Patent ID: 8362786

Claim:
A method for determining a degradation state of an electrical storage device in hybrid construction equipment provided with an engine, a motor-generator, an electrical storage device, an electric power load, and a working machine driven by the electric power load, comprising: a step of checking that at least the working machine has halted; a step of shifting into a degradation state determination time control mode when it is checked that the working machine has halted, and increasing in the electrical storage device from a prescribed start charging voltage to a prescribed end charging voltage by driving the motor-generator at a prescribed rotational speed and with a prescribed torque; a step of calculating a capacitance of the electrical storage device based on values of the rotational speed and the torque of the motor-generator during the degradation state determination time control mode, values of the start charging voltage and the end charging voltage of the electrical storage device, and a time required for the electrical storage device to reach the end charging voltage from the start charging voltage; and a step of determining the degradation state of the electrical storage device by comparing the calculated capacitance of the electrical storage device with a reference capacitance.