DE102014219806B4 - Method and device for testing the functionality of a current sensor and vehicle - Google Patents

Abstract

A method for testing a functionality of a current sensor (2), wherein the current sensor (2) detects a charging or discharging current (I) of a capacitive element, characterized in that at a first time a first state of charge of the capacitive element is determined, wherein a a further state of charge of the capacitive element is determined, wherein an estimated state of charge is determined at a further time as the sum of the first state of charge and an estimated state of charge change, wherein the estimated state of charge change in dependence on a time period between the first and the further time, a capacitance of the capacitive Element and the detected by the current sensor (2) charging or discharging current (I) is determined, wherein a difference between the further state of charge and the estimated state of charge is determined, the operability is detected if an amount of the difference is less than a vorbestimm ter or equal to a predetermined threshold.

Description

The invention relates to a method and a device for testing a functionality of a current sensor and a vehicle.

It is known to use batteries or accumulators, especially in vehicles as energy storage. In particular, batteries may serve as so-called traction batteries, which provide electrical energy for operating an electric machine, which serves to drive the vehicle. A charging or discharging current of such an energy store can be detected by means of a current sensor.

An improperly functioning or even faulty current sensor endangers the correct functioning of the vehicle drive. In particular in so-called hybrid and plug-in hybrid vehicles, a plausibility check of an output signal provided by the current sensor, which can represent a charging or discharging current, is therefore necessary. A plausibility check using redundant current sensors is known. In this case, for example, two current sensors can be provided, with sensor results of the first current sensor being made plausible by means of the second current sensor. This is for example in the DE 10 2011 122 440 A1 described. However, the document also describes a method for operating a current sensor and an improved battery, in which no second current sensor for plausibility of sensor results is required. For this purpose, the document proposes a current sensor comprising a sensor element and a signal processing arrangement. Furthermore, the current sensor comprises a test signal generator coupled to the signal processing arrangement for generating at least one test signal pattern and feeding it into the signal processing arrangement.

The DE 10 2012 205 401 A1 discloses an apparatus comprising a battery having a plurality of battery cells, and a sensor system for redundantly determining a battery current flowing across the poles of the battery, the sensor system comprising a current measuring means for detecting the battery current and providing a current reading. Furthermore, the sensor system comprises a voltage measuring means for separately detecting a time profile of the single-cell voltage of at least one battery cell and providing at least one time profile of a voltage measured value. Furthermore, the sensor system comprises an evaluation unit which is set up for determining the battery current from the at least one time profile of the voltage measurement value and for providing a corresponding current value and for comparing the current value with the current measured value.

The post-published DE 10 2014 216 931 A1 discloses a system for current sensor error detection that enables the detection of a current sensor error. To this end, a difference between a first change in the battery state of charge that is calculated by integrating battery current over time and a second change in the battery state of charge that is calculated based on the battery interlock voltage during the time is determined.

The technical problem arises of providing a method and a device for testing the functionality of a current sensor, which ensure a cost-effective and at the same time reliable plausibility check of the functionality. Furthermore, there is the technical problem of creating a vehicle with such a plausibility check.

The solution of the technical problem results from the objects with the features of claims 1, 11 and 12. Further advantageous embodiments of the invention will become apparent from the dependent claims.

A method for testing a functionality of a current sensor is proposed. The current sensor detects a charging or discharging current of a capacitive element, in particular a time profile of the charging or discharging current.

Here, a current sensor denotes a means for detecting a current, in particular a current intensity and / or a current direction, and for generating a corresponding output signal, which can also be referred to as a current value. The output signal can thus in particular represent a current intensity and a current direction.

The capacitive element may in particular be a battery cell or a battery, more particularly a traction battery of a vehicle. A battery may in this case comprise a plurality of battery cells. In this case, the current sensor can detect a current flowing through poles of the battery (cell).

