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Battery Drain (Yes, Another Thread)

Posted: May 09, 2022 12:15 PM
by Germz
I'm stumped. I've been searching for a battery drain in my e28 for a while now. After a couple days of not driving it, it won't start, not even turn the engine over. I went to the local auto parts story and they charged and tested my battery and said that was good, it is only about a year old.

A while ago I installed a volt meter in place of the cigarette lighter, hoping to keep an eye on volts. But I only watched them drop every time I came out to the car. Yesterday after I got the battery charged at the auto parts store I disconnected the negative cable and hooked up my multimeter in between the battery post and the negative cable. Set the multimeter to amps and was getting .33ma. Which I figured was normal. I disconnected the volt meter at the cig lighter and it dropped to .19ma. Now from what ive been reading online I've been seeing that anything below .50ma should be fine.

Anybody have any idea what could be causing this?

*bonus issue* my brake lights stopped working. I replaced my brake switch at the pedal which fixed it for a while. but now its back to not working. fuse is fine. could this be related, or just coincidental timing?

Re: Battery Drain (Yes, Another Thread)

Posted: May 09, 2022 7:20 PM
by RossDinan6
With the key off, pull each fuse and probe with the amp meter. This will narrow down which circuit is drawing excess current. Then inspect any suspect circuits. My E24 killed the battery a little while ago and it turned out to be the trunk light staying on. The glove box light is a known cause of this.

Re: Battery Drain (Yes, Another Thread)

Posted: May 09, 2022 7:58 PM
by Germz
I tried that yesterday with my multimeter. But the amount of milliamps that is being pulled seems too low to be a problem.

Re: Battery Drain (Yes, Another Thread)

Posted: May 09, 2022 8:33 PM
by Galahad
Are you sure it's not 0.33A (330mA)? 0.33mA is way too low, I could believe 33mA.

Re: Battery Drain (Yes, Another Thread)

Posted: May 14, 2022 12:55 AM
by Germz
Sorry Galahad you were right. I had written it wrong. Right now i checked it and it was .019A. So 19ma.

I’ve resorted to unplugging accessories and letting the car sit and see if anything drains. Im not sure what else to do here.