BMW i3 Battery Drain Nightmare, Owners Report Issues

Hey there! I have some experience working on hybrids and actually had a very similar issue with my 2014 BMW i8. Like you, I was dealing with battery drain problems and those annoying warning lights. Turned out my battery sensor was completely shot, which was causing incorrect readings and draining the battery. Took it to my regular workshop and they diagnosed it pretty quickly. The repair cost me about 315 Euro, but it fixed the problem completely. Haven't had any issues since then. Before you head to the shop though, could you share: How long does the car sit between drives? Are you getting any specific error codes? Have you noticed any other electrical issues? Would also have similar issues with my 's BMW X5 hybrid, so it seems to be somewhat common in these models. Let me know those details and I might be able to help more specifically!

Thanks for sharing your experience! I've got 39876 KM on mine and just had it serviced last month, which makes this issue even more frustrating. My car usually sits for about 2-3 days between drives, and yes, I'm getting the "Battery Discharge" warning along with the "Drivetrain Malfunction" message. The only other electrical issue I've noticed is that the infotainment system occasionally restarts by itself. Your battery sensor suggestion is really interesting, the symptoms sound exactly like what I'm experiencing. Definitely cheaper than what I was worried it might cost! I'll have this checked first when I take it in. Thanks for pointing me in the right direction!

Hey again! Thanks for those extra details, that actually helps confirm my initial thoughts about the battery sensor even more. My i8 had almost the exact same symptoms around the 45000 KM mark, especially that infotainment system restarting issue, it used to drive me crazy! Just for comparison, when my battery sensor was failing, I was also getting those identical warning messages. The "Drivetrain Malfunction" alert is particularly typical of a faulty sensor, because the car's computer gets confused by the incorrect battery readings. One quick test you can try before heading to the shop, check if your battery terminals are clean and properly tight. In my case, they looked fine, but it's worth checking since it's free and easy. When my sensor was bad, even cleaning the terminals made no difference, which was another clue. The 2-3 day sitting period shouldn't cause these issues with a healthy system. My i8 now sits for up to a week sometimes with zero problems since getting that sensor replaced. Keep me posted on what you find out, would be interesting to know if it's the same issue. And hey, at least it's likely not the main battery pack, which would be way more expensive to fix!

Thanks so much for all the detailed help! I just checked the battery terminals like you suggested, they're clean and tight, but the problems are still there. You're right, this really does sound exactly like your sensor issue, especially with the matching warning messages and that annoying infotainment restart problem. I've booked the car in for tomorrow morning and specifically asked them to check the battery sensor first. Really hope it turns out to be the same relatively simple fix as yours, the thought of a major battery problem was keeping me up at night! I'll update this thread once I get the diagnosis. Thanks again for sharing your experience, it's made me feel a lot more confident about handling this!