WO2023222338A1

WO2023222338A1 - Method for determining the temperature in a charging socket of an electric vehicle, and charging socket for an electric vehicle

Info

Publication number: WO2023222338A1
Application number: PCT/EP2023/060821
Authority: WO
Inventors: Stephan Heckelsmüller; Christian Scheibl; Stephan Schafferhans
Original assignee: Lisa Dräxlmaier GmbH
Priority date: 2022-05-16
Filing date: 2023-04-25
Publication date: 2023-11-23
Also published as: DE102022112232B3

Abstract

The invention relates to a method for determining the temperature in a charging socket (10) of an electric vehicle, which charging socket has DC contacts (14) and AC contacts (12) for charging the electric vehicle and temperature sensors (13, 16) for measuring each of the temperatures of the contacts (12, 14), the method comprising the following steps: measuring each of the temperatures (TDC-, TDC+, TAC L1, TAC L2) by means of the temperature sensors (13, 16) while the electric vehicle is being charged via the DC contacts (14) or via the AC contacts (12); providing a thermodynamic model (34) of the charging socket (10), the model depicting a thermal coupling between the temperature sensors (13, 16) and, depending on this, providing estimates (TDC-Schätzung, TDC+Schätzung, TAC L1 Schätzung, TAC L2 Schätzung) for the temperatures of each of the contacts (12, 14); and determining an estimate (TDC-Schätzung, TDC+Schätzung, TAC L1 Schätzung, TAC L2 Schätzung) for the temperature from at least one of the DC contacts (14) or from at least one of the AC contacts (14) by entering the measured temperatures (TDC-, TDC+, TAC L1, TAC L2) into the thermodynamic model (34) of the charging socket (10). The invention further relates to a charging socket (10) for an electric vehicle.

Description

Lisa Dräxlmaier GmbH Landshuter Str. 100 D-84137 Vilsbiburg

METHOD FOR DETERMINING TEMPERATURE IN A CHARGING SOCKET OF AN ELECTRIC VEHICLE AND CHARGING SOCKET FOR AN ELECTRIC VEHICLE

Technical area

The present invention relates to a method for determining the temperature in a charging socket of an electric vehicle and charging socket for an electric vehicle.

State of the art

It is known per se to provide vehicle-side charging sockets for charging the batteries, in particular the traction batteries, in electric vehicles, for example battery-electric passenger cars. There are charging sockets that enable charging with direct current and alternating current. Such charging sockets are also known as combination sockets. With such charging sockets, it is possible, for example, to charge electric vehicles both at standard household sockets and at fast charging stations.

Particularly when charging with high current, the possible wear of high-voltage contacts in the charging socket, which are usually DC contacts for charging with direct current, represents a potential safety risk. In order to still be able to charge an electric vehicle safely, the temperature of these contacts must be determined as precisely as possible needed. However, it may happen that the temperature sensors provided in such charging sockets do not allow a sufficiently precise determination of the temperature, particularly on the high-voltage contacts.

Description of the invention

It is the object of the invention to provide a solution which enables temperature determination in a charging socket of an electric vehicle in a particularly simple and precise manner. This task is solved by the subject matter of the independent claims. Further possible embodiments of the invention are disclosed in the subclaims, the description and the figures.

In the method according to the invention, a temperature is determined at a charging socket of an electric vehicle. The charging socket includes direct current contacts for charging the electric vehicle and electrically separated alternating current contacts for charging the electric vehicle as well as respective direct current contacts and the

Alternating current contacts assigned and spaced temperature sensors for measuring the respective temperatures of the contacts.

The DC contacts and the AC contacts can be pins or sockets. The DC contacts can be high-voltage contacts for charging, especially fast charging, of the electric vehicle. For example, the direct current contacts can be designed to charge a traction battery of the electric vehicle at charging stations designed for this purpose with more than 40 kW or with more than 350 kW at voltages of, for example, 400 V, 800 V or 1000 V. The AC contacts can, for example, be contacts for charging the traction battery on a wallbox, e.g. at 110 V or 230 V. The charging socket is a so-called combo charging socket, which can be operated either with direct current or with alternating current.

