Low voltage after new battery

[Helmsman]

Originally Posted by Redd

How do I check? Cos right now I have zero errors or symptoms.

Have Carly? If so you have a check point of actual alternator current output which would be nice to confirm as a start. Should hover around 30-40 amps during normal conditions.

[Scharbag]

Originally Posted by pbonsalb

It goes from the oil pan to frame rail under the header collector on the driver’s side. They can rot out. Give it a tug.

This made me laugh.

I am such a child.

[Redd]

Originally Posted by Helmsman

Have Carly? If so you have a check point of actual alternator current output which would be nice to confirm as a start. Should hover around 30-40 amps during normal conditions.

I just ordered ISTA+. Will check this first thing the cable gets here. Thanks!

[Redd]

Update - After slightly over 1 month and 1000km, voltages are back up to 13.5-14V regularly. CTEK shows the battery is charging up to 100%.

I didn't do anything or change anything. Seems like the problem just fixed itself, or it's normal after a new battery registration.

[dpaul]

Originally Posted by Redd

Update - After slightly over 1 month and 1000km, voltages are back up to 13.5-14V regularly. CTEK shows the battery is charging up to 100%.

I didn't do anything or change anything. Seems like the problem just fixed itself, or it's normal after a new battery registration.

Registration is irrelevant. Hopefully the problem will not return.

[Helmsman]

Originally Posted by Redd

Update - After slightly over 1 month and 1000km, voltages are back up to 13.5-14V regularly. CTEK shows the battery is charging up to 100%.

I didn't do anything or change anything. Seems like the problem just fixed itself, or it's normal after a new battery registration.

Haha, always exciting to return to an old thread and find I thought I had it all figured out.

Well my turn - Replaced the battery. Once coding and register was confirmed (using Bimmergeek), I all of a sudden get increased charge voltage at 14.8V vs 14.3 isch with the worn out battery. Temperature has fallen to below 0 which apparently is being compensated by the ECU, but reading this thread an old battery apparently should be compensated with higher charge voltage puzzles me. I also went from AGM to flooded which again should lower the voltage if anything.
Yours has been fine since replacement or noticed any further odd behaviour Redd?

[Vuu]

Originally Posted by Helmsman

Haha, always exciting to return to an old thread and find I thought I had it all figured out.

Well my turn - Replaced the battery. Once coding and register was confirmed (using Bimmergeek), I all of a sudden get increased charge voltage at 14.8V vs 14.3 isch with the worn out battery. Temperature has fallen to below 0 which apparently is being compensated by the ECU, but reading this thread an old battery apparently should be compensated with higher charge voltage puzzles me. I also went from AGM to flooded which again should lower the voltage if anything.
Yours has been fine since replacement or noticed any further odd behaviour Redd?

In the same boat as both of you, except I live in SoCal.

Replaced the battery and get the discharged warning. Car has been on a tender ever since.

[Helmsman]

Originally Posted by Helmsman

Haha, always exciting to return to an old thread and find I thought I had it all figured out.

Well my turn - Replaced the battery. Once coding and register was confirmed (using Bimmergeek), I all of a sudden get increased charge voltage at 14.8V vs 14.3 isch with the worn out battery. Temperature has fallen to below 0 which apparently is being compensated by the ECU, but reading this thread an old battery apparently should be compensated with higher charge voltage puzzles me. I also went from AGM to flooded which again should lower the voltage if anything.
Yours has been fine since replacement or noticed any further odd behaviour Redd?

To conclude on this fwiw, turns out the battery mgmt system does more than I understood. This morning coming out from 20C garage the charge voltage on my new battery was 13.9V. On my way back home from office after a day in -5C, charge voltage was back up to 14.8V. So all seem good, temp compensated by the ECU more than I realized.

[Redd]

Originally Posted by Helmsman

Haha, always exciting to return to an old thread and find I thought I had it all figured out.

Well my turn - Replaced the battery. Once coding and register was confirmed (using Bimmergeek), I all of a sudden get increased charge voltage at 14.8V vs 14.3 isch with the worn out battery. Temperature has fallen to below 0 which apparently is being compensated by the ECU, but reading this thread an old battery apparently should be compensated with higher charge voltage puzzles me. I also went from AGM to flooded which again should lower the voltage if anything.
Yours has been fine since replacement or noticed any further odd behaviour Redd?

Mine has been fine aside from the initial period of low voltage. Consistent 13.8-13.9V while driving now. Like u said, I think the new battery registration does more than we realize.

[Helmsman]

Originally Posted by Redd

Mine has been fine aside from the initial period of low voltage. Consistent 13.8-13.9V while driving now. Like u said, I think the new battery registration does more than we realize.

Meeting again on good old subjects Eric....

Replaced my battery (to a 95Ah AGM from an 80Ah acid that went crap in less than 2y...).

Measuring with Carly (an area where Protool do nothing) turns out that the alternator turns down the voltage output and subsequently the current. Not below 12V as in your case but 12.1-12.3, assumingly where a new battery would be with some load without alternator support. It seems to vary the output so occassionaly well over 14V to suddently drop again.
Previous battery always run with a good 14-14.6V.

Found some BMW pwr mgmt stuff that state that the various consumers should use the alternator output as long as possible, to only when not enought start to consume from the battery. Seems the other way around in your and mine case...always something going on with these cars...

So how did it continue in your case, voltage gradually came up and all fine?

