Device and method for monitoring and making symmetrical a multi-cell energy storage stack

The device (10) has a combinatorial circuit (30) connected to energy storage cells (C1-Cn) and a voltage measuring unit (40). Another combinatorial circuit (60) is connected to an energy storage element, the voltage measuring unit and the former combinatorial circuit. A control unit (50) is connected to the voltage measuring unit and controls the combinatorial circuits. The energy storage element is switched selectively in parallel with the energy storage cells by the combinatorial circuits to transfer a portion of electrical charge from an arbitrary cell to another arbitrary cell. An independent claim is also included for a method for monitoring and balancing cell voltages of two electrical energy storage cells of a multi-cell energy storage stack.