Here is a pic of the C&D battery that Tesla currently uses.>I want to say a group 75 battery [Smop]
The U-1 (form factor) battery I listed is reversed, ie POS on lf NEG on rf. MS batt has NEG at left rear & POS at right front thus is a custom battery as there is NO such industry group for this configuration. This from Battery Systems. Also the posts might be a different shape. Hard to tell peering into the limited space above POS terminal with that rat's nest of wires all connecting to the POS post. U1R batt has terms reversed but both in front and is only available NON-AGM.
Bottom Line: Might be best to stick with Tesla keeping your 12v battery up to date & warranted, since the OEM battery is not available and since replacing it is a genuine nightmare. If you install remote terminals inside the Frunk then you can quickly connect a U1 battery into the 12 volt system which is equal or better than the latest Tesla batteries. Or any other 12v battery.
>And how do you pop the trunk with failed 12V? [MK]
@islandbayy: The video you reposted does not answer this question assuming 'trunk' to mean HATCH.
Ok, I levered off the plastic cover and my MS does have the manual release cable to open Hatch. Pry yours off a few times to make it easier to do. This in a car with NO 3rd seats. Problem solved, thanx!