Method and system for operating an energy storage device comprising multiple battery cells - Patents.com

Abstract

The present invention relates to a method for operating an energy storage device (20) comprising a plurality of battery cells (22a-22e, 24a-24e), particularly in a vehicle (300), comprising obtaining a plurality of measurements of terminal voltages of at least one of the battery cells (22a-22e, 24a-24e), filtering the obtained measurements to generate filtered measurements, the filtering of the measurements including a comparison operation, and using the filtered measurements to generate and output output data. The invention further relates to a system (10) for operating an energy storage device (20) comprising a plurality of battery cells (22a, 22b, 22c, 22d, 22e, 24a, 24b, 24c, 24d, 24e), in particular in a vehicle, comprising an acquisition module configured to acquire a plurality of measurements of terminal voltages of at least one battery cell (22a, 22b, 22c, 22d, 22e, 24a, 24b, 24c, 24d, 24e), an evaluation module configured to perform filtering using the acquired measurements and generate a filtered measurement result, the filtering of the measurements comprising a comparison operation, and an output module configured to generate and output an output value using the filtered measurement result.

Description

[Technical field]

[0001] The present invention relates to a method for operating an energy storage device comprising a plurality of battery cells, in particular in a vehicle, and further to a system for operating an energy storage device comprising a plurality of battery cells, in particular in a vehicle. [Background technology]

[0002] The main battery of a vehicle generally consists of several individual battery cells connected in series with each other, for example to achieve the required high voltage. In particular, battery modules with a certain number of battery cells are provided, which are then connected to generate the overall main battery. To monitor the battery, a distributed topology of a battery management system (BMS) is usually provided. A central control unit is provided which is connected via a data connection, in particular via a data bus, to a number of integrated cell monitoring units. In this way, for example cell voltages and temperatures are measured and monitored for the individual battery cells. The cell monitoring units are in particular integrated with the battery modules in an integrated design.

[0003] The integrated cell monitoring units are usually suitable to perform basic data processing, so that every single measurement value does not have to be transmitted to the central controller. This reduces the required bandwidth and the required computing power of the central controller. The effective sampling rate can also be improved in this way.

[0004] The state of charge (SoC) of a battery is a measure of the energy stored in it. Therefore, in the case of a vehicle's main battery, it is also an indicator of the vehicle's remaining range. The available energy in a car battery is the sum of the energies of the individual cells.

[0005] Furthermore, a battery's "state of health" (SoH) may be defined as a measure of its overall condition. In general, the SoH decreases as the battery ages, depending on, among other things, the type of load, the discharge and charge behavior, and environmental influences.

[0006] As the main battery represents a significant part of the overall price of the vehicle, the state of charge is a parameter that not only governs the reliability of range indicators but also enables optimal utilisation of this precious resource. It is therefore of great importance to users that the state of charge is determined as reliably and accurately as possible.

[0007] However, the state of charge cannot be measured directly, but rather needs to be estimated based on the available parameters of the battery and the ambient conditions. An essential parameter that consistently and reliably indicates the state of charge is the terminal voltage of the battery cell while said battery cell is not operating under load (stable cell terminal voltage at no load). However, this value can only be estimated during vehicle operation, since the measurable terminal voltage constantly changes based on the dynamic load being utilized. In particular, the terminal voltage may drop during each short-term peak demand and also rise while the battery is being charged.

[0008] Known solutions for estimating the state of charge include, for example, the use of functions in which an analog-to-digital conversion is performed. Furthermore, an opportunity for averaging over a large number of values ​​may be provided, for example by means of an IIR (Infinite Impulse Response) filter or an FIR (Finite Impulse Response) filter. The filtered measurements are influenced by the individual measurements, including those of cells operating under load. As mentioned above, this leads to a decrease in the accuracy of the state of charge estimation.

