Anti-loosening Solution for New Energy Vehicle Battery Pack Connections: Application Technology of Diamond Friction Shims

I. Technical Challenges of New Energy Vehicle Battery Pack Connections

The battery pack is the core component of new energy vehicles, and the reliability of its connections directly affects driving safety and battery service life. During vehicle operation, the battery pack is subjected to complex operating conditions including continuous vibration, shock loads, temperature fluctuations and electrochemical corrosion. The connecting positions are prone to bolt loosening and preload decay. In severe cases, it may cause seal failure of the battery pack, module displacement and even safety accidents.

Traditional anti-loosening solutions have limitations when applied to battery packs: spring washers can only prevent thread loosening and fail to suppress interfacial micro-slip; thread-locking adhesives may degrade under high-temperature conditions inside battery packs and complicate disassembly for subsequent maintenance. Featuring high friction, superior wear resistance and stable performance over a wide temperature range, diamond friction shims deliver a more reliable anti-loosening solution for battery pack connections.

II. Analysis of Critical Connection Positions of Battery Packs

1. Battery Pack Housing to Chassis Connection The battery pack housing is bolted to the vehicle chassis and bears vibration and shock during driving. Loosening at this joint will lead to abnormal noise and seal failure of the battery pack, and endanger vehicle safety in serious cases. Diamond friction shims increase the friction coefficient of mating surfaces, restrain interfacial micro-slip and maintain long-term connection stability.
2. Battery Module Fixing Connections Battery modules are secured inside the pack by brackets and bolts. Modules are exposed to inertial forces during acceleration, deceleration and steering. Loose connections may result in module displacement, collision and abrasion, impairing battery consistency and service life. High-friction shims stabilize the preload of module fasteners and reduce maintenance frequency.
3. Electric Drive System Connections Connections between the electric motor, reducer and frame endure shock upon motor startup and transmission torque, making them high-risk areas for vibration-induced loosening. Diamond friction shims improve connection stiffness, reduce vibration transmission and protect the electric drive system.
4. High-Voltage Harness Connector Fastening Fixed joints for high-voltage harness connectors require stable preload. Loosening may raise contact resistance, cause overheating and even fire hazards. Ultra-thin diamond friction shims improve connection reliability within limited installation space.
5. Battery Pack Upper Cover Sealing Connection The sealing joint between the upper cover and lower housing demands uniform preload. Preload decay will trigger seal failure, allowing moisture and dust to ingress into the battery pack. Diamond friction shims ensure consistent preload decay across all fastening points and preserve sealing uniformity.

III. Technical Advantages of Diamond Friction Shims

Adopting DAOLER® Diamond Claw® interlocking technology, DAOLER® Diamond Friction Shims offer the following benefits for new energy vehicle battery pack applications:

1. High Friction Coefficient Static friction coefficient ≥0.6, 3–5 times that of ordinary flat washers. Under identical bolt preload, the joint can withstand greater vibration and shock loads and effectively suppress interfacial micro-slip.
2. Suppression of Preload Decay The microscopic mechanical interlocking mechanism physically eliminates interfacial slip, significantly slowing preload decay and extending connection maintenance intervals.
3. Wide Temperature Adaptability Stable performance from -40℃ to 150℃, matching the operating temperature range of battery packs (typically -30℃~60℃, exceeding 80℃ under extreme working conditions).
4. Ultra-Thin & Lightweight Ultra-thin specifications starting from 0.1 mm with minimal weight, meeting lightweight design requirements for new energy vehicles. Direct replacement for original flat washers without modification to connection structures.
5. Corrosion Resistance Nickel-phosphorus diamond composite coating delivers outstanding corrosion resistance, adapting to electrochemical corrosion environments that may exist inside battery packs.
6. Non-Damaging to Mating Surfaces The particle size and interlocking depth of diamond grains are precisely controlled. While achieving high friction, the shim will not damage mating surfaces of aluminum alloy and high-strength steel, protecting battery pack housings and brackets.

IV. Application Effects and Data

When diamond friction shims are applied to new energy vehicle battery pack connections, the following outcomes can be achieved:

• Connection preload decay rate reduced by over 60%, maintenance cycle extended by 2–3 times
• Markedly reduced abnormal noise of battery packs and improved NVH performance
• Enhanced uniformity of preload on sealing joints, lowering risks of seal failure
• Reduced vibration transmission of electric drive systems and improved ride comfort
• Extended bolt fatigue life and decreased risk of bolt fracture
• No thread-locking adhesive required for simpler assembly and maintenance

V. Selection & Installation Guidelines

Selection Guidelines

• Battery pack housing connection: Select standard annular shims of 0.2–0.5 mm
• Module fixing connection: Choose ultra-thin specifications of 0.1–0.3 mm
• Electric drive connection: Adopt high-friction grades of 0.3–0.8 mm
• Aluminum alloy mating surfaces: Verify interlocking depth to avoid surface damage
• Corrosive environments: Select grades with salt-spray passivation treatment

Installation Guidelines

• Clean mating surfaces before installation to remove oil contamination and burrs
• Place diamond friction shim between the two mating surfaces
• Tighten bolts in the specified torque and sequence
• No thread-locking adhesive or other anti-loosening components required
• Carry out a preload inspection after initial assembly

VI. Comparison with Traditional Anti-Loosening Solutions

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VII. Conclusion

Anti-loosening reliability of new energy vehicle battery pack connections is critical to vehicle safety. Centered on DAOLER® Diamond Claw® interlocking technology, DAOLER® Diamond Friction Shims feature a static friction coefficient ≥0.6, ultra-thin specification starting at 0.1 mm and stable performance from -40℃ to 150℃. They provide an independently controllable, high-reliability anti-loosening solution for key joints including battery pack housings, module fastenings and electric drive connections.