Battery system with several self-switching storage units and motor vehicle with this battery system and operating method for the battery system

Abstract

A battery system (12) comprising a plurality of self-switching electrical storage units (14), each having a transceiver circuit (19) configured to exchange communication data (16) containing switching commands from the control circuit (17) and / or measured values ​​from the storage unit (14) via a respective individual radio connection (16) with a common higher-level control circuit (17), characterized in that an individual spreading code (24) is provided in the respective transceiver circuit (19) for operating the individual radio connection (16), and the spreading codes (24) of all transceiver circuits (19) are designed orthogonally to one another according to a code division multiplexing method, and in some or all of the transceiver circuits (19), at least one common multicast spreading code (25) is additionally provided for a respective common multicast radio connection to the control circuit (17),wherein an allocation of the respective spreading code (24, 25) for the individual and / or for at least one common radio connection (16) to the respective transceiver circuits (19) is carried out dynamically and for this purpose, a) the control circuit (17) is designed to transmit a respective new spreading code (24, 25) to be used in the future via the respective individual radio connection (16) to the respective transceiver circuit (19), and / or b) the respective transceiver circuit (19) is configured to determine the new spreading code (24, 25) to be used in the future itself on the basis of at least one memory unit-specific reference value.

Description

[0001] The invention relates to a battery system, such as can be provided in a motor vehicle to supply an electric drive with energy. The battery system has self-switching storage units, i.e., individual storage units each have their own switching unit for switching an electrical current in the storage unit. Switching commands for switching the current can be sent to the storage units from a higher-level central control circuit. The invention also encompasses a motor vehicle with such a battery system and a method for operating the battery system.

[0002] In an electric vehicle, i.e. a motor vehicle with an electric drive, a battery system can be provided to store the required electrical energy. This system can be based, for example, on lithium-ion technology. The energy can thus be stored in galvanic cells, each of which, together with a local cell circuit, represents a so-called battery cell. Several of these battery cells can be interconnected to form so-called battery modules, which in turn can be interconnected to form the battery system. The battery cells are individually monitored by sensors, with sensor data from the battery cells then being communicated to a higher-level control circuit. The central control circuit provided for the entire battery system is called the battery management system (BMS).If several battery cells are connected to form a battery module, the sensor data of these battery cells can also be collected in an intermediate stage in a so-called module management system of the respective battery module, which in turn can communicate with the higher-level battery management system.

[0003] However, there are also approaches where the battery cells communicate directly with the central battery management system, whereby the number of communication participants from the perspective of the battery management system is correspondingly larger than when module management systems are interposed.

[0004] Depending on the design, there can be communication connections between individual battery cells on the one hand and a higher-level battery management module on the other, as well as between battery management modules and the higher-level battery management system, and directly between individual battery cells and the battery management system. CAN (Controller Area Network), such as CAN-FD, has been the primary communication interface between the battery management system and the battery cells or module management systems. However, another, for example, proprietary, communication protocol can also be used. Communication is typically wired.

[0005] A disadvantage of the described communication is that, due to the high levels of electromagnetic radiation in the electric drive train, such as that caused by the power electronics and the electric motor, bit errors or even burst errors can occur in the battery communication network. The resulting retransmission can lead to real-time problems in acquiring the sensor data and / or transmitting the described switching commands. This can also cause undetected transmission errors.

[0006] A further disadvantage is that if the communication bus cables are damaged, for example, due to a cable break after an accident, there is a permanent disruption or interruption in communication, so that the status of the individual battery cells after a vehicle crash, for example, is unknown and can no longer be measured. This can complicate rescue operations, for example.

[0007] A further disadvantage is that, depending on the amount of data communicated, serialization of the data packets may be required, which in turn can lead to transmission delays (latencies) that make real-time requirements difficult in the technical implementation.

