Electronic radio frequency communication system of a battery management system

Abstract

Embodiments of the present invention include an electronic radio frequency communication system (10) of a battery management system (20), this system (10) comprising: - a battery pack (19) including at least one module comprising at least one stack of battery cells (13), each battery cell (13) having its own monitoring device (12), named BMS slave (12); - at least one radio frequency communication device (11a, 11b), said radio frequency master, wherein the electronic radio frequency communication system (10) comprises a radio frequency coupler (32) connecting the monitoring device (12) to the radio frequency communication device (11a, 11b).

Description

ELECTRONIC RADIO FREQUENCY COMMUNICATION SYSTEM OF A BATTERY MANAGEMENT SYSTEMField of the invention

[0001] The present invention relates to an electronic radio frequency (RF) communication system and a battery management system, more specifically a battery pack implemented for example in an electric or hybrid electric vehicle or in a system for storage energy.

[0002] Such a system or method improves and optimizes the operational performance (e.g. autonomy, lifetime, power, ...), production (e.g. costs, weight, complexity, scarcity of raw materials, ...) or recycling (costs, degree of recycling, complexity, ...) of batteries for various uses such as electric mobility, energy storage, to name only two applications.Background of the invention

[0003] The importance of battery-based power systems within today's markets is well understood by one of skill in the art. These battery systems are replacing traditional power systems in several different markets as products are moving towards more environmentally friendly and cost-effective power solutions. For example, markets such as an electrical vehicle and home energy markets are experiencing rapid growth as battery powered systems are becoming more dynamic in their ability to store and deliver power to corresponding products. This movement away from traditional power sources (e.g., fossil fuels, coal, etc.) to battery-based power sources is placing higher performance demands on the management of battery cells to ensure proper operation within ever-increasing complex products.

[0004] Many battery-based power systems have a centralized management controller that communicates with multiple battery management integrated circuits. Each of these battery management integrated circuits manages a plurality of battery cells and performs various tasks. For example,a battery management integrated circuit may sense voltage and charge levels on battery cells, may manage charge by bleeding charge or re-charging cells, as well as perform other sensing operations and low-level battery management functions.

[0005] In this context, there is a need for a more robust and dynamic alternative battery management system solution. In particular, there is a need for :- a RF communication between the master and the slaves,- good isolation between two consecutive slaves, and- a good robustness of the near metallic elements.Summary of the invention

[0006] To this end, the various aspects of the invention relate to an electronic RF communication system of a battery management system and a battery management system disclosed in the set of claims.Brief description of the drawings

[0007] The present invention will be described subsequently in more detail with reference to the attached drawing, given by way of examples, but in no way limited thereto, in which :- Figure 1 is a schematic representation of a battery management system according to embodiments of the invention;- Figure 2 is a block diagram of the battery management system comprising a battery pack divided by several battery stacks, each stack comprising ten cells, ten RF salves, ten RF couplers connected to one power divider according to the embodiments of the invention; and- Figures 3A, 3B, 3C and 3D are schematic representations of a RF couplers, according to embodiments of the invention.Detailedof the invention

[0008] With reference to Figures 1 and 2, a battery management system 20 also known under the acronym “BMS” comprises a battery pack 19 comprising several modules, including cells 13 in series. Inside a module, the cells 13 are preferably mechanically grouped by ten, this group is called stack.

[0009] The battery pack 19 can comprise one-hundred cells (for example limit is one-hundred and twenty cells by the current protocol). The battery stacks are successively connected by short coaxial cables passing through a RF power divider 40 with the acronym PD in figure 2. Each battery stack is separated from another battery stack by this RF power divider 40.

[0010] In this battery pack 19, each battery cell 13 has its own control unit or monitoring device, named BMS slave 12. As we will see, this BMS slave 12 is configured for health, the current, the voltage and the temperature monitoring, and for charge control and is also able to communicate with and are driven by a master electronic control unit named BMS master 15 via a primary and a secondary RF masters 11 a, 11 b for redundancy.

