KR101930646B1 - Apparatus and Method for Estimating Capacity of Battery Using Second Order Differential Voltage Curve - Google Patents

Abstract

According to an aspect of the present invention of a device for estimating a battery capacity using a secondary differential voltage curve, wherein the capacity of the battery is able to be estimated even if the battery is not in a fully discharged state, and the device comprises: a charge time detector for applying a constant current to a test battery in a first SOC state to obtain a voltage curve, and detecting a charging time which is a time at which the test battery reaches a buffer state from the first SOC state on the voltage curve; a buffer time estimating part for correcting a secondary differential voltage curve obtained by secondarily differentiating the voltage curve and a charging time on the basis of a comparison result of a reference voltage curve obtained from a reference battery, and estimating a buffering time which is a time for the test battery to reach a buffering state from a second SOC state; and a capacity estimating part estimating a capacity of the test battery corresponding to the buffering time using a predetermined charging time-capacity model.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and method for estimating battery capacity using a secondary differential voltage curve,

The present invention relates to battery management, and more particularly, to battery capacity estimation.

The capacity of the battery is one of the direct indicators used to determine the state of health (SOH) of the battery. Therefore, a model-based battery capacity estimation method, a learning-based battery capacity estimation method, and an experience-based battery capacity estimation method have been proposed to estimate the battery capacity.

First, a model-based battery capacity estimation method refers to a method of estimating the total capacity of a battery using a predetermined open circuit voltage (OCV) - state of charge (SOC) table. The model based battery capacity estimation method can be used during the actual operation of the battery and the charging state of the battery can be estimated in real time. However, since the OCV-SOC varies with the aging of the battery, Periodic update process is required and it is difficult to apply it in a constant current use environment.

The learning based battery capacity estimation method learns the current and voltage response according to the aging of the battery in advance and estimates the capacity of the battery using the measured voltage or current value. The learning-based battery capacity estimation method has a high estimation accuracy but requires a lot of pre-aging experiment data.

The experience based battery capacity estimation method is a method of estimating the capacity of a battery without fully pre-aging experiments by extracting features that are related to the total capacity of the battery. However, the conventional experience-based battery capacity estimation methods are disadvantageous in that they are not only required to have a low charging current but also can be applied to a specific type of battery such as a lithium iron phosphate battery.

An example of an experience-based battery capacity estimation method is disclosed in Korean Patent Laid-Open No. 10-2016-0144437 (hereinafter referred to as 'prior art'). In the prior art, the maximum value (Peak) of the differential value (dV / dQ) within a certain charging range is found and a method of estimating the SOH using the OCV corresponding to the maximum value is proposed. However, in the case of the prior art, there is a problem that only a very low charging current situation such as 25 / C can be applied in order to obtain OCV.

Korean Patent Publication No. 10-2016-0144437 (Title of the Invention: Method of Estimating Health Status of Batteries, Disclosure Date: December 16, 2016)

The present invention provides a battery capacity estimating apparatus and method using a secondary differential voltage curve capable of estimating the capacity of a battery even when the battery is not in a fully discharged state.

According to another aspect of the present invention, there is provided a battery capacity estimating apparatus and method using a secondary differential voltage curve capable of estimating a capacity of a battery regardless of a magnitude of a charging current.

Another aspect of the present invention is to provide an apparatus and method for estimating battery capacity using a secondary differential voltage curve capable of updating a reference curve used for estimating a capacity of a battery as the battery progresses in aging.

According to an aspect of the present invention, there is provided an apparatus for estimating a battery capacity using a secondary differential voltage curve, the apparatus comprising: a constant current circuit for applying a constant current to a test battery in a first SOC state to obtain a voltage curve, A charge time detector for detecting a charge time, which is a time period from the first SOC state to a buffer state; The charging time is corrected based on a result of comparison between the secondary differential voltage curve obtained by secondary differentiation of the voltage curve and the reference voltage curve obtained from the reference battery to determine the time at which the test battery reaches the buffer state from the second SOC state A buffer time estimating unit for estimating buffer time; And a capacity estimating unit for estimating a capacity of the test battery corresponding to the buffering time using a predetermined charging time-capacity model.

