DE102020214725B3 - Motor vehicle with a high-voltage battery - Google Patents

Abstract

The invention relates to a motor vehicle (2) with a high-voltage battery (12) with a power connection (18), which has two battery strings (52) which are connected by means of a switching unit (58) with a number of switches (60) in such a way that, depending on the setting the switch (60) the battery strings (52) are electrically connected in parallel or in series between the power connection (18). The invention also relates to a high-voltage battery (12) of a motor vehicle (2).

Description

The invention relates to a motor vehicle with a high-voltage battery. The high-voltage battery has two battery strings.

Motor vehicles, such as passenger cars, have a main drive for propulsion, with the main drive increasingly including an electric motor. In this case, for example, only one or more electric motors are used to propel the motor vehicle, so that the motor vehicle is designed as an electric vehicle. In an alternative to this, the motor vehicle also includes an internal combustion engine.

A high-voltage battery is usually used to power the electric motor. The high-voltage battery itself has several battery modules that are mostly identical in construction to one another. Each of the battery modules in turn has a number of individual battery cells, some of which are electrically connected in series and some of which are electrically connected in parallel. Thus, each of the battery modules provides an electrical DC voltage that is a single or multiple of one of the battery cells.

A charging station is usually used to charge the high-voltage battery. By means of this, an electrical direct voltage is usually provided, usually 400 V. So that a charging time is comparatively short even with a comparatively large capacity of the high-voltage battery, it is necessary for a comparatively large electrical current to be fed from the charging station into the motor vehicle. As a result, it is necessary to match the individual components of the motor vehicle to the comparatively large electrical current, in particular to increase a line cross section so that electrical losses are not excessive. This increases the weight of the motor vehicle as well as the manufacturing costs. As an alternative to this, it is possible to increase the electrical voltage provided by the charging station and thus to shorten the charging time. In this case, however, it is necessary to adapt the individual components of the motor vehicle, in particular its vehicle electrical system, to the increased electrical voltage, which also leads to increased production costs.

In DE 10 2017 218 067 A1 a storage system for providing electrical power for a drive system of a vehicle is described. The storage system includes a first and a second storage module for storing electrical energy. The storage system also includes a switching unit that is set up to connect the first storage module and the second storage module in series for a charging process and to connect them in parallel for driving the vehicle.

The invention is based on the object of specifying a particularly suitable motor vehicle with a high-voltage battery, in which case manufacturing costs are advantageously reduced and/or the charging time is reduced.

With regard to the motor vehicle, this object is achieved by the features of claim 1 according to the invention. Advantageous developments and refinements are the subject of the respective dependent claims.

The motor vehicle is preferably land-based and preferably has a number of wheels, of which at least one, preferably several or all, are driven by a main drive. For example, the prime mover is fully electric, and the motor vehicle is an electric vehicle, for example. In an alternative, the drive also has an internal combustion engine, so that the motor vehicle is designed as a hybrid motor vehicle. Suitably one, preferably several, of the wheels is designed to be steerable. It is thus possible to move the motor vehicle independently of a specific roadway, for example rails or the like. It is expediently possible to position the motor vehicle essentially anywhere on a roadway that is made of asphalt, tar or concrete in particular. The motor vehicle is, for example, a commercial vehicle, such as a truck (truck) or a bus. However, the motor vehicle is particularly preferably a passenger car.

The motor vehicle includes a high-voltage battery, which is an electrical energy store. The high-voltage battery includes a power connection that is used to electrically connect the high-voltage battery to other components of the motor vehicle. The power connection is provided and set up for this purpose. In particular, the power connection has two individual poles, with a specific electrical DC voltage being present between them during operation. In particular, electrical energy is fed into the high-voltage battery and electrical energy is delivered in each case via the power connection.

