Method for diagnosing an energy storage device for a motor vehicle, computer program and / or computer-readable medium, data processing device, motor vehicle

Abstract

The invention relates to a method for diagnosing an energy storage device for a motor vehicle, wherein the energy storage device comprises a first storage portion having battery cells and a second storage portion connectable to the first storage portion and having battery cells, wherein the method comprises: detecting a first initial charge state of the first storage portion; determining a first intermediate charge state of the first storage portion; determining a plurality of charging hubs corresponding to a difference between the first intermediate charge state and the initial charge state and an associated plurality of partial charging periods corresponding to a diagnosis period, wherein each of the partial charging periods comprises a partial charging time and a relaxation time; and outputting a control signal on the basis of the plurality of charging hubs and the plurality of partial charging periods in order to charge the first storage portion by discharging the second storage portion.

Description

[0001] Method for diagnosing an energy storage device for a motor vehicle, computer program and / or computer-readable medium, data processing device,

[0002] Motor vehicle

[0003] The present disclosure relates to a method for diagnosing an energy storage device for a motor vehicle, wherein the energy storage device has a first storage section comprising battery cells and a second storage section that can be connected to the first storage section and comprises battery cells. The disclosure also relates to a computer program and / or computer-readable medium, a data processing device, and a motor vehicle.

[0004] Such an energy storage device typically comprises a plurality of battery cells connected in parallel and / or series, thus forming a high-voltage storage device, also known as a traction battery. The energy storage device is configured to discharge the battery cells and provide electrical energy to operate the motor vehicle and / or to provide electrical energy externally, for example, via a charging station, and to be supplied with electrical energy via the charging station and / or through recuperation during a journey in order to charge the battery cells of the energy storage device.

[0005] Accurate modeling of the high-voltage storage system is crucial for its safe, sustainable, and efficient use. Such high-voltage storage systems, or the cells they contain, such as lithium-ion cells, lose capacity over their service life, and their resistance increases, a process known as aging. This can ultimately reduce the range and performance of the vehicle when the cells are used in a motor vehicle. The capacity and resistance, or changes in them, can thus be incorporated into an estimate of the battery cell's condition.

[0006] For a state estimation to characterize the state of the cells and / or the energy storage device, an open-circuit voltage (OCV) and / or an open-circuit potential (OCP) are typically used, i.e., a relationship between a cell's open-circuit voltage or an electrode potential and the cell's state of charge. This can be used, in particular, to estimate the state of charge (SOC) and / or the aging or health state (SOH) of the cell and / or the energy storage device. The open-circuit voltage can also be used to determine a charging strategy for charging the energy storage device or the cells.

[0007] Information about a battery's current state of health can be defined as the currently available capacity compared to the capacity when new. The state of health is of utmost importance for a vehicle's operating strategy, particularly for the design of the charging strategy, for SOC estimation, and for safety. However, degradation of the state of health, or aging, exhibits a complex path dependency: the battery cell can age due to various mechanisms, for example, triggered by temperatures and / or power demands. Such mechanisms can be described by the construct of degradation modes (see CR Birkl, MR Roberts, E. McTurk, PG Bruce, DA Howey, Degradation diagnostics for lithium ion cells, Journal of Power Sources, issue 341, 2017, pages 373–386).Degradation modes model the physico-chemical aging mechanisms and can be characterized by parameters that describe, for example, the loss of active material from an electrode and / or charge carriers such as lithium. These degradation modes can be used to estimate how the storage device will behave in the future and when its service life will be reached.

[0008] To characterize health and aging, the development and provision of generalizable, accurate, and reliable estimation algorithms and methods is desirable. A promising methodology is a voltage curve reconstruction model based on measured half-cell potentials in the new state.

[0009] Methods that use such reconstruction refer to complete charging curves (see, for example, Matthieu Dubarry, Cyril Truchot, Bor Yann Liaw, "Synthesize battery degradation modes via a diagnostic and prognostic model", Journal of Power Sources, issue 219, 2012, pages 204-216). Here, the voltage curves of an aged cell are measured at low charging rates, so-called C-rates. A C-rate is equal to a current divided by a nominal capacity, i.e. the current rate has the unit 1 / h or generally a rate and indicates inversely how quickly the battery is fully charged with a certain current. For example, a cell is fully charged in half an hour at a C-rate of 2; at a C-rate of 1 / 2, a cell is fully charged in two hours.Half-cell potential curves measured in the new state are shifted and compressed to reconstruct the measured voltage curve of the aged cell in such a way that an error between an aged voltage curve reconstructed on the basis of the half-cell potential curves measured in the new state and the measured voltage curve of the aged cell is minimal.

