Method, device, system, electric vehicle, computer program and storage medium for charging or discharging battery cells of an electric energy accumulator

Abstract

The invention presents a method for charging a battery cell of an electrical energy accumulator (1), the method having: A1) placing the battery cell in a charging operation, B1) determining first and second impedance characteristic values representing a complex alternating current impedance of the battery cell, respectively, C1) determining first and second temperature characteristic values representing a temperature of the battery cell, respectively, by means of the respective impedance characteristic values, D1) determining a deviation of the respective temperature characteristic values, and E1) reducing a charging current of the battery cell in the event that the deviation exceeds a predetermined temperature threshold. Furthermore, another method, a corresponding device (3), a system (10), an electric vehicle (100), a computer program and a computer-readable storage medium are presented.

Description

Technical Field

[0001] Fast charging functionality for electric vehicles is a current development focus. Here, one or more battery cells in an electric vehicle operate within their specified limits, which, exceeding those limits, can potentially damage the respective battery cells. Summary of the Invention

[0002] The objective of this invention is to provide an efficient and reliable method for charging individual battery cells of an electric energy storage device, which particularly helps to avoid damaging the charging current intensity of the battery cells during (ultra)fast charging operation without a control device that enhances the calculation of the charging current. Furthermore, a method for efficiently and reliably discharging battery cells should be provided, along with corresponding apparatus, systems, electric vehicles, computer programs, and computer-readable storage media.

[0003] The task is solved by a method for charging individual cells of an electric energy storage device, a method for charging or discharging individual cells of an electric energy storage device, an apparatus for charging or discharging individual cells of an electric energy storage device, a system, an electric vehicle, a computer program for charging or discharging individual cells of an electric energy storage device (1), and a computer-readable storage medium according to the present invention.

[0004] According to a first aspect, the present invention relates to a method for charging a battery cell of an electric energy storage device. In particular, energy storage devices used in electric vehicles can be considered as electric energy storage devices, such as lithium-ion based secondary battery cells.

[0005] The energy storage device may, in particular, have multiple battery cells or groups of battery cells arranged in a battery pack. In the following, the method described using a single battery cell can also be applied to multiple battery cells or groups of battery cells.

[0006] In the method, in step A1), the battery cell is placed in a charging operation, during which a charging current is supplied to the battery cell.

[0007] Therefore, in step B1) following step A1), the first impedance characteristic value and the second impedance characteristic value during charging operation are determined. The first impedance characteristic value and the second impedance characteristic value here represent the complex alternating current impedance of the battery cell, respectively.

[0008] To determine the first and / or second impedance characteristic values, measurements of the complex alternating current impedance representing a single battery cell can be detected, in particular. These measurements are exemplarily obtained by applying an AC voltage signal to the battery cell, detecting time-scan values ​​of voltage and current data, windowing the voltage and current data to the corresponding time domain, and performing a Fast Fourier Transform using the windowed voltage and current data to identify the magnitude of the voltage and current at a particular frequency and thereby calculate the complex alternating current impedance of the battery cell.

[0009] In step C1), which follows step B1), a first temperature characteristic value is determined using a first impedance characteristic value, and a second temperature characteristic value is determined using a second impedance characteristic value. Here, the first temperature characteristic value and the second temperature characteristic value represent the temperature of the individual battery cell, respectively.

[0010] To determine the first and / or second temperature characteristic values, look-up tables can be considered in particular. Such look-up tables, for example, have corresponding temperature characteristic values ​​for the respective impedance characteristic values. The specific frequency and / or state of charge of the battery cell, which are mentioned in advance, can function as additional parameters for determining the temperature characteristic values. Alternatively or additionally, impedance characteristics, such as the real part, imaginary part, amplitude, or phase of the complex alternating current impedance of the battery cell, can be configured, particularly for the temperature characteristic values ​​stored in the look-up table.

[0011] Following step C1), in step D1), the deviation |ΔT|=|T1-T2| between the first temperature characteristic value T1 and the second temperature characteristic value T2 is determined.

[0012] Finally, in step E1), when the deviation |ΔT| exceeds the predetermined temperature threshold T... TH In this case, the charging current to the individual battery cells is reduced. The temperature threshold can be exemplarily between 1°C and 4°C, especially 2°C.

