wrote:
We need to be careful with all the old-wifes tales that are repeated here, the devil is in the details.

Quite right. But we also need to be careful with panglossian optimism.

There are many videos on youtube showing what happens when a battery is grossly mistreated.
The results are somewhat spectacular. But so what, we wouldn't fly with batteries that had
been grossly mistreated, would we?

More interestingly, a very quick search indicated[1] Dell had to recall laptop batteries
3 times in 5 years; the last involved 4,000,000 batteries. If we assume that Dell isn't
staffed by cretins, clearly there are some subtle effects that can cause significant
problems.


Just for experimental purposes, I once put a nail through one of my 2200 AH 3p Lipos and you are right, the fire starts pretty much immediately and is next to impossible to quench. That does not mean they will burst into flames any second.

Just for fun:
- an M67 grenade has a charge of 180g, which probably equates
to around 180000J of energy
- 12V battery discharged at 4A for 1hour releases 172000J of energy


[1] http://www.youtube.com/watch?v=FuNSzs679Sw
bog-standard TV news report, so usual caveats apply