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

Abstract

A method (1) for charging a cell of an electrical energy storage device is presented, the method including: A1) transitioning the cell into a charging operation; B1) determining first and second impedance characteristic values ​​representing a complex AC impedance of one of the cells; C1) determining first and second temperature characteristic values ​​representing a temperature of the cell based on the impedance characteristic values; D1) determining a deviation of the temperature characteristic values; and E1) reducing a charging current of the cell if the deviation exceeds a predetermined temperature threshold. Additionally, still other methods, corresponding apparatuses (3), systems (10), electric vehicles (100), computer programs, and computer-readable storage media are also presented.

Description

[Technical field]

[0001] A method, apparatus, system, electric vehicle, computer program and storage medium for charging or discharging cells of an electric energy storage unit. [Background technology]

[0002] Rapid charging capabilities to charge electric vehicles faster are the subject of recent developments, where one or more battery cells of the electric vehicle are operated at their operating limits, which, if exceeded, could result in potential damage to each battery cell. Summary of the Invention [Problem to be solved by the invention]

[0003] The problem underlying the present invention is to establish an efficient and at the same time safe method for charging cells of an electric energy storage, which helps to avoid charging current intensities that are damaging to the cells, especially in (very) fast charging operations, without much computational control of the charging current. Also, an efficient and safe method for discharging the cells must be presented, and corresponding devices, systems, electric vehicles, computer programs and computer-readable storage media must be embodied for this method. [Means for solving the problem]

[0004] This problem is solved by the features of the independent claims. Advantageous embodiments are characterized in the subclaims.

[0005] According to a first aspect, the invention relates to a method for charging cells of an electric energy store, which may in particular be an energy store for electric vehicles, for example a lithium-ion based secondary battery. In this case, the energy store may in particular comprise a number of cells or a group of cells arranged in a battery pack. The methods described below on the basis of individual cells are also analogously applicable to a number of cells or a group of cells.

[0006] The method includes, in step A1), transitioning the cell into a charging operation in which a charging current is supplied to the cell.

[0007] Next, in step B1), which follows step A1), a first impedance characteristic value and a second impedance characteristic value are determined during the charging operation, each of the first impedance characteristic value and the second impedance characteristic value representing a complex AC impedance of the cell.

[0008] To determine the first and / or second impedance characteristic values, in particular, measurements representative of the complex AC impedance of the cell, respectively, may be obtained by, for example, applying an AC voltage signal to the cell, detecting time samples of the voltage and current data, windowing the voltage and current data over an appropriate time range, and performing a Fast Fourier Transform based on the windowed voltage and current data to determine voltage and current magnitudes at specific frequencies and to calculate the complex AC impedance of the cell therefrom.

[0009] A subsequent step C1) related to step B1) comprises determining a first temperature characteristic value based on the first impedance characteristic value and determining a second temperature characteristic value based on the second impedance characteristic value, wherein the first temperature characteristic value and the second temperature characteristic value are both representative of a temperature of the cell.

[0010] In particular, a look-up table can be used to determine the first and / or second temperature characteristic value. Such a look-up table contains, for example, one temperature characteristic value for each impedance characteristic value. As additional variables for determining the temperature characteristic value, for example the above-mentioned specific frequency and / or the state of charge of the cell can be used. Alternatively or additionally, an impedance index, in particular a real part, an imaginary part, an amplitude or a phase of the complex AC impedance of the cell, can be associated with the temperature characteristic value stored in the look-up table.

[0011] Step C1) is followed in a step D1) by determining the deviation |ΔT|=|T1−T2| of the first temperature characteristic value T1 from the second temperature characteristic value T2.

[0012] Finally, in step E1), the deviation |ΔT| is compared with a predetermined temperature threshold T TH If the temperature exceeds this threshold, the charge current to the cell is reduced. This temperature threshold may be, for example, between 1°C and 4°C, in particular 2°C.

[0013] This aspect of the invention is based on the finding that the two temperature characteristics are equal or nearly equal during normal cell use. However, when the cell is charged with a damaging current, the temperature characteristics diverge from each other because the charging operation has already altered the cell at this point, and the impedance-to-temperature model conditions are violated. Therefore, when a critical difference is exceeded, the current is reduced until the charging operation is completely stopped, to prevent further damage to the battery storage. The capacity loss of the cell caused by the temporary exceedance of the temperature threshold is then negligibly small.