[0013] This aspect of the invention is based on the understanding that the two temperature characteristic values ​​are the same or substantially the same during normal use of a battery cell. If, conversely, the battery cell is charged with a harmful current, the temperature characteristic values ​​deviate from each other because the charging operation has already altered the battery cell to such an extent that the model conditions used to convert impedance to temperature are violated. Therefore, when a critical difference is exceeded, the current decreases until the charging operation is completely interrupted, thereby preventing further damage to the battery pack. The capacity loss caused by a short-term exceedance of the temperature threshold by a battery cell is negligible.

[0014] In a favorable manner, damage to individual battery cells during the charging process can be largely prevented, thus contributing to a reliable and efficient charging process. This is especially true considering the different aging paths of individual battery cells using the proposed method. Therefore, the margin between the theoretically maximum possible charging current and the calculated maximum possible charging current to keep individual battery cells undamaged can be reduced. This allows for the abandonment of complex adjustment methods that involve high parameterization costs and additional computational power required on the battery controller.

[0015] In a design scheme according to the first aspect, the first impedance characteristic value represents the first impedance characteristic at a first moment with respect to a first frequency. Furthermore, the second impedance characteristic value represents the same first impedance characteristic at the same first moment with respect to a second frequency different from the first frequency. Here, the first impedance characteristic represents the real part, imaginary part, amplitude, or phase of the complex alternating current impedance of a single battery cell. Similarly, the second impedance characteristic represents the real part, imaginary part, amplitude, or phase of the complex alternating current impedance of a single battery cell.

[0016] In a design scheme according to the first aspect, a first impedance characteristic value represents a first impedance characteristic at a first moment with respect to a first frequency. Furthermore, a second impedance characteristic value represents a second impedance characteristic different from the first impedance characteristic at the same first moment with respect to the same first frequency. Here, the first impedance characteristic represents the real part, imaginary part, amplitude, or phase of the complex alternating current impedance of a single battery cell. Similarly, the second impedance characteristic represents the real part, imaginary part, amplitude, or phase of the complex alternating current impedance of a single battery cell.

[0017] In one design according to the first aspect, step B1) includes step B1-1), in which a first measurement value is detected at a first moment and a first impedance characteristic value is determined by means of the first measurement value. The first measurement value here represents the complex alternating current impedance of a single battery cell.

[0018] Step B1) further includes steps B1-2), in which at least two second measurements at a second time different from the first time are detected, and a second impedance characteristic value with respect to the first time is determined by interpolation of the at least two second measurements. Here, the at least two second measurements each represent the complex alternating current impedance of a single battery cell.

[0019] Alternatively, in step B1-2), only the second measurement value at the first moment can be detected and the second impedance characteristic value can be determined by means of the second measurement value.

[0020] In a design scheme according to the first aspect, the charging operation is either fast charging operation or ultra-fast charging operation of the battery cells. Fast charging operation, for example, has a C rate of at least 2C. Ultra-fast charging operation, for example, has a C rate of at least 3C. However, the state of charge (SOC) can also be considered here. It is possible that at a low SOC, such as 20%, it is often possible to charge at 3C without problems, while at a higher SOC, such as 80%, this may not be possible without damage. Similarly, temperature applies, where, here at low temperatures <15°C, a reduction in current can be advantageous. However, fast charging can generally be discussed at an average C rate of 2C.

[0021] The descriptions made in the first aspect—unless otherwise stated—are used in the following text for the same concepts or similar characteristics.

[0022] According to a second aspect, the present invention relates to a method for charging or discharging a battery cell for an electric energy storage device.

[0023] In the method, in step A2), the battery cell is placed in a resting phase, in which no current is supplied to or drawn from the battery cell.

[0024] Therefore, in step B2) following step A2), the first impedance characteristic value and the second impedance characteristic value during the resting phase are determined. The first impedance characteristic value and the second impedance characteristic value here represent the complex alternating current impedance of the battery cell, respectively.

[0025] In step C2), which follows step B2), a first impedance characteristic value normalized with respect to a predetermined boundary condition is determined using the first impedance characteristic value, and a second impedance characteristic value normalized with respect to a predetermined boundary condition is determined using the second impedance characteristic value.

[0026] As a standardization of boundary conditions, this refers here and below to the conversion of impedance eigenvalues ​​to impedance eigenvalues ​​under normal operating conditions in a single battery cell. That is, it considers the decisive factors influencing the complex alternating current impedance of the battery cell, such as the cell's state of charge and temperature. Under normal conditions, this can be represented, for example, at a temperature of 25°C and a state of charge of 50%. The state of charge can also be referred to as the "State of Charge" (SoC).

