Battery management system for an electric battery, as well as methods for monitoring the operation of an electric battery

Abstract

The invention relates to a battery management system (20) for monitoring the operation of an electric battery (10) formed from electrically interconnected battery cells (12), comprising several cell monitoring units (30) and a control unit (40), wherein the cell monitoring units (30) are each configured to generate a data packet regarding an operating state of the associated battery cells (12), wherein the control unit (40) is configured to evaluate the data packets generated by the cell monitoring units (30), and wherein the cell monitoring units (30) and the control unit (40) are each equipped with a radio device (36, 46) and are configured to carry out data transmission by means of the radio devices (36, 46), by means of which the data packets generated by the cell monitoring units (30) are transmitted from the cell monitoring units (30) to the control unit (40).To enable particularly reliable and rapid transmission of the data packets, the invention provides for at least one of the cell monitoring units (30) to transmit the data packet generated by that cell monitoring unit (30) in a first step to another cell monitoring unit (30) and, in a subsequent second step, from that cell monitoring unit (30) to the control unit (40). The invention further relates to a corresponding method for monitoring the operation of an electric battery (10).

Description

[0001] The present invention relates to the technical field of monitoring the operation of an electric battery formed from electrically interconnected battery cells, and in particular to a battery management system for monitoring the operation of such an electric battery according to the preamble of claim 1, as well as a corresponding monitoring method.

[0002] The battery may in particular be, for example, a battery used as an energy storage device in an electric or hybrid vehicle, or a battery module of such an energy storage device (which has several such battery modules).

[0003] Such a battery management system, hereinafter also referred to as “BMS”, comprises a plurality of cell monitoring units which can be arranged distributed over the battery and each of which can be electrically connected to associated battery cells, and a control unit, wherein the cell monitoring units are each designed to monitor at least one operating parameter (e.g. cell voltage(s), cell temperature(s), etc.) of the assigned battery cells and to generate therefrom a data packet relating to an operating state of the assigned battery cells, wherein the control unit is designed to evaluate the data packets generated by the cell monitoring units, and wherein the cell monitoring units and the control unit are further each equipped with a radio device and are designed to carry out a data transmission with the aid of the radio devices in accordance with a data transmission algorithm, by means of which the data packets generated by the cell monitoring units are transmitted from the cell monitoring units to the control unit.

[0004] Data transmission in current battery management systems of this type is mostly based on the Bluetooth standard or IEEE802.15.4 derivatives.

[0005] With regard to the wireless transmission of data packets, battery management systems of the type of interest here are also referred to as “wBMS” (for “wireless” BMS).

[0006] Particularly in the automotive sector, it has proven problematic for such wBMS that the fulfillment of requirements, for example with regard to data rates, node latency times and download and upload throughput, for the wireless connection of the cell monitoring units to the control unit (“wBMS central module”) is already reaching its limits in view of the increasing size of batteries.

[0007] In particular, when using electric batteries for larger cars (e.g. SUVs) and commercial vehicles (e.g. trucks), an increasing number of battery cells and thus an increasing number of required cell monitoring units (“wBMS modules”) per battery management system can be expected in the future.

[0008] While cell monitoring units or the electronic components implementing them ("BMS ICs") could be used with a higher number of detection channels and thus a higher number of battery cells monitored, this would lead to correspondingly larger data set sizes for the wirelessly transmitted data packets and thus, disadvantageously, to increased time required to transmit the data packets to the control unit.

[0009] Another problem is that, due to the design of the cell monitoring units, which are usually installed in complex, metallic structures or reflection spaces, there are often significant differences in the radio connection quality between the control unit (e.g. as a "master unit") on the one hand and the cell monitoring units (e.g. as "slave units") on the other hand.

[0010] Cell monitoring units located at a relatively large distance from the associated control unit and / or in an unfavorable installation position, e.g., beyond a double battery layer, generally have significantly worse link budgets and lower RSSI values ​​(keyword: "unreachable node"). In this context, the current state of the art presents a multitude of problems, such as interference effects, shadowing, detuning, multipath fading, etc., that hinder fast and reliable data transmission.

[0011] It is therefore an object of the present invention to show a novel way of monitoring the operation of an electric battery formed from electrically interconnected battery cells, with which the problem explained above is alleviated and thus in particular a reliable and yet rapid transmission of the data packets from the cell monitoring units to the control unit can be realized.

[0012] DE 10 2021 005 087 A1 discloses a method for monitoring a traction battery for an electrically powered vehicle, wherein a plurality of slave controllers each measure cell voltages of a number of battery cells of the traction battery, wherein the slave controllers each wirelessly determine data comprising the cell voltages, a maximum cell voltage, a minimum cell voltage and an error status bit and transmit them to a master controller.

[0013] DE 10 2020 103 480 A1 discloses a battery system with a plurality of self-switching electrical storage units, each having a transceiver circuit configured to exchange communication data containing switching commands from the control circuit and / or measured values ​​from the storage unit via a respective individual radio connection with a common higher-level control circuit. 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. 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.

[0014] DE 10 2009 040 663 A1 discloses a device for monitoring an energy storage device having at least one energy cell from which at least one operating parameter can be read via an electronic unit, wherein the operating parameter can be transmitted to a central unit. According to the invention, the central unit is galvanically isolated from the electronic unit, whose power supply is provided via the energy storage device.

[0015] According to the first aspect of the invention, this object is achieved in a battery management system of the type mentioned at the outset in that, according to the data transmission algorithm for at least one of the cell monitoring units, it is provided that the data packet generated by this cell monitoring unit is first transmitted in a first step to another of the cell monitoring units, hereinafter also referred to as a forwarding unit, and then in a second step is transmitted from the respective forwarding unit to the control unit.

[0016] With such a “forwarding transmission” with the aforementioned first and second steps, data packets can be reliably transmitted to the control unit even if the cell monitoring units in question (which generate the data packets in question) are located relatively far away from the control unit or their radio connection quality is impaired for other reasons such as shadowing, etc.

[0017] The invention can thus advantageously mitigate the problems and limitations of wireless transmission technology described above and, in particular, provide a battery management system which, for example, when used to monitor a battery (traction battery) used as an energy storage device or as a component of such an energy storage device in an electric or hybrid vehicle, particularly meets the requirements therein due to the higher throughput and yet reliable data transmission.

