BMW 7 Series Hybrid Battery Chaos: Multiple System Failures

Hey! I've got some experience with BMW hybrids as I own a 2020 BMW 5 Series Hybrid, and my cousin drives an i4. I had almost identical symptoms last year, weak starts, system warnings all over, and dimming lights. My diagnostic also showed low voltage readings. Turned out my 12V battery was completely drained, likely because I wasn't driving much during that time. Took it to my regular workshop, they tested both the main hybrid battery and the 12V battery. The 12V was beyond saving and needed replacement. Total bill came to 290 Euro including labor and programming the new battery to the car's system. Quick fix really, and the car's been running perfectly since. But before I share more specific advice, what's your typical driving pattern? Do you do lots of short trips or longer drives? Also, how old is your current 12V battery? These details would help figure out if you're facing the same issue.

Thanks for sharing your experience! I also rarely do long drives these days, mostly short trips between my work and home. My car's at 36504 KM and just had its annual service last month. The battery is the original one that came with the car, so it's about 18 months old now. Actually, what you described sounds exactly like what I'm experiencing. The symptoms started appearing after I left the car parked for about a week. I was wondering if it could be the 12V battery, but wasn't sure since the car is relatively new. Good to know there's a potential solution that won't break the bank. Did you have any issues after the battery replacement, like recalibration problems or system resets?

Hey again! Wow, your situation sounds exactly like what I went through. Since I already replaced my battery in my 5 Series, I can tell you the whole story. After the replacement, everything went super smooth, no recalibration issues or system resets at all. The workshop handled all the programming, and honestly, the car felt better than ever. The starts were crisp, all those annoying warning messages disappeared, and the lights went back to full brightness. The thing with these new BMWs, especially the hybrids, is that they're pretty demanding on the 12V battery, even when parked. All those fancy electronics keep drawing power. And yeah, lots of short trips don't help because the battery doesn't get enough time to fully recharge. Even though your battery is only 18 months old, that week-long parking period might have been the final straw. Mine was about 2 years old when it gave up, and I had the same mostly-short-trips driving pattern as you. One tip: after my battery replacement, I bought a trickle charger for those times when I know the car will be sitting for more than a few days. Haven't had any issues since then. The workshop guys actually recommended it, said they see this pretty often with hybrid BMWs.

Thanks so much for all the detailed info! This really helps put my mind at ease. I'll definitely look into getting a trickle charger too, sounds like a smart investment to prevent future issues. Got an appointment at the workshop tomorrow morning, and I'm pretty confident now that it's just the 12V battery. Your experience has been super helpful, exactly the kind of real-world feedback I was hoping for. Really appreciate you taking the time to share all the details, especially about the post-replacement experience. It's good to know everything went smoothly with the programming and there weren't any lingering issues. I'll probably stick to the dealership this time since the car's still under warranty, but at least now I know what to expect. Thanks again for all your help!