KR20070105014A - Degradation correction method of battery cell - Google Patents

Abstract

A method for correcting deterioration of a battery cell is provided to accurately calculate the full charge capacity by gradually reducing the correction voltage point as the number of battery cell cycles. A method for correcting deterioration of a battery cell includes the steps of: calculating the volume of discharge by integrating the discharge current to a pre-set correction voltage point in case of fully discharging the battery cell from the state of full charge; and calculating the new full charge capacity by adding to the integrated discharge volume the value computed by multiplying the remaining capacitance percentage at the correction voltage point and the full charge capacity of prior time. The correction voltage point has less value as the number of charging/discharging cycles of the battery cell is increasing.

Description

Degradation correction method of battery cell

1 is a graph illustrating a method of updating a full charge capacity (“FCC”) of a battery cell.

2 is a graph for explaining a state in which a full charge capacity is reduced due to deterioration of a battery cell as the number of charge / discharge cycles of the battery cell increases.

3 shows that the relative state of charge (“RSOC”) is jumped or kept because the end point of the discharge voltage (“EDV”) of the battery cell does not match the degradation characteristic. This is a graph for explaining the phenomenon.

4 is a block diagram illustrating an example of a controller to which the method for correcting degradation of a battery cell according to the present invention and a peripheral configuration thereof may be applied.

5 is a graph schematically illustrating a method of correcting degradation of a battery cell according to the present invention.

6 is a graph illustrating a correction method when discharged from 100% to 0% of the battery cell deterioration correction method according to the present invention.

7 is a graph showing a change in relative charge capacity after improving the firmware (firm ware) of the control unit by the method according to the present invention.

8 is a graph illustrating a correction method when discharged from 100% to 8% or 3% of the battery cell deterioration correction method according to the present invention.

9 is a graph showing a change in the relative charging capacity after improving the firmware of the control unit by the method according to the present invention.

<Description of Symbols for Main Parts of Drawings>

110; Battery cell 120; Current sensor

130; Voltage sensor 140; Control

141; A first AD converter 142; Current integrator

143; A second A-D converter 144; Calibration voltage point detector

145; Remaining capacity calculator 146; Memory

147 communication processing unit 148; timer

150; External systems

The present invention relates to a method for correcting deterioration of a battery cell, and more particularly, to a method for correcting deterioration of a battery cell capable of accurately calculating a remaining capacity even when the cell deteriorates with an increase in the number of charge / discharge cycles.

In general, it is known that a battery cell is deteriorated due to an increase in the number of charge / discharge cycles and a film formed on the electrode plate, or an increase in the internal resistance of the active material, thereby gradually decreasing the full charge capacity. When the remaining capacity of the battery cell is expressed as a relative value to the full charge capacity, for example, in percentage, it is very important to accurately correct the full charge capacity (FCC). For example, the full charge capacity can be calculated by integrating the charge capacity until the battery cell is completely discharged, or the full charge capacity can be calculated by integrating the discharge capacity until the battery cell is completely discharged. Afterwards, the calculated full charge capacity can be corrected for the previous full charge capacity.

Referring to FIG. 1, a method of updating a full charge capacity (“FCC”) of a battery cell is briefly shown.

In the graph, the X axis represents charge and discharge time, and the Y axis represents Relative State Of Charge (“RSOC”). In addition, in the graph, RC stands for Remain Capacity, meaning remaining capacity, DCR stands for Discharge Counter Register, which means amount of discharge, and EDV stands for End point of Discharge Voltage.

As shown, at the time of full charge, the remaining capacity and the full charge capacity are the same, and the updated new full charge capacity (FCC _new ) is the sum of the discharge amount (DCR) and EDV1 (%) * FCC _old at the time of discharge.

This is expressed as an equation below.

FCC _new = DCR + EDV1 (%) * FCC _old

Referring to FIG. 2, a graph shows a state in which a full charge capacity is reduced by deterioration with increasing number of charge / discharge cycles of a battery cell.

In the graph, the X axis is the full charge capacity of the battery cell, and the Y axis is the voltage of the battery cell. As shown, as the number of charge and discharge cycles of a battery cell increases, its full charge capacity gradually decreases. For example, the full charge capacity is approximately 2600 mAh in the first cycle, but the full charge capacity is reduced to approximately 2100 mAh in the 300th cycle. In addition, as the number of charge / discharge cycles of the battery cell increases, the discharge voltage gradually decreases.

