JP6466287B2 - Battery state measuring method and battery state measuring apparatus - Google Patents

Description

  The present invention relates to a battery state measuring method and a battery state measuring apparatus for measuring a memory effect state in a secondary battery.

  Conventionally, a technique for evaluating the state of a secondary battery by performing complex impedance analysis on the secondary battery has been proposed. According to this method, since the battery state can be evaluated without destroying the secondary battery, the evaluated secondary battery can be used as it is.

  As an example of a technique for evaluating the state of a battery by a complex impedance analysis method, a technique for determining whether or not the capacity ratio between the positive electrode and the negative electrode in a secondary battery is deviated from a desired value is known (for example, Patent Documents). 1). In this technique, complex impedance is measured by applying an alternating voltage to a secondary battery while changing the frequency stepwise, and a Nyquist plot of the measured impedance is obtained. In the Nyquist plot, the capacities of the positive electrode and the negative electrode in the secondary battery when the slope of the line segment connecting two points corresponding to different frequencies included in the portion corresponding to the diffusion resistance region is smaller than the threshold value. It is determined that the ratio deviates from a desired value.

International Publication WO2013 / 115038

  Incidentally, one of the evaluations required for the secondary battery is a memory effect. The memory effect is a phenomenon in which, when a secondary battery is used for a long period of time, an electromotive force changes in the vicinity of the SOC (State of Charge: charged state) that is frequently used. Since this memory effect causes deterioration of the secondary battery, it is desirable to measure the state such as the amount of the memory effect in measuring and evaluating the state of the secondary battery.

  The present invention has been made in view of such circumstances, and the object thereof is a battery state measurement method and a battery state measurement capable of measuring the state of the memory effect in a secondary battery using complex impedance analysis. To provide an apparatus.

  A battery state measuring method for solving the above problem is a battery state measuring method for measuring a state of a memory effect in a secondary battery, and an impedance acquisition step for acquiring a complex impedance corresponding to a diffusion resistance region in the secondary battery; A calculation step of performing a calculation of applying the value based on the acquired complex impedance to a relationship between the value based on the complex impedance determined in advance and the state of the memory effect to determine the state of the memory effect, Based on this, the gist is to measure the state of the memory effect.

  A battery state measuring device that solves the above problem is a battery state measuring device that measures a state of a memory effect in a secondary battery, and an impedance acquisition unit that acquires a complex impedance corresponding to a diffusion resistance region in the secondary battery; A holding unit that holds a relationship between the value based on the complex impedance and the state of the memory effect, a calculation unit that calculates a value based on the complex impedance from the acquired complex impedance, and a value based on the held complex impedance The gist of the present invention is to include a measurement unit that performs an operation of applying a value based on the calculated complex impedance to the relationship with the state of the memory effect to measure the state of the memory effect.

  According to such a method or configuration, the state of the memory effect is calculated based on obtaining the complex impedance corresponding to the diffused resistance region and applying it to the value based on the complex impedance and the state of the memory effect. The Thereby, the state of the memory effect in the secondary battery is measured using the complex impedance analysis.

  As a preferred method, the relationship between the value based on the complex impedance and the state of the memory effect is a relationship between the imaginary value of the complex impedance and the amount of the memory effect, and the imaginary value of the acquired complex impedance is preliminarily calculated in the calculation step. The state of the memory effect is obtained by performing an operation applied to the relationship between the set imaginary value of the complex impedance and the amount of the memory effect.

According to such a method, the amount of the memory effect can be measured from the imaginary value of the complex impedance.
As a preferred method, the relation between the value based on the complex impedance and the state of the memory effect is a relation between the slope of the complex impedance and the amount of the memory effect. In the calculation step, the slope of the acquired complex impedance is preset. The memory effect state is obtained by performing an operation applied to the relationship between the slope of the complex impedance and the amount of the memory effect.

According to such a method, the amount of memory effect can be measured from the slope of the complex impedance.
As a preferred method, the complex impedance corresponding to the diffused resistance region is acquired from a frequency range of 0.01 Hz or more and 0.1 Hz or less.

  In the secondary battery in which the memory effect is generated, a change in complex impedance becomes remarkable in a frequency band of 0.01 Hz or more and 0.1 Hz or less. Therefore, according to such a method, a complex impedance of 0.01 Hz or more and 0.1 Hz or less in the secondary battery to be measured is acquired, and the memory effect state in the secondary battery is acquired based on the acquired complex impedance. Was measured. Thereby, the state of the memory effect can be measured with higher accuracy.

  As a preferred method, the SOC indicating the remaining capacity of the battery storage amount is associated with the relationship between the value based on the complex impedance and the state of the memory effect, and from the secondary battery approximated to the associated SOC. Obtain the complex impedance.

  The relationship between the value based on the complex impedance and the state of the memory effect differs depending on the SOC indicating the remaining capacity of the battery storage amount. Therefore, according to such a method, the secondary battery when the measured complex impedance is acquired is associated with the SOC corresponding to the relationship between the value based on the complex impedance to which the measured complex impedance is applied and the state of the memory effect. Is done. Thereby, the amount of memory effect can be measured with higher accuracy.

