Charger connecting to energy storage device and method of providing user interface thereof

A method comprising:

• providing a user interface in a charge method in which in response to a change in the situation of power supply, a charger receives electric power supplied from a power grid and an energy storage device under the control of the energy storage device, based on the switching or merging of power supply, and then performs power charging for an object in need of charging by using the supplied electric power, to provide a reliable power charging operation;
• displaying a first screen interface for selecting any one of a charge cost method and a charge period method on a screen and receiving a user's input selection;
• displaying a second screen interface for providing detailed information about the charge period method or the charge cost method selected via the first screen interface and receiving a user's input selection;
• and
• displaying information about a charge state via a third screen interface as power charging proceeds based on the detailed information on the charge period method or the charge cost method selected via the second screen interface.

A system comprising:

• an energy storage device connected to a power grid and having a plurality of batteries therein;
• and
• a power charger, having a user interface and operatively connected with and being controlled by the energy storage device, configured to provide electric power from at least one among the power grid and the batteries to an electric vehicle for charging thereof,
• wherein the batteries are capable of relatively high C-rate discharging, and wherein the power charger is capable low C-rate charging and relatively high C-rate charging of the electric vehicle depending upon an electric power situation detected by the energy storage device.