge in the specified period (or the last quick charge in the specified period), and the map shown in Figure 7.

[0046] Furthermore, the battery state estimation device 1 (full charge capacity estimation unit 8) refers to the temperature history, and selects information on the highest average temperature that is higher than the reference temperature T (FIG. 8) from the history of average temperatures during quick charging or the history of average temperatures when the current is maximum (at the start of quick charging) during quick charging, and calculates a correction value [mΩ] of the AC impedance based on the selected information and the map shown in FIG. 8.

[0047] In step S108, the battery state estimating device 1 (full charge capacity estimating unit 8) estimates the full charge capacity of the secondary battery 100.

[0048] Here, the battery state estimation device 1 (full charge capacity estimation unit 8) reads out the calibration curve 9 stored in the correspondence storage unit 7. Then, in characteristic coordinates with the horizontal axis representing AC impedance and the vertical axis representing full charge capacity, the battery state estimation device 1 (full charge capacity estimation unit 8) shifts the calibration curve 9 in the direction decreasing the calibration curve 9 in the vertical axis direction by the shift amount calculated in step S106, to obtain a new calibration curve 9.

[0049] In addition, the battery state estimating device 1 (full charge capacity estimating unit 8) calculates a value (calibration point) on the calibration curve 9 corresponding to the value obtained by subtracting the correction value [mΩ] obtained in step S107 from the AC impedance measured in step S105.

[0050] Furthermore, the battery state estimating device 1 (full charge capacity estimating unit 8) calculates (estimates) the full charge capacity by subtracting the correction value [%] obtained in step S107 from the calibration point.

[0051] Then, the battery state estimating device 1 (full charge capacity estimating unit 8) stores information on the estimated full charge capacity in an associated storage area, and overwrites the correspondence storage unit 7 with information on the calibration curve 9 after the shift.

[0052] In step S109, the battery state estimating device 1 determines whether or not an operation to stop the system has been received from the driver or the like, and if YES, returns (proceeds to step S101), and if NO, returns to step S109.

[0053] The maps shown in Figs. 4 to 8 (and Fig. 9) are preset based on experimental data or the like.

[0054] In addition, in the above flow, the full charge capacity of the secondary battery 100 is estimated by the operation of the driver or the like after a predetermined period (for example, one month) has elapsed, but the full charge capacity may be automatically estimated each time the secondary battery 100 is charged (rapid charging, normal charging). The full charge capacity is displayed, for example, adjacent to the display position of the secondary battery's SOC (charge amount) on the vehicle's instrument panel.

[0055] Incidentally, as shown in FIG. 6, even if the number of times of quick charging is the same, the shift amount of the calibration curve 9 (the degree of deterioration) changes depending on the magnitude of the charging current.

[0056] Generally, the vehicle controller installed in the vehicle controls and limits the charging current by communicating with the quick charger via CAN or other means.

[0057] The vehicle controller detects the temperature and voltage of the secondary voltage and limits the charging current to prevent a sudden rise in temperature, thereby preventing the voltage (open circuit voltage) of the secondary voltage from becoming too high (exceeding the upper limit voltage).

[0058] When the SOC (charge level) of the secondary battery 100 is low, the open circuit voltage of the secondary battery is low, and even if the charging current is increased, it will not exceed the upper limit voltage, so there is no need to limit the charging current and charging is possible at the maximum capacity of the quick charger.

[0059] On the other hand, when the SOC of the secondary battery 100 is high, the open circuit voltage of the secondary battery is high, so that it is necessary to limit the charging current so as not to exceed the upper limit voltage.

[0060] Therefore, if the SOC at the start of charging is lower than a predetermined amount (e.g., 70% relative to the number of rapid charges), a positive correction amount (a correction that increases the shift amount of the calibration curve 9) is set, and if the SOC at the start of charging is equal to or greater than the predetermined amount, a negative correction amount (a correction that decreases the shift amount of the calibration curve 9) is set.

[0061] As shown in FIG. 9, for example, the correction amount when the charge amount is from zero to 50% is a constant positive value, and when the charge amount exceeds 50% the correction amount monotonically decreases, and when the charge amount reaches 70% for example the correction amount becomes zero, and when the charge amount exceeds 70% the correction amount becomes a negative value and continues to monotonically decrease.

[0062] [Effects of this embodiment] According to the battery state estimation method of the present embodiment, in a battery state estimation method for estimating the full charge capacity of the secondary battery 100, the correspondence relationship (calibration curve 9) between the AC impedance of the secondary battery 100 and the full charge capacity of the secondary battery 100 is changed based on the rapid charge history of the secondary battery, and the full charge capacity is estimated from the correspondence relationship (calibration curve 9) changed due to the rapid charge history and the measured value of the AC impedance.

