Method for operating a fuel-cell electric vehicle, and fuel-cell electric vehicle

Abstract

The invention relates to a method for operating a fuel-cell electric vehicle (2) comprising at least one electrical energy store (4) in which electrical useful energy (6) which can be used to operate the electric vehicle (2) can be stored and output again between a minimum state of charge (8) which is not to be fallen below and a maximum state of charge (10) of the electrical energy store (4) which maximum state of charge is not to be exceeded, and charging the electrical energy store (4) is limited to a maximum charging state (12) which is below the maximum state of charge (10) by the amount of an ACTUAL charge reserve (14) to be maintained. The fuel-cell electric vehicle also comprises at least one fuel-cell system (18) which has a liquid-gas tank (20) storing hydrogen and which has at least one fuel cell (22) in which electrical energy can be generated via consumption, in particular via reverse electrolysis, of hydrogen and can be supplied at least to the electrical energy store (4). The fuel-cell system (18) is operated in a follow-up operation immediately after an energy-generating operation has ended. In the follow-up operation, excess electrical energy that has been generated is stored in the ACTUAL charge reserve (14) of the electrical energy store (4). The fuel-cell electric vehicle also comprises at least one control unit (32) which is functionally assigned an energy-store temperature sensor, a fuel-cell temperature sensor and an ambient temperature sensor.

Description

[0001] METHOD FOR OPERATING A FUEL CELL ELECTRIC VEHICLE

[0002] AND FUEL CELL ELECTRIC VEHICLE

[0003] The invention relates to a method for operating a fuel cell electric vehicle and to a fuel cell electric vehicle that can be operated using such a method.

[0004] Methods for operating a fuel cell electric vehicle with at least one electrical energy storage device are known in various embodiments from the prior art.

[0005] Known fuel cell electric vehicles are designed to operate in a run-on mode after the electric motor is switched off. This run-on mode serves to consume unused hydrogen and / or increase the fuel cell temperature to remove water contained in the fuel cell from the fuel cell system.

[0006] In conventional fuel cell systems, hydrogen is introduced on one side, while air is compressed and "preconditioned" on the other. This air contains not only oxygen for the desired reaction, which produces electrical energy and water, but also water. The water produced during the reaction is separated, but water from the air that provides the oxygen can remain in the fuel cell system.

[0007] This reduces the risk of water freezing and / or damage to the fuel cell when the fuel cell electric vehicle is parked, particularly at very low ambient temperatures.

[0008] The electrical energy storage devices provided in the known fuel cell electric vehicles must maintain an actual charge reserve in order to be able to absorb the excess electrical energy generated during the run-on operation of the fuel cell system without damaging the electrical energy storage device, for example due to overcharging.

[0009] In known fuel cell electric vehicles, the actual charge reserve is designed for a worst-case scenario, i.e., for at least one long run-on period or multiple run-on periods. Such a long run-on period can be expected, for example, in an electric vehicle operated only briefly and therefore with a relatively cold fuel cell system and particularly low ambient temperatures, since in such cases the fuel cell system must be operated for a longer period to reach the required fuel cell temperature.

[0010] However, maintaining an actual charge reserve designed for a worst-case scenario reduces the maximum state of charge that can be achieved by charging the electrical energy storage device, since the useful electrical energy that can be used in the electrical energy storage device is composed of the maximum state of charge of the electrical energy storage device by means of charging and the actual charge reserve that must be maintained.

[0011] During normal operation of the electric vehicle, i.e., at moderate ambient temperatures, the excess energy generated during run-on operation is below the actual charge reserve of the electrical energy storage unit. In this case, the useful electrical energy stored in the electrical energy storage unit that can be used to operate the electric vehicle is below the maximum possible value because the actual charge reserve is not fully utilized.

[0012] As a result, the useful electrical energy that can be used to operate the electric vehicle is reduced and charging of the electrical energy storage device, for example by the fuel cell system or by an external charging device such as a charging station, is below the maximum possible value, which can have an unsatisfactory effect on the range and driving performance of the fuel cell electric vehicle as well as on fuel consumption.

[0013] An object of an embodiment of the invention is to provide a method for operating a fuel cell electric vehicle and a fuel cell electric vehicle operable according to such a method, in which the electrical energy storage device can be used in an improved manner.

