Automotive high voltage BMS and energy storage BMS

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With the rapid development of the new energy industry, the importance of high-voltage BMS and energy storage BMS (battery management system) for new energy vehicles has become increasingly prominent, and has also become a hot application in the semiconductor industry. This article describes the BMS architecture, main chips, and popular automotive high-voltage BMS and energy storage BMS solutions.

BMS has different architectures, wireless BMS is the trend

According to the installation and working mode of BMS in battery cells or battery modules, there are several classifications:

Centralized BMS architecture : The battery pack uses a central BMS component. The advantages of centralized BMS are compactness and lower cost. However, many ports are required to connect all battery packs, making maintenance and troubleshooting cumbersome.

Modular BMS topology : The BMS is divided into several modules that are connected to adjacent parts of the battery pack. The cost of modular BMS topology is higher than centralized modules, but troubleshooting and maintenance are easier, and it is relatively easy to scale to larger battery packs.

Master/Slave BMS : The slave modules are limited to relaying measurement data to the master module, while the master module performs calculations, handles control, and external communications. Given the simple functionality of the slave modules, this architecture is generally less expensive.

Distributed BMS architecture : All hardware is integrated on the control board of each battery unit, eliminating the need for bulky wiring and making each BMS more independent. It also makes troubleshooting and maintenance more difficult and more costly.

Battery management has evolved in tandem with the way batteries are designed. One trend in BMS is toward a more centralized wireless BMS concept, alleviating the large amount of wiring required in older architectures, making maintenance easier, and also reducing the weight of the battery pack. In electric vehicles, wireless BMS may enable electric vehicles to travel longer distances before needing to be recharged, reducing the time required to charge the system.

BMS involves 4 types of chips

Regardless of the structure, BMS involves four types of chips, namely battery charging, battery fuel gauge, battery monitoring chip, and battery protection chip. The four types of battery management chips of BMS effectively solve the problems of charge state estimation, battery state monitoring, charging state management, and battery cell balancing, so as to ensure the smooth operation of the battery system and extend the battery life. Xinchacha shows that the main players in domestic battery management chips are still mainly overseas companies, with great differences in operating income and product models.

Functions of various BMS chips: Battery charging chips ensure safe and efficient battery charging by adjusting battery charging parameters such as voltage, current and time. Battery fuel gauge chips intelligently determine charging time and speed based on battery charging requirements and usage. Battery status monitoring chips monitor battery power, temperature, status, etc. in real time, and provide relevant data predictions and warnings. Safety protection chips have functions including overheat protection, overcharge protection, short maintenance protection, etc. to ensure battery charging safety.

Figure Note: Major battery charging IC brands (Source: Xinchacha)

Figure Note: Major brands of battery power chips (Source: Xinchacha)

Figure Note: Major brands of battery monitoring chips (Source: Xinchacha)

Figure Note: Battery protection chip (Source: Xinchacha)

Automotive High Voltage BMS Solution

If electric vehicles want to increase their driving range, speed up charging, and provide a user experience comparable to that of traditional fuel vehicles, BMS is the most critical link. To achieve this goal, high-voltage BMS is an important technical path and has become a hot topic in the field of automotive electrification in recent years.

In response to such design requirements, NXP has launched a new high-voltage BMS solution to accelerate product development and commercialization. The solution includes two high-performance BMS chips from NXP:

Functional safety ASIL-D analog front-end chip MC33774 : supports 18 channels of battery cell voltage acquisition and balancing, with a maximum balancing current of 300mA for a single channel, and supports 9 GPIOs for temperature acquisition.

Powerful daisy chain communication gateway chip MC33665 : supports up to 4 daisy chains, can connect 4 single chains or 2 loopback daisy chains; supports single SPI, dual SPI, UART and CAN/CAN-FD communication with MCU. CAN-FD has a maximum rate of 5Mbps, which can realize a BMS architecture without MCU and software inside the battery pack.

Figure: Brief functional block diagram of high-voltage BMS (Source: NXP)

Energy Storage BMS Solution

Combining Nuvoton's cost-effective MCU and AFE products, China Power Port has developed a complete home/industrial energy storage solution that reaches mass production level. This solution is suitable for power management of up to 22 lithium batteries and has the following functions:

Battery pack information detection, including battery voltage, charge and discharge current, battery temperature, board temperature and other information.

Battery pack status analysis, including battery SOC and battery SOH estimation, etc. Our unique SOC and SOH filtering and correction algorithms can effectively improve the SOC measurement accuracy.

Battery pack safety protection includes timely handling of overvoltage, undervoltage, overcurrent, overtemperature and other faults during charging and discharging. Redundant protection circuits and complete self-test circuits in hardware have fast and multiple protection measures for short circuits, and timely protection and alarm for sudden faults such as short circuits, overcurrent, overtemperature, etc., which greatly improves the reliability and safety level of the system.

Battery pack thermal management heats and dissipates heat from the battery to ensure the ambient temperature for battery use, effectively extending the service life of the battery pack.

Battery pack information management integrates multi-channel 485 and CAN communications, and supports external WiFi or Bluetooth modules to transmit the collected data and information to the background or host through the CAN bus or wirelessly.

The solution supports the use of multiple machines in parallel and has the function of parallel automatic encoding. It is fully applicable to various occasions such as home energy storage, base station energy storage, outdoor energy storage, UPS, etc. An important part of the solution is the upper computer system independently developed by China Power Port for mass production testing: the lithium battery management system, which is fully functional and easy to operate. It helps energy storage product manufacturers to quickly design, test, mass produce, and perform after-sales maintenance, greatly shortening the product development cycle and reducing the workload of designers, testers, and maintenance personnel.

Figure: China Power Port's self-developed energy storage BMS solution (Image source: China Power Port)

summary

New energy vehicles are evolving towards higher voltage 800V systems, which can use electricity more efficiently, improve driving range and acceleration performance. In addition, industrial and household energy storage technologies are also developing rapidly. This is because the popularity and demand for renewable energy have increased, and energy storage systems have become an important part of balancing supply and demand and providing backup power.

Whether it is an electric vehicle or an energy storage system, the role of BMS will become increasingly important. Adopting an overall BMS system solution can help customers reduce development time and costs. First of all, the overall BMS system solution is usually provided by professional suppliers who have rich experience and expertise. This means that customers do not need to design and develop a BMS system from scratch, but can directly use existing solutions. Secondly, the overall BMS system solution is usually highly integrated, which means that the various components have been fully tested and verified and can be seamlessly integrated into electric vehicles or energy storage systems, which reduces the problems and risks that customers may encounter during the integration process. Finally, the overall BMS system solution can also provide better technical support and after-sales service. Since suppliers are responsible for the entire system, they can respond to customer needs more quickly and provide timely technical support and maintenance services.

Huang Hainian

Yanqz

Wireless BMS may enable electric vehicles to travel greater distances before needing to be recharged, reducing the time required to charge the system