Low voltage after new battery

[dnbtse]

Hi thanks both!, i've been monitoring more over the weekend, its actually more 12.8-13.1v range and its not only motoway. It seems its everytime i accelerate, once i let go the throttle or brake the voltages will go back up to 13.8v+ but sometimes it doesnt return back and stay on the lower voltage. will contuine to monitor it, just seems a bit off.

Battery discharge warning hasnt actually returned, so hopefully it was an 1 off. On the brightside everything seems to be working as it should for now.

As you can see, the voltage drops to a concerning level. while the car is accelerating or cruise control on, this is why i am worried.

[Helmsman]

Originally Posted by dnbtse

Hi thanks both!, i've been monitoring more over the weekend, its actually more 12.8-13.1v range and its not only motoway. It seems its everytime i accelerate, once i let go the throttle or brake the voltages will go back up to 13.8v+ but sometimes it doesnt return back and stay on the lower voltage. will contuine to monitor it, just seems a bit off.

Battery discharge warning hasnt actually returned, so hopefully it was an 1 off. On the brightside everything seems to be working as it should for now.

As you can see, the voltage drops to a concerning level. while the car is accelerating or cruise control on, this is why i am worried.

Probably all good. Again the battery is charged (assuming below 80% isch, or else not) when the system judge the occasion right, coasting, down etc. Check the posted documents, its all there.
If you measure after fully charged with external charger, you'll see the voltage go down on low 12v as again the system is designed to keep it between 70-80% charged.

[Redd]

Yeah if you read the first post in this thread, I observed the same weird voltage behavior immediately after registering a new batt. It went away after a few months. I have my own conspiracy theories about why the car behaves like this - the new batt registration routine is nothing more than an emissions/mileage cheat code.

[dnbtse]

Originally Posted by Helmsman

Probably all good. Again the battery is charged (assuming below 80% isch, or else not) when the system judge the occasion right, coasting, down etc. Check the posted documents, its all there.
If you measure after fully charged with external charger, you'll see the voltage go down on low 12v as again the system is designed to keep it between 70-80% charged.

thanks, will just monitor it for a few weeks/months. Saying all this the battery level on the BimmerLink App is never dropped down to below 85% always has been around the 90-95% mark so it is charging and not letting it go down. I wonder what it will be like on a long distance drive though, normally only 60-90 mintues drive.

[dnbtse]

Originally Posted by Redd

Yeah if you read the first post in this thread, I observed the same weird voltage behavior immediately after registering a new batt. It went away after a few months. I have my own conspiracy theories about why the car behaves like this - the new batt registration routine is nothing more than an emissions/mileage cheat code.

So strange, there hasnt been many reports with similar behaviour. Maybe im just over thinking about monitoring it for no reason and stressing myself out lol only reason why i started monitoring because i had an faulty alternator which is now replaced.

Thanks

[Helmsman]

Originally Posted by dnbtse

thanks, will just monitor it for a few weeks/months. Saying all this the battery level on the BimmerLink App is never dropped down to below 85% always has been around the 90-95% mark so it is charging and not letting it go down. I wonder what it will be like on a long distance drive though, normally only 60-90 mintues drive.

Go it. And you have registered the battery with correct number of Ah (so the system is not "fooled" by a different capacity)?

[dnbtse]

Originally Posted by Helmsman

Go it. And you have registered the battery with correct number of Ah (so the system is not "fooled" by a different capacity)?

Orignal battery was 90Ah, replaced with 95Ah. No option to code to 95Ah so only registered as that was what it said to do.

[Helmsman]

Originally Posted by dnbtse

Orignal battery was 90Ah, replaced with 95Ah. No option to code to 95Ah so only registered as that was what it said to do.

Got it, should be close enough imo.

[dnbtse]

Originally Posted by Helmsman

Got it, should be close enough imo.

Thanks bud, i am waiting for the days i will forget about it and not have Bimmerlink App open everytime i drive.

[Helmsman]

Originally Posted by dnbtse

Thanks bud, i am waiting for the days i will forget about it and not have Bimmerlink App open everytime i drive.

