Method and device for diagnosing battery system and method and device for diagnosing vehicle having battery system

Abstract

A vehicle has a battery system with at least one device element and at least one temperature sensor. The temperature sensor is thermally coupled to the respective device element according to the specification, and the measurement signal of the temperature sensor represents the temperature of the temperature sensor during the measurement operation. The temperature sensor is operated in the heating operation such that the temperature sensor produces an increased thermal loss power compared to the measuring operation. A characteristic measure for the thermal influence of the heating operation on the temperature sensor is determined on the basis of a measurement signal of the temperature sensor during the measurement operation. It is determined whether the temperature sensor is predetermined to be thermally coupled to the respective device element according to the predetermined characteristic and the characteristic metric.

Description

Technical Field

[0001] The present invention relates to a method for diagnosing a battery system and a corresponding device and furthermore to a method for diagnosing a vehicle having a battery system and a corresponding device. Background Art

[0002] Battery systems are gaining increasing economic importance, especially in terms of electromobility in vehicles. In the context of reliability, it is important to detect faults in one or more battery cells of a battery system. For this purpose, it is known to use one or more temperature sensors, the measurement signals of which can be used to infer the respective temperature of the respective battery cell. This is then used to detect overheating of the respective battery cell as promptly as possible and / or to protect the battery cell from degradation caused by increased charging or discharging currents of the battery cell. In this way, the longest possible service life of the respective battery cell should be ensured and the occurrence of so-called thermal events, which in extreme cases can lead to the destruction of the respective battery cell, should be prevented. Summary of the invention

[0003] The object to be achieved is to provide a method for diagnosing a battery system as well as a method for diagnosing a vehicle having a battery system and a corresponding device which contribute to a reliable operation of the battery system.

[0004] This object is achieved by the subject matter of the independent claims. Advantageous embodiments of the invention are characterized in the dependent claims.

[0005] According to a first aspect, the invention is characterized by a method for diagnosing a battery system, which comprises at least one system element and at least one temperature sensor, which is thermally coupled to the respective system element in a predetermined manner and whose measurement signal represents the temperature of the temperature sensor during measurement operation. Any desired element, such as a battery cell, a cooling element, etc., may be considered as the respective system element.

[0006] According to a first aspect, in the heating operation, the temperature sensor is operated in such a way that it generates an increased heat loss compared to the measuring operation. The heating operation is thus characterized, for example, in that the temperature sensor is operated in such a way that it has a high heat loss and, more precisely, has a high heat loss compared to the measuring operation, in which the temperature sensor is operated with as little heat loss as possible. In the measuring operation, the temperature sensor is preferably operated in such a way that the power loss of the temperature sensor is low and, more precisely, the power loss enables the temperature of the temperature sensor to be as unaffected as possible and thus contributes to a high measurement quality. In the heating operation, the temperature sensor is operated, for example, in such a way that the generated heat loss is greater than the heat loss in the measuring operation by, for example, at least 25%, further, for example, at least 50%, further, for example, at least 100%, further, for example, at least 300%, in particular with reference to the starting temperature of the temperature sensor before the start of the heating operation.

[0007] According to a first aspect, a characteristic measure for the thermal influence of the heating operation on the temperature sensor is determined from a measurement signal of the temperature sensor in the measuring operation. In addition, it is determined from a predetermined property and the characteristic measure whether the temperature sensor is thermally coupled to the corresponding device element in a predetermined manner.

[0008] Thus, for example, in heating operation with a power loss at the temperature sensor increased by approximately 300%, a warming of 0.3 K is achieved without a predetermined thermal coupling of the temperature sensor to the corresponding device element. This has proven to be sufficient for robust diagnostic accuracy.

[0009] In particular, the feature metric may be: one or more feature values, a variation curve of multiple feature values, or any function related to one or more feature values.

[0010] The predetermined characteristic is selected, in particular, as a function of the specific embodiment of the characteristic measure and is therefore predetermined in such a way that it can be concluded from the predetermined characteristic and the current characteristic measure whether the temperature sensor is thermally coupled to the corresponding device element in a predetermined manner. In a particularly simple embodiment, the predetermined characteristic can be, for example, a predetermined threshold value. However, the predetermined characteristic can also be, for example, a predetermined curve or an arbitrary function, just like the characteristic measure.

