Patent ID: 9026388
Filing Date: 2015-05-05
Classification: H01M,Y02E

Abstract:
1. A method for determining a drop in capacity of a sodium-sulfur battery whereby to determine that the capacity of the sodium-sulfur battery has dropped to an abnormal level when both expression (1) and expression (2) hold, the sodium-sulfur battery being constituted by connecting an s number of electric cells in series to form a string, connecting a u number of the strings in parallel to form a block, connecting a b number of the blocks in series to form a module, and then connecting an m number of the modules in series; where Qe indicates a lowest voltage block depth of discharge Qn indicates a selected block depth of discharge K1 is a setting value indicating a block abnormality determination set point; where K2 is a setting value indicating a depth of discharge abnormality determination set point; where f1 (Vi (t, T, Id)) is a transform function for determining depth of discharge of a block by, for each module in the sodium-sulfur battery, comparing the corrected stable open-circuit voltages of the highest voltage blocks between the modules; determining Vi as an i-th highest voltage among the highest voltage blocks of the modules; and then determining the depth of discharge of the i-th highest voltage block on the basis of the voltage Vi; and where f2 (Vmin (t, T, Id)) is a transform function for determining the depth of discharge of a block by, for each module in the sodium-sulfur battery, comparing the corrected stable open-circuit voltages of the low voltage blocks between the modules; determining Vmin as the lowest voltage among the low voltage blocks of the modules; and then determining the depth of discharge of the lowest voltage block on the basis of the voltage Vmin.