Abstract:
An apparatus and a method to charge a battery, the battery charging apparatus including: a battery unit which is chargeable; a battery charging unit which charges the battery unit; and a controller which adjusts a preset charge voltage of the battery unit based on a charge allowance capacity of the battery unit to have a predetermined value, and controls the battery charging unit to output the adjusted charge voltage and to charge the battery unit. Accordingly, the apparatus and method are capable of charging a battery based on a charge allowance capacity decreased owing to deterioration of the battery to safely use the battery and to extend a life of the battery.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of priority under 35 U.S.C. §119 from Korean Patent Application No. 10-2010-0071536, filed on Jul. 23, 2010 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety. 
     BACKGROUND 
     1. Field of the Invention 
     Apparatuses and methods consistent with the exemplary embodiments relate to an apparatus and a method to charge a battery, and more particularly, to an apparatus to charge a battery which adjusts a preset charge voltage and/or charge current of a chargeable battery unit based on a current charge allowance capacity of the battery unit and charges the battery unit with the adjusted charge voltage and/or charge current, and a method of charging a battery. 
     2. Description of the Related Art 
     An important issue for a portable electronic device is a life expectancy of a chargeable battery. When the battery is repeatedly charged and discharged, ions in a storage cell of the battery deteriorate to become in an unstable state, and accordingly an explosion of the battery or the like may occur. When the battery becomes deteriorated, a full charge capacity (FCC) of the battery is decreased by an amount depending on a deterioration degree. However, when the battery is charged without considering the decreased FCC, a serious accident, such as explosion of the battery, may occur, which can put people and/or other components/items at risk. 
     SUMMARY 
     Accordingly, one or more exemplary embodiments provide an apparatus and a method to charge a battery which charge the battery based on a charge allowance capacity decreased relative to the deterioration amount of the battery, to safely use the battery and to extend a life of the battery. 
     In addition, one or more exemplary embodiments provide an apparatus and a method to charge a battery which adjust a charge voltage and/or charge current output to the battery based on a charge allowance capacity decreased relative to a deterioration amount of the battery, to charge the battery with the adjusted charge voltage and/or the adjusted charge current. 
     Additional features and utilities of the present general inventive concept will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the present general inventive concept. 
     Embodiments of the present inventive concept may be achieved by providing a battery charging apparatus including: a battery unit which is chargeable; a battery charging unit which charges the battery unit; and a controller which adjusts a preset charge voltage of the battery unit based on a charge allowance capacity of the battery unit to have a predetermined value, and controls the battery charging unit to output the adjusted charge voltage and to charge the battery unit. 
     The controller may adjust a preset charge current of the battery unit based on the charge allowance capacity of the battery unit to have a predetermined value, and control the battery charging unit to output the adjusted charge current and to charge the battery unit. 
     The battery charging apparatus may further include an interface unit which communicates with the battery unit and receives information about the battery unit, and the information about the battery unit may include at least one of the preset charge current, the preset charge voltage, a preset charge capacity, and a current charge allowance capacity of the battery unit. 
     The controller may control the battery charging unit to drop the preset charge voltage of the battery unit to a predetermined value based on the charge allowance capacity of the battery unit received through the interface unit so that an adjusted charge voltage is output. 
     The controller may drop the preset charge voltage of the battery unit by a difference between the preset charge capacity and the charge allowance capacity of the battery unit to adjust the charge voltage. 
     The controller may adjust the preset charge current of the battery unit to be decreased by a half of a difference between the preset charge capacity and the charge allowance capacity of the battery unit. 
     The controller may adjust the preset charge current and the preset charge voltage of the battery unit based on the charge allowance capacity to have predetermined values when the charge allowance capacity received through the interface unit is a predetermined value or less. 
     The charge allowance capacity may be distinguished in a plurality of steps, and the preset charge current and the preset charge voltage may be adjusted to have predetermined values preset corresponding to the steps. 
