Battery Light ON, with cold start for few seconds longer

[elrichmeister]

Not sure if its an issue, but recently ive noticed that on a cold start in after the car sits overnight or a couple of days, the battery light hangs on for a few seconds and then turns off.
I had some work done to the car recently, so not sure if its normal, since this is something i never noticed, the battery light used to simultaneously turn off with the oil light.

Here are 2 videos.

https://photos.app.goo.gl/3ZtvgH2yvXi2hMW7A

1st video shows cold start and monitoring the voltage on the meter
2nd video shows battery light hangin on for few seconds. This a few minutes after the initial start


Checking the jump posts in engine bay meter measured about 12.6v. with Key in and accessories on it was about 12.3-12.4 on the meter. The voltage meter in the sunglasses bin is wired from the garage door opener fuse so its only on when acc is on.
With the initial cold start i noticed the voltage drop to low 11v then climbs back up to 14.1-14.3. Believe that is why the battery light hangs on for a few seconds.

Initial concern is that this was not a behavior ive seen with this car since ive owned it, not sure if its a problem that i should be worried about. This only happens if the car has sit for a day or more and its first start of the day. Rest of the day after the car has been ran it does not do this.

Recent Work done:

Battery and OEM radio replaced, i had parasitic from the original radio that would kill my battery if the car would sit for more than 3 days.
- Replaced the battery during troubleshooting and then found the culprit to be the radio.

about 2 months go by and my Alternator goes out, completely stops charging the battery.
- At the shop i replaced alternator, with new Valeo, as the car had Reman Bosch unit
- Replaced deflector and ac tensioner pulleys
- Replaced belt
- Replaced Fan clutch (while i was in there, suspecting weak fan clutch other issue for summer time to check)
- replaced steering guibo (should be unrelated)

Other than that the car runs fine, just not sure if i'm worrying about nothing.

[sapote]

1st video shows cold start and monitoring the voltage on the meter

One of the worst video I have seen -- completely washed out at the most important moment.

I can see that after engine fired up, the voltage is still down around 12v, then a sec later it's up to 14v. It seems yours is a later car with serial data control on the alternator -- what month/year is your car?

The serial data alternator is disabled by DME command during cranking to reduce loading, and it's enabled after engine idling.

[Shonky]

Videos not that bad. Which bit is missing? Can see the short low voltage period after starting.

I wouldn't worry too much. After a few seconds it's charging properly.

[elrichmeister]

One of the worst video I have seen -- completely washed out at the most important moment.

I can see that after engine fired up, the voltage is still down around 12v, then a sec later it's up to 14v. It seems yours is a later car with serial data control on the alternator -- what month/year is your car?

The serial data alternator is disabled by DME command during cranking to reduce loading, and it's enabled after engine idling.

Sorry about the video quality lens was probably smudged and initial upload of video to google photos is usually bad, it should however let you change the resolution after a while i think it takes a while to upload the full resolution. Setting it to 4k does improve the clarity.

Production date is:

2003-09-04

[elrichmeister]

Videos not that bad. Which bit is missing? Can see the short low voltage period after starting.

I wouldn't worry too much. After a few seconds it's charging properly.

Thats what im kind of thinking, but just wanted to be sure.

[sapote]

Production date is:

2003-09-04

For M3 before 2004/03 the batt light is driven by DME directly; from 2004/03 it is controlled by DME via CANbus. However all of them using single serial bus BSD and DME disable alternator during cranking and only enable when engine running. Use inpa to see if you can read error code for alternator as DME knows its status. Does this delay of batt light only happen recently?






From BMW doc:

The following functions have been implemented in the engine control unit for the alternator with BSD interface:

-Activating/deactivating the alternator on the basis of appliable parameters

-Specification of the maximum permitted degree of utilisation of the alternator

-Control of the alternator's load response

-Calculation of the alternator moment degree of utilisation

-Diagnosis of the data line between the alternator and the engine control

-Filing of alternator faults in the defect code memory

Activating the load control lamp in instrument cluster via CAN

In comparison to alternators used so far, the display strategy of the load control lamp does not change when the alternator with BSD interface.

The basic function of the alternator is also ensured if the communication between the alternator and the engine control is interrupted.

[elrichmeister]

For M3 before 2004/03 the batt light is driven by DME directly; from 2004/03 it is controlled by DME via CANbus. However all of them using single serial bus BSD and DME disable alternator during cranking and only enable when engine running. Use inpa to see if you can read error code for alternator as DME knows its status. Does this delay of batt light only happen recently?

Yes recently after replacing reman bosch alternator for new Valeo. I never noticed it with the previous alternator, reason for replacement is it completely stopped charging the battery. Ill check codes with INPA tomorrow. Am i just reading codes from DME for alternator codes?

[sapote]

Read DME code, as inpa can’t reach alternator.

[sapote]

If no alternator related code, then I assume Valeo has more delay in enabling than Bosch.

[elrichmeister]

Ran INPA and BMW Scanner 1.4 i have no codes for the alternator in the DME. So it seems like this is a non issue.

Thanks

[sapote]

Ran INPA and BMW Scanner 1.4 i have no codes for the alternator in the DME. So it seems like this is a non issue.

Thanks

To verify that the red BATT is driven directly from DME or CANbus, you can use NCS-Dummy to read the dash cluster KMB trace file FSW_PSW.TRC, then look for GENERATOR_UEBER_CAN keyword to see if it's enabled or disabled. Yours should be enabled I think.

[elrichmeister]

To verify that the red BATT is driven directly from DME or CANbus, you can use NCS-Dummy to read the dash cluster KMB trace file FSW_PSW.TRC, then look for GENERATOR_UEBER_CAN keyword to see if it's enabled or disabled. Yours should be enabled I think.

So it seems like red BATT light is driven from DME as this feature is not enabled. Am i reading that correctly?
I do notice a longer slower crank time if the car sits for 2+ days.

I have voltage readout on my USB charger so i can monitor the voltage when acc is on. Ill monitor the voltage closer, but when i crank the engine voltage does drop quite a bit as seen on the video posted.


I did chase a parasitic drain a few months ago it should be resolved. I had replaced the battery during trouble shooting.

[sapote]

I wrote “For M3 before 2004/03 the batt light is driven by DME directly; from 2004/03 it is controlled by DME via CANbus.”

Yours is pre 2004 so no CANbus for cluster battery light control, but I mistakenly said the opposite in my previous post. Your KMB data confirms this.

yes, read the voltage before cranking.