[0018] In one embodiment of the invention, the electric battery has an energy storage capacity of at least 10 kWh, in particular at least 20 kWh.

[0019] In one embodiment of the forwarding transmission provided by the invention, in the second step, the relevant data packet is transmitted directly from the relevant forwarding unit to the control unit, i.e., without the interposition of another of the cell monitoring units as a "further forwarding unit." However, as an alternative to this, a multi-stage forwarding transmission could also be provided within the scope of the invention, in which, in the second step, the data packet is first transmitted from the relevant forwarding unit to another of the cell monitoring units (further forwarding unit), and then, in a third step, is transmitted (e.g., directly) from the latter cell monitoring unit to the control unit.

[0020] In one embodiment of the data transmission algorithm, the forwarding transmission with said first and second steps is provided for at least 10%, in particular at least 20%, of the cell monitoring units.

[0021] In contrast, the data packets generated by the remaining cell monitoring units, which may, for example, be cell monitoring units located relatively close to the control unit (geometrically and / or in terms of radio technology), can be transmitted directly to the control unit in one step. In one embodiment of the invention, according to the data transmission algorithm, such direct transmission is provided for at least 10%, in particular at least 20%, of the cell monitoring units.

[0022] In one embodiment of the data transmission algorithm, there is a predetermined fixed assignment between, on the one hand, those cell monitoring units for which the forwarding transmission with the said first and second steps is provided, and, on the other hand, the forwarding units used for this purpose.

[0023] In other words, in this embodiment of the invention, the “transmission path” up to the control unit is clearly and permanently specified for each generated data packet.

[0024] In one embodiment of the data transmission algorithm, each forwarding unit transmits the data packet received in the first step to the control unit in the subsequent second step together with the data packet generated by the forwarding unit itself.

[0025] In this case, the forwarding unit can, for example, be designed to combine the data packet it has generated itself with the data packet received in the first step for forwarding in order to generate a “combined data packet” that contains the information from both data packets and to transmit it to the control unit in the second step (either directly to the control unit or initially to another cell monitoring unit acting as a further forwarding unit).

[0026] In one embodiment of the data transmission algorithm, it is provided that, within the scope of the data transmission, a radio transmission of a data packet by a cell monitoring unit, hereinafter also referred to as uplink, is triggered in each case by a radio reception of a corresponding request (“polling”), wherein a radio transmission of the request, hereinafter also referred to as downlink, is preferably carried out by the unit intended as the receiver of the data packet.

[0027] In one embodiment of the data transmission algorithm, it is provided that the data transmission is repeated regularly, in particular, for example, periodically, wherein the individual data transmissions are each triggered by a downlink of the control unit, and wherein in the individual data transmissions all downlinks and uplinks each take place according to a transmission data frame with several fixed, consecutive time windows (time phases).

[0028] In a particularly advantageous embodiment, it is provided that the transmission data frame for the downlinks and uplinks in the individual data transmissions also provides several different predetermined radio carrier frequencies.

[0029] The transmission data frame can in particular, for example, provide a first time window in which the control unit transmits the triggering downlink on a predetermined first radio carrier frequency (first “radio frequency channel”), hereinafter also referred to as the “main frequency”, and the cell monitoring units addressed thereby according to the data transmission algorithm receive this downlink.

[0030] The transmission data frame can further provide a plurality of further time windows (second time window, third time window, etc.) following sequentially after the first time window, in which a portion of the addressed cell monitoring units responds to the downlink with an uplink to the control unit in order to transmit the data packet generated by the respective cell monitoring unit directly to the control unit with each such uplink.

[0031] Through another part of the addressed cell monitoring units, namely the one or more cell monitoring units acting as forwarding units, downlinks can initially be made in the further time windows in order to trigger a subsequent radio transmission (uplink) of those data packets which, after their reception, are then transmitted by these forwarding units in the further time windows by radio transmission (uplink), directly or indirectly, to the control unit.

[0032] In these further time windows, the above-mentioned forwarding transmission with the said first and second steps can be provided in particular, for example, such that the first step takes place in a specific one of the further time windows and the second step takes place in the immediately following time window.

[0033] In one embodiment of the invention, the radio devices of the battery management system are operated with radio carrier frequencies in a sub-GHz range (ie, less than 1 GHz).

[0034] According to a further aspect of the present invention, the object mentioned above is achieved by an electric battery formed from electrically interconnected battery cells, which is equipped with a battery management system of the type described here for monitoring the operation of the electric battery. Such an electric battery can, in particular, form, for example, an energy storage device, or a component of such an energy storage device, in an electric or hybrid vehicle.

[0035] According to a further aspect of the present invention, the object set out at the outset is achieved by a method for monitoring the operation of an electric battery formed from electrically interconnected battery cells, wherein the electric battery is equipped with a battery management system comprising a plurality of cell monitoring units distributed over the battery and each electrically connected to associated battery cells, and a control unit, and wherein the method comprises the following steps: - detecting, by means of the cell monitoring units, at least one operating parameter (e.g. cell voltage(s) and / or cell temperature(s) etc.) of the assigned battery cells, and generating a data packet relating to an operating state of the assigned battery cells from the at least one detected operating parameter by means of the cell monitoring units, - Evaluation of the data packets generated by the cell monitoring units by means of the control unit, - Carrying out a data transmission according to a data transmission algorithm, by means of which the data packets generated by the cell monitoring units are transmitted from the cell monitoring units to the control unit, with the aid of radio devices with which the cell monitoring units and the control unit are equipped, wherein according to the data transmission algorithm for at least one of the cell monitoring units the data packet generated by this cell monitoring unit is first transmitted in a first step to another of the cell monitoring units, hereinafter referred to as forwarding unit, and then in a second step is transmitted from the respective forwarding unit to the control unit.

[0036] The embodiments and special configurations described here for the battery management system according to the invention can, individually or in any combination, also be provided in an analogous manner as embodiments or special configurations of the method according to the invention, and vice versa.

