On-board system for a vehicle and method for evaluating the SOH of a high-voltage battery

Abstract

The invention relates to an on-board system (100) and a method for evaluating the state of health (SOH) of a high-voltage battery (30) having a plurality of battery cells (31). Functional modules of the on-board system and method steps relate to the processes of: setting (11, S11) a discharge pulse via a measuring resistor (22) and a semiconductor switch (21); measuring (12, S12) cell voltages of individual battery cells (31) at a specified frequency; determining (13, S13) voltage differences between minimum cell voltages and maximum cell voltages; determining (14, S14) the internal resistance of the high-voltage battery (30); and determining (15, S15) the SoH on the basis of a characteristic diagram.

Description

[0001] On-board system of a vehicle and method for evaluating a SOH of a high-voltage battery

[0002] The present invention relates to an on-board system of a vehicle for evaluating a state of aging (SOH) of a high-voltage battery with a plurality of battery cells, and a method for evaluating a state of aging of a high-voltage battery with a plurality of battery cells, as well as an evaluation device for carrying out the method on a vehicle with the high-voltage battery.

[0003] It is known in the art to estimate the state of health (SOH) of a battery storage system, such as a traction battery of an electrically powered vehicle, by measuring resistance and / or capacity at various points in time during battery use. Methods suitable for autonomous offline estimation on board a vehicle are generally complex, based on individual simulation models of the battery, and are not very accurate under fluctuating external influences, which may not be adequately represented in a model.Other estimation methods using a methodology that relies on a large data set must usually be performed online and require a robust cloud-based platform as well as a high-performance and uninterrupted data connection between the mobile application and a data center to perform an online estimation, which can be problematic in mobile applications.

[0004] The aging state of battery cells in a vehicle's traction battery or in a stationary battery storage system represents a significant factor in its economic residual value and technical performance, such as range or capacity. With increasing electrification of transport, there is therefore a fundamental need for solutions for the technical assessment of the aging state of larger-sized, particularly high-voltage battery storage systems.

[0005] It is an object of the invention to provide a technique that enables improved accuracy and / or more flexible application in an assessment of an aging state of a high-voltage battery with individual battery cells.

[0006] The above object is achieved by an on-board system having the features of claim 1, a method having the steps of claim 8 or an implementation of the method with an evaluation device having the features of claim 18. Further features and details of the invention emerge from the subclaims, the description and the drawings.

[0007] Features and details that are described in connection with the on-board system according to the invention naturally also apply in connection with the method according to the invention and vice versa, so that with regard to the disclosure of the individual aspects of the invention, reference is or can always be made to each other.

[0008] The on-board system of a vehicle according to the invention serves to evaluate the aging state of a high-voltage battery having a plurality of battery cells, comprising: voltage sensors for detecting cell voltages of individual battery cells, and a current sensor for detecting a discharge current of the high-voltage battery; a battery monitoring device for monitoring the state of the high-voltage battery, with signal connections to the sensors and a processor for data processing of measured values ​​from the sensors.

[0009] According to the invention, a high-voltage measuring circuit is connected between high-voltage potentials of the high-voltage battery, with a measuring resistor and a semiconductor switch for setting a defined discharge pulse on the high-voltage battery. Essential to the invention is that the battery monitoring device comprises: a discharge setting module for setting a predetermined discharge current of the discharge pulse flowing through the high-voltage measuring circuit, with a signal connection to the semiconductor switch for outputting a control signal to the semiconductor switch; a discharge measuring interval module for measuring cell voltages of individual battery cells and the discharge current at predetermined intervals or at a predetermined frequency using the sensors, and with a memory for storing simultaneously recorded measured values ​​of the cell voltages and the discharge current, assigning a sequence or time;a voltage difference determination module for determining voltage differences between minimum cell voltages and maximum cell voltages among the stored measured values ​​of the simultaneously recorded cell voltages and for determining a maximum voltage difference among the previously determined voltage differences; an internal resistance determination module for determining an internal resistance of the high-voltage battery from the previously determined maximum voltage difference and the discharge current based on a stored formula that includes Ohm's law; and an SOH determination module for determining an SOH of the high-voltage battery from the previously determined internal resistance based on a stored characteristic map that includes an assignment of SOH values ​​of the high-voltage battery to internal resistance values.

