JP7058201B2 - Battery status measuring method and battery status measuring device - Google Patents

Description

The present invention relates to a battery state measuring method for measuring a battery state and a battery state measuring device.

Nickel-hydrogen secondary batteries and lithium-ion secondary batteries are used as in-vehicle power sources for electric vehicles, hybrid vehicles, and the like because of their high energy density.
In order to measure the battery state of such a secondary battery, a technique for performing impedance analysis on the secondary battery has been proposed (see, for example, Patent Document 1).

The impedance measuring device described in Patent Document 1 displays the impedance measurement result in a format that makes it easy to analyze the result. The impedance measuring device connects an AC load to the object to be measured, and obtains the impedance of the object to be measured based on the voltage applied across the object to be measured and the current flowing from the object to be measured. The impedance measuring device constitutes a three-dimensional space by a complex plane formed by a real axis and an imaginary plane and an option axis intersecting the complex plane, and the impedances of a plurality of objects to be measured are set in the three-dimensional space. Display in three dimensions.

Japanese Patent Application Laid-Open No. 2003-14796

By the way, the impedance of a battery is usually measured under a normal usage environment of the battery and used for determining the battery state under the normal usage environment. For example, according to the measuring device or the like described in Patent Document 1, the battery state can be measured by displaying the impedance in a normal usage environment in an easy-to-see manner.

In recent years, in order to grasp the battery status in more detail, there is room for improvement in the measurement of the battery status based on the battery impedance, such as the measurement of the battery impedance is not limited to the case where the battery is in a normal usage environment. be.

It should be noted that these problems are not limited to the measurement of the battery state of the secondary battery, but are also the same in the measurement of the battery state of the primary battery.
The present invention has been made in view of such circumstances, and an object of the present invention is to provide a battery state measuring method and a battery state measuring device capable of measuring a battery state in more detail based on impedance measurement. It is in.

The battery state measuring method for solving the above problem is a battery state measuring method for measuring the state of a battery, in which the upper limit value and the lower limit value are used while changing the charging electric amount of the battery by charging or discharging a DC current. A transient state impedance acquisition step of acquiring a transient state impedance corresponding to the measured measurement frequency that changes by applying an AC current having a measured frequency that changes a predetermined frequency range to be partitioned, and charging of the battery. Based on the balanced state impedance acquisition step of acquiring the balanced state impedance corresponding to the measured frequency by applying the AC current having the measured frequency to the battery while maintaining the amount of electricity, and the transient state impedance. It is provided with a peculiar component calculation step of calculating a transient state peculiar component based on the battery state calculated by the above and the battery state calculated based on the impedance of the equilibrium state.

The battery state measuring device that solves the above-mentioned problems is a battery state measuring device that measures the state of the battery, and changes the amount of charging electricity of the battery by charging or discharging a DC current, and sets the upper limit value and the lower limit value. A transient state impedance acquisition unit that acquires a transient state impedance corresponding to the measured measurement frequency that changes by applying an AC current having a measured frequency that changes a predetermined frequency range to be partitioned, and charging of the battery. Based on the balanced state impedance acquisition unit that acquires the balanced state impedance corresponding to the measured frequency by applying the AC current having the measured frequency to the battery while maintaining the amount of electricity, and the transient state impedance. It is provided with a peculiar component calculation unit for calculating a transient state peculiar component based on the battery state calculated by the above-mentioned battery state and the battery state calculated based on the impedance of the equilibrium state.

According to such a method or configuration, the transition state-specific component indicating the battery state due to the battery being in the transition state can be calculated based on the impedance in the transition state and the impedance in the equilibrium state. become. This makes it possible to measure the battery state in the transition state based on the impedance measurement.

As a preferred method, in the transition state impedance acquisition step, the direct current is a rectangular wave.
According to such a method, it is easy to calculate the change in the charge electricity amount of the battery.

As a preferred method, a determination step of determining the battery state of the battery is provided by comparing the component peculiar to the transition state with a determination threshold value which is a value capable of determining the deterioration of the battery.
According to such a method, the battery state can be determined by comparing the component peculiar to the transient state with the determination threshold value capable of measuring the deterioration of the battery.

As a preferred method, in the transient state impedance acquisition step, when one of the lower limit value and the upper limit value for partitioning the predetermined frequency range is the starting point and the other value is the ending point, the measured frequency is the starting point. The value is changed from the start point to the end point and returned to the value of the start point when the value of the end point is reached. The time from the start point to the end point is changed in 10 seconds or less, and the end point is changed. From to the start point is returned in a time of 10 seconds or less.

According to such a method, since the measurement frequency changes from the start point to the end point, it is easy to grasp the continuous frequency characteristic. In addition, it is easy to generate as a measurement frequency and it is easy to measure. Further, the impedance in the transition state can be measured by repeating the measurement frequency at intervals shorter than the response period in which the battery is in the transition state, for example, 10 seconds.

As a preferred method, in the transition state impedance acquisition step, the upper limit value is 10 kHz or less and the lower limit value is 1 Hz or more, and the measurement frequency is changed in the direction from the upper limit value to the lower limit value.

According to such a method, the impedance of the same frequency can be measured a plurality of times while the battery is in the transition state. This makes it possible to measure the impedance of the transition state when the battery is in the transition state for each change in the amount of charge electricity of the battery.

As a preferred method, the magnitude of the direct current is 25 times or more the magnitude of the amplitude of the alternating current.
According to such a method, the battery can be put into a transition state by a direct current, and the impedance in the transition state can be measured by an alternating current that does not affect the transient state of the battery.

As a preferred method, in the specific component calculation step, the transient state impedance is fitted to the equivalent circuit to obtain the transient equivalent circuit corresponding to the transient battery, and the balanced state impedance is obtained. Fitted to the equivalent circuit to obtain the equivalent circuit in the balanced state corresponding to the battery in the balanced state, and the resistance component of the equivalent circuit in the transient state and the resistance component of the equivalent circuit in the balanced state. The difference between the resistance components corresponding to each other is calculated as the transient state-specific component.

