A refuelable electrochemical battery is provided that features three phases of operation that repeat cyclically. In an intake phase a mixture of electrochemically active particles or pellets (e.g., aluminum pellets) and a suitable electrolyte (e.g., sodium hydroxide, potassium hydroxide) are fed into a cavity or chamber. In a power phase the resulting electrochemical reaction produces electrical energy. The particles are mechanically combined or collected to form one electrode, while a gas-diffusion membrane permeable by oxygen is another electrode. During the exhaust phase, a piston forces the residue of the reaction from the cavity in order to prepare for the next cycle of operation.