     The battery charging apparatus may further include a display unit, and the controller may control the display unit to display that the battery unit needs charging when the charge allowance capacity received through the interface unit is a preset value or less. 
     The controller may control the battery charging unit to prevent the battery unit from being charged when the charge allowance capacity received through the interface unit is the preset value or less. 
     The battery charging apparatus may further include a power supply which provides power to the battery charging unit. 
     The battery unit may include a smart battery. 
     The foregoing and/or other features may also be achieved by providing a battery charging method of a battery charging apparatus, the battery charging method including: receiving information about a preset charge voltage and a charge allowance capacity from a chargeable battery unit through an interface unit; adjusting, by a controller, the preset charge voltage based on the received charge allowance capacity to have a predetermined value; and controlling a battery charging unit to output the adjusted charge voltage and charging the battery unit. 
     The battery charging method may further include: receiving information about a preset charge current from the battery unit through the interface unit; adjusting, by the controller, the preset charge current based on the received charge allowance capacity to have a predetermined value; and controlling the battery charging unit to output the adjusted charge current and charging the battery unit. 
     The adjusting the charge voltage may drop the preset charge voltage to a predetermined value based on the charge allowance capacity to adjust the charge voltage. 
     The adjusting the charge voltage may drop the preset charge voltage of the battery unit by a difference between the preset charge capacity and the charge allowance capacity of the battery unit to adjust the charge voltage. 
     The adjusting the charge current may adjust the preset charge current to be decreased by a half of a difference between the preset charge capacity and the charge allowance capacity of the battery unit. 
     The adjusting may adjust the preset charge current and the preset charge voltage based on the charge allowance capacity to have predetermined values when the charge allowance capacity is a predetermined value or less. 
     The charge allowance capacity may be distinguished in a plurality of steps, and the preset charge current and the preset charge voltage may be adjusted to have predetermined values preset corresponding to the steps. 
     The battery charging method may further include displaying, on a display unit, that the battery unit needs charging when the charge allowance capacity received from the battery unit is a preset value or less. 
     The battery charging method may further include controlling, by the controller, the battery charging unit to prevent the battery unit from being charged when the charge allowance capacity received from the battery unit is the preset value or less. 
     The battery unit may include a smart battery. 
     The foregoing and/or other features may also be achieved by providing a battery charging apparatus, including an interface unit which communicates with a battery unit to determine a chargeable state thereof, a battery charging unit which charges the battery unit, and a controller which adjusts a preset charge power of the battery unit to be in a predetermined range based on a charge allowance capacity of the battery unit and controls the battery charging unit to output the adjusted charge power and to charge the battery unit. 
     As described above, in an apparatus and a method to charge a battery according to an aspect of exemplary embodiments, since a charge allowance capacity is decreased owing to deterioration of a chargeable battery unit, a preset charge voltage and/or a preset charge current of the battery unit is adjusted based on the decreased charge allowance capacity, so that the battery unit is charged with the adjusted charge voltage and/or the adjusted charge current. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and/or other aspects will become apparent and more readily appreciated from the following description of the exemplary embodiments, taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a control block diagram of a battery charging apparatus according to an exemplary embodiment. 
         FIG. 2  is a flowchart illustrating charging control by a battery charging apparatus according to an exemplary embodiment. 
         FIG. 3  illustrates a result of adjusting a charge voltage by the battery charging apparatus according to the exemplary embodiment of  FIG. 2 . 
         FIG. 4  is a flowchart illustrating charging control by a battery charging apparatus according to another exemplary embodiment. 
         FIG. 5  illustrates a result of adjusting a charge current by the battery charging apparatus according to another exemplary embodiment. 
         FIG. 6  is a flowchart illustrating charging control by a battery charging apparatus according to still another exemplary embodiment. 
         FIG. 7  is a flowchart illustrating charging control by a battery charging apparatus according to yet another exemplary embodiment. 
