一、Why do new energy vehicles spontaneously combust？

In the final analysis, the cause of spontaneous combustion of new energy vehicles is mainly concentrated on the battery and its management system. Problems with the battery itself, problems with the battery management system (BMS), external collisions, or the environment can all cause battery failure. As a key component to solve these problems, BMS is responsible for monitoring various parameters of the battery pack, such as voltage, current and temperature, and manages the charging and discharging process through sophisticated algorithms to ensure the safe and efficient use of the battery.

A reliable BMS not only extends battery life, but also prevents safety hazards such as overheating and short circuits that can cause fires. BMS is like the "brain" of electric vehicles, and its health is directly related to the overall performance of the vehicle and the safety of the user's life and property.

Although every car company incorporates these features in the design of BMS systems, why does spontaneous combustion occur? This brings us to electrostatic surge, which is a transient, high-voltage phenomenon that usually occurs during human contact, lightning strikes, or power system fluctuations. Electrostatic surge can affect the normal operation of BMS in many ways. For example, it can cause data transmission errors, damage to electronic components, or even make the entire system fail.

A well-known electric vehicle brand has suffered multiple spontaneous combustion incidents in its early models, ultimately prompting the company to recall 4,803 vehicles carrying a specific batch of power battery packs. The investigation revealed that the cause of the fire was caused by the failure of a battery module located in the front of the vehicle. While the official report does not explicitly point to electrostatic surges as the direct cause, they are a potential risk point in any situation involving electronic devices. In particular, during the charging process, the connector insertion and removal operation is prone to electrostatic discharge, which, if not properly protected, may damage the BMS or other key components, thereby affecting the stability of the entire battery system and increasing the possibility of thermal runaway.

三、Leiditech focus on automotive electronic electrostatic surge protection

In order to effectively prevent the impact of electrostatic surge on BMS, the protection principles such as isolation, shielding and discharge must be followed. Through reasonable circuit design and material selection, the anti-interference ability and reliability of BMS can be greatly improved. The following are Lei MAO Electronics electrostatic surge protection solutions for different interfaces:

l DC 12V power port surge load protection

Adopt high-power TVS or PTC+TVS combination scheme, meet ISO10605-2, grade 4, contact discharge ±15KV, air discharge ±25KV. Leiditech bidirectional TVS diodes SMDJ24CA or P8S33CA are recommended. PPTC adopts Leiditech HL30-300, holding current 3A, triggering current 6A, maximum voltage 30V, DIP package.

l CAN bus port surge electrostatic protection

As shown in the scheme diagram, Lei-Mao Electronics adopts low residual voltage TSS to effectively protect the interface, and the TSS reaction time is ns level, which can not only prevent surge, but also prevent static electricity, and ensure signal integrity. Meet ISO10605-2 (electrostatic contact discharge ±8kV, air discharge ±15KV), in line with the requirements of Beijing automobile enterprise standard BAS582-2019 for CAN bus BC contact discharge ±8KV, air discharge ±15KV.

l LIN electrostatic protection solution：

A single asymmetric bidirectional ESD protection device PESD1LIN was designed for LIN bus. In line with ISO10605-2 (±23kV air discharge, ±23kV contact discharge) standards, meet the requirements of Beijing automobile enterprise standard BAS582-2019 for LIN bus BC contact discharge ±8KV, air discharge ±15KV.

l Esd protection solution for sensors：

Adopts GBLC24C protection 24V power supply sensor chip, small package SOD-323, peak pulse current 8A, peak pulse power 400W, clamp voltage 50V. Meet ISO10605-2, contact discharge ±30kV, air discharge ±30kV.

The recommended material number parameters for the above scheme are as follows:

四、Conclusion

As the core control system of electric vehicle, the stability and safety of BMS directly affect the performance of the vehicle and the safety of the user. As a common source of external interference, electrostatic surge may cause a series of serious consequences, although it may seem insignificant. Therefore, manufacturers and practitioners need to focus on EMC forward design early in the design process.

Leiditech Electronics provides free consulting and sample verification services, and supports free EMC testing to help customers ensure that products meet safety standards!

Leiditech is committed to becoming a leading brand in the supply of electromagnetic compatibility solutions and components, supplying ESD, TVS, TSS, GDT, MOV, MOSFET, Zener, inductors and other products. Leiditech has an experienced R & D team, can provide personalized customized services according to customer needs, to provide customers with the best quality solutions.