from 6 series site
may not be relevant, but I can't see how a battery is the cause
"The SOS emergency call malfunction requires an overnight dealer reflash of the ECU's. I learned it the hard way and had to reflash and recode the entire car all over again.
It kept coming up periodically for me and the SOS button still worked as it should but I was annoyed so I took it in thinking it was a hardware issue. Ended up being software. It started happening at around 2k miles on the odometer."
source:
https://www.6post.com/forums/showthread.php?t=1424625