[0011] By means of the first aspect, an insufficient or non-existent thermal connection of the temperature sensor to the corresponding device element and in particular with regard to its thermal coupling is efficiently contributed to reliably identifying it, and thus corresponding measures for protecting the battery system can be initiated in a timely manner.

[0012] Thus, for example, even within the scope of manufacturing the battery system, it is possible to detect with the aid of the first aspect when a temperature sensor is not thermally coupled to a corresponding device element in accordance with the specification and, for example, to initiate corresponding quality assurance measures. Thus, even after the initial start-up of the battery system, it is possible to contribute to the timely detection of such faults and thus to the highest possible service life and efficiency of the battery system.

[0013] According to a second aspect of the invention, the invention is characterized by a device for carrying out the method according to the first aspect and therefore corresponds accordingly to the method.

[0014] According to a third aspect, the invention is characterized by a method for diagnosing a vehicle having a battery system in which the method according to the first aspect is carried out.

[0015] According to a fourth aspect, the invention is characterized by a device for diagnosing a vehicle, which is designed to carry out the method according to the third aspect.

[0016] Advantageous embodiments are characterized in the dependent claims.

[0017] According to an advantageous embodiment, after the end of the heating operation, the characteristic measure is determined as a function of the measuring operation of the temperature sensor. In this way, the diagnosis can be carried out particularly easily.

[0018] According to another advantageous embodiment, the characteristic measure is determined before the start of the heating operation based on the measuring operation of the temperature sensor. In this way, it can be very helpful to appropriately take into account marginal conditions or conditions shortly before the start of the heating operation. In this regard, in particular, the following knowledge is used, that the starting temperature of the temperature sensor has a decisive influence on its temperature after the heating operation. In this way, the quality of the diagnosis can be improved by corresponding considerations.

[0019] According to another advantageous embodiment, the characteristic measure is determined during at least a short-term interruption of the heating operation based on the measuring operation of the temperature sensor. In this way, a very rapid diagnosis is particularly facilitated.

[0020] According to another advantageous embodiment, the duration of the heating operation is determined before the start of the heating operation as a function of a characteristic value of the temperature of the temperature sensor. In this way, it can be helped in particular to take into account the characteristics of the temperature sensor in terms of the expected heat loss power of the temperature sensor during the heating operation. This is particularly effective in connection with a temperature sensor whose resistance is temperature-dependent.

[0021] According to another advantageous embodiment, in the heating operation, the input of the evaluation unit for acquiring the measurement signal is controlled to a predetermined voltage potential, which causes an increased current in the temperature sensor compared to the measuring operation. In this way, the heating operation can be realized very simply and, if necessary, without hardware changes to the existing evaluation unit. In this regard, it can be particularly advantageous if the input is controlled to ground potential in the heating operation.

[0022] According to an advantageous embodiment of the third or fourth aspect, the method according to the third aspect is carried out during a predetermined stationary operation of the vehicle. In this way, it can be easily ensured that influences that falsify the diagnosis, which may occur outside the stationary operation of the vehicle, are excluded. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Exemplary embodiments of the invention are explained in more detail below with reference to the accompanying schematic drawings.

[0024] in:

[0025] Figure 1 A vehicle having a battery system is shown;

[0026] Figure 2 A battery cell system is shown;

[0027] Figure 3 shows a portion of a battery cell having a temperature sensor in a first state;

[0028] Figure 4 showing a portion of a battery cell having a temperature sensor in a second state;

[0029] Figure 5 An evaluation unit is shown having a circuit component into which a temperature sensor is connected;

[0030] Figure 6 A flow chart is shown;

[0031] Figure 7 showing a first signal variation curve;

[0032] Figure 8 showing a second signal variation curve;

[0033] Fig. 9 A third signal profile is shown. DETAILED DESCRIPTION

[0034] Elements with the same structure or function are provided with the same reference symbols in the various figures.

[0035] Figure 1A vehicle 1 is shown having a battery system 2. The battery system 2 is provided for storing and discharging electrical energy, which can be used, for example, to operate an electric drive of the vehicle.

[0036] Furthermore, a control device 4 is provided in the vehicle 1 and is designed to diagnose the battery system 2. In addition, the control device 4 can also assume other functions in the vehicle or also assume other functions with respect to the battery system 2. Furthermore, in particular, an evaluation unit 6 is formed in the control device 4.