According to such a method, the transition-state-specific component is calculated from the difference between the resistance components of the equivalent circuit in the transition state and the resistance components of the equivalent circuit in the balanced state, which correspond to each other. This makes it possible to reduce the factors caused by the equilibrium state and to extract and measure the battery state in the transition state.

As a preferred method, the equivalent circuit in the balanced state is an equivalent circuit in a specific charging electricity amount selected within a range in which the charging electricity amount of the battery changes due to charging or discharging of the DC current, and the equivalent circuit in the transient state. Is an equivalent circuit when the charging electricity amount of the battery is the specific charging electricity amount.

According to such a method, the resistance component of the equivalent circuit in the transient state and the resistance component of the equivalent circuit in the equilibrium state when the charging electricity amount of the battery is a specific charging electricity amount are targeted. The difference between them can be preferably calculated.

As a preferred method, in the specific component calculation step, the charging electricity amount of the battery is specified based on each frequency included in the measurement frequency and the charging electricity amount of the battery associated with each frequency. The impedance of the transient state with respect to the predetermined frequency range when the amount of charging electricity is estimated is estimated, and the estimated impedance of the transient state is fitted to the equivalent circuit to obtain the equivalent circuit of the transient state.

According to such a method, the transient impedance at a frequency that cannot be measured by a specific charge electricity amount is estimated from the transient state impedance measured while the charge electricity amount of the battery changes due to charging or discharging. be able to. Therefore, the accuracy of the resistance component of the equivalent circuit obtained by fitting can be improved.

According to the present invention, the battery state can be measured in more detail based on the impedance measurement.

The block diagram which shows the schematic structure about one Embodiment which embodied the battery state measuring apparatus. In the same embodiment, a flowchart showing a battery state measurement procedure. In the same embodiment, the flowchart which shows the measurement procedure of the battery state which is an equilibrium state. In the same embodiment, it is a graph which shows an example of the current which measures the impedance of the equilibrium state, (a) is the figure which shows the applied current, (b) is the figure which shows the response voltage. In the same embodiment, the graph which shows an example of the Nyquist diagram based on the impedance of the equilibrium state. In the same embodiment, the circuit diagram which shows an example of the equivalent circuit of a battery. In the same embodiment, the flowchart which shows the measurement procedure of the battery state which is a transient state. In the same embodiment, it is a graph which shows an example of the current which measures the impedance of a transient state, (a) is a figure which shows the applied current, (b) is the figure which shows the response voltage. In the same embodiment, a graph showing an example of a Nyquist diagram based on the impedance in the transition state. In the same embodiment, a graph showing an example of the result of measuring the impedance of a battery in a transition state in three dimensions. In the same embodiment, a graph showing an example of the result of measuring the impedance of a battery in a transition state in three dimensions. In the same embodiment, a graph showing an example of a Nyquist diagram that estimates the impedance of the transition state when the battery in the transition state is in a specific SOC. In the same embodiment, a flowchart showing a measurement procedure of a component peculiar to a transition state. In the same embodiment, a graph showing an example of calculating a component peculiar to a transition state. In the same embodiment, an example of a graph for determining the deterioration state of the battery based on the component peculiar to the transition state. The graph which shows an example which determines the threshold value which determines the input / output performance of a product battery based on the component peculiar to a transient state in the other embodiment which embodies the battery state measuring apparatus.

An embodiment in which the battery state measuring method and the battery state measuring device are embodied will be described with reference to FIGS. 1 to 15. This battery state measuring method and battery state measuring device measures a transient state-specific component obtained from the resistance component of the battery 10 as one of the battery states of the battery 10 such as a secondary battery mounted on a vehicle.

A measuring device 30 as a battery state measuring device for measuring the battery state of the battery 10 will be described with reference to FIG. 1. The measuring device 30 measures the impedance in the equilibrium state, the impedance in the transition state, and the component peculiar to the transition state of the battery 10. Here, the transition state-specific component is a component obtained based on impedance measurement when the battery 10 is in the transition state of being charged and discharged. When the battery 10 is in an equilibrium state maintained at a constant voltage, the active material of the battery 10 is in an electrically uniform state. On the other hand, when the battery 10 is in the transition state, the active material of the battery 10 is temporarily in an electrically non-uniform state. That is, in each active material, the potential and the like may be uneven between the surface and the inside of the active material. In general, it can be determined that the battery performance is good when the unevenness of the electric potential or the like is quickly eliminated in the active material, while the battery performance is deteriorated when it takes time to eliminate the unevenness of the electric potential or the like. can. Therefore, in the present embodiment, the deterioration of the battery performance is determined based on the transient state-specific component obtained based on the impedance measured in the transient state of the battery 10.

As shown in FIG. 1, a measuring charge / discharging device 20 for supplying a direct current and an alternating current is connected to the measuring device 30 between the terminals of the battery 10. Further, the measuring device 30 includes a voltage measuring device 21 for measuring the voltage between the terminals of the battery 10 and a current measuring device 22 for measuring the DC current and the AC current flowing between the charging / discharging device 20 for measurement and the battery 10. Is connected.

The charging / discharging device 20 for measurement includes a DC current unit 20A that adjusts the charge state (SOC: State of Charge) of the battery 10 by charging or discharging, and an AC current unit 20B that outputs an AC current for measuring the impedance of the battery 10. To prepare for. Since the SOC is the ratio [%] of the charging electricity amount to the total battery capacity, it has a relationship of "charging electricity amount = total battery capacity x SOC". In the following, for convenience of explanation, both the charging electric energy and the SOC will be described.

The charging / discharging device 20 for measurement can superimpose the AC current of the AC current unit 20B on the charging / discharging current of the DC current unit 20A. Therefore, the measuring charging / discharging device 20 can cause the measuring device 30 to measure the transient state impedance, which is the transient impedance of the transient state battery 10 in which charging or discharging is continued.

