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Normal overnight battery drain

Tiny
DANNY EREMIAN
  • MEMBER
  • 2005 BMW 325I
  • 1.5L
  • V6
  • AUTOMATIC
  • 89,000 MILES
What would be the normal overnight voltage drain in this car?.03 amps or volts?
Monday, November 26th, 2018 AT 11:08 PM

9 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good morning,

The normal draw is always measured in current draw, not voltage.

The figure is 50-75 milli amps. At that rate the battery will last about two weeks before going low on charge if the car is not started.

Roy
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Tuesday, November 27th, 2018 AT 9:23 AM
Tiny
DANNY EREMIAN
  • MEMBER
  • 8 POSTS
The reason I am asking is, I had a parasitic draw and now I am monitoring the battery everyday. From fully charged Sunday I had 12.60 reading from multi-meter. Monday it was 12.30, Tuesday 12.21. Do these numbers seem normal to the point where that is just basic draw? Thank you for your expertise.
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Tuesday, November 27th, 2018 AT 1:45 PM
Tiny
ASEMASTER6371
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No, I would have the test done to find the issue. That is too much too fast.
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Tuesday, November 27th, 2018 AT 1:53 PM
Tiny
DANNY EREMIAN
  • MEMBER
  • 8 POSTS
Okay, since I am doing this myself, and found a bad window lock switch and replaced, I thought that would be it since that is a common parasitic draw in the BMW's. When I do draw test, I get instant 1.03 reading but in minutes it goes right to.04/.05 and stays there. Does not give me time to pull fuses to isolate. I cannot figure that out. Thanks again, Danny.
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Tuesday, November 27th, 2018 AT 10:41 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
The .04-,05 is good. That is normal.

I would be looking at the battery. Have it load tested as it may have an internal short inside.

Roy

https://www.2carpros.com/articles/car-battery-load-test
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Wednesday, November 28th, 2018 AT 4:57 AM
Tiny
DANNY EREMIAN
  • MEMBER
  • 8 POSTS
Battery two weeks old, old battery was shot from parasitic draw. My problem now is seeing the draw so I can pull fuses and isolate. But draw goes away in few minutes. Does not make sense.
Thanks again
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Wednesday, November 28th, 2018 AT 6:03 AM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Yes it does.

When you first turn off the car, it will have a higher draw until the module see no activity. Then they will go to sleep. That Is when you see the draw drop. It sometimes takes about fifteen to thirty minutes.

That Is the way you check it by letting it sit and letting the modules go to sleep.

Roy
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Wednesday, November 28th, 2018 AT 6:13 AM
Tiny
DANNY EREMIAN
  • MEMBER
  • 8 POSTS
Yes, I make sure the car sleeps before test, on that car p light on shift goes out, that is when I get the short term draw, after asleep. Thanks for your patience and help.
Frustrating, Danny
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Wednesday, November 28th, 2018 AT 7:03 AM
Tiny
ASEMASTER6371
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That draw of 50-75 milli amps is it. That is what is normal. That will not and cannot be changed.

Roy
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Wednesday, November 28th, 2018 AT 7:12 AM

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