Battery monitoring system and method for monitoring state of battery

Abstract

The invention relates to a battery monitoring system (1) for monitoring the state of a battery (2), in particular a traction battery of a vehicle (10), the battery monitoring system (1) being designed to monitor the operating state of the battery (2) by evaluating sensor signals of at least two sensors (3) which detect different physical measured variables. Depending on the detected currently present operating situation P of the battery (2); c; d, the battery monitoring system (1) assigns the sensors to have a hierarchical priority L1; l2; l3, and detecting the critical state of the battery (2) by evaluating the signals of the sensor having the hierarchy with the highest priority L1. The invention further relates to a method for monitoring the state of a battery.

Description

Background Art

[0001] Battery-based drive systems using relatively large batteries are becoming increasingly important. Large batteries carry the risk of triggering strongly exothermic chemical reactions in the event of a defect. If a local short circuit of the internal electrodes occurs in a lithium-ion battery due to mechanical, electrical, and / or thermal loads, such as through contamination or damage, the short-circuit current can heat the surrounding environment of the damaged site to an extent that damages the surrounding area. As a result, the energy stored in the battery is released within a short time. This process is also known as thermal runaway. The thermal runaway of a single lithium-ion battery typically lasts about 20 to 60 seconds. Due to the thermal coupling of individual battery cells, the cells adjacent to the faulty cell may also experience thermal runaway, leading to a sharp increase in heat generation and potentially destroying the entire battery within a few minutes. Therefore, a battery monitoring system is used to ensure the functional safety of battery operation, promptly identify the critical state of the battery, especially damage conditions, and initiate countermeasures, such as disconnecting individual cells, emergency cooling, or driver alerts.

[0002] A battery monitoring system is known from DE102013218681A1, which is configured to monitor the operating state of a battery by analyzing and processing the sensor signals of at least two sensors that detect different physical measurement parameters. Here, a pressure sensor, a temperature sensor, a voltage sensor, and a current sensor are used. Summary of the Invention

[0003] The present invention relates to a battery monitoring system for monitoring the state of a battery, especially a traction battery of a vehicle, wherein the battery monitoring system is configured to monitor the operating state of the battery by analyzing and processing the sensor signals of at least two sensors that detect different physical measurement parameters. According to the present invention, the battery monitoring system at least includes the following devices:

[0004] - A detection device that detects the currently existing operating situation of the battery,

[0005] - An assignment device that assigns sensors to at least two different levels, where the levels are assigned a hierarchical priority from the highest priority to the lowest priority, and the assignment of sensors to levels is performed at least based on the currently existing operating situation of the battery detected by the detection device.

[0006] - An identification device that determines in a first identification step whether there is a critical state of the battery from the sensors assigned to the level with the highest priority, and

[0007] - An implementation device that implements safety measures if the identification device identifies the existence of a critical state of the battery.

[0008] Furthermore, the present invention relates to a method for monitoring the state of a battery, in particular a traction battery of a vehicle, wherein the operating state of the battery is monitored by analyzing and processing sensor signals of at least two sensors that detect different physical measurement parameters. According to the present invention,

[0009] - the currently existing operating situation of the battery is detected,

[0010] - the sensors are assigned to at least two different levels, wherein the levels are assigned a hierarchical priority from the highest priority to the lowest priority, and the assignment of the sensors to the levels is carried out at least based on the detected currently existing operating situation of the battery,

[0011] - in a first recognition step, it is determined whether there is a critical state of the battery from the sensors assigned to the level with the highest priority,

[0012] - if a critical state of the battery is recognized, safety measures are implemented.

[0013] Without limitation, effective battery monitoring is a very important function especially in electric, battery-powered vehicles or hybrid vehicles, which can enable timely recognition of the critical state or damage of the traction battery of the vehicle. In many countries, requirements for battery monitoring are also increasingly being imposed legally.

[0014] The battery monitoring system can, for example, be integrated into an existing battery management system (BMS) for regulating the battery charging and discharging process, or designed as a separate system with an energy supply and data processing independent of the battery management system, and this separate system can also be retrofitted in a vehicle, for example.

