Patent Publication Number: US-2022239148-A1

Title: Battery system for an electric vehicle with electronic energy switch

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to German patent application 102021101314.3, filed Jan. 22, 2021, the content of which is herein incorporated by reference. 
     FIELD OF THE INVENTION 
     The present invention relates to a redundant battery system for an electric vehicle having an electrical energy switch and a method for redundantly supplying an electrical auxiliary unit of an electric vehicle with electrical energy from a battery system of the electric vehicle for driving the electrical auxiliary unit. In particular, the invention relates to a high-voltage electronic contactor for such a power switch. 
     BACKGROUND OF THE INVENTION 
     From the level 3 of automated driving, traction becomes relevant to and for availability and safety. One safety concept is based on dividing the traction battery into two 400V batteries and providing two drive electric motors (front and rear) in a redundancy approach. Two problems arise in this process: 1. when using fuses for the auxiliary unit paths, in the event of a fault, repercussions can occur on the availability-relevant traction on-board network with overcurrent disconnection of the battery due to the inertia of the fuses; and 2. if the auxiliaries are supplied via one of the 400V batteries, this will lead to asymmetrical loading of the batteries. The asymmetrical discharge leads to a limitation of the redundancy concept and therefore of the vehicle range. 
     It is an object of the present invention to create an improved safety concept for automated driving, and in particular a safety concept that also satisfies levels 3 and 4 in automated driving. 
     SUMMARY OF THE INVENTION 
     The present invention is based on the idea of replacing the fuses and contactors for the auxiliary units of the electric vehicle, in particular comfort auxiliary units such as the air-conditioning compressor, with electronic HV (high-voltage) contactors based on HV mosfets or IGBTs. In the event of a fault, these then enable fast, reaction-free shutdown. 
     Furthermore, the auxiliary units are connected to both batteries (e.g., 400V batteries) with two electronic HV switches, which are wired as energy switches. This energy switch allows (while driving) an uninterrupted switching from one battery to the other. This makes it possible to actively balance the batteries by switching the load. 
     The two batteries (e.g., realized as 400V batteries) can still be connected in series to a single battery (e.g., 800V battery) for high power charging via bank switching. The possibility of high current charging (e.g., with 400V) at existing columns is inherently also given. The existing modular system of auxiliary units (e.g., 400V auxiliaries) such as steering assistance, air conditioning compressor, heating can still be used. 
     In contrast to mechanical contacts, which have a large and unpredictable dead time actuation for opening, are therefore for the safety concept required here, not suitable, as the switch-off with the electrical energy switch disclosed here can take place quasi immediately, i.e., without significant dead time. Furthermore, the large number of switching cycles is not feasible for a mechanical contactor. Wear will set in after just a short time, requiring maintenance and thus making autonomous driving inefficient. 
     In accordance with a first aspect of the invention, the problem is solved by a battery system for an electric vehicle, comprising: a first battery connectable to a first electric drive to provide the first electric drive with electric energy for driving the electric vehicle; a second, redundant battery connected to a second, redundant electric drive connectable to provide electrical power to the second electric drive for driving the electric vehicle; and an electrical power switch having a first input terminal, a second input terminal, and an output terminal, the first input terminal being electrically connected to the first battery, the second input terminal being connected to the second battery, and wherein the output terminal is electrically connectable to an electrical accessory of the electric vehicle to provide the electrical accessory with electrical power for driving the electrical accessory, the electrical power switch being configured to switch the output terminal to be electrically connected to the first input terminal or the second input terminal, as desired, to supply electrical power from the first battery or the second battery to the electrical accessory unit, as appropriate. 
     This achieves the technical advantage that the electrical energy switch during which an uninterrupted switching from one battery to the other while driving is provided. This makes it possible to actively balance the batteries by load switching. In the event of a fault, these then enable fast, reaction-free disconnection. 
     According to an exemplary embodiment of the battery system, the battery system is designed according to a redundancy corresponding to safety level C or D of the ASIL (Automotive Safety Integrity Level) standard. 
