Traction battery for a motor vehicle's powertrain, a powertrain, and a motor vehicle

Abstract

The invention relates to a traction battery for a powertrain of a motor vehicle for providing a total battery voltage, comprising at least the following components: - a first battery string to provide an initial DC voltage; - a second battery string to provide a second DC voltage; - a first switch which is arranged such that, in a closed state of the first switch, the first battery string and the second battery string are connected in series to provide the total battery voltage, and - a second switch, which is arranged such that, in the closed state of the second switch, the first battery string or the second battery string is individually connected to provide the total battery voltage and / or the first battery string and the second battery string are connected in parallel to provide the total battery voltage. The traction battery is characterized in particular by the fact that the first switch and the second switch have different current-carrying capacities. By reducing the current-carrying capacity of the switches and adjusting the overall battery voltage to the specific operating range, a cost-effective and highly efficient powertrain can be implemented.

Description

[0001] The invention relates to a traction battery for a drive train of a motor vehicle, a drive train with such a traction battery for a motor vehicle, and a motor vehicle with such a drive train.

[0002] In battery-electric vehicles or hybrid vehicles, traction batteries are used to provide direct current. This direct current is converted into alternating current by an inverter to drive an electric drive motor. The voltage requirement of an electric drive motor depends primarily on the speed of the electric drive motor and, to a lesser extent, on the torque of the electric drive motor. At low speeds, a low alternating current voltage at the electric drive motor is sufficient, and thus also a lower direct current voltage provided by the traction battery. The switching losses in a pulse-controlled inverter are linearly dependent on the voltage. Thus, the power loss in the pulse-controlled inverter decreases linearly with the applied direct current.

[0003] It is also known from industrial practice to provide two separately switchable battery strings, each providing a DC voltage and connectable in parallel or series using switches to provide a higher or lower total battery voltage. This allows the total battery voltage of the traction battery to be adjusted depending on the operating range of the electric drive motor, thus reducing power losses in the pulse-controlled inverter. However, the switches used to switch the battery strings also cause power losses.

[0004] EP 3 514 916 A1 discloses a battery system comprising a plurality of battery modules; a plurality of switches configured to switch a connection state of the plurality of battery modules between a series state and a parallel state; and an electronic control unit configured to control the switching of the plurality of switches; and to set ON-OFF states of the plurality of switches such that the connection state of the plurality of battery modules is the series state or the parallel state when a deterioration parameter indicating a degree of deterioration of a predetermined battery module among the plurality of battery modules reaches a threshold value, wherein the ON-OFF state represents a state in which a switch is open or closed.

[0005] US 2021 / 0 078 442 A1 discloses a battery system comprising first and second battery packs connected to positive and negative DC voltage rails, a contactor switch connected between the battery packs, a semiconductor switch connected in series with the contactor switch, and a controller. A control action includes opening the semiconductor switch to thereby interrupt the current flow between the first and second battery packs.

[0006] Based on this, the present invention is based on the object of at least partially overcoming the disadvantages known from the prior art. The features of the invention are derived from the independent claims, for which advantageous embodiments are presented in the dependent claims. The features of the claims can be combined in any technically reasonable manner, whereby the explanations from the following description as well as features from the figures, which comprise additional embodiments of the invention, can also be consulted for this purpose.

[0007] The invention relates to a traction battery for a drive train of a motor vehicle for providing a total battery voltage, comprising at least the following components: - a first battery string for providing a first DC voltage; - a second battery string for providing a second DC voltage; - a first switch which is arranged such that, in a closed state of the first switch, the first battery string and the second battery string are connected in series to provide the total battery voltage, and - a second switch which is arranged such that, in a closed state of the second switch, the first battery string or the second battery string are individually connected to provide the total battery voltage and / or the first battery string and the second battery string are connected in parallel to provide the total battery voltage.

[0008] The traction battery is mainly characterized by the fact that the first switch and the second switch have different current carrying capacities.

[0009] In the following, reference is made to the specified axis of rotation whenever, without explicit indication to the contrary, the axial direction, radial direction, or the direction of rotation and corresponding terms are used. Ordinal numbers used in the preceding and following descriptions serve only to clearly distinguish them and do not reflect the order or ranking of the designated components. An ordinal number greater than one does not necessarily imply that another such component must be present.

