Patent Publication Number: US-11391779-B2

Title: Battery capacity estimation apparatus and method, and battery management apparatus provided with same and method thereof

Description:
TECHNICAL FIELD 
     The present invention relates to an apparatus and method for estimating the capacity of a battery, and more particularly, to an apparatus and method for estimating the capacity of a battery according to a reduction in the range of voltage used. 
     BACKGROUND ART 
     In recent years, as the demand for portable electronic products such as notebooks and portable telephones has increased sharply, studies on a high performance secondary battery capable of repeated charge and discharge (hereinafter referred to as a battery) have been actively conducted. Currently commercially available batteries include nickel cadmium batteries, nickel metal hydride batteries, nickel-zinc batteries, and lithium batteries. Among them, lithium batteries have less memory effect than nickel batteries, so that they are in the limelight for advantages, for example, free charge/discharge, very low self-discharge rate, high energy density, and the like. 
     On the other hand, as carbon energy is gradually depleted and environmental concerns are rising, demand for hybrid vehicles and electric vehicles is increasing. Since these hybrid vehicles and electric vehicles use the charge and discharge energy of a battery pack to obtain the vehicle driving power, they are more fuel-efficient than the vehicles using only the engine and do not discharge or reduce pollutants. Therefore, they are getting good responses from many consumers. Therefore, more attention and research are focused on automotive batteries, which are key components of hybrid vehicles and electric vehicles. 
     Since the battery is used for mobile devices without being connected to an external power source such as AC power, there is a time limit. However, if the usable time of the battery, i.e., the available time, may not be predicted properly, the user may experience a great deal of difficulty. For example, if the battery available time of an electric vehicle may not be accurately predicted, the battery may be completely discharged during operation, resulting in the vehicle stopping in the middle of the road. 
     In this way, in order to prevent sudden complete battery discharge during use when the user may not predict the discharge of the battery, a technique for estimating the remaining amount of the battery, that is, the state of charge (SOC), and providing it to the user is widely known. The SOC of the battery is generally expressed as a percentage of the remaining capacity of the battery with respect to the full charge capacity (FCC). As a method of estimating the SOC of the battery, various methods may be used. A representative method is a method of estimating the SOC using the current integration method. This current integration method is a mode in which SOC is obtained by integrating the input/output current of the battery and adding/subtracting it from the initial capacity. 
     On the other hand, when the battery pack is mounted on a vehicle or the like, the automobile manufacturer may change the usable voltage range in consideration of battery life and stability. For example, the available voltage range may be reduced from a minimum of 2.4V to a maximum of 4.0V with respect to a battery capable of operating from a minimum of 2.0V to a maximum of 4.2V. However, despite the reduction in usable capacity as the voltage range is reduced, it may not be to SOC and FCC calculation algorithms. That is, the initial residual amount estimation is not performed according to the use range reduction, and this causes a larger error over time. 
     PRIOR ART DOCUMENT 
     Korean Patent Publication No. 2014-0053590 
     DISCLOSURE OF THE INVENTION 
     Technical Problem 
     The present invention provides a battery capacity estimation apparatus and method capable of estimating a capacity of a battery according to a change in a use voltage range, and a battery management apparatus and method including the same. 
     The present invention provides a battery capacity estimation apparatus and method capable of estimating a capacity according to a reduced use voltage range using an initial capacity estimation through an OCV table, and a battery management apparatus and method including the same. 
     Technical Solution 
     In accordance with an exemplary embodiment, a battery capacity estimation apparatus includes: a battery; a sensing unit connected to the battery to measure an OCV of the battery; an SOC estimation unit connected to the sensing unit to estimate an SOC of the battery using the OCV measured from the sensing unit; a memory unit configured to store data including the SOC and the OCV of the battery, the memory unit being connected to the SOC estimation unit; and an operation unit connected to the SOC estimation unit and the memory unit, the operation unit being configured to calculate an SOC reduction degree according to a use voltage range change and re-calculate a changed SOC according to a changed use capacity. 
     The memory unit may match and store a plurality of initial SOCs and a plurality of initial OCVs, and may match and store a plurality of changed SOCs and a plurality of changed OCVs. 
     The operation unit may calculate a changed capacity by [Equation 1] below.
 
 X ′[mAh]= X [mAh]×(1−( A %+ B %))  [Equation 1]
 
     where X′ is a changed capacity, X is an initial capacity, A and B are high and low capacity subtraction ratios, respectively. 
     The operation unit may calculate a changed SOC by [Equation 2] below. 
     
       
         
           
             
               
                 
                   
                     
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                   = 
                   
                     
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                   [ 
                   
                     Equation 
                     ⁢ 
                     
                         
                     
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                     2 
                   
                   ] 
                 
               
             
           
         
       
     
     where I′ is a changed SOC, I is an initial SOC, A and B are high and low capacity subtraction ratios, respectively. 
     In accordance with yet another exemplary embodiment, a battery management apparatus includes: a battery; a sensing unit connected to the battery to measure an OCV of the battery; an SOC estimation unit connected to the sensing unit to estimate an SOC of the battery using the OCV measured from the sensing unit; a memory unit configured to store data including the SOC and the OCV of the battery, the memory unit being connected to the SOC estimation unit; an operation unit connected to the SOC estimation unit and the memory unit and configured to calculate an SOC reduction degree according to a use voltage range change and re-calculate a changed SOC according to a changed use capacity; a control unit connected to at least one of the operation unit and the memory unit to control charging and discharging of the battery according to a state of the battery by referring to the SOC; and a switching unit provided between the battery and a load to charge/discharge the battery according to a control signal of the control unit. 
     The operation unit may calculate a changed capacity by [Equation 1] below and calculate a changed SOC by [Equation 2] below
 
 X ′[mAh]= X [mAh]×(1−( A %+ B %))  [Equation 1]
 
     where X′ is a changed capacity, X is an initial capacity, A and B are high and low capacity subtraction ratios, respectively. 
     