     This achieves the technical advantage that with this battery system an improved safety concept for automated driving can be ensured which also satisfies levels 3 and 4 automated driving. 
     According to an exemplary embodiment of the battery system, the electrical power switch comprises: a first pair of electronic switches connected between the first input terminal and the output terminal; and a second pair of electronic switches connected between the second input terminal and the output terminal. 
     By realizing the energy switch as an electrical energy switch, i.e. based on electronic components, such as semiconductor switches, fast, reaction-free disconnection can be ensured so that there are no repercussions on other systems in the vehicle in the event of a fault. In the conventional solution, on the other hand, protection against short circuits or overcurrent is provided by a fuse. However, this is very slow-acting and requires a high tripping current. This current can lead to a significant voltage drop of the battery and the line paths, which in turn has repercussions on other functions, some of which are safety-related. 
     According to an exemplary embodiment of the battery system, the first pair comprises an electronic switch comprising two series-connected bidirectional HV MOSFETs or IGBTs, each blocking in the opposite direction to each other; and the second pair of electronic switches comprises two series-connected bidirectional HV MOSFETs or IGBTs, each blocking in the opposite direction to each other. 
     The bidirectional design achieves the following advantages: the independence of the two memories inherits the original ASIL level; with bidirectional design, two mosfets (IGBTs) each can block and the ASIL requirement can thus be decomposed. Furthermore, equalization of currents are avoided when both branches are switched through simultaneously. 
     According to an exemplary embodiment of the battery system, a first electronic switch of the first pair of electronic switches is adapted, in response to a first switching signal, to inhibit current flow in a direction from the first battery to the auxiliary electrical unit; wherein a second electronic switch of the first pair of electronic switches is adapted, in response to a second switching signal, to inhibit current flow in a direction from the first battery to the auxiliary electrical unit. A pair of electronic switches is adapted, in response to a second switching signal, to inhibit current flow in the direction from the auxiliary electric unit to the first battery; wherein a first electronic switch of the second pair of electronic switches is adapted, in response to a third switching signal, to inhibit current flow in the direction from the second battery to the auxiliary electric unit; and wherein a second electronic switch of the second pair of electronic switches is adapted, in response to a third switching signal, to inhibit current flow in the direction from the second battery to the auxiliary electric unit. An electronic switch of the second pair of electronic switches is adapted, in response to a fourth switching signal, to block a current flow in the direction from the auxiliary electric unit to the second battery. 
     This achieves the advantage that two electronic switches each lock and each two electronic switches can pass. Thus, the ASIL requirement of levels 3 and 4 can be fulfilled. Furthermore, equalizing currents are avoided when both branches are switched through simultaneously. 
     According to an exemplary embodiment of the battery system, the electrical energy switch further comprises: a second output terminal electrically connectable to a second electrical accessory of the electric vehicle to provide the second electrical accessory with electrical energy for driving the second to supply the electrical auxiliary unit. 
     This has the advantage that two (and more auxiliary units) can be supplied with electrical energy in accordance with the safety concept presented here. 
     According to an exemplary embodiment of the battery system, the electrical power switch further comprises: another first pair of electronic switches connected between the first input terminal and the second output terminal; and another second pair of electronic switches connected between the second input terminal and the second output terminal. 
     Even when several auxiliary units are used, faulty modules are shut down quickly and without feedback. 
     According to an exemplary embodiment of the battery system, the battery system further comprises: a first high-voltage contactor connected between the first input terminal of the electrical energy switch and a drive-side terminal of the first battery, the first high-voltage contactor being configured to disconnect the first input terminal of the electrical energy switch from the drive-side terminal of the first battery in response to a first shutdown signal; and a second high-voltage contactor connected between the second input terminal of the electrical energy switch and a drive-side terminal of the second battery, the second high-voltage contactor being adapted to disconnect the second input terminal of the electrical energy switch from the drive-side terminal of the second battery in response to a second shutdown signal. 
