A motor vehicle multi-voltage battery device, includes: a first electrical output terminal and an electrical ground terminal providing a first rated voltage; a second electrical output terminal and the electrical ground terminal providing a second rated voltage; a first series circuit having a first battery cell group and a first controllable switch between the first electrical output terminal and electrical ground terminal; a protective resistor parallel to the first switch. The first switch configured to bridge the protective resistor in a closed state; a second battery cell group between the second electrical output terminal and the first electrical output terminal connected switchably in series with the first battery cell group; and a battery management assembly configured to switch the first switch into an open state to protect the first battery cell group.