MONITOR CELL, CHARGE/DISCHARGE CONTROL METHOD FOR SODIUM-SULFUR SECONDARY BATTERY, AND METHOD AND APPARATUS FOR MEASURING DISCHARGE DEPTH OF SODIUM-SULFUR SECONDARY BATTERY

PROBLEM TO BE SOLVED: To provide a monitor cell, and a method and an apparatus for measuring discharge depth of sodium-sulfur secondary battery, which can directly measure a discharge depth of a sodium-sulfur secondary battery with precision. SOLUTION: The monitor cell which is inserted into a serial group of the sodium-sulfur secondary batteries to measure the discharge depth of the sodium-sulfur secondary batteries, comprises a solid electrolyte tube 10 which has a sodium ion conductivity; a negative electrode room 12 which is formed inside the solid electrolyte tube and separated from the solid electrolyte tube, and has a negative electrode 11; and a positive electrode room 14 which is formed outside the solid electrolyte tube, and has a positive electrode 13. A sodium 15 as a cathode active substance is housed in the negative electrode room 12, the sodium 15 is housed in the positive electrode room 13, and a resistor 17 for detecting the fluid level of the sodium 15 is set in the negative electrode room 12 and connected to a measurement electrode 19. COPYRIGHT: (C)2006,JPO&NCIPI