[0063] By using the above method, the full charge capacity of the secondary battery 100 can be estimated with high accuracy even when the secondary battery 100 is subjected to rapid charging.

[0064] In this embodiment, in a characteristic coordinate system having AC impedance and full charge capacity as axes, a calibration curve 9 showing the correspondence relationship between AC impedance and full charge capacity when normal charging, in which the input current to the secondary battery 100 is smaller than that of quick charging, is shifted in the direction of the full charge capacity axis of the characteristic coordinate system in a direction decreasing the full charge capacity based on the quick charge history, and the full charge capacity is estimated by identifying a position on the calibration curve 9 corresponding to the measured value of the AC impedance.

[0065] By using the above method, the full charge capacity of the secondary battery 100 can be estimated with high accuracy even when the secondary battery 100 is subjected to rapid charging and then normal charging.

[0066] In this embodiment, as the number of times of rapid charging increases, the calibration curve 9 is shifted in the direction of decreasing the full charge capacity along the axis of the full charge capacity of the characteristic coordinates.

[0067] By using the above method, even if quick charging has been performed once, it is possible to estimate the full charge capacity of the secondary battery 100 with high accuracy, taking this into account.

[0068] In this embodiment, the larger the full charge capacity, the larger the shift amount of the calibration curve 9 is. The larger the full charge capacity, the larger the decrease in the full charge capacity when rapid charging is performed. Therefore, by using the above method, the shift amount of the calibration curve 9 can be changed according to the full charge capacity, and the accuracy of estimating the full charge capacity can be improved accordingly.

[0069] In this embodiment, the shift amount of the calibration curve 9 is increased as the current (charging current) flowing through the secondary battery 100 during quick charging increases. The greater the charging current input to the secondary battery 100 during quick charging, the greater the decrease in full charge capacity. Therefore, by using the above method, the shift amount of the calibration curve 9 can be changed in response to the magnitude of the charging current, thereby improving the estimation accuracy of the full charge capacity.

[0070] In this embodiment, the shift amount of the calibration curve 9 is increased as the cumulative number of quick charges increases. The greater the cumulative number of quick charges, the greater the decrease in full charge capacity during quick charging. Therefore, by using the above method, the shift amount of the calibration curve 9 can be changed in accordance with the cumulative number of quick charges, thereby improving the estimation accuracy of the full charge capacity. When the full charge capacity falls below a predetermined capacity, the influence of the magnitude of the full charge capacity becomes greater than the influence of the cumulative number of quick charges, and the shift amount of the calibration curve 9 becomes smaller.

[0071] In this embodiment, the lower the charge level of the secondary battery 100 at the start of quick charging, the larger the shift amount of the calibration curve 9 is set. In the vehicle, the lower the charge level (SOC) of the secondary battery 100, the larger the charging current is set. Therefore, by using the above method, the shift amount of the calibration curve 9 can be changed according to the charge level (SOC) at the start of quick charging, i.e., the magnitude of the charging current at the start of quick charging, and therefore the accuracy of estimating the full charge capacity can be improved accordingly.

[0072] In this embodiment, the estimated full charge capacity is corrected to be lower as the temperature of the secondary battery 100 decreases during charging of the secondary battery 100. When the temperature of the secondary battery 100 decreases during charging, the viscosity of the electrolyte increases and the ionic conductivity decreases, resulting in a reversible decrease in the full charge capacity. Therefore, the above method estimates the full charge capacity while reflecting the decrease in full charge capacity associated with a decrease in temperature, thereby improving the accuracy of the estimation of the full charge capacity.

[0073] In this embodiment, when the temperature of the secondary battery 100 during rapid charging is higher than a reference temperature, the full charge capacity is estimated based on a value obtained by subtracting a correction value from the measured value, and the correction value is set to a larger value as the temperature of the secondary battery 100 becomes higher than the reference temperature. When the temperature of the secondary battery 100 during rapid charging exceeds the reference temperature (e.g., 25°C), the constituent elements of the positive electrode active material dissolve from the positive electrode into the electrolyte, increasing the AC impedance, but the full charge capacity does not change. Therefore, by correcting the measured value of the AC impedance based on the temperature of the secondary battery 100 during rapid charging, the estimation error of the full charge capacity can be reduced.

[0074] In this embodiment, the temperature history of the secondary battery 100 is recorded, and the correction value is set based on the maximum temperature in the temperature history that is higher than the reference temperature. As described above, when the temperature of the secondary battery 100 during rapid charging exceeds the reference temperature (e.g., 25°C), the constituent elements of the positive electrode active material dissolve from the positive electrode into the electrolyte, increasing the AC impedance, which is an irreversible reaction. Therefore, by appropriately selecting the correction value of the AC impedance using the above method, the estimation error of the full charge capacity can be reduced.