[0010] This optimization or error minimization can also be applied to partial charging curves and even at higher C-rates (see, for example, Julius Schmitt, Mathias Rehm, Alexander Karger, Andreas Jossen, “Capacity and degradation mode estimation for lithium-ion batteries based on partial charging curves at different current rates”, Journal of Energy Storage, Issue 59, 2023, Article 106517).

[0011] The aforementioned state-of-the-art methods utilize time-resolved signals to reconstruct the voltage curve. Thus, these voltage curves contain a wealth of information about the qualitative voltage profile, allowing for an accurate relative fit of the half-cell potential curves. This can have a positive impact on the estimation of degradation modes.

[0012] However, there are multiple solutions at different SOH values ​​that minimize the error function or cost function. A characteristic of these methods is that for a given charging curve, there can be multiple local optima, each of which can lead to a local minimum error. This makes it impossible to reliably reconstruct the voltage curve unambiguously.

[0013] Patent application DE 102022 129 208.8, which was not yet published on the filing date of the present disclosure, describes an alternative method. According to this method, it is possible to use relaxed stress points together with a summed charge throughput to reconstruct the stress curve. This is a comparatively low-effort method for estimating the aging state, since by specifying the amount of charge introduced, the space of possible solutions for the stress curve can be reduced to such an extent that a higher accuracy in the SOH estimation can be achieved. However, it can be more difficult to achieve accurate results in the degradation mode estimation.

[0014] Against the background of this prior art, one object of the present disclosure is to provide a method suitable for enriching the prior art and improving at least the above-mentioned aspects of the prior art. In particular, the object of the disclosure is to enable an alternative, efficient, low-complexity, and reliable estimation of the state of health. This object is achieved by the features of the independent claims. The subclaims contain further developments of the disclosure.

[0015] According to one aspect of the disclosure, the object is achieved by a method for diagnosing an energy storage device for a motor vehicle, wherein the energy storage device has a first storage section comprising battery cells and a second storage section that can be connected to the first storage section and comprises battery cells, the method comprising: detecting a first initial charge state of the first storage section; determining a first intermediate charge state of the first storage section; determining a plurality of charging strokes corresponding to a difference between the first intermediate charge state and the first initial charge state and an associated plurality of partial charging periods corresponding to a diagnosis period, wherein each of the partial charging periods comprises a partial charging time and a relaxation time;and outputting a control signal based on the plurality of charging strokes and the plurality of partial charging periods for charging the first storage section by discharging the second storage section;

[0016] In order to record predefined measuring points with relaxed voltages, a diagnosis can be used in which the first storage section is charged while the second storage section is discharging. The second storage section is therefore discharged in favor of the first storage section. The diagnosis is limited in time by the diagnosis period. It was recognized that different relaxed voltages can be approached or set as measuring points, provided there is sufficient time for the diagnosis, in order to divide the charging into the majority of charging strokes and to provide one of the relaxation times between the charging strokes in which the first storage section or the cells of the first storage section are not charged, but relax into a rest state by the reduction of overvoltages and / or approximate the rest state through relaxation.This makes it possible to record a resting voltage or open circuit voltage as cell voltage.

[0017] It was recognized that modern high-voltage storage systems have an architecture composed of two or more storage sections. It may then be possible, for example, if the vehicle is not in use for an extended period, to use a diagnostic mode for diagnosis. In this mode, the storage sections are set to different charge states via a voltage converter that electrically connects the storage sections. Because the energy is shifted from the first storage section to the second storage section, only a marginal energy loss occurs with respect to the energy storage device, and a defined charge state or voltage point can be reached.These relaxed measurement points, or the ends of the relaxation times, are distributed across the amount of charge introduced by charging and sufficiently meet the criteria for using the measurement points to diagnose the energy storage device, particularly for applying the Delta-Q method. In particular, the open-circuit voltage curve can be sampled over a state-of-charge or voltage range. These measurement points can thus be used to reconstruct the open-circuit voltage characteristic using the Delta-Q method and ultimately estimate the state of health and / or degradation modes.

[0018] It was recognized that the number of usable measurement points for the DeltaQ method is limited by boundary conditions: there should be at least a certain number of measurement points to enable a reliable fit of the open-circuit voltage characteristic, for example, 5 or more measurement points, in particular 10 measurement points; furthermore, the measurement points should be within a specific SOC range to enable a fit of the open-circuit voltage characteristic with the lowest possible error; and the period between point acquisitions should not be too long to avoid a change in the open-circuit voltage characteristic due to degradation between point acquisitions. These boundary conditions can be met reproducibly during diagnosis.The method according to the disclosure thus offers a predefined, reproducible and comparable as well as low-effort recording of these relaxed stress points or measuring points and thus an enormous potential for the broad application of this method to motor vehicles.

