High-Voltage Power Supply in New Energy Vehicle (BMS, BDU, Relay, Integrated Battery Box) Research Report, 2025

The high-voltage power supply system is a core component of new energy vehicles. The battery pack serves as the central energy source, with the capacity of power battery affecting the vehicle's range, charging time, and efficiency. It is also closely related to the overall vehicle cost. The high-voltage power supply system of new energy vehicles studied in this report mainly includes modules such as Battery Management System (BMS), Battery Distribution Unit (BDU), high-voltage DC relays, and integrated battery boxes.

The Shift of Battery Management System (BMS) from Centralized to Distributed Architectures

To increase the vehicle's range and charging speed, new energy vehicle battery packs have larger capacities, higher total voltages (with the mass production of 800V - 1000V platform architectures), and more battery cells. The limited sampling channels, computing performance, and long wiring harnesses of centralized BMS systems struggle to manage these large-scale battery arrays. In contrast, distributed BMS architectures can optimize the management of large battery arrays through local measurement, modular design, and distributed computing, and can provide more accurate and sensitive real-time feedback on the status of power supply system.

The architecture of high-voltage power supply system in new energy vehicles has shifted from a centralized BMS architecture to a distributed one. The distributed BMS architecture can significantly enhance system reliability and safety. It avoids single-point failures; a malfunction in a single slave control module usually does not cause the entire system to collapse and is easier to replace. Moreover, in a distributed architecture, the acquisition circuits are placed close to the battery cells, reducing interference and errors introduced by long wires and enabling more accurate data collection, which helps with more precise safety assessments. The distributed BMS uses bus communication, greatly reducing hardwired connections and making the internal structure of the battery pack more concise and reliable.

The distributed BMS architecture adopts a master-slave structure: one Master manages multiple Slaves. Each slave control module monitors information such as the voltage and temperature of a group of battery cells and reports the data to the master control module for unified processing and protection decisions. Different OEMs adopt different distributed BMS architecture solutions:

• Xiaomi SU7 Max uses a "one master, three slaves" BMS architecture. The master control chip is Infineon TC387, the bridge chip is TI BQ79600, and the slave board AFE chip is TI BQ79616. Each slave board manages 66 battery cells and uses 5 BQ79616 chips in cascade for sampling; communication is achieved through Daisy Chain and Ring topologies.
• NIO ES8 adopts a "one master, sixteen slaves" BMS architecture. The master BMU is provided by Bosch China - the master control chip uses Infineon's TC275TP and Bosch's System Basis Chip (ASIC) 0D273, and the slave control unit CMU is provided by CATL - the core monitoring chip is Analog Devices' LTC6811HG - 2; communication and data transmission between the BMU and CMU are carried out via the CAN bus.
• Tesla's early models used a centralized BMS architecture, while subsequent models (Model 3/Y) evolved to a distributed BMS architecture - a " one master, four slaves" BMS architecture. The main controller is located in the "Penthouse" of bthe attery pack.
• Distributed BMS architectures are commonly used in BYD's mainstream mass-produced electric vehicles.

Challenges in the Promotion of Distributed BMS Architectures:

• Increased System Complexity: The development of software algorithms and the coordination and management of the system become more difficult, requiring more powerful master controllers, more refined monitoring modules, and more complex communication protocols.
• Cost Issues: The hardware and development costs of distributed BMS systems in new energy vehicles are relatively high. Currently, apart from some high-volume automakers that tend to develop BMS systems in-house, many manufacturers choose third-party suppliers.
• Standardization Requirements: The industry urgently needs to promote the standardization of BMS interfaces and communication protocols to reduce the integration difficulties and costs between devices from different suppliers and to facilitate the healthy development of BMS industry.

Take Xiaomi Auto as an example. Its BMS uses a "one master, three slaves"" distributed architecture. The Xiaomi SU7 Ultra uses silicon carbide (SiC) across the board, with SiC chips in the main drive, vehicle power supply, and air conditioner compressor controllers. The vehicle uses 172 SiC chips, mainly sourced from Infineon and ST, and concentrated in:

• Electric Drive System: Each motor controller needs to be equipped with 48 SiC MOSFET chips. The three-motor drive solution results in 144 chips being used in the electric drive part. The suppliers are Inovance Automotive and UAES; for main drive SiC MOSFET chips, they are mainly sourced from Infineon, STMicroelectronics, onsemi, and Bosch.
• Vehicle Power Supply (OBC/DC - DC Two-in-One): 14 SiC chips are used. The supplier is Zhejiang EV-Tech, and its SiC MOSFET chip supplier is Wolfspeed.
• High-Voltage DC - DC Converter: 8 SiC chips are used.
• Air Conditioner Compressor Controller: 6 SiC chips are used. The supplier is Zinsight Technology, which has partnered with STMicroelectronics for SiC MOSFETs.

