JP2017194476A - Battery state estimation apparatus of secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery state estimation apparatus of a secondary battery by calculating internal resistance of the secondary battery with high accuracy, and by reliably estimating battery capacity even if the number of times of performing reset charge/discharge is reduced.SOLUTION: A control unit 6 is connected with an internal resistance calculation unit 9 for calculating internal resistance of a secondary battery. The internal resistance calculation unit 9 executes wavelet transformation from respective measured values by a voltage measuring unit 3 and a current measuring unit 4, acquires wavelet coefficients of the current and voltage for each frequency, and calculates the internal resistance of the secondary battery from ratio of the wavelet coefficients. When relation between the wavelet coefficients of the current and the voltage is linearly approximated, the internal resistance calculation unit 9 excludes the case in which correlation for the wavelet coefficients is lower than a predetermined reference, and calculates the internal resistance of the secondary battery.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to an apparatus that estimates a battery state of a secondary battery by analyzing a current waveform and a voltage waveform by wavelet transform.

  In the secondary battery, with an increase in charge / discharge cycle and aging deterioration, the active material of the positive and negative electrodes, the electrolytic solution, and the like change, and the internal resistance increases and the battery capacity decreases. The internal resistance of the secondary battery is a combination of multiple resistance factors, such as the ion conduction resistance of the separator part, the charge transfer resistance of the positive and negative electrodes, and the resistance due to ion diffusion delay inside the positive and negative electrode active material particles. In addition, an increase in internal resistance causes deterioration of the battery state. Moreover, the battery capacity of a secondary battery is the remaining capacity which can be charged / discharged, and reduction of battery capacity is nothing but the fall of charging / discharging performance.

  Therefore, conventionally, the internal resistance and the battery capacity of the secondary battery have been regarded as important parameters for grasping the battery state of the secondary battery, and these are monitored. In particular, internal resistance can be used to measure individual variations of battery cells from the value of internal resistance and can be used for inspection of defective products at the time of manufacture. Therefore, it is necessary to grasp internal resistance with high accuracy as an important parameter. It has been.

(Internal resistance)
As a method for obtaining the internal resistance of the secondary battery, there are roughly two methods, a DC impedance method and an AC impedance method. The direct current impedance method is a method for obtaining an internal resistance by dividing a change in voltage during charging and discharging by a change in current value at that time. One of the typical methods is the DC pulse method. In the DC pulse method, a constant current pulse is applied to a battery, and an internal resistance component is obtained from a voltage change at the time of application of the constant current pulse or a voltage change that gradually increases during application.

  On the other hand, the AC impedance method is a method in which a battery is connected to a potentiostat and an AC component of a current output is analyzed by inputting a sine wave voltage to obtain an internal resistance. The analysis of the AC component requires a frequency analysis device in addition to the potentiostat, but has the advantage that the internal resistance component can be analyzed in more detail than the DC pulse method.

  As a specific method for calculating the internal resistance of the secondary battery, for example, Patent Documents 1 to 3 have been proposed. In Patent Document 1, the current change amount, the voltage change amount, and the parameter based on the impedance change amount are linearly approximated, and the battery impedance is calculated from the slope of the approximated straight line. In this technique, the deterioration state of the battery is estimated based on the increase rate of the calculated impedance with respect to the initial value.

  In Patent Document 2, a change in current and voltage is separated into a high-frequency component and a low-frequency component using a frequency filter, and a high-frequency component excluding a low-frequency component corresponding to a diffused resistor is extracted as the internal resistance of the battery. . In Patent Document 2, the high frequency component of the current and voltage changes is defined as the internal resistance of the secondary battery.

  In Patent Document 3, the current and voltage changes are each Fourier transformed to determine the signal intensity for each frequency, and the internal resistance is calculated from the ratio of these frequency components. According to this technique, the internal resistance is calculated from a plurality of different frequency components, and the circuit constant is estimated when the secondary battery is represented by an equivalent circuit.

(Battery capacity)
When measuring the battery capacity of a secondary battery, reset charging / discharging is generally performed periodically. Reset charge / discharge is a method of charging and discharging a secondary battery at a constant output (or constant current) from full discharge to full charge and from full charge to full discharge, and actually measuring the charge capacity and discharge capacity. is there. That is, as shown in FIG. 14, the charge capacity is obtained by charging the cell voltage from the lower limit voltage to the upper limit voltage, and the discharge capacity is obtained by discharging the cell voltage from the upper limit voltage to the lower limit voltage.

