Multi-voltage battery device and electrical system for a motor vehicle

1. A multi-voltage battery device for a motor vehicle, comprising:

a first electrical output terminal and an electrical ground terminal for the provision of a first rated voltage;

a second electrical output terminal and the electrical ground terminal for the provision of a second rated voltage;

a first series circuit of a first battery cell group and a first controllable switch between the first electrical output terminal and the electrical ground terminal, wherein the first switch is electrically connected into the first series circuit via two terminals;

a first protective resistor that is electrically connected between the two terminals of the first switch, the first protective resistor being connected in parallel to the first switch;

wherein the first switch is configured to bridge the protective resistor when in a closed switch state;

a second battery cell group, that is electrically connected between the second electrical output terminal and the first electrical output terminal, and is connected switchably in series with the first battery cell group;

a battery management assembly for operating the multi-voltage battery device, the battery management assembly being configured to switch the first switch into an open switch state to protect the first battery cell group in the event of an excessively high current or of an electrical short-circuit between the first electrical output terminal and the electrical ground terminal.

2. The multi-voltage battery device as claimed in claim 1 , further comprising:

a second switch that is electrically connected between the two terminals of the first switch, and in series with the protective resistor;

wherein the battery management assembly is further configured to switch the second switch into a closed switch state in the event of the excessively high current or of the electrical short-circuit between the first electrical output terminal and the electrical ground terminal.

3. The multi-voltage battery device as claimed in claim 2 , wherein the battery management assembly is further configured to switch the first switch into the open switch state and to switch the second switch into the closed switch state in the event that the motor vehicle is in an idle mode.

4. The multi-voltage battery device as claimed in claim 2 , wherein the battery management assembly is further configured to switch the first and the second switches into the open switch state in the event of an internal malfunction or an internal electrical short-circuit in the first battery cell group.

5. The multi-voltage battery device as claimed in claim 2 , wherein the battery management assembly is further configured to switch the first and the second switches into the open switch state in the event of a critical charge state of the first battery cell group.

6. The multi-voltage battery device as claimed in claim 1 , wherein the battery management assembly is electrically connected via electrical supply connections between the first electrical output terminal and the electrical ground terminal, and parallel to the first series circuit.

7. The multi-voltage battery device as claimed in claim 1 , wherein the protective resistor is implemented as a PTC resistor.

8. The multi-voltage battery device as claimed in claim 1 , further comprising:

a unidirectional or bidirectional DC voltage converter that is electrically connected on the input voltage side between the first electrical output terminal and the first battery cell group and on the output voltage side between the second electrical output terminal and the second battery cell group, and which is configured to charge the second battery cell group with current of the first battery cell group and/or the first battery cell group with current of the first battery cell group;

wherein the battery management assembly is further configured to operate the DC voltage converter to charge the first battery cell group with the current of the second battery cell group and/or to charge the second battery cell group with the current of the first battery cell group.

9. The multi-voltage battery device as claimed in claim 1 , further comprising:

a second series circuit consisting of a third controllable switch and the second battery cell group between the second electrical output terminal and the first electrical output terminal;

wherein the third switch here connects the second battery cell group to the first battery cell group in an electrically switchable manner.

10. The multi-voltage battery device as claimed in claim 9 ,

wherein the first and the second series circuits comprise a common circuit segment that electrically connects the first electrical output terminal to the first and the second battery cell groups;

wherein the first switch, or its two terminals are electrically connected into the circuit segment.

11. An on-board electrical system for a motor vehicle, comprising:

a first on-board electrical system branch with a first on-board electrical system voltage;

a second on-board electrical system branch with a second on-board electrical system voltage;

a multi-voltage battery device as claimed in claim 1 , that is electrically connected via the first electrical output terminal to the first on-board electrical system branch and via the second electrical output terminal to the second on-board electrical system branch.

12. The multi-voltage battery device as claimed in claim 3 , wherein the battery management assembly is further configured to switch the first and the second switches into the open switch state in the event of an internal malfunction or an internal electrical short-circuit in the first battery cell group.