METHOD FOR CALCULATING THE STATE OF CHARGE OF A SODIUM-SULFUR BATTERY

An accurately and precisely calculation of the state of charge of a sodium-sulfur battery may be made by determining a state of charge Qr according to expression (1) given below even if the sodium-sulfur battery is applied to compensate for fluctuations in the power generated by a natural energy generating device: Qr = 100x(1-(Qu/(Qa-Qsf))) ... (1) where Qu: used capacity; Qa: product capacity; and Qsf: residual capacity in final year; and Qsf = f1(Cef) ... (2) where f1(Cef): conversion function for determining the residual capacity Qsf in the final year on the basis of the equivalent cycle Cef in final year.