I designed this case in order to make my 18650 2s packs neat and safe, but also as small and light as possible.
Here's a few simple pack assembly instructions, I will try and update this with some photos once I've had a chance to assemble another one.
Pack assembly instructions:
Take your two 18650 cells and solder a 20mm length of wire between the negative (-) and positive (+) terminals at one end of the cells. Be careful to make sure that the wire is well insulated on the positive end as only the centre of the pack is positive. If the wire is allowed to make contact between the centre terminal and the outside of the cell you will have a fire on your hands.
Attach a smaller wire to either end of the joiner piece and run it up the middle of the cells and leave it loose at the other end. This will be used for your the middle lead of balance connector.
Slide the two cells into the main part of the case and apply a drop of glue if required (most brands should be a snug fit).
Connect up the two remaining exposed terminals to the main power connector for your goggles/equipment paying careful attention to polarity.
Hook up an additional wire to each of the main terminals and connect them to your balance connector as shown in the picture above.
Ensure all connections are well insulated, route wires through the hole in the lid and then glue the lid in place.
Needless to say, I hold no responsibility for any injuries or damage you cause whilst trying to assemble this battery so do so at YOUR OWN RISK. If you don't feel comfortable working on bare cells, or are unsure of your abilities/my instructions find someone else to help you.