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