KR101160541B1 - Method for remaing capacity prediction of battery - Google Patents

Abstract

The present invention relates to a method for estimating the remaining capacity of a battery, which more accurately predicts the remaining capacity of a battery by deriving and using a mathematical model based on changes in voltage, current, and temperature of the battery from charge transfer characteristics inside the battery. Sensing unit 10 for measuring the voltage, current or temperature of the battery (1) during charging or discharging; And voltage region information previously divided between the discharge end voltage and the full charge voltage into a low voltage region and a high voltage region centered on the reference voltage, and the correlation between the voltage and the remaining capacity of the battery is high. An estimation unit 20 predicting the remaining capacity of the battery according to the measured value of the sensing unit 10 by dividing it into a voltage domain mathematical model; Sensing step (S100) of measuring voltage, current, and temperature using; A voltage region determination step (S200) of determining which voltage region the measured voltage value belongs to; A battery remaining capacity obtaining step (S300) of calculating a remaining capacity of the battery by substituting a measured voltage value into a mathematical model corresponding to the determined voltage range; It is made, including.

Description

How to estimate remaining battery capacity {METHOD FOR REMAING CAPACITY PREDICTION OF BATTERY}

The present invention relates to a battery remaining capacity prediction method for more accurately estimating the remaining capacity of a battery by deriving and utilizing a mathematical model based on a change in voltage, current and temperature of the battery from the charge transfer characteristics inside the battery.

The battery has a built-in positive electrode, negative electrode, separator and electrolyte to discharge and use the charges charged in the positive electrode and negative electrode, and is divided into one-time primary battery and secondary battery that can be recharged and used repeatedly. In addition to the rapidly increasing portable electronic products, it is indispensable for the devices and devices used to move and use such as electric vehicles.

These batteries are limited in the amount of power they can supply, so you need to know when to replace or recharge them. In this regard, conventional techniques for predicting the remaining capacity of a battery are as follows.

Korean Patent Laid-Open Publication No. 10-2001-003508 'Method and Apparatus for Measuring Remaining Residual Battery' calculates battery deterioration and cycle number to predict battery residual amount. According to this, the deterioration degree of the battery is calculated by comparing the design reference capacity with the actual fully charged capacity, and it is used to measure the remaining capacity by correcting the actual charged capacity and voltage every cycle. The remaining battery capacity was calculated using fuzzy neural network using data such as voltage change, charge current change, and average temperature correction. However, the conventional technology uses a method of determining a state by using a result of an input and an output with the concept of a battery as a black box, so that insight into an internal variable of a battery or information on performance improvement can be obtained. There was no.

Korea Patent Publication No. 10-2008-0071937 'battery remaining amount prediction device' measures the open voltage, the charge current or the discharge current of the battery, and calculated the open voltage of the battery using the initial internal impedance value. At this time, after correcting the difference between the measured open voltage and the calculated open voltage, the internal impedance value was corrected again to predict the remaining battery capacity. However, the prior art, like the Korean Patent Application Publication No. 10-2001-003508, assumes the battery as a black box and predicts the remaining battery capacity using the measured voltage, current, and impedance, and thus predicts the internal reaction of the battery. Or difficult to interpret.

Korean Patent Laid-Open Publication No. 10-1998-0010712 'Method for predicting battery level, a battery unit and a device using the battery unit', predicts a battery level for a plurality of series connected battery cells, that is, a battery unit, and overcharges and overdischarges. Prevention methods were implemented. Here, the remaining amount of the battery unit was calculated based on one of the minimum voltage and the maximum voltage among the battery cells constituting the battery unit. However, the above conventional technique is relatively simple, but does not consider the influence of the discharge current or the charge current, and the correction for the ambient temperature does not proceed.

Korean Patent Laid-Open Publication No. 10-2008-0097128 'Battery Cell Balancing System, Method and Recording Medium Recording the Same', monitors the state of charge of each battery cell when several battery cells are connected in series and in parallel, The balance circuit was intended to be charged. In addition, the above-described prior art measures the voltage and current of the battery, and calculates the state of charge of the battery, that is, the remaining amount by accumulating the current flowing into each battery. However, even in the above-described prior art, it is difficult to analyze the state inside the battery, and it is difficult to design the battery or to derive the factors for improving the performance.

That is, the above conventional techniques do not attempt to calculate the remaining capacity of the battery based on the electrochemical reactions made in the battery, and recognize the battery itself as a black box to measure the voltage, current, and temperature that are changed while using the battery. Since the remaining capacity of the battery is predicted, the remaining capacity can be calculated relatively simply, but it is almost impossible to interpret the battery according to the characteristics of the battery and predict the battery performance. Therefore, the remaining capacity of the battery can be applied within a very limited range.

