Method for controlling and charging a battery, control unit, charging system, battery system and working device

Abstract

Method for controlling charging and in particular a main charging current (I = ) for charging a battery unit (10) based on a battery chemistry with intercalation reaction, with the steps: (i) Providing an alternating current signal as a test signal (I ≈ ), (ii) Applying the test signal (I ≈ ) by superimposing the main charging current (I=) with the test signal (I ≈ ) to a total charging current (I Lade ), (iii) detecting and evaluating a current / voltage response (U) of the battery unit (10) with respect to the test signal (I ≈ ) and (iv) setting a strength and / or a time profile of at least the main charging current (I=) depending on a result of the evaluation, in which, during the evaluation, it is checked whether, which and / or to what extent the current / voltage response (U) of the battery unit (10) or a signal representative thereof in relation to the test signal (I ≈ ) distortions and in particular harmonic distortions, and in which the intensity of the main charging current (I = ) - is increased as long as there is no distortion of the current / voltage response (U) of the battery unit (10) or of the signal representative thereof with respect to the test signal (I ≈ ) does not yet occur or - in particular with regard to an amplitude - is below a certain level, in particular a threshold value, and / or - is reduced until a distortion of the current / voltage response (U) of the battery unit (10) or of the signal representative thereof with respect to the test signal (I ≈) no longer occurs or - in particular with regard to an amplitude - is below a level specified, in particular by a threshold value.

Description

[0001] The present invention relates to a method for controlling the charging and in particular a charging current for charging a battery unit based on a battery chemistry with an intercalation reaction, a method for charging such a battery unit, a control unit for controlling the charging, a charging system, a battery system and a working device and in particular a vehicle.

[0002] Recently, battery systems have been increasingly used to power work equipment and, in particular, vehicles. Lithium-ion battery units are particularly important due to their high energy density and capacity. Safety issues are problematic with such battery units, which must also be considered in connection with charging. Depending on the ambient and operating conditions, as well as the age of the respective battery unit, the applied charging current must not exceed a certain maximum limit to prevent lithium deposition on the anode, a process known as lithium plating.

[0003] The invention is based on the object of providing a method for controlling the charging and in particular a charging current for charging a battery unit based on a battery chemistry with an intercalation reaction, a method for charging such a battery unit, a control unit for controlling the charging, a charging system, a battery system and a working device and in particular a vehicle, in which the charging of a battery unit based on lithium-ion chemistry can be designed particularly effectively in a flexible manner using particularly simple means, in particular in order to keep the charging time as short as possible.

[0004] The object underlying the invention is alternatively achieved by the subject matter having the features of one of claims 1 and 8 to 12. Advantageous further developments are the subject matter of the respective dependent claims.

[0005] According to a first aspect of the present invention, a method for controlling the charging and in particular a main charging current for charging a battery unit based on a battery chemistry with intercalation reaction and in particular on a lithium ion chemistry is provided, which method comprises the steps (i) Providing an alternating current signal as a test signal, (ii) applying the test signal to the battery unit by superimposing the main charging current with the test signal to form a total charging current to be supplied or supplied to the battery unit, (iii) detecting and evaluating a current / voltage response of the battery unit with respect to the test signal or a signal representative thereof and (iv) Adjusting a strength and / or a temporal profile of at least the main charging current depending on a result of the evaluation. The measures provided according to the invention make it possible to derive, in particular, properties of the battery unit with regard to the charging process from the evaluation of the current / voltage response or a signal representative thereof, in order, for example, to adjust a maximum charging current and / or the temporal profile of the charging current accordingly.

[0006] There are many options available for evaluating the current / voltage response of the battery unit to the test signal.

[0007] In a further development of the method according to the invention, the evaluation includes checking whether and / or to what extent the current / voltage response of the battery unit or a signal representative thereof exhibits distortions, particularly harmonic distortions, with respect to the test signal. The type and / or degree of distortion can be used to derive the internal status of the battery unit, particularly with regard to a charging process to be performed, and to adjust the charging current accordingly. A qualitative check can also be performed to determine which distortions occur.

[0008] In another alternative or additional embodiment of the method according to the invention, it is checked whether and / or to what extent the current / voltage response of the battery unit or a signal representative thereof with respect to the underlying test signal exhibits harmonics.