[0008] It is known from US 2016 / 0 056 510 A1 that in a stationary battery storage system, such as one used for temporary energy storage for buildings, the transmission of measurement data within the battery storage system can also be carried out wirelessly. However, if one attempts to provide the described large number of wireless connections between individual battery cells and a central battery management system, a bottleneck in data transmission can arise due to the limited channel bandwidth or wireless bandwidth on the one hand and the large number of required wireless connections on the other.

[0009] The use of the CAN bus and another bus system in connection with communication with a battery management system is described, for example, in US 2016 / 0 288 744 A1.

[0010] JP 2016 / 012 954 A discloses a battery management system in which the battery cells are combined into the described battery modules, which in turn can communicate with the central battery management system. Communication can be wireless. To provide a large number of radio connections simultaneously, several different frequency transmitters are used. However, this can be difficult to implement in a metallic housing of a vehicle battery, as reflections in the housing can cause differences that render some radio channels unusable.

[0011] DE 10 2011 086 612 A1 discloses a battery system equipped with several deactivated electrical storage units. It features a transmission method between sensor nodes and a central control unit, as well as a suitable design of the sensor nodes and control unit. Furthermore, the measured values ​​recorded by the sensors are transmitted wirelessly, e.g., via radio, to the central receiver. The CDMA method is used, and the data streams are encoded with special spreading codes, thus exhibiting certain properties such as orthogonality.

[0012] A contribution by Schneider, M. [et al.] describes the details of a possible implementation for transmitting control commands from the control unit to the battery cells. In the case of the downlink, a multicast transmission takes place, requiring the provision of a corresponding multicast code. (SCHNEIDER, M. [et al.]: Automotive Battery Monitoring by Wireless Cell Sensors. In: IEEE International Instrumentation and Measurement Technology Conference Proceedings, 13-16 May 2012, pp. 816-820. DOI: 10.1109 / I2MTC.2012.6229439)

[0013] TYVA MODULO: TYVA BMS describes a battery system that has at least one master cell, which can also connect to a smartphone via Bluetooth, allowing the app shown there to display a variety of measured parameters of individual cells. (TYVA MODULOO: TYVA BMS, 6-25S Battery Management System, revised June 18, 2018, version 8.0, URL: https: / / tyva-moduloo.com / modular-lithium-battery-unit-systems-and-solutions / lithium-ion-battery-management-system-bms-tyva / ).

[0014] The invention is based on the object of exchanging or transmitting communication data between the electrical storage units of the battery system and the central battery management system in a battery system for a motor vehicle.

[0015] This object is achieved by the subject matter of the independent patent claims. Advantageous embodiments of the invention are described by the dependent patent claims, the following description, and the figure.

[0016] The invention provides a battery system having a plurality of storage units. The battery system can, for example, be designed as a so-called traction battery or high-voltage battery, i.e., designed to generate a high voltage of more than 60 volts. The storage units are designed to be self-switching, which means that a central or higher-level control circuit can issue a control command to such a storage unit, and the storage unit itself can then switch the electrical current it provides. The storage unit is therefore individually switchable. For this purpose, a controller circuit for implementing the switching command of the control circuit and an electrical switching unit for switching the electrical current can be provided in the storage unit. Self-switching storage units are known per se from the prior art.

[0017] In the context of the invention, it is important that several such storage units communicate with a higher-level control circuit or exchange communication data. For this purpose, each storage unit has a transceiver circuit (transmitting-receiving circuit) that is configured to exchange communication data with the common higher-level control circuit via a respective individual radio connection. By "common" is meant here that several storage units, with their respective transceiver circuits, maintain or operate a respective radio connection with one and the same control circuit. The communication data can contain switching commands that are to be transmitted from the control circuit to the storage units, and / or measurement and status values ​​that are to be transmitted from the respective storage unit to the central, higher-level control circuit.The communication in the battery system according to the invention is therefore radio-based due to the radio connections.

