WO2023041727A1 - Batteriemesssystem - Google Patents
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- WO2023041727A1 WO2023041727A1 PCT/EP2022/075813 EP2022075813W WO2023041727A1 WO 2023041727 A1 WO2023041727 A1 WO 2023041727A1 EP 2022075813 W EP2022075813 W EP 2022075813W WO 2023041727 A1 WO2023041727 A1 WO 2023041727A1
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- 238000005259 measurement Methods 0.000 claims abstract description 119
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
- G01R31/389—Measuring internal impedance, internal conductance or related variables
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
- G01R31/382—Arrangements for monitoring battery or accumulator variables, e.g. SoC
- G01R31/3842—Arrangements for monitoring battery or accumulator variables, e.g. SoC combining voltage and current measurements
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
- G01R31/367—Software therefor, e.g. for battery testing using modelling or look-up tables
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
- G01R31/392—Determining battery ageing or deterioration, e.g. state of health
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
- G01R31/396—Acquisition or processing of data for testing or for monitoring individual cells or groups of cells within a battery
Definitions
- the invention relates to a battery cell measuring unit, a measuring unit arrangement, a battery measuring system, a use of the battery measuring system, an electrically operated means of transport, a stationary storage device, e.g. B. for grid frequency regulation or a microgrid memory, and a method for providing a measurement data set of a battery cell unit in a cell string of a battery for determining a state of the battery cell unit.
- a stationary storage device e.g. B. for grid frequency regulation or a microgrid memory
- the status of batteries e.g. batteries in a means of transport or in a stationary storage facility, is usually determined by monitoring cell voltages, currents and temperatures. This method is often imprecise because it does not take into account the complex behavior of the battery. Furthermore, age-related changes are not taken into account.
- the battery can be removed and taken to a measuring stand to obtain a highly accurate status report. An impedance spectrum of the entire battery can then be determined there and compared with reference values. This procedure is cumbersome and expensive and is therefore carried out relatively infrequently. This then has the consequence, for example, that the current status is not constantly available and the expected service life is not sufficiently known. This can lead to dangerous situations, which is why batteries have to be replaced at regular intervals and spare batteries have to be kept on hand.
- the described embodiments relate in a similar way to the battery cell measuring unit, the measuring unit arrangement, the battery measuring system, the use of the battery measuring system, the electrically operated means of transport, the stationary memory and the method for providing a measurement data set of a battery cell unit in a cell string of a battery for determining a state the battery cell unit. Synergy effects may result from various combinations of embodiments, although they may not be described in detail.
- a battery cell measuring unit is provided.
- the measuring unit is set up to record measured variables of a battery cell unit in a cell string of a battery.
- the measuring unit is also set up to record measured variables for determining a state of the battery cell unit during operation of the battery and to provide the measured variables determined as a measured data record to a battery control unit.
- a measuring unit which e.g. B. detects physical or chemical variables that are suitable to describe a state of the battery or environmental conditions of the battery.
- An essential property of the measuring unit is that it is set up to record the measured variables during the intended operation of the battery. This can be, for example, in the case of a means of transport while driving or flying. It is pointed out that the status of the battery system as a whole is not recorded by the measuring unit, but only the status of a battery cell unit. It is also possible to To capture the state of several cell units at the same time. This means that an essential point here is that those cell units for which no measurement is currently being carried out continue to be operational, so that the battery system is or can be in use through these cell units even during the measurement.
- the battery cell units being measured are briefly decoupled from operational operation during the measurement, so that an exact measurement can be carried out without, for example, measuring currents or interference being discharged, as described in more detail in the following embodiments.
- a state is, for example, a state of charge or a "health" state, or a physical or chemical property that may change with use of the battery or over time in general.
- a battery cell unit is the smallest unit that can be measured “from the outside” in terms of voltage, i.e. the unit of cells that makes a common plus and minus pole accessible and thus represents the overall potential of the unit. As a rule, these are battery cells that are connected in parallel or also in series. A battery cell unit can thus have an energy storage element or a plurality of energy storage elements arranged in parallel or in series. The structure of the battery with battery cell units and cell strings is described below.
- the measurement data set can also contain other values that the measuring unit calculates, for example, from the measured variables, such as impedance values.
- the measurement data set does not necessarily contain all measured values.
- the measured variables determined are made available to a battery control unit as a measurement data set.
- the battery control unit controls the measurement, for example, and can evaluate the measurement data, as further explained below.
- the measuring unit is also set up to record the following measured variables: an alternating current injected into the battery cell unit with different frequencies as a stimulus for determining an impedance spectrum, and a voltage and a phase relative to the injected alternating current as a voltage response for determining the impedance spectrum.
