HIGH PRESSURE TANK RESIDUAL PRESSURE DETERMINATION SYSTEM, HIGH PRESSURE TANK RESIDUAL PRESSURE DETERMINATION METHOD, AND FUEL CELL VEHICLE

A computation unit of a residual pressure determination system obtains a corresponding usage limit threshold value corresponding to a measured temperature value of a tank temperature, from a usage limit threshold value line calculated using at least one of a required minimum residual pressure line and an isopycnic line. When having determined that a measured internal pressure value has decreased to the corresponding usage limit threshold value, a determination unit stops release of hydrogen gas from a high pressure tank. A tank internal pressure indicated by the usage limit threshold value line within an allowable temperature range becomes greater than or equal to the tank internal pressure indicated by the isopycnic line or that indicated by a tangent line, and at least a portion of the tank internal pressure indicated by the usage limit threshold value line within the allowable temperature range becomes lower as the tank temperature becomes lower.