21700‑6S4P Cylindrical Lithium Ion Battery Pack

Cylindrical Lithium Ion Battery Pack Structural Overview

Engineers build the 21700 6S4P cylindrical lithium ion battery pack by arranging individual cells into a structured electrical matrix. First, they sort and match all 21700 cells based on capacity, voltage, and internal resistance. Then, they organize the cells into a 6-series and 4-parallel configuration to form a stable pack layout. Meanwhile, insulated cell holders are installed to keep each cylindrical cell in a fixed position and prevent movement during assembly. After positioning, technicians proceed with interconnection preparation and structural alignment.

Cell Material System and Internal Chemistry

Inside each cylindrical cell, manufacturers use a layered electrochemical design. The cathode is typically coated with lithium nickel manganese cobalt oxide on aluminum foil, while the anode uses graphite-based carbon material on copper foil. In addition, a microporous polymer separator is placed between electrodes to allow ion flow while preventing internal short circuits. The electrolyte consists of lithium salts dissolved in organic carbonate solvents, and moisture control is strictly managed before sealing. Furthermore, a steel cylindrical casing provides mechanical strength and internal pressure stability.

Pack Assembly and Electrical Configuration

Technicians first verify all cells to ensure consistent electrical performance. Next, they connect cells using nickel strips through spot welding, forming reliable low-resistance electrical paths. After that, series and parallel connections are completed according to the 6S4P design. Meanwhile, a Battery Management System (BMS) is integrated to monitor voltage, current, and temperature in real time. In addition, wiring harnesses are routed and insulated carefully to prevent short circuits and ensure correct polarity alignment.

Formation Process and Quality Standards

Engineers perform controlled charge-discharge cycling to balance all parallel and series cells. Afterwards, aging tests are conducted to evaluate voltage consistency and internal resistance stability. Finally, insulation resistance testing, weld quality inspection, and full electrical verification are completed. Throughout manufacturing, the cylindrical lithium ion battery pack complies with IEC 62133 and UN38.3 standards, ensuring structural safety, electrical reliability, and transport compliance.