- the measuring unit is also set up to store values of the measured variables recorded and/or values of the Provide the impedance spectrum with a time stamp and make it available to the battery control unit as a measurement data set.
- the impedance spectrum can be determined by the measuring unit, which sends the determined or calculated values of the impedance spectrum to the battery control unit, or the measuring unit sends the raw data to the battery control unit, which then determines values of the impedance spectrum from the raw data received.
- the impedance spectrum shows the impedance of the battery cell unit as a function of frequency.
- Impedance can be represented as magnitude and phase or as real and imaginary parts.
- the frequency range is between a few millihertz and a few kilohertz, for example.
- a sinusoidal (also multi-sinusoidal) current excitation with an integer period is injected into each cell unit and the voltage response is measured with the help of a four-point measurement, for example.
- the complex frequency spectrum of the impedance is obtained by Fourier transformation according to amount and phase (or also real and imaginary part value). Acquiring the AC current and voltage response for impedance spectroscopy is done by the measurement unit for the single battery cell unit.
- the measuring unit is also set up to additionally record one or more of the following measured variables: temperature, pressure in the battery cell unit, chemical and physical parameters.
- the overall state of the battery cell unit can thus be inferred from the individual physical and chemical states, which can influence, for example, a state of charge, a "health" state and/or the service life of the battery.
- the measurement unit can also be set up to provide the measurement data set to the battery control unit wirelessly, e.g. according to a short-range radio standard, or wired, e.g. via Ethernet or a CAN bus.
- a measuring unit arrangement with a plurality of measuring units described herein for a plurality of battery cell units in the battery has a DC bus connection with a plurality of cell strings arranged in parallel on this DC bus connection, each Cell string has one or more battery cell units connected in series. At least some of the cell strings each have one or more measuring units, which each record measured variables of a battery cell unit.
- the one or more measuring units are set up to simultaneously acquire measured variables from battery cell units of the cell string and to organize the acquired measured variables as a measured data record for provision to the battery control unit.
- the number of measuring units can correspond to the number of battery cell units, so that, for example, each battery cell unit is assigned a measuring unit. However, it would also be possible for a number of battery cell units in a cell string to be assigned to a measuring unit. All battery cell units of a cell string are preferably measured simultaneously. This is important insofar as it allows measurements to be made, for example, in a switchable manner for each cell string, as will be described in more detail below, which shortens the measurement time. It is noted here that in this disclosure, a battery cell unit may include multiple cells, also referred to herein as energy storage elements. That is, a measuring unit injects current and measures values for a battery cell unit with several, e.g. 14 cells or energy storage elements. The energy storage elements are not further differentiated in this disclosure.
- the cell strings end at one of their ends in a DC bus connection, which can be realized, for example, by a bus bar or cable connection, at which the battery voltage or the current from all connected cell strings is or is made available.
- the measurement data can be organized, for example, as a measurement data record, which can contain, for example, a number of measurement variables and time parameters, which the measurement units transmit to the battery control unit.
- a battery measurement system which has a measurement unit arrangement described herein with a plurality of measurement units arranged in at least one cell string, as well as a battery control unit and a current source for each measurement unit, which can also work as a sink.
- Each of the Measuring units is assigned to at least one battery cell unit, and each of the measuring units is set up to send measurement data records to the battery control unit.
- the battery control unit is set up to receive measurement data sets from measurement units of at least one cell string.
- the current sources are each set up to inject a current charged with a frequency into the battery cell unit of the associated measuring unit.
- each measuring unit is assigned a current source that injects a current into those battery cell units that are assigned to the measuring unit.
- the current has a frequency.
- the fact that the current has a frequency is to be understood here as meaning that it has at least one frequency or that it represents a superimposition or sequence of currents with different frequencies. The different frequencies can occur simultaneously or sequentially.
- the current source can work as a source and as a sink. From this, the current can be modulated e.g. sinusoidally, i.e. with positive and negative amplitude as excitation.
- the battery control unit is also equipped with a logic that also allows the execution of diagnostic functions.
- the diagnostic functions are based on a model of a machine learning process.
- the battery control unit receives the model or the values of the model parameters via a wireless interface or alternatively via a wired interface from a computing unit, as will be described in more detail below.
- the logic may include hardware and/or software elements. It goes without saying that the battery control unit can have hardware such as processors, logic modules, program memories and registers, clock modules, etc., depending on its tasks.
- the diagnostic functions relate in particular to characteristics of the inside of the battery, current statistics, etc.
- each cell string has a switch or a switchable converter for separating the cell string from the other cell strings, with only those measuring units providing measured variables and measured data sets that cell line are assigned.