[0037] Battery System 2( Figure 2 ) has a plurality of battery cells 8 to 16. The battery cells 8 to 16 may be, for example, lithium-ion battery cells, but the battery cells may also be any other type of battery cells 8 to 16, such as solid battery cells. The single cell form of the battery cells 8 to 16 may also be selected arbitrarily in principle. For example, the battery cells may also be so-called soft-pack cells.

[0038] The battery system 2 further comprises a cooling element 18 which is thermally coupled to one or more of the battery cells 8 to 16 and is designed to dissipate heat from the battery cells 8 to 16 .

[0039] Furthermore, one or more temperature sensors 20 , 22 , 24 , 26 , 28 , 30 are provided, which are thermally coupled to the respective device element in a predetermined manner and whose respective measurement signals represent the temperature of the respective temperature sensor 20 to 30 during measuring operation.

[0040] In this example, the device elements can be, by way of example, the respective battery cells 8 to 16 or, for example, the cooling element 18 .

[0041] With the help of Figure 3 The arrangement of the temperature sensor 20 in relation to the individual battery cells 8 is shown in detail. A hold-down holder 32 is provided which, in cooperation with the connecting element 34 and the thermal coupling element 36 , supports a predetermined thermal coupling to the individual battery cells 8 .

[0042] The hold-down holder is shown dotted in its cross-sectional view in FIG. 32 .

[0043] The connecting element 34 is designed, in particular, for the electrical connection of the temperature sensor 20 and therefore has, in particular, a corresponding conductor structure. The connecting element can be designed, for example, as a so-called flexible printed circuit (FPC).

[0044] If the temperature sensor 20 is thermally coupled as intended to another device element of the battery system 2 , it can be provided in a corresponding arrangement, as is shown here by way of example with reference to the battery cell 8 .

[0045] Figure 4 Shows the following in case of a fault Figure 3 Arrangement structure, wherein the temperature sensor 20 is not thermally coupled to the corresponding device element in a predetermined manner, which device element is the battery cell 8 in this example. Figure 4 As can be seen, the temperature sensor 20 is in this case detached from the thermal coupling element 36 and therefore there is at least one gap between the temperature sensor 20 and the thermal coupling element 36, which gap is filled with air, for example. This leads to a strong increase in the thermal resistance between the temperature sensor 20 and the thermal coupling element 36 and thus to the battery cell 8. The temperature of the temperature sensor 20 is therefore only insufficiently correlated, or even no longer correlated, with the temperature of the battery cell 8 during the measuring operation.

[0046] Figure 5 A circuit arrangement is shown with the temperature sensor 20 , wherein the circuit arrangement can also be used analogously for the temperature sensors 22 to 30 and 38 .

[0047] The temperature sensor 20 is connected in series with a voltage divider resistor 40. VCC represents the supply voltage potential and VGND represents the reference potential. The voltage divider resistor 40 is sized, for example, so that its resistance corresponds approximately to the resistance of the temperature sensor 20 at a predetermined reference temperature, for example 25°C. The voltage divider resistor can have, for example, 10 kΩ. In this case, the temperature sensor preferably has a resistance of approximately 10 kΩ at the reference temperature. The temperature sensor can be constructed, for example, as an NTC resistor, that is, with a negative temperature coefficient. In addition, a low-pass resistor 42 can be optionally provided in the voltage tap 43, which can be part of a low-pass filter not further shown, which therefore also includes a capacitor. The voltage tap 43 is electrically coupled to an input / output terminal 44 of the evaluation unit 6, which can also be referred to as a port. When the input / output terminal 44 is operated as an input terminal, the input terminal can be constructed, for example, for conveying a measurement signal, especially representing the voltage on the voltage tap, to an analog-to-digital converter in the evaluation unit 6. In another state, the input / output terminal 44 can be configured in the evaluation unit 6 so that the voltage divider resistor 40 is bridged. That is, the reference potential VGND is substantially present at the input / output 44. For this purpose, the input / output can be operated, for example, in a so-called open-drain circuit. The optional low-pass resistor 42 is dimensioned so that even when the low-pass resistor is present, the voltage drop between the supply voltage potential VCC and the reference potential VGND also substantially falls across the temperature sensor 20 in this case.