[0027] Following step C2), in step D2), the changes in the standardized first impedance characteristic value I1 and the standardized second impedance characteristic value I2 are determined, and the change I1-I2 is determined in relation to a predetermined impedance change curve I. Ref First impedance reference value I Ref1With the second impedance reference value I Ref2 Change I Ref1 -I Ref2 The deviation |ΔI| = |(I1-I2)-(I Ref1 -I Ref2 )|.

[0028] Finally, in step E2), the charging and / or discharging curves are adapted such that the deviation |ΔI| exceeds a predetermined impedance threshold I. TH In this case, reduce the current to be supplied to or drawn from the battery cells. The predetermined impedance threshold I TH Exemplarily between 1 μQ and 5 μQ, especially 2.5 μQ.

[0029] As a predetermined impedance change curve I Ref In particular, it is important to understand the expected process of the complex alternating current impedance of a battery cell under normal operating conditions at a specific frequency, especially regarding the same impedance characteristics upon which the impedance characteristic value is based. Therefore, in lithium-ion based battery cells, a decrease in the real part of the complex alternating current impedance can be observed in the first 100 charging cycles; subsequently, the real part typically increases again. If the battery cell undergoes detrimental operation, a stronger increase or a less pronounced decrease in the real part may occur in the first charging cycle.

[0030] In other words, this aspect of the invention is based on the understanding that changes in the complex alternating current impedance of a battery cell during the resting phase can be used as an indicator of harmful operation. The operating limits of the battery cell can be adapted below, particularly regarding the charging and discharging of the battery cell. That is, it is also considered here that the complex alternating current impedance of the battery cell also changes during normal operation, however, this occurs through harmful currents, for example, relatively quickly or with the opposite sign.

[0031] In an advantageous manner, one can thus identify a single instance of damage to a battery cell based on the charging or discharging process and correspondingly prevent subsequent damage, thereby contributing to reliable and efficient charging and discharging.

[0032] In a design scheme according to the second aspect, the first impedance characteristic value represents the first impedance characteristic at a first moment with respect to a first frequency. Furthermore, the second impedance characteristic value represents the same first impedance characteristic at a second moment, different from the first moment, with respect to the same first frequency. Here, the first impedance characteristic represents the real part, imaginary part, amplitude, or phase of the complex alternating current impedance of a single battery cell. Similarly, the second impedance characteristic represents the real part, imaginary part, amplitude, or phase of the complex alternating current impedance of a single battery cell.

[0033] In a design scheme according to the first or second aspect, the first frequency is selected to be greater than 500Hz. Furthermore, the first frequency is selected to be greater than 500Hz. In particular, the first and second frequencies are between 500Hz and 10000Hz.

[0034] According to a third aspect, the present invention relates to an apparatus for charging or discharging individual battery cells of an electric energy storage device. The apparatus is designed herein to implement the methods according to the first and / or second aspects. The apparatus may also be referred to as a battery controller.

[0035] According to a fourth aspect, the present invention relates to a system comprising: an apparatus according to a third aspect, an energy storage device including at least one battery cell, and a measuring device coupled to the apparatus according to a third aspect and the at least one battery cell of the energy storage device and controllably designed to detect the complex alternating current impedance of the at least one battery cell and provide it as a measurement value to the apparatus according to a third aspect. The measuring device may be, exemplarily, an IC capable of determining the complex alternating current impedance of each battery cell with sufficient accuracy. Here, a resolution in the range of 1 μO to 2 μO is considered sufficiently accurate, and repeatability should advantageously be in the range of 2 μO to 5 μO. However, measurement unreliability should be significantly greater here. Because the method advantageously involves a conversion to another parameter (temperature), and these characteristic curves are specifically adapted to the battery cell and therefore the chip, system bias is again eliminated by the characteristic curves themselves.

[0036] In one design according to the fourth aspect, the energy storage device is a lithium-ion battery for an electric vehicle.

[0037] According to a fifth aspect, the present invention relates to an electric vehicle having a system according to a fourth aspect, an electric consumer, and a charging interface. The electric consumer and the charging interface are coupled herein to an electric storage device. The means according to a third aspect, included in the system according to a fourth aspect, is further designed to control the charging current to be supplied to the electric storage device through the charging interface. Alternatively or additionally, the means according to a third aspect, included in the system according to a fourth aspect, is designed to control the operating current to be obtained from the electric storage device used for the electric consumer.

[0038] According to a sixth aspect, the present invention relates to a computer program for charging or discharging individual battery cells of an electric energy storage device, having instructions that, when the computer program is implemented by a computer, cause the computer to implement the method according to the first and / or second aspects.

