In this article I will describe how I built a cheap DIY 18650 Lithium-Ion battery pack for my Yaesu FT-817. After 65 SOTA-activations and other outdoor operations like IOTA, WWFF I had to reduce some addional weight of my „go-bag“. I already went from RG-58 coax to RG-174 and also scaled-down the diameter of the antenna wire, but this is a different story. So I looked what is on the regular market and found a lot of people in the amateur radio scene who are using Li-Po (lithium polymer) packs. Those packs are usually made for RC purposes and in the first moment I thought that they perfectly matches all of my needs. They are cheap ($15 per 2500mAh pack) and a 3S pack (3 cells in series) gives 11.1V nominal output.