Accumulator, method, device and storage medium for determining the state of its thermal management system

Abstract

A method for determining a state of a thermal management system of an electrical energy accumulator is described, wherein the electrical energy accumulator has at least one electrical energy accumulator cell and at least one cooling plate in thermal contact with the at least one electrical energy accumulator cell. The method comprises the steps of: a) calculating a second temperature value for the at least one electrical energy accumulator cell based on a determined first temperature value of the electrical energy accumulator cell; b) calculating a third temperature value for the at least one electrical energy accumulator cell based on the determined first temperature value of the electrical energy accumulator cell; c) determining a state of the thermal management system for the at least one electrical energy accumulator cell based at least on the calculated second temperature value and the calculated third temperature value, wherein the state comprises a thermal defect of the thermal management system. Furthermore, a corresponding device, a corresponding electrical energy accumulator cell, a corresponding computer program and a corresponding machine-readable storage medium are described.

Description

Technical Field

[0001] The invention proceeds from a method for determining a state of a thermal management system of an electrical energy storage device, as well as a corresponding device, a corresponding electrical energy storage device, a corresponding computer program and a corresponding machine-readable storage medium. Background Art

[0002] In the course of increasing electrification, in particular of motor vehicles, electrical energy storage devices are becoming increasingly important. There are different levels of electrification. For example, there are vehicles with electric drive without and with an internal combustion engine, as well as vehicles in which the electric motor only temporarily takes over the drive of the vehicle or supports the internal combustion engine. The different forms of electrification typically have different voltage levels and different configurations of the electrical energy storage units used.

[0003] However, what is common to these configurations is that they have a thermal management system in one or another form. Depending on the power level of the electrical energy storage device, passive cooling is sufficient or active cooling is required. The higher the electrical power called up, the higher the requirements on the corresponding thermal management system. Therefore, fluid-based systems are often used, such as water glycol-based systems. They usually provide for the use of one or more cooling plates, which are in thermal contact with the electrical energy storage cells used.

[0004] In order to dissipate the generated heat, a correspondingly good thermal contact between the cooling plate and the electrical energy storage cell is necessary. This contact may be insufficient for adequate heat dissipation for various reasons, for example due to aging or manufacturing errors.

[0005] In order to be able to detect corresponding errors in a timely manner, a diagnosis of the correct functioning of the thermal management system is necessary. Furthermore, within the scope of legal requirements for on-board diagnostics, a diagnosis of the thermal management system is necessary or will be necessary in the future. In particular, in vehicles with an internal combustion engine and an electric motor with an electrical energy storage device, the diagnosis is of great significance, since the thermal management system has an influence on exhaust emissions.

[0006] The publication US 2016 / 0141894 describes an electrical energy storage device in which the temperature of the battery cells is measured in order to operate the battery cells within their temperature specifications. Summary of the invention

[0007] Advantages of the present invention

[0008] Disclosed is a method for determining the state of a thermal management system of an electrical energy storage device having the features of a first independent patent claim.

[0009] The electrical energy storage device has at least one electrical energy storage cell and at least one cooling plate which is in thermal contact with the at least one electrical energy storage cell. Within the method, a second temperature value for the at least one electrical energy storage cell is calculated based on a determined first temperature value of the electrical energy storage cell.

[0010] Furthermore, a third temperature value is calculated for the at least one electrical energy storage cell based on the determined first temperature value of the electrical energy storage cell.

[0011] Furthermore, a state of a thermal management system for the at least one electrical energy storage cell is determined based on the calculated second temperature value and the calculated third temperature value, wherein the state includes a thermal deficiency of the thermal management system.

[0012] This is advantageous because the state of the thermal management system directly influences the performance capacity of the electrical energy storage device and, if applicable, the CO2 emissions, for example when installed in a hybrid vehicle. As a result, timely and appropriate measures can be taken or, if applicable, legal requirements can be met.

