Battery not holding charge


Shawn1112

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So my first issue with the Regal (LS swapped). Car hasnt really held a charge since coming home. It would sit between 7-10 days between starts. So figured it was due to it sitting. But now that I'm out driving it more, it doesnt hold a charge. Pretty much have to jump it or keep battery charger on it if it sits overnight. Battery is brand new and had it tested at 2 different Oreilys yesterday and both said its perfectly fine. 28 mile drive to suspension shop, sat inside overnight and they had to jump it the following day, same thing when I brought it home. Now what I'm leaning towards and not sure how to tell if thats the issue. Original alternator was a 4 pin, I purchased a 250 amp high output alternator for my subs/amp. That alternator is a 2 pin, but wired up using a 1 wire pin, see link. Prior to the swap and having the original alternator, I never had this issue and thats why I'm leaning towards alternator plug. Thoughts and how would I could I test if the 1 wire pin is the issue? Also using below on positive of battery

Amazon product

 

boostedguy05

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If you can go 30 miles I would think the alternator is working fine, but something is drawing power after the car is turned off. Double check radio power source?
 
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Shawn1112

Shawn1112

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If you can go 30 miles I would think the alternator is working fine, but something is drawing power after the car is turned off. Double check radio power source?
Was doing it prior to me putting subs/amp back in this weekend. I'm also wondering now if the positive battery post thing I'm using isnt allowing the alternator to do its job.
 

boostedguy05

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Radio tho brother, I doubt you are using factory head unit in that thing.
 

01Cobra

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On my Cobra I had a battery drain issue and it turned out one of my Mach 460 amps had melted which allowed a constant draw. Silly electrical
 
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Shawn1112

Shawn1112

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On my Cobra I had a battery drain issue and it turned out one of my Mach 460 amps had melted which allowed a constant draw. Silly electrical
All aftermarket amps and was doing this prior to me putting the amps/subs back in last weekend. So I'm 100% positive thats not the issue
 

zenriddles

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To prove it is not the alternator, disconnect the battery with car running. Bad alt= car stalls.

To prove parasitic draw after shut down, disconnect battery as soon as turning off car. Leave overnight. Reassemble in morning and try to start. No start = bad battery.

One can also disconnect positive terminal and test amp draw with key off.
 
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Shawn1112

Shawn1112

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To prove it is not the alternator, disconnect the battery with car running. Bad alt= car stalls.

To prove parasitic draw after shut down, disconnect battery as soon as turning off car. Leave overnight. Reassemble in morning and try to start. No start = bad battery.

One can also disconnect positive terminal and test amp draw with key off.
Totally forgot about disconnecting battery on older cars to check alternator. But being a newer motor (2005) would that still apply?
 

boostedguy05

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Does the car have an under the hood light? Or trunk light that might be staying on?

Power seats? Switch stuck in a movement position?
 
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Shawn1112

Shawn1112

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Does the car have an under the hood light? Or trunk light that might be staying on?

Power seats? Switch stuck in a movement position?
Trunk light, nope. I’ll have to check under the hood as I don’t recall.
Seats are manual.
 

boostedguy05

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Are you talking about this bolt?




3ED5FE5F-5296-4DFC-AE95-6AE70363140D.jpeg


What else has been done around that time?

Ledtails, digital dash?

Any of those still pulling draw after car is turned off?
 
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Shawn1112

Shawn1112

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Are you talking about this bolt?




3ED5FE5F-5296-4DFC-AE95-6AE70363140D.jpeg


What else has been done around that time?

Ledtails, digital dash?

Any of those still pulling draw after car is turned off?
I replaced that with this. Nothing else at all is new, digi dash and LED tails all done prior to the swap.
I had 2 hook up 2 wires for tails that were disconnected for paint, 12v constant and ground. Both were connected exact same way as before paint. Lets just say for shits and giggles one of them were pulling draw, wouldnt the tails and or dash be lit up?

Battery terminal.jpg
 

1quick

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You have an amp meter? Just check battery voltage at idle and it will tell you if the alternator is charging it
 

1quick

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Should be 14.7 ish if I remember right if it’s just around 12 it’s not charging the battery
 
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Shawn1112

Shawn1112

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You have an amp meter? Just check battery voltage at idle and it will tell you if the alternator is charging it
This I do have in my arsenal. Will give that a shot
 

Intel

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also check how many amps are being pulled with the car off.

You are either not charging the battery or you have a drain on the system.
 
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Shawn1112

Shawn1112

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also check how many amps are being pulled with the car off.

You are either not charging the battery or you have a drain on the system.
Been lazy and havent went out in the garage to fuck with it yet. I'm leaning towards the battery not being charged.
 

Intel

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For that connector on the alternator to replicate a alternator light in your dash make sure it is indeed getting 12v by backprobing that connector while the engine is one. If you aren't getting 12v to the sense/field wire the alternater won't charge.

  • Needs to be terminated to a switched 12v source that is "on" while the engine is running.
 
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Shawn1112

Shawn1112

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So just an update. I re-arranged everything on the battery post extender yesterday to make sure everything was making good contact.
Started car at 2:30pm yesterday and battery was at 14.7-14.8 while idling. Also checked alternator with multi meter and it was also at 14.7. Went out to garage every couple of hours and checked battery while car was off. Voltage started at like 13.18 with car off and slowly dropped which I'm assuming is normal. Checked it this morning at 6am and was at like 12.52, just checked right now 13 hours later and was at 12.50. Tried starting and it fired right up and shot up to 14.7 at idle. Does that drop while car is sitting seem normal?
 

Intel

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What is the amperage pull when the car is off it should be in the range of less than 50 milliamps.
 

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