Battery Monitoring Unit

Abstract

The present invention relates to a battery monitoring unit (10), the battery monitoring unit (10) comprising an interface (12) coupled to the battery monitoring unit (10) and configured to receive voltages (14A, 14B) for each battery group (22) comprising at least two battery cells (24) connected in parallel to one another of a battery (1) comprising at least two battery groups (22), and an evaluation unit (16) configured to compare the voltages (14A, 14B) of the at least two series-connected battery groups (22) received from the interface (12) with each other and to output a signal (18) based on the result of the comparison.

Description

[Technical field]

[0001] The invention relates in particular to a battery monitoring unit which monitors the connections of a battery group consisting of battery cells connected in parallel and / or in series and parallel to one another, and further to a corresponding battery or traction battery which is constituted by a battery group for an electric vehicle. [Background technology]

[0002] Electrochemical energy storage devices used as traction batteries, particularly lithium ion batteries, typically have a number of battery cells organized into battery banks that are interconnected in series and / or parallel to form a battery assembly that achieves a desired total capacity and voltage for each end use of the battery, e.g., for a particular traction battery for electric and hybrid vehicles.

[0003] Voltage taps are present between battery groups constituted by battery cells interconnected in parallel, making it possible to determine the voltage applied to each of these battery groups, which can for example be transmitted to a battery management system, where occurrences of overvoltage during charging of a battery cell or undervoltage during discharging of a battery cell can be detected and avoided accordingly by suitable measures, for example by terminating the charging process.

[0004] The cells of such batteries are typically further interconnected to provide a total voltage of several hundreds of volts, particularly when used in hybrid and electric vehicles, with the voltage applied to each battery cell usually being only a few volts due to the series connection. However, if a fault occurs in such a battery, for example if the electrical connections of some or all of the battery cells of the battery are broken, a fraction of the battery voltage, or in extreme cases the total battery voltage, which often even reaches 800V or more, will be applied to this point in the circuit. This can cause a short circuit due to an arc in such a case, which can cause serious damage to the battery or the entire vehicle.

[0005] Failure of battery cells in a battery bank may occur in succession and may be associated with a corresponding step change in the voltage of each battery bank.

[0006] Systems are known that shut down batteries when the voltage measured for a particular battery group exceeds a nominal or previously stored value, but such methods are only reliable to a limited extent. This is because such values ​​may be set for a particular battery configuration or for a battery series that does not exactly match the individual battery to be monitored in a concrete case. Furthermore, the condition of a battery may vary significantly over the life of the battery, for example, influenced by the battery's age, charging and discharging time, application-specific load, operating time, operating conditions, and / or environmental conditions. Such a general nominal value may therefore not be applicable to individual batteries and / or battery conditions, and therefore must include a larger tolerance range. However, as a result, in certain circumstances, a critical condition of the battery can only be determined at a late stage. Therefore, there is a need to enable more accurate battery monitoring that provides early detection of failures, preferably usable across multiple batteries and / or multiple battery types. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] European Patent Application Publication No. 2649700 [Patent Document 2] European Patent Application Publication No. 3370992 [Patent Document 3] DE 102017218560 Summary of the Invention [Problem to be solved by the invention]

[0008] SUMMARY OF THE PRESENT EMBODIMENT It is an object of the present invention to depart from the known prior art and to provide an improved battery monitoring. [Means for solving the problem]

[0009] This object is achieved by a battery monitoring unit having the features of claim 1. Advantageous embodiments can be derived from the dependent claims, the description and the figures.

[0010] Therefore, a battery monitoring unit is proposed, comprising an interface coupled to the battery monitoring unit and configured to receive voltages via respective voltage taps for each battery group of the battery comprising at least two battery cells connected in parallel with each other. According to the invention, an evaluation unit is provided, which is configured to compare the received voltages of the at least two series connected battery groups of the battery with each other and to output a signal based on the result of the comparison.

[0011] A battery group may be formed as a battery module that is mechanically and electrically integrated together, or as a logical unit within a battery module or battery. A battery group is characterized by being composed of at least two battery cells interconnected in parallel, regardless of the mechanical structure and spatial arrangement within the battery, and having its own voltage tap.

