Just to add one data point. New (aftermarket) alternator a few years ago and just installed a new battery in my 4.8is a couple weeks ago. Truck has been sitting in the garage (~78f constant) unlocked since 10/18. Battery voltage (ignition off, truck not yet asleep) measured at jump points under hood was 12.8v. Yesterday 10/25 battery voltage measured 12.26v, again under hood and truck "awake" as I opened the door to pop the hood.

Orange shift light turns off after ~15 minutes after last door closed when left unlocked. Don't know what it does when locking and the alarm is active. I stick a trickle charger on it last night after measuring voltage.

Don't know if that says anything about your situ, but it's data. Good luck, battery draws suck. EHC module put my 4 year old battery in the grave.

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2005 X5 4.4i Build 04/05 Maintenance/Build Log
Nav, Pano, Sport (Purchased 06/14 w/ 109,000 miles) (Sold 8/15 w/121,000 miles)

2006 X5 4.8is Build 11/05 Maintenance/Build Log
Nav, DSP, Pano, Running Boards, OEM Tow Hitch, Cold Weather Pckg (Purchased 08/15 w/ 90,500 miles)

2010 X5 35d Build 02/10
Nav, HiFi, 6 DVD, Sports Pckg, Cold Weather Pckg, HUD, CAS, Running Boards, Leather Dash, PDC, Pano (Purchased 03/17 w/ 136,120 miles)