DE102018006582A1 - Battery for a motor vehicle and vehicle electrical system - Google Patents

Abstract

The invention relates to a battery (1) for a motor vehicle (10), a motor vehicle electrical system and a motor vehicle (10). The battery (1) comprises an electrochemical energy store (20), at least one ground connection (21, 31), a first supply voltage connection (22) and a battery management system (24). A positive pole (201) of the energy store (20) is switchably connected to the first supply voltage connection (22) via a power switching element (23), the power switching element (23) being controllable by the battery management system (24). The battery (1) further comprises a second supply voltage connection (32) which is electrically connected to the positive pole (201) of the energy store (20) via a first circuit device (33), the first circuit device (33) comprising a current limiting device.

Description

The present invention relates to a battery for a motor vehicle, a motor vehicle on-board network and a motor vehicle.

Motor vehicle electrical systems are conventionally equipped with a lead-acid battery, with which a nominal battery voltage of 12 V is provided in the example of a passenger car. The battery is used to start an internal combustion engine and to supply electrical consumers of the motor vehicle network, if no or insufficient electrical power is provided by an internal combustion engine-operated generator.

For future vehicle applications, especially with regard to the desired CO2 or Fuel savings, vehicle batteries with a cell system based on lithium-ion (Li-ion) technology are becoming increasingly important. Vehicle batteries with Li-ion cells have a higher energy storage density than conventional lead-acid batteries, which can be used to reduce weight. Furthermore, the Li-ion cells have a higher charge acceptance than lead-acid batteries, which is particularly advantageous for storing recuperated braking energy.

In addition to the mentioned and other advantages, electrochemical cell systems based on Li-ion technology also have some critical properties. Lithium-ion cells in particular are less resistant to overcharging and overcurrents than conventional lead-acid batteries. Li-ion batteries for motor vehicles are therefore equipped with a battery management system (BMS), which together with a circuit breaker and the electrochemical energy store, i.e. a number of interconnected Li-lon cells are arranged in a common housing. Two terminals are led out of the battery housing, via which a supply voltage and a ground potential for a motor vehicle electrical system are provided. The supply voltage connection is switchably connected to the positive pole of the Li-ion cells via the circuit breaker, the ground connection to the negative pole. The BMS comprises a microprocessor system and various measuring devices with which numerous battery and cell parameters can be monitored. The BMS is also equipped with a data interface for connection e.g. to a CAN or LIN bus of a motor vehicle electrical system, so that communication with the energy or generator management and other control devices is possible. In particular, the BMS is set up to determine the current state of charge (SoC) of the Li-ion battery. If an overcharge or an overcurrent cannot be corrected via the energy management, the circuit breaker can be disconnected for safety reasons.

In addition to low resistance to overcharging and overcurrents, Li-ion batteries are also sensitive to deep discharges, which can lead to cell damage and a shortened lifespan or an immediate failure of the battery. When a motor vehicle is parked, it can therefore be problematic that many of the control units distributed in the vehicle electrical system are put into a standby state, which continue to consume electrical current. Depending on the vehicle model and equipment, the current consumption in a motor vehicle electrical system can add up, for example, in a range between 5 mA and 25 mA. This standby mode can become critical for a Li-ion battery in the motor vehicle on-board network, for example, if the vehicle is parked over a longer period of time, for example weeks and months, within which the battery could be discharged beyond a deep discharge threshold value.

From the DE 10 2012 211 393 A1 a Li-ion battery for a motor vehicle with a deep discharge protection function is known, which is provided by the interaction of an integrated circuit breaker and a BMS. The circuit breaker can be opened as soon as the BMS detects that a deep discharge threshold value for a battery parameter has not been reached. By opening the circuit breaker, all current consumers in the vehicle electrical system are disconnected from the battery cells. The integrated BMS can also be separated from the battery cells in order to efficiently reduce further discharge after a deep discharge protection shutdown.

A disadvantage of the prior art is that a vehicle battery which has been switched off in a protective manner must first be reactivated manually by a vehicle user before one of the electrical vehicle functions is even available.