According to an aspect of the present invention, there is provided a method of estimating a battery capacity using a secondary differential voltage curve, the method comprising: measuring a charging time of a test battery from a first SOC state to a buffer state, ; Extracting a target curve included in the characteristic section from a second differential voltage curve obtained by second differentiating the voltage curve; Determining a time difference between a characteristic section and a similar section having a highest similarity to the target curve on a reference voltage curve for the reference battery; Estimating a buffer time which is a time for the test battery to reach a buffer state from a second SOC state by correcting the charge time using the time difference; And estimating a capacity of the test battery corresponding to the buffering time using a predetermined charging time-capacity model.

According to the present invention, since the charging time of the battery is corrected based on the secondary differential curve of the battery charging voltage and the capacity of the battery can be estimated based on the corrected charging time, the capacity of the battery Can be accurately estimated.

In addition, according to the present invention, since the capacity of the battery can be estimated using the characteristic interval of the secondary differential curve of the battery charging voltage, the capacity of the battery can be accurately estimated even in a low charging current state, The estimation error due to the change can be reduced.

In addition, according to the present invention, since the charging time of the battery and the capacity of the battery are modeled in a linear relation, pre-aging experiment data required for capacity estimation of the battery can be minimized.

In addition, according to the present invention, since the reference curve used for estimating the capacity of the battery is updated according to the aging progress of the battery, the accuracy of the battery capacity estimation can be improved.

FIG. 1 is a block diagram schematically illustrating a configuration of a battery capacity estimating apparatus using a quadratic differential voltage curve according to an embodiment of the present invention. Referring to FIG.
2A is a graph showing an example of a voltage curve obtained from a test battery.
2B is a graph showing an example of a secondary differential voltage curve of the test battery.
2C is a graph showing an example of a reference voltage curve of the reference battery.
FIG. 2D is a conceptual diagram illustrating a method of determining a similar section, which is a section similar to a target curve, on a reference voltage curve.
3 is a conceptual diagram illustrating a method of estimating the capacity of a test battery corresponding to a buffering time using a charge time-capacity model.
4 is a conceptual diagram showing a method of updating a reference voltage curve.
5 is a flowchart illustrating a battery capacity estimation method using a second derivative voltage curve according to an embodiment of the present invention.
6 is a graph showing performance test results of the battery capacity estimation method according to the present invention.
FIG. 7A is a histogram showing an error according to an experience-based battery capacity estimation method using a peak value according to the prior art.
7B is a histogram showing an error of the battery capacity estimation method according to the present invention.
FIG. 8 is a graph showing a result of applying the battery capacity estimation method according to the present invention to batteries of different SOC states.
FIG. 9A is a graph showing an error occurring when applying the experience-based battery capacity estimation method using the peak value according to the prior art for the two batteries shown in FIG.
FIG. 9B is a graph illustrating errors occurring when the battery capacity estimation method according to the present invention is applied to the two batteries shown in FIG. 8. FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The meaning of the terms described herein should be understood as follows.

The word " first, "" second," and the like, used to distinguish one element from another, are to be understood to include plural representations unless the context clearly dictates otherwise. The scope of the right should not be limited by these terms.

It should be understood that the terms "comprises" or "having" does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

It should be understood that the term "at least one" includes all possible combinations from one or more related items. For example, the meaning of "at least one of the first item, the second item and the third item" means not only the first item, the second item or the third item, but also the second item and the second item among the first item, Means any combination of items that can be presented from more than one.

FIG. 1 is a block diagram schematically illustrating a configuration of a battery capacity estimating apparatus using a quadratic differential voltage curve according to an embodiment of the present invention. Referring to FIG.

