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Discussion Starter #1
Just finished my rebuild, put a new fresh battery in the car. Battery had only the positive cable installed. The next day I put the negative cable on and tried to start the car, no joy. Battery was dead would not even turn on the interior lights. Returned the battery, I assumed it was bad from the store. Had the store check the replacement battery, showed 12.6 volts and 800 CCA, so it’s good. Installed the battery again with only the positive cable and the next day the battery was dead. Overnight the key was out of the ignition and no doors were open. Went from fully charged to dead in like 14 hours. After jump starting the car the battery was charging, Alt putting out 12.8 to over 14 volts depending on RPM, so the alt is good, but should have nothing to do with a drain when not running. I then trickled charge the battery to full voltage, and did a parasitic drain test on the negative terminal, I saw about 20 ma which appears to be correct for the non switched radio connection.

This makes no sense to me, without the ground how can there be a drain on the battery and what could be draining the battery that fast. Any thoughts would be appreciated.
 

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I’d try another known good battery. Load tests aren’t absolute and it could be something wrong with the battery that the tester isn’t catching. There is a chance the battery could be grounding somehow though I haven’t ever seen anything like that.

Measure continuity between the negative post and a nearby ground with the negative cable disconnected. If there is continuity the battery is grounding somehow. How? Beats me.

Measure the voltage between the positive terminal and the disconnected negative terminal. If there is any voltage there is somehow a ground.

If it passes both of those tests, no continuity and no voltage the issue is in the battery.
 

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If it really is loosing voltage overnight with the negative cable off, its defective. Have the store keep the battery overnight and then check it. They won't believe you until they see it themselves. How did they test for 400 CCA using those hand held testers they usually have. There is no way they can put that kind of a load on it. You load test it at half the CCA. I have two of these VAT 40 testers out in the garage and at a 400 amp load those cables get hot.

The way this guy checked it in this video is not correct. The VAT40 instructions say to load test it at half the CCA for 15 seconds like this guy does but then it says to wait 15-seconds and load test it a second and if it drops below 9.6V its bad. A lot of times it passes the first load test but not the second. Its simulating engine cranking for 15-seconds. Letting the starter cool down for 15 seconds and then cranking it again for 15 seconds. You don't need one of these fancy testers, you can do the same thing with a voltmeter and using your starter to create the amperage draw. You need to disable the engine so it will not start. Have somebody crank it while you watch your voltmeter. Fully charge up your battery and do a load test on it and see what it does.


I had a one-year old Autozone battery. After being fully charged it would not hold a charge overnight sitting on a bench. It tested bad with my VAT 40 tester. That needle held at about 9.6V for a few seconds and then it fell off to zero. I explained the situation to the store and some pimple faced kid brings his toy battery checker out and says it tests "good". I argued with him that there was no way that tool could properly load test that battery. They would not exchange it. I went up to O' Reilly's, bought another battery. Problem solved and I never went back to Autozone again.
 

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Was the battery recharged after load testing it? That test draws a lot of power. If the negative cable is not connected a battery can not drain. Something is either wrong with the battery or the shop that says it is good, or both. How old is the battery? READING BATTERY DATE CODES
 

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Discussion Starter #5
This happened to 2 new batteries from Pasco. The first was not tested by them, but the 2nd was using the a large tester similar to the once shown by Vintage Ford Guy. The battery 100% in both cases did not have the negative cable attached. I'll check voltage between the positive terminal and unattached negative cable as suggested.
 

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How did they test for 400 CCA using those hand held testers they usually have. There is no way they can put that kind of a load on it. You load test it at half the CCA. I have two of these VAT 40 testers out in the garage and at a 400 amp load those cables get hot.
Modern digital battery testers employ a different testing method than an invasive tester such as a carbon pile type tester like the old Suns. A digital tester does not put a load and draw current from the battery like a carbon pile tester. It sends signals to the battery and monitors how the battery responds and formulates the results from that. It has a baseline of how the battery chemistry should respond under test conditions and uses that as the reference for the test. It doesn’t need a fully charged battery to be able to test the battery. The digital methods use means that are more accurate and faster than the old school invasive testers.
 

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Modern digital battery testers employ a different testing method than an invasive tester such as a carbon pile type tester like the old Suns. A digital tester does not put a load and draw current from the battery like a carbon pile tester. It sends signals to the battery and monitors how the battery responds and formulates the results from that. It has a baseline of how the battery chemistry should respond under test conditions and uses that as the reference for the test. It doesn’t need a fully charged battery to be able to test the battery. The digital methods use means that are more accurate and faster than the old school invasive testers.
I can tell that you in my case the Autozone digital tester did not work. It said my battery was good and my VAT40 said it was bad. The battery was absolutely bad. I charged it fully before taking down Autozone. I actually took it to them twice. I knew it was bad the first when it would not hold a charge for 24 hours after being on a commercial charger all day long. I went home and did it again, same results. After that the new battery sits for months without loosing its charge. I tested batteries almost daily at work for 30-years ad there is no way a VAT40 is going to hurt the battery anymore than a cranking engine does. After that experience why would I trust a digital tester when it screwed me out of my batteries warranty. I think the carbon pile tester, "good ones" are superior but they are probably so expensive nobody buys them. I could say I'm old school and stuck in my ways but the tester Autozone used was a piece of junk.
 

