2x2 18650 battery == 66 x 40.5 x 40.5 mm (with spacers and insulation)
65+1 x 18+18+4.5
for heat-shrink-tube-dat == 106.5 + 10 or 81 + 10
Dimensions Calculation for a 2x2 18650 Battery Pack Layout
The dimensions for a 2x2 layout of 18650 cells are derived from the standard physical specifications of a single cell, where the designation 18650 defines its nominal size:
- 18: Diameter of 18 mm
- 65: Length/Height of 65 mm
- 0: Denotes a cylindrical form factor
For a small 4-cell square assembly, a standard Matrix Layout (flat grid alignment) is preferred over an interleaved honeycomb pattern.
1. Theoretical Minimum Dimensions (Bare Cells Only)
These figures represent the absolute physical boundaries of the cells resting directly against one another without any structural packaging, wiring, or isolation gaps:
- Length (Z-axis): Constant height of a single cell = 65 mm
- Width (X-axis): 2 diameters side-by-side = 18 mm * 2 = 36 mm
- Height/Thickness (Y-axis): 2 diameters stacked = 18 mm * 2 = 36 mm
Ideal Envelope Volume: 65 mm * 36 mm * 36 mm
2. Practical Engineering Dimensions (Recommended for CAD & Enclosure Design)
In real-world applications, cells should not touch metal-to-metal due to short-circuit hazards. You must factor in processing variables and safety materials: 1. Plastic Interlocking Spacers (Brackets): Standard interlocking 18650 grid spacers have an outer edge dimension of 20.2 mm per cell slot to allow air-cooling gaps and structural spacing. 2. Top/Bottom Fishpaper: Adds about 0.3 mm to the longitudinal stackup. 3. Outer PVC Heat-Shrink Tubing: Adds around 0.5 mm to 1.0 mm around the finished perimeter.
Option A: Pack Assembled with Standard Plastic Modular Spacers (Best Practice)
This is the standard for robots, vehicles, and high-vibration applications.
- Length: 65 mm (cell) + 0.3 mm (fishpaper) + 0.7 mm (nickel/wrap tolerance) = 66.0 mm
- Width: 20.2 mm * 2 = 40.4 mm
- Height: 20.2 mm * 2 = 40.4 mm
Option B: Wrapped Pack Without Spacers (Glue + Heat-Shrink Only)
Utilized for tight space constraints where spacers cannot physically fit.
- Length: 66.0 mm
- Width: (18 mm * 2) + 1.0 mm (insulation/wrap allowance) = 37.0 mm
- Height: (18 mm * 2) + 1.0 mm (insulation/wrap allowance) = 37.0 mm
3. Design and Tolerancing Advice
⚠️ Mechanical Clearance Tip: When modeling 3D-printed battery cradles, CNC-machined enclosures, or laser-cut mounting plates for your hardware projects, always implement a 1.0 mm to 1.5 mm design tolerance/clearance buffer on each axis past your option numbers. This prevents assembly interference caused by variations in adhesive thickness, solder joints, or 3D printer material shrinkage.