Ion Battery Challenge
A battery management system is needed to use lithium-ion cells. These cells are indispensable because lithium-ion batteries can be dangerous. If overcharged, they can experience thermal runaway and explosion. If over-discharged, chemical reactions occur within the cell, permanently affecting its ability to hold charge. Both of these cases involve the dangerous and costly loss of batteries. Furthermore, a battery pack is needed because lithium-ion batteries are typically stacked to form a battery bank. Charging stacked batteries is usually done by applying a constant current source parallel to the stack. However, this also presents the challenge of balancing the behavior of keeping all cells in the same state of charge. How can we fully charge or discharge all cells in a battery bank without any single cell being charged or over-discharged? Balancing is one of the many important benefits of a good property management system. The main functions of a property management system include:
• Monitor parameters such as battery voltage, battery temperature, and inlet/outlet current.
• Calculate the inductance by measuring the above parameters, as well as the charge and discharge current within ampere-seconds, using a coulomb counter.
• Cell balancing (passive) to ensure all cells are in the same state
BMS Solution
Analog equipment companies have a wide range of housing management equipment. For example, the Adbms1818, best suited for industrial applications, can measure 18 cells in a battery stack. A microcontroller (MCU) is needed to operate any Adbms IC. The MCU communicates with the system, receives measurement data, and performs calculations to determine the system and other parameters. While most MCUs can communicate with BMS, not all are suitable. A MCU with broad processing capabilities is preferable. This is especially true when a large battery stack is required (some stacks can reach 1500V, with up to 32 Adbms18S connected in a daisy chain), as the system feedback data can be substantial. In such cases, the MCU must have sufficient bandwidth to communicate with the integrated control system of different management systems within the system when processing the results. As part of the housing management platform solution, the MAX32626MKU has two power sources managed by a power path controller. The power path controller prioritizes supplying power based on onboard power requirements (connecting peripherals and handling loads, etc.).
Most ADI monitoring integrated circuits employ a stackable high-voltage system architecture, meaning that multiple analog front-ends (AFES) can be connected in a daisy chain. Therefore, one of the key features of a building management controller board, known as an energy storage controller unit, is that it operates simultaneously with multiple AFES.
A typical BMS block diagram is shown, with CES highlighted in blue. Although the system is not optimized for functional safety applications, users can implement protection circuitry and/or redundancy to meet certain safety integrity level requirements.
BMS controller board hardware and software
Hardware Information
Adi's ESTS interface is compatible with a wide variety of CBM devices (AFE, gas meters, ISPI transceivers). The Housing Management Office Controller Committee's focus on hardware and components is:
• On-board microcontroller: The ARM cortex M4MAX32626 is suitable for energy storage applications. It operates at low power and outperforms other systems in speed due to its internal oscillator running at 96 MHz. In low-power mode, it can operate as low as 4 MHz to save power. It features excellent power management, such as 600 mA low-power mode current and real-time clock enablement. The MAX32626 also accommodates a wide variety of peripherals, including SPI, UART, I/O, 1-wire interface, USB 2.0, pump, 10-bit ADC, etc. A trust protection unit with advanced security features is incorporated into this microcontroller.
• Interfaces: Has multiple interfaces:
IIC
• Robust and secure information transmission over high-voltage barriers
• Power the board and flash the microcontroller
JTAG for microcontroller programming and debugging
• Connectors (allowing for more flexible addition of compatible boards, such as Ethernet shields, sensor shields, or even the original shield)
• Plasma Transceiver: 2 × LTC6820 A single daisy chain is used on the daisy chain to achieve in-direction communication with the integrated control system of the management system. This ensures that the board is fully compatible with the high-voltage battery stack. The presence of dual plasma transceivers provides redundant and reversible isolated communication, with the host microcontroller switching communication ports to monitor signal integrity (future development of this board will include Adbms6822 [dual plasma transceivers] for improved data rates and support for low-power battery monitoring functions in the latest International Association of Building Design (IABD) integrated control system for building management).
• Power Management:
• Power can be supplied via a DC jack or USB 2.0 interface to a PC (USB-C connector is available).
A priority circuit, using the LTC4415, manages and selects the power source. It selects either the DC jack or the USB-C input based on the load of the controller and peripheral devices. For example, if an Aduino shield is connected and running, the board's power consumption will increase beyond what UBC-C can provide. The ideal configuration or architecture of the LTC4415 will then switch to selecting the DC jack as the power source.
• The power chain offers different voltage rails (3.3V, 2.5V, and 5V), which can be configured via jumpers.
• Safety and Protection: The MAX32626 controller isolates the gate driver, ADuM4120, which drives an NFET connected to an external contactor (e.g., on a solar panel). This provides protection because the microcontroller will switch the contactor via the ADuM4120 switching MOSFET and disconnect the battery in emergency or fault situations.
Software Information
On the software side, ADI provides a complete solution, including an open-source graphical user interface (GUI) for communicating with the control board. The GUI supports up to three ADBMS devices connected to the daisy chain.
The user interface communicates with the microcontroller via a well-defined, easily extensible, open-source communication protocol. The protocol defines the messages sent to the microcontroller via serial port. These messages are loop-checked and protected to enable error detection. These messages allow the user to sequentially connect and disconnect the microcontroller, set system parameters, perform measurements, enable and check faults, and write any necessary commands for the Adbms section. The application code in the microcontroller uses free RTOS threads to perform parallel operations. This is useful because the measurement thread can run in parallel with the fault-checking thread, allowing for fault interval settings.
A software interface is provided, which is written along with the management office controller board and in Bitton. The main user components are as follows:
• System Tab: This is the application's main login page. It allows users to establish serial PC communication, select the number of AFE boards to connect, and determine the measurement interval and threshold for overvoltage and overvoltage checks. After clicking Connect, the user is ready to begin measurements. If both system status lights turn green, the Measurement tab will be displayed based on the number of boards entered by the user.
The BMS tab(s) displays measurement results processed by the ECE to each connected AFE. This tab(s) contains cell and GPIO voltage, status, and fault readings from the AFE board. Battery voltage measurements are also graphically represented and plotted in real time.
• References tab: The graphical interface includes a References tab, which represents a high-level chessboard and diagram.
The design drawings and Gerber files, as well as the evaluation firmware, graphical interface, and user guide, are all open source and provided by the Agricultural Development Agency.
In the rapidly evolving energy market, the need for BCES is urgent. A complete, deployable solution is urgently needed. Support is also required to accelerate time-to-market, rather than adding unknown delays. Adidas is prepared to fully meet this need with its SCUE. The SCUE provides the key functionalities required by BCES and offers a complete foundation for flexibility in further development.
By using the building management controller solution based on sustainability initiatives, users will be able to:
Multiple AFESs can be evaluated simultaneously because the solution is designed for stackable and scalable architectures. No additional plasma transceiver boards are required.
Seamlessly debug using onboard JTAG, status LEDs, and a variety of connectors and interfaces.
• Utilize open-source hardware and software to reduce time to market.
