More Cells, More Range: TI’s Wireless Battery Management System Frees EV Space for More Design InnovationJanuary 07, 2021 by Jake Hertz
We spoke with Texas Instruments to learn more about this new tech, which they feel can shake up the EV industry.
You don’t have to be an electrical engineer to know that one of the biggest challenges standing in the way of electric vehicle (EV) adoption is the limited range of the automobile. Consequently, EV manufacturers do everything they can to fit as many battery cells as possible inside their cars, since more cells mean more range.
This technique, however, can come with some notable setbacks—setbacks Texas Instruments hopes to address with what the company is calling "the industry's best-performing wireless battery management solution."
All About Circuits spoke with TI representatives to learn more about the design roadblocks of wired battery monitoring systems (BMS) and how the company's wireless BMS—and others like it—could help.
The Shortcomings of Wired Battery Monitoring Systems
From a systems standpoint, a challenge with incorporating so many cells is that each cell must be continually monitored to optimize health and performance while detecting anomalies.
Diagram of an EV’s wired BMS. Image used courtesy of Texas Instruments
Conventional battery management systems (BMS) have each node physically wired to a monitor. Put into context, the standard EV battery has over 100 cells. Using a wired BMS for a system like this requires feet of cabling to install.
Yet, this is the way most BMS are implemented today. Along with the additional weight that comes with these wires, the wires also take up significant space in the chassis, which could be used for other tech, or even more battery cells.
Many EVs currently include pounds of wires, which can compromise safety, hoard space, and put a drag on vehicle efficiency. Image used courtesy of Texas Instruments
Further, and possibly most importantly, cabling, and subsequent connectors, are often a major source of failure in electrical systems. This means that a wired BMS with hundreds of nodes becomes more susceptible to failures.
The Solution: Go Wireless
Instead, the solution that some manufacturers like Texas Instruments are turning to is wireless BMS.
In a wireless BMS, a wireless interface is used to transmit data from the battery node monitor to the host MCU. The benefit here is, obviously, removing the need for the clunky and fallible cabling. In theory, removing the wires decreases weight and footprint while improving reliability.
Karl-Heinz Steinmetz, TI's general manager of Powertrain in Automotive Systems, describes the benefits of wireless BMS, including "reducing the complexity of the design." He explains, "This [means] a bill-of-materials, wiring harness, connectors, transformers, capacitors, which we no longer have to use. Instead, we are using one single IC."
The top diagram depicts a wired BMS while the bottom illustrates the simplicity of a wireless BMS. Image (modified) used courtesy of Texas Instruments
However, there are certainly legitimate engineering concerns with wireless BMS. For these solutions to be effective, they have to monitor accurately in real-time. This means they capture accurate measurements while transmitting and receiving wireless data with extremely high throughput and low error rates. These multiple tasks become even more difficult when operating in a hot, noisy environment like a car’s chassis.
Further, the system would need to be low power, since significantly draining the battery isn’t a viable option.
Texas Instruments Aims for Real-Time, Wireless BMS
Today, Texas Instruments introduced its own wireless BMS—including a proprietary wireless protocol—that seemingly addresses many of these connectivity challenges. The new solution marries two new chips, the CC266C2R-Q1 wireless MCU and the BQ79616-Q1 battery monitor and balancer.
Diagram of a wireless BMS. Image used courtesy of Texas Instruments
TI claims this solution achieves ±2 mV accuracy, a network packet error rate of less than 10-7, and a network availability of over 99.999%. Other specs include a best-case throughput of 1.2Mbps. This high network availability, along with high throughput, ensures the constant availability of data—meaning reliable, real-time battery monitoring.
Explaining how these results were achieved, Ram Vedantham, TI's manager of the 2.4 GHz Business Line, explained, "Since the car chassis acts as a faraday cage, all of the interferers are known and contained within the system. So, by careful design of our protocol, which is a combination of time-division multiplexing and frequency hopping, we are eliminating any noise to the maximum extent possible."
Making Cars More Intelligent
This system looks promising for the advancement of EVs. While not the first wireless BMS available, the specs of TI’s solution make it a considerable option for replacing wired BMS. Notably, TI’s solution is also the first to receive ASIL-D compliance, the most stringent safety requirements available.
By removing the cabling, wireless BMS generally and TI’s solution specifically may decrease weight, increase reliability, and decrease BMS footprint. With more room in the chassis, designers could easily incorporate more intelligence or add more battery cells, meaning more range for the EV.