Originally, the first year M5 and M6 got a94 AH battery but BMW found out that it couldn't handle the load from all the electronics and caused it to die early. That is the reason why we have 105 AH battery with recent models.
BMW issued a warranty replacement from 94 AH to 105 AH for earlier models to fix reported issues.
You changed from a 105 AH to 94 AH isn’t optimal. You may see issues like the earlier models experienced.
You also need to register the new battery, and code it if you change the from 105 AH to 94 AH, or else the car wont charge it optimally and kills the battery faster.
I wrote an extensive info about OEM battery in another thread. In addition, if you don’t know what you’re doing then pay someone/dealers that can do it right the first time, or else you may end up with more issues and expensive fixes like the person in that thread.
https://www.6post.com/forums/showthread.php?t=1569619
I replaced my car with the battery below and been running without any issues for almost 1 year. I’m confident it is the same as OEM battery. I hope it can help other people because I saw so many wrong info about BMW battery. Replacing the battery isn’t hard but you need to know how to do it right and with the right tools.
https://www.oreillyauto.com/shop/b/b.../m6-gran-coupe
Part #: 95RPLT