[0010] Here, a traction battery for a motor vehicle is proposed, which comprises at least two battery strings. Preferably, the traction battery is a battery for a purely battery-electric motor vehicle. Alternatively, the traction battery is a battery for a hybrid motor vehicle, which comprises an electric drive motor and an internal combustion engine.

[0011] The traction battery can provide a total battery voltage as a direct current. The traction battery can be connected to a pulse-width inverter (PWR), which converts the total battery voltage into an alternating current for the vehicle's electric drive motor.

[0012] For example, the traction battery is a lithium-ion battery.

[0013] The first battery string is configured to provide a first DC voltage.

[0014] The second battery string is designed to provide a second DC voltage.

[0015] Preferably, each of the battery strings comprises a plurality of battery cells. Preferably, each of the battery strings comprises one or more battery modules, each of which comprises a plurality of battery cells.

[0016] Within a battery module, a specific number of battery cells are connected in series to achieve a desired voltage within the battery module. For example, several battery cells are connected in parallel within a battery module to achieve a desired capacity.

[0017] For example, several battery modules within a battery string are connected in series in a certain number to achieve a desired DC voltage of the battery string. Several battery modules within a battery string are connected in parallel, for example, to achieve a desired battery module capacity.

[0018] If the first switch is closed, the first battery string and second battery string are connected in series. Accordingly, due to the series connection, the first DC voltage of the first battery string and the second DC voltage of the second battery string add up to a total battery voltage. For example, the first switch electrically connects or disconnects the first battery string and the second battery string. In this case, a connection point of the traction battery to the pulse-controlled inverter is arranged on the side of the first battery string or the second battery string facing away from the first switch. The first switch is therefore electrically arranged between the first battery string and the second battery string.

[0019] If the second switch is closed, the first battery string and second battery string are connected in parallel, or only one of the two battery strings is connected to the electric drive motor or pulse-controlled inverter in a closed circuit to provide the total battery voltage. The first battery string and second battery string thus provide a common terminal voltage as the total battery voltage, which is calculated according to Kirchhoff's law. Preferably, the first battery string and second battery string are designed to provide the same DC voltage. The first DC voltage therefore corresponds to the second DC voltage.For example, the second switch electrically connects or disconnects the first battery string or the second battery string from the electric drive motor or the remaining electrical circuit supplying the electric drive motor. For example, the second switch is arranged in a conductor track of the first battery string or the second battery string.

[0020] Thus, the traction battery can be switched between a first operating state, in which the first switch is closed, and a second operating state, in which the second switch is closed. Preferably, only the first switch is closed in the first operating state, meaning that other switches provided for connecting the battery strings, such as the second switch, are open. In the first operating state, the first battery string and the second battery string are connected in series. Thus, as already explained, the total battery voltage is the sum of the first DC voltage and the second DC voltage.

[0021] In the second operating state, preferably only one of the two battery strings, for example only the first battery string, is connected to the electric drive motor in a closed circuit. This means that the other battery string, in the example given, the second battery string, does not contribute to the power or total battery voltage of the traction battery. Preferably, in the second operating state, only the second switch is closed, i.e., other switches provided for connecting the battery strings, such as the first switch, are open.

[0022] The first switch and the second switch now have different current carrying capacities. The second switch has a lower current carrying capacity than the first switch.

[0023] The traction battery preferably comprises a control device designed to close the first switch when the electric drive motor is in a first operating range or is to be shifted into the first operating range. Furthermore, such a control device is designed to close the second switch, for example, when the electric drive motor is in a second operating range or is to be shifted into the second operating range. Thus, if the electric drive motor is operated in a first operating range, the traction battery is preferably in the first operating state, and if the electric drive motor is operated in the second operating range, the traction battery is in the second operating state.

[0024] Preferably, the first operating range is an operating range with a higher speed than the second operating range. Alternatively or additionally, the first operating range is an operating range with a greater torque than the second operating range. Thus, the electric drive motor requires more power from the traction battery in the first operating range than in the second operating range. Accordingly, the load due to the current flow on the first switch in the first operating range or in the first operating state differs from the load in the second operating range or the second operating state.

