JP6834849B2 - Impedance estimator - Google Patents

Description

The present invention relates to the technical field of an impedance estimation device that estimates the impedance of a battery mounted on a vehicle or the like.

In this type of device, impedance is estimated, for example, to know the state of the battery. For example, Patent Document 1 discloses a method of determining a deteriorated state of a secondary battery by substituting a value of an adjustment parameter and a reference temperature into a temperature characteristic function to calculate a reference internal impedance.

Further, Patent Document 2 discloses a technique of Fourier transforming a response signal to an input square wave signal and calculating the impedance characteristic of an electrochemical cell based on the calculated frequency characteristic as a method of estimating the impedance of the battery. Has been done.

JP-A-2007-108063 Japanese Unexamined Patent Publication No. 2014-126532

The impedance of the battery is temperature dependent. Therefore, if the correlation between the impedance of the battery and the temperature is known in advance, it is considered that the impedance can be estimated from the temperature of the battery.

However, there is a region where the impedance of the battery changes not only by the temperature of the battery but also by the SOC (State Of Charge). Therefore, in a situation where the SOC is different, it may not be possible to accurately estimate the impedance from the temperature of the battery.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an impedance estimation device capable of accurately estimating the impedance of a battery.

The impedance estimation device according to one aspect of the present invention is based on a value of the complex impedance of a battery acquired at a plurality of different temperatures at a first predetermined frequency and the temperature of the battery when the complex impedance is acquired. Then, a derivation means for deriving a gradient function indicating the relationship between the value of the complex impedance at the first predetermined frequency and the reciprocal of the temperature of the battery, and whether or not the charge amount of the battery is within the first predetermined range. When it is determined that the charge amount of the battery is within the first predetermined range, the determination means for determining whether or not the battery is used, and the inclination function is used to determine the complex impedance corresponding to the desired temperature of the battery. It is provided with an estimation means for estimating a value at a frequency.

It is a block diagram which shows the structure of the impedance estimation apparatus which concerns on this embodiment. It is a graph which shows the waveform of the complex impedance measured under the temperature condition of 20 degreeC, 25 degreeC, and 30 degreeC. It is a graph which shows the waveform of the complex impedance measured under the temperature condition of 40 degreeC, 45 degreeC, and 50 degreeC. It is a flowchart which shows the operation flow of the impedance estimation apparatus which concerns on this embodiment. It is a graph which shows the relationship between the absolute value of complex impedance and the reciprocal of temperature. It is a graph which shows the relationship between the real number component of a complex impedance and the reciprocal of temperature. It is a graph which shows the relationship between the imaginary component of a complex impedance and the reciprocal of temperature. It is a graph which shows the relationship between the value of the complex impedance measured by the different SOC and the reciprocal of temperature. It is a graph which shows the waveform of the complex impedance acquired in the range of SOC 20% to 50%. It is a graph which shows the waveform of the complex impedance acquired in the range of SOC 70% to 80%. It is a graph which shows the intersection of the approximate straight line connecting the complex impedance acquired by SOC 60%, and the real axis. It is a graph which shows the intersection of the approximate straight line connecting the complex impedance acquired by SOC 10%, and the real axis.

An embodiment of the impedance estimation device of the present invention will be described with reference to the drawings. In the following, a case where the impedance estimation device 100 is configured as a device for estimating the impedance of the battery 10 of the vehicle will be described as an example.

(1) Device Configuration First, the configuration of the impedance estimation device 100 according to the present embodiment will be described with reference to FIG. FIG. 1 is a block diagram showing a configuration of an impedance estimation device 100 according to the present embodiment.

As shown in FIG. 1, the impedance estimation device 100 according to the present embodiment is an electronic unit electrically connected to the battery 10 of the vehicle, and is configured as a device for estimating the impedance (that is, complex impedance) of the battery 10. Has been done. The battery 10 is a specific example of the "battery" described later, and is configured as a rechargeable liquid secondary battery such as a lithium ion battery.

The impedance estimation device 100 includes an impedance acquisition unit 110, a temperature acquisition unit 120, a tilt function calculation unit 130, an SOC determination unit 140, and an impedance estimation unit 150 as logical or physical processing blocks realized inside the impedance estimation device 100. It is configured to prepare.

