In an energy storage device comprising a series network of n storage elements C1, . . . Cn, able to provide a continuous voltage across its terminals, a system for equilibrating the elements is envisaged comprising a plurality of charge transfer modules Mi,j, each module Mi,j ensuring a bidirectional transfer of charge linear to first order between two storage elements Ci and Cj of the said network. Each energy storage element is connected to p modules, p≦n−1, each of the p modules pairing the said element with another element of the network. The time required for reequilibrating is thus reduced.