[0012] Typically, the same number of battery cells are provided in each battery group, and the battery cells of a battery group are connected in parallel. When the batteries are in an operational state, if each battery cell has a voltage that is defined for that operational state, a comparison of the voltages of at least two battery groups will result in substantially similar voltages, apart from general measurement variations. However, if one or more battery cells in a battery group are not functioning as defined, the voltage of the battery group taken out will be different from each of the other batteries in the pair of batteries. In other words, by comparing the voltages taken at the voltage taps of at least two series-connected battery groups, even small voltage changes that deviate from normal or expected conditions can be detected.

[0013] Comparison of the voltages taken between the voltage taps of individual groups of cells may be particularly easily achieved by subtracting the measurements: if the cells are operating as expected in normal operation the difference will be substantially zero, and if differences in voltage occur the difference will move away from zero.

[0014] Comparison of the voltages taken between the voltage taps of a group of cells can also be achieved by forming a quotient of the measurements: when the cells are operating in normal operation, the quotient is substantially 1, and when the measured voltages differ, the quotient deviates from 1.

[0015] The comparison of the measured voltages can also be performed by other computational comparison options.

[0016] In this way, a very accurate monitoring of the battery state is possible, since even a small difference in voltage can indicate, for example, a cell loss or an imminent cell loss, which is particularly beneficial when there is a large number of parallelizations in battery groups and a corresponding large number of respective parallel-connected battery cells per battery group, since this allows early detection of existing faults that may otherwise cause serious or even dangerous failures.

[0017] As a safety measure, for example, a membrane-based current-interrupt device (CID) may be provided in the battery cell, which selectively interrupts the electrical contacts in case of excessive gas generation in the battery cell, for example due to aging, production faults or overloading and the associated pressure build-up in the battery cell. Early detection of such an interruption can prevent the triggering of a chain reaction due to a corresponding increased current flow in the remaining battery cells of the respective battery group, thus significantly improving safety. Such a stoppage of one or more battery cells in the battery group can thus be detected by means of the proposed battery monitoring unit.

[0018] Furthermore, the battery monitoring unit makes it possible to perform a global monitoring of the batteries, regardless of the specific battery configuration, since thanks to the relative comparison of at least two series-connected groups of batteries, a comparison of the absolute values ​​of the individual voltages with a voltage defined for each group of batteries depending on their type and / or configuration can be made unnecessary.

[0019] Similarly, determining a difference value, for example for comparison, allows the output of a signal to be performed generally, regardless of the power or the corresponding battery group. Any possible changes in the state of the battery over the service life or lifespan of the battery, for example due to the battery life, charging and discharging time, application-specific load, operating time, operating conditions, and / or environmental conditions, can likewise be automatically taken into account for the respective battery groups of the battery, since they do not change significantly during operation. Thus, an accurate monitoring of the state of the battery is achieved, allowing early detection of failures over the entire lifespan.

[0020] The battery monitoring unit may for example be formed as a separate module or as a component integrated in the control unit of the battery. The battery monitoring unit comprises an evaluation unit for evaluating the received voltage or measurement values ​​and determining or calculating a corresponding comparison for at least two series-connected battery groups. The interface may for example be present as a hardware component enabling an electrical coupling with the respective voltage taps and / or may at least partly comprise a computer-readable logic circuit for transmitting the corresponding measurement signals or data.

[0021] The comparison and, for example, the determination of difference values ​​can further be performed for various series-connected battery groups. Difference values ​​can, for example, be determined for battery groups that are not directly adjacent to each other and / or for battery groups that are interconnected by multiple battery groups and together form a battery group. The respective difference values ​​can be determined substantially simultaneously or successively, so that multiple difference values ​​can be taken into account when a signal is output, or a signal can be output for each individual difference value.

[0022] For example, in the case of multiple groups of cells, the voltages of non-adjacent groups of cells can be compared with each other, and this comparison can be repeated for each subsequent or adjacent group of cells, so that the presence of a potential fault in an individual group of cells can be inferred or determined from these voltage values. However, it may also be possible to compare multiple groups of cells arranged side by side, for example two adjacent groups of cells, with a corresponding number of mismatched groups of cells arranged side by side. In this way, for example, a determination can be drawn regarding the absence or presence of a potential fault in a particular area of ​​the group of cells.

