Resistor arrangement for measuring a battery current of a high-voltage system and measuring arrangement

Abstract

A resistor arrangement (100) for measuring a battery current of a high-voltage system, the resistor arrangement comprising: a first connection element (110), a second connection element (120) and a third connection element (130); wherein a first resistance element (151) having a first width (b1) is arranged between the first (110) and the second connection element (120) and; wherein a second resistance element (152) having a second width (b2) is arranged between the first (110) and the third connection element (130).

Description

[0001] The present invention relates to a resistor arrangement for measuring a battery current of a high-voltage system and to a corresponding measuring arrangement.

[0002] With the ongoing shift toward electromobility, the precise measurement of electrical currents in electric vehicles (EVs) is playing a key role. Safety-critical systems such as battery management systems, in particular, rely on reliable current measurement to efficiently and safely control the energy flow both during driving and charging.

[0003] To measure these currents, resistor arrays consisting of low-ohm measuring resistors and suitable connection structures are typically used. These conventional resistor arrays typically consist of two separate connection elements for current input and output, and a resistance element arranged between them that is electrically and mechanically welded to the connection elements. Current measurement is performed using the four-wire principle via separate measuring terminals.

[0004] A key problem with conventional applications is their lack of flexibility. In vehicles with multiple battery packs, multiple resistor arrays are often required, which are usually permanently connected to the respective battery packs. In particular, when multiple battery packs are connected in series, the resistor arrays are connected in series and thus carry the same current. This leads to increased measurement losses due to the increased line resistance. As soon as the wiring of the battery packs in the high-voltage system changes, the existing sensor infrastructure requires significant adaptation effort or even complete re-arrangements. This leads to increased costs, complex system integration, and reduced ease of maintenance.

[0005] The present invention aims to overcome these disadvantages by reducing the effort for current measurement in high-voltage systems and at the same time achieving greater flexibility towards changing system topologies.

[0006] This object is achieved by the subject matter of the independent claims. Advantageous embodiments of the present invention are the subject matter of the dependent claims.

[0007] The invention relates to the general technical teaching of further developing the known resistor arrangement described above such that electrical currents of different system states can be flexibly detected using a single component. For this purpose, several resistance elements are provided, each of which carries different electrical currents and measures them separately. This makes it possible to precisely monitor multiple current paths within a system using only one component arrangement.

[0008] In particular, the present invention comprises a resistor arrangement for measuring a battery current of a high-voltage system. The resistor arrangement comprises a first connection element, a second connection element, and a third connection element. A first resistor element with a first width is arranged between the first and second connection elements. A second resistor element with a second width is arranged between the first and third connection elements. Advantageously, the first width and the second width can be different.

[0009] High-voltage systems within the meaning of this application are electrical systems with nominal voltages above 30 V alternating voltage (AC) up to and including 1000 V AC or above 60 V direct voltage (DC) up to and including 1500 V DC. They are to be distinguished from low voltages, which range up to and including 30 V AC or 60 V DC, as well as from very low voltages, which are typically below 12 V DC. In electric vehicles, high-voltage systems are used primarily to supply energy to the electric drive train and other power components.

[0010] According to an advantageous development of the present invention, the resistor arrangement is designed to measure a first current via a main measuring path formed between the first and second connection element and to measure a second current via a secondary measuring path formed between the first and third connection element.

[0011] According to an advantageous development of the present invention, the first width is greater than the second width and advantageously the second resistance element has a greater resistance value than the first resistance element.

[0012] For example, the second width of the second resistance element is twice the first width of the first resistance element. For example, the first width is 0.036 m and the second width is 0.018 m.

[0013] According to a further advantageous development of the present invention, the first, second and third connecting elements are each plate-shaped.

[0014] According to a further advantageous development of the present invention, the first, the second and the third connection element comprise a first material and the first and the second resistance element comprise a second material different from the first material.

[0015] According to a further advantageous development of the present invention, the first connection element is arranged on one side of the first and second resistance elements and the second connection element and the third connection element are each arranged on the other side of the first and second resistance elements.

[0016] According to a further advantageous development of the present invention, at least one pair of first measuring contacts for detecting the voltage drop across the first resistance element is arranged between the first connection element and the second connection element. Advantageously, at least one pair of second measuring contacts for detecting the voltage drop across the second resistance element is arranged between the first connection element and the third connection element. Advantageously, the at least one pair of first measuring contacts and the at least one pair of second measuring contacts are arranged directly at the edges of the respective resistance element.

