Abstract:
In order to diagnose the fail possibility and to compensate a charging state of a battery of an electric vehicle, by detecting an operating state of a battery while driving a vehicle that is equipped with a rechargeable battery, the present invention provides a method for controlling the charging state of a battery.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
         [0001]    This application claims priority of Korea patent Application No. 2000-86946, filed on Dec. 30, 2000.  
         BACKGROUND OF THE INVENTION  
         [0002]    (a) Field of the Invention  
           [0003]    The present invention relates to a method for controlling a charging state of a battery for an electric vehicle, and more particularly to a method for controlling a charging state of a battery of an electric vehicle for diagnosing a fail possibility and for compensating a charging state of the battery, by detecting an operating state of the battery while driving a vehicle that is equipped with a rechargeable battery.  
           [0004]    (b) Description of the Related Art  
           [0005]    Generally, an electric vehicle and a hybrid electric vehicle are provided with a rechargeable battery that is to be repeatedly charged and discharged. Therefore, the term “electric vehicle” is hereinafter used to include any kind of vehicle using a battery as a driving power source, such as a hybrid electric vehicle and a fuel-cell electric vehicle.  
           [0006]    [0006]FIG. 1 illustrates a schematic block diagram of an electric vehicle.  
           [0007]    As shown in FIG. 1, an engine  14  generates driving power by using fuel, and the driving power revolves a generator  15 . The generator  15  converts the revolution power of the engine to electric power, a battery  11  is charged by the electric power, and a motor  13  is driven.  
           [0008]    The electric power generated by the generator  15  is charged into the battery after being converted into direct current through a rectifier. The electric power that is generated by the generator  15  or that is outputted by discharge of the battery, is delivered to the motor  13  based on control of a motor controller  12 , and the vehicle is driven by the rotary power of the motor that is delivered to wheels through a power transmission gear.  
           [0009]    A controller  16  detects a state of the motor  13 , battery  11  and engine  14 , and controls an operating state of the motor controller  12  and generator  15  based on a predetermined pattern.  
           [0010]    The controller  16  performs an error decision of the battery when a battery voltage is more than a predetermined critical value or less than another predetermined critical value while charging or discharging.  
           [0011]    Furthermore, the controller  16  determines a battery failure when a voltage difference between a particular battery module and the average voltage of all battery modules exceeds a predetermined value, while charging and discharging.  
           [0012]    However, as described above, since the prior art does not determine a battery state but determines only whether the battery is in a normal state or not, it is impossible to compensate for a faulty battery and to determine a cause thereof.  
         SUMMARY OF THE INVENTION  
         [0013]    It is an objective of the present invention to provide a method for controlling a charging state, for diagnosing a failure possibility and for compensating for a charging state of a faulty battery of an electric vehicle by detecting an operating state of the battery while driving a vehicle that is equipped with a rechargeable battery.  
           [0014]    To achieve the above objective, the present invention provides a method for controlling the charging state of a battery of an electric vehicle, the electric vehicle being a vehicle using a battery as a driving power source, the method comprising:  
           [0015]    collecting data of the charging state of each battery module and individually storing the collected data by control means, during a charging mode of the battery of a vehicle that is equipped with a rechargeable battery;  
           [0016]    collecting data of a charging state of each battery module and individually storing the collected data by control means, in a driving mode of the vehicle; and  
           [0017]    being controlled by the controls means, wherein the control step comprises:  
           [0018]    detecting a data row allotted to each module from storage,  
           [0019]    displaying “a high state” for a battery charging state at a predetermined area of the data row corresponding to a battery module having a high voltage in driving mode and in charging mode;  
           [0020]    displaying “a normal or good state” for a battery charging state at the predetermined range of the data row corresponding to a battery module having a high voltage in driving mode and a low voltage in charging mode;  
           [0021]    displaying “a low state” for a battery charging state at the predetermined range of the data row corresponding to a battery module having a low voltage in driving mode and in charging mode, and overcharging the corresponding battery by a predetermined value during the next charging; and  
           [0022]    displaying “a fail possibility state” for a battery charging state at the predetermined range of the data row corresponding to a battery module having a low voltage in driving mode and a high voltage in charging mode, and warning of maintenance service of the corresponding battery during the next charging or discharging. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]    The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate an embodiment of the invention, and, together with the description, serve to explain the principles of the invention:  
         [0024]    [0024]FIG. 1 illustrates a schematic block diagram of a general hybrid electric vehicle;  
         [0025]    [0025]FIG. 2 illustrates a flowchart of a method for controlling a charging state of a battery of an electric vehicle according to a preferred embodiment of the present invention;  
         [0026]    [0026]FIG. 3 illustrates a flowchart of a data-collecting step in a charging mode of FIG. 2;  
         [0027]    [0027]FIG. 4 illustrates a view of a data row of each battery module;  
         [0028]    [0028]FIG. 5 illustrates a flowchart of a data-collecting step in driving mode of FIG. 2; and  
         [0029]    [0029]FIG. 6 illustrates a flowchart of an analysis/compensation step by using data of a charging and discharging mode of FIG. 2. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0030]    A preferred embodiment of the present invention will hereinafter be described in detail with reference to the accompanying drawings.  