[0018] In order to efficiently utilize the radio bandwidth, which may be restricted by, for example, metallic objects, the invention provides that an individual spreading code is provided in the respective transceiver circuit for operating said individual radio connection, and that the spreading codes of all transceiver circuits are designed orthogonally to one another according to a code division multiplexing method. In other words, the radio connection is individualized in that each transceiver circuit uses an individual or separate spreading code that is different from all spreading codes of the other transceiver circuits that communicate with the same control circuit. By using orthogonal spreading codes, the transceiver circuits and their radio connections do not interfere with one another, even if transmission and / or reception take place simultaneously in the same frequency band used for the code division multiplexing method.However, this results in a large number of individual radio connections on one and the same frequency band, which could lead to a bottleneck in the frequency band.

[0019] Therefore, according to the invention, at least one common spreading code is additionally provided in some or all of the transceiver circuits for a respective common multicast radio connection, which can be operated between the common higher-level control circuit on the one hand and the transceiver circuits on the other. Thus, if the control circuit transmits using a multicast spreading code belonging to the common multicast radio connection, all transceiver circuits that know or use this common spreading code simultaneously receive the communication data transmitted via it.

[0020] For each communication connection, an individual or unique spreading code is used for transmitting the communication data per transceiver circuit. Additionally, for broadcast or multicast, a multicast spreading code is also provided in some or all transceiver circuits. This multicast spreading code is stored and can be used as an additional spreading code in these transceiver circuits. The term "spreading code" refers to the communication method known per se from the state of the art. An example of a spreading code is a Walsh code.

[0021] The use of a code division multiplexing method with an additional multicast spreading code results in two advantageous effects for operating a code division multiplexing method within a battery system between the higher-level control circuit on the one hand and the electrical storage units on the other. The spreading codes cause spreading, i.e., band broadening, which reduces the noise sensitivity of the radio connections. Furthermore, the multicast radio connection can achieve bandwidth-saving, simultaneous communication between the control circuit on the one hand and multiple transceiver circuits on the other with minimal communication data.

[0022] The invention offers economic and real-time advantages: Since all transceiver circuits in the process can use the same carrier frequencies, the communication hardware for all participants can be optimized for these frequencies and developed and produced in exactly the same way. This means that the cells or, in general, the storage units do not need to differ in terms of circuitry. Otherwise, 800 battery cells would require up to 800 different carrier frequencies with a certain bandwidth, which might require dedicated hardware designed for each frequency. Another option for using the same frequencies would be time-division multiplexing. However, this is highly error-prone (if a cell is defective and transmits uncontrollably, this can cause the entire communication to fail).Sporadic messages often lead to pessimistic bus systems in time-division multiplexing, since time must always be reserved for sporadic messages. Since the method according to the invention allows all participants to transmit simultaneously, such waiting times are reduced to enable access to the communication medium.

[0023] In the invention, the respective spreading code for the individual and / or for at least one shared radio connection is assigned to the respective transceiver circuits dynamically, i.e., the transceiver circuits can change the spreading code they use, particularly during operation of the battery system. For this purpose, the control circuit is configured to send a new spreading code to be used in the future to the respective transceiver circuit via the respective individual radio connection. Thus, the shared control circuit specifies the spreading code to be used by each transceiver circuit. Additionally and alternatively, it can be provided that the respective transceiver circuit is configured to determine the new spreading code to be used by it in the future itself based on at least one reference value.Such a reference value can, for example, be a time value that specifies when the transceiver circuit should switch to the new spreading code. The spreading code can be calculated by the transceiver circuit, for example, using a processor or a computational value. This results in a dynamic assignment of spreading codes to the various transceiver circuits. By dynamically assigning the necessary multicast spreading code to the transceiver circuits for multicast radio connections, dynamic generation of communication groups is also possible. This means that during the operation of the battery system, the storage units are regrouped by being assigned the respective spreading code for a communication group.The code change can originate from the control circuit, in which the control circuit transmits the new spreading code to the transceiver circuit. This can be done in encrypted form, thus preventing the possibility of manipulation by another transmitter. Additionally or alternatively, a transceiver circuit can calculate its own spreading code. The described reference value can determine which spreading code it should calculate individually for each transceiver circuit.

[0024] The invention also includes embodiments which provide additional advantages.

