Patent Description:
Recently, there has been a rapid increase in the demand for portable electronic products such as laptop computers, video cameras and mobile phones, and with the extensive development of electric vehicles, accumulators for energy storage, robots and satellites, many studies are being made on high performance batteries that can be repeatedly recharged.

Currently, commercially available batteries include nickel-cadmium batteries, nickel-hydrogen batteries, nickel-zinc batteries, lithium batteries and the like, and among them, lithium batteries have little or no memory effect, and thus they are gaining more attention than nickel-based batteries for their advantages that recharging can be done whenever it is convenient, the self-discharge rate is very low and the energy density is high.

In predicting the performance of a battery, for example, State Of Health (SOH) and State Of Charge (SOC), voltage and current are basically required battery parameters. The capacity of the battery (or its change) may be determined based on the measured current using Coulomb counting.

Differential Voltage Analysis (DVA) determines a differential voltage curve by differentiating a measured voltage curve indicating a correlation between capacity and voltage of the battery, and determines a degradation parameter of the battery based on a change in size and/or position of feature(s) in the differential voltage curve. The degradation parameter includes, for example, a capacity loss of the positive or negative electrode, lithium deposition, etc..

In determining the degradation parameter using DVA, overvoltage reflected on the measured voltage curve acts as noise in the differential voltage curve due to polarization (for example, a concentration gradient on active material surface). Accordingly, to suppress the polarization causing overvoltage, a process of obtaining the measured voltage curve is usually performed by intermittently discharging or charging the battery with low current (for example, less than <NUM> C-rate). As a result, the polarization induced overvoltage is a key parameter that affects the degradation of the battery, but the existing DVA is difficult to obtain the overvoltage characteristics of the battery.

Additionally, to develop batteries having high safety and performance, it is important to identify a correlation between polarization dependent on the use condition of the battery and its resulting overvoltage characteristics.

<CIT> discloses battery state of health estimation based on a differential voltage curve calculation using the voltage values and total discharge values associated with discharge current values.

The present disclosure is designed to solve the above-described problem, and therefore the present disclosure is directed to providing an apparatus and method for evaluating overvoltage characteristics of a battery using Differential Voltage Analysis (DVA).

These and other objects and advantages of the present disclosure may be understood by the following description and will be apparent from the embodiments of the present disclosure.

An overvoltage characteristics evaluation apparatus for a battery according to an aspect of the present disclosure includes a sensing unit configured to measure a current and a voltage of the battery, and a control unit configured to determine a measured capacity history and a measured voltage history indicating a time-series change in capacity and voltage of the battery using sensing information obtained from the sensing unit during a discharge event executed subsequent to polarization-inducing pretreatment for the battery. The control unit is configured to determine a first measured voltage curve indicating a correlation between the measured capacity history and the measured voltage history. The control unit is configured to determine a second measured voltage curve indicating a correlation between a depth of discharge history obtained by normalizing the measured capacity history to a total discharge capacity of the measured capacity history and the measured voltage history. The control unit is configured to determine a differential voltage curve from the second measured voltage curve by differentiating the measured voltage history with respect to the depth of discharge history. The control unit is configured to determine overvoltage characteristics information associated with the polarization-inducing pretreatment by comparing the differential voltage curve with a reference differential voltage curve.

The discharge event may include constant current discharging from a first time point to a second time point. The first time point is a time point at which the voltage of the battery is equal to a first threshold voltage. The second time point is a time point at which the voltage of the battery is equal to a second threshold voltage that is lower than the first threshold voltage.

The control unit may be configured to determine a concentrated overvoltage range which is a range in which a differential voltage difference between the differential voltage curve and the reference differential voltage curve is equal to or larger than a threshold difference in an entire range of the depth of discharge history. The overvoltage characteristics information includes the concentrated overvoltage range.

The control unit may be configured to determine an area of a concentrated overvoltage zone defined by the concentrated overvoltage range, the differential voltage curve and the reference differential voltage curve. The overvoltage characteristics information further includes the area of the concentrated overvoltage zone.

The area indicates a magnitude of overvoltage accumulated in the battery over the concentrated overvoltage range.

