Uninterruptible power supply and control method there of

A control method of an uninterruptible power supply (UPS) that supplies battery power to an external device, the UPS including

• a plurality of power supply units, each belonging to one of an operating system and a standby system, and
• a plurality of battery units each having a battery, each battery unit belonging to one of a power failure standby system and a power failure backup system,
• the method comprising:
• receiving an instruction from an externally-connected management device, the instruction containing information as to whether each of the plurality of power supply units belongs to the operating system or the standby system, and information as to whether each of the plurality of battery units belongs to the power failure standby system or the power failure backup system;
• setting each of power supply units to be in one of the operating system and the standby system in accordance with the received instruction, to thereby manage the power supply units;
• setting each of battery units to be in one of the power failure standby system and the power failure backup system in accordance with the received instruction, to thereby manage the battery units;
• controlling the battery unit in the power failure backup system so that the battery unit supplies power to the external device during a first period of time when the received instruction includes the first period of time for supplying power from the battery unit in the power failure backup system to the external device, and
• controlling the power supply unit so that the battery unit supplies power to both the external device and the batteries in the battery units during a second period of time that is different from the first period of time.