DE102007055486A1 - A method of detecting a leakage of a fuel cell system and fuel cell system - Google Patents

Abstract

The invention relates to a method for detecting a leakage of a fuel cell system comprising an anode compartment comprising an anode compartment in which a pressure prevailing in the anode compartment pressure is adjusted by actuating at least one control element for adjusting a mass flow of an anode gas supplied to the anode compartment, wherein the pressure as a function of time and wherein in a cathode chamber of the fuel cell system by operating at least one control element at least one reference pressure (16, 28) is set, which is detected by the at least one reference pressure (16, 28) in the cathode space-dependent time course of the pressure in the anode space and depending on the time course of the pressure, a leakage which may be present in the anode branch is ascertained. Furthermore, the invention relates to a fuel cell system.

Description

The The invention relates to a method for detecting a leakage of a fuel cell system with an anode compartment comprising an anode compartment, wherein an in the anode chamber prevailing pressure by pressing at least a control element for adjusting a mass flow of the Anode space is supplied to the supply of anode gas, and wherein the pressure is detected as a function of time. Furthermore The invention relates to a fuel cell system.

The WO 2004/112179 A1 describes a method of detecting a leakage of a fuel cell system in which an anode space of the fuel cell system is charged with an anode gas, wherein a pressure of the anode gas is set in the anode space, which is higher than the atmospheric pressure. Simultaneously with the decommissioning of the fuel cell system in each case a valve in a supply line to and a discharge line from the anode compartment is closed. By means of a pressure gauge then the time course of the pressure in the anode chamber is detected. Since the anode gas can penetrate a membrane which separates the anode compartment from a cathode compartment of a fuel cell, the pressure in the anode compartment decreases. In this case, the pressure in the anode chamber falls below the atmospheric pressure, since a higher partial pressure of the anode gas prevails on the anode side of the membrane than on the cathode side.

To reaching a minimum of the pressure in the anode compartment increases Pressure in the anode compartment again, because atmospheric nitrogen penetrates from the cathode side of the membrane. A speed when penetrating the membrane is here for atmospheric nitrogen but less than the rate at which the anode gas the membrane penetrates. Unless the membrane penetrates facilitating the membrane for atmospheric nitrogen Leakage, is the time course of the pressure in the anode compartment different from the temporal pressure curve described above. Thus, due to the leakage of the membrane of the atmospheric Pressure in the anode compartment falls below less than this intact membrane would be the case.

When disadvantageous in such a method for determining a Leakage of the fuel cell system is the fact that a detection of the time course of the pressure in the anode space to for reaching or falling below the atmospheric pressure requires a comparatively long test period and that it is comparatively imprecise. Furthermore is the fuel cell system during the test procedure shut down.

task The present invention is a method of detection a leakage of a fuel cell system or a fuel cell system to create the type mentioned, which is an improved and more precise detection of leakage.

These The object is achieved by a method for detecting a leakage of a fuel cell system with the features of claim 1. According to one Another aspect of the invention, this object is achieved by a fuel cell system solved with the features of claim 14. advantageous Embodiments with expedient developments The invention are defined in the dependent claims specified.

at the method according to the invention for detecting a leakage of a fuel cell system with an anode compartment extensive anode branch, becomes a ruling in the anode compartment Pressure by actuating at least one control element for adjusting a mass flow of an anode compartment feedable Anodengases set. The pressure is recorded as a function of time. In a cathode compartment of the fuel cell system is operated by at least one control element at least set a reference pressure. The dependent on the at least one reference pressure in the cathode compartment time course of the pressure in the anode compartment is detected and depending on the time course of the pressure a detected in the anode branch possibly existing leakage.

To the Adjusting the at least one reference pressure in the cathode compartment of the fuel cell system may be about one in a supply line to the cathode compartment arranged compressor or compressor to Actuation of the cathode chamber is driven with cathode gas and / or a throttle element arranged in a discharge line of the cathode compartment be operated. The setting of the at least one reference pressure but can also by pressing other controls respectively.