[0037] In one embodiment of the invention, the radio device of the control unit is formed from a plurality of radio transmitting and receiving units (transceiver units) that can be controlled independently of one another by the control device of the control unit during operation of the BMS. The data transmission algorithm provides that, during data transmission, the plurality of radio transmitting and receiving units are operated simultaneously, at least temporarily, and at different radio carrier frequencies. During data transmission, a transmission data frame can provide one or more time windows in which, in parallel but on different radio carrier frequencies, a plurality of uplinks from different cell monitoring units and / or a plurality of downlinks from different units (control unit and cell monitoring units) occur.

[0038] According to a further aspect of the present invention, a computer program product comprising a program code is proposed which, when executed on a data processing device, carries out a method for monitoring the operation of an electric battery of the type described here, formed from electrically interconnected battery cells.

[0039] Such program code can advantageously be used in a battery management system of the type described here to control the operation of the cell monitoring units and the control unit, so that the battery management system carries out the monitoring method. These units can each comprise, for example, a program-controlled computer device (e.g., a microcontroller) with an associated memory device for storing program code.

[0040] According to a further aspect of the present invention, the use of a battery management system of the type described here and / or a method of the type described here is proposed for monitoring the operation of an electric battery arranged as an energy storage device in a vehicle (e.g., an electric or hybrid vehicle). The battery can, for example, form an electrical energy storage device intended for supplying energy to an electric drive of the vehicle, or, for example, one of several (e.g., identically designed) battery modules of such an electrical energy storage device.

[0041] The invention will be further described below using exemplary embodiments with reference to the accompanying drawings. They schematically depict: Fig. 1 an electric battery formed from electrically interconnected battery cells and equipped with a battery management system according to a first embodiment, Fig. 2 a data transmission within the battery management system of Fig. 1 usable transmission data frame according to a concept known from the prior art, Fig. 3 a configuration of cell monitoring units and a control unit as a comparative example, Fig. 4 the data transfer in the comparison example of Fig. 3 used transmission data frames according to the concept known from the prior art, Fig. 5 a configuration in one of the Fig. 3 corresponding representation according to a first embodiment of the invention, Fig. 6 the data transfer according to the example of Fig. 5 used transmission data frames, Fig. 7 a configuration in one of the Fig. 3 corresponding representation according to a second embodiment of the invention, Fig. 8 the data transfer according to the example of Fig. 7 used transmission data frames, Fig. 9 a configuration in one of the Fig. 3 corresponding representation according to a third embodiment of the invention, Fig. 10 the data transfer according to the example of Fig. 9 used transmission data frames, and Fig. 11 an electric battery equipped with a battery management system according to a second embodiment.

[0042] Fig. 1 shows a first embodiment of an electric battery 10, which is provided for supplying energy to an electric drive system of a vehicle such as a battery electric vehicle (BEV) or a hybrid electric vehicle (HEV).

[0043] For storing electrical energy, the electric battery 10 has a plurality of electrically interconnected rechargeable battery cells 12, which in the example shown are electrochemical battery cells 12 such as lithium-ion cells.

[0044] The electric battery 10 can as such form an electrical energy storage device of the vehicle intended for the said energy supply, or merely one of several “battery modules” of an electrical energy storage device of the vehicle, which, for example, can comprise several battery modules of the type described in Fig. 1 shown type.

[0045] In Fig. 1 shows an example of a serial connection of several battery cells 12. Such a serial connection advantageously enables the realization of the electric battery 10 with a battery voltage that is many times higher than the voltage of the individual battery cells 12. Although in Fig. 1 not shown for the sake of simplicity of illustration, in the case of the battery 10 or in the case of an electrical energy storage device formed using the battery 10, a parallel connection of several battery cells 12 and / or parallel connection of several series-connected battery cells 12 is also expedient in order to increase the storage capacity as well as the load capacity with regard to charging or discharging of the battery 10 or the energy storage device formed thereby.

[0046] Particularly due to the use of the battery 10 in the vehicle sector (e.g., on board a BEV or HEV), the highest possible energy density of the energy storage is advantageous in order to achieve a long range for the vehicle. However, with increasing energy density, the importance of so-called "battery management" also increases, particularly for the purpose of monitoring and thus hazard prevention in connection with, for example, overvoltage and overtemperature. Electrical energy storage systems in the BEV / HEV sector can comprise one or more batteries, such as those in Fig. 1 and have nominal battery voltages typically between 400 V and 800 V.

[0047] The electric battery 10 is equipped with a battery management system (BMS) 20 for monitoring the operation of the electric battery 10, which comprises a plurality of cell monitoring units 30-1, 30-2, 30-3 and 30-4, which are distributed over the battery 10 and are each electrically connected to associated battery cells 12, and a control unit 40.

[0048] The BMS 20 includes in the example of Fig. 1 shows the four cell monitoring units 30-1, 30-2, 30-3, and 30-4. Deviating from this example, more or fewer cell monitoring units could also be provided. Individual cell monitoring units or the entire cell monitoring units are also referred to below by the reference number "30."

[0049] The cell monitoring units 30 are each designed to detect at least one operating parameter (e.g. cell voltage(s) and cell temperature(s), etc.) of the associated battery cells 12 and to generate therefrom a data packet relating to an operating state of the associated battery cells 12.

[0050] In the schematic representation of the Fig. 1, for the sake of simplicity of illustration, only two battery cells 12 are assigned to each cell monitoring unit 30, whereas in practice the number of assigned battery cells 12 per cell monitoring unit 30 can actually be considerably larger and can, for example, be in the range of 10-20.

[0051] The control unit 40 is designed to receive and evaluate the data packets generated by the cell monitoring units 30 and can be communicatively connected, for example, via a data bus system (not shown), to a higher-level control device of the battery 10 and / or the vehicle (e.g., the vehicle's central control unit). In this case, for example, information from the received data packets and / or information derived therefrom (concerning the battery status) can be communicated from the control unit 40 to the relevant higher-level control device.

[0052] The cell monitoring units 30 and the control unit 40 are each equipped with a radio device 38 (cell monitoring units 30) or 48 (control unit 40) and are configured to carry out data transmission using these radio devices 38, 48, by which the data packets generated by the cell monitoring units 30 are wirelessly transmitted from the cell monitoring units 30 to the control unit 40. In the example, the radio devices 38, 48 are each configured as radio transmitting and receiving devices ("transceivers") in order to be able to both transmit and receive radio transmissions and operate according to a predetermined transmission algorithm or "transmission protocol."