A battery capacity estimation apparatus 100 using a secondary differential voltage curve according to an embodiment of the present invention estimates the capacity of the test battery 110. [

In particular, the battery capacity estimating apparatus 100 according to an embodiment of the present invention estimates the time (hereinafter referred to as 'charge time') from the first SOC state (state of charge) (Hereinafter referred to as " buffer time ") from the second SOC state in which the test battery 110 is fully discharged to the buffer state, The total capacity of the test battery 110 is estimated.

1, a battery capacity estimation apparatus 100 according to an embodiment of the present invention includes a constant current application unit 120, a charge time detection unit 130, a buffer time estimation unit 140, And a capacity estimation unit 150. [ The battery capacity estimation apparatus 100 may further include a reference voltage curve acquisition unit 160, a storage unit 170, and a reference voltage curve update unit 180.

The constant current applying unit 120 charges the test battery 110 by applying a constant current to the test battery 110 in the first SOC state. In the present invention, the reason why the constant current is applied to the test battery 110 to charge the test battery 110 is that since the constant current charge time is proportional to the charge amount charged in the battery, if the constant current charge time is calculated, This is because the capacity of the battery can be calculated.

In one embodiment, the first SOC state may be a state having a higher SOC than the second SOC state in a fully discharged state. That is, according to the present invention, since the test battery 110 is not required to be charged from the fully discharged state in order to estimate the capacity of the test battery 110, the time required for capacity estimation of the test battery 110 is reduced .

The constant current applying unit 120 applies a constant current to the reference battery 200 in the second SOC state so that the reference voltage curve obtaining unit 160 can obtain the reference voltage curve from the reference battery 200 The reference battery 200 may be charged. That is, the constant current applying unit 120 can charge the reference battery 200 by applying a constant current to the reference battery 200 in a fully discharged state. In one embodiment, the reference battery 200 may be a battery of the same type as the test battery 200, or may be a new battery without aging.

The voltage curve acquisition unit 130 acquires the voltage of the test battery 110 that is changed at each time point as the test battery 110 is charged with the constant current applied by the constant current application unit 120, The voltage curve is calculated. An example of a voltage curve obtained from the test battery 110 by the voltage curve acquisition unit 130 is shown in FIG.

2A, the test battery 110 is in a first SOC state S1 at an initial time t = 0 due to a constant current applied from the constant current application unit 120, It can be seen that after the elapse of the time (tcc), the buffer state becomes the buffer state.

On the other hand, the voltage curve acquisition unit 103 acquires the charging time tcc of the test battery 110 on the voltage curve of the obtained test battery 110. At this time, as described above, the charging time tcc refers to the time from when the test battery 110 reaches the buffer state to the first SOC state.

The voltage curve acquisition unit 130 provides the voltage curve of the test battery 110 and the charge time tcc of the test battery 110 to the buffer time estimator 140.

The buffering time estimating unit 140 estimates the buffering time of the test battery 110 based on the charging time tcc of the test battery 110. In one embodiment, the buffering time estimating unit 140 according to the present invention compares the secondary differential voltage curve obtained by secondary differentiating the voltage curve of the test battery 110 with the reference voltage curve obtained from the reference battery 200 And the buffer time of the test battery 110 can be estimated by correcting the charge time based on the comparison result.

1, the buffering time estimating unit 140 according to the present invention includes an operation unit 142, a target curve extraction unit 144, a similarity interval determination unit 146, and a buffering time calculation unit 148).

The calculating unit 142 obtains a first derivative voltage curve by differentiating the voltage curve of the test battery 110 obtained by the voltage curve obtaining unit 130 and re-differentiates the obtained first differential voltage curve to obtain a second differential voltage curve . An example of the second derivative voltage curve obtained by the calculation section 142 is shown in FIG. 2B.

In addition, the arithmetic unit 142 sets the feature section using the first derivative voltage curve. In one embodiment, the operation unit 142 sets a start point (corresponding to t1 in FIG. 2B) corresponding to the first peak value in the first differential voltage curve as the start point of the feature section, The time point corresponding to the first valley value (corresponding to t2 in FIG. 2B) can be set as the end point of the feature section.

