battery module

Abstract

A battery module (1) comprises a housing (2) and a plurality of battery cells (3) arranged in the housing (2). A liquid medium (4) is arranged in the housing (2) around the battery cells (3) so as to apply a hydrostatic pressure to the battery cells (3) within the housing (2). A pressure generating device (5) for regulating the pressure of the liquid medium (4) and a control device (8) for actuating the pressure generating device (5) are also provided, wherein the control device (8) is configured to carry out a test routine for determining aging, wherein pressure pulses are generated by means of the pressure generating device (5), and the resulting pressure and volume changes of the hydrostatic system consisting of the battery cells (3) and the liquid medium (4) are correlated with a reference characteristic curve. In one embodiment, a pressure measuring device (7) for detecting the pressure of the liquid medium (4) and a control device (8) are provided, wherein the control device (5) is configured to generate an alarm signal when a threshold value for the pressure gradient of the liquid medium (4) is detected to be exceeded. Both embodiments can also be combined.

Description

Technical Field

[0001] The present invention relates to a battery module, comprising: a housing; a plurality of battery cells arranged in the housing; a liquid medium arranged in the housing around the battery cells so as to apply hydrostatic pressure to the battery cells in the housing; and a pressure generating device for adjusting the pressure of the liquid medium. Background Art

[0002] Such a battery module is known from DE 10 2018 123 682.

[0003] The battery cells of high-voltage battery modules, such as those used, for example, as traction batteries or buffer stores in vehicles, undergo volume changes during operation (so-called "breathing"). During the charging and discharging processes of the battery module, these volume changes occur due to lattice rearrangement processes that result in the transfer of lithium into and out of the anode and cathode materials (lithiation / delithiation). This breathing of the battery cells can occur with varying degrees of intensity, depending on the cell chemistry. In hydrostatically compressed battery modules, the volume of the hydrostatic system—that is, the total pressurized volume of the battery cells and the liquid medium—changes depending on the state of charge.

[0004] Furthermore, battery cells undergo various aging processes during operation. These aging processes lead to a reduction in the available capacity of the battery module and an increase in its internal resistance over the long term. Both of these can be measured electrically and used to assess the aging state.

[0005] During the aging process, the volume of the battery cells also changes, which is distinguished from the breathing explained above and is called "swelling" because the battery cells remain slightly swollen. The reason for this is that the battery cells release gases due to chemical reactions during aging.

[0006] The two effects of breathing and swelling overlap, making it difficult to distinguish the cause of the volume increase for a battery cell at first glance.

[0007] Expansion is particularly noticeable in "pouch-type" battery cells with flexible film as a sheath. However, volume increases can also be observed in round and prismatic cells, where the metal sheath, while more stable, also exhibits a certain degree of elasticity, just like the film. Swelling due to aging is possible here, just as with "pouch-type" battery cells.

[0008] Battery expansion not only leads to performance degradation but also poses safety risks, as aged cells can crack or enter thermal runaway. Those skilled in the art understand "thermal runaway" to mean overheating of a battery cell due to a self-reinforcing exothermic process. In the worst-case scenario, such a runaway could mean the cell in question explodes, spreading to adjacent cells. Therefore, reliably detecting both aging and safety conditions is crucial.

[0009] As mentioned at the outset, the present invention relates to a battery module in which battery cells are hydrostatically compressed according to the respective cell chemistry. To this end, external pressure is applied to the individual battery cells to ensure their optimal function. Despite volume changes due to breathing and / or expansion, a corresponding compression system with a pressure-generating device can passively apply or actively control the required compression pressure.

[0010] As disclosed in DE 10 2018 123 682 A1, conventional methods for evaluating the state of aging are based on detecting battery electrical parameters such as current, voltage, internal resistance, and capacity. Conventional methods for evaluating the state of aging are based on detecting temperature and the aforementioned battery electrical parameters. In DE 10 2018 123 682 A1, the pressure in the battery module is regulated based on these parameters.

[0011] In this case, the battery electrical parameters are measured for each individual battery cell. Therefore, the corresponding sensor circuits must remain intact throughout their entire service life. This creates redundancy issues in the event of a sensor circuit failure.

[0012] Furthermore, temperature measurement is usually only possible locally and can also be quite slow. Summary of the Invention

[0013] The object of the present invention is to determine the aging state and safety state of individual battery cells in a battery module more precisely and reliably under hydrostatic compression.

