3x AA to D battery adapter (no soldering required)

thingiverse

To run your device, you'll need two units for each one D battery. To make a reliable connection, take note of the D battery's design: it needs a different contact point at either end. To achieve this, wrap aluminum foil around each end slightly differently - just observe how it interacts with the battery to get the hang of it. Here are your operating instructions: To 3D print these parts efficiently, try a fill level of 50% and a layer thickness of 0.25mm. If you're looking for ways to save some filament, consider using a lower fill percentage; it may still yield a suitable outcome.