Interpretation of Sodium‐Sulfur Cell Characteristics Using an Alternating Current Resistance Technique

An alternating current (ac) resistance technique for sodium‐sulfur cells is described. The method has been applied to central sodium and central sulfur cells with between 16 and 650 Ah capacity. The shape of the ac charge resistance‐capacity plot has been correlated with resistive layer composition. Anomalies in direct current (dc) resistances for oriented‐mat sulfur electrode cells are explainable in conjunction with ac analysis. The increased sensitivity of ac compared to dc measurements has been utilized to identify incipient electrolyte failure and sodium electrode problems not discernable by the latter technique.