Patent Publication Number: US-2004059527-A1

Title: Electric appliance, computer apparatus, intelligent battery, battery diagnosis method, program, and storage medium

Description:
BACKGROUND OF THE INVENTION  
       [0001] The present invention relates to an electric appliance having a battery which can be used while being repeatedly charged and discharged and, more particularly, to an electric appliance designed so that a battery is suitably refreshed.  
       [0002] Various electric appliances, e.g., information terminal devices, typified by a notebook type personal computer (notebook PC), Personal Digital Assistants (PDA), MiniDisc (MD) devices, and video cameras are supplied with utility power or power from batteries (storage batteries, secondary batteries) each capable of being used a number of times while being repeatedly charged and discharged. As such batteries, nickel-hydrogen batteries and nickel-cadmium batteries (nicad batteries) having a comparatively large capacity and low-priced are used. Lithium-ion batteries having an energy density per unit weight higher than that of nickel-cadmium batteries, lithium polymer batteries using a solid-state polymer without using a liquid electrolyte, etc., also exist.  
       [0003] In nickel-hydrogen batteries and nickel-cadmium batteries, if incomplete discharge and charge are repeatedly performed by stopping discharge halfway, a memory effect occurs such that the apparent charge capacity is reduced and the time during which the battery can be continuously used is shortened. It is known that the capacity of the battery reduced by such a memory effect can be restored fairly close to the full capacity by repeating adequate discharge and charge two or three times. Thus, even in a case where a memory effect occurs in a battery, the battery can recover after being adequately charged and discharged. However, it is necessary to perform detection of the memory effect as a precondition for the battery recovery operation.  
       [0004] In a memory effect detection method presently known, e.g., one adopted for BQ2060 from Texas Instruments Inc. (formerly Benchmarq), the number of times shallow discharge is repeated is counted and a memory effect is assumed to occur in correspondence with a shallow discharge detection count of, for example, 30.  
       [0005] The above-described method, however, entails a drawback in that a condition not to be considered a memory effect may be recognized as a memory effect since the recognition is based only on the number of counts of incomplete discharge, and that there is also a possibility of failure to detect an actual memory effect. Moreover, there are many users who are so anxious about a memory effect as to frequently perform refreshment. It is possible to limit occurrence of a memory effect by frequently performing the refreshing operation, but an adverse effect on the battery life is thereby caused.  
       [0006] On the other hand, if a battery is left detached from a system for a long time or if the system is not used during a long time while the battery is connected to the system, an error in the remaining capacity of the battery due to self discharge becomes considerably large. If such a capacity error exists, an accurate indication of the remaining capacity cannot be given to a user and there is a need to improve the accuracy of the remaining capacity by minimizing the capacity error. Refreshment of the battery whose remaining capacity is to be indicated is effective in minimizing the capacity error. However, it is difficult to adapt the conventional method of refreshment based on the number of counts of repeated shallow discharge to refreshment for reducing a capacity error.  
       [0007] The present invention has been achieved to solve the above-described technical problems and an object of the present invention is to guide a user in use of a battery so that the user can perform properly timed refreshment of the battery.  
       [0008] Another object the present invention is to enable the remaining capacity of a battery to be accurately grasped.  
       SUMMARY OF THE INVENTION  
       [0009] To attain the above-described problems, the present invention provides an electric appliance which is arranged so that a rechargeable battery can be connected thereto, and which has a main unit supplied with electric power from the battery, the appliance including identifier recognition means for recognizing an identifier for identification of the battery, information storage means for storing information on the date of execution of refreshment of the battery by relating the information to the identifier recognized by the identifier recognition means, output means for urging a user to execute refreshment of the battery after a lapse of a predetermined time period from the date indicated by the information stored in the information storage means, instruction receiving means for receiving a refreshment instruction from a user, and refreshment execution means for executing refreshment of the battery on the basis of the refreshment instruction received by the instruction receiving means.  
       [0010] An electronic appliance to which the present invention is applied may be arranged as an appliance characterized by having a main unit which consumes electric power, and a battery which supplies electric power to the main unit by being charged and discharged, wherein an error in the remaining capacity of the battery due to self discharge is predicted and guidance on refreshment is performed to remove the error.  
       [0011] The main unit may be specially arranged to perform refreshment guidance in a case where the battery is not refreshed during a predetermined period. Advantageously, an error-free indication of the remaining capacity can be given to a user in a certain cycle by doing so.  
       [0012] The electric appliance to which the present invention is applied is characterized in that a display for demanding refreshment is produced after a lapse of a predetermined time period from the last execution of refreshment of the battery regardless of the number of counts of charge and discharge of the battery.  
       [0013] Further, the electric appliance to which the present invention is applied is characterized by having date information storage means for storing information on the date of the last execution of refreshment of the battery, and determination means for making a determination as to necessity to perform refreshment, the determination means determining that there is a need for refreshment after a lapse of a predetermined time period from the date indicated by the information stored in the date information storage means.  