[0017] The present invention also comprises a measuring arrangement for measuring a battery current of a high-voltage system. The measuring arrangement comprises a first battery unit, a second battery unit, a resistor arrangement according to the invention, and a switching device. The switching device is arranged between the first and second battery units and the resistor arrangement and is designed to switch back and forth between a series connection of the first and second battery units and a parallel connection of the first and second battery units. Advantageously, the resistor arrangement is connected to the switching device via the third connection element and is connected to the second battery unit via the second connection element.

[0018] According to a further development of the invention, the measuring arrangement is designed such that when the first and second battery units are connected in series, the resistance arrangement measures the voltage drop across the first resistance element.

[0019] According to a further development of the invention, the measuring arrangement is designed such that when the first and second battery units are connected in parallel, the resistance arrangement measures the voltage drop across both the first resistance element and the second resistance element.

[0020] For a better understanding of the present invention, it will be explained in more detail with reference to the exemplary embodiments illustrated in the following figures. Identical parts are provided with the same reference numerals and component designations. Furthermore, some features or combinations of features from the various embodiments shown and described may represent independent, inventive, or inventive solutions. They show: Fig. 1 shows a plan view of an example of the resistor arrangement according to the invention from a first side; Fig. 2 shows a plan view of a second side of the exemplary resistor arrangement according to the invention; Fig. 3 shows a plan view of the second side of another example of a resistor arrangement according to the invention; Fig. 4 shows an example of a manufacturing step of the resistor arrangement according to the invention; Fig. 5 shows an example of a circuit diagram for a measuring arrangement according to the invention; Fig. 6 shows another example of a circuit diagram for a measuring arrangement according to the invention.

[0021] A schematic representation of the resistor arrangement according to the invention according to a first example is shown in Fig. 1 and is explained in more detail below.

[0022] Fig. Figure 1 shows the resistor assembly 100 according to the invention from a first side and in particular from above. The resistor assembly 100 for measuring a battery current of a high-voltage system has three separate connection elements 110, 120, 130. The connection elements 110, 120, 130 can each be made of copper and / or a copper alloy. For contacting the connection elements 110, 120, 130, they each have contact holes 111, 122, 133.

[0023] A printed circuit board 116 is arranged between the first connection element 110, the second connection element 120, and the third connection element 130. In particular, this printed circuit board can be soldered, welded, or otherwise connected to the sensor. The printed circuit board 116 contains, in particular on the first side, an evaluation unit 115 by means of which the current measurement and, more specifically, the evaluation takes place. The printed circuit board 116 can be rigid or flexible and, in particular, contains a connector for contacting or an evaluation unit by means of which the current measurement and evaluation take place.

[0024] Further advantageous details of the resistor arrangement 100 are shown in Fig. 2 can be seen. Fig. Figure 2 shows the resistor arrangement according to the invention according to the first example from a second side—the underside. The resistor arrangement 100 comprises two separate and insulated resistor elements 151, 152. The first resistor element 151 is arranged between the first connection element 110 and the second connection element 120, and the second resistor element 152 is arranged between the first connection element 110 and the third connection element 130. The two resistor elements 151, 152 are electrically and mechanically connected to the corresponding connection elements. The three connection elements and the two resistor elements are advantageously each plate-shaped. For example, the mechanical connection between the resistor elements and the connection elements can be established by welding or soldering.

[0025] The first and second resistance elements 151, 152 are low-ohm resistors, preferably comprising a copper-manganese-nickel compound. The connection elements and the resistance elements are therefore made of different materials and have different specific electrical resistances.

[0026] As in Fig. As can be seen in Figure 2, the first and second resistance elements 151, 152 are advantageously arranged in a line. The first - common - connection element 110 is arranged on one side of the first and second resistance elements 151, 152, and the second and third connection elements 120, 130 are arranged on the other - the opposite - side of the first and second resistance elements 151, 152.

[0027] During operation, an electric current flows through each of the resistance elements along a current path. Either one of the resistance elements 151, 152 or both can carry a current. When the first and second connection elements 110, 120 are connected, the first resistance element 151 carries current, and when the first 110 and third connection elements 130 are connected, the second resistance element 152 carries current. The corresponding current paths are shown, for example, in Fig. 2 marked with an arrow each.