[0053] In the example shown, the cell monitoring units 30 use a respective detection device 32 to detect as operating parameters at least all cell voltages of the associated battery cells 12 as well as one or more temperatures in the region of these battery cells 12.

[0054] Each detection device 32 has at least one voltage measuring device for this purpose in order to Fig. 1 to effect a measurement of the respective cell voltages to the associated battery cells 12, and also at least one temperature measuring device to effect a measurement of the respective temperature(s).

[0055] In the illustrated embodiment, each cell monitoring unit 30 further comprises a respective balancing device 34, by means of which the respective cell monitoring unit 30, via the Fig. 1 visible electrical connections to the assigned battery cells 12, a so-called “balancing” (charge state equalization) of the respectively assigned battery cells 12 is accomplished.

[0056] In this respect, and generally advantageous within the scope of the invention, the BMS 20 in this example not only monitors the operation of the electric battery 10 in the narrower sense, but also controls or regulates this operation. In addition to the aforementioned balancing, this operational control could also include, for example, deactivating individual or multiple battery cells 12 (by bridging them) in the event of a fault. In energy storage systems of the type of interest here, various fault events can occur in the area of ​​the arrangement of the battery cells 12. These include, for example, defects in individual battery cells, be it due to aging phenomena and / or due to thermal or mechanical influences (e.g. in the event of an accident involving a vehicle in which the battery 10 is installed).

[0057] Furthermore, each cell monitoring unit 30 comprises a program-controlled control device 36 for controlling the operation of the detection device 32 and the balancing device 34 according to a control program running for this purpose in the control device 36.

[0058] The program-controlled control device 36 further serves to generate the data packet (data set) relating to an operating state of the respective assigned battery cells 12, which is calculated by the control device 36 based on the recorded operating parameters. Each such data packet contains (digitally coded) information about the current operating state of the respective battery cells 12. For this purpose, raw data from the recording, in the example, for example, measured values ​​of the cell voltages and / or the temperature(s), can be provided as data elements of the data packet. Alternatively or additionally, each data packet can advantageously also contain data elements relating to a parameter derived from the said raw data (and calculated for this purpose by the control device 36). Such a parameter can be, for example,a parameter relating to the state of charge such as the so-called “State of Charge” (SOC) and / or a parameter relating to the (current) storage capacity such as the so-called “State of Health” (SOH) of the battery cells 12 in question.

[0059] In particular, based on such preprocessing of the acquired raw data by the control device 36, the generated data packets can alternatively or additionally, in the case of an abnormal operating state of the associated battery cells 12, for example, also contain a corresponding error message, which is thus communicated to the control unit 40.

[0060] The control device 36 also controls the operation of the radio device 38 of the relevant cell monitoring unit 30, i.e., for example, a transmitting operation or receiving operation is controlled and, if necessary, a radio carrier frequency provided for this purpose is specified.

[0061] The control unit 40 in turn comprises a program-controlled control device 46 which controls the operation of the aforementioned radio device 48 (e.g. control of transmission mode or reception mode, specification of the radio carrier frequency).

[0062] The data transmission carried out with the aid of the radio devices 38, 48 (i.e., transmission of the data packets generated by the cell monitoring units 30 to the control unit 40) is controlled by the control devices 36, 46 according to a data transmission algorithm. The data transmission algorithm is defined by the program code executing in the control devices 36, 46.

[0063] The basic concept of the BMS 20 with the cell monitoring units 30 and the control unit 40, as described up to this point, is summarized again as follows: A primary task of each cell monitoring unit 30 is the measurement (e.g., periodic) of cell voltages, temperatures, and possibly other operating parameters. These operating parameters and / or information derived therefrom (e.g., calculated) are encoded into corresponding data packets by the control devices 36 and communicated wirelessly to the control unit 40 (also referred to as the "BMS central control unit") via the radio devices 38, 48.The control unit 40 can also perform, for example, "State of Charge" (SOC) and / or "State of Health" (SOH) calculations relating to the battery cells 12 as part of the evaluation of the data packets, provided this is not already done by the respective cell monitoring units 30 as part of their (pre)processing of the recorded operating parameters and corresponding information is encoded into the data packets. The wireless data transfer of the data packets can achieve significant savings in cabling, connectors, and, in particular, in the galvanic isolation of the components.

[0064] Fig. 2 shows a first example of a data transmission within the BMS 20 of Fig. 1, i.e., the transmission of the data packets generated by the cell monitoring units 30 to the control unit 40, according to an exemplary embodiment not according to the invention. In the prior art of such wirelessly transmitting battery management systems ("wBMS"), a standard protocol such as "Bluetooth" or a proprietary protocol is used for the required radio data transmission.

[0065] The transmission data frame 50 is defined by the aforementioned data transmission algorithm and, in turn, defines a specific temporal sequence of individual radio connections or radio transmissions for implementing a data transmission that is repeated periodically during operation of the BMS 20. The data frame 50 therefore refers to a single such data transmission.

[0066] In the example, these are radio transmissions “M⇩”, “S1⇧”, “S2⇧”, “S3⇧” and “S4⇧” on a specific radio carrier frequency (radio frequency channel), which take place in this order in five consecutive time slots in the data frame 50 and have the following meaning: M⇩ Radio transmission of a request by the control unit 40; S1⇧ Radio transmission of a data packet by the cell monitoring unit 30-1 to the control unit 40; S2⇧ Radio transmission of a data packet by the cell monitoring unit 30-2 to the control unit 40; S3⇧ Radio transmission of a data packet by the cell monitoring unit 30-3 to the control unit 40; S4⇧ Radio transmission of a data packet by the cell monitoring unit 30-4 to the control unit 40.

[0067] The symbol "⇩" indicates a so-called "downlink" and the symbol "⇧" a so-called "uplink". During data transmission according to transmission data frame 50 ( Fig. 2) For all cell monitoring units 30, the radio transmission of the data packet by the respective cell monitoring unit 30 (uplink S1⇧, S2⇧, S3⇧ or S4⇧) is triggered by a radio reception of the request (downlink M⇩) sent once per transmission data frame 50 by the control unit 40.

[0068] Thus, there is a hierarchical management of radio communication or radio transmissions on a shared radio frequency channel according to a master-slave concept, which is why the control unit 40 is also referred to below as "master unit" or "master node" and the cell monitoring units 30 are also referred to below as "slave units" or "slave nodes".

