BMW i5 Battery Drain Mystery: Recurring Dead Battery Issues

Hey there! I had a similar issue with my 2022 BMW i4 (also dealt with the i7 before). I have some experience working on EVs. The symptoms you described sound exactly like what I faced, dead battery, weak lights, error codes popping up. After dealing with this headache for a couple weeks, I took it to my regular EV workshop. Turned out the battery sensor was faulty, causing incorrect readings and draining power even when the car was off. Got it replaced for about 315 Euro and haven't had any issues since. Before suggesting anything specific though, could you share: How long does your car typically sit between drives? Are you getting any specific error codes? Did these issues start suddenly or gradually? This info would help confirm if you're dealing with the same problem I had. BMWs can be tricky with electrical issues, but usually, there's a straightforward fix once properly diagnosed.

Hey, thanks for the detailed response! My i5 has 179963 KM and just had its service last month. I typically let it sit for about 2-3 days between drives during weekdays. The issues started gradually over the past few weeks. I'm getting error code "EC-345" on the dashboard, and it seems worse in the mornings. The battery sensor issue you mentioned sounds really similar to what I'm experiencing. I'll definitely get that checked out. It's good to know there might be a relatively simple fix rather than a major system problem. The price you mentioned for the repair seems reasonable too, especially compared to what I was worried it might cost. Did you notice any other warning signs before your sensor completely failed? Just trying to confirm if I'm dealing with the exact same thing before heading to the workshop.

Hey again! Yeah, looking at your details, it's even more convincing that you're dealing with the same battery sensor issue I had. That EC-345 code is exactly what I saw too, it's pretty typical for sensor failures in these models. Before my sensor completely gave up, I noticed a few subtle things that got worse over time. The dashboard would sometimes flicker when starting up in the morning, and occasionally the car would take a few extra seconds to start, especially after sitting for 2-3 days, just like your situation. The really telling sign was that these issues were way more noticeable in the morning after the car had been sitting overnight. Since you mentioned having similar mileage to what I had (I was around 175000 KM when this happened), it makes perfect sense. These sensors tend to start acting up around this mileage. Honestly, I kept putting off getting it checked, thinking it might be something major, but it was such a relief when it turned out to be just the sensor. Quick tip though, when you take it in, have them check the entire charging system while they're at it. My mechanic did that and found that everything else was actually fine, which was reassuring. Been running perfectly for about 8 months now since the fix. Just make sure you go to someone who knows BMWs well, these electrical issues can be tricky if not diagnosed correctly.

Thanks so much for all this detailed info! You've really put my mind at ease. The flickering dashboard and slow morning starts are exactly what I've been experiencing too. It's such a relief to hear that your fix was straightforward and has lasted 8 months without issues. I've actually just scheduled an appointment with a BMW specialist for next week. I'll definitely mention the battery sensor and ask them to check the entire charging system like you suggested. Really appreciate you taking the time to share your experience, it's saved me a lot of worry about potentially major repairs. Makes total sense about the mileage correlation too. I'll update you after the repair if you're interested. Thanks again for walking me through this, it's super helpful to hear from someone who's already dealt with and solved the same problem!