[0009] The terminal voltage of a battery cell operating under load will result in a shift in the average measurement output by the central control unit, which will result in an inaccurate indication of the state of charge and therefore of the remaining driving range of the vehicle.

[0010] DE102015114652A1 discloses a method for estimating the energy capacity of a battery system of a vehicle. This involves determining a voltage offset and an estimated total stack energy of the battery system. Using these values, the energy capacity of the battery system is estimated.

[0011] WO2019 / 025171A1 describes a method for estimating a cell voltage, a state of charge, and a battery state in combination with a load, which includes measuring a first current and a first voltage, and estimating a cell idle voltage of the battery. An energy level of the battery is estimated based on the voltage, the current, and a cost optimization process.

[0012] EP2306214A3 proposes a method for determining the DC impedance of a battery. Summary of the Invention [Problem to be solved by the invention]

[0013] The object of the invention is to provide a method and a system for operating an energy storage device comprising several battery cells, in particular in a vehicle, which makes it possible to determine the state of charge of the battery as accurately, quickly and in a resource-saving manner as possible. [Means for solving the problem]

[0014] This object is achieved by a method and a system according to the independent claims. Advantageous configurations and developments of the invention are set out in the dependent claims.

[0015] A method for operating an energy storage device, particularly in a vehicle, having a plurality of battery cells includes obtaining a plurality of measurements of terminal voltages of at least one of the battery cells, performing filtering using the obtained measurements to generate filtered measurements, filtering the measurements including a comparison operation, and generating and outputting output data using the filtered measurements.

[0016] In particular, the output data may include at least one of the obtained measurements.

[0017] This advantageously makes it possible to output particularly suitable measured values, for example to enable a consistently accurate estimation of the state of charge even under varying operating conditions.

[0018] The central control unit can then calculate the state of charge with improved accuracy and thereby reliably determine the remaining range of the vehicle, which leads to reduced costs as a result of better utilisation of the vehicle's main battery and a better impression on the user as a result of greater reliability of the indicated remaining range or operating time.

[0019] In particular, the method may be performed at the level of an integrated cell monitoring unit that obtains battery cell measurements of a subset of the battery cells of the energy storage device and monitors these battery cells, such that the electronics of this integrated cell monitoring unit may be configured to suit only the total voltage of the battery cells so monitored, and not the total voltage of all of the battery cells of the energy storage device.

[0020] The output data may then be transmitted to a higher-level central controller for further evaluation there, or the central controller may use the received output data to generate control signals for controlling the battery cells or a subset thereof.

[0021] The basic idea of ​​the invention consists in handling the measurement values ​​by a filtering process which includes a comparison operation, so that unsuitable measurement values ​​can be very easily identified and filtered out. Unsuitable measurement values ​​then do not contribute to the output and transmitted data capacity, so that the available bandwidth of the data connection between, for example, the integrated cell monitoring unit and the central control unit is saved. Further processing and / or evaluation of the data can also be performed more efficiently with less computational power. Filtering includes comparing the measurement values ​​with each other and / or with another value, for example a threshold value or a limit of a range of values.

[0022] To reproduce the physical behavior of a battery cell in a theoretical model, the battery cell is generally assumed to have at least one internal impedance, especially a non-reactive component. The terminal voltage varies based on the voltage drop across the cell's internal impedance.

[0023] Therefore, the internal impedance must be included in the calculation of the state of charge, but this parameter cannot be measured directly either. When estimating the value of the internal impedance, a difficulty arises in that this value is influenced by various factors such as the temperature and age of the cell, as well as by the state of charge itself. Therefore, a state of charge estimation method should be chosen in which the influence of the internal impedance value is reduced as much as possible.

[0024] The relevant terminal voltage of the battery cell then most likely corresponds to the state of charge when the cell is operating at minimum load and therefore in this case the state of charge can be determined with the best accuracy. The non-reactive component of the internal impedance reacts particularly quickly to changes in load.

[0025] That is, the assessment of the state of charge of a battery cell requires that the voltage values ​​obtained are taken as far as possible without load.

