BMW 8 Series Battery Drain Mystery Frustrates Owner

Hey there! I can relate, went through something very similar with my 2021 BMW 6 diesel last year. I have some experience working on cars, mostly basic maintenance and troubleshooting. Turns out my battery sensor was faulty, causing similar symptoms to what you're describing, dead battery, weak lights, and starting issues. Took it to my regular workshop after attempting basic checks myself. The mechanic diagnosed it pretty quickly, the sensor wasn't sending correct readings, making the charging system go haywire. Total fix was around 315 Euro, including parts and labor. Before I can help more specifically, what's your exact 8 Series model, and have you noticed any particular pattern when the battery dies? Also, does it happen more when using certain features? The 8 and 6 Series share quite a few electrical components, so your issue might be similar to what I experienced. Let me know these details and I can share more specific info about the repair process.

Thanks for sharing your experience! I'm dealing with the same symptoms with my 8 Series (159932 KM on the clock). The battery usually dies after sitting for about 2-3 days. It's gotten worse lately, especially after using the infotainment system or climate control. Had my last service done just 2 months ago, and they didn't mention any issues with the charging system. I'll definitely have them check the battery sensor based on your experience. The repair cost sounds reasonable if it solves these headaches. Have you had any recurring issues since getting it fixed?

Hey again! Happy to hear back from you about your 8 Series. that situation sounds super familiar, my 6 Series was doing exactly the same thing before I got it fixed, especially with the infotainment system draining power. Since you asked, nope, haven't had any issues since replacing the battery sensor last year. My car's been starting like a champ, even after sitting for a week or so. Running at 142000 KM now and everything's working perfectly on the electrical side. One thing I forgot to mention in my first reply, before going to the workshop, I was getting this weird parasitic drain that would kill the battery even faster when using the climate control, just like you're experiencing. The faulty sensor was causing the system to keep drawing power even when it shouldn't. Quick tip though, when they check your battery sensor, have them look at the wiring harness too. My mechanic found some slight corrosion on the connections while doing the repair. Getting that cleaned up probably helped prevent future issues. Trust me, once you get this fixed, you'll be amazed at how many small electrical quirks disappear. Let me know how it goes after you get it checked out!

Thanks so much for the detailed follow-up! Really helpful to hear that the fix has been lasting for you. I've actually just booked my car in for next week and specifically mentioned the battery sensor and wiring harness check. You're right about those small electrical quirks, I've noticed quite a few lately that I didn't even connect to this issue. Will definitely update you after the repair. Really appreciate you sharing your experience, saved me a lot of troubleshooting time and probably money too! Fingers crossed it's the same issue and I'll be back to normal soon. Thanks again!