KR101646570B1 - Method for estimating life cycle of battery cell and battery management system usint it - Google Patents

Abstract

A method for predicting the life of a battery cell and a battery management system using the same are provided. A method of predicting the life of a battery cell according to an embodiment of the present invention includes: measuring a charge / discharge current of a chargeable and dischargeable battery cell; Calculating a cumulative current amount based on a charging / discharging current of the battery cell; Estimating a charge / discharge cycle of the battery cell based on a set DOD (Depth Of Discharge) and the accumulated current amount; And comparing the life cycle of the battery cell at the set DOD with the charge / discharge cycle to determine whether the battery cell is replaced.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method for predicting the life of a battery cell and a battery management system using the method.

The present invention relates to a method of predicting the life of a battery cell and a battery management system using the method. More particularly, the present invention relates to a method of predicting the life of a battery cell capable of predicting the life of a battery capable of charging / discharging based on charge / And a battery management system using the battery.

Due to the rapid development of electronic products and the high expectations of consumers for high-performance power sources, many energy-intensive products are emerging. For example, demand for portable electronic products such as notebook computers, video cameras, smart phones, and the like has been rapidly increased, and development of batteries, robots, and satellites for energy storage has been accelerated, Research is active. Such a secondary battery is widely used because of its various advantages such as charge / discharge of a lithium secondary battery and low self-discharge rate.

In particular, in recent years, efforts have been made to develop electric vehicles (EV) or hybrid vehicles to reduce pollutants and save energy. In such electric vehicles and the like, a charge and discharge battery that provides the driving power of the electric motor is essentially installed.

Such a charge / discharge battery decreases capacity while continuing charge / discharge. For example, initially the capacity of 1000mAh was reduced to 700, 600, 500mAh while repeatedly charging and discharging several hundred times. Generally, the life cycle is defined as the number of charge / discharge cycles when the capacity is reduced to 80 to 60% of the initial capacity. For example, if the life cycle is 500 cycles, it means 500 cycles at 100% DOD (Depth Of Discharge). Here, DOD stands for Depth Of Discharge.

This discharge depth (DOD) is another method of expressing the state of charge (SOC) of the battery. The discharge depth is the opposite of the remaining capacity. As the discharge depth increases, the remaining capacity decreases. When the remaining capacity is expressed as a percentage value at 100% when the battery capacity is full and when it is 0%, the discharge depth can be expressed in Ah (Ah) and a percentage value have. For example, when the discharge depth of a battery having a capacity of 50 Ah is expressed in amperes, it means that the battery is not discharged (the remaining capacity is 100%) when the discharge depth is 0 Ah. If the discharge depth is 50 Ah, (State where the remaining capacity is 0%). When the discharge depth of a certain battery is expressed as a percentage, the remaining capacity is 0% when the discharge depth is 0%, and the remaining capacity is 0% when the discharge depth is 100%.

Specifically, when the capacity of the battery is 1000 mAh, DOD means 100% of 1000 mAh, which means the life cycle when charged. However, it is common to charge 50 to 80% in practice.

1 is a graph showing a life cycle according to the DOD of a lead-acid battery. Fig. 2 is a table summarizing the graph of Fig. 1 numerically.

Referring to FIGS. 1 and 2, the lifetime cycle of the lead-acid battery according to the DOD setting of 30%, 50%, 70%, and 100% can be known. Reaching point) is significantly different from 100 times to 400 times. That is, it can be seen that the charge / discharge battery has a faster replacement time when charging or discharging a large amount, and a replacement time is slowed when charging / discharging a small amount. From this, depending on how many percent DOD is set, the total capacity of charging and discharging changes until the battery is replaced. Therefore, in the case of a secondary battery which repeats charging and discharging, a method of performing life cycle counting taking such variables into account is required.

Korea Open Patent No. 2012-0140031 (2012.12.28. Disclosed)

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to provide a battery cell which can estimate a life cycle on the basis of charge / discharge current and DOD, predict a lifetime of a chargeable / And a battery management system using the same.

The problems to be solved by the present invention are not limited to the above-mentioned problems, and other matters not mentioned can be clearly understood by those skilled in the art from the following description.

According to another aspect of the present invention, there is provided a method for predicting the life of a battery cell, the method comprising: measuring a charge / discharge current of a battery cell capable of charging / discharging; Calculating a cumulative current amount based on a charging / discharging current of the battery cell; Estimating a charge / discharge cycle of the battery cell based on a set DOD (Depth Of Discharge) and the accumulated current amount; And comparing the life cycle of the battery cell at the set DOD with the charge / discharge cycle to determine whether the battery cell is replaced.

