Wireless BMS system opens doors for innovation in electric vehicle battery system design

Today, driving anxiety in electric and hybrid vehicles is still about range, charging time, and safety. Among them, increasing the battery capacity is an obvious means to increase the cruising range, but in addition to open source, there are many throttling means to increase the cruising range, such as through a more accurate BMS (battery management) system, the third-generation semiconductor fast charging technology, As well as reducing the weight of vehicles and other means to reduce consumer concerns.

Today, driving anxiety in electric and hybrid vehicles is still about range, charging time, and safety. Among them, increasing the battery capacity is an obvious means to increase the cruising range, but in addition to open source, there are many throttling means to increase the cruising range, such as through a more accurate BMS (battery management) system, the third-generation semiconductor fast charging technology, As well as reducing the weight of vehicles and other means to reduce consumer concerns.

A few days ago, Texas Instruments (TI) announced the launch of a functional safety certified wireless BMS solution certified by TÜV SÜD, enabling wireless transmission of battery data and control commands.

Shi Ying, director of embedded and digital optical processing applications in Texas Instruments China, said that at present, all BMSs of electric vehicles use wired systems, which require copper wires to be daisy-chained. Therefore, on the one hand, the complex wiring increases the weight of the whole vehicle. On the other hand, cables and connectors are vulnerable parts. Due to vibration and other conditions, it is easy to cause poor contact, or to be easily damaged by moisture and heat, which reduces the safety level. When there is a problem with these mechanical structures or wiring harnesses, the entire battery pack needs to be replaced. In addition, by reducing wiring, the internal wiring space is reduced, which can further improve the power density of the battery pack.

Since a typical electric vehicle has nearly 100 battery packs in series, requiring several meters of copper wire, removing this connection will undoubtedly better achieve the compact, high-density and high-reliability battery packs required for electric vehicles.

Based on the above considerations, TI has developed a highly reliable wireless BMS system.

Introduction to BMS System Solution

TI’s wireless BMS mainly consists of two parts.

The most important part of it is the SimpleLink CC2662R-Q1 wireless MCU, which is AEC-Q100 compliant. The chip is based on Arm Cortex-M4 and integrates rich analog peripherals and radio frequency subsystems on the chip. The chip integrates a dedicated wireless BMS protocol stack, adopts the 2.4GHz frequency band (2402-2480 MHz), and has a built-in TI-RTOS to support fast networking.

Wireless BMS system opens doors for innovation in electric vehicle battery system design
CC2662R-Q1 system block diagram

Wu Wanbang, TI system engineering manager, said that the power consumption of the CC2662R-Q1 chip is very low, so users do not need to worry about the extra burden on the entire battery system by using wireless.

Wireless BMS system opens doors for innovation in electric vehicle battery system design
Wireless BMS system opens doors for innovation in electric vehicle battery system design
Various types of power consumption are shown in the table.

The other is TI’s battery monitoring chip BQ79616 series, with different products from 12-16 channels, compatible with pins and software, which can provide users with maximum design flexibility and help reduce system costs.

Wireless BMS system opens doors for innovation in electric vehicle battery system design
BQ79616 block diagram

reliability

All along, people are naturally more reliant on wired technology and have doubts about the reliability of wireless technology. To this end, TI’s solution was designed with SÜD’s design goals in mind from the very beginning, fully compliant with ISO 26262’s SÜD design standards, and also certified by TÜV SÜD as ASIL-D compliant, due to the absence of wear and tear, making Wireless technology is more secure and reliable than wired.

Excellent network performance

Shi Ying said that behind the reliability is the wireless protocol stack specially developed by TI for the automotive BMS system. Its network availability index is 99.999%. Even if a 0.001% failure occurs, the entire network restart and rebuild time will not exceed 300ms. , the entire wireless BMS system will not be lost by the host of the car for a long time.

“Because there is one master server in a BMS, there are 8 to 10 slave servers, so when you synchronize from the master server to all the slave servers, the time is not long,” explained Wu Wanbang.

In terms of throughput, the protocol stack adopts a time-slotted communication design, which can greatly improve the data throughput and reduce the communication delay between each node. This further protects data from loss and damage. In terms of throughput, it can achieve a data throughput of 1.2Mbps, and the delay of each node will not exceed 2 milliseconds. Shiying said that the protocol stack can ensure fast and accurate sending of voltage data and cell temperature data to the battery main unit MCU with an error of no more than ±2 mV, and the bit error rate of the entire network data packet will be less than 10-7.

Wireless BMS system opens doors for innovation in electric vehicle battery system design
Measured data map of wireless data transmission

For information security, TI has adopted a proprietary protocol, so the security has been unprecedentedly improved. The unique key exchange and refresh mechanism, as well as the unique device authentication and debugging security and other protection functions, enable the entire wireless BMS system to perform well in information security.

Regarding the EMI and EMC issues concerned by wireless applications, Shiying explained that the BMS wireless protocol stack can form a clean and interference-free communication network through technologies such as frequency modulation. Wu Wanbang said that TI’s wireless BMS has passed the evaluation of some customers and proved that there will be no interference when the 2.4GHz frequency in the car coexists.

Powerful Extensibility

The TI BMS system provides multiple cross-platform freedom for reliable system design, supports modules composed of different cells, and combines with the BQ79616 series to achieve a high degree of scalability and flexibility of the system.

The protocol stack is designed with the BMS system’s requirements for measurement synchronization in mind, and the BQ79616 also supports node measurement synchronization, so no matter how the battery pack platform is scaled, the best performance can be achieved.

The protocol stack supports up to 100 nodes, and no additional isolation design is required due to wireless transmission.

As TI Automotive Product Marketing Engineer Daniel Torres said: “Wireless BMS system design is like designing on a blank canvas. When you don’t have to worry about where to place the wiring harness, you can come up with new ways to use the space and even mix and match Different sizes and types of batteries.”

More friendly development and verification environment

TI.com.cn currently provides wireless BMS development kits including development kits, SDKs and protocol stacks, as well as RF configuration development software SmartRF Studio and current sensing development software Sensor Controller Studio.

Each development kit contains 9 boards, 1 pre-programmed battery control unit and 8 pre-programmed battery sensor units. The wireless BMS EVM can be configured as a battery control unit (primary node) or a battery sensor unit (secondary node). Supports wireless BMS EVM programming and debugging using the standalone XDS110 debug probe.

Wireless BMS system opens doors for innovation in electric vehicle battery system design
At the CES2021 online summit, TI also highlighted the wireless BMS system

Shiying pointed out that the wireless BMS development kit is a complete set of turnkey reference design, including the reference design of the antenna has been included, users can also fine-tune according to their own needs.

The Links:   DMF5010NB-FW-BC LM150X08-A4NK