Batteries
Energy storage systems: How to easily and safely manage your battery pack
By Amina Joerg, field applications engineer, and Paulo Roque, system applications engineer, both with Analog Devices L
ithium-ion (Li-Ion) and other battery chemistries are not only key elements in the automotive world, but they are also predominantly used for energy storage systems (ESS). For instance, gigafactories can produce several MWh per day of energy extracted from renewable generation. How do we account for the various burdens placed upon the energy grid over 24 hours? This can be done by using battery-based grid-supporting energy storage systems (BESS). This article discusses battery management controller solutions and their effectiveness in both the development and deployment of ESS.
Lithium-ion battery challenges A battery management system (BMS) is needed for the use of Li-Ion cells. The BMS is indispensable because Li-Ion cells can be dangerous. If overcharged, they can undergo thermal runaway and explode. If overly discharged, chemical reactions take place within the cell that permanently affect its ability to hold charge. Both cases involve the loss of battery cells in dangerous and expensive ways. Additionally, a BMS is needed since Li-Ion cells are often stacked to form a battery pack. Charging of stacked cells is often done in series by applying a constant current source in parallel with the stack. However, this brings with it the challenge of balancing, which is the act of keeping all cells at the same state of charge (SOC). How can we charge or discharge all cells fully without overcharging or over discharging any one individual cell in the battery stack? Balancing is one of the many critical benefits of a good BMS. The BMS’s primary functions include: Monitoring cell parameters such as cell voltage, cell temperature, and the current flowing in and out of the cell. Calculating the SOC by measuring the above-mentioned parameters as well as the charge and discharge current in ampere- second (A.s) using a coulomb counter. Cell balancing (passive) to ensure that all cells are at the same SOC.
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Figure 1. A simplified BMS block diagram supported with ADI BMS
Battery management system solutions
Analog Devices has an extensive family of BMS devices. The ADBMS1818, for instance, is ideally suited for industrial and BESS applications and can measure a battery stack of 18 cells. A microcontroller is required to operate any ADBMS IC. The microcontroller unit (MCU) communicates with the BMS, receiving the measurement data and performing computations to determine the SOC and other parameters. While most microcontrollers can communicate with a BMS, not all are suitable. A microcontroller with an extensive processing power is desirable. The data that the BMS feeds back can be large, particularly when a large cell stack is required (some stacks can reach 1500V and are composed of up to 32 ADBMS1818s connected in a daisy chain). In this case, the microcontroller must have large enough bandwidth to communicate with the different BMS ICs in the system while processing the results. As part of the BMS platform solution, the MAX32626 microcontroller has two supply sources that are managed through a PowerPath controller. The PowerPath controller prioritises the supply source based on board power demand (connected peripherals and processing load, etc.).
Most ADI monitoring ICs come in a stackable architecture for high voltage
systems, which means that multiple analogue front ends (AFEs) can be connected in a daisy chain. Therefore, one of the main characteristics of the BMS controller board, referred to as the energy storage controller unit (ESCU), is that it works with multiple AFEs at the same time.
Figure 1 illustrates a typical BMS block diagram where the ESCU is highlighted in blue. While the ESCU is not optimised for functional safety applications, the user can implement protection circuits and/ or redundancies to achieve certain Safety Integrity Level (SIL) requirements.
BMS controller board hardware and software
Hardware information
ADI’s ESCU interfaces with a variety of BMS devices (AFE, gas gauge, isoSPI transceiver). The highlights of the BMS controller board’s hardware and components are: On-board MCU: The Arm Cortex-M4 MAX32626 is suitable for energy storage applications. It operates at low power and excels in speed, as it has an internal oscillator running at frequencies up to 96MHz. In low power mode, it can run at speeds as low as 4MHz for power savings.
It has excellent power management features such as a 600nA low power mode current and an enabled real-time clock (RTC). The
MAX32626 also hosts an optimal variety of peripherals including SPI, UART, I2C, 1-Wire interface, USB 2.0, PWM engines, 10-bit ADC, and many others. A trust protection unit (TPU) with advanced security features is incorporated in this MCU. Interfaces: The ESCU hosts multiple interfaces: SPI, I2C, and CAN. isoSPI for robust and safe information transfer across a high voltage barrier.
USB-C to power the board and flash the MCU.
JTAG for microcontroller programming and debugging.
Arduino connector (enables more flexibility for adding Arduino-compatible boards such as an Ethernet shield, sensor boards, or even a Proto Shield). isoSPI transceivers: Contains 2× LTC6820 to achieve the isoSPI communication with the BMS ICs on a daisy chain using a single transformer. This ensures that this board is fully isolated from the BMS ICs connected to large voltage battery stacks. The presence of a dual isoSPI transceiver provides a redundant and reversible isolated communication where the host MCU alternates communication ports to monitor signal integrity (a future development of this board will include the ADBMS6822 (dual isoSPI transceiver) for
Continued on page 22 Components in Electronics April 2025 21
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