Click>>>BOOM...yes Virginia, batteries can and do explode! NAC

[Brett Dikeman]

> Battery water is decomposed into H2 and O2 only when the battery is being
> overcharged

Close but no squeeky toy.

First off, gassing is part of normal battery charging and in some cases is
actually necessary to mix electrolyte with a high specific gravity that has
accumulated at the bottom of the battery(particularly, say, if you've just
topped off the battery with distilled water).  Where gassing starts depends
upon the condition of the battery, but it starts towards the tail end of a
charge to 14.4v.  It should not be substantial nor violent.

Second, gassing occurs when the battery is being charged too quickly.
Lead-acid batteries of almost any type should not be continuously charged(ie,
put on a charger) at currents above C/20, where C is usually the A/hr rating
NOT CCA's.  The A/hr rating is not fixed; as the battery plates sulfate, the
A/hr rating drops...which is why you'll sometimes have a battery which
violently gasses at a rate which should be fine, and you don't have a shorted
cell.  What usually happens next is the gassing causes plate material to break
apart, and THEN you get a shorted cell :-)

> The only open ignition source might be the rotor to cap spark
> gap

Or a relay(starter solenoid), or a DC brush motor(starter) or a metal-on-metal
impact(starter gear->flywheel, unless the gear is bronze) or a corroded
connection(battery terminals), or something breaking apart inside the battery,
perhaps.

Brett