DE102017217523A1 - Method for providing a protective function in an energy storage device of a vehicle - Google Patents

Abstract

The invention relates to methods for providing a protective function in at least one cell (11) for an energy store (10) of a vehicle (1), wherein in an operating state, a power supply to the vehicle (1) through the cell (11) takes place and at a rest state In this case, it is provided that the following steps are carried out in the idle state: a) performing a monitoring by a monitoring device (20), in which repeatedly measured values are detected, which are each specific for a cell voltage at the cell (11) , b) performing at least one safety measure for deactivating the cell (11) if, based on a comparison of at least two of the detected measured values, an error condition is detected at the cell (11) to provide the protective function.

Description

The present invention relates to a method according to the closer defined in the preamble of the independent method claim.

State of the art

From the US 2016/0103188 It is known to identify a battery with an internal short circuit when the open circuit voltage of the battery drops after a prolonged charge.

From the DE 10 2015 200 406 A1 is a battery module with a plurality of interconnected electrochemical units known.

In electrically driven vehicles, it is conventionally possible to use accumulators which are based on lithium chemistry as electrical energy accumulators, since these have a very high energy density and low weight in comparison to nickel- or lead-based accumulators. Often these electrical energy storage are combined in a battery pack, which z. B. is realized by a series connection of single cells or as a combination of series and parallel connection of cells.

Disclosure of the invention

The invention relates to a method having the features of the independent method claim. Further features and details of the invention will become apparent from the respective dependent claims, the description and the drawings.

In this case, a method according to the invention serves to provide a protective function in at least one cell for an energy store of a vehicle. In such a protective function, it may, for. B. to act a safety shutdown of the cell to prevent a critical condition in the cell. Such a critical state can be caused, for example, by a short circuit of the cell. The energy storage device can have at least one cell (in particular a rechargeable battery cell), it also being possible to combine a plurality of cells in a battery pack in order to supply energy, for example, to an electrical system of the vehicle. Thus, an operating state may be provided in which a power supply of the vehicle, for. As the electrical system with electrical loads, done by the cell or the cells of the energy storage. The counterpart to this forms a rest state in which this power supply is suppressed, and the cell is in particular at idle. The battery cells may be lithium-chemistry based battery cells having a high electrical energy density.

1. a) Durchführen einer Überwachung durch eine Überwachungsvorrichtung, bei welcher wiederholt (d. h. insbesondere zyklisch) Messwerte, insbesondere Spannungsmesswerte erfasst werden, welche jeweils für eine Zellspannung bei der Zelle, vorzugsweise für eine Leerlaufspannung der Zelle, spezifisch sind, also in anderen Worten jeweils Spannungsmesswerte sein können,
2. b) Durchführen wenigstens einer Sicherheitsmaßnahme zur Deaktivierung der Zelle, wenn anhand eines Vergleichs von wenigstens zwei der erfassten Messwerte ein Fehlerzustand bei der Zelle detektiert wird, um die Schutzfunktion bereitzustellen, wobei vorzugsweise auch der Vergleich und/oder die Sicherheitsmaßnahme durch die Überwachungsvorrichtung durchgeführt werden.

In the context of the invention it can be provided that the subsequent steps in the idle state - and preferably only outside the operating state - are performed:

1. a) performing a monitoring by a monitoring device, in which repeatedly (ie in particular cyclically) measured values, in particular voltage measured values are detected, which are each specific for a cell voltage at the cell, preferably for an open circuit voltage of the cell, in other words be voltage measured values can,
2. b) carrying out at least one safety measure for deactivating the cell if, based on a comparison of at least two of the acquired measured values, an error condition is detected at the cell to provide the protective function, preferably also the comparison and / or the safety measure being performed by the monitoring device.

Thus, an advantage is achieved in that a technical complexity in the detection of a fault state, such as a cell-internal Kurzschluss, can be reduced. Because traditionally, a high computational effort and a correspondingly powerful electronics are necessary to ensure early detection z. B. based on a cell voltage curve to perform. Accordingly, according to a further advantage of the invention, an execution of the steps of a method according to the invention by a central battery electronics (BCU), in particular a battery management system (BMS), are dispensed with. Therefore, it is also possible for monitoring according to step a) and / or a security measure according to step b) to take place if the BCU is not supplied (eg by the electrical system of the vehicle) and / or the BCU is switched off. In other words, the monitoring can be performed independently of a power supply of the BCU, z. B. in a parking phase of the vehicle with minimal energy consumption. For example. Under the deactivation of the cell is understood as the transfer of the cell into a safe state, for. B. by isolating and / or controlled unloading or the like.