     According to an exemplary embodiment of the battery system, the first input terminal of the electrical energy switch is connected to a first drive-side terminal, in particular a drive-side positive terminal, of the first battery and a first drive-side terminal, in particular a drive-side positive terminal, of the second battery. 
     According to an exemplary embodiment of the battery system, the output terminal of the electrical energy switch can be electrically connected via the electrical auxiliary unit to a second pole of the first battery or the second battery, in particular a negative pole on the drive side or the mains side. 
     According to an exemplary embodiment of the battery system, the battery system further comprises: a third high-voltage contactor connected between a first line-side terminal of the first battery and a charging receptacle, the third high-voltage contactor being adapted to disconnect the first line-side terminal of the first battery from the charging receptacle in response to a third disconnect signal; and a fourth high-voltage contactor connected between a second line-side terminal of the second battery and the charging receptacle, wherein the fourth high-voltage contactor is adapted to disconnect the second line-side terminal of the second battery from the charging socket in response to a fourth disconnection signal. 
     According to an exemplary embodiment of the battery system, the battery system further comprises: a fifth high-voltage contactor connected between the first line-side pole of the first battery and a first line-side terminal of the second battery, wherein the fifth high-voltage contactor is configured to disconnect the first line-side terminal of the first battery from the first line-side terminal of the second battery in response to a fifth disconnect signal. 
     According to an exemplary embodiment of the battery system, the second grid-side terminal of the first battery is electrically connected to the second grid-side terminal of the second battery. 
     According to an exemplary embodiment of the battery system, the electrical energy switch is designed to switch the electrical auxiliary unit from the first battery to the second battery without interruption. 
     According to a second aspect, the invention relates to a method for supplying an electrical auxiliary unit of an electric vehicle with electrical energy from a battery system of the electric vehicle for driving the electric auxiliary unit, the battery system comprising: a first battery connectable to a first electric drive (M 1 ) for supplying the first electric drive (M 1 ) with electric energy for driving the electric vehicle, a second, redundant battery (Bat 2 ) connectable to a second, redundant electric drive (M 2 ) to provide electrical power to the second electric drive (M 1 ) for driving the electric vehicle; and a configurable electrical power switch having a first input terminal, a second input terminal, and an output terminal, wherein the first input terminal is electrically connected to the first battery (Bat 1 ), the second input terminal is electrically connected to the second battery (Bat 2 ), and the output terminal is electrically connected to the auxiliary electric power unit of the electric vehicle to supply the auxiliary electric power unit with electric power for driving the auxiliary electric power unit, the method comprising the steps of: configuring the electrical power switch to electrically connect the output terminal to the first input terminal to supply electrical power from the first battery to the electrical accessory; and optionally reconfiguring the electrical power switch to electrically connect the output terminal to the second input terminal to supply electrical power from the second battery to the electrical accessory to supply the auxiliary unit with electrical energy from the second battery. 
     With such a method, the technical advantage is achieved that the electrical energy switch allows uninterrupted switching from one battery to the other while the vehicle is in motion. This makes it possible to achieve active balancing of the batteries through load switching to be carried out. In the event of a fault, these then enable fast, reaction-free shutdown. 
     For example, the process can run on a controller, such as a vehicle controller or a battery controller. 
     According to a third aspect of the invention, the problem is solved by a computer program comprising a program code for carrying out the method according to the second aspect, when the program code runs on a computer or processor. 
     The computer program can be implemented on a controller, e.g. a vehicle controller or a battery controller. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       Further advantageous features and details of the various embodiments of this disclosure will become apparent from the ensuing description of preferred exemplary embodiments and with the aid of the drawings. The features and combination of features recited below in the description or in the drawings alone, may be used not only in the particular combination recited but also in other combinations on their own, without departing from the scope of the disclosure. 
