"Martin Underwood" <a@b> wrote in message
...
> jeffcoslacker wrote in message
> :
>
> > A little better explanation.
> >
> > As the plates in the grid detiorate over the years, conductive
> > material builds at the bottom of the battery. When it gets deep
> > enough to touch the bottom of the grid, and cause a conductive
> > connection between two plates, those two are effectively shorted. The
> > battery can't do much in this condition, there isn't correct
> > continuity within it. When the battery is moved, the debris will
> > sometimes resettle and the battery will suddenly come to life...
> >
> > Same with charging, the current applied to the battery causes an
> > overloading of the sediment connection, overloading it and causing it
> > to fail, like a fuse. The battery is now in correct condition, and
> > will test as if it is fully charged and fine.
> >
> > This can sometimes lead to explosions on jumpstarting when you produce
> > an arc, as shorting produces loads of hydrogen sulfide gas, so don't
> > fart around with it...replace it
>
> OK. I can see how this sediment could produce an intermittent problem.
> Presumably the sedimentation will build up when the car is not used for a
> few days, and then will be dispersed either due to the vibration of
driving
> or by the act of charging it when the engine is running. I presume that
the
> formation of sediment is irreversable.
>
> When I jump start, I always attach the final terminal of the jump leads at
> the donor battery rather than the dead battery in case hydrogen[*] is
> produced at the dead battery which an arc could ignite.
>
> Interesting that none of the garages or car-spares places that I've taken
> the car to have mentioned about sediment. You'd think they would have
done,
> if they'd been aware of the concept, since it's in their interest to try
and
> sell me a new battery. Unfortunately the battery is a sealed type (doesn't
> need distilled water adding to the electrolyte) so there's no way that a
> garage could test the electrolyte to see if there are traces of sediment,
to
> confirm if this is the problem.
>
> However you've convinced me that the battery is dying, if not actually
dead
> yet. I'll have to go out and buy a new battery - "only" £70 (about $110).
> And this time I'll go for one with a warranty that lasts for more than 2
> years ;-)
>
>
>
>[*] I *think* it's hydrogen rather than hydrogen sulphide - the latter is
> instantly detectable (by the nose!) and I don't think it's flammable. But
I
> could be wrong.
>
>

Both recent replies to your post are good information. Sediment
intermittently shorting out cells is a very rare occurrence but it does
happen. Corroded terminals on the other hand are quite common and both will
cause the symptoms you described. My suggestion would be to buy a new
battery and clean all the battery cable connections. Then you will be done
with it and can have piece of mind knowing that the problem has been fixed.
BTW, you are correct in assuming that sediment problems can not be corrected
with out rebuilding the battery.
--
Kevin Mouton
Automotive Technology Instructor
"If women don't find you handsome, they should at least find you handy"
Red Green