How to Assemble a Prismatic Battery Pack for ESS: OCV Sorting, NG Cell Rejection & Refill

The assembly of a prismatic battery pack for an Energy Storage System (ESS) is a meticulous process requiring precision, quality assurance, and advanced technology. Among the critical steps in this process are OCV sorting, NG cell rejection, and good cell refill. These steps ensure that only the best-performing battery cells are included in the pack, resulting in a reliable and efficient energy storage solution. This article delves into these stages and their significance in producing high-quality battery modules.

 OCV Sorting Workstation

 What is OCV Sorting?

 Open-Circuit Voltage (OCV) sorting is a quality assurance process where the voltage of each battery cell is measured without any external load. This step ensures that only cells with consistent voltage levels are included in the pack, crucial for performance uniformity and long-term reliability.

The OCV Sorting Process

1. Preparation:

Battery cells are fed into the OCV sorting workstation. Each cell is pre-aligned to ensure seamless measurement.

2. Voltage Measurement:

Specialized probes touch the terminals of the cells to measure their OCV. The system uses highly sensitive sensors to detect even the smallest deviations in voltage.

3. Categorization:

Based on pre-set voltage thresholds:

• Good Cells: Cells within the acceptable voltage range are marked for use in assembly.

• NG (No Good) Cells: Cells that fall outside the acceptable range are flagged for rejection.

4. Data Logging:

The workstation records all measurement data, enabling traceability and analysis for future improvement.

Why OCV Sorting Matters

• Uniformity: Ensures consistent voltage across all cells, reducing stress during operation.

• Safety: Identifies and removes faulty cells that could compromise the entire pack.

• Efficiency: Optimizes energy usage and minimizes losses within the system.

NG Cell Rejection

 What Are NG Cells?

 NG cells are those that fail to meet the specified OCV or other quality standards. These cells may have issues such as:

• Voltage deviations.

• Manufacturing defects.

• Potential safety hazards, such as internal short circuits.

Rejection Process

1. Automatic Sorting:

After OCV testing, NG cells are automatically separated from good cells using robotic arms or conveyor systems.

2. Inspection and Classification:

NG cells are categorized based on their defects. Some may be reconditioned for other uses, while severely defective cells are discarded responsibly.

3. Data Analysis:

Manufacturers analyze trends in NG cell rejection to identify root causes, such as production errors or material inconsistencies.

Benefits of NG Cell Rejection

• Enhanced Safety: Removes defective cells that could cause thermal runaway or electrical issues.

• Quality Assurance: Ensures that only optimal cells are used, maintaining the integrity of the pack.

• Sustainability: Allows for the recycling or reuse of rejected cells when possible.

Good Cell Refill

 What is Good Cell Refill?

 Once OCV sorting is complete and NG cells are removed, the good cells are placed into the battery pack module. This stage involves precision placement to ensure proper alignment and connection.

The Refill Process

1. Arrangement:

Good cells are grouped and organized based on their voltage and capacity.

2. Automated Refilling:

Robotic systems handle the placement of cells into their designated slots within the module. Automation reduces human error and speeds up the process.

3. Manual Quality Checks:

Technicians inspect the module to verify that all cells are correctly aligned and free of physical damage.

4. Inter-Cell Connections:

Conductors, such as busbars or welded strips, are used to connect the cells. Proper insulation is applied to prevent electrical shorts.

Importance of Good Cell Refill

• Operational Efficiency: Ensures the battery pack delivers optimal energy output.

• Longevity: Minimizes imbalances that could lead to premature wear or failure.

• Safety: Reduces the risk of thermal or electrical hazards.

Challenges and Solutions

Challenges

1. Detecting subtle defects during OCV testing.

2. Handling NG cells responsibly to minimize environmental impact.

3. Achieving perfect alignment during good cell refill.

Solutions

• Leveraging AI and machine learning to improve defect detection.

• Implementing eco-friendly recycling programs for rejected cells.

• Using advanced robotics to enhance precision in cell placement.

Conclusion

 The OCV sorting workstation, NG cell rejection, and good cell refill are vital steps in assembling a prismatic battery pack for ESS applications. These processes ensure the pack’s reliability, safety, and efficiency, making them indispensable in modern battery manufacturing.

By adopting automated systems and rigorous quality control protocols, manufacturers can produce high-performance battery modules that meet the growing demand for sustainable energy storage solutions.

About Huiyao Laser Technology (Luoyang) Co., Ltd.

 Huiyao Laser Technology (Luoyang) Co., Ltd. is a leading innovator in laser processing and automation solutions. Based in Luoyang, China, the company specializes in providing advanced equipment for energy storage, automotive, and electronics industries. Their cutting-edge technologies include:

1. Laser Welding Systems: Designed for precision assembly of battery packs, ensuring robust and efficient connections.

2. OCV Sorting Workstations: Automated solutions for accurate voltage measurement and cell categorization.

3. Automation Equipment: Customized solutions for improving efficiency and reducing labor costs in manufacturing processes.

Commitment to Excellence

Huiyao Laser Technology prioritizes innovation, quality, and sustainability. By integrating state-of-the-art laser technology with intelligent automation, the company empowers its clients to achieve superior product performance and operational efficiency.