The object of the present invention is therefore to provide an improved deep discharge protection for a vehicle battery, which in particular is user-friendly in connection with long-term parking processes, i.e. when parking a vehicle for a period of, for example, one month and longer.

Accordingly, a battery for a motor vehicle is proposed according to the independent main claim and by an electrical system for a motor vehicle and by a motor vehicle according to the subsidiary claims. Further developments are the subject of the respective subclaims.

According to a first aspect of the invention, the object is achieved by a battery for a motor vehicle which comprises an electrochemical energy store, at least one ground connection, a first voltage connection and a battery management system. A positive pole of the energy store is connected to the first voltage connection via a power switching element and the power switching element can be controlled by the battery management system. The battery further comprises a second voltage connection, which is electrically connected to the positive pole of the energy store via a first circuit device, the first circuit device comprising a current limiting device.

An electrochemical energy store comprises at least one group with a number of electrochemical cells connected in series. The positive pole of the energy store is the positive pole of the series circuit made up of the electrochemical cells, the negative pole is the negative pole of this series circuit, which is preferably defined as a reference or ground potential. The battery voltage is provided between the positive and the negative pole of the energy store and is led out of a battery housing via connection terminals for the first and second voltage connection and the ground connection. The electrochemical cells are preferably Li-ion cells.

A battery management system comprises electronic circuits for controlling and regulating charging and discharging processes of the electrochemical energy store or its individual cells. The battery management system can include a microprocessor system with which battery parameters such as battery voltage, individual cell voltages, temperatures and / or currents are recorded and processed in order to determine further parameters such as the state of charge of the battery. If a critical limit value is reached for at least one parameter, the electronics or the microprocessor of the battery management system can control the power switching element, so that the electrochemical energy store can be separated from at least one connection terminal led out of the battery housing and thus also from a connected vehicle electrical system.

The power switching element is preferably designed in the form of an electromechanical contactor, a so-called main contactor. In principle, a power semiconductor switch can also be used at this point, provided that currents of typically 800 A or current peaks of typically up to 1400 A can be reliably separated. In principle, a power switching element can also be configured with two poles, so that in addition to the first voltage connection, an associated ground connection can also be disconnected from the energy store at the same time.

According to this first aspect of the invention, a second voltage connection is provided on the battery, which, at least in certain cases, does not affect a shutdown of the first voltage connection initiated by the battery management system. An electrical energy supply for selected consumers can thus be provided via this second voltage connection. If the power switching element is separated to protect the battery from deep discharge, it makes sense to supply only electrical consumers for the most important functions. The maximum current that can be emitted via the second voltage connection is therefore limited, so that further discharging of the electrochemical energy store can also be reduced to a minimum.

With the present invention, in addition to the known standby mode and a vehicle electrical system shutdown when a critical state of charge of the battery is reached or undershot, a long-term standby mode is provided with which at least a minimal vehicle electrical system function with low power consumption can be provided.

According to a development of the first aspect of the invention, the battery management system can comprise a timer and a data interface. The battery management system can also be designed to start the timer as a function of first vehicle operating status information received via the data interface. The battery management system can also be designed to control the power switching element as a function of an expired timer in order to electrically separate the positive pole of the energy store from the electrically first voltage connection.

The idea behind this development is to provide preventive deep discharge protection for a battery of a motor vehicle, which is preferably triggered when the state of charge is above a critical lower state of charge. A sufficient charge to start an engine in a motor vehicle can thus possibly be retained in the battery, which can be called up via the first voltage connection after the battery has been reactivated.

Vehicle operating status information can be, for example, a locking signal from a control unit of a central locking system, which can be regarded as a characteristic signal for the start of a parking process. An expiry time of the timer can be selected in such a way that the power switching element only switches the first voltage connection free of battery voltage when a motor vehicle is parked for a longer period of time, within which a deep discharge of the battery threatens. For example, if an expiry time of 30 days is selected, normal recommissioning and starting of the vehicle from standby mode is possible.

According to an alternative or additional development, the battery management system can be designed to detect a state of charge of the energy store and to control the power switching element as a function of falling below a first charge state threshold in order to separate the electrical connection between the positive pole of the energy store and the electrically first voltage connection.