[0025] In one embodiment, the control circuit is configured to send communication data that triggers coordinated operation of the storage units via the multicast radio connection (via which multiple transceiver circuits can simultaneously receive communication data with the same multicast spreading code) to the storage units whose transceiver circuits have or understand the common spreading code. For example, switching operations in the storage units can be controlled in a coordinated manner. Using the multicast radio connection results in no latency or time offset when transmitting the communication data to the different transceiver circuits; rather, all transceiver circuits receive the communication data that triggers coordinated operation simultaneously.

[0026] In said common control circuit, the respective radio connection can end or be implemented in a receiver circuit of the control circuit. In one embodiment, this receiver circuit or receiver unit of the control circuit is configured to simultaneously receive communication data from the transceiver circuits of multiple memory units via several of the individual radio connections. In other words, a received signal is correlated or convolved with several of the spreading codes in the receiver unit, for example through parallel signal processing, in order to identify which symbol from which spreading code is contained in the received signal. In this way, even overlapping communication data from different transceiver circuits can be recognized or detected in the receiver unit of the control circuit.Of course, simultaneous transmission via multiple radio connections can also be implemented in a transmitter unit of the control circuit. For this purpose, several parallel transmission paths can be implemented or provided in the transmitter unit of the control circuit, whose transmitter signals can then be superimposed.

[0027] In one embodiment, the dynamic assignment of new spreading codes occurs cyclically in at least some or all of the transceiver circuits during operation of the battery system. In other words, the spreading code used in these transceiver circuits is changed, in particular at predetermined times, for example, at a time interval ranging from 10 seconds to one day. This makes the battery system's communication tamper-proof.

[0028] In one embodiment, the transceiver circuits of the memory units are identical in construction. In other words, the transceiver circuits have the same blueprint. In order to individualize the transceiver circuits, i.e., to make them suitable for use in one of the memory units, the transceiver circuits each have a memory unit with a volatile data memory and / or a non-volatile data memory. A volatile data memory can be, for example, a RAM (Random Access Memory). A non-volatile data memory can be, for example, an EEPROM - Electrically Erasable Programmable Read-Only Memory or a flash memory. The respective transceiver circuit with its memory unit is configured to store the respective spreading code, in particular the spreading code for the individual radio connection, in the memory unit.In other words, identical transceiver circuits can be installed during the construction of the storage units, and only during operation of the battery system or for the operation of the battery system is each transceiver circuit customized by storing the respective spreading code. This allows identical communication hardware to be used, into which a customized code sequence or spreading code can then be stored as needed. This facilitates mass production of the storage units.

[0029] In one embodiment, the respective transceiver circuit is galvanically isolated from a ground potential of the battery system. In other words, each transceiver circuit is operated "free-floating" with respect to its electrical potential. The transceiver circuits are therefore at different electrical potentials. To supply voltage to the respective transceiver circuit, it is connected to electrical poles or terminals of its own storage unit. In other words, each transceiver circuit is electrically powered by the storage unit in which it is installed. Thus, no low-voltage cabling for operating the transceiver circuits needs to be provided or laid outside the storage units in the battery system. Instead, each transceiver circuit is powered by its own storage unit. This reduces the cabling effort in the battery system.

[0030] So far, communication in the battery system has been described as a radio connection between a control circuit, on the one hand, and a transceiver circuit of a storage unit, on the other. As already mentioned at the beginning, different hierarchical levels for communication can be provided. The central, shared control circuit can therefore be a central battery management system, which then either communicates with storage units in the form of battery modules and / or communicates directly with individual battery cells. However, it can also be provided that the shared control circuit is designed as a module management system of a battery module of the battery system and operates a radio connection with the individual battery cells of the battery system.Thus, one embodiment provides that the common control circuit is configured as a module management system of a battery module of the battery system or, in another embodiment, as a battery management system, i.e., superordinate to the possible battery modules. The storage units can then be individual battery cells of the battery system or each be configured as a battery module. A battery module is a combination of some of the battery cells of the battery system into a structural unit. Thus, battery modules of the battery system or even individual battery cells of the battery system can have a wireless interface or radio interface, via which communication takes place with the central battery management system or with a module management system.Of course, it is also possible for the battery management system to communicate as a central control circuit with the module management systems of several battery modules, and within these battery modules, the module management system, in turn, to communicate as a central control circuit with the individual battery cells. Different radio technologies can also be provided for different communication hierarchies. Within the battery cell, communication domains can also be created that can be separated from one another or rendered interference-free based on different spreading codes and / or frequency bands used.