[0014] This object is achieved by a battery module comprising: a housing; a plurality of battery cells arranged in the housing; a liquid medium arranged in the housing around the battery cells so as to apply a hydrostatic pressure to the battery cells within the housing; and a pressure generating device for regulating the pressure of the liquid medium. The battery module is characterized in particular by the provision of a pressure generating device for regulating the pressure of the liquid medium and a control mechanism for actuating the pressure generating device, wherein the pressure generating device is configured to perform a test routine for determining aging, wherein pressure pulses are generated by the pressure generating device, and the resulting pressure and volume changes of the hydrostatic system consisting of the battery cells and the liquid medium are correlated to a reference characteristic curve.

[0015] The reaction to the pressure pulses can be used to infer the overall extent of breathing and expansion occurring across all individual cells in the battery module. This allows valuable information on the aging state and safety status to be obtained independently of the battery electrical variables or the current temperature.

[0016] This information can itself be the basis for determining the aging state, or it can be combined with the above-mentioned measures, thereby ultimately increasing the safety of the battery.

[0017] The invention can be implemented in hydrostatic tightening systems with little additional effort, since no additional components are required.

[0018] The pressure generating device can thus comprise a pressure piston, wherein a measuring device is also provided for detecting the piston position, the signal of which is used to determine the volume change. In this way, information about the volume change of the hydrostatic system can be obtained with little effort.

[0019] A reference characteristic curve can be predetermined for each battery module and stored, for example, in the control unit. In one embodiment, the reference characteristic curve reflects the correlation between pressure and a variable representing the volume of the hydrostatic system in the unaged state of the battery module. Such a reference characteristic curve can be generated individually for each battery module and stored in the control unit, for example, by applying a test routine to the battery modules in the unaged state.

[0020] If necessary, different reference characteristic curves can be pre-stored for different charging states, and then the current charging state is balanced with the corresponding reference characteristic curve.

[0021] According to another embodiment, the aging state of the battery module can be inferred from the difference between the pressure increase caused by the pressure pulse for a predetermined volume change and a reference characteristic curve. Corresponding comparison parameters can be pre-stored in the control device, for example.

[0022] According to another embodiment, the volume of compressible gas in the battery cells can be inferred from the pressure and volume changes caused by the pressure pulses. The smaller the pressure increase caused by the pressure pulses for a given volume reduction, the higher the compressibility of the hydrostatic system. This compressibility is actually due only to the formation of gas in the battery cells due to expansion. Volume changes caused by breathing do not significantly increase compressibility. This is currently used to determine the volume of gas formed due to aging and, based on this, to infer the aging state.

[0023] The accuracy of expansion-based aging state determination can be further improved by using the volume change between the charge and discharge states of the battery module in an unaged state (i.e., due to breathing) as a reference for determining the volume of compressible gas in the battery cells. This allows for determining which portion of the volume change is due to breathing and which portion is due to expansion based on the state of charge.

[0024] For example, a variable representing the pressure can be obtained from the control parameters of the pressure generating device. However, according to a particular embodiment, a dedicated pressure measuring device is preferably provided for detecting the pressure of the liquid medium, which provides a very precise signal for determining the pressure change, which signal is also used for other purposes, such as pressure monitoring and / or pressure gradient monitoring, independent of the pressure generating device.

[0025] The above-mentioned object is also achieved by a battery module comprising: a housing; a plurality of battery cells arranged in the housing; a liquid medium arranged in the housing around the battery cells so as to apply a hydrostatic pressure to the battery cells within the housing; and a pressure measuring mechanism for detecting the pressure of the liquid medium. The battery module is particularly characterized by the provision of a pressure measuring mechanism for detecting the pressure of the liquid medium and a control mechanism, wherein the control mechanism cooperates with the pressure measuring mechanism and is configured to generate an alarm signal upon detecting that a threshold value for a pressure gradient of the liquid medium has been exceeded.

[0026] High pressure gradients indicate a severe expansion of one or more battery cells, which indicates an impending thermal runaway. This can be used for early identification, in order to improve the detection of safety-critical states. In particular, thermal runaway can be detected before the battery cells rupture and release gases ("outgassing"). This allows for increased redundancy in the early identification of thermal runaway (for example, in conjunction with voltage signals). In comparison, with conventional temperature measurement, thermal runaway would be detected significantly later due to thermal inertia and, in the worst case, the large spatial distance of the runaway battery cell from the temperature measurement point.

