Battery Goop.

[mdsalemi]

I have an OEM MB battery, now about 6 years old.  Has not presented any problems thus far.

My car wintered from late October until this past weekend--about 5 solid months in an unheated garage.   When I went to charge the battery prior to starting on Friday past, the battery was at 75% charge.  Note, this is about where it has been after being idle for so long EVERY YEAR.  Nothing unusual.

After about an hour on the slow charger, it got up to about 90% charge, and after another couple of hours, about 95% charge.  Note, NO battery (my boat batteries, or boat lift batteries) have ever achieved 100% charge according to this charger.  Again, nothing unusual.

However, PRIOR to charging, I went to check the cells to add some distilled water to them--they always need some each season.  I was surprised to see that there was what appeared to be a black greasy gunk all over the underside of the filler caps, and clearly in the battery itself.  Like dirty axle grease.

I drove home yesterday, no issues.  No apparent battery issues either.  But what is this black gunk?  Anybody ever seen it before?

[280SE Guy]

Michael, I saw the same thing on my MB battery on Saturday. Put the caps in the sink with warm soapy water then scrubbed them with a tooth brush. All of the black stuff did not come of so I got out my bottle of full strength Simple Green and scrubbed again then used a que tip for the stubborn areas.

I'm not sure what that stuff is. I thought it might be because I use a Battery Tender but I know you don't use one so that eliminates that theory.

[mdsalemi]

Oh, I cleaned the caps all right, exactly like you did--lots of detergent and a toothbrush.  But the goop is IN the battery.  But I had never seen this before.  Somebody else must have.  Now that makes two of us.

[RickM]

As we all know there's lead in the battery as well as electrolyte (sulfuric acid and demineralized water).  Over time some of the lead from the plates dissolves into the solution.

With the typical charger you're hitting those plates with 14v+ (@ various amperages) and heating up the plates and electrolyte. Perhaps the charging boiled out or gassed vigorously enough to deposit a dissolved lead paste onto the caps.

I have to say I don't recall ever seeing such a substance.

FWIW, a managed float charger (ala Battery Tender) is going to be less harsh on the plates.

[mdsalemi]

As we all know there's lead in the battery as well as electrolyte (sulfuric acid and demineralized water).  Over time some of the lead from the plates dissolves into the solution.

With the typical charger you're hitting those plates with 14v+ (@ various amperages) and heating up the plates and electrolyte. Perhaps the charging boiled out or gassed vigorously enough to deposit a dissolved lead paste onto the caps.

I have to say I don't recall ever seeing such a substance.

FWIW, a managed float charger (ala Battery Tender) is going to be less harsh on the plates.

ahhh, but--the goop was there prior to charging...

Does not appear to be affecting anything at the moment but it has discolored everying in the battery to the point where you can see it through the translucent white case of the battery itself!  A mystery.

[douglas dees]

I have an OEM MB battery, now about 6 years old.  Has not presented any problems thus far.

My car wintered from late October until this past weekend--about 5 solid months in an unheated garage.   When I went to charge the battery prior to starting on Friday past, the battery was at 75% charge.  Note, this is about where it has been after being idle for so long EVERY YEAR.  Nothing unusual.

After about an hour on the slow charger, it got up to about 90% charge, and after another couple of hours, about 95% charge.  Note, NO battery (my boat batteries, or boat lift batteries) have ever achieved 100% charge according to this charger.  Again, nothing unusual.

However, PRIOR to charging, I went to check the cells to add some distilled water to them--they always need some each season.  I was surprised to see that there was what appeared to be a black greasy gunk all over the underside of the filler caps, and clearly in the battery itself.  Like dirty axle grease.

I drove home yesterday, no issues.  No apparent battery issues either.  But what is this black gunk?  Anybody ever seen it before?

Michael: I took my 280Sl out that had not been run for 5 months and checked the levels and found the same thing. I have the proper MB battery and I have seen it in my 1969 280SE coupe as well.
 It does not seem to cause problems . Last year i thought it was sulfating of the battery as it is 4 years old.

Did you get my pictures of the 280SL?

Doug Dees

[Peter van Es]

Could it be lead sulfate that is eliminated when the battery is being charged again?

Peter

[RickM]

+1 to Peter's lead sulfate...

I wrote to Bill Darden from http://www.batteryfaq.org/ posing this question and here is his response:


"If you are only adding distilled water, the black stuff is most probably lead sulfate left as a result of the natural self discharge of your battery and parasitic load over the winter storage period.  Please see Section 13 in the Car and Deep Cycle Battery FAQ on www.batteryfaq.org for more information on sulfation.  If it were my vehicle, I would try to full charge the battery and then have it tested for latent damage from the sulfation.  Several auto parts stores and battery dealers will test batteries for free.

I would also continuously charge the battery while in storage with a "smart" charger like a Battery Tender Plus, to keep it fully charged to prevent sulfation.  Please see Section 16 for more information on sulfation."


At six years I'd imagine the battery is near the end of it's lifespan.

[mdsalemi]

Most definitely it is NOT lead sufate.  Lead sufate is white.

The goop is most likely (after a little consideration) Lead Oxide, which is black and is a component of the battery, and or carbon black, also a component.  I suspect the plates are breaking down a bit (not unexpected or unheard of in 6 years of life) and what I'm seeing is the result.

As Doug Dees pointed out, it does not appear to be causing an issue at the moment--there appears to be plenty of charge and plenty of power.  I will not be surprised however if the next year sees a new battery in the car.