I would be interested to know what battery chemistry is used in these batteries. Lithium based batteries vary hugely in their resistance to thermal runaway. For example Lithium ferro magnesium phosphate batteries are very much safer than the more conventional Li Ion batteries used in computers, at the expense of a slightly lower power density. This is illustrated by the following marketing video from a leading manufacturer. Interesting and sobering!
If you don't trust links posted by new posters, just google Valence. Ironically, these safer batteries are used in Segways, but you can't take these batteries on a plane because they are a Lithium based battery and we know how dangerous these are...