- the cell string in which measurements take place can be separated or decoupled from the DC bus connection and thus, for example, from the load, consumer or an energy source and from other cell strings.
- the isolation can be done galvanically by a switch, e.g. a relay or by a semiconductor, e.g. a transistor in a converter, or by switching an impedance of the converter so that the cell string is only connected to the busbar with high resistance.
- converter is synonymous with the term “converter”.
- Examples of converters are DC/DC converters or DC/AC or AC/DC converters, where “DC” stands for direct current and “AC” for alternating current.
- the battery cell units of a cell string or the battery cell units of a selection of cell strings are preferably measured at a time.
- the other cell strings are isolated from this cell string with high resistance or alternatively galvanically. In this way, the current injected by the source/sink can flow fully into the cells connected to the measurement units of the string and avoid interference from other cell strings.
- the cell strings can, for example, be "activated” while rotating for a measurement or separated from the direct current collector connection.
- cell strings can also be measured in parallel without the cell strings influencing each other.
- a bidirectional converter can be used so that the disconnected string can be reconnected to the DC busbar at any time, regardless of the charging status of the string.
- the battery control unit is set up to generate a feature data record from the measurement data records of the measuring units, to impress a time stamp on the feature data record and to temporarily store the feature data record including the time stamp.
- the characteristic data set can include, for example, impedance values at frequency support points, as well as current and voltage values, statistical information about measured current and voltage ranges, an SoC calculated by means of current integration over the time interval between the last measurement and the current measurement, a temperature, etc. included.
- the battery measurement system has a local memory for storing the feature data records. Furthermore, the battery measuring system can have sensors for measuring a temperature of a battery cell unit in each case, or other sensors which, for example, record environmental parameters such as temperature, humidity, mechanical stress, etc. of the environment.
- the battery measurement system has a computing unit and a communication interface, which can be, for example, local or wired, such as Ethernet, or wireless, such as WiFi, Bluetooth, LTE, 5G, radio, cloud, which are set up, the cached To transfer characteristic data sets to the computing unit, e.g. a server, wherein the computing unit is set up to receive the temporarily stored characteristic data sets and to calculate a model of a machine-learning system cyclically or dynamically on the basis of current characteristic data sets, the model providing diagnostic functions for each measuring unit, and the computing unit is also set up to transmit the model to the battery control unit via the communication interface.
- a communication interface can be, for example, local or wired, such as Ethernet, or wireless, such as WiFi, Bluetooth, LTE, 5G, radio, cloud, which are set up, the cached To transfer characteristic data sets to the computing unit, e.g. a server, wherein the computing unit is set up to receive the temporarily stored characteristic data sets and to calculate a model of a machine-learning system cyclically or dynamic
- the processing unit e.g. a cloud computer, a server or controller, stores all characteristic data records with a time stamp in a database. This creates a digital life/health record with which the most important features of the battery system can be seamlessly monitored. Even at this stage of the data situation, anomalies in the battery system can be detected at the cell unit level by simply checking range limits.
- the cloud computer also makes it possible to train updated models using machine learning methods based on the most recent feature data sets (e.g. from the last 6 months).
- diagnostic functions can thus be provided by the battery control unit, which are periodically updated. Examples of diagnostic functions are the current state of charge (SoC), the state of health (SoH), the temperature of the cell core or a default (recommended) value for the forthcoming maximum power output/consumption of the battery system for protection and life extension. In this case, it is not compulsory for all the diagnostic functions mentioned or provided to be provided by the model.
- the battery measurement system is set up to disconnect the separated cell string for a short time for measurement, while the other cell strings continue to work according to regular operation of the battery.
- Regular operation is understood to mean the operation of the cell according to its purpose, in contrast to a measuring operation. Regular operation can include drawing or supplying electricity, or even a rest phase.
- the battery measurement system furthermore
- the model is a model according to a recurrent (encoder/decoder) neural network method of known or future type, a reinforcement learning method such as e.g. the Distributed Distributional/Deep Deterministic Policy Grading (D4DPG/DDPG) method and/or an ActorZ-critic method, where the reinforcement learning method uses a reward for learning within an environment model.
- the model is an artificial intelligence model (e.g. a neural network) that is set up to generate time stamps from the feature data sets, respectively.
- This embodiment describes the reward function for learning the SoC diagnostic model.
- the agent of the neural network continuously estimates the future diagnosis variable SoC between 0..100%.
- a difference value ASoC can thus also be estimated in each case between directly adjacent time stamps.
- ASoC can thus assume values between -100% and 100%.