[0014] Advantageously, this prevents significant damage to the battery cells due to the charging process, which contributes to a safe and at the same time efficient charging process. In particular, using the proposed method, different aging histories of the battery cells are taken into account. Thus, the margin between the theoretically maximum possible charging current and the calculated maximum possible charging current without any damage to the cells can be reduced. This allows to avoid complex controlled charging methods that are rather cumbersome to parameterize and require computational power from the battery control device.

[0015] In a configuration according to the first aspect, the first impedance characteristic value represents a first impedance index for a first frequency at a first time, and the second impedance characteristic value represents the same first impedance index for a second frequency different from the first frequency at the same first time, where the first impedance index refers to a real part, an imaginary part, an amplitude, or a phase of the complex AC impedance of the cell, and similarly, the second impedance index refers to one of a real part, an imaginary part, an amplitude, or a phase of the complex AC impedance of the cell.

[0016] In a configuration according to the first aspect, the first impedance characteristic value represents a first impedance index for a first frequency at a first time, and the second impedance characteristic value represents a second impedance index different from the first impedance index for the same first frequency at the same first time, where the first impedance index refers to a real part, an imaginary part, an amplitude, or a phase of the complex AC impedance of the cell. Similarly, the second impedance index refers to a real part, an imaginary part, an amplitude, or a phase of the complex AC impedance of the cell.

[0017] In a configuration according to the first aspect, step B1) includes a step B1-1) of detecting a first side position at a first time and determining a first impedance characteristic value based on a first measurement value, where the first measurement value represents a complex AC impedance of the cell.

[0018] Step B1) further includes step B1-2), in which at least two second measurements are detected at a plurality of second times different from the first time, and a second impedance characteristic value for the first time is determined based on the at least two second measurements by interpolating the at least two second measurements, where each of the at least two second measurements represents a complex AC impedance of one of the cells.

[0019] Alternatively, in step B1-2), only one second measurement value may be detected at the first time and the second impedance characteristic value may be determined based on this second measurement value.

[0020] In the embodiment according to the first aspect, the charging operation is a fast or ultra fast charging operation of the cell. A fast charging operation includes, for example, a C rate of at least 2C. An ultra fast charging operation includes, for example, a C rate of at least 3C. However, this may depend on the state of charge. That is, while at a low SOC, for example 20%, charging at 3C is often possible without problems, at a higher SOC, for example 80%, such charging may not be possible without damage. Something similar applies to temperature, where at low temperatures below 15°C it may be useful to reduce the current. Generally, however, a fast charge may refer to an average charging rate of 2C. The explanations given in relation to the first aspect apply in the following to the same terms or similar features, unless otherwise specified.

[0021] According to a second aspect, the invention relates to a method for charging or discharging a cell of an electrical energy store.

[0022] The method includes, in step A2), transferring the cell into a rest phase during which no current is supplied to or extracted from the cell.

[0023] Step A2) is followed by a step B2) in which a first characteristic impedance value and a second characteristic impedance value are determined during the rest phase, the first characteristic impedance value and the second characteristic impedance value now both representing a complex AC impedance of one of the cells.

[0024] In a subsequent step C2) related to step B2), a first impedance characteristic value (first normalized impedance characteristic value) normalized with respect to a predetermined boundary condition is determined based on the first impedance characteristic value, and a second impedance characteristic value (second normalized impedance characteristic value) normalized with respect to the predetermined boundary condition is determined based on the second impedance characteristic value.

[0025] Normalization with respect to boundary conditions means, here and below, that the impedance characteristic values ​​mentioned above are converted to impedance characteristic values ​​during cell operation under normal conditions, i.e. taking into account important factors that affect the complex AC impedance of the cell, such as the cell temperature and state of charge. Normal conditions may for example mean operation of the cell at a temperature of 25° C. and at a state of charge of 50%. The state of charge is sometimes referred to as the “State of Charge” (SoC).