JP 2006-250905 A JP 2005-106616 A JP 2005-221487 A

  Incidentally, in recent years, demand for secondary batteries has been increasing, and there is a demand for using secondary batteries to suppress fluctuations in natural energy. In this case, the above prior art has the following problems. That is, in the technique for obtaining the internal resistance of the secondary battery by using the direct current pulse method, it is difficult to apply a constant current pulse because the charge / discharge current constantly fluctuates. Moreover, in the technique for obtaining the internal resistance of the secondary battery using the AC impedance method, it is necessary to connect a special analyzer for measurement, and it is difficult to obtain the internal resistance during operation of the secondary battery. When a secondary battery is used for suppressing fluctuations in natural energy, it is an urgent need to solve these problems, and the establishment of a technique for obtaining the internal resistance of the secondary battery with high accuracy has been awaited.

  Regarding the measurement of battery capacity, reset charge / discharge is performed to perform charge / discharge control until full charge or complete discharge. For reset charge / discharge, a host device (EMS: Energy Management System) that controls the secondary battery is used. There is a problem that the control timing is limited. That is, since the charge / discharge control of the secondary battery is performed by the charge / discharge command from the host device, the implementation of the reset charge / discharge is limited to when the secondary battery is not in operation.

  In addition, reset charging / discharging has a problem that the time required for measuring the battery capacity is as long as several hours. For example, reset charging / discharging at a time 1C rate (a charging rate at which one hour is sufficient from complete discharge to full charge) takes at least two hours. For this reason, regarding the measurement of the battery capacity, it has been desired to operate the secondary battery with high efficiency by reducing the number of times of reset charging / discharging as much as possible.

  Embodiments of the present invention have been made to solve the above-described problems, and calculate the internal resistance of a secondary battery with high accuracy and ensure battery capacity even when the number of reset charge / discharge operations is reduced. It is an object of the present invention to provide a device that estimates the battery state of a secondary battery by estimating.

In order to achieve the above object, an embodiment of the present invention is characterized by having the following components (a) to (d).
(A) A voltage measuring unit that is connected between the positive electrode terminal and the negative electrode terminal of each battery cell that constitutes the secondary battery and measures the voltage between the terminals.
(B) A current measurement unit that is inserted into a current path and measures a charge / discharge current to the battery cell.
(C) A control unit that controls measurement in the voltage measurement unit and the current measurement unit.
(D) Connected to the control unit, performs wavelet transform from each measurement value from the voltage measurement unit and the current measurement unit, obtains a wavelet coefficient of current and voltage for each frequency, and determines the secondary battery from these ratios An internal resistance calculation unit for calculating internal resistance.
(E) When the internal resistance calculation unit linearly approximates the relationship between the current and voltage wavelet coefficients, the internal resistance calculation unit excludes the case where the correlation is lower than that of a preset reference, and calculates the internal resistance of the secondary battery. Configure to calculate.

Another embodiment of the present invention is characterized by comprising the above-described components (a) to (d) and the components (f) and (g).
(F) A battery characteristic table showing the relationship between the internal resistance of the secondary battery and the battery capacity of the secondary battery, created in advance by a characteristic evaluation test.
(G) A battery capacity estimation unit that estimates the battery capacity of the secondary resistance based on the battery characteristic table from the maximum value of the internal resistance calculated by the internal resistance calculation unit.

Another embodiment of the present invention is characterized by having the above-described constituent elements (a) to (d) and the constituent elements (h) to (k).
(H) A reset charge / discharge control unit that measures the battery capacity of the secondary battery.
(I) A storage unit that records the internal resistance and the battery capacity measured by the reset charge / discharge control unit.
(J) An arithmetic unit that derives a relational expression by performing a single regression analysis on the correlation between the internal resistance stored in the storage unit and the battery capacity.
(K) A battery capacity estimation unit that estimates the battery capacity of the secondary battery from the internal resistance and the relational expression derived by the calculation unit.