[0013] In particular, a mathematical model can be used in the calculation. The mathematical model can include, for example, differential equations or algebraic equations. Furthermore, a data-based characteristic map can also be a component of the mathematical model.

[0014] Further advantageous embodiments of the invention are the subject matter of the dependent claims.

[0015] Expediently, a first temperature value of the at least one electrical energy storage cell is determined. This is advantageous if a corresponding value is not yet available for use in the aforementioned method steps or if a more current value is required than is already available.

[0016] Advantageously, in order to determine the first temperature value, the internal resistance of the at least one electrical energy storage unit and the aging state of the at least one electrical energy storage unit are determined, wherein the first temperature value is determined as a function of the internal resistance and the aging state. This is advantageous, for example, in the case of data that cannot be traced back to a temperature sensor for determining the temperature of the at least one electrical energy storage unit. For example, temperature sensors are usually not attached to all electrical energy storage units in order to save costs. With the disclosed method, the temperature determination and thus the execution of the method for such an electrical energy storage unit are thus also advantageously achieved.

[0017] The first temperature value is advantageously determined by means of a measurement by a temperature sensor, wherein the temperature sensor is preferably arranged at, on or in the at least one electrical energy storage cell. This is advantageous because the value determined in this way can be used directly for determining the state.

[0018] Suitably, a characteristic value (Kennwert) of the efficiency of the thermal management system for the at least one electrical energy storage unit is determined in order to determine the state of the thermal management system for the at least one electrical energy storage unit, wherein the characteristic value is based on the calculated second temperature value and the calculated temperature value. In addition, the determined characteristic value is compared with a predefined threshold value in order to determine the state of the thermal management system for the at least one electrical energy storage unit. In the case where the determined characteristic value is below the threshold value, this can be interpreted as a defect. This is advantageous because a reliable statement about the state of the thermal management system for the at least one electrical energy storage unit can be made in a simple manner based on the characteristic value and the comparison therewith. For example, the threshold value can be defined in such a way that it represents 50% of the cooling power. If the determined characteristic value is below the threshold value, this means that less than 50% of the cooling power of the thermal management system is available. In general, the threshold value depends on the specific application and can be determined, for example, by simulations.

[0019] Advantageously, a component of the thermal management system that controls the thermal power of the thermal management system is actuated based on the state of the thermal management system determined for the at least one battery in order to change, for example, increase the power of the thermal management system, in particular the heat removal. This may be, for example, a pump present in the thermal management system. This is advantageous because in the case of a restricted state of the thermal management system, i.e., a reduced power capacity of the thermal management system, the actuation is adapted accordingly in order to at least partially compensate for the lower power capacity.

[0020] Expediently, for an electrical energy storage device having at least one first, second and third electrical energy storage unit in thermal contact with at least one cooling plate, at least the method steps of calculating the second and third temperature values ​​and determining the state of the thermal management system are performed for each of the electrical energy storage units. Furthermore, for each of the electrical energy storage units, the states of the thermal management system determined during the state determination are compared with one another. Depending on the comparison result, the state of the thermal management system is then limited. This is advantageous because limiting the state allows for a more precise statement about possible fault situations of the thermal management system, which simplifies and accelerates the repair process, in particular by a more precise diagnosis.

[0021] Preferably, at least the following fault conditions are considered for limiting the state of the thermal management system. In the case of a thermal defect in one of the at least three electrical energy storage units, the thermal connection of the electrical energy storage unit to the cooling plate and thus the state of the thermal management system for the corresponding electrical energy storage unit can be classified as faulty. In the case of a thermal defect for all of the at least three electrical energy storage units in thermal contact with the at least one cooling plate, the coolant delivery of the at least one cooling plate of the thermal management system is classified as faulty. In the case of a thermal defect for a plurality of electrical energy storage units arranged one behind the other and / or side by side on the cooling plate, the cooling plate in thermal contact with the plurality of electrical energy storage units is classified as faulty. This is advantageous because a more precise discussion of possible fault conditions of the thermal management system is achieved, which simplifies and accelerates the repair process, in particular by more precise diagnosis. In addition, the current fault condition can be taken into account when adjusting the thermal management system, which is advantageous because this enables at least partial compensation of the fault or a reduction in its influence, if necessary.

