Hello Community,
Here it goes.
Basics:
E61, 2005, M57 engine (525 Diesel), 177hp, currently remmaped to 230hp. Around 200k miles, with service history (although nothing is mentioned about electrical/alternator replacements). Overall, working like a Swiss watch.
Problem statement:
Battery draining over time (2 months was the test period) however no codes being displayed or stored.
I have bimmer tool, inpa, ista, Carly, bimmer code and link. Hardware is bm+ obd reader and kdcan cable.
After doing some research here, I think my ibs is crazy.
Since the ibs is responsible for determining the output voltage of the alternator depending on the status of the battery and conditions (atmosphere, temperature, etc) I am pointing out this to be the main reason, nevertheless, let's expand.
After taking the time to do different tests and measures I managed to establish the following pattern.
As the battery SoC goes lower, the alternator output lowers as well.
Whenever battery is around 50% state of charge, the voltage output drops to 14.2/14.4.
Whenever battery is 80% or more, the voltage goes to 14.8.
To me it doesn't make sense, I would expect the opposite, if less charge then more output (high voltage) to charge it quicker.
Despite having a battery drain somewhere (which I believe I do - did not yet tested what's the consumption after sleep), driving it around should be enough to charge it and this is where I am stuck at the moment.
I can drive 200miles in a row, without extra power consumption and the battery will not charge (but it also does not lower) - I did it and kept the charging readings from the battery terminal.
So, if alternator is doing its work with stable charging outputs (range from 14.2 to 14.8) but the battery is not being charged, although I have normal readings at battery terminals but battery is not charging properly (90AH, dated December 23 and registered). It seems to me that battery is randomly charged, like some days it charges, some days it doesn't. What's wrong?

Points checked/replaced:
- trunk wiring - replaced all broken cables;
- ground cable in the trunk - no rust;

Thank you in advance.

Claudio

 

Not sure what problem you're trying to solve here... BMW charging systems won't automatically try to bring the charge up to 100%. If the battery is being supplied with 14.X volts, it's charging...

 

Hi,
Thank you.
Eventually I ended up losing my focus while I was writing.
The amount of energy produced (although sometimes it reaches 14.x) is not stable enough to charge the battery.
On the print from Ista it's clear that the car is losing battery everyday, although I drive it daily.
The difference from day 2 to day 1 (around 4% of charge) represents more than 300 KM's driven in a row without additional power consumption - aside from the engine itself.
So in one hand, I have a low charge rate/speed. On the other I have a big loss of energy while sleeping.
Can the reason of not charging properly while driving be the same/related to the reason why I am losing energy faster?
Thank you

 

See Is My Battery Bad? - 5Series.net - Forums.