DEVICE AND METHOD FOR TESTING CELL CONTACT OF BATTERY CELLS OF A BATTERY MODULE

Description

[0001] The present invention relates to a device for testing the cell contact of battery cells in a battery module. Furthermore, the present invention relates to a method for testing the cell contact of battery cells in a battery module.

[0002] Battery modules are a well-known technology. They are used, for example, in electric vehicles, employing commercially available lithium-ion batteries. Battery modules consist of multiple batteries, referred to below as battery cells. These battery cells are typically manufactured in AA format and then connected in parallel to form a battery module consisting of, for example, 500 individual cells. To achieve the required operating voltage, it is also known to connect the battery cells in series.

[0003] Larger battery modules, such as those used in electric vehicles or temporary energy storage systems, therefore have a very large number of battery cells connected in parallel and / or in series. This leads to problems with the tests required after the battery module has been manufactured.

[0004] It is also known that the battery cells of a battery module are connected in parallel via busbars. Various connection techniques are known for connecting the battery cells to the busbar. For example, it is known to solder or weld the battery cells at their contact points, with laser or ultrasonic welding being known methods for electrically contacting the battery cells, for example, with the busbars. It is also known to use clamps or plug connectors as connecting means to contact the battery cells. The connections between the battery cells and the corresponding busbar can therefore be made in a variety of ways. The contact points are also known as terminals, connection points, or poles.

[0005] The connection between the busbar and the battery cells is not necessarily direct; connecting conductors, such as wires or cables, can also be used to electrically connect the battery cells to the busbar. To connect a battery cell to a busbar, four electrical connections must be made when using a connecting conductor. The first connecting conductor must be connected at one end to the anode (positive terminal) of the battery cell, and at the other end to the busbar for the positive terminal of the battery cell. The same principle is applied analogously to a second connecting conductor to electrically connect the cathode (negative terminal) to the busbar for the negative terminal of the battery cell.

[0006] It can happen that the electrical connection between the battery cells and the busbars is not electrically conductive or only poorly conductive, for example, because the weld, clamp, or plug connection is inadequately executed. This is undesirable and can occur due to manufacturing variations and tolerances. Therefore, efforts are made to test the electrical contact points of the battery cells. Due to the large number of contact points to be tested, which are referred to as test points, devices for the automated testing of the cell contacts of the battery cells in the battery module are known. For example, such a device is known from document EP 3 114 491 B1. Document EP 3 114 491 B1 describes a device that operates using resistance measurement.The basic principle of the device described there is that the electrical conductivity of the test points is checked by positioning two contact electrodes in pairs at a multitude of test points using an automated positioning system, and measuring the resistance between the two contact electrodes to determine the conductivity of the test point. If the resistance value is too high, a poor test point or poor electrical contact is assumed. A problem with the resistance measurement is that each contact point must be tested individually. This is problematic because the testing process for all individual contact points is time-consuming. Furthermore, it is problematic that the contact electrodes must be brought into direct electrical contact with the test points for the resistance measurement, which requires precise positioning of the contact electrodes.Precise positioning presents a particularly significant challenge because, due to manufacturing and process variations during battery module production, the battery cell contacts are not always in the same position. This means that even with identical battery modules, the test points can be located in different places. This is countered by calibration procedures or adherence to tight manufacturing tolerances, which is complex and time-consuming. Furthermore, the contact electrodes must exert a certain force on the test points to ensure proper contact. It follows that the contact electrodes can therefore wear down, and contamination can lead to inaccurate test results.

[0007] In the priority-establishing German patent application, the German Patent and Trade Mark Office searched the following documents: DE 31 41 315 A1, DE 11 2014 000 982 T5 and EP 2 703 830 A2. Document CN 113296012 A discloses a method and a device for the defect detection of lithium battery packs by means of in-situ magnetic field imaging.

[0008] The object of the present invention is therefore to address one of the aforementioned problems, to improve the general state of the art, or to provide an alternative to what is known. In particular, a solution is to be provided that can accelerate the testing process for the cell contacting of battery cells. Specifically, a simpler and more robust testing system for testing the cell contacting of battery cells is also to be provided.

[0009] To solve this problem, a device for testing the cell contacting of battery cells of a battery module according to claim 1 is proposed.

[0010] A test device is proposed that is designed and configured for testing the cell contacts of battery cells. Testing the cell contacts can also be understood as testing the contact points or connection points of the battery cells where they are electrically connected. The term "battery cell" can also be used synonymously with "battery" or "accumulator" (rechargeable battery). A battery cell is part of a battery module. The battery module consists of a multitude of battery cells that are electrically contacted or connected to one another; for example, the battery cells of the battery module are connected in parallel or in series. The test device is therefore intended to verify the proper electrical connection of a battery module, i.e., whether the electrical connection of the battery cells was correctly established during the manufacturing of the battery module.If the cell contacting of the battery cells, i.e., the creation of an electrically conductive connection, is carried out, for example, using a laser welding process, then the laser-welded connection points or points of the battery module are tested with the test device.

