Quality Assurance – From Pre-Shipment Inspections to Factory Audits

In the first two articles, we systematically found potential suppliers and secured satisfactory quotes and samples through professional negotiation. However, a core challenge remains: how do you ensure that the subsequent thousands of mass-produced units are completely consistent with the perfect sample you approved?

The answer lies in establishing a proactive and systematic Quality Assurance (QA) process. This is more than just "checking"; it's the core of supply chain risk management. Today, we dive into the four key actions to ensure bulk order quality after sample approval.

Part 1: Foundational Work – Establishing an Unshakeable Quality Baseline

Before production begins, vague expectations of "high quality" must be transformed into clear, unambiguous contractual documents.

1. Sign a Detailed Technical Agreement: This is the "constitution" of your QA. It should go beyond a simple datasheet and include:

2. Approved Sample Specification: Clearly state that the "Approved Sample" (with a unique serial number recorded by both parties) is the absolute standard for appearance, performance, and craftsmanship.

3. Acceptable Quality Limits (AQL): Define the acceptable defect levels for critical/major/minor defects for random inspections. (e.g., AQL 0.65 for critical defects, AQL 1.5 for major defects).

4. Detailed Testing Standards: Specify the testing methods, equipment, and pass/fail criteria for key performance parameters (capacity, internal resistance, cycle life test sampling).

5. Finalize the "Golden Sample": Physically seal 2-3 samples approved by both parties, affix labels with signatures and dates, and keep one each. This is the ultimate physical benchmark for resolving any future disputes.

Part 2: Proactive Monitoring – The Power of In-Process Quality Control (IPQC)

Waiting to inspect only at the end is high-risk. For large or critical orders, conducting In-Process Quality Control (IPQC) during production is a game-changer.

• What to Inspect: Focus on processes that directly impact core performance and are hard to remedy later.

• For Lithium-ion Packs: Spot-check welding quality (laser/ultrasonic) for consistency, cell matching grouping data, BMS software version and functional test records, insulation and potting processes.

• For Lead-Acid Batteries: Check plate coating uniformity, acid filling density and temperature control, initial sealing integrity.

• How to Execute: You or a trusted third-party inspector can conduct an unannounced or scheduled visit to the production line to observe these critical processes and review real-time factory QC data.

Part 3: The Final Gatekeeper – Executing a Rigorous Pre-Shipment Inspection (PSI)

This is the mandatory final checkpoint before goods leave the factory. A standard PSI should cover:

1. Quantity & Packaging Check: Verify total cartons, shipping marks, and packaging compliance with your requirements (e.g., moisture-proof, shock-absorbent).

2. Visual & Workmanship Inspection (Based on AQL): Randomly select samples according to the AQL standard (e.g., ANSI/ASQ Z1.4) to check for surface defects, label accuracy, and assembly issues.

3. Critical Dimension & Function Verification: Use calipers, multimeters, etc., to measure key dimensions and basic electrical functions (open-circuit voltage, polarity).

4. Performance Spot-Check (The Most Important): For a smaller sample (e.g., 3-5 pieces), conduct destructive or in-depth tests at the factory's lab, such as:

   • Capacity Test: Verify actual capacity meets the spec.

   • Internal Resistance Test: Ensure consistency (high variance indicates poor cell matching).

   • BMS Function Test: Verify over-charge/discharge protection, balancing, etc.

5. Documentation Review: Check if packing lists, commercial invoices, and mandatory certificates (UN38.3 test report, MSDS) are complete and accurate.

Core Principle: The PSI report is your leverage. It is standard practice to make the balance payment contingent upon receiving a satisfactory PSI report or to agree that defective items found will be replaced before shipment.

Part 4: The Strategic Assessment – The Factory Audit

For strategic, long-term partners, a comprehensive factory audit is the ultimate due diligence. It evaluates the supplier's intrinsic ability to consistently produce quality, going beyond a single batch. Key audit areas include:

• Quality Management System: Is there a certified system (like ISO 9001)? Is it effectively implemented, or just paperwork?

• Testing Equipment & Lab Capability: Are key testing devices (cyclers, resistance testers, safety test chambers) calibrated and operational? Can they perform the tests they claim?

• Supply Chain & Traceability: How do they control incoming raw materials (especially cells)? Is there a batch traceability system from raw material to finished product?

• Production Environment & Technician Skill: Is the workshop clean and orderly (indicating good process discipline)? Are operators trained on standardized work procedures?