In addition, the step of measuring the charging / discharging current may include a step of measuring charging / discharging current of the battery cell in real time.

The step of calculating the accumulated current amount may include calculating a cumulative current amount of the battery cell in real time.

The step of estimating the charge / discharge cycle may include estimating the charge / discharge cycle by dividing the accumulated current amount by the set DOD.

The determining whether or not to replace the battery pack may include determining that replacement of the battery cell is required when the charge / discharge cycle is equal to or greater than the life cycle.

If the replacement of the battery cell is required, the step of warning may be further included.

According to an aspect of the present invention, there is provided a battery management system using lifetime prediction of a battery cell, the battery management system comprising: a battery unit including a plurality of battery cells; A current measuring unit for measuring a charging / discharging current of each battery cell of the plurality of battery cells in real time; An arithmetic unit for calculating a cumulative current amount of each battery cell based on a charge / discharge current of each battery cell, and calculating a charge / discharge cycle of each battery cell based on a set DOD (Depth Of Discharge) and the cumulative current amount; And a battery management unit comparing the lifetime cycle of each battery cell in the set DOD with the charge / discharge cycle of each battery cell to determine a battery cell to be replaced.

In addition, the operation unit can accumulate the charge / discharge currents of the battery cells in real time to calculate the accumulated current amount of each battery cell.

The operation unit may calculate a charge / discharge cycle of each of the battery cells by dividing an accumulated current amount of each battery cell by the set DOD.

The apparatus may further include a DOD setting unit for setting DODs of the plurality of battery cells, respectively.

Also, the DOD setting unit may set the DOD of at least one battery cell in the plurality of battery cells to be different from that of the other battery cells.

In addition, the battery management unit may determine that the battery cells whose charge / discharge cycles are longer than the life cycle of the plurality of battery cells need to be replaced.

The apparatus may further include a switch unit including a plurality of switches respectively connected to the plurality of battery cells.

In addition, when the battery management unit determines that there is a battery cell that needs to be replaced among the plurality of battery cells, the battery management unit may turn off a switch connected to the battery cell.

The battery management unit may turn off a switch connected to a battery cell requiring replacement if the charge / discharge cycle of the battery cell requiring replacement is equal to or greater than a predetermined excess limit cycle.

A warning unit for generating a warning signal for warning a battery cell that needs to be replaced among the plurality of battery cells; And a communication unit for transmitting information of the battery cell in which the warning signal is generated to the outside.

Other specific details of the invention are included in the detailed description and drawings.

According to the present invention, it is possible to estimate the life cycle of a battery cell that can be charged and discharged based on the charge / discharge current and the DOD, and thereby predict the life of the battery cell that can be charged and discharged.

Further, by predicting the replacement time point of the battery cell in accordance with the estimated life cycle of the battery cell, it is possible to replace the battery cell whose lifetime has expired.

1 is a graph showing a life cycle according to the DOD of a lead-acid battery.
Fig. 2 is a table summarizing the graph of Fig. 1 numerically.
3 is a flowchart of a method of predicting the life of a battery cell according to an embodiment of the present invention.
4 is a diagram for comparing the total charge / discharge capacity of the battery cell according to the size of the DOD.
5 is a flowchart of a method of predicting the life of a battery cell according to another embodiment of the present invention.
FIG. 6 is a block diagram of a battery management system using lifetime prediction of a battery cell according to an embodiment of the present invention. Referring to FIG.
FIG. 7 and FIG. 8 are block diagrams showing specific embodiments of a battery management system using life prediction of the battery cell of FIG.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving them will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Is provided to fully convey the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout the specification.

Although the first, second, etc. are used to describe various elements, components and / or sections, it is needless to say that these elements, components and / or sections are not limited by these terms. These terms are only used to distinguish one element, element or section from another element, element or section. It is, of course, also possible that the first element, the first element or the first section mentioned below may be the second element, the second element or the second section within the spirit of the present invention.

The terminology used herein is for the purpose of illustrating embodiments and is not intended to be limiting of the present invention. In the present specification, the singular form includes plural forms unless otherwise specified in the specification. As used herein, the terms "comprises" and / or "made of" means that a component, step, operation, and / or element may be embodied in one or more other components, steps, operations, and / And does not exclude the presence or addition thereof.

Unless defined otherwise, all terms (including technical and scientific terms) used herein may be used in a sense commonly understood by one of ordinary skill in the art to which this invention belongs. Also, commonly used predefined terms are not ideally or excessively interpreted unless explicitly defined otherwise.