It can be provided that the fault condition is a short-circuit in the energy store, preferably a cell-internal short circuit. The security measure can be a control of a safety switch, z. As an electrical or electrochemical switch include. The safety switch is, for example, designed as an irreversible safety switch, so it can thus only once (to interrupt or to produce a circuit) are switched. For example. the safety switch is designed as a power semiconductor switch or as a relay or as a fast-discharge element or as an antifuse element. In particular, the safety switch is integrated into a current path with the cell, e.g. B. connected in series or parallel to the cell.

For example. the energy store comprises at least one cell (in particular battery cell), wherein preferably a plurality of cells are arranged electrically in a series circuit or as a combination of a series and parallel connection. Advantageously, the energy store is designed as a rechargeable battery (rechargeable battery), preferably a battery pack. In addition, the energy storage device can be designed as a traction battery of the vehicle, and preferably serve to supply power to an electrical system of the vehicle, more preferably both a 12 V (volt) electrical system or a 48 V electrical system and a high-voltage network greater than 60V. According to a further advantage, the energy store is designed as a (rechargeable) battery, with a system voltage above 40 V or above 60 V. For example, as a traction battery with 360 V or <770 V nominal voltage.

For traction batteries (eg with a system voltage greater than 60 V) and / or 48 V BRS batteries (BRS = boost recuperation system), the battery can be disconnected when not in use of the vehicle from the respective electrical system of the vehicle, and z. B. parts of the battery electronics are turned off. Alternatively or additionally, if necessary, the parts of the battery electronics, which are supplied directly from the battery cells, can be switched to an energy-saving mode. By disconnecting from the high-voltage or 48 V electrical system can be ensured that no energy from the battery can flow into the vehicle, d. H. In this state, no flow of current through the cells can occur.

According to a further advantage, the vehicle is designed as a motor vehicle and / or passenger vehicle and / or truck and / or electric vehicle and / or hybrid vehicle.

In addition, it may be advantageous in the context of the invention that, according to step b), the error state is detected by detecting a voltage loss in the cell based on the measured values, preferably a respective currently measured value having a (for example cyclically determined or measured value) tracked or predefined and / or pre-stored) detection threshold is compared. Such a comparison is thus also understood as the comparison of at least two of the measured values recorded in the sense of step b). Thus, a voltage loss can be detected in the cell, which goes beyond the normal self-discharge of the cell to detect the fault condition. Since no current can flow through the cell in this state in the quiescent state, the error state, eg. As an internal short circuit of the cell can be detected.

It is also possible for the detection according to step b) to analyze a temporal course of the measured values, the analysis being carried out on the basis of at least one difference of at least two measured values. For example. In this case, the error state can be detected positively if a difference of two measured values (eg the current and the previous measured value) is greater than 30 mV. This allows a particularly simple solution for monitoring a cell voltage.

Optionally, it is provided that the measured values are recorded at a time interval of 100 ms to 500 ms (in particular according to a first rate). In other words, a time interval can be selected for the acquisition of the measured values, which is very large in comparison to an optional voltage measurement in the operating state (eg at least 2 to 100 times greater). As a result, the measured value acquisition can take place with very little expenditure of energy, as a result of which continuous monitoring without significant increase in the self-discharge of the battery is possible even in the quiescent state.

Furthermore, it is advantageous if, after each acquisition according to step a), an (for example arithmetic) averaging of acquired measured values is carried out, so that in each case an average value is determined, and in step b) a respective currently measured value is determined with the respectively currently determined Mean value is compared to detect the error condition. Such a comparison is thus also understood as the comparison of at least two of the measured values recorded in the sense of step b). It can be an advantage if, after each repeated, in particular cyclical, detection according to step a), the averaging is carried out by a specific number of measured values, eg. From 2 to 5 readings to determine the current average. Subsequently, in step b), the respective measured value (previously detected in step a)) can be compared with the respective currently (previously) determined mean value, for example the difference between the measured value and the mean value can be formed. As a result, the robustness of the method according to the invention can be increased and accordingly a false triggering of the safety device can be avoided.