[0009] A respective measure can be compared with one or more predefined threshold values.

[0010] The measure indicating whether and, if so, to what extent the current / voltage response of the battery unit or a signal representative thereof carries distortions and in particular harmonics with respect to the test signal can be determined in different ways, for example isolated and local, cumulative and / or integral, in frequency domain and / or in phase domain.

[0011] In a particularly preferred embodiment of the method according to the invention, the current / voltage response of the battery unit or a signal representative thereof is subjected to a Fourier analysis during the evaluation.

[0012] In this way, a comparison can be made in the frequency domain in a particularly simple and clear way, for example, between an ideally undistorted current / voltage response to the test signal and the distorted form of the current / voltage response of the battery unit.

[0013] For example, individual signal components or harmonics can be detected as peaks in the spectrum. A comparison with corresponding threshold values for the amplitudes allows a determination of whether a distortion is significant, for example, if a threshold is exceeded, or can be disregarded if it falls below a given threshold, because the distortion is then presumably or actually not related to lithium plating.

[0014] Particularly simple conditions arise if, according to another advantageous development of the method according to the invention, a signal with a sinusoidal course in time is used as the test signal.

[0015] Frequencies and amplitudes can be adapted to a specific situation and application.

[0016] However, it is possible to work with a frequency below 1 kHz and preferably above 10 Hz, for example, in this frequency range the test signal can be associated with plating.

[0017] Alternatively or additionally, a test signal current amplitude in the range of 0.5 C to 5 C can be used. 1 C corresponds to the current value obtained by multiplying the nominal capacity by 1 h of a time period. Generally, the current amplitude for the test signal is adjusted with regard to the value of the main charging current, the measurement accuracy of the underlying measurement method, the existing or desired signal-to-noise ratio, and the like.

[0018] The method according to the invention is particularly advantageous in that the procedure according to the invention also enables dynamic operation, for example with an instantaneous and / or situation-adapted setting of the maximum charging current.

[0019] It is therefore conceivable that the intensity of the main charging current is increased for or during adjustment, as long as a distortion of the current / voltage response of the battery unit or of the signal representative thereof with respect to the test signal does not yet occur or - in particular with regard to an amplitude - is below a level specified, in particular by a threshold value.

[0020] In practice, this means that the main charging current, which together with the test signal forms the total charging current for the battery pack, is regulated upwards until analysis of the battery pack's current / voltage response to the test signal reveals significant distortion, indicating the presence of lithium-ion plating. In this case, the main charging current is no longer increased.

[0021] This also means that if, during a charging process, a distortion in the current / voltage response of the battery unit to the test signal or in the signal representative of it with respect to the test signal occurs in a significant manner, the main charging current is reduced until the corresponding distortion no longer occurs or is at least below a predetermined threshold value.

[0022] Additionally or alternatively, for or during adjustment, the intensity of the main charging current is reduced until a distortion of the current / voltage response of the battery unit to the test signal or in the signal representative thereof with respect to the test signal no longer occurs or - in particular with regard to an amplitude - is below a level specified, in particular by a threshold value.

[0023] The present invention also proposes a method for charging a battery unit, in particular based on a battery chemistry with an intercalation reaction and in particular on a lithium-ion chemistry.

[0024] The charging method according to the invention comprises the steps (a) Providing a direct current as the main charging current and (b) applying to the battery unit a total charging current comprising at least the main charging current, wherein the main charging current is controlled or regulated by a method according to the invention for controlling the charging and in particular the charging current.

[0025] Furthermore, the present invention also provides a control unit for controlling charging, and in particular a main charging current for charging, a battery unit based on a battery chemistry with an intercalation reaction, and in particular on a lithium-ion chemistry. The control unit is configured to carry out a method according to the invention for controlling charging, and in particular a main charging current for charging, a battery unit based on lithium chemistry.

[0026] The control unit can be understood as a process unit, particularly in computer-implemented form, as a software unit, or as a computer program, for example, if the entire control method or parts thereof are executed in a freely programmable digital signal processing device. In this context, the method according to the invention runs when the corresponding code is executed or processed.

[0027] Alternatively, the control unit can also be viewed as a device, i.e. as a hardware component, for example as an ASIC or the like.

[0028] Furthermore, mixed forms of freely programmable components and hardware structures are also conceivable.

