Abstract: High temperature secondary cells having a molten salt or fused salt electrolyte are fabricated in ambient atmosphere. Such cells typically have an electrolyte, a positive reactant or a negative reactant which are capable of reacting with moisture or oxygen contained in the atmosphere. The ingredients or materials comprising the positive and negative reactants and the electrolyte are processed in a state in which they do not react significantly with moisture or oxygen in the ambient atmosphere. Thereafter, they are electrically charged in the positive reactant compartment of a cell container at the operating temperature of the cell whereby the negative reactant of the cell is provided in the negative reactant compartment of the cell container and a positive reactant-electrolyte melt is provided in the positive reactant compartment of the cell container.