[0028] The actual current measurement is performed by measuring the electrical voltage drop across the individual resistance elements. The voltage drop is determined by measuring terminals that are electrically and mechanically connected to the individual connection elements. From this, the electrical current flowing through the resistance element can be calculated according to Ohm's law. The so-called four-wire technique offers a measurement method for precisely determining the voltage drop across the resistors.

[0029] Further details on the use of the resistor arrangement according to the invention in a high-voltage system and details on current measurement are described below.

[0030] The first resistance element 151 has a first width b1, and the second resistance element has a second width b2. For example, the first and second widths are different. The figures show an example in which the first width b1 is greater than the second width b2. However, it is also possible for the reverse to be true, with the second width b2 being greater than the first width b1.

[0031] The resistance value of the resistance elements 151, 152 varies depending on the dimensions of the resistance elements. For identical materials, length, and thickness of the elements, a greater width of a resistance element leads to a lower resistance value. In the example shown, the first resistance element therefore has a lower resistance value than the second resistance element. This has the additional manufacturing advantage of the combination shunt that the entire sensor arrangement can be punched from a continuous tri-band (connection element, resistor, connection element) if the alloys are identical. This makes the production of a combination shunt significantly more efficient than two individual sensors. At the same time, the invention does not rule out the possibility of different alloys being welded separately, e.g. manually, to the corresponding contact elements.

[0032] Example values ​​are a first width b1 of 0.036 m and a second width b2 of 0.018 m, with a corresponding resistance value of the first resistance element 151 of 25 µΩ and a resistance value of the second resistance element 152 of 50 µΩ. However, it is clear that other dimensions of the resistance elements and corresponding resistance values ​​are also possible. For example, it is also possible to vary the thickness and / or length of the resistance elements.

[0033] The width of the resistance element in this case is - as in Fig. 2 - the dimension of the resistance element perpendicular to the direction of current flow. The length of the resistance element refers to the dimension of the resistance element along the direction of current flow.

[0034] The resistor arrangement according to the invention is particularly suitable for measuring a battery current of a high-voltage system, such as an electric vehicle. The current path formed between the first and second connection elements 110, 120 represents a main measurement path. The large width b1 of the first resistance element 151 advantageously results in a low overall resistance along this path, which reduces the voltage drop across the first resistance element and thus leads to lower power loss and heat generation.

[0035] The main measurement path is used primarily and is preferably optimized in such a way that it can permanently carry more current due to the larger area of ​​the first resistance element, without the measurement being distorted by effects such as temperature influences.

[0036] The second, parallel current path, which is formed between the first 110 and third connection element 130, represents a secondary measuring path. This is also used for current measurement if required, but lower technical requirements can be placed on it. This allows the secondary current path to be designed with smaller geometric dimensions and thus more space-saving. This is also evident in the figures shown. Further details on the application and measurement using the resistor arrangement according to the invention are described below with reference to the Fig. 5 and Fig. 6 described.

[0037] Additionally, it is of course possible for the arrangement to include additional current measurement paths. For example, the resistor arrangement can have additional connection elements and additional resistance elements. This can create a plurality of main current measurement paths and / or secondary current measurement paths, which are also intended for measuring the battery current.

[0038] The resistor arrangement according to the invention enables both current measurements—the primary measurement path and the secondary measurement path—to be implemented in a single component. By integrating the first and second resistance elements into one component, costs and space requirements can be significantly reduced.

[0039] Current measurement using the resistor array is performed by measuring the voltage drop across the two resistance elements. Measuring contacts are provided for this purpose. Fig. 2 shows an example arrangement of the measuring contacts and Fig. 3 shows another exemplary arrangement.

[0040] A pair of first measuring contacts 161a, 161b for detecting the voltage drop across the first resistance element 151 is arranged between the first connection element 110 and the second connection element 120, in particular on the first resistance element 151. A pair of second measuring contacts 162a, 162b for detecting the voltage drop across the second resistance element 152 is arranged between the first connection element 110 and the third connection element 130, in particular on the second resistance element 152. The measuring contacts are preferably arranged directly at the edges of the resistance elements 15, 152 and thus at the boundary between the connection element and the resistance element. This prevents the voltage measurement from being distorted by the electrical voltage drop within the connection elements.

