> Hydrogen, being lighter than air, rises, not falls so a vent out the
> bottom won't remove the fuel in the explosive mixture..
This is what makes it so dangerous - it is able to sneak through any
breaks in the seal at the top of the battery compartment.
This is also what makes it less dangerous as it dissipates into the
surrounding air very rapidly.
To try to clarify these 2 contradictory statements:
If the hydrogen/oxygen mixture is able to leak from the battery
compartment into an enclosed space - e.g. inside the passenger compartment
of a car - then it has the potential for an 'ignition' which, if it occurs,
will be quite dramatic because of the enclosed space. This is a bit hypo-
thetical as the battery would have to be grossly overcharged for quite a
long time to produce the necessary volume of gas. You would then need an
ignition source - smoking, turning on the ignition, etc.
> In air, hydrogen burns from about 4% hydrogen through at least 80%
> hydrogen, and at some ratios, it burns explosively, maybe most ratios,
> I've not yet confirmed my suspicions that it burns slowly when the
> mixture is way from optimum.
The 4% hydrogen mixture is the theoretical 'danger' point and if the
mixture is ignited, at whatever level, it is always 'explosive' - there
is no 'slow-burn' option!
Cheers,
Dave Harris (former 'battery-explosion' investigator)