The block diagram which shows the structure of 1st Embodiment. The block diagram which shows the structure of 2nd Embodiment. The graph which shows the relationship between a charging / discharging cycle, the internal resistance of a battery cell, and battery capacity. The graph which shows the correlation of internal resistance and battery capacity. The figure which shows a battery characteristic table. The flowchart which shows the estimation process of the battery capacity which concerns on 2nd Embodiment. The block diagram which shows the structure of 3rd Embodiment. The flowchart which shows the estimation process of the battery capacity which concerns on 3rd Embodiment. The figure which shows the database definition of the internal resistance of a battery cell, and a battery capacity. The graph for demonstrating the estimation method using the relational expression (linear approximation) of the internal resistance of a battery cell and a battery capacity. The graph for demonstrating the estimation method using the relational expression (root function) of the internal resistance of a battery cell and battery capacity. The block diagram which shows the structure of 4th Embodiment. The graph which shows transition of the internal resistance of the battery cell used for battery deterioration prediction. The figure which shows the outline of reset charging / discharging.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(1) First Embodiment [Configuration]
The configuration of the first embodiment will be specifically described with reference to FIG. As shown in FIG. 1, in the first embodiment, an assembled battery 2 including a plurality of battery cells 1 connected in series or in parallel is provided. A voltage measuring unit 3 for measuring a voltage between terminals is connected between the positive electrode terminal and the negative electrode terminal of each battery cell 1. A current measuring unit 4 for measuring a charging / discharging current to the battery cell 1 is inserted in the current path.

  A temperature measuring unit 5 that measures the temperature of the battery cell 1 is disposed in the vicinity of the battery cell 1. A controller 6 is connected to the voltage measuring unit 3, the current measuring unit 4, and the temperature measuring unit 5. The control part 6 is a part which controls each measurement part 3-5 and processes the measured value which each measurement part 3-5 measured. The control unit 6 is connected to a storage unit 7 that stores measurement values of the measurement units 3 to 5 and a communication interface 8 that performs communication with the outside.

  An internal resistance calculation unit 9 that calculates the internal resistance of the secondary battery is connected to the control unit 6. The internal resistance calculation unit 9 is a structural feature of the present embodiment, and performs wavelet transform from each measurement value from the voltage measurement unit 3 and the current measurement unit 4 to obtain current and voltage wavelet coefficients for each frequency. The internal resistance of the secondary battery is calculated from these ratios.

The internal resistance calculation unit 9 calculates the internal resistance using wavelet transform as follows. First, the wavelet transform W _Ψ f of the waveform f (t) can be obtained by Expression (1).

Also, Ψa, b (t) is called an analyzing wavelet, and the dilation (enlargement / reduction) parameter is a real number a, and the shift parameter on the t-axis is a real number b. The

Various Ψ (t) have been proposed and can be selected as appropriate. Formula (3) shows the definition of Gabor wavelet as an example.

Assuming that the measured current waveform is i (t) and the voltage waveform is v (t), the respective wavelet transforms are as shown in Equations (4) and (5), and the transformation results are called wavelet coefficients.

Then, the internal resistance can be calculated from the ratio of the current and voltage wavelet coefficients of the same dilation a, shift b, and voltage according to equation (6).

At this time, the dilation a corresponds to the frequency, and if the dilation a is determined, the internal resistance is considered to be constant regardless of the shift b. Therefore, the shift b is changed with respect to a specific dilation a, and the relationship between (W _Ψ ⁱ ) (a, b) and (W _Ψ ^v ) (a, b) is linearly approximated using the least square method. Then, the internal resistance value R (a) for each frequency is calculated from the inclination.

Here, to calculate the coefficient of determination R ² representing the accuracy of the linear approximation. When the dispersion and covariance of (W _Ψ ⁱ ) (a, b) and (W _Ψ ^v ) (a, b) are νwi, νwv, and νwiv, respectively, νwi, νwv, and νwiv can be expressed by equations (7) to (7), 9).

以上のようにして内部抵抗算出部９では、制御部６で処理された各電池セル１の電流値および電圧値を、離散ウェーブレット変換し、それらのウェーブレット係数の比率から、二次電池の内部抵抗を算出する。 ^{_{Thus, (W Ψ i) (a}} , b) and ^{_{(W Ψ v) (a,}} b) determination coefficient ^{R 2} when the linear approximation the relation can be determined by the following equation.

