Voltage equalization control system of accumulator

A maximum/minimum voltage detector (4) detects a maximum terminal voltage and a minimum terminal voltage of a plurality of accumulators (CL). A voltage difference calculator (5) calculates a voltage difference between the maximum terminal voltage and the minimum terminal voltage. A timer setting unit (6) sets an operational time of a timer according to the voltage difference. An operational time controller (7) presets the operational time in the timer (6) to temporally control the operation of the voltage balanced circuit (3). Accordingly, an unnecessary loss of energy due to the long time operation of the voltage balance circuit (3) is prevented, and a performance of the assembled battery (2) is maintained.