[0011] It is proposed that several battery cells of the battery module be electrically connected in parallel via a contacting system. Electrically connected in parallel means that several negative terminals of the battery cells are electrically connected, just as several positive terminals of the battery cells are electrically connected. A contacting system is provided to connect the battery cells. This system is for electrically contacting the battery cells with one another. Additional components of the battery module, such as a battery management system or protective circuits (e.g., for deep discharge or short-circuit protection), can also be connected to the contacting system. The contacting system, therefore, refers to the electrical connection technology.For example, the contacting system consists of several parallel busbars and several connecting conductors that electrically connect the busbars and the battery cells.

[0012] The test device comprises a sensor positioning system for positioning a sensor device at a multitude of test points on the battery module. The sensor positioning system is designed to be movable along a longitudinal axis, a transverse axis, and a vertical axis. These axes define a three-dimensional space, allowing the sensor device to be moved to any point within that space. The sensor positioning system is an automated system for arranging or placing a sensor device at the respective test point. For example, the sensor positioning system is configured, as described in the prior art patent EP 3 114 491 B1, with several independently movable sensor mounts. The sensor positioning system can be used to access multiple test points simultaneously or sequentially.The sensor positioning system positions the sensor device at all contact points of the battery module to be tested, ensuring that all test points can be inspected. This positioning process is automated. To reach all test points, the sensor positioning system is designed to be movable and can move the sensor device along the transverse, vertical, and longitudinal axes. "Movable" can also be interpreted as "movable" or "positionable." The sensor device can therefore be moved freely in three-dimensional space using the sensor positioning system. Movement along the longitudinal axis can be understood as a forward or backward movement. Movement along the transverse axis can be understood as a left or right movement. Movement along the vertical axis can be understood as an upward or downward movement.The design of the sensor positioning system is basically arbitrary; for example, it can be designed with several movable sensor mounts as described in EP 3 114 491 B1, but it can also be designed with an industrial robot or a three-axis movable sensor head, as in a 3D printer.

[0013] Each test point of the battery module is automatically approached by the positioning system, and the sensor device is positioned at each test point to perform a measurement. The positioning of the sensor device by the sensor positioning system can follow a predefined sequence, which is stored, for example, in a control unit of the test device or in the sensor positioning system itself. Once the test at one test point is completed, the sensor positioning system repositions the sensor device at one or more new test points.

[0014] The test device preferably comprises a control unit for controlling the sensor positioning system and for controlling the power generation circuit and is preferably connected via data transmission to an evaluation unit and / or the sensor unit. The control unit is designed and configured to coordinate the test procedure, i.e., to coordinate the approach to the test points with the positioning system, the generation of battery current with the power generation circuit, the measurement process with the sensor unit, and the evaluation process with the evaluation unit.

[0015] The test device also includes a current generation circuit for generating a battery cell current, wherein the battery cell current is either a discharge current from the battery cell or a charging current into the battery cell. It is therefore proposed that a technical device generates a current that is either drawn from the battery cell or fed into the battery cell. The battery cell current is thus an electric current generated by the battery cell. The battery cell therefore acts as a current source. The battery cell current can also be an electric current generated by another current source and then fed into the battery cell. It is understood that the battery cell current is a direct current. It is also understood that the current generation circuit is connected to the battery cell or multiple battery cells in such a way that the discharge current or the charging current is established.The current generation circuit is electrically connected to the contacting system so that the battery cell under test can be discharged or charged via the contacting system and the current generation circuit. It is understood that in the case of discharge, the battery cell is pre-charged. For discharging or charging, a closed circuit is therefore established between the positive and negative terminals of the battery cell under test by means of the current generation circuit, so that the battery cell current flows in or out of the battery cell under test.

[0016] The test device also includes a sensor assembly equipped with at least one field sensor. After the sensor assembly is positioned at one of the test points, the field sensor is configured to detect a field in the vicinity of the test point, which is generated by the battery cell current produced by the current-generating circuit. Such a field arises when a current flows in the vicinity of the test point. The field sensor can also be considered a sensor head. It is known that an electric field is generated by stationary and moving charges, and a magnetic field by moving charges. Moving charges are also synonymously known as electric current. The field therefore refers to a magnetic field and / or an electric field, since it is generated by the battery cell current, i.e., by moving charges. The field sensor is thus a sensor configured to detect a magnetic field and / or an electric field.After positioning the sensor device at the test site, the field sensor detects a magnetic field and / or an electric field generated by the battery cell current, which is produced by the current generation circuit. The magnetic field is characterized by a magnetic flux density (B) and a magnetic field strength (H). The electric field is characterized by an electric flux density (D) and an electric field strength (E). The field sensor can therefore be, for example, a magnetometer and / or an electric field meter. Well-known magnetometers include, for example, Hall effect sensors, coils, Förster probes, SQUIDs (superconducting quantum interference devices), proton magnetometers, and similar devices.

[0017] A test point is a location within the battery cell under test where the field generated by the battery cell current can be measured. Suitable test points include, for example, locations in the immediate vicinity of the battery cell contacts, i.e., in the area of ​​the anode and / or cathode terminals. Another suitable test point is located in the area of ​​the connecting conductors that electrically link the busbar and the battery cells. Furthermore, another suitable test point is a location where a connecting conductor of the battery cell is connected to the busbar.