As a preferred method, the secondary battery is a nickel metal hydride storage battery.
According to such a method, the nickel-metal hydride storage battery is appropriately re-measured by measuring the presence or absence of the memory effect of a nickel-metal hydride storage battery that is a secondary battery that is relatively likely to have a memory effect when used over a long period of time. Can be used.

  According to this battery state measuring method and battery state measuring apparatus, the state of the memory effect in the secondary battery can be measured using complex impedance analysis.

The block diagram which shows the schematic structure about 1st Embodiment which actualized the battery condition measuring apparatus. The graph which shows the relationship between the charging / discharging amount and memory amount in a secondary battery. 5 is a flowchart showing a procedure for calculating a memory amount from an imaginary value of complex impedance in the embodiment. The graph explaining the complex impedance of a secondary battery. The graph which shows the relationship between the complex impedance and memory amount in a secondary battery. In the same embodiment, the graph which shows the relationship between the imaginary value of complex impedance, and a memory amount with a linear expression. In the same embodiment, a graph for explaining the relationship between the SOC and the linear expression indicating the relationship between the imaginary value of the complex impedance and the memory amount, (a) is a graph showing the slope of the linear expression, (b) is a linear expression The graph which shows the intercept of. The block diagram which shows the schematic structure about 2nd Embodiment which actualized the battery state measuring apparatus. 5 is a flowchart showing a procedure for calculating a memory amount from the slope of complex impedance in the embodiment. In the same embodiment, the graph which shows the relationship between the inclination of complex impedance, and the amount of memory with a linear expression. In the same embodiment, a graph for explaining the relationship between the SOC and the linear expression showing the relationship between the slope of the complex impedance and the memory amount, (a) is a graph showing the slope of the linear expression, (b) is a linear expression The graph which shows an intercept. The flowchart which shows the procedure which calculates memory amount from the imaginary value or inclination of complex impedance about other embodiment which actualized the battery state measuring apparatus.

(First embodiment)
1st Embodiment which actualized the battery state measuring method and the battery state measuring apparatus is described according to FIGS.

  As shown in FIG. 1, the battery state measuring method and the battery state measuring apparatus measure the amount of memory effect of a battery 1 such as a secondary battery, specifically, the amount of change in voltage generated in the secondary battery due to the memory effect. Used for. Here, the battery 1 is, for example, a battery mounted on a vehicle as a power source, and the charging and discharging of the vehicle or the like is controlled by a battery control device (not shown). In the present embodiment, the battery 1 is a nickel hydride secondary battery.

First, SOC (State of Charge) of the battery 1 and the memory effect will be described.
Generally, a secondary battery has a problem that battery performance deteriorates when overdischarge or overcharge is performed. For this reason, the SOC of the secondary battery mounted on the vehicle or the like is measured. More specifically, the SOC indicates the ratio of the remaining capacity that is the amount of electricity that is actually charged to the charge capacity that is the amount of electricity that can be charged in the battery 1. Therefore, charge / discharge control of the secondary battery is performed based on the measurement of the SOC. By the way, when the memory effect occurs in the secondary battery, the measurement accuracy of the SOC decreases, and there is a possibility that charge / discharge control for the secondary battery cannot be performed properly. Therefore, the memory effect generated in the secondary battery is acquired as the amount of the memory effect, and the SOC is calculated in consideration of the acquired amount of the memory effect.

In general, the memory effect is achieved by repeatedly charging and discharging a secondary battery, so that the electromotive voltage of the secondary battery increases during charging, and the voltage during discharging decreases, resulting in a decrease in apparent battery capacity. It is a phenomenon. When the memory effect is generated in the secondary battery, for example, the usable time of the secondary battery is shortened. The memory effect is considered to occur because nickel hydroxide Ni (OH) ₂ which is an active material of the positive electrode plate causes a change in crystal structure. In other words, the memory effect is considered to have a higher correlation in the positive electrode state than in the negative electrode state. Since the amount of the memory effect has a correlation between when it is charged and when it is discharged, the amount of change in voltage due to the memory effect when the secondary battery is charged will be described below. That is, by reversing the sign of the amount of change in voltage, the memory effect during discharging can be explained as well as during charging.

  As shown in FIG. 2, the memory effect is a start voltage M1 that is a voltage with respect to the charge capacity of the battery 1 at the start of use and a voltage with respect to the charge capacity of the battery 1 after being used to the extent that the memory effect occurs. It appears as a voltage difference between the voltage M2. That is, the change amount of the memory effect can be acquired as the value of the voltage difference between the starting voltage M1 and the post-use voltage M2, and the difference between the voltages is obtained as a memory effect amount (hereinafter referred to as memory amount) ΔV [ V]. In FIG. 2, the SOC when the battery 1 is fully charged is indicated by “Cx”, for example. For the memory amount ΔV, a value corresponding to the SOC of the battery 1 can be obtained. For convenience of explanation, the memory amount ΔV will be described below when the memory amount ΔV is charged so that the SOC of the battery 1 becomes “60%”. The voltage difference between the hourly voltage M1 and the post-use voltage M2.