[0026] Following step C2), in step D2), a change in the first normalized impedance characteristic value I1 relative to the second normalized impedance characteristic value I2 is determined, and a time-dependent impedance characteristic I of the change I1-I2 is calculated. Ref The first impedance reference value I Ref1 The second impedance reference value I Ref2 Change in I Ref1 -I Ref2 Deviation from |ΔI|=|(I1-I2)-(I Ref1 -I Ref2 )| is determined.

[0027] Finally, in step E2), the deviation |ΔI| is adjusted to a predetermined impedance threshold I THIf the impedance exceeds a predetermined impedance threshold I, the charge and / or discharge profile is adjusted to reduce the current supplied to or drawn from the cell. TH is for example between 1 μΩ and 5 μΩ, in particular 2.5 μΩ.

[0028] A given time-varying impedance I Ref By "complex impedance over time" is meant, in particular, the expected change over time of the complex AC impedance for a particular frequency for a cell operating under normal conditions, and in particular, the expected change over time of the complex AC impedance for the same impedance index based on the impedance characteristic value. In that regard, for a lithium-ion based battery cell, a decrease in the real part of the complex AC impedance is observed during the first 100 charge cycles, after which the real part typically increases again. If the cell is subjected to damaging operations, the real part may increase relatively rapidly or decrease somewhat more slowly during the first charge cycles.

[0029] In other words, this aspect of the invention is based on the knowledge that, from the observation of the complex AC impedance of the cell during the rest phase, the change in the complex AC impedance can be used as an indicator of damaging operation, which in the following makes it possible to adjust the operating limits of the cell, in particular with regard to the charging and discharging of the cell, and in which it is also taken into account that the complex AC impedance of the cell also changes during normal operation, but that the change occurs, for example, relatively quickly or with a reversed sign, when a damaging current is applied.

[0030] Advantageously, this can detect any damage to the battery cells once it has occurred due to the charging or discharging process and prevent subsequent damage accordingly, thereby facilitating safe and efficient charging and discharging.

[0031] In a configuration according to the second aspect, the first impedance characteristic value represents a first impedance index for a first frequency at a first time, and the second impedance characteristic value represents the same first impedance index for the same first frequency at a second time different from the first time, where the first impedance index refers to a real part, an imaginary part, an amplitude, or a phase of the complex AC impedance of the cell. Similarly, the second impedance index refers to one of a real part, an imaginary part, an amplitude, or a phase of the complex AC impedance of the cell.

[0032] In the embodiment according to the first or second aspect, the first frequency is selected to be greater than 500 Hz. Also, the first frequency is selected to be greater than 500 Hz. In particular, the first and second frequencies are between 500 Hz and 10,000 Hz.

[0033] According to a third aspect, the invention relates to an apparatus for charging or discharging cells of an electrical energy store, the apparatus then being configured to carry out a method according to the first and / or second aspect, the apparatus sometimes being called a battery control device.

[0034] According to a fourth aspect, the invention relates to a system comprising the device according to the third aspect, an electrical energy store with at least one cell, and a measuring device connected to the device according to the third aspect and to the at least one cell of the electrical energy store and controllably configured to detect the complex AC impedance of the at least one cell and provide it as a measured value to the device according to the third aspect. The measuring device may for example be an IC capable of determining the complex AC impedance of the individual battery cells with sufficient accuracy. Considered to be sufficiently accurate here is a resolution in the range of 1 μΩ to 2 μΩ, the reproducibility should advantageously be in particular in the range of 2 to 5 μΩ. However, the measurement uncertainty may then obviously be larger. The method advantageously includes a conversion to other variables (temperature) and these characteristic curves are adapted cell-specifically and thus chip-specifically, so that systematic deviations via the characteristic curves themselves are again eliminated.

[0035] In an embodiment according to the fourth aspect, the electrical energy storage unit is a lithium ion battery for an electric vehicle.

[0036] According to a fifth aspect, the invention relates to an electric vehicle comprising a system according to the fourth aspect, an electrical consumer and a charging interface, the electrical consumer and the charging interface being connected to an electrical energy storage. The system according to the fourth aspect also comprises an apparatus according to the third aspect, which is adapted to control a charging current supplied to the electrical energy storage via the charging interface. Alternatively or additionally, the system according to the fourth aspect also comprises an apparatus according to the third aspect, which is adapted to control an operating current drawn for the electrical consumer from the electrical energy storage.