According to the invention, a first state of charge of the capacitive element is determined at a first time. The state of charge can also be referred to as SOC (state of charge). Furthermore, at a further point in time, which in particular follows the first time in time, a further state of charge of the capacitive element is determined. The determination of the charge states to the first Time and at the further time can in this case take place in particular independently of the output signal of the current sensor, that is to say independently of a detected charging or discharging current. This can also be referred to as current sensor-independent determination of a state of charge.

Further, an estimated state of charge at a further time is determined as a sum of the first state of charge and an estimated state of charge change, the estimated state of charge change depending on a time duration between the first and the further time, a capacitance of the capacitive element, and the charge or discharge current detected by the current sensor , In particular the time course of the charging or discharging current between the first and the further time is determined.

bestimmt werden, wobei ΔSOC die geschätzte Ladezustandsänderung, C die Kapazität, I der erfasste Lade- oder Entladestrom und t die Zeit bezeichnet.In particular, the estimated state of charge change as $$\mathrm{\Delta }\text{SOC}=\text{1}/\text{C}\times \text{dl}/\text{dt}$$

where ΔSOC denotes the estimated state of charge change, C the capacitance, I the detected charge or discharge current, and t the time.

For this purpose, it may be necessary to also determine a capacitance of the capacitive element. For example, the capacity can be determined as a predetermined capacity, which is given for example by a manufacturer. Preferably, however, as explained in more detail below, the capacity can be repeated, in particular determined recursively, in each case the last determined capacity is used in the proposed method. For the repeated determination of the capacity, the person skilled in the art can use methods known to him for determining the capacity.

Further, a difference between the further state of charge and the estimated state of charge is determined, wherein the operability of the current sensor is detected if an amount of the difference is smaller than a predetermined threshold or equal to the predetermined threshold. In this case, a corresponding signal can be generated, which represents a given functionality.

If the magnitude of the difference is greater than the predetermined threshold, it is possible that the capacity has been erroneously determined and / or the current sensor is not functional to the desired extent. Thus, in this case can not be concluded directly on a non-existing functionality of the current sensor. However, if the amount is less than or equal to the predetermined threshold, it can be assumed that a functioning current sensor.

In this case, the method can be used in particular in a vehicle, in particular a hybrid vehicle or a plug-in hybrid vehicle or an electric vehicle, wherein the current sensor detects a charging or discharging current of the traction battery.

Overall, it results in an advantageous manner that no further additional current sensor is required to test a functionality of the current sensor and thus to plausibility of the output signal of the current sensor. This saves on the one hand costs and on the other hand space. Further advantageous results that the proposed method allows reliable testing of the functionality.

In a further embodiment, the first and the further state of charge are determined as a function of an open terminal voltage. In particular, the first and the further state of charge can be determined by a so-called OCV calibration (open circuit voltage calibration). This OCV calibration allows the state of charge to be determined as a function of the open terminal voltage.

OCV calibration may require that additional operating conditions be met. For example, it may be required that the capacitive element is no longer discharged by a discharge current or charged by a charging current for a predetermined period of time. The predetermined period of time may be e.g. depend on a temperature and / or a previous energy extraction or absorption (load history).

Overall, however, the determination of the state of charge as a function of the open terminal voltage results in an accurate and reliable determination of the state of charge. In this case, the open terminal voltage can be detected, for example, by at least one voltage sensor. A voltage sensor here denotes a means for detecting a voltage, in particular a voltage amplitude and / or voltage direction, and for providing a corresponding output signal, which may also be referred to as a voltage measurement value.

Alternatively, the first and the further state of charge are determined as a function of a current-voltage model of the capacitive element. The current-voltage model can hereby be a battery model, in particular a battery cell model. The current-voltage model allows a model-based determination of a state of charge as a function of a battery (cell) voltage, the battery (cell) voltage can be detected for example by a voltage sensor. Of course, in this case also a time course of the battery (cell) voltage can be taken into account. In particular, internal resistances of battery cells can be taken into account. These internal resistances may change, for example, depending on an age, a temperature, a state of charge, a charging or discharging current. These changes can also be taken into account by the current-voltage model.