By setting the at least one reference pressure in the cathode space, a time profile of the pressure in the anode space which is dependent on the set reference pressure can be examined as to whether it deviates from a characteristic time profile of the pressure in the anode space, and thus can be attributed to leakage in the anode chamber Anodenzweig be closed. It is not like in the prior art according to the WO 2004/112179 A1 necessary, a drop in pressure to wait in the anode compartment under the atmospheric pressure. This allows a quicker and more precise detection of leakage.

In an advantageous embodiment of the invention will be at least set a reference pressure as at least one operating pressure in the cathode compartment. This makes it particularly advantageous allows the process even during ongoing operation of the fuel cell system perform the fuel cell system during the In particular, continue to carry out the process can supply electrical energy. The operating pressure in the cathode compartment In this case, it can supply a pressure in the cathode space with an energy Normal operation and / or a pressure in the cathode compartment at a Test mode correspond.

Of Furthermore, it is advantageous if the at least one reference pressure a first and a second reference pressure, wherein the first reference pressure less than or equal to an outlet pressure in the Anode space is adjusted, and wherein the second reference pressure is set smaller than the first reference pressure. Here can during a first test phase, the first reference pressure and during a second test phase, the second reference pressure be set, with the first test phase also on time can follow the second test phase.

While in the first test phase, the first reference pressure set in the cathode compartment The pressure in the anode compartment is largely the same, is the beginning of the second test phase quickly set the second reference pressure, which is lower than the pressure in the anode compartment. Will be in the first test phase by sensing the pressure in the anode compartment as a function of time noted a particularly strong pressure drop in the anode compartment, so It can be assumed that in the anode compartment comprising the anode compartment there is a leak.

Becomes in the second test phase, at one compared to the pressure in the anode compartment further reduced second reference pressure in the Kathodenraum a compared to the first test phase larger pressure drop Detected in the anode compartment, this may indicate the presence of a Transfer leakage, so a leakage in one the anode of the cathode separating membrane, or other direct connection between Anode and cathode, close. In a preferred manner is a respective period of the first test phase and the second Test phase here essentially the same.

Of Furthermore, it has proven to be advantageous if before a renewed Setting the second reference pressure a control element in one connecting the anode compartment with the cathode compartment connecting line is opened. The connection line may be around a purge line (purge line) and at the control element around a flushing valve associated flushing valve (Purge valve) act. Here is a discharge point of the purge line in the cathode compartment designed as a pressure control element control element upstream of the reference pressure in the cathode compartment. As a result, in the purge line with open Flush valve prevailing pressure in a pressure control range adjustable which a pressure control range for setting the reference pressure in the cathode compartment corresponds.

While in the first test phase and in the second test phase, the purge valve is kept closed, is in the re-adjustment of the second Reference pressure during a third test phase the purge valve open. This can be used to determine if the transfer leakage a leakage in the anode separating the cathode from the cathode and / or a leakage of the purge valve or another, the anode compartment with the cathode compartment directly connecting connecting line to the cause. Of course, the re-setting the second reference pressure during the third test phase made separately for a plurality of connecting lines become.

From It is also advantageous if, before setting the second reference pressure the pressure prevailing in the anode compartment, in particular the outlet pressure, is increased. This ensures that for the first test phase during which in the cathode compartment the first reference pressure is set and for the second Test phase, during which in the cathode compartment, the second reference pressure is adjusted, substantially similar pressure conditions, in particular output pressure conditions, in the anode compartment are made. This is a particularly good comparability the time course of the pressure in the anode space during which allows two test phases.