       
         
           
             
               
                 
                   
                     
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                   [ 
                   
                     Equation 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     2 
                   
                   ] 
                 
               
             
           
         
       
     
     where I′ is a changed SOC, I is an initial SOC, A and B are high and low capacity subtraction ratios, respectively. 
     In accordance with still another exemplary embodiment, a battery capacity estimation method includes: measuring an OCV of a battery; estimating an initial SOC according to the measured OCV; calculating a changed SOC after calculating a SOC reduction degree according to a use voltage range change; and calculating a changed OCV according to the changed SOC. 
     The method may further include matching and storing a plurality of initial SOCs of the battery and a plurality of initial OCVs according thereto. 
     The initial SOC may be estimated by matching the measured OCV and the initial OCV. 
     The calculating of the changed SOC may include: calculating a SOC change degree according to a use voltage range change; calculating a changed capacity by subtracting from the initial capacity by the SOC change degree; and calculating the changed SOC. 
     The changed capacity may be calculated by [Equation 1] below.
 
 X ′[mAh]= X [mAh]×(1−( A %+ B %))  [Equation 1]
 
     where X′ is a changed capacity, X is an initial capacity, A and B are high and low capacity subtraction ratios, respectively. 
     The changed SOC may be calculated by [Equation 2] below. 
     
       
         
           
             
               
                 
                   
                     
                       I 
                       ′ 
                     
                     ⁡ 
                     
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                       % 
                       ] 
                     
                   
                   = 
                   
                     
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                   [ 
                   
                     Equation 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     2 
                   
                   ] 
                 
               
             
           
         
       
     
     where I′ is a changed SOC, I is an initial SOC, A and B are high and low capacity subtraction ratios, respectively. 
     The method may further include storing a plurality of data by matching the changed SOC and the changed OCV. 
     In accordance with yet still another exemplary embodiment, a battery management method includes: measuring an OCV of a battery; estimating an initial SOC according to the measured OCV; calculating a changed SOC after calculating a SOC reduction degree according to a use voltage range change; calculating a changed OCV according to the changed SOC; and controlling charging/discharging of the battery according to the state of the battery with reference to the changed SOC. 
     The calculating of the changed SOC may include: calculating a SOC change degree according to a use voltage range change; calculating a changed capacity by subtracting from the initial capacity by the SOC change degree; and calculating the changed SOC. 
     The changed capacity may be calculated by [Equation 1] below and the changed SOC may be calculated by [Equation 2] below
 
 X ′[mAh]= X [mAh]×(1−( A %+ B %))  [Equation 1]
 
     where X′ is a changed capacity, X is an initial capacity, A and B are high and low capacity subtraction ratios. 
     
       
         
           
             
               
                 
                   
                     
                       I 
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                       ] 
                     
                   
                   = 
                   
                     
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                     Equation 
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                     2 
                   
                   ] 
                 
               
             
           
         
       
     