         FIG. 8  illustrates a result of adjusting a charge voltage and a charge current by the battery charging apparatus according to the exemplary embodiment of  FIG. 7 . 
         FIG. 9  is a flowchart illustrating charging control by a battery charging apparatus according to yet another exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Below, exemplary embodiments will be described in detail with reference to accompanying drawings so as to be easily realized by a person having ordinary knowledge in the art. The exemplary embodiments may be embodied in various forms without being limited to the exemplary embodiments set forth herein. Descriptions of well-known parts are omitted for clarity, and like reference numerals refer to like elements throughout. 
       FIG. 1  is a control block diagram of a battery charging apparatus according to an exemplary embodiment. 
     The battery charging apparatus  100  of the present embodiment may include any kind of mobile electronic devices including a chargeable battery. For example, the battery charging apparatus  100  may include any portable electronic device including a chargeable battery which is a portable computer system, such as a laptop, a smart book, a mobile internet device (MID), and a netbook, a portable media player (PMP), a navigator, a personal digital assistant (PDA), and the like. 
     When the battery charging apparatus  100  of the present embodiment is a portable computer system, the battery charging apparatus  100  may include a central processing unit (not shown), a main memory (not shown), a memory controller hub (MCH, not shown), an I/O controller hub (ICH, not shown), a graphic controller (not shown), a display unit (not shown), and a peripheral device (not shown), which are generally included in a computer system. The CPU is a component to control an overall operation of the computer system and implements a computer program loaded in the main memory. The CPU communicates with the MCH and the ICH and controls the MCH and the ICH, respectively, when implementing the computer program. The main memory temporarily stores data associated with carrying out an operation of the CPU including computer programs implemented by the CPU. The main memory is a volatile memory and may be realized as a double data rate synchronous dynamic random access memory (DDR SDRAM), for example. The graphic controller processes graphic data to be displayed on the display unit. The peripheral device may be various types of hardware, including a hard disk drive, a flash memory, a CD-ROM, a DVD-ROM, a USB drive, a Bluetooth adaptor, a modem, a network adaptor, a sound card, a speaker, a microphone, a tablet, a touch screen, and the like. The MCH interfaces a component, such as the CPU or the like, with the main memory to read and write a data. The ICH interfaces the CPU with the peripheral device to communicate. Computer programs implemented by the CPU of the present embodiment may include BIOS, an operating system, and applications. In the present embodiment, the BIOS may be stored in a BIOS ROM (not shown), which is a nonvolatile memory, and the operating system and the applications may be installed, for example, in a hard disk drive. 
     The battery charging apparatus  100  according to the present embodiment includes a battery unit  1 , an interface unit  10 , a battery charging unit  20 , a display unit  40 , a power supply  30 , and a controller  50  to control the above components. 
     The battery unit  1  has a predetermined capacity to be charged with power and may be charged with power supplied from the power supply  30 . The chargeable battery unit  1  may include an internal battery included in the battery charging apparatus  100  or an external battery connected to the battery charging apparatus  100  outside. 
     The battery unit  1  may be a smart battery. The smart battery may include a storage cell (not shown) to be charged with power, and a circuit and a memory to identify information about and/or characteristics of the battery and to store the information and/or characteristics. 
     Here, a plurality of storage cells may be included depending on a desired charge capacity of the battery unit  1 . Here, the information about and/or characteristics of the battery may include at least one of unique identification information about the battery unit, a preset charge capacity indicating a chargeable capacity preset when the battery unit  1  is manufactured, a preset charge voltage and/or a preset charge current corresponding to the preset charge capacity, and a charge allowance capacity indicating a total charge capacity currently charged by the battery unit  1 . 