[0069] The downlink sent by the control unit 40 (master node) also has the function of signaling the start of the transmission data frame 50 and thus synchronizing the timing of the subsequent time windows in the transmission data frame 50 for the cell monitoring units 30 (slave nodes).

[0070] A specific radio carrier frequency (radio carrier channel) is provided for all radio transmissions M⇩, S1⇧, S2⇧, S3⇧ and S4⇧ within the duration of a transmission data frame 50, whereby, with regard to the periodic repetition of the data transmission provided for in the example, this frequency can also be changed from data transmission to data transmission (channel change), provided that the data transmission algorithm provides for this.

[0071] In order to be able to carry out such channel changes, the radio devices 38, 48 in question must be designed in such a way that they can each be controlled for transmission and reception on several different radio carrier frequencies.

[0072] Particularly when used for electric batteries for use in the automotive sector, e.g. for larger passenger cars and commercial vehicles, the above-mentioned Fig. 1 and Fig. 2 has certain limits with regard to the required performance and reliability. Depending on the specific installation situation of the units 30, 40 in the electric battery 10, there can be significant differences in the quality of the radio connection between the control unit 40 (master node) and the cell monitoring units 30 (slave nodes). With cell monitoring units 30 that are a large distance from the control unit 40 or in a very unfavorable installation position, interference can often occur. This applies in particular to usage situations in which the general "EMC problem" with regard to nearby radio transmitters plays a role. When used on board a vehicle, possible sources of interference include other wireless communication systems (e.g. Bluetooth, WiFi, mobile communications, etc.) as well as clocked inverters, DC / DC converters, etc.

[0073] With regard to this problem, a significant improvement can be achieved with the present invention. Three exemplary embodiments are described below with reference to the Fig. 5 to 10 explained.

[0074] First, however, with reference to the Fig. 3 and Fig. 4 shows another embodiment example which serves as a realistic “comparative example” in the following, according to the concept known from the prior art (cf. Fig. 2) is shown.

[0075] In the following description of further exemplary embodiments, the same reference numerals are used for components with equivalent functions. In doing so, only the differences from the previously described exemplary embodiment(s) are discussed, and otherwise, explicit reference is hereby made to the description of previous exemplary embodiments.

[0076] Fig. 3 shows, as a comparative example, a configuration of a BMS 20 with 10 cell monitoring units 30-1, 30-2, ...30-10 and a control unit 40, and Fig. 4 shows the associated transmission data frame 50 used in a data transmission according to this example.

[0077] Just like in the previous example of Fig. 2, a new data transmission cycle is also initiated here in a time-division multiplexing process by a "master downlink," the radio transmission M⇩, which contains a corresponding request (command) for all cell monitoring units 30-1, 30-2, ...30-10. These communicatively connected units (e.g., "paired nodes" according to a Bluetooth standard) respond in a fixed time grid of, for example, 2 ms (duration of the individual time windows) with the corresponding response radio transmissions, the "slave uplinks" S1⇧, S2⇧, ..., S9⇧, and S10⇧.

[0078] Assuming no transmission errors occur, 20 ms after the start command (radio transmission M⇩) all 10 response data from all slave nodes (data packets from units 30-1, 30-2, ...30-10) would be at the master node (control unit 40): M⇩ Radio transmission of a request by the control unit 40; S1⇧ Radio transmission of a data packet by the cell monitoring unit 30-1 to the control unit 40; S2⇧ Radio transmission of a data packet by the cell monitoring unit 30-2 to the control unit 40; S9⇧ Radio transmission of a data packet by the cell monitoring unit 30-9 to the control unit 40; S10⇧ Radio transmission of a data packet by the cell monitoring unit 30-10 to the control unit 40.

[0079] In summary, the transmission data frame 50 comprises a total of 11 consecutive time windows, with the last 10 time windows, each of 2 ms in duration in the example, resulting in a “transmission time duration” of 20 ms.

[0080] In this comparison example with a master node and 10 slave nodes, the radio transmissions in transmission data frame 50 occur on a radio carrier frequency known to the master node and the 10 slave nodes, e.g., a frequency that changes from transmission data frame 50 to transmission data frame 50 according to a so-called "pseudo-random sequence." Both the radio device 48 of the control unit 40 (master node) and the radio devices 38 of the cell monitoring units 30 (slave nodes) are inactive for most of the duration of the transmission data frame 50.

[0081] A frequency channel change can occur with each transmission data frame 50, i.e., the downlink M⇩ and the resulting uplinks S1⇧, S2⇧, ..., S9⇧, and S10⇧ within one and the same transmission data frame 50 all occur on a shared radio carrier frequency. This frequency (channel) can be changed for the subsequent transmission data frame 50. The resulting channel change frequency is significantly lower compared to that in typical Bluetooth FHSS systems (typically 600 µs) or IEEE802.15.4 TSCH systems (where the frequency changes in every time slot).

[0082] Fig. 5 shows an embodiment of the invention of a configuration of 10 cell monitoring units 30-1, 30-2, ...30-10 and a control unit 40, and Fig. 6 shows the transmission data frame 50 used in the data transmission according to this example of the invention. In operation of the BMS 20, as in the comparative example ( Fig. 4) a periodically repeated data transfer can be carried out.

[0083] A special feature of this embodiment is that, according to a data transmission algorithm modified compared to the above comparative example, for several of the cell monitoring units 30, in the example these are the four cell monitoring units 30-7, 30-8, 30-9 and 30-10, it is provided that the data packets generated by these cell monitoring units are first transmitted in a first step to a respective other one of the cell monitoring units 30.

[0084] In the example, these are the 4 cell monitoring units 30-3, 30-4, 30-5 and 30-6, which are therefore also referred to as “forwarding units” below.

[0085] Only in a second step are the data packets received in the first step by the cell monitoring units 30-3, 30-4, 30-5 and 30-6 (forwarding units) transmitted by these cell monitoring units 30-3, 30-4, 30-5 and 30-6 to the control unit 40.