The temperature sensors are not arranged directly on the current-carrying contacts, but are arranged at some distance from them, for example on a circuit board. For example, an air gap can be present between the temperature sensors and the respective contacts. The temperature sensor, which is assigned to one of the respective contacts, is in particular arranged closer to this contact than the other temperature sensors. The charging socket is designed in particular in such a way that a high-voltage and a low-voltage electrical system are safely separated from one another.

The power-carrying contacts, i.e. the direct current and alternating current contacts, are monitored using respective temperature sensors. In order to improve any limited accuracy, especially with aged contacts, the temperature sensors on the contacts that are not energized during the respective charging process are also used. While the electric vehicle is connected via the DC contacts or via the Alternating current contacts are charged, so respective temperatures are measured using the temperature sensors assigned to the direct current contacts and the alternating current contacts.

In addition, a thermodynamic model of the charging socket is provided, which maps a thermal coupling between the temperature sensors and, depending on this, provides estimated values for the temperatures of the respective contacts. The thermodynamic model can, for example, depict or describe the heat conduction between the temperature sensors. The thermodynamic model can also describe, for example, the heat conduction between the contacts and the temperature sensors assigned to them. The thermodynamic model can map or describe heat conduction paths between the temperature sensors and the direct current and alternating current contacts.

In the method according to the invention, an estimated value for the temperature of at least one of the DC contacts or of at least one of the AC contacts is determined during the charging process by entering the measured temperatures into the thermodynamic model of the charging socket. The estimated value can be determined repeatedly, in particular in real time, throughout the entire charging process. Estimates of their respective temperatures can also be determined for all contacts by entering the measured temperatures into the thermodynamic model of the charging socket.

In the method according to the invention, a model-based coupling of the temperature sensors takes place, which are responsible for measuring the temperature of the direct current and alternating current contacts. The model is used to establish a thermodynamic relationship between the temperatures measured by the temperature sensors in order to determine said estimated values for the temperatures of the contacts.

For example, if the electric vehicle is charged via the charging socket in direct current operation, the direct current contacts of the charging socket heat up, as these are energized via associated contacts from, for example, a charging gun, with the battery then being fed via corresponding direct current lines. The high current intensity creates heat at the direct current contacts. The heating of the direct current contacts is measured via the respective temperature sensors assigned to them, as a Heat transfer from the direct current contacts to the associated temperature sensors takes place. For this purpose, the direct current contacts can be connected to the associated temperature sensors in a heat-conducting manner. The AC contacts also heat up during the DC charging process, even though they are not energized. The alternating current contacts are heated by heat transfer, in particular by thermal coupling of the temperature sensors to one another, which can be arranged, for example, on the same circuit board.

The temperatures of the contacts measured during the charging process, i.e. temperature data characterizing the measured temperatures, are entered into the thermodynamic model of the charging socket. The result is then, for example, estimated values for the temperatures of the direct current contacts. The invention is based on the finding that if the thermodynamic model is fed both with temperature data from the temperature sensor system for the direct current contacts and with temperature data from the temperature sensor system for the alternating current contacts, the actual temperatures of the high-voltage contacts, i.e. the direct current contacts, can be determined more precisely than if one were to simply use the values of the temperature sensors assigned to the DC contacts. The reverse can also be done when charging with alternating current. In addition, the invention is based on the knowledge that temperatures measured by the direct current sensors can be below the actual temperatures of the direct current contacts. The DC contact temperatures estimated using the thermodynamic model are much closer to the actual DC contact temperatures.

In the method according to the invention, the temperature sensors for the direct current and alternating current contacts work together to estimate particularly precise temperature values for the contacts using the thermodynamic model of the charging socket. Due to the high model-based accuracy in temperature determination, less effort has to be put into the actual physical accuracy, which brings economic and design advantages. The accuracy of the temperature determination at the contacts can be improved using the method according to the invention, especially in the event of a dynamic temperature increase. Existing temperature sensors and existing data processing equipment can be used to implement the method, This results in at most a small design effort when implementing the method according to the invention in the charging socket. Since the temperature sensors work together in the method according to the invention, it offers advantages both when charging with alternating current and when charging with direct current in order to determine the temperatures of the respective current-carrying contacts during the charging process.