The control unit may be configured to determine the threshold difference by dividing an integral value of the differential voltage difference over a reference range of from a predetermined first depth of discharge to a predetermined second depth of discharge in the entire range of the depth of discharge history by a size of the reference range.

The control unit may be configured to determine the concentrated overvoltage range in the reference range.

An overvoltage characteristics evaluation method for a battery according to another aspect of the present disclosure includes determining a measured capacity history and a measured voltage history indicating a time-series change of capacity and voltage of the battery using sensing information of current and voltage of the battery obtained during a discharge event executed subsequent to polarization-inducing pretreatment for the battery, determining a first measured voltage curve indicating a correlation between the measured capacity history and the measured voltage history, determining a second measured voltage curve indicating a correlation between a depth of discharge history obtained by normalizing the measured capacity history to a total discharge capacity of the measured capacity history and the measured voltage history, determining a differential voltage curve from the second measured voltage curve by differentiating the measured voltage history with respect to the depth of discharge history, and determining overvoltage characteristics information associated with the polarization-inducing pretreatment by comparing the differential voltage curve with a reference differential voltage curve.

The step of determining the overvoltage characteristics information associated with the polarization-inducing pretreatment may include determining a concentrated overvoltage range which is a range in which a differential voltage difference between the differential voltage curve and the reference differential voltage curve in an entire range of the depth of discharge history is equal to or larger than a threshold difference.

The step of determining the overvoltage characteristics information associated with the polarization-inducing pretreatment may further include determining an area of a concentrated overvoltage zone defined by the concentrated overvoltage range, the differential voltage curve and the reference differential voltage curve.

According to at least one of the embodiments of the present disclosure, it is possible to evaluate overvoltage characteristics of a battery using Differential Voltage Analysis (DVA). In particular, a correlation between a measured voltage history and a measured capacity history may be converted to a correlation between the measured voltage history and a depth of discharge history. Here, the depth of discharge history may be obtained by normalizing the measured capacity history of a measured voltage curve obtained during a discharge event executed subsequent to polarization-inducing pretreatment for the battery to the depth of discharge history (in the range of <NUM>~<NUM>%). Accordingly, it is possible to obtain, as a result of evaluation, a concentrated overvoltage range in which the overvoltage characteristics of the battery having undergone the polarization-inducing pretreatment are exhibited in a concentrated manner.

In addition, according to at least one of the embodiments of the present disclosure, it is possible to additionally obtain the magnitude of overvoltage accumulated over the concentrated overvoltage range as a result of evaluation.

The effects of the present disclosure are not limited to the effects mentioned above, and these and other effects will be clearly understood by those skilled in the art from the appended claims.

Therefore, the embodiments described herein and illustrations shown in the drawings are just a most preferred embodiment of the present disclosure, but not intended to fully describe the technical aspects of the present disclosure, so it should be understood that a variety of other equivalents and modifications could have been made thereto at the time that the application was filed.

Unless the context clearly indicates otherwise, it will be understood that the term "comprises" when used in this specification, specifies the presence of stated elements, but does not preclude the presence or addition of one or more other elements. Additionally, the term "control unit" as used herein refers to a processing unit of at least one function or operation, and this may be implemented by hardware and software either alone or in combination.

<FIG> is a diagram exemplarily showing a configuration of a battery evaluation system according to the present disclosure, <FIG> is a diagram referenced in describing a relationship between a magnitude of overvoltage and a measured voltage curve, <FIG> is a diagram referenced in describing a result of normalizing the measured voltage curve, <FIG> is a diagram referenced in describing a differential voltage curve corresponding to the measured voltage curve, and <FIG> is a diagram referenced in describing an operation of determining overvoltage characteristics from the differential voltage curve.

Referring to <FIG>, the battery evaluation system <NUM> is provided to evaluate the overvoltage characteristics of a battery B. The battery B may be a lithium ion battery. The battery B is not limited to a particular type and may include any type of battery that can be recharged repeatedly.

The battery evaluation system <NUM> includes an overvoltage characteristics evaluation apparatus <NUM> (hereinafter referred to as the 'evaluation apparatus') and a charge/discharge device <NUM>.