[0018] The field sensor is therefore designed for the contactless detection of a magnetic field and / or electric field in the area of ​​the test point.

[0019] It has been recognized here that, instead of measuring resistance as known from the prior art, e.g., from EP 3 114 491 B1, measuring a magnetic and / or electric field in the area of ​​the test point is particularly advantageous, since it is not necessary to test each contact point on each battery cell individually. This method utilizes the effect that a closed circuit between the positive and negative terminals of the battery cell under test cannot be established if one of the two contact points on the battery cell under test has no or poor electrical contact. If the positive or negative terminal is not properly contacted, no or only a small current is generated in the battery cell, and consequently, no measurable or only a weakly measurable field is induced.This allows a single measurement to determine whether the positive and negative terminals of the battery cells are correctly connected to the contact system. This also means that, for example, if busbars with connecting conductors are used as the contact system, four contact points of the battery cells can be tested simultaneously with a single measurement: the connection between the positive terminal and a first connecting conductor, the connection between the first connecting conductor and the positive busbar to which the positive terminals of the battery cells are connected, the connection between the negative terminal and a second connecting conductor, and the connection between the second connecting conductor and the negative busbar to which the negative terminals of the battery cells are connected. Using a resistance measurement method, all four test points on the battery cell would have to be tested individually.The device and method according to the invention reduce the duration of the test procedure. Furthermore, the field generated by the battery cell current is measured without contact, making the system less susceptible to contamination. In addition, the magnetic field and / or electric field generated by the battery cell current extends over a larger spatial area, meaning the field sensor does not need to be positioned as precisely as in a resistance measurement, where contact points must be precisely located.

[0020] Preferably, the sensor device is configured with the field sensor to detect a magnetic flux density and / or a magnetic field strength, and the device is equipped with an evaluation unit to evaluate the detected magnetic flux density and / or the detected magnetic field strength. It is therefore proposed to use a magnetic field sensor to detect a magnetic field generated by the battery cell current. An advantage of this is that the magnetic flux density and the magnetic field strength depend on the current of the battery cell, and thus different magnetic field strengths are generated at different battery cell currents.By analyzing the magnetic parameters, conclusions can be drawn about the contact quality. For example, a poor electrical contact results in higher resistance and lower current flow compared to a highly conductive contact. Similarly, the magnetic field is lower with a poor electrical contact than with a highly conductive one. It goes without saying that the sensor and evaluation unit are interconnected via data transmission.

[0021] Preferably, the sensor device is configured with the field sensor to detect an electric flux density and / or an electric field strength, and the device is equipped with an evaluation unit to evaluate the detected electric flux density and / or the detected electric field strength. It is therefore proposed to use a field sensor to detect an electric field generated in the area of ​​the test point. The advantage of this is that the electric flux density and the electric field strength allow conclusions to be drawn about the applied electric potential at the test point. By evaluating the electric field, conclusions can thus be drawn about the contact quality and the electric potential applied to the battery contacts. It is understood that the sensor device and the evaluation unit are interconnected via data transmission.

[0022] Preferably, the battery cells are electrically pre-charged, and the current generation circuit is designed as a discharge circuit with a load resistor for discharging the pre-charged battery cells via the contact system in order to generate the battery cell current as a discharge current between the battery cell contacts. In this case, the battery cell(s) act as a current source for generating the battery cell current. The current generation circuit establishes a closed circuit between the positive and negative terminals of the battery cells, so that the battery cells discharge via the contact system and the load resistor. The load resistor is, for example, controllable, and the battery cell contacts can be electrically connected via the load resistor using a controllable switch.The contact points are understood to be the connection points for contacting the battery cell, for example, the terminals for the positive and negative poles. Pre-charging of the battery cells can take place outside the test setup and before the test procedure. Optionally, this pre-charging can also be incorporated into the test procedure, in which case it can be performed immediately after the battery cells are manufactured and at a later time interval from the subsequent steps of the test procedure. An electrically pre-charged state exists when the battery cell is at least partially electrically charged and the battery cell current can be drawn from it as a discharge current.

[0023] Preferably, the battery cells are electrically rechargeable, and the current generation circuit is designed as a charging circuit for charging the battery cells via the contacting system to generate the battery cell current as a charging current between the contact points of the battery cells. In this case, the battery cell(s) operate as an electrical storage device into which the generated battery cell current is fed. The current generation circuit establishes a closed circuit between the positive and negative terminals of the battery cells, enabling the battery cells to be charged via the contacting system. Furthermore, the current generation circuit includes a current source or energy source to generate the battery cell current that is fed into the battery cells operating as energy storage devices. The battery cells can be charged during testing using the test equipment. The current source or energy source...The energy source for charging the battery cells can be, for example, a rectified mains voltage from an electrical supply network. The charging circuit can also be understood as a battery charger. Battery chargers are generally well-known.

