Patent Description:
The present invention relates to an apparatus and method for estimating a capacity of a battery by configuring a model separately for data that is easy to analyze and data that is not easy to analyze.

Recently, research and development of secondary batteries have been actively performed. Herein, the secondary batteries, which are chargeable/dischargeable batteries, may include all of conventional nickel (Ni)/cadmium (Cd) batteries, Ni/metal hydride (MH) batteries, etc., and recent lithium ion batteries. Among the secondary batteries, a lithium ion battery has a much higher energy density than those of the conventional Ni/Cd batteries, Ni/MH batteries, etc. Moreover, the lithium ion battery may be manufactured to be small and lightweight, such that the lithium ion battery has been used as a power source of mobile devices. In addition, the lithium ion battery is attracting attention as a next-generation energy storage medium as a usage range thereof is expanded to a power source of electric vehicles.

Furthermore, the secondary battery is generally used as a battery pack including a battery module where a plurality of battery cells are connected to one another in series and/or in parallel. The battery pack may be managed and controlled by a battery management system in terms of a state and an operation.

Such a secondary battery is subject to a lot assembly test (LAT) in a production process to determine a quality of each cell in production. Generally, one sample may be selected for each lot, which is a unit of a plurality of cells, to perform the LAT. The LAT is intended to check if a capacity of the secondary battery is greater than or equal to a specific level even after <NUM> cycles through accelerated degradation of the secondary battery.

Through the LAT, full charging and discharging may be performed under the same experiment condition for one through <NUM> cycles, and it is determined whether the cell has passed the test based on a state of health (SOH) life in the <NUM> cycles. However, data logged in the LAT may include data that is easy to analyze and data that is not easy to analyze, together, such that there may be a difficulty in analysis of a data value and accuracy may be degraded.

Prior art document <CIT> discloses an arrangement for estimating battery capacity based on voltage/current measurements, involving dividing up measured data into time segments and applying a model thereto.

The present invention has been made to solve the foregoing problems, and aims to provide a battery capacity estimation apparatus and method in which data that is easy to analyze and data that is not easy to analyze are distinguished from among logging data of a battery cell and a capacity estimation model is applied to each data, thereby accurately and efficiently estimating a capacity of the battery cell.

A battery capacity estimation apparatus according to an embodiment of the present invention includes a voltage measuring unit configured to measure a voltage of a battery cell, a filtering unit configured to determine voltage data as first data when a logging pattern of the voltage data of the battery cell deviates from a preset reference range, a statistical analyzing unit configured to determine second data through statistical analysis on the voltage data of the battery cell, and a capacity estimating unit configured to estimate a capacity by applying data, classified by the filtering unit or the statistical analyzing unit for a battery cell that is a measurement target, to capacity estimation models generated separately for the first data and the second data.

A battery capacity estimation method according to an embodiment of the present invention includes measuring a voltage of a battery cell, determining voltage data as first data when a logging pattern of the voltage data of the battery cell deviates from a preset reference range, determining second data through statistical analysis on the voltage data of the battery cell, and estimating a capacity of the battery cell by applying the first data and the second data to capacity estimation models, respectively.

With a battery capacity estimation apparatus and method according to the present invention, data that is easy to analyze and data that is not easy to analyze may be distinguished from among logging data of a battery cell and a capacity estimation model may be applied to each data, thereby accurately and efficiently estimating a capacity of the battery cell.

Hereinafter, various embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this document, identical reference numerals will be used for identical components in the drawings, and the identical components will not be redundantly described.

For various embodiments of the present invention disclosed in this document, specific structural or functional descriptions are only exemplified for the purpose of describing the embodiments of the present invention, and various embodiments of the present invention may be implemented in various forms, and should not be construed as being limited to the embodiments described in this document.

As used in various embodiments, the terms "1st, "2nd", "first", "second", or the like may modify various components regardless of order and/or importance, and do not limit the components. For example, a first component may be named as a second component without departing from the right scope of the present disclosure, and similarly, the second component may be named as the first component.

Terms used in the present document are used for only describing a specific exemplary embodiment of the disclosure and may not have an intention to limit the scope of other exemplary embodiments of the disclosure. It is to be understood that the singular expressions include plural expressions unless the context clearly dictates otherwise.

All of the terms used herein including technical or scientific terms have the same meanings as those generally understood by an ordinary skilled person in the related art. In some cases, the terms defined herein may be interpreted to exclude embodiments of the present disclosure.