[0086] The concrete implementation of this feature is shown in Fig. 6, which provides a total of 7 consecutive time slots with the following radio transmissions: 1. Time slot M⇩ downlink by unit 40 (request to units 30-1, 30-2, ..., 30-6); 2. Time slots S1⇧, R1⇩, R2⇩, R3⇩, R4⇩: uplink through unit 30-1 (to unit 40) and simultaneous downlinks through units 30-3, 30-4, 30-5 and 30-6 (to units 30-7, 30-8, 30-9 and 30-10); 3. Time slots S2⇧, S3⇧, S4⇧, S5⇧, S6⇧: Uplink through unit 30-2 (to unit 40) and simultaneous uplinks through units 30-7, 30-8, 30-9 and 30-10 (to units 30-3, 30-4, 30-5 and 30-6); 4. Time slot R1⇧: Uplink through unit 30-3 (to unit 40); 5. Time slot R2⇧: Uplink through unit 30-4 (to unit 40); 6. Time slot R3⇧: Uplink through unit 30-5 (to unit 40); 7. Time slot R4⇧: Uplink through unit 30-6 (to unit 40)

[0087] Each of the cell monitoring units 30-3, 30-4, 30-5 and 30-6 provided as forwarding units in this example forwards not only one data packet (of the cell monitoring units 30-7, 30-8, 30-9 and 30-10) via the uplinks R1⇧, R2⇧, R3⇧, R4⇧, but also an additional self-generated data packet (or a data packet in which the information from both data packets in question is combined) with the same radio transmission.

[0088] In the wBMS 20 according to this embodiment, in addition to the master node (control unit 40) and “normal” slave nodes, i.e. cell monitoring units 30-1, 30-2, 30-7, 30-8, 30-9 and 30-10, there are also the cell monitoring units 30-3, 30-4, 30-5 and 30-6, which are referred to as “relay nodes”, which have both slave functionality with respect to unit 40, since they send their own (self-generated) BMS data packets on request (M⇩) to the master unit (R1⇧, R2⇧, R3⇧, R4⇧), as well as master functionality with respect to the assigned slave units 30-7, 30-8, 30-9 and 30-10, since they request the transmission of their data packets (R1⇩, R2⇩, R3⇩, R4⇩), and after receipt, forward them combined with their own data packets to the master unit (R1⇧, R2⇧, R3⇧, R4⇧).

[0089] During data transmission, the radio transmission (uplink) of a data packet by a cell monitoring unit 30 is triggered by a previous radio reception of a corresponding request, wherein a radio transmission of the request (downlink) is carried out by the unit intended as the receiver of the data packet.

[0090] Within the scope of the invention, the forwarding transmission described above with the first and second steps is preferably provided for at least 10% of the cell monitoring units. In the example shown by Fig. 5 and Fig. 6, the forwarding transmission is provided for 4 of a total of 10 cell monitoring units 30, i.e., 40% of the cell monitoring units 30. As also provided in the example shown, a predetermined, fixed assignment is usually advantageous between, on the one hand, those cell monitoring units 30 for which the forwarding transmission is provided (here: 30-7, 30-8, 30-9, and 30-10), and, on the other hand, the forwarding units used for this purpose (here: 30-3, 30-4, 30-5, and 30-6). In the example, a "direct" transmission of the data from the forwarding units to unit 40 is provided for in the aforementioned second step.

[0091] In a BMS 20 with data transmission according to this exemplary embodiment, a "multi-channel method" is used in that all downlinks and uplinks for the individual data transmissions take place within a specific time window using several different predefined radio carrier frequencies. The simultaneous radio transmissions (i.e., the radio transmissions within a specific time window) take place on different radio carrier frequencies. In the representation of Fig. 6, each “row” corresponds to a specific radio carrier frequency, which is determined by the respective radio carrier frequencies of all other rows in Fig. 6 is different. As can be seen, in the example, a total of 5 different frequencies are used in the transmission data frame 50, although the specific values ​​of these frequencies can be changed from data transmission to data transmission, ie after each individual transmission data frame 50 (channel change).

[0092] Numerous advantages arise compared to the wBMS known from the prior art. The wBMS or monitoring method according to the invention can, in many cases, be implemented particularly simply and thus advantageously by means of a firmware change concerning the program code running in known chipsets for implementing the units 30, 40 (or the RF modules).

[0093] In the example shown, the Fig. 5, two slave nodes (units 30-1 and 30-2) and an additional four relay nodes (units 30-3, 30-4, 30-5, 30-6) are directly communicatively connected to the master node (unit 40). The timing scheme of the transmission data frame 50 consists of a "master broadcast" (M⇩) and the six response radio transmissions S1⇧, S2⇧, R1⇧, R2⇧, R3⇧, R4⇧. The uplink to the master ultimately consists only of the radio transmissions from six participants (units 30-1 to 30-6), which, as in the example, can be provided with a current "master radio carrier frequency" (main frequency) known to these participants (valid within a transmission data frame 50).

[0094] In the example of Fig. 5, each of the forwarding units 30-3, 30-4, 30-5 and 30-6 has exactly one associated (communicatively connected) slave node: Forwarding Unit 30-3: Associated Cell Monitoring Unit 30-7 Forwarding Unit 30-4: Associated Cell Monitoring Unit 30-8 Forwarding Unit 30-5: Associated Cell Monitoring Unit 30-9 Forwarding Unit 30-6: Associated Cell Monitoring Unit 30-10

[0095] As shown in the example (and preferred, but not mandatory), all units 30-3, 30-4, 30-5, 30-6 repeat the "command broadcast" (M⇩) from the master on four different radio carrier frequencies in parallel, in the same time slot (here: 2nd time slot) in which unit 30-1 responds on the main frequency (S1⇧). These "sub-broadcasts," in the example the downlinks R1⇩, R2⇩, R3⇩, R4⇩ of units 30-3, 30-4, 30-5, 30-6, could deviate from the Fig. However, the example shown in Figure 6 can also be staggered in time, ie not all of them necessarily have to take place in the same time window.