[0031] As already explained, with wired communication, for example based on a CAN bus, one problem is monitoring or analyzing the condition of the battery system after a crash, since if the cable breaks, the sensor circuits in the battery system can no longer be read. A similar problem can arise with radio-based communication if the common control circuit is destroyed. To counteract this, one embodiment provides that the respective transceiver circuit in the storage units is configured to operate a further radio connection with a communication circuit arranged outside the battery system, independent of the common control circuit. In other words, each transceiver circuit can be individually contacted or reached via a further radio connection from outside the battery system.The transceiver circuit is further configured to generate measurement data using a sensor circuit of the respective storage unit and transmit it to the communication circuit via the additional radio connection. In other words, the sensor circuit of each individual storage unit can be accessed or used from outside the battery system via its own radio connection. In particular, it is provided that the transmitter circuit is configured for temperature measurement and that the measurement data are accordingly temperature measurement data. Thus, a measurement can be taken using the sensor circuits of the storage unit at the respective location or position of each storage unit whose transceiver circuit is still functional for operating the additional radio connection.This means that, for example, a fire department or rescue team can use the aforementioned communication circuit to read the measurement data from the storage units that are still capable of communication, without having to rely on the functionality of the battery system's shared control circuit. This can be particularly advantageous for temperature measurements in order to predict a battery fire. For example, a mobile device, such as a smartphone or tablet PC, can be used as the communication circuit. In this case, a program code, a so-called application or app, can then be run in the communication circuit to establish the radio connection with the transceiver circuits of the individual storage units. Of course, a radio connection to the control circuit can also be enabled in order to request the aforementioned measurement data from the control circuit itself.This can then communicate with the transceiver circuits via the internal radio connections.

[0032] It can also be provided that a so-called smart mesh is implemented within the battery system by the control circuit and the multiple transceiver circuits. This allows, in the event of a transceiver circuit failure, for example, an indirect measurement, in particular an indirect temperature measurement, for the failed storage unit to still be possible via neighboring cells. For example, if a storage unit is surrounded by four other storage units, a temperature measurement in the four storage units can allow a conclusion to be drawn about the temperature of the storage unit that is no longer capable of communication by means of interpolation.

[0033] As already explained, the battery system is, in particular, an energy storage device for a motor vehicle. Accordingly, the invention also provides a motor vehicle with an electric drive coupled to an embodiment of the battery system according to the invention. Such a drive can be a purely electric drive or a component of a so-called hybrid drive, in which an internal combustion engine is additionally provided for driving operation. The motor vehicle according to the invention is preferably designed as a motor vehicle, in particular as a passenger car, truck, or motorcycle.

[0034] The operation of the battery system according to the invention results in a method that is also a component of the invention. The method serves to operate a battery system, wherein several self-switching electrical storage units in the battery system each have a transceiver circuit that exchanges communication data containing switching commands from the control circuit and / or measurement and / or status values ​​from the storage unit via a respective individual radio connection with a common higher-level control circuit.The invention provides that an individual spreading code is provided in the respective transceiver circuit for operating the individual radio connection and the spreading codes of all transceiver circuits are designed orthogonally to one another according to a code division multiplexing method and in some or all of the transceiver circuits, at least one common multicast spreading code is additionally provided for a respective common multicast radio connection to the control circuit.

[0035] The invention also includes further developments of the method according to the invention that have features already described in connection with the further developments of the battery system according to the invention. For this reason, the corresponding further developments of the method according to the invention are not described again here.

