Accumulators with acid and alkaline water electrolyte are investigated. Attention is given to a deeper insight in the principles and processes taking place in unbalanced electrochemical systems and optimization of operation modes with respect to the major utility characteristics of accumulators (capacity, cycling lifetime, reliability, efficiency, internal resistance). Research is also focused on suitable additives for active mass, effect of applied pressure, properties of individual operating parts of accumulator, optimization of formation procedure, testing of AGM separators exhibiting the best characteristics for experimental cells.