     where I′ is a changed SOC, I is an initial SOC, A and B are high and low capacity subtraction ratios. 
     Advantageous Effects 
     Embodiments of the present invention may estimate the SOC and the capacity of a battery pack whose use voltage range has been changed according to the needs of a manufacturer installing the battery in an automobile or the like by using the OCV table. For example, according to the request of the manufacturer for the battery pack whose manufacture of the battery pack is completed and where the use voltage range is set, the use voltage range may be changed. In this case, after calculating the current SOC by referring to the OCV table, the degree of SOC reduction is calculated by referring to the OCV table for the upper and lower voltage use ranges, and the FCC capacity is calculated by deducting the amount of SOC reduction, and then a new SOC for the reduced use range is calculated. In such a way, it is possible to prevent the occurrence of an error by estimating the changed SOC according to the reduction of the voltage range, thereby enabling stable use of the battery. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments can be understood in more detail from the following description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a schematic block diagram of an electric vehicle to which SOC estimation of a battery according to embodiments of the present invention is applied; 
         FIG. 2  is a block diagram illustrating a configuration of a battery SOC estimation apparatus according to an embodiment of the present invention; 
         FIG. 3  is an exemplary view of an initial OCV table used in a SOC estimation method of a battery according to an embodiment of the present invention; 
         FIG. 4  is an exemplary view illustrating an OCV table changed according to a voltage range reduced by a SOC estimation method of a battery according to an embodiment of the present invention; 
         FIG. 5  is a schematic view for explaining an SOC estimation method of a battery according to an embodiment of the present invention; 
         FIG. 6  is a graph comparing the initial OCV table and the changed OCV table data; 
         FIGS. 7 and 8  are block diagrams of a battery management apparatus according to an embodiment of the present invention; 
         FIG. 9  is a schematic view for explaining an SOC estimation method of a battery according to an embodiment of the present invention; and 
         FIG. 10  is a flowchart of a SOC estimation method of a battery according to an embodiment of the present invention. 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention may be embodied in different forms and should not be construed as limited to the embodiments set forth herein, and rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present invention to those skilled in the art. 
       FIG. 1  is a schematic block diagram of an electric vehicle in which SOC estimation of a battery according to an embodiment of the present invention is used. 
     Referring to  FIG. 1 , the electric vehicle may include a battery  10  for providing electrical energy, a BMS  20  for managing the battery  10 , an ECU  30  for controlling the state of the electric vehicle, an inverter  40  for driving the motor  50  so as to enable the electric vehicle to travel, and a motor  50  for driving the electric vehicle. 
     The battery  10  is an electric energy source that supplies a driving force to the motor  50  to drive the electric vehicle  1 . The battery  10  may be charged or discharged by the inverter  40  in accordance with the driving of the motor  50  and/or the internal combustion engine (not shown). Here, the battery  10  may include at least one battery pack. Each of at least one battery pack may include a plurality of battery modules. The battery module may include a plurality of chargeable and dischargeable battery cells. The plurality of battery modules may be connected in series and/or in parallel in various ways to meet specifications of vehicles, battery packs, and the like, and a plurality of battery cells may also be connected in series and/or in parallel. Here, the type of the battery cell is not particularly limited and may be, for example, a lithium ion battery, a lithium polymer battery, a nickel cadmium battery, a nickel hydrogen battery, a nickel zinc battery, or the like. 
     The BMS  20  estimates the state of the battery  10  and manages the battery  10  using the estimated state information. For example, the status information of the battery  10  such as the SOC of the battery  10 , the State of Health (SOH), the maximum input/output power allowable amount, and the output voltage is estimated and managed. Then, the charging or discharging of the battery  10  is controlled using such state information. The BMS  20  according to the present invention includes an SOC estimation apparatus for estimating an SOC of a battery. In addition, the BMS  20  controls cell balancing to balance the charge state of each battery cell. That is, a battery cell having a relatively high charge state may be discharged and a battery cell having a relatively low charge state may be charged. 
     An engine controller unit (ECU)  30  is an electronic control unit for controlling the state of an electric vehicle. For example, based on information such as an accelerator, a brake, a speed, and the like, torque degree is determined and the output of the motor  50  is controlled to match the torque information. Further, based on the state information of the SOC, SOH, etc. of the battery  10  transmitted by the BMS  20 , the ECU  30  allows the battery  10  to be charged or discharged. For example, if the SOC delivered from the BMS 20 is 55% or less, the switch of the inverter  40  is controlled to output power in the direction of the battery  10  to charge the battery  10 , and if the SOC is 55% or more, the switch of the inverter  40  is controlled to output power in the direction of the motor  50  to discharge the battery  10 . 
     The inverter  40  drives the motor  50  so that the electric vehicle may travel on the basis of the control signal of the ECU  30 . 
     The motor  50  drives the electric vehicle  1  based on the control information (e.g., torque information) transmitted from the ECU  30  using the electric energy of the battery  10 . 
       FIG. 2  is a block diagram illustrating a configuration of a battery SOC estimation apparatus according to an embodiment of the present invention. That is,  FIG. 2  is a block diagram of a apparatus for estimating an initial SOC of a battery and estimating a changed SOC according to a reduction of a voltage range of a user. In addition,  FIGS. 3 and 4  are views illustrating an example of an OCV table used in an embodiment of the present invention.  FIG. 3  is an exemplary diagram of an initial OCV table.  FIG. 4  is an illustration of an OCV table corrected according to the reduction of the operating voltage range according to the present invention. Then,  FIG. 5  is a schematic view for explaining an SOC estimation method of a battery according to an embodiment of the present invention. One the other hand,  FIG. 6  is a graph comparing the initial OCV table and the changed OCV table data. 
     Referring to  FIG. 2 , the SOC estimation apparatus of the battery according to an embodiment of the present invention includes a sensing unit  100  for sensing voltage and current of the battery  10 , an SOC estimation unit  200  for estimating the SOC of the battery, a memory unit  300  for storing data such as SOC and voltage of the battery  10 , and an operation unit  400  for calculating the degree of SOC reduction due to the change in the use voltage range and recalculating the SOC according to the reduced use range. 
     First, the battery  10  may include a plurality of battery cells  11 ,  12 ,  13 , . . . ,  1   n  that may be charged and discharged. Here, in relation to the battery  10  an even number of battery cells may be connected or an odd number of battery cells may be connected. That is, n may be an even number or an odd number. Also, the plurality of battery cells may be connected in series. That is, the plurality of battery cells have one terminal and another terminal, and one terminal of one battery cell may be connected to the other terminal of the other battery cell. For example, the cathode of the first battery cell  11  may be connected to the anode of the second battery cell  12 , and the cathode of the second battery cell  12  may be connected to the anode of the third battery cell  13 . Further, the plurality of battery cells may have the same capacity and accordingly, the maximum charge voltage may be the same. For example, the maximum charge voltage may be 4.2V. 
