Patent Description:
There is increasing use of rechargeable batteries (secondary batteries) such as in order for stabilization of electric power systems and reduction of exhaust gas. On the other hand, it is required to monitor a state of the rechargeable battery, e.g., the degradation state of the rechargeable battery in order to avoid sudden failure of the battery system.

There are a technique of evaluating the degradation state of the rechargeable battery based on data obtained from the rechargeable battery when a special charge/discharge process is performed and a technique of evaluating the degradation state of the rechargeable battery with an approximation equation (e.g., the Arrhenius approximation equation) such as based on the number of charge/discharge cycles.

Also, as a technique for on-line evaluation of the degradation state of the rechargeable battery, there is a technique of evaluating the degradation state of the rechargeable battery based on data obtained during normal operation of the rechargeable battery. In this technique, there is no need to stop the operation of the rechargeable battery. However, it is necessary to collect a lot of operation data suitable for evaluation in order to evaluate the degradation state of the rechargeable battery.

Patent Literature <NUM> relates to a secondary battery system and method of estimating stress of active material of a secondary battery.

The present embodiments provide an information processing apparatus, an information processing method, a computer program and an information processing system for evaluating a state of a rechargeable battery.

<FIG> is a block diagram of a rechargeable battery evaluation system according to a first embodiment. The rechargeable battery evaluation system in <FIG> includes a rechargeable battery <NUM> and a rechargeable battery evaluation apparatus <NUM>, which is an information processing apparatus according to the first embodiment. The rechargeable battery evaluation apparatus <NUM> includes a data acquirer <NUM>, an operation data DB <NUM>, an evaluation target data extractor <NUM>, an OCV curve estimator (relationship information generator) <NUM>, a voltage corrector (first voltage corrector) <NUM>, an SoC range determiner (range determiner) <NUM>, a state evaluator <NUM>, an evaluation result output device <NUM> and an evaluation function DB <NUM>.

The rechargeable battery <NUM> is a battery capable of charge/discharge. The rechargeable battery <NUM> is also referred to as a secondary battery, but will hereinafter be uniformly referred to as a rechargeable battery. In the present embodiment, a reference to charge/discharge includes at least one of charge and discharge.

As an example, the rechargeable battery <NUM> is a battery provided with a moving vehicle that operates with electric energy as a power source, such as an Electric Vehicle (EV), an electric bus, an electric train, a Light Rail Transit (LRT) system, a Bus Rapid Transit (BRT) system, an Automatic Guided Vehicle (AGV), an airplane or a ship. Alternatively, the rechargeable battery <NUM> may be a rechargeable battery provided with electric equipment (such as a smartphone or a personal computer), a rechargeable battery that stores electric power for the demand response purpose, or the like. The rechargeable battery <NUM> may also be a rechargeable battery for other purposes.

The rechargeable battery <NUM> can be charged by a charger disposed at a charging station, a road shoulder, a parking lot or the like or a charger connected to a receptacle or the like. It may also be possible to perform discharge of electric power accumulated in the rechargeable battery <NUM> into an electric power system via the charger (reverse power flow). The scheme for transmitting electric power from the charger to the rechargeable battery <NUM> may be either a contact charging scheme or a contactless charging scheme.

The rechargeable battery <NUM> includes a plurality of battery units. The plurality of battery units are connected in series or parallel. Alternatively, the plurality of battery units are connected in series and parallel.

<FIG> shows an example configuration of the rechargeable battery <NUM>. The rechargeable battery <NUM> includes battery units <NUM>, <NUM>,. Each battery unit includes a plurality of modules. The battery unit <NUM> includes modules <NUM>-<NUM> to <NUM>-M, the battery unit <NUM> includes modules <NUM>-<NUM> to <NUM>-M, and the battery unit N includes modules N-<NUM> to N-M. The plurality of modules are connected in series, in parallel, or in series and parallel. Although the number of modules included in each battery unit is the same in this example, it need not be the same.

<FIG> shows an example configuration of one module. The module includes a plurality of battery cells. The plurality of battery cells are connected in series, in parallel, or in series and parallel. As an example, a plurality of sets of two or more directly connected battery cells are connected in parallel.

The data acquirer <NUM> acquires time-series operation data from the rechargeable battery <NUM>. The operation data may or may not be acquired at constant time intervals. The data acquirer <NUM> stores the acquired operation data in an operation data database (DB). The operation data may be acquired in units of cells, modules, battery units, or rechargeable batteries (pluralities of battery units connected to each other). In the following description, it is assumed that the operation data is acquired in units of rechargeable batteries.

The operation data includes information on voltage, electric power, SoC (State of Charge), and temperature. The voltage information, i.e., the voltage value corresponds to a first voltage value including charge voltage or discharge voltage. A current value may be acquired instead of the electric power value. In this case, the electric power value may be arithmetically calculated from the current value and the voltage value. In addition, the current value may be acquired instead of the SoC value to calculate the SoC by integrating the current. SoC is an index that indicates the amount of charged electricity of a battery. As an example, it is calculated by dividing the amount of electric power (amount of electric charge) accumulated in the rechargeable battery <NUM> by the capacity of the rechargeable battery <NUM>.

The operation data DB <NUM> stores the operation data acquired by the data acquirer <NUM>.

<FIG> shows an example of the operation data DB <NUM>. There is shown an example of operation data acquired for the rechargeable battery <NUM> at intervals of one second. This operation data includes information on voltage, SoC, electric power and temperature.

The evaluation target data extractor <NUM> extracts operation data targeted for evaluation from the operation data DB <NUM>. The evaluation target data extractor <NUM> extracts the operation data based on a pre-specified condition. For example, the pre-specified condition specifies a date, a period of time or a temperature range.

Also, the evaluation target data extractor <NUM> may exclude, from the extracted operation data, data with many defects or data acquired in a state other than the normal operation state (such as during a test or standby, for example).

For example, if the proportion of the number of pieces of operation data with any defects in the number of pieces of operation data included in the specified date exceeds a threshold, all the pieces of operation data of this date may be excluded. In this case, a user, or an operator, of the present apparatus may specify another date as a condition to perform extraction of operation data.