Due to such a limitation, the prior arts have a problem in that discharging is suddenly terminated even though the remaining capacity of the battery remains more than 20% when discharging at a high current.

KR 10-2001-0035068 A 2001.05.07. KR 10-2008-0071937 A 2008.08.05. KR 10-1998-0010712 A 1998.04.30. KR 10-2008-0097128 A 2008.11.04.

 C. M. Doyle, Design and Simulation of Lithium Rechargeable Batteries, Ph. D. Dissertation, UC Berkeley, Chemical Eng., 1995.  A.J. Bard, L.R. Faulkner, Electrochemical Methods, John Wiley & Sons, Inc., 1980.

Therefore, an object of the present invention can be utilized to improve the design and performance of the battery through a model formula based on the electrochemical reactions made in the inside of the battery, and in particular, a method for estimating battery residual capacity that can predict a low residual capacity with an accurate value. To provide.

The present invention to achieve the above object, the sensing unit 10 for measuring the voltage, current or temperature of the battery (1) during charging or discharging; And voltage region information previously divided between the discharge end voltage and the full charge voltage into a low voltage region and a high voltage region centered on the reference voltage, and the correlation between the voltage and the remaining capacity of the battery is high. An estimation unit 20 predicting the remaining capacity of the battery according to the measured value of the sensing unit 10 by dividing it into a voltage domain mathematical model; Sensing step (S100) of measuring voltage, current, and temperature using; A voltage region determination step (S200) of determining which voltage region the measured voltage value belongs to; A battery remaining capacity obtaining step (S300) of calculating a remaining capacity of the battery by substituting a measured voltage value into a mathematical model corresponding to the determined voltage range; Characterized in that comprises a.

The high voltage domain mathematical model is

[Equation 4]:

The low voltage domain mathematical model is

[Equation 5]:

와 낮은 전압영역 수학적 모델의

는, 전지의 충전 또는 방전시의 전압 변화에 대한 전지 잔여용량의 변화 데이터에 근거하여 얻는 파라미터임을 특징으로 한다.Of the high voltage domain mathematical model

Of low voltage domain mathematical models

Is a parameter obtained based on the change data of the battery remaining capacity with respect to the voltage change during charging or discharging of the battery.

The battery remaining capacity obtaining step (S300) is a mathematical model of the standard current close to the measured current of the sensing unit 10 by using the parameters of the high voltage region mathematical model and the low voltage region mathematical model for each specified standard current, respectively. The remaining capacity is calculated and the estimated battery remaining capacity is estimated according to the measured current by interpolation (S320).

In the acquiring the remaining battery capacity step (S300), after calculating the remaining battery capacity by using the parameters of the high voltage region mathematical model and the low voltage region mathematical model for the designated standard temperature, the pattern of the battery residual capacity change with respect to the temperature change According to the information is characterized in that for correcting to the measured temperature of the sensing unit (10).

The step of determining a voltage region (S200) designates an intermediate voltage region centered on a reference voltage, and the step of acquiring battery residual capacity (S300) includes calculating calculated values of the high voltage region mathematical model and the low voltage region mathematical model. It is characterized by obtaining on average the remaining battery capacity.

In the sensing step (S100), after measuring the voltage at both ends of the battery (1) consisting of the assembled battery in series with the unit cells, the voltage at both ends is divided by the number of cells and used as the average voltage.

The battery remaining capacity acquiring step (S300), the high voltage region mathematical model by dividing the time of charging and discharging the parameters of the high voltage region mathematical model and the low voltage region mathematical model data is divided into the charging time and discharge time It is characterized by calculating the remaining capacity of the battery by applying to the low voltage region mathematical model.

Therefore, the present invention configured as described above does not calculate the battery residual capacity by one model formula, but is suitable for the characteristics having different charge and discharge patterns by the action of the oxidation reaction or the reduction reaction. By separating the domains and modeling them mathematically, not only a more accurate mathematical model can be obtained, but also the equilibrium open-circuit voltage is used instead of measuring the equilibrium open-circuit voltage. There is no need to estimate, making it easier to estimate battery remaining capacity.

In addition, the present invention obtains a mathematical model of the remaining capacity of the battery from the electrochemical reaction, that is, the Butler-Volmer reaction in the cell, the mathematical model obtained at this time is the main reaction during the oxidation and reduction reaction By separating the low voltage range model and the high voltage range model reflecting the elements, it is possible not only to model more accurately, but also to intuitively consider the characteristics of the battery due to the size of the parameter values involved in the mathematical model equation, and to improve the design and performance of the battery. It also has advantages that can be used in poetry.

