A 3D printed 18650 to D-cell adapter would look quite nice… Finally, in order to make the battery spring contact the smaller surface area of the lithium cells, all you have to do is flip it ...

E-bike batteries are, for the most part, a collection of 18650 batteries, packaged together and welded in series and parallel, attached to a battery management system (BMS). A "dead" e-bike battery ...

Easy access to 18650 battery cells and an abundance of used ... you can probably get by with spring contacts. When you need to power an e-bike or other high power application, you need a ...