[0029] In an advantageous development of the control unit according to the invention, this (i') a unit for providing an alternating current signal as a test signal, (ii') a unit for applying the test signal to the battery unit by superimposing the main charging current with the test signal to form a total charging current to be supplied or supplied to the battery unit, (iv') a unit for detecting and evaluating a current / voltage response of the battery unit with respect to the test signal or a signal representative thereof, and (v') a unit for adjusting a strength and / or a time profile of at least the main charging current depending on a result of the evaluation on.

[0030] Furthermore, the present invention also proposes a charging system for charging a battery unit based on a battery chemistry with an intercalation reaction, and in particular on a lithium-ion chemistry. The charging system is configured to be used with a control method according to the invention and in particular to be controlled or to carry out such a method and / or to carry out a charging method according to the invention and / or to be used with such a method.

[0031] In a preferred embodiment of the charging system according to the invention, this (I) a charging unit connectable to the battery unit, which is designed to provide a main charging current and to supply the battery unit with a total charging current comprising the main charging current, and (II) a control unit according to the invention for controlling the operation of the charging unit on.

[0032] Furthermore, the present invention also relates to a battery system which is designed with at least one battery unit and with a charging system according to the present invention for controllably charging the battery unit and for controllably electrically connecting it to the battery unit.

[0033] Finally, the present invention also proposes a working device and in particular a vehicle.

[0034] The working device according to the invention is designed with an electrically drivable unit and in particular with a drive and has a battery system designed according to the invention which is designed for the controllable supply of the unit with electrical energy for its operation. Short description of the characters

[0035] Further details, features and advantages of the invention will become apparent from the following description and the figures. Fig. 1 shows, in schematic form in the manner of a block diagram, aspects of the battery system according to the invention using a charging system according to the invention with a control unit designed according to the invention, which are configured to be used in connection with the methods according to the invention or to carry out these. Fig. 2A and Fig. 2B show in graph form a current / voltage response of a battery unit when a test signal is applied, in undistorted and distorted form, ie in the absence and presence of plating, respectively. Fig. 3A and Fig. 3B show graphs of the current / voltage responses from the Fig. 2A and Fig. 2B.

[0036] The following are based on the Fig. 1 to 3B, exemplary embodiments and the technical background of the invention are described in detail. Identical and equivalent elements and components, as well as those that function in the same or equivalent manner, are designated by the same reference numerals. The detailed description of the designated elements and components is not reproduced in every instance where they appear.

[0037] The features and other properties presented can be isolated from one another in any form and combined with one another in any way without departing from the essence of the invention.

[0038] Fig. 1 shows, in schematic form in the manner of a block diagram, aspects of the battery system 100 according to the invention using a charging system 110 according to the invention with a control unit 50 designed according to the invention, which are configured to be used in connection with the methods according to the invention or to carry out these methods.

[0039] The Fig. The battery system 100 shown in Figure 1 is formed by a battery unit 10 and a charging system 110 for controllably charging the battery unit 10.

[0040] The battery unit 10 itself can be a single cell, a cell assembly, a module, or the like. The underlying electrochemistry for energy storage and release is crucial, preferably based on lithium-ion chemistry, which exhibits a corresponding tendency toward plating formation depending on the magnitude of the applied charging current.

[0041] In principle, the present invention can be used in connection with any battery chemistry based on intercalation reactions. This particularly applies to galvanic cells, in which no transformation or conversion of material occurs, but rather an intercalation. In principle, the present invention can be applied to sodium or magnesium ion batteries in addition to lithium-ion batteries.

[0042] The battery unit 10 is formed with first and second terminals 11 and 12, which serve to deliver electrical energy to supply an external unit during normal operation and to receive electrical energy during charging operation.

[0043] The charging system 110 according to the invention is designed with corresponding first and second charging lines 1 and 2, respectively, which are connected or controllably connectable to the first and second terminals 11, 12 of the battery unit 10.

[0044] The charging system 110 according to the invention has as main components a charging unit 40 and a control unit 50 for controlling the charging unit 40.

[0045] The charging unit 40 is designed to provide a main charging current I =in the form of a direct current in a controllable form and to make it available via first and second connections 41 and 42, respectively, to feed it into the connected or connectable first and second charging lines 1, 2 and thus to supply it to a possibly connected battery unit 10 for charging.