The charge/discharge device <NUM> is electrically connected to a current path for the charge/discharge of the battery B. That is, the charge/discharge device <NUM> is provided to be electrically connectable to the battery B in parallel through a pair of terminals. The charge/discharge device <NUM> may include a constant current circuit to adjust a current rate (referred to as 'C-rate') of the electric current flowing through the battery B. The charge/discharge device <NUM> is configured to adjust the current rate (referred to as 'C-rate') of the electric current for the charge or discharge of the battery B in response to a command from the evaluation apparatus <NUM>. The charge/discharge device <NUM> may provide only one of a constant current discharging function and a constant current charging function.

The evaluation apparatus <NUM> includes a sensing unit <NUM> and a control unit <NUM>. The evaluation apparatus <NUM> may further include at least one of an interface unit <NUM> or a temperature chamber <NUM>. The following description is made under the assumption that the evaluation apparatus <NUM> includes all the sensing unit <NUM>, the control unit <NUM>, the interface unit <NUM> and the temperature chamber <NUM>.

The sensing unit <NUM> includes a voltage sensor <NUM> and a current sensor <NUM>.

The voltage sensor <NUM> is provided to be electrically connectable to the battery B in parallel. The voltage sensor <NUM> is configured to measure a voltage across the battery B, and generate a voltage signal indicating the measured voltage.

The current sensor <NUM> is provided to be electrically connectable to the battery B in series through the current path connecting the battery B and the charge/discharge device <NUM>. The current sensor <NUM> is configured to measure the electric current flowing through the battery B, and generate a current signal indicating the measured current.

The control unit <NUM> may collect sensing information including the voltage signal and the current signal obtained in synchronization from the sensing unit <NUM>.

The control unit <NUM> may be implemented in hardware using at least one of application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), microprocessors or electrical units for performing the other functions. The control unit <NUM> may have a memory embedded therein. The memory may include, for example, at least one type of storage medium of flash memory type, hard disk type, Solid State Disk (SSD) type, Silicon Disk Drive (SDD) type, multimedia card micro type, random access memory (RAM), static random access memory (SRAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM) or programmable read-only memory (PROM). The memory may store data and programs required for the computation operation (methods as described below) by the control unit <NUM>. The control unit <NUM> may record data indicating the result of the computation operation in the memory.

The control unit <NUM> is operably coupled to the charge/discharge device <NUM>, the sensing unit <NUM>, the interface unit <NUM> and the temperature chamber <NUM>. Operably coupled refers to directly/indirectly connected to transmit and receive a signal in one or two directions.

The interface unit <NUM> is configured to support wired or wireless communication between the control unit <NUM> and a user terminal <NUM> (for example, a personal computer). The wired communication may be, for example, controller area network (CAN) communication, and the wireless communication may be, for example, Zigbee or Bluetooth communication. The communication protocol is not limited to a particular type and may include any communication protocol that supports wired/wireless communication between the control unit <NUM> and the user terminal <NUM>. The interface unit <NUM> may include an output device (for example, a display, a speaker) to provide the information received from the control unit <NUM> and/or the user terminal <NUM> in a recognizable format.

The control unit <NUM> may determine a measured capacity history and a measured voltage history based on the sensing information (i.e., time-series of the measured current values and time-series of the measured voltage values) collected from the sensing unit <NUM> at a preset time interval during a discharge event of the battery B. The measured capacity history indicates a time-series change in the discharge capacity of the battery B from beginning to end of the discharge event. The measured voltage history indicates a time-series change in the voltage of the battery B from beginning to end of the discharge event. In the discharge event, a larger discharge capacity of the measured capacity history corresponds to a lower voltage of the measured voltage history.

The control unit <NUM> may record the measured capacity history and the measured voltage history in the memory. The discharge event may include constant current discharging. The discharge event may be executed while the temperature chamber <NUM> maintains the ambient temperature of the battery B at a preset temperature.

The constant current discharging is performed from a first time point at which the voltage of the battery B is equal to a first threshold voltage VTH1 to a second time point at which the voltage of the battery B is equal to a second threshold voltage VTH2 that is lower than the first threshold voltage VTH1. For example, the first threshold voltage VTH1 is an Open Circuit Voltage (OCV) of the battery B when the battery B is fully charged, and may be the same as a preset value, i.e., end-of-charge voltage. The second threshold voltage VTH2 may be equal to a preset value as the OCV when the battery B is fully discharged, i.e., an end-of-discharge voltage. The C-rate of constant current discharging may be, for example, a high current of <NUM> C-rate.

