Recently purchased one of those bicycle lights using the XML T6 LED x3.
Came with a 18650 8.4v 6400mAh Battery Pack and a Pouch with Velcro.The headlight has a voltage status function via a multi color LED but to be honest i am not satisfy with what function so i decided to add a voltage meter.
Furthermore, i decided to forget the pouch as a battery case and make a new one instead.
So, the new battery case it has to be cheap, durable, waterproof, nice, with some extra space and easy to work with.
The answer came from the plumbing tubes!
I have included a lot of pictures, so the whole assembly process is fairly easy to follow.