A semi theoretical explanation of the appearance of a second plateau during the discharge of overcharged nickel oxyhydroxide electrodes (NOHE) is proposed, based on transmission line models of the charge–discharge processes of the active matter. The model takes into account the double electronic and protonic conduction involved in nickel II α and β or nickel III β and γ phases: electrons and protons reach the transformation front inside the matter through the less resistive paths. The secondary plateau may occur when a resistive layer of β(II) isolates the transformation front from the nickel electron sink.