       [0014] In another aspect, the present invention provides a computer apparatus which is arranged so that a rechargeable battery can be connected thereto, and which has a system main unit supplied with electric power from an AC adapter connected to a commercial power supply and/or from the battery, the computer apparatus characterized by having a CPU for executing a program for diagnosis of the battery, a controller which receives from the battery an identifier for identification of the battery, and which outputs the received identifier to the CPU, an information file in which, for example, information on the dates of refreshment of a plurality of batteries is stored, and an AC adapter power stop circuit which supplies/stops electric power from the AC adapter to the system main unit under the control of the controller, wherein the CPU makes a determination as to necessity to perform refreshment by obtaining the date information corresponding to the identifier output from the controller, and the controller stops supply of electric power from the AC adapter to the system main unit by controlling the AC adapter power stop circuit on the basis of a refreshment instruction from the CPU.  
       [0015] Also, the computer apparatus to which the present invention is applied is characterized by having a memory for storing date information on the date of the last execution of refreshment of the battery, and display means for producing a display for recommending a user to perform refreshment in a case where refreshment of the battery is not performed during a predetermined time period after the date indicated by the date information stored in the memory.  
       [0016] The present invention may also be grasped as an intelligent battery connected to an electric appliance and charged and discharged to supply electric power to the electric appliance. This intelligent battery is characterized by having date information storage means for storing information on the date of refreshment, determination means for making a determination as to necessity to perform refreshment, the determination means determining that there is a need for refreshment after a lapse of a predetermined time period from the date indicated by the information stored in the date information storage means, and output means for outputting the result of determination made by the determination means to a controller of the electric appliance.  
       [0017] The present invention may also be grasped as a program for realizing predetermined functions in a computer to which a battery charged and discharged to supply electric power to a main unit can be connected, and as a storage medium on which such a program is stored. The program is characterized by realizing, in the computer, a function for reading out, from a predetermined memory, information on the date of refreshment of the battery, a function for determining that there is a need for refreshment of the battery in a case where a predetermined time period has elapsed from the date indicated by the information read out, a function for producing an output for urging a user to perform refreshment, a function for receiving a refreshment instruction from the user, and a function for storing information on the date of newly performed refreshment in the memory.  
       [0018] The program may comprise one stored in a computer memory or the like to realize the above-described functions. A similar program may be stored in a storage medium formed so as to be readable by the computer. A method for providing such programs may be such that, for example, a program stored on a storage medium such as a CD-ROM is read by a storage medium reading unit, e.g., a CD-ROM drive. Also, such programs may be installed in computers from a program transfer apparatus through a network, e.g., the Internet. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
     [0019]FIG. 1 is a diagram showing a hardware configuration of a computer system to which the present invention is applied;  
     [0020]FIG. 2 is a diagram showing a circuit configuration of a power supply system;  
     [0021]FIG. 3 is a diagram showing processings under a battery diagnosis program (utility program) for determination as to necessity to perform refreshment;  
     [0022]FIG. 4 is a flowchart showing an example of a process of performing a refreshment guidance function in accordance with the present invention;  
     [0023]FIG. 5 is a flowchart showing an example of detection of occurrence of a memory effect in an intelligent battery; and  
     [0024]FIG. 6 is a diagram showing an example of an on-screen display for guiding a user in executing refreshment. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
     [0025] The present invention will be described in detail with respect a preferred embodiment thereof with reference to the accompanying drawings.  
     [0026]FIG. 1 is a diagram showing a hardware configuration of a computer system  10  to which the present invention is applied. A computer apparatus having the computer system  10  is configured as a notebook-type personal computer (notebook PC) on which a predetermined operating system (OS) in accordance with the Open Architecture Developer&#39;s Group (OADG) specifications.  
     [0027] In the computer system  10  shown in FIG. 1, a CPU  11  functions like brains to control the entire computer system  10 , and executes a utility program and various programs under the control of the OS. The CPU  11  are connected to other components of the system by buses in three stages: a front side bus (FSB)  12  provided as a system bus, a Peripheral Component Interconnect (PCI) bus  20  provided as a high-speed I/O bus, and an Industry Standard Architecture (ISA) bus  40  provided as a low-speed I/O bus. To increase the processing speed of the CPU  11 , program codes and data are stored in a cache memory. A memory configuration recently used is such that a SRAM of about 128 Kbytes is incorporated as a primary cache in the CPU  11  and a secondary cache  14  of about 512 K to 2 M bytes is connected to the CPU  11  by a dedicated bus, shown as a back side bus (BSB)  13 , to compensate for a deficiency of capacity. A method of reducing the number of terminals of the CPU package by removing the BSB  13  and connecting the secondary cache  14  to the FSB  12  may be used to reduce the cost of the system.  