However, as described above, the 8% voltage (when the corrected voltage point is fixed at 3.35 V, which is a reference when updating the full charge capacity, and 8% means the ratio of the remaining capacity to the full charge capacity) in one cycle It is determined around the remaining capacity of approximately 2400 mA, but is determined at the remaining capacity of approximately 1400 mA at 300 cycles. That is, in one cycle, the full charge capacity is updated when the actual remaining capacity (8%) of approximately 200 mA remains, but the full charge capacity is updated when the actual remaining capacity (44%) of the approximately 700 mA remains in 300 cycles. Thus, the user feels that the remaining capacity is significantly reduced in 300 cycles of battery cells.

However, in practice here the 8% voltage for the battery cell at 300 cycles is when the battery cell voltage is approximately 3.15V as described in the graph, which must be set to the correction voltage point to update the full charge capacity. However, a method of automatically lowering the correction voltage point according to the number of battery charge / discharge cycles or cell deterioration has not been developed yet. In other words, it is not known how to lower the correction voltage point by a predetermined function or a predetermined equation according to the number of charge / discharge cycles of the battery, that is, the cell deterioration degree.

Table 1 below compares the actual full charge capacity with the smart full charge capacity calculated by the conventional method. Here, ASOC is an abbreviation of Absolute State of charge, and means the actual charge capacity.

TABLE 1

As can be seen in Table 1 above, as the number of charge and discharge cycles increases, the difference between the actual full charge capacity and the full charge capacity calculated by the conventional method becomes larger. Therefore, a user who uses a battery cell that calculates a full charge capacity by using such a conventional calculation method in an external system (for example, a laptop) and uses the battery cell may increase as the number of charge / discharge cycles of the battery cell increases. You will feel much smaller than the actual capacity. Of course, even if the user receives the discharge warning signal from the external system, if the user continues to use the external system without turning off the system, the user can consume all the full charge capacity, but from the user's point of view, the use of the external system is unstable. There is no desire to know more precise full charge capacity.

Meanwhile, referring to FIG. 3, a graph in which a jump or keep phenomenon occurs in a characteristic curve of a relative state of charge (RSOC) because a correction voltage point (EDV) of a battery pack does not correspond to a deterioration characteristic of a cell is shown. Is shown.

FIG. 3 shows a jump or keep at a relative state of charge (“RSOC”) because the end of discharge voltage (“EDV”) point of the battery cell does not meet degradation characteristics. This is a graph for explaining that a phenomenon occurs.

Here, the X axis means a discharge time (Time), the Y axis means a relative charge capacity (RSOC). As shown, since the correction voltage point does not match the deterioration characteristic of the battery cell, a jump phenomenon may occur below 8% correction voltage point [EDV2 (8%)], for example, when the full charge capacity is updated, and 3% A predetermined time retention may occur at the correction voltage point EDV1 (3%), and a predetermined time retention may occur at the 0% correction voltage point EDV0 (0%). In other words, the meaning of such a graph means that when a user uses an external system, at some point, the remaining capacity suddenly drops to a low level compared to the full-discharge charge capacity, or the remaining capacity does not change even after a predetermined time and continues to be maintained for a predetermined time. it means. Therefore, the user is very anxious due to the incorrect remaining capacity indication of the battery cell during use of the external system.

SUMMARY OF THE INVENTION The present invention has been made to overcome the above-mentioned conventional problems, and an object of the present invention is to provide a method for correcting deterioration of a battery cell capable of accurately calculating a remaining capacity even when the cell deteriorates with an increase in the number of charge / discharge cycles.

In order to achieve the above object, the present invention, when discharging the battery cell from the fully charged state to the fully discharged state, the discharge amount is calculated by integrating the discharge current to a predetermined correction voltage point, the remaining capacity at the correction voltage point A method of calculating a new full charge capacity by adding a value obtained by multiplying a percentage (%) by a previous full charge capacity to the accumulated discharge amount, wherein the correction voltage point is calculated as the number of charge / discharge cycles of the battery cell increases. Set it to have a smaller value gradually.

Here, the number of charge and discharge cycles may be increased by one each time the amount of discharge obtained by integrating the discharge current reaches 90 to 100% of the full charge capacity.

Further, the correction voltage point may be determined at at least three points while the remaining capacity of the battery cell is 10% or less than the full charge capacity.

