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Electrical Issue - Battery or Alternator?

commodorev6

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Hi,

I am currently not able to start my VS Ecotec V6. I have tried 2 different batteries both fully charged at 12.6 volts which then start the car and it reaches 14.2 volts on idle.
Both batteries are not brand new however I wouldn't expect such a fast voltage drop from a fully charged battery.

When the car shuts off, the voltage drops from 12.6 to 12.0 and eventually will drop to 9.0 volts meaning the car won't start. I used a multimeter to test the alternator and battery and all have good readings. I cannot find where this drop in voltage could be coming from. Connections look fine, terminals are clean.

One other potential point is the negative battery terminal which will not tighten around the battery. Does anyone else have the same issue? I use a brass connector which seems to fit fine over the positive terminal but very loose on the negative terminal. I haven't found a version like the original that will sit securely. Should I use a battery lead shim?

I have attached 3 photos:

Photo A - Positive Battery terminal. Petroleum jelly has been applied to the positive post to prevent corrosion.
Photo B - Negative Battery terminal. Petroleum jelly has been applied to the negative post. This does not tighten like the positive terminal and could easily be removed by hand.
Photo C - Negative battery terminal on a negative post of the battery. Is there an alternative version or company that makes one that fits tightly? Is a battery lead shim an option?

If anyone has advice or can spot something that isn't working here would be greatly appreciated.

Thank you
 

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chrisp

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Where exactly are you measuring the voltages? Are you measuring directly on the battery posts, or the battery terminals, or are you using a ground point on the body for the negative reference?

It seems like the negative battery terminal might be the problem - assuming that you are seeing >14 volt from the alternator but seeing a lower voltage directly across the battery.

Just for the purposes of testing and diagnosis, try shimming the negative post with some copper, brass or (clean) lead shim and seeing if it resolves the issue.
 

commodorev6

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I am measuring directly on the battery posts to get the voltage when the car is off and then again when it is running. I am also using a ground point for the negative reference.
 

vc commodore

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Replace the negative terminal clamp with one that can be tightened up properly, so it can't be removed by hand then go from there...

Picture 3, the terminal appears to be a positive terminal clamp, rather than a negative terminal clamp....

Head to any auto parts store and they'll have a collection of clamps that can be used
 

gtrboyy

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So if you turn car off multimeter reads 12.0...how does it take to get to 9 volts? Overnight or 30mins?

Not sure if got power drain or dud battery.

Have loose connections or bad earths doesn't help either do voltage drop test everything probably find few extra things to fix.

If starts on 12.6 then has 14.2 tells you alternating is charging doesn't tell if it copes under load with lights etc on or much else.
 

commodorev6

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So if you turn car off multimeter reads 12.0...how does it take to get to 9 volts? Overnight or 30mins?

Not sure if got power drain or dud battery.

Have loose connections or bad earths doesn't help either do voltage drop test everything probably find few extra things to fix.

If starts on 12.6 then has 14.2 tells you alternating is charging doesn't tell if it copes under load with lights etc on or much else.

The recent occurrence saw the voltage drop to 9 volts in less than 15 minutes however a day earlier, the voltage went from 12.6 to 11.8 over 24 hours. One week earlier, a similar scenario occurred. There is no consistency with the voltage drop which makes me think something else like the negative terminal is draining the battery.

When the car is running normal 12.6 volts, the lights on (high beams and hazards) it drops to 10.9 volts.

The wires around the battery to the terminal and alternator are in good condition. I've added insulation tape around to reduce any heat causing issues.

I need to find a proper battery terminal that clamps tightly to the negative terminal and maybe add a battery shim to see if it holds the voltage.
 

gtrboyy

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Loose terminal or connections doesn't drain battery overnight...power drains by something left on or faulty.

Engine running the bad earths or terminals will prevent alternator from recharging battery that eventually not enough voltage to crank engine over.

You have more than issue to fix & insulation doesn't fix power drain or loose terminal or voltage drops
 

Lex

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Hi,

I am currently not able to start my VS Ecotec V6. I have tried 2 different batteries both fully charged at 12.6 volts which then start the car and it reaches 14.2 volts on idle.
Both batteries are not brand new however I wouldn't expect such a fast voltage drop from a fully charged battery.

When the car shuts off, the voltage drops from 12.6 to 12.0 and eventually will drop to 9.0 volts meaning the car won't start. I used a multimeter to test the alternator and battery and all have good readings. I cannot find where this drop in voltage could be coming from. Connections look fine, terminals are clean.

One other potential point is the negative battery terminal which will not tighten around the battery. Does anyone else have the same issue? I use a brass connector which seems to fit fine over the positive terminal but very loose on the negative terminal. I haven't found a version like the original that will sit securely. Should I use a battery lead shim?

I have attached 3 photos:

Photo A - Positive Battery terminal. Petroleum jelly has been applied to the positive post to prevent corrosion.
Photo B - Negative Battery terminal. Petroleum jelly has been applied to the negative post. This does not tighten like the positive terminal and could easily be removed by hand.
Photo C - Negative battery terminal on a negative post of the battery. Is there an alternative version or company that makes one that fits tightly? Is a battery lead shim an option?

If anyone has advice or can spot something that isn't working here would be greatly appreciated.

Thank you
I looked at your pics. There looks like corrosion on the terminal. I have highlighted it.

158825-44ceef10bca121552279a1f20b6175d1.jpg

Why wont the negative terminal tighten up? There seems to ample room?
 

commodorev6

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Loose terminal or connections doesn't drain battery overnight...power drains by something left on or faulty.

Engine running the bad earths or terminals will prevent alternator from recharging battery that eventually not enough voltage to crank engine over.

You have more than issue to fix & insulation doesn't fix power drain or loose terminal or voltage drops

Thanks @gtrboyy boyy - exactly. Agreed. A battery terminal isn't going to drain an entire battery that quickly.

Nothing has been left on, no lights, accessories, or boot light. I've checked all those items. Its something else and its just a matter of finding the cause.
 

rambunctious

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I agree with Lex the clamp will close up tight.
If you have a vice, remove the bolt from the clamp and place the clamp in the vice and close the clamp until the surfaces touch flat where the bolt goes.
Then try it on the battery post.
I am sure it will work.
 
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