[0022] Furthermore, the subject matter of the disclosure is a device for determining the state of a thermal management system of an electrical energy storage device, wherein the electrical energy storage device has at least one electrical energy storage cell and at least one cooling plate, which is in thermal contact with the at least one electrical energy storage cell, wherein the device has at least one electronic control unit, which is configured to carry out the disclosed method. This is advantageous because the advantages of the invention are achieved by means of the device.

[0023] An electronic control unit may be understood in particular to mean an electronic control device which comprises, for example, a microcontroller and / or an application-specific hardware module, such as an ASIC, but may also include a personal computer or a programmable control unit.

[0024] The device expediently comprises a temperature sensor for determining the temperature of the at least one electrical energy storage cell, wherein the temperature sensor is in particular arranged on, at or in the at least one electrical energy storage cell. This is advantageous because the temperature value determined in this way can be used directly for determining the state.

[0025] Advantageously, the device comprises at least one further detection device, such as a current sensor and / or a voltage sensor.

[0026] Furthermore, the subject matter of the disclosure is an electrical energy storage device having the disclosed device. This is advantageous because the advantages mentioned above can be achieved thereby.

[0027] Furthermore, the subject matter of the present disclosure is a computer program which is designed to carry out the disclosed method. This is advantageous because the advantages mentioned above can thereby be achieved.

[0028] Furthermore, the subject matter of the present disclosure is a machine-readable storage medium on which the disclosed computer program is stored. This is advantageous because the advantages mentioned above can thereby be achieved.

[0029] An electrical energy storage unit can be understood in particular as an electrochemical battery cell and / or a battery module having at least one electrochemical battery cell and / or a battery pack having at least one battery module. For example, the electrical energy storage unit can be a lithium-based battery cell or a lithium-based battery module or a lithium-based battery pack. In particular, the electrical energy storage unit can be a lithium-ion battery cell or a lithium-ion battery module or a lithium-ion battery pack. Furthermore, the battery cell can be of the type of a lithium polymer battery, a nickel metal hydride battery, a lead-acid battery, a lithium-air battery or a lithium-sulfur battery or, in general, a battery of any electrochemical composition. A capacitor is also possible as an electrical energy storage unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Advantageous embodiments of the present invention are shown in the drawings and are further described in the following description.

[0031] Figure 1 A flow chart showing the disclosed method according to a first embodiment;

[0032] Figure 2 A diagram showing the relationship between the temperature of an electrical energy storage cell and the internal resistance and the aging state of the electrical energy storage cell;

[0033] Figure 3a A schematic diagram showing a portion of a thermal management system according to one embodiment;

[0034] Figure 3b A schematic cross-sectional view showing a portion of a thermal management system according to the embodiment;

[0035] Figure 4 A flow chart showing the disclosed method according to a second embodiment;

[0036] Figure 5 A flow chart showing the disclosed method according to a third embodiment;

[0037] Figure 6 a schematic diagram showing the disclosed apparatus according to one embodiment; and

[0038] Figure 7 A schematic diagram of the temperature development is shown, which illustrates the determination of the state of the thermal management system. DETAILED DESCRIPTION

[0039] In all the figures, the same reference numerals denote the same device components or the same method steps.

[0040] Figure 1 A flow chart of the disclosed method according to a first specific embodiment is shown. In this case, a method for determining a state of a thermal management system of an electrical energy storage device is used. The electrical energy storage device has at least one cooling plate and an electrical energy storage unit, wherein the at least one electrical energy storage unit is in thermal contact with the at least one cooling plate. In this case, in a first step S11, a second temperature value for the at least one electrical energy storage unit is calculated based on a determined first temperature value of the electrical energy storage unit. In particular, the temperature value for the electrical energy storage unit at a second point in time is thus known.