[0010] Likewise, the method according to the invention serves to evaluate the state of health (SOH) of a high-voltage battery with multiple battery cells, preferably on board a vehicle. The following method steps are essential to the invention:

[0011] - Setting a discharge pulse with a predetermined discharge current which, after a maximum state of charge (SOC) of the high-voltage battery, flows via a measuring resistor and a semiconductor switch between high-voltage potentials of the high-voltage battery, by means of the semiconductor switch;

[0012] - measuring cell voltages of individual battery cells of the high-voltage battery as well as the discharge current of the high-voltage battery at predetermined intervals or at a predetermined frequency by means of voltage sensors on individual battery cells and a current sensor in electrical connection with the high-voltage battery, during a discharge period of the discharge current, and storing simultaneously recorded measured values ​​of the cell voltages and the discharge current in a memory, assigning a sequence or time;

[0013] - Determining voltage differences between minimum cell voltages and maximum cell voltages among the stored measured values ​​of the simultaneously recorded cell voltages and determining a maximum voltage difference among the previously determined voltage differences; - Determining an internal resistance of the high-voltage battery from the previously determined maximum voltage difference and the discharge current, based on a formula that includes Ohm's law; and

[0014] - Determining an SOH of the high-voltage battery from the determined internal resistance based on a map that includes an assignment of values ​​of the SOH of the high-voltage battery to values ​​of the internal resistance.

[0015] The invention thus provides, for the first time, an on-board system for a vehicle that includes an additional, dedicated high-voltage circuit within a conventional high-voltage architecture of electric vehicles. This additional circuit, in the form of the aforementioned high-voltage measuring circuit, contains a resistor, a semiconductor switch, and a fuse, which are selected according to design requirements and arranged specifically in the on-board system, i.e., provided and used in an application-specific manner.

[0016] In terms of process technology, the invention provides, for the first time, the storage of simple formulas for the empirical comparison of measured value data points and Ohm's law for determining a resistance, as well as a final characteristic map with a mapping between a final processed parameter value and an evaluation value of the SOH. The characteristic map contains results from previously determined experimental and empirical studies that require no processing effort in the application.

[0017] As an advantage of the invention, the methodology for evaluating the SOH with regard to an offline application does not involve complex parameter models and simulations. However, the methodology also requires a smaller data basis than conventional online applications, such as those found in a laboratory or maintenance environment. The assessment is supported by the collection and resolution of measurement data in a short measurement process, which, on the one hand, allows for a high degree of accuracy in an assessment result and, on the other hand, can be carried out offline and autonomously within the scope of data processing capabilities in current on-board systems, in particular battery management systems, or other mobile or stationary applications.

[0018] As an advantage of the invention, the measurement data resolution represents real parameters and influences with high accuracy, but the increased data volume of the measurement data resolution is only subjected to simple processing operations without high requirements on processing capacity.

[0019] A further advantage of the methodology is that the characteristic map in the on-board system or other application target can be updated at any time by quickly establishing a data connection, whereby the latest findings from a central development of the evaluation technology can always be incorporated into an improvement in the accuracy of the result of the evaluation procedure in local application.

[0020] Further advantages of the invention include a flexible application of the evaluation, which, as described above, can be carried out offline by implementing it in a battery management system of an on-board system with the dedicated measuring circuit, in a controller of a stationary storage device, or by implementing a mobile or stationary evaluation device with a data interface, e.g., as part of a maintenance equipment for service personnel. Alternatively, the evaluation can be carried out online, by a service provider's data center after transmission of measurement data from a vehicle, from the evaluation device, or other application target.

[0021] A further advantage lies in the use of voltage sensors on the battery cells, which are usually already present as part of a battery management system of a traction battery in the vehicle or, if necessary, on a stationary battery storage system.

[0022] According to one aspect of the invention, the on-board system may comprise a temperature sensor for detecting a battery temperature; wherein the stored characteristic map comprises a specific assignment of the SOH values ​​of the high-voltage battery to the internal resistance values ​​depending on and / or a condition of battery temperature values.

[0023] According to one aspect of the invention, the on-board system can have a voltage sensor for detecting an output voltage of the high-voltage battery; wherein the stored characteristic map comprises a specific assignment of the SOH values ​​of the high-voltage battery to the values ​​of the internal resistance as a function of and / or a condition of the values ​​of the detected output voltage. According to one aspect of the invention, the stored characteristic map can comprise a specific assignment of the SOH values ​​of the high-voltage battery to the values ​​of the internal resistance as a function of and / or a condition of the values ​​of the discharge current.