[0027] Monitoring for exceeding a threshold value for the pressure gradient of the liquid medium can be combined with the above-described measures within the scope of an expanded battery safety concept without significant additional effort.

[0028] Hydrostatic clamping, combined with a battery safety concept based on cell aging, allows for early identification of potential thermal runaway. This ultimately allows for optimal adjustment of the clamping pressure based on the cell's state of charge (SoC), state of aging (SoH), and operating state (charge / discharge). This requires minimal additional equipment expenditure.

[0029] In particular, it is possible to implement the above-described measures in a battery module according to DE 10 2018 123 682 A2 and accordingly supplement the previously described measures for controlling the pressure generating device and for battery management disclosed therein. Accordingly, the relevant disclosure content of DE 10 2018 123 682 A2 is expressly included in the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present invention will be described in more detail below with reference to the embodiments shown in the accompanying drawings.

[0031] Figure 1 A schematic diagram showing an embodiment of a battery module according to the present invention is shown;

[0032] Figure 2 Shown Figure 1 A battery module wherein the compression pressure of the static liquid is controlled during lithiation / delithiation of the battery cells;

[0033] Figure 3 shows the case of a pressure pulse for aging detection Figure 1 battery modules;

[0034] Figure 4 Shown Figure 1 A battery module in which a battery cell begins to thermally runaway;

[0035] Figure 5 shows a graph illustrating the effects of a pressure pulse; and

[0036] Figure 6 Graphs illustrating pressure curves and pressure gradient curves in the event of thermal runaway are shown. DETAILED DESCRIPTION

[0037] Figures 1 to 4 The embodiment in FIG shows a battery module 1 using a high-voltage battery module as an example. The battery module 1 can be used, for example, as a traction battery in a motor vehicle, in particular a passenger car, a commercial vehicle, or other vehicles. Furthermore, use as a stationary electrical buffer is possible.

[0038] The battery module 1 comprises a housing 2 in which a plurality of battery cells 3 are arranged.

[0039] The battery cells 3 can be lithium-ion cells, but can also have other cell types. In particular, the battery cells 3 can have both liquid electrolytes and solid-state cells.

[0040] The battery cells 3 are electrically contact-connected, and the contacts are led outward through the housing 2 .

[0041] For example, the battery cells 3 can be designed as "pouches" with a flexible film as a sheath. With such battery cells 3, aging-related "bulging" (swelling) is particularly pronounced, which in the worst-case scenario can lead to the battery cells 3 cracking or bursting. However, the battery cells 3 can also be designed as round cells, prismatic cells, or other shapes. While most metallic sheaths are more stable, they can also crack if a certain internal pressure within the battery cells 3 is exceeded.

[0042] A liquid medium 4 is arranged in the housing 2, surrounding each battery cell 3. The liquid medium 4 can be, for example, a heat transfer liquid, which can be used to cool each battery cell 3. In the simplest case, the liquid medium 4 passively dissipates heat from the battery cells 3 to the outside via the housing 2. If desired, active cooling can also be achieved by circulating the liquid medium 4 within the housing 2.

[0043] The liquid medium 4 is subjected to a pressure greater than the atmospheric pressure. As a result, a hydrostatic pressure is exerted on each individual battery cell 3. The housing 2 is accordingly designed as a pressure vessel.

[0044] A pressure generating device 5 is provided on the battery module 1 for regulating, in particular controlling, the pressure of the liquid medium 4. The pressure generating device 5 can be used to maintain the hydrostatic pressure acting on the battery cells 3 at a desired level and, if necessary, increase or decrease it.

[0045] The battery cells 3 and the liquid medium 4 are also collectively referred to below as a hydrostatic system, which has a volume loaded with the pressure generated by the pressure generating device 5. This volume can vary, while the other pressures remain constant, in particular due to the breathing and expansion of the battery cells 3. During operation, the pressure can be controlled using the method described in DE 10 2018 123 682 A2.