[0023] Similarly, a level of safety redundancy may be achieved by determining a comparison, e.g., difference, of each battery group with one or more other batteries groups, or with all other batteries groups individually. By comparing all the individual batteries groups with each other, for example, voltage fluctuations may be masked, further increasing the accuracy of the monitoring.

[0024] Preferably, the evaluation unit of the battery monitoring unit is configured to perform a comparison and determine a difference value, for example at least for adjacent battery groups, the term "adjacent" being understood in the sense of, for example, in the direction of the power terminals, or in the successive arrangement of corresponding series voltage taps, such that the voltage of one battery group is compared with the voltage of another battery group, which is located just closer to the power terminals.

[0025] In this way, any faults that may exist for individual battery groups can be determined, without the need for configuration data relating drawn voltages to respective battery groups. In other words, a signal can be output for a specific individual battery group, and very accurate monitoring of the battery's condition can be achieved as well.

[0026] Further preferably, the evaluation unit of the battery monitoring unit is configured to output a signal if the respective difference value exceeds a predefined threshold. The threshold may for example be a value characteristic of an increase in voltage, corresponding to the voltage of one or more battery cells, which may for example supply a normalized power. The threshold may likewise be selected for a predefined increase in ohmic resistance, which resistance is characteristic of the presence of a potential fault, such as a breakage of one or more battery cells. In this regard, the voltage drop across the battery group at a certain current flow rate can be measured, and from the voltage drop the ohmic resistance value of this battery group can be inferred or determined.

[0027] The evaluation unit of the battery monitoring unit may alternatively or additionally also be configured to output a signal when the ratio between the difference value and the voltage value of at least one of the group of batteries generating the difference value is between 0.01:1.0 and 0.25:1.0, preferably between 0.05:1.0 and 0.20:1.0.

[0028] In other words, the difference value can be determined as a percentage of the drawn voltage of a particular battery group, preferably of the respective lower voltage, and a signal can be output if this percentage is between 1 percent and 25 percent of the voltage, or between 5 percent and 20 percent, or exceeds this value. For example, a signal can be output if the difference value exceeds about 15 percent. This percentage can be preset in such a way that typical variations in voltage for the output of the signal are ignored, and a fault is present with sufficient probability, or even a specific fault can be predefined as a percentage. The percentage can thus be selected such that an inspection or action is required if it is exceeded.

[0029] Another advantage of such an embodiment is that the monitoring of the batteries is generally performed independently of the battery configuration. Thus, no absolute values ​​or thresholds of power are necessary, and thus the monitoring of the battery state can be performed for each type of battery, independent of the corresponding configuration of the battery. Thus, a percentage can serve as a threshold, without corresponding to an absolute value of the voltage. This is also beneficial with regard to possible changes in the characteristics of the batteries over their service life, since in particular it can be assumed that the characteristics of the respective battery groups change similarly over time, for example due to charging cycles and operating conditions. The defined ratio or percentage can be meaningful or meaningful for fault detection, independent of the service life.

[0030] To make the output of the signal even more specific or to take into account various operating conditions, the difference values ​​can be determined both in an idle state and in a loaded state under a known current flow rate, and the corresponding difference values ​​can be compared with each other. In this way, the effects of various charge states of the battery cells can be calculated out and taken into account when outputting the signal.

[0031] Such testing can be performed permanently or intermittently during normal or regular operation of the battery. Furthermore, any manufacturing defects can also be detected using this means, for example if the defects are checked or tested as a final test on the line immediately after production in the production factory.

[0032] In this way, defects in the welded joints of, for example, the entire battery group or partial regions of the battery group can be determined, which may be present if, for example, due to manufacturing faults or tolerances, the corresponding connecting ribs or busbars are not correctly positioned, and as a result all or most of the welded joints of the battery group or of the respective parallel-connected battery cells are not correctly performed. When using the battery, such welded joints would possibly break due to excessive boundary resistance. Checking the difference value with a small current outflow therefore has the advantage that such undesirable, possibly dangerous, situations can be detected and avoided.