[0024] According to one aspect of the invention, the processor of the battery monitoring module may have a processing capacity that processes new sets of measured values ​​from the measurements of the discharge measurement interval module that are acquired at a frequency of at least 20 Hz by means of the sensors.

[0025] According to one aspect of the invention, the on-board system may comprise an operating element for operation by a user, having a signal connection to the battery monitoring device, wherein the discharge setting module, the discharge measurement interval module, the voltage difference determination module, the internal resistance determination module and the SOH determination module of the battery monitoring device are activated by means of operation of the operating element.

[0026] According to one aspect of the invention, the high-voltage measuring circuit may include a fuse for protecting against harmful current flow between the high-voltage potentials across the high-voltage measuring circuit, which fuse is connected in series with the measuring resistor and the semiconductor switch.

[0027] According to one aspect of the invention, the method may comprise the optional steps:

[0028] - Measuring a battery temperature using a temperature sensor on the high-voltage battery; and

[0029] - Specifically determining the SOH of the high-voltage battery from the determined internal resistance and the battery temperature based on a map that includes a specific assignment of the values ​​of the SOH of the high-voltage battery to the values ​​of the internal resistance as a function of and / or a condition of values ​​of the battery temperature.

[0030] According to one aspect of the invention, the method may comprise the optional steps of: - measuring a battery voltage by means of a voltage sensor on the high-voltage battery, and

[0031] - Specifically determining the SOH of the high-voltage battery from the determined internal resistance and the battery voltage based on a map that includes a specific assignment of the values ​​of the SOH of the high-voltage battery to the values ​​of the internal resistance as a function of and / or a condition of values ​​of the battery voltage.

[0032] According to one aspect of the invention, the method may comprise the optional step:

[0033] - Specifically determining the SOH of the high-voltage battery from the determined internal resistance and the discharge current based on a map that includes a specific assignment of the values ​​of the SOH of the high-voltage battery to the values ​​of the internal resistance as a function of and / or a condition of values ​​of the discharge current.

[0034] According to one aspect of the invention, the step of measuring and storing at least the individual cell voltages can be carried out by means of the voltage sensors at a frequency of at least 20 Hz.

[0035] According to one aspect of the invention, the method may comprise at least one of the initial steps:

[0036] - Charging the high-voltage battery to the maximum state of charge (SOC) of the high-voltage battery by charging each individual battery cell to a threshold maximum cell voltage at the battery cell, and / or

[0037] - Waiting for a predetermined rest period, preferably a rest period of 45 to 60 minutes, during which the high-voltage battery is in a rest state, after reaching the maximum state of charge (SOC) of the high-voltage battery.

[0038] According to one aspect of the invention, the method may comprise the initial step: - starting the method in response to an actuation of a control element by a user.

[0039] According to one aspect of the invention, the method may comprise one of the initial steps:

[0040] - Disconnecting an electrical connection between the high-voltage battery and a drive train by means of a battery disconnect switch (BDU), and / or

[0041] - Checking the operating condition of the vehicle and an electrical connection between the high-voltage battery and a powertrain, and

[0042] - Allowing the method for assessing an ageing condition to be started depending on a condition that the vehicle is in a rest state and the electrical connection between the high-voltage battery and a powertrain is disconnected.

[0043] According to one aspect of the invention, the method may comprise the initial step:

[0044] - Checking whether the battery temperature of the high-voltage battery is within a predetermined temperature range, preferably a temperature range of 25 to 30 °C, by means of the temperature sensor on the high-voltage battery; and

[0045] - Allowing the method for evaluating an aging condition to be started depending on a condition that the battery temperature is within the predetermined temperature range.

[0046] According to one aspect of the invention, a pulse duration of the discharge pulse may be 5 to 10 seconds.

[0047] Furthermore, the method according to the invention can be carried out with an evaluation device for evaluating the aging state of the high-voltage battery in a vehicle. The evaluation device comprises: a microcomputer for carrying out essential method steps; a high-voltage measuring circuit with a series circuit consisting of a measuring resistor and a semiconductor switch, which are electrically connectable between high-voltage potentials of the high-voltage battery of the vehicle; and a data interface, which is communicatively connectable to a data interface of the vehicle, for transmitting measured values ​​acquired by voltage sensors and a current sensor on the high-voltage battery in the vehicle to the evaluation device.

