Hey, I have a 2005 bmw 325i and I've been having issues with it loosing power. I've replaced the battery and the alternator and it still drains the battery. I'm assuming its a ground wire problem but I'm not entirely sure. I can't Jumpstart the car from the battery I have to connect it to the positive under the hood.
Did you register your battery after you replaced it? When you replace the battery on a BMW, you have to "register it" with the BimmerLink app, Carly app, or with a dealer-level scan tool in order for it to charge properly. Without registering your new battery, the ECU still thinks that the old battery is being used, so it screws up the "smart charging" system they have. Yes, I bet everyone here is going bash on this BMW over-engineered thing lol.
The registration step basically tells the ECU what type of battery it is and the battery's amp rating for proper charging.
Here is a helpful link: https://www.bimmer-tech.net/blog/item/115-bmw-battery-replacement-and-registration
I highly recommend the BimmerLink app ($35 + adapter purchase); their battery registration is super simple AND it gives you access to a whole bunch of BMW-specific diagnostics as well. I use it and it's awesome.
This!!! I never knew about battery registration until I tried to change the battery myself on my BMW.
This is a real thing? Lol I need to do some research
Even if its an old 2005 bmw?
@steelbear60
Yes, according to the link I provided it started in the 2002 model year. I'm pretty certain it's the battery registration that's causing your issue...almost everyone has this issue when they don't register their battery.
Thank you I did a little research and think that's my problem hopefully
Which alternator did you use? (Rebuilt?) For battery drain issue, start here:
https://m.youtube.com/watch?v=B__DqK90IIc
Bought a new one from autozone.
Check for parasitic drain.
One common issue in older models of later years (not sure if your year or model). If your BMW has key less features, check the door handles after your car has been sitting overnight. If any of the handles are warm to the touch, that may very well be the problem.
Otherwise ir is happy hunting.
It drains while driving, drove it 20 miles and all my lights and everything dimmed till the car eventually had no power and left me stranded.
Oh probably not the door handles then.