A subsea piston accumulator for being utilized with blowout preventers in oil and gas well operations comprising: a hydraulic bottle , having a cylinder , an upper bulkhead , and a lower bulkhead , a center bulkhead , a piston rod centered in said center bulkhead having an upper piston , a lower piston wherein said upper bulkhead and said upper piston define an upper chamber and said lower bulkhead and said lower piston define a lower chamber wherein said lower chamber has a first pressure transducer to measure pressure in said lower chamber ; a gas bottle having a chamber for holding gas, a top valve controlled by a top rotary actuator for opening and closing said top valve , a bottom valve controlled by a bottom rotary actuator for opening and closing said bottom valve , and a pressure sensor in said chamber to measure pressure in said chamber; a port between said gas bottle and said upper chamber of said cylinder wherein said port has a second pressure transducer for measuring the pressure of the upper chamber of said cylinder and said chamber of said gas bottle ; a piston position sensor system having a receiving sensor mounted on said hydraulic bottle , a transponder mounted on said piston rod , and wherein said receiver sensor and said transponder are adapted to provide a position of said piston rod in said cylinder ; and a monitoring and display system in communication with said first pressure transducer , said pressure sensor , said second pressure transducer , said receiving sensor , said transponder , said top rotary actuator of said top valve , said bottom rotary actuator of said bottom valve , and wherein said monitoring and display system is adapted to open and close respectively said top valve and said bottom valve as desired. a hydraulic bottle , having a cylinder , an upper bulkhead , and a lower bulkhead , a center bulkhead , a piston rod centered in said center bulkhead having an upper piston , a lower piston wherein said upper bulkhead and said upper piston define an upper chamber and said lower bulkhead and said lower piston define a lower chamber wherein said lower chamber has a first pressure transducer to measure pressure in said lower chamber ; a gas bottle having a chamber for holding gas, a top valve controlled by a top rotary actuator for opening and closing said top valve , a bottom valve controlled by a bottom rotary actuator for opening and closing said bottom valve , and a pressure sensor in said chamber to measure pressure in said chamber; a port between said gas bottle and said upper chamber of said cylinder wherein said port has a second pressure transducer for measuring the pressure of the upper chamber of said cylinder and said chamber of said gas bottle ; a piston position sensor system having a receiving sensor mounted on said hydraulic bottle , a transponder mounted on said piston rod , and wherein said receiver sensor and said transponder are adapted to provide a position of said piston rod in said cylinder ; and a monitoring and display system in communication with said first pressure transducer , said pressure sensor , said second pressure transducer , said receiving sensor , said transponder , said top rotary actuator of said top valve , said bottom rotary actuator of said bottom valve , and wherein said monitoring and display system is adapted to open and close respectively said top valve and said bottom valve as desired. <EOS>