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

3 is a flowchart of a method of predicting the life of a battery cell according to an embodiment of the present invention. 4 is a graph for comparing the total charge / discharge capacity of the battery cell according to the size of the DOD.

Referring to FIG. 3, a method for predicting the life of a battery cell according to an exemplary embodiment of the present invention includes measuring a charge / discharge current of a chargeable and dischargeable battery cell (S110) A charge / discharge cycle of the battery cell is estimated based on the set DOD (Depth Of Discharge) and the cumulative current amount (S130), and the life cycle of the battery cell at the set DOD is compared with the charge / The discharge cycles are compared (S140), and it is determined whether or not the battery cell is replaced (S150). Here, the DOD (Depth Of Discharge) means a discharge depth, and the cumulative current amount is a cumulative amount of the measured current, and has a unit of amperage (Ah). Also, the life cycle is determined according to the DOD of the battery cell, and the charge / discharge cycle can be calculated from the DOD and the accumulated current amount. However, if the charge / discharge cycle is longer than the life cycle at S140 in FIG. 3, it is shown that replacement is necessary, but this is merely an example and may be set to other values.

Referring to FIG. 4, the available capacity of the battery cell varies depending on the set value of the DOD. As shown in FIG. 4, when the DOD is set to 30% in the left battery cell and the DOD is set to 80% in the right battery cell, the total available capacity of the left battery cell is higher than that of the right battery cell .

Taking a 12V 10Ah battery cell as an example, it will have a life cycle of 1200 cycles at 30% DOD charge and 300 cycles at 80% charge. The total capacity of the battery according to each DOD is as follows.

DOD 30%: 0.3 * 10 Ah * 1200 cycle = 3600 Ah (1)

DOD 80%: 0.8 * 10Ah * 300 cycle = 2400 Ah ... (2)

Comparing the above (1) and (2), the total usable capacity at 30% of DOD is 3600 Ah, the usable total capacity at 80% of DOD is 2400 Ah, and the usable total capacity at 30% of DOD is 80% It is known that the total capacity is larger than the available capacity. Therefore, even if the battery cell has the same capacity, the total capacity of the battery can be different depending on the size of the DOD set.

Referring again to FIG. 3, since the chargeable and dischargeable battery cell has a life cycle that can be used in accordance with the DOD, if the cumulative amount of charging / discharging current of the battery cell is measured and the total usable capacity according to each DOD setting is reached, It is determined that the battery is replaced.

At this time, the charging / discharging current of the battery cell can be measured in real time when the charging / discharging current of the battery cell capable of charging / discharging is measured. Also, the amount of accumulated current of the battery cell can be calculated in real time when the accumulated current amount is calculated based on the charging / discharging current of the battery cell. By measuring the current in real time and calculating the accumulated current amount, it is possible to grasp the time required to replace the battery cell in a short time. Also, the cumulative current amount is obtained by accumulating the measured current, and can be calculated by the following equation (1).

Where i is the measured charge / discharge current of the battery cell.

The DOD (Depth Of Discharge) and the accumulated current amount set at the time of estimating the charge / discharge cycle are used. The charge / discharge cycle can be obtained by dividing the accumulated current amount by the set DOD. have.

However, the DOD is represented by amperage (Ah) instead of a percentage, and can be obtained by multiplying the DOD value expressed as a percentage by the rated capacity of the battery cell. For example, for a 10 Ah battery cell, if the percentage value of DOD is 50%, the DOD is 5 Ah. The charge / discharge cycle, which is the actual charge / discharge cycle of the battery cell according to the currently set DOD, can be estimated by Equation (2).

Then, the charge / discharge cycle is compared with the life cycle determined by the set DOD to judge replacement of the battery cell. For example, when the charge / discharge cycle is longer than the life cycle, it can be determined that the battery cell needs to be replaced. However, this is an example, and it may be determined that replacement of the battery cell is required in another range. For example, when the charge / discharge cycle is greater than the life cycle by 20% or more, it may be determined that the battery cell needs to be replaced, or may be set to a different range.

5 is a flowchart of a method of predicting the life of a battery cell according to another embodiment of the present invention.

Referring to FIG. 5, a method for predicting the life of a battery cell according to another embodiment of the present invention includes measuring a charge / discharge current of a chargeable / dischargeable battery cell (S210) (S220). The charge / discharge cycle of the battery cell is estimated based on the set DOD (Depth Of Discharge) and the cumulative current amount (S230), and the life cycle of the battery cell at the set DOD, The discharge cycle is compared (S240), and it is determined whether the battery cell is replaced (S250). If the battery cell needs to be replaced, a warning is given (S260). Here, the method of predicting the life of the battery cell according to the embodiment of the present invention described above is the same as the steps S210 to S250, and thus a detailed description thereof will be omitted.