[0037] According to a sixth aspect, the present invention relates to a computer program for charging or discharging cells of an electrical energy storage comprising instructions which, when executed by a computer, cause the computer to carry out the method according to the first and / or second aspect.

[0038] According to a seventh aspect, the present invention relates to a computer readable storage medium having stored therein a computer program according to the seventh aspect.

[0039] In the following, an embodiment of the invention will be explained in detail with reference to the schematic drawings. [Brief description of the drawings]

[0040] [Figure 1] 1 shows an electric vehicle equipped with a device for charging or discharging cells of an electric energy storage of the electric vehicle; [Diagram 2] FIG. 1 illustrates a method for charging cells of an electric vehicle's electric energy storage. [Diagram 3] FIG. 1 illustrates a method for charging or discharging cells of an electric vehicle's electric energy storage. [Figure 4] FIG. 4 shows an overview of the testing process of the method according to FIGS. 2 and 3. [Diagram 5] FIG. 3 illustrates the estimation of temperature according to the method described with reference to FIG. 2. [Figure 6] 4 is a diagram showing the transition of the imaginary part, the difference in the maximum value, and the difference in the minimum value according to the method described with reference to FIG. 3. FIG. [Figure 7] 4 is a diagram showing the transition of the real part, the difference in the maximum value, and the difference in the minimum value according to the method described with reference to FIG. 3. FIG. [Figure 8] FIG. 13 shows the change in impedance of a cell over multiple cycles. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0041] Components of the same structure or function are labeled with the same reference numerals throughout the figures.

[0042] Fast charging of lithium-ion based batteries can be performed, for example, with a predefined charging profile. The charging profile can then be adjusted depending on the age in order to avoid damage to the battery cells. Another, more sophisticated method is to use models and adaptive tracking of the models (e.g. US 2011 / 0285356 A1). In the laboratory, one-time damage to the battery cells due to the charging process can be easily identified by very precise charging and discharging, so that further damage to the battery reservoir can be prevented by modifying the charging profile. This one-time capacity loss can then vary in the range of parts per thousand.

[0043] When using a predefined profile and tracking with aging indicators such as remaining capacity, the various aging processes of the cell are not taken into account, especially since the internal resistance of the cell is not uniquely and inversely dependent on the remaining capacity.

[0044] A margin must be provided to guarantee a safe and damage-free charging for all ageing processes. Relatively complex and controlled model-based charging methods require a high degree of parameterization effort and additional computing power in the battery control unit. Precise charging and discharging of the entire energy store of an electric vehicle is hardly possible during operation and cannot be imposed on the user of the electric vehicle, since this would severely limit the possibility or readiness of the electric vehicle to be used.

[0045] Using new types of measurement devices, the impedance of the cells can be determined with sufficient accuracy to optimize fast charging and perform further diagnostics regarding degradation.

[0046] With reference to FIG. 1, an apparatus 3 according to the invention for charging cells of an electric energy storage 1 of an electric vehicle 100 as well as a corresponding system 10 and electric vehicle 1 are shown.

[0047] In addition to the device 3 and the energy store 1 with one or more cells, the system 10 comprises at least one measuring device 5, to which at least one of the cells of the energy store 1 is assigned and connected. In particular, it is conceivable that the cells of the energy store 1 are connected to a group of cells, which are monitored by the measuring device 5. The measuring device 5 is also connected to the device 3 and is arranged to provide said device with measurements representative of the complex AC impedance of the cell(s) under monitoring.

[0048] In addition to the system 10, the electric vehicle 100 comprises an electricity consumer 11 as well as a charging interface 13. The electricity consumer 11 can in particular be one or more electric motors of the drive of the electric vehicle 100. The electricity consumer 11 as well as the charging interface 13 are connected to an energy store 1.

[0049] It is proposed to monitor the complex AC impedance of the cells in an electric vehicle during the fast charging process and also during the rest phase. In this case, the frequency range above 500 Hz has proven useful. By calculating the two cell temperatures from the real and imaginary parts of the complex AC impedance, it is possible to identify two temperatures that are the same during normal use of the cell. When the cell is charged with a damaging current, these temperatures will deviate from each other, so that charging can be stopped or the current reduced if a critical difference is exceeded, as will be explained in more detail below with reference to the flow chart of FIG. 2. Furthermore, from the observation of the complex AC impedance during the rest phase, the change in the complex AC impedance can be used as an indicator of damaging operations, so that the operating limits can be adjusted, as will be explained in more detail below with reference to the flow chart of FIG. 3. It is taken into account here that the impedance of the cell changes even during normal operation and changes more rapidly or even with a reversed sign when a damaging operation is involved.