     [0028] The FSB  12  and the PCI bus  20  are connected by a CPU bridge (host-PCI bridge)  15  called a memory/PCI chip. The CPU bridge  15  has a memory controller function for controlling the operation for access to the main memory  16  and includes a data buffer for absorbing the difference between the data transfer speeds of the FSB  12  and the PCI bus  20 . The main memory  16  is a writable memory used as an area to which a program executed by the CPU  11  is read or a work area to which data processed under an executed program is written. For example, the main memory  16  is constituted by a plurality of DRAM chips, has a capacity of 64 MB in standard form, and is expandable to 320 MB. Programs executed by the CPU  11  include the OS, various drivers for hardware operations of peripheral devices, application programs intended for particular tasks, and firmware such as a basic input/output system (BIOS) stored in a flash ROM  44  described below.  
     [0029] A video subsystem  17  is a subsystem for realizing video functions. The video subsystem  17  includes a video controller which executes a drawing instruction from the CPU  11 , writes processed drawing information to a video memory, reads out this drawing information from the memory, and outputs this information as drawing data to a liquid crystal display (LCD)  18 .  
     [0030] The PCI bus  20  is a bus capable of transferring data at a comparatively high rate. The PCI bus  20  is standardized by specifications such that the data bus width is 32 bits or 64 bits, the maximum operating frequency is 33 MHz or 66 MHz, and the maximum data transfer rate is 132 MB/sec or 528 MB/sec. To the PCI bus  20  are respectively connected an I/O bridge  21 , a card bus controller  22 , an audio subsystem  25 , a docking station interface (Dock I/F)  26 , and a mini PCI connector  27 .  
     [0031] The card bus controller  22  is a special controller for direct connection of bus signals from the PCI bus  20  to an interface connector (card bus) in a card bus slot  23 . A PC card  24  can be inserted in the card bus slot  23 . The docking station interface  26  is a piece of hardware for connection of a docking station (not shown) which is a unit for function expansion of the computer system  10 . When the notebook PC is set on the docking station, various hardware units connected to an internal bus of the docking station are connected to the PCI bus  20  through the docking station interface  26 . A mini PCI (mini PCI) card  28  is connected to the mini PCI connector  27 .  
     [0032] The I/O bridge  21  has a function of bridging between the PCI bus  20  and the ISA bus  40 . The I/O bridge  21  also has a DMA controller function, a programmable interrupt controller (PIC) function, a programmable interval timer (PIT) function, an integrated device electronics (IDE) interface function, a universal serial bus (USB) function, and a system management bus (SMB) interface function. Also, the I/O bridge  21  incorporates a real-time clock (RTC).  
     [0033] The DMA controller function is a function for executing data transfer between the main memory  16  and a peripheral device such as a FDD without intervention of the CPU  11 . The PIC function is a function for executing a predetermined program (interrupt handler) in response to an interrupt request from a peripheral device. The PIT function is a function for generating a timer signal in a predetermined cycle. To the interface realized by the IDE interface function, an IDE hard disk drive (HDD)  31  is connected and a CD-ROM drive  32  is also connected by the AT attachment packet interface (ATAPI). A different type of IDE device such as a digital versatile disc (DVD) drive may be connected in place of the CD-ROM drive  32 . Each of the HDD  31 , the CD-ROM drive  32  and other external storage devices is accommodated in an accommodation section called a “media bay” or “device bay” in the body of the notebook PC. These external storage devices provided as standard accessories may be attached exclusively and interchangeably with other devices such as a FDD and a battery pack.  
     [0034] A USB port is provided in the I/O bridge  21 . This USB port is connected to a USB connector  30  provided, for example, in a wall portion of the body of the notebook PC. To the I/O bridge  21  is further connected to an EEPROM  33  for storing information such as password or supervisor password registered by a user, a product serial number, etc. The EEPROM  33  is a nonvolatile memory capable of electrically rewriting contents stored therein.  
     [0035] Further, the I/O bridge  21  is connected to a power supply circuit  50 , which includes an AC adapter  51  for AC/DC conversion connected to, for example, a commercial power supply of AC 100 V, an intelligent battery  52  (secondary battery), a battery switching circuit  54  for charging the intelligent battery  52  and for switching power supply lines from the AC adapter  51  and the intelligent battery  52 , and a DC/DC converter (DC/DC)  55  for producing constant DC voltages of, for example, +15 V, +5 V, and +3.3 V used in the computer system  10 .  
     [0036] On the other hand, in a core chip constituting the I/O bridge  21  are provided an internal register for management of the state of power supply in the computer system  10 , and a logic (state machine) for management of the state of power supply in the computer system  10  including the operation of this internal register. This logic exchanges various signals with the power supply circuit  50  and recognizes, from this signal exchange, the actual state of power supply from the power supply circuit  50 . The power supply circuit  50  controls supply of electric power to the computer system  10  in accordance with instructions from the logic.  
