Method of measuring residual capacity of a Ni/MH cell

Abstract

The present invention relates to a method of measuring residual capacity of a Ni/MH (nickel/metal hydride) cell by measuring the change in the electrical resistivity of a Ni/MH cell according to the change of the concentration of hydrogen in metal hydride. According to the present invention, a method for measuring residual capacity of a Ni/MH cell comprises the steps of measuring electrical resistivity of a first Ni/MH cell, and determining the residual capacity of the first Ni/MH cell (i) from a predetermined data of n-pairs of electrical resistivity values and residual capacity values of a second Ni/MH cell which has substantially the same composition as the composition of the first Ni/MH cell, or (ii) based on a predetermined functional relationship between the electrical resistivity and residual capacity of the second Ni/MH cell. The series of the predetermined data or the predetermined functional relationship represents substantially a linear proportionally between the resistivity and the logarithmic value of the residual capacity. As the discharge reaction proceeds in the cell, metal hydride in the anode is reduced and loses hydrogen, and thus the hydrogen concentration at anode becomes lower. Accordingly, the relationship between the residual capacity and the resistivity of a Ni/MH cell can be obtained by measuring the residual capacity and the resistivity of the cell depending on the degree of discharge, therefore the residual capacity can be readily detected by measuring only the resistivity of the cell.