As described above, the internal resistance calculation unit 9 performs discrete wavelet transform on the current value and voltage value of each battery cell 1 processed by the control unit 6, and calculates the internal resistance of the secondary battery from the ratio of the wavelet coefficients. Is calculated.

  Further, the internal resistance calculation unit 9 calculates the internal resistance of the secondary battery excluding the case where the correlation is lower than the case of the preset reference when linearly approximating the relationship between the current and voltage wavelet coefficients. It is configured as follows.

[Function and effect]
In general, when the charge / discharge current is small, the measurement error of the measured current value and voltage value becomes relatively large due to the influence of measurement accuracy of various measurement sensors. Therefore, in the wavelet coefficients (signal strength) of the current value and voltage value calculated by the discrete wavelet transform, the correlation (determination coefficient) when they are subjected to a single regression analysis tends to be small.

  Therefore, in the internal resistance calculation unit 9 in the present embodiment, when the relationship between the current and voltage wavelet coefficients is linearly approximated, the internal resistance of the secondary battery is excluded except for the case where the correlation is lower than that of a preset reference. It was configured to calculate resistance. Thereby, in the section where the correlation regarding the wavelet coefficient between the current value and the voltage value is small, it is considered that the charge / discharge current value is small and is excluded from the calculation of the internal resistance, thereby improving the calculation accuracy of the internal resistance.

  Also, when the change in the charging current is small in the wavelet transform window section, the error of the internal resistance tends to increase. For this reason, the internal resistance calculation unit 9 calculates the internal resistance of the secondary battery, excluding the case where the calculated wavelet coefficient is less than a predetermined number of samplings. Thereby, the case where there is little change in the charging current in the window section of the wavelet transform can be excluded from the calculation of the internal resistance, and the calculation accuracy of the internal resistance can be improved.

  According to the first embodiment as described above, when the relation between the wavelet coefficients of current and voltage is linearly approximated, the case where the correlation is low is excluded, and the internal resistance is calculated with high accuracy using the wavelet transform. can do. Therefore, the internal resistance of the secondary battery can be obtained even when the charge / discharge current constantly fluctuates, which is also suitable when the secondary battery is used for suppressing fluctuations in natural energy.

(2) Second Embodiment [Configuration]
FIG. 2 shows the configuration of the second embodiment. Note that the same parts as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted. As shown in FIG. 2, in the second embodiment, in addition to the configuration of the first embodiment, the battery characteristic table 10 is held in the control unit 6 and the battery capacity estimation unit 11 is connected. It is characterized by.

  The battery characteristic table 10 is created from the result of the characteristic evaluation test performed in advance, for example, from the measurement result of the internal resistance and the battery capacity of the secondary battery measured for each charge / discharge cycle of the secondary battery. The battery capacity estimation unit 11 is a part that estimates the battery capacity of the secondary resistance based on the battery characteristic table 10 from the maximum value of the internal resistance calculated by the internal resistance calculation unit 9.

  FIG. 3 is a graph showing the relationship between the internal resistance measured for each charge / discharge cycle of the secondary battery and the battery capacity. As can be seen from this graph, as the number of charge / discharge cycles for the secondary battery increases, the internal resistance of the battery cell 1 increases and the capacity retention rate of the secondary battery decreases. The correlation among the number of charge / discharge cycles, the internal resistance, and the battery capacity can be expressed by a functional expression. For example, the graph of FIG. 4 shows an example in which these relationships are expressed by linear approximation. In this embodiment, instead of the method of expressing the characteristics of the battery by a relational expression, the relationship is directly held in the control unit 6 as a battery characteristics table (see FIG. 5) indicating the deterioration state of the battery.

  By the way, in a secondary battery, in a lithium ion secondary battery, in order to prevent the overcharge or overdischarge of a secondary battery, it charges / discharges, monitoring the voltage value for every battery cell 1. FIG. For example, when charging a lithium ion secondary battery, the voltages of all the battery cells in the secondary battery are individually monitored, and charging is stopped when the highest voltage value among them reaches the upper limit voltage. At this time, when the upper limit voltage is reached, there is a case where the charging with the constant output is switched to the constant voltage charging. Therefore, it can be seen that the battery capacity of the secondary battery is affected by the battery cell having the largest internal resistance value in the secondary battery.