The determination on whether operation data that satisfies the specified condition is operation data acquired in a state other than the normal operation state is performed in the following manner, for example. A statistical quantity (such as an average or a standard deviation) is calculated in advance based on operation data acquired in the normal operation state. A statistical quantity is calculated for operation data that satisfies the specified condition. The calculated statistical quantity is compared with the statistical quantity calculated in advance to determine whether the difference is greater than or equal to a threshold. If the difference is greater than or equal to the threshold, it is determined that the operation data that satisfies the specified condition is data acquired in a state other than the normal operation state. Besides, a machine learning technique capable of learning a normal model such as one-class SVM (Support Vector Machine) may be used to determine whether data is acquired in a state other than the normal operation state. In addition, a variable that represents an operation state may be included in the operation data. In this case, it can be determined whether the data is acquired in the normal operation state based on the variable included in the operation data.

The OCV (Open Circuit Voltage) curve estimator (relationship information generator) <NUM> estimates an OCV curve in which SoC and OCV are associated with each other based on the operation data targeted for evaluation. OCV is open voltage (the voltage of an output terminal of a rechargeable battery when nothing is connected to the output terminal). The OCV curve corresponds to an example of first relationship information that represents a relationship between the OCV (a third voltage value) and the SoC (the amount of charged electricity) of the rechargeable battery <NUM>.

<FIG> schematically shows an example of an OCV curve <NUM>. The OCV curve <NUM> shows transition of the open voltage with respect to the SoC. A charge curve <NUM> schematically shows an example of transition of the charge voltage during a charge. The charge curve <NUM> is located above the OCV curve <NUM>. A discharge curve <NUM> schematically shows an example of transition of the charge voltage during a discharge. The discharge curve <NUM> is located below the OCV curve <NUM>.

The voltage included in the operation data is the voltage during a charge (charge voltage) or the voltage during a discharge (discharge voltage) and is different from the open voltage. An example method of estimating an OCV curve will be described below.

As an example, every time the SoC changes by a certain amount during a charge/discharge, the rechargeable battery <NUM> is temporarily stopped, and the open voltage is measured. The measured value is included in the operation data. Open voltage values and SoC values are extracted from the operation data, points of the open voltage values and SoC values are plotted, and a curve that approximates the plotted points is estimated as an OCV curve. Note that the temporarily stopping the rechargeable battery <NUM> for measuring the open voltage needs to be performed in the rechargeable battery <NUM>.

The following is a method of estimating an OCV curve from operation data that does not include open voltage values. A moving average of voltage with respect to SoC is calculated based on SoC values and voltage values in operation data including charge/discharge. Specifically, (SoC value, voltage value) in the operation data are sorted in ascending order of SoC. The moving average of voltage with respect to SoC is calculated based on the sorted data. Data of the moving average of voltage values with respect to SoC is used as OCV estimation data (OCV curve). Since the charge curve transitions at a higher position than the OCV curve and the discharge curve transitions at a lower position than the OCV curve as shown in <FIG>, the OCV curve can be approximately calculated by the moving average of voltage values including charge/discharge.

Another method is to use linear regression. The method of using linear regression uses a nature in which the OCV and the SoC have an approximately linear relationship in a certain SoC range (region). In this range, a regression function in which the charge/discharge voltage is an objective variable and the SoC is an explanatory variable is generated based on SoC values and voltage values (charge/discharge voltage) in operation data including charge/discharge. The generated regression function is used as an OCV curve. The OCV is the output value of the regression function. In a range where the SoC and the OCV can be considered as having a linear relationship, an OCV curve can be estimated by performing linear regression of the SoC and voltage value in this manner. Note that, although the regression function is a straight line and not a curve, it is referred to as an estimated OCV curve in this case as well. The regression function corresponds to an example of first relationship information that represents a relationship between the OCV (a third voltage value) and the SoC (the amount of charged electricity) of the rechargeable battery <NUM>.

<FIG> shows an example in which an OCV graph is calculated by linear regression. A large number of pieces of data are plotted. Each piece of data marked with a circle in the figure corresponds to a set of an SoC value and a voltage value included in operation data. Both of data during a charge and data during a discharge are mixed. A point of an electric power value greater than <NUM> corresponds to data during a charge, and a point of an electric power value less than <NUM> corresponds to data during a discharge. A regression straight line <NUM> that approximates a large number of plotted points is drawn as an OCV graph.

Yet another method is to use a charge curve. Operation data obtained when a charge is performed at a constant charge rate is used. A charge curve is generated by associating voltage values (charge voltage values) and SoC values included in the operation data. The generated charge curve is regarded as an OCV curve. This method is based on the fact that the charge curve approximates a curve obtained by approximately parallel displacement of the OCV curve. The charge curve corresponds to information (second relationship information) that represents a relationship between the charge voltage and the amount of charged electricity, and the second relationship information is regarded as an OCV curve (first relationship information).

The voltage corrector <NUM> corrects a voltage value included in operation data according to an SoC value included in the operation data by using the estimated OCV curve and generates a corrected voltage value (second voltage value). Specifically, the corrected voltage value has a value corresponding to the difference between the voltage value and the OCV corresponding to the SoC value. As an example, the corrected voltage value can be generated by subtracting an OCV value from a voltage value included in the operation data. If the voltage value is greater than the OCV value, the voltage value obtained by the subtraction (the corrected voltage value) is greater than <NUM>. On the other hand, if the voltage value is smaller than the OCV value, the voltage value obtained by the subtraction (the corrected voltage value) is smaller than <NUM>. Alternatively, the corrected voltage value may be generated by subtracting the voltage value from the OCV value. In this case, if the voltage value is greater than the OCV value, the voltage value obtained by the subtraction (the corrected voltage value) is smaller than <NUM>. On the other hand, if the voltage value is smaller than the OCV value, the voltage value obtained by the subtraction (the corrected voltage value) is greater than <NUM>.

