[Mgs] Exploding batteries

[Paul Hunt]

 I was watching an episode in the new series of The Garage on Discovery last
 night about the 'English Mobile Mechanics' (it's actually run by a Scot but
 he is so useless he probably decided to insult us instead) in Spain.  They
 had a BMW with a flat battery so connected a boost charger direct to the 
battery in the boot
(even though my son's BMW has jump-lead connections in the engine 
compartment).
These boost chargers put a very high voltage to the battery and hence a high
 current, a lot of boiling and gassing.  They got it started
 and the boss told one of the mechanics to disconnect the charger, which he
 did - by disconnecting one of the battery clips without turning off the
 charger first.  Big spark from breaking the high current, ignited the gases
 around and inside the battery, and the battery exploded.  The mechanic was
 *very* lucky in that he only got acid up his arm and not in his eyes, nor
 any injuries from plastic 'shrapnel'.

Whilst I suspect that most of us have smaller chargers that would result in 
less gassing and a smaller spark, I wouldn't want to be the one to find out 
just how small a spark and an amount of gas would cause an explosion.  This 
is also whilst the last connection to be made when using jump-leads should 
be made *remote* from the battery.

PaulH.