[0036] The invention also includes combinations of the features of the described embodiments.

[0037] Exemplary embodiments of the invention are described below. Shown are: Fig. 1 A schematic representation of an embodiment of the motor vehicle according to the invention, in which an embodiment of the method according to the invention can be carried out; and Fig. 2 A schematic representation of an embodiment of a memory unit with a transceiver circuit.

[0038] The exemplary embodiments explained below are preferred embodiments of the invention. In the exemplary embodiments, the described components of the embodiments each represent individual features of the invention that can be considered independently of one another, each of which also develops the invention independently of one another. Therefore, the disclosure is intended to encompass combinations of the features of the embodiments other than those shown. Furthermore, the described embodiments can also be supplemented by further features of the invention already described.

[0039] In the figures, the same reference symbols designate elements with the same function.

[0040] Fig. 1 shows a motor vehicle 10, which may be a motor vehicle, in particular a passenger car. An electric drive system 11 may be provided in the motor vehicle 10, which may be provided as a purely electric drive for an electric vehicle or as an electrical component of a hybrid drive. To supply the drive system 11 with electrical energy, a battery system 12 may be provided in the motor vehicle 10, which may, for example, provide a high-voltage voltage 13 for the drive system 11. High-voltage voltage 13 is understood here to mean, in particular, an electrical voltage greater than 60 volts.

[0041] To store the electrical energy and to generate the electrical voltage 13, storage units 14 can be installed in the battery system 12, of which Fig. 1, only three storage units 14 are shown as examples. More than 100 storage units can be provided. Ellipses 15 indicate that the technical details explained below can also apply to the other storage units not shown.

[0042] In Fig. 1, the electrical interconnection of the storage units 14 is not shown for the sake of clarity. For data communication for transmitting communication data 16 between the storage units 14 and a central or higher-level battery management system (BMS) as the control circuit 17, radio connections 18 can be provided instead of or instead of wired data transmission. For this purpose, a transceiver circuit 19 can be provided in each of the storage units 14, which can have an antenna 20 in order to receive a radio signal from the control circuit 17 and / or transmit it to the control circuit 17. An antenna 21 can also be provided in the control circuit 17 in order to provide the radio connections 18. A transmitting circuit 22 and a receiving circuit 23 can be interconnected or electrically coupled to the antenna.

[0043] The radio connections 18 of several different storage units 14 can be provided in a common frequency band. To prevent the transceiver circuits 19 from interfering with each other during the transmission of the communication data 16, an individual set of symbols in the form of a spreading code 24 can be stored in each transceiver circuit 19. For a broadcast or multicast communication connection or radio connection, the same spreading code 25 can additionally be stored in several of the transceiver circuits 19, so that all transceiver circuits 19 equipped with the spreading code 25 can simultaneously receive, evaluate, or understand a message from the control circuit 17 transmitted using this spreading code 25. For example, coordinated switching can be triggered in these memory units 14.

[0044] The transceiver circuits 19 can also be configured to establish or operate a respective additional radio connection 26 independently of the control circuit 17 with an external communication circuit 27, for example, a smartphone or a tablet PC. For example, after a crash of the motor vehicle 10, if, for example, the control circuit 17 is damaged, each transceiver circuit 19 can be individually read out using the communication circuit 27 in order to determine the internal state of the battery system 12 based on the transceiver circuits 19 that are still functional.

[0045] Fig.2 illustrates an exemplary embodiment of a storage unit 14. The illustrated storage unit 14 can be configured as a single battery cell, e.g., as a prismatic battery cell. Alternatively, it can be a pouch cell. It shows how the described electrical energy can be stored in a housing 28 in a galvanic cell 29, which can be realized, for example, on the basis of a so-called cell coil. Cell poles or terminals 30 can be provided for electrically contacting the galvanic cell 29, wherein one or more switching elements 31 can be provided for one of the cell poles or one of the terminals 30 in order to switch the electrical current flowing through the storage unit 14 (switchable terminal). A bypass switch can also be provided as a switching element 31'.To control the respective switching element 31, 31', a controller circuit 32 can be provided, which can be based on a microcontroller or an ASIC (application-specific integrated circuit). Measured values, for example, temperature measurements and / or current measurements and / or voltage measurements and / or pressure measurements and / or impedance measurements, can be generated by means of a sensor circuit 33. The transceiver circuit 19 can be provided in the aforementioned manner to transmit the measured values ​​to the control circuit 17. Switching commands for switching at least one switching element 31 and / or the switching element 31' can also be received via the transceiver circuit 19 as part of the communication data 16.