However, this results in an advantageous manner that the determination of the state of charge is also possible regardless of any necessary conditions for the previously explained OCV calibration.

In a preferred embodiment, the predetermined threshold value is determined as a function of the time duration between the first and the further time. In particular, the predetermined threshold may increase with increasing length of time, e.g. proportional to the duration. In particular, to determine the threshold value, a constant output value can be multiplied by a time-dependent factor, wherein the time-dependent factor increases with increasing duration.

In this way it can be advantageously avoided that e.g. due to a permissible measured noise incorrectly detected current values that are not due to a lack of functionality of the current sensor and that are integrated over time, leading to the detection of a lack of functionality. As a result, the reliability of the proposed method is advantageously increased.

In a further embodiment, the method for checking is performed a plurality of times, wherein a lack of functionality is only detected if the amount of the difference is several times, in particular more than twice, more than three times or more than five times, greater than the predetermined threshold value. This also advantageously reduces an influence of random errors on the method for testing the functionality and increases the reliability of the method.

In a further embodiment, the predetermined threshold value and / or the first state of charge and / or the further state of charge and / or the estimated state of charge change are determined as a function of at least one further influencing factor, wherein the at least one influencing factor determines an accuracy of the determination of the first state of charge and / or the further state of charge and / or the estimated state of charge change.

For example, an influencing factor may represent an accuracy of the current sensor, the accuracy being e.g. may be dependent on a temperature and / or an age of the current sensor. Another influencing factor may e.g. represent an accuracy of a voltage sensor, wherein the accuracy of the voltage sensor e.g. may be dependent on a temperature, an amplitude of the detected voltage and / or an age of the voltage sensor. Another influencing factor can represent a battery (cell) temperature. This influencing factor can e.g. depending on a number of temperature sensors in the battery, an accuracy of a mathematical model for determining the battery (cell) temperature and / or a measurement accuracy of a temperature sensor for detecting the cell temperature can be determined. Another influencing factor may represent an accuracy of an OCV characteristic, the accuracy being e.g. may depend on a temperature, an age of the battery and / or hysteresis characteristics of the battery. Here, the OCV characteristic can specify a relationship between the open terminal voltage and a state of charge. Another influencing factor may represent a self-discharge rate of at least one battery cell, wherein the self-discharge rate may be, for example, dependent on a temperature and an age of the at least one battery cell. Another influencing factor may represent a charging efficiency of at least one battery cell, wherein the charging efficiency may be, for example, dependent on a temperature of the battery cell.

If all the cell chemical influencing factors are known as well as the accuracy of the sensors involved, then the accuracy of the determination of the first state of charge and / or the further state of charge and / or the estimated state of charge change can also be improved. Next advantageous results that usually a temperature of the battery (cell) and a voltage of a battery (cell) is usually detected by already existing sensors.

The determination of the predetermined threshold value and / or the first state of charge and / or the further state of charge and / or the estimated state of charge change as a function of an influencing factor can be carried out, for example, by deterministic or stochastic models which have a relationship between one of the aforementioned variables and the at least one Model influencing factor. Such models may be previously known.

In a further embodiment, the capacity is determined as a function of at least two charge states determined at different times, a period of time between the determined at different times and at least one detected by the current sensor charging or discharging current between the different times. The charge states determined at different times can again be determined independently of the current sensor, as explained above.

Thus, therefore, the capacitance, which in turn itself serves to determine the functionality of the current sensor, depending on current sensor independent determined states of charge and current sensor-dependent output signals representing the charge or discharge current can be determined.

For certain types of errors, in particular for the offset error explained in more detail below, the non-constant gain error and the freeze error, the properties of the errors cause different and non-convergent cell capacity values to be determined at different operating points, the cell capacity depending on the erroneously detected current is determined. This allows the detection of a sensor error for these types of errors.

