Battery Pack Assembly Process: A Step-by-Step Engineering Guide (2026)
Release time:
2026-01-28
The transition from a raw battery cell to a high-voltage battery pack is one of the most critical stages in EV manufacturing. Whether you are dealing with Prismatic, Cylindrical, or Pouch cells, the assembly process determines the safety, efficiency, and longevity of the final product. In this 2026 engineering guide, we break down the automated assembly workflowinto four essential stages focused on high-speed precision.
Introduction: The Critical Transition in EV Manufacturing
The transition from a raw battery cell to a high-voltage battery pack is one of the most critical stages in EV manufacturing. Whether you are dealing with Prismatic, Cylindrical, or Pouch cells, the assembly process determines the safety, efficiency, and longevity of the final product. In this 2026 engineering guide, we break down the automated assembly workflowinto four essential stages focused on high-speed precision.
Step 1: Cell Inspection & Sorting (OCV/IR)
Automated cell qualification is the foundation of pack longevity.Before assembly begins, every incoming cell must pass through an OCV (Open Circuit Voltage) and IR (Internal Resistance) testing station.
OCV Testing:Ensures chemical stability across the entire batch.
IR Testing:Prevents localized overheating caused by resistance imbalances within the pack. In Huiyao’s modern automated systems, 6-axis robots sort these cells into distinct grades with 100% data traceability, ensuring each module contains cells with perfectly matched performance profiles.
Step 2: Module Stacking & Precision Compression
Cells are stacked into modules to achieve the required voltage and capacity.
For prismatic cells, this process requires high-pressure compression to ensure structural rigidity and thermal contact.
Engineering Challenge:Maintaining uniform pressure across the stack without deforming the cell casing.
Huiyao Solution:We utilize servo-driven compression fixtures with active force feedback. This system ensures that every module is compressed to the exact micron, preventing cell swelling and extending the pack’s lifecycle.
Step 3: Busbar Laser Welding (The Heart of Connectivity)
Busbar welding is the most critical electrical connection stage in the assembly line. While older production lines relied on ultrasonic welding, High-Speed Laser Welding has become the global industry standard for 2026 due to its superior penetration depth and speed.
Technical Comparison: Laser Welding vs.Ultrasonic Welding
|
Feature |
Laser Welding (Huiyao Standard) |
Ultrasonic Welding |
|
Bond Strength |
Ultra-High (Fusion Weld) |
Moderate (Friction Weld) |
|
Mechanical Stress |
Zero (Non-contact) |
High (Vibration-based) |
|
Process Speed |
12-30 PPM (High Efficiency) |
Lower (Cycle-limited) |
|
Material Capability |
Thick Copper/Aluminum Busbars |
Limited to thin foils |
Using a High-End Prismatic Assembly Line with integrated smart vision systems can reduce false welding defects by 90%compared to traditional manual or semi-automated methods.
Step 4: EOL (End-of-Line) Testing & Safety Gate
A finished battery pack is not ready for vehicle integration until it passes the EOL safety gate. This final stage validates the “birth certificate”of the pack through three core tests:
1. Leak Testing:Verifying the pack meets IP67 waterproof standardsto ensure environmental protection.
2. BMS Communication:Verifying that the battery management system (the “brain”) correctly communicates with the vehicle’s ECU.
3. Charge/Discharge Cycle:A final “burn-in” test to validate dynamic performance and safety logic under load.
Commercial Turnkey Solutions
Are you planning a new battery pack assembly line? Huiyao Laser provides turnkey assembly solutions used by top European and Asian OEMs. Our automated lines cover the entire lifecycle from cell sorting to final EOL testing, with a specialized focus on high-speed laser welding and MES data integration.
Looking for an Engineering Consultation?
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FAQ
Q: What is the optimal cycle time for a prismatic pack line?
A: A fully automated line usually achieves 12-30 PPM (Packs Per Minute at module level), depending on the complexity.
Q: Laser welding vs. Ultrasonic welding?
A: Laser welding is preferred for thick busbars (copper/aluminum) in EV packs due to higher bond strength and zero mechanical stress on the terminals.
AUTHOR: The Huiyao Laser Engineering Team
A collective of solution architects and process engineers at Huiyao Laser, 100% dedicated to solving the core bottlenecks in EV and ESS battery manufacturing.
© 2026 Huiyao Laser Technology Co., Ltd. All Rights Reserved.
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