Heat is the enemy of lithium cells. A soldering iron held against a cell terminal for too long degrades the internal chemistry. Spot welding delivers a high-current pulse for milliseconds, bonding nickel to the terminal without cooking the cell.
What you need
- A spot welder (battery-powered or mains)
- Pure-nickel or nickel-plated strip sized to your current
- Cell holders to keep alignment
- Kapton tape and barley paper for insulation
The basic workflow
Lay your cells in holders, place the nickel strip across the terminals, and fire two weld points per joint for redundancy. Tug-test every weld — a good weld tears the nickel before it lifts off the cell.
Two welds per joint, always tug-test. A pack is only as reliable as its weakest connection.
Finish with insulation rings on the positive ends and barley paper over the pack face before heat-shrinking. This prevents shorts that can be catastrophic.