[0011] Such BMS system 20 can be comprised in a vehicle, for example an electrical vehicle or a hybrid electrical vehicle like a car or a boat. In this context, in terms of physical / mechanical view, the battery pack 19 could be divided in modules, for instance in a car, a module of sixty cells (or six stacks) and another of forty cells (or four stacks) which are not physically located at the same place. But from the point of view of the BMS master 15 illustrated in figure 1 , it’s a pack of n cells (one hundred in our car). Nevertheless, the mechanical introduces some limitations in terms of energy transfer between cells.

[0012] The battery management system 20 comprises a BMS control system 14 and an electronic radio frequency communication system 10.

[0013] The BMS control system 14 is an electronic control system implementing in a non-limiting and non-exhaustive manner :- all algorithms relating to management of the battery pack 19;- exchanges 18 of data with the battery pack 19 via a RF communication link 34, these data relating to management and functional safety of the battery pack 19;- the wired communication link 21 with a central processing unit 16 of the system 20, for instance a control unit like a VCU (acronym for “ Vehicle Control Unit’).

[0014] In system 20, the electronic RF communication system 10 implements in a non-limiting and non-exhaustive manner :- all algorithms relating to management of battery cell 13;- exchanges 18 of data via a radio frequency (RF) communication link 34 between the BMS control system 14 and the battery pack 19 and more specifically between at least one radio frequency (RF) master 11 a, 11 b and the BMS slave 12 of the battery pack 19.

[0015] The BMS control system 14 comprises the BMS master 15, and the RF masters 11a, 11 b. The BMS master 15 implements in a non-limiting and non-exhaustive manner, all algorithms relating to management and functional safety (e.g. relays state) of the battery pack 19 besides handing the sensors (e.g. battery pack current, voltage), actuators (e.g. open / closing relays) of the battery pack 19 and a communication link 21 to the central processing unit 16 of the system 20, this communication link 21 being for instance a wired communication link 21. The BMS master 15 is also configured to communicate with and to drive the RF slaves 12, based on at last one RF master 11 a, 11 b.

[0016] The RF master 11 a, 11 b is an intelligent main electronic control unit also called “master electronic control unit. This RF master 11 a, 11 b comprises an RF communication module which can be in an active or in a passive operating mode. This RF master 11 a, 11 b implements the IndustrialScientific and Medical radio band (also known under the acronym “ISM”) with BMS slaves 12 of the battery pack 19, and as it will be described hereafter ensures the redundancy of the exchanges of data 18.

[0017] In reference to figures 1 and 2, the BMS control system 14 comprises at least two RF master 11 a, 11 b: a primary and a secondary RF masters 11a, 11 b. These RF masters 11a, 11 b are connected to the BMS master 15 in order to communicate with it. In this context, one of the primary and secondary RF masters 11 a, 11 b is in an active operating mode, the other one is in a passive operating mode. In other words, when the RF communication module of one of the primary and secondary RF masters 11 a, 11 b is in active operating mode, the other RF communication module is in passive operating mode. It can be noticed that in other embodiments, the primary RF master 11 a can be in a passive operating mode instead of the active operating mode, and the secondary RF master 11 b can be in an active operating mode instead of passive operating mode.

[0018] As can be seen in figure 1 , these RF masters 11 a, 11 b are separated from the BMS master 15. In an alternative these RF masters 11a, 11 b can be comprised inside the BMS master 15 in order to be used for the communication with the RF slaves 12.

[0019] According to an architectural setup, the central processing unit 16 communicates with the BMS control system 14 of the battery management system 20. BMS control system 14 is in communication (sending commands and / or receiving information) with the batteries stack 19 by exchanging data 18 relating to management and functional safety of the battery pack 19. These exchanges of data 18 are operated via an RF communication link 34. These exchanges of data 18 are being facilitated by BMS slaves 12, which can be an intelligent electronic control units, including embedded software, an electronic control units or monitoring devices. In the BMS control system 14, the BMS master 15 communicates with the central processing unit 16 of the system 20 via a wired communication link 21 .