[0025] Due to the different current-carrying capacities of the first switch and the second switch, the switches are designed for the respective operating range or operating state. The switch preferably has a lower resistance than the first switch. This allows for lower resistance losses and switching losses for low speed and / or torque ranges of the electric drive motor. Alternatively, or additionally, the switch can be designed more cost-effectively.

[0026] It is further proposed in an advantageous embodiment of the traction battery that the traction battery further comprises a third switch, wherein the second switch and the third switch are arranged such that in a closed state of at least one of the two switches, the battery strings are connected in parallel to provide the total battery voltage of the traction battery and / or only one of the battery strings is closed to provide a total battery voltage of the traction battery.

[0027] According to the embodiment proposed here, the traction battery has a third switch.

[0028] The third switch and the second switch are arranged such that, when at least one of the two switches is closed, the battery strings are connected in parallel, or only one of the two battery strings is connected in a closed circuit with the electric drive motor. Thus, either the DC voltage of one battery string or the combined voltage of the two parallel-connected battery strings, resulting from Kirchhoff's law, is provided as the total battery voltage of the traction battery.

[0029] Preferably, the traction battery or the control device of the traction battery is configured such that only one of the three switches is closed at any one time.

[0030] Preferably, in such an embodiment, when the first switch is closed, a series connection of the two battery strings is implemented; when the second switch is closed, only one of the two battery strings, for example the first battery string, is connected to provide the total battery voltage; and when the third switch is closed, only the other of the two battery strings, for example the second battery string, is connected to provide the total battery voltage. Alternatively, the traction battery or the control device is designed to operate the second switch and the third switch simultaneously in a closed state. In such an embodiment, for example, the two battery strings can be connected in parallel if the third switch and the second switch are closed at the same time.Furthermore, in such an embodiment, the first battery string or the second battery string can be switched on separately if only the second switch or the third switch is closed.

[0031] Preferably, in the second operating state, either the second switch is closed or, equivalently, the third switch is closed. Preferably, in such an embodiment, both battery strings are designed to provide the same DC voltage. Preferably, the control device is designed to switch the second switch and the third switch such that the two battery strings are discharged evenly.

[0032] For example, the second switch is arranged in a conductor track of the first battery string so that the first battery string can be switched on or off, and the third switch is arranged in a conductor track of the second battery string so that the second battery string can be switched on or off.

[0033] It is further proposed in an advantageous embodiment of the traction battery that the third switch has a lower current carrying capacity than the first switch, particularly preferably the same current carrying capacity as the second switch.

[0034] As already explained, the second switch is closed in a second operating state, in which a lower power is delivered from the traction battery to the electric drive motor, or conversely, from the electric drive motor to the traction battery, than in the first operating state. Therefore, a lower current flows in the second operating state, and the current-carrying capacity of the second switch can be designed to be lower than that of the first switch, which is closed in the first operating state.

[0035] For the same reasons, the current-carrying capacity of the third switch is preferably lower than that of the first switch. Particularly preferably, the current-carrying capacity of the second switch is equal to the current-carrying capacity of the third switch. Preferably, the second switch and the third switch are of identical construction.

[0036] It is further proposed in an advantageous embodiment of the traction battery that only the first battery string can be switched on by means of the second switch to provide the total battery voltage, and wherein only the second battery string can be switched on by means of the third switch to provide the total battery voltage.

[0037] According to this embodiment, in the second operating state of the traction battery, either only the first battery string or only the second battery string is connected. "Connected" in this case means that the respective battery string is in a closed circuit with the pulse-controlled inverter or the electric drive motor. For this purpose, as already explained, either only the first switch or the second switch is closed. Thus, the total battery voltage is formed solely by the DC voltage of the first battery string or the DC voltage of the second battery string.

[0038] It is further proposed in an advantageous embodiment of the traction battery that a ratio of the current carrying capacity of the first switch to the current carrying capacity of the second switch is proportional to the ratio between a defined first battery power and a second battery power, preferably proportional to the ratio of the battery powers, wherein the first battery power characterizes a first operating range of the traction battery in which the first switch is closed, preferably represents the maximum total battery power in the event that the first switch is closed, wherein the second battery power characterizes a second operating range of the traction battery in which the second switch is closed, preferably represents the maximum total battery power in the event that the second switch is closed.