Furthermore, it is advantageous if the at least one reference pressure comprises a first and a second reference pressure, wherein the first reference pressure is 65% -100%, preferably 70% -95%, more preferably 75% -90% of an outlet pressure in the anode chamber and wherein the second reference pressure is 3% -35%, preferably 4% -15%, more preferably 5% -10% of the initial pressure. This ensures that in the first test phase in the cathode chamber, a first reference pressure is set, which is the output pressure in the anode compartment is substantially equal. In contrast, the second reference pressure is quickly set at the beginning of the second test phase, which is significantly lower is the outlet pressure in the anode compartment.

In an advantageous embodiment of the invention, the pressure in Anode space at least until reaching an end time of a predetermined period of time and / or at least until reaching a predetermined value of the pressure or a range of values of the pressure recorded as a function of time. So the duration of a test phase be limited to the predetermined period of time, whereby allows a particularly rapid implementation of the method is. Additionally or alternatively, the respective test phase be given so that they reach the given Value of the pressure or the value range of the pressure continues.

Of Furthermore, it is advantageous if the second reference pressure or the first reference pressure substantially immediately after reaching the end time of the predetermined period of time and / or immediately after reaching the predetermined value of the pressure or the value range of Pressure is adjusted. This ensures in an advantageous manner that in particular temperature and humidity conditions in the Fuel cell system, in particular in the anode compartment, while two test phases are at least substantially the same.

Farther it has been shown to be advantageous if a time offset between setting two different reference pressures less than or substantially equal to the predetermined time period and / or less than or substantially equal to a period of time to reach the predetermined value of the pressure or the value range of the pressure selected becomes. As a result, the time offset between two test phases not more than the time necessary to go through a test phase. This can total the time required for performing a test for leakage by means of two test phases while which in each case the first and the second reference pressure in the cathode space be kept within reasonable limits.

In An advantageous embodiment of the invention is a difference between at a start time and at the end time of predetermined period of time detected pressure and / or a period of time for reaching the predetermined value of the pressure or the value range of the pressure. As a result, absolute sizes become Provided, which in a particularly simple manner allow comparison with characteristic values.

In Advantageous embodiment is further a difference between two differences and / or between two time periods with a test value compared, wherein an exceeding or falling below the test value a probability of transfer leakage between the anode compartment and the cathode compartment. Here, the test value corresponds an empirically and / or theoretically determined value, which predetermined is going to be in a particularly simple and reliable way confirm the presence of a transfer leak or to be able to exclude.

is such as the pressure drop in the anode compartment during the second Test phase, during which of the output pressure in the Anode space greatly different and significantly lower second Reference pressure is set, much larger as the pressure drop during the roughly equal first test phase, while which of the outlet pressure in the anode compartment in Substantially equal or slightly lower first reference pressure is set, it can be assumed that a transfer leakage the increased pressure drop compared to the first test phase causally conditioned.

Of Furthermore, it is advantageous if the at least one reference pressure set during a start-up phase of the fuel cell system becomes. So can already before reaching a normal operating state the fuel cell system to determine if a leak, in particular, a transfer leakage in the fuel cell system is present. So can one by performing the procedure causing disruption of the operation of the fuel cell system be avoided. During the subsequent operation the fuel cell system in normal operation is thus an unrestricted Supply of electrical energy allows.

After all it has proven to be advantageous if the at least one reference pressure in a, in particular in a motor vehicle, installed state of the fuel cell system is adjusted. This can be done without a removal of the fuel cell system from the motor vehicle a Leakage of the fuel cell system, in particular a transfer leakage, be found, resulting in a significantly reduced time and Equipment needs brings with it.

So is for dismantling all connecting lines of a fuel cell stack or about to remove the fuel cell stack for an outside of the motor vehicle to be performed Test procedure to detect a leak a full working day of a suitably qualified technician, In addition, a comparatively expensive equipment would be kept on special test equipment. On the other hand, the method described can be particularly simply realized on-board and without removing the fuel cell stack become.

This can be done by inserting a corresponding software component for performing the method in a control or regulating device of the fuel cell system. The method described can be done in less than 10 minutes.