The high-voltage battery also includes two battery strings. Each of the battery strings includes, for example, one or more battery cells and is formed from them, for example. Each battery string particularly preferably comprises one or more battery modules, each of which has a plurality of battery cells include. In this case, the battery cells of each battery module are connected electrically in series and/or in parallel, so that a specific electrical DC voltage is provided by means of each battery module. For example, the battery modules are structurally identical to one another, which reduces manufacturing costs. The battery modules of the battery strings are expediently connected electrically in series, so that each battery string provides a multiple of the electrical voltage that is provided by each of the battery modules. Alternatively or in combination with this, at least some of the battery modules of each battery string are electrically connected in parallel. In particular, each of the battery strings is formed by means of the corresponding battery modules. The two battery strings are preferably structurally identical to one another.

The high-voltage battery also includes a circuit unit which includes a plurality of switches. In this case, the interconnection unit is used for interconnecting the battery strings and for making electrical contact between the battery strings and the power connection. The arrangement of the switches is such that, depending on the setting of the switches, the battery strings are connected electrically in parallel or electrically in series between the power connection. In other words, it is possible to switch the battery strings electrically in parallel or electrically in series by actuating the interconnection unit, in particular by means of one, several or all switches of the interconnection unit. As a result, the electrical voltage applied to the power connection, in particular electrical direct voltage, is equal to the electrical voltage that is provided by one of the battery strings, or twice this, in particular if the two battery strings are structurally identical to one another. In summary, the electrical voltage present at the power connection is dependent on the setting/actuation of the switching unit, and it is possible to set the electrical voltage provided by the high-voltage battery or at least the electrical voltage present at the power connection. In particular, the electrical voltage present at the power connection is either 400 V or 800 V, depending on the setting of the interconnection unit.

In particular, each of the battery strings has two connections, in each case one of the connections of the battery strings is electrically contacted with a possible pole of the power connection via one of the switches of the interconnection unit. The remaining connections are electrically connected to one another by means of a further switch of the interconnection unit. In addition, these connections are each electrically contacted via a further switch of the interconnection unit with the respective other pole of the power connection. The series connection or parallel connection can thus be implemented by means of the switches.

Because of the interconnection unit, it is thus possible to use the high-voltage battery to emit a comparatively low electrical DC voltage, in which case the capacity of the high-voltage battery is increased. With the other setting of the interconnection unit, on the other hand, the electrical voltage present at the power connection is increased, whereas the capacitance is reduced. It is thus possible, for example, to briefly release a comparatively large amount of energy by means of the high-voltage battery, with the electrical current being released not being excessively increased. As a result, an increased line cross section is not required, so that manufacturing costs of the motor vehicle and weight of the motor vehicle are not increased. In summary, it is possible to briefly cover an increased energy requirement of the motor vehicle using the high-voltage battery without the motor vehicle having to be excessively modified.

It is also possible, for example, to charge the motor vehicle with a comparatively high electrical voltage, namely when the two battery strings are electrically connected in series. It is thus possible to shorten the charging time of the high-voltage battery. When the motor vehicle is in operation, on the other hand, the switches are actuated in such a way, for example, that the battery strings are electrically connected in parallel.

In summary, it is possible, when the motor vehicle is in operation, to operate the high-voltage battery with an electrical voltage that differs from the electrical voltage that is used to charge the high-voltage battery. It is thus possible to optimize each of these processes independently of one another. Furthermore, it is possible to use the high-voltage battery in different motor vehicle types that are operated with different electrical voltages. In this case, it is only necessary to adapt the interconnection unit. Consequently, it is possible to use identical parts, which reduces manufacturing costs. It is thus possible, in particular, to vary the voltage level at the power connection by means of the interconnection unit.

For example, the switches and therefore the switching unit are operated manually, this being done, for example, during manufacture of the high-voltage battery or in a workshop. However, the switches are particularly preferably electrically actuated, in particular as a function of externally provided signals, in particular an electrical voltage applied to the switch. This means that the high-voltage battery can be adapted to current requirements improved. The switches are, for example, mechanical switches, for example relays. However, the switches are particularly preferably semiconductor switches, expediently power semiconductor switches, such as field effect transistors, in particular MOSFETs, IGBTs or GTOs. The formation of arcs is thus avoided.