[0041] In a second step S12 , a third temperature value for the at least one electrical energy storage cell is calculated based on the determined first temperature value of the electrical energy storage cell. In particular, the third temperature value for the electrical energy storage cell is therefore known.

[0042] In a third step S13, a state of a thermal management system for the at least one electrical energy storage unit is then determined based at least on the second temperature value calculated in the first step S11 and the third temperature value calculated in the second step S12. The state of the thermal management system includes its own defects. In addition, the determined first temperature value of the electrical energy storage unit can be included in the state determination.

[0043] Figure 2The diagram shows the relationship between the temperature T of an electric energy storage unit and the internal resistance R of the electric energy storage unit and the aging state. The temperature T of the electric energy storage unit is plotted on the ordinate axis and the internal resistance R of the electric energy storage unit is plotted on the abscissa axis. Five curves 21, 22, 23, 24, 25 are shown by way of example, each of which is based on a different aging state of the electric energy storage unit. This relationship can be stored, for example, in a data memory, for example in a control unit.

[0044] In order to determine the temperature of the electrical energy storage unit by means of the internal resistance value R1 and the aging state value, these two values ​​are first determined. The internal resistance value R1 can be determined, for example, by means of a quotient formation of a voltage value and a current value. The aging state can be determined, for example, by referencing the internal resistance value R1 determined in this way to a reference internal resistance value, for example, a reference internal resistance value of a new electrical energy storage unit. Depending on the aging state determined in this way, a corresponding curve is selected, in which Figure 2 The curve 23 is shown in FIG. 1 . The temperature T1 of the electrical energy storage cell is then determined using the internal resistance value R1 . This temperature T1 can then be used, for example, in the known method.

[0045] Figure 3a A schematic diagram of a portion of a thermal management system 300 according to an embodiment is shown. Here, the thermal management system is designed to control the temperature of three modules 331, 332, 333 of electrical energy storage units. The third module 333 includes four electrical energy storage units 313, 314, 315 and 316, which are arranged on a cooling plate 308 and are in thermal contact with it. These modules 306, 307 and 308 are constructed identically here. The thermal management system 300 has an inlet 301 for a cooling fluid, wherein the cooling fluid is distributed to the cooling plates 306, 307, 308 of the modules 331, 332 and 333 by means of a distributor (Verteiler) 305 and lines 302, 303, 304, such as hoses, arranged thereon. After passing through the cooling plates 306 , 307 , 308 , the cooling fluid is discharged via corresponding lines 310 , 311 , 312 and is collected again in a unit 320 and supplied to further circulation lines via an outlet 309 .

[0046] Figure 3bA schematic cross-sectional view of a portion of a thermal management system according to this embodiment is shown. Here, the third module 333 is shown in a cross-sectional view. The four electrical energy storage cells 313, 314, 315, 316 are arranged on the cooling plate 308 and are in thermal contact with it. Here, the electrical energy storage cell 314 has a significantly poorer thermal connection to the cooling plate, which is Figure 4 314 is schematically indicated by a defect 317. Defect 317 has the effect that the heat generated in or at electrical energy storage cell 314 is dissipated more poorly to cooling plate 308. With the aid of the disclosed method, thermal defects can be detected.

[0047] In addition, other fault situations can also be detected using the disclosed method if the state of the thermal connection of each of the electrical energy storage cells 313, 314, 315, 316 is determined and compared with one another. For example, when a defect is determined, only at the electrical energy storage cell 314 the thermal connection there is with a very high probability the only defective and therefore the state of the thermal management system 300 is faulty only at this electrical energy storage cell 314.

[0048] If, alternatively, a faulty thermal connection is determined for all of these electrical energy storage cells 313 , 314 , 315 , 316 that are in thermal contact with cooling plate 308 , then there is a high probability that there is a defective coolant supply to thermal management system 300 .

