A few weeks ago at a nats event here in Australia, a kids orion shorty went up in smoke while still in her car while the father was working on the car. no one knows how it went or what happened, there was no flames luckily, just alot of smoke and heat. Most of the electronics in the car survived, but the battery looked like a giant over cooked marshmallow.
Sometimes it can just happen, no explanation, no nothing.
Whats worse is one of the cells in the battery was still intact after all this and we were just waiting for it to blow from the heat.