[0041] In Fig. 2, the pair of first 161a, 161b and second 162a, 162b measuring contacts is arranged centrally on the corresponding resistance element 151, 152. As a result, the measuring contacts are arranged on the main current path between the connection elements. For example, the two measuring contacts of a pair are arranged symmetrically to each other. Fig. Figure 3 shows another example of the arrangement of the measuring contacts outside the main current path. A pair of third measuring contacts 163a, 163b is arranged offset from one another along the width of the first resistance element 151. Similarly, a pair of fourth measuring contacts 164a, 164b is arranged offset from one another along the width of the second resistance element 152. The measuring contacts can be arranged across the entire width of the resistance element. Fig. 3, for example, one measuring contact 163a, 164a is arranged at one end of the width and on one side of the corresponding resistance element and the second measuring contact 163b, 164b is arranged at the opposite end of the width and on the opposite side of the resistance element.

[0042] A combination of the two alternatives shown is particularly advantageous. In this case, at least one pair of measuring contacts per resistance element is arranged in the main current path, and at least one pair of measuring contacts per resistance element is additionally arranged outside the main current path. This reduces measurement inaccuracies due to shadow effects and reduces the susceptibility to errors due to temperature changes.

[0043] Furthermore, the first and second resistance materials 151, 152 advantageously comprise a temperature-stable material with a low temperature coefficient. An air gap 150 is provided between the first resistance element 151 and the second resistance element 152. This air gap insulates the two elements from each other.

[0044] The pairs of measuring contacts 161a, 161b - 164a, 164b are each arranged on the second side - the underside - of the circuit board 116 and are connected to the evaluation unit 115 via the circuit board 116. The voltage drop across the two resistance elements 151, 152 can be measured via the measuring contacts. From this, the current flowing through the respective resistance element 151, 152 can be determined using Ohm's law, based on the known resistance values ​​of the resistance elements 151, 152.

[0045] Depending on the circuit board layout, the current measurement can be performed within a pair of measuring contacts 161a and 161b. The same applies to measuring contacts 162a, 163a, 164a and 162b, 163b, and 164b. However, the current measurement can also be performed between individual measuring contacts of two different pairs. For example, the measurement can be performed between measuring contacts 161b and 162b. In principle, a current measurement can be performed between any measuring contact via the circuit board and depends solely on the circuit board layout.

[0046] The manufacture of the resistor arrangement according to the invention for measuring a battery current of a high-voltage system is described below with reference to Fig. 4 described.

[0047] First, two connecting strips 191, 192 and one resistance strip 190 are provided. The two connecting strips 191, 192 are made of the same electrically conductive material, for example, aluminum, copper, or a similarly conductive aluminum or copper compound. The resistance material comprises, for example, a copper-manganese-nickel compound. In the resistor arrangement according to the invention, the connecting strips and the resistance strip are therefore made of different materials, which preferably have different specific electrical resistances. The resistance strip 190 is arranged between the two connecting strips 191, 192 in such a way that one edge of the resistance strip 190 abuts one edge of one connecting strip 191, and the opposite edge of the resistance strip abuts one edge of the second connecting strip 192.

[0048] Then, the resistance strip 190 is positively connected to the two connecting strips 191, 192. The edges of the resistance strip 190 are mechanically connected to the corresponding edges of the connecting strips 191, 192 by a joining process such as soldering, welding, or other means.

[0049] The resistor assembly 100 is then cut or punched out of the composite of resistor strips and terminal strips. This is Fig. 4 is indicated by the dashed lines. Finally, the remaining components of the resistor assembly are provided. The desired position of the measuring contacts 161a - 164a, 161b - 164b can be achieved by designing the circuit board layout. The resistor material is contacted depending on the position of the measuring taps on the circuit board. Additionally, the contact holes 111, 122, and 133 are created.

[0050] The resistance material 190 forms the first and second resistance elements 151, 152, which are separated from each other by the air gap 150. The first connection strip 191 forms the first connection element 110, and the second connection strip 192 forms the second and third connection elements 120, 130.

[0051] It is clear that the steps just described can also be carried out in a slightly modified form.

[0052] The described manufacturing process represents a very efficient production concept. Since the composite of resistor strips 190 and connecting strips 191, 192 is manufactured first, a resistor arrangement with differently sized connecting elements can then be flexibly manufactured. Depending on the application requirements, the width of the two resistor elements, and thus also of the connecting elements, can be cut out accordingly without having to modify the entire manufacturing process. Furthermore, the production and application of the resistor elements is simplified because both can be made from the same material and the resistance value can be flexibly adjusted via the variable width of the resistor element.

[0053] The described manufacturing method has the advantage that the entire resistor assembly can be cut from a continuous strip with three sections (connection element, resistance element, connection element). This represents a particularly efficient manufacturing process. Within the scope of the present invention, it is also possible for the resistance elements and the connection elements to be made of different alloys and cut out individually, then joined together, for example, by welding, in a subsequent step.