[0020] According to figure 1 , the electronic RF communication system 10 comprises a plurality of BMS slaves 12, wherein each BMS slave 12 is associated with one battery cell 1 . The functionalities of each BMS slave comprise in a non-limiting and non-exhaustive manner the implementation of:- relay command operations;- battery voltage and current measurement operations;- static cell balancing by current bypass;- dynamic cell balancing by energy transfer between cells 13;- cell internal impedance measurement dendrites reduction by cell heating;- monitoring health, current, voltage, temperature, and charge control;- communication links with the BMS master 15 via at least one RF master 11 a, 11 b.

[0021] The BMS control system 14 and / or the electronic RF communication system 10 includes a redundant communication system for RF communication comprising the primary RF master 11 a and the secondary RF master 11 b. This redundant communication system is connected to the BMS master 15 and to the RF slaves 12.

[0022] In this redundant communication system, the primary RF master 11 a when it is in an active operating mode, receives, calculates and sends data and the secondary RF master 11 b when it is in a passive operating mode only receives data. In this configuration, this primary RF master 11 a receives data from BMS master 15 and sends data to RF slaves 12 and vice versa. The secondary RF master 11 b receives data as the primary RF master 11 a but, sends nothing to the RF slaves 12, or, according to one embodiment to the BMS Master 15.

[0023] In this redundant communication system, the RF master 11 a which is in the active operating mode can be replace by the RF master which is in passive operating mode 11 b, in case of the malfunction of this RF master 11 a in active operating mode. This result increases reliability of the BMS system 20. In other words, the RF communication module of the secondary RF master 11 b is able to switch in the active operating mode when the primary RF master is faulty. In particular, the primary RF master 11 a and the secondary RF master 11 b can switch roles or assignment, namely active role or passive role, when the current RF master 11 a in active operating mode is faulty. Roles can be switched by RF masters 11 a, 11 b themselves or by BMS master 15. In this redundant communication system, the primary RF master 11 a is always in a different operating mode to the secondary RF master 11 b.

[0024] In this redundant communication system, when both primary and secondary RF masters 11 a, 11 b are functioning, the redundancy results in increasement the availability of the information sent back by BMS slaves 12. A such redundant communication system contributes to reduce the cost of such BMS system 20, and provides a full redundant backup only of the RF part.

[0025] The communication channel for exchanging data 18 between the RF master 11 a, 11 b and all BMS slaves 12 is via RF communication 34. The primary 11 a or the secondary 11 b master is able to use a radio transceiver, here the master radio, to generate the radio signals and manage the protocol. Preferably, this communication channel operates in the 2.4 GHz base band (2400 - 2420 MHz), for example based on the basic RF stack of Bluetooth® I ZigBee® (IEEE 802.15) and Wi-Fi® (IEEE 802.11 ) communications with the following configuration: 2-GFSK modulation, 1 MHz bandwidth, 20 channels, 2 Mbps data rate and fixed user payload of 6 bytes. The developed protocol does not follow the IEEE 802.15. xx or IEEE 802.11.xx standards. (Standard protocol was suggested to increase to increase reliability, we prefer to be fast over robustness for data collection from the cells - 20 ms.). This RFcommunication 34 can be composed of several wired transmission lines (present on each module or battery stack panel) and couplers that allow the BMS slaves 12 to connect to a local transmission line on the panel.

[0026] This local transmission line running on the panel as the main communication transmission line. This line is built in the middle layer of the PCB (acronym for “Printed circuit board”), buried between two ground planes, so the electromagnetic radiation is entirely enclosed within a homogeneous dielectric, minimising emissions, and providing natural shielding against incoming signals. This line is adjusted to have an impedance of 50Q.

[0027] In this context, every BMS slave 12 of the corresponding battery cell 13 is connected to the line by means of a RF coupler 32. This coupler 32 design visible in figures 3A to 3D, has the advantage of isolating galvanically each BMS slave from the total module / battery stack voltage which is in the range of 400 V DC; the trend is actually even for higher voltages (800 V DC).

[0028] According to a preferred embodiment, this RF coupler 32 comprising two magnetic loop antennas 30a, 30b configured to interact by near field communication forming a capacitive coupling system.