In <FIG>, the X axis (vertical axis) indicates voltage, and the Y axis (horizontal axis) indicates discharge capacity. A first reference voltage curve <NUM> is pre-acquired through the discharge event for a reference battery (not shown) having undergone reference pretreatment, and a first measured voltage curve <NUM> is acquired through the discharge event for the battery B having undergone polarization-inducing pretreatment. The first reference voltage curve <NUM> indicates a correlation between a reference capacity history and a reference voltage history. The reference capacity history indicates a time-series change in the discharge capacity of the reference battery from beginning to end of the discharge event. The reference voltage history indicates a time-series change in the voltage of the reference battery from beginning to end of the discharge event. The battery B and the reference battery are manufactured with the same electrical and chemical characteristics.

Below is an example of each of reference pretreatment and polarization-inducing pretreatment.

<Reference pretreatment> The reference pretreatment may include a series of the following processes.

<Polarization-inducing pretreatment> The polarization-inducing pretreatment may include a series of the following processes.

When comparing the reference pretreatment with the polarization-inducing pretreatment in the above-described example, the polarization-inducing pretreatment in which the battery B is placed at a second temperature (room temperature), instead of a first temperature (high temperature), is different from the reference pretreatment. Due to this difference, the reference battery undergoes the discharge event in a state that polarization completely disappeared, whereas the battery B undergoes the discharge event in a state that the battery B is still polarized. The reference pretreatment is not limited to the above-described example when the reference pretreatment is performed to reduce the polarization of the battery B to below a predetermined level at the start of the discharge event. Likewise, the polarization-inducing pretreatment is not limited to the above-described example when it is performed to form larger polarization in the battery B than the reference pretreatment.

After the user puts the battery B in the temperature chamber <NUM>, the user may request the evaluation apparatus <NUM> to perform polarization-inducing pretreatment. In response to the request received from the user terminal <NUM> through the interface unit <NUM>, the control unit <NUM> may control the charge/discharge device <NUM> and the temperature chamber <NUM> to perform the processes of the polarization-inducing pretreatment in a sequential order. The temperature chamber <NUM> is a device having an internal space in which the battery B may be received, and the temperature of the internal space (i.e., the ambient temperature of the battery B) may be detected and adjusted. In response to the completion of the polarization-inducing pretreatment, the control unit <NUM> may perform the discharge event for the battery B. Alternatively, the polarization-inducing pretreatment may be performed using a separate tester instead of the evaluation apparatus <NUM>.

It can be seen from <FIG> that a difference between the first reference voltage curve <NUM> and the first measured voltage curve <NUM> corresponding to a polarization difference between the battery B and the reference battery occurs during the discharge event. Specifically, the first measured voltage curve <NUM> shows voltage decrease behaviors generally faster than the first reference voltage curve <NUM>, and it can be seen that the total discharge capacity QB_total of the battery B corresponding to the second threshold voltage VTH2 decreases from the total discharge capacity Qref_total of the reference battery. This is because polarization remaining in the battery B is exhibited as overvoltage by the electric current of the discharge event.

As a result, the reference voltage history of the first reference voltage curve <NUM> and the measured voltage history of the first measured voltage curve <NUM> have the same voltage range, but the reference capacity history of the first reference voltage curve <NUM> and the measured capacity history of the first measured voltage curve <NUM> do not have the same capacity range. Accordingly, for easy comparison between the first reference voltage curve <NUM> and the first measured voltage curve <NUM>, the control unit <NUM> may determine a first depth of discharge history and a second depth of discharge history having the same range of <NUM>-<NUM> or <NUM>-<NUM>% by normalizing the reference capacity history of the first reference voltage curve <NUM> and the measured capacity history of the first measured voltage curve <NUM>, respectively.

The reference capacity history of the first reference voltage curve <NUM> and the first depth of discharge history may have the following relation.