[0014] This object is achieved by a method for operating a fuel cell electric vehicle with at least one electrical energy storage device, in which useful electrical energy that can be used to operate the electric vehicle can be stored and released again between a minimum charge level of the electrical energy storage device that must not be undershot and a maximum charge level of the electrical energy storage device that must not be exceeded, and the charging of the electrical energy storage device is limited to a maximum charge level that is below the maximum charge level by the amount of an actual charge reserve to be maintained, with at least one fuel cell system that comprises a hydrogen-storing liquid gas tank and at least one fuel cell in which electrical energy can be generated by consumption, in particular by inverse electrolysis, of hydrogen and can be fed at least to the electrical energy storage device,wherein the fuel cell system is operated in a run-on mode immediately after the end of an energy generation operation, in which generated excess electrical energy is stored in the actual charge reserve of the electrical energy storage device, and with at least one control unit to which an energy storage temperature sensor, a fuel cell temperature sensor and an ambient temperature sensor are functionally assigned,comprising the steps: a. Detecting an actual fuel cell temperature of the at least one fuel cell by the fuel cell temperature sensor and an actual ambient temperature by the ambient temperature sensor; b. Detecting the duration of the run-on operation and the excess electrical energy generated during the entire run-on operation by the control unit at least based on the detected actual fuel cell temperature and the detected actual ambient temperature; c. Determining a target charge reserve of the electrical energy storage device for storing the detected excess electrical energy by the control unit, and i. Reducing the actual charge reserve if the calculated target charge reserve is less than the current actual charge reserve, and ii. Expanding the actual charge reserve if the calculated target charge reserve is greater than the current actual charge reserve.

[0015] By determining a target charge reserve of the electrical energy storage system for storing the detected excess electrical energy, the actual charge reserve can be optimized. In this case, the actual charge reserve can be configured very low if the actual fuel cell temperature is sufficiently high due to extended operation of the electric vehicle and the ambient temperature is within a normal range, allowing operation in a very short run-on mode.

[0016] In such a case, during a short run-on operation, the excess electrical energy generated that must be stored in the actual charge reserve is significantly lower than the actual charge reserve of the electrical energy storage system designed for the worst case. Such a worst case is designed, for example, in such a way that the fuel cell electric vehicle is operated at least once only briefly and at particularly low ambient temperatures. In such a case, due to the very short operation of the fuel cell system, the actual fuel cell temperature is particularly low. In combination with the particularly low ambient temperatures, a particularly long run-on operation is to be expected in the worst-case scenario and, as a result, a very high expected excess electrical energy that must be stored in the actual charge reserve of the electrical energy storage system.

[0017] The actual charge reserve and the target charge reserve refer to a capacitive reserve of the electrical storage system that is available for absorbing or storing electrical energy. This is part of the storage capacity of the electrical storage system.

[0018] By recording the actual fuel cell temperature and the recorded actual ambient temperature, the target charge reserve can be better adapted to the expected excess electrical energy.

[0019] The expected excess electrical energy comprises the portion of the electrical energy generated by the fuel cell system during run-on that is not consumed by any consumer. For example, part of the electrical energy generated during run-on may be consumed by a seat heater, a radio, a console module, or similar devices.

[0020] Furthermore, the method according to the invention, in which steps a. to c. are carried out regularly at least during operation of the fuel cell electric vehicle, in particular at regular intervals, is adaptable to changing parameters. The actual charge reserve to be maintained for the electrical energy storage device can be particularly low if the detected actual fuel cell temperatures and the detected actual ambient temperatures are sufficiently high to trigger a brief run-on operation, for example, after extended operation of the fuel cell electric vehicle with a short parking period and subsequent restart of the fuel cell electric vehicle.

[0021] In addition, the method according to the invention also automatically detects a worst-case scenario, for example when a fuel cell electric vehicle that has been parked for a long time is only put into operation for a short time, for example to repark, and a particularly long run-on operation is necessary due to particularly low actual fuel cell temperatures and particularly low ambient temperatures.

[0022] The purpose of run-on operation is to consume residual hydrogen in the fuel cell, for example through inverse electrolysis, and / or to establish a sufficiently high actual fuel cell temperature to prevent water from freezing in the fuel cell system and the resulting damage to the fuel cell.

[0023] “Consuming” hydrogen in the fuel cell means reversing the electrolysis reaction.

[0024] The recorded excess electrical energy can include all the electrical energy generated by the fuel cell system. Furthermore, portions of the generated electrical energy can be supplied to consumers, for example, electrical consumers in the electric vehicle, such as navigation devices, music systems, seat heaters, auxiliary electric heaters for thermal comfort in the interior, and the like, which continue to operate even when the electric motor is switched off. In this case, the excess electrical energy comprises the difference between the generated electrical energy and the electrical energy consumed by the consumers.

[0025] The electrical energy storage device can be a battery or a supercapacitor.

