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      01-07-2025, 11:50 AM   #1
neilum
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Battery Not Charging

Hey All, looking for some troubleshooting help from people who know more than me about this issue!

I think my car is having an issue with its battery. Two weeks ago I came out to a completely dead car and it had to be jumped to start. Fine, battery was dead no problem. Car went to Indy for a new OEM battery that was coded properly.

I do take mostly shortish trips <15 minutes daily so I am keeping it on a battery tender to keep battery happy. However, the tender never goes fully green. I can leave it on there for 48 hours and its still not showing as fully charged. I have a CTEK 7002 and another tender that both work fine on my other car so its not the tender.

Tender shows red whether hooked up to terminals under the hood or direct to the battery.

Has anyone seen this issue before?

I would rule out the alternator because it should be irrelevant considering it looks like a charging issue when the car is off and parked perhaps a draw on the battery? How would I chase this down?

I do also get a consistent yellow bulb warning everyday, even the day I got the new battery last week. There are no lightbulbs out in the headlight assembly

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      01-07-2025, 03:48 PM   #2
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A bad voltage regulator in the alternator can kill a battery. You should always get battery and alternator checked.
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      01-07-2025, 04:09 PM   #3
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Yeah how about actually getting some empirical values posted?

Like spammy alluded to, what is the voltage with the car running? What is the OCV with the car asleep at the terminal?

Get a good multi meter and record results.
Also get a good scanner and scan for codes on the FRM.
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      01-07-2025, 04:56 PM   #4
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When my battery was needing replacing I went to Advance and had the battery and alternator tested. Pretty straightforward, and the measure values can help in chasing down the issue.

Last edited by a5m; 01-07-2025 at 04:57 PM..
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      01-07-2025, 05:12 PM   #5
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Quote:
Originally Posted by RocketyMan View Post
Yeah how about actually getting some empirical values posted?

Like spammy alluded to, what is the voltage with the car running? What is the OCV with the car asleep at the terminal?

Get a good multi meter and record results.
Also get a good scanner and scan for codes on the FRM.
Thanks for the troubleshooting tips, this is what I was looking for! I will circle back
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      01-07-2025, 09:58 PM   #6
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Quote:
Originally Posted by neilum View Post
Thanks for the troubleshooting tips, this is what I was looking for! I will circle back
Great. Let us know the results and findings.
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      01-08-2025, 09:54 AM   #7
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Quote:
Originally Posted by a5m View Post
When my battery was needing replacing I went to Advance and had the battery and alternator tested. Pretty straightforward, and the measure values can help in chasing down the issue.
To follow up on this. I did just get a new battery.

My concern is the new battery is not charging fully.

I am not understanding how it this is at all related to the alternator though. It's a new battery and the issue I am having is that the car is not charging fully when the car is completely turned off. I've never seen a tender remain on a very new battery for days at a time and not show fully charged.
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      01-08-2025, 10:53 AM   #8
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Quote:
Originally Posted by neilum View Post
To follow up on this. I did just get a new battery.

My concern is the new battery is not charging fully.

I am not understanding how it this is at all related to the alternator though. It's a new battery and the issue I am having is that the car is not charging fully when the car is completely turned off. I've never seen a tender remain on a very new battery for days at a time and not show fully charged.
The E9X DME signals to the Alternator how much charge is needed based upon the previous battery coding or new coding done at the time of battery replacement. Because different battery types and specs exist for replacement market E9X M3 batteries, the DME needs to 'know' the new specs of the new battery installed in the car. Otherwise the alternator will either produce too much charge or too little charge. Example: Suppose the new battery is a 90ah AGM spec but the DME code value from a previous battery is 80ah then the battery will never be fully charged because the DME only knows the specs of the previous battery. Another solution is to install a new battery with exactly the same specs as the previous battery thereby making the need for new battery coding unnecessary. To code the new specs of the new battery you have various options: 1) Dealer 2) ISTA 3) Other 3rd party hand held scanner or code reader with this type of capability. The forum has almost as many threads about battery replacement and coding as it does oil viscosity and type. Good luck.
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      01-08-2025, 11:07 AM   #9
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Coding =/= registering. Two different functions people often lump together as coding. I had an aftermarket interstate battery coded in with bimmercode by a previous owner, but not registered in bimmerlink. When I read the battery state in INPA there were no new entries in at all for registration date/mileage. Even seasoned bmw master techs missed that detail.
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      01-08-2025, 11:53 AM   #10
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Quote:
Originally Posted by spammysammich View Post
Coding =/= registering. Two different functions people often lump together as coding. I had an aftermarket interstate battery coded in with bimmercode by a previous owner, but not registered in bimmerlink. When I read the battery state in INPA there were no new entries in at all for registration date/mileage. Even seasoned bmw master techs missed that detail.
thank you, I just checked with my multimeter and its reading 11.9-12. Checked 3 times.

