High voltage battery system and method for controlling same

The system has battery modules (4) electrically connected in series by an operating current line (5) such that an operating current flows through the current line during operation. A battery system monitoring electronics unit incorporates a module monitoring unit (11) that monitors a bypass battery module (6) and detects a fault state of the module. The electronics unit measures current flow in the current line and switches a bypass switch (7) i.e. magnetic switch, from a normal operating position into a bypass position at a time at which the current flow is less than a preset limit value. Independent claims are also included for the following: (1) an electric vehicle comprising a controller for controlling an electric motor (2) a method for controlling a high-current battery system.