I had not researched this one to death, but I recall running across the problem and read about the alternator bracket. This is like the BMW I6 Oil Filter Housing Gaskets that leak all the time, same thing. But it sounds like the good news is with the oil cooler, I do not have the larger alternator bracket. I will check into this a bit more for future reference.

Yup. I have an E46 too, an 06 ZHP. Have done the VC, OFHG and CCV on that as well.

The problem/issue with any of the OBDII tools is they derive the Voltage from the OBDII port. This can be OK in some cases, but in others can be a bit misleading and you may have to come up with a "correction" factor.

I have not fully researched the E70 charging system, but it is very different then earlier models, this is why the battery registration is important. As I recall the alternator may not actually have a Voltage regulator and the DME controls the charging. There are some electrical interfaces back near the battery as I recall, I will see if I can find the info I have on the E70 charging system.

I just checked it again before I started tearing everything apart and it back to 14.24V car running, 12.7V car off!

I'd rather it just be dead than an intermittent problem!

I'm taking these measurements across the battery terminals with my Fluke meter. They are also exactly what the BlueDriver reported for "module voltage".

This may be of use - http://www.bmwmotorsports.org/pdf/e7...0and%20Bus.pdf

Not what I was looking for, but very close.

You also need to be aware that many of the newer vehicles do not always run the alternator as well. My 2005 GMC truck actually will turn the alternator off quite often and run just on the battery. This is the way the vehicle is designed and has often caused a lot of confusion for people trying to troubleshoot charging issues.

This is where the Logging features in tools like BlueDriver, Touch Scan and OBDFusion are very helpful. You can actually Log what is going on and see if there is a pattern and what is actually going on.

Yeah that's taken out of TIS. I have that and I'll look for info on the charging system. The thing you're talking about where the alternator cycles on/off BMW calls Brake Energy Regeneration where the alternator only kicks on during braking, coasting or deceleration. I'm like 99% certain my E70 doesn't have it but I'll double check. The newer models that have it actually have a light on the dash that tells when it's active.

I do not know if BMW shuts off the alternator, they may. My GMC truck does this for fuel economy and reduced load on the engine. There is actually a current loop on the accessory side of the battery cable that monitors current draw and will actually shut the alternator off.

At times you can see the Charging/Battery Voltage drop to like 12.4 Volts, which is NORMAL the way the system is set up on my GMC.

GM had to send out all sorts of Technical Service Bulletins because dealer technicians were replacing alternators left and right for no reason because they did not pay attention to the training info when these models came out.

I also know some performance cars also have full throttle alternator cut outs as well to reduce the load on the engine and try to get more power to the road.

You have to be careful on some of these newer cars and trucks before you write off and alternator and even then many shops have a hard time testing the alternators if they do not have internal Voltage regulators.

When I plugged it in to my charger the 100% light was flashing, the next lower light is 75% so all this tells me is it was between 76-99%. When my charger said it was 100% I took it to Autozone and their tester also said 100% so I'm now confident my charger does work properly and can charge it completely, making some progress.

While it was charging I've been doing some thinking and have a theory:

This is just a THEORY, PLEASE DON'T HESITATE TO SHOOT HOLES IN IT!

Couple things I'm certain of:

1. I know there was something wrong with the battery
2. Our cars have an Intelligent Battery Sensor on the battery (IBS)
3. The output of the alternator is controlled by some module and not a simple voltage regulator.
4. When installing a new battery you need to reset the charge adaptation in INPA.

When I read 12.x volts with the car running my old school brain tells me the alternator is not working, but what if instead of not working or deactivated as the new cars do, it's actually working just not trying to charge the battery.

It would work something like this:

When the system is charging the battery it knows the alternator output voltage and via the IBS it knows how much current is going through the battery to charge it. As the battery voltage rises the current will decrease and eventually plateau when that battery reaches it's maximum charge. As the battery ages the max output voltage decreases. Let's say for a specific battery it now at 12.5V. The car will remember that and when it gets back to 12.5V it will reduce the output of the alternator to 12.5V. At that point it will no longer be trying to charge the battery (better for battery) and it will be the minimum load needed on the alternator to operate the electrical system (better mpg).

There would also be an amount of hysteresis to prevent the alternator from constantly turning on/off. Lets say it's .1V, that would mean on my example above that the voltage would be allowed to drop down to 12.4V before the system would kick back in to charge mode and the alternator would put out 14.x volts until the battery was brought back to it's max of 12.5V where the system would kick back in to "cruise" mode and only output 12.5V.

This would explain why I'm getting reading that seem lower than expected and also why it's necessary to reset the stored battery info when installing a new battery.

And I haven't yet reset the battery in INPA. When I put the new battery in and read 14.x volts I assumed the problem was solved and haven't driven or had time to work on it again until now so that's the project for today along with adding the trailer hitch I installed a while back to the vehicle order.

My understanding is if you install pretty much the same AH battery you do not need to register/program for it. I would just for kicks check fuses. I think my 2008 4.8l charges all the time, but be careful and let the car run or drive it to make sure there is no charging going on. Some of the BMWs take up to 30-60 to start charging.

And through all of this there has never been an indication that there is a Charging/Battery/Alternator problem from the car?? Something is wrong here and I do not think it is actually the alternator, but I would have to study up on the power distribution system.