  Moreover, a secondary battery connects the battery cell 1 in series or in parallel, and comprises a secondary battery with a higher voltage and a large capacity. When the battery cells 1 are connected in parallel, the voltages of these battery cells 1 are always kept constant. However, when the battery cells 1 are connected in series, there is a difference in cell voltage due to variations in the individual battery cells 1. As the battery cell deteriorates, the cell voltage variation is considered to increase, and the influence of the battery cell 1 having a large internal resistance is considered to increase.

  Therefore, in the second embodiment, as shown in the flowchart of FIG. 6, after measuring the current, cell voltage, and battery temperature (S101), the internal resistance of the battery cell 1 is calculated by the internal resistance calculation unit 9 (S102). ), The largest value among the calculated internal resistances of the respective battery cells is calculated (S103). Subsequently, based on the battery characteristic table 10, the battery capacity estimation unit 11 estimates the battery capacity of the secondary resistance from the maximum value of the internal resistance calculated by the internal resistance calculation unit 9 (S104).

[Function and effect]
According to the second embodiment as described above, the battery capacity of the secondary battery is reliably estimated by using the battery characteristic table 10 in addition to the operational effects of the first embodiment using the wavelet transform. And the secondary battery can be operated with high efficiency. In particular, in a lithium ion secondary battery that charges and discharges while monitoring the voltage value of each battery cell 1, it is possible to prevent overcharge or overdischarge of the secondary battery, and the battery capacity of the lithium ion secondary battery is reduced. It is suitable for grasping.

(3) Third Embodiment [Configuration]
FIG. 7 shows the configuration of the third embodiment. Note that the same parts as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted. As shown in FIG. 7, in the third embodiment, in addition to the configuration of the first embodiment, the control unit 6 includes a reset charge / discharge control unit 12, a calculation unit 13, and a battery capacity estimation unit 14. It is characterized by being connected.

  The reset charge / discharge control unit 12 controls reset charge / discharge, which actually measures the battery capacity of the secondary battery, and measures the chargeable / dischargeable capacity. The storage unit 7 records the internal resistance of the battery cell 1, the measurement result of the reset charge / discharge control unit 12, the parameters of the relational expression obtained by the calculation unit 13, and the like.

  The calculation unit 13 is a part that derives a relational expression by performing a single regression analysis on the correlation between the measurement results of the internal resistance and the battery capacity stored in the storage unit 7. When performing a single regression analysis of the correlation between the internal resistance and the battery capacity, the calculation unit 13 selects the approximate expression having the highest correlation from the approximate expressions assumed as approximate expressions representing the battery deterioration, and identifies the parameters. (This point will be described in detail later in paragraph 0056). The battery capacity estimation unit 14 is a part that estimates the battery capacity of the secondary battery from the value of the internal resistance calculated by the internal resistance calculation unit 9 and the relational expression derived by the calculation unit 13.

  When the battery capacity of the secondary battery is estimated using the battery characteristic table 10 as in the second embodiment, a charge / discharge cycle test is performed on the secondary battery, and the internal resistance value and the battery capacity associated with the battery deterioration. Therefore, it is necessary to create the battery characteristic table 10 in advance. Normally, this charge / discharge cycle test takes a lot of time and cost. Moreover, when the change of the battery characteristic accompanying improvement of the battery cell 1 arises, the evaluation test must be performed again, which is troublesome.

  Therefore, in the third embodiment, the conventional reset charge / discharge is used for the estimation of the battery capacity of the secondary battery. As described above, reset charging / discharging cannot be performed while the secondary battery is in operation (controlled by the host monitoring device). However, if reset charging / discharging is performed, battery cells 1 are connected in series. / It is possible to accurately and reliably grasp the battery capacity that is the current chargeable / dischargeable capacity in a state of being combined in parallel.

  FIG. 8 shows a flowchart according to the third embodiment. In 3rd Embodiment, it transfers to the maintenance mode of the storage battery system to which 3rd Embodiment is applied first (S201), the reset charging / discharging control part 12 performs reset charging / discharging (S202), and chargeable / dischargeable capacity | capacitance is carried out. Measure (S203).