[0048] According to one aspect of the invention, the evaluation device may have a data connection to an external data processing device which carries out at least steps S11 to S15.

[0049] Further advantages, features, and details of the invention will become apparent from the following description, which describes embodiments of the invention in detail with reference to the drawings. The features and embodiments mentioned in the claims and in the description may be essential to the invention individually or in any combination. They show schematically:

[0050] Fig. 1 is a block diagram of the on-board system of a vehicle in which the technique for evaluating an SOH in a first embodiment of the invention is implemented;

[0051] Fig. 2 is a block diagram of an on-board system of a vehicle and an evaluation device connected thereto, in which the technique for evaluating an SOH is implemented in a second embodiment of the invention;

[0052] Fig. 3 is a flow chart illustrating an exemplary sequence of method steps for evaluating an SOH according to the invention; and

[0053] Fig. 4 shows a time course and mutual relationship of a cell voltage and a discharge current during a pulsed discharge via the measuring circuit.

[0054] Fig. 1 shows a block diagram of the essential components of an on-board system 100 of a vehicle in a first embodiment of the invention. The on-board system 100 comprises a battery monitoring device 10, also called a battery management system (BMS), which is equipped with sensors, hardware, and software for measuring and processing measurement data, for monitoring the operating states of a high-voltage battery 30. The high-voltage battery 30 is a traction battery for an electric drive train 50, in particular an inverter and an electric motor of the vehicle. A disconnecting device 40, also called a battery disconnect unit (BDU), is arranged between the high-voltage battery 30 and the drive train 50 in order to electrically disconnect the drive train 50 from a high-voltage supply line or to switchably reconnect it.

[0055] A dedicated high-voltage measuring circuit 20 is arranged between the high-voltage battery 30 and the isolating device 40 in the high-voltage supply path, i.e., between the potential terminals of the high-voltage battery 30. The high-voltage measuring circuit 20 comprises a measuring resistor 22, a semiconductor switch 21, i.e., a power electronics transistor, and a fuse (not shown), which are connected in series between the potentials of the high-voltage battery 30.

[0056] In the high-voltage battery 30, a plurality of battery cells 31 are grouped in battery modules (not shown) and electrically interconnected so that a battery voltage or output voltage of, for example, 400 V or 800 V is present between the potential terminals of the high-voltage battery 30. A cell voltage sensor 32, which measures the cell voltage of the relevant battery cell 31, is arranged on the arresters of the battery poles of several or preferably all battery cells 31. In addition, a current sensor 33 is arranged in an electrical connection to the potential terminals and measures a battery current or output current, i.e., subsequently in particular the discharge current discharged from the high-voltage battery 30. In a modification of the invention, this current sensor can also be arranged in the high-voltage measuring circuit 20.Furthermore, a voltage sensor (not shown) for detecting the output voltage at the potential terminals or the high-voltage supply line of the high-voltage battery 30 is optionally arranged on the high-voltage battery 30 or the high-voltage measuring circuit 20. Likewise, a temperature sensor for detecting a battery temperature is optionally arranged in or on the high-voltage battery 30.

[0057] The battery monitoring device 10 is connected to the aforementioned sensors 32, 33 via signal connections and processes and stores data from measured values ​​acquired by the sensors 32, 33. The battery monitoring device 10 carries out essential components of the inventive assessment of an SOH, wherein the hardware and software of the battery monitoring device 10 for this purpose comprise the functional sections of a discharge setting module 11, a discharge measurement interval module 12, a voltage difference determination module 13, an internal resistance determination module 14, and an SOH determination module 15. A function of the listed modules will be referred to later in the context of similarly designated method steps for assessing the SOH. The SOH assessment is initiated based on user input via an operating element 60, such as a switch on the vehicle's dashboard or a menu item in an operating system.

[0058] Fig. 2 shows, in a second embodiment of the invention, an evaluation device 200 connected to a conventional on-board system of a vehicle, which also includes essential components described above. In contrast to the first embodiment, the evaluation device 200 comprises the high-voltage measuring circuit 20 as a separate component, which is electrically connected to the potential terminals of the high-voltage battery 30 by means of suitable terminals or to the high-voltage supply line of the conventional on-board system of the vehicle by means of service connections provided on the vehicle.