The DC current unit 20A has a charging function of charging the battery 10 with a predetermined amount of DC current and a discharging function of discharging the DC current of a predetermined amount of current from the battery 10. The direct current unit 20A sets a predetermined amount of current for charging and discharging the battery 10 from a current amount smaller than the rated current amount (1C) of the battery 10 (for example, 0.1C) to a current amount larger than 1C (for example). It can be selected from 10C and 20C). The direct current unit 20A can continuously flow the selected predetermined amount of current as a rectangular wave shown in the graph L31 of FIG. 8A from the start to the end of charging / discharging. The charging / discharging device 20 for measurement can measure the impedance in the transient state having a large difference from the impedance in the balanced state by passing a current larger than 1C through the DC current unit 20A through the battery 10. Further, the charging / discharging device 20 for measurement can maintain the period in which the battery 10 is in the transient state for a long time by passing a current larger than 1C through the DC current unit 20A to the battery 10. In order to increase the difference between the impedance in the equilibrium state and the impedance in the transition state, it is preferable to charge the battery 10 at 10 C or more, preferably 20 C or more.

The alternating current unit 20B has a function of supplying an alternating current for measuring the alternating current impedance to the battery 10. The alternating current unit 20B can generate an alternating current having a set amplitude and a set frequency, and apply the generated alternating current between the terminals of the battery 10. Further, the AC current unit 20B can sweep the frequency of the AC current, and the measurement frequency is unidirectional until the upper limit value or the lower limit value is reached within a predetermined frequency range divided by the upper limit value and the lower limit value. Change. The upper limit value and the lower limit value are different values, and a relatively high frequency is set as the upper limit value and a low frequency is set as the lower limit value. For example, the AC current unit 20B outputs an AC current having an amplitude of a predetermined magnitude as an AC current that changes from an upper limit value of 10 kHz to a lower limit value of 1 Hz in 10 seconds.

It is preferable that the frequency of the alternating current does not change during one cycle. Further, in the predetermined frequency range, the upper limit value may be higher than 10 kHz or the lower limit value may be lower than 1 Hz as long as the impedance of the battery 10 in the transition state can be measured. However, the lower limit is preferably a frequency or higher that does not change the degree of the transition state due to the direct current during one cycle. Further, if the lower limit value is lowered, the time required for measurement increases, so that the frequency is preferably 1 Hz or higher, although it depends on the period during which the battery 10 can be maintained in the transition state. For example, referring to FIG. 5, the measurement frequency does not include the “diffusion region d” whose frequency is 0.1 Hz or less and the portion of the “reaction resistance region c” whose frequency is less than 1 Hz, while “reaction”. A portion of the resistance region c having a frequency of 1 Hz or higher, a circuit resistance region a, and a solution resistance region b are included.

In the charging / discharging device 20 for measurement, the amount of direct current and the magnitude of the amplitude of alternating current are determined so that the transient impedance can be measured. The length of time during which charging / discharging is in a transient state differs depending on the type and characteristics of the battery 10. For example, in the measuring charging / discharging device 20, the amount of direct current is 2 of the magnitude of the amplitude of alternating current. It is preferably fold or more, preferably 10 times or more, and more preferably 25 times or more.

In the measuring charge / discharging device 20, the current amount and voltage of the direct current, the amplitude and voltage of the alternating current, the upper limit value and the lower limit value of the frequency, the sweep period and the like are set by the measuring device 30. Further, the charging / discharging device 20 for measurement outputs or stops the direct current or the alternating current according to the output start signal and the output stop signal of the direct current input from the measuring device 30, the output start signal and the output stop signal of the alternating current. I do.

On the contrary, the charging / discharging device 20 for measurement outputs the set value and the current value of the DC current to be output, and the set value and the current value of the AC current to be output to the measuring device 30.
The voltage measuring device 21 outputs a voltage signal corresponding to the AC voltage and the DC voltage measured between the electrodes of the battery 10 to the measuring device 30.

The current measuring device 22 outputs a current signal corresponding to the alternating current and the direct current measured between the charging / discharging device 20 for measurement and the battery 10 to the measuring device 30.
The measuring device 30 measures the transient state-specific component of the battery 10 and determines the battery state based on the measurement result. The measuring device 30 may display the battery status of the battery 10 or output it to the outside. For example, the external battery control device (not shown) may perform charge / discharge control on the battery 10 according to the battery state of the battery 10 output from the measuring device 30.

The measuring device 30 acquires the voltage between the terminals of the battery 10 based on the voltage signal input from the voltage measuring device 21, and the charging / discharging device 20 for measurement and the battery 10 based on the current signal input from the current measuring device 22. Get the current flowing between them. The measuring device 30 acquires the setting information of the direct current and the alternating current from the signal input from the charging / discharging device 20 for measurement.

The measuring device 30 includes a processing unit 40 that performs a calculation process for measuring the transition state-specific component of the battery 10, and a storage unit 50 that holds data used for measuring the transition state-specific component of the battery 10.

The storage unit 50 is a non-volatile storage device such as a hard disk or a flash memory, and holds various data. In the present embodiment, the storage unit 50 holds the parameter 51 required for measuring the transient state-specific component and the determination data 52 for determining the battery state. As the determination data 52, a determination threshold value (see, for example, FIG. 15) for determining the deterioration state of the battery 10 theoretically determined in advance based on the component peculiar to the transition state is set.

The processing unit 40 includes a microcomputer composed of a CPU, ROM, RAM, and the like. The processing unit 40 can use information such as voltage, current, and measurement frequency acquired by the measuring device 30. Further, the processing unit 40 is connected to the storage unit 50, and data can be exchanged between the processing unit 40 and the storage unit 50. The processing unit 40 executes various processes in the processing unit 40 by, for example, executing various programs held in the ROM or RAM by the CPU.

The processing unit 40 measures the impedance of the SOC adjusting unit 41 that adjusts the SOC of the battery 10, the equilibrium state impedance measuring unit 42 that measures the impedance of the battery 10 in the equilibrium state as the equilibrium state impedance, and the impedance of the battery 10 in the transition state. A transition state impedance measuring unit 43 for measuring as a transition state impedance is provided. The equilibrium state impedance measuring unit 42 constitutes an equilibrium state impedance acquisition unit, and the transition state impedance measuring unit 43 constitutes a transition state impedance acquisition unit. Further, the processing unit 40 includes a Nyquist diagram creating unit 44 that creates a Nyquist diagram, and a parameter calculation unit 45 as a unique component calculation unit that fits the impedance measurement result to the equivalent circuit to calculate the resistance component of the equivalent circuit. And a determination unit 48 for determining the battery state.