[0019] Optionally, the sum of the majority of partial charging periods is less than the diagnostic period. This ensures that the scheduled charging can be completed within the diagnostic period and that a symmetrical state of the storage sections with regard to their charge levels can be established. A user of the motor vehicle is thus unaffected with regard to the diagnosis. Alternatively or additionally, the sum of the majority of charging strokes is equal to the difference between the first intermediate charge level and the first initial charge level. This ensures that the scheduled charging can be carried out from the initial charge level to the first intermediate charge level in order to record suitable measuring points for the diagnosis.

[0020] Optionally, the charging strokes, the partial charging periods, and / or the relaxation times of the partial charging periods are equal to one another. This makes it possible to arrange possible measuring points equidistant in time within the diagnostic period and / or equidistant in charge-related terms between the first initial state of charge and the first intermediate state of charge in order to be able to comprehensively sample the open-circuit voltage curve. In other words, the charging strokes are optionally equal to one another. Alternatively or additionally, the partial charging periods are equal to one another. Alternatively or additionally, the relaxation times of the partial charging periods are equal to one another. In particular, for example, a first charging stroke, a first partial charging period, a final charging stroke, and a final partial charging period can nevertheless be different in order to enable advantageous temporal and / or charge-related equidistance between the remaining charging strokes and / or partial charging periods.

[0021] Optionally, the control signal defines a charging of the second storage section when the first storage section is discharged after the first storage section has been charged. It was recognized that by charging the second storage section when the first storage section is discharged after the first storage section has been charged, a symmetrical state of the storage sections can be restored, i.e. approximately the same charge states in the storage sections, and / or a final charge state of the respective storage sections can be established that corresponds to the initial charge state of the respective storage sections. Optionally, the charging of the second storage section when the first storage section is discharged after the first storage section has been charged takes place within the diagnostic period in order to enable a symmetrical state of the storage sections after the diagnosis.

[0022] Optionally, the discharging of the first storage section is defined such that a first final charge state after discharging the first storage section corresponds to the first initial state. This makes it possible to provide a particularly user-friendly diagnosis in which the user is unaffected by the balancing of the charging and / or discharging of the storage sections. For discharging the first storage section from the first intermediate charge state to the first initial charge state, what was described with reference to charging from the first initial state to the first intermediate charge state optionally applies: The discharging of the first storage section from the first intermediate charge state to the first initial charge state accordingly takes place according to a plurality of charging strokes and a plurality of partial charging periods.Optionally, the sum of all partial charging periods, i.e. the partial charging periods for charging the first storage section and the partial charging periods for charging the second storage section, is less than or equal to the diagnostic period. This ensures that the scheduled charging can be completed within the diagnostic period. A user of the motor vehicle is thus unaffected with regard to the diagnosis. Alternatively or additionally, the sum of the majority of the charging strokes is equal to the difference between the first intermediate charging state and the first final charging state. Optionally, the charging strokes, the partial charging periods and / or the relaxation times of the partial charging periods are equal to one another. The charging strokes for charging the first storage section can be offset from the charging strokes for charging the second storage section in order to be able to record different measuring points.

[0023] Optionally, the method comprises: detecting a diagnostic request. It has been recognized that the diagnosis may require a considerable amount of time for the use of the motor vehicle. Therefore, the diagnosis may be advantageous for the use of the motor vehicle, taking into account a diagnostic request from a user, an operator, and / or a manufacturer. Diagnostic information may be output in response to the diagnostic request. The diagnostic information may include an estimate of the end time of the diagnosis. The diagnostic information may include a request for confirmation by the user that the diagnosis has been performed.

[0024] Optionally, determining the plurality of charging strokes and the plurality of partial charging periods includes optimization with a predetermined minimum number of partial charging periods and a minimum duration of the individual partial charging periods and / or the associated relaxation times as a constraint. It was recognized that the charging requirement and / or the difference between the initial state of charge and the final state of charge, as well as the diagnostic period, allow for various options for selecting the charging strokes and defining the partial charging periods. Furthermore, it was recognized that it can be crucial for the quality of the diagnosis that a certain minimum number of measuring points are approached in order to enable a voltage curve to fit with the smallest possible error and / or that a certain minimum time is defined as the relaxation time in order to reliably sample the open-circuit voltage characteristic curve.

[0025] Optionally, the method includes recording a cell voltage at each end of the relaxation time of one of the partial charging periods. The end of the relaxation time can thus be used as a measurement point. At the end of the relaxation time, a particularly reproducible and comparable sampling of the resting voltage is possible.

