PT115439B - LITHIUM ION TRACTION BATTERY CELL MANAGEMENT SYSTEM WITH INFRARED COMMUNICATIONS AND DISTRIBUTED ARCHITECTURE AND IMPLEMENTATION METHOD - Google Patents

Abstract

THIS INVENTION REFERS TO A LITHIUM-ION TRACTION BATTERY MANAGEMENT SYSTEM WITH A FULLY DISTRIBUTED ARCHITECTURE OF THE MASTER-SLAVE TYPE, IN WHICH THE CIRCUITS RESPONSIBLE FOR MONITORING THE BATTERY CELLS, DESIGNATED BY SLAVES ABILITY TO SELF-CONFIGURE WHEN PUTTING INTO THE SYSTEM. THESE CIRCUITS COMMUNICATE WITH THE MAIN BATTERY MANAGEMENT CIRCUIT, DESIGNATED BY MASTER, THROUGH INFRAREDS AND ARE NOT CONNECTED TO EACH OTHER BY CABLES. THE AUTO-CONFIGURATION MECHANISM INCLUDES THE AUTOMATIC ASSIGNMENT OF A UNIQUE IDENTIFIER TO THE SLAVE LOCATED IN EACH BATTERY CELL AND THE AUTOMATIC DETECTION OF IDENTIFIER DUPLICATION. THE BATTERY MANAGEMENT SYSTEM HAS THE CAPACITY TO MONITOR THE VOLTAGE AND TEMPERATURE OF EACH ONE OF THE BATTERY CELLS IN ORDER TO PERFORM THE INDIVIDUAL VOLTAGE BALANCING OF EACH CELL. THE SYSTEM INTEGRATES AN AUXILIARY BATTERY, A BATTERY (1) THAT INCORPORATES CELLS (2), MAIN MANAGEMENT CIRCUIT (3), CELL MONITORING CIRCUIT (4).

Description

DESCRIPTION

LITHIUM ION TRACTION BATTERY CELL MANAGEMENT SYSTEM WITH INFRARED COMMUNICATIONS AND DISTRIBUTED ARCHITECTURE AND IMPLEMENTATION METHOD

Scope of the Invention

This invention fits into battery management systems, more specifically to a method for self-organizing distributed lithium-ion traction battery management systems with fully distributed infrared-based communications.

Background of the Invention

Currently, there are already battery management systems with point-to-point infrared communication. Typically, these architectures use infrared for communication between the battery and the outside, or between the battery and the charger or the engine driver, rather than between the cell monitoring circuits (slaves) located in each battery cell and the main load management (master), and do not have the capacity for self-organization by the distributed elements.

This document describes a lithium-ion traction battery management system, with a fully distributed architecture, master-slave type, in which the circuits responsible for monitoring the battery cells, called slaves, have the ability to auto-configure when they are placed on the system. These circuits communicate with the main battery management circuit, called the master, via infrared and are not connected by cables.

The self-configuration system includes the automatic assignment of a unique identifier to the slave located in each battery cell, the automatic detection of duplicate identifiers, useful in case a cell with a slave previously configured in another system is placed in the battery, thus allowing to reduce the system assembly and configuration time, as well as facilitating assembly, configuration, maintenance and repair actions, ensuring greater reliability. The battery management system has the ability to monitor the voltage and temperature of each of the battery cells in order to individually balance the voltage of each cell.

To reduce the time for sending/receiving information, which can be critical in these types of systems, a non-destructive real-time bit-by-bit arbitration method has been developed that allows destructive collisions between messages sent by infrared from of different cells are avoided.

Background of the invention

Some documents were found that refer to infrared communication in battery management systems, which are referred to below. However this communication is point-to-point and not fully distributed and is applied to different parts of the vehicle load management process.

CN 103915877A - The invention described in this document presents a system and a method for managing the balance of batteries in a battery pack. However, unlike the present invention, the architecture is not distributed, the infrared link is point-to-point and only between the monitoring block and the central control block and between the central control block and the balancing block. Does not include: fully distributed infrared communication, self-configuration system, automatic real-time detection of duplicate identifier system, and real-time non-destructive bitwise arbitration in infrared communications.

