This battery case can be printed in several parts if your printer is not big enough to do it in one time.
It fit 2 batteries pack like this :

Spec.
Capacity: 5000mAh
Voltage: 3S1P / 3 Cell / 11.1V
Discharge: 25C Constant / 35C Burst
Weight: 354g (including wire, plug & case)
Dimensions: 162x21x46mm
Balance Plug: JST-XH
Discharge Plug: 5.5mm Bullet

You can find them on hobbyking.
two packs connected in serie, will make a 6S 5000mah pack.
Should be enough for 10km range.

I just printed the 4 parts using my prusa i3.
Printed in ABS, heated bed at 100deg, nose at 250, 0.2mm layer, speed 80mm/s
Once the parts are printed, you can weld them together using ACETONE.
juste take a dish, put a thin layer of acetone inside.
put the frame of the box in the acetone for 10s or so, then stick the cover on it.
Keep them joined together few minutes, it should stick.
Then it will solder together and become harder when the acetone will be dry.