[0059] The evaluation device 200 comprises a data interface 230, such as a CAN bus or similar data infrastructure, which is connected to the battery monitoring device 10 or directly to the sensors 32, 33 via a corresponding connection of a vehicle-side data interface. Thus, the evaluation device 200 controls a pulsed discharge process of the high-voltage battery 30 via the high-voltage measuring circuit 20 and obtains measured values ​​from the sensors 32, 33 located in the vehicle, in particular in the high-voltage battery 30, via the data interface 230. Subsequent processing of the measured values ​​takes place either in a microcomputer whose hardware and software comprise the same functional sections of the previously mentioned modules 11, 12, 13, 14, and 15 of the battery monitoring device 10.Alternatively, in a modification of the second embodiment, the data is transmitted to an external data center via a data connection. The evaluation device 200 or the external data center performs the method steps for evaluating the SOH offline or online, which are similarly named to the listed modules and are described below.

[0060] Fig. 3 shows a flowchart with an exemplary sequence of initial steps (shown in dashed lines), optional steps and essential steps of the evaluation procedure.

[0061] First, in an initial step S70, the high-voltage battery 30 is fully charged, i.e., until a state of charge (SOC) is substantially 100% with respect to an application-specific permissible operating range. To achieve this state of charge, each battery cell 31 is charged and only disconnected from a charging current when the respective cell voltage has reached a predetermined maximum threshold.

[0062] Thereafter, in an initial step S71, a waiting period of approximately 45 to 60 minutes is preferably observed, while an operating state of the high-voltage battery 30 and a driving state of the vehicle are in a rest state. During this time, the high-voltage battery 30 can cool down internally to a preferred operating temperature. Ensuring the rest state is accompanied by the fact that, in an initial step S40, an electrical connection between the drive train 50 and the high-voltage battery 30 is severed by means of the separating device 40.

[0063] In a preferred initial step S60, the evaluation of the SOH is requested and triggered by a user command, for example in the form of a user actuation.

[0064] In an optional initial step S41, as part of a safety function, after activation of the SOH assessment, it can first be checked whether the vehicle is actually in the idle state and whether the drive train 50 is actually disconnected from the high-voltage battery 30. Likewise, in an optional initial step S80, it can first be checked whether the battery temperature, which is detected by the temperature sensor in or on the high-voltage battery 30, is within a preferred temperature range of 25°C to 30°C. The checks from steps S41 and S80 serve as a preferred prerequisite or as a basic condition for starting the SOH assessment.

[0065] In an essential step S11, by controlling and regulating the semiconductor switch 21, a discharge current pulse with a rectangular shape, i.e., essentially with vertical edges and a constant current magnitude, is set between the high-voltage potentials over a pulse duration or discharge duration of the discharge current of approximately 5 to 10 seconds via the high-voltage measuring circuit 20 with the measuring resistor 22. The control of the semiconductor switch 21 can be implemented, for example, by high-frequency, i.e., high-resolution pulse width modulation, for which a suitable driver is implemented in the battery monitoring device 10 or the evaluation device 200.

[0066] In a simultaneous, essential step S12, cell voltages of individual battery cells 31 are recorded and stored by means of the cell voltage sensors 32 during the duration of the discharge pulse at a frequency of at least 20 Hz. Furthermore, a profile of the discharge current discharged from the high-voltage battery 30 via the high-voltage measuring circuit 20 during the duration of the discharge pulse is recorded and stored by means of the current sensor 33. The simultaneously recorded measured values ​​of the cell voltages of different battery cells 31 are preferably stored in common measured value sets with a numbered sequence or a time stamp. Furthermore, the measured values ​​of the discharge current are preferably also assigned to the measured values ​​of the cell voltages in the measured value sets with a similar or lower temporal resolution.

[0067] In an optional step S12A, the battery temperature or a battery temperature profile can be recorded using the temperature sensor in temporal relation to the duration of the discharge pulse and stored associated with the other measured values. In a further optional step S12B, a battery temperature profile, i.e., the output voltage between the high-voltage potentials, can be recorded using the voltage sensor and stored associated with the other measured values.