The impedance acquisition unit 110 is configured to be able to acquire the complex impedance of the battery 10. The impedance acquisition unit 110 acquires complex impedance by applying an AC voltage to the battery 10 while changing the frequency, for example. Since the existing technique can be appropriately adopted as the method for acquiring the complex impedance, detailed description here will be omitted. The complex impedance of the battery 10 acquired by the impedance acquisition unit 110 is output to the tilt function derivation unit 130 and the SOC determination unit 140.

The temperature acquisition unit 120 is configured to be able to acquire the temperature of the battery 10 (preferably the temperature of the electrodes). In particular, the temperature acquisition unit 120 acquires the temperature when the impedance acquisition unit 110 acquires the complex impedance of the battery 10. Since the existing technology can be appropriately adopted as the temperature acquisition method, detailed description here will be omitted. The temperature of the battery 10 acquired by the temperature acquisition unit 120 is output to the inclination function derivation unit 130 and the SOC determination unit 140.

The slope function calculation unit 130 is a specific example of the “deriving means” in the appendix described later, and is a relationship between the complex impedance of the battery 10 acquired by the impedance acquisition unit 110 and the temperature of the battery 10 acquired by the temperature acquisition unit 120. Derivation of the slope function indicating. The slope function will be described in detail later, but it is a function showing that the complex impedance of the battery 10 and the reciprocal of the temperature of the battery 10 have a linear relationship. The tilt function calculated by the tilt function calculation unit 130 is output to the impedance estimation unit 150.

The SOC determination unit 140 is a specific example of the “determination means” in the appendix described later, and the SOC (that is, the charge amount) of the battery 10 is set in the first predetermined range by using the complex impedance acquired by the impedance acquisition unit 110. Judge whether or not it is within. The first predetermined range is a threshold value set for determining whether or not the SOC of the battery 10 is within the range in which the inclination function is established. The determination process executed by the SOC determination unit 140 will be described in detail later, but whether or not the process by the impedance estimation unit 150 is executed depends on the determination result of the SOC determination unit 140.

The impedance estimation unit 150 is a specific example of the “estimation means” in the appendix described later, and estimates the complex impedance of the battery 10 at a predetermined reference temperature by using the slope function derived by the slope function calculation unit 130. .. More specifically, the value that would have been acquired when the battery 10 had a predetermined reference temperature is estimated from the complex impedance acquired by the impedance acquisition unit 110. The value of the complex impedance estimated by the impedance estimation unit 150 is output to the outside of the apparatus and is used as a parameter for estimating the current state of the battery 10, for example.

(2) Temperature Dependence of Complex Impedance and Problems Next, the temperature dependence of the complex impedance of the battery 10 will be described with reference to FIGS. 2 and 3. FIG. 2 is a graph showing waveforms of complex impedance measured under temperature conditions of 20 ° C, 25 ° C, and 30 ° C. Further, FIG. 3 is a graph showing waveforms of complex impedance measured under temperature conditions of 40 ° C., 45 ° C., and 50 ° C. The data shown in FIGS. 2 and 3 were measured when the SOC of the battery 10 was 95%.

As shown in FIGS. 2 and 3, when the complex impedances acquired at the temperatures of the battery 10 at 20 ° C., 25 ° C., 30 ° C., and 40 ° C., 45 ° C., and 50 ° C. are plotted on the complex plane, respectively, It is drawn as a separate curve that slides to the right each time the temperature drops. This indicates that the complex impedance of the battery 10 has a large temperature dependence. The temperature dependence of the complex impedance is due to charge transfer and lithium ion diffusion inside the battery 10.

As described above, the complex impedance of the battery 10 changes greatly depending on the temperature of the battery 10 at the time of measurement. Therefore, when trying to estimate the state of the battery 10 using the complex impedance, it is preferable to use the complex impedance measured at a predetermined reference temperature. That is, it is preferable to use the complex impedance measured under predetermined temperature conditions. However, it is not easy to carry out the measurement after setting the temperature of the battery 10 to a predetermined reference temperature. In particular, it is very difficult to maintain the battery 10 at the reference temperature because the temperature of the battery 10 rises and falls due to the charging and discharging operations while the vehicle equipped with the battery 10 is running.