There may be multiple types or types of errors for a current sensor failure. For the following explanation, reference is made to a sensor characteristic which represents a relationship between an actual, ie true, current value and a measured value measured by the current sensor. Here, e.g. on an abscissa of a coordinate system, the actual current value and on an ordinate of the measured value. The types of faults explained below can be explained with reference to an ideal characteristic of a fault-free current sensor, the ideal characteristic describing a course of measured values over a plurality of actual current values.

For example, the ideal characteristic can pass through an origin of the coordinate system explained above and have a true, in particular constant, slope. The slope here may represent a gain factor of the current sensor.

A first type of error can be a so-called offset error. In the case of an offset error, the above-explained characteristic curve does not run through the origin, whereby in the case of an actual current value of zero a non-zero measured value is generated.

A second type of error can be called a so-called freeze error. With this type of error, the measured value does not change for different true current values.

A third type of error may be referred to as a non-constant gain error. For a non-constant gain error, a difference between a gain of a faultless current sensor and a gain of a faulty current sensor may be different for different actual current values, that is, vary.

For example, if the ideal gain factor is constant, then in the case of a non-constant gain error, the gain factor of the faulty current sensor may be different for different actual current values. In other words, a relationship between the actual current value and the measured value may be described by a non-linear characteristic of the faulty current sensor. The slope of this characteristic may be different for different actual current values. Thus, therefore, no linear course of the characteristic is given more.

A fourth type of error can be referred to as a constant gain error. For a constant gain error, a difference between a gain factor of a faultless current sensor and a gain factor of a faulty current sensor may be equal but different than zero for different actual current values.

If a constant amplification factor is assumed for a fault-free current sensor, a constant amplification factor of the faulty current sensor, ie a linear relationship between the actual current value and the measured value, can likewise be assumed for this type of fault, but this amplification factor is too high or too low. Thus, the linear characteristic of the faulty current sensor may have an incorrect slope.

Of course, several types of errors may be present in a current sensor, for example, an offset error and a constant or non-constant gain error.

Depending on the capacity thus determined, e.g. a lack of functionality of the current sensor can be detected. For example, the capacity may be determined at least twice, but preferably more than twice, in a predetermined period of time.

By an offset error, for example, an amount of the difference between the further state of charge and the estimated state of charge will be greater than the predetermined amount. In this case, the capacity can be appropriately corrected by suitable methods for determining the cell capacity become. For different current readings and for different durations, however, different amounts of the previously explained difference will result because the offset on the one hand does not change its sign even with a change in current direction and on the other hand the amount of the difference depends on the value of the offset as well as the determination period. Thus, a symmetry breaking is given, which is reflected in the form of a sign as well as in a height of the difference. Because of these properties of the offset error, a capacity determined according to the invention will change for different measurements and a varying difference between the further charge state and the estimated state of charge will result. As a result, it can be detected that a current sensor error is present in the form of an offset error.

In the above-discussed freezing error, varying capacities as well as varying differences under different measuring conditions will result in the same way. Thus, such a freezing error can be detected.

Even with a non-constant gain error, varying capacities as well as varying differences between the other state of charge and the estimated state of charge will result. Thus, such a non-constant gain error can also be detected.

However, given a constant gain error, particularly a constant gain error without offset error, there will be no varying capacitance and hence no varying difference under different measurement conditions due to the lack of variation in the gain error. Thus, a constant gain error alone by the test is not reliable depending on the magnitude of the difference.

If the capacity in the predetermined time period changes by more than a predetermined amount, in particular for different values of charging or discharging current, this change may in principle be caused by a current sensor which does not function as desired and / or by an actual change in the capacity. However, by a suitable choice of the period, it can be ruled out with high probability that there is an actual change in the capacity, since this usually changes only very slowly. The predetermined period may be 24 hours or several weeks. Thus, in this case, a lack of functionality of the current sensor can be detected. Also in this case, a corresponding signal can be generated, which represents a lack of functionality.

