Semi [OT]: What is the black deposit on the underside of wet lead acid battery vent caps?

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Does anyone know what the black smudgy deposit is that forms on the
underside of wet cell lead acid automotive batteries is?

It looks a little like soot and is easily wiped away.

I've heard it can suggest the battery is failing. Is there any substance to
this or is it just an anecdotal red herring?

Cheers
D.



Re: Semi [OT]: What is the black deposit on the underside of wet lead acid battery vent caps?
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The technical term is "Krud" :-)
Might be worn off the casing ??


Re: Semi [OT]: What is the black deposit on the underside of wet lead acid battery vent caps?

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I nearly used the common trade term of "black shit", "krud" is more
professional.

It could be from the casing but I wouldn't think so as it's to be deposited
on the bottoms of the vent plugs as if carried there by the electrolyte
"bubbles" during charging.



Re: Semi [OT]: What is the black deposit on the underside of wet lead acid battery vent caps?
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a by product of the charging , when enough "black shite" accuumuates the
battery is buggered

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Re: Semi [OT]: What is the black deposit on the underside of wet lead acid battery vent caps?
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Ahhh ! THAT Krud !

Didn't come up in the original post :-)

Re: Semi [OT]: What is the black deposit on the underside of wet lead acid battery vent caps?

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  No.  It is from a failed or failing cell.

 Pretty much, you are "really full of it".

Re: Semi [OT]: What is the black deposit on the underside of wet lead acid battery vent caps?
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Oxide
  is bad

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Re: Semi [OT]: What is the black deposit on the underside of wet lead acid battery vent caps?

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It could be lead oxide - googling had found nothing but I just looked at
lead oxides and found this:

"The so-called black lead oxide, which is a mixture of PbO and fine-powdered
metal Pb and used in the production of lead acid batteries."

http://en.wikipedia.org/wiki/Lead_oxide


We've got a few vehicles and most of them seem to have it to some degree -
even on a couple of batteries that are only 6 months old.



Re: Semi [OT]: What is the black deposit on the underside of wet lead acid battery vent caps?

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Defo lead oxide...



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