  As shown in FIG. 1, a battery 1 made of a nickel metal hydride secondary battery includes a power supply unit 2 that supplies an alternating current for impedance measurement to the battery 1 and a voltage measurement that measures an alternating voltage between electrodes of the battery 1. A device 5 and a current measuring device 6 for measuring an alternating current flowing between the power supply unit 2 and the battery 1 are connected. As shown in FIG. 1, a measuring device 10 that measures the memory amount of the battery 1 is connected to a power supply unit 2, a voltage measuring device 5, and a current measuring device 6. In the present embodiment, the battery state measurement device includes the measurement device 10.

  The power supply unit 2 generates an alternating current having a predetermined frequency in response to an instruction from the measuring apparatus 10 and supplies the generated alternating current between the electrodes of the battery 1. The alternating current is, for example, a sinusoidal waveform current. Further, the power supply unit 2 can change the frequency of the alternating current. When the current magnitude and the frequency range are set, the power supply unit 2 can output the alternating current having the set magnitude amplitude by sequentially changing the frequency within the set frequency range. it can. The range of frequencies to be set includes, for example, “100 kHz” on the high frequency side and “1 mHz” on the low frequency side, but is not limited to this. The value may be higher or lower than this. In the present embodiment, for example, the high frequency side is “1 kHz” and the low frequency side is “0.01 Hz”.

  The power supply unit 2 outputs signals related to the set current and set frequency of the output alternating current to the measuring apparatus 10. Further, the power supply unit 2 outputs and stops the alternating current according to the output start and stop signals input from the measurement apparatus 10.

The voltage measuring device 5 outputs a voltage signal corresponding to the measured AC voltage between the electrodes of the battery 1 to the measuring device 10.
The current measuring device 6 outputs a current signal corresponding to the current measured between the power supply unit 2 and the battery 1 to the measuring device 10.

  The measuring device 10 measures the memory amount ΔV of the battery 1. The measuring device 10 can use the calculated memory amount ΔV for calculation of the battery SOC or can output it to the outside. The measuring device 10 acquires a voltage from the voltage signal input from the voltage measuring device 5 and acquires a current from the current signal input from the current measuring device 6. The measuring apparatus 10 may acquire the set current and set frequency of the alternating current from the signal input from the power supply unit 2.

  The measuring apparatus 10 also includes an FRA (Frequency Response Analyzer) unit 30 that measures the frequency characteristics of the battery 1 that is the measurement target. The measuring apparatus 10 includes a processing unit 40 that performs a process of calculating the memory amount ΔV, and a storage unit 20 as a holding unit that holds data used for calculating the memory amount ΔV.

  The FRA unit 30 gives a sinusoidal signal to the object to be measured and obtains its frequency response. The FRA unit 30 outputs an instruction signal to the power supply unit 2 so as to output a sine wave signal necessary for frequency characteristic measurement, and causes the power supply unit 2 to output an alternating current corresponding to the instruction signal. Further, the FRA unit 30 inputs a voltage signal from the voltage measuring device 5 to calculate an AC voltage between the electrodes of the battery 1, inputs an electric current signal from the current measuring device 6, and flows an AC current between the battery 1. Is calculated. Therefore, the FRA unit 30 acquires the inter-terminal voltage and the input / output current of the battery 1 to which the current is supplied from the voltage measuring device 5. Then, the FRA unit 30 analyzes or acquires the frequency characteristics of the battery 1 based on information such as the magnitude and frequency of the sine wave supplied to the battery 1 and the voltage between the terminals of the battery 1 and the input / output current. Or For example, the FRA unit 30 calculates a response gain and a phase for each frequency of the alternating current to be supplied. In this way, the frequency characteristics of the battery 1 are obtained. For example, a Bode diagram or a Nyquist diagram can be drawn from the frequency, gain, and phase information indicating the frequency characteristics.

  In the present embodiment, the FRA unit 30 measures the complex impedance Z of the battery 1 based on the acquired voltage and current. The unit of the complex impedance Z is [Ω] (ohms), and is expressed by the following equation (1) by the real component Zr [Ω] and the imaginary component Zi [Ω] which are vector components. “J” is an imaginary unit. Hereinafter, the unit [Ω] is omitted.

Then, the FRA unit 30 outputs information indicating frequency characteristics such as the calculated complex impedance Z to the processing unit 40.
The processing unit 40 includes a computer and includes an arithmetic device, a volatile memory, a nonvolatile memory, and the like. Further, the processing unit 40 can exchange data with each of the FRA unit 30 and the storage unit 20.

  The storage unit 20 is a non-volatile storage device such as a hard disk or a flash memory, and holds various data. That is, the storage unit 20 stores parameters and the like necessary for calculating the memory amount ΔV.

  The storage unit 20 stores imaginary value-memory amount correlation data indicating the relationship between the imaginary value in the diffusion resistance region of the complex impedance and the memory amount ΔV as correlation data indicating the relationship between the value based on the complex impedance and the state of the memory effect. 21 is set and held. The imaginary value-memory amount correlation data 21 is data that can calculate the memory amount ΔV by applying an imaginary value of complex impedance, and is a functional expression here. Further, since the correlation between the imaginary value and the memory amount differs depending on the SOC of the battery 1, the imaginary value-memory amount correlation data 21 has correlation data separately for the SOC of the battery 1.