[0048] In heating operation AB, temperature sensor 20 is operated in such a way that it generates an increased heat loss power compared to measuring operation MB. Figure 5In the circuit arrangement shown, measuring mode MB is implemented in that input / output 44 is coupled to an internal analog-digital converter and is therefore high-impedance, whereby supply voltage VCC is applied to temperature sensor 20 relative to reference potential VGND in accordance with the ratio of the resistance of temperature sensor 20 to the voltage divider resistor.

[0049] In heating operation AB, reference potential VGND is essentially present at input / output 44, whereby essentially the entire voltage between supply voltage potential VCC and reference potential VGNT is then present at temperature sensor 20. Thus, in this case, for example for a temperature corresponding to the reference temperature, the power loss is approximately four times greater than in measuring operation.

[0050] Figure 6 The flowchart of a program is shown, which can be stored in particular in the evaluation unit 6 and executed there during operation. Alternatively, the program can also be stored and / or executed in another unit of the control device 4 or partially in another unit of the control device.

[0051] The program can be started at any time in step S2. Thus, for example, the program can be started at the end of production of the battery system 2 within the scope of a so-called end-of-line test. However, the program can also be started at a later time in principle at any time.

[0052] In step S4, it is checked whether the vehicle 1 is in a predetermined stationary operation. For example, stationary operation can be identified as follows, that is, the high voltage supply of the battery system 2 is disconnected and / or the protection of the battery system 2 is disconnected. In general, stationary operation is characterized by the fact that the vehicle 1 is not in operation. In this way, it can be easily ensured that influences caused by, for example, active heating of the battery cells 8 to 16 during the implementation of the diagnosis lead to undesirable temperature changes, or that any acceleration processes of the vehicle lead to high power outflows in the battery cells 8 to 16, which can lead to a significant increase in the cell temperature of the corresponding battery cells 8 to 16 within a very short time range, for example within a few seconds.

[0053] If it is determined in step S4 that the vehicle 1 is in stationary operation, the processing is continued in step S6 . Otherwise, the processing ends in step S10 .

[0054] In step S6, the temperature sensors are operated in the heating operation AB for a predetermined heating duration. Preferably, the temperature sensors 20 to 30 are operated in the measuring operation MB very shortly before the start of the heating operation and characteristic values ​​are determined for the starting temperatures of the temperature sensors 20 to 30. The heating duration can then also be determined, for example, based on the characteristic values ​​for the starting temperature.

[0055] In step S8, which is executed temporally subsequent to step S6 or alternatively can also be executed intermittently relative to step S6 if necessary multiple times, a characteristic measure for the thermal influence of the heating operation on the temperature sensors 20 to 30 is determined from the measurement signals of the temperature sensors 20 to 30 in the measuring operation MB. A more detailed example of this method will be explained in more detail below with reference to further figures.

[0056] Furthermore, in step S8 it is determined based on the predetermined properties and characteristic measures whether temperature sensor 20 is thermally coupled in a predetermined manner to the respective device element. The respective device element may be, for example, the respective battery cell 8 to 16 or, for example, also the cooling element 18 .

[0057] The predetermined characteristic can be particularly simply predetermined in the form of a threshold value, but it can also be predetermined in the form of a predetermined variation curve or an arbitrary function and more precisely, in particular, predetermined according to the selection of the corresponding characteristic measure. Here, the predetermined characteristic is preferably determined in advance by a corresponding test having the following arrangement structure, in which the temperature sensors 20 to 30 are thermally coupled to the corresponding device elements as specified or are just not thermally coupled to the corresponding device elements as specified. Based on this, a corresponding diagnosis or diagnostic report can then be performed in step S8 by the thermal coupling of the corresponding temperature sensor as specified or not as specified. In this way, it can be recognized very promptly that the corresponding temperature sensor 20, for example, has not had sufficient thermal connection during assembly or has lost the thermal connection during operation due to mechanical separation. In this way, it can then be quickly recognized that it is no longer possible to infer the overheating of the corresponding battery cell 8 to 6 from the measurement signal of the temperature sensor in the corresponding fault situation, and corresponding measures can be introduced. In this way, measures can be introduced in the event of a fault in order to protect the battery cell from degradation caused by excessive charging and / or discharging currents of the battery cell. In this way, a particularly long service life can be ensured and so-called thermal events can also be prevented.