CN204905916U - This utility model describes a battery management system that includes an infrared link between the main processor and the charger. Infrared connection is point-to-point. The architecture does not appear to be distributed. Unlike the present invention, it does not include: fully distributed infrared communication, self-configuration system, automatic real-time detection of duplicate identifier system, and real-time non-destructive bitwise arbitration in infrared communications.

CN205596123U - This document presents a bicycle battery management system with infrared communication module, battery management system, etc. The challenges related to managing the battery of a bicycle are not the same as those of a car so it is not comparable. Only an infrared point-to-point connection is implemented. Does not include: fully distributed infrared communication, self-configuration system, automatic real-time detection of duplicate identifiers, and real-time non-destructive bitwise arbitration in infrared communications.

CN107611506A - Describes a distributed battery management system connected by cables through a CAN bus and an automatic method to change the assignment of identifiers to transceivers in the network in order to prevent or correct the existence of duplicate identifiers. This method applies a pre-established setup process, which is fixed. In addition to the cable connections related to the CAN network, this implementation requires the existence of an additional sequential cable connection between the management system of each cell and the next cell, making the assembly, maintenance and repair of the system more time-consuming than than in a cable-free solution. On the other hand, identifier assignment schemes in CAN networks are well known and are used by various application layer protocols, such as the CANOpen protocol. In the method described, it is not clear how the main computer can measure the total number of nodes in the network, since, in a CAN network, if there are repeated identifiers, this is not detectable by the receiver. In this implementation the issue of galvanic isolation between the battery and the battery management system is not addressed and, depending on how the implementation is done, it may not be guaranteed. Does not include: fully distributed infrared communication, self-configuration system, automatic real-time detection of duplicate identifier system, and real-time non-destructive bitwise arbitration in infrared communications.

Other documents that refer to similar techniques were also found.

DIY Electric Car Forums, April 2010 - Master slave system for collecting the temperature value of the battery cells. Round-robin communication scheme. Communication is done with a PCB board that is wired to 6 battery cells and therefore the management system architecture is not fully distributed. The type of battery technology is different. Does not include: fully distributed infrared communication, self-configuration system, automatic real-time detection of duplicate identifiers, and real-time non-destructive bitwise arbitration in infrared communications.

https://pplware.sapo.pt/motores/bmw-i3-modificado-consegue700-quílometros-de-autonomia/, 12 September 2018

Online article about the new BMS of the BMWÍ3 where it is mentioned that an infrared communication system was also introduced, which significantly reduces the amount of cables in the cells, reducing weight and space occupied. No details are given. Only the advantage of using infrared in reducing battery wiring is mentioned. Battery setup, maintenance and repair procedures are not mentioned. Does not include: fully distributed infrared communication, self-configuration system, automatic real-time detection of duplicate identifier system, and real-time non-destructive bitwise arbitration in infrared communications.

The article Smart cells for embedded battery management by S. Steinhorst et. al. published in the ^2nd IEEE International Conference on Cyber-Physical Systems Networks and Applications in 2014, proposes a battery management system using only fully distributed controllers placed locally in the battery cells. It also states that in order for the control of the charge status of cells in a cooperative way to be carried out effectively, it will be necessary to carry out some type of coordination through the communication system chosen for the implementation. Some of the capabilities that smart monitoring cells must have are mentioned including the ability to uniquely identify themselves in the network. It mentioned the need for a reliable communication network and at the same time to minimize the necessary cabling. Concrete solutions are not presented, neither for the type of technology to be used in communications nor for the methods necessary to guarantee the described functionalities. The issue of maintenance and repair of the system is not mentioned. In later articles they propose the use of the CAN bus (articles from 2015 and 2016). Does not include: fully distributed infrared communication, self-configuration system, automatic real-time detection of duplicate identifier system, and real-time non-destructive bitwise arbitration in infrared communications.