     1. Sensing Unit 
     The sensing unit  100  is provided for sensing the state of the battery  10  and senses the voltage and current of the battery  10 , for example. Here, the sensing unit  100  may sense voltage and current of the battery pack, the battery module, and the battery cell. For this, the sensor unit  100  may include a plurality of sensors, for example, at least one voltage sensor (not shown) and at least one current sensor (not shown). The voltage sensor may measure the voltage of at least one of the battery pack, the battery module or the battery cell. For example, a voltage sensor may be used to measure the voltage of a battery pack, and after the BMS is enabled, it is possible to measure the stabilized voltage, i.e. OCV, from the battery pack after a predetermined time. The current sensor may measure the current of the battery pack. The current sensor may include, for example, a Hall current transformer (Hall CT) that measures current using a Hall element and outputs a signal corresponding to the measured current. Meanwhile, the sensing unit  110  may further include a temperature sensor (not shown) for measuring the battery  10  or the ambient temperature. The temperature sensor may measure the temperature of one area or a plurality of areas of the battery pack or the battery module, and at least one temperature sensor may be provided for this purpose. In order to sense the voltage, current, temperature, etc. of the battery  10  using the sensing unit  100 , the sensing unit  100  may be connected to the battery  10  through a plurality of connection lines as shown in  FIG. 2 . For example, each of the plurality of battery cells  11 ,  12 ,  13 ,  14 , . . . ,  1   n  may be connected to the sensing unit  100  through a plurality of connection lines. As a specific example of this, the positive electrode of the first battery cell  11  and the sensing unit  100  are connected through a connection line and a point between the first battery cell  11  and the second battery cell  12  is connected to the sensing unit  100  through the connection line. Each of the plurality of battery cells  11 ,  12 ,  13 ,  14 , . . . ,  1   n  connected in series is connected to the sensing unit  100  through a connection line, and accordingly, the sensing unit  100  may sense the states of the plurality of battery cells  11 ,  12 ,  13 ,  14 , . . . ,  1   n.    
     2. SOC Estimation Unit 
     The SOC estimation unit  200  estimates the SOC of the battery  10 . There are various methods to estimate the SOC. For example, the SOC of the battery  10  may be estimated using the capacity of the battery  10  estimated from the SOH estimation unit (not shown) and the current of the battery  10  measured from the sensing unit  100 . That is, the SOC estimation unit  200  integrates a current value measured for a predetermined time from the sensing unit  100 , and divides it by the estimated battery capacity from the SOH estimation unit to estimate the SOC of the battery  10 . Also, the SOC estimation unit  200  may estimate the SOC using the Open Circuit Voltage (OCV) of the battery  10 . That is, the SOC may be estimated by referring to the initial OCV table stored in the memory unit  300  and extracting the SOC matched to the OCV measured by the sensing unit  100 . For example, if the OCV measured from the sensing unit  100  is 3560 mV, it may be estimated that the SOC is 40% by referring to the OCV table of  FIG. 3 . Then, the SOC estimation unit  200  may estimate the SOC through various methods for measuring the impedance of the battery  10  and estimating the SOC. The embodiment of the present invention estimates the SOC by matching the OCV measured from the sensing unit  100  with the OCV table stored in the memory unit  300 . 
     3. Memory Unit 
     The memory unit  300  may store various data for operating the battery  10 . In particular, the memory unit  300  may store the SOC and the OCV. At this time, the SOC and the OCV may be matched and stored. That is, various experimentally measured SOCs and corresponding OCVs may be stored in the memory unit  300 . For example, as shown in  FIG. 3 , SOCs ranging from 0% to 100% and OCVs according to respective SOCs may be measured, and they may be matched and stored. The SOC and OCV stored in the memory unit  300  may be measured and stored in various ways. As one method, for example, the battery cell of the same specification as that of the battery cell used as the battery  10  of the present invention is charged with 0.5 C and 50 mA cutoff from 3 V to 4.2 V, maintained for 5 hours, and then discharged to 3 V with 0.01 C. The voltage of the battery cell is periodically measured during discharge. This process is repeated a plurality of times, for example, 7 to 8 times, so that SOC and OCV averages are calculated to provide SOC and OCV tables. As another method, the charge OCV is measured periodically while the battery cell is charged to 0.001 C (i.e., charged for 1000 hours), and the discharging OCV is periodically measured while discharged to 0.001 C (i.e., discharged for 1000 hours). The SOC and OCV tables may be prepared by calculating the average of the charge OCV and the discharge OCV and calculating the SOC at this time. As another method, the cylindrical battery cell is fully fixed using a mechanical fixture, and the + and − terminals of the charger and loader are contacted with the + and − terminals of the cylindrical battery cell using a screw. After a plurality of sets of structures in which the battery cells are in contact with the charger and the loader are manufactured and are placed in a constant temperature and humidity chamber to extract the SOC and OCV at a constant temperature. On the other hand, OCV and SOC are matched and stored, and the temperature and internal resistance at this time may also be stored. That is, the memory unit  300  may separately obtain the capacity decrease coefficient depending on the ambient temperature of the battery, the internal resistance, or the temperature, and store it in advance. In addition, the newly corrected OCV and SOC according to a change in a use voltage range may be matched and stored in the memory unit  300 . For example, as shown in  FIG. 4 , the newly estimated SOC and the corresponding OCV may be matched and stored according to the reduction of the use voltage range. At this time, the newly corrected OCV table may be stored by updating the initial OCV table or may be stored separately from the initial OCV table. That is, newly calculated SOC and OCV data may be overwritten and stored in the initial OCV table, or a new OCV table may be stored as data separate from the initial OCV table. Meanwhile, the memory unit  300  may be provided in the BMS  20 , and may be separately provided in addition to the BMS  20 . The memory unit  300  may include nonvolatile memory such as a hard disk drive, a flash memory, an electrically erasable programmable read-only memory (EEPROM), a static random access memory (SRAM), a ferro-electric random access memory (FRAM), and a phase change random access memory (PRAM). 
     4. Operation Unit 
     The operation unit  400  calculates an SOC reduction degree according to the change of the use voltage range and re-calculates the SOC accordingly. For this, the operation unit  400  first calculates the degree of SOC reduction using the upper and lower of the use voltage range according to the use voltage range change. That is, the operation unit  400  detects the upper and lower levels of the use voltage range by referring to the initial OCV table of the memory unit  300 , and calculates the degree of SOC reduction according to the detected OCV table. For example, if the use voltage range is 4.0 V to 2.4 V, the OCV table of  FIG. 3  is referenced to detect the SOC according to the voltage, that is, 90% and 5% and accordingly it is calculated that the degree of SOC reduction is the upper 10% and the lower 5%. Also, the operation unit  400  calculates the changed capacity by subtracting the FCC capacity from the initial capacity by the degree of SOC reduction, and calculates a new SOC according to the reduced use range. Here, the operation unit  400  calculates the changed capacity using Equation 1, and calculates the changed SOC using Equation 2. 
     