[0046] The control circuit 17 can be the said battery management system or a module management system which can be provided for battery cells connected together to form a battery module.

[0047] The core concept of the idea presented here is based on using wireless communication with code division multiplexing as a bus system. Each battery cell should have its own spreading code, unique within the network, for communication from the cell to the BMS and from the BMS to the cell. To enable the BMS to address multiple cells simultaneously, there can also be a broadcast or one or more multicast channels. By dynamically assigning cells to the multicast channels, it is possible to create dynamic communication groups, for example, to remove defective or unaffected cells from a communication channel. The length of the spreading codes for the code division multiplexing is selected to achieve the best possible ratio of interference immunity to possible user data rate for the respective system.By using code sequences that are as orthogonal as possible, such as Walsh codes, correlation between individual channels is minimized. Dynamic assignment of spreading codes is intended to guarantee information security, similar to the UMTS mobile communications standard.

[0048] The advantages are: a) By using spreading codes, the bandwidth of the transmitted signal is artificially broadened, which improves the EMC properties of the communication system. The longer the spreading codes used, the better the interference immunity of the respective channel. b) Since there is no hard-wired communication medium between the cells, permanent communication errors, such as those caused by cable breakage, are avoided. This behavior increases functional safety in the event of an accident, as the cells can continue to communicate with the BMS over the air. c) Due to the use of code division multiplexing, it is possible for all network nodes to transmit simultaneously. This can dramatically reduce latency, especially when there are a large number of bus nodes, such as when the BMS communicates directly with the individual cells. d) Wireless communication also offers the advantage of making the location of a cell much more flexible. This allows cells to be installed at various points in the vehicle without increasing costs and weight due to a longer bus medium. e) Wireless communication systems typically have the disadvantage that it is easy for hackers to eavesdrop on and manipulate communications. Using dynamic spreading codes that change cyclically can make eavesdropping and manipulating communications in real time significantly more difficult, even impossible. f) In contrast to wireless communication systems based on frequency division multiplexing, code division multiplexing allows network participants to transmit at the same transmission frequency. This allows all cells to be equipped with the same communication hardware, which significantly simplifies production and management.

[0049] Each cell can be equipped with an antenna that supports the network's transmission frequency. For point-to-point communication between the BMS and the cell, each cell manages a spreading code or code sequence for receiving data from the BMS and a spreading code or code sequence for sending data to the BMS. Depending on the number of broadcast and multicast channels, additional code sequences are also stored on the cells. In contrast to the cells, the BMS must be far more complex and must manage all the spreading codes used in the network and assign new code sequences to the cells as needed. The transmitted data of a channel can be extracted by correlating the received signal with the respective code sequence of a channel. This can be done using a digital signal processor or a CDMA ASIC, for example.

[0050] Thus, a code multiplex access method is used within a battery system, rather than frequency and time division multiplexing. This means that the BMS communicates directly with the battery modules or directly with the battery cells using code multiplexing.

[0051] Overall, the examples show how the invention can provide code-multiplex-based intra-vehicle communication for the electric drive train of a motor vehicle.