       In the following, advantageous examples of the invention are explained with reference to accompanying figures, wherein: 
         FIG. 1  depicts a schematic representation of a conventional HV traction on-board network in simplified form; 
         FIG. 2  depicts a schematic representation of the implementation of a safety concept in 
       autonomous driving with redundancy of the sources and the drive; 
         FIG. 3  depicts a schematic representation of the configuration according to the invention with HV energy switch; 
         FIG. 4  depicts a schematic representation of the configuration according to the invention with HV energy switch for alternate supply of a compressor via both batteries; and 
         FIG. 5  depicts a schematic representation of a method according  500  to the invention for supplying power to an electrical auxiliary unit. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As used throughout the present disclosure, unless specifically stated otherwise, the term “or” encompasses all possible combinations, except where infeasible. For example, the expression “A or B” shall mean A alone, B alone, or A and B together. If it is stated that a component includes “A, B, or C”, then, unless specifically stated otherwise or infeasible, the component may include A, or B, or C, or A and B, or A and C, or B and C, or A and B and C. Expressions such as “at least one of” do not necessarily modify an entirety of the following list and do not necessarily modify each member of the list, such that “at least one of” “A, B, and C” should be understood as including only one of A, only one of B, only one of C, or any combination of A, B, and C. 
     In the following detailed description, reference is made to the accompanying drawings, which form a part hereof and in which, by way of illustration, specific embodiments are shown in which the invention can be carried out. It is understood that other embodiments may also be used, and structural or logical changes may be made without departing from the concept of the present invention. Therefore, the following detailed description is not to be understood in a limiting sense. It is further understood that the features of the various embodiments described herein may be combined with each other, unless otherwise specifically indicated. 
     Aspects and embodiments are described with reference to the drawings, wherein like reference signs generally refer to like or related elements. In the following description, for purposes of explanation, numerous specific details are set forth to provide an in-depth understanding of one or more aspects of the invention. However, it may be apparent to one skilled in the art that one or more aspects or embodiments may be described with a lesser degree of specific details but can still be carried out. In other cases, known structures and elements are shown in schematic form to facilitate describing one or more aspects or embodiments. It is understood that other embodiments may be used and structural or logical changes may be made without departing from the concept of the present invention. 
     Fig. shows  1  a schematic diagram of a conventional HV traction on-board network  100  in simplified form. 
     A battery  110 , e.g., 400V battery, is via switch and power  111 , 112  as well as electronics  113  connectable to a drive motor  101  to drive the electric vehicle. Connections branch off from the positive terminal of the battery  110  to the auxiliary units  140  to supply electrical power from the battery  110  to the auxiliary units  140 . Further switches  114 , 124  can be used to connect  130  the battery to a DC charging socket  110  for charging. 
     This configuration is not suitable for autonomous driving because no redundancy is available. In particular, an ASIL C or D safety level on the availability of the traction is not possible, since many single point faults can potentially lead to a failure of the traction. 
     The Automotive Safety Integrity Level (ASIL) is a risk classification scheme defined in the standard ISO 26262—Functional Safety for Road Vehicles. This is an adaptation of the Safety Integrity Level (SIL) used in IEC 61508 for the automotive industry. This classification helps to define the safety requirements necessary to comply with the ISO 26262 standard. The ASIL is established through a risk analysis of a potential hazard, taking into account the severity, exposure and controllability of the vehicle operating scenario. The safety objective for this hazard in turn carries the ASIL requirements. 
     There are four ASILs identified by the standard: ASIL A, ASIL B, ASIL C, ASIL D. ASIL D prescribes the highest integrity requirements for the product and ASIL A the lowest. 
       FIG. 2  shows a schematic diagram of the implementation of a safety concept in autonomous driving with redundancy of the sources and the drive. Two drive motors  101 , 102  and two batteries  110 , 120  are provided in this on-board power supply or battery system in order to implement the safety concept with redundant sources  110 , 120  and drives  101 , 102 . 