       
         
           
             
               
                 
                   
                     
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                   [ 
                   
                     Equation 
                     ⁢ 
                     
                         
                     
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                     1 
                   
                   ] 
                 
               
             
             
               
                 
                   
                     
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                   [ 
                   
                     Equation 
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                     2 
                   
                   ] 
                 
               
             
           
         
       
     
     A schematic diagram for calculating the changed capacity X′ and the changed SOC I′ is shown in  FIG. 5 . As shown in  FIG. 5 , the maximum voltage and the minimum voltage are denoted by Vfc and Ve, respectively, and the maximum and minimum SOC are 100% and 0%, respectively. In addition, the upper and lower capacity subtraction rates are denoted by A % and B %, respectively, and the initial and changed SOC are denoted by I and I′, respectively. Then, the changed maximum voltage and minimum voltage are denoted by V′fc and V′e, respectively. As shown in Equation 1, the changed capacity X′ may be calculated by multiplying the initial capacity X by a value obtained by subtracting 1 from the sum of the upper capacity reduction ratio A % and the lower capacity reduction ratio B %. In addition, as shown in Equation 2, the changed SOC I′ is calculated by dividing a value obtained by subtracting the lower capacity reduction ratio B % from the initial SOC I by a value obtained by subtracting the sum of the upper capacity subtraction rate A % and the lower capacity subtraction rate B % from 100%. For example, under the assumption that the maximum and minimum voltages are 4.2 V and 2.0 V, the initial SOC is 40%, and the high capacity reduction ratio A % and the low capacity reduction ratio B % are 10% and 5%, respectively, the changed capacity is calculated as 1275 mAh by Equation 1, and the changed SOC is calculated as 41% by Equation 2. Table 1 shows examples of the changed capacity and SOC calculated by Equations 1 and 2 according to initial capacity and initial SOC and upper and lower capacity subtraction rates. 
     
       
         
           
               
               
               
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                 Exam- 
                 Exam- 
                 Exam- 
                 Exam- 
                 Exam- 
                 Exam- 
                 Exam- 
               
               
                   
                 ple 
                 ple 
                 ple 
                 ple 
                 ple 
                 ple 
                 ple 
               
               
                   
                 1 
                 2 
                 3 
                 4 
                 5 
                 6 
                 7 
               
               
                   
               
             
            
               
                 Initial 
                 1500 
                 3000 
                 2800 
                 2200 
                 3000 
                 2400 
                 2400 
               
               
                 capacity 
                   
                   
                   
                   
                   
                   
                   
               
               
                 (mAh) 
                   
                   
                   
                   
                   
                   
                   
               
               
                 Upper  
                 10% 
                 15% 
                  7% 
                  0% 
                  2% 
                  10% 
                 10% 
               
               
                 capacity 
                   
                   
                   
                   
                   
                   
                   
               
               
                 sub-  
                   
                   
                   
                   
                   
                   
                   
               
               
                 traction 
                   
                   
                   
                   
                   
                   
                   
               
               
                 rate (%) 
                   
                   
                   
                   
                   
                   
                   
               
               
                 Lower  
                  5% 
                  3% 
                  0% 
                  7% 
                  8% 
                   3% 
                  3% 
               
               
                 capacity 
                   
                   
                   
                   
                   
                   
                   
               
               
                 sub-  
                   
                   
                   
                   
                   
                   
                   
               
               
                 traction 
                   
                   
                   
                   
                   
                   
                   
               
               
                 rate (%) 
                   
                   
                   
                   
                   
                   
                   
               
               
