TI vs. NXP vs. Analog: Comparing Battery Management Systems
Recently, Analog Devices has added to its battery management system portfolio. Since EV systems are quickly advancing, the question of how does this system compare to others?
For electric vehicles (EVs), one of the main dilemmas to address for increasing sales is getting consumers to buy into the fact that the EVs can charge quickly and stay charged for a long enough distance.
Designers can look at the energy density and battery storage to monitor and prevent overvoltage or over-temperature phenomena. An increase in battery size can directly affect the weight, cost, and safety of the EV, making a well-equipped battery management system (BMS) one of the best methods of shrinking the size of the battery.
A general overview of a standard BMS. Image used courtesy of Toradex
Over time, Analog Devices (ADI) has showcased an extensive portfolio of BMS products through 5-generations of consistent updates. Keeping up with its trend, ADI recently introduced two multicell battery monitors. These monitors are Automotive Safety Integrity Level-D (ASIL-D) certified with new low-power features to enable continuous battery monitoring even after the car has been turned off.
This article aims to explore ADI's monitors and how it looks compared to a few competitors like Texas Instruments and NXP.
ADI’s New Multicell Battery Monitor
Since 2008, ADI has designed and manufactured BMS solutions to meet the growing demand for effective EV technology and keeping safety in mind enough to achieve an ASIL-D rating. ADI's latest addition to its BMS portfolio claims to handle 6-18 cell modules with low-power consumption.
Utilizing ADI's 8 or 12 channel monitors in a BMS allows for continuous verification of each battery cell's charge, even after the EV is turned off. It takes roughly 304 μs to measure all cells in a system.
ADI's ADBMS6815 multicell battery stack monitor is optimized for 12 series-connected battery cells with data accumulated under high noise mitigation. Meanwhile, the second product announced, the ADBMS6817, is identical in characteristics, only differing in handling 8 series-connected battery cells.
Wiring diagram of ADI’s 12-Channel Multicell Battery Monitor which is designed for use in ISO 26262 applications for ASIL-D compliance. Image used courtesy of Analog Devices
ADI has improved battery cell monitor technology by having the daisy-chained cells be bidirectional. This ability can help diagnostics locate faults that could occur on the communication line that connects each cell. Each cell has a dedicated pulse-width modulation (PWM) duty cycle control that adds passive cell balancing to the equation.
With its past innovations, ADI certainly has the attention of EV manufacturers, in addition to its latest stackable battery monitors; however, there may be some competition that holds advantages and disadvantages over them.
Texas Instruments’ BMS Features Wireless Communication
Texas Instruments (TI) is a distinguished manufacturer in the vast world of electronics known for creating affordable semiconductors for various applications. For decades, TI has been designing hybrid and EV powertrain systems that include BMS technology. TI was also the first BMS manufacturer to receive an ASIL-D rating.
TI’s 16 in series cell monitoring IC is coupled with a battery balancer that is fully autonomous with auto-pause and resumes abilities for robust cell balancing. Screenshot used courtesy of Texas Instruments
As for some specifications, TI's battery management integrated circuit (BMIC) offers 128 μs, accurate cell voltage measurements across all 16 channels. The option for 12, 14, and 16 series-connected cells, offering more design flexibility than ADI's latest battery monitor.
Since the ability to extend EV's driving range comes from having a more prominent battery source, TI holds a slight advantage compared to ADI by having 12-16 cell options.
Both BMS solutions offer daisy chain communication for optimal monitoring and share a similar balancing current. Also, they can both filter for unwanted distortions and have a passive balancing architecture.
One increasing benefit is how TI states it has implemented a wireless data transfer that removes several connectors and cabling from the BMS.
With TI being at the forefront of that specific technology, ADI has yet to announce a wireless BMS product that can compare to TI; however, it does have a line of wireless power transfer products, including receiver/chargers and transmitters.
Keeping that in mind, it might be possible for EV manufacturers to see ADI developing a wireless BMS product in the foreseeable future.
Removing the wireless aspect to the BMS, another comparison is with NXP's latest BMS.
NXP’S 14-Channel Battery Cell IC
NXP's 14-channel battery cell controller (BCC) IC can monitor between 7 to 14 in series cells through daisy-chained communication or capacitor isolation. What stands out about NXP is the scalability expectations; NXP's BCC could be on the cusp of becoming a game-changer for future battery design with potentially 800 cells per daisy chain.
Compared to ADI and TI's battery monitors, NXP's BCC, MC33771C, has an isolated communication speed of 4 Mbps, double the speed, and offers a two-wire twisted pair versus a single use for Serial Peripheral Interface (SPI) communication. This SPI is advantageous since a faster SPI can boost the short-distance comms for the BMS.
NXP's MC33771C applications diagram with SPI. Image used courtesy of NXP
This battery monitor component can be easily integrated into energy storage systems (ESS) and uninterruptible power supply (UPS) for EVs and industrial applications. In addition, NXP's BCC is equipped with passive balancing and can operate in sleep mode just as ADI's solution.
Through looking at the different options for BMS, it becomes prevalent to see how vital this system is and how so many top companies are approaching it in similar yet, drastically different ways.
The Importance of BMS
An EV is only as good as its battery system. The aesthetically pleasing features within the cabin can draw customers in, but what gets people to invest in the transition to renewable energy-based transportation is the driving range and price.
To drive longer on a single charge requires an extensive enough battery and storage system. No one wants a trunk-filled battery supply, which is why designers and engineers are addressing the battery setup. The fundamentals of a robust and efficient EV powertrain is a well-equipped BMS.
ADI, TI, and NXP all share the concept of stackable battery cells with daisy-chained communication to save on space and bring design flexibility into the equation. Temperature control becomes essential when the heat begins to dissipate from the multicell configurations.
Each manufacturer offers a product that can easily monitor temperature and run diagnostics for potential faults from cell to cell. In addition, NXP and TI have discussed ways of going wireless or cloud-based to free up more space for potentially more battery cells.
The global focus on EVs can bring more and more technology like BMS further into the future. As a result, newer and more innovative systems are sure to be on the horizon.