The first state of charge threshold can advantageously be chosen such that a state of charge remains in the energy store of the battery, which state of charge is sufficient at least for an engine start of a motor vehicle without the energy store reaching a critical deep discharge state.

According to a further embodiment of the first aspect of the invention, the battery management system can also be assigned a second circuit device which is designed to interrupt a supply voltage at least for parts of the battery management system as a function of a separate power switching element.

The battery management system with an integrated microprocessor and associated circuit devices for recording and processing measured physical operating parameters also represents a consumer that continues to consume electrical current in standby mode, which must be provided by the electrochemical energy store of the battery. With an interruption in the supply voltage, at least for parts of the battery management system, as a function of a separate power switching element, the discharge of the energy store can be reduced further.

According to a further development, a monitoring device can also be provided, which is designed to detect a voltage across the number of interconnected battery cells and to compare it with a lower voltage threshold value.

Even in a long-term standby mode, a lower charge state threshold can be continuously monitored in order to counter damage to the electrochemical energy store or impending cell defects. The lower state of charge threshold can be monitored on the basis of a corresponding minimum voltage value between the positive and the negative pole of the energy store. The monitoring device provides a deep discharge monitoring that is independent of the battery management system, with which the state of charge of the battery can be continuously calculated and monitored. The battery management system can thus be deactivated during a long-term standby mode.

In addition, the monitoring device can be designed to control the first circuit device in order to electrically separate the positive pole of the energy store from the second voltage connection when the voltage drops below the lower voltage threshold.

When a critical lower state of charge threshold is reached, a long-term standby mode can be ended, so that the battery or its cells are protected against further discharge.

According to a development, the monitoring device can comprise an analog comparator circuit with at least one operational amplifier and a reference voltage formwork device.

Corresponding analog circuits are characterized by a current consumption in the range of a few µA, while a microprocessor-based battery management system requires between 1-3 mA in operation. Energy-saving deep discharge protection is thus provided in particular for a long-term standby mode.

According to a further development, the first circuit device of the battery can comprise a power transistor, a measuring device and driver logic. The measuring device can be designed to detect a load current flowing through the power transistor. The driver logic can be designed to control the power transistor as a function of the load current and as a function of falling below the lower voltage threshold.

In cooperation with the associated measuring device and driver logic, the power transistor combines a current limiting device with a power switch in a semiconductor component. The power transistor, measuring device and driver logic can preferably be combined in one monolithic integrated circuit (IC).

According to a further development, the first circuit device can be designed to detect a current pulse by means of the measuring device. The first can also be designed to send a wake-up signal to the battery management system as a function of a detected current pulse.

One idea behind the present invention is also to provide a convenient way of ending a long-term standby mode or reactivating a respective vehicle electrical system. A current pulse provides a simple way of communication between a control device connected to the second supply voltage connection, e.g. that of the central locking system and battery electronics. In connection with a central locking module of the motor vehicle, the current pulse that arises when actuating corresponding actuators can be used as an implicit wake-up signal, so that no additional signal has to be generated.

According to an alternative embodiment, the first circuit device can comprise a fuse and an electromechanical circuit breaker.

In this configuration, the functions of the current limiting device and the circuit breaker are separated from one another. The fuse is a simple overcurrent limitation, in particular in the event of a fault. The electromechanical circuit breaker can be designed as a relay which is designed for a low maximum current in accordance with a nominal current of the fuse.

According to a second aspect of the invention, the object is achieved by a motor vehicle electrical system which comprises a first sub-electrical system with a first voltage supply line, a second sub-electrical system with a second voltage supply line and a battery according to the first aspect of the invention. The first voltage supply line of the first sub-electrical system is connected to a first supply voltage connection of the battery. The second voltage supply line is connected to a second supply voltage connection of the battery. The second voltage supply line is designed for a lower maximum current than the first voltage supply line.

