I kinda also misunderstood that this was all about storage, not at all charging. I refuse to charge my batteries with my stored ones. For charging, I now put everything on my very heavy steel table in the well-ventilated smithing shop, but I used to use a mailbox with charge leads grommetted through the side. To use, I would set the box on two red bricks outdoors.
I really don't trust the bat-safe video due to the simulated voice, and the fact that the person or people who released the video are using it to promote their KickStarter fund. Neither video shows what's inside he box, one can only speculate.
This video however, while the can contents are again not actually shown, and the audio was removed, they run through several ammo can tests, as well as 2 battery bags. To me it appears as though a moderate amount of gas containment is better than none, as well as too much being bad seeing how the open lid can shows proof that the gasses do react with atmosphere while testing poorly. The seal removed can seems best after watching it, but still add a good layer of tile or fiberglass fabric inside it, and the floor won't scorch the way it did for the seal-less can in the following:
-One conclusion I've made from all 4 of the vidjyos so far is that if drilling is to be done, do it in one location, do not spread out your holes, it will make a draft path. You don't want draft through the storage container, because you want the remaining fire in the box to starve. Better yet, leave the seal, drill a big hole, and use one screw to hold a piece of steel shipping strap over it.
-Needless to say, bigger battery = bigger reaction..
I'll also add that I haven't actually done any searching, the video I posted here was in the related area on YouTube.