The present paper aims at discussing efficiency tests, which particularly examine the response on discharge to an increasing charge duration, in a galvanostatic mode, for beta (II)-type zinc-substituted nickel hydroxides. The influence of a preliminary formation of the materials in a low-concentration electrolyte is underlined and the effect of zinc on the inhibition of the transformation of the beta (III)-phase into the gamma -one is also demonstrated. It is shown that the presence of zinc increases the cell voltage as a result of the large size of zinc ions as compared to nickel ions.