<FIG> is a block diagram of a general battery rack.

Referring to <FIG>, a battery control system including a battery rack <NUM> and a upper-level controller <NUM> included in a upper-level system according to an embodiment of the present invention is schematically shown.

As shown in <FIG>, the battery rack <NUM> may include a battery module <NUM> that includes one or more battery cells and is chargeable/dischargeable, a switching unit <NUM> serially connected to a positive (+) terminal side or a negative (-) terminal side of the battery module <NUM> to control a charging/discharging current flow of the battery module <NUM>, and a battery management system (e.g., RBMS) <NUM> for control and management to prevent over-charging and over-discharging by monitoring a voltage, a current, a temperature, etc., of the battery rack <NUM>. The battery rack <NUM> may include a plurality of battery modules <NUM>, sensors <NUM>, switching units <NUM>, and battery management systems <NUM>.

Herein, as the switching unit <NUM> which is an element for controlling a current flow for charging or discharging of the plurality of battery modules <NUM>, for example, at least one relay, magnetic contactor, etc., may be used according to specifications of the battery rack <NUM>.

The battery management system <NUM>, which is an interface for receiving measurement values of the above-described various parameters, may include a plurality of terminals and a circuit, etc., connected thereto to process input values. The battery management system <NUM> may control on/off of the switching unit <NUM>, e.g., a relay, a contactor, etc., and may be connected to the battery module <NUM> to monitor the state of each battery module <NUM>.

Meanwhile, the battery management system <NUM> according to the present invention may perform regression analysis on a voltage of a battery cell through a separate program, as will be described below. An abnormal type of the battery cell may be classified using a calculated regression equation.

The upper-level controller <NUM> may transmit a control signal for the battery module <NUM> to the battery management system <NUM>. Thus, the battery management system <NUM> may also be controlled in terms of an operation thereof based on a signal applied from the upper-level controller <NUM>. Meanwhile, the battery cell according to the present invention may be included in the battery module <NUM> used for an energy storage system (ESS). In this case, the upper-level controller <NUM> may be a controller (BBMS) of a battery bank including a plurality of racks or an ESS controller for controlling the entire ESS including a plurality of banks. However, the battery rack <NUM> is not limited to such a purpose.

Such configurations of the battery rack <NUM> and the battery management system <NUM> are well-known configurations, and thus will not be described in detail.

<FIG> is a block diagram showing a structure of a battery capacity estimation apparatus according to an embodiment of the present invention.

Referring to <FIG>, a battery capacity estimation apparatus <NUM> according to an embodiment of the present invention may include a voltage measuring unit <NUM>, a filtering unit <NUM>, a static analyzing unit <NUM>, and a capacity estimating unit <NUM>. For example, the battery capacity estimation apparatus <NUM> according to an embodiment of the present invention may estimate a capacity of the battery cell by analyzing charging and discharging data of the battery in real time, or may perform a test by sampling a failure before mounting in a module in manufacturing of the battery cell.

The voltage measuring unit <NUM> may measure a voltage of the battery cell. In this case, the voltage measuring unit <NUM> may measure the voltage of the battery cell at specific time intervals. For example, the voltage measuring unit <NUM> may measure a voltage for a rest period after charging or discharging of the battery cell. In addition, the voltage measuring unit <NUM> may measure current flowing in the battery cell.

When a logging pattern of voltage data of the battery cell deviates from a preset reference range, the filtering unit <NUM> may determine the voltage data as first data. More specifically, when at least one of a logging time and the number of voltage data of the battery cell deviates from a reference range, the filtering unit <NUM> may determine the voltage data as the first data.

For example, the logging pattern of the voltage data of the battery cell may be intended to extract four voltage data in the unit of <NUM> minutes. In this case, there may be an error in a logging time like when a logging time of the voltage data of the battery cell is (<NUM>, <NUM>, <NUM>, <NUM> minutes) or specific logging data may be omitted like when a logging time is (<NUM>, <NUM>, <NUM> minutes) or (<NUM>, <NUM>, <NUM> minutes), etc. In this case, the filtering unit <NUM> may classify corresponding data as the first data.

The statistical analyzing unit <NUM> may determine second data through statistical analysis on the voltage data of the battery cell. In this case, the statistical analyzing unit <NUM> may perform statistical analysis on data other than data determined as the first data by the filtering unit <NUM>. The statistical analyzing unit <NUM> may calculate differential data dV/dt, for the battery cell, of a voltage with respect to a time. As will be described below, the differential data of the voltage with respect to the time shows more prominent tendency than logged voltage data, such that the statistical analyzing unit <NUM> may use the differential data of the voltage with respect to the time.