However, it is possible that in the case of a constant gain error, no change in the capacitance is determined, whereby a functioning current sensor is erroneously detected. If, therefore, a change in the capacitance which is less than or equal to the predetermined amount is determined in the predetermined period of time, a current reference value can additionally be determined, the current sensor error, in particular a constant amplification error, depending on the at least a current reference value is detected.

As previously discussed, an inaccurate current sensor may result in an inaccurate determination of capacitance. In the subsequent determination of the functionality, therefore, both the inaccurate capacity and the inaccurate current measured value will influence the result of the test. However, it is possible, in particular by means of a plurality of measurements of the capacitance, to determine current sensor errors, in particular the constant and non-constant amplification errors explained above, in which case a more accurate capacitance determination is possible as a function of this particular current sensor error. For this purpose, as explained in more detail below, it may be necessary to determine a current reference value which is independent of current sensor errors, in particular free of current sensor errors.

However, the previously described determination of the capacity advantageously results in a simple determination of the capacity, which requires no further means, in particular no further sensors.

In a further embodiment, a sensor-related portion of the difference is differentiated from a capacity change-related portion of the difference.

A sensor-related portion of the difference may in this case denote a portion which is generated on the basis of current sensor errors. The capacity change-related proportion may denote a proportion based on a deviation of the capacity taken into account according to the method and the capacity actually present. The different components of the difference can be determined in particular as a function of differences determined at several points in time. The proportions can in turn be taken into account advantageously in the previously explained determination of the capacity and / or the determination of the estimated state of charge change.

The determination of the proportions enables a differentiation between a sensor error resulting in a difference greater than the predetermined one Threshold is, lead, and a capacity error, which can also lead to a difference that is greater than the predetermined threshold.

For example, so-called battery cell breaks can be detected, wherein battery cell breaks may signify a separation of at least one battery cell from the remaining entirety of battery cells. Furthermore, depending on the components determined in this way, a corresponding error signal can be generated, wherein the error signal can represent whether there is a current sensor error or a capacitance error. Such an error signal may be provided to a motor vehicle driver or maintenance personnel.

In a further embodiment, a plurality of differences between further charge states and estimated charge states are determined, in particular at different additional times. Furthermore, depending on the plurality of differences, a difference-independent first component and in each case a difference-dependent additional component are determined. In this case, difference-independent means that the first component in each of the specific differences is equal or approximately equal, that is, constant or approximately constant for the plurality of differences. Difference-dependent means here that the further proportion in each of the specific differences can be different. In this case, the difference-independent first component may correspond to the component caused by the capacitance change, and the respective further component may correspond to the current sensor-related component.

It can be assumed that the capacitance of the at least one capacitive element does not change at all or only to a small extent between different points in time that are not longer than a predetermined period of time, for example not more than 24 hours or a few weeks. Thus, it can also be assumed that the capacity change-related proportion of the difference does not change or changes only to a small extent.

This results in an advantageous manner as accurate as possible determination of the capacity change-related proportion and the respective current sensor-related proportion.

The distinction between a capacity change-related proportion and a current sensor-related proportion can be made on the basis of a non-linear and optionally cell-specific course of the OCV curve. While a capacitance change, regardless of an absolute magnitude of the state of charge and regardless of a magnitude of a previous state of charge change (SOC stroke), will equally affect the determined difference, inaccuracies of the current sensor will be a function of the state of charge and a profile of the charge - or discharge in different ways to the difference.

