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Strange Discoloration on Battery

birdman

Jr. Member
Joined
Feb 15, 2006
Messages
99
Loc.
Napa
My battery ran low the other day and when I went to put a charge on it I noticed some black discoloration that was on the positive post and onto the cable a bit as well. At first I thought it might be oil or grease because that is kind of what it looks like but it is not. It almost looks like charring as if it was hot.
Any ideas? I know that this has not always been there and it is something new because I have been trying to trouble shoot a charging problem I am having.

Thanks
 

SaddleUp

Bronco Guru
Joined
May 23, 2004
Messages
9,655
Loc.
Vancouver, WA
Check the voltage on the battery. I've seen this under 2 conditions. First is when a cell gets shorted in the battery and the other is when the battery is over charged. (They amount to the same thing since a shorted cell means the battery is getting more charge than it can handle)
 
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birdman

Jr. Member
Joined
Feb 15, 2006
Messages
99
Loc.
Napa
I'll check that.

But, if I check that now won't that give me a different reading since I noticed this after my battery is probably 75% discharged. I know that the last time I put a charge on the battery there was no discoloration and this must have occured as I was driving. Make sense?
 

SaddleUp

Bronco Guru
Joined
May 23, 2004
Messages
9,655
Loc.
Vancouver, WA
birdman said:
I am getting a 12.8 reading that about where it should be right?
Yes, that is where it should be. Turn the headlights or other high discharge item on for a few seconds and make sure it doesn't drop to 11 volts or less right away. Next start it up and see how many volts it has when it is being charged. If it's over about 13.8 then the alternator is probably overcharging it. If I'm correct the black stuff is oxidation caused from the battery boiling over.
 
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birdman

Jr. Member
Joined
Feb 15, 2006
Messages
99
Loc.
Napa
Interesting, I know that I am not over 13.8 when it is charging because the battery is not charging while I run it and that is what I have been trying to figure out. With the engine running I am getting about 12.7 to 13.0 out of it and to my understanding this is not enough. I also took the alternator down to the autoparts store to get it bench tested and they said everything was o.k.
Any other ideas?
 

SaddleUp

Bronco Guru
Joined
May 23, 2004
Messages
9,655
Loc.
Vancouver, WA
birdman said:
Interesting, I know that I am not over 13.8 when it is charging because the battery is not charging while I run it and that is what I have been trying to figure out. With the engine running I am getting about 12.7 to 13.0 out of it and to my understanding this is not enough. I also took the alternator down to the autoparts store to get it bench tested and they said everything was o.k.
Any other ideas?
Take the battery down and have them test it as well. If they do a good test then they will put it on a high draw (kind of like the headlight deal I mentioned above) and see if it holds the charge like it should. It still sounds like a battery issue to me. As far as the amount of charge from the alternator 12.7 to 13 is perfectly normal if the battery has a full charge. When the battery drops to less then it can go as high as 13.8 when it is charging. Also where are you measuring the charge? If your voltmeter isn't measuring it right at the battery then it could show less due to resistance in the wires.
 

Solar Aviator

Full Member
Joined
Nov 26, 2005
Messages
179
You might check the connection(s) at the battery post. A small amount of resistance can cause it to heat up and the battery not to charge. I have also found a bad crimp on a battery terminal caused a dealer to change out an alternator and 2 batterys. It ran fine and all of the electrical system worked but after the a period of time it would no longer start. There was just enough resistance in the bad crimp to cause about a one volt drop so the battery would not accept a charge. I found the problem when I pulled the plastic guard off to jump it. The terminal and post was hotter-n-heck.
 
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birdman

Jr. Member
Joined
Feb 15, 2006
Messages
99
Loc.
Napa
Thank you, I have 2 volt meters and tested with both and got the same readings with both. I also replaced the cable with a brand new because the PO had a 3.5 ft cable that he had wrapped down under the frame and back up so I cleaned that up with a new cable and I still am running into the same problems.
I will bring both the battery and the alt. down to get them tested tomorrow.
Thanks for your input.
 
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birdman

Jr. Member
Joined
Feb 15, 2006
Messages
99
Loc.
Napa
Just took both the battery and alt. down to Kragen and they both passed. I even had them do it a few times to make sure. Another thing I just noticed is my radio is not working maybe there is a bad ground I guess. Any other ideas?
 

SaddleUp

Bronco Guru
Joined
May 23, 2004
Messages
9,655
Loc.
Vancouver, WA
birdman said:
Just took both the battery and alt. down to Kragen and they both passed. I even had them do it a few times to make sure. Another thing I just noticed is my radio is not working maybe there is a bad ground I guess. Any other ideas?
A bad ground could do it. Is it a stock externally regulated alternator or an internally regulated one. If external then the regulator might also be the culprit.
 

Skuzzlebutt

PhD, Dr. of Broncology
Joined
May 26, 2001
Messages
4,393
Loc.
Honeymoon Bay
Do not trust Kragen to test anything! I have known so many people who have been stranded due that chain (Schucks/Kragen/Checker) giving false "good" test results on bad batteries and alternators.
 
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