The second sub-electrical system is provided according to an idea behind the second aspect of the invention for the electrical energy supply of selected control devices which, in a long-term standby mode, have a smaller power or current consumption than the sum of all control devices during a conventional standby mode. The design for a lower maximum current enables smaller line cross sections to be provided for the second voltage supply line than for the first voltage supply line, at least in one line section between the first supply voltage connection of the battery and a first fuse box.

According to a third aspect of the invention, the object is achieved by a motor vehicle with a motor vehicle electrical system according to the second aspect of the invention.

• 1 ein Kraftfahrzeug mit einem Kraftfahrzeugbordnetz und einer Fahrzeugbatterie;
• 2 eine Fahrzeugbatterie;
• 3 eine erste Ausgestaltung einer ersten Schaltungseinrichtung der Fahrzeugbatterie;
• 4 eine zweite Ausgestaltung einer ersten Schaltungseinrichtung der Fahrzeugbatterie.

Further features and details result from the following description, in which - if necessary with reference to the drawing - at least one exemplary embodiment is described in detail. Described and / or illustrated features form the subject matter, either individually or in any meaningful combination, if appropriate also independently of the claims, and in particular can also be the subject of one or more separate applications. Identical, similar and / or functionally identical parts are provided with the same reference symbols. Show:

• 1 a motor vehicle with a vehicle electrical system and a vehicle battery;
• 2 a vehicle battery;
• 3 a first embodiment of a first circuit device of the vehicle battery;
• 4 a second embodiment of a first circuit device of the vehicle battery.

In the 1 is schematically a motor vehicle 10 with a battery according to the invention 1 and a vehicle electrical system according to the invention. The motor vehicle electrical system comprises two electrical systems, a first electrical system extending to the left of the battery and a first supply line 2 having a first supply voltage connection 22 the battery 1 connected is. A second electrical system with a second supply line 3 is to the right of the battery 1 shown. The motor vehicle electrical system can have a common ground potential for both sub-electrical systems, wherein an electrically conductive body can act as a ground line.

Both sub-systems each provide a 12 V nominal supply voltage for the electrical power supply of electrical vehicle components. An essential difference between the first and second sub-electrical system is that the second supply line 3 and the second supply voltage connection 32 the battery 1 are designed for a lower maximum current than the first supply line 2 and the first supply voltage connection 22 the battery 1 , The second supply voltage connection 32 the battery 1 thus provides an additional low power outlet (LPO) of the battery according to the invention 1 represents.

On the first supply line 2 numerous electrical vehicle components are connected, one example being a generator 7 and a resistor are shown. The resistor is representative of a large number of electronic control units or other electrical consumers 8th of the vehicle electrical system, which require electrical energy. The supply lines for the generator 7 and the electrical consumers 8th are each for protection against overcurrents with fuses 9 hedged.

The second supply line 3 provides an electrical power supply for a central locking module 5 ready. The central locking module 5 is equipped with a radio receiver that transmits a radio signal 40 can be received by a key remote control.

The motor vehicle electrical system also includes a data transmission network, which can be designed as a CAN or LIN bus system and enables communication between numerous electronic control units in the motor vehicle electrical system. In particular, the central locking module 5 and the battery 1 with the data line 4 connected to the data transmission network.

The 2 shows a battery according to the invention 1 for a motor vehicle 10 , which comprises a first pair of terminals for providing a battery voltage for the first sub-electrical system. The 12 V nominal supply voltage is provided by a series connection of a number of Li-ion cells that hold the electrochemical energy store 20 the battery. A negative pole of the electrochemical energy storage 20 is with a ground connection 21 of the first pair of terminals is electrically connected. An electrical connection of a positive pole 201 of the energy storage 20 with the first voltage connection 22 is switchable via a power switching element 23 ,

The battery 1 also includes a battery management system (BMS) 24 , which is used to monitor, regulate and protect the electrochemical energy store 20 or each of its Li-lon cells. The BMS 24 comprises a microcontroller system with associated measuring electronics, with which, for example, the battery current and the voltages and temperatures of the individual lithium-ion cells or that of the entire electrochemical energy store 20 can be recorded and monitored. The microcontroller system is set up to process the measurement values acquired by measurement, so that the current state of charge (SoC) of the energy store 20 can be determined with the lithium-ion cells. The microcontroller system provides a data interface 14 ready from a battery case 1 led out and for connection to the CAN or LIN based data line 4 in a motor vehicle 10 can be connected. In cooperation with a control device of a generator 7 can the BMS 24 a charge management for the battery 1 provide.

