Motor vehicle with liquid container

1. A motor vehicle, comprising:

a liquid container for receiving an operating liquid;

a cooling circuit for cooling a drive motor of the motor vehicle via a cooling liquid circulating in the cooling circuit;

at least one heating coil arranged in the liquid container, the heating coil being operatively attached to the cooling circuit so that the cooling liquid is to flow through the heating coil and thereby heat the operating liquid;

a connection line operatively attached to the cooling circuit to thereby form a secondary circuit through which the cooling liquid is to flow, wherein the heating coil is arranged in the secondary circuit; and

at least one valve arranged in the connection line to cut off the secondary circuit from the cooling circuit while the cooling circuit is in an operating state, wherein the cooling circuit, in said operating state, is conducted through the at least one heating coil.

2. The motor vehicle of claim 1 , wherein the connection line is arranged in the liquid container.

3. The motor vehicle of claim 1 , wherein the connection line is arranged outside of the liquid container.

4. The motor vehicle of claim 1 , further comprising a pump, arranged in the connection line, to circulate the cooling liquid within the secondary circuit.

5. The motor vehicle of claim 4 , wherein the pump is arranged in the liquid container or that the pump is arranged outside the liquid container in the vicinity of the liquid container.

6. The motor vehicle of claim 4 , wherein the pump is arranged outside of the liquid container.

7. The motor vehicle of claim 1 , further comprising at least one valve, arranged in the cooling circuit, to fluidically separate the cooling circuit from the secondary circuit while the secondary circuit is in an operating state.

8. The motor vehicle of claim 1 , further comprising at least one secondary connection line, arranged in parallel to the connection line and operatively attached to the cooling circuit.

9. The motor vehicle of claim 8 , further comprising at least one valve, arranged in the at least one secondary connection line.

10. The motor vehicle of claim 1 , further comprising at least one electrical heating device, arranged on the secondary circuit, to heat the cooling liquid in the secondary circuit.

11. The motor vehicle of claim 10 , wherein the electrical heating device is arranged in the liquid container or that the electrical heating device is arranged outside the liquid container in the vicinity of the liquid container.

12. The motor vehicle of claim 10 , wherein the electrical heating device is arranged outside of the liquid container.

13. The motor vehicle of claim 1 , wherein the at least heating coil comprises a smooth tube or a corrugated tube that is composed of a thermoplastic material, or a non-ferrous metal material, or aluminum, or stainless steel, or a composite material.

14. A system for a motor vehicle, the system comprising:

a liquid container for receiving an operating liquid;

a cooling circuit for cooling a drive motor of the motor vehicle via a cooling liquid circulating in the cooling circuit;

at least one heating coil arranged in the liquid container, the heating coil being operatively attached to the cooling circuit so that the cooling liquid is to flow through the heating coil and thereby heat the operating liquid;

a connection line operatively attached to the cooling circuit to thereby form a secondary circuit through which the cooling liquid is to flow, wherein the heating coil is arranged in the secondary circuit; and

at least one valve arranged in the connection line to cut off the secondary circuit from the cooling circuit while the cooling circuit is in an operating state, wherein the cooling circuit, in said operating state, is conducted through the at least one heating coil.

15. The motor vehicle of claim 14 , further comprising:

a pump, arranged in the connection line, to circulate the cooling liquid within the secondary circuit;

at least one secondary connection line, arranged in parallel to the connection line and operatively attached to the cooling circuit; and

at least one electrical heating device, arranged on the secondary circuit, to heat the cooling liquid in the secondary circuit.

16. The motor vehicle of claim 15 , further comprising:

at least one valve, arranged in the connection line, to cut off the secondary circuit from the cooling circuit while the cooling circuit is in an operating state;

at least one second valve, arranged in the cooling circuit, to fluidically separate the cooling circuit from the secondary circuit while the secondary circuit is in an operating state; and

at least one third valve, arranged in the at least one secondary connection line.

17. A method for heating an operating liquid in a liquid container of a motor vehicle, the method comprising:

providing the motor vehicle with:

a liquid container for receiving an operating liquid;

a cooling circuit for cooling a drive motor of the motor vehicle via a cooling liquid circulating in the cooling circuit;

at least one heating coil arranged in the liquid container, the heating coil being operatively attached to the cooling circuit so that the cooling liquid is to flow through the heating coil and thereby heat the operating liquid;

a connection line operatively attached to the cooling circuit to thereby form a secondary circuit through which the cooling liquid is to flow, wherein the heating coil is arranged in the secondary circuit; and

at least one valve arranged in the connection line to cut off the secondary circuit from the cooling circuit while the cooling circuit is in an operating state, wherein the cooling circuit, in said operating state, is conducted through the at least one heating coil,

activating the secondary circuit or maintaining the secondary circuit in an active operating state, upon identifying a predefined activation condition; and/or

deactivating the secondary circuit or maintaining the secondary circuit in a deactive operating state, upon identifying a predefined deactivation condition.

18. The method of claim 17 , wherein:

activation of the secondary circuit comprises activating a pump and deactivating an electrical heating device switched;

deactivation of the secondary circuit comprises deactivating the pump and the electrical heating device.

19. The method of claim 17 , wherein:

the predefined activation condition comprises a predefined low threshold value of an engine temperature, and/or a predefined low threshold value of an outside temperature; and

the predefined deactivation condition comprises a predefined high threshold value of the engine temperature, and/or a predefined high threshold value of the outside temperature.