Calling shop that installed new battery now.
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      01-08-2025, 01:30 PM   #11
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Maybe try taking the battery out and putting it on the tender to see if it charges then? Can rule out alternator that way. Did you get it tested btw?
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      01-08-2025, 01:44 PM   #12
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Quote:
Originally Posted by a5m View Post
Maybe try taking the battery out and putting it on the tender to see if it charges then? Can rule out alternator that way. Did you get it tested btw?
I did just check the battery when the car was running and it was a steady 14.7v.

That sounds normal right? At least from my research it is.
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      01-08-2025, 02:00 PM   #13
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Quote:
Originally Posted by neilum View Post
I did just check the battery when the car was running and it was a steady 14.7v.

That sounds normal right? At least from my research it is.
Sounds right, but when I had mine tested I held the RPMs at 3k steady while it ran the loaded test I think. Here are the pics I took. Might get additional info from a battery/alternator tester vs multimeter.
Attached Images
  
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      01-09-2025, 04:57 PM   #14
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Quote:
Originally Posted by neilum View Post
I did just check the battery when the car was running and it was a steady 14.7v.

That sounds normal right? At least from my research it is.
No, 14.7v is not right. That's too high with AGM batteries as this would cause excess gassing. This would most likely be indicative for a battery that's not coded correctly or voltage regulation issues.

The target voltage is sustained 14.2v charging and with all loads on--such as max AC fan, lights on, brights on, music on loud, and all windows rolling up at the same time.

The ripple describes what the diodes are doing in terms of their switching current leakage. This value will be more exacerbated with the above mentioned loads on. The target is under 500 mV as this is the maximum ripple before modules will start complaining. On this particular platform, the alternator has transistor diodes and uses the LIN bus from the DME to compensate for voltage drop.


https://batteryuniversity.com/articl...ging-lead-acid
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      01-10-2025, 05:48 AM   #15
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Quote:
Originally Posted by neilum View Post
I did just check the battery when the car was running and it was a steady 14.7v.

That sounds normal right? At least from my research it is.
Quote:
Originally Posted by RocketyMan View Post
No, 14.7v is not right. That's too high with AGM batteries as this would cause excess gassing. This would most likely be indicative for a battery that's not coded correctly or voltage regulation issues.

The target voltage is sustained 14.2v charging and with all loads on--such as max AC fan, lights on, brights on, music on loud, and all windows rolling up at the same time.

The ripple describes what the diodes are doing in terms of their switching current leakage. This value will be more exacerbated with the above mentioned loads on. The target is under 500 mV as this is the maximum ripple before modules will start complaining. On this particular platform, the alternator has transistor diodes and uses the LIN bus from the DME to compensate for voltage drop.


https://batteryuniversity.com/articl...ging-lead-acid
Up to 14.7v is okay (for a AGM while a lead acid will start gas at 14.4v) when the alternator have decided its time to boost some charge. I see this on my car now and then.

Btw as discussed in another thread, the voltage can drop towards 12v making (me at the time) believe the alternator is broken. However turns out our system is "smart" and charging to 70-80% only to save space for downhill etc charging. The lowering of alternator output should only happen when the battery is "full" i.e. 80%. If charge voltage is low and the battery still isn't charged, there is a problem.
For my use case the system isn't optimal but is what it is. For interest attached a note explaining the charge system.

Edit: Saw OP replaced the battery which I guess will fix the issue as it apparently didn't accept charge even with a CTEK.

Last edited by Helmsman; 01-10-2025 at 05:58 AM..
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      01-10-2025, 12:19 PM   #16
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That's some great reference info. From that explanation, it looks to be operational range is above 11.8v and below 14.8v. Interesting!
Although, a battery at 11.8v I suspect would def have struggles restarting the vehicle and supporting all the modules.