- This ASoC value is also available in the Coulomb counter of the battery control unit (integration of the current value) as a measured variable as a very precise variable.
- the comparison between the estimated ASoC and the measured ASoC values can be used in the environment model for evaluating/rewarding the "absolute SoC" diagnostic variable to be estimated. Since the SoC is technically limited between 0..100%, the learning procedure continuously improves not only the estimate of the ASoC, but also (indirectly) the estimate of the absolute SoC.
- the model is an artificial intelligence model that is further set up to estimate a SoC state value, a SoH state value, a state value with regard to a temperature, a chemical and/or a physical property.
- Artificial intelligence is also understood here to mean neural networks or machine learning.
- the learning can also be supported by a simulation.
- software running on a PC or laptop runs through a predefined, typical performance profile, for example of a forklift truck or another means of transport.
- the power unit here has drivers that represent a power source and provide a charging current, or units that represent a load and draw the battery current.
- the measurement data are sent to the computing unit in order to calculate the model or the values for the parameters of the model.
- the model can be transferred to the battery control unit and used for real operation, e.g. of the means of transport, and thus for constant monitoring of the battery during operation.
- a method for providing a measurement data set of a battery cell unit of a cell string of a battery for determining a state of the battery cell unit is provided, with the following steps:
- a use of a battery measurement system presented here is provided in an electrically operated means of transport, a stationary storage of electrical energy, for e.g. grid frequency regulation or in a microgrid.
- an electrically operated means of transportation or a stationary storage of electrical energy which has a battery measurement system described here.
- the method may be performed, at least in part, by a computer program element executing on one or more processors.
- the computer program element can be part of a computer program, but it can also be a whole program in itself.
- the computer program element can be used to update an already existing computer program in order to arrive at the present invention.
- the computer-readable medium can be considered to be a storage medium, such as a thumb drive, CD, DVD, data storage device, hard drive, or any other medium on which a program element as described above can be stored.
- a computer program may be stored/distributed on any suitable medium, such as an optical storage medium or a semiconductor medium, supplied together with or as part of other hardware, but may also be distributed in other forms, for example over the Internet or other wired or wireless telecommunications systems be. Any reference signs in the claims should not be construed to limit the scope of the claims.
- Fig. 1 A general overview of a battery measuring system
- Fig. 6 is a diagram of a measurement circuit in a measurement unit
- Fig. 7 is a block diagram of an artificial intelligence
- FIG. 8 shows a flow chart of a method for providing a measurement data set of a battery cell unit
- FIG. 11 shows a block diagram with a test arrangement of the battery measuring system
- FIG. 1 shows a block diagram with an overall overview of a battery measuring system 100, which has a battery control unit 104, a measuring unit arrangement 106 with measuring units, which are provided with reference symbols 213 and 218 in FIG.
- the components mentioned can be individual devices or integrated into a housing.
- the data connections can be wireless and/or wired.
- each of the battery cell measuring units 213...218 of the measuring unit assembly 106 is connected to a battery cell unit 223...228.
- the cell strings 202 and 204 with the battery cell units 223...225 or 226...228 are each connected at one of their ends to the DC busbar 240, which is connected to a load or consumer or a power generator (not shown). .
- Each of the battery cell measuring units 213...218 detects measured variables such as current and voltage of the assigned battery cell unit 223...228 of a cell string 202, 204 of a battery during its operation. This allows you to record the condition of the battery cell units.
- the state of the battery system 110 can thus be estimated through the entire arrangement 106 .
- the measuring units 213 . . . 218 make the determined measured variables available to the battery control unit 104 shown in FIG. 1 as a characteristic data record with a time stamp.
- the memory volume of the battery control unit 104 is large enough so that all measurement data obtained can also be temporarily stored over several days.
- the battery control unit 104 controls the measurements and evaluates them, sending the measurement data to the computing unit 102 for the evaluation or parts of the evaluation.
- the battery control unit 104 has, for example, a common radio interface such as WiFi, Bluetooth, LTE, 5G, etc.
- the computing unit 102 is, for example, a cloud computer with high computing power and, in addition to one or more processing units 112 or controllers 112, has a memory 114 in which both the current feature data records and earlier feature data records are stored.
- the computing unit 102 also houses artificial intelligence such as a neural network. The computing unit trains the neural network so that an up-to-date diagnostic model is obtained for each cell unit.
- the battery control unit 104 cyclically receives the current diagnostic model for each cell unit via the radio interface from the cloud computer 102, which on the central battery control unit 104 based on current characteristic data sets important diagnostic functions such as the current state of charge (State of Charge, SoC), the state of health (State of Health ), the temperature of the cell core or a default value for the forthcoming maximum power output/consumption of the battery system for protection and service life extension.