[0026] The method optionally includes: determining a voltage curve based on the cell voltage and a charge quantity corresponding to the cell voltage. It was recognized that during charging, the charge or charge quantity can be determined as a charge quantity via the charging current and time. Based on the charge quantity, the state of charge can be calculated, and vice versa. Determining the voltage curve based on the cell voltage and the charge quantity can correspond to the DeltaQ method.

[0027] In other words, the above description can be summarized as follows, with reference to a specific embodiment that is described as non-limiting to the present disclosure: The disclosure relates to an application of the Delta-Q method for SOH and degradation mode estimation by utilizing the redistribution of electrical energy between two storage halves. Prior art methods and algorithms utilize time-resolved signals to reconstruct the voltage curve. Thus, these voltage curves contain a great deal of information about the qualitative voltage profile, and an accurate relative fit of the half-cell potential curves can be achieved. This can have a positive effect on the degradation mode estimation. However, there are multiple solutions at different SOH values ​​that minimize the cost function.The DeltaQ methodology, on the other hand, offers a low-effort method for estimating SOH. By specifying the amount of charge introduced, the space of possible solutions is already reduced, allowing for greater accuracy in SOH estimation. However, accurate results in degradation mode estimation can be more difficult to achieve. Furthermore, the filtering of usable data points per vehicle is strict: There should be at least 10 data points, a specific SOC range should be included, the period for recording points should not be too far in the past, etc. A predefined, low-effort recording of these relaxed voltage points offers enormous potential for the widespread application of this method to vehicles. Modern high-voltage storage systems, for example, have an 800V architecture consisting of two pack halves, each with 400V.To record predefined, relaxed voltage points, it is possible – if the vehicle is not used for an extended period, possibly triggered by a "diagnostic mode" – to set the two storage halves to different charge states via charging or discharging by connecting them to a DC / DC converter. Because energy flows from one half to the other, hardly any energy is lost, and a defined charge state or voltage point can be reached. These points can later be used by the DeltaQ method to characterize the entire storage system or even the storage halves. A user parks their vehicle overnight with a charge state of 50%, but does not want to charge it. They trigger a diagnostic mode in the vehicle menu, which takes a certain amount of time.Storage half 1 is discharged to 25% SOC via a continuous discharge, while storage half 2 is charged to 75% SOC by supplying energy from storage half 1. The charging or discharging is then interrupted to relax the voltage, for example, for 1-3 hours. This point is then recorded for later use in the DeltaQ method. It is also possible to approach several points in succession to generate more relaxed voltage points. Ultimately, the invention allows for the targeting of predefined points, which have been proven to contribute to high accuracy.

[0028] According to one aspect of the disclosure, a computer program and / or a computer-readable medium is provided. The computer program and / or the computer-readable medium comprise instructions which, when the program or instructions are executed by a data processing device, cause the device to perform the method according to the disclosure and / or steps thereof. Optionally, the computer program and / or the computer-readable medium comprises instructions which, when the program or instructions are executed by a data processing device, cause the device to perform the method steps described as advantageous or optional in order to achieve an associated technical effect.

[0029] According to one aspect of the disclosure, a data processing device for a motor vehicle is provided. The data processing device is configured to perform the method described above. Optionally, the data processing device is configured to perform a method step described as advantageous or optional and / or to implement a method feature in order to achieve an associated technical effect.

[0030] According to one aspect of the disclosure, a motor vehicle comprising the data processing device described above is provided. Optionally, the data processing device of the motor vehicle and / or the motor vehicle is configured to perform a method step described as advantageous or optional and / or to implement a method feature in order to achieve an associated technical effect.

[0031] Each embodiment will be described below with reference to the figures. Figure 1 schematically shows a motor vehicle according to one aspect of the disclosure;

[0032] Fig. 2 schematically shows a charging curve for a method according to one aspect of the disclosure and an energy storage device for a motor vehicle according to one aspect of the disclosure;

[0033] Fig. 3 schematically shows a flow diagram of a method according to one aspect of the disclosure; and

[0034] Fig. 4 shows a schematic representation of a computer program and / or computer-readable medium according to one aspect of the disclosure.

[0035] Figure 1 schematically shows a motor vehicle 50 according to one aspect of the disclosure.

[0036] The motor vehicle 50 has an energy storage device 55 and an electric drive 52. The energy storage device 55 has a plurality of battery cells 56, which and their number are shown only schematically.

[0037] The energy storage device 55 or the battery cells 56 are configured to be supplied with electrical energy in order to charge the battery cells 56, i.e. to increase a state of charge SOC_1, SOC_2 of the battery cells 56. The energy storage device 55 or the battery cells 56 are configured to provide electrical energy for operating the motor vehicle 50 and / or the electric drive 52, wherein the battery cells 56 are discharged, i.e. the state of charge SOC_1, SOC_2 of the battery cells 56 decreases. During charging and discharging as well as over time, i.e. due to calendar effects, the battery cells 56 can age, i.e. the battery cells 56 can be characterized by a state of health SOH that changes over time and / or with the use of the energy storage device 55.