[0068] In a subsequent essential step S13, the stored measured values ​​of the cell voltages are averaged using an empirical formula, i.e., average values ​​are created for characteristic measurement points. In particular, simultaneously recorded minimum cell voltages among the battery cells 31 are combined to form an average minimum cell voltage, and simultaneously recorded maximum cell voltages among the battery cells 31 are combined to form an average maximum cell voltage, and the respective voltage difference is calculated from this. Subsequently, a maximum voltage difference is determined from a curve of the calculated voltage differences, i.e., a snapshot with the greatest difference between the average minimum cell voltage and the average maximum cell voltage among the battery cells 31 with the same time reference.

[0069] In a subsequent essential step S14, the internal resistance of the high-voltage battery 30 is determined according to Ohm's law based on the determined maximum voltage difference divided by a simultaneous discharge current. Thus, a value of the internal resistance of the high-voltage battery 30 is determined based on the maximum average voltage difference among the battery cells 31 within the course of the discharge current pulse.

[0070] Subsequently, in a final, essential evaluation step S15, the determined value of the internal resistance of the high-voltage battery 30 is compared with a map, also called a look-up table. The map contains values ​​assigned to different internal resistance values ​​for the evaluation of the SOH or aging state of the high-voltage battery 30, which were previously predetermined in experimental and empirical studies.

[0071] In further embodiments with an optional more specific determination of the SOH, additional recorded parameters can be included in the evaluation, whereby their influence on the measurement conditions or their cause in the battery is taken into account in advance in a further dimension of the characteristic map.

[0072] Thus, in a step S15A, the internal resistance together with the battery temperature can be compared with the characteristic map, wherein the characteristic map contains a specific evaluation of the SOH relative to the internal resistance as a function of an influence of the battery temperature measurement or as a function of a characteristic cause in the battery on a development profile of the battery temperature. Similarly, in a step S15B, the internal resistance together with the battery voltage, i.e. the output voltage, can be compared with the characteristic map, wherein the characteristic map contains a specific evaluation of the SOH relative to the internal resistance as a function of an influence on the battery voltage measurement or as a function of a characteristic cause in the battery on a development profile of the battery voltage.

[0073] Likewise, in a step S15C, the internal resistance together with the discharge current can be compared with the characteristic map, wherein the characteristic map contains a specific evaluation of the SOH to the internal resistance depending on an influence on the measurement of the discharge current or depending on a characteristic cause in the battery on a development curve of the battery voltage.

[0074] Of course, steps S15A, S15B and S15C can be combined individually or together in the comparison with the map in step S15.

[0075] Fig. 4 shows parallel exemplary temporal profiles of a voltage response of a detected cell voltage of a battery cell 31 during a detected discharge current of a set discharge pulse. The discharge current is regulated at a constant plateau during a rectangular pulse. A voltage difference of a spontaneous voltage change, i.e., with a substantially vertically falling edge, is measured at the battery cells and used as an average value to determine the voltage difference. A remaining voltage drop results from a lower state of charge (SOC) after the discharge pulse and also contains information on the aging state (SOH).

[0076] In this context, in step S14 of the evaluation, Ohm's law is applied:

[0077] R = AU / 1 to determine the internal resistance of the high-voltage battery 30 in the form:

[0078] Internal resistance = voltage difference / current value. The above explanations of the embodiments describe the present invention exclusively within the framework of examples. Of course, individual features of the embodiments can be freely combined with one another, provided they are technically feasible, without departing from the scope of the present invention.

[0079] List of reference symbols

[0080] 10 Battery monitoring device (BMS)

[0081] 11 Discharge adjustment module

[0082] 12 Discharge measurement interval module

[0083] 13 Voltage difference determination module

[0084] 14 Internal resistance determination module

[0085] 15 SOH determination module

[0086] 20 High-voltage measuring circuit

[0087] 21 semiconductor switches

[0088] 22 Measuring resistor

[0089] 30 high-voltage battery

[0090] 31 battery cells

[0091] 32 cell voltage sensors

[0092] 33 Current sensor

[0093] 40 Separator Device (BDU)