     Initially, the charge allowance capacity of the battery  1  is substantially the same as the preset charge capacity. However, when charging/discharging of the battery unit  1  is repeated, ions in the storage cell deteriorate to continually decrease the charge allowance capacity, and accordingly a life of the battery unit  1  is gradually reduced. Further, the charge allowance capacity may be changed by various factors, such as a surrounding temperature and conditions for use, in addition to a number of charging/discharging times. Thus, the charge allowance capacity of the smart battery may be measured and determined periodically to identify a state of the battery unit  1 . 
     The interface unit  10  communicates with the battery unit  1  to receive information about and/or characteristics of the battery unit  1 , such as, for example, the chargeability status of the battery unit  1 , as discussed in more detail below. The interface unit  10  requests information about the battery unit  1  from the battery unit  1  by control of the controller  50 , and receives the information about the battery unit  1  in response to the request to transmit such information to the controller  50 . 
     When the battery unit  1  is realized as a smart battery, the interface unit  10  may be provided as a control communication bus of a peripheral device of a computer, which is referred to as SMbus. 
     The battery charging unit  20  includes a charging circuit to charge the battery unit  1 . The battery charging unit  20  outputs a charge voltage and/or a charge current to the battery unit  1  by control of the controller  50  so that the battery  1  is charged with power. Hereinafter, an operation of the controller  50  will be described further. 
     The power supply  30  may provide power to a component of the battery charging apparatus  100 . The power supply  30  may further include an alternating current-direct current (AC-DC) converter (not shown) to covert common AC power input from an external source to DC power. Thus, the converted power may be supplied to the component of the battery charging apparatus  100 . 
     Further, the converted power may be provided to the battery charging unit  20  by control of the controller  50  so that the battery unit  1  can be charged. 
     The display unit  40  can display information regarding whether the battery unit  1  needs charging by control of the controller  50  when the charge allowance capacity of the battery unit  1  is in a preset value or less. The display unit  40  may be provided as one of a variety of display panels, such as a liquid crystal display (LCD). 
     The controller  50  adjusts the preset charge voltage of the battery unit  1  to be in a predetermined range based on the charge allowance capacity of the battery unit  1 , and controls the battery charging unit  20  to output the adjusted charge voltage and to charge the battery unit  1  accordingly. 
     Further, the controller  50  adjusts the preset charge current of the battery unit  1  to be in a predetermined range based on the charge allowance capacity of the battery unit  1 , and controls the battery charging unit  20  to output the adjusted charge current and to charge the battery unit  1  accordingly. 
     In addition, the controller  50  respectively adjusts the preset charge voltage and the preset charge current of the battery unit  1  to be in a predetermined range based on the charge allowance capacity of the battery unit  1 , and also controls the battery charging unit  20  to output power having the adjusted charge voltage and the adjusted charge current and to charge the battery unit  1  accordingly. 
     The controller  50  may be realized as a microcomputer in the battery charging apparatus  100 . 
     Hereinafter, a control operation of the controller  50  is described further with reference to the drawings. 
       FIG. 2  is a flowchart illustrating charging control by a battery charging apparatus according to an exemplary embodiment. 
     As shown in  FIG. 2 , the controller  50  controls the interface unit  10  to receive information about the battery unit  1  from the battery unit  1  that is connected to the battery charging apparatus  100  at operation S 11 . The information about the battery unit  1  may include at least one of unique identification information about the battery unit  1 , a preset charge capacity indicating a chargeable capacity preset when the battery unit  1  is manufactured, a preset charge voltage and/or a preset charge current corresponding to the preset charge capacity, and a charge allowance capacity indicating a total charge capacity currently charged by the battery unit  1 . 
     The controller  50  compares the preset charge capacity of the battery unit  1  with the charge allowance capacity among the information about the battery unit received through the interface unit  10 . When the charge allowance capacity is decreased as compared with the preset charge capacity, a decreased amount is calculated. Then, a charge voltage is adjusted by subtracting the decreased amount of the charge allowance capacity from the preset charge voltage received through the interface unit. 