- the battery control unit 104 receives characteristic data records from measuring units 213...218 of at least one cell string 202, 204.
- a cell string 202, 204 can have one or more battery cell units.
- a battery cell unit in turn, can be a single cell or multiple cells connected in parallel or in series, so that the battery cell unit forms a module.
- the battery cell units 223...225 of a cell string 202 are preferably measured simultaneously during a first period of time and the battery cell units 226...228 of a cell string 204 are measured simultaneously during a second period of time different from the first period of time. This avoids mutual interference in the cell strings 202, 204.
- the capacity, in particular the storage and computing capacity of the battery control unit 104 and/or the computing unit 102 only part of the battery cell units 223...225 or can also be measured within a string and then another part.
- This decoupling can be done for example by a switch, such as a simple relay.
- switches 331 and 332 are located, which can perform such a decoupling for each phase.
- Electronic solutions such as transistors can also be used here.
- a main contactor 333 with which the consumers/generators 340 in operation can be separated from the cell strings 202, 204 during the measurement, as well as a controlled voltage source 342 for displaying a variable standby current.
- the cell strings 202, 204 each have their own DC/DC converter at the positive end, for example. This is e.g. This is the case, for example, in large stationary storage systems. These DC/DC converters actually ensure that the voltage levels between the strings can be "controlled” balanced. These can be used and switched in such a way that they act as "relays" 331 and 332, which isolates the strand to be measured from the other strands with high resistance. For example, this can be a DC/DC resonant converter so that the impedance can be controlled via the switching frequency, or a converter that can be used as a switch.
- the source/sink 11 314 is part of the battery measuring unit 213, which in this example can spectroscopy the three energy storage elements 311, 312, 313 in series of the first string 202 at the same time.
- the number of battery measuring units required per string is (N DIV K) + 1, where N is the number of energy storage elements per string, DIV is an integer division and K is the maximum number of energy storage elements on which per measuring unit 213...218 the voltages, the temperatures and the current from 11 314, and thus the impedance spectrum can be measured.
- the resistance R2 326 and the capacitance C1 327 symbolize a possible load of the battery, which must be supplied by the unmeasured string 204 during the rod 202 impedance measurement. Impedances should only be measured by the battery measuring units when the cell units to be measured are "at rest", i. H. almost no current flows into or out of the cell units to be measured. These "rest phases" occur in many battery systems during normal operation with regard to the entire battery:
- a forklift is briefly left by the driver so that he can pursue an order picking task.
- a stationary storage system currently consumes or emits almost no electrical power if switching off/switching off a string continues to ensure the operation of the battery system.
- a single string can be isolated for the measurement, as already described, which then has no current flow during the measurement or current drain.
- the other cell strings can then be used to maintain a small current.
- the strands can be measured in turn.
- the measurement of the impedance spectrum can be interrupted immediately and the string via the associated switch, z. B. 331 or 332 back to the whole battery system can be switched on. In this way it is prevented that all strings maintain an almost identical state of charge even after the measurement.
- the source/sink 11 314 can be operated with a single sinusoidal excitation with, for example, a frequency of 10 Hz, or with several sinusoidal currents of the same amplitude, which have different frequencies, for example in the range of 25 mHz...1.5 kHz.
- the measuring time can be shortened by the simultaneous injection of several currents.
- the sinusoidal excitation then follows according to the following series function:
- a Fourier analysis can be performed to evaluate the current and/or voltage measurements for the impedance spectrum.
- the Fourier analysis can be carried out in the battery control unit, for example, or already in the respective measuring units 213 ... 218. It is advantageous for the digital Fourier analysis if 02 ... cos are multiples of toi, epi , ... , cp 5 can then be optimized offline in such a way that the overall excitation has the smallest possible amplitude when the individual current components are superimposed. This ensures that the small-signal properties are met during the measurement. It can be mathematically proven, for example, that with an optimized choice of epi ,... , cp its total maximum amplitude of 2.3* lampi is not exceeded Without an optimized choice of epi ,... , cps the total amplitude could be a maximum of 5* lampi in the worst case.
- the impedance can be evaluated with high precision using the fast Fourier transformation (FFT) digitally.
- FFT fast Fourier transformation
- DC components or "interfering frequencies” can be easily filtered out of the measured spectrum of the current and the cell voltages.
- FIG. 4 shows an example diagram of impedance spectra of a battery cell unit calculated in the battery control unit with the real part (x-axis) and imaginary part (y-axis) of the impedance Z in ohms, according to the current and voltage values recorded by a measuring unit.