                 Initial  
                 40% 
                 60% 
                 55% 
                 64% 
                 60% 
                  95% 
                  2% 
               
               
                 SOC(%) 
                   
                   
                   
                   
                   
                   
                   
               
               
                 Changed 
                 1275 
                 2460 
                 2604 
                 2046 
                 2700 
                 2088 
                 2088 
               
               
                 capacity 
                   
                   
                   
                   
                   
                   
                   
               
               
                 (mAh) 
                   
                   
                   
                   
                   
                   
                   
               
               
                 Changed  
                 41% 
                 70% 
                 59% 
                 61% 
                 58% 
                 106% 
                 −1% 
               
               
                 SOC(%) 
               
               
                   
               
            
           
         
       
     
     However, when the changed SOC exceeds the reduced range, it is calculated as over SOC or under SOC. That is, as shown in Example 6, since the changed SOC is 11% larger than the initial SOC, which exceeds the reduction range of 10%, it is calculated as over SOC, and as shown in Example 7, the changed SOC is 3% smaller than the initial SOC, which is the same as the reduced range 3%, it is calculated as under SOC. On the other hand, the operation unit  400  calculates the SOC and the OCV according thereto depending on the calculated use voltage change, that is, use voltage reduction, and stores them in the memory unit  300 . That is, the newly calculated OCV table is updated and stored in the existing OCV table. At this time, the new data may be stored in the form of overwriting the existing data or may be stored as data separate from the existing data. In the new OCV table, the maximum voltage 4V set by the user is set to SOC 100%, the minimum voltage 2.4V is set to SOC 0%, and the SOC due to OCV therebetween may be calculated and stored as Equation 1. An example of such a new OCV table is shown in  FIG. 4 , and a graph comparing the initial OCV table and the changed OCV table data is shown in  FIG. 6 . 
     As described above, the SOC estimation apparatus for a battery according to an embodiment of the present invention includes a sensing unit  100 , an SOC estimation unit  200 , a memory unit  300 , and an operation unit  400 . Depending on the needs of a manufacturer that mounts the battery in a vehicle, the capacity of the battery whose use voltage range is changed may be estimated using the initial SOC of the OCV table. For example, the use voltage range may be changed according to the manufacturer&#39;s request for the battery having the use voltage range set as the manufacturing of the battery is completing. In this case, the current voltage SOC is calculated by referring to the OCV table, and the upper and lower voltage use ranges of the manufacturer are calculated by referring to the OCV table. FCC capacity is calculated by deducting the reduction amount, and a new SOC corresponding to the reduced use range is re-calculated. Therefore, it is possible to prevent the occurrence of an error by estimating the changed SOC according to the reduction of the voltage range of the user, thereby enabling stable use of the battery. 
     Meanwhile, the capacity of the battery  10  whose use voltage range is changed as described above may be estimated using the SOC estimation apparatus of the present invention, and the battery  10  whose use voltage range has been changed may be charged and discharged using the battery management apparatus.  FIGS. 7 and 8  show a battery management apparatus including the SOC estimation apparatus of the present invention.  FIG. 7  is a block diagram of a battery management apparatus according to an embodiment of the present invention, and  FIG. 8  is a block diagram of a battery management apparatus for explaining a configuration of a switching unit of a battery management apparatus. 
     Referring to  FIG. 7 , a battery management apparatus according to an exemplary embodiment of the present invention includes a battery  10  including a plurality of battery cells  11 ,  12 ,  13 ,  14 , . . . ,  1   n , a sensing unit  100  for sensing the state of the battery  10 , an SOC estimation unit  200  for estimating an SOC of the battery, a memory unit  300  for storing data such as SOC and voltage of the battery  10 , an operation unit  400  for calculating the degree of SOC reduction according to the use voltage range change and outputting the SOC according to the reduced use range, a control unit  500  for controlling the charging and discharging of the battery  10  according to the state of the battery  10  with reference to the re-calculated SOC, and a switching unit  600  for controlling the connection between the battery  10  and the load according to a control signal of the control unit  500 . That is, the battery management apparatus of the present invention is configured further including a control unit  500  and a switching unit  600  in the SOC estimation apparatus including the sensing unit  100 , the SOC estimation unit  200 , and the operation unit  400 . Here, since the SOC estimation apparatus has already been described, the control unit  500  and the switching unit  600  of the battery management apparatus of the present invention will be described in detail as follows. 
     5. Control Unit 