Alternatively, the capacity change-related proportion is determined as a function of a cell model. The cell model may in this case correspond to or comprise the previously explained current-voltage model of the capacitive element. In this case, a change in capacitance as a function of at least one predetermined influencing factor, for example a course of a charging and / or discharging current, a temperature profile, an aging, a state of charge or a state of charge change, can be modeled. A model-based determination of the capacity change-related proportion for a plurality of battery cells in a battery, in particular a traction battery, can also take place, wherein the change in capacitance is determined in such a way that the capacitance changes of the plurality of battery cells do not deviate from one another or no more than a predetermined amount. It can be assumed that the multiple battery cells are exposed to the same influences.

In another embodiment, a constant gain error or one of the constant gain error of different current sensor errors is determined or classified. These current sensor errors have been explained in detail earlier.

In the previously described determination of the capacitance as a function of measured values of the current sensor, constant amplification errors under different measurement conditions can result in the determination of the same capacitance value, but this capacitance value is subject to errors. A determination or classification of such a constant gain error will be explained in more detail below. Current sensor errors which differ from constant amplification errors lead, under different measuring conditions, to the determination of mutually different capacitance values which deviate from one another by more than one permissible value, in particular by a jump. Depending on this deviation, the detection of these current sensor errors takes place.

In a further embodiment, in particular if no one of a constant gain error of different gain errors is determined, at least one current reference value is determined, wherein a constant gain error is determined or classified in dependence on the at least one current reference value. In this case, the current reference value denotes an actual, ie true, current value, which may be different in particular from zero.

Depending on the true current value and the current value detected by the current sensor, the current sensor error, for example in the form of an error factor, can then be determined. This may be done, for example, when a difference or an amount of the difference between the true current value and the detected current value is greater than a predetermined threshold.

It can e.g. assume that in a no-load condition, that is, when no charge or discharge current is flowing, there is an actual current value of zero. Thus, an actual gain factor is determined from the current reference value in a load state and the no-load state. The constant gain error is then determined from the difference between an existing gain factor and this actual gain factor.

This advantageously results in a reliable determination of the constant gain error.

In dependence on the determined or classified current sensor errors, in particular a current measured value for the above-described determination of the capacitance can be corrected. If, for example, an error of the amplification factor as well as an error of the offset are known, then an inaccurate or erroneous measured current value can be corrected accordingly. Thus, i.a. allows a more accurate determination of capacity.

In a further embodiment, the difference between the further state of charge and the estimated state of charge is weighted as a function of basic conditions. Framework conditions may include, for example, an ambient temperature, a measurement accuracy of further sensors, e.g. a voltage sensor, in particular a cell voltage sensor, and be further framework conditions. A weighting can take place via a predetermined deterministic or stochastic weighting model.

Thus, advantageously, it results that e.g. at extremely high or extremely low ambient temperatures, a difference greater than the predetermined threshold does not automatically result in the detection of a fault condition.

Further proposed is a device for testing a functionality of a current sensor, wherein the current sensor detects a charging or discharging current of a capacitive element. The device comprises the current sensor and at least one evaluation device.

According to the invention, a first state of charge of the capacitive element can be determined by means of the evaluation device at a first time, whereby a further state of charge of the capacitive element can be determined at an additional time, wherein an estimated state of charge can be determined as the sum of the first state of charge and an estimated state of charge wherein the estimated state of charge change in dependence on a time duration between the first and the further time, a capacity and the detected by the current sensor charging or discharging current can be determined. Further, a difference between the further state of charge and the estimated state of charge can be determined, wherein the operability is detectable if an amount of the difference is less than a predetermined or equal to a predetermined threshold value. The proposed device advantageously makes it possible to carry out a method according to one of the previously described embodiments.

Further proposed is a vehicle comprising a device according to the previously described embodiment.

The invention will be explained in more detail with reference to an embodiment. The single FIGURE shows a schematic block diagram of a device according to the invention.

In 1 is a device 1 for testing a functionality of a current sensor 2 shown. The device 1 includes the current sensor 2 and an evaluation device 3 , which may be formed for example as a microcontroller. The evaluation device 3 is in this case data and / or signaling technology with the current sensor 2 connected, which is shown schematically by dashed lines. Also shown is a voltage sensor 4 , which also data and / or signal technology with the evaluation 3 can be connected. The voltage sensor 4 may also be part of the proposed device 1 be.