         [0031]    The term “electric vehicle” used hereinafter includes any kind of vehicle using a battery as a driving power source, such as a hybrid electric vehicle and a fuel-cell electric vehicle.As shown in FIG. 2, a control means collects data of the battery during a charging mode at step ST 20 .  
         [0032]    As shown in FIG. 3, in such a charging mode, a data-collecting step of a battery state initiates a variable Vm for storing the voltage value of each battery module (Vm=0), and sets a critical value (Vs) of an allowable charging voltage difference between the battery modules while charging, at step ST 21 .  
         [0033]    Furthermore, the control means organizes a data row for detecting a module state of each battery, and stores the organized data row in storage, for example in a memory.  
         [0034]    As shown in FIG. 4, each data row includes a module number column, a voltage value column, a count column, a high voltage/low voltage column and a battery state column.  
         [0035]    Cells in the module number column are individually allotted to each battery module within the battery, and cells in the voltage value column are individually used for displaying the detected voltage value of the corresponding battery module. The high/low voltage column is used for designating high or low values of the corresponding module voltage, and the battery state column is used for designating an error capability of a battery.  
         [0036]    Next, the control means control to perform normal charging on the basis of a charge mode of the battery. Preferably, a normal charge state includes three charge modes, for example, an FP charge mode for charging at the maximum electric power, a CC1 charge mode for charging at a first predetermined current value, and a CC2 charge mode for charging at a second predetermined current. This is shown as steps ST  22  to ST 24 .  
         [0037]    If the charge is performed on the basis of the predetermined charge mode, the control means reads voltage values of each module of the total N modules, and stores them individually in a V [N−1] matrix at step ST 25 .  
         [0038]    Next, the control means sums each voltage value stored in the V [N−1] matrix, calculates an average voltage value of the battery modules by dividing the sum by the number of battery modules, N, and renews the variable Vm as the calculated average voltage value at step ST 26 .  
         [0039]    When the average voltage value is calculated, the control means determines whether there is a battery module having a voltage greater than Vm+Vs. If a battery module having a voltage greater than Vm+Vs is detected, the control means adds 1 to the value of the count column of a data cell of the corresponding module, and displays “a high voltage” in the high/low voltage column at step ST 27 .  
         [0040]    Moreover, the control means determines whether there is a battery module having a voltage lower than Vm−Vs, and if so the control means adds 1 to the value of the count column of a data cell of the corresponding module, and displays “a low voltage” in the high/low voltage column at step ST 28 .  
         [0041]    The control means then determines whether charging is completed, at step ST 29 .  
         [0042]    If charging is not completed at step ST 29 , the method returns to step ST 25  after waiting for a predetermined time. Preferably, the waiting time is set as one minute, at step ST 30 .  
         [0043]    Furthermore, if the charge of the battery is completed at step ST 29 , the control means reads data of each battery module, and stores the data of three detected modules of which the count column value is high and also the high/low voltage column is displayed as high or low voltage, at step ST 31 .  
         [0044]    As described above, a data-collecting step in the charge mode is performed.  
         [0045]    Next, as shown in FIG. 2, the control means collects data in driving mode at step ST 40 , while the vehicle is driven.  
         [0046]    As shown in FIG. 5, in the data-collecting step in driving mode, the control means organizes a data row for each module, and initiates the variable Vm for storing an average voltage value, and sets a critical value Vd of the allowable discharge voltage difference between the modules in discharge of the battery at step ST 41 .  
         [0047]    Moreover, the control means measures a discharge electric current value I of a battery at step ST 42 , and it determines whether the measured discharge electric current value I falls within the predetermined critical value at step ST 43 .  
         [0048]    The control means may start data collection in the same state as in a discharge capacity test of a battery in order to minimize the voltage difference based on the internal resistance of the battery, by determining whether the measured discharge electric current value falls within the predetermined critical value. Preferably, a lower limit of the discharge electric current critical range is set as the predetermined value −10%, and an upper limit is set as the predetermined value +10%.  
         [0049]    If the detected discharge electric current I does not fall within the discharge electric current critical range, the control means determines whether a starting key is at an on state. If a starting key is at an on state, the control means controls step ST 43  to return to step ST 42  at step ST 44 .  