[0046] The control unit 50 is connected or connectable to the charging unit 40 via a control line 53 and to the battery unit 10 via a detection and control line 54.

[0047] The control line 53 serves the control unit 50 to control the charging unit 40 by outputting control signals, for example to regulate the value and / or the time profile of the main charging current I = .

[0048] The detection and control line 54 serves the control unit 50 to determine the current / voltage response U of the battery unit 10 to a test signal I via first and second detection and control lines 54-1 and 54-2, respectively.≈ to detect, here in particular by direct tapping at the first and second terminals 11 and 12 of the battery unit 10. A third detection and control line 54-3 can be used for further control of the battery unit 10 by the control unit 50.

[0049] The control unit 50 further comprises first and second signal lines 51 and 52, respectively, which serve the control unit 50 to transmit a test signal I generated and provided by the control unit 50 by means of a unit 50-1 for providing an alternating current signal. ≈ into the first and second charging lines 1 and 2 of the charging unit 40, so that by superimposing the test signal I ≈ with the main charging current I carried via the first and second charging lines 1, 2 = a total charging current I Lade results, for example, in the sense of the following relationship (1) lLoad(t)=l=(t)+l≈(t).

[0050] The control unit 50 further comprises a unit 50-2 for applying the test signal I to the battery unit 10. ≈ by superimposing the main charging current I = with the test signal I ≈ to the total charging current I supplied to the battery unit 10 Lade on.

[0051] Furthermore, the control unit 50 is designed with a unit 50-3 for detecting and evaluating the current / voltage response U or a signal representative thereof.

[0052] Finally, a unit 50-4 for setting a value for the main charging current I = as a component of the charging unit 50. In practice, this means that the unit 50-4 generates a corresponding control signal, which, for example, determines the value of the main charging current I = and which is sent via the control line 53 to the charging unit 40 for setting the main charging current I =is transmitted on the first and second charging lines 1, 2.

[0053] The units 50-1 to 50-4 of the control unit 50 can be combined and grouped together as separate modules or in any form and can be implemented in both software and hardware or as a combination thereof.

[0054] Since the superimposed charging current with the aforementioned values of 0.5 C to 5 C may be relatively high under certain circumstances, it is advantageous to also generate the test signal with the power electronics of the charging unit 40, so that the unit 50 can in this case essentially be designed as a signal processing unit and already generates a common setpoint value for the main charging current and for the test signal via an additional input of the charging unit 40.

[0055] The Fig. 2A and Fig. 2B show in the form of graphs 20, 20' a current / voltage response U of a battery unit 10 when a test signal I is applied ≈ , in undistorted form in Fig. 2A or in distorted form in Fig. 2B, i.e. in the absence or presence of plating.

[0056] On a respective abscissa 21 of the graphs 20, 20', the time t is plotted in multiples of the period T. On the ordinate 22, the current / voltage response U(t) or a signal representative thereof is shown in time-dependent form.

[0057] Lane 23 in the Fig. Figure 2A shows the undistorted shape of the current / voltage response U(t) of the battery unit 10 when a test signal I is applied. ≈ to the main charging current I = to the total charging current I Lade or the signal representative of it.

[0058] This case occurs when the total charging current I Ladedoes not lead to lithium plating in the battery unit 10 to be charged. In terms of signals, this means specifically that the test signal I ≈ in its form the Fig. 2A corresponds to the time course of the current / voltage response U(t). The test signal I ≈ and the current / voltage response U(t) correspond in form and are identical except for the normalization of the amplitudes and the phase shift. In this case, the test signal I ≈ and the undistorted current / voltage response U(t) is represented by a pure sine function. However, this form is purely exemplary and not mandatory; other, even non-periodic, signal shapers can be used as test signal I ≈ be used, e.g. pulses or the like.

[0059] Track 24 from Fig. Figure 2B shows a distorted form of the current / voltage response U(t) or the signal representative of it.

[0060] This signal form describes the case in which lithium plating is present in the underlying battery unit 10, which, due to the non-linear nature of additional current paths, leads to signal distortion in the current / voltage response U(t) to the test signal I ≈ leads.