  The storage unit 7 records the chargeable / dischargeable capacity (S204). The calculation unit 13 derives a relational expression by single regression analysis (S205), and the storage unit 7 records parameters of the relational expression (S206). In the initial operation of the secondary battery, calculation of the internal resistance of the battery cell 1 and measurement of the battery capacity, accumulation in the database in the storage unit 7, and derivation of the relational expression by single regression analysis are repeated, and then the normal mode is restored ( S207).

  In the third embodiment, the storage unit 7 creates a database of the correlation between the battery capacity of the secondary battery actually measured by the reset charge / discharge control unit 12 and the internal resistance of the battery cell 1 (illustrated in FIG. 9). The calculation unit 13 derives a relational expression by performing a single regression analysis of the correlation.

  When the calculation of the battery capacity is requested from the host device (S208), the battery capacity estimation unit 14 calculates the battery capacity from the current internal resistance of the battery cell 1 using the relational expression derived by the calculation unit 13. This is estimated (S209), and this is notified to the outside (S210). At this time, in order to estimate the battery capacity from the relational expression, it is performed based on the value of the battery cell 1 having the largest deterioration, that is, the largest internal resistance among the battery cells 1 in the secondary battery. In addition, after updating the record of the relational expression in S206, the battery capacity estimation unit 11 uses the maximum value of the internal resistance calculated by the internal resistance calculation unit 9 based on the battery characteristic table 10 as in the second embodiment. The battery capacity of the secondary resistance may be estimated, and a form that is constantly notified to the host device may be taken.

  Here, using the graph of FIG. 10, the calculation unit 13 derives a relational expression between the battery capacity and the internal resistance by single regression analysis, and the battery capacity estimation unit 14 calculates the internal resistance and the calculation unit of the current battery cell 1. It will be described that the battery capacity can be estimated using the relational expression derived by FIG. The battery capacity is a value calculated from the result of reset charge / discharge by the reset charge / discharge control unit 12. Further, the internal resistance may be a value calculated by the internal resistance calculation unit 9, and since the number of charge / discharge cycles correlates with an increase in the internal resistance of the battery cell 1, an estimated value from the charge / discharge data. But you can.

For example, when the relationship between the internal resistance and the calculation result of the battery capacity is expressed by linear approximation as shown in Equation (11), parameters a ₀ and a ₁ that minimize the residual S are determined from the idea of the least square method. To do.

残差Ｓが最小となるようなパラメータａ₀およびa₁を求めるには、式（１２）をパラメータａ₀およびa₁でそれぞれ偏微分して、その値が０となるようにする。

Here, the residual S of the approximate expression (11) for the internal resistance estimation and the battery capacity calculation result is expressed by the following expression (12).

In order to obtain the parameters a ₀ and a ₁ that minimize the residual S, the equation (12) is partially differentiated with respect to the parameters a ₀ and a ₁ so that the value becomes zero.

When the simultaneous equations of the above equations (13) and (14) are solved, the parameters a ₀ and a ₁ that minimize the residual S can be obtained by the following equations.

式（１８）から残差Ｓが最小となるようなパラメータａ₀およびa₁を求めるためには、式（１８）をパラメータａ₀およびa₁でそれぞれ偏微分して、その値が０となるようにすればよい。 The relationship between the internal resistance and the battery capacity is expressed using these parameters, and the battery capacity estimation unit 14 estimates the battery capacity. In addition, when the relationship between the internal resistance and the battery capacity calculation result is expressed by the root function of Expression (17) (shown in FIG. 11), the residual S is expressed by Expression (18).

In order to obtain the parameters a ₀ and a ₁ that minimize the residual S from the equation (18), the equation (18) is partially differentiated by the parameters a ₀ and a ₁ , and the value becomes zero. What should I do?

  Secondary battery deterioration modes usually include calendar deterioration that deteriorates depending on the number of working days and cycle deterioration that deteriorates depending on the charge / discharge cycle. May be approximated by a linear equation for the number of cycles. As described above, the deterioration mode of the secondary battery varies depending on the use situation. For this reason, the calculation unit 13 of the third embodiment represents the approximate expression having the highest correlation (small residual) in the above-described linear approximation, polynomial, root function, and the like. Thereby, the estimation precision of battery capacity can be raised further.

[Function and effect]
According to the third embodiment as described above, based on the correlation analysis between the internal resistance of the battery cell 1 and the battery capacity, in addition to the function and effect of the first embodiment using the wavelet transform, The battery capacity can be estimated accurately and reliably. Therefore, the number of reset charging / discharging operations can be greatly reduced, and the secondary battery can be operated with high efficiency.

