soldering-materials-dat
soldering wire
Nickel, Copper, and Sandwich (For 18650/21700)
| Material | Best Use Case | Pros | Cons |
|---|---|---|---|
| Pure Nickel | Standard DIY packs (5A-15A) | Easiest to spot weld; corrosion resistant. | Higher resistance than copper; heats up at high current. |
| Pure Copper | High-performance (30A+) | Lowest resistance; minimal heat generation. | Extremely difficult to spot weld (requires laser/ultrasonic). |
| Sandwich | High-current DIY (Nickel + Copper) | Better conductivity than pure nickel; weldable with high-power spot welders. | Hard to tune welding parameters; risk of "cold" welds or blow-through. |
2. Al-Ni (Aluminum-Nickel) Composite Strips
Primary Purpose: Transitioning between dissimilar metals.
- When to use: Specifically for Pouch Cells or Prismatic Cells where the positive terminal (tab) is made of Aluminum.
- Why: Aluminum and Nickel do not bond well through standard spot welding.
-
How it works: The strip is bi-metallic (half Al, half Ni).
- Al side is welded to the battery's Aluminum tab.
- Ni side provides a weldable surface for standard nickel busbars or wires.
- Summary: It is a "bridge" material, not for 18650s (which use steel/nickel caps), but for batteries with raw aluminum electrodes.
18650 Interconnect Materials: Why vs. Why Not
| Material | Conductivity | Weldability | Best Used For... |
|---|---|---|---|
| Pure Nickel | Good (~25% of Cu) | Excellent | Standard DIY packs, Robotics (Rover V2), Electric bikes. |
| Pure Copper | Best (100%) | Very Poor | Ultra-high performance racing drones or EV modules. |
| Sandwich | High | Difficult | High-current DIY builds (Copper strip under a Nickel strip). |
Why we choose Pure Nickel for 18650s:
- High Resistance (Ideal for Welding): Spot welding relies on electrical resistance to generate heat. Nickel resists current just enough to melt instantly at the contact point, creating a strong bond.
- Thermal Control: Copper is a "heat sink"—it pulls heat away so fast that the weld point never gets hot enough to melt, but the battery cell underneath gets dangerously hot.
- Corrosion Resistance: Nickel does not rust or oxidize easily. Copper turns green (oxidizes) over time, which increases resistance and creates "hot spots."
- Tool Compatibility: Most hobbyist spot welders (Sunkko, Malectrics, Kweld) are designed specifically for the physics of nickel.