[0049] If, alternatively, a thermal defect is present for only three of the four electrical energy storage cells 313 , 314 , 315 , 316 , then there is a high probability that a defect is present at the cooling plate. The defect may be, for example, a mechanical break in the cooling plate that affects the thermal connection.

[0050] Figure 4 A flow chart of the disclosed method according to a second specific embodiment is shown. In this case, a method for determining a state of a thermal management system of an electrical energy storage device is used, wherein the electrical energy storage device has at least one electrical energy storage cell and at least one cooling plate, the at least one electrical energy storage cell being in thermal contact with the at least one cooling plate. In a first step S41, a first temperature value of the at least one electrical energy storage cell is determined, preferably by a temperature sensor which is arranged on, at or in the at least one electrical energy storage cell.

[0051] In a second step S42 , a second temperature value is determined for the at least one electrical energy storage cell based on the determined first temperature value of the electrical energy storage cell. This is done with the aid of formula 1:

[0052]

[0053] In this case, T0 is the temperature value determined in the first step S41 , which is determined at the time t1 , the start time of the integration. This represents the lost heat which is generated in the battery due to joule losses and chemical processes. represents the heat exchange with the air and represents the heat exchange with the thermal management system. These heat components can be determined using methods known from the prior art, for example from thermodynamics or thermodynamics. For example, Here, represents the thermal conductivity; represents the temperature of the cooling plate or the cooling medium, and represents the temperature of the electrical energy storage unit. On both sides of the equal sign and the integral is typically solved numerically, the temperature of the electrical energy storage cell on the right side of the equal sign of formula 1 is then It is initialized with the initial value at time t1, for example, with the temperature value T0, that is, the measured value at the beginning of the integration. The temperature value on the left side of the equal sign in formula 1 The initial value is then calculated and is calculated for the next point in time in the numerical integration. In the next integration step, the exact calculated value on the left side of the equal sign is then calculated. The temperature development of the electrical energy storage cell is therefore calculated recursively for the time period from t1 to t2 and is given by k is the efficiency factor of the heat exchange between the electrical energy storage unit and the thermal management system and is set to 1 in the second step S42, which indicates a perfect function of the thermal management system. At time t2, the calculated second temperature value is thus present. .

[0054] In a third step S43, a third temperature value is determined for the at least one electrical energy storage unit based on the determined first temperature value of the electrical energy storage unit. This is done in a similar manner to that described in the second step S42, wherein in the third step S43 the efficiency factor k is selected to be 0, i.e. no heat exchange between the electrical energy storage unit and the thermal management system is present in the calculation. At the end of the calculation or integration period, the calculated third temperature value is thus present. .

[0055] In a fourth step S44, a characteristic value for the efficiency of the thermal management system of the at least one electrical energy storage unit is calculated. Determined according to the following formula:

[0056]

[0057] in, and , and T mess is the temperature of the electrical energy storage cell determined at the end of a calculation or integration period, which is preferably determined by a temperature sensor, wherein the temperature sensor is arranged on, at or in the at least one electrical energy storage cell.

[0058] In the fifth step S45, the characteristic value determined in the fourth step S44 is is compared with a threshold value in order to determine the state of the thermal management system for the at least one electrical energy storage unit. If the threshold value is exceeded, there is no thermal defect in the thermal management system for the at least one electrical energy storage unit, but the thermal management system is functioning satisfactorily. Conversely, if the threshold value is undershot, there is a thermal defect. This can be displayed within the scope of on-board diagnostics in order to repair the thermal management system if necessary.

[0059] The efficiency characteristic value described in step S44 The calculation of applies when the cooling function of the thermal management system is switched on. Alternatively, the efficiency characteristic value when the heating function is switched on It is calculated as follows:

[0060] .

[0061] Figure 5 A flow chart of the disclosed method according to a third specific embodiment is shown. A method for determining the state of a thermal management system of an electrical energy storage device is used, wherein the electrical energy storage device has at least one first, second and third electrical energy storage unit and at least one cooling plate, wherein the at least one first, second and third electrical energy storage unit is in thermal contact with the at least one cooling plate. Method steps S51, S52, S53, S54 and S55 are performed for the first, second and third electrical energy storage unit, respectively. These method steps correspond to the method described in the description of the thermal management system of an electrical energy storage device. Figure 4 Method steps S41, S42, S43, S44 and S45 described in the description of .