Hahaha, know the feeling mate! Been having both Protool and Carly hanging there constantly during period of times! (better not forget the OBD dongle, consuming power...:-). Btw with Carly its possible to measure outgoing alternator current which has been quite useful for me during my battery "issues". Would have loved Protool to read all live data but seems one need a couple of scanners to survive.

[dnbtse]

Originally Posted by Helmsman

Hahaha, know the feeling mate! Been having both Protool and Carly hanging there constantly during period of times! (better not forget the OBD dongle, consuming power...:-). Btw with Carly its possible to measure outgoing alternator current which has been quite useful for me during my battery "issues". Would have loved Protool to read all live data but seems one need a couple of scanners to survive.

Haha, yup! i unplug the ODB after every journey annoying but i want to make sure cars ok and dont break down on me. I used to have Carly but scrap them after they started a annual payment! know use Bimmerlink and Code 1 of payment and thats. I think the "battery current measured by IBS" is alternator current but dont actually understand it. reading it, i think when the numbers become negative that is when it is charging battery. There are a few other live datas i have pick but have no clue what they are. For now im just going monitor as i have done so and hope for the best lol.

[Impastokitsch]

had similar incident: Lufi reading constant 14.1v until recent audio work which i believe the door being opened and probably drain some battery but its only a 1hour job lol

now the lufi read
12.4 - 12.8 when u give input to gas
brake doesn't immediately increase but coasting increases to 14.1-14.3

and similarly to Author, whenever i signaled/ open close window, open door (after drive), it increases to 14.1-14.3v

was told this is normal how BER works for E9X M3 but whats puzzling me was why it was constant 14.1v previously

intending to use ctek to charge my 5months old battery later

[Edwardsc1]

Hey guys, wanted to get your input on this before going back to the shop.

I got a new battery in January. Got it at the dealership, had them code it and everything. My car died on the way to work 2 weeks ago, and my local shop & the dealer both agreed it was the alternator starting to fail. I replaced the alternator myself, and now the voltage readings are all over the place.

I let the car sit on a CTEK trickle charger for two days straight and the battery is reading ~12.2-12.3V when the car is off according to the hidden cluster menu. All good there. When I start the car, it goes up to ~13.8-13.9V, and rarely I might see 14-14.3V for a very short time.

But, if I stop for a short time (ie get gas) turn the car off, and then turn it back on, it'll read 11.8-11.9V. And it won't ever go above that. At least not within a 20-30 minute drive. One time it even dropped to around 11.3V by the time I got to my destination. But then the car will sit overnight, I'll go to work the next morning, and all will be good - it'll read around 13.8V while driving.

I know the voltage should never drop below the 13-14V range when driving, so there has to be some issue somewhere that causes the erratic voltage. I'll be checking my ground strap here in the next couple days when I get some time to get it up on the lift, but wanted to get someone's opinion on this, or see if anyone has had this issue before?

[Redd]

Now, assuming your ground strap is ok and your new alt is original BMW (I've seen weird behavior with new OEM alts) the weird voltage reading you're seeing might be normal. As long as your car starts and doesn't throw any errors, it could be normal behavior after a new batt registration. Monitor it for a few weeks - around 1000 kms - and see if it sorts itself out.

[Edwardsc1]

Originally Posted by Redd

Now, assuming your ground strap is ok and your new alt is original BMW (I've seen weird behavior with new OEM alts) the weird voltage reading you're seeing might be normal. As long as your car starts and doesn't throw any errors, it could be normal behavior after a new batt registration. Monitor it for a few weeks - around 1000 kms - and see if it sorts itself out.

Appreciate the reply. I should be able to check my ground strap this weekend.

I've been able to replicate the problem every time now. The voltage only drops below 13.5V when I turn the car off for a short period and then turn it back on (getting gas, going to the store). It will then sit around 12V and slowly drop down during the duration of my drive. Usually down around 11.4-11.5V after a 30 minute drive. If the car sits for a few hours, or overnight, then it's perfectly fine. Running between 13.5 - 14.3V.

I did get a Bosch/ Valeo unit from FCP Euro, it was not directly from BMW or a BMW branded alternator.

Edit: I did not re-register my battery after replacing the alternator. Just replaced the alternator and plugged the battery back up.