     Here, when the charge voltage is adjusted, the controller  50  may consider a number of storage cells included in the battery unit and a voltage resolution of the storage cells. The voltage resolution of the storage cells may be various such as an 8 bit resolution, a 16 bit resolution, and the like. A resolution of the storage cells is divided into a plurality of steps, and any step of the steps corresponding to the charge allowance capacity may be considered, which is expressed by the following equation.
 
Adjusted charge voltage=preset charge voltage−(1−charge allowance capacity)×(number of storage cells/step)
 
     Thus, based on the equation of adjusting a charge voltage, the controller  50  calculates a charge voltage adjusted by substituting the charge allowance capacity and the preset charge voltage received from the interface unit  10  at operation S 12 . 
     The controller  50  controls the battery charging unit  20  to output power having the calculated charge voltage and to charge the battery unit  1  accordingly at operation S 13 . When the battery unit  1  is completely charged, the controller  50  controls the battery charging unit  20  to no longer charge the battery unit  1 , so that charging of the battery unit  1  terminates. 
     In addition to adjusting the charge voltage by the battery charging apparatus according to the embodiment as described above, the controller  50  may decrease the preset charge current received through the interface unit  10  by a predetermined range using a known method to adjust the charge current and control the battery charging unit  20  to output power having the adjusted charge current. For example, the controller  50  can adjust the received preset charge current to have 0.7 times the charge current and can control the battery charging unit  20  to output power having the adjusted charge current. 
       FIG. 3  illustrates a result of adjusting a charge voltage by the battery charging apparatus according to the present exemplary embodiment. 
       FIG. 3  shows that a charge voltage is adjusted by the battery charging apparatus according to the present embodiment, as described with reference to  FIG. 2 . 
     According to a conventional battery charging method, when charge power output from a battery charging unit is adjusted to charge a battery unit, only a preset charge current of the battery unit is adjusted, but a preset charge power value of the battery unit is not adjusted. (See the solid black curve in the graph of  FIG. 3 .) 
     However, when charge power output from the battery charging unit is adjusted to charge the battery unit by the battery charging apparatus according to the present embodiment, the preset charge voltage of the battery unit is adjusted, so that the battery unit  1  may be charged with power having the adjusted charge voltage. 
     In the graph of  FIG. 3 , an x-axis represents a percentage of the charge allowance capacity with respect to the preset charge capacity of the battery unit  1 , and a y-axis represents a charge voltage (V). In the battery charging apparatus according to this embodiment, the charge voltage is adjusted to be low as the charge allowance capacity decreases. (See the dotted gray curve in the graph of  FIG. 3 .) 
     Thus, the charge voltage may be adjusted linearly corresponding to the current charge allowance capacity of the battery unit by the battery charging apparatus according to the present embodiment. 
       FIG. 4  is a flowchart illustrating charging control by a battery charging apparatus according to another exemplary embodiment. 
     As shown in  FIG. 4 , the controller  50  controls the interface unit  10  to receive information about the battery unit  1  from the battery unit  1  connected to the battery charging apparatus at operation S 21 . The information about the battery unit  1  is described above with reference to  FIG. 2 , and thus a repeated description thereof is omitted herein for brevity. 
     The controller  50  compares the preset charge capacity of the battery unit  1  with the charge allowance capacity among the information about the battery unit  1  received through the interface unit  10 . When the charge allowance capacity is decreased as compared with the preset charge capacity, a decreased amount is calculated. Then, a charge voltage is adjusted by subtracting a half of the decreased amount of the charge allowance capacity from the preset charge current received through the interface unit, which is expressed by the following equation.
 
Adjusted charge current=preset charge current−(preset charge capacity−charge allowance capacity)/2
 
     Thus, based on the equation of adjusting a charge current, the controller  50  calculates a charge current adjusted by substituting the charge allowance capacity and the preset charge current received from the interface unit  10  at operation S 22 . 