[0039] According to a seventh aspect, the present invention relates to a computer-readable storage medium on which a computer program according to a sixth aspect is stored. Attached Figure Description

[0040] Embodiments of the invention are described in more detail below with the aid of the illustrated drawings.

[0041] In the attached diagram:

[0042] Figure 1 An electric vehicle is shown, including a device for charging or discharging the battery cells of the electric energy storage device for the electric vehicle.

[0043] Figure 2 A method for charging individual battery cells of an electric vehicle's energy storage device is shown.

[0044] Figure 3 A method for charging or discharging battery cells of an electric vehicle's energy storage device is shown.

[0045] Figure 4 Showing according to Figure 2 and 3 An overview of the testing process for the method;

[0046] Figure 5 Showing according to the means Figure 2 Temperature estimation using descriptive methods;

[0047] Figure 6 Showing according to the means Figure 3 The curve depicting the change of the imaginary part of the method, the difference between the maximum values, and the difference between the minimum values;

[0048] Figure 7 Showing according to the means Figure 3 The curve depicting the change of the real part of the method, the difference between the maximum and minimum values; and

[0049] Figure 8 This shows the change in impedance of a single cell over multiple cycles. Detailed Implementation

[0050] Elements with the same structure or function are represented by the same reference numerals in each of the accompanying drawings.

[0051] Fast charging of lithium-ion batteries can be exemplarily implemented using predetermined charging profiles. To avoid damage to individual battery cells, time-dependent adaptation of the charging profile can be performed here. Other, more costly methods specify the use of models and adaptive tracking of these models (e.g., US 2011 / 0285356 A1). In the laboratory, the initial damage to individual battery cells during the charging process can be easily demonstrated through high-precision charging and discharging, and thus further damage to the battery pack can be prevented by converting the charging profile. The initial capacity loss here fluctuates in the per mille range.

[0052] When using predetermined curves and tracking of aging indicators, such as remaining capacity, the different aging paths of individual cells are not taken into account, especially since the internal resistance of individual cells does not depend reversibly on the remaining capacity.

[0053] Therefore, a safety margin must be established to ensure reliable and non-harmful charging of the battery throughout the entire aging process. More complex, model-based, and regulated charging methods require significant parameterization costs and additional computational power on the battery controller. High-precision charging and discharging of the entire battery bank in an electric vehicle is virtually impossible during operation and should not be demanded of users, as this severely limits the usability or readiness of the vehicle.

[0054] The use of novel measuring devices makes it possible to determine the impedance of individual battery cells with sufficient accuracy, thereby optimizing fast charging and enabling other diagnostics about degradation.

[0055] With the help of Figure 1 The apparatus 3 according to the present invention, as well as the corresponding system 10 and the electric vehicle 100, are shown for charging the battery cells of the electric energy storage device 1 of the electric vehicle 100.

[0056] In addition to the device 3 and the energy storage unit 1 comprising one or more battery cells, the system 10 also includes at least one measuring device 5, wherein at least one battery cell of the energy storage unit 1 is configured to be coupled to and from the measuring device 5. Specifically, it is conceivable that multiple battery cells of the energy storage unit 1 are connected to form a battery cell group and monitored by the measuring device 5. The measuring device 5 is further coupled to the device 3 and designed to provide the device with a measurement representing the complex alternating current impedance of the monitored battery cell.

[0057] In addition to system 10, electric vehicle 100 has an energy consumer 11 and a charging interface 13. The energy consumer 11 is particularly considered as one or more electric motors that are the drive unit of electric vehicle 100. The energy consumer 11 and the charging interface 13 are coupled to energy storage device 1.

[0058] The proposed method involves monitoring the complex alternating current impedance of individual battery cells in an electric vehicle during both the fast charging process and the resting phase. Frequency ranges greater than 500Hz have proven significant. Two temperatures, identical during normal battery cell operation, can be determined by calculating the real and imaginary parts of the complex alternating current impedance from the two battery cell temperatures. Figure 2 As illustrated in more detail in the flowchart, if the battery cells are charged with a harmful current, their temperatures deviate from each other, allowing charging to be stopped or the current reduced when a critical difference is exceeded. Furthermore, as by means of… Figure 3 As detailed in the flowchart, the change in the complex alternating current impedance during the rest phase can be used as an indicator for harmful operation, thereby allowing for adaptation to operating limits. Here, it is considered that the impedance of individual cells also changes during normal operation and changes more rapidly or even with the opposite sign during harmful operation.

