With the proliferation of charging pile brands in the current market, product quality varies significantly. Consequently, the material selection standards and processing craftsmanship for charging pile wire harnesses and connectors serve as the cornerstone of overall system quality. Our company frequently receives inquiries regarding automation solutions for new energy vehicle (EV) charging infrastructure. Having successfully delivered automated production lines for charging harnesses and connectors, we aim to clarify the critical knowledge, processing workflows, and industry standards in this sector to address common client concerns.

EV charging pile wire harnesses (including charging gun cables and internal high-voltage harnesses) are critical safety components in the EV charging ecosystem. Their specifications and processing requirements are extremely stringent, governed by Chinese National Standards (GB), Energy Industry Standards (NB/T), and International Standards (such as IEC and UL). The following is a detailed analysis of these specifications and process requirements.

I. Core Specification Standards

1. Cable Body Standards

• GB/T 33594-2017 "Cables for Electric Vehicle Charging": This is the core domestic specialized standard.
  • Applicability: Rated AC voltage ≤ 0.6/1kV; Rated DC voltage ≤ 1.5kV.
  • Conductor Specifications: Common cross-sectional areas include 0.5, 1, 1.5, 2.5, 4, 6, 10, 16, 25, 35, 50, and 70 mm².
    • Low Power (7kW): Typically utilizes 3×6mm² or 3×10mm² configurations.
    • High Power (60kW - 120kW+): Typically utilizes 35mm², 50mm², or larger, often incorporating liquid cooling technology.
  • Structural Requirements: Conductor + Separator + Insulation + Inner Sheath + Shielding Layer (if applicable) + Outer Sheath.
  • Material Characteristics: Must use Oxygen-Free Copper (purity ≥ 99.9%). Insulation and sheathing materials must possess excellent oil resistance, ozone resistance, weather resistance (UV stability), and flame retardancy (typically requiring VW-1 or FT1 ratings).
  • Flexibility Requirements: Charging gun cables undergo frequent bending and dragging. Standards mandate rigorous bending life testing (typically requiring tens of thousands of cycles without fracture).

2. Connection System and Interface Standards

• GB/T 20234 Series: Defines physical interface dimensions and electrical parameters.
  • GB/T 20234.1 (General Requirements)
  • GB/T 20234.2 (AC Charging Interface)
  • GB/T 20234.3 (DC Charging Interface)
• NB/T 33002-2018 "Technical Conditions for EV AC Charging Piles" & NB/T 33001: Specify connection norms and temperature rise limits for the charging pile assembly and internal harnesses.

3. Safety and Performance Standards

• GB/T 18487 Series: General requirements for conductive charging systems and Electromagnetic Compatibility (EMC).
• UL 2251 / IEC 62196: For export products, compliance with US UL or international IEC standards is required, imposing additional requirements on fire resistance ratings and mechanical strength.

II. Key Processing Craftsmanship Requirements

The manufacturing of charging pile harnesses must be conducted in a highly controlled environment. The primary processes and standards are as follows:

1. Cutting and Stripping

• Precision Control: Length tolerance is typically controlled within ±1mm.
• Zero-Damage Tolerance: It is strictly prohibited to damage conductor strands during stripping. For multi-strand, fine-twisted high-flexibility cables, laser stripping or precision mechanical stripping must be employed to ensure a 0% strand breakage rate. Broken strands can lead to reduced current-carrying capacity and localized overheating.

2. Terminal Crimping

• Crimping Standards: Must comply with QC/T 29106 or USCAR-21 standards.
• Key Indicators:
  • Pull-out Force: Must meet the minimum tensile force specified by standards (ranging from hundreds to thousands of Newtons depending on wire gauge).
  • Crimp Height/Width: Must remain within tolerance to minimize electrical contact resistance.
  • Micro-Metallographic Analysis: Regular cross-sectioning is required to verify a proper metal interdiffusion layer between the conductor and terminal, ensuring no oxidation or voids.
• Terminal Types: High-current terminals often utilize copper-aluminum transitions or silver/tin plating to reduce contact resistance and prevent oxidation.

3. Shielding Treatment

• Objective: To prevent high-frequency interference during the charging process (EMC).
• Process:
  • For braided shielding meshes, coverage density is typically required to be ≥85%.
  • Shield grounding must utilize dedicated shield clips or a 360-degree ring termination process to ensure effective grounding for both low and high frequencies.
  • Foil shielding must be secured with conductive tape, with an overlap width of ≥5mm.

4. Overmolding and Assembly

• Connector Overmolding: The junction between the charging gun head and the cable typically employs a two-shot molding process.
  • Temperature/Pressure Control: Parameters must be strictly controlled to avoid air bubbles, short shots, or scorching.
  • Strain Relief: The molded structure must incorporate a Strain Relief design to prevent bending forces on the cable from transferring to the terminal crimp area.
• Seal Installation: Charging guns must achieve protection ratings of IP54 (wall-mounted) or IP65/IP67 (outdoor/DC piles). Seal compression rates must be controlled between 20%-30%, utilizing dedicated tooling for installation.

5. Special Process: Liquid-Cooled Cable Manufacturing

• Targeted at ultra-fast charging (480kW+) cables containing internal coolant lines.
• Sealing Integrity: Pipe connections must undergo extremely high-standard sealing tests to ensure zero leakage of the coolant (typically ethylene glycol-water solution).
• Fluid Testing: Flow rate and pressure tests are mandatory post-assembly.

III. Inspection and Testing Standards (Quality Control)

Finished harnesses must pass the following rigorous tests before release:

1. Electrical Performance Testing

• Withstand Voltage Test: AC 2500V/5min or DC 3500V/1min, with no breakdown or flashover.
• Insulation Resistance: ≥100 MΩ·km (at 500V DC).
• Conduction Resistance: Resistance per meter must meet the lower limit specified by national standards to ensure temperature rise remains within limits under high current.

2. Mechanical Performance Testing

• Bending Test: Simulating actual usage, typically requiring ≥10,000 cycles (up to 30,000 cycles) of reciprocating bending without jacket rupture or core breakage.
• Tensile Test: Verifies cable tensile strength.
• Torsion Test: Verifies resistance to twisting.

3. Environmental Adaptability Testing

• Thermal Cycling: Cycles between -40°C and +90°C (or higher) to ensure materials do not become brittle or sticky.
• Salt Spray Test: Metal components must pass 48h - 96h neutral salt spray testing with no red rust.
• Oil/Chemical Resistance: After immersion in gasoline, engine oil, or coolant for a specified duration, the volume change rate and hardness change of the sheath must remain within standard limits.
• Flame Retardancy Test: Vertical burning test; the material must self-extinguish upon removal of the flame, and dripping particles must not ignite cotton.

4. Identification and Traceability

• Cable surfaces must feature clear ink-jet coding including: Specification/Model, Voltage Rating, Executive Standard (e.g., GB/T 33594), Production Date, and Manufacturer Code. The marking must be abrasion-resistant.

Conclusion

EV charging pile wire harnesses are not ordinary power cords; they are special components characterized by high voltage, high current, high flexibility, and high weather resistance. Their production must comply with mandatory standards such as GB/T 33594. Critical process controls focus on damage-free conductor stripping, micro-quality of terminal crimping, shielding integrity, and injection molding sealing. Furthermore, rigorous aging, bending, and environmental testing are prerequisites before these components can be put into service.