I saw the video. It was a very small car, the kind you would see in a small apartment building - something like 4 feet square or 1.25m square, if even. Basically a closet. Edit: to add it wasn't the whole bike but the battery pack itself. It was in his hand.

Here's a NSFL link of what appears to be the video for those wanting to see just how engulfing it was https://streamable.com/y47pm1

For those wanting to stick to descriptions: the entire elevator (albeit a smaller one) is goes from normal to completely filled with burning toxic gasses in 2 seconds. If it were a large elevator and a phone battery you could probably escape most of the damage by being at the opposite end and exiting quickly after. With a batter that large though it's a bit of a different story.

Being trapped in an enclosed space with something like that, which supplies its own oxidizer and burns very hot, would be a nightmare. It's like wondering if your food can retreat to the safe corner of your oven or BBQ, away from the burner.

As stupid kids, my friends and I found an unused emergency road flare and played with it, outside on a sand pile, where we thought it safe. I still managed to get give myself some lung injury from inhaling a shallow breath from the invisible convection gases rising off it about 3 feet above.

The video shows the entire elevator being engulfed in fire, fumes and light. It was a small lift, but I'd doubt any part of any normal lift would have a safe spot.

Pretty small, but I'm not sure if it matters. If any battery starts out-gassing when you're in an elevator, you're probably as good as dead, because the hydrogen fluoride release will quickly cause tremendous damage to you or just flat out kill you; I doubt there's much you can do about it.

So I definitely think that the moral of the story is simply never, ever take a large battery onto an elevator

Maybe solid state batteries can some day give us more peace of mind.