Audi RS7 Alarm Failure Linked to Secondary Battery Issue

Had a similar electrical issue with my 2016 Audi RS5 last winter. The auxiliary battery failure caused the car alarm system to malfunction completely. The secondary battery in these Audi models powers the alarm system independently from the main car battery. When it starts failing, the alarm becomes unreliable or stops working entirely. This is actually a common issue once these auxiliary batteries reach about 8-10 years of age. The repair itself is straightforward, it requires replacing the auxiliary battery unit. The tricky part is accessing it, as its usually tucked away under several components. In my case, the mechanic needed special diagnostic tools to reset the alarm system after the battery replacement. This was not a serious mechanical issue, but leaving it unfixed can drain your main car battery over time. The auxiliary battery problem can also trigger other electrical system warnings. The repair took about 2 hours at the shop. Make sure to use an authorized repair center for this fix, as the alarm system needs proper recoding after the battery replacement. Ask them specifically about their experience with Audi auxiliary battery systems.

Thanks for sharing your experience with the RS5 auxiliary battery replacement. Pretty much matches my symptoms, alarm going crazy then completely dying. Did you remember roughly how much you paid for the complete fix? Been a while since you had it done, any other electrical issues pop up afterwards? Just want to make sure the battery signal problems didnt cascade into other problems before I book it in. My car battery itself seems fine, but these secondary battery problems seem to crop up quite a bit in older Audis from what I hear.

After getting my RS5 fixed at the shop, I can confirm it cost 330 Euro for the complete auxiliary battery replacement. This included the battery itself plus labor for installation and system recoding. The car alarm has worked flawlessly since the repair, with no additional battery alarm notifications or electrical issues popping up. The system diagnosis confirmed it was just the auxiliary battery showing signs of age-related deterioration. Once replaced, the alarm system returned to normal operation. The main car battery remained unaffected, which was a relief since replacing both would have been considerably more expensive. Its been about 8 months now since the fix, and I havent experienced any cascade failures or related electrical problems. The auxiliary battery replacement seems to have completely resolved the alarm system defects. Just make sure your shop properly recodes the system after installation, thats crucial for these Audi auxiliary systems to work correctly.

Thanks for the input. I went ahead and got it fixed last week. Turns out the system diagnosis was spot on, it was the auxiliary battery causing all the trouble. Found a specialized shop that knew their way around Audi alarm systems. Total bill came to 380 Euro, slightly more than expected but worth it for the proper fix. They had to remove quite a few parts to access the battery location but got it done in about 2.5 hours. The alarm system works perfectly now and all those battery signal warnings have disappeared from the dash. They also checked the main car battery which thankfully tested fine. Good to have peace of mind that this common battery problem is finally sorted. Worth mentioning they did a full system reset after the installation which apparently is crucial, learned something new there. Been a week now with zero issues.