[0038] The energy storage device 55 has a first storage section 57 and a second storage section 58. Each of the storage sections 55, 57 has a plurality of battery cells 56. In the example shown, the energy storage device 55 has two storage sections 57, 58, and the storage sections 57, 58 each have the same number of battery cells 56. In another embodiment (not shown), the energy storage device 55 has more than two storage sections 57, 58, and / or the storage sections 57, 58 have different numbers of battery cells 56.The first storage section 57 and the second storage section 58 are interconnected in such a way to establish an electrical connection between the storage sections 57, 58, to charge the first storage section 57 while discharging the second storage section 58, and to charge the second storage section 58 while discharging the first storage section 58. For this purpose, the motor vehicle 50 and / or the energy storage device has a voltage converter 59 (see Figure 2) and a plurality of switching elements. In addition, the first storage section 57 and the second storage section 58 are interconnected in such a way to interrupt the electrical connection between the storage sections 57, 58, in order to prevent a charge exchange between the storage sections 57, 58.

[0039] The battery cells 56 of the energy storage device 55 can be characterized by a voltage curve 65, in particular an open-circuit voltage curve. The voltage curve 65 is a relationship between a voltage U and the state of charge SOC_1, SOC_2 of the battery cell 56. The voltage curve 65 changes with the state of health SOH.

[0040] The motor vehicle 50 according to Figure 1 has a data processing device 51. The data processing device 51 is, for example, a battery control module and is configured to control and monitor the operation of the energy storage device 55. For this purpose, the data processing device 51 is configured, for example, to define a charging profile with a current I for charging the energy storage device 55 and to measure a cell voltage U of one of the battery cells 56. Thus, the data processing device 51 can charge the battery cells 56, in particular in a voltage-controlled manner.

[0041] Figure 1 also shows a charging station 91 and a vehicle-external network 90. ​​The charging station 91 and the motor vehicle 50 are configured to be electrically and communicatively connected to each other. This allows the energy storage device 55 to be supplied with electrical energy from the vehicle-external network 90 via the charging station 91 to charge the battery cells 56.

[0042] The motor vehicle 50 or the data processing device 51 is configured to carry out the method 100 described with reference to Figure 3 and to perform a diagnosis of the energy storage device 55. In this case, the state of charge SOC_1, SOC_2 between the storage sections 57, 58 is specifically raised or lowered according to a charging curve 66. Such a charging curve 66 is described with reference to Figure 2. For this purpose, the data processing device 51 according to Figure 1 is configured to detect a diagnostic request 75 for a diagnosis of the battery cell 56. The diagnostic request 75 is specified, for example, by a user and / or by the manufacturer for diagnostic purposes. The diagnostic request 75 is detected via a user interface (not shown) and / or via a communication interface (not shown). Alternatively, the diagnostic request 75 can be generated by the data processing device 51 itself.

[0043] The data processing device 51 is configured to output diagnostic information 77 relating to the execution of the diagnosis and perceivable by a user of the motor vehicle 50. The diagnostic information 77 is output on a user interface of the motor vehicle 50, via the charging station 91, and / or via the communication interface, for example, on a user's terminal device.

[0044] The data processing device 51 is configured to output a control signal 76 for diagnosing the battery cells 56. The control signal 76 is transmitted, for example, to the voltage converter 59 and the switching device in order to perform the diagnosis.

[0045] The data processing device 51 is configured to detect a cell voltage U and to determine a voltage curve 65, in particular an open-circuit voltage curve, based on the cell voltage U and a charge quantity Q corresponding to the cell voltage U. Based on the voltage curve 65, the data processing device 51 can determine the state of health SOH. Additionally or alternatively, the data processing device 51 can determine parameters relating to aging mechanisms based on the voltage curve 65.

[0046] Figure 2 schematically shows a charging curve 66 for a method 100 according to one aspect of the disclosure and an energy storage device 55 for a motor vehicle 50 according to one aspect of the disclosure. Such a charging curve 66 can be determined by a data processing device 51 according to Figure 1 to perform a diagnosis. Figure 2 will be described with reference to Figure 1.

[0047] Figure 2 is divided into six sections (A) to (F), each of the sections showing an example of a section of the charging curve 66 and the energy storage device 55, the storage halves 57, 58 of the energy storage device 55 being connected in each of the sections in such a way that the corresponding section of the charging curve 66 is set as illustrated by double arrows with a dotted line.

