Originally Posted by
Octane
MMC,
Sorry, you are misinformed. Lithium reacts spectacularly when combined with water. google it....
Sorry, in this case I'm afraid it is you who is misinformed.
The amount of Lithium in these cells is negligeable. It is <1,5% of the mass. And it is in bound form ,not pure.
So, yes pure Lithium will burn when getting in contact with water. A Lithium Battery: Not so. I have seen discharged defective cells cut open and water dripped on them. No obvious reaction.
I've personally extinguished a fire of a 1 lbs 5 cell Lithium Polymer battery with water. Works excellently. You need enough water but it extinguished the fire instantly but couldn't prevent the neigbouring cells from going off as well. So each cell had to be extinguished consecutively. Once started it was almost impossible to stop the runaway.
Each of the cells weighing roughly 5 ounces produced a fireball of nearly 0,5m diameter.
Edit: The amount of water to extinguish was almost a litre for each cell so for the 1lbs battery pack it was about 4 litres it took to put it out. And that didn't prevent the next cell from overheating. Therefore you would have needed more permanent cooling and thus more water. It was easier to extinguish the fire than to prevent it from going off in the first place once the runaway started.