Parasitic battery draw

Tiny
ASIROSKE
  • MEMBER
  • 2000 MERCURY MARQUIS
  • 4.6L
  • V8
  • 2WD
  • AUTOMATIC
  • 150,000 MILES
My battery reads 12.2 volts. It starts and runs fine. When I do a parasitic test it reads.15 mamp. Why is my battery at 12.2 volts when running it reads over 14 volts?
Monday, November 19th, 2018 AT 7:25 PM

3 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,716 POSTS
Hi and thanks for using 2CarPros.com.

The draw you have on the battery is normal. Although everything is off. There are still electronics working. For example, a clock and radio memory always draw power.

A .15 milliamp draw is completely acceptable. In new cars, it is not uncommon to see up to a .85 milliamp draw.

To answer your next question, with the engine off 12.2 volts is great from the battery. When running, it should be around 14 volts while being recharged by the alternator.

If you have concerns related to the battery or alternator, here are a couple links that describe how they are checked:

https://www.2carpros.com/articles/how-to-check-a-car-alternator

https://www.2carpros.com/articles/car-battery-load-test

Honestly, everything you described sounds perfectly normal and would not create a concern to me. Also, just to recap, 12.2 volts with the engine off is good. When running and the alternator charging, it should be around 14 volts, so everything sounds good. The parasitic draw you have is normal.

Please feel free to ask more questions if you have them.

Take care,
Joe
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Monday, November 19th, 2018 AT 7:47 PM
Tiny
ASIROSKE
  • MEMBER
  • 2 POSTS
Sorry, I am using a Harbor Freight multi-meter at a 10amp setting. So my parasitic draw reading is.15 amps.
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Tuesday, November 20th, 2018 AT 3:08 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,716 POSTS
Welcome back:

Okay, that is equal to 150 mamps and a concern. Is the battery going dead over night?

What I want you to do is review this link. It discusses electrical draws. In the beginning, it will show things to check. Next, it will discuss how to check for a draw using a test light which you have already done with the multi-meter. Then it discusses specific things to check and explains if the problem is not found, to remove one fuse at a time until the draw stops. When it does, you have located the circuit.

Take a look and let me know if it helps or if you have other questions.

https://www.2carpros.com/articles/car-battery-dead-overnight

If I do not hear from you over the next couple of days, I just want to wish you and your family a Happy Thanksgiving.

Take care,
Joe
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Tuesday, November 20th, 2018 AT 6:09 PM

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