As will be described later, in the present embodiment, the degradation state of the rechargeable battery <NUM> is evaluated by focusing on dispersion (for example, the standard deviation) of corrected voltage values. As can be seen from the OCV curve shown in <FIG>, the OCV tends to be larger as the SoC is higher, and accordingly, the measured voltage value also tends to be larger as the SoC is higher. Thus, when the SoC range of the operation data used for evaluation of the rechargeable battery <NUM> is narrow, the effect of change in OCV is small in the range, and thus it is possible to use voltage values in the range to calculate dispersion and evaluate the degradation state of the rechargeable battery based on the dispersion. That is, this technique uses the fact that the dispersion of voltage values increases as the degradation proceeds with respect to the OCV (see <CIT>, for example). However, when the SoC range is wide, variation in OCV due to variation in SoC effects largely, and the dispersion of voltage values cannot be appropriately evaluated. Thus, the present embodiment discloses a technique of evaluating dispersion of corrected voltage values corresponding to the difference between voltage values and OCV values. This enables excluding the effect of variation in OCV due to SoC and evaluating the degradation state by using operation data in any SoC range. In the case of performing evaluation by using dispersion of voltage values in a narrow SoC range in the above-described technique, it is necessary to acquire a sufficient number of pieces of data in the narrow SoC range. However, it takes time until a sufficient amount of data is acquired, and the evaluation cannot be appropriately performed. In contrast, in the present embodiment, since the evaluation can be performed by using data in a wide SoC range, it is only required to acquire a number of pieces of data in the wide SoC range. Therefore, in the present embodiment, it is possible to accurately perform evaluation of the degradation state even with a rechargeable battery in which only a short time has elapsed from the start of operation.

<FIG> shows a specific example of generating corrected voltage values. Corrected voltage values corresponding to the difference between voltage values and OCV are generated based on the OCV graph in <FIG>, and the calculated corrected voltage values are plotted. Data of a voltage value (corrected voltage value) of <NUM> means that the voltage value before the correction is the same voltage as the OCV.

Note that, in the case of a technique of using a charge curve as an OCV curve, the absolute value of a corrected voltage value may have a large difference from the absolute value of the corrected voltage value in the case of using another technique described above. However, in the evaluation in the present embodiment, since it is a technique of analyzing a relative relationship, the magnitude of the absolute value has no effect.

The SoC range determiner <NUM> determines an SoC range (charged-electricity range) to be used for evaluation of the state (in this example, the degradation state) of the rechargeable battery <NUM>. As an example, a predetermined SoC range may be determined. Also, a range from the minimum value to the maximum value of the SoC values included in the operation data targeted for evaluation may be determined. Also, an SoC range in which a certain number or more of pieces of data are included may be determined. Also, a plurality of SoC ranges may be selected. It is also effective to determine the SoC range in the following method.

An example is a method of determining the SoC range based on estimation errors of the OCV curve estimated by the OCV curve estimator <NUM>. Specifically, the SoC range is determined based on the difference between the voltage values in the operation data and the OCV. For example, for each SoC, the maximum value of the voltage values in the operation data is found, and it is determined whether the difference between the found maximum value and the estimated OCV value is greater than or equal to a threshold. If the difference is greater than or equal to the threshold, it is determined that the estimation error of the OCV is large. If the difference is less than the threshold, it is determined that the estimation error of the OCV is small. Another statistical quantity such as an average value or the minimum value may also be used instead of the maximum value. The OCV curve estimator <NUM> selects, as the SoC range, a set of SoC values with small estimation errors.

As a specific example, for SoC values of <NUM> to <NUM>, it is determined whether the estimation error is large for each of <NUM>, <NUM>, <NUM>,. , <NUM> and <NUM>. It is assumed that it is determined that the estimation error is small for <NUM> to <NUM> and <NUM> to <NUM> and the estimation error is large for <NUM> to <NUM>, <NUM> to <NUM> and <NUM> to <NUM>. In this case, <NUM> to <NUM> and <NUM> to <NUM> are selected as the SoC range.

Another example is a method of determining the SoC range based on distribution of electric power values or temperature for SoC. A plurality of SoC sections with certain widths are set as candidates of the SoC range. Distribution of electric power values or temperature is calculated for each section. The SoC range is selected based on the distribution of each section. SoC sections with a large inter-distribution distance are excluded, and a set of the remaining SoC sections is used as the SoC range. For example, an average of inter-distribution distances is calculated, and SoC sections for which the difference between its inter-distribution distance and the average is greater than or equal to a threshold are excluded. The inter-distribution distance includes an index such as the KL distance (KL: Kullback-Leibler), the L2 distance or the Pearson distance. A statistical quantity such as an average or variance of distribution may also be used instead of an index.

The state (in this example, the degradation state) of the rechargeable battery <NUM> is evaluated by the state evaluator <NUM> by using corrected voltage values based on data belonging to the SoC range. In the present embodiment, an evaluation function in which a corrected voltage value is an input variable (explanatory variable) and the degradation state of the rechargeable battery <NUM> is an output variable (objective variable) is used. The degradation state is evaluated by using a phenomenon in which dispersion of voltage values acquired during operation increases in a battery with a high degree of degradation. In the present embodiment, the degradation state is evaluated by using dispersion of corrected voltage values, which are relative values with respect to OCV, as described above, instead of directly using the voltage values.

The evaluation function DB <NUM> stores data of evaluation functions. The evaluation functions are stored for respective battery hierarchies such as battery cell, module, battery unit and the entire battery. The state evaluator <NUM> reads, from the evaluation function DB <NUM>, an evaluation function for the same hierarchy as the battery hierarchy for which data used for the current evaluation is acquired. If a particular hierarchy is determined as the hierarchy targeted for evaluation, only an evaluation function for the particular hierarchy may be stored in the evaluation function DB <NUM>.

A numerical representation of the dispersion of corrected voltage values is defined as a feature FV. As an example of the feature FV, a standard deviation or variance of the corrected voltages can be used. Alternatively, if data of a charge and a discharge is included, the difference between an average of corrected voltage during a charge and an average of corrected voltage during a discharge, the difference between a median value of corrected voltage during a charge and a median value of corrected voltage during a discharge or the like can also be used as the feature FV. Using the feature FV, the evaluation function for the degradation state of the rechargeable battery can be represented in the following equation. SoH (State of Health) is an index that represents the degradation state of the rechargeable battery. As an example of SoH, a ratio of the capacity of the rechargeable battery and its rated capacity can be used. The letters "a" and "b" are coefficients and are calculated in advance by learning.

Equation (<NUM>) is a linear equation, but may be of any type as long as it is a technique of constructing a regression model, such as non-linear regression, machine learning (such as a neural network, random forests or SVR (Support Vector Regression)). A model by a linear equation, a non-linear equation or machine learning may include a statistical quantity of at least one of temperature and electric power values as an input variable. A plurality of models may be combined. Also, classification by the temperature or electric power value (the charge rate or discharge rate may also be used) may be performed to generate an evaluation function for each class.

