The invention relates to a 
battery system (10) for an 
electric vehicle, comprising: a 
battery pack (5) having a positive 
electrode (22), a negative 
electrode (21), at least one 
battery cell (2) and a pack 
voltage divider (25); and at least one 
coupling network having a negative connection (11) and a positive connection (12), wherein the group 
voltage divider (25) comprises a positive group 
resistor (RP2) and a positive sub-group 
resistor (RSP2), which are connected in series with each other between the positive 
electrode (22) and a reference point (50), and a negative group 
resistor (RP1) and a negative sub-group resistor (RSP1), which are connected in series with each other between the negative electrode (21) and the reference point (50). The at least one 
coupling network has a 
coupling voltage divider (15), the coupling 
voltage divider comprises a positive coupling resistor (RK2) and a positive partial coupling resistor (RSK2), which are connected in series with each other between the positive connection (12) and the reference point (50), and a negative coupling resistor (RK1) and a negative partial coupling resistor (RSK1), which are connected in series with each other between the negative connection (11) and the reference point (50). The invention also relates to a method for diagnosing a 
battery system (10) according to the invention, wherein a positive group voltage (UP2) occurring at the positive component-group resistor (RSP2) is measured, a negative group voltage (UP1) occurring at the negative component-group resistor (RSP1) is measured, a positive coupling voltage (UK2) occurring at the positive component-coupling resistor (RSK2) is measured, a negative coupling voltage (UK1) occurring at the negative component-coupling resistor (RSK1) is measured, and the measured voltages (UP1, UP2, UK1, UP2, UK1, UP2, UK1, UK2, UK1, UK1, UK2, UK1, UK2, UK1, UK2, UK1, UK2, UK1, UK2, UK1, UK2, UK1, UK2, UK1, UK2, UK1, UK2, UK1, UK2, UK1, UK2, UK1, UK2, UK1 The invention also relates to an 
electric vehicle comprising a 
battery system (10) according to the invention.