As for arbitration systems in infrared communications, there is the Wi-Fi Standard IEEE802.il (1997) protocol that implements the CSMA/CA method, avoiding collisions by monitoring the communication channel, introducing a random waiting time before the transmission and systems of acknowledgment of receipt and time reservation on the channel through the exchange of RTS and CTS packets between the nodes of the network that are going to communicate. The detailed version of these systems is presented in the IEEE802.il Standard. A summarized version of the systems used can be found in the article The Infrared Physical Layer of the IEEE 802.11 Standard for Wireless Local Area Networks, by R. Vaiadas et. al, published in IEEE Communications Magazine, vol. 36, issue 12 December 1998. It is clear from these descriptions that the implementation of the systems implies the exchange of several messages between the sender and the receiver, adding an overhead time associated with the transmission that is very penalizing in cases where the useful information to be transmitted is made up of a few bytes, as is the case with the battery cell voltage and temperature monitoring application. Implementing such systems also results in complex and expensive hardware.

In applications with Wi-Fi communications, the duplication of identifiers is avoided by associating a unique identifier to each hardware module developed in the manufacturing phase, which requires the payment of a license and the consequent increase in the final cost of the product.

Advantages of the invention

Compared to the aforementioned systems, the management system of the present invention has several advantages, such as having a fully distributed master-slave architecture, the circuits responsible for monitoring the battery cells, having the ability to self-configure when placed in the system and communicate with the main battery management circuit via infrared, rather than being wired together.

Brief description of the figures

These and other features can be easily understood from the accompanying drawings, which are to be considered as mere examples and in no way restrictive of the scope of the invention. In the drawings, and for illustrative purposes, the measurements of some of the elements may be exaggerated and not drawn to scale. Absolute dimensions and relative dimensions do not correspond to actual ratios for carrying out the invention.

Figure 1 shows a scheme of the system of the invention.

Figure 2 shows a detail of the master circuit and its power supply.

Figure 3 shows a detail of the slave circuit and its power supply.

In figure 4 it is possible to observe the diagram of operating states of the master circuit in the configuration phase.

Figure 5 shows the diagram of operating states of a slave circuit in the configuration phase.

Figure 6 shows the operating state diagram of the master circuit in the utilization phase.

Figure 7 shows the diagram of operating states of the slave circuit in the usage phase.

In the figures, the elements and components of the equipment of the present invention are indicated:

- Traction battery

- Cells

- Main management circuit

- Cell monitoring circuit

- Auxiliary battery

Detailed Description of the Invention

In the various embodiments, various specific details are presented in order to provide a complete understanding of the invention. However, it is understood by any person skilled in the art that these details are to be viewed as embodiments and not limiting of the present invention.

By architecture or distributed management system is meant the system which comprises several independent (and even different) components, connected through a data network, which presents itself as a single and coherent system, in which communication is made with based on messages.

By master-slave system is meant the system in which one component (master) has control over others (slaves).

By passive balancing is meant the method that uses dissipation techniques, removing excess energy through a resistance until the voltage or load of the cells reaches the desired value.

By indication of the instant of time or time stamp, terms that derive from the English term tímestamp, it is understood the string of characters that indicates the moment in which a certain event occurred. The string is usually presented in a consistent format, allowing for easy comparison between different instants of time.

Introduction

Referring to the figures, by way of example, the traction battery (1) shown in Figure 1 is composed of 16 cells (2), when typically the number of cells (2) of the traction battery (1) in traction applications is superior or even much superior.

In traditional implementations, the cells communicate with each other and/or with the master through communication protocols that use cabling, making the time to assemble the cables an important factor in defining the costs and reliability of the product. In practice, it is found that many of the problems that arise in batteries during their use in vehicles are due to issues related to the wiring, either as a result of inaccuracies in the assembly phase or due to deterioration caused by the vibration to which they are subjected during the use.

In the construction of batteries, the following factors are fundamental:

- the individual configuration time of the equipment associated with each cell;

- the ability to automatically identify repeated identifiers in order to minimize human error;

- the assembly time of the cables;

- the size, weight and cost of the equipment to be placed in each cell;

- the electrical consumption of the equipment to be installed in each cell;

- the existence of galvanic isolation between the battery and the rest of the vehicle;

- electromagnetic compatibility;

- the communication time between each slave circuit installed in each cell and the master circuit installed in the battery box, when using a fully distributed battery management architecture or system.

