Battery Drain, What am I missing?

[GSEninja 12]

I’ve been having a drain in my battery for the last month, and can’t figure out where it’s coming from. Car was perfectly fine for 6 months, then spent 6 months in the paint shop. I’ve checked the grounds for all lights, can’t find an issue.

The car is a 1969 Mustang, American Autowire Harness installed throughout, 100amp alternator, battery is installed in the trunk with 2ga wire running to a fender mounted start solenoid. 

When I test for a parasitic draw, I get 6.4 on the 200mA setting. Does this mean 6.4mA? If so, then that seems low enough to be a non-issue.

https://imgur.com/a/EwH8TcN

 

What I’ve done:

- Tested the battery at home on my Schumacher BT-100 and took it to the local auto parts store, all good

- Ensured the alternator  is charging at 14.1v, removed the negative cable while running and the car stays on, all good

- installed a master disconnect switch that cuts the battery voltage from the entire car, still get voltage drop overnight

- ensured the primary ground is clean and secured

- removed the negative cable overnight, voltage still drops

Can this still be a battery issue even though the cranking amps read normal? 
 

thanks!

[LoneWolf2U 136]

From my past, A battery disconnected and still drops overnight is a battery with bad plates inside. Soon to have a short and complete failure.

[Midlife 814]

Yes, 6.4 milliamps.  That's an excellent number and shouldn't give you problems.  I tend to agree with Mr. Mach1Rider.

[GSEninja 12]

2 hours ago, Mach1Rider said:

From my past, A battery disconnected and still drops overnight is a battery with bad plates inside. Soon to have a short and complete failure.

Huge thanks! I keep going back to the battery, but cranking amps (to me) was always the signal of a good or bad battery. Good to know I need to dig a little deeper in the future.

Any idea how I can test for this?

 

41 minutes ago, Midlife said:

Yes, 6.4 milliamps.  That's an excellent number and shouldn't give you problems.  I tend to agree with Mr. Mach1Rider.

Thanks! I didn’t think I was crazy. 

[69RavenConv 286]

Good advice from our esteemed colleagues above.

An old-fashioned cheese grater battery tester is still a great way to test a weak or failing battery (and this is from a guy who spent a few years of my career working on a high-tech, electronic lead-acid battery tester to compete with Midtronic's high-tech electronic lead-acid battery testers*). Load tests don't lie, and those load testers are cheap.

Since you've just been to the body shop, don't rule out the possibility they nicked or squashed a wire while removing and replacing trim and body parts, creating a short to ground.

 

*We got pretty good at it but their lawyers convinced our lawyers not to go to market :).

[Midlife 814]

1 hour ago, GSEninja said:

Huge thanks! I keep going back to the battery, but cranking amps (to me) was always the signal of a good or bad battery. Good to know I need to dig a little deeper in the future.

Any idea how I can test for this?

 

Thanks! I didn’t think I was crazy. 

Uhhh...we never said you weren't crazy.  How many fingers do I presently hold up?  When was the last time you kicked the dog?  Do you always moon Chebbys? 

[GSEninja 12]

2 hours ago, 69RavenConv said:

Good advice from our esteemed colleagues above.

An old-fashioned cheese grater battery tester is still a great way to test a weak or failing battery (and this is from a guy who spent a few years of my career working on a high-tech, electronic lead-acid battery tester to compete with Midtronic's high-tech electronic lead-acid battery testers*). Load tests don't lie, and those load testers are cheap.

Since you've just been to the body shop, don't rule out the possibility they nicked or squashed a wire while removing and replacing trim and body parts, creating a short to ground.

 

*We got pretty good at it but their lawyers convinced our lawyers not to go to market :).

I’ll check all grounds again, thank you! And thanks for the “cheese grater” reference.. with this BT-100 I knew exactly what you were talking about! 

1 hour ago, Midlife said:

Uhhh...we never said you weren't crazy.  How many fingers do I presently hold up?  When was the last time you kicked the dog?  Do you always moon Chebbys? 

6, last week, and I want my lawyer

[Mach1 Driver 560]

10 hours ago, GSEninja said:

6, last week, and I want my lawyer

Excellent, you'll fit right in with the rest of us.