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If the negative cable is not connected a battery can not drain. Something is either wrong with the battery or the shop that says it is good, or both. How old is the battery? READING BATTERY DATE CODES
Bad production run of batteries where there is an internal issue with the pile. Most likely that's what's going on.
A lead acid automobile battery can also discharge with no cables attached and no internal MANUFACTURING issues.
(grid material flaked off and is sitting at the bottom of the case, shorting out the plates...... old battery though, takes a long time to happen)

Once upon a time I worked for AC Delco and did battery autopsies in the Orange CA Delphi plant.
 
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Discussion Starter #9
Bad production run of batteries where there is an internal issue with the pile. Most likely that's what's going on.
A lead acid automobile battery can also discharge with no cables attached and no internal MANUFACTURING issues.
(grid material flaked off and is sitting at the bottom of the case, shorting out the plates...... old battery though, takes a long time to happen)

Once upon a time I worked for AC Delco and did battery autopsies in the Orange CA Delphi plant.
I'll return the 2nd battery and see if they can determine if there is an issue. I ran a test with my boat battery, with only the positive terminal connected I do not see voltage with the meter connected to the negative terminal when I touch the block, firewall or starter ground.

I'm using a 1 wire ALT setup. Is there any way the ALT circuit could be draining the battery? I don't see how that could happen without the negative cable attached.
 

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I think the carbon pile tester, "good ones" are superior but they are probably so expensive nobody buys them. I could say I'm old school and stuck in my ways but the tester Autozone used was a piece of junk.
Digital testers range in price from under a hun to over a grand. I wouldn’t doubt that what’s likely a low buck handheld was either used incorrectly or missed your diagnosis for whatever reason. While you may think conductive testers aren’t good most of the rest of the automotive field disagrees. A top of the line Midtronics is just over a grand as is a top of the line Snap On which is a rebadged Midtronics. A name brand carbon pile tester is a couple/few hundred. You don’t see that depth of conductive technology yet because the patent Midtronics had recently expired. I’d expect the extra features and capability to make it into lower cost tools. The cheapies have good basic capabilites but not the software and exact methodology that Midtronics have.
 

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Did you have the hood closed and is it contacting the negative post? Otherwise it HAS to be a defective battery, unless the battery fairy is sneaking in your garage overnight or your best buddy is pranking you by dropping an Alka-Seltzer in it when you're not looking....
 

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I can't remember what I paid for my two Sun VAT40s? My friend I've known since Kindergarten, his family owned a Cadillac repair shop from the 1960s until just a couple year's ago. They called me up and made a good offer on all the tools. Nobody was fixing the older Cadillac Eldorado's and Seville's anymore and newer ones have 100,000 mile warranty's I use to hangout there when there would be 20 Cadillacs being worked on at the same time. It got down to only one or two a week. The neighborhood turned ghetto and they all wanted to retire. I bought the two VAT40s, Sun Scope , Sun Distributor machine. brake drum/rotor lathe, 40 ton hydraulic press. Snap-On computerized wheel balancer, Coats Tire machine (old school), valve grinder and all kinds of smaller tools.
 

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Discussion Starter #14
Did you have the hood closed and is it contacting the negative post? Otherwise it HAS to be a defective battery, unless the battery fairy is sneaking in your garage overnight or your best buddy is pranking you by dropping an Alka-Seltzer in it when you're not looking....
Hood does not touch the terminals. Garage is locked so no fairy getting in and kids are not smart enough to prank me. I can't see 2 brand new defective batteries. I'm going to simulate this again with my boat battery, 1 year old and trickle charged over the winter, known good battery. Will see what it looks like Wednesday.
 

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Discussion Starter #16
I believe I now understand what is happening. After closer inspection I discovered that at idle the alternator is putting out 13-14 volt, but as soon as I go off idle the volts jump into the 17-18 volt range. Looks like the regulator has failed.
Both times I installed a brand new battery, started the car and drove for 30 minutes, parked the car and disconnected the battery. The next day or so the battery was dead.

Outstanding question is if you apply 17 plus volts for 30 minutes to a fully charged battery will it break the internals of the battery?
 

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I believe I now understand what is happening. After closer inspection I discovered that at idle the alternator is putting out 13-14 volt, but as soon as I go off idle the volts jump into the 17-18 volt range. Looks like the regulator has failed.
Both times I installed a brand new battery, started the car and drove for 30 minutes, parked the car and disconnected the battery. The next day or so the battery was dead.

Outstanding question is if you apply 17 plus volts for 30 minutes to a fully charged battery will it break the internals of the battery?
Won't be the best thing for the battery but probably won't do much more than evaporate some electrolyte. What's probably bad is the regulator and that can be responsible for your overnight current drain.
 

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^ What he said.
 

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Discussion Starter #20
Won't be the best thing for the battery but probably won't do much more than evaporate some electrolyte. What's probably bad is the regulator and that can be responsible for your overnight current drain.
I solved this last month but failed post my findings. The issue was two fold, the alternator was bad, (putting out over 17 VDC) and the green wire with red stripe going back to the ignition was broke, (making partial contact). These issues caused the battery to drain over night. I still don't understand why, but a 3rd battery, new alternator and the wire corrected have resulted in no battery issue for over a month.
 
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