The in connection with the method according to the invention for detecting a leakage of the fuel cell system described preferred embodiments and advantages also apply to the fuel cell system according to the invention.

The, especially for mobile applications, preferably in one Motor vehicle, usable fuel cell system includes this a fuel cell stack having a plurality of individual fuel cells, which are associated with the anode compartment and the cathode compartment. In the fuel cell is the anode of the cathode through a separator, such as a polymer electrolyte membrane (PEM) or proton exchange membrane (proton exchange membrane, PEM), separated. The PEM is the usual way Part of a membrane-electrode assembly (MEA).

Of Further, both on the cathode compartment and on the anode compartment corresponding supply lines and discharge lines be provided, which in each case for supplying anode gas to the anode compartment and to discharge exhaust gas from the anode compartment or for supplying cathode gas to the cathode compartment and provided for discharging exhaust gas from the cathode compartment are. It may in particular in a the anode compartment comprehensive Anode branch Return lines for recycling exhaust gas from the anode compartment into the supply conduit to the anode compartment be provided.

The supplied anode gas can be hydrogen or a hydrogen-containing Be gas as fuel. The supplied cathode gas can Oxygen or an oxygen-containing gas, e.g. As air, as an oxidizing agent be.

Of Further, in the anode compartment and in the cathode compartment or in the corresponding supply lines and discharge lines control elements for reducing a cross-section of the conduits, such as valves, throttle bodies or metering devices may be provided. The cathode compartment is preferred acted upon by a compressor or compressor with the cathode gas. By means of suitable pressure measuring devices, the pressure in the anode compartment and determined in the cathode compartment or in the corresponding lines become. The above description of components of the fuel cell system is exemplary and not exhaustive or limiting to understand, and there may be a variety of other common components To be available.

Further Advantages, features and details of the invention will become apparent the following description of a preferred embodiment and with reference to the drawings, in which like and functionally identical Elements are provided with identical reference numerals. Showing:

1 a first diagram with determined in carrying out a method for detecting a leakage of a fuel cell system temporal curves of the method characterizing parameters, in which no transfer leakage between an anode compartment and a cathode compartment of the fuel cell system is detected; and

2 one of the 1 according to diagram on the basis of a presence of a transfer leakage between the anode compartment and the cathode compartment of the fuel cell system is closed.

The arranged in a motor vehicle fuel cell system, based on which in the diagrams according to 1 and 2 have been determined, includes a fuel cell stack having a plurality of fuel cells. An anode space which can be acted upon by an anode gas, for example by hydrogen gas, is separated by means of a membrane from a cathode space which can be acted upon by a cathode gas, for instance by atmospheric air.

In 1 is a time course of a pressure related to the atmospheric pressure in bar in the anode space, which is associated with an anode branch of the fuel cell system, by a curve I in a pressure-time diagram 10 shown.

It can be seen that during a first period of time 12 , which corresponds to a first test phase, the pressure drops in the anode compartment.

The pressure-time diagram 10 further shows a curve II, which indicates the time course of a set in the cathode compartment of the fuel cell system reference pressure. The pressure in the anode chamber according to the curve I and the reference pressure in the cathode chamber according to the curve II is detected here in each case at the inlet of a supply line leading to a fuel cell stack.

An initial time 14 the first time span 12 is in this case determined by reaching a pressure in the anode compartment, which is 0.9 bar to 1.0 bar above the atmospheric pressure. To adjust this pressure, the anode compartment with the anode gas is applied, for example, by means of a high-pressure valve, a supply of anode gas from a high-pressure tank is made possible to the anode compartment. A corresponding time profile of a voltage applied to the high-pressure valve pressure is in the pressure-time diagram 10 characterized by a curve III.

So correspond phases of a voltage applied to the high pressure valve high pressure with a corresponding action on the anode compartment with anodic gas, being above the atmospheric Pressure is set in the anode chamber. By opening the high-pressure valve can thus set the pressure in the anode compartment be, by the anode compartment a certain mass flow of the anode gas is supplied.