In addition, the present invention can predict the correct battery remaining capacity according to the actual charging and discharging conditions by the current correction and temperature correction, and is also accurate for the low voltage region and the high voltage region that require more accuracy during charging or discharging. While providing a model, the mean voltage region is supplemented by averaging by the formula of both voltage regions, thereby providing a suitable model for the main purpose of predicting the remaining battery capacity as a whole.

1 is a method of predicting remaining battery capacity according to an embodiment of the present invention, wherein the correlation between the remaining capacity (Q, SOC) of the battery with respect to the voltage (V) is expressed by Equation 4 and Equation 5. Graph showing the modeling process.
2 is a block diagram of an apparatus for implementing a battery remaining capacity prediction method according to an embodiment of the present invention.
Figure 3 is a flow chart of the mathematical modeling process for the battery remaining capacity prediction method according to an embodiment of the present invention.
Fig. 4 is a graph of battery capacity change when a battery is discharged at a temperature of -20 ° C, -10 ° C, 0 ° C and 25 ° C, and the discharge current is 0.2C at each temperature.
5 is a flowchart of a method of predicting remaining battery capacity according to an embodiment of the present invention.
6 is a graph comparing the actual measured value and the value according to a mathematical model by applying the battery remaining capacity prediction method according to the present invention at the time of charging the battery.
7 is a graph comparing the actual measured value and the value according to a mathematical model equation by applying the battery remaining capacity prediction method according to the present invention when the battery is discharged.
8 is a graph showing a method for estimating remaining battery capacity according to the present invention by measuring an equilibrium open voltage at the time of charging a battery and comparing the measured value with a mathematical model.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. In the following description of the present invention, if it is determined that a detailed description of a related known function or known configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

Mathematical Model

) 및 온도(T)의 관계식으로 표현할 수 있다.In general, electrochemical reactions that occur inside a cell include steps of transferring charge from the electrolyte to the surface of the electrode, transferring charge from the surface of the electrode to the active surface, reaction of transferring charge from the electrode active surface, and the like. It is divided into three stages [Ref .: CM Doyle, Design and Simulation of Lithium Rechargeable Batteries, Ph. D. Dissertation, UC Berkeley, Chemical Eng., 1995.]. Here, the internal reaction of the battery is a charge transfer reaction on the active surface, which is Butler-Bolmer (Equation 1), which is determined by the rate of oxidation and reduction of the anode and cathode electrodes. Volmer) (Ref .: AJ Bard, LR Faulkner, Electrochemical Methods, John Wiley & Sons, Inc., 1980).

) And temperature (T).

는 전극반응에서의 교환전류값(exchange current), a는 전달계수, n은 전극 활성표면에의 반응 전자수(number of electrons involved in the electrode reaction), F는 페러데이(Faraday) 상수, R은 기체상수, T는 절대온도(absolute temperature),

는 충전 또는 방전시의 전압(V)에서 평형상태 전압(

: equilibrium potential, 충전 또는 방전이 멈춘 후에 내부에서 전하전달반응이 안정화된 상태의 개방전압)을 차감하여 얻는 과전압을 나타낸다. 이때, 충전 전압은 평형상태 전압보다 크게 되고, 방전 전압은 평형상태 전압보다 작게 된다.here,

Is the exchange current in the electrode reaction, a is the transfer coefficient, n is the number of electrons involved in the electrode reaction, F is the Faraday constant, and R is the gas Constant, T is the absolute temperature,

Is the equilibrium voltage (V) at the voltage at charging or discharging

: Equilibrium potential, overvoltage obtained by subtracting the open voltage after the charge or discharge stops internally. At this time, the charging voltage becomes larger than the equilibrium voltage, and the discharge voltage becomes smaller than the equilibrium voltage.

The present invention derives a correlation between the battery voltage (V) and the remaining battery capacity under the assumption that the current (I) and temperature (T) is constant through mathematical modeling based on Equation 1 above. . In addition, according to the battery remaining capacity prediction method described below, correction is performed on the current I and the temperature T.

)하여 얻어지며, 적분해야 할 [수학식 1]을 보면 2개의 항으로 이루어진다.The battery capacity (Q) at the time of charging or discharging the battery integrates the current over time (

), Which is obtained by integration and consists of two terms.