[0039] According to this embodiment, a ratio is defined between the current-carrying capacity of the first switch and the second switch. This ratio corresponds to a ratio between a first battery power and a second battery power.

[0040] The first battery power characterizes the first operating state of the traction battery, which is assigned to the first operating range of the electric drive motor, as explained above. The first operating state therefore preferably results from a first speed range and a first torque range of the electric drive motor. The first battery power is preferably the maximum total battery power permissible in this operating state of the traction battery. This characterizing first battery power therefore also determines the maximum current flowing through the switch in this first operating state. In the first operating state, the first switch is closed, so that the design of the current-carrying capacity of the first switch is based on the total battery power in the first operating state.

[0041] The second battery power accordingly characterizes the second operating state of the traction battery, which is assigned to the second operating range of the electric drive motor, as explained above. The second operating state therefore preferably results from a second speed range and a second torque range of the electric drive motor. The second battery power is preferably the maximum total battery power permissible in this operating state of the traction battery. This characterizing second battery power therefore also determines the maximum current flowing through the switch in this second operating state. In the second operating state, the second switch and / or the third switch is closed, so that the design of the current-carrying capacity of the second switch and / or the third switch is based on the total battery power in the second operating state.

[0042] It is further proposed in an advantageous embodiment of the traction battery that at least one of the switches, preferably all switches, are designed to switch under flowing current, preferably the switches are solid state relays.

[0043] According to this embodiment, the switches are designed to switch under flowing current. Preferably, the switches are MOSFET switches (metal-oxide-semiconductor-field-effect transistors).

[0044] The preferred switches are solid state relays.

[0045] It is further proposed in an advantageous embodiment of the traction battery that at least one of the switches, preferably at least the second and / or third switch, is a silicon-based semiconductor switch or a gallium nitride-based semiconductor switch.

[0046] The low currents in the second operating state of the traction battery allow the second and / or third switch to be implemented as a silicon-based semiconductor switch (Si switch) or a gallium nitride-based semiconductor switch (GaN switch). This enables a particularly cost-effective design of the traction battery.

[0047] It is further proposed in an advantageous embodiment of the traction battery that the traction battery comprises a control device for controlling the switches, wherein the switches are switched by means of the control device depending on the speed and / or torque.

[0048] As already explained, the traction battery can be switched from a first operating state to a second operating state by means of the control device by closing and opening the switches. The operating state of the traction battery depends on the operating range of the electric drive motor. The operating range of the electric drive motor is defined by its speed and torque. Power loss in the pulse-controlled inverter and the electric drive motor is essentially dependent on the speed. In one embodiment, the switches are therefore controlled solely as a function of the speed. In an alternative embodiment, the switches are also controlled as a function of the torque.

[0049] According to a further aspect, a drive train for a motor vehicle is proposed, comprising at least the following components: - a traction battery according to an embodiment as described above for providing a total battery voltage as a direct voltage; - an electric drive machine; and - a pulse inverter which connects the electric drive motor to the traction battery in order to provide an alternating voltage for the drive motor based on the total battery voltage.

[0050] According to a further aspect, a motor vehicle is proposed, wherein the motor vehicle has at least the following components: - a drive train according to an embodiment as described above for providing a drive torque; and - at least one drive wheel connected to the drive train in a torque-transmitting manner to generate propulsion.

[0051] The motor vehicle is preferably a purely battery-electric motor vehicle. Alternatively, the motor vehicle is a hybrid motor vehicle, which includes an internal combustion engine in addition to the electric drive motor.

[0052] For example, the motor vehicle comprises an electric drive motor per axle or per wheel.

[0053] For example, the motor vehicle comprises four wheels, of which two or four are preferably designed as drive wheels. For example, the motor vehicle comprises a transmission and / or a differential, by means of which the torque-transmitting connection is provided.

[0054] The invention described above is explained in detail below against the relevant technical background with reference to the accompanying drawings, which show preferred embodiments. The invention is in no way limited by the purely schematic drawings, whereby it should be noted that the drawings are not to scale and are not suitable for defining proportions. It is shown in Fig. 1: a drive train of a motor vehicle in a circuit diagram; Fig. 2: relative loss changes due to voltage halving on a pulse inverter in a diagram; Fig. 3: relative loss changes due to voltage halving on an electric drive machine in a diagram; Fig. 4: relative loss changes due to voltage halving for the drive train; and Fig. 5: Motor vehicle in a schematic plan view with a drive train according to Fig. 1.