When i is a natural number of <NUM> or greater, Qref_total is the total discharge capacity of the first reference voltage curve <NUM>, Qref[i] is the discharge capacity of the reference battery determined at the ith time during the discharge event, and DoDref[i] is a value obtained by normalizing Qref[i] using Qref_total. The first depth of discharge history may be a set (time-series) of DoDref[i] during the discharge event.

The measured capacity history of the first measured voltage curve <NUM> and the second depth of discharge history may have the following relation.

When j is a natural number of <NUM> or greater, QB_total is the total discharge capacity of the first measured voltage curve <NUM>, QB[j] is the discharge capacity of the battery B determined at the ith time during the discharge event, and DoDB[j] is a value obtained by normalizing QB[j] using QB_total. The second depth of discharge history may be a set (time-series) of DoDB[j] during the discharge event.

In <FIG>, the X axis (vertical axis) indicates voltage, and the Y axis (horizontal axis) indicates the depth of discharge corresponding to the discharge capacity of <FIG>. Referring to <FIG>, the control unit <NUM> may determine a second reference voltage curve <NUM> from the first reference voltage curve <NUM> by converting a correlation between the reference capacity history and the reference voltage history to a correlation between the first depth of discharge history and the reference voltage history.

Likewise, the control unit <NUM> may determine a second measured voltage curve <NUM> from the first measured voltage curve <NUM> by converting a correlation between the measured capacity history and the measured voltage history of the first measured voltage curve <NUM> to a correlation between the second depth of discharge history and the measured voltage history. As a result, the reference voltage history of the second reference voltage curve <NUM> and the measured voltage history of the second measured voltage curve <NUM> are scaled with respect to the depth of discharge in the common range of <NUM>-<NUM>%.

In <FIG>, the X axis (vertical axis) indicates a differential voltage, the Y axis (horizontal axis) is the same as the Y axis of <FIG>. The differential voltage dV/dQ is a ratio of a change dV in voltage to a change dQ in discharge capacity (or depth of discharge).

Referring to <FIG>, the control unit <NUM> may determine a reference differential voltage curve <NUM> from the second reference voltage curve <NUM> by differentiating the reference voltage history of the second reference voltage curve <NUM> with respect to the first depth of discharge history.

Alternatively, the reference differential voltage curve <NUM> may be recorded in the memory according to a result of a test conducted in advance, instead of being determined by the control unit <NUM>. That is, the reference differential voltage curve <NUM> may be preset as a differential voltage curve when the discharge event is executed in a zero polarization state of the battery B, i.e., the battery B did not yet undergo the polarization-inducing pretreatment, and.

The control unit <NUM> may determine a differential voltage curve <NUM> from the second measured voltage curve <NUM> by differentiating the measured voltage history of the second measured voltage curve <NUM> with respect to the second depth of discharge history. The differential voltage curve <NUM> may indicate a time-series of a ratio of a change in voltage to (i) the depth of discharge (or its corresponding discharge capacity) and (ii) a unit change of the depth of discharge (or a change of corresponding discharge capacity, in the entire range of <NUM>-<NUM>%.

The control unit <NUM> determines overvoltage characteristics information of the battery B from the differential voltage curve <NUM> by comparing the reference differential voltage curve <NUM> with the differential voltage curve <NUM>. The control unit <NUM> may associate the overvoltage characteristics information to the polarization-inducing pretreatment and record in the memory.

<FIG> is a graph exemplarily showing a polarization comparison curve <NUM> indicating a correlation between a differential voltage difference ΔdV/dQ and the depth of discharge over a reference range ΔRref. In <FIG>, the X axis (vertical axis) indicates the differential voltage difference ΔdV/dQ, and the Y axis (horizontal axis) is the same as the Y axis of <FIG>.

The control unit <NUM> may determine the differential voltage difference ΔdV/dQ between the reference differential voltage curve <NUM> and the differential voltage curve <NUM> with respect to the depth of discharge in the reference range ΔRref. The differential voltage difference ΔdV/dQ corresponding to each depth of discharge may be a value obtained by subtracting the differential voltage of the reference differential voltage curve <NUM> from the differential voltage of the differential voltage curve <NUM>. The reference range ΔRref is from a predetermined first depth of discharge DoD<NUM> (for example, <NUM>%) larger than <NUM>% to a predetermined second depth of discharge DoD<NUM> (for example, <NUM>%) smaller than <NUM>%. The reason of using the reference range ΔRref is that the discharge reaction of the battery B is very unstable in the range of <NUM> % ~ the first depth of discharge DoD<NUM> and the range of the second depth of discharge DoD<NUM> - <NUM>%.