[0029] In this context, this RF coupler 32 comprises one loop connected to the BMS slave 12 of a battery cell 13 and the other loop is connected to the RF master 11 a, 11 b via a connection link 31 comprising the buried grounded coplanar waveguide and a power divider 40, such as Wilkinson power divider for each battery stack.

[0030] According to figures 3A to 3D, four embodiments of RF coupler 32 are disclosed, in particular configured to be disposed on FR4 type a first PCB printed circuit board (or first PCB). The first PCB printed circuit board or the first PCB can also be called a first PCB panel.

[0031] According to figure 3A, the size of the loops is adjusted to get or experiment correct resonance. The length L1 is about 27mm, and the width L2 is about 22mm. According to figure 3B, the length of loops is adjusted toreduce the total occupied surface; two meanders are included. The length L1 is about 22mm, and the width L2 is about 14mm. According to figure 3C, width L2 is about 11 ,6 mm and a length L1 is about 22mm, and it has only one meander. The occupied surface is reduced. The total electrical length of the loop is constant. Because of parasitic capacitors the total length must be increased to compensate; increasing length adding self-inductance. According to figure 3D external dimensions are identical to previous figure 3C, and the meander being flared at its end.

[0032] Preferably, the loops are arranged opposite each other in a symmetrical, inverted manner.

[0033] Preferably, each loop comprises at least one meander or one serpentine.

[0034] Preferably, the loops form a square, or rectangle.

[0035] Preferably, the loops are configured to maximize perimeter and to minimize surface.

[0036] These embodiments take into account capacitive and inductive losses as well as the board size on which the RF coupler 32 was placed. Losses at 2.5 GHz were reduced and practically no communication is present between the slaves.

[0037] Preferably RF couplers 32 are connected on a printed circuit board that includes a grounded coplanar waveguide (CPW).

[0038] The BCPW is built in the middle layer of a second PCB printed circuit board (or second PCB), buried between two ground planes, so the electromagnetic radiation is entirely enclosed within a homogeneous dielectric, minimizing emissions, preventing unwanted radiation emission from the RF transmission line and providing natural shielding against incoming signals. The coplanar waveguides (CPW, BCPW) are adjusted to have an impedance of 50Q. The second PCB printed circuit board can also be called a second PCB panel.

[0039] In this context, every BMS slave 12 of the corresponding battery cell 13 is connected to the buried grounded coplanar waveguide by means of a RF coupler 32.

[0040] This RF coupler 32 design has the advantage of isolating galvanically each BMS slave 12 from the total module / battery stack voltage which is in the range of 400 V DC; the trend is actually even for higher voltages (800 V DC). All the power is transmitted in the nearfield region, so only the nearfield region has influence.

[0041] This RF coupler 32 design is immune to the surrounding metallic elements building the structure and provides a good RF isolation between neighbor modules. The RF coupler 32 uses the top and bottom layers of the first PCB. Between the two copper layers, there is 1.6 mm of FR4 epoxy (Flame retardant epoxy resin and glass fabric composite used for both first and second PCB manufacturing), this means that the breakdown voltage is around 30 kV. The design is optimized to use a minimum of board space. The gain of the RF coupler 32 is -11 .6 dB in the direction of the metallic elements, and - 30 dB in the direction of the other BMS slaves. All the power is transmitted to the other branch of the RF coupler 32. Theses radiations are the main reasons of the -0.4 dB losses inside the RF coupler 32. This RF coupler 32 is a galvanic short between the RF signal and the ground plane, but it is a matched loop for RF frequencies.

[0042] The battery stacks are successively connected by short coaxial cables passing through a RF power divider (acronym PD) 40, see figure 2. Each battery stack is separated from another battery stack by this RF power divider 40. In this configuration, a star connection is a compromise between parallel and serial connections to the BMS slaves. According to one embodiment, a Wilkinson power divider is designed to parallelize the packs, and the buried grounded coplanar waveguide (BCPW) is designed to serialize the batteries.