[0033] Similarly, the process requirements for electrical contact of the battery cells can be relatively minimal, particularly since failures can be reliably detected retrospectively, and therefore production can be simplified or made easier, and in some cases, faster and more cost-effective.

[0034] The behavior of each battery group, or the progression of each battery group over its useful life, may further vary and may also experience fluctuations or variations depending on the operating conditions. Furthermore, current interrupt devices may not be activated despite potential failures in individual battery cells. However, the characteristics of individual battery cells may deteriorate over the battery's useful life, which is reflected in the corresponding voltages.

[0035] The evaluation unit of the battery monitoring unit can therefore be configured to record the course or progression of the respective comparison value, e.g. the difference value, and to output a signal if the progression deviates from the predetermined progression. In this way, adverse trends can be detected at an early stage and the respective battery group can be identified, so that defective battery cells of this battery group, battery groups with defective battery cells, battery modules with battery groups with defective battery cells or the entire battery can be subsequently replaced if necessary. The predetermined progression can be stored in the battery monitoring unit and can be taken into account together with the recorded progressions as part of the comparison, e.g. the determination of the difference value or when outputting a signal.

[0036] The predetermined progression may include, for example, an expected progression of the difference value over a particular service life, or a more complex polynomial progression may be defined that is compared to the recorded progression, for example using statistical evaluation and correlation, and a signal may be output if the correlation deviates from a specified tolerance range.

[0037] Preferably, the evaluation unit of the battery monitoring unit is configured to determine a total resistance of the respective battery group (or groups) based on the respective comparison, e.g. difference value, which total resistance is characteristic of the operating state of the battery group. In this way, an ohmic resistance expected in the operating state can be input to the evaluation of the difference value and to the output of a signal, which resistance may be higher, e.g. in the case of maximum operation or full load, due to a relatively high temperature. However, if the total resistance, e.g. in normal operation, differs from the defined or assumed total resistance and this resistance is higher thereto, then the higher total resistance may be characteristic of the presence of a cell breakage and therefore a signal can be output.

[0038] Furthermore, the evaluation unit of the battery monitoring unit may be configured to have a current / voltage characteristic curve and to output a signal based on the respective difference value and the current / voltage characteristic curve. A change in the corresponding resistance value of each battery group for each specific difference value, which may be specific to the presence of a specific fault, may be calculated based on the current / voltage characteristic curve, e.g. based on experimental values. In other words, a more accurate fault detection may be performed based on the characteristic curve.

[0039] It may also be possible to provide the characteristic curves from a central unit, such as a server or a central vehicle control system. Thus, preferably, the evaluation unit of the battery monitoring unit may be configured to receive characteristic data relating to the battery via the interface, to transmit or inform said data to the central unit, and to receive from the central unit at least one current / voltage characteristic curve depending on the transmitted characteristic data, the battery monitoring unit being configured to output a signal based on the respective difference value and the current / voltage characteristic curve. The battery monitoring unit may comprise a communication module or be communicatively coupled to a communication module of the control unit of the battery in order to transmit and receive the corresponding data. Among other things, the acquisition of the at least one characteristic curve has the advantage that updated characteristic curves may be available and that the specific characteristic data can be taken into account so that the characteristic curve of the respective battery can be identified.

[0040] The characteristic data may include the type of battery, the number of parallel-connected battery cells per battery group, the type of cells, the number of series-connected battery groups, the use of the battery, and / or operational data regarding the battery. Thus, a characteristic curve can be further specified, which can be tailored to the battery, the structure of the battery, the usage of the battery, and / or the progress of the battery over its useful life. This allows, for example, a change in the total resistance to be very accurately determined based on a comparison, for example, between the difference value and the characteristic curve, thus further improving early detection of potential failures. Any thresholds can be adapted as necessary, and the tolerance range can be reduced.

[0041] Furthermore, based on the characteristic data it may be possible to obtain only the characteristic curve relevant to that battery. The characteristic curve provided by the central unit may be based on experimental values ​​of actually drawn voltages and / or comparison data and / or difference values ​​actually determined for batteries with comparable characteristic data. Thus, preferably, the battery monitoring unit is adapted to transmit the received voltages and / or the respective comparison data and / or the respective difference values ​​to the central unit, and the received current / voltage characteristic curve is based on the voltages and / or comparison data and / or difference values ​​evaluated by the central unit for a number of batteries with corresponding characteristic data.