  The processing unit 40 includes an SOC input unit 41 that inputs the SOC of the battery 1 and a Nyquist diagram creation unit 42 as an impedance acquisition unit that obtains complex impedance and creates a Nyquist diagram. The processing unit 40 includes a feature value acquisition unit 43 as a calculation unit that acquires a feature value (imaginary value) from the complex impedance. Further, the processing unit 40 performs an operation to apply the value based on the complex impedance acquired by the processing unit 40 to the relationship between the value based on the complex impedance set and held in the storage unit 20 and the state of the memory effect, And a memory amount calculation unit 45 as a measurement unit for obtaining the amount.

  The SOC input unit 41 inputs the SOC measured by a control device or the like that controls charging / discharging of the battery 1. Note that the measuring apparatus 10 may calculate the SOC of the battery 1 from the acquired voltage and current of the battery 1 or information on frequency characteristics.

  The Nyquist diagram creation unit 42 acquires information on frequency characteristics such as the complex impedance Z from the FRA unit 30 (impedance acquisition step). The Nyquist diagram creation unit 42 creates a Nyquist diagram based on the value of the real component Zr and the value of the imaginary component Zi, which are vector components included in the complex impedance Z measured at a plurality of frequencies. Therefore, an impedance curve L1 (see FIG. 4) is created on the complex plane as a Nyquist diagram.

  The feature value acquisition unit 43 acquires the value of the imaginary component Zi as an imaginary value from the impedance curve L1 created by the Nyquist diagram creation unit. Note that the value of the imaginary component Zi may be acquired as an imaginary value from the vector component included in the measured complex impedance Z.

  The memory amount calculation unit 45 refers to the imaginary value calculated by the feature value acquisition unit 43, the SOC input from the SOC input unit 41, and the imaginary value-memory amount correlation data 21, and acquires the complex impedance Z A memory amount ΔV corresponding to is calculated (calculation step).

  Next, a procedure for measuring the battery state measurement method and the memory amount ΔV of the battery state measurement device in the measurement device 10 will be described with reference to FIG. The battery state measurement is started as the memory amount ΔV needs to be calculated.

  When the measurement of the battery state is started, the measuring apparatus 10 acquires the SOC by the SOC input unit 41 of the processing unit 40 (step S10), and measures the impedance at the frequency of the diffusion region by the FRA unit 30 (step S11). ). The SOC may be acquired from the outside or may be calculated by the measuring apparatus 10. As the impedance, the impedance measured by the FRA unit 30 is input to the processing unit 40. The measuring apparatus 10 extracts an imaginary value from the impedance Z by the feature value acquisition unit 43 of the processing unit 40 (step S20). The measurement apparatus 10 refers to the relational expression between the imaginary value and the memory amount held in the storage unit 20 by the memory amount calculation unit 45 of the processing unit 40 (step S21), and the imaginary value extracted to the referenced relational expression. Is applied to calculate the memory amount ΔV (step S22). Since the relational expression between the imaginary value and the memory amount is set for each SOC, the measuring apparatus 10 refers to the relational expression corresponding to the SOC based on the acquired SOC. Thereby, the memory amount ΔV is calculated from the imaginary value of the impedance, that is, the memory amount ΔV is measured. Then, the measurement of the memory amount ΔV is finished.

Next, the fact that the memory amount ΔV can be calculated from the imaginary value of impedance will be described.
First, with reference to FIGS. 4 and 5, the relationship between the impedance curve and the positive electrode drawn in the Nyquist diagram and the relationship between the impedance curve and the memory amount will be described in order.

  FIG. 4 shows an impedance curve L1 of the battery 1, a positive impedance curve L2, and a negative impedance curve L3 on the complex plane. Here, the positive impedance curve L2 and the negative impedance curve L3 are values measured by providing the battery 1 with a reference electrode, and need not be created.

  The impedance curve L1 schematically shows a plot of the magnitude of the real component Zr and the imaginary component Zi of the complex impedance Z on the complex plane. The horizontal axis is the real component Zr, and the vertical axis is the imaginary component Zi. The impedance curve L1 is measured by changing the frequency f of the alternating current supplied from the power supply unit 2 to the battery 1. The frequency f at which the complex impedance is measured is, for example, “0.01 Hz” at the point f1, “0.1 Hz” at the point f2, “1.0 Hz” at the point f3, “10 Hz” at the point f4, and “100 Hz at the point f5”. ”And“ 1 kHz ”at the point f6. A point f0 included in the negative electrode impedance curve L3 has a frequency of “1 mHz”. By the way, the impedance curve L1 changes with the value of SOC. Moreover, it changes also with battery types, such as a nickel-hydrogen secondary battery and a lithium ion secondary battery. Furthermore, even when the same battery type is used, the number of cells, capacity, and the like are different. In this embodiment, when the memory amount ΔV is measured, the battery type is a nickel hydride secondary battery, and the conditions such as the SOC value of the battery 1, the number of cells, and the capacity are the same.