The method according to the invention therefore enables a particularly simple and precise solution for measuring the temperature in a charging socket of an electric vehicle.

A possible embodiment of the invention provides that a current intensity is regulated during the charging process depending on the estimated value for the temperature of at least one of the direct current contacts or of at least one of the alternating current contacts. The regulation can be carried out, for example, using a charging control device. For example, as the estimated temperature increases, the charging power can be reduced to avoid overheating of the relevant contacts. For example, a temperature limit can be specified. If this is reached or exceeded by the estimated value, the current intensity during the charging process can be reduced, for example. This means that a particularly safe charging process can be achieved at any time.

In a further possible embodiment of the invention, it is provided that the thermodynamic model of the charging socket takes into account the heat conduction between the temperature sensors and the contacts. Other aspects of heat transfer can also be taken into account in the model, such as thermal radiation or convection. By taking heat conduction into account, the model can enable particularly precise temperature estimation by taking thermal couplings between the temperature sensors into account.

According to a further possible embodiment of the invention, it is provided that the thermodynamic model of the charging socket is provided in the form of an empirical model. This means that a model is used that is relatively easy to create and can still provide very precise estimated values for the temperatures of the direct current and alternating current contacts.

A possible embodiment of the invention provides that the empirical model contains the estimated values for the temperatures of the contacts using respective calculation formulas determined, which include the measured temperatures and time derivatives of the measured temperatures, each multiplied by a parameter. The measured temperatures and their time derivatives are therefore related to one another in order to determine the estimated values. The calculation formula can, for example, be structured as follows:

This calculation formula can be used for a charging socket with two direct current and two alternating current contacts, with a temperature sensor assigned to each of the contacts. It could be, for example, a CCS1 charging socket. The charging socket therefore contains four temperature sensors, two of which are arranged on the DC contacts TDC- and TDC+, and two on the AC contacts TACLI and TACL2. The temperatures TDC-, TDC+, TACLI and TAC L2 are each the measured values of the temperature sensors. TDC+ estimate, TAC L1 estimate and TAC L2 estimate can be determined analogously. The parameters Ci to Cs can be determined using curve fitting algorithms, where reference sensors can measure the actual temperature of the DC and AC contacts. Because the reference sensors do not require HV-NV separation and are only needed for a one-off experimental setup, high-precision and high-priced reference sensors can be used. One possibility would be flexible film sensors, which are glued over a large area to the surface of the pin contacts. With the help of such empirical models in the form of calculation formulas, the estimated values in charging operation can be determined particularly quickly, since only the measured yield has to be entered into the calculation formula. This is not very computationally intensive, so the temperature changes at the contacts can be estimated in real time.

An alternative possible embodiment of the invention provides that the thermodynamic model of the charging socket is provided in the form of a physical model which maps the heat conduction paths between the temperature sensors and the contacts using a thermal equivalent circuit model of the charging socket. This offers a particularly accurate way to estimate the temperatures of the direct current and alternating current contacts. In a further possible embodiment of the invention, it is provided that in the thermal equivalent circuit model the contacts, the temperature sensors and a circuit board on which the temperature sensors are arranged are approximated by respective thermal masses which are linked together by thermal resistors. The temperatures of the contacts measured by the temperature sensors serve as input variables in this model. By modeling the contacts, temperature sensors and the circuit board in the form of thermal masses of respective heat conduction paths between these elements in the form of thermal resistances, the heat transfers between the elements can be depicted particularly realistically; This means that the temperatures of the respective contacts can then be estimated particularly precisely using the model.

