BMW X7 Battery Drain Mystery: Real Owner Reports Needed

Hey there! I had a similar issue with my 2017 BMW X5 40i last winter. The battery warning started showing up out of nowhere, and the car would sometimes struggle to start, especially after sitting for a few days. Took it to my mechanic who ran a full diagnostic. Turned out it wasn't just the battery, there was a parasitic drain caused by a faulty control module that was preventing the car from going into proper sleep mode. The module was constantly drawing power, which drained the battery even when the car was off. They had to replace both the battery and the faulty module. It wasn't a quick fix since they needed to identify which module was causing the drain, but once fixed, the problem never came back. Was a serious issue that could've left me stranded if not addressed. Based on your symptoms, it sounds very similar to what I experienced. You'll want a thorough electrical system diagnosis, not just a battery check. The undervoltage errors are definitely a red flag that points to a bigger electrical issue. Hope this helps with your troubleshooting.

Thanks for sharing your experience! It does sound exactly like what I'm dealing with. Your solution makes a lot of sense, especially with that control module issue. By the way, how much did you end up paying for the whole repair? Also, just curious, have you had any other electrical gremlins pop up since getting it fixed?

Hey again! Glad I could help! Just wanted to follow up, since my last post, I actually got the issue fully resolved. The Terminal 30 continuous plus problem was the culprit, and getting that fixed solved everything. Total bill came to 290 € for diagnosing and fixing the "Battery heavily discharged" warning. And to answer your questions, nope, haven't had a single electrical gremlin since the repair. The car starts perfectly now, even after sitting unused for days. It's like having a completely different vehicle! The battery warning hasn't flashed once, and all those annoying undervoltage errors are history. You know how BMWs can be picky with electrical stuff, but once you get the right fix, they're solid. Just make sure whoever works on it knows their way around BMW electrical systems, it makes all the difference. My mechanic mentioned these issues are pretty common in newer BMWs, so you're definitely not alone. Let me know how it goes with yours!

Thanks so much for the detailed follow-up! I actually just got back from the mechanic today, and you won't believe it, my issue was somewhat similar but with a twist. Turned out my battery wasn't the main problem at all. Had a faulty alternator that wasn't charging properly, plus some weird wiring issue near the trunk that was causing a constant power drain. The fix was pricier than yours, about 800 bucks total, but honestly, it's worth every penny. The car starts like a dream now, no more warning messages, and that annoying startup hesitation is completely gone. My mechanic actually showed me the old alternator, and it was pretty shot. Really appreciate you sharing your experience, it gave me the push I needed to get a proper diagnosis instead of just hoping it would fix itself. These luxury cars sure can be finicky with their electrical systems, but at least now I know what to watch out for! Thanks again for all your help. Time to enjoy my properly functioning X7!

Headlights brake lights flicker when switched on as the brake pedal is pressed I’ve changed terminal 30b and the relay under the bonnet the blue one checked earth on rear lights but the flicker is still a mystery

Check the battery connections and ensure they are clean and tight. Corroded or loose connections can cause flickering lights. If the issue persists, consider inspecting the alternator for proper function, as it might not be providing consistent voltage. Let me know how it goes or if you have further questions!