The SOC adjustment unit 41 adjusts the SOC of the battery 10 to an SOC or the like suitable for measuring the impedance in the equilibrium state, measuring the impedance in the transition state, or the like. The SOC adjusting unit 41 adjusts the battery 10 to a predetermined SOC by instructing the charging / discharging device 20 for measurement to charge / discharge the current. The SOC adjusting unit 41 calculates the SOC by measuring the battery 10 by a well-known method, and calculates the SOC based on the integration of the amount of electricity being charged and discharged.

The balanced state impedance measuring unit 42 performs a process (balanced state impedance measuring step) of measuring the balanced state impedance, which is the impedance measured at the measurement frequency while the battery 10 is in the balanced state. The balanced state impedance measuring unit 42 instructs the measuring charging / discharging device 20 to charge / discharge the direct current so that the battery 10 is in the balanced state, and also instructs the supply / discharge of the alternating current for the measurement. The equilibrium state impedance measuring unit 42 measures the impedance Z of the battery 10 based on the voltage and current acquired from the start to the end of the measurement. The unit of impedance Z is [Ω] (ohm). Impedance Z is represented by the vector component Zr [Ω] and the imaginary number component Zi [Ω] as shown in the equation (1). Note that "j" is an imaginary unit. Hereinafter, the unit [Ω] is omitted.

Z = Zr-jZi ... (1)
The transient state impedance measuring unit 43 performs a process (transient state impedance measuring step) of measuring the transient state impedance, which is the impedance repeatedly measured at the measurement frequency while the battery 10 is in the transient state. The transient state impedance measuring unit 43 instructs the measuring charging / discharging device 20 to charge / discharge the direct current so that the battery 10 is in the transient state, and also instructs the supply / discharge of the alternating current for the measurement. The transition state impedance measuring unit 43 measures the impedance Z of the battery 10 based on the voltage and current acquired from the start to the end of the measurement.

The Nyquist diagram creating unit 44 creates a Nyquist diagram from the real number component Zr and the imaginary number component Zi, which are vector components thereof, based on the impedance Z of each of the plurality of frequencies included in the measurement frequency.

As shown in FIG. 5, the Nyquist diagram creating unit 44 creates an impedance curve L21 on a complex plane in which the horizontal axis is the real number axis and the vertical axis is the imaginary number axis. The impedance curve L21 is an example of a Nyquist diagram corresponding to the battery 10 in an equilibrium state maintained at a predetermined SOC. The impedance curve L21 is a plot of the magnitudes of the real number component Zr and the imaginary number component Zi of the impedance Z on the complex plane. This impedance curve L21 is based on the impedance Z measured for each frequency by changing the measurement frequency of the alternating current supplied from the measurement charge / discharge device 20 to the battery 10.

Each point in the impedance curve L21 indicates one of the measured frequencies. In FIG. 5, the lower side is the high frequency side and the upper side is the low frequency side. The impedance curve L21 changes depending on the SOC of the battery 10 and the battery temperature. It also changes depending on the battery type such as nickel-metal hydride secondary battery and lithium-ion secondary battery. Furthermore, even if the battery type is the same, it will change if the number of cells, capacity, etc. are different.

The impedance curve L21 of the battery 10 is divided into a plurality of regions corresponding to the characteristics of the battery 10. The plurality of regions are divided into a "circuit resistance region a", a "solution resistance region b", a "reaction resistance region c", and a "diffusion region d" from the high frequency side to the low frequency side of the measurement frequency.

For example, according to the impedance curve L21 shown in FIG. 5, the frequency range corresponding to the “diffusion region d” is “0.1 Hz” or less, and the frequency range corresponding to the “reaction resistance region c” is “0.1 Hz”. It is larger and less than "100 Hz". Further, the frequency range corresponding to the "solution resistance region b" is higher than "100 Hz" and its vicinity, and the frequency range corresponding to the "circuit resistance region a" is higher than "100 Hz".

Further, with reference to FIG. 1, the Nyquist diagram creating unit 44 performs a process of representing the impedance curves L41, L42, etc. (see FIG. 9) of the transient response impedance created on the complex plane in three dimensions. The Nyquist diagram creation unit 44 performs a time axis addition process for adding a time axis to the complex plane (see FIG. 10), an axis conversion process for converting the added time axis to SOC (see FIG. 11), and a specific SOC (see FIG. 11). An estimation process (see FIG. 12) for estimating the Nyquist diagram in terms of charging electricity amount) is performed.

As shown in FIG. 10, in the time axis addition process, the Nyquist diagram creation unit 44 makes the complex plane three-dimensional by adding a time axis indicating the measurement time. The measurement points constituting the two-dimensional plurality of impedance curves L41 and L42 (see FIG. 9) are also acquired when the measurement time is measured for the transient response impedance. For example, when the transient response impedance is measured 9 times at the measurement frequency, the graph shows the Nyquist diagrams L51-L59 where the measurement started from time t0-t8. The Nyquist diagram L50 shows an example of an impedance curve when it is sufficient to express it in a complex plane because the measurement timing does not affect the measurement result.

As shown in FIG. 11, in the axis conversion process, the Nyquist diagram creating unit 44 associates the time t0 to t8 on the time axis with the SOC values c0 to c8 of the battery 10. In the impedance measurement in the transition state, since the amount of current to be charged / discharged is fixed, the SOC of the battery 10 corresponding to the elapsed time from the start of charging / discharging can be calculated.