The BMS 24 is via a first control line 25 with the power switching element 23 connected to various protective functions for the electrochemical energy storage 20 or to provide the lithium-ion cells. The positive pole 201 of the energy storage 20 can from the BMS 24 by driving the power switching element 23 electrically from the first supply voltage connection 22 be separated. The BMS controls in connection with a deep discharge protection function mentioned at the beginning 24 the power switching element 23 and separates the positive pole 201 of the energy storage 20 from the first supply voltage connection 22 as soon as a lower threshold for the SoC of the battery 1 is reached.

The power switching element 23 can be designed as an electromechanical switch, for example as a contactor. The contactor, which is also referred to as the main contactor of a battery, can also be designed with two poles, so that the positive pole 201 and the negative pole 202 of the energy storage 20 from the first supply voltage connection 22 and from the ground connection 21 of the first pair of terminals are electrically separable. The power switching element 23 can also be designed as a power semiconductor switch.

The battery according to the invention 1 includes a second supply voltage connection 32 which has a first circuit device 33 with the positive pole 201 of the energy storage 20 is switchably connected. The second supply voltage connection 32 can have a second ground connection 31 be assigned so that a second pair of terminals is provided.

The second supply voltage connection 32 provides an additional low power outlet (LPO) of the battery 1 ready with that from the first supply voltage connection 22 independent current and voltage to supply selected Vehicle electrical system components, for example that in the 1 Central locking module shown 5 is available. At the first supply voltage connection 22 and at the second supply voltage connection 32 the same battery voltage of 12 V from the energy storage 20 provided. The difference between the voltage connections is that the second supply voltage connection 32 is limited to a maximum output current that is much smaller than the maximum output current of the first supply voltage connection 22 , The first supply voltage connection 22 can provide output currents of up to 800 A, for example, with current peaks of up to 1400 A possible. During standby operation of a motor vehicle, up to 25 mA continuous current can be delivered to the vehicle electrical system.

The second supply voltage connection 32 is intended for a permanent current output of a maximum of 2 mA, with a current limiting device of the first circuit device 33 should allow higher currents for a short time.

The BMS 24 the battery 1 is set up the battery 1 switch from a standby mode to a long-term standby mode as soon as a switchover criterion has been fulfilled. A switchover criterion is a timer expiration of 30 days, for example. The timer starts when the BMS 24 via the data interface 14 a locking signal from the central locking module from the CAN or LIN bus 5 receives. If the central locking module releases an unlock signal before the timer expires 5 via the data interface 14 received, the timer is stopped or reset. If the timer expires, the switchover criterion is met and the BMS 24 controls via the control line 25 the power switching element 23 so that a current output of 5 mA-25 mA via the first supply voltage connection 22 is interrupted. The central locking module 5 with a continuous current requirement of 1 mA to 2 mA while it is ready to receive via the second supply voltage connection 32 provided.

The BMS 24 is preferably at least partially deactivated during a long-term standby mode by one from the energy store 20 to reduce the current provided between 1 mA and 3 mA. If the microcontroller system is deactivated, the BMS 24 no longer monitor a critical lower SoC. In order to provide a deep discharge protection function even during a long-term standby mode, there is an additional monitoring device 34 intended. This includes, for example, an analog comparator circuit with an operational amplifier and a reference voltage circuit device with which a lower voltage value of the energy store is reached 20 can be detected. The lower voltage value corresponds to a critical lower SoC. If the lower voltage value is reached, the first circuit device 33 via the third control line 36 controlled so that the second supply voltage connection 32 from the positive pole 201 of the energy storage 20 is electrically separated. In this case, the long-term standby mode is ended in favor of a deep discharge protection shutdown.