[0026] In a further development of the method, it proves to be advantageous if the control unit detects an actual charge state of the electrical energy storage device and an actual energy storage device temperature via the energy storage device temperature sensor and / or if the adjustment of the actual charge reserve of the electrical energy storage device to the desired charge reserve of the electrical energy storage device is additionally carried out on the basis of the actual charge state of the electrical energy storage device and the actual energy storage device temperature. The adjustment of the actual charge reserve of the electrical energy storage device to the desired charge reserve of the electrical energy storage device can comprise reducing or increasing the actual charge reserve.

[0027] If the control unit records the actual charge level of the electrical energy storage unit and the actual energy storage unit temperature, the actual charge reserve to be maintained can be further optimized. Furthermore, the risk of damage to the electrical energy storage unit is reduced.

[0028] The electrical energy that can be stored in an electrical energy storage device depends, among other things, on the actual energy storage temperature. For example, more electrical energy can be stored in a warm electrical energy storage device than in a cold one. If the control unit detects a low actual energy storage temperature, the actual charge reserve of the electrical energy storage device must be adjusted accordingly.

[0029] The electrical energy storage device can comprise an energy storage management system assigned or assignable to the control unit, by means of which the state of charge of the electrical energy storage device and the actual energy storage temperature can be forwarded to the control unit.

[0030] In a further development of the latter embodiment, it proves to be advantageous if the electrical energy storage device is cooled or heated by at least one heating unit of the electric vehicle for heating or cooling the electrical energy storage device when the detected actual energy storage temperature exceeds or falls below a target temperature range.

[0031] By heating the electrical energy storage device when a target temperature is detected and cooling the electrical energy storage device when an actual energy storage temperature is detected that is above a target temperature range, the electrical energy storage device can be maintained within a specific temperature range. This keeps the amount of electrical energy that can be stored in the electrical energy storage device at a constant value or within a range. The amount of electrical energy that can be absorbed by the electrical energy storage device can thus be designed efficiently and optimally.

[0032] The method can be further improved if expanding the actual charge reserve of the electrical energy storage device comprises a. limiting charging of the electrical energy storage device to a maximum charge level that is below the maximum charge level of the electrical energy storage device by the amount of the determined target charge reserve, if the actual charge level of the electrical energy storage device is below the maximum charge level of the electrical energy storage device; and / or b.Discharging the electrical energy storage device, in particular by operating the heating unit, to an actual charge level of the electrical energy storage device that is below the maximum charge level of the electrical energy storage device, which is below the maximum charge level by the amount of the determined target charge reserve, when the actual charge level of the electrical energy storage device is above the maximum charge level of the electrical energy storage device and when the electric vehicle is out of operation and the fuel cell system is in run-on mode.

[0033] If the actual charge level of the electrical energy storage device is below the maximum charge level of the electrical energy storage device, the actual charge reserve does not need to be actively expanded. Instead, it is sufficient for the electrical energy storage device currently being charged to be adjusted to its maximum charge level. Once the maximum charge level is reached, the electrical energy storage device is blocked from further charging by the fuel cell system or an external energy source.

[0034] However, if it is detected that the current ACTUAL state of charge of the electrical energy storage device is above the maximum state of charge of the electrical energy storage device, the electrical energy storage device must be partially discharged so that the partially occupied ACTUAL charge reserve corresponds to the determined free TARGET charge reserve. If the electric vehicle is simultaneously out of operation and the fuel cell system is in run-on mode, the additional unused electrical energy that can now be expected is higher than the available ACTUAL charge reserve can absorb. This can lead to damage to the electrical energy storage device. In such cases, it is advantageous if the electrical energy storage device is discharged to a maximum state of charge at which the ACTUAL charge reserve corresponds to the determined TARGET charge reserve.

[0035] A situation in which the actual charge level of the electrical energy storage device is above the maximum charge level of the electrical energy storage device can occur, for example, if the electric vehicle is restarted and briefly moved immediately after the end of run-on operation. In this case, the electrical energy storage device is maximally charged, and run-on operation begins again when the electric vehicle is turned off. However, the actual charge level of the electrical energy storage device is so high that the electrical energy storage device has almost no actual charge reserve left and, in particular, cannot absorb the excess energy now generated by the renewed run-on operation.

[0036] Discharging the electrical energy storage device when the electric vehicle is not in operation can be easily accomplished if the operation of the heating unit for discharging the electrical energy storage device includes simultaneous or alternating heating and cooling of the electrical energy storage device.

[0037] In such cases, the electrical energy storage device can be heated or cooled by the heating unit to consume sufficient electrical energy until the electrical energy storage device again has an actual charge reserve that corresponds to the target charge reserve. To keep the electrical energy storage device within the temperature range, simultaneous heating and cooling can be used to discharge the electrical energy storage device more quickly.

