You need to read my post about discharging my battery:
https://f80.bimmerpost.com/forums/sh...hlight=battery. I thought it was dead and I ruined it.
Are you sure your battery is completely discharged? The battery saving circuitry may have kicked in and prevented it from being completely discharged and it might still be able to be revived. It might be worth getting the CTEK Lithium US that I mentioned in my post and seeing it that can revive it. Certainly worth $100 to try before shelling out for a new battery.