[0048] Figure 2 shows the charging curve 66 as a relationship between a cell voltage U and time t. The solid line shows a first cell voltage U1 of battery cells 56 of the first storage section 57, and the dashed line shows a first cell voltage U2 of battery cells 56 of the second storage section 58.

[0049] In the first section (Figure 2 (A)), a rest state is established in which no current flows between the storage sections 57, 58. The first initial charge state SOC1_S is constant, and the second initial charge state SOC2_S is constant. In the example shown, the initial charge states SOC1_S and SOC2_S are equal, which means that the first cell voltage U1 is also equal to the second cell voltage U2.

[0050] In the second section (Figure 2 (B)), the storage halves 57, 58 are connected to one another by the voltage converter 59 during a partial charging time LZ in such a way that the first state of charge SOC_1 of the battery cells 56 of the first storage section 57 increases, as schematically illustrated by an upward arrow, and the second state of charge SOC_2 of the battery cells 56 of the second storage section 58 decreases, as schematically illustrated by a downward arrow. Thus, energy or charge passes from the second storage section 58 to the first storage section 57: the second storage section 58 is discharged and the first storage section 57 is charged. In the process, the first voltage U1 rises and the second voltage U2 falls. At the end of the second section, the first storage section 57 reaches a first intermediate charge state SOC1_Z and the second storage section 58 reaches a second intermediate charge state SOC2_Z.

[0051] In the third section according to Figure 2 (C), a rest state is established over a relaxation time RZ. For this purpose, an electrical connection between the storage sections 57, 57 is interrupted: no current flows between the storage sections 57, 58. This allows overvoltages to dissipate during the relaxation time RZ. The relaxation time RZ enables the cells 56 to relax, i.e., the overvoltages to decay and thus an approximation of a rest voltage value. The first intermediate charge state SOC1_Z is constant and the second intermediate charge state SOC2_Z is constant. At one end E of the relaxation time RZ, the voltage U is recorded for diagnosis and / or to approximate the rest voltage characteristic. The end E of the relaxation time RZ is thus a measuring point. This allows relaxed values ​​of the first cell voltage U1 and the second cell voltage U2 to be measured.

[0052] Sections (B) and (C) define a partial charging period PTL, which includes the partial charging time LZ and the relaxation time RZ.

[0053] In the fourth section, Figure 2 (D), the storage halves 57, 58 are connected to one another by the voltage converter 59 over a partial charging time LZ in such a way that the first state of charge SOC_1 of the battery cells 56 of the first storage section 57 decreases, as schematically illustrated by a downward-pointing arrow, and that the second state of charge SOC_2 of the battery cells 56 of the second storage section 58 increases, as schematically illustrated by an upward-pointing arrow. Thus, energy or charge passes from the first storage section 57 to the second storage section 58: the first storage section 57 is discharged and the second storage section 58 is charged. In the process, the first voltage U1 decreases and the second voltage U2 increases. At the end of the fourth section, the first storage section 57 reaches a first discharge state SOC1_E and the second storage section 58 reaches a second discharge state SOC2_E.

[0054] In the fifth section (Figure 2 (E), a rest state is established in which no current flows between the storage sections 57, 58. The first discharge state SOC1_E is equal to the first initial charge state SOC1_S, and the second discharge state SOC2_E is equal to the second initial charge state SOC2_S. The voltages U1, U2 still relax to the same value.

[0055] In the sixth section (Figure 2 (F)), a rest state is established in which no current flows between the storage sections 57, 58. The first discharge state SOC1_E is constant, and the second discharge state SOC2_E is constant. In the example shown, the discharge states SOC1_S and SOC2_S are equal, which means that the first cell voltage U1 is also equal to the second cell voltage U2.

[0056] The diagnostic period TD describes the period from the second section (B) to the fifth section (E). For illustrative purposes, only one charging stroke LH and correspondingly only one partial charging time LZ and accordingly only one relaxation time RZ are illustrated. According to the method 100, any number of partial charging periods PTL and charging strokes LH can be approached between the initial charging states SOC1_S, SOC2_S and the intermediate charging states SOC1_Z, SOC2_Z as well as between the intermediate charging states SOC1_Z, SOC2_Z and the final charging states SOC1_E, SOC2_E in order to be able to record a corresponding number of measuring points. Each of the partial charging periods PTL comprises a partial charging time LZ and a relaxation time RZ. Charging or discharging takes place during the partial charging time LZ.During the partial charging time LZ, the state of charge SOC_1, SOC_2 of the battery cells 56 of one of the storage sections 57, 58 and the corresponding voltage U1, U2 increase, while at the same time the state of charge SOC_1, SOC_2 of the battery cells 56 of the other storage section 57, 58 and the corresponding voltage U1, U2 decrease. This creates overvoltages. After the partial charging time LZ of one of the partial charging periods PTL, a relaxation time RZ follows within the partial charging period PTL, i.e. before the next partial charging period PTL or between the partial charging times LZ of the adjacent partial charging periods PTL. The relaxation time RZ enables the cells 56 to relax, i.e. the overvoltages to decay and thus an approximation of an open-circuit voltage value. Each of the relaxation times RZ or each partial charging period PTL has the end E of a relaxation time RZ, as schematically illustrated by a cross.At the end E of the relaxation time RZ, the voltage U is measured for diagnosis and / or to approximate the open-circuit voltage characteristic. The end E of the relaxation time RZ is thus a measurement point. The charging strokes LH, the partial charging periods PTL, and the relaxation times RZ of the partial charging periods PTL are equal to each other.