[0015] In principle, the battery monitoring system can use sensor data of different sensors, wherein the sensors are particularly selected from the group of the following sensor types: temperature sensors for determining temperature, sensors for determining electrical characteristic parameters of the battery, pressure sensors, gas sensors, and particle sensors. The battery monitoring system can have multiple sensors of each of the above sensor types. In any case, at least two sensors should detect different physical measurement parameters. Particularly preferably, the battery monitoring system has sensors that detect at least three different measurement parameters. In the case of three sensors, it is advantageous if at least one of the sensors detects electrical characteristic parameters of the battery, another sensor detects the temperature in or on the battery, and the third sensor detects the pressure or gas composition or gas constitution in the environment of the battery. The sensors can be constructed as separate sensors, or can also be constructed as sensors that are partially jointly installed in a sensor module.

[0016] The temperature sensor can detect, for example, the cell temperature of the battery, the temperature of the coolant of the battery, or the module temperature of the battery module.

[0017] Sensors for determining the electrical characteristic parameters of the battery can detect, for example, the cell impedance, the cell voltage, or the current intensity supplied by the battery. The interrelated electrical measurement parameters can be detected directly at the cell (individual cell voltage, cell impedance), directly at the module (cell-specific charge / discharge current), and at the battery pack level (load current).

[0018] The pressure sensor can be installed, for example, on the housing wall of the cell of the battery, or on or in the module of the battery, or at the battery pack level. For example, the pressure wave generated due to the opening of the safety valve or the explosion of individual cells and propagated through the battery module or the entire battery pack can be very well detected using a dynamic low-pressure sensor. If a pressure wave is identified, this is an early indication of an abnormal state of the battery. However, in a closed module, before the safety valve opens, an open cell can also cause a gradually increasing pressure that persists for a long time within the module. Here, in addition to or instead of the propagated pressure wave, the pressure sensor can also detect this pressure increase. Therefore, both a pressure wave, for example, and a static pressure increase or decrease can be detected within a closed battery module or battery pack.

[0019] The gas sensor can be configured to identify the concentration of gas components (such as H2, CO, CO2) in the gas due to electrolyte leakage or due to the thermal decomposition of the electrolyte material or other cell components, or to identify changes in the gas composition of the gas. The following gas components can be detected using the gas sensor: the gas components enter the ambient air of the battery module or battery pack through the evaporation, decomposition, and / or partial oxidation of the electrolyte or other components of the battery from mechanically damaged and / or overheated cells. For NMC batteries (NMC: nickel manganese cobalt, which is the cathode material of typical lithium-ion batteries) using a standard electrolyte, such as dimethyl carbonate (DMC), it is suitable to detect hydrogen in the surrounding environment of the battery ("ambient air") (for example, by means of a hydrogen sensor, which can be configured as a threshold sensor with a trigger threshold of 10 ppm H2), but gas sensors for detecting other main components (for example, undecomposed electrolyte, carbon dioxide, and / or carbon monoxide) can also be used.

[0020] The particulate sensor can inspect the particles in the gas mixture of the battery, and preferably a smoke sensor can be used here to detect smoke particles.

[0021] In the context of the present application, the battery state is understood as a state of the battery that can include an assessment of the current electrical performance, the functions of the battery, and / or a prediction of the development of the performance or the further course of the battery functions. Battery state recognition can also enable statements about the expected compliant operation of the battery in the current mode, such as recognizing critical states or damage conditions of the battery. Without being limited thereto, this can particularly include a continuous assessment or an assessment carried out at time intervals of the state of charge (SoC) or the state of health (SoH) of the battery.

[0022] In the context of the present application, the operating conditions of the battery refer to the state, mode, or type of operation in which the battery operates in principle, i.e., for example, the state of charge under load, the state during charging, or the state when the electrical appliance connected to the battery is turned off. In the case of the traction battery of a battery - electric vehicle (BEV), the operating conditions of the battery depend in principle on the type of use of the vehicle and can initially be roughly divided into: the situation when the vehicle is driving (D: Drive), the situation when the vehicle is parked without charging (P: Park), and the situation when the battery is being charged (C: Charge). However, in addition, of course, further differentiations can also be made. Thus, for example, during charging, a distinction can be made between rapid charging and normal charging. During driving, a distinction can be made, for example, between driving states at partial load or full load. When parked, a distinction can be made, for example, between the situation where the subsequent operation of the vehicle's battery management system occurs (Nachlauf) or the situation where the vehicle is parked for a long time. The operating conditions can be directly detected by the battery monitoring system, for example, by means of data transmitted by the control device (ECU) or corresponding signals of the battery management system.