Also shown is a battery 5 , which may be in particular a traction battery of a vehicle, in particular a hybrid vehicle or plug-in hybrid vehicle. The battery 5 may in particular consist of several battery cells, which are electrically connected and provide a battery voltage. Also shown is a charging or discharging current I , where in 1 a discharge current is indicated by a direction of an arrow.

The voltage sensor 4 can be an open terminal voltage of the battery 5 to capture. The evaluation device 3 can be a state of charge of the battery depending on the open terminal voltage 5 determine. This can be done as part of a so-called OCV calibration.

By means of the evaluation device 3 can thus at a first time T1 a first state of charge of the capacitive element in response to the open terminal voltage at this first time T1 are determined. After this time, a further charging state can be determined as a function of the open terminal voltage at a further point in time T2.

wobei SOC(T2) den Ladezustand zum weiteren Zeitpunkt T2, SOC(T1) den Ladezustand zum ersten Zeitpunkt T1 und C eine Kapazität der Batterie 5 bezeichnet.Between the first and the further time T1, T2 becomes a temporal current course of the charging or discharging current I through the current sensor 2 detected. Next, the following difference is determined. $$\mathrm{\Delta }=\text{SOC}\left(\text{T2}\right)-\left(\text{SOC}\left(\text{T1}\right)+1/\text{C}\times {\displaystyle {\int }_{\text{T1}}{}^{\text{T2}}}\text{ldt}\right)$$

wherein SOC (T2) the state of charge at the further time T2, SOC (T1) the state of charge at the first time T1 and C is a capacity of the battery 5 designated.

ausgewertet, wobei k ein Skalierungsfaktor für die Differenz zwischen dem weiteren Zeitpunkt T2 und dem ersten Zeitpunkt T1 bezeichnet. Ist diese Bedingung erfüllt, so wird eine Funktionsfähigkeit des Stromsensors 2 detektiert.The following becomes the criterion $$\mathrm{\Delta }\le \text{thr}\times \left(\text{T2}-\text{T1}\right)\times \text{k}$$

where k denotes a scaling factor for the difference between the further time T2 and the first time T1. If this condition is met, then a functionality of the current sensor 2 detected.

If this condition is not fulfilled, then an error signal can be generated, wherein the error signal represents that there is a faulty capacity and / or a faulty current sensor. This has been explained previously.

bestimmt werden. Hierbei bezeichnet SOC(Tstart) ein Ladezustand zu einem Startzeitpunkt, der beispielsweise in Abhängigkeit einer offenen Klemmenspannung bestimmt werden kann, und SOC(Tend) ein Ladezustand zu einem Endzeitpunkt, der wiederum in Abhängigkeit einer offenen Klemmenspannung am Endzeitpunkt bestimmt werden kann. Startzeitpunkt Tstart und Endzeitpunkt Tend können hierbei von dem vorhergehend erläuterten ersten Zeitpunkt T1 bzw. weiteren Zeitpunkt T2 verschieden oder gleich diesen Zeitpunkten T1, T2 sein.The capacity can be used as $$\text{C}={\displaystyle {\int }_{\mathbf{T}\text{begin}}{}^{T\text{end}}}\text{l dt}/(\left|\text{SOC}\left(\text{Tstart}\right)-\text{SOC}\left(\text{tend}\right)\right|$$

be determined. Here, SOC (Tstart) denotes a state of charge at a start time, which can be determined, for example, as a function of an open terminal voltage, and SOC (Tend) a state of charge at an end time, which in turn can be determined in dependence on an open terminal voltage at the end time. Starting time Tstart and end time Tend can in this case of the previously explained first time T1 or further time T2 different or equal to these times T1 . T2 be.