[0050] The device 3 has associated therewith a data memory and a program memory in which is stored at least one of the programs described below with reference to the flow charts of FIGS.

[0051] The program according to Fig. 2 starts in step A), in which variables are for example initialized. The program then continues in step A1), in which the cell is put into charging operation and a charging current is supplied to the cell. For example, the start of the program is triggered in this context by connecting the charging interface 13 to an external energy source.

[0052] The program then continues with step B1), in which a first and a second impedance characteristic value I1, I2 are determined. For example, for this purpose, two measured values ​​M1, M2, which represent the complex AC impedance of the cell at a first time, are detected by the measuring device 5 and provided to the device 3. For example, the measured values ​​M1, M2 are measured simultaneously. With reference to FIG. 2, an alternative case is shown in which simultaneous measurements are not possible. In this case, first (step B1-1)), a first measured value M1 is detected at a first time, on the basis of which a first impedance characteristic value I1 is determined. Also (step B1-2)), at least two further measured values ​​M1, which also represent the complex AC impedance of the cell, are detected. 2-1 ,M 2-2 is detected (preferably around the first time) and provided to the device 3. Further measured values ​​M 2-1 ,M 2-2 are interpolated to the same time basis so that they can be compared with the first impedance characteristic value I1 at a common time. The impedance characteristic values ​​I1 and I2 are used below as a basis for comparison and as a basis for determining whether the current needs to be reduced during fast charging.

[0053] The first impedance characteristic value I1 has one of the following impedance indices for a given frequency at a first time: real part, imaginary part, magnitude or phase of the complex AC impedance of the cell.

[0054] In a first embodiment, the second impedance characteristic value I2 has the same impedance index for another frequency at a first time.

[0055] In contrast, in the second embodiment, the second impedance characteristic value I2 has a different impedance index for the same predetermined frequency at a first time.

[0056] Thus, either way, one is dealing with two different impedance indices (Re (real part), Im (imaginary part), Abs (magnitude) or phase) or the same impedance indices at different frequencies.

[0057] The two impedance characteristic values ​​may for example be the real and imaginary parts of an impedance measurement at a frequency of 3125 Hz, or for example two imaginary parts at different frequencies.

[0058] The program then continues with step C1), in which first and second temperature characteristic values ​​T1, T2, both representative of the temperature of the cell, are determined based on the impedance characteristic values ​​I1, I2. The impedance values ​​are converted to the cell temperature, for example, using a look-up table (see for example DE 10 2013103921 A1).

[0059] The program then continues with step D1), in which the deviation |ΔT|=|T1-T2| of the temperature characteristic values ​​T1, T2 is determined.

[0060] The program then continues with step E1), in which the determined deviation |ΔT| is first compared (step E1-1) with a predefined temperature threshold T TH It is checked whether it exceeds

[0061] This check ensures that the deviation |ΔT| does not exceed the given temperature threshold T TH If so, the program continues at step E1-2, otherwise the program continues at step F1.

[0062] In step E1-2) the charging current is reduced or the charging operation is stopped. In the following step F) the method ends.

[0063] In step F1), the charging operation continues with the same or possibly increased charging current depending on the charging profile. The program then continues in step B1, for example after a predefined period of time, in order to continue to monitor the charging operation.

[0064] For example, the above program steps may be used to measure impedance during fast charging of an electric vehicle, and to compare the measured impedance with a function T Re (Re(Z)) and T Im The temperature in each cell is determined from (Im(Z)). The difference T Re -T Im is the temperature threshold T TH If it is greater, the charging profile is adjusted. Also, tracking of the function can be performed during the thermal equilibrium phase (e.g., the electric vehicle 100 has been stationary for 20 minutes). Generalization of the function to other operating regions (e.g., high-speed discharge) is also conceivable.