This upper end seems to coincide with Enersys as excess voltage would cause the valve to open and off-gas. For their batteries the range to charge ideally is 14.2v to 14.5v. [page 10]

https://www.odysseybattery.com/wp-co...nce-manual.pdf
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      01-10-2025, 03:17 PM   #17
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Quote:
Originally Posted by RocketyMan View Post
That's some great reference info. From that explanation, it looks to be operational range is above 11.8v and below 14.8v. Interesting!
Although, a battery at 11.8v I suspect would def have struggles restarting the vehicle and supporting all the modules.

This upper end seems to coincide with Enersys as excess voltage would cause the valve to open and off-gas. For their batteries the range to charge ideally is 14.2v to 14.5v. [page 10]

https://www.odysseybattery.com/wp-co...nce-manual.pdf
That paper is interesting isn't it, after 11 years with the car (+electro eng) I finally started to understand how the battery in these bloody cars is charged...
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      01-11-2025, 07:42 AM   #18
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Originally Posted by Helmsman View Post
That paper is interesting isn't it, after 11 years with the car (+electro eng) I finally started to understand how the battery in these bloody cars is charged...
I got a green light, the car is fully charged! I also learned a lot while figuring this out as I've owned a lot of cars over the years and this one by far has the most complex battery and electrical dynamics. I would charge the car a bit and it would show 12.9V, unplug the tender (without opening the doors or waking the car up) and an hour later it would show 12.5V. I would run the car, get a normal 14.7V, turn the car off, test it around 12.7V, then before it went to sleep it was down to 12.0V. I don't know....

It's a super finicky car for sure with the battery. I also only started to dig into it because my battery died sending me down this rabbit hole. I've owned a few E9X cars over the years and never had to troubleshoot the battery, so hopefully this blows over and I don't have to think about it again.




Also, for future reference this tender does not charge our cars, at least mine even after 48 hrs on the battery. I don't think its strong enough -https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1


The CTEK 7002 had it charged within 12 hrs however.
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      01-11-2025, 01:06 PM   #19
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Quote:
Originally Posted by neilum View Post
I got a green light, the car is fully charged! I also learned a lot while figuring this out as I've owned a lot of cars over the years and this one by far has the most complex battery and electrical dynamics. I would charge the car a bit and it would show 12.9V, unplug the tender (without opening the doors or waking the car up) and an hour later it would show 12.5V. I would run the car, get a normal 14.7V, turn the car off, test it around 12.7V, then before it went to sleep it was down to 12.0V. I don't know....

It's a super finicky car for sure with the battery. I also only started to dig into it because my battery died sending me down this rabbit hole. I've owned a few E9X cars over the years and never had to troubleshoot the battery, so hopefully this blows over and I don't have to think about it again.


Also, for future reference this tender does not charge our cars, at least mine even after 48 hrs on the battery. I don't think its strong enough -https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1


The CTEK 7002 had it charged within 12 hrs however.
Okay. That's good information!

That tender should be perfectly fine. 750mA is enough to overcome any tiny parasitic draw. The goal is under 50 to 85mA. And the 750mA would def overcome that.

I can usually test the battery voltage by simply leaving the hood open and measuring at the jump-start terminals. It's good you understand when modules go to sleep and such and how that has an effect on the OCV of the battery. So I would be curious if you measure the OCV after an extended time of the car sitting. Once when the car goes to sleep (your 12.5V) and then a day or two later. If the voltage is dropping much lower than 12.5V, then I think you might have some sort of parasitic draw happeneing.

I do recall somewhere on the forum a module has been known to not fall asleep causing the battery draw. Let's see if I can try searching for this.
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      01-11-2025, 01:38 PM   #20
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OP, here is a good idea of a video for a faulty module that is something similar to our cars. You see that the module was drawing 140 mA.

This is kinda neat.

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      01-11-2025, 05:03 PM   #21
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Quote:
Originally Posted by RocketyMan View Post
OP, here is a good idea of a video for a faulty module that is something similar to our cars. You see that the module was drawing 140 mA.

This is kinda neat.
Here's another piece that you might find interesting to add mate:
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File Type: pdf 03_Power Management.pdf (1.07 MB, 10 views)
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      01-11-2025, 05:13 PM   #22
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Quote:
Originally Posted by RocketyMan View Post
Okay. That's good information!

That tender should be perfectly fine. 750mA is enough to overcome any tiny parasitic draw. The goal is under 50 to 85mA. And the 750mA would def overcome that.
Well I am telling you that the tender linked above did not charge the battery after 2- 3 days on there. Draw your own conclusions I guess but thank you everyone for helping as mentioned I learned a lot!
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