[0054] A measuring arrangement as part of which the resistor arrangement according to the invention can function and be used is shown by way of example in Fig. 5 shown.

[0055] The measuring arrangement 140 is preferably used for measuring battery currents in high-voltage systems, such as an electrically powered vehicle. The measuring arrangement according to the invention, and in particular the resistor arrangement according to the invention, allows the battery current to be measured both during battery discharging and during battery charging.

[0056] During driving (discharging) mode, the current flows from the high-voltage battery via the power electronics to the motors and other consumers. During this phase, the resistor arrangement enables continuous and accurate current measurement, which is essential for range estimation, power management, and safety.

[0057] During charging, however, the charger feeds a current in the opposite direction into the battery. Here, too, the resistor arrangement ensures precise control of the charging currents through current measurement, which is particularly important with regard to cell balancing, thermal management, and protection against overcurrents.

[0058] Using the same resistor arrangement, the current of high-voltage batteries can be reliably measured, and the measurement can be adapted to the battery wiring.

[0059] The measuring arrangement 140 comprises a first battery unit 181, a second battery unit 182, a switching device 170, and the resistor arrangement 100. The measuring arrangement 140 also has two connection nodes 101, 102. For example, the positive input voltage HV+ is applied to the first connection node 101, and the negative input voltage HV- is applied to the second connection node 102. The first connection node 101 is connected to the switching device 170 and the first battery unit 181, and the second connection node 102 is connected to the first connection element 110 of the resistor arrangement 100.

[0060] The resistor arrangement 100 is connected to the switching device 170 via the third connection element 130 and is connected to the second battery unit 182 via the second connection element 120. The switching device 170 is arranged between the first 181 and second battery units 182, the resistor arrangement 100, and the first connection node 101. The switching device 170 enables switching back and forth between a series connection and a parallel connection of the first and second battery units 181, 182.

[0061] An exemplary embodiment of the switching device 170 in the form of three switching elements 171, 172, 173 is shown in Fig. 5. A first switching element 171 is arranged between the first and second battery units 181, 182 via a third connection node 103 and a fourth connection node 104. A second switching element 172 is arranged between the first battery unit 181 and the third connection element 130 via the third connection node 103, and the third switching element is arranged between the second battery unit 182 and the first connection node 101 via the fourth connection node.

[0062] However, the switching device 170 can also be configured differently and, in particular, have a different number of switching elements. For example, only one switching element can be provided, which also allows switching back and forth between a series connection and a parallel connection of the battery units.

[0063] In the first state, for example, a discharging operation, the first and second battery units 181, 182 are connected in series via the first switching element 171. The first switching element 171 is closed and establishes a conductive path between the first and second battery units 181, 182, and the second switching element 172 and third switching element 173 are open. In this state, the current is measured by means of the resistor arrangement 100 via the second connection element 120 and the first connection element 110. Both battery units supply the same current, so only one current measurement is necessary. Thus, only the main measuring path via the connection element 110 and the second connection element 110, 120 needs to be operated for current measurement, while the secondary measuring path arranged in parallel via the third and the first connection element 130, 110 is not used for current measurement.

[0064] For example, a voltage of 400 V is applied to each of the two battery units 181, 182, and thus a voltage of 800 V is applied between the second and first connection elements 120, 110. Accordingly, the components of the main measurement path of the resistor arrangement 100 are dimensioned to withstand this high voltage. In particular, the first resistor element 151 has a large area (large width), which allows the main measurement path to permanently carry more current without the measurement being distorted by effects such as temperature influences. As a result, the first resistor element 151 has a low resistance value, for example in the range of less than 30 µΩ, preferably 25 µΩ. The low overall resistance reduces the voltage drop across the first resistor element and thus leads to lower power loss and heat generation.

[0065] In the second state, for example a charging operation, the first and second battery units 181, 182 are connected in parallel via the switching device 170. In the Fig. In the example shown in Figure 6, the first switching element 171 is opened and placed in a non-conductive state, while the second and third switching elements 172, 173 are closed and become conductive. When the two battery units 181, 182 are connected in parallel, the currents flowing therein must be measured separately.

[0066] The current of the second battery unit 182 is measured via the main measurement path via the second and first connection elements 120, 110. The secondary measurement path is now also used to measure the current of the first battery unit 181 via the third and first connection elements 130, 110. With two 400 V battery units, a voltage of 400 V is present in each measurement path.