[0038] Embodiments of the method are conceivable in which the detection of the duration of the run-on operation and the excess electrical energy generated in the entire run-on operation by the control unit at least on the basis of the detected actual fuel cell temperature and the detected actual ambient temperature comprises access to and a comparison with a data table in which at least each pairing of actual fuel cell temperature and actual ambient temperature is assigned a duration of the run-on operation and the total excess electrical energy generated in the run-on operation or a calculation of the duration of the run-on operation and the total excess energy generated in the run-on operation stored by one or more formulas with the detected actual fuel cell temperature and the detected actual ambient temperature as calculation parameters.

[0039] If the recording of the duration of the run-on operation and the excess electrical energy generated in the entire run-on operation by the control unit is assigned a duration of the run-on operation and the total excess energy generated in the run-on operation at least on the basis of the recorded actual fuel cell temperature and actual ambient temperature, a fast and energy-efficient recording of the duration of the run-on operation and the excess electrical energy generated is provided.

[0040] If the duration of the overrun operation and the excess energy generated during the overrun operation are calculated using one or more formulas, the method is independent of a complete and accurate stored data table.

[0041] Recording the duration of the overrun operation and the excess electrical energy generated during the entire overrun operation can therefore involve accessing and comparing it with a data table or a calculation.

[0042] Furthermore, embodiments of the method are conceivable in which the determination of the TARGET charge reserve of the electrical energy storage device for storing the detected excess electrical energy by the control unit involves access to and comparison with a data table in which at least each ACTUAL energy storage temperature is assigned a TARGET charge reserve or a calculation of the TARGET charge reserve stored by one or more formulas, which includes the ACTUAL energy storage temperature as a calculation parameter.

[0043] If the control unit determines the target charge reserve of the electrical energy storage device for storing the detected excess electrical energy by accessing and comparing it with a data table, the target charge reserve can be determined quickly and energy-efficiently. If the control unit determines the target charge reserve of the electrical energy storage device for storing the detected excess electrical energy by calculating it using one or more formulas, the determination of the target charge reserve is independent of the completeness and accuracy of the data in a data table.

[0044] In this case, determining the target charge reserve of the electrical energy storage device may involve accessing and comparing it with a data table or performing a calculation.

[0045] In addition, mixed forms are also conceivable, in which both access and comparison with a data table as well as a calculation are carried out, as well as a learning system in which a calculation is carried out with a more or less complete data table and the results of the calculation are stored in the data table.

[0046] This applies both to determining the target charge reserve and to recording the duration of the run-on operation and the excess electrical energy generated during the entire run-on operation.

[0047] The process can be designed to be energy efficient if the run-on operation is automatically terminated when a target fuel cell temperature and target outside temperature stored in the control unit are reached or exceeded.

[0048] The target fuel cell temperature and target outside temperature include values ​​that ensure that water in the fuel cell is sufficiently evaporated due to the target fuel cell temperature in order to avoid freezing and thus damage to the fuel cell.

[0049] Furthermore, embodiments of the method are conceivable in which steps a., b. and c. of claim 1 are carried out permanently or at intervals periodically during the energy generation operation of the electric vehicle, during the run-on operation of the fuel cell system and / or in a parking phase of the electric vehicle in which the run-on operation is terminated and the electric vehicle is out of operation.

[0050] If steps a., b., and c. of claim 1 are performed continuously, constant up-to-dateness and optimal adjustment of the actual charge reserve can be guaranteed. If steps a., b., and c. of claim 1 are performed at intervals, the energy consumption of the method can be reduced. Performing the aforementioned steps at intervals is particularly justifiable if, for example, a certain actual temperature of the fuel cell system is reached during energy generation operation of the electric vehicle and the actual ambient temperature remains essentially constant. In this case, it is not to be expected that a significant change will occur between the recording at one point in time and a subsequent, further point in time.

[0051] The same applies if the electric vehicle is in a parking phase for an extended period of time and the actual fuel cell temperature and the actual ambient temperature are almost unchanged.

[0052] In a further development of the latter embodiment, it proves to be advantageous if the control unit is placed into a sleep mode once or repeatedly for a predetermined period of time during the parking phase of the electric vehicle and is placed into a working mode after the expiry of the period of time, wherein in the working mode at least the steps a., b. and c. of claim 1 are carried out and wherein the control unit rests in the sleep mode without supervision.

[0053] By putting the control unit into sleep mode, the vehicle's energy consumption can be reduced.