In the battery repair and maintenance phases, the following features are important:

- the ability to quickly identify each battery cell individually;

- the individual configuration time of the equipment associated with each cell;

- the ability to automatically identify repeated identifiers in order to minimize human error;

- the time of assembly and disassembly of the cables.

Technical description of the system and methods The system is composed of a main management circuit (3) or master circuit that is placed inside the traction battery box (1) and by several monitoring circuits of the cells (4) or slave circuits, a for each cell (2) . The cell monitoring circuits (4) are powered directly from the cells (2) of the traction battery (1) while the main management circuit (3) is powered from the auxiliary battery (5) of the vehicle.

There are no physical cable connections between any of these elements.

Both the cell monitoring circuits (4) and the main management circuit (3) are capable of sending and receiving data via infrared, and the communication between them takes place through this means.

The described power supply scheme combined with the type of communication used, via infrared, allows to reduce the use of wiring to a minimum, with the advantage of preventing failures due to loss of contact resulting from vehicle vibration as well as reducing costs, weight and time of assembly.

Infrared communication allows:

- guaranteeing galvanic isolation between the battery and the charge management system;

- promote electromagnetic compatibility;

- eliminate the use of cables for communication, reducing assembly time, eliminating faults associated with the cables and reducing the weight and cost of implementation;

- guarantee low consumption, a determining characteristic for slave circuits;

- ensure a reduced size and cost for the slave circuits.

In this type of application, the consumption of the cell monitoring circuits (4) is critical since they are directly powered from the voltage of the cells (2) they are monitoring. Other wireless communication options, such as Bluetooth or Wi-Fi, require much larger components, more expensive and with much higher consumption, so they are not recommended for this application.

The system operates in two phases: an initial configuration phase and a subsequent use phase.

During the configuration phase, the cell monitoring circuits (4) are added to the infrared network one at a time, according to the procedure described below:

a) The main management circuit (3) is mounted in the traction battery box (1) and powered from the auxiliary battery (5) of the vehicle;

b) The cell monitoring circuit (4) is placed in its respective cell (2) and is powered from it;

c) The cell monitoring circuit (4) starts its operation and upon verifying that it is being turned on for the first time, it asks the main management circuit (3) to assign it an identifier, this request being made through a message sent, by infrared, to the main management circuit (3) containing an indication of the instant of time;

d) The main management circuit (3) sends to the cell monitoring circuit (4), via infrared, a message containing the identifier referred to in the previous step that allows each cell monitoring circuit (4) to identify itself in a way. unique in the infrared communications network, and also sends in the same message an indication of the instant of time it had previously received;

e) The cell monitoring circuit (4) receives a message and checks the indication of the received time instant;

f) If the instant of time received is the same as the one sent previously, it accepts the identifier and sends to the main management circuit (3), via infrared, a message confirming its reception;

g) The cell monitoring circuit (4) stores in persistent memory the value of the identifier assigned to it, ensuring that during the system use phase it is not necessary to carry out a new self-configuration operation;

h) The process is repeated from step b) for each monitoring circuit of the cell (4) that is placed in the network; typically one cell monitoring circuit (4) will be placed for each cell (2) to be monitored, which may correspond to several tens or even hundreds of cell monitoring circuits (4).

This setup procedure allows:

- to reduce the configuration time, since this is automatic, contrary to what is common in this type of systems where an individual configuration of the slave circuit hardware with human intervention is usually necessary to define the unique identifier of each slave circuit;

- eliminate the human error associated with the repetitive assignment of individual identifiers;

- eliminate the cabling between all slave circuits and between them and the master circuit, necessary in other systems for configuration and information transport.

After the configuration phase, all messages sent by the cell monitoring circuit (4) contain the identifier that allows the main management circuit (3) to uniquely identify the cell (2) of origin of the messages with the data relating to voltage and temperature.

When all the cell monitoring circuits (4) are placed in the network and have their identifier assigned, the main management circuit (3) switches to the usage mode during which it proceeds with the typical control cycle of a management system. of batteries. This cycle consists of monitoring the voltage and temperature of each cell (2), deciding whether to carry out the balancing or not, and subsequently sending, via infrared, the balancing command to the cells (2), when necessary.