[0061] Even a direct geometric comparison of tracks 23 and 24 reveals a clear difference, which is reflected in the distortion of the signal shape in track 24 compared to track 23.

[0062] In order to quantify this difference, various methods can be used. Fig. 3A and Fig. 3B show, in the form of graphs 30, 30', evaluations of the current / voltage responses U(t) from the Fig. 2A and Fig. 2B.

[0063] The frequency f is plotted on the abscissas 31, and the value of the Fourier transform of the current / voltage response U(t) or the representative signal is plotted on the ordinates 32. Trace 33 from Fig. 3A shows the Fourier transform of track 23 from Fig. 2A. Track 34 from Fig. 3B outputs the Fourier transform of track 24 Fig. 2B again.

[0064] It can be seen that according to Fig. 3A for the undistorted current / voltage response U(t) according to trace 23 from Fig. 2A essentially a single frequency component is decisive, which is marked with peak 35.

[0065] At lane 34 from Fig. 3B, in addition to the main component for the current / voltage response U(t) marked by peak 35, one can see trace 24 from Fig.2B shows further components designated as peaks 36 and 37, namely the second and third harmonics, respectively. The first harmonic of peak 36 comes into play with an intensity above the threshold value 38, whereas the second harmonic of peak 37 is spaced from the threshold value 38 at a value indicated by the double arrow 39, at lower values, and can be considered, for example, as insignificant.

[0066] These and other features and characteristics of the present invention are further explained with reference to the following statements:

[0067] The fast charging capability of a cell based on lithium-ion chemistry - understood as a battery unit 10 in the sense of the present invention - is limited by the limiting current above which lithium deposition - the so-called lithium plating - occurs at the anode.

[0068] Typical control parameters for preventing lithium plating during fast charging are voltage, current, and temperature. Conventional methods currently specify fixed limits, which are often maintained throughout the entire service life of the battery cell.

[0069] The point in time at which lithium plating begins or starts cannot be precisely controlled by the aforementioned control variables. Therefore, a safety problem or increased aging can arise if the specified limit values are selected progressively, thus resulting in a maximum charging current that already results in lithium plating. Or, if the charging current is too low, not all potential is utilized. This means that the battery cell 10—considered an energy storage device—is charged with a current lower than the maximum possible. This creates a disadvantage compared to a competitor whose vehicle can be charged in a shorter time.

[0070] Furthermore, the control is not directly directed to a value that represents the limit of the safer range, i.e., operation without plating, but rather only based on indirect variables. This prevents the design of an optimal control system.

[0071] According to the basic idea of the present invention, the finding is exploited that due to the plating, a second current path becomes active parallel to the actual current path, namely, for example, the current path into the underlying graphite, which contains a pronounced nonlinearity.

[0072] Since lithium ions are only deposited at a potential of 0 V relative to elemental lithium, and below this limit, incorporation into the graphite is preferred, harmonic distortion occurs when the charging current is superimposed with a sinusoidal signal, for example. One aspect of the present invention is to base the control of the maximum charging current on the occurrence of such harmonic distortion.

[0073] It is important that this superimposed excitation, understood as test signal I ≈ within the meaning of the present invention, in the frequency range of lithium plating. Furthermore, the excitation can also take forms other than a pure sinusoidal signal.

[0074] The inventive approach has the advantage of enabling improved and, in particular, optimal control of the maximum possible charging current at which slight plating occurs. Compared to previously defined limit values, this also allows adaptation to changes in the dynamics of the lithium-ion cell 10 that occur over its lifetime. List of reference symbols: 1 (first) charging cable 2 (second) charging cable 10 Battery unit 11 (first) connection 12 (second) connection 20 graphs 20' Graph 21 Abscissa 22 ordinates 23 lane 24 track 30 graphs 30' graph 31 Abscissa 32 ordinates 33 lane 34 track 35 Main peak / main component 36 (first) harmonic peak / harmonic component 37 (second) harmonic peak / harmonic component 38 Threshold 39 Distance to threshold 40 loading units 41 (first) connection 42 (second) connection 50 control unit 50-1 Unit for providing an alternating current signal / test signal I ≈ 50-2 Unit for applying the test signal I ≈ by overlaying 50-3 Unit for recording / evaluating a current / voltage response U 50-4 Unit for setting the main charging current I = 51 (first) signal line 52 (second) signal line 53 Control line 54 Detection and control line 54-1 (first) detection and control line 54-2 (second) detection and control line 54-3 (third) detection and control line 100 battery system 110 charging system

