As I've been recommending each time this topic comes up...you can go with the expensive BMW labeled battery (won't be same mfg as from the factory)...or ANY 49/H8 or 95R/H9 battery. You can go lead-acid or AGM with either of the aforementioned battery class sizes.
The specs of the 49/H8 & 95R/H9 battery are usually higher or similar to the original battery...and can cost much less money. There are 3 big battery manufactures in the USA that supply most of the battery brands. The case color and labels may be different, but many of them are made by the same 3 companies...and may only have slight differences in specs. The big 3 are:
- Johnson Controls
- Exide
- East Penn
You can see in the East Penn chart below...what the "common" specs of the lead-acid & AGM (absorbent glass mat) 49/H8 & 95R/H9 batteries are vs the smaller 48/H6 & 94R/H7 batteries:
These specs carry over to the Exide & JC batteries...like the Duralast H8 Platinum (AGM) or Duralast H8 DLG...or batteries by NAPA...and other brands.
I was just at Sams Club & Batteries PLus...and you can see the specs of their 49/H8 & 95R/H9 lead-acid & AGM batteries: