Battery Boiling Over
Thread Starter
Burning Brakes
Joined: Jan 2006
Posts: 1,073
Likes: 331
From: Clear Lake Shores Texas
2016 C3 of Year Finalist
Battery Boiling Over
The 13 year old AGM battery in my 72 LT-1 seemed to be going a little flat so I replaced it with a Walmart Maxx 75N with 700 CCA. It works great but on two different occasions it seems to have boiled over. The ammeter shows normal charging activity with more charging initially before gradually going to a neutral reading on the gauge after a few miles. I tried to check the electrolyte level but was unable to without potentially screwing up the case. I put the old battery back in after sitting for two months and got a reading of 12.69 volts before starting and 14.4 volts immediately after. Again, the ammeter reading seemed normal. I’m thinking the new battery is defective somehow, especially since it only did this twice out of approximately 10 similar trips of around 10 miles each. Has anyone else experienced this?
Thanks.
Thanks.
Drifting
Joined: Nov 2013
Posts: 1,572
Likes: 486
From: Loud, Raw and Dangerous 1968 327 4S in Southern California
More important to see where the voltage is ending up after a charge period. See if it is backing off from the 14.4 volts to something more like high 12's or low 13''s. If this is happing then I too would suspect the new battery is bad. If the voltage stays high then yes the voltage regulator is either bad or not working right for the car. Also for me I had to go to a solid state regulator rather than a mechanical one for my car to get a reasonable charge profile.
Race Director
Joined: Sep 2001
Posts: 10,560
Likes: 439
From: Wellington, FL
St. Jude Donor '11 thru '25
Overcharging is generally the culprit for boiling over. Put a voltmeter on the battery with the engine running. Proper reading should be a little over 14 volts.
Thread Starter
Burning Brakes
Joined: Jan 2006
Posts: 1,073
Likes: 331
From: Clear Lake Shores Texas
2016 C3 of Year Finalist
Thanks, Jud. I just checked the voltage (running) after a 10 mile drive and the voltage was right at 14 volts, so I'm guessing the battery is defective.
Drifting
Joined: Nov 2007
Posts: 1,716
Likes: 279
From: New York
I had that happen. Corvettes had regulator and alternator in one unit (they used to be separate).
Going to Lime Rock my battery boiled over. It got so hot that it melted a some plastic that had fallen on it. The alternator charge was OK. But the alternator never stopped charging.
Changing to a new Delcotron alternator solved the issue. So I may be at 14 volts, it just never stops charging.
Going to Lime Rock my battery boiled over. It got so hot that it melted a some plastic that had fallen on it. The alternator charge was OK. But the alternator never stopped charging.
Changing to a new Delcotron alternator solved the issue. So I may be at 14 volts, it just never stops charging.
Melting Slicks
Joined: Mar 2005
Posts: 2,094
Likes: 298
From: Midlothian VA
You should check the condition of the sensing wire connected to the alternator.
Over time the wire strands wear/break right at the connector or the connector can become corroded preventing the alternator from knowing when the battery has reached full charge which leads to overcharging.
Over time the wire strands wear/break right at the connector or the connector can become corroded preventing the alternator from knowing when the battery has reached full charge which leads to overcharging.
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
A little food for thought about the ALT not sensing when to stop doing its thing.
On the Alt is one big red wire, one GRD wire, plus the dual wire plastic connector that clips in on the ALT case. Depending on how the ALT is clocked for mounting purposes, that plastic clip connector may be pointing straight up.
Checking my voltage with engine running at that connector, I noticed some engine grunge down inside the case. Any oil vapors, anti-freeze, road grime, you name it, ends up in the hole.
After removing the connector, I took a Q-Tip saturated with carb cleaner and cleaned the two brass spades of the ALT. You would not believe the crap that builds up down in that port if its facing upward.
Did it make any difference in my voltage output? No. But it's a thought.
On the Alt is one big red wire, one GRD wire, plus the dual wire plastic connector that clips in on the ALT case. Depending on how the ALT is clocked for mounting purposes, that plastic clip connector may be pointing straight up.
Checking my voltage with engine running at that connector, I noticed some engine grunge down inside the case. Any oil vapors, anti-freeze, road grime, you name it, ends up in the hole.
After removing the connector, I took a Q-Tip saturated with carb cleaner and cleaned the two brass spades of the ALT. You would not believe the crap that builds up down in that port if its facing upward.
Did it make any difference in my voltage output? No. But it's a thought.
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