[0059] The device 3 is configured with a data and program memory, on which at least one program is stored, which is then used by means of... Figure 2 and 3 The flowchart depicts the procedure.

[0060] according to Figure 2 The program begins in step A), where variables are initialized, for example. The program then continues in step A1), where the battery cells are placed into charging operation and charging current is supplied to the battery cells. Exemplarily, the start of the program is triggered in this regard by the coupling of the charging interface 13 to an external energy source.

[0061] The procedure then continues in step B1), where first and second impedance characteristic values ​​I1 and I2 are determined. For example, this is done by measuring device 5 detecting two measured values ​​M1 and M2 and providing them to device 3; these measured values ​​represent the complex alternating current impedance of a single battery cell at a first moment. The measured values ​​M1 and M2 are exemplarily measured simultaneously. Using… Figure 2 This deviates from the scenario where simultaneous measurements are impossible. Here, firstly (step B1-1) a first measurement value M1 is detected at a first moment, and a first impedance characteristic value I1 is determined using this first measurement value. Furthermore (step B1-2) at least two additional measurement values ​​M1 are detected. 2-1 M 2-2 (Preferably before and after the first moment) and provided to device 3, the two additional measurements also represent the complex alternating current impedance of a single battery cell. To determine the second impedance characteristic value I2, the additional measurement value M... 2-1 M 2-2 Interpolated to the same time base, so that a comparison with the first impedance characteristic value I1 at a common time can be achieved. The impedance characteristic values ​​I1 and I2 then serve as the basis for the comparison and for reporting whether the current must be reduced during fast charging.

[0062] The first impedance characteristic value I1 has one of the following impedance characteristics at a first moment with respect to a predetermined frequency: the real part, imaginary part, amplitude, or phase of the complex alternating current impedance of the battery cell.

[0063] In the first implementation variant, the second impedance characteristic value I2 has the same impedance characteristic with respect to another frequency at a first moment.

[0064] In the second implementation variant, the second impedance characteristic value I2 has a different impedance characteristic at the first moment with respect to the same predetermined frequency, in contrast to the second impedance characteristic value I2.

[0065] Therefore, in each case, two different impedance characteristics (real part, imaginary part, amplitude or phase) or the same impedance characteristics are involved at different frequencies.

[0066] The two impedance characteristic values ​​are, for example, the real and imaginary parts of an impedance measurement at a frequency of 3125 Hz, or, for example, two imaginary parts at different frequencies.

[0067] The procedure then continues in step C1), in which first and second temperature characteristic values ​​T1 and T2, representing the temperature of a single battery cell, are determined using impedance characteristic values ​​I1 and I2, respectively. The conversion of impedance values ​​to battery cell temperature is exemplarily performed with the aid of a look-up table (see, for example, DE 10 2013 103 921 A1).

[0068] The procedure then continues in step D1), in which the deviation of each temperature characteristic value T1, T2, |ΔT|=|T1-T2| is determined.

[0069] The procedure then continues in step E1), where, firstly (step E1-1), it is tested whether the determined deviation |ΔT| exceeds the predetermined temperature threshold T. TH .

[0070] If the test results show that the deviation |ΔT| exceeds the predetermined temperature threshold T TH If the condition is met, the program continues in step E1-2; otherwise, the program continues in step F1.

[0071] In steps E1-2), the charging current is reduced or the charging operation is interrupted. Then, in the subsequent step F), the method is terminated.

[0072] In step F1), the charging operation continues with an unchanged charging current or, if necessary, an increased charging current according to the charging curve. The procedure may then, exemplarily, continue in step B1 after a predetermined time period for further monitoring of the charging operation.

[0073] The impedance measurement during fast charging of an electric vehicle is exemplarily performed through the described procedure steps, and the results are obtained from the measured impedance and the function T. Re (Re(Z)) and T Im(Im(Z)) determines the internal temperature of a single battery cell. When the difference T Re -T Im greater than the temperature threshold T TH If necessary, the charging curve can be adapted. Furthermore, the function can be tracked during the thermal equilibrium phase (e.g., electric vehicle 100 stops after 20 minutes). It is also conceivable to apply the function to other operating ranges (e.g., high-rate discharge).

[0074] according to Figure 3 The program begins in step A), where variables are initialized, for example. The program then continues in step A2), where the battery cells are placed in a resting phase, and no charging current is supplied to the battery cells through charging interface 13, and no operating current is drawn from the battery cells to run the power consumer 11. Exemplarily, the start of the program is triggered in this respect by the end of the charging or operating process of the electric vehicle 100.