[0046] In one embodiment variant, the pressure generating device 5 may comprise a pressure cylinder 5a having a pressure piston 5b, such as Figures 1 to 4 When the pressure piston 5b moves a distance s, the volume change of the hydrostatic system can be determined from the position of the pressure piston 5b and the cross section of the pressure cylinder 5a.

[0047] In one embodiment variant, a measuring device 6 is also provided for detecting the piston position of the pressure piston 5b. Its signal is used to determine the volume change, as explained above. However, it is also possible to determine the volume change of the hydrostatic system by other means and methods.

[0048] Furthermore, the battery module 1 may include a pressure measuring device 7 for detecting the pressure of the liquid medium 4. The pressure measuring device 7 may optionally be part of the pressure generating device 5, but may also be a separate unit or be present in addition to the pressure generating device 5. However, the pressure of the liquid medium 4 may optionally also be derived from parameters for controlling the pressure generating device 5, so that a dedicated pressure measuring device 7 may also be omitted.

[0049] The actuator and the sensor device can in particular also be implemented as described in more detail in DE 10 2018 123 682 A2.

[0050] This exemplary embodiment further shows a control device 8 for actuating the pressure generating device 5 . The control device 8 is configured to execute a test routine for determining aging. Corresponding algorithms are stored in the control device 8 .

[0051] The test routine involves generating a pressure pulse by correspondingly actuating the pressure generating device 5 . This pressure pulse occurs during a short, preferably slight, loading or unloading of the hydrostatic system consisting of the battery cells 3 and the liquid medium 4 . The duration of such a pressure pulse is preferably in the range of 0.01 to 5 seconds. However, depending on the transmission ratio of the pressure generating device 5 , for example, its piston, even very long pressure pulses of 30 to 60 seconds are possible. The loading or unloading is preferably within a range of preferably a maximum of + / - 30% of the normal contact pressure of the battery module 1 , and alternatively, within a range of + / - 10%, + / - 50%, or + / - 100% (depending on the selected absolute pressure).

[0052] To apply a pressure pulse, the pressure piston 5b can be moved, for example, by a certain distance Δs, whereby the pressure in the hydrostatic system increases or decreases depending on the direction.

[0053] This change is used to determine the aging state of the battery cell 3 , as will be explained in more detail below.

[0054] For this purpose, the pressure change and volume change of the hydrostatic system caused by the pressure pulse are related to a reference characteristic curve.

[0055] The reference characteristic curve can be predetermined for the battery module 1 and stored, for example, in the control unit 8. When the pressure generating device 5 with the pressure cylinder 5a and the pressure piston 5b shown in the figure is used, the volume V can be reduced to the distance s of the pressure piston 5b, that is, the pressure of the liquid medium 4 is expressed as a function of the piston distance s, as shown in FIG. Figure 5 However, it should be emphasized that the reduction to the distance is only one possible embodiment and that the volume change can also be detected in other ways and methods.

[0056] exist Figure 5 It is assumed for example only that the battery module 1 is in a state with a pressure p2,start and a piston distance s2,start (or a corresponding volume) before the pressure pulse. In this case, the pressure is increased by the pressure generating device 5 so that the pressure piston moves a distance Δs. Figure 5 In this case, the piston travel decreases from s2,start to s2, resulting in a decrease in the volume of the hydrostatic system. The pressure increases to varying degrees. Characteristic curve A represents the battery module 1 in its unaged state. Here, only breathing occurs at the battery cells 3, meaning that the volume changes only slightly with the state of charge (SoC). The entire hydrostatic system remains relatively rigid. Accordingly, the pressure increase from the initial pressure p2,start to p2,solid is very large.

[0057] In one embodiment variant, a characteristic curve A can be used as a reference characteristic curve for determining aging. This characteristic curve can initially be generated for each battery module 1 in an unaged state using a test routine and stored in the control device 8. For different states of charge of unaged battery modules, corresponding characteristic curves A can be generated as reference characteristic curves, if necessary.

[0058] Alternatively, a reference characteristic curve can be determined for a battery module type, for example experimentally, optionally also taking other influences into account, and the reference characteristic curve can be pre-stored in the control device 8 .

[0059] The compressibility of a hydrostatic system increases with gas formation in the battery cells 3 due to aging processes. Characteristic curve B represents a first aging state. In this aging state, the pressure rises less rapidly to a pressure p2,gasB with a piston travel Δs. The difference from p2,solid can now be evaluated as a variable for the aging state of the battery module 1.