[0096] During the time windows in which the forwarding units (here: 30-3, 30-4, 30-5, 30-6) transmit their downlinks, they are inactive with respect to unit 40 and can therefore transmit on a different frequency. Each of the units 30-3, 30-4, 30-5, 30-6 uses its own frequency, which differs from both the main frequency and those of the other units 30-3, 30-4, 30-5, 30-6 (cf. arrangement of the symbols M⇩, S1⇧, etc. in Fig. 6 in different rows). In the simplest case, each of the radio carrier frequencies of the forwarding units 30-3, 30-4, 30-5, 30-6 has an individual, constant distance from the main frequency. However, more complex, associated sequences (e.g., using pseudo-random methods) can also be used, which are known to the communicatively connected units. The requests, which are temporally parallel in the example (occurring in the same time window of the transmission data frame 50), each trigger the generation of the requested data packets by the assigned slave nodes (in the example: units 30-7, 30-8, 30-9, 30-10). The slave nodes are not communicatively connected directly to the master, but only directly to the "relay nodes."

[0097] In the subsequent time window, in which the slave node 30-2 sends its data to the master node (S2⇧), the uplink (S3⇧, S4⇧, S5⇧, S6⇧) of the data packets from the slave nodes (in the example: units 30-7, 30-8, 30-9, 30-10) to the assigned relay nodes (in the example: forwarding units 30-3, 30-4, 30-5, 30-6) takes place in parallel (in the same time window). These transmissions take place on the current radio carrier frequencies for the respective forwarding unit 30-3, 30-4, 30-5, or 30-6.

[0098] In the 4 additional time slots provided in the example shown, the “combined data packets” of the respective relay and assigned slave nodes are uploaded to the master node (R1⇧, R2⇧, R3⇧, R4⇧).

[0099] Doubling the data volume at the relay nodes may require a slight extension of the duration of the relevant time slots. At current physical bit rates and payload lengths, this results in an extension of approximately 0.5 ms.

[0100] Overall, this example results in Fig. 5 nevertheless a significant reduction in the total uplink time of about 30% compared to the comparison example ( Fig. 4).

[0101] A further significant advantage of the invention is the possibility of linking slave nodes that are potentially weakly connected to a master node (e.g., nodes located further away and / or nodes shaded by the installation situation) to the master node by means of relay nodes that are better connected to the master node.

[0102] Another advantage is that increasing the number of channels per transmission data frame from 50, in this example from 1 to 5, more clearly takes into account the basic principle of so-called "Frequency Hopping Spread Spectrum" (FHSS). A narrowband interferer on a radio carrier frequency of a relay node results in far less data loss than interference on the main frequency, which can result in the complete loss of data in the transmission data frame. Furthermore, the shortened duration of the transmission data frames correspondingly reduces channel occupancy.

[0103] Fig. 7 shows in one of the Fig. 3 and 5, respectively, a further embodiment of the invention of a configuration of 10 cell monitoring units 30-1, 30-2, ...30-10 and a control unit 40, and Fig. 8 shows in one of the Fig. 4 or 6, respectively, shows the transmission data frame 50 used in the data transmission according to this example.

[0104] In this embodiment of Fig. 8, the time required for individual data transfers is further reduced by further “clustering” the slave nodes to the relay nodes.

[0105] In contrast to the previous embodiment of Fig. 6 there is in this example of Fig. 8 also relay nodes (here: units 30-4 and 30-5), to which several (here: 2 each) slave nodes are assigned, which reduces the number of relay nodes required and thus advantageously leads both to a reduction in the number of different radio carrier frequencies required in the transmission data frame 50 (in the example: only 4) and to a shortening of the total uplink duration per transmission data frame 50.

[0106] Although a certain adjustment of the time window durations must be taken into account in this example, because in some time windows the data from three data packets must be transmitted, this example nevertheless results in an overall reduction of the total uplink duration of approximately 35% compared to the comparison example ( Fig. 4).

[0107] Fig. 9 shows in a Fig. 3, Fig. 5 and Fig. 7 corresponding representation of yet another embodiment of the invention and Fig. 10 shows in a Fig. 4, Fig. 6 and Fig. 8 corresponding representation of the transmission data frame 50 used in the data transmission.

[0108] This example illustrates an extreme but quite realistic scenario with a configuration of 22 cell monitoring units 30-1, 30-2, ...30-22 and one control unit 40 (for example for use in electric batteries, e.g. in the SUV and truck sector).

[0109] In this example, a clustering of up to 5 slave nodes in association with a relay node is provided, which advantageously results in a reduction of the total uplink duration of up to about 57% compared to the comparison example ( Fig. 4) is possible.

[0110] Fig. 11 shows a further embodiment of an electric battery 1 equipped with a battery management system (BMS) 20. With regard to the structure and function of the electric battery 1 as well as the BMS 20, reference is essentially made to the embodiments already described above.

[0111] A special feature of the example of Fig. 11, however, is that the radio device 48 of the control unit 40 is formed from a plurality of radio transmitting and receiving units (transceiver units) 48-1, 48-2, 48-3, which can be controlled independently of one another by the control device 46 during operation of the BMS 20, wherein the data transmission algorithm used provides that the plurality of radio transmitting and receiving units 48-1, 48-2, 48-3 are operated with different radio carrier frequencies (channels) during data transmission.

[0112] Deviating from the example shown, the control unit 40 could also use more than three, or fewer than three (ie, only two), such radio transmitting and receiving units. The specific values ​​of the several different radio carrier frequencies can be changed from data transmission to data transmission, ie, after each individual transmission data frame 50 (channel change).

[0113] By adding additional transceivers to the master node (control unit 40), the BMS 20 can be advantageously implemented with an even higher number of slave nodes (cell monitoring units 30) and scaled up cost-effectively. The respective master transceiver units can communicate with their respective dedicated slave nodes in parallel on their own channels.

[0114] In the example of Fig. 11, for example, a fixed assignment could be provided as follows: radio transmitting and receiving unit 48-1 communicates with slave unit 30-1; radio transmitting and receiving unit 48-2 communicates with slave unit 30-2; radio transmitting and receiving unit 48-3 communicates with slave units 30-3 and 30-4.

[0115] Within the scope of the invention, the special feature of the multiple radio transmitting and receiving units (48-1, 48-2, 48-3) of the control unit (40) can preferably be used, in particular, to provide one or more time windows during data transmission in the transmission data frame 50, in which multiple uplinks from different slave nodes occur in parallel, but on different channels (radio carrier frequencies). This advantageously allows a further significant reduction in the total uplink duration.