[0042] Thus, for example, data of a number of batteries of a corresponding number of vehicles can be collected centrally and evaluated in an anonymous manner, and a characteristic curve is adapted based on the collected data and the state of the corresponding batteries. Preferably, the characteristic curve received from the battery monitoring unit thus corresponds to the experimental values ​​of a battery having a corresponding battery state. As a result, fault detection can be made more accurate and voltage changes that would also be detected based on the (real) characteristic curve and would otherwise cause a signal to be output can be ignored based on the experimental values.

[0043] As described above, the corresponding current flow rate can be determined based on the current / voltage characteristic curve corresponding to the retrieved voltage or comparison, e.g., the determined difference value characteristic of the voltage change. Thus, based on the current flow rate and the difference value, the total resistance value of each battery group can be calculated or determined, which allows a more accurate decision regarding a potentially occurring fault. More preferably, the battery monitoring unit is configured to receive the current flow rate from each current sensor for the at least two series-connected battery groups via the interface, and further output a signal based on each current flow rate, in order to more accurately determine the potential increase in the total resistance value.

[0044] This reduces the number of unknown variables and, in addition, provides feedback of the expected current flow rate based on the characteristic curve, further increasing the reliability of the output signal.

[0045] The evaluation unit of the battery monitoring unit may also be configured to perform the comparison in real time or at specific time intervals, for example to determine the comparison, for example the respective difference value. In this way the state of the battery can be continuously monitored so that in case of a serious fault a signal can be output immediately. However, since the safety of the battery is increased by the battery monitoring unit by determining the respective difference value, in particular in such a way that even the slightest indications of a fault can be detected, a regular or intermittent determination of the difference value may also be performed or may be sufficient. The determination of the difference value may for example only be performed during normal or normal operation, the determination being preferably performed within a time interval of 1 minute to 1 hour, more preferably 5 minutes to 10 minutes.

[0046] The signals may include battery warnings, maintenance signals, and / or control signals.

[0047] For example, based on the determined difference value, it may be evaluated or determined that at least one battery cell in a particular battery group is damaged or is about to be damaged within a predetermined time. In this case, it may be sufficient in some cases to output a warning signal to draw the user's attention to the absence or presence of a fault, for example by means of a communication module. A maintenance signal may also be output, for example as part of the warning signal, to indicate that measures are needed to avoid any potential damage to the battery and the vehicle, for example that a particular battery group or battery module needs to be inspected or repaired, or that the corresponding battery cell, battery group, battery module, or the entire battery needs to be replaced.

[0048] Furthermore, in the case of, for example, a sudden fault, a control signal can be output to initiate a protection measure. In this way, the power of the battery can be limited so that the maximum current load is limited. The battery can also be isolated from the consumer side by a contactor to prevent current flow. Thanks to the early detection of a fault and the output of a corresponding signal, the safety of the battery and also its ability to not affect the components can thus be significantly increased. Even if the early detection of a potential fault can largely avoid possible chain reactions of the membrane-based current interruption devices described above, for example due to aging or overload, such protection measures can still be provided to ensure sufficient battery safety in emergency situations.

[0049] The battery monitoring unit may be suitable for a number of applications and battery types. Preferably, the battery monitoring unit is configured to monitor a traction battery. The battery monitoring unit may thereby be formed as a module for the traction battery of, for example, an electric vehicle.

[0050] The above object is further achieved by a traction battery comprising a battery monitoring unit according to the invention.

[0051] The traction battery may represent, for example, corresponding series-connected battery groups, each comprising parallel-connected battery cells, with each battery group being provided with a voltage tap capable of communicating with and / or electrically coupled to an interface of the battery monitoring unit. More preferably, each battery group may comprise a plurality or a multiplicity of cylindrical battery cells. The interface may be present as a stand-alone component of the battery monitoring unit or as part of the traction battery's control unit, if the monitoring unit is designed accordingly. The traction battery may further comprise contactors enabling isolation from the consumer side, and further comprises power terminals, which may be configured or designed for the specific application of the battery. Preferably, the traction battery is configured for an electric vehicle.

