Time to take charge of the situation
I knew that I wanted to replace my battery since I got the car but I never got around to it. The primary reason for the lack of motivation was because the car was always on the tender when parked in the garage and I never seen any issues with discharging over the few days I drive in a row.
Initially, I wanted one of the antigravity batteries but I think at the end of the day I didn't really need to save that much more weight for $800+.
From the forums, I've seen others use a Z4M 70Ah battery so I went to my local dealership and got a 70Ah AGM battery.
Part no: 61-21-5-A40-E19 (This is the new part number that supercedes the original Z4M 811 part number)
Weight: 45lbs
CCA: 680
The battery I pulled out my car was a 90Ah 900CCA battery. For those who have OE batteries in their car, the negative terminal shows a date in the format of WW/YY. Mine was 15/10 which meant April 2010, over 608weeks ago! Who else has their original battery from 2010?!
Anyways, the original battery was 60lbs so there was net loss of 15lbs due to the smaller CCA and group size. As you can see in the picture, it is definitely smaller!
Installing was uneventful:
I coded 70Ah AGM into the CAS module
Synced time with my laptop via ISTA
Registered the new AGM battery via the barcode and mileage
Tada!
I'm still amazed that AGM battery survived for so long.