  The impedance curve L1 of the battery 1 can be divided into four regions. The four regions are a region a corresponding to circuit resistance, a region b corresponding to solution resistance, a region c corresponding to reaction resistance, and a region (diffusion resistance region) d corresponding to a substantially linear diffusion resistance from the high frequency side. Consists of. The circuit resistance is an impedance or the like of a wiring made of an active material or a contact resistance in the current collector. The solution resistance is an electron movement resistance such as a resistance when ions in the electrolytic solution in the separator move. The reaction resistance is a resistance of charge transfer in an electrode reaction. The diffusion resistance is an impedance in which material diffusion is involved. Since each resistor affects each other, it is difficult to divide each region a, b, c, d into only a portion affected by each resistor, but at least each region a of the impedance curve L1. , B, c, and d are associated with the behavior of the curve depending on the resistance most affected.

  By the way, the impedance curve L1 of the battery 1 is obtained by synthesizing the positive impedance curve L2 and the negative impedance curve L3. That is, in the frequency range “0.01 Hz” or more and “0.1 Hz” or less of the points f1 to f2 included in the region d corresponding to the diffused resistance, the change in the positive electrode impedance curve L2 is large, while the impedance of the negative electrode The change of the curve L3 is small. From this, it can be said that the area | region d corresponding to the diffusion resistance of the impedance curve L1 is an area | region where the influence of the impedance curve L2 of a positive electrode is large. That is, the state of the positive electrode is reflected in the region d corresponding to the diffused resistor. On the other hand, in the frequency range of points f2 to f5 included in the region c corresponding to the reaction resistance, the change in the negative electrode impedance curve L3 is large, while the change in the positive electrode impedance curve L2 is small. From this, it can be said that the area | region c corresponding to the reaction resistance of the impedance curve L1 of the battery 1 is an area | region where the influence of the impedance curve L3 of a negative electrode is large. That is, the state of the negative electrode is reflected in the region c corresponding to the reaction resistance.

  From this, the inventors found that the memory amount ΔV caused by the state of the positive electrode is correlated with the complex impedance in the region d corresponding to the diffusion resistance of the impedance curve L1 of the battery 1. That is, it has been found that there is a correlation between the memory amount ΔV and the complex impedance Z in the region d corresponding to the diffusion resistance of the impedance curve L1 of the battery 1. Note that the memory effect also has a correlation with the positive electrode impedance curve L2, but as described above, in order to measure the positive electrode impedance curve L2, the battery 1 is disassembled and referenced in the battery case. Since it is necessary to install an electrode, there is a problem that it is difficult to reuse the battery 1 whose memory amount ΔV is measured. On the other hand, as described in this embodiment, since the impedance curve L1 of the battery 1 can be created without disassembling the battery 1, the memory amount ΔV is calculated by calculating the memory amount ΔV using the impedance curve L1 of the battery 1. The state of the memory effect can be acquired while maintaining the availability of the battery 1 such that the battery 1 can be used even after the calculation of ΔV.

  FIG. 5 also shows an impedance curve L11 based on the complex impedance of the starting voltage M1 in the initial battery 1 and an impedance curve L12 based on the complex impedance of the post-use voltage M2 in the battery 1 when the memory effect occurs. ing. The complex impedance of the starting voltage M1 and the complex impedance of the after-use voltage M2 are measured, for example, when the battery SOC is “60%”. In each of the impedance curves L11 and L12, a linear portion from the frequency “0.01 Hz” at the point f1 to the frequency “0.1 Hz” at the point f2 is included in the “region d corresponding to the diffused resistance”. Is greatly affected by the impedance curve L2. Therefore, the inventor further found that a correlation between the usage state of the battery 1 and the memory amount ΔV appears in the linear portions of the impedance curves L11 and L12.

  More specifically, the difference between the imaginary value of the impedance curve L12 corresponding to the post-use voltage M2 and the imaginary value of the impedance curve L11 corresponding to the starting voltage M1 is when the frequency at the point f1 is “0.01 Hz”. The difference between the imaginary values at the frequency “0.1 Hz” at the point f2 is smaller than the difference between the imaginary values. Therefore, at the frequency “0.01 Hz” at the point f1, the imaginary value of the impedance curve L12 corresponding to the post-use voltage M2 is smaller than the imaginary value of the impedance curve L11 corresponding to the starting voltage M1 (absolute Value is a large value).

  Thus, as the battery 1 was used, it was found that the imaginary value of the impedance curve L12 corresponding to the post-use voltage M2 was smaller than the imaginary value of the impedance curve L11 corresponding to the starting voltage M1. . Further, as the battery 1 is used, as the battery 1 is used, the post-use voltage M2 rises compared to the starting voltage M1, and the memory amount ΔV increases. And it became clear that there is a correlation in which the memory amount ΔV increases in accordance with the small imaginary values of the impedance curves L11 and L12.

  That is, as shown in FIG. 6, as a relationship between the imaginary value and the memory amount ΔV, a linear function relationship such as a graph Lv1 in which the memory amount ΔV increases as the imaginary value decreases is obtained. Therefore, the memory amount ΔV is expressed by the following equation (2), where the slope of the graph Lv1 is the slope a1 and the intercept of the graph Lv1 is the intercept b1.