[0052] Further preferred embodiments of the invention will be explained in more detail by the following description of the drawings. [Brief description of the drawings]

[0053] [Figure 1] FIG. 2 is a schematic diagram of a battery monitoring unit. [Diagram 2] FIG. 2 is a schematic diagram of an arrangement of series-connected battery groups providing voltage for adjacent battery groups. [Diagram 3] FIG. 3 is a schematic diagram of an arrangement according to FIG. 2 for alternatively supplying the voltage of a number of battery groups. [Figure 4] FIG. 3 is a schematic diagram of an arrangement according to FIG. 2 for alternatively supplying voltages of non-adjacent battery groups. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0054] In the following, preferred embodiments will be described by referring to the figures, in which identical, similar or analogous elements in various figures are given the same reference numerals, and repeated descriptions of these elements will be partially omitted to avoid redundancy.

[0055] In Fig. 1 a battery monitoring unit 10 is shown diagrammatically, optionally formed as a module that can be communicatively connected to a control unit of the battery. The battery monitoring unit 10 comprises an interface 12, as diagrammatically indicated by an arrow, configured to receive voltages 14A, 14B from battery groups 22 of the battery 1, comprising at least two battery cells 24 connected in parallel with one another. The voltages 14A, 14B of each battery group 22 are provided, for example, via voltage taps 28A, 28B, ...28E. This will be clearly presented again below with reference to Figs. 2 to 4.

[0056] The first voltage 14A and the second voltage 14B of the two groups of cells connected in series with each other are received via the interface 12 and according to the present embodiment by an evaluation unit 16 which, in the specific embodiment described herein, compares the received voltages 14A, 14B with each other and determines a difference value from the received voltages 14A, 14B. Alternatively, a quotient can be generated from the voltages 14A, 14B.

[0057] The voltages 14A, 14B to be compared with each other can each be measured via two conductors, and the cells may be adjacent to each other or spaced apart from each other.

[0058] In other words, one or more additional battery groups may be present between the battery groups for which the voltages of 14A and 14B are measured. Similarly, the voltages 14A and 14B may also be measured for multiple battery groups in sequence via their respective conductors.

[0059] The voltages 14A, 14B may each be measured across one battery group or across multiple batteries, so that multiple batteries, rather than pairs of batteries, may similarly be compared with a corresponding number of other batteries, as shown in the figures below.

[0060] The difference value is then compared to a threshold value, which may for example be in the form of an absolute value or a percentage. The absolute value may include both negative and positive values, so that for each group of cells both overvoltages and undervoltages can be taken into account. Furthermore, the determined or obtained difference value may be present as a percentage of the drawn voltage, preferably the respective lower voltage, of the group of cells generating the difference value, and this percentage is then compared to a predefined percentage, which may be considered as a threshold value.

[0061] Based on a comparison of the difference value with a threshold, if the threshold is exceeded, a signal 18 may be output accordingly via interface 12. However, it may alternatively be implemented such that a difference value of a particular magnitude, or greater than a predetermined minimum difference value, causes signal 18 to be output automatically, for example via suitable circuitry.

[0062] In this case, signal 18 optionally includes a warning signal and possibly a control signal depending on the magnitude of the respective determined difference value. In this way, a warning signal can be output if the determined difference value indicates, for example, the possibility that one or more battery cells may be damaged in the near future, and a control signal can be output if the difference value indicates a particularly serious potential failure.

[0063] The signal 18 can initiate safety measures, for example by limiting the power of the battery so that the maximum current load is limited. Similarly, the battery can be isolated from the consumer side by a contactor to prevent current flow and, for example, the triggering of a chain reaction when a current interrupt device is activated.

[0064] In Fig. 1, an optional communication module 20 is further shown, which is communicatively coupled bidirectionally to the evaluation unit 16, as indicated by the corresponding arrow. The communication module 20 can, for example, enable communication with the central unit 100 and / or with a control device of the battery. Via the communication module 20, further application-specific signals or data can also be transmitted. In this way, for example, a maintenance signal can also be transmitted to a maintenance service, where a warning signal can be displayed, for example, on a display. The central unit 100 can, for example, be a central vehicle control system.