[0055] In Fig. 1 shows a circuit diagram of a drive train 14 of a motor vehicle 2. The drive train 14 comprises a traction battery 1, which is connected to an electric drive motor 15 by means of a pulse-controlled inverter 16. The traction battery 1 is designed to provide a total battery voltage 3. For this purpose, the traction battery 1 comprises a first battery string 4 with a first direct voltage 6 and a second battery string 5 with a second direct voltage 7. The battery strings 4, 5 can be connected to or disconnected from a circuit with the pulse-controlled inverter 16 or the electric drive motor 15 by means of three switches 8, 9, 10.

[0056] The pulse-controlled inverter 16 comprises a plurality of semiconductors, for example, which convert the total battery voltage 3 of the traction battery 1 into an alternating voltage 17, so that the drive motor 15 generates a torque 23 or the traction battery 1 can be charged by a generator current generated by the electric drive motor 15. Alternatively or additionally, a generator separate from the electric drive motor 15 is provided, for example, by means of which the traction battery 1 can be charged for recuperation.

[0057] The battery strings 4, 5 here comprise a plurality of battery modules (not shown here), which can be connected to one another in parallel and / or in series, so that a predetermined DC voltage and battery capacity can be provided for each battery module.

[0058] The switches 8, 9, 10 are arranged such that when the first switch 8 is closed and the second switch 9 and third switch 10 are open, the first battery string 4 and the second battery string 5 are connected in series. In this first operating state of the traction battery 1, the first direct voltage 6 of the first battery string 4 and the second direct voltage 7 of the second battery string 5 thus add up to the total battery voltage 3, which is present at the connection points 25 on the pulse-controlled inverter 16. When the first switch 8 and second switch 9 are open and the third switch 10 is closed, only the second direct voltage 7 of the second battery string 5 is present as the total battery voltage 3 at the pulse-controlled inverter 16. If the second switch 9 is closed and the first switch 8 and the third switch 10 are open, the first direct voltage 6 of the first battery string 4 is present as the total battery voltage 3 at the pulse-controlled inverter 16.For this purpose, the first switch 8 is arranged between the battery strings 4, 5, the second switch 9 in a first conductor track 27 of the first battery string 4 and the third switch 10 in a second conductor track 28 of the second battery string 5.

[0059] Preferably, the first DC voltage 6 and the second DC voltage 7 are equal. Thus, the states in which the second switch 9 or the third switch 10 are closed form an identical, second operating state of the traction battery 1 with respect to the total battery voltage 3 present at the connection points 25. In this case, the total battery voltage 3 is therefore twice as high in the first operating state of the traction battery 1 as in the second operating state.

[0060] The switches 8, 9, 10 can be controlled by means of a control device 13 (not shown here).

[0061] The second switch 9 and third switch 10 have a lower current carrying capacity than the first switch 8. Current carrying capacity is understood to be the highest permissible current that (in this case) a switch 8, 9, 10 can continuously carry under specified conditions without a permissible steady-state temperature of the conductor exceeding a predetermined value.

[0062] The traction battery 1 is switched between the first operating state and the second operating state by means of the control device 13, depending on an operating range 11, 12 of the electric drive machine 15. In the first operating range 11 of the electric drive machine 15, in which the traction battery 1 is switched to the first operating state, the electric drive machine 15 draws greater maximum power from the traction battery 1 than in the second operating range 12, in which the traction battery 1 is switched to the second operating state. Thus, in the first operating state, greater currents flow through the first switch 8 than in the second operating state through the second switch 9 or the third switch 10. Thus, a second switch 9 or third switch 10 can be represented with a reduced current carrying capacity compared to the first switch 8.Due to the lower current carrying capacity of the second and third switches 9, 10, the drive train 14 can be designed more cost-effectively and with lower losses. Furthermore, optimization of the different operating ranges, which require different voltages at different times, can be implemented with lower losses (see . Fig. 2 to Fig. 4). By means of the total battery voltage 3 divided here into the first DC voltage 6 and the second DC voltage 7, a targeted control of the operating ranges or a reduction of the total battery voltage 3 at the power components can also be achieved.