[0065] The program according to Fig. 3 starts in a step A), in which variables are for example initialized. The program then continues in a step A2), in which the cell is transferred to a rest phase, in which no charging current is supplied to the cell via the charging interface 13 and no operating current is drawn for operating the electricity consumers 11. For example, the start of the program is triggered in this context by the end of a charging process or an operating process of the electric vehicle 100.

[0066] The program then continues with step B2), in which the first and second impedance characteristic values ​​I1, I2 are determined. For example, for this purpose, a first measured value M1, which represents the complex AC impedance of the cell at a first time, and a second measured value M2, which represents the complex AC impedance of the cell at a second time, are determined by the measuring device 5 and provided to the device 3. For example, the measured values ​​M1, M2 are measured simultaneously. The impedance characteristic values ​​I1, I2 are used in the following as a basis for comparison and as a basis for determining whether the current needs to be reduced during fast charging.

[0067] The first impedance characteristic value I1 has one of the following impedance indices for a given frequency at a first time: real part, imaginary part, magnitude or phase of the complex AC impedance of the cell.

[0068] The second impedance characteristic value I2 has the same impedance index for the same frequency at a second time.

[0069] Thus, in any case, we are dealing with two identical impedance indices (Re (real part), Im (imaginary part), Abs (amplitude) or phase) at the same frequency at different times.

[0070] The two impedance characteristic values ​​are, for example, the real and imaginary parts of an impedance measurement at a frequency of 781 Hz.

[0071] The program then continues with step C2), in which first and second normalized impedance characteristic values ​​I^1, I^2 are determined based on the impedance characteristic values ​​I1, I2, which respectively represent the complex AC impedance of the cell at normal conditions of 25° C. and 50% SOC. Based on this conversion, it is preferable to record the measurements when the vehicle is stopped (current=0, temperature uniform).

[0072] The program then continues with step D2), where first (step D2-1)) a change amount ΔI^=I^1-I^2 of the first normalized impedance characteristic value I^1 relative to the second normalized impedance characteristic value I^2 is determined. Next, in step D2-2), a predetermined time-varying impedance I^ that is approximately obtained from the expected time-varying impedance of this change amount ΔI^ is calculated. Ref The first impedance reference value I Ref1 The second impedance reference value I Ref2 Deviation from the change in |ΔI|=|ΔI^-(I Ref1 -I Ref2 )| is determined.

[0073] In step D2) a comparison of the change in impedance values ​​over time is made, for example of the real part. In contrast to step D1, here the sign of the change ΔI^ can also be reversed. If another trend contrary to the normal aging appears, damage to the cell can be concluded. Here, the normal aging may show a decrease in the real part in the first 100 cycles and an increase only afterwards.

[0074] The program then continues with step E2), in which it is determined first (step E2-1)) whether the determined deviation |ΔI| is greater than or equal to a predetermined impedance threshold I TH It is checked whether it exceeds

[0075] This check ensures that the deviation |ΔI| does not exceed a given impedance threshold I TH If so, the program continues at step E2-2, otherwise the program continues at step F2.

[0076] In step E2-2) the charge and / or discharge profile is adjusted such that the maximum current supplied to the cell in a subsequent charging process or the maximum current taken from the cell in a subsequent discharging process is reduced. In the following step F) the method is terminated.

[0077] In step F2) the charging and / or discharging profile continues unchanged. The program may then continue in step A2 after a period during which driving and / or charging operation of the electric vehicle may be performed, for example to allow further monitoring of the energy store.

[0078] For example, the above-mentioned program steps allow an impedance measurement to be performed during a rest phase of the electric vehicle, the impedance being measured under equilibrium conditions (open circuit voltage and temperature), and the rate of change of the impedance (real or imaginary part) can be determined and compared with a normal value.

[0079] The overview of the test process (Figure 4) shows several fast charging cycles (P1-P10) [multiple data] with different magnitudes of charging voltage U or different potential for damage, versus time t.

[0080] According to the temperature estimation from the real and imaginary parts at frequency f = 3125 Hz by the method described with reference to Fig. 2 (Fig. 5), profiles 6, 9 and 10 show the deviation ΔT of the temperature determined separately from the imaginary and real parts. sim From this, it can be concluded that the model used for the estimation is insufficient compared to the other profiles, which is probably due to the so-called “plating”. Also, profiles P5 and P8 show a relatively large deviation ΔT just before the end of charging. sim It can be seen that this has been achieved.