As a countermeasure to the above-mentioned problem, a method of converting (correcting) the complex impedance acquired at an arbitrary temperature into the complex impedance acquired at the reference temperature can be considered. However, when trying to convert complex impedance using existing technology, relatively advanced and complicated processing such as Fitting analysis is required. Therefore, for example, when the complex impedance is measured in real time in a traveling vehicle or the like, it is not easy to convert the complex impedance into a value corresponding to the reference temperature each time.

The impedance estimation device 100 according to the present embodiment executes the operations described in detail below in order to solve the above-mentioned problems.

(3) Operation Description The process executed by the impedance estimation device 100 according to the present embodiment will be described with reference to FIG. FIG. 4 is a flowchart showing an operation flow of the impedance estimation device according to the present embodiment.

In FIG. 4, when the impedance estimation device according to the present embodiment is operating, first, a plurality of complex impedances are acquired under a plurality of temperature conditions (step S11). More specifically, the complex impedance of the battery 10 is acquired by the impedance acquisition unit 110, and the temperature of the battery 10 at that time is acquired by the temperature acquisition unit 120.

The acquired complex impedance of the battery 10 can be separated for each frequency, and in the following processing, the complex impedance at the first predetermined frequency is acquired. In this case, the absolute value of the complex impedance at the first predetermined frequency, the real number component (that is, the real number part) and the imaginary number component (that is, the imaginary number part) are acquired. The "first predetermined frequency" here is a frequency corresponding to the slope component of the complex impedance plotted by Core-Cole (that is, the linear portion in FIGS. 2 and 3).

The acquired complex impedance of the battery 10 (hereinafter, its value is referred to as Z0) and the temperature of the battery 10 when the complex impedance is acquired (hereinafter, its value is referred to as T0) are calculated by a slope function. It is input to the unit 130 and a slope function for estimating the complex impedance is derived. The tilt function calculation unit 130 converts the complex impedance value Z0 at a predetermined frequency of the battery 10 and the temperature T0 of the battery 10 when the complex impedance is acquired into a mathematical formula (formula (1) described later) stored in advance. Substitute (step S12).

According to the research of the inventor of the present application, it has been found that the relationship of the following mathematical formula (1) is established between the value Z of the complex impedance at a predetermined frequency and the temperature T of the battery 10.

logZ = A × (1 / T) + B ・ ・ ・ (1)
Therefore, if the slope A and the intercept B are obtained after substituting the actually acquired complex impedance value Z0 and temperature T0 of the battery 10 into the equation (1) (step S13), the complex impedance value Z and temperature of the battery 10 are obtained. A slope function showing the relationship with T can be derived.

Next, the SOC determination unit 140 determines whether or not the SOC of the battery 10 is within the first predetermined range by using the complex impedance of the battery 10 acquired by the impedance acquisition unit 110 (step S14). Then, when it is determined that the SOC of the battery 10 is within the first predetermined range (step S14: YES), the impedance estimation unit 150 substitutes a predetermined reference temperature for T in the inclination function to determine a predetermined temperature. The value Z of the complex impedance corresponding to the reference temperature is calculated (step S15). On the other hand, when it is determined that the SOC of the battery 10 is not within the first predetermined range (step S14: NO), the impedance estimation unit 150 does not calculate the complex impedance value Z (that is, the process of step S15 is omitted. ).

(4) Derivation Method of Slope Function Next, a specific method for deriving the slope function described above will be described with reference to FIGS. 5 to 8. FIG. 5 is a graph showing the relationship between the absolute value of the complex impedance and the reciprocal of the temperature, and FIG. 6 is a graph showing the relationship between the real number component of the complex impedance and the reciprocal of the temperature. Further, FIG. 7 is a graph showing the relationship between the imaginary component of the complex impedance and the reciprocal of the temperature, and FIG. 8 is a graph showing the relationship between the value of the complex impedance measured at different SOCs and the reciprocal of the temperature. .. The numerical values on the horizontal axes of FIGS. 5 to 8 are numerical values when the temperature T is calculated in absolute temperature.

