UWB is a new way to use it in cars. Can wireless BMS also use it?

Ultra-wideband (UWB) technology is not uncommon in the automotive industry. From car keys to liveness detection, this new transmission method can be used. Today, let's look at a more innovative application - NXP recently launched a wireless battery management system (BMS) using UWB technology.

In addition to NXP, major BMS manufacturers including ADI and TI have also set their sights on wireless BMS. Why is this so?

Wireless communication within a battery pack reliably transmits battery cell information, such as voltage and temperature measurements, from one module to a battery management unit without the need for wiring. It helps ensure optimal performance and prevents conditions that could lead to premature failure or safety hazards.

NXP's UWB wireless BMS technology separates mechanical and electrical development, providing electric vehicle manufacturers with greater flexibility, faster time to market and lower development costs, while keeping the system fully scalable across different platforms.

“Our wireless battery management system solution is the industry’s first to feature UWB technology, providing EV manufacturers with state-of-the-art technology to power the electric vehicles of the future,” explained Naomi Smit, general manager and vice president of battery management systems at NXP. “Trimension UWB provides simple, secure and robust wireless communication within the BMS, outperforming existing narrowband solutions. We are proud to work with our customers to make the promise of wireless a reality.”

Implementing wireless technology within the reflective enclosure of a battery pack is challenging. Rather than modulating a carrier frequency (sinusoidal signal) such as the narrowband 2.4 GHz, such as BLE-based technologies, UWB uses high-bandwidth pulses. This provides greater immunity to reflections and frequency-selective fading, resulting in more robust and reliable data transmission.

NXP’s ultra-wideband wireless battery management system solution will be available for OEMs to evaluate and develop starting in the second quarter of 2025.

The solution is part of NXP's FlexCom chipset and supports both wired and wireless technologies, providing OEMs and Tier 1 suppliers with greater flexibility in vehicle architecture and technology selection. Its common software architecture and safety libraries for both BMS configurations enable them to reuse software on different platforms, further reducing development efforts.

The NXP FlexCom BMS chipset also includes NXP’s recently announced MC33777 battery junction box (BJB) IC, which provides accurate voltage, chassis isolation and current measurement for high voltage systems. The BJB is part of NXP’s complete turnkey battery management system offering and can be used with wired and wireless battery management solutions and NXP’s software and applications, without the need for manufacturers to recruit additional partners.

Traditional battery management systems (BMS) usually use wired connections to monitor and manage the status of batteries. This connection method involves multiple components, including battery cells, battery monitoring units (BMUs), battery management units (BMUs), and central control units. Although the wired connection method of traditional BMS is mature and reliable, it also has some limitations, such as complex wiring, difficult maintenance, high costs, and low design flexibility. With the development of wireless communication technology, wireless BMS has gradually become an attractive alternative, which replaces traditional wired connections with wireless communication and improves the flexibility and reliability of the system.

Wireless BMS will greatly simplify the battery life cycle management process. Source: ADI

Wireless BMS has the following advantages:

Reduced Weight: Wireless BMS reduces the mechanical challenges, failure points and costs of traditional wiring harnesses.

Improved energy density: By eliminating connectors and cables between battery cells, energy density can be increased, helping to achieve longer driving range.

Design flexibility: Wireless BMS offers greater design flexibility, enabling OEMs to leverage robotic manufacturing capabilities to scale up EV production.

Simplified assembly: Wireless solutions improve efficiency in electric vehicle assembly by reducing the use of complex wiring harnesses in battery packs and reducing error-prone manual labor in the production process.

Improve battery safety, reliability and maintainability: Wireless BMS reduces the risk of failure and improves the overall reliability of the battery system by reducing wiring harnesses and connectors.

Support ASIL-D level functional safety: Wireless BMS supports ASIL-D level functional safety.

Network availability: Wireless BMS solutions can provide the industry's best network availability (over 99.999%).

Reduce costs: Wireless BMS reduces design complexity and cost. For example, every 50,000 vehicles produced will save 500km of wires and 25,000kg of connectors and transformers.

Easy to maintain and upgrade: Wireless BMS facilitates quick removal of the battery pack for repair and helps seamlessly transition to the battery second-life stage.

Support wireless software updates: Wireless BMS supports wireless software updates, which helps improve battery performance and extend battery life.

Wireless BMS topology results, source ADI

According to the introduction, NXP's UWB has multiple advantages over previous wireless BMS. The most important reason is that the RF environment in the battery pack is very special, which is very different from most wireless systems optimized for open-air communications.

Modular battery packs consist of multiple battery modules enclosed in a metal casing. The metal casing generates many reflections and the signal bounces around for a period of time, creating a rich multipath environment. This frequency selective fading depends largely on the location of the antennas and the location of the openings and channels between the modules. In addition, other unpredictable interference from operating in the same frequency band may also affect the transmission in the battery pack. These two factors severely affect narrowband systems, meaning that complex and adaptive channel selection algorithms are required. Since each antenna may require a different frequency for optimal communication in a narrowband system, this also limits broadcast type communications.

With UWB type pulse signals, because the energy is emitted over a wide bandwidth, narrow frequency gaps in the band have little impact on signal quality. This ensures reliable communication for all transmit and receive links within the battery pack, enabling broadcast messages. Due to its robustness in the battery pack environment, UWB supports reliable communication at raw data rates up to 7.8 Mbps. This is much higher than many narrowband technologies and enables new applications with faster measurement cycles and/or high data rates.

Another benefit of UWB is its very precise timing and synchronization capabilities, taking advantage of the narrow pulse/high bandwidth nature. While BMS applications currently primarily require its data communications capabilities, UWB’s exceptionally precise timing allows extremely precise synchronization of measurements, such as current and voltage (typically measured on different subsystems in a battery pack), at well below µs, while most of today’s narrowband technologies stop at a few µs.

In addition to the general advantages of UWB over narrowband solutions, NXP's ultra-wideband wireless BMS implementation includes several specific enhancements that improve reliability and predictability.

One enhancement is the use of an optimized UWB packet structure designed to maximize performance in battery environments.

The second enhancement is the use of a time slot scheduling approach. As shown in the figure, each node has a fixed time slot to receive or transmit. This eliminates the need for complex channel access and allocation schemes, which are necessary in general systems where network configuration needs to be flexible. The design is frequency hopping-free, conflict-free, and has strong time predictability.

NXP says it has achieved a packet error rate of less than 10-6 in a single transmission. This enables packet designs to have fewer iterations and are less susceptible to design optimization.

Due to this approach and the higher data rates (up to 7.8 Mbps), the same amount of data can be transmitted in a shorter period, and NXP's UWB BMS consumes less average power than other wireless or wired technologies.

In addition to RF-specific advantages, NXP has implemented several other features that benefit this application. The system ensures the privacy and integrity of messages by using a built-in hardware security engine for encryption, preventing eavesdropping and false message insertion.

Short-term session keys, where every message is encrypted using AES-128 (or optionally AES-256), are a widely accepted solution.

As the first company in the industry to introduce wireless BMS technology, ADI's products have been applied in many scenarios. The SmartMesh wireless network provides high reliability (>99.999%) of data transmission and can maintain stable communication even in harsh electromagnetic interference environments.

Wireless BMS allows for flexible placement of battery modules in the vehicle and the installation of sensors in locations that were previously unsuitable for wiring.