To provide a highly accurate charge/discharge controller, control method and program, and a battery control system.

When a variation in capacity (Qd) exceeds a prestored specified value, SOC being converted from Qmin may not be recovered up to the central value of control. An apparent SOC is thereby operated and informed to an HVECU 18 thus preventing such a trouble as the HVECU 18 cannot issue an instruction for stopping charging for ever. The apparent SOC is operated as a large value depending on the magnitude of variation in capacity (Qd). When a battery ECU informs the SOC thus operated to the HVECU, a decision can be made that the central value of control is exceeded. Consequently, a controller, control method and program capable of controlling charge/discharge of a battery pack more accurately regardless of variation in capacity (Qd) can be provided and a battery control system can also be provided.