Yeah, the fact it blew out the end is a good sign, anything that has the potential to explode would be best going AWAY from my face. While the possibility of this happening is scary, at least the batteries seem to be designed in such a way that gives them a weak point that shoots it out the other end and not towards the vapers face. Perhaps a good sign that Joye is designing their batteries correctly and may be yet another good reason to stick to name brands.
I just wonder what this guys true story was, like if he has ever over-charged his battery and how old that battery was. My guess is that it exploded because it was fully charged and had been sitting there trickle charging for hours on end.
Because one thing to note about li-ion batteries is that as they age and if they ever get trickle charged, their usable voltage will eventually start to drop. So if the charger was trying to get the battery to full voltage when it should have stopped well below what a new fresh charged battery was, that could very well explain the situation. For example, say a new fresh charged battery is fully charged at 4.20v, well over time and if the battery has been improperly charged repeatedly, its maximum voltage threshold could be at 4.0v or lower, and if the charger kept charging past that point (trying to charge it to 4.2v) it becomes incredibly dangerous and unstable. Smart chargers are a must when it comes to li-ions, and sadly the ones used for most ecigs are probably anything but smart.
This is why I heavily suggest that people remove the batteries from chargers as soon as they turn green, preferably at the 90% charge level if possible. Undercharging a li-ion battery is perfectly Ok and actually preferred, overcharging just introduces a host of problems further down the road.