Here, the battery capacity Q is generally referred to as a state of charge (SOC), and is represented by a full charge state of 100 and a discharge end state of zero. That is, the battery capacity starts from the discharge end state and increases in proportion to the amount of charged charges until it reaches a full charge state, and the voltage also increases according to the amount of charged charges.

)는 [수학식 1]의 첫번째 항만 포함된 다음의 [수학식 2]로 근사화하고, 낮은 전압 영역에서의 전류는 환원방응의 영향이 크므로 중간 영역을 기준으로 낮은 전압 영역에서의 전류(

)는 [수학식 1]의 두번째 항만 포한된 다음의 [수학식 3]으로 단순화한다.At this time, according to the present invention, when the reference voltage is set near the middle between the full charge state voltage and the discharge end state voltage, the current in the high voltage region based on the reference voltage has a large influence on the oxidation reaction, so Current in the high voltage region

) Is approximated by the following [Equation 2] containing only the first term of [Equation 1], and the current in the low voltage region (

) Is simplified to Equation 3, which contains only the second term in Equation 1.

)과 낮은 전압 영역에 대한 전지 용량(

)을 나타내는 식을 다음의 [수학식 4]와 [수학식 5]로 근사화할 수 있다.The battery capacity for the high voltage region is obtained by integrating Equations 2 and 3 with respect to time.

) And battery capacity for low voltage areas (

) Can be approximated by the following [Equation 4] and [Equation 5].

와 [수학식 5]의

는 전지 잔여용량을 결정짓는 파라미타로서 상수이며, 전지를 충전하거나 방전시키는 과정에서 전류의 누적으로

및

에 대한 데이터를 얻고 전압의 변화를 측정하여 V에 대한 데이터를 얻으면, 상기 [수학식 4, 5]으로 모델링할 수 있는 파라미터를 얻을 수 있는 것이다.
Where [Equation 4]

And of Equation 5

Is a constant that determines the battery's remaining capacity and is a constant, and is the accumulation of current in the process of charging or discharging the battery.

And

By obtaining the data for and measuring the change in voltage to obtain the data for V, the parameters that can be modeled by Equations 4 and 5 can be obtained.

,

) 데이터를 좌표상에 표시하고, 표시된 지점들에 최적화된 곡선을 이루도록 상기 [수학식 4,5]의 파라미터를 결정짓는 것이다. 이때, 낮은 전압 영역과 높은 전압 영역을 구분하여 서로 다른 [수학식 4]와 [수학식 5]로 모델링한다.1 is a graph showing a process of modeling the correlation between the remaining capacity (Q) of the battery with respect to the voltage (V) by the equation (4) and (5). According to FIG. 1, the cumulative current (charge amount :) for the voltage V data.

,

) To display the data on the coordinates and determine the parameter of Equation (4,5) to form a curve optimized for the marked points. In this case, the low voltage region and the high voltage region are distinguished and modeled by different [Equation 4] and [Equation 5].

On the other hand, as shown in FIG. 1, in the middle region near the reference voltage which is the boundary point between the high voltage region and the low voltage region, the graph modeled by Equation 4 and the graph modeled by Equation 5 are mutually different. It is preferable to superimpose and average the result of [Equation 4] and [Equation 5] in which parameters are determined. That is, by averaging the values of the equations (4) and (5) with the reference voltage as an intermediate region, the error value in the approximation process is compensated for. Here, the reference voltage can be determined as an appropriate value based on the experience obtained by the repeated implementation of the present invention, because the characteristics of the battery is slightly different depending on the type of battery, and then the voltage in the intermediate region determined based on the reference voltage. The region width can also be determined to an appropriate value based on the experience gained from the repeated practice of the present invention.

It is also preferable to increase the reference voltage when the current at the time of charge or discharge is large. In other words, when the current is large, the low voltage region increases and the high voltage region decreases. This can be seen by looking at the measured data when the current value is changed in the following examples. When the current value is relatively large when the mathematical model is constructed with [Equation 4] and [Equation 5], the reference voltage is reduced. The higher you get, the more accurate the mathematical model can be.

2 is a block diagram of an apparatus for implementing a method for measuring battery remaining capacity according to an embodiment of the present invention.

The battery remaining capacity measuring apparatus according to FIG. 2 includes: a sensing unit 10 measuring voltage, current, or temperature of the battery when the battery 1 is charged or discharged under the control of the charge / discharge circuit 2; And an estimator 20 predicting the remaining capacity of the battery based on the measured value of the sensing unit 10. It is configured to include. In addition, the battery remaining capacity measuring apparatus may further include a display unit (not shown) that outputs the estimated remaining capacity of the battery from the estimator 20 or an interface (not shown) that can be transmitted as a signal to an external device. It may be. In addition, the battery remaining capacity measuring apparatus shown in FIG. 1 may also perform a mathematical modeling process to be described later to store data obtained in the mathematical modeling process, and to predict the remaining capacity of the battery based on the stored data. .