As shown in FIGS. 5 to 7, a plurality of types of slope functions are derived using each of the absolute value | Z | of the complex impedance, the real number component Z', and the imaginary number component Z', that is, the absolute value | Z. The slope function for |, the slope function for the real number component Z', and the slope function for the imaginary number component Z'are derived separately. However, the gradient function may not necessarily be derived for all of the absolute value | Z |, the real number component Z', and the imaginary number component Z', and at least one of the absolute value | Z |, the real number component Z', and the imaginary number component Z'. The inclination function may be derived for each of them.

In FIG. 5, the absolute value | Z | of the complex impedance measured when the temperature T of the battery 10 is in the range of 20 ° C. to 50 ° C. changes linearly with the fluctuation of the temperature T. Specifically, a straight line (see the broken line in the figure) can be drawn by connecting points corresponding to the same frequency. In this way, by using the absolute value | Z | of the complex impedance and the temperature T when the value is acquired, the absolute value | Z of the complex impedance | Z is obtained by obtaining an approximate straight line connecting the plotted points. The slope function for | can be derived.

In FIG. 6, the real number component Z'of the complex impedance measured when the temperature T of the battery 10 is in the range of 20 ° C. to 50 ° C. also changes due to the fluctuation of the temperature T, similarly to the absolute value | Z | shown in FIG. On the other hand, it changes linearly. Therefore, if the real number component Z'of the complex impedance and the temperature T when the value is acquired are used, the slope of the real number component Z'of the complex impedance is obtained by obtaining an approximate straight line connecting the plotted points. Functions can be derived.

In FIG. 7, the imaginary component Z of the complex impedance measured when the temperature T of the battery 10 is in the range of 20 ° C. to 50 ° C. is also the absolute value | Z | shown in FIG. 5 and the real number component Z shown in FIG. In the same way as', it changes linearly with the fluctuation of the temperature T. Therefore, if the imaginary component Z of the complex impedance and the temperature T when the value is acquired are used, the points obtained by plotting them can be obtained. By finding the approximate straight line to connect, the slope function for the imaginary component Z "of the complex impedance can be derived.

In FIG. 8, a straight line corresponding to the same slope function is superimposed on each graph when the complex impedance value Z0 and the temperature T0 of the battery 10 are acquired with different SOCs (that is, 95%, 60%, 10%). Is illustrated. Then, in each graph of the absolute value | Z |, the real number component Z', and the imaginary number component Z', it can be seen that a plurality of points corresponding to the same frequency are connected by a straight line.
This indicates that the same slope function is derived for each of the absolute value | Z |, the real number component Z', and the imaginary number component Z', even when the SOCs are different from each other.

However, the imaginary component Z "has a large deviation from the straight line in the data at SOC 10%. That is, the imaginary component Z" may have a non-negligible error depending on the situation at the time of measurement. .. Therefore, in a situation where the absolute value | Z | and the real number component Z'are sufficient for the impedance value Z to be calculated, the inclination function is derived for at least one of the absolute value | Z | and the real number component Z'. (That is, the tilt function is not derived for the imaginary component Z ").

In the examples shown in FIGS. 5 to 7, the slope function is derived as an approximate straight line connecting a plurality of points, but if either the slope A or the intercept B of the slope function is already known, 1 An approximate straight line (that is, a slope function) can be derived from even one point. In other words, if the slope A or intercept B of the slope function is known, it is not necessary to obtain a plurality of complex impedance values Z0 and temperature T0, and the slope function can be obtained only from a set of complex impedance values Z0 and temperature T0. Can be derived.

However, if a plurality of points are not used, it is expected that the influence of the measurement error when measuring the complex impedance and the temperature of the battery 10 will be large. Specifically, it becomes impossible to remove the influence of noise by using a plurality of points. Therefore, when deriving the slope function from one point, the data measured at a temperature at which the measurement accuracy is guaranteed is used. The "temperature at which the measurement accuracy is guaranteed" is the temperature of the battery 10 corresponding to a situation in which it is considered unlikely that an event that causes a decrease in the measurement accuracy has occurred.

For example, the battery 10 may have internal temperature variations due to temperature changes, and the temperature T may not be accurately measured. Therefore, it is not possible to derive an accurate slope function by using the data measured under such circumstances. Therefore, when deriving the slope function from one point, it is preferable to use the data measured in a situation where there is no temperature variation inside the battery 10. An example of a situation in which the temperature does not vary inside the battery 10 is immediately after the vehicle equipped with the battery 10 is started.