As shown in FIGS. 11 and 12, in the estimation process, the Nyquist diagram creating unit 44 determines the transient response impedance measured at the measurement frequency (range from the upper limit value to the lower limit value) at a specific SOC. presume. For example, in FIG. 11, the Nyquist diagrams L51 to L59 connect measurement points having the same frequency to each other by a line LC so that the impedance with respect to the SOC between the two measurement points can be estimated on the line LC. can. For example, the intersection of the line LC connecting the measurement points and the plane parallel to the complex plane corresponding to each SOC is estimated as the impedance curve L6 of the transient response estimated for each SOC. In this way, the impedance curve L71 (see FIG. 12) of the transient response estimated corresponding to the specific SOC value cx is obtained. That is, the impedance curve L71 (Nyquist diagram) in a specific SOC is acquired from the transient state impedance measured by repeating the measurement frequency with respect to the battery 10 in the transient state.

The parameter calculation unit 45 sets the equivalent circuit GC (see FIG. 6) as the equivalent circuit corresponding to the battery 10. The parameter calculation unit 45 calculates various parameters set in the equivalent circuit by fitting the impedance measurement result to the equivalent circuit GC. Further, the parameter calculation unit 45 acquires a transition state-specific component based on the parameter of the equivalent circuit fitted to the balanced state impedance and the parameter of the equivalent circuit fitted to the transition state impedance (specific component calculation step). The parameter of the equivalent circuit is one aspect indicating the battery state.

As shown in FIG. 6, an example of the equivalent circuit GC showing the characteristics of the battery 10 is a parallel circuit of the inductance L1, the resistance R1, the resistance R2 and the capacitance C2, and the parallel to the resistance R3 and the diffusion resistance Wo1 connected in series. It is composed of a series circuit in which a parallel circuit having a connected capacitance C1 is connected in series. The value of each passive element of the equivalent circuit GC constitutes the parameter of the equivalent circuit GC.

In the fitting analysis, the set equivalent circuit GC is fitted to the impedance curve (for example, the impedance curve L21). By this fitting analysis, a parameter that makes the frequency response of the equivalent circuit GC equivalent to the impedance curve is set in each passive element of the equivalent circuit GC.

Further, as shown in FIG. 14, the parameter calculation unit 45 acquires a component peculiar to the transition state. The parameter calculation unit 45 determines a specific SOC and calculates the parameters of the equivalent circuit GC fitted to the equilibrium state impedance in the specified SOC. Further, the parameter calculation unit 45 calculates the parameters of the equivalent circuit GC fitted to the transient state impedance estimated for the specific SOC. Then, the parameter calculation unit 45 acquires the transition state-specific component based on the difference between the parameter of the equivalent circuit GC corresponding to the balanced state impedance and the parameter of the equivalent circuit GC corresponding to the transition state impedance.

For example, as shown in the graph L83 of FIG. 14, the parameter calculation unit 45 has a value of the resistance R3 of the equivalent circuit GC corresponding to the balanced state impedance and a value of the resistance R3 of the equivalent circuit GC corresponding to the transient state impedance. The difference is calculated as the transient state specific component ΔR3. Similarly, as shown in the graph L81 of FIG. 14, the parameter calculation unit 45 has the value of the resistance R1 of the equivalent circuit GC corresponding to the balanced state impedance and the resistance R1 of the equivalent circuit GC corresponding to the transient state impedance. The difference from the value may be calculated as the transient state specific component ΔR1. Further, as shown in the graph L82 of FIG. 14, the parameter calculation unit 45 has a value of the resistance R2 of the equivalent circuit GC corresponding to the balanced state impedance and a value of the resistance R2 of the equivalent circuit GC corresponding to the transient state impedance. The difference may be calculated as the transient state specific component ΔR2.

As shown in FIG. 1, the determination unit 48 compares the transient state-specific component ΔR3 with the determination threshold value for determining the deterioration state of the battery 10, and if the transient state-specific component ΔR3 is equal to or greater than the determination threshold value, the battery 10 is deteriorated. If the transient state-specific component ΔR3 is less than the determination threshold value, it is determined that the battery 10 has not deteriorated. As shown in the graph L91 of FIG. 15, as the deterioration of the battery 10 progresses due to a long period of use or an increase in the number of times of use, the transition state-specific component ΔR3 (resistance value) tends to increase. That is, if the magnitude of the transition state-specific component ΔR3 is less than the determination threshold value, the battery 10 is in the use OK range that is appropriate for use, and conversely, if the magnitude of the transition state-specific component ΔR3 is equal to or larger than the determination threshold value. For example, it is in the range of NG for use, which is inappropriate for use. Such a determination threshold is determined by experience and experiment.

The determination unit 48 may determine the deterioration of the battery 10 by comparing the transition state-specific component ΔR2 or the transition state-specific component ΔR1 with the determination threshold value for determining the deterioration state of the battery 10. At this time, as shown in FIG. 14, each transient state-specific component ΔR3, ΔR2, ΔR1 corresponding to each resistance R3, R2, R1 of the equivalent circuit GC has a relationship of “ΔR3> ΔR2> ΔR1”. Therefore, the determination threshold value for determining the deterioration state of the battery 10 to be compared with the transition state-specific components ΔR3, ΔR2, and ΔR1 is also set as different values corresponding to each of the resistances R3, R2, and R1.

Further, the measuring device 30 can output the determination result of the battery state to the outside as the measurement result regarding the deterioration of the battery 10.
Next, the procedure of the battery state determination process performed in the measuring device 30 based on the measurement of the component peculiar to the transition state will be described.

The battery status determination process is started automatically or in response to an external instruction as the battery status determination is required. Further, the battery state can be similarly measured whether the battery 10 is charged or discharged. Hereinafter, the case where the battery state is determined when the battery 10 is discharged will be described, and the case where the battery state is determined when the battery 10 is charged will be omitted for convenience of explanation.

As shown in FIG. 2, when the battery state determination process is started, the measuring device 30 includes an equilibrium state impedance acquisition step (step S10 in FIG. 2), a transient state impedance acquisition step (step S11 in FIG. 2), and the like. A state determination step (step S12 in FIG. 2) is performed.