If an evaluation function corresponding to the battery hierarchy targeted for evaluation is not stored in the evaluation function DB <NUM>, the evaluation target data extractor <NUM> may correct voltage values, electric power values and the like included in the operation data. For example, it is assumed that the evaluation function is a function for the hierarchy of battery cell, and the battery hierarchy targeted for the current evaluation is module. In this case, the correction of electric power values is performed by dividing the electric power values by the number of cells included in the module. The correction of voltage values is performed by dividing the voltage values by the number of series connections of cells (the number of cells connected in series).

An evaluation result (SoH) that represents the degradation state calculated by the state evaluator <NUM> is output by the evaluation result output device <NUM>. As an example, the evaluation result output device <NUM> is a display that displays data, such as a liquid crystal display, an organic EL display or a plasma display. Alternatively, the evaluation result output device <NUM> may be a communication device that sends data to another communication device in a wired or wireless manner or a printer that prints data.

<FIG> shows an example of output of an evaluation result. There is shown an example of graphical representation of transition of SOH calculated by evaluating the degradation state of battery units <NUM> to <NUM> every month. In this example, the horizontal axis indicates the month. However, the horizontal axis may indicate the date, the cumulative value of the amount of usage of the battery (Ah or Wh) or another unit such as a value that standardizes them (equivalent cycle count). Also, if the present apparatus is provided with a moving vehicle, the horizontal axis may indicate the total travel distance. Also, although transition of the SoH of a plurality of different battery units is displayed at the same time in this example, only transition of the SoH of a single battery unit may be displayed.

A point that indicates an evaluation result may be selected by the user, or the operator, of the present apparatus. A GUI (Graphical User Interface) such as a keyboard, a mouse or a touch panel can be used for the selection. When the point of a certain evaluation result is selected by the user via the GUI, the evaluation result output device <NUM> may display operation data used for calculation of the selected evaluation result or information based on the operation data.

A displayed variable includes a voltage, current, electric power value, SoC, SoH, temperature or the like. As a form of display, a table that includes statistical quantities such as an average, variance, minimum value and maximum value may be displayed. Alternatively, a trend graph that shows time-series transition such as with time on the horizontal axis and voltage on the vertical axis may be displayed. Alternatively, a graph (QV plot) with SoC on the horizontal axis and voltage on the vertical axis may be displayed. The form of display and displayed variable may be switched by the user via the GUI.

The present apparatus may be provided to a moving vehicle such as an EV (Electric Vehicle), and the display device may be disposed to the dashboard of the driver's seat. The current SoH may be displayed on the display device.

<FIG> is an example of displaying an indication on the display device of the EV that the current speed is <NUM>/h, the distance to empty is <NUM> and the SoH of the rechargeable battery <NUM> is <NUM> during travel in a driving mode. A horizontal line L indicates an SoH of <NUM>.

<FIG> is a flow chart of an example of operations of the rechargeable battery evaluation apparatus <NUM> according to the first embodiment.

The data acquirer <NUM> acquires operation data from the rechargeable battery <NUM> and stores the acquired operation data in the operation data DB <NUM> (S101).

The evaluation target data extractor <NUM> extracts operation data targeted for evaluation from the operation data DB <NUM> (S102).

The OCV curve estimator <NUM> estimates an OCV curve with respect to SoC based on the operation data targeted for evaluation (S103).

The voltage corrector <NUM> generates a corrected voltage value according to the difference between an OCV value corresponding to an SOC value and a voltage value for each piece of operation data based on the OCV curve (S104).

The SoC range determiner <NUM> determines an SoC range used for evaluation of the degradation state based on at least the former of the operation data and the OCV curve (S105).

The state evaluator <NUM> evaluates the degradation state of the rechargeable battery <NUM> by using the standard deviation of the first voltage and the evaluation function in the evaluation function DB <NUM> (S106).

The evaluation result output device <NUM> outputs an evaluation result (S107).

As above, according to the first embodiment, it is possible to evaluate the degradation state of the rechargeable battery <NUM> by using operation data in a wide SoC range, and thus accurately evaluate the degradation state of the rechargeable battery <NUM> at an early stage from the start of operation of the rechargeable battery <NUM>.

In the first embodiment, a value corresponding to the difference between a voltage value and an OCV value is used as a corrected voltage value, and a standard deviation of corrected voltage values is used as a feature. In the present variation, the difference between a charge voltage and a discharge voltage at the same SoC value is calculated based on operation data acquired when charge/discharge is performed in a charge/discharge pattern including both of charge and discharge, and the calculated difference is used as a corrected voltage value. A value based on corrected voltage values (for example, an average value, minimum value, maximum value or median value of the corrected voltage values) is used as a feature. The process of calculating the difference between the charge voltage and the discharge voltage at the same SoC value corresponds the process of calculating a corrected voltage value obtained by correcting the charge voltage or discharge voltage according to the SoC value.

<FIG> is an illustrative diagram of the present variation. It is assumed that charge/discharge is performed in a charge/discharge pattern in which the charge is started from when the SoC is near <NUM>, the discharge is started when the SoC reaches near <NUM> during the charge, and the discharge is stopped when the SoC is near <NUM>. A graph <NUM> represents transition of the charge voltage in this process, and a graph <NUM> represents transition of the discharge voltage. The horizontal axis indicates the SoC, and the vertical axis indicates the voltage. Operation data obtained when charge/discharge of the rechargeable battery <NUM> is performed in this charge/discharge pattern is acquired by the data acquirer <NUM>.

The state evaluator <NUM> calculates the difference between the charge voltage and discharge voltage at the same SoC (reference character K in <FIG>), and the calculated difference is used as a corrected voltage value. In the present variation, the process of the OCV curve estimator <NUM> is unnecessary. The state evaluator <NUM> calculates a feature based on the calculated corrected voltage value and estimates the SoH in a manner similar to the first embodiment.

The SoC range determiner <NUM> may determine an SoC range used for evaluation in a manner similar to the first embodiment. For example, when the difference between the charge voltage and discharge voltage at a certain SoC value is greater than or equal to a threshold, it may be determined that the rechargeable battery <NUM> is not in the normal operation state, and the SoC may not be included in the SoC range used for evaluation.

According to the present variation, it is unnecessary to calculate the OCV curve, and it is possible to reduce the processing load as compared to the first embodiment. Also, implementation is possible with a simpler configuration than in the first embodiment.