[0081] With reference to FIG. 6 (left), the change over time of the imaginary part of profile P10 at frequency f=781 Hz is shown, according to the method described with reference to FIG. 3. Focusing on the maximum values, the maximum temperature T is obtained depending on the profile. The difference in the maximum values ​​within one cycle c for profiles P1-P10 is shown in the upper right. Here, it can be seen that the impedance Z changes rapidly against the trend in profiles P6, P9 and P10.

[0082] Profile P1 also exhibits non-standard characteristics at the temperature peaks (artifacts).

[0083] If we look at the minima in Fig. 6 (left), we see that a constant minimum temperature T is obtained, regardless of the profile. The difference in the minima within one cycle c for profiles P1-P10 is shown in the bottom right. Here, the inductance generally increases (capacitance decreases) and the usual time evolution corresponds to a continuous trend. For profiles P6, P9 and P10, the impedance Z changes abruptly, counter to the trend.

[0084] With reference to FIG. 7 (left), the evolution over time of the real part of profile P10 at frequency f=781 Hz is shown, according to the method described with reference to FIG. 3. If we focus on the maximum, we obtain a constant minimum temperature T, regardless of the profile. The difference in the maximum value within one cycle c for profiles P1-P10 is shown at the top right. Here, the real part decreases over several cycles c. In contrast to the imaginary part in profile P6, here no trend change is observed, which can only be identified in profile P10.

[0085] Focusing on the minimum values ​​in Fig. 7 (left), the maximum temperature T is obtained depending on the profile. The difference in the minimum values ​​within one cycle c for profiles P1-P10 is shown in the lower right. Here, for profiles P6, P9 and P10, the real part within one profile increases.

[0086] Referring to FIG. 8, the change in impedance Z over several cycles c is shown.

[0087] Charging profiles P1-P10 were run for four cycles each according to their numbers, with three normal cycles each in between (see Figure 4).

[0088] Typically, lithium-ion cells will show a high frequency (here 781 Hz) decrease in the real part in the first cycle c, followed by an increase in the real part again (e.g. after 100 cycles c, depending on the cell). If the cell is operated in the damaging range, the real part will increase relatively rapidly in the first cycle c, or decrease less rapidly. This is the case for charging profiles P8 and P10. [Explanation of symbols]

[0089] 100 Electric Vehicles 1 Energy storage unit 3 equipment 5. Measuring Equipment 10. System 11 Consumption Department 13 Charging interface M1, M2, M 2-1 ,M 2-2 Measurements I1, I2 impedance characteristic values I^1, I^2 normalized impedance characteristic values T1, T2 temperature characteristic values T temperature |ΔT|,ΔT sim |ΔI| Deviation I Ref1 ,I Ref2 Impedance Reference Value I Ref Time-dependent impedance I TH Impedance Threshold U Charging voltage t time c-cycle Z impedance P1-P10 charging profile AF Program Step

Claims

1. 1. A method of charging a cell of an electrical energy storage device, comprising the steps of: A1) transitioning the cell to a charging operation in which a charging current is supplied to the cell; B1) A first impedance characteristic value (I １ ) and a second impedance characteristic value (I ２ ) and determining a first impedance characteristic value (I １ ) and the second impedance characteristic value (I ２ ) each represents the complex AC impedance of one of the cells, C1) First impedance characteristic value (I １ ) based on a first temperature characteristic value (T １ ) and a second impedance characteristic value (I ２ ) based on the second temperature characteristic value (T ２ ) and determining a first temperature characteristic value (T １ ) and the second temperature characteristic value (T ２ ) each represents a temperature of the cell, and D1) a first temperature characteristic value (T １ ) the second temperature characteristic value (T ２ ) (|ΔT|), E1) The deviation (|ΔT|) is a predetermined temperature threshold (T ＴＨ ) the charge current to the cell is reduced The method has the steps.

2. 2. The method of claim 1 , - first impedance characteristic value (I １ ) represents a first impedance index for a first frequency at a first time; - second impedance characteristic value (I ２ ) represents the same first impedance index at the same first time for a second frequency different from the first frequency, the first impedance index and the second impedance index each have a real part, an imaginary part, an amplitude or a phase of the complex AC impedance of the cell; method.