[0057] The data processing device 51 according to Figure 1 is configured to determine the plurality of charging strokes LH and the plurality of partial charging periods PTL based on an optimization with a predetermined minimum number of partial charging periods PTL and / or the associated relaxation times RZ as a secondary condition. For example, a user parks his motor vehicle 50 with a state of charge SOC_1, SOC_2 of 50% overnight, but does not want to charge the motor vehicle 50. He triggers a diagnostic mode in the menu of the motor vehicle 50 using a diagnostic request 75, which requires a specific diagnostic time TD. The first storage half 57 is discharged to a first intermediate charge state SOC1_Z of 25% via continuous discharge, while the second storage half 58 is charged to a second intermediate charge state SOC2_Z of 75% SOC by supplying energy from the first storage half 57. The charge orDischarge is interrupted in order to relax the voltage U during the relaxation time RZ, e.g. for 1-3 hours. This measurement point is now recorded in order to use it later for the DeltaQ method. The charging strokes LH and the times are purely exemplary and can differ from the example shown. Ultimately, the invention can be used to approach predefined points that demonstrably contribute to high accuracy. Figure 3 schematically shows a flow diagram of a method 100 according to one aspect of the disclosure. The method 100 according to Figure 3 is a method 100 for diagnosing an energy storage device 55 for a motor vehicle 50, wherein the energy storage device 55 has a first storage section 57 comprising battery cells 56 and a second storage section 58 that can be connected to the first storage section 57 and comprises battery cells 56.Such a motor vehicle 50 is described with reference to Figure 1, and a charging curve 66 for charging such an energy storage device 55 is described with reference to Figure 2. Figure 3 is described with reference to Figures 1 and 2.

[0058] The method 100 according to Figure 3 comprises: detecting 105 a diagnostic request 75.

[0059] The method 100 comprises: detecting 110 a first initial state of charge SOC1_S of the first storage section 57.

[0060] The method 100 comprises: determining 120 a first intermediate charge state SOC1_Z of the first storage section 57.

[0061] The method 100 comprises: determining 130 a plurality of charging strokes LH corresponding to a difference between the first intermediate charge state SOC1_Z and the first initial charge state SOC1_S and an associated plurality of partial charging periods PTL corresponding to a diagnostic period TD, wherein each of the partial charging periods PTL comprises a partial charging time LZ and a relaxation time RZ.

[0062] Determining 130 the plurality of charging strokes LH and the plurality of partial charging periods PTL comprises an optimization with a predetermined minimum number of partial charging periods PTL and / or the associated relaxation times RZ as a constraint.

[0063] The method 100 comprises: outputting 140 a control signal 76 based on the plurality of charging strokes LH and the plurality of partial charging periods PTL for charging the first storage section 57 by discharging the second storage section 58. The control signal 76 defines a charging of the second storage section 58 upon discharging of the first storage section 57 after charging the first storage section 57. The discharging of the first storage section 57 is defined such that a first final charging state S0C1_E after discharging the first storage section 57 corresponds to the first initial state S0C1_A.

[0064] The method 100 comprises: detecting 150 a cell voltage U at a respective end E of the relaxation time RZ of one of the partial charging periods PTL.

[0065] The method 100 comprises: determining 160 a voltage curve 65 based on the cell voltage U and a charge quantity Q corresponding to the cell voltage U.

[0066] The person skilled in the art will recognize that the method 100 according to Figure 3 can also be performed in a different order than that shown. In particular, it is possible for steps of the method 100 to be interchanged, shifted, and / or performed simultaneously.

[0067] Figure 4 shows a schematic representation of a computer program and / or computer-readable medium 200 according to one aspect of the disclosure. The computer program and / or computer-readable medium 200 includes instructions (not shown) which, when the program or instructions are executed by a data processing device 51, cause the device 51 to perform the method 100 and / or the steps of the method 100 according to Figure 3.