For example, the high-voltage battery has exactly two battery strings. Alternatively, the high-voltage battery includes a plurality of battery strings of this type, with the interconnection unit being adapted to the number of battery strings. In this case it is possible, in particular, to connect all battery strings electrically in parallel or electrically in series by means of the connection unit. However, it is at least possible to connect some of the battery strings electrically in series and some of the battery strings electrically in parallel. Flexibility is thus further increased. For example, the number of battery strings is equal to three, four, five, six or more. Suitably the number of battery strings is a multiple of two.

The high-voltage battery is suitably a component of a high-voltage battery system that also includes a connection unit. The connection unit is expediently in electrical contact with the power connection, and the high-voltage battery system is preferably designed as a common structural unit. A number of connections are preferably provided by means of the connection unit, so that connection to the motor vehicle is simplified. The connection unit preferably includes one or more protective devices, such as circuit breakers or fuses. As a result, security is increased. The connection unit preferably includes a connection for pre-charging certain components of the motor vehicle. In this case, a maximum electrical power output via the connection is limited, so that an overload of the high-voltage battery and the specific components is avoided.

The motor vehicle preferably includes a charging connection. In particular, the charging connection is introduced into a body of the motor vehicle and closed, for example, by means of a pivotable cover. The charging connection is used to connect to an external charging infrastructure and is suitable for this purpose, in particular provided and set up. For this purpose, the charging connection has, for example, a number of contacts, expediently at least two. In this case, one of the possible poles of the high-voltage battery is assigned in particular to each of the contacts. The charging connection is in electrical contact with the high-voltage battery, so that an electrical current flow between the charging connection and the high-voltage battery is at least partially possible. For example, the charging connection is in direct contact with the high-voltage battery or via any connection unit. During operation, only an electrical DC voltage is expediently present at the charging connection. The charging connection is suitable for this, in particular provided and set up. For example, the charging connection is designed in the manner of a plug or has a cable. The charging connector expediently meets a specific standard, for example type 1 or 2. In particular, the charging connector has a lock so that a cable can be connected to the charging connector, with the locking preventing unwanted detachment. Because of the charging connection, it is thus possible to charge the high-voltage battery from outside the motor vehicle.

In particular, the motor vehicle includes a control unit which is, for example, a component of the high-voltage battery or is separate therefrom. The switching unit is set and thus actuated by means of the control unit. The control unit is suitable for this, in particular provided and set up. The control unit is, for example, an application specific integrated circuit (ASIC) or includes this. As an alternative to this, the control unit comprises a microprocessor, for example. The control unit sets the interconnection unit as a function of an electrical voltage present at the charging connection. The control unit is thus operated accordingly. In other words, the control unit carries out a method in which the interconnection unit is set as a function of the electrical voltage present at the charging connection. In particular, only an electrical DC voltage can be applied to the charging connection. The switching unit is thus set by means of the control unit as a function of the level of the electrical voltage present at the charging connection, ie in particular the value of the electrical direct voltage.

The battery strings are expediently connected in parallel to one another by means of the connection unit if the electrical voltage present at the charging connection is below a limit value or equal to a specific value. In particular, the parallel connection takes place when an electrical voltage of between 350 V and 450 V and for example of essentially 400 V is present at the charging connection. On the other hand, the interconnection unit is set in such a way that the battery strings are electrically connected in series if the electrical voltage present at the charging connection is greater than the limit value or equal to another value. Preferably, the electrical series connection occurs when the charger is connected Finally, an electrical voltage between 750 V and 850 V and, for example, essentially 800 V is present. Due to the different wiring, the high-voltage battery can be charged with different electrical voltages, with manual adjustment or switching not being necessary. In this case, the charging time of the high-voltage battery is shortened when there is an increased electrical voltage present.

Preferably, when the motor vehicle is in operation, ie in all states except when charging the high-voltage battery, the battery strings are electrically connected in parallel by means of the interconnection unit, so that the reduced electrical voltage is present at the power connection. As a result, the motor vehicle only carries the reduced electrical voltage during operation, so that the individual components of the motor vehicle can be configured cost-effectively. In addition, it is possible to provide any common-mode interference suppression capacitances/capacitors only for the lower electrical voltage, which is why production costs are further reduced.

