Device for operating an accumulator unit

The device has a monitoring circuit (20) monitoring operating parameters of cells (11) of an accumulator unit (10). The monitoring circuit is arranged between switching conditions (1, 2) depending on the operating parameters. The cells form a common current path in one of the switching conditions, where one of the cells is energetically separated from a cell assembly in another switching condition. The monitoring circuit is provided with a protective circuit (30), which is activatable during change between the switching conditions. An independent claim is also included for a method for charging and/or discharging an accumulator unit.