[0054] Furthermore, it proves to be advantageous if, during the parking phase of the electric vehicle and when a drop in the actual fuel cell temperature below a parking fuel cell temperature is detected, the target charge reserve of the electrical energy storage device is set to a maximum value of the charge reserve.

[0055] If the actual fuel cell temperature drops below a parking fuel cell temperature, the electrical energy storage device can be discharged in such a way that the actual charge reserve includes a worst-case scenario. This means that the target charge reserve of the electrical energy storage device is set to a maximum value of the charge reserve, and the actual charge reserve is adjusted accordingly. The control unit can then be put into sleep mode until the electric vehicle is operated again.

[0056] In a further development of the latter embodiment, it proves to be advantageous if, after the actual charge reserve has been adjusted to the desired charge reserve comprising the maximum value, monitoring of the actual fuel cell temperature is paused until the electric vehicle is started again.

[0057] This makes the process energy efficient.

[0058] The method can be suitable for various types of electric vehicles. Embodiments are conceivable in which the electrical energy storage unit of the fuel cell electric vehicle can be charged to its maximum charge level by the fuel cell system and, if necessary, by an external energy source, such as a charging station.

[0059] In this case, the fuel cell electric vehicle can draw power from an external energy source to charge the electrical energy storage system. This reduces the vehicle's fuel consumption.

[0060] Furthermore, the object is achieved by a fuel cell electric vehicle which can be operated by a method having at least one of the aforementioned features, with at least one electrical energy storage device in which useful electrical energy which can be used to operate the electric vehicle can be stored and released again between a minimum charge level of the electrical energy storage device which must not be undercut and a maximum charge level of the electrical energy storage device which must not be exceeded, and the charging of the electrical energy storage device is limited to a maximum charge level which is below the maximum charge level by the amount of an actual charge reserve to be maintained, with at least one fuel cell system which comprises a liquid gas tank storing hydrogen and which comprises at least one fuel cell in which electrical energy can be generated by consumption, in particular by inverse electrolysis, of hydrogen,wherein the fuel cell system is operated in a run-on mode immediately after the end of an energy generation operation, in which excess electrical energy generated is stored in the actual charge reserve of the electrical energy storage device, and with at least one control unit to which an energy storage temperature sensor, a fuel cell temperature sensor and an ambient temperature sensor are functionally assigned.

[0061] Finally, it proves to be advantageous if the fuel cell electric vehicle comprises at least one connection means by which the electrical energy storage device can be connected to an external electrical energy source, in particular it proves to be advantageous if the fuel cell electric vehicle comprises a plug-in fuel cell electric vehicle and / or if the electrical energy storage device comprises a battery, a high-voltage battery or a supercapacitor.

[0062] Further features, details and advantages of the invention emerge from the appended patent claims, from the drawings and the following description of a preferred embodiment of the fuel cell electric vehicle and the method.

[0063] The drawing shows:

[0064] Figure 1 A schematic representation of the individual components of the electric vehicle in a trailing operation;

[0065] Figure 2 A schematic representation of an electrical energy storage system with actual charge reserve for a worst-case scenario;

[0066] Figure 3 A schematic representation of an electrical energy storage device with an actual charge reserve under normal conditions;

[0067] Figure 4 A schematic flow diagram of a method according to the invention;

[0068] Figure 5 A status overview of individual components of the electric vehicle for different parameter values.

[0069] Figure 1 shows a schematic representation of a fuel cell electric vehicle 2. In the schematic overview diagram shown in Figure 1, the fuel cell electric vehicle 2 comprises a so-called plug-in fuel cell electric vehicle 2. This comprises an electrical energy storage device 4 in which useful electrical energy 6 (see Figures 2 and 3) that can be used to operate the electric vehicle 2 can be stored between a minimum charge level 8 that must not be undershot and a maximum charge level 10 of the electrical energy storage device 4 that must not be exceeded. By providing a minimum charge level 8 that must not be undershot, complete emptying of the electrical energy storage device 4 is avoided, thereby increasing the service life of the electrical energy storage device 4.By providing a maximum charge level 10 of the electrical energy storage device 4 that must not be exceeded, overcharging of the electrical energy storage device 4 is prevented. The maximum charge level 12 in the electrical energy storage device 4 by charging the electrical energy storage device 4 is limited by the provision of an actual charge reserve 14. The maximum useful electrical energy 6 that can be used to operate the electric vehicle 2 is composed of the sum of the maximum charge level 12 and the actual charge reserve 14, if the actual charge reserve 14 is occupied with energy.