The time course of the reference pressure in the cathode space described by curve II becomes before the start time 14 the first test phase increased by the fact that the cathode chamber is subjected to an increased mass flow of cathode gas. The time course of the mass flow of the cathode gas is in the pressure-time diagram 10 represented by a curve IV.

At the beginning time 14 the first time span 12 is thus a first reference pressure 16 adjusted, which is about 80% of an outlet pressure 18 in the anode space amounts. The first time span 12 , which delimits the first test phase, in this case has a duration of 20 seconds. With reaching an end time 20 ie after the first period of time has passed 12 of 20 seconds duration, the one in the anode compartment becomes the end time 20 prevailing pressure according to the curve I found.

Subsequently, a difference 22 between at the start time 14 and at the end time 20 the first time span 12 each recorded pressure determined. A size one during the first period of time 12 determined pressure drop in the anode compartment can provide information on whether there is any leakage in the anode branch. The leakage leads to a loss of anode gas at one or more points of the anode branch.

Preferably, there is a difference between the output pressure 18 in the anode compartment and the first reference pressure 16 in the cathode room around 200 mbar.

The pressure in the anode compartment becomes after the lapse of the first period of time 12 increased again by opening the high pressure valve. This exceeds according to 1 the pressure in the anode compartment short-term the value of 1.0 bar based on the atmospheric pressure.

Only with falling below the pressure of 1.0 bar in the anode compartment is another start time 24 a second period of time 26 achieved, which describes the beginning of a second test phase. At the beginning of the second period 26 the mass flow of the cathode gas supplied to the cathode space is greatly reduced and a throttle valve arranged in a discharge line of the cathode space is opened particularly wide.

Accordingly, during the second test phase, a second reference pressure 28 set, which in the present case about 8% of the output pressure set in the anode compartment 18 is. Correspondingly, the curve II describing the reference pressure in the cathode compartment has the beginning of the second time period 26 a particularly strong drop, so a strong negative slope on.

A duration of the second period of time 26 In this case corresponds to the duration of the first period 12 and is 20 seconds. With reaching a second end time 30 the second time span 26 , ie ending a second test phase, it will become the end time 30 found in the anode space prevailing pressure and a difference 32 between at the start time 24 and at the end time 30 the second time span 26 detected each detected pressure.

A time offset is preferred 34 between the end time 20 the first time span 12 and the beginning time 24 the second time span 26 significantly smaller than the duration of the time span 12 . 26 , In this way, first, a total duration of the process comprising the two test phases for detecting the leakage of the fuel cell system is kept low.

Preferably, a period is from the beginning of the start time 14 the first time span 12 until the end time 30 the second time span 26 around a minute.

Secondly, it is ensured that temperature and moisture conditions, in particular in the anode compartment and in the cathode compartment, are approximately constant from the beginning of the first test phase until the end of the second test phase. A cooling water temperature in the fuel cell stack is according to 1 represented by a curve V. This is in the in 1 shown pressure-time diagram 10 constant.

From the difference determined in the second test phase 32 will now be the difference determined in the first test phase 22 deducted. According to 1 be the difference runs 32 exemplarily to a value of 0.132 bar, the difference 22 however, to a value of exemplarily 0.134 bar. The difference of -0.002 bar comes with a check value 36 which was empirically and theoretically determined here exemplarily to 0.140 bar.

Below the test value 36 suggests that there is no significant transfer leakage between the anode compartment and the cathode compartment. This is due to the fact that the difference 32 writable drops in pressure in the anode compartment during the second period of time 26 almost equal to that by the difference 22 writable drop in pressure during the first period of time 12 is. However, during the second period of time 26 between the pressure in the anode compartment and the second reference pressure 28 set a strong pressure gradient in the cathode compartment. If there was a transfer leak, it would have been during the second period 26 an increased loss of anode gas from the anode compartment, so an increased drop in pressure, must be determined.

