Buying Cells against Buying Packs and Where Responsibility Sits
Buying cells requires owning BMS development, weld quality, thermal isolation, and pack safety files; buying packs trades unit margin for transferred liability.
Nickel Tab
Meaning
A strip of nickel or nickel-plated copper used to connect the internal electrodes of a cell to external terminals or busbars. This nickel tab is chosen for its excellent corrosion resistance and weldability to other metals. In battery sourcing, this component is a primary element of the current path that affects both resistance and cost.
The tab’s boundary starts at the internal electrode foil and ends at the external terminal connection of the casing. It applies to pouch and cylindrical formats, and it does not apply to directly bolted terminals.
Material Properties
High-purity nickel is used for these strips because it resists electrochemical corrosion in the electrolyte. This material has lower electrical conductivity than copper but is easier to weld to steel cans. To optimize performance, manufacturers use nickel-plated copper strips which combine conductivity with ease of welding.
The thickness of the strip is designed to handle the maximum continuous discharge current without overheating. If the strip is too thin, it acts as a fuse and melts under high current loads. These components are stamped to precise dimensions to ensure consistent assembly in high-speed automated lines.
Sourcing Choice
Procurement specialists select these components based on their metal purity and dimensions. The nickel tab must be free of surface oils and oxidation to ensure strong welds. Sourcing teams negotiate with suppliers who provide certified material test reports to verify the nickel content.
Cheap substitutes using low-grade steel plating will rust and increase contact resistance. Buyers check the dimensional tolerances to prevent alignment errors during the automated tab-folding process. This scrutiny prevents assembly line stoppages and reduces scrap rates.
Connection Risk
Poor quality strip materials lead to weak welds and high electrical resistance at the connection points. This nickel tab must be welded with correct energy parameters to prevent damage to the cell seal. If the weld energy is too high, it punctures the cell and causes electrolyte leakage.
This leak leads to cell dry-out and premature capacity loss. Weak welds can break during transit or under road vibrations, causing open circuits. This failure mode disables the entire series string and requires expensive pack rework.