A management unit and method for managing electric energy stored in a battery composed of a number of series-connected cells, the management unit having: a main equalizing circuit, which forms the primary of an electric transformer and has a constant alternating-current generator powered by the battery and which feeds alternating current of constant intensity through the main equalizing circuit; and, for each cell of the battery, a secondary equalizing circuit, which forms the secondary of the electric transformer, is connected parallel to the cell, has a one-way electronic device which imposes electric current flow to the cell in one direction only, and is connected to a drive device that can be activated to zero the voltage applied to the cell by the secondary equalizing circuit.