batteries connected in parallel;

battery control units, each battery control unit having at least one fuse and at least one battery current measurement unit, the battery control units respectively connected to the batteries;

a battery connection panel connecting the battery control units to one connection point, the battery connection panel having a contact point current measurement unit;

a control unit configured to sum first current values respectively measured by the battery current measurement units at a negative terminal of the battery connection panel and a second current value measured by the contact point current measurement unit at the negative terminal of the battery connection panel, and to detect a presence of an overcurrent or an internal short circuit based on the sum, wherein the control unit detects a high resistance internal short circuit according to insulation breakdown of a battery cable, wherein the control unit detects the insulation breakdown based on a short circuit strength curve and a battery control unit fuse curve on a graph of time on a Y axis of the graph and current on an X axis of the graph, and wherein the insulation breakdown occurs at a right side of the short circuit strength curve if the battery control unit fuse curve is to a left of the short circuit strength curve; and

a power conditioning system connected to the battery connection panel, the power conditioning system being configured to convert electrical characteristics so as to receive electrical energy from an electricity generation device to charge the battery, or to emit energy stored in the battery to an electric power system, wherein the internal short circuit is located in the current protection system at a location other than a battery, and wherein when the presence of an overcurrent or an internal short circuit is detected by the control unit, the control unit generates a trip signal to melt the at least one fuse to block the overcurrent or short-circuit current to stop the energy storage system.