A further possible embodiment of the invention provides that in the thermal equivalent circuit model, respective heat flows to the contacts are specified as a function of respective temperature gradients, which result from the measured temperatures. The temperature gradients actually cause corresponding heat flows in the corresponding directions that the model calculates. If one DC contact heats up faster than the other, e.g. due to wear of the coating, a heat flow occurs between these DC contacts. The thermal equivalent switching model is based on the assumption that the deviation of the measured temperature from the actual temperature is approximately proportional to the heat flow in the direction of the corresponding element. In the equivalent switching model, this heat flow is fed to the corresponding direct current or alternating current contact, which enables a particularly precise temperature estimate. The resulting heat flow reflects the heating of the respective contact due to the ohmic resistance of the contacts and associated lines.

According to a further embodiment of the invention, it is provided that the heat flows to the contacts are increased by respective constant factors. The factors can be chosen, for example supported by experiments, so that the resulting heat flows correspond particularly precisely to the actual heat flows. This leads to a particularly good temperature estimate of the contacts. In a further embodiment of the invention, it is provided that the thermal equivalent circuit model is determined depending on the geometry of the charging socket, material characteristics of the charging socket and/or based on an experimental setup. For example, the thermal masses, the thermal resistances and/or the factors can be determined depending on the geometry of the charging socket, material characteristics of the charging socket and/or using an experimental setup. The determination based on the geometry and/or material characteristics can also be understood as a physical determination of the parameters in question. Fine tuning can then be carried out using an experimental setup. This enables particularly good modeling of the thermal equivalent circuit model.

A further possible embodiment of the invention provides that a level of detail of the thermal equivalent circuit model and a time step size are set so that a data processing device can determine the estimated value for the temperature of at least one of the direct current contacts or of at least one of the alternating current contacts in real time. The operation of the data processing device, in which the temperature of at least one of the contacts or all contacts is estimated, runs simultaneously, or almost simultaneously, with the actual change in the temperatures of the direct current and/or alternating current contacts. The level of detail of the thermal equivalent circuit model and the time step between which the respective estimates of the temperatures are made are selected taking into account the performance of the data processing device so that a real-time estimate of the temperature of at least one of the contacts or all contacts is possible during a charging process. This means that the charging process and any temperature changes that may occur at the contacts can be monitored particularly precisely.

The charging socket according to the invention for an electric vehicle comprises DC contacts for charging the electric vehicle and AC contacts that are electrically separated from these for charging the electric vehicle; respective the DC contacts and the

Alternating current contacts assigned and spaced temperature sensors for measuring the respective temperatures of the contacts; and a data processing device which is set up for this purpose, based on a thermodynamic model of the charging socket, which depicts a thermal coupling between the temperature sensors and, depending on this, estimated values for the temperatures of the respective contacts, to determine an estimated value for the temperature of at least one of the DC contacts or of at least one of the AC contacts when the temperatures measured by the temperature sensors are entered into the thermodynamic model of the charging socket. Possible configurations of the method according to the invention can be viewed as possible configurations of the charging socket and vice versa. The charging socket can in particular have means for carrying out all process steps.

A possible embodiment of the charging socket provides that a heat-conducting connection is established between the temperature sensors via copper lines, thermal paste and/or a circuit board. This results in a particularly good heat-conducting connection between the temperature sensors, as a result of which the actual temperatures at the DC and AC voltage contacts can be estimated particularly precisely using the thermodynamic model of the charging socket.

Further advantages, features and details of the invention can be found in the following description of possible exemplary embodiments and in the drawing. The features and combinations of features mentioned above in the description as well as the features and combinations of features shown below in the description of the figures and/or in the figures alone can be used not only in the combination specified in each case, but also in other combinations or on their own, without the scope of the invention to leave.

Short character description

The drawing shows in:

Fig. 1 is a schematic representation of a charging socket for an electric vehicle, which has direct current contacts for charging with direct current and alternating current contacts for charging with alternating current and a temperature sensor for each contact, which are arranged on a common circuit board;

2 shows a schematic representation of a method for determining temperatures of the direct current contacts during a charging process with direct current; Fig. 3 temperature curves during the charging process with direct current, which were measured or estimated using different temperature sensors or actually occur;

Fig. 4 shows a thermal equivalent switching model of the charging socket.