The target curve extracting unit 144 extracts a target curve included in the characteristic section from the secondary differential voltage curve of the test battery 110 calculated by the calculating section 142. 2B, the target curve extracting unit 144 extracts a curve Tcurve between the start point t1 and the end point t2 of the characteristic interval on the secondary differential voltage curve as a target curve Tcurve, .

As described above, according to the present invention, not only the entire section of the secondary differential voltage curve is used for estimating the capacity of the test battery 110 but the voltage curve of the characteristic section that can be regarded as representing the characteristic for the low charge current on the secondary differential voltage curve It is possible to accurately estimate the capacity of the test battery 110 even when the charge current state is not low because the target curve Tcurve is used for estimating the capacity of the test battery 110. As a result, Can be reduced.

The similar section determining unit 146 selects a similar section having the highest degree of similarity to the target curve Tcurve among the reference voltage curves by comparing the target curve Tcurve with the reference voltage curve as shown in FIG. And calculates the time difference with the similar section. In one embodiment, as shown in FIG. 2D, the similar-interval determining unit 146 shifts the target curve (Tcurve) on the reference voltage curve while changing the voltage curve interval having the highest similarity to the target curve (Tcurve) It can be determined as a section.

For example, as shown in FIG. 2D, the similar section determining section 146 shifts the target curve Tcurve on the reference voltage curve to a predetermined time unit? T, and calculates a voltage curve section that is most similar to the target curve Tcurve (Scurve) is determined as a similar section. At this time, the starting point of the similar section may be (t1 +? _Min T) and the end point may be (t2 +? _Min T), and? _Min T represents the time difference between the characteristic section and the similar section. Here,? Represents the number of samples, and T represents a sampling period.

In one embodiment, the similarity interval determiner 146 may determine a value that minimizes the result of Equation (1) below on the reference voltage curve as the time difference between the similar interval and the characteristic interval.

In Equation (1), a represents a sampling number on a reference voltage curve, T represents a sampling period, t1 represents a start time point of the characteristic section, t2 represents an end point of the characteristic section, and Vref represents a voltage curve acquisition section 130 And Vin represents the voltage curve of the test battery 110 obtained by the voltage curve acquiring unit 130. The voltage curve of the reference battery 200 shown in FIG.

The buffer time calculating unit 148 calculates the buffer time tcc of the test battery 110 received from the voltage curve obtaining unit 130 based on the time difference between the similar section and the feature section calculated by the similar section determining unit 146 It corrects the charge time (tcc) of the test battery (110) by adding the α _min T). The charging time tcc of the test battery 110 is corrected by the buffer time calculator 148 so that the test battery 110 can be fully charged or discharged from the second SOC state, It is possible to obtain the time tmax. This can be expressed by the following equation (2).

In Equation (2), tmax represents the buffering time, and tcc represents the charging time.

The capacity estimator 150 estimates the total capacity of the test battery 110 using the buffer time of the test battery 110 calculated by the buffer time calculator 148. [ In one embodiment, the capacity estimator 150 may estimate the capacity Cmax of the test battery 110 corresponding to the buffer time using the charge time-capacity model as shown in FIG. This can be expressed by the following equation (3).

In Equation 3, Cmax represents the capacity of the test battery 110, b1 represents the slope of the predetermined charge time-capacity model, and b2 represents the slice value of the charge time-capacity model.

3, the charge time-capacity model is modeled on the assumption that the charge time of the battery and the capacity of the battery are linear, and by measuring the buffer time of the battery and the capacity of the battery through two or more experiments in advance, The slope b1 and the slice b2 that define the time-capacity model can be calculated. As described above, according to the present invention, since the charge estimating unit 150 can model the charge time-capacity model with at least two pieces of pre-aging test data (buffer time and capacity), it is possible to minimize the experimental data required for battery capacity estimation .

The reference voltage curve acquiring unit 160 acquires the reference voltage curve of the reference battery 110 that is changed at each time point as the reference battery 110 is charged by the constant current applied to the reference battery 200 from the constant current application unit 120. [ And the voltage curve of the reference battery 200 is calculated.