In an alternative embodiment of the method, instead of the time periods 12 . 26 a value or a range of values of a pressure in the anode space are determined, and the time necessary to reach the set value or range of the pressure is detected. A faster pressure drop during the second test phase, in which the second reference pressure 28 is set, would in this case when exceeding or falling below a specified test value 36 indicate the presence of a transfer leak.

2 shows the pressure-time diagram 10 according to 1 wherein the curves I-V characterize a test course, on the basis of which a presence of a transfer leakage between the anode compartment and the cathode compartment can be concluded.

In contrast to the time course of the curves I-V according to 1 is in 2 one at the end time 20 the first time span 12 determined difference 22 represented, which corresponds to a pressure drop of the pressure in the anode space of 0.29 bar. The first reference pressure 16 is according to 2 around 80% of the outlet pressure 18 in the anode room and is until the end time 20 The first test phase is largely constant.

At the end time 20 the first time span 12 will be under the reference pressure 16 dropped pressure in the anode chamber again increased to a value of about 1 bar above atmospheric pressure. The period required for this, ie the time offset 34 until the start time 24 the second time span 26 , is according to 2 less than 1 second.

At the beginning time 24 becomes the second reference pressure very quickly by reducing the mass flow of the cathode gas according to the curve IV and by opening the throttle valve in the discharge line of the cathode compartment 28 which sets about 8% of the outlet pressure set in the anode compartment 18 is. The after the second test phase, so the end time 30 the second time span 26 determined difference 32 results according to 2 to 0.44 bar.

By subtracting the value of the difference 32 from the value of the difference 22 value obtained of 0.15 bar is greater than the test value 36 of 0.140 bar. This suggests that in the second period 26 stronger pressure drop in the anode compartment has a transfer leakage between the anode compartment and the cathode compartment to the cause.

Of course, the in 1 and 2 through the second period of time 26 characterized test phase also before the time by the first time period 12 marked test phase are performed.

In addition to the use of the test value 36 In order to determine the presence of the transfer leakage, the data obtained during the procedure may be used to quantify the transfer leakage.

The The method for detecting leakage of the fuel cell system described above becomes in the present case carried out on the fuel cell system installed in the motor vehicle. This can be especially in the context of a motor vehicle service on especially simple way, especially during a start-up phase of the fuel cell system. Thus, it can be stated whether the fuel cell system, in particular the polymer electrolyte membrane fuel cell system (PEMFC), the motor vehicle due to a transfer leakage at the end has reached a lifetime.

through of the presently described method can thus be determined be whether an expansion of at least parts of the fuel cell system is justified for checking leaks.

One In this case, a transfer leak can be a service technician be displayed in a suitable manner. So can optimal Service intervals for performing the present be determined method described.

The method described here is much more reliable than methods in which, for example, a sensor for determining a hydrogen partial pressure in the exhaust gas of the fuel cell system or at another point of the anode branch is used.

The described method for detecting a leakage of the fuel cell system in particular during operation of the fuel cell system be carried out without an energy delivery of the Fuel cell system must be adjusted. Likewise, it is conceivable the method during shutdown of the fuel cell system perform.

10

Pressure-time diagram

12

first Period of time

14

Start time

16

first reference pressure

18

output pressure

20

end time

22

difference

24

Start time

26

second Period of time

28

second reference pressure

30

end time

32

difference

34

time offset

36

check value

I

curve (Pressure anode space)

II

curve (Reference pressure cathode compartment)

III

curve (Pressure high pressure valve)

IV

curve (Mass flow cathode gas)

V

curve (Cooling water temperature)

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• WO 2004/112179 A1 [0002, 0009]

Claims (14)