In addition, the correction voltage point may be a voltage at which residual capacity is detected at 8%, 3%, and 0% of the full charge capacity.

In addition, the correction voltage point of the remaining capacity of 8% can be calculated by the following equation.

8% compensation voltage point = 8% point voltage according to the number of cycles pre-tabled in memory + (8% degradation compensation value * current / number of parallel battery cells / resolution)

In addition, the 8% deterioration correction value may be calculated by Equation 2 when the following Equation 1 is satisfied.

Equation 1

(FCC0-FCC8) / FCC8〉 3%

Equation 2

8% deterioration correction = previous 8% deterioration correction-(FCC0-FCC8) / FCC8 * Experiment constant

Where FCC0 is the capacitive learning at 0% calibrated voltage point and FCC8 is the capacitive learning at 8% calibrated voltage point

In addition, the 8% deterioration correction value may be calculated by Equation 2 when the following Equation 1 is satisfied.

Equation 1

(FCC0-FCC8) / FCC8 <-2%

Equation 2

8% deterioration correction value = previous 8% deterioration correction value + (FCC0-FCC8) / FCC8 * experimental constant

Where FCC0 is the capacitive learning at 0% calibrated voltage point and FCC8 is the capacitive learning at 8% calibrated voltage point

In addition, the 3% deterioration correction value may be calculated by Equation 2 when the following Equation 1 is satisfied.

Equation 1

(FCC0-FCC3) / FCC3〉 3%

Equation 2

3% deterioration correction = last 3% deterioration correction-(FCC0-FCC3) / FCC3 * Experiment constant

Where FCC0 is the capacity learning at 0% calibrated voltage point and FCC3 is the capacity learning at 3% calibrated voltage point

In addition, the 3% deterioration correction value may be calculated by Equation 2 when the following Equation 1 is satisfied.

Equation 1

(FCC0-FCC3) / FCC3 <-2%

Equation 2

3% deterioration correction = previous 3% deterioration correction + (FCC0-FCC3) / FCC3 * experimental constant

Where FCC0 is the capacity learning at 0% calibrated voltage point and FCC3 is the capacity learning at 3% calibrated voltage point

In addition, the present invention to calculate the discharge amount by integrating the discharge current to a predetermined correction voltage point when the battery cell is discharged from the full charge state to the full discharge state to achieve the above object, and the correction voltage A method for calculating a new full charge capacity by adding a value obtained by multiplying a percentage of remaining capacity at a point by an existing full charge capacity to the accumulated discharge amount, wherein the corrected voltage point is a charge / discharge cycle of a battery cell. It can be set to gradually decrease as the number of times increases.

Here, the number of charge and discharge cycles may be increased by one each time the amount of discharge obtained by integrating the discharge current reaches 90 to 100% of the full charge capacity.

Further, the correction voltage point may be determined at at least one point while remaining capacity of the battery cell is 10% or less.

In addition, the correction voltage point may be a voltage detected at 8% or 3% of the remaining capacity relative to the full charge capacity.

In addition, the correction voltage point of the remaining capacity of 8% can be calculated by the following equation.

8% compensation voltage point = 8% compensation voltage point according to the number of cycles pre-tabled in memory + (8% degradation compensation value * current / number of parallel battery cells / resolution)

In addition, the 8% deterioration correction value may be calculated by Equation 2 when the following Equation 1 is satisfied.

Equation 1

(FCC0-FCC8) / FCC0〉 5%

Equation 2

8% degradation correction value = (last 8% degradation correction value + degradation prediction table) / 2

Here, FCC0 is a capacity learning value at 0% correction voltage point, FCC8 is a capacity learning value at 8% correction voltage point, and the degradation prediction table is a correction value according to the degree of degradation previously stored in the memory.

In addition, the correction voltage point of the remaining capacity 3% can be calculated by the following equation.

3% compensation voltage point = 8% compensation voltage point according to the number of cycles pre-tabled in memory + (3% degradation compensation value * current / number of parallel battery cells / resolution)

In addition, the 3% deterioration correction value may be calculated by Equation 2 when the following Equation 1 is satisfied.

Equation 1

(FCC0-FCC3) / FCC0〉 5%

Equation 2

3% degradation correction value = (3% degradation correction value + degradation prediction table) / 2

Here, FCC0 is the capacity learning value at the 0% correction voltage point, FCC3 is the capacity learning value at the 3% correction voltage point, and the degradation prediction table is a correction value according to the degree of degradation previously stored in the memory.