The reference voltage curve obtaining unit 160 obtains a first differential voltage curve by differentiating the voltage curve of the reference battery 200 and obtains a reference voltage curve by differentiating the obtained first differential voltage curve again. An example of the reference voltage curve obtained by the reference voltage curve obtaining section 160 is shown in FIG. 2C.

The storage unit 170 stores the secondary differential voltage curve of the test battery 110 calculated at predetermined intervals by the calculation unit 142. [

The reference voltage curve updating unit 180 updates the reference voltage curve used for estimating the capacity of the test battery 110. [ Specifically, the reference voltage curve updating unit 180 updates the previous reference voltage curve Vref, old to the new reference voltage curve Vref, new, as shown in FIG. 4, when a predetermined condition is satisfied.

In one embodiment, the reference voltage curve updating unit 180 may determine any one of the plurality of secondary differential voltage curves stored in the storage unit 170 as a new reference voltage curve.

The reference voltage curve updating unit 180 updates the capacity of the test battery 110 calculated at the first time point and the capacity of the test battery 110 calculated at the second time point after a predetermined time elapses from the first time point If the difference exceeds the reference value, it can be determined to update the reference voltage curve.

The reason why the reference voltage curve is updated by using the reference voltage curve updating unit 180 in the present invention is that when the test battery 110 is aged and the non- The target curve and the reference voltage curve to be compared with each other are updated in accordance with the aging of the test battery 110 because the error in detecting the similarity between the target curve and the reference voltage curve of the feature section of the test battery 110 can be generated.

Hereinafter, a battery capacity estimation method using a quadratic differential voltage curve according to the present invention will be described.

5 is a flowchart illustrating a battery capacity estimation method using a second derivative voltage curve according to an embodiment of the present invention. The battery capacity estimating method using the secondary differential voltage curve shown in FIG. 5 can be performed by the battery capacity estimating apparatus shown in FIG.

First, the battery capacity estimating apparatus obtains a voltage curve by applying a constant current to the test battery in the first SOC state (S500).

Thereafter, the battery capacity estimating apparatus obtains a first differential voltage curve by differentiating the voltage curve, and obtains a second differential voltage curve by again differentiating the first differential voltage curve (S510).

Then, the battery capacity estimation apparatus extracts a target curve included in the characteristic section from the secondary differential voltage curve (S520).

In one embodiment, the battery capacity estimation apparatus sets a time point corresponding to a first peak value of a first differential voltage curve of a test battery as a start time point of a characteristic interval, By setting the corresponding point in time to the end point of the characteristic section, the secondary differential voltage curve belonging to the characteristic section can be extracted as the target curve.

Then, the battery capacity estimation apparatus determines a similar section having the highest degree of similarity to the target curve on the reference voltage curve obtained from the reference battery (S530), and calculates the time difference between the similar section and the characteristic section (S540). At this time, the reference voltage curve can be obtained by applying a constant current to the reference battery in a fully discharged state to obtain a voltage curve and secondary differentiating the obtained voltage curve.

In one embodiment, the battery capacity estimation apparatus may determine a value that minimizes Equation (1) as a time difference between a similar section and a feature section. A concrete method of calculating the time difference is already described in the section of Equation (1), so that a detailed description thereof will be omitted.

Thereafter, the battery capacity estimating apparatus estimates a buffer time, which is a time required for the test battery to reach the buffer state from the second SOC state by adding the time difference calculated in S540 to the charge time of the test battery (S550). In this case, the second SOC state means a state in which the test battery is completely discharged, and the first SOC state means a state having a higher SOC than the second SOC state.

Then, the battery capacity estimating apparatus estimates the capacity of the test battery corresponding to the buffering time using the predetermined charging time-capacity model (S560).

Meanwhile, although not shown in FIG. 5, the battery capacity estimation method according to the present invention may further include a process of updating a reference voltage curve used for estimating the battery capacity.