More specifically, the statistical analyzing unit <NUM> may extract principal component data for voltage data by performing principal component analysis (PCA) on the differential data.

The statistical analyzing unit <NUM> may calculate a plurality of clusters through k-means clustering on the principal component data, and determine differential data included in a particular cluster as second data and differential data not included in the cluster as the first data.

For example, the first data may be data in which the voltage data of the battery cell is in a discontinuous form, and the second data may be data in which the voltage data of the battery cell is in a continuous form. That is, the first data may be data that is not be easy to analyze and the second data may be data that is easy to analyze.

As such, the battery capacity estimation apparatus <NUM> according to an embodiment of the present invention may apply a capacity estimation model separately for the first data and the second data which have different general shapes, thereby improving accuracy in comparison to when data where the first data and the second data are combined is used conventionally. For example, with the battery capacity estimation apparatus <NUM> according to an embodiment of the present invention, in charging and discharging of the battery, when a capacity of <NUM> cycles is predicted using data regarding initial <NUM> cycles, accuracy may be improved by separately applying data to the capacity estimation model.

The capacity estimation unit <NUM> may estimate a capacity by applying data, classified by the filtering unit <NUM> or the statistical analyzing unit <NUM> for the battery cell that is a measurement target, to the capacity estimation model generated separately for the first data and the second data. For example, the capacity estimation model may be a long short-term memory networks (LSTM) model. In this case, the capacity estimation model generated for each of the first data and the second data may include a different parameter value.

Meanwhile, although not shown in <FIG>, the battery capacity estimation apparatus <NUM> according to an embodiment of the present invention may include a storing unit. In this case, the storing unit may store various data such as voltage data measured by the voltage measuring unit <NUM>, voltage data classified by the filtering unit <NUM> and the statistical analyzing unit <NUM>, a capacity estimation program, etc. The battery capacity estimation apparatus <NUM> according to an embodiment of the present invention may operate by transmitting and receiving the above-described data in communication with an external server through a communicating unit (not shown), instead of including the storing unit.

As such, with the battery capacity estimation apparatus <NUM> according to the present invention, data that is easy to analyze and data that is not easy to analyze may be distinguished from among logging data of a battery cell and a capacity estimation model may be applied to each data, thereby accurately and efficiently estimating a capacity of the battery cell.

<FIG> is a flowchart showing an operation, performed by a battery capacity estimation apparatus, of classifying data according to an embodiment of the present invention.

Referring to <FIG>, the battery capacity estimation apparatus according to an embodiment of the present invention may determine whether a battery cell is currently in a rest state (that is, current = <NUM>) in operation S310. When the battery cell is in the rest state, it may be determined whether voltage data is logged according to a preset scheme, in operation S320. For example, the logging scheme may be logging four voltage data at an interval of <NUM> minutes.

When the voltage data is out of the preset logging scheme (NO), the voltage data may be classified as the first data in operation S330. On the other hand, when the voltage data is logged normally according to the preset scheme (YES), differential data dV/dt of the voltage data with respect to a time may be calculated in operation S340.

Then, feature (principal component) data may be extracted through PCA with respect to the differential data of the voltage. In this case, by performing PCA on the differential data, a dimension of data may be reduced. By applying k-mean clustering to the principal component data, the data may be classified into a plurality of clusters in operation S360.

When the classified data is not included in a particular cluster (e.g., Cluster <NUM>) (NO), the data may be classified as the first data in operation S370. On the other hand, when the data is included in the particular cluster (YES), the data may be classified as second data in operation S380.

As such, with the battery capacity estimation apparatus according to an embodiment of the present invention, voltage data may be identified by checking a time unit of logging data and using PCA and a k-mean clustering algorithm. Thus, data having similar features may be classified, thereby efficiently and accurately performing battery capacity estimation.

<FIG> is a diagram showing a correlation between logging data and a capacity of a battery cell.

In <FIG>, a left graph may indicate a correlation with a battery capacity (e.g., a SOH) (a y axis) with respect to each of differential data (dV1, dV2, dV3, and dV4) (an x axis) of a voltage with respect to a time after charging and discharging, and a right table may indicate logging data of a voltage after charging and discharging of the battery.

