Patent ID: 7602150

Claim:
An electronic apparatus comprising: a power supply unit, a power management unit, a display unit, a first secondary battery interface, and a separable battery device, wherein: said power management unit causes information representative of a run time of said separable battery device to be indicated on said display unit, and said separable battery device comprises: a rechargeable secondary battery adapted to supply power to said power supply unit, a second secondary battery interface, coupled to said first interface, a fuel cell to supply power to said power supply unit, and a battery run time computing unit receiving, from said rechargeable secondary battery, data representative of a characteristic of voltage versus residual-capacity of said rechargeable secondary battery and receiving, from said fuel cell, data representative of a residual capacity of said fuel cell, wherein: said battery run time computing unit determines data representative of a residual capacity of said rechargeable secondary battery and a run time of said rechargeable secondary battery in accordance with said data representative of the characteristic of voltage versus residual-capacity and with supply voltage and supply current of said rechargeable secondary battery, determines a run time of said fuel cell in accordance with said data representative of the residual capacity of said fuel cell and with supply current of said fuel cell, and estimates which of the respective power capacities of said rechargeable secondary battery and said fuel cell reaches a corresponding one of the respective, predetermined residual capacities earlier, if it is estimated that the power capacity of said fuel cell reaches its predetermined residual capacity earlier, said battery run time computing unit determines a run time of said separable battery device, in accordance with said data representative of the rechargeable secondary battery residual capacity, said data representative of the fuel cell residual capacity, and said respective supply currents of said rechargeable secondary battery and of said fuel cell, if it is estimated that the power capacity of said rechargeable secondary battery reaches its predetermined residual capacity earlier, said battery run time computing unit determines the run time of said separable battery device in accordance with the run time of said rechargeable secondary battery, and said battery run time computing unit supplies data representative of the thus determined run time of said separable battery device to said power management unit through said second secondary battery interface and said first interface.