At this time, the memory amount ΔV is related to the SOC size.
That is, as shown in FIG. 7A, it is clear that the relationship between the SOC and the slope a1 in the equation (2) is such that the slope a1 increases as the SOC increases, as shown in the graph LA1. became. Further, as shown in FIG. 7B, the relationship between the SOC and the intercept b1 in the equation (2) clearly shows that the intercept b2 increases as the SOC increases, as shown in the graph LB1. became.

  In other words, in this embodiment, the imaginary value-memory amount correlation data 21 holds the above-described equation (2), and the slope a1 and the intercept b1 applied to the equation (2) according to the SOC. Is retained. Note that the imaginary value-memory amount correlation data 21 is held in the form of map data or a table even if the data is held as a function, as long as the data capable of calculating the memory amount ΔV is held. It may be.

As described above, according to the battery state measuring method and the battery state measuring apparatus of the present embodiment, the effects listed below can be obtained.
(1) The memory effect state (memory amount ΔV) is calculated based on obtaining a complex impedance corresponding to the diffused resistance region d and applying it to the value based on the complex impedance and the memory effect state. . Thereby, the state of the memory effect in the battery 1 which is a secondary battery is measured using the complex impedance analysis.

  (2) By making the relationship between the value based on the complex impedance and the state of the memory effect the imaginary value of the complex impedance and the amount of the memory effect, the amount of memory effect (memory amount ΔV) can be measured from the imaginary value of the complex impedance. become.

  (3) In the battery 1 that has produced the memory effect, the change in complex impedance becomes significant in a frequency band of 0.01 Hz or more and 0.1 Hz or less. Therefore, a complex impedance of 0.01 Hz or more and 0.1 Hz or less in the measurement target battery 1 is acquired, and the state of the memory effect in the battery 1 is measured based on the acquired complex impedance. Thereby, the state of the memory effect can be measured with higher accuracy.

  (4) The relationship between the value based on the complex impedance and the state of the memory effect differs depending on the SOC indicating the remaining capacity of the battery storage amount. Therefore, the battery 1 when the measured complex impedance is acquired is associated with the SOC corresponding to the relationship between the value based on the complex impedance to which the measured complex impedance is applied and the state of the memory effect. Thereby, the amount of memory effect can be measured with higher accuracy.

  (5) Since the battery 1 is a nickel-metal hydride storage battery, the nickel-metal hydride storage battery is a battery 1 that is relatively prone to have a memory effect when used over a long period of time. The storage battery can be reused appropriately.

(Second Embodiment)
A second embodiment in which the battery state measurement method and the battery state measurement device are embodied will be described with reference to FIGS. This embodiment is different from the first embodiment in that the amount of memory is calculated based on the slope of the complex impedance. Therefore, in the following, the configuration that is mainly different from the first embodiment will be described in detail, and for convenience of description, the same reference numerals are given to the same configuration and the detailed description is omitted.

  As shown in FIG. 8, in this embodiment, the storage unit 20 stores, as correlation data indicating the relationship between the value based on the complex impedance and the state of the memory effect, the gradient indicating the relationship between the gradient of the complex impedance and the memory amount. -Memory amount correlation data 22 is set and held. That is, slope-memory amount correlation data 22 is held instead of the imaginary value-memory amount correlation data 21 of the first embodiment.

The processing unit 40 includes an inclination calculation unit 44 as a calculation unit that calculates the inclination of the complex impedance from the complex impedance, instead of the feature value acquisition unit 43 of the first embodiment.
The slope calculating unit 44 acquires the slope of the impedance curve L1 created by the Nyquist diagram creating unit. For example, based on the measurement of each impedance at two different measurement frequencies included in the region d corresponding to the diffused resistor, the inclination with respect to the real axis of the line segment connecting the two measured impedances is calculated. A plurality of impedances having different measurement frequencies can be acquired from the FRA unit 30.

  The memory amount calculation unit 45 corresponds to the acquired complex impedance Z by referring to the slope of the impedance calculated by the slope calculation unit 44, the SOC input from the SOC input unit 41, and the slope-memory amount correlation data 22. A memory amount ΔV to be calculated is calculated.

  Next, with reference to FIG. 9, the procedure for measuring the battery state measurement method and the memory amount of the battery state measurement device in the measurement apparatus 10 will be described. The battery state measurement is started as the memory amount ΔV needs to be calculated.

  When the measurement of the battery state is started, the measuring apparatus 10 acquires the SOC (Step S10) and measures the impedance at the frequency of the diffusion region (Step S11). The measuring apparatus 10 calculates the inclination of the straight line portion of the impedance curve L1 from the plurality of impedances Z by the inclination calculation unit 44 of the processing unit 40 (step S30). The measuring apparatus 10 refers to the relational expression between the inclination and the memory amount held in the storage unit 20 in the memory amount calculation unit 45 of the processing unit 40 (step S31), and the inclination of the impedance curve L1 is referred to this relational expression. Is applied to calculate the memory amount ΔV (step S32). Since the relational expression between the inclination and the memory amount is set for each SOC, the measuring apparatus 10 refers to the relational expression corresponding to the SOC based on the acquired SOC. Thus, the memory amount ΔV is calculated from the impedance gradient, that is, the memory amount ΔV is measured. Then, the measurement of the memory amount is finished.

Subsequently, the fact that the memory amount ΔV can be calculated from the slope of the impedance will be described.
Here, the content of the inclination-memory amount correlation data 22 will be described.