[0068] The instructions can be present as program code in any code or in any language, in particular in a code suitable for controlling and / or monitoring motor vehicles 50 or their energy storage devices 55. The computer program and / or computer-readable medium 200 can be or comprise any digital data storage device, such as a USB stick, a hard drive, a CD-ROM, an SD card, or an SSD card. The computer program does not necessarily have to be stored on such a computer-readable storage medium, but can also be accessible via the Internet or otherwise. Reference symbol (part of the description)

[0069] 10 users

[0070] 50 motor vehicles

[0071] 51 Data processing device

[0072] 52 drive

[0073] 53 Communication interface

[0074] 55 Energy storage device

[0075] 56 battery cells

[0076] 57 first storage section

[0077] 58 second storage section

[0078] 59 voltage converters

[0079] 65 Voltage curve

[0080] 66 Charging curve

[0081] 75 Diagnostic request

[0082] 76 Control signal

[0083] 77 Diagnostic information

[0084] 100 procedures

[0085] 105 Entering a diagnostic request

[0086] 110 Recording a first initial state of charge

[0087] 120 Determining an intermediate charge state

[0088] 130 Determining a plurality of charging strokes and a plurality of partial charging periods

[0089] 140 Outputting a control signal

[0090] 150 Detecting a cell voltage

[0091] 160 Determining a voltage curve

[0092] 200 Computer program and / or computer-readable medium

[0093] I Current

[0094] LH loading hub

[0095] LZ Partial charging time PTL Partial charging period

[0096] Q Load size

[0097] RZ relaxation time

[0098] SOH health status SOC1 first charge state

[0099] SOC1 E first discharge state

[0100] SOC1_S first initial state of charge

[0101] SOC1 Z first intermediate charge state

[0102] SOC2 second state of charge SOC2 E second state of discharge

[0103] SOC2_S second initial state of charge

[0104] SOC2 Z second intermediate charge state

[0105] TD diagnostic period

[0106] U cell voltage, voltage U1 first voltage

[0107] U2 second voltage

Claims

Claims 1. A method (100) for diagnosing an energy storage device (55) for a motor vehicle (50), wherein the energy storage device (55) has a first storage section (57) comprising battery cells (56) and a second storage section (58) which can be connected to the first storage section (57) and comprises battery cells (56), wherein the method (100) comprises: - detecting (110) a first initial state of charge (SOC1_S) of the first storage section (57); - determining (120) a first intermediate charge state (SOC1_Z) of the first storage section (57); - determining (130) a plurality of charging strokes (LH) corresponding to a difference between the first intermediate charge state (SOC1_Z) and the first initial charge state (SOC1_S) and an associated plurality of partial charging periods (PTL) corresponding to a diagnostic period (TD), each of the partial charging periods (PTL) comprising a partial charging time (LZ) and a relaxation time (RZ); and - Outputting (140) a control signal (76) based on the plurality of charging strokes (LH) and the plurality of partial charging periods (PTL) for charging the first storage section (57) by discharging the second storage section (58).

2. The method (100) of claim 1, wherein the control signal (76) defines a charging of the second memory section (58) upon discharging of the first memory section (57) after charging of the first memory section (57).

3. The method (100) according to claim 2, wherein the discharging of the first storage section (57) is defined such that a first final charge state (SOC1_E) after the discharging of the first storage section (57) corresponds to the first initial state (SOC1_A).

4. Method (100) according to one of the preceding claims, wherein the method (100) comprises: - Recording (105) a diagnostic request (75).

5. Method (100) according to one of the preceding claims, wherein the determining (120) of the plurality of charging strokes (LH) and the plurality of partial charging periods (PTL) comprises an optimization with a predetermined minimum number of partial charging periods (PTL) and a Minimum duration of the individual partial charging periods (PTL) and / or the associated relaxation times (RZ) as a side condition.

6. Method (100) according to one of the preceding claims, wherein the method (100) comprises: - detecting (150) a cell voltage (II) at a respective end (E) of the relaxation time (RZ) of one of the partial charging periods (PTL).

7. The method (100) of claim 6, wherein the method (100) comprises: - Determining (160) a voltage curve (65) based on the cell voltage (II) and a charge quantity (Q) corresponding to the cell voltage (II).

8. Computer program and / or computer-readable medium (200) comprising instructions which, when executed by a data processing device (51), cause the device (51) to carry out the method (100) according to one of claims 1 to 7.

9. Data processing device (51) for a motor vehicle (50), wherein the data processing device (51) is configured to carry out the method (100) according to one of claims 1 to 7.

10. Motor vehicle (50) comprising the data processing device (51) according to claim 9.

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