BMW i3 Battery Warning Signals Point to Sensor Issue

I had nearly identical issues with my 2016 BMW i8 Hybrid last winter. The symptoms match exactly what you're describing, battery warnings, sluggish starts, and dimming lights. After taking it to the dealership, it turned out to be a defective battery sensor that wasn't correctly reading the charge levels. The sensor replacement wasn't a super complex job, but it needed special diagnostic tools to properly calibrate the new sensor with the car's computer system. The mechanics also had to clear all the error codes afterward. It wasn't a major issue in terms of car safety, but it needed fixing soon because wrong readings could eventually lead to battery damage. The sensor is actually a crucial part of the hybrid system's power management. I'd recommend getting it checked soon, with these symptoms, it's better to address it before you end up stranded somewhere with a car that won't start.

Thanks for sharing your experience! That's really helpful to know it was the battery sensor in your case. Since we have such similar issues, I'm definitely leaning towards getting mine checked out at the dealership too. Do you happen to remember roughly how much the sensor replacement and calibration ended up costing you? Also, just curious, have you had any other electrical gremlins pop up since getting it fixed?

Hey again! Glad I could help point you in the right direction. After seeing your follow-up, I wanted to let you know that I ended up paying 315 € for the whole sensor replacement job, including the calibration work. It was totally worth it though, the fix solved all those annoying battery warnings and performance issues I was having. Since getting the sensor replaced, my i8 has been running perfectly on the electrical side. No more warning lights, no dim headlights, and the starts are nice and strong again. The battery monitoring system is working exactly as it should now. Honestly, it's been such a relief not having to worry about whether the car will start properly every morning! I'd definitely recommend just getting it sorted at the dealership. The peace of mind alone is worth it, and you really don't want to risk damaging your hybrid battery system by leaving a faulty sensor in place. Plus, these cars need proper diagnostic equipment to get everything calibrated correctly.

Thanks a lot for the detailed info about the costs and the follow-up experience! I actually bit the bullet and took my i3 to the dealership yesterday. You were spot on, it was indeed the battery sensor causing all the trouble. The repair bill came to about 330 €, pretty close to what you paid. The mechanic was really thorough and explained that the old sensor was giving false readings, which was messing with the whole hybrid system. They showed me the worn-out sensor and I could see why it was causing problems. The replacement process took about two hours, including all the computer calibration stuff. Drove it home afterward and wow, what a difference! The car feels completely normal again, no more warning lights, strong starts, and all the electrical systems are working perfectly. Really glad I didn't wait any longer to get it fixed. Thanks again for helping me make the right call on this one!