The control unit <NUM> may determine a concentrated overvoltage range ΔRop, i.e., a range in which the differential voltage difference ΔdV/dQ of the polarization comparison curve <NUM> is equal to or larger than a threshold difference ΔD in the entire range (i.e., <NUM>~<NUM>%) of the depth of discharge history. The overvoltage characteristics information may include the concentrated overvoltage range ΔRop. For example, in <FIG>, the differential voltage of the differential voltage curve <NUM> is kept higher by at least the threshold difference ΔD than the differential voltage of the reference differential voltage curve <NUM> over the concentrated overvoltage range ΔRop from the first depth of discharge DoDA to the second depth of discharge DoDB. The threshold difference ΔD may be a preset value. Alternatively, the control unit <NUM> may determine the threshold difference ΔD based on an integral value of the differential voltage difference ΔdV/dQ over the reference range ΔRref. For example, the control unit <NUM> may determine the threshold difference ΔD to be equal to a value obtained by dividing the integral value by the size of the reference range ΔRref(i.e., DoD<NUM> - DoD<NUM>).

The control unit <NUM> may be further configured to determine an area of a concentrated overvoltage zone <NUM>. The concentrated overvoltage zone <NUM> is a zone defined by the concentrated overvoltage range ΔRop, the differential voltage curve <NUM> and the reference differential voltage curve <NUM>. The area of the concentrated overvoltage zone <NUM> is a difference between a voltage change of the second measured voltage curve <NUM> and a voltage change of the second reference voltage curve <NUM> over the concentrated overvoltage range ΔRop. That is, the area of the concentrated overvoltage zone <NUM> indicates the magnitude of overvoltage accumulated in the battery B over the concentrated overvoltage range ΔRop. The overvoltage characteristics information may further include the area the concentrated overvoltage zone.

<FIG> is a flowchart exemplarily showing a method for evaluating overvoltage characteristics of a battery according to a first embodiment of the present disclosure. The method of <FIG> is performed after the polarization-inducing pretreatment for the battery B is completed.

Referring to <FIG>, in step S610, the control unit <NUM> determines a measured capacity history and a measured voltage history indicating a time-series change in capacity and voltage of the battery B during the discharge event of the battery B, respectively. The measured capacity history is based on the accumulated value of the electric current measured by the current sensor <NUM> at a predetermined time interval during the discharge event. The measured voltage history is based on the voltage across the battery B measured by the voltage sensor <NUM> at the predetermined time interval during the discharge event.

In step S620, the control unit <NUM> determines a first measured voltage curve <NUM> indicating a correlation between the measured capacity history and the measured voltage history.

In step S630, the control unit <NUM> determines a second measured voltage curve <NUM> indicating a correlation between a depth of discharge history corresponding to the measured capacity history and the measured voltage history by normalizing the measured capacity history to the total discharge capacity QB_total of the measured capacity history.

In step S640, the control unit <NUM> determines a differential voltage curve <NUM> from the second measured voltage curve <NUM> by differentiating the measured voltage history with respect to the depth of discharge history.

In step S650, the control unit <NUM> determines a differential voltage difference between the differential voltage curve and the reference differential voltage curve with respect to the depth of discharge in the reference range ΔRref.

In step S660, the control unit <NUM> determines a concentrated overvoltage range ΔRop, i.e., a range in which the differential voltage difference is equal to or larger than a threshold difference ΔD in the reference range ΔRref. The threshold difference ΔD may be pre-recorded in the memory.

In step S670, the control unit <NUM> determines an area of a concentrated overvoltage zone <NUM> defined by the concentrated overvoltage range ΔRop, the differential voltage curve <NUM> and the reference differential voltage curve <NUM>. The step S670 may be omitted from the method of <FIG>.

In step S680, the control unit <NUM> outputs an evaluation message indicating overvoltage characteristics information of the battery B. The overvoltage characteristics information includes at least one of the concentrated overvoltage range ΔRop or the area of the concentrated overvoltage zone <NUM>. The interface unit <NUM> may transmit the evaluation message to the user terminal <NUM> or output visual and/or audible information corresponding to the evaluation message.