- Each measurement point (frequency reference point) represents the impedance for a frequency that corresponds to the frequency of the injected current.
- the spectrum represents the impedance spectra for three different points in time “Time 1”, “Time 2”, “Time 3”, which are shown in 4 are characterized by different geometric shapes of the measuring points.
- the state of health and the state of charge of the battery cell unit can be inferred from the spectrum, for example by comparison with reference curves. Another possibility for estimating the state of health and the state of charge is the application of artificial intelligence, for example through neural networks, as described herein.
- FIG. 5 shows an example diagram with impedance spectra of a number of battery cell units or cells of a string, which are accordingly based on the measurement of a number of measuring units.
- the spectra are shown at three different points in time “Time 1”, “Time 2” and “Time 3”, which can be distinguished by the different geometric shapes of the measuring points. It can be seen that the "curves" of the different battery cell units behave similarly at one point in time, whereas the behavior at different points in time differs significantly.
- Fig. 6 shows a simplified diagram of a measurement circuit 600 of a measurement unit 213...218.
- the measurement is controlled by a microprocessor 602.
- the microprocessor 602 outputs superimposed signals 604 of different frequencies, which are converted to analog 606 and reach a multiplexer 608 as superimposed sinusoidal currents.
- the microprocessor 602 uses the channel signal 610 to select the cell or battery cell unit to be measured, into which the superimposed sinusoidal currents are injected, and the voltage of which is measured in response to the currents with a 4-point measurement 612 and is given differentially to a demultiplexer 614 .
- the current to be injected at the multiplexer 608 is measured with the current sensor 614 and the current measurement is also passed to the demultiplexer 614 so that the microprocessor can query the measured current for the channel selected above and the measured associated voltage at the demultiplexer 614.
- the voltage here is the sum of the individual voltages resulting from the injected superimposed sinusoidal currents. Both values are converted into a digital value by an analog-to-digital converter 616 and applied to a high-speed microcontroller interface of the microprocessor 602 as an input signal.
- the microprocessor 602 can now send the values to the battery controller 104 and/or, if powerful enough, perform a Fourier analysis to obtain the impedance spectrum.
- FIG. 7 shows a diagram of an artificial intelligence for estimating the state of charge and/or state of health of the battery cell units.
- a possible implementation of machine learning methods are so-called actor/critic networks, which, for example, as Deep Deterministic Policy Grading (DDPG) procedures are implemented.
- DDPG Deep Deterministic Policy Grading
- the cloud computer 102 accesses several thousand feature data sets from the past (eg from the last 6 months to the present).
- the cloud computer 102 creates a so-called “replay buffer” for this.
- a feature data set consists of the time stamp, all measured impedance values of the recorded spectrum (typically within a few mHz and a few kHz), the average temperature of the battery cell unit, and a list of measured current and voltage values of the battery cell unit, e.g. over the past hour before the time stamp considered.
- the amount of charge transferred in ampere-seconds [As] can be obtained for the last time stamp by integrating the sampled current value over time (Coulomb counting). Based on the nominal capacity of the battery cell units, a difference value of a recharged state of charge can be calculated as a percentage.
- ZN Last complex impedance value of the cell unit at the last measured frequency support point (magnitude and phase or real and imaginary part)
- T Mean temperature of cell unit
- I25%/U25% Lower quartile of the measured current-Zvoltage values from the immediate past for f_meas(k)
- Such a feature data set is already created in the central battery control unit and, if there is a radio connection to the cloud computer, transferred to the digital life record.
- the agent 702 continuously estimates the target variable (here the absolute SoC£ S ([f meas (k)]) by not only using the arbitrarily chosen, k-th characteristic data set from the replay buffer with the characteristic data sets for the estimation , but also uses other characteristic data records, which are chronologically in the direct temporal past of the selected time stamp.
- this direct temporal "proximity" is given for a number of characteristic data records (e.g. M pieces) whose time stamp is 8- 12 hours in the past to the selected time stamp Within these time differences, a very precise ASoC value is available as a difference value using the Coulomb Counting method.
- the agent 702 estimates the SoC as an absolute variable based on the current agent model SoC£ S ([f meas (k)], SoC £ S ([f meas (k-1)], , SoC £ S ([f meas (kM)].
- a calculation rule as shown in FIG. 10 can now be used to evaluate the “estimation quality” of a selected feature data record as a reward value.
- the overall reward value determined in this way is a suitable measure for the fact that the individual absolute estimated values SoC Es t[tmeas(k)], SoC Es t[tmeas(k-1)], ... , SoC Es t[tmeas(kM )] must in most cases match the actual, absolute, but unknown SoC values for the available time stamps.