[0075] The procedure then continues in step B2), in which first and second impedance characteristic values ​​I1 and I2 are determined. For example, for this purpose, a first measured value M1 representing the complex alternating current impedance of a battery cell at a first moment and a second measured value M2 representing the complex alternating current impedance of a battery cell at a second moment are detected by measuring device 5 and provided to device 3. The measured values ​​M1 and M2 are measured simultaneously, exemplarily. The impedance characteristic values ​​I1 and I2 then serve as the basis for the comparison and for reporting whether the current must be reduced during fast charging.

[0076] The first impedance characteristic value I1 has one of the following impedance characteristics at a first moment with respect to a predetermined frequency: the real part, imaginary part, amplitude, or phase of the complex alternating current impedance of the battery cell.

[0077] The second impedance characteristic value I2 has the same impedance characteristic with respect to the same frequency at the second time.

[0078] Therefore, each case involves two identical impedance characteristics (real part, imaginary part, amplitude, or phase) at the same frequency at different times.

[0079] The two impedance characteristic values ​​are, for example, the two real or imaginary parts of an impedance measurement at a frequency of 781 Hz.

[0080] The procedure then continues in step C2), in which standardized first and second impedance characteristic values ​​are determined using impedance characteristic values ​​I1 and I2. , The standardized first and second impedance characteristic values ​​represent the complex alternating current impedance of a single battery cell under normal conditions of 25°C and 50% SOC, respectively. Based on this conversion, measurement data acquisition under vehicle stationary conditions (current = 0, temperature uniformity) is preferred.

[0081] The procedure then continues in step D2), in which, firstly (step D2-1), a standardized first impedance characteristic value is determined. With the standardized second impedance characteristic value Change Next, in step D2-2), the change is determined. With the predetermined impedance change curve I Ref First impedance reference value I Ref1 With the second impedance reference value I Ref2 Deviation of change The predetermined impedance change curve is, for example, derived from the expected impedance change curve.

[0082] In step D2), a comparison is made of the change in impedance value, for example, the real part, over time. Conversely, in step D1, a change can also occur here. The sign of the curve is reversed. If an opposite trend to the normal curve appears, damage to the battery cell can be inferred. The normal curve can here show a decrease in the real part during the first hundred cycles, followed by an increase.

[0083] The procedure then continues in step E2), where, firstly (step E2-1), a test is performed to determine whether the determined deviation |ΔI| exceeds a predetermined impedance threshold I. TH .

[0084] If the test results show that the deviation |ΔI| exceeds the predetermined impedance threshold I TH If the condition is met, the program continues in step E2-2; otherwise, the program continues in step F2.

[0085] In step E2-2), the charging and / or discharging profiles are adapted such that the maximum current to be delivered to the battery cell is reduced during subsequent charging, or the maximum current to be obtained from the battery cell is reduced during subsequent discharging. In the subsequent step F), the method then terminates.

[0086] In step F2), the charging and / or discharging curves continue unchanged. The procedure may then, exemplarily, continue in step A2 after a predetermined time period to enable further monitoring of the energy storage device, during which charging and / or driving operations of the electric vehicle can be performed.

[0087] Impedance measurement during the resting phase of an electric vehicle is exemplarily performed via the aforementioned procedural steps, wherein the impedance measurement is conducted under balanced conditions (idle voltage and temperature). Furthermore, the rate of change of impedance (real or imaginary part) and a comparison of said rate of change with a typical value can be made.

[0088] Overview of the testing process ( Figure 4 In the data, multiple fast charging cycles (P1-P10) with different intensities or damages with charging voltage U are shown at time t[data].

[0089] At a frequency of f=3125Hz, the real and imaginary parts are determined by... Figure 2 Temperature estimation by description method ( Figure 5 Curves 6, 9, and 10 show a strong deviation ΔT in temperature determined by the imaginary and real parts. sim Therefore, it can be inferred that the model used for estimation is insufficient compared to other curves, which may be attributed to the so-called "plating." Furthermore, it can be seen that curves P5 and P8 reach a higher deviation ΔT at the end of the charging process. sim .

[0090] With the help of Figure 6 (Left) shows the result at the frequency f=781Hz of curve P10, according to the method of... Figure 3 The development of the imaginary part of the method is described. When the maximum value is observed, the highest temperature T is obtained by referring to the curves respectively. The difference between the maximum values ​​within a period c is shown in the upper right for curves P1-P10. Here, as can be seen from curves P6, P9, and P10, the resistance Z changes strongly and opposite to the stated trend.

