Based on the static equilibrium of electrochemical reaction kinetics, i.e, the same static reaction current density of forward and backward reactions, a relationship has been established between the equilibrium potential during discharge (E-e) and hydrogen concentration (C-H) in a hydride alloy (Mm(0.4)Ml(0.6)Ni(3.8)Co(0.5)Al(0.3)Mn(0.4)) at an equilibrium discharge condition. The theoretical results are in an agreement with the experimental electrochemical data in the two-phase (alpha-beta) region of the hydrogen-absorbing alloy. The enthalpy (Delta H) and entropy (Delta S), which is a function of hydrogen concentration in the electrode alloy, were obtained by fitting the curve of the equilibrium potential vs hydrogen concentration.