Referring to <FIG>, the x axis may indicate voltage differential data dV1, dV2, dV3, and dV4 after charging and voltage differential data dV1, dV2, dV3, and dV4 after discharging. In this case, in the graph of <FIG>, a correlation with a battery capacity may be high as a y-axis value is close to <NUM> or -<NUM> and a length of a vertical bar is short. That is, it may be seen that data (<NUM> and <NUM>) immediately after charging and discharging has a higher correlation with a battery capacity value than other data. This is because a voltage change immediately after charging and discharging is more distinct than a voltage change thereafter.

<FIG> is a diagram showing that logging data of a battery cell is classified into a plurality of clusters by a battery capacity estimation apparatus according to an embodiment of the present invention.

Referring to <FIG>, an x axis may indicate the number of charging and discharging cycles of a battery cell and a y axis may indicate differential data dV1 through dV4 of a voltage with respect to a time in a rest period after charging and discharging of the battery cell. Cluster <NUM> may indicate the above-described first data and Cluster <NUM> may indicate the above-described second data.

As shown in <FIG>, the first data belonging to Cluster <NUM> may indicate that data is relatively discontinuous. That is, the first data may be irregular by nature, and thus may not be easy to perform battery capacity analysis thereon.

Meanwhile, the second data belonging to Cluster <NUM> may be continuous and have a gentle curve when compared to the first data. That is, the second data may have more constant tendency than the first data and may be easy to analyze.

<FIG> is a diagram showing that logging data of all battery cells are classified into a plurality of clusters by a battery capacity estimation apparatus according to an embodiment of the present invention.

Referring to <FIG>, an x axis may indicate the number of charging and discharging cycles of a battery cell, and a y axis may indicate differential data dV2 of a voltage with respect to a time in a rest period after charging and discharging of the entire battery cell.

Like in <FIG>, even when data of the entire battery cells are summed, data belonging to Cluster <NUM> may often protrude irregularly from an upper end or a lower end. On the other hand, data belonging to Cluster <NUM> may have a gentle form when compared to Cluster <NUM>. Thus, a result may be more accurately calculated in capacity estimation of the battery.

<FIG> shows an example of an LSTM of a battery capacity estimation apparatus according to an embodiment of the present invention.

The capacity estimation model shown in <FIG> may indicate an LSTM. In <FIG>, C may indicate long-term information, h may indicate information in a previous step, σ and tanh may indicate activation functions, W may indicate a weight value, and b may indicate noise. The LSTM of <FIG> may include a forget gate layer, a decision layer, a new state value updating operation, and an output value deciding operation.

More specifically, the forget gate layer may determine whether to retain (<NUM>) or discard (<NUM>) certain information with an input of ht-<NUM> and Xt having an output value between <NUM> and <NUM>. In addition, in the decision layer, a value to be updated for storing a new state may be determined. In this case, a value to be updated may be determined in the input gate layer, and a vector C of new candidate values to be newly added to a cell state may be generated in the tanh layer.

Moreover, in the new cell state updating operation, an old cell state Ct-<NUM> may be updated into a new cell state Ct. In the output value determining operation, a value to be output may be determined and a value between -<NUM> and <NUM> for a cell state may be extracted through a tanh function, after which an output value may be multiplied by the output value of the forget gate layer.

As such, when the foregoing time-series voltage data is input to the capacity estimation model shown in <FIG>, a capacity value (e.g., a capacity %) of the battery cell may be output through the foregoing processes. Meanwhile, the LSTM model of <FIG> has a known configuration and thus will not be described in detail.

However, the LSTM of <FIG> is merely an example, such that the capacity estimation model according to the present invention is not limited thereto and various estimation models may be used.

<FIG> is a flowchart showing a battery capacity estimation method according to an embodiment of the present invention.

Referring to <FIG>, a battery capacity estimation method according to an embodiment of the present invention measures a voltage of a battery cell in operation S810. In this case, in operation S810, the voltage of the battery cell may be measured at specific time intervals. For example, a voltage may be measured for a rest period after charging or discharging of the battery cell.

When a logging pattern of voltage data of the battery cell deviates from a preset reference range, the voltage data may be determined as the first data, in operation S820. More specifically, when at least one of a logging time and the number of voltage data of the battery cell deviates from the reference range, the voltage data may be determined as the first data. For example, the logging pattern of the voltage data of the battery cell may be intended to extract four voltage data in the unit of <NUM> minutes.