In one embodiment, the battery capacity estimation apparatus may determine any one of the plurality of second differential voltage curves obtained in a predetermined period as a new reference voltage curve. According to this embodiment, the battery capacity estimation apparatus may determine to update the reference voltage curve when the difference between the capacity of the test battery calculated at the first time point and the capacity of the test battery calculated at the second time point exceeds the reference value .

6 is a graph showing performance test results of the battery capacity estimation method according to the present invention. In the experiment shown in FIG. 6, the test battery used for estimating the capacity of the battery is an 18650 type lithium ion battery having an NMC anode and a graphite cathode, and five batteries B1 to B5 The battery capacity estimation method according to the present invention is applied. At this time, each of the five batteries (B1 to B5) was discharged at a current of 1C to 5C and the charging was progressed to 0.5C, thereby aging each of the batteries (B1 to B5).

6A is a graph showing the secondary differential voltage curves of the first battery B1 and the fifth battery B5 arranged in relation to the reference voltage curve based on the reference voltage curve, And a similar section set for the curve. In the case of the fifth battery shown in FIG. 6B, the reference voltage curve is updated and the reference voltage curve is not updated.

FIG. 6C shows the estimated capacities calculated according to the charging time and capacity model for the five test batteries B1 to B5, and FIG. 6D shows the error of the estimated capacity. As can be seen from FIG. 6D, it can be seen that estimation errors within 2% are generated in all the batteries B1 to B5, and 520th cycle data of the fifth battery B5 shown in FIG. It can be confirmed that the error is within 2%.

FIG. 7A shows a histogram showing an error according to the experience-based battery capacity estimation method using a peak value according to the prior art, FIG. 7B shows a histogram showing an error of the battery capacity estimation method according to the present invention, . As can be seen from FIGS. 7A and 7B, the maximum error is similar to 1.6% in both methods, but it can be seen that the error of the battery capacity estimation method according to the present invention is distributed more than 0%. It can be seen that the battery capacity estimation method is more accurate than the experience based battery capacity estimation method using the peak value.

 FIG. 8 shows a result of applying the battery capacity estimation method according to the present invention to batteries having different SOC states. 8A is a graph showing a result of applying the battery capacity estimation method according to the present invention while changing the SOC of the second battery B2 to 0%, 10%, and 15%. FIG. ) Of SOC is changed to 0%, 10%, and 15%, and the battery capacity estimation method according to the present invention is applied. As can be seen from FIG. 8, it can be seen that the secondary differential voltage curve of each battery can be accurately aligned on the basis of the similar interval set for the reference voltage curve even in the situation where the initial SOC changes, , It can be seen that the battery capacity estimation method according to the present invention is applicable even in a situation where the initial SOC changes.

FIG. 9A is a graph showing an error occurring when applying the experience-based battery capacity estimation method using the peak value according to the prior art for the two batteries shown in FIG. 8, and FIG. A battery capacity estimation method according to an embodiment of the present invention will be described with reference to FIG. As can be seen from FIG. 9, until the total capacity of the test battery drops to 76.5% from the initial value, it can be seen that the battery capacity estimation method according to the present invention has an estimation error of less than 2% despite the initial SOC change.

It will be understood by those skilled in the art that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof.

It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. The scope of the present invention is defined by the appended claims rather than the detailed description and all changes or modifications derived from the meaning and scope of the claims and their equivalents are to be construed as being included within the scope of the present invention do.

100: Battery capacity estimation device 110: Test battery
120: Constant current application unit 130: Voltage curve acquisition unit
140: Buffer time estimation unit 150: Capacity estimation unit
160: Reference voltage curve acquisition unit 170:
180: Reference voltage curve updating unit 200: Reference battery

Claims (15)