Did you test the alternator yourself or handed it in?

Thanks
Nik

Ps. Adding mentioned desciption.

[Helmsman]

Originally Posted by Helmsman

Meeting again on good old subjects Eric....

Replaced my battery (to a 95Ah AGM from an 80Ah acid that went crap in less than 2y...).

Measuring with Carly (an area where Protool do nothing) turns out that the alternator turns down the current output and subsequently the voltage. Not below 12V as in your case but 12.2-12.3, assumingly where a new battery would be with some load without alternator support. It seems to vary the output so occassionaly well over 14V to suddently drop again.
Previous battery always run with a good 14-14.6V.

Found some BMW pwr mgmt stuff that state that the various consumers should use the alternator output as long as possible, to only when not enought start to consume from the battery. Seems the other way around in your and mine case...always something going on with these cars...

So how did it continue in your case, voltage gradually came up and all fine?

Did you test the alternator yourself or handed it in?

Thanks
Nik

Ps. Adding mentioned desciption.

Thought worth an update for the next guy.

Here I am thinking I understand simple pwr mgmt systems...while as usual Redd is right.
Logging some more data (using Carly) it does seems like the battery is feeding everything till a certain point when the alternator is switched on. For instance turning on the fan (big consumer, like 30 amps) the alternator is switched on.

Never seen this with previous two battery replacement but seems to be the case. It is strange in my mind that the battery is allowed down to by Redd mentioned 70% or so before being supported by the alternator, as close to full maintain life time better. Also strange that the alternator seemingly haven't shut off after external/trickle charger been on. Learning stuff after 10y with this car!

Means that the BMW doc I posted above stating "The alternator is designed to supply current to all electrical loads and charge the battery.
If the alternator is not able to supply sufficient current to the electrical loads the additional current requirement is taken from the battery", doesn't seem to apply to our cars.

[Redd]

Thanks for reviving this old thread! I think it has helped me solve an issue I had with LiFePo4 batts.

Couple years back I tried using LiFePo4 batt. Registered it as a 72Ah AGM batt. The LiFePo4 batt worked fine for the first 200-300km, then strange things started to happen. For some reason, the alt would not charge the batt. It would let the batt run to 0% (even while I was driving the car), I'd have to jump start the car, then the alternator would charge the batt to 100%. After that full charge, it would let it run flat again. Rinse and repeat. During this time there was no increased battery discharge issues.

Alternator checked out ok. Removing and subsequently replacing the IBS battery cable did not solve the issue. In the end I went back to a normal AGM batt and everything was OK again. I never managed to get to the bottom of the issue, just chalked it up to incompatible battery (it was a China brand) and never used it again. Strangely, that same battery works fine in my Alfa 159 and other non-M3 BMWs.

This thread has reminded me again of the weird charging behaviour of our M3 alts. Maybe what was happening is that - for some reason - the DME keeps thinking the LiFePo4 batt is above 70% charge and does not activate the alt to charge the batt. Maybe cos the LiFePo4 current/voltage is high indicating strong charge or something.

With this new revelation I might try the LiFePo4 batt again but this time without registering the batt to see if it makes a difference.

[Helmsman]

Originally Posted by Redd

Thanks for reviving this old thread! I think it has helped me solve an issue I had with LiFePo4 batts.

Couple years back I tried using LiFePo4 batt. Registered it as a 72Ah AGM batt. The LiFePo4 batt worked fine for the first 200-300km, then strange things started to happen. For some reason, the alt would not charge the batt. It would let the batt run to 0% (even while I was driving the car), I'd have to jump start the car, then the alternator would charge the batt to 100%. After that full charge, it would let it run flat again. Rinse and repeat. During this time there was no increased battery discharge issues.

Alternator checked out ok. Removing and subsequently replacing the IBS battery cable did not solve the issue. In the end I went back to a normal AGM batt and everything was OK again. I never managed to get to the bottom of the issue, just chalked it up to incompatible battery (it was a China brand) and never used it again. Strangely, that same battery works fine in my Alfa 159 and other non-M3 BMWs.

This thread has reminded me again of the weird charging behaviour of our M3 alts. Maybe what was happening is that - for some reason - the DME keeps thinking the LiFePo4 batt is above 70% charge and does not activate the alt to charge the batt. Maybe cos the LiFePo4 current/voltage is high indicating strong charge or something.

With this new revelation I might try the LiFePo4 batt again but this time without registering the batt to see if it makes a difference.

I bet you're right (again) Eric. The Lithium batteries I had in my boat kept an impressive 13.2 volt basically regrdless of load and pretty much stable down to finished. Great characteristics in most applictions but maybe not in the M3. Clearly guys like Antigravity have solved this with their product.

I guess battery voltage and Ah capacity are used in some clever algorithm where the latter must be quite imprecise after some time.

Cheers

Edit: Found another piece on the alternator that says: "Higher capacity reserve as battery is never fully charged. A fully charged battery (100 % charged) cannot accept energy and is therefore avoided as part of the intelligent alternator control strategy."
Assumingly to leave space for the alternator to do its job when it's deemed most efficient. So starting to make sense; the alternator does provide all current needed and when not enough the battery takes on. BUT with the difference that the battery not is meant to be fully charged but should be kept at 70-80% capacity.
Redd, maybe one way to align the system to your Lithium is to change the voltage regulator in the alt. Takes a bit of research though...:-)