Re: Bad smells from over charging lead acid batteries

On Mon, 16 Mar 2009 11:10:20 -0700 (PDT), Tim Shoppa
<shoppa@xxxxxxxxxxxxxxxxx> wrote:

On Mar 16, 1:15 pm, ethan.peter...@xxxxxxxxx wrote:
Over the weekend someone had left a charger on a lead acid battery,
seriously overcharging the battery.  It stunk up the whole shop with a
sulfur smell.  I know when you overcharge you get hydrogen and oxygen
gas, and from the smell there is obviously some sulfur.  That exhausts
my knowledge of battery chemistry, does anyone know what the actual
chemistry is?

Actually the "sulfur smell" is hydrogen sulfide. Sulfur by itself
doesn't smell that bad. There was no shortage of hydrogen produced in
overcharging the battery, but hydrogen by itself doesn't really have a
smell. The free hydrogen combines with other random atoms it finds,
and even though sulfur isn't the most common element, when hydrogen
combines with sulfur in a confied space the result stinks to high

Nearby we had some copper tubing that was discolored.  Some of the
shop guys blamed that on the gas from the battery.  Is that plausable?

The green tinted copper corrosion is copper sulfate. I think the
relation to your previous question, is that this shows that there is
no real shortage of sulfur compounds in your room. Blaming the
hydrogen for the presence of sulfur compounds is a little like blaming
the sun for letting you see ugly women :-).

Seriously overcharged lead acid batteries emit more than just
hydrogen. The bursting bubbles cause electrolyte misting and
evaporation, with enough flow rate to carry significant acid out of
the battery, and in severe cases the electrolyte can boil. There are
also a number of other reactions going on including one which releases
small amounts of Stibene from the Antimony (Sb) used to strengthen the
lead alloy plates.

(Normal charging releases pretty much the same stuff in smaller
quantities; hence TFM recommends ventilation.)

From Wikipedia, the free encyclopedia

Stibine is the chemical compound with the formula SbH3. This
colourless gas is the principal covalent hydride of antimony and a
heavy analogue of ammonia. The molecule is pyramidal with H?Sb?H
angles of 91.7° and Sb?H distances of 1.707 Å (170.7 pm). This gas has
an offensive smell like hydrogen sulfide (rotten eggs).


SbH3 is an unstable flammable gas. It is highly toxic, with an LC50 of
100 ppm in mice. Fortunately, SbH3 is so unstable that it is rarely
encountered outside of laboratories.


The toxicity of stibine is distinct from that of other antimony
compounds, but similar to that of arsine.[6] Stibine binds to the
haemoglobin of red blood cells, causing them to be destroyed by the
body. Most cases of stibine poisoning have been accompanied by arsine
poisoning, although animal studies indicate that their toxicities are
equivalent. The first signs of exposure, which can take several hours
to become apparent, are headaches, vertigo and nausea, followed by the
symptoms of hemolytic anemia (high levels of unconjugated bilirubin),
hemoglobinuria and nephropathy.