Hi! Ever since i bought my E61 530XD in april this year i've been experiencing some weird voltage issues, it started with my old battery going bad so i had it replaced but i've now noticed that my voltage fluctuates alot, but my alternator seems to be working. With the car on (Idle, driving) the voltage usually fluctuates between 13.4-14,8v but ive noticed it go even lower or higher, ive seen it drop beneath 12v when running, and today i saw 15.4v when driving, but as soon as i turn the car off the voltage goes down to 11.5-11.8v almost instantly. Usually i'd suspect a faulty battery but as i've just bought the battery i'm thinking it has to be something else. I have also noticed that the positive terminal on the battery gets very hot, cant touch it longer than a second or i'll burn myself. So my theory is faulty alternator regulator or bad contact somewhere, either ground or on the positive terminal as that is where it gets hot. Car always feels like it lacks current when i start it, but as it always starts and cranks i haven't bothered caring to much, but now that its getting colder i feel like it would be good to find the culprit.
Very thankful for any help!

 

See Is My Battery Bad? - 5Series.net - Forums and check your B+ and GND connections. BTW, when you replaced the battery, did you register it?

 

I haven't registered it yet, i know it is important to do but didnt think it could cause something like this.

 

BMW charging system is complex and so you cannot troubleshoot it like a simple system.

IBS can adjust the charging voltage and so it won't always read the same. It helps tremendously to check the battery charge status and histogram. Read the BMW-specific codes. Test the battery via the link I posted. I've had experience with more than one supposed brand-new battery was bad.

 

I personally don’t think you should be seeing the voltage fluctuate like that. Mine is extremely constant when the engine is on. BMW did talk about a bit of regenerative braking around the time of the E60 but I have searched extensively and cannot find any evidence of the E60 supporting this. I’m leaning toward voltage regulator.

 

In the link I posted, voltage regulator is one of the tests. There’s a kit you can buy that has regulator, brushes and slip ring. It’s pretty easy to replace.