[0060] Under still more violent expansions, the pressure increase is correspondingly weaker, e.g. Figure 5This is shown by the characteristic curve C in FIG. Here, the pressure only increases to p2,gasC. A further increase in compressibility compared to the characteristic curves A and B can be inferred as a greater formation of gas in the battery cell 3 and thus as a further advanced state of aging.

[0061] In the present case, reaching a limiting characteristic curve, such as characteristic curve C, can be evaluated, for example, as an indication of a shutdown of the relevant battery module 1 .

[0062] Figure 5 This is merely an illustration of the principle of the present invention. It is readily apparent to a person skilled in the art based on characteristic curves A to C that, for example, a pressure pulse need not always occur over a predetermined distance Δs. Based on knowledge of the reference characteristic curve, any pair of values ​​generated by a pressure pulse, consisting of the resulting pressure and volume variables, can be used to determine the aging state.

[0063] To improve the accuracy, the influence of breathing can be calculated from the reference characteristic curve by additionally taking the state of charge (SoC) of the battery module 1 into account in the test routine.

[0064] Figure 1 The battery module 1 according to the invention is shown in a new state. The battery cells 3 in the battery module 1 are acted upon by pressure (ie, are hydrostatically compressed) by means of a pressure generating device 5 in order to adjust the pressure of the liquid medium 4 .

[0065] In this initial state, in which the battery cells 3 have not aged, a pressing pressure p0 is preset. In this case, the pressure piston 5b is regulated in position s0. Therefore, if it is assumed that the liquid medium 4 is incompressible, the volume of the entire hydrostatic system can be determined in the initial state, or only the volume of the battery cells 3 can be determined. This state is stored as a reference. However, the volume V0 cannot be inferred from the initial state in position s0 alone. Only through aging of the battery cells 3 will the volume of the battery cells 3 in the system increase, resulting in a different pressure piston position. The volume change within the battery cells can be inferred from the difference in the pressure piston positions.

[0066] As the operating time in the initial state increases, a certain volume increase in the form of breathing can be observed at the battery cell 3. Figure 2 As explained in [1], the volume of the battery cells 3 changes due to the lithiation and delithiation of the battery cells 3. This depends in particular on the type of battery cell used and can vary from one battery cell 3 to another. The system pressure p1 of the liquid medium 4 and, therefore, the contact pressure acting on the battery cells 3 can be dynamically adapted via the pressure generating device 5.

[0067] By tracking the pressure piston 5b to the corresponding compression pressure p1, the volume change of the battery cell 3 caused by breathing during normal operation can be measured. At the same time, the best compression of the battery cell is ensured.

[0068] The corresponding desired compression pressure can be preset via, for example, a target value model stored in the control mechanism 8 and regulated via the pressure generating device 5. The target value model can additionally use the actual pressure of the liquid medium 4 and the following parameters as input variables - individually or in combination or in sub - combinations - namely the state of charge (SoC), the state of health (SoH), the temperature, and the current operating state (charging / discharging).

[0069] Figure 3 It shows how the aging state can be determined in a battery module 1 of the above - mentioned type. The battery cell 3 in which volume increase occurs due to lithiation (breathing) is actually not compressible. In contrast, the battery cell 3 in which volume increases due to gas formation (expansion) - which is understood as aging - is compressible.

[0070] The gas generated is compressed by a pressure pulse which is applied as a test signal via the pressure generating device 5. Then a pressure p2,gas ( Figure 5 in characteristic curve B or C) appears at the liquid medium 4. If no gas is generated, the entire hydrostatic system is almost incompressible and reacts to the pressure pulse with a pressure p2,solid ( Figure 5 in characteristic curve A). Therefore, if gas is generated, as a response to the pressure pulse, the pressure increase will be less than the case where no gas is generated. Thus, p2,gasB,C < p2,solid applies. Therefore, the aging state of the battery module 1 can be inferred based on the response to the pressure pulse.

[0071] The battery cell 3 becomes increasingly compressible or loses rigidity due to expansion. When the movement of the pressure piston 5b is preset during the pressure pulse, due to the increased compressibility of the entire hydrostatic system, p2,gasB,C < p2,solid occurs. By balancing parameters and comparing them with the data in the initial state according to Figure 1 a first evaluation of the aging state of the battery module 1 can be made.