The motor vehicle expediently includes the main drive, which is used to propel the motor vehicle. The main drive itself comprises at least one electric motor, which is preferably designed to be brushless. The motor vehicle is therefore designed to be at least partially electrified and is, for example, an electric vehicle or a hybrid vehicle. For example, each of the wheels of the motor vehicle is assigned an electric motor, or, for example, two wheels of the motor vehicle are each driven by an electric motor. As an alternative to this, the motor vehicle comprises only a single electric motor for propulsion. In particular, a converter is assigned to the/each electric motor, by means of which the respective electric motor is operated. The electric motor is electrically connected to the high-voltage battery by means of a first high-voltage vehicle electrical system, also referred to as a high-voltage network. The first high-voltage vehicle electrical system suitably carries an electrical voltage of essentially 400V. In particular, any converter is connected between the electric motor and the first high-voltage vehicle electrical system, or at least the high-voltage battery. Consequently, the converter is fed by the high-voltage battery, by means of which the electric motor is supplied with current. In particular, the connection unit is present here, which at least partially forms the first high-voltage vehicle electrical system.

The first high-voltage electrical system preferably includes a switch so that an electrical connection between the electric motor and the high-voltage battery can be interrupted. For example, the switch is or at least includes a semiconductor switch. The switch is suitably designed as a contactor and/or is a component of any connection unit. Due to the design as a contactor, it is possible to electrically isolate the electric motor/main drive from the high-voltage battery, so that if the wiring of the battery strings is changed, a reaction to the main drive can be avoided. In particular, the contactor is actuated when the interconnection unit has a specific switching state, ie when the battery strings are electrically connected in parallel or electrically in series, for example. The contactor is preferably actuated when the switching unit is actuated. In summary, it is possible to adapt the main drive to just one of the voltage levels of the high-voltage battery and to operate it with it. This voltage level is expediently the electrical voltage that is present when the two battery strings are electrically connected in parallel, ie the lower electrical DC voltage is present. It is thus possible to manufacture the main drive comparatively inexpensively. Due to the separation, ie the actuation of the contactor, a reaction to the main drive is avoided, so that further safety measures are not required for the main drive/electric motor and these forgotten ones can therefore be manufactured inexpensively.

In particular, the contactor is actuated when the high-voltage battery is being charged, for example always, or only when the battery strings are electrically connected in series. If the high-voltage battery is charged, it is not necessary or possible to move the motor vehicle. As a result, an electrical disconnection of the electric motor from the high-voltage battery is possible without a loss of comfort for a user of the motor vehicle. It is also possible to use an operating point for charging the high-voltage battery that deviates from the operating point of the operation of the main drive, so that these two processes can be designed to be comparatively efficient.

The motor vehicle expediently has a first ancillary unit that is operated using the high-voltage battery. The motor vehicle includes a second high-voltage electrical system, the first ancillary unit being in electrical contact with the high-voltage battery by means of the second high-voltage electrical system. Thus, even when the contactor, if any, is actuated, operation of the first ancillary unit is possible. The second high-voltage vehicle electrical system includes a direct voltage converter (DC/DC converter), which is arranged between the high-voltage battery and the first auxiliary unit. As a result, operation of the first ancillary unit is always possible, regardless of the setting of the interconnection unit, using the DC voltage converter, in particular the different levels of the electrical DC voltage present at the current output are compensated. In other words, the first ancillary unit can be operated independently of the setting of the interconnection unit. Consequently, in particular, operation of the first ancillary unit is also possible when the high-voltage battery is charged with the increased electrical direct voltage. Consequently, comfort for a user is increased. In addition, because of the DC-DC converter, it is possible to use an auxiliary unit as the first auxiliary unit that can only be operated with a specific electrical voltage, so that it can be manufactured comparatively inexpensively. It is also possible to operate the first ancillary unit at the one preferred operating point/working point, with this being set by means of the DC-DC converter.