As shown in FIG. 3, when the equilibrium state impedance acquisition step shown in step S10 of FIG. 2 is started, the measuring device 30 acquires the SOC of the battery 10 by the SOC adjusting unit 41, and obtains the SOC of the battery 10. An SOC adjustment step (step S20 in FIG. 3) for adjusting the SOC for measurement is performed. When the SOC of the battery 10 is adjusted to the SOC for measurement, the measuring device 30 measures the balanced state impedance in the balanced state impedance measuring step (step S21 in FIG. 3). In the measurement of the balanced state impedance, the measuring device 30 applies an alternating current for measuring the balanced state impedance to the battery 10 adjusted to a specific SOC to acquire a response voltage. The alternating current applied at this time is the alternating current shown in the graph L11 of FIG. 4A, and the response voltage is obtained as the voltage shown in the graph L12 of FIG. 4B. When an alternating current is applied, a direct current for charging and discharging is not applied.

As shown in FIG. 3, when the measuring device 30 acquires the response voltage, it determines whether or not to readjust the SOC of the battery 10 (step S22 in FIG. 3). The measurement SOC is set, for example, from 40% to 60% every 5%, and the SOC needs to be readjusted until the equilibrium state impedance is measured for all measurement SOCs. When the equilibrium state impedance is measured, there is no need to readjust the SOC.

When the measuring device 30 determines that the SOC readjustment is necessary (YES in step S22 in FIG. 3), the process is returned to the SOC adjustment step, and the equilibrium state impedance of the battery 10 adjusted to the next measurement SOC is determined. Make a measurement.

When the measuring device 30 determines that the SOC readjustment is unnecessary (NO in step S22 of FIG. 3), the Nyquist diagram for each measurement SOC is created in the Nyquist diagram creating step (step S23 of FIG. 3). .. From the equilibrium state impedance, a Nyquist diagram as shown in the impedance curve L21 of FIG. 5 is created. Further, the measuring device 30 analyzes the created Nyquist diagram and fits it to the equivalent circuit GC shown in FIG. 6 to perform a parameter calculation step (fitting) for calculating the parameters of the equivalent circuit GC (FIG. 3). Step S24). Then, when the parameter calculation step is completed, the measuring device 30 ends the equilibrium state impedance acquisition step.

Next, the measuring device 30 starts the transition state impedance acquisition step shown in step S11 of FIG.
First, as shown in FIG. 7, the measuring device 30 acquires the SOC of the battery 10 by the SOC adjusting unit 41, and performs an SOC adjustment step (step S30 in FIG. 7) for adjusting the SOC of the battery 10 as necessary. conduct. When the SOC of the battery 10 is adjusted in the SOC adjustment step, the measuring device 30 executes the measurement of the transient state impedance for one cycle in the transient state impedance measuring step (step S31 in FIG. 7). Here, in one cycle, the measurement frequency of the alternating current changes the range of the measurement frequency from the upper limit value as the start point to the lower limit value as the end point in one direction from the start point to the end point. In the measurement of the transition state impedance, an alternating current for measuring the transition state impedance is applied to the battery 10 to acquire the response voltage. The alternating current applied at this time is the alternating current shown in the graph L31 of FIG. 8A, and the alternating current having a magnitude smaller than the direct current is superimposed while discharging the direct current by a predetermined amount of current. It is a current, and the response voltage is obtained as the voltage shown in the graph L32 of FIG. 8 (b). More specifically, the graph L32 is obtained as a voltage in which the battery 10 is discharged with a DC current of a predetermined amount of current and the voltage drops, and the response voltage to the AC current for measurement is superimposed.

As shown in FIG. 7, in the transition state impedance measurement step (step S31 in FIG. 7), when one cycle of the measurement frequency is completed, it is determined whether or not to execute the next cycle (step S32 in FIG. 7). The cycle can be repeated until the battery 10 approaches the target SOC.

When the measuring device 30 determines that the next cycle is to be executed (YES in step S32 of FIG. 7), the measuring device 30 shifts the process to step S31 of FIG. 7 and executes the transition state impedance measuring step (1 cycle).

On the other hand, when the measuring device 30 determines that the next cycle is not executed (NO in step S32 of FIG. 7), the Nyquist diagram creation unit 44 performs a Nyquist diagram creation process (steps S33 to FIG. 7). S36).

More specifically, in the Nyquist diagram creation process, the measuring device 30 has a Nyquist diagram creation step (two-dimensional) (step S33 in FIG. 7) and a Nyquist diagram creation step (time axis addition) for adding a time axis. (Step S34 in FIG. 7) and a Nyquist diagram creating step (SOC axis conversion) (step S35 in FIG. 7) for converting the time axis to the SOC axis are executed. Further, the measuring device 30 selects a specific SOC from the SOCs for which the equilibrium state impedance is measured, and estimates the impedance curve corresponding to the selected specific SOC. Nyquist diagram creation step (same SOC estimation) (FIG. 7). Step S36) is executed.

As shown in FIG. 9, the measuring device 30 creates one Nyquist diagram for each cycle in the Nyquist diagram creating step (two-dimensional) (step S33 in FIG. 7). For example, the impedance curve L41 in FIG. 9 is a Nyquist diagram of the cycle starting from time t0 (see FIG. 10), and the impedance curve L42 is a Nyquist diagram of the cycle starting from time t8 (see FIG. 10). .. Then, in the range sandwiched between the impedance curve L41 and the impedance curve L42, Nyquist diagrams of cycles starting from each of the times t1 to t7 are arranged.

As shown in FIG. 10, in the Nyquist diagram creating step (addition of time axis) (step S34 in FIG. 7), the measuring device 30 has a time axis orthogonal to the real axis and the imaginary axis with respect to the Nyquist diagram shown in FIG. Is added to represent the Nyquist diagram in three dimensions. Since it takes time for the measurement frequency to move from the upper limit value to the lower limit value in one cycle, the Nyquist diagrams L51 to L59 are graphs that move in the direction in which time elapses as the frequency becomes lower. In FIG. 10, it becomes a curve that bends upward. The Nyquist diagram L50 is an example in which the passage of time is not taken into consideration.

