flearider
they prob went for cheap cells .. simples .. instead of going with lg 25amp or sony vtc4's
that's the problem with 18650's they have to be able to take the charge or drain .. cheap one's cant ..
my guess is they used ultrafire or trustfire branded cells .. complete rubbish ..
I doubt any manufacturer would use xFire cells, which are generally just rebranded/QC-failed/recycled cells from the actual manufacturers. They're not a wholesale brand themselves AFAIK.
It would be interesting to know if this happened on the charge or discharge cycle. The thing with LiIons is the protection circuitry has to be properly functional and they shouldn't be abused. It only takes some out-of-tolerance protection circuitry to allow a cell to overdischarge and become a danger upon the next charge cycle for instance.