[0024] Preferably, the field sensor has at least two sensors, one of which is configured to detect a field generated in the region of an anode contact point of the battery cell, and another sensor is configured to detect a field generated in the region of a cathode contact point, in particular to simultaneously check the field at the anode contact point and at the cathode contact point of the battery cell. It is therefore proposed to arrange at least two sensors on a sensor head with which the contact point at the anode and at the cathode of the battery cell is checked simultaneously. The cathode contact point refers to the negative terminal or the cathode connection of the battery cell. The anode contact point refers to the positive terminal or the anode connection of the battery cell. In a particular embodiment, the two sensors are arranged in pairs opposite each other and spaced apart.If two sensors are used for the field sensor, it is advantageous to be able to compare the detected field in the area of ​​the anode contact point with the detected field in the area of ​​the cathode contact point. Furthermore, the two acquired signals can be averaged to compensate for measurement inaccuracies, and the use of two sensors increases the measuring range, thus reducing the need for precise sensor positioning. The distance between the sensors is preferably chosen to correspond to the distance between the anode and cathode contact points. For variable application, it is preferred that this distance be adjustable. For example, the sensors can be slidably mounted for this purpose.

[0025] Preferably, the field sensor is designed with a Hall sensor and / or an electrical coil. It is therefore proposed to design the field sensor as a magnetic sensor. Hall sensors and electrical coils for measuring a magnetic field are generally known. These two sensor types are particularly robust and reliable.

[0026] Preferably, the sensor device comprises a plurality of field sensors to simultaneously test several test points of the battery module, each with its own field sensor. The plurality of field sensors are mounted on a sensor holder of the positioning system. The sensor holder is movable along the longitudinal, transverse, and vertical axes to allow the simultaneous movement of the plurality of field sensors. It is therefore proposed to use a plurality of measuring heads to test several test points in parallel and simultaneously. This reduces the duration of the battery module test procedure. The sensor holder is a bracket or support structure to which the field sensors or the sensor device are attached. The sensor device, along with the plurality of field sensors, is thus mechanically connected to the sensor holder, so that any movement of the sensor holder directly affects the sensor device.The numerous field sensors attached to the sensor holder are moved simultaneously. The sensor holder is part of the sensor positioning system and is therefore movable, as previously described. It is preferable that the field sensors of a sensor assembly are arranged on the sensor holder with variable distances relative to each other. This allows the sensor assembly to be used flexibly for different battery modules by arranging the field sensors relative to each other in such a way that they correspond to the pattern of the contact points to be tested. In this way, the assembly can be adapted for use with different types of battery modules.

[0027] Preferably, the positioning system comprises several sensor mounts, each independently movable along a longitudinal axis, a transverse axis, and a vertical axis, with a plurality of field sensors attached to each sensor mount to test multiple test points of the battery module. It is therefore proposed that the positioning system has several independently movable sensor mounts, each with a plurality of field sensors or sensor heads attached. For example, independently movable sensor mounts with a plurality of field sensors can be used. This allows a plurality of test points to be tested simultaneously and independently. This reduces the duration of the battery module testing procedure.The numerous field sensors are arranged at intervals and fixed to the mounting bracket, preferably with a spacing that corresponds to the spacing of the battery cells. It is therefore proposed that the spacing between the field sensors matches the spacing between the battery cells. Thus, the spacing of the field sensors is adapted to the spacing of the battery cells. As previously mentioned, it is advantageous if this spacing is adjustable to allow for testing different battery modules.

[0028] Preferably, the test device includes an evaluation unit for assessing the field detected in the area of ​​the test point. This evaluation unit is configured to determine and / or visually display the contact quality based on the detected field. Preferably, the evaluation unit has a visual display with which an evaluation result can be shown. It is therefore proposed to provide an evaluation unit that evaluates the sensor signals. For this purpose, the evaluation unit can include an evaluation algorithm that is implemented as a computer program within the evaluation unit. The result of the evaluation can be a characteristic value for the contact quality. If the specified characteristic value falls below a predetermined threshold, for example, a faulty contact point is inferred, and an error is displayed or reported.

[0029] In a particularly preferred embodiment, the evaluation device is configured to determine the contact quality of the cell contacts at the test point or at multiple test points by evaluating the measured flux density and / or the measured field strength. The flux density and field strength refer to both the magnetic field and the electric field. It is therefore proposed that the evaluation device evaluates the flux density and / or the field strength using signal or data processing. This evaluation can include comparison or signal analysis. The measured flux density and / or field strength can then be compared with other measurements or reference values ​​to determine the quality of the cell contacts.

[0030] Preferably, the evaluation device includes a comparison database containing comparative data, and is configured to compare the measured flux densities and / or field strengths with this comparative data to determine the contact quality. It is understood that the evaluation device includes a data storage unit for this purpose. The comparison database contains, for example, comparative values ​​for flux densities and / or field strengths. The evaluation device includes, for example, a computer program or algorithm that compares the measured field strength and / or flux density with the database.

[0031] As a further aspect of the invention, a method for testing the cell contacting of battery cells in a battery module is proposed. The method comprises the following steps: providing a battery module, wherein the battery module has several battery cells electrically connected in parallel via a contacting system; positioning a sensor device at at least one test location of the battery module with a sensor positioning system; generating a battery cell current between the contact points of the battery cells by discharging or charging the battery cells; detecting a field in the region of the at least one test location that is generated by the battery cell current; and evaluating the detected field to determine the contact quality of the cell contacting at the at least one test location.