     The control unit  500  generates a control signal according to the voltage of each of the plurality of battery cells measured by the sensing unit  100  to control the switching unit  600  between the battery  10  and the load, thereby controlling the charging/discharging of the battery  10 . Therefore, overcharge or overdischarge of the battery cell may be prevented. For example, the control unit  500  compares the first set voltage for stopping the charging operation and the second set voltage for performing the charging operation with the voltages of the plurality of battery cells measured by the sensing unit  100 . If the measured voltage is higher than or equal to the first set voltage, the control unit  500  generates a control signal for stopping the charging operation of the battery cell, and if the measured voltage is lower than or equal to the second set voltage, the control unit  500  may generate a control signal for charging operation of the battery cell. Here, when the maximum charging voltage of each of the plurality of battery cells is 4.0 V, in order to prevent overcharging, for example, the first set voltage may be set to 3.8V. The second set voltage may be set to, for example, 2.4 V to prevent over discharge of each of the plurality of battery cells. In addition, the control unit  500  may control the charging/discharging of the battery cell by changing the set voltage of the battery cell according to the changed capacity of the battery cell. For example, when the maximum charge voltage is changed from 4.0V to 3.8V and the minimum voltage is changed to 2.5V, the control unit  500  may change the first and second set voltages and compare the data with the data of the memory cell using the operation result of the operation unit  400  or the data updated and stored in the memory unit  300 . For example, when the first set voltage is changed to 3.8V and the minimum charge voltage is changed to 2.5V, the first set voltage is changed to 3.6 V and the minimum charge voltage is changed to 2.6 V and compared with the data of the memory cell. Therefore, it is possible to control the charging and discharging of the battery cell according to the change of the maximum charging voltage and the minimum charging voltage of the battery cell, thereby preventing overcharge and overdischarge of the changed battery cell. 
     6. Switching Unit 
     The switching unit  600  is provided between a current path between the battery  10  and the load, and controls the charging and discharging of the battery  10  by the control unit  500 . The switching unit  600  may include a first switch  610  and a second switch  620  as shown in  FIG. 8 . That is, the switching unit  600  is provided between the battery  10  and the load. The first switch  610  may be provided on the side of the battery  10  and the second switch  620  may be provided on the load side. The first and second switches  610  and  620  are driven according to the control signal generated by the control unit  500  and may be driven at the same time when the battery  10  is charged and discharged and either one of them may be driven. For example, the first switch  610  may be driven when the battery  10  is charged, and the second switch  620  may be driven when the battery  10  is discharged. Here, the load may include an external power source for charging the battery  10 , and an electronic device to which the battery  10  driven according to the discharge voltage of the battery  10  is mounted. That is, when the battery  10  is charged, the battery  10  may be connected to an external power source, and when the battery  10  is discharged, the battery  10  may be connected to the electronic device. 
     The first switch  610  may include a first FET  610   a  and a first parasitic diode  610   b . The first FET  610   a  has a source terminal and a drain terminal provided between the battery  10  and the first node Q 1  and a gate terminal is connected to the control unit  500 . Accordingly, the first FET  610   a  is driven according to a control signal output from the controller  500 , and functions to apply a current to the battery  10  during charging. The first parasitic diode  610   b  is connected in parallel to the first FET  610   a . That is, the first parasitic diode  610   b  is connected in a forward direction between the battery  10  and the first node Q 1 . This first parasitic diode  610   b  sets the discharge path of the battery  10  when the first FET  610   a  is turned off. That is, the battery  10  may be charged through the first FET  610   a , and the battery  10  may be discharged through the first parasitic diode  610   b.    
     The second switch  620  may include a second FET  620   a  and a second parasitic diode  620   b . The second FET  620   a  has a source terminal and a drain terminal provided between the first node Q 1  and the load, and a gate terminal connected to the control unit  500 . Accordingly, the second FET  620   a  is driven according to a control signal output from the controller  500 , and functions to apply the discharge current of the battery  10  to the connected electronic device during the discharge. The second parasitic diode  620   b  is connected in parallel to the second FET  620   a . That is, the second parasitic diode  620   b  is connected in the reverse direction between the first node Q 1  and the load. The second parasitic diode  620   b  sets the path of the charging current when the battery  10  is charged. That is, the battery  10  may be charged through the first FET  620   a , and the battery  10  may be discharged through the first parasitic diode  610   b.    
     In relation to the switching unit  600 , the control unit  500  is connected to the gate terminal of the first FET  610   a  and the gate terminal of the second FET  620   a , so that the first and second FETs  610   a  and  620   a  are driven according to a control signal outputted from the control unit  500 , respectively. The control unit  500  turns on the first FET  610   a  and turns off the second FET  620   b  when the battery  10  is charged. Thus, the battery  10  is charged from the load, i.e., the external power supply, through the second parasitic diode  620   b  and the first FET  610   a . In addition, the controller  500  turns on the second FET  620   a  and turns on the second FET  610   a  when the battery  10  is discharged. Thus, the battery  10  is discharged from the battery  10  through the first FET  610   a  and the second parasitic diode  620   b . At this time, the control signal for turning on the first and second FETs  610   a  and  620   a , respectively, may be a logic high signal, and the control signal for turning off the first and second FETs  610   a  and  620   a , respectively, may be a logic low signal. 
     As described above, the battery control apparatus according to an embodiment of the present invention may control the charging/discharging of the battery  10  after sensing the state of the battery  10 . Also, the battery control apparatus may control the charging/discharging of the battery  10  according to the capacity of the battery  10  changed after the capacity and SOC of the battery  10  are changed by the SOC estimation apparatus. When the capacity of the battery  10  is reduced, the charging/discharging of the battery may be controlled by lowering the set voltage according to the reduced capacity. 
       FIG. 9  is a flowchart illustrating an SOC estimation method according to an embodiment of the present invention, and  FIG. 10  is a detailed flowchart of a process. 