Here, the sensing unit 10 may include a voltmeter 11 measuring voltages at both ends of the battery 1, an ammeter 12 measuring currents charged or discharged through both ends of the battery 1, and a battery ( It is configured to include a thermometer 13 for measuring the temperature of 1), and as described later, by substituting the voltage measured by the voltmeter 11 into a mathematical model to predict the remaining capacity of the battery, the current measured by the ammeter 12 Correct the battery remaining capacity according to the size of, and to correct the battery remaining capacity according to the height of the temperature measured by the thermometer (13).

Hereinafter, a mathematical modeling process performed by the estimator 20 based on the value sensed by the sensing unit 10 and a process of estimating battery remaining capacity based on the mathematical model will be described in detail.

Mathematical Modeling Process

3 is a flowchart of a mathematical modeling process for a method of measuring a remaining battery capacity according to an embodiment of the present invention.

Before applying the mathematical modeling process shown in FIG. 3, it should be considered that the charging or discharging characteristics of the battery are different depending on the current value, and thus the mathematical modeling process for all the current values cannot be performed. By specifying the standard current values, the mathematical modeling process of FIG. 3 is performed for each designated standard current value.

In general, the current size of the battery is expressed as C-Rate, which is the value of the current used by the battery divided by the battery capacity. For example, in the case of discharging or charging at 2A in a battery having a battery capacity of 10 Ah, the C-rate value is expressed as 2A / 10Ah C and becomes 0.2C. The battery voltage and remaining capacity are measured while gradually increasing the discharge or charge current value in the low range. Charging generally proceeds in the range of 0.2C to 0.5C. In special cases, such as fast charging, charge is performed in the range of 0.5C to 1.0C. In the case of discharging, as in charging, a current from 0.2C to 0.5C is often used, but sometimes up to 2.0C. Currents above 2.0C are often only allowed within a short time, usually less than one minute.

Accordingly, the present invention designates a standard current value in advance, and in the specific embodiment described below, the standard current value is set to 0.25C, 0.5C, or 1C to perform the mathematical modeling process of FIG. 3 for each current value.

That is, the mathematical modeling process for any one of the specified standard current values is obtained by obtaining the voltage, current, and temperature data by using the sensing unit 10 while integrating the specified standard current and integrating the current to obtain the charged charge data. Step S10; A voltage region designating step (S20) for dividing and designating a voltage region into a low voltage region, an intermediate voltage region and a high voltage region as shown in FIG. 1; A parameter obtaining step S30 for acquiring a parameter of Equation 5 using data in a low voltage region and acquiring a parameter of Equation 4 using data in a high voltage region (S30). It is done by

Here, the data acquisition step (S10) detects a change in temperature by measuring the temperature. In other words, the derivation of Equations 4 and 5 shows that the parameter constants A and B vary according to the temperature T, and thus the charge / discharge characteristics are also changed when the temperature T fluctuates. To keep track of whether Moreover, it is preferable to also provide the means for keeping the temperature of a battery constant. In addition, when performing the mathematical modeling process according to the discharge characteristics, it is applied to [Equation 4, 5] by subtracting the discharged charge from the charge amount in the full charge state.

In the voltage region designation step S20, as described above, the voltage region designation step may be variably designated according to the magnitude of the current value. For example, the larger the current value, the larger the width of the lower voltage region.

In the parameter obtaining step (S30), the model equation of [Equation 5] for the low voltage region and the equation of [Equation 4] for the high voltage region are superimposed on the intermediate region designated as the reference voltage. When estimating the remaining capacity, the values calculated in Equations 5 and 4 are averaged.

The mathematical modeling process performed as described above stores parameters obtained for each standard current value by performing the specified standard current value. For example, to obtain and store parameters for each of 0.25C, 0.5C, and 1C as in the embodiment described below.

In addition, since the mathematical model equations of [Equation 5] and [Equation 4] completed by acquiring the parameters may be changed according to the temperature, information for correction should also be stored in case of deviation from the designated temperature.