[0032] The provided battery module can be pre-charged or uncharged. Furthermore, battery cells of the module can also be connected in series to set a predetermined battery output voltage. The sensor positioning system is configured as described above or below. The generation of the battery cell current is carried out by a current generation circuit, as described above or below. The detection of a field in the area of ​​the at least one test point is performed by a sensor device with at least one field sensor, as described above or below. The field refers to a magnetic field and / or an electric field.

[0033] Preferably, the method is carried out using a device for testing the cell contacting of battery cells of a battery module according to one of the above embodiments.

[0034] The explanations, definitions and advantages described for the test device apply analogously to the previously described test procedure.

[0035] The present invention will now be explained in more detail below by way of example embodiments with reference to the accompanying figures, whereby the same reference numerals are used for identical or similar assemblies: Fig. 1 schematically shows a perspective view of a test device according to the invention in one embodiment. Fig. 2 schematically shows a battery cell of a battery module and the positioning of a field sensor in the area of ​​a test point. Fig. 3 schematically shows a battery cell of a battery module with a current generation circuit and an evaluation device in one embodiment. Fig. 4 schematically shows a battery cell of a battery module with a current generation circuit and an evaluation device in another embodiment. Fig. 5 schematically shows a battery cell of a battery module and a field sensor with two sensors in one embodiment. Fig. 6 schematically shows a battery cell of a battery module and several test points in the area of ​​the battery cell.Figure 7 schematically shows a sensor positioning system for positioning a sensor device with a plurality of field sensors and two independently movable sensor mounts. Figure 8 schematically shows a flowchart of the test method according to the invention.

[0036] The Figure 1 Figure 100 shows a device 100 for testing the cell contacting of battery cells 102 of a battery module 104, in which several battery cells 102 of the battery module 104 are electrically connected in parallel via a contacting system 106, 107. The contacting system comprises at least a first busbar 106 for the positive terminals 115 (positive pole) of the battery cells 102 and a second busbar 106 for the negative terminals 116 of the battery cells 102. The busbars 106 are electrically contacted, i.e., electrically connected, to the battery cell via connecting conductors 107. As the Figure 1As can be seen, the three battery cells 102 are electrically connected in parallel. The contact points 115, i.e., the positive terminals of the battery cells 102, are each connected to a busbar 106 via a connecting conductor 107. Furthermore, the contact points 116, i.e., the negative terminals of the battery cells 102, are also connected to a busbar 106 via a connecting conductor 107. The three battery cells 102 shown are representative of a large number of battery cells in the battery module 104. In addition, the Figure 1 The dashed lines indicate that further battery cells 103 may be part of the battery module 104, for example, connected in series with the battery cells 102. The series connection of the battery cells 103 is made to set a desired output voltage at the battery module 104, since the voltages of the individual battery cells 102 and 103 add up when connected in series.

[0037] The contacting system is therefore formed from busbars 106 and connecting conductors 107, and it serves the purpose of electrically connecting the battery cells 102 and, if necessary, the further battery cells 103.

[0038] The contact points 115 and 116, i.e., the positive and negative terminals of the battery cells 102, are arranged on the same side. It is also known that the positive terminal 115 and the negative terminal 116 are arranged on opposite sides of the battery cells 102, as is common in commercially available batteries.

[0039] The test device 100 also includes a sensor positioning system 108 for positioning a sensor device 110 at a plurality of test points 112 of the battery module 104, wherein the sensor positioning system is designed to be movable along a longitudinal axis X, a transverse axis Y and a vertical axis Z for positioning the sensor device. The test points 112 are described in more detail in the Figure 6 illustrated.

[0040] The sensor device 110 has a plurality of field sensors 118 to simultaneously test several test points 112 of the battery module 104, each with one field sensor 118. The plurality of field sensors 118 are attached to a sensor holder 126 of the positioning system 108. The sensor holder 126 is designed to be movable along a longitudinal axis X, a transverse axis Y, and a vertical axis Z in order to move the plurality of field sensors 118 simultaneously. The sensor holder 126 can therefore be lowered or raised, moved to the right and left, and moved forward and backward. This is illustrated by the indicated coordinate system. The plurality of field sensors 118 are spaced apart from one another and fixed to the holder 126, with a spacing that corresponds to the spacing of the battery cells 102.It is therefore proposed that the spacing between the field sensors 118 should correspond to the spacing between the battery cells 102, so that several test points 112 can be accessed simultaneously. For example, the three field sensors 118 shown can be used to test the three battery cells 102 shown simultaneously.

[0041] In the Figure 1 Although only one sensor holder 126 is shown, the positioning system 108 can also have several sensor holders 126, each of which is independently movable along the longitudinal axis X, a transverse axis Y and a vertical axis Z, and a plurality of field sensors 118 can be attached to each of the sensor holders in order to test several test points 112 of the battery module 104. This is shown, for example, in the Figure 7 depicted.