[0070] The electrical energy storage device 4 according to Figure 1 can generally be charged by an external energy source 16. Figure 1 shows the fuel cell electric vehicle 2 in a run-on mode of a fuel cell system 18. The fuel cell system 18 comprises a liquid gas tank 20 in which hydrogen can be stored. The liquid gas tank 20 is connected to at least one fuel cell 22, wherein hydrogen from the liquid gas tank 20 is burned in the fuel cell 22 and converted into electrical energy. The electrical energy storage device 4 can be supplied with electrical energy by the fuel cell 22. In the exemplary embodiment shown in Figure 1, a current converter 24 is arranged between the fuel cell 22 and the electrical energy storage device 4, through which current from the fuel cell 22 can be supplied to the electrical energy storage device 4 on the one hand and to a consumer 26 of the fuel cell electric vehicle 2 on the other.

[0071] The electrical energy storage device 4 can supply an electric motor 28 with electrical energy as well as a heating unit 30 by means of which the electrical energy storage device can be heated and / or cooled.

[0072] Figure 1 shows the fuel cell electric vehicle 2 in run-on mode, i.e., after the end of an energy generation operation. During run-on mode, the fuel cell 22 continues to operate and heat up to consume any remaining unused hydrogen and, by ensuring a sufficiently high actual fuel cell temperature, to drain water from the fuel cell 22 to prevent icing and possible damage.

[0073] The method according to the invention is described using the schematic flow diagram according to Figure 4, with reference to the schematic representation in Figure 1 and the different charging states according to Figures 2 and 3.

[0074] In a first step 100, a control unit 32 detects an actual fuel cell temperature of the at least one fuel cell 22 using a fuel cell temperature sensor of the control unit 32, and an actual ambient temperature using an ambient temperature sensor of the control unit 32. In a subsequent step 101, the duration of the run-on operation and the excess electrical energy generated during the entire run-on operation are detected by the control unit 32. This is done at least on the basis of the detected actual fuel cell temperature and the detected actual ambient temperature.

[0075] The duration of the run-on operation and the excess electrical energy generated during the entire run-on operation can be recorded by accessing and comparing the data with a data table in which each pairing of the actual fuel cell temperature and the actual ambient temperature is assigned a duration of the run-on operation and the total excess electrical energy generated during the run-on operation. In addition or alternatively, the duration of the run-on operation and the excess electrical energy generated during the entire run-on operation can also be recorded through a calculation in which the actual fuel cell temperature and the actual ambient temperature represent calculation parameters.

[0076] In a subsequent step 102, the control unit 32 determines the target charge reserve of the electrical energy storage device 4 for storing the excess electrical energy. The determination of a target charge reserve of the electrical energy storage device 4 for storing the detected excess electrical energy can also comprise a comparison and access to a database in which at least each actual energy storage temperature is assigned a target charge reserve and / or a calculation thereof.

[0077] For this purpose, in a further development of the method, it can be provided that, in order to determine the desired charge reserve, the control unit 32 additionally determines an actual charge state of the electrical energy storage device 4 and the actual energy storage temperature of the electrical energy storage device 4.

[0078] Based on the now determined TARGET charge reserve of the electrical energy storage device 4, the ACTUAL charge reserve 14 can be reduced in a step 103a if the calculated TARGET charge reserve is smaller than the current ACTUAL charge reserve 14. In this case, an ACTUAL charge reserve 14 is represented as shown in Figure 3. However, if the calculated TARGET charge reserve is greater than the current ACTUAL charge reserve 14, the ACTUAL charge reserve 14 is expanded in a step 103b. The expansion of the ACTUAL charge reserve 14 according to step 103b can either take place in a step 104a by arranging the maximum state of charge 12 available to the electrical energy storage device 4 when charging the electrical energy storage device 4 to a level by the TARGET charge reserve below the maximum state of charge 10.This is the case when the actual charge state of the electrical energy storage device is below the maximum charge state 12 of the electrical energy storage device 4.

[0079] As a result, no active steps are necessary, but the electrical energy storage device 4 can only maintain the new actual charge reserve 14 for storing a new, maximum charge state 10 of the electrical energy storage device 4 by charging.

[0080] However, if the actual state of charge of the electrical energy storage device 4 is above the maximum state of charge 12 of the electrical energy storage device 4 and if the electric vehicle 2 is out of operation and the fuel cell system 18 is in run-on mode, in a step 104b the electrical energy storage device 4 is actively discharged, in particular by operating the heating unit 30, to an actual state of charge of the electrical energy storage device 4 which is below the maximum state of charge 12 of the electrical energy storage device 4 and which is below the maximum state of charge 10 by the amount of the determined target charge reserve.