Power Battery Electronic Components, Such as BMS And BDU, Tend to Converge and Develop Towards High-Voltage Integrated Battery Boxes

Many companies have proposed integration solutions for power battery electronic components, such as BMS and BDU, to make the design of battery packs more concise and efficient:

• Intelligent Control has proposed several integration solutions for high-voltage BMS and other components, such as the integration of CSC + BMU and BDU; integrating the high-voltage BMS - BMU into the vehicle domain controller and the MCU high-voltage domain controller respectively.
• Aptiv shared two BDU solutions: First, as customers' pursuit of the performance of 800V high-performance vehicle BDUs becomes more extreme, and they also put forward refined platform design requirements, Aptiv has launched the latest liquid cooling solution in cooperation with customers. Second, in-depth integration of major components such as BDU, BMS, OBC, and DC - DC, which are arranged on the second layer of the battery pack, can improve the vehicle's space utilization and assembly efficiency and reduce development costs.
• GAC's early BDU integration with BMU physically combines the two, which not only increases the usable space of entire battery pack, leaving more room for battery cells to function, but also saves on plastic parts.
• UAES integrates BMS and BDU into a Powerbox, and its Powerbox has entered mass production. The integrated components have a higher value.
• Schaeffler believes that in addition to physical integration, BMS also involves algorithm integration. It aims to simplify actuators as much as possible, that is, to consider all signal collection and contactor control in the battery pack as one actuator. At the same time, software functions can be moved upward and placed in any controller. For example, integrating BMS functions into the zonal controller or main controller can remove the microcontroller (uC) and reduce the BOM. Currently, Schaeffler has mass-produced BMS integrated with BDU, wireless BMS, etc. in Europe, North America, and China.

In March 2025, UAES launched a new generation of HVDU intelligent integration solution integrating the Battery Management Unit (BMU):

• In-depth Integration of BMU and Related Components: UAES breaks through the traditional separate architecture. Based on BMU and current sensors, with mature and reliable integration processes, it continuously innovates and expands its product line. Currently, the relays have successfully entered mass production and are deeply integrated.
• Modular Platform Design to Meet Full-Scenario Requirements: Based on the concept of platform expansion, the HVDU supports flexible configuration within a rated current range of 150A - 500A, is compatible with 400V/800V voltage platforms, and can quickly adapt to different vehicle models such as BEV and PHEV by adding or reducing relay modules. Compared with current industry products, the integration solution reduces space occupation by 50% and shortens the development cycle by 40%.
• While focusing on the development of second-generation HVDU, UAES simultaneously conducts pre-research on new HVDU technologies, such as advanced system architectures and high-voltage switching technologies that replace relays with electronic switches E-fuses, and the deeper integration of HVDU and the integration of CharCon into the Powerbox. These technologies help customers reduce system costs and improve system performance.

Currently, major OEMs have launched integrated products of BDU and BMS, such as NIO, Li Auto, XPeng, Dongfeng, BYD, GAC, etc., providing solutions for extreme cost reduction in battery systems:

• In NIO's electrification solution, BDU is integrated with BMU, high-voltage connectors, thermal runaway sensors, DC - DC, and other components.
• GAC's BDU integration with BMU physically integrates BDU, BMU, DC - DC, thermal runaway sensors, and fast-change connectors. This not only increases the usable space of the entire battery pack, leaving more room for the battery cells to function, but also saves on plastic parts.
• Inside the ""second layer"" at rear of Qilin battery pack of Xiaomi SU7, EE components such as BMS, CCU, and relay boxes are placed. The high-voltage electrical area of the BMS and relay box is mainly for high-voltage series - parallel connection and low-voltage control. The vehicle charging control unit CCU (integration of OBC + DC - DC) provides the voltage conversion function during the charging process. The relay box is arranged below the BMS, and an aluminum Busbar heat sink is installed on the bottom surface to dissipate the heat generated by high-power charging and discharging.
• XPeng's high-voltage power distribution box X-BMU integrates BDU + BMS. It includes a housing, a flexible circuit board, multiple electrical component modules, and a battery management system (BMS). Each component is integrated in the housing and is electrically connected through the flexible circuit board, replacing traditional wiring harnesses/plugs.

The Increasing Prominence of BMS Chips in the 800V Architecture

Automotive-grade BMS chips have indeed become the core components of BMS systems in the 800V high-voltage architecture. They act as the ""intelligent brain"" of battery pack, need to address numerous challenges brought about by higher voltages, and play a crucial role in the safety, efficiency, and performance of entire battery system.

To address the cost and availability challenges of high-voltage components (such as traction inverters) in 800V platform and to be compatible with existing 400V charging piles, a switchable 2x400V/800V architecture has emerged. The BMS needs to intelligently manage the switching of two battery groups between parallel (driving) and series (fast charging) states. This increases system complexity and places higher demands on the control logic and reliability of BMS chips.

Suppliers have introduced more powerful BMS chips. For example, NXP's MC33774 AFE chip supports 18-channel voltage acquisition and a 300mA equalization current; and the MC33665 gateway chip supports CAN FD communication and Daisy Chain topologies, helping to simplify the architecture.

For Wireless BMS Systems (wBMS), NXP released a new-generation UWB BMS solution in the field of wireless BMS systems (wBMS) in November 2024. Unlike the modulated carrier frequencies (sinusoidal signals) used in 2.4 GHz narrow-band technologies such as Bluetooth® Low Energy (BLE), UWB utilizes high-bandwidth pulses. This unique feature enhances its resistance to reflection and frequency-selective fading, guaranteeing more stable and reliable data transmission. The chipset designed for wireless battery management systems includes the BMA6060 and BMA6061.

NXP's BMS chips leverage three core technologies: highly integrated AFE (BMx73x8), innovative UWB wireless technology, and EIS health diagnosis (DNB1168). These technologies have enabled NXP to establish deep partnerships with leading customers such as CATL and Geely. As a result, NXP takes a leading position in the industry in terms of wireless BMS mass production progress and long - lifespan energy storage solutions.