As shown in FIG. 11, the measuring device 30 converts the time axis into the SOC axis in the Nyquist diagram creating step (SOC axis conversion) (step S35 in FIG. 7). The SOC of the battery 10 is calculated by subtracting the discharge amount of the direct current and the amount of electricity calculated by the passage from the time t0, where the SOC of the battery 10 is the value c0 at the time t0 at the start of measurement. Therefore, the time axis of the Nyquist diagram of FIG. 11 can be associated with an SOC value (for example, values c0 to c8) that changes with the amount of discharged electricity. At this time, by complementing each Nyquist diagram between L51 and L59, the impedance corresponding to the unmeasured SOC is estimated.

As shown in FIG. 12, the measuring device 30 creates a Nyquist diagram L6 corresponding to the transient response impedance when the SOC is constant in the Nyquist diagram creation step (same SOC estimation) (step S36 in FIG. 7). Then, from these created Nyquist diagrams L6, the Nyquist diagram L71 corresponding to the specific SOC to be measured is selected. As a result, the Nyquist diagram L71 of a specific SOC can be obtained from the transition state impedance measured from the transient state battery 10 in which the SOC changes.

Then, as shown in FIG. 7, the measuring device 30 analyzes the Nyquist diagram estimated for a specific SOC and fits it to the equivalent circuit GC (see FIG. 6) to fit each parameter of the equivalent circuit GC. Is performed in the parameter calculation step (step S37 in FIG. 7). When the parameter calculation process is completed, the measuring device 30 ends the transition state impedance acquisition process.

Next, as shown in FIG. 2, a state determination step (step S12 in FIG. 2) for determining the battery state of the battery 10 is started.
As shown in FIG. 13, when the state determination step (step S12 in FIG. 2) is started, the measuring device 30 selects the parameters of the equivalent circuit GC based on the balanced state impedance corresponding to the specific SOC (FIG. 13). Step S40) and parameter selection of the equivalent circuit GC based on the transition state impedance (step S41 in FIG. 13) are performed.

Next, the measuring device 30 calculates the resistance component peculiar to the transient state by the parameter calculation unit 45 (step S42 in FIG. 13). That is, the measuring device 30 calculates the transition state-specific component ΔR3, which is the difference between the value of the resistance R3 of the equivalent circuit GC in the balanced state and the value of the resistance R3 of the equivalent circuit GC in the transition state (see FIG. 14).

Subsequently, the measuring device 30 performs a state determination process for determining the deterioration of the battery state by the determination unit 48 (step S43 in FIG. 13). In the state determination process, if the calculated transient state-specific component ΔR3 is equal to or greater than the determination threshold set as the battery deterioration index, it is determined that the battery is deteriorated, and if it is less than the determination threshold value, the battery is deteriorated. It is judged that there is no such thing.

Then, the procedure of the battery state determination process is completed.
Next, the effect of this embodiment will be described.
(1) The transition state-specific component indicating the battery state caused by the battery 10 being in the transition state can be calculated based on the impedance in the transition state and the impedance in the equilibrium state. This makes it possible to measure the battery state in the transition state based on the impedance measurement.

(2) It is easy to calculate the change in the charge electricity amount of the battery by making the direct current a rectangular wave.
(3) The battery state can be determined by comparing the component peculiar to the transient state with the determination threshold value capable of measuring the deterioration of the battery 10.

(4) Since the measurement frequency changes from the start point (upper limit value) to the end point (lower limit value), it is easy to grasp the continuous frequency characteristics. In addition, it is easy to generate as a measurement frequency and it is easy to measure. Further, the impedance in the transition state can be measured by repeating the measurement frequency at intervals shorter than the response period in which the battery 10 is in the transition state, for example, 10 seconds.

(5) By setting the upper limit value to 10 kHz or less and the lower limit value to 1 Hz or more, the impedance of the same frequency can be measured a plurality of times while the battery 10 is in the transition state. This makes it possible to measure the impedance of the transition state when the battery 10 is in the transition state for each change in the amount of charging electricity of the battery 10.

(6) If the magnitude of the amplitude of the alternating current is set to, for example, twice, ten times, or 25 times or more, the battery can be put into a transient state by the direct current, and the alternating current that does not affect the transient state of the battery can be made. The impedance in the transient state can be measured by the current.

(7) The difference (transient) between the resistance components (for example, the value of the resistance R3) corresponding to each other among the resistance component of the equivalent circuit GC in the transient state and the resistance component of the equivalent circuit GC in the equilibrium state in which the component peculiar to the transient state is transient. It is calculated as a state-specific component ΔR3). This makes it possible to reduce the factors caused by the equilibrium state and to extract and measure the battery state in the transition state.

(8) Since the resistance component of the equivalent circuit GC in the transient state and the resistance component of the equivalent circuit GC in the equilibrium state when the SOC of the battery 10 is a specific SOC are targeted, the difference between the corresponding resistance components is preferably used. Can be calculated.

(9) From the transient impedance measured while the SOC of the battery 10 changes due to charging or discharging, the transient impedance at a frequency that cannot be measured by a specific SOC can be estimated. Therefore, the accuracy of the resistance component of the equivalent circuit GC obtained by fitting can be improved.

(Other embodiments)
In addition, this embodiment can be changed and carried out as follows. The present embodiment and the following modified examples can be implemented in combination with each other within a technically consistent range.

-The quality of the input / output performance of the battery may be determined based on the resistance component peculiar to the transient state. Generally, as shown in the graph L101 of FIG. 16, the input / output performance of the product battery becomes “high” when the resistance component peculiar to the transition state becomes low, and becomes “low” when the resistance component peculiar to the transition state becomes high. Further, the input / output performance of the battery can set a threshold value between the "OK region" when it is good and the "NG region" when it is bad. At this time, the input / output performance of the battery is determined to be appropriate when the resistance component peculiar to the transition state is a low value at which the input / output performance of the battery is good, and the resistance component peculiar to the transition state is the input / output of the battery. If it is a high value that causes poor performance, it is determined to be inappropriate. This makes it possible to determine the input / output performance of the product battery based on the component peculiar to the transition state.

-In the above embodiment, the case where the balanced state impedance is measured and then the transition state impedance is measured has been illustrated, but the present invention is not limited to this, and the transition state impedance may be measured and then the balanced state impedance may be measured. , The transition state impedance and the balanced state impedance may be measured alternately.

