The present invention relates to a high power battery system having a battery system monitoring electronics and battery modules being electrically connected in series via an operating current line. At least one battery module is a bypass battery module comprising a bypass switch and a bypass line for electrically bypassing the battery module. For each bypass battery module a module monitoring unit of the monitoring electronics monitors the assigned battery module and detects a fault state. In the fault state, the battery system monitoring electronics measures the current flow in the operating current line connecting the battery modules and switches the bypass switch of the bypass battery module concerned from a normal operating position to a bypass position at a time when the current flow in the operating current line is lower than a predetermined limit value.