     Referring to  FIGS. 9 and 10 , the SOC estimation method according to an embodiment of the present invention includes measuring OCV and current of the battery  10  (S 100 ), matching the measured OCV with an initial OCV stored in the memory unit  300  and extracting an initial SOC according to the initial OCV (S 200 ), calculating the degree of SOC reduction according to the use voltage range change and re-calculating the SOC according to the reduced use range (S 300 ), and calculating and storing the calculated SOC and OCV according to the use voltage reduction (S 400 ). In addition, the re-calculating of the SOC S 300  may include calculating the degree of SOC reduction using the upper and lower use voltage ranges according to the use voltage range change (S 310 ), calculating the changed capacity by subtracting the FCC capacity from the initial capacity by the degree of SOC reduction (S 320 ), and calculating a new SOC corresponding to the reduced use range (S 330 ). The SOC estimation method according to an embodiment of the present invention will now be described in detail. 
     S 100 : The voltage of the battery  10  is measured using the sensing unit  100 . That is, the voltage, that is, the OCV, which is stabilized after a predetermined time from the battery pack after the BMS is enabled by using the voltage sensor, is measured. Also, the sensing unit  100  may measure the current of the battery pack using a current sensor. 
     S 200 : The SOC estimation unit  200  matches the measurement OCV with the initial OCV stored in the memory unit  300  and estimates an initial SOC according thereto. Various data for operating the battery  10  may be stored in the memory unit  300 , and in particular, various experimentally measured initial SOCs and corresponding initial OCVs may be matched and stored. For example, the SOC from 0% to 100% and the OCV according to each SOC may be measured, and they are matched and stored as shown in  FIG. 3 . Therefore, the OCV measured from the sensing unit  100  may be compared with the initial OCV stored in the memory unit  300 , and the initial SOC may be extracted accordingly. 
     S 300 : The operation unit  400  calculates the degree of SOC reduction according to the use voltage range change and re-calculates the SOC according to the reduced use range. The SOC re-calculation process according to the change of the use voltage range is as shown in  FIG. 7  as follows. 
     S 310 : The operation unit  400  calculates the degree of SOC reduction using the upper and lower of the use voltage range according to the use voltage range change. That is, the operation unit  400  calculates the degree of SOC reduction by referring to the upper and lower of the use voltage range of the initial OCV table of the memory unit  300 . For example, if the use voltage range is 4.0 V to 2.4 V, the OCV table of  FIG. 3  is referenced to detect the SOC according to the voltage, that is, 90% and 5% and accordingly it is calculated that the degree of SOC reduction is the upper 10% and the lower 5%. 
     S 320  and S 330 : The operation unit  400  calculates the changed capacity by subtracting the FCC capacity from the initial capacity by the degree of SOC reduction, and calculates a new SOC according to the reduced use range. Here, the operation unit  400  calculates the changed capacity using Equation 1, and calculates the changed SOC using Equation 2. As shown in Equation 1, the modified capacity X′ may be calculated by multiplying the initial capacity X by a value obtained by subtracting 1 from the sum of the upper capacity reduction ratio A % and the lower capacity reduction ratio B %. In addition, as shown in Equation 2, the changed SOC I′ is calculated by dividing a value obtained by subtracting the lower capacity reduction ratio B % from the initial SOC I by a value obtained by subtracting the sum of the upper capacity subtraction rate A % and the lower capacity subtraction rate B % from 100%. For example, under the assumption that the maximum and minimum voltages are 4.2 V and 2.0 V, the initial SOC is 40%, and the high capacity reduction ratio A % and the low capacity reduction ratio B % are 10% and 5%, respectively, the modified capacity is calculated as 1275 mAh by Equation 1, and the modified SOC is calculated as 41% by Equation 2. 
     S 400 : The operation unit  400  calculates the SOC and the OCV according thereto depending on the calculated use voltage change, and they are stored in the memory unit  300 . That is, the newly calculated OCV table is updated and stored in the existing OCV table. At this time, the new data may be stored in the form of overwriting the existing data or may be stored as data separate from the existing data. In the new OCV table, the maximum voltage 4V set by the user is set to SOC 100%, the minimum voltage 2.4V is set to SOC 0%, and the SOC due to OCV therebetween may be calculated and stored as Equation 1. An example of this new OCV table is shown in  FIG. 4 . 
     Meanwhile, the capacity of the battery  10  whose use voltage range is changed as described above may be estimated using the SOC estimation apparatus shown in  FIGS. 7 and 8 , and the battery  10  whose use voltage range has been changed may be charged and discharged using the battery management apparatus. That is, the control unit  500  may control the charging/discharging of the battery cell by changing the set voltage of the battery cell according to the changed capacity of the battery cell. For example, when the maximum charge voltage is changed from 4.0V to 3.8V and the minimum voltage is changed to 2.5V, the control unit  500  may change the first and second set voltages and compare the data with the data of the memory cell using the operation result of the operation unit  400  or the data updated and stored in the memory unit  300 , and then, may control charging/discharging of the battery cell. That is, it is possible to control the charging and discharging of the battery cell according to the change of the maximum charging voltage and the minimum charging voltage of the battery cell, thereby preventing overcharge and overdischarge of the changed battery cell. 
     On the other hand, although the technical idea of the present invention is specifically described with reference to the above embodiments, it should be noted that the above embodiments are for the purpose of explanation and not for the purpose of limitation. It will be apparent to those skilled in the art that various modifications and variations may be made in the present invention without departing from the spirit and scope of the invention.