Appropriately, the DC-DC converter - from the point of view of the high-voltage battery - is operated as a step-down converter. Thus, the electrical voltage carried in the second high-voltage vehicle electrical system is preferably at most the electrical voltage present at the current output. In particular, by means of the second high-voltage vehicle electrical system, at least electrically after the DC voltage converter, an electrical voltage of essentially 400V is conducted, or at least the same as with the possible first high-voltage vehicle electrical system. Appropriately, it is also possible to operate the DC-DC converter—from the point of view of the first ancillary unit—as a step-up converter, so that electrical energy can be fed back from the second high-voltage vehicle electrical system. In this case, the motor vehicle preferably includes an AC connection which is connected to the second high-voltage vehicle electrical system, in particular via a rectifier. Consequently, it is also possible to charge the motor vehicle using alternating current. The rectified voltage fed via the AC connection is preferably increased by means of the DC voltage converter, so that the high-voltage battery can be charged efficiently.

For example, the DC-DC converter operates only when the battery strings are electrically connected in series. If the battery strings are electrically connected in parallel, the DC-DC converter is not operated, so that the same electrical voltage is present at the first ancillary unit as is also present at the power connection. Consequently, electrical losses are reduced. As an alternative to this, the DC voltage converter is always operated, so that it stabilizes the electrical DC voltage carried in the second high-voltage vehicle electrical system. As a result, this is not required to be done by the first accessory, and manufacturing costs are reduced. For example, the first ancillary unit is a water heater, an air conditioning compressor, or an air heater. For example, such a heater is used to heat a window pane. The motor vehicle preferably includes a plurality of such first ancillary units which are each electrically connected in parallel with one another and are therefore each electrically connected to the high-voltage battery via the DC voltage converter.

For example, the DC voltage converter is designed to be galvanically non-isolating. As a result, it is possible to use a comparatively inexpensive DC/DC converter. In particular, the DC-DC converter is designed as a buck converter, for example as a buck converter. Particularly preferably, however, the DC-DC converter is designed to be galvanically isolating and, for example, comprises a switched-mode power supply or at least includes this. Because of the galvanic isolation, safety is increased, and it is not necessary to provide galvanic isolation for the first ancillary unit, which is why it can be manufactured comparatively inexpensively.

In particular, the motor vehicle includes a second ancillary unit that is connected to a low-voltage vehicle electrical system. During operation, the low-voltage vehicle electrical system carries an electrical direct voltage which is in particular less than 100 V and, for example, equal to 12 V, 24 V or 48 V. For example, the low-voltage electrical system is powered by a separate battery. However, the low-voltage vehicle electrical system is particularly preferably fed by the high-voltage battery, so that no further components are required in the motor vehicle, which is why no additional weight or additional installation space is required. The low-voltage vehicle electrical system includes a second DC voltage converter, ie a DC/DC converter, which is preferably designed to be electrically isolating. In this case, the electrical DC voltage provided by the high-voltage battery is lowered to the electrical DC voltage of the low-voltage vehicle electrical system by means of the second DC voltage converter. For example, the second DC voltage converter is fed directly by means of the high-voltage battery, in particular by means of any connection unit. However, the second DC-DC converter is particularly preferably fed with the possible second high-voltage vehicle electrical system, so that the second DC-DC converter can be arranged separately from the high-voltage battery. Consequently, flexibility and a modular structure are made possible. The second ancillary unit is, for example, an electric adjustment drive, such as an electric seat adjustment or a multimedia system. Preferably, this includes power vehicle several such second ancillaries.

The high-voltage battery is part of a motor vehicle and includes a power connection and at least two battery strings. Each battery string expediently comprises a number of battery modules, each of which has a number of battery cells. The individual battery modules are each preferably electrically connected in series to the respective battery strings. The battery strings are connected between the power connection by means of a switching unit, so that the power connection is fed by the two battery strings. Consequently, it is possible to feed electrical energy into the high-voltage battery via the power connection and thus into the battery strings and vice versa. The battery strings are connected between the power connection by means of the interconnection unit, the interconnection unit having a plurality of switches. Depending on the setting of the switches, the battery strings are electrically connected in parallel between the power connection or electrically in series. Consequently, the electrical DC voltage present at the power connection, ie the level, is dependent on the setting of the interconnection unit.

