NOVELTY - The accumulator (10) has a connecting rod arranged between pistons. A pressure relief valve and a check valve are in pressure communication between a gas precharge pressure chamber and a pressure relief chamber. The pressure relief valve is set to a preselected value within a range of pressure safely containable by a housing. A longitudinally movable pressure barrier is engageable with a stop feature on the connecting rod such that increase in ambient chamber pressure compresses gas discharged into the relief chamber back into the gas precharge chamber through the check valve.    USE - Temperature compensated accumulator for use in hydraulically-operated systems to provide a reserve source of pressurized hydraulic fluid i.e. silicone oil, for equipment or device such as subsea test tree equipment and blowout preventer equipment.    ADVANTAGE - The accumulator increases efficiency during operations over wide range of temperatures when constant gas pressure can be maintained. The relief valve and the check valve are installed in suitably formed receptacle in the housing of the accumulator to allow the valves to be changed out without disassembling the accumulator. The ambient pressure outside the accumulator compresses vented excess pressure back into the gas precharge chamber. The accumulator allows pressurization of the accumulator gas to maximum working pressure of the accumulator housing without including to account for temperature changes during operations to cause the gas precharge pressure to increase over the maximum pressure. The accumulator provides hydraulic fluid under pressure to operate different valves and controls in the subsea test tree.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for a method for operating a temperature compensated accumulator.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of a subsea wellbore with a subsea test tree attached to temperature compensated accumulator.    Temperature compensated accumulator (10)    Riser (12)    Subsea test tree (14)    Hydraulic lines (16)    Subsea wellbore (18)