[Jachu Z4]

Reviving an old thread...
You probably saved my night tonight, and I'll sleep soundly.
I had a new, low-capacity lead-acid battery (61Ah), but it was incorrectly coded, and the alternator wouldn't charge it. When I checked it this morning, it showed 11.8V. That's very low for a three-day-old battery. I checked the charge with a multimeter, and it showed 15.4V. As it turns out, the coded battery was a 70Ah AGM. Today I bought a 70Ah AGM, registered it as new, and INPA showed a charge of 11.8V. I was scared and angry. But I found this thread. There's an attachment in post #35 that explains everything.
1. When the battery is charged (mine was 13.4V when I installed it), the alternator doesn't charge (11.8V).
2. When the car accelerates hard, the alternator doesn't charge (unless it has to if the battery is weak).
3. When the car is idling, the alternator doesn't charge (unless it has to if the battery is weak).
4. The alternator charges at full power, just like a vehicle:
- when moving when you take your foot off the gas pedal above 10 km/h,
- when the vehicle brakes.

It charges at full power only when it doesn't need to use fuel. This is to avoid overloading the engine and avoid generating more exhaust gas.

The attachment provided by Helmsman provides a detailed description, explanation, and even a diagram of how the intelligent charging system works. It also explains why an AGM battery is so important in cars with regenerative braking.

Thank you for this thread, for your described cases, and for this attachment. Otherwise, I'd probably be replacing the alternator tomorrow.

Best regards, Jachu.

[Helmsman]

Originally Posted by Jachu Z4

Reviving an old thread...
You probably saved my night tonight, and I'll sleep soundly.
I had a new, low-capacity lead-acid battery (61Ah), but it was incorrectly coded, and the alternator wouldn't charge it. When I checked it this morning, it showed 11.8V. That's very low for a three-day-old battery. I checked the charge with a multimeter, and it showed 15.4V. As it turns out, the coded battery was a 70Ah AGM. Today I bought a 70Ah AGM, registered it as new, and INPA showed a charge of 11.8V. I was scared and angry. But I found this thread. There's an attachment in post #35 that explains everything.
1. When the battery is charged (mine was 13.4V when I installed it), the alternator doesn't charge (11.8V).
2. When the car accelerates hard, the alternator doesn't charge (unless it has to if the battery is weak).
3. When the car is idling, the alternator doesn't charge (unless it has to if the battery is weak).
4. The alternator charges at full power, just like a vehicle:
- when moving when you take your foot off the gas pedal above 10 km/h,
- when the vehicle brakes.

It charges at full power only when it doesn't need to use fuel. This is to avoid overloading the engine and avoid generating more exhaust gas.

The attachment provided by Helmsman provides a detailed description, explanation, and even a diagram of how the intelligent charging system works. It also explains why an AGM battery is so important in cars with regenerative braking.

Thank you for this thread, for your described cases, and for this attachment. Otherwise, I'd probably be replacing the alternator tomorrow.

Best regards, Jachu.

Hope it gets sorted mate. Here's a bonus input; seems the charge scheme "to keep energi consumption down" only works for a while (some suspect to match test cycle). Alternator goes back to "normal" i.e. full speed after a few k miles. Reset and it comes down again...to come back up.
Anyways, suits me better to get the battery max charged.

[Jachu Z4]

Today I tested the charging while stationary by turning on the blower, two heated seats, and the heated steering wheel. The charging current is 14.5V.
While driving, when accelerating, I get 12.8V. When I accelerate and take my foot off the gas, the charging current is exactly 14.8V.
Today I'm going to bed completely peacefully.
Helmsman, thanks to your information in the attachment to post #35, I now clearly understand how the BMW intelligent charging system works.

[Helmsman]

Originally Posted by Jachu Z4

Today I tested the charging while stationary by turning on the blower, two heated seats, and the heated steering wheel. The charging current is 14.5V.
While driving, when accelerating, I get 12.8V. When I accelerate and take my foot off the gas, the charging current is exactly 14.8V.
Today I'm going to bed completely peacefully.
Helmsman, thanks to your information in the attachment to post #35, I now clearly understand how the BMW intelligent charging system works.

Sound great. And again, don't be surprised when the charge cycle according to the BMW doc not is followed a short while after reset...