The derived tilt function does not change unless the configuration of the battery 10 changes. That is, as long as the battery 10 is not replaced with a new one, it is possible to estimate the complex impedance using the same slope function. Therefore, once the slope function is derived, it is not necessary to derive a new slope function each time.

If the complex impedance of a plurality of types of batteries 10 is estimated, a plurality of slope functions corresponding to each of the plurality of types of batteries 10 may be used. In this case, the inclination function may be newly derived at the timing when the type of the battery 10 is changed, or a plurality of inclination functions corresponding to the plurality of types of batteries 10 are derived and stored in advance from among them. The slope function to be used may be selected as appropriate.

In order to select the slope function to be used from the plurality of stored slope functions, the complex impedance value Z of the battery 10 may be measured under temperature conditions where the measurement accuracy is guaranteed. Since the complex impedance value Z and the temperature T measured in this way have high measurement accuracy and are accurate values, if a slope function that holds by substituting these values is found, the slope function to be used (that is, that is, The tilt function corresponding to the battery 10 at that time) can be appropriately selected.

(5) SOC Dependency of Complex Impedance and Problems Next, the SOC dependence of the complex impedance of the battery 10 will be specifically described with reference to FIGS. 9 and 10. FIG. 9 is a graph showing the waveform of the complex impedance acquired in the range of SOC 20% to 50%. FIG. 10 is a graph showing waveforms of complex impedance acquired in the range of SOC 70% to 80%. The plurality of data shown in FIGS. 9 and 10 were measured under the same temperature conditions.

As shown in FIG. 9, the complex impedance of the battery 10 acquired in the range of SOC 20% to 50% has a slope as long as the temperature of the battery 10 is the same, even if the SOCs are different from each other. The components are almost the same (see the area surrounded by the dashed line in the figure). This means that if the temperature of the battery 10 is the same, the complex impedance does not change even if the SOC changes. Therefore, if the SOC is in the range of 20% to 50%, the relationship between the complex impedance of the battery 10 and the temperature is constant.

On the other hand, as shown in FIG. 10, the complex impedance of the battery 10 acquired in the range of SOC 70% to 80% has a slope component when the SOCs are different from each other even if the temperature of the battery 10 is the same. Do not match (see the area surrounded by the dashed line in the figure). This means that even if the temperature of the battery 10 is the same, the complex impedance changes due to the change in SOC. Therefore, in the range of SOC 70% to 80%, the relationship between the complex impedance of the battery 10 and the temperature is not constant.

According to the research of the inventor of the present application, it has been found that the SOC dependence of the complex impedance as described above occurs only in a specific SOC range. Specifically, in addition to the SOC of 70% to 80% shown in FIG. 10, in the range of SOC 0% to 15% and in an extremely narrow range around SOC 100%, the complex impedance also depends on the SOC of the battery 10. It fluctuates relatively greatly. This is due to a change in the diffusion coefficient of graphite, which is the negative electrode active material of the battery 10, and a change in the diffusion of lithium ions in the active material.

In the range where the complex impedance changes depending on the SOC (that is, the range of SOC 70% to 80%, SOC 0% to 15%, SOC 100%), the relationship between the complex impedance of the battery 10 and the temperature is not constant. Even with the slope function described above, it may not be possible to estimate the exact complex impedance value Z. On the other hand, in other ranges (that is, in the range of SOC 15% to 70% and SOC 80% to 99%), the relationship between the complex impedance of the battery 10 and the temperature is constant, so by using the slope function, An accurate complex impedance value Z can be estimated. That is, the accurate value of the complex impedance Z cannot be estimated only in the range where the SOC dependence occurs in the complex impedance, and in the other range, the accurate value of the complex impedance Z can be estimated.

The SOC determination unit 140 performs a process of determining the SOC of the battery 10 (that is, the process of step S14 in FIG. 4) with the SOC range in which the above-mentioned accurate value of the complex impedance Z can be estimated as the “first predetermined range”. Running.