<FIG> is a block diagram of a rechargeable battery evaluation apparatus <NUM> according to a second embodiment. An evaluation function generator <NUM>, a reference DB <NUM>, a measurement target data extractor <NUM>, an evaluation function updater <NUM> and a capacity measurement DB <NUM> are added to the rechargeable battery evaluation apparatus <NUM> of the first embodiment (<FIG>). The same elements as in <FIG> are given the same reference characters, and their descriptions will be omitted as appropriate except for extended or modified processes.

The reference DB <NUM> stores training data used for training the evaluation function.

<FIG> and <FIG> show examples of training data stored in the reference DB <NUM>. The training data in <FIG> includes operation data (such as battery ID, time, voltage, SoC, electric power and temperature) acquired from the rechargeable battery <NUM> and SoH corresponding to each battery ID. The SoH is measured in advance and stored in the reference DB <NUM>. For example, the internal resistance of the rechargeable battery <NUM> may be measured to calculate the SoH based on the amount of change in the internal resistance from its initial value. The SoH may also be calculated based on the amount of charged electricity required to put the rechargeable battery <NUM> from a predetermined electricity storage state (e.g., a fully-discharged state) to a fully-charged state. The SoH may be calculated by another method. Here, IDs of battery cells are used as the battery IDs.

The training data in <FIG> is data generated from the training data in <FIG>, and includes SoH, FV value, average electric power, electric power standard deviation, average temperature, temperature standard deviation and the like. The method of calculating the FV value (in this example, a standard deviation) is similar to that in the first embodiment. The calculation of the FV value may be performed by using the state evaluator <NUM>, the OCV curve estimator <NUM>, the voltage corrector <NUM> and the SoC range determiner <NUM>, in a manner similar to the first embodiment. Alternatively, the FV value may be calculated in a procedure similar to that in the first embodiment in an apparatus different from the present apparatus.

The training data of the form in <FIG> may not be stored in the reference DB <NUM>. In this case, the training data of the form in <FIG> is generated from the training data of the form in <FIG> by an external apparatus and is stored in the reference DB <NUM>.

The evaluation function generator <NUM> generates an evaluation function based on the training data of the form in <FIG> in the reference DB <NUM>. The evaluation function generator <NUM> generates an SoH estimation model in which the SoH is an objective variable and some or all items including the feature (FV) are explanatory variables. The estimation technique may be of any type as long as it is a technique of constructing a regression model, such as linear regression, non-linear regression, machine learning (such as a neural network, random forests or SVR (Support Vector Regression)). A plurality of models may be combined, or a statistical quantity of at least one of temperature and electric power values may be included as an input variable. Also, classification by the temperature or electric power value (the charge rate or discharge rate may also be used) may be performed for construction for each class. Equation (<NUM>) mentioned above is an example of generating the SoH estimation model by linear regression. The generated estimation model corresponds to the evaluation function.

The measurement target data extractor <NUM> extracts data targeted for capacity measurement based on the operation data DB <NUM>. The data targeted for capacity measurement is data in which the measured voltage monotonously increases from a lower-limit voltage indicating the fully-discharged state to an upper-limit voltage indicating the fully-charged state. The voltage values may be smoothed in advance. A period in which the upper-limit voltage is reached from the lower-limit voltage is referred to as a capacity measurement period.

<FIG> shows an example of data in which the measured voltage monotonously increases from the lower-limit voltage indicating the fully-discharged state to the upper-limit voltage indicating the fully-charged state. A period P is the capacity measurement period.

The measurement target data extractor <NUM> integrates current values in the capacity measurement period to measure the amount of electric charge (AH) charged during the period. The measured amount of electric charge is divided by the rated value of the battery to measure the SoH.

The measurement target data extractor <NUM> stores the battery ID, the time, the measured SoH and the charge rate in the capacity measurement DB <NUM>. The measurement target data extractor <NUM> may calculate various statistical quantities based on the extracted data and further store the calculated statistical quantities in the capacity measurement DB <NUM>.

<FIG> shows an example of the capacity measurement DB <NUM>. The time is the time at which the SoH is measured. However, another time such as the starting or ending time of the extracted data may also be used. The charge rate is calculated by analyzing the current and electric power values in the data in the capacity measurement period to determine by which of constant current charge and constant power charge the charge is performed. As statistical quantities, statistical quantities (an average and a standard deviation) of temperature are stored.

The evaluation function updater <NUM> determines whether it is necessary to update the evaluation function in the evaluation function DB <NUM> based on the capacity measurement DB <NUM>, and when determining that update is necessary, updates the evaluation function.

As an example, the difference between an SoH estimated by the state evaluator <NUM> based on the same data as in the capacity measurement period and an SoH measured from the data in the capacity measurement period is calculated.

<FIG> shows an example of difference absolute values D1 and D2 between SoHs estimated by the state evaluator <NUM> and SoHs measured from the data in the capacity measurement period. The solid-line graph indicates transition of the SoH estimated by the state evaluator <NUM>. Point Y1 and point Y2 indicate SoHs measured from the data in the capacity measurement period.

The evaluation function updater <NUM> updates the evaluation function when the difference is greater than or equal to a threshold. For example, a coefficient is added to the evaluation function such that the estimated SoH is equal to the measured SoH. In the example of <FIG>, when the difference absolute value D1, which is greater than the threshold, is calculated, a coefficient (constant) to subtract from the D1 is added to the evaluation function. Alternatively, the evaluation function may be multiplied by a coefficient corresponding to D1. Alternatively, a coefficient (constant) to subtract or add an average value (or the maximum value, minimum value or the like) of a plurality of difference absolute values may be added to the evaluation function. For example, a constant to subtract an average value (or the maximum value, minimum value or the like) of D1 and D2 is added to the evaluation function. Alternatively, the evaluation function may be multiplied by a coefficient corresponding to the average value.

The evaluation function may also be updated by a method other than adding or multiplying a coefficient (constant). For example, a linear regression equation is calculated by performing linear regression of measured values of SoH from estimated values of SoH. The output value of the evaluation function is used an explanatory variable of the linear regression equation. The linear regression equation in which the output value of the evaluation function is assigned to the explanatory variable is used as an updated evaluation function. The output of the linear regression equation is the estimated SoH.

Also, the evaluation function may be recreated by using the FV value and the SOH in the capacity measurement DB <NUM> at the same time.

The above-described methods of updating the evaluation function may be switched according to the number of samples. For example, when the number of samples is less than a threshold, the evaluation function is updated by adding or multiplying a coefficient. When the number of samples is greater than or equal to a threshold, the method of performing linear regression of measured values of SoH from estimated values of SoH is used. Alternatively, the evaluation function may be recreated by using the FV value calculated by the state evaluator <NUM> and the SoH in the capacity measurement DB <NUM>.

