Abstract: An electrochemical cell including an electrode assembly including a winding core, a first electrode, a second electrode, and a separator, the first electrode, the second electrode, and the separator being wound around the winding core, a current collector connected to the first electrode, and a case that accommodates the wound electrode assembly and the current collector. The winding core is welded to the current collector.

Abstract: A method is provided for determining a state variable such as aging of an electrochemical cell comprising an electrode plate group, that includes analyzing at least a portion of a response spectrum of the electrochemical cell to application of an electromagnetic wave in a frequency ranging from 10 kHz to 10 GHz, so as to determine an indicator of the value of the state variable.

Abstract: A method for balancing a battery (C) comprising a plurality of branches (Ba, Bb, . . . , Bn) in parallel, each branch comprising at least two electrochemical cells in series (E1a, E2a, E3a, E1b, E2b, E3b), with an activatable electrical energy discharge or transfer device (Rb) being connected across the terminals of each electrochemical cell, comprises activating the electrical energy discharge or transfer devices connected across the terminals of the cells of the branch that includes the electrochemical cell having the lowest voltage, with the exception of the electrical energy discharge or transfer device associated with the electrochemical cell having the lowest voltage, and simultaneously deactivating the electrical energy discharge or transfer devices connected across the terminals of the cells of the branch or branches that do not include the electrochemical cell with the lowest voltage.