Detecting a bad contact of a charging cable

1. A method for detecting a bad contact of a charging cable, the method comprising:

measuring a cooling fluid temperature of a cooling fluid flowing through the charging cable;

measuring a connector base temperature of a connector base of the charging cable, which connector base carries an electrical contact element of the charging cable;

estimating a contact temperature of the electrical contact element from the connector base temperature and the cooling fluid temperature, wherein the estimated contact temperature increases, when the difference of the connector base temperature and the cooling fluid temperature increases; and

deciding presence of a bad contact, when the estimated contact temperature is higher than a threshold temperature.

2. The method of claim 1 , wherein the estimated contact temperature is equal to the cooling fluid temperature, when the connector base temperature and the cooling fluid temperature are equal.

3. The method of claim 2 , wherein the estimated contact temperature is the cooling fluid temperature plus the difference of the connector base temperature and the cooling fluid temperature multiplied by a constant factor.

4. The method of claim 2 , wherein the connector base comprises a cavity through which cooling fluid is guided.

5. The method of claim 2 , wherein the connector base temperature is measured with a temperature sensor attached to an inside of the connector base.

6. The method of claim 2 , wherein the connector base temperature is measured with a temperature sensor attached to an outside of the connector base.

7. The method of claim 1 , wherein the estimated contact temperature is the cooling fluid temperature plus the difference of the connector base temperature and the cooling fluid temperature multiplied by a constant factor.

8. The method of claim 1 , wherein the connector base comprises a cavity through which cooling fluid is guided.

9. The method of claim 1 , wherein the connector base temperature is measured with a temperature sensor attached to an inside of the connector base.

10. The method of claim 1 , wherein the connector base temperature is measured with a temperature sensor attached to an outside of the connector base.

11. The method of claim 1 , wherein the connector base is cooled with cooling fluid;

wherein the cooling fluid temperature is measured with a temperature sensor arranged in a cooling fluid flow returning from the connector base; or

wherein the cooling fluid temperature is measured with a temperature sensor arranged in a cooling fluid flow flowing towards the connector base.

12. The method of claim 1 , wherein the cooling fluid is pumped from a tank through a hose in the charging cable between the tank and the electrical contact.

13. The method of claim 12 , wherein the cooling fluid temperature is measured with a temperature sensor in the tank.

14. The method of claim 1 , wherein the cooling fluid is a cooling oil.

15. A method for charging an electrical device, the method comprising:

charging the electrical device via a charging cable by generating a current in the charging cable;

detecting a bad contact of the charging cable with at least the following steps:

measuring a cooling fluid temperature of a cooling fluid flowing through the charging cable;

measuring a connector base temperature of a connector base of the charging cable, which connector base carries an electrical contact element of the charging cable;

estimating a contact temperature of the electrical contact element from the connector base temperature and the cooling fluid temperature, wherein the estimated contact temperature increases, when the difference of the connector base temperature and the cooling fluid temperature increases;

deciding presence of a bad contact, when the estimated contact temperature is higher than a threshold temperature; and

interrupting the current, when a bad contact has been detected.

16. A controller for a charging station comprising:

a memory structured to store a set of instructions; and

a processor structured to execute the set of instructions stored by the memory effective to:

receive a cooling fluid temperature of a cooling fluid flowing through the charging cable,

receive a connector base temperature of a connector base of the charging cable, which connector base carries an electrical contact element of the charging cable,

estimate a contact temperature of the electrical contact element from the connector base temperature and the cooling fluid temperature, wherein the estimated contact temperature increases, when the difference of the connector base temperature and the cooling fluid temperature increases, and

decide presence of a bad contact, when the estimated contact temperature is higher than a threshold temperature.

17. A charging station comprising:

a charging cable with a plug comprising electrical contact elements;

a cooling system for cooling the charging cable by generating a flow of cooling fluid through the charging cable and the plug;

a first temperature sensor for measuring a cooling fluid temperature of the cooling fluid;

a second temperature sensor for measuring a connector base temperature of a connector base arranged in the plug; and

a controller comprising:

a memory structured to store a set of instructions; and

a processor structured to execute the set of instructions stored by the memory effective to:

receive the cooling fluid temperature of the cooling fluid flowing through the charging cable,

receive the connector base temperature of the connector base of the charging cable, which connector base carries an electrical contact element of the charging cable,

estimate a contact temperature of the electrical contact element from the connector base temperature and the cooling fluid temperature, wherein the estimated contact temperature increases, when the difference of the connector base temperature and the cooling fluid temperature increases, and

decide presence of a bad contact, when the estimated contact temperature is higher than a threshold temperature.

18. The charging station of claim 17 ,

wherein the cooling system comprises pipes in the charging cable for transporting the cooling fluid;

wherein the cooling system comprises a pump for pumping cooling fluid through the charging cable;

wherein the cooling system comprises a tank for storing cooling fluid.

19. The charging station of claim 18 , wherein the charging station and the charging cable are adapted for charging an electric vehicle.

20. The charging station of claim 17 , wherein the charging station and the charging cable are adapted for charging an electric vehicle.