NOVELTY - The circuit has multiple of cell-supervision circuits (102, 103) fixed at a flex board (100) in a material engaged manner using a wave soldering technology, plunger soldering technology, through-hole-reflow-soldering technology and/or welding technology. One of the supervision circuits (103) is imprinted on the board using surface mounted device technology. Conducting paths (101) i.e. bridging circuits, are provided on the flex board. The cell-supervision circuits are adjusted to number of cells according to the conducting paths that are provided on the flex board.    USE - Monitoring electronic circuit for monitoring a battery e.g. high-voltage battery and lithium-ion-battery, in a battery system (claimed), which is utilized in electrical or hybrid vehicles, and back-up-system e.g. solar-or wind turbine, telecommunication system i.e. decentralized system e.g. base station and distributor box, and laptop.    ADVANTAGE - The cell- supervision circuits are fixed at the flex board in a material engaged manner without the need of plug contacts, cable and copper sheet metal, thus connecting the flex board and the cell-supervision circuits in a reliable, vibration-resistive and economical manner using reduced components, and avoiding corrosion of plug contacts. The monitoring electronic circuit possesses increased service life and reduced error rate. The fixation avoids the need for manual welding of the cables, thus implementing fixation in an automatic manner. The cell- supervision circuits are robust against surrounding area influences, during application in the vehicles. The material engaged connection enables achieving reduced contact resistance at contact points.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for the following:    (1) a battery system comprising a cell terminal    (2) a method for attachment of a monitoring electronic circuit for the battery.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view illustrating a connection of cell-supervision circuits and the flex board.    Flex board (100)    Conducting paths (101)    Cell-supervision circuits (102, 103)    Connection of cell-supervision circuits and flex board (104)    Communication connector (105)