[0026] Measurements of the terminal voltages are taken in a manner known per se. Measurements may be taken for each single battery cell, or in other embodiments, this may be done simultaneously for a defined set of battery cells, for example a set of battery cells connected in series.

[0027] A measurement of the temperature of at least one battery cell may also be obtained, for example at the same time that the terminal voltage is obtained.

[0028] In one embodiment of this method, a number of measurements are taken as a time series.

[0029] By way of example, the measurements are taken successively in time, for example with a predefined acquisition frequency. In particular, the measurements can be performed at regular time intervals from one another.

[0030] The measured values ​​are in particular taken over a predefined period, which can furthermore be configurable. For example, the measured values ​​can be stored in a memory. In order to always evaluate a predefined number of the most recently taken measured values, or the most recently taken measured values ​​within a predefined period, the most recent measured values ​​can furthermore repeatedly replace the oldest measured value of the plurality of measured values, for example in a ring memory.

[0031] The filtering and generation of output data may occur at predefined times, for example at regular intervals with a frequency that may be predefined and configurable, or upon receipt of a request signal.

[0032] In another embodiment, the comparison operation includes determining a maximum or minimum measurement value among a plurality of measurements, i.e. the comparison operation includes measurements being compared to one another, particularly measurements taken within a particular time period.

[0033] In particular, the output data includes the maximum and / or minimum values ​​of the measurements taken.

[0034] In another embodiment, a predefined, possibly configurable, number of maximum or minimum measured values ​​can be determined. Such a set of maximum or minimum measured values ​​can also be used to determine an average value.

[0035] In another embodiment, the median of the measurements or a particular subset thereof is determined, i.e. the median is determined using a comparison of the measurements with each other, the median being in each case greater or less than each half of the measurements, the value thus obtained being less susceptible to short-term dispersion than the arithmetic mean.

[0036] The filtering process may further include a smoothing operation over the total amount of measurements taken, for example calculating a moving average.

[0037] In one development, the comparison operation comprises comparing the measured value with at least one limit value, where a lower limit value and / or an upper limit value can be provided, the comparison with both the lower limit value and the upper limit value determining whether the measured value is within a particular range.

[0038] A fixed limit value may in this case be predefined, for example by a system setting.

[0039] Dynamic limits may also be predefined, for example to determine a measurement value below or above the average of the sum of the measurements being filtered. Furthermore, other dynamically determined limits may be provided, which may for example be determined based on the measurements or are predefined by settings.

[0040] In one embodiment, an operating condition is detected and measurements are taken based on the operating condition, and the detected operating condition is used as a basis for triggering a control signal to reset the taken measurements, the control signal being generated such that measurement taking is resumed only after the event has ended and / or such that measurements taken during the event are removed.

[0041] In one embodiment, the comparison operation includes determining the number of measurements within a range, in which case output data can optionally be generated that includes information regarding the distribution of the measurements, which may be the absolute number of measurements taken, but may also be expressed as a percentage of the total number of measurements.

[0042] Alternatively or additionally, it may be possible to determine within what period the in-range measurements were taken.

[0043] One or both limits of a range limited at one or both ends may in this case be predefined by the setting.

[0044] In another embodiment, the comparison operation determines at least one limit of the range.

[0045] In such cases, one or both limits of a range bounded at one or both ends can be dynamically determined based on a number of measurements taken, for example to determine the number of measurements above an average of the measurements taken, or to determine the number of measurements within a range above or below the average.

[0046] In one example, the maximum value of the measurements is first determined, then the number of measurements within a certain range below this maximum is determined, which makes it possible to ascertain whether the maximum is a short-term peak or whether it is in the region of a plateau in the values ​​of the terminal voltage.

[0047] Determining the number of measurements within a range can be utilized, for example, to perform a plausibility check.