LIST OF REFERENCE NUMBERS

1

contraption

2

current sensor

3

evaluation

4

voltage sensor

5

battery

I

Charging or discharging current

Claims (12)

A method for testing a functionality of a current sensor (2), wherein the current sensor (2) detects a charging or discharging current (I) of a capacitive element, characterized in that at a first time a first state of charge of the capacitive element is determined, wherein a a further state of charge of the capacitive element is determined, wherein an estimated state of charge is determined at a further time as the sum of the first state of charge and an estimated state of charge change, wherein the estimated state of charge change in dependence on a time period between the first and the further time, a capacitance of the capacitive Element and the detected by the current sensor (2) charging or discharging current (I) is determined, wherein a difference between the further state of charge and the estimated state of charge is determined, the operability is detected if an amount of the difference is smaller than a predetermined mter or equal to a predetermined threshold. Method according to Claim 1 , characterized in that the first and / or the further state of charge as a function of an open terminal voltage are determined and / or that the first and / or the further state of charge as a function of a current-voltage model of the capacitive element are determined. Method according to one of Claims 1 or 2 , characterized in that the predetermined threshold value is determined depending on the time duration between the first and the further time. Method according to one of Claims 1 to 3 , characterized in that the method for checking is performed several times, wherein a lack of functionality is detected only if the amount of the difference is several times greater than the predetermined threshold. Method according to one of Claims 1 to 4 characterized in that the predetermined threshold value and / or the first state of charge and / or or the further state of charge and / or the estimated state of charge change is determined as a function of at least one further influencing factor, wherein the at least one influencing factor influences an accuracy of the determination of the first state of charge and / or the further state of charge and / or the estimated state of charge change. Method according to one of Claims 1 to 5 , characterized in that the capacitance is determined as a function of at least two charge states determined at different times, a time duration between the different times and at least one charge or discharge current (I) detected by the current sensor (2) between the different times. Method according to one of Claims 1 to 6 , characterized in that a sensor-related portion of the difference is distinguished from a capacitance change-related portion of the difference, wherein a sensor error and a capacitance error is differentiated by the determination of the proportions. Method according to Claim 7 , characterized in that a plurality of differences between other states of charge and estimated states of charge are determined, depending on the plurality of differences, a difference-independent first portion and a respective difference-dependent further component is determined, the difference-independent first portion of the capacitance change-related share and the respective further shares the current sensor related Shares correspond or that the capacity change-related proportion is determined depending on a cell model. Method according to one of Claims 1 to 8th Characterized in that a constant gain error or different from the constant gain error current sensor error is determined, wherein a different by a constant gain error current sensor error is detected when different capacity values are determined under different measuring conditions from each other, which differ by more than a permissible level from each other, determining a constant gain error as a function of at least one current reference value, the at least one current reference value being determined, the current reference value designating an actual current value, an actual gain being determined from the current reference value in a load condition and a no load condition, the constant gain error being determined from the Difference between an existing gain factor and the actual gain factor is determined. Method according to one of Claims 1 to 9 , characterized in that the difference is weighted depending on conditions. Device for testing a functionality of a current sensor (2), wherein the current sensor (2) detects a charging or discharging current (I) of a capacitive element, wherein the device (1) comprises the current sensor (2) and at least one evaluation device (3), characterized in that by means of the evaluation device (3) at a first time a first state of charge of the capacitive element can be determined, at a further time another state of charge of the capacitive element can be determined, wherein an estimated state of charge at the further time as the sum of the first state of charge and an estimated state of charge change is determinable, wherein the estimated state of charge change in dependence on a time duration between the first and the further time, a capacity and of the current sensor (2) detected charge or discharge current (I) can be determined, wherein a difference between the other State of charge and estimated state of charge is determinable, wherein the operability is detectable if an amount of the difference is less than a predetermined or equal to a predetermined threshold value. Vehicle, comprising a device (1) according to Claim 11 ,

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