The invention also relates to a high-voltage battery system that includes a corresponding high-voltage battery. Furthermore, the high-voltage battery system includes a connection unit, by means of which one or more connections for a high-voltage vehicle electrical system and/or a low-voltage vehicle electrical system are provided. In particular, a connection to a charging connection is also provided by means of the connection unit. The connection unit makes electrical contact with the high-voltage battery, namely the power connection, preferably directly. The connection unit is suitably attached to the high-voltage battery so that it is present as a common structural unit.

If a component is referred to as the first, second, ... component, this is to be understood in particular as merely referring to a specific component. In particular, this does not mean that a specific number of such components is present. In particular, this does not imply that the first high-voltage vehicle electrical system is present if the second high-voltage vehicle electrical system is present.

The developments and advantages explained in connection with the motor vehicle can also be transferred to the high-voltage battery/the high-voltage battery system and to each other and vice versa.

• 1 schematisch vereinfacht ein Kraftfahrzeug mit einer Hochvoltbatterie, und
• 2 ein Blockschaltbild des Kraftfahrzeugs.

An exemplary embodiment of the invention is explained in more detail below with reference to a drawing. Show in it:

• 1 schematically simplified a motor vehicle with a high-voltage battery, and
• 2 a block diagram of the motor vehicle.

Corresponding parts are provided with the same reference symbols in all figures.

In 1 a motor vehicle 2 in the form of a passenger car is shown in a schematically simplified manner. Motor vehicle 2 designed as an electric vehicle has four wheels 4 which are driven by a main drive 6 . The main drive 6 comprises two sub-units 8, with each of the sub-units 8 driving two of the wheels 4 in each case. The sub-units 8 are each powered by a high-voltage battery system that includes a high-voltage battery 12 . The motor vehicle 2 also has a charging connection 14 which is in electrical contact with the high-voltage battery system 10 and the high-voltage battery 12 and which is installed in a body 16 of the motor vehicle 2 . It is possible here to feed electrical energy into the high-voltage battery 12 from outside the motor vehicle 2 by means of the charging connection 14 .

In 2 the motor vehicle 2 is shown schematically simplified as a block diagram in excerpts. The high-voltage battery system 10 has the high-voltage battery 12 which includes a power connection 18 . A connection unit 20 of the high-voltage battery system 10 is connected to the power connection 18 , by means of which a first high-voltage vehicle electrical system 22 is partially formed. The main drive 6 and thus the two subunits 8 , which each have an electric motor 24 and a converter 26 , are supplied with current by means of the first high-voltage vehicle electrical system 22 . The electric motors 24 are designed to be brushless and are operated by means of the respective associated converter 26 , which in turn is in turn fed by means of the first high-voltage vehicle electrical system 22 . The first high-voltage vehicle electrical system 22 includes two contactors 28, by means of which it is possible to electrically isolate the two sub-units 8 from the power connection 18. In summary, the electric motors 24 are in electrical contact with the high-voltage battery 12 by means of the first high-voltage vehicle electrical system 22 , the first high-voltage vehicle electrical system 22 having the two contactors 28 which are part of the connection unit 20 .

Furthermore, a DC voltage converter 30 of a second high-voltage vehicle electrical system 32 is electrically connected to the power connection 18 by means of the connection unit 20 , so that the DC voltage converter 30 can be fed by means of the high-voltage battery 12 . The DC-DC converter 30 is designed to be galvanically isolating and includes a switched-mode power supply that is not shown in detail. The voltage converter 30 is followed by a rectifier 34 switches, which is electrically contacted with an AC connection 36, which is part of the charging connection 14 or a component separate therefrom. The DC-DC converter 30 and the rectifier 34 are in this case implemented as a common structural unit. In a variant that is not shown, the DC-DC converter 30 and the rectifier 34 are two separate components.