[0048] Evaluating the number of measured values ​​within the range also makes it possible to obtain information about the condition of the battery cells, for example to identify ongoing deviations from recommended parameters (which may indicate, for example, a malfunction or damage to the battery cells).

[0049] In various embodiments, the output data may include a combination of different information.

[0050] In one example, the output data includes the maximum value from a number of acquired measurements and further the number of measurements within a range limited at one or both ends. The combination of this information makes it possible, firstly, to determine the measurement taken as the off-load voltage, while, secondly, to perform a plausibility check.

[0051] In one development, a configuration signal is also received and the measurement values ​​are evaluated based on the configuration signal, the configuration signal including, in particular, configuration data for an integrated cell monitoring unit, for example.

[0052] The evaluation of the measurement values ​​particularly concerns the filtering and / or comparison operations involved therein, although other evaluation steps may also be arranged to be performed on the basis of the setting signals.

[0053] The range of the plurality of measurements can be configurable. In particular, the configuration signal sets the length of the time interval during which the measurements are taken. The number of measurements may also be configured as in each case the plurality of taken measurements. The frequency of taking the measurements may also be configured.

[0054] By way of example, such configuration signals may be used to control how many measurements are taken and / or how frequently and / or over what period of time the taking takes place. The configuration signals may further be used to control particular algorithms or functions for filtering, so that, among other things, the output data contains the respective desired information. To achieve smoothing of the output data and / or the taken measurements, the configuration signals may further be used to control whether and how a smoothing operation is performed.

[0055] The configuration signal may further be used to select particular battery cells for taking measurements.

[0056] The configuration signal may further be used to configure acquisition such that terminal voltages of a subgroup of battery cells are acquired for measurement.

[0057] The set signal may further include one or more thresholds, which are used in the comparison operation. For example, the set signal may be used to deliver a threshold against which the measurements are compared, and then, for example, the number of measurements below or above the threshold may be determined and output together with the output data.

[0058] The configuration signal can further be used to transmit a number of thresholds that can be used to define ranges and perform binning of the measurements, i.e. the measurements are compared to the thresholds and assigned to respective ranges between the thresholds. By outputting the number of measurements within a range it is possible to show the distribution of the measurements. Roughly speaking, what is known as "binning" results in, for example, a target amount of an attribute being divided into ranges in ascending order according to size, and then all attribute values ​​are replaced by a representative value of the range in which the value falls.

[0059] In one embodiment, an operating condition is also detected and measurements are taken based on the operating condition. The detected operating condition may optionally be used as a basis for triggering a control signal for resetting the taken measurements. In particular, an operating condition is detected and / or evaluated for the energy storage device and / or at least one battery cell. For example, an operating condition may be detected and / or evaluated for battery cells coupled to the integrated cell monitoring unit individually and / or collectively.

[0060] The operating state may relate to the energy storage device and the battery cells that compose it. In particular, the operating state may relate to a connected load or charging device. That is, the operating state may depend on whether and to what extent the energy storage device is loaded by a load, whether the energy storage device is charging or disconnecting the load when power is not required. The operating conditions may be detected, for example, by obtaining voltage, current, and / or requested power.

[0061] The detected operating state may also be a charging process, i.e. a check is performed to see whether the battery cells are being charged, for example during a regeneration process. This may include, among other things, obtaining the direction of the current flow and thereby determining whether charging is taking place.

[0062] The detected operating conditions may also be utilized as a basis for triggering and processing control signals for resetting the acquired measurements. By way of example, an event leading to a distortion of the acquired measurements can be detected. For example, a regenerative process leading to charging of a battery cell or an energy storage device and therefore to an increase in the terminal voltage can be detected. A control signal may be generated such that the acquisition of measurements is resumed only after the end of the event and / or such that measurements acquired during the event are removed.

[0063] In another embodiment, the output values ​​are used to determine and output a state of charge of at least one battery cell and / or a state of charge of an energy storage device. By way of example, the integrated cell monitoring unit may generate output data and transmit it to an external unit, such as a central controller, which determines the state of charge.