[0062] In a sixth step S56 , it is checked whether method steps S51 to S55 have been carried out for the at least three electrical energy storage units. If not, the process continues with step S51 for the next electrical energy storage unit. If so, step S57 follows.

[0063] In a seventh step S57, the states determined in the fifth step S55 are compared with one another. Thus, it is compared whether a thermal defect is present in the electrical energy storage unit. This comparison can, for example, reveal that a thermal defect is present only for one of the electrical energy storage units.

[0064] In an eighth step S58, the comparison result is taken into account in order to limit or specify the state of the thermal management system as a whole. If, for example, a thermal defect is present only in one of the electrical energy storage units, the state of the thermal connection is classified as faulty and thus the state of the thermal management system for the corresponding electrical energy storage unit is classified as faulty. This can be displayed within the scope of the on-board diagnostics in order to repair the thermal connection of the corresponding electrical energy storage unit in a targeted manner if necessary and thus simplify the repair.

[0065] Figure 6 A schematic diagram of a disclosed device 60 according to one embodiment is shown, which is used to determine the state of a thermal management system of an electric energy accumulator. In this case, the device includes an electronic control unit, not shown here, which is configured to implement the disclosed method. The device is installed in particular in a vehicle having the electric energy accumulator. The device 60 is configured to communicate with a thermal management system 61 in order to transmit control instructions for increasing or reducing the power of the thermal management system to the thermal management system in particular. In addition, the device 60 may include sensors, not shown here, in order to detect in particular the current, voltage and temperature of the electric energy accumulator or at least one electric energy accumulator unit of the electric energy accumulator. Alternatively, the sensor may also be connected to the device 60 only indirectly, for example via a connection connected by a cable, without being directly associated with the device.

[0066] Alternatively and in Figure 6 Although not shown in the figure, the device can also be located externally, that is, outside the vehicle. The device then exchanges temperature data, for example, with the vehicle, in particular with a vehicle control unit. The state of the thermal management system is thus determined outside the vehicle and therefore also independently of its data storage capacity and computing power.

[0067] Figure 7 A schematic diagram of the temperature development is shown which illustrates the determination of the state of the thermal management system and in particular depicts the temperature changes with respect to the thermal management system. Figure 4The temperature T of the energy storage unit is plotted on the ordinate axis and the time t is plotted on the abscissa axis. At time t1, the determination of the state of the thermal management system begins and the thermal management system is activated at the same time. This can be done, for example, when the vehicle is started. In this case, the temperature value T0 of the energy storage unit is determined, for example, measured. min = 0 and k max = 1 This indicates two extreme cases, namely: heat dissipation via the thermal management system is no longer possible or heat dissipation functions as well as technically possible, see also Figure 4 The temperature T in a specific application without faults mess Most will occur during this period, so that the efficiency characteristic values ​​can be determined in accordance with the above description. These values ​​T max and T min Therefore, it is the calculated temperature value, and the temperature value T mess Shows the temperature of the electrical energy storage unit.