[0094] 50 Powertrain

[0095] 60 control element

[0096] 100 on-board system

[0097] 200 evaluation device

[0098] 230 Data interface

Claims

Patent claims 1. On-board system (100) of a vehicle for evaluating a state of aging (SOH) of a high-voltage battery (30) with a plurality of battery cells (31), comprising: Voltage sensors (32) for detecting cell voltages of individual battery cells (31), and a current sensor (33) for detecting a discharge current of the high-voltage battery (30); a battery monitoring device (10) for monitoring a state of the high-voltage battery (30), with signal connections to the sensors (32, 33) and a processor for data processing of detected measured values from the sensors (32, 33); characterized in that a high-voltage measuring circuit (20) is connected between high-voltage potentials of the high-voltage battery (30), with a measuring resistor (22) and a semiconductor switch (21), for setting a defined discharge pulse on the high-voltage battery (30);wherein the battery monitoring device (10) comprises: a discharge setting module (11) for setting a predetermined discharge current of the discharge pulse flowing via the high-voltage measuring circuit (20), with a signal connection to the semiconductor switch (21) for outputting a control signal to the semiconductor switch (21); a discharge measuring interval module (12) for measuring cell voltages of individual battery cells (31) and the discharge current at predetermined intervals or at a predetermined frequency by means of the sensors (32, 33), and with a memory for storing measured values of the cell voltages and the discharge current while assigning a sequence or time; a voltage difference determination module (13) for determining voltage differences between minimum cell voltages and maximum cell voltages; Cell voltages among the stored measured values of the cell voltages and for determining a maximum voltage difference among the determined voltage differences; an internal resistance determination module (14) for determining an internal resistance of the high-voltage battery (30) from the previously determined maximum voltage difference and the discharge current based on a stored formula that includes Ohm's law; and an SOH determination module (15) for determining an SOH of the high-voltage battery (30) from the previously determined internal resistance based on a stored characteristic map that includes an assignment of values of the SOH of the high-voltage battery (30) to values of the internal resistance.

2. On-board system (100) according to claim 1, comprising a temperature sensor for detecting a battery temperature; wherein the stored characteristic map comprises a specific assignment of the values of the SOH of the high-voltage battery (30) to the values of the internal resistance as a function of and / or a condition of values of the battery temperature.

3. On-board system (100) according to claim 1 or 2, comprising a voltage sensor for detecting an output voltage of the high-voltage battery (30); wherein the stored characteristic map comprises a specific assignment of the values of the SOH of the high-voltage battery (30) to the values of the internal resistance as a function of and / or a condition of values of the detected output voltage.

4. On-board system (100) according to one of claims 1 to 3, wherein the stored characteristic map comprises a specific assignment of the values of the SOH of the high-voltage battery to the values of the internal resistance as a function of and / or a condition of values of the discharge current.

5. On-board system (100) according to one of claims 1 to 4, wherein the processor of the battery monitoring module (10) has a processing capacity that processes new sets of measured values from the measurements of the discharge measuring interval module (12) that are acquired at a frequency of at least 20 Hz by means of the sensors (32, 33).

6. On-board system (100) according to one of claims 1 to 5, comprising an operating element (60) for actuation by a user, with a signal connection to the battery monitoring device (10), wherein the discharge setting module (11), the discharge measuring interval module (12), the voltage difference determination module (13), the internal resistance determination module (14) and the SOH determination module (15) of the battery monitoring device (10) are activated by actuation of the operating element (60).

7. On-board system (100) according to one of claims 1 to 6, wherein the high-voltage measuring circuit (20) comprises a fuse (23) for protecting against a harmful current flow between the high-voltage potentials via the high-voltage measuring circuit (20), which fuse is connected in series with the measuring resistor (22) and the semiconductor switch (21).

8. Method for evaluating a state of aging (SOH) of a high-voltage battery (30) with a plurality of battery cells (31), preferably on board a vehicle, comprising the steps - setting (S11) a discharge pulse with a predetermined discharge current which, after a maximum state of charge (SOC) of the high-voltage battery (30), flows via a measuring resistor (22) and a semiconductor switch (21) between high-voltage potentials of the high-voltage battery (30), by means of the semiconductor switch (21); - measuring (S12) cell voltages of individual battery cells (31) of the high-voltage battery (30), as well as the discharge current of the high-voltage battery (30) at predetermined intervals or at a predetermined frequency by means of voltage sensors (32) on individual battery cells (31) and a current sensor (33) in electrical connection with the high-voltage battery (30), during a discharge period of the discharge current, and storing simultaneously recorded measured values of the cell voltages and the discharge current in a memory, assigning a sequence or time; - Determining (S13) voltage differences between minimum cell voltages and maximum cell voltages among the stored Measuring the simultaneously recorded cell voltages and determining a maximum voltage difference among the previously determined voltage differences; - determining (S14) an internal resistance of the high-voltage battery (30) from the previously determined maximum voltage difference and the discharge current, based on a formula including Ohm's law; and - Determining (S15) an SOH of the high-voltage battery (30) from the determined internal resistance based on a characteristic map comprising an assignment of values of the SOH of the high-voltage battery (30) to values of the internal resistance.