Claims

[1] Method for controlling charging and in particular a main charging current (I = ) for charging a battery unit (10) based on a battery chemistry with intercalation reaction, with the steps: (i) Providing an alternating current signal as a test signal (I ≈ ), (ii) Applying the test signal (I ≈ ) by superimposing the main charging current (I=) with the test signal (I ≈ ) to a total charging current (I Lade ), (iii) detecting and evaluating a current / voltage response (U) of the battery unit (10) with respect to the test signal (I ≈ ) and (iv) setting a strength and / or a time profile of at least the main charging current (I=) depending on a result of the evaluation, in which, during the evaluation, it is checked whether, which and / or to what extent the current / voltage response (U) of the battery unit (10) or a signal representative thereof in relation to the test signal (I ≈ ) distortions and in particular harmonic distortions, and in which the intensity of the main charging current (I = ) - is increased as long as there is no distortion of the current / voltage response (U) of the battery unit (10) or of the signal representative thereof with respect to the test signal (I ≈ ) does not yet occur or - in particular with regard to an amplitude - is below a certain level, in particular a threshold value, and / or - is reduced until a distortion of the current / voltage response (U) of the battery unit (10) or of the signal representative thereof with respect to the test signal (I ≈) no longer occurs or - in particular with regard to an amplitude - is below a level specified, in particular by a threshold value. [2] Method according to claim 1, wherein during the evaluation it is checked whether, which and / or to what extent the current / voltage response (U) of the battery unit (10) in relation to the underlying test signal (I ≈ ) or a signal representative of it has harmonics. [3] Method according to one of the preceding claims, in which a respective measure is compared with one or more predetermined threshold values. [4] Method according to one of the preceding claims, in which, during the evaluation, the current / voltage response (U) of the battery unit (10) or a signal representative thereof is subjected to a Fourier analysis. [5] Method according to one of the preceding claims, in which the test signal (I ≈) a signal with a sinusoidal shape in time is used, in particular with a frequency below 100 Hz and preferably above 10 Hz and / or with a current amplitude in the range from 2 A to 20 A. [6] Method for charging a battery - in particular based on a battery chemistry with intercalation reaction and / or on a lithium ion chemistry - Battery unit (10), with the steps: (a) Providing a direct current as the main charging current (I=) and (b) applying to the battery unit (10) a total charging current (I Lade ), wherein the main charging current (I=) is controlled or regulated by a method according to one of the preceding claims. [7] Control unit (50) for controlling the charging and in particular a main charging current (I = ) for charging a battery unit (10) based on a battery chemistry with intercalation reaction, - which is arranged to carry out a method according to one of claims 1 to 5 and - which in particular (i') a unit (50-1) for providing an alternating current signal as a test signal (I ≈ ), (ii') a unit (50-2) for applying the test signal (I ≈ ) by superimposing the main charging current (I=) with the test signal (I ≈ ) to a total charging current (I Lade ), (iv') a unit (50-3) for detecting and evaluating a current / voltage response (U) of the battery unit (10) with respect to the test signal (I ≈ ) as well as (v') has a unit (50-4) for adjusting a strength and / or a time profile of at least the main charging current (I=) depending on a result of the evaluation. [8] Charging system (110) for charging a battery unit (10) based on a battery chemistry with intercalation reaction, - which is designed to be used and / or controlled with a method according to one of claims 1 to 5 and / or to be used in a method according to claim 6 and / or to carry out such a method and - which in particular (I) a charging unit (40) connectable to the battery unit (10) for providing a main charging current (I=) and for supplying the battery unit (10) with a total charging current (I Lade ) is trained, and (II) a control unit (50) according to claim 9 for controlling the operation of the charging unit (40). [9] Battery system (100), with - at least one battery unit (10) and - a charging system (110) according to claim 8, which is arranged for controllably charging the battery unit (10) and for controllably electrically connecting it to the battery unit (10). [10] Working device and in particular vehicle, with - an electrically driven unit and in particular with a drive, and - a battery system (100) according to claim 9, which is designed to controllably supply the unit with electrical energy for its operation.

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