With the rapid development of new energy vehicles and energy storage technologies, the safety and reliability of battery systems, as core energy carriers, have attracted much attention. As the supporting and protective structure of the battery module, the electrical insulation performance of the battery tray is directly related to the safe operation of the vehicle, battery life and personal safety of the user. The electrical safety design of the battery tray is the cornerstone of battery system safety. Through multi-level protection, such as insulation, structure, heat, and monitoring, it ensures stable operation of the battery under complex working conditions, reduces the risk of fire, explosion, or electric shock caused by electrical failure, and extends battery life and improves system reliability.

This article focuses on the electrical insulation safety of battery trays, systematically explains its design principles, the verification method of pressure resistance performance, and the root cause analysis and improvement strategies of typical failure cases, in order to provide theoretical support and practical reference for the high-safety design of battery systems.

Previous article - Design points

The core of the electrical safety design of the battery system lies in the trinity of "prevention-control-emergency": prevent failures through insulation isolation, reliable connection, thermal management and other measures; achieve real-time control with the help of sensors and BMS; use fire prevention, pressure relief and other designs to deal with extreme situations. All key points need to work together to ensure the safety and reliability of the battery system throughout its life cycle, while taking into account maintainability and compliance. The battery tray is not only a structural support in the battery system, but also has multiple functions such as electrical isolation, thermal management, anti-slip, mechanical protection, grounding and modular design, which is crucial to ensuring the electrical safety of the battery system.

1-Structural support ensures electrical connection reliability

The battery tray ensures the reliability and safety of electrical connections under complex working conditions by fixing battery modules, reducing mechanical stress, resisting vibration and shock, maintaining alignment, and integrating environmental protection and thermal management.

Figure 1 Battery tray

A.Physical support and fixation ensure the precise alignment of electrical connection points (such as busbars, wiring harnesses, and connectors) to avoid poor contact caused by structural deformation or displacement; provide a rigid frame to fix battery modules and connectors to prevent loosening or breakage caused by vibration or impact.

B.Environmental isolation and protection: prevent the intrusion of water vapor, dust, salt spray, etc. through sealing design (such as IP67/IP68), avoid short circuits caused by corrosion or insulation failure; block external mechanical shock or foreign body impact to protect high-voltage connection components.

C.Thermal management synergy: integrated heat dissipation structure (such as liquid cooling plate, thermal pad) balances temperature to prevent local overheating from causing oxidation or welding of connection points; reduce thermal interference between adjacent modules through thermal insulation design to avoid material expansion differences caused by temperature gradients.

D.Electromagnetic compatibility (EMC) support: suppress electromagnetic interference through metal shielding layer or conductive coating to protect low-voltage signal lines (such as BMS communication lines) from high-voltage circuit interference.

2-Isolation protection builds an efficient isolation environment

The focus of battery electrical isolation design is to create an environment that can effectively isolate high voltage electricity and ensure efficient operation of the system, ensuring that the battery module can be safely packaged under any operating conditions, preventing accidental release of electrical energy, and thus avoiding potential electrical risks.

A.The battery tray structure takes into account both load-bearing and isolation protection:

l Aluminum alloy materials, such as extruded aluminum alloy, are preferred to achieve lightweight while maintaining high rigidity and impact resistance. The outer frame is used to bear the weight of the entire battery system and external impact. Closed-section profiles are used to enhance structural strength. The inner frame is designed to support battery modules and water-cooled plates, etc., to ensure their stability and heat dissipation requirements.

l Insulating materials are used as pads or coatings to ensure good electrical isolation between the battery module and the tray. The high-voltage wiring harness should have a dedicated management path and insulating sheath to ensure electrical clearance and creepage distance with the tray.

l Advanced welding technologies such as stir friction welding are used to improve connection strength while reducing heat-affected zones, avoiding deformation and potential cracks. For parts that are inconvenient to weld, bolt connections or riveting are used, combined with sealants, to ensure the reliability of mechanical connections and electrical isolation.

l Modularity is considered during design to facilitate battery replacement and maintenance without affecting the stability of the overall structure.