As described above, the method for correcting degradation of a battery cell according to the present invention gradually lowers the correction voltage point as the number of cycles of the battery cell increases, thereby enabling accurate full charge capacity calculation.

In addition, the present invention calculates the full charge capacity not only at one of the correction voltage points but at least three points, whereby more accurate full charge capacity is calculated.

In addition, the present invention provides a relatively accurate deterioration correction value by providing a deterioration correction value using an average value of a correction value at a predetermined voltage and a correction value prestored in a memory even when the battery cell is discharged to near a discharge voltage instead of a full discharge and then recharged or disabled. Full charge capacity is calculated.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings such that those skilled in the art may easily implement the present invention.

4 is a block diagram illustrating an example of a controller to which the method for correcting degradation of a battery cell according to the present invention and a peripheral configuration thereof may be applied. The control unit may actually be a microcomputer or a Fuel Guage IC, but the present invention is not limited to this kind.

As shown, the overall configuration is based on a value obtained from a chargeable and dischargeable battery cell, a current sensor for sensing the current of the battery cell, a voltage sensor for sensing the voltage of the battery cell, and values obtained from the current sensor and the voltage sensor. And a controller for calculating the full charge capacity and the remaining capacity, and an external system provided with information such as the full charge capacity and the remaining capacity by being connected to the controller through SMBus or the like.

The battery cell may be any rechargeable battery such as a lithium ion battery, a lithium polymer battery, a nickel-hydrogen battery, a nickel-cadmium battery, or the like. Of course, these battery cells may be in a state where a plurality of them are connected in series and / or in parallel.

The current sensor may be a sensor resistor connected in series with a charge / discharge line of the battery cell, which converts a voltage applied to the sensor resistor into a current and outputs the current. Thus, the controller obtains current information using the voltage information of the battery cell.

The voltage sensor is connected to the battery cell in parallel to output voltage information of the battery cell.

The control unit includes a first A-D converter for converting an analog current value into a digital current value, a current integrating unit for integrating the current obtained from the first A-D converter, and converting the analog voltage value into a digital voltage value. Calculate a discharge amount on the basis of the value obtained from the second A-D converter to be converted, the correction voltage point detector to detect a correction voltage point based on the value obtained from the second A-D converter, and A remaining capacity calculating unit for calculating a remaining capacity based on a value obtained from the correction voltage point detector, a memory for pre-stored predetermined data in the form of a table in operation of the remaining capacity calculating unit, and providing the same upon request of the remaining capacity calculating unit; And a communication processor for providing a result of the remaining capacity calculator to an external system through SMBus. do. Here, a timer is connected between the first A-D converter and the second A-D converter, so that the first A-D converter and the second A-D converter can sample and output a current signal and a voltage signal per predetermined time. have.

The external system may be an electronic device having a charger. For example, the external system may be a laptop including a charger. Thus, the external system may not only charge the battery cell to a predetermined voltage and current, but may also be driven by the power supply of the battery cell. Of course, the external system is connected to the communication processing unit of the control unit, so that the full charge capacity and the remaining capacity information can be obtained from the control unit. As is well known, for example, in the case of a notebook, a power management program is provided so that the remaining capacity information is always displayed relative to the full charge capacity of the battery cell. In this case, a discharge warning signal is output, and when the remaining capacity of the battery cell is less than 3%, the current data is automatically saved and shut down. Of course, this behavior can be changed to any value by the user.

5 is a graph schematically illustrating a method of correcting degradation of a battery cell according to the present invention.

In the graph, the X axis is the discharge time (min) of the battery cell, and the Y axis is the voltage (mV) of the battery cell. As shown, for example, at the first charge / discharge cycle of the battery cell, an 8% correction voltage point (voltage when the remaining capacity is 8% of the full charge capacity) is approximately 10.2V. By the way, if the correction voltage point is fixed as it is even in the 100th charge / discharge cycle of the battery cell, it is calculated as 8% of remaining capacity in approximately 90 minutes even though it can actually be discharged for about 108 minutes. That is, an error occurs between the actual remaining capacity and the calculated remaining capacity. This error becomes larger as the number of charge and discharge cycles increases. Therefore, the main idea of the present invention is that as the number of charge and discharge cycles increases as described above, the correction voltage point is also reduced, so that more accurate remaining capacity is calculated.