The implementation of the control cycle is carried out in the use phase as follows:

a) The main management circuit (3) asks each cell monitoring circuit (4) to send information regarding the voltage and temperature of the cell (2) to which it is connected, this request being made by sending a infrared message;

b) Each cell monitoring circuit (4) receives the data request message and responds by sending the information regarding the temperature and voltage of its cell (2) using a message sent by infrared;

c) The main management circuit (3) collects the information, processes it according to the chosen balancing algorithm and, as necessary, sends a message to the cell monitoring circuit (4), through infrared, indicating whether it should start or stop the process of balancing the voltage of its cell (2);

d) The balancing used is of the passive type using a resistance, located in each of the cell monitoring circuits (4), for cell discharge (2).

In order to facilitate the maintenance and repair phases of the system, a message was created, to be sent from the main management circuit (3) to the cell monitoring circuits (4), which allows them to identify themselves visually, namely but not exclusively, through an LED, thus allowing to identify each monitoring circuit of the cell (4), and consequently, each cell (2) of the traction battery (1), from its visual identifier.

If, during the maintenance and/or repair phase of the traction battery (1), a cell (2) with a cell monitoring circuit (4) is placed in the network, already configured with an identifier equal to another one already existing in the network, this will be detected as follows:

a) Each cell monitoring circuit (4) monitors the information sent by the main management circuit (3) and by the other cell monitoring circuits (4);

b) If it detects the existence in the network of another cell (2) using the same identifier as its own, it switches to configuration mode and sends a new request for the assignment of an identifier to the main management circuit (3);

c) The main management circuit (3) assigns the identifier in the way already described in the configuration phase of the cell monitoring circuits (4), with the use of the indication of the time that allows the cell monitoring circuits (4) understand which identifier is being assigned to each of them;

d) In order to guarantee data integrity, a 16-bit field containing an error detection code of the CRC type is included in all messages sent, which is then checked at the receiver.

This method of self-organization allows the intervention of the assembly technician to be limited to the placement and supply of the cell monitoring circuit (4) in the respective cell (2), dispensing with any type of local intervention for the individual configuration of the monitoring circuit of the cell (4) and allows the number of monitoring circuits of cells (4) in the network to be dynamically calculated as they are inserted into the network. The configuration is carried out automatically according to the procedure already described.

The inclusion of the visual identification capability of each cell monitoring circuit (4) makes it possible to facilitate and reduce system maintenance and repair time.

In order to minimize the time for exchanging data messages during the control cycle, broadcast commands are used, which allow with a single message from the master to address all the slaves in the network.

A non-destructive arbitration system was also created that allows the arbitration of the communication channel bit by bit, in real-time, allowing all slaves to start sending their data commands and that, in real-time, the channel is assigned to just one of them without overload times associated with the arbitration procedure.

There are two signal levels in the network: recessive level, which corresponds to the infrared emitter being turned off, and the dominant level, which corresponds to the infrared emitter being transmitting. Bits are sent using this encoding. The signal is sent for the entire duration of the bit.

This arbitration system works as follows:

a) All senders expect the communication channel to be free for a fixed period of time and slightly longer than the sending time of a byte;

b) After verifying the above condition, all senders who want to transmit start sending their messages;

c) The senders, whenever they emit a bit of the message, simultaneously monitor the reception channel;

d) When the senders send a recessive or dominant bit, and detect the same type of bit, they continue to send their message;

e) When senders send a recessive bit and receive a dominant bit, they suspend the sending of their message and can retry sending when the condition of step a) is verified again.

In this way, no time is wasted with the exchange of individual data request messages between the master and each of the slaves, all the slaves responding in an orderly manner to the same global data request.