(4) Fourth Embodiment [Configuration]
FIG. 12 shows the configuration of the fourth embodiment. Note that the same parts as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted. As shown in FIG. 12, in the fourth embodiment, a battery capacity estimation unit 15 and an internal resistance estimation unit 16 are connected to the control unit 6.

  The battery capacity estimation unit 15 is configured to obtain a change rate of the battery capacity by plotting the estimated battery capacity in time series, and to estimate a future battery capacity from the obtained change rate. As shown in FIG. 13, the internal resistance estimation unit 16 is configured to obtain an increase rate of the internal resistance by time-series plotting the internal resistance of the battery cell 1 and estimate the future internal resistance. . The period included in the future here includes a long span such as several years later.

[Function and effect]
According to the fourth embodiment as described above, in addition to the function and effect of the first embodiment using the wavelet transform, the deterioration of the secondary battery is estimated in the future based on the correlation analysis between the internal resistance and the battery capacity. can do. Therefore, the secondary battery can be operated with high efficiency.

(5) Other Embodiments The above-described embodiment is presented as an example in the present specification, and is not intended to limit the scope of the invention. In other words, the present invention can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the invention described in the claims and the equivalents thereof as well as included in the scope and gist of the invention.

Symbol name

DESCRIPTION OF SYMBOLS 1 ... Battery cell 2 ... Assembly battery 3 ... Voltage measurement part 4 ... Current measurement part 5 ... Temperature measurement part 6 ... Control part 7 ... Memory | storage part 8 ... Communication interface 9 ... Internal resistance calculation part 10 ... Battery characteristic table 11,14, DESCRIPTION OF SYMBOLS 15 ... Battery capacity estimation part 12 ... Reset charge / discharge control part 13 ... Calculation part 16 ... Internal resistance estimation part

Claims (5)

A voltage measuring unit that is connected between the positive electrode terminal and the negative electrode terminal of each battery cell constituting the secondary battery, and measures a voltage between the terminals;
A current measurement unit that is inserted into a current path and measures a charge / discharge current to the battery cell;
A control unit for controlling measurement in the voltage measurement unit and the current measurement unit;
Connected to the control unit, performs wavelet transform from each measurement value from the voltage measurement unit and the current measurement unit, obtains a wavelet coefficient of current and voltage for each frequency, and calculates the internal resistance of the secondary battery from these ratios An internal resistance calculation unit for calculating,
The internal resistance calculation unit has an internal resistance estimation unit that calculates a change rate of internal resistance by plotting the internal resistance calculated in time series, and estimates a future internal resistance from the calculated change rate of internal resistance. A battery state estimating device for a secondary battery. A battery characteristic table that is created in advance by a characteristic evaluation test and shows the relationship between the internal resistance of the secondary battery and the battery capacity of the secondary battery;
2. The battery capacity estimation unit according to claim 1, further comprising: a battery capacity estimation unit configured to estimate a battery capacity of a secondary resistance based on the battery characteristic table from a maximum value of the internal resistance calculated by the internal resistance calculation unit. Battery state estimation device for secondary battery. A reset charge / discharge control unit for measuring the battery capacity of the secondary battery;
A storage unit for recording the internal resistance and the battery capacity measured by the reset charge / discharge control unit;
A calculation unit for deriving a relational expression by performing a single regression analysis on the correlation between the internal resistance and the battery capacity stored in the storage unit;
The battery state estimation device for a secondary battery according to claim 1, further comprising a battery capacity estimation unit that estimates a battery capacity of the secondary battery from the internal resistance and the relational expression derived by the calculation unit. .   When the arithmetic unit performs a single regression analysis of the correlation between the internal resistance and the battery capacity, the approximate expression having the highest correlation is selected from the approximate expressions assumed as the approximate expression representing the battery deterioration, and the parameter is identified. The battery state estimation device for a secondary battery according to claim 3. The battery capacity estimation unit is configured to obtain a battery capacity change rate by plotting the estimated battery capacity in time series, and to estimate a future battery capacity from the obtained change rate. The battery state estimation apparatus of the secondary battery of any one of 2-4.

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