[0023] Safety measures are understood as a measure that is initiated by the battery monitoring system when a critical state of the battery or a damage condition of the battery is recognized, in order to avoid accidents, property damage, or harm to vehicle occupants or persons who may be located near the battery. Here, the measure can be initiated directly by the battery monitoring system or indirectly by the battery monitoring system causing the vehicle control device to initiate the measure. The battery monitoring system can preferably initiate the measure through the battery management system (BMS) or the vehicle control device (ECU). The measure can particularly consist of activating the emergency cooling of the battery, reducing the electrical power output (Leistungsentnahme) from the battery, deactivating individual cells of the battery, separating the battery from the charging station, issuing an alarm prompt to the vehicle driver, initiating an emergency stop of the vehicle, etc.

[0024] Advantages of the Invention

[0025] The battery monitoring system described here, or the method for monitoring the state of a battery described here, advantageously enables dynamic prioritization of the sensors used for monitoring, resulting in a significant improvement over the prior art. In this way, the reliability of the monitoring of the battery state is significantly improved by prioritizing different sensors that detect different physical measurement variables as the situation requires and by possible data redundancy. The possible data redundancy can advantageously be used for an improved function of validating the battery state. The sensors can be installed in or on the battery, or in the ambient space around the battery. In particular, it is possible to better avoid: completely failing to respond to a critical state of the battery ("no alarm" or false negative alarm), or falsely identifying a critical state ("false alarm" or false positive alarm). Depending on the operating conditions of the battery, in individual cases, initially only a part of all available sensors can be used, where, for example, a measurement principle with low power consumption can be advantageously used, so that the energy consumption can be reduced during the operating conditions (for example, when the vehicle is parked).

[0026] Advantageous configurations and refinements of the invention implement the features contained in the dependent claims.

[0027] Thus, for example, if a critical state of the battery is identified in a first identification step, the identification device can, in a second identification step, analyze the sensor signals of the sensors assigned to a lower-priority level in order to quantify this critical state of the battery. "Quantify" is understood as detecting the degree of individuality or the specific dynamics of the critical state. Thus, for example, not only can a critical state of the battery be identified, but in addition, the exact type and exact degree of this state can be better estimated in order to appropriately match the safety measures. In this way, for example, a better distinction can be made between less problematic faults and states that require immediate action.

[0028] Furthermore, if the existence of a critical state of the battery cannot be excluded in a first identification step, the sensor signals of the sensors assigned to a lower-priority level can be analyzed in a second identification step in order to better identify whether there is a critical state of the battery. In this way, false positive alarms and false negative alarms can be better avoided. Thus, for example, a battery state can be detected by means of the sensors assigned to the highest level, in which there is some suspicion of a possible critical state, if necessary, or in which the existence of a critical state or an impending critical state cannot be excluded. Here, analyzing the sensor signals of the low-level sensors, which are only switched on when in doubt, can provide clarity.

[0029] To save battery consumption particularly advantageously, the battery monitoring system can continuously activate or periodically activate at a pre-given time interval the sensors assigned to the hierarchy level with the highest priority, and activate only the sensors assigned to the hierarchy levels with lower priorities when the identification device identifies in a first identification step the existence of a critical state of the battery or when in the first identification step the existence of a critical state of the battery cannot be excluded. In this way, the energy consumption of the battery monitoring system can be optimized. For example, in the "parked" operating situation, continuously measuring all the cell voltages and the temperature at the module level may be associated with an unfavorably high energy consumption. In addition, these sensors are usually connected via the central control unit of the battery management system, and this central control device conventionally has to actively request the measurement. Therefore, this central control unit itself has to be periodically activated from a potentially energy-saving mode. Thus, advantageously in this operating situation, it is reasonable to assign a higher priority to those sensors that on the one hand monitor the battery and on the other hand are characterized by a particularly energy-saving operation. For example, a pressure sensor or a gas sensor can be assigned to the hierarchy level with the highest priority, and in this way, when parked, changes in the pressure or gas composition in the atmosphere of the battery module or battery pack can be detected. When a critical state is identified, the electrical sensors and thermal sensors can then be activated as secondary sensors to verify the fault.

[0030] Advantageously, for different operating situations of the battery, the pre-given assignment of sensors to hierarchy levels can be stored separately in a memory. Once the detection device detects the operating situation, the corresponding assignment of sensors to hierarchy levels is read out from the memory and implemented accordingly by the assignment device.