(5) SOC Determination Method Next, a specific process executed by the SOC determination unit 140 to determine the SOC of the battery 10 will be specifically described with reference to FIGS. 11 and 12. FIG. 11 is a graph showing the intersection of the approximate straight line connecting the complex impedances acquired at SOC 60% and the real axis. FIG. 12 is a graph showing the intersection of the approximate straight line connecting the complex impedances acquired at SOC 10% and the real axis.

As shown in FIG. 11, the SOC determination unit 140 connects the values of a plurality of complex impedances acquired under different temperature conditions at the second predetermined frequency (0.1 Hz in the example of the figure) on the complex plane. Calculate the approximate straight line. The data acquired by the impedance acquisition unit 110 and the temperature acquisition unit 120 may be used to calculate the approximate straight line. After that, the SOC determination unit 140 calculates the intersection of the calculated approximate straight line and the real axis (that is, the axis of the real number component).

Here, in particular, according to the research of the inventor of the present application, it is found that the distribution of the intersections of the calculated approximate straight line and the real axis converges within the second predetermined range in the range where the complex impedance does not depend on the SOC. doing. As can be seen from the figure, in the data measured in the state where the complex impedance does not depend on the SOC and the SOC is 60%, the intersection of the calculated approximate straight line and the real axis is within the second predetermined range.

On the other hand, as shown in FIG. 12, in the data measured in the state where the complex impedance depends on the SOC at 10% SOC, the intersection point between the calculated approximate straight line and the real axis deviates greatly from the second predetermined range. (Compared to FIG. 11, the position of the intersection is largely shifted to the left).

As described above, if it is determined whether or not the calculated intersection is within the second predetermined range, whether or not the SOC of the battery 10 is within the first predetermined range (in other words, using the inclination function). Whether or not an accurate value of the complex impedance Z can be estimated) can be preferably determined. The second predetermined range may be determined in advance by a simulation or the like in advance.

By the way, whether or not the SOC of the battery 10 is within the first predetermined range can be determined from the specific SOC value of the battery 10. However, it is difficult to accurately estimate the SOC of the battery 10 in a situation where an accurate complex impedance cannot be estimated. However, according to the method described above, it is possible to determine whether or not the SOC of the battery 10 is within the first predetermined range even when the SOC of the battery 10 is not exactly known at this time. That is, it can be determined whether or not the accurate value of the complex impedance Z can be estimated by using the slope function without calculating the specific value of the battery SOC.

(6) Technical Effect As described above, according to the impedance estimation device according to the present embodiment, by using a slope function showing the relationship between the complex impedance value Z of the battery 10 and the reciprocal of the temperature T, The value Z of the complex impedance corresponding to the desired temperature can be estimated relatively easily. Therefore, for example, even if the complex impedance is measured under any temperature condition, it can be converted into the value Z of the complex impedance corresponding to a predetermined reference temperature. In other words, it is possible to know the value Z of the complex impedance that would be measured when the battery 10 is at a predetermined reference temperature without actually setting the temperature of the battery 10 to a predetermined reference temperature. As a result, the state estimation of the battery 10 using the value Z of the complex impedance can be preferably performed.

Further, in the present embodiment, the complex impedance value Z is estimated when the SOC of the battery 10 is determined to be in the first predetermined range, and the complex impedance value Z is not estimated otherwise. As a result, when the relationship indicated by the slope function is not established between the value Z of the complex impedance and the temperature T (specifically, when the complex impedance also changes depending on the SOC of the battery 10), The value Z of the complex impedance cannot be estimated. Therefore, it is possible to prevent the erroneous complex impedance value Z from being estimated, and it is possible to more preferably estimate the complex impedance value Z.

<Additional notes>
Various aspects of the invention derived from the embodiments described above will be described below.

(Appendix 1)
The impedance estimation device according to Appendix 1 is based on the value of the complex impedance of the batteries acquired at a plurality of different temperatures at the first predetermined frequency and the temperature of the battery when the complex impedance is acquired. Derivation means for deriving a tilt function indicating the relationship between the value of the complex impedance at the first predetermined frequency and the reciprocal of the temperature of the battery, and whether or not the charge amount of the battery is within the first predetermined range. The determination means for determining and when it is determined that the charge amount of the battery is within the first predetermined range, the tilt function is used at the predetermined frequency of the complex impedance corresponding to the desired temperature of the battery. It is provided with an estimation means for estimating the value.

