Method for preparing the supply of electrical power to a vehicle having a supply device with a supply device providing at least one supply voltage, said vehicle and said supply device being designed separately from one another and being releasably electrically connected to one another by means of a plug contact (2, 6) between the supply device of the vehicle and the supply device, in which method during the preparation of the power supply after the supply device of the vehicle has been electrically connected to the supply device - the supply device determines, via a first communication path in the form of a pipe (10, 20) closed via the plug contact (2, 6,) a specific voltage which characterises the voltage class of the vehicle and, based on the determined specific voltage, identifies the voltage class of the vehicle, characterised in that the pipe (10, 20) is a connection pipe provided in addition to HV pipes (HV+, HV-) of the vehicle designed as high-voltage pipes and a voltmeter is connected with the connection pipe and the specific voltage which characterises the voltage class of the vehicle is generated on the vehicle side a) by a voltage source of the supply device of the vehicle or b) by the voltage drop on a voltage divider having resistors (R1, R2, R4a, R4b, R4c) and wherein a second communication path is provided in the form of a power pipe communication (4, 9), wherein - the supply device reports back the determined voltage class to the supply device of the vehicle via the second communication path in the form of the power pipe communication (4, 9), - the supply device of the vehicle transmits the value of the maximum supply voltage which may be applied to supply energy to the vehicle, to the supply device by means of power pipe communication (4, 9), - the supply device compares the maximum value of the supply voltage assigned to the identified voltage class with the transmitted value of the maximum supply voltage which may be applied to supply energy to the vehicle, and - in which the supply device allows a continuation of the energy supply process in the preparation phase of the energy supply, if the maximum value of the supply voltage assigned to the identified voltage class is less than or equal to the transmitted value of the maximum supply voltage which may be applied to supply energy to the vehicle. - the supply device determines, via a first communication path in the form of a pipe (10, 20) closed via the plug contact (2, 6,) a specific voltage which characterises the voltage class of the vehicle and, based on the determined specific voltage, identifies the voltage class of the vehicle, characterised in that the pipe (10, 20) is a connection pipe provided in addition to HV pipes (HV+, HV-) of the vehicle designed as high-voltage pipes and a voltmeter is connected with the connection pipe and the specific voltage which characterises the voltage class of the vehicle is generated on the vehicle side a) by a voltage source of the supply device of the vehicle or b) by the voltage drop on a voltage divider having resistors (R1, R2, R4a, R4b, R4c) and wherein a second communication path is provided in the form of a power pipe communication (4, 9), wherein a) by a voltage source of the supply device of the vehicle or b) by the voltage drop on a voltage divider having resistors (R1, R2, R4a, R4b, R4c) and wherein a second communication path is provided in the form of a power pipe communication (4, 9), wherein - the supply device reports back the determined voltage class to the supply device of the vehicle via the second communication path in the form of the power pipe communication (4, 9), - the supply device of the vehicle transmits the value of the maximum supply voltage which may be applied to supply energy to the vehicle, to the supply device by means of power pipe communication (4, 9), - the supply device compares the maximum value of the supply voltage assigned to the identified voltage class with the transmitted value of the maximum supply voltage which may be applied to supply energy to the vehicle, and - in which the supply device allows a continuation of the energy supply process in the preparation phase of the energy supply, if the maximum value of the supply voltage assigned to the identified voltage class is less than or equal to the transmitted value of the maximum supply voltage which may be applied to supply energy to the vehicle.