<FIG> is a flowchart exemplarily showing a method for evaluating overvoltage characteristics of a battery according to a second embodiment of the present disclosure. The method of <FIG> is performed after the polarization-inducing pretreatment for the battery B is completed. In describing the second embodiment, a repeated description in common with the first embodiment may be omitted herein.

<FIG> and <FIG>, in step S710, the control unit <NUM> determines a measured capacity history and a measured voltage history indicating a time-series change in capacity and voltage of the battery B during the discharge event of the battery B.

In step S720, the control unit <NUM> determines a first measured voltage curve <NUM> indicating a correlation between the measured capacity history and the measured voltage history.

In step S730, the control unit <NUM> determines a second measured voltage curve <NUM> indicating a correlation between a depth of discharge history corresponding to the measured capacity history and the measured voltage history by normalizing the measured capacity history to the total discharge capacity QB_total of the measured capacity history.

In step S740, the control unit <NUM> determines a differential voltage curve <NUM> from the second measured voltage curve <NUM> by differentiating the measured voltage history with respect to the depth of discharge history.

In step S750, the control unit <NUM> determines a differential voltage difference between the differential voltage curve <NUM> and the reference differential voltage curve <NUM> with respect to the depth of discharge in the reference range ΔRref.

In step S752, the control unit <NUM> determines whether an integral value of the differential voltage difference over the reference range ΔRref is larger than a reference integral value. When a value of the step S752 is "Yes", step S756 is performed. The value of the step S752 being "No" may indicate that a computation error occurred in the steps S710-S750. When the value of the step S752 is "No", step S754 is performed.

In step S754, the control unit <NUM> outputs a fault message. The interface unit <NUM> may transmit the fault message to the user terminal <NUM> or output visual and/or audible information corresponding to the fault message. The steps S752 and S754 may be omitted from the method of <FIG>, and after the step S750, step S756 may be performed.

In step S756, the control unit <NUM> determines a threshold difference ΔD based on the integral value of the differential voltage difference over the reference range ΔRref.

In step <NUM>, the control unit <NUM> determines a concentrated overvoltage range ΔRop, i.e., a range in which the differential voltage difference is equal to or larger than the threshold difference ΔD in the reference range ΔRref.

In step S770, the control unit <NUM> determines an area of a concentrated overvoltage zone <NUM> defined by the concentrated overvoltage range ΔRop, the differential voltage curve <NUM> and the reference differential voltage curve <NUM>. The step S770 may be omitted from the method of <FIG>.

In step S780, the control unit <NUM> outputs an evaluation message indicating overvoltage characteristics information of the battery B. The overvoltage characteristics information includes at least one of the threshold difference ΔD, the concentrated overvoltage range ΔRop or the area of the concentrated overvoltage zone <NUM>.

The embodiments of the present disclosure described hereinabove are not implemented only through the apparatus and method, and may be implemented through programs that perform functions corresponding to the configurations of the embodiments of the present disclosure or recording media having the programs recorded thereon, and such implementation may be easily achieved by those skilled in the art from the disclosure of the embodiments previously described.

Claim 1:
An overvoltage characteristics evaluation apparatus (<NUM>) for a battery, comprising:
a sensing unit (<NUM>) configured to measure a current and a voltage of the battery (<NUM>); and
a control unit (<NUM>) configured to determine a measured capacity history and a measured voltage history indicating a time-series change in capacity and voltage of the battery using sensing information obtained from the sensing unit during a discharge event executed subsequent to polarization-inducing pretreatment for the battery,
determine a first measured voltage curve indicating a correlation between the measured capacity history and the measured voltage
characterised in that the control unit is further configured to
determine a second measured voltage curve indicating a correlation between a depth of discharge history obtained by normalizing the measured capacity history to a total discharge capacity of the measured capacity history and the measured voltage history,
determine a differential voltage curve from the second measured voltage curve by differentiating the measured voltage history with respect to the depth of discharge history, and
determine overvoltage characteristics information associated with the polarization-inducing pretreatment by comparing the differential voltage curve with a reference differential voltage curve.