Claims

[1] Battery system (12) with a plurality of self-switching electrical storage units (14), each having a transceiver circuit (19) which is designed to exchange communication data (16) containing switching commands from the control circuit (17) and / or measured values ​​from the storage unit (14) via a respective individual radio connection (16) with a common higher-level control circuit (17), characterized bythat an individual spreading code (24) is provided in the respective transceiver circuit (19) for operating the individual radio connection (16), and the spreading codes (24) of all transceiver circuits (19) are designed orthogonally to one another according to a code division multiplexing method, and in some or all of the transceiver circuits (19) at least one common multicast spreading code (25) is additionally provided for a respective common multicast radio connection to the control circuit (17), wherein an allocation of the respective spreading code (24, 25) for the individual and / or for at least one common radio connection (16) to the respective transceiver circuits (19) takes place dynamically, and for this purpose a) the control circuit (17) is designed to transmit a respective new spreading code (24, 25) to be used in the future via the respective individual radio connection (16) to the respective transceiver circuit (19), and / or b) the respective transceiver circuit (19) is configured to determine the new spreading code (24, 25) to be used in the future itself on the basis of at least one memory unit-specific reference value. [2] Battery system (12) according to claim 1, wherein the control circuit (17) is configured to send communication data (16) which trigger a coordinated operation of these storage units (14) via the multicast radio connection (16) to the storage units (14) whose transceiver circuit (19) has the common multicast spreading code (25). [3] Battery system (12) according to one of the preceding claims, wherein a receiver unit (23) of the control circuit (17) is configured to simultaneously receive communication data (16) from the transceiver circuits (19) of a plurality of storage units (14) via a plurality of the individual radio connections (16). [4] Battery system (12) according to one of the preceding claims, wherein in at least some of the transceiver circuits (19) the dynamic allocation of new spreading codes (24, 25) is repeated cyclically during operation of the battery system (12). [5] Battery system (12) according to one of the preceding claims, wherein the transceiver circuits (19) are identical in construction and each have a memory unit with a volatile data memory and / or a non-volatile data memory and the respective transceiver circuit (19) is configured to store the respective spreading code (24, 25) of at least the respective individual radio connection (16) in the memory unit. [6] Battery system (12) according to one of the preceding claims, wherein the respective transceiver circuit (19) is galvanically isolated from a ground potential of the battery system (12) and is connected to electrical terminals (30) of its own storage unit (14) for a voltage supply. [7] Battery system (12) according to one of the preceding claims, wherein the common control circuit (17) is designed as a module management system of a battery module of the battery system (12) or as a battery management system (BMS) and the storage units (14) are individual battery cells of the battery system (12) or each a battery module with some battery cells of the battery system (12). [8] Battery system (12) according to one of the preceding claims, wherein the respective transceiver circuit (19) is configured to operate, independently of the control circuit (17), a further radio connection (26) with a communication circuit (27) arranged outside the battery system (12) and to determine measurement data, in particular temperature measurement data, by means of a sensor circuit (33) of the respective storage unit (14) and to transmit them to the communication circuit (27) via the further radio connection (26). [9] Motor vehicle (10) with an electric drive (11) coupled to a battery system (12) according to one of the preceding claims. [10] Method for operating a battery system (12) according to one of claims 1 to 8, wherein in the battery system (12) a plurality of self-switching electrical storage units (14) each have a transceiver circuit (19) which exchanges communication data (16) containing switching commands from the control circuit (17) and / or measured values ​​from the storage unit (14) via a respective individual radio connection (16) with a common higher-level control circuit (17), characterized by , that in the respective transceiver circuit (19) for operating the individual radio connection (16), an individual spreading code (24) is provided, and the spreading codes (24) of all transceiver circuits (19) are designed orthogonally to one another according to a code division multiplexing method, and in some or all of the transceiver circuits (19), at least one common multicast spreading code (25) is additionally provided for a respective common multicast radio connection to the control circuit (17), wherein an allocation of the respective spreading code (24, 25) for the individual and / or for at least one common radio connection (16) to the respective transceiver circuits (19) takes place dynamically, and for this purpose a) the control circuit (17) transmits a respective new spreading code (24, 25) to be used in the future via the respective individual radio connection (16) to the respective transceiver circuit (19), and / or b) the respective transceiver circuit (19) determines the new spreading code (24, 25) to be used in the future on the basis of at least one memory unit-specific reference value.

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