Charging chinese 12v battery

srnet:
I was sat in my workshop, as I am now, looking at my PC screen.

On the shelf to my left, around 50cm away, I heard an odd noise, sounded like pressure in a bit of plastic.

I looked up and a Lithium battery I was charging, 3S 1500mah, was bulging, odd I thought. I grabbed it and threw it out the door.

It exploded in a large fireball before it hit the ground outside.

Talk about luck...

Was that a random accident or were you doing something incorrectly with the battery at the time?