[0067] Due to the special design of the resistor arrangement 100 and in particular due to the division into main and secondary measuring paths, the resistor arrangement can be manufactured more compactly and cost-effectively and still enables the current measurement of differently connected battery units in one measuring arrangement. List of reference symbols: 100 resistor arrangement 101 first connection node 102 second connection node 103 Third connection node 104 Fourth connection node 110 first connecting element 111 Contact hole 115 Evaluation unit 116 circuit board 120 second connecting element 122 contact hole 130 third connection element 133 contact hole 140 measuring arrangement 150 air gap 151 first resistance element 152 second resistance element 161a, 161b first measuring contacts 162a, 162b second measuring contacts 163a, 163b third measuring contacts 164a, 164b fourth measuring contacts 170 switching device 171 first switching element 172 second switching element 173 third switching element 181 first battery unit 182 second battery unit 190 resistance strips 191 first connecting strip 192 second connecting strip b1 first width b2 second width

Claims

[1] A resistor arrangement (100) for measuring a battery current of a high-voltage system, the resistor arrangement comprising: a first connection element (110), a second connection element (120) and a third connection element (130); wherein a first resistance element (151) having a first width (b1) is arranged between the first (110) and the second connection element (120) and; wherein a second resistance element (152) having a second width (b2) is arranged between the first (110) and the third connection element (130). [2] Resistor arrangement (100) according to claim 1, wherein the first width (b1) and the second width (b2) are different. [3] Resistor arrangement (100) according to one of the preceding claims, wherein the resistor arrangement (100) is designed to measure a first current via a main measuring path formed between the first and second connection element and to measure a second current via a secondary measuring path formed between the first and third connection element. [4] Resistor arrangement (100) according to one of the preceding claims, wherein the first width (b1) is greater than the second width (b2). [5] Resistor arrangement (100) according to one of the preceding claims, wherein the second resistance element (152) has a greater resistance value than the first resistance element (151). [6] Resistor arrangement (100) according to one of the preceding claims, wherein the first width (b1) is 0.036 m and the second width (b2) is 0.018 m. [7] Resistor arrangement according to one of the preceding claims, wherein the first (110), the second (120) and the third connection element (130) are each plate-shaped. [8] Resistor arrangement (100) according to one of the preceding claims, wherein the first (110), the second (120) and the third terminal element (130) comprise a first material and wherein the first (151) and the second resistance element (152) comprise a second material different from the first material. [9] Resistor arrangement (100) according to one of the preceding claims, wherein the first terminal element (110) is arranged on one side of the first (151) and second resistance elements (152) and the second terminal element (120) and the third terminal element (130) are each arranged on the other side of the first (151) and second resistance elements (152). [10] Resistor arrangement (100) according to one of the preceding claims, wherein at least one pair of first measuring contacts (161a, 161b) for detecting the voltage drop across the first resistance element (151) is arranged between the first connection element (110) and the second connection element (120); and wherein at least one pair of second measuring contacts (162a, 162b) for detecting the voltage drop across the second resistance element (152) is arranged between the first connection element (110) and the third connection element (130). [11] Resistor arrangement according to claim 10, wherein the at least one pair of first measuring contacts (161a, 161b) is arranged directly at the edges of the first resistance element (151) and the at least one pair of second measuring contacts (162a, 162b) is arranged directly at the edges of the second resistance element (152). [12] A measuring arrangement (140) for measuring a battery current of a high-voltage system comprising: a first battery unit (181) and a second battery unit (182), a resistor arrangement (100) according to one of claims 1-11, a switching device (170) which is arranged between the first (181) and second battery units (182) and the resistor arrangement (100) and is designed to switch back and forth between a series connection of the first and second battery units (181, 182) and a parallel connection of the first and second battery units (181, 182); wherein the resistor arrangement is connected to the switching device (170) via the third connection element (130) and is connected to the second battery unit (182) via the second connection element (120). [13] Measuring arrangement (140) according to claim 12, wherein the measuring arrangement (140) is designed such that when the first (181) and second battery unit (182) are connected in series, the resistance arrangement measures the voltage drop across the first resistance element (151). [14] Measuring arrangement (140) according to one of claims 12 or 13, wherein the measuring arrangement (140) is designed such that when the first (181) and second battery unit (182) are connected in parallel, the resistance arrangement measures the voltage drop across both the first resistance element (151) and the second resistance element (152).

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