     [0037] ISA bus  40  is a bus of a transfer rate lower than that of the PCI bus  20  (the ISA bus  40  having a bus width of 16 bits and a maximum data transfer rate of 4 MB/sec, for example). To the ISA bus  40  are connected an embedded controller  41  connected to a gate array logic  42 , a CMOS  43 , the flash ROM  44 , and a super I/O controller  45 . The ISA bus  40  is also used to connect a peripheral device such as a keyboard/mouse controller having comparatively low operating speed. An I/O port  46  is connected to the super I/O controller  45  to control drive of an FDD, parallel data input/output (PIO) through a parallel port, and serial data I/O (SIO) through a serial port.  
     [0038] The embedded controller  41  controls a keyboard (not shown). The embedded controller  41  is connected together with the gate array logic  42  to the power supply circuit  50  to perform some of power management control functions by an incorporated power management controller (PMC).  
     [0039] Next a power supply system which characterizes this embodiment will now be described.  
     [0040]FIG. 2 is a diagram showing a circuit configuration of a power supply system to which the present invention is applied. This power supply system is formed by adding the embedded controller  41 , an AC adapter power stop circuit  80 , etc., to the power supply circuit shown in FIG. 1.  
     [0041] The power supply system shown in FIG. 2 includes the AC adapter  51 , which is a power supply unit connected to a commercial power supply, and the intelligent battery  52 , which is a secondary battery system constituted by a nickel-hydrogen battery, a nickel-cadmium battery or the like used by being repeatedly charged and discharged, and which is in conformity with the Smart Battery System (SBS). Power from the AC adapter  51  and the intelligent battery  52  is output to the main-unit system circuit in the computer system  10  via the DC/DC converter shown in FIG. 1.  
     [0042] The power supply system shown in FIG. 2 has, on the main-unit system side, the embedded controller  41 , which communicates with the intelligent battery  52  over a communication line  74 , a voltage measuring circuit  75 , which measures a voltage at the time of excessive discharge and notifies the embedded controller  41  of the measured voltage, and a battery connection check terminal  76  for checking whether the intelligent battery  52  is connected at the time of excessive discharge. The power supply system also has the AC adapter power stop circuit  80 , which stops supply of power from the AC adapter  51  to the main-unit system on the basis of an instruction from the embedded controller  41  to refresh the intelligent battery  52 , and first and second diodes (D 1 )  77  and (D 2 )  78 , which rectify a current from the AC adapter  51  and a current from the intelligent battery  52 , respectively, to avoid conflict between power supply from the AC adapter  51  and power supply from the intelligent battery  52 .  
     [0043] The AC adapter  51 , which is a power supply unit, is ordinarily provided outside the body of an appliance, e.g., the notebook PC incorporating the main-unit (internal) system, i.e., the computer system  10 . In some case, however, it is provided inside the body of an electric appliance. The main-unit system may be configured so as to have an AC inlet or a DC inlet into which a cable connector, for example, is detachably inserted. The AC inlet or a DC inlet is formed so that, if the AC adapter  51  is provided outside, a connector projecting from a cable connected to the AC adapter is detachably inserted and, if the AC adapter  51  is provided inside the main-unit system, a connector directly connected from a commercial power supply is detachably inserted. The intelligent battery  52  is may be of a type such as to be detachable as a battery pack from the main-unit system or may be provided inside the body of the electric appliance.  
     [0044] An internal configuration of the intelligent battery  52  will next be described. As shown in FIG. 2, the intelligent battery  52  has a group of single cells  61  each capable of being charged and discharged, a CPU  62  which controls intelligent battery  52  and communicates with the embedded controller  41  over the communication line  74 , a current measuring circuit  63  for measuring the value of a charging or discharging current through the intelligent battery  52 , a voltage measuring circuit  70  for measuring the voltage across the group of cells  61 , and a temperature measuring circuit  90  for measuring the temperature of the cells  61 . The cells  61  are, for example, six nickel-hydrogen or nickel-cadmium battery cells: three in series in each of two parallel rows (1.8 Ah/cell).  
     [0045] The CPU  62  incorporated in this intelligent battery  52  perform analog to digital (A/D) conversion of analog signals supplied as measuring results from the current measuring circuit  63 , the voltage measuring circuit  70  and the temperature measuring circuit  90  to grasp information on the battery, e.g., information on the capacity of the battery. It also stores information on an identifier (serial number) of the battery. The grasped information on the battery and the serial number is transmitted to the embedded controller  41  on the system side over the communication path, i.e., the communication line  74  by using, for example, the SBS protocol.  
     [0046] In the current measuring circuit  63 , a potential difference is first produced as a voltage of I×RS across a resistor (RS)  64  by a current I flowing from the cells  61 . This voltage is differentially amplified by an operational amplifier (AMP 1 )  65 . A current I1 proportional to the output voltage of the operational amplifier (AMP 1 )  65  is caused to flow through a resistor (R 1 )  67  by an operational amplifier (AMP 2 )  66  and a transistor  68 . The value of current I of the intelligent battery  52  can be finally converted into the voltage I1×R 2  generated cross the resistor (R 2 )  69 . This voltage (I1×R 2 ) is output to an A/D#2 port of the CPU  62  to be A/D converted in the CPU  62 .  