[0058] Without the approach described in the previous steps, this fault scenario can only be detected in the case of very rapid temperature changes of the corresponding battery cells 8 to 16 or cooling bodies through current or coolant flow. In such a case, however, temperature spreads may also occur in the battery system 2 due to technical reasons, so that poorly connected temperature sensors 20 to 30 can only be detected with difficulty. In addition, a diagnosis based on such effects is not suitable for so-called end-off-line tests in the battery system 2. The corresponding fault situation may then have an impact only during operation and lead to an unplanned workshop stop or a complete recall.

[0059] In a subsequent step S10 , the program then ends and can then be restarted in step S2 after a predetermined period of time or upon the occurrence of a predetermined event.

[0060] Figure 7 Two signal curves recorded over time t are shown, wherein the upper signal curve shows whether the temperature sensor is operated in measuring mode MB or in heating mode AB. Figure 7 The time axis and time reference in the two curves of are the same. T represents temperature. Starting from the starting temperature T0, the heating operation starts at time t1 and the heating operation is carried out in principle at least until time t2. In this example, intermittently, in particular, the signal variation curve above is emphasized by the arrow and briefly switched to the measurement operation MB. In this way, it is possible to determine the characteristic measure of the thermal influence of the heating operation on the temperature sensor during the heating operation AB, that is to say, for example, by means of interpolation to evaluate the temperature variation curve of the temperature sensor. In this way, it is possible to identify very quickly whether the temperature of the temperature sensors 20 to 30 has a variation curve, for example, according to the reference numeral 46 or the reference numeral 48 in other cases. The temperature variation curve 46 represents the temperature variation curve when the temperature sensor 20 is thermally coupled to the corresponding device element according to the regulations, and the temperature variation curve 48 represents that the temperature sensor 20 is not thermally coupled to the corresponding coupling element according to the regulations. Then, for example, the characteristic measure of the thermal influence of the heating operation can be determined according to the approximate temperature variation curve. In a particularly simple design, the characteristic measure can be determined by simply using the corresponding measurement signal at time t2 to determine the characteristic measure, and the predetermined characteristic can be the corresponding threshold value at this time. The threshold value can be selected such that a distinction can be made between a first temperature range 50 and a second temperature range 52 , wherein in the second temperature range 52 it can be concluded that the temperature sensors 20 to 30 are thermally coupled to the respective device element in a prescribed manner, whereas in the first temperature range 50 it can be concluded that the respective temperature sensors 20 to 30 are not thermally coupled to the respective device element in a prescribed manner.

[0061] It can be seen from the temperature curves 46 and 48 that a step response is caused by the activation of the heating operation. In the context of the diagnosis, the following knowledge is also used, that the corresponding temperature sensor 20, including its mechanical fastening and all elements involved in the mechanical fastening, with which a thermal coupling can be achieved, has a thermal capacity that is several orders of magnitude smaller than the corresponding device element, which can be, for example, a battery cell 8 to 16 or, for example, a heat sink 18. The increased power loss in the case of the heating operation AB is dissipated into the corresponding device element with very low thermal resistance in the case of a proper thermal coupling to the device element. Therefore, in this case, only a relatively small temperature increase of the temperature sensors 20 to 30 relative to the starting temperature T0 occurs.

[0062] In the case of a poor or non-existent thermal connection of the respective temperature sensor 20 to 30 to the respective device element, the resulting power loss can be discharged substantially only via the ambient air and, if necessary, the supply lines, which each have a relatively high thermal resistance. This results in a significantly greater temperature increase of the temperature sensors 20 to 30 relative to the starting temperature. After the start of self-excitation, that is to say after the start of the control of the heating operation AB, the temperature curve of the temperature sensors 20 to 30 characterizes the quality of the thermal coupling of the temperature sensors 20 to 30 to the respective device element due to the relatively increased current supply.

[0063] With the help of Figure 8 and 9 Another example for implementing the diagnosis is shown, which can also be used in accordance with Figure 7 way combination.

[0064] After the measuring operation MB, the heating operation AB starts at time t4 and ends at time t6. Figure 8 and 9 The curves shown in represent the corresponding measurement signals of temperature sensors 20 to 30 in a measuring operation.

[0065] according to Fig. 9 , corresponding to Figure 8 After the measuring operation, the heating operation is started in step t8 and ended at time t10. Under the same starting conditions, that is to say in particular also at the same starting temperature, the durations between times t6 and t4 and t10 and t8 are in particular the same. Figure 8 The measured signal curves of represent the measured signal curves which occur when the temperature sensors 20 to 30 are thermally coupled to the corresponding device elements as specified, while Fig. 9 The measured signal curve of shows the measured signal curve when the temperature sensors 20 to 30 are not thermally coupled to the corresponding device elements as required. 54 represents a reference line, which is determined, for example, based on the starting temperature before the start of the heating operation AB.