[0065] 2 to 4 show schematic diagrams of an arrangement of series-connected cells 22 constituting the battery 1, with a load here connected to the power terminals .

[0066] The battery group 22 supplies, among other things, voltages 14A, 14B for checking the operating state of each of the battery group, and the battery monitoring unit 10 shown in FIG. 1 is able to receive the voltages 14A, 14B via the interface 12.

[0067] It should be understood that this arrangement, in this case, is a schematic representation of a battery module, and that there is no limit to the number of series-connected battery groups 22. Each battery group 22 further comprises a predetermined number (again, not limited in the figure) of battery cells 24 connected in parallel within the respective battery group 22.

[0068] The battery modules as shown diagrammatically here may be designed to constitute, for example, a traction battery of an electric vehicle and may be electrically connected or coupled accordingly to a respective load via power terminals 26. To constitute battery 1, there are typically several battery modules, which are connected together in series or in parallel, for example to achieve a desired capacity and nominal voltage.

[0069] According to Fig. 2, the voltages 14A, 14B of adjacent battery groups 22 are tapped via corresponding voltage taps 28A, 28B, 28C. Thus, the voltage 14A of the battery group 22 at the top of the figure is measured via voltage taps or conductors 28A and 28B, and the voltage 14B of the immediately adjacent battery group 22 (located directly below in the figure) is measured via voltage taps 22B and 22C. The difference values ​​determined by the battery monitoring unit 10 for the adjacent battery groups 22 make it possible to output a signal 18 for a specific or specific individual battery group 22, likewise realizing a very accurate monitoring of the battery state. A potential fault in a specific battery group 22 can then be determined in this way based on the difference values ​​and the determination of the difference values ​​with respect to the adjacent battery groups 22.

[0070] The fault 30 is symbolically shown, in this example, in the upper battery group 22, at the right-hand side of the arrangement, at the battery cell 24. Thus, exceeding the threshold may indicate an increase in the voltage of this particular battery group 22, which may result in, for example, activation of a membrane-based current interrupt device in the battery cell 24, allowing early detection of this fault 30 and avoiding further damage from a potential chain reaction.

[0071] An alternative difference value determination is shown in figures 3 and 4, where in the embodiment according to figure 3 the tapped voltage 14A of one group of cells 22, i.e. the two upper cells 22, is compared or fed with the tapped voltage 14B of one group of the two lower cells 22. Thus, voltage taps 28A and 28C are used for voltage 14A, while voltage taps 28C and 28E are used for voltage 14B. The diversity of the respective cells 22 allows for a simplified monitoring, for example a decision or assessment of the presence of a potential fault in a particular area of ​​the cell group. Such an indication by means of signal 18 of an area can be beneficial, for example, for batteries with a large number of series-connected cells. Furthermore, by this measure the required computing power can also be reduced overall, or existing computing power can be utilized, so that the determination of the difference value and the output of the signal can be performed with improved time division.

[0072] Another alternative is shown in Fig. 4, where voltages 14A, 14B of non-adjacent battery groups 22 are received or provided. Such detection of voltages 14A, 14B via voltage taps 24A, 24B and 24C, 24D may be beneficial, for example, when adjacent battery groups 22 may possibly affect each other under certain operating conditions, thereby allowing operational variations to be ignored. In this way, under certain circumstances, the determined difference value may be more meaningful and possible thresholds may include smaller operational tolerances.

[0073] Moreover, the determination of the difference value can also be made or carried out in this way for successive groups of cells 22, where according to this embodiment the voltage 14A of the upper group of cells 22 is first compared with the voltage 14B of the adjacent group of cells 22, and then subsequently with the group of cells 22 arranged below, etc., thus achieving a certain safety redundancy. Such a successive (or parallel) determination of such a difference value is shown, for example, by the combination of figures 2 and 4. In an advantageous embodiment, the voltage 14A is compared with all the voltages of the respective individual groups of cells 22. In this way, not only the voltages of adjacent groups of cells 22, but also the voltages of pairs of groups of cells of groups of cells 22 that are not directly adjacent to each other, can be compared with each other in order to determine the respective difference values.