Identical or functionally identical elements are provided with the same reference numerals in the figures.

A charging socket 10 for an electric vehicle, for example in the form of a purely electrically powered passenger car, is partially shown in a schematic representation in Fig. 1. The charging socket 10 is a combo charging socket, by means of which the electric vehicle can be charged with both direct current and alternating current. The charging socket 10 has two AC contacts 12 and two DC contacts 14 for this purpose. A temperature sensor 13, 16 is assigned to each of the AC contacts 12 and each of the DC contacts 14. The temperature sensors 13, 16 are arranged on a circuit board 18.

In Fig. 2, a method for determining temperatures of the direct current contacts 14 during a charging process with direct current is shown in the form of a flow chart 20. A current conduction path 22 for one of the direct current contacts 14 is indicated on the far left. A charging gun 24 is inserted into the charging socket 10, not shown here, and contacts of the charging gun 24 are contacted with the DC contacts 14. Direct current then flows, for example at 250 amps, through the direct current contacts 14 via direct current lines 26 to a traction battery, not shown here, of the electric vehicle in which the charging socket 10 is installed. Due to the current flow, the direct current contacts 14 heat up.

A heat flow 30 then flows from the direct current contacts 14 both to the temperature sensors 16 assigned directly to them and to the temperature sensors 13 further away from them. There is a thermal coupling 32, indicated schematically here, between the temperature sensors 13, 16.

Using the temperature sensors 13, 16, respective temperatures are measured in the vicinity of the alternating current contacts 12 and the direct current contacts 14 and fed to a thermodynamic model 34 of the charging socket 10. The Model 34 will also be certain parameters from a provided parameter set 36 are supplied, which enable the thermodynamic modeling of the model 34 to be as realistic as possible. Based on the measured temperatures, a respective temperature of the direct current contacts 14 is estimated using the model 34. This can be done by a data processing device 38, which can be part of the charging socket 10. Depending on the estimated temperatures of the direct current contacts 14, a charging control device 40 regulates a current intensity with which the charging gun 24 carries out the charging process.

In Fig. 3, various temperature curves 42, 44, 46, 48 are plotted in a diagram during the charging process with direct current. The temperature profile 42 characterizes the actual temperature at one of the direct current contacts 14, the temperature profile 44 the temperature estimated using the model 34, the temperature profile 46 the temperature measured by means of the temperature sensor 16 arranged closest to the direct current contact 14 and the temperature profile 48 the temperature measured by means of one of the temperature sensors 13 measured temperature.

The model 34 can be an empirically based model, for example. The empirical model 34 can be represented by the following calculation formula:

The temperatures TDC- and TDC+ are the temperatures measured by the temperature sensors 16. The temperatures TAC LI and TAC L2 are the temperatures measured by the temperature sensors 13. TDC estimate is the estimated temperature of one of the DC contacts 14. The remaining estimated temperatures TDC+ estimate, TAC L1 estimate and TAC L2 estimate can be determined analogously.

The parameters Ci to Cs can be determined using curve fitting algorithms, where reference sensors can measure the actual temperature of the DC contacts 14 and AC contacts 12. The reference sensors do not require any separation between the high-voltage and low-voltage systems and are only required for a one-off experimental setup. Therefore, high-precision and high-priced reference sensors can be used for these reference sensors. For example, as Reference sensors will use flexible film sensors that are glued over a large area to the surfaces of the contacts 12, 14.

Alternatively, it is also possible to use a physical model for the model 34 of the charging socket 10, which depicts the actual thermal conduction within the charging socket 10 using a thermal equivalent circuit model 50, as shown in FIG. 4. In the thermal equivalent circuit model 50, the alternating current contacts 12, the temperature sensors 13, 16, the direct current contacts 14 and the circuit board 18 are each assigned a thermal mass. The respective heat transport between these elements is simulated by thermal resistances. The temperatures TDC- and TDC+ measured by means of the temperature sensors 16 and the temperatures TAC LI and TAC L2 measured by means of the temperature sensors 13 flow into the thermal equivalent circuit model 50 as input variables. The respective estimated values TDC estimate, TDC+ estimate, TAC LI estimate and TAC L2 estimate for the contacts 12, 14 are obtained as output variables using the thermal equivalent circuit model 50.