6 is a graph illustrating a correction method when discharged from 100% to 0% of the battery cell deterioration correction method according to the present invention.

In the graph, the X axis shows the discharge time of the battery cell, and the Y axis shows the relative remaining capacity of the battery cell. Also, in the graph, FCC8 is the capacity learning value at 8% correction point, FCC3 is the capacity learning value at 3% correction point, and FCC0 is the capacity learning value at 0% correction point. Basically, the present invention allows FCC8 = FCC3 = FCC0 when the discharge voltage correction is appropriate. To this end, the present invention creates a variable parameter of 8% point deterioration correction, 3% deterioration correction. That is, these parameters are changed so that FCC8 = FCC3 = FCC0.

A method of adjusting the parameters as described above will be described.

Of course, in the present invention, when the battery cell is discharged from the fully charged state to the fully discharged state, the discharge amount is calculated by integrating the discharge current up to a predetermined correction voltage point, and the remaining capacity percentage at the correction voltage point ( The new full charge capacity is calculated by adding the value obtained by multiplying%) by the previous full charge capacity to the accumulated discharge amount.

Here, the correction voltage point is detected by the correction voltage point detection unit as shown in FIG. 4 and informs the remaining capacity calculator, and the calculation of the discharge amount is calculated by the current integrator and notified to the remaining capacity calculator.

Meanwhile, the correction voltage point is set to have a gradually smaller value as the number of charge / discharge cycles of the battery cell increases. For example, the number of charge / discharge cycles has been described above, where the remaining capacity calculation unit increases by 1 each time the current accumulating unit accumulates the discharge current to reach 90 to 100% of the full charge capacity. In addition, the remaining capacity calculation unit allows the correction voltage point to be determined at at least three points while the remaining capacity of the battery cell is 10% or less of the full charge capacity. For example, the correction voltage point may be a voltage at which residual capacity is detected at 8%, 3%, and 0% of the full charge capacity.

The correction voltage point of 8% of the remaining capacity may be calculated by Equation 1 below.

[Equation 1]

8% compensation voltage point = 8% point voltage according to the number of cycles pre-tabled in memory + (8% degradation compensation value * current / number of parallel battery cells / resolution)

Here, the 8% deterioration correction value may be calculated by Equation 3 when the following Equation 2 is satisfied.

[Equation 2]

(FCC0-FCC8) / FCC8〉 3%

[Equation 3]

8% deterioration correction = previous 8% deterioration correction-(FCC0-FCC8) / FCC8 * Experiment constant

Here, FCC0 is the capacity learning value at the 0% correction voltage point, and FCC8 is the capacity learning value at the 8% correction voltage point. In addition, the experimental constant may be 100 * 1.5 as an example, but the present invention is not limited thereto.

That is, the present invention determines that the correction voltage point is set too high when FCC8 is significantly smaller than FCC0, thereby forcibly lowering the correction voltage point.

Meanwhile, the 8% deterioration correction value may be calculated by Equation 5 when the following Equation 4 is satisfied.

[Equation 4]

(FCC0-FCC8) / FCC8 <-2%

[Equation 5]

8% deterioration correction value = previous 8% deterioration correction value + (FCC0-FCC8) / FCC8 * experimental constant

Here, FCC0 is the capacity learning value at 0% correction voltage point, and FCC8 is the capacity learning value at 8% correction voltage point. In addition, the experimental constant may be, for example, 100 * 0.6, but the present invention is not limited thereto.

That is, the present invention determines that the correction voltage point is set too low when the FCC0 is significantly smaller than the FCC8, thereby forcibly raising the correction voltage point.

Of course, when the value of (FCC0-FCC8) / FCC8 is within -2% to 3%, it is determined that the error range is not large in calculating the remaining capacity, and thus the correction using the above equation is not performed.

Subsequently, the 3% deterioration correction value may be calculated by Equation 7 when the following Equation 6 is satisfied.

[Equation 6]

(FCC0-FCC3) / FCC3〉 3%

[Equation 7]

3% deterioration correction = last 3% deterioration correction-(FCC0-FCC3) / FCC3 * Experiment constant

Here, FCC0 is the capacity learning value at the 0% corrected voltage point, and FCC3 is the capacity learning value at the 3% corrected voltage point. In addition, the experimental constant may be 100 * 1.5 as an example.

