Establishment of the relationship between capacity and impedance of trickle-charge nickel/cadmium cells by using electrolyte-deficient model cells

A relationship is established between the capacity and the impedance of trickle-charged nickel/cadmium cells by using electrolyte-deficient model cells. Loss of capacity is strongly related to cell weight and the logarithm of the impedance. Since the decrease in cell weight is thought to be caused by electrolyte loss, an electrolyte-deficient model cell has been prepared to simulate the deterioration conditions. The model cell and deteriorated cells exhibit linear relationships between cell capacity and the logarithm of impedance where its imaginary part is zero on a Cole-Cole plot. Furthermore, a linear relationship is obtained that follows closely the relationship obtained from measured data by modifying the relationship for the model cells by substituting for the capacity of the fresh (non-deteriorated) cell. This method provides an effective and time-saving way for obtaining the relationship because is not necessary to test many deteriorated cells or to carry out accelerated tests.