Pure Nickel Interconnects for a High-Current Lithium Battery Pack

Project Overview

A battery developer needed custom interconnects for a high-current cylindrical-cell pack used in mobile industrial equipment. Early prototypes relied on standard nickel strip widths and several overlapping pieces. Although the design functioned at low load, the assembly required too many welds and created inconsistent current paths across the cell groups.

The customer asked us to develop a cleaner interconnect layout that could be welded repeatably, fit the existing cell holder, and support the target current. We produced a combination of pure nickel strips and wider nickel bar sections shaped specifically for the pack architecture.

The Engineering Challenge

Battery interconnect design affects electrical resistance, heat generation, mechanical reliability, and manufacturing time. A solution that focuses only on material thickness can overlook the importance of current distribution and weld placement.

Uneven Current Paths

In the original layout, cells near the output terminal had a shorter conductive path than cells at the opposite side of the group. The revised pattern used wider collection areas and a more balanced route toward the terminal connection. This helped reduce localized loading within the interconnect network.

Limited Welding Access

The cell holder provided narrow access around several rows. Weld points had to remain clear of plastic ribs while maintaining sufficient contact area on each cell terminal. We repositioned bridges and added shaped reliefs so the welding electrodes could approach each planned point consistently.

Material Selection

Pure nickel was specified for the cell-level connections because of its corrosion resistance, weldability, and predictable performance in battery assemblies. Material thickness and width were reviewed together with the proposed current path, the number of parallel cells, and the welding process.

Pure Nickel Verification

Material identity is important because nickel-plated steel and pure nickel can look similar. The production material was controlled through supplier documentation and incoming inspection. Thickness and surface condition were checked before cutting, and samples were retained for batch traceability.

Strip and Bar Geometry

Narrower sections were used where flexibility and individual cell welding were priorities. Wider nickel bar areas collected current across the group and provided a stable interface for the main connection. Corners were rounded to reduce handling hazards and avoid sharp projections near insulation components.

Prototype and Weld Trials

The first prototype set was fitted to an empty cell holder to confirm alignment. A second trial used representative cells and the customer’s welding equipment.

Parameters Evaluated

• Interconnect flatness on the cell terminals
• Electrode access and spacing between welds
• Surface marking and weld consistency
• Pull strength on sample joints
• Clearance to the holder and adjacent insulation
• Temperature behavior during a controlled load test

The trials revealed that one collection tab needed additional support during welding. A small geometry change stabilized the area without adding another component.

Production Method and Inspection

The approved interconnects were precision cut to maintain consistent pitch across the cell pattern. Burr control was especially important because the parts were installed close to insulating rings and plastic holders.

Dimensional inspection covered cell pitch, overall profile, terminal features, and the position of all reliefs. Parts were kept clean and flat during packaging so they could be transferred directly to the welding fixture.

Packaging for Efficient Assembly

Interconnects were separated by type and packed in the order used at the workstation. Orientation labels reduced handling, while rigid backing protected the thin nickel parts from bending during transport.

Project Results

The custom layout replaced several overlapping generic strips with fewer purpose-designed components. This reduced the total number of handling steps and made weld placement more consistent across the pack.

The balanced collection geometry also supported more uniform current flow compared with the early prototype. During pilot assembly, the parts aligned correctly with the cell holder and required no manual cutting or reshaping.

Building a Production-Ready Connection System

This project showed why battery interconnects should be developed as part of the complete pack rather than selected only by strip width. Cell arrangement, current path, welding access, insulation, fixture design, and packaging all influenced the final result. By combining pure nickel strips with custom nickel bar features, the customer gained a reliable interconnect system ready for repeatable production.