That is, the present invention determines that the correction voltage point is set too high when FCC3 is significantly smaller than FCC0, thereby forcibly lowering the correction voltage point.

In addition, when the 3% degradation correction value satisfies Equation 8 below, it may be calculated by Equation 9.

[Equation 8]

(FCC0-FCC3) / FCC3 <-2%

[Equation 9]

3% deterioration correction = previous 3% deterioration correction + (FCC0-FCC3) / FCC3 * experimental constant

Here, FCC0 is the capacity learning value at the 0% corrected voltage point, and FCC3 is the capacity learning value at the 3% corrected voltage point. In addition, the experimental constant may be 100 * 0.6, for example.

That is, the present invention determines that the correction voltage point is set too low when FCC0 is significantly smaller than FCC3, and forcibly raises the correction voltage point.

Of course, when the value of (FCC0-FCC3) / FCC3 is within -2% to 3%, it is determined that the error range is not large in calculating the remaining capacity, and thus the correction using the above equation is not performed.

7 is a graph showing a change in relative charge capacity after improving the firmware (firm ware) of the control unit by the method according to the present invention.

In the figure, the X axis represents the capacity of the battery cell (mAh), and the Y axis represents the relative full charge capacity (RSOC). In addition, the battery cell is the present invention is applied to a battery cell that completed the charge and discharge of 300 cycles.

As shown, it can be observed that during the first 1 to 3 cycles after the application of the present invention, a jump phenomenon occurs in a state in which the battery cell displays the remaining capacity of about 10%. However, after three cycles, no jump phenomenon is observed in the relative full charge capacity, and the correct relative full charge capacity is displayed.

8 is a graph illustrating a correction method when discharged from 100% to 8% or 3% of the battery cell deterioration correction method according to the present invention. In fact, users of external systems rarely discharge battery cells to 0%. That is, users tend to recharge the battery cells before the battery cells are fully discharged. As described above, the battery cell degradation correction method will be described when the user discharges the battery cells to approximately 8% or 3% instead of 0% of the remaining capacity.

When the battery cell is discharged from the fully charged state to near the fully discharged state, calculating the discharge amount by integrating the discharge current up to a predetermined correction voltage point, and the existing capacity percentage (%) at the correction voltage point. In a method of calculating a new full charge capacity by adding a value obtained by multiplying a full charge capacity to the accumulated discharge amount, the present invention sets the correction voltage point to gradually decrease as the number of charge / discharge cycles of a battery cell increases. do. The idea of this invention is as described above.

As described above, the number of charge and discharge cycles is increased by one each time the discharge amount obtained by integrating the discharge current reaches 90 to 100% of the full charge capacity. Further, the correction voltage point may be determined at at least one point while remaining capacity of the battery cell is 10% or less.

The correction voltage point may be a voltage detected at 8% or 3% of the remaining capacity relative to the full charge capacity.

Here, since the correction voltage point is not actually discharged to 0% of the remaining capacity of the battery cell, it is difficult to determine the exact full charge capacity, and thus, the table stored in the memory is experimentally and theoretically calculated in advance according to the number of charge / discharge cycles of the battery cell. Use That is, the correction voltage point is calculated by averaging the calculated value at the 8% or 3% and the value previously stored in the table.

First, the correction voltage point of the remaining capacity of 8% may be calculated by Equation 10 below.

[Equation 10]

8% compensation voltage point = 8% compensation voltage point according to the number of cycles pre-tabled in memory + (8% degradation compensation value * current / number of parallel battery cells / resolution)

Here, the 8% deterioration correction value may be calculated by Equation 12 when the following Equation 11 is satisfied.

[Equation 11]

(FCC0-FCC8) / FCC0〉 5%

[Equation 12]

8% degradation correction value = (last 8% degradation correction value + degradation prediction table) / 2

Here, FCC0 is the capacity learning value at the 0% correction voltage point, FCC8 is the capacity learning value at the 8% correction voltage point, and the degradation prediction table is a correction value according to the degree of degradation previously stored in the memory.

An example of the deterioration prediction table is shown in the table below.

Degradation Degree (FCC8 / Design Capacity) 8% deterioration correction value 3% deterioration correction value 100% 128 128 95% 120 120 90% 108 108 80% 88 88 70% 80 80 50% 80 80

An example of an 8% degradation correction value is calculated using Equation 12 and the degradation prediction table as described above. When FCC0 is Design Capacity, if 8% degradation compensation value is 128 and FCC8 / DC is 90%, 8% degradation compensation value can be calculated as follows.

