Battery Light ON, with cold start for few seconds longer

[elrichmeister]

Almost 2 years with it, with same behavior, only cold start battery light hangs a little longer. No issues to report car seems fine.
Only aftermarket stuff is, Dashcam wired to homelink power leads in the sunroof control area, and USB-C charger wired to the same power for homelink in the glovebox fuse box for my Bluetooth adapter and phone charger.
Those devices shouldn't pull too much of a load.

[sapote]

only cold start battery light hangs a little longer. .

measure batt voltage before starting -- if it's too low, this would place a big load on the alternator and pull its output much lower than 14v and the cause of the delay on red batt light. Normal batt should be around 12.48v to 12.6v

[Hotchkess]

Normal batt should be around 12.48v to 12.6v

Measuring mine after it's been sitting overnight, it measures at 12.31. So not super low, but also not where it seems like it should be. The battery is only a couple of years old (BMW AGM battery from November of 2023), but I could look into replacing it again and see if the issue persists after.

[elrichmeister]

measure batt voltage before starting -- if it's too low, this would place a big load on the alternator and pull its output much lower than 14v and the cause of the delay on red batt light. Normal batt should be around 12.48v to 12.6v

On first post, I mentioned that battery voltage was 12.6 with car off, key in position 2 voltage drops to 12.3. then when car is started i see a drop to 11v then jumps to 14.1v, There is a link to some videos, the 2nd video shows the voltage meter

Ill check later today to see what it does now.

[sapote]

On first post, I mentioned that battery voltage was 12.6 with car off

The 1st video shows it's either 12.2 or 12.1v on two devices, not 12.6v, before beeping -- key was at ON or acc position?
Then key turned to x position and it's beeping then it shows 12.47v or something -- key turned to OFF?

It's confusing. Should measure with key off first, then turned ON if you want to.

[elrichmeister]

The 1st video shows it's either 12.2 or 12.1v on two devices, not 12.6v, before beeping -- key was at ON or acc position?
Then key turned to x position and it's beeping then it shows 12.47v or something -- key turned to OFF?

It's confusing. Should measure with key off first, then turned ON if you want to.

Here is a new video.

https://youtu.be/qnFmJE7pUdE?si=Va2KmNKXQ6pRttE5

Car off: 12.43v
Key In position 1: 12.32v
Key In Position 2: droops to below 12v then climbs back up to like 12.09v
Then cranking it droops down to 9v then climbs back to charging voltage 14.1v

Noticed the battery light go away faster than usual. Last day I drove the car was on Sunday.

[sapote]

Interesting that the red batt turned off when the voltmeter still shown only 11.69v in the video. Where was the meter connected? I also wonder if the DMV reflesh/sampling rate is too slow to cause the delay on the 11.69 value.

12.43v is not too low in cold weather, so the batt is ok.

[elrichmeister]

Interesting that the red batt turned off when the voltmeter still shown only 11.69v in the video. Where was the meter connected? I also wonder if the DMV reflesh/sampling rate is too slow to cause the delay on the 11.69 value.

12.43v is not too low in cold weather, so the batt is ok.

I connected the multimeter to front jump posts in the engine bay.

[sapote]

I wonder why the voltage dropped from 11.89v at 0:44 to 11.50v at 0:45 in the video. With engine RPM close to 2000, what load that sucked the voltage from 11.89 to 11.5v in 1sec?

[nextelbuddy]

I can confirm I had a genuine BMW alternator that died on me last year.. before it died my battery light always turned off at the same time as the oil light

After swapping it out for a brand new Valeo unit from AutoZone, ever since then regardless of cold start or warm start... Every start the battery light stays lit a little bit longer and then goes away.

It's annoying because I notice it but I've never had any issues

MSS54HP with 24H cluster with alternator via canbus

[elrichmeister]

I can confirm I had a genuine BMW alternator that died on me last year.. before it died my battery light always turned off at the same time as the oil light

After swapping it out for a brand new Valeo unit from AutoZone, ever since then regardless of cold start or warm start... Every start the battery light stays lit a little bit longer and then goes away.

It's annoying because I notice it but I've never had any issues

MSS54HP with 24H cluster with alternator via canbus

Thanks for feedback, seems like new Valeo units have this behavior. No other issues other than that on my end since replacement.

[ejendow]

Thought something was up with my car, but I too have the same issue with my new (not reman'd) Valeo Alternator.

[sapote]

I can confirm I had a genuine BMW alternator that died on me last year.

I'm guessing it died due to worn out brushes which can easily be replaced for couple dollars for the cost new brushes. How many miles when this happened? BMW alternator brushes should be replaced at 170k miles.

[nextelbuddy]

I'm guessing it died due to worn out brushes which can easily be replaced for couple dollars for the cost new brushes. How many miles when this happened? BMW alternator brushes should be replaced at 170k miles.

I wish it was just the brushes.

The bearings went bad

[sapote]

The bearings went bad

This issue is rare for stock alternator, but I think the higher rpm of M3 might add to this.