[0042] The test device 100 also includes a current generation circuit 114 for generating a battery cell current, wherein the battery cell current I is a discharge current from the battery cell 102 or a charging current into the battery cell 102. The current generation circuit 114 is, for example, in the Figure 3 or 4 shown in more detail. The power generation circuit 114 is connected to the battery cells in such a way that the battery cell current I is established. In the Figure 1 The power generation circuit 114 is connected to the positive and negative busbar 106.

[0043] The test device 100 also includes the sensor device 110, which is equipped with at least one field sensor 118. In the Figure 1Three field sensors 118 are shown as examples. After positioning the sensor device 110 at a test point 112, the field sensor 118 is configured to detect a field in the area of ​​the test point 112, which is generated by the battery cell current I produced by the current generation circuit 14. This principle is described in the Figures 2 to 6 illustrated in more detail.

[0044] The sensor device 110 is, for example, equipped with the field sensor 118 to detect a magnetic flux density B and / or a magnetic field strength H, and / or the sensor device 110 is equipped with the field sensor 118 to detect an electric flux density D and / or an electric field strength E.

[0045] The test device 100 is equipped with an evaluation unit 120 to evaluate the detected magnetic flux density B and / or the magnetic field strength H of the detected field and / or to evaluate the detected electric flux density D and / or the electric field strength E of the detected field.

[0046] The device 100 therefore has an evaluation unit 120 for evaluating the field recorded in the area of ​​the test station 112.

[0047] The evaluation unit 120 is designed to determine the contact quality of the cell contacting at the test point 112 or at several test points 112 by evaluating the recorded flux density B, D and / or the recorded field strength H, E.

[0048] The evaluation unit 120 can also include a comparison database 126 containing comparative data to compare the recorded flux densities and / or field strengths with the reference data and to draw conclusions about the contact quality. For example, if no or only a low field strength is measured, a contact defect can be assumed.

[0049] The field sensor 118 is designed, for example, to detect a magnetic field with a Hall sensor and / or with an electrical coil.

[0050] Not in the Figure 1A control unit is shown, which is configured to control the sensor positioning system and the power generation circuit and is connected to an evaluation unit and the sensor unit via data transmission. The control unit is designed and configured to coordinate the test procedure, i.e., to control the approach to the test points with the positioning system 108, the generation of the battery current I with the power generation circuit 114, the measurement process with the sensor unit 110, and the evaluation process with the evaluation unit 120.

[0051] The Figure 2Figure 1 schematically shows a battery cell 102 of a battery module 104 and the positioning of a field sensor 118 in the area of ​​a test point. The field sensor 118 was thus positioned in the area of ​​test point 112 using the sensor positioning system 118. In this case, test point 112 is located between contact points 115 and 116. This test point is advantageous because a field in the area of ​​contact point 115 as well as in the area of ​​contact point 116 can be detected. This is illustrated by the two dashed arrows.

[0052] In the Figure 2A current generation circuit is shown. The current generation circuit 114 generates a battery cell current I, which in the example shown flows from the positive terminal of battery 102 to the negative terminal 116 of battery cell 102. The current generation circuit 114 thus establishes a closed circuit between the two contact points 115 and 116. Due to the current flow, a magnetic field MF is generated. A ring-shaped magnetic field is generated around the connecting conductor 107, since this is a current-carrying conductor. According to the right-hand rule, a magnetic field is formed which is located in the Figure 2 This is schematically illustrated as MF. The magnetic field generated by the battery cell current I is only shown at the connecting conductor 107, which is connected to the positive busbar 106.

[0053] The Figure 2This also illustrates that the negative terminal of battery cell 102 can also be located on the underside of the battery cell.

[0054] Furthermore, in the Figure 2 It can be seen that, in order to connect the battery cell 102 to busbars 106, four electrical connections must be made using connecting conductors 107. The first connecting conductor 107a is electrically connected at one end to the anode contact 115 (positive terminal) of the battery cell 102 and at the other end to the busbar 106a. The connection points can be, for example, laser-welded or ultrasonically welded. Further battery cells with their anode contacts are connected in parallel to the busbar 106a, as in the Figure 1As shown. This type of contact is carried out analogously for the second connecting conductor 107b in order to electrically connect the cathode contact 116 (negative terminal) and the busbar 106b for the negative terminal of battery cell 102. In total, battery cell 102 has therefore been electrically contacted at four connection points. These connection points must be checked to ensure they are electrically conductive. This check verifies that a properly functioning battery module is ready, in which all battery cells are properly connected.

[0055] Figure 3Figure 1 shows a current generation circuit 114 in an embodiment as a discharge circuit. The battery cell 102, which is exemplary for a multitude of other battery cells, is electrically pre-charged. It is sufficient to only partially charge or pre-charge the battery cell 102, for example, to 10% to 20% of its maximum storage capacity. The current generation circuit 114 is designed as a discharge circuit with a load resistor 122 for discharging the pre-charged battery cells via the contacting system 106 in order to generate the battery cell current as a discharge current between contact points 115, 116 of the battery cells 102. When the switch 124, which is controllable, is closed, a current I flows, namely the battery current or battery cell current, since a closed circuit exists. The battery cell current generates a magnetic field MF, which can be detected with the field sensor 118. If one of the four connection points, which are connected to the Figure 2If the contacts described were damaged or non-conductive, the circuit would not be closed. Therefore, if no field is measured in the area of ​​the test point, one of the four contacts is defective. If only a weak magnetic field is measured, a poorly conducting electrical connection at one of the four connection points mentioned can be assumed. Furthermore, in the Figure 3 The evaluation unit 120 is illustrated, which is connected to the sensor head 118 in terms of data technology.