According to the impedance estimation device described in Appendix 1, the tilt function is based on the value of the complex impedance of the batteries acquired at a plurality of different temperatures at a predetermined frequency and the temperature of the battery when the complex impedance is acquired. Derived. This slope function is derived as a function showing the relationship between the value of the complex impedance at a predetermined frequency and the reciprocal of the battery temperature. Therefore, by using the slope function, it is possible to estimate the value of the complex impedance corresponding to the desired temperature of the battery at a predetermined frequency. In other words, it is possible to estimate the complex impedance under a predetermined temperature condition regardless of the actual battery temperature.

However, the complex impedance of the battery also changes depending on the amount of charge of the battery. Specifically, when the charge amount of the battery is within the first predetermined range, the relationship indicated by the tilt function is established between the complex impedance of the battery and the temperature, but the charge amount of the battery is the first predetermined range. If it is not within the range, the relationship indicated by the tilt function does not hold between the complex impedance of the battery and the temperature.

Therefore, if the charge amount of the battery is not within the first predetermined range, the complex impedance of the battery cannot be accurately estimated even if the tilt function is used. However, in the impedance estimation device described in Appendix 1, when it is determined that the charge amount of the battery is within the first predetermined range, the value of the complex impedance at the predetermined frequency is estimated by using the slope function. This prevents an incorrect complex impedance value from being estimated, and makes it possible to estimate a more accurate complex impedance value.

(Appendix 2)
In the impedance estimation device according to Appendix 2, the determination means is (i) a plurality of the complex impedances acquired at a plurality of different temperatures on a complex plane centered on the real number component and the imaginary number component of the complex impedance. The intersection of the approximate straight line connecting the values at the second predetermined frequency and the axis of the real number component is calculated, and (ii) the battery is charged when the calculated intersection falls within the second predetermined range. It is determined that the amount is within the first predetermined range.

According to the impedance estimation device described in Appendix 2, on the complex plane, an approximate straight line connecting the values of a plurality of complex impedances acquired at a plurality of different temperatures at a second predetermined frequency to each other and an axis of a real number component are used. And the intersection of are calculated. Then, when the calculated intersection falls within the second predetermined range, it is determined that the charge amount of the battery is within the first predetermined range.

According to the research of the inventor of the present application, when the relationship indicated by the slope function is established between the complex impedance of the battery and the temperature (in other words, when the charge amount of the battery is within the first predetermined range). ), It is known that the distribution of the above-mentioned intersections converges within a certain range. Therefore, it can be determined whether or not the charge amount of the battery is within the first predetermined range depending on whether or not the calculated intersection is within the second predetermined range.

The present invention can be appropriately modified within a range not contrary to the gist or idea of the invention that can be read from the claims and the entire specification, and an impedance estimation device accompanied by such a modification is also included in the technical idea of the present invention. ..

10 Battery 100 Impedance estimation device 110 Impedance acquisition unit 120 Temperature acquisition unit 130 Tilt function calculation unit 140 SOC judgment unit 150 Impedance estimation unit

Claims (2)

Based on the value at the first predetermined frequency corresponding to the tilt component in the Core-Cole plot of the complex impedance of the batteries acquired at a plurality of different temperatures and the temperature of the battery when the complex impedance was acquired. Derivation means for deriving a tilt function indicating the relationship between the value of the complex impedance at the first predetermined frequency and the reciprocal of the temperature of the battery.
A determination means for determining whether or not the charge amount of the battery is within the first predetermined range in which the inclination function is established, and
When it is determined that the charge amount of the battery is within the first predetermined range, the inclination function is used to estimate the value of the complex impedance corresponding to the desired temperature of the battery at the first predetermined frequency. An impedance estimation device including an estimation means. The determination means (i) corresponds to (i) a tilt component in a Cole-Cole plot of a plurality of the complex impedances acquired at a plurality of different temperatures on a complex plane centered on the real number component and the imaginary number component of the complex impedance. an approximate straight line connecting together the value of the second predetermined frequency, the calculating the intersection of the axis of the real component, (ii) in a second predetermined range intersection the calculated is determined according to the first predetermined range The impedance estimation device according to claim 1, wherein it is determined that the charge amount of the battery is within the first predetermined range.