8% degradation deterioration value = (128 + 108) / 2 = 118

Of course, when the value of (FCC0-FCC8) / FCC0 is 5% or less, it is determined that the error range is not large in calculating the remaining capacity, and thus the correction using the above equation is not performed.

In addition, the correction voltage point of the remaining capacity 3% can be calculated by the following equation (13).

[Equation 13]

3% compensation voltage point = 8% compensation voltage point according to the number of cycles pre-tabled in memory + (3% degradation compensation value * current / number of parallel battery cells / resolution)

Here, the 3% deterioration correction value may be calculated by Equation 15 when the following Equation 14 is satisfied.

[Equation 14]

(FCC0-FCC3) / FCC0〉 5%

[Equation 15]

3% degradation correction value = (3% degradation correction value + degradation prediction table) / 2

Here, FCC0 is the capacity learning value at the 0% correction voltage point, FCC3 is the capacity learning value at the 3% correction voltage point, and the degradation prediction table is a correction value according to the degree of degradation previously stored in the memory.

Of course, when the value of (FCC0-FCC3) / FCC0 is 5% or less, it is determined that the error range is not large in calculating the remaining capacity, and thus the correction using the above equation is not performed.

9 is a graph showing a change in the relative charging capacity after improving the firmware of the control unit by the method according to the present invention.

In the figure, the X axis represents the capacity of the battery cell, and the Y axis represents the relative full charge capacity (RSOC). In addition, the battery cell is the present invention is applied to a battery cell that completed the charge and discharge of 300 cycles.

As shown, if the number of charge and discharge cycles after applying the present invention is approximately eight or more, it can be seen that the jumping phenomenon of the relative full charge capacity gradually decreases. That is, as shown, when the number of charge / discharge cycles is about 8 or more, the relative full charge capacity may be displayed in a nearly straight form. Accordingly, the battery cell or the battery pack to which the present invention is applied obtains almost one remaining capacity information regardless of the number of charge / discharge cycles, that is, the degree of deterioration, thereby optimizing power management of the external system.

Here, even though the number of cycles increases, the reason why the RSOC straight line is displayed in the approximately 1000 mAh range is that the battery cells are not discharged to 0%. However, it is possible to obtain a linear RSOC to the point near the full discharge capacity, which has the significance of the present invention.

As described above, the deterioration correction method of the battery cell according to the present invention has the effect of accurately calculating the full charge capacity by gradually lowering the correction voltage point as the number of cycles of the battery cell increases.

In addition, the present invention has the effect that the full charge capacity can be calculated more precisely because the full charge capacity calculation is not performed at any one correction voltage point but at least three points.

In addition, the present invention provides a relatively accurate full charge by providing a deterioration correction value by using an average value of a correction value at a predetermined voltage and a correction value prestored in a memory even when the battery cell is discharged to a predetermined voltage and not recharged. The total capacity can be calculated.

What has been described above is just one embodiment for carrying out the method for correcting deterioration of a battery cell according to the present invention, and the present invention is not limited to the above-described embodiment, as claimed in the following claims. Without departing from the gist of the present invention, those skilled in the art to which the present invention pertains to the technical spirit of the present invention to the extent that various modifications can be made.

Claims (17)