4 is a graph showing changes in battery capacity when the battery temperature is specified as -20 ° C, -10 ° C, 0 ° C, and 25 ° C, respectively, and the battery is discharged with a discharge current of 0.2C at each temperature. It is. The characteristic graph outside the specified temperature can be estimated by interpolation. Based on the change characteristic of the battery capacity with respect to the temperature thus obtained, a correction pattern of the battery capacity with respect to the change in temperature can be obtained. In the present invention, information on the obtained correction pattern is stored, and the battery remaining capacity estimation described later is estimated. It is used in the process. For example, when performing a mathematical modeling process for each designated current value, 25 ° C. is maintained, and when the temperature of the battery deviates from 25 ° C. in the battery remaining capacity estimation process described later, the battery remaining capacity is corrected according to a correction pattern.

<Method of predicting battery remaining capacity based on mathematical model>

5 is a flowchart of a method of predicting remaining battery capacity according to an embodiment of the present invention.

The method of estimating battery remaining capacity shown in FIG. 5 is a method of estimating capacity remaining in a battery by using parameter values for each standard current value and voltage region stored in a memory in the above-described mathematical modeling process and temperature correction pattern information. to be.

Referring to FIG. 5, the method for predicting battery remaining capacity according to an embodiment of the present invention includes: a sensing step (S100) of measuring voltage, current, and temperature using the sensing unit 10; A voltage region determination step (S200) of determining which voltage region the measured voltage value belongs to; A battery remaining capacity obtaining step (S300) of calculating a remaining capacity of the battery by substituting a measured voltage value into a mathematical model corresponding to the determined voltage range; It is made, including.

Specifically, in the voltage region determination step (S200), the voltage measured by the voltmeter 11 of the sensing unit 10 is high by designating an intermediate voltage region centered on a reference voltage that separates the high voltage region and the low voltage region. One of the voltage range, the low voltage range and the intermediate voltage range is determined.

The battery remaining capacity obtaining step (S300) determines whether the current value measured in the sensing step (S100) is one of the standard current values (S321), and corresponds to the corresponding standard current value if it corresponds to the standard current value. The remaining battery capacity is calculated by calling the parameter (S310).

Specifically, if the parameter corresponding to the standard current value is called and used, but if the measured voltage belongs to the high voltage region, the parameter corresponding to the high voltage region is substituted into [Equation 4] and the measured voltage is substituted for the remaining battery capacity. If the measured voltage is in the low voltage range, substitute the parameter corresponding to the low voltage range into [Equation 5] and substitute the measured voltage to calculate the remaining capacity of the battery. Battery to be estimated by substituting the measured voltage in [Equation 4] in which the parameter corresponding to the high voltage region is substituted and [Equation 5] in which the parameter corresponding to the low voltage region is substituted. Get the remaining capacity.

If the measured current does not correspond to the standard current value, the standard current values close to the measured current value are selected, and the parameter corresponding to the selected standard current values is called, and the equation (4) or [mathematical formula] for each of the above-described voltage regions is called. After calculating the battery remaining capacity according to Equation 5 (S322), the calculated battery remaining capacity is corrected according to the interpolation method (S323) to obtain the corrected battery remaining capacity (S320). For example, when the measured current value I is I1 <I <I2 between the standard current value I1 and the standard current value I2, the parameter corresponding to the standard current value I1 and the parameter corresponding to the standard current value I2 are mathematically calculated. The remaining battery capacity Q1 and Q2 calculated by substituting the model equation ([Equation 4] or [Equation 5]) was obtained, and the estimated battery remaining capacity was Q1 + [(I-I1) / (I2-I1)] * It is obtained by (Q2-Q1).

In the battery remaining capacity obtaining step (S300), by selectively substituting a measured voltage into a mathematical model formula ([Equation 4] or [Equation 5]) divided by voltage region, the battery remaining capacity is calculated and measured. Although the parameters determined by the current are corrected for the current value by applying the mathematical model equation, the battery remaining capacity is also corrected according to the battery temperature. That is, as described in the above-described <mathematical modeling process>, the parameter of the mathematical model according to the present invention is obtained with a different value depending on the current value, but also obtained by a different value depending on the temperature, thereby supporting the current temperature If the standard temperature is monitored (S331) and the standard temperature is deviated, the battery residual capacity is corrected based on the temperature correction pattern described in the above-described <mathematical modeling process> (S332) to obtain the electric residual capacity. (S330).

Here, the temperature correction obtains current value and voltage area-specific parameters for different standard temperature values which are previously specified similarly to the method of correcting the battery residual capacity with respect to the current value, and accordingly, the temperature correction is applied to the standard temperature value close to the measured temperature. A method of calculating a battery residual capacity using a corresponding parameter and correcting the result by an interpolation method may be adopted. However, as described with reference to FIG. 4, the variation of battery residual capacity with respect to different temperature values forms a constant pattern. Performs temperature correction using this pattern information.