Figure 2 Schematic diagram of electrical clearance and creepage distance

B. Key points of high and low voltage isolation design:

l The positive and negative points of the battery system must be isolated from the low-voltage power supply system and the battery tray to ensure that there is sufficient electrical clearance and creepage distance between the high-voltage circuit and the low-voltage control circuit to meet safety standards and prevent high voltage leakage to the low-voltage system.

l The high-low voltage isolation design needs to consider electromagnetic compatibility (EMC) to ensure that the isolation measures will not introduce interference and keep the system running stably.

l High-impedance connection, the high and low systems are connected through high-impedance, and only the vehicle body ground (battery tray) is allowed to limit the flow of current to ensure that the high-voltage system fault spreads to the low-voltage system.

l Physical isolation measures, when designing the battery tray, the high-voltage and low-voltage components can be arranged in different closed chambers to reduce mutual influence through physical separation; use insulating materials as pads between the battery module and the tray, such as polymer plastics or rubber, to ensure physical and electrical isolation.

l Consider the maintainability of the isolation measures during design to ensure that they can be repaired or replaced safely when necessary.

C.Key points of contact protection design:

l High-voltage harness management: High-voltage harnesses should be properly wrapped in insulating sheaths and managed in an orderly manner through fixing clips or wire troughs to avoid exposure and reduce the risk of direct contact.

l Safety partitions: Insulating partitions are set between battery modules and between battery modules and tray walls to prevent the risk of indirect electric shock caused by electrolyte leakage when the battery is damaged.

l High-voltage component packaging: Key components such as high-voltage connectors and relays are packaged to ensure that these components will not be directly touched by accident even inside the tray.

l Enclosed design: The battery tray is designed as a closed structure as a whole, using a metal or composite shell to ensure that the internal high-voltage components are not exposed, and the shell itself must also have good insulation properties.

l Locking mechanism: For maintainable high-voltage connection points, a locking mechanism is used to ensure that they will not be easily opened during non-professional operations, reducing the risk of accidental contact.

l Insulating material application: Insulating materials are used as an isolation layer between the battery tray and the battery module to ensure that even if the tray is damaged, the human body can be prevented from directly contacting the live parts. These materials include but are not limited to polymer plastics, rubber gaskets or coatings.

3-Electrical Logo Design

The electrical identification of the battery tray can not only improve the safety of operation, but also simplify the maintenance process and reduce the risk of incorrect operation.

A.Clear identification

l Clearly mark warning signs such as "High Voltage Danger" and "Do Not Touch" on the battery tray and surrounding high-voltage components to ensure quick identification even in an emergency.

l Use internationally accepted color coding, such as red or orange to mark high-voltage areas and blue for direct current, to intuitively distinguish different electrical characteristics.

l Apply standardized electrical safety symbols, such as the graphic symbols in IEC 60417, to indicate high voltage, grounding, power-off points, etc. to ensure global understandability of information.

l Include the serial number, production date and batch information of the battery tray for easy tracking and recall management.

l Select wear-resistant and corrosion-resistant materials and printing technologies to ensure that the label remains clear and readable throughout the life cycle of the battery tray.

B.Warning signs

l High voltage hazards are clearly marked on the battery tray and surrounding areas to remind maintenance personnel to pay attention to electrical safety and comply with operating procedures.

l Indicate safe operating distances, especially near high-voltage connectors and exposed locations, to remind people to keep an appropriate distance.

C.Operation guide

l Clearly mark the grounding locations of the battery system and the tray to ensure proper implementation of grounding measures.

l Identify safe test points and maintenance access points, which should be designed to operate at low voltage or non-powered conditions.

l Basic operating and safety instructions can be briefly listed in non-critical areas of the tray to guide the correct operating process.

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