Receives the central locking module 5 a radio signal during a long-term standby mode 40 with an unlock command from a key remote control, not shown in the figures, corresponding central locking actuators, not shown in the figures, can be activated by the central locking module 5 in the motor vehicle 10 can be controlled to unlock the door. One from central locking module 5 The output control pulse briefly increases its current consumption to a value above the 1-2 mA prevailing during the readiness to receive. The one from the battery 1 via their second supply voltage connection 32 emitted current pulse for unlocking the motor vehicle 10 could in the first circuit device 33 or in the monitoring facility 34 can be detected with appropriate circuit devices, so that via the second control line 35 or via the fourth control line 37 a signal to reactivate the BMS 24 can be spent.

The long-term standby mode can thus be comfortably ended with the receipt of an unlock command from the key remote control, in which the at least partially deactivated BMS 24 through the central locking module 5 is woken up. The reactivated BMS 24 can the power switching element 23 over the first control line 25 control and close so that over the first supply voltage connection 22 the supply voltage for the first supply line 2 is provided again.

The BMS 24 can alternatively by the central locking module 5 can be woken up directly by a wake-up function in a transceiver for the data interface 14 of the BMS 24 is integrated. During a long-term standby mode, it can be provided via the data line 4 no signals to exchange. Receives and verifies the central locking module 5 a valid unlock command, can be done via the data line 4 a wake-up signal to the BMS 24 the battery 1 be sent.

In the 3 is a first embodiment of the first circuit device 33 a battery according to the invention 1 , The first circuit device 33 includes an input voltage contact 331 the one with the positive pole 201 of the energy storage 20 can be connected or is connected. An output voltage contact 332 is with the two supply voltage connection 32 connectable or connected. A signal input 333 is used for the electrical connection to the monitoring device 34 via the third control line 36 , The first circuit device 33 includes a circuit breaker 336 , which is designed for example as a relay or as a semiconductor switch. Is at the signal input 333 a signal for a deep discharge protection shutdown, the circuit breaker disconnects 336 the input voltage contact 331 from the output voltage contact 332 ,

The first circuit device 33 also includes a backup 335 , for example a fuse with a nominal current of 2 mA. The fuse preferably has an inert tripping characteristic, so that an output current of the second supply voltage connection limited to 2 mA 32 the battery 1 can be exceeded briefly. A diode 337 can be provided for safety reasons to an incorrect, ie an undesired charging current via the second supply voltage connection 32 to suppress.

The 4 shows an alternative second embodiment of the first circuit device 33 , which essentially consists of an integrated so-called Smart High-Side Power Switch. A smart high-side power switch is essentially an integrated circuit with a power MOS transistor for controlling a supply voltage and control and diagnostic electronics. The in the 4 alternative integrated first circuit device shown 33 includes an input voltage contact 331 , an output voltage contact 332 and a signal input 333 that are functionally referencing the connectors already 3 described first execution correspond.

The integrated circuit has a power MOS transistor 3310 with the one of the energy storage 20 provided voltage from the input voltage contact 331 on the output voltage contact 332 can be switched through. With a measuring device 3311 can by the power MOS transistor 3310 flowing load current are continuously monitored. In cooperation with a driver logic 3312 to control the power MOS transistor 3310 can with the measuring device 3311 a current limit for the second supply voltage connection 32 the battery 1 to be provided. Also a current pulse for unlocking the motor vehicle 10 could in the interaction of measuring device 3311 and driver logic 3312 be detected so that a signal to wake up the BMS 24 via a signal output 334 can be spent.

Although the subject has been illustrated and explained in detail by means of exemplary embodiments, the invention is not restricted by the disclosed examples and other variations can be derived therefrom by a person skilled in the art. It is therefore clear that there are a variety of possible variations. It is also clear that exemplary embodiments are only examples which are not to be interpreted in any way as a limitation of the scope, the possible applications or the configuration of the invention. Rather, the preceding description and the description of the figures enable the person skilled in the art to specifically implement the exemplary embodiments, the person skilled in the art being able to make various changes, for example with regard to the function or the arrangement of individual elements mentioned in an exemplary embodiment, in knowledge of the disclosed inventive concept, without the To leave the scope of protection, which is defined by the claims and their legal equivalents, such as further explanations in the description.