<FIG> is a flow chart showing an example of processes of the evaluation function generator <NUM>. The evaluation function generator <NUM> reads training data from the reference DB <NUM> (S201). An evaluation function is generated based on the read training data (S202). The generated evaluation function is stored in the evaluation function DB <NUM> (S203).

<FIG> is a flow chart of an example of processes of the measurement target data extractor <NUM> and the evaluation function updater <NUM>. The measurement target data extractor <NUM> extracts data in the capacity measurement period from the operation data DB (S301). The measurement target data extractor <NUM> measures the SoH based on the extracted data (S302). The battery ID, time, measured SoH and charge rate are stored in the capacity measurement DB <NUM> (also S302). The measurement target data extractor <NUM> may calculate various statistical quantities based on the extracted data and further store the calculated statistical quantities in the capacity measurement DB <NUM>. The evaluation function updater <NUM> updates the evaluation function in the evaluation function DB <NUM> based on the capacity measurement DB <NUM> (S303).

By generating and updating the evaluation function in the above-described manner, it is possible to perform more accurate evaluation while reducing the number of pieces of data required for evaluation of the degradation state.

<FIG> is a block diagram of a rechargeable battery evaluation system according to a third embodiment. An SoC corrector <NUM> and an SoC_DB <NUM> are added.

The SoC corrector <NUM> corrects an SoC value included in operation data. Since the SoC value is calculated based on the current, if there are errors in current measurement, errors also accumulate in the SoC value. If the rechargeable battery <NUM> is operated for a long time, the errors in the SoC value may increase. The SoC corrector <NUM> performs correction to reduce the errors in the SoC value.

As a correction method, an electricity storage state (the amount of electric power) at the start of a previous charge, an electricity storage state (the amount of electric power) at the end of the charge, and an SoC value at the end of the charge are associated with the charge rate and saved in the SoC_DB <NUM>. Similarly, an electricity storage state (the amount of electric power) at the start of a previous discharge, an electricity storage state (the amount of electric power) at the end of the discharge, and an SoC value at the end of the discharge are associated with the charge rate and saved in the SoC_DB <NUM>. The electricity storage state at the start of the charge or the electricity storage state at the start of the discharge corresponds to a reference electricity storage state. The information saved in the SoC_DB <NUM> corresponds to reference data including the reference electricity storage state and the amount of charged electricity in the reference electricity storage state (a first amount of charged electricity).

It is assumed that the operation data (or part of the operation data) extracted by the evaluation target data extractor <NUM> is operation data acquired when the rechargeable battery <NUM> is charged from a first electricity storage state to a second electricity storage state at a first charge rate. The SoC value in the second electricity storage state is compared with the SoC value when a previous charge is performed from the first electricity storage state to the second electricity storage state at the same first charge rate. When the difference between the SoC values is greater than or equal to a threshold, the SoC value in the operation data is corrected based on the difference between the SoC values. For example, the difference between the SoC values is divided by the number of pieces of data in the operation data, and the value obtained by the division is added to the SoC value in the operation data. Correction of the SoC value can be performed similarly in the case of a discharge from the second electricity storage state to the first electricity storage state. This can suppress accumulation of errors in calculating the SoC value. The OCV curve estimator <NUM>, the voltage corrector <NUM>, the SoC range determiner <NUM> and the state evaluator <NUM> perform processes based on the corrected SoC value. As an example, the first electricity storage state and the second electricity storage state correspond to the electricity storage state at the start of the charge or the electricity storage state at the start of the discharge.

Note that the SoC corrector <NUM> may not perform correction if a previous charge or discharge has not been performed in the same conditions.

<FIG> is a flow chart of an example of operations of the rechargeable battery evaluation apparatus <NUM> according to the third embodiment. Step S111 is added between steps S102 and S103 in the flow chart in the first embodiment. In step S111, the SoC corrector <NUM> performs correction of an SoC value included in operation data. Other steps are similar to those in the first embodiment.

As above, according to the third embodiment, it is possible to reduce errors in the calculated SoC value, and thus more accurately evaluate the degradation state.

<FIG> is a block diagram of a rechargeable battery evaluation system according to a fourth embodiment. A voltage corrector <NUM> (second voltage corrector) and a ratio DB <NUM> are added to the rechargeable battery evaluation apparatus <NUM> in the third embodiment. The voltage corrector <NUM> and the ratio DB <NUM> may be added to the rechargeable battery evaluation apparatus <NUM> in the first embodiment or second embodiment.

The magnitude of internal resistance of a rechargeable battery (the rechargeable battery <NUM> or another rechargeable battery of the same type) corresponding to the SoC is measured in advance. A particular SoC is defined as a reference SoC. The ratio of the internal resistance at an SoC at least other than the reference SoC with respect to the internal resistance at the reference SoC is stored in the ratio DB <NUM>. For example, it is assumed that the internal resistance at an SoC of <NUM>% is measured as <NUM> times with respect to the internal resistance at an SoC <NUM>%. This ratio is stored in the ratio DB <NUM>. The information stored in the ratio DB <NUM> corresponds to ratio data in which a plurality of SoCs (amounts of charged electricity) and a plurality of ratios are associated with each other.

The voltage corrector <NUM> corrects a voltage value included in operation data according to an SoC value included in the operation data. The voltage corrector <NUM> corrects the voltage value included in the operation data by dividing it by a ratio with respect to the SoC value included in the operation data. In the case of the above example, the voltage value included in operation data with an SoC value of <NUM>% is divided by <NUM> to correct the voltage value. When the SoC value is the reference SoC, the ratio is <NUM> and thus the voltage value does not change by the correction. When the SoC value is the reference SoC, the correction of the voltage value may not be performed. The voltage corrector <NUM> performs processing on the voltage value after being corrected by the voltage corrector <NUM>. Alternatively, it is also possible that the voltage corrector <NUM> performs correction on the voltage value after being corrected by the voltage corrector <NUM>.

<FIG> is a flow chart of an example of operations of the rechargeable battery evaluation apparatus <NUM> according to the fourth embodiment. Step S121 is added between steps S103 and S104 in the flow chart in the third embodiment. In step S121, the second voltage corrector <NUM> corrects the voltage value included in the operation data based on the ratio DB <NUM> and the SoC value included in the operation data. Other steps are similar to those in the first embodiment.