[0031] Advantageously, depending on a pre-givably different battery type (where the battery type is defined by the chemistry of the cells and the structural form of the battery), the sensors can be additionally assigned to the at least two different hierarchy levels. For different battery types, different processes may occur in case of a fault. By taking into account the battery type, the monitoring can be optimally matched to the battery type. Description of the Drawings

[0032] Possible embodiments of the present invention will be explained below with reference to the attached drawings. Shown in the drawings are:

[0033] Figure 1 Schematic diagram of a battery-powered electric vehicle having a battery monitoring system according to the present invention,

[0034] Figure 2 Three different operating situations of the battery of a battery-powered electric vehicle,

[0035] Figure 3 Exemplary assignment of different sensors in a hierarchy level having three different priority levels,

[0036] Figure 4 Flowchart of a method for monitoring the state of a battery according to the present invention. Detailed implementation

[0037] Figure 1 Fig. shows a schematic view of a battery-powered electric vehicle 10 having a battery monitoring system 1 according to the present invention. The battery monitoring system can be an integral part of the battery management system, where sensor analysis and processing also take place. The battery monitoring system 1 includes, for example, an electronic circuit and sensors 3. The vehicle also has a battery 2. The battery 2 consists, for example, of a battery pack having a large number of cells, which can be combined in modules. This battery can be the traction battery or drive battery of the vehicle 10, which provides the energy required by the vehicle drive. The vehicle 10 can also have a control device 44, which is required especially for driving functions. In addition, the vehicle 10 can also have a battery management system (not shown).

[0038] In Figure 1 Fig., the reference numeral 31 denotes a pressure sensor, which is arranged, for example, on the housing wall of the battery 2. In addition, the vehicle 10 has a gas sensor 37, which can detect the concentration or change in the gas composition (e.g., H2, CO, CO2) in one or more battery modules of the battery 2. In addition, another gas sensor 34 can identify the concentration of the gas composition in the surroundings of the battery 2. A temperature sensor 35 can, for example, detect the temperature of the battery module. Another temperature sensor 36 can, for example, detect the coolant temperature of the battery 2. The sensors 32 and 33 detect electrical characteristic parameters of the battery 2, such as the cell impedance, cell voltage, and / or current intensity of the battery 2. The sensor 38 is configured as a particulate sensor. All sensors 3 can be installed in or on the battery 2 or the battery pack.

[0039] As Figure 1 Fig. also shows, the battery monitoring system 1 further includes a detection device 11, which detects the current operating conditions existing in the battery 2 and associated with the driving situation of the vehicle 10 in the illustrated embodiment. In Figure 2 Fig., three basic operating conditions of the vehicle 10 are shown.

[0040] The operating conditions are, for example: the situation when the vehicle is driving (D: Drive), the situation when the vehicle is parked without charging (P: Park), and the situation when the battery is being charged (C: Charge). However, in addition, as described above, of course, further differentiations (not shown here) can also be achieved. The detection device 11 can automatically detect the current existing operating conditions P; C; D by analyzing vehicle data or by, for example, the vehicle control device 44 transmitting corresponding information to it.

[0041] In addition, the battery monitoring system 1 includes an assignment device 12 which assigns all sensors 3 connected to the battery monitoring system 1 to different levels. In the embodiment shown here, for example, it relates to three levels with hierarchical priorities L1 to L3, where L1 is the highest priority level and L3 is the lowest priority level. Naturally, there can also be more than three or only two priority levels. The assignment can be stored, for example, in a callable memory 15 which can be accessed by the assignment device 12. For Figure 3 the embodiment in shows a possible assignment. This assignment can be pre-given according to the battery type. For other battery types, other assignment tables can be saved. In the example shown, for example, in the parked operating condition P, the sensor signal of the pressure sensor 31 is assigned to the level L1 with the highest priority, while the gas sensor and the particulate sensor are assigned to the medium priority L2, and the remaining sensors 32, 33 and 35, 36 are assigned to the lower level L3. Conversely, in the driving operating condition D, the sensors 32, 33 for detecting electrical characteristic variables are assigned to the highest level L1, while the pressure sensor 31 and the gas sensor are assigned to the level L2 with a lower priority.

[0042] In addition, the battery monitoring system 1 has an identification device 13 which determines from the sensors 3 assigned to the level L1 with the highest priority according to the operating conditions D; C; P whether there is a critical state of the battery 2. If this is the case, the implementation device 14 initiates a safety measure 105.