When charging with direct current, a temperature gradient is created from the alternating current contacts 12 to the direct current contacts 14. The temperature gradient causes a heat flow from the direct current contacts 14 to the alternating current contacts 12, and therefore also correspondingly from the temperature sensors 16 to the temperature sensors 13. If one of them also heats up DC contacts 14 faster than the other, for example due to wear on the coating of the relevant contact 14, a heat flow between the DC contacts 14 is also added.

The thermal equivalent circuit model 50 is based on the assumption that the deviation of the measured temperature from the actual temperature is somewhat proportional to the heat flow in the direction of the corresponding temperature sensor 13, 16. In the thermal equivalent circuit model 50, this heat flow is supplied to the corresponding DC contact 14, whereby it can be amplified by a constant factor. The resulting heat flow represents the heating of the relevant direct current contact 14 due to the ohmic resistance of the contact parts and lines.

In the case shown here as an example, the thermal equivalent circuit model 50 is based on 9 thermal masses, which are linked to one another by 10 thermal resistors. The Heat flows in the direction of the contacts 12, 14 are increased by four factors. A total of 23 parameters must be specified. The parameters can be determined physically or empirically. The parameters can, for example, first be determined physically, namely based on the geometry of the charging socket 10 and respective material characteristics. The parameters can then be fine-tuned using an experimental setup. The level of detail of the thermal equivalent circuit model 50 and a time step size can be adjusted to enable real-time operation.

REFERENCE SYMBOL LIST

10 charging socket

12 AC contacts

13 temperature sensors

14 DC contacts

16 temperature sensors

18 circuit board

20 flowchart

22 current conduction path

24 loading gun

26 DC line

28 thermal coupling

30 heat flow

32 thermal coupling

34 thermodynamic model of the charging socket

36 parameter set

38 data processing device

40 charge control unit

42 Temperature history

44 Temperature history

46 Temperature history

48 Temperature history

50 thermal equivalent circuit model

C1 to C8 Parameters of the calculation formula

TDC-, TDC+, TAC LI, TAC L2 measured temperatures

TDC- estimate, TDC+ estimate, TAC L1 estimate, TAC L2 estimate estimated temperatures

Claims

PATENT CLAIMS Method for determining the temperature in a charging socket (10) of an electric vehicle, the direct current contacts (14) for charging the electric vehicle and electrically separated alternating current contacts (12) for charging the electric vehicle as well as respective ones assigned to the direct current contacts (14) and the alternating current contacts (12). and temperature sensors (13, 16) spaced apart therefrom for measuring the respective temperatures of the contacts (12, 14), comprising the following steps:

Measuring respective temperatures (TDC-, TDC+, TAC LI, TAC L2) using the temperature sensors (13, 16) assigned to the DC contacts (14) and the AC contacts (12) while the electric vehicle is powered via the DC contacts (14) or via the AC contacts (12 ) is loaded;

Providing a thermodynamic model (34) of the charging socket (10), which depicts a thermal coupling between the temperature sensors (13, 16) and, depending on this, estimates (TDC estimate, T _D c+ estimate, TAC LI estimate, T _A c L2 estimate ) for the temperatures of the respective contacts (12, 14);

Determining an estimate (TDC estimate, TDC+ estimate, TAC L1 estimate, TAC L2 estimate) for the temperature of at least one of the DC contacts (14) or of at least one of the AC contacts (14) by using the measured temperatures (TDC-, TDC+ , TAC LI, TAC L2) are entered into the thermodynamic model (34) of the charging socket (10). Method according to claim 1, characterized in that depending on the estimated value (TDC estimate, T _D C+ estimate, TAC L1 estimate, TAC L2 estimate) for the temperature of at least one of the DC contacts (14) or of at least one of the AC contacts (14), a current intensity is regulated during the charging process. Method according to claim 1 or 2, characterized in that the thermodynamic model (34) of the charging socket (10) takes into account the heat conduction between the temperature sensors (13, 16) and the contacts (12, 14).