[0081] After completion of steps 103a, 104a and 104b, the method is repeated starting from step 100.

[0082] Figure 5 shows the different components of the fuel cell electric vehicle 2 at different temperatures and operating conditions of the components. Under T amb indicates the ambient temperature. The actual fuel cell temperature is shown below.

[0083] The actual charge reserve 14 of the electrical energy storage device 4 is indicated under SoC.

[0084] Under PwT sAn operating state of the control unit 32 is specified. Until point 1 is reached, the fuel cell electric vehicle 2 is operated in energy generation mode. The actual charge reserve 14 is minimal. The ambient temperature and the fuel cell temperature are also at a value that is above a necessary temperature. Between 1 and 2, a run-on operation of the fuel cell system 18 takes place. Between 2 and 3, the control unit 32 is transferred to a sleep mode and reactivated between points 3 and 4. Between points 3 and 4, the actual fuel cell temperature and the actual ambient temperature are still sufficiently high, so that only a minor expansion of the actual charge reserve 14 is necessary. After the control unit 32 is transferred back to sleep mode between points 4 and 5, the control unit 32 is put back into operation between points 5 and 6.This detects that both the actual fuel cell temperature and the actual ambient temperature have fallen below a level that indicates extended run-on operation. In such a case, the control unit 32 assumes a worst-case scenario and discharges the electrical energy storage device 4 to an actual charge state in which a maximum possible actual charge reserve 14 is maintained.

[0085] The features of the invention disclosed in the above description, in the claims and in the drawings can be essential both individually and in any combination in the realization of the invention in its various embodiments.

[0086] List of reference symbols

[0087] Fuel cell electric vehicle electrical energy storage useful electrical energy minimum charge level maximum charge level maximum charge level actual charge reserve external energy fuel cell system liquid gas tank fuel cell power converter consumer electric motor heat unit control unit -b process steps

