Years ago a relative who was a mechanic in his fathers shop had a battery explode in his face. He knew what to do and didn't suffer any damage but the memory stays with me. I would never try anything like this unless all other options were exhausted and it was a Dire Emergency.

I was cringing when Les Stroud used fuel from the plane and sparks from a battery to start a fire in winter on one episode. I would keep a flashlight and a 12v auto light in my car or use light from my cell phone or anything else I could think of, before I decided to resort to something like this. But as a Very Last Resort light or fire starter, maybe.....