     The controller  50  controls the battery charging unit  20  to output a power having the calculated charge current and to charge the battery unit  1  accordingly at operation S 23 . When the battery unit  1  is completely charged, the controller  50  controls the battery charging unit  20  to no longer charge the battery unit  1 , so that charging of the battery unit  1  terminates. 
     When the charge current is adjusted by the battery charging apparatus  100  according to this embodiment, as described above, the controller  50  may apply the preset charge voltage received from the interface unit  10  as it is, while adjusting the charge current, to control the battery charging unit  20  to charge the battery unit  1 . 
       FIG. 5  illustrates a result of adjusting a charge current by the battery charging apparatus according to this exemplary embodiment. 
       FIG. 5  shows that a charge current is adjusted by the battery charging apparatus according to the embodiment described with reference to  FIG. 4 . 
     According to a conventional battery charging method, when charge power output from a battery charging unit is adjusted to charge a battery unit, a preset charge current of the battery unit is adjusted to have 0.7 times the preset charge current. (See the solid black curve in the graph of  FIG. 5 .) 
     However, when the preset charge current of the battery unit is adjusted by the equation of adjusting the charge current mentioned with reference to the embodiment of  FIG. 4  by the battery charging apparatus  100 , the charge current has a lower value than the charge current adjusted by the conventional method. 
     In the graph of  FIG. 5 , an x-axis represents a percentage of the charge allowance capacity with respect to the preset charge capacity of the battery unit, and a y-axis represents a charge current (mA). In the battery charging apparatus according to the present embodiment, the charge current is adjusted to have a lower value than by the conventional method. (See the dotted gray curve in the graph of  FIG. 5 .) 
     Thus, a battery according to the present embodiment can have a longer life than by the conventional battery charging method. 
       FIG. 6  is a flowchart illustrating charging control by a battery charging apparatus according to another exemplary embodiment. 
     In the battery charging apparatus according to this embodiment of  FIG. 6 , the controller  50  adjusts the preset charge voltage and the preset charge current of the battery unit  1  based on the charge allowance capacity of the battery unit  1  using both the adjustment of the charge voltage described in the embodiment of  FIG. 2  and the adjustment of the charge current described in the embodiment of  FIG. 4 , and controls the battery charging unit  20  to output power having the adjusted charge voltage and the adjusted charge current. 
     As shown in  FIG. 6 , the controller  50  controls the interface unit  10  to receive information about the battery unit  1  from the battery unit  1  which is currently connected to the battery charging apparatus  100  at operation S 31 . The information about the battery unit  1  is described above with reference to  FIG. 2 , and thus a description thereof is omitted herein for brevity. 
     The controller  50  calculates a percentage of the charge allowance capacity with respect to the preset charge capacity of the battery unit  1  using the information about the battery unit  1  received from the interface unit  10 . Then, the controller  50  determines whether the calculated percentage of the charge allowance capacity is a predetermined value or more at operation S 32 . According to an embodiment, when the predetermined value is 80% or more, the controller  50  determines the calculated percentage of the charge allowance capacity. Then, when the calculated percentage of the charge allowance capacity is identified to be 80% or more, the controller  50  controls the battery charging unit  20  to output a power having the preset charge voltage and the preset charge current received through the interface unit  10  as they are to the battery unit  1  (operation S 33 ). 
     When the calculated percentage of the charge allowance capacity is less than 80%, the controller  50  respectively adjusts the preset charge voltage and the preset charge current of the battery unit  1  received through the interface unit  10  based on the charge allowance capacity to have a predetermined value, and controls the battery charging unit  20  to output a power having the adjusted charge voltage and the adjusted charge current. 
     According to an embodiment, the controller  50  may adjust the preset charge voltage by the equation of adjusting the charge voltage described in the embodiment of  FIG. 2  and may also adjust the preset charge current by the equation of adjusting the charge current described in the embodiment of  FIG. 4 . 