[0064] Advantageously, this method can be utilized to obtain particularly accurate and reliable range estimates using filtered measurements.

[0065] In another embodiment, the output data may be used to determine a "State of Health" (SoH) of the energy storage device or a subset of battery cells. By way of example, this may be accomplished by determining a current distribution of measurements for a particular operating condition in particular. The current distribution may then be compared to a previous distribution obtained at a comparable operating condition at an earlier time. The change in distribution may then be used to determine a change in the state of health of the measured battery cells. In particular, the SoH may be expressed as a quality factor in percent. By way of example, this may indicate the degree of deterioration of the energy storage device's state of health with increasing age.

[0066] A system for operating an energy storage device comprising a plurality of battery cells, in particular in a vehicle, comprises an acquisition module configured to acquire a plurality of measurements of terminal voltages of at least one battery cell, an evaluation module configured to perform filtering using the acquired measurements to generate filtered measurements, the filtering of the measurements including a comparison operation, and an output module configured to generate and output output data using the filtered measurements.

[0067] This system is specifically designed to carry out the present method and therefore has the same advantages as the method according to the invention.

[0068] In particular, the acquisition module, the evaluation module and the output module are integrated in a cell monitoring unit which is associated to at least one battery cell and which is coupled to a central control device via a data connection, in particular a data bus.

[0069] The acquisition module may be designed to acquire the terminal voltage in a manner known per se. The acquisition module may furthermore be used to acquire the temperature and / or further parameters of the at least one battery cell. The acquisition module may in particular be integrated into a battery cell or cell module. For example, an integrated cell monitoring unit with an acquisition module may be provided for each cell module of the energy storage device.

[0070] In particular, the system also has a memory module, which the integrated cell monitoring unit can also be equipped with. The acquired measured values ​​are then stored in the memory module and are available for evaluation, for example by filtering. The memory module may be formed in such a way that the most recently acquired measured values ​​overwrite the oldest measured values ​​in each case, for example in the manner of a ring memory.

[0071] The integrated cell monitoring unit may further include a reset function for said values ​​to eliminate inappropriate measurements during voltage rises during regenerative braking of the vehicle. Resetting the memory causes all values ​​of the measurements in the memory module to be overwritten and evaluation is performed only after the measurements have been taken again.

[0072] The output data may be transmitted from the output module to a central controller.

[0073] Configuration signals can be sent from the central controller to the integrated cell monitoring units in the manner described above to control the acquisition and / or evaluation by filtering of the measured values.

[0074] The data transmission between the integrated cell monitoring units of the cell modules of the energy storage device and the central control device can take place via a data connection, for example via a data bus, in particular in a ring configuration. The data transmission in this case is protected against a partial failure of the data bus, since the data transmission can take place in two directions. Alternatively, a track configuration for the data transmission can also be provided. The cell modules of the energy storage device are in particular electrically isolated apart from the series or parallel connections with one another.

[0075] The central control device may be configured to detect charging of the energy storage device or charging of at least one battery cell, then generate a reset signal, and then send said reset signal to an integrated cell monitoring unit designed to start acquiring the plurality of measurements again.

[0076] The invention further relates to a vehicle comprising an energy storage device comprising a plurality of battery cells, an electric load, such as an electric motor, a heating device and / or a lighting device, and further a control unit, the control unit being configured to operate the energy storage device according to the method of the invention.

[0077] The invention is explained in more detail below on the basis of the accompanying drawings. [Brief description of the drawings]

[0078] [Figure 1] FIG. 1 illustrates an exemplary embodiment of a system. [Diagram 2] FIG. 1 illustrates an exemplary embodiment of a vehicle. [Diagram 3] 1 shows a graph of a typical voltage response of a battery cell. [Figure 4] FIG. 1 illustrates an exemplary embodiment of a method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0079] An exemplary embodiment of the system is described with reference to FIG.

