18650 vs 21700 vs 32650: Nickel Strip Sizing Guide

Battery Component Guide · Arambhika Enablers

Cylindrical lithium-ion cells are named by their dimensions: the first two digits give the diameter in millimetres, and the remaining digits give the height in millimetres. So an 18650 cell is about 18mm in diameter and 65mm tall, a 21700 cell is about 21mm in diameter and 70mm tall, and a 32650 cell is about 32mm in diameter and 65mm tall. The larger the cell, the more energy it typically holds — but it also changes how you should plan your nickel strip layout.

Cell dimensions at a glance

Why cell size affects strip choice

A larger cell diameter means more space across the top of each cell for the strip to land on, and often a higher per-cell current contribution. This is why Arambhika Enablers offers different pre-formed 2P strip widths for each cell type — for example, a 26mm-wide 2P strip is sized for an 18650 row, while 31mm and 36.5/46.5mm strips are sized for 21700 and 32650 rows respectively, with options available with or without a center "holder" cut-out for consistent weld placement.

Matching strip thickness to current

As a rough field guide used widely in the spot-welding community, a single layer of 0.15mm nickel strip can carry roughly 5-10A continuously, while 0.2mm can handle roughly 10-15A — actual capacity depends on strip width, ambient temperature, and whether the load is continuous or pulsed. Most affordable spot welders also struggle to weld through strip thicker than about 0.15mm in a single pass.

The standard solution for higher-current packs is not to jump straight to a much thicker strip, but to stack multiple layers of 0.15mm strip and spot-weld them together — each additional layer roughly adds to the total cross-sectional area and current capacity, while keeping each individual weld within the welder's capability. For applications that genuinely need a heavier single piece (e.g. main pack interconnects rather than cell taps), 0.3mm strip is used.

1P vs 2P strips — which do you need?

• 1P (flat) strips — used for general series/parallel connections between cell terminals or as simple busbar links. Available in widths from 6mm to 10mm and thicknesses of 0.15mm/0.3mm.
• 2P pre-formed strips — shaped to bridge a pair of cells in a row, sized to match the cell diameter (18650, 21700 or 32650), and often available with or without a center holder cut-out for automated or manual placement consistency.
• ZigZag strips — used where cells are arranged in an offset/staggered pattern within a module, common in higher cell-count 18650/21700 packs.

Nickel-plated or pure nickel?

For most pack designs, nickel-plated steel strip offers a good balance of cost, weldability and corrosion resistance. For packs where minimizing resistance is critical — high-discharge EV packs or long-life ESS — pure nickel strip is the better choice. See our full comparison of nickel-plated vs pure nickel strip for details.