     The controller  50  controls the battery charging unit  20  to output a power having the adjusted charge voltage and the adjusted charge current and to charge the battery unit  1  accordingly at operation S 34 . When the battery unit  1  is completely charged, the controller  50  controls the battery charging unit  20  to no longer charge the battery unit  1 , so that charging of the battery unit  1  terminates. 
       FIG. 7  is a flowchart illustrating charging control by a battery charging apparatus  100  according to yet another exemplary embodiment. 
     In the charging control by the battery charging apparatus according to this embodiment as compared to the previous embodiment, the charge allowance capacity of the battery unit is different in a plurality of steps, and the preset charge voltage and the preset charge current of the battery unit  1  are adjusted to have a predetermined value preset in each step. 
     As shown in  FIG. 7 , the controller  50  controls the interface unit  10  to receive information about the battery unit  1  from the battery unit  1  which is currently connected to the battery charging apparatus  100  at operation S 41 . The information about the battery unit  1  is described above with reference to  FIG. 2 , and thus a description thereof is omitted herein for brevity. 
     The controller  50  calculates a percentage of the charge allowance capacity with respect to the preset charge capacity of the battery unit  1  using the information about the battery unit  1  received from the interface unit  10 . Then, the controller  50  determines whether the calculated percentage of the charge allowance capacity is 80% or more at operation S 42 . When the calculated percentage of the charge allowance capacity is identified to be 80% or more, the controller  50  controls the battery charging unit  20  to output a power having the preset charge voltage and the preset charge current received through the interface unit  10  as they are to the battery unit  1  (operation S 43 ). 
     When the calculated percentage of the charge allowance capacity is 60% or more and less than 80% (operation S 44 ), the controller  50  adjusts the preset charge voltage of the battery unit  1  received through the interface unit  10  by subtracting 0.05V from the preset charge voltage, adjusts the preset charge current by the equation of adjusting the charge current described in the embodiment of  FIG. 4 , and controls the battery charging unit  20  to output a power having the adjusted charge voltage and the adjusted charge current at operation S 45 . 
     When the calculated percentage of the charge allowance capacity is determined to be 60% or less (operation S 44 ), the controller  50  adjusts the preset charge voltage of the battery unit  1  received through the interface unit  10  by subtracting 0.1V from the preset charge voltage, adjusts the preset charge current by the equation of adjusting the charge current described in the embodiment of  FIG. 4 , and controls the battery charging unit  20  to output a power having the adjusted charge voltage and the adjusted charge current at operation S 46 . 
     The controller  50  controls the battery charging unit  20  to output a power having the adjusted charge voltage and the adjusted charge current and to charge the battery unit  1  accordingly. When the battery unit  1  is completely charged, the controller  50  controls the battery charging unit  20  to no longer charge the battery unit  1 , so that charging of the battery unit  1  terminates. 
     The charge allowance capacity is different in three separate sections in the present embodiment, but is not limited thereto. The charge allowance capacity may be different in several to tens of sections depending on the setting. 
       FIG. 8  illustrates a result of adjusting a charge voltage and a charge current by the battery charging apparatus according to still another exemplary embodiment. 
     In the battery charging apparatus according to this embodiment, when the charge allowance capacity of the battery unit is different in the three separate sections, the adjusted charge voltage (CV) and the adjusted charge current (CC) are seen according to a charging time in  FIG. 8 . 
     In a first step where the calculated percentage of the charge allowance capacity is 80% or more, power having the preset charge voltage and the preset charge current of the battery unit is output as they are. 
     In a second step where the calculated percentage of the charge allowance capacity is 60% or more and less than 80%, power having a charge voltage and a charge current is output, the charge voltage being adjusted by subtracting 0.05V from the preset charge voltage of the battery unit  1  and the charge current being obtained by adjusting the preset charge current of the battery unit  1  by the equation of adjusting the charge current described in the embodiment of  FIG. 4 . 