As above, according to the fourth embodiment, it is possible to reduce errors in the calculated SoC value, and thus more accurately evaluate the degradation state.

According to the present embodiment, it is possible to accurately evaluate the degradation state by correcting the voltage value by taking into consideration variation in the internal resistance due to difference in the SoC.

<FIG> is a block diagram of a rechargeable battery evaluation system according to a fifth embodiment. Although the present embodiment shows an example of extending the rechargeable battery evaluation system in the fourth embodiment, similar extension can be applied to the rechargeable battery evaluation system in the first to third embodiments.

The rechargeable battery <NUM> includes a controller <NUM>. A connection line <NUM> is provided for feedback of information from the state evaluator <NUM> to the controller <NUM> of the rechargeable battery <NUM>.

The state evaluator <NUM> provides the SoC value (current SoC value) in the latest operation data accumulated in the operation data DB <NUM> and information on the SoC range selected by the SoC range determiner <NUM> to the controller <NUM> of the rechargeable battery <NUM>.

<FIG> shows an example internal configuration of the rechargeable battery <NUM>. The controller <NUM> and a plurality of battery units <NUM> to N are provided. The controller <NUM> controls the plurality of battery units <NUM> to N. The controller <NUM> determines a charge/discharge command assigned to each battery unit such that operation data is acquired within the SoC range notified from the state evaluator <NUM>, and provides the charge/discharge command to each battery unit. Each battery unit performs charge/discharge according to the charge/discharge command. If the rechargeable battery evaluation system is provided with a moving vehicle, the regenerative ratio when the moving vehicle performs braking may be controlled such that operation data at an SoC included in the SoC range is acquired.

As above, according to the fifth embodiment, the state evaluator <NUM> feeds back information based on operation data to the controller <NUM> of the rechargeable battery <NUM>, so that a lot of data effective for evaluation of the degradation state can be acquired. Therefore, it is possible to enhance the accuracy of evaluation of the degradation state.

The present embodiment shows an example configuration in which the rechargeable battery evaluation system is provided with a moving vehicle or an example configuration in which the rechargeable battery evaluation system is distributed over a system including a moving vehicle and a server. However, the moving vehicle is an example, and it is also possible to use any other apparatus with computer resources instead of the moving vehicle.

<FIG> shows an example in which the rechargeable battery evaluation system in <FIG> according to the first embodiment is provided with a moving vehicle <NUM>. The moving vehicle <NUM> includes the rechargeable battery <NUM>, the data acquirer <NUM>, and an evaluator <NUM>. The evaluator <NUM> includes elements other than the data acquirer <NUM> in the rechargeable battery evaluation apparatus in <FIG> (the operation data DB <NUM>, the evaluation target data extractor <NUM>, the state evaluator <NUM>, the OCV curve estimator <NUM>, the voltage corrector <NUM>, the SoC range determiner <NUM>, the evaluation result output device <NUM> and the evaluation function DB <NUM>). The evaluator <NUM> may further include the SoC corrector <NUM> and the SoC_DB <NUM> in <FIG>. Also, the evaluator <NUM> may further include the voltage corrector <NUM> and the ratio DB <NUM> in <FIG>. The configuration in <FIG> enables constant (real-time) evaluation of the rechargeable battery <NUM> provided with the moving vehicle <NUM> during operation.

<FIG> shows an example in which the rechargeable battery evaluation system in <FIG>, <FIG> or <FIG> is distributed over the moving vehicle <NUM> and an evaluation server <NUM>. The same elements as in <FIG> are given the same reference characters, and their descriptions will be omitted as appropriate. The moving vehicle <NUM> includes the rechargeable battery <NUM>, the data acquirer <NUM>, the evaluator <NUM> and a data communicator <NUM> (first data communicator). The evaluation server <NUM> includes an evaluation function learner <NUM> and a data communicator <NUM> (second data communicator). The rechargeable battery <NUM>, the data acquirer <NUM> and the evaluator <NUM> of the moving vehicle <NUM> are the same as in <FIG>.

The data communicator <NUM> of the moving vehicle <NUM> performs wired or wireless communication with the data communicator <NUM> of the evaluation server <NUM>. The evaluation function learner <NUM> of the evaluation server <NUM> includes the measurement target data extractor <NUM>, the capacity measurement DB <NUM>, the evaluation function updater <NUM>, the evaluation function generator <NUM> and the reference DB <NUM> in <FIG>. Elements that require a lot of computing resources are provided to the evaluation server <NUM>.

The data communicator <NUM> of the moving vehicle <NUM> sends the operation data acquired by the data acquirer <NUM>. The data communicator <NUM> of the evaluation server <NUM> receives the operation data from the moving vehicle <NUM> and sends data of the evaluation function generated or updated by the evaluation function learner <NUM> to the data communicator <NUM> of the moving vehicle <NUM>. The configuration in <FIG> enables constant (real-time) evaluation of the rechargeable battery <NUM> provided with the moving vehicle <NUM> during operation.

<FIG> shows another example in which the rechargeable battery evaluation system in <FIG>, <FIG> or <FIG> is distributed over the moving vehicle <NUM> and the evaluation server <NUM>. The moving vehicle <NUM> includes the rechargeable battery <NUM>, the data acquirer <NUM> and the data communicator <NUM> (first data communicator). The evaluation server <NUM> includes the data communicator <NUM> (second data communicator), the evaluator <NUM> and the evaluation function learner <NUM>. Unlike the configuration in <FIG>, the evaluator <NUM> is provided to the evaluation server <NUM> instead of the moving vehicle <NUM>. The same elements as in <FIG> are given the same reference characters, and their descriptions will be omitted as appropriate.

The data communicator <NUM> of the moving vehicle <NUM> sends the operation data acquired by the data acquirer <NUM>. The evaluation server <NUM> sends the evaluation result of the evaluator <NUM> to the moving vehicle <NUM>. Alternatively, the evaluation server <NUM> may send the evaluation result to a predetermined server on a communication network such as the Internet or to a predetermined e-mail address. The predetermined e-mail address is, for example, an e-mail address of an owner of the moving vehicle <NUM>.

The configuration in <FIG> further reduces the required computing resources of the moving vehicle <NUM> as compared to the configuration in <FIG> or <FIG>.

