Balancing converter for batteries comprising a diagnosis means

The converter has a switch matrix (MC) including switches e.g. static relays, connected to cells (C) of an electric battery. A balancing system is connected to the switch matrix for charging and discharging each cell by controlling the switch matrix. The balancing system includes a cell diagnostic system (DIA) connected to the switch matrix, so that switching control enables connection of the diagnostic system to a cell to be diagnosed. The diagnostic system determines state of charge and/or condition of the cell.