[0063] In Fig. Figure 2 shows relative loss changes due to voltage halving at a pulse-width inverter 16. It thus shows how the power loss changes in the second operating state of the traction battery 1 compared to the first operating state when the battery strings 4, 5 are of the same design, i.e., provide the same voltage.

[0064] The ordinate shows the rotational speed 24 of the drive motor 15, and the abscissa shows the torque 23 of the drive motor 15. The relative loss change is represented by numerical values ​​on lines, which indicate the respective course of a relative loss change of a corresponding amount. Negative values ​​indicate a reduction in losses. The WLTP 26 [Worldwide Harmonized Light-Duty Vehicles Test Procedure] is located in an operating range of the electric drive motor 15, shown in dashed lines. Preferably, the second operating range 12 of the electric drive motor 15, in which the traction battery 1 is switched to the second operating state, comprises at least the WLTP range. Within this WLTP range, a loss reduction of up to 50% can be achieved by switching the traction battery 1 to the second operating state, as shown.The WLTP 26 represents a measurement method for determining exhaust emissions (pollutant and CO2 emissions) and fuel / electricity consumption of motor vehicles 2.

[0065] The course of the lines shows that, especially for high speed ranges, the power loss is essentially speed-dependent, while for low speed ranges, torque 23 becomes more influential. The control of traction battery 1 or the switching of switches 8, 9, 10 is accordingly either purely speed-dependent or also dependent on torque 23.

[0066] If the intention is to minimize power loss in the pulse-controlled inverter 16, the dividing line between the first operating range 11 and the second operating range 12 of the electric drive motor 15, i.e., the line at which the traction battery 1 is switched between the first operating state and the second operating state, runs along the line marked 0 [zero]. At this dividing line, the losses in the PWR and for the first and second operating states of the traction battery 1 are the same, i.e., independent of the total battery voltage 3.

[0067] In Fig. 3 shows relative loss changes due to voltage halving on an electric drive unit 15. The loss changes shown here refer to the electric drive unit 15 of a drive train 14 according to Fig. 1, the diagram being essentially the same as in Fig. 2, so only the differences will be explained here.

[0068] It can also be seen here that the line indicating a loss that is independent of the voltage (the line marked with 0) also runs almost vertically, but is slightly shifted toward higher speeds 24. Furthermore, especially in the range of low speeds 24, the power loss is more dependent on the torque 23.

[0069] In Fig. 4 shows relative loss changes due to voltage halving for the drive train 14. The loss changes shown here are a balance of the two previous diagrams from Fig. 2 and Fig. 3. Here again, the almost vertical boundary of the two operating ranges 11, 12 is shown by means of the loss change lines, whereby the loss change lines are dependent on the operating ranges 11, 12 and these are strongly dependent on the speed 24 of the drive motor 15. Within the WLTP 26 range, the loss changes result in a reduction in power losses of up to 30% if the voltage at the connection points 25 is halved, i.e. the second switch 9 or third switch 10 is closed instead of the first switch 8. Preferably, the dividing line between the first operating range 11 and the second operating range 12 of the electric drive motor 15, i.e. the line at which the traction battery 1 is switched between the first operating state and the second operating state, runs along the line marked 0 [zero].At this dividing line, the losses via the pulse inverter 16 and the electric drive motor 15 are the same for the first and second operating states of the traction battery 1, i.e., independent of the total battery voltage 3.

[0070] In Fig. 5 is a motor vehicle 2 in a schematic plan view with a drive train 14 according to Fig. 1. The drive train 14 comprises a traction battery 1, a drive motor 15, and a pulse-controlled inverter 16, with the traction battery 1 being connected to a control device 13. The drive motor 15 is configured to convert the total battery voltage 3 from the traction battery 1 into a torque 23. The torque 23 is transmitted to the drive wheels 18 via a transmission 21 and a differential 22.