08/04/2021

Claims (12)

1. Lithium-ion traction battery cell management system consisting of a main management circuit (3) implemented in the traction battery (1), a traction battery (1) incorporating a set of cells (2) individually associated with cell monitoring circuits (4), in which the communication between the circuits (3) (4) is carried out via infrared, as the management system architecture is distributed and because it incorporates a self-configuration system for the circuits. cell monitoring (4) characterized in that the cell monitoring circuit (4), when starting its operation and verifying that it is being turned on for the first time, asks the main management circuit (3) to assign it an identifier. 2. System according to the preceding claim, characterized in that it incorporates an automatic detection system in real-time of the duplication of identifiers. 3. System according to the preceding claims, characterized in that it incorporates a non-destructive bit-by-bit arbitration system in real-time in infrared communications. System according to the preceding claim, characterized in that the cell monitoring circuits (4) have a visual identifier. 5. System according to the preceding claim, characterized in that the visual identifier is an LED light. System according to claim 1, characterized in that the main management circuit (3) is supplied by an auxiliary battery (5). System according to claim 1, characterized in that the supply to the monitoring circuits of the cells (4) is carried out by the cells (2). 8. Method of implementing the self-configuration system claimed in claim 1, characterized in that in the configuration phase the cell monitoring circuits (4) are added to the network, one at a time, according to the following steps: a) The main management circuit (3) is mounted in the traction battery box (1) and is powered from the auxiliary battery (5) of the vehicle; b) the cell monitoring circuit (4) is placed in its respective cell (2) and is powered from it; c) The cell monitoring circuit (4) starts its operation and upon verifying that it is being turned on for the first time, it asks the main management circuit (3) to assign it an identifier, this request being made through a message sent by infrared to the main management circuit (3) containing an indication of the instant of time; d) The main management circuit (3) sends to the cell monitoring circuit (4), via infrared, a message containing the identifier and the indication of the instant of time referred to in the previous step; e) The cell monitoring circuit (4) receives a message and checks the indication of the received time instant; f) If the instant of time received is the same as the one sent previously, it accepts the identifier and sends to the main management circuit (3), via infrared, a message confirming its reception; g) The cell monitoring circuit (4) stores in persistent memory the value of the identifier assigned to it; h) The process is repeated from step b) for each monitoring circuit of the cell (4) that is placed in the network. 9. Method of implementing the self-configuration system claimed in claim 1, characterized in that in the use phase the implementation of the control cycle is carried out according to the following steps: a) The main management circuit (3) asks each cell monitoring circuit (4) to send information regarding the voltage and temperature of the cell (2) to which it is connected, this request being made by sending a infrared message; b) Each cell monitoring circuit (4) receives the data request message and responds by sending the information regarding the temperature and voltage of its cell (2) using an infrared message; c) The main management circuit (3) collects the information, processing it according to the chosen balancing algorithm and, as necessary, sends a message to the cell monitoring circuit (4), through infrared, indicating whether it should start or stop the process of balancing the voltage of its cell (2) . 10. Method according to the preceding claim characterized in that the balancing used is of the passive type using a resistance, located in each of the monitoring circuits of the cells (4). 11. Method of implementing the auto-configuration system claimed in claim 1, characterized in that the detection of placing in the network a cell (2) with a cell monitoring circuit (4) already configured with an identifier equal to another one already existing in the network is performed according to the following steps: a) Each cell monitoring circuit (4) monitors the information sent by the main management circuit (3) and by the other cell monitoring circuits (4); b) If it detects the existence in the network of another cell (2) using the same identifier as its own, go to configuration mode and send a new request to assign the identifier to the main management circuit (3); c) The main management circuit (3) proceeds with the assignment of the identifier in the way already described in the configuration phase of the cell monitoring circuits (4), with the use of the indication of the instant of time that allows the cell monitoring circuits (4) understand which identifier is being assigned to each of them; d) In order to guarantee data integrity, a 16-bit field containing an error detection code of the CRC type is included in all messages sent, which is then checked at the receiver. 12. Method of implementing the arbitration system claimed in claim 3, characterized in that it is carried out according to the following steps: a) All senders wait for the communication channel to be free for a fixed period of time and slightly longer than the sending time of a byte; b) After verifying the above condition, all senders who want to transmit start sending their messages; c) The senders, whenever they emit a bit of the message, simultaneously monitor the reception channel; d) When the senders send a recessive or dominant bit and detect the same type of bit, they continue to send their message; e) When senders send a recessive bit and receive a dominant bit, they suspend the sending of their message and can retry sending when the condition of step a) is verified again. 08/04/2021