An accumulator arrangement for providing constant pressure high flow rates in hydraulic systems. The accumulator piston has a piston area directly connected to a container of pressurized gas and an annular piston area of larger diameter which is connected to the container through a pressure regulator. The regulator senses the container pressure and the pressure acting on the annular piston area and increases the pressure on the annular piston area as the container pressure decreases during expansion. Between high flow periods, when the accumulator is refilled by hydraulic fluid under pressure, the gas acting on the small diameter piston is recompressed and forced back into the container and the gas acting on the annular piston area is vented to the atmosphere through the regulator.