[0091] Curve P1 also shows the behavior of deviating from the normal during the temperature peak (artifact).

[0092] In observation Figure 6 At the minimum value (left), the lowest constant temperature T is obtained independently of the curve. The difference between the minimum values ​​within each period c is shown on the lower right for curves P1-P10. Here, the inductance typically increases (capacitance decreases), and the normal process corresponds to a continuous trend. In curves P6, P9, and P10, the impedance Z changes strongly and opposite to the trend.

[0093] With the help of Figure 7 (Left) shows the result at the frequency f=781Hz of curve P10, according to the method of... Figure 3The development of the real part of the method is described. When observing the maximum value, the lowest constant temperature T is obtained independently of the curve. The difference between the maximum values ​​within a period c is shown in the upper right for curves P1-P10. Here, the real part decreases over period c. Unlike the imaginary part in curve P6, no change in the opposite trend is observed here; only in curve P10 can a change in the opposite trend be determined.

[0094] During observation Figure 7 At the minimum value (left), the highest temperature T is obtained by referring to the curves respectively. The difference between the minimum values ​​within a period c for each curve P1-P10 is shown in the lower right. Here, for curves P6, P9, and P10, the real part within the curve increases.

[0095] With the help of Figure 8 The impedance Z is shown to change over multiple periods c.

[0096] Charging curves P1-P10 correspond to their respective numbers and undergo four cycles c, including three normal cycles in between (reference). Figure 4 ).

[0097] In a typical lithium-ion battery cell, a decrease in the real part is observed at high frequencies (781 Hz in this case) during the first cycle c, followed by an increase in the real part (depending on the specific cell, e.g., from 100 cycles c). If the cell is operating within a harmful range, the real part increases more strongly or decreases less strongly during the first cycle c. This is the case here for charging curves P8 and P10.

[0098] List of reference numerals

[0099] 100 electric vehicles

[0100] 1 accumulator

[0101] 3 devices

[0102] 5. Measuring device

[0103] 10 system

[0104] 11 Consumables

[0105] 13 charging ports

[0106] M1, M2, M 2-1 M 2-2 Measured values

[0107] I1, I2 impedance characteristic values

[0108] , Standardized impedance characteristic value

[0109] Temperature characteristic values ​​of T1 and T2

[0110] Temperature

[0111] |ΔT|、ΔT sim |ΔI| Deviation

[0112] I Ref1 I Ref2 Impedance reference value

[0113] I Ref Impedance variation curve

[0114] I TH Impedance threshold

[0115] U charging voltage

[0116] T time

[0117] C cycle

[0118] Z-impedance

[0119] P1-P10 charging curves

[0120] AF procedure steps

Claims

1. A method for charging a single battery cell of an electric energy storage device, the method comprising the following steps: A1) The battery cell is placed in charging operation, during which charging current is supplied to the battery cell. B1) Determine the first impedance characteristic value (I1) and the second impedance characteristic value (I2) during charging operation, wherein, The first impedance characteristic value (I1) and the second impedance characteristic value (I2) represent the complex alternating current impedance of a single battery cell, respectively, wherein step B1) has: B1-1) Detect the first measurement value (M1) at the first moment, wherein the first measurement value (M1) represents the complex alternating current impedance of the battery cell, and determine the first impedance characteristic value (I1) with the aid of the first measurement value (M1). B1-2) Detect at least two second measurements (M) at a second time point different from the first time point. 2-1 M 2-2 ), wherein the at least two second measurements (M) 2-1 M 2-2 ) represent the complex alternating current impedances of individual battery cells, and are determined by means of the at least two second measurements (M) 2-1 M 2-2 ) by measuring the at least two second measurements (M) 2-1 M 2-2 The interpolation of ) determines the second impedance characteristic value (I2) with respect to the first time. C1) A first temperature characteristic value (T1) is determined using a first impedance characteristic value (I1), and a second temperature characteristic value (T2) is determined using a second impedance characteristic value (I2), wherein the first temperature characteristic value (T1) and the second temperature characteristic value (T2) represent the temperature of a single battery cell, respectively. D1) Determine the deviation (|ΔT|) between the first temperature characteristic value (T1) and the second temperature characteristic value (T2). E1) When the deviation (|ΔT|) exceeds the predetermined temperature threshold (T) TH In the case of ), the charging current to the individual battery cells is reduced.