[0080] The system 10 includes an energy storage device 20 .

[0081] The energy storage device 20 includes a number of cell modules 22, 24, which in turn each include a number of battery cells 22a, 22b, 22c, 22d, 22e, 24a, 24b, 24c, 24d, 24e. Additional cell modules are also shown in FIG.

[0082] The cell modules 22, 24 are conductively coupled to each other, e.g., connected in series with each other. The cell modules 22, 24 may also be connected in parallel with each other, such that a particular total voltage and a particular capacity of the energy storage device 20 is achieved by a combination of the series and parallel connected cell modules 22, 24 of the energy storage device 20.

[0083] The battery cells 22a, 22b, 22c, 22d, 22e, 24a, 24b, 24c, 24d, 24e of the cell modules 22, 24 are specifically connected in series, although, again, other circuits and configurations can be provided.

[0084] In this example, each cell module 22, 24 comprises an integrated cell monitoring unit 32, 34, which is here coupled to the individual battery cells 22a, 22b, 22c, 22d, 22e, 24a, 24b, 24c, 24d, 24e.

[0085] A data bus 40 connects the integrated cell monitoring units 32, 34 to the central controller 30 for data transfer purposes. In an exemplary embodiment, the data bus 40 is in the form of a ring bus. In other exemplary embodiments, the data connection may be made in another manner, for example via a wireless connection.

[0086] The integrated cell monitoring units 32, 34 comprise an acquisition module, an evaluation module and an output module.

[0087] The acquisition module is configured to acquire, in a manner known per se, a measurement value of the terminal voltage of each of the connected battery cells 22a, 22b, 22c, 22d, 22e, 24a, 24b, 24c, 24d, 24e, and further measurements are acquired, also in a manner known per se, for the temperature of the battery cells 22a, 22b, 22c, 22d, 22e, 24a, 24b, 24c, 24d, 24e.

[0088] The terminal voltage measurements of the individual battery cells 22a, 22b, 22c, 22d, 22e, 24a, 24b, 24c, 24d, 24e are taken as a time series, and the particular length of the time interval for taking the measurements is predetermined. In an exemplary embodiment, this time interval may be adapted by a configuration signal from the central controller 30.

[0089] In another exemplary embodiment, it may be provided that the cell monitoring units 32, 34 use the obtained measurements of the terminal voltages of each of the connected battery cells 22a, 22b, 22c, 22d, 22e, 24a, 24b, 24c, 24d, 24e to check whether these values ​​form a new maximum value with respect to the previous measurements, in which case this new maximum value is stored and output to the control unit 30 in case of interrogation.

[0090] In particular, the output data can essentially only contain one measured value. The required memory of the cell monitoring units 32, 34 can also be reduced so that only the current maximum value is stored in each case.

[0091] In particular, this example involves measurements being taken at uniform time intervals, ie with a substantially constant acquisition frequency, and stored by memory modules of the integrated cell monitoring units 32,34.

[0092] An exemplary embodiment of a vehicle is described with reference to figure 2. The starting point for this is the exemplary embodiment of the system described above.

[0093] In this exemplary embodiment, vehicle 200 is equipped with a system in a similar form to the exemplary embodiment of system 10 described with reference to FIG.

[0094] The vehicle 200 in this case comprises an energy storage device 210 which is coupled to an electrical load 220 and supplies electrical energy to said load.

[0095] The electrical load 220 may be, for example, a drive motor or other electric motor. Other electrical loads 220 are also possible, for example a heating device or a lighting device.

[0096] Conversely, electrical energy may be delivered from electrical load 220 to energy storage device 210, such as when providing power during regeneration.

[0097] The vehicle 200 also comprises a central controller 230, which is connected to the energy storage device 210 and the electric loads 220 for data transfer purposes. The data connections can be used by the central controller 230 to receive and transmit data, in particular measurements are taken and control data is generated using the measurements.