Two first ancillary units 38 are electrically connected to the second high-voltage vehicle electrical system 32 and are therefore also electrically connected to the high-voltage battery 12 and consequently fed by means of the latter. One of the first ancillaries 38 is an electric air conditioning compressor and the other is a water heater. Furthermore, a second DC-DC converter 40 is connected by means of the second high-voltage vehicle electrical system 32 and is fed via the second high-voltage vehicle electrical system 32 by means of the high-voltage battery 12 . A low-voltage vehicle electrical system 42 is fed with the 2 second DC-DC converter 40, with which a second ancillary unit 44 and other second ancillary units (not shown) are operated. Such a second ancillary unit 44 is, for example, an electric seat adjustment. In summary, the second ancillary unit 44 is connected to the second DC voltage converter 40 by means of the low-voltage vehicle electrical system 42 , which in turn is fed by means of the high-voltage battery 12 .

Furthermore, the charging connection 14 is in electrical contact with the power connection 18 via the connection unit 20, with a fuse 46 and two circuit breakers 48 being arranged between them. Furthermore, the connection unit 20 includes a connection 50 which is also in electrical contact with the power connection 18 . The connection 50 serves to pre-charge certain components of the motor vehicle 2, and a maximum of electrical energy conducted via the connection 50 is limited.

The high-voltage battery 12 itself comprises two battery strings 52 which are structurally identical to one another and which have a plurality of battery modules 54, four of which are shown here. An electrical DC voltage of 400 V is applied to each of the battery strings 52 . The battery modules 54 of each battery string 52 are electrically connected in series and each have the same construction as one another. Each of the battery modules 54 includes a plurality of battery cells 56 which are electrically connected in parallel and electrically in series with the respective battery module 54 .

In addition, the high-voltage battery 12 includes a switching unit 58, which includes a plurality of switches 60, five of which are shown here. Using the switch 60, it is possible to connect the two battery strings 52 electrically in parallel or electrically in series between the power connection 18, in particular between the two poles of the power connection 18. For this purpose, each of the battery strings 52 also has two poles, between which one during operation electrical voltage is present, namely 400 V. By means of some of the switches 60, each of the poles of each battery string 52 is routed to one of the poles of the power connection 18, so that when these switches 60 are actuated, i.e. conductive, the two battery strings 52 are parallel to one another are switched. Consequently, volts are also present at the power connection 18 in this case.

Furthermore, two of the poles of the battery strings 52 make direct electrical contact with one another via one of the switches 60 of the interconnection unit 58 , and the remaining poles of the two battery strings 52 each make contact with one of the poles of the power connection 60 using one of the switches 60 . When these switches 60 are actuated, the two battery strings 52 are connected in series between the power connection 18, so that 800 V is present at this connection.

The switches 60 are in the form of semiconductor switches, such as MOSFETs, and are actuated by a control unit 62 so that the switching unit 58 is actuated by the control units 62 . In this case, the switches 60 and/or the switching unit 58 are set by means of the control unit 62 as a function of an electrical voltage present at the charging connection 14 . If no electrical voltage is present at the charging connection 14, the motor vehicle 2 is not being charged via the charging connection 14, and the switches 60 are actuated in such a way that the two battery strings 52 are electrically connected in parallel. Thus, an electrical DC voltage of 400 V is present at the power connection 18, by means of which the main drive 6 can be operated. The contactors 58 are closed by means of the control unit 62. The second high-voltage vehicle electrical system 32 is also supplied via the DC voltage converter 30 and the low-voltage vehicle electrical system 42 via the second DC voltage converter 40, so that operation of the first ancillary units 38 and the second ancillary units 44 is possible. In this case, the electrical direct voltage of 400 V is also carried in the second high-voltage network 32 and an electrical direct voltage of 48 V is carried in the low-voltage vehicle electrical system 42 .

If the motor vehicle 14 is being charged, the control unit 62 checks how high the electrical voltage present at the charging connection 14 is. If this is also 400 V, the switching state of the switches 60 is not changed, so that the battery strings 52 are charged in each case. Here it is possible Actuate contactors 28 so that the main drive 6 cannot be energized and any current peaks do not lead to damage to the respective sub-units 8 . Because of the galvanic isolation provided by the DC/DC converter 30, such voltage spikes do not cause damage or unsafety to the first 38 and second 44 accessories. If the current spikes are excessive, the circuit breaker 48 or fuse 46 is actuated to prevent damage.

