2x 18650, Parallel or Series, uses cheap and easy to obtain contacts from these "less than awesome" sleds on Amazon... http://amzn.com/B00YBMZ80K

This is based on the Keystone 1048/49 style sleds, but with wider contact slots for the much cheaper contacts.

Just pull the contacts from the other sleds, nip the solder tag, and press into your new sled. (Note: Do not solder on the contacts while they are in the sled, even the keystone sleds will melt)

There is a thin channel across the ends of the sled to help guide your wires out of the way, make note of where to solder onto the tabs when they are in the sled (use a sharpie) to make sure you line up with the wire guide.

There are 2 versions, 1 without support of any kind (not needed really) and 1 "with ears" which adds flush "helpers" to add print surface area for better initial bed adhesion, and to help prevent edge curling due to adhesion problems, often cause by high speed, sharp directional changes during printing. The ears are very thin, and are easily trimmed off with an Xacto/Hobby knife. (If you ever have adhesion issues, try adding these ears to your project, easy to work with and make a huge difference)

Something cool I have been doing, is using heat sensitive, color change filament to print these. In the event that your batteries start to get warm, the sled will change colors to indicate that your batteries are being stressed. Hopefully this would assist in preventing thermal runaway, or potential failure of the cell, in high-stress usage, through visual indicator. =)

Feel free to share and modify, as I would love to see any remixes.