[0043] Thus, such BMS system permits to reduce the cost, weight, and connectivity issues (risk of bad contacts), the idea is to replace the wired communication (mainly CAN bus) between the RF master 11 a, 11 b and all the BMS slaves by a radio wave transmission. In order to minimize the transmission power (thus the energy used), the disturbing radiations and the transmission errors, the idea is to use a coaxial cable, connected to the RF master 11a, 11 b and running as close as possible to the BMS slaves, which are provided with an antenna in order to homogenize the reception levels between all the BMS slaves. An alternative to be evaluated would be to replace the coaxial cable with a copper footprint on the second PCB or on an additional PCB.

[0044] It can be noted that one BMS slave 12 should activate the coil to send the data back. Each BMS slave 12 has a based coil system in order to transfer energy to its left and right neighbors. There is also a heater system in order to reduce the dendrites issue. Data (measures, states, ... ) are provided to the BMS master via RF only.

[0045] Regarding these BMS slaves, they can each manage one battery cell, as well as wireless communication technology with the RF master which is in an active operating mode, here the primary RF master, via its radio transceiver to generate the radio signals and manage the protocol.

[0046] Thus, such system permits to reduce the cost, weight, and connectivity issues (risk of bad contacts), the idea is to replace the wired communication (mainly CAN bus) between the BMS master 11 a, 11 b and all the BMS slaves 12 by a radio wave transmission. In order to minimize the transmission power (thus the energy used), the disturbing radiations and the transmission errors, the idea is to use a coaxial cable, connected to the BMS master 11 a, 11 b and running as close as possible to the BMS slaves 12, which are provided with an antenna in order to homogenize the reception levels between all the BMS slaves 12. An alternative to be evaluated wouldbe to replace the coaxial cable with a copper footprint on the second PCB or on an additional PCB.

Claims

CLAIMS1. An electronic radio frequency communication system (10) of a battery management system (20), this system (10) comprising:- a battery pack (19) including at least one module comprising at least one stack of battery cells (13), each battery cell (13) having its own monitoring device (12), named BMS slave (12);- at least one radio frequency communication device (11 a, 11 b), said radio frequency master, wherein the electronic radio frequency communication system (10) comprises a radio frequency coupler (32) connecting the monitoring device (12) to the radio frequency communication device (11 a, 11 b).

2. Electronic radio frequency communication system (10) according to the preceding claim, wherein radio frequency coupler (32) is connected to the radio frequency communication device (11 a, 11 b) by connection link (31 ) comprising a buried grounded coplanar waveguide and a power divider (40) of the system (10).

3. Electronic radio frequency communication system (10) according to one of the preceding claims, wherein the radio frequency coupler (32) comprises two magnetic loop antennas (30a, 30b) configured to interact by near field communication forming a capacitive coupling system.

4. Electronic radio frequency communication system (10) according to the preceding claim, wherein the radio frequency coupler (32) is configured to operate in the part of a radio spectrum corresponding to 2.4 GHz ISM band.

5. Electronic radio frequency communication system (10) according to claims 2 to 4, comprising a first PCB panel, wherein the radio frequency coupler (32) is connected to the buried grounded coplanar waveguide in a second PCB panel, preferably buried between two ground planes of the second PCB panel.

6. Electronic radio frequency communication system (10) according to the preceding claim, comprising at least one power divider (40) connected to the radio frequency communication device (11 a, 11 b) wherein the radio frequency coupler (32) is connected to the power divider (40) via the buried grounded coplanar waveguide of the second PCB panel.

7. Electronic radio frequency communication system (10) according to the preceding claim, comprising a plurality of power dividers (40), each power divider (40) being associated with a set of radio frequency couplers (32), wherein power dividers (40) are connected in a star connection configuration with the radio frequency communication device (11 a, 11 b).

8. A battery management system (20) comprising the electronic radio frequency communication system (10) according to one of the preceding claims, the system (20) comprising an electronic control system (14) including a master electronic control unit (15), said battery management system master and the radio frequency communication device (11 a, 11 b), the master electronic control unit (15) being configured to exchange data with the monitoring device (12) via the radio frequency communication device (11 a, 11 b).

9. Electrical vehicle comprising the battery management system (20) according to the preceding claim.

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