Meanwhile, the battery 1 may be formed of a unit cell composed of a single cell, but may also be formed of a multi-cell in which a single cell is connected in series or in parallel. Do the following:

In the case of the assembled battery consisting of a combination of single cells connected in series, the current flowing through the external terminals of the assembled battery is used as is, and the average voltage of the single cells is calculated by dividing the voltage applied between the external terminals by the number of cells. The average voltage is substituted into the above mathematical model equation.

In addition, in the case of a battery pack in which a plurality of single-cell combinations connected in series are connected in parallel to each other, the current flowing through the external terminals is divided by the number of parallel circuits to calculate the average current and correct the current according to the calculated average current. . In this case, the average voltage is calculated by dividing the terminal voltage by the number of unit cells connected in series in the same manner as described above.

Meanwhile, when the present invention is applied to a primary battery, the present invention can be implemented by extracting a sample from the same primary batteries and performing a mathematical modeling process according to discharge characteristics.

The following specific examples are provided to aid the understanding of the present invention, and the present invention is not limited to the following specific examples.

In order to verify the performance of the battery residual capacity prediction method according to the present invention, it was applied to the charging characteristics of the lithium secondary battery. At this time, the applied lithium battery has a positive electrode formed of lithium cobalt oxide oxide, a negative electrode formed of graphite, a separator formed of polyethylene porous membrane, and an electrolyte composed of a carbonate-based organic compound. The average voltage is 3.7 V and the maximum charging voltage is 4.2 V and nominal The capacity was 10AH, the standard charging current was 0.25C and the charging termination current was 300mA at 4.2V. In the case of discharge, the termination voltage was 3V and it can proceed continuously up to 2.0C.

The charging current was divided into two types, 0.25C and 0.5C, and the charging method was the constant current-constant voltage method. The constant voltage was 4.2V and the charge termination current was 300mA.

FIG. 6 is a value comparing a residual capacity value measured by charging a lithium secondary battery with a predicted residual capacity value by applying a mathematical model equation. Equation 4 is applied in the High Voltage Region, Equation 5 is applied in the Low Voltage Region, and the middle region selected based on the reference voltage is Equation 4. ] And [Equation 5] were averaged. In addition, the reference voltage when charging at 0.5C was higher than the reference voltage when charging at 0.25C.

The parameter values of [Equation 4] and [Equation 5] used here are shown in Table 1 below.

electric current
(C-Rate)
Low voltage region standard
Voltage
(V) High Voltage Region

B

A 0.25 -1.767 -0.624 5.7
x 10 ^-13 0.137 3.80 102.05 3.847 -49.74 0.214 0.5 -2.642 -1.106 7.9
x 10 ^-16 0.127 3.85 97.58 3.896 -45.42 0.196

As can be seen from FIG. 6, the estimated values of the measured residual capacity (SOC) and the mathematical model were almost identical to those in the low range of 0 to 30% and the high range of 70% to 100%. .

The battery residual capacity prediction method according to the present invention was applied to the discharge characteristics of the lithium secondary battery, and the lithium secondary battery used was the same as the battery used in [Example 1].

The discharge current was made into three types such as 0.25C, 0.5C and 1.0C, and the discharge was applied with the constant current method, and the discharge termination voltage was 3V.

FIG. 7 is a graph comparing the remaining capacity value measured by discharging a lithium battery with a predicted remaining capacity value by applying a mathematical model equation. In addition, the magnitude of the reference voltage is specified to be lower as the discharge current is larger as opposed to when charging, and the reason for this can be seen from the trend of the residual capacity data as shown in the graph of FIG. 7.

The parameter values of [Equation 4] and [Equation 5] used here are shown in Table 2 below.

electric current
(C-Rate)
Low voltage region standard
Voltage
(V) High Voltage Region

B

A -0.25 -0.975 -0.270 7.8
x 10 ^-12 0.133 3.65 115.22 3.690 -68.90 0.318 -0.5 -0.918 -0.321 3.6
x 10 ^-12 0.129 3.6 117.13 3.640 -70.86 0.338 -One -3.758 -1.051 5.5
x 10 ^-10 0.181 3.5 127.88 3.541 -82.61 0.453

As can be seen in FIG. 7, the estimated values of the measured residual capacity (SOC) and the mathematical model are almost in the low range of 0 to 30% and the high range of 60% to 100%. Matched

In the present embodiment, the correlation between the equilibrium open-circuit open-circuit voltage and the battery remaining capacity when the battery applied to [Example 1] is charged is applied by the mathematical model equations of [Equation 4] and [Equation 5]. will be. That is, since the battery is in an equilibrium state, no current flows, and an open circuit voltage (OCV) is measured to obtain a parameter of a mathematical model equation.