     [0047] In the voltage measuring circuit  70 , the voltage of the intelligent battery  52  is measured. More specifically, the voltage across the group of cells  61  in the intelligent battery  52  is converted by being differentially amplified by an operational amplifier (AMP 3 )  71  to drop temporary to a lower level and is delivered to an A/D#1 port of the CPU  62  to be A/D converted in the CPU  62 .  
     [0048] In the temperature measuring circuit  90 , a thermistor (thermal sensor)  91  voltage divided by a resistor is placed in the vicinity of the cells  61 , as shown in FIG. 2, and a voltage generated across the thermistor  91  is delivered to an A/D#3 port of the CPU  62 . The voltage from the thermistor  91  is thus read to the CPU  62  and AND converted in the CPU  62  to measure the temperature. In this manner, information on the temperature in the cells can be grasped in the intelligent battery  52 .  
     [0049] The CPU  62  thus reads the charge/discharge current measured with the current measuring circuit  63 , the battery voltage measured with the voltage measuring circuit  70 , the temperature information obtained from the temperature measuring circuit  90  to manage the capacity, etc., of the intelligent battery  52  (cells  61 ). The CPU  62  also transmits data on the battery to the embedded controller  41  over the communication line  74 . The embedded controller  41  operates on the basis of the grasped condition of the battery to execute, for example, control to make the AC adapter power stop circuit  80  stop power supply from the AC adapter  51 .  
     [0050] The system shown in FIG. 2 is arranged to execute a guidance function with respect to the intelligent battery  52  having the CPU  62  provided in a battery pack, for example. However, a dumb battery without internal CPU  62  may be used instead of the intelligent battery  52  and a guidance function may be executed with respect to the dumb battery. The dumb battery may be arranged so as to have its serial number or the like stored in a PROM or the like for discrimination from others. Preferably, a current measuring circuit for measuring dumb battery charge and discharge currents and a voltage measuring circuit for measuring the voltage of the dumb battery are provided on the main-unit system side (in the system) to enable the embedded controller  41  to grasp the condition of the dumb battery including the battery capacity.  
     [0051] It is known that if incomplete discharge and charge are repeatedly performed on a nickel-hydrogen battery or a nickel-cadmium battery by stopping discharge halfway, a “memory effect” occurs such that the apparent charge capacity is reduced and the time during which the battery can be continuously used is shortened. By considering this, the system is arranged to count the number of times incomplete charge and discharge have been performed and to urge a user to execute “refreshment” for completely discharging the battery when it is supposed from the count (e.g., 20 to 30) that a memory effect has occurred in the battery. This refreshment is performed by supplying power from the battery to the system even when the AC adapter  51  is connected.  
     [0052] The AC adapter power stop circuit  80  will next be described.  
     [0053] The AC adapter power stop circuit  80  has a function of stopping power supply from the AC adapter  51 . The main-unit system, i.e., the computer system  10 , is arranged so that electric power can be supplied from one of the AC adapter  51  and the secondary battery or intelligent battery  52  higher in voltage than the other to the main-unit circuit by means of the first diode  77  and the second diode  78 . When the AC adapter  51  is connected, power is supplied from the AC adapter  51  to the main-unit circuit via the first diode  77  since the voltage on the AC adapter side  51  is usually higher than that on the intelligent battery  52  side.  
     [0054] At this step, when a user gives permission to execute “refreshment”, power supply from the connected AC adapter  51  is stopped by the AC adapter power stop circuit  80  to enable complete discharge of the intelligent battery  52 . That is, to execute complete discharge of the secondary battery or intelligent battery  52 , an ACDC-OFF signal of the embedded controller  41  is set to high level to turn on a first transistor (TR 1 )  82  of the AC adapter power stop circuit  80 . The turn-on of the first transistor (TR 1 )  82  causes a second transistor (TR 2 )  83  to turn off. The turn-off of this transistor causes a FET (FET 1 )  81  to turn off, thereby stopping supply from the AC adapter  51  and, hence, supply of power to the first diode  77 . Thus, supply of power from the intelligent battery  52  to the main-unit circuit via the second diode  78  is enabled even when the AC adapter  51  is connected.  
     [0055] When the battery is refreshed (completely discharged), the ACDC-OFF signal is set to low level to turn off the first transistor (TR 1 )  82  of the AC adapter power stop circuit  80 . The turn-off of the first transistor (TR 1 )  82  causes the second transistor (TR 2 )  83  to turn on. This turn-on causes the FET (FET 1 )  81  to turn on. Electric power is thereby supplied from the AC adapter  51  higher in voltage than the intelligent battery  52  to the main-unit circuit (main-unit system). It is possible to remove the memory effect from the intelligent battery  52  by the above-described sequence of operations.  