[0098] An exemplary embodiment of the method is explained with reference to figures 3 and 4. The starting point for this is the exemplary embodiment of the system described above, which is further detailed below.

[0099] In a first step 410, measurements of the terminal voltage of at least one battery cell 22a, 22b, 22c, 22d, 22e, 24a, 24b, 24c, 24d, 24e are obtained, in this example as a time series having a configurable, predefined length.

[0100] 3, a graph is shown plotting the response 300 of the voltage V(t), specifically the terminal voltages of the battery cells 22a, 22b, 22c, 22d, 22e, 24a, 24b, 24c, 24d, and 24e, over time t. A steady-state voltage level 310 can be seen that substantially corresponds or is comparable to the load-disconnect voltages of the battery cells 22a, 22b, 22c, 22d, 22e, 24a, 24b, 24c, 24d, and 24e, i.e., the terminal voltages without any electrical load requiring power.

[0101] A negative peak 320 in the response can also be seen as the terminal voltage drops, indicating that electrical energy is being drawn from the battery cells 22a, 22b, 22c, 22d, 22e, 24a, 24b, 24c, 24d, and 24e, i.e., the connected load is operating at the particular power provided by the battery cells 22a, 22b, 22c, 22d, 22e, 24a, 24b, 24c, 24d, and 24e.

[0102] Measurements representative of the load-disconnect levels of terminal voltage are shown as crosses (x) in graph 300. Other measurements that correspond or are comparable to the voltage response while battery cells 22a, 22b, 22c, 22d, 22e, 24a, 24b, 24c, 24d, 24e are under load are shown as circles (o).

[0103] To be able to determine the state of charge of the battery cells 22a, 22b, 22c, 22d, 22e, 24a, 24b, 24c, 24d, 24e and hence the state of charge of the energy storage device 20, values ​​of the terminal voltages obtained at load disconnection are required that correspond to or are comparable to the measured load disconnection levels 310.

[0104] In step 420, a filtering process is performed on the series of measurements taken in the first step 410. This step includes a comparison operation, in particular a comparison of the measurements taken with each other, in order to determine a maximum value.

[0105] In the graph shown in FIG. 3 it becomes clear that this maximum value corresponds substantially to the absolute value of the load shedding level 310 .

[0106] In step 430, a further filtering step is performed by determining the number of measurements above a certain threshold.

[0107] The threshold may be fixedly predefined or may be dynamically determined, for example 10% below a predetermined maximum value.

[0108] If the thus determined number of measurements above the threshold is itself above a certain threshold, e.g. more than 20% of the measurements, then the maximum value can be considered not to be an abnormal deviation from the voltage load shedding level 310. Thus, in this way, a plausibility check can be performed.

[0109] Then, in step 440, output data is generated. In this example, these include the determined maximum value and the number of measurements above the threshold. These output data are transmitted via a data bus to a central controller where they can be further processed to determine, for example, the state of charge of the energy storage device 20 or the state of charge of the battery cells 22a, 22b, 22c, 22d, 22e, 24a, 24b, 24c, 24d, 24e. In other exemplary embodiments, the output data may also be transmitted to the central controller via a different form of data connection, for example a wireless connection.

[0110] In an exemplary embodiment, the central controller 30 also monitors the operating state of the energy storage device 20. This is achieved, among other things, by obtaining how much current is being provided by the energy storage device 20. The direction of this current can be used to detect, among other things, when the energy storage device 20 is being charged by regeneration or otherwise. In the graph 300 shown in FIG. 3, this would result in an upward deviation, so that the determination of the maximum measured value would not provide a suitable database for determining the state of charge. If charging of the energy storage device 20 or charging of at least one of the battery cells 22a, 22b, 22c, 22d, 22e, 24a, 24b, 24c, 24d, 24e is detected, a "reset" signal is generated and sent to the integrated cell monitoring units 32, 34. The units then start taking measurements again. A reset signal may also be generated if other events are detected that distort the measurements. [Explanation of symbols]

