The battery connection on FED3 is pretty annoying, as it is right next to the stepper and is difficult to plug in when swapping batteries.  As a workaround I looked online for a small 2-pin LiPo extension cable be couldn't find one.  The closest I found was this JST jumper, which won't do it, or this long extension, which won't fit inside of FED.   If anyone can point me to a short extension that would be great!

Anyway as I couldn't find one to purchase, I designed a small PCB to fit this need.  Here is a link where you can purchase it from Oshpark, the PCB costs 25 cents each.

You will also need a JST PH 2.0 2-pin female connector with cable, and a male through-hole connector (here). Watch out when buying these parts from Amazon and make sure to read the reviews, apparently the polarity (red/black wire locations) can be reversed from some suppliers. 

Solder the JST female pigtail and male connector into the PCB and plug the cable into the Adalogger on the FED3. Now you have a battery extension that makes it much easier to swap out the battery!