     The first battery  110 , implemented for example as a 400V battery, is connectable to the first drive motor  101  via switches  111 ,  112  and power electronics  113  to drive the electric vehicle. Connections branch  110  from the positive terminal of the first battery to the auxiliary units  140  are provided to supply the auxiliary units  140  with electrical energy from the first battery  110 . Further switches  114 ,  124 ,  125  can be used to connect the first battery  110  to a DC charging socket  130  for charging. 
     The second battery  120 , e.g., realized as 400V battery, is provided as redundant battery. The second battery  120  is connectable to the second drive motor  102  via switches  121 ,  122  and power electronics  123  to drive the electric vehicle. The switches  124 , 125 , 114  can be used to connect the second battery  120  to the DC charging socket  130  for charging. 
     An auxiliary unit  140  can be, for example, the compressor for air conditioning the batteries. This is not relevant to safety for a short-term transition to the safe state (thermal inertia of the battery). However, for the function it would be useful to maintain the supply of this aggregate, even if a battery has to be shut down or relieved. Furthermore, in this arrangement the ancillary units  140  load a battery (asymmetrical load). For the above reasons, it is desirable to be able to switch the supply of the auxiliary units  140  between the sources, i.e. the batteries  101 , 102 . Such a solution is presented in  FIG. 3 . 
     According to the state of the art, solutions with two batteries for a redundant traction supply are known with two compressors each for the first and the second battery. The dual design of the compressor is necessary here because it is not possible to switch from one battery to the other. 
       FIG. 3  shows a schematic diagram of the configuration according to the invention with 300 HV energy switch  310 . Here, the energy switch can consist of a pair of bidirectional HV Mosfets or IGBTs. 
     The battery system  300  for an electric vehicle as shown in  FIG. 3 , comprises: a first battery  110  connectable to a first electric drive  101  to provide electrical energy to the first electric drive to power the electric vehicle; a second, redundant battery  120  connectable to a second, redundant electric drive to provide electrical energy to the second electric drive to power the electric vehicle; and a second, redundant battery  120  connectable to a second, redundant electric drive  102  to provide electrical energy to the second electric drive to provide electrical power to drive the electric vehicle; and an electrical power switch  310 . 
     An energy switch in the context of the present disclosure is a switch that can transfer energy via two different paths in a manner analogous to a mechanical switch. The energy can come from a first source or battery or from a second source or battery. The energy switch can switch the source path via which a consumer, e.g., an auxiliary unit, draws its electrical energy. An electrical energy switch can switch the paths by means of electronic switches, e.g., Mosfets or IGBTs. 
     A Mosfet is a metal-oxide-semiconductor field-effect transistor, i.e., a form of a transistor belonging to the family of insulated-gate field-effect transistors. Usually, this form is based on a layer stack consisting of a metallic gate electrode, a semiconductor, and the oxide dielectric in between. This represents a metal-insulator-semiconductor structure. 
     An insulated-gate bipolar transistor, IGBT, is a semiconductor device used in power electronics because it combines advantages of the bipolar transistor such as good forward conductivity, high reverse voltage, robustness, and advantages of a field-effect transistor such as nearly powerless driving. 
     The electrical power switch  310  includes a first input terminal  321 , a second input terminal,  322  and an output terminal  331 . The first input terminal is electrically connected  321  to the first battery  110  (via the switch  111 ). The second input terminal  322  is electrically connected to the second battery  120  (via the switch  121 ). 
     The output terminal  331  is electrically connectable to an electrical accessory  140  of the electric vehicle to provide the electrical accessory  140  with electrical energy to drive the electrical auxiliary unit  140 . 
     The electrical power switch  310  is configured to electrically connect the output terminal  331  to either the first input terminal  321  or the second input terminal  322 , as desired, to provide electrical power to the auxiliary electrical power unit  140  accordingly from the first battery  110  or the second battery  120 . 
     The battery system  300  can be designed according to a redundancy corresponding to safety level C or D of the ASIL (Automotive Safety Integrity Level) standard. 