     In a third step where the calculated percentage of the charge allowance capacity is less than 60%, power having a charge voltage and a charge current is output, the charge voltage being adjusted by subtracting 0.1V from the preset charge voltage of the battery unit and the charge current being obtained by adjusting the preset charge current of the battery unit by the equation of adjusting the charge current described in the embodiment of  FIG. 4 . 
     In the embodiments of  FIG. 2  and  FIG. 4 , the charge voltage or the charge current adjusted based on the charge allowance capacity of the battery  1  is calculated, and as a result, the controller  50  may have a heavy load. Thus, in the present embodiment, the percentage of the charge allowance capacity of the battery unit is different in a plurality of sections, and a charge voltage is preset corresponding to a section, and thus the controller  50  may have fewer loads in calculation than in the embodiments of  FIGS. 2 and 4 . 
       FIG. 9  is a flowchart illustrating charging control by a battery charging apparatus according to yet another exemplary embodiment. 
     When the battery unit  1  which is completely discharged is to be charged, the charge allowance capacity decreases substantially, and thus full charging becomes small. 
     Thus, in the battery charging apparatus according to this embodiment, when the charge allowance capacity of the battery unit  1  is a preset value or less, the controller  50  may control the display unit  40  to display that charging is needed in order to warn a user, or control the battery charging unit  20  so that the battery unit  1  is minimally charged. 
     As shown in  FIG. 9 , the controller  50  controls the interface unit  10  to receive information about the battery unit  1  from the battery unit  1  connected to the battery charging apparatus at operation S 51 . The information about the battery unit  1  is described above with reference to  FIG. 2 , and thus description thereof is omitted herein. 
     The controller  50  calculates a percentage of the charge allowance capacity with respect to the preset charge capacity of the battery unit  1  using the information about the battery unit  1  received from the interface unit  10 . Then, the controller  50  determines whether the calculated percentage of the charge allowance capacity is 10% or more at operation S 52 . When the calculated percentage of the charge allowance capacity is identified to be 10% or more, the controller  50  adjusts the preset charge voltage of the battery unit  1  received through the interface unit  10  by the equation of adjusting the charge voltage described in the embodiment of  FIG. 2 , adjusts the preset charge current by the equation of adjusting the charge current described in the embodiment of  FIG. 4 , and controls the battery charging unit  20  to output power having the adjusted charge voltage and the adjusted charge current at operation S 53 . 
     When the calculated percentage of the charge allowance capacity is less than 10%, the controller  50  controls the display unit  40  to display that charging is needed in order to warn the user at operation S 54 . 
     Alternatively, when information that the battery unit  1  is no longer of any use is received from the interface unit  10 , the controller  50  controls the display unit  40  to display that the battery unit  1  needs replacing in order to warn the user. 
     In the present embodiment, the display unit  40  may be realized as a light emitting diode (LED) generally disposed around a keyboard of a personal computer (PC) or a touch pad and displaying a state of the battery unit  1  to be charged or not when the battery charging apparatus  100  is provided as the portable PC. Alternatively, the display unit  40  may be realized as a display screen of the portable PC to display a user interface (UI) indicating whether the battery unit  1  needs charging or replacing, the UI being generated by a UI generation unit (not shown) by control of the controller  50 . 
     When the battery unit  1  is compulsorily charged to a point in which a full charge capacity is limited substantially, explosion or deformation of the battery unit may occur. In this case, charging the battery unit  1  may be prevented. 
     Thus, when the calculated percentage of the charge allowance capacity is identified to be 10% or less, the controller  50  adjusts the preset charge voltage and the preset charge current of the battery unit  1  received through the interface unit  10  nearly to 0 and controls the battery charging unit  20  to output having the adjusted charge voltage and the adjusted charge current, thereby preventing the battery unit from being charged at operation S 54 . 
     Although a few exemplary embodiments have been shown and described, it will be appreciated by those skilled in the art that changes may be made in these exemplary embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.