<FIG> shows another example in which the rechargeable battery evaluation system in <FIG>, <FIG> or <FIG> is distributed over the moving vehicle <NUM>, a management server <NUM> (first server) and the evaluation server <NUM> (second server). The moving vehicle <NUM> includes the rechargeable battery <NUM>, the data acquirer <NUM> and the data communicator <NUM> (first data communicator). The evaluation server <NUM> includes the data communicator <NUM> (third data communicator), the evaluator <NUM> and the evaluation function learner <NUM>. The management server <NUM> includes an ID converter (identifier determiner) <NUM>, a data communicator <NUM> (second data communicator) and a management DB <NUM>. The same elements as in <FIG> are given the same reference characters, and their descriptions will be omitted as appropriate.

The management server <NUM> is provided between the moving vehicle <NUM> and the evaluation server <NUM>. The data communicator <NUM> of the management server <NUM> performs wired or wireless communication with the data communicator <NUM> of the moving vehicle <NUM> and the data communicator <NUM> of the evaluation server <NUM>.

The data communicator <NUM> of the moving vehicle <NUM> adds identification information (moving vehicle ID) of the moving vehicle <NUM> to the operation data acquired from the rechargeable battery <NUM> and sends it to the management server <NUM>. The data communicator <NUM> of the management server <NUM> receives the operation data from the moving vehicle <NUM>.

The management DB <NUM> of the management server <NUM> stores information in which the moving vehicle ID and an analysis ID are associated with each other in the management DB <NUM>. Furthermore, the management DB <NUM> may store an e-mail address corresponding to the moving vehicle <NUM>. The e-mail address is, as an example, an e-mail address of an owner of the moving vehicle <NUM>.

<FIG> shows an example of the management DB <NUM>. Moving vehicle IDs, analysis IDs and e-mail addresses are included.

The ID converter <NUM> determines an analysis ID corresponding to the moving vehicle ID added to the operation data received from the moving vehicle <NUM>. The moving vehicle ID added to the operation data is replaced with the analysis ID. The management server <NUM> sends the operation data to which the analysis ID is added to the evaluation server <NUM>.

The data communicator <NUM> of the evaluation server <NUM> receives the operation data to which the analysis ID is added. The evaluator <NUM> of the evaluation server <NUM> evaluates the degradation state of the rechargeable battery <NUM>. The data communicator <NUM> adds the same analysis ID as the analysis ID added to the operation data to the evaluation result and sends it to the management server <NUM>.

The data communicator <NUM> of the management server <NUM> receives the evaluation result from the evaluation server <NUM>. The ID converter <NUM> finds the moving vehicle ID corresponding to the analysis ID added to the evaluation result in the management DB <NUM>. The data communicator <NUM> of the management server <NUM> sends the evaluation result to the moving vehicle <NUM> having the found moving vehicle ID. The moving vehicle ID may be sent together with the evaluation result. Also, the management server <NUM> may send the evaluation result to a server on a communication network such as the Internet or may send the evaluation result to the e-mail address corresponding to the moving vehicle ID.

With the configuration in <FIG>, it is possible to perform evaluation of the rechargeable battery <NUM> provided with the moving vehicle <NUM> in the evaluation server <NUM> without disclosing information identifying the moving vehicle <NUM> to the evaluation server <NUM>.

<FIG> shows an example hardware configuration of the rechargeable battery evaluation apparatus <NUM> according to the embodiments of the present invention. This hardware configuration can be applied to the rechargeable battery evaluation apparatus <NUM> according to each embodiment described above. The hardware configuration in <FIG> is configured as a computer <NUM>. The computer <NUM> includes a CPU <NUM>, an input interface <NUM>, a display <NUM>, a communication device <NUM>, a primary storage device <NUM> and an external storage device <NUM>, and these are communicatively connected to each other by a bus <NUM>.

The input interface <NUM> acquires measurement data of the rechargeable battery <NUM> via wiring or the like. The input interface <NUM> may be an operating device by which the user provides instructions to the present apparatus. Examples of the operating device include a keyboard, a mouse and a touch panel. The communication device <NUM> includes a wireless or wired communicator and performs wired or wireless communication with an EV <NUM>. The measurement data may be acquired via the communication device <NUM>. The input interface <NUM> and the communication device <NUM> may be composed of separate circuits such as integrated circuits or may be composed of a single circuit such as an integrated circuit. The display <NUM> is, for example, a liquid crystal display device, an organic EL display device, a CRT display device or the like. The display <NUM> corresponds to the evaluation result output device <NUM> in <FIG>.

The external storage device <NUM> includes, for example, storage media such as an HDD, SSD, memory device, CD-R, CD-RW, DVD-RAM, DVD-R and the like. The external storage device <NUM> stores a program for causing the CPU <NUM>, which is a processor, to execute the functions of the processing elements of the rechargeable battery evaluation apparatus <NUM>. The DBs included in the rechargeable battery evaluation apparatus <NUM> are also included in the external storage device <NUM>. Although only one external storage device <NUM> is shown here, there may be a plurality of external storage devices <NUM>.

Under control of the CPU <NUM>, the primary storage device <NUM> develops a control program stored in the external storage device <NUM> and stores data required for executing the program, data generated by the execution of the program and the like. The primary storage device <NUM> includes any memory or storage such as a volatile memory (such as a DRAM or SRAM) or a non-volatile memory (such as a NAND flash memory or MRAM), for example. The control program developed on the primary storage device <NUM> is executed by the CPU <NUM>, and the functions of the processing elements of the rechargeable battery evaluation apparatus <NUM> are thereby executed. The DBs included in the rechargeable battery evaluation apparatus <NUM> may also be included in the primary storage device <NUM>.

Claim 1:
An information processing apparatus (<NUM>) for estimating a degradation state of a rechargeable battery (<NUM>) characterized in that the apparatus comprises:
a first voltage corrector (<NUM>) configured to correct a first voltage value of the rechargeable battery according to a difference between the first voltage value and a third voltage value to generate a second voltage value, the first voltage value including one of a charge voltage or discharge voltage, and the third voltage value depending on an amount of charged electricity of the rechargeable battery at the first voltage value;
a state evaluator (<NUM>) configured to evaluate the degradation state of the rechargeable battery based on the second voltage value; and
a relationship information generator (<NUM>) configured to generate first relationship information between the third voltage value and the amount of charged electricity of the rechargeable battery based on data, the data including the first voltage value and the amount of charged electricity, wherein
the first voltage corrector corrects the first voltage value based on the first relationship information.