     [0056] On the other hand, on the system side, the remaining capacity (e.g., the charge level (%)) is displayed by using, for example, LCD  18  on the basis of the value of remaining capacity obtained from the intelligent battery  52 . The remaining capacity can be grasped by the CPU  62  in the intelligent battery  52  on the basis of, for example, the current value measured with the current measuring circuit  63  and the voltage value measured with the voltage measuring circuit  70 . There is a problem of an error in the remaining capacity due to self discharge becoming considerably large in a situation where the intelligent battery  52  is left for a long time (a predetermined period) after being removed from the system (computer system  10 ), or in a situation where the system is not used during a long time (a predetermined period) while the intelligent battery  52  is connected to the system. In such a situation, refreshment (complete discharge) is required to improve the accuracy of the remaining capacity by removing the capacity error for the purpose of achieving indication of the remaining capacity with the desired accuracy, etc. However, a refreshment execution method, such as that used in the conventional art, based on the number of counts of incomplete charge and discharge is not effective in reducing the capacity error.  
     [0057] Then, a battery diagnosis program for executing refreshment (a utility program executed by the CPU  11  in the computer system  10 ) is written so that the identifier (serial number) of the intelligent battery  52  and the date on which complete discharge of the intelligent battery  52  is last performed (the date on which refreshment is executed or the date on which the battery is completely discharged by being used for battery drive by a user) are recorded in a file (or a memory). This program makes it possible to urge the user by using, for example, the LCD  18  to perform refreshment for indication of the remaining capacity with improved accuracy even in a case where the intelligent battery  52  is not completely discharged during a predetermined period and the error in the remaining capacity is large.  
     [0058]FIG. 3 is a diagram showing processings under the battery diagnosis program (utility program) for determination as to whether there is a need for refreshment. When a user executes the diagnosis program (utility program)  98 , the diagnosis program communicates data to and from the embedded controller  41  and outputs a diagnosis result to the user (through a display, for example). In an information file  99 , information including the identifier of the intelligent battery  52  and information on the date of the last refreshment related to the identifier are stored. For example, the information file  99  may be stored in the HDD  31  shown in FIG. 1. Also the information file  99  may be stored in another storage in the computer system  10 .  
     [0059] At this step, after confirming the connection of intelligent battery  52  through the battery connection check terminal  76 , the embedded controller  41  receives the identifier (serial number) of the intelligent battery  52  through the communication line  74  by, for example, SBS communication. On the other hand, the identifier of the intelligent battery  52  and information on the date of the last execution of the refreshment function, etc., are stored in the information file  99 , as described above. The diagnosis program (utility program)  98  obtains the current date from the OS and, if a predetermined period of time, e.g., one month or longer has passed since the date of the last execution of the refreshment function, urges the user through a display to execute the refreshment function and displays (makes active) a button to be operated by the user to designate the refreshment function. When the user clicks the button in this display to execute the refreshment function, the date related to the identifier in the information file  99  is updated.  
     [0060] At this step, the predetermined time period is set to, for example, one month to cope with a memory effect resulting from an actual mode of use by a user in which charge and discharge are each performed one time in a day and the use period in one month is 20 to 22 days (that is, incomplete charge and discharge are repeated 20 to 22 times in one month). This method times execution of refreshment more suitably with respect to actual use by a user than the method using an ordinary count (e.g., 30 times). Since it is desirable to show the remaining capacity to a user by removing an error in a cycle of about “one month”, “one month”, for example, is selected as the above-mentioned predetermined period. The predetermined period can be set as desired according to a kind of battery, a mode of use, etc.  
     [0061] Further, the first time the intelligent battery  52  is connected, no refreshment date information to be stored in the information file  99  exists. The first time the intelligent battery  52  is connected, therefore, the date of connection is stored as a date information initial value by being related to the identifier obtained from the battery.  
     [0062] Next, a process including the above-described processings will next be described.  
     [0063]FIG. 4 is a flowchart of the process of performing the refreshment guidance function in accordance with the present invention. If the diagnosis program (utility program)  98  is executed (step  101 ), it reads the identifier from the intelligent battery  52  through the embedded controller  41  (step  102 ). The diagnosis program (utility program)  98  also reads date information corresponding to the read identifier from the information file  99  (step  103 ).  
     [0064] Next, for determination as to necessity to perform refreshment, a determination is made as to whether a predetermined period (fixed period), e.g., one month has passed from the date designated by the read date information (step  104 ). If the period has not yet passed, a condition relating to occurrence of a memory effect is read out (step  105 ). More specifically, a situation to be checked as data for ascertaining whether a memory effect has occurred, e.g., a situation in which incomplete charge and discharge have been repeated 30 times is read out. From such a situation read out, a determination is made as to whether a memory effect has occurred (step  106 ). If occurrence of a memory effect is not recognized, the process returns to step  101 . If it is determined that a memory effect has occurred, the process advances to step  107 .  
