[DanBC]

Explosion: A release of mechanical, chemical, or nuclear energy in a sudden and often violent manner with the generation of high temperature and usually with the release of gases.

This is definitely a description of what happens to the batteries.

[throwanem]

I think he's trying to argue that because they deflagrate instead of detonating, it's incorrect to call the process an explosion. That's the only thing I can see that makes sense, at least, incorrect and apparently disingenuous though it is in this context.