     The electrical power switch  310  may further comprise: a first pair  311  of electronic switches connected between the first input terminal  321  and the output terminal  331 ; and a second pair  312  of electronic switches connected between the second input terminal  322  and the output terminal  331 . 
     The first pair  311  of electronic switches may comprise two series connected bidirectional HV MOSFETs or IGBTs, Q 1 , Q 2 , each blocking in the opposite direction to each other. The second pair  312  of electronic switches may comprise two series connected bidirectional HV MOSFETs or IGBTs, Q 3 , Q 4 , each blocking in the opposite direction to one another other in order to lock to each other. 
     A first electronic switch Q 1  of the first pair  311  of electronic switches may be configured, in response to a first switching signal, to inhibit current flow in a direction from the first battery  110  to the auxiliary electrical unit  140 . A second electronic switch Q 2  of the first pair  311  of electronic switches may be configured, in response to a second switching signal, to block a flow of current in a direction from the auxiliary electrical unit to  140  the first battery  110 . 
     A first electronic switch Q 3  of the second pair  312  of electronic switches may be configured, in response to a third switching signal, to inhibit current flow in a direction from the second battery  120  to the electrical accessory  140 . A second electronic switch Q 4  of the second pair  312  of electronic switches may be configured, in response to a fourth switching signal, to inhibit current flow in a direction from the second battery  120  to the electrical accessory  140 . 
     The electrical power switch  310  may further comprise: a second output terminal  332  electrically connectable to a second electrical accessory  140  of the electric vehicle, to allow the second electrical accessory  140  with electrical energy to drive the second electrical auxiliary unit  140 . A corresponding output connector may be provided for each auxiliary unit  140  to selectively connect the corresponding auxiliary unit  140  to the first or second battery. 
     Auxiliary power units in this disclosure are high voltage auxiliary power units which are powered by the traction batteries  110 ,  120  and not by simple 12V batteries. They may be a compressor for the air conditioning system, steering assist or a heater, which, for operation, requires a high voltage, such as 400 volts. 
     The electrical power switch  310  may further comprise: another first pair  313  of electronic switches connected between the first input terminal  321  and the second output terminal  332 ; and another second pair  314  of electronic switches connected between the second input terminal  322  and the second output terminal  332 . 
     The battery system  300  may further include a first high voltage contactor  111  connected between the first input terminal  321  of the electrical power switch  310  and a drive side terminal  116  of the first battery  110 . The first high voltage contactor  111  is configured to disconnect the first input terminal  321  of the electrical power switch  310  from the drive side terminal  116  of the first battery  110  in response to a first disconnect signal. 
     The battery system  300  may further include a second high voltage contactor  121  connected between the second input terminal  322  of the electrical power switch  310  and a drive side terminal  126  of the second battery  120 . The second high voltage contactor  121  is configured, in response to a second shutdown signal, to turn off the second input terminal  322  of the electrical energy switch  310  from the drive side terminal  126  of the second battery  120 . 
     The first input terminal  321  of the electrical energy switch  310  may be connected to a first drive-side pole  116 , in particular, a drive-side positive pole, the first battery  110  and a first drive-side terminal  126 , in particular a drive-side positive terminal, of the second battery  120  be electrically connected. 
     The output terminal  331  of the electrical energy switch  310  may be connected  140  to a second terminal  117 , 127  of the first battery via the auxiliary electrical unit  110  or the second battery  120 , and in particular a drive-side  117 ,  127  or mains-side negative terminal  128 , can be electrically connected. 
     The battery system  300  may further include a third high voltage contactor  114  connected between a first line side terminal  119  of the first battery  110  and a charging socket  130  wherein the third high voltage contactor  114  is configured to disconnect the first line side terminal  119  of the first battery  110  from the charging receptacle in response to a third disconnect signal. 
     The battery system  300  may further include  124  a fourth high-voltage contactor that is connected between a second line-side terminal  128  of the second battery  120  and the charging receptacle  130 , wherein the fourth high-voltage contactor  124  is configured to disconnect the second line-side terminal  128  of the second battery  120  from the charging receptacle in response to a fourth disconnect signal. 