Claims

1. A method for determining a state of a thermal management system of an electrical energy storage device, wherein the electrical energy storage device comprises at least one electrical energy storage device cell and at least one cooling plate, wherein the at least one electrical energy storage device cell is in thermal contact with the at least one cooling plate, the method comprising the steps of: a) calculating a second temperature value for the at least one electrical energy storage cell based on the determined first temperature value of the electrical energy storage cell according to the following formula 1: Wherein T0 is the determined first temperature value, which is determined at time point t1, i.e., the start time point of the integration; This represents the lost heat which is generated in the battery due to joule losses and chemical processes; represents the heat exchange with the air, and represents the heat exchange with the thermal management system; T cell represents the temperature development of the electrical energy storage unit; k is here the efficiency factor of the heat exchange between the electrical energy storage unit and the thermal management system and is selected to be 1; at time t2 the calculated second temperature value (T cell，t2,2 ); b) calculating a third temperature value for the at least one electrical energy storage unit based on the determined first temperature value of the electrical energy storage unit according to the formula 1, wherein the efficiency factor k is selected to be 0, so that at the end of the calculation or integration period the calculated third temperature value (T cell，t2,3 ); c) based at least on the calculated second temperature value (T cell，t2,2 ) and the calculated third temperature value (T cell，t2,2 ) determining a state of the thermal management system for the at least one electrical energy storage unit, wherein the state comprises a thermal defect of the thermal management system, Therein, to determine the first temperature value, an internal resistance of the at least one electrical energy storage cell and an aging state of the at least one electrical energy storage cell are determined, wherein the first temperature value is determined as a function of the internal resistance and the aging state.

2. The method according to claim 1, further comprising: d) Determining the first temperature value of the at least one electrical energy storage cell for use in steps a) and b). 3 . The method according to claim 2 , wherein the determination in step d) is performed by means of a measurement by a temperature sensor, wherein the temperature sensor is arranged on or in the at least one electrical energy storage cell.

4. The method according to any of the preceding claims 1 to 3, wherein the step c) of determining the state of the thermal management system for the at least one electrical energy storage unit comprises: e) determining a characteristic value for the efficiency of the thermal management system of the at least one electrical energy storage unit, wherein the characteristic value is based at least on the calculated second temperature value and the calculated third temperature value; f) comparing the determined characteristic value with a threshold value in order to determine a state of the thermal management system for the at least one electrical energy storage cell.

5. The method according to any one of claims 1 to 3, wherein the method further comprises: g) actuating a component of the thermal management system which controls the thermal power of the thermal management system, the component comprising a pump, based on the state of the thermal management system determined for the at least one electrical energy storage unit.

6. The method according to any one of the preceding claims 1 to 3, wherein the electrical energy storage device comprises at least one first, second and third electrical energy storage unit which are in thermal contact with the at least one cooling plate, wherein at least the method steps a), b) and c) are performed for each of the three electrical energy storage units, and step c) further comprises: h) carrying out a comparison of the states of the thermal management system determined in step c) with one another for each of the electrical energy storage units; i) limiting the state of the thermal management system according to the comparison result.

7. The method according to claim 6, wherein at least one of the following fault conditions is taken into account for limiting: i. in the event of a thermal defect in one of the at least three energy storage units, classifying the thermal connection of the energy storage unit to the cooling plate as faulty and thus classifying the state of the thermal management system for the respective energy storage unit as faulty; ii. in the event of a thermal defect for all of the at least three electrical energy storage cells in thermal contact with the at least one cooling plate, classifying the coolant supply of the at least one cooling plate of the thermal management system as faulty; iii. In the event of a thermal defect for a plurality of electrical energy storage cells arranged one behind the other and / or next to one another on the at least one cooling plate, the cooling plate in thermal contact with the plurality of electrical energy storage cells is classified as faulty.

8. A device for determining the state of a thermal management system of an electric energy accumulator, wherein the electric energy accumulator has at least one electric energy accumulator cell and at least one cooling plate, the at least one cooling plate being in thermal contact with the at least one electric energy accumulator cell, wherein the device has at least one electronic control unit, the electronic control unit being configured to implement the steps of the method according to any one of claims 1 to 7. 9 . The device according to claim 8 , further comprising a temperature sensor for determining the temperature of the electrical energy storage cell. 10 . An electrical energy storage unit having a device according to claim 8 or 9 .

11. Computer program product comprising a computer program which is designed to carry out all the steps of the method according to any one of claims 1 to 7 when the computer program is run on a processor. 12 . A machine-readable storage medium having a computer program stored thereon, the computer program being designed to carry out all the steps of the method according to claim 1 when executed on a processor.

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