Electrodes prepd. from Mg-based mechanical alloys of 99.8+% pure Ni, Mn and Al used in atomic ratios and mixed with 10% powd. Ni, were preactivated. in: (a) 0.06 M NH4F, (b) 0.5 M KF, (c) 1 M KF, (d) 2 M KF, (e) 6 M KOH, (f) hot charging. The pretreatment was intended to increase porosity, Ni metal content, and electrode surface area. Mode a resulted in 100% capacity of the electrodes in 10 charging/discharging cycles. Regardless of mode, and even nonactivated, the Mg1.5Mn0.5Ni showed nearly 100% capacity with respect to max. discharge capacity. Mode (f) was ineffective.