In a further option, it may be provided that, after step a), a detection threshold is determined on the basis of an averaging of acquired measured values, and preferably, in step b), a currently detected measured value is compared with the detection threshold. Alternatively or additionally, it may be possible for a result of the comparison in accordance with step b) to be averaged over several detection cycles, for example over two to five measured values or cycles, and only then the error state is detected positive if this averaged result is a detection criterion Fulfills. The detection criterion (eg for the detection of a short circuit) is met, for example, if the average result is less than (or equal to) the mean value and / or less than the detection threshold (thus as the triggering threshold).

It may also be possible for the detection criterion to be fulfilled if at least one current measured value (or also the current last measured values) is smaller than the mean value of the preceding measured values minus a fixed value for a detection threshold. For example, the previous reading may be 3.89V, and the fixed value for the detection threshold may be 0.3V, so that a reading that results in detection is 3.58V.

In addition, it is advantageous if, within the scope of the invention, the detection according to step a) is carried out at a first (temporal) rate, in particular only if in the comparison according to step b) the currently detected measured value is greater than the detection threshold, and possibly the detection according to step a) is carried out at a second rate greater than the first rate, in particular only if in the comparison according to step b) the currently detected measured value is less than or equal to the detection threshold. In particular, the detection threshold can not be a fixed value, but z. B. the average of the previous measured values minus a fixed value for the detection threshold. Thus, a further advantage can be achieved, since after a detected falling below the detection threshold (ie the triggering event), the sampling rate of the cell voltage measurement is increased, and so a sufficiently fast detection and sufficient robustness against false triggering can be ensured. In particular, only the error state can be positively detected and / or the safety measure can be carried out, for. For example, the safety device may be activated if the fault condition is confirmed upon detection at the second (higher) rate. This is the case, for example, when the measured values over several cycles, ie for example at least 4 or at least 6 measured values, are always below the detection threshold (ie in each case less than or equal to the detection threshold) during the cyclic detection with the second rate. This enables a so-called debouncing of the triggering event.

It is further advantageous if steps a) and b) are carried out by the monitoring device, which, for this purpose, is designed as electronics associated with the cell (cell-associated electronics) independently of a battery management system. The term "cell-associated" advantageously refers to the fact that the electronics (ie the monitoring device) is arranged on the cell and / or attached to the cell and / or is electrically integrated into a circuit with the cell and / or, preferably completely and / or exclusively powered by the cell. For example. For example, the monitor is designed as an application specific integrated circuit (ASIC) mounted on the cell. With multiple cells of the energy storage device, a monitoring device may be mounted on each of the cells, and includes e.g. B. an analog-to-digital converter (ADC) for cell voltage detection and possibly other logic elements, eg. B. to activate a safety device of the cell. According to a further advantage, the monitoring device can therefore also be designed as a control device. For example. For example, the power supply to the monitoring device is completely established by the cell voltage, so that the monitoring device can operate autonomously (i.e., independently of the BMS) to measure the cell voltage.

Furthermore, it can be provided in the context of the invention that the steps a) and b) are carried out in the idle state, in which the cell is connected to other cells, and also be carried out in a transport state of the cell, in which the cell is electrically further Cells is electrically isolated, preferably in idle state as well as in the transport state, the cell is switched to idle (and / or load-free). Switched unloaded here refers to the fact that an electrical switch, z. As a contactor or semiconductor switch or the like, for connection to a load of the vehicle (eg., A vehicle electrical system with electrical consumers) is open, so possibly the cell is transferred to an idle. In the idle state, the cell can always be switched load-free, it being possible to switch over to the operating state only from the idle state (and not in the transport state). In the operating state, the electrical switch can be closed accordingly to enable the power supply of the load. In particular, it is an advantage here if the monitoring device carries out the monitoring according to step a) and / or performs the detection according to step b) and / or the execution of the Safety measure according to step b) can initiate, since then the steps can be performed independently of a battery management system and thus in the transport state. For example. If the cell is not connected to other cells in the transport state, it is thus not in a battery pack (unlike, if applicable, in the idle state and operating state). In a further possibility, it can be provided that steps a) and b) are carried out continuously in the idle state and in the transport state. In this way, reliable protection can be provided by permanent monitoring, with steps a) and / or b) being suspended exclusively in the operating state if the protective function is provided by the BMS instead.

For example. Both the monitoring according to step a) and the detection according to step b) can be carried out continuously and cyclically in the idle state and / or in the transport state, eg. B. can be performed after step a) always step b). This allows for permanent monitoring and thus an increase in security.

