Bicycle light battery case

There are many cheap and very bright headlights on the market, but most of them come with a battery of poor quality. At the same time high quality 18650 Li-Ion cells are easily available and widely used, yet rarely found in form of separate cells in end user products. Here I present a battery case that allows to replace the cells on the go, which gives you the opportunity to easily carry energy for several nights, at very low cost. The use of protected cells is highly recommended, the cells can be taken out of the case and charged separately in a universal charger.
I provide a “package” of 3D-print parts (battery case, different case mounts), that can be assembled with some additional parts (battery connectors, cable, plug). Together with 18650cells, a charger and some headlight it builds a high end MTB light bundle.
The battery pack provides an output voltage of 6.4 to 8.4V. It has to be used with an appropriate headlight (most headlights with this connector work on this voltage).