3. 2. The method of claim 1 , - first impedance characteristic value (I １ ) represents a first impedance index for a first frequency at a first time; - second impedance characteristic value (I ２ ) represents a second impedance index different from the first impedance index for the same first frequency at the same first time, the first impedance index and the second impedance index each have a real part, an imaginary part, an amplitude or a phase of the complex AC impedance of the cell; method.

4. 4. A method according to any one of claims 1 to 3, comprising: Step B1) is B1-1) A first measurement value (M １ ) and detect a first measurement value (M １ ) represents the complex AC impedance of the cell, the first measurement of which (M １ ) based on a first impedance characteristic value (I １ ) is determined, B1-2) At least two second measurement values ​​(M ２－１ , M ２－２ ) and detecting at least two second measurements (M ２－１ , M ２－２ ) each represents a complex AC impedance of one of the cells, and at least two second measurements (M ２－１ , M ２－２ ) to obtain at least two second measurements (M ２－１ , M ２－２ ) based on the second impedance characteristic value (I ２ ) to determine The method includes:

5. 5. A method according to any one of claims 1 to 4, comprising: The charging operation is performed as a fast charging operation or an ultra fast charging operation. method.

6. 1. A method of charging or discharging a cell of an electrical energy storage device, comprising the steps of: A2) transitioning the cell into a rest phase in which no current is supplied to or drawn from the cell; B2) A first impedance characteristic value (I １ ) and a second impedance characteristic value (I ２ ) and determining a first impedance characteristic value (I １ ) and the second impedance characteristic value (I ２ ) each represents the complex AC impedance of one of the cells, C2) the first impedance characteristic value (I １ ) and the second impedance characteristic value (I 2 ), a first normalized impedance characteristic value (I^ １ ) and the second normalized impedance characteristic value (I ２ ) is determined, D2) First normalized impedance characteristic value (I^ １ ) the second normalized impedance characteristic value (I ２ ) and determining a change (ΔI^) in impedance (I Ｒｅｆ ) the first impedance reference value (I Ｒｅｆ１ ) the second impedance reference value (I Ｒｅｆ２ ) deviation (|ΔI|) from the change in E2) The deviation (|ΔI|) is a predetermined impedance threshold (I ＴＨ ) the charge and / or discharge profile is adjusted to reduce the current supplied to or drawn from the cell. The step includes: a first impedance characteristic value (I 1 ) representing a first impedance index for a first frequency at a first time; a second impedance characteristic value (I 2 ) representing the same first impedance index for the same first frequency at a second time instant different from the first time instant; the first impedance index (I 1 ) and the second impedance index (I 2 ) respectively comprise the real part, the imaginary part, the magnitude or the phase of the impedance of the cell; method.

7. 7. A method according to any one of claims 1 to 6, comprising: The first frequency and the second frequency are between 500 Hz and 10,000 Hz. method.

8. A device (3) for charging or discharging cells of an electrical energy storage (1), comprising: Configured to carry out a method according to any one of claims 1 to 7 Device (3).

9. 9. The device (3) according to claim 8, an electric energy storage (1) with at least one cell, and a measuring device (5) connected to the device (3) and to the electric energy storage (1) and controllably configured to detect the complex AC impedance of the at least one cell and provide the complex AC impedance of the at least one cell as a measured value to the device (3). A system (10) having:

10. 10. The system (10) according to claim 9, wherein the electrical energy storage (1) is configured as a lithium-ion battery for an electric vehicle (100).

11. An electric vehicle (100) comprising a system (10) according to any one of claims 9 or 10, an electric consumer (11) and a charging interface (13), the electric consumer (11) and the charging interface (13) being connected to an electric energy storage unit (1), and the device (3) being configured to control a charging current supplied to the electric energy storage unit (1) via the charging interface (13) and / or an operating current drawn from the electric energy storage unit (1) for the electric consumer (11).

12. A computer program for charging or discharging cells of an electric energy store (1), comprising instructions which, when executed by a computer, cause the computer to carry out a method according to any one of claims 1 to 7.

13. A computer readable storage medium having stored therein the computer program according to claim 12.

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