[0075] In this embodiment, the frequency of the high frequency applied to the secondary battery 100 is set to 1 kHz to 100 kHz, and the AC impedance is measured using this high frequency. This allows the AC impedance to be measured at a frequency to which the electrolyte of the secondary battery 100 responds strongly, making it possible to detect changes in the AC impedance with high sensitivity.

[0076] The battery state estimation device 1 of this embodiment is a battery state estimation device 1 that estimates the full charge capacity of a secondary battery 100, and includes a quick charge recording unit that records the quick charge history of the secondary battery 100, a measuring means that measures the AC impedance of the secondary battery 100, and a full charge capacity estimation unit 8 that changes the correspondence relationship (calibration curve 9) between the AC impedance and the full charge capacity based on the quick charge history, and estimates the full charge capacity from the correspondence relationship (calibration curve 9) that has changed due to the quick charge history and the measured value of the AC impedance.

[0077] With the above configuration, even if the secondary battery 100 is subjected to rapid charging, the full charge capacity of the secondary battery 100 can be estimated with high accuracy.

[0078] Although the embodiments of the present invention have been described above, the above-mentioned embodiments merely show some of the application examples of the present invention, and the technical scope of the present invention is not limited to the specific configurations of the above-mentioned embodiments. In addition, the above-mentioned embodiments can be appropriately combined. [Explanation of symbols]

[0079] 1 Battery state estimation device, 2 Temperature detection unit, 3 AC impedance detection unit, 4 Current detection unit, 5 Temperature history recording unit, 6 Quick charge history recording unit, 7 Correspondence storage unit, 8 Full charge capacity estimation unit, 9 Calibration curve, 100 Secondary battery

Claims

1. 1. A battery state estimation method for estimating a full charge capacity of a secondary battery, comprising: A battery state estimation method comprising: changing a correspondence relationship between the AC impedance of the secondary battery and the full charge capacity of the secondary battery based on a history of rapid charging of the secondary battery; and estimating the full charge capacity from the correspondence relationship changed due to the history of rapid charging and a measured value of the AC impedance.

2. 2. The method for estimating a battery state according to claim 1, further comprising the steps of: shifting a calibration curve, which indicates a correspondence relationship between the AC impedance and the full charge capacity when the secondary battery is subjected to normal charging, in which an input current to the secondary battery is smaller than that of the quick charging, in a characteristic coordinate system having axes representing the AC impedance and the full charge capacity, along an axial direction of the full charge capacity on the characteristic coordinate system in a direction in which the full charge capacity is decreased based on a history of the quick charging; and estimating the full charge capacity by identifying a position on the calibration curve which corresponds to the measured value of the AC impedance.

3. 3. The method for estimating a battery state according to claim 2, wherein the calibration curve is shifted in the axial direction of the full charge capacity of the characteristic coordinates in a direction in which the full charge capacity decreases as the number of times the quick charge is increased.

4. The method for estimating a battery state according to claim 3 , wherein the shift amount of the calibration curve is increased as the full charge capacity during the rapid charging is increased.

5. 4. The method for estimating a battery state according to claim 3, wherein the shift amount of the calibration curve is increased as the current flowing through the secondary battery during the rapid charging is increased.

6. The method for estimating a battery state according to claim 3 , wherein the shift amount of the calibration curve is increased as the integrated number of times the quick charging is performed is increased.

7. 4. The method of estimating a battery state according to claim 3, wherein the shift amount of the calibration curve is increased as the charged amount of the secondary battery at the start of the quick charging is lower.

8. 8. The method of estimating a battery state according to claim 1, wherein the estimated full charge capacity is corrected to be lower as the temperature of the secondary battery during charging of the secondary battery decreases.

9. When the temperature of the secondary battery during the rapid charging is higher than a reference temperature, the full charge capacity is estimated based on a value obtained by subtracting a correction value from the measured value; The method for estimating a battery state according to claim 2 , wherein the correction value is set to be larger as the temperature of the secondary battery becomes higher than the reference temperature.

10. Recording the temperature history of the secondary battery; The method for estimating a battery state according to claim 9 , wherein the correction value is set based on a maximum temperature in the temperature history that is higher than the reference temperature.

11. The method for estimating a battery state according to any one of claims 1 to 9, wherein a frequency of a high frequency applied to the secondary battery is set to 1 kHz to 100 kHz, and the AC impedance is measured by the high frequency.

12. A battery state estimation device that estimates a full charge capacity of a secondary battery, comprising: a rapid charge recorder that records a history of rapid charging of the secondary battery; A measuring means for measuring an AC impedance of the secondary battery; a full charge capacity estimation unit that changes a correspondence relationship between the AC impedance and the full charge capacity based on a history of the rapid charging and estimates the full charge capacity from the correspondence relationship changed due to the history of the rapid charging and a measured value of the AC impedance; A battery state estimation device comprising:

Images