[0066] Obviously, in Figure 8 The measured signal is compared to Fig. 9The reference line 54 is approached again much faster. This can therefore be taken into account when determining the characteristic measure and also the predetermined characteristic. Thus, for example, after a predeterminable duration after the end of the measuring operation MB, the measurement signal can be acquired once or several times in the measuring operation MB and the characteristic measure can be determined from this and then, for example, compared with a threshold value. In a more complex design, for example, the integral between the measurement signal and the reference line 54 can also be determined and the characteristic measure can be determined in this way. For example, it has been shown that already after about two minutes of the heating operation AB, in the temperature sensors 20 to 30 that are not thermally coupled according to the regulations, a temperature increase relative to the starting temperature T0 that is about three times as high occurs compared to the device elements that are thermally coupled according to the regulations.

[0067] Reference numerals list

[0068] 1 Vehicle

[0069] 2 Battery System

[0070] 4 Control device

[0071] 6 Evaluation Units

[0072] 8-16 battery cells

[0073] 18 cooling body

[0074] 20-30 Temperature Sensor

[0075] 32 Press retainer

[0076] 34 Connecting elements

[0077] 36 Thermal coupling element

[0078] VCC supply voltage potential

[0079] VGND reference potential

[0080] 40 Voltage divider resistor

[0081] 42 Low pass resistance

[0082] 43 Voltage tap

[0083] 44 Input / output terminals

[0084] t time

[0085] T Temperature

[0086] T0 starting temperature

[0087] AB heating operation

[0088] MB measurement operation

[0089] 46 Temperature change curve

[0090] 48 Temperature change curve

[0091] 50 First temperature range

[0092] 52 Second temperature range

[0093] 54 Reference Lines

[0094] Steps S2-S10

Claims

1. A method for diagnosing a battery system (2), the battery system having at least one device element and at least one temperature sensor (20 to 30), the temperature sensor being thermally coupled to the respective device element in a predetermined manner and the measurement signal of which represents the temperature of the temperature sensor (20 to 30) in a measuring mode (MB), In the method, the temperature sensor (20 to 30) is operated in a heating mode (AB) such that the temperature sensor generates an increased heat loss power compared to the measuring mode (MB). determining a characteristic measure for the thermal influence of the heating operation (AB) on the temperature sensors (20 to 30) from the measurement signals of the temperature sensors (20 to 30) in the measuring operation (MB), and It is determined based on the predetermined characteristic and the characteristic measure whether the temperature sensor (20 to 30) is thermally coupled to the corresponding device element in a predetermined manner.

2. The method according to claim 1, wherein: After the heating operation (AB) has ended, the characteristic variable is determined based on a measuring operation (MB) of the temperature sensor (20).

3. The method according to any one of the preceding claims, wherein: The characteristic variable is determined before the start of the heating operation (AB) based on a measuring operation (MB) of the temperature sensors (20 to 30).

4. The method according to any one of the preceding claims, wherein: During at least one short-term interruption of the heating operation (AB), the characteristic variable is determined based on a measuring operation (MB) of the temperature sensors (20 to 30).

5. The method according to any one of the preceding claims, wherein: Before the start of the heating operation (AB), the duration of the heating operation (AB) is determined based on characteristic values ​​of the temperature of the temperature sensors (20 to 30).

6. The method according to any one of the preceding claims, wherein: An input / output (44) of an evaluation unit (6) for acquiring the measurement signal is controlled in the heating mode (AB) to a predetermined voltage potential which causes an increased current in the temperature sensors (20) to (30) compared to the measuring mode (MB).

7. A method for diagnosing a vehicle (1) having a battery system (2), the battery system having at least one device element and at least one temperature sensor (10) to (20), the temperature sensor being thermally coupled to the respective device element in a prescribed manner and the measurement signal of the temperature sensor representing the temperature (T) of the temperature sensor (10) to (20) in a measuring operation (MB), in which the method according to one of the above claims is implemented.

8. The method according to claim 7, wherein: A method according to one of the preceding claims is carried out during a predetermined stationary operation of the vehicle (1). 9 . A device designed to carry out the method according to claim 1 .

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