     The battery system  300  may further comprise a fifth high voltage contactor  125  connected between the first line side terminal  119  of the first battery  110  and a first line side terminal  129  of the second battery  120 , wherein the fifth high voltage contactor  125  is configured to, in response to a fifth disconnect signal, disconnect the first mains-side terminal  119  of the first battery  110  from the first mains-side terminal  129  of the second battery  120 . 
     The shutdown signals described here can be generated by a control unit, e.g., a vehicle control unit or controller or a battery control unit or controller according to a logic. 
     The second line-side terminal  128  of the first battery  110  is electrically connected to the second line-side terminal  128  of the second battery  120 . 
     The electrical energy switch  310  can switch the auxiliary electrical unit  140  from the first battery  110  to the second battery  120  without interruption. 
       FIG. 4  shows a schematic representation of the configuration according to the invention with HV energy switch  310  for the alternate supply of a compressor  141  via both batteries  110 , 120 . 
     The configuration is the same as described  3  above for Figure. In  FIG. 4 , an exemplary auxiliary unit  140  is a compressor  141  of a refrigeration system. The input port  142  of the compressor  141  is connected in this example to the second output  332  of the electrical energy switch, and the output terminal  143  of the compressor  141  is connected  120  (via the switch  122 ) to the drive-side negative terminal  127  of the second battery. Alternatively, the output terminal  143  of the compressor  141  can also be connected (via the switch  112 ) to the drive-side negative terminal  117  of the first battery  110 , or to the line-side negative terminal  128  of the first and second battery  110 , 120 . 
       FIG. 4  shows how, as an example, a compressor  141  can be supplied via both batteries  110 ,  120 . This arrangement is particularly advantageous because the air conditioning must also be active for longer periods when the vehicle is stationary and a symmetrical loading of the two batteries  110 ,  120  can only be carried out via such an energy switch  310 . 
       FIG. 5  shows a schematic representation of a method  500  according to the invention for the powering an electrical auxiliary unit. 
     The method  500  is for redundantly supplying electrical energy from a battery system  300 ,  400  to an auxiliary electrical unit  140  of an electric vehicle, the electric vehicle as described above with respect to  FIGS. 3 and 4  driving the electric auxiliary power unit. The battery system  300 ,  400  includes the following components: a first battery  110  connectable to a first electric drive  101  to provide electrical energy to the first electric drive  101  to power the electric vehicle, as described above with respect to  FIGS. 3 and 4 ; a second, redundant battery  120  connectable to a second, redundant electric drive  102  is connectable to provide electrical power to the second electric drive  102  to drive the electric vehicle, as described above with respect to  FIGS. 3 and 4 ; and a configurable electrical power switch  310  having a first input port  321 , a second input port  322 , and an output port,  331 , the first input port  321  being connected to the first battery  110  electrically connected as described above with respect to  FIGS. 3 and 4 . The second input terminal  322  is electrically connected to the second battery  120 , and the output terminal  331  is electrically connected to the electrical accessory  140  of the electric vehicle to provide electrical power to the electrical accessory to drive the electrical accessory, as described above with respect to  FIGS. 3 and 4 . 
     The method  500  comprises the steps of: configuring  501  the electrical power switch  310  to electrically connect the output port  331  to the first input port to provide  321 , the electrical accessory  140  with electrical power from the first battery  110 ; and selectively reconfiguring  502  the electronic power switch  310  to electrically connect the output terminal  331  to the second input terminal  322  to provide electrical power from the second battery  120  to the electrical accessory  140 . 
     Since the embodiments and inventions described in detail above are exemplary embodiments, they can be modified to a large extent in the usual way by a person skilled in the art without leaving the field of invention. In particular, the arrangements and the proportions of the individual elements to each other are simply exemplary. Having described some aspects of the present disclosure in detail, it will be apparent that further modifications and variations are possible without departing from the scope of the disclosure. All matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.