Claims

Patent claims for a method for operating a fuel cell electric vehicle (2) with at least one electrical energy storage device (4) in which usable electrical energy (6) for operating the electric vehicle (2) can be stored and released between a minimum state of charge (8) and a maximum state of charge (10) of the electrical energy storage device (4) that cannot be undercut, and the charging of the electrical energy storage device (4) is limited to a maximum state of charge (12) that is below the maximum state of charge (10) by the amount of a required actual charge reserve (14), with at least one fuel cell system (18) comprising a liquid gas tank (20) storing hydrogen and at least one fuel cell (22) in which electrical energy is generated by consumption, in particular by inverse electrolysis,hydrogen can be generated and supplied at least to the electrical energy storage (4), wherein the fuel cell system (18) is operated in a run-on mode immediately after the end of an energy generation operation, in which generated excess electrical energy is stored in the IST charging reserve (14) of the electrical energy storage (4), and with at least one control unit (32) to which an energy storage temperature sensor, a fuel cell temperature sensor and an ambient temperature sensor are functionally assigned,with the following steps: a. Determining the actual fuel cell temperature of the at least one fuel cell (22) by the fuel cell temperature sensor and the actual ambient temperature by the ambient temperature sensor; b. Determining the duration of the after-run operation and the excess electrical energy generated during the entire after-run operation by the control unit (32) at least on the basis of the determined actual fuel cell temperature and the determined actual ambient temperature; c. Determining a target charge reserve of the electrical energy storage device (4) for storing the determined excess electrical energy by the control unit (32); and i. Reducing the actual charge reserve (14) if the calculated target charge reserve is smaller than the current actual charge reserve (14). ii. Extending the actual charge reserve (14) if the calculated target charge reserve is greater than the current actual charge reserve (14). Method according to claim 1, characterized in that the control unit (32) detects an actual charge state of the electrical energy storage device (4) and an actual energy storage device temperature via the energy storage device temperature sensor and / or that the adjustment of the actual charge reserve (14) of the electrical energy storage device (4) to the target charge reserve of the electrical energy storage device (4) is additionally based on the actual charge state of the electrical energy storage device (4) and the actual energy storage device temperature.A method according to claim 2, characterized in that the electrical energy storage device (4) is cooled or heated by at least one heating unit (30) of the electric vehicle (2) when the detected actual energy storage device temperature exceeds or falls below a target temperature range. A method according to claim 2 or 3, characterized in that extending the actual charge reserve (14) of the electrical energy storage device (4) a. limits the charging of the electrical energy storage device (4) to a maximum charge state (12) that is below the maximum charge state (10) of the electrical energy storage device (4) by the amount of the determined target charge reserve when the actual charge state of the electrical energy storage device (4) is below the maximum charge state (12) of the electrical energy storage device (4); and / or b.Discharging the electrical energy storage device (4), in particular by operating the heating unit (30) to an actual state of charge of the electrical energy storage device (4) that is below the maximum state of charge (12) of the electrical energy storage device (4), which is below the maximum state of charge (10) by the amount of the determined target charge reserve, if the actual state of charge of the electrical energy storage device (4) is above the maximum state of charge (12) of the electrical energy storage device (4) and if the electric vehicle (2) is out of operation and the fuel cell system (18) is in after-run operation; Method according to claim 4, characterized in that the operation of the heating unit (30) for discharging the electrical energy storage device (4) comprises simultaneous or alternating heating and cooling of the electrical energy storage device (4).A method according to one of the preceding claims, characterized in that the detection of the duration of the after-run operation and the excess electrical energy generated during the entire after-run operation by the control unit (32) at least on the basis of the detected actual fuel cell temperature and the detected actual ambient temperature includes access to and comparison with a data table in which at least each pairing of actual fuel cell temperature and actual ambient temperature is assigned a duration of the after-run operation and the total excess electrical energy generated during the after-run operation, or a calculation of the duration of the after-run operation and the total excess energy generated during the after-run operation, using the detected actual fuel cell temperature and the detected actual ambient temperature as calculation parameters, is based on one or more formulas.A method according to any of the preceding claims, characterized in that determining the target charge reserve of the electrical energy storage device (4) for storing the detected excess electrical energy by the control unit (32) involves accessing and comparing it with a data table in which at least each actual energy storage temperature is assigned a target charge reserve, or a calculation of the target charge reserve based on one or more formulas that include the actual energy storage temperature as a calculation parameter. A method according to any of the preceding claims, characterized by terminating the after-run operation upon reaching or exceeding a target fuel cell temperature and target ambient temperature stored in the control unit (32). A method according to any of the preceding claims, characterized in that steps a., b., and c.of claim 1, permanently or periodically at time intervals during the energy generation operation of the electric vehicle (2), during the after-run operation of the fuel cell system (18) and / or in a parking phase of the electric vehicle (2) in which the after-run operation is terminated and the electric vehicle (2) is out of operation. A method according to claim 9, characterized in that the control unit (32) is placed in a standby mode once or repeatedly for a predetermined period of time during the parking phase of the electric vehicle (2) and is placed in a working mode after the period of time has elapsed, wherein at least steps a., b. and c. of claim 1 are carried out in the working mode and wherein the control unit (32) rests without monitoring in the standby mode. A method according to claim 9 or 10, characterized in that during the parking phase of the electric vehicle (2) and upon detection of a drop in the actual fuel cell temperature below a parking fuel cell temperature, the target charge reserve of the electrical energy storage device (4) is set to a maximum charge reserve value. A method according to claim 11, characterized in thatthat after the actual charge reserve (14) has been adjusted to the target charge reserve, which comprises the maximum value, monitoring of the actual fuel cell temperature is paused until the electric vehicle (2) is restarted. A method according to one of the preceding claims, characterized in that the electrical energy storage device (4) of the fuel cell electric vehicle (2) can be charged by the fuel cell system (18) and optionally by an external energy source (16), such as a charging station, up to the maximum charge level (12). A fuel cell electric vehicle (2) that can be operated according to a method according to one of claims 1 to 13, with at least one electrical energy storage device (4).in the electrical energy usable for the operation of the electric vehicle (2) (6) can be stored and released between a minimum charge level (8) and a maximum charge level (10) of the electrical energy storage device (4), and the charging of the electrical energy storage device (4) is limited to a maximum charge level (12) which is below the maximum charge level (10) by the amount of a required actual charge reserve (14), with at least one fuel cell system (18) comprising a liquid gas tank (20) storing hydrogen and at least one fuel cell (22) in which electrical energy can be generated by consuming hydrogen, in particular by inverse electrolysis, wherein the fuel cell system (18) is operated in a run-on mode immediately after the end of an energy generation operation, in which any excess electrical energy generated is stored. Energy is stored in the IST charge reserve (14) of the electrical energy storage device (4), and with at least one control unit (32) to which an energy storage device temperature sensor, a fuel cell temperature sensor, and an ambient temperature sensor are functionally assigned. Fuel cell electric vehicle (2) according to claim 14, characterized by at least one connection means by which the electrical energy storage device (4) can be connected to an external electrical energy source (16), in particular characterized in that the fuel cell electric vehicle (2) comprises a plug-in fuel cell electric vehicle (2) and / or that the electrical energy storage device (4) comprises a battery, a high-voltage battery, or a supercapacitor.

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