- Another critic network is trained in the machine learning method, with which the future cumulative total reward of the actor network is estimated.
- the network of critics thus supplies an estimate with which the "generalized quality" of the agent network can be evaluated.
- FIG. 8 shows a flow chart of a method 800 for providing a measurement data set of a battery cell unit in a cell string of a battery for determining a state of the battery cell unit, having the steps:
- recurrent neural network In another embodiment of artificial intelligence, so-called recurrent (encoder/decoder) networks can be used. Feedback between neurons in the same layer or in previous layers is also possible in a recurrent neural network.
- the topology of the network can be selected in such a way that SoC£ S ([f meas (k)], SoC£ S ([f meas (k-1)] are present as the previous neuron layer (hidden neurons).
- the battery cell units can be cells connected in series and/or in parallel and, connected in series, form a battery module.
- a battery consists of several battery modules connected in series, which form a battery string.
- Several battery strings can be connected in parallel to increase the total capacity of the battery.
- the condition is, for example, the state of health SoH as a ratio of the existing capacity to the nominal capacity of the cells and one aging-related parameter, for example the aging-related relevant impedance, which is a measure of the available power
- learning can be divided into two phases: a first learning phase in which the status parameters of the battery cell units are measured directly. For example, for the first 500-800 battery modules, the capacity (Ah) and the aging impedance of each battery cell unit is measured directly. Although these measurements are relatively slow because the battery modules must be fully charged and discharged, they serve as the data basis for machine learning.
- limit values or ranges for capacities and aging-related parameters can be defined that divide the condition into quality classes.
- the various above-mentioned parameters such as impedance spectrum, temperature, etc., can be measured or determined and assigned to the areas and fed to the machine learning algorithm as learning input variables and target variables.
- the machine learning algorithm thus learns the connection between the measurement parameters and capacity and aging-related parameter, so that no direct SoH determination has to be carried out in the second phase.
- the state for example the SoH
- the state is estimated indirectly through machine learning. This allows the status to be determined quickly.
- the battery measuring system can be used operationally for provided battery modules both in the first learning phase and in the second learning phase.
- a battery with 12 battery modules, each with 8 battery cell units is used in a vehicle, for example a used electric car, to provide energy.
- the state of health SoH of the battery modules is unknown.
- the battery management system of the used electric car does not show any errors on the battery side. It can be assumed that the battery has the same good properties across all battery modules with regard to the SoH and that they are functional for the operation of the electric car. At least two battery modules are selected first.
- the SoH must be recorded directly, as shown in structure chart 1200 in FIG. 12 .
- the relevant feature data sets are stored as a parameter set in a central database 1214, as already described above. For example, if the battery modules are not among the first 500-800 modules since the start of the battery measurement system, the SoH of the 2x8 cells is measured directly in accordance with the first learning phase. For this purpose, the battery modules are first charged to 100% SoC in step 1202 . Subsequently, in step 1204, the discharging process of the battery module is started.
- step 1206 the relevant features/parameters for the machine learning method are measured at selected states of charge in step 1208 and the current is integrated in step 1210 to detect the amount of charge transferred.
- Parameters for example for determining the impedance spectrum and other parameters as already described herein, are determined by measurements.
- the direct measurements of the SoH of the two battery modules serve to check the equally good properties. For example, the SoH of all cell units is 90%.
- the measurement data and measurement results are then made available to the machine learning program. Only the direct SoH measurement is used to assess the condition.
- the machine learning program is used to estimate the SoH in step 1306, as shown in structured chart 1300 of FIG. A direct measurement of the SoH is no longer necessary for this, but after discharging/charging to the next suitable state of charge with the aim of a short measurement time in step 1302, only measurements in step 1304 to determine the impedance spectrum and other parameters that were recorded at a selected operating point .
- the vehicle's battery is defective.
- a battery cell unit within a battery module is defective or at least in an unsatisfactory state of health.
- the state of health is determined as in the first example. If this shows that, for example, one battery cell unit has a SoH value of only 60%, while the remaining battery cell units have a SoH value of 90%, a request is triggered in the cloud with a selection of suitable used replacement modules with the same or at least of a comparable quality as the intact battery cells of the module or the battery cell units. Since the battery measuring system records all measured battery modules in a central database, it is possible to identify a suitable replacement module from an existing inventory.
- the suitable used replacement module is balanced cell-by-cell with regard to their voltages in such a way that all battery cell units in the battery have the same voltage value. This means that after the replacement module has been installed, the repaired battery is in a balanced condition and can be used again immediately.