     [0065] If it is determined in step  104  that a period of time equal to or longer than one month has passed, and if it is determined in step  106  that a memory effect has occurred, refreshment guidance using, for example, LCD  18  is given to the user (step  107 ). For example, a button (execution start instruction button) is shown to the user to urge the user to perform refreshment. A determination is then made as to whether the user under this guidance has input an instruction to execute refreshment (step  108 ). If the user has not input any instruction, the process returns to step  101 . If the user has input the instruction, date information is written to the information file  99  (step  109 ), thereby completing the process.  
     [0066]FIG. 5 is a flowchart showing an example of processing in step  106  shown in FIG. 4, i.e., processing for detecting a memory effect in the intelligent battery  52 . The CPU  62  of the intelligent battery  52  makes a determination as to whether the battery is completely discharged (step  111 ). “Complete discharge” not only denotes full discharge to 0% but also covers a case where discharge is performed to a charge level low enough to remove a memory effect (for example, a charge level of 3% or 5% or the like). If it is determined in step  111  that complete discharge has been effected, it is then determined that no memory effect has occurred (step  112 ). On the other hand, if it is determined in step  111  that that battery is not completely discharged, a determination is made as to whether the number of times incomplete discharge has been performed, counted by the CPU  62 , exceeds, for example,  30  (step  113 ). If the number of counts of incomplete discharge does not exceed  30 , it is determined that no memory effect has occurred (step  112 ). If the number of counts exceeds  30 , it is determined that a memory effect has occurred (step  114 ).  
     [0067] As a memory effect occurrence detection method, a method is known which is characterized by taking notice of the fact that a battery in which a memory effect has occurred has a nominal voltage value smaller than that of a normal discharge characteristic. That is, this method comprises-measuring the voltage of the battery during discharge and determining that a memory effect has occurred when detecting a battery voltage level excessively low with respect to the discharge current value. This method enables more accurate detection of a memory effect during ordinary operation.  
     [0068] An example of an output to a user will next be described. FIG. 6 is a diagram showing an example of an on-screen display for guiding a user to execution of refreshment. Such refreshment guide information is displayed, for example, on the liquid crystal display (LCD)  19  shown in FIG. 1 by execution of the diagnosis program (utility program)  98  receiving information from the embedded controller  41 . In the example of the display shown in FIG. 6, a state of a battery after  48  charge/discharge cycles is indicated. A reduction of 5% from the initial 100% capacity has been caused and the full charge capacity is 95% of the initial capacity. A color display of the capacity with a stepped or continuous change in color, for example, may be produced. For example, when the full charge capacity is 51 to 100%, there is no need to change the battery and a graph indicating the capacity is therefore displayed in green. When the full charge capacity is 31 to 50%, the graph is displayed in yellow for indication of the time to change the battery. When the full charge capacity is 0 to 30%, there is a possibility of occurrence of a functional fault such as low hibernation and the graph is therefore displayed in red. In this manner, the user can be visually informed of the degree of degradation of the battery and the time to change the battery.  
     [0069] At this step, a low battery hibernation function may be used which is a function for forcibly saving various statuses in PC operation to a disk when a predetermined lower limit capacity level of the battery (intelligent battery  52 ) is reached. Ordinarily, even when the lower limit capacity level of the battery is reached, power remaining in the battery can be used to operate the disk so as to complete the necessary saving operation. However, if the battery is degraded, there is a possibility of the capacity decreasing abruptly when the predetermined lower limit capacity level is reached. In such an event, supply of power from the battery may be stopped before the saving operation is completed. In this embodiment, therefore, the necessary indication is given in red to specially alert the user to the possibility of such a failure. Further, in this embodiment, simultaneously with the above-described display, a refreshment instruction button  201  and a refreshment recommendation message  202  are displayed. The refreshment recommendation message  202  includes a message “Battery Refresh Recommended” and information on the date of most recent (last) execution of refreshment. Through this display, it is possible to recommend (urge) the user to start the refreshment operation at a suitable time without the risk of reducing the battery life. When the refreshment instruction button  201  is clicked by the user, the diagnosis program (utility program)  98  issues a refreshment instruction to the embedded controller  41 . Then, the embedded controller  41  sets the ACDC-OFF signal to high level to turn off the FET (FET 1 )  81  in the AC adapter power stop circuit  80 , thereby stopping power supply from the AC adapter  51 . Refreshment is thus executed.  
     [0070] In this embodiment, as described above, a user is guided in starting refreshment of the battery at a suitable time in such a manner that occurrence of an error in the remaining capacity of the battery is predicted and guidance for refreshment (complete discharge) is given to the user, thus making it possible to show the remaining capacity to the user without an error. Although there is a problem of an error in the remaining capacity of the battery due to self discharge becoming considerably large if the battery is left detached from a system for a long time or if the system is not used during a long time while the battery is connected to the system, the system in this embodiment is capable of refreshment for reducing the capacity error for the purpose of improving the accuracy of the remaining capacity and, therefore, capable of indicating the remaining capacity of the battery to the user with accuracy.  