[0056] Figure 4Figure 1 shows a power generation circuit 114 in an embodiment as a charging circuit. The battery cell 102, which is representative of a multitude of other battery cells, is electrically uncharged or partially charged, i.e., not fully charged. The power generation circuit 114 includes a DC power source 128 with which the battery cell current I is generated as the charging current. The DC power source 128 can, for example, be supplied from the electrical supply network 130. It is understood that the DC power source 128 includes a rectifier, since the electrical supply network 130 is an AC network, as the battery cells 102 are known to be charged with a DC current and a DC voltage. The charging current refers to the current intensity with which a battery is charged. In addition, the power generation circuit 114 optionally includes a charging resistor 123 to limit the charging current.The power generation circuit 114 is thus designed to charge the battery cells 102 via the contact system 106, in order to feed the battery cell current into the battery cells 102 as a charging current. When the switch 124, which is controllable, is closed, a charging current I flows, namely the battery current or battery cell current, since a closed circuit exists. The battery cell current I generates a magnetic field MF, which can be detected with the field sensor 118. If one of the four connection points leading to the... Figure 2 If the contacts described were damaged or non-conductive, the circuit would not be closed. If no field is measured at the test point during charging, one of the four contacts is defective. If only a weak magnetic field is measured, a poorly conductive electrical connection at one of the four connection points mentioned can be assumed.

[0057] Figure 5Figure 118 shows a field sensor 118 configured with two sensors 124 and 125. Sensor 124 is configured to detect a field MF generated in the area of ​​an anode contact point 115 of the battery cell 102, and sensor 125 is configured to detect a field MF generated in the area of ​​a cathode contact point 116. The field MF is thus simultaneously measured at both the anode and cathode contact points of the battery cell.

[0058] Figure 6This shows examples of where suitable test points can be located on battery cell 102. A test point is, fundamentally, a location on the battery cell 102 under test where the field MF generated by the battery cell current I can be measured. Suitable test points include, for example, locations in the immediate vicinity of the battery cell contacts, i.e., in the area of ​​the anode and / or cathode terminals of the battery cells, such as test points P1 and / or P2. Another suitable test point is located in the area of ​​the connecting conductors that electrically connect the busbar and the battery cells, such as test points P3 and / or P4. Furthermore, another suitable test point is located where a connecting conductor of the battery cell is connected to the busbar, such as test points P5 and P6. Additionally, a test point P7 can also be located between the anode and cathode terminals.

[0059] Figure 7 schematically shows a sensor positioning system 108 for positioning a sensor device 110 with a plurality of field sensors 118 and two independently movable sensor holders, which are designed to be movable with a drive device 134.

[0060] The sensor device 110 shown has a plurality of field sensors 118 to simultaneously test several test points 112 of the battery module 104, each with one field sensor 118, wherein the field sensors 118 are attached to a sensor holder 126a of the positioning system 108. The sensor holder 126a is designed to be movable along the longitudinal axis X, the transverse axis Y and the vertical axis Z in order to move the plurality of field sensors simultaneously.

[0061] Furthermore, in the Figure 7It was also shown that the positioning system 108 has several sensor mounts 126a, 126b, each of which is independently movable along a longitudinal axis X, a transverse axis Y and a vertical axis Z, and wherein a plurality of field sensors 118 are attached to each sensor mount 126a, 126b in order to test several test points 112 of the battery module 104.

[0062] Furthermore, in the Figure 7 shown that the sensor holders 126a and 126b are equipped with a drive unit 132.

[0063] To support the drive unit and the sensor mounts 126a and 126b, a support structure 134 may be provided, which is made of a structurally rigid material.

[0064] The Figure 8 Figure 1 schematically shows a procedure for testing the cell contact of battery cells 102 of a battery module 104. The procedure comprises the following steps: S1: Providing a battery module 104, wherein the battery module 104 has several battery cells 102 electrically connected in parallel via a contacting system 106, as for example in the Figure 1 S2: Positioning a sensor device 110 at at least one test point 112 of the battery module 104 with a sensor positioning system 108, as shown, for example, in Figure 1 or 7. S3: Generating a battery cell current I between contact points 115, 116 of the battery cells 102 by discharging or charging the battery cells 102, as shown, for example, in the Figures 2 to 4 shown. S4: Detection of a field MF in the area of ​​at least one test point 112, which is generated by the produced battery cell current I, as for example in the Figures 3 to 5 shown. S5: Evaluation of the recorded field MF to determine the contact quality of the cell contacting at the at least one test point 112, as for example in the Figure 1 , 3 or 4 shown. Reference symbol list