  FIG. 5 of the first embodiment shows an impedance curve L11 in the initial battery 1 and an impedance curve L12 in the battery 1 when the memory effect occurs. In the first embodiment, it has been described that there is a correlation between the imaginary value of the complex impedance in the diffusion resistance region d and the memory amount ΔV, and the correlation is shown as in FIG. In addition, in the present embodiment, the present inventors indicate that the imaginary value of the complex impedance described above in the diffused resistance region d is the slope of a line connecting two values of the complex impedance having different frequencies in the diffused resistor region d. It was also found that there is also a correlation, and the correlation is often shown as the angle of the line in the diffusion resistance region d shown in FIG. Therefore, in such a case, instead of the imaginary value of the complex impedance, the slope of the line connecting the two complex impedance values can be used for the calculation of the memory amount.

  Specifically, as the battery 1 is used, the inclination described above becomes negatively larger. That is, the slope (−θ2 °) of the impedance curve L12 corresponding to the post-use voltage M2 is smaller (negatively larger) than the slope (−θ1 °) of the impedance curve L11 corresponding to the starting voltage M1.

  That is, as shown in FIG. 10, the relationship between the impedance slope and the memory amount ΔV is a linear function such as the graph Lv2 in which the memory amount ΔV increases as the slope [deg] (°) decreases. It was. Therefore, the memory amount ΔV is expressed by the following equation (3), where the slope of the graph Lv2 is the slope a2 and the intercept of the graph Lv2 is the intercept b2.

At this time, the memory amount ΔV is related to the SOC size.
That is, as shown in FIG. 11A, it is clear that the relationship between the SOC and the slope a2 of Equation (3) is such that the slope a2 increases as the SOC increases, as shown in the graph LA2. became. Further, as shown in FIG. 11 (b), it is clear that the relationship between the SOC and the intercept b2 in the equation (3) is such that the intercept b2 increases as the SOC increases, as shown in the graph LB2. became.

  That is, in the present embodiment, the slope-memory amount correlation data 22 holds the above-described formula (3), and holds the slope a2 and the intercept b2 applied to the formula (3) according to the SOC. Has been. Note that the inclination-memory amount correlation data 22 is stored in the form of map data or a table even if the data is stored as a function as long as the data capable of calculating the memory amount ΔV is stored. May be.

  As described above, the battery state measurement method and the battery state measurement device according to the present embodiment have the following effects in addition to the effects (1) to (5) described in the first embodiment. Have.

  (6) By making the relationship between the value based on the complex impedance and the state of the memory effect the relationship between the slope of the complex impedance and the amount of the memory effect, the amount of the memory effect can be measured from the slope of the complex impedance.

(Other embodiments)
In addition, each said embodiment can also be implemented with the following aspects.
In the first embodiment, the state of the memory effect is measured using the relationship between the imaginary value of 0.01 Hz and the memory amount ΔV (see FIG. 6), but other frequencies (for example, 0.1 Hz) The imaginary value of may be used. A low frequency such as 0.01 Hz is preferable in terms of accuracy because a large imaginary value difference can be obtained before and after the occurrence of the memory effect. On the other hand, a high frequency such as 0.1 Hz is preferable in terms of practicality because the measurement time can be shortened.

  In the first embodiment, the measurement apparatus 10 calculates the memory amount ΔV from the imaginary value of the impedance, and in the second embodiment, the measurement apparatus 10 calculates the memory amount ΔV from the slope of the impedance. did. However, the present invention is not limited to this, and if the memory amount ΔV can be measured, the measuring apparatus may have a configuration for calculating the memory amount ΔV from an imaginary value of impedance and a configuration for calculating from the slope of impedance. Good. At this time, for example, the storage unit 20 includes imaginary value-memory amount correlation data 21 and slope-memory amount correlation data 22, and the processing unit 40 includes a feature value acquisition unit 43 that constitutes a calculation unit. And an inclination calculating unit 44 constituting the calculating unit. Then, the memory amount calculation unit 45 refers to the data corresponding to either the imaginary value calculated by the feature value acquisition unit 43 or the inclination calculated by the inclination calculation unit 44 from the data in the storage unit 20 and stores the memory. The amount ΔV may be calculated.

  With reference to FIG. 12, the procedure for measuring the battery state measurement method and the memory amount of the battery state measurement device in the measurement apparatus 10 will be described. When the measurement of the battery state is started, the measuring apparatus 10 acquires the SOC (Step S10) and measures the impedance at the frequency of the diffusion region (Step S11). Then, depending on the condition, it is determined whether the feature value acquisition unit 43 calculates an imaginary value or the inclination calculation unit 44 calculates an inclination. In the present embodiment, the measurement apparatus 10 determines whether or not the number of acquired impedance points having different measurement frequencies is less than two (step S12). For example, when it is desired to measure the memory amount ΔV in a short time, the memory amount ΔV can be calculated from an imaginary value, and when the complex impedance for a plurality of frequencies can be measured, the memory amount ΔV can be calculated from the slope. Note that such conditions can be set so that a calculation method of the memory amount ΔV suitable for each time is selected. If it is determined that the number of acquired impedance points having different measurement frequencies is less than two (YES in step S12), the measuring apparatus 10 calculates the memory amount ΔV from the imaginary value (steps S20 to S22). On the other hand, when it is determined that the number of acquisition points of impedances having different measurement frequencies is not less than two (NO in step S12), the measuring apparatus 10 calculates the memory amount ΔV from the inclination (steps S30 to S32). Thereby, the memory amount ΔV is calculated (measured) from the imaginary value or slope of the impedance.