Next, second data may be determined through statistical analysis on the voltage data of the battery cell, in operation S830. Differential data dV/dt, for the battery cell, of a voltage with respect to a time may be calculated in operation S830. More specifically, principal component data for voltage data may be extracted by performing PCA on the differential data, in operation S830. A plurality of clusters may be calculated through k-means clustering on the principal component data, and differential data included in a particular cluster may be determined as the second data and differential data not included in the cluster as the first data.

Last, the first data and the second data extracted in operations S820 and S830 may be applied to the capacity estimation model, respectively, thereby estimating the capacity of the battery cell in operation S840. For example, the capacity estimation model may be an LSTM model. In this case, the capacity estimation models of the first data and the second data may be identical, but parameter values input to the capacity estimation models may be different.

As such, with the battery capacity estimation method according to the present invention, data that is easy to analyze and data that is not easy to analyze may be distinguished from among logging data of a battery cell and a capacity estimation model may be applied to each data, thereby accurately and efficiently estimating a capacity of the battery cell.

<FIG> is a block diagram showing a hardware structure of a battery abnormality diagnosis apparatus according to an embodiment of the present invention.

Referring to <FIG>, a battery capacity estimation apparatus <NUM> according to an embodiment of the present invention may include a microcontroller unit (MCU) <NUM>, a memory <NUM>, an input/output interface (I/F) <NUM>, and a communication I/F <NUM>.

The MCU <NUM> may be a processor that executes various programs (e.g., a battery capacity estimation program, a principal component analysis program, a k-means clustering program, etc.) stored in the memory <NUM>, processes various data for data classification, capacity estimation, etc., of the battery cell through these programs, and executes the above-described functions of <FIG>.

The memory <NUM> may store various programs regarding statistical analysis, capacity estimation, etc., of the battery cell. Moreover, the memory <NUM> may store various data such as voltage data of the battery cell, differential data of a voltage of the battery cell, etc..

The memory <NUM> may be provided in plural, depending on a need. The memory <NUM> may be a volatile or nonvolatile memory. For the memory <NUM> as the volatile memory, random access memory (RAM), dynamic RAM (DRAM), static RAM (SRAM), etc., may be used. For the memory <NUM> as the nonvolatile memory, read only memory (ROM), programmable ROM (PROM), electrically alterable ROM (EAROM), erasable PROM (EPROM), electrically erasable PROM (EEPROM), flash memory, etc., may be used. The above-listed examples of the memory <NUM> are merely examples and are not limited thereto.

The input/output I/F <NUM> may provide an interface for transmitting and receiving data by connecting an input device (not shown) such as a keyboard, a mouse, a touch panel, etc., and an output device such as a display (not shown), etc., with the MCU <NUM>.

The communication I/F <NUM>, which is a component capable of transmitting and receiving various data to and from a server, may be various types of devices capable of supporting wired or wireless communication. For example, a program for statistical analysis and capacity estimation or various data may be transmitted and received to and from a separately provided external server through the communication I/F <NUM>.

As such, a computer program according to an embodiment of the present invention may be recorded in the memory <NUM> and processed by the MCU <NUM>, thus being implemented as a module that performs function blocks shown in <FIG>.

Even though all components constituting an embodiment of the present invention have been described above as being combined into one or operating in combination, the present invention is not necessarily limited to the embodiment. That is, within the object scope of the present invention, all the components may operate by being selectively combined into one or more.

Moreover, terms such as "include", "constitute" or "have" described above may mean that the corresponding component may be inherent unless otherwise stated, and thus should be construed as further including other components rather than excluding other components. All terms including technical or scientific terms have the same meanings as those generally understood by those of ordinary skill in the art unless defined otherwise. The terms used generally like terms defined in dictionaries should be interpreted as having meanings that are the same as the contextual meanings of the relevant technology and should not be interpreted as having ideal or excessively formal meanings unless they are clearly defined in the present invention.

Claim 1:
A battery capacity estimation apparatus comprising:
a voltage measuring unit (<NUM>) configured to measure a voltage of a battery cell;
a filtering unit (<NUM>) configured to determine voltage data as first data when a logging pattern of the voltage data of the battery cell deviates from a preset reference range;
a statistical analyzing unit (<NUM>) configured to determine second data through statistical analysis on the voltage data of the battery cell; and
a capacity estimating unit (<NUM>) configured to estimate a capacity by applying data, classified by the filtering unit or the statistical analyzing unit for a battery cell that is a measurement target, to capacity estimation models generated separately for the first data and the second data.