A charge time detecting unit for obtaining a voltage curve by applying a constant current to a test battery in a first SOC state and detecting a charge time at which the test battery reaches the buffer state from the first SOC state on the voltage curve;
The charging time is corrected based on a result of comparison between the secondary differential voltage curve obtained by secondary differentiation of the voltage curve and the reference voltage curve obtained from the reference battery to determine the time at which the test battery reaches the buffer state from the second SOC state A buffer time estimating unit for estimating buffer time; And
And a capacity estimator for estimating a capacity of the test battery corresponding to the buffer time using a predetermined charge time-capacity model. The method according to claim 1,
The buffer time estimator may include:
A target curve extracting unit for extracting a target curve included in the characteristic section from the secondary differential voltage curve;
A similar section determining unit for determining a similar section having the highest similarity between the reference voltage curve and the target curve by shifting the target curve on the reference voltage curve and determining a time difference between the characteristic section and the similar section; And
And a buffer time calculator for calculating the buffer time by adding the time difference to the charging time. 3. The method of claim 2,
Wherein the similar section determining unit determines, on the reference voltage curve,

Where T denotes a sampling period, t1 denotes a starting point of the characteristic section, and t2 denotes a sampling period of the characteristic section, Vref denotes the reference voltage curve, and Vin denotes the voltage curve. The battery capacity estimating apparatus according to claim 1, 3. The method of claim 2,
Wherein the starting point of the characteristic section corresponds to a first peak value of a first differential voltage curve obtained by first differentiating the voltage curve and an end point of the characteristic section is a first peak of the first differential voltage curve, And a second time point corresponding to a valley of the battery. The method according to claim 1,
Further comprising a reference voltage curve obtaining unit for obtaining the reference voltage curve by second differentiating a voltage curve obtained by applying a constant current to the reference battery in a fully discharged state, . The method according to claim 1,
A storage unit for storing the second differential voltage curve obtained at a predetermined period; And
And a reference voltage curve updating unit for updating the reference voltage curve using one of the secondary differential voltage curves stored in the storage unit. The method according to claim 6,
Wherein the reference voltage curve updating unit updates the reference voltage curve when the difference between the capacity of the test battery calculated at the first time point and the capacity of the test battery calculated at the second time point exceeds the reference value. An apparatus for estimating battery capacity using a voltage curve. The method according to claim 1,
Wherein the second SOC state is a state in which the test battery is fully discharged and the first SOC state has a higher SOC than the second SOC state. Detecting a charge time on the voltage curve for the test battery, the time at which the test battery reaches a buffered state from a first SOC state;
Extracting a target curve included in the characteristic section from a second differential voltage curve obtained by second differentiating the voltage curve;
Determining a time difference between a characteristic section and a similar section having a highest similarity to the target curve on a reference voltage curve for the reference battery;
Estimating a buffer time which is a time for the test battery to reach a buffer state from a second SOC state by correcting the charge time using the time difference; And
And estimating a capacity of the test battery corresponding to the buffering time using a predetermined charging time-capacity model. 10. The method of claim 9,
In the step of determining the time difference, on the reference voltage curve,

Where T denotes a sampling period, t1 denotes a starting point of the characteristic section, and t2 denotes a sampling period of the characteristic section, Wherein Vref represents the reference voltage curve, and Vin represents the voltage curve. The method of claim 1, 10. The method of claim 9,
The starting point of the characteristic section corresponds to the first peak value of the first derivative voltage curve that is the first derivative of the voltage curve and the end point of the characteristic section corresponds to the first valley value of the first differential voltage curve Wherein the battery capacity estimating method uses the second differential voltage curve. 10. The method of claim 9,
Further comprising the step of obtaining a reference voltage curve by secondary differentiating a voltage curve obtained by applying a constant current to the reference battery in a fully discharged state to obtain the reference voltage curve. 10. The method of claim 9,
Further comprising the step of updating the reference voltage curve using any one of a plurality of secondary differential voltage curves acquired at predetermined periods. 14. The method of claim 13,
Wherein the reference voltage curve is updated when the difference between the capacity of the test battery calculated at the first time point and the capacity of the test battery calculated at the second time point exceeds the reference value in the step of updating the reference voltage curve A battery capacity estimation method using a second derivative voltage curve. 10. The method of claim 9,
Wherein the second SOC state is a state in which the test battery is fully discharged and the first SOC state has a higher SOC than the second SOC state.

Images