[0072] In addition, in this way and method, it is also possible to determine the entire compressible volume in the hydrostatic system, which actually corresponds to the gas volume in the battery cell 3, and thereby infer the exact aging state of all battery cells 3.

[0073] Here, the volume change caused by breathing in the initial state ( Figure 2 ) can be used as a reference to more accurately determine the expansion ratio caused by the aging process.

[0074] Furthermore, the pressure measuring device 7 of the hydrostatic tightening system can be used to detect thermal runaway of the battery cells 3 at an early stage in order to improve the detection of safety-critical states. In the event of thermal runaway, an undesirable and uncontrolled chemical chain reaction occurs in the battery cells 3, which is accompanied by violent gas formation. This is like Figure 4 As explained in FIG, this is associated with a substantial increase in the volume of the relevant battery cell 3. Therefore, while the system volume V0 remains constant, the pressure p3 in the liquid medium 4 suddenly rises sharply, as shown in FIG. Figure 6 This can be detected by means of the pressure measuring device 7. Thermal runaway can be inferred from a pressure increase that occurs rapidly in time, ie a high gradient of the pressure p, to be more precise, usually significantly before measuring the temperature increase in the liquid medium 4.

[0075] If thermal runaway of a battery cell 3 cannot be prevented, the cell housing of the battery cell 3 ruptures, allowing hot gases from the exothermic chain reaction to enter the liquid medium 4. This bursting of the battery cell 3 is detected by a characteristic pressure signal in the pressure measuring device 7 of the pressing system. Furthermore, thermal runaway of an individual battery cell 3 can be detected through cell monitoring, for example, based on its cell voltage. Adjacent battery cells 3 are also heated due to the local high energy release and temperature increase, so thermal runaway can also occur in these cells, creating a risk of heat propagation.

[0076] When the hydrostatic system is compressed using the pressure measuring device 7 , a pressure increase in the hydrostatic system can be observed in the early stages of thermal runaway, usually even before the battery cells 3 rupture, which occurs significantly faster than in the case of breathing or expansion. The corresponding classification of the thermal runaway can thus be detected very reliably.

[0077] A major advantage is that thermal runaway in a battery cell 3 at any location in the hydrostatic system is detected very early. In comparison, with conventional temperature measurement, thermal runaway would be detected significantly later due to thermal inertia and, in the most unfavorable case, the large spatial distance of the runaway battery cell 3 from the temperature measurement point.

[0078] Detecting thermal runaway using gas sensors external to the battery cells 3 in the system is typically only possible when the battery cells 3 rupture due to their increased internal pressure. Determining thermal runaway using temperature and voltage sensors can also be delayed or ambiguous. In contrast, using the pressure measurement system 7 of the hydrostatic clamping mechanism allows for the observation of a pressure increase in the hydrostatic system even in the early stages of thermal runaway, before the battery cells 3 rupture. This allows for significantly faster detection.

[0079] An algorithm for early detection of thermal runaway can be stored, for example, in the control device 8, in which the signal of the pressure measuring device 7 is evaluated accordingly. Threshold , a warning signal is generated.

[0080] The invention described above uses the usually already existing hydrostatic tightening system of a battery module 1 in order to determine the aging state and safety state of the battery cells 3 of this battery module as precisely and reliably as possible, so that appropriate countermeasures can be taken in a timely manner.

[0081] For the simultaneous measurement of all battery cells 3 , only a pressure measuring device 7 is required, which is usually already present in the case of pressure control of a hydrostatic tightening system.

[0082] Accurate knowledge of the state of aging (SoH) of the battery cells 3 enables efficient regulation of the optimal pressing pressure.

[0083] Furthermore, the detection of accelerated aging effects or of malfunctioning behavior of individual battery cells 3 results in an increase in battery safety.

[0084] In combination with an existing battery management system, such as that described in DE 10 2018 123 682 A2, this provides the possibility for redundancy as well as increased accuracy and reliability.

[0085] The battery module 1 also provides for rapid and reliable detection of thermal runaway of one or more battery cells 3 .

[0086] Furthermore, redundancy can be implemented within the battery management system when detecting thermal runaway of battery cells 3. This detection can be achieved, on the one hand, by measurements via the electronics (cell monitoring, e.g., voltage signals, temperature), and, now, additionally, by detecting characteristic pressure signals in the hydrostatic tightening system when a critical battery cell 3 swells and / or ruptures.