[0043] According to Figure 4 , a more in-depth look at the method for monitoring the state of the battery performed by the battery monitoring system 1. In block 101, the current operating condition P, C or D is detected and transmitted to block 102. In block 102, the assignment table corresponding to the battery type is loaded according to the battery type T, and, in another method step, the sensors 3 are assigned to the corresponding different levels according to the currently detected operating condition P, C or D, where, for simplicity, only two levels are shown here. For example, for the operating condition D, the assignment is as follows: the sensors 32, 33 and 35, 36 are assigned to the level L1 with the highest priority, and the sensors 31 and 34, 37, 38 are assigned to the level L2 with a lower priority.

[0044] In Figure 4In block 103, first, a first recognition step 103a is performed. In this first recognition step, it is determined whether there is a critical state of the battery 2 from the sensors assigned to the level with the highest priority L1. If this is not the case, the recognition step 103a can be repeated. If a critical state is recognized in the first recognition step 103a, then in the second recognition step 103b, the sensor signals of the sensors 3 (i.e., in the example, the pressure sensor 31 and the gas sensors 34, 37) assigned to the level with the lower priority L2 are considered for quantifying the critical state of the battery 2 in the second recognition step 103b.

[0045] Then, in the last block 104, one or more safety measures 105 are implemented. The safety measures can, in particular based on the signals from block 103b, consist of activating emergency cooling of the battery, reducing the electrical power output from the battery, bridging and / or decoupling individual cells or modules of the battery, separating the battery from the charging station, issuing an alarm prompt to the vehicle driver, initiating an emergency stop of the vehicle, etc.

[0046] From the above description, it can be seen that there are multiple different implementation possibilities.

[0047] In the above embodiment, for example, if there is an operating condition D of driving, the electrical characteristic parameters of the battery system (e.g., the measured cell-individualized voltages and impedances and the module current) together with the sensor signals of the temperature sensors 35; 36 are assigned to the level with the highest priority L1 and are processed as first-level sensor data or as first-level sensors. Thus, during vehicle driving, a continuous battery state assessment is performed, especially continuously determining the SoC and SoH based on this first-level sensor data. Here, the critical temperature, current, and / or cell voltage data indicate an impending or already occurred overheating state in a section of the battery. In the operating condition D of driving, the main task of the battery monitoring system can be to warn the vehicle occupants in the case of thermal runaway of one or more cells in the battery pack. To avoid false positive identifications here, multiple sensor signals are incorporated into the evaluation of thermal events according to the hierarchical priority. Thus, in the operating condition D of driving, the sensors 32; 33 for detecting electrical data (i.e., e.g., the load current and the cell voltage) and the temperature sensors 35, 36 for monitoring the coolant and module temperature can be continuously active to determine the state of charge and health state of the battery or the battery pack during driving. Thus, ideally, these sensors are also considered for identifying thermal runaway in the battery 2.

[0048] The pressure sensor 31, the gas sensors 34, 37, and the particulate sensor 38 - which record, for example, dynamic pressure changes on the battery module and changes in the gas composition or smoke particles in the ambient air of the battery - can be assigned to a level with a lower priority L2 during the driving operating condition D and are thus processed as secondary sensor data. Therefore, the pressure sensor 31 and / or the gas sensors 34, 37 are considered for use with a lower analysis and processing priority compared to the primary sensors. To detect the pressure threshold generated when the cell opens due to overpressure inside the cell during thermal runaway of the battery, it is advisable to continuously operate the pressure sensor also in this operating mode. Here, for example, a sampling rate of 10 to 100 Hz can be envisaged to detect characteristic pressure increases. In contrast, the gas sensors can be activated as secondary sensors, for example, only after being triggered by the primary sensors (electrical sensors, temperature), or can also be activated as tertiary sensors with a priority L3 after a pressure increase is recognized by the pressure sensor. Thus, for example, differently from that shown in Figure 3 In a slightly modified embodiment, the gas sensors 34, 37 can also be assigned to a level with a priority L3.