A method of detecting a leakage of a fuel cell system having an anode compartment comprising an anode compartment, wherein a pressure prevailing in the anode compartment is adjusted by operating at least one control element to adjust a mass flow of an anode gas to be fed to the anode compartment, and wherein the pressure is detected as a function of time, characterized in that in a cathode chamber of the fuel cell system by actuating at least one control element at least one reference pressure ( 16 . 28 ) set by the at least one reference pressure ( 16 . 28 ) is detected in the cathode space-dependent temporal course of the pressure in the anode chamber and in dependence on the time profile of the pressure in the anode branch optionally present leakage is detected. Method according to claim 1, characterized in that the at least one reference pressure ( 16 . 28 ) is set as at least one operating pressure in the cathode compartment. Method according to claim 1 or 2, characterized in that the at least one reference pressure ( 16 . 28 ) a first and a second reference pressure ( 16 . 28 ), wherein the first reference pressure ( 16 ) is less than or equal to an outlet pressure ( 18 ) is set in the anode space, and wherein the second reference pressure ( 28 ) smaller than the first reference pressure ( 16 ) is set. Method according to claim 3, characterized in that before a second setting of the second reference pressure ( 28 ) a control element is opened in a connecting the anode chamber with the cathode space connecting line. A method according to claim 3 or 4, characterized in that before setting the second reference pressure ( 28 ) the pressure prevailing in the anode chamber, in particular the outlet pressure ( 18 ), is increased. Method according to one of claims 3 to 5, characterized in that the first reference pressure ( 16 ) 65% to 100%, preferably 70% to 95%, more preferably 75% to 90% of the initial pressure ( 18 ) in the anode space, and wherein the second reference pressure ( 28 ) 3% to 35%, preferably 4% to 15%, more preferably 5% to 10% of the initial pressure ( 18 ) is. Method according to one of claims 1 to 6, characterized in that the pressure in the anode compartment at least until reaching an end time ( 20 . 30 ) a predetermined period of time ( 12 . 26 ) and / or at least until reaching a predetermined value of the pressure or a range of values of the pressure as a function of time is detected. Method according to claim 7 and one of claims 3 to 6, characterized in that the second reference pressure ( 28 ) or the first reference pressure ( 16 ) substantially immediately after reaching the end time ( 20 . 30 ) and / or immediately after reaching the predetermined value. Method according to claim 8, characterized in that a time offset ( 34 ) between setting two different reference pressures ( 16 . 28 ) less than or substantially equal to the predetermined period of time ( 12 . 26 ) and / or less than or substantially equal to a period of time to reach the predetermined value or value range. Method according to one of claims 7 to 9, characterized in that a difference ( 22 . 32 ) between at an initial time ( 14 . 24 ) and at the end time ( 20 . 30 ) of the predetermined period of time ( 12 . 26 ) and / or a time period for reaching the predetermined value or the value range is determined. Method according to claim 10, characterized in that a difference between two differences ( 22 . 32 ) and / or between two time periods with a test value ( 36 ), whereby exceeding or falling below the test value ( 36 ) describes a probability of transfer leakage between the anode compartment and the cathode compartment. Method according to one of claims 1 to 11, characterized in that the at least one reference pressure ( 16 . 28 ) is set during a start-up phase of the fuel cell system. Method according to one of claims 1 to 12, characterized in that the at least one reference pressure ( 16 . 28 ) is set in a, in particular in a motor vehicle, installed state of the fuel cell system. A fuel cell system comprising an anode compartment comprising an anode compartment, wherein a pressure prevailing in the anode compartment pressure is adjustable by actuating at least one control element for adjusting a mass flow of an anode gas can be supplied to the anode compartment, and the pressure as a function of time is detected, characterized in that in a cathode compartment of the fuel cell system by actuating at least one control element at least one reference pressure ( 16 . 28 ) is adjustable, which of the at least a reference pressure ( 16 . 28 ) in the cathode space-dependent time course of the pressure in the anode space can be detected and in dependence on the time profile of the pressure in the anode branch optionally present leakage is detected.