9. A method for assessing an aging condition according to claim 8, comprising the optional steps: - measuring (S12A) a battery temperature by means of a temperature sensor on the high-voltage battery (30); and - Specifically determining (S15A) the SOH of the high-voltage battery (30) from the determined internal resistance and the battery temperature based on a characteristic map comprising a specific assignment of the values of the SOH of the high-voltage battery (30) to the values of the internal resistance as a function of and / or a condition of values of the battery temperature.

10. A method for assessing an ageing condition according to claim 8 or 9, comprising the optional steps: - measuring (S12B) a battery voltage by means of a voltage sensor on the high-voltage battery (30), and - Specific determination (S15B) of the SOH of the high-voltage battery (30) from the determined internal resistance and the battery voltage based on a map that allows a specific assignment of the values of the SOH of the high-voltage battery (30) to the values of the Internal resistance depending on and / or a condition of battery voltage values.

11. A method for assessing an aging condition according to any one of claims 8 to 10, comprising the optional step: - Specifically determining (S15C) the SOH of the high-voltage battery (30) from the determined internal resistance and the discharge current based on a characteristic map comprising a specific assignment of the values of the SOH of the high-voltage battery (30) to the values of the internal resistance as a function of and / or a condition of values of the discharge current.

12. A method for evaluating an aging state according to one of claims 8 to 11, wherein the step of measuring (S12) and storing at least the individual cell voltages is carried out by means of the voltage sensors (32) at a frequency of at least 20 Hz.

13. A method for assessing an aging condition according to any one of claims 8 to 12, comprising at least one of the initial steps: - charging (S70) the high-voltage battery to the maximum state of charge (SOC) of the high-voltage battery (30) by charging each individual battery cell (31) up to a threshold value of a maximum cell voltage at the battery cell (31), and / or - Waiting (S71) for a predetermined rest period, preferably a rest period of 45 to 60 minutes, in which the high-voltage battery (30) is in a rest state, after reaching the maximum state of charge (SOC) of the high-voltage battery (30).

14. A method for assessing an aging condition according to any one of claims 8 to 13, comprising the initial step: - Starting (S60) the method in response to an actuation of an operating element (60) by a user.

15. A method for assessing an aging condition according to any one of claims 8 to 14, comprising at least one of the initial steps: - Disconnecting (S40) an electrical connection between the high-voltage battery (30) and a drive train (50) by means of a disconnect switch (BDU) (40), and / or - checking (S41) an operating state of the vehicle and an electrical connection between the high-voltage battery (30) and a drive train (50), and - allowing the method for evaluating an ageing state to be started depending on a condition that the vehicle is in a rest state and the electrical connection between the high-voltage battery (30) and a drive train (50) is disconnected.

16. A method for assessing an aging condition according to any one of claims 8 to 15, comprising the initial step: - checking (S80) whether the battery temperature of the high-voltage battery (30) is within a predetermined temperature range, preferably a temperature range of 25 to 30 °C, by means of the temperature sensor on the high-voltage battery (30); and - Allowing the method for evaluating an aging condition to be started depending on a condition that the battery temperature is within the predetermined temperature range.

17. A method for evaluating an aging condition according to any one of claims 8 to 16, wherein a pulse duration of the discharge pulse is 5 to 10 seconds.

18. Evaluation device (200) for evaluating an aging state of the high-voltage battery (30) on a vehicle with the high-voltage battery (30), by carrying out the method according to one of claims 8 to 17, comprising: a microcomputer for carrying out at least the steps S11 to S15; a high-voltage measuring circuit (20) with a series circuit of a measuring resistor (22) and a semiconductor switch (21), which is connected between High-voltage potentials of the high-voltage battery (30) of the vehicle are electrically connectable; and a data interface (230) which is communicatively connectable to a data interface of the vehicle, for transmitting measured values recorded by voltage sensors (32) and a current sensor (33) on the high-voltage battery (30) in the vehicle to the evaluation device (200).

19. Evaluation device (200) according to claim 18, comprising a data connection to an external data processing device which carries out at least steps S11 to S15.

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