[0049] However, in an embodiment not shown in the figures, it is also conceivable to analyze and process the pressure sensor 31 and / or the gas sensors 34, 37 at a level with the highest priority L1 and, for example, to consider using the electrical data of the sensors 32, 33 only for confirmation. This is particularly advantageous in the following battery types: in those battery types in which, before thermal runaway can be determined from the electrical data, the opening of the cell membrane or cell valve caused by pressure occurs. As described above, the sensors can be assigned to different levels according to the pre-given battery type T. Thus, for example, for pouch cells, gas sensors can be given priority because, before damage to the battery housing caused by pressure, trace gases (e.g., hydrogen) can diffuse through the battery housing at the beginning of thermal runaway and can be detected in the battery 2 using sensitive gas sensors 34, 37. In this way, the vehicle can subsequently be brought into an emergency operating mode that enables the driver to park the vehicle safely. By giving priority to the pressure sensor and / or the gas sensors, a time advantage can be obtained for this battery type compared to embodiments that mainly monitor using electrical sensors.

[0050] In the first embodiment, in the charging operating condition C, the electrical sensors 32; 33 and the temperature sensors 35; 36 can all be actively considered for identifying the charging progress and the operating temperature of the battery pack. Different from the driving mode, in the charging operating condition C, the pressure sensor 31 and the gas sensors 34; 37 can also be analyzed and processed, for example, at the level with the highest priority L1, because critical states in many battery types usually occur during charging. If a critical state is identified, in addition to a warning message, an interruption of the charging process can also be initiated here as a safety measure to reduce the additional risk due to the input energy when (imminent) thermal runaway is recognized.

[0051] As described above, in the parking operating condition P, it must be noted that continuously measuring all the cell voltages and the temperature at the module level may be associated with significant energy consumption. In addition, in practice, such sensors are usually also connected via the central control unit of the battery management system, which must actively request the measurements. Therefore, the central control unit of the battery management system must also be periodically awakened from the potential "low power consumption" mode. However, in the parking operating condition P, it is necessary to achieve the lowest possible energy consumption to be able to achieve a long operating duration with the supply battery. Therefore, in this case, it is reasonable to prioritize higher an autonomous battery monitoring and / or additional sensors characterized by particularly energy-efficient operation. Thus, in Figure 3 the embodiment of, for example, the pressure sensor 31 is used with the highest priority L1 for detecting the opening of a cell due to thermal runaway. Here, the sampling rate of the pressure sensor 31 can be, for example, in the range of 1 to 20 Hertz. If the pressure sensor identifies a critical state, the gas sensors 34; 37 and the particulate sensor 38 can be considered for use with a lower priority L2. If a characteristic pressure change is identified and subsequently a change in the gas composition is detected by the gas sensor, the battery monitoring system can, for example, wake up the battery management system in the sleep mode by a "wake-up" signal, so that the sensor data of the electrical sensors 32, 33 and the temperature sensors 35, 36 can become available and can be considered as tertiary sensor data.

[0052] In Figure 3 another embodiment not shown, instead of or in addition to the pressure sensor, a gas sensor can also be considered, which can sense a change in the gas composition in the atmosphere of the battery module or the battery pack as a primary sensor. Then, when such a state is identified, after warning the battery management system, the electrical sensor and the thermal sensor can be activated as secondary sensors for verification.

Claims

1. A battery monitoring system (1) for monitoring the state of a battery (2), in particular a traction battery of a vehicle (10), wherein, The battery monitoring system (1) is configured to monitor the operating state of the battery (2) by analyzing sensor signals of at least two sensors (3) that detect different physical measurement parameters, characterized in that the battery monitoring system (1) at least comprises the following devices: - a detection device (11) that detects the currently existing operating situation (P; C; D) of the battery (2), - an assignment device (12) that assigns the sensors (3) to at least two different levels, wherein the levels are assigned a hierarchical priority (L1; L2; L3) from the highest priority (L1) to the lowest priority (L3), and wherein the assignment of the sensors (3) to the levels is carried out at least according to the currently existing operating situation (P; C; D) of the battery (2) detected by means of the detection device (11), - an identification device (13) that determines in a first identification step (103a) whether a critical state of the battery (2) exists among the sensors (3) assigned to the level with the highest priority (L1), and - an implementation device (14) that implements a safety measure (105) if the identification device (13) identifies the existence of a critical state of the battery (2).