-In the above embodiment, the battery 10 may be an assembled battery or a single battery.
-In the above embodiment, the case where the battery 10 is a lithium ion secondary battery has been illustrated, but the battery is not limited to this, and the battery is an alkaline secondary battery such as a nickel hydrogen secondary battery or a nickel cadmium secondary battery. May be good. Further, the battery may be a primary battery.

-In the above embodiment, the case where the charging / discharging device 20 for measurement outputs an alternating current according to the current value and the frequency range input from the measuring device 30 is exemplified. However, the present invention is not limited to this, and the charging / discharging device for measurement may output a predetermined alternating current while changing it in a predetermined frequency range, regardless of the instruction from the measuring device.

-In the above embodiment, the case where the charging / discharging device 20 for measurement is configured to include the alternating current unit 20B and the direct current unit 20A has been illustrated, but these devices may be provided separately. ..

-In the above embodiment, the case where the equivalent circuit GC having the configuration shown in FIG. 6 is set is illustrated. However, the equivalent circuit is not limited to this, and may have a configuration capable of modeling a battery based on impedance.

-In the above embodiment, the case where the battery 10 is mounted on the vehicle is illustrated. This vehicle includes electric vehicles, hybrid vehicles, as well as battery-powered gasoline-powered vehicles and diesel-powered vehicles. Further, if the battery is required as a power source, it may be used as a moving body other than an automobile, a fixedly installed power source, or a power source other than a motor.

10 ... Battery, 20 ... Charging / discharging device for measurement, 20A ... DC current section, 20B ... AC current section, 21 ... Voltage measuring device, 22 ... Current measuring device, 30 ... Measuring device, 40 ... Processing section, 41 ... SOC adjustment Unit, 42 ... Equivalent state impedance measurement unit, 43 ... Transient state impedance measurement unit, 44 ... Nyquist diagram creation unit, 45 ... Parameter calculation unit, 48 ... Judgment unit, 50 ... Storage unit, 51 ... Parameter, 52 ... For determination Data, C1, C2 ... capacitance, GC ... equivalent circuit, L1 ... inductance, R1, R2, R3 ... resistance, Wo1 ... diffusion resistance.

Claims (10)

It is a battery condition measurement method that measures the battery condition.
While changing the charge electricity amount of the battery by charging or discharging a direct current, the change is made by applying an alternating current having a measurement frequency that changes a predetermined frequency range divided by an upper limit value and a lower limit value to the battery. The transient state impedance acquisition process for acquiring the transient state impedance corresponding to the measured frequency, and
A balanced state impedance acquisition step of acquiring an impedance in a balanced state corresponding to the measured frequency by applying the alternating current having the measured frequency to the battery while maintaining the charging electricity amount of the battery.
A battery state measuring method comprising a battery state calculated based on the impedance of the transition state and a peculiar component calculation step of calculating a component peculiar to the transition state based on the battery state calculated based on the impedance of the equilibrium state. .. The battery state measuring method according to claim 1, wherein in the transition state impedance acquisition step, the direct current is a square wave. The battery state measuring method according to claim 1 or 2, further comprising a determination step of determining the battery state of the battery by comparing the transient state-specific component with a determination threshold value which is a value capable of determining the deterioration of the battery. .. In the transient state impedance acquisition step, when one of the lower limit value and the upper limit value for partitioning the predetermined frequency range is the start point and the other value is the end point, the measurement frequency is set from the start point to the end point. It changes in the direction and returns to the value of the start point when the value of the end point is reached. The value from the start point to the end point is changed in a time of 10 seconds or less, and from the end point to the start point. The battery state measuring method according to any one of claims 1 to 3, wherein the product is returned in a time of 10 seconds or less. The battery state according to claim 4, wherein in the transition state impedance acquisition step, the upper limit value is 10 kHz or less and the lower limit value is 1 Hz or more, and the measurement frequency is changed in the direction from the upper limit value to the lower limit value. Measuring method. The battery state measuring method according to any one of claims 1 to 5, wherein the magnitude of the direct current is 25 times or more the magnitude of the amplitude of the alternating current. In the specific component calculation step, the transient state impedance is fitted to the equivalent circuit to obtain the transient equivalent circuit corresponding to the transient battery, and the balanced state impedance is fitted to the equivalent circuit. The equivalent circuit in the balanced state corresponding to the battery in the balanced state is obtained, and the resistance component of the equivalent circuit in the transient state and the resistance component of the equivalent circuit in the balanced state are mutually obtained. The battery state measuring method according to any one of claims 1 to 6, wherein the difference between the corresponding resistance components is calculated as the transient state-specific component. The equivalent circuit in the transient state is defined as an equivalent circuit in a specific charging electricity amount selected within a range in which the charging electricity amount of the battery changes due to charging or discharging of the DC current.
The battery state measuring method according to claim 7, wherein the equivalent circuit in the balanced state is an equivalent circuit when the charging electricity amount of the battery is the specific charging electricity amount. In the specific component calculation step, the charging electricity amount of the battery is the specific charging electricity amount based on each frequency included in the measurement frequency and the charging electricity amount of the battery associated with each frequency. The battery state according to claim 8, wherein the impedance of the transient state with respect to the predetermined frequency range is estimated, and the estimated impedance of the transient state is fitted to the equivalent circuit to obtain the equivalent circuit of the transient state. Measuring method. It is a battery condition measuring device that measures the condition of the battery.
While changing the charge electricity amount of the battery by charging or discharging a direct current, the change is made by applying an alternating current having a measurement frequency that changes a predetermined frequency range divided by an upper limit value and a lower limit value to the battery. The transient state impedance acquisition unit that acquires the transient state impedance corresponding to the measured frequency,
A balanced state impedance acquisition unit that acquires a balanced state impedance corresponding to the measured frequency by applying the alternating current having the measured frequency to the battery while maintaining the charging electricity amount of the battery.
A battery state measuring device including a battery state calculated based on the impedance of the transition state and a peculiar component calculation unit for calculating a component peculiar to the transition state based on the battery state calculated based on the impedance of the equilibrium state. ..

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