BMW Diesel Battery Woes: Electrical System Mayhem

Hey there! I had a similar issue with my 2008 BMW 5 Series diesel last month. The symptoms were exactly like yours, dash errors, start-stop failure, and sluggish starts. Turned out both my main and auxiliary batteries were failing. Had it checked at the garage, the aux battery wasn't holding charge anymore and was affecting other electrical systems. The mechanics found that the charging system wasn't properly distributing power between both batteries. They had to replace both batteries and recalibrate the charging system. It was a serious job because these dual-battery systems are quite complex. The mechanic mentioned that letting it go too long could've damaged other electrical components. The whole process took about half a day to complete. My advice would be to get it checked soon, auxiliary battery issues can cascade into bigger problems if left unattended. Make sure to find a shop that specializes in BMW electrical systems, they'll know exactly what to look for. Best of luck sorting it out.

Hey, thanks for sharing your experience! That's super helpful since it sounds exactly like what I'm dealing with. Really good to know about both batteries needing replacement, makes sense with the symptoms I'm seeing. Just wondering, do you remember roughly how much you ended up paying for the whole job? Also, has everything been running smoothly since the fix, or have you noticed any other electrical quirks popping up? Thanks again for the detailed response!

Hey again! Happy to give you an update! The repair worked out great, after they fixed the auxiliary battery malfunction, everything's been running like clockwork. Cost me 290 € in total for the battery charging system repair, which honestly wasn't as bad as I expected given how complex these BMW electrical systems can be. My start-stop is working perfectly now, no more warning lights on the dash, and the car starts up instantly every time. It's such a relief not having those electrical gremlins anymore! Haven't had a single issue since the repair, which was about two months ago now. Trust me, getting it sorted sooner rather than later was definitely the right call. My BMW 5 Series feels like a different car now, all those little electrical quirks completely disappeared after they fixed the charging system. If you end up getting it repaired, let me know how it goes! Always interested to hear if others have similar experiences with these dual-battery setups.

Thanks for the follow-up! I actually bit the bullet and got it fixed yesterday. You were absolutely right about getting it done quickly. Found a great mechanic who specializes in BMW electrical systems. Turned out my issue was pretty much identical to yours. They replaced both batteries and recalibrated the system. The bill came to around 300 €, a bit more than yours but still reasonable considering the work involved. The difference is like night and day! No more warning lights, the start-stop works perfectly, and the car fires up instantly. The mechanic was really thorough and explained everything they did. They even showed me the old batteries, they were definitely shot. Really glad I asked here first. Your experience helped me know what to expect and gave me confidence to get it sorted. The mechanic said leaving it any longer could've caused more expensive problems down the line. Thanks again for all your help with this! I'll definitely keep an eye on the electrical system from now on.