Abstract: A chargeable battery or a battery pack stores electrical energy, and supplies the electrical energy to a portable terminal device connected to the battery pack. A display device of the battery pack derives a value of a current flowing through a sensor which is connected to the chargeable battery. The display device derives the remaining amount of electrical energy stored in the chargeable battery, by adding up the derived current value. The display device includes a plurality of photodiodes, and shows the remaining amount of electrical energy stored in the chargeable battery, by lighting up corresponding number of photodiodes corresponding to the derived remaining amount.

Abstract: A chargeable battery or a battery pack stores electrical energy, and supplies the electrical energy to a portable terminal device connected to the battery pack. A display device of the battery pack derives a value of a current flowing through a sensor which is connected to the chargeable battery. The display device derives the remaining amount of electrical energy stored in the chargeable battery, by adding up the derived current value. The display device includes a plurality of photodiodes, and shows the remaining amount of electrical energy stored in the chargeable battery, by lighting up corresponding number of photodiodes corresponding to the derived remaining amount.

Abstract: A battery pack comprises a solar panel, a battery, a connector, and a charge/discharge circuit. The solar panel converts light energy into electric energy. The battery is charged with the electric energy from the solar panel. The connector supplies the electric energy to a portable terminal device. The charge/discharge circuit supplies the electric energy from the solar panel to the connector, and supplies the electric energy from the battery to the connector or charges the battery with part of the electric energy from the solar panel, in accordance with the amount of electric energy to be used by said portable terminal device, while the portable terminal device is in operation.

Abstract: A battery pack comprises a solar panel, a battery, a connector, and a charge/discharge circuit. The solar panel converts light energy into electric energy. The battery is charged with the electric energy from the solar panel. The connector supplies the electric energy to a portable terminal device. The charge/discharge circuit supplies the electric energy from the solar panel to the connector, and supplies the electric energy from the battery to the connector or charges the battery with part of the electric energy from the solar panel, in accordance with the amount of electric energy to be used by said portable terminal device, while the portable terminal device is in operation.

Abstract: A voltage detection circuit 2 detects a voltage of a battery 1 and, when the voltage thus detected is within a tolerable input voltage of a power source unit 5, an on/off signal transmitter circuit 4 allows an on/off signal generator circuit 3 to transmit an on/off signal S2 to the power source unit 5. When the voltage of the battery 1 becomes lower than a lower limit of the tolerable input voltage range of the power source unit 5 due to increase of a power consumption of a load 6 thereof, the on/off signal transmitter circuit 4 transmits an off signal S3 to the power source unit 5 regardless of the on/off signal S2 from the on/off signal generator circuit 3. Thus, it is possible to prevent an erroneous operation of the load due to abnormal operation of the power source unit.

Abstract: The output of the power unit 21 varies on the basis of the output of the power unit 22, and temperature-compensated in accordance with an ambient temperature. The control is performed by the output voltage control circuit 3. The output voltage of the power unit 21 is varied with an output voltage ratio between the outputs of the power units, and by compensating an output voltage of the power unit 22 in accordance with the ambient temperature, the output voltage of the other power unit 21 can be temperature-compensated by the control circuit 3.