On Feb 25, 7:56*am, bildan wrote:
On Feb 25, 8:48*am, Mike the Strike wrote:

Years ago, a lab next to the one I worked in had experimental
batteries under development. *All the high energy density ones utilize
very reactive elements, of which lithium is one. *However, nothing
would beat the sodium-sulfur battery in its capacity to "go
Vesuvius". *It was colloquially referred to as "the fire and brimstone
battery". *The lab had a sulfurous smell that reminded one of the
entrance to nether regions.

I'm going to stick with lead-acid, thanks very much!

Mike

If you think lead-acid gel-cells are safe, try a dead short on a fully
charged one. *Splattering hot gelled acid is pretty nasty stuff.

Who exactly flies with gel-cells? There is no gelled anything inside
the VRLA (Valve Regulated Lead Acid) aka SLA (Sealed Lead Acid) or
often incorrectly called "gell cell" batteries almost universally used
in gliders. There is a surprisingly small amount of liquid
electrolyte, sulfuric acid electrolyte, basically the same as inside a
regular car battery but here used to moisten the thin fiberglass mats
between the plates.

But yes the dead short scenario is a worry and people need to be
careful. These little batteries can source hundreds of amps. Most
likely is not a destructive failure of the VRLA battery but damage
caused by the wire shorting across the battery, getting red hot,
burning molten PVC insulation, etc. burning somebody or causing a
fire. There is a misconception as well that VRLA/SLA batteries are
sealed and they will explode if the pressure inside gets too high.
They are vented with neoprene valves that will release pressure so
they won't just pressurize and eventually explode, but they still can
suffer catastrophic case failure in some situations. And they can also
cause explosions if overcharged in confined spaces from the hydrogen
leaking out the neoprene valves.

Darryl