[0111] 10. System 20 Energy storage device 22 Cell module 22a, 22b, 22c, 22d, 22e Battery Cells 24 cell module 24a, 24b, 24c, 24d, 24e Battery Cells 30 Central Control Unit 32 Integrated Cell Monitoring Unit 34 Integrated Cell Monitoring Unit 40 Data Bus 200 vehicles 210 Energy Storage Device 220 Electrical Load 230 Central Control Unit 300 Graph (Voltage Response) 310 Load disconnect voltage 320 Load Peak 410, 420, 430, 440 steps

Claims

1. A method for operating an energy storage device (20) comprising a plurality of battery cells (22a-22e, 24a-24e), in particular in a vehicle (300), comprising: A plurality of measurements of terminal voltages of at least one battery cell (22a-22e, 24a-24e) are obtained; A filtering process is performed based on the acquired measurements to generate filtered measurements; and said filtering of said measurements comprises a comparison operation; A method wherein output data is generated and output based on the filtered measurements.

2. The method of claim 1 , wherein the plurality of measurements are taken as a time series.

3. 3. The method according to claim 1 or 2, further comprising detecting an operating condition, the measurements being taken in response to the operating condition, and a control signal for resetting the taken measurements being triggered based on the detected operating condition, the control signal being generated such that the taking of the measurements is resumed only after an event has ended and / or such that measurements taken during the event are removed.

4. 4. A method according to any one of claims 1 to 3, wherein the act of comparison comprises determining a maximum or minimum measurement value of the plurality of measurements.

5. 5. A method according to any one of claims 1 to 4, wherein the comparison operation comprises comparing the measured value with at least one limit value.

6. 6. A method according to any one of claims 1 to 5, wherein the comparison operation comprises determining the number of measurements within a range.

7. 7. The method of claim 6, wherein the comparing operation results in at least one limit of the range being determined.

8. 8. The method according to any one of claims 1 to 7, further comprising receiving a setting signal and evaluating the measured values ​​based on the setting signal.

9. 9. The method according to any one of claims 1 to 8, further comprising obtaining an operating state, obtaining and / or evaluating said measurement values ​​based on said operating state, and optionally triggering a control signal for resetting said obtained measurement values ​​in response to said obtained operating state.

10. 10. The method according to any one of claims 1 to 9, characterized in that the output value is used to determine and output a state of charge of at least one battery cell (22a, 22b, 22c, 22d, 22e, 24a, 24b, 24c, 24d, 24e) and / or a state of charge of the energy storage device (20).

11. A system (10) for operating an energy storage device (20) comprising a plurality of battery cells (22a, 22b, 22c, 22d, 22e, 24a, 24b, 24c, 24d, 24e), in particular in a vehicle, comprising: an acquisition module configured to acquire a plurality of measurements of terminal voltages of at least one battery cell (22a, 22b, 22c, 22d, 22e, 24a, 24b, 24c, 24d, 24e); performing a filtering process based on the acquired measurements to generate the filtered measurements; an evaluation module configured such that the filtering of the measurements comprises a comparison operation; an output module configured to generate and output output data based on the filtered results; In particular, the acquisition module, the evaluation module and the output module are integrated into a cell monitoring unit associated with the at least one battery cell (22a, 22b, 22c, 22d, 22e, 24a, 24b, 24c, 24d, 24e) and coupled to a central control device via a data connection, in particular a data bus.

12. 12. The system of claim 11, wherein the central controller (230) is configured to detect charging of the energy storage device (20) or charging of the at least one battery cell (22a, 22b, 22c, 22d, 22e, 24a, 24b, 24c, 24d, 24e) and then generate a reset signal and send the reset signal to an integrated cell monitoring unit (32, 34), which is then configured to resume obtaining the plurality of measurements.

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