BMW 7 Series Electrical Gremlins: Battery Issues & Fixes

Hey there! I have some experience working on cars and had a similar issue with my 2005 BMW 5 series last year. Those symptoms sound really familiar, I was getting unusual error messages and had starting problems too. Took it to my regular workshop and it turned out the battery was pretty much dead, plus the charging system wasn't working properly. The whole repair, including a new battery and system check, cost me about 290 Euro. After fixing it, all those annoying electrical gremlins disappeared. Before I share more specific details, can you tell me if you've checked the battery voltage or had any warning lights specifically about the charging system? Also, how many miles are on your 7 series? This would help me understand if you might be dealing with the exact same issue I had. If you want, feel free to update me with those details and I can tell you more about what my mechanic did to diagnose and fix the problem.

Thanks for sharing your experience! My car has 137152 KM on the clock and was last serviced about 3 months ago. I haven't checked the battery voltage myself, but I'm getting that battery warning light occasionally, especially during cold starts. The weird thing is that sometimes it starts perfectly fine, and other times it struggles. I'm really hoping it's just the battery like in your case, though I've heard these issues can get pretty complex with BMWs. Did your mechanic mention anything about the alternator when they fixed yours? Just wondering if I should be prepared for more than just a battery replacement.

Hey again! Thanks for those details, that mileage is actually pretty close to what my 5 series had when I ran into similar issues (mine was around 145000 KM). Yeah, that intermittent starting behavior is exactly what I experienced, some mornings it would fire up perfectly, and others it would barely crank. My mechanic actually did check the alternator during diagnostics, and funny enough, it was putting out slightly low voltage which wasn't helping the situation. But in my case, the alternator didn't need replacement, it just needed some adjustment to the voltage regulator. The really tricky part with these BMWs is that when the battery starts failing, it can trigger all sorts of weird electrical gremlins that make it seem way worse than it is. My car was throwing what seemed like unusual error codes, kind of like yours. The start-stop system was one of the first things to act up because it's super sensitive to battery voltage. Since your symptoms are so similar to what I dealt with, I'd bet you're looking at a battery replacement at minimum. Given that your car was serviced recently but these issues are still happening, I'd definitely get both the battery and charging system checked. My total repair ended up being cheaper than I expected because it was mainly just the battery, but it's always good to be prepared for the alternator possibility. Want me to share what specific tests my mechanic ran to diagnose the problem? Might help you avoid getting overcharged for unnecessary work.

That would be super helpful, thanks! Your experience is giving me some hope that this might not be as expensive as I feared. It's really interesting that your alternator just needed an adjustment rather than a full replacement, I didn't even know that was possible. The similarity between our issues is pretty striking, especially with the unusual error codes and that intermittent starting problem. I'll definitely get both the battery and charging system checked out. Would really appreciate knowing what tests your mechanic ran, that way I can make sure my mechanic does a thorough job and I'm not just throwing parts at the problem. I think I'll schedule an appointment for next week. Thanks again for all the detailed info, it's been really helpful having someone who's been through the same thing with their BMW!