LIST OF REFERENCE NUMBERS

1

battery

2

first supply line

3

second supply line

4

data line

5

Central module

6

fuse

7

generator

8th

consumer

9

fuse

10

motor vehicle

14

Data Interface

20

electrochemical energy storage

201

positive pole

202

negative pole

21

ground connection

22

first supply voltage connection

23

Power switching element

24

Battery management system (BMS)

25

first control line

31

ground connection

32

second supply voltage connection

33

first circuit device

34

monitoring device

35

second control line

36

third control line

37

fourth control line

331

Input voltage Contact

332

Output voltage Contact

333

signal input

334

signal output

335

fuse

336

breakers

337

diode

3310

Power MOS transistor

3311

measuring device

3312

driver logic

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102012211393 A1 [0006]

Claims (12)

Battery for a motor vehicle (10), comprising an electrochemical energy store (20), at least one ground connection (21, 31), a first supply voltage connection (22) and a battery management system (24), a positive pole (201) of the energy store (20) is switchably connected to the first supply voltage connection (22) via a power switching element (23) and the power switching element (23) can be controlled by the battery management system (24), further comprising a second supply voltage connection (32) connected via a first switching device (33) is electrically connected to the positive pole (201) of the energy store (20), the first circuit device (33) comprising a current limiting device. Battery according to the above Claim 1 , wherein the battery management system (24) comprises a timer and a data interface (14), the battery management system (24) being designed to start the timer as a function of a first vehicle operating status information received via the data interface (14), and wherein the battery management system (24) is furthermore is designed to control the power switching element (23) as a function of an expired timer in order to electrically separate the positive pole (201) of the energy store (20) from the first supply voltage connection (22). Battery according to one of the above Claims 1 or 2 The battery management system (24) is designed to detect a state of charge of the energy store (20) and to control the power switching element (23) as a function of falling below a first charge state threshold in order to establish the electrical connection between the positive pole (201) of the energy store (20). and to separate the first supply voltage connection (22). Battery according to one of the above Claims 1 to 3 The battery management system (24) is also assigned a second circuit device which is designed to interrupt a supply voltage at least for parts of the battery management system (24) as a function of a separate power switching element (23). Battery according to one of the above Claims 1 to 4 , further comprising a monitoring device (34) which is designed to detect a voltage between the positive pole (201) and a negative pole (202) of the energy store (20) and to compare it with a lower voltage threshold value. Battery according to the above Claim 5 , wherein the monitoring device (34) is further configured to control the first circuit device (33) in order to electrically separate the positive pole (201) of the energy store (20) from the second supply voltage connection (32) when the voltage drops below the lower voltage threshold. Battery according to one of the above Claims 5 or 6 , wherein the monitoring device (34) comprises an analog comparator circuit with at least one operational amplifier and a reference voltage circuit device. Battery according to one of the above Claims 5 to 7 , wherein the first circuit device (33) comprises a power transistor (3310), a measuring device (3311) and driver logic (3312), the measuring device (3311) being designed to detect a load current flowing through the power transistor (3310) and wherein the Driver logic (3312) is designed to control the power transistor (3310) as a function of the load current and as a function of falling below the lower voltage threshold. Battery according to the above Claim 8 , wherein the first circuit device (33) is designed by means of the measuring device (3311) to detect a current pulse and the first circuit device (33) is further designed to send a wake-up signal to the battery management system (24) as a function of a detected current pulse. Battery according to one of the above Claims 1 to 7 , wherein the first circuit device (33) comprises a fuse and an electromechanical circuit breaker. Motor vehicle electrical system comprising a first electrical system with a first voltage supply line (2), a second electrical system with a second voltage supply line (3) and a battery (1) according to one of the preceding Claims 1 - 10 , wherein the first voltage supply line (2) is connected to a first supply voltage connection (22) of the battery (1) and the second voltage supply line (3) is connected to a second supply voltage connection (32) of the battery (1), the second voltage supply line ( 3) is designed for a lower maximum current than the first voltage supply line (2). Motor vehicle comprising a vehicle electrical system according to the above Claim 11 ,

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