4. Method according to one of the preceding claims, characterized in that the thermodynamic model (34) of the charging socket (10) is provided in the form of an empirical model.

5. The method according to claim 4, characterized in that the empirical model determines the estimated values (T _D C- estimate, T _D C+ estimate, TAC L1 estimate, TAC L2 estimate) for the temperatures of the contacts (12, 14) using respective calculation formulas , which contain the measured temperatures (TDC-, TDC+, T _A C LI , T _A C L2) and time derivatives of the measured temperatures (TDC-, TDC+, T _A C LI , T _A C L2), each multiplied by a parameter ( Ci, C2, C3, C4, C5, Ce, C7, Cs).

6. The method according to claim 5, characterized in that the parameters (Ci, C2, C3, C4, C5, Ce, C7, Cs) are determined using a curve fitting algorithm, using means attached directly to the contacts (12, 14). Reference sensors measure the actual temperatures of the contacts (12, 14).

7. The method according to claim 6, characterized in that flexible film sensors are used as reference sensors, which are glued flat to the surfaces of the contacts (12, 14).

8. The method according to one of claims 1 to 3, characterized in that the thermodynamic model (34) of the charging socket (10) is provided in the form of a physical model which shows the heat conduction paths between the temperature sensors (13, 16) and the contacts (12 , 14) using a thermal equivalent circuit model (50) of the charging socket (10). 9. The method according to claim 8, characterized in that in the thermal equivalent circuit model (50) the contacts (12, 14), the temperature sensors (13, 16) and a circuit board (18) on which the temperature sensors (13, 16) are arranged , are approximated by respective thermal masses, which are linked together by thermal resistances.

10. The method according to claim 9, characterized in that in the thermal equivalent circuit model (50), respective heat flows to the contacts (12, 14) are specified depending on the respective temperature gradients, which result from the measured temperatures (TDC-, TDC+, TAC LI, TAC L2).

11. The method according to claim 10, characterized in that the heat flows to the contacts (12, 14) are increased by respective constant factors.

12. The method according to claim 11, characterized in that the thermal equivalent circuit model (50) is determined depending on the geometry of the charging socket (10), material characteristics of the charging socket (10) and / or based on an experimental setup.

13. The method according to one of claims 8 to 12, characterized in that a level of detail of the thermal equivalent circuit model (50) and a time step size are set so that a data processing device (38) determines the estimated value (TDC - estimate, TDC + estimate, TAC L1 Estimate, TAC L2 estimate) for the temperature of at least one of the DC contacts (14) or of at least one of the AC contacts (12) can be determined in real time.

14. Charging socket (10) for an electric vehicle, comprising DC contacts (14) for charging the electric vehicle and electrically separated AC contacts (12) for charging the electric vehicle; respective temperature sensors (13, 16) assigned to the direct current contacts (14) and the alternating current contacts (12) and spaced therefrom for measuring the respective temperatures of the contacts (12, 14); a data processing device (38), which is set up for this purpose, based on a thermodynamic model (34) of the charging socket (10), which maps a thermal coupling between the temperature sensors (13, 16) and, depending on this, estimated values (TDC estimate, T _D c+ estimate, T _A c LI estimate, TAC L2 estimate) for the temperatures of the respective contacts (12, 14), an estimate (TDC estimate, TDC+ estimate, TAC L1 estimate, TAC L2 estimate) for the temperature of at least one of the DC contacts (14) or of at least one of the AC contacts (12) when the temperatures (TDC-, TDC+, TAC LI, TAC L2) measured by the temperature sensors (13, 16) are incorporated into the thermodynamic model (34) of the charging socket (10) can be entered. Charging socket (10) according to claim 14, in which a heat-conducting connection between the temperature sensors (13, 16) is established via copper lines, thermal paste and/or a printed circuit board (18).