[0116] Another special feature of the example of Fig. 11 is that the radio devices 48, 38 of the control unit 40 and the cell monitoring units 30 are operated at radio carrier frequencies of less than 1 GHz. This allows for low-interference data transmission, for example, with regard to other communication systems (such as Bluetooth, mobile radio, etc.) located nearby during the usage situation, the bandwidth of which is sufficient, particularly due to the inventive communication design using forwarding units.

[0117] For example, the radio transmitting and receiving units 48-1, 48-2, 48-3 in the example of Fig. 11 operate on radio carrier frequencies of 433 MHz, 868 MHz and 915 MHz.

[0118] The aforementioned advantage of a radio carrier frequency in a sub-GHz range also exists to a certain extent for all embodiments already described above, so that this measure is generally interesting within the scope of the invention.

[0119] In summary, the invention enables reliable yet rapid transmission of data packets from the cell monitoring units to the control unit when monitoring the operation of an electric battery formed from electrically interconnected battery cells, which can in particular also be a module of an electrical energy storage system formed from several such batteries. Essential for this is the use of a forwarding method using some of the cell monitoring units present in the battery management system (BMS). In particular, a multi-channel forwarding method can be provided for further optimization, by means of which, for example, the following advantages can be achieved: - By triggering the data generation in the slave nodes largely in parallel (e.g. by A / D conversion of sensor-detected measured variables) or generally shortening the duration of the transmission data frame, a "jitter" between the acquired analog data of the respective channels can be reduced and thus the data quality can be increased. - Heavily built-up "unreachable" nodes with very poor master connection can be reached by means of the inventive design, without a significant increase in the time required for data transmission. - The spatial, temporal and frequency redundancy of the BMS can be advantageously increased. - By providing channel switching, greater resilience against narrowband interference and jamming can be achieved. It also improves interception security. List of reference symbols 10 electric batteries 12 battery cells 20 Battery management system 30 cell monitoring units 32 Recording device 34 Balancing device 36 Control device 38 radio equipment 40 Control unit 48 radio equipment 50 transmission data frames

Claims

[1] Battery management system (20) for monitoring the operation of an electric battery (10) formed from electrically interconnected battery cells (12), comprising a plurality of cell monitoring units (30) which can be arranged distributed over the battery (10) and each electrically connectable to associated battery cells (12), and a control unit (40), wherein the cell monitoring units (30) are each designed to detect at least one operating parameter of the associated battery cells (12) and to generate therefrom a data packet relating to an operating state of the associated battery cells (12), wherein the control unit (40) is designed to evaluate the data packets generated by the cell monitoring units (30), and wherein the cell monitoring units (30) and the control unit (40) are each further equipped with a radio device (38, 48) and are designed to carry out a data transmission with the aid of the radio devices (38, 48) according to a data transmission algorithm, by means of which the data packets generated by the cell monitoring units (30) are transmitted from the cell monitoring units (30) to the control unit (40), characterized by that according to the data transmission algorithm for at least one of the cell monitoring units (30) it is provided that the data packet generated by this cell monitoring unit (30) is first transmitted in a first step to another of the cell monitoring units (30), hereinafter referred to as forwarding unit, and then in a second step is transmitted from the respective forwarding unit to the control unit (40). [2] Battery management system (20) according to claim 1, wherein according to the data transmission algorithm, the forwarding transmission with said first and second steps is provided for at least 10%, in particular at least 20%, of the cell monitoring units (30). [3] Battery management system (20) according to one of the preceding claims, wherein, according to the data transmission algorithm, a predetermined fixed assignment is provided between, on the one hand, those cell monitoring units (30) for which the forwarding transmission with said first and second steps is provided, and, on the other hand, the forwarding units used for this purpose. [4] Battery management system (20) according to one of the preceding claims, wherein, according to the data transmission algorithm, each forwarding unit transmits the data packet received in the first step to the control unit (40) in the subsequent second step together with the data packet generated by the forwarding unit itself. [5] Battery management system (20) according to one of the preceding claims, wherein according to the data transmission algorithm it is provided that, within the scope of the data transmission, a radio transmission of a data packet by a cell monitoring unit (30), hereinafter referred to as uplink, is triggered in each case by a radio reception of a corresponding request, wherein a radio transmission of the request, hereinafter referred to as downlink, is carried out by the unit (40, 30) provided as the receiver of the data packet. [6] Battery management system (20) according to claim 5, wherein according to the data transmission algorithm it is provided that the data transmission is repeated periodically, wherein the individual data transmissions are each triggered by a downlink of the control unit (40), and wherein in the individual data transmissions all downlinks and uplinks each take place according to a transmission data frame (50) with a plurality of fixed, predetermined consecutive time windows and preferably also a plurality of mutually different predetermined radio carrier frequencies. [7] Electric battery (10) comprising electrically interconnected battery cells (12), equipped with a battery management system (20) according to one of the preceding claims for monitoring the operation of the electric battery (10). [8] Method for monitoring the operation of an electric battery (10) formed from electrically interconnected battery cells (12), wherein the electric battery (10) is equipped with a battery management system (20) which comprises a plurality of cell monitoring units (30) distributed over the battery (10) and each electrically connected to associated battery cells (12), and a control unit (40), wherein the method comprises the following steps: - detecting, by means of the cell monitoring units (30), at least one operating parameter of the associated battery cells (12), and generating a data packet relating to an operating state of the associated battery cells (12) from the at least one detected operating parameter by means of the cell monitoring units (30), - evaluating the data packets generated by the cell monitoring units (30) by means of the control unit (40), - carrying out a data transmission according to a data transmission algorithm, by means of which the data packets generated by the cell monitoring units (30) are transmitted from the cell monitoring units (30) to the control unit (40), with the aid of radio devices (38, 48) with which the cell monitoring units (30) and the control unit (40) are equipped, characterized by that according to the data transmission algorithm for at least one of the cell monitoring units (30), the data packet generated by this cell monitoring unit (30) is first transmitted in a first step to another of the cell monitoring units (30), hereinafter referred to as forwarding unit, and then in a second step is transmitted from the respective forwarding unit to the control unit (40). [9] Use of a battery management system according to one of claims 1 to 5 and / or a method according to claim 8 for monitoring the operation of an electric battery arranged as an energy storage device in a vehicle. [10] Computer program product comprising a program code which, when executed on a data processing device, carries out a method according to claim 8.

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