Strange Battery Drain Issue

The Era of The Square Body Racing Comets
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chartwig1980
Posts: 16
Joined: Wed Nov 01, 2017 6:48 pm
Location: South Florida

Strange Battery Drain Issue

Post by chartwig1980 »

Hello everyone. I've looked at the other battery drain posts but none of them address my issue or have the same variables so I wanted to start a new post.

64 Comet
200 6 Cylinder/Automatic
Generator/Regulator
Brand new Interstate battery

My Comet is experiencing battery drain with the cables connected but not with the cables disconnected. I've monitored the drain over the past week and metered a change from 13.27 volts on 1/4/18 to a voltage drop to 12.67 volts today 1/11/18.
I've checked for battery drain using two meters including using a brand new, never used multimeter. The only way the meters ever change from 0 is if I open a door and trigger the interior lights. Then I get a draw of about 2.8 amps. Otherwise it doesn't read a drain at 10 amps, 20m or 200m.

If anyone has any suggestions about the next steps I should take; I would appreciate any feedback. Thank you!
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1964 Mercury Comet Caliente Convertible
200 - 6 Cylinder
74K Miles
Built in Oakville Canada

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loman
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Joined: Sat Dec 28, 2013 9:03 am
Location: Missouri

Re: Strange Battery Drain Issue

Post by loman »

My first thought would be not to worry. You say you have 12.6 volts and that is what a 12 V battery should be. 2.1 volts per cell. As for tracking any possible drain, I would take all the fuses out but 1 and let it sit then monitor your voltage drop over a given time frame. Do that for each circuit to isolate the drain. Then if you find the draining circuit start eliminating things on that circuit until you find it. Very time consuming but that's what I would try to do. I'm sure someone else might have an easier way and will chime in.
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chartwig1980
Posts: 16
Joined: Wed Nov 01, 2017 6:48 pm
Location: South Florida

Re: Strange Battery Drain Issue

Post by chartwig1980 »

loman wrote:My first thought would be not to worry. You say you have 12.6 volts and that is what a 12 V battery should be. 2.1 volts per cell. As for tracking any possible drain, I would take all the fuses out but 1 and let it sit then monitor your voltage drop over a given time frame. Do that for each circuit to isolate the drain. Then if you find the draining circuit start eliminating things on that circuit until you find it. Very time consuming but that's what I would try to do. I'm sure someone else might have an easier way and will chime in.
I may have jumped the gun on this post. I've let the car sit for a week and taken measurements that are within specs.


12.96 volts 1/11/2018 - 9:00 pm (15 Minutes after charge)
12.62 volts 1/18/2018 - 6:00 pm

I plan to take another measurement Saturday and then turn it over and see what I've got.

My biggest concern is my multi-meter(s) read no amp draw yet the battery does drop voltage gradually and I want to know at what point should I be concerned about it?
Image
1964 Mercury Comet Caliente Convertible
200 - 6 Cylinder
74K Miles
Built in Oakville Canada

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poboyjo65
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Posts: 7037
Joined: Thu Oct 20, 2011 9:40 pm
Location: Camden, Tenn.

Re: Strange Battery Drain Issue

Post by poboyjo65 »

Take a battery cable off & touch it back to the battery post & watch for a spark,best to do it at night. if you see a small spark then something is drawing current.
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Johno

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chartwig1980
Posts: 16
Joined: Wed Nov 01, 2017 6:48 pm
Location: South Florida

Re: Strange Battery Drain Issue

Post by chartwig1980 »

Well I let the car sit until this morning and checked my voltage. Still sitting at 12.62 volts. I think my issue was a combination of two things:

1. Lack of knowledge that a battery needs time to cool down after an initial charge to get an accurate reading.
2. My incorrect assumption the battery drain was a repeat issue because the first battery was bad. I replaced battery #1 with brand new battery #2 and due to step 1...made the incorrect assumption that the battery was draining when it was actually coming down from being "excited" by a full charge.

Lesson learned....do not meter a freshly charged battery. Wait a couple hours or until the next day to get a proper voltage reading.
Image
1964 Mercury Comet Caliente Convertible
200 - 6 Cylinder
74K Miles
Built in Oakville Canada

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