[0071] By means of the control device 13, comprising a data memory 19 and a computing unit 20, the switches 8, 9, 10 of the traction battery 1 and the drive train 14 can be opened or closed according to the currently prevailing operating range 11, 12. Due to the halving of the total battery voltage 3 in the second operating range 12 of the traction battery 1, a reduction in the current carrying capacity in the second and third switches 9, 10 can be achieved, so that the drive train 14 can be designed more cost-effectively and, due to the loss reduction, also more efficiently.

[0072] By reducing the current carrying capacity of the switches and adjusting the total battery voltage to suit the operating range, a cost-effective and highly efficient powertrain can be implemented. List of reference symbols 1 traction battery 2 motor vehicles 3 Total battery voltage 4 first battery string 5 second battery string 6 first DC voltage 7 second DC voltage 8 first switch 9 second switch 10 third switch 11 first operating area 12 second operating area 13 Control device 14 Powertrain 15 electric drive motor 16 pulse inverters 17 alternating voltage 18 Drive wheel 19 data storage 20 computing units 21 gearboxes 22 Differential 23 torque 24 speed 25 Junction 26 WLTP range 27 first conductor track 28 second conductor track

Claims

[1] Traction battery (1) for a drive train (14) of a motor vehicle for providing a total battery voltage (3), comprising at least the following components: - a first battery string (4) for providing a first DC voltage (6); - a second battery string (5) for providing a second DC voltage (7); - a first switch (8) which is arranged such that, in a closed state of the first switch (8), the first battery string (4) and the second battery string (5) are connected in series to provide the total battery voltage (3), and - a second switch (9) which is arranged such that, in a closed state of the second switch (9), the first battery string (4) or the second battery string (5) are individually connected to provide the total battery voltage (3) and / or the first battery string (4) and the second battery string (5) are connected in parallel to provide the total battery voltage (3), characterized by that the first switch (8) and the second switch (9) have different current carrying capacities, wherein the second switch (9) has a lower current carrying capacity than the first switch (8). [2] Traction battery (1) according to claim 1, wherein the traction battery (1) further comprises a third switch (10), wherein the second switch (9) and the third switch (10) are arranged such that in a closed state of at least one of the two switches (9, 10), the battery strings (4, 5) are connected in parallel to provide the total battery voltage (3) of the traction battery (1) and / or only one of the battery strings (4, 5) is closed to provide a total battery voltage (3) of the traction battery (1). [3] Traction battery (1) according to claim 1 or claim 2, wherein the third switch (10) has a lower current carrying capacity than the first switch (8). [4] Traction battery (1) according to claim 2 or claim 3, wherein only the first battery string (4) can be switched on to provide the total battery voltage (3) by means of the second switch (9), and wherein only the second battery string (5) can be switched on to provide the total battery voltage (3) by means of the third switch (10). [5] Traction battery (1) according to one of the preceding claims, wherein a ratio of the current carrying capacity of the first switch (8) to the current carrying capacity of the second switch (9) is proportional to the ratio between a defined first battery power and a second battery power, wherein the first battery power characterizes a first operating range (11) of the traction battery (1) in which the first switch (8) is closed, wherein the second battery power characterizes a second operating range (12) of the traction battery (1) in which the second switch (9) is closed. [6] Traction battery (1) according to one of the preceding claims, wherein at least one of the switches (8, 9, 10) is designed to switch under flowing current. [7] Traction battery (1) according to one of the preceding claims, wherein at least one of the switches (8, 9, 10) is a silicon-based semiconductor switch or a gallium nitride-based semiconductor switch. [8] Traction battery (1) according to one of the preceding claims, wherein the traction battery (1) comprises a control device (13) for controlling the switches (8,9,10), wherein the switches (8,9,10) are switched in a speed-dependent and / or torque-dependent manner by means of the control device (13). [9] Drive train (14) for a motor vehicle (2), comprising at least the following components: - a traction battery (1) according to one of the preceding claims for providing a total battery voltage (3) as a direct voltage; - an electric drive machine (15); and - a pulse inverter (16) which connects the electric drive motor (15) to the traction battery (1) in order to provide an alternating voltage (17) for the drive motor (15) on the basis of the total battery voltage (3). [10] Motor vehicle (2), wherein the motor vehicle (2) comprises at least the following components: - a drive train (14) according to claim 9 for providing a drive torque; and - at least one drive wheel (18) connected to the drive train (14) in a torque-transmitting manner for generating propulsion.

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