When it is necessary to replace the battery cell, it is necessary to inform the user of the replacement of the battery cell that needs to be replaced, thereby preventing a system or the like from being fixed by the battery cell. The replacement warning of the battery cell may include an audible means such as a warning sound or voice or a visual means for displaying a warning indication on an LCD monitor or an LED. Such replacement warning of the battery cell may be remotely transmitted using wired / wireless communication means.

FIG. 6 is a block diagram of a battery management system using lifetime prediction of a battery cell according to an embodiment of the present invention. Referring to FIG. 7 and 8 are block diagrams illustrating a battery management system using the life prediction of the battery cell of FIG.

6 to 8, the battery management system 100 using the life prediction of a battery cell according to an exemplary embodiment of the present invention includes a battery unit 110, a current measurement unit 120, an operation unit 130, And a battery management unit 140. The battery management system 100 using the life prediction of the battery cell includes a DOD setting unit 150, a switch unit 160, a warning unit 170, and a communication unit 180, . ≪ / RTI >

6, the battery management system 100 includes a battery unit 110 including a plurality of battery cells Cell1... CellN, a plurality of battery cells A current measuring unit 120 for measuring a charging / discharging current of the cell in real time, a calculating unit 120 for calculating a cumulative current amount of each battery cell on the basis of a charging / discharging current of each battery cell, a set DOD (Depth Of Discharge) (130) for calculating a charge / discharge cycle of each of the battery cells based on the life cycle of each of the battery cells in the set DOD and a charge / discharge cycle of each of the battery cells, And a battery management unit 140 for determining the battery.

7 and 8, the battery management system 100 includes a setting unit 150 for setting the DOD of each of the plurality of battery cells (Cell1 ... CellN), a plurality of battery cells A warning unit 170 for generating a warning signal for warning a battery cell to be replaced, and a control unit 170 for controlling information of the battery cell in which the warning signal is generated, And a communication unit 180 for transmitting the data to the mobile communication terminal.

The battery unit 110 includes a plurality of battery cells Cell1... CellN. As shown in FIGS. 7 and 8, a converter 10 for power conversion is connected to the battery cells. Also, the switch S may be connected to each battery cell of the battery unit 110, and the DOD of each battery cell may be set by the DOD setting unit 150.

The current measuring unit 120 measures the charging and discharging current of each battery cell in real time, and a current measuring sensor can be connected to each battery cell.

The calculation unit 130 calculates the accumulated current amount of each battery cell by accumulating charge / discharge currents of the battery cells in real time, divides the accumulated current amount of each battery cell by the set DOD, can do. Specifically, the cumulative current amount can be obtained by the equation (1), and the charge / discharge cycle can be obtained by the equation (2).

The battery management unit 140 determines which battery cells need to be replaced. For example, among the plurality of battery cells (Cell1, ..., CellN), it is possible to determine that battery cells whose charge / In addition, the battery management unit 140 may turn off the switch S connected to the battery cells to be replaced for stability of the system. This will be described later.

The DOD setting unit 150 sets the DODs of the plurality of battery cells (Cell1 ... CellN), respectively, and the life cycle of each battery cell is determined by the set DOD. The DOD setting unit 150 may set the DOD of at least one battery cell in the plurality of battery cells Cell1 to CellN to be different from those of the other battery cells. Therefore, the stability of the power system and the electric vehicle can be improved by designing that the replacement timing of each battery cell is not the same in a power system or an electric vehicle to which a plurality of battery cells (Cell1 ... CellN) are applied. The set value of the DOD by the DOD setting unit 150 may be input by the operator of the system or may be actively allocated to each battery cell in the DOD setting unit 150 by default at the time of initial design.

The switch unit 160 includes a plurality of switches S connected to the plurality of battery cells Cell1 ... CellN. The switch cell 160 includes a plurality of battery cells (Cell1 ... CellN) In this case, the stability of the system can be improved by turning off the switch connected to the battery cell that needs to be replaced. For example, as shown in FIG. 8, when it is determined that the cell 2 needs to be replaced, the battery management unit 140 disconnects the switch S connected to the cell 2, thereby blocking problems that may occur by the cell 2 .

