Core Function: Connect battery modules to high-voltage components such as motors and charging piles, transmitting hundreds of volts of high-voltage electricity (e.g., the voltage of Tesla Model 3 battery pack is 350V, with a peak current exceeding 400A).
Technical Features:
Conductor Material: High-purity copper (conductivity >99.97%) is preferred; aluminum bars are used in some scenarios for weight reduction (density is only 1/3 of copper, but conductivity is 30% lower).
Cross-Sectional Area Calculation: Designed according to a current density of 6-8A/mm² (e.g., a 400A current requires a 50mm² copper cable). An overly thin harness will cause temperature rise exceeding 50℃, while an overly thick one increases weight (a 50mm² copper cable weighs 0.5kg per meter).
Core Function: Transmit voltage and temperature collection signals (with an accuracy of ±1mV) from the BMS (Battery Management System) and control commands (such as relay on/off signals).
Technical Features:
Multi-Core Shielded Cable: Each cable carries 1-4 signal channels, with an outer layer wrapped in aluminum foil + braided mesh shielding (shielding efficiency >90%) to resist electromagnetic interference (EMI) from motors and charging piles.
Differential Signal Transmission: For example, CAN bus uses twisted pairs (twist pitch 5-10mm) to suppress common-mode interference, ensuring data transmission delay <10μs.
Material Selection:
Copper bars: Suitable for fixed connections (e.g., parallel connections between modules), with tin plating (thickness 5-10μm) on the surface to prevent oxidation, and contact resistance <100μΩ.
Cables: Suitable for dynamic connections (e.g., between battery packs and motors), using multi-strand soft copper wires (single wire diameter <0.1mm) with a bending radius >5 times the cable diameter to avoid metal fatigue and breakage.
Material Requirements:
High-voltage insulation: Cross-linked polyethylene (XLPE, temperature resistance 150℃) or silicone rubber (temperature resistance 200℃) is used, with insulation resistance >100MΩ・km and breakdown voltage >15kV/mm.
Low-voltage insulation: Polyvinyl chloride (PVC) or TPE materials are used, with temperature resistance 85℃, and flame retardancy (UL94 V-0 grade) and oil resistance (to prevent electrolyte corrosion).
Physical Protection:
Corrugated tubes: Made of PA66 nylon material (temperature resistance -40℃~150℃) with compressive strength >50N/mm, protecting wiring harnesses from stone impacts (e.g., wiring harnesses for under-chassis battery packs).
Heat-shrinkable tubes: With a shrinkage ratio of 2:1, they seal terminal blocks and achieve an IP67 waterproof rating (no water ingress after 30 minutes of immersion in 1-meter-deep water).
Temperature Rise Control: The temperature rise of wiring harnesses must be <50K (surface temperature <75℃ at an ambient temperature of 25℃). Exceeding 80℃ will accelerate insulation layer aging (halving service life). Reduce resistance by increasing cross-sectional area or paralleling wiring harnesses (e.g., NIO ET7 battery pack uses parallel double wiring harnesses, reducing resistance by 40%).
Shielding: The shielding layer of low-voltage wiring harnesses must be grounded at both ends (ground resistance <1Ω), improving shielding efficiency for high-frequency interference (>10MHz) to 95%.
Distance: The spacing between high-voltage and low-voltage wiring harnesses must be >50mm, and they should be laid vertically when crossing to reduce electric field coupling interference (e.g., insufficient spacing in a certain vehicle model increased BMS data error rate by 20%).
Filtering: Add common-mode inductors (inductance 10-20μH) at signal input ends to filter out high-frequency noise above 100kHz.
Vibration Resistance: Wiring harnesses must pass a 20g acceleration (5-2000Hz) vibration test, with fixed point spacing <300mm, using a dual fixing method of clips + cable ties (e.g., Tesla battery pack wiring harnesses have a fixed point density of 5 per meter).
Temperature Cycle Resistance: After 1000 cycles of -40℃~85℃, the insulation layer crack rate must be <5% and conductor elongation >20%.
Heat Avoidance Layout: Keep wiring harnesses away from heat sources (e.g., contactors, fast-charging interfaces) with a spacing >20mm from heat-generating components.
Heat Dissipation Assistance: Spray thermal silica gel (thermal conductivity 1.5W/(m・K)) on the surface of high-voltage wiring harnesses to conduct heat to the battery pack shell, reducing conductor temperature by 5-10℃.
Interface Unification: Use standardized terminals (e.g., TE's HSD high-voltage connectors with >500 insertion/extraction cycles) to support 3-minute quick replacement.
Modular Wiring Harnesses: CATL's CTP technology integrates wiring harnesses into the module frame, reducing scattered wiring by 90% and improving assembly efficiency by 40%.
Causes: Poor terminal crimping (insufficient crimping depth increases contact resistance by 30%), insufficient cross-sectional area of wiring harnesses (current density exceeding 10A/mm²).
Solution: Use ultrasonic welding instead of crimping to reduce contact resistance to below 50μΩ, and monitor wiring harness temperature in real-time with infrared thermal imagers (accuracy ±2℃).
Causes: Insulation layer corrosion by electrolyte (HF gas accelerates aging), mechanical wear (water ingress after corrugated tube rupture).
Prevention: Use acid and alkali-resistant fluororubber insulation layers (resistant to HF concentration >50ppm), and install anti-wear bushings (e.g., polytetrafluoroethylene material) along the wiring harness path.
Phenomenon: Fluctuations in cell voltage collected by BMS exceed 5mV, leading to SOC estimation errors over 5%.
Countermeasures: Use single-ended grounding for the shielding layer of low-voltage wiring harnesses (end grounding for high-frequency interference, start grounding for low-frequency interference), and add signal repeaters (1 every 5 meters to amplify attenuated signals).
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