If, on the other hand, an increased voltage of 800 V is present at the charging connection 14, the switches 60 are actuated by means of the control unit 62 in such a way that the two battery strings 52 are electrically connected in series, so that an electrical voltage of essentially 800 V is also applied to the power connection 18 applied. Furthermore, the two contactors 28 are actuated so that the electrical voltage of 800 V is not applied to the main drive 6 and consequently the main drive 6 does not have to be adapted to the possibility of an electrical voltage of 800 V. It is therefore not necessary to dimension the subunits 8, such as the electric motor 24 and/or a converter 26m, accordingly, which is why comparatively inexpensive components can be used. The two circuit breakers 48 are then closed, so that electrical energy is fed into the battery strings 52 . Due to the increased electrical voltage, the charging time is comparatively short. Meanwhile, the DC voltage converter 30 is operated in such a way that the electric DC voltage of 800 V, by means of which it is supplied, is reduced to 400 V. The second high-voltage vehicle electrical system 32 thus continues to carry essentially 400 V, at least electrically after the DC voltage converter 30. Consequently, undisturbed operation of the first ancillary units 38 and the second DC voltage converter 40 is also possible, without it being necessary to adapt them to the increased electrical DC voltage at the Adjust power connector 18. Due to the galvanic isolation, safety is also provided here. In summary, it is possible for a user to use the first ancillary units 38 and the second ancillary units 44 when the motor vehicle 2 is being charged. On the other hand, it is not possible to use the main drive 6, although this is not necessary during loading either.

If AC charging is to take place, the rectifier 34 is fed via the AC connection 36, and the electrical voltage provided in this way is increased to a desired value, namely 400 V, by means of the DC voltage converter 30, so that feeding into the battery strings 52 via the Power connection 18 is possible.

The invention is not limited to the embodiment described above. On the contrary, other variants of the invention can also be derived from this by a person skilled in the art without departing from the subject matter of the invention. In particular, all of the individual features described in connection with the exemplary embodiment can also be combined with one another in other ways without departing from the subject matter of the invention.

Reference List

2

motor vehicle

4

wheel

6

main drive

8th

subunit

10

high-voltage battery system

12

high-voltage battery

14

charging port

16

body

18

power connection

20

connection unit

22

first high-voltage electrical system

24

electric motor

26

converter

28

contactor

30

DC converter

32

second high-voltage electrical system

34

rectifier

36

AC connection

38

first ancillary unit

40

second DC converter

42

low-voltage electrical system

44

second auxiliary unit

46

fuse

48

circuit breaker

50

connection

52

battery string

54

battery module

56

battery cell

58

interconnection unit

60

Switch

62

control unit

Claims (5)

Motor vehicle (2) with a high-voltage battery (12) with a power connection (18), which has two battery strings (52) which are interconnected by means of a switching unit (58) with a number of switches (60) in such a way that, depending on the setting of the switch (60 ) the battery strings (52) are electrically connected in parallel or in series between the power connection (18), and with a first ancillary unit (38), which is electrically connected to the high-voltage battery (12) by means of a second high-voltage vehicle electrical system (32), the second High-voltage electrical system (32) comprises a DC-DC converter (30) which is arranged between the high-voltage battery (12) and the first auxiliary unit (38). Motor vehicle (2) after claim 1 , characterized by a charging connection (14), which is electrically connected to the high-voltage battery (12), and a control unit (62), wherein the switching unit (58) by means of the control unit (62) as a function of an electrical current present at the charging connection (14). voltage is set. Motor vehicle (2) after claim 1 or 2 , characterized by a main drive (6) which has an electric motor (24) which is in electrical contact with the high-voltage battery (12) by means of a first high-voltage vehicle electrical system (22), the first high-voltage vehicle electrical system (22) having a contactor (28). Motor vehicle (2) according to one of Claims 1 until 3 , characterized in that the DC voltage converter (30) is designed to be galvanically isolating. Motor vehicle (2) according to one of Claims 1 until 4 , characterized by a second auxiliary unit (44) which is connected by means of a low-voltage vehicle electrical system (42) to a second DC-DC converter (40) which is fed by means of the high-voltage battery (12).

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