At this time, the battery management unit 140 does not immediately turn off the switch S when it is determined that the replacement is necessary, and when the charge / discharge cycle of the battery cell to be replaced is greater than a preset excess limit cycle, Can be turned off. This is because, even if the battery cell needs to be replaced, it is possible to continuously charge and discharge the battery cell for a certain period of time. For example, in FIG. 8, even if it is determined that the lifetime cycle of Cell 2 is 1200 and the charge / discharge cycle is longer than the lifetime cycle, if the excess limit cycle is set to 2400, the actual charge / The battery management unit 140 turns off the switch S connected to the cell 2.

The warning unit 170 generates a warning signal for notifying a battery cell requiring replacement, and may be an audible indication means such as a warning sound or voice, or a visual indication means such as an LCD monitor or an LED. The battery management unit 140 controls the warning unit 170 to notify a warning sound for notifying a battery cell to be replaced or blink an LED installed in a battery cell to be replaced so that the position of the battery cell to be replaced can be guided.

The communication unit 180 transmits the information of the battery cell in which the warning signal is generated to the outside, and the communication unit 180 can perform wired communication and / or wireless communication with the external device 20. The external device 20 may be a variety of communication devices such as a 2G / 3G / 4G, a terminal capable of WiBro wireless network service, a PDA, a smart phone, etc., and may be an interface for wireless LAN connection such as an IEEE 802.11 wireless LAN network card Or the like. Further, the external device 20 can be connected to the communication unit 180 via a network, and the network includes a wireless network as well as a wired network. Such networks include the Internet and the like. The communication unit 180 can inform the external device 20 of the information of the battery cell that needs to be replaced, so that it is possible to deal with the battery cell quickly, which improves the stability of the system employing the plurality of battery cells.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, You will understand. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

110: battery unit 120: current measuring unit
130: Operation unit 140: Battery management unit
150: DOD setting unit 160:
170: warning section 180: communication section

Claims (16)

Measuring a charging / discharging current of the battery cell capable of charging / discharging;
Calculating a cumulative current amount based on a charging / discharging current of the battery cell;
Estimating a charge / discharge cycle of the battery cell by dividing the accumulated current amount by a set DOD (Depth Of Discharge); And
And comparing the life cycle of the battery cell at the set DOD with the charge / discharge cycle to determine whether the battery cell is to be replaced. The method according to claim 1,
Wherein the step of measuring the charging / discharging current includes measuring a charging / discharging current of the battery cell in real time. 3. The method of claim 2,
Wherein the step of calculating the cumulative current includes calculating a cumulative current amount of the battery cell in real time. delete The method according to claim 1,
Wherein the step of determining whether or not to replace the battery cell includes determining that replacement of the battery cell is required when the charge / discharge cycle is equal to or greater than the life cycle. The method according to claim 1,
Further comprising the step of alerting the battery cell when it is necessary to replace the battery cell. A battery unit including a plurality of battery cells;
A current measuring unit for measuring a charging / discharging current of each battery cell of the plurality of battery cells in real time;
An arithmetic unit for calculating a cumulative current amount of each battery cell based on a charge / discharge current of each battery cell, and calculating a charge / discharge cycle of each battery cell based on a set DOD (Depth Of Discharge) and the cumulative current amount; And
And a battery management unit for comparing a life cycle of each battery cell in the set DOD with a charge / discharge cycle of each battery cell to determine a battery cell to be replaced,
Wherein the operation unit calculates a charge / discharge cycle of each battery cell by dividing an accumulated current amount of each battery cell by the set DOD. 8. The method of claim 7,
Wherein the operation unit accumulates the charging and discharging currents of the battery cells in real time to calculate a cumulative current amount of each of the battery cells. delete 8. The method of claim 7,
Further comprising a DOD setting unit for setting the DODs of the plurality of battery cells, respectively. 11. The method of claim 10,
Wherein the DOD setting unit sets the DOD of at least one battery cell in the plurality of battery cells to be different from that of the other battery cells. 8. The method of claim 7,
Wherein the battery management unit determines that a battery cell having a charge / discharge cycle of at least a life cycle of the plurality of battery cells is required to be replaced. 8. The method of claim 7,
Further comprising a switch unit including a plurality of switches respectively connected to the plurality of battery cells. 14. The method of claim 13,
Wherein the battery management unit turns off a switch connected to a battery cell requiring replacement when it is determined that there is a battery cell that needs to be replaced among the plurality of battery cells. 15. The method of claim 14,
Wherein the battery management unit turns off a switch connected to a battery cell requiring replacement when the charge / discharge cycle of the battery cell requiring replacement is equal to or greater than a preset excess limit cycle. 8. The method of claim 7,
An alarm unit for generating a warning signal for warning a battery cell requiring replacement among the plurality of battery cells; And
And a communication unit for transmitting information of the battery cell in which the warning signal is generated to the outside.

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