[0065] 100 Device or test device 102 Battery cell 104 Battery module 106 Busbar 107 Connecting conductor 108 Sensor positioning system 110 Sensor device 112 Test point 114 Power generation circuit 115 Contact point (positive terminal) 116 Contact point (negative terminal) 118 Field sensor 120 Evaluation device 122 Load resistor 124 Sensors 126 Sensor holder 128 DC power source 130 Power supply network 132 Drive device 134 Support structure

Claims

1. An apparatus (100) for testing a cell contact of battery cells (102) of a battery module (104), wherein a plurality of battery cells (102) of the battery module (104) are electrically connected in parallel via a contacting system (106, 107), the apparatus comprising: - a sensor positioning system (108) for positioning a sensor device (110) at a plurality of test points (112) of the battery module (104), wherein the sensor positioning system is configured to be displaceable along a longitudinal axis (X), a transverse axis (Y) and a vertical axis (Z) for positioning the sensor device; and - a current generation circuit (114) for generating a battery cell current, wherein the battery cell current (I) is a discharge current from the battery cell (102) or a charging current into the battery cell (102), wherein - the sensor device (110) is configured with at least one field sensor (118), wherein after positioning the sensor device at one of the test points (112) the field sensor (118) is designed to detect a field which is in the region of the test point (112) and which is generated by the battery cell current (I) generated by the current generation circuit (114), the field sensor (118) having at least two sensors (124, 125), and wherein the apparatus also has - an evaluation device for evaluating the field detected in the region of the test point, characterised in that the evaluation device is designed to determine a contact quality of the cell contact at the test point or at a plurality of test points by evaluating the detected flux density and / or the detected field strength, wherein one of the sensors (124) is configured to detect a field generated in the region of an anode contact point (115) of the battery cell (102) and another of the sensors (125) is configured to detect a field generated in the region of a cathode contact point (116), in particular in order to test simultaneously the field at the anode contact point and the cathode contact point of the battery cell.

2. The apparatus (100) according to Claim 1, wherein - the sensor device (110) is designed to detect with the field sensor (118) a magnetic flux density (B) and / or a magnetic field strength (H), and wherein the apparatus (100) is designed to evaluate with an evaluation device (120) the detected magnetic flux density (B) and / or the magnetic field strength (H) of the detected field; and / or - the sensor device (110) is designed to detect with the field sensor (118) an electrical flux density (D) and / or an electrical field strength (E), wherein the apparatus (100) is designed to evaluate with an evaluation device (120) the detected electrical flux density (D) and / or the electrical field strength (E) of the detected field.

3. The apparatus (100) according to Claim 1 or 2, wherein the battery cells (102) are electrically pre-charged and the current generation circuit (114) is configured as a discharge circuit with a load resistor (122) to discharge the pre-charged battery cells via the contacting system (106) in order to generate the battery cell current as discharge current between contact points (115, 116) of the battery cells (102).

4. The apparatus (100) according to one of the preceding claims, wherein the battery cells (102) are electrically chargeable and the current generation circuit (114) is configured as a charging circuit for charging the battery cells (102) via the contacting system (106) in order to generate the battery cell current as a charging current between contact points (115, 116) of the battery cells (102).

5. The apparatus (100) according to one of the preceding claims, wherein the field sensor (118) is configured with a Hall sensor and / or with an electrical coil.

6. The apparatus (100) according to one of the preceding claims, wherein the sensor device (110) has a plurality of field sensors (118) in order to test simultaneously a plurality of test points (112) of the battery module (104) in each case with a field sensor (118), wherein the plurality of field sensors (118) are fastened to a sensor holder (126) of the positioning system (108) and the sensor holder (126) is configured to be displaceable along the longitudinal axis (X), the transverse axis (Y) and the vertical axis (Z) in order to displace the plurality of field sensors simultaneously.

7. The apparatus (100) according to one of the preceding claims, wherein the positioning system has a plurality of sensor holders (126) which are configured in each case to be displaceable independently of one another along a longitudinal axis (X), a transverse axis (Y) and a vertical axis (Z), and wherein a plurality of field sensors (118) are fastened to each sensor holder in order to test a plurality of test points (112) of the battery module (104).

8. The apparatus (100) according to one of the preceding claims, wherein the evaluation device has a comparison database in which comparison data are stored, and the evaluation device is designed to compare the detected flux densities and / or field strengths with the comparison data in order to draw conclusions about the contact quality.

9. A method for testing a cell contact of battery cells (102) of a battery module (104), comprising the steps: - providing (S1) a battery module (104), wherein the battery module (104) has a plurality of battery cells (102) electrically connected in parallel via a contacting system (106); - positioning (S2) a sensor device (110) at at least one test point (112) of the battery module (104) with a sensor positioning system (108); - generating (S3) a battery cell current (I) between contact points (115, 116) of the battery cells (102) by discharging the battery cells (102) or charging the battery cells (102); - detecting (S4) a field (B) in the region of the at least one test point (112) which is generated by the generated battery cell current (I); and - evaluating (S5) the detected field (B) for determining a contact quality of the cell contact at the at least one test point (112), wherein the method is carried out by means of an apparatus (100) for testing a cell contact of battery cells (102) of a battery module (104) according to one of the preceding Claims 1 to 8.