         [0050]    If the detected discharge electric current value I falls within the discharge electric current critical range at step ST 43 , the control means reads a voltage value of each module of the total N modules, and individually stores them in a V [N−1] matrix at step ST 45 .  
         [0051]    Next, the control means calculates an average voltage value Vm by respectively using the voltage values stored in the V [N−1] matrix at step ST 46 .  
         [0052]    After the average voltage value Vm is calculated at step ST 46 , the control means determines whether there is a battery module having a voltage greater than Vm+Vs. If a battery module having a voltage greater than Vm+Vs is detected, the control means adds 1 to the value of the count cell of the corresponding module, and displays “a high voltage” in the high/low voltage cell at step ST 47 .  
         [0053]    Moreover, if a battery module having a voltage lower than Vm−Vs is detected, the control means controls to add 1 to the value of the count cell of the corresponding module, and displays “a low voltage” in the high/low voltage column at step ST 48 .  
         [0054]    The control means then determines whether a starting key is at an on state by detecting a received signal from an ignition switch at step ST 49 . If the starting key is at an on state at step ST 49 , the control means controls for step ST 49  to return to step ST 42 .  
         [0055]    On the contrary, if the starting key is at an off state at step ST 44  or step ST 49 , the control means reads data of each battery module, and stores the data of three detected modules of which the count column value is relatively high, and the high/low voltage column is displayed as high or low voltage, at step ST 50 .  
         [0056]    As described above, the data-collecting step in the driving mode is performed.  
         [0057]    Referring to FIG. 2, after the data about the battery state in the charging mode and driving mode of the vehicle are collected, an analysis and compensation thereof is performed by using the collected data in the charging and discharging mode of the battery at step ST 60 .  
         [0058]    Referring to FIG. 6, in the analysis and compensation step, the control means reads all data cells allotted to each battery module from the storage at step ST 61 .  
         [0059]    Next, the control means determines whether there is a battery module having a high voltage in the driving mode and also in the charging mode, at step ST 62 .  
         [0060]    If the battery module satisfies the condition of step ST 62 , the control means controls to display “a high state” for a battery charging state (SOC) at the battery state column within the data cell of the corresponding module at step ST 63 .  
         [0061]    If the battery charging state is displayed as the high state as described above, it means that a charging state of the corresponding battery is extremely good or normal. Therefore, in this case compensation control is not performed separately.  
         [0062]    If the battery module does not satisfy the condition of step ST 62 , or if step ST 63  is completed, the control means determines whether there is a battery module having a high voltage at the driving mode and a low voltage at the charging mode, by reading all data cells of each battery module, at step ST 64 .  
         [0063]    Then, if the battery module satisfies the condition of step ST 64 , the control means controls to display “a good or normal state” for a battery charging state at the battery state column within the data cell of the corresponding module at step ST 65 .  
         [0064]    Moreover, if the battery module does not satisfy the condition of step ST 64 , or if step ST 64  is completed, the control means determines whether there is a battery module having a low voltage at the driving mode and a low voltage at the charging mode, by reading all data cells of each battery module, at step ST 66 .  
         [0065]    If the battery module satisfies the condition of step ST 66 , the control means controls to display “a low state” for a battery charging state at the battery state column within the data cell of the corresponding module at step ST 67 .  
         [0066]    The control means then suitably allows charging and compensating of the battery displaying “a low state” when in charging mode thereafter, and it preferably may compensate for the low charging state of the battery by overcharging it by a predetermined value at step ST 68 .  
         [0067]    Moreover, if the battery module does not satisfy the condition of step ST 66 , or if step ST 66  is completed, the control means determines whether there is a battery module having a low voltage at the driving mode and a high voltage at the charging mode, by reading all data cells of each battery module, at step ST 69 .  
         [0068]    If the battery module satisfies the condition of step ST 69 , the control means controls to display “a high impedance” for a battery charging state at the battery state column within the data cell of the corresponding module at step ST 70 .  
         [0069]    In this case, since the corresponding battery is under-performing and has a fail possibility, the control means controls to warn a user of the fail possibility at step ST 71 , in the next instance of when the starting key is in the on state or the battery enters into the charging mode.  
         [0070]    As described above, the present invention detects and stores data about a battery state, before determining whether a state of the battery is normal or not. Therefore, the present invention results in increasing a driving distance of a vehicle and preventing acceleration performance from declining thereafter, by suitably compensating for a state of the battery on the basis of the data of the battery state.  
         [0071]    For example, in the case of fail possibility of the battery, the present invention can compensate a charging state of the battery by using a charger.  
         [0072]    Moreover, the present invention results in preventing an increase in maintenance costs and a repair of a driving impossibility state, because it informs the user to check the corresponding battery, by displaying a fail possibility lamp before a battery failure occurs.  
         [0073]    While this invention is described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the sprit and scope of the appended claims.