In each of the above embodiments, the battery 1 may be an assembled battery or a single battery.
In each of the above embodiments, the case where the power supply unit 2 outputs an alternating current corresponding to the current value or the frequency range input from the measuring device 10 is illustrated. However, the present invention is not limited to this, and a predetermined alternating current may be changed and output within a predetermined frequency range without depending on an instruction from the measuring apparatus.

  In each of the above embodiments, the case where the power supply unit 2 outputs an alternating current is illustrated. However, the present invention is not limited to this, and the power supply unit may output an alternating voltage. In this case, the power supply unit may exchange a signal related to the voltage with the measuring device.

  In each of the above embodiments, the battery 1 is not illustrated for connection destinations other than the battery state measurement device, but may be connected to a load such as a motor or a charger such as a power source or a regenerative device, for example. . For example, a configuration in which a battery state measuring device is provided in a battery mounted on a vehicle can be employed. The load can be used when decreasing the battery SOC, and the charger can be used when increasing the battery SOC. Further, by providing a switch in the middle of the circuit from the battery, the connection between the battery and the battery state measuring device, the load, the charger, etc. can be opened and closed as necessary. As a result, the battery SOC can be appropriately measured.

  In each of the above embodiments, the case where the battery 1 is a nickel hydride secondary battery is illustrated. However, the present invention is not limited to this, and the battery may be a secondary battery (storage battery) such as a nickel cadmium secondary battery or a lithium ion secondary battery. Note that although the amount of memory effect generated in lithium ion secondary batteries is less than that of nickel metal hydride secondary batteries, the amount of memory effect can be measured using the above configuration for such memory effects. Is possible.

  In each of the above embodiments, the case where the battery 1 is mounted on a vehicle is illustrated. Such vehicles include electric vehicles and hybrid vehicles, as well as gasoline vehicles and diesel vehicles equipped with batteries. If the battery is required as a power source, the battery may be used as a mobile body other than an automobile, a fixed power source, or a power source other than a motor. For example, power sources other than automobiles include moving bodies such as railways, ships, airplanes, and robots, and power supplies for electrical products such as information processing apparatuses.

  DESCRIPTION OF SYMBOLS 1 ... Battery, 2 ... Power supply part, 5 ... Voltage measuring device, 6 ... Current measuring device, 10 ... Measuring apparatus, 20 ... Memory | storage part, 30 ... FRA part, 40 ... Processing part, 41 ... SOC input part, 42 ... Nyquist diagram creation unit, 43... Feature value acquisition unit, 44... Tilt calculation unit, 45.

Claims (7)

A battery state measurement method for measuring a memory effect state in a secondary battery,
An impedance acquisition step of acquiring a complex impedance corresponding to a diffusion resistance region in the secondary battery;
A calculation step of performing a calculation of applying the value based on the acquired complex impedance to a relationship between the value based on the complex impedance determined in advance and the state of the memory effect to determine the state of the memory effect; And measuring the state of the memory effect based on the above. The relationship between the value based on the complex impedance and the state of the memory effect is the relationship between the imaginary value of the complex impedance and the amount of the memory effect,
The state of the memory effect is obtained by performing an operation that applies the imaginary value of the acquired complex impedance to a preset relationship between the imaginary value of the complex impedance and the amount of the memory effect in the calculation step. The battery state measuring method as described. The relationship between the value based on the complex impedance and the state of the memory effect is the relationship between the slope of the complex impedance and the amount of the memory effect,
The state of the memory effect is obtained by performing an operation in which the slope of the acquired complex impedance is applied to a preset relation between the slope of the complex impedance and a memory effect amount in the calculation step. Battery state measurement method. The battery state measurement method according to any one of claims 1 to 3, wherein a complex impedance corresponding to the diffusion resistance region is acquired from a frequency range of 0.01 Hz or more and 0.1 Hz or less. The relationship between the value based on the complex impedance and the state of the memory effect is associated with SOC indicating the remaining capacity of the battery storage amount, and the complex impedance is calculated from the secondary battery approximated to the associated SOC. The battery state measuring method according to any one of claims 1 to 4. The battery state measuring method according to any one of claims 1 to 5, wherein the secondary battery is a nickel metal hydride storage battery. A battery state measuring device for measuring a state of a memory effect in a secondary battery,
An impedance acquisition unit for acquiring a complex impedance corresponding to a diffusion resistance region in the secondary battery;
A holding unit that holds a relationship between a value based on the complex impedance and a state of the memory effect;
A calculation unit for calculating a value based on the complex impedance from the acquired complex impedance;
A measuring unit that measures the state of the memory effect by performing an operation that applies the value based on the calculated complex impedance to the relationship between the value based on the complex impedance to be held and the state of the memory effect. Battery state measuring device.