2. The method according to claim 1, wherein, - The first impedance characteristic value (I1) represents the first impedance characteristic with respect to the first frequency at the first moment, and - The second impedance characteristic value (I2) represents the same first impedance characteristic at the same first moment with respect to a second frequency different from the first frequency, where, - The first impedance characteristic and the second impedance characteristic respectively have the real part, imaginary part, amplitude or phase of the complex alternating current impedance of the battery cell.

3. The method according to claim 1, wherein, - The first impedance characteristic value (I1) represents the first impedance characteristic with respect to the first frequency at the first moment, and - The second impedance characteristic value (I2) represents a second impedance characteristic that differs from the first impedance characteristic at the same first moment with respect to the same first frequency, where, - The first impedance characteristic and the second impedance characteristic respectively have the real part, imaginary part, amplitude or phase of the complex alternating current impedance of the battery cell.

4. The method according to any one of claims 1 to 3, wherein, The charging operation is implemented as a fast or ultra-fast charging operation.

5. The method according to claim 2, wherein, The first and second frequencies are between 500Hz and 10000Hz.

6. A device (3) for charging individual battery cells of an electric energy storage device (1), wherein, The device (3) is designed to carry out the method according to any one of claims 1 to 5.

7. A computer program for charging individual battery cells of an electric energy storage device (1), comprising instructions that, when the computer program is executed by a computer, cause the computer to execute the method according to any one of claims 1 to 5.

8. A computer-readable storage medium on which a computer program according to claim 7 is stored.

9. A method for charging or discharging a battery cell in an electric energy storage device, the method comprising the following steps: A2) The battery cell is placed in a resting phase, during which no current is supplied to or drawn from the battery cell. B2) Determine the first impedance characteristic value (I1) and the second impedance characteristic value (I2) during the rest phase, wherein, The first impedance characteristic value (I1) and the second impedance characteristic value (I2) represent the complex alternating current impedance of a single battery cell, respectively. C2) Determine the first impedance characteristic value normalized with respect to the predetermined boundary conditions using the first impedance characteristic value (I1). ), and using the second impedance eigenvalue (I2) to determine the second impedance eigenvalue normalized with respect to the predetermined boundary conditions ( ), D2) Determine the standardized first impedance characteristic value ( ) and the standardized second impedance characteristic value ( ) change ( ), and determine the changes ( ) and the predetermined impedance change curve (I Ref The first impedance reference value (I) Ref1 ) and the second impedance reference value (I Ref2 The deviation of the change (|ΔI|). E2) Adapt the charging and / or discharging curves such that the deviation (|ΔI|) exceeds a predetermined impedance threshold (I TH In cases where the current to be supplied to or drawn from the battery cells is reduced, The conversion of impedance characteristic value to impedance characteristic value in the operation of a battery cell under normal conditions can be understood as a standardization of boundary conditions, which takes into account the charging state and temperature of the battery cell, which affect the complex alternating current impedance of the battery cell.

10. The method according to claim 9, wherein, - The first impedance characteristic value (I1) represents the first impedance characteristic with respect to the first frequency at the first moment, and - The second impedance characteristic value (I2) represents the same first impedance characteristic at a second time different from the first time with respect to the same first frequency, where, - The first impedance characteristic and the second impedance characteristic respectively have the real part, imaginary part, amplitude or phase of the impedance of the battery cell.

11. A device (3) for charging or discharging individual battery cells of an electric energy storage device (1), wherein, The device (3) is designed to carry out the method according to claim 9 or 10.

12. A system (10) comprising: an apparatus (3) according to claim 11, an energy storage device (1) including at least one battery cell, and a measuring device (5) coupled to the apparatus (3) and the energy storage device (1) and controllably designed to detect the complex alternating current impedance of the at least one battery cell and provide it as a measurement value to the apparatus (3).

13. The system (10) according to claim 12, wherein, The energy storage device (1) is configured as a lithium-ion battery for use in an electric vehicle (100).

14. An electric vehicle (100), the electric vehicle comprising: The device (3) comprises a system (10) according to claim 12 or 13, an energy consumer (11), and a charging interface (13), wherein the energy consumer (11) and the charging interface (13) are coupled to an energy storage device (1), and the device (3) is designed to control the charging current to be supplied to the energy storage device (1) through the charging interface (13) and / or the operating current to be obtained from the energy storage device (1) for the energy consumer (11).

15. A computer program for charging or discharging a battery cell of an electric energy storage device (1), having instructions that, when the computer program is executed by a computer, cause the computer to execute the method according to claim 9 or 10.

16. A computer-readable storage medium on which a computer program according to claim 15 is stored.

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