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

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.

Reply to
Dennis
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The technical term is "Krud" :-) Might be worn off the casing ??

Reply to
Rheilly Phoull

Oxide is bad

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Reply to
atec77

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."

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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.

Reply to
Dennis

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.

Reply to
Dennis

a by product of the charging , when enough "black s**te" accuumuates the battery is buggered

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Reply to
atec77

No. It is from a failed or failing cell.

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

Reply to
Chieftain of the Carpet Crawle

Ahhh ! THAT Krud !

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

Reply to
Rheilly Phoull

Defo lead oxide...

Reply to
TTman

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