2. The battery monitoring system according to claim 1, wherein The identification device (13): - if in the first identification step (103a) the existence of a critical state of the battery (2) is identified, analyzes in a second identification step (103b) the sensor signals of the sensors (3) assigned to the levels with lower priorities (L2; L3) in order to quantify the critical state of the battery (2), - or if in the first identification step (103a) the existence of a critical state of the battery cannot be excluded, analyzes in a second identification step (103b) the sensor signals of the sensors assigned to the levels with lower priorities (L2; L3) in order to identify whether a critical state of the battery (2) exists.

3. The battery monitoring system according to any one of claims 1 or 2, characterized in that The battery monitoring system (1) continuously activates or periodically activates at a pre-given time interval the sensors (3) assigned to the level with the highest priority (L1), and activates the sensors (3) assigned to the levels with lower priorities (L2; L3) only if the identification device identifies in the first identification step (103a) the existence of a critical state of the battery (2) or if in the first identification step (103a) the existence of a critical state of the battery (2) cannot be excluded.

4. The battery monitoring system according to any one of the preceding claims, characterized in that, For the different operating situations (P; C; D) of the battery (2), the pre-given assignment of the sensors (3) to the levels is stored in a memory (15).

5. The battery monitoring system according to any one of the preceding claims, characterized in that, The assignment device (12) assigns the sensors (3) to the at least two different levels according to a pre-givably definable battery type (T).

6. The battery monitoring system according to any one of the preceding claims, characterized in that The battery (2) is a traction battery of a battery-powered electric vehicle (10), and the detection device (11) identifies at least three different operating conditions (P; C; D) of the battery in the case of the vehicle during vehicle driving (D), vehicle parking (P), and charging of the battery (C).

7. The battery monitoring system according to any one of the preceding claims, characterized in that, The sensor (3) is selected from the group of the following sensor types: - Temperature sensors (35; 36) for determining a temperature, in particular the cell temperature of the battery, the coolant temperature of the battery, or the module temperature of the battery (2), - Sensors (32; 33) for determining electrical characteristic parameters of the battery, the electrical characteristic parameters being in particular the cell impedance, the cell voltage, or the current intensity, - Pressure sensors (31), in particular pressure sensors mounted on the housing wall of a cell of the battery (2) or in or on a module of the battery, - Gas sensors (34; 37), which are configured to identify a concentration of a gas component in a gas or a change in the gas composition in a gas, - Particle sensors (38), in particular smoke sensors, which identify particles in the gas mixture of the battery.

8. The battery monitoring system according to claim 7, characterized in that The battery monitoring system (1) has at least one sensor (32; 33) for determining electrical characteristic parameters of the battery (2), at least one temperature sensor (35; 36), and at least one further sensor configured as a pressure sensor (31) and / or a gas sensor (34; 37).

9. A method for monitoring the state of a battery (2), in particular a traction battery of a vehicle (10), wherein, The operating state of the battery (2) is monitored by analyzing sensor signals of at least two sensors (3) that detect different physical measurement parameters, characterized in that - the currently present operating condition (P; C; D) of the battery (2) is detected, - the sensors (3) are assigned to at least two different levels, where the levels are assigned a hierarchical priority (L1; L2; L3) from the highest priority (L1) to the lowest priority (L3), and the assignment of the sensors (3) to the levels is carried out at least based on the detected currently present operating condition (P; C; D) of the battery (2), - in a first identification step (103a), it is determined whether there is a critical state of the battery (2) from the sensors (3) assigned to the level with the highest priority (L1), - if it is identified that there is a critical state of the battery (2), safety measures (105) are implemented.

10. The method according to claim 9, wherein The sensors (3) assigned to the level with the highest priority (L1) are continuously activated or periodically activated at a pre-given time interval, and the sensors (3) assigned to the levels with lower priorities (L2; L3) are only activated if it is identified in the first identification step (103a) that there is a critical state of the battery or if it cannot be excluded in the first identification step (103a) that there is a critical state of the battery (2).

11. The method according to any one of claims 9 or 10, characterized in that For the different operating conditions (P; C; D) of the battery (2), the pre-given assignment of the sensors (3) to the levels is used respectively.

12. The method according to any one of claims 9 to 11, characterized in that, The sensor (3) is assigned to the at least two different levels according to a predefinable battery type (T).

13. The method according to any one of claims 9 to 12, characterized in that, The battery (2) is a traction battery of a battery-powered electric vehicle (10), and at least three different operating states (P; C; D) of the battery are recognized in the case of the vehicle during vehicle driving (D), vehicle parking (P), and charging (C) of the battery (2).

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