     [0071] As mentioned above, “complete discharge” referred to in the description of this embodiment not only denotes full discharge to 0% but also covers discharge to a charge level of about 3% to 5%, necessary for removing a memory effect. Then, “refreshment” can be defined as continuing discharge until a predetermined battery capacity value is reached while no charging power is supplied to the battery (intelligent battery  52 ). The arrangement may be such that this capacity can be set by a user. Examples of a mode of discharge recognized as “completion of refreshment” are (1) continuous discharge to a capacity of 10% in a case where the lower limit capacity is set to 10% by a user, (2) continuous discharge to a capacity of 3% (according to the Windows (R) specifications provided by Microsoft Corp., discharge to a level lower than 3% is to be avoided), and ( 3 ) continuous discharge to a capacity of 0%. Most preferably, the lower limit of the battery capacity is set to about 3% by considering computation of the full charge capacity of the battery based on integration of the amount of discharge from the battery, or for the purpose of effectively removing a memory effect in the battery.  
     [0072] “Refreshment” may be started in such a manner that if a user selects the refreshment function in the diagnosis program (utility program)  98  in the PC (on main unit side), the PC stops charge from the AC adapter  51  to the battery to start power supply from the battery to the main unit. Thus, a user may intentionally start refreshment. Also, refreshment may be completed in such a manner that the predetermined capacity value is reached during a process in which supply of power from the battery to the main unit is continued without connecting the AC adapter  51 .  
     [0073] The above-described diagnosis program (utility program)  98  may be provided in such a manner that it is installed in the computer system  10  in advance or it is read from a CD-ROM provided as a program storage medium by the CD-ROM drive  32  to be executed. Also, the diagnosis program may be installed from an external program transfer device through a network, e.g., the Internet.  
     [0074] In the above-described arrangement, the information file  99  shown in FIG. 3 is provided on the system side and nonperformance of refreshment of the battery through a time period equal to or longer than a certain period is detected by the diagnosis program (utility program)  98 . The arrangement may alternatively be such that date information is provided in the intelligent battery  52  and the CPU  62  in the intelligent battery  52  detects nonperformance of refreshment of the battery through a time period equal to or longer than a certain period.  
     [0075] In such a configuration, the intelligent battery  52  stores information on the date of most recent (last) execution of refreshment thereof in a memory, e.g., one incorporated in the CPU  62 . In this case, there is no need to prepare the information file  99  shown in FIG. 3, or the like for storing date information corresponding to the identifiers of different batteries. The CPU  62  makes determination as to necessity to perform refreshment by using such date information if a predetermined period (e.g., one month or longer) has passed. The result of this determination can be transmitted to the system side through the embedded controller  41  by using the SBS protocol. The utility program informed of necessity to perform refreshment displays on the LCD  18  information such as shown in FIG. 6 and waits for a refreshment instruction from a user. When the refreshment operation is completed after receiving the refreshment instruction, the CPU  62  of the intelligent battery  52  updates the date information and stores this information in a predetermined memory.  
     [0076] The configuration in which information on the date of the most recent (last) execution of refreshment is held in the intelligent battery  52  and the system is notified of a result of determination as to necessity to perform refreshment is advantageous in that the need for identification of each of intelligent battery  52  with respect to variations in technologies and different makers is eliminated. Also, one intelligent battery  52  can be suitably used in a plurality of computer systems  10 . The utility program used in such a mode has the function of producing an on-screen display such as shown in FIG. 6 by receiving information from the embedded controller  41 , recognizing the user operation on a refreshment instruction button  201  such as shown in FIG. 6, and transmitting the recognized instruction to the embedded controller  41 . According to the present invention, as described above, a user can be guided in making a suitably timed start on refreshment of a battery.  
     Description of Symbols  
     [0077] 10  . . . Computer system  
     [0078] 11  . . . CPU  
     [0079] 18  . . . Liquid crystal display (LCD)  
     [0080] 41  . . . Embedded controller  
     [0081] 31  . . . IDE hard disk drive (HDD)  
     [0082] 50  . . . Power supply circuit  
     [0083] 51  . . . AC adapter  
     [0084] 52  . . . Intelligent battery  
     [0085] 61  . . . Cell  
     [0086] 62  . . . CPU  
     [0087] 63  . . . Current measuring circuit  
     [0088] 70  . . . Voltage measuring circuit  
     [0089] 74  . . . Communication line  
     [0090] 75  . . . Voltage measuring circuit  
     [0091] 76  . . . Battery connection check terminal  
     [0092] 77  . . . First diode (D 1 )  
     [0093] 78  . . . Second diode (D 2 )  
     [0094] 80  . . . AC adapter power stop circuit  
     [0095] 81  . . . FET (FET 1 )  
     [0096] 82  . . . First transistor (TR 1 )  
     [0097] 83  . . . Second transistor (TR 2 )  
     [0098] 90  . . . Temperature measuring circuit  
     [0099] 98  . . . Diagnosis program (utility program)