[0087] In particular, a rupture or bursting of a cell 3 during its swelling can be predicted within a certain timeframe using the pressure measurements present in the hydrostatic tightening system, thereby enabling early countermeasures, for example by warning the occupants in advance and / or increasing rescue time.

[0088] The present invention has been described in more detail above based on various embodiments and implementation variants. This serves to demonstrate the feasibility of the invention. The various technical features explained above in the context of other individual features can also be implemented independently of these features and in combination with other individual features, even if this is not explicitly described, as long as this is technically feasible. Therefore, the present invention is expressly not limited to the specifically described embodiments, implementation variants, and modifications, but rather encompasses all designs defined by the present invention.

[0089] List of reference numerals:

[0090] 1 battery module

[0091] 2 shell

[0092] 3 battery cells

[0093] 4Liquid medium

[0094] 5. Pressure generating device

[0095] 5a pressure cylinder

[0096] 5b pressure piston

[0097] 6. Measuring mechanism for detecting piston position

[0098] 7. Pressure measurement mechanism

[0099] 8 Control mechanism

[0100] A, B, C characteristic curves

[0101] pi compression pressure

[0102] pressure gradient

[0103] Threshold for pressure gradient

[0104] p2, gas response to pressure pulse (gas has been generated)

[0105] p2, solid response to pressure pulse (no gas generated yet)

[0106] si piston stroke

[0107] Δs distance during pressure pulse

[0108] Vi is the volume of the hydrostatic system.

Claims

1. A battery module (1), comprising: Housing (2); A plurality of battery cells (3) arranged in the housing (2); a liquid medium (4) arranged in the housing (2) around the battery cells (3) in order to apply a hydrostatic pressure to the battery cells (3) in the housing (2); a pressure generating device (5) for adjusting the pressure of the liquid medium (4); It is characterized by A control device (8) for actuating the pressure generating device, the control device being configured to carry out a test routine for determining aging, wherein pressure pulses are generated by means of the pressure generating device (5) and the resulting pressure and volume changes of a hydrostatic system consisting of a battery cell (3) and a liquid medium (4) are correlated with a reference characteristic curve.

2. The battery module (1) according to claim 1, characterized in that The pressure generating device (5) comprises a pressure piston (5b) and is provided with a measuring mechanism (6) for detecting the position of the pressure piston (5b), the signal of the measuring mechanism being used to determine the volume change.

3. The battery module (1) according to claim 1 or 2, characterized in that The reference characteristic curve reflects the dependency of the pressure on a variable representing the volume of the hydrostatic system in an unaged state of the battery module (1).

4. The battery module (1) according to claim 1 or 2, characterized in that The aging state of the battery module (1) is inferred from the difference in the pressure increase for a predefined volume change caused by the pressure pulse compared to a reference characteristic curve.

5. The battery module (1) according to claim 1 or 2, characterized in that The size of the compressible gas volume in the battery cell (3) is inferred from the pressure change and the volume change caused by the pressure pulse.

6. The battery module (1) according to claim 5, characterized in that The volume change between the charged and discharged states of the battery module (1) in an unaged state is used as a reference when determining the size of the compressible gas volume in the battery cell (3).

7. The battery module (1) according to claim 1 or 2, characterized in that A pressure measuring device (7) is provided for detecting the pressure of the liquid medium (4), and a signal of the pressure measuring device is used to determine a pressure change.

8. A battery module (1), comprising: Housing (2); A plurality of battery cells (3) arranged in the housing (2); a liquid medium (4) arranged in the housing (2) around the battery cells (3) in order to apply a hydrostatic pressure to the battery cells (3) in the housing (2); and A pressure measuring mechanism (7) for detecting the pressure of the liquid medium (4); It is characterized by A control mechanism (8) which cooperates with the pressure measuring mechanism (7) and is configured to detect when a threshold value for the gradient of the pressure rise of the liquid medium (4) is exceeded. Generates an alarm signal.

9. The battery module (1) according to claim 8, which is improved according to any one of claims 1 to 6.

10. The battery module (1) according to claim 1 or 8, characterized in that The battery module is a traction battery module for a vehicle.

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