It may also be possible that upon positive detection of the fault condition, ie when a voltage dip greater than the detection threshold is detected and / or confirmed, a safety device of the affected cell is activated to prevent a critical local overheating within the cell.

According to a further advantage, it may be provided in the method according to the invention that the monitoring and / or detection in step a) or in step b) is deactivated (eg paused) before the energy store is connected to a vehicle network (vehicle electrical system). This is necessary because the detection threshold for detection of internal short circuits is significantly lower than the voltage changes that are caused by the use of the energy storage by a discharge current. As a further advantage, in this case a communication of the monitoring device with the central battery electronics can be carried out, in which commands for switching off and activating the cell-near monitoring (eg the detection and / or detection according to step a) or b)) are used. In particular, the BCU can be the command generator here. If, for example, the need of the vehicle for high-voltage supply is then detected, the near-cell monitoring of internal short-circuits can first be deactivated and, if appropriate, then the detection of cell-internal short circuits can be carried out by software of the BCU. It can be provided that only then is the energy store connected to the vehicle electrical system, that is to say connected to a load (for example the vehicle electrical system with a consumer).

Furthermore, it may be possible that after an end of the battery use (of the driving cycle) with separate from the vehicle electrical system energy storage, the detection of internal shorts by software in the BCU remains active until relaxation and cooling processes are largely completed. If no significant voltage change is to be expected here for a faultless cell, the detection function (ie the detection) in the cell-near electronics (monitoring device) can be activated and the central electronics (the BCU) can be switched off.

Optionally, it is possible for the monitoring device to be deactivated for near-cell monitoring when a resistive cell balancing is activated, since the switching on of the balancing resistor can lead to a collapse in the cell voltage measurement value. Furthermore, it may optionally be possible for the entire duration of the resistive balancing (ie a so-called resistive cell compensation) to switch the detection of internal short circuits implemented near the cell by the monitoring device to a second (eg lower) detection threshold, which in particular also major changes z. B. the cell voltage tolerated. Alternatively or additionally, it may be possible that an implementation of steps a) and / or b) is prevented in the operating state, and in particular the implementation before connecting the cell for powering the vehicle, preferably by a battery management system, preferably by deactivating the monitoring device and / or switching the detection threshold is disabled.

Furthermore, it is optionally provided that the monitoring device and / or a near-cell implemented detection of internal short-circuits (ie the monitoring according to step a) and / or detection according to step b)) is implemented on a module electronics. In this case too, a different detection threshold can be used if necessary. The present invention is also directed to a monitoring device in which the method according to the invention is stored in a memory of the monitoring device, wherein the monitoring device is used in particular for carrying out the method according to the invention. The invention also comprises at least one energy store, in particular in the form of at least one battery cell and / or a battery pack based on lithium chemistry with the monitoring device according to the invention.

• 1 einen Verlauf erfasster Messwerte zur Visualisierung eines erfindungsgemäßen Verfahrens,
• 2 einen Verlauf erfasster Messwerte zur Visualisierung eines erfindungsgemäßen Verfahrens,
• 3 ein Fahrzeug mit einem Energiespeicher.

Further advantages, features and details of the invention will become apparent from the in the following description, in which embodiments of the invention are described in detail with reference to the drawings. The features mentioned in the claims and in the description may each be essential to the invention individually or in any desired combination. Each show schematically:

• 1 a course of detected measured values for visualizing a method according to the invention,
• 2 a course of detected measured values for visualizing a method according to the invention,
• 3 a vehicle with an energy storage.

1 schematically shows the visualization of a method according to the invention 100 a possible temporal cell voltage course in the event of a cell-internal short circuit. Advantageously, a detection of the measured values 110 according to step a) of a method according to the invention 100 performed and after each acquisition a tracked detection threshold 120 calculated. The detection threshold can be 120 as the average of the last 5 readings 110 according to the currently measured value 110 be calculated. The recorded measured values 110 Here are examples of improved visualization of the inventive idea of an actual voltage 130 compared.