FIG. 8 is a graph of data obtained by charging the battery for 1 minute with a standard charging current and then performing the next charge when the battery voltage changes within 1 mV for 1 minute while maintaining a rest period for 1 hour. Repeat this process until the battery is fully charged and measure the open circuit voltage (OCV). Equation 4 was applied at high voltage, and Equation 5 was applied at low voltage, and the parameters of Equations 4 and 5 were obtained as shown in Table 3 below.

electric current
(C-Rate)
Low voltage region standard
Voltage
(V) High Voltage Region

B

A 0 -0.035 0.663 1.1
x 10 ^-10 0.112 3.67 139.83 3.70 -87.14 0.554

As can be seen from FIG. 8, the values estimated by applying the measured SOC and the mathematical model were almost identical in the range of 0 to 100%.

As shown in [Example 3], when estimating the remaining capacity of the battery by the equilibrium open-circuit voltage, the open-circuit voltage starts at the point where the current is cut off and only after a sufficient idle time has elapsed to obtain an accurate equilibrium voltage. When estimating the remaining capacity of the battery by modeling the open-circuit voltage in [Equation 4, 5], care should be taken when measuring the open-circuit voltage.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, . &Lt; / RTI &gt; Therefore, such modifications should also be regarded as belonging to the scope of the present invention, and the scope of the present invention should be determined by the claims below.

Claims (7)

delete Sensing unit 10 for measuring the voltage, current or temperature of the battery (1) during charging or discharging; And voltage region information previously divided between the discharge end voltage and the full charge voltage into a low voltage region and a high voltage region centered on the reference voltage, and the correlation between the voltage and the remaining capacity of the battery is high. In the battery region capacity estimation method for estimating the remaining capacity of the battery; Estimator 20 for predicting the remaining capacity of the battery according to the measured value of the sensing unit 10 by dividing into a voltage domain mathematical model,
A sensing step (S100) of measuring a voltage, a current, and a temperature by using the sensing unit 10;
A voltage region determination step (S200) of determining which voltage region the measured voltage value belongs to;
A battery remaining capacity obtaining step (S300) of calculating a remaining capacity of the battery by substituting a measured voltage value into a mathematical model corresponding to the determined voltage range;
, &Lt; / RTI &gt;
The high voltage domain mathematical model is
[Equation 4]:

With
The low voltage domain mathematical model is
[Equation 5]:

,
High voltage domain mathematical model

Of low voltage domain mathematical models

Is a parameter obtained based on the change data of the battery remaining capacity with respect to the voltage change during charging or discharging of the battery.
The method of claim 2,
The battery remaining capacity obtaining step (S300),
Using the parameters of the high voltage region mathematical model and the low voltage region mathematical model for each designated standard current, the remaining battery capacity is calculated using the mathematical model of the standard current close to the measured current of the sensing unit 10. Estimation according to the measurement current by interpolation method (S320) characterized in that the remaining battery capacity estimation method.
The method of claim 3, wherein
The battery remaining capacity obtaining step (S300),
After calculating the remaining battery capacity using the parameters of the high voltage region mathematical model and the low voltage region mathematical model for the specified standard temperature, the measured temperature of the sensing unit 10 according to the pattern information of the change of the battery residual capacity with respect to the temperature change Battery residual capacity prediction method characterized in that for correcting.
The method of claim 2,
The voltage region determination step (S200),
Specify an intermediate voltage range around the reference voltage,
The battery remaining capacity obtaining step (S300),
And calculating the remaining battery capacity by averaging the calculated values of the high voltage region mathematical model and the low voltage region mathematical model.
6. The method of claim 5,
The sensing step (S100),
A method for estimating remaining battery capacity, comprising measuring the voltage at both ends of an assembled battery in which battery cells are connected in series and dividing the voltage at both ends by the number of cells.
The method of claim 2,
The battery remaining capacity obtaining step (S300),
The parameters of the high voltage region mathematical model and the low voltage region mathematical model, which are divided into charging and discharging time data, are applied to the high voltage region mathematical model and the low voltage region mathematical model to distinguish between charging and discharging time. A method for estimating battery remaining capacity, comprising calculating a capacity.

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