Publisher Summary This chapter describes the regular primary alkaline manganese dioxide-zinc system and the new rechargeable system. The chapter addresses the question if mercury-free cells are possible by examining the comparisons made in very specific applications. The alkaline MnO2-Zn primary cell represents a major advantage in portable power sources over the conventional Leclanché cell, which is often called carbon-zinc cell because of the carbon-rod collector in the center of the MnO2-“bobbin”. It has a higher capacity compared with Leclanché cells, especially at high discharge and continuous discharge rates. Alkaline MnO2-Zn primary cells in general use macroporous separators made from woven, bonded or felted materials. Several battery manufacturers have tried to reduce the mercury content of cylindrical alkaline MnO2-Zn primary cells. Mercury-free cylindrical alkaline MnO2-Zn primary cells are produced in a pilot production. The chapter elaborates on the rechargeable alkaline manganese dioxide-zinc batteries (RAM CELLS) where the major design changes were made to primary alkaline cells: (1) the use of improved cathode and anode formulations, (2) the limitation of the anode capacity to approximately 1/3 of the cathode capacity to prevent overdischarge of the cathode, (3) the application of improved separators, and (4) the integration of means to enable moderate cell abuse. Cell components (cans and closures) and raw materials (EMD, graphite, zinc) used are identical to the ones used in primary alkaline cells. The electrode capacity balance accounts for the reduced capacity of RAM cells when compared to primary alkaline cells of similar size.