It is a cell voltage determination at a first rate and correspondingly lower measurement frequency by an arrow 150 characterized. When an event occurs 154 , which is specific to an error case (eg, an internal short circuit), affects the event 154 on the cell voltage 130 out. It comes to the voltage drop of the cell voltage 130 what by correspondingly lower and decreasing readings 110 is marked. When falling below the measured value for the first time 110 below the detection threshold 120 there is a switch to a cell voltage determination at a second rate (debouncing the event 154 with high measuring frequency). The switchover is indicated by an arrow 153 and the cell voltage determination at the second rate by another arrow 151 , As in the example according to 1 the error is confirmed (ie also the other measured values 110 are below the detection threshold 120 ), then a safety measure is triggered (represented by an arrow 152 ). This requires, for example, a confirmation of 4 to 6 measured values 110 take place so that at the 6th measured value, in succession below the detection threshold 120 the security measure is initiated. To carry out the security measure, for example, a security device 30 controlled, z. B. a safety switch is opened or closed to interrupt a circuit or close. This causes z. As the separation of the cell from the electrical system and / or a transfer of the cell in a secure state (eg, by a controlled discharge of the cell). In 1 this is due to another faster drop in cell voltage 130 characterized.

In 2 is shown a course of the measured values, where a measured value 110 by an extraordinary disturbance the detection threshold 120 falls short without a cell-internal short circuit, so an event 154 , is present. Since the first step is not directly triggered the safety measure, but instead first the rate of cell voltage detection (ie the detection of the measured values 110 ), this disturbance can be recognized as such relatively quickly. It is then returned to the cell voltage determination according to the first rate (arrow 150 ).

3 shows an example of a vehicle 1 with an energy storage 10 , The energy storage 10 includes in particular several cells 11 which each have a monitoring device 20 and a security device 30 can be assigned. It is still a battery management system 3 shown separately from the monitoring devices 20 can be trained.

The above explanation of the embodiments describes the present invention solely by way of example. Of course, individual features of the embodiments, if technically feasible, can be combined freely with one another, without departing from the scope of the present invention.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 2016/0103188 [0002]
• DE 102015200406 A1 [0003]

Claims (11)

Method (100) for providing a protective function in at least one cell (11) for an energy store (10) of a vehicle (1), wherein, in an operating state, a power supply to the vehicle (1) takes place through the cell (11) and in an idle state this power supply is inhibited, characterized in that the following steps are carried out in the idle state: a) carrying out a monitoring by a monitoring device (20), in which repeatedly measured values (110) are detected which are in each case for a cell voltage at the cell (11) b) carrying out at least one safety measure for deactivating the cell (11) if, based on a comparison of at least two of the acquired measured values (110), an error condition is detected at the cell (11) to provide the protective function. Method (100) according to Claim 1 , characterized in that according to step b) the error state is detected by detecting a voltage loss in the cell (11) on the basis of the measured values (110), for which a respective currently measured value (110) is compared with a detection threshold (120) becomes. Method (100) according to Claim 1 or 2 characterized in that for the detection according to step b) a temporal course of the measured values (110) is analyzed, the analysis being carried out on the basis of at least one difference of at least two measured values (110). Method (100) according to one of the preceding claims, characterized in that the measured values (110) are recorded at a time interval of 100 ms to 500 ms. Method (100) according to any one of the preceding claims, characterized in that an averaging of detected measured values (110) is carried out after each acquisition according to step a), so that in each case an average value is determined, and at step b) a respective currently detected measured value is compared with the currently determined average value to detect the error state. Method (100) according to one of the preceding claims, characterized in that, temporally after step a), a detection threshold (120) is determined on the basis of an averaging of measured values (110), and in step b) a currently detected measured value (110) is determined Detection threshold (120) is compared. Method (100) according to Claim 6 , characterized in that the detection according to step a) is performed at a first rate, when in the comparison according to step b) the currently detected measured value (110) is greater than the detection threshold (120), and the detection according to step a) a second rate greater than the first rate is performed when in the comparison according to step b) the currently detected measured value (110) is less than or equal to the detection threshold (120). Method (100) according to one of the preceding claims, characterized in that the steps a) and b) are carried out by the monitoring device (20), which is configured as an electronics associated with the cell (11) independently of a battery management system (3) , Method (100) according to one of the preceding claims, characterized in that steps a) and b) are carried out in the idle state, in which the cell (11) is connected to further cells (11) and also in a transport state of the cell ( 11) are performed, in which the cell (11) is electrically isolated from other cells (11), wherein preferably in both the idle state and in the transport state, the cell (11) is switched without load. Method (100) according to Claim 9 , characterized in that the steps a) and b) are carried out continuously in the idle state and in the transport state. Method (100) according to any one of the preceding claims, characterized in that an implementation of steps a) and / or b) is prevented in the operating state, and in particular the implementation before connecting the cell (11) to the power supply of the vehicle (1), preferably by a battery management system (3) is deactivated.

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