ParaHO, i’ve found some interesting articles on the net:
http://www.abc.net.au/science/articles/2006/11/30/1799366.htm
“It is theoretically possible to set off a petrol fire with a phone. The amount of energy needed for a spark to ignite petrol vapour is 0.2 mJ, which is roughly one five-millionth of the energy stored in a fully-charged phone battery. The difficulty is that the phone is not designed to make sparks.
The lithium battery could explode while charging if its internal regulator circuit was very faulty. But you don’t normally simultaneously charge and talk on your mobile phone while refuelling your car. The internal electronics of the phone could fail and make a spark – but the spark would be too small.
And why worry about the phone battery when you have batteries in your iPod, CD player, mini-torch, and yes, don’t forget the big 15 kg car battery that powers the electrics of your car?”