Re: Battery gassing ?

[Lee Hart <leeahart@earthlink.net>]

> ...do they gas while being discharged and is it about the same
> amount?

I don't know if we answered this for the more common lead-acids before
wandering off to nicads and other less-common batteries.

So for the record: No, lead-acid batteries do not normally gas during
discharge. They only gas during charging, and then only at the end of
the charge cycle, when they are nearly full and there is nowhere else
for the energy to go.

It is *possible* to make them gas under fault conditions. For instance,
you can short them or overload them so heavily that they boil the
electrolyte; the gas liberated is then water vapor (steam!). This
usually causes fountains of water/acid spray out the vents, or blows off
the vent caps or bursts the case from the excessive pressure inside the
case.

You can also let them run so low on water that the plates are exposed;
it is then possible to liberate hydrogen sulfide (rotten egg odor).

Or if you have a seriously out-of-balance pack and run it very dead, you
can reverse one or more cells during discharge. In effect, you are
charging the reversed cells in the wrong direction. Since charging is
going on, you can generate hydrogen gas if you manage to fully recharge
these cells in the wrong direction.
-- 
Lee A. Hart                     Ring the bells that you can ring
4209 France Ave. N.             Forget the perfect offering
Robbinsdale, MN 55422 USA       There is a crack in everything
phone (612) 533-3226            That's how the light gets in
leeahart@earthlink.net                  Leonard Cohen