Backup power storage system with removable secondary battery, and method of operating same

A method for charging/discharging a chargeable/dischargeable and removable secondary battery, the method comprising:

• adjusting a charging voltage of an external power source, via a voltage adjuster, to a predetermined voltage corresponding to the secondary battery, wherein the external power source supplies electric power to the secondary battery and to an external device;
• charging the secondary battery, via the external power source;
• detecting an input voltage via a voltage detector;
• detecting an input current via a current detection resistor;
• determining whether the external power source is operating normally, via a controller, based on the input voltage and the input current;
• adjusting an output voltage of the secondary battery to a predetermined voltage corresponding to the external device, and
• outputting the electric power to be output from the secondary battery to the external device, based on whether the external power source is operating normally.

A battery unit comprising:

• a chargeable/dischargeable and removable secondary battery;
• an input/output terminal connected to an external power source and an external device;
• a charging path for inputting electric power, supplied from the external power source via the input/output terminal, to the secondary battery;
• a discharging path for outputting electric power, accumulated in the secondary battery, to the external device via the input/output terminal;
• a voltage adjuster that is provided in the charging path and the discharging path and is configured to adjust a charging voltage of the external power source to a predetermined voltage corresponding to the secondary battery to output electric power received as an input via the input/output terminal, or adjust an output voltage of the secondary battery to a predetermined voltage corresponding to the external device to output electric power received as an input from the secondary battery, to the external device via the input/output terminal;
• a switching element in the charging path and the discharging path between the secondary battery and the voltage adjuster and configured to open the charging path and the discharging path when a failure occurs in the battery unit;
• and
• a controller configured to control an operation of the voltage adjuster in accordance with charge or discharge of the secondary battery,
• wherein:
• the charging path and the discharging path are formed of common circuit wiring, and
• the voltage adjuster has:
• a current path connecting one end on the input/output terminal side and the other end on the secondary battery side,
• a bypass path of the current path,
• a converter provided in the bypass path and capable of changing input electric power to a predetermined voltage corresponding to the secondary battery or a predetermined voltage corresponding to the external device in accordance with the charge or discharge of the second battery, and
• a path selector configured to select a path to be used out of the current path or the bypass path in accordance with the charge or discharge of the secondary battery.