- FIG. 11 shows a block diagram with an arrangement with which these tests can be carried out in the learning phases described.
- Block 1102 represents a battery module 1102 with multiple battery cell units 1104.
- the number of cell units 1104 is eight here, but can be more cells.
- block 1106 represents the source/sink connected to the general AC power grid, which may supply, for example, up to 3.5 kW.
- the source/sink 1106, which corresponds e.g. to the source/sink 331 in Fig. 3, converts the AC mains voltage into 2V to 60V or vice versa and thus allows selective charging/discharging of the entire battery module 1102 or of an individual battery cell unit 1104
- other voltage sources can be available for the internal voltage supply of the battery measuring system.
- Block 1108 represents, for example, the measuring unit 213 from FIG. 2 or the measuring unit shown in FIG.
- Block 1110 represents, for example, a processing unit with the microprocessor 602 shown in FIG. 6.
- the processing unit 1110 also has LAN, WLAN, USB and HDMI interfaces.
- the battery or at least the modules 1102 that are subjected to the test can be placed in a thermal chamber so that they can be tested at defined temperatures, which can also be different.
- the impedance spectrum is of this arrangement, as already described in detail herein.
- the LAN or WLAN connections are used, for example, to transmit the measured parameters to a memory and to the machine learning program, to communicate with a control PC, to receive the diagnostic model, and to select the replacement modules.
- a web server can also be provided via the WLAN/LAN connection as a user interface for controlling the battery measuring system and displaying the relevant data.
- an HDMI interface is also available for connecting a display.
- Input devices, external storage devices and other devices known to those skilled in the art can be connected to the USB interface.
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Abstract
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CA3231626A CA3231626A1 (en) | 2021-09-16 | 2022-09-16 | Battery measuring system |
IL311494A IL311494A (en) | 2021-09-16 | 2022-09-16 | Battery measurement system |
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US20120306504A1 (en) * | 2011-06-01 | 2012-12-06 | Johannes Petrus Maria Van Lammeren | Battery impedance detection system, apparatus and method |
US20180143257A1 (en) * | 2016-11-21 | 2018-05-24 | Battelle Energy Alliance, Llc | Systems and methods for estimation and prediction of battery health and performance |
US20200164763A1 (en) * | 2017-07-21 | 2020-05-28 | Quantumscape Corporation | Predictive model for estimating battery states |
CN112289385A (zh) * | 2020-09-17 | 2021-01-29 | 西南交通大学 | 大功率质子交换膜燃料电池电堆电化学阻抗谱预测方法 |
US20210231743A1 (en) * | 2020-01-29 | 2021-07-29 | Dynexus Technology, Inc. | Cross Spectral Impedance Assessment For Cell Qualification |
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DE102013218081A1 (de) | 2013-09-10 | 2015-03-12 | Robert Bosch Gmbh | Batteriemoduleinrichtung und Verfahren zur Bestimmung einer komplexen Impedanz eines in einer Batteriemoduleinrichtung angeordneten Batteriemoduls |
DE102017218588A1 (de) | 2017-10-18 | 2019-04-18 | Bayerische Motoren Werke Aktiengesellschaft | Detektion kritischer Betriebszustände in Lithiumionenzellen |
DE102019111979A1 (de) | 2019-05-08 | 2020-11-12 | TWAICE Technologies GmbH | Charakterisierung von wiederaufladbaren Batterien |
JP7205410B2 (ja) | 2019-07-26 | 2023-01-17 | 株式会社デンソー | 電池監視装置 |
DE102019126245A1 (de) | 2019-09-30 | 2021-04-01 | Dr. Ing. H.C. F. Porsche Aktiengesellschaft | System und Verfahren zur Bestimmung des Funktionszustandes und/oder Gesundheitszustandes einer elektrischen Batterie |
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US20120306504A1 (en) * | 2011-06-01 | 2012-12-06 | Johannes Petrus Maria Van Lammeren | Battery impedance detection system, apparatus and method |
US20180143257A1 (en) * | 2016-11-21 | 2018-05-24 | Battelle Energy Alliance, Llc | Systems and methods for estimation and prediction of battery health and performance |
US20200164763A1 (en) * | 2017-07-21 | 2020-05-28 | Quantumscape Corporation | Predictive model for estimating battery states |
US20210231743A1 (en) * | 2020-01-29 | 2021-07-29 | Dynexus Technology, Inc. | Cross Spectral Impedance Assessment For Cell Qualification |
CN112289385A (zh) * | 2020-09-17 | 2021-01-29 | 西南交通大学 | 大功率质子交换膜燃料电池电堆电化学阻抗谱预测方法 |
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