When the battery cell is discharged from the fully charged state to the fully discharged state, the discharge amount is calculated by integrating the discharge current up to a predetermined correction voltage point, and the previous full charge capacity is added to the percentage of remaining capacity at the correction voltage point (%). In the method for calculating a new full charge capacity by adding the value obtained by multiplying to the accumulated discharge amount, And the correction voltage point is set to have a smaller value as the number of charge / discharge cycles of the battery cell increases. The method of claim 1, wherein the number of charge and discharge cycles increases by one each time the amount of discharge obtained by integrating the discharge current reaches 90 to 100% of the full charge capacity. 2. The method of claim 1, wherein the correction voltage point is determined at at least three points while the remaining capacity of the battery cell is 10% or less of the full charge capacity. The method of claim 1, wherein the correction voltage point is a voltage at which residual capacity is detected at 8%, 3%, and 0% of the full charge capacity. The method of claim 4, wherein the correction voltage point of 8% of the remaining capacity is calculated by the following equation. 8% compensation voltage point = 8% point voltage according to the number of cycles pre-tabled in memory + (8% degradation compensation value * current / number of parallel battery cells / resolution) The method of claim 5, wherein the 8% degradation correction value is calculated by Equation 2 when the following Equation 1 is satisfied. Equation 1 (FCC0-FCC8) / FCC8〉 3% Equation 2 8% deterioration correction = previous 8% deterioration correction-(FCC0-FCC8) / FCC8 * Experiment constant Where FCC0 is the capacitive learning at 0% calibrated voltage point and FCC8 is the capacitive learning at 8% calibrated voltage point The method of claim 4, wherein the 8% degradation correction value is calculated by Equation 2 when the following Equation 1 is satisfied. Equation 1 (FCC0-FCC8) / FCC8 <-2% Equation 2 8% deterioration correction value = previous 8% deterioration correction value + (FCC0-FCC8) / FCC8 * experimental constant Where FCC0 is the capacitive learning at 0% calibrated voltage point and FCC8 is the capacitive learning at 8% calibrated voltage point The method of claim 4, wherein the 3% degradation correction value is calculated by Equation 2 when the following Equation 1 is satisfied. Equation 1 (FCC0-FCC3) / FCC3〉 3% Equation 2 3% deterioration correction = last 3% deterioration correction-(FCC0-FCC3) / FCC3 * Experiment constant Where FCC0 is the capacity learning at 0% calibrated voltage point and FCC3 is the capacity learning at 3% calibrated voltage point The method of claim 8, wherein the 3% degradation correction value is calculated by Equation 2 when the following Equation 1 is satisfied. Equation 1 (FCC0-FCC3) / FCC3 <-2% Equation 2 3% deterioration correction = previous 3% deterioration correction + (FCC0-FCC3) / FCC3 * experimental constant Where FCC0 is the capacitive learning at 0% calibrated voltage point and FCC3 is the capacitive learning at 3% calibrated voltage point In the case of discharging the battery cell from the fully charged state to the fully discharged state, calculating the discharge amount by accumulating the discharge current up to a predetermined correction voltage point, and the existing capacity percentage (%) at the correction voltage point. In the method of calculating the new full charge capacity by adding the value obtained by multiplying the full charge capacity to the accumulated discharge amount, And the correction voltage point is set to become smaller as the number of charge / discharge cycles of the battery cell increases. 11. The method of claim 10, wherein the number of charge and discharge cycles increases by one each time the amount of discharge obtained by integrating the discharge current reaches 90 to 100% of the full charge capacity. The method of claim 10, wherein the correction voltage point is determined at at least one point while remaining capacity of the battery cell is 10% or less. The method of claim 10, wherein the correction voltage point is a voltage detected at 8% or 3% of the remaining capacity relative to the full charge capacity. The method of claim 13, wherein the correction voltage point of 8% of the remaining capacity is calculated by the following equation. 8% compensation voltage point = 8% compensation voltage point according to the number of cycles pre-tabled in memory + (8% degradation compensation value * current / number of parallel battery cells / resolution) 15. The method of claim 14, wherein the 8% degradation correction value is calculated by Equation 2 when the following Equation 1 is satisfied. Equation 1 (FCC0-FCC8) / FCC0〉 5% Equation 2 8% degradation correction value = (last 8% degradation correction value + degradation prediction table) / 2 Here, FCC0 is a capacity learning value at 0% correction voltage point, FCC8 is a capacity learning value at 8% correction voltage point, and the degradation prediction table is a correction value according to the degree of degradation previously stored in the memory. The method of claim 13, wherein the correction voltage point of 3% of the remaining capacity is calculated by the following equation. 3% compensation voltage point = 8% compensation voltage point according to the number of cycles pre-tabled in memory + (3% degradation compensation value * current / number of parallel battery cells / resolution) The method of claim 16, wherein the 3% degradation correction value is calculated by Equation 2 when the following Equation 1 is satisfied. Equation 1 (FCC0-FCC3) / FCC0〉 5% Equation 2 3% degradation correction value = (3% degradation correction value + degradation prediction table) / 2 Here, FCC0 is the capacity learning value at the 0% correction voltage point, FCC3 is the capacity learning value at the 3% correction voltage point, and the degradation prediction table is a correction value according to the degree of degradation previously stored in the memory.

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