[0074] Where applicable, all individual features presented in the embodiments may be combined with one another and / or exchanged without departing from the scope of the invention. [Explanation of symbols]

[0075] 1 battery 10 Battery monitoring unit 12 Interface 14A First Voltage 14B Second Voltage 16 Evaluation Units 18 signal 20 Communication Module 22 Battery group 24 Battery Cells 26 Power terminal 28A~28E Voltage Tap 30 Malfunction 100 Central Unit

Claims

1. A battery monitoring unit (10) including an interface (12) coupled to the battery monitoring unit (10) and configured to receive voltages (14A, 14B) for each battery group (22) of a battery (1) including at least two battery cells (24) connected in parallel with each other, the interface (12) including: an evaluation unit (16) is provided, configured to compare the voltages (14A, 14B) of at least two series-connected battery groups (22) received from the interface (12) with each other and to output a signal (18) based on the result of the comparison; the evaluation unit (16) is configured to compare the voltages (14A, 14B) received from the interface (12) by determining a difference value of the voltages and / or a quotient of the voltages and to output a signal based on the difference value and / or the quotient, The battery monitoring unit (10), wherein the evaluation unit (16) is configured to determine a difference in resistance values ​​of the respective battery groups (22) based on the difference value and / or the quotient, the difference in resistance values ​​being specific to an operating state of the battery groups (22).

2. 2. The battery monitoring unit (10) of claim 1, wherein the evaluation unit (16) is configured to output the signal (18) if the difference value exceeds a predetermined threshold or if the quotient deviates from 1 by a predetermined limit.

3. 3. The battery monitoring unit (10) of claim 1 or 2, wherein the evaluation unit (16) is configured to output the signal (18) when a ratio between the difference value and a voltage value of at least one of the batteries (22) generating the difference value is between 0.01:1.0 and 0.25:1.0, preferably between 0.05:1.0 and 0.20:1.

0.

4. A battery monitoring unit (10) according to any one of claims 1 to 3, configured to record a progression of the result of the comparison, preferably the difference value and / or the quotient, and to output the signal (18) if the progression deviates from a predetermined progression.

5. 5. The battery monitoring unit (10) of claim 1, wherein the evaluation unit (16) comprises a current / voltage characteristic curve and is configured to output the signal (18) based on the respective comparison and the current / voltage characteristic curve.

6. 6. A battery monitoring unit (10) according to claim 1, configured to receive characteristic data of the battery (1) via the interface (12), to transmit the characteristic data to a central unit (100), and to receive from the central unit (100) at least one current / voltage characteristic curve corresponding to the transmitted characteristic data, wherein the evaluation unit (16) is configured to output the signal (18) based on the respective comparison and the current / voltage characteristic curve.

7. The battery monitoring unit (10) of claim 6, wherein the characteristic data includes the type of battery, the number of battery cells connected in parallel per battery group, the type of cells, the number of battery groups connected in series, the use of the battery (1), and / or operational data of the battery (1).

8. A battery monitoring unit (10) as described in claim 6 or 7, configured to transmit the received voltages (14A, 14B) and / or the respective results of the comparison, preferably the difference value and / or the quotient, to the central unit, wherein the received current / voltage characteristic curve is based on voltages evaluated by the central unit for a plurality of batteries (1) having corresponding characteristic data and / or on the results of the comparison.

9. 9. The battery monitoring unit (10) of claim 1, wherein the evaluation unit (16) is further configured to receive current flow rates from respective current sensors for the at least two series-connected battery groups (22) via the interface (12) and to continually output the signal (18) based on the respective current flow rates.

10. 10. The battery monitoring unit (10) of any one of the preceding claims, wherein the evaluation unit (16) is configured to perform the respective comparisons in real time or at predefined time intervals.

11. The battery monitoring unit (10) of any one of the preceding claims, wherein the signals (18) comprise warning, maintenance and / or control signals for the battery (1).

12. The battery monitoring unit (10) according to any one of the preceding claims, wherein the comparison is performed for adjacent battery groups (22) respectively.

13. A traction battery comprising a battery monitoring unit (10) according to any one of claims 1 to 12 and at least two battery groups (22), each battery group (22) comprising a plurality of cylindrical battery cells (24) interconnected in parallel.

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