Method for operating a battery system, which comprises a plurality of parallel connected strings, each having at least one battery module (18, 20, 22, 23), in which a plurality of battery cells (24, 26, 28, 30) are connected in a series circuit and/or in a parallel circuit, wherein the strings can be switched on and off from one another, and wherein individual battery cells (24, 26, 28, 30) and/or individual battery cell packs, each comprising a plurality of battery cells (24, 26, 28, 30) connected in parallel, can be switched on and off from one another and can be bypassed, comprising at least the following method steps: - detecting a fault in a battery cell (24, 26, 28, 30); - switching off and bypassing the faulty battery cell (24, 26, 28, 30) and/or the faulty battery cell pack in which the faulty battery cell (24, 26, 28, 30) is located; - switching off the faulty string which has the faulty battery cell (24, 26, 28, 30) and/or the faulty battery cell packet; - comparing the string voltage of the faulty string with the string voltage of the respective intact strings in which no faults have been detected; - discharging the intact strings if voltage differences between the intact strings exceed a voltage threshold value, - switching on the faulty string, if the string voltages of the respective intact strings have almost matched the level of the string voltage of the faulty string, or if a recuperation process takes place during the discharging of the intact strings. the strings can be switched on and off from one another, and wherein individual battery cells (24, 26, 28, 30) and/or individual battery cell packs, each comprising a plurality of battery cells (24, 26, 28, 30) connected in parallel, can be switched on and off from one another and can be bypassed, comprising at least the following method steps: - detecting a fault in a battery cell (24, 26, 28, 30); - switching off and bypassing the faulty battery cell (24, 26, 28, 30) and/or the faulty battery cell pack in which the faulty battery cell (24, 26, 28, 30) is located; - switching off the faulty string which has the faulty battery cell (24, 26, 28, 30) and/or the faulty battery cell packet; - comparing the string voltage of the faulty string with the string voltage of the respective intact strings in which no faults have been detected; - discharging the intact strings if voltage differences between the intact strings exceed a voltage threshold value, - switching on the faulty string, if the string voltages of the respective intact strings have almost matched the level of the string voltage of the faulty string, or if a recuperation process takes place during the discharging of the intact strings. - detecting a fault in a battery cell (24, 26, 28, 30); - switching off and bypassing the faulty battery cell (24, 26, 28, 30) and/or the faulty battery cell pack in which the faulty battery cell (24, 26, 28, 30) is located; - switching off the faulty string which has the faulty battery cell (24, 26, 28, 30) and/or the faulty battery cell packet; - comparing the string voltage of the faulty string with the string voltage of the respective intact strings in which no faults have been detected; - discharging the intact strings if voltage differences between the intact strings exceed a voltage threshold value, - switching on the faulty string, if the string voltages of the respective intact strings have almost matched the level of the string voltage of the faulty string, or if a recuperation process takes place during the discharging of the intact strings.